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Showing papers by "Eindhoven University of Technology published in 1996"


Journal ArticleDOI
TL;DR: In this article, a consistent numerical solution procedure of the governing partial differential equations is presented, which is shown to be capable of properly simulating localization phenomena, and the introduction of higher-order deformation gradients in the constitutive model is demonstrated to be an adequate remedy to this deficiency of standard damage models.
Abstract: SUMMARY Conventional continuum damage descriptions of material degeneration suffer from loss of well-posedness beyond a certain level of accumulated damage. As a consequence, numerical solutions are obtained which are unacceptable from a physical point of view. The introduction of higher-order deformation gradients in the constitutive model is demonstrated to be an adequate remedy to this deficiency of standard damage models. A consistent numerical solution procedure of the governing partial differential equations is presented, which is shown to be capable of properly simulating localization phenomena.

1,207 citations


Journal ArticleDOI
TL;DR: In this paper, a comprehensive survey of experimental studies on the magnetic anisotropy in metallic multilayers containing Fe, Co or Ni is presented and commented on, with the help of some dedicated experimental studies.
Abstract: Ferromagnetic materials exhibit intrinsic `easy' and `hard' directions of the magnetization. This magnetic anisotropy is, from both a technological and fundamental viewpoint one of the most important properties of magnetic materials. The magnetic anisotropy in metallic magnetic multilayers forms the subject of this review article. As individual layers in a multilayer stack become thinner, the role of interfaces and surfaces may dominate that of the bulk: this is the case in many magnetic multilayers, where a perpendicular interface contribution to the magnetic anisotropy is capable of rotating the easy magnetization direction from in the film plane to perpendicular to the film plane. In this review, we show that the (in-plane) volume and (perpendicular) interface contribution to the magnetic anisotropy have been separated into terms related to mechanical stresses, crystallographic structure and the planar shape of the films. In addition, the effect of roughness, often inherent to the deposition techniques used, has been addressed theoretically. Several techniques to prepare multilayers and to characterize their growth as well as methods to determine the magnetic anisotropy are discussed. A comprehensive survey of experimental studies on the perpendicular magnetic anisotropy in metallic multilayers containing Fe, Co or Ni is presented and commented on. Two major subjects of this review are the extrinsic effects of strain, roughness and interdiffusion and the intrinsic effect of the crystallographic orientation on the magnetic anisotropy. Both effects are investigated with the help of some dedicated experimental studies. The results of the orientational dependence studies are compared with ab initio calculations. Finally, the perpendicular surface anisotropy and the in-plane step anisotropy are discussed.

1,099 citations


Journal ArticleDOI
TL;DR: In this article, the sulfidation of crystalline MoO3 and the thermal decomposition of (NH4)2MoO2S2 to MoS2 via an {MoOS2} oxysulfide intermediate have been studied by means of monochromatic X-ray photoelectron spectroscopy (XPS) and IRES.
Abstract: The sulfidation of crystalline MoO3 and the thermal decomposition of (NH4)2MoO2S2 to MoS2 via an {MoOS2} oxysulfide intermediate have been studied by means of monochromatic X-ray photoelectron spectroscopy (XPS) and infrared emission spectroscopy (IRES) Several basic steps of the sulfidation reaction could be resolved and explained in terms of the structure of crystalline MoO3 The sulfidation reaction starts at low temperatures with an exchange of terminal O2- ligands of the oxide for S2- by reaction with H2S from the sulfiding atmosphere In subsequent Mo−S redox reactions, bridging S22- ligands and Mo5+ centers are formed Lattice relaxation and further sulfur uptake are the main processes before, at temperatures above 200 °C, direct reactions with H2 occur, during which the Mo5+ centers are converted into the 4+ oxidation state The decomposition experiments with (NH4)2MoO2S2 show that terminal O2- ligands serve as the reactive sites The conversion of terminal MoOt to MoS entities and the subsequent

418 citations


Journal ArticleDOI
TL;DR: For all constantsk,l, explicit algorithms that, given a graphG=(V,E) with a tree-decomposition ofG with treewidth with useO(|V|) time are given, which do not rely on non-constructive reasoning and are single exponential inkandl.

