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NASA NTRS1997

Models of Speed Discrimination

The prime purpose of this project was to investigate various theoretical issues concerning the integration of information across visual space. To date, most of the research efforts in the study of the visual system seem to have been focused in two almost non-overlaping directions. One research focus has been the low level perception as studied by psychophysics. The other focus has been the study of high level vision exemplified by the study of object perception. Most of the effort in psychophysics has been devoted to the search for the fundamental "features" of perception. The general idea is that the most peripheral processes of the visual system decompose the input into features that are then used for classification and recognition. The experimental and theoretical focus has been on finding and describing these analyzers that decompose images into useful components. Various models are then compared to the physiological measurements performed on neurons in the sensory systems. In the study of higher level perception, the work has been focused on the representation of objects and on the connections between various physical effects and object perception. In this category we find the perception of 3D from a variety of physical measurements including motion, shading and other physical phenomena. With few exceptions, there seem to be very limited development of theories describing how the visual system might combine the output of the analyzers to form the representation of visual objects. Therefore, the processes underlying the integration of information over space represent critical aspects of vision system. The understanding of these processes will have implications on our expectations for the underlying physiological mechanisms, as well as for our models of the internal representation for visual percepts. In this project, we explored several mechanisms related to spatial summation, attention, and eye movements. The project comprised three components: 1. Modeling visual search for the detection of speed deviation. 2. Perception of moving objects. 3. Exploring the role of eye movements in various visual tasks.

Source record↗
DOE OSTI2019

Building Towards Discovery: Preparing for New Physics at the LHC [Final papers]

Particle physics today is at a crossroads. The Standard Model (SM) has survived four decades of experimental scrutiny and spurred multiple landmark discoveries, culminating with the 2012 discovery of the Higgs boson at the Large Hadron Collider (LHC). Yet we know that this model is incomplete. We live in a universe dominated by matter and energy unaccounted for by the SM– and the Higgs boson itself is improbably light. It falls to the current generation of high-energy physicists to go beyond the model and enter a new era of discovery. Andeen is leading a new research group at the University of Texas at Austin (UT-Austin) that is endeavoring to reveal novel physical phenomena through the discovery of new particles with the ATLAS detector at the LHC. A key element of our experience thus far has been collaborating closely with theorists to identify both interesting new physics models. In addition we work closely with electrical engineers in detector development. Our approach is therefore unique in its integration of theory, analysis and instrumentation, and is encapsulated in a three-pronged strategy. First is the essential task of analyzing our rapidly expanding dataset. I am directing my group in searches for vector-like quarks (VLQs). Should they exist, these hypothetical particles would indicate physics scenarios beyond the SM. Experimental constraints suggest VLQs decay preferentially to a third generation quark and a Higgs, W or Z boson. Today at 13 TeV, both multi-lepton (electron and muon) and jet substructure signatures are sensitive to identifying the VLQ decay products. The large Run 2 dataset (collected through 2018) of up to 150 fb -1 will allow us to simultaneously use multi-lepton signatures with jet-substructure in searches for new physics. UT-Austin is well positioned to be a leader in this area. Prof. P. Onyisi’s postdoctoral researchers and graduate students are searching for ttH signatures in three- and four-lepton channels and we benefit from their experience. We are also aided by the availability of the Texas Advanced Computing Center, which provides us with easy access to several high performance computing (HPC) systems. My previous experience in VLQ searches propels the work today. I have published both the first investigation into the single production of top partners (signatures of composite Higgs Models) of any LHC experiment 1 as well as one of the first analyses utilizing jet-substructure techniques to search for the single production of vector-like quarks. 2 Adding to this is my group’s work with the Liquid Argon (LAr) calorimeter, the primary instrument we use in detecting electrons. Second, my group is contributing to the operations of the LAr calorimeter while preparing to install and commission new electronic hardware (the Phase 1 upgrade) to this crucial component of the ATLAS detector. I have played a leading role in the development of a critical, radiation-hard, high-speed Analog-to-Digital Convertor (ADC) that is essential inselecting data collected by the LAr calorimeter. 3 This upgrade will improve the e!ciency with which we can select events in our detector. Postdoctoral researcher N. Nikiforou (based at CERN May 2016 onward) and graduate students (one based at CERN from the start of 2018 onward, with one additional graduate students from summer 2018) are growing our already deep experience in the operation of the LAr calorimeter to prepare for installation and commissioning of the new trigger readout in 2018-2019. My group will then be positioned to be the first to exploit the potential of the improved triggers in our multi-lepton searches for new physics. Third, a suite of preparations for a major detector upgrade, scheduled to be completed in 2024, are underway. My group is building hardware that will improve the electronic readout of the ATLAS detector. I am partnering with a group in the Electrical and Computer Engineering (ECE) Department at UT-Austin (Prof. N. Sun) to employ his work at the cutting edge of ADC research. We will support an ECE grad student for the layout of this design, and collaborate with engineering groups at Nevis Laboratory and the Electrical Engineering Department (Prof. P. Kinget) at Columbia University to integrate our ADC with gain selection circuits. We will provide this critical component of the ASIC at the challenging boundary of the analog and digital signals in the LAr calorimeter readout chain. Furthermore UT-Austin will lead the testing of this device during development and production (approximately 55,000 four-channel chips). This effort compliments my work as the deliverables manager for the LAr front-end ASICs for the US ATLAS HL-LHC project and strengthens the US commitment to that upgrade.In so doing, my group at the UT-Austin will be at the forefront of efforts to probe the structure of the universe to an unmatched degree both at the current LHC and with its future upgrades. Through both the ongoing analysis of data at the ATLAS detector and improvements to the detector itself, an answer to what lies beyond the SM may come within our grasp. My background in instrumentation and analysis allows my group to establish a singular research effort on the ATLAS experiment. In addition to answering fundamental questions about the subatomic world, the technologies developed could advance the broader scientific community and result in valuable spin-offs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Robustness of Deep Learning Classification to Adversarial Input on GPUs: Asynchronous Parallel Accumulation Is a Source of Vulnerability

