Digital Commons Network^™

Modeling Of Multi-Terminal Vsc-Based Hvdc Systems, Mohammed Mabrook Alharbi

Masters Theses

"Improving the efficiency and operation of power transmission is important due to the continual increase in demand for electric power. In addition, many remote areas throughout the world lack sufficient access to electricity. Unfortunately, utilities cannot satisfy the high demand of power by building new power stations because of economic and environmental reasons. However, utilities can increase generation and transmission line efficiencies by controlling the power flow through their systems. One new attractive technology that enables the control of power flow in the system is Voltage-Source-Converter High Voltage Direct Current (VSC-HVDC) transmission.

Multi-terminal-HVDC (M-HVDC) can be built using VSC technology. …

Data Mining And Statistical Analysis Of Completions In The Canadian Montney Formation, Mustafa Adil Al-Alwani

Masters Theses

"This thesis documents a data-mining study and statistical analysis of well completion methods and their impact on production for more than 3300 horizontal wells in the Canadian Montney resource play.

The statistical software JMP is used to analyze well and production data for both horizontal Montney gas and oil wells, examining production trends with changes in completion parameters, such as the type of completion, fluid volume pumped, proppant load, number of fracture stages and completion costs. The analysis also provides a general understanding of average treatment characteristics, and how completions have changed with time for the Montney play.

Among the …

The Effects Of Advanced Structural Materials To Mitigate Explosive And Impact Threats, Caleb Michael Baumgart

Masters Theses

"In a world of ever newer and modified improvised explosive devices (IEDs) that are very common in certain parts of the world, it is always more important to improve the devices used for protection. This research endeavors to design and analyze a blast barrier using three different media types to mitigate the high pressures from an IED or a car bomb. The three media types used in this research are pumice, steel grit, and foam. Six barriers were built to test the three media types and account for the changes from a standard solid concrete barrier to a barrier with …

Crime Pattern Detection Using Online Social Media, Raja Ashok Bolla

Masters Theses

"In this research, we show online social networks can be used to study crime detection problems. Crime is defined as an act harmful not only to the individual involved, but also to the community as a whole. It is also a forbidden act that is punishable by law. Crimes are social nuisances that place heavy financial burdens on society. Here we look at use of data mining followed by sentiment analysis on online social networks, to help detect the crime patterns. Twitter is an online social networking and microblogging service that enables users to post brief text updates, also referred …

Energy Efficient Scheduling And Allocation Of Tasks In Sensor Cloud, Rashmi Dalvi

Masters Theses

"Wireless Sensor Network (WSN) is a class of ad hoc networks that has capability of self-organizing, in-network data processing, and unattended environment monitoring. Sensor-cloud is a cloud of heterogeneous WSNs. It is attractive as it can change the computation paradigm of wireless sensor networks. In Sensor-Cloud, to gain profit from underutilized WSNs, multiple WSN owners collaborate to provide a cloud service. Sensor Cloud users can simply rent the sensing services which eliminates the cost of ownership, enabling the usage of large scale sensor networks become affordable. The nature of Sensor-Cloud enables resource sharing and allows virtual sensors to be scaled …

Effects Of Grain Properties And Compaction On Single-Tool Normal Indentation Of Granular Materials, Dennis Chieze Duru

Masters Theses

"The behavior of three granular materials; filter sand, crushed garnet, and shale cutting, were investigated in an effort to evaluate the effect of grain size and shape, and material compaction under single tool load-indentation test. Force-penetration data was collected continuously through the end of each test and specific energy and specific penetration was calculated from the data.

Grain size and compaction affected the force penetration behavior. The higher the grain size, the more the fluctuation in the force of penetration. In addition, compaction reduces the force fluctuation in the fine aggregate grains, but increases the magnitude of the force fluctuations …

Influence Of Erosional Unloading On The State Of Stress For Low Amplitude Single-Layer Buckle Folds - Implications For Tensile Fracture Occurrence, Mengke Li

Masters Theses

"The existence of fractures associated to buckle folds is related to the strain distribution of the fold. The erosional unloading process can amplify the remnant strain in the folded layer. Two-dimensional plane strain Finite Element Analysis (FEA) is used to investigate the influence of the erosional unloading step on both the evolution of the state of stress and the associated failure patterns in low amplitude buckle folds. Sensitivity analyses on different input parameters, including viscosity, shortening ratio, and overburden pressure, are performed. Based on the simulation results, tensile stress can be initiated both in the crest and in the limb …

Small-Signal Modeling Of Grid-Supporting Inverters In Droop Controlled Microgrids, Jacob Andreas Mueller

