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  • 1
    Publikationsdatum: 2014-01-01
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
    Publiziert von Springer
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  • 2
    Publikationsdatum: 2014-01-01
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
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  • 3
    Publikationsdatum: 2014-01-01
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
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  • 4
    Publikationsdatum: 2014-01-01
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
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  • 5
    Publikationsdatum: 2014-01-01
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
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  • 6
    Publikationsdatum: 2014-01-01
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
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  • 7
    Publikationsdatum: 2014-11-08
    Print ISSN: 1867-4828
    Digitale ISSN: 1869-0238
    Thema: Informatik
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  • 8
    Publikationsdatum: 2014-12-14
    Beschreibung: The multiple sequence alignment (MSA) problem has become relevant to several areas in bioinformatics from finding sequences family, detecting structural homologies of protein/DNA sequences, determining functions of protein/DNA sequences to predict patients diseases by comparing DNAs of patients in disease discovery, etc. The MSA is a NP-hard problem. In this paper, two new methods based on a cultural algorithm, namely the method of musical composition, for the solution of the MSA problem are introduced. The performance of the first and second versions were evaluated and analyzed on 26 and 12 different benchmark alignments, respectively. Test instances were taken from BAliBASE 3.0. Alignment accuracies are computed using the QSCORE program, which is a quality scoring program that compares two multiple sequence alignments. Numerical results on the tackled instances indicate that the performance levels of the proposed versions of the MMC are promising. In particular, the experimental results show that the second version found the best alignment reported in the specialized literature in 25  \(\%\) of the tested instances. Besides, for 50  \(\%\) of the tested instances, the second version achieved the second best alignment. Finally, the significance of the numerical results were analyzed according to the Wilcoxon rank-sum test, which indicated that the second proposed version is statistically similar to some state-of-the-art techniques for the MSA problem.
    Print ISSN: 0010-485X
    Digitale ISSN: 1436-5057
    Thema: Informatik
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  • 9
    Publikationsdatum: 2014-12-14
    Beschreibung: In an amplify-and-forward cooperative network, a closed-form expression of the a priori distribution of the complex-valued gain of the global relay channel is intractable, so that a priori information is often not exploited for estimating this gain. Here, we present two iterative channel gain and noise variance estimation algorithms that make use of a priori channel information and exploit the presence of not only pilot symbols but also unknown data symbols. These algorithms are approximations of maximum a posteriori estimation and linear minimum mean-square error estimation, respectively. A substantially reduced frame error rate is achieved as compared to the case where only pilot symbols are used in the estimation.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 10
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    Springer
    Publikationsdatum: 2014-12-17
    Beschreibung: Nowadays, with the advance of technology, many applications generate huge amounts of data streams at very high speed. Examples include network traffic, web click streams, video surveillance, and sensor networks. Data stream mining has become a hot research topic. Its goal is to extract hidden knowledge/patterns from continuous data streams. Unlike traditional data mining where the dataset is static and can be repeatedly read many times, data stream mining algorithms face many challenges and have to satisfy constraints such as bounded memory, single-pass, real-time response, and concept-drift detection. This paper presents a comprehensive survey of the state-of-the-art data stream mining algorithms with a focus on clustering and classification because of their ubiquitous usage. It identifies mining constraints, proposes a general model for data stream mining, and depicts the relationship between traditional data mining and data stream mining. Furthermore, it analyzes the advantages as well as limitations of data stream algorithms and suggests potential areas for future research.
    Print ISSN: 0219-1377
    Digitale ISSN: 0219-3116
    Thema: Informatik
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  • 11
    Publikationsdatum: 2014-12-18
    Beschreibung: To be successful, cybercriminals must figure out how to scale their scams. They duplicate content on new websites, often staying one step ahead of defenders that shut down past schemes. For some scams, such as phishing and counterfeit goods shops, the duplicated content remains nearly identical. In others, such as advanced-fee fraud and online Ponzi schemes, the criminal must alter content so that it appears different in order to evade detection by victims and law enforcement. Nevertheless, similarities often remain, in terms of the website structure or content, since making truly unique copies does not scale well. In this paper, we present a novel optimized combined clustering method that links together replicated scam websites, even when the criminal has taken steps to hide connections. We present automated methods to extract key website features, including rendered text, HTML structure, file structure, and screenshots. We describe a process to automatically identify the best combination of such attributes to most accurately cluster similar websites together. To demonstrate the method?s applicability to cybercrime, we evaluate its performance against two collected datasets of scam websites: fake escrow services and high-yield investment programs (HYIPs). We show that our method more accurately groups similar websites together than those existing general-purpose consensus clustering methods.
    Print ISSN: 1687-4161
    Digitale ISSN: 1687-417X
    Thema: Informatik
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  • 12
    Publikationsdatum: 2014-11-06
    Print ISSN: 0937-6429
    Digitale ISSN: 1861-8936
    Thema: Informatik , Wirtschaftswissenschaften
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  • 13
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    Springer
    Publikationsdatum: 2014-11-06
    Beschreibung: Domänenspezifische Modellierungssprachen (engl.: “domain-specific modeling languages”, DSMLs) versprechen deutliche Vorteile gegenüber universellen Modellierungssprachen. Ihr Entwurf ist allerdings mit einer essentiellen Herausforderung verbunden. Um ansehnliche Skaleneffekte zu erreichen, empfiehlt sich die Entwicklung von DSMLs, die in einer größeren Nutzungsbandbreite einsetzbar sind. Gleichzeitig spricht der Gewinn an Modellierungsproduktivität im Einzelfall für Sprachkonzepte, die an individuelle Anforderungen angepasst sind. In dem vorliegenden Beitrag wird ein neuartiger Ansatz zur konzeptuellen Modellierung wie auch zur Konstruktion von Informationssystemen präsentiert, der durch die faktische Nutzung von Fachsprachen inspiriert ist – die Mehrebenen-Modellierung. Im Unterschied zu traditionellen Spracharchitekturen wie der „Meta Object Facility“ (MOF) basiert er auf einer rekursiven Architektur, die eine beliebige Zahl von Klassifikationsebenen ermöglicht und dadurch den Entwurf von Sprachhierarchien – von einer Referenz-DSML bis hin zu „lokalen“ DSMLs – erlaubt. Auf diese Weise wird nicht nur der essentielle Konflikt des Entwurfs von DSMLs deutlich entschärft, sondern auch die Wiederverwendung und Integration von Software-Komponenten im Allgemeinen gefördert. Zudem ermöglicht der Ansatz die Reduktion von Modellkomplexität, indem er die Dichotomie von Spezialisierung und Instanzierung teilweise aufhebt. Darüber hinaus integriert er eine Metamodellierungssprache mit dem Metamodell einer Metaprogrammiersprache, wodurch ausführbare Modelle ermöglicht werden. Die Spezifikation der Spracharchitektur wird ergänzt durch die Darstellung von Anwendungsszenarien, die die Potentiale der Mehrebenen-Modellierung verdeutlichen, sowie eine kritische Betrachtung ihrer Besonderheiten.
    Print ISSN: 0937-6429
    Digitale ISSN: 1861-8936
    Thema: Informatik , Wirtschaftswissenschaften
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  • 14
    Publikationsdatum: 2014-11-08
    Beschreibung: Background: Accurate prediction of cancer prognosis based on gene expression data is generally difficult, and identifying robust prognostic markers for cancer remains a challenging problem. Recent studies have shown that modular markers, such as pathway markers and subnetwork markers, can provide better snapshots of the underlying biological mechanisms by incorporating additional biological information, thereby leading to more accurate cancer classification. Results: In this paper, we propose a novel method for simultaneously identifying robust synergistic subnetwork markers that can accurately predict cancer prognosis. The proposed method utilizes an efficient message-passing algorithm called affinity propagation, based on which we identify groups ? or subnetworks ? of discriminative and synergistic genes, whose protein products are closely located in the protein-protein interaction (PPI) network. Unlike other existing subnetwork marker identification methods, our proposed method can simultaneously identify multiple nonoverlapping subnetwork markers that can synergistically predict cancer prognosis. Conclusions: Evaluation results based on multiple breast cancer datasets demonstrate that the proposed message-passing approach can identify robust subnetwork markers in the human PPI network, which have higher discriminative power and better reproducibility compared to those identified by previous methods. The identified subnetwork makers can lead to better cancer classifiers with improved overall performance and consistency across independent cancer datasets.
    Print ISSN: 1687-4145
    Digitale ISSN: 1687-4153
    Thema: Biologie , Informatik
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  • 15
    Publikationsdatum: 2014-11-11
    Print ISSN: 0340-1200
    Digitale ISSN: 1432-0770
    Thema: Biologie , Informatik , Physik
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  • 16
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    Springer
    Publikationsdatum: 2014-11-11
    Digitale ISSN: 1867-0202
    Thema: Informatik , Wirtschaftswissenschaften
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  • 17
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    Springer
    In: Computing
    Publikationsdatum: 2014-11-11
    Beschreibung: When optimizing performance on a GPU, control flow divergence of threads in one warp can make up the possible performance bottlenecks. In our hand-coded GPU stencil computation optimization, with a view to remove this control flow divergence brought by conventional mapping method between global memory and shared memory, we devise a new mapping mechanism by modeling the coalesced memory accesses of GPU threads and the aligned ghost zone overheads to remove conditional statements of the boundary XY-tile stencil computation points for improved performance. In addition, we utilize only one XY-tile loaded into registers in every stencil computation iteration, common sub-expression elimination and software prefetching to reduce overheads. Finally, detailed performance evaluation demonstrates that global memory access traffic is close to the idealized lower bound value through our optimized policies, that is to say, in every computed point of one XY-tile the memory access traffic is roughly 6 and 4 % more than 8 bytes per XY-tile point of the idealized lower bound memory access traffic in which ghost zone overheads are not taken into consideration on Tesla C2050 and Kepler K20X respectively.
