Engineering Commons^™

Probing Spin, Charge And Lattice Coupling In Manganites, Zhiqiang Chen

Dissertations

Complex oxides such as the manganites exhibit an intimate coupling of the electron spin, charge and lattice degrees of freedom. The characteristic feature of these materials is the existence of a ground state topology with many closely lying minima. The system can be switched from one minimum to another by the application of external parameters such as strain, temperature, magnetic fields, or electrical fields. These materials thus exhibit large responses to these external parameters and can be used as novel sensors in data storage and other applications. Understanding the couplings will have an impact on the fundamental science of highly …

Novel Polypropylene Based Microporous Membranes Via Spherulitic Deformation, Kuan-Yin Lin

Dissertations

A novel method for creating a microporous polypropylene membrane via spherulitic deformation is described. The microporous structure was generated by the combination of intra-spherulitic and inter-spherulitic deformations. Polypropylene was selected due to its unique cross-hatched lamellar morphology facilitating inter-spherulitic deformation. A precursor film with a spherulitic structure was made under low-stress melt processing condition. A tangential lamellae-rich spherulite was created and identified with a positive birefringence sign. A sequential annealing process improved the crystalline structure, and in particular the thickness of the tangential lamellae. The annealing process proved to be critical for initiating the inter-spherulitic deformation. The post-extrusion process conditions …

Ionic Liquids As Additives For Biodegradable Polyactic Acid, Ku-Il Park

Dissertations

In this study, two ionic liquids (IL) with different anions (decanoate, tetrafluoroborate) but with the same phosphonium based cation were evaluated as potential plasticizers and lubricants for polylactic acid (PLA) and also for their effects on its hydrolytic and thermal degradation. Both ILs at 5wt% were well dispersible and partly miscible with PLA as evidenced by scanning electron microscopy/energy dispersive x-ray scattering, SEMIEDX, and glass transition temperature, T_g, characterization, as well as from solubility parameters calculations.

The effects of the IL containing a decanoate anion were more pronounced on lubrication and degradation as evidenced by reduced melt viscosities …

Multi-Functional, Self-Sensing And Automated Real-Time Non-Contact Liquid Dispensing System, Qiong Shen

Dissertations

Liquid dispensing in the order of pico-liter has become more and more important in biology, electronics and micro-electronic-mechanical-system (MEMS) during the past two decades due to the rapid progress of researches on the deoxyribonucleic acid (DNA) microarray, compact and low-cost direct write technology (DWT), organic semiconductors and nano-particles.

The existing approaches, commercialized or experimental, to liquid dispensing in minute amounts have one common shortcoming: open loop control, i.e., they have no direct control on the quality of dispensed liquid. In contrast, the SmartPin has intrinsic self-sensing capability to not only control the process of liquid dispensing, but also the results …

Degradation Of Polylactic Acid In The Presence Of Microsize And Nanosize Fillers, Quyuan Zhou

Dissertations

Polylactide (PLA)-cationic (montmorillonite, MMT) and anionic (hydrotalcite, HT) clay micro- or nanocomposites based on semicrystalline and amorphous polymers and unmodified and organomodified as well as calcined or non-calcined clays at 5wt% concentration are produced by melt mixing. Depending on the clay type, presence of organomodifiers and calcination, micro- or nanocomposites are produced, as confirmed by XRD and SEM analysis.

