107 research outputs found
Het huisvesten van kennis: Een plek die ons stimuleert zo vrij mogelijk te denken
No full textRobbert Dijkgraaf is sinds mei 2008 voorzitter van de Koninklijke Nederlandse Akademie van Wetenschappen. Hij is cum laude gepromoveerd, staat bekend als een briljant wetenschapper die de wetenschap toegankelijk maakt voor een groter publiek. FMI trad in gesprek met hem over wetenschappelijk denken en de huisvesting die hier het beste bij past.Real Estate and Housin
Oplossingen voor Dreshers hoger lager spel voor N <= 980
No full textMelvin Dresher beschouwde in zijn boek uit 1961 over speltheorie een getallenraadspel over N getallen. Hij liet zien hoe de optimale strategieën van beide spelers kon worden gevonden met behulp van lineair programmeren. Later toonde Selmer Johnson oplossingen voor N<=11 en merkte op dat de berekeningen steeds complexer werden bij toenemende N. Deze thesis beschrijft technieken om het spel op te lossen voor N<=980. Het algoritme van Dresher vormt nog steeds de basis, maar er zijn enkele aanpassingen. Niet alle voorwaarden worden bijvoorbeeld in het begin gegenereerd. Voorwaarden worden alleen op het moment dat ze nodig zijn gevonden met een subroutine. Dit is een vorm van delayed column generation. Er wordt ook gebruik gemaakt van heuristieken, zoals het schatten van de optimale kansverdeling van één van de spelers. Dit werk verschaft meer inzicht in het patroon van de oplossingen van dit spel en of enkele eerder geformuleerde vermoedens van Selmer Johnson en Edgar Gilbert over dit spel kloppen
Akiyama's Nim
No full textAkiyama’s Nim is een 3d versie van een onpartijdig combinatorisch spel genaamd Wythoffs Nim. Het spel van Wythoff kan met twee stapels munten gespeeld worden. Elke positie in dit spel komt overeen met een getal dat als temperatuur te zien is waarbij posities met temperatuur 0 koud genoemd worden. Er is een makkelijke formule voor de koude posities van Wythoffs spel. Voor hogere temperaturen zijn geen gesloten formules bekend. Door het aantal toegestane zetten te beperken is wel een formule voor posities met hogere temperaturen te vinden. De formule voor posities met temperatuur 1 en 2 worden voor deze beperkte versie gegeven. Nu kan het spel van Akiyama bekeken worden, dit is een versie van Wythoff met 3 stapels munten. Van dit spel is geen formule voor de koude posities bekend. Het is al heel moeilijk om een correct algoritme te maken. Daarom bekijk ik in dit verslag een vereenvoudigd algoritme. Van dit algoritme kunnen de onder- en bovengrenzen worden berekend die een indicatie geven van de afstand tussen koude posities. Het vermoeden is dat deze koude posities op een lijn liggen en er wordt een vermoeden van de helling van deze lijn gegeven
Tree-child Network Containment
No full textInterest in phylogenetic trees for histories of species and DNA has spawned many problems, one of which is TreeContainment; a problem that asks whether a tree is contained within a network. The TreeContainment problem is proven to be NP-hard for general trees and networks, however it is solvable in polynomial time for networks that meet the tree-child restriction. An algorithm to solve TreeContainment for binary tree-child networks has been created previously with quadratic running time (van Iersel, Semple, Steel, 2010). Janssen and Murakami have recently created a new algorithm that solves a larger problem NetworkContainment, for semi-binary tree-child networks (Janssen, Murakami, 2019). This new algorithm uses tree-child sequences introduced by Linz and Semple, but there has not been an implementation of it until now. In this paper I show an implementation (using Python) of this algorithm, in which I have made a modification that increases its speed on networks with large indegrees. Furthermore I have proven in this paper that the output of this algorithm remains correct under this modification, and that the running time of the modified algorithm is now linear without requiring a constant maximum indegree at all.Applied Physic
Evaluation of a zinc chelate on clinical swine dysentery under field conditions
No full textBackground Brachyspira hyodysenteriae is the primary cause of swine dysentery, characterized by bloody to mucoid diarrhea due to mucohaemorhagic colitis in pigs and primarily affects pigs during the grow/finishing stage. Control and prevention of B. hyodysenteriae consists of administration of antimicrobial drugs, besides management and adapted feeding strategies. A worldwide re-emergence of the disease has recently been reported with an increasing number of isolates demonstrating decreased susceptibility to several crucially important antimicrobials in the control of swine dysentery. A novel non-antibiotic zinc chelate has been reported to demonstrate positive effects on fecal quality and consistency, general clinical signs, average daily weight gain and B. hyodysenteriae excretion during and after a 6-day oral treatment. The objective of the present study was to evaluate the zinc chelate (Intra Dysovinol(R) 499 mg/ml (ID); Elanco) on naturally occurring swine dysentery due to B. hyodysenteriae under field conditions in the