Showing papers by "University of Paderborn published in 2006"
TL;DR: In this paper, the authors identify service support and personal interaction as core differentiators, followed by a supplier's know-how and its ability to improve a customer's time to market.
Abstract: Many business customers today consolidate their supply bases and implement preferred supplier programs. Consequently, vendors increasingly face the alternative of either gaining a key supplier status with their customers or being pushed into the role of a backup supplier. As product and price become less important differentiators, suppliers of routinely purchased products search for new ways to differentiate themselves in a buyer–seller relationship. This research investigates avenues for differentiation through value creation in business-to-business relationships. The results suggest that relationship benefits display a stronger potential for differentiation in key supplier relationships than cost considerations. The authors identify service support and personal interaction as core differentiators, followed by a supplier's know-how and its ability to improve a customer's time to market. Product quality and delivery performance, along with acquisition costs and operation costs, display a moderate potential to help a firm gain and maintain key supplier status. Finally, price shows the weakest potential for differentiation.
1,006 citations
TL;DR: In this article, the influence of a simple semi-empirical van der Waals (vdW) correction on the description of dispersive, covalent, and ionic bonds within density functional theory is studied.
Abstract: The influence of a simple semiempirical van der Waals (vdW) correction on the description of dispersive, covalent, and ionic bonds within density functional theory is studied. The correction is based on the asymptotic London form of dispersive forces and a damping function for each pair of atoms. It thus depends solely on the properties of the two atoms irrespective of their environment and is numerically very efficient. The correction is tested in comparison with results obtained using the generalized gradient approximation or the local density approximation for exchange and correlation. The results are also compared with reference values from experiment or quantum chemistry methods. In order to probe the universality and transferability of the semiempirical vdW correction, a range of solids and molecular systems with covalent, heteropolar, and vdW bonds are studied.
712 citations
TL;DR: In this paper, the authors explored the relationship value as a key constituent of relationship quality, i.e., commitment, satisfaction, and trust, and found that relationship value is an antecedent to relationship quality and behavioural outcomes in the nomological network of relationship marketing.
Abstract: Purpose – Established models of buyer-seller relationships do not reflect managerial emphasis on supplier performance evaluation when modelling business relationships. Proposes that relationship value should be included as a key constituent in such models. Aims to explore the construct's links with key constituents of relationship quality, i.e. commitment, satisfaction, and trust. Design/methodology/approach – A two-stage research design was used. First, depth-interviews were conducted with ten senior-level purchasing managers in US manufacturing companies. Second, data were gathered in a nation-wide mail survey among 400 purchasing professionals. Findings – The findings suggest that relationship value is an antecedent to relationship quality and behavioural outcomes in the nomological network of relationship marketing. Value displays a stronger impact on satisfaction than on commitment and trust. Value also directly impacts a customer's intention to expand business with a supplier. In turn, its impact on the propensity to leave a relationship is mediated by relationship quality. Contrary to previous research, trust does not appear in this study as an antecedent of behavioural outcomes, but as a mediator of the satisfaction-commitment link. Research limitations/implications – Confirms the role of value as a key relationship building-block. Researchers should integrate this cognitive performance-based construct in models of business relationships. Limitations and research directions refer to the sampling procedure, the need to include the supplier's value perceptions, the possibility of conducting longitudinal research, and the opportunity to assess additional moderating variables. Practical implications – When the goal is to increase business with an existing customer, managers should focus on relationship value. In turn, when managers are concerned with the risk of customers leaving a relationship, they should focus on relationship quality. Trust appears as an important ingredient in stabilising existing business relationships. Originality/value – Stresses the pivotal role of relationship value in marketing. Contributes to a better fit between relationship marketing models and managerial practice in business markets.
692 citations
TL;DR: In this paper, the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbon monoxide, carbonyl sulfide, decane, hydrogen sulfide and fluoromethane.
