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Showing papers by "Technische Universität Darmstadt published in 1997"


Journal ArticleDOI
TL;DR: An introduction to the field of fault detection and diagnosis is given, which begins with a consideration of a knowledge-based procedure that is based on analytical and heuristic information, and different methods of Fault detection are considered, which extract features from measured signals and use process and signal models.

1,090 citations


Proceedings ArticleDOI
13 Apr 1997
TL;DR: The results clearly show that MAX-MIN Ant System has the property of effectively guiding the local search heuristics towards promising regions of the search space by generating good initial tours.
Abstract: Ant System is a general purpose algorithm inspired by the study of the behavior of ant colonies. It is based on a cooperative search paradigm that is applicable to the solution of combinatorial optimization problems. We introduce MAX-MIN Ant System, an improved version of basic Ant System, and report our results for its application to symmetric and asymmetric instances of the well known traveling salesman problem. We show how MAX-MIN Ant System can be significantly improved, extending it with local search heuristics. Our results clearly show that MAX-MIN Ant System has the property of effectively guiding the local search heuristics towards promising regions of the search space by generating good initial tours.

884 citations


Journal ArticleDOI
TL;DR: For the first time, by means of magnetoencephalography a periodotopic organization of the human auditory cortex is demonstrated and its spatial relationship to the tonotopic organizations is analysed by using a range of stimuli with different temporal envelope fluctuations and spectra and a magnetometer providing high spatial resolution.
Abstract: Timbre and pitch are two independent perceptual qualities of sounds closely related to the spectral envelope and to the fundamental frequency of periodic temporal envelope fluctuations, respectively. To a first approximation, the spectral and temporal tuning properties of neurons in the auditory midbrain of various animals are independent, with layouts of these tuning properties in approximately orthogonal tonotopic and periodotopic maps. For the first time we demonstrate by means of magnetoencephalography a periodotopic organization of the human auditory cortex and analyse its spatial relationship to the tonotopic organization by using a range of stimuli with different temporal envelope fluctuations and spectra and a magnetometer providing high spatial resolution. We demonstrate an orthogonal arrangement of tonotopic and periodotopic gradients. Our results are in line with the organization of such maps in animals and closely match the perceptual orthogonality of timbre and pitch in humans.

207 citations


Journal ArticleDOI
TL;DR: Efficient incorporation was observed into isoprene emitted by Populus, Chelidonium, and Salix, and into the phytol moiety of chlorophylls in a red alga, in two green algae, and a higher plant.

182 citations


Journal ArticleDOI
TL;DR: In this article, an extensive Round Robin test programme on compressive softening was carried out by the RILEM Technical Committee 148-SSC to measure strain softening response of concrete under uniaxial compression, and the main variables in the test programme were the specimen slenderness h/d and the boundary restraint caused by the loading platen used in the experiments Both high friction and low friction loading systems were applied.
Abstract: 0025-5432/97 © RILEM tory cast its own specimens following a prescribed recipe The pre-peak behaviour was found to be independent of specimen slenderness when low friction loading platens were used However, for all loading systems a strong increase of (post-peak) ductility was found with decreasing specimen slenderness Analysis of the results, and comparison with data from literature, showed that irrespective of the loading system used, a perfect localization of deformations occured in the post-peak regime, which was first recognised by Van Mier in a series of uniaxial compression tests on concrete between brushes in 1984 Based on the results of the Round Robin, a draft recommendation will be made for a test procedure to measure strain softening of concrete under uniaxial compression Although the post-peak stress-strain behaviour seems to be a mixture of material and structural behaviour, it appears that a test on either prismatic or cylindrical specimens of slenderness h/d = 2, loaded between low friction boundaries (for example by inserting sheets of tef lon between the steel loading platen and the specimen), yields reproducible results with relatively low scatter For normal strength concrete, the closed-loop test can be controlled by using the axial platen-to-platen deformation as a feed-back signal, whereas for high-strength concrete either a combination of axial and lateral deformation should be used, or a combination of axial deformation and axial load FOREWORD An extensive Round Robin test programme on compressive softening was carried out by the RILEM Technical Committee 148-SSC “Test methods for the Strain Softening response of Concrete” The goal was to develop a reliable standard test method for measuring strain softening of concrete under uniaxial compression The main variables in the test programme were the specimen slenderness h/d and the boundary restraint caused by the loading platen used in the experiments Both high friction and low friction loading systems were applied Besides these main variables, which are both related to the experimental environment under which softening is measured, two different concretes were tested: a normal strength concrete of approximately 45 MPa and a higher strength concrete of approximately 75 MPa In addition to the prescribed test variables, due to individual initiatives, the Round Robin also provided information on the effect of specimen shape and size The experiments revealed that under low boundary friction a constant compressive strength is measured irrespective of the specimen slenderness For high friction loading systems (plain steel loading platen), an increase of specimen strength is found with decreasing slenderness However, for slenderness greater than 2 (and up to 4), a constant strength was measured The shape of the stress-strain curves was very consistent, in spite of the fact that each laboraRILEM TC 148-SSC: TEST METHODS FOR THE STRAIN-SOFTENING RESPONSE OF CONCRETE

