A variety of biological and organic reaction mechanisms are studied using powerful tools from experimental and theoretical chemistry. These tools include the precise measurement of kinetic isotope effects (KIEs) and the use of theoretical calculations to predict KIEs as well as determine factors that contribute to reaction acceleration and selectivity. Theoretical analysis of the Swain-Schaad relationship involves the prediction of a large number of isotope effects and establishes the semiclassical boundaries of the relationship. Studies on the mechanism of oxidosqualene cyclase involve the determination of a large number of precise KIEs simultaneously. Transition state models for the Sharpless asymmetric epoxidation have been developed that explain the versatility, high selectivities, and ligand accelerated catalysis of the reaction. Theoretical predictions on the proposed enzymatic mechanism of flavin dependent amine oxidation suggest a hydride transfer mechanism and rules out mechanisms involving covalent intermediates. Finally, a theoretical analysis of Diels-Alder reactions successfully describes the unexpected exo selectivity in some of these reactions.

A variety of organic reactions provide experimental observations that are not explained by current models of reactivity and selectivity. This dissertation describes a combination of experimental and theoretical studies of such reactions. In the ene reaction of singlet oxygen with tetramethylene, it is found that standard statistical rate theories fail to account for the observed kinetic isotope effects, particularly with regard to their broad temperature independence. Dynamics trajectories are found to account for the observed isotope effects. In the dimerization of cyclopentadiene, novel "dynamic" isotope effects are observed on the 13C distribution in the product, and a method for the prediction of these isotope effects is developed here. In the cycloaddition of diazomethane with dimethylfulvene, it is found that the current model of the mechanism as a [6 + 4] cycloaddition is incorrect, and a new mechanism is proposed. Isotope effects have been measured for the recently reported unusual "on water" quadricyclane cycloadditions, and the implications of these observations toward the mechanism are discussed.

Coronary stents are generally tubular-shaped expandable devices which function to hold open a segment of a blood vessel. They are particularly suitable for use to support and hold back a dissected lumen. This study aims to improve the existing designs of coronary stents through geometry design. This study focuses on the flexible mechanism and planar strut of a thin wall tubular stent to design a new type of coronary stent. A good coronary stent has to meet various requirements. First of all, a coronary stent has to be strong enough to support the wall of the blood vessel. Secondly, it has to be elastic enough. Thirdly, the longitudinal length shorten with dilatation should be as less as possible, otherwise it is difficult to implant precisely. Computer aided design software Pro Engineer is used to build the solid model and then CAE software ANSYS is used to analyze the dilatation of the new stent. After several modifications, a new type of stent with no longitudinal shortening is designed.

Flexible Printed Circuit Board (FPCB) will have more and more requirements in the future. It¡¦s very important to quickly product it. For punch the FPCB with high quality and high speed, we will analysis the geometric of the punch mechanism. And synthesis the mechanism with new dimensions. And then, design many kinds of motion curves of motor to compare their characters. Finally, we will find it¡¦s works to design motion curves for FPCB punch mechanism to improve the punch quality.

The purpose of this study is to design an innovative mechanism for robot dog's legs, including analyzing the existing commercial robot dogs, modeling the characteristic of entity by Pro/Engineer, and simulating the mechanism by Visual Nastran. The leg designed in this study is a five-bar linkage with pantograph mechanism. This leg mechanism has two degrees of freedom. In order to control the motion of legs easily, a method which converts the locus of movement into the control parameters of motor is introduced by analyzing the mechanism of the robot dog's legs. The result of computer simulation shows that the designed mechanism can achieve slow movement smoothly. The gait of the designed legs is based on the motion pictures of a real dog. The movement of legs of the designed robot dog is then simulated by computer program involved Visual Nastran and then compare to that of a real dog.

All-terrain vehicle(ATV) is very popular in Europe and North America because of its excellent riding performance. The Design of suspension and steering mechanism is one of the most important parts in ATV design, because it is much related to the riding performance of ATVs. Therefore, this research focuses on investigating the design of suspension and steering mechanism for ATVs. There are two main objectives to be achieved in this research. One is to build the analysis theory, and the other is to develop a systematic design process of suspension and steering mechanism for ATVs. Firstly, we survey papers about suspension and steering mechanism to find its basic functions and properties. Secondly, we use engineering design method to classify the design requirements and frame the design process. Thirdly, we list new suspension and steering mechanisms by applying the creative mechanism design procedure, then separate the new mechanisms separate into two types. One type is suitable only for back-wheel drive vehicles, and the other type is suitable for back-wheel drive and four-wheel drive vehicles. Finally, we complete the kinematic design of the type1.1(double-wishbone) and type8.3(new mechanism) suspension and steering mechanisms based on the Genetic algorithm (GA), and we can obtain the better mechanism dimensions than Yamaha 660 and 450 ATV.

Transmission mechanism is usually modeled as a rigid component in most control tasks of manufacturing processes. Nevertheless, experimental studies have shown that the inherent compliant characteristic of transmission mechanisms seriously degrades the whole system¡¦s performance. This paper presents an adaptive control strategy to overcome positioning difficulty of a transmission system with a variable compliance. A flexible joint, consisting of sixteen linear springs, is designed for actual positioning experiments. In order to enhance variation of the compliance, an eccentric load is located behind the flexible joint. Therefore, the axial compliance is not fixed and will change according to the load¡¦s angular position. The proposed controller is developed on an adaptive control structure to provide capability of fast adaptation to compliance variation. Besides, the robustness of the control system is also specifically emphasized to improve positioning performance with respect to model uncertainty and unknown disturbances. The control law is obtained by applying the Lyapunov¡¦s theorem. Effectiveness of the presented control method is demonstrated on trajectory control of an experimental transmission mechanism with the flexible joint under variable compliance conditions.

Now there are three judgments in the mechanical or electric coin mechanism , involved shapes , materials and weight . Mechanical coin mechanism usually measures by slits and cradles . Slits are constructed by slanting channels , they are like the arranging mechanisms of automatic productions . Electric coin mechanisms differentiate from the different coins by examining the variation of voltages when coins pass through electric coils . Actually , the traditional coin mechanisms still have many disadvantages , so we will adopt the multi-function way to raise the identifying ability . This research uses the TRIZ method during the design process and operates the contradiction matrix to find out the feasible and requisite design . We believe that this research could be good for the market development of coin mechanisms .

ABSTRACT The wheelchair is an auxiliary tool for people who have defective legs. In the viewpoint of mechanical efficiency, the typical manual wheelchair does not provide optimal efficiency, and the wheelchair occupant can¡¦t travel easier and faster for longer distances. The regular, standard manual wheelchair is only suitable for residential environment and short-distance movement, and it¡¦s unsuitable for outdoor long-distance movement. The purpose of this study is to design a new-pattern manual wheelchair for outdoor recreation and long-distance movement, so that the users can expand their living space beyond the residential areas. In order to enhance the efficiency of propulsion for manual wheelchairs, the new-pattern wheelchair has a new type of dive system. In this study , we will design a detachable drive mechanism for manual wheelchairs. The new-pattern wheelchair has two kinds of different propulsive modes, the wheelchair occupant can depend on his requirement to decide what propulsive mode he needs. At last, we hope that we can promote the performance of wheelchair effectively by means of study and design.,and that is the principal objective for this study.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Rodney G. Roberts, Florida State University, College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed June 15, 2004). Includes bibliographical references.