Specific energy consumption of metal cutting with thin abrasive discs

The aim of this research is to provide an in-depth understanding of energy consumption in abrasive disc cutting processes. The specific energy consumed in cutting is measured,analysed, and then characterised in to three components. To this end, an experimental device is built using an Arduino-controlled grinder to measure the specific energy consumed by cutting at different feed rates. Using a model, the experimental data is validated and the Specific Energy Consumed is separated into three energy components: sliding, ploughing and specific cutting energy. Furthermore, the influence of cutting conditions and material properties significantly influenced the specific energy consumption and its components. To analyse the effect of grain shape and the relative dependence of the different components of the Specific Energy Consumed as a function of material removal rate, integral models of specific ploughing energy, specific sliding energy and specific cutting energy are developed. Conventional and super abrasive cubitron abrasive grains were used. Cutting with pyramidal abrasive discs (cubitron) was used for the determination of the relative components of the specific energy consumed. It was found that the specific ploughing energy is more sensitive to the change in material removal rate compared to the sliding energy. Due to the fast shearing and precisely shaped cubitron grains, the transition from sliding to a specific shear regime was so fast for some materials that the magnitude of the ploughing energy was found to be negligible.However, the model implementation for some materials showed that the absence or presence of ploughing energy also depends on the rate of material removed. Finally, the development of a cutting grain model is presented which will allow the study of the chip compression ratio which is not possible to characterise by means of a single cutting grain in metal cutting with thin abrasive discs. This latest development is the beginning of a study of chip formation in the primary cutting zone of an abrasive grain. This research provides a machine and a methodology to characterise cutting with commercially available abrasive discs in terms of the Specific Energy Consumed parameter.El objetivo de esta investigación es proporcionar un conocimiento profundo sobre el consumo de energía en los procesos de corte con discos abrasivos. Se mide y analiza la energía específica consumida en el corte, caracterizando dicha energía en tres componentes. Para ello se construye un dispositivo experimental que utiliza una amoladora controlada por un Arduino, para medir la energía específica consumida por el corte a diferentes velocidades de alimentación. Utilizando un modelo, se validaron los datos experimentales y se separa la Energía Específica Consumida en tres componentes energéticos: deslizamiento, arado y energía de corte específica. Además, la influencia de las condiciones de corte y las propiedades del material influyeron significativamente en el consumo de energía específico y sus componentes. Para analizar el efecto de la forma del grano y la dependencia relativa de las diferentes componentes de la Energía Específica Consumida en función de la tasa de remoción de material. Se desarrollan modelos integrales de energía de arado específica, energía de deslizamiento específica y energía de corte específica. Se utilizaron granos abrasivos convencionales y súper abrasivos de Cubitrón. El corte con discos abrasivos de granos piramidales (cubitron) se utilizaron para la determinación de las componentes relativas de la energía específica consumida. Se encontró que la energía de arado específica es más sensible al cambio en la tasa de remoción de material en comparación con la energía de deslizamiento. Debido a los granos de Cubitrón de corte rápido y de forma precisa, la transición de deslizamiento a un régimen de corte específico fue tan rápida para algunos materiales que la magnitud de la energía de arado resultó ser insignificante. Sin embargo, la implementación del modelo para algunos materiales demostró que la ausencia o presencia de energía de arado también depende de la tasa de material removido. Por último se presenta el desarrollo de un modelo de grano de corte que permitirá estudiar la relación de compresión de la viruta que no es posible caracterizar a través de un solo grano de corte en el corte de metales mediante discos abrasivos delgados. Este último desarrollo es el comienzo de un estudio de la formación de viruta en la zona primaria de corte de un grano abrasivo. Esta investigación proporciona una máquina y una metodología para caracterizar el corte con disco abrasivos, disponibles comercialmente, en términos del parámetro Energía Específica Consumida.Postprint (published version

Antecedents of Dividend Policy: Empirical Evidence from Banking Sector of Pakistan

This paper explores the determinants of dividend policy of commercial banks operating in Pakistan. Dividend decision of any bank primarily depends upon its profitability, retained earnings, cash flows, corporate taxes and leverage. This study is an attempt to find out key determinants and their impact on cash payout and total payout ratios. It also aims to test the implication of dividend theories on Pakistani banks using data for a period of 8 years ranging from 2006 to 2013. Balanced panel data regression with fixed effects model has been used in this study. All independent variables - PAT, SLACK, EPS, CTA and TD[1] reported significant results. We found significant role of profitability theory, packing order theory, free cash flow theory and agency cost theory in determining dividend policies whereas, tax effect and financial slack has no effect in banking sector of Pakistan. [1] Profitability, retained earnings, earnings per share, cash flows, and leverag

