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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Intracluster light in clusters of galaxies at redshifts $0.4 < z < 0.8$

The study of intracluster light can help us to understand the mechanisms taking place in galaxy clusters, and to place constraints on the cluster formation history and physical properties. However, owing to the intrinsic faintness of ICL emission, most searches and detailed studies of ICL have been limited to redshifts z<0.4.We search for ICL in a subsample of ten clusters detected by the ESO Distant Cluster Survey (EDisCS), at redshifts 0.4<z<0.8, that are also part of our DAFT/FADA Survey. We analyze the ICL by applying the OV WAV package, a wavelet-based technique, to deep HST ACS images in the F814W filter and to V-band VLT/FORS2 images of three clusters. Detection levels are assessed as a function of the diffuse light source surface brightness using simulations. In the F814W filter images, we detect diffuse light sources in all the clusters, with typical sizes of a few tens of kpc (assuming that they are at the cluster redshifts). The ICL detected by stacking the ten F814W images shows an 8sigma detection in the source center extending over a ~50x50kpc2 area, with a total absolute magnitude of -21.6 in the F814W filter, equivalent to about two L* galaxies per cluster. We find a weak correlation between the total F814W absolute magnitude of the ICL and the cluster velocity dispersion and mass. There is no apparent correlation between the cluster mass-to-light ratio (M/L) and the amount of ICL, and no evidence for any preferential orientation in the ICL source distribution. We find no strong variation in the amount of ICL between z=0 and z=0.8. In addition, we find wavelet-detected compact objects (WDCOs) in the three clusters for which data in two bands are available; these objects are probably very faint compact galaxies that in some cases are members of the respective clusters. We have shown that ICL is important in clusters at least up to z=0.8.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Consumption study and identification of methyl salicylate in spicy cassava chips

Spicy cassava chips is a popular snack. However, some news in electronic media reported addition of balsam which is a banned food additives in that product to give extra spicy flavor. This study aimed to determine ITB students’ pattern of consumption, health problems caused by spicy chips consumption, and knowledge about illicit use of food additives in that product, and identify the main content of balsam namely methyl salicylate in 10 samples of spicy cassava chips taken from inside and outside about ITB campus. A total of 300 questionnaires distributed to ITB students then data processing was performed. Spicy cassava chips sample macerated in 50 mL of methanol for 24 hours at room temperature, filtered and analyzed using gas chromatography capillary column with OV-1, nitrogen carrier gas and flame ionization detector. Based on questionnaires, 292 (97%) of 300 respondents had consumed spicy chips. A total of 247 (85%) from 292 respondents spicy chips consumed less than 3 times a week. A total of 195 respondents (67%) had experienced health problems after eating spicy chips. There were 137 (47%) of the 292 respondents who knew about the illicit addition of food additives into spicy chips; only 35 respondents (12%) who knew about balsam’s addition. There were 126 respondents (43%) who did not pay attention to their health because they will keep eating spicy chips despite the addition of banned food additives. Through the verification of the standard addition method in gas chromatography system with a hydrogen pressure of 1.5 bar, injector temperature 200 °C, detector temperature 230 °C, oven temperature 60 °C for 2 minutes and then increased to 230 °C with rate 6 °C/menit; linearity, limit of detection, limit of quantitation, accuracy, precision, and specificity parameters met the acceptance limits. From 10 spicy cassava chips samples which were analyzed, they did not reveal any content of methyl salicylate. Methyl salicylate contained in the positive control was 1.273 mg/mL.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

GPU acceleration of rank-reduced coupled-cluster singles and doubles

Here, we have developed a graphical processing unit (GPU) accelerated implementation of our recently introduced rank-reduced coupled-cluster singles and doubles (RR-CCSD) method. RR-CCSD introduces a low-rank approximation of the doubles amplitudes. This is combined with a low-rank approximation of the electron repulsion integrals via Cholesky decomposition. The result of these two low-rank approximations is the replacement of the usual fourth-order CCSD tensors with products of second- and third-order tensors. In our implementation, only a single fourth-order tensor must be constructed as an intermediate during the solution of the amplitude equations. Owing in large part to the compression of the doubles amplitudes, the GPU-accelerated implementation shows excellent parallel efficiency (95% on eight GPUs). Our implementation can solve the RR-CCSD equations for up to 400 electrons and 1550 basis functions—roughly 50% larger than the largest canonical CCSD computations that have been performed on any hardware. In addition to increased scalability, the RR-CCSD computations are faster than the corresponding CCSD computations for all but the smallest molecules. We test the accuracy of RR-CCSD for a variety of chemical systems including up to 1000 basis functions and determine that accuracy to better than 0.1% error in the correlation energy can be achieved with roughly 95% compression of the ov space for the largest systems considered. We also demonstrate that conformational energies can be predicted to be within 0.1 kcal mol -1 with efficient compression applied to the wavefunction. Finally, we find that low-rank approximations of the CCSD doubles amplitudes used in the similarity transformation of the Hamiltonian prior to a conventional equation-of-motion CCSD computation will not introduce significant errors (on the order of a few hundredths of an electronvolt) into the resulting excitation energies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Asteroseismic analysis of the CoRoT target HD 49933

