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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Morphology Characterization of Bulk Heterojunction Solar Cells

Abstract Revealing the nanostructure of bulk‐heterojunction (BHJ) photovoltaic blends is a critical task in the field of organic photovoltaics. The complicated morphology, ranging from binary blends to ternary mixtures, shows quite varied structural details that need to be fully characterized in terms of correlating them with device performance. The nonequilibrium nature of the BHJ thin‐film morphology makes the structure optimization difficult, and fundamental principles that relate to chemical structure, processing methods, and device performances have not yet been fully understood. On the other hand, various high‐powered techniques ranging from in‐house instrumentation to synchrotron techniques have been applied to this tremendously difficult research topic. More structural details, including length scale of phase separation, structural ordering, chain/molecular orientation, surface topology, etc., can be obtained in a quantitative manner, which finally allows the structure–property relationships to be determined. Here, the most important characterization techniques in understanding the morphology of BHJ solar cells are summarized, targeting chemists and materials scientists.

Song, Jingnan↗
DOE OSTI2017

Exploring the Promotion of Synthons of Choice: Halogen Bonding in Molecular Lanthanide Complexes Characterized via X-ray Diffraction, Luminescence Spectroscopy, and Magnetic Measurements

Promotion of a synthon of choice for the non-covalent assembly of lanthanide tectons represents both a noteworthy challenge and opportunity within Ln(III) hybrid materials. We have developed a system wherein some control can be exercised over supramolecular assembly and, as part of continued efforts to improve this process we have generated a family of ten new lanthanide (Ln = Sm 3+ -Lu 3+ )-2,4,6-trichlorobenzoic acid-1,10- phenanthroline molecular complexes. Delineation of criteria for promoting assembly via halogen based interactions was introduced previously and is refined herein based on the characterization of complexes 1-10 via single crystal X-ray diffraction. Direct comparison of means of supramolecular assembly for 1-10 with isostructural Ln-pchlorobenzoic acid-1,10-phenathroline analogues verifies that increasing the number of halogens at the periphery of a tecton is one route that increases the frequency of halogen bonding interactions. Additionally, solid-state visible and near-IR photoluminescence and luminescent lifetime data were collected for complexes 1 (Sm 3+ ), 2 (Eu 3+ ), 4 (Tb 3+ ), 5 (Dy 3+ ), 6 (Ho 3+ ), 7 (Er 3+ ), and 9 (Yb 3+ ) and characteristic emission was observed for all complexes except 6. Further, direct current magnetic susceptibility measurements were carried out for complexes 5 (Dy 3+ ) and 7 (Er 3+ ), and two slow magnetic relaxation processes were characterized using alternating current magnetic susceptibility measurements for 5.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Recent In Situ/Operando Characterization of Lithium-Sulfur Batteries

To address the ever-increasing energy demand due to the increase in the population and at the same time depleting fossil fuel reserves, new energy storage systems, such as batteries, are being developed. Among various battery systems, Li-S batteries have comparatively high theoretical energy density and lower cost, making Li-S batteries very promising for next-generation secondary batteries. However, the current energy density and capacity decay with cycling of Li-S batteries do not fulfill the industrialization needs. To overcome the drawbacks of Li-S batteries and improve its performance, better mechanism understanding is necessary. A great deal of ex situ characterization research has been conducted making a lot of progress in the understanding of the working mechanism. Considering the complexity of the intermediate lithium polysulfides and the inherent multi-electron reaction pathways, advanced in situ/operando techniques are highly required. In this chapter, recent progress of a few typical in situ/operando characterization techniques used in Li-S battery studies is reviewed. These techniques provide more in-depth understanding of Li-S batteries in different aspects and could be enlightening for other energy storage systems too.

