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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Teoria de semigrupos e controlabilidade de sistemas neutros / Semigroup theory and controllability of neutral systems

Michelle Fernanda Pierri Mariano 17 March 2006 (has links)
Neste trabalho de dissertação de mestrado, fazemos algumas observações a respeito de dois¶ artigos de pesquisa recentes, os quais estabelecem resultados falsos sobre existência de soluções controlabilidade exata de sistemas de controle abstratos do tipo neutro modelados na forma¶8<:¶ d ¶ dt ¶(x(t) + G(t, xt)) = Ax(t) + F(t, xt) + Cu(t), t 2 I = (0, a],¶ x0 = ',¶ (4)¶ onde A é o gerador infinitesimal de um C0-semigrupo de operadores lineares definidos sobre um espaço de Banach X; a função xt representa a história do estado no tempo t; C : U ! X ´e um¶ perador linear limitado, U é um espaço de Banach e F,G são funções apropriadas.¶ Motivados pelo anterior, neste trabalho estudamos a existência de soluções fracas para o sistema ¶ abstrato 8<:¶ d¶ dt¶ [(I &#8722; B)x(t)] = Ax(t) + F(t, x(t)), t 2 I = (0, a],¶ x(0) = x0 2 X,¶ (5)¶ onde B : X ! X é um operador linear limitado. Além do anterior, introduzimos e estudamos a “¶ controlabilidade [D(A)]-aproximada ” para o sistema de controle¶ 8<:¶ d¶ dt¶ [(I &#8722; B)x(t)] = Ax(t) + Cu(t) + f(t, x(t)), t 2 I = (0, a],¶ x(0) = x0 2 X.¶ (6)¶. Observamos que nossos comentários relacionados com a controlabilidade exata de sistemas¶ neutros, foram publicados recentemente em journal Computers & Mathematics with Applications,¶ veja [12] para detalhes. Também mencionamos que no pre-print [16] são resumidos nossos resultados¶ relacionados a existência de soluções fracas de (5) e a controlabilidade do sistema de controle (6). / In this work, we report two technical errors in some recent papers treating on existence and¶ xact controllability of solutions for a class of partial neutral functional differential control systems¶ described in the abstract form¶ 8<:¶ d¶ dt¶ (x(t) + G(t, xt)) = Ax(t) + F(t, xt) + Cu(t), t 2 I = (0, a],¶ x0 = '.¶ (1)¶ In this system A is the infinitesimal generator of an C0-semigroup of bounded linear operators¶ defined on a Banach space X; the functions xt are the histories, C : U ! X is a bounded operator,¶ U is a Banach space and and F,G are appropriate functions.¶ Additionally, by using some simple perturbation criterion, we discuss the existence of mild¶ solution for the system¶ 8<:¶ d¶ dt¶ [x(t) + Bx(t)] = Ax(t) + f(t, x(t)), t 2 I = [0, a],¶ x(0) = x0 2 X,¶ (2)¶ where B is a bounded linear operator. We also introduce the concept of approximate [D(A)]-¶ controlability and establish conditions under which the associated control system¶ 8<:¶ d¶ dt¶ [x(t) + Bx(t)] = Ax(t) + Cu(t) + f(t, x(t)), t 2 I = [0, a],¶ x(0) = x0 2 X,¶ (3)¶ is approximate [D(A)]- controllable.¶ We mention that our observation on exact controllability of abstract neutral system was recently¶ published in journal Computers & Mathematics with Applications, see [12] for details. We also note,¶ that the pre-print [16] contain some new results concerning existence of solutions and controllability¶ for the systems (2) and (3) respectively.
2

Teoria de semigrupos e controlabilidade de sistemas neutros / Semigroup theory and controllability of neutral systems

