共查询到19条相似文献，搜索用时 62 毫秒
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英犁 《绿色中国(A版)》2011,(6)
今天,你秒杀了吗?时下,许多网购爱好者都在津津乐道于秒杀话题:马尔代夫度假秒杀价1999元;iPhone手机秒杀价399元……果真有这样的好事?秒杀,就是以压倒性优势一招致命;在极短时 相似文献
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英犁 《绿色中国(综合版)》2011,(14):63-65
4月22日中午,傅蔚冈发微博：＂从今日起到4月30日00：00,凡转一次本微博,我将为张妙女士的女儿捐助1元人民币,有愿意转？!＂随后网友大量转载。5月16日深夜,知名投资人王功权在微博上发表：＂各位亲友,各位同事,我放弃一切,和王琴私奔了＂。一时间,＂微博私奔＂成了最火爆的网络热词。 相似文献
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黄蓉 《绿色中国(综合版)》2012,(2):60-62
＂想用价值400元的有机山茶油换个新豆浆机,有人有兴趣吗？＂;＂我用单位发的600元海鲜大礼包提货券换450元的超市卡。家里人不喜欢吃海鲜,超市卡则可以买我们喜欢的东西。＂;＂公司发的健康体检卡一张,体检项目挺多,换购物卡和花生油都可以＂; 相似文献
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<正>6月12日,一场林权拍卖会在洪江市林业产权交易中心大厅热闹开拍。"雪峰山国有林场213亩山场经营权,标的价90万元!"拍卖师亮出了底价。"90.1万元",台下马上有人举起了竞价牌。90.2万元、90.3万元……最后这块山场在激烈 相似文献
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铁铮 《绿色中国(A版)》2014,(17):43-45
如今,＂国家公园＂成了一个炙手可热的词汇。它和一般概念的公园有什么区别？它是字面上的＂国家＂与＂公园＂两个词的简单相加吗？在我国应该如何减速国家公园体系的步伐？带着这些问题,记者走访了北京林业大学自然保护区学院院长雷光春教授。 相似文献
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Annika Kangas Mikko Nurmi Jussi Rasinmäki 《Scandinavian Journal of Forest Research》2014,29(7):154-165
The Finnish state forest enterprise, Metsähallitus, defines the regional harvest levels for a 10-year period in a strategic-level natural resources plan. Although this plan defines stand-level harvest schedules for all stands, in practice, it cannot be used, as the harvests need to be clustered in time and in space. It is applied by giving each subregion goals they need to fulfill in a tactical level planning process, and the harvests are manually clustered into predefined groups of adjacent stands (departments). In this study, we developed a hierarchical optimization process making use of departments for clustering the harvests. For each of the departments, 91 different stand-level harvest schedules (plans) were determined using incomes from one period and the forest value at the end as objectives. The department-level plans were then used as alternatives in a region-level goal optimization problem. The resulting hierarchic plan was compared to the stand-level solution of the strategic-level plan which served as a benchmark plan. The hierarchical plan clustered the harvests and achieved the goals set better than the benchmark plan, but the net present income was 3.3% lower. The approach turned out usable, but further developing of the approach is needed to reduce the costs of clustering. 相似文献
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Soil changes after traffic with a tracked and a wheeled forest machine: a case study on a silt loam in Sweden 总被引：2，自引：0，他引：2
Alterations to some soil physical parameters were evaluatedafter passes by a tracked forest machine and a wheeled one ofequal mass (about 20 000 kg). Measurements were made after arange of machine passes, with a maximum of eight. The measuredsoil physical parameters were dry bulk density, penetrationresistance, intrinsic air permeability, saturated hydraulicconductivity, porosity and pore-size distribution. Rut depthwas also measured. Although the wheeled machine caused deeper ruts than the trackedone, alterations caused by the two machines to the measuredsoil parameters were similar, except in the uppermost 5–10cm. The wheeled machine caused a decrease in bulk density at5 cm depth, whereas the tracked machine caused an increase,despite its lower ground pressure. 相似文献
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Kebin Zhang Rui Li Yunfang Liu Baitian Wang Xiaohui Yang Ruiping Hou 《Frontiers of Forestry in China》2008,3(3):326-333
The spatial distribution characteristics of plant communities in a wetland-dry grassland ecosystem in arid and semi-arid regions
in northwestern China and the main factors affecting the distribution pattern were studied. The Siertan wetland in the Haba
Lake Nature Reserve was the study area. Four transect lines, each about 1 km long, were set up in the growing season along
the biotope gradient in four directions: east, northeast, west and northwest. Attributes measured include frequency of occurrence,
height, density, coverage, biomass and environmental soil factors. The data were analyzed using a two-way indicative species
