Showing papers by "General Dynamics published in 1990"

Higher-ordered and intraconnected bidirectional associative memories

Abstract: The relationship between autocorrelators and heterocorrelators is examined. A review of the encoding algorithms, recall operations, stability proofs, and capacity arguments of first- and higher-order autocorrelator, commonly referred to as Hopfield associative memories (HAMs), and referred to as bidirectional associated memories (BAMs), is presented. Higher-ordered BAM's and first- and higher-ordered intraconnected BAM's are introduced. The encoding, recall, and stability procedures of each are discussed. Simulation results that compare the storage capacity and storage efficiency of three heterocorrelators, the heteroassociative HAM (HHAM), the BAM, and the intraconnected BAM (IBAM), are presented. The simulation suites were conducted for first-order, direct second-order, and general second-order heterocorrelators with a total pattern dimensionality of 4, 10, 20, 50, and 100. Each suite consisted of between 150 and 1000 separate program executions. >

High power laser array with stable wavelength

Abstract: A semiconductor diode laser is aligned to a waveguide with two sections, a first section being a passive low-loss waveguide and a second section being a Bragg grating. The first section works to increase the total cavity length l of the laser by about 1 to 2 cm. The lengthening of the cavity reduces the longitudinal mode spacing Δλ according to the equation Δλ=λ 2 /2nl, and provides a higher average output power level because it is substantially immune to mode hop-induced fluctuations. The second section causes the output to be centered at the desired wavelength depending on the grating spacing. An array of diode lasers with an array of waveguides as described above provides a high power source with a controlled bandwidth. The high power laser array with stabilized output wavelength is used to pump a solid state laser crystal.

Reconciling steady-state Kalman and alpha-beta filter design

Abstract: The deterministic design of the alpha-beta filter and the stochastic design of its Kalman counterpart are placed on a common basis. The first step is to find the continuous-time filter architecture which transforms into the alpha-beta discrete filter via the method of impulse invariance. This yields relations between filter bandwidth and damping ratio and the coefficients, alpha and beta . In the Kalman case, these same coefficients are related to a defined stochastic signal-to-noise ratio and to a defined normalized tracking error variance. These latter relations are obtained from a closed-form, unique, positive-definite solution to the matrix Riccati equation for the tracking error covariance. A nomograph is given that relates the stochastic and deterministic designs. >

Payload adapter ring

Abstract: A payload interface ring adapted to releasably secure a payload to a multiple payload adapter arranged to be carried into outer space by a launch vehicle for positioning of the payload in a suitable orbit relative to the earth. The interface ring includes a latching mechanism secured to a base to receive a berthing pin carried by the payload and to releasably latch the berthing pin for securing of the payload for transport of the payload to a desired orbit. A plurality of springs cooperate with the berthing pins and the latching mechamism to secure the payload in a desired latched position during transport to the desired orbit. An electrical solenoid cooperates with the biasing springs and the latching mechanism to simultaneously unlatch the latching mechanisms to free the berthing pins and actuate a spring loaded actuator whereby the payload previously secured as to the payload interface ring is released from the interface ring and the spring loaded actuator forcibly separates the payload from the interface ring.

Low-speed unsteady aerodynamics of a pitching straked wing at high incidence-Part II: Harmonic analysis

Abstract: Part I of this paper described the wind-tunnel model and test program. This part presents data from the test that are amenable to harmonic analysis that limits the amplitudes to about ±4 or ±6 deg but does not limit mean angles or frequencies. Those results are applicable to flutter and dynamic response problems as well as stability and control characteristics at high incidences. Force, pressure, and flow-visualization data are used to describe the perceived flow phenomena and how they interact with the model to produce the aerodynamic forces*

Method and apparatus for inducing grain orientation by magnetic and electric field ordering during bulk superconductor synthesis

Abstract: A process is described for enhancing superconductor characteristics by application of strong magnetic and/or electric fields to the constituent component materials from which ceramic superconductors are being formed and during the time that these superconductors are being synthesized. This process has particular applicability to the production of superconducting oxide ceramics such as the cuprates. The required magnetic fields are on the order of 1-10 tesla and the required electric fields are on the order of 0.1-1 MV/cm. The fields act as ordering mechanisms and induce grain orientation. The magnetic field aligns the magnetic moment of the grains. The electric field induces electric polarization in the grains and then aligns them. The superconducting structure formation occurs during the sintering, cooling and annealing phases of the fabrication process. Superconductivity is strongly affected by the oxygen stoichiometry in the lattice elemental cell. Applied electric fields cause elongation of the unit cell. This accelerates oxygen diffusion throughout the lattice and this gives better control of the oxygen content of the sample. Applied magnetic fields exert a magnetic pressure on the sample. This invention produces ceramic superconducting materials with a high degree of grain orientation and current density properties equivalent to or exceeding many of the existing superconducting materials.

