Transformation of inert PbSO4 deposit on the negative electrode of a lead-acid battery into its active state

Different forms of lead sulfate (PbSO₄) are produced in both the cathode and anode in the course of discharging of a lead-acid battery. However, their difference in reaction activity has not been well recognized up to now. From this work, it is shown the cathode product PbSO₄(O) due to oxidation of Pb is rather inert and its accumulation could lead to decrease of the battery capacity and life; on the other hand, the anode product PbSO₄(R) due to reduction of PbO₂ has a much active property and is readily reversible in the charging-discharging recycles. To restore the battery capacity, it is critical to solve the deactivation of cathode by transforming PbSO₄(O) into PbSO₄(R). For such a purpose, inverse charging is performed, and a procedure from PbSO₄(O) to PbO₂ and to PbSO₄(R) is conducted under a series of measurements with cyclic voltammetry, electrochemical impedance spectroscopy, scanning electronic microscopy and X-ray diffraction spectroscopy. The results of inverse charging tests show that the new capacity of a sulfated battery is more than twice of the initial value, which proves the validity of the mechanism outlined.     

Inverse docking method for new proteins targets identification: A parallel approach

Molecular docking is a widely used computational technique that allows studying structure-based interactions complexes between biological objects at the molecular scale. The purpose of the current work is to develop a set of tools that allows performing inverse docking, i.e., to test at a large scale a chemical ligand on a large dataset of proteins, which has several applications on the field of drug research. We developed different strategies to parallelize/distribute the docking procedure, as a way to efficiently exploit the computational performance of multi-core and multi-machine (cluster) environments. The experiments conducted to compare these different strategies encourage the search for decomposing strategies since it improves the execution of inverse docking.     

Infrared to visible upconversion luminescence in Er/Yb co-doped CeO2 inverse opal

Infrared to visible upconversion luminescence has been investigated in Er³⁺/Yb³⁺ co-doped CeO₂ inverse opal. Under the excitation of 980 nm diode lasers, visible emissions centered at 525, 547, 561, 660 and 680 nm are observed, which are assigned to the Er³⁺ transitions of ²H_11/2 → ⁴I_15/2 (525 nm), ⁴S_3/2 → ⁴I_15/2 (547, 561 nm), ⁴F_9/2 → ⁴I_15/2 (660 and 680 nm), respectively. The effect of photonic band gap on the upconversion luminescence intensity was also obtained. Additionally, the upconversion luminescence mechanism was studied. The dependence of Er³⁺ upconversion emission intensity on pump power reveals that it is a two-photon excitation process.     

Non-contact measurement of acoustic emission in materials by laser interferometry

The non-contact measuring system of acoustic emission (AE) by laser interferometry was developed to detect AE signals and analyze microfracture quantitatively during materials testing. The capability of this system was estimated by comparison between simulated AE signals due to glass capillary breaking and calculations using the finite element method. The systemcould measure AE signals during practical tensile tests of carbon fiber reinforced plastics. This technique was also applied to the thermal cycle test of ceramic/metal coatings, and AE signals during cooling were successfully detected and analyzed by a deconvolution method to evaluate quantitatively the microfracture process.     

Mathematical Theory of Probability and Statistics

Two test statistics are suggested for discriminating between the exponential model and the more general Weibull or gamma models, and these are compared to some previously used test statistics by Monte Carlo methods. The results of estimating reliability under an exponential assumption when the true model is Weibull is also investigated. These results as well as the tests mentioned above indicate that the exponential model is often not adequate when the more general models hold. In contrast to this result it was found that the Weibull model was quite robust relative to the generalized gamma distribution with regard to reliability estimation. Some general pivotal function properties are presented for the maximum likelihood estimator of reliability for the generalized gamma distribution and similar results also hold for the Weibull procedure under a generalized gamma assumption. These results made a Monte Carlo study of this problem feasible. Since the maximum likelihood estimators are apparently ill-behaved for smaller sample sizes and since the Weibull model is robust it appears little is gained by using the generalized gamma distribution for samples of size less than 200 to 400.     

Boundary element methods for boundary condition inverse problems in elasticity using PCGM and CGM regularization

For an isotropic linear elastic body, only displacement or traction boundary conditions are given on a part of its boundary, whilst all of displacement and traction vectors are unknown on the rest of the boundary. The inverse problem is different from the Cauchy problems. All the unknown boundary conditions on the whole boundary must be determined with some interior points' information. The preconditioned conjugate gradient method (PCGM) in combination with the boundary element method (BEM) is developed for reconstructing the boundary conditions, and the PCGM is compared with the conjugate gradient method (CGM). Morozov's discrepancy principle is employed to select the iteration step. The analytical integral algorithm is proposed to treat the nearly singular integrals when the interior points are very close to the boundary. The numerical solutions of the boundary conditions are not sensitive to the locations of the interior points if these points are distributed along the entire boundary of the considered domain. The numerical results confirm that the PCGM and CGM produce convergent and stable numerical solutions with respect to increasing the number of interior points and decreasing the amount of noise added into the input data.     

Antenna model of the horizontal grounding electrode for transient impedance calculation: Analytical versus boundary element method

The paper deals with a simple and efficient procedure for the calculation of the transient impedance of the horizontal grounding electrode. This work represents an extension of a previous paper, published by the authors, on the antenna modeling of the grounding electrode with corresponding Pocklington integro-differential equation. The governing equation is solved in the frequency domain, both numerically and analytically, thus obtaining the solution for the current induced along the electrode. The numerical solution is undertaken via Galerkin–Bubnov scheme of the Indirect Boundary Element Method. Scattered voltage along the electrode is then calculated using Generalized Telegrapher?s equation. Time domain scattered voltage is evaluated via the Inverse Fast Fourier Transform. Subsequently, transient impedance is determined as a ratio of time domain voltage and current at the feeding point. Results obtained via different methods seem to agree satisfactorily.     

High efficiency solution infiltration routes to thin films with photonic properties

A chemical bath deposition (CBD) method has been developed to prepare three-dimensionally-ordered macroporous films of CdS and TiO₂, using colloidal crystals as templates. A series of sequential, short infill/rinse/anneal steps are employed to effect complete infiltration of SiO₂ (opal) thin films with CdS or TiO₂. Removal of templates allows fabrication of macroporous inverse replica structures that exhibit periodic modulation of dielectric behaviour and have potential for use in photonic applications. A study of the photonic properties of films indicates that the multi-step CBD method is a useful approach for infiltration of opal interstices.     

Microstructural characteristics of the surface layer in high-pressure die castings

A thin layer of distinct microstructure, commonly called the surface layer, is often present near the surface of high-pressure die cast (HPDC) components. Although the surface layer formation has been previously investigated, its salient microstructural features in recent studies are significantly different. Therefore, this research aims to gain a better understanding of the surface layer’s microstructural characteristics and the surface layer formation. Microstructural analysis was performed on complex-geometry, industrial-part Al-11Si-2Cu-1Fe (ADC12) and Zn-4Al (Zamak3) HPDC specimens and Al-5Mg-2Si-0.7Mn U-shaped HPDC specimens. The characterized microstructural features suggest that the surface layer starts to form during die filling and becomes stagnant at the die wall. When the inner material moves past the surface layer, primary crystals in the inner material migrate away from the surface layer, resulting in a region adjacent to the surface layer containing only solute-enriched liquid. The solute-enriched liquid in this region subsequently solidifies into the surface-layer edge.