Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by James Raymond Downer. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 212-215. / by Paul Alan Basore. / Ph.D.

This dissertation analyzes the internal mechanics of parallel wire strands as found in the main cables of suspension bridges. Parallel wire strands of reduced order (7-wire, 19-wire, and 61-wire strands made of steel and aluminum) are fabricated and subjected to various boundary conditions and external loads (tension, clamping, twist, etc.). Neutron diffraction is used as an elastic strain measurement tool for its ability to penetrate bulk materials and/or layers of a multi-body system without disturbing the sample. Firstly, this thesis aims to quantify the development length – the distance over which a broken wire within a strand regains near-full service strain – as a function of various boundary conditions and failure scenarios. The feasibility of using neutron diffractometers to measure in situ elastic strains on civil-engineering-scale samples under both tensile load and radial confinement is validated using strands fabricated from steel bridge wire. Results from various 7-wire strands indicate that friction and mechanical interference on the microscopic level play a significant role in the load partitioning. Furthermore, wires that have been broken – either pre-cracked or fractured live and in situ during tensile loading – are capable of regaining significant stresses from their neighbors over a distance of tens of centimeters. The contribution of both friction force and mechanical interference on elastic strain redevelopment in broken wires should be included in analytical models designed to simulate failure processes. The second part of this thesis aims to measure the internal mechanics of larger parallel wire strands in response to various confinement (clamping) forces. 19 and 61 aluminum wire strands are fabricated and the internal strains of all constituent wires mapped in three orthogonal directions under various clamping loads. The strain distributions for both 19-wire and 61-wire strands show a surprising degree of heterogeneity. An increase in clamping force homogenizes the distribution to a degree, but only at unfeasibly high clamping forces. The results suggest that microscale variations in wire diameter dominate the internal mechanics of parallel wire strands. The stochastic distribution of wire sizes due to manufacturing tolerances throughout a strand cross-section creates a randomly ordered network of over- and under-sized wires. This imperfectly packed lattice results in large wire-to-wire variations in clamping constraint. The up-scaling in strand size from 19 to 61 wires increases the resolution of the experiment but does not reduce the heterogeneity of the strain distribution. Ergo, the assumption of perfect hexagonal packing in parallel wire strands is weak, and mean field distributions do not accurately describe the internal mechanics of such structures.

A new Direct Simulation fibre model was developed which allowed flexibility in the fibre during the simulation of fibre suspension flow.This new model was called the �Chain-of-Spheres �model.It was hypothesised that particle shape and deformation could signi ficantly a ffect partic e dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that flexible fibres in shear flow resulted in an order of 7 −10% bulk relative viscosity increase over the �rigid �fibre result.Results also es- tablished the existence of a relationship between bulk viscosity and particle sti ffness.In comparison with experimental results,other more conventional rigid fibre based methods appeared to underpredict relative viscosity.The flexible fibre method thus markedly improved the ability to estimate relative viscosity.The curved rigid fibre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid fibre suspension.With such sensitivity to fibre shape,this result has some important implications for the quality of fibre inclusions used.For consistent viscosity,the shape quality of the fibres was shown to be important. The �Chain of Spheres �simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian flow field.This new �3D Particle �simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex flow fields.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear flow. In later sections, the simulation demonstrated inertia-induced particle migration inthe non-linear shear gradient Couette cylinder flow,and was used to predict the fibre orientation within a diverging channel flow.The performance of the method was verified against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great fidelity. The broad aim of this research was to better understand the microstruc- tural dynamics within the fibre-filled suspension and from it,derive useful engineering information on the bulk flow of these fluids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may bene fit from the new approaches and algorithms developed here.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "August 2005." Includes bibliographical references (leaves 102-114). Online version available on the World Wide Web.

