Showing papers by "Karlsruhe Institute of Technology published in 2005"

Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy

Abstract: Gaussian basis sets of quadruple zeta valence quality for Rb-Rn are presented, as well as bases of split valence and triple zeta valence quality for H-Rn. The latter were obtained by (partly) modifying bases developed previously. A large set of more than 300 molecules representing (nearly) all elements-except lanthanides-in their common oxidation states was used to assess the quality of the bases all across the periodic table. Quantities investigated were atomization energies, dipole moments and structure parameters for Hartree-Fock, density functional theory and correlated methods, for which we had chosen Moller-Plesset perturbation theory as an example. Finally recommendations are given which type of basis set is used best for a certain level of theory and a desired quality of results.

The HITRAN 2008 molecular spectroscopic database

Abstract: This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, added line-shape formalisms, and validity. Moreover, molecules, isotopologues, and perturbing gases have been added that address the issues of atmospheres beyond the Earth. Of considerable note, experimental IR cross-sections for almost 300 additional molecules important in different areas of atmospheric science have been added to the database. The compilation can be accessed through www.hitran.org. Most of the HITRAN data have now been cast into an underlying relational database structure that offers many advantages over the long-standing sequential text-based structure. The new structure empowers the user in many ways. It enables the incorporation of an extended set of fundamental parameters per transition, sophisticated line-shape formalisms, easy user-defined output formats, and very convenient searching, filtering, and plotting of data. A powerful application programming interface making use of structured query language (SQL) features for higher-level applications of HITRAN is also provided.

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

Abstract: Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aube rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

Evolutionary optimization in uncertain environments-a survey

Abstract: Evolutionary algorithms often have to solve optimization problems in the presence of a wide range of uncertainties. Generally, uncertainties in evolutionary computation can be divided into the following four categories. First, the fitness function is noisy. Second, the design variables and/or the environmental parameters may change after optimization, and the quality of the obtained optimal solution should be robust against environmental changes or deviations from the optimal point. Third, the fitness function is approximated, which means that the fitness function suffers from approximation errors. Fourth, the optimum of the problem to be solved changes over time and, thus, the optimizer should be able to track the optimum continuously. In all these cases, additional measures must be taken so that evolutionary algorithms are still able to work satisfactorily. This paper attempts to provide a comprehensive overview of the related work within a unified framework, which has been scattered in a variety of research areas. Existing approaches to addressing different uncertainties are presented and discussed, and the relationship between the different categories of uncertainties are investigated. Finally, topics for future research are suggested.

Sequencing of Aspergillus nidulans and comparative analysis with A. fumigatus and A. oryzae

Abstract: The aspergilli comprise a diverse group of filamentous fungi spanning over 200 million years of evolution. Here we report the genome sequence of the model organism Aspergillus nidulans, and a comparative study with Aspergillus fumigatus, a serious human pathogen, and Aspergillus oryzae, used in the production of sake, miso and soy sauce. Our analysis of genome structure provided a quantitative evaluation of forces driving long-term eukaryotic genome evolution. It also led to an experimentally validated model of mating-type locus evolution, suggesting the potential for sexual reproduction in A. fumigatus and A. oryzae. Our analysis of sequence conservation revealed over 5,000 non-coding regions actively conserved across all three species. Within these regions, we identified potential functional elements including a previously uncharacterized TPP riboswitch and motifs suggesting regulation in filamentous fungi by Puf family genes. We further obtained comparative and experimental evidence indicating widespread translational regulation by upstream open reading frames. These results enhance our understanding of these widely studied fungi as well as provide new insight into eukaryotic genome evolution and gene regulation.

Polynomial time algorithms for multicast network code construction

Abstract: The famous max-flow min-cut theorem states that a source node s can send information through a network (V, E) to a sink node t at a rate determined by the min-cut separating s and t. Recently, it has been shown that this rate can also be achieved for multicasting to several sinks provided that the intermediate nodes are allowed to re-encode the information they receive. We demonstrate examples of networks where the achievable rates obtained by coding at intermediate nodes are arbitrarily larger than if coding is not allowed. We give deterministic polynomial time algorithms and even faster randomized algorithms for designing linear codes for directed acyclic graphs with edges of unit capacity. We extend these algorithms to integer capacities and to codes that are tolerant to edge failures.

Automotive Control Systems

Abstract: Introduction * Thermodynamic Engine Cycles * Engine Management Systems * Engine Control Systems * Driveline Control * Vehicle Modelling * Vehicle Parameters and States * Vehicle Control Systems * Road and Driver Models * Appendix/Nomenclature.