The frequency ratios r {sub 10} and r {sub 01} of HD 49933 exhibit an increase at high frequencies. This behavior also exists in the ratios of other stars, which is considered to result from the low signal-to-noise ratio and the larger linewidth at the high-frequency end and could not be predicted by stellar models in previous work. Our calculations show that the behavior not only can be reproduced by stellar models, but can be predicted by asymptotic formulas of the ratios. The frequency ratios of the Sun, too, can be reproduced well by the asymptotic formulas. The increased behavior derives from the fact that the gradient of mean molecular weight at the bottom of the radiative region hinders the propagation of p-modes, while the hindrance does not exist in the convective core. This behavior should exist in the ratios of stars with a large convective core. The characteristic of the ratios at high frequencies provides a strict constraint on stellar models and aids in determining the size of the convective core and the extent of overshooting. Observational constraints point to a star with M = 1.28 ± 0.01 M {sub ☉}, R = 1.458 ± 0.005 R {sub ☉}, t = 1.83 ± 0.1 Gyr, r{sub cc} = 0.16 ± 0.02 R {sub ☉}, α = 1.85 ± 0.05, and δ{sub ov} =0.6 ± 0.2 for HD 49933.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

DETECTING THE RISE AND FALL OF THE FIRST STARS BY THEIR IMPACT ON COSMIC REIONIZATION

The intergalactic medium was reionized before redshift z {approx} 6, most likely by starlight which escaped from early galaxies. The very first stars formed when hydrogen molecules (H{sub 2}) cooled gas inside the smallest galaxies, minihalos (MHs) of mass between 10{sup 5} and 10{sup 8} M{sub Sun }. Although the very first stars began forming inside these MHs before redshift z {approx} 40, their contribution has, to date, been ignored in large-scale simulations of this cosmic reionization. Here we report results from the first reionization simulations to include these first stars and the radiative feedback that limited their formation, in a volume large enough to follow the crucial spatial variations that influenced the process and its observability. We show that, while MH stars stopped far short of fully ionizing the universe, reionization began much earlier with MH sources than without, and was greatly extended, which boosts the intergalactic electron-scattering optical depth and the large-angle polarization fluctuations of the cosmic microwave background significantly. This boost should be readily detectable by Planck, although within current Wilkinson Microwave Anisotropy Probe uncertainties. If reionization ended as late as z{sub ov} {approx}< 7, as suggested by other observations, Planck will thereby see the signature of the first stars at high redshift, currently undetectable by other probes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

A study of convective core overshooting as a function of stellar mass based on two-dimensional hydrodynamical simulations

ABSTRACT We perform two-dimensional (2D) numerical simulations of core convection for zero-age main-sequence stars covering a mass range from 3 to 20 M⊙. The simulations are performed with the fully compressible time-implicit code music. We study the efficiency of overshooting, which describes the ballistic process of convective flows crossing a convective boundary, as a function of stellar mass and luminosity. We also study the impact of artificially increasing the stellar luminosity for 3 M⊙ models. The simulations cover hundreds to thousands of convective turnover time-scales. Applying the framework of extreme plume events previously developed for convective envelopes, we derive overshooting lengths as a function of stellar masses. We find that the overshooting distance (dov) scales with the stellar luminosity (L) and the convective core radius (rconv). We derive a scaling law $d_{\rm ov} \propto L^{1/3} r_{\rm conv}^{1/2}$, which is implemented in a one-dimensional stellar evolution code and the resulting stellar models are compared to observations. The scaling predicts values for the overshooting distance that significantly increase with stellar mass, in qualitative agreement with observations. Quantitatively, however, the predicted values are underestimated for masses ≳10 M⊙. Our 2D simulations show the formation of a nearly adiabatic layer just above the Schwarzschild boundary of the convective core, as exhibited in recent three-dimensional simulations of convection. The most luminous models show a growth in size with time of the nearly adiabatic layer. This growth seems to slow down as the upper edge of the nearly adiabatic layer gets closer to the maximum overshooting length and as the simulation time exceeds the typical thermal diffusive time-scale in the overshooting layer.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Engineered core/shell quantum dots as phosphors for solid-state lighting

