Influence of hydrogen content on the tensile properties and fracture of austenitic stainless steel welds

This study evaluates the effects of internal hydrogen on the tensile properties and fracture behaviours of a tungsten inert gas (TIG) weld and an autogenous electron beam (EB) weld of a 304L steel tube. Tensile specimens were thermally charged with hydrogen gas to achieve three different levels of hydrogen in these materials. Metallographic examination revealed that the TIG weld contained skeletal and lathy ferrite, whilst the EB weld displayed a fine dispersion of skeletal and vermicular ferrite. Average volume fractions of ferrite in these welds were 8% and 1%, respectively. The tensile data showed that hydrogen increased the yield and tensile strength, and caused a significant loss in ductility, particularly for the TIG weld. Fractographic analysis revealed that hydrogen induced a change in the fracture mode of the welds and promoted cracking at or near ferrite–austenite interfaces. The TIG weld was found to exhibit a higher susceptibility to hydrogen embrittlement than that of the EB and base metal.     

Toxicity of Phenolic Compounds Extracted from Bark Residues of Different Ages

In Quebec, Canada, industrial bark wastelands cover several hundred hectares of land. Bark residue that has piled up for decades tends to remain free of vegetation for years. To assess the revegetation potential of such sites, we sought to determine those factors responsible for poor plant growth. Phenolic compounds from fresh to 20-year-old bark residues were extracted with four solvents and quantified by high-performance liquid chromatography (HPLC). We simulated solutions (mixtures of standard phenolic compounds) to evaluate the potential toxic effects of phenolic compounds on the rhizobial growth, germination index, plant growth, nodule number, and nitrogen fixation activity of two legume species under laboratory conditions. The concentration of individual phenolic compounds varied from none detected to 350 μg/g bark residue. The extracted phenolic compounds differed among solvents and bark residues. The highest concentration of total phenolic compounds was from fresh bark; most of these were soluble in water or 0.1 M NaOH. For older bark residues, the total phenolic content depended on solvent strength, generally in the order of 2.0 M NaOH > 0.1 M NaOH = hot water > cold water. The biological activity of the simulated bark extracts was not established with the rhizobial growth inhibition test but with the germination index and rhizobium–legume symbiosis tests. With these, the toxicity of the simulated phenolic extracts decreased from fresh to the older bark residues. Plant dry weight, nodule number, and nitrogen fixation activity of vetch (Vicia sativa L.) were less negatively affected by high concentrations of phenolics than birdsfoot trefoil (Lotus corniculatus L.), although birdsfoot trefoil grew at lower concentrations. The rhizobium–legume symbiosis has potential for revegetating bark wastelands with less than 1 year old and older bark residues.     

Unconfined compressive strength prediction of soils stabilized using artificial neural networks and support vector machines

This study aims to improve the unconfined compressive strength of soils using additives as well as by predicting the strength behavior of stabilized soils using two artificial-intelligence-based models. The soils used in this study are stabilized using various combinations of cement, lime, and rice husk ash. To predict the results of unconfined compressive strength tests conducted on soils, a comprehensive laboratory dataset comprising 137 soil specimens treated with different combinations of cement, lime, and rice husk ash is used. Two artificial-intelligence-based models including artificial neural networks and support vector machines are used comparatively to predict the strength characteristics of soils treated with cement, lime, and rice husk ash under different conditions. The suggested models predicted the unconfined compressive strength of soils accurately and can be introduced as reliable predictive models in geotechnical engineering. This study demonstrates the better performance of support vector machines in predicting the strength of the investigated soils compared with artificial neural networks. The type of kernel function used in support vector machine models contributed positively to the performance of the proposed models. Moreover, based on sensitivity analysis results, it is discovered that cement and lime contents impose more prominent effects on the unconfined compressive strength values of the investigated soils compared with the other parameters.     

Synthesis of some new disperse anthraquinone dyes

1-Hydroxy and/or 1-aminoanthraquinone was allowed to react with formaldehyde in an alkaline medium to give 1-hydroxy or 1-amino-2-hydroxymethyl-9,10-dihydroxy-anthracenes, which gave on air oxidation, hydroxymethylanthraquinone derivatives (I). Interaction of 1-amino-2-hydroxymethylanthraquinone or its 4-bromo derivative with carbonyl compounds in the presence of an acid catalyst gave (1,3)oxazine derivatives (II). The methylene group in position-2 of the (1,3)oxazine ring was found to be highly reactive and reacted with carbonyl compounds to form the corresponding arylidenes (III). Selective oxidation of dimethyl oxazine derivatives with SeO₂ gave the corresponding dialdehyde (IV), which interacted with aromatic amines to give the corresponding Schiff bases (V). The bromine atom in the 6-position of II was easily replaced by aromatic amines to give blue disperse dyes (VI).     

Numerical Modeling of Insulating Particles Trajectories in Roll-type Corona-Electrostatic Separators

The trajectories of the insulating particles in roll-type corona-electrostatic separators depend on the configuration of the electrode system, the applied high voltage, the roll speed, the size of the particles and the relative humidity of the ambient air. The aim of this work was to point out how numerical modeling can be of use in the study of the effects of these factors. Particle charging is modeled using the Pauthenier?s equation for spheres in uniform electric field. The equation of particle discharging was obtained after an experimental study of the surface potential decay of a granular layer of insulating material in contact with an electrode. The trajectories are computed based on the balance equation of the electrical and mechanical forces that act on such charged particles. The numerical results are in good agreement with the experimental findings.     

A GENETIC ALGORITHM FOR THE SHAPE OPTIMIZATION OF PARTS SUBJECTED TO THERMAL LOADING

In many technical situations, the optimization of the mechanical behavior of structures proceeds from the search for the ideal shape satisfying thermal, mechanical, technological, and geometrical constraints. In this article, the shape optimization of mono- and two-dimensional structures is handled by means of a new genetic algorithm (GA). The method is in general well suited to the resolution of nonconstrained optimization problems: The algorithm presented here has been modified by taking into account the imposed design constraints in the selection of the "individuals" belonging to a given population. The crossover operation between individuals and the mutation process in their original forms are applied to derive the optimal shape of parts subjected to thermal loadings. The algorithm exhibits a good convergence toward the optimal solution and the numerical results of its application show a good numerical accuracy.     

Carbon nanotubes: properties,synthesis, purification,and medical applications

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.     

Comparative immunohistological study on using capsaicin,piperine, and okadaic acid for the transepithelial passage of the inactivated viral and bacterial vaccines in fish

The practical difficulty of parenteral application of fish vaccines against devastating fish diseases diverted the interest toward oral vaccination. Search for effective methods to enhance the oral uptake of viral and bacterial vaccines is continuing. The current research focus on a new role of mucosal fish vaccine adjuvants inducing the antigen uptake by enhancing vascularity or increasing intestinal permeability. Some inflammatory substances cause reversible pathology to the intestinal epithelium, which could be employed for the transepithelial passage of vaccine particles. The natural inflammatory substances used were capsaicin, piperine, and okadaic acid as 1 mg, 2 mg, and 1 μg/fish, respectively. Two inactivated vaccines were used as antigens to test the effect of these inflammatory substances in two different fish hosts. Tested vaccines were inactivated redspotted grouper nervous necrosis virus vaccine in sevenband grouper (Epinephelus septemfasciatus) and inactivated Edwardsiella tarda vaccine in red sea bream (Pagrus major) fish models. The inflammatory substances and each vaccine were anally intubated to fish. Capsaicin proved to be effectively aiding the transepithelial passage of vaccine particles more than piperine, while okadaic acid had no detectable effect.