Interacting electrons in disordered wires: Anderson localization and low-T transport

Abstract: We study the conductivity $\ensuremath{\sigma}(T)$ of interacting electrons in a low-dimensional disordered system at low temperature $T$ For weak interactions, the weak-localization regime crosses over with lowering $T$ into a dephasing-induced ``power-law hopping'' As $T$ is further decreased, the Anderson localization in Fock space crucially affects $\ensuremath{\sigma}(T)$, inducing a transition at $T={T}_{c}$, so that $\ensuremath{\sigma}(Tl{T}_{c})=0$ The critical behavior of $\ensuremath{\sigma}(T)$ above ${T}_{c}$ is $\mathrm{ln} \ensuremath{\sigma}(T)\ensuremath{\propto}\ensuremath{-}(T\ensuremath{-}{T}_{c}{)}^{\ensuremath{-}1/2}$ The mechanism of transport in the critical regime is many-particle transitions between distant states in Fock space

Magnetic Metamaterials at Telecommunication and Visible Frequencies

Abstract: Arrays of gold split rings with a 50-nm minimum feature size and with an LC resonance at 200 THz frequency (1.5 microm wavelength) are fabricated. For normal-incidence conditions, they exhibit a pronounced fundamental magnetic mode, arising from a coupling via the electric component of the incident light. For oblique incidence, a coupling via the magnetic component is demonstrated as well. Moreover, we identify a novel higher-order magnetic resonance at around 370 THz (800 nm wavelength) that evolves out of the Mie resonance for oblique incidence. Comparison with theory delivers good agreement and also shows that the structures allow for a negative magnetic permeability.

Geographic routing in city scenarios

Abstract: Position-based routing, as it is used by protocols like Greedy Perimeter Stateless Routing (GPSR) [5], is very well suited for highly dynamic environments such as inter-vehicle communication on highways. However, it has been discussed that radio obstacles [4], as they are found in urban areas, have a significant negative impact on the performance of position-based routing. In prior work [6] we presented a position-based approach which alleviates this problem and is able to find robust routes within city environments. It is related to the idea of position-based source routing as proposed in [1] for terminode routing. The algorithm needs global knowledge of the city topology as it is provided by a static street map. Given this information the sender determines the junctions that have to be traversed by the packet using the Dijkstra shortest path algorithm. Forwarding between junctions is then done in a position-based fashion. In this short paper we show how position-based routing can be aplied to a city scenario without assuming that nodes have access to a static street map and without using source routing.

Text2Onto: a framework for ontology learning and data-driven change discovery

Abstract: In this paper we present Text2Onto, a framework for ontology learning from textual resources. Three main features distinguish Text2Onto from our earlier framework TextToOnto as well as other state-of-the-art ontology learning frameworks. First, by representing the learned knowledge at a meta-level in the form of instantiated modeling primitives within a so called Probabilistic Ontology Model (POM), we remain independent of a concrete target language while being able to translate the instantiated primitives into any (reasonably expressive) knowledge representation formalism. Second, user interaction is a core aspect of Text2Onto and the fact that the system calculates a confidence for each learned object allows to design sophisticated visualizations of the POM. Third, by incorporating strategies for data-driven change discovery, we avoid processing the whole corpus from scratch each time it changes, only selectively updating the POM according to the corpus changes instead. Besides increasing efficiency in this way, it also allows a user to trace the evolution of the ontology with respect to the changes in the underlying corpus.

Learning concept hierarchies from text corpora using formal concept analysis

Abstract: We present a novel approach to the automatic acquisition of taxonomies or concept hierarchies from a text corpus. The approach is based on Formal Concept Analysis (FCA), a method mainly used for the analysis of data, i.e. for investigating and processing explicitly given information. We follow Harris' distributional hypothesis and model the context of a certain term as a vector representing syntactic dependencies which are automatically acquired from the text corpus with a linguistic parser. On the basis of this context information, FCA produces a lattice that we convert into a special kind of partial order constituting a concept hierarchy. The approach is evaluated by comparing the resulting concept hierarchies with hand-crafted taxonomies for two domains: tourism and finance. We also directly compare our approach with hierarchical agglomerative clustering as well as with Bi-Section-KMeans as an instance of a divisive clustering algorithm. Furthermore, we investigate the impact of using different measures weighting the contribution of each attribute as well as of applying a particular smoothing technique to cope with data sparseness.

