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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Screening Compounds for Fast Pyrolysis and Catalytic Biofuel Upgrading Using Artificial Neural Networks

Abstract There is significant interest among researchers in finding economically sustainable alternatives to fossil-derived drop-in fuels and fuel additives. Fast pyrolysis, a method for converting biomass into liquid hydrocarbons with the potential for use as fuels or fuel additives, is a promising technology that can be two to three times less expensive at scale when compared to alternative approaches such as gasification and fermentation. However, many bio-oils directly derived from fast pyrolysis have a high oxygen content and high acidity, indicating poor performance in diesel engines when used as fuels or fuel additives. Thus, a combination of selective fast pyrolysis and chemical catalysis could produce tuned bioblendstocks that perform optimally in diesel engines. The variance in performance for derived compounds introduces a feedback loop in researching acceptable fuels and fuel additives, as various combustion properties for these compounds must be determined after pyrolysis and catalytic upgrading occurs. The present work aims to reduce this feedback loop by utilizing artificial neural networks trained with quantitative structure-property relationship values to preemptively screen pure component compounds that will be produced from fast pyrolysis and catalytic upgrading. The quantitative structure-property relationship values selected as inputs for models are discussed, the cetane number and sooting propensity of compounds derived from the catalytic upgrading of phenol are predicted, and the viability of these compounds as fuels and fuel additives is analyzed. The model constructed to predict cetane number has a test set prediction root-mean-squared error of 9.874 cetane units, and the model constructed to predict yield sooting index has a test set prediction root-mean-squared error of 13.478 yield sooting index units (on the unified scale).

09 BIOMASS FUELS↗
DOE OSTI2017

Genome Stability in Engineered Strains of the Extremely Thermophilic Lignocellulose-Degrading Bacterium Caldicellulosiruptor bescii

Caldicellulosiruptor bescii is the most thermophilic cellulose degrader known and is of great interest because of its ability to degrade nonpretreated plant biomass. For biotechnological applications, an efficient genetic system is required to engineer it to convert plant biomass into desired products. To date, two different genetically tractable lineages of C. bescii strains have been generated. The first (JWCB005) is based on a random deletion within the pyrimidine biosynthesis genes pyrFA , and the second (MACB1018) is based on the targeted deletion of pyrE , making use of a kanamycin resistance marker. Importantly, an active insertion element, IS Cbe4 , was discovered in C. bescii when it disrupted the gene for lactate dehydrogenase ( ldh ) in strain JWCB018, constructed in the JWCB005 background. Additional instances of IS Cbe4 movement in other strains of this lineage are presented herein. These observations raise concerns about the genetic stability of such strains and their use as metabolic engineering platforms. In order to investigate genome stability in engineered strains of C. bescii from the two lineages, genome sequencing and Southern blot analyses were performed. The evidence presented shows a dramatic increase in the number of single nucleotide polymorphisms, insertions/deletions, and IS Cbe4 elements within the genome of JWCB005, leading to massive genome rearrangements in its daughter strain, JWCB018. Such dramatic effects were not evident in the newer MACB1018 lineage, indicating that JWCB005 and its daughter strains are not suitable for metabolic engineering purposes in C. bescii . Furthermore, a facile approach for assessing genomic stability in C. bescii has been established. Caldicellulosiruptor bescii is a cellulolytic extremely thermophilic bacterium of great interest for metabolic engineering efforts geared toward lignocellulosic biofuel and bio-based chemical production. Genetic technology in C. bescii has led to the development of two uracil auxotrophic genetic background strains for metabolic engineering. We show that strains derived from the genetic background containing a random deletion in uracil biosynthesis genes ( pyrFA ) have a dramatic increase in the number of single nucleotide polymorphisms, insertions/deletions, and IS Cbe4 insertion elements in their genomes compared to the wild type. At least one daughter strain of this lineage also contains large-scale genome rearrangements that are flanked by these IS Cbe4 elements. Finally, in contrast, strains developed from the second background strain developed using a targeted deletion strategy of the uracil biosynthetic gene pyrE have a stable genome structure, making them preferable for future metabolic engineering studies.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

A Hybrid Reduced-Order Model of Fine-Resolution Hydrologic Simulations at a Polygonal Tundra Site

