Simulation of Time-Dependent Viscoelastic Fluid Flows by Spectral Elements

The research work reported in this dissertation is aimed to develop efficient and stable numerical schemes in order to obtain accurate numerical solution for viscoelastic fluid flows within the spectral element context. The present research consists in the transformation of a large class of differential constitutive models into an equation where the main variable is the logarithm of the conformation tensor or a quantity related to it in a simple way. Particular cases cover the Oldroyd-B fluid and the FENE-P model. Applying matrix logarithm formulation in the framework of the spectral element method is a new type of approach that according to our knowledge no one has implemented before. The reformulation of the classical constitutive equation using a new variable namely the logarithmic formulation, enforces the eigenvalues of the conformation tensor to remain positive for all steps of the simulation. However, satisfying the symmetric positive definiteness of the conformation tensor during the simulation is the necessary condition for stability; but definitely, it is not the sufficient condition to reach meaningful results. The main effort of this research is devoted to introduce a new algorithm in order to overcome the drawback of direct reformulating the classical constitutive equation to the logarithmic one. To evaluate the capability of the extended matrix logarithm formulation, comprehensive studies have been done based on the linear stability analysis to show the influence of this method on the resulting eigenvalue spectra and explain its success to tackle high Weissenberg numbers. With this new method one can treat high Weissenberg number flows at values of practical interest. One of the worst obstacles for numerical simulation of viscoelastic fluids is the presence of spurious modes during the simulation. At high Weissenberg number, many schemes suffer from instabilities and numerical convergence may not be attainable. This is often attributed to the presence of solution singularities due to the geometry, the dominant non-linear terms in the constitutive equations, or the change of type of the underlying mixed-form differential system. Refining the mesh proved to be not very helpful. In this study, to understand more deeply the mechanism of instability generation a comprehensive study about the growth of spurious modes with time evolution, mesh refinement, boundary conditions and Weissenberg number or any other affected parameters has been performed. Then to get rid of these spurious modes the filter based stabilization of spectral element methods proposed by Boyd was applied with success