Masters Theses

"An approach to modeling externally controlled inverters in droop controlled microgrids is presented. A generic three-phase grid-tied inverter and control system model is derived in synchronous reference frame. The structure of this inverter is intended to be similar in composition to other three-phase inverters whose models and dynamics are well understood. This model is used as a starting point in the development of a more comprehensive model, which is capable of representing the coupling between complex power, bus voltage, and frequency that occurs in a microgrid. This new model is a combination of the generic inverter and an autonomous, grid-forming …

Top-K With Diversity-M Data Retrieval In Wireless Sensor Networks, Kiran Kumar Puram

Masters Theses

"Wireless Sensor Network is a network of a few to several thousand sensors deployed over an area to sense data and report that data back to the base station. There are many applications of wireless sensor networks including environment monitoring, wildlife tracking, troop tracking etc. The deployed sensors have many constraints like limited battery, limited memory and very little processing capacity. These constraints show direct effect on the network life time.

In many applications of Wireless Sensor Networks, such as monitoring chemical leak, the user is not interested in all the data points from the entire region, but may want …

Shear-Wave Splitting And Mantle Deformation Beneath The Western Tibetan Plateau, Melissa Ann Ray

Masters Theses

"The Tibetan Plateau has been an enigma to the scientific community since scientists first began to focus their attention on the area. Numerous studies over the decades were conducted to address how the plateau formed, mostly in the central and eastern portions of the Tibetan Plateau. Many questions still remain regarding the western Tibetan Plateau, and this study will add constraints to the mechanisms which regulated the formation of the plateau.

Data was acquired from over 13,000 measurements from 172 stations covering the western region of the plateau encompassing the Qiangtang Terrane, the Lhasa Terrane, and the Himalayan Orogenic Zone. …

An Iterative Algorithm For Variational Data Assimilation Problems, Xin Shen

Masters Theses

"Data assimilation is a very powerful and efficient tool to use collected raw data for improving model prediction in numerical weather forecasting, hydrology, and many other areas of geosciences. In this thesis, an iterative algorithm [23] of variational data assimilation with finite element method is utilized to study different models. One motivation for this fundamental mathematical study is to provide a potential tool for simulation of CO₂ sequestration by extending it to more realistic and sophisticated models in the future. The basic idea of variational data assimilation is to utilize the framework of optimal control problems. We apply the …

On Temporal And Frequency Responses Of Smartphone Accelerometers For Explosives Detection, Srinivas Chakravarthi Thandu

Masters Theses

"The increasing frequency of explosive disasters throughout the world in recent years have created a clear need for the systems to monitor for them continuously for better detection and to improve the post disaster rescue operations. Dedicated sensors deployed in the public places and their associated networks to monitor such explosive events are still inadequate and must be complemented for making the detection more pervasive and effective. Modern smart phones are a rich source of sensing because of the fact that they are equipped with wide range of sensors making these devices an appealing platform for pervasive computing applications. The …

Ecology Of A Declining Great Plains Fish, Fundulus Sciadicus, In The Missouri Ozarks, Gregory Travis Thompson

Masters Theses

"Anthropogenic habitat disturbances are of growing concern due to their impacts on native biota, especially in freshwater ecosystems. Damming, channelization, urbanization, wetland draining, and non-native fish introductions all play large roles in habitat homogeneity, fragmentation, and species competition. This has negative effects on native fish and invertebrate species. In the Midwestern United States, the plains topminnow (Fundulus sciadicus) has been declining across its range, to the point of becoming a species of special concern in Missouri. This is possibly due to a combination of the above anthropogenic habitat disturbances. To better understand the ecology of the plains topminnow …

Analysis And Modeling Of Resilience For Networked Systems, Kamlesh Ashok Joshi

Masters Theses

"A cyber physical system (CPS) has two main subsystems; a physical infrastructure that is responsible for managing and implementing physical tasks, e.g., generation and distribution of a physical commodity, and a cyber infrastructure that is used to support and enhance these physical operations through computing, communication, and control. Imperfect cyber control can lower the efficacy and even reliability of existing physical infrastructures. As such, justifiable reliance on CPSs requires rigorous investigation of the effect of incorporating cyber infrastructure on functional and non-functional aspects of system performance. One non-functional metric of note is resilience, defined as the ability of a system …

Numerical Simulations For Wellbore Stability And Integrity For Drilling And Completions, Nevan Christopher Himmelberg

Masters Theses

"Conventional wellbore trajectory planning is commonly based on an Andersonian state of stress [SoS] and the optimum well azimuth and inclination for a specific depth can be determined using stereographic projections of the safe mud weight window. In this thesis a new methodology using the complete stress tensor is developed to determine optimal well trajectories for complex in-situ stress scenarios. This study uses a 3D finite element analysis to simulate the SoS based on an integrated 3D MEM. The model yields the complete stress tensor at every location for a planned future well path. Using standard equations to determine the …

Improving Plasma Actuator Performance At Low Pressure, And An Analysis Of The Pointing Capabilities Of Cubesats Using Plasmonic Force Propulsion (Pfp) Thrusters, Paul Daniel Friz

Masters Theses

"This thesis details the work done on two unrelated projects, plasma actuators, an aerodynamic flow control device, and Plasmonic Force Propulsion (PFP) thrusters, a space propulsion system for small satellites.

