Effects of tightening speed on torque coefficient in lag screw timber joints with steel side plates

To investigate the effects of tightening speed on the torque coefficient in lag screw timber joints with steel side plates, tightening tests were conducted on main timber members made from Cryptomeria japonica, Chamaecyparis obtusa and Pseudotsuga menziesii, under four tightening speed conditions (1, 4, 10, and 20 rpm). Major stick-slip behavior was observed in C. obtusa based on the relationship of tightening angle with clamp force, tightening torque, and thread torque at tightening speeds of 1 and 4 rpm. In addition, tightening speed’s effects on the torque coefficient (K) varied depending on the wood species of the main member. In P. menziesii, K was not affected by the tightening speed: the ratio of torque expended on tightening was 25% on average, and the ratio of torque expended on bearing surface friction was higher than the ratio of torque expended on thread friction.     

输电塔-螺旋锚基础-土体系相互作用的影响因素分析

提出了2种计算输电塔-螺旋锚基础-土体系相互作用的简化计算模型,用有限元原理编程分析了风荷载作用下计算模型不同、锚杆直径变化、土质状况差异对体系相互作用的影响,为螺旋锚基础的推广和设计理论的完善提供了一定的理论基础。     

林用门式起重机主要部分杆件应力的技术测定方法

本文对林用门式起重机主要部分杆件进行了应力分析,并利用应变片电测法对其应力进行了测定。结果表明,实测应力与计算应力相近,实测应力小于计算应力的居多数,个别杆件的实测应力略大于计算应力。     

Relationship between clamp force and pull-out strength in lag screw timber joints

This study empirically examines the relationship between clamp force and pull-out strength in lag screw joints of timber members, using data obtained in tightening tests and pull-out tests. Maximum clamp force per unit screw length as determined from the tightening tests was lower than the lower bound for the 95% tolerance range for pull-out strength per unit screw length as determined from the pull-out tests. Moreover, X-ray CT (computed tomography) observations of anchor members from both tests revealed that failure behavior clearly differed between the tightening test and the pull-out test: tightening caused damage to the wooden, female thread in addition to major splitting damage in the wood perpendicular to the grain near the tip of the lag screw.     

A comparison of six parallel levers and two joysticks for the maneuverability of forwarders

In order to clarify the operational features of two types of controllers, which were six parallel levers and two joysticks, a comparative investigation was conducted for three different forwarders. From the results of a detailed time and operational analysis, operations of a grapple crane which were related to slewing, boom and arm functions were proved to be the main functions in loading and unloading. In regard to the six parallel levers, the following four defects were pointed out. The positions assigned for the functions, slewing, arm and rotator were not in natural relations to those movements. A lever for extension is difficult to operate. Very difficult operations occurred simultaneously controlling more than three functions. Movements of hands and fingers were very complex. In regard to the two joysticks, there was no serious problem in operations, then again, movements of the joysticks were simple. Operating with the two joysticks seemed not to be difficult even if a few extra functions were added. Thus it was advisable to equip a forwarder with the two joysticks as a controller.     

带锯机杠杆压砣式张紧系统的研究

根据以前对带锯机杠杆压砣式张紧系统振动的分析,设计了一新型装置,并用试验进行了对比分析,证实采用改进后的杠杆压砣系统可大大降低锯条的振动。为改善带锯机的动态特性提供了一条有效的途径。     

高枝修剪机剪枝运动学和动力学分析

高枝修剪机在修剪过程中锯切力大小不断变化,圆锯片、齿轮副及操作杆承受的作用力和力矩也随之变化,这些因素都会影响修剪杌工作的稳定性.通过对高枝修剪机在工作过程中的运动学和动力学分析,建立相关修枝动力学模型,确定影响锯切平衡的主要因素,为高枝修剪机的结构优化设计提供理论依据.     

强化碳汇概念,探索保护森林与环境的新思路

从森林碳汇角度阐述了森林的价值及其价值实现的方式,提出应大力发展碳汇经济,利用经济杠杆保护森林与环境。     

木工带锯条系统固有频率声学测量

采用声学测量法测试木工带锯条系统的固有频率,对带锯条研发与检测技术具有一定的应用价值,并为各类木工机械与刀具系统的固有频率测试提供借鉴的方法.     

基于MATLAB的数字信号基带传输系统仿真

SIMULINK是MATLAB中动态系统建模、仿真和分析的一个集成环境 ,文中按照仿真过程基本步骤用MATLAB的仿真工具SIMULINK实现了数字信号基带传输系统的仿真过程 ,对系统性能进行了分析     

木工适张带锯条的振动分析

应用振动理论,对经过适张处理后的木工带锯条进行研究,确定张紧力与系统固有频率之间的关系,提出将带锯条的振动简化为弦的振动与受拉伸的梁振动.用电测法测应变换算张紧力,用频谱分析法测量系统的固有频率,理论解得到试验支持,同时计算张紧力和张紧应力.     

