Theses and Dissertations

The human mind is very imprecise and uncertain most of the time. We are allowed to think as we wish, as things really are. This, however, is not how computers are designed to allow us to solve realistic problems. Now the question arises: how do we represent uncertainty and impreciseness using very accurate devices? In order to add flexibility into mechanical design, fuzzy logic can be used to represent the imprecise data, such as how humans think.

The purpose of this thesis is to design a 3-D exoskeleton model based on the mechanism of a kind of two degree-of-freedom suspension system. There are two main systems in the exoskeleton, including weight support system and walking assistive system. The weight support system consists a series of linkages, pulleys and springs, which is able to compensate wearer's weight, make wearer feel much more easier when keeps a crouching posture. The walking assistive system consists clutch system and cable release system, which is able to help exoskeleton walk when led by wearer.

The electromagnetic properties of a live biological system are extremely important to many medical applications. While information about electromagnetic properties of tissues are available in the literature, little or no data are available for a single cell or subcellular structures. Microwave biological/cell detection has been demonstrated to be useful and promising in many medical applications due to its internal properties such as non-invasive, fast and label-free.

Origami and its related fields of paper art are known to map to mechanisms, permitting kinematic analysis. Many origami folds have been studied in the context of engineering applications, but a sufficient foundation of principles of the underlying class of mechanism has not been developed.

For the first time, the impedance spectrum of live Jurkat T-lymphocytes human cells was characterized in a single sweep spanning six decades of frequency from 9 kHz to 9 GHz. The ultrawide bandwidth bridged the traditional impedance spectroscopy at kilohertz to megahertz frequencies with the recently developed microwave dielectric spectroscopy, which can probe the cell interior without being hindered by the cell membrane.

Dimensional synthesis of the four-bar mechanism could not be determined precisely due to many constraints such as manufacturing tolerance, joint clearance, thermal deformation, the deflection and so on. All of these constraints are included in the uncertainty of the dimensions of the four-bar mechanism. In this research, this uncertainty will be modeled based on the fuzziness one of the precision points of Freudenstein's equation that builds intervals of link's dimensions with membership functions.

A closed-loop capacitance sensing and control mix-mode circuit with a dedicated sensor electrode and a proportional-integral controller was designed for MEMS varactors. The control was based on tuning the bias magnitude of the MEMS varactor according to t

Vehicles need to have regular maintenance and repair so that hoods need to be easy to opened and closed. With the addition of more women car owners, this requirement that automobile hoods requiring lower opening and closing efforts become even more important. This research looks into vehicle engine hood mechanisms that incorporate a pin go to assist in the opening of the hood. The design of such mechanisms as divided into two steps. The first is carried out using three position synthesis.

For the first time, wafer-scale fabrication of PtSe2 MOSFETs was demonstrated by photolithography. The on PtSe2 is grown by thermally assisted conversion (TAC) of Pt films under Se vapor at 400 °C. Taking advantage of the unique property of PtSe2 to transition from semiconductor to semimetal as its thickness increases beyond a few monolayers, channel recess was adapted for improving gate control while keeping the contact resistance as low as 0.008 Ω∙cm. The wafer-scale fabrication resulted in uniform device characteristics so that average vs. best results were reported, as well as RF vs.

This thesis consists of two parts, with two linkage mechanisms investigated: A spring-loaded four-bar linkage mechanism and the compound bow mechanism (a band-drive mechanism). In the first part of this thesis, a spring-loaded four-bar linkage mechanism is designed in one-step. This design includes kinematic synthesis, analysis, virtual work, static balancing and optimization.

The purpose of the research is to analyze a real system that is used to assist patients for lower-limb rehabilitation. The mechanism is based on a rotatable parallelogram linkage structure. Two groups of extension springs are used to suspend the weight of both the system and patients. During application, an adjustable proportion of users' body weight can be suspended. In an ideal design, equations have been derived for determining the spring constants for any given suspended weight. These equations govern both initial conditions and adjustment conditions.