Orientador: Marco Aurelio Pinheiro Lima / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-06T20:07:28Z (GMT). No. of bitstreams: 1 Oliveira_ElianeMarquesde_M.pdf: 1735401 bytes, checksum: 96cad8d360043e7a2e9b4a6b65936027 (MD5) Previous issue date: 2006 / Resumo: A relação entre ressonâncias de Feshbach e excitações eletrônicas é bem conhecida no caso de espalhamento de elétrons por moléculas de H2, mas ainda pouco explorada no espalhamento de pósitrons, tornando interessante, portanto, um estudo comparativo. Porém, antes de pensarmos em comparações, nos preocupamos em tentar entender se, de fato, uma ressonância de Feshbach se manifesta no espalhamento de pósitrons por moléculas de H2. Esta preocupação foi motivada devido à não observação experimental desta ressonância em investigação realizada logo após nosso grupo de pesquisa ter publicado um estudo no qual havia evidências para a existência de uma ressonância de Feshbach em colisões pósitron-H2, obtida num cálculo realizado na aproximação de núcleos fixos para a distância internuclear de equilíbrio Ro=1.4ao. Nossa estratégia foi calcular seções de choque, ainda na aproximação de núcleos fixos, para diversas distâncias internucleares em torno de Ro. Os resultados obtidos sugerem que a ausência experimental da ressonância esteja ligada à abertura de um novo canal eletrônico para R > Ro. Para esses cálculos utilizamos o Método Multicanal de Schwinger (SMC), para obtenção dos parâmetros de colisão (posição e largura da ressonância), em combinação com a aproximação do Potencial Complexo Local (também conhecido por Boomemng Model), para inclusão do acoplamento dos graus de liberdade vibracionais. A ausência da ressonância para algumas distâncias internucleares no espalhamento de pósitrons impede o cálculo de seções de choque vibracionalmente resolvidas através da aproximação local. Por outro lado, para o espalhamento de elétrons, que é um desafio como problema teórico, realizamos os cálculos e encontramos acordo razoável com os dados experimentais disponíveis / Abstract: The relationship between Feshbach resonances and electronic excitation is well known in electron scattering by Hydrogen molecules, but still little exploited in the positron scattering case, making interesting, a comparative study. However, before thinking about comparisons, we have to address the question if, in fact, a Feshbach resonance manifests itself in the positron scattering by Hydrogen molecules. This issue is motivated by the fact that recent measured cross sections have not shown the same features presented by our earlier calculated Feshbach resonance in positron-Hydrogen collisions, carried out in the fixed-nuclei approach for the equilibrium internuclear distance, Ro=1.4ao. Our strategy was to calculate cross sections, still in the fixed nuclei approach, for several internuclear distances around Ro. The obtained results suggest that the experimental absence of the resonance is related to the opening of a new electronic channel for R > Ro. For these calculations we have used the Schwinger Multichannel Method (SMC) to obtain the collision parameters (position and width of the resonances) in combination with the Local Complex Potential approach (also known for Boomerang Model), for inclusion of the coupling of the vibrational degrees of freedom. The absence of the resonance for some internuclear distantes prevents the calculation of vibrationally resolved cross sections by positron impact using the local approach. On the other hand, for the electron scattering case, which is also a challange as a theoretical problem, we have carried out the calculation and have found good agreement with available experimental data / Mestrado / Física Atômica e Molecular / Mestre em Física

The estimation of power spectral densities is a critical step in many speech enhancement algorithms. The demand for multi-channel speech enhancement systems is high with applications in teleconferencing, cellular phones, and hearing aids. The first objective of the thesis is to develop a general multi-channel framework to solve for the diffuse noise power spectral densities whenever the spatial correlation or coherence matrix is pre-estimated and the number of speakers is less than the number of microphones. The second objective is to develop closed-form analytical solutions. The performance of the developed algorithms is evaluated with pre-existing algorithms using prescribed performance measures.

Niche banks emerged from deregulation of the financial market and from the increasing distrust of the established banking oligopoly in Sweden. From its establishment, niche banks narrowed their scope and targeted certain profitable segments of the banking market. The proliferation of the technological development of Customer Relationship Management (CRM) enables banks to collect information and gain more control over its customer base. To create meaningful relationships and retain customers, niche banks reaches out through the convenience of both online and offline channels to provide their products and services. With the support of two Swedish niche banks, namely Länsförsäkringar Bank and ICA Bank, the objective of this study is to understand how Swedish niche banks operate their CRM strategies and how they retain customers across channels. A mixture of deductive and inductive approaches has been used in handling our data. The empirical data collected from interviews was analysed together with secondary data to fulfil our research purpose. The result from this thesis illuminates that there are contrasting views of how CRM systems are used practically within the chosen niche banks. LF Bank’s CRM system falls back on the human factor rather than the technological advancement, while ICA Bank utilizes their CRM as a digital fundament in customer building.

