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31.
Chain-like systems have been studied by many researchers for their simple structure and wide range of application. Previously, the damage in a chain-like system was detected by the reduction of the mass-normalized stiffness coefficient for certain elements as reported by Nayeri et al. (2008 [16]). However, some shortcomings exist in that approach and for overcoming them; an improved approach is derived and presented in this paper. In our improved approach, the mass normalized stiffness coefficients under two states (baseline state and potentially damaged state) are first estimated by a least square method, then these mass-stiffness coupled coefficients are decoupled to derive stiffness and mass relative change ratios for individual elements. These ratios are assembled in a vector, which is defined as damage indication vector (DIV). Each component in DIV is normalized individually to one to get multiple solutions. These solutions are averaged for estimating relative system changes, while abnormal solutions are discarded. The work of judging a solution as normal or abnormal is done by a cluster analysis algorithm. The most intriguing merit of this improved approach is that the relative stiffness and mass changes, which are coupled in the previous approach, can be separately identified. By this approach, the damage (single or multiple) extent and location can be correctly detected under operational conditions, meanwhile the proposed damage index has a clear physical meaning and is directly related to the stiffness reduction of corresponding structural elements. For illustrating the effectiveness and robustness of the improved approach, numerical simulation of a four floor building was carried out and experimental data from a structure tested at the Los Alamos National Laboratory was employed. Identified structural changes with both simulation and experimental data properly indicated the location and extent of actual structural damage, which validated the proposed approach. 相似文献
32.
Dongsheng Xu Ming Lu Changzhi Jia Zhongling Hu 《Journal of Russian Laser Research》2017,38(3):285-293
We propose an improved optical image encryption scheme. By illuminating original images positioned in the input plane of the 4-f correlator and introducing reference waves with different incident angles in the output plane, we accomplish multiple-image encryption. To enhance the feasibility of the system and decrease the coding compliance for random phase mask, we apply the random amplitude masks and some digital manipulations in the encryption and decryption procedure. We also analyze the encryption and decryption quality of the method proposed together with the influence of different random number generators. Numerical simulation has proved the validity of the architecture suggested. 相似文献
33.
A highly efficient and environmental-benign oxidation by dioxygen (or air) as the sole oxidant was first applied for the conversion of 2-imidazoline-5-carboxylic derivatives to imidazole-5-carboxylic derivatives in very good and excellent yields. The substituent effect on 2-imidazoline ring was investigated. This protocol was also suitable for the synthesis of 2-imidazoles in relatively large scale. 相似文献
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35.
Aboubacar Sidiki Sougoule Cheick Abdoul balde Namory Keita Xiao Xiao Xiao Han Jingwen Liang Dongsheng Zhu 《Heteroatom Chemistry》2015,26(5):382-390
A new tetranuclear organotin carboxylate {[(n‐Bu2SnO)2L]2}n (complex 1 ) was synthesized by the reaction of di‐n‐butyltin oxide with (p‐carboxymethoxy‐phenoxy) acetic acid (LH2) and characterized by elemental analyses: IR, UV–visible, 1H, 13C, 119Sn NMR spectroscopy and single crystal X‐ray study. X‐ray crystallography diffraction data revealed that the complex 1 was polymeric fashion with a chain structure containing a ladder‐like tetranuclear organo‐oxotin cluster. In the complex 1 , the ligand LH2 is coordinated to the central tin(IV) atoms via the carboxylato‐O atoms. The tetranuclear tin system is formed by the bridges through the carbonyl oxygen atom of the carboxylate moieties and making the tin atom of pentacoordinated in distorted trigonal bipyramidal geometry. Single crystal X‐ray data indicate that the complex 1 crystallized in the cubic system with the space group C2/c. 相似文献
36.
为了解中药重金属污染情况,测定了市售常用15种中成药中重金属铅、镉、铜的含量,其中铅、镉采用石墨炉原子吸收法,铜采用火焰原子吸收法测定.结果表明,15种中成药均不同程度被这3种重金属污染,通心络中铅、镉、铜含量都已超标,桑菊感冒片镉超标,中药重金属污染问题仍然存在. 相似文献
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为寻找具有更高生物活性、更环保的新农药杀菌剂,基于杀菌剂氟咯菌腈设计并合成了10个新型吡唑联吡咯类杂环化合物,以吡唑环代替氟咯菌腈上原有的苯环,以期提高其杀菌活性.采用1H NMR,FTIR,单晶X射线衍射、元素分析和熔点测定等测试手段对目标化合物及其中间体的结构进行了表征与确认,并通过挥发法培养得到了6个目标化合物的单晶.还对其中6个化合物进行了生物活性测试,测试结果表明各化合物对水稻纹枯病、黄瓜灰霉病、黄瓜霜霉病均表现出一定的抑菌效果,可作为先导化合物对其结构进行深入的研究,为新农药杀菌剂的开发提供了理论支持. 相似文献
39.
报道了一台全光纤结构主振荡功率放大(MOPA)型掺镱脉冲光纤激光器,以光纤光栅为腔镜,光纤型声光调Q的光纤激光器为种子源,通过两级掺镱双包层光纤放大器实现功率放大。对声光调Q的光纤激光器输出特性进行了研究,比较了不同泵浦波长、不同重复频率对激光输出功率和脉冲宽度的影响,并实现了最短脉冲宽度25 ns、单脉冲能量45 μJ的脉冲激光输出。在重复频率50 kHz时,对脉冲宽度130 ns、平均功率0.6 W的种子光进行放大,得到了平均功率102.5 W、脉冲宽度约240 ns的激光输出。 相似文献
40.