Energy and economic analysis of evaporative vacuum easy desalination system with brine tank

Please read abstract in the article.http://link.springer.com/journal/109732020-11-02hj2020Mechanical and Aeronautical Engineerin

Performance of cooperative amplify-and-forward protocols in vehicular ad-hoc networks

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Cooperative diversity is a technique where the diversity associated with spatially distributed users is exploited to overcome violent fading in wireless channels. In vehicle-to-vehicle (V2V) communication systems, where fading is severe due to mobility of both transmitters and receivers, cooperative diversity is an acceptable technique to enhance the performance of high-rate communications. In this paper, we investigate a single-relay half-duplex system and deal with the performance of three time-division-multiple-access (TDMA) amplify-and-forward protocols over double-Rayleigh fading channels. In a mobile-to-mobile (M2M) communication system, the communication channel is often modeled as a cascaded Rayleigh fading channel. We determine pairwise error probability (PEP) for the studied protocols, then we investigate optimal power allocation for these cooperative protocols, where the optimality is determined in terms of minimizing the bit error rate (BER) of the system. Based on the relay position and modulation type, optimization of power allocated to source and relay results performance improvement up to 3dB for Protocols I and II, and up to 7dB for Protocol III

Performance of cooperative amplify-and-forward protocols in vehicular ad-hoc networks

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Cooperative diversity is a technique where the diversity associated with spatially distributed users is exploited to overcome violent fading in wireless channels. In vehicle-to-vehicle (V2V) communication systems, where fading is severe due to mobility of both transmitters and receivers, cooperative diversity is an acceptable technique to enhance the performance of high-rate communications. In this paper, we investigate a single-relay half-duplex system and deal with the performance of three time-division-multiple-access (TDMA) amplify-and-forward protocols over double-Rayleigh fading channels. In a mobile-to-mobile (M2M) communication system, the communication channel is often modeled as a cascaded Rayleigh fading channel. We determine pairwise error probability (PEP) for the studied protocols, then we investigate optimal power allocation for these cooperative protocols, where the optimality is determined in terms of minimizing the bit error rate (BER) of the system. Based on the relay position and modulation type, optimization of power allocated to source and relay results performance improvement up to 3dB for Protocols I and II, and up to 7dB for Protocol III

An evaluation model of artificial neural network to predict stable width in gravel bed rivers

Regime width of alluvial channels is a vital problem in river morphology and channel design. Many equations are available in literature to predict regime width of alluvial rivers. In general, there are many approaches to estimate regime width; however, none of them is widely accepted at present. This is due to the fact that most hypotheses have to many constrains, which may lead to simplify governing conditions, in addition to lack of knowledge of some physical process associated with channel formation and maintenance. Intelligent models are a new approach to describe complex problems one of which is artificial neural networks. In this research, initially, gravel bed rivers database was used in bank full discharge condition to train various dimensional and non-dimensional neural network schemes with three and four variables as input data, respectively. Then, the same database was applied to fit regression analysis to estimate regime width; this led to drive dimensional and non-dimensional equations. Finally, dimensional and non-dimensional neural network models and regression equations were compared together based on 50% error bands with other data set. Results show that neural network can adequately estimate the regime width in gravel bed rivers and multilayer perceptron network with one hidden layer and 8 hidden neurons based on dimensional data set was selected as optimum network to predict regime width. A sensitivity analysis also shows that bank full discharge has a greater influence on regime width of gravel bed channels than the other independent parameters in dimensional scheme of neural network

Comparison of 2D triangular C-grid shallow water models

An ideal two-dimensional (2D) shallow water model should be able to simulate correctly various types of waves including pure gravity and inertia-gravity waves. In this paper, two different triangular C-grid methods are considered, and their dispersion of pure gravity waves, frequencies of inertia-gravity waves and geostrophic balance solutions are investigated. The proposed C-grid methods employ different spatial discretization schemes for coupling shallow water equations together with the various reconstruction techniques for tangential velocity estimation. The proposed reconstruction technique for the second method, which is analogous to a hexagonal C-grid scheme, is shown to be energy conservative and satisfies the geostrophic balance exactly while it supports the unphysical geostrophic modes for hexagonal C-grid. Because of the importance of the application of 2D shallow water models on fully unstructured grids, particular attention is also given to various types of isosceles triangles that may appear in such grids. For the gravity waves, the results of the phase speed ratio of the computed phase speeds over the analytical one are shown and compared. The non-dimensional frequencies of various modes for inertia-gravity waves are also investigated and compared in terms of being monotonic and isotropic respect to the continuous solution. The analyses demonstrate some advantages of the first method in phase speed behaviour for gravity waves and monotonicity of inertia-gravity dispersion. The results of the dispersion analysis are verified through a number of numerical tests. The first method, which is shown to have a better performance, examined through more numerical tests in presence of various source terms and results confirm its capability. 2017 Elsevier LtdThe authors acknowledge the support by NPRP grant # 4-935-2-354 .Scopu

Thermal analysis of porous fins enclosure with the comparison of analytical and numerical methods

In this study, heat transfer though a porous fin with rectangular cross section is investigated. The Darcy model is utilized to simulate heat transfer in this porous media. It is assumed that the fin is one-dimensional, homogenous, the flow is laminar, and the generated heat is a linear function of temperature. In this research, three different analytical methods are used to obtain the temperature distribution after deriving the heat transfer equation. In order to validate the obtained solution the collocation method (CM) is compared with the results by a numerical method, in order to validate the solutions, homotopy perturbation method (HPM) and homotopy analysis method (HAM) are employed. This problem is solved for the general case, and the output is obtained as a relationship for one iteration. The effects of various parameters including convection (Nc), porosity (Sh), Rayleigh number (Ra) are examined in this research.http://link.springer.com/journal/109732020-04-26hj2020Mechanical and Aeronautical Engineerin