High-resolution predictions of land surface hydrological dynamics are desirable for improved investigations of regional- and watershed-scale processes. Direct deterministic simulations of fine-resolution land surface variables present many challenges, including high computational cost. We therefore propose the use of reduced-order modeling techniques to facilitate emulation of fine-resolution simulations. We use an emulator, Gaussian process regression, to approximate fine-resolution four-dimensional soil moisture fields predicted using a three-dimensional surface-subsurface hydrological simulator (PFLOTRAN). A dimension-reduction technique known as “proper orthogonal decomposition” is further used to improve the efficiency of the resulting reduced-order model (ROM). The ROM reduces simulation computational demand to negligible levels compared to the underlying fine-resolution model. In addition, the ROM that we constructed is equipped with an uncertainty estimate, allowing modelers to construct a ROM consistent with uncertainty in the measured data. The ROM is also capable of constructing statistically equivalent analogs that can be used in uncertainty and sensitivity analyses. We apply the technique to four polygonal tundra sites near Barrow, Alaska that are part of the Department of Energy’s Next-Generation Ecosystem Experiments (NGEE)-Arctic project. The ROM is trained for each site using simulated soil moisture from 1998-2000 and validated using the simulated data for 2002 and 2006. The average relative RMSEs of the ROMs are under 1%.

58 GEOSCIENCES↗
DOE OSTI2013

Task I: Dark Matter Search Experiments with Cryogenic Detectors: CDMS-I and CDMS-II Task II: Experimental Study of Neutrino Properties: EXO and KamLAND

Dark Matter Search - During the period of performance, our group continued the search for dark matter in the form of weakly interacting massive particles or WIMPs. As a key member of the CDMS (Cryogenic Dark Matter Search) collaboration, we completed the CDMS II experiment which led the field in sensitivity for more than five years. We fabricated all detectors, and participated in detector testing and verification. In addition, we participated in the construction and operation of the facility at the Soudan Underground Laboratory and played key roles in the data acquisition and analysis. Towards the end of the performance period, we began operating the SuperCDMS Soudan experiment, which consists of 15 advanced Ge (9 kg) detectors. The advanced detector design called iZIP grew out of our earlier DOE Particle Detector R&D program which demonstrated the rejection of surface electrons to levels where they are no longer the dominant source of background. Our group invented this advanced design and these larger detectors were fabricated on the Stanford campus in collaboration with the SLAC CDMS group and the Santa Clara University group. The sensitivity reach is expected to be up to 5 times better than CDMS II after two years of operation. We will check the new limits on WIMPs set by XENON100, and we expect improved sensitivity for light mass WIMPs beyond that of any other existing experiment. Our group includes the Spokesperson for SuperCDMS and continues to make important contributions to improvements in the detector technology which are enabling the very low trigger thresholds used to explore the low mass WIMP region. We are making detailed measurements of the charge transport and trapping within Ge crystals, measuring the diffusive trapping distance of the quasiparticle excitations within the Al phonon collector fins on the detector surface, and we are contributing to the development of much improved detector Monte Carlos which are essential to guide the detector design and optimize the analysis. Neutrino Physics – In the period of performance the neutrino group successfully completed the construction of EXO-200 and commissioned the detector. Science data taking started on Jun 1, 2011. With the discovery of the 2-neutrino double-beta decay in 136-Xe and the first measurement of the 0-neutrino mode resulting in the most stringent limit of Majorana masses, our group continues to be a leading innovator in the field of neutrino physics which is central to DOE-HEP Intensity Frontier program. The phenomenon of neutrino oscillations, in part elucidated by our earlier efforts with the Palo Verde and KamLAND experiments, provides the crucial information that neutrino masses are non-zero and, yet, it contains no information on the value of the neutrino mass scale. In recent times our group has therefore shifted its focus to a high sensitivity 0-neutrino double beta decay program, EXO. The 0-neutrino double beta decay provides the best chance of extending the sensitivity to the neutrino mass scale below 10 meV but, maybe more importantly, it tests the nature of the neutrino wave function, providing the most sensitive probe for Majorana particles and lepton number violation. The EXO program, formulated by our group several years ago, plans to use up to tonnes of the isotope 136-Xe to study the 0-neutrino double beta decay mode. The EXO-200 detector is the first step in this program and it represents the only large US-led and based experiment taking data. The EXO-200 isotope enrichment program broke new grounds for the enterprise of double beta decay. The detector design and material selection program paid off, resulting in a background that is among the very best in the field. The “first light" of EXO-200 was very exciting with the discovery -in the first month of data- of the rarest 2-neutrino double beta decay mode ever observed. The lower limit on the 0-neutrino double beta decay half-life, published in Phys. Rev. Lett. and based on the first 120 days of data is the second best but, when translated into a Majorana mass scale, it is one of the most stringent constraint we have on neutrino masses. Indeed, such a limit was the first result to contradict a claim of discovery in 76-Ge for most nuclear matrix elements calculations. As we continue data taking and plan some modest upgrades to EXO-200 our group is also very active in the design of nEXO, a 5 tonne detector based on the technology demonstrated by EXO-200. Over the years we have made it a tradition to explore the frontier and not to be shy about looking in new directions and re-inventing ourselves to best take advantage of the precious few opportunities provided by Nature. We have also cultivated a number of young people at all levels and, by now, many of the undergraduates, graduate students and postdocs educated by this group have leading positions in academia and industry around the world.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Progress Report on Alloy 617 Time Dependent Allowables

