Engineering Commons^™

Intermodal Commuter Network Planning, Maria P. Boile

Dissertations

An intermodal commuter network is an integration of passenger transportation systems, or modes, to a single comprehensive system that provides connections among the various modes, and improved travel choices to users. In the system examined in this dissertation, commuters access their final destination via auto, rail, and intermodal auto-to-rail modes. There are numerous highway paths by which a commuter can reach the final destination. Once on the highway, the commuter can switch to rail at stations along the rail route. The commuter may also choose to walk to the rail station closest to the trip's origin.

The main focus of …

Removal Of Vocs From Air By Absorption And Stripping In Hollow Fiber Devices, Tarun K. Poddar

Dissertations

Large volumes of exhaust air streams contaminated with volatile organic compounds (VOCs) such as toluene, xylene, acetone etc. are discharged into the atmosphere by various industrial facilities. Common technologies for VOC emission abatement e.g., activated carbon adsorption, absorption in a liquid, incineration and catalytic oxidation, have many strengths as well as considerable limitations. In this study, a regenerative absorption-based removal of VOCs from N₂ in an inert, nonvolatile, organic liquid flowing in compact hollow fiber devices has been developed. The process eliminates flooding, loading and entrainment encountered in conventional absorption devices.

Contaminated air/N₂ stream was fed through the …

Computer-Aided Process Design For Waste Minimization, Konstadinos Abeliotis

Dissertations

Problems related to process design with environmental considerations have been studied in this dissertation. A new heuristic design methodology has been formulated with the objective of minimizing the adverse environmental impact of chemical processes.

This hierarchical methodology starts with the definition and analysis of a process flowsheet followed by quantification of the process environmental loads. The quantification of environmental loads is an essential aspect of this methodology, because it serves as the comparative measure for environmental performance.

If the calculated environmental loads do not satisfy the environmental constraints (e.g., regulatory limits), waste minimization is investigated in the following order:

• Pollution …

A Theoretical Analysis Of Volatile Contaminant Removal By The Pneumatic Fracturing Process, Yuan Ding

Dissertations

A mathematical model that simulates the process of contaminant removal from a pneumatically induced fracture within a porous medium is presented. It includes: (1) model development; (2) parameter evaluation; (3) statistical sensitivity analysis; and (4) model validation.

Based on the dual porosity approach, a mathematical model for a fractured porous formation is developed for both two dimensional and axial symmetrical cases. This model constitutes a pair of coupled partial differential equations for the porous medium and discrete fracture, respectively. The initial and boundary conditions have been determined based on field considerations of a soil vapor extraction system. By means of …

Vibration As An Aid In Robotic Peg-In-Hole Assembly, Hsin-Te Liao

Dissertations

This dissertation presents an analytical and experimental investigation of vibration assisted engagement for parts mating. A dynamic model of assembly is established by using Lagrange's equation for impact to derive impact equations for a robotic manipulator in peg-in-hole assembly. The model can be used to analyze part motion and contact force in the mating of parts by robots. The impact equations of a SCARA robot are derived using this model and utilized to investigate how robot configuration, insertion speed, chamfer angle, coefficient of restitution and other system parameters affect impulsive force and departure angle in the assembly of a peg …

Particle Deposition On Surfaces In A Divergent Channal Flow, Ding Sun

Dissertations

Particle trajectory and deposition of two phase gas-solid flows in a convergent or divergent two-dimensional channel are investigated numerically in a wide range of parameters. For the fluid phase, a two dimensional, incompressible laminar fluid flow is considered in the analysis. The particle phase is a diluted suspension. The effects of inertia, gravity, viscous force and electrostatic image force are included in the computational model.

