1. Field of the Invention
The present invention relates generally to the field of tissue treatment, and more specifically to a system and method for applying reduced pressure at a tissue site.
2. Description of Related Art
Clinical studies and practice have shown that providing a reduced pressure in proximity to a tissue site augments and accelerates the growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but application of reduced pressure has been particularly successful in treating wounds. The treatment of wounds using reduced pressure is sometimes referred to in the medical community as “negative pressure tissue treatment,” “reduced pressure therapy,” or “vacuum therapy.” This type of treatment provides a number of benefits, including faster healing, and increased formulation of granulation tissue.
Reduced pressure treatment systems are often applied to large, highly exudating wounds present on patients undergoing acute or chronic care, as well as other severe wounds that are not readily susceptible to healing without application of reduced pressure. Low-severity wounds that are smaller in volume and produce less exudate have generally been treated using advanced dressings instead of reduced pressure treatment.
Currently, the use of reduced pressure treatment is not considered a viable or affordable option for low-severity wounds due to the manpower required to monitor and change system components, the requirement for trained medical personnel overseeing treatment, and the high cost of treatment. For example, the complexity of current reduced pressure treatment systems precludes a person with little or no specialized knowledge from administering such treatment to oneself or others. The size and power consumption characteristics of current reduced pressure treatment systems also limit the mobility of both the treatment system and the person to whom the treatment is being applied. Also, the high cost of current reduced pressure treatment systems can preclude the accessibility of such treatment systems to some users. Current reduced pressure treatment systems are also typically non-disposable after each treatment, and require electrical components or other powered devices in order to generate the reduced pressure used in treatment.
While reduced pressure could be applied to low-volume and low-exudating wounds using traditional reduced pressure treatment systems, a need exists for a more simple system that allows reduced pressure treatment to be administered without specialized medical training A need further exists for a system that uses little power and is compact, allowing a user of the system to remain mobile and participate in normal day-to-day activities. Finally, a system is needed that is inexpensive so that the system can economically be used by a single patient and then disposed of following the end of treatment for that patient.


The invention relates to a partially spring-mounted drive, particularly for electrically-powered rail vehicles, of the type having a gear which, including an encapsulating gear housing, is seated on the wheel axle, and a pinion that is seated in the gear housing, with the coupled motor being fixedly secured to the truck and the resilient, elastic fastening of the gear housing to the truck being effected by at least two elastic spring elements that are mounted nearly vertically and diametrically opposite the pinion shaft, and whose lines of influence extend through the center of the pinion shaft. A drive of this type is known from the document DE-A-91 16 159.
There are numerous embodiments of partially spring-mounted drives having a transverse traction motor. In a drive according to DE-AS 12 14 263, the gear, including an encapsulating gear housing, is seated on the wheel axle, and the motor pinion or pinion is seated in the gear housing. In this instance, the motor is fixedly secured to the truck, and the gear housing is movably secured. On the one hand, a pendulum-motion suspension is effected via a connecting rod and, on the other hand, a resilient, elastic support against the truck is effected by way of two elastic spring elements that are mounted nearly vertically and diametrically (central-symmetrically) opposite the pinion shaft, and whose lines of influence extend through the center of the pinion shaft. A coupling is also typically disposed between the motor and the motor pinion or pinion.
The document mentioned at the outset, DE-A-91 16 159, discloses an axle drive, particularly for a rail vehicle wheel-set axle disposed in a truck, in which the axle of the drive motor extends parallel to the wheel-set axle, and the motor, which drives the wheel-set axle by way of a spur gear that is fixedly connected to the wheel-set axle, also drives a universal coupling and is fixedly connected to the truck. The wheel-set axle is resiliently connected to the truck in such a way that the spring path is larger by a multiple in the one, direction that is, the vertical direction, than in the other, direction that is, the horizontal direction. The spur gear is supported opposite the truck by means of a torque-converter bearing provided with universal joints. The axis of the torque-converter bearing intersects the axis of the drive shaft of the spur gear approximately perpendicularly, or passes close by it and extends in the direction of the largest spring path of the wheel-set axle. Thus, a fixing resilience of the universal joints at the ends of the torque-converter bearing is provided that permits, above all, a resilience in the vertical direction, while the transverse resilience permits only a very limited horizontal flexibility for the purpose of fixing the torque-converter bearing.
These constructions have system-stipulated disadvantages. With the increase in driving speeds and motor rpms over time in the quest for more lightweight construction, the motor bearings can be reduced in desirable fashion, but the gear bearings must retain their size due to the predetermined axle loads, or even be enlarged because of larger axle diameters. Because of high rpms in the event of a drive power outage, these bearings are in great danger because a stabilizing radial load is no longer present on account of the small gear mass that is to be provided for the high-speed range.
It is the object of the invention to remedy this situation and provide a simple fastening of the gear housing to the truck with which a stabilizing effect can be attained for protecting the bearings, in addition to an economical minimization of the deformation losses of the coupling.


