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Showing papers by "General Electric published in 1984"


Journal ArticleDOI
TL;DR: The longitudinal (T1) and transverse (T2) hydrogen (1H) nuclear magnetic resonance (NMR) relaxation times of normal human and animal tissue are compiled and reviewed as a function of tissue type, NMR frequency, temperature, species, in vivo versus in vitro status, time after excision, and age.
Abstract: The longitudinal (T1) and transverse (T2) hydrogen (1H) nuclear magnetic resonance (NMR) relaxation times of normal human and animal tissue in the frequency range 1-100 MHz are compiled and reviewed as a function of tissue type, NMR frequency, temperature, species, in vivo versus in vitro status, time after excision, and age. The dominant observed factors affecting T1 are tissue type and NMR frequency (V). All tissue frequency dispersions can be fitted to the simple expression T1 = AVB in the range 1-100 MHz, with A and B tissue-dependent constants. This equation provides as good or better fit to the data as previous more complex formulas. T2 is found to be multicomponent, essentially independent of NMR frequency, and dependent mainly on tissue type. Mean and raw values of T1 and T2 for each tissue are tabulated and/or plotted versus frequency and the fitting parameters A, B and the standard deviations determined to establish the normal range of relaxation times applicable to NMR imaging. The mechanisms for tissue NMR relaxation are reviewed with reference to the fast exchange two state (FETS) model of water in biological systems, and an overview of the dynamic state of water and macromolecular hydrogen compatible with the frequency, temperature, and multicomponent data is postulated. This suggests that 1H tissue T1 is determined predominantly by intermolecular (possibly rotational) interactions between macromolecules and a single bound hydration layer, and the T2 is governed mainly by exchange diffusion of water between the bound layer and a free water phase. Deficiencies in measurement techniques are identified as major sources of data irreproducibility.

1,166 citations



Journal ArticleDOI
Krishnamurthy1
TL;DR: This-paper generalizes the ideas of Fiduccia and Mattheyses and suggests a class of increasingly sophisticated heuristics, and shows that the computational complexity of any specific heuristic in the suggested class remains linear in the size of the network.
Abstract: Recently, a fast (linear) heuristic for improving min-cut partitions of VLSI networks was suggested by Fiduccia and Mattheyses [6]. In this-paper we generalize their ideas and suggest a class of increasingly sophisticated heuristics. We then show, by exploiting the data structures originally suggested by them, that the computational complexity of any specific heuristic in the suggested class remains linear in the size of the network.

373 citations


Journal ArticleDOI
TL;DR: In this paper, a low-power breadboard operating at 200-300 kHz has been built for switching power supplies and battery chargers, which can operate in either the step-up or step-down mode.
Abstract: Transistor dc-dc converters which employ a resonant circuit are described. A resonant circuit is driven with square waves of current or voltage, and by adjusting the frequency around the resonant point, the voltage on the resonant components can be adjusted to any practical voltage level. By rectifying the voltage across the resonant elements, a dc voltage is obtained which can be either higher or lower than the input dc voltage to the converter. Thus, the converter can operate in either the step-up or step-down mode. In addition, the switching losses in the inverter devices and rectifiers are extremely low due to the sine waves that occur from the use of a resonant circuit (as opposed to square waves in a conventional converter); also, easier EMI filtering should result. In the voltage input version, the converter is able to use the parasitic diode associated with an FET or monolithic Darlington, while in the current input version, the converter needs the inverse blocking capability which can be obtained with an IGT or GTO device. A low-power breadboard operating at 200-300 kHz has been built. Two typical application areas are switching power supplies and battery chargers. The converter circuits offer improvements over conventional circuits due to their high efficiency (low switching losses), small reactive components (high-frequency operation), and their step-up/stepdown ability.

371 citations


Journal ArticleDOI
TL;DR: A newly developed sparse implementation of an optimization method using exact second derivatives is applied to the optimal power flow problem, and an option to add shunt capacitors in the event of hopeless infeasibility guarantees an optimal solution for many difficult to solve systems.
Abstract: A newly developed sparse implementation of an optimization method using exact second derivatives is applied to the optimal power flow problem. Four utility systems are studied using a variety of objective functions, including fuel costs, active and reactive losses, and new shunt capacitors. Systems solved range from 350 buses to 2000 buses. Comparisons are made with an older algorithm which uses an Augmented Lagrangian to demonstrate the advantages of run time and robustness of the new method. The algorithm and accompanying software represent a technological breakthrough, since they are suitable for solving systems on the order of 2000 buses and demonstrate solution speeds of 5 minutes on large mainframe computers. The method is particularly well suited to infeasible, or even divergent starting points. An option to add shunt capacitors in the event of hopeless infeasibility guarantees an optimal solution for many difficult to solve systems. An automatic scaling feature is added to correct numerical ill-conditioning resulting from series compensation or poor R/X ratios.

