Engineering Commons^™

Characterization And Modeling Of Low-Frequency Noise In Hf-Based High -Kappa Dielectrics For Future Cmos Applications, Purushothaman Srinivasan

Dissertations

The International Technology Roadmap for Semiconductors outlines the need for high-K dielectric based gate-oxide Metal Oxide Semiconductor Field Effect Transistors for sub-45 nm technology nodes. Gate oxides of hafnium seem to be the nearest and best alternative for silicon dioxide, when material, thermal and structural properties are considered. Usage of poly-Si as a gate electrode material degrades the performance of the device and hence gate stacks based on metal gate electrodes are gaining high interest. Though a substantial improvement in the performance has been achieved with these changes, reliability issues are a cause of concern. For analog and mixed-signal applications, …

Ion Assisted Magnetron Sputtering Of Tantalum Thin Film Deposition And Characterization, Hua Ren

Dissertations

The purpose of this research was to investigate the effects of ion bombardment on the crystallographic phases of tantalum films during their deposition by magnetron sputtering process, and to gain understanding of the mechanism of the ion-solid interactions during the thin film growth. Tantalum (Ta) exists in two distinct crystallographic phases: a stable α-phase with a body centered cubic (bcc) lattice structure and a metastable β-phase with a tetragonal lattice structure. The tough and ductile α-phase Ta is desired in most industrial applications, such as diffusion barrier layers in integrated circuits, metallic corrosion protective layers, and in biomedical devices. The …

Novel Model Of Cerebrospinal Fluid Dynamics Based On Hemodynamically Driven Cyclic Brain Compliance Variation, Bruno A. Mantilla

Dissertations

This study provides a novel explanation for the CerebrQ-Spinal Fluid (CSF) flow pattern observed in phase contrast cine-MRJ studies. CSF dynamics has been traditionally explained as a bulk flow from the site of production to the site of absorption. Studies done with phase contrast cine-MRI show a more complex CSF movement, that is not explainable by the bulk flow paradigm. This study describes a mechanism explaining how the energy delivered by the heart in each cycle is responsible not only for the blood flow, but also for the CSF circulation. This mechanism is based on a cyclic variation of brain …

Automatic Physical Database Design : Recommending Materialized Views, Wugang Xu

Dissertations

This work discusses physical database design while focusing on the problem of selecting materialized views for improving the performance of a database system. We first address the satisfiability and implication problems for mixed arithmetic constraints. The results are used to support the construction of a search space for view selection problems. We proposed an approach for constructing a search space based on identifying maximum commonalities among queries and on rewriting queries using views. These commonalities are used to define candidate views for materialization from which an optimal or near-optimal set can be chosen as a solution to the view selection …

New Approaches To Scaled-Up Carbon Nanotube Synthesis And Nanotube-Based Metal Composites And Sensors, Amit Goyal

Dissertations

The first phase of the work presented in this dissertation is the development of a scaleable process for the cost-effective synthesis of single walled carbon nanotubes (SWNTs) by thermally-induced catalytic chemical vapor deposition (CVD). With the goal of understanding the growth mechanism and optimize the synthesis process, the effect of CVD and catalyst parameters on nanotube formation was investigated in detail. It was found that nucleation and growth of SWNTs occurred within a few seconds of the introduction of the carbon source, carbon monoxide, at temperatures above 675°C over a Co-Mo/MgO catalyst/support system, resulting in the formation of high quality …

Drying Behavior Of Fractionated Fibers, Hussam E. Alkahasawneh

Dissertations

This dissertation studies water removal from paper produced using fractionated fibers. One of the principal aims of fiber fractionation is to separate long fibers from fines and then to use these long fibers in paper grades that require high bulk and high water absorption. However, during the paper manufacturing process, the bulk of these materials may be reduced by mechanically pressing the paper to remove water. Also the drying rate of the high bulk paper may be lower than conventional paper due to changes in the resistance to heat transfer. The main objective of this dissertation is to further develop …

A Study To Investigate The Relationship Between A User’S Thermal Comfort And Seat Pan Materials, Anil Raghavendra Kumar

Dissertations

Workers performing sedentary tasks in job types such as administrative, technical, customer service and executive could be seated for four or more hours during their normal work shift. Due to the prolonged periods of sitting, a worker could experience dissatisfaction, discomfort, and fatigue, which could lead to reduced performance. Symptoms of discomfort could over time lead to injuries and illnesses such as low back pain, cumulative trauma disorders, disc herniation, and pressure ulcers.

Materials And Processes For Printed Electronics: Evaluation Of Gravure Printing In Electronics Manufacture, Erika Hrehorova

Dissertations

The primary goal of printing electronics is to create structures and devices that are functionally similar to conventional electronics, but at greater speed, lower cost and less production complexity. There are advantages and challenging disadvantages of using printing processes to manufacture electronic devices. Printing has been very well optimized for printing visual images that meet the requirements of human eye. However in the production of functional electronic devices, there are more stringent requirements on resolution, registration and quality of printed features and functional layers.

