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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.
71

Wavelet packet based multicarrier modulation code division multiple access system

Zhang, Yifeng. January 2000 (has links)
Thesis (Ph. D.)--Ohio University, June, 2000. / Title from PDF t.p.
72

Multiuser detection in TH-UWB communication systems

Hosseini, Iraj. January 2009 (has links)
Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Aug. 14, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Communications, Department of Electrical and Computer Engineering, University of Alberta." Includes bibliographical references.
73

Clustered multicarrier systems for very wideband wireless communications

Vajipeyajula, Mani Kishore. January 2005 (has links)
Thesis (M.E.E.)--University of Delaware, 2005. / Principal faculty advisor: Leonard J. Cimini, Dept. of Electrical and Computer Engineering. Includes bibliographical references.
74

The multiple access broadcast channel : protocol and capacity considerations

January 1978 (has links)
by John Ippocratis Capetanakis. / Originally presented as the author's thesis, (Ph.D.) in the M.I.T. Dept. of Electrical Engineering and Computer Science, 1978. / Prepared under Office of Naval Research Contract ONR-N00014-64-C-1183. / Includes bibliographical references.
75

Κατανεμημένη παρατήρηση-εκτίμηση συνολικών πόρων μεγάλων συνόλων δικτυακών κόμβων και εφαρμογή αυτών σε δικτυακή εφαρμογή διαμοιρασμού βίντεο πραγματικού χρόνου

Δανούσης, Σπυρίδων 13 October 2013 (has links)
Τα τελευταία χρόνια είδαν την άνθιση διαδικτυακών εφαρμογών και υπηρεσιών διαμοιρασμού αντικειμένων πολυμέσων. Την τιμητική τους είχαν τα αντικείμενα οπτικοακουστικού περιεχομένου (video), δίνοντας πρωταγωνιστικό ρόλο στην ανάπτυξη συστημάτων διαμοιρασμού βίντεο. Μάλιστα, ανταποκρινόμενα στην δυνατότητα των χρηστών για επιλογή περιεχομένου, που παρείχαν η ραγδαία αύξηση της χρήσης του διαδικτύου και η βελτίωση των υποδομών αυτού, έγιναν ιδιαίτερα δημοφιλή τα συστήματα και οι υπηρεσίες διαμοιρασμού βίντεο κατόπιν ζήτησης Ωστόσο οι αυξημένες απαιτήσεις τους σε κλιμάκωση, προσαρμοστικότητα, απόδοση και ανεκτικότητα σε σφάλματα, κατέστησαν απαραίτητη την υποστήριξή τους από κατανεμημένες ή και παράλληλες αρχιτεκτονικές. Μία αρκετά υποσχόμενη προσέγγιση προς αυτή την κατεύθυνση είναι τα διομότιμα συστήματα καθώς οι ίδιοι οι χρήστες των εφαρμογών διαθέτουν ένα τεράστιο σύνολο από δικτυακούς και υπολογιστικούς πόρους. Στα συστήματα αυτά το περιεχόμενο που κατεβάζουν οι χρήστες διασπάται σε κομμάτια τα οποία ανταλλάσσονται από αυτούς ,με σκοπό την τελική επανασύνδεση και ανάκτηση του συνολικού μεγέθους των δεδομένων. Σκοπός αυτής της διπλωματικής είναι η μελέτη της αξιοποίησης του εύρους ζώνης στα πλαίσια ενός διομότιμου συστήματος διαμοιρασμού βίντεο κατόπιν ζήτησης με πολλαπλά κανάλια. Η παρατήρηση του τρόπου συμπεριφοράς των χρηστών και του συνολικού συστήματος ως προς τον πολύτιμο αυτό δικτυακό πόρο, μπορεί να αποτελέσει την βάση για την ανάπτυξη εφαρμογών με μεγαλύτερη αποδοτικότητα, πιο οικονομικών στην λειτουργία τους, και με βελτιωμένη ευελιξία. / The last year saw the flourishing of Internet applications and services sharing media objects. Their honor were the objects of audiovisual content (video), giving a leading role in the development of video sharing. Indeed, in response to users' ability to select content, provided by the rapid growth of internet usage and to improve the infrastructure of this, became very popular in the systems and services for sharing video on demand However, the increased demands on scalability, flexibility, performance and fault tolerance, made it necessary to support them or from distributed and parallel architectures. A very promising approach in this direction is the diomotima systems and the users themselves applications have a huge amount of network and computing resources. In these systems the content download users cleaved into pieces which are exchanged by them, with the final reconnection and recovery of the total size of data. The aim of this thesis is to study the utilization of bandwidth within a peer sharing system video on demand with multiple channels. The observation of how user behavior and the overall system to this valuable web resource, can provide the basis for developing applications with greater efficiency, more economical to operate, and with improved flexibility.
76