348 citations


Book ChapterDOI
J. V. Crivello1
01 Jan 1984
TL;DR: In this article, the authors proposed a new class of photoinitiators of cationic polymerization which fall into two basic types based on the mechanisms of their photolysis.
Abstract: Diaryliodonium, triarylsulfonium, dialkylphenacylsulfonium and dialkyl-4-hydroxyphenylsulfonium salts are versatile new classes of photoinitiators of cationic polymerization which have been reported in the last few years. These photoinitiators fall into two basic types based on the mechanisms of their photolysis. The first class comprises diaryliodonium and triarylsulfonium salts which undergo photoinduced fragmentations to generate aryl radicals and either aryliodinium or diarylsulfinium cation-radicals. On the other hand, dialkylphenacylsulfonium and dialkyl-4-hydroxyphenylsulfonium salts generate ylides and Bronsted acids by a reversible photolysis. Both classes of onium salts can be photosensitized to respond to long wavelength UV and visible light. Photosensitization occurs chiefly by an electron transfer process. Photogenerated free radicals can also be employed to induce the decomposition of diaryliodonium and certain triarylsulfonium salts by a chain reaction. Modifications within the cations and anions of the above onium salts have a marked influence on the course of the cationic polymerizations which are initiated using these photoinitiators. The structure of the cations exerts a dominant role in the photochemistry and determines the rate at which initiator fragments are produced. The reactivity and propensity of the initiator fragments to undergo termination are controlled by the nature of the anion. Photoinitiated cationic polymerizations using iodonium and sulfonium salts are currently finding use in a number of commercial applications including coatings, adhesives, inks and novel photoresists.

329 citations


Journal ArticleDOI
TL;DR: In this article, a simple beam line is suggested which would allow a substantial increase in low energy X-ray flux (measurements down to Al and Si) with the sample and detector in a He atmosphere.
Abstract: The problem of absorption of soft X-rays by thick Be windows in hard X-ray beam lines is well known. Although the signal at 2.4 keV was reduced by ∼ 103 we have routinely measured the absorption spectra of S (2472 eV) and elements at higher energies including Cl, Ar and K. These spectra were obtained on hard X-ray beam lines at Stanford Synchrotron Radiation Laboratory (SSRL) with Si(111) monochromator crystals and a fluorescent ion chamber detector [1]. Higher energy harmonics were minimized by detuning and the end station was enclosed in a helium bag to prevent absorption by air. Although the diminished X-ray flux and decreasing fluorescent yield were serious negative factors at these low X-ray energies the spectra from thick samples were of excellent quality with sufficient sensitivity to characterize 1% S in coal. Representative spectra are shown comparing data from focused and unfocused beam lines and with S data from JUMBO [2]. Comparison of Ar and KCl data to excellent data found in the older literature [3–5] allow a confirmation of the resolution function (energy bandpass) of the monochromator. A simple new beam line is suggested which would allow a substantial increase in low energy X-ray flux (measurements down to Al and Si) with the sample and detector in a He atmosphere.

291 citations



Patent
29 Jun 1984
TL;DR: In this article, the circuit protection and relay functions are provided by common circuit elements under the control of a single processor unit, where voltage and current values are obtained on a continuous basis and these values are continuously monitored within the processor to determine the electrical status of a protected power distribution system.
Abstract: Circuit protection and protective relay functions are provided by common circuit elements under the control of a single processor unit. Voltage and current values are obtained on a continuous basis and these values are continuously monitored within the processor to determine the electrical status of a protected power distribution system. Upon the occurrence of an overcurrent or undervoltage condition, the circuit is interrupted by operation of a circuit breaker trip solenoid causing the breaker contacts to open. When the overcurrent or undervoltage condition ceases to exist, the circuit breaker contacts could be closed by operation of a controlled relay. The ROM and RAM storage elements within the processor unit are continuously tested and the circuit breaker contacts are opened upon indication that the ROM or RAM element is nonfunctional.

