A nonlinear eigenvalue problem from thin-film flow

Steady solutions of a fourth-order partial differential equation modeling the spreading of a thin film including the effects of surface shear, gravity, and surface tension are considered. The resulting fourth-order ordinary differential equation is transformed into a canonical third-order ordinary differential equation. When transforming the problem into standard form the position of the contact line becomes an eigenvalue of the physical problem. Asymptotic and numerical solutions of the resulting eigenvalue problem are investigated. The eigenvalue formulation of the steady problem yields a maximum value of the contact angle of 63.4349^?.     

Applying artificial optimization methods for transformer model reduction of lumped parameter models

Detailed R-C-L-M models of power transformers, which are based on lumped parameters, are used extensively not only for transient analysis of power transformers to determine electrical stresses in windings, but also for studying transients in power systems. Models with few elements are generally more practicable for power system studies but at the expense of accuracy. The use of artificial methods to reduce an R-C-L-M model is the main contribution of this paper. Advantages of the suggested method include: (1) a reduced loss of accuracy compared with the original model and (2) the flexibility to choose the number of model elements to achieve the desired model depending on size and accuracy. The ability of three different artificial methods, genetic algorithm, particle swarm optimization, and bacterial foraging algorithm, to model reduction is evaluated using measurements on an actual 400 kV test object and the results are compared with those obtained by common analytical formulae.     

Equilibrium and kinetic studies of azo dye (Basic Red 18) adsorption onto montmorillonite: Numerical simulation and laboratory experiments

Adsorption of BR 18 dye onto nano-clay adsorbent was investigated. Nano-clay was characterized by using FTIR, SEM, TEM, XRD and BET analysis. The percent removal increased by increasing nano-clay dose, while pH and stirring speed had no significant effect on the adsorption rate. It was observed that the uptake of dye onto nano-clay initially increased rapidly, and then decreased slowly until the equilibrium was reached. The adsorption capacity rose with an increase in temperature. Moreover, the adsorption kinetics was very fast and followed a pseudo second-order. The intra-particle diffusion was observed to be the rate-controlling step. In addition, equilibrium data fitted well with the Langmuir adsorption model. This paper also presents a numerical simulation incorporating the second-order kinetic expression using COMSOL Multiphysics software. The numerical modelling results and the experimental data were in excellent agreement.     

Failure Analysis and Remedy Procedure for Cracking of Fuel Nozzles in a Gas Turbine

A common failure in a certain type of gas turbine, observed during the first periodic inspection, is radial cracks in the tip plate of gas fuel nozzles. Here, each gas turbine has 18 nozzles. In all nozzles and in all similar units, these cracks of lengths ranging from 1 mm to a maximum of 14.5 mm are observed. As prescribed by the manufacturer, the defective part must be removed and replaced by welding and machining of a new one. But this problem is repeated and observed in the next periodic visits, and in all units. Depending on the number of nozzles in each gas turbine unit and the number of units in total, these repairs are very expensive and time-consuming. In this paper, the failure is analyzed and the causes of the cracks in the nozzles are investigated. Studies show that the main causes of nozzle failure are residual stresses caused by welding and thermal stresses caused by the start-up and shutdown processes. According to results, a solution has been proposed to release these residual and thermal stresses. After the implementation of this method in 1998, no more failure has been reported by the repair team, which proves the effectiveness of this solution. Since this paper has been prepared based on technical reports from the years between 1996 and 1998, the cited references of this paper are these technical reports.     

Interpretation of viscoelastic behaviour of sweet cherries using rheological models

Viscoelastic behaviour of some commercial sweet cherry cultivars of Iran has been studied in current research. For this purpose, stress relaxation test was conducted on five cultivars of sweet cherry including Siah Mashhad, Abarde, Victoria, Dovom Ras and Tak Dane. Two common models (Generalised Maxwell model and Peleg model) were fitted to the experimental data. Both models could describe stress relaxation behaviour of cherries (R² = 0.99), but Generalised Maxwell model had lower root mean square error (RMSE) than Peleg model. Based on analysis of stress relaxation data using models constants, Tak Dane exhibited more solid properties, while Victoria showed less elastic behaviour than other cultivars. The results revealed that relaxation ratio (R%) and the area under the stress relaxation curve could be effective alternative to models with easier mathematical procedure.     

