Combined Computational and Experimental Study on the Adsorption and Inhibition Effects of N2O2 Schiff Base on the Corrosion of API 5L Grade B Steel in 1 mol/L HCI

The electrochemical behavior of low carbon steel （API 5L grade B） in 1 mol/L HCI solution with different concentrations of N,Nr-bis（4-formylphenol）-trimethylenediamine Schiff base was studied by electrochemical techniques and density functional theory analysis. The inhibition efficiency was found to increase with increasing inhibitor concentration and decreased with increasing temperature. The high inhibition efficiency was attributed to the blocking of active sites by adsorption of inhibitor molecules on the steel surface. Thermodynamic parameters for the adsorption and activation processes were determined. Galvanostatic polarization data indicated that Schiff base act as a mixed-type inhibitor and the adsorption isotherm obeyed the Langmuir adsorption isotherm. Results obtained from quantum chemical studies show excellent correlations between the quantum chemical parameters and the experimental inhibition efficiencies using density functional theory at the B3LYP/6-31G（d,p） and B3LYP/3-21G basis set levels and ab initio calculations using HF/6-31G（d,p） and HF/3-21G methods.     

A nondominated ranked genetic algorithm for bi-objective single machine preemptive scheduling in just-in-time environment

Motivated by just-in-time (JIT) manufacturing, we study the bi-objective scheduling problem of minimizing the total weighted earliness and the number of tardy jobs on a single machine, in which machine idle time and preemption are allowed. The problem is known to be NP-hard. In this paper, we propose a new mathematical model, with nonlinear terms and integer variables which cannot be solved efficiently for medium- and large-sized problems. A method combining the new ranked-based roulette wheel selection algorithm with Pareto-based population ranking algorithm, named nondominated ranking genetic algorithm (NRGA), has been presented to find nondominated solutions in a reasonable time. Various operators and parameters of the proposed algorithm are reviewed to calibrate the algorithm by means of the Taguchi method. A number of numerical examples are solved to demonstrate the effectiveness of the proposed approach. The solutions obtained via NRGA are compared against solutions obtained via ε-constraint method in small-sized problems. Experimental results show that the proposed NRGA is competitive in terms of the quality and diversity of solutions in medium- and large-sized problems.     

Influence of substrate rotation speed on the nanostructure of sculptured Cu thin films

Different rotation speeds of the substrate about its surface normal were used to produce sculptured copper thin films of ∼ 90 nm thickness. X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to obtain nano-structure and morphology of these films. Their optical properties were measured by spectrophotometry in the spectral range of 340-850 nm. Real and imaginary refractive indices, film thickness and fraction of metal inclusion in the film structure were obtained from optical fitting of the spectrophotometer data.     

Emergence of non-group A streptococcal necrotizing diabetic foot infections

Recently the authors have noted a disturbing trend toward an increased incidence of necrotizing infections caused by non-group A streptococcal species. This article describes the typical clinical course of such an infection. Prompt surgical intervention, coupled with an antibiotic regimen aimed at mitigating exotoxin release, may be both limb- and life-preserving.     

Placental chorioangioma: prenatal diagnosis and clinical significance

We report the prenatal diagnosis of placental chorioangioma in a 32-week intrauterine pregnancy associated with polyhydramnios and enlarged fetal cardiac size that resulted in intrauterine fetal death. Ultrasound appearance, pathophysiology, and clinical significance of this entity are discussed.     

Size effect and fracture energy studies using compact compression specimens

The size effect has been investigated and fracture energy, G_F, determined for a range of different strength concretes. The test specimen geometry used in the study was a compact compression prism. Five sizes of geometrically similar specimens with increasing square cross-sectional area (length=depth) and constant thickness (100 mm) were used in the experimental work; the length/depth dimensions of the test specimens were 100, 150, 200, 300, and 400 mm, giving an overall size range ratio of 1:4. The grades of concrete used in this study were C50, C70, C80, C90, and the maximum coarse aggregate (crushed limestone) size was 10 mm. A strong size effect was observed in the results and it is concluded that the test geometry is good for size effect studies in concrete. Furthermore, it was observed that with increasing strength the size effect becomes more pronounced as the brittleness is increased.

