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Dissertations / Theses on the topic 'Chemical control'

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Published: 4 June 2021
Last updated: 1 August 2024

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1

Chu, C. C., and T. J. Henneberry. "Chemical Control Studies of Silverleaf Whitefly Control." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/210866.

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Chemical control studies for silverleaf whitefly, Bemisia argentifolii Bellows and Perring, control on cotton showed that fenpropathrin-acephate, fenpropathrin-endosulfan, and endosulfan-bifenthrin mixtures gave adequate control and increased cotton yields were obtained as compared within untreated cottons. Pyriproxyfen, applied biweekly or alternated with fenpropathrin-acephate, Nicotiana, and a fenpropathrin-mycotrol mixture also gave effective control.
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2

Ydstie, Birger Erik. "Robust adaptive control of chemical processes." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/8295.

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3

Hought, Julian L. "Advanced control of batch chemical reactions." Thesis, University of Huddersfield, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314422.

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4

West, Jon. "Chemical control of Armillaria root rot." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386565.

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5

Kotzeva, Vega Petrova. "Chemical sensors for automotive emission control." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620419.

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6

Wang, Chuangnan. "Ultrasonic technique for chemical process control." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24442.

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Ultrasound has found application in chemical processing control using both low power, high frequency monitoring techniques and high power, low frequency process enhancement approaches. In many cases, standard ultrasonic systems are retrofitted to a process and while these produce efficiency improvements, the design of bespoke systems may offer more potential. In particular, this Thesis has considered two techniques used in the biomedical field; harmonic imaging and high intensity focused ultrasound (HIFU) and has translated these into ultrasonic transducers for use in an industrial process control system. Traditional ultrasound monitoring techniques are based on operation in the linear domain and are used to monitor chemical processes by measurement of material acoustic velocity, attenuation or based on spectral analysis. Both active and passive methods have been reported for application in this industrial sector. One issue is the presence of multiple reflections in the received ultrasonic signal which can mask the signals of interest from the load medium. This Thesis has considered a new ultrasonic monitoring approach using a combination of both linear and nonlinear spectral components. This was applied to high-throughput products and a dual frequency transducer designed and fabricated to acquire the ultrasonic backscattered signals in both the fundamental and second harmonic frequency regimes. The additional information provided by the harmonic device enabled discrimination between shampoo and conditioner products with the same density, but different molecular weights. HIFU transducer array designs are then considered for high power, low frequency chemical process enhancement applications. Typical applications of high power ultrasound use single or multiple discrete transducers to insonify a process. These are effective, but inflexible in the delivery of the ultrasonic field. The application of a HIFU array would provide control of the high power focal region in the load medium, which offer advantages to industry. Two transducer array approaches have been considered in this Thesis based on piezoelectric composite configurations. Three HIFU arrays based on the 1-3 piezocomposite have been fabricated to operate between 200-400kHz and fully characterised to evaluate their high power performance. A second transducer configuration was based on a novel 2-2 piezocomposite with a 2 layer stacked configuration. Simulation of this transducer design illustrated its potential for high power applications, although a number of fabrication issues resulted in the manufactured array not operating at full capacity. Importantly, the transducer configurations developed in this Thesis are shown to induce cavitation through the standard aluminium foil test.
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7

Blandy, Jack. "Soft chemical control of layered oxychalcogenides." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:0fcc2604-0e0d-4206-a0aa-3fdcc611e357.

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The structure, magnetic behaviour and chemistry of layered oxychalcogenides of composition A2MO2X2Ch2 (where A = Sr, Ba; M = Mn, Co, Ni, Cu, Zn; X = Cu, Ag and Ch = S, Se, Te) has been investigated by the synthesis of new compounds of this type and control of the properties of these compounds by oxidative deintercalation of Cu/Ag. I2 can be used to oxidatively deintercalate Cu from Sr2MnO2Cu1.5S2, forming Sr2MnO2Cu1.33S2, an incommensurately modulated compound, with a completely different Cu/vacancy ordering and antiferromagnetic ordering structure to the parent. This reaction is also probed in real-time, using in situ powder X-ray diffraction. Sr2MnO2Ag1.5Se2 was found to have an A-type magnetic ordering structure, similar to Sr2MnO2Cu1.5Se2. Sr2MnO2Cu1.8Te2 on the other hand with a lower Mn oxidation state shows only two-dimensional magnetic correlations, rather than long-range order. Extending the reaction with I2 to several Co-containing analogues revealed that ~ 25% Ag could be removed from Sr2CoO2Ag2Se2, sufficient to observe a change in magnetic behaviour, from antiferromagnetic to ferromagnetic. By contrast only ~11% Cu can be deintercalated from Sr2CoO2Cu2S2 and even less (~5%) from Sr2CoO2Cu2Se2. Neutron diffraction was used to examine the resultant changes in magnetic ordering. The novel compounds Sr2CuO2Cu2Se2 and Ba2CuO2-xCu2Se2 are related by substitution of the alkali-earth metal, but while Sr2CuO2Cu2Se2 is a stoichiometric compound with metal-like character, Ba2CuO2-xCu2Se2 is an oxygen-deficient semiconductor, with tuneable oxygen content. Unusual features are observed in the magnetic susceptibility measurements of Sr2NiO2Cu2Se2 that appear unrelated to this compound's long-range magnetic ordering, as probed by neutron diffraction. Furthermore, unusual peak splitting is observed in low-temperature powder X-ray diffraction patterns of this compound; this may plausibly be due to a photon-induced effect arising from the use of a high-energy beamline; although further measurements are required to examine this. Overall the work shows the flexibility and range of behaviour exhibited by a series of the transition metal oxide chalcogenides.
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8

Shen, Gwo-Chyau. "Adaptive inferential control for chemical processes /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487329662147068.

