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Articles 6091 - 6120 of 8341

Full-Text Articles in Physical Sciences and Mathematics

Improving Liquid State Machines Through Iterative Refinement Of The Reservoir, R David Norton Mar 2008

Improving Liquid State Machines Through Iterative Refinement Of The Reservoir, R David Norton

Theses and Dissertations

Liquid State Machines (LSMs) exploit the power of recurrent spiking neural networks (SNNs) without training the SNN. Instead, a reservoir, or liquid, is randomly created which acts as a filter for a readout function. We develop three methods for iteratively refining a randomly generated liquid to create a more effective one. First, we apply Hebbian learning to LSMs by building the liquid with spike-time dependant plasticity (STDP) synapses. Second, we create an eligibility based reinforcement learning algorithm for synaptic development. Third, we apply principles of Hebbian learning and reinforcement learning to create a new algorithm called separation driven synaptic modification …

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Software Assurance Best Practices For Air Force Weapon And Information Technology Systems - Are We Bleeding?, Ryan A. Maxon Mar 2008

Software Assurance Best Practices For Air Force Weapon And Information Technology Systems - Are We Bleeding?, Ryan A. Maxon

Theses and Dissertations

In the corporate world, "bits mean money," and as the Department of Defense (DoD) becomes more and more reliant on net-centric warfare, bits mean national security. Software security threats are very real, as demonstrated by the constant barrage of Internet viruses, worms, Trojans, and hackers seeking to exploit the latest vulnerability. Most organizations focus their resources on reactive defenses such as firewalls, antivirus software, and encryption, however as demonstrated by the numerous attacks that are successful, those post facto measures are not enough to stop the bleeding. The DoD defines software assurance (SwA) as the "level of confidence that software …

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Demonstration Of A Strategy To Perform Two-Dimensional Diode Laser Tomography, Ryan N. Givens Mar 2008

Demonstration Of A Strategy To Perform Two-Dimensional Diode Laser Tomography, Ryan N. Givens

Theses and Dissertations

Demonstration of a strategy to perform two-dimensional diode laser tomography using a priori knowledge from symmetry arguments and computational fluid dynamic (CFD) calculations is presented for a flat flame burner. The strategy uses an optimization technique to determine flame diameter and location using a vector quantization approach. Next, the variance in a training set, produced from CFD calculations, is captured using principal components analysis. The information in the training set allows interpolation between beam paths resulting in temperature and density maps. Finally, the TDLAS temperature and density maps are shown to agree with traditional thermocouple measurements of the flat flame …

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An Image Based Bidirectional Reflectivity Distribution Function Experiment, Michael T. Hagg Mar 2008

An Image Based Bidirectional Reflectivity Distribution Function Experiment, Michael T. Hagg

Theses and Dissertations

The temperature dependence of Bidirectional Reflectivity Distribution Functions (BRDFs) is not well documented. For the sake of time and customer demand, current measurements are taken at room temperature, but the reflectivity of a material changes as a function of temperature. The assumption is that this change is uniform, and as such, the BRDF will retain its relative angular shape but perhaps be scaled in magnitude as a function of temperature. When BRDFs are to be used at elevated temperatures, a scaling factor is then applied. In addition, BRDF as a function of rate of change of temperature has been identified …

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Approximations With Improving Error Bounds For Makespan Minimization In Batch Manufacturing, Whitney Samuel Weyerman Mar 2008

Approximations With Improving Error Bounds For Makespan Minimization In Batch Manufacturing, Whitney Samuel Weyerman

Theses and Dissertations

Multipurpose batch manufacturing systems allow a suite of job types to be processed with a fixed set of machines. These types of systems are commonly found in chemical processing, as well as in computer systems and the service industry. In this thesis we consider the problem of sequencing jobs entering the manufacturing system in order to minimize makespan, or total time to complete processing of the jobs. We formulate this problem as a dynamic programming problem and illustrate the computational difficulty of solving this problem. We give a method for simulation of the system by representing each machine in the …

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Error Sensor Strategies For Active Noise Control And Active Acoustic Equalization In A Free Field, Ryan T. Chester Mar 2008

Error Sensor Strategies For Active Noise Control And Active Acoustic Equalization In A Free Field, Ryan T. Chester

Theses and Dissertations

Several measurements may be used as error signals to determine how to appropriately control a sound field. These include pressure, particle velocity, energy density and intensity. In this thesis, numerical models are used to show which signals perform best in is free-field active noise control (ANC) using error sensors located in the near field of the sound sources. The second is equalization in a free field and a semi-free field. Minimized energy density total power output (MEDToPO) plots are developed; these indicate the maximum achievable attenuation for a chosen error sensor as a function of location. A global listening area …

