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Showing papers by "University of Paderborn published in 2008"


Posted Content
TL;DR: In this paper, the impact of national banking market concentration on European banks' financial soundness while controlling for macroeconomic, bank-specific, supervisory and institutional factors using bank balance sheet data from banks across the EU-25 for the period of 1997-2005.
Abstract: This paper studies the impact of national banking market concentration on European banks' financial soundness while controlling for macroeconomic, bank-specific, supervisory and institutional factorsUsing bank balance sheet data from banks across the EU-25 for the period of 1997-2005 we find that market concentration has a negative impact on banks' financial soundness as measured by the Z-score technique As we additionally find a negative effect of financial openness on stability despite actual market concentration and throughout all regression specifications, we conclude that rising competition and reducing margins provide an incentive for European banks to accept higher risk exposures

466 citations


Proceedings ArticleDOI
03 Mar 2008
TL;DR: MiXiM as mentioned in this paper joins and extends several existing simulation frameworks developed for wireless and mobile simulations in OMNeT++, providing detailed models of the wireless channel, wireless connectivity, mobility models, models for obstacles and many communication protocols especially at the medium access control (MAC) level.
Abstract: Wireless communication has attracted considerable interest in the research community, and many wireless networks are evaluated using discrete event simulators like OMNeT++. Although OMNeT++ provides a powerful and clear simulation framework, it lacks of direct support and a concise modeling chain for wireless communication. Both is provided by MiXiM. MiXiM joins and extends several existing simulation frameworks developed for wireless and mobile simulations in OMNeT++. It provides detailed models of the wireless channel (fading, etc.), wireless connectivity, mobility models, models for obstacles and many communication protocols especially at the Medium Access Control (MAC) level. Further, it provides a user-friendly graphical representation of wireless and mobile networks in OMNeT++, supporting debugging and defining even complex wireless scenarios. Though still in development, MiXiM already is a powerful tool for performance analysis of wireless networks. Its extensive functionality and clear concept may motivate researches to contribute to this open-source project [4].

372 citations


Journal ArticleDOI
TL;DR: In this paper, the emitted radiation from semiconductor nanostructures due to the excitation with intense ultrashort optical laser pulses is analyzed and the Semiconductor Bloch equations that consistently describe the coupled light-field-induced interband and intraband dynamics are solved numerically.
Abstract: The emitted radiation from semiconductor nanostructures due to the excitation with intense ultrashort optical laser pulses is analyzed. Semiconductor Bloch equations that consistently describe the coupled light-field-induced interband and intraband dynamics are solved numerically. It is demonstrated that the intraband dynamics considerably influences the light emission in the regime of extreme nonlinear optics. In particular, the intraband acceleration significantly modifies the dynamics of the interband polarization which results in a strong enhancement of high-harmonic generation.

281 citations


Journal ArticleDOI
TL;DR: In this article, the authors use data from a developing country, South Africa, to empirically identify the determinants of start-up rates across different sub-national regions and in particular to investigate the role of access to finance on a regional (sub-national) level on start-ups.
Abstract: In this paper we use data from a developing country, South Africa, to empirically identify the determinants of start-up rates across different sub-national regions and in particular to investigate the role of access to finance on a regional (sub-national) level on start-ups. We find that the most important determinants of start-up rates across South Africa's magisterial districts are profit rates, educational levels, agglomeration as measured by the economic size of a district, and access to formal bank finance. Profits have by far the strongest effect on start-up rates. This, together with the insignificance of unemployment for start-ups, may imply that start-ups in South Africa are mainly opportunity-driven, as opposed to being necessity driven. It is also found that access to formal bank finance matter for regional start-up rates, which is not typical for a developing country and that market-size (agglomerations) is negatively associated with start-up rates in South Africa–an unexpected finding which m...

