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The uptime of machinery in continuous flow process industries such as steel manufacturing plants puts pressure on the maintenance function. This in turn contributes to sustaining reliable physical assets. As absence of reliable physical assets highly affects the competitive advantage. Turnaround maintenance is a common practice in such production setups and requires top-of-the-line managerial attention to be planned,executed and assessed in an efficient manner. By applying an abductive approach and combining the qualitative and quantitative research approaches, this thesis aims to explore the managerial issue of coordinating turnaround maintenance within a continuous flow process industry. The research questions that guide this thesis consist of describing how turnaround maintenance can be coordinated and its associated challenges. By comparing publicly available literature and empirical evidence provided by performing a case study, it is confirmed that the main challenges for conducting efficient turnaround maintenance comes down to the management in all stages associated with the turnaround. To coordinate turnaround maintenance activities in the most efficient manner, several challenges must be overcome. Aligning organisational goals and generating management commitment is the first prerequisite before any improvements can be done. It is necessary to define a common scope that strives for creating reliable physical assets to enhance the competitive advantage. The defined challenges in coordination are related to before, during and after the turnaround execution. These relate to creating a cyclical process for the turnaround where previously acquired knowledge is used for improving future turnarounds. While detailed planning is necessary for each turnaround, a high level of contingency is also necessary. To achieve this and succeed, it is argued that a high level of visibility during the turnarounds and the use of standardised methods is required. / Drifttiden för maskiner i industrier med kontinuerligt flöde, såsom ståltillverkningsanläggningar, sätter press på underhållsverksamenheten. Detta för att i sin tur bidra till att upprätthålla tillförlitliga fysiska tillgångar. Eftersom avsaknad av tillförlitliga fysiska tillgångar påverkar konkurrensfördelen i hög grad. Storaunderhållstopp där den kontinuerliga produktionslinan stoppas, är en vanligt förekommande praxis i sådana produktionsanläggningar vilket kräver ledningens uppmärksamhet för att planera och utvärdera på ett effektivt sätt. Genom att tillämpa ett abduktivt tillvägagångssätt och kombinera kvalitativ och kvantitativ forskningsmetodik, syftar detta examensarbete till att utforska den ledarskapsrelaterade frågan om att koordinera underhållsaktiviteter för stora underhållstopp inom processindustrier med kontinuerligt flöde. Forskningsfrågorna som vägleder detta examensarbete består av att beskriva hur större underhållstopp kan koordineras och dess associerade utmaningar. Genom att jämföra offentligt tillgänglig litteratur och empiriska bevis från en fallstudie, bekräftas att de största utmaningarna för att genomföra ett effektivt underhållstopp beror på ledningen i alla steg som är förknippade med underhållstoppet. För att samordna underhållsaktiviteterna på ett så effektivt sätt som möjligt måste flera utmaningar övervinnas. Att anpassa organisationens mål och skapa engagemang hos ledningen är den första förutsättningen innan fler förbättringar kan utföras. Det är nödvändigt att definiera gemensamma mål som strävar efter att skapa tillförlitliga fysiska tillgångar för att i sin tur öka konkurrensfördelen. De definierademanagementutmaningarna sammankopplas till före, under och efter underhållsstoppet. Utmaningarnahandlar om att skapa en cyklisk process för underhållsstoppen där tidigare förvärvad kunskap nyttjas för att förbättra framtida stopp. Även om detaljerad planering är nödvändig för varje underhållstopp, är en hög nivå av beredskap också nödvändig. För att uppnå och lyckas med detta krävs en hög grad av visibilitet under underhållsstoppen och användning av standardiserade metoder.

