We study the behaviors of thermalization in Fermi–Pasta–Ulam–Tsingou(FPUT) system with small number of particles using periodic boundary conditions. The total energy has initially equidistributed among some of the ...We study the behaviors of thermalization in Fermi–Pasta–Ulam–Tsingou(FPUT) system with small number of particles using periodic boundary conditions. The total energy has initially equidistributed among some of the lowest frequency modes. The thermalization time t_(eq) depending on system's energy density ε scales as t_(eq) ∝ε^(-4) only within a certain range of nonlinearity. In this range of nonlinearity, energies can interchange between the initial excited modes and other modes continuously with time until reaching the thermalized state. With a further decreasing nonlinearity, a steeper growth than ε^(-4) will appear. In the very weakly nonlinear regime, energies on low frequency modes are found to be frozen on large time scales. Redistribution of mode energies happens through the resonances of high frequency modes.展开更多
The Lagrangian equations of motion of small particle in turbulent boundary layer flows, taking into account the effects of the drug force caused by the wall presence, the Saffman and the Magus lift forces et al., is s...The Lagrangian equations of motion of small particle in turbulent boundary layer flows, taking into account the effects of the drug force caused by the wall presence, the Saffman and the Magus lift forces et al., is studied. Using the spectral method, analytical expression relating to the Lagrangian power spectra of particle velocity to that of the fluid are developed and the results are used to evaluate various responses statistics. In this paper, the results clearly show that the turbulent diffusivity of the particle may be larger than that of the fluid for a period of long-time.展开更多
Light scattering by small particles has a long and interesting history in physics.Nonetheless,it continues to surprise with new insights and applications.This includes new discoveries,such as novel plasmonic effects,a...Light scattering by small particles has a long and interesting history in physics.Nonetheless,it continues to surprise with new insights and applications.This includes new discoveries,such as novel plasmonic effects,as well as exciting theoretical and experimental developments such as optical trapping,anomalous light scattering,optical tweezers,nanospasers,and novel aspects and realizations of Fano resonances.These have led to important new applications,including several ones in the biomedical area and in sensing techniques at the single-molecule level.There are additionally many potential future applications in optical devices and solar energy technologies.Here we review the fundamental aspects of light scattering by small spherical particles,emphasizing the phenomenological treatments and new developments in this field.展开更多
Silicoaluminophosphates SAPO-11 molecular sieves with small particle size and hierarchical pores were synthesized using the directing agent method.The effect of crystallization time on the particle structure,morpholog...Silicoaluminophosphates SAPO-11 molecular sieves with small particle size and hierarchical pores were synthesized using the directing agent method.The effect of crystallization time on the particle structure,morphology,pore structure properties,and acid properties of SAPO-11 molecular sieves were investigated.Unlike the SAPO-11 molecular sieves synthesized with the conventional method,the results of XRD,SEM,BET and NH3-TPD analyses showed that the SAPO-11 molecular sieves synthesized by the directing agent method in a shorter crystallization time exhibited fine and uniform morphology.By increasing the crystallization time,the particle size of SAPO-11 molecular sieve was significantly reduced,and the mesoporous structure(intercrystalline pores)was formed.Furthermore,the external specific surface area and the total specific surface area reached 81.7 m^2/g and 192.0 m^2/g,respectively,which effectively reduced the pore mass transfer resistance and significantly increased the number of acid sites.The results of n-dodecane hydroisomerization revealed that the Pt/SAPO-11 prepared with the novel method exhibited higher catalytic activity and better hydroisomerization selectivity than that synthesized by the conventional hydrothermal method.Thus,the small particle molecular sieve showed a promising industrial application prospect to be used as catalyst support.展开更多
Using a core (142 nm) made of linear polystyrene (PS) chains as a seed, we further polymerized a thin layer of cross-linked PS shell (7 nm) on it in water to form a core-shell particle. Such a particle swells in...Using a core (142 nm) made of linear polystyrene (PS) chains as a seed, we further polymerized a thin layer of cross-linked PS shell (7 nm) on it in water to form a core-shell particle. Such a particle swells in toluene, which enables linear PS chains inside the core to gradually diffuse out through the porous shell. Using a combination of static and dynamic laser light scattering, we examined the chain diffusion process by following the change of the scattering intensity (i.e. the average molar mass of the particles). For the first time, we have revealed that the diffusion exhibits three stages. In the first stage, the chain diffusion through the shell is even faster than their translational diffusion in a dilute solution. The three stages respectively correspond to the change of the solution in the core from concentrated to semidilute and then from semidilute to dilute.展开更多
