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NASA NTRS1990

VLA neutral hydrogen imaging of compact groups

Images of the neutral hydrogen (H I) in the direction of the compact groups of galaxies, HCG 31, HCG 44, and HCG 79 are presented. The authors find in HCG 31 and HCG 79, emission contained within a cloud much larger than the galaxies as well as the entire group. The H I emission associated with HCG 44 is located within the individual galaxies but shows definite signs of tidal interactions. The authors imaged the distribution and kinematics of neutral hydrogen at the two extremes of group sizes represented in Hickson's sample. HCG 44 is at the upper limit while HCG 18, HCG 31, and HCG 79 are at the lower end. Although the number of groups that have been imaged is still very small, there may be a pattern emerging which describes the H I morphology of compact groups. The true nature of compact groups has been the subject of considerable debate and controversy. The most recent observational and theoretical evidence strongly suggests that compact groups are physically dense, dynamical systems that are in the process of merging into a single object (Williams and Rood 1987, Hickson and Rood 1988, Barnes 1989). The neutral hydrogen deficiency observed by Williams and Rood (1987) is consistent with a model in which frequent galactic collisions and interactions have heated some of the gas during the short lifetime of the group. The H I disks which are normally more extended than the luminous ones are expected to be more sensitive to collisions and to trace the galaxy's response to recent interactions. Very Large Array observations can provide in most cases the spatial resolution needed to confirm the dynamical interactions in these systems.

Williams, B. A.↗

NASA NTRS1992

Compton backscattered annihilation line emission: A new diagnostic of accreting compact sources

It is shown that Compton scattering of 511 keV electron-positron annihilation radiation produces a line like feature at approx. 170 keV from backscattered photons. Assuming a simple model of an accretion disk around a compact source, the spectrum is explored of the spectrum of Compton scattered annihilation line emission for a range of conditions. It is further shown that such Compton baskscattering of annihilation line emission from the inner edge of an accretion disk could account for the previously unidentified 170 keV line emission and high energy continuum observed from a variable, compact source, or sources, of annihilation radiation near the Galactic Center. Identification of the observed 170 keV line as an annihilation line reflection feature provides strong new evidence that the source of the emission is an accreting compact object. Further study of these features in existing spectra and in forthcoming GRO observation of these and other sources can provide unique new diagnostics of the innermost regions of accretion disks around compact objects.

Lingenfelter, Richard E.↗

NASA NTRS1995

Comparative study of numerical schemes of TVD3, UNO3-ACM and optimized compact scheme

Three different schemes are employed to solve the benchmark problem. The first one is a conventional TVD-MUSCL (Monotone Upwind Schemes for Conservation Laws) scheme. The second scheme is a UNO3-ACM (Uniformly Non-Oscillatory Artificial Compression Method) scheme. The third scheme is an optimized compact finite difference scheme modified by us: the 4th order Runge Kutta time stepping, the 4th order pentadiagonal compact spatial discretization with the maximum resolution characteristics. The problems of category 1 are solved by using the second (UNO3-ACM) and third (Optimized Compact) schemes. The problems of category 2 are solved by using the first (TVD3) and second (UNO3-ACM) schemes. The problem of category 5 is solved by using the first (TVD3) scheme. It can be concluded from the present calculations that the Optimized Compact scheme and the UN03-ACM show good resolutions for category 1 and category 2 respectively.

Lee, Duck-Joo↗

NASA NTRS1995

Spacecraft Applications of Compact Optical and Mass Spectrometers

Optical spectrometers, and mass spectrometers to a lesser extent, have a long and rich history of use aboard spacecraft. Space mission applications include deep space science spacecraft, earth orbiting satellites, atmospheric probes, and surface landers, rovers, and penetrators. The large size of capable instruments limited their use to large, expensive spacecraft. Because of the novel application of micro-fabrication technologies, compact optical and mass spectrometers are now available. The new compact devices are especially attractive for spacecraft because of their small mass and volume, as well as their low power consumption. Dispersive optical multi-channel analyzers which cover the 0.4-1.1 micrometer wavelength are now commercially available in packages as small as 3 x 6 x 18 mm exclusive of drive and recording electronics. Mass spectrometers as small as 3 x 3 mm, again without electronics, are under development. A variety of compact optical and mass spectrometers are reviewed in this paper. A number of past space applications are described, along with some upcoming opportunities that are likely candidate missions to fly this new class of compact spectrometers.