Antecedents of Dividend Policy: Empirical Evidence from Banking Sector of Pakistan

This paper explores the determinants of dividend policy of commercial banks operating in Pakistan. Dividend decision of any bank primarily depends upon its profitability, retained earnings, cash flows, corporate taxes and leverage. This study is an attempt to find out key determinants and their impact on cash payout and total payout ratios. It also aims to test the implication of dividend theories on Pakistani banks using data for a period of 8 years ranging from 2006 to 2013. Balanced panel data regression with fixed effects model has been used in this study. All independent variables - PAT, SLACK, EPS, CTA and TD[1] reported significant results. We found significant role of profitability theory, packing order theory, free cash flow theory and agency cost theory in determining dividend policies whereas, tax effect and financial slack has no effect in banking sector of Pakistan. [1] Profitability, retained earnings, earnings per share, cash flows, and leverag

Conservative Bridge Preparation By Using Natural Tooth As A Pontic With Ribbond Fiber: A Case Report At IIDH Islamabad

Summary: Traumatic damage to anterior teeth is a common form of dental injury, particularly in younger people. The abutment teeth only need to be slightly prepared for the conservative bridge preparation, as the name suggests. The final prosthesis can be fixed to the adjacent natural teeth in no time. This case reports a chair-side conservative and esthetic restoration in a 19-year-old girl who came with grade 3 mobility in her upper left central incisor by using her natural tooth as a pontic with ribbond fibre. Keywords: Conservative, Dental trauma, Ribbond fiber

Machine learning-based prediction of specific energy consumption for cut-off grinding

Cut-off operation is widely used in the manufacturing industry and is highly energy-intensive. Prediction of specific energy consumption (SEC) using data-driven models is a promising means to understand, analyze and reduce energy consumption for cut-off grinding. The present article aims to put forth a novel methodology to predict and validate the specific energy consumption for cut-off grinding of oxygen-free copper (OFC–C10100) using supervised machine learning techniques. State-of-the-art experimental setup was designed to perform the abrasive cutting of the material at various cutting conditions. First, energy consumption values were predicted on the bases of input process parameters of feed rate, cutting thickness, and cutting tool type using the three supervised learning techniques of Gaussian process regression, regression trees, and artificial neural network (ANN). Among the three algorithms, Gaussian process regression performance was found to be superior, with minimum errors during validation and testing. The predicted values of energy consumption were then exploited to evaluate the specific energy consumption (SEC), which turned out to be highly accurate, with a correlation coefficient of 0.98. The relationship of the predicted specific energy consumption (SEC) with material removal rate agrees well with the relationship depicted in physical models, which further validates the accuracy of the prediction models.Peer ReviewedPostprint (published version

Antioxidant activities of aqueous extracts from nine different rose cultivars

Rose petals have been applied as food additives in teas, cakes and flavor extracts. The aim of this research study was to explore and reveal the antioxidant potential of aqueous extracts of rose petals belonging to nine genotypes of rose (wild as well as hybrid). The in vitro antioxidant activities of roses were studied by lipid peroxidation assay, DPPH radical scavenging assay, iron chelation assay, phosphomolybdenum reduction assay and total phenolic and flavonoid contents. The aqueous extract showed inhibition against lipid peroxidation (TBARS), induced by prooxidants (10 µM FeSO4) in mice liver homogenate. The free radical scavenging activities of the extracts were determined by scavenging of the DPPH radical. Extracts also showed metal chelating activities and high antioxidant activity in the phosphomolybdenum assay. The high content of phenolics and flavonoids detected in aqueous extracts may be responsible for the antioxidant activity. Amongst the different rose genotypes, screened, Rosa moschata (musk rose) was found to carry slightly higher antioxidant potential, owing to its higher phytochemical content

Knowledge, attitude and perception of Pakistanis towards COVID-19; a large cross-sectional survey

