汽车变速器齿轮修形仿真分析

汽车变速器的关键部件齿轮因其加工和装配质量的影响,工作时容易引起振动噪声大及承载能力降低等问题,而齿轮修形是解决这些问题的有效方法,且成本较低。针对某款汽车变速器,利用Romax对齿轮进行修形分析。结果表明,修形后减小了齿轮的传动误差和最大接触应力,齿面载荷分布更加合理。有效改善了齿轮的传动性能,增加了齿轮寿命。     

基于土地整治的三门峡库区(华阴段)现代农业发展模式研究

土地整治与现代农业的结合研究有利于区域现代农业的快速发展。三门峡库区(华阴段)自然社会条件复杂,农业经济基础薄弱,土地利用方式落后。针对土地整治后期效益不可持续性的问题,认为土地整治与现代农业在实现阶段和目标上存在耦合联系,并针对三门峡库区(华阴段)区域特征,将土地整治"3集"模式、生态农业建设模式和新农村发展模式有机统一,以期实现以土地整治为契机,加速区域现代农业模式快速发展。     

黄河宁蒙河段泥沙加入量分析及防治对策

利用1950—2005年黄河干流泥沙分布特征值资料与干流任意河段年平均泥沙加入公式对黄河干流宁蒙河段年平均泥沙加入进行了计算分析。结果表明,1950—2005年宁蒙河段每年都有大量泥沙加入,并且加入量随时间呈波动变化。通过数据分析与实地调查发现,造成该河段泥沙大量加入以及随时间呈波动变化的原因主要是宁蒙河段穿越腾格里沙漠、河东沙地、乌兰布和沙漠以及库布齐沙漠,沙漠与河流交互作用,使其具备风沙直接入黄以及支流泥沙入黄的条件;尤其以"十大孔兑"河道上游比降大,河道两岸地表沙物质易蚀性高,从而导致大量泥沙通过洪水过程进入黄河。黄河宁蒙河段的泥沙防治关键在于减少入黄泥沙量,特别是要加强"十大孔兑"地区的水土保持综合防治力度。     

Species composition of Modellidae and Cerambycidae (Coleoptera) in a coppice woodland

A continuous sampling of canopy beetles was carried out to determine variations in the abundance, species diversity, richness, and composition of the Mordellidae and Cerambycidae in a coppice woodland. Changes in the abundance and the species richness were monitored at three heights in the forest throughout the season in 1999, using yellow and blue water pan traps. The results showed significant variations in the abundance of Mordellidae among the canopy layers, while little variation was found for Cerambycidae. The abundance, species diversity, and richness were generally greater in summer. The results showed distinct species compositions in both families among layers.     

抚育间伐技术目标管理新方法

本文利用林层结构划分条件、林分起源、林层年龄、树种组成等因子,将松江河林区的幼、中龄林划分为四个林相组和九个林相类型。在此基础上编制了幼、中龄林林相类型表。用该表能指导幼、中龄林的调查、设计和抚育间伐。该目标管理技术环节易于掌握,并可提高抚育质量。     

泡沫分离器在循环水养殖系统中的水处理效果

对泡沫分离器生产运用中的注意事项进行了探讨,并对生产中不同工况下的水处理效果进行比较,结果表明泡沫分离器对水体中微小悬浮颗粒、溶解有机物有良好去除效果,并能脱去部分氨氮.在不同工况下,随着进水流量的减小,泡沫分离器对这三种水质指标的去除效率逐渐增加,分别由水力停留时间为2.5 min时的45.15%、18.71%、8.50%,增加到水力停留时间为3.8 min时的 72.66%、34.11%、18.89%;同时,泡沫分离器不同工况对流经水体的溶解氧和pH都能有很好的调节作用.     

帕米尔高原真藓科6种植物的解剖学观察

[目的]为了对新疆帕米尔地区6种真藓科植物进行解剖学研究。[方法]应用石蜡切片和电镜扫描技术,对6种真藓科植物茎、叶的微结构进行了较详细地观察和分析。[结果]垂蒴真藓茎横切面的边缘平整,细胞排列整齐;叶细胞角质层厚,表面较粗糙,有细小的颗粒状和鳞片状附属物分布。灰黄真藓茎表皮细胞强烈凹陷,茎横切面边缘不整齐,细胞镶嵌排列;叶背、腹面相邻细胞的细胞壁呈"菌褶状",细胞表面较光滑。宽叶真藓茎横切面五角形;叶片背卷,多数叶细胞中内含物浓厚,叶背、腹面细胞壁呈规则"网格状",叶背面有细小的附属物零星分布,角质层皱折不多;叶腹面细胞表面较光滑。紫色真藓茎横切面不规则多边形;叶背、腹面细胞壁上零星分布着一些不规则的附属物,背面细胞排列呈不规则"网格状",腹面细胞排列呈整齐的"竹节状"。拟三列真藓茎内皮部具体积大的薄壁细胞,中轴分化明显;叶背、腹面细胞壁凹陷相对浅些,3～5个单疣或分叉疣分布于凹陷的细胞壁上,疣上有条状纹饰。湿地真藓茎细胞壁薄,均有角隅加厚现象,叶边内卷,叶背、腹面细胞壁呈挤压状不规则排列,角质层纹饰细小,数量较多。[结论]6种真藓科植物的茎、叶的微结构均存在一定的差异,具有重要的分类学意义。     

The performance of community organisers in promotion of community forestry in Leyte Province,Philippines

A study was conducted to assess the role and effectiveness of community organisers in supporting the development of people’s organisations in achieving community-based forest management objectives in Leyte Province Philippines. Community organisers were found to be effective in forming people’s organisations (POs), motivating people to participate in voluntary activities organised by POs and encouraging cohesiveness among PO members. Community organisers manage to raise the level of environmental awareness and knowledge of members of people’s organisations, develop leadership interest and skills, create various livelihood opportunities and provide direction and facilitate the establishment of large tree plantations. However, the short duration of community organisers’ contracts (typically two years) is insufficient to establish mature and cohesive POs prepared to assume management on their own, including the management of tree plantations. Further, lack of training and funding support, low wages, delayed payment of salaries and limited time to work with people’s organisations, as well as the pressure to produce tangible outputs such the establishment of large tree plantations, prevents them from placing greater emphasis on the development and empowerment of the people.     

Long-term growth analyses of Japanese cedar trees in a plantation: neighborhood competition and persistence of initial growth deviations

The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37–0.46) of the variation in dbh growth during a 5–11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09–0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50–0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.     

我国森林土壤健康评价研究进展

保持和提高森林土壤健康是实现森林健康的基础。本文综述了森林土壤健康的概念、评价指标、评价方法及其优缺点。森林土壤健康评价是相对的而不是绝对的,主要以土壤的功能为基础,不同类型土壤的评价应采用不同的标准。因此,须进一步加强评价指标的标准化、综合化和应用化,选择适宜的方法来评价森林土壤健康,从而探索有利于某地区森林土壤健康的管理措施,以实现森林土壤的可持续发展。