Software-defined radio: basics and evolution to cognitive radio

Abstract: We provide a brief overview over the development of software-defined or reconfigurable radio systems. The need for software-defined radios is underlined and the most important notions used for such reconfigurable transceivers are thoroughly defined. The role of standards in radio development is emphasized and the usage of transmission mode parameters in the construction of software-defined radios is described. The software communications architecture is introduced as an example for a framework that allows an object-oriented development of software-defined radios. Cognitive radios are introduced as the next step in radio systems' evolution. The need for cognitive radios is exemplified by a comparison of present and advanced spectrum management strategies.

Decoherence in a superconducting quantum bit circuit

Abstract: Decoherence in quantum bit circuits is presently a major limitation to their use for quantum computing purposes. We present experiments, inspired from NMR, that characterize decoherence in a particular superconducting quantum bit circuit, the quantronium. We introduce a general framework for the analysis of decoherence, based on the spectral densities of the noise sources coupled to the qubit. Analysis of our measurements within this framework indicates a simple model for the noise sources acting on the qubit. We discuss various methods to fight decoherence.

Defect Chemistry of Donor-Doped and Undoped Strontium Titanate Ceramics between 1000° and 1400°C

Abstract: The electrical conductivity, sigma, of donor-doped and undoped strontium titanate (SrTiO3) ceramics and, in some cases, single crystals, Sr1-xLaxTiO3 (0 ≤ to x ≤ 0.1), was investigated in the temperature range of 1000°-1400°C under oxygen partial pressures, PO2, of 10-20-1 bar. In conjunction with Hall data and thermopower data from related papers, a set of constants for a defect-chemical model was determined, precisely describing point-defect concentrations and transport properties of these materials. In contrast to former works, temperature-dependent transport parameters and their non-negligible influence on the determination of the constants was considered, as well as the equilibrium restoration phenomena of the cation sublattice, which can be studied only at such high temperatures. It was shown that defects in the cation sublattice completely govern the electrical behavior of donor-doped and undoped SrTiO3. In the latter case, frozen-in strontium vacancies act as intrinsic acceptors, determining the sigma(PO2) curves at lower temperatures. This intrinsic acceptor concentration also can be calculated with this model. The very good agreement between calculation and measurement is shown in many examples.

Cut-wire pairs and plate pairs as magnetic atoms for optical metamaterials

Abstract: We study the optical properties of metamaterials made from cut-wire pairs or plate pairs. We obtain a more pronounced optical response for arrays of plate pairs, a geometry that also eliminates the undesirable polarization anisotropy of the cut-wire pairs. The measured optical spectra agree with simulations, revealing negative magnetic permeability in the range of telecommunications wavelengths. Thus nanoscopic plate pairs might serve as an alternative to the established split-ring resonator design.

Modeling Elementary Heterogeneous Chemistry and Electrochemistry in Solid-Oxide Fuel Cells

Abstract: This paper presents a new computational framework for modeling chemically reacting flow in anode-supported solid-oxide fuel cells (SOFC). Depending on materials and operating conditions, SOFC anodes afford a possibility for internal reforming or catalytic partial oxidation of hydrocarbon fuels. An important new element of the model is the capability to represent elementary heterogeneous chemical kinetics in the form of multistep reaction mechanisms. Porous-media transport in the electrodes is represented with a dusty-gas model. Charge-transfer chemistry is represented in a modified Butler-Volmer setting that is derived from elementary reactions, but assuming a single rate-limiting step. The model is discussed in terms of systems with defined flow channels and planar membrane-electrode assemblies. However, the underlying theory is independent of the particular geometry. Examples are given to illustrate the model.

Tailoring Porphyrins and Chlorins for Self-Assembly in Biomimetic Artificial Antenna Systems

Abstract: There is much diversity in the way in which photosynthetic organisms harvest sunlight. In chromophore−protein complexes, an exact orientation of pigments by the protein matrix ensures an efficient stepwise energy transfer to the reaction center where charge separation occurs. The charge separation and subsequent electron transfer steps are, however, very similar in all organisms, proving that there must exist a common ancestor. The architectural principle of chromophore−protein complexes is too complicated to be replicated in artificial light-harvesting devices. A simpler principle employs self-assembling chromophores that early green photosynthetic bacteria use in their chlorosomal antenna systems. Efforts in mimicking this self-assembly algorithm with fully synthetic pigments are presented. The fact that, as in the natural system, after self-assembly, concentration quenching is not operating due to the very orderly manner in which the chromophores are positioned lends hope for applications in artificial...

Supercritical water as a solvent.