Time dependent allowable stresses are required in the ASME Boiler and Pressure Vessel Code for design of components in the temperature range where time dependent deformation (i.e., creep) is expected to become significant. There are time dependent allowable stresses in Section IID of the Code for use in the non-nuclear construction codes, however, there are additional criteria that must be considered in developing time dependent allowables for nuclear components. These criteria are specified in Section III NH. St is defined as the lesser of three quantities: 100% of the average stress required to obtain a total (elastic, plastic, primary and secondary creep) strain of 1%; 67% of the minimum stress to cause rupture; and 80% of the minimum stress to cause the initiation of tertiary creep. The values are reported for a range of temperatures and for time increments up to 100,000 hours. These values are determined from uniaxial creep tests, which involve the elevated temperature application of a constant load which is relatively small, resulting in deformation over a long time period prior to rupture. The stress which is the minimum resulting from these criteria is the time dependent allowable stress St. In this report data from a large number of creep and creep-rupture tests on Alloy 617 are analyzed using the ASME Section III NH criteria. Data which are used in the analysis are from the ongoing DOE sponsored high temperature materials program, form Korea Atomic Energy Institute through the Generation IV VHTR Materials Program and historical data from previous HTR research and vendor data generated in developing the alloy. It is found that the tertiary creep criterion determines St at highest temperatures, while the stress to cause 1% total strain controls at low temperatures. The ASME Section III Working Group on Allowable Stress Criteria has recommended that the uncertainties associated with determining the onset of tertiary creep and the lack of significant cavitation associated with early tertiary creep strain suggest that the tertiary creep criteria is not appropriate for this material. If the tertiary creep criterion is dropped from consideration, the stress to rupture criteria determines St at all but the lowest temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Residual Stresses and Other Properties of Teardrops

The Department of Energy’s 3013 Standard for packaging plutonium-bearing materials for storage up to fifty years specifies a minimum of two individually welded, nested containers herein referred to as the 3013 outer and the 3013 inner.1 Stress corrosion cracking (SCC) is a potential failure mechanism for 3013 inner containers.2,3 The bagless transfer container (BTC), a 3013 inner container used by Hanford and Savanna River Site (SRS) made from 304L stainless steel (SS), poses the greatest concern for SCC.4,5 The Surveillance and Monitoring Program (SMP) use stressed metal samples known as teardrops as screening tools in SCC studies to evaluate factors that could result in cracks in the 3013 containers.6,7 This report provides background information on the teardrops used in the Los Alamos National Laboratory (LANL) SMP studies including method of construction, composition and variability. In addition, the report discusses measurements of residual stresses in teardrops and compares the results with residual stresses in BTCs reported previously.4 Factors affecting residual stresses, including teardrop dimensions and surface finish, are also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Data Quality Objectives Supporting Radiological Air Emissions Monitoring for the PNNL-Richland Campus: North Campus Construction (Rev. 3)

Starting in fiscal year 2023, the north area of the PNNL-Richland Campus will undergo development. Initially, infrastructure (water, electrical) improvements will be installed. Later development includes the construction of several new office buildings. The area to be developed currently contains no buildings but does have two existing solar-powered ambient air sampling stations. Under the requirements of Washington State Department of Health Radioactive Air Emissions License -005, the PNNL-Richland Campus must operate and maintain a radiological air monitoring program. This revision documents and evaluates how the new North Campus construction impacts ambient air surveillance stations within the development region. This revision also considers current stack configurations and uses an updated environmental dispersion model and updated meteorological data. The DQO team concluded that one sampling station in the construction area will be relocated and the other remain in place. The evaluations conducted for this DQO also identified a third sampling station outside the development area that is recommended for relocation as a result of updated dispersion modeling. Recommended sites for the relocations are presented. Considerations for sampling in and around a construction zone are also addressed. Additionally, programmatic improvements to the ambient air sampling program were identified in the DQO process.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

