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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

The Impact of Local and Regional Disease Extent on Overall Survival in Patients With Advanced Stage IIIB/IV Non-Small Cell Lung Carcinoma

Purpose: Patients with advanced stage IIIB or stage IV non-small cell lung carcinoma are typically treated with initial platinum-based chemotherapy. A variety of factors (eg, performance status, gender, age, histology, weight loss, and smoking history) are generally accepted as predictors of overall survival. Because uncontrolled pulmonary disease constitutes a major cause of death in these patients, we hypothesized that clinical and radiographic factors related to intrathoracic disease at diagnosis may be prognostically significant in addition to conventional factors. The results have implications regarding the selection of patients for whom palliative thoracic radiation therapy may be of most benefit. Methods and Materials: We conducted a pooled analysis of 189 patients enrolled at a single institution into 9 prospective phase II and III clinical trials involving first-line, platinum-based chemotherapy. Baseline clinical and radiographic characteristics before trial enrollment were analyzed as possible predictors for subsequent overall survival. To assess the relationship between anatomic location and volume of disease within the thorax and its effect on survival, the pre-enrollment computed tomography images were also analyzed by contouring central and peripheral intrapulmonary disease. Results: On univariate survival analysis, multiple pulmonary-related factors were significantly associated with worse overall survival, including pulmonary symptoms at presentation (P=.0046), total volume of intrathoracic disease (P=.0006), and evidence of obstruction of major bronchi or vessels on prechemotherapy computed tomography (P<.0001). When partitioned into central and peripheral volumes, central (P<.0001) but not peripheral (P=.74) disease was associated with worse survival. On multivariate analysis with known factors, pulmonary symptoms (hazard ratio, 1.46; P=.042), central disease volume (hazard ratio, 1.47; P=.042), and bronchial/vascular compression (hazard ratio, 1.54; P=.022) remained significant. Conclusions: Patients with bulky central disease, bronchial/vascular compression, and/or pulmonary symptoms exhibited worse overall survival after first-line, platinum-based chemotherapy. A subset of these patients may be studied to determine whether early, planned palliative thoracic radiation could also be of benefit.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

COMPRESSIBLE RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE IN MAGNETICALLY DOMINATED PLASMAS AND IMPLICATIONS FOR A STRONG-COUPLING REGIME

In this Letter, we report compressible mode effects on relativistic magnetohydrodynamic (RMHD) turbulence in Poynting-dominated plasmas using three-dimensional numerical simulations. We decomposed fluctuations in the turbulence into 3 MHD modes (fast, slow, and Alfvén) following the procedure of mode decomposition in Cho and Lazarian, and analyzed their energy spectra and structure functions separately. We also analyzed the ratio of compressible mode to Alfvén mode energy with respect to its Mach number. We found the ratio of compressible mode increases not only with the Alfvén Mach number, but also with the background magnetization, which indicates a strong coupling between the fast and Alfvén modes. It also signifies the appearance of a new regime of RMHD turbulence in Poynting-dominated plasmas where the fast and Alfvén modes are strongly coupled and, unlike the non-relativistic MHD regime, cannot be treated separately. This finding will affect particle acceleration efficiency obtained by assuming Alfvénic critical-balance turbulence and can change the resulting photon spectra emitted by non-thermal electrons.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Yield asymmetry design of magnesium alloys by integrated computational materials engineering

Deformation asymmetry of magnesium alloys is an important factor on machine design in the automobile industry. Represented by the ratio of compressive yield stress (CYS) against tensile yield stress (TYS), deformation asymmetry is strongly related to texture and grain size. A polycrystalline viscoplasticity model, modified intermediate Φ-model, is used to predict the deformation behavior of magnesium alloys with different grain sizes. Validated with experimental results, integrated computational materials engineering is applied to find out the route in achieving desired asymmetry via thermomechanical processing. For example, CYS/TYS in rolled texture is smaller than 1 under different loading directions. In other textures, such as extruded texture, CYS/TYS is large along the normal direction. Starting from rolled texture, asymmetry will increase to close to 1 along the rolling direction after being compressed to a strain of 0.2. Our modified Φ-model also shows that grain refinement increases CYS/TYS. Along with texture control, grain refinement also can optimize the yield asymmetry. After the grain size decreases to a critical value, CYS/TYS reaches to 1 because CYS increases much faster than TYS. By tailoring the microstructure using texture control and grain refinement, it is achievable to optimize yield asymmetry in wrought magnesium alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2013