Yang, Yan↗
DOE OSTI2017

Characterization of the Hydrothermal Corrosion Behavior of Ceramics for Accident Tolerant Fuel Cladding

Accident-tolerant fuel (ATF) is an increasingly important research topic for the nuclear industry, and ceramics such as SiC are strong contenders for deployment as ATF cladding. The hydrothermal corrosion characteristics of SiC and Al2O3 were investigated via constantly-refreshing autoclave corrosion and post exposure characterization. Four different types of chemical vapor deposited (CVD) SiC specimens were examined (two with high electrical resistance, one with low electrical resistance, and a single crystal 4H structural variant). Al2O3 specimens were prepared in single crystal and polycrystalline states. PWR primary water, BWR–HWC, and BWR–NWC environments were maintained throughout the experiments. Characterization conducted using SEM and EDS was used to determine factors affecting corrosion rates and susceptibility to grain boundary attack in each water chemistry condition. Raman spectroscopy was also used to determine chemical variation of the surface with corrosion. Grain boundary attack was found to be significant for both alumina and SiC polycrystalline variants.

Doyle, Peter↗
DOE OSTI2020

3D Characterization of the Columnar-to-Equiaxed Transition in Additively Manufactured Inconel 718

Additive manufacturing (AM) provides enormous processing flexibility, enabling novel part geometries and optimized designs. Access to a local heat source further permits the potential for local microstructure control on the scale of individual melt pools, which can enable local control of part properties. In order to design tailored processing strategies for target microstructures, models predicting the columnar-to-equiaxed transition must be extended to the high solidification velocities and complex thermal histories present in AM. Here, we combine 3D characterization with advanced modeling techniques to develop a more complete understanding of the solidification process and evolution of microstructure during electron beam melting (EBM) of Inconel 718. Full calibration of existing microstructure prediction models demonstrates the differences between AM processes and more conventional welding techniques, underlying the need for accurate determination of key parameters that can only be measured directly in 3D. The ability to combine multisensor data in a consistent 3D framework via data fusion algorithms is essential to fully leverage these advanced characterization approaches. Thermal modeling provides insight on microstructure development within isolated solidification events and demonstrates the role of Marangoni effects on controlling solidification behavior.

Polonsky, Andrew↗
DOE OSTI2023

Experimental Characterization of OpenMP Offloading Memory Operations and Unified Shared Memory Support

The OpenMP specification recently introduced support for unified shared memory, allowing implementation to leverage underlying system software to provide a simpler GPU offloading model where explicit mapping of variables is optional. Support for this feature is becoming more available in different OpenMP implementations on several hardware platforms. A deeper understanding of the different implementation’s execution profile and performance is crucial for applications as they consider the performance portability implications of adopting a unified memory offloading programming style. This work introduces a benchmark tool to characterize unified memory support in several OepnMP compilers and runtimes, with emphasis on identifying discrepancies between different OpenMP implementations as to how they various memory allocation strategies interact with unified shared memory. The benchmark tool is used to characterize OpenMP compilers on three leading High Performance Computing platforms supporting different CPU and device architectures. The benchmark tool is used to assess the impact of enabling unified shared memory on the performance of memory-bound code, highlighting implementation differences that should be accounted for when applications consider performance portability across platforms and compilers.

Elwasif, Wael↗
DOE OSTI2024

Characterizing 4-string contact interaction using machine learning

Abstract The geometry of 4-string contact interaction of closed string field theory is characterized using machine learning. We obtain Strebel quadratic differentials on 4-punctured spheres as a neural network by performing unsupervised learning with a custom-built loss function. This allows us to solve for local coordinates and compute their associated mapping radii numerically. We also train a neural network distinguishing vertex from Feynman region. As a check, 4-tachyon contact term in the tachyon potential is computed and a good agreement with the results in the literature is observed. We argue that our algorithm is manifestly independent of number of punctures and scaling it to characterize the geometry ofn-string contact interaction is feasible.

