机动车辅助制动系统

当车辆在高速行驶中遇特殊情况紧急制动时,由于惯性它不会立即停止。许多车祸就发生在车辆行驶中驾驶员未及时发现范围距离内有障碍物,待发现并紧急制动后由于车辆先期的高速行驶所储存的势能而继续滑行的过程中。尽管现代汽车采用了如ABS系     

一种基于Sigmoid函数的自动驾驶车辆运动规划方法

自动驾驶汽车包含感知定位、规划控制等主要模块,其中运动规划的任务就是规划车辆行驶的轨迹和速度,运动规划需要在满足车辆的运动模型和状态边界条件下,同时保证生成的轨迹平滑,速度可控。针对运动规划中的速度规划模块,基于Sigmoid函数设计了一套速度和加速度规划方法。该方法能够满足车辆速度及加减速限制问题,同时可以保证在车辆整个行驶过程中速度和加速度变化连续,确保了车辆行驶过程中的舒适性。     

智轨电车直线行驶性能研究

智轨电车属于多编组全轴转向车辆,容易存在直线跑偏、“C”字型、“Z”字型及偏斜直行等直线行驶问题。通过对影响车辆直线行驶的悬架K&C特性研究,优化悬架硬点,改善轮跳造成的轮转向问题;通过对底盘参数及传感器零位研究,完善底盘调试工艺,消除由上述参数不正确引起的车辆直线行驶问题。     

集运材车辆轮胎气压最优控制原理及其方法

集运材作业中,作业车辆轮胎的气压状态和地面土壤状态直接影响作业车辆行驶阻力的大小。对于后者,若做到完全控制比较困难;对于前者却比较容易控制。根据行驶路面支承情况,控制车辆轮胎气压,减小行驶阻力,提高通过性能。这是森工发达国家十分重视的新技术。本文对轮胎气压控制的基本理论作了较详细的阐述,并对目前国外存在的控制方法作以介绍。     

林道路面不平度的统计特性

运材车辆在路面不平的林道上行驶时,将引起车体的振动,使运材车辆系统的动载荷增加,零部件变形,连接松动,加速有关零部件的磨损甚至破坏。因而增大了车辆的保修量,降低了利用率和生产率,不仅增加了运材成本,而且加剧了林道的破损。同时,当运材车辆行驶过程中的垂直振动加速度达到一定程度时,乘坐不舒适性增强,影响行驶速度;强烈振动所引起的轮胎上下跳动,使运材车辆难以操纵,影响行车安全。为了改善上述状况,合理使用和改进运材车     

对林区公路路面强度的探讨

公路路面应具有一定的强度,这是车辆行驶对公路的基本要求;尤其林区公路上行驶的运材车辆轴重较大,对路面强度要求更高。如何保证路面具有足够的强度,以满足车辆行驶的要求,这是一个比较复杂而又十分重要的问题,除了与路面本身结构层次的选择,路面的厚度及施工方法有关外,还与路基的强度和稳定性有关。     

三角履带式集材机的设计与分析

通过对集材机行走系统的研究,设计了一台三角履带式集材机。介绍了集材机整机结构、三角履带结构,并分析计算了牵引力、功率。利用MATLAB对车辆稳定性进行分析,发现降低质心高度、减小质心偏移距离、增加轨距可提高车辆稳定性。计算得出其空载纵向上、下坡最大行驶坡度分别为38.4°、33.2°,满载时分别为37.6°、38.1°,横向匀速直线和匀速转弯最大行驶角度为26.4°、22.8°。利用Adams对坡度为25°时车辆上、下坡及横向直线行驶运动进行仿真,结果表明:车辆有良好的爬坡能力和行驶稳定性。该研究对集材机的发展有一定参考意义。     

履带式集材车辆振动的模拟及行驶平顺性的研究

本文从研究履带式集材车辆的振动和行驶平顺性出发,提出一种履带式集材车辆随机振动的计算模拟方法,将该型车辆简化为三自由度集材机-座位系统力学模型。以国产集材50型集材机为对象,在DPS 8型计算机上进行了模拟计算。通过实地试验,表明试验结果与模拟计算结果能较好吻合。此外还利用模型研究了车辆结构参数对行驶平顺性的影响,并对集材50型集材机的行驶平顺性进行了评价,提出了改善平顺性的具体建议。     

运材车辆轮胎使用情况的分析

本文从穆棱林业局运材车辆轮胎使用中存在的问题入手,用数理统计和因果分析排列图的方法,对轮胎行驶里程、轮胎非正常磨损等情况进行分析和计算,并用比较法找出了不同车型全年完成商品木材立米数和轮胎消耗费用间的关系。指出了提高轮胎行驶里程的措施,有利于林区今后运材车辆轮胎的管理及行驶里程科学合理的确定,降低运材成本。     

浅析高速公路交通安全标线施工技术

随着我国高速公路建设日益迅速发展,高速公路安全行驶显得尤为重要,而高速公路交通安全标线的设置为确保道路畅通和车辆安全行驶起到了至关重要的作用.简述了高速公路交通安全标线的施工方法,以供相关人员参考.     

