220 research outputs found
Centralized and decentralized control of structural vibration and sound radiation
No full textThis paper examines the performance of centralized and decentralized feedback controllers on a plate with multiple colocated velocity sensors and force actuators. The performance is measured by the reduction in either kinetic energy or sound radiation, when the plate is excited with a randomly distributed, white pressure field or colored noise. The trade-off between performance and control effort is examined for each case. The controllers examined are decentralized absolute velocity feedback, centralized absolute velocity feedback control and linear quadratic Gaussian (LQG) control. It is seen that, despite the fact that LQG control is a centralized, dynamic controller, there is little overall performance improvement in comparison to decentralized direct velocity feedback control if both are limited to the same control effort
embalming and reperfusion of porcine kidneys
No full text<p>These are the data of the following article:</p>
<p>Understanding Thiel embalming in pig kidneys to develop a new circulation model</p>
<p>First author: Wouter Willaert</p
Does Indonesia have a"low-pay"civil service?
No full textGovernment officials and polcy analysts maintain that Indonesia's civil servants are poorly paid and have been for decades. This conclusion is supported by anecdotal evidence and casual empiricism. The authors systematically analyze the realtionship between government and private compensation levels using data from two large household surveys carried out by Indonesia's Central Bureau of Statistics: the 1998 Sakernas and 1999 Susenas. The results suggest that government workers with a high school education or less, representing three-quarters of the civil service, earn a pay premium over their private sector counterparts. Civil servants with more than a high school education earn less than they would in the private sector but, on average, the premium is far smaller than commonly is alleged and is in keeping with public/private differentials in other countries. These results prove robust to varying econometric specifications and cast doubt on low pay as an explanation for government corruption.Decentralization,Public Health Promotion,Health Monitoring&Evaluation,National Governance,Knowledge Economy,Health Monitoring&Evaluation,NationalGovernance,Knowledge Economy,Education for the Knowledge Economy,Parliamentary Government
Effects of Power and Heating Sector Integration for the Future Dutch High-Voltage Electricity Grid: Development of a Representative Model of the Dutch High-Voltage Electricity Grid
No full textWe are on the verge of a global energy system revolution. By signing and ratifying global treaties, the groundwork for this revolution is laid. The objective is to limit global warming to two degrees Celsius above pre-industrial levels and stabilise greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system, before 2050. This requires a carbon-free electricity system, which implicates that existing fossil sources of electricity need to be replaced by renewable sources. Most of these sources are weather-dependent and follow seasonal patterns. This leads to a variable, uncertain, and uncontrollable electricity supply. Energy system integration is posed as a key concept to provide the much-needed flexibility to the electricity grid and has been the subject of extensive research. However, there still is a considerable need for further research in the field of energy system integration. Part of the research gap is validation and substantiation of the proposed energy system integration policies and investment decisions. An indispensable component for filling the research gap is a numerical model of the energy system.In this context, the author of this thesis developed a numerical model of the Dutch high-voltage electricity grid. The model can be used to analyse proposed energy system integration policies, optimise the electricity system investment decisions, and prioritise the bottlenecks in the electricity system. The model is used to analyse the effects of several power and heating sector integration scenarios for 2050. The model is constructed in the pandapower framework. The framework is coded in the Python programming language. The model parameters are based on open data and the model input is derived from national sector outlooks and the Energy Transition Model from Quintel Intelligence. Due to the unavailability of operational data from the reference system, the accuracy of the model is determined by evaluating the underlying assumptions and performing a sensitivity analysis. Once the model is validated, the effects of power and heating sector integration on the Dutch high-voltage electricity grid are analysed and the bottlenecks are identified. The results show a substantial increase in grid loading. The highest grid loading occurs when a large portion of the heating demand is electrified, and a large portion of the electricity supply is generated by variable renewable energy sources.The bottleneck analysis of power and heating sector integration scenarios presents one of the use cases of the created representative model of the Dutch high-voltage electricity grid. As the model is based on open data, it is the intention of the author to make the model publicly available as well. This allows other entities to perform a broad range of analysis on the electricity system.Electrical Engineering | Sustainable Energy Technolog
