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171.
172.
ABSTRACTThe iridium is an important metal which has excellent resistance to corrosion at high temperature. L12 intermetallic compounds i.e. Ir3Nb and Ir3Zr, with similar lattice parameters are ideal for working at high temperature. They are fully soluble due to their low lattice misfit. A first-principle investigation into the effect of doping Zr with different concentrations on the electronic structure, mechanical and thermodynamic properties of NbIr3 has been studied to prompt the development of novel high-temperature materials. Nine ZrxNb8?xIr24 compounds are carefully considered. The results show that adding Zr into these compounds can strengthen their structural stability and ductility. Nevertheless, it reduces the elastic modulus and elastic stiffness. Simultaneously, with the increase of Zr content, the thermodynamic properties of these compounds decrease. It is also found that the changes of elastic modulus are mainly attributed to the variations of bonds in these compounds. 相似文献
173.
174.
This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo-induced single-electron-transfer(SET)of an electron donor-accepter(EDA)complex.The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate.In these two processes,another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.The mechanistic studies have been carried out by control experiments,kinetic and spectroscopic analyses,deuterium labeling experiments to support these two chain processes. 相似文献
175.
Samples of 5Cr2NiMoVSi die steel which underwent thermal fatigue with different fatigue cycles have been studied by using microhardness and positron lifetime measurements. It is found that the microhardness and the positron lifetime parameters increase and decrease alternatively with increasing the number of the fatigue cycles. The experimental results reveal that the fatigue strain, the dynamical recovery, and recrystallization and the precipitation are main causes of variation of the defects in the process of thermal fatigue. 相似文献
176.
通过将系统参数定义为参数变量, 构成参数空间,研究齿轮传动系统在参数空间和状态空间耦合下的非线性全局动力学特性,以及多参数、多初值和多稳态行为之间的关联特性.首先设计了一个两空间耦合下非线性系统多稳态行为的计算和辨识方法.其次,基于该方法并结合相图、Poincaré映射图、分岔图、最大Lyapunov指数、吸引域等,研究齿轮传动系统在不同参数平面上多稳态行为的存在区域和分布特性,以及多稳态行为在状态平面上的分布特性,揭示了参数平面和状态平面上系统可能隐藏的多稳态行为和分岔,并分析了多稳态行为的形成机理. 结果发现,两空间耦合下系统在参数平面上存在大量多稳态行为并呈"带状"分布, 状态平面上多稳态行为出现两种不同的侵蚀现象, 即内部侵蚀和边界侵蚀.分岔点或分岔曲线对初值的敏感性导致多稳态行为的出现.当齿侧间隙和误差波动在较小的范围内变化时,系统全局动力学特性受间隙和误差扰动的影响较小,受啮合频率的影响较大.两空间耦合下系统全局动力学特性变得丰富和复杂. 相似文献
177.
Meccanica - In this paper, we develop a framework of time optimization path planning for robotic manipulators surrounded by static obstacles. Our approach is based on the recursive dynamics method... 相似文献
178.
The Reynolds averaged N-S equation and dynamic equation for nanoparticles are numerically solved in the two-phase flow around cylinders, and the distributions of the concentration M0 and geometric mean diameter dg of particles are given. Some of the results are validated by comparing with previous results. The effects of particle coagulation and breakage and the initial particle concentration m00 and size d0 on the particle distribution are analyzed. The results show that for the flow around a single cylinder, M0 is reduced along the flow direction. Placing a cylinder in a uniform flow will promote particle breakage. For the flow around multiple cylinders, the values of M0 behind the cylinders oscillate along the spanwise direction, and the wake region in the flow direction is shorter than that for the flow around a single cylinder. For the initial monodisperse particles, the values of dg increase along the flow direction and the effect of particle coagulation is larger than that of particle breakage. The values of dg fluctuate along the spanwise direction; the closer to the cylinders, the more frequent the fluctuations of dg values. For the initial polydisperse particles with d0 = 98 nm and geometric standard deviation σ = 1.65, the variations of dg values along the flow and spanwise directions show the same trend as for the initial monodisperse particles, although the differences are that the values of dg are almost the same for the cases with and without considering particle breakage, while the distribution of dg along the spanwise direction is flatter in the case with initial polydisperse particles. 相似文献
179.
The Cu/SiO2 catalyst prepared by incipient wetness method exhibited very high activity and selectivity for the vapor-phase synthesis of JV-butylaniline from aniline and 1-butanol. When Cu loading was 0.70 mmol/g-SiO2 and the catalyst precursor was calcined at 500 ℃, 1-butanol conversion reached 99%, and the selectivity of JV-butylaniline exceeded 97%. 相似文献
180.
Gold nanoparticles functionalized with self-assembled films of ferrocenylhexanethiol and mercaptoundecanoic acid (MUA) were used for the determination of ascorbic acid (AA). The modified nanoparticles (mNPs) were prepared by a combination of the modified Schifrin’s and the place-exchange methods. Well-organized films were obtained due to electrostatic attraction between the carboxy groups of MUA and cationic surface of poly(diallyldimethylammonium chloride). The mNP films are highly stable and can be exploited to fabricate an enzyme-less sensor for AA whose function is based on the highly electrocatalytic activity of ferrocene in the mNPs towards AA. The sensor was characterized by cyclic voltammetry and chronoamperometry. Under optimal conditions, the response current towards AA is proportional to its concentration in the range from 8.0 μM to 6.0 mM, with a detection limit of 0.14 μM (at a signal-to-noise ratio of 3). This work represents a simple controlled test-bed for fundamental studies on the use of self-assembled mNPs for sensor applications. 相似文献