236 citations


Posted Content
TL;DR: In this article, the authors provide an endogenous growth model to illuminate the role of entrepreneurial start-up firms in structural economic transformation and show how opportunity-driven entrepreneurship can drive structural transformation through innovation, provision of intermediate inputs and services, and by increasing employment and productivity in both the modern and traditional sectors.
Abstract: A stylized fact of economic development is the structural transformation of countries from traditional, mainly agricultural societies to modern economies dominated by manufacturing and services. In this paper we provide an endogenous growth model to illuminate the role of entrepreneurial start-up firms in structural economic transformation. We follow the Lewis-model?s distinction between a traditional and modern sector, and underpin this with micro-foundations. We specify mature and start-up entrepreneurs and make a distinction between survivalist self-employment activities in the traditional sector, and opportunity-driven entrepreneurship in the modern sector. The model shows how opportunity-driven entrepreneurship can drive structural transformation through innovation, provision of intermediate inputs and services (which permits greater specialization in manufacturing), and by increasing employment and productivity in both the modern and traditional sectors.

204 citations


Proceedings ArticleDOI
09 Dec 2008
TL;DR: The design considerations for a re-architected global networking architecture which delivers dissemination and non-dissemination objects only to consenting recipients, reducing unwanted traffic, linking information producers with consumers independently of the hosts involved, and connects the digital with the physical world are presented.
Abstract: The existing Internet ecosystem is a result of decades of evolution. It has managed to scale well beyond the original aspirations. Evolution, though, highlighted a certain degree of inadequacies that is well documented. In this position paper we present the design considerations for a re-architected global networking architecture which delivers dissemination and non-dissemination objects only to consenting recipients, reducing unwanted traffic, linking information producers with consumers independently of the hosts involved, and connects the digital with the physical world. We consider issues ranging from the proposed object identifier/locator split to security and trust as we transition towards a Network of Information and relate our work with the emerging paradigm of publish/subscribe architectures. We introduce the fundamental components of a Network of Information, i.e., name resolution, routing, storage, and search, and close this paper with a discussion about future work.

193 citations


Book ChapterDOI
02 Sep 2008
TL;DR: The approach to detecting and resolving differences between process models, in the absence of a change log is presented, based on computing differences and deriving change operations for resolving differences, thereby providing a foundation for variant and version management in these cases.
Abstract: Business-driven development favors the construction of process models at different abstraction levels and by different people. As a consequence, there is a demand for consolidating different versions of process models by detecting and resolving differences. Existing approaches rely on the existence of a change log which logs the changes when changing a process model. However, in several scenarios such a change log does not exist and differences must be identified by comparing process models before and after changes have been made. In this paper, we present our approach to detecting and resolving differences between process models, in the absence of a change log. It is based on computing differences and deriving change operations for resolving differences, thereby providing a foundation for variant and version management in these cases.

168 citations


Journal ArticleDOI
TL;DR: Seven unusual chromanones were isolated together with secalonic acid B from Blennoria sp.
Abstract: Blennolides A-G (2-8), seven unusual chromanones, were isolated together with secalonic acid B (1) from Blennoria sp., an endophytic fungus from Carpobrotus edulis. This is the first reported isolation of the blennolides 2 and 3 (hemisecalonic acids B and E), the existence of which as the monomeric units of the dimeric secalonic acids had long been postulated. A compound of the proposed structure 4 (beta-diversonolic ester) will need to be revised, as its reported data do not fit those of the established structure of blennolide C (4). Other monomers, the blennolides D-F (5-7) seem to be derived from blennolides A (2) and B (3) by rearrangement of the hydroaromatic ring. The heterodimer 8, composed of the monomeric blennolide A (2) and the rearranged 11-dehydroxy derivative of blennolide E (6), extends the ergochrome family with an ergoxanthin type of skeleton. The structures of the new compounds were elucidated by detailed spectroscopic analysis and further confirmed by an X-ray diffraction study of a single crystal of 2. The absolute configurations were determined by TDDFT calculations of CD spectra, including the solid-state CD/TDDFT approach. Preliminary studies showed strong antifungal and antibacterial activities of these compounds against Microbotryum violaceum and Bacillus megaterium, respectively. They were also active against the alga Chlorella fusca and the bacterium Escherichia coli.

