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Competing role of catalysis-coagulation and catalysis-fragmentation in kinetic aggregation behaviours

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Chinese Physics B 2010年第12期19卷 559-570页

作者：李晓东林振权宋美霞柯见洪 department of Physics Wenzhou University

We propose a kinetic aggregation model where species A aggregates evolve by the catalysis-coagulation and the catalysis-fragmentation, while the catalyst aggregates of the same species B or C perform self-coagulation processes. By means of the generalized Smoluchowski rate equation based on the mean-field assumption, we study the kinetic behaviours of the system with the catalysis-coagulation rate kernel K（i,j;l） l^v and the catalysis-fragmentation rate kernel F（i,j; l） l^μ, where l is the size of the catalyst aggregate, and v and μ are two parameters reflecting the dependence of the catalysis reaction on the size of the catalyst aggregate. The relation between the values of parameters v and μ reflects the competing roles between the two catalysis processes in the kinetic evolution of species A. It is found that the competing roles of the catalysis-coagulation and catalysis-fragmentation in the kinetic aggregation behaviours are not determined simply by the relation between the two parameters v and μ, but also depend on the values of these two parameters. When v 〉 μ and v ≥0, the kinetic evolution of species A is dominated by the catalysis-coagulation and its aggregate size distribution αk（t） obeys the conventional or generalized scaling law; when v 〈 μ and v ≥ 0 or v 〈 0 but μ≥ 0, the catalysis-fragmentation process may play a dominating role and ak（t） approaches the scale-free form; and in other cases, a balance is established between the two competing processes at large times and ακ（t） obeys a modified scaling law.

关键词： kinetic aggregation behaviour catalysis-coagulation catalysis-fragmentation rate equations

Dynamics of particles around a pseudo-Newtonian Kerr black hole with halos

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Chinese Physics B 2012年第5期21卷 88-99页

作者：王颖伍歆 department of Physics Nanchang University

The regular and chaotic dynamics of test particles in a superposed field between a pseudo-Newtonian Kerr black hole and quadrupolar halos is *** particular,the dependence of dynamics on the quadrupolar parameter of the halos and the spin angular momentum of the rotating black hole is *** is found that the small quadrupolar moment,in contrast with the spin angular momentum,does not have a great effect on the stability and radii of the innermost stable circular orbits of these test *** addition,chaos mainly occurs for small absolute values of the rotating parameters,and does not exist for the maximum counter-rotating case under some certain initial conditions and *** means that the rotating parameters of the black hole weaken the chaotic *** is also found that the counter-rotating system is more unstable than the co-rotating ***,chaos is absent for small absolute values of the quadrupoles,and the onset of chaos is easier for the prolate halos than for the oblate ones.

关键词： pseudo-Newtonian potential Kerr black hole chaos

Broadening of Cr nanostructures in laser-focused atomic deposition

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Chinese Physics B 2010年第12期19卷 168-173页

作者：卢向东李同保马艳 department of Physics Tongji University

This paper presents the experimental progress of laser-focused Cr atomic deposition and the experimental condition. The result is an accurate array of lines with a periodicity of 212.8±0.2 nm and mean full-width at half maximum as approximately 95 nm. Surface growth in laser-focused Cr atomic deposition is modeled and studied by kinetic Monte Carlo simulation including two events： the one is that atom trajectories in laser standing wave are simulated with the semiclassical equations of motion to obtain the deposition position; the other is that adatom diffuses by considering two major diffusion processes, namely, terrace diffusion and step-edge descending. Comparing with experimental results （Anderson W R, Bradley C C, McClelland J J and Celotta R J 1999 Phys. Rev. A 59 2476）, it finds that the simulated trend of dependence on feature width is in agreement with the power of standing wave, the other two simulated trends are the same in the initial stage. These results demonstrate that some surface diffusion processes play important role in feature width broadening. Numerical result also shows that high incoming beam flux of atoms deposited redounds to decrease the distance between adatoms which can diffuse to minimize the feature width and enhance the contrast.

关键词： atom optics laser-focused atomic deposition kinetic Monte Carlo simulation surface growth

Dynamic magnetic behavior of the mixed spin (2, 5/2) Ising system with antiferromagnetic/antiferromagnetic interactions on a bilayer square lattice

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Chinese Physics B 2013年第12期22卷 160-167页

作者： Mehmet Ertas Mustafa Keskin department of Physics Erciyes University

Using the mean-field theory and Glauber-type stochastic dynamics, we study the dynamic magnetic properties of the mixed spin （2, 5/2） Ising system for the antiferromagnetic/antiferromagnetic （AFM/AFM） interactions on the bilayer square lattice under a time varying （sinusoidal） magnetic field. The time dependence of average magnetizations and the thermal variation of the dynamic magnetizations are examined to calculate the dynamic phase diagrams. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and the effects of interlayer coupling interaction on the critical behavior of the system are investigated. We also investigate the influence of the frequency and find that the system displays richer dynamic critical behavior for higher values of frequency than that of the lower values of it. We perform a comparison with the ferromagnetic/ferromagnetic （FM/FM） and AFM/FM interactions in order to see the effects of AFM/AFM interaction and observe that the system displays richer and more interesting dynamic critical behaviors for the AFM/AFM interaction than those for the FM/FM and AFM/FM interactions.

