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2007

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Articles 2131 - 2160 of 6758

Full-Text Articles in Physical Sciences and Mathematics

Strain-Free Ge/Gesisn Quantum Cascade Lasers Based On L-Valley Intersubband Transitions, Greg Sun, H. H. Cheng, J. Menéndez, Jacob B. Khurgin, R. A. Soref Jun 2007

Strain-Free Ge/Gesisn Quantum Cascade Lasers Based On L-Valley Intersubband Transitions, Greg Sun, H. H. Cheng, J. Menéndez, Jacob B. Khurgin, R. A. Soref

Physics Faculty Publications

The authors propose a Ge/Ge0.76Si0.19Sn0.05 quantum cascade laser using intersubband transitions at L valleys of the conduction band which has a “clean” offset of150 meV situated below other energy valleys (Γ,X). The entire structure is strain-free because the lattice-matched Ge and Ge0.76Si0.19Sn0.05 layers are to be grown on a relaxed Ge buffer layer on a Si substrate. Longer lifetimes due to the weaker scattering of nonpolar optical phonons reduce the threshold current and potentially lead to room temperature operation.

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Identifying Patients Who Need Additional Biomarkers For Better Prediction Of Health Outcome Or Diagnosis Of Clinical Phenotype, Lu Tian, Tianxi Cai, L. J. Wei Jun 2007

Identifying Patients Who Need Additional Biomarkers For Better Prediction Of Health Outcome Or Diagnosis Of Clinical Phenotype, Lu Tian, Tianxi Cai, L. J. Wei

Harvard University Biostatistics Working Paper Series

No abstract provided.

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Conceptual Xml For Systems Analysis, Reema Al-Kamha Jun 2007

Conceptual Xml For Systems Analysis, Reema Al-Kamha

Theses and Dissertations

Because XML has become a new standard for data representation, there is a need for a simple conceptual model that works well with XML-based development. In this research we present a conceptual model for XML, called C-XML, which meets this new need of systems analysts who store their data using XML. We describe our implementation of an automatic conversion from XML Schema to C-XML that preserves information and constraints. With this conversion, we can view an XML Schema instance graphically at a higher level of abstraction. We also describe our implementation of an automatic conversion from C-XML to XML Schema. …

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Identifying Effect Modifiers In Air Pollution Time-Series Studies Using A Two-Stage Analysis, Sandrah P. Eckel, Thomas A. Louis Jun 2007

Identifying Effect Modifiers In Air Pollution Time-Series Studies Using A Two-Stage Analysis, Sandrah P. Eckel, Thomas A. Louis

Johns Hopkins University, Dept. of Biostatistics Working Papers

Studies of the health effects of air pollution such as the National Morbidity and Mortality Air Pollution Study (NMMAPS) relate changes in daily pollution to daily deaths in a sample of cities and calendar years. Generally, city-specific estimates are combined into regional and national estimates using two-stage models. Our two-stage analysis identifies effect modifiers of the relation between single-day lagged PM10 and daily mortality in people age 65 and older from the 50 largest NMMAPS cities. We build on the standard approach by "fractionating" city-specific analyses to produce month-year-city specific estimated air pollution effects (slopes) in Stage I. In Stage …

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An Investigation Into The Energy Efficiency Of Pure And Slotted Aloha Based Reid Anti-Collision Protocols, Dheeraj Klair, K. W. Chin, R. Raad Jun 2007

An Investigation Into The Energy Efficiency Of Pure And Slotted Aloha Based Reid Anti-Collision Protocols, Dheeraj Klair, K. W. Chin, R. Raad

Faculty of Informatics - Papers (Archive)

This paper investigates the energy efficiency of RFID anti-collision protocols and their suitability for use in RFID-enhanced wireless sensor networks (WSNs). We present a detailed analytical methodology and an in-depth qualitative and Aloha anti-collision protocols and their variants. We find that Slotted Aloha variants that employ muting with early-end are the most energy efficient, but are computationally expensive. Overall, for all Aloha variants we investigated, if the offered load is very high, tag responses cause a bottleneck at the reader. Thereby, resulting in no tags being identified and incur significant identification delays - thus severely impacting a sensor node's battery …

