Showing papers by "Technische Universität Darmstadt published in 2004"
TL;DR: In this article, the authors present a short introduction to the field and show some applications for an actuator, a passenger car, and a combustion engine, as well as other types of systems.
1,344 citations
08 Jul 2004
TL;DR: In this paper, the Laplacian of the mesh is enhanced to be invariant to locally linearized rigid transformations and scaling, which can be used to perform surface editing at interactive rates.
Abstract: Surface editing operations commonly require geometric details of the surface to be preserved as much as possible. We argue that geometric detail is an intrinsic property of a surface and that, consequently, surface editing is best performed by operating over an intrinsic surface representation. We provide such a representation of a surface, based on the Laplacian of the mesh, by encoding each vertex relative to its neighborhood. The Laplacian of the mesh is enhanced to be invariant to locally linearized rigid transformations and scaling. Based on this Laplacian representation, we develop useful editing operations: interactive free-form deformation in a region of interest based on the transformation of a handle, transfer and mixing of geometric details between two surfaces, and transplanting of a partial surface mesh onto another surface. The main computation involved in all operations is the solution of a sparse linear system, which can be done at interactive rates. We demonstrate the effectiveness of our approach in several examples, showing that the editing operations change the shape while respecting the structural geometric detail.
1,143 citations
TL;DR: The nature of beauty is rather self-oriented than goal-oriented, whereas goodness relates to both; both were related to each other as long as beauty and goodness stress the subjective valuation of a product.
Abstract: Two studies considered the interplay between user-perceived usability (i.e., pragmatic attributes), hedonic attributes (e.g., stimulation, identification), goodness (i.e., satisfaction), and beauty of 4 different MP3-player skins. As long as beauty and goodness stress the subjective valuation of a product, both were related to each other. However, the nature of goodness and beauty was found to differ. Goodness depended on both perceived usability and hedonic attributes. Especially after using the skins, perceived usability became a strong determinant of goodness. In contrast, beauty largely depended on identification; a hedonic attribute group, which captures the product's ability to communicate important personal values to relevant others. Perceived usability as well as goodness was affected by experience (i.e., actual usability, usability problems), whereas hedonic attributes and beauty remained stable over time. All in all, the nature of beauty is rather self-oriented than goal-oriented, whereas goodness relates to both.
1,028 citations
TL;DR: Mössbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematITE-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing Basaltic rock (Bounce rock).
Abstract: Mossbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.
742 citations
TL;DR: Because the regulation of root architecture is a key determinant of nutrient- and water-use efficiency in plants, protozoa provide a model system that may considerably advance the understanding of the mechanisms underlying plant growth and community composition.
Abstract: All nutrients that plants absorb have to pass a region of intense interactions between roots, microorganisms and animals, termed the rhizosphere. Plants allocate a great portion of their photosynthetically fixed carbon to root-infecting symbionts, such asmycorrhizal fungi; another part is released as exudates fuelling mainly free-living rhizobacteria. Rhizobacteria are strongly top-down regulated by microfaunal grazers, particularly protozoa. Consequently, beneficial effects of protozoa on plant growth have been assigned to nutrients released from consumed bacterial biomass, that is, the 'microbial loop'. In recent years however, the recognition of bacterial communication networks, the common exchange of microbial signals with roots and the fact that these signals are used to enhance the efflux of carbon from roots have revolutionized our view of rhizosphere processes. Most importantly, effects of rhizobacteria on root architecture seem to be driven in large by protozoan grazers. Protozoan effects on plant root systems stand in sharp contrast to effects of mycorrhizal fungi. Because the regulation of root architecture is a key determinant of nutrient- and water-use efficiency in plants, protozoa provide a model system that may considerably advance our understanding of the mechanisms underlying plant growth and community composition.
644 citations
TL;DR: In this article, changes in annual, June-September and March-May rainfall and rainy days have been analyzed based on 11 key stations located in different climatic zones of Ethiopia over the common period 1965-2002.
