Naval Postgraduate School

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.

Round Robin computer simulation of ejection probability in sputtering

Abstract: We have studied the ejection of a copper atom through a planar copper surface as a function of recoil velocity and depth of origin. Results were obtained from six molecular dynamics codes, four binary collision lattice simulation codes, and eight Monte Carlo codes. Most results were found with a Born-Mayer interaction potential between the atoms with Gibson 2 parameters and a planar surface barrier, but variations on this standard were allowed for, as well as differences in the adopted cutoff radius for the interaction potential, electronic stopping, and target temperature. Large differences were found between the predictions of the various codes, but the cause of these differences could be determined in most cases. A fairly clear picture emerges from all three types of codes for the depth range and the angular range for ejection at energies relevant to sputter ejection, although a quantitative discussion would have to include an analysis of replacement collision events which has been left out here.

Prediction and diagnosis of tropical cyclone formation in an NWP system. Part I: The critical role of vortex enhancement in deep convection

Abstract: This is the first of a three-part investigation into tropical cyclone (TC) genesis in the Australian Bureau of Meteorology’s Tropical Cyclone Limited Area Prediction System (TC-LAPS), an operational numerical weather prediction (NWP) forecast model. The primary TC-LAPS vortex enhancement mechanism is presented in Part I, the entire genesis process is illustrated in Part II using a single TC-LAPS simulation, and in Part III a number of simulations are presented exploring the sensitivity and variability of genesis forecasts in TC-LAPS. The primary vortex enhancement mechanism in TC-LAPS is found to be convergence/stretching and vertical advection of absolute vorticity in deep intense updrafts, which result in deep vortex cores of 60–100 km in diameter (the minimum resolvable scale is limited by the 0.15° horizontal grid spacing). On the basis of the results presented, it is hypothesized that updrafts of this scale adequately represent mean vertical motions in real TC genesis convective regions, and perhaps that explicitly resolving the individual convective processes may not be necessary for qualitative TC genesis forecasts. Although observations of sufficient spatial and temporal resolution do not currently exist to support or refute this proposition, relatively large-scale (30 km and greater), lower- to midlevel tropospheric convergent regions have been observed in tropical oceanic environments during the Global Atmospheric Research Programme (GARP) Atlantic Tropical Experiment (GATE), the Equatorial Mesoscale Experiment (EMEX), and the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE), and regions of extreme convection of the order of 50 km are often (remotely) observed in TC genesis environments. These vortex cores are fundamental for genesis in TC-LAPS. They interact to form larger cores, and provide net heating that drives the system-scale secondary circulation, which enhances vorticity on the system scale akin to the classical Eliassen problem of a balanced vortex driven by heat sources. These secondary vortex enhancement mechanisms are documented in Part II. In some recent TC genesis theories featured in the literature, vortex enhancement in deep convective regions of mesoscale convective systems (MCSs) has largely been ignored. Instead, they focus on the stratiform regions. While it is recognized that vortex enhancement through midlevel convergence into the stratiform precipitation deck can greatly enhance midtropospheric cyclonic vorticity, it is suggested here that this mechanism only increases the potential for genesis, whereas vortex enhancement through low- to midlevel convergence into deep convective regions is necessary for genesis.

Measuring user satisfaction in an outsourcing environment

Abstract: Outsourcing is a term that encompasses a variety of approaches to contracting for information technology (IT) services. It is defined as a transfer of any particular IT activity or a combination of activities from an organization using them to one or more external service providers. IT outsourcing leads to significant changes in the management processes of the IT organization. For example, while IT managers have always had the responsibility for ensuring that users within their organization maintain a high degree of satisfaction, they now have to monitor the quality of service, even though they are no longer the providers of the service. This gets further complicated when only some parts of the IT functions are outsourced while others are provided by an internal IT department. Thus, developing a comprehensive set of measurement tools and mechanisms is an important step toward monitoring the quality of service provided by both an outside source and an IT department. This paper investigates the usefulness of an existing user-satisfaction measurement instrument for identifying problem areas in a multiprovider outsourcing environment, where an external service provider and an internal IT department each has different roles in the system. It discusses the rationale for measuring user satisfaction and the instruments to carry out the measurement procedure. It reports the results of implementing and testing a previously developed, documented, and validated user-satisfaction instrument in an outsourcing environment and draws practical conclusions from the results.

Not by the sword alone: : soft power, mass media, and the production of state sovereignty

Abstract: Scholars of civil conflict have long recognized the importance of state strength in the suppression of nascent insurgencies. However, previous empirical investigations have generally focused on the material and coercive dimensions of state power, obscuring the critical role played by the generation of widespread voluntary compliance through processes of political communication, that is, the production of �soft power.� In contrast, in this article I focus on a factor�mass communication technology�that can enhance state capacity only by strengthening the state's ability to broadly and publicly disseminate political messages. I argue that the enhanced capacities for large-scale normative influence generated by mass communication technologies can be expected to produce substantial barriers to the mobilization of militarized challenges to state rule, by strengthening economies of scale in the marketplace of ideas. Utilizing newly compiled cross-national data on mass media accessibility in the post�World War II period, I show that densely constituted mass media systems dramatically reduce the probability of large-scale civil violence, thereby providing new evidence for the fundamental importance of nonmaterial state capacities in the suppression of internal armed conflicts.

Navigation system design using time-varying complementary filters

Abstract: A new methodology for the design of navigation systems for autonomous vehicles is introduced. Using simple kinematic relationships, the problem of estimating the velocity and position of an autonomous vehicle is solved by resorting to special bilinear time-varying filters. These are the natural generalization of linear time-invariant complementary filters that are commonly used to properly merge sensor information available at low frequency with that available in the complementary region. Complementary filters lend themselves to frequency domain interpretations that provide valuable insight into the filtering design process. This work extends these properties to the time-varying setting by resorting to the theory of linear differential inclusions and by converting the problem of weighted filter performance analysis into that of determining the feasibility of a related set of linear matrix inequalities (LMIs). Using this set-up, the stability of the resulting filters as well as their "frequency-like" performance can be assessed using efficient numerical analysis tools that borrow from convex optimization techniques. The mathematical background that is required for complementary time-varying filter analysis and design is introduced. Its application to the design of a navigation system that estimates position and velocity of an autonomous vehicle by complementing position information available from GPS with the velocity information provided by a Doppler sonar system is described.