Tensile Properties of Martensitic Stainless Steels at Elevated Temperatures

Tensile properties of quenched and tempered martensitic alloys EP-823, HT-9, and 422 were evaluated at temperatures ranging from ambient to 600 °C as a function of three different tempering times. The results indicated that the yield strength, ultimate tensile strength, and the failure strength were gradually reduced with increasing temperature. The ductility parameters were enhanced at elevated temperatures due to increased plastic flow. However, the tempering time did not significantly influence these properties. The evaluation of the fracture surfaces by scanning electron microscopy revealed reduced cracking and dimpled microstructures, indicating enhanced ductility at higher testing temperatures

Medical Students’ Perceptions of Peer Assessment in a Problem-based Learning Curriculum

Objectives: Peer assessment (PA) is believed to support learning and help students develop both professionally and personally. The aim of this study was to examine medical students’ perceptions of intragroup PA in a problem-based learning (PBL) setting. Methods: This study was carried out between September and November 2014 and involved six random groups of fourth-year undergraduate medical students (n = 60) enrolled at the Arabian Gulf University in Manama, Bahrain. While working on set tasks within a curriculum unit, each student evaluated a randomly selected peer using an English language adapted assessment tool to measure responsibility and respect, information processing, critical analysis, interaction and collaborative skills. At the end of the unit, students’ perceptions of PA were identified using a specifically-designed voluntary and anonymous selfadministered questionnaire in English. Results: A total of 55 students participated in the study (response rate: 92%). The majority of students reported that their learning (60%), attendance (67%), respect towards group members (70%) and participation in group discussions (71%) improved as a result of PA. Regarding problem analysis skills, most participants believed that PA improved their ability to analyse problems (65%), identify learning needs (64%), fulfil tasks related to the analysis of learning needs (72%) and share knowledge within their group (74%). Lastly, a large proportion of students reported that this form of assessment helped them develop their communication (71%) and self-assessment skills (73%), as well as collaborative abilities (75%). Conclusion: PA was well accepted by the students in this cohort and led to self-reported improvements in learning, skills, attitudes, engagement and other indicators of personal and professional development. PA was also perceived to have a positive impact on intragroup attitudes

Evidence-based assessment of antiosteoporotic activity of petroleum-ether extract of Cissus quadrangularis Linn. on ovariectomy-induced osteoporosis

The increasing incidence of postmenopausal osteoporosis and its related fractures have become global health issues in the recent days. Postmenopausal osteoporosis is the most frequent metabolic bone disease; it is characterized by a rapid loss of mineralized bone tissue. Hormone replacement therapy has proven efficacious in preventing bone loss but not desirable to many women due to its side-effects. Therefore we are in need to search the natural compounds for a treatment of postmenopausal symptoms in women with no toxic effects. In the present study, we have evaluated the effect of petroleum-ether extract of Cissus quadrangularis Linn. (CQ), a plant used in folk medicine, on an osteoporotic rat model developed by ovariectomy. In this experiment, healthy female Wistar rats were divided into four groups of six animals each. Group 1 was sham operated. All the remaining groups were ovariectomized. Group 2 was fed with an equivolume of saline and served as ovariectomized control (OVX). Groups 3 and 4 were orally treated with raloxifene (5.4 mg/kg) and petroleum-ether extract of CQ (500 mg/kg), respectively, for 3 months. The findings were assessed on the basis of animal weight, morphology of femur, and histochemical localization of alkaline phosphatase (ALP) (an osteoblastic marker) and tartrate-resistant acid phosphatase (TRAP) (an osteoclastic marker) in upper end of femur. The study revealed for the first time that the petroleum-ether extract of CQ reduced bone loss, as evidenced by the weight gain in femur, and also reduced the osteoclastic activity there by facilitating bone formation when compared to the OVX group. The osteoclastic activity was confirmed by TRAP staining, and the bone formation was assessed by ALP staining in the femur sections. The color intensity of TRAP and ALP enzymes from the images were evaluated by image analysis software developed locally. The effect of CQ was found to be effective on both enzymes, and it might be a potential candidate for prevention and treatment of postmenopausal osteoporosis. The biological activity of CQ on bone may be attributed to the phytogenic steroids present in it

The Impact of Capital Structure on the Financial Performance of Hotel Industry and Automobile Industry

The capital structure of a firm is the mix of stock and debt it uses to maximize shareholder returns. One of the most important duties of every company's management is to find the ideal funding - a mix of equity and debt - where the cost of capital is decreased and the company's performance is maximized. The study attempts to solve how capital structure influences a company’s profitability. In this research we have considered Hotel Industry and Automobile Industry as they are 2 of the fastest growing industries of the Indian economy and accounts for about 8% and 9% of the country’s GDP respectively. The capital structure and profitability for the last 10 years of 5 major automobile and hotel firms are taken. To check if there is any relation between the capital structure variables and profitability variables, regression analysis is used. The effect of dependent variables (Debt Equity Ratio and Debt Asset Ratio) on the independent variables (Return on Assets, Return on Equity, Return on Capital Employed, & Net Profit Ratio) was found using Karl Pearson's correlation analysis. The comparison between capital structures of the selected industries is done using line graphs