160 citations


Journal ArticleDOI
TL;DR: The findings suggest that with increasing skill level, golfers have developed task solving strategies including focussed attention and an economy in parietal sensory information processing which lead to more successful performance.
Abstract: A skilled player in goal-directed sports performance has the ability to process internal and external information in an effective manner and decide which pieces of information are important and which are irrelevant. Focused attention and somatosensory information processing play a crucial role in this process. Electroencephalographic (EEG) recordings are able to demonstrate cortical changes in conjunction with this concept and were examined during a golf putting performance in an expert-novice paradigm. The success in putting (score) and performance-related cortical activity were recorded with an EEG during a 5 x 4 min putting series. Subjects were asked to putt balls for four min at their own pace. The EEG data was divided into different frequencies: Theta (4.75-6.75 Hz), Alpha-1 (7-9.5 Hz), Alpha-2 (9.75-12.5 Hz) and Beta-1 (12.75-18.5 Hz) and performance related power values were calculated. Statistical analysis shows significant better performance in the expert golfers (P < 0.001). This was associated with higher fronto-midline Theta power (P < 0.05) and higher parietal Alpha-2 power values (P < 0.05) compared to the novices in golf putting. Frontal Theta and parietal Alpha-2 spectral power in the ongoing EEG demonstrate differences due to skill level. Furthermore the findings suggest that with increasing skill level, golfers have developed task solving strategies including focussed attention and an economy in parietal sensory information processing which lead to more successful performance. In a theoretical framework both cortical parameters may play a role in the concept of the working memory.

135 citations


Journal ArticleDOI
TL;DR: In this article, the existence of low-barrier routes to molecular hydrogen formation on the polycyclic aromatic hydrocarbon (PAH) molecule coronene via Eley-Rideal abstraction reactions was revealed.
Abstract: We present first-principle calculations which reveal the existence of low-barrier routes to molecular hydrogen formation on the polycyclic aromatic hydrocarbon (PAH) molecule coronene via Eley-Rideal abstraction reactions and show that such processes could indeed be active under interstellar conditions. The calculations indicate that in regions of low UV flux, coronene, and larger PAHs might be found in superhydrogenated states. Furthermore, the calculations imply that not only edge carbon atoms but also carbon atoms on the inner rings of the coronene molecule can be hydrogenated. Such superhydrogenated PAHs are expected to exhibit significantly changed absorption and emission spectra.

134 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present results from a systematic study linking material microstructure to monotonic and fatigue properties of NiTi shape memory alloys, including hot-rolled and cold-drawn materials.
Abstract: We present results from a systematic study linking material microstructure to monotonic and fatigue properties of NiTi shape memory alloys We consider Ni-rich materials that are either (1) hot rolled or (2) hot rolled and cold drawn In addition to the two material processing routes, heat treatments are used to systematically alter material microstructure giving rise to a broad range of thermal, monotonic and cyclic properties The strength and hardness of the austenite and martensite phases initially increase with mild heat treatment (300 °C), and subsequently decrease with increased aging temperature above 300 °C This trend is consistent with transmission electron microscopy observed precipitation hardening in the hot-rolled material and precipitation hardening plus recovery and recrystallization in the cold-drawn materials The low-cycle pseudoelastic fatigue properties of the NiTi materials generally improve with increasing material strength, although comparison across the two product forms demonstrates that higher measured flow strength does not assure superior resistance to pseudoelastic cyclic degradation Fatigue crack growth rates in the hot-rolled material are relatively independent of heat treatment and demonstrate similar fatigue crack growth rates to other NiTi product forms; however, the cold-drawn material demonstrates fatigue threshold values some 5 times smaller than the hot-rolled material The difference in the fatigue performance of hot-rolled and cold-drawn NiTi bars is attributed to significant residual stresses in the cold-drawn material, which amplify fatigue susceptibility despite superior measured monotonic properties

