This invention relates to a method and system for the preparation of specimens for analysis by electron microscopy, and more particularly to a method and system for the milling of specimens using an ion beam.
Ion beam milling systems are used for the preparation of specimens whose internal and surface structures are then analyzed using transmission electron microscopy (TEM) or scanning electron microscopy (SEM). Many techniques have been developed which have included the use of mechanical cutting, grinding, and/or polishing operations in combination with ion beam bombardment. In many instances, such techniques have required that the specimen be repeatedly moved from one apparatus to another (either different preparation devices or observation devices) and/or be moved or realigned while mounted in a cuffing, grinding, or milling device.
Transmission electron microscopy is an important technique for studying the detailed microstructure of many materials. Improvements in the design and operation of electron microscopes have generated considerable interest in obtaining atomic resolution images of various materials. However, the preparation of specimens for atomic resolution transmission electron microscopy is demanding, requiring a final specimen which is very thin (i.e.,  less than 50 nm) and free from artifacts. Typically, specimen preparation involves initial slicing, sectioning, trepanning, and/or grinding operations to produce a relatively thin (100-200 xcexcm) disk of approximately 3 mm diameter.
Ion beam milling systems have been used to prepare specimens of various materials including ceramics, semiconductors, metals, and combinations thereof for atomic resolution transmission electron microscopy. In such ion beam milling systems, such as the system disclosed in commonly-assigned U.S. Pat. No. 5,009,743, to Swann, specimens are mounted on holders and placed in the path of one or more ion beams. The ion beams gradually remove atoms from the surface of the specimen until a small perforation is formed in the center of the specimen. Generally, the area immediately around the perforation is then thin enough (i.e.,  less than 50 nm) for atomic resolution analysis by a transmission electron microscope.
Swann et al, U.S. Pat. No. 5,472,566, provides a specimen holder adapted to permit the simultaneous two-sided ion beam milling of a specimen at very low angles of beam incidence, down to 0xc2x0, from both sides of the specimen through the use of one or more support arms to secure the specimen. This produces both rapid milling as well as reducing artifacts to provide high quality specimens for transmission electron microscopy analysis.
In such ion beam milling systems, the ion milled specimens have to be removed from the specimen holders and loaded in a TEM holder for imaging. Clearly, loading and unloading of the specimen from the holders increases the potential of damage to fragile specimens. Additionally, if the specimen is not completely electron transparent upon initial TEM examination, it must be returned to the ion mill for further thinning. Multiple milling steps may be required, depending upon thickness requirements at the area of interest in the specimen.
Slope cutting by directing an ion beam at a masking screen located at or near a specimen surface is also known. The masking screen protects a portion of the specimen, while the remainder of the specimen is milled by the ion beam to reveal desired profiles. This technique is capable of providing cross-sectional profiles of layered structures, the surfaces of which can then be studied by scanning electron microscopy. For example, Hauffe, East German published Patent Application No. 201,538, teaches an apparatus and method for preparing specimens for SEM analysis by providing an ion gun inside the specimen chamber of a scanning electron microscope. A mask is positioned adjacent the sample and is used, in conjunction with the ion gun, to remove material from the specimen.
Double slope cutting to produce a very thin film of a specimen for TEM analysis has also been developed. Yoshioka et al, U.S. Pat. No. 5,907,157, describe a method and apparatus for preparing a specimen adapted for electron microscopy which includes an evacuated specimen-processing chamber. A specimen having a surface to be processed is placed inside the processing chamber and a beam-blocking member is placed close to the processed surface so as to block a part of an etching beam. A first etching step is performed by directing the beam at the specimen via the blocking member. Then, the specimen and the blocking member are moved relative to each other to expose another portion of the specimen. A second etching step is then performed by directing the beam at the specimen via the blocking member. As a result, the specimen is thinned and can be observed with an electron microscope. However, the requirement that the specimen and blocking member be moved relative to one another to perform the second etching step complicates the process and introduces the potential for errors as the relative positions of the two must be controlled to within an accuracy on the order of a few hundred nanometers (10xe2x88x929 meters) or less.
Mitro et al, U.S. Pat. No. 5,922,179, teaches an apparatus and process for etching and coating specimens in a single vacuum chamber, to minimize handling and transfer. The apparatus includes a sealed chamber and a vacuum pump for forming and maintaining a vacuum in the chamber, a first ion gun positioned in the chamber to etch a specimen, a sputtering target in the chamber, and at least one additional ion gun positioned in the chamber to cause material from the target to be directed onto the specimen.
Techniques have also been developed in the preparation of specimens for scanning electron microscopy in which the specimen may be observed by a SEM during preparation thereof. For example, Grxc3xcnewald, U.S. Pat. No. 5,986,264, teaches an ion beam milling system using two ion guns for use in the preparation of samples to be used in both SEM and TEM analysis. The system uses an SEM as a high resolution imaging device to observe the progress of the ion milling of a sample and to determine when a proper sample thickness has been achieved. Also, as the sample stage can be tilted, the system is also taught to be useful for slope cutting of specimens.
The inadequacy in localized thinning of TEM specimens with broad ion beams, coupled with the ability of focused ion beam (FIB) to micro-machine materials, has led to the development of FIB milling systems. The first FIB based instrument (Precision Ion Milling System (PIMS)), became commercially available in 1984 from Gatan, Inc. Since the introduction of this instrument, several other commercial FIB systems have become available. These machines are capable of both imaging and milling selected areas within TEM and SEM specimens with submicron resolutions. The PIMS system is a gas ion source (argon) instrument, whereas the newer generation FIB systems employ liquid metal (gallium) ion sources having superior milling and imaging capabilities.
Specimens are normally milled in gallium based FIB systems with higher energy ions (compared to the PIMS), which may produce a thick amorphous surface artifact (damaged layer). This damaged layer should be removed to produce high quality specimens. Post-FIB milling in broad ion beam systems for final milling and cleaning of such specimens is a common practice. Specifically, FIB milled specimens have been re-milled and cleaned in broad ion beam machines using the specimen holder described in the above-mentioned U.S. Pat. No. 5,472,566 to improve specimen quality. However, again, this requires moving the specimen among various specimen preparation systems and the final TEM or SEM.
Others have reported the use of a wire shadow technique for TEM specimen preparation. Senz et al, Ultramicroscopy 70 (1997) pp. 23-28, and Langer, Elektronenoptische Untersuchung des Werkstoffverhaltesn in mechanisch belasteten Mikrobauteilen (1996) teach gluing a wire onto a specimen surface and exposing the surface to ion milling by a Gatan Duo-Mill. The non-shadowed areas of the specimen are removed, and a thin area is produced in the wire shadow.
However, a need still exists in this art for simplified methods and techniques for specimen preparation for both SEM and TEM analysis.
The present invention provides a method and system for the preparation of specimens for analysis by electron microscopy which utilizes ion beam milling, but without the need for multiple positioning, cutting, and/or handling steps. The system and process are especially useful for the preparation for analysis by either TEM or SEM of semiconductors, metals, alloys, ceramics, and other inorganic materials.
In accordance with one aspect of the present invention, a system and process are provided for the preparation of specimens for analysis by transmission electron microscopy. The system includes a specimen processing chamber, at least two ion beam generators, and a specimen support or holder. Preferably, the system also includes the ability to view the progress of the milling operation and may include an imaging device such as a light microscope which permits monitoring of the area of interest on a specimen as the specimen is milled.
Specimens are prepared by initially forming, cutting, and/or polishing the specimen into a piece having a preferred maximum length of about 3 mm, a width of from about 500-1000 microns, and a thickness of from about 20-150 microns. The edge (thickness dimension and surface of interest for analysis) of the specimen should be relatively flat. A preferred shape for the specimen is a generally semi-circular disc having a radius of about 3 mm and a thickness of from about 20-150 microns, although other shapes may be utilized.
An ion beam masking member is then secured to the edge (thickness dimension and surface of interest for analysis) of the specimen using a suitable adhesive such as an epoxy glue or using a suitable mechanical attachment mechanism. The ion beam masking member is preferably a fiber having a diameter of less than about 100 microns, preferably less than about 80 microns, and most preferably less than about 35 microns. The fiber preferably has a length which approximates the length of the edge of the specimen, although the length of the fiber need only be as long as the area of interest on the specimen. Fibers having diameters down to about 7 microns have been found to be suitable for use. Alternatively, the ion beam masking member may have a non-circular cross-section including square, rectangular, elliptical, or other geometric shape. Preferably, the ion beam masking member comprises an amorphous or single crystal material such as carbon (either amorphous, graphitic, or diamond), silicon carbide, or sapphire. In one embodiment of the invention, the ion beam masking member may be pre-milled prior to securing it to the specimen through ion beam exposure to reduce its diameter or cross-section. This permits a more precise mounting and placement of the masking member on the surface of the specimen relative to features of interest on or in the specimen.
For TEM analysis, once the specimen has been mounted onto a support or holder and installed in the processing chamber, the specimen and ion beam masking member are exposed to two or more ion beams to mill and thin exposed areas on the edge of the specimen. Generally, the surface of interest on the specimen will be positioned perpendicular or nearly perpendicular to the direction of the ion beams. Preferably, an ion beam having a higher intensity in the center of the beam is utilized. That is, for an ion beam having a generally circular cross-section, the intensity at or near the center of the circle is higher than at the edges.
The ion beams will mill both the ion beam masking member as well as the specimen surface causing a necking or thinning of the masking member as milling is continued. Likewise, the masked area of the specimen beneath the ion beam masking member will also be thinned as milling continues because of the thinning of the masking member. The protected area beneath the masking member may be monitored using a suitable imaging device such as an optical or scanning electron microscope which is arranged generally perpendicular to the axis of the ion beams and which provides real time information concerning the progress of the milling process. Alternatively, a light emitting diode and photodetector may be arranged to provide an indication of when the specimen has been sufficiently thinned to become optically transparent. Additionally, if the ion beam masking member is electrically conductive, its electrical resistance may be measured and monitored such that a change in resistance is measured when the milling process causes the member to be severed (i.e., a gap forms).
Once the specimen has been thinned sufficiently to be electron transparent (i.e., less than about 200 nanometers, and preferably less than about 100 nanometers), it is removed from the processing chamber and is ready for TEM analysis. During milling, the specimen and ion beam masking member are positioned in tandem so that there is no relative movement between them. This avoids the need to stop the milling operation and accurately reposition the ion beam masking member prior to the resumption of milling as in some prior art processes.
In an alternative embodiment, the present invention provides a system and process for the preparation of specimens for analysis by a scanning electron microscope. In one form, the system includes a specimen processing chamber, at least one ion beam generator, and a specimen support or holder. Preferably, a second ion beam generator is also included. Generally, a specimen will be prepared so that it has a length of from about 4-8 mm, preferably about 6 mm; a height of from about 6 to about 12 mm, preferably about 8 mm; and a thickness of from about 250-750 microns, preferably about 500 microns.
Preferably, the system also includes the ability to view the progress of the milling operation, in real time, and may include an imaging device such as a light microscope which permits monitoring of the area of interest on a specimen as the specimen is milled. Preferably, the system also includes a sputtering target which may be positioned so that one or both of the ion beam generators can sputter material from the target onto the specimen to coat its surface. Thus, once the specimen is etched and coated, it can be moved to an SEM for analysis.
In a preferred form, the specimen is secured to a rotatable specimen stage for milling. After milling has been completed, the specimen stage is rotated (e.g., 90xc2x0) to a position where the surface of the specimen is etched (cleaned). The specimen stage is then rotated back to its original position for sputter coating using one of the ion beam generators and a sputtering target.
In yet another embodiment of the present invention, the present invention provides a system and process for the preparation of specimens for analysis by a scanning electron microscope in a processing chamber which also includes an SEM. The SEM is arranged such that the specimen milling and preparation process is observable with the SEM being utilized as a high resolution imaging device. The ability to observe the milling process in real time permits precise positioning of the specimen and monitoring of the process. Further, the milled specimen can be analyzed directly in the chamber without movement to a separate apparatus.
Accordingly, it is a feature of the present invention to provide a method and system for the preparation of specimens for analysis by electron microscopy which utilizes ion beam milling, but without the need for multiple cutting, positioning, and/or handling steps. It is another feature of the invention to provide a system and process which is adaptable for specimen preparation for both TEM and SEM analysis. These, and other features and advantages of the present invention, will become apparent from the following detailed description, the accompanying drawings, and the appended claims.


