Household air pollution (HAP) is responsible for almost 4 million premature deaths every year, a burden that is primarily carried by women and children in developing countries. The mortality and morbidity impact of HAP can be significantly alleviated through clean cookstove interventions. However, for these interventions to be effective, the new intervention stove must be a substantially cleaner technology and adoption should be high and sustained over time. Woody biomass is the fuel of choice in many developing communities, and contributes substantially to HAP. Several organizations have launched clean cooking interventions to address this issue. However, the majority of those interventions do not address adoption related challenges, that they often face. This thesis explores previous studies on Human-Centered Design (HCD) and the impact of feedback and data access on behavior change. It details a HCD process and methodology applied during the design process of an air quality feedback system, to improve adoption of liquefied petroleum gas (LPG) cookstoves in Rwanda. The feedback system is intended to provide real-time air quality information to stove users and potentially encourage them to abandon traditional biomass cookstoves in favor of the cleaner LPG stoves.

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In this thesis, the development of a novel electro-thermally actuated bi-stable out-of-plane two way actuated buckled micro-bridge for a potential application in optical switching is presented. The actuator consists of a bridge supported by 'legs' and springs at its four corners. The springs and the bridge are made of a tri-layer structure comprising of 2.5??m thick low-stress PECVD oxide, 1??m thick high-stress PECVD oxide and 2??m thick heavily phosphorus doped silicon. The legs, on the other hand, are 2??m thick single layer heavily phosphorus doped silicon. Both legs and springs provide elastically constrained boundary conditions at the supporting ends, without of which important features of the micro-bridge actuator could not have been achieved. This microbridge actuator is designed, simulated using ANSYS, fabricated and tested. The results from the testing have shown a good agreement with analytical prediction and ANSYS simulation. The actuator demonstrated bi-stability, two-way actuation and 31??m out-of-plane movement between the two-states using low voltage drive. Buckled shape model, design method for bi-stability and thermo-mechanical model are developed and employed in the design of the micro-bridge. These models are compared with Finite Element (FE) based ANSYS simulation and measurements from the fabricated micro-bridge and have shown a good agreement. In order to demonstrate the potential application of this actuator to optical switching, ANSYS simulation studies have been performed on a micro-mirror integrated with the micro-bridge actuator. From these studies, the optimum micro-mirror size that is appropriate for the integration has been obtained. This optimal mirror size ensures the important features of the actuator. Mirror fabrication experiments in (110) wafer have been carried out to find out the appropriate compensation mask size for a given etch depth and the suitable wafer thickness that can be used to fabricate the integrated system.

Powder injection molding (PIM) is a net fabrication technique that combines the complex shape-forming ability of plastic injection molding, the precision of die-casting, and the material selection flexibility of powder metallurgy. For this study, the design issues related to PIM for fabrication of thin-walled high-aspect ratio geometries were investigated. These types of geometries are typical to the field of microtechnology-based energy and chemical systems (MECS). MECS are multi-scale (sizes in at least two or more different length scale regimes) fluidic devices working on the principle of heat and mass transfer through embedded micro and nanoscale features. Stainless steel was the material chosen for the investigations because of its high-thermal resistance and chemical inertness necessary for typical microfluidic applications. The investigations for the study were performed using the state-of-the-art computer aided engineering (CAE) design tool, PIMSolver��. The effect of reducing part thickness, on the process parameters including melt temperature, mold temperature, fill time and switch over position, during the mold-filling stage of the injection molding cycle were investigated. The design of experiments was conducted using the Taguchi method. It was seen that the process variability generally increased with reduction in thickness. Mold temperature played the most significant role in controlling the mold filling behavior as the part thickness reduced. The effects of reducing part thickness, process parameters, microscale surface geometry and delivery system design on the occurrence of defects like short shots were also studied. The operating range, in which the mold cavity was completely filled, was greatly reduced as the part thickness was reduced. The single edge gated delivery system designs, with single or branched runners, resulted in a completely formed part. The presence of microchannel features on the part surface increased the possibility of formation of defects like short shots and weld-lines when compared to a featureless part. The study explored some typical micro-fluidic geometries for fabrication using PIM. The final aspect of this study was the PIM experiments performed using a commercial stainless steel feedstock. Experiments were performed to study the mold-filling behavior of a thin, high aspect ratio part and also to study the effect of varying processing conditions on the mold-filling behavior. These experiments also provided correspondence to the mold filling behavior simulated using PIMSolver��. The PIMSolver�� closely predicted the mold-filling patterns as seen in the experiments performed under similar molding conditions. The study was successful in laying down a quantitative framework for using PIM to fabricate micro-fluidic devices. / Graduation date: 2005

