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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Electromagnetic induction by finite wavenumber source fields in 2-D lateral heterogeneities - The transverse electric mode

Electromagnetic induction in a laterally homogeneous earth is analyzed in terms of a source field with finite dimensions. Attention is focused on a time-varying two-dimensional current source directed parallel to the strike of a two-dimensional anomalous structure within the earth, i.e., the E-parallel mode. The spatially harmonic source field is expressed as discontinuities in the magnetic (or electric) field of the current in the source. The model is applied to describing the magnetic gradients across megatectonic features, and may be used to predict the magnetic fields encountered by a satellite orbiting above the ionosphere.

Hermance, J. F.↗
NASA NTRS1986

Boron determination in steels by Inductively-Coupled Plasma spectometry (ICP)

The sample is treated with 5N H2SO4 followed by concentrated HNO3 and the diluted mixture is filtered. Soluble B is determined in the filtrate by Inductively-Coupled Plasma (ICP) spectrometry after addition HCl and extraction of Fe with ethyl-ether. The residue is fused with Na2CO3 and, after treatment with HCl, the insoluble B is determined by ICP spectrometry as before. The method permits determination of ppm amounts of B in steel.

Coedo, A. G.↗
NASA NTRS1986

Automation of preparation of nonmetallic samples for analysis by atomic absorption and inductively coupled plasma spectrometry

For a rapid preparation of solutions intended for analysis by inductively coupled plasma emission spectrometry or atomic absorption spectrometry, an automatic device called Plasmasol was developed. This apparatus used the property of nonwettability of glassy C to fuse the sample in an appropriate flux. The sample-flux mixture is placed in a composite crucible, then heated at high temperature, swirled until full dissolution is achieved, and then poured into a water-filled beaker. After acid addition, dissolution of the melt, and filling to the mark, the solution is ready for analysis. The analytical results obtained, either for oxide samples or for prereduced iron ores show that the solutions prepared with this device are undistinguished from those obtained by manual dissolutions done by acid digestion or by high temperature fusion. Preparation reproducibility and analytical tests illustrate the performance of Plasmasol.

Wittmann, A.↗
NASA NTRS1988

Multiple-Coil, Pulse-Induction Metal Detector

Multiple-head, pulse-induction metal detector scans area of 72 feet squared with combination of eight detector heads, each 3 ft. square. Head includes large primary coil inducing current in smaller secondary coils. Array of eight heads enables searcher to cover large area quickly. Pulses applied to primary coil, induced in secondary coils measured to determine whether metal present within range of detector head. Detector designed for recovery of Space Shuttle debris.

Lesky, Edward S.↗
NASA NTRS1987

Inductance effects in the high-power transmitter crowbar system

The effective protection of a klystron in a high-power transmitter requires the diversion of all stored energy in the protected circuit through an alternate low-impedance path, the crowbar, such that less than 1 joule of energy is dumped into the klystron during an internal arc. A scheme of adding a bypass inductor in the crowbar-protected circuit of the high-power transmitter was tested using computer simulations and actual measurements under a test load. Although this scheme has several benefits, including less power dissipation in the resistor, the tests show that the presence of inductance in the portion of the circuit to be protected severely hampers effective crowbar operation.

Daeges, J.↗
NASA NTRS1989

Low-Inductance Capacitor For Low Temperatures

Planar capacitor made on epoxy/fiberglass printed-circuit board. Planar design and flat copper plates ensure low inductance and low series resistance. Planar construction minimized effects of thermal contraction, and epoxy/fiberglass substrate ensured high breakdown voltage. Design is simple, and this type of capacitor easy for any printed-circuit-board facility to fabricate. Design suitable for any small-capacitance, high-voltage capacitor, whether operating at low or high temperature.

