158 research outputs found
Recherches géomorphologiques sur le relief karstique des Causses de Martel et de Gramat, par Mohammed-Fayed Haj-Hassan. Thèse de Doctorat «nouveau régime», Université de Bordeaux III, soutenue le 7 janvier 1987 - Université de Bordeaux III, Institut de Géographie et d'études régionales, Laboratoire de Géographie physique appliquée
No full textChoppy Jacques, Reffay Annie. Recherches géomorphologiques sur le relief karstique des Causses de Martel et de Gramat, par Mohammed-Fayed Haj-Hassan. Thèse de Doctorat «nouveau régime», Université de Bordeaux III, soutenue le 7 janvier 1987 - Université de Bordeaux III, Institut de Géographie et d'études régionales, Laboratoire de Géographie physique appliquée. In: Karstologia : revue de karstologie et de spéléologie physique, n°10, 2e semestre 1987. La table ronde franco-polonaise (1-8 juin 1987) p. 64
Biochemical assessments of thyroid profile, serum 25-hydroxycholecalciferol and cluster of differentiation 5 expression levels among children with autism
No full textTarek Desoky,1 Mohammed H Hassan,2 Hanan M Fayed,3 Hala M Sakhr4 1Department of Neuropsychiatry, 2Department of Medical Biochemistry and Molecular Biology, 3Department of Clinical and Chemical Pathology, 4Department of Pediatrics, Qena Faculty of Medicine, Qena University Hospitals, South Valley University, Qena, Egypt Background: The exact pathogenesis of autism is still unknown. Both thyroid hormones and 25(OH)D are important for brain development, in addition to CD5; all have immunomodulatory actions by which their dysregulation may have a potential role in autism pathogenesis.Objectives: The objectives of this study were to assess the thyroid profile, serum 25(OH)D levels and CD5 expression levels among autistic patients and to find out the correlations between the measured biomarkers with each other on one side and with the disease severity on the other side.Patients and methods: This cross-sectional case–control study has been conducted on 60 children with autism and 40 controls, recruited from Qena Governorate, Upper Egypt. Childhood Autism Rating Scale (CARS) score was used to assess the included patients. Biochemical assays of thyroid function in the form of free triiodothyronine (FT3), free tetraiodothyronine (FT4), thyroid-stimulating hormone (TSH) and 25(OH)D were done using commercially available enzyme-linked immunosorbent assay (ELISA) kits, while CD5 expression levels were measured using flow cytometry (FCM) analysis for all the included patients and controls.Results: The overall measurement results show significant higher mean serum TSH levels, mean CD5 expression levels with significant lower mean serum 25(OH)D levels among autistic children when compared with the control group (p<0.05 for all). Significant negative correlations between CD5 with FT3, FT4 and 25(OH)D were observed. CARS score showed significant negative correlations with both FT3 and 25(OH)D, while it was positively correlated with CD5 in a significant manner (p<0.05 for all).Conclusion: Elevated CD5 expression and decreased 25(OH)D stores could play a potential role in the pathogenesis of autism via their immune-modulator actions. High TSH serum levels among autistic children, although within the physiological range, reflect the presence of thyroid dysfunction among such children, which needs further assessment. Keywords: thyroid hormones, 25(OH)D, CD5, autism, flow cytometry, ELISA 
Stresses at the Intersection of Sphere and Cylinder by a Variant Finite-Difference Method
No full textThe aim of this paper is the determination of stresses at the intersection of cylinder with the sphere using a variant finite-difference technique. Mesh lines are drawn on the cross section of the body which are roughly parallel and perpendicular to the boundary, and which the author calls natural meshes. Discretization of the governing differential equations must be carried out to reduce the continuous problem to a discrete problem, this discretization converts the problem into a set of linear simultaneous equations for the functions under consideration at a set of mesh points. The derivatives to be inserted in the governing equations and boundary conditions are found by writing Taylor series expansions at a point in terms of five neighboring points in the case where the point is an internal point (four for a boundary point). By an elimination process the derivatives can be eliminated for each point, and we are left with the unknown functions only.</jats:p
Particles and Bubbles Collisions Frequency in Homogeneous Turbulence and Applications to Minerals Flotation Machines
No full textThe collisions frequency of dispersed phases (particles, droplets, bubbles) in a turbulent carrier phase is a fundamental quantity that is needed for modeling multiphase flows with applications to chemical processes, minerals flotation, food science, and many other industries.
