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Bakgrund: Med digital utveckling ökar användandet av digitala kanaler för att köpa produkter. Utvecklingen sätter ökad press på handeln att utveckla sitt digitala erbjudande. Problemformulering: Förutsättningarna att driva handel skiljer sig åt online jämfört med offline, sett både ur perspektiv från återförsäljare och köpare. Begränsad yta i en fysisk butik i närområdet jämfört med stort centralt lager för e-handel ger olika förutsättningar för vilka produkter som kan erbjudas. Konsumenten med tillgång till näst intill oändligt antal affärer digitalt med enkel jämförelse av pris och produkter. Syfte: Syftet med denna uppsats är att undersöka hur försäljningskoncentrationen av produkter i dagligvaruhandeln i Sverige skiljer sig mellan e-handel och fysisk butik. Forskningsfrågor: Hur fördelas försäljningen av produkter online jämfört med fysisk butik?  Är försäljningen i fysisk butik mer koncentrerad till färre produkter jämfört med online handel? Teori: Både longtail-fenomenet och paretoprincipen existerar praktiskt och litterärt, men det beror på vilken typ av produkt, period och marknad det gäller om begreppen är sanna eller inte. Metod: Kvantitativ metod med primärdata från dagligvaruhandeln där 2 585 produkters försäljning online och offline analyserats med en kombination av RStudio och Microsoft Excel. Slutsatser: Försäljningen är mer koncentrerad till ett lägre antal produkter online jämfört med offline. Det finns dock variationer mellan produktkategorier. Nyckelord: Longtail, pareto, superstars, dagligvaror, e-handel, omni-channel, multi-channel, försäljningskoncentration. / Background: Digital development has increased the use of digital channels to buy products. This development puts increased pressure on the retail sector to enhance its digital offerings. Problem statement: The conditions for buying and selling products differ online compared to offline for both the buyer and seller. Limited space in a physical store in the local area compared to a large central warehouse for e-commerce. Consumers have access to nearly an infinite number of digital stores with easy comparisons of prices and products. Purpose: The purpose of this thesis is to examine how the sales concentration of products in the grocery retail sector in Sweden differs between e-commerce and physical stores. Research questions: How does the distribution of product sales differ online compared to physical stores? Is the sales concentration in physical stores more focused to fewer products compared to e-commerce? Theory: Both the longtail phenomenon and the Pareto principle exist practically and literarily, but their validity depends on the type of product, period, and market in question. Method: Quantitative method using primary data from the grocery retail sector, where the sales of 2 585 products online and offline have been analyzed using a combination of RStudio and Microsoft Excel. Conclusions: Sales are more concentrated to fewer products online compared to offline, there are however variations between product categories. Keywords: Long tail, Pareto, superstars, grocery, e-commerce, omni-channel, multi-channel, sales concentration.

