• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 9
  • 7
  • 5
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 32
  • 32
  • 7
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 3
  • 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.
11

Phase/amplitude estimation for tuning and monitoring

Gyongy, Istvan January 2008 (has links)
The benefits of good loop tuning in the process industries have long been recognized. Ensuring that controllers are kept well-configured despite changes in process dynamics can bring energy and material savings, improved product quality as well as reduced downtime. A number of loop tuning packages therefore exist that can, on demand, check the state of a loop and adjust the controller as necessary. These methods generally apply some form of upset to the process to identify the current plant dynamics, against which the controller can then be evaluated. A simple approach to the automatic tuning of PI controllers injects variable frequency sinewaves into the loop under normal plant operation. The method employs a phase-locked loop-based device called a phase-frequency/estimation and uses 'design-point' rules, where the aim is for the Nyquist locus of the loop to pass through a particular point on the complex plane. A number of advantages are offered by the scheme: it can carry out both 'one shot' tuning and continuous adaptation, the latter even with the test signal set to a lower amplitude than that of noise. A published article is included here that extends the approach to PID controllers, with simulations studies and real-life test showing the method to work consistently well for a for a wide range of typical process dynamics, the closed-loop having a response that compares well with that produced by standard tuning rules. The associated signal processing tools are tested by applying them to the transmitter of a Coriolis mass-flow meter. Schemes are devised for the tracking and control of the second mode of measurementtube oscillation alongside the so-called 'driven mode', at which the tubes are usually vibrated, leading to useful information being made available for measurement correction purposes. Once a loop has been tuned, it is important to assess it periodically and to detect any performance losses resulting from events such as changes in process or disturbance dynamics and equipment malfunction such as faulty sensors and actuators. Motivated by the effective behaviour of the controller tuners, a loop monitor developed here, also using probing sinewaves coupled with 'design-point' ideas. In this application, the effect on the process must be minimal, so the device must work with lower still SNRs. Thus it is practical to use a fixed-frequency probing signal, together with a different tool set for tracking it. An extensive mathematical framework is developed describing the statistical properties of the signal parameter estimates, and those of the indices derived from these estimates indicating the state of the loop. The result is specific practical guidelines for the application of the monitor (e.g. for the choices of test signal amplitude and test duration). Loop monitoring itself has traditionally been carried out by passive methods that calculate various performance indicators from routine operating data. Playing a central role amongst these metrics is the Harris Index (HI) and its variants, which compare the output variance to a 'minimum achievable' figure. A key advantage of the active monitor proposed here is that it is able not only to detect suboptimal control but also to suggest how the controller should be adjusted. Moreover, the monitor’s index provides a strong indication of changes in damping factor. Through simple adjustments to the algorithm (by raising the amplitude of the test signal or adding high frequency dither to the control signal), the method can be applied even in the presence of actuator non-linearity, allowing it to identify the cause of performance losses. This is confirmed by real-life trials on a non-linear flow rig.
12

Řízení procesů a dokumentace v dozorovém orgánu / Process Management and Document Control in a Market Surveillance Authority

Manová, Dana January 2011 (has links)
This diploma thesis deals with the process analysis and documentation of the Czech Trade Inspection Authority, a market surveillance authority in the state administration. The main objective of this thesis is the mapping of operational processes within the organization and identification of their potential weak points. The author of the thesis then proposes ideas for their improvement. The main tool for process analysis is the 5. criterion of the CAF model (Common Assessment Framework), which takes into consideration the specific needs of public administration. The thesis then focuses on the analysis of documentation, tries to find its strengths and weaknesses and finally ideas for its improvement.
13

Ανάπτυξη αλγόριθμου για την αυτόματη βελτιστοποίηση της παραγωγής βιοαερίου από αναερόβιους χωνευτήρες

