Showing papers by "Eindhoven University of Technology published in 1993"
01 Jan 1993
TL;DR: Different types of sequencing and scheduling problems are discussed, and different types of algorithms and the concepts of complexity theory are described.
Abstract: Publisher Summary This chapter discusses different types of sequencing and scheduling problems, and describes different types of algorithms and the concepts of complexity theory. A class of deterministic machine scheduling problems has been introduced in the chapter. The chapter also deals with the single machine, parallel machine and multi-operation problems in this class, respectively. The two generalizations of the deterministic machine-scheduling model have been presented in the chapter. A deterministic scheduling model may give rise to various stochastic counterparts, as there is a choice in the parameters that are randomized, in their distributions, and in the classes of policies that can be applied. A characteristic feature of these models is that the stochastic parameters are regarded as independent random variables with a given distribution and that their realization occurs only after the scheduling decision has been made. In the deterministic model, one has perfect information, and capitalizing on it in minimizing the realization of a performance measure may require exponential time.
551 citations
TL;DR: The role of the centrifugal barrier in the final collision channel in reducing the loss of atoms from the trap due to transitions induced by the magnetic dipole-dipole interaction is discussed.
Abstract: We study the magnetic-field dependence of the cross sections for elastic and inelastic collisions of pairs of ultracold cesium atoms in a magnetic trap, calculated with the coupled-channels method. We pay special attention to atoms in the f=3, mf=-3 weak-field seeking state of the lower hyperfine manifold. The cross sections show a pronounced resonance structure. We discuss its origin, starting from the pure bound singlet and triplet rovibrational Cs2 states and introducing perturbations due to the hyperfine and Zeeman interactions. We also discuss the role of the centrifugal barrier in the final collision channel in reducing the loss of atoms from the trap due to transitions induced by the magnetic dipole-dipole interaction
484 citations
TL;DR: In this paper, a simple annealing treatment was proposed to rejuvenate poly(R)-3-hydroxybutyrate (PHB) while preventing subsequent aging. But the results showed that PHB can be rejuvenated while subsequent ageing is prevented to a large extent, which might enlarge the applicability of PHB.
237 citations
TL;DR: In this article, the authors made an inventory of exploratory learning processes by observing 17 students working with a computer simulation and analyzing students' thinking-aloud protocols and found that students were reluctant to apply learning processes that are considered characteristic for exploratory or discovery learning.
Abstract: Computer simulations create a context that is well fitted for exploratory or discovery learning. The aim of the present two studies was to gain deeper insight into what constitutes exploratory learning and to assess the effects of a number of instructional support measures. The domain involved was control theory at the university level. In the first study we made an inventory of exploratory learning processes by observing 17 students working with a computer simulation and analyzing students' thinking-aloud protocols. Subjects received a structured assignment with hints as an instructional support measure. In the second study, 91 students received an open-ended assignment with instructional support that consisted of an information sheet and a set of fill-in forms. On both sheets and forms, six cells were presented. A cell was given for each of the following six learning processes: identifying variables and parameters, generating hypotheses, designing an experiment, predicting, interpreting data, and drawing of conclusions. Information sheets were either of a domain specific or of a general nature. The set of fill-in forms were either free or had the cell HYPOTHESIS already filled in. The statements of the students on the fill-in forms were analyzed in a stepwise order. Twenty-two detailed learning processes were identified and classified. Two of the main classes of processes are transformative and regulative. Both studies showed that students were reluctant to apply learning processes that are considered characteristic for exploratory learning. Furthermore, students had problems with the exploratory learning processes, especially with the processes of generating hypotheses, interpreting data, and drawing conclusions. Effects of the instructional support measures were not conclusive. Hints did not result in significant improvements of the study process. Supporting learning processes with information sheets appeared to help students in performing learning processes, but no different effects of domain specific and general information could be found. Students who were provided with hypotheses showed a higher global activity level and higher scores in domain correctness of their learning processes.