Abstract: Changes in annual, June–September and March–May rainfall and rainy days herein (defined as a day with rainfall greater than 1 mm) have been analysed based on 11 key stations located in different climatic zones of Ethiopia over the common period 1965–2002. The progressive Mann–Kendall trend test shows that there is no trend in the annual rainfall total, the seasonal rainfall total or rainy days over central, northern and northwestern Ethiopia in the period 1965–2002. In contrast, the annual and the June–September total rainfalls for the eastern (Jijiga, 137 mm/decade), southern (Negele, 119 mm/decade) and southwestern (Gore 257 mm/decade) stations show a significant decline since about 1982. Correlation analysis shows that the decline of rainfall in eastern, south and southwestern Ethiopia is caused by the corresponding persistent warming of the South Atlantic Ocean over the period approximately from 1986 to 2002. The sea-surface temperature (SST) over the tropical eastern Pacific Ocean is not significantly correlated with the main rainfall of the semi-arid lowland areas of eastern, southern, and southwestern Ethiopia, except at marginal zones in transition to the Ethiopian Highlands.
June–September rainfall over the Ethiopian Highlands is positively correlated to the equatorial east Pacific sea-level pressure and the southern oscillation index, and negatively correlated to SST over the tropical eastern Pacific Ocean as expected, confirming again that warm El Nino–southern oscillation episodes are associated with below-average June–September rainfall over the Ethiopian Highlands. Copyright © 2004 Royal Meteorological Society
504 citations
27 Aug 2004
TL;DR: The physical model is derived from continuum mechanics, which allows the specification of common material properties such as Young's Modulus and Poisson's Ratio and it is demonstrated how to solve the equations of motion based on these forces, with both explicit and implicit integration schemes.
Abstract: We present a method for modeling and animating a wide spectrum of volumetric objects, with material properties anywhere in the range from stiff elastic to highly plastic. Both the volume and the surface representation are point based, which allows arbitrarily large deviations form the original shape. In contrast to previous point based elasticity in computer graphics, our physical model is derived from continuum mechanics, which allows the specification of common material properties such as Young's Modulus and Poisson's Ratio.In each step, we compute the spatial derivatives of the discrete displacement field using a Moving Least Squares (MLS) procedure. From these derivatives we obtain strains, stresses and elastic forces at each simulated point. We demonstrate how to solve the equations of motion based on these forces, with both explicit and implicit integration schemes. In addition, we propose techniques for modeling and animating a point-sampled surface that dynamically adapts to deformations of the underlying volumetric model.
453 citations
TL;DR: Examination of quantitative census data for CAM diversity and biomass suggests that the larger CAM domains are those systems which are governed by a network of interacting stress factors requiring versatile responses and not systems where a single stress factor strongly prevails.
439 citations
TL;DR: Soils of north temperate forests harbor a tremendous diversity of microorganisms and invertebrates, whose distribution and abundance can be substantially altered by earthworm invasion, and invasive earthworms can affect understory plant communities, raising concerns over the loss of rare native herbs.
Abstract: Exotic earthworms from Europe and Asia are invading many northern forests in North America that currently lack native earthworms, providing an opportunity to assess the role of this important group of invertebrates in forest ecosystems Research on earthworm invasions has focused on changes in soil structure and carbon (C) and nitrogen (N) cycling that occur following invasion These changes include the mixing of organic and mineral soil horizons, decreases in soil C storage, and equivocal effects on N cycling Less well studied are changes in the soil foodwebs that accompany earthworm invasion Soils of north temperate forests harbor a tremendous diversity of microorganisms and invertebrates, whose distribution and abundance can be substantially altered by earthworm invasion Furthermore, invasive earthworms can affect understory plant communities, raising concerns over the loss of rare native herbs in some areas The ecological consequences of earthworm invasion are mediated through physical, geochemica
414 citations
TL;DR: In this paper, stable isotope ratios (15N/14N) in a diverse group of soil microarthropods, oribatid mites, were evaluated to evaluate trophic niche differentiation.
Abstract: The large number of animals that coexist in soil without any clear niche differentiation has puzzled biologists for a long time. We investigated stable isotope ratios (15N/14N) in a diverse group of soil microarthropods, oribatid mites, to evaluate trophic niche differentiation. The natural variation of the stable isotopes 15N/14N was measured in 36 species/taxa from four beech and beech-oak forests. Signatures of δ15N formed a gradient spanning over 12 δ units suggesting that (a) different species occupy different trophic niches and (b) oribatid mites span three to four trophic levels. This study for the first time documented strong trophic niche differentiation in decomposer microarthropods. The results suggest that trophic niche differentiation within taxonomic groups significantly contributes to the high diversity of soil animal taxa.
327 citations
TL;DR: In this article, mathematical models of suspensions with variable dampers and springs as well as active components are derived, and feedback principles are derived for controlling the damping ratio of dampers with proportional magnetic valve actuators.
