913 resultados para one way delay


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Mode of access: Internet.

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Mode of access: Internet.

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We show that the one-way channel formalism of quantum optics has a physical realization in electronic systems. In particular, we show that magnetic edge states form unidirectional quantum channels capable of coherently transporting electronic quantum information. Using the equivalence between one-way photonic channels and magnetic edge states, we adapt a proposal for quantum state transfer to mesoscopic systems using edge states as a quantum channel, and show that it is feasible with reasonable experimental parameters. We discuss how this protocol may be used to transfer information encoded in number, charge, or spin states of quantum dots, so it may prove useful for transferring quantum information between parts of a solid-state quantum computer

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There is an alternative model of the 1-way ANOVA called the 'random effects' model or ‘nested’ design in which the objective is not to test specific effects but to estimate the degree of variation of a particular measurement and to compare different sources of variation that influence the measurement in space and/or time. The most important statistics from a random effects model are the components of variance which estimate the variance associated with each of the sources of variation influencing a measurement. The nested design is particularly useful in preliminary experiments designed to estimate different sources of variation and in the planning of appropriate sampling strategies.

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In Statnote 9, we described a one-way analysis of variance (ANOVA) ‘random effects’ model in which the objective was to estimate the degree of variation of a particular measurement and to compare different sources of variation in space and time. The illustrative scenario involved the role of computer keyboards in a University communal computer laboratory as a possible source of microbial contamination of the hands. The study estimated the aerobic colony count of ten selected keyboards with samples taken from two keys per keyboard determined at 9am and 5pm. This type of design is often referred to as a ‘nested’ or ‘hierarchical’ design and the ANOVA estimated the degree of variation: (1) between keyboards, (2) between keys within a keyboard, and (3) between sample times within a key. An alternative to this design is a 'fixed effects' model in which the objective is not to measure sources of variation per se but to estimate differences between specific groups or treatments, which are regarded as 'fixed' or discrete effects. This statnote describes two scenarios utilizing this type of analysis: (1) measuring the degree of bacterial contamination on 2p coins collected from three types of business property, viz., a butcher’s shop, a sandwich shop, and a newsagent and (2) the effectiveness of drugs in the treatment of a fungal eye infection.

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In IP networks, most of packets, that have been dropped, are recovered after the expiration of retransmission timeouts. These can result in unnecessary retransmissions and needless reduction of congestion window. An inappropriate retransmission timeout has a huge impact on TCP performance. In this paper we have proved that CSMA/CA mechanism can cause TCP retransmissions due to CSMA/CA effects. For this we have observed three wireless connections that use CSMA/CA: with good link quality, poor link quality and in presence of cross traffic. The measurements have been performed using real devices. Through tracking of each transmitted packet it is possible to analyze the relation between one-way delay and packet loss probability and the cumulative distribution of distances between peaks of OWDs. The distribution of OWDs and the distances between peaks of OWDs are the most important parameters of tuning TCP retransmission timeout on CSMA/CA networks. A new perspective through investigating the dynamical relation between one-way delay and packet loss ratio depending on the link quality to enhance the TCP performance has been provided.

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Wireless mesh networks present an attractive communication solution for various research and industrial projects. However, in many cases, the appropriate preliminary calculations which allow predicting the network behavior have to be made before the actual deployment. For such purposes, network simulation environments emulating the real network operation are often used. Within this paper, a behavior comparison of real wireless mesh network (based on 802.11s amendment) and the simulated one has been performed. The main objective of this work is to measure performance parameters of a real 802.11s wireless mesh network (average UDP throughput and average one-way delay) and compare the derived results with characteristics of a simulated wireless mesh network created with the NS-3 network simulation tool. Then, the results from both networks are compared and the corresponding conclusion is made. The corresponding results were derived from simulation model and real-worldtest-bed, showing that the behavior of both networks is similar. It confirms that the NS-3 simulation model is accurate and can be used in further research studies.

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Доклад, поместен в сборника на Националната конференция "Образованието в информационното общество", Пловдив, май, 2012 г.

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In the last decade, both scientific community and automotive industry enabled communications among vehicles in different kinds of scenarios proposing different vehicular architectures. Vehicular delay-tolerant networks (VDTNs) were proposed as a solution to overcome some of the issues found in other vehicular architectures, namely, in dispersed regions and emergency scenarios. Most of these issues arise from the unique characteristics of vehicular networks. Contrary to delay-tolerant networks (DTNs), VDTNs place the bundle layer under the network layer in order to simplify the layered architecture and enable communications in sparse regions characterized by long propagation delays, high error rates, and short contact durations. However, such characteristics turn contacts very important in order to exchange as much information as possible between nodes at every contact opportunity. One way to accomplish this goal is to enforce cooperation between network nodes. To promote cooperation among nodes, it is important that nodes share their own resources to deliver messages from others. This can be a very difficult task, if selfish nodes affect the performance of cooperative nodes. This paper studies the performance of a cooperative reputation system that detects, identify, and avoid communications with selfish nodes. Two scenarios were considered across all the experiments enforcing three different routing protocols (First Contact, Spray and Wait, and GeoSpray). For both scenarios, it was shown that reputation mechanisms that punish aggressively selfish nodes contribute to increase the overall network performance.