Both convergent and divergent channel flow are solved by the finite element method based on the software FIDAP. The flow separations will appear in a divergent channel and their separation positions are obtained in the …

Performance Analysis For Genetic Algorithms., Hermrean Wong

Dissertations

Genetic algorithms have been shown effective for solving complex optimization problems such as job scheduling, machine learning, pattern recognition, and assembly planning. Due to the random process involved in genetic algorithms, the analysis of performance characteristics of genetic algorithms is a challenging research topic. Studied in this dissertation are methods to analyze convergence of genetic algorithms and to investigate whether modifications made to genetic algorithms, such as varying the operator rates during the iterative process, improve their performance. Both statistical analysis, which is used for investigation of different modifications to the genetic algorithm, and probability analysis, which is used to …

The Effect Of Chlorine, Sulfur And Phosphorus Compounds On Deactivation Of Palladium Catalysts, Tai-Chiang Yu

Dissertations

The effects of HCl, H₂S, tributyl phosphate (TBP), P₂O₅, and zinc dialkyldithophosphate (ZDP) as catalyst poisons for methane oxidation over palladium catalysts supported on γ-alumina were investigated in this study. The overall reaction rate of methane oxidation over palladium catalysts can be simplified into a pseudo first order reaction under excess oxidation conditions.

The deactivation of the catalyst poisoned by HCl is attributed to the loss of active sites due to volatilization of PdCl₂. H₂ treatment at 200 °C can reactivate the catalyst poisoned by HCl at temperatures of up to …

Shear Strength And Fatigue Crack Propagation In Concrete By Energy Method, Wei Wang

Dissertations

The limit analysis methods have been commonly used to predict the ultimate flexure strength of reinforced concrete members over 50 years. However, current design formulas for shear in structural concrete are mostly empirical. In part one of this dissertation, attempts are made to apply the theory of plasticity to predict the shear strengths of reinforced concrete structures.

The modified Coulomb-Mohr failure criterion is used as the constitutive law of concrete, and the plastic flow is assumed to be associated with this failure criterion. A generalized formulation for energy dissipation in accordance with the failure criterion and associated flow rule is …

A Nondestructive Method For The Determination Of Fracture Energy In Concrete Structures, Been-Jyh Yu

Dissertations

It is generally believed that linear elastic fracture mechanics concepts can not be employed in determining fracture parameters in concrete, and therefore most of the current research effort has focused on applying the principles in yielding fracture mechanics. Despite all these efforts, comparison of results reported by many investigators indicate wide variations in fracture toughness values even for essentially similar materials. The main source of discrepancy in the observed results is the existence of a large process zone at the crack tip. Hence, the amount of energy consumed in advancing the crack will depend on the size of the process …

Composite Beam Analogy Fracture Model (Cbafm) : A Non-Linear Fracture Mechanics Model For Concrete, Mohammed Enamul Haque

Dissertations

The main objective of this dissertation is to develop a simple non-linear fracture mechanics model for the determination of fracture mechanics parameters for concrete, such as fracture process zone length (rp), critical fracture energy release rate (Gic), critical stress intensity factor (KO and fracture energy (GF). The fracture process zone (FPZ) is modeled as a damaged non-elastic cohesive band where the extent of damage due to microcracking varies from no damage at the boundary of FPZ to complete crack surface separation at the notch or macro-crack tip. The proposed method can predict theoretically both the pre-peak and post-peak load versus …

Grain-Size Optimization And Scheduling For Distributed Memory Architectures, Jing-Chiou Liou

Dissertations

The problem of scheduling parallel programs for execution on distributed memory parallel architectures has become the subject of intense research in recent, years. Because of the high inter-processor communication overhead in existing parallel machines, a crucial step in scheduling is task clustering, the process of coalescing heavily communicating fine grain tasks into coarser ones in order to reduce the communication overhead so that the overall execution time is minimized.

