梁非线性动力分析中剪力和轴力的相互影响

考虑梁的几何非线性动力问题，研究了其动力分析的中剪力和轴力相互影响的重要性，提出了剪力和轴力的相互影响是考虑系统非线性影响的关键。     

真空堆载联合预压法在某工程中的应用分析

本文通过对某工程孔隙水压力及水平位移资料的观测，分析了通过真空一堆载联合预压法加固软上地基，土颗粒所受侧压力、渗流力、抗剪力的变化，揭示了真空一堆载联合预压法在地基水平位移方面的相互作用．以及地下水位的变化对其加固效果的影响。     

Combined effect of wood moisture content,drill bit rotational speed and feed rate on drilling resistance measurements in Norway spruce (Picea abies (L.) Karst.)

ABSTRACT

An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the combined effect of wood moisture content (MC), drill bit rotational speed and feed rate on drilling resistance (DR) and feeding force (FF). Tests were made with Norway spruce (Picea abies (L.) Karst.) conditioned in a normal climate (20°C/65% RH), at 20°C/95% RH, vacuum-pressure impregnated in water, and oven-dried. Rotational speeds and feed rates had an impact on feed rate per cutting edge for the major cutting edge of the drill bit which was used for correlation with DR and FF for various MC. Impact of MC on DR and FF depended on rotational speeds and feed rates of the drill bit. For feed rates per cutting edge less than 0.09?mm, DR was higher for water saturated (WS) specimens. Negligible differences between DR for various MC were found for feed rates per cutting edge between 0.09 and 0.15?mm. DR was higher at low MC for feed rates per cutting edge which were higher than 0.15?mm. FF extremely increased in conditioned (20°C/95% RH) and WS specimens at feed rates per cutting edge less than 0.1?mm.     

锯齿磨损变钝程度对木质材料切削力影响的研究

采用锯齿磨损变钝程度不同的硬质合金切削刀具对三种木材(杉木、樟子松、水曲柳)和两种人造板(中密度纤维板、刨花板)进行闭式切削实验,研究锯齿磨损变钝程度对木质材料切削力的影响规律。实验结果表明,随着刀具磨损变钝程度的增加,主切削力和法向力都呈增大趋势,且法向力的增幅更明显。负间隙C对中纤板主切削力、法向力以及刨花板法向力的影响曲线类似,均为先缓慢上升,再急剧增加,然后又趋于平缓;刨花板主切削力随负间隙C的增加而不断增加。     

玉溪市林分植被覆盖变化及驱动力分析

林分植被覆盖在很大程度上能够反映林分生态系统的健康与否,其时空变化是林分生态系统发展方向的判断依据。对玉溪市2010—2019年林分植被覆盖的时空格局变化进行了分析,并利用单因素和多元回归分析方法分别建立回归模型探索了林分植被覆盖改善与退化的驱动因素。结果表明:林分植被覆盖整体呈向好趋势,各驱动因素与斜率均不是简单线性关系;道路和居民区与林分植被覆盖改善速度呈负相关、与退化速度呈正相关;DEM、坡度、大型水体、公益林管护与林分植被覆盖改善速度呈正相关、与退化速度呈负相关;坡向与林分植被覆盖改善速度呈正相关,地形起伏度与林分植被覆盖退化速度呈负相关。林分植被覆盖改善与退化的驱动力不尽相同,影响机制也存在差异,这为更好制定生态保护相关政策提供了有力的科学依据。     

基于库兹涅茨曲线的中国南方集体林区森林质量转型动因分析

森林转型理论提供了全球可能经历的森林恢复途径,但已有研究主要关注森林数量.文中从广义上提出森林多维转型并重点关注森林质量转型,从森林生长性、树种多样性、结构稳定性和森林健康性4个方面对森林质量进行衡量,通过构建森林转型影响因素分析框架对中国南方集体林区10个省(区)(浙江、安徽、福建、江西、湖北、湖南、广东、广西、贵州...     

A biomechanical analysis of industrial forest plantation workers in East Kalimantan

The objectives of this study are to clarify physiological work loads and physical loads acting on the lumbar region of workers and to propose a safe work environment in tropical forestry operations. The research was conducted in the industrial forest plantations of East Kalimantan, Indonesia, in 1996. In this study, heart rates and the physical lumbar burden of industrial forest plantation workers were measured for three types of work, that is, weeding, planting and path clearing. In addition, the load moment at the L₅/S₁ and the disc compression force were calculated using low-back biomechanical models. As a result, compression forces at the L₅/S₁ disc during weeding, planting and path clearing were estimated and found to be below the Action Limit (AL) by National Institute for Occupational Safety and Health (NIOSH). However, it was also found that some work posture types during path clearing by chain saw were sometimes above the AL. A part of this paper was orally presented at the 108th Annual Meeting of the Japanese Forestry Society (1997).     

9FQM1000型树枝秸秆粉碎机的设计

针对新型农业经济组织每年秸秆和废残树枝产量大、利用率低、传统焚烧易污染环境等问题,采用双通道喂入方式,运用盘式切碎加锤片粉碎的基本工作原理,对树枝秸秆粉碎机的结构和传动系统进行了设计,设计出能够对树枝秸秆进行精细粉碎的9FQM1000型树枝秸秆粉碎机并进行试制。样机试验表明,9FQM1000型树枝秸秆粉碎机组合粉碎结构可靠,生产效率为3 000 kg·h^-1。     

防疲劳驾驶系统的设计

设计一套集疲劳驾驶计时功能、疲劳驾驶检测功能、疲劳驾驶警示灯显示功能、GPS疲劳语音提示功能及GPS定位功能于一体的防疲劳驾驶系统,绘制工作流程图.通过模拟驾驶器模拟实际驾驶,对比分析头部位置检测系统、车道偏离报警系统、转向盘监测系统、驾驶员警示系统及PERCLOS系统检测疲劳驾驶的优缺点,得出了PERCLOS系统为最优疲劳驾驶检测方法.依据人因工程理论,给出了车体外部警示灯的位置和颜色的设计方案.