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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Theory and Practice in Measuring In-Vitro Extensibility of Growing Plant Cell Walls

This chapter summarizes four extensometer techniques for measuring cell wall extensibility in vitro and discusses how the results of these methods relate to the concept and ideal measurement of cell wall extensibility in the context of plant cell growth. These in-vitro techniques are particularly useful for studies of the molecular basis of cell wall extension. Measurements of breaking strength, elastic compliance and plastic compliance may be informative about changes in cell wall structure, whereas measurements of wall stress relaxation and creep are sensitive to both changes in wall structure and wall-loosening processes, such as those mediated by expansins and some lytic enzymes. As a result, a combination of methods is needed to obtain a broader view of cell wall behavior and properties connected with the concept of cell wall extensibility.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The application of cinematic rendering to CT evaluation of upper tract urothelial tumors: principles and practice

Upper tract urothelial carcinoma (UTUC) is a relatively uncommon but aggressive genitourinary malignancy for which multi-phase contrast-enhanced computed tomography (CT) plays an important role in evaluation and staging. 3D imaging with maximum intensity projection (MIP) and volume-rendered (VR) images has been described as a useful means of evaluating UTUC. In this study, we describe the technique of a novel 3D methodology known as cinematic rendering (CR) and provide clinical examples of UTUC visualized with CR. CR utilizes a complex universal lighting model in order to create photorealistic images with improved detail and depth in comparison to MIP or VR images. In the case of UTUC, CR can be used in different contrast phases to show abnormally thickened and enhancing urothelium or filling defects in the renal collecting system or ureters in the excretory phase. CR images can also be manipulated in order to generate translucent views of the upper urinary tract in order to add conspicuity to intraluminal findings.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Quantitative analysis of Raman spectral parameters for carbon fibers: practical considerations and connection to mechanical properties

Although the literature on the Raman spectra of carbon fibers is vast, no consistent, robust predictive relationship between mechanical properties of carbon fibers and spectral parameters exists. This shortcoming is due to the use of numerous fitting functions to evaluate Raman spectra of carbon fibers and the inconsistencies in establishing the best fitting models in a statistically robust fashion. To address this gap, we present a comprehensive work on the Raman spectra of carbon fibers that combines a vast library of experimental data with a robust numerical analysis and a statistical evaluation of a wide range of suggested fitting models. This manuscript begins with a brief review of the commonly applied fitting models. Then, the Raman spectra of 32 commercially available polyacrylonitrile-based carbon fibers collected at excitation wavelengths 532, 633, and 785 nm are presented and the best fit for all fibers is evaluated based on several statistical criteria in conjunction with numerical calculations and physical arguments. The results suggest that high-performance fibers must be fit with at least five peaks, whereas high-tensile modulus fibers are best fit with at least six distinct peaks. Finally, we employ simultaneous fitting of the Raman spectra of specific fibers and wavelengths and demonstrate that strong correlations exist between mechanical properties and the D1 peak position and shape across the range of evaluated mechanical properties. Finally, we suggest straightforward improvements in fitting analysis procedures that can be implemented to increase coherency in the understanding of the underlying carbon fiber microstructure intuited from Raman spectroscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Controversy and consensus: common ground and best practices for life cycle assessment of emerging technologies

This manuscript explores six controversial topics regarding LCA of emerging technologies: (1) appropriate use of LCA, (2) uncertainty assessment, (3) comparison with incumbents, (4) adopting standards, (5) system scale-up, and (6) stakeholder engagement. These topics encompass key issues vigorously debated during a series of workshop-style discussions convened by the LCA of Emerging Technologies Research Network (currently hosted by ACLCA). This paper represents the main points of support and opposition for a declarative resolution representing each topic, along with points of consensus, held amongst research network of LCA practitioners and experts. These debates and associated open questions are intended to build awareness amongst practitioners and decision-makers of the common challenges associated with assessing emerging technologies, while fostering evidence-based and context-informed discussions that are both transparent and impactful for the broader community.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2024

Decarbonization of heat pump dual fuel systems using a practical model predictive control: Field demonstration in a small commercial building