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Analysis Of Time-Series Modis 250 M Vegetation Index Data For Crop Classification In The U.S. Central Great Plains, Brian D. Wardlow, Stephen L. Egbert, Jude H. Kastens Jun 2007

Analysis Of Time-Series Modis 250 M Vegetation Index Data For Crop Classification In The U.S. Central Great Plains, Brian D. Wardlow, Stephen L. Egbert, Jude H. Kastens

Drought Mitigation Center: Faculty Publications

The global environmental change research community requires improved and up-to-date land use/land cover (LULC) datasets at regional to global scales to support a variety of science and policy applications. Considerable strides have been made to improve large-area LULC datasets, but little emphasis has been placed on thematically detailed crop mapping, despite the considerable influence of management activities in the cropland sector on various environmental processes and the economy. Time-series MODIS 250 m Vegetation Index (VI) datasets hold considerable promise for largearea crop mapping in an agriculturally intensive region such as the U.S. Central Great Plains, given their global coverage, intermediate …

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Xml Interfaces: A Growing Need For Standardization, Elizabeth A. Jackson Jun 2007

Xml Interfaces: A Growing Need For Standardization, Elizabeth A. Jackson

Regis University Student Publications (comprehensive collection)

The incentive for this research came from the need to solve a fundamental problem many companies face when transferring data across multi-platform applications: how to deploy XML interfaces that integrate easily with other systems. The goal of this project was to identify a solution for Company ABC when integrating XML interfaces with customers, partners, and vendors. The project researches the need and development of data standards that can solve one of the key problems with XML - interoperability. Through the use of a common language, companies can utilize data formats and schemas developed by data standards organizations operating in their …

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A Coupled Remote Sensing And Simplified Surface Energy Balance Approach To Estimate Actual Evapotranspiration From Irrigated Fields, Gabriel B. Senay, Michael Budde, James P. Verdin, Assefa M. Melesse Jun 2007

A Coupled Remote Sensing And Simplified Surface Energy Balance Approach To Estimate Actual Evapotranspiration From Irrigated Fields, Gabriel B. Senay, Michael Budde, James P. Verdin, Assefa M. Melesse

Department of Earth and Environment

Accurate crop performance monitoring and production estimation are critical for timely assessment of the food balance of several countries in the world. Since 2001, the Famine Early Warning Systems Network (FEWS NET) has been monitoring crop performance and relative production using satellite-derived data and simulation models in Africa, Central America, and Afghanistan where ground-based monitoring is limited because of a scarcity of weather stations. The commonly used crop monitoring models are based on a crop water-balance algorithm with inputs from satellite-derived rainfall estimates. These models are useful to monitor rainfed agriculture, but they are ineffective for irrigated areas. This study …

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The Freak Wave Mystery ??A New Hypothesis For Its Occurrence, Nai-Kuang Liang Jun 2007

The Freak Wave Mystery ??A New Hypothesis For Its Occurrence, Nai-Kuang Liang

Journal of Marine Science and Technology

Freak waves are known as a maritime myth, which have damaged large cargo and cruise ships. So far freak waves are explained by strong current focusing and nonlinear wave interaction. The latter may results in a single large wave. However this can still not explain the disappearance of the cargo ship Muenchen in December, 1978. This paper proposes a new hypothesis which stems from the wave/ swell energy flux accumulation due to the moving wind system. Nature might play the game by controlling the moving speed to approach the wave/swell group velocity.