Netherlands. Results Oral administration of zinc chelate resulted in improvement of general clinical signs from 3 days onwards in the ID-treated group combined with a significantly better total fecal score at 14 days post-treatment. Overall, average daily weight gain was better in the ID-treated group over the entire study period (0-14 days) and during the 8 days following the end of ID-treatment. A significant reduction (4.48 vs. 0.63 log(10) cfu/g feces; ID-treated vs. control) in B. hyodysenteriae excretion was observed during the 6-day treatment period with a high percentage of animals (58.3 vs. 12.3%; ID-treated vs. control) with no excretion of B. hyodysenteriae from their feces. No additional antimicrobial treatment was needed in the ID-treated group, whereas 35% of the pigs in the control group were treated with an antibiotic at least once. No mortality occurred in both groups. No adverse events were reported during and following the ID-treatment. Conclusions Zinc chelate - administered as a Zn-Na-2-EDTA complex - is a non-antibiotic treatment for swine dysentery that reduces B. hyodysenteriae shedding with 4.48 log(10) cfu/g feces within its 6-day treatment while improving general clinical signs (90.0 vs. 73.6% animals with normal score) and total fecal score within 2-4 days following administration in naturally infected pigs. The positive effects of ID treatment remain for at least 8 days after cessation of oral ID therapy. Pigs remaining in a highly contaminated environment may be re-infected following the end of ID treatment, however, this is not different to standard antimicrobial therapy. Therefore, control of swine dysentery should combine an efficacious treatment with additional management practices to reduce the environmental infection pressure in order to limit re-infection as much as possible. The ID treatment resulted in a higher growth rate and improved general health, whereas no mortality was observed and no additional therapeutic treatments were necessary in contrast to the control pigs.The study was funded by Elanco Animal Health, which facilitated the conduct of the field trial.Vangroenweghe, F (reprint author), Elanco, BU Food Anim, Plantijn Moretuslei 1-3rd Floor, B-2018 Antwerp, Belgium.
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Treewidth based algorithms for Tree Containment in phylogenetics
No full textTreeContainment is a well-known problem within phylogenetics, which asks whether a binary phylogenetic tree is embedded in a binary phylogenetic network. For this problem, Jones, Weller and van Iersel (2022) have created an algorithm that uses dynamic programming on tree-decompositions to achieve a running time that is exponential in the tree-width parameter instead of in the number of reticulations. However, due to the implicit formulations of two crucial steps in this algorithm, this running time cannot be achieved in practice without finding ways to generate the required structures explicitly. This paper provides two new sub-algorithms that can do that. To further improve the performance of the algorithm, I introduce a number of criteria and other methods that can be used to reduce the number of structures generated. Additionally, I describe a way to manipulate the nice tree-decompositions to create a more favorable order of bags for the dynamic programming. These sub-algorithms and improvements are used by two new algorithms TWITCH and PITCH, whose implementations are compared to a brute force algorithm and a new branching cherry-picking algorithm named BOTCH. The latter has an FPT running time that is exponential in the number of vertices that have only reticulations as children. The comparisons show that the implementations of the dynamic programming algorithms TWITCH and PITCH are slower in practice than the brute force algorithm, despite their numerous improvements. Of the four new implementations, BOTCH has the best test results and it is shown to be fast in practice. Applied Mathematic
Fuelling the hydrogen economy: Scale-up of an integrated formic acid-to-power system
No full textTransitioning from fossil fuels to sustainable and green energy sources in mobile applications is a difficult challenge and demands sustained and highly multidisciplinary efforts in R&D. Liquid organic hydrogen carriers (LOHC) offer several advantages over more conventional energy storage solutions, but have not been yet demonstrated at scale. Herein we describe the development of an integrated and compact 25 kW formic acid-to-power system by a team of BSc and MSc students. We highlight a number of key engineering challenges encountered during scale-up of the technology and discuss several aspects commonly overlooked by academic researchers. Conclusively, we provide a critical outlook and suggest a number of developmental areas currently inhibiting further implementation of the technology.ChemE/Inorganic Systems EngineeringChemE/Algemee
Breeding against osteochondrosis : phenotypic and genetic analyses in horses and pigs