Discrete element modeling was used to investigate the effect of particle size distribution on the small strain shear stiffness of granular soils and explore the fundamental mechanism controlling this small strain shea...Discrete element modeling was used to investigate the effect of particle size distribution on the small strain shear stiffness of granular soils and explore the fundamental mechanism controlling this small strain shear stiffness at the particle level. The results indicate that the mean particle size has a negligible effect on the small strain shear modulus. The observed increase of the shear modulus with increasing particle size is caused by a scale effect. It is suggested that the ratio of sample size to the mean particle size should be larger than 11.5 to avoid this possible scale effect. At the same confining pressure and void ratio, the small strain shear modulus decreases as the coefficient of uniformity of the soil increases. The Poisson's ratio decreases with decreasing void ratio and increasing confining pressure instead of being constant as is commonly assumed. Microscopic analyses indicate that the small strain shear stiffness and Poisson's ratio depend uniquely on the soil's coordination number.展开更多
Succeeding the first two successful conferences, APT 2000 (Bangkok, Thailand, 2000) and APT 2003 (Penang, Malaysia, 2003), the Third Asian Particle Technology Symposium, APT 2007, was held from September 3 to 5 in Bei...Succeeding the first two successful conferences, APT 2000 (Bangkok, Thailand, 2000) and APT 2003 (Penang, Malaysia, 2003), the Third Asian Particle Technology Symposium, APT 2007, was held from September 3 to 5 in Beijing. The theme of APT 2007 was Small Particle Technology, to reflect one of the most advanced sectors both in forefront fundamental research and in application of particles at the nanometer and sub-micron scales. More than 14 countries and 315 participants attended the symposium presenting about 150 papers published in two volumes of proceedings.展开更多
基金supported by the Fundamental Research Funds for the Central Universities,China (Grant Nos. 2017B17114 and B210202152)。
文摘We study the behaviors of thermalization in Fermi–Pasta–Ulam–Tsingou(FPUT) system with small number of particles using periodic boundary conditions. The total energy has initially equidistributed among some of the lowest frequency modes. The thermalization time t_(eq) depending on system's energy density ε scales as t_(eq) ∝ε^(-4) only within a certain range of nonlinearity. In this range of nonlinearity, energies can interchange between the initial excited modes and other modes continuously with time until reaching the thermalized state. With a further decreasing nonlinearity, a steeper growth than ε^(-4) will appear. In the very weakly nonlinear regime, energies on low frequency modes are found to be frozen on large time scales. Redistribution of mode energies happens through the resonances of high frequency modes.
文摘The Lagrangian equations of motion of small particle in turbulent boundary layer flows, taking into account the effects of the drug force caused by the wall presence, the Saffman and the Magus lift forces et al., is studied. Using the spectral method, analytical expression relating to the Lagrangian power spectra of particle velocity to that of the fluid are developed and the results are used to evaluate various responses statistics. In this paper, the results clearly show that the turbulent diffusivity of the particle may be larger than that of the fluid for a period of long-time.
基金Work at ORNL was supported by the United States Department of Energy,Basic Energy Sciences,Materials Sciences and Engineering Division.
文摘Light scattering by small particles has a long and interesting history in physics.Nonetheless,it continues to surprise with new insights and applications.This includes new discoveries,such as novel plasmonic effects,as well as exciting theoretical and experimental developments such as optical trapping,anomalous light scattering,optical tweezers,nanospasers,and novel aspects and realizations of Fano resonances.These have led to important new applications,including several ones in the biomedical area and in sensing techniques at the single-molecule level.There are additionally many potential future applications in optical devices and solar energy technologies.Here we review the fundamental aspects of light scattering by small spherical particles,emphasizing the phenomenological treatments and new developments in this field.
