International Journal of Engineering
Volume:25 Issue: 2, Apr 2012

In this paper the dynamic response of tube-in-tube systems for tall building structures is investigated. Inner and outer tubes are modeled using equivalent continuous orthotropic membranes; in which, each tube is individually modeled by a cantilever box beam. By applying the compatibility conditions on deformation of the two tubes, the governing dynamic equations of the tube-in-tube structure and their associated boundary conditions are derived using the variational principle of virtual work. Appling differential calculus and some simplifications, and deriving non-trivial solution of these equations, a closed form solution is presented to obtain natural frequency and mode shape of tube-in-tube structures. A quick estimate of these quantities is of particular importance at the early stages of tube-in-tube systems design, prior to a full dynamic analysis. In order to illustrate the efficiency of the proposed model two symmetrical buildings are analyzed and comparisons are made with more accurate results obtained by 3D computer dynamic analysis and previous published methods.

This paper investigates the reliability characteristics of a complex system having nine subsystems arranged in the form of 3x3 matrix in which each row contains three subsystems. The configuration of the row is of the type 2-out-of-3: F. Each subsystem has n units connected in series. The system fails if any one row containing three subsystems fails. The considered system analyzed incorporating different types of power failure which also leads to failure of the system. With the help of Supplementary variable technique, Laplace transformations and copula methodology the transition state probabilities, asymptotic behavior, availability, reliability, M.T.T.F., busy period, sensitivity analysis and cost effectiveness of the system have been evaluated. At last some particular cases and numerical examples have been taken to describe the model.

The quality is typically modeled as the univariate or multivariate distribution of quality characteristic/s. In recent applications of statistical process control, quality profiles in which the relationship between a response and explanatory variable/s is captured and monitored are increasingly used to model the quality. Several techniques have been developed to enhance the speed of detecting changes in parameters of polynomial profiles. In this paper, we consider the effect of allocating the explanatory variable X in optimizing the performance of one of well-known methods referred to as EWMA4 method. An optimization model is built and solved using the genetic algorithm to find the optimal location of - values that minimizes the average of the run length distribution (ARL). The effect of location optimization is studied using a simulation study and results are compared with non-optimized strategies in terms of average run length criterion.

An Ant Colony Optimization (ACO) algorithm is proposed for optimal tree-structured natural gas distribution network. Design of pipelines, facilities, and equipment systems are necessary tasks to configure an optimal natural gas network. A mixed integer programming model is formulated to minimize the total cost in the network. The aim is to optimize pipe diameter sizes so that the location-allocation cost is minimized. Pipeline systems in natural gas network must be designed based on gas flow rate, length of pipe, gas maximum drop pressure allowance, and gas maximum velocity allowance. We use the information regarding gas flow rates and pipe diameter sizes considering gas pressure and velocity restrictions. We apply the Minimum Spanning Tree (MST) technique to obtain a network with minimum number of arcs, spanning all the nodes with no cycle. As a main contribution here, we present and use an ant colony optimization algorithm for solving the problem. The proposed method is applied to a real life situation. Our obtained results are compared with the ones obtained by an exact method. The results show that ACO is an effective approach for gas distribution network optimization. A case study in Mazandaran gas company in Iran is conducted to illustrate the validity and effectiveness of the proposed approach.

In this research Bi2O3 was doped with mixtures of 8, 10, 12 and 18 mol % of Y2O3 and Yb2O3 to stabilizing the δ-Bi2O3 phase using solid state reaction technique. Experimental samples were fabricated by isostatic pressing and sintering at 850 °C for 24 h. X-ray diffraction analysis detected cubic phase (δ-Bi2O3) as the sole stable crystalline phase in samples including 12 and 18 mol % of Y2O3 and Yb2O3. The tetragonal phase was also observed in samples with 8 and 10% mol additives. X-ray diffraction analyses on aged samples at 600 oC with 12 mol % additives revealed that the δ-Bi2O3 phase was transformed to the tetragonal polymorph form. Results of ionic conductivity measurements showed that samples with 12 mol % additives (88 mol % Bi2O3, 8 mol % Y2O3 and 4 mol % Yb2O3) had a higher ionic conductivity than the other samples.

In the present study, the effects of wavy wall’s properties on mixed convection heat transfer of Water-Al2O3 Nanofluid in a lid-driven cavity are investigated using the Lattice Boltzmann Method. The Boundary Fitting Method with second order accuracy at both velocity and temperature fields is used to simulate the curved boundaries in the LBM. The problem is investigated for different Richardson numbers (0.1-10), volume fractions of nanoparticles (0-0.05), curve amplitudes (0.05-0.25) and phase shifts of corrugated wall (0-270) when the Reynolds number is equal to 25. The results represent the effective role of corrugated wavy wall on rate of nanofluid heat transfer. It is observed that increasing of the wavy wall’s amplitude leads to a decrease of the average Nusselt number in high Richardson number. It is found that the increasing the volume fraction of nanoparticles enhances the rate of heat transfer. Results also show that adding nanoparticles to the base fluid has significant effects on both fluid flow and temperature field of the mixed convection, especially for low Richardson number.

This investigation deals with a software reliability model based on Markov process. For formulating the model, we define a random variable representing the cumulative number of faults successfully corrected upto a specified point of time. This model is based on the assumption that there are two types of software failures. Further the concepts of imperfect debugging environment and error generation phenomenon are taken into consideration. Transient analysis based on Laplace transform and matrix approach has been done to find the solution of the system of difference differential difference equations. Several performance indices for software reliability assessment are derived for this model. Numerical results with the help of Runge-Kutta Method show that the proposed framework incorporating both concepts of imperfect debugging phenomenon and error generation for two types of faults has a fairly accurate prediction capability

In this paper consider a two-fluid model consisting of a core region of suspension of all the erythrocytes (particles) in plasma (fluid) assumed to be a particle-fluid mixture and a peripheral layer of cell-free plasma (Newtonian fluid), has been proposed to represent blood flow in small diameter tubes with effects of magnetic. The analytical results obtained in the proposed model for effective viscosity, velocity profiles and flow rate have been evaluated numerically for various values of the parameters. Quantitative comparison has shown that present model suitability represents blood flow at hematocrit (≤ 40%) and in vessels up to 70μm in diameter. Using experimental values of the parameters, the flow rate for normal and diseased blood has been computed and compared with corresponding values obtained from a well known experimentally tested model in the literature.