The main goal of this work is to form a starting point to a bigger picture …

In Vitro Studies Of Degradation And Bioactivity Of Aliphatic Polyesther Composites, Georgia Chouzouri

Dissertations

In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation.

Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive …

Low Jitter Phase-Locked Loop Clock Synthesis With Wide Locking Range, Adnan Gundel

Dissertations

The fast growing demand of wireless and high speed data communications has driven efforts to increase the levels of integration in many communications applications. Phase noise and timing jitter are important design considerations for these communications applications. The desire for highly complex levels of integration using low cost CMOS technologies works against the minimization of timing jitter and phase noise for communications systems which employ a phase-locked loop for frequency and clock synthesis with on-chip VCO. This dictates an integrated CMOS implementation of the VCO with very low phase noise performance. The ring oscillator VCOs based on differential delay cell …

Direct Simulations Of Cells Motions And Deformations In Flow, Quan Jin

Dissertations

Direct numerical simulations (DNS) are used to study the motions and deformations of blood cells, especially leukocytes, in pressure driven flows in parallel plate channels with both smooth and uneven walls under adhesion force between the leukocytes and the channel wall.

Leukocytes are represented by two composite fluid models. The first model is the compound-drop model in which the cytoplasm and the nucleus are modeled as fluids, and the second one is the drop-rigid-particle model in which the cytoplasm is modeled as a fluid and the nucleus as a rigid particle. The adhesion force is computed using two adhesion force …

Formation Of Rdx Nanoparticles By Rapid Expansion Of Supercritical Solution : In Situ Characterization By Laser Scattering, Takuya Matsunaga

Dissertations

Cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), a well-known energetic material, is highly explosive. Reduction of the sensitivity of RDX is desired for safe handling and

storage in military applications. Data on the sensitivity of RDX in the 10-1000 µm crystal size range suggested that the impact sensitivity could be further reduced by reduction of the crystal size to the sub-micron or nano-scale (Armstrong, 1990). Recent research with nano-RDX obtained using Rapid Expansion of Supercritical Solutions (RESS) confirmed these expectations (Stepanov, 2005).

RESS process appeared to be one out of a few techniques of production of nanoscale energetic materials free of the risk of explosion. …

Analysis Of Truck Delays At Container Terminal Security Inspection Stations, Dae-Gwun Yoon

Dissertations

After September 11, 2001, special attention has been given to the vulnerability at container transportation to terrorist activities. United States Customs and Border Protection (CBP) has set up inspection stations for containers at seaport terminals to screen containers, but this practice affects the truck turnaround time in the seaport by generating additional processing delays.

This dissertation analyses the additional truck turnaround time incurred at the inspection stations under various levels of security. Queuing models were used to estimate truck delay as containers are inspected at two successive security inspection stages. Each stage may utilize one or more inspection equipment. The …

Synthesis And Analysis Of Reactive Nanocomposites Prepared By Arrested Reactive Milling, Swati M. Umbrajkar

Dissertations

Different types of reactive nanocomposites have been synthesized by Arrested Reactive Milling (ARM). The technical approach was to increase the interface area available for heterogeneous reaction between solid fuel and oxidizer components. Using aluminum as the main fuel and different metal oxides as oxidizers, highly energetic reactive nanocomposites with different degrees of structural refinement were synthesized. Specifically, stoichiometric Al-MoO₃, Al-CuO, and Al-NaNO₃ material systems were studied in detail.

The correlation of heterogeneous exothermic reactions occurring in the nanocomposite powders upon their heating at low rates and ignition events observed for the same powders heated rapidly was of …

Reliability Studies Of Tin/Hf-Silicate Based Gate Stacks, Naser Ahmed Chowdhury

Dissertations

Hafnium-silicate based oxides are among the leading candidates to be included into the first generation of high-Κ gate stacks in nano-scale CMOS technology because of their distinct advantages as far as thermal stability, leakage characteristics, threshold stability and low mobility degradation are concerned. Their reliability, which is limited by trapping at pre-existing and stress induced defects, remains to be a major concern.

Energy levels of electrically active ionic defects within the thick high-Κ have been experimentally observed in the context of MOS band diagram for the first time in Hf-silicate gate stacks from low temperature and leakage measurements. Excellent match …

Central And Peripheral Autonomic Influences : Analysis Of Cardio-Pulmonary Dynamics Using Novel Wavelet Statistical Methods, Anne Marie Petrock

Dissertations

The development and implementation of novel signal processing techniques, particularly with regard to applications in the clinical environment, is critical to bringing computer-aided diagnoses of disease to reality. One of the most confounding factors in the field of cardiac autonomic response (CAR) research is the influence of the coupling of respiratory oscillations with cardiac oscillations.

