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Articles 2131 - 2160 of 2496

Full-Text Articles in Physical Sciences and Mathematics

Automated Software Testing Using Covering Arrays, Chinmay P. Jayaswal Dec 2006

Automated Software Testing Using Covering Arrays, Chinmay P. Jayaswal

Computer Science and Engineering Theses

Modern society is increasingly dependent on the quality of software systems. Software testing is a widely used approach to ensure software quality. Since exhaustive testing is impractical due to resource constraints, it is necessary to strike a balance between test efforts and quality assurance. Interaction testing is one approach to marrying these two qualities. It characterizes the system under test by a set of parameters and the respective test values (domain size) for each parameter. Instead of testing all possible combinations of values for all the parameters, interaction testing constructs a covering array as a test set to cover all …

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End-To-End Optimal Algorithms For Traffic Engineering, Failure Detection And Recovery In Connectionless Networks, Sukruth Srikantha Dec 2006

End-To-End Optimal Algorithms For Traffic Engineering, Failure Detection And Recovery In Connectionless Networks, Sukruth Srikantha

Computer Science and Engineering Theses

In this thesis we propose a novel scheme to achieve intra-domain Traffic Engineering (TE), Failure Detection and Recovery (FR) in connectionless networks. This scheme addresses rate adaptation, load balancing and stability issues of the OSPF protocol namely, network convergence times and route flapping. With the current default settings of the OSPF parameters, the network takes several tens of seconds to recover from a failure. The main component in this delay is the time required to detect the failure using the Hello protocol. Route flap is another undesirable phenomenon and needs to be eliminated to achieve greater stability and robustness in …

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Evading Existing Stepping Stone Detection Methods Using Buffering, Madhu Venkateshaiah Dec 2006

Evading Existing Stepping Stone Detection Methods Using Buffering, Madhu Venkateshaiah

Computer Science and Engineering Theses

To gain anonymity and complicate their apprehension, attackers launch attacks not from their own systems but from previously compromised systems called stepping stones. An effective way to detect stepping stones is by comparing of incoming and outgoing connections in a network to find correlations. For the sake of simplicity, earlier approaches ignore that an attacker can add chaff to a traffic stream. But in reality, the attacker may be able to modify applications to use cover traffic. We loosen some assumptions made by earlier researchers and propose a simple buffering technique that could be used by an attacker to evade …

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A Distributed Sensor Data Management Infrastructure Based On 802.15.4/Zigbee Networks, Tianqiang Li Dec 2006

A Distributed Sensor Data Management Infrastructure Based On 802.15.4/Zigbee Networks, Tianqiang Li

Computer Science and Engineering Theses

Wireless sensor networks consist of a certain number of autonomous devices with sensor, every device has certain detection functionality like light, temperature pressure etc. Communication by using the radio frequency make these spatially distributed devices feasible to oversee the activities in a large scale of area/space. 802.15.4/ZigBee networks are slated to run in the unlicensed frequencies. It is a packet-based radio protocol aimed at very low-cost, battery-operated widgets and sensors that can intercommunicate and send low-bandwidth data to each other. This thesis covers the content of a software solution of data management for an 802.15.4 networks. Its main contribution lies …

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Tracing And Replay Of Real-Time Concurrent Programs In Vxworks, Daxa Keshavji Patel Dec 2006

Tracing And Replay Of Real-Time Concurrent Programs In Vxworks, Daxa Keshavji Patel

Computer Science and Engineering Theses

Real-time concurrent programs are difficult to analyze, debug and test because of the existence of race conditions. In particular, cyclic debugging requires the ability to reproduce a failed execution. That is, when a failure is observed during a test run, it is often necessary to reproduce the test run as an effort to locate the bug that has caused the failure. However because of the variations in thread scheduling and signal latency, a real-time concurrent execution may not be reproduced simply by re-executing the program under test. In this thesis, we describe a language-based framework for tracing and replay of …

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Performance Analysis Of The Beacon Period Contraction Mechanism In Wimedia Mac For Uwb, Shenjin Sun Dec 2006