Abstract: In a preceding project, functional forms for “short” Helmholtz energy equations of state for typical nonpolar and weakly polar fluids and for typical polar fluids were developed using simultaneous optimization. In this work, the coefficients of these short forms for the equations of state have been fitted for the fluids acetone, carbon monoxide, carbonyl sulfide, decane, hydrogen sulfide, 2-methylbutane (isopentane), 2,2-dimethylpropane (neopentane), 2-methylpentane (isohexane), krypton, nitrous oxide, nonane, sulfur dioxide, toluene, xenon, hexafluoroethane (R-116), 1,1-dichloro-1-fluoroethane (R-141b), 1-chloro-1,1-difluoroethane (R-142b), octafluoropropane (R-218), 1,1,1,3,3-pentafluoropropane (R-245fa), and fluoromethane (R-41). The 12 coefficients of the equations of state were fitted to substance specific data sets. The results show that simultaneously optimized functional forms can be applied to other fluids out of the same class of fluids for which they were optimized without significant loss of a...
629 citations
TL;DR: The Self Consistent Charge Density Functioning Tight Binding (SCC-DFTB) as mentioned in this paper is an approximate quantum chemical method derived from density functional theory (DFT) based on a second-order expansion of the DFT total energy expression.
Abstract: The Self-consistent charge density functional tight-binding (SCC-DFTB) is an approximate quantum chemical method derived from density functional theory (DFT) based on a second-order expansion of the DFT total energy expression. Here, we review in detail the application of SCC-DFTB to biological systems and several extensions of the original formalism. The biological systems discussed turn out to be a challenge for DFT due to the occurrence of weak binding forces and charge transfer problems, both of which are not properly described by recent DFT-GGA functionals. Possible solutions and alternative strategies are presented and the role of SCC-DFTB in a general quantum chemical approach to biological systems is discussed
352 citations
TL;DR: In the optimization kernel, a combination of linear programming, constraint programming, and (meta-)heuristics for the home health care problem is used, and it is shown how to apply these different heuristics efficiently to solve home health health care problems.
314 citations
TL;DR: In this article, the authors explore whether different stages of the relationship life cycle moderate the relative importance of value-creating dimensions and find that a key supplier's potential for value creation in customer's operations increases in relative importance as relationships move through the life cycle.
300 citations
TL;DR: In this paper, the magnetic shape memory properties of a single crystal Ni 2 MnGa alloy were characterized through monitoring magnetic field induced strain (MFIS) as a function of compressive stress, and applied stress induced strain as the function of magnetic field.
294 citations
TL;DR: In this paper, the authors describe how lifelong learning has emerged as the central strategy in EU education and training policy, and provide a closer look at the EU's underlying concept of lifelong learning and its objectives.
Abstract: Lifelong learning has become a (still) increasingly popular slogan in the field of EU educational policy. Embedded in an international and historical account of the discourse on lifelong learning since the 1970s, this paper describes how lifelong learning has emerged as the central strategy in EU education and training policy, and provides a closer look at the EU’s underlying concept of lifelong learning and its objectives. Based on these illustrations, it provides some critical thoughts on the EU’s use of the term lifelong learning and its lifelong learning principles. Within this context, it calls for cautiousness: is lifelong learning just used as a powerful label, i.e. an elastic concept tailorable to any needs, or is it underpinned by a solid, comprehensive concept and strategy of lifelong learning? Following this line of argumentation, this paper also sets the EU’s lifelong learning policies in the broader light of the highly debated EU convergence policy in the field of education and training.
289 citations
TL;DR: Free energy perturbation and boundary potential methods for treating long-range electrostatics were implemented to test the robustness of QM/MM results for protein systems, and modifications were made to an approximate density functional theory to improve the description of proton affinity and hydrogen-bonding, which are crucial for the treatment of PT in polar systems.