Physics↗
DOE OSTI2021

Characterizing Topological Order with Matrix Product Operators

One of the most striking features of gapped quantum phases that exhibit topological order is the presence of long-range entanglement that cannot be detected by any local order parameter. The formalism of projected entangled-pair states is a natural framework for the parameterization of gapped ground state wavefunctions which allows one to characterize topological order in terms of the virtual symmetries of the local tensors that encode the wavefunction. In their most general form, these symmetries are represented by matrix product operators acting on the virtual level, which leads to a set of algebraic rules characterizing states with topological quantum order. This construction generalizes the concepts of $\mathsf G$- and twisted injectivity; the corresponding matrix product operators encode all topological features of the theory and provide a complete picture of the ground state manifold on the torus. We show how the string-net models of Levin and Wen fit within this formalism and in doing so provide a particularly intuitive interpretation of the pentagon equation for F-symbols as the pulling of matrix product operators through the string-net tensor network. Our approach paves the way to finding novel topological phases beyond string nets and elucidates the description of topological phases in terms of entanglement Hamiltonians and edge theories.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Efficacy of perfusion CT in differentiating of pancreatic ductal adenocarcinoma from mass-forming chronic pancreatitis and characterization of isoattenuating pancreatic lesions

Purpose: Multidetector computed tomography (MDCT) is routinely used in the diagnosis of pancreatic ductal adenocarcinoma (PDAC), but it may be inadequate in some cases, especially mass-forming chronic pancreatitis (MFCP) and isoattenuating pancreatic lesions. Perfusion CT (pCT) may help resolve this problem. The aim of this study was to evaluate whether pCT could help differentiating PDAC from MFCP and in characterization of isoattenuating pancreatic lesions. Materials and methods: This prospective study included 89 cases of pancreatic lesions detected by MDCT and further analyzed with pCT. Sixty-one cases with final pathological diagnosis PDAC and 12 cases with MFCP were included from the study. Blood volume (BV), blood flow (BF), mean transit time (MTT), and permeability surface area product (PS) maps were obtained. Perfusion values obtained from the lesions and normal parenchyma were compared. Results: Compared with normal parenchyma, BV, BF, PS were lower and MTT was longer in PDAC and MFCP (p < 0.05). Compared with MFCP, BV, BF, PS were lower and MTT was longer in PDAC (p < 0.001). Compared with normal parenchyma, BV, BF, PS were lower and MTT was longer in isoattenuating lesions, (p < 0.001). Cutoff values of 7.60 mL/100 mL, 64.43 mL/100 mL/min, 28.08 mL/100 mL/min for BV, BF, PS, respectively, provided 100% sensitivity and specificity and 7.47 s for MTT provided 98.3% sensitivity, 80% specificity for distinguishing PDAC from MFCP. Conclusion: pCT is a useful technology that can be helpful in overcoming the limitations of routine MDCT in diagnosing PDAC and characterization of isoattenuating lesions.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Usefulness of rapid kV-switching dual energy CT in renal tumor characterization

Purpose: To investigate whether iodine content can discriminate between benign or malignant renal tumors, malign tumor subtypes, low-grade and high-grade tumors on rapid kv-switching dual-energy CT (rsDECT). Methods: This prospective study enrolled 95 patients with renal tumors who underwent rsDECT for tumor characterization between 2016 and 2018. Attenuation on true and virtual unenhanced images, absolute enhancement and enhancement ratio and iodine content of each lesion on nephrographic phase iodine density images were measured. Histopathological diagnosis was obtained following either surgery or core biopsy. Results: Eighty-five tumors were renal cell carcinoma (RCC) (56 clear cell, 20 papillary, 9 chromophobe) and 10 were benign (6 angiomyolipoma,4 oncocytoma). 46 tumors were low-grade and 23 high-grade. There was significant difference between iodine content of clear cell and non-clear cell (papillary + chromophobe) RCC (p < 0.001). However, no significant iodine content differences were found between papillary and chromophobe RCC, benign and malignant tumors, low-grade and high-grade tumors. The best cut-off iodine content for differentiating clear cell from non-clear cell RCC was 3.2 mg/ml and clear cell from papillary RCC was 2.9 mg/ml with a high sensitivity and specificity. Also, significant difference was found between attenuation values of true and virtual unenhanced images (p = 0.007). Mean iodine content, absolute enhancement and enhancement ratio were highly correlated. Conclusion: rsDECT contributes to renal tumor characterization by showing higher iodine content in clear cell RCCs compared with non-clear cell RCCs.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Extended abdominopelvic MRI versus CT at the time of adnexal mass characterization for assessing radiologic peritoneal cancer index (PCI) prior to cytoreductive surgery

