车厢可旋转式多角度自卸车的设计

设计了一种可多角度倾卸货物的自卸车车厢旋转机构,以满足道路狭窄及卸货方向多变的要求。经过稳定性分析和强度校核,满足工程实际需要。     

低速载货汽车的定位与设计探讨

分析了低速载货汽车存在的现状，阐述未来低速载货汽车“创新适用”的定位方向，指出要以合理的整车匹配，人性化的设计理念来满足这一要求。     

载货汽车驾驶室基本力学性能有限元分析

建立了某正在研发的轻型载货汽车驾驶室有限元模型,应用有限元方法对其扭转工况下的静力学性能、固有振型及频率等动力学性能进行了分析。结果表明,驾驶室整体结构满足静力学性能的要求,但存在局部薄弱环节且在车辆怠速时易与发动机产生共振。针对分析得到的局部薄弱和共振问题提出了加强和改进的建议,为设计企业改进货车驾驶室结构提供了依据。     

汽车燃气加热器与LNG发动机联合运行试验

设计重型卡车汽车燃气加热器与液化天然气(LNG)发动机联合运行系统,以解决LNG重型卡车寒区起动困难问题。通过联合运行试验,研究联合运行稳定性及联合运行对LNG发动机冷车起动性的影响。试验结果表明:联合运行过程中,汽车燃气加热器起动顺利,燃烧稳定;利用汽车燃气加热器加热发动机冷却液,对LNG发动机的冷起动改善效果明显。因此,采用联合运行可以有效改善LNG发动机在寒区的起动性。     

Global population decline of the Great Slaty Woodpecker (Mulleripicus pulverulentus)

The Great Slaty Woodpecker (Mulleripicus pulverulentus) of South and Southeast Asia, the third largest woodpecker species in the world, is currently in the IUCN Red List category of Least Concern. This woodpecker appears associated with old-growth forests, and the rapid reductions in forest cover and old-growth area in Southeast Asia urged examination of its global population trends. We assessed population densities, tree diameter use by the woodpecker, and logging disturbance at 21 transects in four regions across the range of the species: west Borneo, Lingga Island (Riau Archipelago, Indonesia), Tenasserim (Myanmar), and west-central Myanmar. Transect survey effort was 937 km. We assessed rates of deforestation and loss of old-growth forest in the range of the species from expert review reports. By combining population density and forest cover data sets we calculated the global population trend of the species. We found a preference for large diameter trees by foraging and nesting Great Slaty Woodpeckers, and a reduction of the frequency of such trees in logged forests. Across the four study regions, between old-growth forests and logged forests, densities of Great Slaty Woodpeckers were reduced by 80-94%. Although Great Slaty Woodpeckers occur in 15 countries, ca. 70% of the global population occurs in just four countries (Myanmar, Indonesia, Cambodia, and Malaysia), three of which have high annual rates of deforestation and loss of old-growth forest. Our population calculations show that over the past century at least 90% of the global population of the Great Slaty Woodpecker has been lost. At present 26,000-550,000 individuals remain. The current global decline rate of ca. 59% ± SD 17% in three generations justifies IUCN Vulnerable or Endangered status. Contributing factors to the steep decline rate of the species are a long generation time of 5.9-8.2 years and an association with old-growth, lower elevation forests. The Great Slaty Woodpecker case adds an Asian example to a global pattern of specialized woodpeckers that are associated with old or natural forests.     

Bird use of logging gaps in a subtropical mountain forest: The influence of habitat structure and resource abundance in the Yungas of Argentina

Selective logging is one of the main economical activities in tropical and subtropical forests. While most of the effects of this activity on bird communities have been studied by comparing exploited vs. non-exploited areas; the use of human-created treefall gaps by birds is relatively unknown. We studied habitat structure, resource abundance (fruits, flowers and arthropods) and bird activity in logging gaps of different age (1-year-old and 10- to 20-year-old) in a mountain forest (Yungas) of northwest Argentina in both dry and wet seasons. In less than a year after creation, short herbs colonize logging gaps increasing the abundance of arthropods in the ground and the activity of understory insectivores. During dry seasons recently created gaps become an important source of resources for understory frugivores-insectivores. Later on in succession logging gaps are invaded by exotic graminoid vegetation and tall herbs (dispersed through extraction tracks) which can impede the colonization and development of pioneer trees and natural regeneration. Probably as a consequence of a high abundance of fruits and flowers in the understory and a very low abundance of these resources in the canopy, old gaps were mainly used by understory frugivores-insectivores while arboreal frugivores were rare. Because arboreal frugivores disperse most tree seeds in tropical and subtropical forests, the low activity of this guild in logging gaps contribute to the low observed regeneration. Sustainable timber harvest in tropical and subtropical forests should include gap and logging track management to minimize the invasion by exotic graminoid vegetation and facilitate natural succession.     