In order to satisfy the global requirement for transport fuel sustainably, renewable liquid biofuels must be developed. Currently, two biofuels dominate the market; bioethanol for spark ignition and biodiesel for compression ignition engines. However, both fuels exhibit technical issues such as low energy density, poor low temperature performance and poor stability. In addition, bioethanol and biodiesel sourced from first generation feedstocks use arable land in competition with food production, and can only meet a fraction of the current demand. To address these issues it is vital that biofuels be developed from truly sustainable sources, such as lignocellulosic waste resources, and possess improved physical properties. To improve and control the physical properties of a fuel for specific application, one must be able to tailor the products formed in its production process. All studies within this thesis, therefore, have the aim of assessing the fuels produced for their variability in physical property, or the aim of directing the process considered to specific fuel molecules. In Chapter 2, spent coffee grounds from a range of geographical locations, bean types and brewing processes were assessed as a potential feedstock for biodiesel production. While the lipid yield was comparable to that of conventional biodiesel sources, the fatty acid profile remained constant irrespective of the coffee source. Despite this lack of variation, the fuel properties varied widely, presumably due to a range of alternative biomolecules present in the lipid. Though coffee biodiesel was produced from a waste product, the fuel properties were found to be akin to palm oil biodiesel, with a high viscosity and pour point. The blend level would therefore be restricted. In Chapter 3 the coffee lipid, as well as a range of microbial oils potentially derived from renewable sources were transformed into a novel aviation and road transport fuel through cross-metathesis with ethene. Hoveyda-Grubbs 2nd generation catalyst was found to be the most suitable, achieving 41% terminal bond selectivity under optimum conditions. Metathesis yielded three fractions: an alkene hydrocarbon fraction suitable for aviation, a shorter chain triglyceride fraction that upon transesterification produced a short chain biodiesel fuel, and a multifunctional volatile alkene fraction that could potentially have application in the polymer industry. Though there was variation for the road transport fuel fraction due to the presence of long chain saturates, the compounds fell within the US standard for biodiesel. The aviation fraction lowered the viscosity, increased the energy density, and remained soluble with Jet A-1 down to the required freezing point. Oleaginous organisms generally only produce a maximum of 40% lipid, leaving a large portion of fermentable biomass. In Chapter 4, a variety of ethyl and butyl esters of organic acids – potentially obtainable from fermentation – were assessed for their suitability as fuels in comparison to bioethanol. One product, butyl butyrate, was deemed suitable as a Jet A-1 replacement while four products, diethyl succinate, dibutyl succinate, dibutyl fumarate and dibutyl malonate, were considered as potential blending agents for diesel. Diethyl succinate, being the most economically viable of the four, was chosen for an on-engine test using a 20 vol% blend of DES (DES 20) on a chassis dynamometer under pseudo-steady state conditions. DES20 was found to cause an increase in fuel demand and NOx emissions, and a decrease in exhaust temperature, wheel force, and CO emissions. While fermentation is generally directed to one product, producing unimolecular fuels, they do not convert the entirety of the biomass available. An alternative chemical transformation is pyrolysis. In Chapter 5, zeolite-catalysed fast pyrolysis of a model compound representative of the ketonic portion of biomass pyrolysis vapour – mesityl oxide – was carried out. The aim of this study was to understand the mechanistic changes that occur, which could lead to improved bio-oil yields and more directed fuel properties of the pyrolysis oil. While HZSM-5 and Cu ZSM-5 showed no activity for hydrogenation and little activity for oligomerisation, Pd ZSM-5 led to near-complete selective hydrogenation of mesityl oxide to methyl isobutyl ketone, though this reduced at higher temperatures. At lower temperature (150-250 °C), a small amount of useful oligomerisation was observed, which could potentially lead to a selective pyrolysis oligomerisation reaction pathway.