High-Temperature Oxidation Behavior of Wrought and Additive Manufactured H282 in Direct-Fired Supercritical CO2 Power Cycle Environments

Materials selection is a key concern for corrosion resistance in high temperature and pressure direct-fired supercritical CO2 power cycles. The effect of elevated pressure on corrosion resistance can be critical, as impurities within the supercritical fluid such as H2O and O2 can result in additional corrosion behaviors. Utilizing additive manufacturing (AM) methods for construction of power cycle components requiring both compact and complex designs could be advantageous. AM H282 produced by laser powder bed fusion was exposed to direct-fired conditions (95CO2 – 4H2O – 1 O2) at 750 °C at both atmospheric pressure and supercritical conditions (20 MPa) for up to 4,000 hours. Oxidation behavior, sub-surface carbide formation, and chromia scale volatilization was dependent upon AM preparation techniques and surface modifications. These results are discussed in terms of the potential compatibility issues that may arise when using AM alloys in high temperature regions of direct-fired sCO2 power cycles, particularly for thin-walled components.

Carney, Casey↗
DOE OSTI2021

The Last Journey. II. SMACC—Subhalo Mass-loss Analysis Using Core Catalogs

Here we introduce Subhalo Mass-loss Analysis using Core Catalogs (SMACC). SMACC adds a mass model to substructure merger trees based on halo "core tracking." Our approach avoids the need for running expensive subhalo finding algorithms and instead uses subhalo mass-loss modeling to assign masses to halo cores. We present details of the SMACC methodology and demonstrate its excellent performance in describing halo substructure and its evolution. Validation of the approach is carried out using cosmological simulations at significantly different resolutions. We apply SMACC to the 1.24-trillion-particle Last Journey simulation and construct core catalogs with the additional mass information. These catalogs can be readily used as input to semianalytic models or subhalo abundance matching approaches to determine approximate galaxy distributions, as well as for in-depth studies of small-scale structure evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Distance Estimate Method for Asymptotic Giant Branch Stars Using Infrared Spectral Energy Distributions

We present a method to estimate distances to asymptotic giant branch (AGB) stars in the Galaxy, using spectral energy distributions (SEDs) in the near- and mid-infrared. By assuming that a given set of source properties (initial mass, stellar temperature, composition, and evolutionary stage) will provide a typical SED shape and brightness, sources are color matched to a distance-calibrated template and thereafter scaled to extract the distance. The method is tested by comparing the distances obtained to those estimated from very long baseline interferometry or Gaia parallax measurements, yielding a strong correlation in both cases. Additional templates are formed by constructing a source sample likely to be close to the Galactic center, and thus with a common, typical distance for calibration of the templates. These first results provide statistical distance estimates to a set of almost 15,000 Milky Way AGB stars belonging to the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey, with typical distance errors of ±35%. With these statistical distances, a map of the intermediate-age population of stars traced by AGBs is formed, and a clear bar structure can be discerned, consistent with the previously reported inclination angle of 30° to the GC–Sun direction vector. These results motivate deeper studies of the AGB population to tease out the intermediate-age stellar distribution throughout the Galaxy, as well as determining statistical properties of the AGB population luminosity and mass-loss-rate distributions.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1974

Ultrasonic filtration of industrial chemical solutions

The practical results obtained as a result of filtering industrial chemical solutions under continuous flow conditions with the aid of an ultrasonic filter are presented. The main part of the assembly consists of an ultrasonic generator with an output power of about 400 W and the filtration assembly, in which there is a magnetostrictive amplifier constructed for 20.5 kHz. In addition to ensuring a continuous flow of filtered solution, ultrasonic filters can be replaced or cleaned at intervals of time that are 8-10 times greater than in the case of mechanical filters. They yield considerably better results as far as the size of the filtered particles is concerned. The parameters on which filtration quality depends are also presented.

Cosma, T.↗
NASA NTRS1974

Martian volcanism - Additional observations and evidence for pyroclastic activity

Inspection of the Mariner 9 B-camera (resolution 100-200 m) and A-camera (resolution 1-2 km) photographs of Mars reveals numerous analogs of terrestrial and lunar volcanic features. In addition to the exceptionally large constructional features in the Tharsis region, many other large and small landforms present probably are related to endogenic processes.

