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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Top-k Differential Queries in Graph Databases

Vasilyeva, Elena, Thiele, Maik, Bornhövd, Christof, Lehner, Wolfgang 03 February 2023 (has links)
The sheer volume as well as the schema complexity of today’s graph databases impede the users in formulating queries against these databases and often cause queries to “fail” by delivering empty answers. To support users in such situations, the concept of differential queries can be used to bridge the gap between an unexpected result (e.g. an empty result set) and the query intention of users. These queries deliver missing parts of a query graph and, therefore, work with such scenarios that require users to specify a query graph. Based on the discovered information about a missing query subgraph, users may understand which vertices and edges are the reasons for queries that unexpectedly return empty answers, and thus can reformulate the queries if needed. A study showed that the result sets of differential queries are often too large to be manually introspected by users and thus a reduction of the number of results and their ranking is required. To address these issues, we extend the concept of differential queries and introduce top-k differential queries that calculate the ranking based on users’ preferences and therefore significantly support the users’ understanding of query database management systems. The idea consists of assigning relevance weights to vertices or edges of a query graph by users that steer the graph search and are used in the scoring function for top-k differential results. Along with the novel concept of the top-k differential queries, we further propose a strategy for propagating relevance weights and we model the search along the most relevant paths.
232

Search for heavy Higgs bosons A/H decaying to a top-quark pair in pp collisions at \sqrt(s)=8 TeV with the ATLAS detector

Stănescu-Bellu, Mădălina 30 April 2021 (has links)
In dieser Dissertation wird die Suche nach schweren neutralen pseudoskalaren A und skalaren H Higgs-Bosonen vorgestellt, die in gg-Fusionen erzeugt werden, und in ein Top-Antitop-Quark-Paar zerfallen. Gesucht wurde im vollständigen Datensatz von Proton–Proton-Kollisionen bei einer Schwerpunktsenergie von 8 TeV die vom ATLAS-Detektor am Large Hadron Collider aufgezeichnet wurde und einer integrierten Luminosität von 20.3 fb−1 entspricht. Der Signalprozess und der Haupthintergrund aus der Top-Quark-Paar-Produktion über starke gg-Fusionen-Prozesse, interferieren heftig, was zu einer Verzerrung des reinen Breit-Wigner-Resonanzpeak in eine Peak-Dip-Struktur führt. Diese Analyse ist die erste am LHC, die die Interferenz zwischen Signal und Hintergrundprozessen vollständig berücksichtigt. Die Suche stützt sich auf die statistische Analyse des invarianten Top-Quark-Paar-Massenspektrum, welches aus Ereignissen mit einem Elektron oder Myon mit hohem Transversalimpuls, einer hohen fehlenden Transversalenergie von dem nicht detektierten Neutrino und mindestens vier Jets rekonstruiert wird. In den Daten wird keine signifikante Abweichung vom erwarteten Standardmodell-Hintergrund beobachtet. Die Ausschließungsgrenzen wurden abgeleitet im Kontext des Typ II Two-Higgs-Doublet Model, für Higgs-Bosonen mit einer Masse von 500 und 750 GeV und mit niedrigerem tan(\beta)-Parameter, bei der tan(\beta) das Verhältnis der Vakuumerwartungswerte der beiden Higgs-Dublett-Felder ist. Diese Parameterregionen sind weitgehend unerforscht in Untersuchungen von beliebigen Endzuständen. / In this thesis a search is presented for heavy neutral pseudoscalar A and scalar H Higgs bosons, produced in gg fusion and decaying into a top-antitop quark pair. The search is conducted on the full proton-proton collisions dataset recorded by the ATLAS detector at the Large Hadron Collider at a centre-of-mass collision energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb−1. The signal process and the main background from top quark pair production via the gg fusion strong process, interfere heavily, distorting the signal shape from the pure Breit-Wigner resonance peak to a peak-dip structure. This analysis is the first one at the LHC that fully takes into account the interference between a signal and the background processes. The search relies on the statistical analysis of the top quark pair invariant mass spectrum, which is reconstructed in signal candidate events with a high-transverse momentum electron or muon, large missing transverse energy from the undetected neutrino and at least four jets. No significant deviation from the expected SM background is observed in data. Exclusion limits are derived in the context of the type-II Two-Higgs-Doublet Model, for Higgs boson masses of 500 and 750 GeV and in the low tan(\beta) parameter region, where tan(\beta) is the ratio of the vacuum expectation values of the two Higgs doublet fields. These parameter regions have been largely unexplored by searches in any final state.
233

