1,433 research outputs found
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
MultiRec: Effects of multiple extrusion in cast and blown film applications
No full textThe MultiRec project investigates the degradation of physicochemical and mechanical properties in linear low-density polyethylene granulate subjected to multiple reprocessing cycles without intermediate additivation. This reprocessed granulate is incorporated into stretch films for automatic wrapping. To ensure industry relevance, additional case studies benchmark commercially available virgin films and films with recycled content from MultiRec partners. Two virgin films and two films with 30% post-consumer recyclate (PCR), each 20–24 µm thick, were evaluated. Characterization includes a standard tensile test (ISO 527-3) and a stretch-specific test (ASTM D5459) to assess permanent deformation and stress retention at prestretch values of 200% (safe), 300% (challenging for films with PCR), and 400% (extreme). Transport simulations involve wrapping column-stacked pallets with these films, followed by horizontal shock tests, some preceded by vibrations or exposure to humid, hot conditions, and additional tilt tests at 26°. Video analysis tracks tilting during simulations, while layer displacement is measured before and after. Virgin films have slightly higher maximum stress than films with PCR, with averages of 46.6 ± 4.2 MPa and 45.1 ± 12.7 MPa for virgin films compared to 41.7 ± 1.9 MPa and 40.5 ± 3.1 MPa for films with PCR. No clear trend was observed for strain at break. Prestretch level significantly influences stress retention and permanent deformation, higher prestretch reduces stress retention and increases permanent deformation. Stress retention ranges from 73% at 200% prestretch to 65% at 400%, while permanent deformation ranges from 54% at 200% to 76% at 400%. These findings indicate that commercially available films with recycled content, likely reprocessed only once, have comparable tensile properties to virgin films. The presentation will include transport simulation results and preliminary findings on films with multi-reprocessed granulate compared to these commercial standards
FDG PET/CT during neoadjuvant chemotherapy may predict response in ER-positive/HER2-negative and triple negative, but not in HER2-positive breast cancer
No full textAbstract not availableBas B. Koolen, Kenneth E. Pengel, Jelle Wesseling, Wouter V. Vogel, Marie-Jeanne T.F.D. Vrancken Peeters, Andrew D. Vincent, Kenneth G.A. Gilhuijs, Sjoerd Rodenhuis, Emiel J.Th. Rutgers, Renato A. Valdés Olmo
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
No full textDe 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
Effect of Nanoparticle Incorporation on Functional Properties and Migration of Ag/polyhydroxyalkanoate Nanocomposites
No full textSilver-nanocomposites offer great potential as active packaging material due to their antimicrobial properties. However, limited understanding of silver nanoparticle (Ag NP) release mechanisms, especially from biodegradable nanocomposites, poses challenges in terms of human health and environmental risks, resulting in restrictive regulatory measures. This study aims to understand how the incorporation of Ag NPs affects dispersity, functional properties and Ag°/Ag+ migration from Ag/poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx) nanocomposite films. Commercial spherical polyvinylpyrrolidone-coated Ag NPs of 40 nm were incorporated in PHBHHx (0.2-2 wt.%) via melt extrusion (Dry-mix method). Alternatively, a Masterblend method was applied by pre-dispersing the NPs via solvent casting, before extrusion. Nanocomposite films were obtained via subsequent hot-pressing for further characterization. Specific migration was assessed by full immersion tests, using Milli-Q water and food simulants A and B at 40 °C (EU Regulation 10/2011). The leachate was analysed over 10 days via Single Particle Inductively Coupled Plasma Mass Spectrometry to monitor NP size, particle number concentration and dissolved concentrations. The Dry-mix approach seems optimal in terms of time efficiency and NP dispersity. The latter is evidenced by colour, opacity, UV-VIS transmittance and scanning electron microscopy analyses. Interestingly, using both methods, the tensile properties, crystallinity and thermal stability do not change significantly when varying NP loading up to 2 wt.%. In addition, a 30 % reduction in oxygen permeability is achieved for the highest NP loading. Although increasing NP loading did result in an incremental release of Ag°/Ag+, the migration remained under the specific migration limit of 50 µg Ag/kg food for all food simulants, with the highest migration in the acidic food simulant B. So far, we conclude that the fabricated Ag/PHBHHx films show potential as safe, non-transparent active food packaging material with improved oxygen barrier properties
Effect of Nanoparticle Incorporation on Functional Properties and Migration of Ag/polyhydroxyalkanoate Nanocomposites
