30 research outputs found
Using a Physics-Informed Neural Network to solve the Ideal Magnetohydrodynamic Equations
No full textIn this work we investigate neural networks and subsequently physics-informed neural networks. Physicsinformed neural networks are away to solve physical models that are based on differential equations by using a neural network. The wave equation, Burgers’ equation, Euler’s equation, and the ideal magnetohydrodynamic equations are introduced and solved with physics-informed neural networks. The solutions to the first equations were captured well. The solution to the ideal magnetohydrodynamic equations contained some problems. These problems include transitions between different types of behaviour and exact values of constant sections. On the other hand, general shape and behaviour of the curve and locations of contact discontinuities were predicted well.Applied Mathematics | Applied Physic
Using Nearest-Neighbors to Evaluate Overlap in Causal Inference
No full textTo validate the results of a medical trial, there must be an overlap between the treatment and control groups. This implies the crucial need for good evaluation methods. This study, therefore, aimed to evaluate the overlap between causal classes using the Nearest Neighbours’ methods. Firstly, a case study was built around the common failures of those methods (i.e. dependencies on hyper-parameters and sensitivity to increasing features, samples, and outliers). Secondly, a comparison of the Nearest Neighbours to other already existing approaches was made, to determine if they vary from the standard solution. The results demonstrated that the methods can be used to assess overlap but had too much dependency on hyper-parameters, no drastic sensitivity to increasing sample and feature, and varied performance to outliers depending on their position. Additionally, the set of Nearest Neighbours methods predicted a smaller overlapping area compared to the established methods, emphasizing the caution with which the forecasts should be taken into account.CSE3000 Research ProjectComputer Science and Engineerin
Total Least Squares: Comparing Least Squares Methods for Signal Reconstruction
No full textA common problem in wireless communication is the existence of multipath propagation. This means that a transmitted signal is received multiple times because of reflections caused by the environment. We present two ways of modeling multipath propagation of an acoustic underwater signal. We discretise these models to solve them numerically. During the solving process, we are presented with inconsistent, overdetermined systems of linear equations. We investigate two methods to go about these systems: the ordinary least squares method and the total least squares method. We reconstruct a signal using both of these methods and compare their results. The method of least squares reconstructs the signal moderately well. For the total least squares method this is not the case. It turns out that it is not straightforward to formulate a total least squares problem in the corresponding model. We suspect that, in part, this is why the signal reconstruction does not work well for the total least squares method.Applied Mathematic
Optimization of a District Heating Network with the focus on heat loss
No full textIn the Netherlands most houses and buildings are connected to a gas network since the nineteen seventies to heat our houses and cook. In march of this year the new Dutch government announced that to meet the climate accord of Paris all dutch household should be of the gas net in 2030. To do this multiple alternatives to heat homes are available and one of those which has proven to be feasible over the last years is district heat. In a district heating network hot water is pumped round a city through a network of pipe lines to houses and other buildings. The network is split into a primary and a secondary network. In the primary network the heat is transported from the source, and in the secondary network the heat is pumped from a substation to the customers. The heat usually is rest heat of a STEG- or waste incineration power plant. With the increasing demand for heat due to the disconnection of the gas network, and at the same time the search for a more sustainable heat source for the district heating network like geothermal heat the prices and costs rise rapidly. This makes the heat loss in the system a more important issue also from a financial perspective. The current installed networks are all series 1 single pipe lines of ST/PUR/PE, this means the inner pipe through which the water flows is steal, followed by an insulating PUR layer which is covered by a protective PE layer. To decrease the heat loss from the pipe lines Nuon is looking at two possible options. Series 2 single piping which has a thicker insulating PUR layer and second the twin pipeline where both the steal supply and return lines areembedded into one insulating PUR layer and a protective PE shell. The heat loss calculations for the buried pipelines in the ground are done using empirical formulas found in literature. These are checked numerical using a pde-solver. Comparing both results it was the concluded the empirical formulas give a good approximation of the heat loss. It also showed the heat loss is for a great deal depended on the temperature in the pipe and the ground temperature. In current heat loss calculations done by Nuon the temperature gradient of the water entering the network and leaving the network in not taken into consideration. By using the ambient temperature and a formula formulated in literature an estimation of the ground temperature at the buried depth of the pipelines