This research had three objectives. The first was the assessment of central autonomic influence over heart rate oscillations when the pulmonary system is damaged. The second was to assess the link between peripheral and central autonomic control schema by evaluating the heart rate variability (HRV) …

Design And Performance Of Cdma Codes For Multiuser Communications, Radharani Poluri

Dissertations

Walsh and Gold sequences are fixed power codes and are widely used in multiuser CDMA communications. Their popularity is due to the ease of implementation. Availability of these code sets is limited because of their generating kernels. Emerging radio applications like sensor networks or multiple service types in mobile and peer-to-peer communications networks might benefit from flexibilities in code lengths and possible allocation methodologies provided by large set of code libraries.

Walsh codes are linear phase and zero mean with unique number of zero crossings for each sequence within the set. DC sequence is part of the Walsh code set. …

Numerical Study Of Flow In Three-Dimensional Fiber Networks And Sedimentation Of Curved Fiber By Lattice Boltzmann Method, Xiaoying Rong

Dissertations

Fiber network is modeled as a three-dimensional random cylindrical fiber network. Nonlinear behavior of fluid flowing through the fiber network is numerically simulated by using the lattice Boltzmann (LB) method. Nonlinear relationship between the friction factor and the modified Reynolds number is simulated and analyzed by using the Fochheimer equation, which includes the quadratic term of velocity. There is a transition from linear to nonlinear region when the Reynolds numbers are sufficiently high, reflecting the inertial effect of the flows. The simulated permeability of such fiber network is compared to the experimental results and the finite element simulations.

Dynamic motions …

Hydrodynamics Investigation Of In-Vitro Dissolution Testing, Ge Bai

Dissertations

Dissolution testing is routinely carried out in the pharmaceutical industry to determine dissolution rate of solid dosage forms. The United States Pharmacopoeia (USP) Dissolution Apparatus II is the device most commonly used for this purpose. Despite its widespread use, dissolution testing remains susceptible to significant error and test failures. Limited information is available on the hydrodynamics of this apparatus, although hydrodynamic effects can play a major role on test performance.

Laser-Doppler Velocimetry (LDV) and Computational Fluid Dynamics (CFD) were used here to experimentally map and computationally predict the velocity distribution inside a standard USP Apparatus II under the typical operating …

Some Contributions On Mimo Radar, Nikolaus Lehmann

Dissertations

Motivated by recent advances in Multiple Input Multiple Output (MIMO) wireless communications, this dissertation aims at exploring the potential of MIMO approaches in the radar context. In communications, MIMO systems combat the fading effects of the multi-path channel with spatial diversity. Further, the scattering environment can be used by such systems to achieve spatial multiplexing. In radar, a complex target consisting of several scatterers takes the place of the multi-path channel of the communication problem. A target's radar cross section (RCS), which determines the amount of returned power, greatly varies with the considered aspect. Those variations significantly impair the detection …

Nanoparticle Formation And Coating Using Supercritical Fluids, Abhijit Aniruddha Gokhale

Dissertations

Jet breakup phenomenon and nanoparticle formation

The focus of this dissertation is to study the SAS process to manufacture nanoparticles with minimum agglomeration, controlled size and size distribution. Solution jet breakup and solvent evaporation into supercritical fluid (SC CO₂) is studied using high speed charged coupled device (CCD) camera facilitated with double shot particle image veloimetry (PIV) laser and a high pressure view cell. Particles formation using SAS is studied. Polyvinylpyrrolidone (PVP) particles are formed using micron size capillary nozzles and combination of thermodynamically good and poor solvents in order to achieve nano-sized particles with reduced agglomeration and …

Solvent Resistant Microporous/Nanoporous Polymeric Hollow Fiber And Flat Film Membranes And Their Applications, Praveen B. Kosaraju

Dissertations

The separation and purification of organic-solvent-based process streams may be carried out by membrane processes such as nanofiltration/ultrafiltration/microfiltration and membrane solvent extraction. Lack of solvent stability and chemical stability of most commercially available membranes is limiting the utilization of the above mentioned membrane technologies. This dissertation was primarily focused on developing solvent resistant hollow fiber and flat film membranes for separation and purification of organic-solvent-based process streams.

