1,365 research outputs found
sj-docx-1-eso-10.1177_23969873221145771 – Supplemental material for Association between type of intervention center and outcomes after endovascular treatment for acute ischemic stroke: Results from the MR CLEAN Registry
No full textSupplemental material, sj-docx-1-eso-10.1177_23969873221145771 for Association between type of intervention center and outcomes after endovascular treatment for acute ischemic stroke: Results from the MR CLEAN Registry by Susanne GH Olthuis, Wouter H Hinsenveld, Florentina ME Pinckaers, Marzyeh Amini, Hester F Lingsma, Julie Staals, Tobien HCML Schreuder, Wouter J Schonewille, Lonneke SF Yo, Yvo BWEM Roos, Alida A Postma, Diederik WJ Dippel, Wim H van Zwam, Robert J van Oostenbrugge and Inger R de Ridder in European Stroke Journal</p
Digging through the dirt: a general method for abstract discrete state estimation with limited prior knowledge
No full textAutonomous robots are often successfully deployed in controlled environments. Operation in uncontrolled situations remains challenging; it is hypothesized that the detection of abstract discrete states (ADS) can improve operation in these circumstances. ADS are high-level system states that are not directly detectable and influence system dynamics. An example of a typical ADS problem that is used in this thesis is that of a wheeled robot driving through puddles of mud that, when entered, alters the velocity of the robot. When the robot is in such a puddle, it is in an ADS 'mud', and when it is not, it is in an ADS 'free'. ADS can be indirectly inferred through the analysis of lower-level data such as the velocity of the robot. The goal of this thesis is to design a general abstract discrete state estimator (ADSE) operating with limited prior knowledge. An ADSE is a hierarchical system for detecting changes in ADS. The ADSE should be general; applicable to multiple ADSE problems. The ADSE should further operate under limited prior knowledge: only assuming that the amount of ADS and the ADS that describes the regular operation are known. The basis for the ADSE designed in this thesis is a Gaussian hidden Markov model (GHMM), a hidden Markov model enhanced with Gaussian emissions. Randomly generated experiments are done on a simple but general ADSE problem. Two unsupervised learning methods derived from Expectation Maximization are evaluated, namely Baum-Welch (BW) and forward extraction (FWE). FWE is introduced in this thesis and is a simpler implementation of Viterbi extraction, leveraging assumptions of ADSE to in theory gain computational efficiency. We found that both BW and FWE exhibit superior performance compared to a likelihood-based baseline estimator when the maximum score of the learning curve is considered. When the final score is considered, in some cases, FWE displays a deteriorating learning curve, resulting in worse final scores compared to the baseline. Furthermore, it was found that the lower the overlap coefficient (therefore the less similar the ADS), the higher the maximum reached score. It was further shown that BW exhibits better convergence than FWE to the true model parameters. Besides this, FWE obtained comparable or in some cases even superior scores compared to BW. In general, from the results, the diversity of the experiments conducted, and the assumptions made we can conclude that the GHMM can be a general method for an ADSE with limited prior knowledge. To quantify the suitability of the GHMM for ADSE, further research should include the evaluation of different ADSE methods on the same problem. There exists a tradeoff between the lower computational cost FWE and the more stable but more computationally intensive BW learning. Therefore, future research can include a combination of these methods. Other extensions include extending the GHMM to a Gaussian mixture hidden Markov model to allow for the modeling of more complex distributions, or the application to multiple states or a changing environment.https://github.com/Wouter-deBoer/adseMechanical Engineering | Vehicle Engineering | Cognitive Robotic
High pressure gas-liquid mixtures generated in a micro-electrolysis cell
No full textIn this work a micro-electrolysis cell is presented that allows the rapid generation of high pressure gas-liquid mixtures. The stainless steel electrolysis cell (150 µl volume) is constructed as an integral part of an automotive pressure sensor, allowing the on-line monitoring of the generated pressure. By the application of an electric current between two platinum electrodes inserted in the electrolyte filled cell, hydrogen and oxygen gas was generated with pressures up to 1350 bar. First experiments were performed to investigate the catalytic back-reaction of the generated hydrogen/oxygen mixture at the surface of the platinum electrodes. By the application of a compensation current to keep the internal pressure at a constant value, the rate of the back reaction could be established. It follows that the catalytic back-reaction rate increases exponentially above a pressure of 800 bar. As the proposed method of in-situ high pressure gas generation is intrinsically fast and safe due to the small cell volume, a large number of these cells/reactors can form a platform for (chemical) high throughput experimentation (HTE)
Finding a good hydrogel composition for hydrogel based microvalves