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9

Brunkow, Glenn Edward. "Chemical control of rough-leaved dogwood." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2268.

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10

Seki, Hiroya. "Feedback Control of Nonlinear Chemical Reactors." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149439.

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11

Bailey, D. A. "Chemical Height Control of Florists' Hydrangeas." College of Agriculture, University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/215854.

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XE-1019 (2 foliar sprays of 10, 2Q or 30 mg-liter⁻¹) was applied to plants of Hydrangea macrophylla Ser. 'Rose Supreme' during greenhouse forcing. Doses applied resulted in excessive reductions in shoot elongation and inflorescence diameters and delayed anthesis. Shoot growth was reduced with increasing XE-1019 concentration. Shoot length was reduced 46 %; stem dry weight was reduced 31 %; leaf area per shoot was reduced 44 %; inflorescence height was cut by 45 %; and inflorescence mass was reduced 48% with the 30 mg-liter⁻¹ XE-1019 treatment. Specific leaf weight increased with increased XE -1019 concentration (192% increase with the 30 mg-liter⁻¹ treatment) resulting in thicker leaves at anthesis. XE-1019 is an effective height control agent for florists' hydrangeas, and shows significant activity at very low (less than 0.2 mg a.i. per plant) doses.
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12

Linkous, Emily Kathryn. "Integrating biological control and chemical control of cabbage caterpillar pests." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366362436.

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13

Shah, Nirali. "Simulation of Model Predictive Control using Dynamic Matrix Control algorithm." Thesis, California State University, Long Beach, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1604872.

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Model Predictive Control has emerged as a very powerful technology in the area of process control for three decades. The objective of this work was to develop Dynamic Matrix Control Algorithm, one of the most widely used Model Predictive Control Algorithms using MATLAB and simulate it for a real world Single Input Single Output system. This thesis focuses on the impacts and importance of the tuning parameters of Dynamic Matrix Control along with an overview of the general Model Predictive Control strategy. The tuning of the Dynamic Matrix Controller was done by trial and error based on the knowledge of the simulated system under consideration and the control strategy. The Control Signal computed was then implemented on the system to study its effect on the system output using a discrete transfer function model. The results of the tuned controller were observed to be similar to the other tuning methods discussed in the literature.

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14

Mühleisen, Martin Bernd. "Chemical weed control : options in fibre flax." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0031/MQ64411.pdf.

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15

Meadowcroft, Thomas Andrew. "Modular multivariable control." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12554.

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16

Balanos, George M. "The chemical control of the pulmonary circulation." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275649.

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17

Kapetanopoulos, Panagiotis. "Feedback and Control of Coupled Chemical Oscillators." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515350.

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18

Papazoglou, Michael. "Multivariate statistical process control of chemical processes." Thesis, University of Newcastle Upon Tyne, 1998. http://hdl.handle.net/10443/408.

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The thesis describes the application of Multivariate Statistical Process Control (MSPC) to chemical processes for the task of process performance monitoring and fault detection and diagnosis. The applications considered are based upon polymerisation systems. The first part of the work establishes the appropriateness of MSPC methodologies for application to modern industrial chemical processes. The statistical projection techniques of Principal Component Analysis and Projection to Latent Structures are considered to be suitable for analysing the multivariate data sets obtained from chemical processes and are coupled with methods and techniques for implementing MSPC. A comprehensive derivation of these techniques are presented. The second part introduces the procedures that require to be followed for the appropriate implementation of MSPC-based schemes for process monitoring, fault detection and diagnosis. Extensions of the available projection techniques that can handle specific types of chemical processes, such as those that exhibit non-linear characteristics or comprise many distinct units are also presented. Moreover, the novel technique of Inverse Projection to Latent Structures that extends the application of MSPC-based schemes to processes where minimal process data is available is introduced. Finally, the proposed techniques and methodologies are illustrated by applications to a batch and a continuous polymerisation process.
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19

Hong, Tao. "Non-linear predictive control of chemical processes." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245078.

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20

Willis, Mark J. "Control of a class of chemical reactors." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315920.

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21

Liu, Ru-Shi. "The chemical control of high temperature superconductivity." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240144.

