Practicing engineers need an integrated building, HVAC and control simulation tool for optimum HVAC design and retrofit. Various tools are available to the researchers, but these are not appropriate for the consulting engineer. To provide the engineer with a tool which can be used for typical HVAC projects, new models for building, HVAC and control simulation are introduced and integrated in a user-friendly, quick-to-use tool. The new thermal model for buildings is based on a transfer matrix description of the heat transfer through the building shell. It makes provision for the various heat flow paths that make up the overall heat flow through the building structure. The model has been extensively verified with one hundred and three case studies. These case studies were conducted on a variety of buildings, ranging from a 4m2 bathroom, to a 7755 m2 factory building. Eight of the case studies were conducted independently in the Negev Desert in Israel. The thermal model is also used in a program that was custom-made for the AGREMENT Board (certification board for the thermal performance of new low-cost housing projects). Extensions to the standard tool were introduced to predict the potential for condensation on the various surfaces. Standard user patterns were incorporated in the program so that all the buildings are evaluated on the same basis. In the second part of this study the implementation of integrated simulation is discussed. A solution algorithm, based on the Tarjan depth first-search algorithm, was implemented. This ensures that the minimum number of variables are identified. A quasi-Newton solution algorithm is used to solve the resultant simultaneous equations. Various extensions to the HVAC and control models and simulation originally suggested by Rousseau [1] were implemented. Firstly, the steady-state models were extended by using a simplified time-constant approach to emulate the dynamic response of the equipment. Secondly, a C02 model for the building zone was implemented. Thirdly, the partload performance of particular equipment was implemented. Further extensions to the simulation tool were implemented so that energy management strategies could be simulated. A detailed discussion of the implications of the energy management systems was given and the benefits of using these strategies were clearly illustrated, in this study. Finally, the simulation tool was verified by three case studies. The buildings used for the verification ranged from a five-storeyed office and laboratory building, to a domestic dwelling. The energy consumption and the dynamics of the HVAC systems could be predicted sufficiently accurately to warrant the use of the tool for future building retrofit studies / Thesis (PhD)--University of Pretoria, 1997. / gm2014 / Mechanical and Aeronautical Engineering / unrestricted

Complex assembly systems are made up of hundreds, and in some cases, thousands of parts, that all need to be managed in a proper manner so part arrivals will coincide to meet a build plan, and ensure production requirements are satisfied. A major challenge faced by manufacturers for these complex systems is that many parts have long and complex supply chains, which result in long and highly variable supply lead times. The high cost and low volume makes holding large stocks of these components unviable. Thus, the need arises for the development of a simulation tool that can predict the time all of the required parts are ready for assembly, and allow for comparison of various ordering and inventory strategies. Two strategies were tested, the current practice of ordering to an agreed upon quoted lead time, and a strategy which accounts for lead time variability through advanced ordering. The results of these two strategies displayed the benefits of synchronizing the system through advance ordering, as a potential 60% reduction in inventory was observed. Future development in the tool would incorporate more granular steps of the build sequence, as well as the inclusion of quality non-conformance (QN) issues.

Volvo trucks can be ordered with many options to meet customers' demands. This challenges the efficiency of the manufacturing process, especially at the final assembly line where bare chassis are customised with parts and accessories. In the future, assembly lines may be more flexible to allow for assembly of different parts at higher efficiency. This thesis presents problem areas in traditional assembly lines and proposes a proof-of-concept for future flexible assembly line sequencing, as well as a computer simulation tool with the capability to evaluate variances in production capacity when trucks of different size and parts are assembled in consecutive order. Virtual models of flexible assembly lines are constructed as part of a software solution and used to simulate production sequences of varying truck configurations. Data collected from all simulations show a correlation between production capacity and the order in which vehicles are produced. The assembly line configuration itself has also shown to greatly impact efficiency and might lead to an improvement of at least 39%, as well as limitations of tools and workers with specific capabilities. However, the presented performance numbers do not represent all possible simulation outcomes, which beyond the assembly line configuration also depend on things like product complexity and the assembly sequence of individual products.

