112 research outputs found
Up and beyond: Building a mountain in the Netherlands
Get PDFWe discuss the idea of building a 2 km high mountain in the Netherlands. In this paper, we give suggestions on three important areas for the completion of this project. Issues like location, structure and sustainability are investigated and discussed in detail
Image recognition of shape defects in hot steel rolling
No full textA frequently occurring issue in hot rolling of steel is so-called tail pinching. Prominent features of a pinched tail are ripple-like defects and a pointed tail. In this report two algorithms are presented to detect those features accurately in 2D gray scale images of steel strips. The two ripple detectors are based on the second order Gaussian derivative and the Gabor transform, a localized Fourier transform, yielding the so-called rippleness measures. Additionally a parameter called tail length is defined which indicates to what extent the overall shape of the tail deviates from an ideal rectangular shape. These methods are tested on images from the surface inspection system at Tata Hot Strip Mill 2 in IJmuiden, it is shown that by defining a simple criterion in the feature space spanned by these two parameters a given set of strips can correctly be classified into pinched and nonpinched strips. These promising results open the way for the development of an automatic pinch detection system
Polling models : from theory to traffic intersections
Get PDFThe subject of the present monograph is the study of polling models, which are queueing models consisting of multiple queues, cyclically attended by one server. Polling models originated in the late 1950s, but did not receive much attention until the 1980s when an abundance of new applications arose in computer networks and in communication protocols. The name polling model originates from this application area, where central bank computers serve ("poll") their branch terminals in a cyclic fashion. Because of this renewed practical relevance, a huge literature on polling models has appeared throughout the years. The contribution of the present monograph is twofold. Firstly, it introduces polling models with features that are well-known in the context of single-queue systems, but have remained unexplored in polling systems. For example, we study polling models with customer priority levels, impatience and abandonments, and varying arrival rates. The second contribution is to provide a new approach to analyse vehicle actuated traffic intersections with exhaustive service, by applying and extending recent results in the polling literature. The thesis is divided into three parts. The first part, which starts after a general introduction and an extensive literature review, studies different types of customer behaviour in polling models. In particular, smart, stupid, and impatient customers are discussed. In the second part we study system behaviour in the sense that we introduce customer priority levels and discuss several service policies based on these priority levels. The third part focusses on traffic intersections and new approaches to apply results from the polling literature to this application area. We discuss the three parts in more detail below. As stated before, Part I introduces new types of customer behaviour in polling models. In Chapter 3 we study a polling model with arrival rates that depend on the server position. This extension destroys the convenient property that an arbitrary arriving customer sees the system in equilibrium, and a novel analysis technique is required to circumvent this complication. The model is practically relevant because it allows customers to choose which queue they want to join, knowing which queue is being served at their arrival epoch. Besides the practical relevance of the model, the analysis and the insights gained from it have great merit for future studies. This is illustrated by the model studied in Chapter 4, which is an extension of a vacation model with customer impatience, studied in existing literature. Using the analysis methodology of Chapter 3, we are able to obtain new results for the vacation model, and extend it to the context of polling models. In polling models, this is the first appearance of customer impatience, in queueing literature often referred to as reneging. Part II studies system behaviour through the introduction of customer priority levels. We study the impact of changing the order in which customers are served based on these priority levels. For example, we illustrate the effect of giving higher priority to customers with less service requirement. In Chapter 5 we study priorities in a standard polling system. Chapter 6 discusses the impact of using different service disciplines for customers with different priority levels, and shows how this can be used as a strategy to give even more advantages to customers with a higher priority level. The third part of the thesis is mainly dedicated to polling models for traffic intersections. Polling models have been applied to road traffic before, but only in the situation that one lane on a single road is blocked and traffic has to share the other lane. In Chapter 7 we develop a novel closed-form waiting time approximation for polling systems. The manner in which this approximation is created lends itself perfectly for adaption to the scenario where groups of multiple queues receive service simultaneously, as is the case in signalised traffic intersections. Chapter 8 presents this adaptation for traffic signals. Another aspect that is new in the analysis of delays at traffic intersections, is the analysis of conflicting traffic flows receiving a green light simultaneously. For this purpose, we use the approximation developed in Chapter 7 in combination with the results on polling models with priorities from Chapter 5
