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Institution

Naval Postgraduate School

EducationMonterey, California, United States
About: Naval Postgraduate School is a education organization based out in Monterey, California, United States. It is known for research contribution in the topics: Tropical cyclone & Boundary layer. The organization has 5246 authors who have published 11614 publications receiving 298300 citations. The organization is also known as: NPS & U.S. Naval Postgraduate School.


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Journal ArticleDOI
31 May 2010
TL;DR: A field experiment was conducted on a high energy macro-tidal beach (Perranporth, UK) to examine rip current dynamics over a low-tide transverse bar/rip system in response to changing tide and wave conditions as discussed by the authors.
Abstract: A field experiment was conducted on a high energy macro-tidal beach (Perranporth, UK) to examine rip current dynamics over a low-tide transverse bar/rip system in response to changing tide and wave conditions. Hydrodynamic data were collected using an array of in situ acoustic doppler current meters and pressure transducers, as well as 12 GPS-tracked Lagrangian surf zone drifters. Inter-tidal and subtidal morphology were measured through RTK-GPS and echo-sounder surveys. Data were collected for eight consecutive days (15 tides) over a spring-neap tidal cycle with tidal ranges of 4‐6.5m and offshore significant wave heights of 1‐2m and peak periods of 5‐12s. The hypothesis that rip current dynamics in a macro-tidal setting are controlled by the combination of variations in wave dissipation and morphological flow constriction, modulated by changes in tidal elevation was tested. During the measurement period, rip circulation was characterised by a large rotational surf zone eddy O(200m) extending offshore from the inner-surf zone to the seaward face of the inter-tidal transverse bar. During high- and mid-tide, water depth over the bars was too deep to allow wave breaking, and a strong longshore current dominated the surf zone. As the water depth decreased towards low-tide, wave breaking was concentrated over the bar crests initiating the rotational rip current eddy. Peak rip flow speeds of 1.3ms ! 1 were recorded around low-tide when the joint effects of dissipation and morphological constriction were maximised. At low tide, dissipation over the bar crests was reduced by partial bar-emergence and observations suggested that rip flows were maintained by morphological constriction and the side-drainage of water from the transverse bars.

108 citations

Journal ArticleDOI
TL;DR: In this article, a stationary SST model is proposed to understand the physical mechanisms responsible for the phase transition of the El Nino-Southern Oscillation, which is also season dependent.
Abstract: A stationary SST mode is proposed to understand the physical mechanisms responsible for the phase transition of the El Nino-Southern Oscillation. This stationary SST mode differs from the original delayed oscillator mode and the slow SST mode in the sense that it considers both balanced and unbalanced thermocline depth variations and does not take into account the zonal propagation of SST. Within this mode, the Walker circulation acts as a positive feedback mechanism to amplify and maintain an existing interannual SST anomaly, whereas the Hadley circulation acts as a negative feedback mechanism that dismisses the original anomaly and causes the phase shift from a warm (cold) to a cold (warm) episode. The key to the cause of interannual oscillations in the stationary SST mode lies in the zonal-mean thermocline depth variation that is not in equilibrium with the winds. Because of the nonequilibrium, this part of the thermocline depth anomaly tends to have a phase lag with the wind (or SST) anomaly and therefore holds a key for the interannual oscillation. The zonally asymmetric part of the thermocline depth anomaly, on the other hand, is always in Sverdrup balance with the winds. Such a phase relationship agrees well with observations and with GCM simulations. The stationary SST mode strongly depends on the basin width, on the air-sea coupling strength, and on the seasonal-cycle basic state. For a reasonable parameter regime, it depicts an interannual oscillation with a period of 2-7 years. This stationary SST mode is also season dependent: it has a maximum growth rate during the later part of the year and a negative growth rate during the northern spring, which may explain the occurrence of the mature phases of the El Nino in the northern winter and a rapid drop of the lagged correlation of the Southern Oscillation index in the boreal spring.

108 citations

Journal ArticleDOI
TL;DR: In this article, the reflection coefficient for an inductive strip is obtained by cascading two scattering matrices separated by a distance equal to the stripwidth, which is valid up to moderate bandwidths, except for the narrowband design at the higher waveguide frequency range.
Abstract: Waveguide E-plane filters with all-metal inserts are designed by a procedure based on the reflection coefficients of axial inductive strips. The scattering matrix, representing the junction in a bifurcated waveguide, is calculated by a mode-matching method. The reflection coefficient for an inductive strip is then obtained by cascading two scattering matrices separated by a distance equal to the stripwidth. The design is valid up to moderate bandwidths, except for the narrowband design at the higher waveguide frequency range, where both the center frequency and the bandwidth are inaccurate. Possible sources of error are studied and a method minimizing the error is proposed.

108 citations

Proceedings ArticleDOI
05 Dec 2004
TL;DR: Three applications of agent-based simulations used to analyze military problems are presented, including the MANA model to explore the ability of the U.S. Army's network-based Future Force to perform with degraded communications and how unmanned surface vehicles can be used in force protection missions with the Pythagoras model.
Abstract: There continues to be increasing interest from a broad range of disciplines in agent-based and artificial life simulations. This includes the Department of Defense - which uses simulations heavily in its decision making process. Indeed, military conflicts can have many attributes that are consistent with complex adaptive systems - such as many entities interacting with some degree of autonomy, each of which is continually making decisions to satisfy a variety of sometimes conflicting objectives. In this paper, we present three applications of agent-based simulations used to analyze military problems. The first uses the MANA model to explore the ability of the U.S. Army's network-based Future Force to perform with degraded communications. The second studies how unmanned surface vehicles can be used in force protection missions with the Pythagoras model. The last example examines the standard Army squad size with an integrated effort using MANA, Pythagoras, and the high-resolution simulation JANUS.

108 citations

Journal ArticleDOI
TL;DR: The issues involved in the design of computationally efficient algorithms for spectral correlation estimation and the resulting impact on high-speed digital realization are addressed and related special issues are discussed.
Abstract: The issues involved in the design of computationally efficient algorithms for spectral correlation estimation and the resulting impact on high-speed digital realization are addressed. The spectral correlation analyzer is characterized as a periodically time-varying quadratic system with a kernel possessing certain gross properties. The mean and variance of the output are expressed in terms of the kernel and the spectral correlation function of the input. Three realizations are analyzed in detail. One is based on the frequency-smoothing method of cross spectral analysis. The others are variants of the time-smoothing method. For each of these realizations, an exact expression for the quadratic system kernel is given, the digital implementation is developed, and a detailed complexity analysis is presented. High-speed pipeline realizations of the algorithms are analyzed, and related special issues are discussed. Examples involving the calculation of the spectral correlation function in near-real-time for broadband communications signals are discussed. >

108 citations


Authors

Showing all 5313 results

NameH-indexPapersCitations
Mingwei Chen10853651351
O. C. Zienkiewicz10745571204
Richard P. Bagozzi104347103667
Denise M. Rousseau8421850176
John Walsh8175625364
Ming C. Lin7637023466
Steven J. Ghan7520725650
Hui Zhang7520027206
Clare E. Collins7156021443
Christopher W. Fairall7129319756
Michael T. Montgomery6825814231
Tim Li6738316370
Thomas M. Antonsen6588817583
Nadia Magnenat-Thalmann6552114850
Johnny C. L. Chan6126114886
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202331
2022151
2021321
2020382
2019352
2018362