The prospect of replacing existing fixed networks with cheap, flexible and evenmobile low-power wireless network has been a strong research driver in recent years.However, many challenges still exist: reliability is hampered by unstable and burstycommunication links; the wireless medium is getting congested by an increasingnumber of wireless devices; and life-times are limited due to difficulties in developingefficient duty-cycling mechanisms. These challenges inhibit the industry to fullyembrace and exploit the capabilities and business opportunities that low-powerwireless devices offer. In this thesis, we propose, design, implement, and evaluateprotocols and systems to increase flexibility and improve efficiency of low-powerwireless communications. First, we present MobiSense, a system architecture for energy-efficient communicationsin micro-mobility sensing scenarios. MobiSense is a hybrid architecturecombining a fixed infrastructure network and mobile sensor nodes. Simulations andexperimental results show that the system provides high throughput and reliabilitywith low-latency handoffs. Secondly, we investigate if and how multi-channel communication can mitigate theimpact of link dynamics on low-power wireless protocols. Our study is motivated bya curiosity to reconcile two opposing views: that link dynamics is best compensatedby either (i) adaptive routing, or (ii) multi-channel communication. We perform acomprehensive measurement campaign and evaluate performance both in the singlelink and over a multi-hop network. We study packet reception ratios, maximumburst losses, temporal correlation of losses and loss correlations across channels.The evaluation shows that multi-channel communication significantly reduces linkburstiness and packet losses. In multi-hop networks, multi-channel communicationsand adaptive routing achieves similar end-to-end reliability in dense topologies,while multi-channel communication outperforms adaptive routing in sparse networkswhere re-routing options are limited. Third, we address the problem of distributed information exchange in proximitybasednetworks. First, we consider randomized information exchange and assess thepotential of multi-channel epidemic discovery. We propose an epidemic neightbordiscoverymechanism that reduces discovery times considerably compared to singlechannelprotocols in large and dense networks. Then, the idea is extended todeterministic information exchange. We propose, design and evaluate an epidemicinformation dissemination mechanism with strong performance both in theory andpractice. Finally, we apply some of the concepts from epidemic discovery to the designof an asynchronous, sender-initiated multi-channel medium access protocol. Theprotocol combines a novel mechanism for rapid schedule learning that avoids perpacketchannel negotiations with the use of burst data transfer to provide efficientsupport of ’multiple contending unicast and parallel data flows. / De senaste åren har forskning inom trådlös kommunikation drivits av önskemåletom att kunna ersätta nuvarande trådbundna kommunikationslänkar med trådlösa lågenergialternativ.Dock kvarstår många utmaningar, såsom instabila och sporadiskalänkar, överbelastning på grund av en ökning i antal trådlösa enheter, hur maneffektivt kan växla duty-cycling mekanismen för att förlänga nätverkens livstid,med flera. Dessa utmaningar begränsar industrin från att ta till sig och utnyttjade fördelar som trådlösa lågenergialternativ kan medföra. I den här avhandlingenföreslår, designar, implementerar och utvärderar vi protokoll och system som kanförbättra de nuvarande trådlösa lågenergialternativen. Först presenterar vi MobiSense, en systemarkitektur för energibesparande kommunikationi mikro-mobila sensorscenarier. MobiSense är en hybridarkitektur somkombinerar ett fast infrastrukturnätverk med rörliga sensornoder. Simulerings- ochexperimentella resultat visar att systemet uppnår en högre överföringskapacitet ochtillförlitlighet samtidigt som överlämnandet mellan basstationer har låg latens. I den andra delen behandlar vi hur effekterna från länkdynamiken hos protokollför lågenergikommunikation kan minskas, och försöker förena idéerna hos två motståendesynsätt: (i) flerkanalskommunikation och (ii) adaptiv routing. Vi analyserarenkanals- och flerkanalskommunikation över en-stegslänkar i termer av andelenmottagna paket kontra andelen förlorade, den maximala sporadiska förlusten avpaket, tidskorrelation för förluster och förlustkorrelation mellan olika kanaler. Resultatenindikerar att flerkanalskommunikation med kanalhoppning kraftigt minskardet sporadiska uppträdandet hos länkarna och korrelationen mellan paketförluster.För flerstegsnätverk uppvisar flerkanalskommunikation och adaptiv routingliknande tillförlitlighet i täta topologier, medan flerkanalskommunikation har bättreprestanda än adaptiv routing i glesa nätverk med sporadiska länkar. I den tredje delen studeras distribuerat informationsutbyte i närhetsbaseradenätverk. Först betraktas det slumpmässiga fallet och vi fastställer potentialen hosflerkanalig indirekt utforskning av nätverket. Vi analyserar ett trestegs protokoll,som möjliggör en snabbare utforskning av nätverket. Sedan föreslår vi en ny algoritmför att upptäcka grannarna i ett flerkanalsnätverk, som kraftigt minskarutforskningstiden i jämförelse med ett enkanalsprotokoll. Vi utökar även problemettill det deterministiska fallet och föreslår en mekanism för informationsspridningsom påskyndar utforskningstiderna för deterministiska protokoll. Utvidgningen hartvå huvudförbättringar som leder till kraftigt ökad prestanda samtidigt som degaranterar att utforskningsprocessen är deterministisk. Till sist applicerar vi koncepten rörande indirekt utforskning för att designa,implementera och evaluera ett asynkront sändare-initierat flerkanals MAC protokollför trådlös lågenergikommunikation. Protokollet kombinerar en ny mekanism försnabbt lärande av tidsschemat, vilket undviker kanalförhandling för varje paket,med sporadisk dataöverföring. Detta möjliggör ett effektivt tillhandahållande avflera konkurrerande och parallella dataflöden. / <p>QC 20151204</p>