    Print ISSN: 0010-485X
    Digitale ISSN: 1436-5057
    Thema: Informatik
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  • 18
    Publikationsdatum: 2014-11-05
    Beschreibung: A variety of applications, such as information extraction, intrusion detection and protein fold recognition, can be expressed as sequences of discrete events or elements (rather than unordered sets of features), that is, there is an order dependence among the elements composing each data instance. These applications may be modeled as classification problems, and in this case the classifier should exploit sequential interactions among the elements, so that the ordering relationship among them is properly captured. Dominant approaches to this problem include: (i) learning Hidden Markov Models, (ii) exploiting frequent sequences extracted from the data and (iii) computing string kernels. Such approaches, however, are computationally hard and vulnerable to noise, especially if the data shows long range dependencies (i.e., long subsequences are necessary in order to model the data). In this paper we provide simple algorithms that build highly effective sequential classifiers. Our algorithms are based on enumerating approximately contiguous subsequences from the training set on a demand-driven basis, exploiting a lightweight and flexible subsequence matching function and an innovative subsequence enumeration strategy called pattern silhouettes , making our learning algorithms fast and the corresponding classifiers robust to noisy data. Our empirical results on a variety of datasets indicate that the best trade-off between accuracy and learning time is usually obtained by limiting the length of the subsequences by a factor of \(\log {n}\) , which leads to a \(O(n\log {n})\) learning cost (where \(n\) is the length of the sequence being classified). Finally, we show that, in most of the cases, our classifiers are faster than existing solutions (sometimes, by orders of magnitude), also providing significant accuracy improvements in most of the evaluated cases.
    Print ISSN: 1384-5810
    Digitale ISSN: 1573-756X
    Thema: Informatik
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  • 19
    Publikationsdatum: 2014-11-05
    Beschreibung: An important challenge in the domain of vehicular ad hoc networks (VANET) is the scalability of data dissemination. Under dense traffic conditions, the large number of communicating vehicles can easily result in a congested wireless channel. In that situation, delays and packet losses increase to a level where the VANET cannot be applied for road safety applications anymore. This paper introduces scalable data dissemination in vehicular ad hoc networks (SDDV), a holistic solution to this problem. It is composed of several techniques spread across the different layers of the protocol stack. Simulation results are presented that illustrate the severity of the scalability problem when applying common state-of-the-art techniques and parameters. Starting from such a baseline solution, optimization techniques are gradually added to SDDV until the scalability problem is entirely solved. Besides the performance evaluation based on simulations, the paper ends with an evaluation of the final SDDV configuration on real hardware. Experiments including 110 nodes are performed on the iMinds w-iLab.t wireless lab. The results of these experiments confirm the results obtained in the corresponding simulations.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 20
    Publikationsdatum: 2014-11-05
    Beschreibung: Adaptive spatial multiplexing (SM) Multiple Input Multiple Output (MIMO) techniques enhance the spectral efficiency of wideband wireless communications in favorable radio channel conditions. In this study, we show the benefits of combining a traditional fixed-beam scheme and multiuser opportunistic radio resource allocation in space-time-frequency domains. This combining is feasible in wideband Orthogonal Frequency Domain Multiple Access (OFDMA) systems such as the Universal Mobile Telecommunications System (UMTS) Long Term Evolution (LTE). This study brings novel knowledge which indicates that an orthogonal fixed beam approach benefits from opportunistic radio resource allocation clearly more than a conventional antenna domain approach in frequency-selective radio channels. It was found out that the fixed beam radio link performance is enhanced in wideband adaptive radio links due to the fact that orthogonal beams reduce correlation between the MIMO channels in the allocated sub-bands. Moreover, beamforming gains bring higher Eigenvalues of the MIMO channel matrix in the opportunistically selected sub-bands. It is shown that the fixed beam deployment changes the distribution of the MIMO channel correlation values and Eigenvalues in a manner which enhances opportunistic multiuser gains in wideband time-frequency-selective MIMO radio channels. Simulation results with 2 x 2 spatial multiplexing in an OFDMA uplink indicate that the proposed beam domain scheme gives up to 80% data throughput gain over the corresponding antenna domain scheme in a pedestrian microcell environment.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 21
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    Springer
    Publikationsdatum: 2014-11-05
    Beschreibung: There is excitement within the algorithms community about a new partitioning method introduced by Yaroslavskiy. This algorithm renders Quicksort slightly faster than the case when it runs under classic partitioning methods. We show that this improved performance in Quicksort is not sustained in Quickselect; a variant of Quicksort for finding order statistics. We investigate the number of comparisons made by Quickselect to find a key with a randomly selected rank under Yaroslavskiy’s algorithm. This grand averaging is a smoothing operator over all individual distributions for specific fixed order statistics. We give the exact grand average. The grand distribution of the number of comparison (when suitably scaled) is given as the fixed-point solution of a distributional equation of a contraction in the Zolotarev metric space. Our investigation shows that Quickselect under older partitioning methods slightly outperforms Quickselect under Yaroslavskiy’s algorithm, for an order statistic of a random rank. Similar results are obtained for extremal order statistics, where again we find the exact average, and the distribution for the number of comparisons (when suitably scaled). Both limiting distributions are of perpetuities (a sum of products of independent mixed continuous random variables).
    Print ISSN: 0178-4617
    Digitale ISSN: 1432-0541
    Thema: Informatik , Mathematik
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  • 22
    Publikationsdatum: 2014-11-05
    Beschreibung: Data mining is the process of determining new, unanticipated, valuable patterns from existing databases by considering historical and recent developments in statistics, artificial intelligence, and machine learning. It can help companies focus on the most important information in their data warehouses. Association rule mining is one of the most highly researched and popular data mining techniques for finding associations between items in a set. It is frequently used in marketing, advertising, and inventory control. Typically, association rules only consider items in transactions (positive association rules). They do not consider items that do not occur together, which can be used to create rules that are also useful for market basket analysis. Also, existing algorithms often generate too many candidate itemsets when mining the data and scan the database multiple times. To resolve these issues in association rule mining algorithms, we propose SARIC (set particle swarm optimization for association rules using the itemset range and correlation coefficient). Our method uses set particle swarm optimization to generate association rules from a database and considers both positive and negative occurrences of attributes. SARIC applies the itemset range and correlation coefficient so that we do not need to specify the minimum support and confidence, because it automatically determines them quickly and objectively. We verified the efficiency of SARIC using two differently sized databases. Our simulation results demonstrate that SARIC generates more promising results than Apriori, Eclat, HMINE, and a genetic algorithm.
    Print ISSN: 0219-1377
    Digitale ISSN: 0219-3116
    Thema: Informatik
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  • 23
    Publikationsdatum: 2014-11-05
    Beschreibung: The wideband code division multiple access (WCDMA) network planning problem requires to determine the location and the configuration parameters of the base stations (BSs) so as to maximize the capacity and minimize the installation cost. This problem can be formulated as a complex set covering problem. Compared to the classical set covering problems, the coverage area of each BS is unknown in advance. This makes that the selection of each BS location and configuration parameters is determined by the location and configuration parameters of the neighbor BSs. Accordingly, we will conduct a competition and cooperation model based on the re-covered area of the BSs to measure the relationship of the BSs. Then, an efficient genetic operation based on this model is proposed to generate new-quality solutions. Further, four BS configuration parameters, i.e., the antenna height, antenna tilt, sector orientation and pilot signal power, are taken into account as well. Since there are too many combination levels of the configuration parameters, an encoding method based on orthogonal design is presented to reduce the search space. Subsequently, we merge the proposed encoding method and genetic operation into the multiobjective evolutionary algorithm-based decomposition (MOEA/D-M2M) to solve the WCDMA network planning problem. Simulation results show the efficacy of the proposed encoding and genetic operation in comparison with the existing counterpart.
    Print ISSN: 0219-1377
    Digitale ISSN: 0219-3116
    Thema: Informatik
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  • 24
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    Springer
    Publikationsdatum: 2014-12-19
    Beschreibung: We study an online version of linear Fisher market. In this market there are \(m\) buyers and a set of \(n\) dividable goods to be allocated to the buyers. The utility that buyer \(i\) derives from good \(j\) is \(u_{ij}\) . Given an allocation \(\hat{U}\) in which buyer \(i\) has utility \(\hat{U}_i\) we study a quality measure that is based on taking an average of the ratios \(U_{i}/\hat{U}_i\) with respect to any other allocation \(U\) . Market equilibrium allocation is the optimal solution with respect to this measure. Our setting is online and so the allocation of each good should be done without any knowledge of the upcoming goods. We design an online algorithm for the problem that is only worse by a logarithmic factor than any other solution with respect to this quality measure, and in particular competes with the market equilibrium allocation. We prove a tight lower bound which shows that our algorithm is optimal up to constants. Our algorithm uses a primal dual convex programming scheme. To the best of our knowledge this is the first time that such a scheme is used in the online framework.
    Print ISSN: 0178-4617
    Digitale ISSN: 1432-0541
    Thema: Informatik , Mathematik
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  • 25
    Publikationsdatum: 2014-12-19
    Beschreibung: Zur analytischen Vorausberechnung des vollständigen Feldspektrums von Drehfeldmaschinen ist es wichtig, neben den Wicklungsfeldern, die über den konstanten mittleren magnetischen Leitwert erregt werden, auch die parametrischen Feldanteile, d. h. die über die Schwankungen des Luftspaltleitwerts erregten Feldwellen, bestmöglich zu erfassen. Dies gilt insbesondere für Synchronmaschinen, die durch die Pollücke bzw. die Erregernutung gegenüber Induktionsmaschinen zusätzliche starke und noch dazu niederpolige Leitwertschwankungen aufweisen. In diesem Artikel sollen darum verschiedene Ansätze zur Berechnung des Beitrags von Schenkelpolläufern zum resultierenden Luftspaltleitwert von Schenkelpolsynchronmaschinen vorgestellt und miteinander verglichen werden. Dabei sollen auch die Abhängigkeiten der Leitwertfunktion von unterschiedlichen Parametern aufgezeigt werden.
    Print ISSN: 0932-383X
    Digitale ISSN: 1613-7620
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 26
    Publikationsdatum: 2014-12-19
    Beschreibung: In der Entwicklung von Traktionsmotoren führt die zusehends höhere thermische Auslastung zur Notwendigkeit einer genauen Prognose der im Ventilationssystem auftretenden Druckverluste und Strömungsverhältnisse sowie der im Innern der Maschine vorherrschenden Temperaturen. Die CFD-Methode eignet sich hier als nützliches Werkzeug zur Vorausberechnung sowohl der erwarteten Fördermenge des Ventilators als auch der Erwärmung der kritischen Bauteile. In dieser Arbeit wird ein kurzer Überblick über die CFD-Methode gegeben sowie die analytische Abschätzung der Fördermenge eines Ventilators in einer Traktionsmaschine. Als Anwendung der CFD-Methode wird in einer Strömungsanalyse die Optimierung einer Ventilatorgeometrie vorgestellt sowie die thermische Berechnung einer flüssigkeitsgekühlten Maschine durchgeführt.