This invention relates to novel glass-ceramics and, more particularly, to glass-ceramics suitable for use as a light filter and, more particularly, to glass-ceramics suitable for use as a band-pass filter and a gain flattening filter. The invention relates also to a light filter using such glass-ceramics.
There are light filters which cut or pass light of a specific wavelength and there are also light filters which reduce intensity of light without depending upon wavelength. The former includes a band-pass filter which passes only a specific wavelength, a notch pass filter which cuts a specific wavelength and high-pass and low-pass filters which pass only wavelengths shorter or longer than a specific wavelength. The latter includes an ND filter.
Light filters can be classified also into an absorption type filter and an interference type filter. A representative absorption type filter is the ND filter and a representative interference type filter is the band-pass filter. A substrate made of plastic is used for absorption type filters such as those for photography. Since a substrate for light filters which are subject to a strong laser beam requires durability and heat resistance property, amorphous glass is exclusively employed for such substrate.
The band-pass filters are made by forming, on a substrate made of, e.g., glass, a multi-layer film of dielectric by alternately laminating an H layer of a dielectric thin film having a high refractive index and an L layer of a dielectric thin film having a low refractive index.
In a band-pass filter which is used for the WDM(wavelength division multiplexing) optical communication system, temperature stability of the center wavelength of the band poses a problem when a narrow band width for passing wavelengths is set for applying the band-pass filter to a wavelength of a higher density. More specifically, the band-pass filter is a sensitive element in which the center wavelength of the band varies even with a slight variation in temperature and, therefore, temperature compensation should be made by a temperature controller when the band-pass filter is used. Such temperature controller, however, cannot actually be employed because of limitation in the space where the band-pass filter is located. The temperature stability has become a matter of increasing importance since it is necessary to reduce the band width as the amount of light information increases.
In the past, amorphous glass has been used as a substrate for the band-pass filter. This prior art substrate is not sufficient in its compressive stress to the film and its durability since its thermal expansion property and mechanical strength are not sufficiently high. Further, amorphous glass has low mechanical strength and therefore tends to produce micro-cracks in processing with resulting cracking or chipping off of corner portions of the product which reduces the yield of the product. Moreover, in amorphous glass, a relatively large amount of alkali ingredient must be added if a high thermal expansion property is to be provided and this poses a problem of elution of alkali ingredient during and after forming of the dielectric film on the substrate. Thus, amorphous glass cannot sufficiently satisfy the demands for a substrate for a light filter, particularly a substrate for a band-pass filter.
For example, the glass-ceramics of a SiO2xe2x80x94Li2Oxe2x80x94MgOxe2x80x94P2O5 system disclosed in U.S. Pat. No. 5,626,935 containing lithium disilicate (Li2O.2SiO2) and xcex1-quartz (xcex1-SiO2) as main crystal phases and the size of the xcex1-quartz globular grains is controlled. No discussion, however, is made in this patent about optimum values of crystal grain diameter, degree of crystallization and mechanical strength including Young""s modulus and specific gravity which are suitable for use as a light filter.
Japanese Patent Application Laid-open Publication No. Hei 10-45426 discloses a SiO2xe2x80x94Li2Oxe2x80x94K2Oxe2x80x94MgOxe2x80x94ZnOxe2x80x94P2O5xe2x80x94Al2O3 system glass-ceramic or a SiO2xe2x80x94Li2Oxe2x80x94K2Oxe2x80x94MgOxe2x80x94ZnOxe2x80x94P2O5xe2x80x94Al2O3xe2x80x94ZrO2 system glass-ceramic suitable for laser texturing which contains, as its predominant crystal phase or phases, at least one of lithium disilicate (Li2O.2SiO2), a mixed crystal of lithium disilicate and xcex1-quartz (xcex1-SiO2), and a mixed crystal of lithium disilicate and xcex1-cristobalite (xcex1-SiO2). However, no discussion has been made in the prior art publication about optimum values of crystal grain diameter, degree of crystallization, and mechanical strength including Young""s modulus and specific gravity which are suitable for use as a light filter.
Japanese Patent Application Laid-open Publication No. Hei 9-35234 discloses a magnetic disk substrate made of a glass-ceramic of a SiO2xe2x80x94Al2O3xe2x80x94Li2O system having predominant crystal phases of lithium disilicate (Li2O.2SiO2) and xcex2-spodumene (Li2O.Al2O3.4SiO2). This glass-ceramic, however, contains, as its predominant crystal phase, xcex2-spodumene which has a negative thermal expansion characteristic which causes the substrate to have a negative thermal expansion characteristic and, in this glass-ceramic, growth of SiO2 crystals such as xcex1-quartz (xcex1-SiO2) and xcex1-cristobalite (xcex1-SiO2) which have a positive thermal expansion characteristic and thereby cause the substrate to have a positive thermal expansion characteristic is extremely restricted. It is difficult in this prior art glass-ceramic to obtain a coefficient of thermal expansion required in the present invention. Besides, since this glass-ceramic is so hard that excellent processability cannot be obtained. Further, since this glass-ceramic requires a high temperature of 820xc2x0 C. to 920xc2x0 C. for crystallization which prevents a large scale production of the product at a competitive cost. Furthermore, no discussion has been made in the publication as to crystal grain diameter, degree of crystallization and mechanical strength.
International Publication WO97/01164 which includes the above described Japanese Patent Application Laid-open Publication No. Hei 9-35234 discloses a glass-ceramic for a magnetic disk in which temperature for crystallization is reduced (680xc2x0 C.-770xc2x0 C.). A sufficient improvement however cannot be achieved in this substrate. Besides, crystals grown in all examples disclosed are xcex2-eucryptite (Li2O.Al2O3.2SiO2) which has a negative thermal expansion characteristic. Further, no discussion has been made in this publication as to crystal grain diameter, degree of crystallization and mechanical strength so that this glass-ceramic has the same disadvantages as the aforementioned prior art glass-ceramics.
It is, therefore, an object of the invention to provide a material suitable for a substrate for a light filter which has eliminated the above described disadvantages of the prior art substrate and has a thermal expansion property which is sufficient for avoiding variation in the refractive index at a temperature at which a filter formed with a mono-layer or multilayer film is used (i.e., having a high coefficient of thermal expansion and thereby imparting compressive stress to the film to improve temperature stability of the refractive index of the film) and also has a mechanical property which imparts sufficient durability to the filter and further has excellent light transmittance.
Accumulated studies and experiments made by the inventors of the present invention for achieving the above described objects of the invention have resulted in the finding, which has led to the present invention, that a glass-ceramic which is obtained by heat treating within a limited range a SiO2xe2x80x94Li2Oxe2x80x94K2Oxe2x80x94MgOxe2x80x94ZnOxe2x80x94P2O5xe2x80x94Al2O3xe2x80x94ZrO2 system glass contains, as its predominant crystal phase or phases, lithium disilicate (Li2O.2SiO2) or a combination of lithium disilicate and at least one crystal phase selected from the group consisting of xcex1-quartz (xcex1-SiO2), xcex1-quartz solid solution (xcex1-SiO, solid solution), xcex1-cristobalite (xcex1-SiO2) and xcex1-cristobalite solid solution (xcex1-SiO2 solid solution), has crystal grains of the predominant crystal phase or phases having a specific range of grain diameter, and has specific mechanical properties including a coefficient of thermal expansion, Young""s modulus and specific gravity which are suitable for use as a light filter, more particularly, as a band-pass filter or a gain flattening filter.
For achieving the above described object of the invention, there is provided a glass-ceramic comprising, as a predominant crystal phase, lithium disilicate (Li2O.2SiO2) having a crystal grain diameter (average) of 0.05 xcexcm or below.
In another aspect of the invention, degree of crystallization of the lithium disilicate crystal phase is within a range from 3% to 20%.
In one aspect of the invention, the glass-ceramic has Young""s modulus (GPa)/specific gravity of 37 or over.
In another aspect of the invention, the glass-ceramic comprises further at least one crystal phase selected from the group consisting of xcex1-quartz (xcex1-SiO2), and xcex1-quartz solid solution (xcex1-SiO2 solid solution), degree of crystallization of the xcex1-quartz (xcex1-SiO2) and the xcex1-quartz solid solution (xcex1-SiO2 solid solution) being within a range from 5% to 25% and a crystal grain diameter thereof (average) being 0.10 xcexcm or below.
In another aspect of the invention, the glass-ceramic comprises further at least one crystal phase selected from the group consisting of xcex1-cristobalite (xcex1-SiO2) and xcex1-cristobalite solid solution (xcex1-SiO2 solid solution), degree of crystallization of the xcex1-cristobalite (xcex1-SiO2) and the xcex1-cristobalite solid solution (xcex1-SiO2 solid solution) being within a range from 2% to 10% and a crystal grain diameter thereof (average) being 0.10 xcexcm or below.
In another aspect of the invention, the glass-ceramic comprises, as predominant crystal phases, lithium disilicate (Li2O.2SiO2) and at least one crystal phase selected from the group consisting of xcex1-quartz (xcex1-SiO2), xcex1-quartz solid solution (xcex1-SiO2 solid solution), xcex1-cristobalite (xcex1-SiO2) and xcex1-cristobalite solid solution (xcex1-SiO2 solid solution).
In another aspect of the invention, crystal grains of the predominant crystal phase or phases are fine and substantially of a globular shape.
In another aspect of the invention, the glass-ceramic is substantially free of Na2O and PbO.
In another aspect of the invention, the glass-ceramic has a surface roughness Ra (arithmetic mean roughness) after polishing of 5.0 xc3x85 or below.
In another aspect of the invention, the glass-ceramic has a coefficient of thermal expansion within a range from +65xc3x9710xe2x88x927/xc2x0 C. to +130xc3x9710xe2x88x927/xc2x0 C. in a temperature range from xe2x88x9250xc2x0 C. to +70xc2x0 C.
In another aspect of the invention, the glass-ceramic substrate has bending strength of 400 MPa or over.
In another aspect of the invention, the glass-ceramic has a composition which comprises in weight percent:
In another aspect of the invention, the glass-ceramic is obtained by heat treating a base glass for nucleation under a temperature within a range from 500xc2x0 C. to 600xc2x0 C. for one to seven hours and further heat treating the glass for crystallization under a temperature within a range from 700xc2x0 C. to 780xc2x0 C. for one to twelve hours.
In another aspect of the invention, there is provided a glass-ceramic substrate for a light filter using the glass-ceramic described above.
In still another aspect of the invention, there is provided a light filter provided by forming a multi-layer film on the glass-ceramic described above.