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Modeling Of Sbs Phase Conjugation In Multimode Step Index Fibers, Justin B. Spring Mar 2008

Modeling Of Sbs Phase Conjugation In Multimode Step Index Fibers, Justin B. Spring

Theses and Dissertations

Stimulated Brillouin scattering in a multimode step-index fiber can be used to generate a counter-propagating, phase-conjugate beam that would prove useful in many applications, such as near diffraction limited, double-pass high-power amplifiers or coherent beam combination. Relatively little modeling of such a fiber-based phase conjugator has been done, making design decisions regarding type and length of fiber largely guesswork. A numerical model was constructed with the aim of providing educated predictions about the phase conjugate fidelity that could be expected from a given pump intensity input coupled into a specific fiber. A numerical perturbation algorithm was constructed to search for …

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Improving Performance Of The Filtered-X Least Mean Square Algorithm For Active Control Of Noise Contatining Multiple Quasi-Stationary Tones, Stephan P. Lovstedt Mar 2008

Improving Performance Of The Filtered-X Least Mean Square Algorithm For Active Control Of Noise Contatining Multiple Quasi-Stationary Tones, Stephan P. Lovstedt

Theses and Dissertations

The Filtered-X Least-Mean-Square (FXLMS) algorithm is widely used in active noise control due to its robustness, simplicity, and ability to be implemented in real time. In a feedforward implementation of the FXLMS algorithm, a reference signal that is highly correlated with the noise to be controlled is filtered with an estimate of the transfer function of the secondary path. The convergence characteristics of the FXLMS algorithm have been well studied. A convergence parameter is used to optimize the convergence of the algorithm. However, the optimal value for the convergence parameter is frequency dependent. Thus for noise containing multiple tones at …

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An Examination Into How Group Performance Is Influenced By Various Communication Channels, Jason C. Norgaard Mar 2008

An Examination Into How Group Performance Is Influenced By Various Communication Channels, Jason C. Norgaard

Theses and Dissertations

This purpose of this research was to look at the how group performance is influenced by various communication channels. Specifically, this research sought to determine what communication factors are affected when groups are forced to use different communications channels. The three communications channels tested were face-to-face communications, audio conferencing, and computer-mediated communications through an Internet chat program. Each channel was measured on accuracy, efficiency, and total number of ideas generated. The research found that the groups using computer-mediated communications had a difficult time completing the exercises in the allotted time. Additionally, the computer-mediated produced significantly fewer total words and total …

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Cpg: Closed Pseudonymous Groups, Reed S. Abbott Mar 2008

Cpg: Closed Pseudonymous Groups, Reed S. Abbott

Theses and Dissertations

Internet users generally feel their actions are anonymous, but this is often not the case. Users can be tracked and their actions logged for future analysis, which is not the desire of most users. Software and services exist which offer anonymity on the Internet when used correctly. Anonymity on the Internet is useful for many people including whistleblowers, dissidents, law enforcement, and the security conscious, but it can be abused. A user can act maliciously under the guise of anonymity without the fear of retribution. Thus, a level of administrative control over users is desirable, even in an anonymous system. …

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Putting The Web Services Specifications To Rest, Dan R. Olsen Mar 2008

Putting The Web Services Specifications To Rest, Dan R. Olsen

Theses and Dissertations

Web services have become a useful and effective way of sharing information over the World Wide Web. SOAP has become a popular way of providing Web services and has been the focus of the Web Services specifications. The Web Services specifications provide additional capabilities to Web Services such as security and policy exchange. Another popular form of Web services includes light-weight Web or RESTful Web services over HTTP. These light-weight Web services are currently not addressed by the Web Services specifications. In order to provide the same capabilities to RESTful Web services, the Web Services specifications will be used to …

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Extending Web Application Development To The User-Editable Space, Brian S. Goodrich Mar 2008

Extending Web Application Development To The User-Editable Space, Brian S. Goodrich

Theses and Dissertations

The growth of the web increased dramatically when users were provided with applications that let them use just their browser to post and edit content on the World Wide Web. Offering users the ability to use their browser to create their own web applications, instead of just posting text and images, would cause another Internet evolution. This thesis describes the EXPPO system (Extensible Page Productions and Operations), a web application development environment for both end-users and technical-users. EXPPO leverages the end-user's previous experience with internet browsers by using a page based development experience or a Page Oriented Architecture. Because applications …

