DYNAMIC MECHANICAL BEHAVIOR OF MAGNESIUM ALLOYS UNDER SHOCK LOADING CONDITION

The use of magnesium and its alloys, as the lightest structural materials, to decrease the weight, improve the fuel efficiency and reduce the greenhouse gas emissions has significantly increased in the automotive and aerospace industries in recent years. However, magnesium alloys are commonly used as die casting products. The current application of wrought magnesium alloy products is limited because of their poor ductility at room temperature due to the formation of a strong texture and restricted active deformation modes in wrought magnesium products. Moreover, to support the application of magnesium alloys in automobile and airplane components, their dynamic mechanical response must be determined to evaluate their behavior during impact events such as car crash and bird strike in airplanes. Therefore, in this research study, the dynamic mechanical behavior of magnesium alloys at high strain rates was investigated. The effects of initial texture, composition, strain rate and grain size on the deformation mechanism were also determined. Split Hopkinson Pressure Bar was used to investigate the dynamic mechanical behavior of the magnesium alloys. Texture analysis on the alloy prior and after shock loading was done using X-ray diffraction. Scanning electron microscopy was used to study the microstructural evolution in the alloys before and after shock loading. Chemical analysis and phase identification were done by energy dispersive spectroscopy and X-ray diffraction analysis, respectively. Additionally, twinning type and distribution was determined by means of orientation imaging microscopy whereas dislocation types and distribution was determined using transmission electron microscopy. A visco-plastic self-consistent simulation was used to corroborate the experimental textures and possible deformation mechanisms. The dynamic mechanical behavior of cast AZ and AE magnesium alloys with different chemistries was investigated at strain rates ranging between 800 to 1400 s-1 to determine the effects of composition on the response of the alloys to shock loading. It was found that an increase in the aluminum content of the AZ alloys increased the volume fraction of β-Mg17Al12 and Al4Mn phases, strength and strain hardening but, on the other hand, decreased the ductility and twinning fraction, particularly extension twinning fraction, for all the investigated strain rates. In addition, increasing the strain rate resulted in considerable increase in strength of the alloys. Texture measurements showed that shock loading of the AE alloys resulted in development of a stronger (00.2) basal texture in samples with higher content of yttrium at the investigated strain rates. Increasing the yttrium content of the cast AE alloys decreased twinning fraction but increased dislocation density and volume fraction of the Al2Y second phase. As a result, the tensile strength and ductility of the alloys increased which is an interesting result for high-strain rate applications of AE alloys in comparison to AZ alloys. The dynamic mechanical behavior of rolled AZ31B and WE43 magnesium alloys were also studied at strain rates ranging between 600 to 1400 s-1. A strong (00.2) basal texture was observed in all shock loaded AZ31B samples. It was also observed that increasing the strain rate led to an increase in strength and ductility, but to a decrease in twinning fraction. A high degree of mechanical anisotropy was found for all investigated strain rates so that the lowest strength was registered for the samples cut along the direction parallel to the rolling direction. Furthermore, it was found that at high strain rates, fine-grained AZ31B alloy exhibits better ductility and strength compared to coarse-grained alloy. However, the hardening rate of coarse-grained alloy was higher. In the case of rolled WE43 alloy, it was found that the strength and ductility increased and twinning fraction decreased with increase in strain rate. Furthermore, another effect of increase in strain rate was the higher activation of pyramidal slip systems. In addition, degree of stress and strain anisotropy is low particularly at higher strain rates, which is mainly related to the weak initial texture of the samples due to the presence of rare earth elements. Furthermore, strength and ductility were found to decrease with increasing grain size, while twinning fraction, activity of double and contraction twins and strain hardening rate increase with increasing grain size. In both AZ31B and WE43 alloy, the presence of dislocations was confirmed at high strain rates using ‘g.b’ analysis confirming activation of pyramidal slip systems during dynamic shock loading

Presenting a model of green human resources management with a metacombinatiion approach

