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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 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Monolithic 4-Terminal 1.2 kV/20 A 4H-SiC Bi-Directional Field Effect Transistor (BiDFET) with Integrated JBS Diodes

In this paper, we report successful fabrication of the first large area, monolithic, 1.2 kV 4H-SiC Bi-Directional FETs (BiDFETs) with integrated JBS diodes in a 6-inch commercial foundry for use in matrix converters. The fabricated BiDFETs support high voltage (>1.2 kV) in the first and third quadrants. They exhibit very low on-resistance of 50 mΩ in the on-state in both quadrants when the 20 V gate bias is applied to both gates, allowing conduction of 20 A with 1 V drop. Fully gate voltage controlled output characteristics are also confirmed in both quadrants.

4-Quadrant switch↗
DOE OSTI2025

Ultra-Fast 4H-SiC LGAD With Etched Termination and Field Plate

The design, fabrication, and demonstration of a novel Silicon Carbide Low Gain Avalanche Detector (4HSiC LGAD), exhibiting an ultra-fast time response and excellent time resolution, are reported. Here, the use of field plates is proposed to suppress the high electric field caused by the negative bevel-etched angle in 4H-SiC LGADs based on TCAD simulations. Experimental measurements confirm that the field plate significantly increases the breakdown voltage of the 4H-SiC LGADs. Gain and time resolution are measured by using the ultraviolet transient current technique (UV-TCT) showing that 4H-SiC LGADs possess excellent timing performance, with a time resolution better than 35 ps for the injected laser signal with single minimum ionizing particle (MIP) charges generation at room temperature. Additionally, the gain suppression effect in a 4H-SiC LGAD is observed for the first time.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Frequency Response and Congestion Management using Multi-Terminal HVDC Overlay

Continental level power system interconnections using a High Voltage direct current (HVDC) transmission lines have been considered to bring economic benefits such as interregional power exchange. This paper describes the modeling process and studies the technical benefits of having multiple HVDC lines, including a grid of HVDC lines (macrogrid) configuration, connecting the North American Eastern and Western electric power interconnections. The models developed provide steady state and stability analysis for multiple HVDC overlay topologies and provide technical benefit analysis in terms of frequency response and congestions management. The paper also provides a comparison of different HVDC topologies performance and their grid support in case of major disturbances

Tbaileh, Ahmad↗
DOE OSTI2022

Distributed Finite-Time Termination for Consensus Algorithm in Switching Topologies

Here, in this article, we present a finite-time stopping criterion for consensus algorithms in networks with dynamic communication topology. Prior state of the art has established convergence to the consensus value; however, the asymptotic convergence of these algorithms poses a challenge in practical settings where the response from agents is required in finite time. To this end, we propose a maximum-minimum protocol that propagates the global maximum and minimum values of agent states (while running the consensus algorithm) in the network. This article focuses on establishing that the global maximum and minimum values are strictly monotonic even for a dynamic topology, and they can be used to distributively ascertain the closeness to convergence in finite time. We rigorously show that each node can have access to the global maximum and minimum by running the proposed maximum-minimum protocol to realize a finite-time stopping criterion for the otherwise asymptotic consensus algorithm. The practical utility of the algorithm is illustrated through experiments where each agent is instantiated by a NodeJS socket.io server.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Comparative efficacy of valnoctamide and sec ‐butylpropylacetamide ( SPD ) in terminating nerve agent–induced seizures in pediatric rats

Summary Objectives Children and adults are likely to be among the casualties in a civilian nerve agent exposure. This study evaluated the efficacy of valnoctamide (racemic‐VCD), sec ‐butylpropylacetamide (racemic‐SPD), and phenobarbital for stopping nerve agent seizures in both immature and adult rats. Methods Female and male postnatal day ( PND ) 21, 28, and 70 (adult) rats, previously implanted with electroencephalography (EEG) electrodes were exposed to seizure‐inducing doses of the nerve agents sarin or VX and EEG was recorded continuously. Five minutes after seizure onset, animals were treated with SPD , VCD, or phenobarbital. The up‐down method was used over successive animals to determine the anticonvulsant median effective dose (ED 50 ) of the drugs. Results SPD‐ED 50 values in the VX model were the following: PND 21, 53 mg/kg (male) and 48 mg/kg (female); PND 28, 108 mg/kg (male) and 43 mg/kg (female); and PND 70, 101 mg/kg (male) and 40 mg/kg (female). SPD ‐ ED 50 values in the sarin model were the following: PND 21, 44 mg/kg (male) and 28 mg/kg (female); PND 28, 79 mg/kg (male) and 34 mg/kg (female); and PND 70, 53 mg/kg (male) and 53 mg/kg (female). VCD ‐ ED 50 values in the VX model were the following: PND 21, 34 mg/kg (male) and 43 mg/kg (female); PND 28, 165 mg/kg (male) and 59 mg/kg (female); and PND 70, 87 mg/kg (male) and 91 mg/kg (female). VCD ‐ ED 50 values in the sarin model were the following: PND 21, 45 mg/kg (male), 48 mg/kg (female); PND 28, 152 mg/kg (male) 79 mg/kg (female); and PND 70, 97 mg/kg (male) 79 mg/kg (female). Phenobarbital‐ ED 50 values in the VX model were the following: PND 21, 43 mg/kg (male) and 18 mg/kg (female); PND 28, 48 mg/kg (male) and 97 mg/kg (female). Phenobarbital‐ ED 50 values in the sarin model were the following: PND 21, 32 mg/kg (male) and 32 mg/kg (female); PND 28, 58 mg/kg (male) and 97 mg/kg (female); and PND 70, 65 mg/kg (female). Significance SPD and VCD demonstrated anticonvulsant activity in both immature and adult rats in the sarin‐ and VX ‐induced status epilepticus models. Phenobarbital was effective in immature rats, whereas in adult rats, higher doses were required that were accompanied by toxicity. Overall, significantly less drug was required to stop seizures in PND 21 animals than in the older animals, and overall, males required higher amounts of drug than females.

Haines, Kari M.↗