Background: The Novel Coronavirus Disease (COVID-19) has created havoc globally as countries worldwide struggle to combat this pandemic. Since prevention and social isolation are known to be the only ways to prevent the spread of COVID-19, this has created challenges among the lower-middle income countries (LMIC) including Pakistan, as it battles between an under-resourced healthcare, an economic shutdown, and widespread myths and misconceptions. Therefore, a study was conducted to evaluate the knowledge, attitude and perceptions regarding COVID-19 as public understanding is vital to help facilitate the control of this outbreak.Methods: A pre-validated online questionnaire was distributed among the general population of Pakistan from 1st to 12th June 2020. Descriptive statistics were analyzed using SPSS v25. Adequate knowledge was assigned as a score of \u3e 4 (range: 0-8) and good perception as a score of \u3e 3 (range: 0-5). Chi-square test was used to determine the significance of difference in knowledge and perception of COVID-19 with socio-demographic characteristics. Logistic regression analysis was run to identify factors associated with adequate knowledge and perception. P \u3c 0.05 was considered as significant.Results: A total of 1200 respondents participated in this study with a wide range of age groups and education. Majority of the respondents had adequate knowledge (93.3%) with a mean score of 6.59 ± 1.35, and good perception (85.6%) with a mean score of 4.29 ± 0.82. Significant differences in knowledge and perception were observed among genders, age groups, education and between students and employees in the healthcare and non-healthcare department. A multivariate analysis revealed a higher educational status and female gender to be significant predictors of adequate knowledge and perception.Conclusions: Albeit the surge of COVID-19 cases in Pakistan, the participants demonstrated an overall adequate knowledge and good perception towards COVID-19. There is a need to follow the preventive protocols and dissemination of correct information through conducting educational interventions that target safe health practices and provide appropriate information on this infection

Specific energy modeling of abrasive cut off operation based on sliding, plowing, and cutting

Studying the specific energy during material removal mechanism at micro-scale provides a better understanding of energy transition between different material removal regimes. Modeling of specific energy into components of sliding, plowing and cutting helps to analyze the influence of grain properties process parameters, and mechanical properties on energy transition between different phases of material removal. Present research put forth the comprehensive model of specific energy consumption for abrasive cut off operating based on the individual models of primary and secondary rubbing energies, specific plowing energy and specific cutting energy. Materials of SS201, Inconel 718, Al 1100, Al 7075 and oxygen free copper (OFC– C10100) have been employed while cutting with semi super abrasive cubitron cut off wheel. Model validation on experimental data revealed that triangular shape of cubitron grits significantly influenced the plowing energy and played an important role in energy transition between different material removal regimes. Moreover, cutting conditions and material properties also affected the overall specific energy consumption, dominance of particular specific energy components and machinability of the materials.Peer ReviewedPostprint (published version

Design and Energy Analysis of a Solar Desiccant Evaporative Cooling System with Built-In Daily Energy Storage

Heat storage with thermochemical (TC) materials is a promising technology for solar energy storage. In this paper, a solar-driven desiccant evaporative cooling (DEC) system for air-conditioning is proposed, which converts solar heat energy into cooling with built-in daily storage. The system utilises thermochemical heat storage along with the DEC technology in a unique way. Magnesium Chloride (MgCl2·6H2O) has been used, which serves as both a desiccant and a thermochemical heat storage medium. The system has been designed for the subtropical climate of Lahore, Pakistan, for a bedroom with 8 h of cooling requirements during the night. MATLAB has been employed for modelling the system. The simulation results show that 57 kg of magnesium chloride is sufficient to meet 98.8% of cooling demand for the entire month of July at an elevated cooling requirement. It was found that the cooling output of the system increased with increasing heat exchanger effectiveness. The heat exchangers’ effectiveness was increased from 0.7 to 0.8, with the solar fraction increased from 70.4% to 82.44%. The cooled air supplied to the building meets the fresh air requirements for proper ventilation

Spatial, temporal, and demographic patterns in prevalence of chewing tobacco use in 204 countries and territories, 1990-2019 : a systematic analysis from the Global Burden of Disease Study 2019

