Esta tese identificou vários aspectos importantes da estrutura trófica e dinâmica de nutrientes em ecossistemas aquáticos sujeitos a perturbações externas, tais como mudanças no nível da água, aumento de carga de nutrientes e matéria orgânica, biomanipulação e clima. Para descrever tais efeitos sobre a estrutura trófica, um complexo modelo ecológico, com base em processos físicos, químicos e biológicos, foi desenvolvido e aplicado em ecossistemas aquáticos tropicais, subtropicais e temperados. Em tais aplicações, uma análise integrada foi empregada considerando a transferência de impactos da bacia para o ecossistema, com a finalidade de entender a real dinâmica dos ecossistemas aquáticos. As simulações revelaram importantes aspectos sobre a estrutura e funcionalidade dos ecossistemas frente as pertubações. Por exemplo, a lagoa Mangueira, um lago raso subtropical no sul do Brasil, pode oscilar entre dois estados alternativos estáveis (alta e baixa transparência da água), dependendo da concentração de ortofosfato e da túrbidez. Foi sugerido também que podem ocorrer profundas alterações na composição do fitoplâncton com a aumento sistemático da concentração de ortofosfato. Foram constatados significativos gradientes horizontais e verticais na estrutura trófica da lagoa Mangueira, indicando a importância de considerar a heterogeneidade espacial em grandes lagos para melhorar a compreensão dos processos ecológicos e padrões. Cenários críticos de simulação indicaram que o aumento da carga de nutrientes afeta negativamente a transparência da água, diferentemente do efeito de mudanças climáticas. Pequenas alterações na estrutura trófica causadas por esses fatores indicam uma forte resistência da lagoa Mangueira. O modelo ecológico também foi útil para descrever a dinâmica do ecossistema, antes e depois da biomanipulação do lago Engelsholm localizado na Dinamarca. Nesse caso, o modelo conseguiu razoavelmente prever a mudança para um estado de alta transparência da após a biomanipulação, entretanto a mudança na composição do fitoplâncton foi muito mais difícil de representar. Além disso, aplicações mais simples também auxiliaram o processo de tomada de decisão e planejamento. A modelagem ecológica aplicada em ecossistemas aquáticos mostrou ser uma alternativa promissora para a gestão integrada dos recursos naturais. / This thesis identified several important features of the trophic structure and dynamics of nutrients in ecosystems subjected to external disturbances such as changes in the water level, nutrient and organic matter loading, fish communities and climate. To describe such effects on trophic structure, a complex ecological model, based on physical, chemical and biological processes has been developed and applied in tropical, subtropical and temperate aquatic ecosystems. In such applications, an integrated analysis was employed considering the transfer of impacts from the watershed to the ecosystem, in order to bring closer the understading of the ecosystem dynamics. Simulations revealed important features about system structure and functionality in front of disturbances. For instance, lake Mangueira a subtropical lake in Southern Brazil can oscilate between two alternative steady stables (clear or turbid water), depending orthophosphate concentration and water transparency. It was also suggested that can occurs profound changes in phytoplankton composition from increase of orthophosphate concentration. Horizontal and vertical gradients in the trophic structure are notable in lake Mangueira, indicating the importance to consider spatial heterogeneity in large lakes to improve understanding of ecological processes and patterns. Simulation scenarios indicated that increased nutrient loading negatively affects water transparency, differently from climate changes. Slight changes in trophic structure caused by those factors indicate a strong resistence of the lake Mangueira. The ecological model also was useful to describe the ecosystem dynamics before and after biomanipulation of lake Engelsholm located in Denmark. In that case, the model could reasonably well predict a shift to a clear water state, but the changed composition of phytoplankton functional groups was much more hard to represent. Furthermore, simpler applications also provided support for decision making and planning in the ecosystem. Ecological modeling applied in aquatic ecosystems showed be a promising alternative towards the integrated management of natural resources.

No description available.

In the first part there are theoretical basis of work performance. The essential stages of the work performance process are described. The object of the analysis in the practical part is the process of work performance and its stages. The work mostly focuses on the stage of goal setting and monitoring of work performance. The impact of the most recent changes was examined through research and survey on the satisfaction of the employees with the new BI system. In the conclusion there are stated few possible changes that can be made to improve the system and work performance in the company.

