Current regulations specify the minimum number of operators required per nuclear power plant. However, these requirements are based on the operation of large nuclear power plants, which are not inherent safe and can result in a meltdown. For newly developed small nuclear reactors, the current number of operators seems to be excessive causing the technology to be less competitive. Before the number of required operators can be optimised, it should be demonstrated that human errors will not endanger or cause risk to the plant or public. For this study, a small pebble bed High Temperature Reactor (HTR) Nuclear Power Plant (NPP), the Th-100, was evaluated. The inherent safety features of this type of nuclear reactor include independent barriers for fission product capture and passive heat dissipation during a loss of coolant. The control and instrumentation architecture include two independent protection systems. The Control and Limitation System is the first protection system to react if the reactor parameters exceed those of the normal operational safe zone. If the Control and Limitation System fail to maintain the reactor within the safe zone, the Reactor Protection System would at that time operate and force the reactor to a safe state. Both these automated protection systems are installed in a control room local to the reactor building, protected from adverse conditions. In addition, it is connected to a semi-remote control room, anticipated as a multi-unit control room to include the monitoring and control of the auxiliary systems. Probable case studies of human error associated with multi-unit control rooms were evaluated against the logic of the Control and Limitation System. Fault Tree Analysis was used to investigate all possible failures. The evaluation determined the reliability of the Control and Limitation System and highlighted areas which design engineers should take into account if a higher reliability is required. The scenario was expanded, applying the same methods, to include the large release of fission products in order to verify the reliability calculations. The probability of a large release of fission products compared with studies done on other nuclear installations revealed to be much less for the evaluated HTR as was expected. As the study has proved that human error cannot have a negative influence on the safety of the reactor, it can be concluded that the first step has been met which is required, when applying for a waiver to utilise a multi-unit control room for the small pebble bed HTR NPP. Also, from the study, it is recommended that a practical approach be applied for the evaluation of operator duties on a live plant, to optimise the number of operators required. This in turn will position the inherent safe HTR competitively over other power stations. / MIng (Nuclear Engineering), North-West University, Potchefstroom Campus, 2015

By the emergence of electronic commerce and low transaction costs on the Internet, an interest in the design of new auction mechanisms has been arisen. Recently many researchers in computer science, economics, business, and game theory have presented many valuable studies on the subject of online auctions, and auctions theory. When faced from a computational perspective, combinatorial auctions are perhaps the most challenging ones. Combinatorial auctions, that is, auctions where bidders can bid on combinations of items, tend to lead to more efficient allocations than traditional auction mechanisms in multi-item multi-unit situations where the agents&rsquo / valuations of the items are not additive. However, determining the winners to maximize the revenue is NP-complete. In this study, we first analyze the existing approaches for combinatorial auction problem. Based on this analysis, we then choose three different approaches, which are search approach, descending simultaneous auctions approach, and IP (Integer Programming) formulation approach to build our models. The performances of the models are compared using computer simulations, where we model bandwidth allocation system. Finally a combinatorial auction tool is built which can be used for online auctions and e-procurement systems.