    Print ISSN: 0932-383X
    Digitale ISSN: 1613-7620
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 27
    Publikationsdatum: 2014-12-19
    Beschreibung: Dieser Beitrag behandelt die hochdynamische Phasenstrommessung für elektrische Traktionsantriebe mit anisotropen magnetoresistiven (AMR) Sensoren. Das zugrundeliegende Messprinzip sowie die Eigenschaften des ausgewählten Stromsensors werden vorgestellt. Die Ergebnisse der magnetoresistiven Stromermittlung werden mit den Referenzmessungen mittels kompensierender LEM-Stromwandler verglichen. Die Bestimmung der aktuellen Rotorposition von Permanentmagnet-erregten Synchronmaschinen ohne Lagegeber (vor allem bei geringen Drehzahlen und im Stillstand) erfordert eine hochpräzise und hochdynamische Stromerfassung. Stromdifferenzmessungen für das verwendete INFORM Verfahren (Indirekte Flusserfassung durch Online-Reaktanzmessung) werden somit in diesem Artikel als Qualitätskriterium zur Bewertung der Stromsensortechnologien herangezogen.
    Print ISSN: 0932-383X
    Digitale ISSN: 1613-7620
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 28
    Publikationsdatum: 2014-12-19
    Beschreibung: A physical model of a 1 MVA Permanent Magnet Synchronous Generator (PMSG) is derived by reducing the number of poles and the core length. The losses in sinusoidal operation are compared to the inverter-based operation using various switching frequencies. Also, the effects of magnetically conducting slot wedges in the stator are investigated. The model is equipped with a rotor temperature measurement system. Different rotors with surface mounted and embedded magnets are compared using the steady-state magnet-temperature as a measure of the losses in the magnets.
    Print ISSN: 0932-383X
    Digitale ISSN: 1613-7620
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 29
    Publikationsdatum: 2014-12-19
    Beschreibung: This report compares axial flux and radial flux machines for the use in wheel hub drives in terms of their electromagnetic and thermal properties. First, the differences between the topologies of the two types of machines are explained, and a theoretical comparison of the possible power densities is carried out. Then, the machines are designed, using a finite-element software with special consideration on the number of slots per pole and phase. Finally, the designs are thermally and electromagnetically compared.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 30
    Publikationsdatum: 2014-12-19
    Beschreibung: Durch den zunehmenden Einsatz von Hybridfahrzeugen im öffentlichen Nahverkehr und die Hybridisierung von Nutzfahrzeugen besteht ein Bedarf an Leistungsspeichern für den mobilen Einsatz. Im Projekt highFly wurde ein elektro-mechanischer Energiespeicher (Flywheel) mit einem nutzbaren Energieinhalt von 900 Wh und einer Spitzenleistung von 145 kW entwickelt. Es wird ein integriertes Rotorkonzept basierend auf einer synchronen Reluktanzmaschine verwendet, wodurch ein sehr kompaktes Modul realisiert werden kann. Die elektrische Maschine und das mechanische Design wurden für die hohe Drehzahl von bis zu 40.000 min −1 optimiert. Besonderes Augenmerk wurde auf das aktive und passive Sicherheitskonzept gelegt.
    Print ISSN: 0932-383X
    Digitale ISSN: 1613-7620
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 31
    Publikationsdatum: 2014-12-14
    Print ISSN: 0010-485X
    Digitale ISSN: 1436-5057
    Thema: Informatik
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  • 32
    Publikationsdatum: 2014-12-16
    Beschreibung: Diabetic retinopathy is the leading cause of blindness worldwide. It is caused by the abnormal growth of the retinal blood vessels. Plasminogen activator inhibitor1 (PAI1) is the key growth factor and the inhibition of PAI1 can reduce the angiogenesis. In this study, currently available inhibitors are taken and tested for the toxicity, binding affinity, and bioactivities of the compounds by in silico approach. Five toxic free inhibitors were identified, among which N-acetyl-D-glucosamine shows the significant binding affinity and two of the molecules are having the better bioactivity properties. The molecular optimization of 2-(acetylamino)-2-deoxy-A-D-glucopyranose and alpha-L-fucose can be used for the treatment of diabetic retinopathy.
    Print ISSN: 1687-8027
    Digitale ISSN: 1687-8035
    Thema: Biologie , Informatik
    Publiziert von Hindawi
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  • 33
    Publikationsdatum: 2014-12-14
    Beschreibung: This paper reports the observation and analysis of the microbubble motion induced by an underwater shock wave. In the analysis, Herring’s bubble motion equation was numerically solved using an experimental shock wave pressure profile. The pressure attenuation of the rebound shock wave of a microbubble was also estimated by numerical simulation. The motion behaviors of the microbubbles during their interaction with an electric discharge shock wave, such as their rebound, shock wave generation, and microjet formation, were observed by magnified visualization. To improve the observation accuracy, spatial positioning control of the microbubbles was employed. The experimentally determined time variation of the diameter of the microbubbles when they collapsed spherically was in agreement with the results of the numerical analyses, and the latter also revealed a very high pressure of the rebound shock wave. There were, however, discrepancies between the experimental and analytical results for non-spherical collapse. It is thought that spherical collapse produces stronger rebound shock waves and that the probability of such collapse increases with decreasing diameter of the bubble. In addition, it was demonstrated that single and multiple microbubbles moved vigorously after interaction with a shock wave and the latter coalesced into a single bubble within several hundred microseconds. Graphical Abstract
    Print ISSN: 1343-8875
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    Thema: Informatik
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  • 34
    Publikationsdatum: 2014-12-14
    Beschreibung: Experimental studies of supersonic flow over several compression ramps are carried out in a Mach 3.0 wind tunnel; the upstream boundary layers include laminar flow, transitional flow, and turbulent flow. Fine flow structures are obtained via nano-tracer planar laser scattering (NPLS) technique, typical flow structures such as boundary layer, shear layer, and shock wave are visible distinctly. The angle of shock wave and the development of boundary layer are measured by time-averaged flow field, the spatiotemporal evolutions of flow field are revealed by two time-dependent NPLS images. Results indicate that when ramp angles are 25°, a typical separation occurs in laminar flow, and a certain extent separation occurs in transitional flow, while separation does not occur in turbulent flow. When ramp angles are 28°, laminar flow separates further, a typical separation occurs in transitional flow, by comparison, separation region in turbulent flow is small. Significant differences of the three types of ramp flows can be found in shock wave structure and flow separation. Graphical abstract
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  • 35
    Publikationsdatum: 2014-12-14
    Beschreibung: The distribution of water masses has become one of the most important topics in recent oceanic research. Water masses flow dynamically and have interannual variability, and hence the distribution can change dramatically even over short time periods and may differ from year to year. In this paper, we use a high-resolution ocean dataset, which contains multiple ocean variables, to visualize the details of the water mass. Because water mass can be defined by multiple ocean variables (e.g., temperature and salinity), we develop a multi-variate visualization system, which allows us to extract the time-varying distributions of water masses from multiple variables. The visualization is then adjusted by multiple ocean specialists because directly applying the existing definition to extract the water mass would result in incorrect rendering results. This leads to another problem that different ocean specialists may have different perspectives on the distribution of water masses, so that the adjustments would also be different. To solve this problem, an ensemble average process is performed for the adjusted rendering results from multiple ocean specialists. To increase the authenticity, we also add a voting scheme to the system, so that a majority rule can be applied to the ensemble-averaging result. As the application of the proposed voting-based ensemble-averaging visualization system, we first show the interannual variability of the significant water mass and then visualize the dynamic behavior for the period of interest in different years. We also highlight a mixing phenomenon that has a strong influence on the distribution of the water mass. As a result, we can obtain a clear and accurate visualization of the water mass distribution. Graphical Abstract
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    Thema: Informatik
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  • 36
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    Publikationsdatum: 2014-12-14
    Beschreibung: A synthetic jet (SJ) is a fluid flow that is created from an oscillatory process of suction and blowing. A hybrid synthetic jet (HSJ) combines this principle with fluidic pumping through a valveless pump. The present study addresses round HSJs issuing into quiescent surroundings from an actuator orifice 8 mm in diameter. For comparison purposes, a common (zero-net-mass-flux) SJ is used. The working fluid is air, and the maximum Reynolds numbers are 11,000 and 9,000 for HSJs and SJs, respectively. The following five experimental methods are employed: flow visualization using a smoke wire technique, velocity measurements using a hot-wire anemometer, velocity measurements using a Pitot tube, impedance measurements of the actuators, and measurements of the jet momentum using precision scales. Flow visualization demonstrates phase-locked flow fields. The first resonance frequencies are theoretically derived to be 79 and 98 Hz for an SJ and HSJ, respectively. These values are confirmed by all of the experimental methods used. The results demonstrate the advantages of HSJs. The tested HSJ achieves a 24 % higher pumped volume flow rate in comparison to the SJ at a maximum volumetric efficiency of 33 %. Moreover, the overall energy efficiency of the HSJ actuator is 1.8 times higher than that of the SJ actuator. These promising HSJ features, including significantly higher efficiencies, can be useful for various heat transfer applications such as the cooling of highly loaded electronic devices. Graphical Abstract
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  • 37
    Publikationsdatum: 2014-12-14
    Beschreibung: Nanomedicine is becoming an extremely promising research area for healthcare. The visualization and quantification of nanoparticles (NPs) inside the organs of interest pose a significant challenge and therefore, novel image processing approaches are required for a better diagnosis. The purpose of this work was to develop a novel approach for better visualization and quantification of iron oxide NPs in three dimension (3D) high-resolution magnetic resonance (MR) images of an inflammatory model. The proposed procedure focuses on the extraction of NPs from the background surrounding it. It is applied on 2D and 3D images and is based on pre-processing and segmentation by automatic threshold to visualize the NPs inside the mouse calf using a control set of images of the same calf before injecting the NPs. The resulting visualization of the 3D distribution of iron oxide NPs inside the inflamed area of the calf has a potential in the advancement of NPs application in nanomedicine therapy and diagnosis. Graphical abstract
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  • 38
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    Publikationsdatum: 2014-12-16
    Beschreibung: Probabilistic topic modeling of text collections has been recently developed mainly within the framework of graphical models and Bayesian inference. In this paper we introduce an alternative semi-probabilistic approach, which we call additive regularization of topic models (ARTM). Instead of building a purely probabilistic generative model of text we regularize an ill-posed problem of stochastic matrix factorization by maximizing a weighted sum of the log-likelihood and additional criteria. This approach enables us to combine probabilistic assumptions with linguistic and problem-specific requirements in a single multi-objective topic model. In the theoretical part of the work we derive the regularized EM-algorithm and provide a pool of regularizers, which can be applied together in any combination. We show that many models previously developed within Bayesian framework can be inferred easier within ARTM and in some cases generalized. In the experimental part we show that a combination of sparsing, smoothing, and decorrelation improves several quality measures at once with almost no loss of the likelihood.