Rhodes, David B.↗
NASA NTRS1989

Pulse-Population Modulation For Induction Machines

Low-frequency synthesizer developed to provide low-frequency waveform by synthesis from high-frequency power system. Waveform assembled by allowing conduction of discrete half cycles of high-frequency carrier. Frequency of synthesized wave controlled by pulse pattern. By controlling relationship between slip and stator frequencies, one operates induction motor either as motor or generator. Such bidirectional energy transducer used as starter/generator for engine, or as servo-mechanism for control of acceleration and deceleration. Other advantages include operation under controlled voltage-to-frequency ratios to maintain high-efficiency and high power factor, and no reflection of low-frequency noise into 20-kHz distribution bus.

Hansen, Irving G.↗
NASA NTRS1989

Magneto-inductive skin sensor for robot collision avoidance: A new development

Safety is a primary concern for robots operating in space. The tri-mode sensor addresses that concern by employing a collision avoidance/management skin around the robot arms. This rf-based skin sensor is at present a dual mode (proximity and tactile). The third mode, pyroelectric, will complement the other two. The proximity mode permits the robot to sense an intruding object, to range the object, and to detect the edges of the object. The tactile mode permits the robot to sense when it has contacted an object, where on the arm it has made contact, and provides a three-dimensional image of the shape of the contact impression. The pyroelectric mode will be added to permit the robot arm to detect the proximity of a hot object and to add sensing redundancy to the two other modes. The rf-modes of the sensing skin are presented. These modes employ a highly efficient magnetic material (amorphous metal) in a sensing technique. This results in a flexible sensor array which uses a primarily inductive configuration to permit both capacitive and magnetoinductive sensing of object; thus optimizing performance in both proximity and tactile modes with the same sensing skin. The fundamental operating principles, design particulars, and theoretical models are provided to aid in the description and understanding of this sensor. Test results are also given.

Chauhan, D. S.↗
NASA NTRS1990

Adjustable Induction-Heating Coil

Improved design for induction-heating work coil facilitates optimization of heating in different metal specimens. Three segments adjusted independently to obtain desired distribution of temperature. Reduces time needed to achieve required temperature profiles.

Ellis, Rod↗
NASA NTRS1989

Progress in kinetic inductance thermometers for X-ray calorimeters

Conventional X-ray microcalorimeters have so far used ionimplanted resistors for thermometers. Recently, however, several new methods for sensing small temperature changes have been suggested that are nondissipative. Such devices may have intrinsically better energy resolution by eliminating the Johnson noise present in resistive devices. The use of kinetic inductance thermometers for X-ray microcalorimeters is being investigated. This technique exploits the strong temperature dependence of magnetic penetration depth of thin superconducting films. The prototype system, designed for operation at 1.5 K, uses films of aluminum and tin. Once the expected temperature sensitivity and alpha particle detection have been demonstrated, aluminum will be replaced with titanium or another material with a suitable critical temperature and the device will be operated at 0.3 K. At this temperature, the energy resolution from thermal noise should be sufficiently good to allow X-ray detection.

Rawley, G. L.↗
NASA NTRS1991

Self-Oscillating Inductive Boost Regulator

Improved voltage regulator designed for use in solar photovoltaic dc power system utilizing flywheel for energy storage. Includes self-oscillating inductive voltage-boosting circuit, which regulates withdrawal of energy from flywheel and motor/generator when output of solar cells insufficient to maintain load voltage at specified level of 150 Vdc. Features include optical coupling and rapid response.

Paulkovich, John↗
NASA NTRS1992

Axial-Gap Induction Motor For Levitated Specimens

Motor does not obscure view of specimen. Axial-gap induction motor applies torque to rotate electrostatically or electromagnetically levitated specimen of metal. Possible applications include turning specimens for uniform heating under focused laser beams and obtaining indirect measurements of resistivities or of surface tensions in molten specimens.

Sridharan, Govind↗
NASA NTRS1991

Scaling properties of induction times in heterogeneous nucleation

The heterogeneous-to-homogeneous induction time ratio is obtained as a function of the contact angle in the asymptotic limit of a high nucleation barrier. Model-dependent corrections to t(ind) are investigated, particularly in cases of the Turnbull-Fisher model used in numerical simulations by Greer et al. (1990).

