Pattern recognition algorithms have been proposed as a way to control powered lower limb prostheses, specifically for transitioning between the different pre-programmed locomotion modes of the prosthesis (e.g., level ground walking, stair ascent, etc.). However, these algorithms cannot track changes in the statistical characteristics of input signals, and do not...
The purpose of the dissertation is to develop a framework for equilibration of activity-trip chain demand in an integrated system of activity scheduling and travel choices within a dynamic network equilibrium framework. Activity-based modeling systems generate detailed activity chain schedules for individuals, which have to be assigned to transportation networks....
The rapid growth of digital imaging technology and the accumulation of large collections of digital images has created the need for efficient and intelligent schemes for content-based image retrieval. Our goal is to organize the contents semantically, according to meaningful categories. We present a new approach for semantic classification that...
The optical and magneto-optical properties of the ferromagnetic semiconductors, InMnAs and its alloy InMnAsP were investigated to determine the band structure and nature of the ferromagnetism in these materials. Alloys were grown by metal-organic vapor phase epitaxy. Infrared absorption of InMnAs was investigated to determine the presence and properties of...
Ceramic matrix composites are known for their low density, high strength and high stiffness, but lower fracture toughness compared to metal matrix composites. The addition of a reinforcing agent within the matrix can increase the toughness of the composite via many strain energy absorption mechanisms such as plastic deformation. This...
Substrate-mediated delivery involves the immobilization of DNA, complexed with nonviral vectors, to a biomaterial or surface that supports cell adhesion. Cells cultured on the substrate are exposed to elevated DNA concentrations within the local microenvironment, which enhances transfection. As surface properties are critical to this delivery approach, self-assembled monolayers (SAMs)...
Autoxidation is a primary route by which lubricants in working conditions undergo degradation. Degraded lubricants, if not replaced periodically, contribute to increased wear and product failure. Experimental studies of lubricant degradation have yielded useful results but have left important questions unanswered. While many computational studies of degradation have been carried...
In composite manufacturing, Vacuum Assisted Resin Transfer Molding (VARTM) is becoming increasingly important as a cost effective manufacturing method of structural composites. In this process the dry preform (reinforcement) is placed on a rigid tool and covered by a flexible film to form an airtight vacuum bag. Liquid resin is...
Next generation of high performance nano-optoelectronic integrated circuits will require an integral combination of highly efficient all-optical nanophotonic devices and electrically-pumped nanophotonic devices, which will enable the chip to process optical information all optically with ultrafast speed and electro-optically to interface with the electronic control plane. The realizations of such...
As technology moves into deep submicron and nanoscale era, undesirable trends such as increasing power density, leakage power, and temperature variation within chips have made thermal effects emerge as a major bottleneck in further technology scaling. Thermal effects are no longer considered as just a reliability issue, but it also...
This dissertation examines the impact of product returns on effective supply chain management. Within this area of research, known as Closed-Loop Supply Chain Management, we consider both strategic and tactical level reverse logistics and inventory management problems from the perspective of a firm which must efficiently process returned items. More...
Oxide surface structures play a key role in many technological processes, including catalysis, thin film growth, and layered structures, and a thorough understanding of surface structures and surface structure dynamics is required in order to better engineer materials systems for these processes. This research works towards understanding these fundamental principles...
Structural dynamics in three polymer blend systems, differing largely with respect to morphology, have been investigated. The first system, composed of two immiscible homopolymers, exhibits a microstructure of micron-sized droplets dispersed in a matrix phase. We have examined small-angle x-ray scattering (SAXS) as a new approach for conducting in situ...
Living organisms grow precisely controlled assemblies of inorganic crystals using organic substrates. This observation has inspired the strategy of using synthetic organic templates for the growth of tailored inorganic thin films. It has been previously shown that monomolecular organic layers floating on supersaturated aqueous subphases (Langmuir monolayers) select the structure...
The self-assembly of quantum dots (QDs) in thin solid films is an important area of nanotechnology with many relevant applications. In the present thesis, three problems related to the growth and self-assembly of QDs are investigated.
In Chapter 1, a new instability mechanism for the formation of QDs associated with...
Dimensionally constrained material systems are at the forefront of current materials research because of their novel and often enhanced physical, chemical and biological properties. The dimensionality effects are pervasive through different classes of materials including ceramics, metals and polymers. Often times dimensionality effects are manifested as internal structure variations in...
The work presented in this dissertation focuses on ceramic anode materials for solid oxide fuel cells (SOFCs). The primary goal was to characterize the anode and relate the electrochemical behavior to the microstructure. The anode that was most extensively studied in this work was a composite of Gd0.10Ce0.90O1.95 (GDC) and...
Granular matter and living cells represent two extremes of what have come to be regarded as complex systems - systems characterized by a richness in global behavior that is not easily deduced from the interactions of their individual parts, even when those interactions are simple and well understood. On the...
This dissertation demonstrates how self-assembly can direct nanoscale ordering and optimize electronic properties of organic semiconductors, as well as organic-inorganic hybrids. In excitonic solar cells, controlling the ordering and interfaces between electron-transporting (n-type) and hole-transporting (p-type) domains is crucial. In addressing this challenge, hybrid nanostructures were designed by mineralization of...
The current trend of ceramic nanotechnology has motivated an ever-increasing need to achieve exquisite control over size, shape, and spatial confinement for functional oxide architectures, in an equivalent manner demonstrated for semiconductors. However, the unique nature of ceramics has posed major challenges for most traditional nanofabrication technologies, putting the development...