306 citations


Journal ArticleDOI
01 Oct 1996-Polymer
TL;DR: In this paper, a review of recent progress in the synthesis and characterization of well-defined conjugated polymers and oligomers is presented using a subdivision into three main sections, covering hydrocarbon polymers, heterocyclic polymer and the oligomers, respectively.

297 citations


Journal ArticleDOI
TL;DR: Inverted unimol.
Abstract: Inverted unimol. dendritic micelles were prepd. by modification of end groups of poly(propyleneimine) dendrimers with hydrophobic alkyl chains. The dendritic character and micellar structure of the products were studied

263 citations


Journal ArticleDOI
TL;DR: In the aggregated phases, a splitting of the excited state into two exciton levels occurs as mentioned in this paper, and the exciton level is split into two levels of exciton activation.
Abstract: Conformationally disordered poly{3,4-di[(S)-2-methylbutoxy]thiophene} is prepd via monomer polymn by anhyd FeCl3 Optically active ordered polymer is prepd by cooling of the polymer to -30 Deg In the aggregated phases a splitting of the excited state into two exciton levels occurs

258 citations


Journal ArticleDOI
20 May 1996-EPL
TL;DR: In this paper, a summary of experimental results on structure functions obtained using extended self-similarity in various flow configurations (jet, grid, mixing layer, duct flow, cylinder) at Reynolds numbers ranging between 30 and 5000 is presented.
Abstract: A summary of experimental results on structure functions obtained using extended self-similarity in various flow configurations (jet, grid, mixing layer, duct flow, cylinder) at Reynolds numbers ranging between 30 and 5000 is presented.

243 citations


Journal ArticleDOI
TL;DR: In this paper, a concrete method for constructing a consistent set of performance indicators forming the basis of a consistent performance management system is presented, where explicit attention is paid to the relations between PIs.
Abstract: Performance indicators (PIs) and performance measurement are popular topics in management literature nowadays However, hardly ever is attention paid to the consequences of the relationships that often exist between the different PIs for designing effective, consistent performance management systems for organizations as a whole Presents a concrete method for constructing a consistent set of PIs forming the basis of a consistent performance management system, where explicit attention is paid to the relations between PIs Discusses the important role played by the new classification of PIs Provides a case study to illustrate the use of the method in a practical situation

242 citations


Journal ArticleDOI
TL;DR: QFD is more a process than just a tool for product as well as production process development based on the concept of Company Wide Quality Control, with key factor for success is the Cross Functional Management approach.

240 citations


Journal ArticleDOI
TL;DR: In this paper, the authors calculate the vertical excitation energies from the singlet ground state S0 to the first one-photon allowed singlet excited state S1 as well as the energy difference between the ground state and the lowest triplet state T1.
Abstract: On the basis of configuration interaction calculations, we first describe the nature of the lowest singlet and triplet excited states in oligothiophenes ranging in size from two to six rings. We calculate the vertical excitation energies from the singlet ground state S0 to the first one-photon allowed singlet excited state S1 as well as the energy difference between the ground state and the lowest triplet state T1. The computed transition energies are in very good agreement with the measured values and indicate a strong confinement of the lowest triplet. We also uncover the nature of the higher-lying triplet excited state Tn that is coupled via a large oscillator strength to T1. The evolution with chain length of the T1−Tn excitation energies compares well with the experimental evolution based on photoinduced absorption data. Next, we investigate the geometry relaxation phenomena occurring in the S1 and T1 states; more pronounced and localized bond-length deformations are calculated in the triplet state t...