The ability of machine learning (ML) classification models to resist small, targeted input perturbations—known as adversarial attacks—is a key measure of their safety and reliability. We show that floating-point non associativity (FPNA) coupled with asynchronous parallel programming on GPUs is sufficient to result in misclassification, without any perturbation to the input. Additionally, we show that this misclassification is particularly significant for inputs close to the decision boundary and that standard adversarial robustness results may be overestimated up to 4.6 when not considering machine-level details. We first study a linear classifier, before focusing on standard Graph Neural Network (GNN) architectures and datasets used in robustness assessments. We develop a novel black-box attack using Bayesian optimization to discover external workloads that can change the instruction scheduling which bias the output of reductions on GPUs and reliably lead to misclassification. Motivated by these results, we present a new learnable permutation (LP) gradient-based approach to learning floating-point operation orderings that lead to misclassifications. The LP approach provides a worst-case estimate in a computationally efficient manner, avoiding the need to run identical experiments tens of thousands of times over a potentially large set of possible GPU states or architectures. Finally, using instrumentation-based testing, we investigate parallel reduction ordering across different GPU architectures under external background workloads, when utilizing multi-GPU virtualization, and when applying power capping. Our results demonstrate that parallel reduction ordering varies significantly across architectures under the first two conditions, substantially increasing the search space required to fully test the effects of this parallel scheduler-based vulnerability. These results and the methods developed here can help to include machine-level considerations into adversarial robustness assessments, which can make a difference in safety and mission critical applications.

Shanmugavelu, Sanjif [Maxeler Technologies, a Groq↗
DOE OSTI2021

Hydrothermal corrosion of laser printed SiC fibers under extreme environment

We report SiC/SiC fiber composites are proposed cladding materials to improve the accident tolerance of commercial light water nuclear reactor fuel. To evaluate their viability, understanding the kinetics of corrosion under irradiation and high-temperature, high-pressure aqueous environment is critical. In the present work, the microstructure and mechanical properties of novel SiC fibers manufactured by Laser Chemical Vapor Deposition (LCVD) are introduced. The LCVD technology has control over microstructure and stoichiometry while allowing for high purity manufacturing, all key qualities needed in search of an optimum SiC fiber for nuclear energy applications. The isolated hydrothermal corrosion of commercially available carbon-rich Hi-Nicalon Type-S fibers is compared to the LCVD stoichiometric and LCVD silicon-rich fibers. Autoclave testing was carried out at 310°C and 14 MPa in the absence of irradiation. In a separate study, the effect of gamma irradiation on the fibers in the room-temperature environment was analyzed. It was observed from the experiments that the dissolution of the fibers was highly dependent on the stoichiometric ratio, fiber surface morphology and thermal pre-treatment of fibers. Contrary to previous findings, fiber dissolution was also visible under low-temperature gamma irradiation in aqueous environment with LCVD fibers showing lower dissolution.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enhanced ferroelectricity in ultrathin films grown directly on silicon