Abstract: Motivated by the long-term goal of understanding vectorial biological processes such as proton transport (PT) in biomolecular ion pumps, a number of developments were made to establish combined quantum mechanical/molecular mechanical (QM/MM) methods suitable for studying chemical reactions involving significant charge separation in the condensed phase. These developments were summarized and discussed with representative problems. Specifically, free energy perturbation and boundary potential methods for treating long-range electrostatics were implemented to test the robustness of QM/MM results for protein systems. It was shown that consistent models with sufficient sampling were able to produce quantitatively satisfactory results, such as pKa for titritable groups in the interior of T4-lysozyme, while an inconsistent treatment of electrostatics or lack of sufficient sampling may produce incorrect results. Modifications were made to an approximate density functional theory (SCC-DFTB) to improve the descript...
289 citations
TL;DR: In this article, the mixing characteristics of a T-shaped micro-reactor with rectangular cross sections are studied for three different flow regimes, and a measure of the scale of segregation which employs the concept of specific contact area is defined.
26 Jun 2006
TL;DR: Two space bounded random sampling algorithms that compute an approximation of the number of triangles in an undirected graph given as a stream of edges are presented and they provide a basic tool to analyze the structure of large graphs.
Abstract: We present two space bounded random sampling algorithms that compute an approximation of the number of triangles in an undirected graph given as a stream of edges. Our first algorithm does not make any assumptions on the order of edges in the stream. It uses space that is inversely related to the ratio between the number of triangles and the number of triples with at least one edge in the induced subgraph, and constant expected update time per edge. Our second algorithm is designed for incidence streams (all edges incident to the same vertex appear consecutively). It uses space that is inversely related to the ratio between the number of triangles and length 2 paths in the graph and expected update time O(log|V|⋅(1+s⋅|V|/|E|)), where s is the space requirement of the algorithm. These results significantly improve over previous work [20, 8]. Since the space complexity depends only on the structure of the input graph and not on the number of nodes, our algorithms scale very well with increasing graph size and so they provide a basic tool to analyze the structure of large graphs. They have many applications, for example, in the discovery of Web communities, the computation of clustering and transitivity coefficient, and discovery of frequent patterns in large graphs.We have implemented both algorithms and evaluated their performance on networks from different application domains. The sizes of the considered graphs varied from about 8,000 nodes and 40,000 edges to 135 million nodes and more than 1 billion edges. For both algorithms we run experiments with parameter s=1,000, 10,000, 100,000, 1,000,000 to evaluate running time and approximation guarantee. Both algorithms appear to be time efficient for these sample sizes. The approximation quality of the first algorithm was varying significantly and even for s=1,000,000 we had more than 10% deviation for more than half of the instances. The second algorithm performed much better and even for s=10,000 we had an average deviation of less than 6% (taken over all but the largest instance for which we could not compute the number of triangles exactly).
TL;DR: This paper discusses the multi-depot, multi-vehicle-type bus scheduling problem (MDVSP), involving multiple depots for vehicles and different vehicle types for timetabled trips, and uses time–space-based instead of connection-based networks for MDVSP modeling.
TL;DR: In this article, the biexciton is induced via a coherent two-photon process and the measured population oscillation is not purely sinusoidal in excitation pulse area.
Abstract: We report on Rabi oscillations of the biexciton in a single ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}∕\mathrm{Ga}\mathrm{As}$ quantum dot, induced via a coherent two-photon process. In contrast to single-exciton Rabi oscillations the measured population oscillation is not purely sinusoidal in excitation pulse area. The experimental results are well reproduced by a theoretical calculation that relies only on the pulse shape and biexciton binding energy. Dephasing times of the biexciton are similar to those of the single exciton under the applied measurement conditions reaching up to $220\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$.
01 Jan 2006
TL;DR: The non-local semantics of EPCs is formalized as a pair of two corresponding transition relations, which can be considered as a framework for defining non-Local semantics and for resolving the vicious circle inherent to non- local semantics ofEPCs.