No full textSilver-nanocomposites offer great potential as active packaging material due to their antimicrobial properties. However, limited understanding of silver nanoparticle (Ag NP) release mechanisms, especially from biodegradable nanocomposites, poses challenges in terms of human health and environmental risks, resulting in restrictive regulatory measures. This study aims to understand how the incorporation of Ag NPs affects dispersity, functional properties and Ag°/Ag+ migration from Ag/poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx) nanocomposite films. Commercial spherical polyvinylpyrrolidone-coated Ag NPs of 40 nm were incorporated in PHBHHx (0.2-2 wt.%) via melt extrusion (Dry-mix method). Alternatively, a Masterblend method was applied by pre-dispersing the NPs via solvent casting, before extrusion. Nanocomposite films were obtained via subsequent hot-pressing for further characterization. Specific migration was assessed by full immersion tests, using Milli-Q water and food simulants A and B at 40 °C (EU Regulation 10/2011). The leachate was analysed over 10 days via Single Particle Inductively Coupled Plasma Mass Spectrometry to monitor NP size, particle number concentration and dissolved concentrations. The Dry-mix approach seems optimal in terms of time efficiency and NP dispersity. The latter is evidenced by colour, opacity, UV-VIS transmittance and scanning electron microscopy analyses. Interestingly, using both methods, the tensile properties, crystallinity and thermal stability do not change significantly when varying NP loading up to 2 wt.%. In addition, a 30 % reduction in oxygen permeability is achieved for the highest NP loading. Although increasing NP loading did result in an incremental release of Ag°/Ag+, the migration remained under the specific migration limit of 50 µg Ag/kg food for all food simulants, with the highest migration in the acidic food simulant B. So far, we conclude that the fabricated Ag/PHBHHx films show potential as safe, non-transparent active food packaging material with improved oxygen barrier properties
Descriptive study and evaluation of shrink hoods with recycled content for regulatory compliance
No full textIn preparation for the European Commission's Packaging and Packaging Waste Regulation (PPWR), mandating 35% recycled content in tertiary plastic transport packaging by 2030, distributors are already producing films with similar content. As part of the TETRA-CORNET MultiRec project (HBC.2023.0176), funded by VLAIO VLAIO and in collaboration with industry partners, this case study evaluates shrink hoods with 30% and 35% post-consumer recycled (PCR) content, designed to protect palletised loads of 1.3 tons of bricks. This study provides a framework for systematic assessment of these films, enabling their improvement in a later phase, aligning with regulatory requirements and ensuring transport performance, and identifying correlations between mechanical, thermal, and chemical properties as well as transport performance. Key mechanical properties, such as coefficient of friction (dynamic COF: 0.19–0.25), tensile stress, and thermal shrinkage, were analysed, revealing notable variability between films. Differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) assessed thermal transitions (melting peaks: 118–124 °C) and molecular weights, while gas chromatography-mass spectrometry (GC-MS) identified additives. PCR granulates exhibited notable variability, including lower melt enthalpy (95-103 J/g) compared to the full films (>108 J/g), indicating reduced crystallinity. Granulate colour varied noticeably, with lighter ones having lower molecular weight (199.6 kg/mol) than darker ones (275.3 kg/mol). Transport simulations further highlighted performance differences between films, emphasizing the need for tighter control over variables such as PCR composition, compensatory measures in virgin fractions, and production parameters. In conclusion, this study highlights the variability in both PCR granulate and film properties, emphasizing the need for systematic and open research to address performance challenges and support the transition to circular materials while maintaining sufficient transport protection in demanding applications
Can patients who have low-grade hip osteoarthritis expect the same outcome after total hip arthroplasty compared to those who have end-stage osteoarthritis? - A Matched Case-Control Study
No full textBackground
Total hip arthroplasty (THA) is an effective procedure for patients with end-stage hip osteoarthritis (OA). In addition, when hip preservation surgery is no longer indicated due to the presence of early or mild arthritic changes, THA can also be considered. Whether these patients can expect the same outcome after THA as patients who have end-stage OA remains unclear. The goal of this study was to compare the clinical outcomes after THA of patients who have low-grade OA versus a matched cohort with end-stage OA.
Methods
This is a retrospective, single-center, multi-surgeon case-control study in a high-volume referral center. Based on a cohort of 2,189 primary anterior approach THAs (1,815 patients), 50 low-grade OA cases were matched 1:1 by age, sex, and Body Mass Index (BMI) to 50 controls who have end-stage OA. Patient-reported outcomes (PROMS) were Hip Disability and Osteoarthritis Outcome Scores (HOOS) and Short Form-36 (SF-36).
Results
No significant differences in preoperative PROMs between low-grade and end-stage OA patients were found, except for SF-36 pain (33.0 versus 41.0; P = 0.045). In both groups a significant improvement of all PROMs was found postoperatively. However, all HOOS scores were significantly lower in the low-grade OA group compared to the end-stage OA group. In the group with low-grade OA, a significantly lower percentage of patients achieved the minimum clinically important difference (MCID) and substantial clinical benefit (SCB) after THA compared to the group with end-stage OA.
Conclusion
Patients who have low-grade OA can expect substantial clinical improvement after THA. However, the improvement is lower compared to patients who have end-stage OA. A thorough understanding of the factors that may lead to inferior clinical outcomes is imperative to improving the indications for THA in individuals who have low-grade OA.This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors
Influence of processing method on functional properties of Ag/polyhydroxyalkanoate nanocomposite films
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