Validation of TOPAS MC for modelling the efficiency of an extended-range coaxial p-type HPGe detector
No full textTOPAS MC software was used to model the efficiency of a coaxial p-type HPGe detector, type GX9023 from Canberra. The model was validated by comparing experimental efficiencies with efficiencies calculated by TOPAS MC simulations. Three different geometries of radionuclide sources, placed at different heights from the detector endcap, were used to validate the model. The imposed criteria of 5% relative difference was met for a range of radionuclides and gamma-ray energies. As a result, the created detector model with TOPAS MC was considered validated.The research was conducted under a PhD grant at Hasselt University. This work also received support from the open access scheme EUFRAT at the European Commission’s Joint Research Centre in Geel, Belgium. The author would also like to thank the developer team of TOPAS MC for the special licence allowing the use of TOPAS MC for gamma-ray spec-trometry application
Monitoring Variations in Thermal Curing of Nanoparticle Coatings through Confocal Raman Microscopy and Principal Component Analysis
No full textFor paper coatings with organic nanoparticles of poly(styrene-co-maleimide), dispersive Raman spectroscopy and confocal Raman microscopy are applied for qualitative and quantitative analyses of the lateral distribution of chemical moieties as a function of different coating grades (degree of imidization) and thermal curing temperatures (120-250 degrees C). Raman mapping with band intensity ratios, single band intensities, and average spectral intensities illustrates that surface locations with imide moieties are sensitive to the thermal curing temperature due to the reactivity of an amount of ammonolyzed (nonimidized) maleic anhydride, whereas the styrene moieties are not sensitive to the thermal curing. A maximum in imide functionalities at the surface occurs after curing at 135-150 degrees C depending on the coating grade. The surface coverage of the coating moieties is complementary to the cellulose components, but local variations in specific Raman bands for the latter suggest interactions due to hydrogen bonding. Principal component analysis with two parameters allows for a good quantification of the imide content and surface coverage.Samyn, P (reprint author), Univ Hasselt, Inst Mat Res IMO IMOMEC, Appl & Analyt Chem, Agoralaan Gebouw D, B-3590 Diepenbeek, Belgium.
[email protected]
Phase Behavior in the Active Layer of Small Molecule Organic Photovoltaics: State Diagram of p-DTS(FBTTh2)(2):PC71BM
No full textA comprehensive study was undertaken to obtain a more fundamental understanding of the phase behavior of the p-DTS-(FBTTh2)(2):PC71BM system, used in small molecule organic solar cells, with a strong focus on the amorphous phase and its influence on crystallinity. Three dedicated thermal protocols were used in combination with advanced thermal analysis, solid-state NMR, and wide-angle X-ray diffraction. Rapid cooling, to avoid structure formation and gain insight in the amorphous phase, and slow cooling, to promote structure formation, were used as limiting cases to explain the intermediate behavior after device processing from solution. A complete state diagram was developed, and the glass transition (T-g)-composition relationship was determined. In the case of slow cooling and the procedure used for device processing, the rapid crystallization of p-DTS(FBTTh2)(2) leads to an enrichment of the amorphous phase in PC71BM, increasing its T-g and causing vitrification of the mixed amorphous phase before crystallization when the total amount of PC71BM exceeds 70 wt %. The common processing additive 1,8-diiodooctane (DIO) was found to lead to a lower p-DTS(FBTTh2)(2) crystallinity and smaller average crystal size. More importantly, it acts as a strong plasticizer, lowering T-g significantly and thus reducing the morphological stability of the p-DTS(FBTTh2)(2):PC71BM mixtures.The authors acknowledge the financial support of the Agency for Innovation by Science and Technology (IWT) (Ph.D. fellowship to M.D.) and the Research Foundation - Flanders (FWO-Vlaanderen) (project G0B2718N and postdoctoral fellowship to P.V.). The XRD measurements were performed by Bart Ruttens in the group of Jan D'Haen at Hasselt University. This work is supported by Hasselt University and the Research Foundation Flanders (FWO-Vlaanderen; Hercules project GOH3816NAUHL).Van den Brande, N (reprint author), Vrije Univ Brussel, Phys Chem & Polymer Sci FYSC, B-1050 Brussels, Belgium.