Unfilled polymers and their composites are subjected to isothermal degradation in air at 180°C and 200°C. Degradation rate constants are calculated from novel equations incorporating IV. Results show that the thermal degradation rate constants of the amorphous PLA and its composites …

Synthesis And Characterization Of Atmospheric Pressure Chemically Vapor Deposited Aluminum, Sipeng Gu

Dissertations

This study investigates the use of atmospheric pressure chemical vapor deposition (APCVD) to produce high quality aluminum coatings for corrosion protection of steel. The coatings were produced through thermal decomposition of tri-isobutyl-aluminum (TIBAL) over the 275 to 300°C temperature range. Under optimal deposition conditions, growth rates as high as 1.2 um/min were achieved. X-ray photoelectron spectroscopy, auger electron spectroscopy, glow discharge optical emission spectroscopy and nuclear reaction analysis revealed that the coatings consisted essentially of pure aluminum (~99 at.%) with oxygen and carbon present as minor constituents. The coatings were characterized in terms of their morphological, structural, electrical, and mechanical …

Zeolite-Based Nanosized Ti02 Photocatalytic Paper For Antimicrobial Barrier And Toxin Passivation In Packaging: Design, Synthesis And Characterization, Seonghyuk Ko

Dissertations

This dissertation describes comprehensive studies, including design, preparation, characterization and evaluation, to develop an innovative zeolite-based nanosized TiO2photocatalytic paper for disinfection and disintegration of organic toxins.

A novel paper with high photocatalytic performance was successfully prepared using natural zeolite (clinoptilolite)-based nanosized TiO2 photocatalyst in a microparticle retention papermaking system. Photocatalytic material, from its sol-gel derived TiO2 colloids to its anchoring onto zeolite, has been designed, prepared and characterized. Prior to photocatalytic papermaking, the characteristics of sol-gel synthesized TiO2 nanoparticles from colloidal to nanopowder were investigated with various initial sizes of colloidal nanoparticles synthesized in the range of 2.5±0.1 nm and …

A New Rough Wall Layer Modeling For Turbulent Flows Using The Brinkman Equation, Meng-Huang Lu

Dissertations

No abstract provided.

The Effect Of Substrate Properties On Print Attributes For Gravure Printing - From Proof To Press, Yu Ju Wu

Dissertations

Gravure is the major printing process used for publication printing. In gravure printing processes, color proofing is for the purpose of checking the color to ensure that it is as desired. There is no doubt that paper properties have significant effects on the image reproduction for either printing or proofing processes. In order to achieve uniformity of printing and obtain good color reproduction performance, it is important that the all paper properties are well defined and controlled. This study investigates the correlations between paper properties and print quality/color reproduction for gravure publication printing and ink jet printing used in digital …

Density Relaxation Of Granular Matter Through Monte Carlo And Granular Dynamics Simulations, Oleksandr M. Dybenko

Dissertations

Granular materials are the principal ingredients of the industrial complex involved with the handling and processing of bulk solids including pharmaceuticals, chemicals, agricultural and mining materials. Despite the enormous importance of these materials in society, their behavior is not well-understood; in fact, there is no known model available that is capable of predicting the wide range of phenomenon that have been observed. One of the most important of these is known as density relaxation. Here, a granular material undergoes an increase in solids fraction as a result of the application of discrete taps or continuous vibrations.

In this dissertation, the …

Production Of Nanocrystalline Rdx By Ress : Development And Material Characterization, Victor Stepanov

Dissertations

The aim of the present work was to address the hazardous vulnerability of energetic materials to accidental initiation. An improved form of the explosive RDX with a significantly reduced sensitivity to stimuli including shock and impact was sought. The direction of this research was to investigate the effect of RDX crystal size reduction down to nano-scale dimensions on the sensitivity characteristics. Although size reduction of energetic crystals has been demonstrated often to result in a sensitivity reduction, the effect at the nano-scale particle size has not been investigated.