    Print ISSN: 0885-6125
    Digitale ISSN: 1573-0565
    Thema: Informatik
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  • 39
    Publikationsdatum: 2014-12-17
    Beschreibung: This paper is intended to investigate the effect of Narmab storage dam on downstream inundated area for three reservoir operation scenarios. ArcView GIS was coupled with HEC-RAS to produce a flood map for flood discharge of different return periods. Google-Earth software was applied to depict the extent of floodplain in actual landscape. The inflow hydrographs for 4 return periods (50-, 100-, 500- and 1,000-year) were routed through Puls method in order to obtain the outflow hydrographs passing through dam spillway. Results show that, through the operation of reservoir, the downstream inundated area can be reduced up to 75.1 % as a function of reservoir available storage. Furthermore, calculations showed that the reduction rate of inundated area for 50-year floods is largely more than 1,000-year floods, implies the high ability of Narmab dam on flood control especially for floods with shorter return period.
    Print ISSN: 1865-0473
    Digitale ISSN: 1865-0481
    Thema: Geologie und Paläontologie , Informatik
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  • 40
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    Publikationsdatum: 2014
    Print ISSN: 0937-6429
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    Thema: Informatik , Wirtschaftswissenschaften
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  • 41
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    Publikationsdatum: 2014
    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Privacy- und Securityvorfälle stellen eine ernsthafte Bedrohung für den Erfolg eines Unternehmens dar. Während frühere Untersuchungen sich hauptsächlich auf Sekundäreffekte konzentriert haben (d. h. Kapitalmarktreaktionen in Folge von Privacy- und Security-Vorfällen), widmet sich diese Studie Primäreffekten und beleuchtet die direkte Kundenreaktion. In einem Laborexperiment wird zwischen dem Einfluss von Privacy- und Security-Vorfällen auf das Vertrauen und das Verhalten von Personen unterschieden. Es finden sich Hinweise auf das sogenannte Datenschutzparadoxon, wonach sich im Bereich des Datenschutzes die Intention vom Verhalten unterscheidet. Während Privacy sehr wichtig für die Vertrauensbildung ist, wirkt Security stärker auf das tatsächliche Verhalten. Nach den Ergebnissen dieser Studie bleibt die Lücke zwischen Intentionen und Verhalten auch nach dem Auftreten eines Datenschutzvorfalls bestehen.〈/p〉
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  • 42
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  • 43
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  • 44
    Publikationsdatum: 2014
    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Während sich die meisten wissenschaftlichen Studien zum Thema „Big Data“ mit den technischen Möglichkeiten zur Bewältigung von riesigen Datenmengen beschäftigen, sind empirische Untersuchungen in Bezug auf die von Fachleuten verlangten Kompetenzen für das Management and die Analyse von Big Data bislang noch nicht durchgeführt worden. Gleichzeitig diskutiert man in Wissenschaft und Praxis heftig über die Unterschiede und Gemeinsamkeiten von Big Data (BD) einerseits und „traditionellem“ Business Intelligence (BI) andererseits. Der vorliegende Artikel beschreibt die Durchführung einer Latenten Semantischen Analyse (LSA) von Stellenanzeigen auf dem Online-Portal monster.com, um Informationen darüber zu gewinnen, welche Anforderungen Unternehmen an Fachkräfte in den Bereichen BD und BI stellen. Auf Basis einer Analyse und Interpretation der statistischen Ergebnisse der LSA wird eine Taxonomie von Kompetenzanforderungen für BD bzw. BI entwickelt. Die wichtigsten Ergebnisse der Untersuchung lauten: (1) für beide Bereiche, BD und BI, ist Businesswissen genauso wichtig wie technisches Wissen; (2) kompetent sein im Bereich BI bezieht sich vorwiegend auf Wissen und Fähigkeiten in Bezug auf die Produkte der großen kommerziellen Softwareanbieter, während im Bereich BD eher Wissen und die Fähigkeiten in Bezug auf die Entwicklung von Individualsoftware und die Anwendung statistischer Methoden im Vordergrund steht; (3) die Nachfrage nach Kompetenz im Bereich BI ist immer noch weitaus größer als die Nachfrage nach Kompetenz im Bereich BD; und (4) BD-Projekte sind gegenwärtig wesentlich humankapital-intensiver als BI-Projekte. Die Ergebnisse und Erkenntnisse der Studie können Praktikern, Unternehmen und wissenschaftlichen Einrichtungen dabei helfen, ihre BD- bzw. BI-Kompetenz zu bewerten und zu erweitern.〈/p〉
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    Thema: Informatik , Wirtschaftswissenschaften
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  • 45
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    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Mit “Big Data” werden Technologien beschrieben, die nicht weniger als die Erfüllung eines der Kernziele der Wirtschaftsinformatik versprechen: die richtigen Informationen dem richtigen Adressaten zur richtigen Zeit in der richtigen Menge am richtigen Ort und in der erforderlichen Qualität bereitzustellen. Für die Wirtschaftsinformatik als anwendungsorientierte Wissenschaftsdisziplin entstehen durch solche technologischen Entwicklungen Chancen und Risiken. Risiken entstehen vor allem dadurch, dass möglicherweise erhebliche Ressourcen auf die Erklärung und Gestaltung von Modeerscheinungen verwendet werden. Chancen entstehen dadurch, dass die entsprechenden Ressourcen zu substanziellen Erkenntnisgewinnen führen, die dem wissenschaftlichen Fortschritt der Disziplin wie auch ihrer praktischen Relevanz dienen.〈/p〉 〈p〉Aus Sicht der Autoren ist die Wirtschaftsinformatik ideal positioniert, um Big Data kritisch zu begleiten und Erkenntnisse für die Erklärung und Gestaltung innovativer Informationssysteme in Wirtschaft und Verwaltung zu nutzen – unabhängig davon, ob Big Data nun tatsächlich eine disruptive Technologie oder doch nur eine flüchtige Modeerscheinung ist. Die weitere Entwicklung und Adoption von Big Data wird letztendlich zeigen, ob es sich um eine Modeerscheinung oder um substanziellen Fortschritt handelt. Die aufgezeigten Thesen zeigen darüber hinaus auch, wie künftige technologische Entwicklungen für den Fortschritt der Disziplin Wirtschaftsinformatik genutzt werden können. Technologischer Fortschritt sollte für eine kumulative Ergänzung bestehender Modelle, Werkzeuge und Methoden genutzt werden. Dagegen sind wissenschaftliche Revolutionen unabhängig vom technologischen Fortschritt.〈/p〉
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  • 46
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  • 47
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    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Während die klassische Definition von Big Data ursprünglich nur die drei Größen Datenmenge (Volume), Datenrate (Velocity) und Datenvielfalt (Variety) umfasste, ist in jüngster Zeit der Wahrheitsgehalt (Veracity) als weitere Dimension mehr und mehr in den wissenschaftlichen und praktischen Fokus gerückt. Der noch immer wachsende Bereich der Sozialen Medien und damit verbundene benutzergenerierte Datenmengen verlangen nach neuen Methoden, die die enthaltene Datenunschärfe abschätzen und kontrollieren können. Dieser Beitrag widmet sich einem Aspekt der Datenunschärfe und stellt einen neuartigen Ansatz vor, der die Verlässlichkeit von benutzergenerierten Daten auf Basis von wiederkehrenden Mustern abschätzt. Zu diesem Zweck wird eine große Menge von Twitter-Statusnachrichten mit geographischer Standortinformation aus San Francisco untersucht und mit Points of Interest (POIs), wie beispielsweise Bars, Restaurants oder Parks, in Verbindung gebracht. Das vorgeschlagene Modell wird durch kausale Beziehungen zwischen Points of Interest und den in der Umgebung vorliegenden Twitter-Meldungen validiert. Weiterhin wird die zeitliche Dimension dieser Beziehung in Betracht gezogen, um so in Abhängigkeit der Art des POI wiederkehrende Muster zu identifizieren. Die durchgeführten Analysen münden in einem Indikator, der die Verlässlichkeit von vorliegenden Daten in räumlicher und zeitlicher Dimension abschätzt.〈/p〉
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  • 48
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  • 49
    Publikationsdatum: 2014
    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Datenzentrische Ansätze wie Big Data und verwandte Ansätze im Bereich Business Intelligence und Analytics (BI&A) haben in jüngster Zeit viel Aufmerksamkeit auf sich gezogen, da sie versprechen – basierend auf neuen geschäftsrelevanten Erkenntnissen und besseren Entscheidungen – die Leistungsfähigkeit von Unternehmen stark zu verbessern. Die Einbeziehung datenzentrischer Ansätze in die Entscheidungsprozesse von Unternehmen ist herausfordernd und es ist nicht selbstverständlich, dass die erwarteten Nutzen auch realisiert werden. Frühere Studien haben einen mangelnden Forschungsfokus auf den Kontext von Entscheidungsprozessen in datenzentrischen Ansätzen festgestellt. Mittels eines multiplen Fallstudienansatzes werden im vorliegenden Aufsatz unterschiedliche Typen von BI&A-gestützten Entscheidungsprozessen untersucht und die drei folgenden Beiträge gemacht. Erstens wird gezeigt, wie die Facetten von Big Data und verschiede Kompositionen von Mechanismen der Informationsverarbeitung in unterschiedlichen Typen von BI&A-gestützten Entscheidungsprozessen genutzt werden. Zweitens werden neue Erkenntnisse über organisatorische Mechanismen der Informationsverarbeitung und ihre komplementäre Beziehung zu datenzentrischen Mechanismen zur Theorie der Informationsverarbeitung beigetragen. Drittens wird demonstriert, wie die Theorie der Informationsverarbeitung angewendet werden kann, um die Dynamik der Komposition von Mechanismen der Informationsverarbeitung über verschiedene Entscheidungstypen hinweg zu bewerten. Abschließend werden die theoretischen und praktischen Implikationen der Studie diskutiert.〈/p〉
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  • 50
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  • 51
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  • 52
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  • 53
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  • 54
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  • 55
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    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Die starke Verbreitung von Angeboten, die Nachfrager in ihrem Alltag unterstützen, führt innerhalb der Forschung zu einer zunehmenden Auseinandersetzung mit den Nutzungsprozessen der Nachfrager. Eine theoretische Grundlage für diese Auseinandersetzung bietet die Service-Dominant Logic of Marketing. Sie geht davon aus, dass die eigentliche Nutzenentfaltung für einen Nachfrager nicht durch den bloßen Produktbesitz, sondern erst im Nutzungsprozess in Form von Value-in-Use entsteht. Bislang existiert jedoch keine allgemein anerkannte Methode, mit deren Hilfe sich Nutzungsprozesse erfassen und im Hinblick auf den Value-in-Use analysieren lassen. Im Beitrag wird daher eine Methode zur Erfassung des Value-in-Use vorgeschlagen. Hierzu wird auf die Repertory-Grid-Methode zurückgegriffen, welche gemäß den zugrundeliegenden theoretischen Annahmen adaptiert und im Rahmen einer qualitativen Studie zur Smartphone-Nutzung empirisch getestet wird. Die gewonnenen Erkenntnisse ermöglichten die Erarbeitung einer spezifischen Value-in-Use-Skala. Eine quantitative Studie validierte diese abschließend. Die adaptierte Repertory-Grid-Methode wird folglich als ein vielversprechender Ansatz zur Erfassung von Nutzungsprozessen und dem dabei entstehenden Value-in-Use betrachtet.〈/p〉