1. The Field of the Invention
The present invention relates to rendering graphical objects such as text. More specifically, the present invention relates to appropriately rendering a graphical object when a corresponding outline has excessive control points.
2. Background and Related Art
Computing technology has transformed the way we work and play. Computing systems now take a wide variety of forms including desktop computers, laptop computers, tablet PCs, Personal Digital Assistants (PDAs), and the like. Even household devices (such as refrigerators, ovens, sewing machines, security systems, and the like) have varying levels of processing capability and thus may be considered computing systems. As time moves forward, processing capability may be incorporated into a number of devices that traditionally did not have processing capability. Accordingly, the diversity of computing systems may likely increase.
Almost all computing systems that interface with human beings use a display to convey information. In many cases, the appeal of the display is considered an important attribute of the computing system. Display of textual information (e.g., Latin-based characters) typically includes processing glyphs that represent characters of a font. A glyph includes control points and instructions for connecting the control points such that an outline of a corresponding character can be generated in an arbitrary grid space (e.g., a pixel grid). Often, characters will be defined for display at a larger size and higher resolution and then mathematically scaled down (or otherwise manipulated) when the characters are to be rendered at smaller sizes and lower resolutions (or as bold, italic, etc.). Thus, a reduced number of descriptions, and potentially only one description, for a character (per font) need be stored.
To scale down a character, the location of control points can be divided by a scaling factor. For example, to scale a character down by a scaling factor of 10, the coordinates of each control point defining the character (at the higher resolution) can be divided by 10. It may be that control points defining a character for display on a 100×100 grid are to be scaled down for display on a 10×10 grid. Thus, a control point at grid position (50, 30) can be scaled down to a control point at grid position (5, 3), a control point at grid position (70, 70) can be scaled down to a control point at grid position (7, 7), etc. Accordingly, a smaller outline representing the character may be calculated and there is a reduced need for storing a number of different sizes of bit-maps for the character.
The smaller outline can then be analyzed to identify grid locations (e.g., pixels) that are to be turned on and that are to be turned off (a process often referred to as “scan conversion”). One scan conversion algorithm determines if the center of a grid position is inside or outside a resulting scaled down outline. When the center of a grid position is inside the scaled down outline the grid position is turned on. On the other hand, when the center of a grid position is outside the scaled down outline the grid position is turned off.
Unfortunately, at times, and especially at lower resolutions, the results of scan conversion produce an unacceptable representation of a character. Unacceptable character representations can result from rounding errors in the scaling down process or from the scan conversion process itself. Further, rounding errors have a greater affect on character representation when a single grid location (e.g., a pixel) is on scale with the features of a character. For example, a rounding error that causes one grid location to be inappropriately turned on (or turned off) on a 50×50 grid may not even be detectable by the human eye. However, a rounding error that causes one grid location to be inappropriately turned on (or turned off) on a 4×4 grid may result in a character that is perceived as unacceptable to the human eye. Thus, at lower resolutions scan conversion can even fail to preserve the topology of the original outline of the character, for example, causing disconnected grid locations, inappropriately located features, and lack of symmetry.
For example, when an outline has a reduced number of control points associated with a corresponding character feature, scan conversion of the outline can result in the corresponding character feature being rendered at a non-optimal location in a grid space. A number of characters in Latin (Greek, Cyrillic, etc.) fonts have a horizontal stroke (“cross-bar”) somewhere between the top and the bottom of the character. For example, a capital “H” has a cross-bar approximately halfway between the top and the bottom. FIG. 1 depicts an outline 100 of Times New Roman capital “H”. By design, the position of the cross-bar is marginally above the mathematical halfway point of the vertical stroke of the “H”. That is, distance 101 is less than distance 102.
However, by the time the “H” is rendered at a smaller size and lower resolution (e.g., 9 pt on a 96 dpi device), accumulated quantization errors can result in the cross-bar being rendered below the mathematical halfway point. Rendering the cross-bar below the half-way points is less than optimal, since the cross-bar was, by design, to be rendered above the halfway point. Pixel pattern 103 represents the pixels that would be turned on to render Times New Roman capital “H” at 9 pt and at 96 dpi resolution (i.e., the results of performing scan conversion on outline 100). As depicted in pixel pattern 103, the cross-bar is below the mathematical halfway point of the vertical stroke of the “H”.
One cause of non-optimal rendering results from the “H” having control points on the edges of the cross-bar, but not having control points, for example, on an imaginary line (represented by dashed line 104) along the center between the edges of the cross-bar. Traditional hinting solutions thus add a first constraint to a first control point, for example, on the top edge of the cross-bar (control point 107). The first constraint enforces a proportional position of the first control point in vertical direction relative to other control points on the base line (e.g. control point 109) and the caps line (e.g., control point 106). Subsequently, traditional solutions also add a second constraint to a second control point, for example, on the bottom edge of the cross-bar (control point 108). The second constraint enforces a distance between the second control point on the bottom edge and the previously constrained first control point (control point 106) on the top edge.
Since both the first and second constraints will have to round positions in the vertical direction to the nearest grid position (e.g., pixel), each of the first and second constraints can introduce a rounding error of up to half a pixel, either way (up or down). In unfortunate cases, these rounding errors accumulate (e.g., both the first and second constraints round down)—to place the cross-bar below the mathematical halfway point.
Further, when an outline passes through the center of one or more grid locations, scan conversion of the outline can result in the character being rendered asymmetrically in a grid space. Italic fonts pose a particularly challenging problem because the jagged nature of diagonal strokes makes italic fonts more difficult to process, and quantization errors can compound the problem.
As previously mentioned, all scan-converters have to define is an interior pixel, even in cases where a pixel could just as well be an interior or an exterior pixel (e.g., when an outline passes through the center of the pixel). For example, TrueType® defines that when an outline is through the center of a pixel, the pixel is to be turned on. Thus, if an outline is a straight line, and if the line's run and rise (slope) reduce to a pair of odd numbers, the outline will pass through one or more pixel centers, and TrueType® will turn on a pixel, which may look like an extra pixel.
Referring now to FIG. 2, FIG. 2 depicts an Arial Italic Capital “H”. The right edge of the left italic stroke (from control point 211 to control point 214) may rise 5 pixels for every pixel it runs across—a total of 2 pixels over and 10 pixels up, which reduces to a pair of odd numbers 1 and 5—and we can readily observe extra pixels (pixels 231, 232, and 233). Further, even when pixels having their centers exactly on an outline are turned off problems can still occur. For example, in FIG. 2, if pixels whose centers are exactly on the outline were to be turned off (instead of on), there would be two missing pixels (pixels 234 and 236), yielding a discontinuity in the pixel pattern. One approach is to define pixels whose centers are exactly on an outline to alternate between interior and exterior pixels as edges alternate between left and right edges. While this could solve the problem for some italic strokes, such an alternating approach would also introduce new problems on round strokes. For example, such an alternating approach could lead to asymmetrical pixel patterns in characters such as, an “O”.
Further, any movement of control points to comply with constraints can cause control points to be moved to inexact locations. Utilizing a control point that is at an inexact location for further calculations can result in non-optimal rendering of a corresponding character in a grid space. Often, hinting control points can include aligning some control points with other control points. For example, still referring to FIG. 2, control points 212 and 213 may have to be aligned with control points 211 and 214 because control points 211 and 214 may have been moved as a result of complying with their own constraints (e.g., constrained to caps and base lines respectively). While the act of aligning is a mathematically exact concept, its implementation in terms of a font hinting language (e.g., TrueType®) likely introduces numerical inaccuracies, because the internal numerical precision of font hint processors is typically limited. For example, the font hinting language TrueType® uses 6 binary places to store fractional control point location data and thus every numerical result can be accurate to only 26th or 1/64 of a pixel. Accordingly, the result of aligning, for example, control point 212 with its parent points 211 and 214 will be accurate to the nearest 1/64 of a pixel only—at best.
More specifically, since the line from control point 214 to control point 211 is 2 pixels over and 10 pixels up (as depicted in pixel pattern 203), it will run 0.2 pixels over for every pixel up. Accordingly, it should be 1.2 pixels over at control point 3, because control point 3 is 6 pixels up, or in terms of 1/64 of a pixel, it should be 1 12.8/64 pixel over. Unfortunately, 12.8/64 is beyond the precision limit of most, if not all, font hint processors. That is, 12.8/64 simply cannot be represented, and has to be rounded one way or the other (e.g., up or down to the nearest 1/64). Hint processors are typically configured with a default rounding behavior, for example, to always truncate, always round down, or always round up. In FIG. 2, and seemingly by chance, control points of the cross-bar are rounded down, even though rounding up would be a better approximation of the actual value (12.8 is closer to 13 than to 12). This error appears to be harmless, because it led neither to a spurious pixel, nor to a missing pixel.
Conversely, for control point 215, which again is over by 1 12.8/64 pixel, rounding down did lead to a spurious pixel (pixel 235), while rounding up would have prevented it. Moreover, the generality of typical font hint processors can produce results that are off by a fraction of a pixel, irrespective of the direction of rounding. Thus, even if rounding were to be correct, alignment problems can still result.
Additionally, character outlines that have too many control points can result in non-optimal rendering of a corresponding character in a grid space. For example, erroneous pixels can potentially arise when the exact shapes of outlines have increased complexity. For example, FIG. 3 depicts a Palatino Italic “H”. The Palatino Italic “H” includes significantly more control points than the Arial Italic “H” depicted in FIG. 2. The edges of the strokes of the Palatino Italic “H” are slightly curved, and thus include extra control points to model these curves. As depicted in FIG. 3, these control points are positioned in a seemingly random fashion on outline 300. Applying traditional scan conversion to outline 300 would result in a non-optimal pixel pattern, such as, for example, pixel pattern 303.
Unfortunately, some hint processors refer to control points by consecutive number and removing a control point can cause other control points to be renumbered. Thus, renumbering control points can cause existing hinting instructions to refer to incorrect control point numbers. For example, removing what may be viewed as extraneous control points on outline 300 could cause existing hints to be inappropriately applied to any remaining control points (or not be applied at all). Inappropriate application of hints to remaining control points can significantly degrade a corresponding pixel pattern.
Accordingly, to compensate for the sometimes non-optimal or inappropriate results of scan conversion (e.g., at lower point sizes and lower resolutions), a human typographer programmatically controls the scan conversion process on an ad-hoc basis by manually adding delta-exception hints (e.g., TrueType® instructions) to character outlines. Delta-exception hints are hints which are specific to individual characters and specific to a particular type size. That is, for each type size (of a font) at which there is an unfortunate quantization problem, the human typographer has to add possibly a plurality of delta-exception instructions, as appropriate. Since delta-exception hints are so specific, delta-exception hints are typically stored along with the character the delta-exception hints will be applied to (e.g., in a font file). Moreover, the use of delta-exception hints is an iterative process requiring repeated visual inspection of a plurality of type sizes before and after the application of corresponding exception instructions, which is laborious and prone to introduction of inconsistencies.
Due in part to the wide variety of different artistic and technical features in different fonts, delta-exception hints must also be tailored to an individual font. That is, delta-exception hints for one font typically can not be reused for other fonts (even for the same character). Thus, for each new font, a typographer is required to iteratively determine appropriate delta-exception hints. Accordingly, the resources needed to compensate for non-optimal or inappropriate results of scan conversion across a variety of different fonts can be quite large. Therefore, what would be advantageous are mechanisms for automating the optimization of pixel patterns.


