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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.
21

Control techniques applied to integrated ship motion control

Sharif, Mohammed Tariq January 1995 (has links)
Fins stabilisers are devices which are fitted to the hull of a ship and utilised to ameliorate its rolling motions. They apply a regulated moment about the ship's axis of roll in order to oppose the sea induced disturbances. Recognising their unsurpassed performance, the Royal Navy, since the 1950's, equips all its vessels with fin stabilisers. It can be shown that the rudders, in vessels of appropriate size, also have the potential to be harnessed as roll stabilisers Rudder Roll Stabilisation (RRS) without degrading the ship's course-keeping. Thus creating a more stable platform for the human operators and equipment. The reported success of RRS imparted an impetus to the Royal Navy to initiate this study. The objectives are to ascertain whether RRS is possible without rudder modifications and to establish whether enhanced levels of stabilisation would accrue if the fins and RRS were operated in congress. The advantages in this novel approach being: avoidance of redesign and refit of rudders, three modes of operation (fins alone, RRS alone and combined RRS and fins), reduced fin activity and by implication self-generated noise, and amenability to be retrofitted by simple alteration of any existing ship's autopilot software. The study initially examined the mathematical models of the ship dynamics, defining deficiencies and evaluating sources of uncertainty. It was postulated that the dual purpose of the rudder can be separated into non-interacting frequency channels for controller design purposes. An integrated design methodology is adopted to the roll stabilisation problem. Investigating the capabilities of the rudder servomechanism, a new scheme, the Anti-Saturation Algorithm (ASA) was proposed which can eliminate slew rate saturation. Application of the ASA is generic to any servomechanism. The effects of lateral accelerations of the ship on human operators was examined. This resulted in an unique contribution to the Lateral Force Estimator problem in terms of generating time domain models and defining the limitations of the applicability of a control design strategy. Linear Quadratic Guassian and two types of classical controllers were constructed for the RRS and fins. A novel application of linear robust control theory to the ship roll stabilisation problem resulted in H . controllers whose performance was superior to the other design methods. This required the development of weight functions and the identification and quantification of possible sources of uncertainty. The structured singular value utilised this information to give comparable measures of robustness. The sea trials conducted represent the first experience of the integrated ship roll stabilisation approach. Experimental results are detailed. These afforded an invaluable opportunity to validate the software employed to predict ship motion. The data generated from the sea trials concurs with the simulations data in predicting that enhanced levels of roll stabilisation are possible without any modification to the rudder system. They also confirm that when the RRS is acting in congress with the fin stabilisers the activity of both actuators diminishes.
22

Nini Roll Ankers Stampetrilogi : tillkomst, bakgrund, budskap... /

Björkman, Ingrid. January 1979 (has links)
Akademisk avhandling--Litteraturhistoria--Uppsala, 1979. / Résumé en anglais. Bibliogr. de l'œuvre de N.R. Anker, p. 142-143. Bibliogr. p. 143-146. Index.
23

Prunus host range and pollen transmission of elm mosaic virus

Callahan, Kemper Leroy, January 1957 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 41-43).
24

House Roll Call Data

Stewart, Charles 24 June 2005 (has links)
Data taken directly from the web sites of the House and Senate and massaged into usable form. Data are organized by session. Displayed by Congress number, session, and file type. So hou1012 would be data from the house, 101st congress, 2nd session. Code=codebook, Summ= summary file, and Notes= miscellenous notes
25

Senate Roll Call Data

Stewart, Charles 24 June 2005 (has links)
Data taken directly from the web sites of the House and Senate and massaged into usable form. Data are organized by session. Displayed by Congress number, session, and file type. So sen1012 would be data from the senate, 101st congress, 2nd session. Code=codebook, Summ= summary file, and Notes= miscellenous notes
26

Desenvolvimento e fabricação de protótipo de impressão roll-to-roll para estudos de produção em série de dispositivos orgânicos / Development and fabrication of roll-to-roll prototype for series production study of organic devices