Light-emitting diodes (LEDs) for solid state light ing (SSL) typically combine a blue or near- ultraviolet drive LED with one or more dow nconverting phosphors to produce “white” light. Further advances in both efficiency and wh ite-light quality will re quire new phosphors with narrow-band, highly efficient emission, particul arly in the red. A team led by principal investigator Dr. Victor Klim ov of Los Alamos National Labo ratory proposes to develop engineered semiconductor nanocrystal quantum dots (QDs) that combine optimal luminescent properties with long-term stability under ty pical downconverting conditions to enable new performance levels in SSL. The white LED phosphor industry is estimated to have sales of roughly $400 million in 2018 and would significantly benefit from the development of bright and narrow red-emitting QD phosphors because they woul d enable warmer whites without wasting energy by emission of light beyond the response of the human eye. In order to capitalize on the market opportunity, the LANL team is partnering with a local company called UbiQD that will facilitate US manufacturing.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

DHS Chemical and Biological Defense Architecture Development

This report describes application of architecture concepts to the chemical-biological defense space, as requested by the Chemical & Biological Defense (CBD) Program at the Science and Technology Office, U.S. Department of Homeland Security, for purposes of 1) understanding and characterizing system interdependencies and 2) prioritizing program development and allocation of resources. A series of graphical Operational Views (OVs) are presented, characterizing a notional chem-bio architecture at increasing levels of detail. Development best practices are highlighted, as well as potential analytical applications.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2019

SDN-NGenIA, a Software Defined Next Generation Integrated Architecture for HEP and Data Intensive Science

This project aims to enable the LHC and other leading programs in high energy physics and other global science domains funded by the DOE to operate with a new level of efficiency and control, through the development of a Next Generation Integrated Architecture (NGenIA) based on intelligent software defined network (SDN)-driven network systems coupled to high throughput applications. While the initial focus is on the challenging LHC use case, the systems and products being developed are general, and apply to many fields of data intensive science ranging from astrophysical sky surveys to bioinformatics and earth observation, as well as other organizations facing the challenges of extracting knowledge from distributed multi-petabyte data stores. A central concept in this development program is a new paradigm ‘consistent network operations’ among widely distributed computing and storage facilities, where stable high throughput flows, at set rates, cross load-balanced network paths, up to flexible high water marks that are adjusted in real time to accommodate other network traffic. The large smooth flows are launched and managed by SDN services that act in concert with the experiments’ site-resident data distribution and management systems, to meet the expanding needs of the science programs. The technical goals include the construction of autonomous, intelligent site-resident services that interact dynamically with network-resident services, and with the science programs’ principal data distribution and management tools, to request or command network resources in support of high throughput petascale to exascale workflow Specific work items include: 1. Developing compact Data Transfer Nodes (DTNs) with auto-tuning functions that support data transfer rates in the 100 Gbps to the 1 Tbps range when used with high throughput data transfer applications 2. Deep site orchestration among virtualized clusters, storage subsystems and subnets to successfully coschedule CPU, storage and network resources 3. Science-program designed site architectures, operational modes, and policy and resource usage priorities, adjudicated across multiple network domains and virtual organizations, using the orchestration functions and methods 4. Seamlessly extending end-to-end operation across both extra-site and intra-site boundaries through the use of Open vSwitch (OVS), FireQoS + next generation Science DMZs 5. Novel methods of system integration that enable granular control of extreme scale long distance transfers through flow matching of scattered source-destination address pairs to multi-domain dynamic circuits 6. Funneling massive sets of streams to DTNs at the site edge hosting petascale buffer pools configured for flows of 100 Gbps and up, exploiting state of the art data transfers 7. Adaptive scheduling based on pervasive end-to-end monitoring, including DTN or compute-node resident agents providing comprehensive end-system profiling 8. Developing unsupervised and supervised machine learning and modeling methods to optimize the workflow involving terabyte to multi-petabyte datasets.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Phase II Geochemical and Isotopic Evaluation of Groundwater Flow in the Pahute Mesa–Oasis Valley Flow System, Nevada

