746 research outputs found
Marketing Digital Products at Witteveen+Bos
No full textThis graduation thesis for the master Strategic Product Design at the Delft University of Technology is written as a research and advice report for the civil engineering and advice agency Witteveen+Bos. More specifically for the Digital Acceleration product-market combination (PMC). The report answers the following question: “Is Witteveen+Bos as an organization structurally fit for developing, maintaining and marketing digital products?”...https://youtu.be/PAFp5PyltcA Link to video showcaseStrategic Product Desig
Recent and future contributions of Delft University of Technology to smart grids
No full textIn this report, the recent and future contributions of experts and groups of Delft University of Technology (DUT) on the topic of smart grids (SG) are presented. This may provide guidelines on how DUT can contribute in current and future SG projects, such as the current TKI project on “Smart Grid Evolution (SGE): Developing a service platform for the Internet of Energy”. The SGE project is meant to prepare for the realization of a large-scale demonstration case in Netherlands, starting in June 2016. In this demonstration case, a smart grid with at least 100.000 connections will be constructed.1 The 3TU.Federation is involved to contribute to the development of a collaborative design and decision support environment based on state-of-the-art knowledge of smart grid concepts with appropriate tool support. The representatives of DUT are Jok Tang, Cees Witteveen and Kees Vuik. In the groups headed by Cees Witteveen and Kees Vuik, the topic of smart grids is under investigation. Some of the members of these groups are interviewed, and their input is the basis of this document. Also several experts from other groups and faculties of DUT are interviewed. The list of interviewed people is not exhaustive, but it can be interpreted as an overview of the total SG expertise that DUT possesses.Delft Institute of Applied MathematicsElectrical Engineering, Mathematics and Computer Scienc
The voice of the visual : visual learning strategies for problem analysis, social dialogue and mediated participation
No full textThe changing needs for innovative learning strategies in the life sciences results from the growing complexity of societal issues. Nowadays, complex societal issues are also called ‘wicked problems.’ Wicked problems are problems that do not have one single solution that is right or wrong, good or bad or true or false. These are problems in which many stakeholders are involved, all of them framing the problems and issues in a different way. Reflecting on the consequent changing role of scientists and the way they need to be trained, it is realized that innovative learning strategies are needed to enhance problem analysis. This PhD project explored visual learning strategies for problem analysis. In exploring these strategies, the project emphasized dialogue and participation by social actors, (future) practitioners and decision makers involved in wicked problem settings. The project had the twofold aim of exploring the potential of visual learning and defining the design and production of visual learning strategies. The project materialized in a design and research perspective on the production and use of visual learning strategies. The design track resulted in the development of the Visual Problem Appraisal (VPA) and Embedded Filming strategies. At the start of the project these strategies were used in settings of international master course work and adult education. As the project advanced, the attention also focused on using the strategies in the public domain, with a focus on public participation by silenced or overlooked social actors. The VPA design developed with the production and use of the ‘VPA Kerala’s Coast’ (2003 – 2008) and the ‘VPA AIDS & Rural Development in Sub-Saharan Africa’ (2005-2009). Core of the VPA design are filmed stakeholder narratives and a well elaborated methodological approach that creates a learning space where the VPA user meets with these stakeholders as part of a decision making process. The wicked problems addressed in these VPAs focus on integrated coastal zone management in Kerala, India, and on AIDS and rural development in Sub-Saharan Africa. Embedded Filming, designed and produced between 2003 and 2007, also focuses on HIV/AIDS and rural development professionalism in Sub-Saharan Africa and Asia. Embedded Filming involves participation in the production phase by combining action research with a learning process. The film crew, facilitators and participants form an integrated whole. The shared focus of VPA and Embedded Filming is reflected in similarities in the general production and use. The filming process of both strategies focuses on social actors, their perspectives and reflections on reality. This consideration for multiple realities and societal complexity in the films is further underlined in the absence of a voice over or otherwise a steering ‘outsider.’ Although VPA and Embedded Filming have strong similarities, they are also characterized by differences. VPA filming activities are not embedded in a wider activity as is the case for Embedded Filming. Editing in Embedded Filming differs from the editing style of the VPA interviews as it adheres more to conventional documentary editing. The distinctive visual language of each film style was highlighted in the found footage experiment. This experiment showed that the footage of the Embedded Filming series could not be used for the production of VPA narratives because of the film styles not being congruent. The visual learning strategies have been used in an array of situations and with a variety of audiences. They have shown the ability to bring complex realities and a diversity of stakeholders together in spaces of learning, reflection and change. The experiences obtained with Visual Problem Appraisal and Embedded Filming provided the empirical evidence that it is possible to design, produce and use specific visual learning strategies to achieve strategic learning objectives that enhance complex competences for action and change. Research on these experiences is documented in the various chapters of this dissertation. The first chapter provides the background to the study and elaborates on the research design. The second chapter gives a broad introduction to the design, production and use of the ‘VPA Kerala’s Coast.’ It describes the educational design of VPA and the operationalisation during the filming process in Kerala, India. The analysis of the production experiences led to a series of workshops to research the impact of the VPA in the public domain. The evaluation of these workshops provided indications for social learning and stakeholder dialogue. The third chapter elaborates on the effects of the VPA in higher professional education. The study is based on experiences with the ‘VPA Kerala’s Coast,’ lectured in 2007/08 and 2008/09. The VPA design deliberately incorporates a rich variety of instruction strategies to anticipate the diverse learning styles of students in the international and intercultural classroom with a prominent role for visual learning. Students are confronted with a variety of learning activities that provides a challenging environment. They are immersed in the reality of complex multi stakeholder settings and they are stimulated to learn about wicked problems that are not easy to solve. Facilitator’s instructions and precise feedback options stimulate students to reflect on their work and that of their peers. It makes students almost immediately aware of the effects of their actions and the way they learn. The assessment presented indicates that the VPA strategy is effective as a strong and attractive simulation. The created safe space provides students an opportunity to learn from their interaction with un-familiar stakeholders and the VPA enhances critical reflection on learning procedures and patterns. Besides elaborating on the impact in education the chapter also provides insight in the design process of this learning strategy. The fourth chapter presents the process of producing and testing the ‘VPA Kerala’s Coast’ as a complex and intriguing multidisciplinary and multicultural project. We wondered what made the project a success. Framing the project as a space of intercultural communication gave guidance to the questions that articulated our search to understand the process we had been immersed in. In this chapter the events are described and critical incidents are analyzed that occurred during the production and the use of the VPA. The outcome leads to valuable recommendations for international and intercultural teams working on similar production and research projects. The fifth chapter reports on Embedded Filming. The filming and the films of a series of workshops and courses for Rural Development Professionals in Ghana, India, Tanzania and Zambia are analyzed as tools for learning and social change for different audiences. Analyzing the production and consumption processes shows the interconnectedness of the filming and learning during the courses. The results indicate that the films contribute to improved rural development professionalism in the context of HIV/AIDS. Chapter six highlights the potential of ‘mediated participation’ as compared to live participation, especially regarding the inclusion of vulnerable and distanced stakeholders. Mediated participation was explored by studying the production and use of the ‘VPA AIDS & Rural Development in Sub-Saharan Africa’ in workshops in Congo DRC, Ghana, Tanzania, the Netherlands and Zambia. The qualitative assessment was based on production