The purpose of this research is to present a green human resource management model. This research is applicable in terms of purpose, qualitative in terms of the method of data collection, and meta-composite in terms of the research implementation method. The statistical population of the research includes 15 organizational experts, managers and specialists in the field of human resources, who were selected by purposeful sampling. Extracting the components and indicators of green human resources management was obtained from the review of the background and theoretical foundations, and then the fuzzy Delphi method was used for analysis in three rounds. The components and dimensions of green human resources management include 9 dimensions of green process, green strategy, green support, green culture, green training, green reward, green participation, green job analysis and design, green discipline management, and 20 components were identified and confirmed. The results showed that the dimension of green strategy in green human resource management in the first stage acquired with an average of (0.967) and in the second with an average of (0.942), that the obtained numbers almost overlap in the two final stages. Also, the results show that in the dimension of green strategy, the component of green strategic alignment has the highest opinions of experts; in the first stage with an average of (0.990) and in the second with an average of (0.973), which shows the full saturation of experts' opinions and the overlap of these two stages.Extended AbstractIntroductionHuman resource management is one of the main responsibilities of management in any organization, and all managers at multiple levels of the organization have this responsibility in some way (Bombiak & Marciniuk-Kluska, 2018). The high complexity of businesses and jobs in the world has led to their competitiveness, and for this reason, companies should pay special attention to value creation and be responsible in addition to efficiency (Kour & Joshi, 2020). Accountability is not only limited to work and fulfilling obligations to customers. One of the most important things is being responsible for the environment. For this reason, companies should pay attention to environmental issues and move towards "green" processes and actions (Singh et al, 2020). Green management is possible for the realization and convergence of green values and a wide range of economic, social, political and legal motivations only by benefiting from green human resource management (Evazkhah, 2020).Green human resource management includes the process of support strategy and green culture; this means that human resource processes are redesigned based on environmental goals and strategies, and by supporting an environmentally friendly lifestyle, green culture is institutionalized in the organization. For successful implementation, factors at the individual, organizational and extra-organizational levels are effective. Finally, successful implementation leads to positive consequences at the individual, organizational and extra-organizational levels (Yeganegi & Safari, 2020).Therefore, according to the issues raised, the current research aims to answer the question: what is the appropriate model of green human resource management with a metacombination approach?Theoretical frameworkGreen human resource management can be defined as human resource management actions and policies that cause the sustainability of a business and more important than all, prevent the damages caused by anti-environmental activities in organizations. (Yussoff et al, 2020). Organizations, as the largest members of societies, should recognize the effects of their behaviors on the environment and take measures to reduce the negative effects of these behaviors on natural ecosystems. Green human resource management, as a strong tool that assumes the role of human factors, can help organizations to fulfill their social responsibilities in order to protect the environment (Barati, 2021).Hajizadeh et al, (2022) investigated the identification and ranking of the antecedents of green human resource management with fuzzy Delphi approaches and hierarchical analysis. The findings showed that organizational factors with a weight of 0.627 dimensions were ranked 1st, and among its components, the quality of human resources was ranked first with a weight of 0.359. Technological factors were also ranked second with a weight of 0.289, and the advantage component was also ranked first. Environmental factors with a weight of 0.084 dimensions, was obtained with a dimension rank of 3, and among its components, government support with a weight of 0.336 was ranked first. The overall results indicated that the organizational factor ranked first in terms of importance, the technology factor ranked second, and the environmental factor ranked third.Alirezaei et al, (2022) investigated the impact of green transformational leadership on environmental performance with the mediating role of green human resource management and environmental awareness in small and medium businesses of Sirjan Special Economic Zone. The findings of the research indicate that, in general, green transformational leadership has a significant effect on environmental performance with the mediating role of green human resource management and environmental awareness.Research MethodologyThis research is applicable in terms of purpose, qualitative in terms of data collection, and meta-composite in terms of the research implementation method. The statistical population of the research includes 15 organizational experts, managers and specialists in the field of human resources, who were selected by purposeful sampling. Extracting the components and indicators of green human resources management is based on the background and theoretical foundations, and then the fuzzy Delphi method was used for analysis.Research FindingsFor the analysis, the background review and theoretical foundations, and then the fuzzy Delphi method was used. The components and dimensions of green human resources management include 9 dimensions of green process, green strategy, green support, green culture, green training, green reward, green participation, green job analysis and design, green discipline management; and 20 components were identified and confirmed. The results showed that the dimension of green strategy in green human resource management in the first stage obtained with an average of (0.967) and the second with an average of (0.942), that the obtained numbers almost overlap in the two final stages. Also, the results show that in the dimension of green strategy, the component of green strategic alignment has the highest opinions of experts; in the first stage with an average of (0.990) and in the second with an average of (0.973), which shows the full saturation of experts' opinions and the overlap of these two stages.ConclusionThe current research was conducted with the aim of presenting a green human resource management model. The present research is in line with the results of Alirezaei et al, (2022), Hajizadeh et al, (2022), Sidra Munawar et al, (2022), Fazlali & Moazzami (2022), Yu et al, (2020), Rezaei et al, (2020), and Farrokhi et al, (2017). Alam & Bahramzadeh (2022) showed that considering the many environmental problems that the hotel industry is facing, this industry has undergone a lot of pressure to respond to these problems by implementing sustainable strategies such as green human resource management. Their findings showed that there is a direct and significant relationship between green human resource management and green performance related to tasks and innovativeness. Also, green human resource management works have a positive effect on employees' environmental care behaviors, and also promote environmental efficiency programs in the organization. Also, green human resource management is directly and positively related to innovative green performance and the great role of environmental behaviors in the workplace, and confirms an indirect and significant relationship between green human resource management and innovative green performance of employees due to the mediating role of environmental awareness.According to the results obtained, organizations are suggested to pay attention to the review of their human resources management system and move towards green human resources management, such as paying more attention to green criteria in human resources subsystems (such as green recruitment and hiring, green training and development, green performance evaluation, green service compensation). It is suggested that the development of green human resource management strategies should be included in the human resource management agenda of petrochemical companies, considering the concerns and issues of the day. It is suggested to increase the knowledge and awareness of the employees with accurate needs assessment and holding green courses to the senior managers of these companies. It is suggested that human resource managers and senior managers of organizations, after hiring new staff, should consider criteria to evaluate the performance of employees based on the standards, according to which benefits and rewards will be paid to employees