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22

Paulson, Joel Anthony. "Modern control methods for chemical process systems." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109672.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 301-322).
Strong trends in chemical engineering have led to increased complexity in plant design and operation, which has driven the demand for improved control techniques and methodologies. Improved control directly leads to smaller usage of resources, increased productivity, improved safety, and reduced pollution. Model predictive control (MPC) is the most advanced control technology widely practiced in industry. This technology, initially developed in the chemical engineering field in the 1970s, was a major advance over earlier multivariable control methods due to its ability to seamlessly handle constraints. However, limitations in industrial MPC technology spurred significant research over the past two to three decades in the search of increased capability. For these advancements to be widely implemented in industry, they must adequately address all of the issues associated with control design while meeting all of the control system requirements including: -- The controller must be insensitive to uncertainties including disturbances and unknown parameter values. -- The controlled system must perform well under input, actuator, and state constraints. -- The controller should be able to handle a large number of interacting variables efficiently as well as nonlinear process dynamics. -- The controlled system must be safe, reliable, and easy to maintain in the presence of system failures/faults. This thesis presents a framework for addressing these problems in a unified manner. Uncertainties and constraints are handled by extending current state-of-the-art MPC methods to handle probabilistic uncertainty descriptions for the unknown parameters and disturbances. Sensor and actuator failures (at the regulatory layer) are handled using a specific internal model control structure that allows for the regulatory control layer to perform optimally whenever one or more controllers is taken offline due to failures. Non-obvious faults, that may lead to catastrophic system failure if not detected early, are handled using a model-based active fault diagnosis method, which is also able to cope with constraints and uncertainties. These approaches are demonstrated on industrially relevant examples including crystallization and bioreactor processes.
by Joel Anthony Paulson.
Ph. D.
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23

Potter, Earl Douglas Zewail Ahmed H. Zewail Ahmed H. "Ultrafast control and dynamics of chemical reactions /." Diss., Pasadena, Calif. : California Institute of Technology, 1993. http://resolver.caltech.edu/CaltechETD:etd-04042008-113817.

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24

Samardzjia, Nikola. "Nonlinear analysis and control of chemical reactors." Thesis, University of Leeds, 1997. http://etheses.whiterose.ac.uk/728/.

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This thesis carries out a detailed study of a nonlinear spectral theory that is useful for modeling and controlling chemical reactors. The motivation for this work originates from a few reports which have demonstrated in the past that the nonlinear spectral method offers a useful mathematical framework for classifying and quantifying nonlinear complexities of large degrees of freedom, as well as for qualifying a general nonlinear dynamic behavior. We present and discuss this new theory and show that it extends the familiar linear systems notion of characteristic modes (eigenmodes), as well as the notions of mathematical quantities known as the eigenvectors, and eigenvalues, into a multi-dimensional nonlinear domain, i. e., applies to model dimensions one, two, three and higher. This approach offers a new insight into nonlinear phenomena, and as such has a significant theoretical and practical value. In the theory of nonlinear systems the spectral framework provides some useful answers regarding the issues of multivariate process complexity, stability and control. Similarly, in applications it often leads to a simple relation between a desired process behavior and control parameters. We demonstrate this by showing how a process operating point, its behavior, and its domain of attraction are determined by nonlinear structures which characterize both a process and its control realization. In addition, we show that by a correctly modeling and regulating process nonlinearities one can obtain a nonlinear control solution that often outperforms the conventional first-order realizations. That is, there exist important nonlinear structural and dynamic process relations which determine a feasibility of a control realization. This is demonstrated by studying control behaviors of several highly exothermic continuously stirred tank reactor processes.
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25

Zenith, Federico. "Control of Fuel Cells." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1537.

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This thesis deals with control of fuel cells, focusing on high-temperature proton-exchange-membrane fuel cells.

Fuel cells are devices that convert the chemical energy of hydrogen, methanol or other chemical compounds directly into electricity, without combustion or thermal cycles. They are efficient, scalable and silent devices that can provide power to a wide variety of utilities, from portable electronics to vehicles, to nation-wide electric grids.

Whereas studies about the design of fuel cell systems and the electrochemical properties of their components abound in the open literature, there has been only a minor interest, albeit growing, in dynamics and control of fuel cells.

In the relatively small body of available literature, there are some apparently contradictory statements: sometimes the slow dynamics of fuel cells is claimed to present a control problem, whereas in other articles fuel cells are claimed to be easy to control and able to follow references that change very rapidly. These contradictions are mainly caused by differences in the sets of phenomena and dynamics that the authors decided to investigate, and also by how they formulated the control problem. For instance, there is little doubt that the temperature dynamics of a fuel cell can be slow, but users are not concerned with the cell’s temperature: power output is a much more important measure of performance.

Fuel cells are very multidisciplinary systems, where electrical engineering, electrochemistry, chemical engineering and materials science are all involved at various levels; it is therefore unsurprising that few researchers can master all of these branches, and that most of them will neglect or misinterpret phenomena they are unfamiliar with.

The ambition of this thesis is to consider the main phenomena influencing the dynamics of fuel cells, to properly define the control problem and suggest possible approaches and solutions to it.

This thesis will focus on a particular type of fuel cell, a variation of proton-exchange-membrane fuel cells with a membrane of polybenzimidazole instead of the usual, commercially available Nafion. The advantages of this particular type of fuel cells for control are particularly interesting, and stem from their operation at temperatures higher than those typical of Nafion-based cells: these new cells do not have any water-management issues, can remove more heat with their exhaust gases, and have better tolerance to poisons such as carbon monoxide.