关键词： dynamic magnetic behavior of a bilayer Ising system mixed spins glauber-type stochastic dynamics antiferromagnetic/antiferromagnetic interactions

Elastic, thermodynamic, electronic, and optical properties of recently discovered superconducting transition metal boride NbRuB:An ab-initio investigation

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Chinese Physics B 2017年第10期26卷 339-347页

作者： F Parvin S H Naqib department of Physics University of Rajshahi

The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, are investigated using the density functional formalism. Both generalized gradient approximation （GGA） and local density approximation （LDA） are used for optimizing the geometry and for estimating various elastic moduli and constants. The optical properties of NbRuB are studied for the first time with different photon polarizations. The frequency （energy） dependence of various optical constants complement quite well the essential features of the electronic band structure calculations. Debye temperature of NbRuB is estimated from the thermodynamical study. All these theoretical estimates are compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. The NbRuB possesses significant elastic anisotropy. Electronic features, on the other hand, are almost isotropic in nature. The effects of electronic band structure and Debye temperature on the emergence of superconductivity are also analyzed.

关键词： hard materials ternary borides DFT calculations electronic band structure optical properties superconductivity

Highly Dispersed RuOOH Nanoparticles on Silica Spheres:An Efficient Photothermal Catalyst for Selective Aerobic Oxidation of Benzyl Alcohol

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Nano-Micro Letters 2020年第3期12卷 169-178页

作者： Qilin Wei Kiersten G.Guzman Xinyan Dai Nuwan H.Attanayake Daniel R.Strongin Yugang Sun department of Chemistry Temple University

Photothermal catalysis represents a promising strategy to utilize the renewable energy source(e.g.,solar energy)to drive chemical reactions more *** and efficient photothermal catalysis relies on the availability of ideal photothermal catalysts,which can provide both large areas of catalytically active surface and strong light absorption power *** duplex requirements of a photothermal catalyst exhibit opposing dependence on the size of the catalyst nanoparticles,i.e.,smaller size is beneficial for achieving higher surface area and more active surface,whereas larger size favors the light absorption in the *** this article,we report the synthesis of ultrafine RuOOH nanoparticles with a size of 2–3 nm uniformly dispersed on the surfaces of silica(SiOx)nanospheres of hundreds of nanometers in size to tackle this challenge of forming an ideal photothermal *** ultrasmall RuOOH nanoparticles exhibit a large surface area as well as the ability to activate adsorbed molecular *** SiOx nanospheres exhibit strong surface light scattering resonances to enhance the light absorption power of the small RuOOH nanoparticles anchored on the SiOx ***,the RuOOH/SiOx composite particles represent a new class of efficient photothermal catalysts with a photothermal energy conversion efficiency of 92.5%for selective aerobic oxidation of benzyl alcohol to benzylaldehyde under ambient conditions.

关键词： Ultrasmall RuOOH nanoparticles Photothermal catalyst Selective aerobic oxidation Light antenna effect Light scattering resonance

Lasing without inversion in a four-level diamond system

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Chinese Physics B 2012年第12期21卷 243-249页

作者：高强宋同强 department of Physics Ningbo University

We study the lasing without inversion in a four-level diamond configuration in the case of incoherent pumping field within the framework of the bare-state basis. With the strong fields limit, we obtain the approximate steady-state solution, and discuss the dependence of population distribution and system gain on probe detuning and auxiliary field Rabi frequency.

关键词： lasing without inversion four-level diamond system cyclic transition

Hofstadter's Butterfly and Phase Transition of Checkerboard Superconducting Network in a Magnetic Field

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Communications in Theoretical Physics 2010年第3期53卷 587-590页

作者：侯净敏田立君 department of Physics Southeast University department of Physics Shanghai University

We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes- Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter＇s butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter＇s butterfly spectrum.

关键词： superconducting wire network checkerboard lattice Hofstadter's butterfly phase transition

Electrochemical Corrosion Behavior of Nd-Fe-B Sintered Magnets in Different Acid Solutions

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Journal of Rare Earths 2006年第2期24卷 218-222页

作者：郑精武姜力强陈巧玲 department of Chemical and Materials Engineering Zhejiang University of Technology Hangzhou 310014 China department

Electrochemical corrosion behavior of Nd-Fe-B sintered magnets in nitric acid, hydrochloric acid, sulfuric acid, phosphate acid and in oxalic acid was studied. Potentiodynamic polarization curves and immersion time dependence of corrosion rates of Nd-Fe-B sintered magnets in different acid solutions were tested. Microstructures of corroded Nd-Fe-B sintered magnets were investigated by means of SEM and AFM. The results indicate that in strong acid solutions of similar hydrogen ion concentration, the corrosion current increases in the order of HCl 〉 H3SO4 〉 HNO3 solution and Nd-Fe-B sintered magnets are passivated in phosphate acid and oxalic acid. Within 25 min, the corrosion rates of Nd-Fe-B sintered magnets in H2SO4 and H3PO4 solutions show a declining trend with immersion time, while in HNO3 and HCl solutions the corrosion rates are rising. And in H2C2O4 solution, weight of the magnets increases. The brim of Nd-Fe-B sintered magnets is corroded rather seriously and the size of the magnets changed greatly in nitric acid. The surfaces of the corroded magnets in the above mentioned acid solutions are all coarse.

关键词： Nd-Fe-B sintered magnets corrosion acid solution microstructure rare earths