The present invention relates to an improved vibratory screening machine and feeder combination and to an oil or gas earth drilling installation utilizing said vibratory screening machine and feeder combination.
By way of background, a drill platform for drilling for oil or gas includes a drill rig having a drill casing and a bell nipple. Drilling mud is supplied through the drill casing for lubricating the drill and carrying drilled materials back to the surface. The drilled materials carried by the drilling mud are discharged from the bell nipple. The drilled materials may include rock, shale, clay or sand or combinations thereof. The drilling mud is separated from the drilled materials in a vibratory screening machine and reused. A conventional vibratory screening machine includes a feeder which receives the outflow from the bell nipple and an angularly adjustable vibratory frame having a screen bed on which screens are mounted. The feeder discharges the material to be screened onto the screen bed. The screen bed of the vibratory screening machine must be angularly adjusted for properly screening different compositions of drilled materials. The vibratory frame is positioned above a hopper which receives the drilling mud which passes through the screen bed. The height of the hopper determines the elevation of the screen bed, and the outflow from the feeder is above the screen bed. In the conventional screening machine the vibratory frame must have a walled construction proximate the feeder in order to retain the outflow of the feeder on the screen bed. Therefore, the outflow from the feeder has to be at least a foot above the screen bed to get over the walled structure of the vibratory frame. Also, the feeder is not physically connected to the screen bed because otherwise vibrations of the vibratory frame would be transmitted thereto. Additionally the feeder is not connected to the screen bed because the screen bed must be separate from the feeder so that it can be angularly adjusted.
It is conventional to conduct the outflow of the bell nipple to the screening machine by a gravity feed, especially considering that it is impractical to pump drilled materials containing rocks and shale. In order to have the desired gravity feed from the bell nipple, to the feeder of the conventional screening machine, the conventional screening machine must therefore be placed in a lowered position on the drill platform. This may be difficult to achieve because of space and structure limitations on the drill platform. Therefore, the lower the outflow from the feeder, that is, the closer the outflow from the feeder to the screen bed, the easier it will be to have the outflow of the bell nipple higher than the outflow from the feeder without requiring specialized placements of the vibratory screening machine on a drill platform.


The present invention relates to the bending of panels particularly panels to be used as skin for covering a cell within the structure of aircraft, rocket space vehicles or the like. The invention refers specifically to a device for bending panels of the type referred to above wherein the skin on one side carries stiffening ribs forming intersections or nodes and the device for obtaining bending and curving includes adjustable elements and deforming tool members which are operated under exertion of adequate force in order to obtain positive action under utilization of the location of adjacent nodes of the work and under consideration of changes in length wherein those ribs which run in the direction of curvature.
Panels of the types to which the invention pertains and particularly the bending of such panels requires working certain material which has a certain elasticity and plastic behaviour. A conventional material used here is aluminum. Parts are worked in this fashion particularly are required not only to have low weight but to provide low drag resistance as far as air flow is concerned which means that the panel outside has to be as smooth as possible and must not have any bumps, corners or the like, but there should be gradual and smooth transitions and curvature wherever needed, to be as streamlined as possible in order to avoid formation of drag resistance points for air-flow. In addition, such parts should be made in an economic fashion. Panels of the type to which the invention pertain may either be provided with integrated ribs etc. or ribs, strings or the like may have been added subsequently e.g. through rivetting or the like.
European patent No. 78 891 B1 suggests a method and equipment for bending panels particularly for covering cells in aerospace vehicles wherein deformation obtains through plastic straight line length changes of the ribs extending in the direction of curving and wherein the deforming forces in the ribs are provided at such a distance from the skin itself so that the tension in the panel results in a neutral line within the skin.
The present invention refers specifically to improvements in methods and practice as per this particular European patent and has as its specific task to improve equipment such that in between two adjacent nodes of the stiffening ribs the panel and transverse ribs be subjected to bending. These latter ribs are subject to length extension following the deforming. After the deformation process over entire extension has been completed, these ribs are provided with a constant or uniform stress distribution.


1. Technical Field
The invention relates to speed transmission systems for automobiles, trucks, and other machines requiring the input shaft speeds to be different from the output shaft speeds, and in particular positive variable speed transmissions.
2. Background Art
The art useful for the understanding, searching and examination of the invention is that of mechanisms and machine elements in general and more particularly positive variable speed changing mechanisms as classified in Class 74 subclasses 217,230,230.21, 244, 681, and 689.
3. Disclosure of the Invention
The invention improves the conventional speed transmission systems by the introduction of unique moving bevelled mating plates between input and output shafts. The plates, named as "Ruff Plates", have unique surfaces that determines the rotational speed of one shaft to the other by the positioning of a plurality of continuous series of spaced-apart interconnected balls between the plates. The plates are thicker in the center and decrease to practically zero thickness at the peripheral edges. The mating surfaces of the plates comprises concentric series of crests and valleys increasing from the center to the peripheral edges in aligned sectors that allow the balls to pass between.


1. Field of the Invention
The present invention relates to an apparatus and methods for controlling a hydraulic actuator for use in an injection molding machine, and more particularly to controlling such a hydraulic actuator (both linear and rotary) with a processor which is disposed locally near the actuator and/or the hydraulic manifold.
2. Related Art
Injection molding machines produce great quantities of products at high speed. For example, the widely-used PET plastic drink containers are made at production rates of thousands per hour. During these high speed operations, various injection molding machine devices (such as the molding clamp assembly, the injectors, various control switches, and other machine components) are moved using a number of hydraulic actuators. Such hydraulic actuators are supplied with pressurized hydraulic fluid that causes movement of an internal diaphragm or piston which, in turn, drives the molding device. A control valve controls the flow of hydraulic fluid to the actuator to control movement of the diaphragm. FIG. 1 depicts a typical control valve. In FIG. 1, the hydraulic actuator 2 includes a piston 4 which divides a chamber into two halves 6 and 8. Movement of the piston 4 drives a load 10, which, for example, may comprise a mold and clamp mechanism. A position sensor 12 senses the position of the load 10 and provides a feedback signal to a system controller (to be discussed below).
The hydraulic actuator 2 has two hydraulic fluid lines 64 and 84 which allow hydraulic fluid to enter and escape from the chamber halves 6 and 8, respectively. Pressure transducers 66 and 86 respectively monitor the pressure in line 64 and 84 and provide output signals to the system controller.
Hydraulic fluid from a pressure source (typically a hydraulic fluid pump; not shown in FIG. 1) is provided to valve 14 through hydraulic line 74, while hydraulic fluid may be returned from valve 14 to hydraulic fluid storage tank (also not shown in FIG. 1) through hydraulic line 94. Pressure transducers 76 and 96 respectively monitor the pressure in lines 74 and 94 and provide output signals to the system controller.
Valve 14 controls the flow of hydraulic fluid through the chambers of hydraulic actuator 2 to move the piston 4 back and forth thus driving the load 10. Valve 14 has fluid ports A, B, P, and T which are respectively coupled to the hydraulic lines 64, 84, 74, and 94, as shown. The valve 14 has a straight flow section 142 and a cross-flow section 144 which are respectively driven by solenoids 146 and 148 in order to control the flow of fluid within the valve. For example, when the straight flow section 142 is driven to the A, B, P, and T ports, pressurized fluid will flow through lines 74 and 64 into chamber 6, driving the piston 4 toward the load 10. On the other hand, if cross-flow section 144 is driven to the ports A, B, P, and T, then pressurized hydraulic fluid will be provided through lines 74 and 84 to the chamber 8, driving the piston 4 away from the load 10.
In the related art, control of the hydraulic actuator 2 through the valve 14 was a relatively straightforward process. For example, U.S. Pat. No. 5,062,052 (incorporated herein by reference) discloses that such actuators may be controlled with an analog signal processor and/or a programmable logic controller which are disposed at a location remote from the injection molding actuators so that the processing circuitry is not damaged by machine heat and vibration. Typically, the analog signal processor and/or the programmable logic controller will perform closed-loop control of the actuator 2 through valve 14 in order to keep load 10 moving within the prescribed operational ranges. The analog signal processor and/or programmable logic controller will receive feedback signals from the pressure transducer units 66, 76, 86, and 96, and position information from position sensor 12 in order to control valve 14 according to a predetermined control program. The analog signal processor can also effect operational changes in the operation of the actuator 2 through command signals received through the programmable logic controller, for example to change the molding and clamping times used by load 10.
The programmable logic controller stores a plurality of predetermined control programs which cause the analog signal processor to control the analog devices of the injection molding machine. The programmable logic controller may also include circuitry for controlling the digital devices in the injection molding machine, for example, digital solenoid valves and proximity switches. The programmable logic controller thus controls the elements of the injection molding machine either through the analog signal processor or directly through the digital devices.
In the control scheme of the '052 Patent, however, the analog signal processor and the programmable logic controller are required to perform command and control operations for all of the various devices in the machine. This imposes a processing bottleneck. For example, the programmable logic controller may attempt to execute closed-loop control of multiple different analog devices at the same time. Typically, faster and more powerful processors have been used in an attempt to overcome such problems. Such expensive solutions have, nevertheless, been unable to solve the control timing problems experienced in known actuator control architectures.
Another problem with the known control architecture is the reliability of the analog signal processor and the programmable logic controller. If either one of these components fails, the entire machine must be stopped until a replacement is located, installed, and programmed to operate in the specified machine. Since each actuator in every machine has unique operating characteristics, the newly-installed processor(s) must be re-programed and/or re-parameterized with the operating characteristics of the corresponding actuator(s) before full-scale production can be resumed.
Furthermore, the dedicated wiring inter-connections used for communication between the analog signal processor and the programmable logic controller to each actuator results in a plurality of wires which are difficult to install, maintain, and repair.
Thus, a need exists for a control architecture for hydraulic actuators in an injection molding machine which provides fast, flexible, and reliable control of the actuators.


Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. For example, one network may be a 3G (the third generation of mobile phone standards and technology), 4G, 5G, new radio (NR), or later system, which may provide network service via any one of various radio access technologies (RATs) including EVDO (Evolution-Data Optimized), 1×RTT (1 times Radio Transmission Technology, or simply 1×), W-CDMA (Wideband Code Division Multiple Access), UMTS-TDD (Universal Mobile Telecommunications System-Time Division Duplexing), HSPA (High Speed Packet Access), GPRS (General Packet Radio Service), or EDGE (Enhanced Data rates for Global Evolution). Such multiple access networks may also include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier FDMA (SC-FDMA) networks, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) networks, Long Term Evolution Advanced (LTE-A), and NR networks. Other examples of wireless communication networks may include WiFi (in accordance with IEEE 802.11), WiMAX (in accordance with IEEE 802.16), and Bluetooth® networks.
A wireless communication network may include a number of base stations that can support communication for a number of mobile stations. A mobile station (MS) may communicate with a base station (BS) via a downlink and an uplink. The downlink (or forward link) refers to the communication link from the base station to the mobile station, and the uplink (or reverse link) refers to the communication link from the mobile station to the base station. A base station may transmit data and control information on the downlink to a mobile station and/or may receive data and control information on the uplink from the mobile station.
A wireless device such as a BS or MS may include a transmitter and a receiver coupled to an antenna to support two-way communication. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to obtain a modulated RF signal, amplify the modulated RF signal to obtain an output RF signal having the proper output power level, and transmit the output RF signal via the antenna to a receiving device. The transmitter may further include a directional coupler. For data reception, the receiver may obtain a received RF signal via the antenna and may condition and process the received RF signal to recover data sent by the transmitting device.
A wireless device may include one or more transmitters and one or more receivers coupled to one or more antennas. It is desirable to implement the transmitters and receivers to achieve good performance while reducing circuitry and cost.


1. Field of Invention
The present invention relates to a cooling apparatus of an internal combustion engine, and includes not only the cooling apparatus but also an insert disposed in a water jacket of the engine and a cylinder block of the engine.
2. Description of Related Art
In an internal combustion engine, a water jacket is formed around cylinder bores in a cylinder block, and engine cooling water is caused to flow in the water jacket to cool the engine which is heated due to combustion and sliding of a piston. A temperature of a cylinder bore wall is likely to be higher at an upper portion of the cylinder bore wall than at a lower portion of the cylinder bore wall. Therefore, if the cooling water is caused to flow uniformly at an upper portion and a lower portion of the water jacket for preventing the temperature of the upper portion of the cylinder bore wall from being too high, the lower portion of the cylinder bore will be over-cooled, resulting in an increase in a friction loss generated in the sliding of the piston with the cylinder bore.
In order to improve a temperature distribution in the cylinder bore wall, Japanese Utility Model Publication SHO 57-43338 discloses that an insert is disposed in a water jacket. By providing the insert in the water jacket, a heat removed from the cylinder bore wall can be controlled. More particularly, at a portion where the insert is provided, a flow amount is decreased and the temperature of the cylinder bore wall is maintained high (i.e., less of a cooling effect takes place). By the heat control, the temperature distribution of the cylinder bore wall is improved.
In order to insert the insert into the water jacket, in a cylinder block of a closed deck-type, it is conceivable to insert the insert through a water hole formed in an upper deck of the cylinder block.
However, in the closed deck-type cylinder block, the water hole is small due to a structure of a core used in casting and is discontinuous in an extending direction of the water jacket. As a result, a size of the insert is also small, and a clearance between the insert and the cylinder bore wall is large. The insert also is discontinuous in the extending direction of the water jacket. Therefore, a heat amount removed from the cylinder bore wall is large, and the cylinder bore wall is still over-cooled.


As is well known, various tool holders have been utilized in the prior art which interface with a rotating spindle of a machine such as a milling or boring machine to securely interface a cutting tool to the machine during the cutting of a work piece. A rotary cutting machine typically includes a motor-rotated spindle to which a tool holder is attached, the tool holder being configured to accommodate a shank portion of a cutting tool which is ultimately used to cut a work piece. The attachment of the tool holder to the spindle is generally accomplished by providing a cavity in the spindle into which an upper end or shank portion of the tool holder is secured, as with an externally threaded bolt which is advanced through a portion of the spindle and is threadably received into an internally threaded bore extending axially within the shank portion of the tool holder. In most prior art tool holders, a central aperture is also formed in a lower end or mounting portion of the tool holder for receiving the shank portion of the cutting tool which is to be interfaced to the milling or other machine via the tool holder. Subsequent to the insertion of the shank portion of the cutting tool into the central aperture of the tool holder, the shank portion of the tool holder is drawn or pulled tightly into the spindle by the tightening of the above-described bolt so as to rigidly maintain the cutting tool within the tool holder.
Though interfacing the cutting tool to the cutting machine, prior art tool holders typically possess certain deficiencies which detract from their overall utility. More particularly, while slower rotational speeds generally permit the cutting machine to perform adequately, high speed cutting, which is preferred, can cause substantial difficulty in producing a satisfactory work as a result of the development of vibratory forces that occur between the spindle and the tool holder. Specifically, at higher rotational cutting speeds, the cutting tool often begins to chatter or vibrate such that adequate tool control cannot be maintained and damage to the work piece, along with potential injury to the operator, can realistically occur. More particularly, the transfer of the harmonic resonance into the tool holder may give rise to slight movements thereof relative to the spindle, and in extreme cases may result in the tool holder loosening within the spindle. As will be recognized, the resonance of the tool holder relative to the spindle results in the cut in the work piece being substantially out of tolerance.
A further deficiency with prior art tool holders is that the manner in which the shank portion of the cutting tool is secured within the central aperture of the tool holder often results in the non-concentric mounting of the cutting tool within the tool holder. Such non-concentric mounting is unacceptable in modem, high tolerance machining applications such as those performed on a vertical milling machine wherein minor variations in the concentricity of the cutting tool within the tool holder often cause catastrophic failure in the cutting operation.
The present invention addresses these and other deficiencies of the prior art tool holders by providing a tool holder which includes a dampening member for eliminating the harmonic resonance which typically occurs during the use of cutting tools in high speed milling applications. In the tool holder constructed in accordance with the present invention, the non-concentric mounting of the shank portion of the cutting tool within the tool holder is also substantially eliminated by the heat shrinking of the shank portion of the cutting tool within the tool holder. These, as well as other features and advantages attendant to the present invention will be discussed in more detail below.