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Efficient Gps Position Determination Algorithms, Thao Nguyen Jun 2007

Efficient Gps Position Determination Algorithms, Thao Nguyen

Theses and Dissertations

This research is aimed at improving the state of the art of GPS algorithms, namely, the development of a closed-form positioning algorithm for a standalone user and the development of a novel differential GPS algorithm for a network of users. The stand-alone user GPS algorithm is a direct, closed-form, and efficient new position determination algorithm that exploits the closed-form solution of the GPS trilateration equations and works in the presence of pseudorange measurement noise for an arbitrary number of satellites in view. A two-step GPS position determination algorithm is derived which entails the solution of a linear regression and updates …

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Optimized Lane Assignment Using Inter-Vehicle Communication, Thanh-Son Dao, Christopher M. Clark, Jan Paul Huissoon Jun 2007

Optimized Lane Assignment Using Inter-Vehicle Communication, Thanh-Son Dao, Christopher M. Clark, Jan Paul Huissoon

Computer Science and Software Engineering

This paper presents an approach to lane assignment for highway vehicles that increases traffic throughput while ensuring they exit successfully at their destinations. Most of current traffic management systems do not consider lane organization of vehicles and only regulate traffic flows by controlling traffic signals or ramp meters. However, traffic throughput and efficient use of highways can be increased by coordinating driver behaviors intelligently. The goal of this research is to form a distributed control strategy for cars themselves to select lanes using inter-vehicle communication. Initial results are promising and demonstrate that intelligent lane selection can decrease vehicle traffic time.

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Temperature-Dependent Orbital-Moment Anisotropy In Dilute Magnetic Oxides, Jun Zhang, Ralph Skomski, Yongfeng Lu, David J. Sellmyer Jun 2007

Temperature-Dependent Orbital-Moment Anisotropy In Dilute Magnetic Oxides, Jun Zhang, Ralph Skomski, Yongfeng Lu, David J. Sellmyer

David Sellmyer Publications

A striking magnetization anisotropy in thin films of vanadium-doped stannic oxide is reported and investigated. The single-crystalline Sn1-xVxO2 (0≤x≤0.1) thin films, grown on Al2O3 substrate, are (101) oriented and exhibit a temperature-dependent in-plane anisotropy of the saturation magnetization. The in-plane magnetic moment reaches a maximum close to the [101¯] direction, but the anisotropy axis is incompatible with the crystalline structure of the SnO2 thin films. However, it is consistent with V atoms occupying uniaxially distorted octahedral interstices, thus breaking the symmetry of the film. The moment anisotropy decreases gradually with increasing …

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Summary Meeting Minutes - June 13, 2007 Jun 2007

Summary Meeting Minutes - June 13, 2007

Public Meetings

No abstract provided.

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Taunton River Watershed Study Presentation - Part 1 (June 13, 2007 Public Meeting), Horsley Witten Group, Inc. Jun 2007

Taunton River Watershed Study Presentation - Part 1 (June 13, 2007 Public Meeting), Horsley Witten Group, Inc.

Public Meetings

No abstract provided.

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Taunton River Watershed Study Presentation - Part 2: Progress Report/Data Collection/Analysis (June 13, 2007 Public Meeting), Horsley Witten Group, Inc. Jun 2007

Taunton River Watershed Study Presentation - Part 2: Progress Report/Data Collection/Analysis (June 13, 2007 Public Meeting), Horsley Witten Group, Inc.

Public Meetings

No abstract provided.

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Description Of Harmonic Generation In Terms Of The Complex Quasienergy. Ii. Application To Time-Dependent Effective Range Theory, M.V. Frolov, A.V. Flegel, N. L. Manakov, Anthony F. Starace Jun 2007

Description Of Harmonic Generation In Terms Of The Complex Quasienergy. Ii. Application To Time-Dependent Effective Range Theory, M.V. Frolov, A.V. Flegel, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

A formulation for the high-order harmonic generation (HHG) amplitude [M. V. Frolov et al., Phys. Rev. A 75, 063407 (2007), preceding paper] is employed to provide analytical results for HHG rates within our recently developed time-dependent effective range (TDER) theory (for time-dependent problems involving weakly bound electron systems). Exact and approximate (including quasiclassical) TDER HHG rates are employed to analyze the accuracy of common approximate methods for HHG calculations. For various specific negative ions with s and p outer electrons, numerical results for HHG spectra are presented over a wide interval of laser frequencies(extending from the tunneling to the multiphoton …