can be made. By dividing the network into a number of pieces with length 푑푥 and an individual temperature 푇 the temperature gradient overthe entire network is taken into account. Collected data by Nuon concerning the user demand and the ambient temperature makes it possible to simulate what is the mass flow through the system at any given time and to analyze how the system responds to a demand fluctuation. By analyzing what happens in the networks in term of heat loss during a diurnal heat curve the results show that the heat loss stays nearly constant during a day. There are however big differences between different days in different times of the year. Analyzing what happens over the course of a year especially in the summer during times of very low demand the system under performs. A main reason for this is caused by theminimum required temperature of 70 degrees Celsius at the customers due to salmonella regulations. This causes a lot of extra mass flow of hot water pumped around the system which heats up the return flow. This is also clearly notable from the efficiency of the network which drops tremendously in the summer. Comparing the difference in heat loss for the series 1, series 2 and twin system the results where as expected an decrease in the amount of heat lost, by 14.6% for series 2 and 39.70% for twin compared to series 1. The overall image of what happens actually stays the same with high return temperature and relative high heat loss and low efficiency in summer. There are a few options to further improve the performance of the system with a few percent by changing the inlet temperature or the location of the bypass valve. Financially speaking the twin system is also the better choice of the three. Compared to series 1 for series 2 the investment costs will increase because the materialsand instalment costs will increase. For the twin system the prices of the materials will increase and the placements of the welds will become more expansive however only half the number of pipe lines and joints is needed, so in total the prices will stay nearly the same compared to series 1. There is a lot of discussion on whether or not the maintenance costs will increase for the twin system, arguments for both cases are given. However the maintenance costs are so small compared to the costs of the heat loss that in every case the twin system is clearly the better choice.Mechanical Engineerin
FLASH optimisation in clinical IMPT treatment planning: optimisation and evaluation of stereotactic lung treatment plans with proton transmission beams
No full textRadiotherapy (RT) is an important modality in treatment against cancer. Developments in this modality are necessary for improvement of patient complications and survival. Aside from fractionation and precise irradiation, FLASH radiotherapy could be a third way to significantly increase the therapeutic window of radiotherapy.The FLASH effect is a biological, healthy tissue sparing effect that is found in tissue that receive a high dose (>10 Gy) within a very-short irradiation time (<100 ms). Although the mechanics behind the FLASH effect remain unknown, it is found to benefit a large variety of tissues and organs. Nevertheless, FLASH-RT still lacks clinical translation and implementation of FLASH irradiation is limited by current technology. However, the extremely high dose rates required for FLASH can readily be achieved using cyclotron accelerated proton transmission beams. Cancer patients with small lung tumours are a preferred starting point for clinical translation of FLASH because (i) transmission beams are of special benefit for lung tumours since they mitigate for range uncertainties and contain a sharp lateral penumbra, (ii) high doses are required for the FLASH effect to occur and hypofractionation is not uncommon for lung patients, and (iii) the very short irradiation times and high doses in combination with gating allow smaller treatment margins for moving tumours.In this study, we took a first step towards intensity modulated proton therapy (IMPT) with FLASH treatment plan optimisation by (i) investigating the most delivery-time effective way to irradiate a field, (ii) proposing an optimisation method to maximise FLASH within a treatment plan, and (iii)analysing and evaluating FLASH treatment plans. Because increased pencil-beam (spot) separation showed to benefit the pencil-beam scanning(PBS) delivery time of a field, spot overlap minimisation was proposed as optimisation method for FLASH. Treatment plans using 3, 5 and 7 transmission beams were generated with and without FLASH optimisation for 6 small lung tumour patients. Although spot overlap minimisation doesoccasionally improve delivery time for a limited number of beam angles, the overall treatment plan does not benefit from the optimisation. Therefore, spot overlap minimisation cannot be used for FLASH optimisation in clinical IMPT treatment planning. Recommendations for future research include optimisation on PBS delivery time and PBS pattern optimisation
Simulation of gravitational scatterings in <i>N</i> -body Kepler systems
