Convective heat transfer prediction in large rectangular cross-sectional area Earth-to-Air Heat Exchangers

An Earth-to-Air Heat Exchanger (ETAHE) uses the ground's thermal storage capacity to dampen ambient air temperature oscillations by delivering the outdoor air to the indoors through a horizontally buried duct. With their lower airflow resistance, large cross-sectional area ETAHEs have been found to be more energy efficient than the conventional small ones, especially when integrated in hybrid ventilation systems. However, the lack of available methods for determining the heat convection at the duct surfaces has made accurate energy simulation and proper system design overly difficult. In this study, numerical experiments using computational fluid dynamics (CFD) were conducted to investigate the airflow and thermal behavior in the large ducts. A two-layer turbulence model was used to ensure accuracy in resolving the flow information in the near-wall region, which is critical for predicting accurate heat convection. The modeling method was verified by comparing its results with measurements from literature. Parametric studies were conducted to identify the influential design and operation variables for the heat convection. Thirty numerical experimental setups designed with the Latin Hypercube Sampling method were simulated to prepare a database with six design parameters as the simulation inputs and average Nusselt numbers over the duct ceiling, wall, and floor as the outputs. Based on the database an artificial neural network (ANN) model was trained to build a mathematical relation between the design variables and the Nusselt numbers. The developed ANN model showed very accurate prediction when compared with test data.     

From rose petal to bone scaffolds: Using nature to fabricate osteon-like scaffolds for bone tissue engineering applications

In this study, rose petal was used to fabricate osteon-like scaffolds for bone tissue engineering applications. Rose petal was coupled with nanocrystalline forsterite colloid to mimic the lamellar structure of porous osteons. The microstructures on the surface of the petals were utilized as template for pores and lacuna spaces which are suitable for cell attachment. On the other hand, rolling the petals allowed us to form the osteon structure with haversian canal and lacuna spaces on the body of the samples. After trying different temperatures, the results showed that samples annealed at 1100 °C closely mimicked the lacuna spaces, haversian canal, and lamellar structures of osteons. These scaffolds had the pore diameter in the range of about 13–20 μm and presented good bioactivity and biocompatibility. It was found that red rose petal is a good candidate to be used as a template for designing scaffolds for bone tissue engineering applications.     

Antenna Patch Design Using a Photonic Crystal Substrate at a Frequency of 1.6 THz

Wireless Personal Communications - In this paper, the design of a macro strip patch antenna with a photonic crystal structure has been studied. The purpose of this study is to create a photonic...     

The use of a fuzzy multi-objective linear programming for solving a multi-objective single-machine scheduling problem

This paper develops a fuzzy multi-objective linear programming (FMOLP) model for solving a multi-objective single-machine scheduling problem. The proposed model attempts to minimize the total weighted tardiness and makespan simultaneously. In this problem, a proposed FMOLP method is applied with respect to the overall acceptable degree of the decision maker (DM) satisfaction. A number of numerical examples are solved to show the effectiveness of the proposed approach. The related results are compared with the Wang and Liang's approach. These computational results show that the proposed FMOLP model achieves lower objective functions and higher satisfaction degrees.     

Numerical Simulation of Steady Mixed Convection Around Two Heated Circular Cylinders in a Square Enclosure

In this paper, a numerical study has been carried out to investigate the steady-state mixed convection around two heated horizontal cylinders in a square two-dimensional enclosure. The cylinders are located at the middle of the enclosure height and the walls of the cavity are adiabatic. Streamlines and isotherms are produced and the effects of cylinder diameter, Reynolds number, and Richardson number on the heat transfer characteristics are numerically analyzed. The average Nusselt number over the surface of cylinders and average nondimensional temperature in the enclosure are also presented. The results show that both heat transfer rates from the heated cylinders and the dimensionless fluid temperature in the enclosure increase with increasing Richardson number and cylinder diameter. However, the trend of average Nusselt number and nondimensional temperature variation is completely opposite when Reynolds number increases. In addition, by increasing the cylinders diameter and Richardson number, the left cylinder is less affected by the inlet flow than right one.     

Stress analysis in a cracked strip

The stress fields in a strip containing climb and glide edge dislocations are obtained utilizing a complex Fourier transform. The dislocation solutions are then employed to perform integral equations for the analysis of a strip weakened by multiple cracks with any configuration and arrangement. The integral equations are solved numerically for the dislocation density on the cracked surfaces. The stress-intensity factors for two straight cracks compared favorably with the results rendered in literature. Three new examples are solved to demonstrate the applicability of the procedure.