Engineering Commons^™

Fracture Mechanics Of High Strength Concrete Members, Rajendra K. Navalurkar

Dissertations

This study investigates the behavior of High Strength Concrete (HSC) under uniaxial state of stresses. Emphasis is placed on experimental evaluation of important mechanical and fracture properties. Owing to high brittleness of HSC, experimental results especially on tensile behavior have been largely limited and scarce. In this research, direct uniaxial tension tests are employed for determination of the post-peak tensile softening characteristics of HSC. The softening characteristics of high strength concrete is found to be considerably different than that of normal strength concrete (NSC). Fracture energies evaluated form the descending branch of the stress softening reveal significant drop in the …

A Controlled Release Technique Using Microporous Membranes, Stephanie Farrell

Dissertations

A novel controlled release device based on aqueous-organic partitioning is described. The device comprises a reservoir, bounded by a microporous or porous membrane in the form of a hollow fiber or flat film. The reservoir liquid phase and the pore liquid phase are immiscible. The agent partitions between the phases at the aqueous-organic interface of the reservoir and the pore mouth, and then diffuses through the membrane pore liquid into a surrounding aqueous solution. The partition coefficient significantly influences the rate of release of the agent by reducing the driving force for diffusion across the fluid-filled membrane pore. The performance …

Vapor-Liquid Phase Equilibria Of Nonideal Fluids With A Ge-Eos Model, Socrates Ioannidis

Dissertations

This study dealt with the prediction and correlation of vapor-liquid equilibria behavior of nonideal fluids. The thermodynamic formalism of the G^E-EoS models, which combines the two traditional methods γ-Φ and Φ-Φ used so far for low and high pressure phase equilibria correlations respectively, has been combined with the 1FG^E model, based on one-fluid theory, to produce a more consistent approach to the phase equilibrium problem.

In the first part of our study we examine the predictive abilities of our model for vapor-liquid equilibria of highly nonideal fluids. The results establish the fact that the Huron-Vidal mixing rule …

Local Stresses On Lateral Pipe-Nozzle With 45 Degree Angle Intersection, James Jin Xu

Dissertations

This dissertation presents a comprehensive study of local stresses, due to internal pressure around a pipe-nozzle with 45 degree angle intersection_ The resulting circumferential and longitudinal stresses on the pipe around the pipe-nozzle region are normalized as local stress factors and plotted as function of beta, β, (the radius of the nozzle/the radius of the pipe) and gamma, y, (the radius of the pipe/the thickness of the pipe) through the finite element method. The range of beta, [3, is from 0.1, to 1.0, and gamma, y, from 10 to 300. Comprehensive studies were made for the boundary parameters, such as …

Scheduling And Discrete Event Control Of Flexible Manufacturing Systems Based On Petri Nets, Huanxin Henry Xiong

Dissertations

A flexible manufacturing system (FMS) is a computerized production system that can simultaneously manufacture multiple types of products using various resources such as robots and multi-purpose machines. The central problems associated with design of flexible manufacturing systems are related to process planning, scheduling, coordination control, and monitoring. Many methods exist for scheduling and control of flexible manufacturing systems, although very few methods have addressed the complexity of whole FMS operations. This thesis presents a Petri net based method for deadlock-free scheduling and discrete event control of flexible manufacturing systems. A significant advantage of Petri net based methods is their powerful …

Motion Estimation And Video Coding, Xiaochun Xia

Dissertations

Over the last ten years. research on the analysis of visual motion has come to play a key role in the fields of data compression for visual communication as well as computer vision. Enormous efforts have been made on the design of various motion estimation algorithms.

One of the fundamental tasks in motion estimation is the accurate measurement of 2-D dense motion fields. For this purpose. we devise and present in this dissertation a multiattribute feedback computational framework. In this framework for each pixel in an image. instead of a single image intensity. multiple image attributes are computed as conservation …

Study Of Stress In Microelectronic Materials By Photoelasticity, Hancheng Liang

Dissertations

The study of stress is playing an important role in microelectronic technology. In comparison with other techniques, the photoelasticity technique has the advantages of having high spatial resolution and high sensitivity. It can be used in qualitative observation in real-time and quantitative determination of stress distribution in the microelectronic materials and devices.

This dissertation presents a systematic study of photoelastic stress analysis in microelectronic materials and devices, ranged from theoretical study to practical system setup, from measurement methods to their applications. At first, based on the detailed survey on the piezo-optic properties of the crystals used in microelectronics, we apply …

Reaction Kinetics Of Methanol And Mtbe Oxidation And Pyrolysis, Wen-Chiun Ing

Dissertations

This study presents experimental data on the decomposition of methanol in several different reaction environments - fuel lean to stoichiometric at a temperature range of 873 and 1073 K and a pressure range of I and 5 atm. Methane fuel is also added in several of the systems studied in order to provide experimental data to understand the methanol addition effect on the methane oxidation.

