Magnetohydrodynamic Waves in Dynamic Plasmas with Solar Applications: Effect of Thermal Conduction

The highly magnetised coronal loops have been confirmed to support a variety of MHD waves and oscillations which are observed widely in the solar atmosphere and most of them are seen to be rapidly damped. One of these oscillations are interpreted as longitudinal slow (propagating or standing) MHD waves. In the last decade, the slow MHD waves have been subject to many observational and theoretical studies to investigate the dominant damping mechanisms. Thermal conduction is the main dissipation mechanism that is suggested to be the essential cause of the damping when compared to the other mechanisms. Therefore, we concentrate here on the damping of both propagating and standing slow magneto-acoustic waves due to thermal conduction. In the present thesis we examine the effect of the cooling background coronal plasma on damping coronal oscillations. Most of the previous studies have assumed models with a time-independent equilibrium. Here we avoid this restriction and allow the equilibrium to develop as a function of time. The background plasma is assumed to be cooling because of thermal conduction. Moreover, the cooling of the background temperature is assumed to have an exponential profile with characteristic cooling times typical for solar coronal loops. We have investigated the propagating slow magneto-acoustic waves in a homogeneous magnetised plasma embedded in a hot coronal loop. The background plasma is assumed to be cooling due to thermal conduction in a weakly stratified atmosphere. The influence of cooling of the background plasma on the properties of magneto-acoustic waves is examined. The background temperature is found to decrease exponentially with time by solving the background plasma equations. On the other hand, we have considered the influence of a cooling background plasma on the longitudinal standing (slow) magneto-acoustic waves generated in a loop of hot corona. The cooling of the background plasma is dominated by a physically unspecified thermodynamic source. A dominance of the cooling in the absence of any dissipative mechanisms is found to amplify the oscillation amplitude. Thermal conduction, which is presumed to be a weak, is only present in the perturbations, causing a damping for the hot-loop oscillations. The previous study is expanded on investigating the effect of strong thermal conduction on the hot coronal oscillations. The competition between the cooling of plasma and the damping of oscillations can be captured from the behaviour of MHD waves. The hot-loop oscillations undergo strong damping due to thermal conduction, although the cooling coronal plasma exerts resistive role on the damping method by decreasing the rate of decaying for cool coronal oscillations. Contrary to cool loops, the amplitude of very hot loops that undergoes a high amount of cooling experiences faster damping than others. However, the damping of the standing slow (acoustic) waves, because of strong thermal conduction, is brought to an end at a certain time instant and then the rate of damping decreases gradually beyond this limit. In our analytic work for the models assumed above, we have applied the WKB theory to solve the governing equation which is derived and non-dimensionalised. The WKB estimates are used here since they provide good approximations to the properties of MHD waves. Further to this, we have exploited the method of characteristics and the properties of Sturm-Liouville problems to obtain the solution of the temporally evolving amplitude for the propagating and standing slow MHD waves. Numerical evaluations are employed to give clear view into the behaviour of slow acoustic waves, where the variable background plasma comprising the wave amplitude is measured using typical coronal values. In additions to this, the obtained results are compared to observations

"Bitten by the entrepreneur bug" - critiquing discourses on women owner-managers/entrepreneurs in the Kenyan and Omani newspapers

Purpose This paper aims to critically analyze media discourses on women owner-managers/entrepreneurs (OMEs) in the Kenyan and Omani newspapers. Design/methodology/approach A critical discourse analysis is carried out on a total of 408 online media articles (174 articles from Omani newspapers and 234 articles from Kenyan newspapers) on women OMEs over the period 2010–2018. Articles are also classified based on their framing of women’s entrepreneurship. Findings Five main categories of media discourses are identified, i.e. discourses on government/institutional initiatives; women OMEs’ dependency; women OMEs’ femininity; women OMEs’ societal impact; and normalization of women OMEs. These gendered media discourses and underlying assumptions further perpetuate women OMEs’ subordinate position in society, weaken their social legitimacy and trivialize their roles as managers and leaders in society. Research limitations/implications The analysis was limited to online articles published in mainstream media. Future research could focus on offline print media from smaller media distributors or other distribution channels. Practical implications Policymakers and media houses need to pay greater attention to the subtle mechanisms reproducing gender stereotypes. Women OMEs should also take a more active role in constructing their identity in the media. Originality/value This paper highlights the underlying assumptions of media discourses regarding women’s empowerment that negatively impacts their social legitimacy. This paper also draws attention to media’s role in the trivialization of women OMEs’ leadership and managerial roles and subsequent marginalization of their social status

