Digital Commons Network^™

Understanding The Origin Of The Recovery Of Superconductivity In Halogenated Ybco Single Crystal : Atomic Structure Study, Lamine Mohamed Kollakoye Dieng

Dissertations

The recovery of superconductivity in underdoped YBa₂Cu₃O_6+y (YBCO) by exposure to bromine, iodine, chlorine and fluorine is a long-standing problem which has not been clearly resolved. The key question concerns the role of these halogens in the lattice. In order to shed light to this problem, we have performed multiple-edge x-ray absorption fine structure (XAFS) measurements about the Y K, Ba L₃, I L₃, Cu K and Br K-edges at room temperature on brominated (non-brominated) and iodinated (non-iodinated) YBCO single crystals. Our XAFS results at the Br K (brominated) and I …

Performance Evaluation Of Communication Systems With Transmit Diversity, Chunjun Gao

Dissertations

Transmit diversity is a key technique to combat fading with multiple transmit antennae for next-generation wireless communication systems. Space-time block code (STBC) is a main component of this technique. This dissertation consists of four parts: the first three discuss performance evaluation of STBCs in various circumstances, the fourth outlines a novel differential scheme with full transmit diversity.

In the first part, closed-form expressions for the bit error rate (BER) are derived for STBC based on Alamouti's scheme and utilizing M-ary phase shift keying (MPSK) modulation. The analysis is carried out for a slow, flat Rayleigh fading channel with coherent detection …

Efficient Similarity Search In High-Dimensional Data Spaces, Yue Li

Dissertations

Similarity search in high-dimensional data spaces is a popular paradigm for many modern database applications, such as content based image retrieval, time series analysis in financial and marketing databases, and data mining. Objects are represented as high-dimensional points or vectors based on their important features. Object similarity is then measured by the distance between feature vectors and similarity search is implemented via range queries or k-Nearest Neighbor (k-NN) queries.

Implementing k-NN queries via a sequential scan of large tables of feature vectors is computationally expensive. Building multi-dimensional indexes on the feature vectors for k-NN search also tends to be unsatisfactory …

A Discovery And Analysis Of Influencing Factors Of Pair Programming, Kyungsub Steve Choi

Dissertations

The exploration into the underlying psychosocial links of pair programming. a new and unorthodox programming paradigm in which two programmers share one keyboard and monitor during real-time programming sessions, is undertaken. These complex psychosocial relationships, along with cognitive process exchanges, ultimately mold the programming output as well as determine the level of communication, satisfaction. confidence and compatibility. Laying the framework for this research, a through review of traditional and contemporary paradigms with a special focus on their limitations and a list of current software development problems are presented. Next, a detailed summary of pair programming and related agile software paradigms, …

On Ip Over Wdm Burst-Switched Long Haul And Metropolitan Area Networks, Jingxuan Liu

Dissertations

The IP over Wavelength Division Multiplexing (WDM) network is a natural evolution ushered in by the phenomenal advances in networking technologies and technical breakthroughs in optical communications, fueled by the increasing demand in the reduction of operation costs and the network management complexity. The unprecedented bandwidth provisioning capability and the multi-service supportability of the WDM technology, in synergy with the data-oriented internetworking mechanisms, facilitates a common shared infrastructure for the Next Generation Internet (NGJ).

While NGI targets to perform packet processing directly on the optical transport layer, a smooth evolution is critical to success. Intense research has been conducted to …

The Design Of Adjustable Spherical Mechanisms Using Plane-To-Sphere And Sphere-To-Plane Projections, Wen-Tzong Lee

Dissertations

The spherical mechanism is a particular type of spatial mechanism. Due to the orientation of its joint axes and the curvature of its links, the workspaces of spherical mechanisms (whether line segments, closed loops or area regions) are spherical in curvature. This characteristic of spherical mechanisms makes them quite effective and practical in motion path and function generation applications requiring spherical rigid body kinematics.

