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The dissimilar joining of 7075 to AZ31 by the friction stir soldering (FSS) process using a Sn interlayer was performed for the first time. The most appropriate microstructure with the highest shear strength was obtained by the one-pass FSS process via a 120 μm-thick intermediate layer. In the optimum situation, the 7075/solder interface was covered with an uninterrupted wavy layer of Sn solid solution, whereas the AZ31/Solder interface was covered with a thin intermetallic region (IMC) consisting of fine-Mg2Sn intermetallics distributed in an Mg2Sn + βSn eutectic matrix. The thickness of the IMC region increased with the decreasing thickness of the intermediate layer and/or the increasing FSS passes, leading to the deterioration of the joint strength. No Al-Mg intermetallics were detected on either the retreated or the advanced side of the one-pass joints; however, isolated Islands and a continuous network of Al-Mg intermetallics were identified at the advanced and retreated sides of the three-pass joints, respectively. In comparison with the advanced side, the retreated side contained a thinner tin-rich solid solution and a thicker IMC region. Moreover, the probability of crack formation or creation of brittle Al-Mg intermetallics on the retreated side was more than those on the advanced side. [ABSTRACT FROM AUTHOR]

SnCu coatings (Cu between 0–33.0 at.%) were electrodeposited over mild steel. Corrosion analysis was performed over mirror polished SnCu coatings to remove surface morphology effect. Highest corrosion resistance was observed for the SnCu coating with ∼21.2 at.% Cu and lowest corrosion resistance was observed for the SnCu coating with ∼9.9 at.% Cu. Sn-rich phase and Cu6Sn5 intermetallic were present in all the coatings. For lower Cu content (∼6.0 at.% Cu), a significant fraction of Cu was found to be incorporated into the Sn rich solid solution phase, thus increasing strain within the grains. As the Cu content increased, the Cu6Sn5 phase formed predominantly at the Sn-rich phase grain boundaries. For the Sn rich phase, a preferred crystallographic orientation along the (001) was observed in SnCu coating with lower Cu content (Cu < 10 at.%). On the other hand, at high Cu content (Cu > 20 at.%), the low surface energy (100) texture was dominant. Addition of Cu decreased the Sn-rich phase grain size. The SnCu coating with ∼21.2 at.% Cu exhibited highest fraction of low angle grain boundaries (LAGBs) and low energy (031) [ 0 1 ¯ 3 ] twin boundaries. It was established that the presence of low surface free energy (100) atomic planes exposed to corrosive medium, a high fraction of LAGBs, and low energy (031) [ 0 1 ¯ 3 ] twin boundaries yields high corrosion resistance for SnCu coating with 21.2 at.% Cu, while a strong (001) texture and high strain within the grains, increased the corrosion susceptibility of the SnCu coating with ∼9.9 at.% Cu. [ABSTRACT FROM AUTHOR]

We present the new iterative method lpCMFD-SOR, which combines the linear prolongation coarse-mesh finite difference (lpCMFD) scheme with the method of successive overrelaxation (SOR) for neutron transport source iteration (SI). The lpCMFD method is the latest coarse-mesh finite difference (CMFD)–type acceleration scheme and is unconditionally stable and more effective than the standard CMFD method. The SOR method is a variant of the Gauss-Seidel method for solving a linear system of equations, resulting in faster convergence. The idea is to update the scattering source with overrelaxation to speed up the coupled transport-diffusion SI. Fourier analysis shows that the lpCMFD-SOR method converges for a relaxation parameter ω in the range of 0 < ω < 2. It becomes less effective when underrelaxed (i.e., ω < 1) and increasingly more effective as ω increases above 1 until reaching the optimal overrelaxation value, which is, however, problem dependent. The optimal overrelaxation parameter increases with both the scattering ratio and the optical thickness of the problem. Numerical experiments have confirmed the Fourier analysis results. In general, the SOR method can further enhance the convergence rate of the lpCMFD method by more than 40% for neutron transport problems. [ABSTRACT FROM AUTHOR]

Joint modelling skewness and heterogeneity is challenging in data analysis, particularly in regression analysis which allows a random probability distribution to change flexibly with covariates. This paper, based on a skew Laplace normal (SLN) mixture of location, scale, and skewness, introduces a new regression model which provides a flexible modelling of location, scale and skewness parameters simultaneously. The maximum likelihood (ML) estimators of all parameters of the proposed model via the expectation-maximization (EM) algorithm as well as their asymptotic properties are derived. Numerical analyses via a simulation study and a real data example are used to illustrate the performance of the proposed model. [ABSTRACT FROM AUTHOR]

We examined the temporal variation of heavy metals in different sexes of three brackish water shrimp species with emphasis on the relationship between Fulton's K condition indices and metal pollution index (MPI). Zn was the most abundant metal followed by Sn, though levels were below the admissible limits (irrespective of gender). Temporal variation of Zn and Pb was significant (p < 0.01). Drier weather conditions influenced Pb accumulation. Temporal variation of Sn was insignificant (p > 0.05), but temporal variation of Hg was significant only in Penaeus monodon (p < 0.0001). However, the relationship between temporal variation of the above-mentioned metals and gender was insignificant except in Penaeus semisulcatus for Pb (p < 0.02) and Sn (p < 0.04) despite no consistent higher bioaccumulation pattern by one particular sex. There were no significant negative correlations between the Fulton's K condition indices and MPI values in the different sexes. MPI values between the two sexes were insignificant. Any differences in the MPI values between the three species were insignificant. Only Penaeus semisulcatus exhibited significant differences (p < 0.022) in Fulton's K condition indices in relation to gender. Fulton's K condition indices are unreliable indicators of metal-induced stress levels in shrimps. [ABSTRACT FROM AUTHOR]

