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.

Enhanced low dose rate sensitivity (ELDRS) of linear circuits in a space environment

Abstract: To investigate the ELDRS effect in a real space environment, an experiment was designed, launched, and placed in a highly elliptical orbit in November 1997. After its deployment, the electrical responses of several bipolar transistors and linear circuits have been and continue to be recorded once during every 12-hour orbit. System dosimeters are monitored to establish an average accumulated dose per orbit. With this information, the electrical parameter data are correlated with the dosimetry data to determine the total dose response of each device. This paper updates information on the ELDRS experiment through May 14, 1999. As of this date, the experiment has been in flight for a period of 18 months and has accumulated an approximate dose of 18 krd(Si). For comparison, devices, specifically linear circuits with the same date code, were irradiated using Co-60 sources, herein defined as ground-based tests. The ground-based tests are used to evaluate two hardness assurance tests, a room temperature irradiation at 10 mrd(Si)/s and an elevated temperature irradiation at 100/spl deg/C and 10 rd(Si)/s and to evaluate the ELDRS response. To that end, irradiations were performed at room temperature, approximately 22/spl deg/C, at fixed dose rates of 100, 1, and 0.01 rd(Si)/s and at elevated temperature, approximately 100/spl deg/C, at a fixed dose rate of 10 rd(Si)/s. Currently, irradiations are being performed at room temperature at a fixed dose rate of 0.001 rd(Si)/s. Comparing the ground-based data to the flight data clearly demonstrates that enhanced parametric degradation has occurred in the flight parts. The two hardness assurance screens predicted ELDRS but the design margin for the elevated temperature test may not be adequate.

Magnetic dipole localization with a gradiometer: obtaining unique solutions

Abstract: The five independent equations describing the field gradient tensor at a point for a static magnetic dipole source can be inverted to give the bearing vector to the source and the source moment vector divided by the fourth power of the range. The equations have four solutions, two of which are related in a non-trivial way, and two more that are obtained by reflections through the field point. The symmetry of the four solutions in the principal-axis frame of the gradient tensor can be used to express the solutions directly in terms of one another in an arbitrary frame without executing the inversion. This relationship has been exploited to construct explicit proofs that a unique solution for magnetic moment vector and relative position between source and field point can be obtained if either the magnetic field vector, or the rate of change of the gradient tensor and the relative motion of source and field point is known.

Integrated sensing and processing decision trees

Abstract: We introduce a methodology for adaptive sequential sensing and processing in a classification setting. Our objective for sensor optimization is the back-end performance metric-in this case, misclassification rate. Our methodology, which we dub Integrated Sensing and Processing Decision Trees (ISPDT), optimizes adaptive sequential sensing for scenarios in which sensor and/or throughput constraints dictate that only a small subset of all measurable attributes can be measured at any one time. Our decision trees optimize misclassification rate by invoking a local dimensionality reduction-based partitioning metric in the early stages, focusing on classification only in the leaves of the tree. We present the ISPDT methodology and illustrative theoretical, simulation, and experimental results.