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Intelligent Rotoscoping: A Semi-Automated Interactive Boundary Tracking Approach To Video Segmentation, Seth R. Holladay Jun 2007

Intelligent Rotoscoping: A Semi-Automated Interactive Boundary Tracking Approach To Video Segmentation, Seth R. Holladay

Theses and Dissertations

Video segmentation is an application of computer vision aimed at automating the extraction of an object from a series of video frames. However, it is a difficult problem, especially to compute at real-time, interactive rates. Although general application to video is difficult because of the wide range of image scenarios, user interaction can help to reduce the problem space and speed up the computation. This thesis presents a fast object-tracking tool that selects an object from a series of frames based on minimal user input. Our Intelligent Rotoscoping tool aims for increased speed and accuracy over other video segmentation tools, …

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Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang Jun 2007

Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang

Song Zhang

This paper describes a novel phase error compensation method for reducing the measurement error caused by nonsinusoidal waveforms in phase-shifting methods. For 3-D shape measurement systems using commercial video projectors, the nonsinusoidal waveform of the projected fringe patterns as a result of the nonlinear gamma of projectors causes significant phase measurement error and therefore shape measurement error. The proposed phase error compensation method is based on our finding that the phase error due to the nonsinusoidal waveform depends only on the nonlinearity of the projector’s gamma. Therefore, if the projector’s gamma is calibrated and the phase error due to the …

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Changing Band Offsets In Copper Phthalocyanine To Copolymer Poly(Vinylidene Fluoride With Trifluoroethylene) Heterojunctions, Jie Xiao, Andrei Sokolov, Peter A. Dowben Jun 2007

Changing Band Offsets In Copper Phthalocyanine To Copolymer Poly(Vinylidene Fluoride With Trifluoroethylene) Heterojunctions, Jie Xiao, Andrei Sokolov, Peter A. Dowben

Peter Dowben Publications

The authors have fabricated a thin film copper phthalocyanine to crystalline ferroelectric copolymer poly(vinylidene fluoride with trifluoroethylene) heterojunction diode. The formation of a diode is expected from the band offsets between the two thin film molecular systems, as ascertained from combined photoemission and inverse photoemission studies. From the temperature and field dependence of the heterojunction, dipole interactions are implicated at the interface between copper phthalocyanine and poly(vinylidene fluoride with trifluoroethylene) and affect the band offsets and resultant diode properties.

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Numerical Modeling Of A Gravity Wave Packet Ducted By The Thermal Structure Of The Atmosphere, Yonghui Yu, Michael P. Hickey Ph.D. Jun 2007

Numerical Modeling Of A Gravity Wave Packet Ducted By The Thermal Structure Of The Atmosphere, Yonghui Yu, Michael P. Hickey Ph.D.

Publications

A time-dependent and fully nonlinear numerical model is employed to solve the Navier-Stokes equations in two spatial dimensions and to describe the propagation of a Gaussian gravity wave packet generated in the troposphere. A Fourier spectral analysis is used to analyze the frequency power spectra of the wave packet, which propagates through and dwells within several thermal ducting regions. The frequency power spectra of the wave packet are derived at several discrete altitudes, which allow us to determine the evolution of the packet. This spectral analysis also clearly reveals the existence of a stratospheric duct, a mesospheric and lower thermospheric …

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Semantics To Empower Services Science: Using Semantics At Middleware, Web Services And Business Levels, Amit P. Sheth Jun 2007

Semantics To Empower Services Science: Using Semantics At Middleware, Web Services And Business Levels, Amit P. Sheth

Kno.e.sis Publications

No abstract provided.

