• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 33
  • 25
  • 11
  • 10
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 108
  • 54
  • 54
  • 36
  • 32
  • 26
  • 24
  • 17
  • 16
  • 16
  • 14
  • 13
  • 12
  • 11
  • 11
  • 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.
51

Measurement of the neutral current cross section and search for contact interactions with the H1 experiment at HERA

Ellerbrock, Malte. Unknown Date (has links) (PDF)
University, Diss., 2004--Heidelberg.
52

Análisis del ecosistema emprendedor universitario : propuesta de una herramienta de autoevaluación

Camino, María Paz 14 July 2021 (has links)
Todo cambia. El contexto en el cual se desarrolla la educación también. Hoy se les demanda a las Universidades brindar una educación fundamentada en el mundo actual. Ser “emprendedoras” en “época de emprendedores” (Palomo, 2009). Y esa transformación también implica pensarse de una manera crítica y reflexiva incluyendo definir cuál es el aporte y la interacción que le otorga a su propio ecosistema emprendedor. La presente tesis busca contribuir con esa cuestión mediante el diseño de una herramienta de autoevaluación, denominada HERA. Su propósito es hacer una radiografía del nivel de desarrollo del ecosistema emprendedor de una Universidad. Permite relevar las diversas actividades que se realizan en el marco de la temática emprendedora. Los resultados que se obtienen facilitan el análisis y posibilitan la propuesta de acciones que llevan a la institución a convertirse en una Universidad Emprendedora. Para cumplir con el objetivo, en la tesis se realiza un recorrido profundo sobre los términos ecosistema emprendedor, ecosistema emprendedor universitario y universidad emprendedora, y se proponen definiciones propias que le dan el marco conceptual a los desarrollos presentados. Asimismo se incluye un estudio que revela en qué medida las Universidades públicas y privadas de la Argentina están llevando a cabo actividades relacionadas con la cuestión emprendedora y cómo es el grado de desarrollo de los dominios que componen su ecosistema. Para finalizar y a fin de verificar el uso de la herramienta HERA, la misma se aplica en tres Universidades, permitiendo mostrar su funcionamiento y la claridad con la que se exponen los resultados. Se considera que los desarrollos aquí presentados añaden desde lo teórico, elementos que ayudan a comprender el tema bajo estudio. Desde lo práctico, también se otorgan mecanismos para diagnosticar y luego diseñar acciones concretas que permitan consolidar un ecosistema emprendedor universitario sostenible. / Everything changes. The context in which education takes place as well. Nowadays, Universities are demanded to provide an education based on the current world. Be "entrepreneurial" on "Entrepreneurs time" (Palomo, 2009). And this transformation also implies thinking in a critical and thoughtful way, including the definition of what the contribution is and the interaction that is given to its own entrepreneurial ecosystem. This thesis seeks to contribute to this issue by designing a self-assessment tool, known as HERA. Its purpose is to make an X-ray of the Entrepreneurial University Ecosystem development level. It allows to survey the various activities that are carried out in a entrepreneurial theme using as a methodological support the Balance Scorecard framework and the use of indicators. The results obtained facilitate the analysis and allow the proposal of actions that lead the institution to become an Entrepreneurial University. To achieve the objective, on the thesis, a deep journey is made on the terms entrepreneurial ecosystem, entrepreneurial university ecosystem and entrepreneurial university, and own definitions are proposed that give the conceptual framework to the presented developments. Lokewise, a study is included that reveals to what extent Argentinian´s public and private universities are carrying out activities related to the entrepreneurial matter and how the level of development of the domain that make up its ecosystems are. Lastly, in order to validate the use of the HERA tool, it is applied in three universities, allowing in that way to show the performance and clarity in which the results are exposed. It is considered that the developments presented here add from the theoretical, elements that help to understand the subject under study. From the practical perspective, the mechanism to diagnose and design concrete actions that allow the consolidation of a sustainable entrepreneurial university ecosystem are also added.
53

Trigger and reconstruction farms in the HERA-B experiment and algorithms for a Third Level Trigger

