Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 212-224). Also available in electronic version. Access restricted to campus users.

To mitigate high voltages in transmission systems with low demands, traditional solutions often consider the installation of reactive power compensators. The deployment and tuning of numbers of VAr compensators at various locations may not be cost-effective. This thesis presents an alternative method that utilises existing parallel transformers in distribution networks to provide reactive power supports for transmission systems under low demands. The operation of parallel transformers in small different tap positions, i.e. with staggered taps, can provide a means of absorbing reactive power. The aggregated reactive power absorption from many pairs of parallel transformers could be sufficient to provide voltage support to the upstream transmission network. Network capability studies have been carried out to investigate the reactive power absorption capability through the use of tap stagger. The studies are based on a real UK High Voltage distribution network, and the tap staggering technique has been applied to primary substation transformers. The results confirm that the tap staggering method has the potential to increase the reactive power demand drawn from the transmission grid. This thesis also presents an optimal control method for tap stagger to minimise the introduced network loss as well as the number of tap switching operations involved. A genetic algorithm (GA) based procedure has been developed to solve the optimisation problem. The GA method has been compared with two alternative solution approaches, i.e. the rule-based control scheme and the branch-and-bound algorithm. The results indicate that the GA method is superior to the other two approaches. The economic and technical impacts of the tap staggering technique on the transmission system has been studied. In the economic analysis, the associated costs of applying the tap staggering method have been investigated from the perspective of transmission system operator. The IEEE Reliability Test System has been used to carry out the studies, and the results have been compared with the installation of shunt reactors. In the technical studies, the dynamic impacts of tap staggering or reactor switching on transmission system voltages have been analysed. From the results, the tap staggering technique has more economic advantages than reactors and can reduce voltage damping as well as overshoots during the transient states.

The aim of this diploma thesis was to find out the change of the hue lightness saturation after the change of composition of dyeing liquor. The reactive dye Bezaktiv rot S-B was used for dyeing cotton. Dyeing was performed in the laboratory by exhaustion method with two concentrations of dye 0,5 and 2 %. The influence of the change of alkali and electrolyte concentration additions to dyeing bath liquor at different liquors dye ratio was studied. Sodium chloride and Glauber's salt as elektrolyte were used. The dyed samples were washed and then fixed by two types of fixative agents REWIN ACP and REWIN EL. After that the measurement of hue control and the evaluation of fastness to water and rubbing fastness were done. The results were displayed in L*a*b* space and CIE differences between chosen standards and samples were performed by Datacolor International DC 3890.

One of the challenges in understanding polymer flammability is the lack of information about microscopic events that lead to macroscopically observed species, and Reactive Molecular Dynamics is a promising approach to obtain this crucially needed information. The development of a predictive method for condensed-phase reaction kinetics can provide significant insight into polymer ammability, thus helping guide future synthesis of fire-resistant polymers. Through this dissertation, a new reactive forcefield, RMDff, and Reactive Molecular Dynamics program, RxnMD, have been developed and used to simulate such material chemistry. It is necessary to have accurate description of chemical kinetics to describe quantitative chemical kinetics. Typical equilibrium forcefields are inadequate for describing chemical reactions due to the inability to represent bonding transformations. This issue was resolved by developing a new method, RMDff, that allows standard equilibrium forcfields to describe reactive transitions. The chemical reactions are described by employing switching functions that permit smooth transitions between the reactant and product descriptions available from traditional forcefields. Because all of the chemical motions are described, a complete potential energy surface is obtained for the course of the reaction. Descriptions of scission, addition/beta-scission, and abstraction reactions were developed for hydrocarbon species. Reactive potentials were developed using a representative reaction involving small molecules. It is shown that the overall geometric and energetic changes are transferable to larger and substituted molecules. The main source of error found in RMDff resulted from errors within the equilibrium forcefield descriptions. In order to simulate the chemical kinetics, it was necessary to create a molecular dynamics program that could implement the reactions from RMDff. RxnMD was developed as a new C++-based Reactive Molecular Dynamics code to simulate the dynamics using RMDff. Polymer kinetics were predicted for high-density polyethylene and used to test the method and code. Conformational changes and polymer length in the initial polyethylene molecules did not significantly alter the backbone decomposition kinetics. The results also revealed that the backbone carbon-carbon bonds could break with an activation energy approximately 100 kJ/mol below the carbon-carbon bond dissociation energy. This decrease was believed to occur from intramolecular polymer stress, which is relieved via backbone scission. Such stress was also observed to increase the beta-scission reaction rate at high temperatures, apparently because the scission reaction alone is not always sufficient to remove the energy associated with the polymer stress concentrated near the scission location. Finally, the RMD method was also shown to be transferable and applicable in describing the decomposition of novel fire-resistant polymers.