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Distributed Reproducible Research Using Cached Computations, Roger Peng, Sandrah P. Eckel Jun 2007

Distributed Reproducible Research Using Cached Computations, Roger Peng, Sandrah P. Eckel

Johns Hopkins University, Dept. of Biostatistics Working Papers

The ability to make scientific findings reproducible is increasingly important in areas where substantive results are the product of complex statistical computations. Reproducibility can allow others to verify the published findings and conduct alternate analyses of the same data. A question that arises naturally is how can one conduct and distribute reproducible research? This question is relevant from the point of view of both the authors who want to make their research reproducible and readers who want to reproduce relevant findings reported in the scientific literature. We present a framework in which reproducible research can be conducted and distributed via …

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Nonlinear Dynamics In Combinatorial Games: Renormalizing Chomp, Eric J. Friedman, Adam S. Landsberg Jun 2007

Nonlinear Dynamics In Combinatorial Games: Renormalizing Chomp, Eric J. Friedman, Adam S. Landsberg

WM Keck Science Faculty Papers

We develop a new approach to combinatorial games that reveals connections between such games and some of the central ideas of nonlinear dynamics: scaling behaviors, complex dynamics and chaos, universality, and aggregation processes. We take as our model system the combinatorial game Chomp, which is one of the simplest in a class of "unsolved" combinatorial games that includes Chess, Checkers, and Go. We discover that the game possesses an underlying geometric structure that "grows" (reminiscent of crystal growth), and show how this growth can be analyzed using a renormalization procedure adapted from physics. In effect, this methodology allows one to …

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A Fuzzy-Based Approach For Partner Selection In Multi-Agent Systems, Fenghui Ren, Minjie Zhang, Quan Bai Jun 2007

A Fuzzy-Based Approach For Partner Selection In Multi-Agent Systems, Fenghui Ren, Minjie Zhang, Quan Bai

Faculty of Informatics - Papers (Archive)

Traditional negotiation approaches pay intensive attention to decision making models in order to reach the optimal agreements, while placing insufficient efforts on the problem of partner selection. In this paper, a fuzzy-based approach for partner selection in multi-agent systems is proposed. By employing both the fuzzy logic and the extended dual concern model, agents can adapt their individual behaviors for partner selection in negotiation. The proposed approach has three merits, which are: (1) both the agent’s own benefit and its potential partners’ benefits are considered for partner selection in negotiation; (2) by employing the extended dual concern model, agents’ attitudes …

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Numerical Simulation Of Waves And Fronts In Inhomogeneous Solids, A. Berezovski, M. Berezovski, J. Engelbrecht, G. A. Maugin Jun 2007

Numerical Simulation Of Waves And Fronts In Inhomogeneous Solids, A. Berezovski, M. Berezovski, J. Engelbrecht, G. A. Maugin

Publications

Dynamic response of inhomogeneous materials exhibits new effects, which often do not exist in homogeneous media. It is quite natural that most of studies of wave and front propagation in inhomogeneous materials are associated with numerical simulations. To develop a numerical algorithm and to perform the numerical simulations of moving fronts we need to formulate a kinetic law of progress relating the driving force and the velocity of the discontinuity. The velocity of discontinuity is determined by means of the non-equilibrium jump relations at the front. The obtained numerical method generalizes the wave-propagation algorithm to the case of moving discontinuities …

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Internet Enabled Remote Driving Of A Combat Hybrid Electric Power System For Duty Cycle Measurement, Jarrett Goodell, Marc Compere, Wilford Smith, Mark Brudnak, Mike Pozolo, Et Al. Jun 2007

Internet Enabled Remote Driving Of A Combat Hybrid Electric Power System For Duty Cycle Measurement, Jarrett Goodell, Marc Compere, Wilford Smith, Mark Brudnak, Mike Pozolo, Et Al.

