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The finite element models of curved-liner shaped charges penetrating aluminum-alloy thin plates were constructed with the ANSYS/LS-DYNA software to analyze the effect of cavity shapes on the charge penetration with curved liners. The cavity height, radius, and spatial dimensions were numerically simulated. Simulation results indicate that these properties are important factors in determining the penetration of curved-liner charges. The penetration depth exhibits an initial increase followed by a decrease with the fixed cavity radius. When the cavity height is fixed, the penetration depth decreases with the cavity radius. When the cavity is semicircular, the penetration depth first increases and then decreases with the cavity radius and height. [ABSTRACT FROM AUTHOR]

This paper aims to develop a meshless approach based on the Point Interpolation Method (PIM) for numerical simulation of a space fractional diffusion equation. Two fully-discrete schemes for the one-dimensional space fractional diffusion equation are obtained by using the PIM and the strong-forms of the space diffusion equation. Numerical examples with different nodal distributions are studied to validate and investigate the accuracy and efficiency of the newly developed meshless approach. [ABSTRACT FROM AUTHOR]

In this paper, we report a high-power thulium (Tm)-doped superfluorescent fiber source (SFS) in the 2-μm spectral region. The SFS is based on double angle-cleaved facet operation and uses a simple single-stage geometry. The copropagating amplified spontaneous emission (ASE) yields a maximum output of 20.7 W at a center wavelength of 1,960.7 nm, with a full width at half maximum (FWHM) of ~45 nm. The counterpropagating ASE yields a maximum output of 25.2 W at a center wavelength of 1,948.2 nm, with a FWHM of ~50 nm. The maximum combined output of the SFS is as much as 45.9 W, which corresponds to a slope efficiency of 38.9 %. In addition, a model of the ~2 μm SFS in Tm-doped silica fibers pumped at ~790 nm is developed, and the influence of fiber length and end-facet reflectivity on the ASE output performance and the parasitic lasing threshold are studied numerically. [ABSTRACT FROM AUTHOR]

The variational iteration method (VIM) was extended to solve the aeroelastic system of an airfoil with both cubic and nonsmooth stiffnesses (a piecewise freeplay), expressed by integral-differential equations. Limit cycle (LC) frequency and amplitude are unknown to be updated at every iteration stage. If the VIM is routinely applied, the LC solution needs to be embedded into both the integrals and the freeplay, which can result in two intractable problems: (1) the integrals lead to coupled terms between frequency and amplitude and (2) the Fourier expansion of the freeplay cannot be realized. In order to tackle these problems, the solution obtained at the previous iteration rather than the current unknown one is applied to the freeplay and the integrals. By this means, the frequency and amplitude are decoupled, and the freeplay can be expanded as Fourier series. Numerical examples show that very accurate LC solutions can be obtained by the presented method. This method is suitable for solving LCs of nonlinear dynamical systems with nonsmooth nonlinearities. [ABSTRACT FROM AUTHOR]

Highlights: [•] A model investigating the thermal-dynamic performance of scientific balloon is proposed. [•] We calculate the thermal-dynamic performance of a balloon in a real environment. [•] The balloon almost drifts with wind in horizontal direction and its trajectory changes with wind. [•] The maximum film temperature is 230K in ascending process and 280K at floating conditions. [•] The average Helium velocity is 0.65m/s in ascending process and 0.55m/s at floating conditions. [ABSTRACT FROM AUTHOR]

Abstract: Using the Weather Research and Forecasting Model with Chemistry (WRF/Chem) model, we conducted a series of numerical experiments to investigate the relative contributions of climate and emission change to surface ozone (O3) over South China for the period of October in 2005–2007 and 2055–57. WRF/Chem was driven by the outputs of Community Climate System Model version 3 (CCSM3). The simulations predict that on average near-surface temperature and water vapor mixing ratio are projected to increase 1.6 °C and 1.6 g kg− 1 under A1B scenario. In response to the climate change, the emissions of isoprene and monoterpenes in South China increase by 5–55% and 5–40%, respectively. The change of climate and biogenic emission can result in a change of −5 to 5 ppb of afternoon surface O3 mixing ratios, with an average of 1.6 ppb over the land region in South China. Over Pearl River Delta, a region of dense network of cities, the 2000–2050 climate changes increase afternoon mean surface O3 by 1.5 ppb. The change of anthropogenic emission can result in a change of −3–24 ppb of afternoon surface O3 mixing ratios, with an average of 12.8 ppb over the land region in South China. Our analysis suggests that the anthropogenic emissions have greater impact on the change of surface O3 concentration over South China compared to climate change. The combined effect of climate and emission can increase afternoon mean surface O3 over South China by an average of 18.2 ppb in the land region, with the highest increase up to 24 ppb occurring over southeast of Hunan province. [Copyright &y& Elsevier]