Single Molecule with Dual Function on Nanogold: Biofunctionalized Construct for In Vivo Photoacoustic Imaging and SERS Biosensing

Multimodal imaging provides complimentary information that is advantageous in studying both cellular and molecular mechanisms in vivo, which has tremendous potential in pre‐clinical research and clinical translational imaging. It is desirable to design probes for multimodal imaging that can be administered minimally but provides multifaceted information. Herein, we demonstrate the complementary dual functional ability of a nanoconstruct for molecular imaging in both photoacoustic (PA) and surface‐enhanced Raman scattering (SERS) biosensing simultaneously in tandem. To realize this, a group of NIR active organic molecules are designed and synthesized that possess both SERS and PA activity. Nanoconstructs realized by anchoring such molecules onto gold nanoparticles are demonstrated for targeting cancer biomarkers in vivo while providing complimentary information about biodistribution and targeting efficiency. In future, such nanoconstructs could play a major role in identifying surgical margins and also for disease monitoring in translational medicine.     

Cement take estimation using neural networks and statistical analysis in Bakhtiari and Karun 4 dam sites,in south west of Iran

Bulletin of Engineering Geology and the Environment - Water seepage from dam foundations causes reservoir water loss and raises the risk of dam instability. One method of remediation for...     

Application of cubic equation of state models in prediction of vapor–liquid equilibria for binary polyvinyl acetate/solvent solutions

The cubic equation of state (CEoS) is a powerful method for calculation of (vapor + liquid) equilibrium (VLE) in polymer solutions. Using CEoS for both the vapor and liquid phases allows one to calculate the non‐ideality of polymer solutions based on a single EoS approach. In this research, vapor–liquid equilibria calculations of polyvinyl acetate (PVAc)/solvent solutions were performed. In this approach, eight models containing PRSV and SRK CEoS separately combined with four mixing rules namely vdW1, vdW2, Wong–Sandler (WS), and Zhong–Masuoka (ZM) were applied to calculations of bubble point pressure. For the better prediction, the adjustable binary interaction parameters existing in any mixing rule were optimized. The results were very acceptable and satisfactory. Absolute average deviations (%AAD) between predicted results and experimental bubble point pressure data were calculated and presented. The capability of two cubic equations of state had a good agreement with experimental data and predict the correct type of phase behavior in all cases, but the performance of the PRSV + vdW2 was more reliable than the other models with 2.65% in AAD for total of solution systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40651.     

Simulation of gas–solid two-phase flow in the annulus of drilling well

This paper investigates the hydrodynamic behavior of gas–solid two-phase flow in the annular space of an air drilling well under different arrangements by using three-dimensional approach. Two-fluid model is used to solve the governing equations in the Eulerian–Eulerian framework. Effect of eccentricity and drill pipe rotation on the pressure drop, volume fraction and velocity profile are examined. The results are compared with available data in the literature and good agreement is found. The results show that the presence of solid particles in the annulus change the air velocity profile significantly and create two off-center peaks velocity close to the walls instead of one peak velocity in the middle. Eccentricity of drill pipe makes more accumulation of the cuttings in the smaller space of the annulus. Increasing the eccentricity increases pressure drop due to impact of particles with annulus wall and also particles collision with each other. Rotation of the drill pipe shifts maximum air velocity location toward smaller space of the annulus which results more uniform cutting distributions in the annulus and improvement in their transportations. Pressure drop in the annulus increases as eccentricity and rotation of drill pipe increase.     

Hydrodynamics and mass transfer study of aliphatic alcohols in airlift reactors

Gas holdup and gas–liquid mass transfer coefficient were considered in an external airlift reactor. Air was sparged through some aliphatic alcohols (methanol, ethanol, n-propanol, and n-butanol) with different concentrations (0–1%, v/v). It was observed that gas holdup and mass transfer coefficient increased with increasing the number of carbons in alcohols. Furthermore, an increment in alcohols concentration increased gas holdup and mass transfer coefficient. The same behavior was observed in external and internal loop airlift reactors although gas holdup and mass transfer coefficient values were less than those of internal airlift reactor. According to the experiments, two correlations for gas holdup and mass transfer were developed.