Purpose: To evaluate whether extending the MRI scan to include the abdomen at the time of adnexal mass characterization could replace additional CT for peritoneal cancer index (PCI) assessment. Methods: After institutional review board approval for this prospective study, 36 consecutive females with ovarian and FT malignancies were included. All patients signed an informed consent. Patients underwent preoperative CT (32 patients) and MRI (36 patients). Images were interpreted by 2 independent observers. Surgical data were available in 27 patients. Region-by-region analysis was performed for detection rates of peritoneal carcinomatosis (PC). Inter-observer agreement for each region was evaluated by kappa statistics. Radiologic PCI was calculated by CT and MRI independently and inter-observer agreement for CT and MRI as well as agreement between radiologic and surgical PCI were evaluated by weighted-kappa statistics. Results: On region-by-region analysis, the highest detection rates of PC were noted at the central abdomen and pelvis. Detection rates were higher by MRI than CT, mainly in bowel serosal surface, pelvis, and right upper abdomen regions. Inter-observer agreement of MRI was higher than CT in most regions. The median PCI by CT was 5 and 4 for the first and second observers (range 0–21 for both observers), respectively. The median PCI by MRI was 6 (range 0–23 for both observers). The inter-observer agreement of PCI was excellent by both CT and MRI (k = 0.876 and k = 0.912, respectively). The agreement between CT and surgical PCI was 0.660 and 0.590 for the first and second observers, respectively. The agreement between MRI and surgical PCI was 0.797 and 0.798 for the first and second observers, respectively. Conclusions: Extending MRI scan to include the abdomen at the time of adnexal mass characterization allows accurate estimation of PC, with better results than CT, obviating the need for dedicated CT scan of abdomen and pelvis for imaging of PC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Characterization of partially observed epidemics through Bayesian inference: application to COVID-19

We demonstrate a Bayesian method for the "real-time'" characterization and forecasting of partially observed COVID-19 epidemic. Characterization is the estimation of infection spread parameters using daily counts of symptomatic patients.The method is designed to help guide medical resource allocation in the early epoch of the outbreak. The estimation problem is posed as one of Bayesian inference and solved using a Markov chain Monte Carlo technique. The data used in this study was sourced before the arrival of the second wave of infection in July 2020. The proposed modeling approach, when applied at the country level, generally provides accurate forecasts at the regional, state and country level. The epidemiological model detected the flattening of the curve in California, after public health measures were instituted.The method also detected different disease dynamics when applied to specific region of New Mexico

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Characterizing the general chelating affinity of serum protein fetuin for lanthanides

Fetuin is an abundant blood protein that participates in multiple biological processes, including the transport and regulation of calcium. Fetuin is also known to have a high affinity for uranium (as the uranyl dioxo cation) and plutonium, thus it has been suggested as one of the main endogenous chelating biomolecules involved in the transport of actinides following an internal uptake event. Nevertheless, no direct measurements of its affinity for f-elements beside these two actinides have been reported. Here, we investigate the interaction between fetuin and trivalent lanthanides, such as samarium, europium, terbium, and dysprosium, by mass spectrometry and fluorescence spectroscopy. In this work, mass spectrometry results indicated that fetuin has four metal binding sites for the metal ions studied. Upon formation, the metal–protein complexes showed luminescence emission as a result of antenna sensitization of the metal ions, whose photophysics were characterized and exploited to perform direct spectrofluorimetric titrations. Furthermore, the thermodynamic constants were calculated for all complexes, confirming the formation of stable complexes with log $β^{\prime}_4$ values between 26 and 27. In characterizing the affinity of the serum protein fetuin for several f-elements, this study expands upon the initial findings focused on uranyl and plutonium, and contributes to a better understanding of the internal distribution and deposition of lanthanides, potentially representative of trivalent actinides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Characterizing Peatland Microtopography Using Gradient and Microform-Based Approaches