In performing operations within a cased well, such as logging formation properties, it is important to know the exact location of the tool lowered into the well to perform the specific function. Measuring the depth of well logging tools is traditionally made from the surface, by measuring how much of the cable which supports the tools has been deployed. Both wireline tools and while-drilling tools rely on the same basic concept.
The depth of the tool string is commonly determined by passing the cable over a calibrated measurement wheel at the surface of the well. As the tool is deployed, the length of cable unspoiled into the well is monitored as an estimate of tool depth. Depth compensation for cable stretch may be attempted by calculating a theoretical stretch ration based upon cable length, elasticity and tool weight. Even with very elaborate compensation algorithms, however, the actual amount of cable stretching may vary over time and because of unforeseen and unmeasured interactions between the cable and tool string and the well bore (such as tool hang-ups and cable friction) and anomalies such as cable “bounce”. Deviated wells, in which the tool is pulled along the interior surface of the well casing, can present particular problems with variable and inconsistent cable loading, as the stool “sticks” and jumps along the well bore. Such problems are also encountered albeit to a lesser degree, in tubing-conveyed operations in which tubing length is measured by a wheel arranged to roll along the tubing as it is unspoiled. Even very small deployment length measurement error percentages and other discrepancies can result, with either type of deployment, in absolute tool positioning errors of several feet or more in a well of over a mile in depth, for example.
Another approach has been developed that measures the rotations of a set of calibrated wheels contacting the cable under a set force which generates enough friction to transmit any linear velocity of the cable to the perimeter of the wheels, allowing a direct measurement of the corresponding depth increment.
Yet another approach utilizes a pair of sensors located on or within the drill string along with a known reference point within the borehole. Given the distance between the two sensors is determined by the a relatively short piece of drill string, its stretch/compression effects are negligible compared to the stretch and compression observed on the total-length of drill sting, and can be used as a downhole depth gauge by observing that when the second sensor will reach a correlatable event already seen by the first sensor, the depth increment is the distance between the sensors.
Use of downhole sensors is challenging and present even more difficulties in the case of completed wells, in which the casing effects the ability to run certain downhole sensors. For example, steel casing has historically been thought of as a barrier to electromagnetic measurements of the properties of the formation. The problems presented by conductive liners are described by Augustin et al., in “A Theoretical Study of Surface-to-Borehole Electromagnetic Logging in Cased Holes,” Geophysics, Vol. 54, No. 1 (1989); Uchida et al., in “Effect of a Steel Casing on Crosshole EM Measurements,” SEG Annual Meeting, Texas (1991); and Wu et al., in “Influence of Steel Casing on Electromagnetic Signals,” Geophysics, Vol. 59, No. 3 (1994). These prior art references show that coupling between a transmitter and a conductive liner is independent of the surrounding geological formation conductivity for a wide range of practical formation resistivities encountered in the field and that the magnetic field produced inside the conductive liner at a distance of a few meters or less from the transmitter depends only on the conductive liner properties and not on the formation properties.
FIG. 1 shows typical equipment used in the measurement of geological formation 10 resistivity between two drill holes 12a and 12b using electromagnetic induction. A transmitter T is located in one borehole, while a receiver R is placed in another borehole. The transmitter T typically consists of a coil (not shown) having a multi-turn loop (which consists of NT turns of wire) wrapped around a magnetically permeable core (mu-metal, ferrite or other ferro-magnetic material) with a cross section, AT. The transmitter T may further comprise a capacitor (not shown) for tuning the frequency of the coil. When an alternating current, IT, at a frequency of f0 Hz passes through this multi-turn loop, a time varying magnetic moment, MT, is produced in the transmitter. This magnetic moment is defined as follows:MT=NTITAT  (1)
The magnetic moment MT can be detected by the receiver R as a magnetic field, B0. The transmitter T, receiver R, or both are typically disposed in boreholes (e.g., 12a and 12b) in the earth formation 10. In this case, the detected magnetic field, B0, is proportional to the magnetic moment of the transmitter, MT, and to a geological factor, k1, as follows:B0=k1MT  (2)
The geological factor, k1, is a function of the spatial location and orientation of a field component of the magnetic field, B0, with respect to the magnetic moment of the transmitter, MT.
The receiver R typically includes one or more antennas (not shown). Each antenna includes a multi-turn loop of wire wound around a core of magnetically permeable metal or ferrite. The changing magnetic field sensed by the receiver R creates an induced voltage in the receiver coil (not shown). This induced voltage (VR) is a function of the detected magnetic field (BR), the frequency (f0), the number of turns (NR) of wire in the receiver coil, the effective cross-sectional area of the coil (AR), and the effective permeability (Ï□R) of the coil. Thus, VR can be defined as follows:VR=Ï□f0BRNRARÏ□R  (3)
While f0 and NR are known, the product, ARÏ□R, is difficult to calculate. In practice, these constants may be grouped together as kR and equation (3) may be simplified as:VR=kRBR  (4)wherekR=Ï□f0NRARÏ□R.Thus, instead of determining the product ARÏ□R, it is more convenient to determine kR according to the following procedures. First, the receiver coil is calibrated in a known field, at a known frequency. Then, the exact value for kR is derived from the magnetic field (BR) and the measured voltage (VR) according to the following equation:kR=BR/VR  (5)
When this system is placed in a conducting geological formation, the time-varying magnetic field, B0, which is produced by the transmitter magnetic moment, produces a voltage in the geological formation, which in turn drives a current therein, L1. The current, L1, is proportional-to the conductivity of the geological formation and is generally concentric about the longitudinal axis of the borehole. The magnetic field proximate to the borehole results from a free space field, called the primary magnetic field, while the field resulting from current L1 is called the secondary magnetic field.
The current, L1, is typically out of phase with respect to the transmitter current, IT. At very low frequencies, where the inductive reactance is small, the current, L1, is proportional to dB/dt and is 90° out of phase with respect to IT. As the frequency increases, the inductive reactance increases and the phase of the induced current, L1, increases to be greater than 90°. The secondary magnetic field induced by current L1 also has a phase shift relative to the induced current L1 and so the total magnetic field as detected by receiver R is complex.
The complex magnetic field detected by receiver R may be separated into two components: a real component, IR, which is in-phase with the transmitter current, IT, and an imaginary (or quadrature) component, II, which is phase-shifted by 90°. The values of the real component, IR, and the quadrature component, II, of the magnetic field at a given frequency and geometrical configuration uniquely specify the electrical resistivity of a homogeneous formation pierced by the drill holes. In an inhomogeneous geological formation, however, the complex field is measured at a succession of points along the longitudinal axis of the receiver borehole for each of a succession of transmitter locations. The multiplicity of measurements thus obtained can then be used to determine the inhomogeneous resistivity between the holes.
In both cases, i.e., measuring homogeneous geological formation resistivity or measuring inhomogeneous geological formation resistivity, the measurements are typically made before extraction of hydrocarbons takes place. This is because the boreholes typically are cased with conductive liners (e.g., metallic casing; see 16a and 16b in FIG. 3) in order to preserve the physical integrity of the borehole during hydrocarbon extraction. The conductive tubular liners interfere with resistivity measurements and are difficult and costly to remove from the borehole once they are installed. As a result, prior art systems such as that shown in FIG. 1 are not suitable for analyzing hydrocarbon reservoirs once extraction of the hydrocarbons begins.
The net or effective moment, Meff, of a transmitter inside a conductive liner is dictated by the inductive coupling between the transmitter and the conductive liner. Physically, the resistivity of the conductive liner is very low and the inductance relatively high. This property results in a current of almost the same magnitude as that of the transmitter current being induced in the conductive liner. Lenz's Law predicts that the magnetic field generated by this induced current in the conductive liner will oppose the time-varying magnetic field produced by the transmitter current. Thus, the magnetic field generated by the transmitter is mostly cancelled out by the magnetic field generated by the conductive liner. As a result, the magnetic field external to the conductive liner is greatly reduced, and its magnitude is proportional to the difference in currents in the transmitter and the conductive liner. In effect, the conductive liner “shields” the transmitter from any receiver positioned outside of the conductive liner.
An analogous situation is present with respect to a receiver if it is surrounded by a conductive liner. The field to be detected induces currents concentric with the receiver coil whose sense is such as to reduce the field within the liner. The field to be detected is consequently highly attenuated and the measurement is highly influenced by the variations in attenuation caused by the variation in liner properties, and example of which is graphically demonstrated by the slope of curve 10 shown in FIG. 2. The situation is exacerbated if both the transmitter and the receiver are surrounded by conductive liners. Often the design criteria for a crosshole survey of a cased borehole reduces the signal to a level that is undetectable by standard receivers. Moreover, the variance in conductivity, permeability, and thickness along a longitudinal axis of a liner makes difficult determining the attenuation factor at any given point.
The attenuation due to a steel casing surrounding the transmitter for a homogeneous formation is essentially constant a few meters form the source. Since the attenuation is constant the ratio of the fields as described, and incorporated herein, in U.S. Pat. No. 6,294,917 B1, to Nichols, removes the effects of the casing. This constancy of the fields can also be removed by calculating a shift operator as described, and incorporated herein, in U.S. Pat. No. 6,393,363 B1 to Wilt and Nichols. However, for multiple cased boreholes, both the ratio and shift operator methods preferably utilize an extra monitor for the transmitted field.


