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991.
本文结合杭州湾跨海大桥Ⅰ合同段桥墩的施工情况,介绍了海工高性能混凝土的施工特点,对杭州湾跨海大桥中桥墩混凝土裂纹成因进行了分析,并介绍了其预防和处理措施。 相似文献
992.
993.
通过对原有烟雾机性能参数测试手段的改进并完善,设计和开发了基于虚拟仪器技术的烟雾机性能参数测试系统,提出了烟雾机性能参数网络测试系统的设计方法。系统充分利用计算机高速、准确的特性。汲取互联网技术方便、连通的优点,以图形化编程语言LabVIEW和个人计算机为软硬件平台,实现多通道信号的计算机采集与分析功能,简化仪器设备,提高测试效率。 相似文献
994.
杉木营养平衡与苗木干物质的分配关系 总被引:6,自引:3,他引:6
详细研究了不同营养 (N、P、NP)条件下杉木苗木干物质在根冠的分配规律 ,结果表明 ,不同的营养条件可导致苗木光合产物在根冠发生明显再分配 ,苗木的营养状态和根冠干物质分配的关系规律可应用异速生长模型y =axk 来描述和刻划。基于营养与光合产物在根冠的再分配规律及异速生长模型参数k值对营养胁迫反应的敏感性变化规律 ,提出了新的营养平衡理论和营养诊断方法 (称之为苗木群体营养诊断法 )。营养诊断法则为 :(1)在某一营养条件下 ,如果苗木异速生长模型参数k <1时 ,表明根系相对生长速率高于冠层相对生长速率 ,苗木处于营养亏缺状态 ;(2 )当k >1时 ,表明苗木冠层相对生长速率高于根系 ,苗木处于营养过剩状态 ,一般在自然条件下 ,k >1是不会出现的 ;(3)当k =1时 ,表明根系和冠层相对生长速率相等 ,苗木处于营养平衡状态。根据新的营养诊断方法 ,制定了杉木叶片和土壤营养诊断标准 ,并通过大量的杉木幼、中、近熟林施肥试验结果验证了营养平衡理论的正确性。 相似文献
995.
LIN Lanying FU Feng Research Institute of Wood Industry Chinese Academy of Forestry Beijing China 《中国林业科技(英文版)》2007,6(3):17-25
Resonance flexural vibration(Fast Fourier Transform, FFT), ultrasonic wave(Pundit) and stress wave(Metriguard) techniques were examined as means of evaluating the static modulus of elasticity (MOE) and predicting the modulus of rupture (MOR) of finger-jointed lumber specimens made with four kinds of Eucalyptus (Eucalyptus. citriodora, E. exserta, E. grandis x E. urophylla and E. grandis). Dynamic MOE was calculated from frequency and time obtained from forced vibrations and sounds induced in the four species of finger-jointed specimens. It was found that correlation coefficients between density and static MOE and dynamic MOE were statistically significant at the 0.01 level. And it was also found that the three nondestructive techniques can provide rapid and accurate means to determine the MOE, and the dynamic MOE was more accurate to predict static MOE than density. But the correlation coefficient between dynamic MOE, static MOE and MOR were lower than results reported by other researchers for solid wood, and were not statistically significant. It can be concluded that the three nondestructive techniques are useful for evaluating the MOE, but not suitable for predicting the MOR of finger-jointed. 相似文献
996.
4种木材常温下醛和萜烯挥发物的释放 总被引:3,自引:1,他引:3
利用高效液相色谱仪和气相色谱仪分析4种木材(杉木、杨木、马尾松和尾叶桉)中有机挥发物的成分及含量,结果表明:4种木材生材常温均可释放多种醛和萜烯挥发物,其中乙醛的释放量最高;杉木和杨木释放的醛类明显高于马尾松和尾叶桉;杉木释放的萜烯类明显高于其他3种木材;温度由20 ℃上升到40 ℃,杉木醛类和萜烯类释放量显著增加. 相似文献
997.
从澳大利亚引进的两种相思植物光合速率和蒸腾效率的初步研究 总被引:2,自引:1,他引:2
以LCA-4光合蒸腾测定系统进行大腺相思和多花相思叶片气体交换过程的测定。结果如下:(1)净光合速率日变化明显,且变化趋势大体一致,即10:00-13:00具有较高的光合速率,其它测定时间相对较低。(2)两树种净光合速率存在差异。大腺相思高于多花相思,其最大值分别为19.6(10:00),16.1(13:00)μmolm^-2s^-1,日平均值分别为11.9,9.8μmolm^-2s^-1,反映了大腺相思的生长速度较多花相思快。(3)大腺相思和多花相思蒸腾速率日变化明显,正午前后较高,13:00达到最大,日平均值多花相思略高于大腺相思,分别为3.3,3.0mmolm^-2s^-1,表明在相同的环境条件下大腺相思的耗水量低于多花相思。(4)两树种蒸腾效率的日变化趋势大体上也类似,即在9:00-11:00较高,此期间大腺相思和多花相思和多花相思的平均值分别为5.51,4.21μmolCO2/mmolH2O。日平均值大腺厢思和多花相思分别为3.84,2.88μmolCO2/mmolH2O,表明消耗等量的水分大腺相思比多花相思能固定更多的CO2量,即有更高的水分利用效率。 相似文献
998.
Applications of growth retardants, daminozide and CCC (chlormequatchloride), were studied in order to determine their effects on morphology and post-planting growth of silver birch (Betula pendula Roth) container seedlings. Daminozide was sprayed once (on 28 June at concentrations of 1.0 – 6.0 g l–1) and CCC was sprayed twice (on 29 June and 27 July at concentrations of 0.5–3.0 gl–1). Height growth, morphology of seedlings at the end of the growing season, the shoot and root growth potential the following spring and field performance during the following seasons were measured. During the first summer in the nursery, both daminozide and CCC retarded height growth,but daminozide was more effective. The effects of compounds on stem diameter during the summer of application were small. Neither of the compounds affected the field performance of seedlings. The most suitable applications for retardation of height growth, without negative effects on other morphological variables, were 4 g l–1 (32 mg per seedling) for daminozide and 2 g l–1 (16 mg per seedling), sprayed in two applications, for CCC. 相似文献
999.
1000.
Ragil Widyorini Jianying Xu Takashi Watanabe Shuichi Kawai 《Journal of Wood Science》2005,51(1):26-32
The effects of chemical changes in kenaf core binderless particleboards on the bonding performance and thickness swelling of boards were investigated by chemical and spectroscopic analyses. Mild steam-injection treatments (0.6–1.0MPa) caused significant degradation of hemicelluloses, lignin, and cellulose. Conventional hot pressing caused a lower degree of degradation of the chemical components. The hot-pressed kenaf core board without any binders showed poor bonding performance. Thus, it was found that partial degradation of the three major chemical components of the kenaf core by mild steam-injection treatment increased the bonding performance and dimensional stability of the binderless boards, and gave better quality binderless boards than those made by hot-pressing treatments.Part of this report was presented at the 4th International Wood Science Symposium, Serpong, Indonesia, September 2002; and at the 53rd Annual Meeting of The Japan Wood Research Society, Fukuoka, March 2003 相似文献