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91.
92.
Mobile networks are becoming nothing but a way to allow ubiquitous access to multimedia services. To allow efficient use of
resources, new systems provide flexible bandwidth and different error protection techniques to match channel behavior. As
the backbone network is increasingly becoming based on packet techniques and in particular on IP and related transport protocols,
end to end service quality must be analyzed considering both the fixed and the mobile part. Source scalability may help in
coping with a mixed and heterogeneous environment. In this work we present some results of a transmission chain comprising
a scalable MPEG-2 coder, an IP network and a radio access exploiting the availability of satellites. It is shown that for
a given target rate, differentiated coding can be exploited to achieve decodability and good quality at a channel SNR much
lower that single layer streams.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
93.
M. R. JOYCE K. K. LEE S. SYNGELLAKIS P. A. S. REED 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(11):1025-1036
Complex multi‐phase Al–Sn–Si alloys are commonly employed in the manufacture of small automotive plain bearings. The fundamental fatigue initiation behaviour of this class of alloys is currently not well understood. A range of analytical techniques were applied to investigate preferential initiation site location and to attempt to identify critical microstructural features. It was apparent from experimental studies that points of fatigue crack initiation are associated with the Si secondary phase. Using tessellation approaches and subsequently both adaptive numerical modelling and micro‐scale finite element modelling allowed the identification of features affecting the probability that a given Si phase would initiate a fatigue crack. 相似文献
94.
自适应RBF神经网络在CDMA移动通信上行链路功率控制中的应用研究 总被引:1,自引:0,他引:1
提出了一种自适应RBF神经网络功率控制方案。详细研究了该网络在DS-CDMA通信中,进行上行链路闭环功率控制(基于信扰比(SIR))的应用理论,给出了该网络参数的计算方法。最后用计算机仿真法模拟出该控制器的运行性能。结果表明基于SIR的自适应RBF神经网络功率控制器能自适应地调整移动台的发射功率,使基站接收信号的信扰比始终非常接近于一个常数,且有比定步长功率控制更小的SIR跟踪误差,从而可以降低接收信号的中断概率、提高信道容量。 相似文献
95.
One of the main problems faced while configuring or reconfiguring manufacturing systems is to rank alternative designs taking into account all the different aspects involved (both tangible and intangible). For this purpose the Analytic Hierarchy Process (AHP) is a well-known decision making support method that addresses this problem. A major drawback of AHP is that uncertainty in the judgments of the decision makers and the resulting impact on the ranking is not considered. In real situations, however, judgments based on perceived future scenarios are almost always uncertain. To solve this problem in this paper we present the first complete probabilistic extension to the AHP method. The new method provides the decision maker not only with information on the ranking of the alternatives but also the probability that the ranking remains stable even in presence of uncertainty in the judgements. We verified the validity of the new method in a real application developed for the Ferrari racing team. 相似文献
96.
The design of an adaptive nonlinear controller for the control of a fluidized bed reactor is derived by using exact linearization techniques. Reset action and parameter adaptation are used to make more robust the precise compensation of nonlinear terms, which is called for in the linearization technique. A nonlinear antiwindup mechanism is introduced to handle reset windup problem and to provide fast response without large overshoot. Simulation results show that the proposed adaptive controller guarantees good setpoint tracking. The developed estimation algorithm allows accurate estimation of the parameters for which the regressor component is not zero. 相似文献
97.
Ramon R. Costa Liu Hsu 《International Journal of Adaptive Control and Signal Processing》1992,6(1):19-33
A variable structure model reference adaptive controller (VS-MRAC) using only input and output measurements was recently proposed and shown to be globally asymptotically stable with superior transient behaviour and disturbance rejection properties. In this paper a singular perturbation approach is used in order to establish the robustness of the controller in the presence of unmodelled dynamics (parasitics) and disturbances. We develop a new Lyapunov-based technique to analyse the overall system and show that for sufficiently small parasitics the system remains stable and the output error is small in some sense. 相似文献
98.
具有Hammerstein形式的非线性系统广义预测控制 总被引:14,自引:2,他引:12
本文提出了具有Hammerstein形式的非线性系统广义预测控制方法,分析了当控制水平等于1时闭环系统的稳定性,同时还提出了使用线性估计器的非线性自适应广义预测控制算法。仿真结果表明了算法的有效性。 相似文献
99.
Ibrahim H. Osman Nicos Christofides 《International Transactions in Operational Research》1994,1(3):317-336
The capacitated clustering problem (CCP) is the problem in which a given set of weighted objects is to be partitioned into clusters so that the total weight of objects in each cluster is less than a given value (cluster ‘capacity’). The objective is to minimize the total scatter of objects from the ‘centre’ of the cluster to which they have been allocated. A simple constructive heuristic, a R-interchange generation mechanism, a hybrid simulated annealing (SA) and tabu search (TS) algorithm which has computationally desirable features using a new non-monotonic cooling schedule, are developed. A classification of the existing SA cooling schedules is presented. The effects on the final solution quality of the initial solutions, the cooling schedule parameters and the neighbourhood search strategies are investigated. Computational results on randomly generated problems with size ranging from 50 to 100 customers indicate that the hybrid SA/TS algorithm out-performs previous simulated annealing algorithms, a simple tabu search and local descent algorithms. 相似文献
100.
A new multivariable adaptive nonlinear predictive controller is designed using a general nonlinear input-output model and variable transformations. The controller is similar in form to typical linear predictive controllers can be tuned analogously or by specifying a single parameters for each controlled variable. In addition, the design procedure is computationally efficient. The new controller is compared to a multi-loop proportional-integral (PI) controller with one-way static decoupling and to an adaptive linear predictive controller through tests on a simulated nonlinear distillation column. The new controller performed well in an experimental application to a multicomponent distillation column. 相似文献