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2007

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Articles 3451 - 3480 of 6758

Full-Text Articles in Physical Sciences and Mathematics

Professionalism In The Air Force: A Comparative Analysis Of Commissioned Officers With Non-Commissioned Officers, Edward K. Boyd Mar 2007

Professionalism In The Air Force: A Comparative Analysis Of Commissioned Officers With Non-Commissioned Officers, Edward K. Boyd

Theses and Dissertations

Decades ago, military sociologists predicted a rising trend among officers away from traditional institutional military values and toward more economically-based occupational values due to the effects of the transition from a conscription-based military to an all-volunteer force. Subsequent empirical research resulted in data that supports such predictions. More recent researchers have suggested that in addition to the all-volunteer force, an increase on technology may also accelerate the trend toward occupationalism and away from traditional institutional military values and the warrior ethos that typically define successful military organizations. The officer corps may be particularly vulnerable to occupationalism due to increased technical …

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Beyond Passswords: Usage And Policy Transformation, Alan S. Alsop Mar 2007

Beyond Passswords: Usage And Policy Transformation, Alan S. Alsop

Theses and Dissertations

The purpose of this research is to determine whether the transition to a two-factor authentication system is more secure than a system that relied only on what users “know” for authentication. While we found that factors that made passwords inherently vulnerable did not transfer to the PIN portion of a two-factor authentication system, we did find significant problems relating to usability, worker productivity, and the loss and theft of smart cards. The new authentication method has disrupted our ability to stay connected to ongoing mission issues, forced some installations to cut off remote access for their users and in one …

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Hardware Virtualization Applied To Rootkit Defense, Douglas P. Medley Mar 2007

Hardware Virtualization Applied To Rootkit Defense, Douglas P. Medley

Theses and Dissertations

This research effort examines the idea of applying virtualization hardware to enhance operating system security against rootkits. Rootkits are sets of tools used to hide code and/or functionality from the user and operating system. Rootkits can accomplish this feat through using access to one part of an operating system to change another part that resides at the same privilege level. Hardware assisted virtualization (HAV) provides an opportunity to defeat this tactic through the introduction of a new operating mode. Created to aid operating system virtualization, HAV provides hardware support for managing and saving multiple states of the processor. This hardware …

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Development Of An H-Alpha Index For The Detection Of Pms Candidates In Young Open Clusters, Liberty Rae Evanko Mar 2007

Development Of An H-Alpha Index For The Detection Of Pms Candidates In Young Open Clusters, Liberty Rae Evanko

Theses and Dissertations

One phase of formation of medium- and low-mass stars is the optically visible phase known as the pre-main-sequence or PMS phase. In order to further the understanding of this phase, more of these PMS objects need to be identified and classified. Previous techniques have used photometry to identify possible PMS objects by their characteristic Hα emission. Once identified these objects can be studied spectroscopically yielding complete PMS classification. This study develops a method to locate these emission objects that overcomes two limitations of previous techniques. The first limitation is the need for the creation of reddening maps. It is eliminated …

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Observational Studies Of Software Engineering Using Data From Software Repositories, Daniel Pierce Delorey Mar 2007

Observational Studies Of Software Engineering Using Data From Software Repositories, Daniel Pierce Delorey

Theses and Dissertations

Data for empirical studies of software engineering can be difficult to obtain. Extrapolations from small controlled experiments to large development environments are tenuous and observation tends to change the behavior of the subjects. In this thesis we propose the use of data gathered from software repositories in observational studies of software engineering. We present tools we have developed to extract data from CVS repositories and the SourceForge Research Archive. We use these tools to gather data from 9,999 Open Source projects. By analyzing these data we are able to provide insights into the structure of Open Source projects. For example, …

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Universal Transverse Mercator And Lambert's Conformal Conic Projections, Cemal Göçmen Mar 2007

Universal Transverse Mercator And Lambert's Conformal Conic Projections, Cemal Göçmen

Bulletin of the Mineral Research and Exploration

No abstract provided.

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Tracing Lineage Beyond Relational Operators, Mingwu Zhang, Xiangyu Zhang, Xiang Zhang, Sunil Prabhakar Mar 2007

Tracing Lineage Beyond Relational Operators, Mingwu Zhang, Xiangyu Zhang, Xiang Zhang, Sunil Prabhakar

Department of Computer Science Technical Reports

No abstract provided.

