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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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Adjunctive Thermoprotection During Percutaneous Thermal Ablation Procedures: Review of Current Techniques

Although rare, unintended thermal injury to organs surrounding the ablation zone can lead to severe complications. Over the past 15 years, different protective methods have been developed to limit risk of complications, and expand indications to include more challenging lesions in various locations including liver, kidney, lung and bone. The most frequently used techniques include hydrodissection, carbodissection, balloon interposition and probe torqueing. In most cases, tumours can be physically separated from sensitive structures, reducing risk of thermal injury. Endoluminal cooling/warming is an alternative option for complex ablations close to the ureter or major bile ducts. Different techniques may be combined to achieve successful protection in locations with complex anatomy. The purpose of this review is to provide an overview of available protective measures and discuss respective advantages/drawbacks.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Synthesis of CS/PVA Biodegradable Composite Nanofibers as a Microporous Material with Well Controllable Procedure Through Electrospinning

In this study, we have showed a facile route for fabrication of a novel microporous material based on chitosan (CS) and poly(vinyl alcohol) (PVA) biodegradable nanofibers that have high specific surface area, considerable porosity, and small diameter. Scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area analysis, and CHNS/O elemental analyser were applied to characterize the fabricated CS/PVA composite nanofibers. Moreover, the influences of spinning conditions including concentration, voltage, electrospinning distance, and flow rate, on size distribution and pore diameter of the final product were systematically studied using 2{sup k−1} factorial design experiments, and the response surface optimization was used for determining the best synthesis parameter. The results obtained from 2{sup K−1} factorial design experiments showed that electrospinning parameters influenced the size distribution and pore diameter of the CS/PVA microporous material. Based on the response surface methodology, the CS/PVA product could be obtained with a high microporous diameter of 1.8 nm and a small diameter distribution of 15.0 nm under optimized conditions. The obtained results showed that the fabricated samples could be utilized in different applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Chitosan Depolymerization and Nanochitosan Production Using a Single Physical Procedure

The many applications of the chitosan biopolymers in the areas of nanotechnology and nanomaterials have led to the need to develop novel techniques suitable for the production of nanochitosan. At present these typically involve the use of chemical agents to form chitosan nanoparticles. Physical, chemical, and enzymatic methods have been described for the depolymerizatiton of chitosan. In this work, evaluation was made of the efficiency of a combination of physical methods, including milling of the raw material and drying of the final chitosan, in order to obtain nanochitosan with low molar mass. The results revealed the effectiveness of the combination of milling the raw material under controlled conditions for 4.5 h and drying of the chitosan by thermal shock, which provided depolymerization of up to 10× and resulted in chitosan with M{sub v} less than 21 kDa and hydrodynamic diameter below 30 nm.

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

Production Procedure and Characterization of Zn-Doped Y-123 Superconducting Samples Prepared by Sol-Gel Method

The superconducting YBa{sub 2}Cu{sub 3−x}Zn{sub x}O{sub 7} (Y-123) bulk materials have been synthesized by using the sol-gel method. Samples are produced as undoped Y-123 and transition metal (Zn)-doped Y-123. Before the final heat treatment, the samples are calcined at 850 °C for 24 h. This process is repeated three times. Then, samples are sintered at 950 °C for 24 h in an air environment and at 500 °C for 5 h in an oxygen atmosphere. The synthesized products are characterized by XRD, R-T, and Vickers microhardness tester. The XRD investigation revealed that the prepared sample has an orthorhombic structure. According to XRD measurements, an orthorhombic structure has not changed with Zn doping. It was observed that undoped and Zn-doped samples have superconductivity properties by electrical measurements. T{sub c}{sup onset} is 89 K for undoped Y-123 sample, and the T{sub c}{sup onset} value decreases monotically with Zn addition. All samples show metallic behavior above T{sub c}{sup onset} temperature. As a result of Vickers microhardness measurements, it is observed that all samples have reverse indentation size effect (RISE) behavior.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Discretization Procedure for Linear Dynamical Systems

We describe in detail a method of construction of a discrete linear dynamical model of a controllable object in the recurrent Cauchy form corresponding to an initial continuous dynamical system. We describe discretization algorithms for free and forced motion of a linear continuous dynamical system and propose methods of construction of the state, control, and perturbation transition matrices.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

A design procedure for fan-out improvement in all-optical photonic crystal logic design

In this paper, a general method is proposed to improve the fan-out parameter for all-optical logic gates and functions. Two different types of devices are designed to increase the fan-out of a logic operation and its inverted logic. Nonlinear cavities are used to design driving units. Silicon nanocrystal is used as the nonlinear material to create the required frequency shift for different values of input power. Plane wave expansion and finite difference time domain methods are used to simulate and analyze the proposed structures. The propagation delay of the proposed structure is less than 1.5 ps and the maximum required power for fan-out of three is 15 W.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