Abstract Peatlands represent an important component of the global carbon cycle, storing 180–621 Gt of carbon (C). Small-scale spatial variations in elevation, frequently referred to as microtopography, influence ecological processes associated with the peatland C cycle, including Sphagnum photosynthesis and methane flux. Microtopography can be characterized with measures of topographic variability and by using conceptual classes (microforms) linked to function: most commonly hummocks and hollows. However, the criteria used to define these conceptual classes are often poorly described, if at all, and vary between studies. Such inconsistencies compel development of explicit quantitative methods to classify microforms. Furthermore, gradient-based characterizations that describe spatial variability without the use of microforms are lacking in the literature. Therefore, the objectives of this study were to (1) calculate peatland microtopographical elevation gradients and measures of spatial variability, (2) develop three microform classification methods intended for specific purposes, and (3) evaluate and contrast classification methods. Our results suggest that at spatial scales much larger than microforms, elevation distributions are unimodal and are well approximated with parametric probability density functions. Results from classifications were variable between methods and years and exhibited significant differences in mean hollow areal coverages of a raised ombrotrophic bog. Our results suggest that the conceptualization and classification of microforms can significantly influence microtopographic structural metrics. The three explicit methods for microform classification described here may be used and built upon for future applications.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

The preparation and characterization of chemically deuterium incorporated cotton fibers

Preparation of deuterium incorporated cellulose is a vital tool to investigate cellulose internal structure and to expand the application fields of cellulose materials. In this study, cellulosic cotton fibers with anti-rehydration (exchange-resistant) deuterium incorporated in cellulose were prepared by chemical hydrogen–deuterium exchange treatment. The chemical hydrogen–deuterium exchange process, along with exchange time, were characterized by nuclear magnetic resonance hydrogen spectroscopy (1H-NMR). The anti-rehydration deuterium incorporation was determined by Fourier Transform infrared spectroscopy (FTIR) and Stable Isotope Ratio Mass Spectrometer (IRSM). Here, the effect of the deuterium hydroxyl substitution on cotton fiber’s spectral data, microstructure, crystalline information, degree of polymerization, as well as it’s thermogravimetric analysis (charcoalization and combustion) are explored. Analysis of the chemical exchange process indicated that the hydrogen–deuterium exchange occurred preferentially in the amorphous cellulose component over the first several minutes. Deuterium exchange in the anti-rehydration crystalline phase took several hours. Increasing the treatment time, enhanced exchange-resistant deuterium incorporation to as high as about 60% of the cotton fibers’ cellulose hydroxyl groups was achieved. The characterization of FTIR, Fourier transform Raman (FT-Raman), and near-infrared spectra (NIR) all exhibited the deuterium spectral isotope effect on cellulose hydroxl groups. While, apart from the effect of reaction temperature, deuterium incorporation isotope effect did not affect the cellulose microstructure, crystalline index and the degree of polymerization properties. Furthermore, the thermogravimetric analysis of deuterated cotton fibers under N 2 and air atmosphere were both altered due to the thermodynamic isotope effect. These observations revealed the hydrogen–deuterium exchange treatment process and impacts on cellulose fiber properties, which helped us to better understand the cellulose internal structure and may facilitate the potential utilization of deuterated cellulosic materials.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Using a Fluorescent 1-Methyl-4-(2-Pyren-1-Yl-Vinyl)-Pyridinium Iodide to Characterize Solvent Polarities