Davinic, N. M.↗

NASA NTRS1997

Analysis of Technology for Compact Coherent Lidar

In view of the recent advances in the area of solid state and semiconductor lasers has created new possibilities for the development of compact and reliable coherent lidars for a wide range of applications. These applications include: Automated Rendezvous and Capture, wind shear and clear air turbulence detection, aircraft wake vortex detection, and automobile collision avoidance. The work performed by the UAH personnel under this Delivery Order, concentrated on design and analyses of a compact coherent lidar system capable of measuring range and velocity of hard targets, and providing air mass velocity data. The following is the scope of this work. a. Investigate various laser sources and optical signal detection configurations in support of a compact and lightweight coherent laser radar to be developed for precision range and velocity measurements of hard and fuzzy targets. Through interaction with MSFC engineers, the most suitable laser source and signal detection technique that can provide a reliable compact and lightweight laser radar design will be selected. b. Analyze and specify the coherent laser radar system configuration and assist with its optical and electronic design efforts. Develop a system design including its optical layout design. Specify all optical components and provide the general requirements of the electronic subsystems including laser beam modulator and demodulator drivers, detector electronic interface, and the signal processor. c. Perform a thorough performance analysis to predict the system measurement range and accuracy. This analysis will utilize various coherent laser radar sensitivity formulations and different target models.

Amzajerdian, Farzin↗

NASA NTRS2001

Optical Spectrum of the Compact Planetary Nebula IC 5117

High resolution spectroscopic data of the very compact planetary nebula IC 5117 are obtained in the optical wavelengths, 3700A - 10050A, with the Hamilton Echelle Spectrograph at Lick Observatory, and which have been analyzed along with the International Ultraviolet Explorer (IUE) UV archive data. Although a diagnostic diagram shows significant density and temperature fluctuations, our analysis indicates that the nebular gas may be represented by a homogeneous shell of extremely high density gas, N(sub epsilon) approx. 90 000 /cu cm. The average electron temperatures, e.g. indicated by the [OIII] diagnostics, are around 12 000 K. We construct a photoionization model to represent most of the observed line intensities, and the physical condition of this compact nebulosity. Based on the semi-empirical ionization correction approach, and model indications, we derived the elemental abundances: He, C, N, O, Ne, and Ar appear to be normal or marginally depleted compared to the average planetary nebula, while the remaining elements, S, Cl, and K appear to be enhanced. IC 5117 is perhaps a very young compact planetary nebula, slightly more evolved than the other well-known compact planetary nebula IC 4997. The central stellar temperature is likely to be around 120 000 K, evolved from a C-rich AGB progenitor.

Hyung, Siek↗

NASA NTRS2010

Current Status of the Development of a Transportable and Compact VLBI System by NICT and GSI

MARBLE (Multiple Antenna Radio-interferometer for Baseline Length Evaluation) is under development by NICT and GSI. The main part of MARBLE is a transportable VLBI system with a compact antenna. The aim of this system is to provide precise baseline length over about 10 km for calibrating baselines. The calibration baselines are used to check and validate surveying instruments such as GPS receiver and EDM (Electro-optical Distance Meter). It is necessary to examine the calibration baselines regularly to keep the quality of the validation. The VLBI technique can examine and evaluate the calibration baselines. On the other hand, the following roles are expected of a compact VLBI antenna in the VLBI2010 project. In order to achieve the challenging measurement precision of VLBI2010, it is well known that it is necessary to deal with the problem of thermal and gravitational deformation of the antenna. One promising approach may be connected-element interferometry between a compact antenna and a VLBI2010 antenna. By measuring repeatedly the baseline between the small stable antenna and the VLBI2010 antenna, the deformation of the primary antenna can be measured and the thermal and gravitational models of the primary antenna will be able to be constructed. We made two prototypes of a transportable and compact VLBI system from 2007 to 2009. We performed VLBI experiments using theses prototypes and got a baseline length between the two prototypes. The formal error of the measured baseline length was 2.7 mm. We expect that the baseline length error will be reduced by using a high-speed A/D sampler.