Journal ArticleDOI
TL;DR: In this article, an approximate projection scheme based on the pressure correction method is proposed to solve the Navier-Stokes equations for incompressible flow, which is applied to the continuous equations; however, there are no problems concerning the choice of boundary conditions of the pressure step.
Abstract: SUMMARY An approximate projection scheme based on the pressure correction method is proposed to solve the NavierStokes equations for incompressible flow. The algorithm is applied to the continuous equations; however, there are no problems concerning the choice of boundary conditions of the pressure step. The resulting velocity and pressure are consistent with the original system. For the spatial discretization a high-order spectral element method is chosen. The high-order accuracy allows the use of a diagonal mass matrix, resulting in a very efficient algorithm. The properties of the scheme are extensively tested by means of an analytical test example. The scheme is Mer validated by simulating the laminar flow over a backward-facing step. The solution of the Navier-Stokes equations for unsteady incompressible fluid flow is still a major challenge in the field of computational fluid dynamics. An overview of the most important aspects with respect to the solution of the incompressible Navier-Stokes equations can be found in References 1-5. The Navier-Stokes equations form a set of coupled equations for both velocity and pressure (or, better, the gradient of the pressure). One of the main problems related to the numerical solution of these equations is the imposition of the incompressibility constraint and consequently the calculation of the pressure. The pressure is not a thermodynamic variable, as there is no equation of state for an incompressible fluid. It is an implicit variable which instantaneously 'adjusts itself' in such a way that the velocity remains divergence-free. The gradient of the pressure, on the other hand, is a relevant physical quantity: a force per unit volume. The mathematical importance of the pressure in an incompressible flow lies in the theory of saddle-point problems (of which the steady Stokes equations are an example), where it acts as a Lagrangian multiplier that constrains the velocity to remain divergence-free. There are numerous approaches to solve the Navier-Stokes equations. For the solution of unsteady Navier-Stokes flow perhaps one of the most successful approaches to date is provided by the class of projection methods.&' Projection methods have been developed as a useful way of obtaining an efficient solution algorithm for unsteady incompressible flow. In this paper, projection methods are considered that are applied to the set of continuous equations, yielding very efficient and simple-toimplement algorithms. By decoupling the treatment of velocity and pressure terms, a set of easier-tosolve equations arises: a convectiondiffusion problem for the velocity, yielding an intermediate velocity which is not divergence-free; and a Poisson equation for the pressure (or a related quantity).

Journal ArticleDOI
TL;DR: It is shown that preemptive scheduling in a two-stage flow shop with at least two identical parallel machines in one of the stages so as to minimize makespan is NP-hard in the strong sense.

Journal ArticleDOI
TL;DR: Repulsive secondary electrostatic interactions between the cis-amide and uracil carbonyl groups are thought to be responsible for the low association constant of complexes of bis(acylamino)triazines with uracils.
Abstract: The association behavior of several 2,4-diamino-s-triazines, 2,6-diaminopyridines, and their acylated derivatives with uracil derivatives was studied. In solution (1)H-NMR and IR spectroscopy were used, and in the solid state as (co)crystals X-ray diffraction was used. Acylation of 2,6-diaminopyridine leads to an increase of the association constant in CDCl(3) of the complexes with N-propylthymine from 84 to 440-920 M(-)(1), whereas acylation of diamino-s-triazines leads to a dramatic fall in the association constant of the complexes with N-propylthymine from 890 to ca. 6 M(-)(1). This phenomenon is related to different conformational preferences of these compounds. The amide groups in bis(acylamino)pyridines prefer a trans conformation, with the carbonyl group anti with respect to the ring nitrogen and coplanar with the aromatic ring. The amides of bis(acylamino)triazines, however, reside predominantly in a cis conformation. Repulsive secondary electrostatic interactions between the cis-amide and uracil carbonyl groups are thought to be responsible for the low association constant of complexes of bis(acylamino)triazines with uracils. The relatively high dimerization constants of bis(acylamino)triazines have been rationalized by the strong tendency to dimerize via quadruple hydrogen bonding.

