自由空间光通信技术在电力系统的应用

自由空间光通信是一种以大气为信道的宽带激光通信方式,具有高带宽、低成本、便于链路部署等特点,近年来在电信公网及各种专业网络得到一定的应用。文章回顾了自由空间光通信的发展历史,简要介绍其工作原理和技术特点,讨论了自由空间光通信技术的发展优势及难点,以及FSO技术的新进展,通过与几种常用的电力系统通信方式的比较,分析FSO技术在电力系统的应用前景。     

温度对五类非屏蔽双绞线的影响

本文研究介质温度系数对五类非屏蔽双绞线电气性能的影响,讨论传输延迟、UTP电阻以及衰减的温度修正公式.对Fluke测量仪所测试到的数据结果进行详细分析,并对网络综合布线中存在的传输介质工作温度和长度的问题给出提高网络性能的方法,提出选用低值温度系数对UTP进行优化的建议.     

对ITU-R 837-2模式计算中国雨强分布的应用分析

论述了国际电联ITU-R 837-2模式计算雨强值的方法,在地理信息系统。(GIS)和数据库技术的支持下,对该方法进行了应用分析研究。首先对全国2937个县市进行单站点雨强计算;然后选择73°E～135°E,15°N～55°N范围,按几何分辨率即象元大小为经度3’×纬度3’制成格网,并逐栅格点计算雨强,以中国边境为界提取雨强值,并绘制等值线及分布图。经与典型站点分钟雨强值及国军标雨强分布图进行对照分析,指出了该方法在反演中国雨强分布中的可行性与局限性,并提出进一步完善该模型的建议。     

Propagation of spherical shock waves in water

The propagation and attenuation of spherical shock waves in water, produced by the explosion of spherical charge, is studied. Our results compare favourably with experimental data.     

Some perspectives on "the attenuation paradox in test theory."

Clarification is given of the "paradox" posed by Loevinger (see 29: 3299), i.e., "validity" (the product-moment r of test score with the common factor of test items) decreases upon the increase beyond a certain point of item intercorrelations in a test whose items are of equal difficulty. Four points are made: (1) the "region of paradox" is reduced using a curvilinear r rather than the usual product-moment "validity"; (2) the paradox's incidence in aptitude and achievement tests is not as great as is frequently believed; (3) over-all "validity" for a group is inferior to the test's discriminating power for a specified decision problem for a specific examinee; and (4) the conception that "… for optimum results the percentage of correct answers to each item should equal the percentage of examinees to be selected" is correct only if the latter percentage is 50. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cattell replies to Becker's "comments."

A reply to comments made by Becker (see record 1962-03097-001) regarding R. B. Cattel's original article (see record 1962-03095-001). The positive conceptual and experimental contributions of my paper appearing since his comments, he either misses or ignores, since they show: (a) that it was impossible for him to reach any intelligible conclusion on the theory without recognizing and developing the necessary corrections for attenuation and perturbation, and (b) that the facts which he says I must and do recognize are those chosen by Becker from experiments with older techniques. Science moves on, and the new facts which I present from technically more advanced designs show that the same factor simultaneously loads on the hypothesized markers for both the rating and the questionnaire factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

METABOLIC QUOTIENTS OF RESPIRATION-DEFICIENT MUTANTS OF BREWER'S YEAST AND THE APPEARANCE OF A NEGATIVE PASTEUR EFFECT

Four industrial strains of bottom brewer's yeast and a group of their spontaneous respiration deficient (RD) mutants were tested for rates of metabolism of glucose and maltose under aerobic and anaerobic conditions. Q_o2 of all the RD mutants tested (26 isolates) ranged from 1·9 to 6·8 μl/mg yeast dry weight on glucose and was lowered to about one-half on maltose although the original strains had the same Q_o2 values on both sugars. No isolate showed any increase in glucose fermentation in aerobic conditions as compared with the original strains and the decrease of Pasteur effect found in certain isolates was always accompanied by a strong decrease of glycolysis in both aerobic and anaerobic conditions. Two mutants showed a strongly negative Pasteur effect, for their fermentation rates were higher in aerobic conditions than in anaerobic ones. Two other mutants showed a strong negative Pasteur effect only on maltose. The ratio of Q^N_2CO2 on glucose in most mutants was significantly lower than in their parental strains.     

Anaerobic biodegradation of an organic by-products leachate by interaction with different mine tailings

Deinking by-products from paper recycling have been used as cover materials on acid-producing tailings. Due to residual cellulose, anaerobic degradation leads to the production of an organic-rich leachate, which may percolate through the tailings. This study aims at describing the influence of the tailings’ characteristics on the attenuation of organic matter in leachate and at discussing the degradation mechanisms. To this end, leachate was mixed with different types of tailings, including three unoxidized tailings with varying acid generation potentials and one tailing in three states of oxidation. Regularly, selected biochemical parameters were analyzed to access the evolution of organic components. The results show that when leachate from deinking by-products was placed in contact with tailings, phase and acid–base balance reactions took place in the beginning. Subsequently, oxidation–reduction reactions dominated the chemistry of the system. The type, the constituents, and the state of oxidation of the mine tailings condition the mechanisms of biodegradation of organic components. Methanogenesis was predominant in the control sample (pure organic leachate) but was absent in all leachate-tailings mixtures. No biodegradation was observed in the liquid phase for oxidized tailings and the organic concentration remained constant for unoxidized tailings, independently of the acid-generation potential. The biodegradation efficiency was optimal when the leachate was in contact with a mixture of oxidized and unoxidized tailings due to sulfate-reduction.     

钨对AlN基复相材料微波衰减性能影响的研究

以AlN和W为原料，Y203为烧结助剂，在1850℃的N2气氛下热压烧结制备AlN-W复相衰减材料。运用XRD，SEM，网络分析仪等测试手段，研究了W含量、制备工艺对材料的显微结构、相组成、烧结性能及微波衰减性能的影响。结果表明，AlN-W复相衰减材料的衰减量随W含量的增加而增加，当W含量低于柏％时呈现选频衰减特性，而当W含量继续增加到50％时呈现良好的宽频衰减，且衰减量最高达到-1．9dB。探讨了AlN-W复相衰减材料的主要衰减机制。     

纳米加工技术的研究

对纳米加工技术的定义、特点和流程等相关课题进行了深入的研究。其中包括纳米粒子和纳米溶液的基本概念以及纳米加工技术的特色和优势等。结果表明：可以将纳米粒子视为一种新型微观粒子，纳米溶液视为传统胶体化学的溶胶。纳米溶液在纳米加工技术中具有十分重要的作用和深远的意义；纳米溶液模型的建立对于粉体表面实现纳米化和人类居住环境实现无害化都具有深远的影响。