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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A Study of Tensile Flow and Work-Hardening Behavior of Alloy 617

The simple power relationship σ = Κε{sub p}{sup n} satisfactorily expresses the tensile flow behavior of many metals and alloys in their uniform plastic strain regime. However, many FCC materials with low stacking fault energy have opposed such power law relationship. Alloy 617, an age-hardenable Ni-based superalloy is also observed not to obey the simple power law relationship neither in its solution-treated nor in its aged conditions. Various flow relationships were used to obtain the best fit for the tensile data, and different relationships were identified for the different aged conditions. The work-hardening rate (θ) demonstrates three distinct regions for all aged conditions, and there is an obvious change in the trend of θ versus σ. In the initial portion, θ decreases rapidly followed by a gradual increase in the second stage and again a decrease in its third stage is perceived in the Alloy 617. These three-stage characteristics are attributed to a commonly known precipitate, γ′: Ni{sub 3}(Ti, Al) which evolves during aging treatment and well recognized under transmission electron microscopy (TEM) observation. TEM results also reveal a slight degree of coarsening in γ′ over aging. The tensile flow and the work-hardening behavior are well correlated with other microstructural evolution during the aging treatments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Rapid Strengthening Without Loss of Ductility via Electropulsing Treatment in Ti-6Al-4V Alloy

The commercial (hot-rolled and annealed) Ti-6Al-4V alloy subjected to electropulsing was investigated in this study. The results show that the electropulsing-treated sample with optimized parameter exhibits greatly refined microstructure and notable strength improvement without loss of ductility. The main strengthening mechanism is recognized as phase transformation and rapid grain refinement induced by recrystallization under EPT.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Optimization of Hot Deformation Parameters and Constitutive Analysis for As-Cast Mg-5Li-3Zn-0.3Y Alloy Using Processing Maps

Hot deformation behavior of as-cast Mg-5Li-3Zn-0.3Y (wt.%) alloy has been studied by establishing processing maps covering the range of 200-450 °C in temperature and 0.001-10 s{sup −1} in strain rate. The map corresponding to the strain of 0.7 reveals that a domain of dynamic recrystallization occurred at 340-400 °C/0.01-0.158 s{sup −1} with its peak efficiency of approximately 31%. Analysis of the flow behaviors and microstructural observations indicated that dynamic recrystallization occurred in the domain, in which fine microstructure can be achieved. The above conditions represent the optimum processing parameters, and the flow instability regimes are also recognized from the maps. The average deformation in the deformed range was 136.414 kJ/mol which is close to that for lattice self-diffusion in magnesium and far smaller than that for as-cast Mg-5.75Zn-0.73Y-0.36Zr (wt.%) alloy. It is believed that a lower activation energy for Mg-5Li-3Zn-0.3Y alloy can partly result from both the weak particle pinning effects and adding Li into the Mg-Zn-Y-Zr alloy. Results of extrusion experiments conducted at 350 °C show that the alloy can be easily extruded with good mechanical properties of the yield strength of 132 MPa, the fracture strength of 215 MPa and the elongation of 20.9%, and the grains can be well refined.

36 MATERIALS SCIENCE↗
DOE OSTI2019

In Situ Quality Monitoring in AM Using Acoustic Emission: A Reinforcement Learning Approach

Additive manufacturing (AM) has attracted considerable attention in recent years. This technology overcomes the geometrical limits of workpieces produced with the traditional subtractive methods and so gives the opportunity to manufacture highly complex shapes. Unfortunately, the repeatability of the manufacturing process and the monitoring of quality are not reliable enough to be utilized in mass production. The quality monitoring of AM processes in commercial equipment has been largely based on temperature measurements of the process zone or high-resolution imaging of the layers. However, both techniques lack information about the physical phenomena taking place in the depth of the materials medium and this limits their reliability in real-life applications. To overcome those restrictions, we propose to combine acoustic emission and reinforcement learning. The former captures the information about the subsurface dynamics of the process. The latter is a branch of machine learning that allows interpreting the received data in terms of quality. The combination of both is an original method for in situ and real-time quality monitoring. Acoustic data were collected during a real process using a commercial AM machine. The process parameters were selected to achieve three levels of quality in terms of porosity concentration while manufacturing a stainless steel 316L cuboid shape. Using our method, we demonstrated that each level of quality produced unique acoustic signatures during the build that were recognized by the classifier. The classification accuracy reached in this work proves that the proposed method has high potential to be used as in situ and real-time monitoring of AM quality.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Thermally Assisted Adhesion Enhancement in High-Phosphorous Electroless Nickel Plating

