南明河贵阳市城区河段设计洪水水面线的确定

采用水文学的方法，结合南明河“91·7”、“96·7”待大洪水调查资料，对南明河各种频率设计洪水水面线进行推算，取得较精确的成果，为城市建设所采用，并起很好的防洪作用。     

Second harmonic generation investigation on electric poling effects in fused silica

The influence of electric of poling conditions on the optical nonlinearity of fused silica has been investigated by the second harmonic generation (SHG) technique. The SHG intensity of the poled fused silica increased monotonically with increasing the poling voltage or poling time, and reached a maximum at a poling temperature of T = 250°C, but the SHG intensity decreased quickly as the thermal erasure time increased. The experimental results have been explained using an electric field induced dipole orientation model.     

The molecular characterisation and antimicrobial properties of amidated bovine β-lactoglobulin

Amidation of bovine β-lactoglobulin (β-Lg) imparted antimicrobial properties to this protein. Amidated β-Lg was strongly bactericidal against resting cells of Pseudomonas fluorescens, Pseudomonas fragi and Bacillus subtilis, but had a much weaker effect against Escherichia coli, Enterococcus faecalis, Salmonella typhimurium and Listeria monocytogenes. Neither native nor amidated β-Lg was effective against the yeast Saccharomyces cerevisiae and the mould Penicillium candidum. Mass spectrometric analysis demonstrated that amidation of β-Lg converted aspartyl and glutamyl residues to asparaginyl and glutaminyl residues, respectively, and that the amidation reaction did not occur to the same extent on every β-Lg molecule. The charge change was also confirmed by SDS–PAGE, ion exchange chromatography and the change in isoionic point of β-Lg. Reverse-phase chromatography showed that amidation also led to alterations in hydrophobicity of the β-Lg molecule. The antibacterial properties of the amidated β-Lg appear to be dependent on the net positive charge and charge distribution on the molecule.     

One Method for Fast Gate Oxide TDDB Lifetime Prediction

提出了一种快速推算栅极氧化膜TDDB寿命的新方法.该方法可以用于对工艺的实时监控.通常情况下,为了得到栅极氧化膜在器件使用温度下的TDDB寿命,必须得到三个在一定温度下的不同电压下的TDDB寿命.然后使用一定模型(E模型或者1/E模型)和这个三个寿命推算出氧化膜在器件使用温度下的寿命.比较常用的是E模型.但是为了保证使用E模型推得的寿命的准确性,必须尽量使用较低电压下的寿命来推算想要的寿命.显然,为了获得低电压下的TDDB寿命,必须花费相当长的测试时间(甚至1个月).这对于工艺的实时监控来说,是不能接受的.文中提出一种新的推算栅氧化膜TDDB寿命的方法.运用该方法,可以快速、准确获得栅氧化膜的TDDB寿命,而花费的测试时间不到普通方法的1/1000000.在该方法中,巧妙地同时利用了1/E模型和E模型.     

An improved /spl rho/DFIIt structure for digital filters with minimum roundoff noise

In this brief, a new efficient digital filter structure with minimum roundoff noise is derived. This structure can be block-diagrammed as the recently proposed direct-form II transposed (DFIIt) structure in /spl rho/-operator, denoted as /spl rho/DFIIt, in which the first-order /spl rho/ operators are replaced with a set of second-order operators. The corresponding expression for the roundoff noise gain is obtained. The problem of how to choose these second-order operators is investigated in terms of minimizing the roundoff noise gain. Two design examples are given to illustrate the excellent performance of the proposed structure and to confirm the theoretical analysis.     

走向客户端的光通信发展探讨

随着客户端业务对带宽和质量需求的增加,当前光通信的一个特点是客户端已成为光通信最大的技术和市场空间.本文从客户端入手,首先指出光通信走向客户端的发展趋势,分析了走向客户端的光通信的特点,接着介绍了几种走向客户端的技术途径,重点分析了PON在客户端光通信网络中的应用特点,最后对客户端接入的组网方式做了进一步的探讨.     

激光与中学物理教学

本文主要对目前中学在讲授激光时所要用到的一些基础知识作一梗概的介绍。     

水口水电站低温混凝土测温成果统计分析

通过对水口水电站大坝低温混凝土现场测温结果的统计分析，阐述夏季混凝土浇筑时的温度控制与实施情况，进而寻求动态、定量控制浇筑温度的途径。     

DVB-S2中LDPC编解码分析

本文在简要介绍LDPC码的基础上，就DVB—S2标准中LDPC编解码过程进行了详细的分析，指出了值得关注和研究的元素。     

Thermoeconomic optimization for a finned‐tube evaporator configuration of a roof‐top bus air‐conditioning system

This paper presents a methodology of a design optimization technique that can be useful in assessing the best configuration of a finned‐tube evaporator, using a thermoeconomic approach. The assessment has been carried out on a direct expansion finned‐tube evaporator of a vapor compression cycle for a roof‐top bus air‐conditioning (AC) system at a specified cooling capacity. The methodology has been conducted by studying the effect of some operational and geometrical design parameters for the evaporator on the entire cycle exergy destruction or irreversibility, AC system coefficient of performance (COP), and total annual cost. The heat exchangers for the bus AC system are featured by a very compact frontal area due to the stringent space limitations and structure standard for the system installation. Therefore, the current study also takes in its account the effect of the variation of the design parameters on the evaporator frontal area. The irreversibility due to heat transfer across the stream‐to‐stream temperature difference and due to frictional pressure drops is calculated as a function of the design parameters. A cost function is introduced, defined as the sum of two contributions, the investment expense of the evaporator material and the system compressor, and the operational expense of AC system that is usually driven by an auxiliary engine or coupled with the main bus engine. The optimal trade‐off between investment and operating cost is, therefore, investigated. A numerical example is discussed, in which a comparison between the commercial evaporator design and optimal design configuration has been presented in terms of the system COP and evaporator material cost. The results show that a significant improvement can be obtained for the optimal evaporator design compared with that of the commercial finned‐tube evaporator that is designed based on the conventional values of the design parameters. Copyright © 2007 John Wiley & Sons, Ltd.