Ultrathin ferroelectric materials could potentially enable low-power logic and nonvolatile memories. As ferroelectric materials are made thinner, however, the ferroelectricity is usually suppressed. Size effects in ferroelectrics have been thoroughly investigated in perovskite oxides—the archetypal ferroelectric system. Perovskites, however, have so far proved unsuitable for thickness scaling and integration with modern semiconductor processes. In this paper we report ferroelectricity in ultrathin doped hafnium oxide (HfO 2 ), a fluorite-structure oxide grown by atomic layer deposition on silicon. We demonstrate the persistence of inversion symmetry breaking and spontaneous, switchable polarization down to a thickness of one nanometre. Our results indicate not only the absence of a ferroelectric critical thickness but also enhanced polar distortions as film thickness is reduced, unlike in perovskite ferroelectrics. This approach to enhancing ferroelectricity in ultrathin layers could provide a route towards polarization-driven memories and ferroelectric-based advanced transistors. This work shifts the search for the fundamental limits of ferroelectricity to simpler transition-metal oxide systems—that is, from perovskite-derived complex oxides to fluorite-structure binary oxides—in which ‘reverse’ size effects counterintuitively stabilize polar symmetry in the ultrathin regime.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1994

Orbital coplanarity in solar-type binary systems: Implications for planetary system formation and detection

The equatorial inclinations of solar-type stars within visual binary systems are computed by combining v sin i measurements with rotational period information, or with expected rotational velocities based upon the age of the star in question. These inclinations are then compared with the orbital inclinations of the systems to test the alignment between the equatorial and orbital planes, and how the tendency for or against coplanarity varies as a function of parameters such as spectral type, separation, eccentricity, etc. The results are extended to planetary systems in order to determine the appropriateness of basing planetary search strategies upon a parent star's equatorial inclination, and to address issues in planetary system formation and evolution, including the stability of planetary orbits within binary systems. During the course of this project new or improved v sin i measurements are made for over 30 solar-type stars within binary systems, and (for the purposes of the study) tentative orbits are computed for thirteen long-period systems. The results suggest that approximate coplanarity between the equatorial and orbital planes exists solar-type binary systems with separations less than 30-40 AU. The coplanarity tendency, as well as this 'critical separation,' is not significantly affected by most of the other parameters studied. The one significant exception occurs with hierarchical multiple systems, where noncoplanarity may exist at relatively small separations. If it is assumed that planetary distances in our solar system are typical, the results suggest there is no reason to expect planets to orbit in planes significantly different from that of the parent star's equator, in turn suggesting that planetary formation models and search strategies dependent upon this assumption are valid from this standpoint. The results also suggest that noncoplanarity between the components of a binary system is not a significant issue in addressing the stability of planetary orbits within the system.

Hale, Alan↗
DOE OSTI2026

Multi-omic characterization of a soil microbial consortium reveals critical role of succinate and glutamate metabolism during calcium carbonate precipitation