178 citations


Journal ArticleDOI
TL;DR: It is shown that the lack of hemodynamic forces triggers apoptosis in endothelial cells, hinting at mechanical forces as essential stimuli for the maintenance of blood vessels.

172 citations


Journal ArticleDOI
TL;DR: In this article, the electromechanical behavior of WC-Co is modelled using the behaviour of pure WC and Co(W,C) alloys, according to a linear rule of mixtures.
Abstract: In long-life applications, the corrosion properties of cemented carbides can have a large influence on overall performance. Cemented carbides with improved corrosion resistance have been developed and are now commercially available. The understanding of the corrosion behaviour has been mostly empirical and satisfying explanations of the relationship between the electromechanical behaviour and in-service corrosion have been lacking. In this paper, the electromechanical behaviour of WC-Co is modelled using the behaviour of pure WC and Co(W,C) alloys, according to a linear rule of mixtures. By comparing WC-Co with WC-Ni(Cr,Mo) in both normal sulphuric acid and a synthetic mine water, it is shown that the behaviour of the two grades is inherently different. WC-Co exhibits a ‘pseudo-passivity’ during electro-mechanical tests but corrodes actively in industrial applications. In contrast, WC-Ni( Cr,Mo) passivates and the rate of corrosion can be several orders of magnitude lower than that of WC-Co.

163 citations


Journal ArticleDOI
TL;DR: A summary of methods that can be applied to automatic fault diagnosis using fuzzy logic, and some of the ideas which have led to the emerging neuro-fuzzy algorithms are discussed.

151 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe three experiments which exhibit strong pattern formation in the deposits left by successive granular avalanches, showing that at low flow rates continuous deposition, erosion or rotation gives rise to intermittent avalanche release.
Abstract: Three new experiments are described which exhibit strong pattern formation in the deposits left by successive granular avalanches. At low flow rates continuous deposition, erosion or rotation gives rise to intermittent avalanche release. Once in motion kinetic sieving of a bi-disperse granular mixture creates a two-layer shear band in which the larger particles overlie the smaller particles. When this is brought abruptly to rest by the upslope propagation of a shock wave a pair of str ipes is “frozen” into the deposited material. Successive releases create a large scale pattern, which strongly reflects the history of the granular flow. At faster deposition, erosion and rotation rates a new flow regime is entered in which intermittency and shock formation ceases, and the associated patterns change.

148 citations


Proceedings ArticleDOI
01 Nov 1997
TL;DR: A new user behavior model is described and various assumptions made within other models are shown to be unrealistic, including the assumption that long-term effects of user behavior on a single video server are limited to short-term influences.
Abstract: Large scale video-on-demand systems require that the serv ers offering the video retrieval and playback services are arranged as a distributed system in order to support a lar ge number of concurrent streams. If such a system is hierarchical, an end-node serv er handles the requests from a particular area, the ne xt server in the hierarchy takes the request over for several end-node servers if those can not answer the request and so on. This architecture pro vides for cost efficiency, reliability and scalability of serv ers. The end-node servers store only a limited set of the o verall available information which changes over time due to user interests. If a video is requested which is not available, this server contacts the next server in the hierarchy. To decide the size and location of the video serv ers and the location of videos in the hierarch y, the access behaviour of users must be considered. Various models for the simulation of user behavior (and thus, of the load induced on the video serv ers) have been presented in the literature. Only a fe w of these models are designed to take long-term effects into account because the basis for most of the models are short-term influences on a single video server and the load on this single machine. In this paper we describe a new user behavior model and show that various assumptions made within other models are unrealistic.