Abstract: Water is not restricted to moderate temperatures and low pressures, but can exist up to very high temperatures, far above its critical point at 647 K. In this supercritical regime, water can be gradually compressed from gas-like to liquid-like densities. The resulting dense supercritical states have extraordinary properties which can be tuned by temperature and pressure, and form the basis for innovative technologies. This Review covers the current knowledge of the major properties of supercritical water and its solutions with nonpolar, polar, and ionic compounds, and of the underlying molecular processes.

How to correctly determine the different chlorophyll fluorescence parameters and the chlorophyll fluorescence decrease ratio RFd of leaves with the PAM fluorometer

Abstract: This contribution is a practical guide to the measurement of the different chlorophyll (Chl) fluorescence parameters and gives examples of their development under high-irradiance stress. From the Chl fluorescence induction kinetics upon irradiation of dark-adapted leaves, measured with the PAM fluorometer, various Chl fluorescence parameters, ratios, and quenching coefficients can be determined, which provide information on the functionality of the photosystem 2 (PS2) and the photosynthetic apparatus. These are the parameters Fv, Fm, F0, Fm′, Fv′, NF, and ΔF, the Chl fluorescence ratios Fv/Fm, Fv/F0, ΔF/Fm′, as well as the photochemical (qP) and non-photochemical quenching coefficients (qN, qCN, and NPQ). qN consists of three components (qN = qE + qT + qI), the contribution of which can be determined via Chl fluorescence relaxation kinetics measured in the dark period after the induction kinetics. The above Chl fluorescence parameters and ratios, many of which are measured in the dark-adapted state of leaves, primarily provide information on the functionality of PS2. In fully developed green and dark-green leaves these Chl fluorescence parameters, measured at the upper adaxial leaf side, only reflect the Chl fluorescence of a small portion of the leaf chloroplasts of the green palisade parenchyma cells at the upper outer leaf half. Thus, PAM fluorometer measurements have to be performed at both leaf sides to obtain information on all chloroplasts of the whole leaf. Combined high irradiance (HI) and heat stress, applied at the upper leaf side, strongly reduced the quantum yield of the photochemical energy conversion at the upper leaf half to nearly zero, whereas the Chl fluorescence signals measured at the lower leaf side were not or only little affected. During this HL-stress treatment, qN, qCN, and NPQ increased in both leaf sides, but to a much higher extent at the lower compared to the upper leaf side. qN was the best indicator for non-photochemical quenching even during a stronger HL-stress, whereas qCN and NPQ decreased with progressive stress even though non-photochemical quenching still continued. It is strongly recommended to determine, in addition to the classical fluorescence parameters, via the PAM fluorometer also the Chl fluorescence decrease ratio RFd (Fd/Fs), which, when measured at saturation irradiance is directly correlated to the net CO2 assimilation rate (P N) of leaves. This RFd-ratio can be determined from the Chl fluorescence induction kinetics measured with the PAM fluorometer using continuous saturating light (cSL) during 4–5 min. As the RFd-values are fast measurable indicators correlating with the photosynthetic activity of whole leaves, they should always be determined via the PAM fluorometer parallel to the other Chl fluorescence coefficients and ratios.

Highly resolved large-eddy simulation of separated flow in a channel with streamwise periodic constrictions

Abstract: High-resolution large-eddy simulation is used to investigate the mean and turbulence properties of a separated flow in a channel constricted by periodically distributed hill-shaped protrusions on one wall that obstruct the channel by 33% of its height and are arranged 9 hill heights apart. The geometry is a modification of an experimental configuration, the adaptation providing an extended region of post-reattachment recovery and allowing high-quality simulations to be performed at acceptable computing costs. The Reynolds number, based on the hill height and the bulk velocity above the crest is 10595. The simulated domain is streamwise as well as spanwise periodic, extending from one hill crest to the next in the streamwise direction and over 4.5 hill heights in the spanwise direction. This arrangement minimizes uncertainties associated with boundary conditions and makes the flow an especially attractive generic test case for validating turbulence closures for statistically two-dimensional separation. The emphasis of the study is on elucidating the turbulence mechanisms associated with separation, recirculation reattachment, acceleration and wall proximity. Hence, careful attention has been paid to resolution, and a body-fitted, low-aspect-ratio, nearly orthogonal numerical grid of close to 5 million nodes has been used. Unusually, the results of two entirely independent simulations with different codes for identical flow and numerical conditions are compared and shown to agree closely. Results are included for mean velocity, Reynolds stresses, anisotropy measures, spectra and budgets for the Reynolds stresses. Moreover, an analysis of structural characteristics is undertaken on the basis of instantaneous realizations, and links to features observed in the statistical results are identified and interpreted. Among a number of interesting features, a distinct ‘splatting’ of eddies on the windward hill side following reattachment is observed, which generates strong spanwise fluctuations that are reflected, statistically, by the spanwise normal stress near the wall exceeding that of the streamwise stress by a substantial margin, despite the absence of spanwise strain.

