1,720,956 research outputs found
Performance Evaluation of Different Conventional and Intelligent Controllers for Temperature Control of Shell and Tube Heat Exchanger System
Get PDFME, EIEDIn any of the control application, controller design is the most important part.
There are different types of controller architectures available in control literature. The
controller can be conventional in nature or can be intelligent in nature. The conventional
controller doesn’t posses the human intelligence; where in the intelligent controller
human intelligence is embed with the help of certain soft computing algorithms. After the
design of controller is performed, the performance evaluation part comes in to light. The
designed controller has to give optimal control results irrespective of every situation like
plant and equipment non linearity, equipment saturation.
This dissertation looks in to performance evaluation of different conventional and
intelligent controllers implemented with a clear objective to control the outlet fluid
temperature of shell and tube heat exchanger system. First of all mathematical modeling
of the process is performed using experimental plant data. After the mathematical
modeling the control objective is set and different kind of controllers are designed to
meet the control objective. Feedback controller, feedback plus feed forward controller are
implemented to meet the control objective, but due to their inherent disadvantages and
more tuning parameters, these controllers were unable to give satisfactory results. So, a
model based controller is designed which has only one tuning parameter as compared to
three tuning parameters of PID controller. The model based controller gives a satisfactory
result. But to embed some kind of intelligence in the controller, fuzzy logic based
controller is designed. The fuzzy logic based controller meets the control objective.
Comparative analyses of performance evaluation of all controllers are performed.
During the design of fuzzy based hybrid controller, the designer meets two key
design challenges namely, optimization of existing fuzzy rule base and identification,
estimation of new membership function or optimization of existing membership function.
These issues play a vital role in controller design in real time. In real time controller
hardware design there is memory and computational power constraints, so a designer
needs to optimize these two design aspects. This dissertation also looks in to these key
design challenges. For optimization of existing mamdani based fuzzy rule base, a genetic
algorithm approach is used and for identification and estimation of fuzzy membership
function, a neural network based approach is used
Topology, Modeling and Control Aspects of DC-DC Converter for an Off-Grid Operated Fuel Cell Power System Perspective
Get PDFWith ever increasing demand of electricity, the conventional centralized power system have been steadily replaced by distributed power system (DPS). There are several advantages
of DPS such as modularity, better thermal management, and higher efficiency. DPS finds widespread applications in transportation, distributed generation, consumer electronics and data centers. This dissertation investigates the topological, modeling and controller design aspects of DC-DC converter for an off-grid operated fuel cell power system. In distributed generation system, a renewable energy source is used to harvest utility power. To connect the renewable energy source with a stand-alone load or grid, a power conditioning unit (PCU)is used. A comprehensive review of different DC-DC converter used in PCU has been carried out. Furthermore the classification of DC-DC converters according to the conversion ratio has been carried out. For controller design, an accurate model of DC-DC converter is required. The classical modeling techniques such as state-space averaging modelling and generalized state-space averaging modelling of DC-DC converter provide averaged model
which is suitable only for small-signal analysis. Therefore, parametric system identification technique is used to determine the dynamics of DC-DC converter during the closed-loop operation of the converter. Different linear and block-oriented models and Prediction Error Method are used to estimate the parameters of DC-DC converter in closed-loop. Estimated models are validated using different model validation criteria. Some DC-DC converter exhibits non-minimum phase behavior in their mathematical model. Different methods of mitigating the negative aspect of non-minimum phase behavior has been outlined in this
dissertation. Conventional Type-II and Type-III controller are designed for DC-DC boost converter, but the linear controllers is unable to provide satisfactory performance during large changes in source or load profile due to the fixed-gain nature of the controller. Due to the nonlinear nature of the converter dynamics, nonlinear controller are preferred. One of the most widely used nonlinear controller is sliding mode controller. The classical sliding mode controller has some limitations such as variable switching frequency, steady-state error and chattering effect. Variable switching frequency and chattering effect hampers the practical implementation of the control law. The controller also gives steady-state error which is undesired. To overcome such limitations, fixed-frequency sliding mode current controller and double-integral fixed-frequency sliding mode current controller are designed. In fixed-frequency sliding mode current controller and double-integral fixed frequency sliding mode current controller, the controller provides fixed frequency and removes the unwanted steady state error in output voltage. A multi-staged PCU is developed for fuel cell based stand-alone application which acts as a case study of distributed generation scheme. In fuel cell based stand-alone application, different design constraints such as input
ripple current, decoupling of power stages and power quality have been considered. An active-clamp current-fed isolated full-bridge converter is used as the front-end converter
and single-phase voltage source inverter is used for inverter application. Dual-loop control is used for control of front-end converter whereas fixed-frequency sliding mode controller is used to control the inverter. Simulation results have been provided to validate the design
requirements. From the simulation results it is found out that the said controller gives satisfactory results both in steady-state as well as transient state. The harmonics of the load current also obeys the regulation standard (IEEE standard 519 and IEEE standard 1547). This dissertation provides detailed discussion of topological aspect, modeling and system identification aspect and controller design aspect of DC-DC converter for an off-grid fuel cell power system. A large number of DC-DC converter has been studied and comparative analysis has been provided. Due to the said limitations of state-space averaged modeling scheme, a closed-loop system identification based scheme has been developed. In controller design section, both linear as well as nonlinear controller has been studied and their
performance has been investigated. In the end, an off-grid fuel cell based power system has been designed which can provide power during grid-blackout
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Recursive least squares identification of heat exchanger system using block-structured models
Get PDFThis study provides a recursive parametric identification scheme for a liquid-saturated steam heat exchanger system. The recursive identification scheme uses block-structured Wiener and Hammerstein models as model structure and recursive least squares estimation scheme as the parameter estimation method. The estimated block-oriented model provides higher accuracy of estimation than linear models provided in the literature. From the simulation results, it is observed that the Wiener model can provide 88% goodness-of-FIT, whereas Hammerstein model can provide 96% goodness-of-FIT using the said technique. © IMechE 2021.College of Polytechnics Jihlava [1170/10/2137
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
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