Effects of Turbulence on Heliostat Wind Loads

Concentrated solar thermal systems are being increasingly deployed for industrial process heating and large-scale electricity production. A major constituent of a concentrating solar plant is the field of heliostat mirrors, which reflect the sunlight onto a receiver. Heliostats are subjected to fluctuating wind loads arising from atmospheric wind. These forces are important for design of heliostats, which must survive maximum wind loads under extreme conditions. Furthermore, dynamic wind loads which lead to vibrations of the mirror panel can affect the tracking accuracy of a heliostat field. Therefore, knowledge of wind loads is necessary for design and development of a heliostat field. The main source of unsteady loads on heliostats is the fluctuating wind velocity, which results from the turbulence within the atmospheric boundary layer. Furthermore, heliostats during their operation create a blockage in the flow and unstable vortex structures in their wake. The interaction between the wakes of several heliostats in a field with each other and with the incoming atmospheric boundary layer flow affects turbulence and consequently wind loads in a heliostat field. The research presented in this thesis focuses on the development of an in-depth understanding of the effects of turbulence within the atmospheric boundary layer on the wind loads on heliostats. Extensive wind tunnel experiments have been conducted to simulate the atmospheric boundary layer turbulence and establish its effect on unsteady wind loads. Similarities and differences of the turbulence properties with respect to the atmospheric boundary layer are discussed and the requirements for achieving similarity in measurement of wind loads in a wind tunnel are established. A correlation is developed between the intensity and integral length scale of the turbulence and the peak lift and drag forces on a heliostat at stow and vertical positions, which is employed to predict the wind loads on full-scale heliostats in a range of terrains where the turbulence characteristics of the flow vary. In order to develop an understanding of wind loads in a heliostat field, turbulence in the wake of a heliostat in the atmospheric boundary layer is characterised. Based on the findings, variations of flow and turbulence properties in a heliostat field are discussed. Moreover, through analysis of wind loads on a second tandem heliostat placed in the wake of an upstream one, it is demonstrated that wind loads on the second heliostat are correlated with the turbulence properties in the wake. It is concluded that wind loads on a heliostat within a field can be predicted from the approaching wake flow properties. Estimations for variations of wind loads in different regions of a field are thereby made based on the findings. After demonstrating the strong relationship between turbulence and wind loads, the effect of perimeter fences around a heliostat field on the turbulence within the atmospheric boundary layer is investigated. It is demonstrated that the intensity and integral length scale of the turbulence reduce downstream of wire mesh fences. It is found that the reduction in turbulence properties behind a wire mesh fence is mainly correlated with the mesh porosity. Based on the variations of turbulence properties behind a wire mesh fence, the feasibility of reducing the wind loads on heliostats with application of the fences is analysed. The research presented in this thesis provides an improved understanding of the effect of turbulence within the atmospheric boundary layer on the unsteady wind loads on heliostats. The findings of this research can be used to determine the design wind loads based on the turbulence characteristics specific to a given terrain. Recommendations for improvement of heliostat design and reduction of wind loads on heliostats are made based on the results, and potentials for reducing the cost of heliostats through reduction of structural costs related to the wind loads are identified. For instance, it is demonstrated that the peak wind loads on a stowed heliostat can be reduced by 80% by decreasing the height of the heliostat panel at stow. Furthermore, it is shown that there is a potential to reduce the peak drag force on an operating heliostat and the peak lift force on a stowed heliostat by application of wire mesh fences by 48% and 53%, respectively. Moreover, the presented study provides an insight into variations of wind loads within a heliostat field which are necessary to be considered in the design of heliostats. For example, up to 80% increase in the unsteady drag force coefficient on a vertical heliostat and up to 70% increase in the peak hinge moment coefficient on an operating heliostat are predicted for high-density regions of a field. Hence, the findings highlight the need to develop the arrangement of heliostats in a field such that the dynamic wind loads on the in-field heliostats can be reduced. The results of this research provide an opportunity for production of cheaper heliostats by reducing the design wind loads.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 202

Evaluation of Mast Cell Density in Mucoepidermoid Carcinoma and Pleomorphic Adenoma

Statement of the Problem: Mast cells are round to elliptical cells that originate from bone marrow stem cells and enter the peripheral blood. By releasing inflammatory mediators, these cells are involved in type I hypersensitivity, wound healing, defense against pathogens, increased blood vessel formation, and destruction of the extracellular matrix. There are contradictory results regarding the role of mast cells in tumor lesions.Purpose: Considering the contradictory results and few studies on the density of mast cells in salivary tumors, the present study investigated and compared the density of mast cells in two common salivary gland tumors.Materials and Method: In the cross-sectional study after reviewing the records of patients referred to the Pathology Department of the School of Dentistry and Shahid Sadoughi Hospital in Yazd, 15 blocks of each of the mucoepidermoid carcinoma and pleomorphic adenoma tumors were taken. After Giemsa staining of the samples, the average of stained cells in 10 random fields under 400× magnification was counted. The results were analyzed using statistical tests of t-test, ANOVA, Chi-square, and Mann-Whitney in SPSS ver. 22.Results: The average mast cell counts in pleomorphic adenoma (4.2) was higher than muco-epidermoid carcinoma (1.7) but there was no significant relationship (p= 0.305). In mucoepidermoid carcinoma, the numbers of mast cells increased with increasing tumor grade (low: 0/467 moderate: 1/567 high: 2/983) and there was a significant relationship (p= 0.009).Conclusion: According to the results of the present study, it seems that the mast cells accumulation may be secondarily associated with inflammatory responses due to cell accumulation and tissue destruction by tumor cells

Property preserving reformulation of constitutive laws for the conformation tensor