To generate nanocrystalline RDX a recrystallization process was developed based on rapid …

Optimal Allocation Of Blood Products, Godson A. Tetteh

Dissertations

The high cost of collection and the short shelf life of apheresis platelets demand efficient inventory management to reduce outdates and shortages. Apheresis platelets are licensed for seven days, and blood centers are keen on knowing the consequences of various product collection and distribution strategies. To reduce outdates, inventory managers typically distribute the older units first, thereby following first-in first-out (FIFO) policy; however, hospital blood banks would prefer that the blood center issues out the freshest units first, equivalent to a last-in first-out (LIFO) policy. This study addresses the optimal distribution policy to achieve a desired outdate, shortage and average …

Optical Properties And Carrier Transport In Si/ Si1-Xgex Nanostructures, Eun Kyu Lee

Dissertations

Defect-free epitaxial growth of Ge on a ~4 % lattice-mismatched single-crystal Si substrate is achieved using reduced dimension nanoscale heterostructures, where efficient structural relaxation might occur due to an enhanced adatom migrations and high surface-to-volume ratio. For development of novel electronic or optical devices based on these novel structures, understanding of their electrical and optical properties is crucial. This study explores the optical properties and carrier transport in two different types of Si/Si _1-xGe _xnanostructures: Ge nanowires (NWs) forming nanoscale heterojunctions with Si substrates and multilayers of SiGe clusters embedded into a Si matrix.

Micron-long Ge nanowires grown …

Micro, Meso And Macro Materials Processing Using High-Speed Liquid Projectiles, Veljko Samardzic

Dissertations

The objective of this research is developmentof aknowledge base of materials processing by the impact of high-speed liquid projectiles. The work involved experimental study of generation and applications of high-speed liquid projectiles. The projectiles were generated by the launchers, which used gunpowder as an energy source. The experiments were carried out at the low (O.35g of the powder), middle (1.2g) and high (10g to 70g) levels of energy consumptions and at several different launchers modification.

Experimental investigation of effect of gun powder mass on energy of projectile was conducted for ductile and brittle targets. An array of experimental …

Removal And Recovery Of Fermentation-Produced Volatile Organic Compounds By A Novel Liquid Membrane-Based Pervaporation Technique, Atsawin Thongsukmak

Dissertations

Pervaporation is an energy -- efficient alternative to distillation for removing volatile organic compounds (VOCs) from water especially solvents from their dilute solutions in a fermentation broth. Liquid membranes have high selectivities for removing solvents from aqueous solutions compared with polymeric membranes or ceramic membranes; however liquid membranes have stability problems due to various losses. The loss of liquid membrane (LM) to the feed solution leads to toxicity for the organisms in a fermentation broth. A new liquid membrane based pervaporation technique has been developed to achieve high selectivity, ensure stability and prevent contamination of the fermentation broth. Trioctylamine (TOA) …

Modeling Inventory And Responsiveness Costs In A Supply Chain, Robert Nearier

Dissertations

Evaluation of supply chain performance is often complicated by the various interrelationships that exist within the network of suppliers. Currently many supply chain metrics cannot be analytically determined. Instead, metrics are derived from monitoring historical data, which is commonly referred to as Supply Chain Analytics. With these analytics it is possible to answer questions such as: What is the inventory cost distribution across the chain? What is the actual inventory turnover ratio? What is the cost of demand changes to individual suppliers? However, this approach requires a significant amount of historical data which must be continuously extracted from the associated …

Vector Support For Multicore Processors With Major Emphasis On Configurable Multiprocessors, Hongyan Yang

Dissertations

It recently became increasingly difficult to build higher speed uniprocessor chips because of performance degradation and high power consumption. The quadratically increasing circuit complexity forbade the exploration of more instruction-level parallelism (JLP). To continue raising the performance, processor designers then focused on thread-level parallelism (TLP) to realize a new architecture design paradigm. Multicore processor design is the result of this trend. It has proven quite capable in performance increase and provides new opportunities in power management and system scalability. But current multicore processors do not provide powerful vector architecture support which could yield significant speedups for array operations while maintaining …

Multiclass Intermodal Network Model : The Use Of Combined Model On System Evaluations, Yi Deng

Dissertations

United States transportation policy has generally addressed the negative economic and social effects of the standpoint of individual transportation modes and local government involvement. Therefore, there has been an increased focus on the development of intermodal transportation. Integrating the modes and using each of them to its best advantage are strategies to optimize the existing resources and to create new capabilities.