ALACRITY: Analytics-Driven Lossless Data Compression for Rapid In-Situ Indexing, Storing, and Querying. In: Transactions on Large-Scale Data- and Knowledge-Centered Systems X. Lecture Notes in Computer Science, vol 8220

High-performance computing architectures face nontrivial data processing challenges, as computational and I/O components further diverge in performance trajectories. For scientific data analysis in particular, methods based on generating heavyweight access acceleration structures, e.g. indexes, are becoming less feasible for ever-increasing dataset sizes. We present ALACRITY, demonstrating the effectiveness of a fused data and index encoding of scientific, floating-point data in generating lightweight data structures amenable to common types of queries used in scientific data analysis. We exploit the representation of floating-point values by extracting significant bytes, using the resulting unique values to bin the remaining data along fixed-precision boundaries. To optimize query processing, we use an inverted index, mapping each generated bin to a list of records contained within, allowing us to optimize query processing with attribute range constraints. Overall, the storage footprint for both index and data is shown to be below numerous configurations of bitmap indexing, while matching or outperforming query performance.

Compression Ratio↗
DOE OSTI2017

Supernova Driving. IV. The Star-formation Rate of Molecular Clouds

We compute the star-formation rate (SFR) in molecular clouds (MCs) that originate ab initio in a new, higher-resolution simulation of supernova-driven turbulence. Because of the large number of well-resolved clouds with self-consistent boundary and initial conditions, we obtain a large range of cloud physical parameters with realistic statistical distributions, which is an unprecedented sample of star-forming regions to test SFR models and to interpret observational surveys. We confirm the dependence of the SFR per free-fall time, SFR{sub ff}, on the virial parameter, α {sub vir}, found in previous simulations, and compare a revised version of our turbulent fragmentation model with the numerical results. The dependences on Mach number, M, gas to magnetic pressure ratio, β, and compressive to solenoidal power ratio, χ at fixed α {sub vir} are not well constrained, because of random scatter due to time and cloud-to-cloud variations in SFR{sub ff}. We find that SFR{sub ff} in MCs can take any value in the range of 0 ≤ SFR{sub ff} ≲ 0.2, and its probability distribution peaks at a value of SFR{sub ff} ≈ 0.025, consistent with observations. The values of SFR{sub ff} and the scatter in the SFR{sub ff}–α {sub vir} relation are consistent with recent measurements in nearby MCs and in clouds near the Galactic center. Although not explicitly modeled by the theory, the scatter is consistent with the physical assumptions of our revised model and may also result in part from a lack of statistical equilibrium of the turbulence, due to the transient nature of MCs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Analysis of the ratio of ℓ 1 and ℓ 2 norms in compressed sensing

We study the ratio of &#x2113; 1 and &#x2113; 2 norms ( &#x2113; 1 / &#x2113; 2 ) as a sparsity-promoting objective in compressed sensing. We first propose a novel criterion that guarantees that an s-sparse signal is the local minimizer of the &#x2113; 1 / &#x2113; 2 objective; our criterion is interpretable and useful in practice. We also give the first uniform recovery condition using a geometric characterization of the null space of the measurement matrix, and show that this condition is satisfied for a class of random matrices. We also present analysis on the robustness of the procedure when noise pollutes data. Numerical experiments are provided that compare &#x2113; 1 / &#x2113; 2 with some other popular non-convex methods in compressed sensing. Finally, we propose a novel initialization approach to accelerate the numerical optimization procedure. We call this initialization approach support selection, and we demonstrate that it empirically improves the performance of existing &#x2113; 1 / &#x2113; 2 algorithms.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Early evolution of an energetic coronal mass ejection and its relation to EUV waves

We study a coronal mass ejection (CME) associated with an X-class flare whose initiation is clearly observed in the low corona with high-cadence, high-resolution EUV images, providing us a rare opportunity to witness the early evolution of an energetic CME in detail. The eruption starts with a slow expansion of cool overlying loops (∼1 MK) following a jet-like event in the periphery of the active region. Underneath the expanding loop system, a reverse S-shaped dimming is seen immediately above the brightening active region in hot EUV passbands. The dimming is associated with a rising diffuse arch (∼6 MK), which we interpret as a preexistent, high-lying flux rope. This is followed by the arising of a double hot channel (∼10 MK) from the core of the active region. The higher structures rise earlier and faster than lower ones, with the leading front undergoing extremely rapid acceleration up to 35 km s{sup –2}. This suggests that the torus instability is the major eruption mechanism and that it is the high-lying flux rope rather than the hot channels that drives the eruption. The compression of coronal plasmas skirting and overlying the expanding loop system, whose aspect ratio h/r increases with time as a result of the rapid upward acceleration, plays a significant role in driving an outward-propagating global EUV wave and a sunward-propagating local EUV wave, respectively.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