In this dissertation, numerical simulations are performed to determine collisions frequency of bi-dispersed particles (solid particles and bubbles) in homogeneous isotropic turbulence. Both direct numerical simulations (DNS) and Large Eddy simulations (LES) are conducted to determine velocity fluctuations of the carrier phase. The DNS results are used to validate existing theoretical models as well as the LES results. The dissertation also presents a CFD-based flotation model for predicting the pulp recovery rate in froth flotation machines.
In the direct numerical simulations work, particles and bubbles suspended in homogeneous isotropic turbulence are tracked and their collisions frequency is determined as a function of particle Stokes number. The effects of the dispersed phases on the carrier phase are neglected. Particles and bubbles of sizes on the order of Kolmogorov length scale are treated as point masses. Equations of motion of dispersed phases are integrated simultaneously with the equations of the carrier phase using the same time stepping scheme. In addition to Stokes drag, the pressure gradient in the carrier phase and added-mass forces are also included. The collision model used here allows overlap of particles and bubbles. Collisions kernel, radial relative velocity, and radial distribution function found by DNS are compared to theoretical models over a range of particle Stokes number. In general, good agreement between DNS and recent theoretical models is obtained for radial relative velocity for both particle-particle and particle-bubble collisions. The DNS results show that around Stokes number of unity particles of the same group undergo expected preferential concentration while particles and bubbles are segregated. The segregation behavior of particles and bubbles leads to a radial distribution function that is less than one. Existing theoretical models do not account for effects of this segregation behavior of particles and bubbles on the radial distribution function.
In the large-eddy simulations efforts, the dissertation addresses the importance of the subgrid fluctuations on the collisions frequency and investigates techniques for predicting those fluctuations. The cases studied are of particles-particles and particles-bubbles collisions at Reynolds number Reλ = 96. A study is conducted first by neglecting the effects of subgrid velocity fluctuations on particles and bubbles motions. It is found that around Stokes number of unity solid particles of the same group undergo the well known preferential concentration as observed in the DNS. Effects of pressure gradient on the particles are negligible due to their small sizes. Bubbles as a low inertia particles are very sensitive to subgrid velocity and acceleration fields where the effects of pressure gradient in the carrier phase are dominant. However, particle-bubble radial distribution functions from LES are not as low as that from DNS. To account for the effects of subgrid field on the dispersion of particles and bubbles, a new multifractal methodology has been developed to construct a subgrid vorticity field from the resolved vorticity field in frame work of LES. A Poisson's solver is used to obtain the subgrid velocity field from the subgrid vorticity field. Accounting for the subgrid velocity fluctuations (but neglecting pressure gradient) produced minor changes in the radial distribution function for particle-particle and particle-bubble collisions. We conclude from this study that for accurate particle tracking in LES the subgrid velocity fluctuations must be dynamically realizable field (temporally and spatially correlated with the large scale motion). Adding random SGS velocity fluctuations is not enough to capture the correct radial distribution functions of dispersed phases especially for bubbles-particles collisions where the pressure gradient term ( or acceleration Duf′/Dt) is responsible for particle-bubble segregation around particle Stokes number near one.
