Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2009. / Scheduling is a core activity in the manufacturing business. It assists with efficient and effective utilization of capital-intensive resources and increased throughput, thus increasing profitability. The focus in this thesis is on scheduling of manufacturing orders in a make-to-order job-shop enterprise. It is widely accepted that manufacturing of large volumes and production with as few as possible product variants is the most cost-effective business approach, but the need for low volume, once-off engineering parts will always exist. Many approaches to scheduling exist, including translation of a scheduling problem to a Travelling Salesman analogue, while Discrete-event computer simulation is well established as a means to assist with scheduling. Simulation is appealing in the manufacturing environment, as it can realistically imitate dynamic, stochastic processes while being descriptive in forecasting the future. In this thesis, the development and testing of a simulation-based scheduler is described. The scheduler was developed for, and in collaboration with a South African make-to-order job-shop enterprise. A supporting information system was also developed and it is required that the enterprise changes some of its business processes if this scheduler is implemented. The scheduler considers the status of the enterprise each time a new order is received, and the current schedule is reviewed and may be revised at such a point in time, making it a real-time scheduler. Several classic scheduling dispatching rules and –measures were incorporated in the scheduler. These include First-in First-out, Earliest Due Date, Longest Processing Time, Shortest Processing Time, Smallest Slack and Critical Ratio (dispatching rules), while the performance measures are Makespan, Earliness, Lateness, Average Flow Time and Machine Usage. The proposed scheduler has been verified and validated using test data and designed confidence building tests, and its performance was also compared to an actual, historical schedule. The functioning of the scheduler is finally demonstrated using a stochastic test environment. The scheduler has generally performed satisfactorily and should be implemented as the final phase of this project.

This thesis looks at the medium term mine planning process and tools in the Leveäniemi open pit mine operated by LKAB Svappavaara. The current planning process uses software, Chronos, which was previously used successfully to perform medium term planning for the Gruvberget mine, which is also operated by LKAB Svappavaara. Because of scale and geological differences this method is much less successful when applied in Leveäniemi, which has created the need to investigate other possible methods. Since the Maptek scheduling solution Evolution is already available for use, this is the first candidate to be investigated. This report uses a case study approach, where both methods are evaluated in their intended operating environment. Results obtained indicate that Evolution could be a viable replacement to conduct medium term planning. Testing indicates that Evolution is able to produce a schedule satisfying the planning criteria to the desired standard. The fact that Evolution is able to produce schedules with longer time horizons without having to sacrifice detail means that it could also improve the integration between long and medium term planning. Besides replacing Chronos it was demonstrated that there are also some things that can be done using Evolution that are not possible using the Chronos module. From what has been demonstrated it can be concluded that there is a possibility to achieve significant benefit using these extra functions.