Microbially induced calcium carbonate precipitation (MICP) holds potential for use in soil stabilization and carbon sequestration, with the overall efficiency of the process being a major determinant for use in many environmental and civil engineering applications. While the biogeochemical pathways and enzymes driving MICP are known, the microbial metabolic networks and community dynamics underlying such precipitation remain poorly characterized. To address this gap, we developed a four-member consortium of soil bacteria (Curtobacterium flaccumfaciens, Rhodococcus qingshengii, Microbacterium sp., and Bacillus toyonensis), termed carbon storing consortium - A (CSC-A), that is capable of MICP. Prior work shows that MICP production is higher in CSC-A compared to the sum of carbonate produced by each member, suggesting carbonate production is driven by consortium dynamics. To that end we used a multi-omic integration approach of genomics, transcriptomics, and metabolomics to investigate potential inter-species interactions that may influence the MICP phenotype. Genomic life history characterizations identified evidence of niche specialization by B. toyonensis and Microbacterium, while metatranscriptomic analysis suggests R. qingshengii is a keystone species during growth in urea. By comparing individual species’ metabolomes to the metabolic profile of a shared well of precipitated metabolites, we identified over 200 metabolites predicted to be produced or consumed by CSC-A members. Integrating both data types to search the KEGG reactome highlighted a network centered around glutamine metabolism and branched chain amino acid biosynthesis under regulation during CSC-A growth in urea. Succinate metabolism was also a major node in this network and laboratory assays confirmed that increasing the amount of succinate in the growth medium leads to increased carbonate precipitation by CSC-A, a critical confirmation of our modeling approach. By isolating and identifying the interconnected metabolic components underlying MICP in CSC-A, we identified keystone taxa, metabolites, and pathways important for future optimization of the application of this consortia to carbonate precipitation.

carbon storing consortium - A (CSC-A)↗
DOE OSTI2021

Review of the November 11, 1905 Earthquake: Seismic Intensity Data, Magnitude, and Location Report

The macroseismic location and magnitude of the Shoshone 1905 earthquake has been based on the application of objective and quantitative approaches that produce estimates of earthquake source location and magnitude, and associated uncertainties. The performance of all three approaches applied depends critically on the characteristics of the seismic intensity field. Regional intensity attenuation relations were derived based on a calibration set of earthquakes and then, the procedure was validated using three independent very recent events. The macroseismic epicenter location was determined by either a grid search procedure, the spatial distribution of the sites experiencing the largest intensities, or a combination of both. The macroseismic magnitude estimates are based on the derived regional intensity attenuation relations. There is consistency in the location and magnitude of the November 1905 earthquake as obtained by the three methods. The overlapping region of the 68% bootstrap resampling solutions suggests a reliable epicenter location within 41.550N ? 42.060N and 113.478W ? 112.320W. This region encloses the original Oaks (1992) epicenter location. Macroseismic magnitude estimates range between 5.87 and 6.05.

58 GEOSCIENCES↗
NASA NTRSDate not supplied

In-Situ XRD/XRF to Support Life Detection on Mars

X-ray diffraction / X-ray fluorescence (XRD/XRF) analysis provides the most comprehensive mineralogical / compositional characterization of rocks and soils of any flight-capable technique. XRD data provide quantitative mineralogy (including abundance of X-ray amorphous materials) and crystal chemistry (structure, elemental composition and valence state), and XRF data provide complimentary major, minor, and some trace element abundances. Both types of data are important in evaluating habitability (environment of formation) and biosignature preservation/degradation (post-depositional diagenetic change). Whether or not a relict biosignature is detected, the mineral assemblage and its geochemistry can be used to determine the habitability of an ancient environment (e.g., salinity, pH, temperature), and to identify potential sources of energy for life (e.g., elements in different redox states). In this respect, a null result (a habitable environment lacking evidence of life) can play an important role in constraining the parameters of the search. Conversely, diagenetic alteration (taphonomic change) resulting from post-depositional variations in temperature, pressure or fluid chemistry can preserve evidence of biogenicity, erase such evidence completely or indeed can provide for post-depositional habitable conditions in the subsurface. XRD / XRF data are critical to these determinations. The CheMin instrument on the Mars Science Laboratory (MSL) Curiosity rover is the first XRD instrument flown in space. CheMin operates in transmission geometry with a Co X-ray source to minimize fluorescence from iron. Diffracted photons are collected with an energy-sensitive charge-coupled device (CCD). The position of the diffracted photons provides structural information for minerals, whereas the energy of sample-generated X-ray fluorescence photons provides elemental information, though these XRF data are qualitative. Mineralogical data from the CheMin XRD identified the three circumstances above: habitable depositional environments (e.g., Yellowknife Bay), habitable subsurface/diagenetic environments (e.g., throughout the Murray formation), and diagenetic conditions that may destroy evidence of habitability (e.g., oxidative and acidic environments at Vera Rubin ridge). Technological advances in X-ray technology and lessons learned from the operation of CheMin on Mars have resulted in a next-generation XRD/XRF, called CheMinX. Replacement of CheMin’s CCD with an array of hybrid pixel detectors and improvements in focusing optics dramatically decrease analysis time (15 minutes vs. 22 hours for MSL-CheMin) and result in a better angular resolution (0.18 vs. 0.30 °2θ for MSL-CheMin). This increased resolution improves mineral detection, including discrimination between types of pyroxenes, which is not possible with MSL-CheMin data. The hybrid pixel detectors do not require cooling like the MSL-CheMin CCD, therefore reducing the power needed to operate CheMinX. CheMinX has a silicon-drift detector (SDD) to measure fluoresced photons, enabling the quantification of major, minor, and some trace elements via XRF. XRD/XRF data are collected simultaneously in CheMinX, obviating the need for multiple compositional instruments. The CheMinX design also improves upon MSL-CheMin’s sample handling. Instead of sample cells on wheel, which are often not reusable and add complexity in commanding the instrument, CheMinX has single-use cells in a cartridge/dispenser configuration. Because of these improvements, CheMinX is an ideal instrument for Discovery-class life-detection missions, including Mars Life Explorer that was recommended for development in the Planetary Science and Astrobiology Decadal Survey 2023-2032.

