Abstract: A hydrogen-fueled fuel cell reacts residual fuel in the exhaust of the anode flow field either in a catalytic converter or by feeding the anode exhaust into the cathode oxidant stream. Control of flow of anode exhaust into the cathode oxidant stream may be in response to a flammability sensor, a gas composition analyzer, current output, or periodically in response to a timer; the anode exhaust may be fed either upstream or downstream of the cathode air inlet blower.

Abstract: During start up, a fuel cell is warmed to operating temperature by introducing a dilute hydrogen/air mixture into the normal process oxidant channels of the fuel cell where it reacts with a noble metal or noble metal alloy catalyst to produce heat at subflame temperatures. In one embodiment, catalyst is provided in a structure between the cathode and the process oxidant channels; if the structure is not sufficiently hydrophobic to allow the hydrogen/fuel mixture to reach it, such structure may be specially produced with hydrophobic regions to assure ice-free passages; in a structure with sufficient hydrophobic regions, only the catalyst need be added. In embodiments with a hydrophobic cathode, no structural modification is required; or a hydrophilic cathode may be provided with hydrophobic regions.

Abstract: An aircraft autopilot system provides a wind correction angle which is added to the desired course to provide commanded heading, the wind correction angle being generated as a proportional and integral function of ground track error. When the aircraft is off its desired course, it can be returned to the desired course by means of a course intercept angle, added to the desired course, to provide a corrected commanded course, the course intercept angle being a proportional function of the perpendicular error (the lateral distance of the aircraft from the original course) suitably limited to some angle within 90.degree. of the desired course. The course correction angle may be generated as a proportion of the perpendicular course error determined by the degree of importance of accuracy, and may be switched over to a course directly toward a waypoint in dependence upon the importance of efficiency.

Abstract: One or more photonic crystals 11, 22, 40, 58, 59 are formed directly in the path of light within an optical fiber 13, 23, 42, 56. Light processed by the photonic crystal may be transmitted out of the fiber by means of a lens 48 or it may be measured by a photoresistive device 51, 60. The photonic crystal may be formed in a trench 12 as an array of dielectric rods 16 having one or more selective defects 17, or the crystal may be formed by providing holes 20 directly in the optical fiber. Filling the interstices between rods 16 with non-linear optical material, and subjecting the crystal to a varying electric field applied by electrodes or to a varying optical radiation can produce a tunable photonic crystal within an optical fiber.

Abstract: In a rotary wing aircraft, longitudinal groundspeed error and lateral groundspeed error are converted to earth coordinates, and the result scaled and integrated, and retransformed into aircraft coordinates for application to a pitch attitude control system and a roll attitude control system. The invention thus instantly transfers wind trim between the longitudinal and lateral channels, whenever a heading change is undertaken.

Abstract: A proton exchange membrane fuel cell has methanol or ethanol fed into the coolant passages during shut down so as to prevent water trapped therein from freezing in sub-freezing environments. Upon start-up, a controlled amount of air is fed through the cathode reactant flow field so that alcohol diffusing to the cathode catalyst is oxidized, producing heat which will raise the temperature of the fuel cell above freezing, and to a normal operating temperature. A heat exchanger in the coolant water circulating loop may be bypassed during start-up.

Abstract: The airspeed limiting performance envelope of a helicopter is converted to a groundspeed envelope by factoring-in the wind speed and direction. A groundspeed command for an unmanned helicopter is provided as a function of the range to the helicopter's destination. The function may be calculated so as to provide a nominal groundspeed command equal to a nominal groundspeed command limit, or the function may be a fixed function to cause the aircraft to creep toward final approach. The cosine and sine of the desired relative flight direction of the aircraft, which is equal to the true bearing to the destination minus the true heading of the aircraft, are utilized to scale the groundspeed command into a longitudinal groundspeed command and a lateral groundspeed command. If one of the groundspeed commands is over a corresponding limit, the other groundspeed command is scaled back so that the vector addition of the two commands will cause flight in the desired direction.

Abstract: A liquid cryogen withdrawal device includes a plug (14) for insertion into the neck of a cryogen-containing dewar (10) in gas-tight relationship. A withdrawal tube (17) passes through the plug to conduct liquid from the bottom of the dewar through a sintered bronze filter to a container to be filled with cryogen, and a pressure tube (19) fitted with a pump (20). Cryogen is stored in the dewar with a loose fitting cap thereon, with no withdrawal device in the dewar. When liquid is desired to be retrieved from the dewar, the withdrawal device is inserted into the dewar; and the pump is operated to create enough pressure to force a suitable amount of liquid from the dewar. The plug may have a gas pressure relief valve disposed thereon.