<p><a>Disruptive events during recent decades have highlighted the vulnerabilities of complex systems of systems to disruption propagation: </a>Disruptions that start in one part of a system and can propagate to other parts. Such examples include: Fire spreading in building complexes and forests; plant/crop diseases in agricultural production systems; propagating malware in computer networks and cyber-physical systems; and disruptions in supply networks. The impacts of disruption propagation are devastating, with fire causing annual US$23 billion loss in the US alone, plant diseases/crop reducing agricultural productivity 20% to 40% annually, and computer malware causing up to US$2.3 billion loss per event (as a conservative estimate). These problems, the response to disruption propagation (<a>RDP</a>) problems, are challenging due to the involvement of different problem aspects and their complex dynamics. To better design and control the responses to disruption propagation, a general framework and problem-solving guideline for the RDP problems is necessary.<br></p><p><br></p> <p> </p> <p>To address the aforementioned challenge, this research develops the Collaborative Response to Disruption Propagation (<a>CRDP</a>) unifying framework to classify, categorize, and characterize the different aspects of the RDP problems. The CRDP framework allows analogical reasoning across the different problem contexts, such as the examples mentioned above. Three main components applicable to the investigate RDP problems are identified and characterized: (1) The client system as the victims; (2) The response mechanisms as the rescuers/protectors; and (3) The disruption propagation as the aggressors/attackers. This allows further characterization of the complex interactions between the components, which augments the design and control decisions for the response mechanisms to better respond to the disruptions. The new Covering Lines of Collaboration (<a>CLOC</a>) principle, consisting of three guidelines, is developed to analyze the system state and guide the response decisions. The first CLOC guideline recommends the network modeling of potential disruption propagation directions, creating a complex network for better situation awareness and analysis. The second CLOC guideline recommends the analysis of the propagation-restraining effects due to the existence of the response mechanisms, and utilizing this interaction in optimizing response decisions. The third CLOC guideline recommends the development of collaboration protocols between the response decisions to maximize the coverage of response against disruption propagation.</p><p><br></p> <p> </p> <p>The CRDP framework and the CLOC principle are validated with three RDP case studies: (1) Detection of unknown disruptions; (2) Strategic prevention of unexpected disruptions; (3) Teaming and coordination of repair agents against recurring disruptions. Formulations, analytics, and protocols specific to each case are developed. TIE/CRDP, a new version of the Teamwork Integration Evaluator (<a>TIE</a>) software, is developed to simulate the complex interactions and dynamics of the CRDP components, the response decision protocols, and their performance. The evaluator is capable of simulating and evaluating the complex interactions and dynamics of the CRDP components and the response decision protocols. <a>Experiment results indicate that advanced CLOC-based decisions significantly outperform the baseline and less advanced protocols for all three cases, with performance superiority of 9.7-32.8% in case 1; 31.1%-56.6% in case 2; 2.1%-12.1% for teaming protocols, and at least 50% for team coordination protocols in case 3.</a></p>

Cascading failures involve a failure in one system component that triggers failures in successive system components, potentially leading to system wide failures. While frequently used fault tolerant techniques can reduce the severity and the frequency of such failures, they continue to occur in practice. To better understand how failures cascade, we have conducted a qualitative analysis of 55 cascading failures, described in 26 publicly available incident reports. Through this analysis we have identified 16 types of cascading mechanisms (organized into eight categories) that capture the nature of the system interactions that contribute to cascading failures. We also discuss three themes based on the observation that the cascading failures we have analyzed occurred in one of three ways: a component being unable to tolerate a failure in another component, through the actions of support or automation systems as they respond to an initial failure, or during system recovery. We believe that the 16 cascading mechanisms we present and the three themes we discuss, provide important insights into some of the challenges associated with engineering a truly resilient and well-supported system.

Systems such as the power grid, world wide web (WWW), and internet are categorized as complex systems because of the presence of a large number of interacting elements. For example, the WWW is estimated to have a billion webpages and understanding the dynamics of such a large number of individual agents (whose individual interactions might not be fully known) is a challenging task. Complex network representations of these systems have proved to be of great utility. Statistical physics is the study of emergence of macroscopic properties of systems from the characteristics of the interactions between individual molecules. Hence, statistical physics of complex networks has been an effective approach to study these systems. In this dissertation, I have used statistical physics to study two distinct phenomena in complex systems: i) Cascading failures and ii) Shortest paths in complex networks. Understanding cascading failures is considered to be one of the “holy grails“ in the study of complex systems such as the power grid, transportation networks, and economic systems. Studying failures of these systems as percolation on complex networks has proved to be insightful. Previously, cascading failures have been studied extensively using two different models: k-core percolation and interdependent networks. The first part of this work combines the two models into a general model, solves it analytically, and validates the theoretical predictions through extensive computer simulations. The phase diagram of the percolation transition has been systematically studied as one varies the average local k-core threshold and the coupling between networks. The phase diagram of the combined processes is very rich and includes novel features that do not appear in the models which study each of the processes separately. For example, the phase diagram consists of first- and second-order transition regions separated by two tricritical lines that merge together and enclose a two-stage transition region. In the two-stage transition, the size of the giant component undergoes a first-order jump at a certain occupation probability followed by a continuous second-order transition at a smaller occupation probability. Furthermore, at certain fixed interdependencies, the percolation transition cycles from first-order to second-order to two-stage to first-order as the k-core threshold is increased. We setup the analytical equations describing the phase boundaries of the two-stage transition region and we derive the critical exponents for each type of transition. Understanding the shortest paths between individual elements in systems like communication networks and social media networks is important in the study of information cascades in these systems. Often, large heterogeneity can be present in the connections between nodes in these networks. Certain sets of nodes can be more highly connected among themselves than with the nodes from other sets. These sets of nodes are often referred to as ’communities’. The second part of this work studies the effect of the presence of communities on the distribution of shortest paths in a network using a modular Erdős-Rényi network model. In this model, the number of communities and the degree of modularity of the network can be tuned using the parameters of the model. We find that the model reaches a percolation threshold while tuning the degree of modularity of the network and the distribution of the shortest paths in the network can be used as an indicator of how the communities are connected.