An exploratory study to identify critical factors of innovation culture in organizations

During the past two decades, there has been a growing trend on knowledge-based organizations. Innovation, on the other hand, plays essential role on building competitive business units. In this paper, we present an exploratory study to identify critical factors of innovation culture in organizations. We detect important factors influencing innovation culture in construction industry based on the implementation of factor analysis. The proposed study designs a questionnaire and distributes it among 400 experts who are involved in construction industry. Cronbach alpha has been calculated as 0.779, which validates the overall questionnaire. The results of factor analysis have indicated that six factors of building cultural infrastructures, education, organizational vision, established culture, strategic culture and flexible culture are the most important items influencing innovation culture

Effects of Interface Recombination on the Performance of SWCNT\GaAs Heterojunction Solar Cell

AbstractThis paper indicated a theoretical model for describing the effects of the interface recombination on the heterojunction solar cell parameters based on single wall carbon nanotube and GaAs as p-n junction. By choosing the zigzag nanotube and GaAs layer, it is shown that by increasing the interface recombination, short circuit current and open circuit voltage decrease. Depletion current, J-V characteristic and ideality factor variation in terms of interface recombination have been calculated

An exploration study on factors influencing on market orientation: A case study of tourism industry

During the past two decades, tourism industry has become popular among many researchers in developing countries. Tourism is able to attract substantial amount of investment to some areas where many investors are normally unwilling to invest in. This paper, presents important factors influencing market orientation in tourism industry based on the implementation of factor analysis. The proposed study designs a questionnaire and distributes it among 267 experts who are involved in tourism industry. Cronbach alpha has been calculated as 0.873, which validates the overall questionnaire. The results of factor analysis have indicated that six factors of market oriented, limiting rules and regulations, strategic competition, marketing planning culture, financial figures and top management

Texture evolution and plastic anisotropy of commercial purity titanium/SiC composite processed by accumulative roll bonding and subsequent annealing

The final publication is available at Elsevier via https://doi.org/10.1016/j.matchemphys.2018.08.027. © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this study, commercial purity titanium (CPTi) with SiC particle reinforcements produced using accumulative roll bonding (ARB) process and subsequent annealing. Texture evolution and plastic anisotropy in different steps of the process were studied. ARBed material exhibited a significant magnitude of anisotropy of mechanical properties. Moreover, a strong TD split basal texture with basal poles tilted 25° away from the normal direction toward the transverse direction was developed in the ARBed samples. Higher normal anisotropy obtained for ARB–annealed sheet, compared to that of the starting titanium sheet, indicated lower susceptibility to thinning. However, ARB–annealed sheet exhibited higher planar anisotropy ( = 0.048 for ARB–annealed sheet and  = –0.434 for starting titanium). Higher resistance to thinning of the ARB–annealed sheets compared to the starting titanium was ascribed to the higher uniform elongation shown by annealed sheets. Furthermore, it was concluded that finer grain size of ARB–annealed sheet resulted in higher work hardening of the sheet, which in turn, increased the uniform elongation of ARB–annealed sample

