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排序方式: 共有272条查询结果,搜索用时 0 毫秒
1.
采用密度泛函理论(DFT), 在B3LYP/6-311++G(d,p)基组上计算得到了21种N8H8链状异构体, 并研究了这些异构体间可能的互变异构情况. 为了得到更为精确的能量信息, 计算了QCISD(T)/6-311G(d,p)基组水平上各物质的能量. 所得的21种异构体分为4类(4种类型链状化合物): A为直链, B有一个支链, C有2个支链, D有3个支链; D类只有一种, A类稳定构型2种, B类稳定构型12种, C类稳定构型6种; 相对稳定的分别为: B2-1构型, B2-3构型和C23-2构型. 我们研究发现N8H8链状异构体中含有明显N=N双键特征有利于化合物稳定性的提高. 相似文献
2.
《Tetrahedron: Asymmetry》2006,17(1):124-129
Chiral iodo- 9, bromo- 10 and hydroxylactones 12 condensed with the carane system were obtained. In each case, the synthetic pathway led to an enantiomerically pure diastereoisomer to generate two stereogenic centers. Iodo- 9 and bromolactone 10 possess a γ-lactone group while the hydroxylactone 12 possesses a δ-lactone moiety situated trans to the gem-dimethylcyclopropyl ring. The structures of the products were confirmed by X-ray crystallography. These lactones were tested for antifeedant activity against storage pest insects. 相似文献
3.
《Journal of the Less Common Metals》1985,105(2):333-338
Hydrogen potential-temperature diagrams are presented for the V-H, Nb-H and Ta-H systems. The diagrams have been constructed from published thermodynamic data for the single-phase and two-phase regions in conjunction with the temperature-composition phase diagrams. 相似文献
4.
Rui Li Xin Gou Xinyan Li Hainuo Wang Haibo Ruan Yuting Xiong Xianlun Tang Yuanyuan Li Ping-an Yang 《Molecules (Basel, Switzerland)》2022,27(15)
Flexible strain sensors, when considering high sensitivity and a large strain range, have become a key requirement for current robotic applications. However, it is still a thorny issue to take both factors into consideration at the same time. Here, we report a sandwich-structured strain sensor based on Fe nanowires (Fe NWs) that has a high GF (37–53) while taking into account a large strain range (15–57.5%), low hysteresis (2.45%), stability, and low cost with an areal density of Fe NWs of 4.4 mg/cm2. Additionally, the relationship between the contact point of the conductive network, the output resistance, and the areal density of the sensing unit is analyzed. Microscopically, the contact points of the conductive network directly affect the sensor output resistance distribution, thereby affecting the gauge factor (GF) of the sensor. Macroscopically, the areal density and the output resistivity of the strain sensor have the opposite percolation theory, which affects its linearity performance. At the same time, there is a positive correlation between the areal density and the contact point: when the stretching amount is constant, it theoretically shows that the areal density affects the GF. When the areal density reaches this percolation threshold range, the sensing performance is the best. This will lay the foundation for rapid applications in wearable robots. 相似文献
5.
《Tetrahedron》1986,42(15):4203-4210
Ozimes of 1-methyl and 1-phenyl-3(hydroxycyclopentyl)-2-atkanones were prepared in one step with high yeild, from 1 ,4-bis(bromomagnesio) butane and 5-isoxazolones in tetrahydrofuran. This reaction was found to be general and applicable to any hindered 5- isoxazolones providing a facile route for the synthesis of the corresponding spiroisoxazolines. The much larger yeilds of reduction product obtained with 1,5-bis (bromomagnesio)- pentane showed an important difference between five- and six membered annelation process. 相似文献
6.
7.
《Nuclear Physics B》1986,263(2):280-294
Numerical evidence is found for the appearance of a massless vector state, the “photon”, in the broken phase of the lattice Georgi-Glashow model. Data is also presented for the lowest-lying scalar mass in the theory. Our simulations indicate that the transition between symmetric and broken phases is weakly first order for a wide range of couplings. 相似文献
8.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1986,42(7):781-783
The electronic absorption spectra of 5-and 6-fluoroindoles, corresponding to the λ2850 Å system of indole, have been recorded in the vapour phase and analysed, assuming Cs symmetry for the molecules. The observed band system in both the molecules which lies in the region λ3100–2680 Å has been identified as a π* ← π transition corresponding to a 1A′ ← 1A′ transition. The i.r. spectra of these molecules have also been recorded and analysed and the results are used in the analyses of the electronic spectra. These show that there is not much change in the shape and very little change in size of either of these molecules in the excited electronic states. 相似文献
9.
《Sensors and Actuators》1986,9(2):133-145
As part of the research to improve the long-term stability of sintered SnO2 semiconductor gas sensors, we examined the effect of the degree of polymerization (referred to as DP) of ethyl silicate binders added to the sensors on their characteristics. DPs in the range one to four were investigated. By using a binder with a large DP gas sensibility is increased and the sensor resistance is decreased. Humidity dependency and long-term stability are improved by using a binder with a smaller DP. A binder whose DP is more than 2.0 is needed in order to obtain the necessary mechanical strength of the sensor. We concluded that the binder's DP should be 2.5 for the sensor to be stable during long-term operation.Through measurements of H2 oxidation activity and temperature-programmed desorption for H2O and O2, we concluded that the long-term change in the sensor sensitivity is based on the change in its catalytic activity caused by the increase or decrease of the amount of the hydroxyls on its surface. 相似文献
10.
Zou Fan Zuo Jing Geng Chao Li Feng Huang Guan Liu Jiaying Jiang Jiali Fan Zhihua Li Xinyang 《Journal of Russian Laser Research》2021,42(4):462-467
Journal of Russian Laser Research - Laser aiming is one of the key technologies of laser atmospheric transmission. The beam actually is affected by atmospheric turbulence and mechanical vibration;... 相似文献