Performance Analysis Of The Beacon Period Contraction Mechanism In Wimedia Mac For Uwb, Shenjin Sun

Computer Science and Engineering Theses

The WiMedia MAC for UWB based WPANs is currently preferred among standards for wireless network since it requires non-infrastructure for ad hoc network, and also supports for Quality of Service (QoS). Without infrastructure, coordination of devices within radio range is achieved by the exchange of beacon frames, which is an overhead in WiMedia MAC, since no data transmission is allowed during Beacon Period (BP). In a dynamic network, devices might leave or join in, so beacon slots will be released or reoccupied with the changing of network. And BP contraction mechanism is aimed at reusing the released beacon slots in …

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Holographic Patterning Of Polymer Dispersed Liquid Crystal Materials For Diffractive Optical Elements, Robert Allan Ramsey Dec 2006

Holographic Patterning Of Polymer Dispersed Liquid Crystal Materials For Diffractive Optical Elements, Robert Allan Ramsey

Physics Dissertations

Liquid crystals are a soft condensed matter phase that share properties with both isotropic liquids and crystalline solids. Composite materials formed from both low molecular weight liquid crystals and polymers are of both fundamental and technological importance. One method for preparing dispersions of polymers and liquid crystals is polymerization-induced phase separation. Photo-polymerization induced phase separation utilizes a mixture of a liquid crystal and a photo curable polymer contained between two indium tin-oxide (ITO) coated glass substrates. Irradiation of the homogeneous pre-polymer mixture initiates polymerization, which in turn induces a phase separation between the polymer and liquid crystal. Holographically patterned polymer …

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Les For Wing Tip Vortex Around An Airfoil, Jiangang Cai Dec 2006

Les For Wing Tip Vortex Around An Airfoil, Jiangang Cai

Mathematics Dissertations

The wing tip vortex is very important because of its effects on the noise generation, blade/vortex interactions on helicopter blades, propeller cavitations on ships, and other fields. The objective of this work is to use the numerical simulation with high order accuracy and high resolution to investigate the formation and the near field evolution of a wing tip vortex at high Reynolds number. The computational domain includes a rectangular half-wing with a NACA 0012 airfoil section, a rounded wing tip and the surrounding boundaries. The wing has an aspect ratio of 0.75. The angle of attack is 10 degrees. The …

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Faint X‐Ray Structure In The Crab Pulsar Wind Nebula, F. D. Seward, W. H. Tucker, R. A. Fesen Dec 2006

Faint X‐Ray Structure In The Crab Pulsar Wind Nebula, F. D. Seward, W. H. Tucker, R. A. Fesen

Dartmouth Scholarship

We report on a Chandra observation of the Crab Nebula that gives the first clear view of the faint boundary of the Crab's X-ray-emitting pulsar wind nebula. There is structure in all directions. Fingers, loops, bays, and the south pulsar jet all indicate that either filamentary material or the magnetic field is controlling the relativistic electrons. In general, spectra soften as distance from the pulsar increases but do not change rapidly along linear features. This is particularly true for the pulsar jet. The termination of the jet is abrupt; the east side is close to an [O III] optical filament, …

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Mercury Exchange Between The Atmosphere And Low Mercury Containing Substrates, Mae Sexauer Gustin, Mark Engle, Jody Ericksen, Seth N. Lyman, Jelena Stamenkovic, Mei Xin Nov 2006

Mercury Exchange Between The Atmosphere And Low Mercury Containing Substrates, Mae Sexauer Gustin, Mark Engle, Jody Ericksen, Seth N. Lyman, Jelena Stamenkovic, Mei Xin

USU Uintah Basin Faculty Publications

Mercury is emitted to the air from Hg-enriched and low Hg-containing (natural background) substrates. Emitted Hg can be geogenic, or can be derived from the re-emission of Hg that was previously deposited to the soil from the atmosphere. Atmospheric Hg can be derived from natural and/or anthropogenic sources and can be deposited by wet or dry processes. It is important to understand the relative magnitude of emission, deposition, and re-emission of Hg associated with terrestrial ecosystems with natural background soil Hg concentrations because these landscapes cover large terrestrial surface areas. This information is also important for developing biogeochemical mass balances, …

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1021-0304_Mir_Irs, Michael C. Cushing Sep 2006

1021-0304_Mir_Irs, Michael C. Cushing

Publications and Research

No abstract provided.