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第20028号 / 情博第623号 / 新制||情||108(附属図書館) / 33124 / 京都大学大学院情報学研究科社会情報学専攻 / (主査)教授 石田 亨, 教授 多々納 裕一, 教授 山本 章博 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

In Europe, the prices of natural gas and electricity reached an all-time high during 2022. An approach tomitigate these high prices is to expand the district heating systems in urban areas, this will reduceelectric load as well as to increase the power production in combined heat and power plants. Districtheating has been the dominant heat supply technology in urban areas in Sweden since the 1980s.However, as the number of low energy buildings are increasing, district heating distribution losses mustbe reduced to ensure cost-efficient consumer demand supply. This has led to the idea of the 4th-generation district heating which is characterized by low distribution temperatures.The aim of this study is to simulate low temperature distribution systems in a planned future city districtusing a Python based simulation tool and compare the results with a conventional system. Threedifferent types of low temperature distribution systems are investigated: 1) domestic hot water andspace heating separated, 2) apartment heat exchangers, 3) a cascading low temperature system.Focus is on simulating the distribution losses, distribution temperature and mass flow in the area, butthe scope of the analysis also includes an investigation of the effect of lower return temperatures to thecombine heat and power plant. The result indicate which type of system is most beneficial to implementin this specific area.With regards of distribution losses and temperature drop performs the low temperature distributionsystem with apartment heat exchangers better than the cascading system and the system withdomestic hot water and space heating separated. The mass flow is highly dependent of the temperaturedemand in the heating systems in the buildings and is higher for all low temperature distributionsystems compared to a conventional system.

Yes / This paper presents the development and implementation of an Analytical Target Cascading (ATC) Multi-disciplinary Design Optimisation (MDO) framework for the steady state engine calibration optimisation problem. The case is made that the MDO / ATC offers a convenient framework for the engine calibration optimisation problem based on steady state engine test data collected at specified engine speed / load points, which is naturally structured on 2 hierarchical levels: the “Global” level, associated with performance over a drive cycle, and “Local” level, relating to engine operation at each speed / load point. The case study of a gasoline engine equipped with variable camshaft timing (VCT) was considered to study the application of the ATC framework to a calibration optimisation problem. The paper describes the analysis and mathematical formulation of the VCT calibration optimisation as an ATC framework, and its Matlab implementation with gradient based and evolutionary optimisation algorithms. The results and performance of the ATC are discussed comparatively with the conventional two-stage approach to steady state calibration optimisation. The main conclusion from this research is that ATC offers a powerful and efficient approach for engine calibration optimisation, delivering better solutions at both “Global” and “Local” levels. Further advantages of the ATC framework is that it is flexible and scalable to the complexity of the calibration problem, and enables calibrator preference to be incorporated a priori in the optimisation problem formulation, delivering important time saving for the overall calibration development process. / The research work presented in this paper was funded by UK Technology Strategy Board (TSB) through the CREO (Carbon Reduction through Engine Optimisation) project.

No / This paper presents the development of an Analytical Target Cascading (ATC) Multidisciplinary Design Optimization (MDO) framework for a steady-state engine calibration optimization problem. The implementation novelty of this research is the use of the ATC framework to formulate the complex multi-objective engine calibration problem, delivering a considerable enhancement compared to the conventional 2-stage calibration optimization approach [1]. A case study of a steady-state calibration optimization of a Gasoline Direct Injection (GDI) engine was used for the calibration problem analysis as ATC. The case study results provided useful insight on the efficiency of the ATC approach in delivering superior calibration solutions, in terms of “global” system level objectives (e.g. improved fuel economy and reduced particulate emissions), while meeting “local” subsystem level requirements (such as combustion stability and exhaust gas temperature constraints). The ATC structure facilitated the articulation of engineering preference for smooth calibration maps via the ATC linking variables, with the potential to deliver important time saving for the overall calibration development process.