Abstract: One of the most debatable features of Event driven Process Chains (EPCs) is their non-local semantics. It can be shown that a single transition relation cannot precisely capture the non-local semantic of EPCs. Therefore, we formalize the non-local semantics of EPCs as a pair of two corresponding transition relations.Actually, there are different proposals for non-local semantics of EPCs. The technique proposed in this paper can be used for formalizing all kinds of non-local semantics. This way, it can be considered as a framework for defining non-local semantics and for resolving the vicious circle inherent to non-local semantics of EPCs.
01 Oct 2006
TL;DR: This paper employs the visual, formal, and bidirectional transformation technique of triple graph grammars, using this declarative specification formalism, and presents the approach to achieve an incremental model transformation for synchronization purposes.
Abstract: The advent of model-driven software development has put model transformations into focus. In practice, model transformations are expected to be applicable in different stages of a development process and help to consistently propagate changes between the different involved models which we refer to as model synchronization. However, most approaches do not fully support the requirements for model synchronization today and focus only on classical one-way batch-oriented transformations. In this paper, we present our approach for an incremental model transformation which supports model synchronization. Our approach employs the visual, formal, and bidirectional transformation technique of triple graph grammars. Using this declarative specification formalism, we focus on the efficient execution of the transformation rules and present our approach to achieve an incremental model transformation for synchronization purposes. We present an evaluation of our approach and demonstrate that due to the speedup for the incremental processing in the average case even larger models can be tackled.
TL;DR: In this article, the compensation of nonlinear phase noise by a midlink optical phase conjugation (OPC) is studied and a proof-of-principle experiment is presented showing an over 4dB improvement in Q factor when OPC is employed in a differential phase-shift-keying (DPSK) system.
Abstract: Nonlinear phase noise (Gordon-Mollenauer phase noise) can limit the transmission distance for phase-shift-keyed modulation formats. In this paper, the compensation of nonlinear phase noise by a midlink optical phase conjugation (OPC) is studied. A proof-of-principle experiment is presented showing an over 4-dB improvement in Q factor when OPC is employed in a differential phase-shift-keying (DPSK) system. Also, an ultra long-haul OPC-based differential quadrature phase-shift-keying (DQPSK) transmission experiment is studied to show the impact of self-phase modulation (SPM)-induced impairments, including nonlinear phase noise, in a transmission line. OPC results in a 44% increase in transmission distance when compared to a "conventional" transmission system using dispersion compensating fiber (DCF) for chromatic dispersion compensation.
28 May 2006
TL;DR: A verification technique for arbitrarily large multi-agent systems from the mechatronic domain, featuring complex coordination and structural adaptation at run-time, and a symbolic verification procedure that allows the computation on an efficient BDD-based graph manipulation engine.
Abstract: The next generation of networked mechatronic systems will be characterized by complex coordination and structural adaptation at run-time. Crucial safety properties have to be guaranteed for all potential structural configurations. Testing cannot provide safety guarantees, while current model checking and theorem proving techniques do not scale for such systems. We present a verification technique for arbitrarily large multi-agent systems from the mechatronic domain, featuring complex coordination and structural adaptation. We overcome the limitations of existing techniques by exploiting the local character of structural safety properties. The system state is modeled as a graph, system transitions are modeled as rule applications in a graph transformation system, and safety properties of the system are encoded as inductive invariants (permitting the verification of infinite state systems). We developed a symbolic verification procedure that allows us to perform the computation on an efficient BDD-based graph manipulation engine, and we report performance results for several examples.
TL;DR: An energetics motivated framework is established that hinges on the donor/acceptor pKa values and electrostatics due to the environment to argue that the "proton hole" transfer is likely as important as the classical Grotthuss mechanism for proton transport in many complex molecular systems.