The challenge for computational rheologists is to develop efficient and stable numerical schemes in order to obtain accurate numerical solutions for the governing equations at values of practical interest of the Weissenberg numbers. This study presents a new approach to preserve the symmetric positive definiteness of the conformation tensor and to bound the magnitude of its eigenvalues. The idea behind this transformation is lies with the matrix logarithm formulation. Under the logarithmic transformation, the eigenvalue spectrum of the new conformation tensor varies from infinite positive to infinite negative. But, reconstruction the classical formulation from unbounded eigenvalues doesn't achieve meaningful results. This enhanced formulation, hyperbolic tangent, prevails the previous numerical failure by bounding the magnitude of eigenvalues in a manner that positive definite is always satisfied. In order to evaluate the capability of the hyperbolic tangent formulation we performed a numerical simulation of FENE-P fluids in a rectangular channel in the context of the finite element method. Under this new transformation, the maximum attainable Weissenberg number increases 21.4% and 112.5% comparing the standard log-conformation and classical constitutive equation respectively

Topical effectiveness of different concentrations of nanosilver solution on Leishmania major lesions in Balb/c mice

Background & objectives: Cutaneous leishmaniasis is an infection caused by protozoan genus Leishmania. Althoughglucantime is commonly used for the treatment of leishmaniasis, it has some side effects including increased liverenzymes and electrocardiogram changes. In addition, the drug is expensive, the injection is painful, and researchshows that resistance of parasite to glucantime is growing in different parts of the world. Therefore, scientists arepaying more attention to develop new drugs such as nanosilver solution. The present study is an attempt toevaluate the in vivo topical effects of different concentrations of nanosilver solution in the treatment of leishmaniasislesions.Methods: In all, 90 female Balb/c mice aged 6–8 wk were infected with 2×106 viable stationary-phase promastigotesin the base of tail. Different concentrations (60, 80, 120, 130 and 2000 ppm) nanosilver solution were used in thepresent study to test the efficacy in the treatment of lesions. Clinical control of the infection trends was conductedweekly for 5 wk by measuring lesion diameter with standard Kulis-Vernieh. Data were analyzed by paired t-test,analysis of variance (ANOVA), and Tukey test.Results: Mean lesion diameter pre- and post-treatment did not significantly differ between different treatmentgroups (p >0.05). Likewise, a significant difference in splenic parasite load was also not observed between differenttreatment groups.Interpretation & conclusion: Based on our results, different concentrations of nanosilver are ineffective in reducingmean sizes of lesions

Prediction of response to treatment in children with epilepsy

Objective: Predicting the response to treatment in patients treated  with anti-epilepsy drugs are always a major challenge. This study was conducted to predict the response to treatment in patients with epilepsy.Material and Methods: This analytical questionnaire-based study was conducted in 2014 among patients with epilepsy admitted to Mofid Children's Hospital. The inclusion criteria were children 2 months to 12 years of age with epilepsy and patients who experienced fever and seizure attacks at least once were excluded from the study. After the initial recording of patient information, patients were followed up for 6 months and the response to their treatment was recorded. The response to good treatment was defined as the absence of maximum seizure with two drugs during follow up.Result: This study was conducted among 128 children with seizure. 72 patients (56.3%) were boys. The age of the first seizure was under 2 years old in 90 patients (70.3%). History of febrile convulsion, family history of seizure and history of asphyxia was found in 16 patients (12.5%), 41 patients (32%), 27 (21.1%), respectively.  IQ was decreased in 79 patients (61.7%). Seizure etiology was idiopathic in 90 patients (70.3%), and the number of seizures was 1 - 2 in 36 patients (28.1%). 57 patients (44.5%) had cerebral lesion according to CT scan or MRI, and EEG was normal in 21 patients (16.4%) and abnormal in 101 patients (78.9%). In 6-month follow-up, 40 patients (31.3%) responded well to the treatment and 88 patients (68.8%) responded poorly to the treatment. The results of multivariate analysis demonstrated that history of asphyxia (OR = 6.82), neonatal jaundice (OR = 2.81) and abnormal EEG (OR = 0.19) were effective factors in response to treatment.Conclusion: Results of univariate and multivariate analysis indicated that abnormal EEG is an effective factor in treatment response in the children studied