Journal ArticleDOI
TL;DR: In this paper, the isothermal crystallization of three isotactic polypropylene (iPP) types, with different molar mass distributions, was studied after a well defined shear treatment of the melt at an elevated temperature and a subsequent quench to the crystallization temperature.
Abstract: The isothermal crystallization of three isotactic polypropylene (iPP) types, with different molar mass (distributions), was studied after a well defined shear treatment of the melt at an elevated temperature and a subsequent quench to the crystallization temperature. For these experiments a standard rheometer of the cone and plate configuration was used. The development of the crystallization was monitored by dynamic oscillatory measurements. Shearing in the melt was shown to enhance subsequent crystallization at lower temperatures. Not only the total shear at constant rate is of importance, but also the chosen combination of rate and shearing time. Moreover, a pronounced influence of molar mass was detected. The exploration of the melting temperatures and times which are necessary for an erasion of the memory effects showed that the effect of shearing could not completely be erased, possibly as a consequence of mechanical degradation.

Journal ArticleDOI
TL;DR: In this paper, a survey of local search methods for the job shop scheduling problem is presented, with an emphasis on local search, both deterministic and randomized local search and the proposed neighborhoods are discussed.
Abstract: We survey solution methods for the job shop scheduling problem with an emphasis on local search. Both deterministic and randomized local search methods as well as the proposed neighborhoods are discussed. We compare the computational performance of the various methods in terms of their effectiveness and efficiency on a standard set of problem instances.

Journal ArticleDOI
TL;DR: Element Free Galerkin methods are methods for solving partial differential equations with the help of shape functions coming from Moving Least Squares Approximation that are more flexible than the Finite Element method.

Journal ArticleDOI
TL;DR: The purpose of this paper is to examine the problem of controlling a linear time-invariant system subject to input saturation in order to have its output track (or reject) a family of reference (or disturbance) signals produced by some external generator.

Journal ArticleDOI
TL;DR: This paper focuses on the interactions between the elements that constitute such a multi-echelon system, in order to determine several service measures (e.g. external customer service level and inventory holding costs).

Journal ArticleDOI
24 Jul 1996-Langmuir
TL;DR: In this paper, the mass change of a Pt electrode during Ru deposition was measured with the electrochemical quartz crystal microbalance (EQCMB) to obtain the surface content of Ru in rough electrocodeposited PtRu electrodes, and it was shown that there is a correlation between the potential of the surface oxide reduction peak of the PtRu electrode and the surface Ru content.
Abstract: To obtain the surface content of Ru in rough electrocodeposited PtRu electrodes, the mass change of a Pt electrode during Ru deposition was measured with the electrochemical quartz crystal microbalance (EQCMB). It is shown that there is a correlation between the potential of the surface oxide reduction peak of the PtRu electrode and the surface Ru content. With the EQCMB also the methanol oxidation and oxide formation on both Pt and PtRu were studied. Implications for the oxidation of CO and CH3OH are discussed, in the context of which some IR experiments on CO and PtRu are presented as well.

Journal ArticleDOI
TL;DR: In this paper, it was suggested that the decrease in hydrogen chemisorption capacity, hydrogenolysis selectivity, and number of holes in the d-band are related to the change in the structure of the metal-support interface.