experiences, evaluations of participants, and debriefings of workshops. The results indicate that mediated participation is not just a second-best option to live participation. Mediated participation as operationalized in VPA-methodology offers an alternative to learning in face-to-face interactions. The concept of mediated participation that resulted from the study is perceived as a promising concept. This term is used to contrast live presence of silenced and overlooked stakeholders in processes of public participation with participation or representation of these stakeholders’ concerns through the use of media (film). Mediated participation refers in this study to the filmed narrative (or mediated presence) of direct stakeholders who otherwise wouldn’t be present in public policy making processes. Mediated participation enhances social inclusion and equity in problem analysis and decision making by other means than through live participation. The experiences in this study with the design, production and use of VPA and Embedded Filming indicate the relevancy of designing and producing specific visual learning strategies in the context of wicked problems in multi stakeholder settings and sustainable development. It was learned that a specific visual learning strategy requires a particular film style or visual language. It is not film in general that defines the outcome of a learning process; it is the conceptual design, grounded in specific learning and film theories and film making expertise that lays foundations for the process that can be induced by the film. The discussed visual learning strategies overcome physical, cultural and social barriers between vulnerable stakeholders and decision makers. The mediated encounters with ‘the Other’ and ‘meeting’ other realities in social dialogues turned out to contribute to problem analysis. Designing, producing and using visual learning strategies requires due attention, expertise and resources. <br/
Visintrek via het sluizencomplex IJmuiden
No full textDe aanwezigheid van de zeeforel (Sakni Trutta L.) rond het sluizencomplex met de nadruk op het buitenhavengebied. In opdracht van Rijkswaterstaat, Directie Noord-Holland is er door Witteveen+Bos Raadgevende ingenieurs b.v. een onderzoek uitgevoerd naar de aanwezigheid van zeeforel in het buitenhavengebied van het sluizencomplex IJmuiden. Het onderzoek betrof een vervolg op eerdere onderzoeken naar zeeforel in dit gebied en stond in het kader van de op handen zijnde renovatie van het sluizencomplex. In de planfase van deze renovatie is ruimte gereserveerd voor eventuele aanpassingen ter bevordering van de passagemogelijkheden voor diadrome vissoorten; dit als eventueel mocht blijken dat het sluizencomplex een barriere voor de in trek van deze vissen vormt. Het uitgevoerde onderzoek was erop gericht te bepalen hoeveel zeeforel zich op enig moment aan de zeezijde van het sluizencomplex bevindt. In dit kader is er gedurende eEm jaar met drie zalmsteken gevist, zijn er bevissingen met een spankuil uitgevoerd en is er een enquete onder de lokale sport- en beroepsvisserij gehouden (Bijlsma, 1991). De resultaten wijzen uit dat IJmuiden voornamelijk in het late najaar en de winter door zeeforel bezocht wordt. De aantallen zijn echter laag. Blijkens de enquete is dit waarschijnlijk al een groot aantal jaren het geval. Vooralsnog wordt het belang van IJmuiden voor de instandhouding van een zeeforelpopulatie gering ingeschat. Vanwege de lage aantallen kunnen er geen harde uitspraken gedaan worden met betrekking tot de vraag of IJmuiden een barriere voor de in trek vormt. Los van deze onzekerheid verdient het echter aanbeveling te streven naar een optimale passeerbaarheid van het sluizencomplex. Dit kan in verb and met de herintroductie van zalm van groot belang zijn. Het onderzoeken van de mogelijkheden om binnen de huidige infrastruktuur en het huidige gebruik van het sluizencomplex de passeerbaarheid te vergroten is in dit kader aan te bevelen. Omdat rekening gehouden moet worden met sterke aantalsfluctuaties tussen verschillende jaren (bijvoorbeeld als gevolg van fluctuaties in jaarklassterkte) verdient het tevens aanbeveling de visserij met de zalmsteken nog enkele jaren voort te zetten
Gluconate formation and polyol metabolism in Aspergillus niger