High-phosphorus electroless nickel is a widely recognized protective plating for oilfield metallic parts subject to corrosion and wear. In the present investigation, thermally activated diffusion treatment was applied to enhance electroless nickel (10-13 wt.% P) plating adhesion on low-alloy steel (UNS G41400) and reduce the risks of spalling. High-phosphorus electroless nickel (10-13 wt.% P) was applied to a variety of UNS G41400 low-alloy steel test samples as per ASTM B733 that were subsequently heat-treated in air for four distinct temperatures, i.e., 510, 540, 570, and 600 °C for 2-10 h. Following post-plating diffusion heat treatments, the initial amorphous electroless nickel was replaced by Ni{sub 3}P precipitates dispersed in a crystalline nickel-rich phase, with an average hardness improvement from 500 to 700 HK. An increased atomic interdiffusion (from 400 to 3.5 µm) was observed at plating–substrate interfaces, resulting in enhanced adhesion and reduced susceptibility toward spalling. This improvement in adhesion was measured repeatedly through post-bending crack analyses and subsequently validated by interface microindentation. Along with diffusion across plating–substrate interface, nickel oxide formation on surface by oxidation was observed to grow at quasi-parabolic rate with no detrimental impact on spalling. In all cases, plating adhesion was improved by heat treatments due to the diffusion-controlled formation of a seemingly ductile layer.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructural Analysis of Powder Metallurgy Tool Steels in the Context of Abrasive Wear Behavior: A New Computerized Approach to Stereology

The present work describes a new methodology designed to characterize the microstructures of tool steels containing carbide hard phases, with the focus set on their abrasive wear resistance. A series of algorithms were designed and implemented in MATLAB® to (i) recognize each of the features of interest, (ii) measure relevant quantities and (iii) characterize each of the phases and the alloy in function of attributes usually neglected in wear description applications: size distribution, shape and contiguity of the hard phases. The new framework incorporates new parameters to describe each one of these attributes, as observed in SEM micrographs. All three aforementioned stages contain novel contributions that can be potentially beneficial to the field of materials design in general and to the field of alloy design for severely abrasive environments in particular. Models of known geometry and micrographs of different powder metallurgy steels were analyzed, and the obtained results were compared with the obtained by the linear intercept method. The relation between the new parameters and the ones available in the scientific literature is also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Multiscale Modeling Meets Machine Learning: What Can We Learn?

Machine learning is increasingly recognized as a promising technology in the biological, biomedical, and behavioral sciences. There can be no argument that this technique is incredibly successful in image recognition with immediate applications in diagnostics including electrophysiology, radiology, or pathology, where we have access to massive amounts of annotated data. However, machine learning often performs poorly in prognosis, especially when dealing with sparse data. This is a field where classical physics-based simulation seems to remain irreplaceable. In this review, we identify areas in the biomedical sciences where machine learning and multiscale modeling can mutually benefit from one another: Machine learning can integrate physics-based knowledge in the form of governing equations, boundary conditions, or constraints to manage ill-posted problems and robustly handle sparse and noisy data; multiscale modeling can integrate machine learn- ing to create surrogate models, identify system dynamics and parameters, analyze sensitivities, and quantify uncertainty to bridge the scales and understand the emergence of function. With a view towards applications in the life sciences, we discuss the state of the art of combining machine learning and multiscale modeling, identify applications and opportunities, raise open questions, and address potential challenges and limitations. We anticipate that it will stimulate discussion within the community of computational mechanics and reach out to other disciplines including mathematics, statistics, computer science, artificial intelligence, biomedicine, systems biology, and precision medicine to join forces towards creating robust and efficient models for biological systems.