Studies on Stable Crack Growth

The goal of this work is to experimentally investigate the stable crack growth (SCG) fracture behavior of AISI 4340 alloy steel. A series of mode I and mixed mode SCG fracture tests were carried out on 8 mm thick compact tension (CT) specimens subjected to quasistatic loading. The wire cutting technique was used to introduce a pre-notch/ pre-crack of 0.05 mm root radius to the specimen. Five different loading angles Ψ between the loading axis and the crack surface were employed; 90° (mode I), 75°, 65°, 60° and 50°. Five different ratios of original crack length to specimen width ao/w were also employed, 0.41, 0.42, 0.43, 0.44 and 0.45. Different combinations of Ψ and ao/w were used. Data concerned with direction of initial crack extension load-load line displacement (L-LLD) diagrams, initiation and maximum loads, range of stable crack growth, crack blunting, crack front geometry, fracture surfaces, and scanning electron microscope fracto graphs were obtained. A noticeable blunting was observed prior the crack initiation. Although the crack commences its growth from a pre-notch / pre-crack of a straight front it has a considerable tunneling at each stage of stable crack growth. In mixed mode, the crack takes place along a straight-line path initially, inclined with the main crack at an angle equal to the direction of crack extension. The loading angle Ψ and the initial crack length to the specimen width ao/w ratio affect the SCG fracture behavior significantly. The direction of initial stable crack extension was determined through an elastic finite element analysis. There was reasonably good agreement between the experimental and the predicted results

An Assessment of Temperature and Precipitation Change Projections in Muscat, Oman from Recent Global Climate Model Simulations

Oman is vulnerable to the impacts of climate change, the most significant of which are increased temperature, less and more erratic precipitation, see level rise (SLR) and desertification. The objective of this research is to investigate the potential variation of precipitation and temperature in Muscat, the capital city of Sultanate of Oman in future. We used the MIROC general circulation model (GCM) output (maximum and minimum temperatures and precipitation) from the Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5 scenarios of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) for assessing changes in climate in the period of 2080-2099 compared to the baseline period of 1986-2005. The spatial mismatch between GCM grid scale and local scale was resolved by applying the LARS stochastic Weather Generator (WG) model. The results obtained for 4 scenarios indicate a significant warming in future, which ranges from 0.93ᴼC (minimum temperature by 1.1ᴼC and maximum temperature by 0.86ᴼC) for the lowest scenario, RCP 2.6, to 3.1ᴼC (minimum temperature by 3.2ᴼC and maximum temperature by 3.0ᴼC) for the highest one, RCP 8.5, relative to baseline level. The differences in the precipitation projections between the scenarios are much greater compared to consistent warming depicted in temperatures. The results reveal  -36.4% and -36.0% decreases in precipitation for the RCP 2.6 and RCP 4.5 scenarios, respectively, while, RCP 6.0 and RCP 8.5 scenarios predict increase in precipitation in a range from 9.6% to 12.5%, respectively during 2080-2099 compared to 1986-2005 period. These results need to be further improved by adopting more GCMs, which will provide potential changes in a consistent

Prevalence of and Reasons for Patients Leaving Against Medical Advice from Paediatric Wards in Oman

The objective of this study was to determine the prevalence of and reasons for patients leaving against medical advice (LAMA) in a paediatric setting in Oman. This retrospective study was carried out between January 2007 and December 2009 and assessed patients who left the paediatric wards at the Royal Hospital, Muscat, Oman, against medical advice. Of 11,482 regular discharges, there were 183 cases of LAMA (prevalence: 1.6%). Dissatisfaction with treatment and a desire to seek a second opinion were collectively the most cited reasons for LAMA according to data from the hospital’s electronic system (27.9%) and telephone conversations with patients’ parents (55.0%). No reasons for LAMA were documented in the hospital’s electronic system for 109 patients (59.6%). The low observed prevalence of LAMA suggests good medical practice at the Royal Hospital. This study indicates the need for thorough documentation of all LAMA cases to ensure the availability of high-quality data for healthcare workers involved in preventing LAMA