TL;DR: Lichtenthaler et al. as discussed by the authors gave an overview on chemically transforming low-molecular weight carbohydrates into products with versatile industrial application profiles and the potential to replace those presently derived from petrochemical sources.
27 Sep 2004
TL;DR: This paper presents AO4BPEL, an aspect-oriented extension to BPEL4WS that captures web service composition in a modular way and the composition becomes more open for dynamic change.
Abstract: Web services have become a universal technology for integration of distributed and heterogeneous applications over the Internet. Many recent proposals such as the Business Process Modeling Language (BPML) and the Business Process Execution Language for Web Services (BPEL4WS) focus on combining existing web services into more sophisticated web services. However, these standards exhibit some limitations regarding modularity and flexibility. In this paper, we advocate an aspect-oriented approach to web service composition and present AO4BPEL, an aspect-oriented extension to BPEL4WS. With aspects, we capture web service composition in a modular way and the composition becomes more open for dynamic change.
TL;DR: In this paper, a new market-based approach for transmission expansion planning in deregulated environments is presented, which encourages and facilitates competition among all participants, provides nondiscriminatory access to cheap generation for all consumers, and considers all random and nonrandom power system uncertainties and selects the final plan after risk assessment of all solutions.
Abstract: Restructuring and deregulation has exposed transmission planner to new objectives and uncertainties. Therefore, new criteria and approaches are needed for transmission planning in deregulated environments. A new market-based approach for transmission planning in deregulated environments is presented in this paper. The main contribution of this research is: i) introducing a new probabilistic tool, named probabilistic locational marginal prices, for computing the probability density functions of nodal prices; ii) defining new market-based criteria for transmission expansion planning in deregulated environments; and iii) presenting a new approach for transmission expansion planning in deregulated environments using the above tool and criteria. The advantages of this approach are: i) it encourages and facilitates competition among all participants; ii) it provides nondiscriminatory access to cheap generation for all consumers; iii) it considers all random and nonrandom power system uncertainties and selects the final plan after risk assessment of all solutions; and iv) it is value based and considers investment cost, operation cost, congestion cost, load curtailment cost, and cost caused by system unreliability. The presented approach is applied to IEEE 30-bus test system.
TL;DR: In this paper, a series of Au/C catalysts were prepared by the gold sol method with different reducing agents and different kinds of carbon support providing Au mean particle diameters in the range 3-6nm.
TL;DR: The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crater.
Abstract: Mossbauer spectra measured on Mars by the Spirit rover during the primary mission are characterized by two ferrous iron doublets (olivine and probably pyroxene) and a ferric iron doublet (tentatively associated to nanophase ferric iron oxide) Two sextets resulting from nonstoichiometric magnetite are also present, except for a coating on the rock Mazatzal, where a hematite-like sextet is present Greater proportions of ferric-bearing phases are associated with undisturbed soils and rock surfaces as compared to fresh rock surfaces exposed by grinding The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crater
TL;DR: An ArcGIS VBA macro is developed which enables the user to derive criteria weights with the analytical hierarchy process and which allows a mapping of the land use assessment results by a weighted summation of GIS raster data sets.
01 Oct 2004
TL;DR: A man-in-the-middle attack on the Universal Mobile Telecommunication Standard (UMTS), one of the newly emerging 3G mobile technologies, is presented, showing that an attacker can mount an impersonation attack since GSM base stations do not support integrity protection.
Abstract: In this paper we present a man-in-the-middle attack on the Universal Mobile Telecommunication Standard (UMTS), one of the newly emerging 3G mobile technologies. The attack allows an intruder to impersonate a valid GSM base station to a UMTS subscriber regardless of the fact that UMTS authentication and key agreement are used. As a result, an intruder can eavesdrop on all mobile-station-initiated traffic.Since the UMTS standard requires mutual authentication between the mobile station and the network, so far UMTS networks were considered to be secure against man-in-the-middle attacks. The network authentication defined in the UMTS standard depends on both the validity of the authentication token and the integrity protection of the subsequent security mode command.We show that both of these mechanisms are necessary in order to prevent a man-in-the middle attack. As a consequence we show that an attacker can mount an impersonation attack since GSM base stations do not support integrity protection. Possible victims to our attack are all mobile stations that support the UTRAN and the GSM air interface simultaneously. In particular, this is the case for most of the equipment used during the transition phase from 2G (GSM) to 3G (UMTS) technology.
TL;DR: In this paper, a parameter-free prediction is obtained for the scattering of Goldstone bosons off heavy-light pseudo-scalar and vector mesons in terms of the non-linear chiral SU(3) Lagrangian.
