2011 Vol. 40 No. 05
Abstract：
The complexity of catastrophic failure in heterogeneous brittle media is discussed based on experimental phenomena in rocks. A statistical theory of catastrophic failure is reviewed and the theoretical difficulty is analyzed. In addition, some possible approaches for the prediction of catastrophic failure are considered.
The complexity of catastrophic failure in heterogeneous brittle media is discussed based on experimental phenomena in rocks. A statistical theory of catastrophic failure is reviewed and the theoretical difficulty is analyzed. In addition, some possible approaches for the prediction of catastrophic failure are considered.
2011, 40(05): 289-296.
Abstract：
Water exists everywhere; despite this fact the molecular picture of water interaction with solid-state surfaces is poorly understood. Here we review the significant advances during the last two decades in our understanding at the microscopic level of water adsorption and wetting on the surfaces of precious metals. The microscopic behavior of water-surface interaction is analyzed and the lessons we have learned are discussed, with emphasis on the modifications to the ideal "ice bilayer" model originally proposed in the 1980s.
Water exists everywhere; despite this fact the molecular picture of water interaction with solid-state surfaces is poorly understood. Here we review the significant advances during the last two decades in our understanding at the microscopic level of water adsorption and wetting on the surfaces of precious metals. The microscopic behavior of water-surface interaction is analyzed and the lessons we have learned are discussed, with emphasis on the modifications to the ideal "ice bilayer" model originally proposed in the 1980s.
2011, 40(05): 297-303.
Abstract：
Water consists of H and O atoms. It is most important to find an efficient and economic method to dissociate H2O to obtain H2. The adsorption of H2O on solid surfaces is commonly observed, and on the surfaces of certain metals or metal oxides the adsorbed H2O can be dissociated. This paper presents some results on the adsorption and dissociation of H2O on MgO (100) films and Pd/MgO (100) surfaces investigated under ultrahigh vacuum conditions by using photoemission spectroscopy and high resolution electron energy loss spectroscopy. The results indicate that H2O can be partially dissociated on the MgO (100) surface at initial coverages, while the dissociation of H2O on Pd/MgO (100) surfaces is Pd coverage dependent. More fundamental research is needed to understand the mechanism of interaction of water with solid surfaces.
Water consists of H and O atoms. It is most important to find an efficient and economic method to dissociate H2O to obtain H2. The adsorption of H2O on solid surfaces is commonly observed, and on the surfaces of certain metals or metal oxides the adsorbed H2O can be dissociated. This paper presents some results on the adsorption and dissociation of H2O on MgO (100) films and Pd/MgO (100) surfaces investigated under ultrahigh vacuum conditions by using photoemission spectroscopy and high resolution electron energy loss spectroscopy. The results indicate that H2O can be partially dissociated on the MgO (100) surface at initial coverages, while the dissociation of H2O on Pd/MgO (100) surfaces is Pd coverage dependent. More fundamental research is needed to understand the mechanism of interaction of water with solid surfaces.
2011, 40(05): 304-310.
Abstract：
Through millions of years of evolution, life has undergone almost all the processes of intelligent control. Learning from nature is the eternal theme of the development of novel smart materials and new intelligent systems. Biological nanochannels, for example, water channels and ion channels, play a very important role in basic cellular molecular biological processes. Various biomimetic smart single nanochannels which can respond to external stimuli (pH, temperature, ions, etc.) are currently being studied. We report our latest research inspired by water and ion channels, and also present an overview of this research field.
Through millions of years of evolution, life has undergone almost all the processes of intelligent control. Learning from nature is the eternal theme of the development of novel smart materials and new intelligent systems. Biological nanochannels, for example, water channels and ion channels, play a very important role in basic cellular molecular biological processes. Various biomimetic smart single nanochannels which can respond to external stimuli (pH, temperature, ions, etc.) are currently being studied. We report our latest research inspired by water and ion channels, and also present an overview of this research field.
2011, 40(05): 311-315.
Abstract：
The transportation of water across nanochannels has received extensive attention due to potential applications in water treatment and because of its similarities with biological water channels such as aquaporins. This article reviews some recent progress in the understanding of water transportation across nanochannels. We will focus on the on-off gating behavior in response to external mechanical and electrical signals and noise, enhancement by structure outside the channel, and uni-directional transportation driven by charges close to a channel or electric field.
