· · · Institutional Repository

The implementation of hub-and-spoke networks in intermodal transport is suggested as one of the potential solutions for helping to increase the intermodal market share. Traditionally, trains are shunted at hubs; this is a time-consuming process. Since the early 1990s a new type of intermodal terminal, specifically designed for fast tran-shipment at nodes in hub-and-spoke networks, has been introduced in Europe. These hub terminals could replace this time-consuming shunting. Studies on the new hub terminals suggest that they may perform more efficiently than shunting yards. However, a systematic comparison to reveal the operational and costs differences be-tween shunting and these new hub-terminals for a broad range of situations still lacks. The main objective of the study was to develop a model to identify favourable opera-tional conditions for new hub terminals to be implemented and to quantify their op-erational performances in relation to alternative hub exchange facilities. Simulation models were developed to study rail-rail exchange operations at new hub-terminals, hump and flat shuntings yard and road-rail terminals.

For housing associations, maintenance is an opportunity for high quality interaction with their tenants, and thus an opportunity for effectively influencing the quality of service delivery to tenants. Dutch housing associations have a market share of about one third of the entire Dutch housing stock. They spent around 2.8 billion euros a year on the maintenance of dwellings, of which external service suppliers account for approximately 90 percent. These suppliers can be seen as an extension of the housing associations in fulfilling their public tasks and private objectives. At the moment maintenance service delivery appears to be to the tenant of a suboptimal quality leading to a lower than potential tenant satisfaction. With this an essential part of the objectives of housing associations is not fulfilled optimally. This PhD-research reveals the essential determinants of maintenance service quality in order to promote tenant satisfaction. Commodity strategies for the purchasing of maintenance services are developed which make its optimization possible from the perspective of tenant satisfaction.

Positron emission tomography (PET) is a technique for imaging the 3-dimensional distribution of radio-labelled molecules in vivo. This technique plays an increasingly important role in preclinical research involving mice and rats. The small dimensions of these animals impose stringent requirements on both the image resolution and the sensitivity of dedicated small-animal PET systems. Monolithic scintillator detectors enable the construction of PET systems with a system resolution comparable to that of existing systems, but with a strongly improved sensitivity. The detectors consist of a monolithic piece of scintillation material (e.g. LSO) read out by one or more position-sensitive solid state light sensors, such as avalanche photodiodes (APDs). The position of annihilation photons impinging on the detector is derived from the distribution of scintillation light on the light sensors. In this thesis, the performance characteristics of several prototype detectors are determined experimentally and analysed using empirical models. Detector spatial resolutions comparable to the current state-of-the-art are obtained. The spatial resolution is found to be independent of the angle of incidence of the annihilation photons, permitting the use of a thick layer of scintillation material to maximise sensitivity, without degrading the image resolution away from the centre of the field of view (FOV). This is confirmed by Monte-Carlo simulations of PET scanners based on these detectors. These simulations yield image resolutions which are uniform over the FOV, and sensitivities of more than 3 times the current state-of-the art.

In this dissertation, we present bromide and iodide scintillators which have been investigated for the past four years. Three major groups of compounds were studied; lanthanide trihalides LnX3, (pseudo)-elpasolites M2ALnX6 and ternary halides AmLnnXo where M and A are alkali cations, Ln is a rare earth cation and X is a halide anion. Some materials show interesting gamma-ray-scintillation properties. LuI3: Ce3+, one of lanthanide trihalides, has a record high light output of 98,000 photons/MeV and a fast response of 35 ns. Other two groups, (pseudo)-elpasolites and ternary halides, show relatively low light yields. For thermal neutron scintillator, we focused with (pseudo)-elpasolites M2LiLnX6 and ternary halides LimLnnXo groups. Rb2LiYBr6: Ce3+ shows an excellent neutron peak resolution of 3.6%. This is the best neutron peak resolution ever reported. Together with the large Alpha/Beta ratio of 0.74, Rb2LiYBr6: Ce3+ offers the possibility of excellent neutron/gamma-ray discrimination. The highest thermal neutron scintillation light yield of 83,000 photons/neutron is also reported for Rb2LiYBr6: Ce3+.

