A permeable material compacting method includes, forming a cavity between a membrane and a structure, porting fluid to or from the cavity, positioning permeable material adjacent the membrane, generating a differential pressure across the membrane, deforming the membrane, and decreasing volume of the permeable material. An optical element such as a diffraction grating or beam-splitter will have adjacent sections of different indexes of refraction in the same optical material layer. Said calculation program includes instructions for prompting said calculation module CM to use said secret key L and at least one data item ACn,p or Kpc) coming from outside the secure data processing system, in order to calculate an unscrambling key Kp. A measurement device is coupled to the circulation loop and a return port directs the fluid mixture from the circulation loop back to the test container at substantially the same vertical location as the suction port. The rear base coupling and the rear arm coupling essentially restrict lateral movement of the motion control link and permit tuned lateral movement of the frame relative to the rear of the cab to provide lateral motion control at the rear of the cab. In addition, the reverse breakdown voltage of the zener diode is set to a desired value within a range of values by modifying the area of a new opening in one of existing masks.