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41.
Shang Deku 《林业研究》1990,1(1):79-85
An analogy between water flux and the field of temperature gradient in a column of wood fuel chips was discovered by these
experiments. The heat—mass transfer coefficient was determined by least squares method. An equation relating water flux and
temperature gradient was developed and it was demonstrated that the temperature gradient was the main driving force for water
transport. The mechanism was evaporation—condensation of water vapor through natural convection in air phase. The study gives
a theoretical explanation for analyzing the problem of water transport in wood particle material. 相似文献
42.
辽东地区森林可被燃物载量的调查研究 总被引:6,自引:1,他引:6
森林地被可燃物是引起森林火灾的重要原因,掌握森林地被可燃物的载量分布,对森林火灾的预防有着十分重要的意义。通过对辽东地区不同森林类型的调查,搞清楚了一些常见的主要林型地被可燃物平均载量情况,同时对油松人工砘林、落叶松人工纯林和天然阔叶杂木林3个具有代表性的林型,按不同林分密度、林龄、坡向和坡位等因素,进行地被可燃物载量分布状况调查,结果表明,辽东中、北部地区载量大于辽东南部地区;林分密度和林龄愈大,则载量愈高;南坡载量大于北坡,北坡最小;坡位愈高,则载量愈小。 相似文献
43.
44.
Large cardamom (Amomum subulatum Roxb.) is a shade loving plant grown in the Indian hill states of Sikkim and Dargeeling district of West Bengal. About 30 important tree species are used to provide shade to the cardamom plants. Alnus nepalensis, a deciduous, nitrogen fixing and fast growing tree, is the species most commonly underplanted with cardamom. In addition to providing shade, it is also used for fuelwood. The old trees are cut and young plants coming up are allowed to grow in cyclic order. The quick decomposing leaf litter of A. nepalensis also fertilises the cardamom plants. The nitrogen added to the soil in this way has been found to be as high as 249 kg/ha. Large cardamom thrives well in a moist soil, which is maintained by water diverted from seasonal springs on the upper slopes. The system is well suited to conserving soil, water and tree cover of the characteristically steep slopes of the region. Moreover, the management inputs required for growing cardamom are low but the crop gives a higher financial return than rice or maize. The shade trees used in the system are also a major source of fuel, fodder and timber, especially as access to state owned forests is restricted by legislation. However, increasing incidence of viral chirkey and foorkey disease, panicle rot and capsule borer are reducing the cardamom productivity. It has been observed that integrating dairying and apiculture will further augment profitability from large cardamom agroforestry system. 相似文献
45.
46.
以瓦锡兰Sulzer 7RT—flex60C型船用柴油机为研究对象,首先介绍了燃油共轨系统的组成,分析了燃油共轨系统的特性,然后利用流体力学原理构建了燃油共轨系统各个模块的数学模型,最后采用MATLAB/Simulink软件进行仿真计算.仿真结果与船用柴油机台架数据误差符合要求,具有一定的有效性和准确性. 相似文献
47.
The objective was to study the effect of future harvesting and handling technologies on the cost and energy efficiency of supply chains for young dense thinnings. The system costs and energy requirements were modeled using type of stands, products delivered, and transport distances as variables. In total, 14 systems were analyzed, of which five represented future systems. The effects of increasing the payloads of off-road and road transportation of whole tree (WT) parts by 10%, 20%, and 30% were also analyzed. If boom-corridor thinning technologies, optimized bundle-harvesters, and load-compression devices are developed, on average, costs are reduced by 12–27% and 11–30% less energy is required when compared with present systems. For example, at an average harvested tree size of 22 dm3, the supply of WT using future technologies would reduce the cost by up to 15% and the energy requirements by 21%. These effects increase with reduced tree sizes and increased transportation distances. The effects of future technologies are especially significant for tree sizes below 30 dm3, representing a significant part of the potential that could be harvested annually in Sweden. Thus, there should be increased research and development of boom-corridor felling technology, bundle-harvesters, and load-compression devices. 相似文献
48.
49.
在分析生物质成型燃料技术特点和项目社会关系的基础上,选取湖北省1家生物质成型燃料企业为研究对象,对其经济效益进行分析.结果显示,该企业净现值为正值,项目可行;内部收益率14.0%,项目收益较高;动态投资回收期10.7年,项目风险较大.对影响经济效益的不确定性因素分析:成型燃料售价对经济效益影响极其敏感,敏感系数为10.6,其次是原料收购价格,敏感系数为6.4,政府对项目建设补贴较敏感,税收政策影响不敏感,敏感系数分别为1.8和0.55.根据新出台的税优惠政策,内部收益率可提高至21.7%,如政府对成型燃料售价补贴10%,加上税收优惠,内部收益率将达到36.8%,动态授资回收期下降到4.3年,经济效益显著,项目风险低. 相似文献
50.
WANG Mingyu SHU Lifu TIAN Xiaorui LI JieInstitute of Forest Protection Chinese Academy ofForestrv Forest fire management office. State Forestry Administration 《中国林业科技(英文版)》2003,(4)
Lightning fire is one of natural fires; its mechanism is very complex and difficult to control. Daxing'an Mountain is the main region that lightning fires occur in China. Research on lightning fires indicates that special fuel, dry-storm weather and high altitude form the lightning fire environment. Lightning fires have close relation with lights. When lightning occurs, especially dry-lightning which brings little precipitation with surface temperature growing and fuel dehydrating, these often lead to lightning fires. Lightning fires have characteristics of geography, time and topography. The higher altitude forest region in Daxing'an Mountain, the more lightning fires occur. Valley with altitude above 800 m in the north of 51.N and Larix gmelinii-Pinus pumila, Pinus sylvestris var. mongolica -Pinus pumila forests on the top of mountain are the most concentrating region where lightning fires occur. One serial dry-storming can ignites many lightning fires, the furthest between them is as long as 150 km. 相似文献