In contrast to semiconductor production of silicon wafers, which are processed individually, the manufacture of devices such as micromechanical sensors is accomplished using relatively small substrates. In this context, the base substrate is present in the form of a small cylindrical steel element. In order for the manufacturing process and for application of a circuit produced in thin-film technology onto such substrates to be cost-effective, the substrates are processed in multiple fashion. The individual base substrates are therefore retained in large numbers on a workpiece carrier, and processed together.
High-pressure sensors that are utilized in many automotive engineering systems and in automation technology are fabricated on such substrates. Applications include, for example, direct fuel injection, common-rail technology for diesel vehicles, electrohydraulic brake systems, vehicle dynamics control systems, and many more.
Pressure is sensed via the deflection of the sensor membrane, which is coated with a Wheatstone measurement bridge using thin-film technology. The circuit is patterned using a photolithographic manufacturing process. Contacting and passivation can also be performed using a production step of this kind. The quality of high-pressure sensors depends substantially on the accuracy with which the resistance features of the Wheatstone measurement bridge are positioned on the pressure membrane. The resistances must be centered as much as possible on the pressure membrane. This positional accuracy substantially influences the electrical properties of the measurement bridge, for example, the range of the signal furnished by the sensor.
It is believed that the photolithographic process of patterning the functional layer to form the resistances is therefore essential in the production of a high-pressure sensor. A preconditioning of the surface of the functional layer, application of a photosensitive resist onto the functional layer, an oven step to condition the resist for exposure, exposure of the resist through an exposure mask, development of the exposed features, an oven step to condition the developed resist structure for etching, mapping of the resist image into the functional layer using an etching process, and subsequent stripping of the photoresist mask from the completed etched functional structure, are usually performed in this context.
The location of the resistances may be determined in the exposure step. The substrates, previously diced and retained on a workpiece carrier, may then be exposed with sufficient positional accuracy relative to an exposure mask. In contrast to the exposure of silicon wafers in semiconductor production, in which the wafers can be registered as one piece with the exposure mask (e.g. a quartz mask) to be imaged, in the exposure of the previously diced plurality of substrates there may be a positional inaccuracy for each substrate with respect to the imaging exposure mask.
It is believed that the substrates are often handled in immovably bolted-down workpiece carriers that must each be individually registered with respect to the exposure mask. This registration operation is performed manually.
For example, in the projection exposure method of the Nagano Keiki Co. Ltd., a special workpiece carrier that is automatically positionable is provided in each case. This workpiece carrier is not identical for the subsequent processes.


Hitherto, various types of structures of a multilayer printed wiring board including a built-up portion in which a plurality of wiring patterns that are stacked with insulating layers therebetween are electrically connected through via holes provided in the insulating layers have been proposed. For example, in such a multilayer printed wiring board, when a semiconductor device mounted is switched between the on and off states at a high speed, switching noise may be generated, resulting in an instantaneous drop in the electric potential of a power supply line. In order to suppress such an instantaneous drop in the electric potential, connection of a capacitor portion between the power supply line and a ground line to perform decoupling has been proposed. In Patent Document 1, provision of a layered capacitor portion functioning as such a capacitor portion in a multilayer printed wiring board has been proposed.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-68858


The present invention relates generally to protective garments and, more particularly, to an improved, more comfortable, more flexible, protective garment.
Prior to the present invention, technological developments of yarns for protective garments have centered around the use of Kevlar, which is the DuPont trademark for an aramid fiber, as the fiber used in yarns, which yarns are ultimately used in protective garments. By way of example, and not by way of limitation, aramid fibers have been used in yarns with the yarns thereafter knitted to make protective garments including bullet-resistant vests and protective gloves as exemplified by Byrnes, U.S. Pat. No. 3,883,898.
In addition to the use of an aramid yarn as aforesaid, aramid fibers have been utilized in combination with other materials to form a yarn which yarn may be thereafter knitted to form a protective garment such as a protective glove with increased slash or cut resistance. Examples of this concept may be found in Byrnes U.S. Pat. No. 4,004,295, and Byrnes et al. U.S. Pat. No. 4,384,449, each of which describes the use of the Kevlar aramid fiber in combination with wire; the first of these two patents discloses the use of an aramid fiber yarn together with a metal wire and the second of these two patents describes a composite yarn itself; the yarn including a core of aramid fiber plus flexible wire and a covering of aramid fiber.
There are, of course, certain recognized problems with the use of the aramid fiber as the constituent in a yarn to thereafter be utilized in protective garments. For example, aramid fibers weaken in water. Second, the aramid fiber has only a limited resistance to true abrasion. Third, ultraviolet light adversely affects the appearance of the aramid fiber and can cause discolorations in the aramid fiber, discolorations in the yarn and discoloration in the finished product.
Recently, a new high-strength fiber has been announced by Allied Corporation. The fiber is an extended chain polyethylene, which is a polyolefin, and has been sold under the trademark of Spectra with two different fibers being marketed, Spectra 1000 and Spectra 900. We understand that the Spectra 1000 is a 1200 denier fiber and that Spectra 900 is 650 denier fiber.