No full textIn order to find a hydrogel that has good properties for use in microvalve actuators experiments have been conducted to find a hydrogel composition that has good swelling behavior and shows a discontinuous volume transition.During the experiments a number of N-isopropylacrylamide (NIPA) and acrylamide (Am) hydrogels were synthesized with varying amounts of the comonomer acrylic acid (AA). The swelling behavior of these hydrogels was characterized by measuring the swelling in acetone/water mixtures with varying concentrations acetone
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
Nederland op een kantelpunt: Interview met Wouter Veldhuis over het Stedelijk Netwerk Nederland en het sociaal netwerk van woonwijken
Full text linkDe stedenbouwkundige en architect Wouter Veldhuis en landschapsarchitect Jannemarie de Jonge zijn per 1 december 2020 Rijksadviseur voor de fysieke leefomgeving. Later in september 2021 komt daar de architect Francesco Veenstra bij als Rijksbouwmeester en dan is het nieuwe trio College van Rijksadviseurs weer compleet. De uitdagingen voor het college zijn groot. De ruimteclaims die er liggen in stad en land, de hooggestemde ambities om klimaatneutraal en circulair te zijn in 2050, de roep om een minister voor de fysieke leefomgeving en of wonen en weer een echt ministerie met budget. Het enorme probleem op de woningmarkt en de druk om één miljoen woningen ergens bij te bouwen. Op 24 april sprak het team van 1M Homes initiative van de TU Delft met de nieuw benoemde rijksadviseur voor de fysieke leefomgeving Wouter Veldhuis over de aanstaande veranderingen
Ultrasonic distance detection in spinal cord stimulation
Full text linkSpinal cord stimulation (SCS) is a clinical method for primarily the management of chronic, intractable pain. The method is based on electrical stimulation of nerve fibers in the posterior part of the spinal cord. An electric field is applied by an electrode array, implanted medially in the posterior epidural space, at some distance from the spinal cord. An implantable pulse generator provides the electrical stimulation pulses to the electrode array via a cable. When stimulating the spinal cord with pulses of constant amplitude, the current density in the spinal cord and thus the effects on nerve fibers will change with body position and/or posture, due to the varying distance between the spinal cord and the stimulating electrode array. As a result, the pain relieving effect may either vanish (when the distance is too large), or be dominated by uncomfortable sensations. To avoid these adverse conditions the current density in the spinal cord has to remain within a small window. In present SCS systems the stimulus applied by the electrode array is either set at a constant value, or the patient is allowed to select one out of only two preset pulse amplitudes. Therefore, a major improvement would be achieved if the distance between stimulation electrode array and spinal cord could be measured and used as a feedback signal to control the stimulus amplitude in a closed-loop system. Therefore, an ultrasonic distance detection system has been proposed to measure the distance between stimulation electrode array and the spinal cord. The ultrasonic system consists of a piezoelectric transducer and an echo detection circuit. To enable the design and optimization of the piezoelectric transducer an appropriate model description is needed
An integrated sensor system for monitoring washing processes
Full text linkThis thesis deals with the development, realisation and testing of an array of sensors for determining the state of a washing process. To combine the sensors in a single array, some techniques are used. First, the sensors which are integrated are chosen with respect to their fabrication materials and technique. By matching these, the sensors could be combined into a single multi-purpose structure. A reduction of the number of connecting wires is the result, and the single structure will measure all parameters at the same spot in the solution. In addition, together with sensors, also actuators are integrated. This enables the possibility of performing stimulus-response measurements. Such experiments are based on recording the response of solution components on an imposed local disturbance. Sometimes, such dynamic measurements give new information on the solution. Finally, the combination of sensor readings, together with the results of the stimulus-response measurements, yields a set of data which can be used for smart interpretation and decisions. The final result is a system consisting of a small noble metal structure, applied on a carrier, with a size of only one square millimetre. By scheduling this structure in several operational modes, the following washing parameters can be measured: temperature, bleach activity, electrolyte conductivity, movement of the washing water and the temperature dependency of the electrolyte conductivity. The latter one can give information on the individual types of charged particles in the solution. Finally, some suggestions are given in order to implement washing parameters that are missing in the measurable set of variables
A polymer condenser micorphone realised on silicon containing preprocessed integrated circuits
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