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Generalization And Enforcement Of Role-Based Access Control Using A Novel Event-Based Approach, Raman Adaikkalavan Aug 2006

Generalization And Enforcement Of Role-Based Access Control Using A Novel Event-Based Approach, Raman Adaikkalavan

Computer Science and Engineering Dissertations

Protecting information against unauthorized access is a key issue in information system security. Advanced access control models and mechanisms have now become necessary for applications and systems due to emerging acts, such as the Health Insurance Portability and Accountability Act (HIPAA) and the Sarbanes-Oxley Act. Role-Based Access Control (RBAC) is a viable alternative to traditional discretionary and mandatory access control. RBAC has been shown to be cost effective and is being employed in various application domains on account of its characteristics: rich specification, policy neutrality, separation of duty relations, principle of least privilege, and ease of management. Existing RBAC approaches …

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Learning State And Action Space Hierarchies For Reinforcement Learning Using Action-Dependent Partitioning, Mehran Asadi Aug 2006

Learning State And Action Space Hierarchies For Reinforcement Learning Using Action-Dependent Partitioning, Mehran Asadi

Computer Science and Engineering Dissertations

Autonomous systems are often dicult to program. Reinforcement learning (RL) is an attractive alternative, as it allows the agent to learn behavior on the basis of sparse, delayed reward signals provided only when the agent reaches desired goals. Recent attempts to address the dimensionality of RL have turned to principled ways of exploiting temporal abstraction, where decisions are not required at each step, but rather invoke the execution of temporally-extended activities which follow their own policies un- til termination. This leads naturally to hierarchical control architectures and associated learning algorithms. This dissertation reviews several approaches to temporal abstraction and hierarchical …

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Investigation Of The Suitability Of The Biscatecholborate Anion As A Reductive Quencher For Photoexcited Ruthenium Polyphyridyl Complexes, Alper Yarasik Aug 2006

Investigation Of The Suitability Of The Biscatecholborate Anion As A Reductive Quencher For Photoexcited Ruthenium Polyphyridyl Complexes, Alper Yarasik

Chemistry & Biochemistry Theses

Ruthenium polypyridyl complexes [Ru(L-L)3]2+, (L-L = 1,10 - phenanthroline or 2,2'- bipyridine) which covalently linked to electron donor or acceptor units are frequently used in artificial photosystems because of their high emission quantum yields, long excited-state lifetimes, favorable redox properties and excellent chemical stability. The ruthenium dimer P, [(phen)2Ru(tatpp)Ru(phen)2][PF6]4, undergoes multiple photoreductions in the presence of donors such as triethylamine (TEA); however, large amount of donors (0.3 M) are required for efficient reductions. This explores the use of a anionic donor such as [B(cat)2]- with the hypothesis that ion-pairing will result in lower required concentration of the donor. Electrochemical data …

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Novel Approaches To Photoassisted Deposition Of Semiconductors And Nanocomposite Materials, Sashikala Somasundaram Aug 2006

Novel Approaches To Photoassisted Deposition Of Semiconductors And Nanocomposite Materials, Sashikala Somasundaram

Chemistry & Biochemistry Dissertations

This dissertation research begins with the use of TiO2-based photocatalysis for the reduction of metal ions with very negative reduction potentials. The indirect photocatalytic reduction of four metal ions: Cd2+, Zn2+, Mn2+, and Tl+ using formate radical anions generated in UV-irradiated aqueous TiO2 suspensions, is described. Using Tl+ as a model metal ion, a simple kinetics scheme was developed for the indirect reduction route, and the predictions from this model were shown to be in excellent agreement with experimental data. Titania-based photocatalysis was then used for the preparation of MSe/TiO2 "coupled" semiconductors. Heterogeneous photocatalysis using photoexcited TiO2 substrates was shown …