(1) Field of the Invention
The present invention relates to a process for producing aromatic imide polymer hollow filaments. More particularly, the present invention relates to a process for producing aromatic imide polymer hollow filaments useful for separating two or more different gases, for example, hydrogen gas and carbon monoxide gas, from each other with an excellent efficiency or for concentrating the gases from a dope solution of a specific aromatic imide polymer dissolved in a specific phenolic solvent by a wet membrane-forming method.
(2) Description of the Related Art
Various methods for producing aromatic imide polymer semipermeable membranes or hollow filaments from a dope solution of an aromatic imide polymer in a phenolic solvent are disclosed by, for example, U.S. Pat. No. 4,378,400 for H. Makino et al and U.S. Pat. No. 4,378,324 for H. Makino et al.
However, the products of the methods disclosed by the above-mentioned publications are still not satisfactory in the gas-separating properties thereof. That is, the aromatic imide polymer membranes disclosed in the above-mentioned publications are used as a separating membrance for a hydrogen-carbon monoxide mixture gas. The membrance exhibits an unsatisfactory selective gas permeability (P.sub.H.sbsb.2 /P.sub.CO) of about 20 to 65 and an unsatisfactory hydrogen gas permeating rate (P.sub.H.sbsb.2) of about 1.5.times.10.sup.-5 cm.sup.3 /cm.sup.2.sec.cmHg or less.
The term "gas permeating rate" used herein is defined as follows. ##EQU1## wherein X respresents an amount (volume) in cm.sup.3 of the gas passed through a membrane A represents a surface area in cm.sup.2 of the membrane through which the gas passed. T represents a transmission time in sec. of the gas through the membrane and D represents a difference in pressue in cmHg between the gas-supply side and the opposite side of the membrane
Accordingly, it is strongly desirable to provide a process for producing aromatic imide polymer hollow filaments which are useful as gas-separating hollow filaments having an excellent gas selective permeability and a superior hydrogen gas permeating rate (P.sub.H.sbsb.2).


Relay technology has been a hot area of research in wireless communication community in recent years. It is widely accepted that relay or multi-hop networks will become essential for beyond 3G mobile radio systems due to the range problem that appears there. As higher carrier frequencies or center frequencies can be envisaged for future mobile radio communication systems, where the expected center frequencies range up to 5-10 GHz and with bandwidth requirements of up to 100 MHz that can be foreseen, a significantly increased pathloss and noise power level has to be expected, which translates into a significantly reduced area a base station can cover.
Using relaying technology, signals can be transmitted much farther away, R. Pabst, B. Walke, D. Schultz, P. Herhold, H. Yanikomeroglu, S. Mukherjee, H. Viswanathan, M. Lott, W. Zirwas, M. Dohler, H. Aghvami, D. Falconer, and G. Fettweis, “Relay-based deployment concepts for wireless and mobile broadband radio,” IEEE Commun. Mag., vol. 42, no. 9, pp. 80-89, September 2004, J. Zhao, I. Hammerstroem, M. Kuhn, A. Wittneben, M. Herdin, and G. Bauch, “Coverage analysis for cellular systems with multiple antennas using decode-and-forward relays,” in Proc. 65th IEEE Veh. Tech. Conf., Dublin, Ireland, Apr. 22-25, 2007. Furthermore relay signals provide additional diversity and improve the received signal quality, J. N. Laneman, D. N. Tse, and G. W. Wornell, “Cooperative diversity in wireless networks: Efficient protocols and outage behavior,” IEEE Trans. Inform. Theory, vol. 50, no. 12, pp. 3062-3080, December 2004.
In order to circumvent the introduction of a denser grid of base stations (BS), the basic idea is to introduce relay stations (RS), which forward data packets to a mobile station (MS) that is out of reach of the base station. Such relay stations can be realized utilizing additional dedicated infrastructure relay stations having fixed power supplies, or they could be built into other mobile stations. Two main concepts of relaying were identified in the past: Amplify-and-Forward (AF) and Decode-and-Forward (DF). While AF has the advantage of being transparent to modulation and coding since a sampled version of the received signal is stored and retransmitted by the relay station without performing any decoding, DF allows for a separate adaptation to both links and avoids also the effect of noise enhancement since DF means that the relay station decodes and re-encodes the signal.
Current relays cannot transmit and receive signals using the same time and frequency channel (half-duplex relays). Half-duplex generally means that communication is possible in both directions, but only one direction at a time (not simultaneously). Hence, traditional relaying schemes suffer from the spectral efficiency loss due to two channel uses.
Recently, a spectral efficient relaying scheme called two-way relaying has been proposed in B. Rankov and A. Wittneben, “Spectral efficient protocols for half-duplex fading relay channels,” IEEE J. Select. Areas Commun., vol. 25, no. 2, pp. 379-389, February 2007 and in P. Larsson, N. Johansson, and K.-E. Sunell, “Coded bidirectional relaying,” in IEEE Veh. Tech. Conf., vol. 2, Melbourne, Australia, May 7-10, 2006, pp. 851-855. In such a scheme, the source and destination terminals transmit simultaneously in a first time interval. After receiving data signals from the source and the destination terminals in the first time interval, the relay station terminal retransmits the combined or superimposed source and destination data signals in a second time interval. Since both the source and the destination know its own data, respectively, both sides can cancel the so called self-interference, i.e. the own useful data transmitted towards the relay station in the first time interval, and decode the useful data from the other side. Two-way relaying achieves bi-directional transmission between the source and destination in two time intervals or time slots by using half-duplex terminals. Thus it avoids the spectral efficiency loss due to the use of half-duplex relays. Up to now, all the research is focusing on canceling the self-interference instead of utilizing it.
The authors of “Spectral efficient protocols for half-duplex fading relay channels” used a so called superposition coding scheme to re-encode data symbols to be transmitted in the second time interval, while the authors of “Coded bidirectional relaying” applied an XOR-operation on bit level to re-encode the data symbols to be transmitted in the second time interval at the relay station. The comparison of the two re-encoding schemes has been made in I. Hammerstroem, M. Kuhn, C. Esli, J. Zhao, A. Wittneben, and G. Bauch, “MIMO two-way relaying with transmit CSI at the relay,” in Proc. SPAWC, Helsinki, Finland, Jun. 17-20, 2007 and T. J. Oechtering, I. Bjelakovic, C. Schnurr, and H. Boche, “Broadcast capacity region of two-phase bidirectional relaying,” March 2007, submitted to IEEE Transactions on Information Theory.
MIMO (Multiple-Input-Multiple-Output) technology has been a major breakthrough in the area of wireless communication in recent years. The use of multiple antennas can provide significant increase in capacity, I. E. Telatar, “Capacity of multi-antenna Gaussian channels,” Europ. Trans. Telecommun., vol. 10, no. 6, pp. 585-595, November 1999. It is almost certain that most communication systems will be equipped with multiple antennas in the years to come. Accurate channel knowledge may be used in order to take the advantage the MIMO system can offer. However, estimating the channel in a MIMO system is difficult. Traditional channel estimation schemes transmit dedicated, predetermined pilot or training sequences comprising known data symbols on different transmit antennas. Thus the spectrum efficiency is reduced in the traditional channel estimation schemes.
MIMO channel estimation has been a research topic along with MIMO transmission technology. One of the most popular and widely used approaches to estimate a MIMO channel is to transmit orthogonal training sequences from different transmit antennas. The received signal is correlated with the training sequences at the receiver. Based on the received data and the knowledge of the predetermined training sequences, the channel matrices can be calculated. In M. Biguesh and A. B. Gershman, “Training-based MIMO channel estimation: A study of estimator tradeoffs and optimal training signals,” IEEE Trans. Signal Processing, vol. 54, no. 3, pp. 884-893, March 2006, the authors considered linear least squares (LS) and minimum mean-squared-error (MMSE) channel estimation approaches and investigated the optimal choice of training sequences. They showed that transmitting orthogonal training sequences from different antennas is optimal for the LS approach.
Instead of multiplexing the training sequences with data symbols, H. Zhu, B. Farhang-Boroujeny, and C. Schlegel, “Pilot embedding for joint channel estimation and data detection in MIMO communication systems,” IEEE Commun. Lett., vol. 7, no. 1, pp. 30-32, January 2003, investigated the performance of embedding the training sequences with data to estimate the channel. Unlike conventional methods where predetermined pilot symbols are time-multiplexed with useful information data symbols, a pilot-embedding method was proposed in H. Zhu, B. Farhang-Boroujeny, and C. Schlegel, “Pilot embedding for joint channel estimation and data detection in MIMO communication systems,” IEEE Commun. Lett., vol. 7, no. 1, pp. 30-32, January 2003, where low power level predetermined pilots are transmitted concurrently with the useful data, and they are used to obtain an initial estimate of the channel such that a turbo decoding process can be started. Soft information obtained from the turbo decoder is subsequently used to improve channel estimates.
A decision directed iterative channel estimation method was proposed in X. Deng, A. M. Haimovich, and J. Garcia-Frias, “Decision directed iterative channel estimation for MIMO systems,” in Proc. IEEE Int. Conf. on Communications, vol. 4, Anchorage, Ak., May 11-15, 2003, pp. 2326-2329.
All the proposed channel estimation schemes rely on an initial estimation of the MIMO channel based on the transmission of pure predetermined training sequences.