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No. of bitstreams: 1 DISSERTAÇÃO_GUILHERME_MARTINS_COM_FICHA_PARA_ENTREGA.pdf: 778800 bytes, checksum: abd1af0ff0730bab2c999d9451cbed9c (MD5) Previous issue date: 2018-06-19 / Muitas licitações públicas podem ser processadas sob um formato multiunitário, com a divisão de um objeto de características similares em diversos lotes ou mediante a reunião de diferentes bens em um mesmo procedimento. Desse modo, o presente trabalho busca refletir acerca da racionalidade que deve guiar a decisão sobre o fracionamento da licitação sob o prisma da análise econômica do direito. Valendo-se dos resultados teóricos obtidos pela Teoria dos Leilões, busca-se entender qual o comportamento esperado dos licitantes em diferentes tipos de leilões e como a referida teoria pode ser útil para estruturar da melhor forma possível as contratações públicas no Brasil a partir das regras postas para tanto. Com um diagnóstico em relação às principais características dos leilões multiunitários, é realizada uma análise dogmática de modo a concluir quanto à viabilidade de adoção de cada tipo no âmbito do direito brasileiro e quais cuidados devem ser tomados para uma correta implementação prática de cada modelo. O objetivo é identificar as situações em que cada tipo de leilão se torna mais recomendável e como configurar adequadamente os lotes postos à disputa, tudo de modo a otimizar os objetivos pretendidos pela contratação pública. A principal conclusão é a de que o modelo adequado de leilão, bem como a determinação e caracterização dos lotes, deve seguir os objetivos pretendidos pelo administrador. Outrossim, para além de modalidades tradicionais de licitação multiunitária, é possível implementar no Brasil modelos inovadores, tais como o leilão aberto simultâneo e o leilão combinatório, os quais, sob certas circunstâncias, tendem a trazer resultados melhores. / Many public procurement can be processed in a multi-unit format, by dividing an object of similar characteristics into several lots or by assembling different goods in the same procedure. In this way, the work aims to reflect on the rationality that must guide the decision regarding the fractionation of the bidding under the view of law & economics. Taking the theoretical results of Auction Theory into account, the goal is to understand the expected bidders’ behavior in different types of auction and how the theory can be useful to design public contracting in the best possible way based on the current applicable rules. With a diagnosis on the multi-unit auctions main features, a dogmatic analysis is carried out in order to conclude on the feasibility of each type under Brazilian law and what cautions should be observed for a correct practical implementation of each model. The objective is to identify the situations in which is recommended the adoption of each auction type and how to design correctly the lots put into auction, all in order to optimize the objectives intended by public contracting. The main conclusion is that the proper auction model, as well as the determination and characterization of lots, should follow the objectives intended by the administrator. Moreover, in addition to traditional multi-unit bidding modalities, it is possible to implement innovative models in Brazil, such as the simultaneous ascending auction and the combinatorial auction, which, under certain circumstances, tend to produce better results.

Depuis quelques années, l’étude du code neuronal impliqué dans la perception des signaux de communication acoustique est devenue un domaine de recherche considérable. La littérature récente de ce domaine suggère que la discrimination entre ces signaux reposerait plutôt sur une organisation des décharges neuronales en motifs temporels que sur des variations globales de taux de décharge. Ma thèse a eu pour objectif de déterminer dans quelle mesure une régulation des inhibitions corticales peut (i) changer les motifs temporels déclenchés par des vocalisations conspécifiques et hétérospécifiques et (ii) modifier l’information portée par ces motifs sur l’identité des vocalisations. Nous avons enregistré l’activité neuronale dans le cortex auditif de cobayes anesthésiés en 16 sites corticaux lors de la présentation d’un jeu de vocalisations, et avons partiellement bloqué les inhibitions corticales par des applications de Gabazine (4minutes, 10µm). Dans ces conditions, les réponses évoquées sont plus fortes et les motifs temporels plus marqués. L’information mutuelle quantifiée au niveau de chaque site cortical est augmentée mais l’information populationnelle au niveau de l’ensemble des 16 sites enregistrés n’est pas modifiée, un effet qui peut s’expliquer par le fait que la redondance entre les sites corticaux est augmentée. Nous avons ensuite évalué dans quelle mesure une modulation noradrénergique était susceptible de mimer les effets d’un blocage partiel des inhibitions. Bien que les agonistes utilisés (α1, α2 et ) aient tous induit des modifications des réponses évoquées et de la reproductibilité des motifs temporels, aucun d’entre eux n’a induit de changements importants de l’information portée par les réponses neuronales aux vocalisations. En revanche, les effets induits par la phenylephrine, un agoniste α1, sont vraisemblablement sous-tendus par une action sur les inhibitions intra-corticales, ce qui rend plausible l’hypothèse d’une modulation noradrénergique des inhibitions corticales. Il est donc envisageable que l’action coordonnée de plusieurs systèmes neuromodulateurs puisse moduler les inhibitions corticales et ainsi changer la quantité d’information portée par les neurones corticaux sur l’identité des stimuli à discriminer. / Over the last 10 years, the neural code involved in the perception of acoustic communication signals has become a large area of researches. The recent literature suggests that the discrimination between these signals relies more on the temporal organization of neuronal discharges rather than on global changes of firing rate. My PhD thesis aimed at determining to what extent the regulation