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991.
When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 281–288, 1998 相似文献
992.
减背景法是一种有效的运动目标检测方法,但在光照强度发生突然变化时,由于背景模型不能及时反映环境光线的变化,将产生大量的误检测点.因此采用改进的自适应混合高斯模型进行背景建模,并检测提取运动目标;当存在光线突变时,结合基于归一化互相关系数分析去除光线变化导致的误检测点.实验结果表明:新方法能有效地抑制光线变化,得到清晰的运动目标检测结果. 相似文献
993.
In this paper, we consider the classical compound Poisson risk model with two-step premium rate. Using an alternative approach, we find the explicit expressions for the Laplace transforms of joint occupation times over disjoint intervals for this model. The Laplace transforms are expressed in terms of scale functions of L\'{e}vy processes. 相似文献
994.
Namir Ghoraf 《TOP》2008,16(1):62-72
An “m-consecutive-k-out-of-n:F system” consists of n components ordered on a line; the system fails if and only if there are at least m nonoverlapping runs of k consecutive failed components. In this paper, we give a recursive formula to compute the reliability of such a system. Thereafter,
we state two asymptotic results concerning the failure time Z
n
of the system. The first result concerns a limit theorem for Z
n
when the failure times of components are not necessarily with identical failure distributions. In the second one, we prove
that, for an arbitrary common failure distribution of components, the limit system failure distribution is always of the Poisson
class.
相似文献
995.
Genshiro Kitagawa 《Annals of the Institute of Statistical Mathematics》1994,46(4):605-623
A Gaussian-sum smoother is developed based on the two filter formula for smoothing. This facilitates the application of non-Gaussian state space modeling to diverse problems in time series analysis. It is especially useful when a higher order state vector is required and the application of the non-Gaussian smoother based on direct numerical computation is impractical. In particular, applications to the non-Gaussian seasonal adjustment of economic time series and to the modeling of seasonal time series with several outliers are shown. 相似文献
996.
A. A. Melikyan 《Journal of Optimization Theory and Applications》1994,82(2):203-217
For a linear control problem using the traditional open-loop approach, a new representation for the singular control and generalized, invariant conditions for optimality are found. The phase portrait of a nonlinear control problem is considered in the neighborhood of singular trajectories. The singular paths form a hypersurface, approached by regular paths from both sides. The Bellman function for this problem is a classical (smooth) solution to a first-order PDE with nonsmooth Hamiltonian over two smooth (regular) branches, related to the halfneighborhoods of the surface. These solutions are at least twice differentiable and have first discontinuous derivatives of odd order. The invariant form for these necessary conditions is found in terms of Jacobi (Poisson) brackets, consisting of several equalities and inequalities. The latter relations guarantee the validity of the Kelley condition as well as the geometrical constraints for the singular control variables. Thus, the Kelley condition appears to be just a certain property of a smooth solution to a first-order PDE with nonsmooth Hamiltonian. All the relations, including the Hamiltonian equations of singular motion, do not use singular controls; they are based on regular Hamiltonians depending only upon the state vector and the gradient of the Bellman function (adjoint vector).This work was suported by Grant No. 93-013-16285 of the Russian Fund for Fundamental Research. 相似文献
997.
NoělLohoué证明了复对称空间上某种极大函数f+(x)=supt>0(1+t)32|Ptf(x)|的可和性可归结为‖(Δ0)12f‖(x)的可和性.作者证明了上述结果对奇数维实双曲空间成立.由于偶数维实双曲空间的热核表达式不同,因此有必要对偶数维实双曲空间的情形单独给出证明.本文的目的就是证明上述结果对偶数维实双曲空间亦成立. 相似文献
998.
Mehdi Yemloul Vincent Castola Sébastien Leclerc Daniel Canet 《Magnetic resonance in chemistry : MRC》2009,47(8):635-640
In the limit of sufficient sensitivity, natural abundance 13C offers a much better spectral resolution than proton NMR. This is due to an important chemical shift range and to proton‐decoupling conditions that yield one peak per carbon with practically no overlap. However, pulsed gradient spin echo experiments, which lead to the diffusion coefficient associated with each peak, have scarcely been employed. In this article, we present and compare different ways to access this quantity and we have effectively verified that, without any precaution, diffusion coefficients cannot be properly determined from standard procedures. The cause of such a failure is decoupling during the gradient pulses. We have used a very simple remedy that proved to be very successful on a model mixture of three monoterpenes and that appears as being of general applicability. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
999.
1000.
This paper provides a comparative investigation of simulation strategies for measuring the longevity risk associated with
predictions of mortality rates and derived estimates of life expectancy. The study considers the Lee–Carter framework and
a generalised linear Poisson model for representing the dynamics of mortality, as well as enhancements that allow for joint
modelling of the dispersion and the effect of using a negative binomial rather than a Poisson assumption.
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