Abstract: A digitally controlled resistance generator (10) in which resistors (16-38) having values selected according to an expression 2.sup.N-1 (R), where N is equal to the number of terms in the expression, and R is equal to the lowest value of resistance, are electrically inserted into a resistive circuit in accordance with a parallel binary signal provided by an analog-to-digital converter (46) or a programmable computer (75). This binary signal is coupled via optical isolators (50-72) which, when activated by a logical "1," provides a negative potential to some or all of the gate inputs (96) of the normally "on" field effect transistors (98-120) which, when "on," shorts out the associated resistor. This applied negative potential turns the field effect transistors "off" and electrically inserts the resistor coupled between the source terminal (124) and the drain terminal (122) of that field effect transistor into the resistive circuit between the terminals (12, 14).

Abstract: A compact hydride absorption refrigeration system with few moving parts for 10.degree. Kelvin operation is disclosed and comprises liquid hydrogen producing means in combination with means for solidifying and subliming the liquid hydrogen produced. The liquid hydrogen is sublimed at about 10.degree. Kelvin. By using a symmetrical all hydrogen redundant loop system, a 10.degree. Kelvin refrigeration system can be operated for many years with only a fraction of the power required for prior art systems.

Abstract: Disclosed is a method and apparatus for growing in a gravitational field a microscopic crystal from a solution. Solution is held in a vertical chamber which is relatively thin, the thin dimension being generally perpendicular to the vertical. There is a substrate crystal disposed at either the upper or lower end of the chamber and the crystal grows from this substrate crystal in one direction. In accordance with this invention, the temperature conditions of the solution are controlled so that as the crystal forms the effects of buoyant convection within the solution are minimized. This is accomplished in two different ways depending upon whether the crystal is grown from the upper or lower end of the chamber. When grown from the upper end of the chamber, the temperature of the solution is controlled so that it remains essentially isothermal so that there is essentially no heat loss from the solution.

Abstract: The present invention discloses a miniature spectrally selective dosimeter capable of measuring selected bandwidths of radiation exposure on small mobile areas. This is achieved by the combination of photovoltaic detectors, electrochemical integrators (E-cells) and filters in a small compact case which can be easily attached in close proximity to and substantially parallel to the surface being measured. In one embodiment two photovoltaic detectors 13 and 8, two E-cells 15 and 9 and three filters 14 and 16 are packaged in a small case 17 with attaching means consisting of a safety pin 19. In another embodiment, two detectors 31 and 32, one E-cell 33 and three filters 34 and 35 are packaged in a small case 36 with attaching means consisting of a clip 37 to clip over a side piece 38 of an eye glass frame 39. In a further embodiment, the electro-optic elements are packaged in a wristwatch case 51 with attaching means being a watchband 52.

Abstract: A method and apparatus for correcting doppler shifts in synthetic aperture radar data. More particularly, in an optical correlator (10) for synthetic aperture radar data having a means for directing a laser beam (22) at a signal film (12) having radar return pulse intensity information recorded thereon, a resultant laser beam (32) then passing through a range telescope (34), an azimuth telescope (38), and a Fourier transform filter (36) located between the range and azimuth telescopes, thereby forming an image for recordation on an image film (40), a compensation means for doppler shift in the radar return pulse intensity information includes a beam splitter (46) for reflecting the modulated laser beam, after having passed through the Fourier transform filter (36), to a detection screen (48) having two photodiodes (66 and 68) mounted thereon. The photodiodes are positioned on each side of the Gaussian distribution of the Fourier transform spectrum reflected by the beam splitter (46).