272 citations


Journal ArticleDOI
TL;DR: In this paper, the authors derived rapidly converging algorithms for the numerical calculation of the Levy distribution in the Williams-Watts model of dielectric relaxation, which was shown to be directly related to the problem of estimating the weight function of α in the range 0 < α < 1.
Abstract: This paper is concerned with the Levy, or stable distribution function defined by the Fourier transform $$Q_\alpha \left( z \right) = \frac{1}{{2\pi }}\int {_{ - \infty }^\infty \exp \left( { - izu - \left| u \right|^\alpha } \right)du} with 0< \alpha \leqslant 2$$ Whenα=2 it becomes the Gauss distribution function and whenα=1, the Cauchy distribution. Whenα≠2 the distribution has a long inverse power tail $$Q_\alpha \left( z \right) \sim \frac{{\Gamma \left( {1 + \alpha } \right)\sin \tfrac{1}{2}\pi \alpha }}{{\pi \left| z \right|^{1 + \alpha } }}$$ In the regime of smallα, ifα¦logz¦≪1, the distribution is mimicked by a log normal distribution. We have derived rapidly converging algorithms for the numerical calculation ofQ α (z) for variousα in the range 0<α<1. The functionQ α (z) appears naturally in the Williams-Watts model of dielectric relaxation. In that model one expresses the normalized dielectric parameter as $$ \in _n \left( \omega \right) \equiv \in '_n \left( \omega \right) - i \in ''_n \left( \omega \right) = - \int {_0^\infty e^{ - i\omega t} \left[ {{{d\phi \left( t \right)} \mathord{\left/ {\vphantom {{d\phi \left( t \right)} {dt}}} \right. \kern- ulldelimiterspace} {dt}}} \right]} dt$$ with $$\phi \left( t \right) = \exp - \left( {{t \mathord{\left/ {\vphantom {t \tau }} \right. \kern- ulldelimiterspace} \tau }} \right)^\alpha $$ It has been found empirically by various authors that observed dielectric parameters of a wide variety of materials of a broad range of frequencies are fitted remarkably accurately by using this form ofφ(t).e″ n (ω) is shown to be directly related toQ α (z). It is also shown that if the Williams-Watts exponential is expressed as a weighted average of exponential relaxation functions $$\exp - \left( {{t \mathord{\left/ {\vphantom {t \tau }} \right. \kern- ulldelimiterspace} \tau }} \right)^\alpha = \int {_0^\infty } g\left( {\lambda , \alpha } \right)e^{ - \lambda t} dt$$ the weight functiong(λ, α) is expressible as a stable distribution. Some suggestions are made about physical models that might lead to the Williams-Watts form ofφ(t).

271 citations


Patent
15 May 1984
TL;DR: In this article, a reconfigurable remote control transmitter is disclosed that has the ability to learn, store, and repeat the remote control codes from any other infrared transmitter, including an infrared receiver, a microprocessor, nonvolatile and scratch pad random access memories, and an infrared transmitter.
Abstract: A reconfigurable remote control transmitter is disclosed that has the ability to learn, store and repeat the remote control codes from any other infrared transmitter. The reconfigurable remote control transmitter includes an infrared receiver, a microprocessor, nonvolatile and scratch pad random access memories, and an infrared transmitter. The microprocessor application is divided into four main categories: learning, storing, retransmitting, and user interface. In the learning process, the reconfigurable remote control transmitter receives and decodes the transmissions from another remote control transmitter. The process is repeated at least twice for each key to make sure that it has been properly received and decoded. Once the data has been received and decoded, it is stored for later use. In order to do this, the received and decoded data is compressed so that it can fit into the nonvolatile memory. This process is repeated for each of the several remote control transmitters that are to be replaced by the reconfigurable remote control transmitter. When the learning and storing operations have been completed, the reconfigurable remote control transmitter is ready to use.

