  We construct the general model with only parallel positive tension 3-branes
on $M^4 \times R^1$ and $M^4 \times R^1/Z_2$. The cosmology constant is
sectional constant along the fifth dimension. In this general scenario, the
5-dimensional GUT scale on each brane can be indentified as the 5-dimensional
Planck scale, but, the 4-dimensional Planck scale is generated from the low
4-dimensional GUT scale exponentially in our world. We also give two simple
models to show explicitly how to solve the gauge hierarchy problem.
