Engineering Commons^™

Analysis And Comparison Of Popular Models For Current-Mode Control Of Switch Mode Power Supplies, Ramchandra M. Kotecha

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Current-mode control is the most popular scheme used for the operation of SMPS (Switch Mode Power Supplies). Current-mode control, also known as current-programmed mode or current-injected control is a multi-loop control scheme that has an inner loop and an outer voltage loop. The current loop controls the inductor peak current while the voltage loop controls the output voltage. The inner loop follows a set program by the outer loop. Some of the most popular small-signal models that predict the small-signal characteristics of current-mode control scheme have been analyzed and compared in this thesis. A PWM dc-dc buck converter in CCM(Continuous …

Performance Analysis Of Radar Waveforms For Congested Spectrums, Shaun W. Frost

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With more users populating the RF spectrum and hence less available contiguous bandwidth, radar and communication waveforms are slowly forced to become more efficient at using their available frequencies. Two scenarios are considered: operation in a colored interference environment and operation in discontiguous spectral bands. Unconstrained algorithms for designing transmit waveforms and receive filters are evaluated, wherein varying a convex weight trades performance between spectral flatness and side lobe levels. An empirical study provides performance bounds for constrained radar waveform designs for an instantiation of the interference spectrum.

Closed-form predictions for integrated sidelobe ratio (ISLR) and peak-to-sidelobe ratio (PSLR) for …

Cognitively Sensitive User Interface For Command And Control Applications, Michael James Findler

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While there are broad guidelines for display or user interface design, creating effective human-computer interfaces for complex, dynamic systems control is challenging. Ad hoc approaches which consider the human as an afterthought are limiting. This research proposed a systematic approach to human / computer interface design that focuses on both the semantic and syntactic aspects of display design in the context of human-in-the-loop supervisory control of intelligent, autonomous multi-agent simulated unmanned aerial vehicles (UAVs). A systematic way to understand what needs to be displayed, how it should be displayed, and how the integrated system needs to be assessed is outlined …

Quantitative Computed-Tomography Based Bone-Strength Indicators For The Identification Of Low Bone-Strength Individuals In A Clinical Environment, Bino Abel Varghese

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The aim of the current study was to develop quantitative computed-tomography (QCT)-based bone-strength indicators that highly correlate with finite-element (FE)-based strength. We perform a combined numerical-experimental study, comparing FE-predicted surface strains with strain gauge measurements, to validate the FE models of 36 long bones (humerus, radius, femur and tibia) under three-point bending and torsion. The FE models were constructed from trans-axial volumetric CT scans, and the segmented bone images were corrected for partial-volume effects. The material properties (Young's modulus for cortex, density-modulus relationship for trabecular bone and Poisson's ratio) were calibrated by minimizing the error between experiments and simulations among …

A Triangulation-Based Approach To Nonrigid Image Registration, Timothy R. Linden

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A triangulation-based approach to nonrigid image registration is presented. This method builds upon control point projective registration methods. Control points for this method are located using the Harris point detector. An analysis is presented for this detector to show its properties. Projective registration is used as the basis for this non-rigid registration method. Details of the projective registration method used are presented. Nonrigid registration is used to spatially align images of a 3-D scene taken from different views. Projective registration approximates the scene geometry as a plane. This nonrigid approach subdivides the images into small corresponding triangles, to improve the …

Commercial Program Development For A Ground Loop Geothermal System: Energy Loads, Gui, Turbulent Flow, Heat Pump Model And Grid Study, Paul A. Gross Ii

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The use of the earth's thermal energy to heat and cool building space is nothing new; however, the heat transfer approximations used in modeling geothermal systems, leave uncertainty and lead to over sizing. The present work is part of a Wright State effort to improve the computer modeling tools used to simulate ground loop geothermal heating and cooling systems. The modern computer processor has equipped us with the computation speed to use a finite volume technique to solve the unsteady heat equation with hourly time steps for multi-year analyses in multiple spatial dimensions. Thus we feel there is more need …

Computational Modeling And Analysis Of Heavy Fuel Feasibility In Direct Injection Spark Ignition Engine, Suniludaya Simha Moda

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Direct Injection spark ignition (DISI) technology is helpful for the present day engine to increase the fuel efficiency. Power output and the choice of fuel as the demand and scarcity for fossil fuels are increasing. As a new technology DISI engines are employed in some commercial cars like the Pontiac Solstice using gasoline fuel. The advantages of DISI engines like use of different fuels, reduced compression ratio, reduced injection pressure and reduced operating pressures in DISI engines has not been widely tested. As a new technology DISI engines lack experimental results and combustion co-relations that can be directly used as …

Predicting Vigilance Performance Under Transcranial Direct Current Stimulation, Nathaniel Reese Bridges