The effects of video compression on acceptability of images for monitoring life sciences experiments

Future manned space operations for Space Station Freedom will call for a variety of carefully planned multimedia digital communications, including full-frame-rate color video, to support remote operations of scientific experiments. This paper presents the results of an investigation to determine if video compression is a viable solution to transmission bandwidth constraints. It reports on the impact of different levels of compression and associated calculational parameters on image acceptability to investigators in life-sciences research at ARC. Three nonhuman life-sciences disciplines (plant, rodent, and primate biology) were selected for this study. A total of 33 subjects viewed experimental scenes in their own scientific disciplines. Ten plant scientists viewed still images of wheat stalks at various stages of growth. Each image was compressed to four different compression levels using the Joint Photographic Expert Group (JPEG) standard algorithm, and the images were presented in random order. Twelve and eleven staffmembers viewed 30-sec videotaped segments showing small rodents and a small primate, respectively. Each segment was repeated at four different compression levels in random order using an inverse cosine transform (ICT) algorithm. Each viewer made a series of subjective image-quality ratings. There was a significant difference in image ratings according to the type of scene viewed within disciplines; thus, ratings were scene dependent. Image (still and motion) acceptability does, in fact, vary according to compression level. The JPEG still-image-compression levels, even with the large range of 5:1 to 120:1 in this study, yielded equally high levels of acceptability. In contrast, the ICT algorithm for motion compression yielded a sharp decline in acceptability below 768 kb/sec. Therefore, if video compression is to be used as a solution for overcoming transmission bandwidth constraints, the effective management of the ratio and compression parameters according to scientific discipline and experiment type is critical to the success of remote experiments.

Haines, Richard F.↗
DOE OSTI2012

Inspection and Test Report for the Removed 241-C-107 Dome Concrete.

This report presents the results of the examination and testing of the 55 inch diameter concrete dome 'Plug' removed from SST 241-C-107. Photographs and discussion of field inspection of the dome 'Plug' cross section are provided. Fourteen concrete cores removed from the dome 'Plug' were sent offsite for testing. Twelve cores were subject to transverse frequency, elastic modulus, Poisson's ratio, and compression testing. Two cores were subjected to petrographic examination. This report documents represents further implementation of the Single Shell Tank Integrity Project Expert Panel recommendation, SI-5, Test Dome Concrete and Rebar 'Plugs'.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Initial Design and Experimental Results of a Novel Near-Isothermal Compressor for Heat Pump Applications

In efforts to increase the efficiency of residential and commercial air conditioners and heat pumps, it is found that the compressor has the highest electrical energy usage of the system. Therefore, it is appropriate to try to increase the efficiency of this component to reduce its energy usage. Another challenge with heat pump design is that some compressor types have drawbacks that make modulation difficult. To answer these challenges, we are developing an isothermal liquid compressor. The compressor uses propylene glycol to compress carbon dioxide. In the compression chamber the propylene glycol can enter either from the bottom to create a liquid piston for compression or it can enter through a spray nozzle at the top of the chamber. In the latter case, heat transfer from the gas to be compressed to the liquid droplets is high. This allows near isothermal operation of the compressor, which increases the efficiency by 17% to 30%, compared to adiabatic compression. In addition, the isothermal liquid compressor enables very efficient and simple part load modulation.Experimental results demonstrating the operation of the liquid compressor are presented. Initial data demonstrated a temperature rise of 7 K at pressure ratios of almost 4. For comparison at the same initial pressure, temperature, and pressure ratio, adiabatic compression would result in a temperature increase of approximately 70 K. Plotting data on a P-h diagram demonstrates that the compression started at superheated state and ended in supercritical state. Testing was later performed with repeated compressions in the superheated region of the P-h diagram at liquid flow rates of 2 x 10-3 m3/min and 2 x 10-3 m3/min to understand the limitations of the prototype for use with an actual heat pump system. This work demonstrated a novel cycle on a T-s diagram. Results from this work will be used to develop a second-generation prototype where more rapid cycling is possible.

Kowalski, Steve↗
NASA NTRS1933

Effect of orifice length-diameter ratio on fuel sprays for compression-ignition engines

Experimental results on the effect of the length-diameter ratio of the orifice on the spray characteristics, together with a brief analysis of the factors affecting these characteristics, are presented in this report. The length-diameter ratios tested ranged from 0.5 to 10; the orifice diameters from 0.008 to 0.040 inch; and the injection pressures from 2,000 to 8,000 pounds per square inch. The density of the air into which the fuel was discharged was varied from 0.38 to 1.35 pounds per cubic foot.

