Volvo Trucks is one of the world’s largest truck manufacturers, with a cab production plant located in Umeå, Sweden. The variation in batch sizes of the different components causes variation in the length of the production plan of subparts, and thus variation in production lead times. This project aims to examine how equally sized batches affect the length of the production plan, and what batch size is optimal to achieve efficient production planning. The examination was conducted with respect to lean principles and a mathematical model was built to simulate the use of different batch sizes. In order to run the simulation, both historical and new data was used. Parameters interesting to examine for the result are the length and variation of the production plan, number of set-ups, production frequency, inventory levels and the annual production. A batch size of 2.0 hours is optimal as the length of the production plan then varies the least in the allowed interval. Equally sized batches exclusively were not found to contribute to a more efficient production planning. Smaller batch sizes in combination with equally sized batches were however shown to decrease the variation in the production plan, and to result in increased stock turnover and decreased inventory levels. / Volvo Lastvagnar är en av världens största lastbilstillverkare, med en fabrik för tillverkning av hytter placerad i Umeå. Variationen i orderstorlekar för olika komponenter orsakar variation i längden av produktionsplanen, vilket i sin tur leder till varierade ledtider. Detta projekt syftar till att undersöka hur utjämnade orderstorlekar påverkar längden av produktionsplanen och vilken orderstorlek som är optimal för en effektiv produktionsplanering. Projektet utfördes med hjälp av leanprinciper och en matematisk modell av produktionen byggdes för att simulera användningen av olika orderstorlekar. För att köra simuleringen användes både historiskt och nytt data. Intressanta parametrar för resultatet är längden och variationen i produktionsplan, antal verktygsbyten, produktionsfrekvens, lagernivåer och årlig produktion. En orderstorlek på 2,0 timmar är optimal eftersom längden på produktionsplanen då har minst variation inom det tillåtna intervallet. Enbart jämna orderstorlekar visade sig inte bidra till en effektivare produktionsplanering, men mindre orderstorlekar i kombination med jämna orderstorlekar visade sig minska variationen i produktionsplan och resulterade i ökad lageromsättning samt minskade lagernivåer.

This dissertation develops, tests and validates statistical methods for verifying the amount of water conserved as a result of investments in precision leveling, other on-farm conservation measures in place, weather variation and farmer behavior. This evaluation uses a sample of 328 unique fields from Lakeside Irrigation Division in Texas over a six-year period, totaling 966 observations. Results show that precision leveling accounts for a 0.30 acre-feet reduction of irrigation water per acre leveled. This Mixed-Level Model (MLM) estimate for precision leveling water savings is more precise than the estimates either from an Ordinary Least Square Model or a Fixed Effect Model. A meta analysis combines the results from this model with other similar studies. Although the mean estimate of the meta-analysis is similar to the MLM estimate, the meta-analysis further reduces the standard error of the mean precision leveling estimate by 2 percent. A better approximation of the acre-feet water savings per acre farmed translates into less uncertainty for water regulators, managers and policymakers regarding the volume of conserved water that is available for transfer. / text