According to the literature review performed in this research, the research in intermodal transportation system evaluation is far from mature. Most transportation performance measurements are focused on one mode rather than a whole network. In practice, the data necessary …

Design And Analysis Of Scalable Scheduling Schemes For High-Speed Input-Queued Packet Switches, Chuan-Bi Lin

Dissertations

Single-stage input-queued (IQ) switches are attractive for implementation of high performance routers because they require no speedup in the used memory. It has been shown that IQ switches can provide 100% throughput under admissible traffic when using either maximum-weight matching schemes or iterative maximal-weight matching schemes with a significant speedup. These different approaches require either high computation complexity or high memory costs that can make them infeasible. Therefore, there is a need for low-complexity and fast matching schemes that provide high throughput under several admissible traffic patterns, without recurring to speedup nor multiple iterations. In this thesis. the concept of …

Architecture Design And Performance Analysis Of Practical Buffered-Crossbar Packet Switches, Ziqian Dong

Dissertations

Combined input crosspoint buffered (CICB) packet switches were introduced to relax inputoutput arbitration timing and provide high throughput under admissible traffic. However, the amount of memory required in the crossbar of an N x N switch is N²x k x L, where k is the crosspoint buffer size and needs to be of size RTT in cells, L is the packet size. RTT is the round-trip time which is defined by the distance between line cards and switch fabric. When the switch size is large or RTT is not negligible, the memory amount required makes the implementation …

Propagation And Scattering Of Beam Waves In Vegetation Using Scalar Transport Theory, Michael Yu-Chi Wu

Dissertations

Vegetation is a very complex propagation medium, and multiple scattering effects play a significant role in the propagation of microwave and millimeter (mm)-wave signals through foliage. At frequencies above 1 GHz,both the coherent and incoherent field components have to be taken into account and vegetation has to be modeled as a random medium of discrete scatterers having a wide variety of sizes and shapes. Multiscattering can be studied effectively by using transport theory. In prior studies, theories have been developed for microwave and mm-wave propagation in vegetation using transport theory for continuous wave and pulsed signals. In this study, the …

Optimized Scheduling Of Highway Work Zones, Yimin Tang

Dissertations

Highway maintenance activities usually require lane closures and disrupt traffic operations. Because of budget constraints, project deadlines, and the resulting traffic impact, the objective of this dissertation is to improve the efficiencies of traffic operation and maintenance work, and minimize the total project cost (i.e., agency cost and road user cost) by optimizing work zone schedules.

This dissertation focuses on the maintenance projects on multiple-lane highways. The objective total cost function is formulated while considering a discrete maintenance time-cost function and time-dependent traffic diversions. However, the work zone scheduling problem is a combinatorial optimization problem and difficult to solve analytically. …

Development Of A Knowledge Management Strategy For Academic Staff, Leslie Whyte

Dissertations

We are living in a knowledge society. Knowing what we know and managing it better to know more is considered the key enabler to sustainable economic growth. 70 to 80 percent of economic growth is directly attributed to new or better knowledge. With information communication technologies (ICT) readily facilitating the globalisation of economic activity, the key competitive advantage of this era is the ability to create, use and disseminate knowledge effectively. Although traditionally creators, guardians and disseminators of knowledge, universities and institutions need to also adapt to the challenges the knowledge society can bring and evolve their roles in education, …

A Synthesised Knowledge Mapping Framework To Embed A Km Strategy Using Topic Maps And Wikis: The Tao Of Wiki, Colman A.J. Mcmahon

Dissertations

Just getting started with knowledge management can be difficult enough for many organisations, however the real challenge is actually how to embed the new practices. The expression "Success is a journey, not a destination" is particularly apt for KM. This research presents findings from stakeholder analyses carried out in an Irish government agency. The agency has been on its KM journey for nearly four years and has attempted to implement a comprehensive and full-scale strategy. The findings indicate that KM practices have not yet become fully embedded in the organisation. This research uncovers some of the reasons why not. In …

