Some physical properties of crystals differ in direction n because crystal lattices are often anisotropic. A polycrystal is an aggregate of numerous tiny crystallites. Unless the polycrystal is an isotropic aggregate ...Some physical properties of crystals differ in direction n because crystal lattices are often anisotropic. A polycrystal is an aggregate of numerous tiny crystallites. Unless the polycrystal is an isotropic aggregate of crystallites, the physical properties of the polycrystal vary with n. The direction-dependent functions （DDF） for crystals and polycrystals are introduced to describe the variations of the physical properties in direction n. Until now there are few papers dealing systematically with relations between the DDF and the crystalline orientation distribution. Herein we give general expressions of the DDF for crystals and polycrystals. We discuss the applications of the DDF in describing the physical properties of crystals and polycrystals.展开更多
A novel adhesive pad for a climbing robot, inspired by a stick insect's smooth pad, is proposed. The micro structure pattern and inclined fiber of a stick insect's pad are mimicked, and an adhesion force is pr...A novel adhesive pad for a climbing robot, inspired by a stick insect's smooth pad, is proposed. The micro structure pattern and inclined fiber of a stick insect's pad are mimicked, and an adhesion force is produced based on its wet adhesion mechanism. Firstly, the wet adhesion model is discussed and the pad is designed; secondly, the adhesion characteristics, adhesion direction dependence and adaptability are analyzed; finally, the proposed pad is fabricated using a thermoplastic elastomer, which is a hydrophilic and viscoelastic material. Experimental results show that the adhesion performance of the pad is good, and normal adhesion and friction can reach to 0.65 N and 3 N. Furthermore, the adhesion of the pad is direction dependent and self-adaptive.展开更多
Contrary to the superposition principle, it is well known that photorefraction exists in the vacuum with the presence of a strong static field, a laser field, or a rotational magnetic field. Different from the classic...Contrary to the superposition principle, it is well known that photorefraction exists in the vacuum with the presence of a strong static field, a laser field, or a rotational magnetic field. Different from the classical optical crystals, the refractive index also depends on the phase of the strong electromagnetic field. We obtain the phase and direction dependence of the refractive index of a probe wave incident in the strong field of a circular-polarized plane wave by solving the Maxwell equations corrected by the effective Lagrangian. It may provide a valuable theoretical basis to calculate the polarization evolution of waves in the strong electromagnetic circumstances of pulsar or neutron stars.展开更多
基金supported by the National Natural Science Foundation of China (10562004, 10662004)the Jiangxi Project to Nurture Academic and Technical Leaders in Targeted Areas+1 种基金the Research Fund for the Docotoral Program of Higher Education (20070403003)the Natural Science Foundation of Jiangxi of China (2008GZW0005).
文摘Some physical properties of crystals differ in direction n because crystal lattices are often anisotropic. A polycrystal is an aggregate of numerous tiny crystallites. Unless the polycrystal is an isotropic aggregate of crystallites, the physical properties of the polycrystal vary with n. The direction-dependent functions （DDF） for crystals and polycrystals are introduced to describe the variations of the physical properties in direction n. Until now there are few papers dealing systematically with relations between the DDF and the crystalline orientation distribution. Herein we give general expressions of the DDF for crystals and polycrystals. We discuss the applications of the DDF in describing the physical properties of crystals and polycrystals.
基金supported by the National Natural Science Foundation of China (50405045,61040056)the National High-Tech Research & Development Program of China (2007AA04Z253)
文摘A novel adhesive pad for a climbing robot, inspired by a stick insect's smooth pad, is proposed. The micro structure pattern and inclined fiber of a stick insect's pad are mimicked, and an adhesion force is produced based on its wet adhesion mechanism. Firstly, the wet adhesion model is discussed and the pad is designed; secondly, the adhesion characteristics, adhesion direction dependence and adaptability are analyzed; finally, the proposed pad is fabricated using a thermoplastic elastomer, which is a hydrophilic and viscoelastic material. Experimental results show that the adhesion performance of the pad is good, and normal adhesion and friction can reach to 0.65 N and 3 N. Furthermore, the adhesion of the pad is direction dependent and self-adaptive.
基金supported by the National Basic Research Program of China(Grant No.2011CB808104)the National Natural Science Foundation of China(Grant No.11105233)
文摘Contrary to the superposition principle, it is well known that photorefraction exists in the vacuum with the presence of a strong static field, a laser field, or a rotational magnetic field. Different from the classical optical crystals, the refractive index also depends on the phase of the strong electromagnetic field. We obtain the phase and direction dependence of the refractive index of a probe wave incident in the strong field of a circular-polarized plane wave by solving the Maxwell equations corrected by the effective Lagrangian. It may provide a valuable theoretical basis to calculate the polarization evolution of waves in the strong electromagnetic circumstances of pulsar or neutron stars.
