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51.
52.
Morten
rregaard Nielsen 《时间序列分析杂志》2005,26(2):279-304
Abstract. We consider semiparametric estimation in time‐series regression in the presence of long‐range dependence in both the errors and the stochastic regressors. A central limit theorem is established for a class of semiparametric frequency domain‐weighted least squares estimates, which includes both narrow‐band ordinary least squares and narrow‐band generalized least squares as special cases. The estimates are semiparametric in the sense that focus is on the neighbourhood of the origin, and only periodogram ordinates in a degenerating band around the origin are used. This setting differs from earlier studies on time‐series regression with long‐range dependence, where a fully parametric approach has been employed. The generalized least squares estimate is infeasible when the degree of long‐range dependence is unknown and must be estimated in an initial step. In that case, we show that a feasible estimate which has the same asymptotic properties as the infeasible estimate, exists. By Monte Carlo simulation, we evaluate the finite‐sample performance of the generalized least squares estimate and the feasible estimate. 相似文献
53.
54.
55.
李静 《制冷与空调(北京)》2007,7(2):86-88
介绍新型节流装置——线性浮阀的结构、工作原理、特点及其在大型冷水机组中的应用以及实际使用中可能存在的问题,为在设计具有较高能效比的中大型冷水机组中,在节流机构选择应用上提供更大的选择空间。 相似文献
56.
This study is concerned with the stability of a two-dimensional incompressible conducting liquid film surrounded by a passive
conducting medium, when an electric field is applied in a direction parallel to the initially flat bounding fluid interfaces.
Currents generate charges at the bounding interfaces which in turn affect the stress balances there. In the absence of an
electric field, the viscous liquid film is stable (instability can be induced by the inclusion of van der Waals forces for
ultra thin films). A complete model is presented, at arbitrary Reynolds number, which accounts for conductivity and permittivity
contrasts between the fluid and surrounding medium, as well as surface tension. The linear stability of the system is considered
for arbitrary Reynolds numbers and it is shown that the stable film can become unstable if, (i) σ
R
ɛ
p
>1, or (ii) σ
R
ɛ
p
<1 and (σ
R
−1)(1−ɛ
p
)<0, where σ
R
is the ratio of outer to inner conductivity and ε
p
is the ratio of inner to outer permittivity. Instability is possible only if the electric field is non-zero and the scalings
near bifurcation points that can be used to construct nonlinear theories are calculated. Several asymptotic limits are also
considered including zero Reynolds numbers and short or long waves. The instability criteria given above are constructed explicitly
in the case of Stokes flow. 相似文献
57.
In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
58.
CAO Wei-feng WANG Wen-boBeijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2005,12(4)
1IntroductionCurrently,smart antenna technology can greatly en-hance system performance and i mprove the system ca-pacity so that it has been considered as a keytechnologyinthe third generation wireless communicationsystems .The researches on channel model , beamforming algo-rithms and receive algorithms have been widely carriedout and a great many of proposition have beensubmittedtothe 3th Generation Project Partner (3GPP) . Fromthe viewpoint of link-level and system-level research,many asp… 相似文献
59.
对称配筋小偏心受压构件的截面设计 总被引:4,自引:1,他引:3
对小偏心受压构件在对称配筋情况下的截面配筋计算,提出用最佳一次逼近多项式简化基本公式,直接按二次方程求解ξ的近似方法,具有精度高,相对误差小,计算方便等优点,可供工程设计人员参考。 相似文献
60.
基于MATLAB在化工优化设计中的应用 总被引:2,自引:0,他引:2
结合化工优化计算的实例,着重介绍如何应用MATLAB7.0提供的优化工具箱来对线性规划及非线性规划模型进行求解。 相似文献