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151.
介绍了国内外温室测控技术的发展历史、现状、发展趋势及研究动向,提出了进一步发展我国温室测控技术、提高我国温室现代化程度所亟待研究和解决的问题.  相似文献   
152.
以女儿寨小流域为研究对象,着重研究了植被恢复与重建过程中小流域系统的降雨和水沙变化特征,并对植被恢复过程中的总体减沙水平做了分析。结果表明:①受大气环流的影响,小流域年际降雨量差异较大;小流域降雨年内时间分布极为不均,集中性很大,主要集中在汛期(4-8月),但年内降雨量的月间分布趋势基本一致。②小流域迳流年际变化很大,迳流年内分配不均。迳流集中是该小流域迳流变化的一个显著特征:小流域的植被恢复与重建对洪峰的出现和洪峰流量具有明显的延缓和削减作用。③径流(Qi)主要来源于降水(Pi),二者呈明显的一元线型关系:Pi=115.7678+2.7386Qi。④小流域的年输沙模数与年迳流量的变化规律基本一致,小流域年内产沙也高度集中,且与降水、迳流关系密切,小流域的土壤侵蚀主要由汛期的强降水引起。⑤随着小流域大面积、高标准的生态环境建设,1990年至2004年间小流域的输沙模数呈锐减之势,植被恢复与重建起到了显著的减沙效应。  相似文献   
153.
This study examines a method for designing an optimum profile of a forest road in a short matter of time. In this method, a genetic algorithm (GA) searches for points where the gradient changes and dynamic programing (DP) designs the longitudinal slope. This method can be applied to the ground heights of an actual forest road. The evaluation function of the DP assesses the total expenditure. The inverse of this function is the fitness function. Crossover and mutation are operators of an evolution simulation of a GA. They are each repeated 20 times and 420 profiles are designed and assessed, all within about 10 min. A comparison of the profile designed by the GA with that of an actual forest road shows only one section where the formation level differed substantially. Overall, both profiles seem to show a high degree of correspondence. From this result, we believe that the profile designed by the GA is best, or the one of the best. A conventional method takes about 65 h to calculate all changing points of gradients. However, by using the GA, the calculation time was reduced to about 1/389 that of the coventional method, showing that the method which uses the GA through the profile design is very useful.  相似文献   
154.
本文结合大兴安岭地区的实际情况,以实施“天保工程”为出发点,分析了转产项目建设面临的诸多问题,并提出了改革建议和转产项目开发建设应遵循的原则及发展方向。  相似文献   
155.
从我国木材资源的变化看普通刨花板的发展   总被引:2,自引:0,他引:2  
分析了国内普通刨花板及其成套生产设备的现状及与国际先进水平的主要差距。通过对我国木材资源结构变化状况的论述,阐明了普通刨花板产业在我国的适应性以及发展趋势。介绍了苏福马公司在普通刨花板成套生产线设备发展中的实践及发展目标。  相似文献   
156.
据样地调查,该25年生杉木人工林群落的植物有41科84属120种,群落的外貌特征以包括藤本在内的高位芽占绝对优势,叶特征以革质,单叶,中小型叶为主,由于该群落的幼树层以米储和木荷等占优势,若让其自然发展或杉木林采伐后不炼山,并排除其它人为干扰,该群落将向与常绿阔叶林采伐前的群落类型相似的方向演替。  相似文献   
157.
本文对我国森林公园的现状进行了评价。对其发展趋势进行了预测.指出我国森林旅游资源极其丰富,有待加快开发和提高效益;阐明了培养人才、加强管理的重要性.同时,对我国森林公园的发展和森林旅游的需求进行了预测.对了解我国森林旅游业的发展有一定的参考价值.  相似文献   
158.
根据该地层剖面不同时期泥炭地层的孢粉类型、数量的变化,将该不同年龄段剖面中出现的孢粉划分为六个孢粉组合带。利用不同时段孢粉类型及数量变化所反映的森林生态环境,重塑了不同时期的古气候特征。可概括为:从距今1.6万年晚更新世晚期,经冰后期晚更新世与早全新世分界,再经中全新世至晚全新世直到目前,经历了冰后期一个短暂转暖期一寒冷一温冷到温暖一温暖微干一温凉一温暖这一变化趋势。雷波小海子地处凉山州东部边缘,临近金沙江河谷,由于受黄茅埂高山阻隔和金沙江河谷干热气候影响,故自1.6万年以来气候变化波动较小,而与布拖县西溪河火烈湖2.2万年以来古气候有不同变化趋势。  相似文献   
159.
Open pollinated progenies from 15 clones of Japanese black pine (Pinus thunbergii), that had been selected for their tolerance to pine wilt disease, were tested by artificial inoculation with pine wood nematode for six years at a nursery of Kyushu Regional Breeding Office. Family variations in the respective year were all significant. An analysis of variance across the six years’ tests confirmed highly significant effect of year and of families; however, the year by family interaction was significant also. Phenotypic and genetic variances estimated from each year’s result were fitted to a quadratic regression using their mean survival ratio as an independent variable. The variances were greatest at around 0.5 of the mean survival ratio. Estimated heritability showed a similar trend of change, whereas the peak of the expected amount of improvement shifted toward the lower survival range: around 0.4, where a greater selection differential was anticipated. It was concluded that a useful amount of genetic improvement that may be reduced by 30% due to the interaction, would be expected by prescreening seedlings where the mean survival ratio after inoculation was around 0.25 to 0.6.  相似文献   
160.
This study is part of an effort to improve the quality of dried shiitake mushrooms (Lentinula edodes) in accordance with consumer preference. Results are presented of a trend survey that examined the preferences of consumers using questionnaires combined with sensory evaluation. From the original preference (OP) survey, the distributions of OP divided by age class (AC) were statistically equal to the results obtained in 2000. The medians of OP for teenagers and twenties were “neutral” and “slightly like,” respectively. A firm preference change occurred between teenagers and those in their twenties. It is empirically realized that sensory intensity (SI) scores that were too high or too low led to a low hedonic preference (HP) score. The same tendency was seen for “neutralists” and “likers.” In addition, almost all distributions concerned with HP had no significant difference between 2000 and 2005; for example, that of SI divided by AC. These results showed that the preference for dried shiitake mushroom has been unaffected by the passage of the past 5 years. Dried shiitake mushrooms have been used from ancient times and for many dishes; therefore, the overall preference appears to have remained unchanged.  相似文献   
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