Journal ArticleDOI
TL;DR: This paper investigates a region-based approach that performs pixel clustering prior to the processes of attention in contrast to late clustering as done by contemporary methods and indicates that the proposed model has the potential to efficiently integrate the phenomenon of attention into the main stream of machine vision and systems with restricted computing resources can benefit from its advantages.
Abstract: Visual attention is one of the important phenomena in biological vision which can be followed to achieve more efficiency, intelligence, and robustness in artificial vision systems. This paper investigates a region-based approach that performs pixel clustering prior to the processes of attention in contrast to late clustering as done by contemporary methods. The foundation steps of feature map construction for the region-based attention model are proposed here. The color contrast map is generated based upon the extended findings from the color theory, the symmetry map is constructed using a novel scanning-based method, and a new algorithm is proposed to compute a size contrast map as a formal feature channel. Eccentricity and orientation are computed using the moments of obtained regions and then saliency is evaluated using the rarity criteria. The efficient design of the proposed algorithms allows incorporating five feature channels while maintaining a processing rate of multiple frames per second. Another salient advantage over the existing techniques is the reusability of the salient regions in the high-level machine vision procedures due to preservation of their shapes and precise locations. The results indicate that the proposed model has the potential to efficiently integrate the phenomenon of attention into the main stream of machine vision and systems with restricted computing resources such as mobile robots can benefit from its advantages.

Journal ArticleDOI
TL;DR: In this paper, the authors apply two distinct econometric methods to panel data on head coach quality and team performance in Germany's premier soccer league and find that, given a particular amount of spending on players relative to the rest of the league, a team that hires a better quality head coach can expect to achieve improved performance.
Abstract: Although a considerable literature exists on the determinants of managerial compensation, much of it focussing on the role of incentives, there is much less known about the impact of managerial remuneration and quality upon attainment of organizational goals. In this paper we apply two distinct econometric methods to panel data on head coach quality and team performance in Germany’s premier soccer league. We find that, given a particular amount of spending on players relative to the rest of the league, a team that hires a better quality head coach can expect to achieve improved performance.

Journal ArticleDOI
01 Jan 2008
TL;DR: In this article, the concept of left amenability of Banach algebras has been generalized to the notion of hereditary amenability, where a homomorphism from A to B is defined.
Abstract: Generalizing the notion of left amenability for so-called F-algebras [12], we study the concept of -amenability of a Banach algebra A, where is a homomorphism from A to . We establish several characterizations of -amenability as well as some hereditary properties. In addition, some illuminating examples are given.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the determinants of individual absenteeism focusing on the "strictness" of employment protection and the "generosity" of sickness benefits and found that the impact of the institutional framework is smaller than that of some individual worker characteristics.
Abstract: In this article, we analyze the determinants of individual absenteeism focusing on the “strictness” of employment protection and the “generosity” of sickness benefits. The data come from the “European Survey on Working Conditions” launched in 2000. Due to its coverage (the EU-14), the data enable us to identify the relative importance of the institutional framework for explaining differences in absence behavior across nations. Our results reveal that, first, employment protection does not influence the number of absence days while sickness benefits increase absenteeism. And, second, the impact of the institutional framework is smaller than that of some individual worker characteristics.

Journal ArticleDOI
TL;DR: In this article, the authors compare the propagation paths predicted by two different criteria for three-point bending experiments performed on PMMA and conclude that the global criterion gives better results than the local type criterion.
Abstract: Whatever the external loading, a crack front in a solid tries to reach mode I loading conditions after propagation. In mode I + II, the crack kinks to annihilate mode II, kinking angle being well predicted by the principle of local symmetry (PLS) or by the maximum tangential stress criterion (MTS). In presence of mode III, the problem becomes three-dimensional and the proposed propagation criterion are not yet well proved and established. In particular in three point bending experiments (3PB) with an initially inclined crack, the crack twists around the direction of propagation to finally reach a situation of pure mode I. The aim of the paper is to compare the propagation paths predicted by two different criteria for 3PB fatigue experiments performed on PMMA. The first criterion developed by Schollmann et al. (Int J Fract 117(2):129–141, 2002), is a three-dimensional extension of the MTS criterion and predicts the local angles that annihilates mode II and III at each point of the front. The second one developed by Lazarus et al. (J Mech Phys Solids 49(7):1421–1443, 2001b), predicts an abrupt and then progressive twisting of the front to annihilate mode III. Due to presence of sign changing mode II and almost uniform mode III in the experiments, both criteria give good results. However, since mode III is predominant over mode II in the case under consideration, the global criterion gives better results. Nevertheless, the local type criterion seems to be of greater universality for practical engineering applications.