Calibration des algorithmes d'identification des jets issus de quarks b et mesure de la section efficace différentielle de production de paires de quarks top-antitop en fonction de la masse et de la rapidité du système top-antitopdans les collisions p-p à une énergie au centre de masse de 7 TeV auprès de l'expérience ATLAS au LHC.

Tannoury, N. 09 October 2012 (has links) (PDF)
ATLAS, LHC, quark b, quark top, étiquetage des jets issus de quark b, calibration des algorithmes d'étiquetage des jets issus de quark b, quarks top-antitop, section efficace, section efficace différentielle des paires top-antitop, masse du top, rapidité du top, nouvelle physique.
234

Challenges encountered by women who requested termination of pregnancy services in the North West Province of South Africa

Mokgethi, Nomathemba Emily Blaai 08 1900 (has links)
In 1996 the South African government legalised the termination of pregnancy (TOP) services, allowing women to choose to terminate unplanned pregnancies at designated facilities. Although TOP services are available, pregnant women continue to use illegal abortion services, with potentially life-risking consequences. The purpose of this study was to identify challenges encountered by women requesting TOP services, and to make recommendations for improved policies and practices, enabling more women in the North West Province (NWP) to access TOP services. This was a non-experimental, exploratory, descriptive and quantitative study. Structured interviews were conducted with 150 women who had used TOP services in phase 1, with 50 women who were unable to access TOP services in phase 2 and with 20 professional nurses providing TOP services in the NWP in phase 3. In phase 1, 96.0% (n=144) of the women needed transport to access TOP services, and 73.2% (n=109) indicated that nurses put women’s names on waiting lists, posing barriers to such access in the NWP. In phase 2, 92.0% (n=46) of these respondents had reportedly requested TOPs for the first time, but 89.0% (n=44) could not access TOP services. In phase 3, only 14 out of 19 designated facilities in the NWP, and only 20 nurses, provided TOP services during the study period. Out of the 20 interviewed nurses, 74.0% (n=14) regarded the Choice on Termination of Pregnancy Act, Act 92 of 1996 (CTOP Act) was being unclear requiring a revision. These professional nurses provided TOP services in NWP, by choice. Unless more facilities and more nurses can provide TOP services to the women of the NWP, these services will continue to remain inaccessible, necessitating the continued utilisation of illegal abortion services, in spite of the TOP Act’s prescriptions. It is also recommended that management will provide sufficient support and training opportunities for professional nurses working in TOP services in the NWP. / Health Studies / (D. Litt. et Phil. (Health Studies))
235

Datenzentrierte Bestimmung von Assoziationsregeln in parallelen Datenbankarchitekturen