A CFD-based model for minerals flotation machines has been developed in this dissertation. The objective of flotation models is to predict the recovery rate of minerals from a flotation cell. The developed model advances the state-of-the-art of pulp recovery rate prediction by incorporating validated theoretical collisions frequency models and detailed hydrodynamics from two-phase flow simulations. Spatial distributions of dissipation rate and air volume fraction are determined by the two-phase hydrodynamic simulations. Knowing these parameters throughout the machine is essential in understanding the effectiveness of different components of flotation machine (rotor, stator or disperser, jets) on the flotation efficiency. The developed model not only predicts the average pulp recovery rate but also it indicates regions of high/low recovery rates. The CFD-based flotation model presented here can be used to determine the dependence of recovery rate constant at any locality within the pulp based on particle diameter, particle specfic gravity, contact angle, and surface tension.Ph. D
Numerical Simulations of Two-Phase Flow in a Self-Aerated Flotation Machine and Kinetics Modeling
No full textA new boundary condition treatment has been devised for two-phase flow numerical simulations in a self-aerated minerals flotation machine and applied to a Wemco 0.8 m3 pilot cell. Airflow rate is not specified a priori but is predicted by the simulations as well as power consumption. Time-dependent simulations of two-phase flow in flotation machines are essential to understanding flow behavior and physics in self-aerated machines such as the Wemco machines. In this paper, simulations have been conducted for three different uniform bubble sizes (db = 0.5, 0.7 and 1.0 mm) to study the effects of bubble size on air holdup and hydrodynamics in Wemco pilot cells. Moreover, a computational fluid dynamics (CFD)-based flotation model has been developed to predict the pulp recovery rate of minerals from a flotation cell for different bubble sizes, different particle sizes and particle size distribution. The model uses a first-order rate equation, where models for probabilities of collision, adhesion and stabilization and collisions frequency estimated by Zaitchik-2010 model are used for the calculation of rate constant. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) determined by the two-phase simulations are the input for the flotation kinetics model. The average pulp recovery rate has been calculated locally for different uniform bubble and particle diameters. The CFD-based flotation kinetics model is also used to predict pulp recovery rate in the presence of particle size distribution. Particle number density pdf and the data generated for single particle size are used to compute the recovery rate for a specific mean particle diameter. Our computational model gives a figure of merit for the recovery rate of a flotation machine, and as such can be used to assess incremental design improvements as well as design of new machines
Collisions Frequency of Particles and Bubbles Suspended in Homogenous Isotropic Turbulence
No full textPRIMARY SCIENCE TEACHERS' PERCEPTIONS TOWARDS STEM EDUCATION IN QATAR AND CHALLENGES OF ITS IMPLEMENTATION
No full textUnderstanding teachers' perceptions of STEM education is crucial to ensure the quality of teaching and learning provided for the students in the classrooms. This study aimed at investigating science teachers’ perceptions towards STEM education in primary public schools in the State of Qatar, in terms of four domains: teachers' knowledge, STEM teaching requirements, impact on students' outcomes, and the perceived challenges of implementation. This study followed a sequential explanatory mixed-method approach. Quantitative data was collected by surveying (148) science teachers, while qualitative data was obtained using four focus groups. Results highlighted the need to increase teachers’ understanding and knowledge of STEM disciplines and their approaches to integration. Furthermore, various challenges were reported, including insufficient professional development, changing teachers’ beliefs, lack of an integrated curriculum and lack of time. Additionally, results indicated that there were no significant differences in teachers’ perceptions with regard to gender or educational background, while there is differences in relation to teaching experience in the challenges domain. Moreover, results indicated the significant difference in teachers’ perceptions related to the received STEM professional development programs and STEM teaching experience in the first three domains. Based on the results, the study recommended that there is a need to develop STEM integrated curriculum and to provide STEM professional development programs
The smart safety Shoe: A new type of safety shoe that helps prevent lower back problems and opens the door to a new era of preventive safety footwear
No full textThe smart safety shoe is a concept safety shoe that has been in development as a collaboration between Allshoes safety footwear and TU Delft since 2020. Previous work on the shoe consisted of 2 graduation projects and a student course which resulted in the current concept of an injury preventing safety shoe focused on preventing lower back pain in the logistics sector. The shoe works by using pressure sensors and machine learning to detect unhealthy postures while its wearer has to lift various objects as part of their job (manual handling). This project focused on further developing the concept of the smart safety shoe and evaluating the prototypes from the last two projects. Previous projects provided two different pressure sensor layouts which are evaluated using a high-end pressure sensing insole. A manual handling experiment was set up and performed on 16 different participants from a lab and a warehouse. During testing participants were instructed to perform manual handling while holding 5 different postures. It was possible to train a machine learning model using the various pressure profiles gathered from the experiment. Using this model, the two sensor layouts from the previous projects were evaluated for their ability to detect the 5 predetermined postures. It was found that the latest layout outperformed the previous one and was therefore selected for further development of the smart safety shoe.The integration of various other sensors and actuators was evaluated, and the core functions of the shoe were defined with an indication towards future improvements of the smart safety shoe.The shoe has now been publicly presented by Allshoes and the goal is to have the product on the market by the end of 2025. In order for this to happen further prototyping is needed to create an improved machine learning model based on the selected sensor layout. The shoe shows promising responses from current safety shoe clients. When finally launched it will be part of a new type of protective equipment focused on prevention.Design for Interactio
Lectin Histochemistry of the Glandular Part of the Gastric Mucosa of the One Humped Camel (Camelus dromedaries).
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