Leveraging GPUs and the Multiple-Program Multiple-Data (MPMD) Computing Model to Enable Material-Aware Topology Optimization.
Abstract not provided.
Robbins, Joshua↗
SEARCH · Engineering Papers
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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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Total Measurement Uncertainty in Neutron Coincidence Multiplicity Analysis
Neutron multiplicity counting is the most commonly used nondestructive assay technique for determining the plutonium mass within containers of scrap PuO 2 or mixed oxide (MOX). In multiplicity analysis, the 240 Pu eff mass, leakage multiplication, and alpha ratio (the ratio of [α, n]-to-spontaneous fission neutron production) are the three primary unknown sample properties. They must be determined simultaneously. To solve for these three unknowns in a multiplicity assay, three measured values are needed: the singles, doubles, and triples neutron count rates. While the analysis is limited to solving for three unknowns, there are many additional factors that impact the observed count rates and contribute to the measurement uncertainty. In this study we investigate the various uncertainty contributors for the multiplicity analysis through a combination of traditional uncertainty propagation techniques supplemented by Monte Carlo simulations to address the dependences not explicitly expressed by the point source model. Uncertainties arising from counting statistics, calibration parameters, calibration method, nuclear data, and various material characteristics (isotopic abundances, chemical form, density, and impurities) are considered. A Total Measurement Uncertainty (TMU) estimate is then developed from these uncertainty contributors. This study is confined to multiplicity analysis of items commonly encountered in international safeguards applications. That is, the study focused on Pu oxides and MOX materials for the masses ranging up to 4000 grams total Pu. Multiplicity measurements were simulated using MCNP V6 based on the Plutonium Scrap Multiplicity Counter (PSMC), Epithermal Multiplicity Counter (ENMC), Pyrochemical Multiplicity Counter, and Large Epithermal Multiplicity Counter (LEMC) for this study; however, this report focuses on the parameterization of the uncertainties for the PSMC. The performance differences between the PSMC and the other multiplicity counting systems are relatively small, primarily manifesting in the impact on measurement precision so that the evaluation developed for the PSMC can be applied to the other multiplicity counting systems. Finally an analysis tool, the Multiplicity TMU Estimator, was developed from this study to serve as an aid for evaluation of the total measurement uncertainty of multiplicity assay results obtained from the commonly used INCC acquisition and analysis software.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
CD46-Targeted Theranostics for PET and 225 Ac-Radiopharmaceutical Therapy of Multiple Myeloma
Multiple myeloma is a plasma cell malignancy with an unmet clinical need for improved imaging methods and therapeutics. Recently, we identified CD46 as an overexpressed therapeutic target in multiple myeloma and developed the antibody YS5, which targets a cancer-specific epitope on this protein. We further developed the CD46-targeting PET probe [ 89 Zr]Zr-DFO-YS5 for imaging and [ 225 Ac]Ac-DOTA-YS5 for radiopharmaceutical therapy of prostate cancer. These prior studies suggested the feasibility of the CD46 antigen as a theranostic target in multiple myeloma. Herein, we validate [ 89 Zr]Zr-DFO-YS5 for immunoPET imaging and [ 225 Ac]Ac-DOTA-YS5 for radiopharmaceutical therapy of multiple myeloma in murine models. In vitro saturation binding was performed using the CD46 expressing MM.1S multiple myeloma cell line. ImmunoPET imaging using [ 89 Zr]Zr-DFO-YS5 was performed in immunodeficient (NSG) mice bearing subcutaneous and systemic multiple myeloma xenografts. For radioligand therapy, [ 225 Ac]Ac-DOTA-YS5 was prepared, and both dose escalation and fractionated dose treatment studies were performed in mice bearing MM1.S-Luc systemic xenografts. Tumor burden was analyzed using BLI, and body weight and overall survival were recorded to assess antitumor effect and toxicity. [ 89 Zr]Zr-DFO-YS5 demonstrated high affinity for CD46 expressing MM.1S multiple myeloma cells (K d = 16.3 nmol/L). In vitro assays in multiple myeloma cell lines demonstrated high binding, and bioinformatics analysis of human multiple myeloma samples revealed high CD46 expression. [ 89 Zr]Zr-DFO-YS5 PET/CT specifically detected multiple myeloma lesions in a variety of models, with low uptake in controls, including CD46 knockout (KO) mice or multiple myeloma mice using a nontargeted antibody. In the MM.1S systemic model, localization of uptake on PET imaging correlated well with the luciferase expression from tumor cells. A treatment study using [ 225 Ac]Ac-DOTA-YS5 in the MM.1S systemic model demonstrated a clear tumor volume and survival benefit in the treated groups. Our study showed that the CD46-targeted probe [ 89 Zr]Zr-DFO-YS5 can successfully image CD46-expressing multiple myeloma xenografts in murine models, and [ 225 Ac]Ac-DOTA-YS5 can effectively inhibit the growth of multiple myeloma. These results demonstrate that CD46 is a promising theranostic target for multiple myeloma, with the potential for clinical translation.