228 citations
TL;DR: In this paper, the authors compared the results of Ronneberger and Ahrens (1977) with results of linear theory for the propagation of acoustic waves in a pipe with a quiescent fluid.
Abstract: The propagation of plane acoustic waves in smooth pipes and their reflection at open pipe terminations have been studied experimentally. The accuracy of the measurements is determined by comparison of experimental data with results of linear theory for the propagation of acoustic waves in a pipe with a quiescent fluid. The damping and the reflection at an unflanged pipe termination are compared.In the presence of a fully developed turbulent mean flow the measurements of the damping confirm the results of Ronneberger & Ahrens (1977). In the high-frequency limit the quasi-laminar theory of Ronneberger (1975) predicts accurately the convective effects on the damping of acoustic waves. For low frequencies a simple theory combining the rigid-plate model of Ronneberger & Ahrens (1977) with the theoretical approach of Howe (1984) yields a fair prediction of the influence of turbulence on the shear stress. The finite response time of the turbulence near the wall to the acoustic perturbations has to be taken into account in order to explain the experimental data. The model yields a quasi-stationary limit of the damping which does not take into account the fundamental difference between the viscous and thermal dissipation observed for low frequencies.Measurements of the nonlinear behaviour of the reflection properties for unflanged pipe terminations with thin and thick walls in the absence of a mean flow confirm the theory of Disselhorst & van Wijngaarden (1980), for the low-frequency limit. It appears however that a two-dimensional theory such as proposed by Disselhorst & van Wijngaarden (1980) for the high-frequency limit underestimates the acoustical energy absorption by vortex shedding by a factor 2.5.The measured influence of wall thickness on the reflection properties of an open pipe end confirms the linear theory of Ando (1969). In the presence of a mean flow the end correction δ of an unflanged pipe end varies from the value at the high-Strouhal-number limit of δ/a = 0.61, with a the pipe radius, which is close to the value in the absence of a mean flow given by Levine & Schwinger (1948) of δ/a = 0.6133, to a value of δ/a = 0.19 in the low-Strouhal-number limit which is close to the value predicted by Rienstra (1983) of δ/a = 0.26.The pressure reflection coefficient is found to agree with the theoretical predictions by Munt (1977, 1990) and Cargill (1982b) in which a full Kutta condition is included. The accuracy of the theory is fascinating in view of the dramatic simplifications introduced in the theory. For a thick-walled pipe end and a pipe terminated by a horn the end correction behaviour is similar. It is surprising that the nonlinear behaviour at low frequencies and high acoustic amplitudes in the absence of mean flow does not influence the end correction significantly.The aero-acoustic behaviour of the pipe end is dramatially influenced by the presence of a horn. In the presence of a mean flow the horn is a source of sound for a critical range of the Strouhal number.The high accuracy of the experimental data suggests that acoustic measurements can be used for a systematic study of turbulence in unsteady flow and of unsteady flow separation.
226 citations
TL;DR: In this paper, the joint queue length process at polling instants of a fixed queue is shown to be a multitype branching process (MTBP) with immigration, and sufficient conditions for ergodicity and moment calculations are given.
Abstract: The joint queue length process in polling systems with and without switchover times is studied. If the service discipline in each queue satisfies a certain property it is shown that the joint queue length process at polling instants of a fixed queue is a multitype branching process (MTBP) with immigration. In the case of polling models with switchover times, it turns out that we are dealing with an MTBP with immigration in each state, whereas in the case of polling models without switchover times we are dealing with an MTBP with immigration in state zero. The theory of MTBPs leads to expressions for the generating function of the joint queue length process at polling instants. Sufficient conditions for ergodicity and moment calculations are also given.
226 citations
21 Jun 1993
TL;DR: The Interval Timed Colored Petri Net (ITCPN) model as mentioned in this paper is a coloured Petri net extended with time, where time is in tokens and transitions determine a delay for each produced token.