Yes / Batch reactive distillation is well known for improved conversion and separation of desired reaction products. However, for a number of reactions, the distillation can separate the reactants depending on their boiling points of them and thus not only reduces the benefit of the reactive distillation but also offers operational challenges for keeping the reactants together. Methyl lactate (ML) synthesis via the esterification of lactic acid (LA) with methanol in a reactive distillation falls into this category and perhaps that is why this process has not been explored in the past. The boiling points of the reactants (LA, methanol) are about 490 K and 337 K while those of the products (ML, water) are 417 K and 373 K respectively. Clearly in a conventional reactive distillation (batch or continuous) methanol will be separated from the LA and will reduce the conversion of LA to ML significantly. Here, first the limitations of the use of conventional batch distillation column (CBD) for the synthesis of ML is investigated in detail and a semi-batch reactive distillation (SBD) configuration is studied in detail where LA is the limiting reactant and methanol is continuously fed in excess in the reboiler allowing the reactants to be together for a longer period. However, this poses an operational challenge that the column has to be carefully controlled to avoid overflow of the reboiler at any time of the operation. In this work, the performance of SBD for the synthesis of ML is evaluated using model based optimization in which operational constraints are embedded. The results clearly demonstrate the viability of the system for the synthesis of ML.

Organic esters are an important class of industrial and commercial chemicals that can be found in solvents, plasticizer, food flavours, detergents, agrochemicals, and pharmaceuticals. The most common way to synthesis organic esters is with esterification or transesterification. Where esterification was the chosen method in this thesis.  This thesis provides a techno-economic assessment on the production of propyl acetate and glycerol trivalerate through different continuous routes that is than compared with batch production under the same conditions. Simulations was done on trivalerate due to limited literature and data on pentaerythritol tetravalerate. Different continuous technologies that have been assessed in this thesis was plug flow reactor (PFR), Reactive Distillation (RD), and Reactive – Extractive Distillation (RED). The production of mono- and polyol esters with different unit operators was simulated in Aspen Plus V.14. Techno-Economic analysis was conducted with APEA (Aspen Process Economic Analyzer), where cost of raw materials, products, and utilities was inserted to evaluate annual operating cost and product sale. Reaction kinetic for esterification of trivalerate was estimated by obtained values from simulations of a Gibbs reactor in Aspen Plus at four different temperatures. Kinetics was estimated by applying the relation between the chemical equilibrium constant and the Arrhenius equation. Where rate constant and activation energy for forward and revers reaction was obtained by varying min and max values for lsqcurvefit in MATLAB and then validate results with published kinetics.  Results from production of propyl acetate with batch, PFR and RED provides an annual profit of approximately 1 M$ at a capacity of 41.65 kton/year. The three different process provides also approximately an equal capital cost, operating cost, equipment cost, and installed cost according to APEA. RED provided the lowest propyl acetate yield at 93%, batch and PFR provided a propyl acetate yield of 94%.  Results from production of trivalerate with batch, PFR, and RD provides an annual profit of 5.4, 5.78, and 9.2 M$ at a capacity of approximately 5 kton/year. Where RD process provides the lowest capital cost, operating cost, equipment cost, and installed cost compared to batch and PFR processes according to APEA. Obtained results from production of trivalerate can be used to evaluate the economic and technical feasibility of a continuous production plant for pentaerythritol tetravalerate (PETV). Where initial simulations show a good economic and technical viability of a continuous ester production plant.

