Uniform Stabilization of an Axially Moving Kirchhoff String by a Boundary Control of Memory Type

In this paper, we study the stabilization of solutions of an axially moving string of kirchhoff type by a viscoelastic boundary control. We prove that the dissipation produced by the viscoelastic term is sufficient to suppress the transversal vibrations that occur during the axial motion of the string, and we also show that the string displacement decays in an arbitrary rate. When comparing with immobile strings, we conclude that the movement of the string itself produces enough extra damping ensuring the stabilization.     

CFD modeling of a radiant tube heater

This paper reports experimental and Computational Fluid Dynamics (CFD) studies on combustion and radiation heat transfer from a real radiant tube heater. The temperature along the radiant tube as well as at different positions in a test room has been measured. A good agreement between the experimental and predicted results has been found. Based on this validation, the effect of excess air, presented by Air Factor (AF) on efficiency of heater has been studied, theoretically. Moreover, the effect of inlet air preheating on heater efficiency has been examined. The results show that the higher values of excess air can reduce the heater efficiency. The air preheating temperature caused positive effect on heater efficiency. In addition, the results show at higher preheating temperature the effect of AF value on heater efficiency is negligible.     

Electric load forecasting by using dynamic neural network

Electrical energy is fundamental for the wellbeing and for the economic development of any country. However, all countries must ensure access to essential resources and ensure the continuity of its supply. Due to the non-storable nature of electrical energy, the amount of consumed active power should always be equal the produced active power just to avoid power system frequency deviation problem. In order to keep the relationship production–consumption relation in compliance with different standards and to secure profitable operations of power system, electric load consumption must be predicted and controlled instantaneously. Several statistical and classical techniques are proposed in the literature but unfortunately all these methods are not accurate in a satisfactory manner. In this paper, a dynamic neural network is used for the prediction of daily power consumption. The suitability and the performance of the proposed approach is illustrated and verified with simulations on load data collected from French Transmission System Operator (RTE) website. The obtained results show that the accuracy and the efficiency are improved comparatively to conventional methods widely used in this field of research.     

Dynamic matrix control and generalized predictive control,comparison study with IMC-PID

Two of control techniques of the Model Predictive Control (MPC) methodology, which are Dynamic Matrix Control (DMC) and Generalized Predictive Control (GPC), with IMC-PID are disputed in this paper. The main characteristics of these important control techniques, widely used in industry, are presented. The optimum solution of the predicted control inputs and outputs are obtained by minimizing a cost function that contains the squared errors between the reference trajectory and predictions output on the prediction horizon. These controllers are applied on a Process Control Module (PCM), a system with pure time delay, and tested in the light of disturbance rejection and tracking performance for the constant and variable trajectory.     

CFD modeling of flow and heat transfer in a thermosyphon

In the present study a gas/liquid two-phase flow and the simultaneous evaporation and condensation phenomena in a thermosyphon was modeled. The volume of fluid (VOF) technique was used to model the interaction between these phases. Experiments in a thermosyphon were carried out at different operating conditions. The CFD predicted temperature profile in the thermosyphon was compared with experimental measurements and a good agreement was observed. It was concluded that CFD is a useful tool to model and explain the complex flow and heat transfer in a thermosyphon.     

Extended MHD Modelling with the Ten-Moment Equations

High-order moment fluid equations for simulation of plasmas are presented. The ten-moment equations are a two-fluid model in which time dependent equations are used to advance the pressure tensor. With the inclusion of the full pressure tensor Finite Larmor Radius (FLR) effects are captured. Further, Hall-effects are captured correctly by including the full electron momentum equation. Hall and FLR effects are important to understand stability of compact toroids like Field Reversed Configurations (FRCs) and also to detailed understanding of small scale instabilities in current carrying plasmas. The effects of collisions are discussed. Solutions to a Riemann problem for the ten-moment equations are presented. The ten-moment equations show complex dispersive solutions which come about from the source terms. The model is validated with the GEM fast magnetic reconnection challenge problem.     

Diluted Air Combustion and NOx Emission in a HiTAC Furnace

CFD modeling of NOx emission via N₂O-intermediate mechanism was developed to predict the NOx formation in an experimental furnace equipped with high temperature air combustion (HiTAC) system. The good agreement between the predicted and measured results illustrates the superiority of using a N₂O-intermediate model in prediction of NOx emission during low peak temperature, which happens in HiTAC systems. Moreover, the CFD and measured results show that the flame volume as well as NOx emission significantly depends on temperature and oxygen concentration. Lower NOx emission was experimentally and numerically obtained at lower input oxygen concentration conditions.     

Techno-economic analysis and modelling of a remote photovoltaic water pumping system in the desert of Tunisia

For estimating the performance of a photovoltaic (PV) water pumping system without battery storage, a simple algorithm has been developed. This simulation program uses the hourly global solar radiation, the hourly ambient temperature and the hourly wind speed as the input, moreover the characteristics of region (latitude, longitude, ground albedo) and characteristics of PV water pumping system (orientation, inclination, nominal PV module efficiency, NOCT, PV array area, PV temperature coefficient, miscellaneous power conditioning losses, miscellaneous PV array losses, temperature of reference, moto-pump efficiency and inverter efficiency). This work allows evaluating the economic interest of a remote PV water pumping systems in the desert of Southern Tunisia, which will have to satisfy an average daily volume of 45 m³ throughout the year compared to another very widespread energy system in the area, the diesel genset (DG), by using the method of the life-cycle cost (LCC). The cost per m³ of water was calculated for this system. It is found that the LCC for PV system is 0.500 TND/m³ and the LCC DG is 0.837 TND/m³. The present study indicates economic viability of PV water pumping systems in the desert of Tunisia.     

Thermal Conductivity of Silicate and Borate Glasses

Thermal conductivities of silicate and borate glasses were determined at 30°C by steady-state methods. From the experimental data, factors representing the contribution of individual oxides (on a weight-percent basis) were calculated by the least-squares method. The experimental thermal conductivities and those calculated from the factors obtained agree fairly well.