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Composable Distributed Access Control And Integrity Policies For Query-Based Wireless Sensor Networks, David W. Marsh Mar 2008

Composable Distributed Access Control And Integrity Policies For Query-Based Wireless Sensor Networks, David W. Marsh

Theses and Dissertations

An expected requirement of wireless sensor networks (WSN) is the support of a vast number of users while permitting limited access privileges. While WSN nodes have severe resource constraints, WSNs will need to restrict access to data, enforcing security policies to protect data within WSNs. To date, WSN security has largely been based on encryption and authentication schemes. WSN Authorization Specification Language (WASL) is specified and implemented using tools coded in JavaTM. WASL is a mechanism{independent policy language that can specify arbitrary, composable security policies. The construction, hybridization, and composition of well{known security models is demonstrated and shown to preserve …

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Skill Evaluation In Women's Volleyball, Lindsay Walker Florence Mar 2008

Skill Evaluation In Women's Volleyball, Lindsay Walker Florence

Theses and Dissertations

The Brigham Young University Women's Volleyball Team recorded and rated all skills (pass, set, attack, etc.) and recorded rally outcomes (point for BYU, rally continues, point for opponent) for the entire 2006 home volleyball season. Only sequences of events occurring on BYU's side of the net were considered. Events followed one of these general patterns: serve-outcome, pass-set-attack-outcome, or block-dig-set-attack-outcome. These sequences of events were assumed to be first-order Markov chains where the quality of each contact depended only explicitly on the quality of the previous contact but not on contacts further removed in the sequence. We represented these sequences in …

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A Bittorrent Proxy, Robert Brent Larsen Mar 2008

A Bittorrent Proxy, Robert Brent Larsen

Theses and Dissertations

BitTorrent is a peer-to-peer protocol useful for distributing large files over the Internet. Many organizations use BitTorrent to distribute their software in order to reduce client download time and reduce the load on their servers. While there is a lot of legitimate content available via BitTorrent, some organizations ban BitTorrent usage due to concerns over copyright infringement and the amount of bandwidth that peers can consume. A BitTorrent proxy will allow organizations to control those risks and allow its members to use the BitTorrent protocol for approved uses. It will allow the organization to control the files that are downloaded …

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Modulation Response Of Twin Optically Coupled Diode Lasers, Eric M. Golden Mar 2008

Modulation Response Of Twin Optically Coupled Diode Lasers, Eric M. Golden

Theses and Dissertations

Diode lasers are useful in military and commercial applications that have strict requirements for size, weight and power. This includes the use of diode lasers in optoelectronic and photonic integrated circuits, which can lead to new technologies in optical communications and optical interconnects in high performance computing systems. For these systems to be effective, the diode laser must be modulated at frequencies beyond current limits which are typically a few GHz. This barrier can be broken by optically coupling a diode laser with a similar laser. A set of single mode rate equations models the dynamics of twin optically coupled …

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A Formal Specification And Proof Of System Safety Using The Schematic Protection Model, Raymond S. Way Mar 2008

A Formal Specification And Proof Of System Safety Using The Schematic Protection Model, Raymond S. Way

Theses and Dissertations

This research formally specifies the Schematic Protection Model (SPM) and provides a sound, flexible tool for reasoning formally about systems that implement a security model like SPM, to prove its ability to provide security services such as confidentiality and integrity. The theory described by the resultant model was logically proved in the Prototype Verification System (PVS), an automated prover. Each component of SPM was tested, as were several anomalous conditions, and each test produced results consistent with the model. The model is internally modular, and therefore easily extensible, yet cohesive since the theory to be proved encompasses the entire specification. …

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An Analysis Of Groundwater Flow Patterns In A Constructed Treatment Wetland Cell, Rebecca S. Corbin Mar 2008

An Analysis Of Groundwater Flow Patterns In A Constructed Treatment Wetland Cell, Rebecca S. Corbin

Theses and Dissertations

This research effort analyzed groundwater flow paths within a treatment wetland constructed to degrade tetrachloroethylene (PCE) in groundwater. The treatment cell is a vertical flow wetland that allows the water to flow from the bottom to the surface breaking down PCE and daughter products. The method of conducting this research included collecting field data of hydraulic head contours nested piezometers and collecting data from sampling wells to determine hydraulic conductivities in the wetland. The field data was used to create a numerical computer model to determine groundwater flow patterns. The field data and the model demonstrate that there are areas …

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A Hybrid Communications Network Simulation-Independent Toolkit, David M. Dines Mar 2008