Ishii, Atsutoshi↗

NASA NTRS1961

Spontaneous Cracking in Unfired Magnesia Compacts Upon Standing in Air

Analytical-grade magnesium oxide powder without binder was compressed hydrostatically to 50,000 lb. per sq. in. to form compacts. When exposed to moist air immediately after pressing, these compacts developed irregularly shaped cracks. Controlled tests, in which these compacts were exposed for various lengths of time to various atmospheres, indicated that in general water vapor, carbon dioxide, and residual stresses had to be present if cracking was to occur. The probable cause of the cracking was the formation of a less dense and mechanically weak basic carbonate of magnesium at crystallite surface points of high stress concentration which developed during the compacting. The adsorption of dry CO2 at such sites prevented subsequent delayed fracture.

Davies, Myron O.↗

NASA NTRS2016

Dynamic Stall Suppression Using Combustion-Powered Actuation (COMPACT)

Retreating blade stall is a well-known phenomenon that limits rotorcraft speed, maneuverability, and efficiency. Airfoil dynamic stall is a simpler problem, which demonstrates many of the same flow phenomena. Combustion Powered Actuation (COMPACT) is an active flow control technology, which at the outset of this work, had been shown to mitigate static and dynamic stall at low Mach numbers. The attributes of this technology suggested strong potential for success at higher Mach numbers, but such experiments had never been conducted. The work detailed in this report documents a 3-year effort focused on assessing the effectiveness of COMPACT for dynamic stall suppression at freestream conditions up to Mach 0.5. The work done has focused on implementing COMPACT on a high-lift rotorcraft airfoil: the VR-12. This selection was made in order to ensure that any measured benefits are over and above the capabilities of state-of-the-art high-lift rotorcraft airfoils. The detailed Computational Fluid Dynamics (CFD) simulations, wind-tunnel experiments, and system-level modeling conducted have shown the following: (1) COMPACT, in its current state of development, is capable of reducing the adverse effects of deep dynamic stall at Mach numbers up to 0.4; (2) The two-dimensional (2D) CFD results trend well compared to the experiments; and (3) Implementation of the CFD results into a system-level model suggest that significant rotor-level benefits are possible.

Matalanis, Claude G.↗

NASA NTRS2019

The Second LBA Calibrator Survey of Southern Compact Extragalactic Radio Sources – LCS2

We present the second catalogue of accurate positions and correlated flux densities for 1100 compact extragalactic radio sources that were not observed before 2008 at high angular resolution. The catalogue spans the declination range [-90◦, -30◦] and was constructed from 19 24-h VLBI observing sessions with the Australian Long Baseline Array at 8.3 GHz. The catalogue presents the final part of the program that was started in 2008. The goals of that campaign were (1) to extend the number of compact radio sources with precise coordinates and measure their correlated flux densities, which can be used for phase referencing very long baseline interferometry (VLBI) and Atacama Large Millimeter/submillimeter Array (ALMA) observations, geodetic VLBI, search for sources with significant offsets with respect to Gaia positions, and space navigation; (2) to extend the complete flux-limited sample of compact extragalactic sources to the Southern hemisphere; and (3) to investigate the parsec-scale properties of sources from the high-frequency AT20G survey. The median uncertainty of the source positions is 3.5 mas. As a result of this VLBI campaign, the number of compact radio sources south of declination -40◦ that have measured VLBI-correlated flux densities and positions known to milliarcsecond accuracy has increased by over a factor of 6.