No full textThe capacity of A.niger to accumulate metabolites is remarkable. Under all conditions polyols accumulate in the cell and when mycelium in later developmental stages is considered, depending on the carbon source, aeration and external pH, polyols and/or organic acids can be formed in a very efficient way. The aim of this thesis was to obtain a better understanding of the mechanisms governing the metabolism and formation of these metabolites. The first part of this thesis reports a study of gluconic acid formation and the second part involves polyol metabolism in A.niger.The fungus has a general tendency to synthesize organic acids under conditions of good aeration and when sugars like D-glucose or sucrose are available. An important function of the organic acid synthesis might be the acidification of the medium. Combined with the removal of the sugars from the environment this may contribute to the competitiveness of the fungus. A.niger is tolerant to pH values as low as 1.5. When glucose is the carbon source and the culture is well aerated A.niger will produce at neutral or slightly acidic pH mainly gluconate, at very low pH values citrate formation will occur and at intermediate pH oxalate is formed. The result is that A.niger by the consecutive synthesis of a series of organic acids strongly acidifies the medium.In this thesis the formation of gluconic acid was studied in more detail. In Chapter 2 evidence is provided for a cell wall localization of glucose oxidase. Furthermore, it was shown that two catalases are induced in parallel with glucose oxidase, one intracellular (CAT III) and one localized in the cell wall (CAT IV). Two other catalases, also one intracellular (CAT I) and one localized in the cell wall (CAT II), are constitutively present. About 50% of the lactonase activity was measured in the culture fluid. Therefore it was concluded that the whole glucose oxidase system is localized extracellularly, and is mainly localized in the cell wail. The induction of the intracellular CAT Ill may be seen as a second defense barrier, detoxifying hydrogen peroxide that diffuses into the cell.The cell wall-localization of glucose oxidase combined with the easy detection of hydrogen peroxide produced in the enzyme reaction makes visualization of the enzyme in intact hyphae possible. This detection system was used to isolate a series of mutants with altered glucose oxidase induction. In Chapter 3 a phenotypic and genetic characterisation of these mutants is presented. The mutants were classified in 9 different complementation groups, 1 non-producing, 1 low producing and 7 overproducing mutants. From induction experiments with the wild type strain it was concluded that the carbon source and the dissolved oxygen level are main factors determining induction of glucose oxidase. One mutant was found which never synthesized glucose oxidase ( gox C). Only one of the mutant classes was no longer dependent on oxygen for induction ( gox B). Several mutant groups were found with a decreased glucose dependency of induction. Some of these were quite strong ( gox A and gox E) whereas others showed only a minor overproduction under conditions which are only weakly inducing in the wild type. The latter group might in fact influence glucose oxidase induction only indirectly. The genetic analysis provided the information necessary for the construction of recombinant strains containing different gox mutations and other genetic markers. This is essential for further analysis and also an important step in further strain breeding.In Chapter 4 the induction mechanism of glucose oxidase, lactonase and the catalases was analyzed in more detail. For this we used beside the wild type strain gox B, gox C and gox E mutants. These mutants had a clear and pronounced phenotype. It was shown that in a wild type strain induction of all three activities is found only when glucose is present and the culture is well aerated. Induction of all three activities was effected by the gox B mutation. Neither glucose nor high oxygen levels were required for induction. The glucose dependency of glucose oxidase and lactonase induction was affected by the gox E mutation. In this mutant catalase was unaffected and high oxygen was still required. Thus with the gox B and gox E mutants the effects which oxygen and glucose have on induction could be partly separated. None of the activities was induced in the gox C mutant. This mutant could be transformed to a wild type phenotype using the structural gene of glucose oxidase, thus indicating that the mutation concerns the structural gene. The glucose oxidase structural gene was isolated via antibody screening of a cDNA expression library and subsequent homologous screening of a genomic library using the cDNA clone as a probe. Northern blotting showed that both the oxygen and carbon source effects were influencing induction at the transcriptional level. No glucose oxidase mRNA was observed in the gox C mutant. The absence of induction of all three activities in this mutant indicates that glucose oxidase activity is required for induction. It could be shown that hydrogen peroxide, besides gluconate a product of the glucose oxidase reaction, is inducing both catalase and lactonase in this mutant. It was concluded that hydrogen peroxide is the main factor required for the induction of the three activities and that the gox B gene product is involved in mediating this effect. It explained