Assessing The Impact Of Organisational Culture When Introducing Web.2.0 Technologies Into A Non-Profit Organisation For Knowledge Managment, Heather Madden

Dissertations

Some of the key challenges that any organisation faces today are those of knowledge sharing and collaboration. This research investigates knowledge sharing in existing communities of practice in a non-profit organisation and the challenges that are faced by attempting to facilitate online interactions for these communities. Organisation culture can either incentivise or impede this process and this research will describe how people and culture are two of the most important factors when considering a knowledge management initiative. Given that the impact of culture is such a key issue, a number of organisations are interviewed and evaluated to compare and contrast …

Impact Of Mentorship Programs On African-American Male High School Students’ Perception Of Engineering, Cameron De'leon Denson

Dissertations

The purpose of this study was to examine the impact of mentorship programs on African-American male high school students’ perceptions of engineering. In this study, indicators of students’ perceptions included students’ perceptions of engineering, their self-efficacy in the area of math, and their self-efficacy in the area of science. This study used a two-group, posttest only, experimental design with randomly selected participants. A survey was used to collect data from 20 participants attending the Middle College at A&T. Using an independent t-test to determine a difference of statistical significance, inferential statistics were provided to answer the following research questions; (a) …

Building Organisationally Sensitive Technological Solutions For Knowledge Management In It Support Services, David Tonade

Dissertations

With the advent of the internet, information and communications technology has changed the way organisations operate and do business. There now exist an extremely dynamic and competitive business landscape, where information and knowledge are continuously created, used and distributed across business units. People have become more involved with the use of technology to aid them in their business tasks. In the course of generating and transmitting information comes the realization that knowledge is a vital asset of the company. Thus, most firms embark on various initiatives to enable Knowledge Management (KM). This study revolves around the IT tools involved in …

Development Of A Framework To Leverage Knowledge Management Systems To Improve Security Awareness., Dennis Lupiana

Dissertations

Security awareness is very essential in securing intellectual property, in particular internal corporate information assets and its “Knowledge”. The dynamic nature of security attacks and the need to comply with government policies in protecting organisation’s data has a major influence on seeing organisations focus on strengthening against threats from the human element. This is a difficult challenge. Organisations must have a degree of trust their employees. They must trust their employees to interact responsibly as end-users with their information systems. They must trust their employees who work as developers to work responsibly and be motivated to develop systems with the …

The Research And Implementation Of Maintenance Excellence On Clean Utility Systems In The Pharmaceutical Indusry, Padraig Liggan

Dissertations

Maintenance Excellence is the implementation of best maintenance practices within industry; it is the balance of performance, risk, and cost to achieve an optimal solution. This thesis has been structured around the 5 main areas of maintenance excellence; it has documented all the important functions of the maintenance department that contributes towards maintenance excellence. Demonstrating maintenance excellence is a big achievement however demonstrating it on pharmaceutical clean utility systems with strict regulatory controls is a major challenge. Pharmaceutical production is one of the most heavily regulated industries. With such an emphasis on product quality in the pharmaceutical industry, and with …

Elimu 2.0: Investigating The Use Of Web 2.0 For Facilitating Collaboration In Higher Education., Bajuna R. Salehe

Dissertations

The latest web innovations and technologies which has made the Web into a ‘Platform’, are become increasingly applied in the higher education arena. Tools such as Google docs, Google groups, Wikis, Blogs, RSS and Podcasting are gradually becoming more popular within higher education in teaching and learning. Yet their huge potentials have not been fully explored. Collaboration and knowledge sharing are common terms in higher education, and in the corporate world of the today’s knowledge economy. However better infrastructure and facilities that enable these important issues are yet to be set and fully utilised in higher education. In the higher …