The advent of the Internet, the influx of technology comparison shopping, and the evolvement of channels have increased the knowledge base of the consumer to the point where some scholars claim the multichannel consumer has more knowledge and control than the salesperson. Selling to a customer who has the control is a challenge for retailers and their sales forces. The purpose of this research is to examine the underlying decision process of the multichannel consumer and the impact of the retail salesperson. This present study tests a conceptual model that suggests multichannel consumers' perceptions of information asymmetry lead to perceived control and purchase intention. Based upon the model, the salesperson's new role is to motivate purchase intention by using adaptive selling to affect the consumer's perception of information asymmetry and perceived control. Using a scenario-based methodology tested with a sample of 307 multichannel consumers, the current investigation examined the impact of: (1) information asymmetry on the consumer's perceived control, (2) perceived control on purchase intention, (3) perceived control as a mediator between information asymmetry and purchase intention, (4) adaptive selling behavior on the consumer's perception of information asymmetry, and (5) adaptive selling behavior on the consumer's purchase intention. The findings revealed that if the multichannel consumer perceives an advantaged information asymmetry then perceived control and purchase intention will be impacted. Adaptive selling behavior affects the consumer's perceptions of information asymmetry but not perceived control. These findings can be used to help managers devise techniques to support the salesperson's ability to secure the sale with the multichannel consumer.

Vast majority of wireless appliances used in household, industry and medical field share the ISM frequency band. These devices need to coexist and thus are challenged to tolerate their mutual interference. One way of dealing with this is by using frequency hopping; where the device changes its radio channel periodically. Consequently, communications will not suffer from the same interference each time; instead, it should be fairer and more stable. This thesis investigates the aforementioned problem in the field of low power wireless sensor networks and Internet of Things where Contiki OS is used. We introduce a low-power pseudo-random frequency-hopping MAC protocol which is specifically characterized as a duty cycled asynchronous sender-initiated LPL style protocol. We illustrate two flavors of the protocol; one that does not use any dedicated channel and another which allows dedicated broadcast channels that can implement frequency-hopping as well. We implement the protocol in C for real hardware and extensively test and evaluate it in a simulated environment which runs Contiki. It proved to work with Contiki's IPv6 stack running RPL (the standardized routing protocol for low power and lossy wireless networks). We compare the performance of the implemented protocol to the singlechannel ContikiMAC with varying levels of interference. Results show a reduction down to 56% less radio-on time (1.50% vs. 3.4%) and 85% less latency (306 ms vs. 2050 ms) in the presence of noise, while keeping a good basecost in noise-free environments with 1.29% radio duty cycle when using 9 channels with no dedicated broadcast channels (vs. 0.80% for single channel) and 252 ms average latency(vs. 235 ms). Moreover, the results show that the multichannel protocol performance metrics converge to almost the same values regardless of the noise level. Therefore, it is recommended as a good alternative to single channel ContikiMAC in realworld deployments where noise presence is anticipated.

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第22590号 / 情博第727号 / 新制||情||124(附属図書館) / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 橋口 浩之, 教授 山本 衛, 准教授 村田 英一 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

Butiksdöden och Covid-19 har båda ändrat förutsättningarna för hur detaljhandelsföretag behöver tänka kring sina fysiska butiker för att hålla sig konkurrenskraftiga. Det har börjat ske att konsumenter köper allt mer online och med den globala epidemin så innebär det att strategierna som fungerade tidigare möjligen inte längre gör det. Syftet med denna studie är att undersöka vilken påverkan som externa händelser har på hur detaljhandelsföretag arbetar med sina försäljningskanaler. Studien gjordes genom att intervjua fem olika butiks/varuhuschefer inom stora detaljhandelsföretag som är verksamma i Sverige. Studien använder sig av en kvalitativ metod där semistrukturerade intervjuer användas för att samla in empirin. Teorierna som används inom studien delades in i två spår: teorier kring olika flerkanalsstrategier och konsumentbeteende. Resultatet som genererades av studien var att detaljhandelsföretagen inte har kommit fram med helt nya arbetsmetoder och strategier som åtgärd mot covid-19, utan de har istället förbättrat och utvecklat redan befintliga arbetsmetoder och strategier. Detta skiljer sig från påverkan av butiksdöden där dessa företag behövt öppna nya verksamheter och komma fram med nya strategier i samband med användningen av internet. Det här visar även på att företagen inte kan behålla sina vanliga strategier när det förekommer problem utanför deras kontroll. Resultaten visade också att det var Covid-19 som var den händelse som hade störst påverkan angående hur företagen arbetar. / The retail apocalypse and Covid-19 have both changed the landscape of retail businesses and the way these companies have to think about their physical stores. More and more customers are choosing to buy online and Covid-19 has seemed to increase this behavior even further meaning that the old strategies may no longer work. The purpose of this study was to examine what impact external events have on how retail businesses work on their sales channels. This was achieved by interviewing five different store managers in the retail business active in Sweden. The study used a qualitative method where semi structured interviews were used to collect data. The theories used were divided in two categories: theories regarding multi-channel strategies and theories regarding consumer behavior. The results that the study generated were that the retail businesses did not create new methods and strategies as a measure against Covid-19, they had instead improved and developed the already existing methods and strategies. This is in contrast to the effect of the retail apocalypse where these companies have had to open new operations and had to come up with new strategies in conjunction with the usage of the internet. This also shows that these businesses can not retain their regular strategies when faced with problems outside their own control. The results showed that Covid-19 was the event that had the biggest impact on how the companies operated.