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In many research areas (such as public health, environmental contamination, and others) one deals with the necessity of using data to infer whether some proportion (%) of a population of interest is (or one wants it to be) below and/or over some threshold, through the computation of tolerance interval. The idea is, once a threshold is given, one computes the tolerance interval or limit (which might be one or two - sided bounded) and then to check if it satisfies the given threshold. Since in this work we deal with the computation of one - sided tolerance interval, for the two-sided case we recomend, for instance, Krishnamoorthy and Mathew [5]. Krishnamoorthy and Mathew [4] performed the computation of upper tolerance limit in balanced and unbalanced one-way random effects models, whereas Fonseca et al [3] performed it based in a similar ideas but in a tow-way nested mixed or random effects model. In case of random effects model, Fonseca et al [3] performed the computation of such interval only for the balanced data, whereas in the mixed effects case they dit it only for the unbalanced data. For the computation of twosided tolerance interval in models with mixed and/or random effects we recomend, for instance, Sharma and Mathew [7]. The purpose of this paper is the computation of upper and lower tolerance interval in a two-way nested mixed effects models in balanced data. For the case of unbalanced data, as mentioned above, Fonseca et al [3] have already computed upper tolerance interval. Hence, using the notions persented in Fonseca et al [3] and Krishnamoorthy and Mathew [4], we present some results on the construction of one-sided tolerance interval for the balanced case. Thus, in order to do so at first instance we perform the construction for the upper case, and then the construction for the lower case.

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Consumer relations, established between the Consumer and the Creditor, which carry a consequent inequality of contractual positioning between the parties, have been pushing the legislator to adopt more rigid regulations with regard to lending for the purchase of goods or services of consum issues. In this sense, the Decree-Law 359/91 was approved, meanwhile repealed by the Decree-Law 133/2009, which regulates the consumer credit agreement’s regime in the portuguese legal system. Through this contract, the financier makes available to the consumer a certain amount of money, which the consumer must repay, plus the respective remuneration (interest) and other charges, according to a refund plan agreed by the parties. The consumer will be in delay if he breaches this stipulation. In case of default, the creditor, notwithstanding, can choose to wait for the performance by the debtor, promote the loss of benefit of the term or the termination of the contract. From the outset it would seem that, in one way or another, the financier, by imposing a forced shortening of the contract duration initially agreed, will lose the right to remuneration for the provision of capital agreed, but not verified. Nevertheless, unlike presently, the previous regime allowed the parties to rule otherwise, being permitted to agree to the payment of interest of outstanding installments. On the other hand, in the consumer credit contract the principle of freedom of contractual provision of the parties is strongly mitigated by the special legislation, which prevents the waiver of rights by the consumer, and by the regime of general contractual terms, which restricts the freedom of the financier to stipulate the contractual content freely and the freedom of the consumer to negotiate. For all these reasons, associated with the growing need of credit resource to satisfy their needs of consumption, it is confirm the relevance of legislative intervention on consumers protection in the context of hiring credit.

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Consumer relations, established between the Consumer and the Creditor, which carry a consequent inequality of contractual positioning between the parties, have been pushing the legislator to adopt more rigid regulations with regard to lending for the purchase of goods or services of consum issues. In this sense, the Decree-Law 359/91 was approved, meanwhile repealed by the Decree-Law 133/2009, which regulates the consumer credit agreement’s regime in the portuguese legal system. Through this contract, the financier makes available to the consumer a certain amount of money, which the consumer must repay, plus the respective remuneration (interest) and other charges, according to a refund plan agreed by the parties. The consumer will be in delay if he breaches this stipulation. In case of default, the creditor, notwithstanding, can choose to wait for the performance by the debtor, promote the loss of benefit of the term or the termination of the contract. From the outset it would seem that, in one way or another, the financier, by imposing a forced shortening of the contract duration initially agreed, will lose the right to remuneration for the provision of capital agreed, but not verified. Nevertheless, unlike presently, the previous regime allowed the parties to rule otherwise, being permitted to agree to the payment of interest of outstanding installments. On the other hand, in the consumer credit contract the principle of freedom of contractual provision of the parties is strongly mitigated by the special legislation, which prevents the waiver of rights by the consumer, and by the regime of general contractual terms, which restricts the freedom of the financier to stipulate the contractual content freely and the freedom of the consumer to negotiate. For all these reasons, associated with the growing need of credit resource to satisfy their needs of consumption, it is confirm the relevance of legislative intervention on consumers protection in the context of hiring credit.