Δούναβης, Αθανάσιος 28 February 2013 (has links)
H αναερόβια χώνευση είναι η βιολογική διεργασία κατά την οποία παράγεται βιοαέριο (CH4 και CO2) από οργανική ύλη με τη συνδυασμένη δράση μεικτού πληθυσμού μικροοργανισμών, απουσία μοριακού οξυγόνου. Η διεργασία της αναερόβιας χώνευσης είναι μια από τις πιο διαδεδομένες μεθόδους χώνευσης υλύος και εφαρμόζεται κυρίως στην επεξεργασία αποβλήτων με υψηλό οργανικό φορτίο, με σκοπό την παραγωγή βιοαερίου, με ταυτόχρονη παραγωγή ενέργειας καθώς και στην παραγωγή ενέργειας από φυτική βιομάζα ή από στερεά οικιακά απορρίματα. Το πιο σημαντικό πρόβλημα που αντιμετωπίζεται σε μονάδες παραγωγής ενέργειας είναι η μεγιστοποίηση του ρυθμού παραγωγής βιοαερίου για τη χρήση του. Στην παρούσα εργασία μελετήθηκε ένα σύστημα ρύθμισης μεσόφιλου ( 35-37 oC) αναερόβιου χωνευτήρα τύπου CSTR χωρητικότητος τριών λίτρων, ο οποίος εμβολιάστηκε με αναερόβια βιομάζα μεικτής καλλιέργειας μικροοργανισμών από βιολογική μονάδα επεξεργασίας αστικών λυμάτων. Η τροφοδοσία ήταν ένα συνθετικό και αποστειρωμένο διάλυμα οξικού οξέος. Ως αποτέλεσμα, μετά από κάποιο χρονικό διάστημα επικρατεί καλλιέργεια ακετοκλαστικών μεθανογόνων μικροοργανισμών. Με βάση τη συμπεριφορά του αντιδραστήρα για διαφορετική οργανική φόρτιση, αναπτύχθηκε ένα απλοποιημένο μοντέλο δύο μεταβλητών, της βιομάζας και του περιοριστικού υποστρώματος, κατάλληλο για αυτόματη ρύθμιση, το οποίο χρησιμοποιήθηκε στη συνέχεια για τον προσδιορισμό του βέλτιστου χρόνου παραμονής και για την ανάπτυξη ρυθμιστικού αλγορίθμου. Οι κινητικοί παράμετροι του μαθηματικού μοντέλου εκτιμήθηκαν μέσω συλλογής πειραματικών δεδομένων από την διάταξη του αναερόβιου χωνευτήρα. Για τη σταθεροποίηση του συστήματος της αναερόβιας χώνευσης, αναπτύχθηκε ένας αναλογικός νόμος ανάδρασης εξόδου, ο οποίος σταθεροποιεί τη διεργασία σε μία μεγάλη περιοχή γύρω από τη βέλτιστη μόνιμη κατάσταση, όπου η βιομάζα δεν οδηγείται σε έκπλυση. Τέλος, οι προσομοιώσεις και τα πειραματικά αποτελέσματα έδειξαν ότι ο προτεινόμενος νόμος ανάδρασης εξόδου σταθεροποιεί το σύστημα ύστερα υπό παλμική διαταραχή (ανοδική και καθοδική) στη συγκέντρωση της οργανικής φόρτισης της τροφοδοσίας του συστήματος. / Anaerobic digestion is a complex biochemical process and one of the most widespread methods for the treatment of high organic content waste, aiming at the production of biogas(energy), while treating the waste] A common process objective is the maximisation of the biogas production. A 2-state model was developed for the simulation of an experimental reactor (CSTR), fed with acetic acid. This type of feeding is very important, as quite often anaerobic digestion is carried out in two sequential reactors, one hydrogen and fatty acids (mainly acetate) producing hydrolysis reactor followed by a methanogenic reactor which produces biogas (methane and carbon dioxide). The hydraulic retention time which maximizes the production rate of biogas was determined based on the developed process model. A model-based output feedback process control algorithm was utilised to secure fast transition to the new optimal steady state when there are changes in the feed loading rate. The algorithm was first demonstrated to work theoretically and secured minimal losses of methane during a transition. The algorithm was then applied experimentally and succeeded to drive the digester to the new optimum following both step-up and step-down pulse disturbances in the acetate feed concentration.
14

Modelling and control of crystal purity, size and shape distributions in crystallization processes