the requirement of high oxygen levels for induction because glucose oxidase has a high K m for oxygen (K m =0.48 mM at 27°C, Gibson etal., 1964). Even the glucose requirement for induction can be explained this way but the presence of the gox E mutant and the fact that the carbon source was still affecting the level of glucose oxidase in the gox B mutant, which is supposed to be involved in the transduction of the hydrogen peroxide signal, indicates that the induction process is more complicated. Using the plasmid plM503 which carries the structural gene for glucose oxidase multicopy transformants were made. Only a relatively small increase in glucose oxidase activity was observed (3 fold) even though more than 50 copies of the gene were integrated. Transformation of A.nidulans, a fungus that does not have the glucose oxidase gene itself, resulted in strains which produced glucose oxidase. In these strains glucose but not a high oxygen concentration was required for induction. This is indicating that a gox B-like gene is not present in A.nidulans but that the glucose requirement is presumably transduced by a more general system which is not specific for glucose oxidase.Chapters 2,3 and 4 are contributions to a better understanding of how the glucose oxidation system functions and of the molecular mechanism of its induction. Thus far it is the only coordinately regulated enzyme system in A.niger of which regulatory mutants have been isolated and which has been worked out in some detail. However, the understanding of the mechanism is still incomplete, especially the way by which the carbon source is affecting the induction is still unclear. No explanation is yet available why on fructose or D-xylose a basal level of glucose oxidase is found, whereas on acetate, gluconate or glycerol no activity is detected. Somehow the system senses the presence of an easy metabolisable carbon source and low-level induction occurs. The mechanism behind this phenomenon is probably not glucose oxidase-specific since in the A.nidulans transformants still glucose is required for induction. The gox B system is probably more glucose oxidase specific and therefore no oxygen (H 2 O 2 ) effect is found in A.nidulans. For a better understanding of the factors involved in glucose oxidase expression, a detailed analysis of the gox A and gox E mutants and of the functioning of the promoter of glucose oxidase is required. An important consequence of the regulatory mechanism hypothesized in Chapter 4 is a build-in feedback control. Catalase is not only induced by hydrogen peroxide but degrades this inducer as well, thus diminishing the induction. Ever increasing amounts of especially oxygen will be required to cause induction to continue. This will not happen because oxygen is quite soon the limiting factor in gluconate fermentation processes. The feedback mechanism of preventing overinduction is absent in gox B mutants. Therefore these mutants might be valuable in industrial processes.The function of the polyols is different from that of the organic acids. This is already clear from their presence in the fungus during all phases of the life cycle. Organic acids are formed only in late stages of development. Furthermore, the organic acids are excreted whereas the polyols beside being excreted also accumulate in large amounts in the mycelium. Information on carbon metabolism and more specifically polyol metabolism in A.niger was scarce at the start of this project. Therefore it was decided to analyze some metabolic pathways which directly relate to polyol metabolism.In Chapter 5 the characterization of a glycerol kinase mutant is described. Glycerol is one of the main polyols accumulating in A.niger and it was shown that glycerol kinase is involved in the degradation of glycerol. It could be demonstrated that the degradation pathway of glycerol in A.niger is largely the same as in A.nidulans (Hondmann et al., 1990) and N.crassa (Courtright 1975). First phosphorylation to glycerol-3-phosphate occurs and this is followed by its oxidation to dihydroxyacetonephosphate by a mitochondrial FAD-dependent glycerol-3- phosphate dehydrogenase. However, there were some differences with the pathway in A.nidulans. Whereas in the latter fungus dihydroxyacetone was catabolized via glycerol, in A.niger a dihydroxyacetone kinase was present enabling growth of the glycerol kinase mutant on dihydroxyacetone. Combined with an NAD +-dependent glycerol dehydrogenase converting glycerol into dihydroxyacetone this formed an escape route for glycerol catabolism in the glycerol kinase mutant. Growth on D-galacturonate was strongly affected in the glycerol kinase mutant thus demonstrating a D-galacturonate degradation pathway via glycerol.Pentose metabolism is described in Chapter 6. The isolation of a D-xylulose kinase mutant played an essential role in this work. It