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51.
Today's intelligent navigation and transportation systems influence the way travelers access information to plan trips efficiently. By and large, such systems derive their navigational suggestions out of precompiled data regarding direct road connections recorded in their databases. They typically facilitate passenger navigation within predefined geographic regions, provide location tracing and direction functionalities over cellular networks or the Web and deliver accurate but not necessarily optimal transition paths. This article proposes EasyTransport, an intelligent navigation and multimodal transportation guidance system that focuses on near-optimal trajectory planning and informed decision making. EasyTransport introduces a number of novel features. The EasyTransport system helps travelers plan the most efficient route and choose the best modes of transportation in urban or large-scale geographic areas. Users can adapt the generated outcomes through an interactive interface. 相似文献
52.
On average throughput and alphabet size in network coding 总被引:1,自引:0,他引:1
Chekuri C. Fragouli C. Soljanin E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(6):2410-2424
We examine the throughput benefits that network coding offers with respect to the average throughput achievable by routing, where the average throughput refers to the average of the rates that the individual receivers experience. We relate these benefits to the integrality gap of a standard linear programming formulation for the directed Steiner tree problem. We describe families of configurations over which network coding at most doubles the average throughput, and analyze a class of directed graph configurations with N receivers where network coding offers benefits proportional to /spl radic/N. We also discuss other throughput measures in networks, and show how in certain classes of networks, average throughput bounds can be translated into minimum throughput bounds, by employing vector routing and channel coding. Finally, we show configurations where use of randomized coding may require an alphabet size exponentially larger than the minimum alphabet size required. 相似文献
53.
We consider designing near video on demand (NVOD) systems that minimize startup latency while maintaining high image quality. Recently nonuniform segmentation has been used to develop periodic broadcasting techniques for NVOD. These techniques give significant reductions in startup latency as compared with more conventional uniform segmentation. Essentially all of these schemes assume, however, that the videos are CBR-encoded. Since a CBR-encoded video has a larger average rate than an open-loop VBR encoding with the same image quality, there is potential to obtain further performance improvements by using VBR video. In this paper we develop a series of multiplexing schemes for the periodic broadcasting of VBR-encoded video that are based on smoothing, server buffering, and client prefetching. Two key but conflicting performance measures exist when using VBR video: latency and packet loss. By introducing small additional delays in our multiplexing schemes, our trace-based numerical work shows that the schemes can achieve nearly 100% link utilization with negligible packet loss. When the ratio of the CBR rate to the VBR average rate is a modest 1.8, startup latency can be reduced by a factor of four or more for common scenarios.Martin Reisslein: Correspondence to: A shorter version of this paper appeared in Proceedings of IEEE Infocom 99, New York, March 1999, pp 464-471 相似文献
54.
Quantitative polymerase chain reaction (PCR) may be performed by two general approaches, namely, real-time PCR and quantitative competitive PCR (QC-PCR). QC-PCR makes use of the concept of a DNA competitor, which is the "gold standard" approach to circumvent the problem of the variation of amplification efficiency. However, QC-PCR in its classical form is a low-throughput method since it requires titration of each sample with the competitor followed by electrophoresis. The throughput of QC-PCR has been improved by capillary electrophoresis and microtiter well-based hybridization assays. The present work introduces a multiplex QC-PCR method, which is based on a multianalyte hybridization assay that is performed on spectrally encoded microspheres. The DNA competitors use the same primers and have equal size with their corresponding target DNA sequences but differ in a short (24 bp) centrally located sequence. Following multiplex PCR, biotinylated amplification products from all DNA targets and competitors are heat-denatured and hybridized with oligonucleotide probes, which are attached to addressable sets of fluorescent microspheres. The hybrids react with a streptavidin-phycoerythrin conjugate. The microspheres are then analyzed by flow cytometry employing two lasers. A red laser line is used for classification of the microspheres, and a green line excites phycoerythrin, whose fluorescence is related to the concentration of the analyte DNA. As a model, we have developed a multiplex quantitative competitive PCR assay for four targets. The amplification products from targets and competitors (a total of 8 DNA fragments) are determined simultaneously by the multianalyte hybridization assay. The limits of quantification for the hybridization assay of all amplified DNA fragments are below 13 pM. The multiplex quantitative competitive PCR assay detects approximately 500 copies from each target DNA. To our knowledge, the proposed method is the only approach to quantitative PCR that offers such a high potential for multiplexing. 相似文献
55.
Poly(p‐phenylene) (H‐PPP), which is one of the firstly investigated conducting polymer, has the disadvantage of difficult processability because it is infusible and insoluble. The use of biphenyl instead of benzene leads to ortho‐, meta‐, para‐polyphenylenes (H‐PP) which are more soluble and easier to be processed, however their electrical conductivity is lower. Copolymers of polyphenylenes (C1 and C2) and corresponding homopolymers (H‐PPP and H‐PP) were produced by the oxidative cationic polymerization of benzene and/or biphenyl. The soluble (‐S) and the insoluble (‐I) in chlorobenzene polyphenylenes were separated (H‐PP‐I, H‐PP‐S, C1‐I, C1‐S, C2‐I, and C2‐S) and they were doped with a solution of FeCl3. All polyphenylenes were studied by FTIR, XRD, TGA, and their electrical conductivity with constant current was determined. Pronounced differences between the copolymers and the homopolymers were observed, indicating the different structure of the former. The values of the electrical conductivity of doped insoluble copolymers (10?4 and 10?5 S/cm) are between that of H‐PPP (10?3 S/cm) and H‐PP‐I (10?6 S/cm). The values of the electrical conductivity of doped soluble copolymers (10?5 S/cm) are considerably higher than that of H‐PP‐S (10?9 S/cm). The new electrically conductive polyphenylenes that were produced differ significantly from the corresponding homopolymers and combine good electrical conductivity and solubility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
56.