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Wireless data acquisition began with sensors connected to some form of radio. Emergence of the IEEE 802.11 specification made possible the evolution of a high-speed, multi-channel, wireless data acquisition system using COTS, Commercial Off-The-Shelf, technology. After developing a sub-miniature telemetry system in the S-band for the US Air Force, the system delivered to the Air Force evolved into a high-speed, wireless data acquisition system for the commercial market.

Trends in wireless networks are increasingly pointing towards a future with multi-hop networks deployed in multi-channel environments. In this thesis, we present the design for iMAC—a protocol targeted at medium access control in such environments. iMAC uses control packets on a common control channel to faciliate a three-way handshake between the sender and receiver for every packet transmission. This handshake enables the sender and receiver to come to consensus on a channel to use for data transmission and also signals to neighboring nodes about the contention on that channel. iMAC then uses a mechanism similar to 802.11 for data communication. Our evaluation of iMAC shows that it provides significant gains in throughput in comparison with uninformed channel selection, especially when contention for channel bandwidth is neither too low nor too high; intelligent selection of channels by iMAC is necessary to harness available bandwidth resources in the presence of medium levels of contention. / Graduation date: 2011

Multi-hop wireless networks based on 802. 11 are being used more widely as an alternative technology for last-mile broadband Internet access. Their benefits include ease of deployment and lower cost. Such networks are not without problems. Current research on such networks aims at a number of challenges, including overcoming capacity limitation and poor fairness. <br /><br /> The focus of our research is for achieving fairness in multi-channel multi-hop wireless networks. First, we review the literature for different methods for representing link-contention areas, and the existing single-channel fairness computational model. Second, we generalize the fairness constraints applied to each link-contention area, defined in the existing single-channel fairness reference model, to multi-channel models. Third, by adopting the concepts of link-usage matrix and medium-usage matrix to represent network topology and flow status, and using Collision Domain theory and Clique Graph theory to represent link-contention area, we develop a computational model to compute optimal MAC-layer bandwidth allocated to each flow in a multi-channel multi-hop WMN. We simulate various network configurations to evaluate the performance of the fairness algorithm based on the above computational model in different scenarios. We have found that in the multi-channel environment, our extension to the Collision Domain model generally provides a more accurate estimation of network capacity. Based on this model, we have extended the source-rate-limiting mechanism, which limits the flow rate to its fair share computed by the computational model. Experimental results that validate these findings are presented in this thesis.

The term of Cognitive Radio (CR) used to indicate that spectrum radio could be accessed dynamically and opportunistically by unlicensed users. In CR Networks, Interference between nodes, hidden terminal problem, and spectrum sensing errors are big issues to be widely discussed in the research field nowadays. To improve the performance of such kind of networks, this thesis proposes Cognitive Medium Access Control (MAC) protocols for Mobile Ad-Hoc Networks (MANETs). From the concept of CR, this thesis has been able to develop a cognitive MAC framework in which a cognitive process consisting of cognitive elements is considered, which can make efficient decisions to optimise the CR network. In this context, three different scenarios to maximize the secondary user's throughput have been proposed. We found that the throughput improvement depends on the transition probabilities. However, considering the past information state of the spectrum can dramatically increases the secondary user's throughput by up to 40%. Moreover, by increasing the number of channels, the throughput of the network can be improved about 25%. Furthermore, to study the impact of Physical (PHY) Layer errors on cognitive MAC layer in MANETs, in this thesis, a Sensing Error-Aware MAC protocols for MANETs has been proposed. The developed model has been able to improve the MAC layer performance under the challenge of sensing errors. In this context, the proposed model examined two sensing error probabilities: the false alarm probability and the missed detection probability. The simulation results have shown that both probabilities could be adapted to maintain the false alarm probability at certain values to achieve good results. Finally, in this thesis, a cooperative sensing scheme with interference mitigation for Cognitive Wireless Mesh Networks (CogMesh) has been proposed. Moreover, a prioritybased traffic scenario to analyze the problem of packet delay and a novel technique for dynamic channel allocation in CogMesh is presented. Considering each channel in the system as a sub-server, the average delay of the users' packets is reduced and the cooperative sensing scenario dramatically increases the network throughput 50% more as the number of arrival rate is increased.