59 BASIC BIOLOGICAL SCIENCES↗
Differential expression of estrogen receptor α and β isoforms in multiple and solitary leiomyomas
Uterine leiomyomas are benign myometrial neoplasms that function as one of the common indications for hysterectomy. Clinical and biological evidences indicate that uterine leiomyomas are estrogen-dependent. Estrogen stimulates cell proliferation through binding to the estrogen receptor (ER), of which both subtypes α and β are present in leiomyomas. Clinically, leiomyomas may be singular or multiple, where the first one is rarely recurring if removed and the latter associated to a relatively young age or genetic predisposition. These markedly different clinical phenotypes indicate that there may different mechanism causing a similar smooth muscle response. To investigate the relative expression of ERα and ERβ in multiple and solitary uterine leiomyomas, we collected samples from 35 Chinese women (multiple leiomyomas n = 20, solitary leiomyoma n = 15) undergoing surgery to remove uterine leiomyomas. ELISA assay was performed to detect estrogen(E{sub 2}) concentration. Quantitative real-time PCR analysis was performed to detect ERα and ERβ mRNA expression. Western blot and immunohistochemical analysis were performed to detect ERα and ERβ protein expression. We found that ERα mRNA and protein levels of in multiple leiomyomas were significantly lower than those of solitary leiomyomas, whereas ERβ mRNA and protein levels in multiple leiomyomas were significantly higher than those in solitary leiomyomas, irrespectively of the menstrual cycle stage. In both multiple and solitary leiomyomas, ERα expression was higher than that of ERβ. E{sub 2} concentration in multiple and solitary leiomyomas correlated with that of ERα expression. ERα was present in nuclus and cytoplasma while estrogen receptor β localized only in nuclei in both multiple and solitary leiomyomas. Our findings suggest that the difference of ERα and ERβ expression between multiple and solitary leiomyomas may be responsible for the course of the disease subtypes. - Highlights: • In both multiple and solitary leiomyomas, ERα expression was higher than that of ERβ. • ERα was significantly lower, whereas ERβ was significantly higher in multiple leiomyomas than that in solitary leiomyomas. • The differential expression of ERα and ERβ may be responsible for the cause of the disease subtypes.
60 APPLIED LIFE SCIENCES↗
Multiple-Zone Diffractive Optic Element for Laser Ranging Applications
A diffractive optic element (DOE) can be used as a beam splitter to generate multiple laser beams from a single input laser beam. This technology has been recently used in LRO s Lunar Orbiter Laser Altimeter (LOLA) instrument to generate five laser beams that measure the lunar topography from a 50-km nominal mapping orbit (see figure). An extension of this approach is to use a multiple-zone DOE to allow a laser altimeter instrument to operate over a wider range of distances. In particular, a multiple-zone DOE could be used for applications that require both mapping and landing on a planetary body. In this case, the laser altimeter operating range would need to extend from several hundred kilometers down to a few meters. The innovator was recently involved in an investigation how to modify the LOLA instrument for the OSIRIS asteroid mapping and sample return mission. One approach is to replace the DOE in the LOLA laser beam expander assembly with a multiple-zone DOE that would allow for the simultaneous illumination of the asteroid with mapping and landing laser beams. The proposed OSIRIS multiple-zone DOE would generate the same LOLA five-beam output pattern for high-altitude topographic mapping, but would simultaneously generate a wide divergence angle beam using a small portion of the total laser energy for the approach and landing portion of the mission. Only a few percent of the total laser energy is required for approach and landing operations as the return signal increases as the inverse square of the ranging height. A wide divergence beam could be implemented by making the center of the DOE a diffractive or refractive negative lens. The beam energy and beam divergence characteristics of a multiple-zone DOE could be easily tailored to meet the requirements of other missions that require laser ranging data. Current single-zone DOE lithographic manufacturing techniques could also be used to fabricate a multiple-zone DOE by masking the different DOE zones during the manufacturing process, and the same space-compatible DOE substrates (fused silica, sapphire) that are used on standard DOE s could be used for multiple- zone DOE s. DOEs are an elegant and cost-effective optical design option for spacebased laser altimeters that require multiple output laser beams. The use of multiple-zone DOEs would allow for the design and optimization of a laser altimeter instrument required to operate over a large range of target distances, such as those designed to both map and land on a planetary body. In addition to space-based laser altimeters, this technology could find applications in military or commercial unmanned aerial vehicles (UAVs) that fly at an altitude of several kilometers and need to land. It is also conceivable that variations of this approach could be used in land-based applications such as collision avoidance and robotic control of cars, trains, and ships.
