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Frequency stabilizing circuit controls output of multichannel microwave oscillator using passband filters and selector logic to eliminate need for separate crystal diode voltage controlled oscillator (VCO).
The performance and capabilities of the DSN 64 m antennas at X-band are considered including extensive modifications to the XRO cone assemblies. The changes include a feed assembly with a dual hybrid mode horn and orthogonal mode junction, dual traveling wave masers, and receiver mode selector.
The historical origin and general history of vertical current total energy variometer, including its optimum airspeed selector ring are reviewed, and some later developments of it are discussed. Polars of three sailplanes of different spans are charted for straight and circling flight, then plotted to reveal their parabolic anomaly and the effect of circling flight sink rate. These effects are further analyzed for their influence on the transient compensation of NETTO variometers as well as the speed ring. Some other disturbances due to the quality of sailplane preparation and flight dynamics are listed. Conclusions are drawn about the problems to pilots from imperfect NETTO variometer compensation and its effect on the maximization of ground speed from the speed ring. A modification for improvements to the speed ring and computer is suggested.
Two etalons and monochromator mode selector help calibrate spectrometer in selected laser mode. Technique accurately determines free spectral range of etalon. By establishing number of fringes between two modes, both of which have been calibrated with molecular line standards, one finds free spectral range with error inversely proportional to spectral interval between calibration points. Procedure establishes free spectral range of etalon without prior knowledge of its length or refractive index.
Generator rotates electron beam and performs other convenient functions during welding process. Device eliminates time-consuming techniques relying heavily on operator's skill. Welding speed is varied with frequency selector, and amplitudes of x- and y-axes are varied by adjusting phase shift. Both high and low-range adjustments are available, and each axis can be separately controlled. Crosshair is provided for set-up and beam alinements.
The paper describes a 1-m high-resolution wide field-of-view telescope (Starlab) to be used on board the Space Shuttle. The purpose of Starlab is to obtain optical astronomical observations in the UV domain of the spectrum. The discussion focuses on scientific programs and technical description of the Starlab. The use of photographic film and rapid reconfiguration is possible because Starlab is flown in the Shuttle-attached mode. The Starlab uses an f/15-modified Ritchey-Chretien telescope, followed by an instrument selector that gives access to the conventional Cassegrain focus or, by inserting a diagonal mirror, to a radial focal plane. Results of five critical subsystem-design studies confirm the feasibility of using state-of-the-art design practices in meeting the Starlab science and engineering requirements.
The paper deals with an approach which can improve the accuracy of etalon calibration of tunable diode-laser (TDL) spectra in the IR and extend absolute calibration among several isolated modes. Two etalons placed in the laser beam produce a combined fringe pattern that, with the aid of a monochromator mode selector, can be used to establish the number of fringes between any two spectral points separated by a large frequency interval. This technique has been applied to several similar cases for calibration of isolated modes or verification of the identity of lines of known frequency.
A system for automatically verifying the connections between terminals of a patchboard is described. The system includes a back plane having a plurality of plugs corresponding to the pins of the patchboard. A number of decoders are connected to the plugs of the back plane so that a signal can be sequentially applied to each plug of the back plane under control of a stepping register and a control circuit. A plurality of data selectors are also connected to the plugs of the back plane and under control of a second external register. This control circuit sequentially makes connections between an output circuit and the plugs of the back plane so as to patch the signal applied to a respective plug through a patch connection to the output circuit. The precise locations of the patches on the patchboard can be identified and compared with previously stored information in a memory unit.
A redundancy management system is described wherein input signals from a sensor are provided redundantly in parallel so that a primary control signal may be selected. Median value signals for groups of three sensors are detected in median value selectors of selection filter. The detected median value signals are then also compared in a subtractor/comparator to determine whether any of them exceed the others by an amount greater than the signal level for a failed sensor. If so, the exceeding detected medium value signal is sent to a control computer as the primary control signal. If not, the lowest level detected medium value signal is sent as the primary control signal.
A passive hydrogen maser employing a smaller microwave cavity than previous masers is described. The volume of the entire resonator package, including a conventional source, hexapole state selector, and four magnetic shields, is estimated at 20 liters. The techniques for constructing the ceramic cavity, coating it with FEP, and attaching the endcaps to achieve a stable container (to allow its use as a single vacuum system) are described in detail. Frequency stability measurements were made of four such masers, against an NBS-4 cesium primary standard, against each other, and against eight commercial cesium clocks; frequency stability level is reported as 1.7 x 10 to the -12th tau exp -1/2 from 1 to 100,000 sec, and no drift above 1 x 10 to the -15th/day was found. Pressure and temperature effects on frequency stability were found at the 1 x 10 to the -14th level. Noise behavior beyond 200,000 sec is characterized as random walk. The potential use of a compact stable maser as a clock is suggested.