Mapping local patterns of childhood overweight and wasting in low- and middle-income countries between 2000 and 2017

A double burden of malnutrition occurs when individuals, household members or communities experience both undernutrition and overweight. Here, we show geospatial estimates of overweight and wasting prevalence among children under 5 years of age in 105 low- and middle-income countries (LMICs) from 2000 to 2017 and aggregate these to policy-relevant administrative units. Wasting decreased overall across LMICs between 2000 and 2017, from 8.4% (62.3 (55.1–70.8) million) to 6.4% (58.3 (47.6–70.7) million), but is predicted to remain above the World Health Organization’s Global Nutrition Target of <5% in over half of LMICs by 2025. Prevalence of overweight increased from 5.2% (30 (22.8–38.5) million) in 2000 to 6.0% (55.5 (44.8–67.9) million) children aged under 5 years in 2017. Areas most affected by double burden of malnutrition were located in Indonesia, Thailand, southeastern China, Botswana, Cameroon and central Nigeria. Our estimates provide a new perspective to researchers, policy makers and public health agencies in their efforts to address this global childhood syndemic

Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In an era of shifting global agendas and expanded emphasis on non-communicable diseases and injuries along with communicable diseases, sound evidence on trends by cause at the national level is essential. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic scientific assessment of published, publicly available, and contributed data on incidence, prevalence, and mortality for a mutually exclusive and collectively exhaustive list of diseases and injuries. Methods: GBD estimates incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) due to 369 diseases and injuries, for two sexes, and for 204 countries and territories. Input data were extracted from censuses, household surveys, civil registration and vital statistics, disease registries, health service use, air pollution monitors, satellite imaging, disease notifications, and other sources. Cause-specific death rates and cause fractions were calculated using the Cause of Death Ensemble model and spatiotemporal Gaussian process regression. Cause-specific deaths were adjusted to match the total all-cause deaths calculated as part of the GBD population, fertility, and mortality estimates. Deaths were multiplied by standard life expectancy at each age to calculate YLLs. A Bayesian meta-regression modelling tool, DisMod-MR 2.1, was used to ensure consistency between incidence, prevalence, remission, excess mortality, and cause-specific mortality for most causes. Prevalence estimates were multiplied by disability weights for mutually exclusive sequelae of diseases and injuries to calculate YLDs. We considered results in the context of the Socio-demographic Index (SDI), a composite indicator of income per capita, years of schooling, and fertility rate in females younger than 25 years. Uncertainty intervals (UIs) were generated for every metric using the 25th and 975th ordered 1000 draw values of the posterior distribution. Findings: Global health has steadily improved over the past 30 years as measured by age-standardised DALY rates. After taking into account population growth and ageing, the absolute number of DALYs has remained stable. Since 2010, the pace of decline in global age-standardised DALY rates has accelerated in age groups younger than 50 years compared with the 1990–2010 time period, with the greatest annualised rate of decline occurring in the 0–9-year age group. Six infectious diseases were among the top ten causes of DALYs in children younger than 10 years in 2019: lower respiratory infections (ranked second), diarrhoeal diseases (third), malaria (fifth), meningitis (sixth), whooping cough (ninth), and sexually transmitted infections (which, in this age group, is fully accounted for by congenital syphilis; ranked tenth). In adolescents aged 10–24 years, three injury causes were among the top causes of DALYs: road injuries (ranked first), self-harm (third), and interpersonal violence (fifth). Five of the causes that were in the top ten for ages 10–24 years were also in the top ten in the 25–49-year age group: road injuries (ranked first), HIV/AIDS (second), low back pain (fourth), headache disorders (fifth), and depressive disorders (sixth). In 2019, ischaemic heart disease and stroke were the top-ranked causes of DALYs in both the 50–74-year and 75-years-and-older age groups. Since 1990, there has been a marked shift towards a greater proportion of burden due to YLDs from non-communicable diseases and injuries. In 2019, there were 11 countries where non-communicable disease and injury YLDs constituted more than half of all disease burden. Decreases in age-standardised DALY rates have accelerated over the past decade in countries at the lower end of the SDI range, while improvements have started to stagnate or even reverse in countries with higher SDI. Interpretation: As disability becomes an increasingly large component of disease burden and a larger component of health expenditure, greater research and developm nt investment is needed to identify new, more effective intervention strategies. With a rapidly ageing global population, the demands on health services to deal with disabling outcomes, which increase with age, will require policy makers to anticipate these changes. The mix of universal and more geographically specific influences on health reinforces the need for regular reporting on population health in detail and by underlying cause to help decision makers to identify success stories of disease control to emulate, as well as opportunities to improve. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Global age-sex-specific fertility, mortality, healthy life expectancy (HALE), and population estimates in 204 countries and territories, 1950-2019 : a comprehensive demographic analysis for the Global Burden of Disease Study 2019