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Les éleveurs laitiers gèrent des systèmes complexes combinant production animale et production végétale. Dans un contexte d'évolutions rapides, les démarches de conception de systèmes de production doivent être renouvelées, et répondre à la diversité des situations des exploitations agricoles. La co-conception de systèmes innovants avec les producteurs eux-mêmes se présente comme une démarche intéressante. Les modèles d'exploitation permettent de représenter la complexité du système, mais leur utilisation comme outil d'accompagnement interroge les choix de développement. Ce travail propose une démarche d'accompagnement basée sur l'utilisation d'un modèle de simulation pour appuyer les réflexions de l'éleveur sur ses stratégies d'élevage. Les choix de développement s'appuient sur l'analyse du fonctionnement d'un échantillon de six exploitations. Trois exemples d'utilisation du modèle avec les producteurs sont présentés. Ils montrent comment les résultats du modèle alimentent la discussion autour du proj et de l'éleveur. / Dairy farmers have to manage complex and mixed-farming systems. In the moving context of the agricultural sector, methods of conception of production systems must be renewed and fit the diversity of farmers conditions. The co-conception of production systems with farmers is the approach we want to defend. Whole-farm models help to picture the farming system's complexity but their use as advising services' tools raises questions in terms of model design choices. This PhD proposes an approach of advising services based on the use of a simulation whole-farm model to help farmers in designing their livestock strategies. The model design is based on the analysis of six dairy farms that constitute our study sample. We present three case-studies about the use of our model with dairy farmers. The case-studies give us insight about the capacity of the model's outcomes to generate debates with farmers about their own projects.

L’émergence du concept d’un avion plus électrique implique une refonte en profondeur des réseaux embarqués. L’axe principalement développé repose sur une augmentation de la tension du réseau et un passage au bus continu. Le contrôle des actionneurs électriques embarqués passe alors par l’utilisation massive de convertisseurs électroniques qui vont imposer des fronts de tension très raides et des contraintes particulières aux enroulements des machines. Les oscillations pseudopériodiques qui suivent ces fronts raides sont à l’origine de champs électriques intenses qui peuvent dépasser le seuil d’apparition des décharges partielles (PDIV) et de ce fait provoquer une dégradation rapide des isolants classiques qui sont à base de polymères. Le travail effectué dans cette thèse est centré sur l’étude d’une nouvelle méthode de conception des bobinages permettant la réduction des problèmes de décharges partielles. Un dispositif expérimental mis au point dans ce cadre reproduit les contraintes imposées par des convertisseurs modernes et permet de mesurer les tensions inter-spires d’une bobine. L’étude expérimentale met en évidence les phénomènes àprendre en compte avec ce type d’alimentation et donne une première idée des axes d’optimisation envisageables. Un modèle prédictif capable de donner la distribution des tensions inter-spires, en réponse à un front raide de tension, aide à identifier les points critiques. Les paramètres constitutifs de ce modèle ont été déterminés en utilisant des méthodes analytiques, expérimentales et numériques. Compte tenu de la complexité du modèle, un outil numérique automatisé a été élaboré afin de simuler le modèle des bobines étudiées. Plusieurs types de bobinage ont été analysés et optimisés avec succès. Cette optimisation consiste à diminuer la tension inter-spires en agissant sur l’arrangement des fils dans les encoches. L’utilisation des bobines optimisées avec cette méthode permet d’envisager une nette amélioration de la fiabilité des machines électriques. / The emergence of the concept of a more electric aircraft requires a major overhaul of onboard grid. The main developed axis is based on an increase in the grid voltage and a switch to DC bus. In this context, the onboard electric actuators are supplied through power electronic converters that will impose very fast voltage fronts and particular constraints in the windings of the machines. The transient over-voltages that follow the steep-fronted pulses are the source of intense electric fields which may exceed the partial discharge inception voltage (PDIV) and cause a rapid deterioration of polymer based insulators. This thesis focuses on the study of a new design method of the windings in order to reduce problems of partial discharges. An experimental device developed in this framework reproduces the constraints of modern converters and allows measuring the turn-to-turn voltages of a coil. The experimental study shows the phenomena to be considered with this type of power supply and gives an idea of possible areas for optimization. A predictive model able to give the distribution of turn-to-turn voltages, in response to a steep-fronted voltage, helps to identify critical points. The constitutive parameters of this model were determined using analytical, experimental and numerical methods. Given the complexity of the model, an automated numerical tool has been developed in order to simulate the model of studied coils. Several types of coil have been analyzed and optimized successfully. This optimization consists in reducing the turn-to-turn voltages by acting on the arrangement of the wires in the slots. The use of optimized coils with this method allows envisaging a significantimprovement in the reliability of electrical machines.

