EPON媒体接入控制的关键技术研究

文章简要介绍了基于以及太网的无源光网络（EPON）这种新型的接入网技术，将其与基于ATM技术的无源光网络（APON）的优缺点进行了比较，并对其媒体接入控制（MAC）的关键技术测距及上行接入进行了讨论，初步提出了光网络单元（ONU）的软、硬件实现方案。     

Reconstruction of a discontinuous function from a few fourier coefficients using bayesian estimation

The goal of this paper is the application of spectral methods to the numerical solution of conservation law equations. Spectral methods furnish estimates of the firstn Fourier coefficients of the solution. But since the solutions of conservation law equations can have discontinuities, the estimate of the solution by summing the firstn terms of the Fourier series will haveO(1/n) error, even if the Fourier coefficients are known to high accuracy. But if the solution could be accurately reconstructed from its Fourier coefficients, spectral methods could be used effectively in these problems. A method for doing this is to assume a probability distribution for functions. Functions which are smooth away from the discontinuity are assumed to be likely, and those which are not smooth away from the discontinuity are assumed to be unlikely. Then a reconstruction algorithm is chosen by minimizing the expected error over all algorithms. It is possible to put the smoothness assumptions mentioned earlier into an infinite-dimensional Gaussian probability distribution, and then the minimum-error algorithm is well-known and fairly simple to construct and apply. If the Fourier coefficients of the reconstructed function are known exactly, then this approach gives very good results. But when used with Fourier coefficients obtained from a spectral approximation to Burgers' equation, the results were much less impressive, probably because the coefficients were not known very accurately. It is possible to construct filters that reconstruct a function using Legendre or Chebyshev coefficients for information instead Fourier coefficients. It is found that the performance of these filters is similar to the Fourier case.     

接收机有限带宽对多相码数字脉压的影响

限制接收机带宽是雷达系统中提高信噪比(SNR)的常用方法,相应的也会引起输出波形的失真。本文主要分析了多相码数字脉压雷达系统中,接收机有限带宽对脉压输出结果所造成的影响。运用五点滑动窗平均法在计算机上进行了模拟,并给出了仿真结果。     

New method for measuring an optical property of a sample treated by FWA

In this article, a new method for measuring a total spectral radiance factor of a FWA‐treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi‐spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I₁ and I₂ whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi‐spectral luminescent radiance factor by linearly combining I₁ and I₂ with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 195–200, 2007     

Properties of ligno‐cellulose fiber Hildegardia

Studies on some properties such as the density, the degradation temperatures, the morphology and the spectral features of the ligno‐cellulose fiber Hildegardia were carried out in both untreated and alkali treated form. The fibers are found to have good morphology and moderate initial and final degradation temperatures. On alkali treatment, the lignin was found to be eliminated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2216–2221, 2002     

AN EXTENDED MODELING OF TIDE-WAVE MOTION

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｏｓｔｕｄｙｔｈｅｍｏｔｉｏｎｏｆｔｈｅｔｉｄｅ ｗａｖｅｓ,ｔｈｅｓｈａｌｌｏｗｗａｔｅｒｅｑｕａｔｉｏｎｓ ,ｉ.ｅ .ｔｈｅｖｅｒｔｉｃａｌｉｎｔｅｒｇｒａ ｔｉｏｎｏｆｔｈｅｃｏｎｔｉｎｕｉｔｙｅｑｕａｔｉｏｎａｎｄｍｏｍｅｎｔｕｍｅｑｕａ ｔｉｏｎ ,ｉｓｃｏｎｓｉｄｅｒｅｄａｓｔｈｅｇｏｖｅｒｎｉｎｇｅｑｕａｔｉｏｎｓ.Ｂｙａｂｏｖｅｅｑｕａｔｉｏｎｓｔｗｏｅｑｕａｔｉｏｎｓｒｅｌａｔｅｄｔｏｔｈｅｈｏｒｉｚｏｎ ｔａｌｆｌｕｘｏｆｔｈｅｔｉｄｅ ｃｕｒｒｅｎｔｓａ…     

准连续波体制雷达最大熵方法的算法选择

准连续体制作为一种新型雷达体制以其固有的优越性给雷达界带来了巨大的冲击。其数字信号处理系统的开发是进一步完善该体制雷达的关键。本文针对数字信号处理系统中最大熵谱外推电路的算法选择进行了研究。     

Experimental investigation of the normal spectral emissivity and other thermophysical properties of pulse-heated Ni-Ti and Au-Ni alloys into the liquid phase

1. Introduction Metal working industry needs accurate thermo- physical properties of liquid metals and alloys as input data for different simulation routines to im- prove the performance of their products. Within this paper we continue the systematic investigation of the dependence of emissivity of binary alloys on the relative concentration of the constituent elements (for a previous paper see [1]). 2. Experimental method A fast ohmic pulse heating technique is applied to heat metallic wire-s…     

带有块间串扰MC-CDMA的时域信道估计和多用户检测

本文把带有IBI的MC-CDMA系统等效解释为特殊的直接序列码分多址（DS-CDMA）系统，并给出了相应的时域信道估计方法和时域线性最小均方误差（MMSE）多用户检测方法。仿真实验表明了本文方法的性能。     

Spectral color reproduction minimizing spectral and perceptual color differences

In this article, we are combining minimization criteria in the colorant separation process for spectral color reproduction. The colorant separation is performed by inverting a spectral printer model: the spectral Yule‐Nielsen modified Neugebauer model. The inversion of the spectral printer model is an optimization operation in which a criterion is minimized at each iteration. The approach we proposed minimizes a criterion defined by the weighted sum of a spectral difference and a perceptual color difference. The weights can be tuned with a parameter α ∞ [0, 1]. Our goal is to decrease the spectral difference between the original data and its reproduction and also to consider perceptual color difference under different illuminant conditions. In order to find the best α value, we initially compare a pure colorimetric criterion and a pure spectral criterion for the reproduction, then we combine them. We perform four colorant separations: the first separation will minimize the 1976 CIELAB color difference where four illuminants are tested, the second separation will minimize an equally weighted summation of 1976 CIELAB color difference with the four illuminants tested independently, the third colorant separation will minimize a spectral difference, and the fourth colorant separation will combine a weighted sum of a spectral difference and one of the two first colorimetric differences previously introduced. This last colorant separation can be tuned with a parameter in order to emphasize on spectral or colorimetric difference. We use a six colorants printer with artificial inks for our experiments. The prints are simulated by the spectral Yule‐Nielsen modified Neugebauer model. Two groups of data are used for our experiments. The first group describes the data printed by our printing system, which is represented by a regular grid in colorant space of the printer and the second group describes the data which is not originally produced by our printing system but mapped to the spectral printer gamut. The Esser test chart and the Macbeth Color Checker test chart have been selected for the second group. Spectral gamut mapping of this data is carried out before performing colorant separation. Our results show improvement for the colorant separations combining a sum of 1976 CIELAB color difference for a set of illuminants and for the colorant separation combining a sum of 1976 CIELAB color difference and spectral difference, especially in the case of spectral data originally produced by the printer. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 494–504, 2008