Computer codes: ThermCal, ThermSrt and ThermCvt have been developed for the thermal property calculations of stable molecules by the Benson group additivity method and of radicals by the NJIT hydrogen bond increment method.

Pressure dependent …

Experimental And Analytical Investigation Of Waterjet Cleaning Process, Ping Meng

Dissertations

This doctoral dissertation is concerned with the development of water based cleaning technology required by industry which may substitute the traditional approach based upon the use of various chemical cleansers.

The experimental study involves the waterjet removal of various coatings (rust, oil and epoxy based paints, etc.). Cleaning was carried out under a wide range of operational and geometrical conditions (standoff distance, travel speed, water pressure, diameters of sapphire nozzle and focusing tube, nozzle body type). A new designed spiral nozzle body was tested in this work. The use of surfactant was also investigated. Microscope and SEM surface were used …

Characterization And Fabrication Of A (6h)-Sic As A Piezoresistive Pressure Sensor For High Temperature Applications, Robert Sylvester Okojie

Dissertations

A prototype monolithic 6H-SiC pressure sensor operational up to 350°C, with potential to operate up to 600°C, was batch fabricated and tested. At temperatures higher than 450°C, silicon diaphragms creep under minimal load. To operate beyond 450°C, therefore, the use of 6H-SiC was proposed. However, three key technological issues - fabrication, high temperature metallization, and gage factor characterization - had to be resolved. Since conventional fabrication technology is not applicable to SiC due to its near inert chemistry, photoconductive selectivity techniques to etch the piezoresistors were developed. Techniques to wet etch the cavities in a dark current mode were developed, …

Experimental And Numerical Investigation Of Abrasive Waterjet Polishing Technology, Fenggang Li

Dissertations

The objective of this investigation is the development of the abrasive waterjet (AWJ) based polishing technology. The result of the investigation will assist the implementation of AWJ polishing for manufacturing processes and procedures.

Experimental exploration of AWl polishing involving processing of difficultmachine materials such as Alumina ceramic and stainless steel. Surface improvement due to this processing is evaluated by measuring the roughness of the generated surfaces and examining the microhardness and micro-topography of the surfaces using Scanning Electronic Microscopy (SEM). The surface roughness of 0.3 micron was obtained at samples of ceramic and metal alloys at a reasonable rate using …

The Constant Fracture Angle Model For Cementitious Materials, Suk Ki Kim

Dissertations

Fracture mechanics of concrete has been investigated for the past two decades using linear elastic and nonlinear fracture mechanics concepts. The models proposed so far remain questionable largely due to specimen dependency of the proposed fracture parameters.

In this study, a new approach for modeling the fracture characteristics of concrete and fiber reinforced concrete is proposed. The model depends on the load CMOD relationship rather than the traditional load-deflection principle. Although energy consumed during fracture is definitely a direct function of the load displacement response, it was observed that traditional displacement measurement included an extraneous and erratic portion due to …

Emulsion Liquid Membrane Removal Of Arsenic And Strontium From Wastewater : An Experimental And Theoretical Study, Ding-Wei Zhou

Dissertations

The emulsion liquid membrane (ELM) technique has been successfully applied on the removal of arsenic (As) from metallurgical wastewater and the removal of strontium (Sr) horn radioactive wastewater. This study consisted of experimental work and mathematical modeling.

Extraction of arsenic by an emulsion liquid membrane was firstly investigated. The liquid membrane used was composed of 2-ethylhexyl alcohol (2EHA) as the extractant, ECA436OJ as the surfactant, and Exxsol D-8O solvent (or heptane) the diluent. The sulfuric acid and sodium hydroxide solutions were use I as the external and internal phases, respectively. The arsenic removal efficiency reached 92% within 15 minutes in …

Explicit Congestion Control Algorithms For Available Bit Rate Services In Asynchronous Transfer Mode Networks, Ambalavanar Arulambalam

Dissertations

Congestion control of available bit rate (ABR) services in asynchronous transfer mode (ATM) networks has been the recent focus of the ATM Forum. The focus of this dissertation is to study the impact of queueing disciplines on ABR service congestion control, and to develop an explicit rate control algorithm.