TL;DR: In this paper, the meson resonances with quantum numbers JP = 1+ in terms of the chiral SU(3) Lagrangian were studied and a parameter-free prediction was obtained for the scattering of Goldstone bosons off vector mesons with JP=1− once they insist on approximate crossing symmetry of the unitarized scattering amplitude.
31 Oct 2004
TL;DR: This paper presents an analysis of feature-oriented and aspect-oriented modularization approaches with respect to variability management as needed in the context of system families and demonstrates the power of appropriate support for layer modules.
Abstract: This paper presents an analysis of feature-oriented and aspect-oriented modularization approaches with respect to variability management as needed in the context of system families. This analysis serves two purposes. On the one hand, our analysis of the weaknesses of feature-oriented approaches (FOAs for short) emphasizes the importance of crosscutting modularity as supported by the aspect-oriented concepts of pointcut and advice. On the other hand, by pointing out some of AspectJ's weaknesses and by demonstrating how Caesar, a language which combines concepts from both AspectJ and FOAs, is more effective in this context, we also demonstrate the power of appropriate support for layer modules.
15 Nov 2004
TL;DR: This paper proposes a hybrid composition approach that allows for a more modular and flexible web service composition and discusses two alternative technologies for implenting business rules in encapsulated units, using aspects and a rule-based engine.
Abstract: Over the last few years several process-based web service composition languages have erged, such as BPEL4WS and BPML. These languages define the composition on the basis of a process that specifies the control and data flow among the services to be composed. In this approach, the whole business logic underlying the composition including business policies and constraints is coded as a monolithic block. As a result, business rules are hard to change without affecting the core composition logic. In this paper, we propose a hybrid composition approach: The composition logic is broken down into a core part (the process) and several well-modularized business rules that exist and evolve independently. We also discuss two alternative technologies for implenting business rules in encapsulated units, using aspects and a rule-based engine. Our approach allows for a more modular and flexible web service composition.
TL;DR: In this paper, a study of visual and erosion effects of cavitation on simple single hydrofoil configurations in a cavitation tunnel was made, where a thin copper foil was used as an erosion sensor.
01 Aug 2004
TL;DR: A context-based method to determine best matching patches, and then, fit imported patches by aligning them with the surrounding surface by applying a rigid transformation followed by an iterative closest point procedure with non-rigid transformations.
Abstract: Sampling complex, real-world geometry with range scanning devices almost always yields imperfect surface samplings. These "holes" in the surface are commonly filled with a smooth patch that conforms with the boundary. We introduce a context-based method: the characteristics of the given surface are analyzed, and the hole is iteratively filled by copying patches from valid regions of the given surface. In particular, the method needs to determine best matching patches, and then, fit imported patches by aligning them with the surrounding surface. The completion process works top down, where details refine intermediate coarser approximations. To align an imported patch with the existing surface, we apply a rigid transformation followed by an iterative closest point procedure with non-rigid transformations. The surface is essentially treated as a point set, and local implicit approximations aid in measuring the similarity between two point set patches. We demonstrate the method at several point-sampled surfaces, where the holes either result from imperfect sampling during range scanning or manual removal.
01 Jan 2004
TL;DR: This article studies Pareto local optimum sets for the biobjective Traveling Salesman Problem applying straightforward extensions of local search algorithms for the single objective case and indicates the existence of several clusters of near-optimal solutions that are separated by only a few edges.
Abstract: In this article, we study Pareto local optimum sets for the biobjective Traveling Salesman Problem applying straightforward extensions of local search algorithms for the single objective case. The performance of the local search algorithms is illustrated by experimental results obtained for well known benchmark instances and comparisons to methods from literature. In fact, a 3-opt local search is able to compete with the best performing metaheuristics in terms of solution quality. Finally, we also present an empirical study of the features of the solutions found by 3-opt on a set of randomly generated instances. The results indicate the existence of several clusters of near-optimal solutions that are separated by only a few edges.
01 Nov 2004
TL;DR: In this paper, the high-frequency circulating bearing current that may occur in machines of inverter-based drive systems can be described by an eddy-current model and the parameters of an equivalent circuit are derived from the model.