A polling model with reneging at polling instants
No full textIn this paper we consider a single-server, cyclic polling system with switch-over times and Poisson arrivals. The service disciplines that are discussed, are exhaustive and gated service. The novel contribution of the present paper is that we consider the reneging of customers at polling instants. In more detail, whenever the server starts or ends a visit to a queue, some of the customers waiting in each queue leave the system before having received service. The probability that a certain customer leaves the queue, depends on the queue in which the customer is waiting, and on the location of the server. We show that this system can be analysed by introducing customer subtypes, depending on their arrival periods, and keeping track of the moment when they abandon the system. In order to determine waiting time distributions, we regard the system as a polling model with varying arrival rates, and apply a generalised version of the distributional form of Little’s law. The marginal queue length distribution can be found by conditioning on the state of the system (position of the server, and whether it is serving or switching)
A polling model with reneging at polling instants
Get PDFIn this paper we consider a single-server, cyclic polling system with switch-over times and
Poisson arrivals. The service disciplines that are discussed, are exhaustive and gated service. The novel contribution of the present paper is that we consider reneging of customers at polling instants. In more detail, whenever the server starts or ends a visit to a queue, part of the customers waiting in each queue leave the system before having received service. The probability that a certain customer leaves the queue, depends on the queue in which the customer is waiting, and on the location of the server. We show that this system can be analysed by introducing customer subtypes, depending on their arrival periods, and keeping track of the moment when they abandon the system. In order to determine waiting time distributions, we regard the system as a polling model with varying arrival rates, and apply a generalised version of the distributional form of
Little’s law. The marginal queue length distribution can be found by conditioning on the state of the system (position of the server, and whether it is serving or switching)
Platoon forming algorithms for intelligent street intersections
No full textWe study intersection access control for autonomous vehicles. Platoon forming algorithms, which aim to organize individual vehicles in platoons, are very promising. To create those platoons, we slow down vehicles before the actual arrival at the intersection in such a way that each vehicle can traverse the intersection at high speed. This increases the capacity of the intersection significantly, offering huge potential savings with respect to travel time compared to nowadays traffic. We propose several new platoon forming algorithms and provide an approximate mean delay analysis for our algorithms. A comparison between the current day practice at intersections (through a case study in SUMO) and our proposed algorithms is provided. Simulation results for fairness are obtained as well, showing that platoon forming algorithms with a low mean delay sometimes are relatively unfair, indicating a potential need for balancing mean delay and fairness
Heavy-traffic analysis of k-limited polling systems
Get PDFIn this paper we study a two-queue polling model with zero switch-over times and k-limited service (serve at most k_i customers during one visit period to queue i, i = 1,2) in each queue. The arrival processes at the two queues are Poisson, and the service times are exponentially distributed. By increasing the arrival intensities until one of the queues becomes critically loaded, we derive exact heavy-traf¿c limits for the joint queue-length distribution using a singular-perturbation technique. It turns out that the number of customers in the stable queue has the same distribution as the number of customers in a vacation system with Erlang-k_2 distributed vacations. The queue-length distribution of the critically loaded queue, after applying an appropriate scaling, is exponentially distributed. Finally, we show that the two queue-length processes are independent in heavy traf¿c
Visualizing multiple quantile plots
Get PDFMultiple-quantile plots provide a powerful graphical method for comparing the distributions of two or more populations. This article develops a method of visualizing triple-quantile plots and their associated confidence tubes, thus extending the notion of a quantile–quantile (QQ) plot to three dimensions. More specifically, we consider three independent one-dimensional random samples with corresponding quantile functions Q1, Q2, and Q3. The triple-quantile (QQQ) plot is then defined as the threedimensional curve Q(p) = (Q1(p), Q2(p), Q3(p)), where 0 <p< 1. The empirical likelihood method is used to derive simultaneous distribution-free confidence tubes for Q. We apply our method to an economic case study of strike durations and to an epidemiological study involving the comparison of cholesterol levels among three populations. These data as well as the Mathematica code for computation of the tubes are availablein the online supplementary materials
Different Looks For A Child With Multiple Diagnoses: Stability Or Possibility Of Change? [diferentes Olhares Em Relação A Uma Criança Com Múltiplos Diagnósticos: Estabilidade Ou Possibilidade De Mudança?]