Although there are design methods available for spherical mechanisms, most of these methods do not consider the design of a single adjustable spherical mechanism. With an adjustable spherical mechanism, the user could for example, relocate the …

Studies Of Disk Arrays Tolerating Two Disk Failures And A Proposal For A Heterogeneous Disk Array, Chunqi Han

Dissertations

There has been an explosion in the amount of generated data in the past decade. Online access to these data is made possible by large disk arrays, especially in the RAID (Redundant Array of Independent Disks) paradigm. According to the RAID level a disk array can tolerate one or more disk failures, so that the storage subsystem can continue operating with disk failure(s). RAID 5 is a single disk failure tolerant array which dedicates the capacity of one disk to parity information. The content on the failed disk can be reconstructed on demand and written onto a spare disk. However, …

Development Of Dynamic Recursive Models For Freeway Travel Time Predictions, Xiaobo Liu

Dissertations

Traffic congestion has been a major problem in metropolitan areas, which is caused by either insufficient roadway capacity or unforesceable incidents. In order to promote the efficiency of the existing roadway networks and mitigate the impact of traffic congestion, the development of a sound prediction model for travel times is desirable.

A comprehensive literature review about existing prediction models was conducted by investigating the advantages, disadvantages, and limitations of each model. Based on the features and properties of previous models, the base models including exponential smoothing model (ESM), moving average model (MAM), and Kalman filtering model (KFM) are developed to …

A Gibbs Sampling Approach To Maximum A Posteriori Time Delay And Amplitude Estimations, Michele Picarelli

Dissertations

Research concerned with underwater propagation in a shallow ocean environment is a growing area of study. In particular, the development of fast and accurate computational methods to estimate environmental parameters and source location is desired. In this work, only select features of the acoustic field are investigated, namely, the time delays and amplitudes of individual paths, the signal-to-noise ratio, and the number of multi-path arrivals. The amplitudes and delays contain pertinent information about the geometry associated with the environment of interest. Estimating the time delays and amplitudes of select paths in a manner that is both accurate and time efficient, …

Multi-Rate Access Schemes And Successive Interference Cancellation For Wireless Multimedia Mc-Cdma Communications, Mizhou Tan

Dissertations

To catch up with the fast changes of the information challenges, providing multimedia services has become a very important requirement for future wireless communications. A proper system, capable of supporting multi-rate transmissions as well as handling high quality of service (QoS) requirements in hostile wireless communication environments, should be sought. Multi-carrier CDMA (MC-CDMA), a combination of multi-carrier modulation (MCM) and direct-sequence CDMA (DS-CDMA), appears to be one of the most elegant solutions. In this dissertation, four multi-rate access schemes, termed uncoded fixed spreading length (UFSL), coded fixed spreading length (CFSL), multi-code fixed spreading length (MFSL) and variable spreading length (VSL), …

An Approximate Search Engine For Structure, Huiyuan Shan

Dissertations

As the size of structural databases grows, the need for efficiently searching these databases arises. Thanks to previous and ongoing research, searching by attribute-value and by text has become commonplace in these databases. However, searching by topological or physical structure, especially for large databases and especially for approximate matches, is still an art.

In this dissertation, efficient search techniques are presented for retrieving trees from a database that are similar to a given query tree. Rooted ordered labeled trees, rooted unordered labeled trees and free trees are considered. Ordered labeled trees are trees in which each node has a label …

Phase Noise Effects On Ofdm : Analysis And Mitigation, Songping Wu

Dissertations

Orthogonal frequency division multiplexing (OFDM) is a promising technique which has high spectrum efficiency and the robustness against channel frequency selectivity. One drawback of OFDM is its sensitivity to phase noise. It has been shown that even small phase noise leads to significant performance loss of OFDM. Therefore, phase noise effects on OFDM systems need to be analyzed and methods be provided to its mitigation.