Schwanke, Ullrich 30 October 2000 (has links)
Das HERA-$B$-Experiment am Deutschen Elektronen-Synchrotron (DESY) in Hamburg dient der Untersuchung der Physik von Teilchen, die $b$-Quarks enthalten. Der Schwerpunkt des Ex\-pe\-ri\-mentes liegt auf der Messung der CP-Verletzung im System der neutralen $B$-Mesonen. Es wird erwartet, dass die pr\"azise Bestimmung der CP-Asymmetrie im Zerfallskanal $B^0(\bar{B}^0)\to J/\psi K_S^0$ gro{\ss}en Einfluss auf die Weiterentwicklung des Standardmodells der Elementarteilchenphysik und g\"angiger kosmologischer Theorien haben wird. Das HERA-$B$-Experiment nutzt den Protonenstrahl des HERA-Ringes, um in Kollisionen mit einem feststehenden Target paarweise $B$-Hadronen zu erzeugen. Die Wechselwirkungen werden in einem Vorw\"artsspektrometer mit etwa 600.000 Auslesekan\"alen nachgewiesen. Aufgrund der relativ niedrigen Schwerpunktsenergie von 41.6\,GeV sind Ereignisse mit $b$-Quarks im Vergleich zu Wechselwirkungen mit leichteren Quarks um etwa sechs Gr\"o{\ss}enordnungen unterdr\"uckt. Die Selektion von Signalereignissen stellt daher eine besondere Herausforderung dar. Sie wird von einem vierstufigen Datennahme- und Triggerystem \"ubernommen, das die Ereignisrate von 10\,MHz auf etwa 20\,Hz reduziert. Neben speziell entwickelter Elektronik werden im Triggersystem mehrere hundert handels\"ubliche PCs eingesetzt. Die Computer sind in zwei so genannten PC-Farmen mit jeweils mehr als 200 Prozessoren angeordnet, die die Rechenkapazit\"at f\"ur Triggerentscheidungen und die prompte Analyse der Ereignisdaten zur Verf\"ugung stellen. Auf der einen Farm laufen schnelle Triggerprogramme mit einer Rechenzeit von etwa 1--100\,ms pro Ereignis ab. Die andere Farm rekonstruiert die Ereignisse online, bevor die Daten auf Band dauerhaft archiviert werden. Die pro Ereignis aufgewandte Rechenzeit liegt dabei im Bereich einiger Sekunden. Die vorliegende Arbeit behandelt zwei Themenkreise. Einerseits wird die technische Umsetzung der Trigger- und der Rekonstruktionsfarm beschrieben. Besonderes Augenmerk liegt dabei auf den Software-Systemen, die den Farmen erforderliche Kalibrationsdaten verf\"ugbar machen und die zentrale \"Uberwachung der Ergebnisse der ablaufenden Programme gestatten. Der Hauptteil der Arbeit besch\"aftigt sich mit Algorithmen f\"ur eine dritte Triggerstufe, die zus\"atzlich zu existierenden Programmen auf der Triggerfarm zum Einsatz kommen sollen. Der Zerfall $B^0(\bar{B}^0)\to J/\psi X$ hat eine sehr klare Signatur, wenn das $J/\psi$ in ein $e^+e^-$- oder $\mu^+\mu^-$-Paar zerf\"allt. Im Triggersystem wird nach einem Paar entgegengesetzt geladener Leptonen des gleichen Typs gesucht, deren invariante Masse der des $J/\psi$ entspricht und deren Spuren von einem gemeinsamen Vertex in der N\"ahe des Targets ausgehen. Es wird davon ausgegangen, dass die Ausnutzung aller kinematischen Zwangsbedingungen ausreicht, um diesen Zerfallskanal klar von Untergrundereignissen zu trennen. Die dritte Triggerstufe soll dagegen auf Signalprozesse mit weniger kinematischen Beschr\"ankungen angewandt werden. Solche Ereignisse entstehen zum Beispiel dann, wenn zwei in der Proton-Target-Kollision erzeugte $B$-Mesonen semileptonisch zerfallen. Das Triggersystem selektiert lediglich die beiden Leptonen, die aber hier nicht von einem gemeinsamen Vertex kommen. Die dritte Triggerstufe soll f\"ur derartige Zerfallstopologien innerhalb von 100\,ms pro Ereignis weitere Kriterien zur Unterscheidung von Signal- und Untergrundprozessen aus den Daten extrahieren. In der Arbeit wird anhand von Monte-Carlo-Studien untersucht, inwieweit die Daten des Silizium-Vertexdetektors des Experimentes zur Entscheidungsfindung einer dritten Triggerstufe beitragen k\"onnen. Dabei wird die Rekonstruktion von Spuren aus der Zerfallskaskade der $B$-Hadronen zus\"atzlich zu den von der vorhergehenden Triggerstufe selektierten Lep\-ton\-en an\-ge\-strebt. Mithilfe einer schnellen Mustererkennung f\"ur den Vertexdetektor wird gezeigt, dass das Auffinden aller Spuren und die Anwendung von Triggeralgorithmen innerhalb des vorgegebenen Zeitfensters von 100\,ms m\"oglich sind. Die Bestimmung der Spurparameter nahe der Targetregion macht von der Methode des Kalman-Filters Gebrauch, um der Vielfachstreuung im Detektormaterial Rechnung zu tragen. Dabei tritt das Problem auf, dass weder der Impuls der gefundenen Spuren bekannt ist, noch die Materialverteilung im Vertexdetektor aus Zeitgr\"unden in aller Strenge ber\"ucksichtigt werden kann. Durch geeignete N\"aherungen gelingt es, eine ausreichende Genauigkeit f\"ur die Spurparameter zu erreichen. Die aufgefundenen Teilchen bilden den Ausgangspunkt f\"ur Triggeralgorithmen. Hierbei wird untersucht, welche Methoden am besten geeignet sind, um Signal- und