This report presents the results of the Phase II geochemical evaluation for the Pahute Mesa CAUs. The evaluation was performed by multiple organizations including Los Alamos National Laboratory (LANL), Desert Research Institute (DRI), Lawrence Livermore National Laboratory (LLNL), and Navarro. Section 1.0 presents the introduction and describes the objectives for the Phase II geochemical evaluation. Section 2.0 presents the hydrologic setting, including average annual precipitation and net infiltration, hydraulic-head gradients, geology, and hydrostratigraphy of the PM-OV flow system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Large scale SiPM testing for the Cosmic Muon Veto detector

A Cosmic Muon Veto (CMV) detector using extruded plastic scintillators is being built around the mini-Iron Calorimeter (mini-ICAL) detector at the transit campus of the India based Neutrino Observatory, Madurai. The extruded plastic scintillators will be embedded with wavelength shifting (WLS) fibres to absorb scintillating photons and propgate the re-emitted photons to the silicon-photomultipliers for the electronic signals. The CMV detector will require 760 extruded plastic scintillators to shield the mini-ICAL detector, and will require 3040 SiPMs for the readout. The design goal for the cosmic muon veto efficiency of the CMV is $>$99.99\% and fake veto rate less than 10$^{-5}$. Hence, every SiPM used in the detector needs to be characterised to satisfy the design goal of the CMV. For this, a large-scale testing system was developed, using an LED driver, to measure the gain and noise rate of each SiPM, and thus determine it's breakdown voltage ($V_{br}$) and optimum operating overvoltage ($V_{ov}$).

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Understanding the temperature and humidity dependence of the SiPM characteristics

A miniature version of the ICAL experiment at the India-based Neutrino Observatory, the mini-ICALis in operation at the IICHEP, Madurai. The commissioning work of a Cosmic Muon Veto detector (CMVD)on top of the mini-ICAL is continued using extruded plastic scintillators with embeddedWLS fibers and the SiPM as a photo-transducer. The CMVD is being built to study thefeasibility of a cosmic muon veto for a shallow-depth neutrino experiment. The SiPM is calibratedusing an ultrafast LED driver andthe same calibration techniques will be used during the data taking period with a simplified LED in thesame readout PCB. An experimental setup wasdesigned to characterise the SiPMs in a temperature controlled environment. The readout electronicsinvolves trans-impedance amplifiers and a voltage followers of combined gain 1.24 mV/$\mu$A and adigital storage oscilloscope for the data collection with a minimal distortion of SiPM signal.Various characteristics of the Hamamatsu SiPM (S13360-2050VE), e.g. signal shape, optically correlatedand uncorrelated noise, recovery time etc were studied as a function of $V_{ov}$, number of photoelectrons,the ambient temperature and the humidity. This paper will cover the details of those results.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Sub-inertial gravity modes in the B8V star KIC 7760680 reveal moderate core overshooting and low vertical diffusive mixing

Thus far, KIC 7760680 is the richest slowly pulsating B star, exhibiting 36 consecutive dipole (ℓ = 1) gravity (g-) modes. The monotonically decreasing period spacing of the series, in addition to the local dips in the pattern, confirm that KIC 7760680 is a moderate rotator with clear mode trapping in chemically inhomogeneous layers. We employ the traditional approximation of rotation to incorporate rotational effects on g-mode frequencies. Our detailed forward asteroseismic modeling of this g-mode series reveals that KIC 7760680 is a moderately rotating B star with mass ∼3.25 M {sub ⊙}. By simultaneously matching the slope of the period spacing and the number of modes in the observed frequency range, we deduce that the equatorial rotation frequency of KIC 7760680 is 0.4805 day{sup −1}, which is 26% of its Roche break up frequency. The relative deviation of the model frequencies and those observed is less than 1%. We succeed in tightly constraining the exponentially decaying convective core overshooting parameter to f {sub ov} ≈ 0.024 ± 0.001. This means that convective core overshooting can coexist with moderate rotation. Moreover, models with exponentially decaying overshoot from the core outperform those with the classical step-function overshoot. The best value for extra diffusive mixing in the radiatively stable envelope is confined to logD{sub ext}≈0.75±0.25 (with D {sub ext} in cm{sup 2} s{sup −1}), which is notably smaller than theoretical predictions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Exploring the helium core of the δ Scuti star CoRoT 102749568 with asteroseismology