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Orientador: Pilar Rodriguez de Massaguer / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-12T12:11:20Z (GMT). No. of bitstreams: 1 RodriguesJunior_Salatir_D.pdf: 5567332 bytes, checksum: 70d0366fec71ac0d7df65013c7939248 (MD5) Previous issue date: 2008 / Resumo: O presente trabalho teve por objetivo verificar o efeito da tensão de cisalhamento sobre os parâmetros cinéticos de inativação térmica (valores D e z) de Bacillus atrophaeus (antigo B. subtilis ATCC 9372), em suspensão aquosa pH 6,87. A fim de atingir esse objetivo, foi construído um reator de cisalhamento, capaz de aplicar tensões de cisalhamento de até 9,82Pa em temperaturas de pasteurização (90,5 a 96,2ºC ± 0,5ºC). Foi aplicado um Delineamento Composto Central Rotacional, com duas variáveis independentes ¿ Tensão de cisalhamento e Temperatura ¿ e valor D como variável resposta. Foram executados 12 experimentos, e o modelo obtido foi ¿Log (D) = 11,30 ¿ 1,104x10-1 T(ºC) ¿ 1,153x10-2 s(Pa)¿, com R² = 0,97, sendo os termos lineares das variáveis significativos a p < 0,1. Também foram determinados os valores D e z de B. atrophaeus na faixa de temperatura de pasteurização (92~97ºC), pelo método tradicional em tubos TDT (batelada), e usando dados cinéticos adquiridos de uma planta piloto HTST Microthermics (contínuo), em condições de tensão de cisalhamento similares àquelas aplicadas no reator. A fim de avaliar o processamento térmico contínuo aplicado na unidade HTST, foi usada a metodologia de determinação de processo equivalente conhecida como Paired Equivalent Isothermal Exposures ¿ PEIE (Welt et al., 1997). Os valores de z obtidos foram: 11,8ºC ± 1,56ºC pelo método TDT e 6,35ºC ± 0,35ºC no reator de cisalhamento e na primeira seção de retenção da unidade piloto HTST. Diversos autores reportaram mudanças nos parâmetros cinéticos de microrganismos, ao realizar a sua determinação por métodos em batelada (tubos TDT, ou capilar) e em processos contínuos. À semelhança desses autores, foi verificado que os valores D de B. subtilis foram significativamente (p<0.05) inferiores em todos os processos em que foi aplicado cisalhamento. A razão entre os valores D experimentais obtidos no reator de cisalhamento e os valores obtidos pelo modelo estimado pelo método TDT foi calculada, e variou entre 57% e 75%, indicando redução significativa na resistência térmica do microrganismo. Existe, portanto, potencial de aplicação industrial imediata deste tipo de sistema, a fim de causar a redução da resistência de esporos suspensos em líquidos sob processamento térmico, e levando a processos térmicos mais brandos / Abstract: This research aimed to determine the effect of temperature, and shear stress, on Bacillus atrophaeus (former B. subtilis ATCC 9372) spores suspended in sterile distilled water, pH 6.9. To achieve such objective, a Shear Reactor was developed to be capable of applying 9.82Pa shear stress, under pasteurization conditions (90,5 a 96,2ºC ± 0,5ºC). A Central Composite Design of experiments was used and it was composed by two independent variables ¿ Shear stress and Temperature ¿ and one response ¿ the D-value. Twelve experiments were performed, and the model obtained was ¿Log (D) = 11,30 ¿ 1,104x10-1 T(ºC) ¿ 1,153x10-2 s(Pa)¿, with R² = 0,97, and the linear terms statistically significant (p < 0,1). The D and z-values of B. atrophaeus were determined in the pasteurization range of temperature (92~97ºC), using the classical TDT tube method (batch method), and using kinetic data acquired in a Microthermics HTST pilot plant (continuous method), under shear stress conditions similar to shear reactor. The continuous thermal process was evaluated through the Paired Equivalent Isothermal Exposures ¿ PEIE ¿ method (Welt et al., 1997). The z-values obtained were: 11,8 ± 1,56ºC (TDT-method), and 6,35 ± 0,35ºC (Shear reactor and first retention section of the HTST pilot plant). Several authors reported changes in the kinetic parameters of microorganisms, when determining it through batch or continuous methods. Just like them, in this research it was verified that the D-values under shear stress process were statistically lower (p<0.05) than those in batch method (no shear). The ratio between experimental D values obtained in the shear reactor and those obtained from the TDT model was calculated and ranged between 57% and 75%, indicating a significant reduction of the microorganism¿s thermal resistance. Hence there is an immediate potential for industrial application of this kind of process since it causes the reduction of the resistance of spores in fluids under thermal process allowing for less aggressive thermal process / Doutorado / Doutor em Ciência de Alimentos

