Numerical modeling of gas-particle flows inside fluidized beds

Fluidized beds have widespread application in industry due to their increased rate of heat, mass, and momentum transfer. In order to effectively design fluidized beds at the industrial scale, it is essential to have an understanding of the complex hydrodynamic behavior of the dense gas-particle flows inside them. This thesis is focused on the bubbling fluidization of Geldart B particles. The Eulerian–Eulerian “Two-fluid model” (TFM) approach was used to simulate dense gas-particle flows inside two different three-dimensional (3D) bubbling beds. The numerical code Multiphase Flow with Interphase eXchanges (MFIX) was used to perform all the 3D simulations. The results were validated against published experimental data. This manuscript-based thesis documents four different studies. The first study, Chapter 2, reports an in-depth investigation of two different models for the particle stress tensor in the elastic-inertial regime and assesses their ability to predict the hydrodynamics of a 3D cylindrical fluidized bed. Contours of inertial number, defined as the ratio of the inertial forces to the frictional forces, were used to visualize the flow properties. Analysis of the flow properties for a range of gas-particle regimes based on the inertial number enhances our insight into the flow behavior in such a complex system. Chapter 3 reports a comprehensive study to assess the effect of three different particle-wall boundary conditions (BCs) on the structural features of a dense gas-particle flow inside a 3D thin bubbling bed. Accordingly, the effect of each wall model on the velocity field, 3D bubble statistics, gas-pressure fluctuations, and particle resolved-scale Reynolds stress were investigated. Also, the dominant mixing regions inside the bed were identified in order to quantitatively describe the bed performance. Chapter 4 performs an in-depth systematic study that uses a particle energy budget analysis to investigate the dynamics of the bubbling bed discussed in Chapter 3. The budget analysis helps not only to quantify the relative importance of various terms contributing to the energy cascade, but also to identify the regions in the bed where most of the energy transfer takes place. Chapter 5 applies state-of-the-art post-processing methodologies, namely, the Proper Orthogonal Decom- position (POD) and the swirling strength criterion to the fluctuating particle flow fields predicted by the TFM of a bubbling bed to identify and analyze the dominant spatio-temporal patterns of the particulate phase. The variation of the POD temporal coefficients associated with the particle volume fraction fluctu- ation field suggested the existence of a low-dimensional attractor and irregular periodicity in the flow. The particle vortical motions were characterized by their flat structure. POD was used to obtain a reduced-order reconstruction of the particle velocity and volume fraction fields using a subset of eigenmodes. In summary, this thesis attempts to quantitatively describe some important features of bubbling beds dynamics that have received relatively little attention in the literature. To this end, it was observed that the use of inertial number, investigation of the energy cascade process, and studying particle vortical structures were helpful to quantitatively explore the underlying physics of bubbling beds. A major objective was also to identify a set of proper TFM parameters and particle-wall BC for high-fidelity simulation of bubbling beds

Treatment of Furcal Perforation of Primary Molars with ProRoot MTA versus Root MTA: A Laboratory Study

Introduction: Furcal perforations are one of the most challenging causes of endodontic failures. Several materials including MTA have been used for non surgical repair of these perforations. The aim of this study was to compare treatment outcome of furcal perforation treatment in primary molars using Root MTA and ProRoot MTA. Materials and Methods: This in vitro study was conducted on 54 primary first molars that were randomly divided into the two experimental groups of 24 teeth each and two control groups (n=6). After preparation of access cavities, perforations were made and the perforation areas were repaired using either Root or ProRoot MTAs. After staining and preparation of mesiodistal longitudinal sections, dye leakage was measured using a stereomicroscope. The data was analyzed by the Mann Whitney statistical test. Significant level was set at 0.05. Results: The data indicated that the dye leakage of ProRoot MTA is significantly lesser than Root MTA (P=0.001). Conclusion: ProRoot MTA showed good sealing ability in repairing furcal perforations of primary molars

Adhesive Layer Modeling in Concrete Beam Strengthened with FRP in an EFG Framework