E B Rampe↗
DOE OSTI2024

Searching for Suitable Binary Fluid for an Ejector Heat Pump for Domestic Water Heating

Water heating is a major source of energy consumption in the U.S. residential sector. Heat pumps can significantly increase the energy efficiency of water heating. An ejector heat pump (EHP) is a novel, thermally driven heat pump that uses an ejector as a thermocompressor. Choosing suitable working fluids is critical in developing high-performance EHPs. Therefore, this research screens binary fluid pairs (BFPs) for EHPs to produce domestic hot water at a high coefficient of performance (COP). The criteria for screening BFP candidates for EHP water heaters (EHPWHs) are established, and BFP candidates are shortlisted. This study identifies HFE7000, Novec649, HFE7100, HFE7200, and HFE7500 for the primary fluids and RE170, R600a, R600, and R1234ze(Z) for the secondary fluids. The thermodynamic model is employed to investigate the performance of EHPWHs using the shortlisted BFPs under various operating parameters, including the evaporation pressure of the primary working fluid in the high-temperature evaporator and the condensation temperature. In conclusion, the highest heating-cycle COP of 1.328 is achieved by an EHPWH operating with HFE7000/R600 at a condenser temperature of 50 °C and a pressure of 1.69 MPa in the high-temperature evaporator.

42 ENGINEERING↗
NASA NTRS2001

Technology Thrusts for Future Earth Science Applications

This paper presents NASA's recent direction to invest in the critical science instrument and platform technologies in order to realize more reliable, frequent and versatile missions for future Earth Science measurements. Historically, NASA's Earth Science Enterprise has developed and flown science missions that have been large in size, mass and volume. These missions have taken much longer to implement due to technology development time, and have carried a large suite of instruments on a large spacecraft. NASA is now facing an era where the budget for the future years is more or less flat and the possibility for any major new start does not vividly appear on the horizon. Unfortunately, the scientific measurement needs for remote sensing have not shrunk to commensurate with the budget constraints. In fact, the challenges and scientific appetite in search of answers to a score of outstanding questions have been gradually expanding. With these factors in mind, for the last three years NASA has been changing its focus to concentrate on how to take advantage of smaller missions by relying on industry, and minimizing the overall mission life cycle by developing technologies that are independent of the mission implementation cycle. The major redirection of early investment in the critical technologies should eventually have its rewards and significantly reduce the mission development period. Needless to say, in the long run this approach should save money, minimize risk, promote or encourage partnering, allow for a rapid response to measurement needs, and enable frequent missions making a wider variety of earth science measurements. This paper gives an overview of some of the identified crucial technologies and their intended applications for meeting the future Earth Science challenges.