Gelalles, A G↗
NASA NTRS1993

Image and Video Compression with VLSI Neural Networks

An advanced motion-compensated predictive video compression system based on artificial neural networks has been developed to effectively eliminate the temporal and spatial redundancy of video image sequences and thus reduce the bandwidth and storage required for the transmission and recording of the video signal. The VLSI neuroprocessor for high-speed high-ratio image compression based upon a self-organization network and the conventional algorithm for vector quantization are compared. The proposed method is quite efficient and can achieve near-optimal results.

compression artificial neural networks VLSI↗
DOE OSTI2017

Feeding properties and behavior of hammer- and knife-milled pine

This work reports the rheological characterization of hammer and knife-milled lodgepole pine materials as a function of grind size and moisture content. Characterizations included particle size and shape distributions, bulk density, compressibility at 10 kPa uniaxial pressure, elastic recovery from 10 kPa uniaxial pressure, shear strength, effective angle of internal friction, arching in a custom hopper, and feeding performance in volumetric and gravimetric auger feeders. Particle analysis indicates that the width and length distributions of the 3 mm hammer-milled and the 6 mm knife-milled materials are quite similar, and that all the materials have relatively short aspect ratios (< 4). Compressibility and elastic recovery both increased with increasing moisture content with both values increasing more than 10% and the effect being most severe for the 3 mm grind. Adding 3 kPa of pressure increased the critical arching width for all hopper arching tests, except for the 25 mm grind material with 20% MC, for which the critical arching width actually decreased with increased pressure. Interestingly, for materials with smaller particle sizes, the volumetric feed rate tends to decrease as moisture increases even though the density of the material increases with moisture content and the auger speeds are the same. Time variability of volumetric feed rate increased dramatically with increasing particle size but the impact of moisture content was not as clear. For nearly all tests, gravimetric auger feeding resulted in better feeding control and substantially decreased time variability in the material feed rate. These tests show that material feed rate and volumetric auger feed rate variability are dependent upon material shear strength, bulk density, and particle size. Shear tests indicate that material strength generally decreased with increasing particle size, although the impact of moisture was not entirely consistent.

09 BIOMASS FUELS↗
NASA NTRS1943

Requirements for Auxiliary Stiffeners Attached to Panels Under Combined Compression and Shear

Panels of aluminum alloy sheets, framed by side and end stiffeners, were subjected to combined loading by means of offset knife edges applying loads to top and bottom end plates with reacting forces against the end plates supplied by laterally acting rollers. The test specimens were 17S-T aluminum alloy shoots 0.040 inch thick in panels of 10-inch width and three different lengths (approximately 10, 26, and 30 inch). Data were obtained for the bowing of transverse and longitudinal ribs of rectangular cross section and varying depths mounted on one side of the sheet only, for several ratios of compression to shear loads. Limiting values of the moments of inertia were calculated from these measurements. The experimental values exceed the theoretical values given by Timoshenko for the case of simply supported sheets with uniformly distributed boundary stresses. The work reported includes measurements of the effective shear moduli of the nine test panels with and without ribs. These data are compared with values published by Lahdo and Wagner.

ALUMINUM ALLOYS, SHEET - ALCOA 17ST - STRENGTH↗
DOE OSTI2023

Toward continuum gyrokinetic study of high-field mirrors

High-temperature superconducting (HTS) magnetic mirrors under development exploit strong fields with high mirror ratio to compress loss cones and enhance confinement and may offer cheaper, more compact fusion power plant candidates. This new class of devices could exhibit largely unexplored interchange and gradient-driven modes. Such instabilities, and methods to stabilize them, can be studied with gyrokinetics, given the strong magnetization and prevalence of kinetic effects. Our focus here is to (a) determine if oft-used gyrokinetic models for open field lines produce the electron-confining (Pastukhov) electrostatic potential and (b) examine and address challenges faced by gyrokinetic codes in studying HTS mirrors. Here, we show that a one-dimensional limit of said models self-consistently develops a potential qualitatively approaching the analytical Pastukhov level. Additionally, we describe the computational challenges of studying high mirror ratios with open field line gyrokinetic solvers and offer a force softening method to mitigate small time steps needed for time integration in colossal magnetic field gradients produced by HTS coils, providing a 19X speedup.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