Apparatus for cleaning and/or fluxing circuit card assemblies

Abstract: Apparatus and a process are disclosed for cleaning and/or fluxing circuit card assemblies. The assemblies are moved through an enclosure in which they are sprayed with cleaning and/or fluxing liquid from fenestrated cylinders rotating above and below the path of the assemblies and disposed laterally thereacross. The complex spray impact pattern created by the simultaneous movements of the assemblies and the cylinders effects thorough cleaning and/or fluxing of the assemblies. Separate control of liquid pressure from the cylinders prevents unsoldered components from being dislodged from the assemblies during cleaning and or fluxing.

Holographic communications device and method

Abstract: A holographic device and method encrypts a time dependent data signal, s(t), by a complex time dependent phase shifting signal. This produces a new signal whose modulus is equal the absolute value of the data signal, s(t), but has widely spread the frequency of the data signal. This new complex signal is mathematically transformed, producing an amplitude and phase spectrum (or a real and imaginary transform spectrum) of signal components. The amplitude and phase signals are modulated into a radio frequency carrier (or some other radiating source) as quadrature components and transmitted. At the receiver, the quadrature signals are separated into an amplitude and phase components which are then mathematically inverse transformed. The result is a complex signal with a real and imaginary components. The resulting signal is an accurate representation of the original data signal if a complete signal is recovered. If only a portion of the frequencies transmitted are recovered, the modulus is still represents the data signal, but may have artifacts frequencies in the signal. The modulus may then be filtered to remove these artifact frequencies, recovering the reconstructed data signal.

Mechanically actuated swing clamp

Abstract: A swing clamp for clamping work pieces to a fixture is mechanically actuated. The clamp has a body with a base. The base has a threaded hole in it. A mandrel is carried by the body. A clamp member is mounted to one end of the mandrel. A shaft extends through the mandrel and engages a threaded hole in the base. A translational device changes rotational movement of the shaft to linear movement of the mandrel. A guide causes the mandrel to swing about 90 degrees during this linear movement. This releases and actuates the clamp member.

Online adaptive control of unstable aircraft wing flutter

Abstract: The performance of an adaptive flutter suppression system (AFSS) was demonstrated on a flutter model in a wind tunnel. The AFSS used canonical variate analysis (CVA) to identify stable and unstable plants under feedback control. The control laws were developed online using linear quadratic control design and the CVA identified plant. The AFSS was tested for changing wind tunnel conditions, different external store configurations, and a sudden change from a stable plant to an unstable plant by the release of an external store. >

Liquid-solid propulsion system and method

Abstract: A liquid-solid propulsion system having a tank of liquid oxygen and a high pressure chamber loaded with solid grain fuel with a portion of the liquid oxygen being passed through a heat exchanger to convert the liquid oxygen to gaseous oxygen. The gaseous oxygen is directed to the chamber or solid grain fuel to induce a fuel rich gas burn that is directed to a thrust chamber which also receives liquid oxygen to increase the characteristic velocity of the exhaust and thereby provide the specific impulse of the propulsion system. The gaseous oxygen is also directed to the liquid oxygen tank to pressurize the flow of liquid oxygen from the tank. Valves are interposed to control the flow of liquid and gaseous oxygen to provide the required mixture ratio in the thrust chamber for optimum specific impulse or to terminate the thrust of the propulsion system. A method for providing the liquid-solid propulsion system is also disclosed.

Inflatable bladder submunition dispensing system

Abstract: A submunition dispensing system is disclosed which includes inflatable bladders expandable from collapsed to inflated conditions in response to fluid pressure. The bladders are mounted in cavities of a carrier frame underlying subpacks of submunitions. The bladders lie adjacent to the support and central structures of the frame defining the cavities. Each bladder can be configured to have either an unpleated or a pleated configuration in the collapsed condition. The bladder can also be configured for expansion to an overall constant diameter outer shape or to a generally conical outer shape in the inflated condition. Expansion to the conical shape imparts a velocity gradient to the subpack. The dispensing system also includes retaining assemblies for releasably retaining the subpacks in the cavities against the collapsed bladders and a gas generator disposed in a passage of the central structure of the carrier frame. The gas generator is actuated at the proper instant to deliver pressurized fluid to the collapsed bladders expanding them from the collapsed to inflated conditions and causing ejection of the subpacks from the cavities.

Quality Assessment of Hotel & Restaurant Management Graduates: Are we Meeting our Mission?