Borsos, Akos January 2017 (has links)
Crystallization is a key unit operation used for obtaining purified products by many process industries. The key properties of the crystalline products, such as size and shape distribution, purity and polymorphic form are controlled by the crystallization process. All these properties impact significantly the downstream operations such as drying or filtration. Therefore, monitoring and controlling this process is fundamental to ensure the quality of the final product. Process analytical technology (PAT) brings numerous new methods and opportunities in the process analytics and real time process monitoring systems, which can be integrated into the control algorithm and provide high level optimal control strategies as well as deeper understanding of the process. Process monitoring helps develop mathematical models which can, in one hand, help in better understanding the processes and consecvently the development and application of advanced control methods in order to achieve better product quality. In this work, image processing and image analysis based direct nucleation control (IA-DNC) is developed in order to investigate the evolution of the crystal properties, such as crystal size, and crystal shape distribution. The IA-DNC approach is also compared to alternative DNC techniques, in which particle number were measured by Focused Beam Reflectance Measurement (FBRM) in order to control crystal size. A control approach is introduced that control the nucleation and disappearance of crystals during cooling and heating segments related to the changes of the number of counts (measured by Particle Vision Measurment, so called PVM or combination of FBRM and PVM). The approach was applied to investigate crystallization of compounds with different behavior: potassium dihydrogen phosphate (KDP) water, contaminated KDP -water and Ascorbic acid water systems. The results demonstrate the application of imaging technique for model-free feedback control for tailoring crystal product properties. The second main aim of the thesis is to investigate and control crystallization processes in impure media in the presence of multiple impurities, with an impact on the crystal shape via growth kinetics. The broad impact of the crystal growth modifiers (impurities) on the growth kinetics is observed in real time by using in situ video imaging probe and real-time image analysis. A morphological population balance model is developed, which incorporates a multi-site, competitive adsorption mechanism of the impurities on the crystal faces. The kinetic parameters of primary nucleation, growth and impurity adsorption for a model system of potassium dihydrogen phosphate crystallization in water in the presence of two impurities, were estimated and validated with experimental results. It was demonstrated that the model can be used to describe the dynamic evolution of crystal properties, such as size and aspect ratio during crystallization for different impurity profiles in the system. Manual, feedback and hybrid feedback-feedforward control techniques are developed and investigated numerically for continuous processes, while model-based and model-free control approach for crystal shape are developed for batch processes. The developed morphological population balance model is implemented and applied in the model-based control approaches, which are suitable to describe multicomponent adsorption processes and their influence on the crystal shape. Case studies show the effectiveness of crystal growth modifiers based shape control techniques. Comparison of different control approaches shows the effectiveness of the techniques. The third part of the thesis deals with purification of crystals when adsorption of impurities on crystal surfaces and its incorporation into crystals are considered. A purification method, called competitive purity control (CPC) is proposed and investigated. A morphological population balance model, including nucleation, growth and competitive impurity adsorption kinetics is developed to describe the case when multiple impurities can adsorb competitively on the crystal surface. The model is also combined with liquid phase chemical reaction model, in order to investigate the purity control case when an additive is introduced in the system that reacts with the impurity forming a non-adsorbing reaction product. Both competitive purity control approaches proposed: the adsorption based competitive purity control (A-CPC) and the reaction based competitive purity control (R-CPC); are investigated using detailed numerical simulations then compared with the alternative widely used purification method, called recrystallization. In the last contribution chapter, an integrated process optimization of a continuous chemical reactor and crystallizer is performed and studied numerically. The purpose of this study is to show the way in which the byproduct produced in the chemical reactor may affect the crystallization process and how its negative effect can be reduced by applying integrated process optimization. Sensitivity analysis of the system was performed by considering the flow rate and the concentration of substances in the input stream of the chemical reactor as manipulated process variables. Model based integrated process optimization and the sensitivity analysis in order to obtain improved quality product in terms of crystal size, shape and purity.
15

Zlepšování systému řízení neshod / Improvement of noncoformities control system

Turková, Veronika January 2009 (has links)
Bc. Veronika Turková Improvement of nonconformities control system Master´s thesis, Institute of metrology and quality assurance, Brno University of technology This thesis deals with the issue of improving the management system of nonconformities control in a company ALSTOM Power, s.r.o. ALSTOM Group, the Division of boilers production, located in Brno. This thesis contains an analysis of current status of nonconformities control process and designs a new nonconformity control process using a new internal database for resolving of nonconformities. These measures should deal with the efficiency of the management of nonconformities process and reduce current company pains.
16