基金We thank the National Natural Science Fund of China(2016-Z0030)Natural Science Foundation of Liaoning Province(L2017 LQN008,L2019014).
文摘Silicoaluminophosphates SAPO-11 molecular sieves with small particle size and hierarchical pores were synthesized using the directing agent method.The effect of crystallization time on the particle structure,morphology,pore structure properties,and acid properties of SAPO-11 molecular sieves were investigated.Unlike the SAPO-11 molecular sieves synthesized with the conventional method,the results of XRD,SEM,BET and NH3-TPD analyses showed that the SAPO-11 molecular sieves synthesized by the directing agent method in a shorter crystallization time exhibited fine and uniform morphology.By increasing the crystallization time,the particle size of SAPO-11 molecular sieve was significantly reduced,and the mesoporous structure(intercrystalline pores)was formed.Furthermore,the external specific surface area and the total specific surface area reached 81.7 m^2/g and 192.0 m^2/g,respectively,which effectively reduced the pore mass transfer resistance and significantly increased the number of acid sites.The results of n-dodecane hydroisomerization revealed that the Pt/SAPO-11 prepared with the novel method exhibited higher catalytic activity and better hydroisomerization selectivity than that synthesized by the conventional hydrothermal method.Thus,the small particle molecular sieve showed a promising industrial application prospect to be used as catalyst support.
基金This work was financially supported by the Hong Kong Special Administration Region Earmarked(Grants No.CUHK4025/04P,2160242)the Chinese Academy of Sciences(Special Grant KJCX2-SW-H14)the National Natural Science Foundation of China(Key Grant 20574065).
文摘Using a core (142 nm) made of linear polystyrene (PS) chains as a seed, we further polymerized a thin layer of cross-linked PS shell (7 nm) on it in water to form a core-shell particle. Such a particle swells in toluene, which enables linear PS chains inside the core to gradually diffuse out through the porous shell. Using a combination of static and dynamic laser light scattering, we examined the chain diffusion process by following the change of the scattering intensity (i.e. the average molar mass of the particles). For the first time, we have revealed that the diffusion exhibits three stages. In the first stage, the chain diffusion through the shell is even faster than their translational diffusion in a dilute solution. The three stages respectively correspond to the change of the solution in the core from concentrated to semidilute and then from semidilute to dilute.
基金The work presented in this paper was supported by the National Natural Science Foundation of China (Grant Nos. 51308408, 41272291,51238009) and the Fundamental Research Funds for the Central Universities, and the Open Foundation of State Key Labo- ratory of Hydrology-Water Resources and Hydraulic Engineering (Grant No. 2014492311 ).
文摘Discrete element modeling was used to investigate the effect of particle size distribution on the small strain shear stiffness of granular soils and explore the fundamental mechanism controlling this small strain shear stiffness at the particle level. The results indicate that the mean particle size has a negligible effect on the small strain shear modulus. The observed increase of the shear modulus with increasing particle size is caused by a scale effect. It is suggested that the ratio of sample size to the mean particle size should be larger than 11.5 to avoid this possible scale effect. At the same confining pressure and void ratio, the small strain shear modulus decreases as the coefficient of uniformity of the soil increases. The Poisson's ratio decreases with decreasing void ratio and increasing confining pressure instead of being constant as is commonly assumed. Microscopic analyses indicate that the small strain shear stiffness and Poisson's ratio depend uniquely on the soil's coordination number.
文摘Succeeding the first two successful conferences, APT 2000 (Bangkok, Thailand, 2000) and APT 2003 (Penang, Malaysia, 2003), the Third Asian Particle Technology Symposium, APT 2007, was held from September 3 to 5 in Beijing. The theme of APT 2007 was Small Particle Technology, to reflect one of the most advanced sectors both in forefront fundamental research and in application of particles at the nanometer and sub-micron scales. More than 14 countries and 315 participants attended the symposium presenting about 150 papers published in two volumes of proceedings.