Available porous polymeric supports (Polypropylene (PP), Polyethersulfone (PES) and Nylon) suitable for the required solvent-stable applications were chosen first and then the supports were modified to satisfy the requirements for the applications. Membrane …

Flow Characteristics And Phase Interactions Of Evaporating Sprays In Gas-Solid Suspensions, Muhammad Mushahid Rafique Qureshi

Dissertations

Evaporating spray jets have a wide range of applications in many industrial processes such as fluidized catalytic cracking of crude oil in petroleum refinery, coal gasification, fluidized coking to make synthetic crude oil, and condensed mode gas polymerization. The rapid evaporation of spray jets significantly affects the gas-solids mixing, solids concentration, gas/solids temperature and gas/solids velocity acceleration. The complex interactions mechanism of phase change, three phase interaction, heat and mass transfer of gas, solids and evaporating droplets dominate the process efficiency and product quality. In such three-phase flows, the phase transport characteristics are influenced by both droplet-gas interaction and droplet-solid …

Enhancement Of Fluidization And Filtration Using Nanoparticle Agglomerates And Aerogels, Jose A. Quevedo

Dissertations

Previous works have classified the fluidization behavior of nanoparticles as Agglomerate Particulate Fluidization (APF) and Agglomerate Bubbling Fluidization (ABE). These fluidization behaviors are quite different in regard to the fluidized bed expansion, the presence of bubbles and the smoothness of the bed surface, with APF nanopowders showing a much more homogeneous fluidization and a much better dispersion than ABE nanopowders which are generally very difficult to fluidize and show vigorous bubbling. In the present work, the fluidization of APF as well as ABF nanopowders is studied in depth, both conventionally, and in the presence of extemal assistance; several related topics …

Investigation Of Formation And Applications Of High-Speed Liquid Projectiles, Oleg Petrenko

Dissertations

The work comprises experimental and numerical studies of generation and application of high-speed liquid projectiles. Numerical models were created for a projectile formation by two kinds of launchers, water extruder and water cannon. In the water extruder the kinetic energy of a fast moving piston is transferred to the water load and extrudes the load at a high speed. By contrast in the water cannon the water load itself accumulates the kinetic energy from the expanding combustion gasses. Then, in the course of water motion through the converging nozzle the energy is redistributed between head and tail of the projectile. …

Doppler Spread Estimation In Mobile Fading Channels, Hong Zhang

Dissertations

The Doppler spread, or equivalently, the mobile speed, is a measure of the spectral dispersion of a mobile fading channel. Accurate estimation of the mobile speed is important in wireless mobile applications which require such as knowledge of the rate of channel variations. In this dissertation, first the performance of classical crossing- and covariance-based speed estimators is studied. Next, the problem of mobile speed estimation using diversity combining is investigated. Then, a nonparametric estimation technique is proposed that is robust to different channel variations. Finally, cyclostationarity-based speed estimators which can be applied either blindly or with the aid of pilot …

Reactive Modification And Crystallization Behavior Of Foamed Poly(Butylene Terephthalate), Byeong Joon Jeong

Dissertations

The objective of this study is to investigate the feasibility of preparing low density foams based on poly(butylene terephthalate) (PBT) through modification of its molecular structure and rheological characteristics by reactive extrusion. The scientific and/or engineering interpretation of the experimental data was based on fundamentals of extrusion, crystallization mechanisms, as well as information on reactivity and tendency toward degradation of PBT.

As a preliminary study, the extrusion foaming behavior of a commercial linear semi-crystalline PBT with a chemical blowing agent (CBA) was investigated. Foam characteristics were functions of extrusion operational variables, such as die set temperature and screw speed. Gas …

Open Software To Innovation: The Critical Success Factors Of Massively Multiplayer Online Role Playing Games (Mmorpg) In China And Ireland., Wei Chen

Dissertations

This project investigates the factors leading to the success of China’s Massively Multiplayer Online Role Playing Games (MMORPG) market and gives an analysis of how Open source has contributed to these success factors. It then will look at how the use of open source is mirrored in Ireland’s market for example, the software sector to see if the same factors are apparent or there are indicators of these. Knowledge Management plays a very important role for fasten the innovation of Open source software development in China.

A Framework For The Introduction Of Organisational Learning Using Web 2.0 Applications, Joseph M. Reynolds

Dissertations

We are now becoming more and more dependent on web technologies in our personal lives for our communication, information and entertainment needs. But what about using these skills and technologies for our business lives, could they transform the business world in the same way they have transformed our personal world? The purpose of this research was to investigate whether the latest web applications could be successfully implemented into an organisation who wished to transform itself into a modern and flexible organisation. This research was primarily focused on introducing organisational learning into the business through the use of new technology and …

Using Gis To Assess Ireland's Knowledge Economy And Its Readiness For Knowledge Based Activity, Niall Mcguinness

Dissertations

The attractiveness of emerging low wages economics to primary industries such as manufacturing and production is forcing many western economies to transition to knowledge economies. In the absence of many forms of primary industry lost to low wage economies, the European Union and its members are fast realising the importance of attracting knowledge based enterprise in order to maintain Europe’s economic climate. Ireland too has a stated aim to become a knowledge economy by the year 2010. This can be achieved by investing in higher education and attracting knowledge industry to the country. Ireland has made some progress to achieving …