Leonardo Dias Cagnani 21 February 2013 (has links)
Para que a tecnologia de eletrônica orgânica alcance todo o seu potencial é primordial que o processo de fabricação seja rápido e barato, e uma das maneiras de alcançar isto é com a utilização de processos gráficos especialmente adaptados para a produção de eletrônica, processo esse conhecido por roll-to-roll. Uma grande carência mundial se encontra em equipamentos de produção roll-to-roll de porte laboratorial, que possam ser utilizados para estudos de construção dos dispositivos e, mais importante, a transferência das tecnologias desenvolvidas em laboratório para processos que possam ser facilmente expandidos para a indústria. Neste sentido, durante este trabalho foi desenvolvido um sistema roll-to-roll compacto para produção e estudo de dispositivos orgânicos que apresenta as técnicas de deposição por rotogravura, wire-bar e knife-over-edge comutáveis, sendo empregada uma técnica por vez. O equipamento foi projetado e fabricado de forma a permitir a maior quantidade possível de ajustes das variáveis, com um pequeno consumo de material polimérico e de substrato. Além disto, desenvolveu-se um software de controle operado empregando-se o programa LabVIEW para regulagem da temperatura de secagem, velocidades do substrato e impressão. Como primeiro dispositivo fabricado optou-se por células eletroquímicas emissoras de luz (PLEC) por estas apresentarem baixa tensão de operação e uma baixa influência da espessura e dos eletrodos em suas propriedades optoeletrônicas. Desta forma, foi produzido um dispositivo luminescente sobre papel alumínio, flexível, de baixo custo, sem ITO e todo fabricado no equipamento roll-to-roll aqui desenvolvido. Além disto, o processo foi projetado para ser executado no ambiente, isto é, sem etapas que necessitem vácuo ou atmosfera controlada. Estes dispositivos comprovaram a aplicabilidade do sistema desenvolvido para a produção e desenvolvimento da eletrônica orgânica em laboratório visando a produção industrial final. / To develop the entire potential of Organic Electronic (OE) industry, it is necessary to generate processing methods that include high speed production at low cost. One technique that is emerging as very promising is that known as roll-to-roll. Despite the existence of several roll-to-roll machinery in the market, a small prototype that can be used in laboratories certainly will be very useful for research and as first experiments for production. In this work, we developed a compact roll-to-roll system devoted specifically to the production of printable electronic devices. In particular, this machine disposes deposition techniques as rotogravure, wire-bar and knife-over-edge. It is a versatile machine, which allows the operation of several technical parameters, using a relatively low amount of polymer material and substrate. In addition, we developed a numerical control system that is operated by a computer trough a LabWIEW program. This regulates the drying temperature and the substrate speed, parameters of fundamental importance for a good printed product. As first test we opted for building a coated Light Emitting Electrochemical Cell (PLEC), which are optoelectronic devices that uses relatively low operation voltage and does not exhibit critical thickness dependence. We printed this low cost and flexible device onto aluminum paper, then avoiding any other process and the use of ITO. All the coating processing was carried out in environmental conditions, being not necessary vacuum or accurate control of atmosphere. This application gives a strong evidence that this compact roll-to-roll machine presents a good performance in the fabrication of organic optoelectronic devices, being adequate for research and as guide for industrial production.
27

Controlling the Roll Responses of PCTC's

Söder, Carl-Johan January 2013 (has links)
Modern Panamax Pure Car and Truck Carriers (PCTC) have become more vulnerable to critical roll responses as built in margins have been traded against increased transport efficiency. The research presented in this licentiate thesis aims at enhancing the predictability and control of these critical roll responses. The thesis presents the development of a new method for assessing the roll damping, which is a crucial parameter for predicting roll motions. The method involves a unique set up of full scale in-service trials and is straightforward, cost efficient and shows a good potential. The thesis also includes a demonstration of a new application for rudder control to be used for mitigation of parametric roll. This is performed by simulating real incidents that have occurred with PCTC’s in service. Simulations with rudder roll control show promising results and reveal that the approach could be very efficient for mitigation of parametric roll. Last but not least an approach for monitoring of roll induced stresses, so-called racking stresses in PCTC’s, is presented. The approach involves measurement of the ship motions and scaling of pre-calculated structural responses from global finite element analysis. Based on full scale motion and stress measurements from a PCTC in-service the approach is evaluated and demonstrated to be an efficient alternative to conventional methods. / <p>QC 20130424</p>
28

Application of repetitive control to the lateral motion in a roll-to-roll web system