144 citations


Journal ArticleDOI
TL;DR: In this article, the FOPI-facility at GSI Darmstadt was used to study collisions of Au on Au at incident energies of 150, 250 and 400 A ·MeV.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the use of GAs for optimization in nonlinear model-based predictive control, where advanced genetic operators and other new features were introduced to increase the efficiency of the genetic search in order to deal with real-time constraints.

Journal ArticleDOI
TL;DR: In this article, the ground-state hyperfine splitting values of high-Z hydrogen-like ions are calculated and the relativistic, nuclear, and QED corrections are taken into account.
Abstract: The ground-state hyperfine splitting values of high-Z hydrogenlike ions are calculated. The relativistic, nuclear, and QED corrections are taken into account. The nuclear magnetization distribution correction (the Bohr-Weisskopf effect) is evaluated within the single-particle model with the g{sub S} factor chosen to yield the observed nuclear moment. An additional contribution caused by the nuclear-spin-orbit interaction is included in the calculation of the Bohr-Weisskopf effect. It is found that the theoretical value of the wavelength of the transition between the hyperfine-splitting components in {sup 165}Ho{sup 66+} is in good agreement with experiment. {copyright} {ital 1997} {ital The American Physical Society}

Journal ArticleDOI
TL;DR: An overview of presently known neural networks for the identification of nonlinear dynamic systems is given, and two special neural network architectures, one with external and one with internal dynamics, are considered in more detail.

Journal ArticleDOI
TL;DR: In this article, the electron spin relaxation properties of nitrogen atoms encapsulated in C 60 have been studied using pulsed EPR techniques, and it was shown that solvent collision-induced deformations of the carbon shell which modulate the zero-field splitting sensed by the quartet spin state of N@C 60 are the dominant spin relaxation mechanism.

Journal ArticleDOI
TL;DR: It is shown how the resource reservation in advance scheme can be embedded in a general architecture and the design and implementation of a resource management system providing reservations in advance functionality are described.
Abstract: Resource management offers Quality-of-Service reliability for time-critical continuous-media applications. Currently, existing resource management systems in the Internet and ATM domain only provide means to reserve resources starting with the reservation attempt and lasting for an unspecified duration. However, for several applications such as video conferencing, the ability to reserve the required resources in advance is of great advantage. This paper outlines a new model for resource reservation in advance. We identify and discuss issues to be resolved for allowing resource reservation in advance. We show how the resource reservation in advance scheme can be embedded in a general architecture and describe the design and implementation of a resource management system providing reservation in advance functionality.

Journal ArticleDOI
TL;DR: In this article, the authors examined correlations between deposition parameters and the coating properties of RF-sputtered films in deposition conditions and after heat treatment at temperatures up to 700 °C.
Abstract: The aim of this paper was to examine correlations between deposition parameters and the coating properties of RF-sputtered films in deposition conditions and after heat treatment at temperatures up to 700 °C. The investigations deal with titanium-, chromium- and hafnium-based nitrides, borides and ternary alloys. Different materials such as SAE 52100 steel, ASP 23 high-speed steel and Ti6A14V titanium alloy, which are commonly used in the aerospace industry, were coated to analyse the influence of the substrate material. The coatings were tested with respect to their phase composition, microstructure, residual stress, thickness, microhardness and adhesion. It is shown that the deposition parameters, as well as heat treatment at a temperature as low as 400 °C, can change considerably the coating properties.

Journal ArticleDOI
TL;DR: In this paper, the authors describe parameterizations of realistic e±- and γ-beam spectra at future linear e+e−-colliders, focusing on simplicity and reproducibility of the parameterizations.

Journal ArticleDOI
TL;DR: In this paper, a hybrid neuro-fuzzy network with a neural logical operator is proposed for fault detection and diagnosis in a vehicle wheel monitoring system. And an application of the system to the on-line monitoring of air pressure in vehicle wheels is described.

