专用液压驱动链锯马达参数设计计算

对专用液压驱动链锯马达的柱塞、缸体、配流盘进行设计计算,得到了采伐联合作业机专用液压驱动链锯马达的设计参数。     

铣削式营林割灌机液压马达的使用维护

通过对引进设备关键技术液压马达的分析研究,重点介绍了该马达的技术性能和特点,分析了马达磨损形式和影响马达软寿命的因素,提出了马达监控与检测的技术和方法.     

基于MATLAB的机械用举升机构运动学分析

利用MATLAB对机械用举升机构进行运动学和动力学分析,编制相应的程序并通过实例进行分析和计算,这对分析机构稳定性和优化设计都具有一定的参考价值.     

ZL─PW挖穴机具液压系统的研究设计

本文着重论述了ＺＬ─ＰＷ液压系统的设计依据与设计方法及其结构特点     

采伐联合机专用液压驱动链锯马达类型的优化选择

综合分析了齿轮式、叶片式、柱塞式液压马达的特点及工作原理,优化选择确定斜轴式轴向柱塞液压马达作为采伐联合机专用液压驱动链锯马达。     

浅谈液压技术在林业机械中的应用现状与展望

通过对液压技术这一年轻的技术在林业机械中的应用现状进行了分析，展望了其在现代化林业机械中的应用发展趋势。     

液压传动技术在工程机械行走驱动系统中的应用

本文论述了液压传动技术在工程机械行走驱动系统中的应用,并通过对液压传动技术与传统纯机械传动和液力传动的对比,探讨了液压传动技术的优势和未来发展趋势.     

Matlab优化工具箱在液压抓具机构运动学与动力学分析中的应用

运用MATLAB优化工具箱,对一种液压抓具设计中运动学和动力学问题进行分析求解效果较好。     

比例溢流阀在拉力轴承试验液压加载系统中的应用

比较了3种液压加载系统调节方式的原理和特点,介绍了该拉力轴承寿命试验装置中采用电比例溢流阀调节方式的组成及工作原理,重点分析了其在恒力加载状态经过闭环控制的工作特性.试验表明,此加载方式调节方便,加载载荷准确,系统性能稳定可靠,应用效果良好.     

PLC在液压比例控制系统中的应用

电液比例控制系统与电液伺服控制系统相比，具有制造成本低，对液压油的清洁度要求稍宽等许多优点，且比传统电液开关控制液压系统的控制性能大为提高，因此在现代液压技术中广泛应用。可编程序控制器(PLC)具有可靠性高，功能强大，编程较为方便等优点，在现代工业控制领域中应用非常广泛。PLC不仅能进行逻辑控制，而且还具有数学运算、模拟量处理、PID运算、PWM输出和联网通信等功能，     

Variations of root hydraulic conductance of Fraxinus mandshurica seedlings in different concentrations of NH4NO3 solution

Absorbing water from soil by roots in vascular plants is an important physiological function and plays an essential role on their water balance. The root hydraulic conductance (L _P) determined by radical water transport inside the root is a major influence on the shoot water status, plant growth, and development. However, a few studies have focused on the effect of different substances on L _P of roots, and the role of radical water transport was poorly understood. Based on the pressure-flux approach, this study used the roots of Fraxinus mandshurica seedlings with different treatments, i.e., distilled water, NH₄NO₃ solution, and HgCl₂ to determine the effect of various substances on L _P of roots. The objectives are: 1) to evaluate the difference in L _P occurred between distilled water and NH₄NO₃ solution with various concentrations; and 2) to examine the changes of L _P under distilled water and NH₄NO₃ solution with various concentrations after HgCl₂ treatment. The results showed that L _P of roots were 18.85×10⁻⁸ m/(s·MPa) in distilled water, 31.25–34.15×10⁻⁸ m/(s·MPa) in four NH₄NO₃ solutions (2, 4, 8 and 16 mmol/L), 14.69×10⁻⁸ m/(s·MPa) in distilled water after HgCl₂-treated, and 9.63–13.57×10⁻⁸ m/(s·MPa) in four NH₄NO₃ solutions after HgCl₂-treated, respectively. Aquaporins play an important role in regulating water uptake and transport in roots. NH₄ ⁺ and NO₃ ⁻ could stimulate activity of aquaporins, and L _P of roots in NH₄NO₃ solution was distinctly 77% higher than in distilled water. Nevertheless, Hg²⁺ can inhibit activity of aquaporins, and and L _P of roots decreased 22% in distilled water and 68% in NH₄NO₃ solution after treatment by HgCl₂ respectively. These evidences suggested that both Hg²⁺-sensitive aquaporins and ion channels existing in the protoplasm and vacuole membranes could regulate root water uptake, transport, and integral plant water balance. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(5): 706–712 [译自: 植物生态学报, 2005, 29(5): 706–712]     

全数字矢量控制交-交变频调速控制系统在包钢百米高速钢轨主传动系统中的应用

介绍了全数字矢量控制交-交变频调速控制系统在包钢百米高速钢轨主传动系统中的应用,重点阐述了全数字矢量控制交-交变频调速系统的控制原理和系统构成。     

滩地抬田造林对杨树蛀干害虫天牛生态控制效果的初探

抬田造林杨-农（油）-渔复合经营模式对杨树蛀干天牛虫口密度和有虫株率都有明显下降作用。其生态控制的综合效益有以下几方面：（1）促进了杨树的快速生长，提高了杨树迅速生长的经济效益；（2）增加了抬田垛面林下套种农作物和沟内养殖水产品的收入；（3）增加了杨树林内有益生物的多样性；（4）对天牛类蛀干害虫起到了有效地控制作用；（5）天牛严重危害区可合理间种柳树（诱集天牛），并在天牛虫口密度达到饱和时，及时集中防治或？肖灭高虫口密度虫源诱集树（柳树）上的蛀干害虫天牛，可达到控点保面的作用。     