Based on regularities in rotational splitting, we seek possible multiplets for the observed frequencies of CoRoT 102749568. There are 21 sets of multiplets identified, including four sets of multiplets with l = 1, nine sets of multiplets with l = 2, and eight sets of multiplets with l = 3. In particular, there are three complete triplets (f{sub 10}, f{sub 12}, f{sub 14}), (f{sub 31}, f{sub 34}, f{sub 35}), and (f{sub 41}, f{sub 43}, f{sub 44}). The rotational period of CoRoT 102749568 is estimated to be 1.34{sub −0.05}{sup +0.04} days. When doing model fittings, three l = 1 modes (f{sub 12}, f{sub 34}, and f{sub 43}) and the radial first overtone f{sub 13} are used. Our results shows that the three nonradial modes (f{sub 12}, f{sub 34}, and f{sub 43}) are mixed modes, which mainly provide constraints on the helium core. The radial first overtone f{sub 13} mainly provides constraint on the stellar envelope. Hence the size of the helium core of CoRoT 102749568 is determined to be M{sub He} = 0.148 ± 0.003 M{sub ⊙} and R{sub He} = 0.0581 ± 0.0007 R{sub ⊙}. The fundamental parameters of CoRoT 102749568 are determined to be M = 1.54 ± 0.03 M{sub ⊙}, Z=0.006, f{sub ov}=0.004±0.002, log g=3.696±0.003, T{sub eff}=6886±70 K, R = 2.916 ± 0.039 R{sub ⊙}, and L = 17.12 ± 1.13 L{sub ⊙}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

An Independent Asteroseismic Analysis of the Fundamental Parameters and Internal Structure of the Solar-like Oscillator KIC 6225718

Asteroseismology is a useful tool that is usually used to probe stellar interiors and to determine stellar fundamental parameters, such as stellar mass, radius, and surface gravity. In order to probe stellar interiors, making comparisons between observations and models is usually used with the χ{sup 2}-minimization method. The work of Wu and Li reported that the best parameter determined by the χ{sup 2}-matching process is the acoustic radius for pure p-mode oscillations. In the present work, based on the theoretical calculations of Wu and Li, we will independently analyze the seismic observations of KIC 6225718 to determine its fundamental parameters and to investigate its interior properties. First, in order to test the method, we use it in the Sun to determine its fundamental parameters and to investigate interiors. Second, we independently determine the fundamental parameters of KIC 6225718 without any other non-seismic constraint. Therefore, those determined fundamental parameters are independent of those determined by other methods. They can be regarded as independent references in other analyses. Finally, we analyze the stellar internal structure and find that KIC 6225718 has a convective core with the size of 0.078–0.092 R{sub ⊙}. Its overshooting parameter f{sub ov} in the core is around 0.010. In addition, its center hydrogen X{sub c} is about 0.264–0.355.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Development and fabrication of a graphite polyimide box beam

The state-of-the-art of graphite/polyimide structures was evaluated and key design and fabrication issues to be considered in future hardware programs are defined. The fabrication and testing at 500 F of a graphite/polyimide center wing box beam using OV-10A aircraft criteria was accomplished. The baseline design of this box was developed in a series of studies of other advanced composite materials: glass/epoxy, boron/epoxy, and boron/polyimide. The use of this basic design permits ready comparison of the performance of graphite/polyimide with these materials. Modifications to the baseline composite design were made only in those areas effected by the change of materials. Processing studies of graphite fiber polyimide resins systems resulted in the selection of a Modmor II/Gemon L material.

Nadler, M. A.↗
NASA NTRS1973

In-flight and laboratory vacuum-friction test results

Coefficient of friction measurements were made for six unlubricated metal couples exposed to the space environment aboard the OV-1-13 spacecraft and exposed to laboratory vacuum. Materials studied included mutually soluble, partially soluble, and insoluble metal combinations. Two samples of each material couple were tested in space and in the laboratory using the disk and rider technique. Linear velocity was 0.10 cm/s (2.5 in/min) and rider normal load was 4.45 N (1 lb) for the gold versus silver couples and 8.90 N (2lb) for the other combinations. Results showed that friction data obtained in a clean ion-pumped laboratory vacuum of 10 to the minus 10 power materials with low mutual solubility can be correlated to operation in the vicinity of a typical scientific spacecraft that is exposed to an ambient pressure as low as 10 to the minus 12 power torr. The expected increase in coefficient of friction with solubility was shown. Material couples with high mutual solubility present the hazard of unpredictable drastic friction increase in orbit which may not be evident in laboratory testing at levels down to 10 to the minus 10 power torr. It was also shown that gross cold welding of unlubricated metals exposed to a satellite environment does not occur.

Devine, E. J.↗