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41.
Chen Qigao Feng Ya 《保鲜与加工》1993,(1)
This paper analyses the thermal moist characteristics of the hull layer beside an air layer at lower temperature in an envelope for a cold storage and presents a new method of waterproof by air layer. With test data from engineering practice, the theory on the barrier of self moisture proof at the surface sublayer of the hull layer in an attic on a cold storage is proven. The dried zone about three phase point is confirmed. It is a new knowledge for thermophysics on thermal design of a cold storage with an optimum thermal performance. 相似文献
42.
以粮温实测数据为例探讨低温储粮的可行性 总被引:1,自引:0,他引:1
通过对高大平房仓粮温进行跟踪检测,分析比较了粮温变化情况,并探讨了低温储粮的可行性。 相似文献
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广东三岭山森林公园主要人工林碳汇功能及其经济价值评价 总被引:1,自引:0,他引:1
本文以广东三岭山森林公园的马尾松、尾叶桉、大叶相思人工林为研究对象,研究对比它们的碳储量和碳汇经济价值,为评价广东的3个优势造林树种的碳汇能力及为广东的造林选择提供依据。结果表明:3种人工林树种单位碳储量由大到小排列次序为:尾叶桉(166.89 t·hm-2)>大叶相思(128.72 t·hm-2)>马尾松(70.12 t·hm-2)。3种人工林平均碳汇经济价值按大小排列次序为:尾叶桉(45611.04元·hm-2)>大叶相思(35179.18元·hm-2)>马尾松(19163.80元·hm-2)。尾叶桉是这3种人工林中碳储量的主要部分,对广东三岭森林公园发挥着巨大的碳汇功能并具有强大的碳汇经济价值。因此,可以考虑在广东省碳汇造林时选择尾叶桉种植。 相似文献
48.
Recruitment of sympatric vendace (Coregonus albula) and whitefish (C. lavaretus) is affected by different environmental factors
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Vendace and whitefish in Lake Osensjøen (boreal south‐east Norway) were studied by means of gillnet test fishing (1976–2013) and hydro acoustic acquisition (1986–2011). Vendace increased in number between 1998 and 2009 while growth and size at maturity decreased. The relative density of whitefish decreased in the pelagic habitat, whereas growth and size remained the same. Both species exhibited varying year‐class strength. Whereas strong year‐classes of both species became less frequent after 1980 than before this, this seemed to change after 2000, especially for vendace. Generalised additive models suggested a strong positive relationship between July/August mean air temperature and year‐class strength of both vendace and whitefish. Whitefish recruitment was also negatively affected by the new regulation regime implemented since 1981, and positively correlated with water level after hatching and by late ice off. The reason for the diverging impacts of environmental factors on the two species may be that vendace spawn in deeper waters that whitefish do. The results indicate that increasing summer temperatures benefit recruitment of both species, whereas low water level and early ice off will harm whitefish recruitment. Both trends are caused by climate warming. It may be speculated that increased density of the specialised plankton feeding vendace may affect the algal community through increased predation on herbivorous zooplankton and potentially affect the trophic state of the lake. 相似文献
49.
文章介绍了张河湾抽水蓄能电站转子结构特点及安装工艺,分析了转子安装过程中出现的磁轭冲片受损、拉紧度不够等原因及解决办法,介绍了如何解决安装过程中分块式压板的水平度调整。 相似文献
50.
《Communications in Soil Science and Plant Analysis》2012,43(5):483-495
Abstract When sugarbeet seedlings are transferred from a complete nutrient solution to one from which Ca has been withheld, the rootlets and tops fail to develop. The same transfer at the eight‐leaf stage causes the rootlets to become stubby and swollen at the tips and blade expansion becomes modified; particularly the upper portions of the blades attaining nearly full development, which pucker and often develop a cupping or hooding effect; a unique symptom characteristic of Ca deficiency. As each new leaf develops, the blade area becomes smaller until only a black tip remains at the apex of the petiole, which is the symptom referred to as tip‐burn for this petiole and the successively . shorter petioles formed as Ca deficiency increases in severity. Strangely, these symptoms also appear during periods of rapid growth when the nutrient solution contains as much as 10 to 28 milliequivalents per liter of Ca or when soils are high in Ca. This implies that Ca absorption and possibly translocation limits the Ca supply at the growing point. Increasing Mg in the nutrient solution decreases Ca uptake and increases Ca deficiency. Potassium deficiency, unexpectedly, induces Ca deficiency apparently by decreasing the translocation of Ca to the growing point. These phenomena suggest the hypothesis that when ion absorption takes place from the root exchange site that has the affinity for H > Ca > Mg > K > Na, then the H generated internally replaces, and the roots absorb, Na, K and Mg preferentially. Externally, Ca would be adsorbed preferentially from the nutrient solution by the exchange complex, and with the addition of Mg, it would compete for the common adsorption site of Ca and limit Ca absorption internally. Under these conditions potassium‐deficient nutrient solutions would not induce Ca deficiency by decreasing Ca absorption but rather by decreasing Ca translocation. Theoretically, Ba would replace H more readily than Ca on the exchange complex, and therefore, Ba would be adsorbed preferentially and Ca uptake would increase. This effect of Ba was verified experimentally. Since the translocation of 45Ca to the growing point was found to be unrestricted under Ca‐sufficient and Ca‐deficient conditions and since the formation of insoluble Ca compounds such as phosphate or oxalate did not account for the Ca deficiency at the growing point, the cause of the Ca deficiency at the growing point is most likely the higher priority of the storage root for Ca over tops when leaf blades and storage root are both expanding rapidly. However, Ca retransport from older to younger parts of the sugarbeet plant may be restricted by the formation of Ca phosphate under Ca‐deficient conditions and Ca oxalate under Ca‐sufficient conditions. Calcium deficiency increases net photosynthesis per unit blade area initially, probably because of blade puckering, but not on a per unit chlorophyll basis. 相似文献