Legler, Thomas 15 August 2009 (has links) (PDF)
Die folgende Arbeit befasst sich mit der Alltagstauglichkeit moderner Massendatenverarbeitung, insbesondere mit dem Problem der Assoziationsregelanalyse. Vorhandene Datenmengen wachsen stark an, aber deren Auswertung ist für ungeübte Anwender schwierig. Daher verzichten Unternehmen auf Informationen, welche prinzipiell vorhanden sind. Assoziationsregeln zeigen in diesen Daten Abhängigkeiten zwischen den Elementen eines Datenbestandes, beispielsweise zwischen verkauften Produkten. Diese Regeln können mit Interessantheitsmaßen versehen werden, welche dem Anwender das Erkennen wichtiger Zusammenhänge ermöglichen. Es werden Ansätze gezeigt, dem Nutzer die Auswertung der Daten zu erleichtern. Das betrifft sowohl die robuste Arbeitsweise der Verfahren als auch die einfache Auswertung der Regeln. Die vorgestellten Algorithmen passen sich dabei an die zu verarbeitenden Daten an, was sie von anderen Verfahren unterscheidet. Assoziationsregelsuchen benötigen die Extraktion häufiger Kombinationen (EHK). Hierfür werden Möglichkeiten gezeigt, Lösungsansätze auf die Eigenschaften moderne System anzupassen. Als Ansatz werden Verfahren zur Berechnung der häufigsten $N$ Kombinationen erläutert, welche anders als bekannte Ansätze leicht konfigurierbar sind. Moderne Systeme rechnen zudem oft verteilt. Diese Rechnerverbünde können große Datenmengen parallel verarbeiten, benötigen jedoch die Vereinigung lokaler Ergebnisse. Für verteilte Top-N-EHK auf realistischen Partitionierungen werden hierfür Ansätze mit verschiedenen Eigenschaften präsentiert. Aus den häufigen Kombinationen werden Assoziationsregeln gebildet, deren Aufbereitung ebenfalls einfach durchführbar sein soll. In der Literatur wurden viele Maße vorgestellt. Je nach den Anforderungen entsprechen sie je einer subjektiven Bewertung, allerdings nicht zwingend der des Anwenders. Hierfür wird untersucht, wie mehrere Interessantheitsmaßen zu einem globalen Maß vereinigt werden können. Dies findet Regeln, welche mehrfach wichtig erschienen. Der Nutzer kann mit den Vorschlägen sein Suchziel eingrenzen. Ein zweiter Ansatz gruppiert Regeln. Dies erfolgt über die Häufigkeiten der Regelelemente, welche die Grundlage von Interessantheitsmaßen bilden. Die Regeln einer solchen Gruppe sind daher bezüglich vieler Interessantheitsmaßen ähnlich und können gemeinsam ausgewertet werden. Dies reduziert den manuellen Aufwand des Nutzers. Diese Arbeit zeigt Möglichkeiten, Assoziationsregelsuchen auf einen breiten Benutzerkreis zu erweitern und neue Anwender zu erreichen. Die Assoziationsregelsuche wird dabei derart vereinfacht, dass sie statt als Spezialanwendung als leicht nutzbares Werkzeug zur Datenanalyse verwendet werden kann. / The importance of data mining is widely acknowledged today. Mining for association rules and frequent patterns is a central activity in data mining. Three main strategies are available for such mining: APRIORI , FP-tree-based approaches like FP-GROWTH, and algorithms based on vertical data structures and depth-first mining strategies like ECLAT and CHARM. Unfortunately, most of these algorithms are only moderately suitable for many “real-world” scenarios because their usability and the special characteristics of the data are two aspects of practical association rule mining that require further work. All mining strategies for frequent patterns use a parameter called minimum support to define a minimum occurrence frequency for searched patterns. This parameter cuts down the number of patterns searched to improve the relevance of the results. In complex business scenarios, it can be difficult and expensive to define a suitable value for the minimum support because it depends strongly on the particular datasets. Users are often unable to set this parameter for unknown datasets, and unsuitable minimum-support values can extract millions of frequent patterns and generate enormous runtimes. For this reason, it is not feasible to permit ad-hoc data mining by unskilled users. Such users do not have the knowledge and time to define suitable parameters by trial-and-error procedures. Discussions with users of SAP software have revealed great interest in the results of association-rule mining techniques, but most of these users are unable or unwilling to set very technical parameters. Given such user constraints, several studies have addressed the problem of replacing the minimum-support parameter with more intuitive top-n strategies. We have developed an adaptive mining algorithm to give untrained SAP users a tool to analyze their data easily without the need for elaborate data preparation and parameter determination. Previously implemented approaches of distributed frequent-pattern mining were expensive and time-consuming tasks for specialists. In contrast, we propose a method to accelerate and simplify the mining process by using top-n strategies and relaxing some requirements on the results, such as completeness. Unlike such data approximation techniques as sampling, our algorithm always returns exact frequency counts. The only drawback is that the result set may fail to include some of the patterns up to a specific frequency threshold. Another aspect of real-world datasets is the fact that they are often partitioned for shared-nothing architectures, following business-specific parameters like location, fiscal year, or branch office. Users may also want to conduct mining operations spanning data from different partners, even if the local data from the respective partners cannot be integrated at a single location for data security reasons or due to their large volume. Almost every data mining solution is constrained by the need to hide complexity. As far as possible, the solution should offer a simple user interface that hides technical aspects like data distribution and data preparation. Given that BW Accelerator users have such simplicity and distribution requirements, we have developed an adaptive mining algorithm to give unskilled users a tool to analyze their data easily, without the need for complex data preparation or consolidation. For example, Business Intelligence scenarios often partition large data volumes by fiscal year to enable efficient optimizations for the data used in actual workloads. For most mining queries, more than one data partition is of interest, and therefore, distribution handling that leaves the data unaffected is necessary. The algorithms presented in this paper have been developed to work with data stored in SAP BW. A salient feature of SAP BW Accelerator is that it is implemented as a distributed landscape that sits on top of a large number of shared-nothing blade servers. Its main task is to execute OLAP queries that require fast aggregation of many millions of rows of data. Therefore, the distribution of data over the dedicated storage is optimized for such workloads. Data mining scenarios use the same data from storage, but reporting takes precedence over data mining, and hence, the data cannot be redistributed without massive costs. Distribution by special data semantics or user-defined selections can produce many partitions and very different partition sizes. The handling of such real-world distributions for frequent-pattern mining is an important task, but it conflicts with the requirement of balanced partition.
236