Despina Louca T. Egami G. H. Kwei 《Journal of Superconductivity and Novel Magnetism》1999,12(1):291-293
Lattice polarons play an important role in the mechanism of colossal magnetoresistance in the (La/Sr) n+1Mn n O3n+1 manganites. Local lattice distortions were characterized by the pulsed neutron pair density function (PDF) analysis. The result shows that the doped holes form polarons related to the Jahn–Teller (JT) effect, both in the two-dimensional layered crystals (n=2) and in the perovskites (n=∞). The temperature effects are also similar in both systems suggesting that lattice polarons are largely independent of the crystal symmetry. 相似文献
57.
Dumitru Constantin-Teodosiu Despina Constantin 《International journal of molecular sciences》2021,22(21)
Muscle fatigue (MF) declines the capacity of muscles to complete a task over time at a constant load. MF is usually short-lasting, reversible, and is experienced as a feeling of tiredness or lack of energy. The leading causes of short-lasting fatigue are related to overtraining, undertraining/deconditioning, or physical injury. Conversely, MF can be persistent and more serious when associated with pathological states or following chronic exposure to certain medication or toxic composites. In conjunction with chronic fatigue, the muscle feels floppy, and the force generated by muscles is always low, causing the individual to feel frail constantly. The leading cause underpinning the development of chronic fatigue is related to muscle wasting mediated by aging, immobilization, insulin resistance (through high-fat dietary intake or pharmacologically mediated Peroxisome Proliferator-Activated Receptor (PPAR) agonism), diseases associated with systemic inflammation (arthritis, sepsis, infections, trauma, cardiovascular and respiratory disorders (heart failure, chronic obstructive pulmonary disease (COPD))), chronic kidney failure, muscle dystrophies, muscle myopathies, multiple sclerosis, and, more recently, coronavirus disease 2019 (COVID-19). The primary outcome of displaying chronic muscle fatigue is a poor quality of life. This type of fatigue represents a significant daily challenge for those affected and for the national health authorities through the financial burden attached to patient support. Although the origin of chronic fatigue is multifactorial, the MF in illness conditions is intrinsically linked to the occurrence of muscle loss. The sequence of events leading to chronic fatigue can be schematically denoted as: trigger (genetic or pathological) -> molecular outcome within the muscle cell -> muscle wasting -> loss of muscle function -> occurrence of chronic muscle fatigue. The present review will only highlight and discuss current knowledge on the molecular mechanisms that contribute to the upregulation of muscle wasting, thereby helping us understand how we could prevent or treat this debilitating condition. 相似文献
58.
Efficient Broadcasting Using Network Coding 总被引:3,自引:0,他引:3
We consider the problem of broadcasting in an ad hoc wireless network, where all nodes of the network are sources that want to transmit information to all other nodes. Our figure of merit is energy efficiency, a critical design parameter for wireless networks since it directly affects battery life and thus network lifetime. We prove that applying ideas from network coding allows to realize significant benefits in terms of energy efficiency for the problem of broadcasting, and propose very simple algorithms that allow to realize these benefits in practice. In particular, our theoretical analysis shows that network coding improves performance by a constant factor in fixed networks. We calculate this factor exactly for some canonical configurations. We then show that in networks where the topology dynamically changes, for example due to mobility, and where operations are restricted to simple distributed algorithms, network coding can offer improvements of a factor of , where is the number of nodes in the network. We use the insights gained from the theoretical analysis to propose low-complexity distributed algorithms for realistic wireless ad hoc scenarios, discuss a number of practical considerations, and evaluate our algorithms through packet level simulation. 相似文献
59.
Water Resources Management - Providers of municipal water supply services worldwide are facing pressure from climate change and increasing water demand due to growing populations and lifestyle... 相似文献
60.
Despina C. Moschou Giannis P. Kontogiannopoulos Apostolos T. Voutsas 《Microelectronics Reliability》2010,50(2):190-194
In this work we point out the importance of the device parameter Vg,max-Vth (the difference between the gate voltage at maximum transconductance and the threshold voltage obtained from linear extrapolation method) for LTPS TFTs under dc stress. The evolution of this parameter with stress time is monitored for the first time, along with the other typical device parameters (Vth, Gm,max, S) in order to further clarify the nature of the traps generated. In the first dc stress case considered, we observed very different S degradation of the two samples, but very similar Gm,max degradation, as well as similar Vg,max-Vth evolution. Therefore, Gm,max evolution with stress time was found to be related more strongly to tail state generation, probed through Vg,max-Vth, and not to midgap trap generation, probed through S. In the second case, no midgap state generation is observed, but only severe tail state generation. Hence, the nature of the created defects and the reason for the significant Gm,max reduction could only be probed through the observation of Vg,max-Vth, a parameter not utilized until now. Finally, stressing both n- and p-channel devices, we are able to explain the much more intense Gm,max degradation observed for n-channel devices, associating it to the larger tail state generation in n-channel TFTs, also pointed by Vg,max-Vth evolution with stress. 相似文献