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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.
1

A new Propagation Model for Industrial Environments

Dolz, Jose, Marzal, Silvia January 2010 (has links)
<p>This thesis is a project carried out at the “Centre for RF measurements Technology“at the University of Gävle. The first aim was basically the characterization of different industrial indoor environments to get a model that describes dispersive features of each environment.</p><p> </p><p>The results of previous measurements campaign on three industrial environments as steel mill, storage paper and industrial process mill are used. Also new Power Delay Profile (PDP) on corridor and laboratory has been developed.</p><p> </p><p>Measurements for three frequency bands are done (183-683 MHz, 1640-2140MHz and 2200-2700MHz) and for line-of-sight (LOS) and non-line-of-sight (NLOS) industrial and laboratory scenaries cases are presented.</p><p> </p><p>All these models have been compared with other existing models as Saleh-Valenzuela Model, Two Cluster Model and Indoor Power Delay Profile Model (IPDP Model) and fit-line, typical deviation are shown.</p><p> </p><p>Finally we present a study of the different systems used in the industry and the best suited system to the conditions is chosen.</p><p><strong> </strong></p>
2

A new Propagation Model for Industrial Environments

Dolz, Jose, Marzal, Silvia January 2010 (has links)
This thesis is a project carried out at the “Centre for RF measurements Technology“at the University of Gävle. The first aim was basically the characterization of different industrial indoor environments to get a model that describes dispersive features of each environment.   The results of previous measurements campaign on three industrial environments as steel mill, storage paper and industrial process mill are used. Also new Power Delay Profile (PDP) on corridor and laboratory has been developed.   Measurements for three frequency bands are done (183-683 MHz, 1640-2140MHz and 2200-2700MHz) and for line-of-sight (LOS) and non-line-of-sight (NLOS) industrial and laboratory scenaries cases are presented.   All these models have been compared with other existing models as Saleh-Valenzuela Model, Two Cluster Model and Indoor Power Delay Profile Model (IPDP Model) and fit-line, typical deviation are shown.   Finally we present a study of the different systems used in the industry and the best suited system to the conditions is chosen.
3

Cooperative Jamming in Wireless Networks - Turning Attacks into Privacy Protection

Wu, Jingqi 19 December 2008 (has links)
Generally, collisions between packets are undesired in wireless networks. We design this scheme, Cooperative Jamming in Wireless Networks (CJWN), to make use of collision to protect secret DATA packets from being sniffed by a nearby eavesdropper. We are intending to greatly increase the Packet Error Rate (PER) at the eavesdropper when the PER at the receiver is maintained at an acceptable level. This scheme is not intended to completely take the place of various encryption/decryption schemes which are working based on successfully received packets. Adding CJWN to the popular CSMA/CA adopted in IEEE 802.11 will add more security even the key for encryption/decryption is already exposed. Because the overhead of CJWN is very big, we do not suggest using it on every transmission. When some secret packets have a high requirement of confidentiality, CJWN is worth trying at the cost of throughput performance and power.
4

Propagating Changes between Aligned Process Models

Weidlich, Matthias, Mendling, Jan, Weske, Mathias 28 February 2012 (has links) (PDF)
There is a wide variety of drivers for business process modelling initiatives, reaching from organisational redesign to the development of information systems. Consequently, a common business process is often captured in multiple models that overlap in content due to serving different purposes. Business process management aims at exible adaptation to changing business needs. Hence, changes of business processes occur frequently and have to be incorporated in the respective process models. Once a process model is changed, related process models have to be updated accordingly, despite the fact that those process models may only be loosely coupled. In this article, we introduce an approach that supports change propagation between related process models. Given a change in one process model, we leverage the behavioural abstraction of behavioural profiles for corresponding activities in order to determine a change region in another model. Our approach is able to cope with changes in pairs of models that are not related by hierarchical refinement and show behavioural inconsistencies. We evaluate the applicability of our approach with two real-world process model collections. To this end, we either deduce change operations from different model revisions or rely on synthetic change operations.
5

Simulation des conditions de trafic intracellulaire d'un réseau sans fil en milieu industriel par un modèle de propagation composite

Benferhat, Sabri 12 June 2009 (has links) (PDF)
Cette thèse traite de l'utilisation des réseaux locaux sans fil dans un environnement industriel. Nous traitons l'impact des conditions de propagation et leur implémentation, sur des outils de simulations. La première partie s'intéresse au choix du modèle par des méthodes analytiques appliquées sur des mesures. La comparaison des performances obtenues dans un site avec les résultats de simulations montre une nette différence. Elle nous a permis de conclure que les modèles classiques ne permettent pas de simulations pertinentes pour un tel contexte. Pour ces raisons, nous proposons une nouvelle façon de modéliser les conditions de propagation. Notre modèle appelé "split model" permet de distinguer : liens entre stations et point d'accès des liens entre stations. Nous avons utilisé le modèle dans la simulation pour étudier les performances dans une cellule en mode infrastructure de la norme 802.11. Les résultats montrent que des collisions au niveau du point d'accès sont constatées et en résulte une dégradation des performances pour laquelle les mécanismes prévus pour compenser l'effet du terminal caché (RTS/CTS) se sont montrés inefficaces. L'utilisation du split model dans un processus de simulation met en avant les effets dus a l'existence de ces zones cachées et permet d'avoir des résultats obtenus par simulation plus représentatifs du comportement d'une cellule recouvrant une chaîne de production.
6

Lokalizace zařízení v bezdrátovém systému na základě úrovně přijímaného signálu / RSSI based localization of sensor units in wireless network