The first half of the thesis is a paper published in the International Journal of Flow Control on plasma actuators. In this paper the thrust and power consumption of plasma actuators with varying geometries was studied at varying pressure. It was found that actuators with longer buried electrodes produce the most thrust over all and that they substantially improved thrust at low pressure. In particular actuators with 75 mm buried …

Application Of Electrically Invisible Antennas To The Modulated Scatterer Technique, Dylan Andrew Crocker

Masters Theses

"The Modulated Scatterer Technique (MST) has shown promise for applications in microwave imaging, electric field mapping, and materials characterization. Traditionally, MST scatterers consist of dipole antennas centrally loaded with a lumped element capable of modulation (commonly a PIN diode). By modulating the load element, the signal scattered from the MST scatterer is also modulated. However, due to the small size of such scatterers, it can be difficult to reliably detect the modulated signal. Increasing the modulation depth (a parameter related to how well the scatterer modulates the scattered signal) may improve the detectability of the scattered signal. In an effort …

Modelling Of Directed Energy Deposition Processes, Xueyang Chen

Masters Theses

"The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed.

In the heat transfer and fluid flow model, the governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. …

Comparison Of Costs Of Personal Protective Equipment For All Workers To Avoid Costs Of Fall Accidents, Sultan Noori Al-Karawi

Masters Theses

"The construction industry is one of the most important industries in the United States. It is the biggest contributor in the growth of the U.S. economy. Despite the great achievements and prominent role for this sector in the U.S. economy, the construction industry is suffering from neglect and dereliction by related government institutions and private companies. This neglect led to formation of a negative image about the construction industry that has caused a deep impact in productivity and economic growth. One of the reasons is a high percentage of accidents that occur within the construction industry which leads to injuries …

Quantitative Modeling Of Reliability And Survivability For Cyber-Physical Power Systems, Murtadha Nabeel Albasrawi

Masters Theses

"Critical infrastructure systems are increasingly reliant on cyber infrastructure that enables intelligent real-time control of physical components. This cyber infrastructure utilizes environmental and operational data to provide decision support intended to increase the efficacy and reliability of the system and facilitate mitigation of failure. Realistic imperfections, such as corrupt sensor data, software errors, or failed communication links can cause failure in a functional physical infrastructure, defying the purpose of intelligent control. As such, justifiable reliance on cyber-physical critical infrastructure is contingent on rigorous investigation of the effect of intelligent control, including modeling and simulation of failure propagation within the cyber-physical …

An Analytical Pressure Model To Guide Downhole Sensor Placement For Carbon Dioxide Sequestration Monitoring, Yilin Mao

Masters Theses

"Injecting CO₂ into saline aquifers is currently the most viable approach to mitigate global greenhouse gas effect. Various monitoring techniques are required to achieve 99% accuracy in determining the location of the injected CO₂ plume. Sensor locations are critical to the monitoring quality necessary to meet this requirement but have scarcely been discussed. The pressure profile needs to be modeled accurately at the initial stage of CO₂ injection to guide sensor locations. The objective of this thesis was to develop an analytical solution for CO₂ sequestration based on time and distance. This will guide the locations of downhole pressure sensors …

Hard-Switched Switched Capacitor Converter Design, Lukas Konstantin Müller

Masters Theses

"Switched capacitor (SC) converters are becoming quite popular for use in DC-DC power conversion. The concept of equivalent resistance in SC converters is frequently used to determine the conduction losses due to the load current. A variety of methodologies have been presented in the literature to predict the equivalent resistance in hard-switched SC converters. However, a majority of the methods described are difficult to apply to general SC converter topologies. Additionally, previous works have not considered all nonidealities in their analysis, such as switching losses or stray inductances. This work presents a generalized and easy to use model to determine …

The Effect Of Using Different Rock Failure Criteria In Wellbore Stability Analysis, Reza Rahimi