Abstract: Practical experiences show that only timed and coloured Petri nets are capable of modelling large and complex real-time systems. This is the reason we present the Interval Timed Coloured Petri Net (ITCPN) model. An interval timed coloured Petri net is a coloured Petri net extended with time; time is in tokens and transitions determine a delay for each produced token. This delay is specified by an upper and lower bound, i.e. an interval. The ITCPN model allows the modelling of the dynamic behaviour of large and complex systems, without losing the possibility of formal analysis. In addition to the existing analysis techniques for coloured Petri nets, we propose a new analysis method to analyse the temporal behaviour of the net. This method constructs a reduced reachability graph and exploits the fact that delays are described by an interval.
195 citations
TL;DR: An explicit expression is given for the worst-case H/sub 2/ norm when the disturbance system is allowed to vary over all nonlinear, time-varying and possibly noncausal systems with bounded L/ sub 2/-induced operator norm.
Abstract: The worst-case effect of a disturbance system on the H/sub 2/ norm of the system is analyzed. An explicit expression is given for the worst-case H/sub 2/ norm when the disturbance system is allowed to vary over all nonlinear, time-varying and possibly noncausal systems with bounded L/sub 2/-induced operator norm. An upper bound for this measure, which is equal to the worst-case H/sub 2/ norm if the exogeneous input is scalar, is defined. Some further analysis of this upper bound is done, and a method to design controllers which minimize this upper bound over all robustly stabilizing controllers is given. The latter is done by relating this upper bound to a parameterized version of the auxiliary cost function studied in the literature. >
157 citations
TL;DR: In this paper, a production control framework for the engineer-to-order case situation was developed and described in the subsequent sections, where the different production phases and production units in the production process were defined as the first step.
148 citations
TL;DR: It is shown that the channel capacity can be achieved by equiprobable signaling with geometrical, Gaussian-like signal sets, and implicates that it is possible to approach channel capacity without using any kind of shaping codes.
Abstract: For the additive white Gaussian noise channel, there is a gap between the channel capacity and the highest achievable rate of equiprobable uniformly spaced one-dimensional signaling. It is commonly believed that approaching channel capacity requires the constituent one-dimensional signal points to have a Gaussian probability distribution. It is shown that the channel capacity can be achieved by equiprobable signaling with geometrical, Gaussian-like signal sets. Construction of these signal constellations is explicitly given. This result implicates that it is possible to approach channel capacity without using any kind of shaping codes. >
143 citations
TL;DR: The catalytic performance of a standard titanium molecular sieve catalyst, EUROTS-1, has been evaluated at four European universities as discussed by the authors, and the results showed that the calcination conditions of the catalyst, the use of internal standards, and the nature and the amount of the solvent added to the reaction mixture were major factors determining phenol conversion, product selectivity and hydrogen peroxide product yield.
Abstract: The catalytic performance of a standard titanium molecular sieve catalyst, EUROTS-1, has been evaluated at four European universities. The hydroxylation of phenol into catechol and hydroquinone with aqueous H 2 O 2 solution was selected as catalytic test reaction. The use of standard EUROTS-1 catalyst permitted to establish a reproducible standard reaction procedure. The calcination conditions of the catalyst, the use of internal standards, and the nature and the amount of the solvent added to the reaction mixture were found to be major factors determining phenol conversion, product selectivity and hydrogen peroxide product yield.
TL;DR: In this article, the authors experimentally observed an oscillating carrier capture time as a function of quantum well thickness, which correspond to a local capture time oscillating between 0.1 and 1.8 ps.