Two queueing disciplines, namely, First-In-First-Out (FIFO) and per-VC (virtual connection) queueing, are examined. Performance in terms of fairness, throughput, cell loss rate, buffer size and network utilization are benchmarked via extensive simulations. Implementation complexity analysis and trade-offs associated with each queueing implementation are addressed. Contrary to the common belief, our investigation …

Design, Process And Performance Simulation Of A 360x360-Element Very High Frame Rate Burst-Image Sensor, Guang Yang

Dissertations

A process was developed for fabrication of 360x360-element Very High Frame Rate (VHFR) burst-image sensor on the bases of one-dimensional (1-D) and two-dimensional (2-D) device and process simulations using SUPREM III, SUPREM IV, PISCES IIB and ISE-TCAD software, and the process data provided by the David Sarnoff Research Center. This process includes SiO₂-Si₃N₄ gate dielectric, four-levels of polysilicon, three-levels of metal, eight implants, and requires twenty-one mask levels. The imagers with a 2-cmx2-cm chip size were fabricated at the David Sarnoff Research Center. The VHFR burst-image sensor is capable of capturing images at frame rates …

Global Fuzzy Control Based On Cell Mapping, Tea-Quin Kim

Dissertations

Cell mapping methods can generate global optimal controls for nonlinear dynamic systems. However, the implementation of this approach for on-line control is difficult due to its use of a table-based controller which requires a large amount of memory.

In this dissertation, a cell mapping based systematic method is developed to construct a fuzzy controller to replace the table-based controller for global optimal control of dynamic systems. The method consists of four steps: 1) An optimal control table is generated using a cell mapping algorithm. 2) The cells are linked into trajectories to characterize the optimal dynamic evolution of various cell. …

Development Of A Traffic Safety Index For Urban Intersections, Jae-Hong Kang

Dissertations

Conventional safety analysis focuses on the accident environment at specific locations or a limited segment of highways or arterials, and attempts to identify the effects of accident contributing factors. The development of a safety index in the past was based on a statistical summary for county or statewide areas, using general indicators such as population, number of registered vehicles, vehicle miles traveled and so on. This research effort presents a state-of-the-art procedural analytical approach for the safety analysis of Manhattan intersections that are exposed to a unique urban environment. The computed index provides safety ratings that can identify potential safety …

Development Of A Multivariate Qsar Model To Predict Desorption Of Halogenated Aliphatic Hydrocarbons From Activated Sludge Solids, Sudhi Ranjan Mukherjee

Dissertations

Data collected from different wastewater treatment processes have provided statistically significant evidence that many toxic organic contaminants on EPA's list of priority pollutants concentrate several orders of magnitude greater than influent concentrations in industrial and municipal wastewater sludges. Because of the reversibility of sorption processes, it is possible for sorbed organic compounds to desorb at a later time, hence making disposal of these sludges a potential problem. Although a number of models have been developed to predict sorption parameters, they have all been based on empirically derived descriptors whose validity is seriously compromised by the variation in available data for …

A Full Wave Method For Rough Surface Scattering Using Fictitious Current Distributions, Anthony A. Triolo

Dissertations

Rough surface scattering is a current topic of interest in many diverse fields. But, despite its importance, the two most widely used solution methods, the Kirchhoff and first order perturbation methods, are valid only for a restricted range of surface types. There is a large range of surface statistics for which neither of these theories is valid. There are purely numerical solutions to the problem, i.e., the integral equation technique and FDTD method, but these methods require a prohibitively large amount of computer time and storage space for use in practical applications. A full wave method has been introduced by …

Reduction Of Inertia-Induced Forces In A General Spatial Mechanism, Sahidur Rahman

Dissertations

A computer-aided design procedure has been developed for minimizing the adverse effects of the inertia-induced forces by optimum mass redistribution amongst the links of high speed general spatial linkages. The evaluation of an optimality criterion for the mass redistribution of the mechanism will be carried out with the aid of a quadratic programming technique. This has been found to be successful in minimizing inertia induced forces and torques. The validity of the optimization procedure will be demonstrated by application to one kind of spatial linkage.

No literature has been found on the balancing of a general spatial mechanism, since its …

Discrete Element Modeling Of Dry Granular Material Using A Massively Parallel Supercomputer, David W. Washington

Dissertations

It is the state-of -the-art within Geotechnical Engineering to model soils as systems of particles rather than using the traditional continuum approach. Simulating these systems of particles for geotechnical boundary value problems results in systems which are of necessity large, motivating the application of massively parallel supercomputers. This thesis pursues such an approach.

The following work describes numerical experiments using a Discrete Element Method (DEM) paradigm for soils (Trubal) together with massively parallel computers with Single Instruction Multiple Data (SIMD) architecture. The discrete element method describes the behavior of granular assemblies using the classical mechanics of discrete bodies. The computational …

On The Adaptive Multi-Stage Detector For Cancellation Of Multiuser Interference In Cdma Wireless Communication Systems, Nadir Sezgin

Dissertations

The classical multiple access techniques such as Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) schemes are band limited in terms of their capacity to be used for mobile radio communication. Recent developments in the area of digital signal processing, makes Code Division Multiple Access (CDMA) as a possible solution to the demand of capacity for the mobile radio communication. The capacity of CDMA is limited by multiuser interference, that is the interference from the other users.