Challenges encountered by women who requested termination of pregnancy services in the North West Province of South Africa

Mokgethi, Nomathemba Emily Blaai 08 1900 (has links)
In 1996 the South African government legalised the termination of pregnancy (TOP) services, allowing women to choose to terminate unplanned pregnancies at designated facilities. Although TOP services are available, pregnant women continue to use illegal abortion services, with potentially life-risking consequences. The purpose of this study was to identify challenges encountered by women requesting TOP services, and to make recommendations for improved policies and practices, enabling more women in the North West Province (NWP) to access TOP services. This was a non-experimental, exploratory, descriptive and quantitative study. Structured interviews were conducted with 150 women who had used TOP services in phase 1, with 50 women who were unable to access TOP services in phase 2 and with 20 professional nurses providing TOP services in the NWP in phase 3. In phase 1, 96.0% (n=144) of the women needed transport to access TOP services, and 73.2% (n=109) indicated that nurses put women’s names on waiting lists, posing barriers to such access in the NWP. In phase 2, 92.0% (n=46) of these respondents had reportedly requested TOPs for the first time, but 89.0% (n=44) could not access TOP services. In phase 3, only 14 out of 19 designated facilities in the NWP, and only 20 nurses, provided TOP services during the study period. Out of the 20 interviewed nurses, 74.0% (n=14) regarded the Choice on Termination of Pregnancy Act, Act 92 of 1996 (CTOP Act) was being unclear requiring a revision. These professional nurses provided TOP services in NWP, by choice. Unless more facilities and more nurses can provide TOP services to the women of the NWP, these services will continue to remain inaccessible, necessitating the continued utilisation of illegal abortion services, in spite of the TOP Act’s prescriptions. It is also recommended that management will provide sufficient support and training opportunities for professional nurses working in TOP services in the NWP. / Health Studies / (D. Litt. et Phil. (Health Studies))
237

Search for a vector-like quark T' decaying into top+Higgs in single production mode in full hadronic final state using CMS data collected at 8 TeV / Recherche d'un quark vectoriel T¹ qui se désintègre entop+Higgs dans le mode de production célibataire dans le état final hadronique avec les données recueillies par l'expérience CMS à 8 TeV

