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81.
用PBE形式下的广义梯度近似(GGA)赝势平面波方法研究了氮化铂的结构相变以及弹性性质,计算了氮化铂的氯化钠(B1)、氯化铯(B2)、闪锌矿(B3)、纤维矿(B4)等四种结构并应用高压下的焓与压强的关系,得出在常温常压下B4结构是最稳定的结构,这与Yu 等人得的结果一致,且 B4→B1及B1→B2的相变压强分别发生在36.7 GPa和 185.4 GPa,同时,研究了B4结构在高压的弹性性质,发现弹性常数、体模量、剪切模量、压缩波速、剪切波速以及德拜温度均随着压强的增大而单调增大 相似文献
82.
83.
Based on the acoustic radiation theory of a dipole source,the influence of the transducer reception pattern is studied for magnetoacoustic tomography with magnetic induction(MAT-MI).Numerical studies are conducted to simulate acoustic pressures,waveforms,and reconstructed images with unidirectional,omnidirectional,and strong directional transducers.With the analyses of equivalent and projection sources,the influences of the model dimension and the layer effect are qualitatively analyzed to evaluate the performance of MAT-MI.Three-dimensional simulation studies show that the strong directional transducer with a large radius can reduce the influences of equivalent sources,projection sources,and the layer effect effectively,resulting in enhanced pressure and improved image contrast,which is beneficial for boundary pressure extraction in conductivity reconstruction.The reconstructed conductivity contrast images present the conductivity boundaries as stripes with different contrasts and polarities,representing the values and directions of the conductivity changes of the scanned layer.The favorable results provide solid evidence for transducer selection and suggest potential practical applications of MAT-MI in biomedical imaging. 相似文献
84.
Light-Driven Crawling of Molecular Crystals by Phase-Dependent Transient Elastic Lattice Deformation
Yanjun Gong Yongxian Guo Fayuan Ge Wei Xiong Jie Su Yang Sun Chuang Zhang An-Min Cao Yifan Zhang Jincai Zhao Yanke Che 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10423-10428
The light-driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min−1, which is two orders of magnitude faster than the α and β phases. 相似文献
85.
Shotaro Hayashi Fumitaka Ishiwari Takanori Fukushima Shohei Mikage Yutaka Imamura Motomichi Tashiro Michio Katouda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16329-16335
Elastic organic crystals have attracted considerable attention as next-generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10-dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c-axes) of the crystal are contracted upon elongation along the long axis (a-axis). Moreover, we found that the Poisson's ratios along the b-axis and c-axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c-axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other. 相似文献
86.
87.
Shotaro Hayashi Fumitaka Ishiwari Takanori Fukushima Shohei Mikage Yutaka Imamura Motomichi Tashiro Michio Katouda 《Angewandte Chemie (International ed. in English)》2020,59(37):16195-16201
Elastic organic crystals have attracted considerable attention as next‐generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10‐dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c‐axes) of the crystal are contracted upon elongation along the long axis (a‐axis). Moreover, we found that the Poisson's ratios along the b‐axis and c‐axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c‐axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other. 相似文献
88.
为考查阻尼参数对空爆荷载等效静载动力系数的影响,理论推导了空爆荷载下结构等效单自由体系弹塑性位移解及延性比解,设计并计算了阻尼比0.000 1~0.1、延性比1~4的20种典型工况的动力系数,并与现行抗爆设计规范动力系数公式结果进行了对比。结果表明:阻尼比小于0.000 1时可基本代表无阻尼状态,阻尼比0.01的动力系数比无阻尼的最大降低幅度为2.08%,数值差异很小,因此阻尼比为0.01以内时,可忽略阻尼对动力系数的影响;阻尼比0.05的动力系数比无阻尼的降低幅度约9.92%,数值差异较大,认为阻尼比0.05以上时将具有明显的经济效益;现行设计规范动力系数更适用于柔性结构体系,运用于刚性结构抗爆设计时,计算误差较大,对阻尼比较小的结构设计更不利。 相似文献
89.
利用大学物理实验中的光杠杆法测定金属丝弹性模量的原理和设备,对具有超弹性的NiTi丝的弹性滞后环进行了测定结果表明,此种方法可以很好地测定NiTi丝的弹性滞后环,而且操作简单使用方便,是一种非常有效的测定金属细丝弹性滞后环的方法. 相似文献
90.
讨论了小球在杆上任一点的碰撞问题,并指出《大学物理》2006年第5期《小球与均质自由杆的碰撞》一文中"完全非弹性碰撞后两物体不一定粘在一起共同运动"的说法是错误的. 相似文献