Continuous process scale-down and emerging markets for low-power/low-voltage mobile systems call for low-voltage analog integrated circuits. Switched-capacitor circuits are the building blocks for analog signal processing and will encounter severe overdrive problems when operating at low-voltage conditions. There are several well-known techniques to bypass the problem. These approaches include: (1) The clock boosting schemes (e.g. 2VDD clock signal) which cannot be used in submicron low-voltage CMOS processes as gate oxide can only tolerate the technology's maximum voltage (VDD). (2) The use of scaled/lower threshold transistors, which are not always scalable to very low voltage supplies as it could suffer from an unacceptable amount of leakage current (e.g. the switch may not be fully turned off). (3) The use of bootstrapped clocking, which has added loading and possible reliability issues. (4) The switched-opamp (SO) technique which is fully compatible with low-voltage submicron CMOS processes but the operating speed limited due to slow transients from the opamp being switched off and on. In this thesis, the Opamp-Reset Switching Technique (ORST) topology is proposed for low-voltage operation. Instead of opamps being turned on and off as in the switched-opamp technique, the sourcing amplifier is placed in the unity-gain reset configuration to provide reset level at the output. In this way, high-speed operation is possible. The technique is applied to two ADCs as examples of low-voltage design. The first design is a 10-bit 25MSPS pipelined ADC using pseudo-differential structure. It is fabricated in a 0.35-��m CMOS process. It operates at 1.4V and consumes 21mW of total power. The second design is a two-stage algorithmic ADC with highly linear input sampling circuit. In addition to the low-voltage design techniques used in the pipelined ADC, radix-based digital calibration technique for multi-stage ADC is also proposed. The ADC uses a 0.18-��m CMOS technology. It operates at 0.9V supply with total power consumption of 9mW. Experimental results show that the proposed calibration technique reduces spurious free dynamic range from 47dB to 75dB and improves signal-to-noise and distortion ratio from 40dB to 55dB after calibration. / Graduation date: 2003

Multi-level decision feedback equalization (MDFE) is an effective sampled signal processing technique to remove inter-symbol interference (ISI) from disk read-back signals. Parallelism which doubles the symbol rate can be realized by utilizing the characteristic of channel response and decision feedback equalization algorithm. A mixed-signal IC implementation has been chosen for the parallel MDFE. The differential current signals from the feedback equalizer are subtracted from the forward equalizer output at the summing node to cancel the non-causal ISI. A high-speed comparator with 6 bit resolution is used after the cancellation to detect the signal which contains no ISI. In this thesis, a description of the parallel MDFE structure and decision feedback equalization algorithm are presented. The design of a high-speed summing circuitry and a high-speed comparator are discussed. The same comparator design is used for the flash analog-to-digital converter (ADC) which generates error signals for adaptation.The circuits design and layout were carried out in an HP 1.2-��m n-well CMOS process. / Graduation date: 1998

The accomplishments presented in this thesis are the development of three models for simulation of space charge generation in the phosphor layer of alternating current thin-film electroluminescent (ACTFEL) devices and the results from simulation of these models. First, a single sheet charge model is developed and simulated. The single sheet charge model is a model that simplifies the problem of modeling an arbitrary distribution of space charge across the phosphor layer by lumping all of the space charge into a sheet of charge at a specified location in the phosphor layer. In this model and all subsequent models, space charge creation is assumed to occur by field emission from bulk traps or by impact ionization of deep-level traps. A fairly exhaustive parametric variation study of the single sheet charge model is performed and the results are presented and discussed. The results show space charge effects that are quite dependent on several parameters such as the number of bulk traps in the phosphor layer, the location of the sheet of charge, the capture efficiency for space charge annihilation, and the characteristic field for impact ionization of the deep-level traps. The second model considered is a logical extension of the single sheet charge model, the two sheet charge model, which models the space charge distribution as two sheets of charge rather than one. This model has potential application in the simulation of ACTFEL devices which exhibit large and/or symmetrical space charge effects. The final model developed is an equivalent circuit/SPICE model of the single sheet charge model. Actually, two models are developed, one for space charge creation by field emission and one for impact ionization of deep-levels. Two SPICE models are required because of functional differences in the dependencies of space charge creation. The results of a simulation showing overshoot generated by SPICE are given for the field emission equivalent circuit. / Graduation date: 1996

The purpose of this study was to apply instructional system theory to the process of developing authentic English as a foreign language (ESL) materials for Indonesian pre-departure scholars. The researcher established a theoretical framework for the process through an intensive review of instructional system literature and selected an applied process model for adaptation to developing authentic ESL materials. The Stiehl-Schmall ISD model was adapted and later validated using a modified Delphi process. Seventeen panelists, randomly selected from the area of instructional systems design, ESL, and Indonesian EFL practitioners, were involved in the validation process. Feedback from panelists was analyzed and it was determined that the model was applicable for Indonesian intensive English programs. It was also found that the model, as adapted, was considered practical and useful by EFL practitioners, though many of them were not knowledgeable in instructional systems design. Indonesian EFL practitioners expected the development of the model to substantially improve the quality, effectiveness, efficiency, and relevancy of authentic English used in Indonesian intensive English programs. / Graduation date: 1993

This paper seeks to describe the process by which a database-centric web application was redesigned and rewritten to take advantage of Apache’s Lucene - an open-source information retrieval software library written in the Java programming language. After the implementation of a Lucene-based text index of “semi-structured data”, a college radio station's card catalog application was able to deliver higher-quality search results in significantly less time than it was able to do using just a relational database alone. Additionally, the dramatic improvements in speed and performance even allowed the search results interface to be redesigned and enhanced with an improved pagination system and new features such as faceted search/filtering.

This paper describes the design and initial implementation of a web-based financial information system, intended to replace a Microsoft Access financial database in support of a federally funded, international health project. This system is being reimplemented for the web in order to provide stakeholders across the country (and potentially around the world) access to the project's financial information.