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531.
采用Mindlin平板理论,通过最小位能原理建立了各向同性中厚板的伽辽金整体弱式方
程,形函数采用耦合多项式基的径向点插值法构造,可以直接施加本质边界条件. 算例表明,
用耦合多项式基的径向点插值无网格法分析中厚板问题,具有效率高、精度高和易于实现等
优点,可以避免薄板弯曲时的剪切自锁现象. 相似文献
532.
533.
Yujie Dong Junjie Shen Weijun Li Ruiyang Zhao Yuyu Pan Qingbao Song Cheng Zhang 《Tetrahedron》2019,75(18):2670-2675
In this work, we report two isomers composed of 1-phenyl-1H-phenanthro[9,10-d]imidazole (PI), hydroxyl and tetraphenylethylene (TPE), abbreviated as m-PITPE and p-PITPE. It is found that they exhibit similar aggregation-induced emission (AIE) behavior but totally different excited-state intramolecular proton transfer (ESIPT) characteristic, as a result of the different linkage sites of PI on TPE moiety. Theoretical calculations and their different experimental responses to F? demonstrate that only the para-linkage isomer displays ESIPT. In m-PITPE with meta-linkage, the electron cloud distribution only locates at the TPE part in the singlet excited (S1) states, which results in the localized excited state without ESIPT characteristic. 相似文献
534.
The E/Z isomerization reaction is found extensively in most organic molecules containing double bond unit. This limits their practical application as luminescent materials partly, especially under photoirradiation. Therefore, it is important to obtain E/Z isomers with stable configuration in the excited state after photoirradiation. It is well known that cyanostilbene and its analogues play an important role in the development of organic opto/electronic materials. The substituted cyano group on C=C double bonds has strong electron-withdrawing ability and large steric hindrance, which benefits the formation of donor-acceptor (D-A) structures and formation of intramolecular charge transfer. In our previous work, we reported a triphenylamine-cyanostilbene molecule (TPNCF) formed by modifying the cyanostilbene structure with triphenylamine, which maintained a stable E/Z configuration as a film and in high polar solvents. According to solvatochromism mechanisms and the results of theoretical calculations, we proposed that the charge transfer (CT) excited state between the triphenylamine donor and cyanostilbene acceptor groups induced the stable configuration of the E- and Z- isomers under photoirradiation. Under irradiation, the E/Z isomerization process occurring at a higher energy locally excited (LE) state was suppressed by a rapid internal conversion process from the LE to CT state. This work inspired us to provide a universal and effective molecular design strategy by modifying D-A substituents on double bonds that can successfully stabilize E/Z isomers. To further confirm that the CT excited state induced stable E- and Z- isomers in the cyanostilbene structure under photoirradiation, we designed and synthesized a donor-acceptor phenoxazine-cyanostilbene molecule (PZNCF) and successfully characterized its two E/Z isomers. In comparison with the reported TPNCF molecule, the in-situ NMR and UV spectra of E- and Z- isomers of PZNCF demonstrated that the E/Z isomerization rate became slower under photoirradiation, which indicated that the stronger electron-donating group of phenoxazine substituted in the cyanostilbene structure induced a more stable E/Z isomer configuration in its excited state. DFT calculations and photophysical results indicated that a stronger CT state was generated in both E- and Z- isomers of PZNCF. This further confirmed our hypothesized mechanism where the stable E/Z configuration can be obtained under photoirradiation by forming a suitable donor-acceptor structure to suppress the E/Z isomerization reaction in the LE state by a rapid internal crossing process from the LE to CT state. This molecular design strategy is of great significance to organic photochemistry and photoelectronics for molecules with double bond units. 相似文献
535.
设G是2-(v,k,1)设计D上的自同构群的一个子群,且是线-本原.如果(V,k)=k/k2,k2≤10.则G也是点-本原的。 相似文献
536.
叔胺N235萃取柠檬酸的研究 总被引:2,自引:1,他引:1
用正辛醇-叔胺N235石油醚溶液萃取柠檬酸有协同效应,协萃系数R=2.7萃取为一放热反应,H=-14.6kJ.mol^-1一次萃取率可达92.2%,用稀盐酸反萃率为99.3%。测定了协萃有机相的红外光谱。 相似文献
537.
538.
提出了一种基于菲涅耳衍射微透镜的新型光学加速度传感器,它能够解决导航系统中惯性传感器普遍存在的抗电磁干扰和电磁冲击能力差等缺陷。其传感原理是把一个反光膜平行地置于衍射微透镜的后方,加速度的变化会改变反光膜的位置,根据微透镜前方会聚点处光强的变化,感知加速度的大小。介绍了传感器及其动力学系统的工作原理,并对衍射微透镜和动力学系统的微弹性机械结构进行了设计和加工,最后对传感器的性能和误差进行了分析。原理验证性实验的结果表明这种新型光学加速度传感器的原理正确,并且结构简单,灵敏度高。 相似文献
539.
据一项高中学科难度的调查显示,物理排在众学科之首.高中物理为何难学?笔者认为除了其学科本身的抽象性和复杂性外,重要的原因在于我们对物理学习的规律认识还不够清楚,把握不够准确,从而导致教学的力度和效果不够.本文拟从高中生学习的角度来探讨物理学习中的障碍成因,以期为改进高中物理教学提供参照. 相似文献
540.
Weijun Zhou 《Optimization Letters》2013,7(6):1367-1372
To guarantee global convergence of the standard (unmodified) PRP nonlinear conjugate gradient method for unconstrained optimization, the exact line search or some Armijo type line searches which force the PRP method to generate descent directions have been adopted. In this short note, we propose a non-descent PRP method in another way. We prove that the unmodified PRP method converges globally even for nonconvex minimization by the use of an approximate descent inexact line search. 相似文献