Petrov, Leonid↗

NASA NTRSDate not supplied

A Compact Dual-Band Bowtie Antenna for RF and ISM bands Operation

Traditionally, bowtie antennas have been known to exhibit wide impedance characteristics, omnidirectional radiation patterns, and linear polarization. There is a broad range of applications from medical imaging, archaeological survey, and Ground Penetrating Radar (GPR) to trackers and sensor networks where wideband bowtie antenna designs are required for their operations. Broadening the bandwidth of bowtie antenna requires widening the flare angle of the bowtie arms, which consequently results in a large surface area that may not be suitable for space-constrained applications. Moreover, drawback attributes of the wideband bowtie designs feature inconsistent radiation pattern across the bandwidth and low signal-to-noise (SNR) ratios. As it is known, the SNR would be improved in dual- or multi-band antennas due to their reduced bandwidth. To this end, dual-band/multi-band antennas are preferred over wideband antennas in applications where more than a single frequency of interest is present. Previously, a two-port double-dipole elements was reported, whose arms were orthogonally interleaved to facilitate operation in both the standard WLAN frequency bands (J. M. Steyn and et. al, Progress in Electromagnetic Research, Vol. – 10 pp. 151-161). Even though the antenna is not very compact it does exhibit good cross-polarization, moderate gain in both frequency bands. Another dual-band bowtie antenna which excites two bands using a single transmission line was reported (Wen Chao Zheng and et. al, IEEE Trans. Antennas propag., 2014). The design was compact and did not need multi-port feeding network. In this paper, a dual-band compact bowtie antenna operating at 900 MHz (RF band) and 2.45 GHz (ISM band) using a single excitation port is introduced. It is printed on a 1.54mm thick dielectric substrate (εr = 3.38). The antenna consists of two sets of bowtie arms, a microstrip transmission line to feed the bowtie arms, and a ground plane acting as a reflector to partially reduce the back radiation. One of the bowtie arms of each frequency is printed on the top layer and the other arm, which is mirror imaged, is printed on the bottom layer of the substrate. The length of the bowtie controls the resonance frequency of the antenna and the flare angle controls the bandwidth of the antenna. The microstrip transmission line, connected to a 50 Ω SMA probe, feeds the bowtie antenna. The compact antenna can be used for both RF and ISM band applications. The bowtie arms at the lower frequency band are miniaturized by elongating their electrical lengths. The influence of miniaturizing the bowtie arms and the supporting partial ground plane is observed in the reduced peak gain and degraded front-to-back ratio. These are partly neutralized using four quarter-wave choke-slots in the ground plane with two on each side of the feeding transmission line. The proposed antenna is numerically investigated and finalized by the finite-element based full-wave EM solver, ANSYS HFSS. The miniaturization has reduced the ground plane size by ~45% and the arms size by ~41%. In addition to the size reduction benefits, the antenna shows reasonable peak gain and front-to-back ratio in both the bands. The corresponding results will be presented and discussed at the conference.

Saininad Naik↗

NASA NTRSDate not supplied

Microbial Characterization of Heat Melt Compaction for Treatment of Space Generated Solid Wastes

One treatment process in development for solid waste management in space has been the Trash Compaction Processing System (TCPS). Human space mission wastes typically contain large percentages of contaminated wet solid waste. The Heat Melt Compactor (HMC) is being developed to be a multi-function means of water recovery, volume reduction, and the making safe of contaminant-rich trash with the potential for waste stabilization and/or sterilization. To determine the efficacy of the HMC treatment to kill microorganisms in solid waste and remain biologically stable, testing was conducted on three tiles produced by HMC-Gen 2 at Ames Research Center. Samples were shipped to Kennedy Space Center to test for microbial viability after compaction, determine the bio-stability of the HMC disks during storage (43 days), and assess potential airborne contaminate microbial growth on surfaces at low and high humidity conditions. In addition to the products of solid waste processing technologies, there is a concern that the crew might come into contact with hardware surfaces that have been contaminated by microorganisms during waste processing. The extent of microbial surface contamination of waste processing hardware was determined by surface sample swabbing and analysis for total bacterial and yeast counts and cultivable counts of aerobic and anaerobic bacteria, spore-forming bacteria, and fungi. Results indicate that trash processing increased bacterial counts on the surfaces of the compacter. All but one biological indicator spore strip imbedded in the HMC produced tiles were negative for growth after incubation for five days indicating effective sterilization through the heat melt compaction process. Analysis of core samples as well as surface growth of tiles inoculated with Aspergillus niger fungal spores incubated at three levels of humidity indicate that HMC created tiles did not support the proliferation of bacterial and fungal growth.

Mary E Hummerick↗

DOE OSTI2023

Compact laser source with frequency modulators generating multiple lines

A compact laser source and a single sideband modulator used therein is disclosed. The compact laser source includes a seed laser and one or more channels, with each channel generating one or more output laser beams having corresponding different wavelengths. The compact laser source can be formed in whole or in part on a single optical motherboard to thereby minimize space and power requirements. By employing the disclosed single sideband modulator, harmonics in the generated output laser beams can be minimized. The compact laser source finds application in an atom interferometer (AI) system, which may be used to measure gravity, acceleration, or rotation of the AI system.

Lentine, Anthony L.↗

DOE OSTI2023

Refractory high entropy alloy compact heat exchanger

Several innovative technologies, including pressure-drop minimization, advanced refractory high entropy alloys, and advanced manufacturing can provide a compact heat exchanger that extends the state-of-the-art heat-exchanger operating range. The compact heat exchanger can reduce pressure drop losses by 100 to 500%, while retaining most of the heat transfer. The compact heat exchanger can be fabricated from refractory high entropy alloys that have favorable corrosion, thermal fatigue, and creep properties at high temperatures and pressures. Therefore, the compact heat exchanger using high entropy alloys can operate at >800° C. and 80 bars.

