Institution
Naval Surface Warfare Center
Facility•Washington D.C., District of Columbia, United States•
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.
Papers published on a yearly basis
Papers
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01 Sep 2006TL;DR: In this paper, the authors describe the algorithms used to process data from arrays of vector sensors (triaxial particle velocity sensors combined with pressure sensors) and acoustic intensity images produced by simulated radiation from submarine hulls during recent testing at SEAFAC, the U.S. Navy acoustic signature measurement facility in Behm Canal, Alaska.
Abstract: Mappings of sound sources on submarine hulls provide an important diagnostic tool for analyzing the radiated signature, and evaluating noise deficiencies and silencing improvements of U.S. Navy submarines. The acoustic imaging problem is particularly difficult because the resolution of signals required to provide useful information is usually on a scale that it is several times smaller than the acoustic wavelength. Recent testing with acoustic vector sensors (combined pressure and particle velocity sensors) has demonstrated that these devices can provide substantial improvements in source resolution over currently available pressure sensor arrays. The algorithms used to process data from arrays of vector sensors (tri-axial particle velocity sensors combined with pressure sensors) will be described and acoustic intensity images produced by simulated radiation from submarine hulls during recent testing at SEAFAC, the U.S. Navy acoustic signature measurement facility in Behm Canal, Alaska, will be presented.
25 citations
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01 Sep 2006TL;DR: Results from several sea tests are shown and one such system known as the Small Synthetic Aperture Minehunter (SSAM) is described, capable of producing range-independent high-resolution imagery from an array which is small in length.
Abstract: A Synthetic Aperture Sonar (SAS) is capable of producing range-independent high-resolution imagery from an array which is small in length. The ability of these systems to operate at lower frequencies while maintaining high resolution has made them useful for mapping and searching large areas. The US Navy is now focusing on developing SAS systems into a form robust enough for deployment. Here, we will show results from several sea tests and describe one such system known as the Small Synthetic Aperture Minehunter (SSAM).
25 citations
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TL;DR: In this paper, Minniti et al. used a free-running propeller in subsonic flow to predict the acoustic far field from a measurement of the ingested flow and inferred the inflow character from the near-field measurements.
Abstract: Data analysis techniques were previously developed for rotating machinery that predicted the far-field radiation, inferred inflow characteristics, and defined the near-field/far-field acoustic Green's function based on measurements of the pressure near field (Minniti, R. J., Blake, W. K., and Mueller, T. J., Inferring Propeller Inflow and Radiation from Near-Field Response, Part 1: Analytic Development, AIAA Journal, Vol. 39, No. 6, 2000, pp. 1030-1036). The techniques are applied to a free-running propeller in subsonic flow. As a first case, the propeller ingesting large-scale, mean-flow distortions as would be present downstream of stators or inlet guide vanes was considered. This simplified case allowed qualitative analysis in the time domain and complimenting quantitative analysis in the frequency domain. In addition, the case acted as a calibrating configuration to map the frequency response of the individual blades to the incoming flow by varying the number of distortions present and the rotational speed of the propeller. Based on the results of the first case, the analysis was extended to the propeller ingesting grid-generated turbulence. Because of the complex nature of the flow, all analysis was completed in the frequency domain. By the use of the techniques in Inferring Propeller Inflow and Radiation from Near-Field Response, Part 1: Analytic Development, an estimate of the blade summation gain was used to complete the direct solution of the aeroacoustic problem and predict the acoustic far field from a measurement of the ingested flow. Additionally, the inflow character was inferred from the near-field measurements.
25 citations
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05 Nov 2001TL;DR: In this paper, the authors describe the procedures required to successfully place a magnetic gradient sensor array on an AUV and demonstrate the magnetic degradation caused by the presence of the powered AUV's electrical systems.
