When designing and constructing highways or more generally any super structures on dune sands type of soil, it is essential to make sure that the foundation soil is stable and provides good support to the applied loads. Dune sands soil are known to spread in huge areas throughout the kingdom of Saudi Arabia in which thousands of miles of new roads and highways are being constructed every year. Replacing such kind of weak soil is not an economically feasible alternative since it is very costly; besides, the replacement soil is not always available in nearby sites. This study discusses the possibility of dune sands soil stabilization using Portland cement as the stabilizing agent. Various ratios of cement content mixed with dune sands are used to examine the improvement of engineering properties of dune sands in terms of strength characteristics, and shear strength parameters. The results indicate that mixing dune sands with cement stabilizing agents would influence the engineering properties of treated soil. It is determined that the cement stabilization of dune sands improves the strength characteristics of the treated soil so that it becomes usable as a base material for roads construction and proper foundation material for other types of super structures. It was also determined that a cement content more than 9% may not probably cause any additional improvement for the stabilized soil. A suggested relationship is introduced to predict the values of initial tangent elastic modulus for such type of cement-treated dune sands.

This paper uses the perturbation method of multiple scales to obtain a closed form solution for the reflectance of rugate filters. The computational speed of the method is orders of magnitude higher than that of others. This allows studying the effect of filter’s profile modifications and gives insight on the effect of the parameters involved. In addition to that, the method could be used to synthesis the spectral response of rugate filters.

This paper proposes a Virtual Power Producer and Consumer Agent as a methodology aiming to optimize the integrated management of distributed renewable energy resources and to improve control Demand Side Management (DSM) and its aggregated loads. The paper presents a proposed method to coordinate the power generation technologies, the different load types, and the storage system. This method uses a framework based on data-mining techniques to characterize the customers load curve. The optimal power generation technologies dispatching of the smallest equipment of renewable energy resources and storage system is formulated as mixed-integer linear programming problem, due to the presence of the binary and continuous variables in the optimization problem. The model is coded in General Algebraic Modeling Systems (GAMS) and solved by High-performance mathematical programming solver for linear programming, mixed integer programming, and quadratic programming CPLEX solver. The application of methodology to a real case study in an isolated electrical service area in Portugal demonstrates the effectiveness of this method to solve the optimal isolated dispatch of the DC micro-grid renewable energy park. The solution has been converged in 0.09 seconds and 30 iterations.

In the present study, numerical and experimental investigations of heat and mass transfer characteristics of a plate type evaporator immersed in a still humid air environment with the presence of frost formation is carried out. In the numerical investigation, the suggested model considered the frost layer as a porous medium. The solution of a set of partial differential equations characterizing frost formation taking into consideration the variation of air ambient conditions during frost formation process and a diffusion term is preceded. In experimental investigation, the ambient air temperature is changed over a range of 20°C to 25°C and the relative humidity is varied from 41% to 56% while maintaining the plate type evaporator average temperature at nearly -10°C. Also, Rayleigh number was varied from 104 to 1.2x106 and the dimensionless time from zero to 1. The results show that the system coefficient of performance decreases within a range of (10% - 15%), the average Nusselt number varies within a range of (15% - 30%) and the average Sherwood number varies within a range of (25% - 40%).

A numerical investigation was undertaken to investigate heat transfer in three-dimensional laminar mixed convection heat transfer from longitudinal fins in a horizontal rectangular channel. Numerical simulations were conducted at different fin spacing, Reynolds number of 1500 and modified Rayleigh number of 4 x 107 and 2x 108 for fin to channel height ratios of 0.5 and 0.25. Validity of the modelling technique is verified by comparing computational results with corresponding experimental data from literatures. The numerical model is able to simulate the mixed convective flow through a rectangular channel subjected to constant heat flux heating boundary conditions. The predicted heat transfer coefficient and local Nusselt number distribution shows a good agreement with the experimental results and its improvement with higher channel height ratio at the expense of increased pressure drop across the longitudinal fins.