Ramos-Izquierdo, Luis A.↗
The Multiplicity of M Dwarfs in Young Moving Groups
We image 104 newly identified low-mass (mostly M-dwarf) pre-main sequence (PMS) members of nearby young moving groups (YMGs) with Magellan Adaptive Optics (MagAO) and identify 27 stellar binaries with instantaneous projected separation as small as 40 mas. Fifteen were previously unknown. The total number of multiple systems in this sample including spectroscopic and visual binaries from the literature is 36, giving a raw stellar multiplicity rate of at least 35{sub −4}{sup +5}% for this population. In the separation range of roughly 1–300 au in which infrared AO imaging is most sensitive, the raw multiplicity rate is at least 24{sub −4}{sup +5}% for binaries resolved by the MagAO infrared camera (Clio). The M-star subsample of 87 stars yields a raw multiplicity of at least 30{sub −4}{sup +5}% over all separations, 21{sub −4}{sup +5}% for secondary companions resolved by Clio from 1 to 300 au (23{sub −4}{sup +5}% for all known binaries in this separation range). A combined analysis with binaries discovered by the Search for Associations Containing Young stars shows that stellar multiplicity fraction as a function of mass over the range of 0.2 to 1.2 M {sub ☉} appears to be linearly flat, in contrast to the field, where multiplicity increases with mass. After bias corrections are applied, the multiplicity of low-mass YMG members (0.2–0.6 M {sub ☉}) is in excess of the field. The overall multiplicity fraction is also consistent with being constant in age and across YMGs, which suggests that multiplicity rates for this mass range are largely set by 10 Myr without appreciable evolution thereafter.
79 ASTRONOMY AND ASTROPHYSICS↗
Multiple Renal Artery Pseudoaneurysms in Patients Undergoing Renal Artery Embolization Following Partial Nephrectomy: Correlation with RENAL Nephrometry Scores
PurposeTo describe the incidence of multiple renal artery pseudoaneurysms (PSA) in patients referred for renal artery embolization following partial nephrectomy and to study its relationship to RENAL nephrometry scores.Materials and MethodsThe medical records of 25 patients referred for renal artery embolization after partial nephrectomy were retrospectively reviewed for the following parameters: size and number of tumors, RENAL nephrometry scores, angiographic abnormalities, technical and clinical outcomes, and estimated glomerular filtration rates (eGFRs) after embolization.ResultsTwenty-four patients had primary renal tumors, while 1 patient had a pancreatic tumor invading the kidney. Multiple tumors were resected in 4 patients. Most patients (92 %) were symptomatic, presenting with gross hematuria, flank pain, or both. Angiography revealed PSA with (n = 5) or without (n = 20) AV fistulae. Sixteen patients (64 %) had multiple PSA involving multiple renal vessels. Higher RENAL nephrometry scores were associated with an increasing likelihood of multiple PSA. Multiple vessels were embolized in 14 patients (56 %). Clinical success was achieved after one (n = 22) or two (n = 3) embolization sessions in all patients. Post-embolization eGFR values at different time points after embolization were not significantly different from the post-operative eGFR.ConclusionA majority of patients requiring renal artery embolization following partial nephrectomy have multiple pseudoaneurysms, often requiring selective embolization of multiple vessels. Higher RENAL nephrometry score is associated with an increasing likelihood of multiple pseudoaneurysms. We found transarterial embolization to be a safe and effective treatment option with no long-term adverse effect on renal function in all but one patient with a solitary kidney.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Observation of a multiplicity dependence in the $\mathcal{p}_T$-differential charm baryon-to-meson ratios in proton–proton collisions at $\sqrt{s}$ = 13 TeV