Jin, Zhao 04 April 2012 (has links)
In a roll-to-roll web system lateral motion of a web caused by disturbances, which are often periodic, results in poor product quality. To reduce the effect of such disturbances, two control strategies are applied. First, the internal model principle is used to reject a sinusoidal disturbance. Second, repetitive control theory is used to reject a general periodic disturbance. We provide the synthesis procedure for both strategies, and demonstrate its use in several simulation studies on a five-roller web system. The simulation results show that the effect of disturbances, either sinusoidal or triangular, on lateral motion are significantly reduced with the internal model controller or the modified repetitive controller.
29

Vem är controllern? : En kvalitativ studie om controllern i rollen som styrorienterad och traditionell ekonomichef

Wallin, Victor, Wentzel, Niklas January 2011 (has links)
Sammanfattning     Det finns många definitioner av vad yrket controller innebär, vilket visar att yrkestiteln är svårdefinierad. Syftet med studien är att beskriva controllerns arbetsroll i medelstora tillverkande privata företag och om controllerns roll fokuserar mer mot styrorienterade uppgifter eller mer mot traditionella ekonomiuppgifter. Vi utformade därför följande frågeställning: Är dagens controller i tillverkande företag mer styrorienterad eller mer en traditionell ekonomichef? Vi valde att genomföra en kvalitativ studie eftersom det möjliggör en djupare förståelse och sedan använde vi oss av en deduktiv ansats där vi gick från teori till empiri. I vår teoretiska referensram har vi beskrivit olika egenskaper, färdigheter, roller och arbetssätt som ingår i controllerns yrke. Vår empiriska studie omfattade personliga intervjuer med fem controllers som kompletterades med en enkät där respondenterna fick rangordna sina arbetsuppgifter i förhållande till tiden. Resultatet visar att vi inte kan påvisa att controllern arbetar mer med styrorienterade uppgifter eller mer med ekonomiuppgifter, men däremot anser vi att controllern arbetar med både styrorienterade- och ekonomiuppgifter.   Nyckelord: Controller, Roll, Ekonomichef, Styrorienterad roll / Abstract     There are many definitions of what the profession controller imply, which indicates that the profession is difficult to define. The purpose of this study is to describe the controller's job role in medium-sized manufacturing companies within the private sector and if the controller’s role focuses more on controlling-oriented tasks or more on traditional business tasks. Therefore we enunciated the following framing of question: Is today’s controller in manufacturing companies more controlling-oriented or more a traditional chief financial officer? We chose to conduct a qualitative study because it enables a deeper understanding and then we chose a deductive approach where we went from theory to empiricism. In our theoretical framework we described various characteristics, skills, roles and ways of working as part of the controller's profession. Our empirical study involved personal interviews with five controllers, which were supplemented by a survey where the respondents ranked their tasks in relation to time. The result shows that we can’t demonstrate that the controller works with more controlling-oriented tasks or more with traditional business tasks, but we believe that the controller works with both controlling-oriented- and traditional business tasks.   Keywords: Controller, Role, Chief financial officer, Controlling-oriented
30

Design of improvement for the Pinch Roll Unit of Reversing Finishing Mill of Stainless Hot Strip Rolling Mill Line

Huang, Chin-Hsiung 06 September 2006 (has links)
The entry and exit side pinch roll unit of the reversing finishing mill of stainless hot strip rolling mill line bears heat effects during producing. Its transfer convection must be sufficient to maintain its function. According to the original pinch roll unit during producing, there are four questions as follows: (1) Strip marks are formed from the roll surface. (2) High temperature of roll surface cause burning phenomenon and lower the hardness of roll surface. (3) Cracks are formed on the roll surface. (4) There is a deflection of horizontal pipe of rocker arm. The improved pinch roll is called new pinch roll. The original pinch roll is called old pinch roll. First, temperature gradients of each location for the old pinch roll and the new pinch roll are calculated, and the reasons of the abnormal high temperature of roll surface are clarified. Second, for the places of the old and new pinch rolls which are the easiest to crack, its stresses of x-y and y-z directions are analyzed. Influence factors of thermal stress crack are clarified. It is proved that the thermal stress effects of the new pinch roll are less than the old pinch roll. Third, the relations of thermal deflection and heat convection for the original horizontal pipe of rocker arm and for the improved horizontal pipe are analyzed. Furthermore, according to the internal structure of the old and new pinch rolls, the flow resistance of circulating water cooling system for each place is considered. Finally, roll grinder is developed and designed to improve the quality of roll surface.

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