Journal ArticleDOI
TL;DR: Results suggest that salicylate may evoke tinnitus through a combined effect on auditory and non-auditory brain nuclei, while activity in auditory brain stem nuclei is reduced, stress-susceptible areas are activated.
Abstract: SUBJECTIVE tinnitus, a distracting internal noise is experienced by humans and animals. Mongolian gerbils were treated with salicylate as a tinnitus-evoking agent. After salicylate treatment, c-fos expression in auditory brain stem nuclei was as low as after saline treatment (control). Pronounced differences between groups were found, however, in areas susceptible to stress, with many immunoreactive cells in the locus coeruleus, the midbrain periaqueductal grey and the lateral parabrachial nucleus of salicylate-treated animals. These results suggest that salicylate may evoke tinnitus through a combined effect on auditory and non-auditory brain nuclei. While activity in auditory brain stem nuclei is reduced, stress-susceptible areas are activated. It seems possible that the interaction of these effects at particular locations of the brain causes tinnitus.

Proceedings ArticleDOI
03 Jun 1997
TL;DR: A new approach for partial encryption of video data is presented, which allows a security level of nearly every granularity and can be applied to all JPEG-based video compression methods.
Abstract: In multimedia conferencing systems the need for confidentiality gains in importance. This goal can be achieved by encryption. In real-time video processing systems there is a special need for partial data encryption. Existing methods and their weaknesses are investigated. We present a new approach for partial encryption of video data, which allows a security level of nearly every granularity. It can be applied to all JPEG-based video compression methods.

Journal ArticleDOI
TL;DR: For the first time, a complete arrangement of layers is achieved in cellular spheres (stratoids), provided that fully dispersed retinal cells are younger than embryonic day E6, and are reaggregated in the presence of a monolayer of retinal pigmented epithelium (RPE).
Abstract: Reaggregation of dispersed retinal cells of the chick embryo leads to histotypic retinospheroids in which the laminar organization remains incomplete: photoreceptors form rosettes which are surrounded by constituents of the other retinal layers. Here, for the first time, a complete arrangement of layers is achieved in cellular spheres (stratoids), provided that fully dispersed retinal cells are younger than embryonic day E6, and are reaggregated in the presence of a monolayer of retinal pigmented epithelium (RPE). A remarkable mechanism of stratoid formation from 1 to 15 days in vitro is revealed by the establishment of a radial Muller glia scaffold and of photoreceptors. During the first two days of reaggregation on RPE, rosettes are still observed. At this stage immunostaining with vimentin and F11 antibodies for radial Muller glia reveal a disorganized pattern. Subsequently, radial glia processes organize into long parallel fibre bundles which are arranged like spokes to stabilize the surface and centre of the stratoid. The opsin-specific antibody CERN 901 detects photoreceptors as they gradually build up an outer nuclear layer at the surface. These findings assign to the RPE a decisive role for the genesis and regeneration of a vertebrate retina.

Proceedings ArticleDOI
26 Oct 1997
TL;DR: This article introduces the approach to exploit multiscale wavelet methods for texture defect detection and demonstrates the application of the translation invariant a trous algorithm on texture samples.
Abstract: In this article we introduce our approach to exploit multiscale wavelet methods for texture defect detection. Several wavelet bases and decomposition algorithms are examined in regard of applicability, parameterization and computational costs. The article points out specific problems in localizing texture defects in multiscale wavelet representations. Besides the fast dyadic wavelet transform we demonstrate the application of the translation invariant a trous algorithm on texture samples. Feature extraction methods are proposed and examples of successful defect classification results are shown.

Journal ArticleDOI
TL;DR: In this paper, a new approach for identification of nonlinear dynamic systems is proposed based on a combination of generalized orthonormal basis functions and local linear model trees (LOLIMOT), which approximate an unknown function from data by the interpolation of many local linear models.