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Robust Linear Quadratic Regulator: Exact Tractable Reformulation
No full textWe consider the problem of controlling an unknown stochastic linear dynamical system subject to an infinitehorizon discounted quadratic cost. Existing approaches for handling the corresponding robust optimal control problem resort to either conservative uncertainty sets or various approximations schemes, and to our best knowledge, the current literature lacks an exact, yet tractable, solution. We propose a class of novel uncertainty sets for the system matrices of the linear system. We show that the resulting robust linear quadratic regulator problem enjoys a closed-form solution described through a generalized algebraic Riccati equation arising from dynamic game theory.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Peyman Mohajerin EsfahaniTeam Bart De Schutte
Sustainable timber structures: Quantitative research evaluating the potential effects of carbon sequestration and cascading strategies in the Netherlands based on a comparison of the Dutch and European life cycle assessment methodologies
No full textTo meet the climate goals set by the government, the building sector needs to reduce its contribution to the environmental burden on society. However, the current situation in the Netherlands presents a major challenge to build more to reduce the housing shortage, while at the same time reducing its environmental footprint. Therefore, alternative solutions to the status quo should be considered, which can reduce the environmental impact of buildings. The goal of this thesis is to determine the environmental impact of multi-storey timber residential buildings and to make a comparison with a concrete building. Furthermore, the effect of cascading strategies on the environmental impact is analysed and the carbon sequestration potential by timber residential buildings estimated. Firstly, reference projects are studied to determine the trends in the timber construction sector. Based on these results, the main timber typologies and available design choices are mapped as well as the available (engineered) timber products available on the market. Secondly, the sustainability of timber structures is assessed by performing a literature study on three different scales: the macro-, meso- and micro-scale. The macro-scale represents the global forestry level in which the carbon cycle, carbon sequestration (i.e. capture and storage) and forest certification are discussed; the meso-scale represents the building level in which the durability and cascading strategies (i.e. strategies to elongate the lifespan) are discussed; the micro-scale represent the environmental impact of the material itself. Thirdly, the environmental impact is quantified using the fast-track life cycle assessment methodology. Two data sources are evaluated by performing a data analysis. The first being the ‘Nationale Milieu Database’ which is prescribed by the Dutch ‘Milieuprestatie Gebouw’, the second being Environmental Product Declarations according to the European EN15804 standard. For the two main timber typologies (mass timber and post&beam) a variant study is set-up using a parametric environment. The variant study analyses the environmental impact of main load bearing structures, the relative contribution of structural components and the effect of cascading strategies. The research is concluded by a case study in which the environmental impact of a timber alternative is compared with an equivalent concrete benchmark. Based on these results the global warming reduction potential of timber residential buildings is determined. From this research, it was shown that the environmental impact of timber buildings is lower than a concrete equivalent. However, it was found that the production capacity of engineered timber proved to be currently insufficient to reach the market potential, resulting in upscaling challenges for the engineered timber manufacturers when the demand will increase. From the data analysis, it was found that the selection of timber environmental data sources is highly sensitive. Furthermore, it was found that the choice for structural typology does not lead to significant differences for a default design lifespan. Though, the choice for a certain floor system does result in large differences. Overall, it can be concluded that a difference can be made to the environmental impact of the built environment by cascading scenarios, regardless of the choice of construction material. In case of timber structures, additional benefits occur due to the lower relative environmental impact and carbon sequestration.Civil Engineering | Building Engineering - Structural Desig
A Standardised Comparison Model for Offshore Wind to Hydrogen Concepts: Through Industry Validation and Promotion of Widespread Adoption Towards Improved Stakeholder Cooperation in the Energy Transition
No full textTo facilitate the energy transition, effective collaboration among all stakeholders is necessary. However, there is currently a lack of understanding regarding the impact of different components in the value chain on the energy system's overall structure and the final energy price. This knowledge gap poses a significant obstacle to cooperation and progress in the energy transition. It creates the risk that effort goes into developing certain partial solutions when they may not be feasible from a larger system perspective. By focusing on their own component, stakeholders do not fully take into account the needs and interests of others involved. As the development of green hydrogen projects is in its early stages, it is important to think in terms of systems. Stakeholders should establish an ecosystem where players operating in different parts of the value chain are collaborating together. This helps to de-risk projects, share lessons and promote the development of innovative, first-mover initiatives.This study aims to develop a standardised method to evaluate offshore wind to hydrogen concepts through a techno-economic analysis. This analysis method combines technical analysis with economic evaluation of projects and concepts to determine the potential economic outcomes and impacts of implementing a particular technology or project.Through stakeholder interviews, the study found that stakeholders in the offshore wind and hydrogen market have distinct objectives and concerns. Key factors influencing their willingness to contribute include confidentiality, competition, and reputation.To increase the transparency of the model, it was developed in Python. A standard notation system was developed, which was presented alongside the model's results. This should aid in the understanding of the underlying assumptions.Civil Engineering | Hydraulic Engineerin
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