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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Fabrication and Evaluation of a High Performance SiC Inverter for Wireless Power Transfer Applications

In this study, a high power density SiC high efficiency wireless power transfer converter system via inductive coupling has been designed and developed. The detailed power module design, cooling system design and power stage development are presented. The successful operation of rated power converter system demonstrates the feasible wireless charging plan. One of the most important part of this study is the wind bandgap devices packaged at the Oak Ridge National Laboratory (ORNL) using the in-house packaging technologies by employing the bare SiC dies acquired from CREE, which are rated at 50 A / 1200 V each. These packaged devices are also inhouse tested and characterized using ORNL s Device Characterization Facility. The successful operation of the proposed inverter is experimentally verified and the efficiency and operational characteristics of the inverter are also revealed.

Onar, Omer C↗
DOE OSTI2015

Characterization of a three layer Compton telescope for hadron therapy dose monitoring

A Compton telescope for dose monitoring in hadron therapy is under development at IFIC-Valencia. The system consists of three layers of LaBr{sub 3} crystals coupled to silicon photomultiplier arrays. Two- and three-layer versions of the device have been tested in the laboratory. Images of Na-22 sources have been reconstructed. In addition, the two-layer version has been tested in a proton beam. Performance improvement and full characterization of the device are ongoing. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1976

Program to design, fabricate, test, and deliver a thermal control-mixing control device for the George C. Marshall Space Flight Center

The development and testing of a temperature sensor and pulse duration modulation (PDM) diverter valve for a thermal control-mixing control device are described. The temperature sensor selected for use uses a fluidic pin amplifier in conjunction with an expansion device. This device can sense changes of less than 0.25 F with greater than 15:1 signal to noise ratio when operating with a typical Freon pump supplied pressure. The pressure sensitivity of the sensor is approximately 0.0019 F/kPa. The valve which was selected was tested and performed with 100% flow diversion. In addition, the valve operates with a flow efficiency of at least 95%, with the possibility of attaining 100% if the vent flow of the PDM can be channeled through the last stage of the diverter valve. A temperature sensor which utilized an orifice bridge circuit and proportional-vortex combination mixing valve were also evaluated, but the concepts were rejected due to various problems.

Thurston, T. S.↗
NASA NTRS1993

Explosive component acceptance tester using laser interferometer technology

Acceptance testing of explosive components requires a reliable and simple to use testing method that can discern less than optimal performance. For hot-wire detonators, traditional techniques use dent blocks or photographic diagnostic methods. More complicated approaches are avoided because of their inherent problems with setup and maintenance. A recently developed tester is based on using a laser interferometer to measure the velocity of flying plates accelerated by explosively actuated detonators. Unlike ordinary interferometers that monitor displacement of the test article, this device measures velocity directly and is commonly used with non-spectral surfaces. Most often referred to as the VISAR technique (Velocity Interferometer System for Any Reflecting Surface), it has become the most widely-accepted choice for accurate measurement of velocity in the range greater than 1 mm/micro-s. Traditional VISAR devices require extensive setup and adjustment and therefore are unacceptable in a production-testing environment. This paper describes a new VISAR approach which requires virtually no adjustments, yet provides data with accuracy comparable to the more complicated systems. The device, termed the Fixed-Cavity VISAR, is currently being developed to serve as a product verification tool for hot-wire detonators and slappers. An extensive data acquisition and analysis computer code was also created to automate the manipulation of raw data into final results.

Wickstrom, Richard D.↗
DOE OSTI2015

Design of smart 3D-digital X-ray microtomographic scanners for non-destructive testing of materials and components of electronic devices with a multilayered structure

The article studies the operating procedures of an X-ray microtomographic scanner and the module of reconstruction and analysis 3D-image of a test sample in particular. An algorithm for 3D-image reconstruction based on image shadow projections and mathematical methods of the processing are described. Chapter 1 describes the basic principles of X-ray tomography and general procedures of the device developed. Chapters 2 and 3 are devoted to the problem of resources saving by the system during the X-ray tomography procedure, which is achieved by preprocessing of the initial shadow projections. Preprocessing includes background noise removing from the images, which reduces the amount of shadow projections in general and increases the efficiency of the group shadow projections compression. Chapter 4 covers general procedures of defect search, which is based on vector analysis principles. In conclusion, the main applications of X-ray tomography are presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Detection of gas leakage

A method of detecting leaks and measuring volumes as well as a device, the Power-free Pump Module (PPM), provides a self-contained leak test and volume measurement apparatus that requires no external sources of electrical power during leak testing or volume measurement. The PPM is a portable, pneumatically-controlled instrument capable of generating a vacuum, calibrating volumes, and performing quantitative leak tests on a closed test system or device, all without the use of alternating current (AC) power. Capabilities include the ability is to provide a modest vacuum (less than 10 Torr) using a venturi pump, perform a pressure rise leak test, measure the gas's absolute pressure, and perform volume measurements. All operations are performed through a simple rotary control valve which controls pneumatically-operated manifold valves.