The production of prompt D 0 , D$^+_s$, and Λ$^+_c$ hadrons, and their ratios, D$^+_s$/D 0 and Λ$^+_c$/D 0 , are measured in proton–proton collisions at $\sqrt{s}$ = 13 TeV at midrapidity (|y| < 0.5) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum (p T ) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange D$^+_s$/D 0 ratio indicates no significant multiplicity dependence, the baryon-to-meson p T -differential Λ$^+_c$/D 0 ratio shows a multiplicity-dependent enhancement, with a significance of 5.3σ for 1 < p T < 12 GeV/c, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The Λ$^+_c$/D 0 ratios as a function of p T present a similar shape and magnitude as the Λ/K$^0_s$ ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The p T -integrated ratios, extrapolated down to p T = 0, do not show a significant dependence on multiplicity within the uncertainties.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Characterizing Shielded Special Nuclear Material by Neutron Capture Gamma-Ray Multiplicity Counting
We present a new neutron multiplicity counting analysis and measurement method for neutron-shielded fissile material using neutron-capture gamma rays. Neutrons absorbed in shielding produce characteristic gamma rays that preserve the otherwise lost neutron multiplicity signature. Neutron multiplicity counting provides estimates of fission parameters, such as neutron leakage multiplication, spontaneous fissioner (e.g. Pu-240) mass, and (α,n) ratio. Standard neutron multiplicity counting can incorporate the new neutron-capture gamma-ray multiplicity counting technique to characterize previously degenerate or intractable source configurations by maximizing the multiplicity signature. The new method decouples neutron source-detector interferences, such as reflection and thermalization time in the detector, that could improve measurements of the mean neutron lifetime. We also develop a detector prototype for the multiplicity counting of neutron-capture gamma rays and present detector design considerations, such as detection material and shielding, to optimize the detection of the 2.2 MeV hydrogen capture gamma ray. We simulate the prototype neutron- capture gamma-ray multiplicity counter against the BeRP ball in polyethylene shells to inform future measurements.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Multiple Beam Triode Driven RF Sources for Accelerator Applications Phase I Final Report
Calabazas Creek Research, Inc, (CCR), in collaboration with Microwave Power Products, Inc. (MPP), formerly Communications & Power Industries, LLC (CPI,) and JP Accelerator Works, Inc. (JPAW), embarked on a program to develop multiple beam triodes to produce RF power from 350 – 800 MHz with an average power exceeding 200 kW. The effort was motivated by the performance of a triode-based RF source which produces 25 kW of UHF power at 90% efficiency. The CCR effort focused on implementing this technology into a multiple beam device to increase the output power while retaining the low cost, compact size, and high efficiency. The program performed extensive simulations indicating that the goals could be achieved, and a prototype multiple beam triode was built, baked, and tested. Unfortunately, a grid to cathode short terminated the testing before the tube could generate RF power. Nevertheless, the effort demonstrated that a multiple beam triode could be designed, built, baked, and energized to high voltage. The multiple beam triode used oxide cathodes, which are only capable of pulsed operation. The multiple beam triode will be rebuilt using dispenser cathodes, which will allow high duty or continuous operation. The grids were also modified to be more robust to avoid previous issues. The MB triode will provide the beam power for RF generation. The RF is generated by surrounding the triode with input and output cavities to convert beam power to RF power. RF cavities to generate 200 kW CW at 350-450 MHz using the MB triode with dispenser cathodes was assembled during the program. The next Phase of this effort is to assemble the multiple beam triode using the subassemblies built in the Phase I program and test with the RF cavities. The Phase I program also initiated design of a higher frequency, higher power multiple beam triode. That design is forecast to produce approximately 500 kW CW from 350 - 500 MHz.