Grills configured to cook food placed above the heat source are well known. Such a grill is disclosed in GB 2373713 and includes a series of gas jets embedded in a bed of clay litag. The heat from the burning gas rises upwards through the bed of clay litag and so cooks the food located above it. The bed acts to diffuse the heat and does not itself absorb much heat energy. However, known grills may have a bed of heat-absorbing material, for example, lava stones that are heated by the burning gas to a temperature at which the lava stones themselves emit sufficient heat radiation to contribute significantly to the cooking of the food, that is to say, this radiation, in addition to hot gases from the heat source filtering up through the lava stones, cooks the food.
As food cooks on the grill, material such as fat and meat juices drip onto the lava stones or clay litag and also onto the gas jets, which can easy become clogged by the falling material. The material will tend to collect in the bottom of the grill where the heat source is located. To maintain proper operation and hygiene, it is necessary to regularly clean the grill in order to avoid build-up of material and prevent the gas jets from becoming clogged. Over time, it may not be possible to remove all of the material and this may lead to uneven heating by gas jets and consequently uneven cooking of food occurs. Eventually, it may even become necessary to replace the gas jets.
JP10038229 discloses an oven that contains sidewalls enclosing a substantially closed internal space. Within the sidewalls, a rack is provided for holding the food being cooked and, underneath the food, a number of burners are provided to heat the air inside the oven. The burners produce a flame that slants downwardly and include an overhang to prevent juices from the food being cooked falling on the burner nozzles. The flames heat the air in the oven but are not used to heat a solid incandescent radiant body.
JP 20030 47563 discloses a closed oven for cooking food. Burners are provided in compartments adjacent to the sidewalls. The direction of the flames produced by the burners can be adjusted using air drawn in through side vents so that the flame can be made to point upwards or downwards; the object of altering the direction of the flames is to make the heating more even. The flames heat the air in the oven but are not used to heat a solid incandescent radiant body.
JP 2003 033281 discloses a closed oven containing a number of burners for heating the interior of the oven. One set of burners directs flames into the space underneath the food being cooked and is located under a shield so that, if juices drip from the food being cooked, they do not fall on the burner. The flames heat the air in the oven but are not used to heat a solid incandescent radiant body.
JP 2005 237465 discloses a closed oven having burners located above the food being cooked and a further set of burners extending through a side wall of the oven and directing flames to a space underneath the food being cooked. The flames heat the air in the oven but are not used to heat a solid incandescent radiant body.
JP 2000 217718 discloses a closed oven containing burners located adjacent to the side wall of the oven. These burners produce a horizontally extending flame directed to the space underneath the food being cooked and a vertically oriented flame for heating the space above the food. The flames heat the air in the oven but are not used to heat a solid incandescent radiant body.
U.S. Pat. No. 3,667,449 discloses a home grill or barbecue having a tray containing pumice rocks. A central burner is provided that produces flames that extend radially outwards from the burner in a horizontal direction. A domed-shaped ceramic deflector overlying the burner deflects the flames from the burner onto the pumice rocks, which will be heated so that they are incandescent. The food is located above the bed of pumice rocks and is cooked by radiant heat emitted by the incandescent pumice rocks.


1. Field of the Invention
The present invention relates to a levelling method and apparatus and, more particularly, to the improvement in a levelling method and apparatus for levelling an object of which the surface shape or surface roughness is to be measured.
2. The Related Art
Levelling apparatuses for controlling an object which is placed on a mounting member so as to have the desired attitude are known and they are generally used to place an object of measurement, a work, etc. on the mounting members of a surface roughness tester, a three-dimensional measuring apparatus and various working machines.
In the case of a surface roughness tester, for example, if the measuring plane is inclined, the base line is inclined in the result of measurement, as shown in FIG. 15 (A), which is unsuitable for obtaining the data on the surface roughness. Furthermore, if a measurable allowance must be set at a wide range in the case as shown in FIG. 15(A), the discrimination of the measurement is impaired. It is therefore necessary to adjust the mounting attitude so as to level in the direction of scanning by the probe (see FIG. 15(B)).
In the case of outputting the surface roughness three-dimensionally by measuring it several times by feeding the probe little by little in the direction orthogonal to the direction of scanning by the probe, the levelling in the direction orthogonal to the direction of scanning constitutes a very important precondition.
In a conventional levelling apparatus, however, the levelling only in one direction is automatized, and no levelling apparatus which is capable of automatic three-dimensional attitude control of an object placed on a mounting member has ever been produced.
As a result, the three-dimensional attitude of an object placed on the mounting member must be adjusted manually, which takes much labor and time.


2. Prior Art
Prior art methods of removing a broken cork typically require that the remaining cork be pushed into the bottle. The cork is then either retrieved with various wire or net devices, or filtered from the wine.
FIG. 1 is a side view of the side portion of a typical prior art corkscrew. In one embodiment, the current invention provides a substantially larger diameter of the spiral portion in order to avoid the crumbled middle portion of a broken cork, so that the spiral portion may be inserted near the side wall of the cork.
FIGS. 2A-2C is a side view of various prior art cork removal devices which comprise a prior art spiral portion as illustrated in FIG. 1. FIG. 2A shows an example “screwpull” device, FIG. 2B shows an example “waiter's friend” device, and FIG. 2C shows an example “butterfly” device.


The invention relates to the selection of portfolios of diagnostic markers.
A few single gene diagnostic markers such as her-2-neu are currently in use. Usually, however, diseases are not easily diagnosed with molecular diagnostics for one particular gene. Multiple markers are often required and the number of such markers that may be included in a assay based on differential gene modulation can be large, even in the hundreds of genes. It is desirable to group markers into portfolios so that the most reliable results are obtained using the smallest number of markers necessary to obtain such a result. This is particularly true in assays that contain multiple steps such as nucleic acid amplification steps.


1. Field of the Invention
The invention pertains to fire resistant firesleeve assemblies as used with hose or pipe systems, and particularly pertains to the sealing of the cut end of a firesleeve utilizing fibrous heat insulative components.
2. Description of the Related Art
Hose systems, particularly fuel, lubricating and hydraulic hose used within aircraft engine compartments, often require fire resistant protection to minimize the likelihood of fire or high temperatures damaging the flexible elastomeric hose of the hydraulic circuits. Typically, resistance to fire and high temperature is achieved by encompassing the hose and portions of the associated hose fittings with a protective firesleeve. The firesleeve often consists of a silicone rubber tube surrounding the hose and/or fitting and the firesleeve usually includes an inner insulative material such as asbestos or glass fiber to provide insulation against the transfer of heat.
Typically, firesleeve material is shipped and stored in indeterminate lengths, often wound upon reels, and the firesleeve is cut to the desired length to accommodate the length of hose with which it is to be used. As the cutting of the firesleeve to the desired length will expose the end of the firesleeve and the fibrous material thereof it is required that the end of the firesleeve be treated or sealed so as to discourage contamination of the firesleeve inner fibrous material and prevent the "wicking" of moisture, fluids, or other liquids into the fibrous material by capillary action.
To "seal" the cut ends of firesleeves, the conventional practice is to dip the cut firesleeve end into a silicone formulated "end-dip" liquid sealant so as to saturate the braided fibrous material adjacent the firesleeve end. Thereupon, the silicon end dip composition is dried and processed prior to the firesleeve being installed upon the associated hose. Such processing of the ends of firesleeves often requires a 24 hour delay, and the handling of a dipped firesleeve is messy, produces dripping, and such end dipping is hazardous and may not produce a liquid impervious end seal.
Further, the silicone formulated end dip used to seal firesleeves may be classified as a hazardous material requiring special and expensive transportation procedures. Further, end dipped firesleeves do not produce a significant frictional engagement with the hose or hose fitting unless the clamping pressures are unusually high and there is a tendency for the firesleeve to axially slide on the hose, possibly exposing a portion of the hose adjacent the fitting to fire in high temperatures.
3. Objects of the Invention
It is an object of the invention to provide a fluid impervious end seal for hose or pipe firesleeve assemblies which is inexpensive, requires no dipping or application of fluids, requires no hazardous materials, and eliminates assembly and processing delays.
Another object of the invention is to provide a seal for the cut ends of hose or pipe firesleeves wherein the seal is formed by a flexible resilient liquid impervious cuff enclosing the firesleeve cut end which totally confines the cut end to produce an effective liquid seal, enhances fire protection, and produces an attractive aesthetically finished hose assembly.