In a conventional WiMax/WiBro system, it is necessary for a BS to transmit a schedule in a header of each frame so that users may receive or transmit data at some location. In general, this schedule should be decoded by any user even the user with worse channel quality in a cell. Thus, the schedule is processed with lower level of modulation and encoding scheme and retransmitted for several times.


High bandwidth, short reach interconnections between chips or devices using conventional input/output (I/O) interfaces require significant power and chip area; specifically, solutions to maintain signal transfer quality between said chips or devices significantly contributes to the interface power consumption and smaller chip area. As a result, these conventional I/O interfaces are not desirable for low power and/or small chip area circuits.


1. Field of the Invention
The present invention relates to a novel settling accelerator for the epoxidation of a cyclic, at least monounsaturated alkene.
2. Description of the Background
Numerous processes for the epoxidation of alkenes are known and it is possible to use a wide range of different reaction or catalyst systems. The epoxidation of alkenes in a homogeneous, liquid phase using organic hydroperoxides in the presence of catalysts based on molybdenum, tungsten or vanadium is carried out industrially. However, epoxide production is accompanied by formation of equivalent or even greater amounts of the alcohol corresponding to the hydroperoxide, and the need to utilize or recirculate this alcohol greatly restricts industrial use of this process. For this reason, alternative processes for the more direct oxidation (epoxidation) of alkenes are being developed to an increasing extent.
One such process is epoxidation by means of molecular oxygen using silver catalysts. However, this process has only been able to be employed successfully for ethene and has not been able to be applied analogously to the epoxidation of other alkenes of the interest (for example propene).
Another process for direct oxidation of alkenes to epoxides is reaction with hydrogen peroxide. The process has been proposed for various epoxidation reactions because of, in particular, the positive aspect of the use of the oxidant in significantly reducing environmental pollution. Since the activity of hydrogen peroxide toward alkenes is only low, sometimes even completely absent, it is necessary to use activating agents, usually organic acids such as formic acid, acetic acid, etc., in organic solvents to facilitate the oxidation reaction. The acids form peracids in the reaction medium, which represent the actual reactive epoxidation agent, in situ. These processes, too, do not appear to be particularly successful, because it is difficult to obtain the peracids and because of the instability of the epoxides in acidic media, as a result of which varying convenient process conditions are necessary.
Still another method is the oxidation of alkenes by reaction with highly concentrated hydrogen peroxide in a homogeneous, i.e. exclusively organic, liquid phase in the presence of soluble catalyst systems based on elements of Groups 4, 5 and 6 of the Periodic Table (Ti, V, Mo, W) in combination with elements selected from the group consisting of Pb, Sn, As, Sb, Bi, Hg, and the like. Here too, the results of the process do not permit implementation as an industrial process. This is firstly because the reaction proceeds slowly, and secondly the preparation of the catalyst systems, which generally consist of very complicated organic metal compounds and additionally have to be soluble in the organic reaction medium, is complicated and expensive. Furthermore, the use of highly concentrated hydrogen peroxide ( greater than 70%) involves considerable safety risks which cannot easily be overcome in an economical manner.
These processes of the prior art clearly show that the oxidation of alkenes by means of hydrogen peroxide is self-contradictory because the best working conditions in respect of the catalyst system and hydrogen peroxide involve an aqueous, acidic medium while the factors of the oxidation reaction itself and the stability of the epoxide are favored in a neutral organic medium. For this reason, further processes for the epoxidation of alkenes using hydrogen peroxide have been developed, in which either an improved catalyst system based on TiO2/SiO2 in an aqueous phase with addition of primary or secondary alcohols (see EP 0 987 259 A1) or a two phase system containing a catalyst comprising tungstic acid, a quaternary ammonium salt and a phosphorous compound (for example DE 30 27 349) is used.
In the case of alkenes whose epoxides are not hydrolysis-labile and in which the olefinic double bond is not sterically hindered (e.g. cyclic at least monounsaturated alkenes), the known epoxidation using hydrogen peroxide and a tungsten catalyst is the most economical alternative.
For the epoxidation reaction by means of hydrogen peroxide to proceed sufficiently quickly, a phase transfer catalyst (for example, Aliquat(copyright) 336) is usually used in the case of very lipophilic alkenes (for example cyclododecene)(Angew. Chem. (1991), 103(12), 1706-9). However, the desired strong acceleration of the epoxidation by means of the phase transfer catalyst leads to the phases being significantly more difficult to separate after the reaction, because of emulsion formation; the corresponding settling times increase greatly. In addition, the organic phase usually remains very turbid after the separation. To achieve virtually complete phase separation, it is necessary to use either phase separators having a very large volume or suitable centrifuges.
The increased settling times in this process greatly reduce its attractiveness for continuous, industrial-scale use. In particular, the process can usually not be implemented at all in existing plants because of space problems caused by the need for larger phase separators. The use of centrifuges is of little interest in view of the power costs and the maintenance requirement required by moving parts.
It can be said quite generally that settling times of less than 2 minutes are industrially desirable. If, on the other hand, the settling times are more than 4 minutes, an industrial-scale continuous process is difficult to operate economically.
DE 30 27 349 describes a process for the epoxidation of alkenes using hydrogen peroxide, a tungsten compound, a phosphorus compound and a phase transfer catalyst. In this process, solvents such as alkanes or cycloalkanes are absolutely necessary. These solvents are always added to the reaction mixture in large amounts and generally serve either to dissolve a solid material and thus allow it to react, or to improve the reaction conditions, for example to achieve better heat removal.
However, the dilution of starting materials with non-reactive substances such as solvents is undesirable since, firstly, the dilution leads to a reduction in the space-time yield and, secondly, a further separation operation is necessary after the reaction.
Accordingly, one object of the present invention is to provide a settling accelerator, i.e. a compound, which leads to industrially acceptable settling times of the heterogeneous catalyst-containing reaction mixture in the epoxidation of alkenes, which ensures a sufficiently high space-time yield of epoxide, so that this process using the settling accelerator makes it possible for such epoxides to be prepared on an industrial scale.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a method of improving settling times of catalyst in the epoxidation of a cyclic, at least monounsaturated alkene, comprising:
epoxidizing a cyclic, at least monounsaturated alkene having from 8 to 20 carbon atoms in the ring in a reaction medium containing an oxidant and a catalyst system comprising at least one metal of Groups 4, 5 and 6 of the Periodic Table of the Elements, phosphoric acid and a phase transfer catalyst and a cyclic alkane having from 8 to 20 carbon atoms in the ring, which corresponds to the alkene reactant, as settling accelerator in the epoxidation reaction.


Hexagonal containers are an efficient solution to maximize the usable volume within a container, and ultimately the amount of boxed merchandise that can be delivered per shipment. Additionally, hexagonal containers offer the advantage of minimizing the quantity of packaging material (e.g., cardboard) needed to package a given amount of merchandise. While the packaging industry makes use of these advantages, the hexagonal boxes currently available may be improved upon to further minimize the quantity of packaging material and glue necessary to package a given amount of merchandise.


1. Field of the Invention
The invention relates to a mount for reducing vibrations transmitted from a tool to a carrier vehicle, such as a tractor. More specifically, the mount isolates a tractor from the vibrations of a vibratory plow, or similar tool.
2. Description of the Prior Art
In the past, different approaches have been tried to minimize the transfer of vibrations from a tool to a carrier vehicle, such as a tractor. The vibrations generally tire out the tractor operator and cause the bolted parts of the tractor to come apart, necessitating re-tightening of these bolts. The wear on the tractor parts also increases. The vibrating tool, for example a plow, is generally mounted on a sub-frame having a vibrating means attached to the sub-frame. The sub-frame is held by vibration dampening means in a larger frame. Examples of this construction are shown in U.S. Pat. No. 5,526,590 (Palm et al.), U.S. Pat. No. 5,482,121 (Draney et al.), U.S. Pat. No. 3,746,100 (Hall et al.), U.S. Pat. No. 4,140,425 (Flippin) and U.S. Pat. No. 4,164,982 (Draney). These solutions all share the apparent disadvantage of excessive wear and tear on the vibration dampening means, due to the fact that the sub-frame is vibrating in all directions. This subjects the vibration dampening means to compression (tensile) and shear stress. Most vibration means are rubber pads (or similar material), and inherently much less suited to shear stress, as compared to tensile stress. The vibration dampening means therefor wear out excessively fast in these applications. Also, the efficiency of vibration damping is not high enough to properly dampen vibrations from reaching the tractor.
A further attempt to provide a vibratory plow construction with vibration dampening means is disclosed in U.S. Pat. No. 4,867,607 (Johnson et al.). This document discloses a pivotable part of the vibratory plow carrying frame. The frame elements are separated by air cushions (or resilient dampening means of other types), arranged to dampen vertical movement of the frame parts. This construction necessitates the use of extra frame parts, to achieve the pivoting of the frame, thus adding weight, complexity and cost to the construction. If solid rubber vibration dampers are used, they are objected to shear stress, which is detrimental to the life of such dampers.


