Structure of Advection-Dominated Accretion Disks with Outflows: Role of Toroidal Magnetic Field

The main aim of this paper is studying the effect of toroidal magnetic field on the structure of Advection-Dominated Accretion Flows (ADAF) in the presence of the turbulence viscosity and diffusivity due to viscosity and magnetic field respectively. We use self-similar assumption in radial direction to solve the magnetohydrodynamic (MHD) equations for hot accretion disk. We use spherical coordinate $(r, \theta, \varphi)$ to solve our equation. The toroidal component of magnetic field is considered and all three components of the velocity field $\mathbf{v}\equiv (v_{r}, v_{\theta}, v_{\varphi})$ are present in our work. We reduce the equations to a set of differential equations about $\theta$ and apply the symmetric boundary condition at the equatorial plane of the disk. Our results indicate that the outflow region, where the redial velocity becomes positive in a certain inclination angle $\theta_{0}$, always exist. The results represent that the stronger the magnetic field, the smaller the inclination angle, $\theta_{0}$ becomes. It means that a magnetized disk is thinner compared to a non-magnetized disk. According to the work by \citealt{jw}, we can define three regions. The first one is called inflow region, which starts from the disk midplane 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 toward the central object. The outflow region, where $v_{r}(\theta) > 0$, is placed between $\theta_{0}$ and surface of the disk, $\theta_{0} < \theta < \theta_{s}$. In this area, the accretion flow moves away from the central object. The third region, which is located between the surface of the disk and the polar axis, is called wind region.Comment: To appear in MNRA

A Family of Interleaved High Step-Up DC-DC Converters by Integrating a Voltage Multiplier and an Active Clamp Circuits

A family of interleaved current-fed high step-up dc-dc converters are introduced and analyzed here by combining a voltage multiplier (VM) and an active clamp circuit for high-voltage high-power applications. Low input currents and output voltages ripples values and high voltage-gains characteristics of these converters make them suitable for lots of dc-dc applications. All power devices operate entirely under soft switching conditions, even when wide load and input voltage variations are applied. Thus, they can be designed at high switching frequencies to reduce passive components sizes to achieve high-power density, one of the main targets of the power electronics researches. Also, their input and output ports common ground simplifies the gate-drives and control circuits. To verify the given analyses and simulations, a 120-320 V to 1 kV, 50-1300 W three-stage two-leg prototype converter has been implemented at 100 kHz. Based on the experimental results, maximum efficiency of 96.5% is achieved.Comment: 14 pages, 15 figure

Efecto de diferntes parámetros de represas heterogeneas en el factor de seguridad usando redes neuronales. Caso de estudio. Represa Marvak

The drainage system is used to guide the flow of water in the earth dams. Construction of drainage in the dam body to collect and direct the drainage formed in the dam body to keep the slope dry and prevent the increase of pore water pressure in the body. One of the main goals of the designers is to find the minimum factor of safety and, consequently, reduce the cost of construction. In this study, the Marvak dam is modeled with the actual characteristics of the materials in the Geostudio software, and with the change in the dimensions of the drain, the material and the slope of the dam body, the minimum Factor of safety of the dam is obtained. In order to predict the minimum Factor of safety, a two-layer neural network has been used. With the training of the neural network based on the data obtained from heterogeneous dams, a minimum Factor of safety has been extracted for optimization of drainage. Finally, it was determined that the internal friction angle of the body material and the slope of the dam have the greatest effect on the dam factor of safety.El sistema de drenaje se utiliza para guiar el flujo de agua en las presas de tierra. Construcción de drenaje en el cuerpo de la presa para recoger y dirigir el drenaje formado en el cuerpo de la presa para mantener la pendiente seca y evitar el aumento de la presión de agua de los poros en el cuerpo. Uno de los principales objetivos de los diseñadores es encontrar el factor mínimo de seguridad y, en consecuencia, reducir el costo de la construcción. En este estudio, la presa Marvak se modela con las características reales de los materiales en el software Geostudio, y con el cambio en las dimensiones del drenaje, el material y la pendiente del cuerpo de la presa, el factor mínimo de seguridad de la presa es obtenido. Para predecir el Factor mínimo de seguridad, se ha utilizado una red neuronal de dos capas. Con el entrenamiento de la red neuronal basado&nbsp;en los datos obtenidos de represas heterogéneas, se extrajo un Factor mínimo de seguridad para la optimización del drenaje. Finalmente, se determinó que el ángulo de fricción interna del material del cuerpo y la pendiente de la presa tienen el mayor efecto sobre el factor de seguridad de la presa

Bitumen and Its Modifier for Use in Pavement Engineering

This chapter focuses on bitumen specifically. This chapter consists of several parts that can be mentioned, including the history of the appearance of bitumen and the types of constituent elements, as well as its mechanical properties and chemical structure and its thermal sensitivity. In all parts, the effects of bitumen on asphalt are discussed. In the following sections, the bitumen modification mechanism, polymer modifiers, and their behavior on the bitumen resistance to asphalt failures are also discussed. This chapter is very suitable for students and researchers interested in improving polymerization asphalt and bitumen and will help them to carry out research and concepts