[pt] Além de uma crescente importância econômica da produço de petróleo contendo parafina dos recursos águas ultra-profundas, as preocupações coma deposição e gelificação de parafina desempenha uma funcão significativa nesta questão. óleos parafínicos gelificados frequentemente exibem comportamento reológico análoga para fuidos com tensão de cedência. Existe uma tensão crítica, abaixo do qual nenhum fluxo ocorre, mas acima doqual a viscosidade de uma sistema gelificada diminui drasticamente. Assim, para reinício de escoamento de óleo cru gelificado, uma pressão maior do que a pressão de funcionamento normal deve ser aplicada para exceder a tensão de cedência do fluido na parede, esta pressão mínima exegida deve ser determinada. Neste estudo para explorar o conceito de pressão mínima, fluidos com tensão de cedência foram investigados inteiramente. A investigação foi iniciada com o fluido de tensão de cedência simples e, em seguida, avanou com um tixotrpico usando reômetro e configuração experimental para escoamento de fluido em tubo. Em ambos, os casos a condio não deslizamento foi atingido, o comportamento de fluidos com tensão de cedência foi examinado em detalhe, os resultados de experimentos de reometria e transporte de fluido em tubos foram verificados. Com a colocação de todos juntos, a pressão mínima exigida ou em outra palavra a tensão crítica para partida de escoamento de fluidos com tensão de cedência foi descoberta. / [en] Besides an increasing economic importance of producing wax-containing crude oil from ultra deep water resources, concerns about wax deposition and gelation play a significant role in this area. Gelled waxy crude oils often exhibit rheological behavior analogous to yield stress fluids. There is a critical or range of stresses, below which no flow occurs, but above which the viscosity of a gelled system decreases drastically. Thus, in order to restart flow of a gelled crude, a pressure larger than the typical operating pressure should be applied to exceed the yield stress of the fluid at wall, this required minimum pressure should be determined. In this study to explore the minimum pressure notion, yield stress fluids were investigated comprehensively. The investigation was initiated with simpler yield stress fluid and then advanced with thixotropic one using rheometer and designed experimental setup for fluid flow into tube. In both cases no-slip condition was achieved, the behavior of yield stress fluids was screened in detail, the outcomes of fluid transport in tube and rheometric tests were combined and cross checked. Finally with putting all together, the required minimum pressure or in other words, the critical shear stress needed to startup the flow of yield stress fluids was discovered.

This dissertation reports the investigation and combination of optimization methodologies and the result of implementing them within a production environment. A literature survey was conducted on the optimization methodologies Lean Manufacturing and theory of constraints (TOC). A number of production optimization methodologies were studied and considered for application to the case study organisation. Due to the small size and relative simplicity of the operation, these methodologies had to be simplified and combined into a more relevant form. A refractory manufacturer was used as a case study for the investigation into the optimization of the dry batch plant. Lean Manufacturing and TOC are optimization methodologies that could be employed to optimize the dry batch plant. Tools from these methodologies were used to investigate problems identified within the production process that were causing the batching plant to perform non-optimally. A time and motion study was conducted and a process flow chart was created to understand the production process. Wasteful activities were identified using a value stream map and a flow process chart was used to visualise the movement within the production process. A 5-Why analysis was conducted to determine the root causes. An optimization plan was created to eliminate the wasteful activities and the operational measures, that is throughput, inventory and operating expense, were used as to determine what the effect the optimization plan would have on the wasteful activities (Lean Manufacturing) found within the batching plant and the organisation. The results of the combined effect of the optimization plan are discussed focusing on the improvements in the operational measures and the increase in profit from sales. Future research is suggested to improve the benchmarking of the optimization plan and any future improvements that the organisation might implement. / MSc (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