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Thermally Activated, Variable Blazed Grating For Coherent Beam Steering, Matthew T. Johnson Mar 2007

Thermally Activated, Variable Blazed Grating For Coherent Beam Steering, Matthew T. Johnson

Theses and Dissertations

The ability to perform non-mechanical optical beam steering is of critical importance in laser communication and remote sensing; it is as vital as a phased-array antenna is for RADAR. Directed energy transmission and direction-selective reception increase performance and produce tactical advantage in DoD applications. However, specific geometric features of non-mechanical beam steering devices must be designed in proportion to the wavelength of the monochromatic light to be steered. Also, the ability to handle higher energies by reducing the energy per unit requires large areas of uniform properties on the micrometer scale. These challenges have been addressed in the past using …

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Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal Mar 2007

Investigation Of Cdznte Crystal Defects Using Scanning Probe Microscopy, Goutam Koley, J. Liu, K. C. Mandal

Faculty Publications

No abstract provided.

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Assessment Of Optical Turbulence Profiles Derived From Probabilistic Climatology, Brett W. Wisdom Mar 2007

Assessment Of Optical Turbulence Profiles Derived From Probabilistic Climatology, Brett W. Wisdom

Theses and Dissertations

This research effort assesses the performance of the High Energy Laser End-to-End Operational Simulation (HELEEOS) Climatological C2n optical turbulence model. Path-integrated C2n values of two HELEEOS optical turbulence pro les at 3 distinct operational altitudes are compared to values determined from measured thermosonde data. HELEEOS desert and mid-latitude sites are selected from the Extreme and Percentile Environmental Reference Tables (ExPERT) database for comparison to the thermosonde data. Statistical equivalence of the two datasets is determined through a Design of Experiments (DOE) factorial test to within 80% confidence. The HELEEOS profiles are shown to be equivalent to …

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Locating Encrypted Data Hidden Among Non-Encrypted Data Using Statistical Tools, Walter J. Hayden Mar 2007

Locating Encrypted Data Hidden Among Non-Encrypted Data Using Statistical Tools, Walter J. Hayden

Theses and Dissertations

This research tests the security of software protection techniques that use encryption to protect code segments containing critical algorithm implementation to prevent reverse engineering. Using the National Institute of Standards and Technology (NIST) Tests for Randomness encrypted regions hidden among non-encrypted bits of a binary executable file are located. The location of ciphertext from four encryption algorithms (AES, DES, RSA, and TEA) and three block sizes (10, 100, and 500 32-bit words) were tested during the development of the techniques described in this research. The test files were generated from the Win32 binary executable file of Adobe's Acrobat Reader version …

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Direct Diode Pumped Raman Amplifier Based On A Multimode Graded Index Fiberr, Charles James Baird Mar 2007

Direct Diode Pumped Raman Amplifier Based On A Multimode Graded Index Fiberr, Charles James Baird

Theses and Dissertations

The direct pumping of a Raman fiber amplifier (RFA) was attempted using an array of four 25W, fiber pigtailed diodes at 936nm, combined via a 7 channel fiber beam combiner. The initial attempt was conducted using a 1.8 km, 100 micron core, GRIN fiber with an NA of .29 and attenuation 3.6 dB/km at 936nm. While amplification was not achieved, over 200mW of conversion was shown, with 10.4W of pump power and 3.5W of seed. This corresponds to an average conversion efficiency of 2.2%. The subsequent effort utilized a 2km long, 200 micron core, GRIN fiber, with NA of .27 …

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Multi-Dimensional Range Querying Using A Modification Of The Skip Graph, Gregory J. Brault Mar 2007

Multi-Dimensional Range Querying Using A Modification Of The Skip Graph, Gregory J. Brault

Theses and Dissertations

Skip graphs are an application layer-based distributed routing data structure that can be used in a sensor network to facilitate user queries of data collected by the sensor nodes. This research investigates the impact of a proposed modification to the skip graph proposed by Aspnes and Shah. Nodes contained in a standard skip graph are sorted by their key value into successively smaller groups based on random membership vectors computed locally at each node. The proposed modification inverts the node key and membership vector roles, where group membership is computed deterministically and node keys are computed randomly. Both skip graph …

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Stylized Hatching For 3d Animation, Trent Fielding Crow Mar 2007

