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.

Hot, humid air decontamination of a C‐130 aircraft contaminated with spores of two acrystalliferous Bacillus thuringiensis strains, surrogates for Bacillus anthracis

Abstract: Aim To develop test methods and evaluate survival of Bacillus thuringiensis kurstaki cry(-) HD-1 and B. thuringiensis Al Hakam spores after exposure to hot, humid air inside of a C-130 aircraft. Methods and results Bacillus thuringiensis spores were either pre-inoculated on 1 × 2 or 2 × 2 cm substrates or aerosolized inside the cargo hold of a C-130 and allowed to dry. Dirty, complex surfaces (10 × 10 cm) swabbed after spore dispersal showed a deposition of 8-10 log10 m(-2) through the entire cargo hold. After hot, humid air decontamination at 75-80°C, 70-90% relative humidity for 7 days, 87 of 98 test swabs covering 0·98 m(2) , showed complete spore inactivation. There was a total of 1·67 log10 live CFU detected in 11 of the test swabs. Spore inactivation in the 98 test swabs was measured at 7·06 log10 m(-2) . Conclusions Laboratory test methods for hot, humid air decontamination were scaled for a large-scale aircraft field test. The C-130 field test demonstrated that hot, humid air can be successfully used to decontaminate an aircraft. Significance and impact of the study Transition of a new technology from research and development to acquisition at a Technology Readiness Level 7 is unprecedented.

A fast algorithm for computing minimum cross-entropy positive time-frequency distributions

Abstract: An algorithm for obtaining nonnegative, joint time-frequency distributions Q(t, f) satisfying the univariate marginals |s(t)|/sup 2/ and |S(f)|/sup 2/ is presented and applied. The advantage of the algorithm is that large time series records can be processed without the need for large random access memory (RAM) and central processing unit (CPU) time. This algorithm is based on the Loughlin et al. (1992) method for synthesizing positive distributions using the principle of minimum cross-entropy. The nonnegative distributions with the correct marginals that are obtained using this approach are density functions as proposed by Cohen and Zaparovanny (1980) and Cohen and Posch (1985). Three examples are presented: the first is a nonlinear frequency modulation (FM) sweep signal (simulated data); the second and third are of physical systems (real data). The second example is the signal for the acoustic scattering response of an elastic cylindrical shell structure. The third example is of an acoustic transient signal from an underwater vehicle. Example one contains 7500 data points, example two contains 256 data points, and example three contains in excess of 30000 data points. The RAM requirements using the original Loughlin et al. algorithm for a 7500 data point signal is 240 mega bytes and for a 30000 data point signal is 3.5 billion bytes. The new algorithm reduces the 240 mega byte requirement to 1 mega byte and the 3.5 billion byte requirement to 4 million bytes. Furthermore, the fast algorithm runs 240 times faster for the 7500 data point signal and 3000 times faster for the 30000 data point signal as compared with the original Loughlin et al. algorithm.

Underwater Explosion Phenomena and Shock Physics

Abstract: This paper presents a brief introduction to the basic fundamentals of underwater explosions, including discussion of the features of explosive charge detonation, the formation and characterization of the associated shock wave, bulk cavitation effects, gas bubble formation and dynamics, surface effects and shock wave refraction characteristics. Illustrations of each of these fundamental aspects of underwater explosion (UNDEX) loadings are made with a set of videos from a variety of experimental testing events. In addition, analyses of associated measured loading and dynamic response data, as well as descriptions of supporting numerical simulations of these events are presented. At the conclusion of this paper, each of these UNDEX effects are tied together with a summary discussion and illustration.

Enhancement of Magnetostrictive Effects for Sensor Applications

Abstract: We present a new material, amorphous Fe—B—Si alloys, that exhibit the largest sensor figures of merit ever measured. In particular we show that when the material is used as a strain gage, a figure of merit of 4 x 105 is achieved [1]. This is three orders of magnitude larger than that of any presently used strain gage. We will show how other sensors, torque sensors for example, can be constructed.