The presence of acoustic noise in audio recordings is an ongoing issue that plagues many applications. This ambient background noise is difficult to reduce due to its unpredictable nature. Many single channel noise reduction techniques exist but are limited in that they may distort the desired speech signal due to overlapping spectral content of the speech and noise. It is therefore of interest to investigate the use of multichannel noise reduction algorithms to further attenuate noise while attempting to preserve the speech signal of interest. Specifically, this thesis looks to investigate the use of microphone arrays in conjunction with multichannel noise reduction algorithms to aid aiding in speaker identification. Recording a speaker in the presence of acoustic background noise ultimately limits the performance and confidence of speaker identification algorithms. In situations where it is impossible to control the noise environment where the speech sample is taken, noise reduction algorithms must be developed and applied to clean the speech signal in order to give speaker identification software a chance at a positive identification. Due to the limitations of single channel techniques, it is of interest to see if spatial information provided by microphone arrays can be exploited to aid in speaker identification. This thesis provides an exploration of several time domain multichannel noise reduction techniques including delay sum beamforming, multi-channel Wiener filtering, and Spatial-Temporal Prediction filtering. Each algorithm is prototyped and filter performance is evaluated using various simulations and experiments. A three-dimensional noise model is developed to simulate and compare the performance of the above methods and experimental results of three data collections are presented and analyzed. The algorithms are compared and recommendations are given for the use of each technique. Finally, ideas for future work are discussed to improve performance and implementation of these multichannel algorithms. Possible applications for this technology include audio surveillance, identity verification, video chatting, conference calling and sound source localization.

The thesis is concerned with the analysis of measuring pulse wave velocity in human body with the aid of whole-body multichannel bioimpedance which was developed at ISI AS CR, v.v.i.. The evaluation of pulse wave velocity can provide us with important information about the state of vessel compliance which is one of the basic parameters informing on their physiological state. The examination of the state of vascular system is a very important part of early diagnostics because its pathological states are the main contributor to the rise of cardiovascular diseases and disease mortality. The thesis is concerned with the theoretical analysis together with the available methods of valuation of the state of vascular system that use measuring of pulse wave velocity. The main part of the thesis deals with the analysis of the whole-body multichannel bioimpedance measurement. The proposed and programmed protocol that summarizes and visualizes all obtained information is a part of this thesis. This is currently used as an output of the experimental measurement by this method. Data file for statistical processing contains the values of the pulse wave velocity of 35 healthy volunteers and subsequently the properties of pulse wave are assessed at various excitations.

The increasing popularity and widespread deployment of wireless data systems fuel the increasing demand for more spectrum. On the other hand, various studies measuring spectrum utilization show that there is a huge variation in spectrum utilization at different times and locations. In view of this, various dynamic spectrum access (DSA) methods have been proposed in order to achieve more efficient utilization of spectrum resources by virtue of exploiting the variations in spectrum demand over time and space. Implementing DSA systems in a centralized way can lead to complexity and scalability problems due to the extensive control signaling involved. Therefore distributed implementations of DSA systems in which the users can access the system resources at their own discretion have been proposed. These distributed mechanisms typically incorporate cognitive radio systems which act as agents on behalf of users to measure the radio environment and make decisions based on these measurements. On the other hand, the freedom of the users in distributed systems to form their actions can lead each user to try to maximize its benefit from the system without regard the overall performance of the DSA system. Therefore, selfish behavior can prevail in distributed systems, which is likely to degrade the system performance.In this thesis we investigate the implications of selfish decision making in dynamic spectrum access systems. To address this broad problem, we focus our analysis on a particular system which can represent the essential properties of DSA systems and thus can shed light on the performance of the broad class of DSA systems with selfish users. Specifically, we model a DSA system as a multichannel random access system which uses ALOHA for medium access, and we analyze the behavior of the selfish users by modeling the system as a non-cooperative game. In this analysis we incorporate the effect of channel state information on the decision making of the users; we consider both cases when the users act on global (complete) and on local (incomplete) information. We determine the behavior of the selfish users at the Nash equilibria of the non-cooperative game and measure the performance of the system in terms of sum and individual utilities for various user loads and amount of available resources. We try to identify how the performance of the DSA system with selfish users compares with its cooperative counterpart. By performing these analyses we provide insights into the broader question of whether selfish users can utilize spectrum resources in a DSA system as well as cooperative users. / <p>QC 20111208</p> / MultiOperator Dynamic Spectrum access (MODyS)