Orientador: Maria Helena Andrade Santana / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-23T12:48:43Z (GMT). No. of bitstreams: 1 Quinalia_MarianaBeatriz_M.pdf: 3702329 bytes, checksum: 7ed3bbb46f028abad9a9d677dbda482d (MD5) Previous issue date: 2013 / Resumo: Processos de alto cisalhamento têm sido utilizados para redução e homogeneização da distribuição de tamanhos de lipossomas em sua produção escalonável. No entanto, a aplicação do cisalhamento pode modificar estruturalmente essas nanopartículas, influenciando a incorporação de fármacos hidrofóbicos. Neste estudo, a chalcona sintética 3-nitro-2-hidroxi- 4,6-dimetoxichalcona (CH8), fármaco altamente hidrofóbico indicado para tratamento de leishmaniose cutânea, foi incorporada em lipossomas convencionais produzidos por processos escalonáveis de alto cisalhamento. Os lipossomas foram compostos por fosfatidilcolina de ovo e produzidos por injeção de etanol. Foram utilizados agitador mecânico com impelidor Cowles, Ultra Turrax® e microfluidizador para reduzir e homogeneizar o tamanho das partículas. A influência da taxa de cisalhamento foi controlada pelo método de Bangham seguido por extrusão em membranas. Espectros de espalhamento de raios-X a baixo ângulo mostraram que o cisalhamento leva a uma redução na distância interlamelar dos lipossomas, quando comparados ao controle. A distância interlamelar não variou com a intensidade do cisalhamento na faixa de agitação obtida com o impelidor Cowles, mas diminuiu com o aumento do cisalhamento provocado pelo Ultra Turrax®. A constante elástica, relacionada com a rigidez da bicamada e dependente da estrutura dos lipossomas, aumentou proporcionalmente com a taxa de cisalhamento para os dois agitadores. O cisalhamento também diminuiu o diâmetro médio dos lipossomas e a distribuição de tamanhos. Inicialmente, CH8 foi incorporada em lipossomas pré-formados. Os resultados mostraram que a expulsão e precipitação do fármaco incorporado foram proporcionais à intensidade do cisalhamento aplicado. Essa limitação foi contornada pela incorporação de uma baixa concentração de CH8 durante a formação dos lipossomas. A taxa de cisalhamento produzida pelo impelidor Cowles favoreceu a elasticidade da bicamada lipossomal, proporcionando alta eficiência de incorporação e capacidade de carregamento da CH8. Assim, a elasticidade da bicamada é fator determinante para a capacidade de incorporação de fármacos hidrofóbicos em lipossomas. Estas descobertas constituem uma melhoria nos processos de alto cisalhamento utilizados para carreamento de CH8 e contribuem para o desenvolvimento de formas farmacêuticas mais eficazes para o tratamento de leishmaniose cutânea / Abstract: High shear processes have been used to reduce the size and homogenize the size distribution of liposomes in their scalable production. However, high shear rates modify the liposome structure which may affect the loading of hydrophobic drugs. In this study, synthetic chalcone 3-nitro-2-hydroxy-4,6-dimethoxychalcone (CH8), a highly hydrophobic drug indicated to treat cutaneous leishmaniasis, was incorporated in conventional liposomes produced by scalable high shear processes. Liposomes were composed by egg phosphatidylcholine and produced by ethanol injection. Cowles impeller, Ultra Turrax® stirrers and microchannel microfluidizer were used to reduce and homogenize the size of the liposomes. The shear rate was controlled by Bangham's method followed by membrane extrusion. Small angle X-ray scattering spectra showed that the shearing reduced the interlamellar distance of the liposomes compared to the control. The interlamellar distance did not change with the shearing intensity in the range of Cowles stirring, but it decreased for higher shearing provided by the Ultra Turrax®. The elastic constant, which is related to the stiffness and depends on the structure of the liposomes, increased with increasing shearing intensity for both stirrers. The shearing also reduced the mean diameter of the liposomes and the size distributions. Initially, CH8 was incorporated into pre-formed liposomes. The results showed the expulsion and precipitation of loaded CH8 was proportional to the intensity of the applied shear rate. This limitation was circumvented by incorporating a low concentration of CH8 (0.2 mol/m³) during the formation of liposomes. The shear rate provided by the Cowles stirrer favored the elasticity of the bilayer and yielded high incorporation efficiency and CH8-loading. Therefore, the elasticity of the bilayer is a determining factor for the loading of hydrophobic drugs in liposomes. These findings constitute an improvement in the high shear process used to load CH8 and to the development of most effective pharmaceutical forms for the treatment of cutaneous leishmaniasis / Mestrado / Engenharia Química / Mestra em Engenharia Química