Modeling and optimization of a cross-flow, moving-bed, flue gas desulfurization reactor

Duespohl, Dale W. January 1995 (has links)
No description available.
17

Road to Sustainable Integration : Supported by Strategic Management Accounting and Control Process

Biglari, Bahram, Haidari, Nael January 2019 (has links)
Purpose; this thesis is purposed to investigate Strategic Management Accounting and Control process in supporting Sustainable Integration between Strategic Supplier Relationship Management processes and Strategic Customer Relationship Management processes. Methodology; based on the purpose, the study has conducted a literature review of presenting theories to define Sustainable Integration, Strategic Management Accounting and Control process, Strategic Supplier Relationship Management process, and Strategic Customer Relationship Management process. Furthermore, the study defined how Sustainable Integration can be accomplished, which tools, techniques, and procedures are suited for supporting Sustainable Integration, and how controlling process supports the Sustainable phenomenon between business processes. The reasonable methods of conducting qualitative and exploratory studies have been employed to handle empirical gathering data by interviews with strategic business process managers in industrial Swedish Manufacturing cases. Then the data has been analyzed in a Within-case analysis and Cross-case synthesis following by interpretation and implications. Using the regressive method and advanced method, the study sent the manuscript to interviewees and went back from results to theory to add observed and found out knowledge to the theory. Findings; the study found out that Sustainable Integration is accomplished by supporting and controlling processes of harmonized and continuous flows of information, product, technology, and financial resources through strategic close inter-organizational relationship which are conducted by Strategic Management Accounting and Control process. Sustainable and competitive tools, techniques and procedures are employed to support the Sustainable Integration phenomenon between strategic sub-business processes in case of SSRM and SCRM processes. Various levels of Sustainable Integration regards the extent of harmonization and close long-term relationship are occurred based on openness, innovativeness, trust, commitment and transparency between industrial manufacturing Swedish companies. Developed and reconfigured Strategic Management Accounting and Control process supports Sustainable Integration by the aim of achieving Sustainable Competitive Advantages and Sustainable Sourcing.
18

Élaboration d'un système de contrôle de l'espionnage industriel par la fonction contrôle de gestion / Elaboration of a system of control of the industrial espionage by the management control function

Fane, Oumar 12 November 2018 (has links)
Plusieurs problèmes accablent les organisations, mais l’espionnage industriel occupe de plus en plus une place grandissante. Ses conséquences sont catastrophiques, allant des pertes de sommes colossales à la faillite de certaines entreprises. Ce travail de recherche, s’inscrivant dans le champ disciplinaire des Sciences de Gestion, particulièrement du contrôle de gestion, a pour finalité d’appréhender le processus de contrôle de l’espionnage industriel dans les organisations, en élaborant un système de contrôle de l’espionnage industriel par la fonction contrôle de gestion. Après une revue de littérature et une première vague d’entretiens semi-directifs, qui ont montré les limites des protections juridiques et les vides de gestion des protections techniques contre l’espionnage industriel, nous avons construit un modèle théorique du processus de contrôle de l’espionnage industriel par la fonction contrôle de gestion, qui met en interaction les figures imposées / libres, les leviers de contrôle diagnostic / interactif et leurs outils, et les six dimensions d’analyse réajustées. Ensuite, nous avons élaboré un système de contrôle de l’espionnage industriel, en déterminant ses outils et en spécifiant son instrumentation dans les organisations. Une deuxième vague d’entretiens semi-directifs a été effectuée pour justifier la pertinence dudit système auprès des spécialistes professionnels et universitaires du contrôle de gestion. / Several problems overwhelm organizations, but industrial espionage is becoming more and more important. Its consequences are catastrophic, ranging from the loss of colossal sums to the bankruptcy of certain companies. This research work, which is part of the disciplinary field of Management Sciences, particularly management control, aims to understand the process of controlling industrial espionage in organizations by developing a control system of industrial espionage by the management control function. After a literature review and a first wave of semi-directive interviews, which showed the limits of legal protections and management gaps of technical protections against industrial espionage, we constructed a theoretical model of the control process of industrial espionage by the management control function, which puts into interaction the imposed / free figures, the diagnostic / interactive control levers and their tools, and the six readjusted analysis dimensions. Then we developed a system of control of the industrial espionage by determining its tools and specifying its instrumentation in organizations. A second wave of semi-directive interviews was conducted to justify the relevance of this system with professional and academic management control specialists.
19