01 Jan 1996
TL;DR: A taxomomy of finite automata construction algorithms and application of Marcov Decision Processe to Search Problems, p. 51.
Abstract: Reduction and Topology, p. 28. Non Interleaving Process Algebra, p. 17. Design and Analysis of Dynamic Leader Election Protocols in Broadcast Networks, p. 73. A general conservative extension theorem in process algebra, p. 17. Job Shop Scheduling by Constraint Satisfaction, p. 22. A Hierarchical Membership Protocol for Synchronous Distributed Systems, p. 43. Temporal operators viewed as predicate transformers, p. 11. Automatic Verification of Regular Protocols in prr Nets, p. 23. A taxomomy of finite automata construction algorithms. p. 87. A taxonomy of finite automata minimization algorithms. p. 23. A precise clock synchronization protocol,p. Treewidth and Patwidth of Cocomparability graphs of Bounded Dimension, p. 14. Browsing Semantics in the "Tower" Model. p. 19. Verifying Sequentially Consistent Memory using Interface Refinement, p. 20. The object-oriented paradigm, p. 28. Canonical typing and II-conversion. p. 51. Application of Marcov Decision Processe to Search Problems, p. 21. Graph Isomorphism Models for Non Interleaving Process Algebra, p. 18. Fonnal Specification and Compositional Verification of an Atomic Broadcast Protocol, p. 22. Time and the Order of Abstract Events in Distributed Computations, p. 29. Logic Programming and Negation: A Survey. p. 62. A Hierarchical Diagrammatic Representation of Class Structure, p. 22. Process Algebra with Partial Choice, p. 16. 94/10 T. verhoeff 94/11 J. Peleska C. Huizing C. Petersohn 94/12 T. KIoks D. Kratsch H. MUller 94/13 R. Seljee 94/14 W. Peremans 94/15 RJ.M. Vaessens E.H.L. Aarts 1.K. Lenstra 94116 R.c. Backhouse H. Doornbos 94117 S. Mauw M.A. Reniers 94/18 F. Kamareddine R. Nederpelt 94/19 B.W. Watson 94120 R. Bloo F. Kamareddine R. Nederpelt 94/21 B,W. Watson

Journal ArticleDOI
TL;DR: In this article, a review of the available theories is presented which are proper for the creation of a disassembly strategy, together with a new mathematical tool result into a comprehensive methodology for the determination of disassembly strategies.
Abstract: SUMMARY Disassembly is a process which is applied for reusing abandoned goods and materials, the aim is to protect the environment and to regain the value added to products. In addition, by applying disassembly, future high disposal costs imposed by legislation can be avoided. The hazard of the entire disassembly process is enormous because of lack of information concerning the discarded goods. In order to make the disassembly process economically viable at the current state of the art, a comprehensive disassembly strategy is required. Its main task is to determine the disassembly level and disassembly sequences which provide conditions of the generation of profit while the environmental conditions are maintained. A review of the available theories is presented which are proper for the creation of a disassembly strategy. These theories together with a new mathematical tool result into a comprehensive methodology for the determination of a disassembly strategy. This methodology is illustrated by solving a ...

Journal ArticleDOI
TL;DR: The causes for gaps in scheduling are explained, the solutions to improve scheduling are illustrated by way of a case study, and the extent to which a scheduling technique can adequately model the processes on the shopfloor is investigated.
Abstract: Successful implementations of scheduling techniques in practice are scarce. Not only do daily disturbances lead to a gap between theory and practice, but also the extent to which a scheduling technique can adequately model the processes on the shopfloor, and the extent to which the optimization goal of a technique matches the organizational goal are not great enough. Further, the schedulers’ actions may play an important role in the fulfilment of the generated schedules. The organizational structure with its different responsibilities and conflicting goals may also result in the poor performance of scheduling techniques. Besides these, there is the problem of measuring the quality of a schedule. Discusses the causes for these gaps and illustrates the solutions to improve scheduling by way of a case study.

Journal ArticleDOI
TL;DR: This work proposes a framework based on high-level Petri nets that is used to model and analyse business processes and presents the “What, how and by whom?” approach, developed to guide the application of the framework in a BPR setting.

Book ChapterDOI
03 Jun 1996
TL;DR: It is proved that the algorithms proposed have performance bound 2 and (√5 + 1)/2, respectively, and it is shown that for both problems there cannot exist an on-line algorithm with a better performance guarantee.
Abstract: We consider single-machine on-line scheduling problems where jobs arrive over time. A set of independent jobs has to be scheduled on the machine, where preemption is not allowed and the number of jobs is unknown in advance. Each job becomes available at its release date, which is not known in advance, and its characteristics, e.g., processing requirement, become known at its arrival. We deal with two problems: minimizing total completion time and minimizing the maximum time by which all jobs have been delivered. For both problems we propose and analyze an on-line algorithm based on the following idea: As soon as the machine becomes available for processing, choose an available job with highest priority, and schedule it if its processing requirement is not too large. Otherwise, postpone the start of this job for a while. We prove that our algorithms have performance bound 2 and (√5 + 1)/2, respectively, and we show that for both problems there cannot exist an on-line algorithm with a better performance guarantee.