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Résumé On a étudie l'effet de taille et l'énergie de rupture, G_F, déterminés pour une gamme de bétons ayant des résistances différentes. La géométrie des éprouvettes choisie pour cette étude était le prisme compact de compression. Cinq tailles d'éprouvettes de géométrie similaire, ayant une épaisseur constante (100 mm) et de section transversale carrée (longueur=profondeur) croissante ont été utilisées pour ce travail. Les dimensions longueur/profondeur des éprouvettes étaient de 100, 150, 200, 300 et 400 mm, résultant en un rapport général de 1:4. Les bétons utilisés dans cette étude étaient de qualités C50, C70, C80 et C90, et la dimension maximale des granulats (calcaire concassé) était de 10 mm. On a observé dans les résultats un fort effet de taille et on a conclu que la géométrie utilisée pour l'essai convient pour des études d'effet de taille sur le béton. Qui plus est, on a observé qu'avec une résistance croissante, l'effet de taille devient plus prononcé lorsque la fragilité augmente.

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Editorial note Prof. Benjamin I. G. Barr is a RILEM Senior Member. He participates in the Editorial Group of TC 909-FMA, “Fracture Mechanics of Concrete-Applications”, and is a member of TC 162-TDF, “Test and Design Methods for Steel Fibre reinforced Concrete” and TC QFS, “Size effect and Scaling of Quasibrittle Fracture”.     

Simultaneous adsorption of a mixture of paraquat and dye by NaY zeolite covered with alkylsilane

The surfaces of NaY zeolite particles were modified by the alkylsilylation of n-octadecyltrichlorosilane (OTS). Two kinds of modified NaY zeolites were prepared; one with its external surface partially and the other fully covered with alkylsilyl groups. Since the size of OTS is bigger than the pore diameter of NaY, it is attached on the external surface, leaving the internal pore accessible to adsorbate molecules. As a result of alkylsilylation, the adsorption properties of these sorbents were improved. The adsorption properties of these materials were tested by their reaction in a mixture of paraquat and blue dye. The results demonstrate that the alkysilylated NaY materials are capable of simultaneous adsorption of paraquat and blue dye. Paraquat was selectively adsorbed into the internal pore of the zeolite whereas the dye on the externally attached alkylsilyl groups of the sorbent; displaying the unique bimodal amphiphilic character of the alkylsilylated NaY zeolites.     

An experimental investigation of cylindrical wire electrical discharge turning process

The cylindrical wire electrical discharge turning (CWEDT) process was developed to generate precise cylindrical forms on hard, difficult to machine materials. A precise, flexible, and corrosion-resistant submerged rotary spindle was designed and added to a conventional five-axis CNC wire electrical discharge machine (EDM) to enable the generation of free-form cylindrical geometries. The hardness and strength of the work material are no longer the dominating factors that affect the tool wear and hinder the machining process. In this study, the effect of machining parameters on surface roughness (R _a) and roundness in cylindrical CWEDT of a AISI D3 tool steel is investigated. The selection of this material was made taking into account its wide range of applications in tools, dies, and molds and in industries such as punching, tapping, reaming, and so on in cylindrical forms. Surface roughness and roundness are chosen as two of the machining performances to verify the process. In addition, power, pulse off-time, voltage, and spindle rotational speed are adopted for evaluation by full factorial design of experiments. In this case, a 2²?×?3² mixed full factorial design has been selected considering the number of factors used in the present study. The main effects of factors and interactions were considered in this paper, and regression equations were derived using response surface methodology. Finally, the surfaces of the CWEDT parts were examined using scanning electron microscopy (SEM) to identify the macro-ridges and craters on the surface. Cross sections of the EDM parts were examined using the SEM and microhardness tests to quantify the sub-surface recast layers and heat-affected zones under specific process parameters.