The first part of this thesis will be concerned with defining and modelling the dynamic phenomena of interest. Indeed, a common mistake is to assume that fuel cells have a single dynamics: instead, many phenomena with radically different time scales concur to define a fuel-cell stack’s overall behaviour. The dynamics of interest are those of chemical engineering (heat and mass balances), of electrochemistry (diffusion in electrodes, electrochemical catalysis) and of electrical engineering (converters, inverters and electric motors). The first part of the thesis will first present some experimental results of importance for the electrochemical transient, and will then develop the equations required to model the four dynamic modes chosen to represent a fuel-cell system running on hydrogen and air at atmospheric pressure: cathodic overvoltage, hydrogen pressure in the anode, oxygen fraction in the cathode and stack temperature.

The second part will explore some of the possible approaches to control the power output from a fuel-cell stack. It has been attempted to produce a modularised set of controllers, one for each dynamics to control. It is a major point of the thesis, however, that the task of controlling a fuel cell is to be judged exclusively by its final result, that is power delivery: all other control loops, however independent, will have to be designed bearing that goal in mind.

The overvoltage, which corresponds nonlinearly to the rate of reaction, is controlled by operating a buck-boost DC/DC converter, which in turn is modelled and controlled with switching rules. Hydrogen pressure, being described by an unstable dynamic equation, requires feedback to be controlled. A controller with PI feedback and a feedforward part to improve performance is suggested. The oxygen fraction in the cathodic stream cannot be easily measured with a satisfactory bandwidth, but its dynamics is stable and disturbances can be measured quite precisely: it is therefore suggested to use a feedforward controller. Contrary to the most common approach for Nafion-based fuel cells, temperature is not controlled with a separate cooling loop: instead, the air flow is used to cool the fuel-cell stack. This significantly simplifies the stack design, operation and production cost. To control temperature, it is suggested to use a P controller, possibly with a feedforward component. Simulations show that this approach to stack cooling is feasible and poses no or few additional requirements on the air flow actuator that is necessary to control air composition in the cathode.

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26

Alici, Semra. "Dynamic data reconciliation using process simulation software and model identification tools." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025133.

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27

Wilkinson, Darryl. "High performance distillation control." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293203.

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28

Gormandy, Brent Anthony. "Fuzzy model predictive control." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248858.

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29

Zhu, Jianye. "Integrated process design and control of chemical processes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/NQ34864.pdf.

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30

Leach, Christopher. "Novel Internet based methods for chemical information control." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300623.

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31

Nazir, Karnachi Nayeem A. "Control of the chemical quality of industrial wastewater." Thesis, Leeds Beckett University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500766.

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Quality control of wastewater is an important treatment process more so now, tnan ever before. Due to an extremely unpredictable nature of the wastewater, which is a mixture of both inorganic and organic waste, it is very difficult to neutralise. Two approaches have been proposed in developing alternative control strategies as suggestions for the pH control of the wastewater in an industrial plant. The first is to develop a mathematical model of a continuously stirred tank reactor (CSTR) with a possible use of MATLAB®. Three different control methods (linear, nonlinear and adaptive) are subject to vigorous theoretical testing and are proposed as a possible solution. The second, a parallel approach, has been to build a laboratory scale experimental reactor using a seven litre continuously stirred tank with monitors for influent flow, influent pH and reactor tank pH. Results suggest that a more sophisticated controller than the simple PID control, currently in operation, could lend Itself to overcoming the problem of persistent large spikes in the pH of the influent. Further work would consider the implementation of these results to the actual industrial wastewater treatment plant.
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32

Campbell, James Robert. "Recognition mediated control and acceleration of chemical reactions." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364991.

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33

Kandiah, Sivasothy. "Fuzzy model based predictive control of chemical processes." Thesis, University of Sheffield, 1996. http://etheses.whiterose.ac.uk/3029/.