could be demonstrated that L-arabinose and D-xylose are catabolized via a series of reduction and oxidation steps. L-arabinose is reduced to L-arabitol which is oxidized to L-xylulose. L-xylulose is reduced to xylitol which is oxidized to D-xylulose that is phosphorylated to D-xylulose-5-phosphate, an intermediate of the pentose phosphate pathway. D-xylose is reduced to xylitol and subsequently oxidized to D-xylulose-5-phosphate. All the reduction steps are NADPH-dependent and all the oxidation steps NAD +-dependent The equilibrium of the reactions is far in the direction of the polyols, so several unfavourable steps that have to be taken which potentially can obstruct an efficient conversion of L-arabinose to D-xylulose-5- phosphate. The cofactor specificity of the dehydrogenases involved contributes to a higher efficiency since the anabolic reduction charge ([NADPH]/([NADPH]+[NADP +])) is higher than the catabolic reduction charge ([NADH]/([NADH]+[NAD +])) (Führer et al., 1980). A second mechanism for increasing the efficiency of this pathway was found by studying the two xylitol dehydrogenases of the L-arabinose pathway. This is described in Chapter 7. The NADPH-dependent L-xylulose reductase, catalyzing the reduction of L- xylulose to xylitol, was purified and the NAD +-dependent xylitol dehydrogenase, catalyzing the oxidation of xylitol to D-xylulose, was partially purified. Comparison of the two enzymes, which catalyze similar reactions leading to the different stereoisomers, made clear that they differ in two major points. 1) When their affinity for xylitol was compared it was found that the NAD +-dependent enzyme had a much higher affinity for xylitol than the NADPH-dependent enzyme. 2) Near the physiological pH (around 7) the ratio of the rductive relative to the oxidative catalytic activity was higher for the L-xylulose reductase than for the xylitol dehydrogenase. Both characteristics contribute to a more efficient catalysis of the reaction in the in vivo direction.In Chapter 8 an attempt is made to obtain some information on the function of the various polyol pools in A.niger. It was found that glycerol was the main polyol involved in osmotic adjustment in the fungus. Furthermore, glycerol accumulation was observed to be related to fast growing hyphae, whereas mannitol and erythritol accumulated in older hyphae. Mannitol also was an important storage compound in conidiospores. This general scheme of polyol accumulation during different growth phases is modified by environmental parameters like aeration of the culture and the nitrogen source available. Changes in fluxes through metabolic pathways and as a result of that changes in the steady state concentrations of intermediary metabolites from which the polyols derive, presumably play a role in this. It also implies that the function of the polyols in the cell is not completely coupled to specific polyols but can, in part, be taken over by other polyols. It was observed that a considerable part of the accumulated polyols (>50% after 24 h) is found in the medium. Observations made with the glycerol kinase mutant suggested that polyol excretion is a way for the fungus to control the intracellular levels of the polyols, presumably for maintaining the osmotic balance of the cell. Long fermentations (5 days) showed that in late developmental stages the polyol excretion becomes more pronounced. Approximately 45% of the glucose taken up was converted into extracelluar polyols. The type of the polyols excreted was a reflection of the intracellular polyol pool composition.Chapters 5 and 6 describe glycerol and pentose catabolism which has led to a better understanding of carbon metabolism in A.niger. Information on this subject is scarce in this fungus. The isolation of mutants in the degradation of such compounds is quite essential for metabolic studies. It turned out to be very difficult to isolate mutants in carbon metabolism in A.niger and still only a few of these mutants are available now. The reason for this is not known but the high intracellular polyol pools and the excretion of the polyols, resulting in crossfeeding during the filtration enrichment techniques, might play a role in this. The analysis of pentose metabolism and the xylitol dehydrogenases involved is also valuable in the light of understanding the mechanisms that play a role in extracellular enzyme production. The knowledge of the L-arabinose catabolic route has already proven useful in the analysis of the araban degrading system of A.niger. L-arabitol plays a major role in this (vd Veen et al., 1993). The analysis of polyol accumulation in Chapter 8 indicates that different polyols accumulate in different parts of the hyphae depending on their age. There still remains the question whether specific polyols accumulate in specific compartments of the cell, for example in the