摘要:
A system for generating variable substitution boxes from arbitrary keys for use in a block cipher system utilizes an initial set of linearly independent numbers (13) to generate substitution tables (15). The initial set of linearly independent numbers (13) is modulated with the bits of an arbitrary key through operations that result in final sets of linearly independent numbers to form the substitution tables (15). The system also includes an implementation which allows for rapid key changes for the crypto system by only generating portions of the substitution tables as needed for specific blocks of input data to be encrypted or decrypted.
摘要:
Method and apparatus for nonlinearizing modulo 2 addition (24) based encryption by block substitution techniques which allows use of the substitution scheme with relatively simple hardware and yet makes cryptanalysis more difficult. The basic block substitution (22), a one to one mapping of n bit binary numbers onto themselves, is based on the fact that certain permutations of the n bit binary numbers define a block substitution by modulo 2 addition (24) of one permuted set of numbers to another, and that a subset of these define equations having an additive relationship when viewed as vectors. This allows the simple changing of the transformation on a frequent basis. Then the equations are nonlinearized, also in an orderly (34) and readily variable manner, so that the remainder of the set equations may no longer be generated from a limited subset of the equations. Various properties of the transformations and methods of using the same are disclosed.
摘要:
A process for preparing metal oxides from ferrometal and nickel metal alloys is disclosed comprising first providing a ferrometal or nickel metal alloy containing an oxide forming metal, hydriding the alloy to an effective temperature and pressure with hydrogen containing gas, subdividing then carbiding the hydrided product at a temperature above about 500° C to form carbides, then employing an aqueous acid leach to dissolve the iron or nickel carbide and separating the acid soluble from the acid insoluble carbides. The acid insoluble carbides are reacted with oxygen at an elevated temperature for a time sufficient to form the metal oxides of said carbides.
摘要:
A method for preparing and recovering metal oxides from their ferrometal and nickel metal alloys. Exemplary steps of the process include reacting the alloy with hydrogen followed by subdividing the hydrided product and nitriding the subdivided material to form mixed metal nitrides. The mixed metal nitrides are then contacted with an aqueous acid leach portion to dissolve any ferro or nickel nitride present. The insoluble metal nitrides are then reacted to form the metal oxide product.
摘要:
In accordance with the present invention, a BOE-corrected, off-axis image forming apparatus is disclosed. The apparatus (10) has a first stage (12) with a primary reflective member (14) disposed to reflect light incident from an entrance pupil (16) of the apparatus, and a second stage (20) located off-axis with respect to the first stage (12). The second stage (20) is defined by a secondary reflective assembly which includes a secondary reflective member (22) disposed to direct light reflected from the primary reflective member (14), to an image plane (28). A binary optical element (BOE) (26), which has higher order optical power for providing aspheric correction but substantially zero first order optical power, is provided in a plane through one of the stages for correcting, in the image space, aberrations introduced by the reflective members.
摘要:
An aerial gunnery target (42) which is towed behind a towing aircraft (24). The gunnery target includes an extension device (46) that separates a forebody assembly (48) from a visual augmenter (44). The target (42) also includes a vented inflator (56) positioned at the forward end of the visual augmenter (44). The vented inflator (56) maintains the front end of the visual augmenter (44) open during towing. The visual augmenter (44) is generally cylindrical in shape with an open aft end and an adjustment device for varying the size of the aft opening. In addition, the visual body is comprised of a mesh netting (54) which preferably includes a plurality of interconnected strands (94) joined together to form a plurality of diamond shaped openings. The interconnected strands are each formed of a plurality of knitted threads and the strands are preferably joined together by knitting some or all of threads of one strand with some or all of the threads of an interconnecting strand.
