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Institution

Naval Surface Warfare Center

FacilityWashington 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
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Proceedings ArticleDOI
13 Sep 2014
TL;DR: An in situ user study in which participants wore a lifelogging device for a week, answered questionnaires about the collected images, and participated in an exit interview indicates that some people may prefer to manage privacy through in situ physical control of image collection in order to avoid later burdensome review of all collected images.
Abstract: A number of wearable 'lifelogging' camera devices have been released recently, allowing consumers to capture images and other sensor data continuously from a first-person perspective. Unlike traditional cameras that are used deliberately and sporadically, lifelogging devices are always 'on' and automatically capturing images. Such features may challenge users' (and bystanders') expectations about privacy and control of image gathering and dissemination. While lifelogging cameras are growing in popularity, little is known about privacy perceptions of these devices or what kinds of privacy challenges they are likely to create. To explore how people manage privacy in the context of lifelogging cameras, as well as which kinds of first-person images people consider 'sensitive,' we conducted an in situ user study (N = 36) in which participants wore a lifelogging device for a week, answered questionnaires about the collected images, and participated in an exit interview. Our findings indicate that: 1) some people may prefer to manage privacy through in situ physical control of image collection in order to avoid later burdensome review of all collected images; 2) a combination of factors including time, location, and the objects and people appearing in the photo determines its 'sensitivity;' and 3) people are concerned about the privacy of bystanders, despite reporting almost no opposition or concerns expressed by bystanders over the course of the study.

184 citations

Journal ArticleDOI
TL;DR: In this paper, the negative impedance instability of the DC link was examined and a readily implemented albeit nonlinear control strategy was proposed to mitigate this potential problem. But, the proposed strategy is not suitable for a large number of applications, such as locomotives and ships.
Abstract: Induction motor based electric propulsion systems can be used in a wide variety of applications including locomotives, hybrid electric vehicles, and ships. Field oriented control of these drives is attractive since it allows the torque to be tightly and nearly instantaneously controlled. However, such systems can be prone to negative impedance instability of the DC link. This paper examines this type of instability and sets forth a readily implemented albeit nonlinear control strategy to mitigate this potential problem.

181 citations

Journal ArticleDOI
TL;DR: In this article, the shape memory alloy (SMA) stress-strain response associated with martensitic twinning hysteresis and austenite-martensite/austenite superelasticity is modeled using constitutive equations.
Abstract: The shape memory alloy (SMA) stress-strain response associated with martensitic twinning hysteresis and austenite-martensite/martensite-austenite superelasticity is modeled using constitutive equations. Compared to the modeling work done on viscoelastic and viscoplastic be havior, this has been an area of limited study. The equations which are presented here express the growth of inelastic strain in a rate-type formulation similar to viscoplastic laws. This constitutive model is obtained by extending a one-dimensional evolutionary model of SMA behavior to three dimensions. The resulting model is then reduced to meet the loading conditions of three special cases: uniaxial loading, shear loading, and non-proportional biaxial loading (combined axial- torsional loading). The model which is being considered, although nonlinear, is relatively simple in that only two evolutionary equations are required to model inelastic strain and a generalized back stress at a material point. Thus the model being presented use...

180 citations

Journal ArticleDOI
TL;DR: This paper explores several methods for increasing the efficiency and accuracy of particle image velocimetry (PIV) data analysis, and a technique for enhancing PIV images to increase the contrast between the particles and the background is presented.
Abstract: This paper explores several methods for increasing the efficiency and accuracy of particle image velocimetry (PIV) data analysis. The time to directly compute the correlation function to determine the displacement in PIV interrogation windows is reduced using two techniques. First, a scheme that calculates the correlation for 16 pixels in parallel is implemented. A further increase in efficiency results from using a truncated multiplication scheme that calculates 82% of the answer while reducing the work by 84%. Second, advantage is taken of the common practice of overlapping adjacent interrogation windows by not recorrelating the portion of the new window that overlaps the old. For the commonly used 50% overlap, the speed of vector calculation can theoretically be increased 300%. In practice, the improvement depends on the implementation of the method. The most efficient algorithm doubles the processing speed at 50% overlap. Accuracy is increased using three methods. First, a technique for enhancing PIV images to increase the contrast between the particles and the background is presented. This method is particularly useful when experimental exigencies result in low contrast images. Second, a method is presented for resolving the velocity in areas of high velocity gradient where the correlation map contains multiple peaks. Third, equalizing the histogram of sub-pixel adjustments should eliminate peak locking. Sample data show a `decrease' in error of 15%.

180 citations

Journal ArticleDOI
TL;DR: In this article, a scanning electron microscope and electron backscattered diffraction (EBSD) analysis revealed a fine cellular-dendritic (0.5 to 2.μm) substructure inside large irregularly shaped grains.
Abstract: Structure–property relationships of an additively manufactured 316L stainless steel were explored. A scanning electron microscope and electron backscattered diffraction (EBSD) analysis revealed a fine cellular-dendritic (0.5 to 2 μm) substructure inside large irregularly shaped grains (~ 100 μm). The cellular structure grows along the 〈100〉 crystallographic directions. However, texture analysis revealed that the main 〈100〉 texture component is inclined by ~15 deg from the building direction. X-ray diffraction line profile analysis indicated a high dislocation density of ~1 × 1015 m−2 in the as-built material, which correlates well with the observed EBSD microstructure and high-yield strength, via the traditional Taylor hardening equation. Significant variations in strain hardening behavior and ductility were observed for the horizontal (HB) and vertical (VB) built samples. Ductility of HB and VB samples measured 49 and 77 pct, respectively. The initial growth texture and subsequent texture evolution during tensile deformation are held responsible for the observed anisotropy. Notably, EBSD analysis of deformed samples showed deformation twins, which predominately form in the grains with 〈111〉 aligned parallel to the loading direction. The VB samples showed higher twinning activity, higher strain hardening rates at high strain, and therefore, higher ductility. Analysis of annealed samples revealed that the observed microstructures and properties are thermally stable, with only a moderate decrease in strength and very similar levels of ductility and anisotropy, compared with the as-built condition.

178 citations


Authors

Showing all 2860 results

NameH-indexPapersCitations
James A. Yorke10144544101
Edward Ott10166944649
Sokrates T. Pantelides9480637427
J. M. D. Coey8174836364
Celso Grebogi7648822450
David N. Seidman7459523715
Mingzhou Ding6925617098
C. L. Cocke513128185
Hairong Qi503279909
Kevin J. Hemker4923110236
William L. Ditto431937991
Carey E. Priebe434048499
Clifford George412355110
Judith L. Flippen-Anderson402056110
Mortimer J. Kamlet3910812071
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20233
20227
202172
202071
201982
201884