Ruiz Alvarez, José David 21 October 2015 (has links)
Le LHC (Large Hadron Collider) a produit en 2012 des collisions proton proton à une énergie de 8 TeV dans le centre de masse pour les expériences ATLAS et CMS. Ces deux expériences ont été conçues pour découvrir le boson de Higgs et pour rechercher de nouvelles particules prédites par des modèles théoriques. Le boson de Higgs a été découvert le 4 juillet 2012 par les expériences ATLAS et CMS. Cette découverte marque le début d'une nouvelle période de recherche dans le domaine. Avec la confirmation de l'existence du boson de Higgs, les recherches de nouvelle physique liées à ce boson sont devenues prioritaires. Par exemple, on peut chercher dans les données une nouvelle particule massive qui peut se désintégrer dans un boson de Higgs associé à d'autres particules du modèle standard. Une signature attendue est un boson de Higgs avec un quark top, les deux particules les plus lourdes du modèle standard. Le modèle standard prédit une section efficace pour la production du Higgs avec un quark top. Ainsi une mesure de cette section efficace montrant une valeur plus importante prouverait l'existence de physique au-delà du modèle standard. En outre, l'existence de physique au-delà le modèle standard pourrait montrer des résonances qui se désintègrent dans un quark top et un boson de Higgs. Dans la première partie de ce manuscrit, je présente les bases théoriques et expérimentales du modèle standard, ainsi que le dispositif expérimental. Dans le même chapitre théorique je discute une extension du modèle standard dans le cadre d'un modèle effectif englobant ce dernier. De plus, je détaille une étude de faisabilité d'une recherche d'une des nouvelles particules prédites par ce modèle, un quark vectoriel. Dans la deuxième partie, la recherche dans CMS de ce quark vectoriel T_, partenaire du quark top, est décrite. Ce partenaire du top est une nouvelle particule très similaire au quark top du modèle standard, mais beaucoup plus lourde. On considère le cas où ce nouveau quark se désintègre préférentiellement dans un quark top et un boson de Higgs. J'ai fait cette recherche dans le canal hadronique ou le Higgs se désintègre en deux quarks b et le quark top se désintègre en trois quarks, un quark b et deux quarks légers. J'ai reconstruit la masse du T_ à partir de l'identification de tous ses produits de désintégration. Le résultat obtenu est décrit sous forme des limites observées sur la section efficace de production du T_ déduites à partir de cette analyse / During 2012, the Large Hadron Collider (LHC) has delivered proton-proton collisions at 8 TeV center of mass energy to the ATLAS and CMS experiments. These two experiments have been designed to discover the Higgs boson and to search for new particles predicted by several theoretical models, as supersymmetry. The Higgs boson has been discovered by ATLAS and CMS experiments on July, 4th of 2012, starting a new era of discoveries in particle physics domain. With the confirmation of the existence of the Higgs boson, searches for new physics involving this boson are of major interest. In particular, data can be used to look for new massive particles that decay into the Higgs boson accompanied with other particles of the standard model. One expected signature is a Higgs boson produced with a top quark, the two heaviest particles in the standard model. The standard model predicts a cross section of top-Higgs production, then any enhancement of their associated production will be a clear signature of physics beyond the standard model. In addition, the existence of physics beyond the standard model can also be reflected by resonances that decay into a top-quark and a Higgs boson. In the first part of my work I describe the theoretical and experimental foundations of the standard model, as well as the experimental device. In the same theoretical chapter, I also discuss the formulation of an extension of the standard model. In addition, I describe a feasibility study of a search of one of the particles predicted by such model. The second part contains the realization of the search for a top partner, T_, within the CMS experiment. This top partner is a new particle very similar to the standard model top quark, but much heavier, that can decay into a top quark and a Higgs boson. The analysis looks for this particle in the full hadronic final state, where the Higgs boson decays into two b-quarks and the top quark decays into three standard model quarks, a b and two light quarks. In this channel, I reconstruct its mass from the identification of all its decay products. As a result of the analysis, I show the limits on the T_ production cross section from the number of observed events in the specific signature
238

Datenzentrierte Bestimmung von Assoziationsregeln in parallelen Datenbankarchitekturen

