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In this thesis we study the stabilization of closed sets for passive nonlinear control systems, developing necessary and sufficient conditions under which a passivity-based feedback stabilizes a given goal set. The development of this result takes us to a journey through the so-called reduction problem: given two nested invariant sets G1 subset of G2, and assuming that G1 enjoys certain stability properties relative to G2, under what conditions does G1 enjoy the same stability properties with respect to the whole state space? We develop reduction principles for stability, asymptotic stability, and attractivity which are applicable to arbitrary closed sets. When applied to the passivity-based set stabilization problem, the reduction theory suggests a new definition of detectability which is geometrically appealing and captures precisely the property that the control system must possess in order for the stabilization problem to be solvable. The reduction theory and set stabilization results developed in this thesis are used to solve a distributed coordination problem for a group of unicycles, whereby the vehicles are required to converge to a circular formation of desired radius, with a specific ordering and spacing on the circle.

In this thesis we study the stabilization of closed sets for passive nonlinear control systems, developing necessary and sufficient conditions under which a passivity-based feedback stabilizes a given goal set. The development of this result takes us to a journey through the so-called reduction problem: given two nested invariant sets G1 subset of G2, and assuming that G1 enjoys certain stability properties relative to G2, under what conditions does G1 enjoy the same stability properties with respect to the whole state space? We develop reduction principles for stability, asymptotic stability, and attractivity which are applicable to arbitrary closed sets. When applied to the passivity-based set stabilization problem, the reduction theory suggests a new definition of detectability which is geometrically appealing and captures precisely the property that the control system must possess in order for the stabilization problem to be solvable. The reduction theory and set stabilization results developed in this thesis are used to solve a distributed coordination problem for a group of unicycles, whereby the vehicles are required to converge to a circular formation of desired radius, with a specific ordering and spacing on the circle.

An expert system has been constructed for the purpose of assisting in the design and analysis of direct gain passive solar environments. This system has been constructed for the use of senior undergraduate architecture students in a computer-based design studio. The primary use of the system is in the role of an educational tool which generates design recommendations from user input and predicts some physical characteristics of the environment.The system is applicable to passive solar environments with vertical, south-facing glazing. The system incorporates three models. The first model represents an attached sunspace with no thermal mass storage. The second model represents a direct gain living space. The third model represents a direct gain living space integrated with thermal mass storage. The third model allows the use of floors, ceilings, and walls as mass for thermal storage. Four representative mass materials (concrete, adobe, common brick, and dense concrete masonry) have been included for comparison purposes. Four representative sub-climates are also incorporated into the system: cold / arid, hot / arid, hot / humid, and cool / humid. For educational purposes, the system makes separate calculations for identical structures based on models for inhabited and uninhabited cases.The system incorporates scientific and mathematical relationships as well as rulesof thumb which have demonstrated their applicability to passive solar design. The system performs calculations based on work by Balcomb, et al. [5, 9], and Duffle and Beckman [1], to estimate environmental temperature swings, total solar energy input, and thermal absorption by mass storage elements. The system also utilizes models based upon work by Mazria [4] to recommend glazing areas. Recommended glazing areas are calculated from user input variables such as structure type, site latitude, and floor area.The system's ease of use allows it to be adapted for various classroom goals, and its generalized nature permits the instructor to adapt it easily into different areas of architectural design curricula. The system is written for use with the CLIPS expert system shell. / Department of Physics and Astronomy

The plan and design of a large housing development project by itself was a difficult task in the past, the energy issue made the options very limited, and the planner and/or engineer deal with the solution more often technically intended with or without considering the energy problem. This study is centered on the energy issue as part of the design decision making process. This study tries to integrate the energy use effects as part of the basic planning process, such as land use and building style dependent on the land contour as well as solar exposure; and the passive solar energy utilization as part of the design process where the solar use is not an add on solar system but an integrated part of the basic design scheme. A development summary of the analysis and process guideline is introduced for medium-low density housing project in an urban setting with an actual site as a case study to illustrate the process. / Master of Architecture

Widespread public acceptance of heating and cooling systems utilizing alternative energy sources is largely dependent on their ability to replace conventional systems with no appreciable loss in comfort or convenience. Research was done to determine why current passive solar heating systems and double-shell solar heating/ground cooling systems do not have performance comparable to conventional systems. This information was then utilized to develop the concept for a new multifunction wall system for application with solar heating and ground cooling. The concept of this system is to expand the use of the structure and enclosure elements of a building to function additionally as: The ductwork for the solar heated or earth cooled air, the heat transfer membrane between the heated or cooled air and the living environment of the building, the heat storage medium (in winter), and the temperature leveling and control medium. All these functions are integrated into a single wall construction using a new concrete block and other supporting components. In addition to developing the concept, several critical components of the system were physically tested and analyzed. This paper presents the research, concept development, testing, and conclusions for this new system, a multifunction wall system for application with solar heating and ground cooling. / M. Arch.