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A brain stimulation technology called transcranial direct current stimulation (tDCS) may potentially mitigate the vigilance decrement. To practically use such technology, however, a model is necessary that indicates vigilance performance, both when stimulation is being applied and not applied. To address this issue, the author developed models capable of predicting vigilance performance in real and control stimulation conditions using previous tDCS-study data. The "all possible combinations" regression method produced over 200 models, later screened to 10. The model with the best average %error (11.49 ± 0.10) used left hemispheric cerebral blood flow velocity (CBFVL) as its sole input term-accounting for …

Distributed Fault Detection For A Class Of Large-Scale Nonlinear Uncertain Systems, Qi Zhang

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In the distributed large-scale system, the behavior of any subsystem is not only influenced by variables belonging to it (local variables), but also by the variables in other subsystems during its interaction with neighboring subsystems. The effect of the fault in one subsystem will be quickly propagated to other subsystems due to their interconnections. Currently, most of the fault detection and diagnosis schemes are focused on centralized system which do not consider the interaction terms and can not efficiently detect the faults.

In this thesis, a distributed fault detection scheme is developed for a class of large-scale nonlinear uncertain systems …

V1-Derived Renshaw Cells And Ia Inhibitory Interneurons Differentiate Early During Development, Ana Benito González

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Locomotor development is dependent on the maturation of spinal cord circuits controlling motor output, but little is known about the development of the spinal interneurons that control motoneuron activity. This study focused on the development of Renshaw cells (RCs) and Ia inhibitory interneurons (IaINs), which mediate recurrent and reciprocal inhibition, respectively, two basic inhibitory circuits for motorneuron control. Both interneurons originate from the same progenitor pool (p1) giving rise to ventral spinal embryonic interneurons denominated V1. V1-derived interneurons (V1-INs) establish local inhibitory connections with ipsilateral motoneurons and express the transcription factor engrailed-1. This characteristic permitted the generation of transgenic mice …

Large Scale Distributed Semantic N-Gram Language Model, Yuandong Jiang

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Language model is a crucial component in statistical machine translation system. The basic language model is N-gram which predicts the next word based on previous N-1 words. It has been used in the state-of-the-art commercial machine translation systems over years. However, the N-gram model ignores the rich syntactic and semantic structure in natural languages. We propose a composite semantic N-gram language model which combines probabilistic latent semantic analysis model with N-gram as a generative model. We have implemented the proposed composite language model in a super-computer with thousand processors that is trained by 1.3 billion tokens corpus. Comparing with simple …

Energy Reduction For Asynchronous Circuits In Soc Applications, Harish Gopalakrishnan

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As complexity increases and gate sizes shrink for monolithic, mixed-signal integrated circuit (IC) technologies, two problems become dominant: substrate noise caused by digital clocks interfering with highly sensitive analog and radio frequency (RF) components and parametric variations that can cause circuit delays to vary in excess of 35%. Clockless logic (or asynchronous) circuits address both of these issues and more. Clockless, asynchronous circuits are by nature delay-insensitive making them immune to parametric variations. Even more important is the processing characteristics of clockless asynchronous circuits, which eliminate highly intricate clock signals that cause large power spikes every time they switch. Consequently, …

Small-Signal Modeling Of Resonant Converters, Agasthya Ayachit

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Resonant DC-DC converters play an important role in applications that operate at high-frequencies (HF). Their advantages over those of pulse-width modulated (PWM) DC-DC converters have led to the invention of several topologies over the traditional forms of these converters. Series resonant converter is the subject of study in this thesis. By variation in the switching frequency of the transistor switches, the optimum operating points can be achieved. Hence, the steady-state frequency-domain analysis of the series resonant converter is performed. The operational and characteristic differences between the series resonant and parallel resonant and series-parallel resonant configurations are highlighted. In order to …

Niyama Based Taper Optimizations In Steel Alloy Castings, Daniel A. Gorsky

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In the casting process, regions of shrinkage porosity can be reduced or eliminated through the implementation of taper, or small angled additions of mass on the boundaries of the part design, before risers are placed on the casting. Taper supplements the effect of risers so that a smaller riser volume is necessary to make a casting sound. Typically, taper is determined for a casting by using industry guidelines that were developed for simple two-dimensional simplifications of a complex casting. There is no accepted method of defining taper directly on part geometry aside from using expert opinions to make final decisions …

Design Of A Low Power And Area Efficient Digital Down Converter And Sinc Filter In Cmos 90-Nm Technology, Steven John Billman

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A digital down converter (DDC) typically receives a digital input that has been generated by an analog to digital converter (ADC) operating at intermediate frequency (IF) in an RF receiver chain. The function of the DDC is to down convert the IF signal to baseband in phase (I) and quadrature (Q) signals and is a very important component in wireless receivers. A Digital Down Converter (DDC) is developed based on square wave local oscillators facilitating a multiplier-less implementation with no constraints on the sampling frequency. The DDC includes a pseudo multi-rate SINC low pass filter which exhibits better performance compared …