The Mycorrhizal Requirement of the South African Forest Nursery

To achieve smoother and faster handling of timber has always been an important aim for designers of hydraulic loaders on forestry vehicles. Such loaders normally have “open-centre” hydraulic valve assemblies, in which the valves are open and oil flows freely through them when their control levers are in the neutral position.

Control systems of this kind require skilled manipulation if even three of the loader's six basic movements are to be operated together, and the continuous physical and mental strain on the operator is high. Yet timber handling takes up a major part of every forestry vehicle's life.

The article describes a new load-sensing and pressure-compensated system with proportional control—the “ERGO” system—which enables more loader movements to be handled simultaneously, resulting in greater ease and speed of handling, less operator fatigue and a closer bond between man and machine.     

永翠河溪流生态系统珍稀鸟类的保护与管理

在对伊春市带岭区永翠河流域溪流生态系统的鸟类进行系统调查的同时，对列为国家保护的珍稀濒危鸟类的生境、数量及侯鸟迁来和迁离的日期进行了较详细的研究。并找出了生境的破坏、渔猎的压力、吃野味、制标本、旅游业的干扰等促成珍稀鸟类濒危的机制。提出了加强宣传教育、提高认识、提高管理干部素质、加强行政干预、加强管理机构的建设、保护好野生动物的生境等保护和管理措施。     

"十一五"森林采伐管理刍议

在现行的法律、法规的框架下,科学合理地安排好年度森林采伐计划,并从林业产权制度改革后林木采伐主体多样的实际出发,提出简化林木采伐办证手续。通过加大综合执法力度,加强从“源头”上的监管措施,从而达到合理利用和保护好森林资源的目的。     

隔振器式杠杆压砣张紧系统带锯机锯条振动的分析

隔振器式张紧系统带锯机是在原杠杆压砣式张紧系统带锯机的基础上加以改进而形成的一种新式带锯机。通过采用MATLAB软件对带锯机锯条振动实验数据进行分析,从而证明改进后的带锯机锯条振动明显小于原杠杆压砣式带锯机。     

厦门城市绿化树种选择研究

在广泛实地调查的基础上,采用定量与定性相结合的方法,建立了由5个生物生态学特性指标、3个美学价值指标、3个抗逆能力指标、2个管护成本指标组成的厦门市城市绿化树种综合评价指标体系,并对厦门城市绿化50个主要树种进行综合效能测评,进而利用级差法筛选出一级树种14种,二级树种26种,三级树种10种。     

论提高林业的经济效益

我国林业长期以来欠账很多,经济效益低下。解决这些问题,要全面提高林业的经济效益,必须合理利用保护土地资源,同时,改革资金投放方法,加强资金管理,改变经济政策,利用经济杠杆来提高资金的使用效果。再者长期以来,营林生产一直没有进入市场来管理。将营林生产推向市场是必由之路,现在营林生产是林业的重头戏,实现营林生产商品化,是提高林业整体经济效益的根本措施。     

Vibration control of band saws: Theory and experiment

Summary Active vibration control is a key to the improvement of the cutting performance and productivity of band saws. In this paper a new method is presented for active control of band saw vibration. The transfer function of a closed-loop system consisting of the band saw, a feedback control law and the dynamics of the sensing and force actuation devices is derived. Analysis of the root loci of the closed-loop system gives two stability criteria. Stabilizing controller design is carried out for both collocation and dislocation of the sensors and actuators. It is found that vibration in all the modes can be damped through use of only one sensor and one actuator and that the control algorithms presented are realizable in practice. The theory presented is experimentally verified.This work is supported by the National Science Foundation, the University of California Forest Products Laboratory, and the authors' group of industrial sponsors     

Seasonal variation in classification accuracy of forest-cover types examined by a single band or band combinations

In vegetation remote sensing, classification accuracy cannot be fixed, due to seasonal variations in spectral reflectance characteristics. This study aims to clarify the seasonal variability of classification accuracy by forest-cover type. In particular, this paper describes seasonal variability by each band or band combinations. The study area is located in the vicinities of Hisayama and Sasaguri in Fukuoka Prefecture, Japan. Natural broadleaved, coniferous plantation, and bamboo forests were studied. Supervised classification was applied to six SPOT/HRV images taken in 1997. Kappa analysis was applied to assess the classification accuracy and compare any two error matrices. The results revealed that some single band or two-band combinations were as accurate as, or more accurate than, the full band (all three bands). The disadvantages of using a full band were especially apparent in the season with high classification accuracy. This study indicates that using all given bands does not necessarily result in the highest classification accuracy. This study also suggests that band selection within the scope of forest type and seasonal variability can contribute to better forest-cover-type classifications.     

油松天然群体种子、球果形态及同功酶遗传变异研究

对5种油松天然群体同功酶的研究表明：1）5种群体在GOT，ADH，SDH，MDH的分析中均有不同的谱带表现；在ME分析中所有的单株中均有1条清晰的谱带，属于1个染色区，受1个位点控制，该位点只有1个等位基因，属单态位点。2）5种群体在7个位点的等位基因频率和平均期望杂合度在不同酶位点间存在着较大的异质性。3）群体间的遗传分化主要来自群体内个体间，平均占总群体的95．02％。