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The past few years have witnessed a rapid growth in the use of fuzzy logic controllers for the control of processes which are complex and ill-defined. These control systems, inspired by the approximate reasoning capabilities of humans under conditions of uncertainty and imprecision, consist of linguistic 'if-then' rules which depend on fuzzy set theory for representation and evaluation using computers. Even though the fuzzy rules can be built from purely heuristic knowledge such as a human operator's control strategy, a number of difficulties face the designer of such systems. For any reasonably complex chemical process, the number of rules required to ensure adequate control in all operating regions may be extremely large. Eliciting all of these rules and ensuring their consistency and completeness can be a daunting task. An alternative to modelling the operator's response is to model the process and then to incorporate the process model into some sort of model-based control scheme. The concept of Model Based Predictive Control (MB PC) has been heralded as one of the most significant control developments in recent years. It is now widely used in the chemical and petrochemical industry and it continues to attract a considerable amount of research. Its popularity can be attributed to its many remarkable features and its open methodology. The wide range of choice of model structures, prediction horizon and optimisation criteria allows the control designer to easily tailor MBPC to his application. Features sought from such controllers include better performance, ease of tuning, greater robustness, ability to handle process constraints, dead time compensation and the ability to control nonminimum phase and open loop unstable processes. The concept of MBPC is not restricted to single-input single-output (SISO) processes. Feedforward action can be introduced easily for compensation of measurable disturbances and the use of state-space model formulation allows the approach to be generalised easily to multi-input multi-output (MIMO) systems. Although many different MBPC schemes have emerged, linear process models derived from input-output data are often used either explicitly to predict future process behaviour and/or implicitly to calculate the control action even though many chemical processes exhibit nonlinear process behaviour. It is well-recognised that the inherent nonlinearity of many chemical processes presents a challenging control problem, especially where quality and/or economic performance are important demands. In this thesis, MBPC is incorporated into a nonlinear fuzzy modelling framework. Even though a control algorithm based on a 1-step ahead predictive control strategy has initially been examined, subsequent studies focus on determining the optimal controller output using a long-range predictive control strategy. The fuzzy modelling method proposed by Takagi and Sugeno has been used throughout the thesis. This modelling method uses fuzzy inference to combine the outputs of a number of auto-regressive linear sub-models to construct an overall nonlinear process model. The method provides a more compact model (hence requiring less computations) than fuzzy modelling methods using relational arrays. It also provides an improvement in modelling accuracy and effectively overcomes the problems arising from incomplete models that characterise relational fuzzy models. Difficulties in using traditional cost function and optimisation techniques with fuzzy models have led other researchers to use numerical search techniques for determining the controller output. The emphasis in this thesis has been on computationally efficient analytically derived control algorithms. The performance of the proposed control system is examined using simulations of the liquid level in a tank, a continuous stirred tank reactor (CSTR) system, a binary distillation column and a forced circulation evaporator system. The results demonstrate the ability of the proposed system to outperform more traditional control systems. The results also show that inspite of the greatly reduced computational requirement of our proposed controller, it is possible to equal or better the performance of some of the other fuzzy model based control systems that have been proposed in the literature. It is also shown in this thesis that the proposed control algorithm can be easily extended to address the requirements of time-varying processes and processes requiring compensation for disturbance inputs and dead times. The application of the control system to multivariable processes and the ability to incorporate explicit constraints in the optimisation process are also demonstrated.
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Kalamangalam, G. P. "Nonlinear oscillations and chaos in chemical cardiorespiratory control." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296830.

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We report progress made on an analytic investigation of low-frequency cardiorespiratory variability in humans. The work is based on an existing physiological model of chemically-mediated blood-gas control via the central and peripheral chemoreceptors, that of Grodins, Buell & Bart (1967). Scaling and simplification of the Grodins model yields a rich variety of dynamical subsets; the thesis focusses on the dynamics obtained under the normoxic assumption (i.e., when oxygen is decoupled from the system). In general, the method of asymptotic reduction yields submodels that validate or invalidate numerous (and more heuristic) extant efforts in the literature. Some of the physiologically-relevant behaviour obtained here has therefore been reported before, but a large number of features are reported for the first time. A particular novelty is the explicit demonstration of cardiorespiratory coupling via chemosensory control. The physiology and literature reviewed in Chapters 1 and 2 set the stage for the investigation. Chapter 3 scales and simplifies the Grodins model; Chapters 4, 5, 6 consider carbon dioxide dynamics at the central chemoreceptor. Chapter 7 begins analysis of the dynamics mediated by the peripheral receptor. Essentially all of the dynamical behaviour is due to the effect of time delays occurring within the conservation relations (which are ordinary differential equations). The pathophysiology highlighted by the analysis is considerable, and includes central nervous system disorders, heart failure, metabolic diseases, lung disorders, vascular pathologies, physiological changes during sleep, and ascent to high altitude. Chapter 8 concludes the thesis with a summary of achievements and directions for further work.
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35

Cheow, J. C. "Implementation of adaptive control strategies on chemical plants." Thesis, Teesside University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376544.

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36

Johnston, James E. "Synthesis of control structures for complete chemical plants." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/52937.

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37

Pace, Christopher John. "Towards the Chemical Control of Membrane Protein Function." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3039.

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Thesis advisor: Jianmin Gao
The oligomerization of membrane proteins has been shown to play a critical role in a myriad of cellular processes, some of which include signal propagation, cell-to-cell communication, and a cell's ability to interact with its surroundings. Diseases that are associated with disruption of protein-protein interactions in the membrane include cystic fibrosis, certain cancers, and bone growth disorders. Although significant progress has been made in our mechanistic understanding of protein-protein interactions in membranes, it remains difficult to predict the oligomerization state of transmembrane domains and explain the physiological consequences of a point mutation within a membrane embedded protein. The development of novel classes of chemical tools will allow us to better understand the energetics of transmembrane domain association at the molecular level. Herein, we demonstrate that fluorinated aromatic amino acids offer intriguing potential as chemical mediators of transmembrane protein association. We have systematically examined the effects of fluorination on the physical properties of aromatic systems in the context of a soluble protein model system. Our results illustrate the ability of fluorinated aromatic amino acids to simultaneously stabilize protein structure and facilitate highly specific protein self-assembly. An improved understanding of the fundamental energetics of aromatic interactions should allow for their more efficient incorporation into designed inhibitors of transmembrane protein association. In addition to chemical tools, the development of simple methods for directly monitoring transmembrane domain association in vitro and in vivo is necessary to advance our understanding of these interactions. Towards this goal, we have established FlAsH-tetracysteine display as an effective approach to quantifying the association propensities of transmembrane α-helices (TMHs) in vitro. Our assay is compatible with two of the most commonly utilized model membrane systems, detergent micelles and vesicles. The high spatial resolution of FlAsH binding (˂ 10 Å) allows for the differentiation of parallel and antiparallel oligomerization events. Importantly, preliminary studies suggest the assay's ability to detect inhibition from exogenous TMHs. Encouraged by our understanding of aromatic interactions and the success of our assay, we are beginning to incorporate fluorinated aromatics in the model TMHs and monitoring their ability to associate. The ultimate goal is to modulate the association of endogenous TMHs such as ErbB2. Research in this direction is ongoing
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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38