Journal ArticleDOI
TL;DR: This paper summarises a mathematical theory of the measurement of both tangible and intangible factors and its generalisation to dependence and feedback, the Analytic Hierarchy Process and its application to making complex multicriteria decisions.
Abstract: This paper summarises a mathematical theory of the measurement of both tangible and intangible factors, the Analytic Hierarchy Process (AHP) and its generalisation to dependence and feedback, the Analytic Network Process (ANP) and illustrates their application to making complex multicriteria decisions.

Journal ArticleDOI
TL;DR: It is found that chronic supplementation of phosphatidylserine significantly decreases Beta-1 power in right hemispheric frontal brain regions (F8; P < 0.05) before and after induced stress.
Abstract: The aim of this study was to investigate the effect of phosphatidylserine (PS) on cognition and cortical activity after mental stress. After familiarization, 16 healthy subjects completed cognitive tasks after induced stress in a test–re-test design (T1 and T2). Directly after T1, subjects were assigned double-blind to either PS or placebo groups followed by T2 after 42 days. At T1 and T2, cortical activity was measured at baseline and immediately after stress with cognitive tasks using electro-encephalography (EEG). EEG was recorded at 17 electrode positions and fast Fourier transforms (FFT) determined power at Theta, Alpha-1, Alpha-2, Beta-1 and Beta-2. Statistics were calculated using ANOVA (group × trial × time). The main finding of the study was that chronic supplementation of phosphatidylserine significantly decreases Beta-1 power in right hemispheric frontal brain regions (F8; P < 0.05) before and after induced stress. The results for Beta-1 power in the PS group were connected to a more re...

Proceedings ArticleDOI
15 Aug 2008
TL;DR: This work considers a swarm of robots that are capable of supporting and enhancing fire fighting operations co-operatively and investigates how firefighters in the field work with such a swarm.
Abstract: In a variety of emergency settings robot assistance has been identified as highly valuable, providing remote, and thus safe, access and operation. There are many different forms of human-robot interactions, allowing a team of humans and robots to take advantage of skills of each team member. A relatively new area of research considers interactions between human and a team of robots performing as a swarm. This work is concerned with the interactive use of autonomous robots in fire emergency settings. In particular, we consider a swarm of robots that are capable of supporting and enhancing fire fighting operations co-operatively and we investigate how firefighters in the field work with such a swarm. This paper outlines some of the key characteristics of this emergency setting. It discusses possible forms of interactions with swarm robotics being examined in the GUARDIANS project. The paper addresses the use of assistive swarm robotics to support firefighters with navigation and search operations. It reports on existing firefighters operations and how human-swarm interactions are to be used during such operations. The design approaches for human-swarm interaction are described and the preliminary work in the area are outlined. The paper ends by linking current expertise with common features of emergency related interaction design.

Posted Content
TL;DR: In this article, an elementary and self-contained approach to smooth Frechet globalizations of Harish-Chandra modules is presented, with applications to the theory of Eisenstein series and Automatic Continuity.
Abstract: An elementary and self-contained approach to smooth Frechet globalizations of Harish-Chandra modules is presented. We provide applications to the theory of Eisenstein series and Automatic Continuity.

Proceedings ArticleDOI
H. Figge1, T. Grote1, N. Froehleke1, Joachim Boecker1, P. Ide 
15 Jun 2008
TL;DR: In this article, a frequency controlled current balancing is proposed as remedy for the non influenceable tolerances of the circuit elements, especially those of the resonant tank circuit, cause unbalanced power distribution between the paralleled converters, resulting in suboptimal circuit design.
Abstract: Paralleling of two LLC resonant converters leads to a significant reduction of current stress in the output filter capacitor, provided that the driving signals of both converters are of equal frequency and with constant phase shift of 90deg. However, non influenceable tolerances of the circuit elements, especially those of the resonant tank circuit, cause unbalanced power distribution between the paralleled converters, resulting in suboptimal circuit design. Frequency controlled current balancing is proposed as remedy in this paper, and prototype measurements are presented to demonstrate the functional capability.

Journal ArticleDOI
TL;DR: In this paper, the authors consider differences of composition operators between given weighted Banach spaces or Hv0 of analytic functions with weighted sup-norms and give estimates for the distance of these differences to the space of compact operators.
Abstract: We consider differences of composition operators between given weighted Banach spaces or Hv0 of analytic functions with weighted sup-norms and give estimates for the distance of these differences to the space of compact operators. We also study boundedness and compactness of the operators. Some examples illustrate our results.

