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.

Vented Chamber Calorimetry for Impact-Initiated Energetic Materials

Abstract: Over the past several years, the Naval Surface Warfare Center, Dahlgren Division (NSWC-DD) and its contractors have used vented test chambers to evaluate the performance of impactinitiated energetic materials. These chambers are initially sealed but have a thin steel cover plate through which a test specimen is launched onto a steel anvil on the interior. During this impact process, the test specimen perforates the thin plate and leaves a vent hole through which chamber gases are vented as the reaction takes place on the interior. The test chamber includes a variety of pressure and light measurements to gauge the performance of the test specimen. The quasi-static pressures have been the primary performance metric used to judge the performance of the material; these pressures most directly relate to the material’s ability to damage a target. This paper will derive the fundamental relationships between the peak quasistatic pressure and the total energy deposited into the gas within the chamber, thereby allowing calorimetric measurements using the vented chamber system. Particular attention will be paid to the uncertainties and assumptions associated with this derivation, including assumptions about gas properties, venting from the chamber, and distribution of the energy between kinetic and potential energy in the gas-phase.

Reduced-parts-count multilevel rectifiers

Abstract: Multilevel power converters have gained much attention in recent years due to their high power quality, low switching losses, and high-voltage capability. These advantages make the multilevel converter a candidate topology for the next generation of naval ship prolusion systems. The primary disadvantage of these systems is the large number of semiconductors involved. This paper presents a reduced-parts-count rectifier which is well suited for naval rectifier applications where bidirectional power flow is not required. The proposed converter is analyzed and experimentally verified on an 18-kW four-level rectifier/inverter system.

Effect of ion energy upon dielectric breakdown of the capacitor response in vertical power MOSFETs

Abstract: The effect of ion energy upon the ion-induced dielectric breakdown response of the capacitor response in vertical power metal-oxide semiconductor field effect transistors (MOSFETs) was investigated. The single event gate rupture response was experimentally determined using mono-energetic ion beams of copper, niobium, and gold. Irradiations were conducted using an ion species tuned to different energies, producing a range of linear energy transfer (LET) values for that ion. Numerous MOSFETs were characterized to identify the onset of ion-induced dielectric breakdown. These data along with previously taken data demonstrated that the ion-induced dielectric breakdown cannot be adequately described in terms of LET, but is better described in terms of atomic number (Z). Based upon these observations, a new semi-empirical expression is presented describing the critical ion-induced breakdown response in terms of Z instead of LET. This expression is shown to be a better single event gate rupture model of the capacitor response.

Dissolvable Metal Supports for 3D Direct Metal Printing

Abstract: Additive manufacturing (AM) offers the ability to fabricate complex metallic structures and shapes in a layer-by-layer process. However, overhanging surfaces often require support structures to be fabricated and minimize thermally induced distortion. Unlike polymer AM processes, soluble sacrificial support materials have not been identified and characterized for metallic materials, and, as a result, support structures in 3D printed metals must be removed using additional machining operations. In this work, we demonstrate that sacrificial metal supports can be fabricated by taking advantage of differences in the chemical and electrochemical stability between different metals. As a demonstration, a stainless steel bridged structure with a 90° overhang was fabricated using a carbon steel sacrificial support that was later removed through electrochemical etching in 41 wt.% nitric acid with bubbling O2. Open circuit potentials and potentiodynamic polarization curves were gathered to verify etch select...

Do Leadership Training and Development Make a Difference in the Public Sector? A Panel Study

Abstract: Although significant progress has been made in developing leadership theory and understanding the traits, skills, behaviors, and styles that make a good leader, progress in bridging the gap between theory and practice using models of leadership training and development has been slow. This research attempts to answer the question of whether leadership training and development programs in the public sector improve leader and organizational performance. The findings indicate that a combination of coaching, classroom instruction, feedback, and experiential training has a significant impact on leader performance. In addition, organizational effectiveness improves for organizations whose leaders received the intervention. This article enhances our understanding of the impact that training and development can have on leader and organizational outcomes.