Effect of active components on strength development in alkali-activated low calcium fly ash cements

The compressive strength achieved in alkali-activated low-calcium fly ash depends on the total reactive oxide ratios in the activated system, the reactive alumina content in fly ash and the initial molarity of NaOH. The total reactive silica in the system is the reactive silica contributed by the fly ash and soluble silica from the alkaline solution. A minimum molarity of NaOH is required to ensure complete dissolution of the glassy phase present in fly ash. The maximum compressive strength depends on the amorphous reaction product content formed, which is determined by the reactive alumina content in the fly ash. The highest compressive strength is achieved for the ratio of the total reactive silica to sodium ratio in the activated system equal to 4.72 and lower. More Na is incorporated in the reaction product on increasing the Na2O content relative to the reactive oxides

Production and characterization of low-energy Portland composite cement from post-industrial waste

The utilization of post-industrial waste materials is often challenging due to environmental regulations. Additionally, the scarcity of raw materials for producing cement is generating the demand for alternate sources of materials. The current study explores the production of cement and clinker on a large scale using post-industrial waste materials from different sources. Lime sludge generated by the paper mill industry and sponge iron produced during the processing of iron are used as primary source materials for producing clinker. A large-scale vertical kiln is used for clinkering. The unburnt carbon present in the sponge iron is used as an energy source for calcining the raw materials reducing the demand on external fuel. A Portland Composite Cement (PCC) is produced by inter-grinding the clinker with waste generated by the pharmaceutical industry, silico-manganese slag and fly ash. An evaluation of the clinker and the PCC is performed and compared with a commercially available Ordinary Portland Cement (OPC). Hydration studies and characterization of the materials are performed using different analytical techniques. This work provides the fundamental basis for an environmentally sustainable utilization of post-industrial waste in the production of clinker suitable for use in construction

Studies on Aluminosilicate Binder using Alkali activated Low-calcium Fly ash

The broad objective of the work presented in this thesis is to consistently produce an aluminosilicate binder using the typical low calcium fly ash available in India with an efficient use of alkaline activators. Fly ash is used as the source m aterial considering its ready availability in large quantities. The main challenges associated with the use of fly ash as a source material include: gauging its reactive potential, determining the influence of process variables on the dissolution of fly ash and identifying the parameters which influence the strength achieved by alkali activation of fly ash. Producing an aluminosilicate binder using fly ash often involves the excessive use of activators and very high concentrated alkaline solutions. The work outlined in this thesis addresses the key issue of quantifying the contribution of fly ash in an activated system. A fundamental understanding of fly ash dissolution in an alkaline environment and the influence of activated system parameters on the aluminosilicate production is developed. The outcome of the work is a procedure for determining the most effective composition of the alkali activator required to achieve the maximum ultimate compressive strength for a given fly ash. This thesis is focused on developing a fundamental understanding of the activation process of low calcium fly ash using a combination of sodium hydroxide and sodium silicate. Fly ash characterization is performed using multiple techniques to establish the typical range of parameters in multiple fly ash samples collected from different sources. The reactive components in the glassy phase of low calcium fly ash are identified and quantified. The dissolution of the glassy phase in low calcium fly ash in an alkaline environment at different curing temperatures is investigated. The experimental challenge in quantifying the progress of reaction in an alkali activated fly ash system is overcome and a new XRD-based direct decomposition technique is established and calibrated. The extent of dissolution of the fly ash glassy phase and the reaction product contents are directly determined by applying the direct decomposition technique to alkali activated fly ash. The product developed in the alkali activated fly ash system is identified with a sodium aluminosilicate hydrate. An investigation of the activating solution composition on the sodium aluminosilicate produced and the strength development in the alkali activated fly ash systems is presented. The role of the different reactive oxide ratios and total reactive contents on the sodium aluminosiliactes product formed and the influence of the product content on the compressive strength achieved from the alkali-activated fly ash are evaluated. The requirement of initial alkalinity achieved with the sodium hydroxide in the activated mix is established for the reactive glassy content available in the fly ash. The initial solution molarity of sodium hydroxide and temperature enhance the rate of glassy dissolution resulting in a faster gain in strength. The reactive alumina content in fly ash is shown to determine the maximum ultimate compressive strength achieved by alkali activation. The composition of the activated system considering the relative proportions of reactive silica, reactive alumina and sodium are shown to significantly influence the sodium aluminosilicates produced. The ratios of the reactive oxides in the activated fly ash system required to achieve the maximum compressive strength are established. Finally, a procedure for determining the composition of the most efficient activator, with the required sodium hydroxide and sodium silicate, for achieving the maximum ultimate compressive strength for a given fly ash is developed. The work presented in this thesis forms the basis for developing an optimized activator for a low calcium fly ash to produce an aluminosilicates binder meeting specific performance requirement in structural applications