machine learning, multiscale modeling, physics-bas↗
DOE OSTI2016

Thermal stability comparison of nanocrystalline Fe-based binary alloy pairs

Here, the widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest, yet have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dense systems. While traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloy can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdock et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10at.% Mg) with a predicted non-NC stable alloy (Fe-10at.% Cu) using the same processing and characterization methodologies. Results indicate improved thermal stability of the Fe-Mg alloy in comparison to the Fe-Cu, and observed microstructures are consistent with those predicted by Monte Carlo simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Strategy for Texture Management in Metals Additive Manufacturing

Additive manufacturing (AM) technologies have long been recognized for their ability to fabricate complex geometric components directly from models conceptualized through computers, allowing for complicated designs and assemblies to be fabricated at lower costs, with shorter time to market, and improved function. Lacking behind the design complexity aspect is the ability to fully exploit AM processes for control over texture within AM components. Currently, standard heat-fill strategies utilized in AM processes result in largely columnar grain structures. Here, we propose a point heat source fill for the electron beam melting (EBM) process through which the texture in AM materials can be controlled. Using this point heat source strategy, the ability to form either columnar or equiaxed grain structures upon solidification through changes in the process parameters associated with the point heat source fill is demonstrated for the nickel-base superalloy, Inconel 718. Mechanically, the material is demonstrated to exhibit either anisotropic properties for the columnar-grained material fabricated through using the standard raster scan of the EBM process or isotropic properties for the equiaxed material fabricated using the point heat source fill.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Instance Segmentation for Direct Measurements of Satellites in Metal Powders and Automated Microstructural Characterization from Image Data

In this work, we propose instance segmentation as a useful tool for image analysis in materials science. Instance segmentation is an advanced technique in computer vision which generates individual segmentation masks for every object of interest that is recognized in an image. Using an out-of-the-box implementation of Mask R-CNN, instance segmentation is applied to images of metal powder particles produced through gas atomization. Leveraging transfer learning allows for the analysis to be conducted with a very small training set of labeled images. As well as providing another method for measuring the particle size distribution, we demonstrate the first direct measurements of the satellite content in powder samples. After analyzing the results for the labeled data dataset, the trained model was used to generate measurements for a much larger set of unlabeled images. The resulting particle size measurements showed reasonable agreement with laser scattering measurements. The satellite measurements were self-consistent and showed good agreement with the expected trends for different samples. Finally, we present a small case study showing how instance segmentation can be used to measure spheroidite content in the UltraHigh Carbon Steel DataBase, demonstrating the flexibility of the technique.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Molecular Imaging of Cardiac Amyloidosis

Purpose of Review: The aim of this review is to give an update on the molecular imaging tools currently available as well as to discuss the potential roles and limitations of molecular imaging in cardiac amyloidosis. Recent Findings: Molecular imaging plays a central role in the evaluation of patients with suspected cardiac amyloidosis. It can be used to diagnose and distinguish between the different types of cardiac amyloidosis. The diagnostic properties of bone scintigraphy are such that it allows reliable diagnosis of transthyretin cardiac amyloidosis without the need of endomyocardial biopsy in a significant proportion of patients. Furthermore, molecular tracers assessing amyloid plaque burden and sympathetic innervation may be useful for the non-invasive evaluation diagnosis and risk stratification of patients with suspected cardiac amyloidosis. Summary: Cardiac amyloidosis is an under-recognized cause of left ventricular hypertrophy and heart failure in the elderly. The role of molecular imaging in cardiac amyloidosis is expected to grow considering the arrival of new therapies and molecular imaging probes.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Multimodality Imaging for the Assessment of Pericardial Diseases