Compreensão do sistema Last Planner de controle da produção segundo a Perspectiva da Linguagem-Ação

Viana, Daniela Dietz January 2011 (has links)
Desde o surgimento do sistema Last Planner de controle da produção (LPS), no início dos anos 90, vários estudos apontaram a necessidade de compreender a teoria fundamental na qual o sistema é baseado. A Perspectiva da Linguagem‐Ação (LAP) é sugerida na literatura como adequada para compreender o gerenciamento dos compromissos no LPS. Entretanto, os estudos que comparam estas abordagens discutem a relação em um âmbito teórico. Neste sentido, há uma falta de estudos empíricos que tenham investigado as vantagens de compreender um sistema de planejamento segundo a LAP. O objetivo deste trabalho é analisar os benefícios e limitações da utilização da Perspectiva da Linguagem‐ Ação para avaliar sistemas de planejamento e controle da produção, com ênfase nos níveis de médio e curto prazo. Foram realizados dois estudos de caso em empresas diferentes, ambas com um bom nível de maturidade na utilização do LPS, mas que apresentavam diferenças substanciais na forma de realizar o planejamento e controle da produção. Durante a condução dos estudos foram utilizadas entrevistas semiestruturadas com engenheiros, auxiliares e encarregados; observação direta ao canteiro de obras; análise de documentos; e participação nas reuniões de planejamento de médio e curto prazo como fontes de evidência. Em cada um dos casos foi realizado um mapeamento das redes de compromissos relativas ao planejamento, bem como uma análise aprofundada sobre como são realizadas as reuniões, como os compromissos são gerenciados e quem efetivamente participa da tomada de decisão. Em ambos os estudos foi possível rastrear como os compromissos são iniciados. Este rastreamento levou a uma análise sobre a integridade dos ciclos nas redes de compromissos, e as consequências dessas falhas para o sistema de planejamento. Finalizadas as análises individuais foi feita uma análise cruzada dos casos estudados, em que foi possível perceber as diferenças das abordagens de cada empresa na condução do planejamento. As análises dos casos indicaram que existem alguns problemas presentes no sistema de planejamento que são melhor compreendidos através da análise das redes de compromissos. Além disso, as análises das reuniões apontaram algumas limitações no método proposto na literatura para avaliar as discussões entre duas pessoas que levam a execução de uma ação. Desta forma, este estudo elaborou um método que tornou possível analisar os acordos estabelecidos nas reuniões de planejamento, de maneira a contornar as limitações encontradas. / Since the Last Planner™ System (LPS) was devised in the early Nineties, several studies have pointed out the need to understand the underlying theory in which it is based on. The Language‐Action Perspective (LAP) has been suggested as a suitable approach to understand the management of commitments in the LPS. However, there is a lack of empirical studies that have investigated the utility of LAP as a theoretical approach for explaining the LPS. This study aims to investigate the benefits and the limitations of the Language‐Action Perspective for evaluating the effectiveness of planning and control systems, emphasizing medium and short term planning. Two case studies were carried out in different construction companies, both of them highly experienced on the use of LPS. Interviews with the people involved in planning meetings, direct observation of the construction sites, participation in planning meetings, and documents analysis were the main sources of evidence. In each company, the production planning and control system of one project was assessed, based on the mapping of the network of commitments regarding the medium and short term planning levels. Besides, an in‐depth analysis of planning meetings was made, describing how they were carried out, who effectively participated in decision‐making, and how the commitments were managed. In both studies, it was possible to track how the commitments were initiated, and in some cases to analyse the integrity of the workflow loops in the network of commitments, and the consequences of the failures for the planning and control system. A cross‐case analysis was carried out, in order to compare the managerial approaches of the two companies. The results pointed out some problems in the planning and control processes that can be better understood through the mapping of the network of commitments. Moreover, the study indicated some limitations of the method proposed in the literature for analysing people’s speech. For that reason, this study devised a method to perform a detailed analysis of planning meetings, in order to overcome those limitations.
20