A Hybrid Communications Network Simulation-Independent Toolkit, David M. Dines

Theses and Dissertations

Net-centric warfare requires information superiority to enable decision superiority, culminating in insurmountable combat power against our enemies on the battlefield. Information superiority must be attained and retained for success in today’s joint/coalition battlespace. To accomplish this goal, our combat networks must reliably, expediently and completely deliver over a wide range of mobile and fixed assets. Furthermore, each asset must be given special consideration for the sensitivity, priority and volume of information required by the mission. Evolving a grand design of the enabling network will require a flexible evaluation platform to try and select the right combination of network strategies and …

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Multi-Objective Uav Mission Planning Using Evolutionary Computation, Adam J. Pohl Mar 2008

Multi-Objective Uav Mission Planning Using Evolutionary Computation, Adam J. Pohl

Theses and Dissertations

This investigation purports to develop a new model for multiple autonomous aircraft mission routing. Previous research both related and unrelated to this endeavor have used classic combinatoric problems as models for Unmanned Aerial Vehicle (UAV) routing and mission planning. This document presents the concept of the Swarm Routing Problem (SRP) as a new combinatorics problem for use in modeling UAV swarm routing, developed as a variant of the Vehicle Routing Problem with Time Windows (VRPTW). The SRP removes the single vehicle per target restraint and changes the customer satisfaction requirement to one of vehicle on location volume. The impact of …

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Developing A Reference Framework For Cybercraft Trust Evaluation, Shannon E. Hunt Mar 2008

Developing A Reference Framework For Cybercraft Trust Evaluation, Shannon E. Hunt

Theses and Dissertations

It should be no surprise that Department of Defense (DoD) and U.S. Air Force (USAF) networks are the target of constant attack. As a result, network defense remains a high priority for cyber warriors. On the technical side, trust issues for a comprehensive end-to-end network defense solution are abundant and involve multiple layers of complexity. The Air Force Research Labs (AFRL) is currently investigating the feasibility of a holistic approach to network defense, called Cybercraft. We envision Cybercraft to be trusted computer entities that cooperate with other Cybercraft to provide autonomous and responsive network defense services. A top research goal …

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Establishing The Human Firewall: Reducing An Individual's Vulnerability To Social Engineering Attacks, Jamison W. Scheeres Mar 2008

Establishing The Human Firewall: Reducing An Individual's Vulnerability To Social Engineering Attacks, Jamison W. Scheeres

Theses and Dissertations

Hackers frequently use social engineering attacks to gain a foothold into a target network. This type of attack is a tremendous challenge to defend against, as the weakness lies in the human users, not in the technology. Thus far, methods for dealing with this threat have included establishing better security policies and educating users on the threat that exists. Existing techniques aren’t working as evidenced by the fact that auditing agencies consider it a given that will be able to gain access via social engineering. The purpose of this research is to propose a better method of reducing an individual’s …

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Feasibility Study Of Encoding Operational Mission Metadata Into Ipv6 Packet Headers, Timothy R. Policarpio Mar 2008

Feasibility Study Of Encoding Operational Mission Metadata Into Ipv6 Packet Headers, Timothy R. Policarpio

Theses and Dissertations

The purpose of this research is to determine the feasibility of using the header fields and header extensions of IPv6 packets to encode mission metadata into computer network streams. Specifically, this thesis seeks to answer several research questions addressing the performance of different packet header encoding methods, specifically which method provides the least end-to-end delay of a file transfer over a hypothetical network as well as which method produces the least amount of additional network overhead during its operation in the hypothetical network. The research questions are answered through a comprehensive literature review and with the use of several network …

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Behavior-Based Power Management In Autonomous Mobile Robots, Charles A. Fetzek Mar 2008

Behavior-Based Power Management In Autonomous Mobile Robots, Charles A. Fetzek

Theses and Dissertations

Current attempts to prolong the life of a robot on a single battery charge focus on lowering the operating frequency of the onboard hardware, or allowing devices to go to sleep during idle states. These techniques have much overhead and do not come built in to the underlying robotic architecture. In this thesis, battery life is greatly extended through development of a behavior-based power management system, including a Markov decision process power planner, thereby allowing future robots increased time to operate and loiter in their required domain. Behavior-based power management examines sensors needed by the currently active behavior set and …

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Conceptual Study Of Rotary-Wing Microrobotics, Kelson D. Chabak Mar 2008