vacuoles, which are abundant in older hyphae. No information is available on this. It was shown that polyol excretion is a general phenomenon in A.niger. Although it has been observed before (Röhr et al., 1987), it was not considered to be such a common phenomenon in this fungus. The observation of large scale polyol accumulation in the culture fluid of 3-5 days old mycelial cultures grown under low oxygen conditions suggests similarities with organic acid fermentations. These are performed in strongly aerated cultures. An efficient flux to the TCA cycle is apparently not possible under the low aeration conditions used. This results in overflow metabolism in an earlier stage of the catabolic pathway leading to polyol formation. Cofactor regeneration might as well play a role in the polyol accumulation under these conditions
Coordinating autonomous planning and scheduling
No full textSoftware TechnologyElectrical Engineering, Mathematics and Computer Scienc
Fuzzy argumentation for trust
No full textIn an open Multi-Agent System, the goals of agents acting on behalf of their owners often conflict with each other. Therefore, a personal agent protecting the interest of a single user cannot always rely on them. Consequently, such a personal agent needs to be able to reason about trusting (information or services provided by) other agents. Existing algorithms that perform such reasoning mainly focus on the immediate utility of a trusting decision, but do not provide an explanation of their actions to the user. This may hinder the acceptance of agent-based technologies in sensitive applications where users need to rely on their personal agents. Against this background, we propose a new approach to trust based on argumentation that aims to expose the rationale behind such trusting decisions. Our solution features a separation of opponent modeling and decision making. It uses possibilistic logic to model behavior of opponents, and we propose an extension of the argumentation framework by Amgoud and Prade to use the fuzzy rules within these models for well-supported decisions
Coastal erosion study Hoi An
No full textA feasibility study on coastal problems in Hoi An, Vietnam. Finding a solution for the erosion problem of the city of hoi An is affected by in the recent decades.Hydraulic EngineeringCivil Engineering and Geoscience
Context-Aware Route Planning
No full textIn context-aware route planning, there is a set of transportation agents each with a start and destination location on a shared infrastructure. Each agent wants to find a shortest-time route plan without colliding with any of the other agents, or ending up in a deadlock situation. We present a single-agent route planning algorithm that is both optimal and conflict-free. We also present a set of experiments that compare our algorithm to finding a conflict-free schedule along a fixed path. In particular, we will compare our algorithm to the approach where the shortest conflict-free schedule is chosen along one of k shortest paths. Although neither approach can guarantee optimality with regard to the total set of agent route plans — and indeed examples can be constructed to show that either approach can outperform the other — our experiments show that our approach consistently outperforms fixed-path scheduling.Network Architectures & Services (NAS)Electrical Engineering, Mathematics and Computer Scienc
Robust scheduling in an uncertain environment
No full textThis thesis presents research on scheduling in an uncertain environment, which forms a part of the rolling stock life cycle logistics applied research and development program funded by Dutch railway industry companies. The focus therefore lies on scheduling of maintenance operations on rolling stock in the railway industry. The first chapter describes some of the history of the Dutch railways, focusing on the rolling stock used, and it introduces the context in which NedTrain, a major Dutch rolling stock maintenance company, operates. While maintenance of rolling stock is not a new problem, recent changes in the field are identified in this chapter which introduce new challenges: the first is the declining involvement of maintenance experts in the procurement of new rolling stock, the second is the on-going demand for increasing efficiency. Based on this discussion, the goal of this thesis is to devise a method with which schedules can be created based on a flexible process. The schedules resulting from this method are to be both flexible, meaning that they can be adapted easily, and robust, meaning that they are resilient to the effects of uncertain events. Lastly, our goal is to create the schedules in such a way that the effects of disturbances in one team have little or no effect on any other teams in the same workshop. Chapter 2 examines existing research in the context of the formulated research