Motivated by what have been proposed in the literature, the exact signal to interference plus noise ratio (SINR) is derived in this dissertation for arbitrary phase noise levels. In a multiple access environment with multiple …

Ad Hoc Network Security And Modeling With Stochastic Petri Nets, Congzhe Zhang

Dissertations

Advances in wireless technology and portable computing along with demands for high user mobility have provided a major promotion toward the development of ad hoc networks. These networks feature dynamic topology, self-organization, limited bandwidth and battery power of a node. Unlike the existing commercial wireless systems and fixed infrastructure networks, they do not rely on specialized routers for path discovery and traffic routing. Security is an important issue in such networks. Typically, mobile nodes are significantly more susceptible to physical attacks than their wired counterparts.

This research intends to investigate the ad hoc network routing security by proposing a performance …

Uncertainty Analysis In Ecological Risk Assessment Modeling, Tepwitoon Thongsri

Dissertations

A probabilistic approach employing Monte Carlo simulations for assessing parameter and risks as probabilistic distributions was used in an ecological risk assessment (ERA) model to characterize risk and address uncertainty. This study addresses the following sources of uncertainty: parameter inputs in the ERA models, risk algorithms and uncertain input concentrations. To achieve this objective, both sensitivity and uncertainty analyses are being conducted. Monte Carlo simulations were used for generating probabilistic distributions of parameter and model uncertainty. All sensitivity, uncertainty, and variability analyses were coded in Visual Basic as part of the ERA model software version 2001, which was developed under …

Ultra-Wideband Technology For Short-Range Wireless Communication, Li Zhao

Dissertations

The ultra-wideband (UWB) radio core idea is to open large amounts of spectrum to a variety of users with little mutual interference between them. While ultra-wideband is being championed by several commercial companies, this technology has not followed the conventional path where commercial interest is preceded by years of academic research. This work attempts to fill in some of the gap by studying fundamental properties of communications with impulse-based radio UWB signals. We study jam resistance and capacity of UWB. Jam resistance is analyzed for binary pulse position modulation (PPM) with the interference being modeled as correlated Gaussian. Closed-form expressions …

Mixing Enhancement By Dual Speed Rotating Stirrer, Arnaud Goullet

Dissertations

Stirring is a well-known means of fluid mixing due to the emergence of complex patterns in the flow, even at low Reynolds numbers. In this work, we consider a stirrer rotating along a circular trajectory at constant speed. The fluid flow, considered incompressible, inviscid and two dimensional (in a circular container), is modeled by a point vortex model consisting of a vortex rotating in a circular container at constant angular speed. The mixing problem is addressed by considering the Hamiltonian form of the advection equations formulated in a frame of reference moving with the vortex. The dynamics of passive fluid …

Enriching And Designing Metaschemas For The Umls Semantic Network, Li Zhang

Dissertations

The disparate terminologies used by various biomedical applications or professionals make the communication between them more difficult. The Unified Medical Language System (UMLS) of the National Library of Medicine (NLM) is an attempt to integrate different medical terminologies into a unified representation framework to improve decision making and the quality of patient care as well as research in the health-care field. Metathesaurus (META) and Semantic Network (SN) are two main components of the UMLS system, where the SN provides a high-level abstract of the concepts in the META.

This dissertation addresses three problems of the SN. First, the SN's two-tree …

Nonlinear Long-Wave Interfacial Stability Of Two-Layer Gas-Liquid Flow, Tetyana Segin

Dissertations

The flow of two immiscible viscous fluids in a thin inclined channel is considered, in either a cocurrent or countercurrent regime. Following the air-water case, which is found in a variety of engineering systems, we allow the upper fluid to be either compressible or incompressible. The disparity of the length scales and the density and viscosity ratios of the two fluids is exploited through a lubrication approximation of the conservation of mass and the Navier-Stokes equations. As a result of this long-wave theory, a coupled nonlinear system of partial differential equations is obtained that describes the evolution of the interfacial …