Abstract: Proton transfers are fundamental to chemical processes in solution and biological systems. Often, the well-known Grotthuss mechanism is assumed where a series of sequential "proton hops" initiates from the donor and combines to produce the net transfer of a positive charge over a long distance. Although direct experimental evidence for the sequential proton hopping has been obtained recently, alternative mechanisms may be possible in complex molecular systems. To understand these events, all accessible protonation states of the mediating groups should be considered. This is exemplified by transfers through water where the individual water molecules can exist in three protonation states (water, hydronium, and hydroxide); as a result, an alternative to the Grotthuss mechanism for a proton transfer through water is to generate a hydroxide by first protonating the acceptor and then transfer the hydroxide toward the donor through water. The latter mechanism can be most generally described as the transfer of a "proton hole" from the acceptor to the donor where the "hole" characterizes the deprotonated state of any mediating molecule. This pathway is distinct and is rarely considered in the discussion of proton-transfer processes. Using a calibrated quantum mechanical/molecular mechanical (QM/MM) model and an effective sampling technique, we study proton transfers in two solution systems and in Carbonic Anhydrase II. Although the relative weight of the "proton hole" and Grotthuss mechanisms in a specific system is difficult to determine precisely using any computational approach, the current study establishes an energetics motivated framework that hinges on the donor/acceptor pKa values and electrostatics due to the environment to argue that the "proton hole" transfer is likely as important as the classical Grotthuss mechanism for proton transport in many complex molecular systems.
23 Feb 2006
TL;DR: It is shown that the given values for the price of anarchy of weighted and unweighted congestion games with polynomial latency functions also hold for weighted andunweighted network congestion games.
Abstract: We show exact values for the price of anarchy of weighted and unweighted congestion games with polynomial latency functions. The given values also hold for weighted and unweighted network congestion games.
30 Oct 2006
TL;DR: This work proposes to combine MMOGs with a Peer-to-Peer network and introduces a game architecture capable of exploiting the flexibility and scalability of P2P networks.
Abstract: Massive Multiplayer Online Games with their virtual gaming worlds grow in user numbers as well as in the size of the virtual worlds. With this growth comes a significant increase of the requirements for server hardware. Today an MMOG provider usually faces the problem of serving thousands of users with entire server clusters. Peer-to-Peer networks with their high scalability and flexibility meet the requirements of connecting hundreds of thousands of people all over the world without a central server. In doing so the network bandwidth requirements remain at a reasonable level.In this work we propose to combine MMOGs with a Peer-to-Peer network. We introduce a game architecture capable of exploiting the flexibility and scalability of P2P networks. A P2P architecture based on an overlay network using distributed hash tables with support for persistent object storage and event distribution has been developed to meet MMOG requirements.
TL;DR: In this article, the authors completely determine the isomorphism classes of Hv = { f : Ω → C holomorphic : sup z∈Ω |f(z)|v(z) < ∞, where v is a given radial weight function.
Abstract: Let Ω be either the complex plane or the open unit disc. We completely determine the isomorphism classes of Hv = { f : Ω → C holomorphic : sup z∈Ω |f(z)|v(z) < ∞ } and investigate some isomorphism classes of hv = { f : Ω → C harmonic : sup z∈Ω |f(z)|v(z) < ∞ } where v is a given radial weight function. Our main results show that, without any further condition on v, there are only two possibilities for Hv, namely either Hv ∼ l∞ or Hv ∼ H∞, and at least two possibilities for hv, again hv ∼ l∞ and hv ∼ H∞. We also discuss many new examples of weights.
TL;DR: In this article, the structures of new compounds were determined by spectroscopic methods (mainly extensive 1D and 2D NMR experiments and mass spectral measurements) and X-ray single crystal analysis.
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TL;DR: In this paper, the authors present an empirical analysis of the contractual design of entrepreneurial alliances or collaborative agreements entered into by entrepreneurial firms and find that entrepreneurial firms tend to design more complex contracts when the costs of searching for a partner are higher and the strategic importance of the alliance greater.