Buildings, especially in hot climates, consume a lot of energy when people want to be comfortable inside them, which translates to very expensive fees each month. The most innovative response to this problem is renewable energy, that is used, in this case, to run mechanical HVAC systems. Renewable energy is the solution for many problems, but to avoid urban heat islands when using excessive HVAC systems (powered by renewables), and to solve thermal comfort-related problems, there has to be other solution. The major challenge to find it would be to have a change of thinking process. If a building in a hot-arid region uses natural processes to emulate the functions of HVAC systems, and the proper passive strategies, then, it will provide thermal comfort to its users, diminishing the need of a mechanical system. This hypothesis will be carried out by extracting the natural processes found in a specific case in nature, applying them into a building's design, and then simulating its energy efficiency with the adequate software. There will be a comparison of the same proposed building without the natural processes, to have tangible numbers showing that these proposed strategies, in fact, work. With explanatory detailed diagrams and the energy analysis, the hypothesis could be proven correct or incorrect. The significance of this approach relies on the proximity to the natural processes that have been working in different aspects of life since the beginning of time. They have been there all the time, waiting until architects, engineers, and people in general use them, instead of making more new energy-using inventions. By having the numbers from a conventional building and the ones of the proposed building, and the right environmental diagrams, the experiment should be valid. In the near future, there should be more research focused on nature and its processes, in order to be able to reduce the use of mechanical systems, and with that, reduce the energy use and the carbon footprint.

Neste trabalho são apresentados resultados experimentais, de um circuito operando em circulação natural, que permitem analisar o comportamento de um sistema de resfriamento de emergência quando é aberta uma linha de desvio entre a fonte quente e a fonte fria. O trabalho tem ainda a importância de documentar os testes de caracterização hidráulica do circuito experimental, fornecendo inclusive os fatores de perda de pressão específicos para o circuito. Observou-se que, para uma mesma potência, quando é aberta a linha de desvio, a temperatura na saída da fonte quente aumenta substancialmente. Esse aumento ocorre porque a vazão através do aquecedor diminui. A vazão através do trocador de calor (fonte fria) aumenta ligeiramente, sendo sempre a soma das vazões na linha de desvio e no aquecedor. O trabalho mostra ainda que a posição de conexão da linha de desvio com a perna quente determina o sentido de escoamento, podendo ocorrer a inversão a partir de uma determinada cota. Para comprovar a possibilidade de simulação precisa dos experimentos foi ainda desenvolvido um modelo numérico das equações de conservação, utilizando o programa “Engineering Equation Solver" (EES). Esse modelo foi utilizado para reproduzir os experimentos de circulação natural pelo circuito externo. / This work presents experimental results of a circuit when operating in natural circulation. These results allow to analyze the behavior of an emergency core cooling system when a bypass line that connects the hot source with the cold source is opened. This work also reports the hydraulic characterization of the experimental loop, given geometric and hydraulic data including experimental friction factors specific to this circuit. It was observed that, to a fixed thermal power, when the bypass line is opened, the heater outlet temperature increases. This temperature increase is due to the decrease in the flow rate through the heater. The heat exchanger's flow rate is subjected to a small increase. This flow rate is the sum of the bypass line and heater mass flow rates. This work also shows that the vertical position of the connection of the bypass line in the hot-leg determines the flow direction in the bypass line. If the bypass line connection is in the lowest position, the flow is from the cold to the hot-leg. If the bypass connection is in the highest position, the flow is from the hot to the cold-leg. A numerical model used to evaluate friction factors and heat transfer coefficients influence was developed. It was used to confirm the possibility of precise experiments simulation. The conservation equations are solved using “Engineering Equation Solver" (EES), a thermal hydraulics analysis tool. The model was adjusted with natural circulation experimental data and was tested with results of natural circulation without bypass lines.

Thesis (M.Arch.A.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1978. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references. / by Ralph Munroe Lebens. / M.Arch.A.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1983. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH / Includes bibliographical references (p. 69-70). / A prototype for a dwelling heat loss compensator is introduced in this thesis, along with its measured thermal performance and suggestions for its future development. As a heat loss compensator, the Sol-Clad-Siding collects, stores, and releases solar heat at room temperatures thereby maintaining a neutral skin for structures, which conserves energy, rather than attempting to supply heat into the interior as most solar systems do. Inhabitants' conventional objections to passive-solar systems utilized in housing are presented as a contrasting background. The potential of the outer component, a Trans-Lucent-Insulation as a sunlight diffuser and transmitter (65 to 52% of heating season insulation) and as a good insulator [0.62 W/(sq m) (°K) [0.11 Btu/(hr) (sq ft) (°F) 1] are described. The performance of the inner component, a container of phase-change materials as an efficient vertical thermal storage is discussed, and areas for future research are addressed. A very brief application of this passive-solar curtain wall system for dwellings is also given. / by Doru Iliesiu. / M.S.