Journal ArticleDOI
TL;DR: A nuclear magnetic resonance (NMR) imaging system signal-to-noise calibration technique based on an NMR projection of distilled water in a cylindrical bottle is proposed, which can characterize any arrangement of rf coils in any magnetic field as signal to noise per ml times root Hz.
Abstract: A nuclear magnetic resonance (NMR) imaging system signal-to-noise calibration technique based on an NMR projection of distilled water in a cylindrical bottle is proposed. This measurement can characterize any arrangement of rf coils in any magnetic field as signal to noise per ml times root Hz. Inductive losses in a typical patient must be included in the calibration, and such losses can be simulated in a particular system by an externally attached resistor(s) appropriate to that system. Alternatively, an rf inductive damping phantom consisting of a conducting loop of wire containing an appropriate resistor is suggested that can be inserted into any NMR imaging coil to simulate subject Q damping. The same resistor can be used, independent of the details of the coil construction. Furthermore, if the loop inductance is tuned out at each frequency with a series capacitor, then the same loop resistance will serve for all frequencies as a good approximation to human subject damping. This "projection method" signal-to-noise ratio is related to the conventional signal-to-noise ratio measured from a Lorentzian-shaped spectral line as psi P = psi L [2/T2]1/2, where psi stands for signal-to-noise ratio, subscripts P and L stand, respectively, for the projection and "Lorentzian" methods, and T2 is the transverse relaxation time of the spectral line used in the Lorentzian method.

Journal ArticleDOI
TL;DR: In this paper, a three-terminal power device, called the insulated gate transistor (IGT), with voltage-controlled output characteristics is described, where the best features of the existing families of bipolar devices and power MOSFET's are combined to achieve optimal device characteristics for low-frequency power-control applications.
Abstract: A new three-terminal power device, called the insulated gate transistor (IGT), with voltage-controlled output characteristics is described. In this device, the best features of the existing families of bipolar devices and power MOSFET's are combined to achieve optimal device characteristics for low-frequency power-control applications. Devices with 600-V blocking capability fabricated using a vertical DMOS process exhibit 20 times the conduction current density of an equivalent power MOSFET and five times that of an equivalent bipolar transistor operating at a current gain of 10. Typical gate turn-off times have been measured to range from 10 to 50 µs.

Journal ArticleDOI
TL;DR: In this paper, a six-phase six-step voltage-fed induction motor is presented, where the stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees.
Abstract: A six-phase six-step voltage-fed induction motor is presented. The inverter is a transistorized six-step voltage source inverter, while the motor is a modified standard three-phase squirrel-cage motor. The stator is rewound with two three-phase winding sets displaced from each other by 30 electrical degrees. A model for the system is developed to simulate the drive and predict its performance. The simulation results for steady-state conditions and experimental measurements show very good correlation. It is shown that this winding configuration results in the elimination of all air-gap flux time harmonics of the order (6v ±1, v = 1,3,5,...). Consequently, all rotor copper losses produced by these harmonics as well as all torque harmonics of the order (6v, v = 1,3,5,...) are eliminated. A comparison between-the measured instantaneous torque of both three-phase and six-phase six-step voltage-fed induction machines shows the advantage of the six-phase system over the three-phase system in eliminating the sixth harmonic dominant torque ripple.

Journal ArticleDOI
Thomas M. Jahns1
TL;DR: In this article, a self-controlled permanent-magnet (PM) synchronous motor drive with rectangular current excitation has been investigated and it was shown that the pulsating torque can be minimized by a combination of steps including proper adjustment of the rotor magnet pole atc and effective use of rotor speed feedback compensation.
Abstract: Special features of torque production in self-controlled permanent-magnet (PM) synchronous motor drives with rectangular current excitation have been investigated. Addressed issues include the generation of undesired torque pulsations at low speeds and system operating locus limits imposed at high speeds by saturation of the current regulator. Attention is limited to motors in which sources of reluctance torque are suppressed by surface-mounting of the rotor magnets and skewing of the stator slots. Results from the low-speed investigation indicate that the pulsating torque can be minimized by a combination of steps including proper adjustment of the rotor magnet pole atc and effective use of rotor speed feedback compensation. High-speed saturated-regulator performance is significantly influenced by the 120 electrical degree inverter switch conduction intervals inherent with rectangular current excitation. The system torque-speed operating envelope can be expanded by several means, including on-line adjustment of the converter excitation phase angle a, but resulting performance trade-offs require careful scrutiny. A 15-kW prototype PM synchronous motor drive system has been used to confirm key analytical results.