Purpose of Review: The diagnosis of pericardial syndromes, while occasionally straightforward, includes a wide range of pathologies and is often a well-recognized clinical challenge. The aim of this review is to highlight the key role of the various imaging modalities for the diagnosis and management of the spectrum of pericardial diseases. Recent Findings: Cardiac imaging has become an integral part of the diagnostic process often beginning with echocardiography and supported by advanced imaging modalities including computed tomography, magnetic resonance imaging, and positive emission tomography. These modalities go beyond the simple identification of the pericardium, to identifying increased pericardial thickness, active pericardial edema and inflammation, and its effect on cardiac hemodynamics. Summary: Multimodality imaging has significantly facilitated the diagnosis and long-term management of patients with pericardial diseases. The role of these imaging modalities in overall prognosis and prevention remains to be investigated.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

The Onco-cardiologist Dilemma: to Implant, to Defer, or to Avoid Transcatheter Aortic Valve Replacement in Cancer Patients with Aortic Stenosis?

Purpose of Review: Aging is associated with an increased prevalence of both cancer and heart disease. The progression of aortic valve calcification to aortic stenosis may be accelerated by both cardiovascular risk factors and cancer treatments, such as radiotherapy with mediastinal involvement. Symptomatic aortic stenosis is occasionally diagnosed in cancer patients undergoing cardiovascular evaluation; likewise, cancer is often recognized during assessment preceding aortic valve interventions. In these complex cases, physicians face difficult treatment decisions. Due to a myriad of clinical presentations of cancer and valve disease, specific guidelines for this patient population are not currently in place. Management is currently based on clinical judgment, on an individual basis. Recent Findings: Patients with cancer in remission or with a favorable prognosis should be treated according to current cardiovascular guidelines. In these patients, aortic valve replacement can be performed either by surgery or transcatheter. Significant challenges arise in patients with active cancer, especially those receiving anti-cancer treatment. Recent data suggests that these patients can be offered aortic valve replacement, with a trend of favoring the transcatheter route in order to minimize perioperative risk and complications associated with major surgery. Patients with advanced cancer and severe aortic stenosis should be offered palliative care and can benefit from aortic balloon valvuloplasty if indicated. Modern cancer treatments associated with improved long-term prognosis may allow the appropriate cure of aortic stenosis. Summary: We discuss the protocol, outcomes, and evolving recommendations of aortic valve replacement in cancer patients with aortic stenosis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Importance of m N{sup 6}-methyladenosine (m{sup 6}A) RNA modification in cancer

RNA methylation, which was identified back in 1970s, has gained remarkable interest in recent years as it was shown to be a reversible modification involved in many cellular processes like mRNA and miRNA processing, mRNA localisation, translation suppression, or activation. These, in turn, affect important bioprocesses such as tissue development, sex determination, and DNA damage response. Important group of proteins are responsible for adding, recognizing, and removing the methyl group to and from the RNA molecules, which are referred as writers, readers, and erasers, respectively. If any of the processes is not strictly controlled, this can cause abnormalities in gene expression, which result in diseases including cancers such as lung, pancreas, glioblastoma, and breast cancer. Mechanisms of RNA methylation and its role in various cancer types and diagnostic methods for RNA methylation are discussed in this article.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Bone marrow examination in patients with Ewing sarcoma/peripheral primitive neuroectodermal tumor without metastasis based on {sup 18}F-fluorodeoxyglucose positron emission tomography/computed tomography

Ewing sarcoma/peripheral primitive neuroectodermal tumor (ES/PNET) is an aggressive bone tumor. Bone marrow aspiration and biopsy (BMAB) has been recognized as the gold standard for assessing bone marrow status. While the latest guideline suggests the need to omit bone marrow aspiration in patients with no findings on {sup 18}F-fluorodeoxyglucose positron emission tomography ({sup 18}F-FDG PET) based on one retrospective report, there is no study using {sup 18}F-FDG PET/computed tomography (CT). We retrospectively reviewed 26 consecutive, previously untreated, ES/PNET patients. We compare the results of bone marrow aspiration and biopsy (BMAB) and those of {sup 18}F-FDG PET/CT in ES/PNET patients. All of the 21 patients without metastases on {sup 18}F-FDG PET/CT had negative BMAB. The sensitivity of bone marrow involvement in bone metastases positive patients on {sup 18}F-FDG PET/CT was 75% (3/4), and the specificity was 100% (22/22). In addition to the metastatic findings on {sup 18}F-FDG PET/CT, tumor diameter, lactate dehydrogenase level at diagnosis, and the presence or absence of bone metastasis were factors related to bone marrow involvement. It may be a reasonable option to omit BMAB in ES/PNET patients with no distant metastasis based on {sup 18}F-FDG PET/CT findings.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Clinical and morphologic review of 60 hereditary renal tumors from 30 hereditary renal cell carcinoma syndrome patients: lessons from a contemporary single institution series