Journal ArticleDOI
TL;DR: The results of a realtime QPSK transmission system with a 3x3 coupler in the receiver are presented, with the achieved BER at a data rate of 1.4 Gbit/s is well below the FEC threshold.
Abstract: Coherent optical communication systems promise superior performance, but their realization in real time also poses big technical challenges. After an introduction the potential of coherent optical transmission systems is shown as manifested in offline experiments. Then we present key components that are necessary to realize these systems in real time. We review recent achievements in realtime coherent communication and finally present the results of a realtime QPSK transmission system with a 3×3 coupler in the receiver. The achieved BER at a data rate of 1.4 Gbit/s is well below the FEC threshold.

Journal ArticleDOI
TL;DR: In this paper, the authors used in situ digital image correlation to obtain full-field measurements, and they identified the coexistence of modulated martensite phases during the first plateau of the multistage stress-strain curve at room temperature.

Journal ArticleDOI
TL;DR: In this paper, the atomic and electronic structure, zone center phonon frequencies, and optical absorption of ferrolectric materials were calculated from first principles using the $GW$ approach and by solving the Bethe-Salpeter equation.
Abstract: The atomic and electronic structure, zone center phonon frequencies, and optical absorption of $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ are calculated from first principles. The structural and vibrational properties predicted from density functional theory are in good agreement with experiment and earlier theoretical work. The electronic band-structure and optical properties are found to be very sensitive to quasiparticle and electron-hole attraction effects, which are included here using the $GW$ approach and by solving the Bethe-Salpeter equation, respectively. We predict the fundamental gap to be more than $1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ larger than the $3.7\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ frequently cited for ferrolectric $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_{3}$ and calculate optical absorption spectra in good agreement with experiment.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the 3D fatigue crack growth behavior in 3PB-specimens or in cantilever beam specimens under bending or torsion loading, with inclined planes for the initial crack, by the dual boundary element method (DBEM).

Journal ArticleDOI
TL;DR: Kaniuth et al. as discussed by the authors studied the amenability of Banach algebras with respect to a character φ of a character and provided necessary and sufficient conditions of a global and a pointwise nature for a Banach algebra to possess a φ -mean of norm 1.

Journal ArticleDOI
TL;DR: In this paper, several examples for fatigue crack growth in machines and components are shown, and the reason for failures can be found in misconstructions, inappropriate fatigue strength calculations as well as material and manufacturing imperfections.

Journal ArticleDOI
TL;DR: A formula from geometric measure theory is employed to compute both the finest and an integral length scale for micro-mixing, and application to a T-shaped microreactor yields interesting information about how the scales depend on the Schmidt number.

Journal ArticleDOI
TL;DR: In this paper, the effect of the size and volume fraction of Ti 3 N 4 particles in Ti-(50.3-51.5) at % Ni single crys-tals on their martensitic transformation temperatures and temperature hysteresis is studied.
Abstract: The effect of the size and volume fraction of Ti 3 N 4 particles in Ti-(50.3-51.5) at % Ni single crys- tals on their martensitic transformation temperatures and temperature hysteresis is studied. Aging at T = 673- 823 K leads to a nonmonotonic change in the martensitic transformation temperatures and temperature hyster- esis, which is related to a change in the Ni concentration in the matrix, the hardening of the high-temperature phase, a change in the elastic and surface energies generated upon the martensitic transformations, and the inter- nal stresses that appear because of the difference in the lattice parameters of the particles and the matrix. As a result of the high strength of the B 2 phase and the high elastic and surface energies that are generated upon the martensitic transformations due to the precipitation of particles of size d < 40 nm at an interparticle distance λ < 50 nm, the martensitic transformation temperatures decrease down to the suppression of the R - B 19' transi- tions upon cooling to 77 K. A thermodynamic description for the martensitic transformations in heterophase crystals is proposed, and an analogy between the martensitic transformations in heterophase Ti-Ni single crys- tals with nanoparticles of size d = 20-100 nm and those in single-phase Ti-Ni polycrystals with a grain size of 50-200 nm is found.