Fernandes, Winnie Cezario. "Thrips on roses: identification, monitoring and chemical control." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14048.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
The growth in the production of ornamental plants is increasingly significant in Brazil and in the Northeast region, but the occurrence of pests is shown as a limiting factor. To minimize losses, adequate control measures should be employed. Accordingly, the correct identification of pests, population monitoring and studies on managements should be performed. The objective of this study was to identify thrips species in rose, characterize and quantify the damage loss caused by arthropod pests in the production of roses in Serra da Ibiapaba; to assess the fluctuation of thrips species in ten cultivars of rose, at different stages of flower development and monitoring systems, and; evaluate the efficiency of pesticides on Frankliniella spp. The experiments were conducted at the Company âReijers ProduÃÃo de Rosasâ, SÃo Benedito, Cearà State, âLagoa Jussaraâ in planting roses in greenhouses. Three species of thrips have been identified: Frankliniella schultzei (Trybom, 1910), F. occidentalis (Pergande, 1895) and Caliothrips phaseoli (Pergande, 1825) (Thysanoptera: Thripidae) with the largest recorded infestations for F. occidentalis and F. schultzei in phenological phases of roses, especially in flowering. The injury caused by thrips in floral cut roses button affected the quality invalidating them for marketing. There was no difference between the sampling periods (morning and afternoon) and sampling (tray beat and direct view of the floral button) to the ten cultivars of roses, so the choice of the time and method must be reconciled with practicality and cost. The insecticides demonstrated ability to cause mortality of thrips in extreme conditions, within completely enclosed structures (flower buds).
O crescimento na produÃÃo de plantas ornamentais à cada vez mais significativo no Brasil e na regiÃo Nordeste do paÃs, porÃm a ocorrÃncia de pragas mostra-se como fator limitante. Para minimizar as perdas, medidas adequadas de controle devem ser empregadas. Nesse sentido, a identificaÃÃo correta das pragas, seu monitoramento populacional e estudos sobre manejos devem ser realizados. O objetivo deste estudo foi identificar espÃcies de tripes em roseira, caracterizar danos e quantificar as perdas ocasionadas pelo artrÃpode-praga na produÃÃo de rosas na Serra da Ibiapaba; avaliar a flutuaÃÃo populacional das espÃcies de tripes em dez cultivares de roseira, em diferentes fases do desenvolvimento floral e sistemas de monitoramento, e; avaliar a eficiÃncia de produtos fitossanitÃrios sobre Frankliniella spp. Os experimentos foram conduzidos na Empresa Reijers ProduÃÃo de Rosas, Unidade SÃo Benedito/CE, Fazenda Lagoa Jussara, em plantio de roseiras sob cultivo protegido. Foram identificadas trÃs espÃcies de tripes: Frankliniella schultzei (Trybom, 1910), F. occidentalis (Pergande, 1895) e Caliothrips phaseoli (Pergande, 1825) (Thysanoptera: Thripidae) sendo as maiores infestaÃÃes registradas para F. occidentalis e F. schultzei nas diferentes fases fenolÃgicas das roseiras, especialmente na floraÃÃo. As injÃrias causadas pelos tripes no botÃo floral de rosas de corte afetaram aqualidade inviabilizando-as para a comercializaÃÃo. NÃo houve diferenÃa estatÃstica entre os perÃodos de amostragem (manhà e tarde) e os mÃtodos de amostragem (batida de bandeja e visualizaÃÃo direta do botÃo floral) para as dez cultivares de roseiras, assim a escolha do horÃrio e do mÃtodo devem ser conciliadascom praticidade e custo.Os inseticidas demonstraram capacidade de causar mortalidade de tripes em condiÃÃes extremas, ou seja, dentro de estruturas completamente fechadas (botÃes florais).
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39

Rawlings, Blake. "Discrete Dynamics in Chemical Process Control and Automation." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/862.

