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 & Nonlinear system. 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.

A stable tracking control method for an autonomous mobile robot

Abstract: A stable tracking control rule is proposed for nonholonomic vehicles. The stability of the rule is proved through the use of a Liapunov function. Inputs to the vehicle are a reference posture (x/sub r/, y/sub r/, theta /sub r/)/sup t/ and reference velocities ( nu /sub r/, omega /sub r/)/sup t/. The major objective of this study is to propose a control rule to find reasonable target linear and rotational velocities ( nu , omega )/sup t/. Linearizing the system's differential equation is useful for deciding parameters for critical dumping for a small disturbance. In order to avoid slippage, a velocity/acceleration limitation scheme is introduced. Several simulation results are presented with or without the velocity/acceleration limiter. The control rule and limiting method proposed are robot independent and hence can be applied to various kinds of mobile robots with a dead reckoning ability. This method was implemented on the autonomous mobile robot Yamabico-11. Experimental results obtained are close to the results with the velocity/acceleration limiter. >

Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean

Abstract: The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km2 in the open equatorial Pacific Ocean with iron This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturally enriched in iron These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean

A review of biomass burning emissions part III: intensive optical properties of biomass burning particles

Abstract: . The last decade has seen tremendous advances in atmospheric aerosol particle research that is often performed in the context of climate and global change science. Biomass burning, one of the largest sources of accumulation mode particles globally, has been closely studied for its radiative, geochemical, and dynamic impacts. These studies have taken many forms including laboratory burns, in situ experiments, remote sensing, and modeling. While the differing perspectives of these studies have ultimately improved our qualitative understanding of biomass-burning issues, the varied nature of the work make inter-comparisons and resolutions of some specific issues difficult. In short, the literature base has become a milieu of small pieces of the biomass-burning puzzle. This manuscript, the second part of four, examines the properties of biomass-burning particle emissions. Here we review and discuss the literature concerning the measurement of smoke particle size, chemistry, thermodynamic properties, and emission factors. Where appropriate, critiques of measurement techniques are presented. We show that very large differences in measured particle properties have appeared in the literature, in particular with regards to particle carbon budgets. We investigate emissions uncertainties using scale analyses, which shows that while emission factors for grass and brush are relatively well known, very large uncertainties still exist in emission factors of boreal, temperate and some tropical forests. Based on an uncertainty analysis of the community data set of biomass burning measurements, we present simplified models for particle size and emission factors. We close this review paper with a discussion of the community experimental data, point to lapses in the data set, and prioritize future research topics.

A sound type system for secure flow analysis

Abstract: Ensuring secure information flow within programs in the context of multiple sensitivity levels has been widely studied. Especially noteworthy is Denning’s work in secure flow analysis and the lattice model [6][7]. Until now, however, the soundness of Denning’s analysis has not been established satisfactorily. We formulate Denning’s approach as a type system and present a notion of soundness for the system that can be viewed as a form of noninterference. Soundness is established by proving, with respect to a standard programming language semantics, that all well-typed programs have this noninterference property.