Mariano, Michelle Fernanda Pierri 17 March 2006 (has links)
Neste trabalho de dissertação de mestrado, fazemos algumas observações a respeito de dois¶ artigos de pesquisa recentes, os quais estabelecem resultados falsos sobre existência de soluções controlabilidade exata de sistemas de controle abstratos do tipo neutro modelados na forma¶8<:¶ d ¶ dt ¶(x(t) + G(t, xt)) = Ax(t) + F(t, xt) + Cu(t), t 2 I = (0, a],¶ x0 = ',¶ (4)¶ onde A é o gerador infinitesimal de um C0-semigrupo de operadores lineares definidos sobre um espaço de Banach X; a função xt representa a história do estado no tempo t; C : U ! X ´e um¶ perador linear limitado, U é um espaço de Banach e F,G são funções apropriadas.¶ Motivados pelo anterior, neste trabalho estudamos a existência de soluções fracas para o sistema ¶ abstrato 8<:¶ d¶ dt¶ [(I &#8722; B)x(t)] = Ax(t) + F(t, x(t)), t 2 I = (0, a],¶ x(0) = x0 2 X,¶ (5)¶ onde B : X ! X é um operador linear limitado. Além do anterior, introduzimos e estudamos a “¶ controlabilidade [D(A)]-aproximada " para o sistema de controle¶ 8<:¶ d¶ dt¶ [(I &#8722; B)x(t)] = Ax(t) + Cu(t) + f(t, x(t)), t 2 I = (0, a],¶ x(0) = x0 2 X.¶ (6)¶. Observamos que nossos comentários relacionados com a controlabilidade exata de sistemas¶ neutros, foram publicados recentemente em journal Computers & Mathematics with Applications,¶ veja [12] para detalhes. Também mencionamos que no pre-print [16] são resumidos nossos resultados¶ relacionados a existência de soluções fracas de (5) e a controlabilidade do sistema de controle (6). / In this work, we report two technical errors in some recent papers treating on existence and¶ xact controllability of solutions for a class of partial neutral functional differential control systems¶ described in the abstract form¶ 8<:¶ d¶ dt¶ (x(t) + G(t, xt)) = Ax(t) + F(t, xt) + Cu(t), t 2 I = (0, a],¶ x0 = '.¶ (1)¶ In this system A is the infinitesimal generator of an C0-semigroup of bounded linear operators¶ defined on a Banach space X; the functions xt are the histories, C : U ! X is a bounded operator,¶ U is a Banach space and and F,G are appropriate functions.¶ Additionally, by using some simple perturbation criterion, we discuss the existence of mild¶ solution for the system¶ 8<:¶ d¶ dt¶ [x(t) + Bx(t)] = Ax(t) + f(t, x(t)), t 2 I = [0, a],¶ x(0) = x0 2 X,¶ (2)¶ where B is a bounded linear operator. We also introduce the concept of approximate [D(A)]-¶ controlability and establish conditions under which the associated control system¶ 8<:¶ d¶ dt¶ [x(t) + Bx(t)] = Ax(t) + Cu(t) + f(t, x(t)), t 2 I = [0, a],¶ x(0) = x0 2 X,¶ (3)¶ is approximate [D(A)]- controllable.¶ We mention that our observation on exact controllability of abstract neutral system was recently¶ published in journal Computers & Mathematics with Applications, see [12] for details. We also note,¶ that the pre-print [16] contain some new results concerning existence of solutions and controllability¶ for the systems (2) and (3) respectively.
3

Energy optimisation and controllability in complex distillation columns

Serra Prat, Maria 12 September 2000 (has links)
To extend the knowledge of complex distillation arrangements for the separation of ternary mixtures and make them closer to implementation in industry is the motivation of this thesis work. Some design, operation, and control aspects are analysed, having the conventional distillation arrangements as comparison basis. The DWC is a complex distillation arrangement very attractive in terms of energy and cost savings. However, the DWC require large columns in order to be economically advantageous. Therefore, this arrangement is more attractive when the energy cost is high compared to the trays cost. From rigorous simulations of different separation examples, some synthesis rules have been obtained.Designs that minimise the distillation cost have been given special importance. DWC design procedures reported in the literature were based on only two decision variables. A new procedure that uses three decision variables for design optimisation has been proposed. It has been seen that the use of three decision variables is important to avoid excluding possible optimum designs.The control of the DWC is more complex than the control of the other distillation arrangements because the DWC has more operation degrees of freedom. The approach in this work has been to solve the DWC control by levels: stabilisation, composition control, and optimising control. When the manipulated variables for DWC stabilisation control are the distillate and the bottoms flowrate, which is the most common stabilisation control structure in the literature, the DWC presents high directionality and interaction. Besides, this stabilisation control structure is not appropriate to the DWC because the DWC has typically high reflux ratios. When the manipulated variables for stabilisation control are the reflux flowrate and the boilup, the DWC has better controllability and larger stability margins. Linear analysis tools are useful to select the set of manipulated variables for the DWC composition control. The preferred set of manipulated variables and the controllability of the corresponding control structure depend on the nominal operation. The DWC has two extra operation degrees of freedom that permit an operation optimisation. This optimisation is used to minimise the boilup. At a non-optimal operation, the controllability is improved. Therefore, a trade-off appears between operation optimisation and controllability. Changes in the design of the DWC can be used to improve its controllability. High directionality is a problem associated to DWC that may be improved using a large number of trays. On the other hand, DWC optimal designs have an equilibrated distribution of distillation effort between sections which, if broken, may also present improve the controllability. As found for operation, also for design, leaving optimal conditions permits to improve the controllability. Alternatively, for the composition control of the DWC, Dynamic Matrix Control is analysed. It is found that DMC performs worse than the diagonal feedback control strategy. The DWC extra operation degrees of freedom can be used dynamically for optimising control. Due to a marked directionality found in the response surface, DWC operation may be kept close to optimal operation using only one of the operation degrees of freedom. Optimising control of the DWC through the feedback control of a variable that characterises the optimal operation is possible. Some measurable variables are able to maintain optimal conditions with certain accuracy.The controllability of the DWC is compared to the controllability of other distillation arrangements. In general, the complexity of a distillation arrangement makes its energy efficiency better and its controllability worse. However, important exceptions have been found: - The DWC may give important energy savings as well as the best controllability if it is operated at non-optimal conditions. - When the manipulated variables for stabilisation are internal flows (reflux rates and boilups), the controllability of the DWC is better than the controllability of the other distillation arrangements. The DWC controllability is found to be more interesting for long columns. Therefore, the DWC needs long columns to be really attractive in terms of energy as well as in terms of controllability. In the literature, DWC controllability was misevaluate. In this thesis work, it is seen that, thanks to the arrangement complexity, the DWC may give at the same time energy savings and a good controllability, what makes it very attractive. To know the influence of the non-modelled detail and to obtain experimental results for the DWC is the most important step in the way to DWC implementation in industry.
4