43 PARTICLE ACCELERATORS↗
Learning and discovering multiple solutions using physics-informed neural networks with random initialization and deep ensemble
In this work we explore the capability of physics-informed neural networks (PINNs) to discover multiple solutions. Many real-world phenomena governed by nonlinear differential equations (DEs), such as fluid flow, exhibit multiple solutions under the same conditions, yet capturing this solution multiplicity remains a significant challenge. A key difficulty lies in providing appropriate initial conditions or guesses, as widely used time-marching schemes and Newton’s method are highly sensitive to these choices when solving complex computational problems. While machine learning models, particularly PINNs, have shown promise in solving DEs, their ability to capture multiple solutions remains underexplored. In this work, we propose a simple and practical approach using PINNs to learn and discover multiple solutions. We first demonstrate that PINNs, when combined with random initialization and deep ensemble method—originally developed for uncertainty quantification—can effectively uncover multiple solutions to nonlinear ordinary and partial DEs. Although training large ensembles of PINNs may appear computationally demanding, this can be done efficiently using vectorization techniques supported by modern deep learning frameworks, allowing many networks to be trained simultaneously. Our approach highlights the critical role of initialization in shaping solution diversity, addressing an often-overlooked aspect of machine learning for scientific computing. Furthermore, we propose utilizing PINN-generated solutions as initial conditions or initial guesses for conventional numerical solvers to enhance accuracy and efficiency in capturing multiple solutions. Extensive numerical experiments, including the Allen–Cahn equation and cavity flow, where our approach successfully identifies both stable and unstable solutions, validate the effectiveness of our method. These findings establish a general and efficient framework for addressing solution multiplicity in nonlinear DEs.
97 MATHEMATICS AND COMPUTING↗
MicroRNAs in blood and cerebrospinal fluid as diagnostic biomarkers of multiple sclerosis and to monitor disease progression
Multiple sclerosis is a chronic autoimmune disease of the central nervous system. It is the main cause of non-traumatic neurological disability in young adults. Multiple sclerosis mostly affects people aged 20–50 years; however, it can occur in young children and much older adults. Factors identified in the distribution of MS include age, gender, genetics, environment, and ethnic background. Multiple sclerosis is usually associated with progressive degrees of disability. The disease involves demyelination of axons of the central nervous system and causes brain and spinal cord neuronal loss and atrophy. Diagnosing multiple sclerosis is based on a patient’s medical history including symptoms, physical examination, and various tests such as magnetic resonance imaging, cerebrospinal fluid and blood tests, and electrophysiology. The disease course of multiple sclerosis is not well correlated with the biomarkers presently used in clinical practice. Blood-derived biomarkers that can detect and distinguish the different phenotypes in multiple sclerosis may be advantageous in personalized treatment with disease-modifying drugs and to predict response to treatment. The studies reviewed have shown that the expression levels of a large number of miRNAs in peripheral blood, serum, exosomes isolated from serum, and cerebrospinal fluid are altered in multiple sclerosis and can distinguish the disease phenotypes from each other. Further studies are warranted to independently validate these findings so that individual or pairs of miRNAs in serum or cerebrospinal fluid can be used as potential diagnostic markers for adult and pediatric multiple sclerosis and for monitoring disease progression and response to therapy.
60 APPLIED LIFE SCIENCES↗
Validation of the Fast-Neutron Multiplicity Expressions for Fissile Mass Estimation
Neutron multiplicity analysis is a non-destructive assay technique that involves measurement of the multiplets of neutrons that are emitted from fission of fissile material. Typically, multiplicity analysis is conducted by means of a neutron multiplicity counting (NMC) system that uses capture-based thermal-neutron detectors (e.g., 3He-gas detectors). To relieve the reliance on such detectors, we have developed a fast-neutron multiplicity counting (FNMC) system that uses scatter-based, organic scintillators to directly detect the fast fission neutrons emitted from the sample. One challenge with FNMC systems, however, is that they are prone to effects of neutron cross-talk, where a single neutron may scatter and cause more than one detection event. This leads to an overestimate of the fission rate (F) and inaccurate estimation of other sample parameters such as the leakage multiplication (M) and the alpha-ratio (a) when using the traditional capture-based NMC equations. We have formulated fully generalized multiplicity expressions that account for cross-talk effects for any arbitrary order N. The validity of these expressions were verified with MCNPX-PoliMi simulations and experimental measurements; this paper will present the validation of the proposed generalized multiplicity expressions. Californium-252 and Pu metal plates were measured using the FNMC system and the data was used for neutron multiplicity analysis to estimate sample parameters F, M, and a. We demonstrate that accounting for neutron cross-talk effects of order N = 2 and 3 improves the accuracy of the estimated sample parameters.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Study of Multiple Exciton Generation with New Multi-dimensional Spectroscopies