Journal ArticleDOI
TL;DR: In this article, fresh and pretreated nickel and cobalt-phosphorus compounds were characterized by XRD and EM/EDAX and tested in gas phase quinoline hydrodenitrogenation (643 K, 30 bar).

Journal ArticleDOI
TL;DR: In this paper, the authors developed a model for permeation through inert membranes, as encountered in many cases in ultrafiltration and in gas permeation in inert porous plugs, which includes both interspecies (diffusive) and species-wall forces.
Abstract: This paper focuses mainly on the development of a model for permeation through inert membranes, as encountered in many cases in ultrafiltration and in gas permeation through inert porous plugs. The ultrafiltration model is made up of a boundary layer transport model and a porous membrane model in series, which are connected by an equilibrium relation. The boundary layer model is developed with the Vieth approximation for turbulent diffusivity. For the internal membrane transport, a modification of the Maxwell-Stefan-Lightfoot equation is derived (the binary friction model), which in a natural way includes both interspecies (diffusive) and species-wall forces. Application for the partial separation of PEG-3400 from aqueous solution shows that membrane friction coefficients can simply be estimated from membrane resistance measurements and mixture viscosity data. The only adjustable parameter to be determined is the distribution coefficient between the free solution and the membrane pores. The differences between the Lightfoot approach and the dusty gas model (DGM) are shown to stem from errors in the drivations of the latter, thus invalidating the dusty gas approach in the normal region in which viscous friction effects become important. For gases, the binary friction model is developed to include Knudsen and viscous wall friction terms as well as intermolecular diffusion. It is shown to give excellent coverage of the He-Ar diffusion data of Evans et al. (J. Appl. Phys., 33 (1962) 2682; 34 (1963) 2020), with wall friction coefficients derived directly from Knudsen coefficients and gas viscosity data. The apparent success of the DGM in describing the same phenomena is shown to be caused by the relatively small importance of the wall friction forces at elevated pressures, and by the correct transition to Knudsen flow at low pressures. In addition, it is shown that diffusive slip phenomena in capillaries can be described well by the binary friction model.

Journal ArticleDOI
TL;DR: The observed enhanced magnetoresistance as compared to conventional all-metal spin-valves is interpreted with a semiclassical approach in which specular reflections at the metal/insulator barrier are included.
Abstract: We have investigated the giant magnetoresistance of artificial structures containing metallic Co/Cu/Co and ${\mathrm{Ni}}_{80}$${\mathrm{Fe}}_{20}$/Cu/${\mathrm{Ni}}_{80}$${\mathrm{Fe}}_{20}$ spin-valves confined within insulating antiferromagnetic NiO layers. The observed enhanced magnetoresistance as compared to conventional all-metal spin-valves is interpreted with a semiclassical approach in which specular reflections at the metal/insulator barrier are included.

01 Jan 1996
TL;DR: In this paper, a quadriphasic mixture model is used to model the swelling and shrinking behavior of soft biological tissues and the resulting non-linear integral equations are linearized and solved by the Newton-Raphson iteration procedure.
Abstract: The swelling and shrinking behaviour of soft biological tissues is described by a quadriphasic mixture model. In this model four phases are distinguished: a charged solid, a fluid, cations and anions. A description of the set of coupled differential equations of this quadriphasic mixture model is given. These equations are solved by the finite element method using a weighted residual approach. The resulting non-linear integral equations are linearized and solved by the Newton-Raphson iteration procedure. We performed some confined swelling and compression experiments on intervertebral disc tissue. These experiments are simulated by a one-dimensional finite element implementation of this quadriphasic mixture model. In contrast to a triphasic mixture model, physically realistic diffusion coefficients can be used to fit the experiments when the fixed charge density is relatively large, because in the quadriphasic mixture model electrical phenomena are not neglected.