Conceptual Study Of Rotary-Wing Microrobotics, Kelson D. Chabak

Theses and Dissertations

This thesis presents a novel rotary-wing micro-electro-mechanical systems (MEMS) robot design. Two MEMS wing designs were designed, fabricated and tested including one that possesses features conducive to insect level aerodynamics. Two methods for fabricating an angled wing were also attempted with photoresist and CrystalBond™ to create an angle of attack. One particular design consisted of the wing designs mounted on a gear which are driven by MEMS actuators. MEMS comb drive actuators were analyzed, simulated and tested as a feasible drive system. The comb drive resonators were also designed orthogonally which successfully rotated a gear without wings. With wings attached …

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Collision Avoidance For Uavs Using Optic Flow Measurement With Line Of Sight Rate Equalization And Looming, Paul J. Shelnutt Mar 2008

Collision Avoidance For Uavs Using Optic Flow Measurement With Line Of Sight Rate Equalization And Looming, Paul J. Shelnutt

Theses and Dissertations

A series of simplified scenarios is investigated whereby an optical flow balancing guidance law is used to avoid obstacles by steering an air vehicle between fixed objects/obstacles. These obstacles are registered as specific points that can be representative of features in a scene. The obstacles appear in the field of view of a single forward looking camera. First a 2-D analysis is presented where the rate of the line of sight from the vehicle to each of the obstacles to be avoided is measured. The analysis proceeds by initially using no field of view (FOV) limitations, then applying FOV restrictions, …

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A Secure Group Communication Architecture For A Swarm Of Autonomous Unmanned Aerial Vehicles, Adrian N. Phillips Mar 2008

A Secure Group Communication Architecture For A Swarm Of Autonomous Unmanned Aerial Vehicles, Adrian N. Phillips

Theses and Dissertations

This thesis investigates the application of a secure group communication architecture to a swarm of autonomous unmanned aerial vehicles (UAVs). A multicast secure group communication architecture for the low earth orbit (LEO) satellite environment is evaluated to determine if it can be effectively adapted to a swarm of UAVs and provide secure, scalable, and efficient communications. The performance of the proposed security architecture is evaluated with two other commonly used architectures using a discrete event computer simulation developed using MatLab. Performance is evaluated in terms of the scalability and efficiency of the group key distribution and management scheme when the …

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Dynamic Behavior Sequencing In A Hybrid Robot Architecture, Jeffrey P. Duffy Mar 2008

Dynamic Behavior Sequencing In A Hybrid Robot Architecture, Jeffrey P. Duffy

Theses and Dissertations

Hybrid robot control architectures separate plans, coordination, and actions into separate processing layers to provide deliberative and reactive functionality. This approach promotes more complex systems that perform well in goal-oriented and dynamic environments. In various architectures, the connections and contents of the functional layers are tightly coupled so system updates and changes require major changes throughout the system. This work proposes an abstract behavior representation, a dynamic behavior hierarchy generation algorithm, and an architecture design to reduce this major change incorporation process. The behavior representation provides an abstract interface for loose coupling of behavior planning and execution components. The hierarchy …

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Exploitation Of Self Organization In Uav Swarms For Optimization In Combat Environments, Dustin J. Nowak Mar 2008

Exploitation Of Self Organization In Uav Swarms For Optimization In Combat Environments, Dustin J. Nowak

Theses and Dissertations

This investigation focuses primarily on the development of effective target engagement for unmanned aerial vehicle (UAV) swarms using autonomous self-organized cooperative control. This development required the design of a new abstract UAV swarm control model which flows from an abstract Markov structure, a Partially Observable Markov Decision Process. Self-organization features, bio-inspired attack concepts, evolutionary computation (multi-objective genetic algorithms, differential evolution), and feedback from environmental awareness are instantiated within this model. The associated decomposition technique focuses on the iterative deconstruction of the problem domain state and dynamically building-up of self organizational rules as related to the problem domain environment. Resulting emergent …

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Applying Automated Theorem Proving To Computer Security, Kelly K. Mcelroy Mar 2008

Applying Automated Theorem Proving To Computer Security, Kelly K. Mcelroy

Theses and Dissertations

While more and more data is stored and accessed electronically, better access control methods need to be implemented for computer security. Formal modelling and analysis have been successfully used in certain areas of computer systems, such as verifying the security properties of cryptographic and authentication protocols. However, formal models for computer systems in cyberspace, like networks, have hardly advanced. A highly regarded graduate textbook cites the Take-Grant model created in 1977 as one of the \current" examples of security modelling and analysis techniques. This model is rarely used in practice though. This research implements the Take-Grant Protection model's four de …

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