Stylized Hatching For 3d Animation, Trent Fielding Crow

Theses and Dissertations

Much research has been done in creating non-photorealistic renderings of objects that mimic the look of hand-made drawings by traditional artists. This thesis extends work in this area by presenting an NPR hatching method that can be applied to 3D animated films to help them feel more hand drawn. In contrast to most other NPR methods, this method preserves the 3D lighting and effects of the film that make it interesting to watch. This process includes a procedural algorithm to create a hatching pattern that can be easily integrated into any film's pipeline that uses Renderman. In addition, we create …

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A Time Delay For The Cluster‐Lensed Quasar Sdss J1004+4112, J. Fohlmeister, C. S. Kochanek, E. E. Falco, J. Wambsganss, N. Morgan, C.W. Morgan, E.O. Ofek, D. Maoz, C.R. Keeton, J.C. Barentine, G. Dalton, J. Dembicky, W. Ketzeback, R. Mcmillan, C.S. Peters Mar 2007

A Time Delay For The Cluster‐Lensed Quasar Sdss J1004+4112, J. Fohlmeister, C. S. Kochanek, E. E. Falco, J. Wambsganss, N. Morgan, C.W. Morgan, E.O. Ofek, D. Maoz, C.R. Keeton, J.C. Barentine, G. Dalton, J. Dembicky, W. Ketzeback, R. Mcmillan, C.S. Peters

Dartmouth Scholarship

We present 426 epochs of optical monitoring data spanning 1000 days from 2003 December to 2006 June for the gravitationally lensed quasar SDSS J1004+4112. The time delay between the A and B images is tBA . 38: 42: 0 days (2 . 4) in the expected sense that B leads A and the overall time ordering is C-B-A-D-E. The measured delay invalidates all published models. The models probably failed because they neglected the perturbations from cluster member galaxies. Models including the galaxies can fit the data well, but conclusions about the clustermass distribution should await themeasurement of the longer, and …

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Large Merger Recoils And Spin Flips From Generic Black Hole Binaries, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower, David Merritt Mar 2007

Large Merger Recoils And Spin Flips From Generic Black Hole Binaries, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower, David Merritt

Physics and Astronomy Faculty Publications and Presentations

We report the first results from the evolution of generic black hole binaries, i.e., binaries containing unequal-mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2 : 1, consists of an initially nonspinning hole orbiting a larger, rapidly spinning hole (specific spin a/m = 0.885), with the spin direction oriented -45° with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km s-1, more than twice as large as the maximum kick from nonspinning binaries. The remnant …

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A New Age Recovery About The Mining History In Anatolia; An Ore Hull Of 2500 Year Old, Ahmet Kartalkanat Mar 2007

A New Age Recovery About The Mining History In Anatolia; An Ore Hull Of 2500 Year Old, Ahmet Kartalkanat

Bulletin of the Mineral Research and Exploration

No abstract provided.

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A Study Of Different Angles For The New Spread Matrix For Bsofdm In Uwb Channels, Ibrahim S. Raad, Xiaojing Huang, Darryn Lowe Mar 2007

A Study Of Different Angles For The New Spread Matrix For Bsofdm In Uwb Channels, Ibrahim S. Raad, Xiaojing Huang, Darryn Lowe

Faculty of Informatics - Papers (Archive)

This paper presents a study into different angles for the New spread matrix developed for BSOFDM. It varies the angles for the matrix to develop different constellation schemes which are useful in overcoming the frequency selective channels which are encountered in mobile communication systems. Previously it has been discussed that this new matrix (the rotation matrix) has some advantages over Hadamard and the rotated Hadamard matrix in certain channels. This paper presents a study of varies angles with this new matrix over the UWB channels CM1 to CM4.

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Hybrid Automatic Repeat Requests For Mb-Ofdm Ultra-Wideband, Darryn Lowe, Xiaojing Huang Mar 2007

Hybrid Automatic Repeat Requests For Mb-Ofdm Ultra-Wideband, Darryn Lowe, Xiaojing Huang

Faculty of Informatics - Papers (Archive)

This paper analyzes the design and performance of hybrid automatic repeat request (HARQ) extensions to the multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) standard. It is shown how both Type-I and Type-III HARQ can significantly reduce the packet error rate (PER) in realistic frequency-selective channels. An exhaustive search is used to find an optimal low-complexity Type-III HARQ scheme by deriving the distance spectra and bit error upperbound for all sets of complementary puncturing matrices. The consequences of selecting sub-optimal puncturing matrices are also quantified.