In the transition from fossil fuel to electrified heating, a concerning trend is emerging in certain regions of the US. Owners of buildings with gas-based systems leave them in place after adding heat pumps (HPs). Existing control solutions for these hybrid (dual fuel) systems are rudimentary and fall short of realizing the full carbon reduction potential of these systems. Model predictive control (MPC) is often regarded as the benchmark for achieving optimal control in integrated systems. However, in the case of small-medium commercial buildings (SMCBs), the control and communication infrastructure required to facilitate the implementation of such advanced controls is often lacking. This paper presents a field implementation of easy-to-deploy MPC for a dual fuel heating system consisting of HPs and a gas-fired furnace (GF) for SMCBs. The control system is deployed on an open-source middleware platform and utilizes low-cost sensor devices to be used for real SMCBs without major retrofits. Here, we demonstrated this MPC in a real office building with 5 HPs and 1 GF for 2 months. The test results showed that MPC reduced 27% of cost while completely eliminating GF usage by shifting 23% of the thermal load from occupied-peak time to non-occupied-non-peak times.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Ultrathin platinum nanowire based electrodes for high-efficiency hydrogen generation in practical electrolyzer cells

Significant reduction of noble metal catalyst loading and simplification of electrode fabrication are urgently needed in order to lower the cost of proton exchange membrane electrolyzer cells (PEMECs) for large-scale hydrogen production. Herein, we report an integrated electrode design comprising in-situ grown platinum nanowires (PtNW) on ultrathin titanium liquid/gas diffusion layers (LGDLs) via a cost-effective and green chemical synthesis approach. The ultrathin integrated PtNW electrodes showed a low cell voltage of 1.643 V and high efficiency of 90.08% at 1000 mA cm -2 using about 15 times lower catalyst loadings than a conventional catalyst-coated membrane in PEMEC tests. Ex-situ electrochemical characterizations and microscale visualizations further reveal that PtNW electrodes display highly efficient hydrogen evolution reactions and excellent electrode durability due to high active surface area, favorable bubble detachment, and structural stability. This work provides new insights into catalyst layer design and facile ultrathin electrode fabrication for more compact and low-cost PEM electrolyzers, fuel cells and other systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Balanced Fast-SpaciMS capillary configurations provide practically noninvasive channel-average measurements in catalytic monoliths

Spatially resolved capillary-inlet mass spectrometry (SpaciMS) provides a detailed picture of the spatiotemporal evolution of reaction network in catalytic monoliths. In the present work, we combine the SpaciMS experiments with a newly developed non-isothermal 3D CFD model for heterogeneously catalyzed reactive flows, including diffusion and permeation through the coated catalyst and channel wall. We explore how the capillary size and sampling rate can be balanced to minimize the impact on probed-channel conversions and provide species concentration measurements representative of the free channel average. In all studied configurations, the balanced sampling-rate fraction is noticeably higher than the corresponding capillary occlusion fraction. For a typical 350-micron capillary that occupies 11% of the channel cross- section, the balanced sampling rate represents 43% of the channel flow. Furthermore, the present work shows that together, a balanced SpaciMS configuration and numerical simulation provide accurate channel-averaged information of a monolithic catalyst under realistic operation conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Protorheology in practice: Avoiding misinterpretation

Protorheology is the paradigm that any observed flow or deformation is a chance to infer quantitative rheological properties. While this creates many opportunities for insight, there is significant risk of misunderstanding the physics involved, e.g. misinterpreting a liquid as a solid or mistaking viscous flow time as viscoelastic relaxation time. We describe these and other potential mistakes, use case studies to show how serious the problems can be, and contrast misinterpretations with correct approaches and interpretations. Some issues are especially important with materials involving colloidal particles and flows involving surface tension. Whether the reader is making inference from a tilted vial, time-lapse gravity-driven flow, a bounce test, die swell, or any other protorheology observation, the examples here serve as a guide for avoiding bad data in protorheology.

42 ENGINEERING↗
DOE OSTI2021

Practical algorithms for multivariate rational approximation

We present two approaches for computing rational approximations to multivariate functions, motivated by their effectiveness as surrogate models for high-energy physics (HEP) applications. Our first approach builds on the Stieltjes process to efficiently and robustly compute the coefficients of the rational approximation. Our second approach is based on an optimization formulation that allows us to include structural constraints on the rational approximation (in particular, constraints demanding the absence of singularities), resulting in a semi-infinite optimization problem that we solve using an outer approximation approach. We present results for synthetic and real-life HEP data, and we compare the approximation quality of our approaches with that of traditional polynomial approximations.

97 MATHEMATICS AND COMPUTING↗