The thesis of this research is that the task of exposing the parallelism in a given application should be left to the algorithm designer. On the other hand, the task of …

Investigation Of Hybrid Message-Passing And Shared-Memory Architectures For Parallel Computer : A Case Study : Turbonet, Xi Li

Dissertations

Several DSP (Digital Signal Processing) algorithms are developed for the MIT TurboNet parallel computer. In contrast to other parallel computers that implement exclusively in hardware either the message-passing or the shared-memory communication paradigm, or employ distributed shared-memory architectures characterized by inefficient implementation of the shared-memory paradigm, the hybrid architecture of TurboNet supports direct, efficient implementation of both paradigms. Three versions of each algorithm are developed, if possible, corresponding to message-passing, shared-memory, and hybrid communications, respectively. Theoretical and experimental comparisons of algorithms are employed in the analysis of performance. The results prove that the hybrid versions generally achieve better performance than …

Biodegradation Of Mixed Wastes : Basic Kinetics And Reaction Engineering For Cyclic Reactor Operation, Kung-Wei Wang

Dissertations

This study dealt with the determination of the detailed kinetics of the biodegradation of mixed substrates by pure cultures, and with reaction engineering studies of bioreactors employed in treatment of substitutable substrates under cyclic operation.

In the first part of the study the degradation of phenol and 4-chlorophenol (4-CP) by two strains of Pseudomonas species was investigated. Strain P. putida 0 was found to be capable of utilizing both phenol and 4-CP as sole carbon and energy sources. This suggests that this strain follows the ortho-cleavage pathway for the aromatic ring. Strain P. putida N could grow on phenol, and …

Micromechanics Of Hot Mix Asphalt Material Formulation And Numerical Simulation, Kuo-Neng G. Chang

Dissertations

Hot Mix Asphalt (HMA), a highway and airfield pavement material, is heterogeneous, granular, and composite. It is traditionally modeled as a homogeneous material using continuum mechanics or semi-empirical methods. As a result, the above models either neglect or over-simply component reactions, failing to predict field performance problems resulting from particle segregation. This research presents micromechanical modeling, a novel approach that accounts for the components.

A micromechanical model is developed for HMA by modeling it as an assembly of asphalt cement coated particles. The asphalt cement is modeled as a viscoelastic material. To represent asphalt cement, several viscoelastic elements (i.e. Maxwell, …

Experimental And Numerical Determination Of Fluid Velocity Profiles And Turbulence Intensity In Mixing Vessels, Chun-Chiao Chou

Dissertations

In this study, both a laser-Doppler velocimeter (LDV) and a computational fluid dynamic (CFD) software package (FL UENI) were used to experimentally determine and numerically predict the velocity distribution of an unbaffled and a baffled mixing vessel. Two types of impellers were employed, namely a flat blade turbine (FBT) and a pitched blade turbine (PBT). These impellers were studied in a single-impeller or multiple-impeller configuration in the unbaffled and baffled vessels. The flow characteristics in the impeller regions were measured by LDV and used as boundary conditions in the numerical computation. Turbulence effects were numerically simulated using either the k-c …

A Petri-Net Based Methodology For Modeling, Simulation, And Control Of Flexible Manufacturing Systems, Venkatesh Kurapati

Dissertations

Global competition has made it necessary for manufacturers to introduce such advanced technologies as flexible and agile manufacturing, intelligent automation, and computer-integrated manufacturing. However, the application extent of these technologies varies from industry to industry and has met various degrees of success. One critical barrier leading to successful implementation of advanced manufacturing systems is the ever-increasing complexity in their modeling, analysis, simulation, and control. The purpose of this work is to introduce a set of Petri net-based tools and methods to address a variety of problems associated with the design and implementation of flexible manufacturing systems (FMSs). More specifically, this …

Theory, Design And Applications Of Linear Transforms For Information Transmission, Adil Benyassine

Dissertations

The aim of this dissertation is to study the common features of block transforms, subband filter banks, and wavelets, and demonstrate how discrete uncertainty can be applied to evaluate these different decomposition techniques. In particular, we derive an uncertainty bound for discrete-time functions. It is shown that this bound is the same as that for continuous-time functions, if the discrete-time functions have a certain degree of regularity.