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Adaptive Time-Frequency Codes For Ultra-Wideband, Darryn Lowe, Xiaojing Huang Mar 2007

Adaptive Time-Frequency Codes For Ultra-Wideband, Darryn Lowe, Xiaojing Huang

Faculty of Informatics - Papers (Archive)

This paper investigates inter-piconet interference (IPI) in the multi-band orthogonal frequency division multi-plexing (MB-OFDM) ultra-wideband (UWB) standard. IPI is caused when the time-frequency codes (TFCs) that delineate MB-OFDM piconets collide. An upper-bound on the severity of the IPI problem is obtained through a theoretical analysis of data-rate-specific punctured convolutional codes. Using these results, several methods for adaptive TFCs are proposed and analyzed. Comprehensive simulation results show how packet error rates (PERs) for simultaneous operating piconets (SOPs) can be improved by up to 2 dB by enabling adaptive TFCs at the transmitter. Several combinations of data rate, TFC, channel model and …

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The First Findings On The Origin Of Alveolar Disintegration At The Western Shores Of Geli̇bolu Peninsula, Ahmet Evren Ergi̇nal, Ahmet Gönüz, Mustafa Bozcu, A. Suat Ateş, Ziya S. Çeti̇ner Mar 2007

The First Findings On The Origin Of Alveolar Disintegration At The Western Shores Of Geli̇bolu Peninsula, Ahmet Evren Ergi̇nal, Ahmet Gönüz, Mustafa Bozcu, A. Suat Ateş, Ziya S. Çeti̇ner

Bulletin of the Mineral Research and Exploration

No abstract provided.

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Sger-Exploring The Use Of Quantum Dots To Detect The Physiology Of Intact Phytoplankton Cells By Flow Cytometry, Karen Orcutt Mar 2007

Sger-Exploring The Use Of Quantum Dots To Detect The Physiology Of Intact Phytoplankton Cells By Flow Cytometry, Karen Orcutt

University of Maine Office of Research Administration: Grant Reports

The PIs will to apply the emerging technology of Qdots in biological oceanography, particularly in studying phytoplankton. Qdots have unique fluorescence properties with tremendous potential for probing cell structure and function. They are inorganic fluorophores that can be conjugated to biological materials such as antibodies or DNA for use in cell detection. Molecular conjugates of Qdots offer a wide spectrum of applications such as multi-labeling of proteins and fluorescent in situ hybridization of DNA. The PIs will explore a new approach to an established research topic and venture into the emerging research area of nano-materials.

The novel approach may improve …

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Anthropogenical Effects On The Processes In The Göksu Delta, Mersi̇n-Turkey, Mustafa Keçer, Tamer Y. Duman Mar 2007

Anthropogenical Effects On The Processes In The Göksu Delta, Mersi̇n-Turkey, Mustafa Keçer, Tamer Y. Duman

Bulletin of the Mineral Research and Exploration

No abstract provided.

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Vegetation Water Content During Smex04 From Ground Data And Landsat 5 Thematic Mapper Imagery, M. Tugrul Yilmaz, E. Raymond Hunt, Jr., Lyssa D. Goins, Susan L. Ustin, Vern C. Vanderbilt, Thomas J. Jackson Mar 2007

Vegetation Water Content During Smex04 From Ground Data And Landsat 5 Thematic Mapper Imagery, M. Tugrul Yilmaz, E. Raymond Hunt, Jr., Lyssa D. Goins, Susan L. Ustin, Vern C. Vanderbilt, Thomas J. Jackson

United States National Aeronautics and Space Administration: Publications

Vegetation water content is an important parameter for retrieval of soil moisture from microwave data and for other remote sensing applications. Because liquid water absorbs in the shortwave infrared, the normalized difference infrared index (NDII), calculated from Landsat 5 Thematic Mapper band 4 (0.76–0.90 μm wavelength) and band 5 (1.55–1.65 μm wavelength), can be used to determine canopy equivalent water thickness (EWT), which is defined as the water volume per leaf area times the leaf area index (LAI). Alternatively, average canopy EWT can be determined using a landcover classification, because different vegetation types have different average LAI at the peak …

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Semiparametric Bivariate Quantile-Quantile Regression For Analyzing Semi-Competing Risks Data, Daniel O. Scharfstein, James M. Robins, Mark Van Der Laan Mar 2007