Wresting And Arresting Sense In Academe: The Complicated Discursive Structures Of Female Assistant Professors, Alana M. Nicastro Edd

Dissertations

Women in academe often become entangled in an intricate equation of sensemaking as they work to balance the professional demands of teaching, research, and service, while at the same time learning the political and moral meanings of being a scholar. Structuration theory offers avenues for closely examining communicative strategies women utilize to navigate their roles as assistant professors. Through intensive interviews with seven female assistant professors this research investigates their process of wresting and arresting sense of the complicated roles, rules, and structures in academe. Analysis of interview data reveals the multiple discourses that frame organizational practices that facilitate and …

Organizational Structure And The Creative Process, Edward C. Bowen Edd

Dissertations

A creative edge can be a powerful source of competitive advantage in business, in war, in the arts, in science, and in life. In fact, creativity, innovation and the ability to adapt and change organizational structures in response to an increasingly fast-paced and competitive business environment are increasingly seen as essential for the success of many organizations. A current trend in organizational theory associates increases in formalization and both horizontal and vertical integration with decreases in an organization's ability to innovate and adapt. Consequently, organizational change efforts often involve moving from traditional, hierarchical structures toward flatter, more flexible types of …

Implementing Student Learning Outcomes: The Link To Accreditation In California Community Colleges, Lori Waite Edd

Dissertations

As the public demands accountability in higher education, regional accrediting bodies are under pressure from external governmental agencies, as well as from key stakeholders, to demonstrate their effectiveness and more specifically, provide evidence of student learning. All regional accrediting agencies now have incorporated some level of student learning outcomes into their criteria for reaffirmation of accreditation. This case study describes how three California public community colleges are implementing student learning outcomes on their campuses. Administrators, faculty and staff were interviewed about perceptions and insights related to learning outcomes. Artifact analysis was conducted to establish credibility and data triangulation. Findings suggest …

Explicit Writing Instruction: Effects On Sixth Grade Students’ Writing And Reading Achievement, Jennifer Hamby Edd

Dissertations

The purpose of this quantitative study was to examine the effect of explicit writing instruction on sixth grade students' writing growth and achievement as measured by holistic and analytic assessment. This research responds directly to the need for additional research on effective reading and writing instruction (Langer & Allington, 1992; The College Board, 2003). The preponderance of research in writing has been devoted to early writing. Less evidence is available to examine the effect of writing instruction at the sixth grade level. Writing samples from 124 sixth grade students at two elementary schools were used in this study. The two …

Use Of Evaluation Findings In Michigan’S 21St Century Community Learning Center Programs, Wendy L. Tackett

Dissertations

There is a lack of empirical evidence demonstrating the use of evaluation findings within grant programs such as the 21st Century Community Learning Centers programs (CCLCs). This study was designed using Michigan's federally-funded CCLCs to meet the following purposes: to explore the use of evaluation findings; to determine the relationship of the use of evaluation findings by local school administrators to the employment of an internal or external evaluator; to identify evaluator qualifications connected to evaluation use; and to determine whether there are relationships between the Program Evaluation Standards (Joint Committee on Standards for Educational Evaluation, 1994) utility domains and …

Using The History Of Research On Sickle-Cell Anemia To Affect Preservice Teachers’ Conceptions Of The Nature Of Science, Eric M. Howe

Dissertations

Preservice elementary teachers enrolled in an elective biology course participated in an eight-class unit of instruction based on the history of research in understanding the disease sickle-cell anemia. Students were introduced to the disease as a “mystery” for them to solve, and subsequently developed an understanding of the disease from several disciplines in biology (e.g., genetics, ecology, evolution, molecular biology). The unit involved open-ended problems in which students examined evidence and developed explanations in a manner analogous to the reasoning used by Anthony C. Allison and his colleagues during the early to middle part of the twentieth century.