Global, regional, and national mortality due to unintentional carbon monoxide poisoning, 2000–2021: results from the Global Burden of Disease Study 2021

Background Unintentional carbon monoxide poisoning is a largely preventable cause of death that has received insufficient attention. We aimed to conduct a comprehensive global analysis of the demographic, temporal, and geographical patterns of fatal unintentional carbon monoxide poisoning from 2000 to 2021. Methods As part of the latest Global Burden of Diseases, Injuries, and Risk Factors Study (GBD), unintentional carbon monoxide poisoning mortality was quantified using the GBD cause of death ensemble modelling strategy. Vital registration data and covariates with an epidemiological link to unintentional carbon monoxide poisoning informed the estimates of death counts and mortality rates for all locations, sexes, ages, and years included in the GBD. Years of life lost (YLLs) were estimated by multiplying deaths by remaining standard life expectancy at age of death. Population attributable fractions (PAFs) for unintentional carbon monoxide poisoning deaths due to occupational injuries and high alcohol use were estimated. Findings In 2021, the global mortality rate due to unintentional carbon monoxide poisoning was 0·366 per 100 000 (95% uncertainty interval 0·276–0·415), with 28 900 deaths (21 700–32 800) and 1·18 million YLLs (0·886–1·35) across all ages. Nearly 70% of deaths occurred in males (20 100 [15 800–24 000]), and the 50–54-year age group had the largest number of deaths (2210 [1660–2590]). The highest mortality rate was in those aged 85 years or older with 1·96 deaths (1·38–2·32) per 100 000. Eastern Europe had the highest age-standardised mortality rate at 2·12 deaths (1·98–2·30) per 100 000. Globally, there was a 53·5% (46·2–63·7) decrease in the age-standardised mortality rate from 2000 to 2021, although this decline was not uniform across regions. The overall PAFs for occupational injuries and high alcohol use were 13·6% (11·9–16·0) and 3·5% (1·4–6·2), respectively. Interpretation Improvements in unintentional carbon monoxide poisoning mortality rates have been inconsistent across regions and over time since 2000. Given that unintentional carbon monoxide poisoning is almost entirely preventable, policy-level interventions that lower the risk of carbon monoxide poisoning events should be prioritised, such as those that increase access to improved heating and cooking devices, reduce carbon monoxide emissions from generators, and mandate use of carbon monoxide alarms.publishedVersio

The global burden of cancer attributable to risk factors, 2010-19 : a systematic analysis for the Global Burden of Disease Study 2019

Background Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. Methods The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk-outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. Findings Globally, in 2019, the risk factors included in this analysis accounted for 4.45 million (95% uncertainty interval 4.01-4.94) deaths and 105 million (95.0-116) DALYs for both sexes combined, representing 44.4% (41.3-48.4) of all cancer deaths and 42.0% (39.1-45.6) of all DALYs. There were 2.88 million (2.60-3.18) risk-attributable cancer deaths in males (50.6% [47.8-54.1] of all male cancer deaths) and 1.58 million (1.36-1.84) risk-attributable cancer deaths in females (36.3% [32.5-41.3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20.4% (12.6-28.4) and DALYs by 16.8% (8.8-25.0), with the greatest percentage increase in metabolic risks (34.7% [27.9-42.8] and 33.3% [25.8-42.0]). Interpretation The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.Peer reviewe

Numerical study of the lattice vacancy effects on the quantum transport of four-terminal graphene nanodevice

The electronic transport properties of four-terminal graphene nanodevice have been investigated by means of the Landauer approach using tight-binding model. The effects of single vacancy and divacancy on transport properties of the electron injected into the system have been studied. The existence of single vacancy along with the magnetic field creates additional band between Landau levels, this effect is appeared by enhancing the transmission. It is also found that in the presence of divacancy with small distance, the coupling between two vacancies due "vacancy molecules", that the bonding between these vacancies can be tuned by the magnetic field. The effect of vacancies decreases when the size of conductor region increases. The theoretical results obtained, can be a base for development in designing graphene nanodevice