Measurement of the J/ψ meson and b-hadron production cross sections in pp̄ collisions at √s = 1960 GeV

Abstract: The authors present a new measurement of the inclusive and differential production cross sections of J/{psi} mesons and b-hadrons in proton-antiproton collisions at {radical}s = 1960 GeV The data correspond to an integrated luminosity of 397 pb{sup -1} collected by the CDF Run II detector They find the integrated cross section for inclusive J/{psi} production for all transverse momenta from 0 to 20 GeV/c in the rapidity range |y| 125 GeV/c They find the total cross section for b-hadrons, including both hadrons and anti-hadrons, decaying to J/{psi} with transverse momenta greater than 125 GeV/c in the rapidity range |y(J/{psi})| < 06, is 0330 {+-} 0005(stat){sub -0033}{sup +0036}(syst) {mu}b Using a Monte Carlo simulation of the decay kinematics of b-hadrons to all final states containing a J/{psi}, they extract the first measurement of the total single b-hadron cross section down to zero transverse momentum at {radical}s = 1960 GeV They find the total single b-hadron cross section integrated over all transverse momenta for b-hadrons in themore » rapidity range |y| < 06 to be 176 {+-} 04(stat){sub -23}{sup +25}(syst) {mu}b« less

A conversational agent as museum guide: design and evaluation of a real-world application

Abstract: This paper describes an application of the conversational agent Max in a real-world setting. The agent is employed as guide in a public computer museum, where he engages with visitors in natural face-to-face communication, provides them with information about the museum or the exhibition, and conducts natural small talk conversations. The design of the system is described with a focus on how the conversational behavior is achieved. Logfiles from interactions between Max and museum visitors were analyzed for the kinds of dialogue people are willing to have with Max. Results indicate that Max engages people in interactions where they are likely to use human-like communication strategies, suggesting the attribution of sociality to the agent.

Highway hierarchies hasten exact shortest path queries

Abstract: We present a new speedup technique for route planning that exploits the hierarchy inherent in real world road networks. Our algorithm preprocesses the eight digit number of nodes needed for maps of the USA or Western Europe in a few hours using linear space. Shortest (i.e. fastest) path queries then take around eight milliseconds to produce exact shortest paths. This is about 2 000 times faster than using Dijkstra’s algorithm.

Detection and imaging of atmospheric radio flashes from cosmic ray air showers

Abstract: The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10(20) eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within approximately 50 Mpc through interactions with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.

Quantum information processing and communication: strategic report on current status, visions and goals for research in Europe

Abstract: We present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission, http://www.cordis.lu/ist/fet/qipc-sr.htm). This document has been elaborated, following a former suggestion by FET, by a committee of QIPC scientists to provide input towards the European Commission for the preparation of the Seventh Framework Program. Besides being a document addressed to policy makers and funding agencies (both at the European and national level), the document contains a detailed scientific assessment of the state-of-the-art, main research goals, challenges, strengths, weaknesses, visions and perspectives of all the most relevant QIPC sub-fields, that we report here.

Methane reforming kinetics within a Ni–YSZ SOFC anode support

Abstract: This paper reports experimental and modeling investigations of thermal methane reforming chemistry within porous Ni–YSZ anode materials. Because the reforming chemistry is difficult to observe directly in an operating fuel cell, a specially designed experiment is developed. In the experiment a 0.75 mm-thick anode is sandwiched between two small co-flowing gas channels. One channel represents the fuel channel of a solid-oxide fuel cell (SOFC). The composition in the other channel carries the species that would be produced in an operating fuel cell by the electrochemical charge-transfer reactions in the thin three-phase regions near the interface between the anode and the dense electrolyte membrane (i.e., H2O and CO2). Because the anode structure is porous (and there is no dense electrolyte or cathode applied), there is convective and diffusive species flux between the two flow channels. The entire assembly is maintained at approximately 800 ° C in a furnace. The results of heterogeneous reforming kinetics are determined by using mass spectrometry to measure the species composition at the outlet of both channels. Experimental results are interpreted using a computational model that incorporates channel gas flow, porous-media transport, and elementary heterogeneous chemical kinetics. The overall objective is to develop quantitative models of non-electrochemical heterogeneous reforming chemistry within a Ni–YSZ anode.