This dissertation also deals with spectral modeling in filter banks. It is shown, both theoretically and experimentally, that subspectral modeling is superior to full spectrum modeling if performed before the rate change. The …

Robust Approach To Object Recognition Through Fuzzy Clustering And Hough Transform Based Methods, Tianxiong Fu

Dissertations

Object detection from two dimensional intensity images as well as three dimensional range images is considered. The emphasis is on the robust detection of shapes such as cylinders, spheres, cones, and planar surfaces, typically found in mechanical and manufacturing engineering applications. Based on the analyses of different HT methods, a novel method, called the Fast Randomized Hough Transform (FRHT) is proposed. The key idea of FRHT is to divide the original image into multiple regions and apply random sampling method to map data points in the image space into the parameter space or feature space, then obtain the parameters of …

Design And Micro-Fabrication Of Tantalum Silicide Cantilever Beam Threshold Accelerometer, Chang Joo Kim

Dissertations

Microfabricated threshold accelerometers were successfully designed and fabricated following a careful analysis of the electrical, mechanical, and fabrication issues inherent to micron-sized accelerometers. A uniform cantilever beam was chosen because of the simplicity of design and fabrication. New models for the electrostatic force exerted on the cantilever beam were developed and calculations were made that accurately predicted the electrical characteristics of the accelerometer. The calculations also provided design guidelines for optimizing the accelerometer dimensions. Computer simulation demonstrated that the error of the electrostatic force, calculated using the most accurate model, was within 2% of the actual force which was obtained …

Combustion Of Methyl Chloride, Monomethyl Amine, And Their Mixtures In A Two Stage Turbulent Flow Reactor, Fuhe Mao

Dissertations

The feasibility of converting fuel-bound chlorine and nitrogen into HCl and N₂ with reduced pollutant emissions of CO, NO, and unburned hydrocarbons was investigated in a two-stage turbulent flow reactor. The study consists of four segments: completion and validation of the experimental facility, experimental and modeling studies of methyl chloride (CH₃Cl) combustion, similar studies on monomethyl amine (CH₃NH₂), and finally studies on simultaneous CH₃Cl and CH₃NH₂ combustion.

Validation of the experimental facility was made by combustion of ethylene (C₂H₄) and air under both fuel-lean …

Electrical Characteristics Of Novel Heterojunction Diodes Of Thin Relaxation Semiconductors/P-Si/, Hyung Joo Lee

Dissertations

The relaxation semiconductor is defined as one in which the dielectric relaxation time (τd;resistivity times permittivity) is greater than lifetime (τo). Non-hydrogenated amorphous Silicon Carbide (SiC) and KrF excimer laser induced disordered Si were used for the relaxation semiconductors. Both semiconductors have high resistivity, wide energy gap, and numerous defects. A novel diode, consisting of those semiconductors on p-type crystalline Silicon (c-Si), was fabricated. In the diode structure, an injecting contact was made on the relaxation material and a Schottky barrier contact was made on the c-Si.

Electrical characteristics of both diodes were found to have interesting …

Analysis Of Plates And Reinforced Concrete Columns By Cubic B-Spline Function, Gang Wang

Dissertations

Applying spline functions to numerical structural analysis has been more common in recent years. The recent increase use of spline functions is mainly due to their excellent characteristics, such as sectionalized continuity, linear combination, flexibility, and easy use for various boundary conditions. The whole deformed shape of some structures or substructures can be described with one displacement function constructed by a series of spline functions. By doing this, the mesh generation and the huge computer memory space are no longer needed because only one single superelement can be used in the whole process. The choice of spline functions as displacement …

On Adaptive Code Division Multiple Access Detectors, Wenping Chen

Dissertations

Several variations of adaptive CDMA synchronous receiver schemes which can automatically adjust to the system parameters, are studied in this dissertation. Unlike their non-adaptive counterparts, these adaptive detectors require no knowledge of the received signals' energies and have similar or better performance.

Minimum energy and decorrelating criterion are used to update the weights. Since weights are updated according to the changes of the detector's outputs, hence no training sequence is required. The convergences of some of the aforementioned adaptive detectors are also disscussed.

The detectors proposed in this dissertation are near-far resistant,thus rendering the high-precision power control unnecessary. Among them, …