排序方式: 共有20条查询结果,搜索用时 31 毫秒
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Nitin R. Anturkar James O. Wilkes Tasos C. Papanastasiou 《Polymer Engineering and Science》1993,33(23):1532-1539
In industrial coextrusion operations, multiple layers are frequently brought in contact with each other at different temperatures to “match” viscosities and to reduce interfacial instability. Here, a linear stability analysis of multilayer plane Poiseuille flow is carried out for real, specific polymer melts in terms of process parameters, such as temperatures and flow rates. However, heat transfer across the layers is neglected as a first approximation. Previously, it was observed that below a certain Reynolds number and above a certain relaxation time, the flow-rate ratio (or the depth ratio), above which the flow is stable to all wavelengths, can be estimated by the long-wavelength asymptotic analysis (1,3). The Reynolds numbers for the industrial flows are smaller, and the relaxation times are larger than the corresponding critical values by several orders of magnitude. Therefore, the critical stability parameters can be estimated in the present study for industrial cases using the asymptotic stability analysis at long wavelengths. Although a large number of earlier parametric studies of model fluids indicate the influence of various theological parameters, only the viscosity stratification plays an important role in the interfacial instability within the operating range of industrial coextrusion processes. 相似文献
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Switching of two-layer coded video signals in an ATM environment is considered. To eliminate the output contention of the switch, cells from both layers are stored either in a separate or a joint buffer. The impact of these buffers on the cell loss rates and the delay variation between the two layers is investigated. An alternative buffering mechanism which enhances the switch performance is given.<> 相似文献
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Ilias Politis Michail Tsagkaropoulos Tasos Dagiuklas Stavros Kotsopoulos 《Mobile Networks and Applications》2008,13(3-4):274-284
This paper proposes a power efficient multipath video packet scheduling scheme for minimum video distortion transmission (optimised Video QoS) over wireless multimedia sensor networks. The transmission of video packets over multiple paths in a wireless sensor network improves the aggregate data rate of the network and minimizes the traffic load handled by each node. However, due to the lossy behavior of the wireless channel the aggregate transmission rate cannot always support the requested video source data rate. In such cases a packet scheduling algorithm is applied that can selectively drop combinations of video packets prior to transmission to adapt the source requirements to the channel capacity. The scheduling algorithm selects the less important video packets to drop using a recursive distortion prediction model. This model predicts accurately the resulting video distortion in case of isolated errors, burst of errors and errors separated by a lag. Two scheduling algorithms are proposed in this paper. The Baseline scheme is a simplified scheduler that can only decide upon which packet can be dropped prior to transmission based on the packet’s impact on the video distortion. This algorithm is compared against the Power aware packet scheduling that is an extension of the Baseline capable of estimating the power that will be consumed by each node in every available path depending on its traffic load, during the transmission. The proposed Power aware packet scheduling is able to identify the available paths connecting the video source to the receiver and schedule the packet transmission among the selected paths according to the perceived video QoS (Peak Signal to Noise Ratio—PSNR) and the energy efficiency of the participating wireless video sensor nodes, by dropping packets if necessary based on the distortion prediction model. The simulation results indicate that the proposed Power aware video packet scheduling can achieve energy efficiency in the wireless multimedia sensor network by minimizing the power dissipation across all nodes, while the perceived video quality is kept to very high levels even at extreme network conditions (many sensor nodes dropped due to power consumption and high background noise in the channel). 相似文献
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Nadia Magnenat-Thalmann Achille Peternier Xavier Righetti Mingyu Lim George Papagiannakis Tasos Fragopoulos Kyriaki Lambropoulou Paolo Barsocchi Daniel Thalmann 《The Visual computer》2008,24(7-9):827-836
In this paper, we introduce a European research project, interactive media with personal networked devices (INTERMEDIA) in which we seek to progress beyond home and device-centric convergence toward truly user-centric convergence of multimedia. Our vision is to make the user the multimedia center: the user as the point at which multimedia services and the means for interacting with them converge. This paper proposes the main research goals in providing users with a personalized interface and content independent of physical networked devices, and space and time. As a case study, we describe an indoors, mobile mixed reality guide system: Chloe@University. With a see-through head-mounted display (HMD) connected to a small wearable computing device, Chloe@University provides users with an efficient way to guide someone in a building. A 3D virtual character in front of the user guides him/her to the required destination. 相似文献
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Ilias Politis Lampros Dounis Tasos Dagiuklas 《Signal Processing: Image Communication》2012,27(8):814-826
This paper studies the impact of mobility management and seamless handover mechanisms on the perceived quality of video streaming applications. A seamless handoff scheme is proposed that incorporates IEEE 802.21 Media Independent Handover framework and a QoE-driven rate adaptation scheme, for both scalable and single layer coding. Quality of Experience (QoE) has been considered as an important parameter for network selection. The proposed scheme has been implemented and evaluated in a real test-bed network. Objective and subjective quality evaluation measurements for both H.264/AVC and H.264/SVC have been carried out. Through experimentation, QoE driven mobility of video streaming can be better maintained with H.264/SVC under the combined seamless handoff and rate adaptation functionality. 相似文献
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This paper investigates the use of the scaled conjugate gradient (SCG) algorithm in temporal-difference (TD) learning for
time series prediction. Special emphasis is given on the implementation details, after examining the theoretical background
of the algorithm and the learning methodology and how these could be combined. Simple time series (linear, sinusoidal, etc.)
as well as more complex ones, coming from real data, are used to examine the behavior of this novel combination of learning
algorithm and methodology. Preliminary experimental results indicate that the implementation as presented in this paper indeed
works, but the performance (in terms of learning speed and generalization ability) of TD learning using the SCG algorithm
is not as good as expected, at least on the representative problems examined. An attempt to rationalize these results is presented. 相似文献
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Rasool Saqib Iqbal Muddesar Dagiuklas Tasos Ul-Qayyum Zia Li Shancang 《Mobile Networks and Applications》2020,25(1):153-163
Mobile Networks and Applications - Mobile Ad-hoc Cloud (MAC) is the constellation of nearby mobile devices to serve the heavy computational needs of the resource-constrained edge devices. One of... 相似文献