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71.
采用固化剂缩短酚醛胶刨花板热压时间的研究 总被引:5,自引:0,他引:5
采用添加固化剂的方法,对降低酚醛树脂胶刨花板的热压时间进行了研究。通过筛选试验,选出了加速酚醛胶固化效果比较好的固化剂N,同时探讨了固化剂N的用量与酚醛树脂胶聚合时间之间的关系,进而确定了固化剂N的合适用量。试验结果表明,当固化剂用量为2%时,16mm厚的酚醛树脂胶刨花板的热压时间可以从14min缩短到10min,热压时间缩短了28.57%。 相似文献
72.
设施葡萄主栽品种需冷量测定及其应用研究 总被引:5,自引:0,他引:5
根据葡萄生物学特性,采用水浸枝蔓法和试区12年来晚秋稳定通过≤7.2℃气温的平均初始日期,测算出目前设施葡萄栽培中矢富罗莎等6个主栽品种的需冷量及相应的适宜扣棚升温时间。依据需冷量、果实生育期、果品品质3指标,筛选出了河西5市日光温室葡萄高效栽培的适栽品种5个,对设施葡萄大面积推广栽培具有较高的实用价值。 相似文献
73.
74.
Xu Jun-liang Ma Lv-yi 《中国林学(英文版)》2007,9(4):251-255
In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity (SFV) of Platycladus orientalis and Pinus tabulaeformis, effective solar radiation (ESR) and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe (TDP) system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5–3 hours later than those of solar radiation and there were small differences between Platycladus orientalis and Pinus tabulaeformis. But peak times and stopping times of sap flow varied con-siderably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalis and Pinus tabu-laeformis were about 0–3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR (sunrise effect). Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized. 相似文献
75.
在充分考虑数控车床加工表面特征的基础上,对以往仿真模型的不足进行了分析,提出了基于螺旋曲面的加工表面模型。该模型充分考虑了数控程序中主轴转速和进给速率两个重要参数,并提出了数控车床动态加工过程仿真的时间驱动机制。 相似文献
76.
77.
Atsushi IKEDA 《中国林业科技(英文版)》2002,(4)
Chinese fir (Cunninghamia lanceolata) and poplar (Populus spp.) wood meal were phenolated in the presence of sulfuric acid used as a catalyst. The effects of reaction time and reaction temperature on the wood liquefaction were investigated. The results showed that the reaction temperature had the greater influence on the residue content than reaction time. Additionally, the liquefaction curve for the Chinese fir and Poplar were similar in general. 相似文献
78.
P. J. Maille 《Agroforestry Systems》1991,14(2):145-148
When evaluating the economics of a joint production agroforestry system two rules should be followed: (1) all benefits and costs need to be included and (2) revenue streams over time should be compared using the net present value of an infinite set of rotations. To illustrate both points, previously presented data on the economics of eucalyptus plantings around agricultural fields are reevaluated below. 相似文献
79.
徐朴 《中南林业科技大学学报(自然科学版)》1989,(1)
本文运用统计模式识别原理,提出了一种以内燃机声响信号的时间序列自回归系数及自回归倒谱系数作为模式的特征参数,对参考模式和待检模式用灰色系统的关联测度、Mahalanobis距离测度和Kullback-leiber信息量距离测度同时进行识别,并用层次分析法对识别结果进行综合,从而达到诊断故障目的的方法。通过实验验证,表明其是有效而可行的方法。 相似文献
80.
Uma Shankar 《New Forests》2006,31(2):305-320
In species with seeds losing viability shortly after dispersal and exhibiting inherently low germination, quick decisions are required with respect to seeds that should be selected to maximize germination success and vigorous growth of seedlings. In ‘hollong’ (Dipterocarpus macrocarpus Vesque), I address the following questions: (a) are seeds that germinate randomly distributed within a seed population, (b) are subpopulations of viable and non-viable seeds separable, (c) does seed size predict which seeds germinate and (d) does seed size predict time required for germination and seedling vigour? Two estimators of seed size, diameter and weight, demonstrated a significant positive linear relationship endorsing assumption that accumulation of mass increases with increase in diameter of seeds. A threshold for selection of potential seeds for germination could not be derived from diameter measurements since seeds in an entire range of diameter did or did not germinate. All seeds <11 g did not germinate, but this threshold lies at the far lower end of the weight range and allows rejection of only a few seeds and acceptance of many seeds that will not germinate. A risk of potential seeds being rejected or non-viable seeds being picked exists if selection was derived from either diameter or weight. However, viable seeds could be better predicted from a scatter-plot of diameter on x-axis and weight on y-axis. Seeds showed a fan-shaped scatter and those developing the lower blade of the fan did not germinate while those following the handle were successful. Hence, two subpopulations segregated, but with a fuzzy edge. Mean diameter and mean weight of germinated seeds were significantly greater than those of ungerminated seeds. Most ungerminated seeds were those that had relatively smaller weight compared to their diameter. Although some large diameter seeds with small weight did germinate, but failed to develop into seedlings. Germination time and seedling vigour parameters (height, leaf number and collar diameter) were correlated both with diameter and weight. However, weight appears to have mattered more than diameter in germination success and early seedling growth. 相似文献