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Context Aware Energy Conservation In Pervasive Computing Environments, Prathiba Joseph Aug 2006

Context Aware Energy Conservation In Pervasive Computing Environments, Prathiba Joseph

Computer Science and Engineering Theses

Extending battery lifetime is one of the most critical and challenging problems in mobile systems. When the mobile device sounds a low battery alarm, the user is given an ultimatum to quickly find a power source or suspend work. The greatest utility of mobile devices is their ability to be used anywhere, and at anytime. But power limitations of these devices seem to hinder this goal. The ever-growing needs of mobile users for increased lifetime of wireless devices imply that emerging wireless systems must be more energy-efficient than ever before. Cyber foraging or remote resource exploitation may be an efficient …

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Evaluating Indexing And Routing Schemes For Spatial Queries In Sensor Networks, Raja Rajeshwari Anugula Aug 2006

Evaluating Indexing And Routing Schemes For Spatial Queries In Sensor Networks, Raja Rajeshwari Anugula

Computer Science and Engineering Theses

Recent advances in low-power sensing devices coupled with widespread availability of wireless ad-hoc networks, has fueled the development of sensor networks. These senor networks have various applications such as to monitor conditions at different locations (temperature, pressure, rainfall, vibrations etc.,), tracking of objects and so on. Each device is equipped with an energy source (usually with a battery), memory, CPU and communication bandwidth, which is severely constrained. Hence each sensor network is comprised of hardware for sensing, software for communication and computational algorithms. Spatial queries are commonly applied to sensor network, for example: "Find the highest temperature sensed in a …

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An Application Of Parallel And Distributed Computing Methods To Approximate Pattern Matching Of Genetic Regulatory Motifs, Tushar Kumar Jayantilal Aug 2006

An Application Of Parallel And Distributed Computing Methods To Approximate Pattern Matching Of Genetic Regulatory Motifs, Tushar Kumar Jayantilal

Computer Science and Engineering Theses

Bioinformatics is a relatively new scientific field concerned with providing computational means and support to research in molecular biology and genetics. It draws from many different areas of computer science, including database theory, algorithm design and analysis, and artificial intelligence, to name just a few. In many applications, such as one described in this thesis, a biologist is interested in locating a particular pattern, or sequence motif, in a given string or set of strings over the four-letter DNA alphabet. In this thesis we present an efficient approach to locating promoter and other regulatory sequences in entire genomes or in …

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Selenium Speciation Along A Groundwater Flow Path In The Carrizo Aquifer, Southeastern Texas, Usa, Rituparna Basu Jul 2006

Selenium Speciation Along A Groundwater Flow Path In The Carrizo Aquifer, Southeastern Texas, Usa, Rituparna Basu

Earth & Environmental Sciences Theses

Selenium concentration and speciation [Se (VI), Se (IV) and Se (-II)] was determined along a flow path in the Carrizo Sand aquifer (southeastern Texas). Groundwater sampling was carried out in March 2006, from ten wells located along the flow path. The collected samples were filtered through 0.45 µm filters and then acidified to pH <2 using ultra pure HCl. Analysis for Se concentration and speciation was done using selective hydride generation>- Atomic Absorption spectrometry (HG-AAS). Additional in situ measurements from each well included determination of pH, alkalinity, oxidation-reduction potential (Eh in mV), dissolved iron speciation, dissolved sulfide concentrations and dissolved manganese concentrations. Selenium concentrations in groundwaters of the Carrizo Sand aquifer are very low (i.e., nanomolal …

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Investigation Of Ruthenium (Ii) Polypyridyl Dimers As Potential Chemotherapeutic Agents, Thamara K. Janaratne Jul 2006