1. Field of the Invention
This invention relates to a decoder of a convolutional coded data stream. More particularly this invention relates to an improved traceback facility for a Viterbi decoder.
2. Description of the Related Art
Viterbi decoders are important in modern telecommunications, in which digital signals are convolutionally encoded. In a modern application, coded orthogonal frequency division multiplexing ("COFDM") requiring a convolutional code has been proposed in the European Telecommunications Standard DRAFT pr ETS 300 744 (May 1996), which specifies the framing structure, channel coding, and modulation for digital terrestrial television. This standard was designed to accommodate digital terrestrial television within the existing spectrum allocation for analog transmissions, yet provide adequate protection against high levels of co-channel interference and adjacent channel interference. A flexible guard interval is specified, so that the system can support diverse network configurations, while maintaining high spectral efficiency, and sufficient protection against co-channel interference and adjacent channel interference from existing Phase Alternating Line System ("PAL")/Sequential Coleur A'Memorie ("SECAM") services. Two modes of operation are defined: a "2K mode", suitable for single transmitter operation and for small single frequency networks with limited transmitter distances, and an "8K mode". The latter can be used for either single transmitter operation or for large single frequency networks. Various levels of quadrature amplitude modulation ("QAM") are supported, as are different inner code rates, in order to balance bit rate against ruggedness. The system is intended to accommodate a transport layer according to the Moving Picture Experts Group ("MPEG"), and is directly compatible with MPEG-2 coded TV signals (International Organization for Standardization/International Electrotechnical Commission ("ISO/IEC") Specification 13818).
In the noted European Telecommunications Standard data carriers a COFDM frame can be either quadrature phase shift keyed ("QPSK"), 16-QAM, 64-QAM, non-uniform 16-QAM, or non-uniform 64-QAM using Gray mapping.
In the following discussion reference may be to FIG. 1, which illustrates a simplified transition trellis diagram 167 according to a one-step Viterbi decoding process at a coding rate of 1/2, according to convolutional encoding with a constraint length K=3, and a generator polynomial EQU G(x)=(x.sup.2 +x+1, x.sup.2 +1). (1)
The rate 1/2 indicates that for every one bit input, the encoder generates two bits. The constraint length K is the maximum number of signals that can be used to generate an output. Using a transition trellis diagram such as diagram 167, and an incoming data sequence, it is possible to generate an output stream following a sequence of states S. In the diagram 167 a particular state S.sub.t can be represented by two bits. For example, state S.sub.t can assume the value 2 (binary 10), indicated by reference numeral 169. In the representation of diagram 167, in state S.sub.t+1 the bits of state S.sub.t are shifted by one position, and an incoming data bit occupies the rightmost (least significant bit) position. Thus, the state value 169 can legally transition to values 171 and 173 in state S.sub.t+1. For these two transitions, the convolutional encoder will produce values 175 and 177 respectively, indicated more generally as x.sub.t y.sub.t. All possible state transitions can be calculated for the encoder, i.e. given S.sub.t and data bit d.sub.t, the next state S.sub.t+1, x.sub.t and y.sub.t can be evaluated.
The path metric is a measurement of the likelihood that the state is on the original encoder state sequence at that time. The smaller the path metric, the more probable the state is, and vice versa. The branch metric is a measurement of the probability value attached to each branch depending on the input. The branch metric is taken as the Hamming weight, which is the number of differing bits between a received symbol xy.sub.rx and an expected symbol xy along every branch in each transition as shown in FIG. 1. Traceback is the method of going back through the trellis to find the initial state which produced the state with the smallest path metric.
In the preferred embodiment a 2-step decoding process is employed, corresponding to moving through the trellis two steps at a time. This doubles the time to calculate each step, and each traceback yields two bits, rather than one. However the number of calculations required at each state has also doubled, as each state now has four possible paths to be calculated. Only one path is required to be maintained in memory for each state. That path, known as the surviving path, is the one having the smallest path metric and is thus the most likely path.
Puncturing has the effect of producing a higher rate of data transmission, as the code is more efficient. In exemplary Table 2, the convolutional encoder (not shown) encodes data to produce symbols x.sub.t and y.sub.t, which are then punctuated according to the puncturing matrix
x: 1 0 PA1 y: 1 1
to produce x'.sub.t and y'.sub.t, which are then retimed to be transmitted as I,Q in quadrature phase shift keyed modulation. When decoding with punctured data, the omitted bits do not contribute to the branch metric calculation.
TABLE 1 ______________________________________ data d.sub.0 d.sub.1 d.sub.2 d.sub.3 d.sub.4 ______________________________________ xy x.sub.0 y.sub.0 x.sub.1 y.sub.1 x.sub.2 y.sub.2 x.sub.3 y.sub.3 x.sub.4 y.sub.4 x'y' x.sub.0 y.sub.0 y.sub.1 x.sub.2 y.sub.2 y.sub.3 x.sub.4 y.sub.4 IQ x.sub.0 y.sub.0 y.sub.1 x.sub.2 y.sub.2 y.sub.3 x.sub.4 y.sub.4 ______________________________________
In the simple example given above, branch metrics were calculated using the Hamming Weight. Significant improvements result if, instead of receiving either a 1 or 0, we receive a multiple bit representation of each x.sub.rx and y.sub.rx showing the relative likelihood of the signal being a 1 or 0. Thus, in a 16 level (4-bit) soft decoding, a 1 is represented by 15 (binary 1111).
In 16 level decoding, if, for example, xy.sub.rx =(3, 14) are received, the branch metrics may be calculated as shown in Table 2. When calculating new path metrics, the respective path metrics are calculated using these soft-calculated branch metrics, giving significant improvements in decoder performance. In the preferred embodiment, an 8 level (3-bit) soft decoding is used. Traceback is implemented using a systolic array, as explained below in detail.
TABLE 2 ______________________________________ expected xy.sub.rx branch calculation result ______________________________________ 00 0 .vertline.0-3.vertline. + .vertline.0-14.vertline. 17 01 1 .vertline.0-3.vertline. + .vertline.15-14.vertline. 4 10 2 .vertline.15-3.vertline. + .vertline.0-14.vertline. 26 11 3 .vertline.15-3.vertline. + .vertline.15-14.vertline. 13 ______________________________________
In the preferred embodiment, data is convolutionally encoded using a constraint length K=7, which corresponds to a trellis having 64 states. A partial representation of a 2-step transition trellis diagram for this situation is illustrated in FIG. 2.
In the noted European Telecommunications Standard there is an outer Reed-Solomon code, and an inner punctured convolutional code, based on a mother convolutional code of rate 1/2 with 64 states, and having generator polynomials G.sub.1 =171.sub.OCT for X output and G.sub.2 =133.sub.OCT for Y output. In one mode of operation, other punctured rates of 2/3, 3/4, 5/6 and 7/8 are allowed.
During the Viterbi decoding process, traceback requires a substantial amount of processing time and hardware resources. The traceback module in a Viterbi decoder also represents an important production cost.