Thins films play a critical role in many technical fields today, such as optics, semiconductor, and tool manufacturing. A widely used method for thin film deposition is magnetron sputtering, with Direct-Current Magnetron Sputtering (DCMS) being the most conventional approach. DCMS is very capable at depositing pure metallic (e.g. Al, Ti) or non-metallic (e.g. C, B) films, but encounters problems when depositing compound films, such as oxides or nitrides, in a process known as reactive DCMS (R-DCMS). The process tends to drift into either metallic mode, characterized by high deposition rate but lacking compound formation, or poisoned mode, where compound forms, but with significantly lower deposition rate. Ideally, the process should be maintained in the transition region in-between the two, but this mode is very unstable and further complicated by a hysteresis effect when switching between metallic and poisoned modes. An alternative approach is High-Power Impulse Magnetron Sputtering (HiPIMS) which has been shown to mitigate or remove the instability and hysteresis seen in R-DCMS, as well as improving film density, adhesion and film uniformity on complex geometries. In many cases however, feedback control is needed to stabilize the transition region in reactive HiPIMS (R-HiPIMS). This thesis presents a novel, non-invasive control method for R-HiPIMS using Plasma Emission Monitoring (PEM) to automatically adjust the HiPIMS pulse repetition rate to maintain the delicate transition region. The method was tested on growth of titanium oxide (TiOx) using an industrially relevant deposition system. It was bench-marked against deposition in poisoned mode, and against a control method based on peak discharge current. Results are promising, with higher deposition rate than poisoned mode deposition, and better process stability than peak current control. Challenges remain in making the controller more robust to changes in plasma characteristics due to moving parts, in this case a moving substrate carrier.

Gameplay programming is vital for video game development and benefits from good tools and techniques. However, techniques are still used in the industry that involves describing how the computer operates. Reactive programming is a way to describe eventful and stateful computer programs declaratively, focusing on what the program should accomplish. This thesis uses the reactive library UniRx with the game engine Unity 5 to create an FPS with reactive techniques, and discusses the advantages and disadvantages of these. Object-oriented reactive programming is used to combine reactive objects with Unity’s component-based framework without using wrappers for non-reactive objects. The results include static methods for observable user input, patterns when defining game components with reactive content, and communication between game objects through interface components. It can be concluded that reactive programming for game programming enables the programmer to describe and understand game logic in a declarative manner. However, combining UniRx and Unity 5 led to complex patterns. Suggestion for future work is using reactive programming with game engines that allows to design game objects that are fully reactive. / Gameplay-programmering är avgörande för utveckling av videospel och har nytta av bra verktyg och tekniker. Dock används tekniker i spelbranschen som kräver att programmeraren beskriver hur datorn utför uppgifter. Reaktiv programmering är ett sätt att beskriva händelserika och föränderliga datorprogram med fokus på vad programmet ska utföra. Denna avhandling använder det reaktiva biblioteket UniRx med spelmotorn Unity 5 för att skapa en FPS med reaktiva tekniker, samt diskuterar fördelarna och nackdelarna med dessa. Objektorienterad reaktiv programmering används för att kombinera reaktiva objekt med Unity’s komponentbaserade ramverk utan att använda wrappers för icke-reaktiva objekt. Resultaten inkluderar statiska metoder för observerbar användarinput, programmeringsmönster för definition av spelkomponenter med reaktivt innehåll och kommunikation mellan spelobjekt via gränssnittskomponenter. Man kan dra slutsatsen att reaktiv programmering för spelprogrammering gör det möjligt för programmeraren att beskriva och förstå spellogik på ett deklarativt sätt. Kombinationen av UniRx och Unity 5 ledde emellertid till komplexa mönster. Förslag till framtida arbete är att använda reaktiv programmering med spelmotorer som gör det möjligt att designa spelobjekt som är helt reaktiva.

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