Abstract: Presents an empirical analysis of the contractualdesign of entrepreneurial alliances or collaborative agreements entered into byentrepreneurial firms. First, a series of arguments based on transaction costtheory is used to generate a number of hypotheses regarding the determinants ofthe contractual complexity of collaborative agreements. Taken together, these hypotheses predict that the contractual complexity ofan entrepreneurial alliance will be negatively related to relational capitaland positively related to asset specificity, the costs of searching for apartner, and the strategic importance of the alliance. Data from a survey of 66entrepreneurial firms in the German telecommunications industry are used totest the hypotheses. Analysis of the data reveals that entrepreneurial firms tend to design morecomplex contracts when the costs of searching for a partner are higher and thestrategic importance of the alliance greater. In other words, only two of thehypotheses are viable. These results underscore the fact that governancestructures and contractual forms have different antecedents for entrepreneurialfirms. (SAA)
TL;DR: In this paper, experimental investigations on both mixed mode overloads, which are interspersed into a Mode I baseline level loading, and mixed mode block loadings are presented, and it is shown that the retardation effect decreases with an increasing amount of Mode II of the overload.
TL;DR: A holistic view of fault modelling is introduced that is carried out as a complementary step to system modelling, enabling a scalability of the test process, and providing considerable potential for automation.
Abstract: With the growing complexity of computer-based systems, their graphical user interfaces have also become more complex. Accordingly, the test and analysis process becomes more tedious and costly. This paper introduces a holistic view of fault modelling that is carried out as a complementary step to system modelling, enabling a scalability of the test process, and providing considerable potential for automation. Event-based notions and tools are used to generate and select test cases systematically. The elements of the approach are illustrated and validated by a case study. This paper does not claim to introduce a novel theoretic approach; rather, it makes use of graph-theoretic results for a practical and simple, but nevertheless powerful, view of modelling, analysis and testing of graphical user interfaces. Copyright © 2005 John Wiley & Sons, Ltd.
10 Oct 2006
TL;DR: Sign change attacks on elliptic curve scalar multiplications as discussed by the authors exploit different number representations as they are often employed in modern cryptographic applications and produce points which do not leave the curve and are not easily detected.
Abstract: We present a new type of fault attacks on elliptic curve scalar multiplications: Sign Change Attacks. These attacks exploit different number representations as they are often employed in modern cryptographic applications. Previously, fault attacks on elliptic curves aimed to force a device to output points which are on a cryptographically weak curve. Such attacks can easily be defended against. Our attack produces points which do not leave the curve and are not easily detected. The paper also presents a revised scalar multiplication algorithm that protects against Sign Change Attacks.
TL;DR: A set of collective reaction coordinates is proposed for characterizing the progress of long-range proton transfers; unlike previous suggestions, the new coordinates can describe PT along highly nonlinear three-dimensional pathways.
Abstract: Motivated by the long-term goal of theoretically analyzing long-range proton transfer (PT) kinetics in biomolecular pumps, researchers made a number of technical developments in the framework of quantum mechanics-molecular mechanics (QM/MM) simulations. A set of collective reaction coordinates is proposed for characterizing the progress of long-range proton transfers; unlike previous suggestions, the new coordinates can describe PT along highly nonlinear three-dimensional pathways. Calculations using a realistic model of carbonic anhydrase demonstrated that adiabatic mapping using these collective coordinates gives reliable energetics and critical geometrical parameters as compared to minimum energy path calculations, which suggests that the new coordinates can be effectively used as reaction coordinate in potential of mean force calculations for long-range PT in complex systems. In addition, the generalized solvent boundary potential was implemented in the QM/MM framework for rectangular geometries, which is useful for studying reactions in membrane systems. The resulting protocol was found to produce water structure in the interior of aquaporin consistent with previous studies including a much larger number of explicit solvent and lipid molecules. The effect of electrostatics for PT through a membrane protein was also illustrated with a simple model channel embedded in different dielectric continuum environments. The encouraging results observed so far suggest that robust theoretical analysis of long-range PT kinetics in biomolecular pumps can soon be realized in a QM/MM framework.
TL;DR: In this paper, the authors investigate the design of entrepreneurial firms' alliances in more fine-grained terms by focusing on the specific contractual provisions that firms negotiate into their alliance contracts, and examine the determinants of the contractual complexity of collaborative agreements in the German telecommunications industry.