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991.
以1,3-(4,4’-二吡啶基)丙烷为母体, 合成了N,N’-二乙基、二丁基、二己基以及二辛基1,3-(4,4’-二吡啶基)丙烷衍生物. 利用1H NMR技术和紫外吸收光谱法, 考察了Q[7]与上述链状吡啶衍生物的相互作用. 实验结果表明, Q[7]与客体PC0, PC2作用, 瓜环包结客体的二吡啶基丙烷部分形成1∶1的包结配合物; 对于取代烷基碳链数大于4的N,N’-二烷基-1,3-(4,4’-二吡啶基)丙烷衍生物, 随着主体与客体摩尔比值的增加, 体系中主-客体相互作用的主导模式是Q[7]逐渐包结了客体二吡啶基丙烷部分, 进而形成Q[7]包结客体两端取代烷基, 甚至形成一个客体分子上“挂满”3个主体瓜环的包结物. 相似文献
992.
为加快张量积型 Said-Ball曲面渐近迭代逼近法的收敛速度,探讨了张量积型Said-Ball曲面渐近迭代逼近法的预处理技术。首先利用对角补偿约化技术构造了预处理子,然后结合矩阵Kronecker积性质,采取预处理渐近迭代逼近法求解张量积型Said-Ball曲面。为进一步降低计算量并提高算法的稳定性,利用广义极小残差法求解预处理方程,得到预处理渐近迭代逼近法的非精确求解方法。分析了预处理渐近迭代逼近法及非精确求解方法的收敛性。最后用数值实例说明预处理子能大大减小迭代矩阵的谱半径,令预处理技术及其非精确求解方法的计算效率明显提高。此外,由于对角补偿预处理子能改善配置矩阵的谱分布,因此也可用于对广义极小残差法的预处理,以改善其收敛性。 相似文献
993.
采用ABAQUS有限元仿真软件对激光加载L2铝板材高速成形进行数值模拟,研究了单脉冲激光冲击下成形的瞬态响应过程,获得了激光加载冲击成形过程中位移、速度、应变及应变率等特征量的变化特点.模拟表明,冲击后靶材中心区域发生明显塑性变形,变形截面呈锥形.高速成形过程中,金属板材首先发生振荡幅度非常大的快速弹性变形,其后进入减幅振荡直至静态,激光冲击成形时间在毫秒量级.板材不同节点的位移变化趋势相同,靠近中心区域位移大,边界区域位移小.成形中板材的中心区域速度最大达3 700m/s,变形过程前2μs内应变率急剧变化,最大达104~105 s-1量级. 相似文献
996.
《Current Applied Physics》2014,14(3):371-377
In this study, we proposed a novel salt-leaching method using PCL and NaCl powders, known as the SLUP (salt leaching using powder) technique, which has several advantages: this technique does not require solvent, pressure, or unnecessary expensive devices. First, PCL powder (100–180 μm size) and NaCl powder (350–400 μm size) were prepared. Second, the PCL and NaCl powders were mixed at a certain ratio, and then the mixed powder was poured into a mold. Afterward, the mold was heated to melt the PCL powder in an oven at 80 °C for 15 min. Subsequently, after the PCL/NaCl mixture was separated from the mold, the PCL/NaCl mixture was soaked in D.I. water for 24 h to leach out the NaCl particles. Consequently, the remaining PCL structure was porous and could be used as a scaffold. To analyze the compressive modulus of the fabricated scaffold, a uniaxial compression test was performed using a UTM (universal testing machine), and the surface characteristics of the scaffold were observed using an SEM (scanning electron microscope). Additionally, cell-culture experiments were performed using hMSCs (human mesenchymal stem cells), and the cell-culture characteristics were assessed and compared with the characteristics from a conventional salt-leaching scaffold. 相似文献
997.
C,igahertz longitudinal acoustic phonons originating from ultrafast ligand field transitions in hematite thin films 下载免费PDF全文
The creation and propagation of longitudinal acoustic phonons (LAPs) in high quality hematite thin films (α-Fe203) epitaxially grown on different substrates (BaTiO3, SrTiO3, and LaAlO3) are investigated using the femtosecond pump- probe technique. Transient reflection measurements (AR/R) indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of -500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400- nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates. 相似文献
998.
Martin Hempel Jens W. Tomm Fangyu Yue Mauro A. Bettiati Thomas Elsaesser 《Laser \u0026amp; Photonics Reviews》2014,8(5):L59-L64
Infrared emission from 980‐nm single‐mode high power diode lasers is recorded and analyzed in the wavelength range from 0.8 to 8.0 μm. A pronounced short‐wavelength infrared (SWIR) emission band with a maximum at 1.3 μm originates from defect states located in the waveguide of the devices. The SWIR intensity is a measure of the non‐equilibrium carrier concentration in the waveguide, allowing for a non‐destructive waveguide mapping in spatially resolved detection schemes. The potential of this approach is demonstrated by measuring spatially resolved profiles of SWIR emission and correlating them with mid‐wavelength infrared (MWIR) thermal emission along the cavity of devices undergoing repeated catastrophic optical damage. The enhancement of SWIR emission in the damaged parts of the cavity is due to a locally enhanced carrier density in the waveguide and allows for an analysis of the spatial damage patterns. The figure shows a side view of a diode laser during catastrophic degradation as recorded by a thermocamera within 5 successive current pulses. The geometry of the device is given in grayscale. The position of the laser chip is indicated by the dotted line. The thermal signatures of the internal degradation of the diode laser are overlaid in color. The bi‐directional spread of the damage along the laser cavity is clearly visible. 相似文献
999.
1000.
介绍了物联网的定义及结构;从感知层和网络层角度,探讨了光通信技术(光纤通信和无线通信)在物联网中的应用现状和前景.光纤通信、近距离无线通信、移动通信是物联网开发的基础,制定物联网各个层面上统一的、标准化协议和技术标准是物联网未来发展必须解决的关键和难点. 相似文献