Five-axis CNC milling machine tools bring great facility to produce complex workpieces with increased dimensional accuracy and better surface quality in shorter machining times. However, kinematics of five-axis machine tools has a complex form which makes it difficult to operate these machine tools properly. The difficulty arises from the complexity of NC-Code generation and tool path verification. Collision of machine tool or setup components with each other is a severe problem in five-axis machining operations and usually results from inadequate postprocessors or insufficient collision checking due to absence of well-prepared simulation and verification programs. Five-axis CNC machine tool owners may get rid of this problem by purchasing commercial postprocessors, simulation and verification programs. However, these programs are expensive and small and medium enterprises (SME&rsquo / s) usually cannot afford the costs of these programs. In the related libraries of commercial programs, there is great number of CNC machine tools, which is generally unnecessary for SME&rsquo / s. An alternative to overcome this problem is to develop particular program, which is capable of postprocessing, simulating and verifying milling operations, for each certain five-axis CNC machine tool. In this study, a software named &ldquo / Manus 1.0&rdquo / , which performs postprocessing and simulation processes, has been developed for the high speed &ldquo / Mazak Variaxis 630-5X&rdquo / CNC five-axis machine tool, located in METU-BILTIR Center. Moreover, tool path verification algorithms have been developed to detect collisions. The software has been written in Borland C++ Builder5.0. The developed program has been tested in sample milling operations and satisfactory results have been achieved.

Enabling vehicles to preempt the normal operation of traffic signals has the potential to improve the safety and efficiency of both the requesting vehicle and all of the other vehicles. Little is known about which strategy is the most effective to exit from preemption control and transition back to the traffic signals normal timing plan. Common among these traffic signal transition strategies is the method of either increasing or decreasing the cycle length of the signal timing plan, as the process followed to return to the coordination point of the effected signal timing plan, to coordinate its operation with adjacent traffic signals. This research evaluates commonly available transition strategies: best way, long, short, and hold strategies. The major contribution of this research is enhancing the methodology to evaluate the impacts of using these alternative transition strategies. Part of this methodology consists of the "software-in-the-loop" simulation tool which replicates the stochastic characteristics of traffic flow under different traffic volume levels. This tool combines the software from a traffic signal controller (Gardner NextPhase Suitcase Tester, version 1.4B) with a microscopic traffic simulation model (CORSIM, TSIS 5.2 beta version). The research concludes that a statistically significant interaction exists between traffic volume levels and traffic signal transition strategies. This interaction eliminates the ability to determine the isolated effects of either the transition strategies on average travel delay and average travel time, or the effects of changes in traffic volume levels on average travel delay and average travel time. Conclusions, however, could be drawn on the performance of different transition strategies for specific traffic volume levels. As a result, selecting the most effective transition strategy needs to be based on the traffic volume levels and conditions specific to each traffic signal or series of coordinated traffic signals. The research also concludes that for the base traffic volume and a 40% increase in traffic volume, the most effective transition strategies are the best way, long or hold alternatives. The best way was the most effective transition strategy for a 20% increase in traffic volume. The least effective strategy is the short transition strategy for both the base and 40% increase in traffic volume, and the long and short for a 20% increase in traffic volume. Further research needs to be conducted to assess the performance of different transition strategies in returning to coordinated operation under higher levels of traffic volume (e.g., approaching or exceeding congested flow regime), with varying cycle lengths, with different signal timing plans, and when different roadway geometric configurations (e.g., turn lanes, length of turn lanes, number of lanes, spacing between intersections) are present. / Ph. D.

Wireless Sensor Networks (WSNs) are rapidly gaining popularity in various critical domains like health care, critical infrastructure, and climate monitoring, where application builders have diversified development needs. Independent of the functionalities provided by the WSN applications, many of the developers use visualization, simulation, and programming tools. However, these tools are designed as separate stand-alone applications, which force developers to use multiple tools. This situation often poses confusion and hampers an efficient development experience. To avoid the complexity of using multiple tools, a new, extensible, multi-platform, scalable, and open-source framework called PROVIZ is designed. PROVIZ is an integrated visualization and programming framework with the following features: PROVIZ 1) visualizes sensor nodes and WSN traffic by parsing the data received either from a packet sniffer (e.g., a sensor-based sniffer, or a commercial TI SmartRF 802.15.4 packet sniffer), or from a simulator (e.g., OMNeT); 2) visualizes a heterogeneous WSN consisting of different sensor nodes sending packets with different packet payload formats; and 3) provides a programming framework, which provides a graphical and script-based programming functionality, for developing WSN applications. Also, PROVIZ includes built-in extensible visual demo deployment capabilities that allow users to quickly craft network scenarios and share them with other users. Additionally, a secure and energy efficient wireless code dissemination protocol, named SIMAGE, was developed. SIMAGE is used by PROVIZ to wirelessly reprogram the sensor nodes. SIMAGE uses a link quality cognizant adaptive packet-sizing technique along with energy-efficient encryption protocols for secure and efficient code dissemination. In this thesis, the various features of PROVIZ's visualization and programming framework are explained, the functionality and performance of SIMAGE protocol is described, an example WSN security attack scenario is analyzed, and how PROVIZ can be used as a visual debugging tool to identify the security attack and aid in providing a software fix are discussed.