Ellipsometry is a technique of non-destructive measurement allowing optical characterisation of a sample having a specular or quasi-specular surface. The term ellipsometry is used as a collective term for denoting various methods for studying the physical properties of test samples by means of measuring the amount by which they change the polarization of a polarized light beam. In principle, a beam with a known state of polarization is reflected from or transmitted through the test sample. After reflection at the test sample or after the light has passed through the test sample, the physical properties of the test sample can be ascertained from the change in polarization, using optical calculations.
Ellipsometry is based on the fact that a monochromatic electromagnetic wave changes its intensity and state of polarization if it non-perpendicularly strikes the interface between two dielectric media (for example, a substrate coated with a film). The ellipsometer linearly polarizes the light beam before it strikes the sample surface; linear (or circular) polarization indicates that the light gets only two perpendicular components having the same amplitude. The beam, after going through the interface between the surface film and substrate, is reflected and changes its polarization, i.e. both the ratio amplitude of the two components (Ψ) and their phase (Δ) are modified. The two components of the reflected light are no longer mutually perpendicular and have a different amplitude; hence the polarization becomes elliptical and the technique is called ellipsometry. The ellipsometer measures the experimental values of the two components of the reflected light, giving the values Ψ and Δ. The value Ψ is calculated by multiplying the ratio of amplitudes of the incident beam by the amplitudes of the reflected beam; the value Δ comes from the difference of their phases.
Ellipsometry can be implemented in situ and therefore is well suited to the study of the mechanisms of thin layer growth, the formation of interfaces and the control of the processes used to form these layers and interfaces. For example, during semiconductor fabrication, thin films are deposited on a wafer. The thickness of the films is critical and may be readily determined from ellipsometric measurements. There are numerous other manufacturing processes that also require accurate deposition of thin films. Ellipsometers are routinely used to measure the quality of these processes by analyzing the film properties.
The ellipsometric measurements can be made at one fixed wavelength or at several wavelengths (i.e. spectroscopic ellipsometry). According to the wavelength region of the source (near ultra violet, visible, near infra red, infra red, etc.) it is possible to analyze different properties of layers or of bulk materials. In the ultra violet and visible regions, the depth of penetration of the radiation is often slight. These wavelengths are often used for the study of surfaces and interfaces. Generally this does not allow access to layer volumetric properties of materials which can, however, be obtained through measurements in the infra red region. Infra red is also well suited to measurements of vibrational absorption (chemical bonds).
In reflection ellipsometry, the test sample has a reflective surface on which the light beam impinges with an oblique angle of incidence. The ellipsometric data obtained can be used for ascertaining the refractive index and the extinction coefficient of the surface material of the test sample. If the test sample is covered with a dielectric film, it is possible to determine the thickness and the refractive index of the film. Reflection ellipsometry is the most sensitive and most accurate method for measuring such films or layers. Instead of using a reflected beam, it is also possible to analyze the light beam which is transmitted through the test sample. This method is referred to as transmission ellipsometry. The same procedure which is used for measuring the change in polarization in transmission ellipsometry can also be employed for studying bulk properties of transparent materials, for example the birefrigence of crystals or optical rotation of a sugar solution. The latter is conventionally referred to as polarimetry, but it falls within the general term of ellipsometry. For the sake of simplicity hereinafter, reference will primary be made to reflection ellipsometry but it should be appreciated that, unless stated otherwise, the information and procedures set forth herein also apply to transmission ellipsometry and polarimetry as referred to above.
In ellipsometry, the physical parameters of the test sample, which are the aspects of interest, simultaneously affect the relative intensity and the phase delay of the two polarization components of the light beam. As external influences affect the two polarization components to the same degree, ellipsometry is very insensitive with respect to such external influences. That also explains the extremely high degree of accuracy of ellipsometric measuring methods in conventional laboratory equipment.
An ellipsometer essentially comprises a light source for emitting polarized light, a test sample and an analyser which analyses polarization of the light after it has been reflected at the test sample or after it has been transmitted through the test sample. More particularly, an ellipsometer typically comprises a light source and a detector together with two polarizers, one of which is disposed near the light source and is conventionally referred to as the polarizer, while the other is disposed in the vicinity of the analyzing means and is generally referred to as the analyzer. The test sample is disposed between the polarizer and the analyzer, and the assembly may include one or two devices for altering or modifying the polarization of the light, referred to as polarization modifying devices or polarization modulating devices. The polarization modulating devices may be polarizers which produce a partial polarization effect, birefrigent devices (which are referred to as compensators), or optical rotators and/or geometrical rotators. If, for example, the polarizer is rotated relative to the test sample, that is a geometrical rotation. The differences between the individual kinds of ellipsometers arise out of the choice of the device used for modifying the state of polarization. By virtue of the particular design construction selected, ellipsometers have different properties, for example in regard to accuracy, high measuring speed and suitability for operation with multiple wavelengths.
Because of the non-directional nature of optical laws, the sequence in which the optical components are disposed may be interchanged between the two polarizers. The mode of operation of the overall assembly then remains the same.
In order to carry out ellipsometric measurements, the surface of a sample is illuminated by a light beam and the state of polarization of an incident beam i is compared with that of the reflected beam r or the transmitted beam. A polarization electric field vector E is generally represented by its projections ES and EP, respectively perpendicular and parallel to the plane of incidence. The projections ES and EP are complex amplitudes.
In the domain of linear ellipsometry, the polarization reflectance ratio is traditionally defined to be the ratio of the reflection coefficients p- to s-polarized lightρ=RP/RS=(EP/ES)r/(EP/ES)i  (1)and is indicative of the modifications to the state of polarization produced by the surface being studied. ρ is a complex number, therefore two ellipsometric parameters must be obtained in order to determine ρ, which is generally represented in the form:ρ=tan Ψ·eiΔ=(EP/ES)r/(EP/ES)i  (2)
The two parameters Ψ and Δ describing the change in polarization are thus combined in the complex quantity ρ. The parameter Ψ is a measure of the relative intensities (the amplitude ratio) of the p-to-s polarization states of the probe light beam, and the parameter Δ is a measure of the relative phase shift between the p and s polarization states. The parameters Ψ and Δ, and hence the number ρ, depend, at the same time, on the surface properties of the sample, the angle of incidence of a beam and the measurement wavelength. The expression of Ψ and Δ, or of ρ, as a function of these parameters, is given by the equations of Fresnel, as is well known in the art.
As a conventional method of obtaining these ellipsometric parameters Ψ and Δ, the null ellipsometry method is known. In null ellipsometry, the change in the state of polarization which is caused by the test sample is compensated by suitable adjustment of the polarization modulating device so that the light beam is extinguished by the analyser. Adjustment to a minimum level of received intensity may be effected either manually or automatically. The measurement result is then the position of the polarization modulating device upon extinction of the light beam. In this method, a polarized beam is radiated from a light source onto a measurement target at a predetermined angle with respect to the target, and a beam reflected by the target, which is elliptically polarized, is transmitted through a λ/4 (quarter wave) plate and an analyzer to be guided to a light-receiving unit. While optical intensity signals obtained by the light-receiving unit are observed through, e.g., a measuring unit, the λ/4 plate and the analyzer are rotated to obtain a rotational angle at which the minimum optical intensity is observed. The above-mentioned ellipsometric parameters are calculated on the basis of this rotational angle, as is known in the art.
Second harmonic generation (SHG) and sum-frequency generation (SFG), which are the respective frequency doubling and frequency mixing of light, have emerged as powerful ellipsometric probes for characterizing oriented surface systems. By nature of the unique symmetry of SHG and SFG measurements, the detected signals are often dominated by the oriented chromophores at interfaces and are largely insensitive to greater numbers of randomly oriented species in the bulk. This symmetry condition has been exploited with great success in surface-specific spectroscopic measurements by SHG and SFG at solid/liquid, liquid/liquid, liquid/air, solid/air, semi-conductor, polymer and biological interfaces.
The intensity of the second order nonlinear beam generated from an oriented uniaxial organic film between two isotropic media is dependent on the nonlinear optical susceptibility (described by the rank three x(2) tensor), the incident intensity or intensities, the polarization states of the incident and exigent light, and the linear optical properties of the interfacial system. A routine approach for isolating relative values of the x(2) tensor elements is to compare the intensities of the s- or p-polarized nonlinear beams measured as functions of the polarization state(s) of the incident beam(s). For example, the expressions in Eqs. 3 and 4 below (or variations thereof) are commonly used in reflection SHG measurements of achiral uniaxial interfacial films performed using linearly polarized incident light with the plane of polarization rotated away from purely p-polarized by the angle γ.Is2ω=C·¼ sin2(2γ)|s1xXXZ|2(Iω)2  (3)Ip2ω=C·|s6xZXX+cos2γ(−s3xXXZ+s5xZXX−s6xZXX+s7xZZZ)|2(Iω)2  (4)In standard reflection and transmission measurements of achiral films far from resonance, relative values of the tensor elements are easily obtained from the ratios of the second harmonic intensities measured under different polarization conditions or from nonlinear curve-fitting.
As new samples, unique substrates and diverse interfacial systems are increasingly investigated by SHG and SFG, many of the simplifying assumptions routinely used to treat polarization measurements may not hold. For example, the Fresnel factors that describe the electric fields at an interface will be complex-valued in studies conducted in total internal reflection or in studies of multilayer films. The Fresnel factors will also generally be complex in systems in which the nonlinear film, the substrate, or the ambient medium absorbs either the incident or exigent light (e.g., in spectroscopic studies). Finally, if the nonlinear surface layer absorbs one or more of the incident or exigent optical frequencies, the x(2) tensor elements themselves will also be complex-valued. In any or all of these instances, even the simple expressions in Eqs. 3 and 4 (or variations thereof) describing SHG can become complicated. Expansion of the expressions in Eqs. 3 and 4 in the most general case of SHG measurements with complex fitting coefficients and complex tensor elements yields the expressions in Eqs. 5 and 6.
                              I          s                =                                  C                                1            4                                                                        sin                2                                                          (                                  2                                                                                γ                                )                                                                [                                                                                Re                                                                                (                                                              s                                1                                                            )                                                                                2                                                                                Re                            (                                                          χ                              XXZ                                                        )                                                    2                                                                    +                                              Im                                                                                (                                                          s                              1                                                        )                                                    2                                                                                Im                            (                                                          χ                              XXZ                                                        )                                                    2                                                                    +                                                                                Re                            (                                                          s                              1                                                        )                                                    2                                                                                Im                            (                                                          χ                              XXZ                                                        )                                                    2                                                                    +                                                                                Im                            (                                                          s                              1                                                        )                                                    2                                                                                Re                            (                                                          χ                              XXZ                                                        )                                                    2                                                                                ]                                                          (        5        )                                                                                I                p                            =                                                                            C                                                                              {                                                                                