用拓扑变换原理设计空间四连杆机构

空间两轴垂直交叉的RSSR曲柄摇杆机构和RSSP曲柄滑块机构,是空间连杆机构中应用最广泛的四杆机构。本文运用拓扑变换原理,对RSSR和RSSP两机构,按极限位置和行程速比的设计进行了分析研究。导出了其尺寸参数的计算公式,并提出了计算机辅助设计和绘图的程序框图,以定量的方法分析设计机构的可动性。这一方法图文并茂,形数结合,结论准确,容易理解,特别是利用计算机辅助设计,使用极其方便,因而是一种较为理想的新方法。     

用拓扑变换作空间机构的可动性分析

本文运用拓扑变换原理,对空间四杆机构的可动性进行了分析研究。得出了含两个球面副的RSSR、RSSP以及含一个球面副的RSRC、RSCR等空间四杆机构的能装配成机构的最大和最小连杆长度的清晰解答。並得出了能用F·格拉肖夫(Grashof)思想表示的机构曲柄存在条件。这是分析空间连杆机构的一种新方法。     

拓扑变换在空间连杆机构中的应用

本文较详细地论述了应用拓扑变换原理,进行空间四连杆机构的极限位置和曲柄存在条件的分析,以及实现给定极限位置的机构进行尺度综合的图解法。通过对空间RSSR和RSSP四连杆机构的分析表明,采用这种图解法作图简便,构图清晰,形象直观,容易掌握,是分析综合空间连杆机构的新方法。     

按传动角设计尺寸和最小的双曲柄机构设计

提出了一种按照传动角设计尺寸和最小的双曲柄机构设计新方法,并将这种方法推广到最佳传动双曲柄机构设计中。本方法可直接给出解析解,避免了优化计算。     

板件垛搬运机构方案设计与优化

比较了几种板件垛搬运装置解决方案,决定选用曲柄摇块机构或曲柄摇杆机构作为搬运机构。建立了2种搬运机构的数学模型,运用MATLAB编程,确定了最优设计参数,进行了机构运动仿真、运动与动力学特性分析。研究表明,2种机构从动件均可出现一段几乎竖直向上的线段,可以满足搬运板件垛的要求。但在曲柄摇杆机构的从动件x轴方向运动速度曲线中,有一段比较稳定的区间,因此更适合作为板件垛搬运机构。     

基于TRIZ理论的曲柄滑块机构演化与创新

基于TRIZ理论,分析了将曲柄滑块机构演化为正弦机构、间歇运动的导槽机构、等径凸轮机构和液压伺服控制机构的演化过程,提出了各演化过程所应用的TRIZ理论方法,总结了机构创新所遵循的TRIZ理论进化法则,为机构创新提供了参考依据。     

偏置双曲柄滑块机构设计

偏置双曲柄滑块机构不仅具有k>3的超急回运动特性,而且具有可变急回运动特性,机构中各构件尺寸一定时,仅仅改变其相对安装位置,便可获得不同的行程速比系数。本文分析偏置双曲柄滑块机构的急回运动特性,给出了按最小传动角设计偏置双曲柄滑块机构的设计方法和设计曲线。     

最新中国林业专利选粹

曲柄摇杆式原木抓斗旋转机构申请号：92226205.5申请人：上海铁路局工业公司南昌机修厂摘要：一种与电动旋转原木抓斗配套使用的旋转机构。该机构由电机、减速机构、旋转机构和旋转轴组成。减速机构由小三角胶带轮、三角胶带、大三角胶带轮和蜗轮蜗杆组成；旋转机构由曲柄、连杆和摇杯组成。曲柄每旋转180°，摇杆摆动90°，亦带动旋转轴转动90°。该机构结构紧凑，省去了一个齿轮减速器，体积减少了40％。该机构使原木抓斗在水平方向旋转不大于90°，可有效地防止抓斗旋转拉断电源线的事故发生，且转向明确，操作方便。木材干燥窑微机群控…     

同步齿形带传动实现从动件准确直移的设计初探

１引言同步齿形带是综合了带传动和链传动优点的环形带。目前在磨床、纺织机械、电子计算机等机电设备中均已有所应用。但目前的带传动应用通常都是用来改变从动件的运动速度，而不能改变从动件的运动形式。下面我们将要探讨的是同步齿形带传动用于改变从动件的运动形式，即实现从动件的准确直移。２实现准确直移的原理如图１所示，ＡＢＣ为曲柄与连杆等长的正置曲柄滑块机构，当曲柄ＡＢ转至铅垂位置附近，即Ｃ点在Ａ点附近时，压力角很大，影响机构的正常工作。现延长ＡＢ，过Ｃ点作其运动方位的垂线，两直线的交点Ｐ即为连杆２的速度瞬心…     

泥炭块制作机的研制

介绍了泥炭块制作机的结构和工作原理,分析了泥炭块成型过程,对该机分度凸轮机构和曲柄滑块机构进行了运动学计算.     