The transportation of water across nanochannels has received extensive attention due to potential applications in water treatment and because of its similarities with biological water channels such as aquaporins. This article reviews some recent progress in the understanding of water transportation across nanochannels. We will focus on the on-off gating behavior in response to external mechanical and electrical signals and noise, enhancement by structure outside the channel, and uni-directional transportation driven by charges close to a channel or electric field.
2011, 40(05): 316-320.
Abstract：
We demonstrate quasi-phase-matched Cerenkov second-harmonic and sum-frequency generation in a two-dimensional optical superlattice waveguide. Multiple radiation spots with different azimuth angles are simultaneously exhibited from such a hexagonally poled waveguide. The fundamental understanding and potential applications of such Cerenkov effects are presented and discussed.
We demonstrate quasi-phase-matched Cerenkov second-harmonic and sum-frequency generation in a two-dimensional optical superlattice waveguide. Multiple radiation spots with different azimuth angles are simultaneously exhibited from such a hexagonally poled waveguide. The fundamental understanding and potential applications of such Cerenkov effects are presented and discussed.
Abstract：
Ions are commonly approximated to classical point-like particles in traditional ab initio studies. However, in certain systems, their quantum effects are crucial to the physical properties and physical processes. A full quantum calculation, which includes this quantum effect, shows unique advantages in such systems. Path Integral Molecular Dynamics (PIMD) has become the most widely used full quantum simulation method. Ab initio PIMD keeps the electron structure and ground state energy of ab initio calculations, while the ions move according to a set of equations which contain the nuclear quantum effect. Proton transfer in BaZrO3 has been studied by PIMD. The results show that the nuclear quantum effect has different influences on the two different subprocesses, reducing the barrier of the transfer process more significantly than the reorientation process, which makes the transfer process faster. This agrees with the experimental observations but differs from the results of early ab initio simulations without the full quantum effect, which indicate that the transfer process is rate-limiting.
Ions are commonly approximated to classical point-like particles in traditional ab initio studies. However, in certain systems, their quantum effects are crucial to the physical properties and physical processes. A full quantum calculation, which includes this quantum effect, shows unique advantages in such systems. Path Integral Molecular Dynamics (PIMD) has become the most widely used full quantum simulation method. Ab initio PIMD keeps the electron structure and ground state energy of ab initio calculations, while the ions move according to a set of equations which contain the nuclear quantum effect. Proton transfer in BaZrO3 has been studied by PIMD. The results show that the nuclear quantum effect has different influences on the two different subprocesses, reducing the barrier of the transfer process more significantly than the reorientation process, which makes the transfer process faster. This agrees with the experimental observations but differs from the results of early ab initio simulations without the full quantum effect, which indicate that the transfer process is rate-limiting.
2011, 40(05): 326-332.
Abstract：
The all-optical switch (AOS) is a key device for future all-optical communication and all-optical computing.There are many types of AOSs that have been investigated;one of them is the fiber-grating AOS,which is easily matched with fiber systems.We first describe two kinds of ordinary silica single fiber-grating AOSs based on the fiber Bragg grating (FBG) and the long-period fiber grating (LPFG),respectively.Both of these require kilowatt switching powers,so they cannot be used in practice.Secondly, we introduce two kinds of highly nonlinear fiber-grating AOSs,one based on a single nonlinear FBG and the other a pair of linear LPFGs connected by a nonlinear fiber.The nonlinear fibers that we use are rare-earth doped silica fibers.Both of the nonlinear fiber-grating AOSs have low milliwatt-level switching powers,and thus may be used in applications.
The all-optical switch (AOS) is a key device for future all-optical communication and all-optical computing.There are many types of AOSs that have been investigated;one of them is the fiber-grating AOS,which is easily matched with fiber systems.We first describe two kinds of ordinary silica single fiber-grating AOSs based on the fiber Bragg grating (FBG) and the long-period fiber grating (LPFG),respectively.Both of these require kilowatt switching powers,so they cannot be used in practice.Secondly, we introduce two kinds of highly nonlinear fiber-grating AOSs,one based on a single nonlinear FBG and the other a pair of linear LPFGs connected by a nonlinear fiber.The nonlinear fibers that we use are rare-earth doped silica fibers.Both of the nonlinear fiber-grating AOSs have low milliwatt-level switching powers,and thus may be used in applications.