Popovec, Juraj January 2014 (has links)
This thesis describes processing of RSSI parameter and its subsequently use for cal- culating distance of wireless node. This thesis also describes analysis of radio model environment and calibration of key variables needed for localization. There is also sys- tem realized for localization of wireless nodes in sensor network. It uses dynamically calibrated variables for calculations, which describes radio model.
7

Návrh rádiové části sítě LTE / Radio Network LTE Design

Tribula, David January 2017 (has links)
The diploma thesis deals with the design of the LTE radio part using the ICS Designer program. First, the work describes the signal processing in the physical layer LTE system, for downlink and uplink. Subsequently, it was made simple block diagram. The next part deals with models of signal propagation in the radio environment. The last part is an introduction to the ICS Designer. This section describes the base station design and demonstration of some simulations. The last part is devoted to the design of the mobile network in the given area, its simulation and subsequent comparison with the existing mobile network.
8

Einfluss der vertikalen Auflösung der Eingangsprofile bei einem Schallstrahlenmodell

Wilsdorf, Michael, Fischer, Gabi, Ziemann, Astrid 26 September 2017 (has links)
In der folgenden Ausarbeitung soll der Einfluss der vertikalen Auflösung der Eingangsprofile auf die Schallausbreitungsrechnungen eines Schallstrahlenmodells näher untersucht werden. Der Grund hierfür liegt in dem Auftreten eines „Schichtenproblems“ bei der Arbeit mit einem solchen Modell. Das bedeutet, dass je größer die vertikale Auflösung der Eingangsprofile ist, desto mehr weicht die mit dem Computermodell bestimmte Lösung von der analytischen ab. Im folgenden Beitrag werden verschiedene vertikale Auflösungen untersucht und es wird gezeigt, dass eine höhere Auflösung dieses Problem lösen kann. Die Berechnungen erfolgen mit dem Schallstrahlenmodell SMART. Dieses Modell basiert auf der Berechnung des Weges, den der Schall in einer geschichteten Atmosphäre zurücklegt. Die Berechnungsgrundlage für das Strahlenmodell bilden dabei aus Radiosondendaten interpolierte, sowie klimatologisch klassifizierte Temperatur- und Windprofile. Diese Untersuchungen stellen eine notwendige Grundlage bei der Analyse und Interpretation der durch ein Strahlenmodell gewonnenen Dämpfungsberechnungen dar. / In the following article, effects of the vertical resolution of input data on numerical sound attenuation simulations are investigated. The reason for this lies in the occurrence of a „layer problem“ during work with such a model. That means, even larger the vertical resolution of the input profiles is, so much more the calculated answer deviates from the analytic. Therefore, different vertical resolutions are examined. The analyzed results show that a higher resolution can solve this problem. Calculations are carried out using the sound ray model SMART which considers the dependency of sound ray propagation on stratified atmosphere. As a basis for calculating the sound ray paths interpolated and climatologically classified profiles of temperature and wind obtained from radiosonde data are utilized. These investigations provide a basis for the analysis and interpretation of attenuation calculations derived from a sound ray model.
9

Reconstruction Methods for Optical Molecular Tomography

Cong, Alexander Xiao 25 January 2013 (has links)
Molecular imaging plays an important role for development of systems biomedicine, which non-invasively extracts pictorial information on physiological and pathological activities at the cellular and molecular levels. Optical molecular tomography is an emerging area of molecular imaging. It locates and quantifies a 3D molecular probe distribution in vivo from data measured on the external surface of a small animal around the visible and infrared range. This approach can facilitate or enable preclinical applications such as cancer studies, involving angiogenesis, tumor growth, cell motility, metastasis, and interaction with a micro-environment. The reconstruction of diffuse light sources is the central task of optical molecular tomography, and generally ill-posed and rather complex. The key element of optical molecular tomography includes the geometrical model, tissue properties, photon characteristics, transport model, and reconstruction algorithm. This dissertation focuses mainly on the development optical molecular tomography methods based on bioluminescence/fluorescence probes to solve some well-known challenges in this field. Our main results are as follows. We developed a new algorithm for estimation of optical parameters based on the phase-approximation model.  Our iterative algorithm takes advantage of both the global search ability of the differential evolution algorithm and the efficiency of the conjugate gradient method. We published the first paper on multispectral bioluminescence tomography (BLT). The multispectral BLT approach improves the accuracy and stability of the BLT reconstruction even if data are highly noisy. We established a well-posed inverse source model for optical molecular tomography. Based on this model, we proposed a differential evolution-based reconstruction algorithm to determine the source locations and strengths accurately and reliably. Furthermore, to enhance the spatial resolution of fluorescence molecular tomography, we proposed fluorescence micro-tomography to image cells in a tissue scaffold based on Monte Carlo simulation on a massive parallel processing architecture. Each of these methods shows better performance in numerical simulation, phantom experiments, and mouse studies than the conventional methods. / Ph. D.
10

A Propagation Simulator for Land Mobile Satellite Communications

Suh, Seong-Youp 28 April 1998 (has links)
The performance of a mobile satellite communications link can be determined by the propagation path between a satellite and mobile users. Some of the most important factors are multipath propagation and vegetative shadowing. System designers should have the most reliable information about the statistics of fade duration in order to determine fade margin or to compensate for the fades using modulation and coding scheme. This report describes a simulator, PROSIM, developed at Virginia Tech for simulating a propagation model in land mobile satellite communications. The simulator is based on a random number generator that generates data sets to compute statistics of the propagation channel. Performance of the simulator was evaluated by comparing statistics from an analytical model and experimental data provided by W. Vogel of Univ. of Texas at Austin and J. Goldhirsh of the Applied Physics Laboratory. New expressions for phasor plot and its mathematical expression for lognormal channel were derived and were simulated. Finally, the advantages of the simulator using random number generator in simulating the propagation model are described. / Master of Science

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