This paper uses local dual weighted residual (DWR) error indicators to flag cells for goal-based refinement in a 1-D diamond difference (DD) discretisation of the discrete ordinate (SN) neutron transport equations. Goal-orientated adaptive mesh refinement (GO-AMR) aims to produce a mesh that is optimal for a given goal or QoI (Quantity of Interest). h, p and hp refinement is implemented and applied to various test cases. A merit function is derived for the combined hp algorithm and is calculated for each refinement option within each flagged cell. The refinement option with the highest merit function is chosen for a given flagged cell. This paper also investigates the use of the DWR error estimation as a correction term for the originally calculated QoI. If error correction and GO-AMR are combined the DWR error indicators do not always give an optimal mesh for the corrected value of the QoI. Therefore, refinement indicators based on the error in the error correction term are used and tested in this work. [ABSTRACT FROM PUBLISHER]

Multiwalled carbon nanotubes (MWCNTs) were successfully coated and filled with Sn using a simple method. Bulk thermal conductivity of Sn/SnO filled and coated multiwalled carbon nanotubes (MWCNTs) of ∼1 mm thickness pellet by laser method reveals surge in hybrid carbon nanotubes in comparison to pristine nanotubes. The thermal diffusivity and thermal conductivity of hybrid nanotubes are increased to 4.41 mm2/sec, 5.39 Wm−1K−1of as compared to 0.36 mm2/sec and 0.28 Wm−1K−1of the pristine nanotubes. The enhancement in thermal conductivity is attributed to the presence of Sn coating on surface and inside the carbon nanotubes and the formation of compact structures by reducing the air gaps between nanotubes because of their joining during compression and sintering. [ABSTRACT FROM AUTHOR]

In the present paper, the influences of the addition forms of Sn, such as nanoparticles or ingot, on the microstructure and properties of magnesium alloy matrix were investigated. It was found that the size of as-formed Mg2Sn phases was in nano scale for the sample with Sn nanoparticles addition. While Mg2Sn phases were in macro scale for the sample with Sn ingot addition. The strength and plasticity of the AZ31 alloy matrix were improved because of the Sn additions regardless of nanoparticle or ingot. However, the AZ31 alloy with Sn ingot addition exhibited better mechanical properties than the sample with the nanoparticle addition, which could be owing to the loss of Sn nanoparticles in the processing of smelting and existence of nanoscopic Mg2Sn phase as particle clusters in the matrix. [ABSTRACT FROM AUTHOR]

We present the calculations of electrical resistivity, thermo-electric power and thermal conductivity based on the self-consistent approximation. The pseudopotential due to Hasegawaet al. [J. Non-Cryst. Solids117/118, 300 (1990)] for full electron–ion interaction, which is valid for all electrons and contains the repulsive delta function to achieve the necessary s-pseudisation, was used in the calculation. Temperature dependence of structure factor is achieved through temperature-dependent potential parameter in the pair-potential. The outcome of the present study is discussed in the light of other such results and with predictions of Wiedemann and Franz law up to moderately high temperature. Specially, high-temperature resistivity data necessitates the careful investigation of electron energy dispersion close to the Fermi level and possible metal to non-metal transition while going from dense-fluid to low density-fluid state. In the absence of experimental data at high temperature, these findings may serve as future guideline. [ABSTRACT FROM AUTHOR]

Standard second-order self-adjoint forms of the transport equation, such as the even-parity, odd-parity, and self-adjoint angular flux equation, cannot be used in voids. Perhaps more important, they experience numerical convergence difficulties in near-voids. Here we present a new form of a second-order self-adjoint transport equation that has an advantage relative to standard forms in that it can be used in voids or near-voids. Our equation is closely related to the standard least-squares form of the transport equation with both equations being applicable in a void and having a nonconservative analytic form. However, unlike the standard least-squares form of the transport equation, our least-squares equation is compatible with source iteration. It has been found that the standard least-squares form of the transport equation with a linear-continuous finite-element spatial discretization has difficulty in the thick diffusion limit. Here we extensively test the 1D slab-geometry version of our scheme with respect to void solutions, spatial convergence rate, and the intermediate and thick diffusion limits. We also define an effective diffusion synthetic acceleration scheme for our discretization. Our conclusion is that our least-squares Sn formulation represents an excellent alternative to existing second-order Sn transport formulations. [ABSTRACT FROM AUTHOR]

The effect of native oxide films on the reaction of liquid Sn with stainless steels has been investigated by analysing the growth of intermetallic layers. The diversity of the oxide layers has been employed by exposure of various stainless steels [martensite stainless steel (MSS), austenite stainless steel (ASS) and duplex stainless steel (DSS)] in air for different times. Liquid tin was prone to metallurgically interact with MSS by formation of interfacial (Fe, Cr)Sn2 intermetallics. The native oxide film on MSS decreased (Fe, Cr)Sn2 layer thickness growth but cannot prevent the intermetallic formation. The reaction of Sn with ASS was hindered by the native oxide layer, and the thickness and coverage ratio of the (Fe, Cr)Sn2 intermetallics decreased with the increasing exposure time in air. The oxide film grown on DSS was stable enough to prevent the formation of (Fe, Cr)Sn2 and changed the tin from metallurgical interaction to physical attachment. [ABSTRACT FROM AUTHOR]