[en] The vibrational density of states and phonon specific heat of Si nanocrystals are studied by means of a lattice dynamical calculation. The vibrational density of states of Si nanocrystals is distinct from the bulk one at low and high frequencies owing to the finite-size effect. At low frequencies there is an excess of the vibrational modes, while there is a deficit at high frequencies. At low frequencies the dependence of the vibrational density of states on frequency is intermediate between linear and quadratic. The specific heat of Si nanocrystals is enhanced as compared to that of the bulk with a maximal excess at around 90 K. The dependence of the specific heat on temperature deviates from the known T³-law for crystalline systems at low temperatures. (author). Letter-to-the-editor

[en] MCAM (Monte Carlo Automatic Modeling program for particle transport simulation) was developed by FDS Team as a bi-directional interface program between general CAD systems and Monte Carlo particle transport simulation codes. The physics and material modeling and void space modeling functions were improved and the free-form surfaces processing function was developed recently. The applications to the ITER (International Thermonuclear Experimental Reactor) building model and FFHR (Force Free Helical Reactor) model have demonstrated the feasibility, effectiveness and maturity of MCAM latest version for nuclear applications with complex geometry. (author)

[en] MCAM (Monte Carlo Automatic Modeling program for particle transport simulation) was developed by FDS Team as a CAD based bi-directional interface program between general CAD systems and Monte Carlo particle transport simulation codes. The physics and material modeling and void space modeling functions were improved and the free form surfaces processing function was developed recently. The applications to the ITER (International Thermonuclear Experimental Reactor) building model and FFHR (Force Free Helical Reactor) model have demonstrated the feasibility, effectiveness and maturity of MCAM latest version for nuclear applications with complex geometry. (author)

[en] Using a perturbative method, we carefully calculate seventh- and ninth-order expressions for electromagnetic field components for a fundamental Gaussian beam (i.e., a focused TEM₀₀ mode laser beam) propagating in the medium analogous to vacuum. The interaction of a single electron and a focused laser pulse in vacuum has a promising application in the design of a powerful electron accelerator which could compete with the traditional ones. For this, ninth-order accuracy in the expansion describing the focused laser beam is required. When the vector potential corresponds to polarization along the direction of propagation, the number of electromagnetic field components can be reduced from 5 or 6 to 3. Furthermore, we find two rules obeyed by all orders of the vector potential, which greatly simplify the calculation procedure of the vector potential order by order, and make it possible to investigate the behavior of high orders

[en] Using a multivariable series method, we calculated the eighth-order expression of the vector potential of a fundamental Gaussian beam, thereby correcting the mistake in our previous paper [Phys. Rev. E 72, 046501 (2005)]

[en] The AgI nanowire arrays were prepared in the ordered porous alumina membrane by an electrochemical method. Transmission electron microscopy observation shows that the AgI nanowires are located in the channels of the alumina membrane. In situ x-ray diffractions show that the nanowire arrays possess hexagonal close-packed structure (β-AgI) at 293 K, orienting along the (002) plane, whereas at 473 K, the nanowire arrays possess a body-centered cubic structure (α-AgI), orienting along the (110) plane. The AgI nanowire arrays exhibit a negative thermal expansion property from 293 to 433 K, and a higher transition temperature from the β to α phase. We ascribe the negative thermal expansion behavior to the phase transition from the β to α phase, and the elevated transition temperature to the radial restriction by the channels of alumina membrane

[en] The main problem determining whether the method of characteristics (MOC) can be used in complicated and highly heterogeneous geometry is how to combine an effective geometry processing method with MOC. In this study, a new idea making use of MCAM, which is a Mutlti-Calculation Automatic Modeling for Neutronics and Radiation Transport program developed by FDS Team, for geometry description and ray tracing of particle transport was brought forward to solve the geometry problem mentioned above. Based on the theory and approach as the foregoing statement, a two dimensional neutron transport code was developed which had been integrated into VisualBUS, developed by FDS Team. Several benchmarks were used to verify the validity of the code and the numerical results were coincident with the reference values very well, which indicated the accuracy and feasibility of the method and the MOC code. (authors)

[en] CAD/Image-based Modeling Program for Nuclear and Radiation System (MCAM) has been widely used for nuclear analysis of complex devices. It helps to produce suitable models with radiation transport simulation codes in an efficient, less error-prone way. In order to further improve the efficiency for complex problems, this study introduced and implemented a similarity estimation based model reuse technique. The method retrieves the solids in an expert library and the history of the algorithm execution and then estimates the similarity between the target solid and the retrieved solid. The history result could be reused with a transformation between the two solids. The test results with some fusion reactor models showed that the method could improve the efficiency of the modeling process. (authors)

[en] Hierarchical structured SiO₂-γ-AlOOH spheres were fabricated in one step by using silica colloidal spheres as a template. Scanning electron microscopy and transmission electron microscopy investigation showed that the shell is composed of large amounts of nanoscale γ-AlOOH lamellas. The growth mechanism was proposed as silica template-induced heterogeneous deposition of γ-AlOOH lamellas. The adsorption properties of hierarchical SiO₂-γ-AlOOH spheres annealed at different temperatures were investigated through the removal test of Cr(VI) ions in model wastewater, and the nanostructures annealed at 400 deg. C showed good adsorption capability of Cr(VI) ions.

[en] FLUKA is a fully integrated particle physics Monte Carlo simulation package. It is necessary to create the geometry models before calculation. However, it is time- consuming and error-prone to describe the geometry models manually. This study developed an automatic modeling method which could automatically convert computer-aided design (CAD) geometry models into FLUKA models. The conversion program was integrated into CAD/image-based automatic modeling program for nuclear and radiation transport simulation (MCAM). Its correctness has been demonstrated. (authors)