Interpretation Chewing tobacco remains a substantial public health problem in several regions of the world, and predominantly in south Asia. We found little change in the prevalence of chewing tobacco use between 1990 and 2019, and that control efforts have had much larger effects on the prevalence of smoking tobacco use than on chewing tobacco use in some countries. Mitigating the health effects of chewing tobacco requires stronger regulations and policies that specifically target use of chewing tobacco, especially in countries with high prevalence. Findings In 2019, 273 center dot 9 million (95% uncertainty interval 258 center dot 5 to 290 center dot 9) people aged 15 years and older used chewing tobacco, and the global age-standardised prevalence of chewing tobacco use was 4 center dot 72% (4 center dot 46 to 5 center dot 01). 228 center dot 2 million (213 center dot 6 to 244 center dot 7; 83 center dot 29% [82 center dot 15 to 84 center dot 42]) chewing tobacco users lived in the south Asia region. Prevalence among young people aged 15-19 years was over 10% in seven locations in 2019. Although global agestandardised prevalence of smoking tobacco use decreased significantly between 1990 and 2019 (annualised rate of change: -1 center dot 21% [-1 center dot 26 to -1 center dot 16]), similar progress was not observed for chewing tobacco (0 center dot 46% [0 center dot 13 to 0 center dot 79]). Among the 12 highest prevalence countries (Bangladesh, Bhutan, Cambodia, India, Madagascar, Marshall Islands, Myanmar, Nepal, Pakistan, Palau, Sri Lanka, and Yemen), only Yemen had a significant decrease in the prevalence of chewing tobacco use, which was among males between 1990 and 2019 (-0 center dot 94% [-1 center dot 72 to -0 center dot 14]), compared with nine of 12 countries that had significant decreases in the prevalence of smoking tobacco. Among females, none of these 12 countries had significant decreases in prevalence of chewing tobacco use, whereas seven of 12 countries had a significant decrease in the prevalence of tobacco smoking use for the period. Summary Background Chewing tobacco and other types of smokeless tobacco use have had less attention from the global health community than smoked tobacco use. However, the practice is popular in many parts of the world and has been linked to several adverse health outcomes. Understanding trends in prevalence with age, over time, and by location and sex is important for policy setting and in relation to monitoring and assessing commitment to the WHO Framework Convention on Tobacco Control. Methods We estimated prevalence of chewing tobacco use as part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2019 using a modelling strategy that used information on multiple types of smokeless tobacco products. We generated a time series of prevalence of chewing tobacco use among individuals aged 15 years and older from 1990 to 2019 in 204 countries and territories, including age-sex specific estimates. We also compared these trends to those of smoked tobacco over the same time period. Findings In 2019, 273 & middot;9 million (95% uncertainty interval 258 & middot;5 to 290 & middot;9) people aged 15 years and older used chewing tobacco, and the global age-standardised prevalence of chewing tobacco use was 4 & middot;72% (4 & middot;46 to 5 & middot;01). 228 & middot;2 million (213 & middot;6 to 244 & middot;7; 83 & middot;29% [82 & middot;15 to 84 & middot;42]) chewing tobacco users lived in the south Asia region. Prevalence among young people aged 15-19 years was over 10% in seven locations in 2019. Although global age standardised prevalence of smoking tobacco use decreased significantly between 1990 and 2019 (annualised rate of change: -1 & middot;21% [-1 & middot;26 to -1 & middot;16]), similar progress was not observed for chewing tobacco (0 & middot;46% [0 & middot;13 to 0 & middot;79]). Among the 12 highest prevalence countries (Bangladesh, Bhutan, Cambodia, India, Madagascar, Marshall Islands, Myanmar, Nepal, Pakistan, Palau, Sri Lanka, and Yemen), only Yemen had a significant decrease in the prevalence of chewing tobacco use, which was among males between 1990 and 2019 (-0 & middot;94% [-1 & middot;72 to -0 & middot;14]), compared with nine of 12 countries that had significant decreases in the prevalence of smoking tobacco. Among females, none of these 12 countries had significant decreases in prevalence of chewing tobacco use, whereas seven of 12 countries had a significant decrease in the prevalence of tobacco smoking use for the period. Interpretation Chewing tobacco remains a substantial public health problem in several regions of the world, and predominantly in south Asia. We found little change in the prevalence of chewing tobacco use between 1990 and 2019, and that control efforts have had much larger effects on the prevalence of smoking tobacco use than on chewing tobacco use in some countries. Mitigating the health effects of chewing tobacco requires stronger regulations and policies that specifically target use of chewing tobacco, especially in countries with high prevalence. Copyright (c) 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.Peer reviewe