We used 1-methyl-4-(2-pyren-1-yl-vinyl)-pyridinium iodide, a pyridinium derivative fluorescent dye, as a solvatochromic and solvatofluorchromic probe to straightforwardly characterize the solvent polarity. The absorption and fluorescence spectra of 1-methyl-4-(2-pyren-1-yl-vinyl)-pyridinium iodide show a dramatic dependence on solvent polarities in the high-polar range. It exhibits two absorption peaks around 400 and 450 nm, as well as an emission maximum at 605 nm. Several parameters (ratio of the two absorption peaks, wavelength of the principal absorption peak, fluorescence signal, and ratio of fluorescence intensities excited at the two absorption bands) are linearly dependent on the solvent polarity–polarizability values. Strong correlations have been also obtained with the P' and P{sub y} polarity scales with small deviations. Moreover, 1-methyl-4-(2-pyren-1-yl-vinyl)-pyridinium iodide possesses high fluorescence quantum yield (0.38–0.54) and relatively long lifetime (2.2–2.6 ns) in all studied organic solvents. All these optical properties make 1-methyl-4-(2-pyren-1-yl-vinyl)-pyridinium iodide a favorable probe to quantitatively characterize the solvent polarities in the high-polar range through a multiparametric approach.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Advanced ACTPol Low-Frequency Array: Readout and Characterization of Prototype 27 and 39 GHz Transition Edge Sensors

Advanced ACTPol (AdvACT) is a third-generation polarization upgrade to the Atacama Cosmology Telescope, designed to observe the cosmic microwave background (CMB). AdvACT expands on the 90 and 150 GHz transition edge sensor (TES) bolometer arrays of the ACT Polarimeter (ACTPol), adding both high-frequency (HF, 150/230 GHz) and low-frequency (LF, 27/39 GHz) multichroic arrays. The addition of the high- and low-frequency detectors allows for the characterization of synchrotron and spinning dust emission at the low frequencies and foreground emission from galactic dust and dusty star-forming galaxies at the high frequencies. The increased spectral coverage of AdvACT will enable a wide range of CMB science, such as improving constraints on dark energy, the sum of the neutrino masses, and the existence of primordial gravitational waves. The LF array will be the final AdvACT array, replacing one of the MF arrays for a single season. Prior to the fabrication of the final LF detector array, we designed and characterized prototype TES bolometers. Detector geometries in these prototypes are varied in order to inform and optimize the bolometer designs for the LF array, which requires significantly lower noise levels and saturation powers (as low as ~1 pW) than the higher-frequency detectors. Here we present results from tests of the first LF prototype TES detectors for AdvACT, including measurements of the saturation power, critical temperature, thermal conductance, and time constants. Finally, we also describe the modifications to the time-division SQUID readout architecture compared to the MF and HF arrays.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

RF Plasma Polymerization of Orange Oil and Characterization of the Polymer Thin Films

The present study describes an environmentally friendly approach to fabricate hydrocarbon-rich polymer thin films from a bio-renewable precursor, orange oil, cold extracted from orange peels using radio frequency plasma polymerization. The polymer thin films fabricated at different RF power level (10–75 W) were characterized with variable angle spectroscopic ellipsometry, UV–visible spectroscopy, Fourier transform infrared spectroscopy and atomic force microscopy. Optical characterization showed that independent of deposition power films exhibited good transparency (~ 90%) in the visible region and a refractive index of 1.55 at 500 nm. The optical band gap measured around 3.60 eV and falls within the insulating region. The atomic force microscopic images revealed that the surface is pinhole-free in nature and smooth at nanoscale, with average surface roughness dependent on the deposition power. Film hardness increased from 0.50 to 0.78 GPa as applied power increased from 10 to 75 W.

36 MATERIALS SCIENCE↗