Journal ArticleDOI
TL;DR: A theory of temporal analysis of periodic signals is presented which is adequate to explain details of response properties of neurons in the auditory midbrain as well as psychophysical pitch effects and may be adequate to provide the adequate framework for the understanding of relative and absolute pitch perception.
Abstract: Periodic signals are generated by vocal chords and many other physical sound sources. A theory of temporal analysis of such periodic signals is presented which is adequate to explain details of response properties of neurons in the auditory midbrain as well as psychophysical pitch effects. According to this theory, such signals are coded in the temporal domain by neuronal activity synchronized to the signal periodicities and are processed by neuronal mechanisms, involving intrinsic oscillations synchronized to signal envelope, temporal integration of signal fine structure, and coincidence detection. Spikes from the oscillator and the integrator have different delays and may coincide only when the envelope periodicity is adequate for the compensation of this difference. Neurons in the auditory midbrain function as corresponding coincidence detectors and transfer the temporal information into a rate-place code. Coincidence neurons are arranged topographically, orthogonal to the tonotopic organization in the midbrain. An orthogonal representation of pitch and frequency was found also in the human auditory cortex. This theory allows to relate neuronal processing to certain auditory percepts. It may be adequate to provide the adequate framework for the understanding of relative and absolute pitch perception.

Proceedings ArticleDOI
11 Dec 1997
TL;DR: This paper presents an architecture for a mobile agent system which guarantees security for the host as well asSecurity for the agent, and additionally offers fault tolerance for the whole agent system at a high level.
Abstract: Mobile agents are no longer a theoretical issue since different architectures for their realization have been proposed. With the increasing market of electronic commerce it becomes an interesting aspect to use autonomous mobile agents for electronic business transactions. Being involved in money transactions, supplementary security features for mobile agent systems have to be ensured. In this paper we present an architecture for a mobile agent system which guarantees security for the host as well as security for the agent. This architecture additionally offers fault tolerance for the whole agent system at a high level. To handle these issues for mobile agents we use various encryption mechanisms and we apply a novel method for mobile agent systems by using distributed transactions processing based on the OMG Object Transaction Service in our architecture. With this security architecture an agent will be enabled to do money transactions.

Journal ArticleDOI
TL;DR: In this paper, a nonlinear fuzzy model with transparent inner structure is used for the generation of relevant symptoms, and the resulting symptom patterns are classified with a new self-learning classification structure based on fuzzy rules.

Journal ArticleDOI
TL;DR: In this article, the potential of mean force along the coordinate perpendicular to the window connecting two supercages of the zeolite was determined by means of constrained reaction coordinate dynamics, and the changes in the orientation of the aromatic ring during the cage-to-cage jump were explicitly examined.
Abstract: The diffusion of benzene and p-xylene in zeolite NaY at infinite dilution is studied by means of constrained reaction coordinate dynamics. Molecular dynamics (MD) simulations are used to determine the potential of mean force along the coordinate perpendicular to the window connecting two supercages of the zeolite. A comparison of the results of simulations with a fixed and with a flexible lattice shows that the consideration of lattice flexibility does not significantly influence the potential of mean force for cage-to-cage jumps. The changes in the orientation of the aromatic ring during the cage-to-cage jump are explicitly examined. The transition states for cage-to-cage migration are defined by a plane perpendicular to the reference coordinate. The components of the force along the reaction coordinate are studied as functions of the position, and the orientation is studied for the transition states. Differences between the results for benzene and p-xylene are discussed.

Book ChapterDOI
23 Aug 1997
TL;DR: This paper introduces a simply-typed lambda calculus with both modal and linear function types through the use of subtyping extra term formers associated with modality and linearity, and studies the basic metatheory of this system including existence and inference of principal types.
Abstract: This paper introduces a simply-typed lambda calculus with both modal and linear function types. Through the use of subtyping extra term formers associated with modality and linearity are avoided. We study the basic metatheory of this system including existence and inference of principal types.

Journal ArticleDOI
TL;DR: A framework for analyzing DIS structures and dynamics is suggested to help companies from the content, communications, computing and financial services industries optimize their DIS capabilities.
Abstract: Digital interactive services (DISs) define a new utility for facilitating electronic markets and commerce. Companies from the content, communications, computing and financial services industries are already merging to optimize their DIS capabilities. This article suggests a framework for analyzing DIS structures and dynamics.