No full textProfessional practice directed to children with organic problems and unfavorable prognosis deserves attention since it is directly related to the psychological development of the child. It is presented the case study of a child with diagnoses of organic problems and behavioral complaints characterized as aggressive and competitive. It was analyzed the participation of the child, during three years, in a project of intervention in groups, with focus on modes of participation and peer interaction. The analysis allowed the identification of competencies and cooperative modalities of participation, which became more diversified and complex during the period of observation. With this study, it was possible to take a wider perspective of the possibilities and difficulties of the child, suggesting the need of broader analyses of the development of children with multiple developmental complaints.244720729Amaral, L.A., Deficiência: Questões conceituais e alguns de seus desdobramentos (1996) Cadernos de Psicologia, 1, pp. 3-12Amiralian, M.L.T.M., Deficiências: Um novo olhar Contribuições a partir da psicanálise winnicottiniana (2003) Estudos em Clínica, 15 (8), pp. 94-111Batista, C.G., Crianças com problemas orgânicos: Contribuições e riscos de prognósticos psicológicos (2004) Educar em Revista, 23, pp. 45-63Batista, C.G., Laplane, A.L.F., Modalidades de atendimento especializado: O grupo de convivência de crianças com deficiência visual (2007) A pessoa com deficiência visual: Um livro para educadores, pp. 85-111. , E. F. S. Masini (Ed.), São Paulo, SP: VetorCarvalho, A.M.A., Beraldo, K.E.A., Interação criança-criança: De uma área de pesquisa e suas perspectivas (1989) Cadernos de Pesquisa, 71, pp. 55-61Carvalho, A.M.A., Pedrosa, M.I.M., Cultura no grupo de brinquedo (2002) Estudos de Psicologia, 7 (1), pp. 181-188(1994), Declaração de Salamanca e linhas de ação sobre necessidades educativas especiais. Brasília, DF: Corde(2008) Dispõe sobre o atendimento educacional especializado, regulamenta o parágrafo único do art, , Decreto No 6.571. (17 set.). 60 da Lei no 9.394. Brasília, DF: Presidência da RepúblicaHueara, L., Souza, C.M.L., Batista, C.G., Melgaço, M.B., Tavares, F.S., O faz-de-conta em crianças com deficiência visual: Identificando habilidades (2006) Revista Brasileira de Educação Especial, 12 (3), pp. 351-368Kassar, M.C.M., (1995) Ciência e senso comum no cotidiano das classes especiais, , Campinas, SP: PapirusLudke, M., André, M., (1986) Pesquisa em Educação: Abordagens qualitativas, , São Paulo, SP: Editora Pedagógica UniversitáriaMoysés, M.A.A., Collares, C.A.L., Inteligência abstraída, crianças silenciadas: As avaliações de inteligência (1997) Psicologia USP, 8 (1), pp. 63-89Moysés, M.A.A., Collares, C.A.L., Geraldi, J.W., As aventuras do conhecer: Da transmissão à interlocução (2002) Educação & Sociedade, 78 (23), pp. 91-116Palacios, J., Hidalgo, V., Desenvolvimento da personalidade nos anos pré-escolares (1993) Desenvolvimento psicológico e educação: Psicologia evolutiva, pp. 178-189. , C. Coll, J. Palacios, & A. Marchesi (Eds.), Porto Alegre, RS: Artes MédicasSouza, C.M.L., Batista, C.G., Interação entre crianças com necessidades especiais em contexto lúdico: Possibilidades de desenvolvimento (2008) Psicologia Reflexão e Crítica, 21 (3), pp. 383-391Vygotsky, L.S., (1991) A formação social da mente, , (4. ed.). São Paulo, SP: Martins FontesVygotsky, L.S., (1997) Obras escogidas: Fundamentos de Defectología, 5. , (J. G. Blank, Trad., N. J. V. Vargas & I. Filanova, Revs.). Madri, España: Visor. (Original work published, 1974)Vygotsky, L.S., (2000) Obras escogidas, 3. , Problemas del desarrollo de la psique, (L. Kuper, Trad., N. J. V. Vargas & I. Filanova, Revs.). Madri, España:Visor. (Original work published 1983)The management of low vision of childhood (1992) Proceedings of WHO/PBL Consultation Bangkok, , World Health Organization. Geneva, Switzerland: Author, Jul
Image Recognition of Shape Defects in Hot Steel Rolling
Get PDFA frequently occurring issue in hot rolling of steel is so-called tail pinching. Prominent features of a pinched tail are ripple-like defects and a pointed tail. In this report two algorithms are presented to detect those features accurately in 2D gray scale images of steel strips. The two ripple detectors are based on the second order Gaussian derivative and the Gabor transform, a localized Fourier transform, yielding the so-called rippleness measures. Additionally a parameter called tail length is defined which indicates to what extent the overall shape of the tail deviates from an ideal rectangular shape. These methods are tested on images from the surface inspection system at Tata Hot Strip Mill 2 in IJmuiden, it is shown that by defining a simple criterion in the feature space spanned by these two parameters a given set of strips can correctly be classified into pinched and non-pinched strips. These promising results open the way for the development of an automatic pinch detection system
- …