Abstrakčių automatų valdomumo tyrimo programinė įranga / Software for research of circuit controllability

Survila, Vytautas 27 May 2005 (has links)
One of possible expenditures of reduction and testability process acceleration choices is to increase circuit’s testability. It means to increase controllability and observability of the circuit. As to determine the circuit’s controllability and observability manually takes lots of time, it is meaningful to automate this process. The main purpose is to determine and improve the controllability of the circuit by offering some suggestions to system on chip’s designers how to improve circuit’s controllability. We try to analyze if it is possible to do this only by using created software. This software’s architecture uses client-server mode and all computations are performed on a server side. The system is realized on Apache server with Linux OS. System modules are realized using C++, PHP, JAVA, HTML and JavaScript programming languages. In this paper it is being introduced the definition of controllability, explored methods of controllability estimation and increase. Also there is introduced the research how to improve accuracy of software results. The methods of the controllability estimation for “white box” are modified to work with “black box”. Assumptions made during the research were validated by experiments.
5

Control analysis and design using symbolic computation

Su, Huijuan January 2002 (has links)
No description available.
6

Nonreligious Coping, Religious Coping, and Self-conscious Emotions as Predictors of Expressed Emotion in Relatives of Patients with Schizophrenia

Wasserman, Stephanie 14 May 2010 (has links)
Expressed emotion (EE) is a measure of the family environment reflecting the amount of criticism and emotional over-involvement expressed by a key relative towards a family member with a disorder or impairment (Hooley, 2007). Patients with high EE relatives have a poorer illness prognosis than do patients with low EE relatives. Despite EE's well-established predictive validity, however, questions remain regarding why some family members express high EE attitudes while others do not. Based on indirect evidence from previous research, the current study tested whether religious and nonreligious coping and shame and guilt about having a relative with schizophrenia serve as predictors of EE. A sample of 72 family members of patients with schizophrenia completed an EE interview, along with questionnaires assessing situational nonreligious coping, religious coping, and self-conscious emotions. In line with hypotheses, results indicated that nonreligious coping predicted EE. Specifically, less use of adaptive emotion-focused coping predicted high EE. Also consistent with predictions, religious coping predicted high EE above and beyond nonreligious coping. Finally, higher levels of both shame and guilt about having a relative with schizophrenia predicted high EE. Results of the current study elucidate the EE construct and have implications for working with families of patients with schizophrenia.
7