The main challenging issue in concrete beam strengthening with FRP plates is the insurance of their joint performance. As been reported, the external load is mainly the primary reason for plate separation. The applied force corresponding to the moment of failure is called the debonding load. This load is of great importance. Besides, the determination of shear stress in the adhesive layer and tensile strain of the FRP plate is of the topics raised in empirical research. This study recommends using numerical methods to avoid the high cost of empirical studies. Here, failure concepts of the cohesive element are utilized. Horizontal and vertical springs are used to represent the properties of this element in which springs’ stiffness deputizes cohesive element characteristics and can be adjusted in three linear, nonlinear, and zero-stiffness steps. Springs’ stiffness is related to point displacements. So in an element-free Galerkin (EFG) method formulation, a set of springs, beam, and FRP is used to determine these displacements. Using these estimated nodes’ displacement values and utilizing springs’ stiffness, the unknown parameters inclouded debonding load, glue shear stress, and the tensile strain produced in the FRP plate can be determined. Whole calculations are coded in Matlab software. The results have been compared with the experimental outcomes of Kim and her colleagues’ work. These results indicate glue performance can be investigated through spring modeling based on the cohesive element in an EFG framework with adequate accuracy. So, the significant parts of an experimental setup can be avoided

Evaluation of Attention to the Pattern of Iranian Muslim Woman in Content of Religion and Life Books in Lower Secondary Schools

The present study has been compiled in order to analyze the content of the textbooks of Religion and Life in lower secondary school for attention to the formation of the Iranian Muslim Woman Pattern. The main purpose of this study is to investigate the content of religion and life textbooks in the lower secondary school on explaining the characteristics of the Iranian Muslim Woman Pattern for female students. To achieve this goal, content of this books analysis with William Romey method and then data gathered with researcher-made questionnaire and analyzed the results with using SPSS24 statistical software. The statistical sample of the study includes 306 female students and 19 teachers of religion and life lesson in lower secondary school in 9th district of Tehran who were studying and teaching in public schools. Findings indicate that there is a significant difference in the views of students and teachers regarding the content of this books. In such a way that the students had a more favorable view of the content of this books in reaching the pattern of the Iranian Muslim Woman, while from the teachers' point of view, the content of this books does not help us enough to reach the pattern of the Iranian Muslim Woman. The results of the quantitative analysis by the researchers indicate that the content of three books of religion and life in lower secondary school is primarily in the category of “monotheism and theism”, “religious ethics”, “rules” and then “women, family and society”. And the content of the books is lacking in terms of guiding students to reach the pattern of Iranian Muslim Women

A Histopathological Comparison of Pulpotomy with Sodium Hypochlorite and Formocresol

Introduction: Formocresol is widely used in primary teeth pulpotomies; however it is known to have several side effects. The purpose of this study was to assess pulpal changes of primary teeth pulps after pulpotomy with sodium hypochlorite and formocresol.Materials and Methods: In this randomized clinical trial, 22 teeth were selected. These teeth were randomly divided into 2 groups (formocresol; n=11 and sodium hypochlorite n=11). Two months post-operatively teeth were extracted and pulpal responses were evaluated by recording the degree of inflammation and extent of pulpal involvement. Dentinal bridge formation was also evaluated. Finally the data was analyzed with McNemartest. Results: The formocresol group demonstrated mild inflammation in 4 cases whereas sodium hypochlorite had mild inflammation in six cases. Severe inflammation was only found in 1 case in the sodium hypochlorite group, but it was present in 4 cases in the formocresol group. In sodium hypochlorite group there were no cases of necrosis, and dentinal bridge was found in 3 cases, unlike, the formocresol group which had necrosis but no dentinal bridge formation.  Conclusion: Based on the results of this study sodium hypochlorite may be a suitable solution for conducting pulpotomy in primary teeth.

Histopathological Evaluation of Primary Teeth after Pulp Capping with Calcium-Enriched Mixture and Bioactive Glass

Introduction: Direct pulp capping (DPC) is a conservative vital pulp therapy, which has some limitations in primary dentition. The aim of this study was to evaluate pulpal response of primary teeth after DPC with two biocompatible materials naming calcium-enriched mixture (CEM) and bioactive glass (BAG). Methods and Materials: This study was designed as a randomized clinical trial. After obtaining informed consent, 20 sound primary canines scheduled for orthodontic extraction, were selected. Following mechanical pulp exposure, the exposed site was capped with either CEM cement or BAG and then restored with amalgam. Teeth were extracted after two months and examined histopathologically. Parameters of hard tissue bridge (HTB) formation, its type and pulpal inflammation scores, were compared between the two groups. Data were analysed using the Fisher’s exact test. Results: All CEM specimens showed inflammation scores of 0 (less than 10%). In the BAG group, inflammation scores of 0, 1 and 2 were observed in 7, 2 and 1 specimens, respectively. Fisher’s exact test showed no significant differences (P>0.05). All CEM specimens (100%) formed HTB, which was irregular in all cases. In 7 of 10 teeth in BAG, HTB formed and was irregular. Fisher’s exact test revealed no significant differences between the two groups in this regard (P<0.001). Conclusion: Both CEM and BAG are suitable DPC agents in terms of HTB formation and pulp inflammation scores.Keywords: Bioactive Glass; Calcium-Enriched Mixture; Direct Pulp Capping; Primary Teet