Habib, Shahid↗
DOE OSTI2019

Materials Discovery of Stable and Nontoxic Halide Perovskite Materials for High‐Efficiency Solar Cells

Abstract Two critical limitations of organic–inorganic lead halide perovskite materials for solar cells are their poor stability in humid environments and inclusion of toxic lead. In this study, high‐throughput density functional theory (DFT) methods are used to computationally model and screen 1845 halide perovskites in search of new materials without these limitations that are promising for solar cell applications. This study focuses on finding materials that are comprised of nontoxic elements, stable in a humid operating environment, and have an optimal bandgap for one of single junction, tandem Si‐perovskite, or quantum dot–based solar cells. Single junction materials are also screened on predicted single junction photovoltaic (PV) efficiencies exceeding 22.7%, which is the current highest reported PV efficiency for halide perovskites. Generally, these methods qualitatively reproduce the properties of known promising nontoxic halide perovskites that are either experimentally evaluated or predicted from theory. From a set of 1845 materials, 15 materials pass all screening criteria for single junction cell applications, 13 of which are not previously investigated, such as (CH 3 NH 3 ) 0.75 Cs 0.25 SnI 3 , ((NH 2 ) 2 CH)Ag 0.5 Sb 0.5 Br 3 , CsMn 0.875 Fe 0.125 I 3 , ((CH 3 ) 2 NH 2 )Ag 0.5 Bi 0.5 I 3 , and ((NH 2 ) 2 CH) 0.5 Rb 0.5 SnI 3 . These materials, together with others predicted in this study, may be promising candidate materials for stable, highly efficient, and nontoxic perovskite‐based solar cells.

Jacobs, Ryan↗
DOE OSTI2019

Accuracy of Fukuoka and American Gastroenterological Association Guidelines for Predicting Advanced Neoplasia in Pancreatic Cyst Neoplasm: A Meta-Analysis

Background: A differential diagnosis of advanced pancreatic cystic neoplasms (PCNs) is critical to determine optimal treatment. The Fukuoka and American Gastroenterological Association (AGA) guidelines are the most widely accepted criteria for the management of PCNs. Objective: This study aimed to evaluate the diagnostic value of these guidelines in predicting advanced neoplasia (AN). Methods: A comprehensive electronic search of the PubMed, EMBASE, Web of Science, Cochrane Library, and Scopus databases was conducted to identify all relevant studies evaluating the Fukuoka and AGA guidelines in surgically resected and histologically confirmed PCNs. Pooled sensitivity, specificity, and diagnostic odds ratios (DORs) were calculated as compound measures of diagnostic accuracy using the random-effects model. Summary of receiver operating characteristic (SROC) curves and the area under the curve (AUC) were also performed. Results: A total of 21 studies with 3723 patients were included in this meta-analysis. Of these studies, 15, 4, and 2 evaluated the Fukuoka guidelines, the AGA guidelines, and both guidelines, respectively. For AN prediction, the Fukuoka guidelines had a pooled sensitivity of 0.67 (95% confidence interval [CI] 0.64–0.70), pooled specificity of 0.64 (95% CI 0.62–0.66), and pooled DOR of 6.28 (95% CI 4.38–9.01), with an AUC of the SROC of 0.78. AGA guidelines showed a pooled sensitivity of 0.59 (95% CI 0.52–0.65), pooled specificity of 0.77 (95% CI 0.74–0.80), and pooled DOR of 5.84 (95% CI 2.60–13.15), with an AUC of 0.79 (95% CI 0.70–0.88). Conclusion: When used alone, the Fukuoka and AGA guidelines showed similar but unsatisfactory diagnostic accuracy in the risk stratification of malignant potential of PCN. Thus, we recommend that they be applied only as a broad framework in clinical practice.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS2000

Technology Thrust for Future Earth Science Applications

This paper presents NASA's recent direction to invest in the critical science instrument and platform technologies in order to realize more reliable, frequent and versatile missions for future Earth Science measurements. Traditionally, NASA's Earth Science Enterprise has developed and flown science missions that have been large in size, weight and volume. These missions have taken much longer implementation due to technology development time and have carried a large suite of instruments on a large-size spacecraft. NASA is also facing an era where the budget for the future years is more or less flat and the possibility for any major new start does not vividly appear on the horizon. Unfortunately, the scientific goals have not shrunk to commensurate with the budget constraints. In fact, the challenges and scientific appetite in search of answers to a score of outstanding questions have been gradually expanding. With these factors in mind, for the last three years NASA has been changing its focus to concentrate on how to take advantage of smaller missions by relying on industry, and minimizing the overall life cycle by infusing technologies that are being developed independently of any planned mission's implementation cycle. The major redirection of early investment in the critical technologies should have its rewards and significantly reduce the mission development period. Needless to say, in the long run this approach should save money, minimize risk, promote or encourage partnering, and allow for more frequent missions or earth science measurements to occur. This paper gives an overview of some of the identified crucial technologies and their intended applications for meeting the future Earth Science challenges.