analysis (TWINSPAN), detrended correspondence analysis (DCA) and Spearman correlation coefficients. On this basis, the vegetation
in the Siertan wetland was classified into three types and 14 associations. The first vegetation type was halophytic marsh
vegetation, mainly distributed in the wetland zone. This type largely contains halophyte and hygric plants and its representative
association is Phragmites communis + Kalidium foliatum. The second type was meadow vegetation, distributed in the ecotone. The meadow vegetation species are mainly mesophytic and
their representative association is Nitraria tangutorum + Pennisetum flaccidum. The third vegetation type is grassland vegetation, which mainly consists of mesophytic and xerophytes, distributed in the
arid grassland zone. The representative association of the third vegetation type is the association of Anaeurolepidium secalium + Saussurea runcinata. Correlation analysis between the axes of DCA and environmental soil factors shows that soil moisture content, organic matter,
soil salt content and total nitrogen are the main environmental factors affecting the pattern of vegetation distribution along
the biotope gradients from wetland to arid grassland. Other factors affecting the vegetation are microtopography and grazing
pressure. Additionally, we have reported modifications and improvements to the importance value methodology.
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Translated from Journal of Beijing Forestry University, 2008, 30(1): 6–13 [译自: 北京林业大学学报] 相似文献
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利用RSM模型模拟计算三维水力旋流器模型,分析了计算结果,并且与相关文献比较后认为：三维模型模拟水力旋流器具有一定的可行性,而二维轴对称模型与实际有一定的差距。 相似文献
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The Silvopastoral Project is being implemented by CATIE in the Atlantic humid lowland of Costa Rica, in order to develop alternatives
to the current destructive mode of livestock production. The overall approach is briefly described and two superimposed on-farm
experiments are discussed in more detail. The main constraints for on-farm research within the project are analysed: the limited
previous knowledge of the area and of the local species, the difficulty of achieving a common understanding about research
with collaborating farmers, the need for additional staff supervision and the complexity of the statistical analyses. An attempt
is made to draw lessons from the ongoing project regarding how to resolve the apparent contradiction between rigorous scientific
requirements and questions of immediate value to extension, the compromises to be achieved between different types of evaluation
(statistical, risk, etc.) and the potentials and limitations of farmers' participation in research. 相似文献
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为适应我国山地丘陵多、坡度陡和绞盘机作业强度大、维护不便等特点,提升绞盘机的操作性和转运能力,设计了一种无卷筒离合器的轻型绞盘机,阐述了绞盘机总体布置方案和工作原理,设计了采用齿轮传动的新型选筒机构,取代传统绞盘机的卷筒离合器,传动可靠,制造工艺简单,对选筒机构的花键轴和齿轮进行了强度校核,并对绞盘机传动系统的主要零部件进行了选型与设计,利用Matlab对绞盘机卷筒进行了轻量化优化设计,利用Solidworks进行了卷筒三维建模和有限元分析。结果表明,优化后的卷筒强度满足要求。该绞盘机采用新型的选筒机构,结构紧凑,安全可靠,整机轻量化程度高,便于运输,操作简便,可以有效提升绞盘机的工作效率。 相似文献
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Wind Measurements in a Pine Forest During a Destructive Gale 总被引：3，自引：0，他引：3
Anemometer readings were recorded during a gale which blew downsome of the trees in an even-aged 16 m stand of Pinus sylvestrison sandy soil at Thetford forest. Gusts at the top of the canopyattained 17•5 m/sec. Wind profiles agreed well with thetheoretical logarithmic profile above the canopy and the exponentialprofile below. During the gale the zero plane displacement androughness length values were similar to those at lower windspeeds. It is therefore possible to estimate wind profiles andthe forces to which a tree in the crop is subjected from measurementsof wind speed at a single point within or above the forest.The wind speeds which blew trees down were much lower than thosepredicted as necessary from ‘tree pulling’ studiesin the same forest. This discrepancy suggests that any considerationof windthrow must take into account the effects of tree vibrationon the deterioration in the strength of the root-soil complex. 相似文献