对国有林场管理体制和经营机制改革问题的思考

分析了国有林场改革试点工作中所面临的重点难点问题,并从搞活经营机制、多渠道妥善安置富余职工、解决历史欠账、优化资源配置、整合生产要素等方面提出了发展建议。     

入世对我国林业的影响及对策

加入WTO,面临众多机遇和挑战,竞争更加激烈,争夺市场、资源、劳动力等的斗争将更加激烈和残酷。针对我国林业的发展现状和存在问题,作为国民经济重要组成部分的林业要进一步加快林业产业结构调整,加快资源培育步伐,建立合理的市场体系,深化科技体制改革,从而适应新时期经济形势的要求。     

Modelling the long-term impacts of selective logging on genetic diversity and demographic structure of four tropical tree species in the Amazon forest

In the last three decades, Amazon tropical forests have experienced high rates of deforestation, both by clearing for agriculture and by logging. In this study, we use computer simulations to examine the potential effects of forest logging on genetic diversity and demographic recovery (basal area development) of four neotropical tree species over a time frame reflecting multiple logging events. The study species, Bagassa guianensis Aubl., Hymenaea courbaril L., Manilkara huberi (Ducke) Chevalier, and Symphonia globulifera L.f., are all taxa which are commonly exploited for timber in the Brazilian Amazon. The simulations were parameterized using empirical data from field studies in the Tapajós National Forest, Pará State, Brazil, including genotypes at microsatellite loci, demography, ecology and growth for each species. Eight scenarios, combining two different cutting cycles and two minimum cutting diameters, were examined for each of the four species. The scenarios represent the actual forest practices used in Brazil and French Guiana (cutting diameter 45 and 60 cm, and cutting cycle of 30 and 65 years, respectively). Logging scenarios were applied for six cutting cycles, and final genetic and demographic data were compared to baseline data from corresponding control scenarios. At the end of the simulated period the basal area was strongly reduced under all conditions in B. guianensis, H. courbaril, and M. huberi. In only two scenarios was a species able to recover its basal area following logging (S. globulifera with both 45- and 60-cm cutting diameters under a 65-year cutting cycle). In the logging scenarios, all species showed a loss of alleles and genotypes and an increased genetic distance (calculated between each population at the start and the end of the simulations). These effects were higher under the most intensive logging cycles (30 years, 45 cm). However, effective number of alleles, expected and observed heterozygosities, and the fixation index were little affected by the logging simulations. Over all, we conclude that, even under very optimistic conditions for growth and recruitment, current logging practices are not sustainable in terms of basal area. Our simulations show that different species respond differently to logging, both demographically and genetically. No single set of logging parameters can be applied to the forest as a whole. Rather, forest management practices must be species-specific, taking into account not only growth parameters but also ecological and reproductive variables, in order to move toward long-term forest sustainability.     

海岸带风口沙地木麻黄无性系造林与根系生长特性

从 2 0 0 0年 5月起在福建省东山县赤山林场临海风口干旱沙地进行 3年试验研究 ,从 7个参试无性系中选择惠 1#、粤 70 1#、东 980 1#等 3个造林保存率达 6 1 9%～ 6 9 5 %的无性系 ,在此类特殊困难立地防护林植物材料选择方面取得突破。通过对风口沙地前沿高地和后沿低洼地 2种微地形条件木麻黄无性系造林效果的比较分析 ,后者造林保存率提高约 5 % ,且林木生长较快。 2种微地形条件林木根系生长状况 ,风口前沿高地林木根系分布深、数量多、结构密集、吸收根系网络发达 ,有助于逃避大气干旱和土壤干旱。并揭示根系分布深度、数量、密集程度、网络结构与土壤含水率大体呈负相关的趋势。研究揭示 ,风口干旱沙地造林成活的机制 ,是由于林木形成发达、庞大的根系网络的生理和形态特性 ,以适应干旱生境和保证造林成活。不同造林方式的试验结果表明 ,丛状、团状等植生组造林方式可提高保存率约 10 % ,在生产实践上有推广应用价值。     

长江三角洲地区森林资源可持续利用的法律保障

森林是陆地生态系统的主体,是经济社会发展不可替代的战略资源。长江三角洲地区森林资源分布极不均衡、结构不合理,在开发利用过程中存在着区域法规缺乏统一性、产权归属不清晰、流转机制不健全、林业执法监督体制滞后等问题。要实现该地区森林资源的可持续利用,就应该借鉴国内外的先进经验,建立该地区的法制协调机构,统一该地区的林业立法、执法活动,促进法规优化,强化森林开发利用各环节的法律保障措施。     

生态视角下我国空间规划体系的演变特征及其驱动机制

我国空间规划体系正处于转型变革的关键时期，理清空间规划体系的演变特征及其驱动机制，对生态文明建设背景下区域空间发展具有重要作用。文中构建了“利益格局变化—主体行为博弈—政策制度调整”的逻辑分析框架，并以新疆为例，分析了生态视角下空间规划体系从无到有、从波动分化到转型引领的演变特征，指出其大致可概括为4个阶段特征:1）1949—1978年五年计划主导时期:作为政策实施的载体；2）1979—1999年国土规划主导时期:作为集权与分权博弈的反映；3）2000—2011年“多规”并驱时期:作为地方政府经济增长的工具；4）2012年至今规划重组时期:作为国土空间治理的手段。在此基础上，进一步探究了不同时期空间规划体系演变中的普适性、特殊性与指向性，阐明演变的驱动机制，以期为我国生态文明时期的国土空间规划体系构建提供参考。