Unter\-grund\-ereignisse voneinander zu trennen. Es erweist sich, dass das Auffinden von Spuren mit gro{\ss}em Impaktparameter aussichtsreichere Ans\"atze als eine Suche nach Sekund\"arvertices bietet. / The HERA-$B$ experiment at Deutsches Elektronen-Synchrotron (DESY) Hamburg aims at investigating the physics of particles containing $b$ quarks. The experiment focusses on measuring CP violation in the system of neutral $B$ mesons. It is expected that the precise determination of the CP asymmetry in the channel $B^0(\bar{B}^0)\to J/\psi K_S^0$ will have an impact on the further development of the Standard Model of Elementary Particle Physics and cosmological theories. The HERA-$B$ experiment uses the proton beam of the HERA storage ring in fixed-target mode. $B$ hadrons are produced in pairs when protons from the beam halo interact with target nuclei. The interactions are recorded by a forward-spectrometer with roughly 600.000 readout channels. At the HERA-$B$ centre-of-mass energy of 42.6\,GeV, the $b\bar{b}$ cross section is only a tiny fraction of the total inelastic cross section. Only one in about 10$^6$ events contains $b$ quarks, which turns the selection of signal events into a particular challenge. The selection is accomplished by a four-stage data acquisition and trigger system reducing the event rate from 10\,MHz to about 20\,Hz. Besides custom-made electronics, several hundreds of PCs are used in the trigger system. The computers are arranged in two so-called PC farms with more than 200 processors each. The PC farms provide the computing capacity for trigger decisions and the prompt analysis of event data. One farm executes fast trigger programs with a computing time of 1--100\,ms per event. The other farm performs online reconstruction of the events before data are archived on tape. The computing time per event is in the range of several seconds. This thesis covers two topics. In the beginning, the technical implementation of the trigger and the reconstruction farm are described. In doing so, emphasis is put on the software systems which make calibration data available to the farms and which provide a centralised view on the results of the executing processes. The principal part of this thesis deals with algorithms for a Third Level Trigger. This trigger is to come into operation on the trigger farm together with existing programs. Processes of the type $B^0(\bar{B}^0)\to J/\psi X$ have a very clean signature when the $J/\psi$ decays to a $e^+e^-$ or $\mu^+\mu^-$ pair. The trigger system attempts to identify two unlike-sign leptons of the same flavour whose invariant mass matches the $J/\psi$. In later steps, the tracks are required to originate from a common vertex close to the target. It is assumed that these kinematic constraints are sufficient to pick out events of this type among the copious background processes. In contrast, the Third Level Trigger is to be applied to signal processes with fewer kinematic constraints. Such events occur for example when two $B$ mesons, which were created in a proton-target collision, decay semileptonically. The trigger system selects merely the two leptons which do not originate from a common vertex in this case. The Third Level Trigger has 100\,ms at its disposal to extract further criteria from the data which can serve to distinguish between signal and background events. This thesis investigates with the aid of Monte-Carlo simulations how the data of the experiment's silicon vertex detector can contribute to the decisions of a Third Level Trigger. The trigger aims at reconstructing tracks from the decay cascade of $B$ mesons in addition to the leptons selected by the preceding trigger levels. A fast pattern recognition for the vertex detector demonstrates that the reconstruction of all tracks and the application of trigger algorithms are possible within the given time slot of 100\,ms. The determination of track parameters in the target region exploits the Kalman-filter method to account for the multiple scattering of particles in the detector material. The application of this method is, however, made difficult by two facts. First, the momentum of the reconstructed tracks is not known. And, second, the material distribution in the detector cannot be taken into consideration in detail due to timing limitations. Adequate approximations for the momentum and the material traversed by a particle help to accomplish a sufficient accuracy of the track parameters. The reconstructed tracks constitute the starting point of several trigger algorithms, whose suitability to select signal events is investigated. Our studies indicate that the reconstruction of tracks with large impact parameters is a more promising approach than a search for secondary vertices.
54