Bloodstain pattern analysis has been used in criminal investigations for more than 100 years. It provides valuable information about the events that took place prior to the formation of bloodstains at a crime scene. Forensic scientists use empirical laws to make a deduction from bloodstains, but the validity of these conclusions has been challenged in courts due to a lack of understanding of the underlying fluid mechanics. With this motivation, this thesis illustrates how mathematical modeling and numerical simulation can help gain insight into the spreading of blood droplets which eventually leads to the formation of a bloodstain. Understanding the fluid mechanics of droplet spreading and sliding has been accomplished with the help of the lubrication approximation which simplifies the Navier-Stokes equations to a more tractable form, i.e. a coupled set of non-linear partial differential equations. The resulting highly non-linear coupled set of equations is discretized using Finite-Difference. The resulting algebraic system is solved via an efficient Multigrid algorithm. These equations are modified to understand the effects of contact angle hysteresis, fluid rheology and absorptive properties of substrates on sliding dynamics. Variations in the inclination of the substrate cause the droplets to attain different advancing and receding contact angles as they slide down the incline under gravitational pull. This work explores a new way to introduce contact angle hysteresis in the numerical simulation to predict the different phases of a sliding droplet. Experiments of fluid droplet spreading/sliding on inclined surfaces have been performed to measure the terminal sliding velocity. A simplified hysteresis model has been proposed. This model automatically locates the section of the contact line which is advancing and the section which is receding which enables the application of the contact angles for the advancing and receding fronts and therefore takes into account contact angle hysteresis. A simplified analytical model is also suggested for droplets moving down the incline with near circular footprints. With the inclusion of the contact angle hysteresis, simulation results were brought in closer agreement with the experimental ones and the results from both were compared with the results from the analytical model. Blood is a shear-thinning fluid. One of the main objectives of this study is to investigate numerically the effect on the spreading and/or sliding of non-Newtonian fluid droplets on surfaces. To achieve this, the effect of rheology on the leveling of thin fluid films on horizontal solid substrates is first investigated as a preliminary investigation since this problem does not involve a contact line and is therefore more tractable. A mathematical model based on the lubrication approximation which defines non-Newtonian rheology using a power-law model is presented. Results for the leveling of sinusoidal perturbations of the fluid film highlight important differences between the leveling of shear-thinning and shear-thickening fluids. Namely, the onset of leveling occurs earlier for the shear-thinning fluid than for the shear-thickening one. However, the rate of leveling is higher for the shear-thickening fluid than the shear-thinning one. An important aspect of this part of the work is the verification of the numerical implementation using the Method of Manufactured Solutions (MMS). This leveling study also highlights differences between the leveling of two-dimensional and three-dimensional perturbations. This verified numerical formulation is then used to study the effects of rheology on the spreading/sliding of droplets. Results for the spreading of fully wetting droplets on a horizontal substrate show that, for all other quantities being equal, an increase of the flow index leads to a more rapid wetting. It also shows that, even for non-Newtonian fluids, the droplet velocity asymptotes to a constant value when sliding down an inclined substrate. This terminal velocity is strongly dependent on the rheological parameters and as it is reached, the droplets travel with a visibly constant profile. Finally, the numerical simulations revealed the formation of a tail at the rear of the droplet as it slides down the incline plane in the case of shear-thickening fluids. Finally, a more complex dynamics of fluid being absorbed in a porous substrate as it slides/spreads is considered. A mathematical model based on the lubrication approximation which defines the absorptive property of a substrate using a Darcy’s model is presented. This numerical model is verified with the help of comparison between the analytical and numerical solutions for the absorption of thin film on horizontal porous substrates. Results show that physical properties of the substrates, i.e. permeability, porosity, capillary pressure and equilibrium contact angle affect the rate of absorption of the fluid. Adding inclination to the problem, introduces the gravitational pull in the absorption dynamics. This directly shows its effects on the footprints formed inside the porous substrates. The following papers, based on sections of this thesis, have appeared or been accepted for publication: - Ahmed, G., Sellier, M., Lee, Y., Jermy, M., and Taylor, M. (2013). Modeling the spreading and sliding of power-law droplets. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 432:2–7. - Ahmed, G., Sellier, M., Lee, Y., Jermy, M., and Taylor, M. (2014). Rheological effects on the leveling dynamics of thin fluid films. Accepted for publication in the International Journal of Numerical Methods for Heat and Fluid Flow. - Ahmed, G., Sellier, M., Jermy, M., and Taylor, M. (2014). Modelling the effects of contact angle hysteresis on sliding of droplets on inclined surfaces. Submitted for peer review in The European Journal of Mechanics - B/Fluids.