1. Field of the Invention
The present invention relates to a DC-DC voltage converter. More particularly, the present invention relates to a DC-DC voltage converter with an output voltage lower than a reference voltage.
2. Description of Related Art
As electronic information technique advances, circuit designs of various electronic products become increasingly complex. For many circuit designs, cell voltage is converted to lower power supply voltage, for example mobile phone, PDA and other hand held equipment with power supplied by cell. For example, for portable computer, voltage converter is used in a common power supplier to serve as a basic voltage adjuster, so increasingly more DC-DC voltage converters are used in various electronic products.
The function of the DC-DC voltage converter is outputting an output voltage smaller than an input voltage, and stabilizing the voltage. Referring to FIG. 1, a well-known DC-DC voltage converter 100 is shown. During operation of the DC-DC voltage converter 100 as shown in FIG. 1, it receives a DC input voltage Vin provided by an alkaline cell or a lithium cell, and the DC input voltage Vin is converted to a lower fixed DC output voltage Vout. After the output voltage Vout is fed back by a feedback circuit 101, it is compared with a reference voltage Vref through a comparator 103, and a control signal is generated to a driving circuit 105 according to a comparing result. The driving circuit 105 sends a driving signal to a power circuit 107 according to the received control signal. The power circuit 107 is connected to the input voltage Vin and a voltage stabilizing circuit 109. The power circuit 107 controls conducted/non-conducted state between the input voltage Vin and the voltage stabilizing circuit 109 according to the received driving signal, and then outputs a stable output voltage Vout after being stabilized by the voltage stabilizing circuit 109.
However, in most of the portable electronic products, alkaline cells or lithium cells are used as the electric source. The voltage of the cell may be increasingly reduced with operation time and using time, so in order to obtain a stable output voltage, under many situations, the DC-DC voltage converter adopts boost-buck two-stage voltage converter.
In Taiwan patent No. 1281305, a dual-input voltage converter is provided, which includes a comparator for comparing the output Vout and a reference voltage Vref to generate a signal to a controller, and the controller determines to switch a first voltage converting circuit or a second voltage converting circuit. Referring to FIG. 2, a schematic view of an embodiment of this patent is shown. The first voltage converting circuit is composed of transistors SW1 and SW2, an inductor L and a capacitor Co, and the second voltage converting circuit is composed of transistors SW2 and SW3, the inductor L, and the capacitor Co. The controller 201 switches the transistors SW1 and SW2 to generate a current I to charge the capacitor Co through the inductor L to obtain an output voltage Vout. The comparator 203 compares the output voltage Vout and the reference voltage Vref. When the output voltage Vout is lower than the reference voltage Vref, an output signal Se of the comparator 203 makes the controller 201 turn off the transistor SW1, such that a voltage VDD is converted to a voltage VPP after being boosted by a boost converter 205. The controller 201 switches the transistors SW2 and SW3 to convert the voltage VPP to the output voltage Vout, such that the dual-input voltage converter 200 can be considered as a boost-buck two-stage voltage converter, and avoids the situation that the output voltage Vout is reduced due to the reduce of the input voltage Vin and thus causing an unstable output. However, the current DC-DC converter still has some defects which are described as follows.
1. Although the two-stage voltage converter can solve the situation that the reduction of the input voltage Vin results in the unstable output voltage Vout, it cannot operate under a state that the output voltage Vout is smaller than the reference voltage Vref, and it depends on the boost converter to make the output voltage Vout maintain at the state of being larger than the reference voltage Vref. However, low operating voltage enables the electronic product integrate more transistors on a single chip, so in practical application, various electronic products use low voltage increasingly. Through prediction of “International Technology Roadmap for Semiconductors (ITRS)” issued by Semiconductor Industry Association (SIA), in the period from now to the year of 2016, operating voltage and operating current of IC will respectively show falling and rising trends. It can be known that the output voltage Vout of the voltage converter required by many electronic products becomes increasingly smaller, so as to directly result in the difficulty of selecting value of the reference voltage Vref. A situation that the output voltage Vout is smaller than the reference voltage Vref occurs more frequently. It is impossible for the conventional DC-DC voltage converter to operate under the situation that the output voltage Vout is smaller than the reference voltage Vref, and it is a blind spot in the design of the DC-DC voltage converter.
2. Under the situation that the output voltage Vout is smaller than the reference voltage Vref, the dual-input voltage converter adopts the method of boosting and then bucking. However, it is necessary to add a boost converter, a voltage converting circuit, and some other related electronic components in the circuit. However, PCB space of the current DC-DC voltage converter is quite limited, which does not satisfy the developing trend of the modern electronic product of “a small size with big function”. The DC-DC voltage converter is widely used in the electronic products, and the increase of the electronic components in the DC-DC voltage converter will result in the increase of manufacturing cost.


As is generally known, computers are used to manipulate data under the control of software. Software is typically written in a high level programming language such as C, which is then compiled by a compiler program into binary machine language instructions which can be executed by a central processing unit in the computer. Software written in programming languages other than the machine language instructions are relatively much easier to understand and use. A very common strategy to simplify computer programming is to group frequently called portions of a program in subroutines, or functions, which perform a certain task. Functions may generally be called or executed as needed from anywhere else in the program each time the task is to be performed. Thus, rather than repeating the program instructions for the task each time the task is performed, the program instructions appear only once in the software, reducing the size of the resulting software.
However, including functions in software can have a negative impact on the performance of the software. Information must often be passed along to the functions as formal parameters, and functions may return information as return values. Passing formal parameters and return values to and from functions requires that a compiler generate additional machine language instructions, making extra work which slows the computer. Additionally, each time a function is called, the computer must save the state of the processor before jumping to the function in the program, in effect saving its place before executing the function. Once the function has finished executing, the computer must restore the state of the processor before returning to the instruction following the function call. These additional tasks can greatly slow the execution of software, particularly if the software includes many small functions. In the extreme, these additional tasks such as passing parameters and return values and saving the state of the processor can be more work for the processor than the actual function.
Most compilers include optional optimization tools which give the programmer the option of optimizing the software for speed as it is compiled. One such tool, called inlining, replaces function calls with the body of the function each time the function call appears. Thus multiple copies of a function will appear inline with the rest of the program, rather than being a single independent copy which can be called from multiple places. Actual arguments to an operation are substituted for formal parameters and the state-saving instructions are omitted. Since this increases the size of the software, compilers typically attempt to determine which functions would be good candidates for inlining and which are not. The criteria used by compilers include information such as the size of a function, the frequency with which it is called, and the number of places from which it is called. For example, large functions which are called infrequently but from many points, or call sites, in a program would be poor candidates for inlining as they would greatly increase the size of the software. In contrast, small functions which are called frequently from only a few call sites would be good candidates for inlining.
However, the traditional software environment in which a program is written, compiled, then executed on a single type of computer is changing with the increasing desire for hardware independent software which can be executed on multiple different types of computers. To achieve hardware independence in software, software is typically either manipulated after compilation (e.g., translated) or is compiled piecemeal as the software is executed.
Another departure from the traditional compilation environment is dynamic translation, wherein software in binary machine language form, written for execution on a first type of computer, is translated as it is executed on a second type of computer. Dynamic translators operate by translating each word of the non-native code into a corresponding word or words of native code for execution by the computer. However, dynamic translators do not scan, evaluate and modify software before executing, and thus do not have detailed information about the software prior to execution. Without additional information about the code it is very difficult, if not impossible, to achieve full inlining of the program to improve performance, particularly in machine language code.
A need therefore exists for a method of enabling function inlining and related optimizations during execution of a program, whether native or non-native to the computer. A further need exists for a method of enabling function inlining and related optimizations during execution of a program in machine language binary format. A further need exists for a method of providing information about an executing program to facilitate dynamic optimization of the program.


The present invention relates to a process and apparatus for forming plastic sheet. In particular, the present invention relates to a process and apparatus for forming plastic sheet having low residual stress and high surface quality. Plastic sheet formed according to the process of the present invention is particularly useful in optical and electronic display applications, such as, for example, optical windows, optical filters, recording media, and liquid crystal displays (LCD).
Sheets of optical quality glass or quartz are used in electronic display applications as "substrates." In such applications, a "substrate" is a sheet of material used to build an electronic display. Such substrates can be transparent, translucent or opaque, but are typically transparent. In general, such sheets have conductive coatings applied thereto prior to use as substrates. Such substrates often have stringent specifications for optical clarity, flatness and minimal birefringence, and typically must have high resistance to gas and solvent permeation. Mechanical properties such as flexibility, impact resistance, hardness and scratch resistance are also important considerations. Glass or quartz sheets have been used in display applications because these materials are able to meet the optical and flatness requirements and have good thermal and chemical resistance and barrier properties; however, these materials do not have some of the desired mechanical properties, most notably low density, flexibility and impact resistance.
Because of the mechanical limitations of glass or quartz sheet in optical or display applications, it is desirable to use plastic sheet in such applications. Although plastic sheets have greater flexibility, are more resistant to breakage, and are of lighter weight than glass or quartz sheets of equal thickness, it has been very difficult to produce plastic sheet having the requisite optical specifications needed for use in optical and display applications at reasonable costs. Moreover, many types of plastic sheet undergo unacceptable dimensional distortion when subjected to substrate processing conditions during manufacture of the display devices, particularly with respect to temperature.
There are several commercially utilized methods for producing plastic sheet, including casting, extrusion, molding, and stretching operations. Of these methods, several are not suitable for producing high quality plastic sheet. As used throughout this specification, the term "high quality" is used to describe plastic sheet having the following characteristics: low surface roughness, low waviness, low thickness variation, and minimal amount of polymer chain orientation (for example, as measured by asymmetric physical properties, birefringence or thermal shrinkage).
For example, injection molding is likely to produce high amounts of polymer chain orientation, especially for thin sheets (i.e., 1 mm thickness or less), due to the flow of molten plastic into the mold, which unacceptably increases birefringence for polymers with non-negligible photoelasticity coefficients. Injection compression molding is an improved molding process which allows squeezing of the polymer after injection for the purpose of improving surface quality and reducing polymer chain orientation. However, even with these improvements, injection compression molding has limited ability to produce high quality sheet.
Compression molding and press polishing may be used to produce sheets with good surface quality; however, the squeezing flow inherent in such processes results in polymer chain orientation which results in unacceptable shrinkage during thermal cycling. Moreover, these processes are not continuously operable and therefore increase labor and production costs.
Stretching operations (for example, for the production of uniaxially- or biaxially-oriented films) and blown film extrusion inherently introduce large amounts of polymer chain orientation and are unsuited for the production of high quality plastic sheet.
Solvent casting can be used to produce high quality film; however, there are practical limitations to the maximum film thickness which can be produced by this method. In addition, the solvent used in the casting must be removed after formation of the sheet.
Sheet extrusion is run as a continuous operation, but this process introduces unacceptable polymer chain orientation due to the nature of the polymer flow in the die and between the polished rollers in the roll stack.
There is therefore a continuing need for a method for producing relatively inexpensive, high quality plastic sheet in a continuous fashion, wherein the resultant plastic sheet is capable of use as a substrate in optical and electronic display applications.