摘要:
A modular air-driven pump (10) includes an air motor and various sized fluid pumps (14) which are interchangeably mountable to the air motor. The air motor includes first and second bulkheads (28, 30), a motor cylinder held between the first and second bulkheads, and a motor piston (24) within the motor cylinder (22). An air control system (26) supplies air from an air inlet (42) to the motor cylinder (34) alternately on each side of the motor piston while venting the motor cylinder on an opposite side of the motor piston to an air outlet (44) to reciprocate the motor piston. The first bulkhead has an opening substantially coaxial with the motor cylinder and first and second cylindrically-shaped and coaxial recesses (48, 50) at an outward side of the first bulkhead which surround the opening. The second recess has a larger diameter and a smaller depth than the first recess so that they are stair stepped. Each of the first and second fluid pumps include an end block (74), a pump cylinder (82) held between the end block and the first bulkhead coaxial with the motor cylinder and within one of the recesses, and a pump piston (76) within said pump cylinder. The pump piston is removably connected to the motor piston through the opening for reciprocable movement of the pump piston with the motor piston. The pump cylinder of the first fluid pump is sized and shaped for cooperating with the first recess of the first bulkhead and the pump cylinder of the second fluid pump is sized and shaped for cooperating with the second recess of the first bulkhead. An air-motor enclosure surrounds the air motor and a fluid-pump enclosure surrounds the fluid pump. The fluid-pump enclosure forms an exhaust plenum in fluid communication with the air outlet and has an exhaust outlet to reduce noise created by exhausting air.
摘要:
Nickel-base alloys with improved elevated temperature creep and stress rupture lives are disclosed which are particularly useful for components in gas turbine engines exposed to high temperatures and stresses for long periods of time. The alloys are nickel-based consisting essentially of 0.005 to 0.15 % C, 0.10 to 11 % Mo, 0.10 to 4.25 % W , from 12 to 31 % Cr, 0.25 to 21 % Co, up to 5 % Fe, 0.10 to 3.75 % Nb, 0.10 to 1.25 % Ta, 0.01 to 0.10 % Zr, 0.10 to 0.50 % Mn, 0.10 to 1 % V, 1.8-4.75 % Ti, 0.5 to 5.25 % Al, less than 0.003 % P, and 0.004 to 0.025 % B. Key to the improvement of creep and stress rupture lives is the extremely low P content in conjunction with high B contents.
摘要:
Nb 47 wt.% Ti compositions having an increased iron content of from greater than 200 to about 2000 ppm have improved superconducting properties. Preferred levels for high energy physics applications are about 46 to 48 wt.% titanium, about 500 to 700 ppm iron and about 400 to 700 ppm oxygen and preferred levels for energy storage and MRI applications are about 52 to 55 wt.% titanium, about 500 to about 1000 ppm iron, and about 350 to 500 ppm oxygen. These compositions develop a fine, distributed ribbon shaped precipitate morphology when made into wires which increases the upper critical field. This permits the flow of high critical current density in the 5 to 10 Tesla range at 4.2 Kelvin. Multifilamentary wires made of these compositions form superconducting products having about the same critical current properties at 5 Tesla as products made with less than 200 ppm iron. However, they have improved upper critical field strength and an improved critical current value at all fields above 5 Tesla as compared to the lower iron containing compositions. Preferable compositions have an upper critical field strength which is at least 0.25 Tesla greater than that of the lower iron containing compositions.
摘要:
A controlled acceleration platform (32) which provides a horizontally quiet platform capable of accurate acceleration and angular control. An object at or near the center of percussion of the pendulum assembly experiences reduced seismic and cultural ground vibration, and experiences negligible hysteresis and stiction for minute adjustment in inclination. By ridigly attaching the device to a single pivot or flexure (36) so as to isolate the accelerometer (42) from seismic or cultural vibration, the small tilt associated with pendulous motion at the proper radius from the flexure completely cancels the inertial term. The suspended item is also isolated from small error producing effects such as earth tide, local ground swell from solar heating, and far field gravity changes as produced by the sun and the moon. The lateral acceleration sensed by the suspended item may be adjusted by controlling tilt of the platform. This can be done by adding weight at a distance from the center line. With an accelerometer attached, the platform can also be used to measure very minute applications of force.