Hereditary renal cell carcinoma syndromes (HRCCS) are characterized by the presence of pathogenic germline variants that predispose patients to renal cell carcinomas as well as additional extra-renal manifestations. The importance of identifying HRCCS patients cannot be overemphasized, as patients and their families can begin surveillance for syndrome-associated manifestations once identified. The present study is a retrospective clinical and morphologic review of 60 hereditary renal tumors from 30 HRCCS patients treated at our institution with either Von Hippel-Lindau disease (VHL), Birt-Hogg-Dubé syndrome (BHD), tuberous sclerosis complex (TSC), hereditary leiomyomatosis and renal cell cancer syndrome, or succinate dehydrogenase (SDH) deficiency syndrome. Hereditary renal cell carcinoma syndromes kidney tumors often demonstrate specific morphologic features, characteristic background changes in renal parenchyma, and extra-renal manifestations, which, when recognized by the pathologist, can trigger genetic testing referral for specific familial cancer syndromes. Our study demonstrates the majority of tumors were consistent with the anticipated clinicopathologic profile of renal tumors found within HRCCS patients, although we found some unique characteristics within this cohort including a case of clear cell papillary renal cell carcinoma within a VHL patient, and a unique renal tumor with tubulopapillary features present in a patient with a germline SDHD mutation. Additionally, although the literature reports the presence of epithelioid angiomyolipoma (AML) as a common occurrence in TSC patients, our cohort of 3 patients with AMLs demonstrated only classic features. The findings we describe facilitate pathologist-based recognition of HRCCS and can prompt genetic evaluation for relevant patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Liver graft rejection following immune checkpoint inhibitors treatment: a review

Immune checkpoint inhibitors (ICIs) have demonstrated remarkable efficacy in a variety of solid tumors; nonetheless, they have not been well investigated and are still recognized as a relative contraindication for patients with a liver transplantation (LT) history, since ICIs treatment might potentially lead to graft rejection. The program death-1 (PD-1) and the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) pathways are implicated in the tolerance of transplanted organ, as well as blockade of the pathways, which contribute to eliminating tumors and may inadvertently lead to peripheral transplant rejection. Currently, no guidelines are available regarding the treatment for ICIs patients with a prior LT history. Therefore, this study was carried out to review the recent studies, attempting to introduce the ICIs-related graft rejection after LT from various aspects. We believed that ICIs could be given for the well-informed patients receiving LT and developed recurrence in a controlled setting. Typically, these patients should be treated according to a clinical care path or a prospective clinical trial, so as obtain a persistent anti-tumor immune response in the meantime of avoiding graft rejection, adjust the immunosuppression, reduce the possibility of graft loss following rejection, and have the opportunity to develop biomarkers for tumor response and transplant rejection.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Timed to save: the added value of accounting for hourly incidence of electricity savings from residential space-conditioning measures

Abstract Previous research has recognized that the value of measures that reduce electricity usage depends upon the timing of the savings generated, but the lack of hourly savings shapes has limited the demonstration of this concept. We develop empirical hourly savings shapes for residential space-conditioning measures from nearly 18,000 efficiency projects in California and show how they combine with the diurnal and seasonal variation in electricity system costs. We find that these measures (cooling replacements; windows, doors, and skylights; and other envelope measures) tend to save electricity when system costs are highest and that the hourly savings account for 1.4–1.5 times as much value as non-time-sensitive estimates of efficiency would predict. We present these impact multipliers for each measure to quantify the additional value revealed by the time-sensitive approach. We show that this additional value is similar in an evolving electricity grid with storage, rather than natural gas generation, as the marginal resource.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