With invoking analytical formulae in number theory and numerical calculations, we calculate the number of microstates in microcanonical ensemble for free particles in a single harmonic trap which in whole space defines a thermodynamic system but not a spatially homogeneous one. Once the number of excitation quanta m is larger than the square of the particle number N as m⪰ O( N) when N≫1, the number of microcanonical microstates for an ideal, harmonically trapped Bose or Fermi gas gradually converge to the Boltzmann microcanonical microstates for the classical particles with a proper consideration of the indistinguishability. [ABSTRACT FROM AUTHOR]

An iterative Time-Reversal Mirror (TRM) method is proposed to Detect and Image the buried target beneath ground surface. Unlike the conventional TRM methods which treat the information of the ground as clutters and directly delete them, the iterative TRM imaging method proposed in this paper utilizes the information of rough ground surface as a useful knowledge. The new approach is consisted of two TRM procedures. In the first TRM procedure, it aims to image the rough surface where the propagation environment for electromagnetic wave is free space. The second TRM procedure aims to image the buried target. In this step, the information of the rough surface estimated by the first TRM procedure will be treated as newly updated propagation environment. Then conventional TRM is applied to image the buried target. By applying this iterative TRM method, the information of the rough ground can be well considered in the whole TRM procedure. Numerical simulations prove that this method performs significantly better image contrast comparing with the results obtained by using conventional TRM. 4-5 dB improvement on the imaging SNR has been achieved. Furthermore, the target can be located more accurately. [ABSTRACT FROM AUTHOR]

According to the equivalence principle, the aperture near-field can be expressed as the convolution of the aperture field and the spatial network response function. Therefore the aperture near-field angular spectrum can be expressed as the product of the angular-domain spectrum of the aperture field and the angular-domain spectrum of the spatial network response function. The spatial network function acts as an angular spectrum filter. Based on the aperture field convolution method, the near-field radiation of several electrically large apertures has been computed and compared in the spatial and angular domains, including a circular aperture, a square aperture and a well-designed serrated edge aperture. The following facts have been demonstrated by the numerical results: The serrated edge aperture has the most uniform near-field amplitude and phase distribution, both in the transverse plane and in the central axis. The plane-wave spectrum components received by a certain observation plane are related to its position, size and shape. The direct wave and edge diffraction waves can be observed qualitatively and quantitatively in the angular domain. The edge diffraction waves cannot be distinguished when the transverse size of the observation plane is less than a certain value. Finally, based on general rules of compact antenna test range design, the angular-domain analysis applications for the evaluation of the aperture shape design and the diagnosis of the aperture deformation are presented. All the three aperture diameters are limited to 150 wavelengths in free space. Inverse Fourier transform with a Hamming window has been adopted for the spatial-angular transform. [ABSTRACT FROM AUTHOR]

The machining accuracy of computer numerical control (CNC) machine tools largely depends on the interpolation algorithms implemented. In this paper, a real-time high-precision interpolation algorithm for a general-typed parametric curve is proposed. As with other time-partition interpolation algorithms, the linear motion trajectory (employed to approximate the real trajectory) in a sampling cycle is determined from the current position of the tool to another point (target point) on the target trajectory. To determine the target point in a sampling cycle, a neighbourhood interval containing the point is first determined, the target point is then iteratively approached by means of the bi-section or secant method for equation resolutions. Simulation results show that the order of magnitude of the maximum feedrate relative errors (the relative deviation of the computed feedrate from the desired one) is -8 or less, while the order of magnitude of the maximum chord errors in the unit of meter is -6 or less. The performance indices can be further improved with more computation iteration in each sampling cycle. The algorithm is general, and applicable to any smooth curve that can be formulated in parametric equations. [ABSTRACT FROM AUTHOR]

A hybrid technique combines the finite element (FEM) and boundary integral (BI) methods is used to analyze electromagnetic scattering problems from structures consisting of an inhomogeneous dielectric body attached to perfectly conducting bodies. The hybrid approach takes advantage of the strengths of each numerical technique in order to solve problems that neither technique alone could model efficiently. Numerical results are presented to validate the accuracy and demonstrate the application of this method. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present a random walk model for approximating a Lévy–Feller advection–dispersion process, governed by the Lévy–Feller advection–dispersion differential equation (LFADE). We show that the random walk model converges to LFADE by use of a properly scaled transition to vanishing space and time steps. We propose an explicit finite difference approximation (EFDA) for LFADE, resulting from the Grünwald–Letnikov discretization of fractional derivatives. As a result of the interpretation of the random walk model, the stability and convergence of EFDA for LFADE in a bounded domain are discussed. Finally, some numerical examples are presented to show the application of the present technique. [Copyright &y& Elsevier]