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  • 56
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  • 57
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    Publikationsdatum: 2014
    Beschreibung: 〈h3〉Zusammenfassung〈/h3〉 〈p〉Domänenspezifische Modellierungssprachen (engl.: “domain-specific modeling languages”, DSMLs) versprechen deutliche Vorteile gegenüber universellen Modellierungssprachen. Ihr Entwurf ist allerdings mit einer essentiellen Herausforderung verbunden. Um ansehnliche Skaleneffekte zu erreichen, empfiehlt sich die Entwicklung von DSMLs, die in einer größeren Nutzungsbandbreite einsetzbar sind. Gleichzeitig spricht der Gewinn an Modellierungsproduktivität im Einzelfall für Sprachkonzepte, die an individuelle Anforderungen angepasst sind. In dem vorliegenden Beitrag wird ein neuartiger Ansatz zur konzeptuellen Modellierung wie auch zur Konstruktion von Informationssystemen präsentiert, der durch die faktische Nutzung von Fachsprachen inspiriert ist – die Mehrebenen-Modellierung. Im Unterschied zu traditionellen Spracharchitekturen wie der „Meta Object Facility“ (MOF) basiert er auf einer rekursiven Architektur, die eine beliebige Zahl von Klassifikationsebenen ermöglicht und dadurch den Entwurf von Sprachhierarchien – von einer Referenz-DSML bis hin zu „lokalen“ DSMLs – erlaubt. Auf diese Weise wird nicht nur der essentielle Konflikt des Entwurfs von DSMLs deutlich entschärft, sondern auch die Wiederverwendung und Integration von Software-Komponenten im Allgemeinen gefördert. Zudem ermöglicht der Ansatz die Reduktion von Modellkomplexität, indem er die Dichotomie von Spezialisierung und Instanzierung teilweise aufhebt. Darüber hinaus integriert er eine Metamodellierungssprache mit dem Metamodell einer Metaprogrammiersprache, wodurch ausführbare Modelle ermöglicht werden. Die Spezifikation der Spracharchitektur wird ergänzt durch die Darstellung von Anwendungsszenarien, die die Potentiale der Mehrebenen-Modellierung verdeutlichen, sowie eine kritische Betrachtung ihrer Besonderheiten.〈/p〉
    Print ISSN: 0937-6429
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    Thema: Informatik , Wirtschaftswissenschaften
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  • 58
    Publikationsdatum: 2014
    Print ISSN: 0937-6429
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    Thema: Informatik , Wirtschaftswissenschaften
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  • 59
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    Publikationsdatum: 2014
    Print ISSN: 0937-6429
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    Thema: Informatik , Wirtschaftswissenschaften
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  • 60
    Publikationsdatum: 2014-12-06
    Beschreibung: Graphical Abstract
    Print ISSN: 1343-8875
    Digitale ISSN: 1875-8975
    Thema: Informatik
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  • 61
    Publikationsdatum: 2014-12-09
    Beschreibung: Learning to recognise objects and faces is an important and challenging problem tackled by the primate ventral visual system. One major difficulty lies in recognising an object despite profound differences in the retinal images it projects, due to changes in view, scale, position and other identity-preserving transformations. Several models of the ventral visual system have been successful in coping with these issues, but have typically been privileged by exposure to only one object at a time. In natural scenes, however, the challenges of object recognition are typically further compounded by the presence of several objects which should be perceived as distinct entities. In the present work, we explore one possible mechanism by which the visual system may overcome these two difficulties simultaneously, through segmenting unseen (artificial) stimuli using information about their category encoded in plastic lateral connections. We demonstrate that these experience-guided lateral interactions robustly organise input representations into perceptual cycles, allowing feed-forward connections trained with spike-timing-dependent plasticity to form independent, translation-invariant output representations. We present these simulations as a functional explanation for the role of plasticity in the lateral connectivity of visual cortex.
    Print ISSN: 0340-1200
    Digitale ISSN: 1432-0770
    Thema: Biologie , Informatik , Physik
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  • 62
    Publikationsdatum: 2014-12-09
    Beschreibung: In order to find patterns in data, it is often necessary to aggregate or summarise data at a higher level of granularity. Selecting the appropriate granularity is a challenging task and often no principled solutions exist. This problem is particularly relevant in analysis of data with sequential structure. We consider this problem for a specific type of data, namely event sequences. We introduce the problem of finding the best set of window lengths for analysis of event sequences for algorithms with real-valued output. We present suitable criteria for choosing one or multiple window lengths and show that these naturally translate into a computational optimisation problem. We show that the problem is NP-hard in general, but that it can be approximated efficiently and even analytically in certain cases. We give examples of tasks that demonstrate the applicability of the problem and present extensive experiments on both synthetic data and real data from several domains. We find that the method works well in practice, and that the optimal sets of window lengths themselves can provide new insight into the data.
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  • 63
    Publikationsdatum: 2014-12-09
    Beschreibung: In this paper, we present an algorithm for partitioning any given 2D domain into regions suitable for quadrilateral meshing. It is able to preserve the symmetry of the domain if any, and can deal with inner boundaries and multidomain geometries. Moreover, this method keeps the number of singularities at the junctions of the regions to a minimum. Although each part of the domain, being four-sided, can be easily meshed using a structured method, we provide a meshing process that guarantees near perfect quality for most quadrilaterals of the resulting mesh. The partitioning stage is achieved by solving a PDE-constrained equation based on the geometric properties of the domain boundaries. An analysis of the generated mesh quality is provided at the end, showcasing that the meshes obtained through our algorithm are especially suitable for finite element methods.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
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  • 64
    Publikationsdatum: 2014-12-09
    Beschreibung: Dynamic adaptive streaming over HTTP (DASH) has become a promising solution for video delivery services over the Internet in the last few years. Currently, several video content providers use the DASH solution to improve the users' quality of experience (QoE) by automatically switching video quality levels (VQLs) according to the network status. However, the frequency of switching events between different VQLs during a video streaming session may disturb the user's visual attention and therefore affect the user's QoE. As one of the first attempts to characterize the impact of VQL switching on the user's QoE, we carried out a series of subjective tests, which show that there is a correlation between the user QoE and the frequency, type, and temporal location of the switching events. We propose a novel parameter named switching degradation factor (SDF) to capture such correlation. A DASH algorithm with SDF parameter is compared with the same algorithm without SDF. The results demonstrate that the SDF parameter significantly improves the user's QoE, especially when network conditions vary frequently.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 65
    Publikationsdatum: 2014-12-09
    Beschreibung: The interaction between an expansion fan and a shock wave and the resulting flow field are of importance both from a research and an applied perspective. Interesting flow phenomena arise from this interaction which are significant in supersonic engine inlet design and aircraft store carriage and release. This paper focuses on the use of various schlieren techniques to experimentally visualize an expansion fan/shock wave interaction. The expansion fan was generated by a single wedge and the shock wave by another, at various Mach numbers. Three cut-off techniques were investigated: a knife edge, a tri-colour mask and a band lattice mask. Each of these cut-offs was placed in three orientations, parallel to the freestream flow direction, at −45° and perpendicular to the flow, to determine the effects of the directional sensitivity of the system. The different cut-off techniques and respective orientations were evaluated on the efficacy of visualizing flow features of interest, namely the expansion fan and deflection thereof, shock curvature and sliplines formed as a result of the interaction. Each technique produced visualization with varying degrees of clarity. There was a dependence on the system’s directional sensitivity when visualizing both the expansion fan deflection and the shock curvature. The visualization of the expansion fan/shock wave interaction using the band lattice mask parallel to the freestream was particularly effective as it showed all the features of interest (excepting the sliplines as these formed a region of varying entropy rather than occurring as discrete lines). Consequently, it was shown that schlieren is a valuable tool in the experimental visualization of an expansion fan/shock wave interaction. Graphical Abstract
    Print ISSN: 1343-8875
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    Thema: Informatik
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  • 66
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    Publikationsdatum: 2014-11-06
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 67
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    Springer
    Publikationsdatum: 2014-11-06
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 68
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    Publikationsdatum: 2014-11-06
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 69
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    Publikationsdatum: 2014-11-06
    Beschreibung: Alle Programme, die auf Computern und Mikrochips ausgeführt werden, auch Krypto- Algorithmen, beeinflussen physikalische Parameter der Hardware wie zum Beispiel den Stromverbrauch. Über solche sogenannten Seitenkanäle können Geheimnisse, die auf einem Chip verarbeitet werden, wie z. B. kryptographische Schlüssel, extrahiert werden. Um zu sicheren Implementierungen zu gelangen, muss dieser Angriffspfad berücksichtigt und entsprechende Gegenmaßnahmen während der Entwicklung getroffen werden.