The present invention relates to a roller formed of a sintered alloy having high wear resistance and assembled in a rotary compressor having high fluid tightness.
In a recent trend, a rotary comprressor for use with domestic electrifications becomes light in weight and more compact in size. Further, for the reduction of production cost and for high performance of the compressor, improvements have been made on materials of respective mechanical components of the compressor.
A rotary compressor mainly includes, as shown in FIGS. 1 and 2, an outer case 10, a cylindrical housing 11 assembled in the case 10 and formed with a vane groove 11A extending in radial direction of the housing, a roller 13 rotatable eccentrically in the housing 11, a shaft 14 integrally fixed to the roller 13 for its rotation, and a vane 12 slidably disposed in a vane groove 11A and moved in radial direction of the roller 13. A compression spring 15 is disposed in the groove 11A to urge the vane 12 radially inwardly. Therefore, a radially inner end face of the vane 12 is in slide contact with an outer peripheral surface of the roller 13. A working chamber is provided by a space defined between the housing 11 and the roller 13, and the vane 12 divides the chamber into intake and discharge chambers. The intake chamber is connected to an intake port 16 and the discharge chamber is connected to a discharge port 17. A fluid sucked in the working chamber is compressed and fed out by the eccentric rotation of the roller 13.
Among those components, the vane 12 and roller 13 perform relative sliding motion at high load, and therefore, these components must have high wear resistances. On this standpoint, various materials, for example, sintered alloy, have been proposed for the materials of the vane and roller.
However, regarding the material of the vane, SKH51 has been still a major material in an actual production. SKH 51 is defined by JIS (Japanese Industrial Standard), which is a high-speed tool steel, containing 0.80 to 0.90% of C, 3.80 to 4.50% of Cr, 4.50 to 5.50% of Mo, 5.50 to 6.70% of W, 1.60 to 2.20% of V and balance Fe.
Further, regarding the material of the roller, a sintered material has been employed as described above rather than a cast iron. According to the proposed sintered material, a hard metal carbide and a metal oxide formed by a steam treatment are dispersed in a matrix. Such sintered alloy is disclosed in Japanese Patent Application Kokai Nos. 60-73082 and 60-174853.
More specifically, according to the publication No. 60-174853, it discloses a sintered alloy consisting of 3-10% by weight of chromium, 1-5% by weight of graphite and balance iron and impurities. Metal carbide, metal oxide and free graphite are dispersed in the tempered martensitic matrix. The metal oxide is formed at interiors of sintered voids by steam treatment. This metal oxide seals the sintered voids to thereby obtain lubrication oil retainability.
According to the publication No. 60-73082, it discloses a rotary compressor. A rotor and/or a vane are formed of ferrous sintered alloy. Metal carbide and metal oxide are formed during tempering and are dispersed in the tempered martensitic matrix. Further, nitrogen is solid-solved in the martensitic matrix.
The above sintered material for the roller is intended to improve wear resistance and fluid-tightness. The metal oxide which seals sintered pores serves to enhance fluid-tightness of the compressor. However, with the use of such sintered material, a compressor roller has been burdened with much higher load because of the recent use of an inverter system. Accordingly, such sintered material may be worn out and undergoes scuffing if applied in the inverter system. In order to overcome this problem, there is a further demand for further improvement on wear resistivity and scuffing by using specific composition instead of conventional metal carbide dispersed in the matrix.


This invention relates to an accumulation system for driverless vehicles of the type which are propelled along a track by frictional contact between a drive wheel and a rotating drive shaft. In particular, this invention relates to the deceleration and accumulation of a number of driverless vehicles along a track without the need for direct cooperation between one vehicle and a fixed cam on the rear end of an adjacent vehicle. This invention may also be utilized to cause the vehicle to reverse its direction of motion along the track.
An accumulation system for driverless vehicles is shown in U.S. Pat. No. 3,818,837 and includes a speed control device or tail which is attached to the rear end of the vehicle for cooperation with a drive control member on the front end of the next adjacent vehicle. The speed control device is typically in the form of a cam. The contact between the tail on one vehicle and the drive control member on an adjacent vehicle on the track causes the trailing vehicle to accumulate or stop adjacent to the forward vehicle. Release of the forward vehicle will also cause a corresponding release of the trailing vehicle. The cam on the tail is contoured such that the change in speed of the trailing vehicle is effectuated gradually.


With the development of intelligent mobile terminals and the popularity of social communication networks, the social communication scope of an intelligent mobile terminal user is greatly expanded. Therefore, the mobile terminal user has lots of contact information to manage. The current contact management manner has some obvious disadvantages in managing large amounts of contact information. For example, a contact is difficult to search for or find because the contact is generally searched for by using the first letter of an alphabetic identifier of the contact, that is, inputting the first letter of the contact in a contact search box. Because the contact information is huge, a large number of contacts having the same first letter may be searched out or found by using the first letter. These contacts having the same first letter are all displayed. In this case, the user is only capable of finding needed contact information by browsing or scrolling pages. This process is time-consuming, and does not satisfy a user's expectation for quickly searching for and locating a contact. In addition, user experience on the intelligent mobile terminal is reduced.


1. Field of the Invention
The present invention relates generally to a microwave oven of the type including a duty cycle control which periodically energizes and de-energizes the microwave generating system during the cooking process and, more particularly, to a circuit arrangement for providing an improved delay start feature in such an oven without costly changes in the programming or circuitry which controls oven operation.
2. Description of the Prior Art
It is common in commercially available, electronically controlled microwave ovens to provide a delay start feature. Such a feature permits a microwave oven user to program the control circuitry of the oven so that a cooking operation begins at a later time, the delay time being entered by the user into the oven controls. Thus, an operator of an oven desiring to use such a feature places food in the oven; selects a particular power level at which he desires to cook the food and the time duration for the food to cook and enters this information into the oven control system; selects and enters a time delay (usually in the form of a preselected number of minutes) into the control, then usually presses a "start" button on the control signalling the completion of cooking instructions, and leaves the oven unattended.
Microwave ovens heat food by subjecting it to microwave radiation generated by a magnetron. Most microwave ovens vary the cooking power level by using a duty cycle control to operate the magnetron. In the operation of a duty cycle control, the magnetron is switched between a full-on condition and a full-off condition with the percentage of "on" time compared to the total time of each timing period (duty cycle) being varied to change the cooking power delivered to the food. Various specific circuits to provide this duty cycle are well known in the art. These range from simple cam operated mechanical timers having electrical controls to operate the magnetron to more sophisticated systems employing electronic solid state timing and switching elements. Since the duty cycle control does not form a part of this invention, it will not be described in detail. The magnetron therefore represents a first class of load in a microwave oven which is energized intermittently during the cooking process.
As contrasted to the intermittent operation of the magnetron, the microwave oven also includes various other electrical loads which are desirably energized continuously during the cooking process, such as the mode stirrer motor, the magnetron cooling blower and the filament heater for the magnetron.
In microwave ovens having a delay start feature, provision is usually made to control the continuously energized loads separately from the magnetron. More specifically, it is not possible to control these continuously energized loads using the same switching device that controls the magnetron because the latter is operated in an intermittent or duty cycle controlled fashion.
One solution to this problem is to turn on the constantly energized loads when the oven user completes entry of the delay start instructions into the oven controls. In this arrangement, the mode stirrer motor, blower, etc., are energized by activating the start button, or other equivalent input control device and remain energized continuously during the delay time period when the magnetron is idle, waiting for the beginning of the cooking cycle.
The obvious disadvantage of such a scheme is that power used to drive these loads is wasted during the time when they are not functionally needed to support the cooking operation. In addition, the noise caused by operation of these loads is undesirable and distracting.
Another solution to the above mentioned problem is to control the continuously energized loads by means of a separate independent signal developed by the oven control after the time delay period has passed at the beginning of the cooking cycle, i.e. when the magnetron is initially energized. This may be typically done by utilizing an additional input/output port on the microprocessor control with appropriate programming to carry out this function. In addition, an electronic switching element, associated drive electronics and isolators must be employed to implement this approach, resulting in a significantly additional cost. Moreover, it is sometimes difficult to couple additional electronics to an already existing control package without a significant redesign effort.