Abstract: The detection and localization of targets of interest in the very shallow water areas and especially in the surf zone are much more difficult problems than in the deep ocean. To overcome these problems, it is necessary to augment existing fleet sensor capability with additional technology. Furthermore in keeping with Navy policy, it is desirable to remove the diver from harms way. A potential solution is to utilize a small autonomous underwater vehicle (AUV) instrumented with both a buried target sonar and the real time tracking gradiometer (RTG). This paper describes the procedures required to successfully place a magnetic gradient sensor array on an AUV. The first step was to magnetically characterize the AUV. This was accomplished by passing the AUV by a stationary RTG and then by externally mounting that RTG at several locations on the AUV which was then placed in simulated at-sea motion on a nonmagnetic three-axis motion table. Analysis of the data revealed that the favored location of a magnetic sensor is near the nose of the vessel and that the initial degradation, in this location, caused by the presence of the powered AUV was 30 dB above sensor noise. The degradation was caused primarily by the vehicle's electrical systems. Initial measurements also revealed the presence of several ferromagnetic components that should be replaced with nonmagnetic equivalents when practical. A detailed plan of magnetic noise mitigation is also presented. It involves several steps for implementation, including the substitution of nonferrous components for ferrous, maximizing the separation between the sensor and magnetic field sources, minimizing current loops and using auxiliary current and magnetic field sensors capable of generating noise-canceling signals.
25 citations
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TL;DR: The structure and magnetic properties of Fe/Cu multilayered films with a constant total Fe thickness of 1050 A but varying Fe-layer thickness from 6.3 to 42 A and varying Cu to Fe thickness ratio from 1 to 3 were investigated using x-ray diffraction, XRD, XAFS, and magnetic measurements.
Abstract: The structure and magnetic properties of Fe/Cu multilayered films with a constant total Fe thickness of 1050 A but varying Fe-layer thickness from 6.3 to 42 A and varying Cu to Fe thickness ratio from 1 to 3 were investigated using x-ray diffraction (XRD), x-ray absorption fine-structure (XAFS) spectroscopy, and magnetic measurements. Samples were prepared at room temperature on mica, glass, and silicon substrates using the dc-magnetron-sputtering method. For films with the same Fe-layer thickness, it was found that the magnetic moment of Fe decreases with increasing thickness ratio of Cu to Fe. For films with a Cu to Fe thickness ratio of 3, it was found that the magnetic moment of Fe decreases with decreasing thickness of the individual Fe layers. XRD and XAFS results revealed that in the multilayered films, Cu has a well-defined fcc structure with minimal amount of structural disorder independent of the individual layer thickness or thickness ratio. On the other hand, quantitative analysis of EXAFS data revealed that the crystal structure of Fe changes with decreasing thickness of the Fe layers from distorted bcc (for 42- and 21-A-thick Fe layers) to fcc (for 10.5- and 6.3-A-thick Fe layers) in films with the Cu layermore » three times thicker than the Fe layer. The single-phase fcc Fe of the 6.3-A Fe/19-A Cu multilayered film was found to have a lattice constant of 3.596 A and is ferromagnetic with a Curie temperature of 210 K and a spontaneous magnetization of [similar to]690 emu/cm[sup 3].« less
25 citations
Authors
Showing all 2860 results
Name | H-index | Papers | Citations |
---|---|---|---|
James A. Yorke | 101 | 445 | 44101 |
Edward Ott | 101 | 669 | 44649 |
Sokrates T. Pantelides | 94 | 806 | 37427 |
J. M. D. Coey | 81 | 748 | 36364 |
Celso Grebogi | 76 | 488 | 22450 |
David N. Seidman | 74 | 595 | 23715 |
Mingzhou Ding | 69 | 256 | 17098 |
C. L. Cocke | 51 | 312 | 8185 |
Hairong Qi | 50 | 327 | 9909 |
Kevin J. Hemker | 49 | 231 | 10236 |
William L. Ditto | 43 | 193 | 7991 |
Carey E. Priebe | 43 | 404 | 8499 |
Clifford George | 41 | 235 | 5110 |
Judith L. Flippen-Anderson | 40 | 205 | 6110 |
Mortimer J. Kamlet | 39 | 108 | 12071 |