Re                                  (                                                                      s                                    6                                                                    )                                                                                Re                                  (                                                                      χ                                    ZXX                                                                    )                                                                                -                                                                                Im                                  (                                                                      s                                    6                                                                    )                                                                                Im                                  (                                                                      χ                                    ZXX                                                                    )                                                                                +                                                                                cos                                2                                                                                γ                                                                                [                                                                                -                                                                                Re                                                (                                                                                s                                                  3                                                                                )                                                                                Re                                              (                                                                                χ                                                XXZ                                                                                )                                                                                +                                                                                Re                                              (                                                                                s                                                5                                                                                )                                                                                Re                                              (                                                                                χ                                                ZXX                                                                                )                                                                                -                                                                                Re                                              (                                                                                s                                                6                                                                                )                                                                                Re                                              (                                                                                s                                                7                                                                                )                                                                                Re                                              (                                                                                χ                                                ZZZ                                                                                )                                                                                +                                                                                Im                                                (                                                                                s                                                  3                                                                                )                                                                                Im                                              (                                                                                χ                                                XXZ                                                                                )                                                                                -                                                                                Im                                              (                                                                                s                                                5                                                                                )                                                                                Im                                              (                                                                                χ                                                ZXX                                                                                )                                                                                +                                                                                Im                                              (                                                                                s                                                6                                                                                )                                                                                Im                                              (                                                                                s                                                7                                                                                )                                                                                Im                                              (                                                                                χ                                                ZZZ                                                                                )                                                                                ]                                                                                }                                        2                                                  +                                                                                C                                                                      {                                                                                Re                                (                                                                  s                                  6                                                                )                                                                                Im                                (                                                                  χ                                  ZXX                                                                )                                                                                +                                                                                Im                                (                                                                  s                                  6                                                                )                                                                                Re                                (                                                                  χ                                  ZXX                                                                )                                                                                +                                                                                cos                              2                                                                                γ                                                                                [                                                                                -                                                                                Re                                              (                                                                                s                                                3                                                                                )                                                                                Im                                            (                                                                                χ                                              XXZ                                                                                )                                                                                +                                                                                Re                                            (                                                                                s                                              5                                                                                )                                                                                Im                                            (                                                                                χ                                              ZXX                                                                                )                                                                                -                                                                                Re                                            (                                                                                s                                              6                                                                                )                                                                                Im                                            (                                                                                χ                                              ZXX                                                                                )                                                                                +                                                                                Re                                                                                (                                                                                s                                                7                                                                                )                                                                                Im                                            (                                                                                χ                                              ZZZ                                                                                )                                                                                -                                                                                Im                                              (                                                                                s                                                3                                                                                )                                                                                Re                                            (                                                                                χ                                              XXZ                                                                                )                                                                                +                                                                                Im                                            (                                                                                s                                              5                                                                                )                                                                                Re                                            (                                                                                χ                                              ZXX                                                                                )                                                                                -                                                                                Im                                            (                                                                                s                                              6                                                                                )                                                                                Re                                            (                                                                                χ                                              ZXX                                                                                )                                                                                +                                                                                Im                                            (                                                                                s                                              7                                                                                )                                                                                Re                                                                                (                                                                                χ                                                ZZZ                                                                                )                                                                                ]                                                                                }                                    2                                                                                (        6        )
It is immediately apparent that extracting the real and imaginary components of the three independent tensor elements present in SHG from the second harmonic intensity measured as a function of γ is nontrivial. Even assuming the x(2) tensor elements are purely real, Eqs. 5 and 6 yield a minimum of two possible solutions for the relative tensor elements (for xZXX and xXXZ of like and opposite sign).
An alternative detection approach was pioneered during the emergence of nonlinear optical surface measurements of uniaxial films in which a rotating polarizer is placed between the sample and the detector. As described hereinabove, rather than compare normalized intensity ratios, the rotation angle of the polarizer that resulted in extinction of the nonlinear beam was used to determine relative values of the tensor elements and subsequently molecular orientation. Using this type of approach, the ambiguity regarding the relative sign between xZXX and xXXZ in principle can be removed. However, this rotating polarizer approach will only produce a true null provided the nonlinear beam is linearly polarized, which generally limits its reliable application to standard reflection and transmission measurements of vanishingly thin transparent films far from resonance (in which case both the x(2) tensor elements and the Fresnel factors are purely real).