This dissertation reports the investigation and combination of optimization methodologies and the result of implementing them within a production environment. A literature survey was conducted on the optimization methodologies Lean Manufacturing and theory of constraints (TOC). A number of production optimization methodologies were studied and considered for application to the case study organisation. Due to the small size and relative simplicity of the operation, these methodologies had to be simplified and combined into a more relevant form. A refractory manufacturer was used as a case study for the investigation into the optimization of the dry batch plant. Lean Manufacturing and TOC are optimization methodologies that could be employed to optimize the dry batch plant. Tools from these methodologies were used to investigate problems identified within the production process that were causing the batching plant to perform non-optimally. A time and motion study was conducted and a process flow chart was created to understand the production process. Wasteful activities were identified using a value stream map and a flow process chart was used to visualise the movement within the production process. A 5-Why analysis was conducted to determine the root causes. An optimization plan was created to eliminate the wasteful activities and the operational measures, that is throughput, inventory and operating expense, were used as to determine what the effect the optimization plan would have on the wasteful activities (Lean Manufacturing) found within the batching plant and the organisation. The results of the combined effect of the optimization plan are discussed focusing on the improvements in the operational measures and the increase in profit from sales. Future research is suggested to improve the benchmarking of the optimization plan and any future improvements that the organisation might implement. / MSc (Development and Management Engineering), North-West University, Potchefstroom Campus, 2015

彈幕作為一種新型的實時評論工具，源自日本，發展至中國大陸後被廣泛應用到電影、電視、影音網站、廣告、電子書等諸多領域。隨著彈幕經濟的增長，這個源自於ACG（Animation、Comic、Game）產業的小眾文化漸漸走入大眾視野，彈幕背後的生活方式正在被越來越多的人接受，彈幕影音的使用者也呈現爆發式的增長。 本研究以中國大陸的彈幕影音為例，試圖以沈浸理論來探討彈幕觀影行為。本研究希望探討閱聽眾在彈幕觀影中的沈浸過程，以挑戰與技巧、目的來探討閱聽眾的彈幕觀影的沈浸前因，以愉悅感、注意力和時間扭曲來探討彈幕觀影的沈浸經驗，以使用意願來探討彈幕觀影沈浸的結果。 本研究收集有效問卷556份，結果發現彈幕觀影的沈浸包含愉悅感、時間扭曲感兩項，彈幕觀影技巧、彈幕觀影的目的對彈幕觀影沈浸有顯著正向影響；彈幕閱聽眾的沈浸狀態則會顯著正向影響其使用意願。

Quando ar escoa em regime transiente através do duto de admissão, câmaras e válvulas de um motor de combustão interna, alguns efeitos tais como atrito e forças inerciais têm influência direta sobre a eficiência volumétrica do sistema. O presente trabalho, intitulado “Estudo numérico do processo de admissão em um motor de combustão interna utilizando uma metodologia baseada na massa específica pré-condicionada para baixo número de Mach com comparação experimental”, estuda o processo de admissão em um motor de combustão interna simplificado e objetiva investigar o comportamento pulsante presente no duto de admissão e discutir as predições do escoamento através da válvula de admissão por meio da utilização inédita de uma metodologia numérica baseada na massa específica com précondicionamento para baixo número de Mach, incluindo a modelagem tridimensional do duto de admissão na simulação fluidodinâmica. O movimento da válvula de admissão origina números de Mach moderados durante sua abertura. Com o fechamento, o escoamento é restringido abruptamente e uma série de ondas de pressão se propaga através do fluido com baixo número de Mach. Embora a metodologia baseada na massa específica com précondicionamento para baixo número de Mach pareça atrativa, o estudo do escoamento em processos de admissão não tem sido realizado com a utilização desta metodologia, provavelmente por limitações impostas pela robustez e esforço computacional. De modo a verificar a solução numérica, os resultados são comparados a dados experimentais coletados em uma bancada de fluxo construída especificamente com este propósito. Os resultados numéricos mostram-se satisfatórios e diferentes aspectos do jato originado pelo movimento da válvula são expostos e discutidos. / When air flows unsteadily in an internal combustion engine through its inlet pipe, chambers and valves, some effects such as friction and inertial forces have direct influence on the volumetric efficiency of the system. The present work, titled “Numerical study of the intake process of an internal combustion engine using a low Mach preconditioned densitybased method with experimental comparison”, aims to investigate the pulsating phenomena present in an intake pipe of a simplified internal combustion engine and discuss the intake jet flow predictions through the inlet valve by means of the novel use of a low Mach preconditioned density-based method, including the three-dimensional modeling of the intake pipe in the fluid dynamic simulation. Inlet valve movement promotes moderate values of Mach numbers during its opening phase. After closing, the flow is abruptly restricted and a series of pressure waves propagate through the fluid at low Mach numbers. Although low Mach preconditioned density-based method seems to be very attractive in this case, the study of the intake flow process has not been performed using this method, probably due to robustness issues and simulation effort. In order to evaluate the numerical solution, these results are compared to experimental data collected from a flow test bench constructed specifically for this purpose. Numerical results were satisfactory for the amplitudes and the resonance frequencies in the air intake system and different aspects of the jet flow inside the cylinder are exposed and discussed.