排序方式: 共有38条查询结果,搜索用时 78 毫秒
1.
对连轧材产生的表面缺陷(裂纹)进行了深入细致的调查工作,已查找其可能产生的原因.通过对缺陷产生主要原因的分析,提出了防止产生表面缺陷的措施. 相似文献
2.
Wenwei Wang Cuijuan Jiang Ledong Zhu Nana Liang Xuejiao Liu Jianbo Jia Chengke Zhang Shumei Zhai Bin Zhang 《International journal of molecular sciences》2014,15(9):15981-15993
Soluble carbon nanotubes (CNTs) have shown promise as materials for adsorption of environmental contaminants such as Bisphenol A (BPA), due to the high adsorption capacity and strong desorption hysteresis of BPA on CNTs. The adsorption of BPA to CNTs may change the properties of both BPA and CNTs, and induce different toxicity to human and living systems from that of BPA and CNTs alone. Herein, we report that oral exposure of BPA/MWCNT–COOH (carboxylated multi-walled carbon nantubes) adduct to mice during gestation and lactation period decreased the male offspring reproductive toxicity compared with those induced by BPA alone. The adduct decreased malondialdehyde (MDA) level in testis and follicle-stimulating hormone (FSH) in serum, but increased the level of serum testosterone in male offspring in comparison to BPA alone. Our investigations broadened the knowledge of nanotoxicity and provided important information on the safe application of CNTs. 相似文献
3.
Xiaoliang Meng Ledong Zhu Zhenshan Guo 《Frontiers of Architecture and Civil Engineering in China》2011,5(4):510-517
By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between
the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated
via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method.
The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and
that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward
bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially
by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise,
the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations
are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind
fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward
and leeward bridges. 相似文献
4.
在TJ3风洞中,对浦东一拟建大楼与其周边建筑群之间的风环境群体干扰效应做了试验研究。分别对仅单体建筑、仅周边建筑群、单体建筑和周边建筑群三种情况进行了风洞试验。分析试验数据,得出各测点处平均风速系数rM和阵风风速系数rG随风向角的变化,进而得到周边建筑群对试验建筑风速系数的干扰因子IF1和试验建筑对周边建筑群风速系数的干扰因子IF2随风向角的变化。试验结果表明:处于高层建筑的尾流区或者当建筑并排布置形成街道峡谷时,干扰效应十分显著;矩形截面建筑的尖角效应比较明显;试验建筑建成后对原周边风环境的影响不可忽略。 相似文献
5.
以泉州海湾桥两种结构形式双幅桥面主梁方案为背景,通过数值计算研究了两种双幅桥面结构的结构动力特性;通过风洞试验研究了桥梁颤振稳定性和涡激共振性能。研究结果表明,是否存在桥面横向连接对双幅桥的结构固有动力特性影响较大,无横向连接双幅桥面较有横向连接双幅桥面的模态特征更复杂,其竖弯和扭转基频均会出现双幅桥面同向运动和反向运动两种模态;在气流作用下,无横向连接双幅桥面和有横向连接双幅桥面的主梁运动形式不同,两种结构形式双幅桥面的颤振稳定性能和涡激共振性能存在显著差异,双幅有横向连接主梁的气动稳定性优于双幅无横向连接主梁,但前者的涡激共振性能要差于后者。 相似文献
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7.
Quanshun Ding Ledong Zhu Haifan Xiang 《Journal of Wind Engineering & Industrial Aerodynamics》2010,98(12):911-918
The flutter derivatives of bridge decks can be determined in a unique manner on condition that the complex modal parameters of the system at one reduced frequency are obtained. Based on the idea, a new method of identifying the flutter derivatives of bridge decks is proposed and it can overcome some shortcoming of the existing method and extend the applicability of the free vibration technique at high wind velocity. The identified results have agreements with the target ones of an ideal thin-plate section and those of a thin-plate section measured by the forced vibration technique. The proposed method is reliable and effective to extract the flutter derivatives from coupled free vibration. 相似文献
8.
Rui Gao Ledong Zhu Qingzhu Zhang Wenxing Wang 《International journal of molecular sciences》2014,15(3):5032-5044
The mechanism for OH and NO3 radical-initiated oxidation reactions of methyl methacrylate (MMA) was investigated by using density functional theory (DFT) molecular orbital theory. Geometrical parameters of the reactants, intermediates, transition states, and products were fully optimized at the B3LYP/6-31G(d,p) level. Detailed oxidation pathways were presented and discussed. The rate constants were deduced by the canonical variational transition-state (CVT) theory with the small-curvature tunneling (SCT) correction and the multichannel Rice-Ramspergere-Kassele-Marcus (RRKM) theory, based on the potential energy surface profiles over the general atmospheric temperature range of 180–370 K. The calculated results were in reasonable agreement with experimental measurement. 相似文献
9.
悬索桥施工阶段全过程动力特性分析 总被引:2,自引:0,他引:2
在悬索桥施工过程中,随着主梁拼装长度的增加,对悬索桥固有动力特性影响较大的主缆拉力和形状也不断变化。因此在对悬索桥作施工全过程动力特性分析之前,必须首先计算各状态的主缆轴力和几何形状。本文编制了用于悬索体系非线性静力分析的有限元程序SUSCAB,并以广东虎门珠江大桥为工程背景,给出了悬索桥施工全过程动力特性分析的基本步骤,讨论了整个施工过程中结构固有动力特性的演变情况和主梁抗扭刚度的不同取值对结构扭频的影响。 相似文献
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