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 70
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    Publikationsdatum: 2014-11-06
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 71
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    Publikationsdatum: 2014-11-06
    Beschreibung: Hardware-Sicherheitsmodule haben heute ihren festen Platz in der IT-Sicherheitsarchitektur. Immer mehr Anwendungen und Applikationen nutzen Hardware-Sicherheitsmodule und bieten entsprechende Schnittstellen. Der Beitrag gibt einen überblick über die Historie und grundsätzliche Entwicklung von Hardware-Sicherheitsmodulen und geht auf die Situation im Bereich der Applikation Interfaces (API) für HSM ein.
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 72
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    Publikationsdatum: 2014-11-06
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 73
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    Publikationsdatum: 2014-11-06
    Beschreibung: Auf den ersten Blick ist der Gerichtshof den Schlussanträgen des Generalanwaltes gefolgt und hat die Nichtigkeit der RL 2006/24/EG mangels Verhältnismäßigkeit festgestellt. Die genauere Analyse zeigt, dass er in seiner Begründung teilweise deutlich andere Nuancierungen vornimmt, welche über den Anlassfall hinaus hohe „Sprengkraft“ für die Ermittlungsmethoden der Strafverfolgungsbehörden bergen. Zudem stellt sich in dieser Form erstmals die Frage nach der praktischen Bedeutung der Rückwirkung der Nichtigerklärung.
    Digitale ISSN: 1862-2607
    Thema: Informatik , Rechtswissenschaft
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  • 74
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    Springer
    Publikationsdatum: 2014-11-23
    Beschreibung: This work evaluates the potential for producing quantitative data of the density field using a two-dimensional colour schlieren system within the test section of a shock tube. Density gradient components, magnitude and direction, form the basis of the quantitative evaluation. These are encoded onto an imaging plane by means of a colour-coded source mask placed along the optical axis of the schlieren system. Direction is indicated by the relative ratios of the three primary colours: red, green and blue (RGB). Magnitude is indicated by the relative intensities of the RGB values. Sensitivity of the system is adjusted by an iris diaphragm placed in the cutoff plane. The method described is applied to the focusing of a shock wave in a parabolic cavity. The experimental results of the schlieren technique are compared to computational simulations with synthetic two-dimensional colour and magnitude coding applied to the results. The source masks designed and used proved to require a greater intensity light source and thus the design of an LED light source was developed. The CFD solutions were converted into an image format directly comparable to the photographic images obtained. Image processing techniques have been employed to deconstruct photographs to allow for quantitative comparisons with a calibration lens. Density gradient direction has been conclusive; however, density gradient magnitude is not yet accurately determined due to light source constraints. Graphical Abstract
    Print ISSN: 1343-8875
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  • 75
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    Publikationsdatum: 2014-11-29
    Beschreibung: Stability issues in the electric power grid originate from the rising of renewable energy generation and the increasing number of electric vehicles. The uncertainty and the distributed nature of generation and consumption demand for optimal allocation of energy resources, which, in the absence of sufficient control reserve for power generation, can be achieved using demand-response. A price signal can be exploited to reflect the availability of energy. In this paper, market-based energy allocation solutions for small energy grids are discussed and implemented in a simulator, which is released for open use. Artificial neural network controllers for energy prosumers can be designed to minimize individual and overall running costs. This enables a better use of local energy production from renewable sources, while considering residents’ necessities to minimize discomfort.
    Print ISSN: 1865-2034
    Digitale ISSN: 1865-2042
    Thema: Informatik
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  • 76
    Publikationsdatum: 2014-11-29
    Beschreibung: XML has become the standard document representation for many popular tools in various domains. When multiple authors collaborate to produce a document, they must be able to work in parallel and periodically merge their efforts into a single work. While there exist a small number of three-way XML merging tools, their performance could be improved in several areas. We present a three-way XML merge algorithm that is faster, uses less memory and is more precise than previous algorithms. It uses a specialized versioning tree data structure that supports node identity and change detection. The algorithm applies the traditional three-way merge found in GNU diff3 to the children of changed nodes. The editing operations it supports are addition, deletion, update, and move. The algorithm is evaluated by comparing its performance to that of the previous algorithms, using synthetically generated XML documents of a range of sizes and modified by varying numbers of random editing operations. The prototype merge tool used in these tests also includes a simple graphical interface for visualizing and resolving conflicts.
    Print ISSN: 1865-2034
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    Thema: Informatik
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  • 77
    Publikationsdatum: 2014-11-29
    Beschreibung: This paper describes a method for taking the forecasting uncertainty into account when assessing the impact of volatile generation on power grids. To this end the generation of feed-in scenarios for generation plants that include the uncertainty of the weather forecast is described. With a three-step model that firstly forecasts local weather parameters and, secondly, generates scenarios for these parameters, thirdly, a reduced number of resulting feed-in profile scenarios for each plant is computed. With these scenarios the assessment of the grid-impact of the plants can be calculated taking into account the uncertainty of the prognosis. In a case study, feed-in profiles for the plants in an exemplary region are generated which can be used for an assessment of the grid impact in this region using probabilistic load flow calculation.
    Print ISSN: 1865-2034
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    Thema: Informatik
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  • 78
    Publikationsdatum: 2014-11-29
    Beschreibung: Electric vehicle charging is considered as a prime case of load flexibility in future smart grids. We examine a scenario where electric vehicles are charged in a car park with local photovoltaic (PV) generation. In this setting, temporal charging flexibility can be leveraged to increase utilization of local generation. To incentivize flexible loads we apply a deadline differentiated pricing scheme. Prices are set by the car park operator in a profit-maximizing manner in settings with varying PV capacity and costs of conventional generation. This allows us to assess the value of flexibility passed on to customers in form of discounts. Furthermore, we determine the minimum flexibility level qualifying for this discount. By and large, absolute price levels and flexibility discounts are mainly driven by the cost of conventional generation. On the other hand, the minimum flexibility requirements are affected by both the costs of conventional generation as well as the local PV capacity: higher costs of conventional generation as well as larger PV capacities will decrease this threshold.
    Print ISSN: 1865-2034
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    Thema: Informatik
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  • 79
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    Publikationsdatum: 2014-11-29
    Beschreibung: The data storage paradigm has changed in the last decade, from operational databases to data repositories that make easier to analyze data and mining information. Among those, the primary multidimensional model represents data through star schemas, where each relation denotes an event involving a set of dimensions or business perspectives. Mining data modeled as a star schema presents two major challenges, namely: mining extremely large amounts of data and dealing with several data tables at the same time. In this paper, we describe an algorithm— Star FP Stream , in detail. This algorithm aims for finding the set of frequent patterns in a large star schema, mining directly the data, in their original structure, and exploring the most efficient techniques for mining data streams. Experiments were conducted over two star schemas, in the healthcare and sales domains.
    Print ISSN: 1384-5810
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  • 80
    Publikationsdatum: 2014-11-29
    Beschreibung: Evaluation of land cover/use change and its impact on hydrological design aspects plays a vital role in assessing the capacity of existing storm water conveyance systems and its capability towards the anticipated peak flow. This paper attempts to illustrate an application of Soil Conservation Service (SCS-CN) method for runoff estimation using continuous time series rainfall. And also, the present work proposes a Land use factor based on the Curve Number to correct the infiltration rate according to the prevailing land cover/use. Indian remote sensing (IRS) satellite data for the years 1989, 1992, 1995, 1998, 2001, 2004, 2007, and 2010 are used to evaluate the growth of Tiruchirapalli city, India city and to assess its impact on surface runoff. The Geographical information system (GIS) is used to prepare the different layers belonging to various land covers identified from remotely sensed data. The sub-watersheds are created using Digital Elevation Model (DEM) prepared by ARC GIS software. The single storm event and 50-year return period rainfall data are used as a hydrological input to the model to evaluate the increase in runoff over the years due to change in the land cover of the study area. The study reveals that the impact of land cover/use change is more significant for longer duration storm than short duration storm at the same magnitude. Further, it is noticed from the study that the runoff depth and runoff co-efficient is large for short duration rainfall than long duration rainfall at the same magnitude.
    Print ISSN: 1865-0473
    Digitale ISSN: 1865-0481
    Thema: Geologie und Paläontologie , Informatik
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  • 81
    Publikationsdatum: 2014-11-29
    Beschreibung: To use data proficiently and efficiently, scientists require comprehensive metadata. This is very difficult to reconstruct conceptually, positionally and temporally far from the time and place of data acquisition. The European Commission funded Eurofleets project, whose mission is to build an integrated European oceanographic research vessel fleet, is developing a system that aims to address this issue by capturing metadata in a uniform way at time of observation. As this is a European-wide initiative, the problems associated with the desired level of integration are also broad. Having so many partners, different paradigms, schools, practices and vocabularies must be taken into consideration. Assuming that this divergence is natural and even somehow positive in the perspective of adapting to a changing environment, we detail how bridging can take place using a systemic approach. In the Eurofleets experience, this relied on the definition of a boundary object: that is an artifact that can be used by each of the diverging communities, since it embeds the core, shared conceptual entities. The structure of the boundary object is based on an event model, its ontology and the controlled vocabularies linked to it. All conceptual entities, and indeed the structure of the boundary object itself, resulted from wide discussions among the divergent communities. These discussions, allowed the extension of meaning from a semantic perspective to the pragmatic scope, where theoretical and cultural matters can also be considered, so that, eventually, the knowledge represented by the boundary object is more likely to be understood across the divergent communities. To exploit the possibilities offered by the boundary object, specific software has been developed that, using the event model and ontology, allows easier deployment across the project partners of a system intended to address the heterogeneity of the research vessel fleet. In this paper we describe in detail the underlying ontology.