Patent
15 May 1984
TL;DR: In this article, a reconfigurable remote control transmitter is disclosed that has the ability to learn, store, and repeat the remote control codes from any other infrared transmitter, including an infrared receiver, a microprocessor, nonvolatile and scratch pad random access memories, and an infrared transmitter.
Abstract: A reconfigurable remote control transmitter is disclosed that has the ability to learn, store and repeat the remote control codes from any other infrared transmitter. The reconfigurable remote control transmitter includes an infrared receiver, a microprocessor, nonvolatile and scratch pad random access memories, and an infrared transmitter. The microprocessor application is divided into four main categories: learning, storing, retransmitting, and user interface. In the learning process, the reconfigurable remote control transmitter receives and decodes the transmissions from another remote control transmitter. The process is repeated at least twice for each key to make sure that it has been properly received and decoded. Once the data has been received and decoded, it is stored for later use. In order to do this, the received and decoded data is compressed so that it can fit into the nonvolatile memory. This process is repeated for each of the several remote control transmitters that are to be replaced by the reconfigurable remote control transmitter. When the learning and storing operations have been completed, the reconfigurable remote control transmitter is ready to use.

Patent
17 Jul 1984
TL;DR: In this paper, a digital implementation of the overcurrent determination and time delay before tripping in a static circuit breaker trip unit allows the trip unit circuit to be manufactured in a single chip configuration.
Abstract: Digital implementation of the overcurrent determination and time delay before tripping in a static circuit breaker trip unit allows the trip unit circuit to be manufactured in a single chip configuration. The signal after A/D conversion is compared within a magnitude comparator to determine pickup. A pulse stream proportional to the square of the overcurrent signal is developed by multiplying the outputs of two magnitude comparators which compare the A/D level with a continuous binary count. The time delay determination is obtained by means of 3 cascade connected divide by two counters with their outputs connected to a data selector, or by a rate-limiter circuit which uses a fixed frequency to gate a pulse stream proportional to the overcurrent level squared.

Proceedings ArticleDOI
01 Dec 1984
TL;DR: In this article, realistic robot dynamic models are presented that have been validated over the frequency range 0 to 50 Hz and exhibit a strong influence of drive system flexibility, producing lightly damped poles in the neighborhood of 8 Hz, 14 Hz and 40 Hz, all unmodeled by the conventional rigid body multiple link robot dynamic approach.
Abstract: The objective of this paper is a redefinition of the robot control problem, based on realistic (1) models for the industrial robot as a controlled plant, (2) end effector trajectories consistent with manufacturing applications, and (3) the need for end-effector sensing to compensate for uncertainties inherent to most robotic manufacturing applications. Based on extensive analytical and experimental studies, realistic robot dynamic models are presented that have been validated over the frequency range 0 to 50 Hz. These models exhibit a strong influence of drive system flexibility, producing lightly damped poles in the neighborhood of 8 Hz, 14 Hz, and 40 Hz, all unmodeled by the conventional rigid body multiple link robot dynamic approach. The models presented also quantify the significance of nonlinearities in the drive system, in addition to those well-known in the linkage itself. Realistic simulations of robot dynamics and motion controls demonstrate that existing controls coupled with effective path planning produce dynamic path errors that are acceptable for most manufacturing applications. Major benefits are projected, with examples cited, for use of end-effector sensors for position, force, and process control that compensate for uncertainties encountered on the factory floor.

D. Purdy1
01 Feb 1984
TL;DR: The Structures, Materials, and Mechanisms Panel was divided into four basic categories that fit the overall responsibilities of the panel: materials, mechanisms, structural design, and analysis.
Abstract: Structures, materials, and mechanisms is one of the older technologies in the aerospace business. The Structures, Materials, and Mechanisms Panel was divided into the four basic categories that fit the overall responsibilities of the panel: materials, mechanisms, structural design, and analysis.

Patent
15 Nov 1984
TL;DR: In this article, a gamma correction amplifier and video driver are combined with the video transfer function of the CRT to create an antilogarithmic image brightness which approximates an exponential transfer function.
Abstract: A video brightness control system for high performance CRT displays including a buffer amplifier for receiving high speed video information and applying it to a gain control variable resistor serving as a contrast control. An ambient light sensor drives a nonlinear amplifier to provide an ambient light signal which is in proportion to the logarithm of the ambient light level over a wide range. A manual brightness control potentiometer is adjustable to provide a constant brightness signal. The video information signal, the ambient light signal, and the manual brightness control signal are added together by a summing device, with the resultant signal approximating a logarithmic characteristic. The output of the summing device is applied to a gamma correction amplifier which drives a video driver amplifier, the video amplifier, in turn, drives the CRT. The gamma correction amplifier and video driver in combination with the video transfer function of the CRT approximates an exponential transfer function, thereby creating CRT screen brightness which is an antilogarithmic function of the total video signal appearing at the gamma correction amplifier input. This results in automatic brightness control as a function of ambient light level, minimum interaction between brightness and contrast controls, and a gamma characteristic which provides a reasonable approximation to the variation of brightness difference threshold of the eye.

