Engineering Commons^™

Selective Neural Stimulation By Leveraging Electrophysiological Diversity And Using Alternative Stimulus Waveforms, Bemin Ghobreal

Dissertations

Efforts on finding the principle mechanism for selective neural stimulation have concentrated on segregating the neurons based on their size and other geometric factors. However, neuronal subtypes found in different parts of the nervous system also differ in their electrophysiological properties. The primary objective of this study is to investigate the feasibility of selective activation of neurons by leveraging the diversity seen in passive and active membrane properties.

Using both a local membrane model and an axon model based on the CRRSS, the diversity of electrophysiological properties is simulated by varying four model parameters (membrane leakage-Gleak and capacitance-Cm, temperature coefficient-Ktemp, …

Biomechanical Loading Changes Between Species In Mild Blast-Induced Traumatic Brain Injury, Jose Juan Rodriguez

Dissertations

Blast-induced traumatic brain injury (bTBI) has become one of the leading injury modalities in military personnel and is considered a signature injury in veterans returning from conflicts in the Middle East. One of the main concerns in studying bTBI is translating animal experiments to clinical applications that can service veterans. Significant advances have been made using animal models in relating external shock waves to emerging neuropathophysiological and behavioral outcomes. However, it is unknown if these results are applicable to humans; and if so, can an interspecies transfer function be developed based on size, shape, and material response. This work aims …

An Investigation Of Three Subjective Rating Scales Of Mental Workload In Third Level Education, Nha Vu Thanh Nguyen

Dissertations

Mental Workload assessment in educational settings is still recognized as an open research problem. Although its application is useful for instructional design, it is still unclear how it can be formally shaped and which factors compose it. This paper is aimed at investigating a set of features believed to shape the construct of mental workload and aggregating them together in models trained with supervised machine learning techniques. In detail, multiple linear regression and decision trees have been chosen for training models with features extracted respectively from the NASA Task Load Index and the Workload Profile, well-known self-reporting instruments for assessing …

Numerical Simulation And Modeling Of Combustion In Scramjets, Ryan James Clark

Dissertations

In the last fifteen years the development of a viable scramjet has quickly approached the following long term goals: responsive sub-orbital space access; long-range, prompt global strike; and high-speed transportation. Nonetheless, there are significant challenges that need to be resolved. These challenges include high skin friction drag and high heat transfer rates, inherent to vehicles in sustained, hypersonic flight. Another challenge is sustaining combustion. Numerical simulation and modeling was performed to provide insight into reducing skin friction drag and sustaining combustion.

Numerical simulation was used to investigate boundary layer combustion, which has been shown to reduce skin friction drag. The …

Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy

Dissertations

The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …

Analyses Of Groundwater Contribution To A Riverine Wetland, Farzad Mahmoodinobar

Dissertations

Rainfall, runoff, overbank flow and groundwater, all contribute water to wetlands. Each transport element is associated with unique modeling approaches and uncertainties. Transpiration is perhaps the hardest to quantify as it is subject to all the variability of plant growth. Transpiration causes land area to lose moisture and the loss amount depends on precipitation incidence, the temperature and type and extent of vegetation. Plants can intercept virtually all recharge during the growing season and almost none from late fall to early spring in northeastern United States. Thus, an improvement in the transpiration element can contribute considerably to an improved groundwater …

The Incorporation Of Electrohydrodynamics And Other Modifications Into A Dry Spinning Model To Develop A Theoretical Framework For Electrospinning, Yuki Imura

Dissertations

The objective of this research was the development of a mathematical model of the electrospinning process using dry spinning modeling principles as a basis. This model is directed at the identification of parameters which influence final fiber characteristics, e.g., solvent concentration, temperature, spin line tension, and electric field. Preliminary computer simulations were performed; however, the generated data was inconclusive and was determined to be due in part to the complexity of the modeled system and the subsequent computational difficulties encountered. Although a comprehensive computational model of the electrospinning process has not yet been demonstrated, the theoretical development that was undertaken …

Influence Of Defects And Impurities On Solar Cell Performance, Vinay Budhraja

Dissertations

Multicrystalline silicon (mc-Si) solar cells exhibit high impurity content and higher density of crystal defects such as grain boundaries, dislocations, stacking faults and impurity precipitates. Even though the effect of dislocations on mc-Si solar cell performance has been studied, a severe lack of understanding of the quantitative effects of dislocations on cell parameters still exists. Some correlation has been reported under the assumption of a uniform distribution of dislocation density and a negligible effect of front and back surface recombination velocity. This assumption can cause a significant error as the current mc-Si technology provides good surface passivation by SiN:H and …

Constitutive Modeling Of The Thermo-Mechanics Associated With Crystallizable Shape Memory Polymers, Gautam Barot

Dissertations

This research addresses issues central to material modeling and process simulations. Here, issues related for developing constitutive model for crystallizable shape memory polymers are addressed in details. Shape memory polymers are novel material that can be easily formed into complex shapes, retaining memory of their original shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered by a suitable mechanism such heating the polymer above a transition temperature. Crystallizable shape memory polymers are called crystallizable because the temporary shape is fixed by a crystalline phase, while return to the original shape …

Mobile Agent Based Distributed Network Management : Modeling, Methodologies And Applications, Jian Ye

Dissertations

The explosive growth of the Internet and the continued dramatic increase for all wireless services are fueling the demand for increased capacity, data rates, support of multimedia services, and support for different Quality of Services (QoS) requirements for different classes of services. Furthermore future communication networks will be strongly characterized by heterogeneity. In order to meet the objectives of instant adaptability to the users' requirements and of interoperability and seamless operation within the heterogeneous networking environments, flexibility in terms of network and resource management will be a key design issue. The new emerging technology of mobile agent (MA) has arisen …

The Use Of A Water Quality Model To Evaluate The Impacts Of Combined Sewer Overflows On The Lower Hudson River, Wen-Pin Shu

Dissertations

CSO discharges have long been recognized as a significant source of water pollution. While many sources of water pollution have been controlled over the past 20 years, CSOs continue to be a main environmental concern in several areas, especially in old cities. In the past, most CSO research focused on the CSO control processes, including floatables and suspended solids removal. Few studies have been conducted in the area of the impacts of CSO discharge on the receiving water quality. To achieve this purpose, a powerful water-modeling tool, WASP 6.1, is utilized in this study. The Lower Hudson River is selected …