Engineering Commons^™

Modeling Fluid Structure Interaction Over A Flexible Fin Attached To A Naca0012 Airfoil, Srinivasa Ravindra Pantula

Dissertations

Flow separation control is of importance to the performance of air vehicles. Generally, it is desired to postpone separation such that the overall drag is reduced, stall is delayed, lift is enhanced, and pressure recovery is improved. This work explores a new concept of post-stall flow control for airfoils and wings by using a thin flexible fin attached on the upper surface of an airfoil to passively manipulate flow structures in the fully separated flows for drag reduction and lift enhancement. The flow induced oscillations combined with the shape deformations change the overall pressure distribution on the fin, which in …

Atomistic-Based Finite Element Simulation Of Carbon Nanotubes, Yang Yang

Dissertations

Since first found in the form of multi-walled carbon nanotubes (MWNTs) by Iijima(1991), carbon nanotube (CNT) for its outstanding and unique properties have gained overwhelming attentions from across the spectrum of the science and engineering fields. CNTs are structurally perfect, small size, low density, high stiffness, high strength (Qian et al., 2002), and their electronic properties depend on the particular distortion as well as the initial tube diameter and chirality, ranging from narrow-gap or moderate-gap semiconducting to metallic (Pantano et al., 2004b), which can be utilized in nanoscale sensors and devices. These appealing characteristics provide strong drives for the possible …

Flexography Printing Of Silver Based Conductive Inks On Packaging Substrates, Ramesh Chandra Kattumenu

Dissertations

Printing technologies for the production of flexible electronics have gained much interest due to its potential as a means to reduce the complexity and costs of present technology. High volume printing techniques like flexography are of great importance in order to produce rolls of flexible electronics printed directly on paper substrates. The proposed research will be focused on RFID components being in-line printed using flexography printing as the manufacturing platform. The properties of substrates and inks and printing process parameters are evaluated to study their effect on printed traces and RFID antenna. It was found in the study that properties …

Service Supply Chain Management : A Hierarchical Decision Modeling Approach, Roger Angel Solano-Cayama

Dissertations

A Service Supply Chain (SSC) may be described as a network of service provider facilities (in-house or outsourced), each of which is able to process one or more service tasks on an as needed basis. Two key characteristics of a SSC are (i) the business service is decomposable into several sequential tasks that can be processed by different service providers, and (ii) the primary capacity resource is skilled labor. SSCs are increasingly being developed by companies that experience a high variability of demand for their services (e.g., loan processing, analytical consulting services, emergency repair crews, claims processing, etc.). Typically, the …

Investigation Into The Acupuncture And Meridian System, Jingong Pan

Dissertations

The Meridian system conceived by the ancient Chinese has been described and referenced for more than a thousand years. The Meridians meaning paths are the main trunks that run longitudinally within the body. The Meridian system consists of about 400 acupuncture nodes and 20 Meridian channels connecting most of these points. It deals with the routing and distribution of certain signals that may affect physiological functions. It integrates meridians, tissues and organs into a complex system.

Initially, modeling of the acupuncture system is investigated. The physical effect of injecting an acupuncture needle at a node is suggested by an equivalent …

Modeling Edge Effects Of Mesa Diodes For Silicon Photovoltaics, Jesse S. Appel

Dissertations

A mesa diode has been modeled and its performance under dark and illuminated conditions has been simulated using a commercial finite element software package. These simulations have led to a determination of the self-consistent solution to the continuity equations for electrons and holes using the steady-state drift-diffusion model for carrier dynamics coupled with electric potential determined from Poisson's equation. The purpose of these simulations has been to determine the influence of edge conditions on the overall performance of mesa diodes under dark and illuminated conditions.

Mesa diode arrays are fabricated on crystalline silicon solar cells. They are an array of …

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 …

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

Dissertations

No abstract provided.

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 …

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. …