The goal of this dissertation is to improve the multiuser CDMA detector with high Bit Error Rate (BER) performance, low …

Real Time Control Of Nonlinear Dynamic Systems Using Neuro-Fuzzy Controllers, Amitava Jana

Dissertations

The problem of real time control of a nonlinear dynamic system using intelligent control techniques is considered. The current trend is to incorporate neural networks and fuzzy logic into adaptive control strategies. The focus of this work is to investigate the current neuro-fuzzy approaches from literature and adapt them for a specific application. In order to achieve this objective, an experimental nonlinear dynamic system is considered. The motivation for this comes from the desire to solve practical problems and to create a test-bed which can be used to test various control strategies. The nonlinear dynamic system considered here is an …

Investigation Of Dynamic Friction In Lubricated Surfaces, Hanuman Rachoor

Dissertations

The research reported in this dissertation is concerned with the development of friction models for lubricated contacts. A few analytical models have been developed to investigate the friction under dynamic velocity conditions. In this study, two different tribological situations such as conformal and non-conformal contacts have been chosen. Friction modeling covers boundary, mixed and full fluid film friction regions. A new theory based on the elastic properties of the surface materials, and fluid film properties of the lubricant at the contact has been developed to determine the dynamic friction in boundary, mixed and full hydrodynamic lubrication regions. In the full …

Adaptive Space-Time Processing For Wireless Communications, Xiao Cheng Bernstein

Dissertations

Adaptive space-time processing techniques have been found to increase the capacity of two major, multiple-access wireless communication systems: Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA).

In an IS-54 TDMA system, the frequency re-use factor has to be set to 7 so that cells with the same spectrum are separated far enough to meet a required carrier-to-interference ratio (CIR). Space processing uses multiple antennas which, in turn, provide alternative signal paths in order to cancel interferences and combat multipath fading. We have proposed the eigencanceler method and have reviewed the theoretical optimum combining and the feasible direct …

On Optimal Design And Applications Of Linear Transforms, Mehmet V. Tazebay

Dissertations

Linear transforms are encountered in many fields of applied science and engineering. In the past, conventional block transforms provided acceptable answers to different practical problems. But now, under increasing competitive pressures, with the growing reservoir of theory and a corresponding development of computing facilities, a real demand has been created for methods that systematically improve performance. As a result the past two decades have seen the explosive growth of a class of linear transform theory known as multiresolution signal decomposition. The goal of this work is to design and apply these advanced signal processing techniques to several different problems.

The …

On The Optimization Problems In Multiaccess Communication Systems, Gangsheng Wang

Dissertations

In a communication system, the bandwidth is often a primary resource. In order to support concurrent access by numerous users in a network, this finite and expensive resource must be shared among many independent contending users. Multi-access protocols control this access of the resource among users to achieve its efficient utilization, satisfy connectivity requirements and resolve any conflict among the contending users. Many optimization problems arise in designing a multi-access protocol. Among these, there is a class of optimization problems known as NP-complete, and no polynomial algorithm can possibly solve them. Conventional methods may not be efficient arid often produce …

Anaerobic Digestion And Acid Hydrolysis Of Nitrocellulose, Fong-Jung Tai

Dissertations

In this investigation, studies were conducted to evaluate the biodegradation of nitrocellulose in anaerobic batch reactors with and without the supplemental carbon inducers, such as cellulose, cellobiose, and lactose. Results from the anaerobic study show that degradation of nitrocellulose alone is difficult and that nitrocellulose degradative enzymes could be induced by the three inducers tested. As high as 48.91% conversion could be obtained at Cellulose/Nitrocellulose ratio of 1 to I. Studies also indicated that type 20 and 50 celluloses would be more effective and optimum pH was about 6.4 in biodegradation of nitrocellulose. Three testing systems, namely, single-stage, two-stage, and …

An Investigation Of The Mechanism Of Advanced Oxidation Processes (Aop) Involving Free Radicals And Charged Species., Yaw-Kuen Lin

Dissertations

Hydrogen peroxide is a key component in Advanced Oxidation Processes (AOP). Its decomposition at different pH conditions has been studied and some interesting results were observed. When the pH value of hydrogen peroxide solution is less than 9, its rate of decomposition is independent of pH. On the other hand, in the pH range of 9-12.6, its rate of decomposition increases as pH increases, and goes through a maximum value then suddenly decreases with respect to pH. A reaction kinetic model with three rate constants in the form of beta probability function was used to describe the experimental data of …