林木低磷胁迫适应机制研究进展

土壤有效磷缺乏在自然环境中是一种非常普遍的现象,近年来世界各国针对植物的觅磷和耐磷机制进行了大量研究,然而目前相关的综述性报道多限于农作物,对林木低磷胁迫适应性的综述性报道尚不多见。在长期进化过程中,林木为利用土壤中现有的含量极低的有效磷,形成了各种适应低磷胁迫的机制。文中从林木根系的形态学变化、根系分泌物对土壤难溶性磷的活化作用、林木对土壤低浓度有效磷的吸收利用以及应对低磷胁迫的遗传调控等方面综述了低磷环境中林木的适应机制,为揭示林木对缺磷环境的适应机理、发掘林木自身对土壤有效磷高效率的吸收利用能力、以及进一步筛选林木的磷高效品种和合理经营管理人工林提供参考。     

Current Research and Development on Deformation and Fixation of Bended Wood and Wood-based Composites

There are many advantages of bended wood,such as good-looking shape,simple process and low cost.The product,however,is easy to get recovery,which is urgent to be dealt with.This paper concludes the features of deformation and recovery of bended wood and wood-based composites and summarizes four treating methods to keep dimensional stability.Compared to bended solid wood,some elementary perspectives on the research of bended wood-based composites are presented.The purpose of this paper is to suggest:1)to investigate the optimum heating time and temperature that bended wood and wood-based composites need from the formation of deformation to the recovery and to the permanent fixation,according to its changes of dimensional stability such as curvature radius;2)to measure the composites comprised of wood and adhesives on the changes of stress relaxation,dynamic viscoelasticity and crystal1ization field;3)to quantitatively analyze changes of the major components in wood cell wall polymers as well as the composites under heat/steam treatment and untreated conditions.It will be helpful for subsequent research to clarify on the mechanisms of permanent fixation of bended wood and also contribute to that of wood-based composites.     

培育森林资源要走内涵增长的新路子

本文提出了培育森林后备资源的指导思想要实现６个转变：（１）森林更新方式由营造成片人工纯林为主向“人天混”上转变，（２）森林培育方式由粗放经营向集约经营上转变；（３）森林培育重点由人工造林向抚育天然幼壮林上转变；（４）种苗工作由常规技术向生物遗传工程技术上转变；（５）经营机制由单一全民造林向多元化造林上转变；（６）营林机构单一职能部门向公司化转变。这些举措对森林经营和营林体制改革都具有现实意义。     

板栗优质高产途径及其技术措施的研究

增加结果母枝粗度、减少生理落果、改善内腔光照条件、适当控制树冠体积、提高栗棚内的栗果数与栗果重、缩短由小年到大年的时间,以及适时防治病虫害是板栗优质高产的有效途径。同时提出了实现各途径的主要技术措施。     

The challenges of effective model scoping: A FLORES case study from the mafungautsi forest margins,Zimbabwe

This paper explores the challenge of defining the scope of a systems model, emphasising three aspects: boundary, granularity and conceptual scope. The significance of these is illustrated by reference to a model of land-use decisions made in villages bordering on the Mafungautsi forest in Zimbabwe. The purpose of this model was to help policy players (Forestry Commission staff, non-governmental organisations, researchers and local people) to understand the impact of policy interventions on local people’s livelihoods. Scoping decisions that were made in building the Mafungautsi model were deliberately liberal, to encompass the interests of all participants in the modelling process. These decisions now present a range of serious challenges: the difficulty of model calibration, the computational expense of running simulations, and the difficulty for new users to understand the model. Facilitators of modelling teams need to consider the serious implications of giving everyone what they want and including all participants’ ideas in a model. In the long run, it may be better to be tough and reject many suggestions at the outset. The former approach is unlikely to lead to a tractable model, while the latter may ultimately offer greater satisfaction for all. We are grateful to the UK’s Department for International Development (DFID) and the European Community for financial support of this project. Thanks also to all of the ACM team who have contributed ideas on the process and content of the modelling work and who make it fun to undertake collaborative research. Thanks also to the participants in the Zimbabwe FLAC workshops for their input into the specification of the Mafungautsi model. Finally thanks to Robert Muetzelfeldt, Jasper Taylor, Jonathan Massheder, Fergus Sinclair and Jerry Vanclay for helping us to ride on the FLORES bandwagon.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