goals. It is shown that the well-known Resource-Constrained Project Scheduling Problem (RCPSP) can be mapped to the problem of scheduling maintenance tasks on trains in the NedTrain workshops. The most important methods to solve the RCPSP are discussed, among which are many exact methods. Both the scale of the problem and the requirement of having a flexible schedule instead of a fixed time assignment for the tasks prohibit using these methods. Among the heuristic methods discussed, the Precedence Constraint Posting method turns out to be an especially good fit: it is able to solve large-sized problems very quickly, and it uses a Simple Temporal Network (STN) as a way of representing many different solutions to the original problem, offering a lot of flexibility. Based on the research discussed, research questions are formulated to answer the research goals. - The first question asks how to define criteria encapsulating the notion of flexibility as posed by our research goals, and how to measure the flexibility of a schedule. - The second question asks how we can make the best use of available flexibility to attain robustness. - The third question asks if there is also a way to extend the concept of temporal flexibility to include a form of sequential flexibility. - The last question asks how we can use our work on robustness to decouple schedules, ensuring that disturbances in the schedule for one agent have no impact on any other agents. The third chapter investigates criteria corresponding to our intuitive notion of flexibility in scheduling. The concept of interval schedules serves as a basis for this investigation: the idea is that each task in the schedule is assigned an interval from which its start time can be picked, and the length of all these intervals serves as a representation for the flexibility of the schedule. We show that flexibility measures in existing research lead to an over-estimation of the total available flexibility, because dependencies between tasks are not taken into account properly: simply adding the interval sizes for two dependent tasks causes over-estimation, because the picked time for one task can reduce the interval size for another task. Our first major contribution is an independence requirement for the creation of these intervals: we state that intervals should be constructed in such a way that any choice in one interval has no impact on the available choices in any of the other intervals. Our second major contribution is a method to actually construct such intervals, which results in a valid interval schedule for an \stn, allowing efficient schedule execution under dynamic circumstances. Additionally, we note that an interval schedule can also serve as a mechanism to decouple a schedule, giving a partial answer to the last research question. In the fourth chapter, we investigate how to make use of the available flexibility to ensure that schedules are robust. We show that having a maximal total amount of flexibility does not imply that the schedule is as robust as possible: maximization might lead to a very skewed distribution of flexibility over the schedule. Different ways of distributing flexibility over a schedule are proposed and analyzed in an experimental setting. From the experiments it can be clearly concluded that sacrificing some of the total flexibility to improve the distribution of flexibility can have a positive influence on the robustness of the schedule. We also propose a different maximization strategy: one which maximizes the minimum of the interval sizes for the schedule. This strategy is shown to work especially well for small delays. So far we only discussed strategies concerning temporal flexibility, i.e., those in which start times remain flexible instead of fixed. Chapter 5 introduces a novel representation of solutions for planning problems in which not all ordering decisions needed to avoid resource contention are made in advance. This is achieved by grouping tasks which need to be executed sequentially together, in such a way that either ordering of the tasks remains feasible during execution time. An analysis using simulation experiments shows that this technique results in higher robustness, at the cost of somewhat lower resource utilization. The proposed algorithm to construct such schedules offers limited control over the size of the grouped tasks. The experiments show a slightly counter-intuitive results: schedules with larger groups offer lower robustness than those with smaller groups. A plausible explanation is the fact that delays can occur at any place in a schedule. Having multiple smaller groups instead of a few very large ones increases the chance that such a delay can be compensated for using a task group.Software TechnologyElectrical Engineering, Mathematics and Computer Scienc
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