Kustas, Andrew↗

DOE OSTI2024

Post-irradiation Heating Tests of As-Irradiated AGR-3/4 TRISO Fuel Compacts

Four post-irradiation heating tests of fuel compacts from the U.S. Advanced Gas Reactor (AGR)-3/4 irradiation experiment were completed. In addition to tristructural isotropic (TRISO)-coated driver fuel, each compact contained designed-to-fail (DTF) particles with fuel kernels coated only in pyrocarbon so as to simulate exposed kernels. Tests at 1600/1700°C, 1400°C, and 1200°C were performed to measure fission product release as a function of time and temperature. Silver release was highest in the 1200°C test, supporting the observation that silver release rates are highest in the 1100–1300°C range. Compared to tests of AGR-1 compacts with no exposed kernels, the Cs-134 and Kr-85 releases were noticeably higher in AGR-3/4. The exposed kernels’ contributions to Eu and Sr release are inconclusive, due to the difficulty in distinguishing among the combined effects of higher irradiation temperatures in these particular AGR-3/4 compacts, the presence of the DTF particles, and the Fuel Accident Condition Simulator (FACS) test temperatures. These data can be used to make inferences about fission product retention in exposed kernels as a function of time and temperature.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2021

All-in-one bipolar electrode: A new concept for compact and efficient water electrolyzers

Highly compact and efficient proton exchange membrane electrolyzer cells (PEMECs) are strongly desired for commercializing hydrogen production. Here, a novel concept of all-in-one bipolar electrode (AIOBE) is proposed for high-efficiency and compact PEMECs with the help of 3D printing and sputtering coating. AIOBE ideally integrated catalyst layer (CL)/gas diffusion layer/bipolar plate/current distributor/gasket, which significantly reduced component quantity on the cathode side of PEMECs from 5 to 1, cut down on part weight and volume, and drastically accelerated the fabrication and maintenance processes. Moreover, AIOBE with the micro-scale flat surface and nano-scale rough CL provided an ultralow ohmic resistance (~100 mOhm cm 2 ) and a high catalyst utilization. Finally, AIOBE delivered a practical voltage of 1.62 V and a high energy efficiency of 91% at 1000 mA/cm 2 , and its mass activity (4.48 A/mg Pt ) was 14 times higher than conventional PEMECs. In conclusion, this work provides a new route for developing highly compact electrochemical devices, such as fuel cells, electrolyzers for N 2 reduction and CO 2 conversion, and many more.

3D printing↗

DOE OSTI2022

Physical Compact Model for Three-Terminal SONOS Synaptic Circuit Element

A well-posed physics-based compact model for a three-terminal silicon–oxide–nitride–oxide–silicon (SONOS) synaptic circuit element is presented for use by neuromorphic circuit/system engineers. Based on technology computer aided design (TCAD) simulations of a SONOS device, the model contains a nonvolatile memristor with the state variable QM representing the memristor charge under the gate of the three-terminal element. By incorporating the exponential dependence of the memristance on QM and the applied bias V for the gate, the compact model agrees quantitatively with the results from TCAD simulations as well as experimental measurements for the drain current. The compact model is implemented through VerilogA in the circuit simulation package Cadence Spectre and reproduces the experimental training behavior for the source–drain conductance of a SONOS device after applying writing pulses ranging from –12 V to +11 V, with an accuracy higher than 90%.

42 ENGINEERING↗

DOE OSTI2023

Graph-based Compact Modeling (GCM) of CMOS transistors for efficient parameter extraction: A machine learning approach

Parameter extraction of compact transistor models is an expensive process, heavily relying on engineering knowledge and experience. To automate such a process, we propose a novel approach, Graph-based Compact Model (GCM), that integrates physical modeling and data-driven learning. GCM utilizes Graph Neural Networks (GNNs) to establish the model structure, while retaining the physicality in compact models. Here, we implement our GCM in Verilog-A to support circuit simulations. As demonstrated with an academic 7 nm FinFET PDK, the new approach automatically generates a GCM model within a minute, and achieves excellent accuracy and efficiency in SPICE.

42 ENGINEERING↗