Human Micro-Range/Micro-Doppler Signature Extraction, Association, And Statistical Characterization For High-Resolution Radar, Orelle Ryan Fogle

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Recently, the use of micro-Doppler (μD) radar signatures for classification has become an area of focus, in particular for the case of dynamic targets where many components are interacting over time. To fully exploit the signature information, individual scattering centers may be extracted and associated over the full target observation. Due to the complexity of the target signature, the automated analysis is very difficult. However, the availability of ultra-fine resolution or micro-range (μR) resolution along with target scattering knowledge, can aid this process immensely. Here, we describe a feature extraction algorithm which utilizes both μD and …

Framework For Cohesive Zone Model Based Multiscale Damage Evolution In A Fatigue Environment, Michael Andrew Thomas

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The focus of this research is to develop a framework to track damage evolution in a structural model subjected to a fatigue environment. This framework incorporates a micromechanical approach of continuous damage modeling, where damage in a homogenized representative microstructure is introduced at the continuum scale through the material constitutive matrix. In this research, damage in the representative microstructure is simulated utilizing cohesive zone models (CZM) whose properties are a function of the magnitude of applied stresses and the resulting separation. In order to minimize the mesh dependence of the cohesive zone model an adaptive meshing technique is employed. A …

Self-Calibrating Cricket Motes For Indoor Navigation, Yogendra Jayant Patil

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Global Positioning System (GPS) plays a vital role for providing localization to the autonomous robots. But the quality of the GPS signal degrades in an indoor location and hence GPS cannot be used for indoor localization. Cricket motes are location-aware system that can provide localization service to its users in an indoor location. Cricket motes apply the acoustic ranging technique to find distance between two points. But before a user can use this localization system, assigning coordinate system to the motes requires manual assistance. This project presents a novel algorithm for self-calibration of the cricket motes to a coordinate system …

Multi-Objectivization In Genetic Algorithms, Darrell F. Lochtefeld

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Multi-objectivization is the process of reformulating a single-objective problem into a multi-objective problem and solving it with a multi-objective method in order to provide a solution to the original single-objective problem. Multi-objectivization differs from other traditional divide-and-conquer techniques-the method splits the objective function rather than the search space. Prior to recent evidence, such reformulations were thought to make a problem more complex. However, more recent research suggests that decomposition in the objective space can lead to useful optimization techniques when coupled with a population-based search. Machine based optimization techniques are varied but often based upon an analogy to real-world phenomena. …

Influence Of Design Parameters On Cup-Stem Orientations For Impingement Free Range Of Motion In Hip Implants, Dishita Prakashbhai Patel

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The objective of this investigation is to determine the optimum positions of the prosthesis in total hip arthroplasty that produce least amount of impingement. Theoretical ranges of six basic hip motions were determined under walking, stumbling, internal rotation at 90 flexion and external rotation at 0 extension with 15 abduction, using mathematical models and validated for impingement using finite element analysis. A generalized approach, where impingement does not occur, was developed in this study to understand influence of design parameters such as head-neck ratio, neck-shaft angle, oscillation angle, and stem offset on cup-stem orientations such as cup inclination, cup anteversion, …

Surface Stress Sensors For Closed Loop Low Reynolds Number Separation Control, Christopher R. Marks

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Low Reynolds number boundary layer separation causes reduced aerodynamic performance in a variety of applications such as MAVs, UAVs, and turbomachinery. The inclusion of a boundary layer separation control system offers a way to improve efficiency in conditions that would otherwise result in poor performance. Many effective passive and active boundary layer control methods exist. Active methods offer the ability to turn on, off, or adjust parameters of the flow control system with either an open loop or closed loop control strategy using sensors. This research investigates the use of a unique sensor called Surface Stress Sensitive Film (S3F) in …

Highly Active Porous Catalysts Fabricated By Attachment Of Palladium Nanoparticles On Hierarchical Carbon Structures, Hema Vijwani

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The effectiveness of metal-based catalysts can be significantly enhanced by increasing the available surface area relative to the volume through the creation of hierarchical nanostructures. The catalyst demonstrated here is palladium, which is a widely recognized heterogeneous catalyst suitable for a variety of industrial applications such as water purification, hydrogen storage, and electrochemical devices. In this study, a novel multi-scale supporting material developed in this group, has been used as support. It consists of micro-porous graphitic carbon with strongly attached carbon nanotubes. This can increase the surface area by orders of magnitude without increasing the size or weight while still …

Multidisciplinary Optimization Framework For High Speed Train Using Robust Hybrid Ga-Pso Algorithm, Veera Venkata Sunil Kumar Vytla