of cortical inhibition may (i) change the temporal patterns triggered by conspecific and heterospecific vocalizations and (ii) modify the information carried by these patterns on the vocalization identity. Neuronal activity was recorded in the auditory cortex of anesthetized guinea pigs in 16 cortical sites during presentation of a set of vocalizations, and a partial blockage of intra-cortical inhibition was performed by Gabazine application (4 minutes, 10μm). Under these conditions, evoked responses were stronger and the temporal patterns were reinforced. Mutual information quantified at each cortical site was increased but the information computed at the populationnal level did not change, an effect that could be explained by the fact that the redundancy between cortical sites was increased. We then assessed to which extent the noradrenergic modulation can mimic the effects of a partial blockage of inhibitions. Although all the tested drugs modulated both the evoked responses and the spike-timing reliability, none of the noradrenergic agonists used here (α1, α2 and ) induced significant changes in the information carried by neuronal responses. However, the effects induced by phenylephrine, an α1 agonist, seemed to involve an action on the intra-cortical inhibition, which suggests that a noradrenergic modulation of cortical inhibition can operate in the auditory cortex. It is therefore possible to envision that the coordinated action of several neuromodulatory systems modulates cortical inhibition and thus changes the information carried by cortical neurons on the stimuli identity.

A crucial limitation of research on strategic planning is that it has always viewed strategic planning as a single process in a corporation. In practice, strategic planning in complex multi-business corporations has evolved into a network of multi-level and multi-unit strategic planning processes. This makes it challenging for managers and strategists to undertake the activities needed to run those strategic planning systems effectively. The interactions between strategy practitioners as they enact those planning processes play a crucial role in determining effectiveness of the planning process as a whole. Therefore, this thesis is based on a conceptual framework that represents strategic planning as a network of collaboration amongst quasi-independent processes taking place across multiple levels and units. This thesis adopts an embedded design within two in-depth case studies and one pilot case study to examine the strategising activities, practices and interaction dynamics of strategic planning within the M-form based firms. The result articulates the dynamics of strategy practitioners’ interactions in a series of four generic interaction patterns: (1) the Bilateral Scheme, (2) the Cohesive Facilitation Scheme, (3) the Ambassadorial Coordination Scheme, and (4) the Supervisory Driven Scheme. The result also sheds light on the extended roles of strategic planning within a multi-level and multi-unit environment, and on how different actors contribute to the vertical and horizontal aspects of strategic planning. The findings of this research have implications for both theory and practice. This thesis mainly contributes to strategy as practice perspective, strategic planning literature, organisational theory, situated learning literature, sensemaking perspective on practice, power theory, and agency theory. Theoretically, this study introduces a new method for examining the practice of strategic planning based on studying strategic planning links between practitioners representing horizontally as well as vertically differentiated units. In doing so, I have represented strategic planning as a multi-unit as well as a multi-level process, and hence have been able to show how it operates as a network of collaborative relationships and activities. This extends the view of strategic planning prevailing in the literature, which portrays a largely hierarchical, vertically-based structure. Practically, the results provide managers and practitioners with an illustration of how different practitioner roles and managerial levels contribute in distinctive ways to strategic planning from both horizontal and vertical perspectives. It is apparent from my investigation of the case study firms that their planning and decentralised decision-making mechanisms are linked together heterarchically as well as hierarchically.

Allocation of objects or resources to competing agents is a ubiquitous problem in the real world. For example, a federal government may wish to allocate different types of spectrum licenses to telecom service providers; a search engine has to assign different sponsored slots to the ads of advertisers; etc. The agents involved in such situations have private preferences over the allocations. The agents, being strategic, may manipulate the allocation procedure to get a favourable allocation. If the objects to be allocated are heterogeneous (rather than homogeneous), the problem becomes quite complex. The allocation problem becomes even more formidable in the presence of a dynamic supply and/or demand. This doctoral work is motivated by such problems involving strategic agents, heterogeneous objects, and dynamic supply and/or demand. In this thesis, we model such problems in a standard game theoretic setting and use mechanism design to propose novel solutions to the problems. We extend the current state-of-the-art in a non-trivial way by solving the following problems: Optimal combinatorial auctions with single minded bidders, generalizing the existing methods to take into account multiple units of heterogeneous objects Multi-armed bandit mechanisms for sponsored search auctions with multiple slots, generalizing the current methods that only consider a single slot. Strategyproof redistribution mechanisms for heterogeneous objects, expanding the scope of the current state of practice beyond homogeneous objects Online allocation mechanisms without money for one-sided and two-sided matching markets, extending the existing methods for static settings.