Leakage suppressed despite O-ring wear. New design eliminates leakage in vacuum selector valve on Space Shuttle waste-control subsystem. Applied to improve sealing in laboratory and industrial vacuum systems and other plumbing involving switching among lines with pressure differentials of order of 1 atmosphere (0.1 MPa).
At an altitude of 1890m, a pre-test with an Air shower (AS) core selector and a small acoustic array set up in an anechoic pool with a volume of 20x7x7 cu m was performed, beginning in Aug. 1984. In analyzing the waveforms recorded during the effective working time of 186 hrs, three acoustic signals which cannot be explained as from any source other than AS cores were obtained, and an estimation of related parameters was made.
Digital values in a moving window are compared by an operator having nine comparators connected to line buffers for receiving a succession of central pixels together with eight neighborhood pixels. A single bit of program control determines whether the neighborhood pixels are to be compared with the central pixel or a threshold value. The central pixel is always compared with the threshold. The omparator output plus 2 bits indicating odd-even pixel/line information about the central pixel addresses a lookup table to provide 14 bits of information, including 2 bits which control a selector to pass either the central pixel value, the other 12 bits of table information, or the bit-wise logical OR of all nine pixels through circuit that implements a very wide OR gate.
The objective is to extend the recent advances in robust control system design of multivariable systems to sensor failure detection, isolation, and accommodation (DIA), and estimator design. This effort provides analysis tools to quantify the trade-off between performance robustness and DIA sensitivity, which are to be used to achieve higher levels of performance robustness for given levels of DIA sensitivity. An innovations-based DIA scheme is used. Estimators, which depend upon a model of the process and process inputs and outputs, are used to generate these innovations. Thresholds used to determine failure detection are computed based on bounds on modeling errors, noise properties, and the class of failures. The applicability of the newly developed tools are demonstrated on a multivariable aircraft turbojet engine example. A new concept call the threshold selector was developed. It represents a significant and innovative tool for the analysis and synthesis of DiA algorithms. The estimators were made robust by introduction of an internal model and by frequency shaping. The internal mode provides asymptotically unbiased filter estimates.The incorporation of frequency shaping of the Linear Quadratic Gaussian cost functional modifies the estimator design to make it suitable for sensor failure DIA. The results are compared with previous studies which used thresholds that were selcted empirically. Comparison of these two techniques on a nonlinear dynamic engine simulation shows improved performance of the new method compared to previous techniques
Recent advances in multivariable robust control system design are extended to sensor failure, detection, isolation, and accommodation (FDIA) and estimator design. A new concept called threshold selector is introduced. It represents a significant and innovative tool for the analysis and synthesis of FDIA algorithms. Analytical results are obtained for the SISO case to compute optimal thresholds and size of minimum detectable failures, and a computer-aided technique is developed for the multivariable case. The techniques have been applied to sensor FDIA for an aircraft turbine engine control system.
A pattern recognition system was developed that successfully recognizes simulated spectra of five different types of transportation noise sources. The system generates hyperplanes during a training stage to separate the classes and correctly classify unknown patterns in classification mode. A feature selector in the system reduces a large number of features to a smaller optimal set, maximizing performance and minimizing computation.
A calibration model for the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) is studied. This model not only removes major drawbacks of the current calibration model but also helps us understand the performance degradation of the aging instrument. The current Nimbus-7 SMMR calibration algorithm was derived without considering the interference effect between the two orthogonally polarized signals merging at a ferrite polarization selector switch. The resulting calibrated brightness temperatures, considered as a function of scan angle phi, are not symmetric around phi=0. However, neither the origin of the asymmetry nor the manner in which the two orthogonal components are mixed is fully understood. The proposed calibration model incorporates all the leakage factors associated with the ferrite switches along the signal paths. The resulting calibration equations clarify how the orthogonal components of surface brightness are coupled at radiometers. As a consequence, the origin of the asymmetry is clearly identified and explained. In addition, the feasibility of absolute calibration using in-orbit data is discussed.
The objective is to familiarize students with steady and unsteady heat transfer by conduction and with the effect of thermal conductivity upon temperature distribution through a homogeneous substance. The elementary heat conduction experiment presented is designed for associate degree technology students in a simple manner to enhance their intuition and to clarify many confusing concepts such as temperature, thermal energy, thermal conductivity, heat, transient and steady flows. The equipment set is safe, small, portable (10 kg) and relatively cheap (about $1200): the electric hot plate 2 kg (4.4 lb) for $175: the 24 channel selector and Thermocouple Digital Readout (Trendicator) 4.5 kg (10 lb) for about $1000; the three metal specimens (each of 2.5 cm diameter and 11 cm length), base plate and the bucket all about 3 kg (7 lb) for about $25. The experiment may take from 60 to 70 minutes. Although the hot plate surface temperature could be set from 90 to 370 C (maximum of 750 watts) it is a good practice to work with temperatures of 180 to 200 C (about 400 watts). They may experiment in squads of 2, 3 or even 4, or the instructor may demonstrate it for the whole class.