The main aim of radiotherapy techniques is to deliver the dose to the target volume while sparing as much as possible the healthy tissue. Dose verifications prior the treatment of the patient are mandatory in order to guarantee high accuracy to the treatment. We have developed a 2D dose imaging system for dose delivery verification in hadron therapy. The system consists of two cascaded Gas Electron Multipliers (GEMs) in an Ar/CF4 scintillating gas mixture. A GEM is a copper clad thin kapton foil with a regular pattern of sub-mm holes. The primary electrons, created in the detector's sensitive volume by the incoming beam, drift in an electric field towards the GEMs and undergo gas multiplication in the GEM holes. During this process light is emitted by the excited Ar/CF4 molecules and detected by a mirror-lens-CCD camera system. The measured 2D light intensity distribution is proportional to the 2D distribution of the energy deposited in the sensitive volume by the hadron beam. When the thickness of a water bellows phantom, mounted upstream the detector, is varied from zero up to beyond the hadron range, a 3D dose distribution can be reconstructed easily. The response of the detector was studied in a proton, alpha and clinical carbon beam. The main result of this work is that the energy dependence of the detector response in high LET (Linear Energy Transfer) beams is quite small compared to state-of-the-art 2D dosimeters with a millimetre resolution. The scintillating GEM detector is a promising device for dose verification, especially in case of high LET beams for checking treatment plans composed of several beam energies. Its fast signal response opens the possibility for online monitoring of a 2D scanning beam as well.

The purpose of this thesis was to extend recent works on structure and dynamics of hydrogen bonded crystals to model biomolecular systems and biological processes. The tools that we have used are neutron scattering (NS) and density functional theory (DFT) and force field (FF) based simulation methods. The quantitative and parameterfree link (in the case of DFT methods) between structure and dynamics has been applied to strong hydrogen bonded crystals and bio-polymers such as collagen and DNA. In several SSHB crystals, DFT normal modes and molecular dynamics calculations revealed the mechanism of proton transfer as being driven by low frequency phonons. The natural extension of these methods was oriented to polymers. Due to the lack of long range order, obtaining structural information of amorphous bio-polymeric systems requires the determination of the amide bands, which are the vibrations of the peptide groups C(=O)-N-H. We have used the DFT and inelastic neutron scattering approach to determine the spectral profile of the amide-V band and therefore the packing of 2D molecular sheets in Kevlar and the signature of the tertiary structure in Collagen. Depending on the secondary structure, the trends of the amide-I band has been well reproduced for simple polypeptides chains like polyglycine and polyproline. Water surrounding the protein is a huge subject of research. Water molecules are linked together to form different amorphous hydration shells. DFT methods are seen to suffer from a poorly defined minimum in the PES, resulting in negative frequencies in a normal mode analysis. Using force fields methods overcomes this problem but introduces a parameterization of the total energy calculation. In DNA, the structure-dynamics-function that we have focused on is base-pair opening, which is related to various bio-physical processes like replication and transcription. We used force field methods and normal mode analysis to identify modes with base-pair opening character. The oriented DNA films for experiments were made using the wet spinning method and the equipment was successfully installed and modernized during the thesis at ILL.

Probabilistic techniques in engineering problems are needed because they provide a deeper understanding of failure mechanisms and occurrence probabilities than deterministic techniques. In addition, they draw our attention to the consequences of failure at an early stage in the design process. However, to achieve these advantages, a well-defined model of the structure together with a robust reliability technique is needed. On the other hand, complex engineering problems with complicated boundary conditions usually are analysed with the finite element technique as presented. The finite element method provides an implicit approximation to the limit state equation (LSE) that is far more accurate than other approaches. Therefore, if one wants to have the full advantage of the probabilistic approach one needs both an advanced model and a supporting reliability technique. Known reliability techniques can be classified in three levels according to their performance. For the reliability analysis of engineering structures a variety of methods is known, of which Monte Carlo simulation is widely considered to be among the most robust and most generally applicable. The absence of systematic errors and the fact that its error analysis is well-understood are properties that many competing methods lack. A drawback is the often large number of runs needed, particularly in complex models, where each run may entail a finite element analysis or other time consuming procedure. Variance reduction methods may be applied to reduce simulation cost. This study describes methods to reduce the simulation cost even further, while retaining the accuracy of Monte Carlo, by taking into account widely-present monotonicity in limit state equations or other prior information. This dissertation focuses on problems where a highly accurate estimate of the failure probability is required, but an explicit expression for the limit state equation is unavailable and the limit state equation can only be evaluated without loss of accuracy via finite element analysis or some other time consuming process.