The average and local glass transition temperatures (Tgs) and physical aging behavior of various confined polymers were studied in order to gain an understanding of these surface/interface effects and their propagation into the polymer. Using a novel multilayer/fluorescence method, the Tgs of layers at the free surface, substrate-polymer interface, and...
Atrial fibrillation (AF) is the most common supraventricular tachyarrhythmia and its prevalence is expected to increase with the aging population. However, the mechanisms AF initiation, maintenance and termination are not completely understood. The surface electrocardiogram (ECG) characteristics are a direct reflection of pathophysiologic events in the atria and can be...
In recent years, research has expanded the uses of triblock copolymer gels to a wide variety of applications including everything from ceramics processing to regenerative medicine and drug delivery. The research presented in this dissertation focuses on a physically crosslinked, block copolymers gel system in a selective solvent. This system...
Motivated by performance requirements of future medical stent applications, experimental research addresses the design of novel TiNi-based, superelastic shape-memory alloys employing nanoscale precipitation strengthening to minimize accommodation slip for cyclic stability and to increase output stress capability for smaller devices. Using a thermodynamic database describing the B2 and L21 phases...
Increasing interest in long-life bone implants with reduced mechanical properties reducing the stress-shielding effect and a structure mimicking bone porous architecture has encouraged study and development of fabrication methods for porous NiTi. The main objective of this work was to advance these goals by developing new processing procedures for porous...
Recent work points out the importance of the solid-solid interface in explaining the high photoactivity of mixed phase TiO2 catalysts. The goal of this research was to probe the synthesis-structure-function relationships of the solid-solid interfaces created by the reactive direct current (DC) magnetron sputtering of titanium dioxide. I hypothesize that...
As device sizes decrease, more functionality can be placed in an integrated circuit. Therefore, the design complexity of these circuits increases. To deal with complexity, designers move to higher abstraction levels. Currently, the highest abstraction level is the system-level. In our work we investigate the synthesis and verification problem at...
A multicomponent bimodal poly(vinyl acetate) (PVAc) polymer composite has been scientifically designed to increase biaxial plastic flow stabilization for the achievement of large biaxial deformations. For this, a systems-based approach was used for the computational materials design of a high performance bubblegum whose mean in-vivo bubble diameter exceeds that of...
Tissue engineering offers a promising approach for the replacement of diseased or injured tissues, and is based upon the premise that cells can be induced to form new tissues when presented with the appropriate set of environmental cues. Polymer scaffolds play a central role in most tissue engineering strategies by...
A critical challenge in improving the quality of life for spinal cord injury survivors is to restore the capacity to grasp and manipulate objects. While progress has been made to restore hand function by using functional electrical stimulation (FES) to activate muscles, providing the means to control the multiple degrees...
Recent assessment of material property requirements for blast resistant applications, especially for the naval ship hulls, has defined the need to design steels with high stretch ductility and fragment penetration resistance, along with high strength and adequate toughness. Using a system based computational materials design approach, two series of austenitic...
This thesis focuses on resource allocation in wireless communication and networking. Resource allocation has been studied widely, for example, to maximize the system-wide throughput or to minimize the average delay per user. Moreover, the utility-based framework is becoming an important tool for addressing fairness and Quality-of-Service (QoS) for individual users....
The research reported in this dissertation covers the development of two high-performance concrete materials, Very-High-Strength Concrete (VHSC) and Frangible Concrete, and the philosophy of engineering the microstructure of these materials to produce their specific beneficial traits. The underlying problem addressed was how to optimize their design to maximize their desirable...
Wood-derived ceramics and composites have been of interest in recent years due to their unique microstructures, which lead to tailorable properties. The porosity and pore size distribution of each wood type is different, which yields variations in properties in the resultant materials. The thermal properties of silicon carbide ceramics and...
ZnO is a member of the unique class of materials known as transparent conducting oxides (TCOs). TCOs are currently used for many applications including flat panel displays, solar cells, and energy efficient windows. Of particular interest is the possibility of developing materials that have high electron mobilities, such that conductivities...
This dissertation examines growth of platinum nanoparticles from vapor deposition on SrTiO3 using a characterization approach that combines imaging techniques and X-ray methods. The primary suite of characterization probes includes atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and X-ray absorption spectroscopy...
While self-consolidating concrete (SCC) may no longer be considered a "new concrete", there are still significant challenges to overcome before there is broader acceptance of SCC. One of these challenges concerns the formwork pressure exerted by SCC. A major advantage of SCC is the accelerated casting process due to the...
The adoption of surfactant replacement therapy (SRT) for the treatment of neonatal respiratory distress syndrome (nRDS) is one of the main contributors to the dramatic decline in infant mortality rates observed in the 1980s. Despite the significant efficacy of animal-derived surfactant preparations, there are still some concerns associated with their...
With the rapidly growing global demand in energy nowadays, innovation and technology become critical for a transition to renewable energy, high energy efficiency or low-carbon emission. Thin-film materials are especially favorable in energy management due to the easy integration into devices. The transport properties for heat and electrical conduction are...
Self-assembly is an important process in biological system to build various bioactive structures from small amphiphilic molecules. The structural versatility of amphiphile self- assembly also provides a unique platform for the design of functional soft materials with controllable structural features. However, little is known about the correlation between external stimuli,...
The ribosome, the cell’s machine for synthesizing proteins, can be thought of as the chef of the cell. Just as a chef reads a recipe and combines ingredients to create a dish, the ribosome reads cellular instructions and connects building block molecules (amino acids) to construct proteins. Like the final...