Journal ArticleDOI
TL;DR: The creation of a field-controlled variation of the index of refraction in a liquid crystal cell has been analyzed and experimentally verified and near diffraction-limited performance in terms of the optical transfer function is predicted.
Abstract: The creation of a field-controlled variation of the index of refraction in a liquid crystal cell has been analyzed and experimentally verified. To obtain a spherical lens utilizing a simple electrode structure and capable of focusing arbitrary incoming polarizations requires four flat nematic liquid crystal cells. With electrodes fabricated well within the current capability of photolithography, near diffraction-limited performance in terms of the optical transfer function is predicted. The focusing capability of a liquid crystal lens was demonstrated using a single cell with linear transparent electrodes. A plano-convex cylindrical lens for a single incoming polarization was thus created. While the cell had a crude electrode structure, it affirmed all the major qualitative predictions. The fringing along the edge of the electrodes required for eventually obtaining near diffraction-limited performance was observed.

Journal ArticleDOI
TL;DR: In this paper, the analytical electron microscope (AEM) was used to examine the microstructure of type 316LN stainless steel alloys which had been annealed for 50 to 300 hours in the temperature range 600 to 700 °C.
Abstract: The analytical electron microscope (AEM) was used to examine the microstructure of type 316LN stainless steel alloys which had been annealed for 50 to 300 hours in the temperature range 600 to 700 °C. The M23C6 carbide chemistry and distribution are described as a function of heat treatment.X-ray spectroscopy in the AEM revealed significant chromium depletion at grain boundaries in the vicinity of carbides for samples aged at 50 and 100 hours at 650 °C and 100 and 300 hours at 700 °C, with lower grain boundary chromium values observed at 650 °C than at 700 °C. The width of the chromium depleted zone normal to the grain boundaries increased with increasing annealing time and/or temperature. Measurements of chromium concentration along the grain boundaries away from a carbide were made after aging at 700 °C for 100 hours, and the chromium level rose steadily until the bulk value was reached at a distance of ~3μm from the carbide. The width of the chromium depleted zone normal to the boundaries in the same sample was an order of magnitude less. Some molybdenum depletion was also found at the grain boundaries, and the Mo-depletion profiles were in form and extent similar to the chromium results. Simple thermodynamic models were used to calculate the equilibrium value of chromium at the carbide-matrix interface, and the chromium distribution along and normal to the grain boundaries. The results of these models agreed well with the AEM results, and the agreement can be improved by considering the effect of electron probe configuration on the AEM measurements. The calculated thermodynamic data and the AEM results were related to the corrosion behavior of the alloys. The occurrence of severe asymmetries in some concentration profiles normal to the grain boundaries, which increased with increasing annealing temperature or time, was shown to be due to boundary movement during the discontinuous precipitation of M23C6 carbides.

Journal ArticleDOI
Hassan Gomaa1
TL;DR: DARTS—a design method for real-time systems—leads to a highly structured modular system with well-defined interfaces and reduced coupling between tasks.
Abstract: DARTS—a design method for real-time systems—leads to a highly structured modular system with well-defined interfaces and reduced coupling between tasks.

Journal ArticleDOI
TL;DR: Proton magnetic resonance (MR) images were obtained of the human head in magnetic fields as high as 1.5 Tesla using slotted resonator high radio-frequency (RF) detection coils to allow the combined assessment of anatomy, metabolism, and biochemistry in both the normal and diseased brain.
Abstract: Proton magnetic resonance (MR) images were obtained of the human head in magnetic fields as high as 1.5 Tesla (T) using slotted resonator high radio-frequency (RF) detection coils. The images showed no RF field penetration problems and exhibited an 11 (+/- 1)-fold improvement in signal-to-noise ratio over a .12-T imaging system. The first localized phosphorus 31, carbon 13, and proton MR chemical shift spectra recorded with surface coils from the head and body in the same instrument showed relative concentrations of phosphorus metabolites, triglycerides, and, when correlated with proton images, negligible lipid (-CH2-) signal from brain tissue on the time scale of the imaging experiment. Sugar phosphate and phosphodiester concentrations were significantly elevated in the head compared with muscle. This method should allow the combined assessment of anatomy, metabolism, and biochemistry in both the normal and diseased brain.

