Vertically Self-Gravitating ADAFs in the Presence of Toroidal Magnetic Field

Force due to the self-gravity of the disc in the vertical direction is considered to study its possible effects on the structure of a magnetized advection-dominated accretion disc. We present steady-sate self similar solutions for the dynamical structure of such a type of the accretion flows. Our solutions imply reduced thickness of the disc because of the self-gravity. It also imply that the thickness of the disc will increase by adding the magnetic field strength.Comment: Accepted for publication in Astrophysics and Space Science

Structure of advection-dominated accretion discs with outflows: the role of toroidal magnetic fields

The main aim of this article is to study the effect of toroidal magnetic fields on the structure of advection-dominated accretion flows (ADAFs) in the presence of turbulence viscosity and diffusivity due to viscosity and magnetic field respectively. We use the self-similar assumption in the radial direction to solve the magnetohydrodynamic equations for a hot accretion disc. We use spherical coordinates (r, theta, phi) to solve our equation. The toroidal component of magnetic field is considered and all three components of the velocity field v equivalent to (v(r),v(o), v(psi)) are present in our work. We reduce the equations to a set of differential equations in theta and apply a symmetric boundary condition at the equatorial plane of the disc. Our results indicate that the outflow region, where the radial velocity becomes positive at a certain inclination angle theta(0), always exists. The results illustrate that the stronger the magnetic field, the smaller the inclination angle theta(0) becomes. This means that a magnetized disc is thinner compared with a non-magnetized disc. According to the work of Jiao & Wu, we can define three regions. The first is called the inflow region, which starts from the disc mid-plane and extends to a certain inclination theta(0) where v(r)(theta(0)) = 0. In this region, the velocity has a negative value and the accretion material moves towards the central object. The outflow region, where v(r)(theta) > 0, is placed between theta(0) and the surface of the disc, theta(0) < theta < theta(s). In this area, the accretion flow moves away from the central object. The third region, which is located between the surface of the disc and the polar axis, is called the wind region. This area is very narrow and material is blown out from the surface in the form of wind. In this article, we consider two parameters to illustrate the magnetic field effects. These parameters are the ratio of gas pressure to magnetic pressure in the equatorial plane of the disc, beta(0), and also the magnetic diffusivity parameter, eta(0). Numerical calculations with our model have revealed that the toroidal component of magnetic field has a significant effect on the vertical structure of an accretion disc

The uplift load capacity of an enlarged base pier embedded in dry sand

The purpose of this research is to determine the capability of (and the factors which affect the performance of) an enlarged base pier in resisting uplift capacity. Experiments were conducted in the reinforced bin box of an enlarged base pier with a shaft diameter ranging from 30 to 50 mm, base diameters between 75 and 150 mm and base angles of a = 30°, a = 45° and a = 60°. Tests were conducted in both loose and dense sand packing. A failure mechanism was studied in a glass box for loose and dense sand packing. A dry sand with a unit weight of ?d = 14.80 kN/m3 and ?d = 17. 0 kN/m3 was achieved for loose and dense packing, respectively. Increasing the bell angle and shaft diameter would result in a decrease of the net uplift capacity and failure displacement. This is due to the reduction in the amount of the sand column above the bell that resists the uplift of the pile. Failure displacements at a constant base diameter generally increased considerably with the increase of the embedment ratio but decreased with the increment of the sand density. It is thus apparent that the shaft diameter, bell diameter and bell angle are geometric factors which, together with the embedment ratio and the sand density, should be taken into account in the design of enlarged base piers

A systematic review and meta-analysis of artificial neural network application in geotechnical engineering: theory and applications

Artificial neural network (ANN) aimed to simulate the behavior of the nervous system as well as the human brain. Neural network models are mathematical computing systems inspired by the biological neural network in which try to constitute animal brains. ANNs recently extended, presented, and applied by many research scholars in the area of geotechnical engineering. After a comprehensive review of the published studies, there is a shortage of classification of study and research regarding systematic literature review about these approaches. A review of the literature reveals that artificial neural networks is well established in modeling retaining walls deflection, excavation, soil behavior, earth retaining structures, site characterization, pile bearing capacity (both skin friction and end-bearing) prediction, settlement of structures, liquefaction assessment, slope stability, landslide susceptibility mapping, and classification of soils. Therefore, the present study aimed to provide a systematic review of methodologies and applications with recent ANN developments in the subject of geotechnical engineering. Regarding this, a major database of the web of science has been selected. Furthermore, meta-analysis and systematic method which called PRISMA has been used. In this regard, the selected papers were classified according to the technique and method used, the year of publication, the authors, journals and conference names, research objectives, results and findings, and lastly solution and modeling. The outcome of the presented review will contribute to the knowledge of civil and/or geotechnical designers/practitioners in managing information in order to solve most types of geotechnical engineering problems. The methods discussed here help the geotechnical practitioner to be familiar with the limitations and strengths of ANN compared with alternative conventional mathematical modeling methods

Effect of propolis intake on serum C-Reactive Protein (CRP) and Tumor Necrosis Factor-alpha (TNF-α) levels in adults: a systematic review and meta-analysis of clinical trials

Background Propolis is a natural Product and the antioxidant properties of Propolis appear to be principally responsible for its therapeutic effects. However, several studies have shown the positive effect of Propolis on the reduction the levels of inflammatory markers; some others have revealed non-significant impacts on them. Hence, the present systematic review and meta-analysis aimed to investigate the effects of Propolis intake on C-reactive protein (CRP) and tumor necrosis factor-alpha (TNF-α). Methods The systematic search was undertaken in scientific databases that included: PubMed, Embase, Scopus and Web of Science to find studies assessing the effects of Propolis on CRP and TNF-α up to December 2019. Standardized mean difference (SMD) and 95 % confidence intervals (CI) were pooled using a random-effects model. Potential publication bias was tested using Egger’s test. Results Six studies comprising 406 participants were included in the meta-analysis. Compared to controls, Propolis intake significantly reduced serum TNF-α (SMD = −0.48, 95 % CI = [−0.69, −0.26], P < 0.0001, I2 = 66.9 %) and CRP (SMD = −0.38, 95 % CI = [−0.68, −0.07], P = 0.01, I2 = 44.4 %) levels. No evidence of publication bias was found in the meta-analyses. Conclusion The present study concluded in the statistically and clinically reduction of serum CRP and TNF-α levels following Propolis intake