Sharif Digital Repository

In this article, the problem of combined forced and natural convection in a vertical porous channel for both regular fluids and nanofluids has been solved by perturbation and numerical methods, taking into account the influences of viscous heating and inertial force. In this regard, various types of viscous dissipation models, including the Darcy model, the power of drag force model, and the clear fluid compatible model, were considered to account for viscous heating. In addition, the mass flux of nanoparticles was also considered in terms of Brownian and thermophoresis mechanisms. The velocity and temperature distributions of both the regular fluid and nanofluid and the Nusselt number... 

Liquid-liquid equilibrium (LLE) data, density, viscosity, and interfacial tension for the ternary system of toluene-acetic acid-water were measured at 298.15 K and 101.7 kPa. The Othmer-Tobias and the Hand correlations were used to check the reliability of the experimental tie-lines. Moreover, the distribution coefficient and the separation factor were explored. It was found from the experimental results that a maximum separation factor value happens at an acetic acid mass fraction of 0.02 in the organic phase. Density, viscosity, and interfacial tension were correlated using the appropriate correlations such that the predicted results have excellent agreement with the experimental data. The... 

Biomass residues due to their low bulk density typically require frequent transportation from biomass plantations in rural areas to conversion bio-energy power plants. This issue contrasts with environmental protection strategies, especially when power plants are facing different carbon reduction policies that enforce them to emit less than a given specific carbon amount. Although several researchers have investigated bio-energy supply chains concerning environmental policies, the majority of studies have been devoted to strategic decisions over a single planning period. This paper presents a multi-period bio-energy supply chain under carbon pricing (carbon tax) and carbon trading... 

Tow-mode theories explain that risky behaviors in young individuals may be the result of competition between an affective system (e.g., Empathizing system) and a deliberative system (e.g., Systemizing system). We aimed to investigate a total of 134 children aged 7-12. years old on scores of risky decision making and empathizing and systemizing measures. The primary analysis indicated that systemizers showed higher sensitivity to punishment than those in balanced or empathizer classes (F (2,130) = 14.8, p < 0.001). Furthermore empathizers indicated higher level of risk taking than balanced and empathizer children (F (2,130) = 5.027, p = 0.005). Providing further support for two-mode theories... 

Detection of rolling bearing faults by vibration analysis is an important part of condition monitoring programs. In this paper a new method for detection of bearing defects based on a new concept of local surface roughness, is proposed. When a defect in the bearing grows then roughness of the defective surface increases and measurement of the roughness can be a good indicator of the bearing defect. In this paper a method of indirectly measuring surface roughness by using vibration signal is introduced. Several attached examples including both numerically simulated signals and actual experimental data show the effectiveness of the new, easy-to-implement method  

In this study, the energy method has been used to develop a finite-element code for studying the effects of loose rotating discs on the rotor-bearing systems' response. A mathematical model of the loose disc has resulted in terms similar to unbalance and gyroscopic effects in the equation of motion of the system. Results of this study show that rotor response and beating phenomena are a function of measurement location, loose disc mass and inertia, ratio of rotating speed to the speed of loose disc, and clearance between the loose disc and shaft considering constant speed for loose disc and shaft. The developed finite-element model can numerically give the response of rotors with any number... 

During backward rub in a turbomachine, rotor is compelled by frictional forces into a severe precessional sliding motion inside stationary parts such as seals or journal bearings in opposite direction of rotor's rotation. Backward rub occurs with high frequency and high amplitude of vibration and can deteriorates rubbing surfaces just for few moments. This paper presents and investigates the idea of clearance profile alteration from annular form to non-annular 3-lobed form in order to affect the reverse rub's characteristics. For this purpose, a test setup consisting of a lightly damped rotor-stator system is designed and built in SUT's condition-monitoring laboratory for testing the... 

Today, turbomachinery designers are trying to attain zero clearances for optimizing performance and efficiency of machine by designing advanced compliant-segmented seals. This trend involves secondary issues such as rotor-to-stator contact interaction which is to be treated with more technical knowledge in rotordynamic design and condition monitoring programs. The aim of this paper is to gain insight into dynamic interaction between a flexible rotor and a set of compliant arc-shaped segments as stator system. Specifically, the unbalanced-induced forward rubbing response is investigated in tight clearance condition during resonance-passing situations. A Jeffcott rotor modeling is used for... 

This paper presents the experimental results of an investigation on the response and efficiency of floating pontoon type breakwaters. Random waves modeled by the Pierson Moskowits wave spectrum are used for various configurations of floating breakwaters. The experimental results are presented in graphs for the transmission coefficient as a function of incident wave length and height for breakwaters used in this study. The obtained results for the breakwaters of this study show that by increasing the wave period and length, the transmission coefficient increases, while increase in the mass and draft of the floating breakwater causes the transmission coefficient to reduce. © Shiraz University