Mechanical polishing,surface roughness,near‐surface deformation,and electrochemical corrosion of Alloy 690TT

The effects of mechanical grinding/polishing, surface roughness, and near‐surface deformation on the electrochemical corrosion behavior of thermally treated (TT) Alloy 690 were studied in a sodium chloride solution. The X‐ray photoelectron spectroscopy and transmission electron microscopy analyses revealed that mechanical grinding/polishing can change the ratio of the elements at the surface of the as‐received Alloy 690TT specimen by removing its Cr‐rich outer layer and causing deformation at the near‐surface microstructure, something which has a direct impact on the rate of the oxygen reduction reaction (ORR), the pitting potential (E_pit), and the corrosion potential (E_corr) of Alloy 690TT. It was observed that the ratio of Cr in the surface is a significant factor that controls the rate of the ORR and the corrosion parameters such as E_corr. Higher amounts of Cr at the surface accelerate the ORR. The near‐surface deformation shifts the E_pit values towards less positive potentials. It was also found that due to the different near‐surface chemical composition of the as‐received Alloy 690TT specimen compared with the ground and the polished specimens, the surface roughness parameters do not have a regular correlation with the rate of the ORR and the values of the E_corr and the E_pit. Only the passive current density increases when the surface roughness is increased. Copyright © 2015 John Wiley & Sons, Ltd.     

A new element for analyzing large deformation of thin Naghdi shell model. Part II: Plastic

In this paper a new element is developed that is based on Cosserat theory. In the finite element implementation of Cosserat theory shear locking can occur, especially for very thin shells. In the present investigation the director vector is constrained to remain perpendicular to the mid surface during deformation. It will be shown that this constraint yields accurate results in very large deformation of thin shells also the rate of convergency is very good. For plastic formulation, the model introduced by Simo is used and it has been reduced for constrained director vector and the consistent elasto-plastic tangent moduli is extracted for finite element solution. This model includes both kinematic and isotropic hardening. For numerical investigations an isoparametric nine node element is employed then by linearization of the principle of virtual work, material and geometric stiffness matrices are extracted. The validity and the accuracy of the proposed element is illustrated by the numerical examples and the results are compared with those available in the literature.     

New enclosure algorithms for the verified solutions of nonlinear Volterra integral equations

This paper is concerned with new algorithms which provide the sharp bounds that are guaranteed to contain the exact solutions of nonlinear Volterra integral equations. We develop new enclosure algorithms based on the interval methods which was first introduced by Moore in [24] together with the Taylor polynomials to improve the accuracy of the scheme by reducing the width of interval solutions. The modified methods calculate a priori bound automatically in parallel with the computation of solutions of integral equations. We will show that the accuracy of the proposed algorithms is dependent on the number of interval subdivisions. Some numerical experiments are also included to demonstrate the validity and applicability of the scheme and showing a marked improvement in comparison with the recent existing numerical results.     

Neutron elastic scattering from 116,118,120,122,124Sn

Accurate measurements of neutron differential elastic cross sections have been obtained from even isotopes of Sn. Data are presented for the elastic scattering of 11 MeV neutrons from ^{116, 118, 120, 122, 124}Sn, the elastic scattering for 24 MeV neutrons from ^{116, 118, 124}Sn and the neutron total cross section from ^{118, 120, 122, 124}Sn in the energy ranges 5.0–10.6 MeV and 20.0–26.0 MeV. The elastic scattering data are analyzed in terms of an empirical optical-model potential. The obtained optical-potential parameters are analyzed in terms of energy and isospin dependence and compared with those obtained from proton elastic scattering on even Sn isotopes.     

Three-Dimensional Low-Momentum Interaction in Two-Body Bound State Calculations

The deuteron binding energy and wave function are calculated by using the recently developed three-dimensional form of low-momentum nucleon–nucleon (NN) interaction. The homogeneous Lippmann–Schwinger equation is solved in momentum space by using the low-momentum two-body interaction, which is constructed from Malfliet–Tjon potential. The results for both, deuteron binding energy and wave function, obtained with low-momentum interaction, are compared with the corresponding results obtained with bare potential.     