O processo de planejamento de empreendimentos residenciais verticais no Brasil tem apresentado deficiências principalmente quanto do confronto das programações que balizam a decisão de investir, da tomada de risco do empreendimento, versus os resultados obtidos a partir do controle de sua implantação. As discrepâncias observadas entre o desempenho esperado na programação e aquelas obtidas nos processos de controle, principalmente quanto a indicadores de prazo e de alocação de recursos mostram a necessidade de se buscar sucessivos aprimoramentos dos processos da programação orientada a prazos. Aspectos como maior consistência no mapeamento de escopo na elaboração do planejamento operacional suportados por redes lógicas, além de uma adequada correlação entre as durações das atividades com as respectivas alocações e nivelamento de recursos merecem ser aprimorados. Uma abordagem para o desenvolvimento de programações operacionais, contemplando recursos para fazer frente aos aspectos acima citado se torna necessária. A ênfase se dá no estreitamento da correlação entre a estimativa das durações das atividades com as respectivas alocações de recursos. O objetivo deste trabalho é propor um método de nivelamento de recursos desenvolvido com o emprego de princípios da Theory of Constraints (TOC). O método de nivelamento consiste de regras heurísticas para programação operacional, complementado por procedimentos para o mapeamento de escopo e de uma biblioteca de redes lógicas elementares para edifícios residenciais verticais. Estes complementos têm por objetivo assegurar um nível mínimo de consistência e adequação do emprego do método de nivelamento ora proposto. Foram desenvolvidos 16 estudos de caso para suportar estes processos complementares, além de 171 testes em 21 redes lógicas para avaliar: os princípios da TOC, calibrar o método, analisar o seu desempenho e demonstrar sua aplicabilidade. Finalmente, concluiu-se que as regras heurísticas que compõem o método proposto nesta Tese são de fácil aplicação, e apresentaram desempenho igual ou superior as melhores regras existentes. / The planning process of construction of vertical housings used in Brazil have shown lacks, mainly when confronting the scheduling guiding the decision-making to invest, concerning the risk of the enterprise, versus the results obtained during the execution control. The discrepancies observed between the expected results regarding scheduling and those observed in the execution control processes, especially those about timeframe and resource allocation indicators, show the necessity to adjust and improve constantly the scheduling processes. Aspects such as greater consistency in defining scope and in the design of operational planning supported by logical networks, along with an appropriate correlation between the duration of activities and the corresponding resource allocation, deserve to be optimized. This study focus on the development of operational scheduling techniques, contemplating resource allocation to deal with those aspects above mentioned. Emphasis is given to the reinforcement of correlation between estimated timeframes for activities and the corresponding resource allocation. The objective of this research work is to propose one method of resource levelling developed using the principles of the Theory of Constraints (TOC). This method consists of a heuristic scheduling process oriented towards operational schedule, complemented by procedures for mapping of scope for the construction of vertical residential buildings and a library of elementary logical networks also oriented towards this type of buildings. The objective of these complements is to guarantee a minimum level of consistency for the simulated implementation model, as well as to insure the adequate use of the levelling resource process proposed here. Sixteen cases studies were developed to support these complementary processes, beyond 171 tests in twenty one logical networks to evaluate the principles of the TOC, to calibrate the method, to analyze its performance and to demonstrate its applicability. Finally, it was concluded that the heuristics rules proposal that compose the method in this Thesis is of easily application, and presented a performance equally or higher than the best existent rules.

This study deals with a very common problem encountered in many automotive industries. Automotive companies try to level the production of different models over time based on the demands for these models in the market. In order to achieve this, they introduce a leveled stream of cars in the beginning of the production line. But because of many reasons this leveled stream gets disturbed in its course. In order to re-level the stream, buffers are used between the shops. One such buffer is called as selectivity bank and it sits between paint shop and assembly shop. This buffer receives a disturbed sequence from the paint shop. The thesis tries to develop different algorithms that can be used to discharge cars from this buffer in order to achieve better leveling in the presence of rework and assembly constraints. These algorithms continuously try to steer the system from an undesirable state to a more desirable state by keeping track of current conditions in the plant. A simulation model is developed, which gives a platform for comparing relative performance of these logics under different conditions. The simulation tool is also helpful in designing optimum size of this buffer that will result in desired leveling performance.