Abstract: We experimentally observed an oscillating carrier capture time as a function of quantum well thickness. The capture times were obtained in a separate confinement quantum well structure by subpicosecond rise time measurements of the quantum well luminescence as well as by pump-probe correlation measurements of the population decay in the barrier layer. Both experimental techniques yield an oscillating capture time between 3 and 20 ps, in excellent agreement with the theoretical predictions. In a classical picture, our results correspond to a local capture time oscillating between 0.1 and 1.8 ps. Furthermore, the dependence of the capture time on the excitation energy is analyzed and the time-dependent position of the quasi-Fermi-level in the barrier layer is tracked experimentally. We find that the carrier capture time is very sensitive to the detailed structure parameters as well as to the carrier distribution in the barrier. Carrier capture is found to be an ambipolar process in which the oscillations of the observed capture times are due to the quantum-mechanical oscillation of the electron wave-function overlap above the well. Finally, electron capture is demonstrated to be dominated by LO-phonon emission.
TL;DR: In this article, the first dorsal interosseus muscle contraction was recorded from the right hand and onsets were visually determined in the raw EMG, compared with the onsets produced by the automated methods on the rectified and low-pass filtered EMG.
Abstract: Many researchers have used off-line techniques for the automatic detection of electromyogram (EMG) onset. However, very little is known about the accuracy of these methods. In the present study, five such methods are evaluated and their accuracy is reported. Five subjects were asked to produce fast (ballistic) and slow (ramp) contractions with thumb and index finger of the right hand in a simple reaction time task. EMG was recorded from the first dorsal interosseus muscle, and onsets were visually determined in the raw EMG. These onsets were compared with the onsets produced by the automated methods on the rectified and low-pass filtered EMG. Four of the automated methods produced very reliable estimates of the visually determined onsets, at least when additional constraints upon the initial estimates were made. Studies using automated methods for EMG onset detection should report findings about their accuracy.
TL;DR: In this article, a rotating disc electrode covered with hydrogel layer was used to determine the effective diffusion coefficients (Deff) of oxygen, hydrogen peroxide and hydroquinone in a water-based sensor.
TL;DR: In this article, a technique for measuring moisture concentration profiles based on scanning neutron radiography is presented, and the isothermal moisture diffusivity as a function of moisture content is determined directly from these profiles.
23 Aug 1993
TL;DR: In this article, a syntactical format, the path format, was proposed for structured operational semantics in which predicates may occur. But it is not suitable for CCS, CSP, and ACP.
Abstract: We proposed a syntactical format, the path format, for structured operational semantics in which predicates may occur. We proved that strong bisimulation is a congruence for all the operators that can be defined within the path format. To show that this format is useful we provided many examples that we took from the literature about CCS, CSP, and ACP; they do satisfy the path format but no formats proposed by others. The examples include concepts like termination, convergence, divergence, weak bisimulation, a zero object, side conditions, functions, real time, discrete time, sequencing, negative premises, negative conclusions, and priorities (or a combination of these notions).
TL;DR: A molecular mechanism, based on the charge transfer between the atomic hydrogen ions and the rovibrationally excited hydrogen molecules, is presented that explains the observed fast recombination.
Abstract: Langmuir-probe measurements in a hydrogen-containing plasma jet show anomalous fast recombination that cannot be attributed to atomic processes such as radiative or three-particle recombination. In this paper a molecular mechanism, based on the charge transfer between the atomic hydrogen ions and the rovibrationally excited hydrogen molecules (H[sub 2][sup [nu],][ital J]+H[sup +][r arrow]H[sub 2][sup +]+H), is presented that explains the observed fast recombination.
TL;DR: In this paper, the authors studied the deformation and breakup process of single droplets in well-defined fields of flow and showed that when the shear rate is very slowly increased, allowing for almost equilibrium deformation, the results of the critical capillary number Cacrit as a function of viscosity ratio, as reported in the literature, are reproduced.
TL;DR: In this article, a relationship between the macroscopic toughness, the intrinsic network (entanglement and/or crosslink) density and the relative thickness of polymeric systems is presented.
TL;DR: In this article, the influence of maleicanhydride-modified polypropylene (m-PP) on monotonic mechanical properties of continuous-glass-fibre-reinforced poly-propylene composites was investigated.