An efficient cost reduction procedure for bounded-control LQR problems

A novel approach has been developed for approximating the solution to the constrained LQR problem, based on updating the final state and costate of a related regular problem, and on slightly shifting the switching times (the instants when the control meets the constraints). The main result is the expression of a suboptimal control in feedback form using the solution of some compatible Riccati equation. The gradient method is applied to reduce the cost via explicit algebraic formula for its partial derivatives with respect to the hidden final state/costate of the related regular problem and to the switching times. The numerical method is termed efficient because it does not involve integrations of states or cost trajectories, and reduces to its minimum the dimension of the unknown parameters at the final condition. All the relevant objects are calculated from a few auxiliary matrices, which are computed only once. The scheme is here applied to two case studies whose optimal solutions are known. The first example is a two-dimensional model of the ‘cheapest stop of a train’ problem. The second one refers to the temperature control of a metallic strip leaving a multi-stand rolling mill, a problem with a high-dimensional state.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Development of the multigroup cross section library for the CASL neutronics simulator MPACT: Method and procedure

The MPACT neutronics module of the Consortium for Advanced Simulation of Light Water Reactors (CASL) core simulator is a 3D whole core transport code being developed for the CASL toolset known as the Virtual Environment for Reactor Analysis (VERA). Key characteristics of the MPACT code include a subgroup method for resonance self-shielding and a whole-core transport solver with a 2D/1D synthesis method. The AMPX and SCALE code packages have been significantly improved to include intermediate resonance parameters, as well as new modules to enhance the accuracy of resonance data and scattering matrices for the Bondarenko approach and transport cross sections of hydrogen. In addition, CASL XSTools have been developed to generate the MPACT multigroup cross section library. A simple super-homogenization method for 238U has been developed to resolve reaction rate discrepancy issues caused by angle-dependent total cross sections, poor scattering matrices, and a poor resonance interference model at coarse group structure. Here, due to the limitation of computing capacity that can occur even in high performance computing, a new 51-group structure has been developed for efficient simulation that is applicable for both pressurized water reactor (PWR) and boiling water reactor (BWR) simulations. A new ENDF/B-VII.1 MPACT 51-group library has been developed using the AMPX/SCALE and XSTools code packages, and it has been verified and validated by performing various benchmark calculations.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2014

Uncertainty Estimation Improves Energy Measurement and Verification Procedures

Implementing energy conservation measures in buildings can reduce energy costs and environmental impacts, but such measures cost money to implement so intelligent investment strategies require the ability to quantify the energy savings by comparing actual energy used to how much energy would have been used in absence of the conservation measures (known as the baseline energy use). Methods exist for predicting baseline energy use, but a limitation of most statistical methods reported in the literature is inadequate quantification of the uncertainty in baseline energy use predictions. However, estimation of uncertainty is essential for weighing the risks of investing in retrofits. Most commercial buildings have, or soon will have, electricity meters capable of providing data at short time intervals. These data provide new opportunities to quantify uncertainty in baseline predictions, and to do so after shorter measurement durations than are traditionally used. In this paper, we show that uncertainty estimation provides greater measurement and verification (M&V) information and helps to overcome some of the difficulties with deciding how much data is needed to develop baseline models and to confirm energy savings. We also show that cross-validation is an effective method for computing uncertainty. In so doing, we extend a simple regression-based method of predicting energy use using short-interval meter data. We demonstrate the methods by predicting energy use in 17 real commercial buildings. We discuss the benefits of uncertainty estimates which can provide actionable decision making information for investing in energy conservation measures.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Towards the development of a standardized testing protocol for overhead island kitchen exhaust devices: Procedures, measurements and paths forward

Cooking is one of the most important sources of airborne pollutants in the indoor environments of residential buildings. Elevated concentrations of NO 2 due to cooking have been reported widely (Garret et al. 1998; Garrett et al. 1999; Mullen et al. 2016; Ryan et al. 1988; Schwab et al. 1994; J. Spengler et al. 1994; J. D. Spengler et al. 1983; Wilson et al. 1995). Many researchers have attributed elevated particulate concentrations to cooking, and some have attributed extremely high short-term concentrations of fine particles (>300 μg/m3) and ultrafine particles (>105 μg/m3) to cooking events (Abdullahi et al. 2013; Abt et al. 2000; Afshari et al. 2005; Buonanno et al. 2009; He et al. 2004; Kearney et al. 2011; Lance A. Wallace et al. 2004; See and Balasubramanian 2008; Stieb et al. 2008; Wallace and Ott 2011; Wheeler et al. 2011; Zhang et al. 2010). Cooking is also a source of other gas-phase pollutants including carbon monoxide, formaldehyde, acrolein, and other volatile organic compounds (Garret et al. 1998; Garrett et al. 1999; Logue et al. 2013; Mullen et al. 2016; Ryan et al. 1988; Schwab et al. 1994; J. Spengler et al. 1994; J. D. Spengler et al. 1983; V. Seaman et al. 2007; Wilson et al. 1995). Lastly, cooking can be a significant source of water vapor, and the water vapor produced from cooking can eventually lead to moisture-related problems (Parrott and Emmel 2003)

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