In this study, improved cross-search, bicubic spline interpolation and finite element (FE) methods are implemented into conventional digital image speckle correlation algorithm in order to reduce correlation computational time, to increase deformation measurement accuracy, and to smooth deformation distribution. With the improved correlation algorithms, an integrated computer-aided-measurement system, called micro-digital image speckle correlation (μ-DiSC) is built. This system is then applied to characterize the thermal property and fracture behavior of the plastic ball grid array (BGA) assembly and underfill thin film, and employed to validate the material constitutive relationship for a flip chip package and the fatigue life prediction model for a BGA assembly. The demonstration results are found to be in good agreement with those obtained from thermo-mechanical analyzer (TMA), finite element modeling (FEM), moiré interferometry (MI), and accelerated temperature cycling (ATC) test. Therefore, the system can be used as an effective experimental tool to characterize properties of electronic materials and verify findings of theoretical and numerical models for the establishment of reliability design methodology. [ABSTRACT FROM AUTHOR]

The experiment on the adhesion coefficient of a wheel–rail system has been carried out by means of a full-scale test facility under the condition of different axle loads and rolling speeds. The effects of the condition of the wheel–rail contact surfaces, such as a clean and dry surface, water and oil contamination and slip, on the adhesion coefficient have been investigated in the experiment. The experimental results show that, when the rolling speed of the wheelset increases, the adhesion coefficient decreases under the condition of the constant creepage and water contamination on the contact surfaces, but it increases for oil contamination. Using the data obtained by statistics and analysis of the experimental results and Kalker's rolling contact theory with Hertzian form modified by the present authors, a numerical analysis concerning the effect of wheelset rolling speed on the adhesion coefficient and the distribution of the stick–slip area in the contact area has been made. The numerical results are in good agreement with those obtained by experiment. They are very useful in designing the traction power of a locomotive at higher speeds. [ABSTRACT FROM AUTHOR]

A pseudospectral time-domain (PSTD) method is developed for solutions of Maxwell's equations. It uses the fast Fourier transform (FFT), instead of finite differences on conventional finite-difference–time-domain (FDTD) methods, to represent spatial derivatives. Because the Fourier transform has an infinite order of accuracy, only two cells per wavelength are required, compared to 8–16 cells per wavelength required by the FDTD method for the same accuracy. The wraparound effect, a major limitation caused by the periodicity assumed in the FFT, is removed by using Berenger's perfectly matched layers. The PSTD method is a factor of 4D–8D more efficient than the FDTD methods (D is the dimensionality). © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 15: 158–165, 1997. [ABSTRACT FROM AUTHOR]

A capacitively loaded dual-band internal handset antenna (lHA) with a novel planar structure is presented. Numerical results based on the finite element method for input return loss and radiation gain pattern are investigated and are in agreement with measured results. Effects of the parameters, such as locations of shorten pin, and the value of the loaded capacitor, on the lHA's performance are also extensively studied. [ABSTRACT FROM AUTHOR]

Abstract: Fractional partial differential equations have been applied to many problems in physics, finance, and engineering. Numerical methods and error estimates of these equations are currently a very active area of research. In this paper we consider a fractional diffusion-wave equation with damping. We derive the analytical solution for the equation using the method of separation of variables. An implicit difference approximation is constructed. Stability and convergence are proved by the energy method. Finally, two numerical examples are presented to show the effectiveness of this approximation. [Copyright &y& Elsevier]

Abstract: The growth behavior of the second phase particles (SPPs) in a Zr–Sn–Nb–Fe–Cr–Cu alloy during aging (600–700°C, 30–1800min) has been investigated using scanning electron microscopy (SEM) and an image analysis technique. Microstructural observations show that the precipitated SPPs distribute linearly along the boundaries of α plates at the initial aging stage. As the aging time prolongs and/or temperature increases, the linear distribution feature of SPPs weakens gradually and finally a random distribution is formed. A numerical analysis confirms that the growth of SPPs follows well the second order kinetics of Kahlweit theory and the activation energy is experimentally determined to be 194kJ/mol. The reason for the larger growth activation energy of the SPPs in the experimental alloy, compared to that in Zircaloy-4, is discussed and ascribed to the addition of Nb element. [Copyright &y& Elsevier]

Abstract: Mass and energy balances are required in power generation, chemical, pharmaceutical, food and commodity transfer processes in order to achieve efficient utilization of energy and raw materials. There is a need for accurate, reliable, on-line, continuous and non-invasive measurement of solids'' mass flow rate in many industrial processes mentioned above. Thermal flowmeters, in theory, provide a true indication of the mass flow of solids in pneumatic conveying pipelines. A complicated heat transfer between a pipe wall and a gas–solid flow in a conveying pipeline inevitably takes place in a thermal solids'' mass flow measurement process. A study of heat transfer mechanisms to pneumatically conveyed gas–solid dense phase flow as a means to mass flow rate measurement has been conducted experimentally and numerically to evaluate the heat transfer coefficient between the hot wall and the gas–solid dense phase flow. The prediction of the heat transfer coefficient is compared with the experimental findings. It was found that the heat transfer coefficient between the pipe wall and the gas–solid dense flow is a function of solids loading ratio. Increasing the gas stream velocity significantly augments the heat transfer between the hot wall and the gas–solid dense phase flow. [Copyright &y& Elsevier]