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.

RCS characterization using the alpha-stable distribution

Abstract: The radar backscatter from complex sources, such as ships and ocean waves, can vary rapidly with target aspect or time. The radar cross section (RCS) of such targets is usually described in statistical terms using one of the many statistical models that are available. These models, however, tend to fit less well when the amplitude fluctuations begin to vary over wider extremes and become impulsive in nature. To better handle this condition, the alpha-stable distribution is shown to model RCS over a wide range of amplitudes. The alpha-stable distribution is derived from the generalized central limit theorem and contains the Gaussian (or Rayleigh) distribution as a subset. The alpha-stable distribution is shown to fit examples of ship RCS as well as sea clutter examples. The performance of various envelope detectors including the maximum likelihood detector for the alpha-stable distribution is shown for a low signal-to-noise (SNR) case.

KDNP – A Lead Free Replacement for Lead Styphnate

Abstract: Efforts directed towards creating new environmentally friendly replacements for existing primary explosives have resulted in development of potassium 5,7-dinitro-[2,1,3]-benzoxadiazol-4-olate 3-oxide (KDNP). The chemical and physical properties of this material have been investigated and it appears that KDNP is a suitable drop-in replacement for lead styphnate in a variety of ordnance applications. KDNP is easily prepared, has excellent thermal stability and has safety and performance properties, which are equivalent to or exceed those for lead styphnate. KDNP has been qualified for military use per NAVSEAINST 8020.5C.

Experimental observation of stochastic resonance in a magnetoelastic ribbon.

Abstract: We report the observation of stochastic resonance in a parametrically driven bistable magnetoelastic buckling-ribbon experiment. We have found that the parametric addition of white noise increases the signal-to-noise ratio of the response of the ribbon by 10 to 12 dB relative to that of the ribbon with no externally added noise. We have also observed a characteristic spectrum for the probability of residence times for this weakly bistable system

Quasi-Static Transduction Characterization of Galfenol

Abstract: The objective of this work is to characterize the magnetoelastic transduction properties of single-crystal and textured polycrystalline Fe-Ga alloys (Galfenol) under controlled mechanical, magnetic, and thermal conditions. Polycrystalline samples of interest include a directionally solidified specimen, which possesses a favorable saturation magnetostriction output, and an extruded specimen, whose magnetostriction properties are significantly reduced by annealing. A brief discussion of the thermally controlled transducer used for the magnetic testing is presented first. Thereafter, the single-crystal response to major- loop cyclic magnetic fields under different temperature and stress conditions, as well as its response to minor-loop cyclic magnetic fields and major-loop cyclic stress are examined. Next, the magnetic and magnetostrictive responses to major-loop cyclic magnetic field conditions are compared for the directionally solidified, extruded, and single-crystal specimens. The paper concludes with a magnetic characterization summary of the different Fe-Ga alloys examined.

Explorations of Hybrid Sandwich Panel Concepts for Projectile Impact Mitigation

Abstract: Previous studies have shown that while stainless-steel sandwich panels with pyramidal truss cores have a superior blast resistance to monolithic plates of equal mass per unit area, their ballistic performance is similar to their monolithic counterparts. Here, we explore concepts to enhance the ballistic resistance without changing the volumetric efficiency of the panels by filling the spaces within the core with combinations of polyurethane, alumina prisms, and aramid fiber textiles. The addition of the polyurethane does not enhance the ballistic limit compared with the equivalent monolithic steel plate, even when aramids are added. This poor performance occurs because the polymer is penetrated by a hole enlargement mechanism which does not result in significant projectile deformation or load spreading and engagement of the steel face sheets. By contrast, ceramic inserts deform and erode the projectile and also comminute the ceramic. The ceramic communition (and resultant dilation) results in stretching of both steel face sheets and leads to significant energy dissipation. The ballistic limit of this hybrid is about twice that of the equivalent monolithic steel plate. The addition of a Kevlar fabric to the ceramic hybrid is shown to not significantly change the ballistic limit but does reduce the residual velocities of the debris.