Legler, Thomas 22 June 2009 (has links)
Die folgende Arbeit befasst sich mit der Alltagstauglichkeit moderner Massendatenverarbeitung, insbesondere mit dem Problem der Assoziationsregelanalyse. Vorhandene Datenmengen wachsen stark an, aber deren Auswertung ist für ungeübte Anwender schwierig. Daher verzichten Unternehmen auf Informationen, welche prinzipiell vorhanden sind. Assoziationsregeln zeigen in diesen Daten Abhängigkeiten zwischen den Elementen eines Datenbestandes, beispielsweise zwischen verkauften Produkten. Diese Regeln können mit Interessantheitsmaßen versehen werden, welche dem Anwender das Erkennen wichtiger Zusammenhänge ermöglichen. Es werden Ansätze gezeigt, dem Nutzer die Auswertung der Daten zu erleichtern. Das betrifft sowohl die robuste Arbeitsweise der Verfahren als auch die einfache Auswertung der Regeln. Die vorgestellten Algorithmen passen sich dabei an die zu verarbeitenden Daten an, was sie von anderen Verfahren unterscheidet. Assoziationsregelsuchen benötigen die Extraktion häufiger Kombinationen (EHK). Hierfür werden Möglichkeiten gezeigt, Lösungsansätze auf die Eigenschaften moderne System anzupassen. Als Ansatz werden Verfahren zur Berechnung der häufigsten $N$ Kombinationen erläutert, welche anders als bekannte Ansätze leicht konfigurierbar sind. Moderne Systeme rechnen zudem oft verteilt. Diese Rechnerverbünde können große Datenmengen parallel verarbeiten, benötigen jedoch die Vereinigung lokaler Ergebnisse. Für verteilte Top-N-EHK auf realistischen Partitionierungen werden hierfür Ansätze mit verschiedenen Eigenschaften präsentiert. Aus den häufigen Kombinationen werden Assoziationsregeln gebildet, deren Aufbereitung ebenfalls einfach durchführbar sein soll. In der Literatur wurden viele Maße vorgestellt. Je nach den Anforderungen entsprechen sie je einer subjektiven Bewertung, allerdings nicht zwingend der des Anwenders. Hierfür wird untersucht, wie mehrere Interessantheitsmaßen zu einem globalen Maß vereinigt werden können. Dies findet Regeln, welche mehrfach wichtig erschienen. Der Nutzer kann mit den Vorschlägen sein Suchziel eingrenzen. Ein zweiter Ansatz gruppiert Regeln. Dies erfolgt über die Häufigkeiten der Regelelemente, welche die Grundlage von Interessantheitsmaßen bilden. Die Regeln einer solchen Gruppe sind daher bezüglich vieler Interessantheitsmaßen ähnlich und können gemeinsam ausgewertet werden. Dies reduziert den manuellen Aufwand des Nutzers. Diese Arbeit zeigt Möglichkeiten, Assoziationsregelsuchen auf einen breiten Benutzerkreis zu erweitern und neue Anwender zu erreichen. Die Assoziationsregelsuche wird dabei derart vereinfacht, dass sie statt als Spezialanwendung als leicht nutzbares Werkzeug zur Datenanalyse verwendet werden kann. / The importance of data mining is widely acknowledged today. Mining for association rules and frequent patterns is a central activity in data mining. Three main strategies are available for such mining: APRIORI , FP-tree-based approaches like FP-GROWTH, and algorithms based on vertical data structures and depth-first mining strategies like ECLAT and CHARM. Unfortunately, most of these algorithms are only moderately suitable for many “real-world” scenarios because their usability and the special characteristics of the data are two aspects of practical association rule mining that require further work. All mining strategies for frequent patterns use a parameter called minimum support to define a minimum occurrence frequency for searched patterns. This parameter cuts down the number of patterns searched to improve the relevance of the results. In complex business scenarios, it can be difficult and expensive to define a suitable value for the minimum support because it depends strongly on the particular datasets. Users are often unable to set this parameter for unknown datasets, and unsuitable minimum-support values can extract millions of frequent patterns and generate enormous runtimes. For this reason, it is not feasible to permit ad-hoc data mining by unskilled users. Such users do not have the knowledge and time to define suitable parameters by trial-and-error procedures. Discussions with users of SAP software have revealed great interest in the results of association-rule mining techniques, but most of these users are unable or unwilling to set very technical parameters. Given such user constraints, several studies have addressed the problem of replacing the minimum-support parameter with more intuitive top-n strategies. We have developed an adaptive mining algorithm to give untrained SAP users a tool to analyze their data easily without the need for elaborate data preparation and parameter determination. Previously implemented approaches of distributed frequent-pattern mining were expensive and time-consuming tasks for specialists. In contrast, we propose a method to accelerate and simplify the mining process by using top-n strategies and relaxing some requirements on the results, such as completeness. Unlike such data approximation techniques as sampling, our algorithm always returns exact frequency counts. The only drawback is that the result set may fail to include some of the patterns up to a specific frequency threshold. Another aspect of real-world datasets is the fact that they are often partitioned for shared-nothing architectures, following business-specific parameters like location, fiscal year, or branch office. Users may also want to conduct mining operations spanning data from different partners, even if the local data from the respective partners cannot be integrated at a single location for data security reasons or due to their large volume. Almost every data mining solution is constrained by the need to hide complexity. As far as possible, the solution should offer a simple user interface that hides technical aspects like data distribution and data preparation. Given that BW Accelerator users have such simplicity and distribution requirements, we have developed an adaptive mining algorithm to give unskilled users a tool to analyze their data easily, without the need for complex data preparation or consolidation. For example, Business Intelligence scenarios often partition large data volumes by fiscal year to enable efficient optimizations for the data used in actual workloads. For most mining queries, more than one data partition is of interest, and therefore, distribution handling that leaves the data unaffected is necessary. The algorithms presented in this paper have been developed to work with data stored in SAP BW. A salient feature of SAP BW Accelerator is that it is implemented as a distributed landscape that sits on top of a large number of shared-nothing blade servers. Its main task is to execute OLAP queries that require fast aggregation of many millions of rows of data. Therefore, the distribution of data over the dedicated storage is optimized for such workloads. Data mining scenarios use the same data from storage, but reporting takes precedence over data mining, and hence, the data cannot be redistributed without massive costs. Distribution by special data semantics or user-defined selections can produce many partitions and very different partition sizes. The handling of such real-world distributions for frequent-pattern mining is an important task, but it conflicts with the requirement of balanced partition.
239