    Print ISSN: 1865-0473
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    Thema: Geologie und Paläontologie , Informatik
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  • 82
    Publikationsdatum: 2014-11-29
    Beschreibung: With the development of mobile internet, protecting location privacy has already been an importantissue. Based on previous studies and the drawback of traditional algorithms, the paper proposes anovel algorithm for protecting location privacy. The algorithm is based on the voronoi map of aroad network, considers the problem of side-weight inference, and utilizes the information entropy asmetrics. Meanwhile, the algorithm can defense the attack of side-weight inference and replay. Lastly,we verified the algorithm based on the real data of the road network. Results of experiences show thatthe improved algorithm has the better performance on some key performance metrics.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 83
    Publikationsdatum: 2014-11-29
    Beschreibung: In this paper, we propose a model for mobile application profiles, wireless interfaces, and cloud resources. First, an algorithm to allocate wireless interfaces and cloud resources has been introduced. The proposed model is based on the wireless network cloud (WNC) concept. Then, considering power consumption, application quality of service (QoS) profiles, and corresponding cost functions, a multi-objective optimization approach using an event-based finite state model and dynamic constraint programming method has been used to determine the appropriate transmission power, process power, cloud offloading and optimum QoS profiles. Numerical results show that the proposed algorithm saves the mobile battery life and guarantees both QoS and cost simultaneously. Moreover, it determines the best available cloud server resources and wireless interfaces for applications at the same time.
    Print ISSN: 1687-1472
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 84
    Publikationsdatum: 2014-12-01
    Beschreibung: Combining ontologies in expressive fragments of Description Logics in inherently distributed peer-to-peer settings with autonomous peers is still a challenge in the general case. Although several modular ontology representation frameworks have been proposed for combining Description Logics knowledge bases, each of them has its own strengths and limitations. In this paper, we consider networks of peers, where each peer holds its own ontology within the \({\mathcal {SHIQ}}\) fragment of Description Logics, and subjective beliefs on how its knowledge can be coupled with the knowledge of others. To allow peers to reason jointly with their coupled knowledge, while preserving their autonomy on evolving their knowledge, data, and subjective beliefs, we propose the \(E\text {-}{\mathcal {SHIQ}}\) representation framework. The article motivates the need for \(E\text {-}{\mathcal {SHIQ}}\) and compares it to existing representation frameworks for modular Description Logics. It discusses the implementation of the \(E\text {-}{\mathcal {SHIQ}}\) distributed reasoner and presents experimental results on the efficiency of this reasoner.
    Print ISSN: 0219-1377
    Digitale ISSN: 0219-3116
    Thema: Informatik
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  • 85
    Publikationsdatum: 2014-12-02
    Beschreibung: In this paper, we present a new queueing model providing the accurate average system time forpackets transmitted over a cognitive radio (CR) link for multiple traffic classes with the preemptiveand non-preemptive priority service disciplines. The analysis considers general packet service time,general distributions for the channel availability periods and service interruption periods, and aservice-resume transmission. We further introduce and analyze two novel priority service disciplinesfor opportunistic spectrum access (OSA) networks which take advantage of interruptions to preemptlow priority traffic at a low cost. Analytical results, in addition to simulation results to validate theiraccuracy, are also provided and used to illustrate the impact of different OSA network parameters onthe average system time. We particularly show that, for the same average CR transmission linkavailability, the packet system time significantly increases in a semi-static network with longoperating and interruption periods compared to an OSA network with fast alternating operating andinterruption periods. We also present results indicating that, due to the presence of interruptions,priority queueing service disciplines provide a greater differentiated service in OSA networks than intraditional networks. The analytical tools presented in this paper are general and can be used toanalyze the traffic metrics of most OSA networks carrying multiple classes of traffic with priorityqueueing service differentiation.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 86
    Publikationsdatum: 2014-12-03
    Beschreibung: In einem bestehenden Mittelspannungsnetz wurde als Pilotprojekt ein neues Erdschlussortungs-System nach dem KNOPE-Verfahren ( K urzzeitige N ieder- O hmige P hasen- E rdung) eingeführt, ohne dabei die Sternpunktbehandlung zu ändern und ohne Änderungen im Netz vornehmen zu müssen. Lediglich ein Mittelspannungsabgang im Umspannwerk wird neben dem Strombegrenzungswiderstand für das KNOPE-System benötigt. Nach vorbereitenden Erdungsmessungen und Laborversuchen mit den realen Schutzrelais erfolgten Versuche mit einem kleinen Testnetz mit isoliertem Sternpunkt und anschließend im realen Netz. Die Labor- und Netzversuche deckten sich vollständig mit den modellbasierten Erwartungen. Kurz nach der Aktivierung der Einrichtung kam es zu einem realen Fehler, welcher ebenfalls konzeptgemäß und vollständig zufriedenstellend ablief.
    Print ISSN: 0932-383X
    Digitale ISSN: 1613-7620
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 87
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    Springer
    Publikationsdatum: 2014-12-04
    Beschreibung: The order- \(k\) Voronoi diagram of line segments has properties surprisingly different from its counterpart for points. For example, a single order- \(k\) Voronoi region may consist of \(\varOmega (n)\) disjoint faces. In this paper, we analyze the structural properties of this diagram and show that its combinatorial complexity is \(O(k(n-k))\) , for \(n\) non-crossing line segments, despite the presence of disconnected regions. The same bound holds for \(n\) intersecting line segments, for \(k\ge n/2\) . We also consider the order- \(k\) Voronoi diagram of line segments that form a planar straight-line graph, and augment the definition of an order- \(k\) diagram to cover sites that are not disjoint. On the algorithmic side, we extend the iterative approach to construct this diagram, handling complications caused by the presence of disconnected regions. All bounds are valid in the general \(L_p\) metric, \(1\le p\le \infty \) . For non-crossing segments in the \(L_\infty \) and \(L_1\) metrics, we show a tighter \(O((n-k)^2)\) bound for \(k〉n/2\) .
    Print ISSN: 0178-4617
    Digitale ISSN: 1432-0541
    Thema: Informatik , Mathematik
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  • 88
    Publikationsdatum: 2014-12-05
    Beschreibung: Multiuser cooperative communication significantly improves the performance of wireless communication networks. One key challenge of multiuser cooperative communication is how to design a cooperative mechanism to incentivize potential relay nodes to help a source node in its data transmission. In this paper, to address this problem, a contract-based principal-agent framework is proposed in the context of a cognitive-radio-based wireless relaying networks in which the sources' wireless characteristics constitute hidden information which is not known by the relay. The problem is modeled as a monopolist's problem, in which a mobile relay node acts as the principal who designs incentive-compatible (IC) and individually rational (IR) contract items, consisting of a set of rate-price pairs. Subsequently, contract items can be broadcast by the relay to nearby mobile users that want to send data. Once these sources optimally select an item and notify the relay that they are willing to accept it, the relay then chooses one source based on the highest revenue for which to provide service. The cooperative gain, relay's revenue, and expected data rate are characterized for the optimal contract under complete information and incomplete information. Theoretical analysis and numerical results show that this pricing mechanism can lead to a win-win situation in which source nodes get good communication service and relay nodes maximize their own profit that can, in turn, be used to purchase the relay service of other nodes when needed in the future. Moreover, the proposed mechanism is shown to also exhibit other important features such as low complexity and low signaling overhead.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 89
    Publikationsdatum: 2014-12-06
    Beschreibung: Due to renewable energies, the feed-in to the power grid will fluctuate increasingly. As long as no highly efficient storage technology is found, the importance of demand side management (DSM) will grow. Different algorithms have been proposed for managing the consumers. However, they cannot be easily compared due to a lot of different assumptions while generating the consumption curves and pursuing different goals in each DSM-algorithm. This paper describes a method to transparently generate a data-basis as input for the DSM-algorithms to produce comparable results. A number of quality-functions (Q-functions) are mathematically described and discussed. The Q-Functions allow a consistent evaluation of DSM-algorithms by analysing managed and unmanaged (original) consumption curves.
    Print ISSN: 1865-2034
    Digitale ISSN: 1865-2042
    Thema: Informatik
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  • 90
    Publikationsdatum: 2014-01-12
    Beschreibung: Location-based social networks (LBSNs) have attracted an increasing number of users in recent years, resulting in large amounts of geographical and social data. Such LBSN data provide an unprecedented opportunity to study the human movement from their socio-spatial behavior, in order to improve location-based applications like location recommendation. As users can check-in at new places, traditional work on location prediction that relies on mining a user’s historical moving trajectories fails as it is not designed for the cold-start problem of recommending new check-ins. While previous work on LBSNs attempting to utilize a user’s social connections for location recommendation observed limited help from social network information. In this work, we propose to address the cold-start location recommendation problem by capturing the correlations between social networks and geographical distance on LBSNs with a geo-social correlation model. The experimental results on a real-world LBSN dataset demonstrate that our approach properly models the geo-social correlations of a user’s cold-start check-ins and significantly improves the location recommendation performance.
    Print ISSN: 1384-5810
    Digitale ISSN: 1573-756X
    Thema: Informatik
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  • 91
    facet.materialart.
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    Springer
    Publikationsdatum: 2014-01-12
    Beschreibung: In this research we present a novel approach to the concept change detection problem. Change detection is a fundamental issue with data stream mining as classification models generated need to be updated when significant changes in the underlying data distribution occur. A number of change detection approaches have been proposed but they all suffer from limitations with respect to one or more key performance factors such as high computational complexity, poor sensitivity to gradual change, or the opposite problem of high false positive rate. Our approach uses reservoir sampling to build a sequential change detection model that offers statistically sound guarantees on false positive and false negative rates but has much smaller computational complexity than the ADWIN concept drift detector. Extensive experimentation on a wide variety of datasets reveals that the scheme also has a smaller false detection rate while maintaining a competitive true detection rate to ADWIN.