Abstract: The high-frequency circulating bearing current that may occur in machines of inverter-based drive systems can be described by an eddy-current model. The parameters of an equivalent circuit are derived from the model. The ratio between bearing current and common-mode current amplitudes for different machines is calculated. The theoretical maximum ratio is about 0.35. Copper loops applied for bearing current measurement may decrease the circulating bearing currents up to almost 40%
22 Mar 2004
TL;DR: First steps toward a AOP concepts integration in Steamloom, an extension of IBM's Jikes Research Virtual Machine, are presented, and initial experimental results indicate that aspect-aware VMs and fluid code are promising w.r.t performance.
Abstract: A widespread implementation approach for the join point mechanism of aspect-oriented languages is to instrument areas in code that match the static part of pointcut designators, inserting dynamic checks for that part of matching that depends on run-time conditions, if needed. For performance reasons, such dynamic checks should be avoided whenever possible. One way to do so is to postpone weaving of advice calls until run-time, when conditions determining the emergence of join points hold. This calls for fluid code---code that adapts itself to the join point emergence at run-time, and suggests that AOP concepts should be integrated into the execution model underlying a VM. In this paper, we present first steps toward such an integration in Steamloom, an extension of IBM's Jikes Research Virtual Machine. Steamloom is fairly restricted, but our initial experimental results indicate that aspect-aware VMs and fluid code are promising w.r.t performance. While the focus in this paper is on performance, there are other advantages of aspect-aware VMs to be investigated in the future.
Book•
01 Jan 2004TL;DR: The authors focus on bootstrap signal detection in Gaussian and non-Gaussian interference as well as bootstrap model selection, which includes applications to real-world problems in areas such as radar and sonar, biomedical engineering and automotive engineering.
Abstract: The statistical bootstrap is one of the methods that can be used to calculate estimates of a certain number of unknown parameters of a random process or a signal observed in noise, based on a random sample. Such situations are common in signal processing and the bootstrap is especially useful when only a small sample is available or an analytical analysis is too cumbersome or even impossible. This book covers the foundations of the bootstrap, its properties, its strengths and its limitations. The authors focus on bootstrap signal detection in Gaussian and non-Gaussian interference as well as bootstrap model selection. The theory developed in the book is supported by a number of useful practical examples written in MATLAB. The book is aimed at graduate students and engineers, and includes applications to real-world problems in areas such as radar and sonar, biomedical engineering and automotive engineering.
TL;DR: In this article, Pareto local optimum sets for the bi-objective Traveling Salesman Problem (TSP) have been studied and 3-opt local search has been applied for the single objective case.
Abstract: In this article, we study Pareto local optimum sets for the biobjective Traveling Salesman Problem applying straightforward extensions of local search algorithms for the single objective case. The performance of the local search algorithms is illustrated by experimental results obtained for well known benchmark instances and comparisons to methods from literature. In fact, a 3-opt local search is able to compete with the best performing metaheuristics in terms of solution quality. Finally, we also present an empirical study of the features of the solutions found by 3-opt on a set of randomly generated instances. The results indicate the existence of several clusters of near-optimal solutions that are separated by only a few edges.
TL;DR: In this article, the authors report on bulk Si-Al-O-C ceramics produced by pyrolysis of commercial poly(methylsilsesquioxane) precursors.
Abstract: Here we report on bulk Si–Al–O–C ceramics produced by pyrolysis of commercial poly(methylsilsesquioxane) precursors. Prior to the pyrolysis the precursors were cross-linked with a catalyst, or modified by the sol-gel-technique with an Al-containing alkoxide compound, namely alumatrane. This particular procedure yields amorphous ceramics with various compositions (Si1.00O1.60C0.80, Si1.00Al0.04O1.70C0.48, Si1.00Al0.07O1.80C0.49, and Si1.00Al0.11O1.90C0.49) after thermal decomposition at 1100 °C in Ar depending on the amount of Al-alkoxide used in the polymer reaction synthesis. The as-produced ceramics are amorphous and remain so up to 1300 °C. Phase separation accompanied by densification (1300–1500 °C) and formation of mullite at T > 1600 °C are the stages during heat-treatment. Bulk SiAlOC ceramics are characterized in terms of microstructure and crystallization in the temperature regime ranging from 1100 to 1700 °C. Aluminum-free SiOC forms SiC along with cracking of the bulk compacts. In contrast, the presence of Al in the SiOC matrix forms SiC and mullite and prevents micro cracking at elevated temperatures due to transient viscous sintering. The nano-crystals formed are embedded in an amorphous Si(Al)OC matrix in both cases. Potential application of polysiloxane derived SiOC ceramic in the field of ceramic micro electro mechanical systems (MEMS) is reported.