Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Generalized magnetic gradient contraction based method for detection, localization and discrimination of underwater mines and unexploded ordnance

Abstract: We report significant progress toward full development of a unique magnetic-gradient-tensor-based "scalar triangulation and ranging (STAR)" method for detection, localization and classification (DLC) of magnetic targets. The STAR method converts magnetic tensors to rotationally invariant scalar parameters that are virtually unaffected by the effects of sensing platform motion. Thus, the STAR method is particularly appropriate for magnetic target DLC using highly mobile sensing platforms such as autonomous underwater vehicles (AUV). Prior work has resulted in development of a two-dimensional (2D) magnetic target-homing concept for fully autonomous localization of mines using crawler-type AUVs. However, the simple 2D STAR approach cannot effectively discriminate between magnetic clutter and mine-like target signatures. Improved, 3D simulations demonstrate that the STAR concept can be applied to measurements of the vector positions and dipole signatures of magnetic objects. The new results indicate that an improved STAR system will provide an enhanced capability for discrimination between magnetic clutter and real targets such as magnetic mines and Unexploded Ordnance (UXO). Consequently, further development of the advanced STAR concept will provide high-mobility autonomous sensing platforms (such as AUVs and man-portable systems) with a uniquely effective modality for DLC of magnetic mines and UXO

Origins of total-dose response variability in linear bipolar microcircuits

Abstract: LM111 voltage comparators exhibit a wide range of total-dose-induced degradation. Simulations show this variability may be a natural consequence of the low base doping of the substrate PNP (SPNP) input transistors. Low base doping increases the SPNPs collector to base breakdown voltage, current gain, and sensitivity to small fluctuations in the radiation-induced oxide defect densities. The build-up of oxide trapped charge (N/sub OT/) and interface traps (N/sub IT/) is shown to be a function of pre-irradiation bakes. Experimental data indicate that, despite its structural similarities to the LM111, irradiated input transistors of the LM124 operational amplifier do not exhibit the same sensitivity to variations in pre-irradiation thermal cycles. Further disparities in LM111 and LM124 responses may result from a difference in the oxide defect build-up in the two part types. Variations in processing, packaging, and circuit effects are suggested as potential explanations.

Processing of ZrC–Mo Cermets for High Temperature Applications, Part II: Pressureless Sintering and Mechanical Properties

Abstract: Pressureless sintering of ZrC-Mo cermets was investigated in a He/H 2 atmosphere and under vacuum. A large density increase was observed for specimens with > 20 vol% Mo after heating at 2150°C for 60 min in a He/H 2 atmosphere. The increase in density was attributed to the formation of Mo 2 C during heating and its subsequent eutectic reaction with Mo, which produced rounded ZrC grains in a Mo-Mo 2 C matrix. Sintering in vacuum did not produce the same increase in density, due to the lack of Mo 2 C formation and subsequent lack of liquid formation, which resulted in a microstructure with irregular ZrC grains with isolated areas of Mo. Mechanical properties testing showed a decrease in Young's modulus with increasing Mo content that was consistent with the models presented. Flexure strength of ZrC-Mo cermets sintered in He/H 2 atmosphere materials increased with increasing Mo content from 320 MPa at 20 vol% Mo to 410 MPa at 40 vol% Mo. Strength was predicted by adapting theories developed previously for WC-Co cermets.

Lithium-ion Battery Thermal Safety by Early Internal Detection, Prediction and Prevention

Abstract: Temperature rise in Lithium-ion batteries (LIBs) due to solid electrolyte interfaces breakdown, uncontrollable exothermic reactions in electrodes and Joule heating can result in the catastrophic failures such as thermal runaway, which is calling for reliable real-time electrode temperature monitoring. Here, we present a customized LIB setup developed for early detection of electrode temperature rise during simulated thermal runaway tests incorporating a modern additive manufacturing-supported resistance temperature detector (RTD). An advanced RTD is embedded in a 3D printed polymeric substrate and placed behind the electrode current collector of CR2032 coin cells that can sustain harsh electrochemical operational environments (acidic electrolyte without Redox, short-circuiting, leakage etc.) without participating in electrochemical reactions. The internal RTD measured an average 5.8 °C higher temperature inside the cells than the external RTD with almost 10 times faster detection ability, prohibiting thermal runaway events without interfering in the LIBs’ operation. A temperature prediction model is developed to forecast battery surface temperature rise stemming from measured internal and external RTD temperature signatures.