昆明市引种的园林树木适应性研究

依据对昆明市现有园林树木(包括外地园林树木和本地野生树种引种的种类)的生物学、生态学习性以及生活力表现等的调查资料，对其引种园林树种的适应性作出了初步评价。昆明市栽培的园林树木计有84科240属623种(包括变种、变型及品种)。其中531种适应或基本适应昆明的园林环境条件，占总数的85％。在原产于北热带的树种中，适应或基本适应的占36％，不适应的占64％，其中濒死或死亡的占30％；原产南亚热带的树种，适应或基本适应的占70％，不适应的占30％；原产亚热带和暖温带的树种均能适应或基本适应昆明的园林环境条件；在原产温带的树种中，适应或基本适应的占88％，不适应的占12％。昆明野生树种适应性较好，而原产高海拔地区的树种适应性较差。在原产国外的树种中，引自北美洲西南部、中美洲高原、澳洲东南部、日本、欧洲地中海沿岸、印度、缅甸的树种适应性较好；而引自非洲、美洲、澳洲、东南亚、南亚热带地区的树种适应性差。     

我国油茶产业发展现状与对策建议

为梳理制约我国油茶产业发展的瓶颈问题,文中介绍我国油茶产业发展历程,综述油茶产业发展现状,从良种繁育、栽培管理、加工和科技服务等方面分析存在的问题,并针对问题提出相应的建议:加大良种选育监管力度,限制认可度低的良种推广应用;建立良种基地动态评估和奖惩机制,加大育种资金投入;整改现有采穗圃,提高良种繁育单位准入门槛;扩大优良良种使用范围,加强良种繁育技术培训;分地区细化高效栽培和低产林改造技术;建立高产示范基地和专家库,引导经营者科学经营;推进油茶全产业链机械化建设步伐,完善加工工艺;制定油茶产品质量标准,建立油茶产业高质量发展公共服务平台;加强公共品牌建设与宣传,提高消费者对油茶品牌认知度;组建油茶科技服务团队,完善油茶科技服务体系。期望通过这些建议能够助力我国油茶产业高质量发展,使油茶产业加速从千亿向万亿规模迈进。     

外来杨树遗传资源及其存在的问题

简要回顾了我国不同时期引进的杨树遗传资源。在总结了外来杨树资源对推进我国杨树栽培品种化和育种上起到了重大作用的同时，针对目前存在的问题提出了今后应加强的研究工作：必须加强对基因资源研究的投入，建立完善的资源保存基地，增强今后杨树育种创新能力；扩大资源评价研究的规模和深度，使外来杨树资源利用更有预见性；杂种杨树的基因渗入可能会改变原有乡土杨树的遗传多样性和完整性，对人工育成品种导人不育基因是防止基因污染的关键技术措施，应作为今后推广新品种的一项必备新指标；为应对我国气候变化可能为杨树集约栽培带来的有益性（栽培区北移和生长期延长）和潜在的生态风险（干旱缺水）及病虫灾害所需求新品种作前瞻性准备，必须从现在起开始新一轮杨树种质资源的收集和研奔。     

Acoustoelastic birefringence effect in wood II: influence of texture anisotropy on the polarization direction of shear wave in wood

Ultrasonic shear waves were propagated through the breadth direction of a wood beam which was subjected to a bending load such that it was in a plane-stress state. The oscillation direction of the shear waves with respect to the wood beam axis was varied by rotating an ultrasonic sensor, and the relationship between the shear wave velocity and the oscillation direction was examined. The results indicate that when the oscillation direction of the shear wave corresponds to the tangential direction of the wood beam, the shear wave velocity decreases sharply and the relationship between shear wave velocity and rotation angle tends to become discontinuous. When the oscillation of the shear waves occurs in the anisotropic direction of the wood beam instead of in the direction of principal stress, the shear wave velocity exhibits a peak value. In addition, the polarization direction was found to correspond to the direction of anisotropy of the wood beam according to the theory of acoustoelastic birefringence with respect to plane stress. This indicates that when the acoustoelastic birefringence method is applied to stress measurement of wood, it is appropriate to align the oscillation direction of the shear wave with the principal axial direction of anisotropy in order to carry out ultrasonic measurement.