Abstract: Sixty employers who hired graduates from the Division of Hotel and Restaurant Management at the University of North Texas were surveyed. The purpose of the study was to assess the of quality of the graduates based upon their level of competence in their current managerial positions. The levels of manager satisfaction with 36 manager-trainee competencies were identified by the researchers. The findings of this survey can assist in developing the appropriate curriculum to meet this program's educational mission.

Method of monolithic temperature-stabilization of a laser diode by evanescent coupling to a temperature stable grating

Abstract: An integral waveguide is formed in the epitaxial layers as a continuation of a diode laser. The waveguide runs away from the laser active region. Light is coupled out of the laser and its integral waveguide into a dielectric waveguide which runs parallel and adjacent to the integral waveguide. Processing to form the temperature-stabilized Bragg grating, therefore, need not be performed on the laser substrate directly adjacent to the active area, but can be done some distance away to avoid damage to the laser's active area.

The mean flow structure on the symmetry plane of a turbulent junction vortex

Abstract: A two-channel, two-color LDV system allowed nonintrusive measurements of the two velocity components on the symmetry plane. Extensive measurements were made in and around the separation point and within the junction vortex system, both very close to the floor and to the leading edge of the body generating the vortex system

Demonstration of probabilistic-based durability analysis method for metallic airframes

Abstract: Two different variations of a probabilistic-based durability analysis method are demonstrated and evaluated for countersunk fastener holes in the lower wing skin (7475-T7351 aluminum) of a fighter aircraft. The initial fatigue quality of the fastener holes is represented by an equivalent initial flaw size (EIFS) distribution/Probability of crack exceedance predictions at any service time are based on an EIFS distribution and two different service crack growth approaches. The service crack growth is divided into two segments. Segment 1 covers the small crack size region (e.g., 1.27 mm). Approach I treats the service crack growth as deterministic for both segments. In approach II, the service crack growth is treated as deterministic in segment 1 and stochastic in segment 2. Analytical predictions for the extent of damage (i.e., number of fastener holes exceeding specified sizes), based on approaches I and II, are compared and correlated with experimental results. Good correlations are obtained for both approaches. Approach II was found to be more conservative than approach I. Nomenclature #0 = reference crack size 0 (0) = EIFS at time t = 0 a(t) = crack size at time t AL, AU = lower and upper bound crack sizes, respectively, defining the range of fractographic data used for determining EIFS b\,b2 - crack-growth-rate exponents for crack growth segments 1 and 2, respectively (b\-bi=\\ used herein) fx(u) = probability density function of the lognormal random variable X

Rugate filter on diode laser for temperature stabilized emission wavelength

Abstract: The rugate filter comprises a glass film which is deposited on one or both end facets of a diode laser. The glass film has a continuously varying refractive index with thickness, usually in the form of a sine wave or a "windowed" sine wave. Such a film may be deposited by ion-assisted co-deposition techniques in which the concentration of the higher refractive index material is periodically varied according to the period required to produce the desired filter. The glass of which the rugate filter is formed has an average refractive index which does not vary with temperature by more than 10-6 /°C. By reflecting light at the peak wavelength back into the laser, the laser is caused to emit at the desired wavelength. Since the rugate filter selectively reflects light within a narrow band of the desired wavelength, the laser emits light within a narrow peak on the order of 10 Å or less.

Method and apparatus of integrating Global Positioning System and Inertial Navigation System without using accelerometers

Abstract: A method and arrangement for integrating a Global Positioning System and an Inertial Navigating System without the use of accelerometers to provided a velocity steering signal that is utilized in the guidance of a flying vehicle, such as a space craft. The method and arrangement do not require the use of accelerometers. A mechanization for interfacing the integrated Global Positioning System and the Inertial Navigating System with a flight control system which controls a flying vehicle is disclosed.

Effect of shaft rotation on the incompressible flow in a labyrinth seal

Abstract: A computational/experimental study was conducted concerning the incompressible flow in a labyrinth seal at low leakage rates over a wide range of seal rotation rates. The predictions were obtained using a finite-difference code that utilized a higher order differencing scheme (QUICK) to reduce the effects of false diffusion. Measured inlet boundary conditions for the axial and swirl velocity components as well as turbulence kinetic energy were employed. This yielded fair agreement between velocity predictions and hot-film anemometer measurements. The effects of seal rotation rate on the overall pressure drop are presented in terms of a loss coefficient. It was determined that when the rotation rate is increased beyond a certain point, a second recirculation zone (SRZ) forms inside the seal cavity. This dramatically alters the flowfield in the cavity and results in a substantial increase in the pressure drop across it. A flow map is presented indicating the approximate rotation rate required to produce this phenomenon at a given leakage rate. Unfortunately, for most practical applications, the SRZ will not form until an extremely high shaft speed is reached.