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High speed trains are the most efficient means of public transportation. However the speed of the train needs to be increased (> 350 km/hr) to cover large distances in a short time to make it accessible to large population. With the increase in speed, number of issues related to efficiency, safety and comfort like the aerodynamic drag, structural strength, as well as the noise levels inside and outside of the train etc. need to be considered in the design of the high speed trains. Hence making it a multi disciplinary design problem. There are a large number of parameters from …

A Study On The Effects Of Coil Wedge During Rewinding Of Thin Gauge Metals, Jantzen L. Hinton

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With the increase in demand for high quality thin gauge metals improvements to control systems that monitor strip characteristics must first be acquired. During the rewinding of sheet metal, little insight is known as to what stresses are attributed to the actual winding process, not simply those induced by the mill. When winding effects become too severe they will alter control system readings, prompting the need for a rapid model that can predict winding effects and filter them from current control systems. This research develops a new method to determine a 4th order Airy function that predicts the 2D stress …

Computational Investigation Of Optimal Heavy Fuel Direct Injection Spark Ignition In Rotary Engine, Asela A. Benthara Wadumesthrige

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The main objective of this computational study is to investigate the optimum injection and spark parameters for the direct injection spark ignition (DISI) Wankel rotary engine using diesel fuel. Currently only port fuel injected gasoline rotary engines are available in the automotive industry. Compared to reciprocating type engines rotary engine is mechanically simple, less vibrate, have higher power to weight ratio and achieve better performance at high rpm. Due to the inherent low fuel efficiency of rotary engine and increasing gas prices, application of the rotary engine in conventional automobiles is decreasing. This project seeks to introduce DISI technology to …

A Probabilistic Assessment Of Vertebral Cortical Bone Fracture Of Intraosteonal Structures, Isaac Graham Mabe

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Cortical bone is a porous structure. The presence of these pores creates the possibility of a local overstressed area that has the likelihood of premature failure. Some failure modes of the vertebral endplates, for example subsidence which occurs at rates as high as 77 percent, can be better predicted with further understanding of failure mechanisms and the ability to predict those mechanisms. A probabilistic assessment of the pore size and its contribution to the fracture toughness has not been investigated in the cortical shell of the vertebral endplates. This research develops a probabilistic model that has the ability to determine …

Weapon Engagement Zone Maximum Launch Range Approximation Using A Multilayer Perceptron, Brian Michael Birkmire

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This thesis investigates the use of an artificial neural network (ANN), in particular a Multi-Layer Perceptron (MLP), to perform function approximation on truth data representing a weapon engagement zone's (WEZ) maximum launch range. The WEZ of an air-to-air missile represents the boundaries and zones of effectiveness for a one-vs-one air-to-air combat engagement [13]. The intent is for the network to fuse table lookup and interpolation functionality into a physically compact and computationally efficient package, while improving approximation accuracy over conventional methods. Data was collected from simulated firings of a notional air-to-air missile model and used to train a two layer …

Design And Development Of A Fall Detection Device With Infrared Receiving Capabilities, Ammari Ramzi

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Fall related injuries are the leading cause of death and hospitalization among the elderly. Falls among older people become a major problem facing hospitals and nursing homes. In this study we put an effort to design a wireless device capable of detecting falls with the hope that this study will provide a path towards better healthcare monitoring and better independent living for the elderly.

In this project I showed how the fall detection device can be interfaced with different systems to achieve functionality without adding extra cost. For seniors who prefer to stay at their homes and live independently, the …

An Implicit High-Order Spectral Difference Method For The Compressible Navier-Stokes Equations Using Adaptive Polynomial Refinement, Caleb J. Barnes

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A high/variable-order numerical simulation procedure for gas dynamics problems was developed to model steep grading physical phenomena. Higher order resolution was achieved using an orthogonal polynomial Gauss-Lobatto grid, adaptive polynomial refinement and artificial diffusion activated by a pressure switch. The method is designed to be computationally stable, accurate, and capable of resolving discontinuities and steep gradients without the use of one-sided reconstructions or reducing to low-order. Solutions to several benchmark gas-dynamics problems were produced including a shock-tube and a shock-entropy wave interaction. The scheme's 1st-order solution was validated in comparison to a 1st-order Roe scheme solution. Higher-order solutions were shown …

Fusion Of Video And Multi-Waveform Fmcw Radar For Traffic Surveillance, Nicholas C. Gale

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Modern frequency modulated continuous wave (FMCW) radar technology provides the ability to modify the system transmission frequency as a function of time, which in turn provides the ability to generate multiple output waveforms from a single radar unit. Current low-power multi-waveform FMCW radar techniques lack the ability to reliably associate measurements from the various waveform sections in the presence of multiple targets and multiple false detections within the field-of-view. Two approaches are developed here to address this problem.

The first approach takes advantage of the relationships between the waveform segments to generate a weighting function for candidate combinations of measurements …