    Print ISSN: 0885-6125
    Digitale ISSN: 1573-0565
    Thema: Informatik
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  • 92
    Publikationsdatum: 2014-01-16
    Beschreibung: The paper presents a method for constructing space-time block codes for multiple-input multipleoutputchannels by concatenating orthogonal designs with the so-called diversity transform. Relyingon unitary transforms, the diversity transform increases the channel alphabet without sacrificing informationrate, bandwidth, or Euclidean distance. The distribution of the resulting channel alphabetis shown to quickly become Gaussian-like. Specific code matrices are constructed and optimizedbased on the cutoff rate. Both optimum and, reduced-complexity, suboptimum detection algorithmsare presented. Simulation results are provided for demonstrating the gains attainable when using theproposed codes.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 93
    Publikationsdatum: 2014-01-16
    Beschreibung: Digital image splicing blind detection is becoming a new and important subject in information security area. Among various approaches in extracting splicing clues, Markov state transition probability feature based on transform domain (discrete cosine transform or discrete wavelet transform) seems to be most promising in the state of the arts. However, the up-to-date extraction method of Markov features has some disadvantages in not exploiting the information of transformed coefficients thoroughly. In this paper, an enhanced approach of Markov state selection is proposed, which matches coefficients to Markov states base on well-performed function model. Experiments and analysis show that the improved Markov model can employ more useful underlying information in transformed coefficients and can achieve a higher recognition rate as results.
    Print ISSN: 1687-1472
    Digitale ISSN: 1687-1499
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Informatik
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  • 94
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    Springer
    Publikationsdatum: 2014-01-16
    Beschreibung: Several methods to incorporate semantic awareness in genetic programming have been proposed in the last few years. These methods cover fundamental parts of the evolutionary process: from the population initialization, through different ways of modifying or extending the existing genetic operators, to formal methods, until the definition of completely new genetic operators. The objectives are also distinct: from the maintenance of semantic diversity to the study of semantic locality; from the use of semantics for constructing solutions which obey certain constraints to the exploitation of the geometry of the semantic topological space aimed at defining easy-to-search fitness landscapes. All these approaches have shown, in different ways and amounts, that incorporating semantic awareness may help improving the power of genetic programming. This survey analyzes and discusses the state of the art in the field, organizing the existing methods into different categories. It restricts itself to studies where semantics is intended as the set of output values of a program on the training data, a definition that is common to a rather large set of recent contributions. It does not discuss methods for incorporating semantic information into grammar-based genetic programming or approaches based on formal methods. The objective is keeping the community updated on this interesting research track, hoping to motivate new and stimulating contributions.
    Print ISSN: 1389-2576
    Digitale ISSN: 1573-7632
    Thema: Informatik
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  • 95
    Publikationsdatum: 2014-01-17
    Beschreibung: In dem Artikel skizzieren wir einige der Herausforderungen, die in zukünftigen Forschungsaktivitäten für eine modellbasierte Entscheidungsunterstützung in Produktions- und Dienstleistungsnetzwerken zu adressieren sind. Das beinhaltet die Betrachtung von Integrationsaspekten, insbesondere auch unter Berücksichtigung der Autonomie von Entscheidungsträgern und Informationsasymmetrie, die Modellierung von Präferenzen der Entscheider, die effiziente Ermittlung robuster Lösungen, d. h. Lösungen, die unempfindlich bezüglich Änderungen in den Problemdaten sind, und eine Verkürzung der Zeit zur Modellerstellung und -nutzung. Der Problemlösungszyklus umfasst eine Problemanalyse, den Entwurf geeigneter Algorithmen sowie deren Leistungsbewertung. Wir sind an einer prototypischen Integration der vorgeschlagenen Methoden in Anwendungssysteme interessiert. Daran anschließend können Feldtests mit den so erweiterten Anwendungssystemen durchgeführt werden. Die vorgeschlagene Forschungsagenda erfordert eine interdisziplinäre Zusammenarbeit von Wirtschaftsinformatikern mit Kollegen aus der Betriebswirtschaftslehre, der Informatik und dem Operations Research. Außerdem werden exemplarisch einige Beispiele für relevante Forschungsergebnisse vorgestellt.
    Print ISSN: 0937-6429
    Digitale ISSN: 1861-8936
    Thema: Informatik , Wirtschaftswissenschaften
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  • 96
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    Springer
    Publikationsdatum: 2014-01-18
    Beschreibung: We study three complexity parameters that, for each vertex v , are an upper bound for the number of cliques that are sufficient to cover a subset S ( v ) of its neighbors. We call a graph k-perfectly groupable if S ( v ) consists of all neighbors, k-simplicial if S ( v ) consists of the neighbors with a higher number after assigning distinct numbers to all vertices, and k-perfectly orientable if S ( v ) consists of the endpoints of all outgoing edges from v for an orientation of all edges. These parameters measure in some sense how chordal-like a graph is—the last parameter was not previously considered in literature. The similarity to chordal graphs is used to construct simple polynomial-time approximation algorithms with constant approximation ratio for many NP-hard problems, when restricted to graphs for which at least one of the three complexity parameters is bounded by a constant. As applications we present approximation algorithms with constant approximation ratio for maximum weighted independent set, minimum (independent) dominating set, minimum vertex coloring, maximum weighted clique, and minimum clique partition for large classes of intersection graphs.
    Print ISSN: 0178-4617
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    Thema: Informatik , Mathematik
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  • 97
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    Springer
    Publikationsdatum: 2014-01-18
    Beschreibung: We present a data structure for maintaining the geodesic hull of a set of points ( site s) in the presence of pairwise noncrossing line segments ( barrier s) that subdivide a bounding box into simply connected faces. For m barriers and n sites, our data structure has O (( m + n )log n ) size. It supports a mixed sequence of O ( m ) barrier insertions and O ( n ) site deletions in $O((m+n) \operatorname{polylog}(mn))$ total time, and answers analogues of standard convex hull queries in $O(\operatorname{polylog}(mn))$ time. Our data structure supports a generalization of the sweep line technique, in which the sweep wavefront is a simple closed polygonal curve, and it sweeps a set of n points in the plane by simple moves . We reduce the total time of supporting m online moves of a polygonal wavefront sweep algorithm from the naïve $O(m\sqrt{n} \operatorname{polylog}n)$ to $O((m+n) \operatorname{polylog}(mn))$ .
    Print ISSN: 0178-4617
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    Thema: Informatik , Mathematik
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  • 98
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    Springer
    Publikationsdatum: 2014-01-18
    Beschreibung: We investigate the computational complexity of the empire colouring problem (as defined by Percy Heawood in Q. J. Pure Appl. Math. 24:332–338, 1890 ) for maps containing empires formed by exactly r 〉1 countries each. We prove that the problem can be solved in polynomial time using s colours on maps whose underlying adjacency graph has no induced subgraph of average degree larger than s / r . However, if s ≥3, the problem is NP-hard even if the graph is a for forests of paths of arbitrary lengths (for any r ≥2, provided $s 〈 2r - \sqrt{2r + \frac{1}{4}}+ \frac{3}{2}$ ). Furthermore we obtain a complete characterization of the problem’s complexity for the case when the input graph is a tree, whereas our result for arbitrary planar graphs fall just short of a similar dichotomy. Specifically, we prove that the empire colouring problem is NP-hard for trees, for any r ≥2, if 3≤ s ≤2 r −1 (and polynomial time solvable otherwise). For arbitrary planar graphs we prove NP-hardness if s 〈7 for r =2, and s 〈6 r −3, for r ≥3. The result for planar graphs also proves the NP-hardness of colouring with less than 7 colours graphs of thickness two and less than 6 r −3 colours graphs of thickness r ≥3.
    Print ISSN: 0178-4617
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    Thema: Informatik , Mathematik
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  • 99
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    Unbekannt
    Springer
    Publikationsdatum: 2014-01-18
    Beschreibung: Inspired by the CONFIDANT protocol (Buchegger and Boudec in Proceedings of the 3rd ACM International Symposium on Mobile Ad Hoc Networking & Computing, pp. 226–236, 2002), we define and study a basic reputation-based protocol in multihop wireless networks with selfish nodes. Its reputation mechanism is implemented through the ability of any node to define a threshold of tolerance for any of its neighbors, and to cut the connection to any of these neighbors that refuse to forward an amount of flow above that threshold. The main question we would like to address is whether one can set the initial conditions so that the system reaches an equilibrium state where a non-zero amount of every commodity is routed. This is important in emergency situations, where all nodes need to be able to communicate even with a small bandwidth. Following a standard approach, we model this protocol as a game, and we give necessary and sufficient conditions for the existence of non-trivial Nash equilibria. Then we enhance these conditions with extra conditions that give a set of necessary and sufficient conditions for the existence of connected Nash equilibria. We note that it is not always necessary for all the flow originating at a node to reach its destination at equilibrium. For example, a node may be using unsuccessful flow in order to effect changes in a distant part of the network that will prove quite beneficial to it. We show that we can decide in polynomial time whether there exists a (connected) equilibrium without unsuccessful flows. In that case we calculate (in polynomial time) initial values that impose such an equilibrium on the network. On the negative side, we prove that it is NP-hard to decide whether a connected equilibrium exists in general (i.e., with some nodes using unsuccessful flows at equilibrium).
    Print ISSN: 0178-4617
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    Thema: Informatik , Mathematik
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  • 100
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    Springer
    Publikationsdatum: 2014-01-18
    Beschreibung: In this paper we investigate dynamic speed scaling, a technique to reduce energy consumption in variable-speed microprocessors. While prior research has focused mostly on single processor environments, in this paper we investigate multiprocessor settings. We study the basic problem of scheduling a set of jobs, each specified by a release date, a deadline and a processing volume, on variable-speed processors so as to minimize the total energy consumption. We first settle the problem complexity if unit size jobs have to be scheduled. More specifically, we devise a polynomial time algorithm for jobs with agreeable deadlines and prove NP-hardness results if jobs have arbitrary deadlines. For the latter setting we also develop a polynomial time algorithm achieving a constant factor approximation guarantee. Additionally, we study problem settings where jobs have arbitrary processing requirements and, again, develop constant factor approximation algorithms. We finally transform our offline algorithms into constant competitive online strategies.
    Print ISSN: 0178-4617
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    Thema: Informatik , Mathematik
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