Physical metallurgy of modern creep-resistant steel for steam power plants: microstructure and phase transformations

The fact that the microstructure of steel depends on its composition and the heat treatment given to it has been heavily exploited in the design of steel for power plant applications. To obtain a steel that can function at the higher temperature where power plants operate without failure for extended life, heat treatment is needed to produce fine and highly stable dispersion of carbides, nitrides, and intermetallic compounds in the microstructure of the material. A significant contribution also comes from solid solution strengthening by substitutional solutes. We review here various types of phases, microstructures, functions, and interacting effects of the various alloying elements in the design of steel for modern power plant application

Examining the psychological wellbeing of refugee children and the role of friendship and bullying

BACKGROUND: Refugee children might have experienced violent and traumatic events before settling into a new country. In the United Kingdom, the number of refugee children is increasing; however, little is known about their psycho-social and physical well-being. AIM: This study aims to investigate the psychological well-being and behaviour of refugee children compared to British-born children on a number of psychological, social, behavioural, and health-related issues and to investigate the role of friendship as a protective factor. SAMPLES: This study utilized a sample of 149 refugee children recruited from two charities, 79 of which are children aged 6-10 years and 70 older refugee children aged 11-16 years. The study also included 120 non-refugee children recruited from primary schools aged 6-10 years. METHODS: This is a cross-sectional study that investigates the psycho-social well-being of refugee children compared to non-refugee British-born children. The study explored symptoms of posttraumatic stress disorder, emotional and behavioural problems (Strengths and Difficulties Questionnaire), self-esteem, friendships and popularity, bullying and victimization, physical health, and psychosomatic problems. RESULTS: Young refugee children reported more peer problems, functional impairment, physical health, and psychosomatic problems compared to the control children and older refugee children groups. On the other hand, older refugee children had lower self-esteem (academic and social self-peers) compared to the younger refugee children group. The differences between the groups were explained by friendship quality, number of friends, peer bullying/victimization, or sibling bullying/victimization except for physical health and psychosomatic problems. CONCLUSIONS: While refugee children were found to be at risk on various levels, the findings also point to the fact that social relationships including friendship quality and number of friends played an essential protective role. Conversely, bullying was a risk factor that explained many of the refugees' problems. These findings pave the way for future research to further probe into the well-being of refugee children in the United Kingdom while also targeting relevant intervention schemes specifically tailored to address their needs

Review of Physical Metallurgy of Creep Steel for the Design of Modern Steam Power Plants – Fundamental Theories and Parametric Models

The need for electricity supply has increased tremendously in recent time thereby necessitating an improvement in the efficiency of steam power plant. A greater efficiency leads to a saving in fuel for a given electricity output with a consequential reduction in the rate at which damage is done to the earth’s environment. This paper looks at the physical metallurgy theories and parametric models that have been the bases in the design of steel for power plant applications

Effect of Electrode Types on the Solidification Cracking Susceptibility of Austenitic Stainless Steel Weld Metal

The effect of electrode types on the solidification cracking susceptibility of austenitic stainless steel weld metal was studied. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. Metallographic and chemical analyses of the fusion zones of the joints were conducted. Results indicate that weldments produced from E 308-16 (rutile coated), E 308-16(lime-titania coated) electrodes, and TIG welded joints fall within the range of 1.5≤Creq./Nieq.≤1.9 and solidified with a duplex mode and were found to be resistant to solidification cracking. The E 308-16 weld metal had the greatest resistance to solidification cracking. Joints produced from E 310-16 had Creq./Nieq. ratio < 1.5 and solidified with austenite mode. It was found to be susceptible to solidification cracking. E 312-16 produced joints having Creq./Nieq. ratio > 1.9 and solidified with ferrite mode. It had a low resistance to solidification cracking

Effects of Mycobacterium Tuberculosis Macrophage Interaction: Surface Energetic Mechanism

The mechanisms effects of mtb  macrophage using surface energetic in determining the interaction processes with the surface interfacial energies explained using van der Waals concept of particle  particle interactions. The Lifshitz derivations for van der Waals forces were applied as an alternative to the contact angle approach which has been widely used in other biological systems. The methodology involved taking sputum samples from twenty infected persons and from twenty uninfected persons for absorbance measurement using a digital Ultraviolet visible Spectrophotometer. Matlab software tools were used in the mathematical analysis of the data generated from the absorbance values. The values of A132abs = 0.21631x10-21Joule (for mtb infected sputum) and Ã132abs = 0.18825x10-21Joule (for mtb/HIV infected sputum) were obtained. The free energies of adhesion calculated were found to be negative with combined Hamaker coefficient positive. The implication of this result is the positive value of the absolute combined Hamaker coefficient which entails net positive van der waals forces demonstrating an attraction between mtb and the macrophage. This however, implies that infection is very likely to occur. It was also shown that in the presence of HIV, the interaction energy is reduced by 13% confirming adverse effects observed in HIV patients suffering from tb. Negative Hamaker coefficient (-0.22669x10-19mJ/m2) indicated that separation of mtb is practical. The condition was sought for repulsion to occur and that condition was based on the value of A33 that would render the absolute combined Hamaker coefficient A131abs negative. Mathematically it was derived as A330.9527x10-21Joule which satisfies this condition for negative A132abs. To achieve the condition of A33 above, possible additive(s) in form of drugs to the sputum should be required