Four-Boson Systems Close to a Universal Regime

Universal properties of weakly-bound four-boson systems near the scaling limit are discussed by considering recent results obtained from the solution of Faddeev-Yakubovsky (FY) equations, which confirm a previous conjecture on a four-body scale dependence. In the present contribution, within a discussion on our numerical results obtained for the binding energies of two consecutive tetramer states, we are analyzing the relative relevance of the two possible configurations of the four-body system.     

Three Lead(II) Complexes in One Coordination Polymer, [Pb(TpyCl)Cl][Pb(TpyCl)Cl2][PbCl3](CH3OH)

[Pb(TpyCl)Cl][Pb(TpyCl)Cl₂][PbCl₃](CH₃OH) ( 1 ), a new coordination polymer of divalent lead with the ligand 4′‐chloro‐2,2′:6′,2"‐terpyridine (TpyCl), was obtained as single crystals by the branched tube method. The crystal structure contains three complexes, the cationic [Pb(TpyCl)Cl]⁺, the neutral [Pb(TpyCl)Cl₂] and the anionic [PbCl₃]^–, which are connected through bridging chlorides and hydrogen bonds to a two‐dimensional coordination polymer. In all three complexes, the arrangement around the Pb²⁺ ion suggests the existence of a stereoactive lone pair.     

Simultaneous kinetic spectrophotometric determination of Cu(II), Co(II) and Ni(II) using partial least squares (PLS) regression

A partial least squares (PLS-1) calibration model based on kinetic—spectrophotometric measurement, for the simultaneous determination of Cu(II), Ni(II) and Co(II) ions is described. The method was based on the difference in the rate of the reaction between Co(II), Ni(II) and Cu(II) ions with 1-(2-pyridylazo)2-naphthol in a pH 5.8 buffer solution and in micellar media at 25°C. The absorption kinetic profiles of the solutions were monitored by measuring the absorbance at 570 nm at 2 s intervals during the time range of 0–10 min after initiation of the reaction. The experimental calibration matrix for the partial least squares (PLS-1) model was designed with 30 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 0.1-2 μg mL⁻¹ for each cation. The proposed method was successfully applied to the simultaneous determination of Cu(II), Ni(II) and Co(II) ions in water and in synthetic alloy samples.      

Spectral,structural and theoretical study of the effects of thiocyanato and dicyanamido ligands on the geometry of PbII complexes containing a triazinic ligand

Two lead(II) complexes of 5,6‐bis(furan‐2‐yl)‐3‐(pyridin‐2‐yl)‐1,2,4‐triazine (DFPT), namely one‐dimensional (1D) catena‐poly[[bis[5,6‐bis(furan‐2‐yl)‐3‐(pyridin‐2‐yl‐κN)‐1,2,4‐triazine‐κN²]lead(II)]‐di‐μ‐thiocyanato‐κ²N:S;κ²S:N], [Pb(NCS)₂(C₁₆H₁₀N₄O₂)₂]_n, 1 , and binuclear di‐μ‐dicyanamido‐κ²N¹:N⁵;κ²N⁵:N¹‐bis{[5,6‐bis(furan‐2‐yl)‐3‐(pyridin‐2‐yl‐κN)‐1,2,4‐triazine‐κN²](nitrato‐κ²O,O′)lead(II)}, [Pb₂(C₂N₃)₂(NO₃)₂(C₁₆H₁₀N₄O₂)₄], 2 , as well as DFPT itself, were prepared and identified by elemental analysis, FT–IR, ¹H NMR spectroscopy and single‐crystal X‐ray structural analyses. In the double‐chain 1D coordination polymer of 1 and the binuclear structure of 2 , the Pb atom has a hemidirected‐PbN₆S₂ and a rare holodirected‐PbN₆O₂ environment, respectively, with a distorted cubic geometry. All the coordination modes of dicyanamide ligands within lead complexes were studied using the Cambridge Structural Database (CSD) to compare them with the structures of 1 and 2 . In addition to hydrogen bonds, the crystal networks are stabilized by π–π stacking interactions between the triazine, furyl and pyridine aromatic rings. The most stable theoretical structures of the title compounds predicted by density functional theory (DFT) calculations were compared with the solid‐state results.