West, M.↗
NASA NTRS1975

A preliminary investigation of the potential applicability of the IPAD system to non-aerospace industry

A study of the applicability of the planned Integrated Programs for Aerospace-Vehicle Design (IPAD) system to the design activities of non-aerospace industries was carried out. It was determined that IPAD could be of significant benefit to a number of industries, with the most likely users being the heavy construction and automotive industries. Two additional short studies were initiated to investigate the possible impact of IPAD on a national energy program and on urban and regional planning activities of local and state governments. These initial studies indicated the possibility of significant payoff in these areas and the need for further investigations. It was also determined that utilization of IPAD by non-aerospace industries will probably involve a long stepwise process, since these industries maintain a policy of gradual introduction of new technology.

Hulbert, L. E.↗
NASA NTRS1979

Analysis and design of a second-order digital phase-locked loop

A specific second-order digital phase-locked loop (DPLL) was modeled as a first-order Markov chain with alternatives. From the matrix of transition probabilities of the Markov chain, the steady-state phase error of the DPLL was determined. In a similar manner the loop's response was calculated for a fading input. Additionally, a hardware DPLL was constructed and tested to provide a comparison to the results obtained from the Markov chain model. In all cases tested, good agreement was found between the theoretical predictions and the experimental data.

Blasche, P. R.↗
NASA NTRS1980

Development of an experiment of opportunity test payload for the space transportation system

This paper describes a means for flying existing Sounding Rocket payloads aboard the Space Shuttle by developing small experiment carriers which become detached from the Orbiter and are later retrieved and reused. An effort is underway at the Goddard Space Flight Center to develop such a carrier which would be flown as an Experiment of Opportunity Payload (EOP). The activity is viewed as a feasibility test, and success will encourage the construction of similar packages for additional sounding rocket experiments, for eventual evolution of p

Shrewsberry, D. J.↗
NASA NTRS1980

Dynamic response of a forward-swept-wing model at angles of attack up to 15 deg at a Mach number of 0.8

Root mean square (rms) bending moments for a dynamically scaled, aeroelastic wing of a proposed forward swept wing, flight demonstrator airplane are presented for angles of attack up to 15 deg at a Mach number of 0.8 The 0.6 size semispan model had a leading edge forward sweep of 44 deg and was constructed of composite material. In addition to broad band responses, individual rms responses and total damping ratios are presented for the first two natural modes. The results show that the rms response increases with angle of attack and has a peak value at an angle of attack near 13 deg. In general, the response was characteristic of buffeting and similar to results often observed for aft swept wings. At an angle of attack near 13 deg, however, the response had characteristics associated with approaching a dynamic instability, although no instability was observed over the range of parameters investigated.

Doggett, R. V., Jr.↗
NASA NTRS1983

The IRAS project organisation and mission operations

The project organisation of IRAS is described, showing the tasks assigned to each project group during post-launch operations. The satellite is described, emphasizing the detectors. In the task division, the role of the U.S. is to construct the telescope and survey instrument, launch the satellite, process final science data for the survey instrument, and provide certain standard satellite items. The Netherlands construct the spacecraft and three additional instruments, integrates and tests the overall satellite, and designs and participates in the development of the operational system. The U.K. provides the operational control center and primary tracking station, generates a system for preliminary science analysis of the survey data, provides housekeeping analysis software and science data distribution software, and staffs the control center operations. The teams involved in mission planning and operations, and their roles, are identified, and a block diagram of the operations organisation is presented.

Van Holtz, R. C.↗
NASA NTRS1984

Topics in electrochemical degradation of photovoltaic modules

Electrochemical degradation of photovoltaic modules was examined. It is found that the extent of electrochemical damage is dependent on the integrated leakage current. The PV electrochemical degradation mechanisms in the two polarities are different: (1) degradation rates in the two polarities are of the same order of magnitude; (2) center tapped grounded arrays are a preferred system configuration to minimize electrochemical degradation. The use of thicker pottant layers and polymer substrate films to reduce equilibrium leakage current values is suggested. A metallized substrate layer, if used, should be isolated from the pottant and the frame by polyester layers, and EVA modules appear to be consistent with 30 year life allocation levels for electrochemical damage. Temperature acceleration factors are well behaved and moderately well understood; humidity acceleration factors vary radically with module construction and materials and require additional research.

Mon, G. R.↗