Throughout the …

Studies Of Atomic And Molecular Dynamics Using Photoelectron Spectroscopy, Sophie E. Canton

Dissertations

Photoexcitation and photoionization studies of free atoms and molecules in the gas phase provide a unique view into various aspects of radiation-matter interactions that are used as basic building blocks in many branches of physics, such as Solid State, Plasma Physics, Photochemistry or Astrophysics. With the advent of third generation synchrotron light sources delivering high photon flux (>10¹⁵ photons/s) with unprecedented resolving power over a broad energy range, it has become possible to investigate in great detail not only the internal structure of the targets, but also the dynamics of the process. Born in the 1960s,photoelectron spectroscopy specifically …

Chemical And Isotopic Investigation Of Groundwater In Eastern United Arab Emirates (Uae), Ahmed Ali Abdalla Murad

Dissertations

UAE is located at the southeast of Arabian Peninsula. Two main aquifers occupy the study area: the Eastern Gravel Plain and Ophiolite aquifer. Increasing salinity of groundwater and depletion of aquifers are a major concern in the UAE. Previous studies suggest that groundwater, particularly in the Eastern Gravel Plain aquifer, is affected by seawater intrusion and evaporation. Isotopes of oxygen, hydrogen, carbon and chlorine, and chemical analyses were used to investigate this problem in detail. Samples of groundwater from the Eastern Gravel Plain aquifer have R³⁶Cl values in the range of 13.3 to 17.4 x10^-15 while those …

Comparative And Contributive Effects Of Process And Human Performance Improvement Strategies, Joseph R. Sasson

Dissertations

Organizational leaders know that the success of their organization depends on the organization's ability to either produce better products or produce equally good products at a lower cost to consumers. Interventions aimed at improving organizational performance stem from two primary perspectives. One perspective emphasizes changing system factors (e.g., equipment and processes) and the other perspective emphasizes changing human performance factors (e.g., performance specifications and behavioral consequences). The current study evaluated the comparative and contributive effects of process improvement techniques (Kock, 1999; Melan, 1992; Rummler & Brache, 1995) and human performance improvement techniques (Daniels, 1989; Gilbert, 1996; Rummler & Brache, 1995), …

A Study Of The Relationship Between Transformational Leadership And Organizational Culture, Mildred Patricia Howard

Dissertations

The research study examines teachers' perspectives on leadership and Organizational Culture in elementary schools within the state of Michigan. Teachers respond to more than 90 survey questions from the Leadership Practices Inventory and the Instructional Climate Inventory.

The purpose of the study is to determine the relationship that exists between Transformational Leadership and Organizational Culture. The study also considers school size as an interval variable. Statistical tests used to determine possible relationships include F-Tests, T-Test and Canonical Correlations.

Findings suggest that additional studies may be warranted based on particular subscales of Transformational Leadership and also size as it relates to …

Adaptive Learning For Event Modeling And Pattern Classification, Shuangshuang Dai

Dissertations

It is crucial to detect, characterize and model events of interest in a new propulsion system. As technology advances, the amount of data being generated increases significantly with respect to time. This increase substantially strains our ability to interpret the data at an equivalent rate. It demands efficient methodologies and algorithms in the development of automated event modeling and pattern recognition to detect and characterize events of interest and correlate them to the system performance. The fact that the information required to properly evaluate system performance and health is seldom known in advance further exacerbates this issue.

Event modeling and …

Virtual Teams Combining Mobile Devices With Web-Based Communication On Group Decision Making, Hyo-Joo Han

Dissertations

Organizations have moved from a face-to-face team environment to a virtual team environment using communication technology during the last decade. More and more workers use asynchronous tools (including email, discussion groups, information sharing tools, and group calendaring systems), and synchronous tools, such as instant messaging and web-based chatting features, to coordinate and share information with people within and outside of organizations. This empirical study on how virtual teams work, integrating mobile devices with web-based group communication for decision-making tasks, examines which technologies and communication modes are the best for distributed group teamwork, and, mainly, what are the predictive characteristics making …