Study of chic production using HERA-B data

Aleksandrov, Aleksandar 12 August 2010 (has links)
In dieser Arbeit wurde die Produktion der Charmonium-Zust\"ande $\chi_{c1}$ und $\chi_{c2}$ in Proton-Kern-Wechselwirkungen bei einer Proton-Nukleon-Schwerpunktenergie von $\sqrt{s}=41.6~{\rm GeV}$ untersucht. Die f\"ur die Analyse verwendeten Daten wurden mit dem HERA-B-Experiment genommen, das die Streuung von Protonen des HERA-Rings an feststehenden Draht-Targets verschiedener Materialien untersucht. Die Analyse basiert auf etwa $10\,000$ radiativen $\chi_{c}$-Zerf\"allen, $\chi_{c}\rightarrow J/\psi\gamma$, die aus mehr als $122\cdot10^{3}$ myonischen $J/\psi$-Zerf\"allen, $J/\psi\rightarrow\mu^{+}\mu^{-}$, rekonstruiert wurden. Das Verh\"altnis der Rate der $J/\psi$, die aus $\chi_{c}$-Zerf\"allen stammen, zu der Gesamtrate der $J/\psi$, $R_{\chi_{c}}=\sum_{i=1,2}{\sigma(\chi_{ci})Br(\chi_{ci}\rightarrow J/\psi\gamma)/\sigma(J/\psi)}$, wurde in dem kinematischen Bereich $-0.35 / In this thesis the production of the charmonium states $\chi_{c1}$ and $\chi_{c2}$ in proton-nucleus collisions at a proton-nucleon center-of-mass energy $\sqrt{s}=41.6~{\rm GeV}$ was studied. The data used for the analysis have been taken by the fixed-target experiment HERA-B that uses the HERA proton beam to scatter protons off the nuclei of different wire targets. About $122\cdot10^{3}$ recorded muonic $J/\psi$ decays, $J/\psi\rightarrow\mu^{+}\mu^{-}$, resulted in almost $10\,000$ reconstructed $\chi_{c}\rightarrow J/\psi\gamma$. The ratio $R_{\chi_{c}} = \sum_{i=1,2}{\sigma(\chi_{ci}) Br(\chi_{ci}\rightarrow J/\psi\gamma) /\sigma(J/\psi)}$, which is the ratio of $J/\psi$ from $\chi_c$ decays to all produced $J/\psi$, was measured in the kinematical range $-0.35
55

Optimization of Cubesat-Compatible Plasma Ion Analyzer for Asteroid Composition Analysis

