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排序方式: 共有1405条查询结果,搜索用时 218 毫秒
961.
962.
Ivan Kuneš Martin Baláš Tereza Koňasová Ondřej Špulák Vratislav Balcar Kateřina Bednářová Millerová Dušan Kacálek Michal Jakl Daniel Zahradník Jan Vítámvás Jaroslava Št́astná Jana Jaklová Dytrtová 《Environmental management》2014,54(6):1421-1433
The article summarizes outcomes of a biomass study conducted in a young speckled alder plantation on a cold mountain site. At this location, the previously existing old forest was clear felled because of damage from air pollution, and present-day surface humus is in need of restoration. The intention of this study was to quantify the biomass and nutrients accumulated by alders and their components and assess whether the initial fertilization resulted in increased biomass production and nutrient accumulation in the biomass. Besides the control, two fertilized treatments were installed. In the surface treatment (SUT), the amendment was applied as a base dressing in small circles around trees. In the planting-hole treatment (PHT), the amendment was incorporated into soil inside the planting holes. Five growth seasons after planting and fertilization, six alders from each treatment were harvested including roots. Their biomass was quantified and analyzed for macroelements. The greatest pool of dry mass (DM) was branches in the control and stem wood in the fertilized treatments. The greatest pools of macroelements were leaves and branches. The most pronounced effects of fertilization were recorded in the DM and consequently in the absolute quantities of nutrients. The DM of an average tree in the control, SUT, and PHT was 85, 226, and 231 g, respectively. The absolute contents of nutrients per tree in the fertilized treatments showed the following increases, as compared with the control: (N) 2.5–2.6 times; (P) 1.6–2.4 times; (K) 1.8–2.1 times; and (Mg) 1.8–2.0 times, respectively. Speckled alder responded positively to fertilization. 相似文献
963.
南水北调中线工程与汉江中下游地区农业的持续发展 总被引:7,自引:4,他引:7
南水北调中线工程是指从汉江的丹江口水库引水供给华北地区,同时考虑鄂,豫两省汉江唐白河流域和淮河流域的需水要求的战略性工程,是调整水资源的空白布局,解决我国北方缺水问题的紧迫任务。汉江中下游地区是湖北省的粮仓和重要的产业基地,是汉江流域经济发展的中心。由于调水的影响,汉江丹江口以下的流量及季节性分配将发生变化,航运,水质,农业灌溉,工业生产以及城市发展等将受到不同程度的影响,直接关系到汉江中下游地区 相似文献
964.
重庆市机动车尾气对大气环境的影响分析及减缓措施 总被引:7,自引:0,他引:7
在对重庆市机动车保有量、主城区交通状况进行深入调查的基础上,对机动车尾气排放对大气环境的影响进行了细致的分析与评估。阐述了机动车尾气是造成重庆市大气污染的重要因素。同时结合国内外一些先进的预防、控制和处理汽车尾气污染的方法,及近年来的观察、研究和试验,提出了合理减缓、控制机动车尾气污染的措施,以防止机动车尾气污染进一步蔓延。 相似文献
965.
966.
Peili Zhang Yang Du Yi Zhou Sheng Qi Songlin Wu Jiafeng Xu 《Journal of Loss Prevention in the Process Industries》2013,26(6):1279-1284
In order to investigate the effects of branch tunnels on explosion propagation, experiments were performed in five different configuration tunnels (straight configuration and configurations with 1 branch, 2 branches, 3 branches and 4 branches). Pressure and flame transducers were used to record the history of the pressure development and track the velocity of the flame front. It was shown that the branch tunnels had ability to enhance the maximum overpressure, rate of overpressure rise, and deflagration index (KG) of the gasoline–air mixture explosion due to the turbulence induced by the branch tunnels. The overpressure rise rate and KG of the explosion increased as a function of the number of branch tunnels. Experiments also showed that the maximum flame speed increased as the branch number increasing from 0 to 3 due to the enlargement of turbulence induced by the branch tunnels. However, an increase of branch number did not always lead to an enhancement of flame speed because the heat loss was intensified resulting from the increase of flame surface caused by the branch tunnels. When the number of branch tunnels exceeded 3, the maximum flame speed dropped. 相似文献
967.
应用模糊数学系统聚类方法对陕西1949~1990年自然灾害造成的人口死亡、房屋倒塌和农田成灾面积进行了聚类分析,划分出相似成灾年份及相应损失指标,同时通过总损失价值计算进行了逐年损失等级划分,建立了各级等级标准和灾害年景序列。 相似文献
968.
山东新汶矿业集团翟镇煤矿通过不断引进、消化和吸收国内外先进生产技术,走科技创新之路,这个昔日饱受顶板破碎干扰、生产条件复杂的大型矿井在短短几年的时间内实现了采掘机械化、辅助自动化、控制智能化,先后有136项科技项目首开国内先河,其中32项达到了国际先进水平。为推动“科技兴矿”战略的实施,翟镇煤矿采取了一系列有效措施: 相似文献
969.
杜卓勋 《湖南环境生物职业技术学院学报》2001,7(2):49-50
针对“极限”概念提出了一些见解,并从理论上描述和给出了“极限”的精确定义,从该定义出发,更有助正确理解和掌握“极限”的内在含义。 相似文献
970.