[ES] En los últimos años, el crecimiento y la complejidad de los sistemas multi unidad han planteado desafíos significativos en términos de mantenimiento y operación eficiente. Estos sistemas, compuestos por un conjunto de unidades independientes, como líneas de producción, redes de distribución, flotas de vehículos o infraestructuras complejas, requieren un enfoque estratégico para garantizar su funcionamiento óptimo y minimizar los costos asociados con el mantenimiento. El mantenimiento de los sistemas multi unidad implica la planificación y ejecución de actividades de mantenimiento preventivo y correctivo en cada una de las unidades que los componen. Esta tarea se vuelve aún más desafiante debido a las interacciones entre unidades, el conjunto de componentes que les permiten realizar su función y la necesidad de coordinar las actividades de mantenimiento de manera efectiva, considerando las limitaciones de recursos, los tiempos de inactividad y la optimización de los costos. En este contexto, los modelos de simulación se han convertido en una herramienta valiosa para el análisis y la optimización de sistemas multi unidad. Estos modelos permiten simular el comportamiento del sistema en diferentes escenarios, teniendo en cuenta variables como el rendimiento, la confiabilidad, la disponibilidad y los tiempos de mantenimiento. Asimismo, brindan la capacidad de evaluar diferentes estrategias de mantenimiento y apoyar la toma de decisiones para mejorar la eficiencia y la rentabilidad del sistema. El objetivo de esta tesis es desarrollar un modelo de simulación para la toma de decisiones sobre las políticas de mantenimiento en sistemas multi unidad, para lograr este objetivo se creó un simulador basado en sistemas de eventos discretos descrito formalmente en redes de Petri interpretadas y coloreadas de un sistema de flotas de unidades de componentes intercambiables y su gestor de mantenimiento. El simulador pretende analizar la interacción entre las unidades y evaluar el impacto de diferentes políticas de mantenimiento incluida la canibalización en el rendimiento global del sistema. Además, se buscará identificar las ventajas de esta política, su impacto en los tiempos de inactividad, disponibilidad y costos asociados. Mediante el estudio y la aplicación de modelos de simulación en sistemas multi unidad, esta investigación contribuirá al desarrollo de un enfoque sistemático y eficiente para la gestión del mantenimiento en entornos complejos cuando se hace uso de la canibalización como política híbrida complementaria a las políticas que comúnmente son utilizadas en los sistemas de mantenimiento de flotas. Los resultados obtenidos podrán ser aplicados en diferentes sectores industriales, como la manufactura, el transporte, la energía y la logística, entre otros, con el fin de ser más resiliente al retardo, carencia o sobre costo de componentes críticos de repuesto de su flota y que permitan comprender operacionalmente los efectos de utilizar políticas de canibalización en busca de mejorar la eficacia operativa y optimizar los recursos disponibles. / [CA] En els últims anys, el creixement i la complexitat dels sistemes multiunitat han plantejat desafiaments significatius en termes de manteniment i operació eficient. Estos sistemes, compostos per un conjunt d'unitats independents, com a línies de producció, xarxes de distribució, flotes de vehicles o infraestructures complexes, requerixen un enfocament estratègic per a garantir el seu funcionament òptim i minimitzar els costos associats amb el manteniment. El manteniment dels sistemes multiunitat implica la planificació i execució d'activitats de manteniment preventiu i correctiu en cadascuna de les unitats que els componen. Esta tasca es torna encara més desafiadora a causa de les interaccions entre unitats, el conjunt de components que els permeten realitzar la seua funció i la necessitat de coordinar les activitats de manteniment de manera efectiva, considerant les limitacions de recursos, els temps d'inactivitat i l'optimització dels costos. En este context, els models de simulació s'han convertit en una ferramenta valuosa per a l'anàlisi i l'optimització de sistemes multiunitat. Estos models permeten simular el comportament del sistema en diferents escenaris, tenint en compte variables com el rendiment, la confiabilitat, la disponibilitat i els temps de manteniment. Així mateix, brinden la capacitat d'avaluar diferents estratègies de manteniment i donar suport a la presa de decisions per a millorar l'eficiència i la