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Formal verification has previously been applied to chemical plant control and automation systems to ensure that they operate as intended. This dissertation examines the related objective of proving that a particular control system does not operate as intended. To this end, we present a set of specifications that address certain aspects of the correct operation of a general control system. Some of those specifications, which relate to invariance and reachability of states that satisfy given logical constraints, do not fall within the classes of specifications that have been addressed in previous work related to the falsification of hybrid systems. For a specification from this class, a sound falsification algorithm is presented which can guarantee that a hybrid system does not meet the specification. The algorithm involves abstraction, as a finite-state discrete system, of the infinite-state hybrid dynamical system that arises when discrete control is applied to a continuous process. The falsification result relies on new results that we present which concern the supervisory control of discrete event systems subject to specifications that involve multiple reachability requirements. The methods we present are applied to two industrial case studies, which were provided by The Dow Chemical Company. We also present two software tools which apply the methods that we have developed. The first tool, SynthSMV, is an extension of the model checking solver NuSMV that can solve some supervisory control problems. NuSMV was chosen as the basis for our work in falsification because previous work has shown that its symbolic model checking algorithms can handle models of industrial-scale control systems in the context of verification. The second tool, st2smv, translates industrial control code to a formal model that can be solved using SynthSMV. The approach is similar to what has been done in previous work that focused on model checking and verification, with some extensions to enable the application of our work concerning supervisory control and falsification.
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40

Watson, Theo F. "Chemical Control of the Sweetpotato Whitefly in Cotton." College of Agriculture, University of Arizona (Tucson, AZ), 1993. http://hdl.handle.net/10150/209566.

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Both registered and experimental insecticides were evaluated for effectiveness against the sweetpotato whitefly in several field experiments at Yuma, Arizona. Best results were obtained with combinations of two insecticides, particularly a pyrethriod and an organophosphate, rather than with individual materials. Results of these experiments indicate that unusually heavy infestations can be currently controlled even though sustained use of these insecticides would probably lead quickly to the development of resistance.
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41

Watson, T. F., A. Telles, and M. Peña. "Chemical Control of the Sweetpotato Whitefly in Cotton." College of Agriculture, University of Arizona (Tucson, AZ), 1994. http://hdl.handle.net/10150/209618.

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Various registered and experimental insecticides were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control in several field experiments at Yuma, Arizona in 1993. Best controls were obtained with insecticide mixtures, particularly a pyrethroid and an organophosphate, rather than with individual materials. Results of these experiments indicate that severe population densities can be controlled using insecticide combinations, even though sustained use of these insecticides would probably lead quickly to the development of resistance.
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42

Watson, T. F., M. A. Tellez, and M. Peña. "Chemical Control of the Sweetpotato Whitefly in Cotton." College of Agriculture, University of Arizona (Tucson, AZ), 1995. http://hdl.handle.net/10150/210295.

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Various registered and experimental insecticides were evaluated for sweetpotato whitefly (Bemisia tabaci Gennadius) control in several field experiments at Yuma, Arizona in 1994. Best controls were obtained with insecticide mixtures, particularly a pyrethroid and an organophosphate, rather than with individual materials. Results of these experiments indicate that severe population densities can be controlled using insecticide combinations, even though sustained use of these insecticides would probably lead quickly to the development of resistance.
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43

Ellsworth, Peter C., R. Gibson, D. Howell, S. Husman, S. Stedman, and B. Tickes. "Lygus Chemical Control: Are Combinations Sprays Worth It?" College of Agriculture, University of Arizona (Tucson, AZ), 1998. http://hdl.handle.net/10150/210368.

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We need efficient sampling methods, appropriate thresholds based on a well -defined Lygus density yield relationship, and knowledge of the most effective chemical controls available. Insecticides were evaluated for control of Lygus at 5 'at risk' grower locations, as well as at 4 other experimental sites. Application methods were different at each site according to grower practice or experimental protocol (5-20 GPA; by ground, air, or electrostatically-assisted ground sprayers). Evaluations were made based on the number of Lygus per 100 sweeps. Orthene®, Vydate® or to a lesser degree, Monitor® used alone and at high rates appeared to perform adequately at all sites. Both rates of Regent™, a new chemistry under development by Rhône- Poulenc, provided excellent levels of control comparable to Orthene in a high density test. In this same test, none of the experimental and registered pyrethmids provided adequate control when used alone. Thiodan®, when mixed with Mustang®, provided some level of control. Over all tests measured for yield, a positive net return was possible with no more than 2 sprays of solo materials which yielded between 0.3 and 0.5 bales/A more than untreated comparisons or between $51-130/A net return. Also, at one site where yields were in excess of 4.2 bales/A, optimum planting and fruit-set prior to heavy Lygus pressures and monsoon-associated heat stress was an important cultural tactic for avoiding losses to Lygus - the check yielded over 3.7 bales /A! As seen at grower sites and confirmed in experimental studies, solo compounds, at appropriate rates, performed as well or better than any combination tested. And, mixtures at this time do not appear to provide any additive, synergistic or economic benefits in the control of Lygus. Combinations, unless indicated by another pest problem (e.g., whiteflies), are not "worth it," and needlessly expose the grower to larger input costs, "empty" applications, and higher risks of resistance, pest resurgence, secondary pest outbreaks, and phytotoxic effects by insecticides.
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44

