1,721,069 research outputs found
Model reference adaptive control을 이용한 증기 발생기 수위 제어 시스템 설계
No full text학위논문(석사) - 한국과학기술원 : 핵공학과, 1988.2, [ [vi], 49 p. ]A new approach of the adaptive control, MRAC, is proposed here for the level control of the steam generators. A model reference adaptive system is composed of four elements; a reference model, an adjustable system, a subtractor, and an adaptation mechanism. A reference model specifies the desired performance; the performance of an adjustable system should be as close as possible to that of the reference model. A subtractor forms the error between the outputs of the reference model and of the adjustable system and an adaptation mechanism processes the auxiliary error in order to modify the parameters of the adjustable system.
The parallel configuration is used to estimate the parameters since the structure is robust to noises. The parameters of the controller are estimated directly by the modified recursive least square method. The perturbation signal is added to the steam flow rate to estimate well the parameters of the steam flow rate.
The reference model is chosen which shows the swell phenomenon but does not show the shrink phenomenon. The variations from steady-state conditions are used to generate the control input, which gives the more robust algorithm and reduces the input variations. Cost function is derived to contain the squared error between the outputs of the reference model and of plant and the squared error between the steam flow rate and the feedwater flow rate. Using the cost function makes the integral action unnecessary and gives good performance in spite of the major disturbance of the load change. The present algorithm has the one tuning parameter of the input weighting factor: the tuning of the present controller is easier than that of the P-I controller which has four tuning parameters.한국과학기술원 : 핵공학과
적응 Pole assignment에 의한 증기발생기 수위제어기의 설계
No full text학위논문(박사) - 한국과학기술원 : 원자력공학과, 1992.8, [ xi, 137 p. ]In this thesis an adaptive observer is designed and a pole assignment technique is applied in order to accomplish a satisfactory automatic control of steam generators from zero to full power.
The change of the water level of a steam generator is caused by three effects; mass capacity, swelling and shrinking, and mechanical oscillations. The knowledge of the water level contributions caused by these effects will be helpful in controlling the water level. The state observer is designed in order to use state feedback. The obvious result of introducing state feedback is to change the undesired open-loop system into the desired overall closed-loop system. Since a nuclear steam generator is controllable and observable, it is possible to design a state observer. Also, since a steam generator is subject to parameter variation according to the change of operating conditions, an adaptive observer must be used. The adaptive observer estimates the parameters and states of the steam generator simultaneously. A fourth-order linear model is presented and, on the basis of this model, an adaptive observer is designed.
Since an implicit-type adaptive observer is applied, a state reconstruction process and a parameter adaptation one are separated and system inputs and outputs are unnecessary to be bounded for the stability. The time-varying problem of the steam generator is resolved by estimating at every time step the parameters which change according to the operating conditions. A pole assignment controller is derived on the basis of the adaptive observer. The characteristics of the overall closed-loop control system can be expressed in terms of its assigned poles. The troublesome tuning procedure of the conventional P-I controller is reduced to the determination of the desired poles only. The proposed algorithm is compared with the P-I controller through numerical simulations.
Also, the adaptive pole assignment controller is studied experimentally by implementing it to the ...한국과학기술원 : 원자력공학과
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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