The PhD degree requires 90 credit hours of graduate study with 60 credit hours beyond the master's degree.
We encourage students to begin research early in their programs.
The comprehensive examination, taken during the first year of study, is a requirement for continuation in the PhD program.
All doctoral students must pass a PhD qualifying examination and submit a written PhD thesis proposal in their third years of full-time graduate study. Each student who passes the PhD qualifying examination is assisted in matters pertaining to his or her thesis research by a faculty thesis advisory committee. The student's research advisor serves as chair. The committee meets with the student at least once each year.
The Department's graduate research is partitioned roughly into a few categories, many of which overlap depending on the type of research that the student undertakes. As examples, signal and image processing projects are important in biomedical ultrasound and implemented in VLSI technology, and opto-electronics and solid-state electronics often overlap.
Biomedical Ultrasound and Biomedical Engineering
High-frequency sound (ultrasound) is used in many areas of medicine to obtain images of soft organs of the body. High-intensity ultrasound is used to destroy kidney and gallstones without surgery (lithotripsy). Basic scientific investigations focus on the interactions of ultrasonic energy with biological materials ranging from heart and liver tissues, to bones and kidney and gallstones. Studies are also underway to demonstrate applications of ultrasonic contrast-producing agents similar to radiological contrast and tracer techniques. The results from these efforts are used to improve or extend clinical applications of ultrasonic techniques, both in diagnosing diseases of the heart and liver, and in therapeutic users such as lithotripsy. This work is also used to set standards for exposure of patients during examination and to improve the application of high-intensity sound for therapy.
Signal and Image Processing and Communications
Research in this area includes studies of wide-band radar and sonar systems design, digital image and video processing, very low bitrate video compression, and medical image processing. Communications research focuses on frequency hop codes for multiple-access-spread-spectrum communications, designed to minimize interference in radar and sonar systems. Among the digital image processing projects are image enhancement and restoration, image segmentation/recognition, and processing of magnetic resonance images. Active research is being conducted on all aspects of digital video processing, including 2-D and 3-D motion estimation techniques, deformable motion analysis, stereoscopic image analysis, standards conversion and high-resolution image reconstruction, and object-based methods for very low bitrate video compression. The emphasis of biomedical signal processing is on applications in ultrasound and magnetic resonance imaging. Research projects include spectral analysis in one, two, and three-dimensional spaces, analysis and algorithms for computed tomography, and inverse scattering techniques for imaging tissue characterization.
Integrated Electronics and Computer Engineering
Department research in VLSI and CAE addresses topics in integrated circuit design methodologies and automation. Specific system-oriented research includes an analytical model for multi-access protocols with prioritized messages and distributed control architecture. Design for testability studies are exploring operational parallelism in any testing process to determine the set of automated test procedures which minimizes the silicon area consumed by the built-in self-test structures. A program in Low Temperature Superconducting Digital Electronics, described in more detail below, is applying VLSI design and analysis techniques to the development of new ultrafast superconducting digital integrated circuits. Other research in this area focuses on the design and analysis of high performance VLSI-based digital and analog integrated circuits and their systems. Specifically, speed, area, and power dissipation tradeoffs are investigated in terms of application-specific constraints and their fundamental circuit level limitations. System architectural issues which directly affect performance are considered, such as pipelining, retiming, and the design of clock distribution networks. System performance can also be improved by applying innovative technologies. Thus, specialized circuits, developed using advanced technologies, and their related design techniques and methodologies are investigated to permit the development of high-speed and low-power integrated systems.
Superconductivity and Solid-State Electronics
A major focus for research in the Department involves design, fabrication, and testing of ultrafast superconducting digital integrated circuits. This is carried out under the auspices of the University research initiative in Low-Temperature Superconducting Digital Electronics. This research is leading toward the development of integrated circuits that can carry out digital signal processing and analog-to-digital conversion at unprecented rates, using the new "single-flux quantum logic." In the area of ultrafast electronics, picosecond electrical and optical pulses probe the transient response of semiconducting and superconducting devices, such as Metal-Semiconductor-Metal (MSM) photodiodes and tunnel junctions. Research in high-temperature superconductivity is concentrated on developing thin-film devices based on Y-Ba-Cu-O for applications including high-speed electronic interconnects, passive microwave circuits, high-frequency Josephson junctions, and optoelectronic hybrid and monolithic devices. Also under study is a superconducting implementation of quantum computation, in which Josephson-junction based circuits may manipulate quantum superposition states to efficiently perform specialized computational tasks. Formerly believed intractable, computational problems such as factoring large numbers may eventually be implemented in such quantum computers.
Information processing with optical pulses offers data rates much in excess of what is available with electronic signals. Examples are long-haul and local-area-fiber networks, and optical computing. Optoelectronics research is directed at obtaining a detailed understanding of ultrafast phenomena and ultrafast nonlinearities in semiconductors and high-temperature superconductors, and at using silicon quantum dots and nanometer-size objects in optoelectronics and biosensing. Using these basic results, novel optoelectronic and opto-optic devices are designed. This work is a combination of laser technology, solid-state physics, materials science, and device physics and engineering. Recent research includes the study of electron and hole thermalization and recombination in semiconductors and semiconductor quantum wells, and the optoelectronic properties of porous silicon, which unlike crystalline silicon emits light efficiently at room temperature. Studies span the range from fundamental materials characterization to device fabrication and testing. In the area of superconducting optoelectronic devices, studies have included laser processing of Y-Ba-Cu-O epitaxial thin films into oxygen-rich (superconducting) and oxygen-poor (semiconducting) regions, together with pump-probe femtosecond reflectivity measurements of both phases to determine relevant response times.
Microelectromechanics and Electrostatics
Research in the microelectromechanics area is directed to the development of small integrated sensors and transducers, using microfabrication techniques developed for silicon microelectronic circuits. Efforts are focusing on issues of noise and sensitivity in displacement sensors and accelerometers. Cryogenic electro-mechanical transducers and vacuum tunneling transducers sensitive to sub-Angstrom displacements are also being developed. Research on particle electro-mechanical interactions exhibited by particles in the size range from 5 to 500 microns when electric or magnetic fields are present. Dielectrophoretic levitation techniques have been developed for investigating di-electric properties of individual metallic or dielectric particles or even biological cells. The levitation systems used are based on a variety of custom-designed controller boards that interface a computer to various video cameras and linear diode arrays. These unique facilities can perform automated variable-frequency measurements upon individual particles. The flow of powders and granular media under the influence of electric or magnetic fields is another topic of interest. A 2-D flow visualization technique is being applied to the study of 100 micron magnetic carrier particles in realistic models for magnetic brush xerographic devices. Some very practical research on electrostatic hazards is driven by the needs of industry to avoid serious explosions that may plague liquid and dry chemical and electronic production facilities. Recent effort has been devoted to development of a very general model for predicting the relaxation and dissipation of electrical charge within insulating materials such as liquids and dry powders.