Lai, Tsai-Ta Christopher. "Control of polymorphism in continuous crystallization." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104203.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Continuous manufacturing has gained significant interest in recent years as the ultra-lean mode of pharmaceutical production. Albeit the increasing number of studies on the process dynamics in continuous crystallization, in particular in yield improvement and impurity separation, the research community lacks the systematic understanding of the control of polymorphism in continuous crystallization. Variations in the polymorphism of the active pharmaceutical ingredient can undermine the bioavailability and the downstream processability of the drug substance. Thus, precise control of the drug polymorphism is pivotal for delivering quality drug products to the patients. In this thesis work, we aimed to develop a series of steps forward in understanding the polymorph dynamics in continuous crystallization, notably in mixed-suspension, mixed-product removal (MSMPR) crystallization. We first elucidated the major intrinsic and extrinsic factors which govern the process polymorphism in both monotropic and enantiotropic polymorphic compounds. Using the monotropic L-glutamic acid as the model compound, two temperature regimes each with distinctive kinetic and thermodynamic characteristics were identified. It is found that at high temperatures, the polymorph dynamics is mediated by the relative thermodynamics of the polymorphs. The most stable form is likely to be the dominant form at steady state. On the other hand, at low temperatures, the interplay of the crystal growth and nucleation kinetics is found to play an important role in determining the final polymorphism. Similar results were identified in the enantiotropic p-aminobenzoic acid system where three temperature regimes were identified. The additional regime is located near to the transition temperature where the chemical potential of the two polymorphs are identical. The steady state polymorphism is thereby determined by the kinetic energy barriers for the crystallization of the polymorphs. The study of polymorphism was also conducted in cooling-antisolvent crystallization and the effect of solvent composition on the polymorph dynamics was studied. In addition, the dynamic pathways connecting the startup states to the metastable steady states and the stable steady states were determined. The polymorphic transition between these steady states was observed and analyzed. The fundamental understanding of the kinetic competition and the governing dynamics in polymorphic crystallization forms the backbone for developing the polymorph control strategies in this thesis. Based on the polymorph dynamic studies, we designed MSMPR cascade systems to control the process polymorphism. In addition, systematic procedures are established to facilitate the design and optimization of continuous crystallization with the objectives to control polymorphism, optimize process yield and achieve the target crystal size distribution. The operational window is determined within which these control objectives are achieved. As there are increasing interests in transitioning pharmaceutical manufacturing from batch to continuous processing, the results in this thesis should develop a substantial position in the body of scientific literature.
by Tsai-Ta Christopher Lai.
Ph. D.
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45

Powers, Mark J. (Mark James). "Substratum control of hepatocyte aggregate morphology." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/43328.

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46

Mkhize, Sikhumbuzo Cazwell. "Dynamic matrix control of milling circuits." Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/22050.

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Bibliography: pages 82-87.
The main aim of the study was to investigate the suitability of DMC for milling circuit control. This was conducted through simulation studies using models of two different milling circuits. A generalised software package was developed for the application and analysis of DMC. DMC was developed in the United States of America by Shell Oil Company (Cutler and Ramaker, 1979; Prett and Gillete, 1979). It falls under the class of controllers which is termed Model Predictive Control (MPC). The control algorithms falling into this category are multivariable and model-based, and as such are expected to improve control of processes which exhibit strong interactions, non-minimum phase behavior, and operate at constraints. Other control schemes falling into this category are Model Algorithmic Control (MAC) and Internal Model Control (IMC). Details of MAC are largely proprietary, while the frequency-based IMC method does not permit direct handling of constraints. Thus the focus of this project was on the DMC algorithm and its variants; Linear Dynamic Matrix Control (LDMC) and Quadratic Dynamic Matrix Control (QDMC).
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47

Rahman, Alireza. "Control release from biopolymers." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6074/.

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Control release from biopolymer is an important issue for flavour perception following to reduce flavour content such as salt in food formulation without any tangible change in taste. The experiments presented release behaviour from low acyl gellan gum gel. Attempts were focused to find a link between mechanical properties and microstructure of the gel. After conducting the compression tests, a number of parameters were investigated and the consist of the effect of the gellan concentration, salt concentration and cyclic compression on the mechanical properties of the gel. According to the results, mechanical properties of the gellan gels were remarkably affected by the gellan concentration, salt concentration and cyclic compression. It was shown that the gellan concentration, salt concentration and cyclic compression play a main role on the microstructure of the gel. The release experiments were carried out using uniaxial and cyclic compression to investigate the salt and riboflavin release from the gellan gel to identify the parameters which play a role on release from the gellan gel. Release experiments have shown that release profile is affected by the gellan concentration, salt concentration and number of cyclic compression. Results demonstrated that release profile can be affected by molecular weight of the releasable material.
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48

Yan, Ming. "Multi-objective, plant-wide control and optimization of chemical processes /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9918.

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49

Kawka, Dariusz Wlodzimierz. "A calendering model for cross-direction control." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ44473.pdf.

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50

Van, Schalkwyk Theo. "Multivariable control of a rougher flotation cell." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/11550.

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This project focussed on the investigation, development and evaluation of a closed loop control system on a rougher flotation cell that could improve PGM flotation performance. A PGM rougher flotation cell equipped with Online Stream Analysis (OSA) and machine vision system (SmartFroth) was used during the investigation. Online measurements included bubble velocity, average bubble area, bubble colour; Pt, Ni and Cu concentrate grade and concentrate flow rate and density. Air addition and pulp level was used as the manipulated variables.
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