Analýza využití multikanálového retailingu ve vybraném maloobchodním subjektu / Analysis of the use of multichannel retailing in selected retail entity

MAZANCOVÁ, Kateřina January 2010 (has links)
The aim of this thesis was to analyze the use of multichannel retailing in Globus hypermarket in České Budějovice. Dispensation was done according to Levy and Weitz (2009) into three main channels {--} retail store, catalogue and the internet which were supplemented by some components of the communication mix. On the basis of the case studies and marketing situation analysis of Globus hypermarket in České Budějovice some measures were proposed to improve the competitive position of this company by the use of multichannel retailing. Partial proposals were devided by particular channels. One of them was also economically evaluate.
77

Advantageous for Who? : A Study of How Delivery and Return Policies Affect Customer Perception of Multichannel Retailers

Heed, Niklas, Granlund, Jakob January 2018 (has links)
In today’s retail landscape, the goal of retaining loyal customers is a pivotal part of success. Multichannel retailers offer an extended service package which increases the chances of totally satisfied customers, a requirement for loyalty. In 2017, 20-30 percent of all purchased e-commerce goods were returned. This aroused an interest in how consumer behaviour is influenced by a multichannel retailers’ delivery- and return policies, and so the purpose of this study was defined. The nature of the purpose directed the study to a quantitative form, where primary data was collected by conducting a survey on Lulea University of Technology (LTU) students. A requirement for the participants was to have experience in online purchasing from a multichannel retailer, such as Zara. A theoretical framework consisting of hypotheses and the main theories of the study were formed to conceptualise the potential relations. This framework was then used as a basis throughout the data analysis that made use of established measures, which were performed by means of multiple regressions and correlations on the data. The analysis revealed mixed results, some rejecting the null hypotheses and some confirming it. In other words, there exists a relation and direct link between delivery- and return policies towards brand image. This study could not prove a direct connection between delivery- and return policies towards brand loyalty, potentially due to a small sample size. A false negative also deemed the final connection between brand image and brand loyalty as inconclusive, however a larger survey sample would probably have resulted in a proven relation. This study has begun filling the gap between how delivery- and return policies influence multichannel retailers brand image and brand loyalty, an area with scarce information. The research team recommends future studies to conduct qualitative approaches to gain deeper insight into the mind of the consumer and their thoughts regarding the discussed policies. In addition, future research could view it from a company perspective to create a circumferential information stream. Most importantly, a large sample should be obtained to make sure that the relations expected to exist, can be proven.
78

Investigation of Implantable Multichannel Neurostimulators

January 2015 (has links)
abstract: There is a strong medical need and important therapeutic applications for improved wireless bioelectric interfaces to the nervous system. Multichannel devices are desired for neural control of robotic prosthetics that interface to remaining nerves in limb stumps of amputees and as alternatives to traditional wired arrays used in for some types of brain stimulation. This present work investigates a new approach to ultrasound-powering of implantable microelectronic devices within the tissue that may better support such applications. These devices are of ultra-miniature size that is enabled by a wireless technique. This study investigates two types of ultrasound-powered neural interfaces for multichannel sensory feedback in neurostimulation. The piezoceramics lead zirconate titanate (PZT) ceramic and polyvinylidene fluoride (PVDF) polymer were the primary materials used to build the devices. They convert ultrasound to electricity that when rectified by a diode produce a current output that is neuro stimulatory to peripheral nerve or the neurons in the brain. Multichannel devices employ a form of spatial multiplexing that directs focused ultrasound towards localized and segmented regions of PVDF or PZT that allows independent channels of nerve actuation. Different frequencies of ultrasound were evaluated for best results. Firstly, a 2.25 MHz frequency signal that is reasonably penetrating through body tissue to an implant several centimeters deep and also a 5 MHz frequency more suited to application for actuation of devices within a less than a centimeter of nerve. Results show multichannel device performance to have a complex inter-relationship with frequency, size and thickness, angular incidence, channel separations, and number of folds (layers connected in series and parallel). The output electrical port impedances of PVDF devices were examined in relationship to that of stimulating electrodes and tissue interfaces. Miniature multichannel devices were constructed using an unreported method of employing state of the art laser cutting systems. The results show that PVDF based devices have advantages over PZT, because of better acoustic coupling with tissue, known better biocompatibility, and better separation between multiple channels. However, the PZT devices proved to be better overall in terms of compactness and higher outputs for a given ultrasound power level. / Dissertation/Thesis / Masters Thesis Bioengineering 2015
79