Framework for Investigating the Level of Compliance to the OHS Regulatory by the Small and Medium Construction Companies in Oman

The construction industry is characterized with a high rate of work-related accidents. Some of the accidents result in severe injuries and sometimes death. One of the reasons for such happenings is due to the noncompliance of the construction companies to the Occupational Health and Safety (OHS) regulatory framework. This paper briefly describes the preliminary results of the first part of an ongoing study. The study is composed of three parts studying the OHS practices in small and medium construction companies in Oman. The three parts are (1) identifying the level of compliance of the small and medium construction companies to the OHS regulatory framework, (2) comprehensively identifying the causation of the non-compliance and the risk generated, and (3) proposing a framework for “Paving Zero Accident Vision” in Oman. Oman’s OHS regulatory framework was used to construct an evaluation survey. Sixty small and medium construction companies from two different governorates, Muscat and South Al Batinah, were involved in the study. Three evaluation results related to the construction site fencing, the nature of the project site, and the level of compliance to providing personal protective equipment were reported. The results showed that the 75.5% on an average, the construction companies fenced their construction site; for 59% on average the project site is a construction and an accommodation site at the same time, and the level of compliance to providing Personal Protective Equipment (PPE) is varying in both locations. However, both locations showed similar results in providing ear protection, eye protection, and safety shoes

Experimental and modeling study of the phase behavior of synthetic crude oil + CO2

A full understanding of the phase behavior of CO2–hydrocarbon mixtures at reservoir conditions is essential for the proper design, construction and operation of carbon capture and storage (CCS) and enhanced oil recovery (EOR) processes. While equilibrium data for binary CO2–hydrocarbon mixtures are plentiful, equilibrium data and validated equations of state having reasonable predictive capability for multi-component CO2–hydrocarbon mixtures are limited. In this work, a new synthetic apparatus was constructed to measure the phase behavior of systems containing CO2 and multicomponent hydrocarbons at reservoir temperatures and pressures. The apparatus consisted of a thermostated variable-volume view cell driven by a computer-controlled servo motor system, and equipped with a sapphire window for visual observation. Two calibrated syringe pumps were used for quantitative fluid injection. The maximum operating pressure and temperature were 40 MPa and 473.15 K, respectively. The apparatus was validated by means of isothermal vapor–liquid equilibrium measurement on (CO2 + heptane), the results of which were found to be in good agreement with literature data. In this work, we report experimental measurements of the phase behavior and density of (CO2 + synthetic crude oil) mixtures. The ‘dead’ oil contained a total of 17 components including alkanes, branched-alkanes, cyclo-alkanes, and aromatics. Solution gas (0.81 methane + 0.13 ethane + 0.06 propane) was added to obtain live synthetic crudes with gas-oil ratios of either 58 or 160. Phase equilibrium and density measurements are reported for the ‘dead’ oil and the two ‘live’ oils under the addition of CO2. The measurements were carried out at temperatures of 298.15, 323.15, 373.15 and 423.15 K and at pressures up to 36 MPa, and included vapor–liquid, liquid–liquid and vapor–liquid–liquid equilibrium conditions. The results are qualitatively similar to published data for mixtures of CO2 with both real crude oils or and simple hydrocarbon mixtures containing both light and heavy components. The present experimental data have been compared with results calculated with two predictive models, PPR78 and PR2SRK, based on the Peng–Robinson 78 (PR78) and Soave–Redlich–Kwong (SRK) equations of state with group-contribution formulae for the binary interaction parameters. Careful attention was paid to the critical constants and acentric factor of high molar-mass components. Since the mixture also contained several light substances with critical temperatures below some or all experimental temperatures, we investigated the use of the Boston–Mathias modification of the PR78 and SRK equations. The results showed that these models can predict with reasonable accuracy the vapor–liquid equilibria of systems containing CO2 and complex hydrocarbon mixtures without the need to regress multiple binary parameters against experimental data