O processo de planejamento de empreendimentos residenciais verticais no Brasil tem apresentado deficiências principalmente quanto do confronto das programações que balizam a decisão de investir, da tomada de risco do empreendimento, versus os resultados obtidos a partir do controle de sua implantação. As discrepâncias observadas entre o desempenho esperado na programação e aquelas obtidas nos processos de controle, principalmente quanto a indicadores de prazo e de alocação de recursos mostram a necessidade de se buscar sucessivos aprimoramentos dos processos da programação orientada a prazos. Aspectos como maior consistência no mapeamento de escopo na elaboração do planejamento operacional suportados por redes lógicas, além de uma adequada correlação entre as durações das atividades com as respectivas alocações e nivelamento de recursos merecem ser aprimorados. Uma abordagem para o desenvolvimento de programações operacionais, contemplando recursos para fazer frente aos aspectos acima citado se torna necessária. A ênfase se dá no estreitamento da correlação entre a estimativa das durações das atividades com as respectivas alocações de recursos. O objetivo deste trabalho é propor um método de nivelamento de recursos desenvolvido com o emprego de princípios da Theory of Constraints (TOC). O método de nivelamento consiste de regras heurísticas para programação operacional, complementado por procedimentos para o mapeamento de escopo e de uma biblioteca de redes lógicas elementares para edifícios residenciais verticais. Estes complementos têm por objetivo assegurar um nível mínimo de consistência e adequação do emprego do método de nivelamento ora proposto. Foram desenvolvidos 16 estudos de caso para suportar estes processos complementares, além de 171 testes em 21 redes lógicas para avaliar: os princípios da TOC, calibrar o método, analisar o seu desempenho e demonstrar sua aplicabilidade. Finalmente, concluiu-se que as regras heurísticas que compõem o método proposto nesta Tese são de fácil aplicação, e apresentaram desempenho igual ou superior as melhores regras existentes. / The planning process of construction of vertical housings used in Brazil have shown lacks, mainly when confronting the scheduling guiding the decision-making to invest, concerning the risk of the enterprise, versus the results obtained during the execution control. The discrepancies observed between the expected results regarding scheduling and those observed in the execution control processes, especially those about timeframe and resource allocation indicators, show the necessity to adjust and improve constantly the scheduling processes. Aspects such as greater consistency in defining scope and in the design of operational planning supported by logical networks, along with an appropriate correlation between the duration of activities and the corresponding resource allocation, deserve to be optimized. This study focus on the development of operational scheduling techniques, contemplating resource allocation to deal with those aspects above mentioned. Emphasis is given to the reinforcement of correlation between estimated timeframes for activities and the corresponding resource allocation. The objective of this research work is to propose one method of resource levelling developed using the principles of the Theory of Constraints (TOC). This method consists of a heuristic scheduling process oriented towards operational schedule, complemented by procedures for mapping of scope for the construction of vertical residential buildings and a library of elementary logical networks also oriented towards this type of buildings. The objective of these complements is to guarantee a minimum level of consistency for the simulated implementation model, as well as to insure the adequate use of the levelling resource process proposed here. Sixteen cases studies were developed to support these complementary processes, beyond 171 tests in twenty one logical networks to evaluate the principles of the TOC, to calibrate the method, to analyze its performance and to demonstrate its applicability. Finally, it was concluded that the heuristics rules proposal that compose the method in this Thesis is of easily application, and presented a performance equally or higher than the best existent rules.