Background: Accurate and up-to-date assessment of demographic metrics is crucial for understanding a wide range of social, economic, and public health issues that affect populations worldwide. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 produced updated and comprehensive demographic assessments of the key indicators of fertility, mortality, migration, and population for 204 countries and territories and selected subnational locations from 1950 to 2019. Methods: 8078 country-years of vital registration and sample registration data, 938 surveys, 349 censuses, and 238 other sources were identified and used to estimate age-specific fertility. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate age-specific fertility rates for 5-year age groups between ages 15 and 49 years. With extensions to age groups 10–14 and 50–54 years, the total fertility rate (TFR) was then aggregated using the estimated age-specific fertility between ages 10 and 54 years. 7417 sources were used for under-5 mortality estimation and 7355 for adult mortality. ST-GPR was used to synthesise data sources after correction for known biases. Adult mortality was measured as the probability of death between ages 15 and 60 years based on vital registration, sample registration, and sibling histories, and was also estimated using ST-GPR. HIV-free life tables were then estimated using estimates of under-5 and adult mortality rates using a relational model life table system created for GBD, which closely tracks observed age-specific mortality rates from complete vital registration when available. Independent estimates of HIV-specific mortality generated by an epidemiological analysis of HIV prevalence surveys and antenatal clinic serosurveillance and other sources were incorporated into the estimates in countries with large epidemics. Annual and single-year age estimates of net migration and population for each country and territory were generated using a Bayesian hierarchical cohort component model that analysed estimated age-specific fertility and mortality rates along with 1250 censuses and 747 population registry years. We classified location-years into seven categories on the basis of the natural rate of increase in population (calculated by subtracting the crude death rate from the crude birth rate) and the net migration rate. We computed healthy life expectancy (HALE) using years lived with disability (YLDs) per capita, life tables, and standard demographic methods. Uncertainty was propagated throughout the demographic estimation process, including fertility, mortality, and population, with 1000 draw-level estimates produced for each metric. Findings: The global TFR decreased from 2·72 (95% uncertainty interval [UI] 2·66–2·79) in 2000 to 2·31 (2·17–2·46) in 2019. Global annual livebirths increased from 134·5 million (131·5–137·8) in 2000 to a peak of 139·6 million (133·0–146·9) in 2016. Global livebirths then declined to 135·3 million (127·2–144·1) in 2019. Of the 204 countries and territories included in this study, in 2019, 102 had a TFR lower than 2·1, which is considered a good approximation of replacement-level fertility. All countries in sub-Saharan Africa had TFRs above replacement level in 2019 and accounted for 27·1% (95% UI 26·4–27·8) of global livebirths. Global life expectancy at birth increased from 67·2 years (95% UI 66·8–67·6) in 2000 to 73·5 years (72·8–74·3) in 2019. The total number of deaths increased from 50·7 million (49·5–51·9) in 2000 to 56·5 million (53·7–59·2) in 2019. Under-5 deaths declined from 9·6 million (9·1–10·3) in 2000 to 5·0 million (4·3–6·0) in 2019. Global population increased by 25·7%, from 6·2 billion (6·0–6·3) in 2000 to 7·7 billion (7·5–8·0) in 2019. In 2019, 34 countries had negative natural rates of increase; in 17 of these, the population declined because immigration was not sufficient to counteract the negative rate of decline. Globally, HALE increased from 58·6 years (56·1–60·8) in 2000 to 63·5 years (60·8–66·1) in 2019. HALE increased in 202 of 204 countries and territories between 2000 and 2019