Multiple exciton generation is a process that can occur in semiconductor nanocrystals small enough that their electronic properties deviate from that of the bulk semiconductor. Such small nanocrystals are known as quantum dots. At the time this project began, there were reports that multiple exciton generation in quantum dots was far more efficient than the analogous process of charge carrier multiplication in bulk semiconductors. In bulk semiconductors, this effect requires ultraviolet light, but is used for high energy photo-detectors. By exploiting enhanced photocurrent from photons with more than twice the bandgap energy, carrier multiplication is a potential route to more efficient photovoltaics using quantum dots with infrared bandgaps. The reports of enhanced multiple exciton generation in such materials motivated the fundamental investigations of the multiple exciton generation mechanism in this project. These experimental investigations showed that the initial charge carrier dynamics after exciting low bandgap quantum dots with photons far above bandgap are not those of the bound electron-hole pairs known as excitons, but rather those of the rapidly separating charge carriers found in the bulk semiconductor at similar excitation energies. This result was theoretically explained in terms of new fundamental criteria for size dependent changes in the optical properties of semiconductors. This result indicates that any new mechanism for multiple exciton generation must arise from the larger surface area to volume ratio of quantum dots. Several artifacts arising from repetitive excitation, poorly passivated quantum dot surfaces, and oxygen exposure were found. After eliminating these artifacts, investigations of the backward reaction have confirmed that its rate does increase as size decreases, in accord with theory, but were not able to isolate surface effects. Using two-dimensional electronic spectroscopy to investigate the influence of the surface upon excitation at the bandgap found no measurable effect. These studies indicate that better control of the quantum dot surface would be required to optimize multiple exciton generation for photovoltaics.
14 SOLAR ENERGY↗
Computationally Guided Design of Multiple Impurities Tolerant Electrode (Final Report)
The current project was based on a combined experimental and computational approach, which can help recommend better cathode materials under multiple impurities conditions. The PI will mainly take in charge of experimental and computational thermodynamics of the selected cathode materials for the SOFC applications under multiple impurities. While the co-PI will run the electrochemical tests of the cathodes recommended and eventually the long-term degradation tests. At the end of the project, a multiple tolerant cathode material based on the combined experimental and computational approach will be recommended and the reliability of the commonly used accelerated testing will be evaluated. It will address multiple impurities poisoning effect of SO2, CO2, Cr and H2O on the LSM, LSCF and LNO cathodes by identifying the formation of the detrimental secondary phases by XRD, SEM and TEM techniques. And further recommended cathode material will be subjected to electrochemical testing and the most promising ones will be applied to long-term tests. The hybrid approach the PI proposed will not only be applied to the design of multiple impurities tolerant cathodes but will also be considered in the future oxygen electrode applications in SOECs or reversible SOCs. This hybrid computational and experimental approach includes four sections: 1) Investigation of single impurity poisoning on LSM, LSCF and LNO cathodes in the presence of SO2, CO2, Cr. In this section, LSM, LSCF cathodes from FuelCellMaterials and LNO cathodes from Sol-Gel synthesis will be heat-treated in the above single impurity. And the formation of the secondary phases as well as the corresponding simulations will be cross compared, which shows good agreement between each other. Meanwhile, the accelerated testing approach will be evaluated in these systems compared with the previous published work to understand the reliability of the approach. 2) Investigation of multiple impurities poisoning on LSM, LSCF and LNO cathodes in the presence of Cr+H2O, SO2+Cr and SO2+Cr+H2O conditions. We have also applied these 3 candidate cathodes under these multiple impurities’ conditions and the long-term degradation mechanism of the multiple impurities will be understood with the help of the combined experimental and computational approach. Meanwhile, the synergistic effect of those impurities will be compared with the individual ones in the same cathode system to further reveal the actual operating conditions. 3) Electrochemical testing and polarization of the recommended cathode. We have demonstrated very low polarization resistance in LSCF (core)-LSM (shell) electrodes using MSD process and analyzed impedance spectra using DRT analysis and confirming that the low polarization resistance in LSM infiltrated MSD cells is due to reduction in polarization resistance associated with O2-adsorption process. 4). Long-term degradation testing. We have developed a versatile MSD-based process to deposit various continuous coatings onto porous scaffolds and established baseline for longer term Cr-impurity testing in future projects.