This dissertation research explored the capabilities of neuronal networks grown on substrate integrated microelectrode arrays in vitro with emphasis on utilizing such preparations in three specific application domains: pharmacology and drug development, biosensors and neurotoxicology, and the study of burst and synaptic mechanisms. Chapter 1 details the testing of seven novel AChE inhibitors, demonstrating that neuronal networks rapidly detect small molecular differences in closely related compounds, and reveal information about their probable physiological effects that are not attainable through biochemical characterization alone. Chapter 2 shows how neuronal networks may be used to classify and characterize an unknown compound. The compound, trimethylol propane phosphate (TMPP) elicited changes in network activity that resembled those induced by bicuculline, a known epileptogenic. Further work determined that TMPP produces its effects on network activity through a competitive inhibition of the GABAA receptor. This demonstrates that neuronal networks can provide rapid, reliable warning of the presence of toxic substances, and from the manner in which the spontaneous activity changes provide information on the class of compound present and its potential physiological effects. Additional simple pharmacological tests can provide valuable information on primary mechanisms involved in the altered neuronal network responses. Chapter 3 explores the effects produced by a radical simplification of synaptic driving forces. With all synaptic interactions pharmacologically limited to those mediated through the NMDA synapse, spinal cord networks exhibited an extremely regular burst oscillation characterized by a period of 2.9 ± 0.3 s, with mean coefficients of variation of 3.7, 4.7, and 4.9 % for burst rate, burst duration, and inter-burst interval, respectively (16 separate cultures). The reliability of expression of this oscillation suggests that it may represent a fundamental mechanism of importance during periods of NMDA receptor dominated activity, such as embryonic and early postnatal development. NMDA synapse mediated activity produces a precise oscillatory state that allows the study of excitatory-coupled network dynamics, burst mechanisms, emergent network properties, and structure-function relationships.

This study investigated the consumers' intention towards multi-channel shopping and the function of synergy in a multi-channel retailing format (i.e., brick-and-mortar stores, catalogs, and the Internet). Two questionnaires were developed, one for the multi-channel consumers and the other for the multi-channel retailers. The structural equation modeling was used to predict the effect of shopping benefits and costs perceived from each channel on the consumer's purchase intention. Data analysis (N = 500) indicated that the purchase intentions were affected by different shopping benefit and cost variables. Qualitative analysis of retailers (N= 10) revealed that the retailers considered synergy to be an important part of their multi-channels. Also, there existed a high level of synergy among the existing three retail channels.

The process of mixing tracks for a live stage performance or studio session is both time consuming and expensive with assistance of professionals. It is also difficult for individuals to remain competitive against established companies, since multiple tracks must be properly mixed in order to achieve well-enhanced elements -- generally, a poor mix makes it difficult for the listener to distinguish the different elements of the mix. The developed method during this thesis work aims at facilitating the mixing work for live performances and studio sessions. The implemented system analyzes the energy spectrum of the tracks included in the mix. By unmasking spectral components, the spectral overlap of the tracks is minimized. The system filters non-characteristic frequencies, leaving significant frequencies undisturbed. Five tracks have been used from the final mix of a successful radio song. These tracks have been analyzed and used to illustrate and validate the developed method. The system was successfully implemented in MATLAB with promising results and conclusions. The processed mix unmasks frequency content and is perceived to sound clearer compared to the unprocessed mix by a number of test individuals. The method reminds of a multi-band compressor that analyzes the spectral information between tracks. Thus, by use of inter-spectral dependencies, the thesis investigates the possibility to control the amplitudes in time by filtration in frequency domain. The compression rate in time domain is reflected in regard to a trade-off between conservation of characteristic frequencies and reduction of spectral overlaps.