Journal ArticleDOI
T. J. E. Miller1
TL;DR: The line-start PM motor as discussed by the authors is a very high efficiency synchronous motor designed to operate at fixed voltage and frequency from the same power supplies as induction motors, and it can accelerate the motor from standstill when started ''across the line''.
Abstract: The line-start PM (permanent magnet) motor is a very high efficiency synchronous motor designed to operate at fixed voltage and frequency from the same power supplies as induction motors. The excitation is provided partly by the magnets, which are mounted in the rotor, and partly by the line current. A squirrel cage is provided to accelerate the motor from standstill when started ``across the line.'' This paper describes the synchronizing process and the characteristics of PM motors that lead to an inherently higher starting capability than that of comparable reluctance motors. The starting performance is described with the aid of computed transient torque/speed and related trajectories. The results have been verified with reference to detailed tests on a 25-hp motor that has been described in earlier papers. Two basic configurations of PM motor are shown in Fig. 1. On the left is a four-pole arrangement with radially magnetized magnets, and on the right a six-pole arrangement with circumferentially magnetized magnets.

Journal ArticleDOI
01 Jan 1984-Carbon
TL;DR: In this article, it was found that graphite with organic phosphate and phosphite esters has an increased resistance to air oxidation at elevated temperatures, and that a hydrophilic residue strongly adsorbed on the graphite surface at active sites where oxidation normally occurs.

Patent
16 Aug 1984
TL;DR: In this article, an advanced object generator is used for retrieving and processing the object data for outputting to a span processor for controlling the pixel-by-pixel video output signal for a video display.
Abstract: A computer video image generating system including a computer memory having three dimensional object data stored therein employs an advanced object generator for retrieving and processing the object data for output to a span processor for controlling the pixel-by-pixel video output signal for a video display. The advanced object generator includes a translucency processor, an edge-on fading processor, a level of detail blending processor and a bilinear interpolator for texture smoothing.

Patent
02 Apr 1984
TL;DR: In this paper, a multiple-impingement cooled structure for turbine shroud assembly is described, which includes a plurality of baffles which define with an element to be cooled, such as a turbine shroud, with holes in one of the baffles to impinge upon only the portion of the shroud in a first cavity.
Abstract: A multiple-impingement cooled structure, such as for use as a turbine shroud assembly The structure includes a plurality of baffles which define with an element to be cooled, such as a shroud, a plurality of cavities Impingement cooling air is directed through holes in one of the baffles to impinge upon only the portion of the shroud in a first cavity That cooling air is then directed to impinge again upon the portion of the shroud in a second cavity


Patent
29 Nov 1984
TL;DR: In this article, a low cost, true-perspective texture/shading processor for a raster graphics display is based on a mathematical model which defines modulations globally over the entire simulated, visual environment.
Abstract: A low cost, true-perspective texture/shading processor (16) for a raster graphics display is based on a mathematical model which defines modulations globally over the entire simulated, visual environment. The model uses planes defined in three-dimensional space to define the modulation. These texture planes are all orthogonal to a single gradient in a flat reference plane and cut across any number of faces. The texture/shading processor is used in a computer image generator of the type wherein a first group (11) manages a visual data base (10) and transfers data to the active environment storage of a second group (12). The second group reduces the three-dimensional description of the environment supplied by the first group to a two-dimensional description, makes perspective transformation of data into coordinates of a view window and assigns a priority to each surface of the computed scene. A third group reduces the two-dimensional description generated by the second group to a scan line by generating edge data (14) to locate where edges cross the scan line and responds to the assigned priorities (15) to eliminate hidden surfaces and generates the video for display ( 17) including edge smoothing, shading and texture effects. The second group further includes a face modulation processor (13) for computing data describing each texture and shading model and data describing the plane of each textured or shaded face. The texture/shading processor (16) is in the third group and is responsive to initialization data from the first group and the data computed by the face modulation processor for computing texture and shading modulation signals.