INFLUENCES OF A FOREST ON THE HYDRAULIC GEOMETRY OF TWO MOUNTAIN STREAMS1

ABSTRACT The influence of a forest on the formation of steps in two small streams of the Colorado Rocky Mountains was studied. Steps provided by logs fallen across the channel added to flow energy reduction. The streams required additional gravel bars to adjust to slope. Average step length between logs and gravel bars was strongly related to channel gradient and median bed material size. Based on the average number of log steps per 50 feet of channel, an average of 116 percent of gravel bars were added at Fool Creek and 60 percent at Deadhorse Creek. The latter had 52 percent more logs in the channel and therefore required less bed material movement than the former. Although these are “rushing mountain streams,” most flow velocities ranged between 0.5 and 2.5 f.p.s. Exponents of a function relating rate of change of depth or velocity to discharge indicated that dynamic stream equilibrium was attained. Implications for forest management are that sanitation cuts (removal of dead and dying trees) would not be permissible where a stream is in dynamic equilibrium and bed material movement should be minimized.     

通俗易懂地讲解“物质的量“的概念

"物质的量"是国际单位制中七个基本物理量之一,其概念抽象、理论性强,学生掌握难度较大.因此,用通俗易懂的类比法探讨了"物质的量"的概念,又用类比法推出了"物质的量"的单位--摩尔,指出了摩尔的适用范围,易于学生理解和掌握,提高了学生学习化学的兴趣,提高了教学质量.     

室内环境中化学污染物质测定法研究

室内环境中化学污染物质的测定是研究和解决室内环境问题的基础。本文以甲醛和挥发性有机化合物两种室内环境中的主要化学污染物质为例,介绍了目前世界各国采用的各种测定法及其动向,并探讨了测定时期、测定时间、采样点布置等有关问题,提出了一些看法供参考。     

Preparation and characteristics of high performance paper containing titanium dioxide photocatalyst supported on inorganic fiber matrix

A novel paper-based material containing titanium dioxide (TiO₂) photocatalyst was successfully prepared by a papermaking technique with the internal addition of inorganic fibers on which TiO₂ particles were supported. Photodegradation performance of acetaldehyde gas, an indoor pollutant, and the durability of the TiO₂-containing papers were investigated under UV irradiation. Ceramic fiber suspension and polydiallyldimethylammonium chloride as a cationic flocculant were mixed, followed by the addition of TiO₂ suspension and anionic polyacrylamide. Subsequently, the inorganic mixture was poured into a pulp suspension, and TiO₂ handsheets then prepared by a papermaking method. The tensile strength of TiO₂-containing paper without a ceramic carrier decreased by more than 30% after 240-h UV irradiation (2 mW/cm²), although the strength of the TiO₂ sheet with ceramic fibers remained reasonably stable. The efficiency of acetaldehyde decomposition by the TiO₂ paper containing an inorganic carrier was nearly equal to that of the carrier-free TiO₂ paper. Scanning electron microscopic observation suggested that most TiO₂ particles were predominantly supported on the inorganic fiber matrix, and were mostly out of contact with organic pulp fibers. The TiO₂ paper with an inorganic carrier demonstrated both excellent photocatalytic performance and durability, which before had been mutually incompatible for organic materials containing TiO₂ photocatalyst. The two-stage mixing procedure for TiO₂ sheet-making is promising for the simple manufacture of high performance paper with photocatalytic ability.     

CHANNEL CHANGES DOWNSTREAM FROM A DAM1

ABSTRACT: A flood-control dam was completed during 1979 on Bear Creek, a small tributary stream to the South Platte River in the Denver, Colorado, area. Before and after dam closure, repetitive surveys between 1977 and 1992 at five cross sections downstream of the dam documented changes in channel morphology. During this 15-year period, channel width increased slightly, but channel depth increased by more than 40 percent. Within the study reach, stream gradient decreased and median bed material sizes coarsened from sand in the pools and fine gravel on the rime to a median coarse gravel throughout the reach. The most striking visual change was from a sparse growth of streamside grasses to a dense growth of riparian woody vegetation.     

磨料水射流除鳞技术在钢厂的应用

为了暴露各种钢材在热轧过程中产生的表面缺陷，需清除附于其上的氧化铁皮，称之为“除鳞”。传统的除鳞方法有酸洗、表面剥皮、喷丸处理等，这些方法存在很多缺点。本文介绍已在湖南涟钢用于生产的磨料水射流除鳞生产线，用磨料水射流除鳞具有速度快、质量高、成本低、操作简便等独特的优点。     

牡蛎生物环境标准样品的研制

文章对我国环境保护系统研制出用于海洋和江河水域环境监测的牡蛎生物环境标准样品的一些情况做了详细介绍;尤其对牡蛎环境标样的制备过程,牡蛎标样的作用,均匀性、稳定性检测和分析定值进行了较为充分的论述。     

冷却法净化焦油脱水尾气的研究

炭黑厂焦油脱水过程中产生的尾气（苯、甲苯等苯系物）用冷却法能用效冷凝其中大量有机物，且冷却水温度愈低冷却效果愈好，当水温降至５℃左右时，尾气中的有机物基本能全部冷凝除去，冷凝油相中除苯系物外还萘，冷凝水相的ＢＯＤ５／ＣＯＤＣＲ比值大于０．５，具有很好的可生化性。     

我国铁路危险货物运输安全管理及防护对策

危险货物、运输风险性大,管理难度大,一旦发生事故,不仅会造成人民生命财产的巨大损失,还会产生严重的社会影响,为此,研究了危险货物的爆炸、燃烧、毒害、放射和腐蚀等5种危险特性及其近些年发生的事故教训,分析了我国铁路危险货物运输安全防护中存在的问题,提出了依法行政、依法治路、加强技术设备管理、运输组织管理以及建立事故应急预案等方面的安全防护对策。通过提高安全管理人员的技术业务素质;充分认识危险货物的特性和铁路危险货物运输状况;不断进行管理创新、制度创新;积极开展信息化建设;把握运输安全的特点和规律;在实践中不断改进,努力做到与时俱进,使铁路危险货物运输安全管理工作平稳有序。     

材料和结构的损伤与安全性

本文介绍了材料和结构损伤与安全性的研究进展.首先从损伤所造成危害的严重性来说明研究材料和结构损伤的重要性,介绍目前材料和构件损伤问题研究所遇到的现状.进一步对材料和结构损伤做了归纳,并介绍了几种典型损伤的研究方法,以及损伤程度对结构安全性的影响.最后指出了材料和结构损伤及安全性研究发展趋势.