47 OTHER INSTRUMENTATION↗
DOE OSTI2012

Patterning graphene nanoribbons using copper oxide nanowires

We present a fabrication technique for graphene nanoribbons (GNRs) that employs copper oxide nanowires as the etch masks. We demonstrate that these etch masks have numerous advantages: they can be synthesized simply by heating a copper foil in air, deposited on graphene from a solution, they are inert to oxygen plasma, and can be removed from the substrate by dissolution in mild acids. We fabricated GNRs in the device configuration and tested their electrical properties. Depending on the duration of the plasma etching, GNR devices exhibiting either standard ambipolar electric field effects or p-type transistor behaviors with ON-OFF ratios > 50 can be fabricated. The resulting devices based on narrow GNRs are demonstrated to exhibit promising electronic properties, which can be exploited in studies where GNR devices are required.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Multipath/RFI/modulation study for DRSS-RFI problem: Voice coding and intelligibility testing for a satellite-based air traffic control system

Analog and digital voice coding techniques for application to an L-band satellite-basedair traffic control (ATC) system for over ocean deployment are examined. In addition to performance, the techniques are compared on the basis of cost, size, weight, power consumption, availability, reliability, and multiplexing features. Candidate systems are chosen on the bases of minimum required RF bandwidth and received carrier-to-noise density ratios. A detailed survey of automated and nonautomated intelligibility testing methods and devices is presented and comparisons given. Subjective evaluation of speech system by preference tests is considered. Conclusion and recommendations are developed regarding the selection of the voice system. Likewise, conclusions and recommendations are developed for the appropriate use of intelligibility tests, speech quality measurements, and preference tests with the framework of the proposed ATC system.

Birch, J. N.↗
NASA NTRS1973

A study of vertical motion requirements for landing simulation

Tests were conducted to determine the significance of vertical acceleration cues in the simulation of the visual approach and landing maneuver. Landing performance measures were obtained for four subject pilots operating a visual landing simulation mechanized in the Ames Height Control Test Apparatus, a device that provides up to plus or minus 40 ft of vertical motion. Test results indicate that vertical motion cues are utilized in the landing task, and that they are particularly important in the simulation of aircraft with marginal longitudinal-handling qualities. To assure vertical motion cues of the desired fidelity in the landing task, it appears, that a simulator must have excursion capabilities of at least 20 ft in either direction.

Bray, R. S.↗
NASA NTRS1973

Evaluation of effectiveness of various devices for attenuation of trailing vortices based on model tests in a large towing basin

The effectiveness of various candidate aircraft-wing devices for attenuation of trailing vortices generated by large aircraft is evaluated on basis of results of experiments conducted with a 0.03-scale model of a Boeing 747 transport aircraft using a technique developed at the HYDRONAUTICS Ship Model Basin. Emphasis is on the effects produced by these devices in the far-field (up to 8 kilometers downstream of full-scale generating aircraft) where the unaltered vortex-wakes could still be hazardous to small following aircraft. The evaluation is based primarily on quantitative measurements of the respective vortex velocity distributions made by means of hot-film probe traverses in a transverse plane at selected stations downstream. The effects of these altered wakes on rolling moment induced on a small following aircraft are also studied using a modified lifting-surface theory with a synthesized Gates Learjet as a typical example. Lift and drag measurements concurrently obtained in the model tests are used to appraise the effects of each device investigated on the performance characteristics of the generating aircraft.

Kirkman, K. L.↗
DOE OSTI2017

Methodology for Wide Band-Gap Device Dynamic Characterization

Here, the double pulse test (DPT) is a widely accepted method to evaluate the dynamic behavior of power devices. Considering the high switching-speed capability of wide band-gap devices, the test results are very sensitive to the alignment of voltage and current (V-I) measurements. Also, because of the shoot-through current induced by Cdv/dt (i.e., cross-talk), the switching losses of the nonoperating switch device in a phase-leg must be considered in addition to the operating device. This paper summarizes the key issues of the DPT, including components and layout design, measurement considerations, grounding effects, and data processing. Additionally, a practical method is proposed for phase-leg switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200-V/50-A SiC MOSFETs, the test results show that this method can accurately evaluate the switching loss of both the upper and lower switches by detecting only one switching current and voltage, and it is immune to V-I timing misalignment errors.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1983

Testing and characterizations of infrared sensor over the temperature range of 2 Kelvin to 300 Kelvin

Various cryogenic techniques were used to evaluate state of the art electro-optic devices. As research, development, and production demands require more sensitive testing techniques, faster test results, and higher production throughput, the emphasis on supporting cryogenic systems increases. The three traditional methods currently utilized in electro-optic device testing are discussed: (1) liquid contaiment dewars; (2) liquid transfer systems; and (3) closed cycle refrigeration systems. Advantages, disadvantages, and the current state of the art of each of these cryogenic techniques is discussed.

Hansen, R. G.↗