Design and fabrication of novel microfluidic systems for microsphere generation

Song, Ki-Young 30 May 2011
<p>In this thesis, a study of the rational design and fabrication of microfluidic systems for microsphere generation is presented. The required function of microfluidic systems is to produce microspheres with the following attributes: (i) the microsphere size being around one micron or less, (ii) the size uniformity (in particular coefficient of variation (CV)) being less than 5%, and (iii) the size range being adjustable as widely as possible.</p> <p>Micro-electro-mechanical system (MEMS) technology, largely referring to various micro-fabrication techniques in the context of this thesis, has been applied for decades to develop microfluidic systems that can fulfill the foregoing required function of microsphere generation; however, this goal has yet to be achieved. To change this situation was a motivation of the study presented in this thesis.</p> <p>The philosophy behind this study stands on combining an effective design theory and methodology called Axiomatic Design Theory (ADT) with advanced micro-fabrication techniques for the microfluidic systems development. Both theoretical developments and experimental validations were carried out in this study. Consequently, the study has led to the following conclusions: (i) Existing micro-fluidic systems are coupled designs according to ADT, which is responsible for a limited achievement of the required function; (ii) Existing micro-fabrication techniques, especially for pattern transfer, have difficulty in producing a typical feature of micro-fluidic systems - that is, a large overall size (~ mm) of the device but a small channel size (~nm); and (iii) Contemporary micro-fabrication techniques to the silicon-based microfluidic system may have reached a size limit for microspheres, i.e., ~1 micron.</p> <p>Through this study, the following contributions to the field of the microfluidic system technology have been made: (i) Producing three rational designs of microfluidic systems, device 1 (perforated silicon membrane), device 2 (integration of hydrodynamic flow focusing and crossflow principles), and device 3 (liquid chopper using a piezoelectric actuator), with each having a distinct advantage over the others and together having achieved the requirements, size uniformity (CV ⤠5%) and size controllability (1-186 &#x00B5;m); (ii) Proposing a new pattern transfer technique which combines a photolithography process with a direct writing lithography process (e.g., focused ion beam process); (iii) Proposing a decoupled design principle for micro-fluidic systems, which is effective in improving microfluidic systems for microsphere generation and is likely applicable to microfluidic systems for other applications; and (iv) Developing the mathematical models for the foregoing three devices, which can be used to further optimize the design and the microsphere generation process.</p>
8

Design and fabrication of novel microfluidic systems for microsphere generation

Song, Ki-Young 30 May 2011 (has links)
<p>In this thesis, a study of the rational design and fabrication of microfluidic systems for microsphere generation is presented. The required function of microfluidic systems is to produce microspheres with the following attributes: (i) the microsphere size being around one micron or less, (ii) the size uniformity (in particular coefficient of variation (CV)) being less than 5%, and (iii) the size range being adjustable as widely as possible.</p> <p>Micro-electro-mechanical system (MEMS) technology, largely referring to various micro-fabrication techniques in the context of this thesis, has been applied for decades to develop microfluidic systems that can fulfill the foregoing required function of microsphere generation; however, this goal has yet to be achieved. To change this situation was a motivation of the study presented in this thesis.</p> <p>The philosophy behind this study stands on combining an effective design theory and methodology called Axiomatic Design Theory (ADT) with advanced micro-fabrication techniques for the microfluidic systems development. Both theoretical developments and experimental validations were carried out in this study. Consequently, the study has led to the following conclusions: (i) Existing micro-fluidic systems are coupled designs according to ADT, which is responsible for a limited achievement of the required function; (ii) Existing micro-fabrication techniques, especially for pattern transfer, have difficulty in producing a typical feature of micro-fluidic systems - that is, a large overall size (~ mm) of the device but a small channel size (~nm); and (iii) Contemporary micro-fabrication techniques to the silicon-based microfluidic system may have reached a size limit for microspheres, i.e., ~1 micron.</p> <p>Through this study, the following contributions to the field of the microfluidic system technology have been made: (i) Producing three rational designs of microfluidic systems, device 1 (perforated silicon membrane), device 2 (integration of hydrodynamic flow focusing and crossflow principles), and device 3 (liquid chopper using a piezoelectric actuator), with each having a distinct advantage over the others and together having achieved the requirements, size uniformity (CV ⤠5%) and size controllability (1-186 &#x00B5;m); (ii) Proposing a new pattern transfer technique which combines a photolithography process with a direct writing lithography process (e.g., focused ion beam process); (iii) Proposing a decoupled design principle for micro-fluidic systems, which is effective in improving microfluidic systems for microsphere generation and is likely applicable to microfluidic systems for other applications; and (iv) Developing the mathematical models for the foregoing three devices, which can be used to further optimize the design and the microsphere generation process.</p>
9

Perspectives in control of conditionally controllable problems

Ghorbani Faal, Siamak 24 October 2018 (has links)
Limitations imposed on control functions can significantly affect the performance of a linear controller. When applied to the real physical system, such limitations convert a linear function to a nonlinear input signal that alters the convergence or stability of the solution. The main focus of this study is to identify, classify and propose appropriate techniques to overcome such problems. In this regard, we propose an exact definition for a conditionally controllable problem and investigate control function formulations for such problems under the lenses of planning-based and optimization-based methods.
10

Positive Controllability of Systems with Nearly-Non-Negative Matrices

Perry, Theodore Sonne 01 May 1976 (has links)
This paper analyzes the controllability of constant coefficient linear differential equations and presents two proofs of a major theorem on controllability. Properties of nearly-non-negative matrices are discussed and in particular a theorem on the behavior of the exponential matrix of nearly-non-negative matrices is proven. These results are then used to prove that the reachable set for systems with nearly-non-negative matrices is limited to the positive hyperoctant.

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