Investigation Of Ruthenium (Ii) Polypyridyl Dimers As Potential Chemotherapeutic Agents, Thamara K. Janaratne

Chemistry & Biochemistry Dissertations

The exploration of transition metal complexes as chemotherapeutic agents is still a relatively unexplored but promising area of research. Chapter 1 highlights the most successful anticancer drugs and potential drugs based on metal complexes, with an emphasis of platinum and ruthenium complexes. In Chapter 2, the biological activity of a series of novel ruthenium dimers is investigated with special attention given to evaluating their potential as anticancer chemotherapeutic agents. A partial list of the compound prepared includes: [Ru(bpy)(CO)2}2tpphz]4+ (74+), [Ru(bpy)(CH3CN)2}2tpphz]4+ (84+),[Ru(bpy)(C2O4)}2tpphz] (9), [Ru(bpy)(CO)(Cl)}2tpphz]2+ (102+), [(bpy)2Ru(tpphz)Ru(bpy)2]4+ (114+), [(phen)2Ru(tpphz)Ru(phen)2]4+ (124+), [(phen)2Ru(tatpp)Ru(phen)2]4+ (Pp4+), [(phen)2Ru(tatpq)Ru(phen)2]4+ (Qp4+), [(bpy)2Ru(tatpp)Ru(bpy)2]4+ (Pb4+) and [(bpy)2Ru(tatpq)Ru(bpy)2]4+ (Qb4+). Systematic changes in …

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A Relational Database Approach For Frequent Subgraph Mining, Subhesh Kumar Pradhan Jul 2006

A Relational Database Approach For Frequent Subgraph Mining, Subhesh Kumar Pradhan

Computer Science and Engineering Theses

Data mining aims at discovering interesting and previously unknown patterns from data sets. Further more, graph-based data mining represents a collection of techniques for mining the relational aspects of data represented as a graph. Complex relationships in data can be represented using graphs and hence graph mining is appropriate for analyzing data that is rich in structural relationships. Database mining of graphs, on the other hand, aims at directly mining graphs stored in a database using SQL queries. Several SQL-based mining algorithms have been developed successfully and their efficiency and scalability have been established. One of them is HDB-Subdue which …

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A Graph-Based Approach For Modeling And Indexing Video Data, Jeongkyu Lee Jun 2006

A Graph-Based Approach For Modeling And Indexing Video Data, Jeongkyu Lee

Computer Science and Engineering Dissertations

With the advances in electronic imaging, storage, networking and computing, the amount of digital video has grown tremendously. The proliferation of video data has led to significant amount of research on techniques and systems for efficient video database management. In particular, extensive research has been done on video data modeling to manage and organize the data that is semantically rich and complicated. However, the enormous amount of data size and its complexity have restricted the progress on video data modeling, indexing and retrieval. In order to get around the problems, we turn to a graph theoretical approach for video database. …

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Studies Toward The Enantioselective Total Synthesis Of The Martinella Alkaloids, Vivek Badarinarayana Jun 2006

Studies Toward The Enantioselective Total Synthesis Of The Martinella Alkaloids, Vivek Badarinarayana

Chemistry & Biochemistry Dissertations

This dissertation consists of two parts. The first part describes the enantioselective total synthesis of martinellic acid. The Martinella alkaloids have attracted considerable attention in the synthetic community over the past few years. This interest is due in large part to their unique structure and useful biological activity (bradykinin receptor antagonist). In model systems we have successfully used the [3+2] azomethine ylide-alkene cycloaddition to construct the heterocyclic core of these alkaloids. The enantioselective approach described herein also involves the azomethine ylide-alkene cycloaddition as a key step in the total synthesis. The pyrrolo[3,2-c]quinoline core of this alkaloid was constructed in an …

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Simulation Of Sensor Responses Of Advanced Security Systems, Janakiram Natarajan Jun 2006