Masters Theses

"Determination of the appropriate drilling fluid density by rock failure analysis is an essential step to control wellbore instability. To determine wellbore failure stresses, the rock strength has to be known, an appropriate constitutive model has to be selected, and finally an accurate rock failure criterion must be chosen. Linear-poro elastic modeling of the mechanical wellbore failure is the most common approach to investigate wellbore instability. Numerous failure criteria have been used for the rock failure analysis but there is not any commonly accepted agreement of which failure criteria to use. Rock failure criteria differ in two main characteristics. First, …

M-Grid : A Distributed Framework For Multidimensional Indexing And Querying Of Location Based Big Data, Shashank Kumar

Masters Theses

"The widespread use of mobile devices and the real time availability of user-location information is facilitating the development of new personalized, location-based applications and services (LBSs). Such applications require multi-attribute query processing, handling of high access scalability, support for millions of users, real time querying capability and analysis of large volumes of data. Cloud computing aided a new generation of distributed databases commonly known as key-value stores. Key-value stores were designed to extract value from very large volumes of data while being highly available, fault-tolerant and scalable, hence providing much needed features to support LBSs. However complex queries on multidimensional …

Feasibility Study Of A Two-Fluid Small Modular Molten Salt Reactor With In Core Heat Removal Capability, Brandon James Lahmann

Masters Theses

"A feasibility study of a two-fluid small modular molten salt reactor (MSR) with in core heat removal was performed. The initial fuel block dimension for the configuration was based on the Fuji MSR. The fuel was a mixed fluoride salt of density 3.25 g/cc, composed of 71 LiF - 16 BeF₂ - 12 ThF₄- 1 ²³³UF₄ molar percentages. The coolant salt was Li₄(FLiBe) of density 1.94 g/cc. The work set out to establish whether or not such a reactor is thermodynamically feasible when optimized for various neutronics parameters. A Java based API was …

Performance Analysis Of Cutting Graphite-Epoxy Composite Using A 90,000 Psi Abrasive Waterjet, Aiswarya Choppali

Masters Theses

"Graphite-epoxy composites are being widely used in many aerospace and structural applications because of their properties: which include lighter weight, higher strength to weight ratio and a greater flexibility in design. However, the inherent anisotropy of these composites makes it difficult to machine them using conventional methods. To overcome the major issues that develop with conventional machining such as fiber pull out, delamination, heat generation and high tooling costs, an effort is herein made to study abrasive waterjet machining of composites. An abrasive waterjet is used to cut 1" thick graphite epoxy composites based on baseline data obtained from the …

Fisa Reform, Laura K. Donohue

Georgetown Law Faculty Publications and Other Works

Congress and the Executive Branch are poised to take up the issue of FISA reform in 2014. What has been missing from the discussion is a comprehensive view of ways in which reform could be given effect—i.e., a taxonomy of potential options. This article seeks to fill the gap. The aim is to deepen the conversation about abeyant approaches to foreign intelligence gathering, to allow fuller discussion of what a comprehensive package could contain, and to place initiatives that are currently under consideration within a broader, over-arching framework. The article begins by considering the legal underpinnings and challenges to the …

Ensemble Artifact Design For Context Sensitive Decision Support, Shah Jahan Miah, John G. Gammack

All Works

Although an improvement of design knowledge is an essential goal of design research, current design research predominantly focuses on knowledge concerning the IT artifact (tool) design process, rather than a more holistic understanding encompassing the dynamic usage contexts of a technological artifact. Conceptualising a design in context as an "ensemble artifact" (Sein et al., 2011) provides the basis for a more rigorous treatment. This paper describes an IS artifact design framework that has been generated from the development of several practitioner-oriented decision support systems (DSS) in which contextual aspects relevant to practitioners' decision making are considered as integral design themes. …

Mini-Track Introduction: Information Economics, Competition, Regulation, Law And Society, Eric K. Clemons, Robert John Kauffman, Thomas A. Weber

Research Collection School Of Computing and Information Systems

This mini-track is informed by the most modern thinking in information economics and competitive strategy, and includes many interdisciplinary applications of IS and technology.

Prediction Method Of The Vortex Induced Vibration Of A One Degree-Of-Freedom Spring-Mass System., Marina Iizuka Reilly-Collette

Open Access Master's Theses

Vortex Induced Vibrations (VIV) are a critical problem in the offshore industry, where interaction between flexible immersed marine structures and natural currents result in large structural oscillations. These vibrations can result in fatigue life reductions, increased factors of safety, risk of unplanned failure, reduction in operational time, and may require costly mitigation strategies. Present methods of modeling VIV used largely in industry are limited to considering motion restricted to the transverse direction relative to flow. Semi-empirical prediction methods of VIV offer a good estimate for these vibrations, but expanding them to include inline body motion would create a prohibitive increase …