Publications

This paper describes a human-in-the-loop motion-based simulator interfaced to hybrid-electric power system hardware, both of which were used to measure the duty cycle of a combat vehicle in a virtual simulation environment. The project discussed is a greatly expanded follow-on to the experiment published in [1,7]. This paper is written in the context of [1,7] and therefore highlights the enhancements. The most prominent of these enhancements is the integration (in real-time) of the Power & Energy System Integration Lab (P&E SIL) with a motion base simulator by means of a “long haul” connection over the Internet (a geographical distance of …

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Finding Termination And Time Improvement In Predicate Abstraction With Under-Approximation And Abstract Matching, Dritan Kudra Jun 2007

Finding Termination And Time Improvement In Predicate Abstraction With Under-Approximation And Abstract Matching, Dritan Kudra

Theses and Dissertations

The focus of current formal verification methods is mitigating the state explosion problem. One of these formal methods is predicate abstraction, which reduces concrete states of a system to bitvectors of true/false valuations of a set of predicates. Predicate abstraction comes in two flavors, over-approximation and under-approximation. A drawback of over-approximation is that it produces too many spurious errors for data-intensive applications. A more recent under-approximation technique which does not produce spurious errors, does abstract matching on concrete states (AMCS). AMCS adds behaviors to an abstract system by augmenting the set of initial predicates, making use of a theorem prover. …

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The Deep X-Ray Radio Blazar Survey. Iii. Radio Number Counts, Evolutionary Properties, And Luminosity Function Of Blazars, Paolo Padovani, Paolo Giommi, Hermine Landt, Eric S. Perlman Jun 2007

The Deep X-Ray Radio Blazar Survey. Iii. Radio Number Counts, Evolutionary Properties, And Luminosity Function Of Blazars, Paolo Padovani, Paolo Giommi, Hermine Landt, Eric S. Perlman

Aerospace, Physics, and Space Science Faculty Publications

Our knowledge of the blazar surface densities and luminosity functions, which are fundamental parameters, relies still on samples at relatively high flux limits. As a result, our understanding of this rare class of active galactic nuclei is mostly based on relatively bright and intrinsically luminous sources. We present the radio number counts, evolutionary properties, and luminosity functions of the faintest blazar sample with basically complete (∼95%) identifications. Based on the Deep X-Ray Radio Blazar Survey (DXRBS), it includes 129 flat-spectrum radio quasars ( FSRQs) and 24 BL Lac objects down to a 5 GHz flux and power ∼50 mJy and …

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The New Class Of Dusty Daz White Dwarfs, Ted Von Hippel, Et Al. Jun 2007

The New Class Of Dusty Daz White Dwarfs, Ted Von Hippel, Et Al.

Publications

Our mid-infrared survey of 124 white dwarfs with the Spitzer Space Telescope and the IRAC imager has revealed an infrared excess associated with the white dwarf WD 2115-560 naturally explained by circumstellar dust. This object is the fourth white dwarf observed to have circumstellar dust. All four are DAZ white dwarfs, i.e., they have both photospheric Balmer lines and photospheric metal lines. We discuss these four objects as a class, which we abbreviate "DAZd," where the "d" stands for "dust." Using an optically thick, geometrically thin disk model analogous to Saturn's rings, we find that the inner disk edges are …

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Stable Aqueous Nanoparticle Film Assemblies With Covalent And Charged Polymer Linking Networks, Lesley E. Russell, Anne A. Galyean, Sherilyn M. Notte, Michael C. Leopold Jun 2007

Stable Aqueous Nanoparticle Film Assemblies With Covalent And Charged Polymer Linking Networks, Lesley E. Russell, Anne A. Galyean, Sherilyn M. Notte, Michael C. Leopold

Chemistry Faculty Publications

The construction of highly stable and efficiently assembled multilayer films of purely water soluble gold nanoparticles is reported. Citrate-stabilized nanoparticles (CS-NPs) of average core diameter of 10 nm are used as templates for stabilization-based exchange reactions with thioctic acid to form more robust aqueous NPs that can be assembled into multilayer films. The thioctic acid stabilized nanoparticles (TAS-NPs) are networked via covalent and electrostatic linking systems, employing dithiols and the cationic polymer poly(l-lysine), respectively. Multilayer films of up to 150 nm in thickness are successfully grown at biological pH with no observable degradation of the NPs within the film. The …

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