Microleakage of CEM Cement and ProRoot MTA as Furcal Perforation Repair Materials in Primary Teeth

Introduction: Iatrogenic furcal perforation is a procedural accident in endodontic treatments of primary/permanent teeth; prognosis may be favorable if a complete seal with biomaterial is immediately established. The purpose of this in vitro study was to evaluate microleakage of calcium enriched mixture (CEM) cement and ProRoot mineral trioxide aggregate (MTA) for sealing primary molar furcal perforations. Materials and Methods: This study was conducted on 38 extracted human primary molars. Furcation perforations were created in the pulp chamber floor. The teeth were divided randomly in two experimental groups (n=17) and two positive and negative controls (n=2). Perforations were then repaired with biomaterials. After 72 h, the teeth were submerged in 2% fuchsin dye solution for 24h. The samples were sectioned longitudinally and evaluated for dye leakage. Data analyzed statistically using ANOVA test. Results: The negative and positive controls behaved as expected. Dye microleakage was observed in all experimental samples; however, there was no statistically significant difference between the microleakage of MTA (4.411±2.042 mm) and CEM (3.647±1.040 mm) groups (P>0.05). Conclusion: Based on the findings of this in vitro study, CEM and tooth-colored ProRoot MTA have similar sealing ability for furcal perforation repair of primary molar teeth

Comparative Evaluation of Clinical and Radiographic Success of MTA and Propolis in Pulpotomy of Primary Molars

Introduction: In this study, the results of using MTA and propolis in the pulpotomy of primary molar teeth are evaluated clinically and radiographically. Methods and Methods: A total of 25 healthy 4 to 8 year old children each having two carious primary molar teeth in one arch, based on inclusion criteria were selected. In each child, random assignment of the pulpotomy medicaments was done as follows: Group I, MTA in one side; Group II, Propolis in another side. All the pulpotomized teeth were evaluated at 3, 6, and 9 month clinically and radiographically, based on the scoring criteria system. Finally data was analyzed using GEE analysis. Results: Results showed that the effects of treatment and time on two scores were tested. Based on the results of this model, the chances of having clinical score 2, versus score 1 are about 2.7 times higher in MTA treatment than in propolis (P=0.001). Similarly, the chance of having a clinical score 2 relative to its one, at 9th month is approximately 6.8 times higher than the 3th month (P=0.000) and at 6th month is approximately 2.8 times higher than the 3th month (P=0.005). The chance of having higher scores of radiographies in treatment of propolis is approximately 6.5 times than that of MTA (P=0.000). Also, the chance of having higher scores of radiographic index at 6th month is approximately 5 times and at 9th month is approximately 27 times more than the 3th month (P=0.00). Conclusions: Based on the results of this experimental study, teeth treated with MTA showed more suitable clinical and radiographic results as compared to propolis at 9 months follow-up.Keywords: Mineral Trioxide Aggregate; Primary Teeth; Propolis; Pulpotom

Association of sleep quality with body fat mass and metabolic factors in Iranian adults in 2020

Background: Poor sleep quality is increasingly recognized as a risk factor for poor health outcomes such as obesity, diabetes and cardiovascular diseases. This study aimed to investigate the association between sleep quality, obesity and glycemic and lipid profiles in Iranian adults in 2020.Methods: 353 adults aged 18-60 years from community centers in Tehran municipality took apart in this cross-sectional study by convenience sampling. Information on anthropometric measurements, physical activity and dietary intake were collected. Sleep quality was assessed through Pittsburgh Sleep Quality Index. Body composition was measured through BIA method. Auto analyzer was used to measure fasting blood sugar (FBS)and lipid profile and ELISA method was used to measure Insulin.Results: The mean age was 42.92±11.34 and 39.16±14.18 for women and men, respectively. Each one score increase in total sleep quality, was related to 0.1 cm increase in waist circumference and 0.3 % increase in body fat percent (P <0.05). BMI had a positive correlation with subscales of “sleep disturbances” and “use of sleep medication” (P <0.001). Physical activity had a significant negative correlation with subscales of “subjective sleep quality” and “sleep latency”. FBS and triglyceride had positive correlation with “sleep latency” and “Subjective sleep quality”, respectively (P <0.05).Conclusion: Some determinants of sleep quality are associated with obesity, disorders of glucose and triglyceride metabolism and low level of physical activity.Keywords: Sleep quality; PSQI questionnaire; Body fat mass; Fasting Blood Sugar; Lipid profil