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: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

A Comprehensive Sub-Grid Air Entrainment Model for RaNS Modeling of Free-Surface Bubbly Flows

Abstract: The simulation of free surface bubbly flows using a two-fluid model remains a challenging problem in part due to the lack of a comprehensive air entrainment model that can predict the rate and location of air entrainment for a wide range of flows. In this study we derive a sub-grid model and implement it in a computational multiphase fluid dynamics (CMFD) framework to solve the Reynolds-averaged two-fluid equations. We assess the performance of our model in simulating bubbly flows underneath a plunging liquid jet and a hydraulic jump while varying the characteristic velocity. We compare the void fraction predictions with their experimental counterparts and conclude that the air entrainment model and the two-fluid modeling approach yield accurate results everywhere for the plunging jet and in the turbulent shear layer for the hydraulic jump. The inability of the proposed approach to recover the high void fraction in the roller region of the hydraulic jump is attributed to the failure of RaNS model to resol...

Block Copolymer-Templated Nanocomposite Electrodes for Rechargeable Lithium Batteries

Abstract: Department of Chemistry, Northeastern University, Boston, Massachusetts 02115-5000, USAA self-organizing, nanocomposite electrode~SONE! system was developed as a model lithium alloy-based anode for rechargeablelithium batteries. In situ X-ray adsorption spectroscopy, galvanostatic testing, cyclic voltammetry, X-ray diffraction, and trans-mission electron microscopy were used to analyze the electrode, which was fabricated from a polyethylene oxide-based blockcopolymer, single-walled carbon nanotubes, and gold salt. Processing involved a single mixing step without need of a reducingagent. It was found that thermodynamic self-assembly of the block copolymer could provide a template for incorporation of boththe gold salt and nanotubes. Electrochemical testing and subsequent analysis showed that owing to the small particle size and thesurrounding block copolymer matrix, the SONE system could cycle over 600 cycles with rates varying between C/1.8 and 8.8Cwith little evidence of decrepitation or coarsening.© 2002 The Electrochemical Society. @DOI: 10.1149/1.1518482# All rights reserved.Manuscript submitted February 6, 2002; revised manuscript received June 13, 2002. Available electronically October 31, 2002.

Production planning for remanufactured products

Abstract: This paper presents a methodology for production planning within facilities involved in the remanufacture of products Remanufacturing refers to the process of accepting inoperable units, salvaging good and repairable components from those units, and then re-assembling good units to be re-issued into service These types of facilities are common, yet many suffer from the unpredictability of good and repairable component yields, as well as processing time variation These problems combine to make it extremely difficult to predict whether overall production output will be sufficient to meet demand Low yields of key components can lead to shortages which require the facility to purchase new components for legacy systems, often with long lead times, thus causing overall delays The approach developed here is a probabilistic form of standard material requirements planning (MRP), which considers variable yield rates of good, bad, and repairable components that are harvested from incoming units, and probabilist

Solubility Properties in Biological Media. 12. Regarding the Mechanism of Nonspecific Toxicity or Narcosis by Organic Nonelectrolytes

Abstract: Narcotic effects of organic nonelectrolytes to the tadpole (logC), minimum blocking concentrations for stoppage of electrical activity in the muscle of the frog, Rana pipiens (logMBC), and binding of nonelectrolytes to bovine serum albumin (log1/C) are well correlated by the following equations, where VI is the intrinsic (van der Waals) molar volume, and π*, βm and αm are the solvatochromic parameters that scale solute dipolarity/polarizability, hydrogen bond acceptor basicity, and hydrogen bond donor acidity. That increasing solute π* leads to lesser partition into the biosystem compared with its aqueous environment, but also leads to greater toxicity or anesthetic effect is suggested to implicate in the mechanism of toxicity or narcosis a specific association effect between the more dipolar solutes (toxicants) and a molecule involved in the transmission of nervous impulses.

Properties of ceramics in the system ZrB2–Ta5Si3

Abstract: Ceramics in the system ZrB2–Ta5Si3 were studied as candidates for the development of new ultra high-temperature ceramic materials. The ceramics were prepared by hot pressing at 1900–2200 °C in He. Mutual additions of ZrB2 and Ta5Si3 even in small amounts had significant densifying effects due to chemical interactions and solid solubility between the components, which have not been reported in the literature. Materials containing between 8 and 30 vol% Ta5Si3 exhibited less oxidation than pure ZrB2, which is the result of phase separation in surface borosilicate glass induced by Ta2O5. For higher concentrations, oxidation resistance substantially decreased with increasing Ta5Si3 content. The trend in the oxidation behavior of the materials showed significant dependence on the volume of oxidation products. Ceramics containing up to 10 mol% (30 vol%) Ta5Si3, which showed the highest oxidation resistance, also had the highest strength and hardness in the system, and are of interest for high-temperature structural applications in oxidizing environments.