The stability of natural circulation boiling water reactors is investigated with a strong emphasis on experiments. Two different facilities are used for such a task: the GENESIS facility (to which a void reactivity feedback system is artificially added) and the CIRCUS facility. In addition, numerical codes are also used in the investigation.

According to EC forecasts, if energy efficiency could be increased 1% annually until 2010, two-thirds of the potential energy saving in the EU could be achieved. This would comply with 40% of the EU's Kyoto obligation to reduce greenhouse gas emissions by 8% on the 1990 level by 2010-12, by cutting 200 million tonnes of CO2 emissions per year. Improving energy efficiency in existing buildings is often considered to be one of the most cost-effective ways of cutting carbon emissions. Current policy measures, however, seem to be decided with little reference to the specific needs of renovation in the housing sector instead of basing policy measures on detailed sets of requirements and actual costs. The research provides information for national governments in the EU on how to improve their sustainable building policies so as to increase carbon reductions in the existing housing stock. It addresses the question of the extent to which stronger government intervention is possible and necessary for circumnavigating barriers and the policy approaches that are likely to be feasible, effective, cost-efficient and legitimate.

Urban renewal through the large-scale restructuring of post-war neighbourhoods is a major challenge throughout Europe in the decades ahead. Current urban restructuring programmes in the Netherlands focus on the demolition and replacement of the existing housing stock. The motivation behind this strategy is creating a better social mix between 'poor¿ and 'better-off¿ households, to improve the general quality of the housing stock and to create a financially viable restructuring programme. The general aim is to improve various aspects of sustainability in urban neighbourhoods. Are demolition and replacement strategies the most effective and efficient way to achieve this objective? In this book, we examine the effects of demolition and replacement strategies on sustainability from different perspectives.

The passing by the European Parliament of the Energy Performance of Buildings Directive (EPBD) in 2003 obliges all European member states to implement energy regulations for buildings based on the concept of energy performance by the year 2009 ultimately. Given the importance of the development of innovations in energy technology, and a transition to a sustainable energy supply system, it is necessary that policy instruments for energy conservation in the building sector stimulate the development and diffusion of innovations. This thesis contributes to knowledge about the content of energy performance policy and concludes that the effect of Dutch energy performance policy in encouraging innovation is limited. Energy efficiency improvements, by energy performance policy, seem to have come from the overall optimisation of all the energy related features of residential buildings. Insulation levels improved, although not spectacularly. Efficiencies of heating technology improved, although this seems partly to be as a result of the ongoing development that started in the 1980s. The efficiency of fans used for ventilation improved, as did the efficiency of all sorts of auxiliary devices needed in heating technology, as well as the efficiency of heat recovery in balanced ventilation systems. Although energy performance policy seems to have contributed to the optimisation of all energy related features of residential buildings, it did not cause a breakthrough of innovative technology such as solar thermal systems or heat pumps. The study of the innovation system of the Dutch construction industry identifies how the project-based nature of the construction industry is an obstacle to "learning-rich" collaboration between the various stakeholders. The study contributes to the discussion about the impact of government policy for energy conservation in the building sector, in the context of climate change policy.