Semiparametric Bivariate Quantile-Quantile Regression For Analyzing Semi-Competing Risks Data, Daniel O. Scharfstein, James M. Robins, Mark Van Der Laan

Johns Hopkins University, Dept. of Biostatistics Working Papers

In this paper, we consider estimation of the effect of a randomized treatment on time to disease progression and death, possibly adjusting for high-dimensional baseline prognostic factors. We assume that patients may or may not have a specific type of disease progression prior to death and those who have this endpoint are followed for their survival information. Progression and survival may also be censored due to loss to follow-up or study termination. We posit a semi-parametric bivariate quantile-quantile regression failure time model and show how to construct estimators of the regression parameters. The causal interpretation of the parameters depends on …

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Heuristically Driven Search Methods For Topology Control In Directional Wireless Hybrid Network, Roger L. Garner Mar 2007

Heuristically Driven Search Methods For Topology Control In Directional Wireless Hybrid Network, Roger L. Garner

Theses and Dissertations

Information and Networked Communications play a vital role in the everyday operations of the United States Armed Forces. This research establishes a comparative analysis of the unique network characteristics and requirements introduced by the Topology Control Problem (also known as the Network Design Problem). Previous research has focused on the development of Mixed-Integer Linear Program (MILP) formulations, simple heuristics, and Genetic Algorithm (GA) strategies for solving this problem. Principal concerns with these techniques include runtime and solution quality. To reduce runtime, new strategies have been developed based on the concept of flow networks using the novel combination of three well-known …

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An Artificial Immune System-Inspired Multiobjective Evolutionary Algorithm With Application To The Detection Of Distributed Computer Network Intrusions, Charles R. Haag Mar 2007

An Artificial Immune System-Inspired Multiobjective Evolutionary Algorithm With Application To The Detection Of Distributed Computer Network Intrusions, Charles R. Haag

Theses and Dissertations

Today's predominantly-employed signature-based intrusion detection systems are reactive in nature and storage-limited. Their operation depends upon catching an instance of an intrusion or virus after a potentially successful attack, performing post-mortem analysis on that instance and encoding it into a signature that is stored in its anomaly database. The time required to perform these tasks provides a window of vulnerability to DoD computer systems. Further, because of the current maximum size of an Internet Protocol-based message, the database would have to be able to maintain 25665535 possible signature combinations. In order to tighten this response cycle within storage constraints, …

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Corporate Entrepreneurship Assessment Instrument (Ceai): Refinement And Validation Of A Survey Measure, Michael S. Cates Mar 2007

Corporate Entrepreneurship Assessment Instrument (Ceai): Refinement And Validation Of A Survey Measure, Michael S. Cates

Theses and Dissertations

The study of corporate entrepreneurship has established itself as a valuable area of research for both public and private-sector organizations. The measurement instrument known as the Corporate Entrepreneurship Assessment Index (CEAI) has been designed to tap the climate-related organizational factors that represent and potentially encourage corporate entrepreneurship. This study is an attempt to refine the CEAI. The core constructs of the CEAI are redefined, the items are tested for content validity, the factor structure is analyzed, and the CEAI is correlated to other known measures to validate the CEAI. Through this testing, the CEAI was refined and found to be …

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The Green Beam—Lidar Investigations Of The Mesosphere, Vincent B. Wickwar Mar 2007

The Green Beam—Lidar Investigations Of The Mesosphere, Vincent B. Wickwar

Presentations

No abstract provided.

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Calculating Van Der Waals-London Dispersion Spectra And Hamaker Coefficients Of Carbon Nanotubes In Water From Ab Initio Optical Properties, Roger H. French Mar 2007

Calculating Van Der Waals-London Dispersion Spectra And Hamaker Coefficients Of Carbon Nanotubes In Water From Ab Initio Optical Properties, Roger H. French

Faculty Scholarship

The van der Waals-London dispersion (vdW-Ld) spectra are calculated for the [9,3,m] metallic and [6,5,s] semiconducting single wall carbon nanotubes (SWCNTs), graphite, and graphene (a single carbon sheet of the graphite structure) using uniaxial optical properties determined from ab initio band structure calculations. The [9,3,m]⁠, exhibiting metallic optical properties in the axial direction versus semiconducting optical properties in the radial direction, highlights the strong anisotropic nature of metallic SWCNTs. Availability of both efficient ab initio local density band structure codes and sufficient computational power has allowed us to calculate the imaginary parts of the frequency dependent dielectric spectra, which are …

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