Shneidman, Vitaly A.↗
NASA NTRS1993

Fuzzy efficiency optimization of AC induction motors

This paper describes the early states of work to implement a fuzzy logic controller to optimize the efficiency of AC induction motor/adjustable speed drive (ASD) systems running at less than optimal speed and torque conditions. In this paper, the process by which the membership functions of the controller were tuned is discussed and a controller which operates on frequency as well as voltage is proposed. The membership functions for this dual-variable controller are sketched. Additional topics include an approach for fuzzy logic to motor current control which can be used with vector-controlled drives. Incorporation of a fuzzy controller as an application-specific integrated circuit (ASIC) microchip is planned.

Jani, Yashvant↗
NASA NTRS1993

Steady induction effects in geomagnetism. Part 1B: Geomagnetic estimation of steady surficial core motions: A non-linear inverse problem

The problem of estimating a steady fluid velocity field near the top of Earth's core which induces the secular variation (SV) indicated by models of the observed geomagnetic field is examined in the source-free mantle/frozen-flux core (SFI/VFFC) approximation. This inverse problem is non-linear because solutions of the forward problem are deterministically chaotic. The SFM/FFC approximation is inexact, and neither the models nor the observations they represent are either complete or perfect. A method is developed for solving the non-linear inverse motional induction problem posed by the hypothesis of (piecewise, statistically) steady core surface flow and the supposition of a complete initial geomagnetic condition. The method features iterative solution of the weighted, linearized least-squares problem and admits optional biases favoring surficially geostrophic flow and/or spatially simple flow. Two types of weights are advanced radial field weights for fitting the evolution of the broad-scale portion of the radial field component near Earth's surface implied by the models, and generalized weights for fitting the evolution of the broad-scale portion of the scalar potential specified by the models.

Voorhies, Coerte V.↗
NASA NTRS1993

The PIT MkV pulsed inductive thruster

The pulsed inductive thruster (PIT) is an electrodeless, magnetic rocket engine that can operate with any gaseous propellant. A puff of gas injected against the face of a flat (spiral) coil is ionized and ejected by the magnetic field of a fast-rising current pulse from a capacitor bank discharge. Single shot operation on an impulse balance has provided efficiency and I(sub sp) data that characterize operation at any power level (pulse rate). The 1-m diameter MkV thruster concept offers low estimated engine mass at low powers, together with power capability up to more than 1 MW for the 1-m diameter design. A 20 kW design estimate indicates specific mass comparable to Ion Engine specific mass for 10,000 hour operation, while a 100,000 hour design would have a specific mass 1/3 that of the Ion Engine. Performance data are reported for ammonia and hydrazine. With ammonia, at 32 KV coil voltage, efficiency is a little more than 50 percent from 4000 to more than 8000 seconds I(sub sp). Comparison with data at 24 and 28 kV indicates that a wider I(sub sp) range could be achieved at higher coil voltages, if required for deep space missions.

Dailey, C. Lee↗
NASA NTRS1953

An analytical study of the comparative performance of six air-induction systems for turbojet-powered airplanes designed to operate at Mach numbers up to 2.0

A study is presented of inlet designs and aerodynamic characteristics of air-induction systems intended for operation with a turbojet engine operating with a constant-volume air-flow process. Two-dimensional inlet designs similar to those discussed in NACA RM A52C14, plus a fixed-geometry inlet with a convergent-divergent diffuser, and an additional variable-geometry inlet are considered for Mach numbers from 0.85 to 2.0 from sea level to the stratosphere. For best performance throughout this range of Mach numbers and altitudes, it was shown that the geometry of the inlet must be such as to insure a high pressure recovery, as well as to provide for a variable entrance area. The inlets are compared on the basis of a drag evaluation neglecting viscosity.

DIFFUSERS, SUBSONIC↗