This dissertation discusses how the importance of river flow-sustained ecosystems for local communities can be quantified for the purpose of balancing water supply and demand in Integrated Water Resources Management. Due to the development of water resources, for example through the construction of reservoirs, the natural flow regime is altered which results in changes in the river and floodplain ecosystem. Environmental flows describe the river flow regime necessary to protect the river ecosystem. The importance of this ecosystem for peoples' food, income, health or other purposes, are referred to in this thesis as the human well-being values of environmental flows. The thesis provides an approach to quantify the relationship between river flows, the river ecosystem and human well-being values and discusses the application of this approach in two case studies, in Bangladesh and in Iran. The approach proved to facilitate a structured assessment and to yield additional useful information that can contribute to the enhancement of social equity in Integrated Water Resources Management.

This research concerns the fuel cycle and safety aspects of a Gas Cooled Fast Reactor, one of the so-called "Generation IV" nuclear reactor designs. The Generation IV Gas Cooled Fast Reactor uses helium as coolant at high temperature. The goal of the GCFR is to obtain a "closed nuclear fuel cycle", where only natural uranium is used as raw material, and only fission products are discharged to a repository. Uranium and heavier isotopes (plutonium, americium, etc) are recycled in the reactor and are eventually fissioned. Since the heavy isotopes determine the long-term radiotoxicity of the nuclear waste, application of a closed fuel cycle maximizes the energy output of the fuel material, and can significantly reduce the lifetime of nuclear waste. It is shown that it is possible to obtain a closed fuel cycle with the GCFR. Coated particle fuel and ceramic plate fuel are discussed as fuel candidates for GCFR. A theoretical framework is derived using a combination of eigenvalue perturbation theory and nuclide perturbation theory to estimate the Breeding Gain of the reactor, and the change of Breeding Gain due to changes of the initial fuel composition. It is shown that the GCFR has some potential as an actinide transmutation reactor. To increase the safety of the GCFR, passive elements have been designed to automatically shut down the reactor in case of incidents. These elements use liquid Li-6, which is introduced into special assemblies if necessary. It has been shown that with these elements the reactor can withstand transients without damage to the fuel. The research has been performed in a European framework.

The global petroleum demand is projected to increase in the next decennia as oil is expected to remain the primary source of energy around the globe contributing to approximately 40% of the total consumption. The production of high-quality fuels from crude oil involves physical separation steps but also catalytic processes to remove contaminants (hydrotreating), shift the boiling point (alkylation and hydrocracking) and increase fuel quality (isomerisation). In hydrotreating sulfur, nitrogen, oxygen and metal atoms are removed from the different petroleum streams and unsaturated hydrocarbons are hydrogenated. The main reasons for refineries to perform hydrotreating are of environmental and economic nature. Besides protection of downstream catalysts from poisoning by sulfur, stringent environmental legislation has been aimed at the reduction of sulfur oxide emissions from fuel combustion. The environmental regulations on transportation fuel quality and the diminishing supplies of lighter types of crude oil necessitate further improvement of hydrotreating processes. An important approach is then to further optimize the catalytic activity of hydrotreating catalysts. In spite of the substantial progress made in the fundamental understanding of the active phase morphology, the metal-support interaction and reaction mechanisms, many details about the nature and stability of the active sites have not yet been elucidated. One specific issue not widely addressed is the influence of the sulfidation pressure on the active phase in hydrotreating catalysts. In industrial practice, catalysts are brought in their active, sulfided form at elevated pressure. The main objective of the present study was to understand the effect of the sulfidation pressure on the active phase structure in CoMo and NiW catalysts

Dutch city dwellers take accessible green areas for granted. They might easily forget that considerable resources and regulations have been applied to protect and improve these areas. This dissertation considers the implications if, in line with the neo-liberalization of the state, this approach changes. A multi-theory approach based on Grounded Theory was developed as a methodological basis to the investigation. The limited applicability of Transaction Cost Theory was also explored. The analysis addresses why in many cases, cross-subsidizing green areas with built developments is not a viable financing solution. It explains why a combination of hierarchical and network-oriented approaches works best in practice. It investigates tensions between strategic spatial planning, operational spatial planning, and operational land development and their consequences for green metropolitan areas. It also explains why "Slow Planning" can help to preserve dynamic green areas near cities, and why this requires incremental institutional change.