Habib, Shahid↗
DOE OSTI2019

Quantum control landscape of bipartite systems

The control landscape of a quantum system A interacting with another quantum system B is studied. Only system A is accessible through time dependent controls, while system B is not accessible. The objective is to find controls that implement a desired unitary transformation on A, regardless of the evolution on B, at a sufficiently large final time. The freedom in the evolution on B is used to define an extended control landscape on which the critical points are investigated in terms of kinematic and dynamic gradients. A spectral decomposition of the corresponding extended unitary system simplifies the landscape analysis which provides: (i) a sufficient condition on the rank of the dynamic gradient of the extended landscape that guarantees a trap free search for the final time unitary matrix of system A, and (ii) a detailed decomposition of the components of the overall dynamic gradient matrix. Consequently, if the rank condition is satisfied, a gradient algorithm will find the controls that implements the target unitary on system A. It is shown that even if the dynamic gradient with respect to the controls alone is not full rank, the additional flexibility due to the parameters that define the extended landscape still can allow for the rank condition of the extended landscape to hold. Moreover, satisfaction of the latter rank condition subsumes any assumptions about controllability, reachability and control resources. Here satisfaction of the rank condition is taken as an assumption. The conditions which ensure that it holds remain an open research question. We lend some numerical support with two common examples for which the rank condition holds.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Best practices for photovoltaic performance loss rate calculations

Abstract The performance loss rate (PLR) is a vital parameter for the time-dependent assessment of photovoltaic (PV) system performance and health state. Although this metric can be calculated in a relatively straightforward manner, it is challenging to achieve accurate and reproducible results with low uncertainty. Furthermore, the temporal evolution of PV system performance is usually nonlinear, but in many cases a linear evaluation is preferred as it simplifies the assessment and it is easier to evaluate. As such, the search for a robust and reproducible calculation methodology providing reliable linear PLR values across different types of systems and conditions has been the focus of many research activities in recent years. In this paper, the determination of PV system PLR using different pipelines and approaches is critically evaluated and recommendations for best practices are given. As nonlinear PLR assessments are fairly new, there is no consent on how to calculate reliable values. Several promising nonlinear approaches have been developed recently and are presented as tools to evaluate the PV system performance in great detail. Furthermore, challenges are discussed with respect to the PLR calculation but also opportunities for differentiating individual performance losses from a generic PLR value having the potential of enabling actionable insights for maintenance.

14 SOLAR ENERGY↗
NASA NTRS1992

Laminar flow control - Introduction and overview

A development history and a development-trends evaluation are presented for laminar flow controlled airfoil technologies and design concepts, including the search for 'natural' laminar flow and actively controlled flow via suction through small pores on the airfoil surface. While most NASA activities in this field have been concerned with subsonic aircraft, it has been projected that the control of boundary layer turbulence may be even more critical to the aerodynamic efficiency of supersonic aircraft. Developmental programs for these techniques have been conducted with several modified conventional aircraft.

Hefner, Jerry N.↗
NASA NTRS2002

Workshop on Spectroscopy of the Martian Surface: What Next?

Members of the Mars infrared spectral community desired to assess what spectral instrument will best serve the Mars program and spectral community after the successful flight of currently planned instruments. It was felt this issue needed to be addressed, given the shift of the NASA Mars program toward a search for regions conductive to the preservation of biomarkers, and the desire for sample return. To this end, leaders of the planetary community with expertise in spectroscopy and remote mineral identification met to discuss the state of understanding of Mars surface composition, and to assess what critical gaps may exist: 1) after the successful completion of planned measurements of Mars; and 2) in research programs to support investigations of the current and planned data sets. Participants also discussed the proposed Mars airplane. This report summarizes our consensus.

Kirkland, L.↗