Simulation Of Sensor Responses Of Advanced Security Systems, Janakiram Natarajan

Computer Science and Engineering Theses

Security systems are becoming an increasingly important area of research. Advanced security detection and surveillance systems that integrates a variety of detection mechanisms, like signals from different kinds of sensors, is expected to yield more accurate assessment than any one sensor analyzed individually. Designing and investigating these systems, to date, has relied primarily on physical deployments and experimentation. While the quality of the results from such efforts is excellent, the need to work with the physical systems directly imposes a substantial research impediment. One obvious possibility for widening the scope of what can be investigated is to employ simulation as …

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Exception Handling Using Class Diversity, Qizhi Ye Jun 2006

Exception Handling Using Class Diversity, Qizhi Ye

Computer Science and Engineering Theses

Software reliability has been received more and more attention not only in mission critical system but also in commercial software system. Developing robust software must consider faults caused by abnormal situations or exceptions. Although modern programming languages like Java and C++ provide sophisticated exception handling mechanisms for detecting and handling exceptions, many potential runtime exceptions are not caught and handled because runtime exceptions could occur anywhere and could be numerous in a typical program. If an uncaught runtime exception occurs during program execution, then the execution will terminate abnormally, resulting in a system crash. The thesis proposes a framework that …

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Australia's National Security: An Interview With Dr Katina Michael, G. Messaris, K. Michael May 2006

Australia's National Security: An Interview With Dr Katina Michael, G. Messaris, K. Michael

Professor Katina Michael

No abstract provided.

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Chowan River Basin North Carolina Riparian Shoreline Assessment Report – Data, Marcia Berman, Harry Berquist, Carl Hershner, Sharon Killeen, Karinna Nunez, Karen Reay, Tamia Rudnicky, David Weiss May 2006

Chowan River Basin North Carolina Riparian Shoreline Assessment Report – Data, Marcia Berman, Harry Berquist, Carl Hershner, Sharon Killeen, Karinna Nunez, Karen Reay, Tamia Rudnicky, David Weiss

Data

No abstract provided.

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Supervised Learning From Embedded Subgraphs, Joseph T. Potts May 2006

Supervised Learning From Embedded Subgraphs, Joseph T. Potts

Computer Science and Engineering Dissertations

We develop a machine learning algorithm which learns rules for classification from training examples in a graph representation. However, unlike most other such algorithms which use one graph for each example, ours allows all of the training examples to be in a single, connected graph. We employ the Minimum Description Length principle to produce a novel performance metric for judging the value of a learned classification. We implement the algorithm by extending the Subdue graph-based learning system. Finally, we demonstrate the use of the new system in two different domains, earth science and homeland security.

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Conditions For Wave Propagation Along Solar Magnetic Flux Tubes, Swati Routh May 2006

Conditions For Wave Propagation Along Solar Magnetic Flux Tubes, Swati Routh

Physics Theses

There is an intimate relation between all aspects of the solar activity and the presence of solar magnetic fields. Observations showed that the magnetic field at the photospheric level consists of magnetic flux tubes, which are located at supergranule boundaries. The flux tubes interact with the solar granulation and convection and, as a result, longitudinal, transverse and torsional magnetic tube waves are generated. These waves are responsible for carrying the energy to the upper parts of the solar atmosphere and heating the atmosphere to temperatures much higher than the solar photosphere. The energy carried by transverse and torsional waves may …

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Derivation Of Generalized Lorenz Systems To Study The Onset Of Chaos In High Dimension, Dipanjan Roy May 2006

Derivation Of Generalized Lorenz Systems To Study The Onset Of Chaos In High Dimension, Dipanjan Roy

Physics Theses

This thesis provides a new method to derive high dimensional generalized Lorenz systems. Lorenz system is a celebrated nonlinear dynamical dissipative system which was originally derived by Lorenz to study chaos in weather pattern. The classical two dimensional and dissipative Rayleigh-Benard convection can be approximated by Lorenz model, which was originally derived by taking into account only the lowest three Fourier modes. Numerous attempts have been made to generalize this 3D Lorenz model as the study of this high dimensional model will pave the way to better understand the onset of chaos in high dimensional systems of current interest in …

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