Zankov, Ivan January 2019 (has links)
Many space probes have conducted in situ explorations of asteroids, in recent decades, intent on identifying evidence of the solar system's earliest processes of formation within the asteroids' interiors. Several future asteroid missions are planned, among which include ESA's Hera mission to explore the Didymos binary asteroid pair. An ion mass analyzer is currently being designed at the Swedish Institute of Space Physics for use as part of the Hera mission. This thesis aims to optimize the instrument such that each of its parameters meets the requirement for performance. A computer simulation is used to calculate the trajectories of low-energy ions inside the instrument, where the electrostatic potential are imposed by grids and electrodes embedded inside the instrument. From the data analysis of the simulation results, the performance for each parameter can be derived. By changing the settings of the grids and electrodes (e.g., positions and voltages), the instrument parameters are to be optimized. Two tasks are set up in this project--- the first task is to optimize the focusing system of the incoming ions at the instrument's entrance, and the second task is to investigate the reflectron system so that the mass resolution of the instrument can be optimized via reducing the spread of the ions' time of flight spectra. The focusing system is found to already be optimized, but instead, a relation between its position of the grid at the instrument's entrance and the instrument's performance is derived. The method of and parameters for optimization within the reflectron are extensively tested individually during this project. Although several performances in each trial from the reflectron analysis cannot meet at least one of the requirements, enough scenarios are examined such that every parameter tested ends with a value suitable to be applied individually to optimize the ion mass analyzer. The findings from the individual tests done in this project can be applied to further optimization, particularly to optimize multiple parameters simultaneously in the near future.
56

Nivoi koncentracija i upravljanje perzistentnim organskim polutantima u heterogenom sistemu deponija komunalnog otpada / Concentration levels of persistent organic pollutants and management of POP inheterogeneous system of municipal waste landfills

Đogo Maja 21 September 2017 (has links)
<p>Istraživanje u okviru doktorkse disertacije obuhvata reprezentativan izbor tačaka uzorkovanja na deponijskim lokalitetima Bečej, Subotica, Sombor, Zrenjanin, Pančevo, Bačka Palanka, Vrbas, Temerin, Novi Sad i Ruma, primenu savremenih metodologija uzorkovanja, pripremu i analizu uzoraka najnovijim metodama determinacije organskih polutanata, statističku obradu podataka, procenu uticaja na humanu populaciju i ključne kompartimente životne sredine i razvoj metodologije kreiranja budućeg istraživačkog i kontrolnog monitoring programa. Dobijeni rezultati obrađeni su primenom metode analiza glavnih komponenti i hijerarhijske klaster analize. Procena uticaja kontaminanata i statusa životne sredine sprovedena je primenom jedne od metodologija evropske komisije za procenu i predikciju različitih efekata na humanu populaciju i životnu sredinu dejstvom toksičnih hemijskih supstanci. Na osnovu eksperimentalnih rezultata i stečenih tehničko-inženjerskih iskustava razvijena je Metodologija kreiranja budućeg istraživačkog i kontrolnog monitoring programa heterogenog medijuma deponijskih tela sa ciljem unapređenja upravljanja frakcijama komunalnog otpada koji generiše POP.</p> / <p>The selection of representative municipal solid waste landfill locations (Bečej, Subotica,<br />Sombor, Zrenjanin, Pančevo, Bačka Palanka, Vrbas, Temerin, Novi Sad and Ruma),<br />the application of contemporary sampling methodologies, preparation, extraction and<br />analyses of samples using modern analitical methods and techiques, statistical data<br />evaluation, human and environment risk assessment, HERA, and the development of<br />methodology for designig of future research and control monitoring programmes have<br />been conducted within doctoral dissertation. Obtained results for POPs and PAHs were<br />evaluated applying principal component analysis (PCA) and hierarchical cluster<br />analysis (CA). HERA was conducted using recommended EPA methodolgy for<br />assessment and prediction of hazard effectes of toxic chemical substances on human<br />population and environment. On the basis of experimental results and the levels of<br />obtained technico-engineering experience Methodology for designig of future research<br />and control monitoring programmes for landfilld heterogeneous system was developed<br />in order to improve the POP waste management practice.</p>
57

Hadronic fragmentation studies in ep scattering at HERA

Donovan, Keith Thomas January 1998 (has links)
No description available.
58

Diffractive and non-diffractive charm production in deep inelastic scattering at HERA

Hall-Wilton, Richard John January 1999 (has links)
No description available.
59

Rho prime electroproduction at HERA

Cocks, Stuart Peter January 1998 (has links)
No description available.
60

Measurement of the charm contribution to the proton structure function at Hera

Sideris, Dimitrios January 1998 (has links)
No description available.

Page generated in 0.0568 seconds