TL;DR: It is concluded that SSCP using CE in a polymer network is a powerful method for the detection of point mutations in DNA sequences.
28 Jun 1993
TL;DR: An algorithm is given that constructs a model which is reduced w.r.t. a specific formula, hence, the reduced model allows model checking of any ACTL* formula and provides diagnostic information.
Abstract: In the first part of the paper, we present an algorithm for the construction of a quotient model under the equivalence induced by ACTL, the universal fragment of CTL. As this equivalence coincides with simulation equivalence, the achieved reduction is better than reductions achieved by methods based on bisimulation. Simulation equivalence is also the equivalence that is induced by ACTL*, hence, the reduced model allows model checking of any ACTL* formula. Furthermore it provides diagnostic information. In the second part, we restict our attention to single ACTL formulae. An algorithm is given that constructs a model which is reduced w.r.t. a specific formula.
TL;DR: The “Boom hierarchy” is a hierarchy of types that begins at the level of trees and includes lists, bags and sets, which forms the basis for the calculus of total functions developed by Bird and Meertens.
Abstract: The “Boom hierarchy” is a hierarchy of types that begins at the level of trees and includes lists, bags and sets. This hierarchy forms the basis for the calculus of total functions developed by Bird and Meertens, and which has become known as the “Bird-Meertens formalism”.
TL;DR: In this article, the tensile and fatigue behavior of unidirectional carbon-high-performance polyethylene/epoxy hybrid composites has been studied, including the effect of hybrid design and surface treatment of the high-performance PU fibres.
TL;DR: A majority coset decoding (MCD) procedure that can be applied to an arbitrary geometric code is discussed and a strictly smaller cost containing the error vector is obtained.
Abstract: A majority coset decoding (MCD) procedure that can be applied to an arbitrary geometric code is discussed. In general, the basic algorithm for decoding of algebraic-geometric codes does not correct up to the designed minimum distance. In MCD, a reduction step is added to the basic algorithm. In case the basic algorithm fails, a majority scheme is used to obtain an additional syndrome for the error vector. Thus a strictly smaller cost containing the error vector is obtained. In this way, the basic algorithm is applied to a decreasing chain of cosets and after finitely many steps the coset will be small enough for successful application of the basic algorithm. >
TL;DR: In this article, a unified continuum approach to brittle and fatigue damage is presented, where a scalar variable is used to represent the damage state and general forms of the constitutive equations are established on a thermodynamic basis.
TL;DR: A definition of demonic composition is proposed in which angelic composition is restricted by means of a so-called ‘monotype factor’, characterised by a Galois connection similar to theGalois connection between composition and factorisation of binary relations.
Abstract: This paper tackles the problem of constructing a compact, point-free proof of the associativity of demonic composition of binary relations and its distributivity through demonic choice. In order to achieve this goal, a definition of demonic composition is proposed in which angelic composition is restricted by means of a so-called ‘monotype factor’. Monotype factors are characterised by a Galois connection similar to the Galois connection between composition and factorisation of binary relations. The identification of such a connection is argued to be highly conducive to the desired compactness of calculation.
TL;DR: In this technical note a different approach is presented, based on the use of a digital image technique for the measurement of nonhomogeneous strain distributions, finite element modeling and theUse of a minimum-variance estimator.
01 Jan 1993
TL;DR: In this paper, an extension of pure type systems (PTSs) with definitions is presented, and it is shown that this extension preserves many of the properties of PTS's.
Abstract: In this paper, an extension of Pure Type Systems (PTS's) with definitions is presented. We prove this extension preserves many of the properties of PTS's. The main result is a proof that for many PTS's, including the Calculus of Constructions, this extension preserves strong normalisation.
TL;DR: In this paper, a model is given for the calculation of migration times of components applying sample stacking, and the effects of sample stacking in CZE on resolution, calibration graphs and pH are discussed.