Abstract: A hand-held cryosurgical instrument is provided with an insulating, cold-resistive, non-slip grip, which fits onto the neck of a cryosurgical instrument by means of machined threads. The grip has a lip for the users hand to rest against to protect it from the cold metal of the instrument.

Abstract: A fiber laser 10 with square inner cladding 12, 29 may have a single core 11 codoped either with Ytterbium or Erbium or with Thulium and Holmium at a ratio of at least 10:1 operating in a single mode to provide eye-safe radiation with wavelengths above 1.5 micron. The single core laser has a pump clad cross sectional area about 2(10).sup.3 greater than the cross sectional area of the core. A multi-core laser has a plurality of single mode cores 28 doped with any rare earth ions, the cores equally spaced by at least two core diameters in an isometric array, in a cavity having a finesse of greater than ten, to produce a single, very bright phase-locked beam in the fundamental supermode. A method starts with hexagonal cladded-core rods 35, 36 in an isometric array, which are then fused and drawn down.

Abstract: A lens system for protecting high gain optical systems (eyes or equipment) from high intensity laser radiation includes a second mirror disposed on an exit lens, a first mirror formed by half silvering the inner surface of a focusing entry lens, and a medium such as sugar water containing aerosol particles of three-micron carbon, which induces ionization that will absorb the incoming laser radiation. One binocular embodiment uses the foregoing medium; a second binocular embodiment uses a solid lens material laden with aerosol particles.

Abstract: A microlens 30 is formed on the outer surface of an optical fiber 20 having an in-fiber Bragg grating 24 (FBG) formed in the core 21, 36 thereof, to focus light diffracted by the FBG onto other fibers or optical devices, or to focus light received at the fiber onto the FBG. Various single- and multi-microlens configurations of one or more fibers perform a variety of functions such as signal coupling, multiplexing, signal splitting, spectrography, tapped delay, timed-delay phase adjusting, circulating storage, and so forth. The microlenses may employ angle-increasing prisms and may comprise Fresnel lenses.

Abstract: In a cryosurgical instrument having a dewar and a cap which is threaded onto the dewar when in use, with a main valve portion secured to the cap by threads, the handedness of the threads on the main valve portion are opposite to the handedness of the cap threads, whereby applying thrust through the main valve portion to remove the cap from the dewar will tend to tighten, rather than loosen the main valve portion in the cap.

Abstract: The cap which is threaded onto the dewar of a cryosurgical instrument has a vent hole therethrough which is normally closed off by a gasket when the cap is secured to the dewar, but which can allow the venting of gaseous cryogen therethrough when the cap is loosened. The threads of the cap have a scalloped region in which the threads have been machined away so as to provide a passage for gaseous cryogen, whereby, when the cap is loosened on the dewar, pressure therein is released by gas escaping either through the hole or through the scalloped region of the threads.

Abstract: A pizza pan has a short vertical wall extending upwardly from near the center of its bottom so as to form a flat annular cooking surface. The bottom has no hole at the center of the annular cooking surface. A disclosed method of cooking pizza includes forcing the dough blank over and around the wall, and crimping the dough adjacent the wall as well as the dough at the outer periphery of the blank, so as to hold the cheese and sauce between crimps.

Abstract: An anchor 14 for a building roof structure tie-down strap 12 comprises a rectangular hollow steel box 27 having a keyhole 26 formed at one end of one surface, which slips over the head 24 of an anchor pin 17 permanently fixed in the foundation 19 of a building, and a pair of bolt holes 29 formed at an opposite end in a pair of adjacent surfaces to receive a bolt 30 for fastening a strap-tightening ratchet 13 to the box 27.

Abstract: A cargo restraint or net is formed of black longitudinal stringers 8, 9, yellow lateral stringers 10, 11 and a pair of yellow loops 12, 13 fastened to the stringers. Each end of the stringers has an adjustable jam cleat-type hook 18 thereon. Various net configurations are shown.

Abstract: A cargo restraint or net is formed of black longitudinal stringers 8, 9, yellow lateral stringers 10, 11 and a pair of yellow loops 12, 13 fastened to the stringers. Each end of the stringers has an adjustable jam cleat-type hook 18 thereon. Various net configurations are shown.