rendibilitat del sistema. L'objectiu d'esta tesi és desenvolupar un model de simulació per a la presa de decisions sobre les polítiques de manteniment en sistemes multiunitat, per a aconseguir este objectiu es va crear un simulador a esdeveniments discrets descrit formalment en xarxes de Petri interpretades i acolorix-dones d'un sistema de flotes d'unitats de components intercanviables i el seu gestor de manteniment. El qual pretén analitzar la interacció entre les unitats i avaluar l'impacte de diferents polítiques de manteniment inclosa el canibalisme en el rendiment global del sistema. A més, es buscarà identificar els avantatges d'esta política, el seu impacte en els temps d'inactivitat, disponibilitat i costos associats. Mitjançant l'estudi i l'aplicació de models de simulació en sistemes multiunitat, esta investigació contribuirà al desenvolupament d'un enfocament sistemàtic i eficient per a la gestió del manteniment en entorns complexos quan es fa ús del canibalisme com a política híbrida complementària a les polítiques que comunament són utilitzades en els sistemes de manteniment de flotes. Els resultats obtinguts podran ser aplicats en diferents sectors industrials, com la manufactura, el transport, l'energia i la logística, entre altres, amb la finalitat de ser més resilient al retard, manca o sobre cost de components crítics de recanvi de la seua flota i que permeten comprendre operacionalment els efectes d'utilitzar polítiques de canibalisme a la recerca de millorar l'eficàcia operativa i optimitzar els recursos disponibles. / [EN] In recent years, the growth and complexity of multi-unit systems have posed significant challenges in terms of maintenance and efficient operation. These systems, composed of independent units, such as production lines, distribution networks, vehicle fleets, or complex infrastructures, require a strategic approach to ensure optimal operation and minimize the costs associated with maintenance. The maintenance of multi-unit systems involves the planning and execution of preventive and corrective maintenance activities in each of the component units. This task becomes even more challenging due to the interactions between units, the components that allow them to perform their function, and the need to coordinate maintenance activities effectively, considering resource constraints, downtime, and cost optimization. In this context, simulation models have become a valuable tool for the analysis and optimization of multi-unit systems. These models allow for simulating the system's behavior in different scenarios, taking into account variables such as performance, reliability, availability, and maintenance times. Additionally, they provide the capability to evaluate different maintenance strategies and support decision-making to improve the system's efficiency and profitability. The objective of this thesis is to develop a simulation model for decision-making regarding maintenance policies in multi-unit systems. To achieve this objective, a discrete event simulator was created, formally described using interpreted and colored Petri nets for a fleet system of interchangeable component units and its maintenance manager. This model aims to analyze the interaction between the units and evaluate the impact of different maintenance policies, including cannibalization, on the overall system performance. Furthermore, it seeks to identify the advantages of this policy, its impact on downtime, availability, and associated costs. Through the study and application of simulation models in multi-unit systems, this research will contribute to the development of a systematic and efficient approach for maintenance management in complex environments when using cannibalization as a hybrid policy complementary to the policies commonly used in fleet maintenance systems. The results obtained can be applied in various industrial sectors, such as manufacturing, transportation, energy, and logistics, among others, in order to be more resilient to delays, shortages, or over costs of critical spare components in their fleet and to operationally understand the effects of using cannibalization policies in the pursuit of improving operational efficiency and optimizing available resources. / Diaz Benachi, E. (2024). Marco de trabajo para modelar sistemas de gestión de mantenimiento de sistemas multi unidad, para la selección de políticas de mantenimiento incluida la canibalización evaluando fiabilidad en componentes [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/209809