This research examines different techniques and proposes a Computational Fluid Dynamics (CFD) model as a robust tool for flow characterization of load leveling valves. The load leveling valve is a critical component of an air suspension system since it manages air spring pressure, a key function that directly impacts vehicle dynamic performance in addition to maintaining a static ride height. Efficiency of operation of a load leveling valve is established by its flow characteristics, a metric useful in determining suitability of the valve for application in a truck-suspension configuration and for comparison among similar products. The disk-slot type load leveling valve was chosen as the subject of this study due to its popularity in the heavy truck industry. Three distinct methods are presented to model and evaluate flow characteristics of a disk-slot valve. First is a theoretical formulation based on gas dynamic behavior through an orifice; second is an experimental technique in which a full pneumatic apparatus is used to collect instantaneous pressure data to estimate air discharge; and third is a CFD approach. Significant discrepancies observed between theoretically estimated results and experimental data suggest that the theoretical model is incapable of accurately capturing losses that occur during air flow. These variations diminish as the magnitude of discharge coefficient is altered. A detailed CFD model is submitted as an effective tool for load leveling valve flow characterization/analysis. This model overcomes the deficiencies of the theoretical model and improves the accuracy of simulations. A 2-D axisymmetric approximation of the real fluid domain is analyzed for flow characteristics using a Realizable k-ϵ turbulence model, scalable wall functions, and a pressure-based coupled algorithm with a second order discretization function. The CFD-generated results were observed to be in agreement with the experimental findings. CFD is found to be advantageous in the evaluation of flow characteristics as it furnishes precise data without the need to experimentally evaluate a physical model/prototype of the valve, thereby benefitting suspension engineers involved in the development and testing of load leveling valve designs. This document concludes with a sample case study which uses CFD to characterize flow in a modified disk-slot load leveling valve, and discusses the results in light of application on a heavy truck. / MS

This research provides a thorough flow characterization study to compare the functionality of two types of load-leveling valves that are commonly used for air suspension systems of commercial trucks. The first valve features a simple disk/slot design and is relatively compact for installation. The second type is larger and has a sophisticated, chambered design, which allows for considerably quicker fill and exhaust response times in the transient region. A new approach is introduced to estimate the transient mass flow rate of a load-leveling valve under different suspension pressures, without requiring a mass flow meter. An extensive series of dynamic tests are conducted to characterize and compare the two load-leveling valves. A generic heavy-truck pneumatic suspension, consisting of load-leveling valves, airspring, air tank, and air-hose fittings, is configured for testing. The test setup is used to evaluate the transient performance of each type of load-leveling valve in a typical truck suspension. The flow behavior of the system is validated by the force/pressure responses of the air spring due to various displacement excitations. The experimental results describe the detailed flow behavior of both valves. The flow characterization results can be incorporated as one of the most critical parameters for future model development of pneumatic systems. The tests indicate that the leveling valve with chambered design has a far faster transient flow response than the disk valve, although it is more complicated in its mechanical design and therefore costs more. To take advantage of the design simplicity of the disk valve, while also enabling it to have a faster transient response (compared with the chambered design), it is re-designed with larger flow openings and other elements to match the performance of the chambered valve for transient flow. A comparison of the experimental results and simulations validates that the re-designed rotary disk valve performs nearly the same as the chambered valve, but is simpler and costs less. The study's results are directly applicable to improving the transient dynamics of heavy truck air suspensions by providing a better understanding of how load-leveling valves can be used not only to provide ride-height control, but also to influence the roll and pitch dynamics of heavy trucks. / Master of Science

No description available.

With carbon dioxide levels in our atmosphere reaching record highs and 2020 quickly approaching, California is expected to pave the way for the United States in terms of replacing fossil fuel generation facilities with various renewable energy power plants. It is well documented that the inherent variability and limited duty cycle of renewables has hindered their growth. Energy storage technologies represent the bridge that can help us cross the divide from where we stand to where we must stand in the next 6 years. Utility companies value services such as peak shaving, voltage support, and frequency regulation, all of which energy storage technologies can provide. Commercial and residential clients’ of the utility will begin to install their own storage systems once properly incentivized. In this paper, a control algorithm for Sodium Sulfur batteries is proposed with hopes that the aforementioned services will be provided to the utilities while system owners realize profit.