Finite element analysis of the human left ventricle in diastole and systole

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Previously, at Brunel University, two computer programs had been developed to facilitate the analysis of the diastolic material properties of the human left ventricle. These two computer programs consisted of; a finite element program, "XL1", which ran upon a Cray-1S/1000 and a post-processor and pre-processor, "HEART", which ran upon the Multics computer system. The computer program "HEART" produced the finite element model, which was then solved by "XL 1", and it also allowed for plotting the results in graphical form, The patient data was supplied by the Royal Brompton Hospital in the form of digitised cine-angiographic X-ray data plus pressure readings. The first stage was to transfer the two separate computer programs "HEART" and "XL 1" to the Sun Workstation system. The two programs were then combined to form a single package which can be used for the automated analysis of the patient data. An investigation into the effect that the elastic modulus ratio has upon the deformation of the left ventricle during diastole was performed. It was found that the effect is quite small and that using this parameter to match overall shape deformation would be extremely sensitive to the accuracy of the initial data. The main part of this work was the implementation of active cardiac contraction, by means of a thermal stress analogy, into the finite element program. This allows the systolic part of the cardiac cycle to be analysed. The analysis of the factors that affect cardiac contraction, including the material properties and boundary conditions was performed. This model was also used to investigate the effect that conditions such as ischaemia and the formation of scar tissue have upon the systolic left ventricle. The use of the thermal stressing analogy for cardiac contraction was demonstrated to mirror global and local deformation when applied to a realistic ventricular geometry.Mechanical Engineering Department of Brunel Universit

Partially prestressed concrete internal square panel

This work is concerned with the general behaviour of an internal panel in a column supported multi-bay floor structure, under the influence of various prestressing tendon arrangements. The prestressing effects are studied with the help of a finite element package (PAFEC), representing the prestressing forces by equivalent vertical loads. From a variety of possible spacing arrangements, the distribution of prestressing moments is shown to be most effective in counteracting the moments due to externally imposed load when the tendons are narrowly banded in the column vicinity. The effects of tendon arrangement on slab behaviour are further investigated by means of an experimental programme comprising three series of ten tests of 1.5m span partially prestressed panel with typical span to depth ratio, levels of loading, levels of prestress and geometry of tendon profiles. The models were fixed along the edges to simulate the continuity of an internal panel in a multi-panel slab system. Post-tensioned tendons were arranged in various patterns, as currently employed in construction practice, to induce either a medium or a low level of prestress in the test panel, conforming to the design recommendations of a number of codes of practice. Test results indicated that the serviceability behaviour of the slabs with a low level of prestress was strongly influenced by the tendon distribution and the amount of non-prestressed reinforcement. Slabs with tendons banded closely in the column area exhibited a higher cracking load and were stiffer after cracking. The flexural strength of the test slabs was found to be greater than that predicted by yield line theory and the increase was attributed to membrane action. The experimental values of tendon stress at ultimate load and of punching shear were compared with those obtained by various design methods

1999 Flight Mechanics Symposium

This conference publication includes papers and abstracts presented at the Flight Mechanics Symposium held on May 18-20, 1999. Sponsored by the Guidance, Navigation and Control Center of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

Space transfer concepts and analysis for exploration missions

Covered here is the second phase of a broad scoped and systematic study of space transfer concepts for human lunar and Mars missions. The study addressed issues that were raised during Phase 1, developed generic Mars missions profile analysis data, and conducted preliminary analysis of the Mars in-space transportation requirements and implementation from the Stafford Committee Synthesis Report

Vision 21: Interdisciplinary Science and Engineering in the Era of Cyberspace

The symposium Vision-21: Interdisciplinary Science and Engineering in the Era of Cyberspace was held at the NASA Lewis Research Center on March 30-31, 1993. The purpose of the symposium was to simulate interdisciplinary thinking in the sciences and technologies which will be required for exploration and development of space over the next thousand years. The keynote speakers were Hans Moravec, Vernor Vinge, Carol Stoker, and Myron Krueger. The proceedings consist of transcripts of the invited talks and the panel discussion by the invited speakers, summaries of workshop sessions, and contributed papers by the attendees

5 European & African Conference on Wind Engineering

The 5th European-African Conference of Wind Engineering is hosted in Florence, Tuscany, the city and the region where, in the early 15th century, pioneers moved the first steps, laying down the foundation stones of Mechanics and Applied Sciences (including fluid mechanics). These origins are well reflected by the astonishing visionary and revolutionary studies of Leonardo Da Vinci, whose kaleidoscopic genius intended the human being to become able to fly even 500 years ago… This is why the Organising Committee has decided to pay tribute to such a Genius by choosing Leonardo's "flying sphere" as the brand of 5th EACWE

Advanced Solar-propelled Cargo Spacecraft for Mars Missions

Three concepts for an unmanned, solar powered, cargo spacecraft for Mars support missions were investigated. These spacecraft are designed to carry a 50,000 kg payload from a low Earth orbit to a low Mars orbit. Each design uses a distinctly different propulsion system: A Solar Radiation Absorption (SRA) system, a Solar-Pumped Laser (SPL) system and a solar powered magnetoplasmadynamic (MPD) arc system. The SRA directly converts solar energy to thermal energy in the propellant through a novel process. In the SPL system, a pair of solar-pumped, multi-megawatt, CO2 lasers in sunsynchronous Earth orbit converts solar energy to laser energy. The MPD system used indium phosphide solar cells to convert sunlight to electricity, which powers the propulsion system. Various orbital transfer options are examined for these concepts. In the SRA system, the mother ship transfers the payload into a very high Earth orbit and a small auxiliary propulsion system boosts the payload into a Hohmann transfer to Mars. The SPL spacecraft and the SPL powered spacecraft return to Earth for subsequent missions. The MPD propelled spacecraft, however, remains at Mars as an orbiting space station. A patched conic approximation was used to determine a heliocentric interplanetary transfer orbit for the MPD propelled spacecraft. All three solar-powered spacecraft use an aerobrake procedure to place the payload into a low Mars parking orbit. The payload delivery times range from 160 days to 873 days (2.39 years)