Forested land-cover patterns and trends over changing forest management eras in the Siberian Baikal region

Remote sensing observations over areas of the former Soviet Union suggest that there may be important ongoing influences on forested landscapes resulting from divergent land use and forest management associated with the Soviet versus post-Soviet eras. As the Russian Federation implements its new Forest Code and associated regulations, knowledge of existing forest patterns and trends, plus the development of methods with which to understand the landscape-level influence of different forest management strategies is increasingly important. We developed spatial–temporal models and projections of forest patterns and trends over Soviet and early post-Soviet forest management eras for a study site in the Lake Baikal region in southern Siberia. We used Landsat-derived land-cover data, logistic regressions, and Markov and cellular automata methods (CA–Markov) to characterize patterns and trends 1975–1989 and 1990–2001, and to develop predictive scenarios through 2013. Relationships of forest types (Conifer, Mixed, Deciduous) and Agriculture to other explanatory environmental variables indicated mostly consistent forest–environment relationships, but some different spatial relationships between eras were found for Cut and Regeneration disturbance types. Landscape proportional trends showed greater differences between eras. Cut proportions observed via Landsat in 2001 were approximately 74% lower, and the area of Conifer observed was approximately 14% higher, than modeled proportions predicted for 2001 using 1975–1989 Soviet era transition rates. The proportion of Cut projected for 2013 was about 80% lower when based on early post-Soviet era probabilities. Overall, modeled results indicate that should early post-Soviet trends continue, low rates of logging, some agricultural abandonment, re-growing forests especially near access routes, increases in deciduous cover, along with continued or increased fire events in mixed and conifer forests will define the landscape. Should forest management change, for example to Soviet era rates and patterns of harvest, different outcomes are projected. More broadly, results highlight the real and prospective effects that divergent management strategies can have on forested landscapes, and demonstrate that land-cover data combined with emerging spatial–temporal modeling methods provide an approach to understand and project the complex and ongoing influences associated with changing forest management at landscape scales.     

Impacts of summer versus winter logging on understory vegetation in the Chequamegon-Nicolet National Forest

In seasonal climates the timing of logging operations can be adjusted to avoid the major growing periods of understory plants and seedlings. We evaluated the understory vegetation at five pairs of hardwood-dominated sites in northern Wisconsin, U.S.A. where one site in each pair was logged during winter and the other during summer. All sites were dominated by sugar maple (Acer saccharum) and basswood (Tilia americana), with varying amounts of other native tree species. Most (84%) of the 247 vascular plant species recorded during the study are indigenous to the region. Winter-logged sites supported significantly higher numbers and percent cover of ecologically vulnerable native plant species as defined by independently established coefficients of conservatism. These differences between winter-logged and summer-logged sites suggest that winter logging may have fewer negative impacts than summer logging on vulnerable plant species and, in the long run, may help maintain plant biodiversity in managed forests of this region. In both types of sites, understory plant richness and diversity were significantly higher near logging roads, due largely to higher numbers of alien species and early successional native plants. Away from roads, neither species richness nor diversity differed between winter-logged and summer-logged sites. Studies that fail to account for differences in species composition and studies that fail to include samples of access roads or skid trails are likely to ignore important impacts of logging activities.     

重型自卸汽车车架模态试验与分析

采用试验模态分析技术对某重型自卸汽车车架动态性能进行了研究,得到了该车架的各阶模态频率、模态阻尼以及模态振型等,为进一步研究整车振动、疲劳、噪声等问题奠定了基础,也为车架结构的优化设计提供了参考依据。     

矿用电传动自卸车燃油经济性路试检测手段与反常数据分析

本文针对大型矿用电传动自卸车燃油经济性路试的检测手段既介绍了经典的、常用的容积式油耗仪,又介绍了最新发展的便携式双通道超声波流量计,并对两种仪器的使用性能进行了对比阐述。文中还就矿用电传动自卸车燃油消耗量路试结果中的反常数据的典型案例从能耗入手进行了计算分析,找出了影响因素,指明了确保测试精确性的有效途径。