空间五杆机构的可动性分析

机构的第2类可动性。是机构分析与综合所要探讨的基本问题之一。本文对一般形式的空间RRRSR五杆机构的可动性进行分析。通过拆开运动副,分析运动轨迹,根据其雅可比矩阵奇异获得各位形分支的边界后,采用拓朴变换原理,讨论得出该机构的装配条件和连架杆的运动情况。为空间多杆机构的第2类可动性分析,提供了一条方便、实用的途径。     

害虫综合控制中的合理用药与环境保护

化学农药在除治农林害虫方面起到了很大的作用。但由于盲目地使用化学农药，也造成了严重的环境污染。本文阐述了化学农药造成的环境污染并探讨了如何利用害虫综合控制机制，科学有效地使用化学农药，减少环境污染，保护环境的途径。     

林业机械驱动桥壳的可靠性设计

目前，林业机械正向高作业效率、高机动性能、高生产能力和优良的可靠性目标的方向发展。可见应该大力推广建立在概率统计理论基础上的可靠性设计方法，摒弃旧的安全系数的概念和相应的估计方法，这样不仅能解决过去用传统设计方法所不能处理的一些问题，而且能有效地增强...     

异龄林收获调整的动态优化及其计算机仿真

本文在异龄林生长矩阵模型基础上,研究了异龄林动态优化问题,建立了相应的计算机仿真模型。此模型采用自动扩大调整分期的方法,来寻求使异龄林林分由当前状态调整到理想状态的最短且效益最高的采伐轨线,并在FACOMM-340S中型机上开发了相应的软件。本文的方法在确定异龄林收获调整问题的可行域和最短调整时间方面具有明显优点,对森林经营者进行采伐决策和预测工作有实用价值。     

A new method for estimating stiffness and strength in bolted timber-to-timber joints and its verification by experiments (II): bolted cross-lapped beam to column joints

Bolted cross-lapped joints (BCLJs) are one of the basic jointing methods used in Japan and European countries. There are, however, some problems in the design of BCLJs. With increasing use of large-scale wooden frame structures in Japan, it is necessary to establish proper estimating methods for predicting actual characteristics. A new approach was developed, using Saint Venant torsion theory, to estimate the performance of bolted timber joints in a more practical manner than using computer simulations. The calculated values were compared with the experimental results, indicating that the rotational stiffness and yield moment of BCLJs would be precisely predicted using the proposed theory. It was also found that the rotational stiffness calculated using the design method rooted on Coulombs torsion theory is about two times higher than the experimental results in the case of a rectangular arrangement of bolts.     

自由基加成反应合成萜基甲硫醚

自由基加成反应应用于萜类化学为萜基甲硫醚的选择性合成提供了一条新的、简便的、有效的途径。在这一反应中，考察了反应时间、底物的比例、引发剂的种类及用量对转化率和产物的选择性的影响，并对反应的机理进行了探讨。     

Acaricides in modern management of plant-feeding mites

This review focuses on biological profiles of contemporary acaricides, acaricide resistance, and other up-to-date issues related to acaricide use in management of plant-feeding mites. Over the last two decades a considerable number of synthetic acaricides emerged on the global market, most of which exert their effects acting on respiration targets. Among them, the most important are inhibitors of mitochondrial electron transport at complex I (METI-acaricides). Discovery of tetronic acid derivatives (spirodiclofen and spiromesifen) introduced a completely new mode of action: lipid synthesis inhibition. Acaricide resistance in spider mites has become a global phenomenon. The resistance is predominantly caused by a less sensitive target site (target site resistance) and enhanced detoxification (metabolic resistance). The major emphasis in current research on acaricide resistance mechanisms deals with elucidation of their molecular basis. Point mutations resulting in structural changes of target site and leading to its reduced sensitivity, have recently been associated with resistance in Tetranychus urticae Koch and other spider mites. The only sustainable, long-term perspective for acaricide use is their implementation in multitactic integrated pest management programs, in which acaricides are applied highly rationally and in interaction with other control tactics. Considering that the key recommendation for effective acaricide resistance management is reduction of the selection for resistance by alternations, sequences, rotations, and mixtures of compounds with different modes of action, the main challenge that acaricide use is facing is the need for new active substances with novel target sites. Besides implementation of advanced technologies for screening and design of new synthetic compounds, wider use of microbial and plant products with acaricidal activity could also contribute increased biochemical diversity of acaricides.     

微生物降解合成洗涤剂的研究进展

对合成洗涤剂的化学组成、环境效应进行了简要分析,论述了合成洗涤剂的使用所带来的环境问题,详细阐述了有关微生物对合成洗涤剂的降解机理、途径,以及微生物在对合成洗涤剂所造成的环境问题治理及其在环境保护措施中的利用,并对微生物在洗涤剂业中的应用前景做出了展望。     

IMPRESSIONS OF FORESTRY IN SOUTHERN EUROPE

The bonding of wood by means of glue has been practised for many centuries.

Adhesion between an adhesive and wood is the result of unbalanced secondary valency forces (Van der Waal's forces) present on the interfaces. It is fundamental to good adhesion that the adhesive must (a) wet the surface it is required to adhere to and (b) penetrate the wood capillaries. The phenomenon of “wetting” is indicated by the contact angle the adhesive forms on the wood surface as well as its ability to penetrate the wood capillaries. Maximum penetration of the capillaries is inhibited in practice due to air becoming trapped in “inkpot” type capillaries caused by the sawblade tearing the wood fibres over in the direction of the cut. Several ways to increase capillary penetration are suggested.

The anisotropic chemical reactivity of wood is theorized in so far that a unit area of wood substance (excluding lumen openings) cut on the cross-sectional plane cannot be as effectively glued as a unit area of wood substance on the radial and tangential plane. This is due to the positioning of the chemically reactive groups on the cellulose chains which are predominantly oriented parallel to the fibre axis.

The engineered design of joints is briefly discussed and mathematical expression given as to how incorrect joint design can be detrimental to the ultimate joint strength.

The general character of the better-known synthetic adhesives is briefly discussed. Little detail is given as excellent hand books exist on this specific subject.