M.Ing. / Previous research have entailed developing various network traffic models which describe network traffic behaviour, but no model describes differential traffic treatment to such an extent to be able to relate the impact different rates have on the various traffic classes. The main reason for this being the amount of parameters that needs to be taken into consideration. Previous research performed in this field, analysed certain schedulers according to fixed parameters, thus having a very limited results base. No detailed comparison of these schedulers behaviour in a Differentiated Services (DiffServ) environment is available since the parameters under which their analysis were performed are different. A first objective entailed performing a thorough literature survey concerning DiffSery to summarize the research material that is available. This gives us as well as the reader a foundation to start any future research and the means to make good use of this information. Secondly, a DiffSery module was ported from an old version of Ns-2 which was developed for an older Linux kernel and GCC version; to the newest available. Ns-2 was also limited in respects to traffic generation. We developed a traffic generator that generates traffic according to a certain statistical distribution. This generation is performed according to packet size since distributions according to arrival time was partially implemented already. Our aim is to provide an in depth study regarding the performance of the various schedulers in the network and the effect various network parameters have on them. Since no real-network trace data is available, we resort to computer simulations. With Ns-2, we implement four different standardized perhop-behaviours (PHBs), namely expedited forwarding (EF), assured forwarding (AF1, AF2) and besteffort (BE). The evaluation focuses mainly on the EF PHB in regards to the other PHBs. The priority queuing (PQ), start-time fair queuing (SFQ), self-clocked fair queuing (SCFQ), weighted fair queuing (WFQ), worst-case weighted fair queuing plus (WF2Q+) and low latency queuing (LLQ) scheduling mechanisms are analysed to find their performance in relation to EF traffic and BE traffic. The QoS metrics that are focused on are: one-way delay (OWD), inter-packet delay variation (IPDV) and packet loss. We used Analysis of Variance (ANOVA) to analyse the impact of the various DiffSery node configuration parameters such as rates, packets sizes, schedulers and queue weights have on the output QoS metrics mentioned previously. Regression is then used to explain the relationship between several of these factors and metrics.

In this dissertation, a multiprocess scheduling model is developed and a set of performance theorems is constructed for the set of scheduling functions associated with the model. Each theorem describes the conditions under which a scheduling function exhibits a particular type of performance.

Linear Scheduling Method is a powerful graphical scheduling method which is best suited for scheduling projects involving repetitive activities. Highway construction projects are excellent examples of projects displaying repetitive characteristics. The research explores usefulness of linear scheduling in highway construction. The Linear Scheduling Method (LSM) was implemented in the field to schedule highway projects. Problems encountered during the field experience were studied and responses to the problems were identified. The research resulted in a number of advancements to the technique. These are reported in the thesis. The advancements exploit the simplicity and graphical nature of this technique. The research identified the true potential of a graphical technique in communicating information, and in evaluating scheduling alternatives. The importance of visualization and the role of LSM in planning, execution, and control phases of a project are discussed. The concepts of lateral float and use of LSM as a graphical simulation tool are presented. A comprehensive description of the linear schedule's format and symbols is presented in the thesis and this will lead the technique towards a standard format. The enhancements to the format and symbols, reported in the thesis, will make the technique more robust, increase its effectiveness, and help in scheduling complex projects using the technique. The need for representing the information contained in the linear schedules in tabular formats was identified during the field implementation of the technique. The concept of Crew Movement Chart (CMC), which shows deployment and movement of various crews in the project in a tabular format, is presented. The use of spreadsheets and databases to generate the CMC is discussed and a computer software package, LINC, which can be used to generate CMC by input through user-interface screens, is presented. The need for an interface between the Critical Path Method (CPM) and the Linear Scheduling Method (LSM) was identified during the field experience. This thesis presents a discussion on the development of the computer interface, the Linear Scheduling Software (LSS). A combined computer scheduling system comprising of the LSS and LINC, which can be used to generate linear schedules as well as tabular reports, is presented. / Master of Science

Reinforcement learning (RL) has received attention in recent years from agent-based researchers because it can be applied to problems where autonomous agents learn to select proper actions for achieving their goals based on interactions with their environment. Each time an agent performs an action, the environment¡Šs response, as indicated by its new state, is used by the agent to reward or penalize its action. The agent¡Šs goal is to maximize the total amount of reward it receives over the long run. Although there have been several successful examples demonstrating the usefulness of RL, its application to manufacturing systems has not been fully explored. The objective of this research is to develop a set of guidelines for applying the Q-learning algorithm to enable an individual agent to develop a decision making policy for use in agent-based production scheduling applications such as dispatching rule selection and job routing. For the dispatching rule selection problem, a single machine agent employs the Q-learning algorithm to develop a decision-making policy on selecting the appropriate dispatching rule from among three given dispatching rules. In the job routing problem, a simulated job shop system is used for examining the implementation of the Q-learning algorithm for use by job agents when making routing decisions in such an environment. Two factorial experiment designs for studying the settings used to apply Q-learning to the single machine dispatching rule selection problem and the job routing problem are carried out. This study not only investigates the main effects of this Q-learning application but also provides recommendations for factor settings and useful guidelines for future applications of Q-learning to agent-based production scheduling.

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