Don't be evil : En studie av Googles varumärkesstrategi och användaruppfattningar

Hallberg, Catherine, Eriksson, Sara January 2016 (has links)
Företaget Google är i dag ett av världens mest kända varumärke och deras sökmotor står för 70 % av internetsökningarna i USA och 90 % i Europa. De har lyckats få en dominans på sökmotorsmarknaden framför sina konkurrenter som Yahoo, Ask och Bing. Människor över hela världen använder flera utav Googles tjänster varje dag och många av dem reflekterar inte över den makt som Google har. Kan den här monopolliknande positionen Google har vara så pass transparent att användarna inte ens reflekterat över det? Vår önskan med uppsatsen är att ge läsaren en inblick i Googles varumärkesstrategi och hur användarnas attityder är gentemot företaget. Vi vill ta reda på om användarnas attityder stämmer överens med vad Google vill kommunicera till sina användare och om användarna reflekterar över den maktposition och dominans Google har på internet. För att samla empiriska data, valde vi att göra en webbenkät som besvarades av medie- och kommunikationsstudenter på Högskolan i Jönköping. Utifrån resultatet kunde vi konstatera att en stor del av respondenterna är väl medvetna om den dominans och maktposition som Google har på marknaden. Trots denna medvetenhet har vi inte sett detta påverka respondenternas generella attityder om Google som företag. Däremot kunde vi urskilja viss skepticism hos respondenterna när det kom till en del av Googles funktioner. / Google is today one of the world’s most known brand and their search engine stand for 70 % of the internet searches i the U.S. and 90 % for those i Europe. That means that they have managed to reach monopoly on the search engine market prior to its competitors such as Yahoo, Ask and Bing. People all over the world use several of Google’s services each day and many of them doesn’t reflect over the power that Google has. Can this monopoly and their positions of power be that translucent that the users don’t reflect on it? Our desire with this thesis is to give the reader a deeper understanding about Google’s marketing strategy and about the user’s attitudes towards the company. We want to find out if the attitudes of the user’s correspond to what Google wants to communicate to its users. We also want to find out if the users reflect any on the monopoly and positions of power that Google has on the Internet. To be able to gain empirical data, we chose to design a web-based survey and had media and communications student at Jönköping University to answer it. From the results we found that a large proportion of the respondents is very much aware of the monopoly and positions of power that Google has on the market. However, despite this awareness we could not see that this affected the user’s general attitudes towards the company. On the other hand, we could notice some skepticism when it came to some of the functions of Google’s services.
240

Ants and spiders in grassland food webs / Top-down control and intraguild interactions / Ameisen und Spinnen in Grasland Nahrungsnetzen / Top-down Wirkung und Intraguilden Interaktionen

Sanders, Dirk 24 January 2008 (has links)
No description available.

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