No full text Osteochondrosis (OC) is a disturbance in the process of endochondral ossification during skeletal growth. The objectives of this thesis were to assess the prevalence and genetic parameters of OC, and to facilitate optimization of breeding against OC in horses and pigs. In the Dutch warm blood horse, 70% of individuals showed joint abnormalities in at least one of the 28 locations examined. Joint abnormalities were divided into flattened bone contours and bone fragments. Genetic parameters were estimated for flattened bone contours, fragments and overall OC. Heritability was 0.08 for flattened bone contours, 0.22 for fragments, and 0.23 for overall OC. In fattening pigs, the prevalence of OC was 41%, and 12% of the individuals had severe OC. The prevalence was highest for individuals kept on a concrete, partially slatted floor with ad libitum feeding (58%), and lowest for individuals kept on a deep litter floor with restricted feeding (34%). These results demonstrate that the prevalence of OC can be reduced by applying deep litter floors and restricted feeding. The differences in growth patterns between pigs with and without OC were investigated also. After 28 days of age, piglets with severe OC at slaughter started to grow faster, and were significantly heavier after 70 days of age than pigs without OC at slaughter. These results suggest that OC might be related to high growth rates during a specific time period. To evaluate prospects for breeding against OC, selection responses were compared between breeding schemes using phenotypic selection based on own performance or progeny testing and genomic selection. The results show that, when genomic information has an equal accuracy as phenotypic information before selection, it will have a lower equilibrium response to selection because it has a larger Bulmer effect. Especially for low heritable traits, genomic selection was of additional value over traditional selection. The general discussion argues that OC has both economical and practical relevance for the current horse industry. Simulations showed potential for genomic selection compared to the current breeding program in the Dutch warmblood horse (KWPN), even with small reference populations. In pigs, OC is a more serious problem in sows than in fattening pigs, because sows live longer. A decrease in OC prevalence will, therefore, yield larger economic and welfare benefits then apparent from results on fattening pigs. Also for pigs, simulations indicated possibilities for genomic selection. The final section of the general discussion proposes directions for future research.</p
A co-creational approach in the Dutch infrastructure sector: Exploring the added value of implementing a co-creational approach in the pre-contractual phase
No full textRecently a new phenomenon introduced itself in the Dutch infrastructure sector called co-creation. It is described in literature as ‘the joint creation of value between a company and its consumers’. It marks a shift in thinking and became a popular concept to increase the participation of consumers around the year 2000. Since then it has spread to other industries. In the service-and product design it already proved to be a good method as benefits such as increased satisfaction among consumers, cost reduction for the firm and innovative ideas has been mentioned in literature. . In this research, seven elements are identified that are found as necessary conditions for the co-creation concept. With decomposing it into elements it was found that the concept became less abstract, making it more practical for project leaders to implement the concept in their projects. Co-creation in the infrastructure sector is about placing the stakeholder in a central position and together identify their needs and investigate how value can be created jointly
Assessing the performance of the sonAIR aircraft noise model in predicting noise levels at Schiphol Airport
No full textAircraft noise is a significant problem for communities surrounding airports. Accurate prediction models are needed to estimate noise levels from aircraft operations. In this research, the accuracy of the sonAIR aircraft noise model is evaluated in predicting noise levels around Schiphol airport by comparison to measurement data from NOMOS and the current best-practice modelling approach Doc29. Results show a significant but consistent underestimation of noise levels by sonAIR, mainly due to a generalisation of emission models. The standard deviation of differences between model results and measurements is lower for sonAIR than for Doc29 by up to 1 dB. Differences between measurement and model results were found in the relation between N1 and noise levels, maximum noise levels and frequency spectra. These results demonstrate that sonAIR provides more reliable predictions of noise levels on the single flight event level than Doc29. Additionally, this study shows agreement with results from a previous validation study in Zürich, thereby confirming the applicability of sonAIR to another airport. This research contributes to better aircraft noise predictions, which will have implications ultimately leading to a better quality of life for communities affected by aircraft noise.Aerospace Engineerin
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