Exploring risk management during transition to omnichannel

Hagström, Oscar January 2018 (has links)
Major changes with regards to digitalization and new customer behaviours have transformed the retail industry in many ways. One of the latest trends in retail is the focus on omnichannel, in order to stay competitive in today's changing market conditions. Omnichannel is about creating a seamless distribution and experience for the customers between channels. These changes that come with digitalization come with strategical and developmental challenges. As well as an increased pressure to work more efficiently and at an accelerated speed to cope with new trends. This can be hard to accomplish, to embark into unknown territory since no organization truly has reached omnichannel. Whilst speed and innovation play a vital part in adapting to new rules of conduct within retail, risk management is still a part of their project management tasks. The purpose of this thesis is to explore how management is working with handling risks that can occur in the transition processes to omnichannel. This thesis is based on a qualitative research design where seven semi-structured interviews have been conducted with managers from various large Swedish retail organizations. The conclusion shows three main themes from the empirical findings, which are the following: Operational risks are more common and manageable than strategical, Depending on project scope; risk assessment and mitigation differs and the diversity and roles of employees.
80

O aprimoramento do método multicanal de Schwinger para o espalhamento de pósitrons por átomos/moléculas / The improvement of the Schwinger multichannel method for positron-atom/molecule scattering

Sanchez, Sergio d'Almeida 28 March 2008 (has links)
Orientador: Marco Aurelio Pinheiro Lima / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T14:55:41Z (GMT). No. of bitstreams: 1 Sanchez_Sergiod'Almeida_D.pdf: 887623 bytes, checksum: a388fbed10300eb250bcf6c18f5bc257 (MD5) Previous issue date: 2008 / Resumo: Neste trabalho são apresentadas três modificações realizadas no Método Multicanal de Schwinger (SMC) para o espalhamento de pósitrons por moléculas (átomos): a inclusão de um potencial complexo para simular a absorção de partículas, a inclusão de um potencial delta real, proveniente de correções relativísticas, e a exibilização da base com a inclusão de funções que descrevem orbitais atômicos do tipo f (com momento angular l = 3). Os resultados para o potencial complexo mostram que sua influência é muito pequena se comparada ao potencial Coulombiano e os resultados obtidos para o parâmetro de aniquilação são os mesmos dos calculados sem a sua presen¸ ca. Além disso, foi verificado que não é possível utilizá-lo para calcular o parâmetro de aniquilação diretamente pelo SMC por problemas de precisão numérica. Um teste da influência do potencial absorvedor mostrou que sua inclusão no método, apesar de afetar as seções de choque de espalhamento, não modifica o balanço entre os potenciais atrativos e repulsivos sentidos pelo pósitron, ou seja, não há competição com o potencial espalhador real e ele apenas simula a absorção dos pósitrons incidentes. Um potencial tipo de delta real, contudo, compete diretamente com o potencial Coulombiano. No entanto, foi verificado que sua utilização para ajudar na escolha das melhores funções de base para descrever o processo de aniquilação não é eficaz, pois modifica o problema que está sendo estudado. A última modificação no método, a inclusão de funções orbitais f, trouxe importantes resultados e melhorou significativamente os dados de seção de choque previamente obtidos para o átomo de Hélio e para a molécula de H2 . Sua aplicação para sistemas maiores e para o caso de espalhamento de elétrons por átomos ou moléculas é um importante passo a ser dado / Abstract: In this work, three modifications in the Schwinger Multichannel Method (SMC) for positron-molecule(atom) scattering are presented: the inclusion of a complex potential to simulate the absorption of particules, the inclusion of a real delta potential, whose physical origin can be found in the relativistic corrections, and the improvement in the basis set used in the method with the inclusion of functions that describes the f -type atomic orbitals. The results for the complex potential show that its in uence is very small when compared to the Coulomb potential and the new data obtained for the annihilation parameter are not different from the ones calculated without its presence. It was also verified that one can not use the absorption potential to calculate the annihilation parameter directly in the SMC method due to numerical precision problems. We also tested the in uence of the complex potential which shows that, although it affects the scattering cross sections, it does not modify the balance between the atractive and the repulsive potential experienced by the positron, i.e., there is no competition between the real scattering potential and the complex potential. All the later does is simulate the absorption of particules. A real delta potential, however, competes directly with the Coulomb potential. Its use in the selection of basis set to obtain a better description of the annihilation process is impraticable, since it modifies the problem we are studying. The last modification of the method, the inclusion of the f -type orbital, brought important results and significantly enhanced the quality of our cross section data for the Helium atom and the H2 molecule. Its use on bigger molecules and in the electron scattering problem is an important step to be taken / Doutorado / Física Atômica e Molecular / Doutor em Ciências

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