No full textThis research investigates the impact of gravitational scatterings caused by close encounters between particles in an N-body Kepler system, addressing three main questions: (1) the influence of scatterings on system evolution, (2) the correspondence between simulated and expected average times between scatterings, and (3) the effect of increasing different parameters individually on the average scattering time. Simulations demonstrate an average scattering angle of 15.2 degrees for particles involved in the top 10 percent of scatterings. This would indicate a non-negligible impact of gravitational scatterings, especially for systems with heavier bodies. The results indicate that the simulated average time between scatterings is higher than the expected average, necessitating further research for accurate estimation. Moreover, the time between scatterings decreases over time, before reaching a stationary state after roughly 300 scatterings. On this domain, the correlation coefficient between the scattering time and the scattering counter was found to be -0.08. By varying the test domains for different parameters, a new expression for the expected time between two scatterings is proposed based on simulation data. A clear connection was found between the scattering time and the number of particles, the maximum orbital radius and the maximum inclination angle. The study acknowledges limitations, including the non-stationary initialization state and linear approximations to most computations, suggesting avenues for future improvement. Overall, this research aims to find the role of gravitational scatterings in Kepler systems and underscores the need to consider these interactions, which are now often considered to be negligible.Applied Mathematics | Applied Physic
The Revival of the Social Housing Community: Providing security and shelter for the urban poor
No full textAdequate housing has long been considered a basic human right. Trends of globalisation, financialisation and urbanisation are oppressing this right. Social housing is neglected by authorities and stigmatised by society. Local, low-income residents are dispossessed and displaced, and social housing is close to disappearance. London has become a fragmented and unequal city, with an unbalanced governance. The power of the private investors induces that residents cannot make use of their right to the city. To recover the right to the city for all residents and to counteract the displacement and dispossession, a shift has to be made towards a revival of the social housing community, providing secure tenure and quality housing for the entire population. This graduation project introduces a community land trust growth model. By gradually taking land out of the market into a CLT, the residents are able to make their own decisions and improve their living conditions. The model provides tenure security and permanent affordability. The project designs a transparent and modular People’s Plan with a holistic, multiscalar vision providing secure tenure and quality housing for the urban poor.Architecture, Urbanism and Building Science
Lateral subtalar dislocation: Case report and review of the literature
No full textA case of complicated lateral subtalar dislocation is presented and the literature concerning this injury is reviewed. Subtalar joint dislocations are rare and often the result of a high-energy trauma. Complications include avascular necrosis of the talus, infection, posttraumatic osteoarthritis requiring arthrodesis and chronic subtalar instability. Negative prognostic factors include lateral and complicated dislocations, total talar extrusions, and associated fractures. A literature search was performed to identify studies describing outcome after lateral subtalar joint dislocation. Eight studies including fifty patients could be included, thirty out of 50 patients suffered a complicated injury. Mean follow-up was fifty-five months. Ankle function was reported as good in all patients with closed lateral subtalar dislocation. Thirteen out of thirty patients with complicated lateral subtalar joint dislocation developed a complication. Avascular necrosis was present in nine patients with complicated injury. Four patients with complicated lateral subtalar dislocation suffered deep infection requiring treatment with antibiotics. In case of uncomplicated lateral subtalar joint dislocation, excellent functional outcome after closed reduction and immobilization can be expected. In case of complicated lateral subtalar joint dislocation immediate reduction, wound debridement and if necessary (external) stabilisation are critical. Up to fifty percent of patients suffering complicated injury are at risk of developing complications such as avascular talar necrosis and infection
Paediatric forearm fracture with a twist: a proximal radioulnar translocation combined with radial head fracture
No full textKnowledge Management Dynamics in Offshore Wind Farms in the Netherlands
Get PDFOffshore wind farm development is a is a highly complex process. The societal and political pressure to implement is high while environmental responses and future developments in the global energy network are uncertain. Moreover, many interests in maritime space are at stake. The dependency on knowledge for decision-making is high, but the capacity to use knowledge is limited. In this paper we investigate the role of ecosystem knowledge in offshore wind farm planning and management. We have identified 4 types of research arenas: (1) government driven (e.g., monitoring programs) (2) subsidized research (national or EU), (3) industrial or PPS (Public-private partnerships), and (4) research by universities. This study considers the way in which knowledge from different arenas is or could be taken up and used in policy. We identify that particularly government-driven research (monitoring) is used in policymaking. The analysis of policy documents, in-depth expert interviews and focus groups reveals that the distance between knowledge developers and knowledge users may differentiate from purely transactional relations to co-production-relations. However, co-production is rare beyond the monitoring programs directly initiated by the government agencies.Policy Analysi
