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.

Comparison of ionizing-radiation-induced gain degradation in lateral, substrate, and vertical PNP BJTs

Abstract: A comparison is presented of ionizing-radiation-induced gain degradation in lateral, substrate, and vertical PNPs. The dose-rate dependence of current gain degradation in lateral PNP BJTs is even stronger than the dependence previously reported for NPN BJTs. Various mechanisms are presented and their relative significance for gain degradation in the lateral, substrate, and vertical PNPs is discussed. A detailed comparison of the lateral and substrate PNP devices is given. The specific lateral and substrate devices considered here are fabricated in the same process and possess identical emitters. Even though these devices have identical emitters and undergo the same processing steps, the lateral devices degrade significantly more than the substrate devices.

Experimental observation of on-off intermittency

Abstract: We observe on-off intermittency in a nonlinear electronic circuit tuned near a Hopf bifurcation point. The circuit is driven randomly through the bifurcation point, resulting in intermittent switching between a fixed point (laminar phase) and a limit cycle. The distribution of lengths of laminar phases exhibits -3/2 power law scaling for shorter phases, and an exponential drop for longer phases, due to noise in the system. These results agree with a theoretically predicted distribution. In addition, the crossover from power law to exponential decay obeys the predicted scaling law.

A Statistical Method for Profiling Network Traffic

Abstract: Two clustering methods are described and applied to network data. These allow the clustering of machines into "activity groups", which consist of machines which tend to have similar activity profiles. In addition, these methods allow the user to determine whether current activity matches these profiles, and hence to determine when there is "abnormal" activity on the network. A method for visualizing the clusters is described, and the approaches are applied to a data set consisting of a months worth of data from 993 machines.

Directional perfect absorption using deep subwavelength low-permittivity films

Abstract: We experimentally demonstrate single beam directional perfect absorption (to within experimental accuracy) of $p$-polarized light in the near-infrared using unpatterned, deep subwavelength films of indium tin oxide (ITO) on Ag. The experimental perfect absorption occurs slightly above the epsilon-near-zero (ENZ) frequency of ITO, where the permittivity is less than 1 in magnitude. Remarkably, we obtain perfect absorption for films whose thickness is as low as \ensuremath{\sim}1/50th of the operating free-space wavelength and whose single pass attenuation is only \ensuremath{\sim}5%. We further derive simple analytical conditions for perfect absorption in the subwavelength-film regime that reveal the constraints that the thin layer permittivity must satisfy if perfect absorption is to be achieved. Then, to get a physical insight on the perfect absorption properties, we analyze the eigenmodes of the layered structure by computing both the real-frequency/complex-wavenumber and the complex-frequency/real-wavenumber modal dispersion diagrams. These analyses allow us to attribute the experimental perfect absorption condition to the crossover between bound and leaky behavior of one eigenmode of the layered structure. Both modal methods show that perfect absorption occurs at a frequency slightly larger than the ENZ frequency, in agreement with experimental results, and both methods predict a second perfect absorption condition at higher frequencies, attributed to another crossover between bound and leaky behavior of the same eigenmode. Our results greatly expand the list of materials that can be considered for use as ultrathin perfect absorbers and provide a methodology for the design of absorbing systems at any desired frequency.