Long duration spaceflight missions out of lower earth orbit, back to the lunar surface, or possibly to Mars highlight the importance of preserving muscle mass and function. Muscle atrophy occurs within days of exposure to microgravity and prevailing thought is that a primary mechanism for muscle atrophy is a reduction in skeletal muscle protein synthesis. This dissertation examines the ability of skeletal muscle to recover muscle protein synthesis with slight perturbation, such as ambulatory reloading during disuse as well as partial loading, similar to body mass seen on the moon or Mars. We use traditional precursor-product labeling to measure protein synthesis, but use a relatively novel tracer, deuterium oxide, in order to make cumulative measures of protein synthesis over 24 h. The overarching goal of this dissertation is to define the response of skeletal muscle protein synthesis to different loading parameters in order to better understand the contribution of protein synthesis to skeletal muscle mass during disuse. In the first study, we demonstrate that muscle atrophy during 5 days of hindlimb unloading is in part due to a decrease in protein synthesis. We also highlight the ability of skeletal muscle to adapt by allowing two 1 h ambulatory reloading sessions on days 2 and 4. Although this countermeasure is able to rescue protein synthesis in soleus and gastrocnemius, it is unable attenuate any losses in muscle mass. In the second study, we compare partial weight loading to traditional hindlimb unloading. Weight bearing of 1/3 or 1/6 body weight is able to attenuate losses in muscle mass seen with unloading. Protein synthesis is maintained after 21 days of the experimental protocol, suggesting that protein synthesis is responsive to load and is likely not the only mechanism for determining muscle mass. In the final study, the effects of < 1 Gy x-ray exposure and partial weight suspension are measured to better understand the complex space environment, which includes a wide variety of radiation. Surprisingly, we found no effects of radiation on muscle protein synthesis in 1 G or partial loading. Targeting only protein synthesis may not be enough of a stimulus as evidenced by the data in this dissertation. Future plans should use a multiple-systems approach to counteract atrophy by increasing protein synthesis to maintain/elevate muscle mass during periods when it is otherwise compromised.

­^¤åºK­n The purpose of this work is to provide a design procedure of rear suspension mechanisms of mountain bikes by using the concept of engineering design method. First, the conditions and particularities of mountain biking are investigated and the performance specification of rear suspension mechanisms is set by focusing the investigations on the requirements of rear suspension mechanisms. Second, the requirements and constraints of generating different types of rear suspension mechanisms are developed and the systematic process of creative mechanism design is followed. Third, the different types of rear suspension mechanisms resulted from creative mechanism design are analyzed to realize the property of each type of rear suspension mechanisms and the procedure of kinematic design is developed by using the algorithm of heuristic combinatorial optimization method. Finally a computer aided design program written in Visual BASIC 6.0 programming language is developed to be the powerful tool of performance analysis and kinematic design of rear suspension mechanisms.

With the prevalence of leisure sport, riding mountain bikes becomes an enormous vogue today. The mountain bikes undoubtedly have become one of the most popular products in the leisure sport market. Based on its superior standard of operating quality and the demand of comfortableness, the requirement of the outstanding rear suspension mechanism of mountain bikes is one of the crucial components in the design procedure. The purpose of this work is to provide a design procedure of the system of rear suspension mechanisms of mountain bikes by using the concept of engineering design method. First, to investigate the essential requirements of the system of rear suspension mechanisms of mountain bikes is started. Then the design targets of this research are decided further in order to establish the requirement book for the system of rear suspension mechanisms of mountain bikes. Second, the kinematic design of rear suspension mechanisms is proceeding. Computer Aided Tried and Error program is utilized for synthesizing the dimensions of rear suspension mechanisms to meet the requirement of functions. Finally, topology theory is applied to synthesize the frames of mountain bikes. Furthermore, the systematic design procedure is developed to perform the embodiment design of the system of rear suspension mechanisms of mountain bikes.

Thèse de doctorat : Sciences et environnement. Physique de l'environnement : Bordeaux 1 : 2008. / Titre provenant de l'écran-titre.

Thesis (Ed. D.)--University of La Verne, 2002. / Includes bibliographical references (leaves 119-123).