Digital pulse processor for determining leading and trailing time-of-arrival

Abstract: A Digital Pulse Processor (DPP) designed to accept pulsed inputs and produce digital pulse descriptor word (PDW) outputs accepts pulsed signals from three adjacent channelized inputs. The DPP then derives a measurement of pulse amplitude from the peak value in the center frequency channel. The relative peak amplitudes between channels are used to establish aa fine frequency offset. The fine frequency offset is used in conjunction with coarse frequency inputs to compute a pulse frequency estimate. An internal counter generates a time reference for time of arrival (TOA) and pulse width measurements. The TOA and pulse width measurements are based on calculations to establish three dB points on the leading and trailing edges of the pulse. This pulse characterization information is produced in real time at the optimum signal-to-noise ratio, and is independent of incoming amplitude, rise/fall time, and pulse width. The pulse characterization information is accumulated and formatted into four 16-bit PDWs for output during the subsequent pulse processing period A RESET output is generated to mark the end of the pulse processing period, both for normal operation and for cases where a pulse is expected (based on normal input control) but is not detected.

Apparatus for detecting sonar signals embedded in noise

Abstract: Apparatus for detecting sonar signals embedded in noise includes a neural network trained to detect signals in response to the slope of amplitude rank ordered noise corrected powers. A detector detects an analog waveform. Means samples and digitizes the analog waveform to obtain digital samples which in turn are passed through a cosine window. The digital samples are Fourier transformed into conjugate sets of complex numbers representing amplitude and phase. One conjugate set of the complex numbers are discarded, and the remaining complex numbers ranked according to frequency. The sum of the square of the real and imaginary component of each of the remaining complex numbers in a frequency band are provided to obtain a corresponding series of representing estimated power ranked by frequency over the band. The noise contained in subbands of the band is estimated. Each estimated power is then divided by the estimated noise of the subband containing the estimated power to obtain corresponding noise corrected powers, which are ranked ordered according to amplitude. The amplitude rank ordered noise powers are provided to corresponding inputs of the neural network.

Steady and unsteady force testing of fighter aircraft models in a water tunnel

Abstract: The force testing of small-scale models in a water tunnel was investigated as an inexpensive and quick means to obtain static and dynamic force and moment data representative of full-scale fighter aircraft maneuvering in the post-stall regime. Force tests of flat plate and three-dimensional full span models were conducted in General Dynamicsf 24 x 24 in2 horizonal flow water tunnel using a special balance developed and built by General Dynamics. Steady incidence sweeps and unsteady pitch-pulse motions to a maximum angle of 90 deg were YKvestigated for several planforms and models. Some specific objectives of this study were to: (1) verify that static and dynamic force and moment measurements from water tunnel testing were representative of large-scale wind tunnel tests; (2) demonstrate the importance of model three-dimensionality; (3) evaluate the effects of planform geometry; and (4) investigate dynamic stability and controllability aspects of the "Cobraw maneuver performed by Pougachev in a Russian SU-27.

Radome diagnostic system

Abstract: A radome diagnostic system comprises a rotatably mounted turntable having support memebers for supporting a radome in a radome support area on the turntable, and a scanning assembly on the turntable for supporting a probe antenna in the radome support area and for translating the probe antenna in perpendicular x and y directions to cover a predetermined planar scanning area. A reference antenna is mounted on the turntable to provide a reference signal, and both the reference antenna and the probe antenna are connected to a suitable receiver for receiving signals from them and for suitably analyzing the collected data. A transmitter is located at a position remote from the turntable to direct radiation towards a radome mounted on the turntable. The probe antenna will detect radiation as degraded or modified by the effect of the presence of the radome in the radiation path. The reference antenna receives unperturbed radiation.

Emitter identification from radio signals using keyclick algorithm

Abstract: An algorithm for emitter identification of a transmitting platform using microphone keyclick analysis, and a system utilizing said algorithm, wherein said algorithm processes audio signals to detect transmission activity on a radio channel in the audio frequency range, detects the boundaries of transmitter keyclicks at the beginning and end of said transmission; extracts keying envelopes from said detected keyclick boundaries; and analyzes said keying envelopes to extract features characteristic of said keyclicks. The algorithm and system then proceed to execute a decision function based on said extracted characteristic features to identify the platform of said transmitter based on the features of said keyclick. A second algorithm, which may be executed in parallel with the first by said system, processes said transmission data using a fast fourier transform, detecting gaps in said processed transmission data. It then extracts spectral features consisting of normalized energy per unit frequency from said gaps; and correlates identification of said emitter platforms based on said extracted spectral features with identification of said emitter platforms based on said extracted keyclick features.