Compreensão do sistema Last Planner de controle da produção segundo a Perspectiva da Linguagem-Ação

Viana, Daniela Dietz January 2011 (has links)
Desde o surgimento do sistema Last Planner de controle da produção (LPS), no início dos anos 90, vários estudos apontaram a necessidade de compreender a teoria fundamental na qual o sistema é baseado. A Perspectiva da Linguagem‐Ação (LAP) é sugerida na literatura como adequada para compreender o gerenciamento dos compromissos no LPS. Entretanto, os estudos que comparam estas abordagens discutem a relação em um âmbito teórico. Neste sentido, há uma falta de estudos empíricos que tenham investigado as vantagens de compreender um sistema de planejamento segundo a LAP. O objetivo deste trabalho é analisar os benefícios e limitações da utilização da Perspectiva da Linguagem‐ Ação para avaliar sistemas de planejamento e controle da produção, com ênfase nos níveis de médio e curto prazo. Foram realizados dois estudos de caso em empresas diferentes, ambas com um bom nível de maturidade na utilização do LPS, mas que apresentavam diferenças substanciais na forma de realizar o planejamento e controle da produção. Durante a condução dos estudos foram utilizadas entrevistas semiestruturadas com engenheiros, auxiliares e encarregados; observação direta ao canteiro de obras; análise de documentos; e participação nas reuniões de planejamento de médio e curto prazo como fontes de evidência. Em cada um dos casos foi realizado um mapeamento das redes de compromissos relativas ao planejamento, bem como uma análise aprofundada sobre como são realizadas as reuniões, como os compromissos são gerenciados e quem efetivamente participa da tomada de decisão. Em ambos os estudos foi possível rastrear como os compromissos são iniciados. Este rastreamento levou a uma análise sobre a integridade dos ciclos nas redes de compromissos, e as consequências dessas falhas para o sistema de planejamento. Finalizadas as análises individuais foi feita uma análise cruzada dos casos estudados, em que foi possível perceber as diferenças das abordagens de cada empresa na condução do planejamento. As análises dos casos indicaram que existem alguns problemas presentes no sistema de planejamento que são melhor compreendidos através da análise das redes de compromissos. Além disso, as análises das reuniões apontaram algumas limitações no método proposto na literatura para avaliar as discussões entre duas pessoas que levam a execução de uma ação. Desta forma, este estudo elaborou um método que tornou possível analisar os acordos estabelecidos nas reuniões de planejamento, de maneira a contornar as limitações encontradas. / Since the Last Planner™ System (LPS) was devised in the early Nineties, several studies have pointed out the need to understand the underlying theory in which it is based on. The Language‐Action Perspective (LAP) has been suggested as a suitable approach to understand the management of commitments in the LPS. However, there is a lack of empirical studies that have investigated the utility of LAP as a theoretical approach for explaining the LPS. This study aims to investigate the benefits and the limitations of the Language‐Action Perspective for evaluating the effectiveness of planning and control systems, emphasizing medium and short term planning. Two case studies were carried out in different construction companies, both of them highly experienced on the use of LPS. Interviews with the people involved in planning meetings, direct observation of the construction sites, participation in planning meetings, and documents analysis were the main sources of evidence. In each company, the production planning and control system of one project was assessed, based on the mapping of the network of commitments regarding the medium and short term planning levels. Besides, an in‐depth analysis of planning meetings was made, describing how they were carried out, who effectively participated in decision‐making, and how the commitments were managed. In both studies, it was possible to track how the commitments were initiated, and in some cases to analyse the integrity of the workflow loops in the network of commitments, and the consequences of the failures for the planning and control system. A cross‐case analysis was carried out, in order to compare the managerial approaches of the two companies. The results pointed out some problems in the planning and control processes that can be better understood through the mapping of the network of commitments. Moreover, the study indicated some limitations of the method proposed in the literature for analysing people’s speech. For that reason, this study devised a method to perform a detailed analysis of planning meetings, in order to overcome those limitations.

Page generated in 0.0716 seconds