36 MATERIALS SCIENCE↗
Clutter mitigation, multiple peaks, and high-order spectral moments in 35 GHz vertically pointing radar velocity spectra
Abstract. This study presents and applies three separate processing methods to improve high-order moments estimated from 35 GHz (Ka band) vertically pointing radar Doppler velocity spectra. The first processing method removes Doppler-shifted ground clutter from spectra collected by a US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program Ka-band zenith pointing radar (KAZR) deployed at Oliktok Point (OLI), Alaska. Ground clutter resulted from multiple pathways through antenna side lobes and reflections off a rotating scanning radar antenna located 2 m away from KAZR, which caused Doppler shifts in ground clutter returns from stationary targets 2.5 km away. After removing clutter in the recorded velocity spectra, the second processing method identifies multiple separate and sub-peaks in the spectra and estimates high-order moments for each peak. Multiple peaks and high-order moments were estimated for both original 2 and 15 s averaged spectra. The third processing step improves the spectrum variance, skewness, and kurtosis estimates by removing velocity variability due to turbulent broadening during 15 s averaging intervals. Applying the multiple peak processing to Doppler velocity spectra during liquid-only clouds can identify cloud and drizzle particles and during mixed-phase clouds can identify liquid cloud and frozen hydrometeors. Consistent with previous studies, this work found that spectrum skewness assuming only a single spectral peak was a good indicator of two hydrometeor populations (for example, cloud and drizzle particles) being present in the radar pulse volume. Yet, after dividing the spectrum into multiple peaks, velocity spectrum skewness for individual peaks is near zero, indicating nearly symmetric peaks. This suggests that future studies should use velocity skewness of single-peak spectra as an indicator of possible multiple hydrometeor populations and then use multiple-peak moments for quantitative studies. Three future activities will continue this work. First, KAZR spectra from several ARM sites have been processed and are available in the ARM archive as a principal investigator (PI) product. ARM programmers are evaluating these processing methods as part of future multiple-peak products generated by ARM. Third, MATLAB code generating the Oliktok Point products has been uploaded as supplemental material for public dissemination.
47 OTHER INSTRUMENTATION↗
Feed System Design Considerations for Large Space Antenna Systems. Part 1: Multiple Apertures with Non-overlapping Feeds
A feed system design for large space antenna systems was considered. A multiple aperture system with nonoverlapping feeds is examined. Circular and quadrant aperture reflector radiation patterns are compared and the effect of adjacent aperture on radiation patterns of multiple aperture reflector antennas is illustrated. The following systems are examined: (1) feed design optimization for a multiple aperture reflector antenna; (2) radiation pattern for two quadrant reflector with optimized feed design; (3) multiple beam concept utliizing apertures and nonoverlapping feeds; (4) beam contours for two quadrant of multiple beam multiple aperture concept; (5) superposition of beams from two quadrants of multiple beam multiple aperture concent; (6)compensation for mislalignment of interleaved beams from two quadrants; and (7) beam quality improvement due to reorienting feed for offset reflector.
Bailey, M. C.↗
Adaptation of the Electra Radio to Support Multiple Receive Channels
Proposed future Mars missions plan communication between multiple assets (rovers). This paper presents the results of a study carried out to assess the potential adaptation of the Electra radio to a multi-channel transceiver. The basic concept is a Frequency Division multiplexing (FDM) communications scheme wherein different receiver architectures are examined. Options considered include: (1) multiple IF slices, A/D and FPGAs each programmed with an Electra baseband modem; (2) common IF but multiple A/Ds and FPGAs and (3) common IF, single A/D and single or multiple FPGAs programmed to accommodate the FDM signals. These options represent the usual tradeoff between analog and digital complexity. Given the space application, a common IF is preferable; however, multiple users present dynamic range challenges (e.g., near-far constraints) that would favor multiple IF slices (Option 1). Vice versa, with a common IF and multiple A/Ds (Option 2), individual AGC control of the A/Ds would be an important consideration. Option 3 would require a common AGC control strategy and would entail multiple digital down conversion paths within the FPGA. In this paper, both FDM parameters as well as the different Electra design options will be examined. In particular, signal channel spacing as a function of user data rates and transmit powers will be evaluated. In addition, tradeoffs between the different Electra design options will be presented with the ultimate goal of defining an augmented Electra radio architecture for potential future missions.
Time Division multiplexing↗