Viscoelastic damping of beams

The composite damping characteristics of a viscoelastic sandwich beam are investigated. The sandwich consists of an elastic central layer coated on both sides with a viscoelastic material and two outer layers made out of the same material as the central layer. The composite beam is investigated for damping effectiveness. As in the work of DiTaranto and Kerwin, and also Mead, the energy dissipation due to the vibratory motion of the system is assumed to take place due to the shear deformation of the viscoelastic layer only. The assumption that the outer layers do not stretch or contract during bending, further enhances the composite system\u27s ability to dissipate energy in shear. The assumptions used lead to a fourth order differential equation of motion as opposed to the customary sixth order equation derived in the literature. A closed form solution to the problem of vibration of the composite beam under no load is obtained. A set of boundary conditions are derived using the energy method. The analytical solution is also shown to reduce to that of an equivalent elastic beam under the same conditions when the viscoelastic term is removed by setting the shear modulus equal to zero. When the same process is used on the composite beam characteristic equation, the result is identical to the frequency equation of an elastic beam

THE EFFECTS OF REDUCED GAMES FOR THE DEVELOPMENT OF THE QUALITY OF SPEED IN THE YOUNG ALGERIANS FOOTBALLERS

Physical quality is an important factor in the modern football and especially the speed, which we considered it necessary to investigate on the article "The effects of games reduced for the development of the quality of speed in the young soccer players of Algerians under the age 14yo in the club of me R. Mécheria", considering that the speed in soccer seems to be neglected in the training (formation) at the level of the young soccer players. Being essential in soccer, our research work recommends using the reduced games (sets) for improving speed qualities. So for our study, we chose the club of Mécheria; for that, we chose 20 players. The training program suggested realizing a positive development between both tests in the tests of speed in favour of the experimental group. This indicates the impact of the workout program in the evaluation of the level of the quality of speed in the (experimental) sample of the search (research). On the basis of all these results (profits) which were statistically significant, it is suggested the need of using the games (sets) reduced for the development of this quality.  Article visualizations

Maximum Power Point Tracking for Cascaded PV-Converter Modules Using Two-Stage Particle Swarm Optimization

The paper presents a novel two-stage particle swarm optimization (PSO) for the maximum power point tracking (MPPT) control of a PV system consisting of cascaded PV-converter modules, under partial shading conditions (PSCs). In this scheme, the grouping method of the shuffled frog leaping algorithm (SFLA) is incorporated with the basic PSO algorithm, ensuring fast and accurate searching of the global extremum. An adaptive speed factor is also introduced to improve its convergence speed. A PWM algorithm enabling permuted switching of the PV sources is applied. The method enables this PV system to achieve the maximum power generation for any number of PV and converter modules. Simulation studies of the proposed MPPT scheme are performed on a system having two chained PV buck-converter modules and a dc-ac H-bridge connected at its terminals for supplying an AC load. The results show that this type of PV system allows each module to achieve the maximum power generation according its illumination level without affecting the others, and the proposed new control method gives significantly higher power output compared with the conventional P&O and PSO methods

A new improved DTC of doubly fed induction machine using GA-based PI controller

This paper presents a new improved Direct Torque Control of doubly fed induction motor using PI controller tuned using genetic algorithm. The classical DTC control of DFIM is well known and is widely used due to its simplicity and easy implementation. However, the performances of conventional DTC are often characterized by high torque and flux ripples as well as variable switching frequency. To overcome the previous drawbacks of the classical DTC control, a new combined DTC-GA method using PI controller optimized by genetic algorithm is presented. The GA selects PI parameters that optimize the performances of conventional DTC. The PI parameters are optimized in offline mode where several values have been tested; then the best PI gains are used in online mode. The proposed DTC-GA method applied to DFIM has been validated using Matlab/Simulink environment. Many improvements related to torque and flux ripples overshoot and response time have been demonstrated. Which torque and flux ripple have been reduced more than 64.44% and 50 % respectively. The speed overshoot and torque overshoot have been reduced about 90% and 86% respectively. In addition, more details are presented and discussed in this paper. Keywords: Double Feed Induction Machine, Genetic algorithm, PI controller, Direct Torque Control, Reducing of torque and flux ripple

A New Adaptive Neuro-Fuzzy Inference System (ANFIS) Controller to Control the Power System equipped by Wind Turbine

This study proposes a new Adaptive Neuro-Fuzzy Inference System (ANFIS) controller to control the power system tuned by a wind turbine. The purpose of design is to improve the dynamical response of power systems after fault which the voltage controller has been improved. The effectiveness of the proposed approach is studied under different situations of three machines 9 bus power systems which the wind turbine is replaced by wind turbine equipped by ANFIS controller. The simulation results confirm that the tuning method is able to preserve optimal performances over wide range of disturbances. The results have demonstrated the high performances of the proposed technique in terms of low oscillation, ripple, rapidity and accuracy

A novel single-phase thirteen level inverter for photovoltaic application

This paper proposed a Single-Phase 13-level inverter with voltage control method using semiconductor power devices for photovoltaic systems. The multilevel voltage source inverters unique configuration allows them to make high voltages with low harmonics without use of transformers or series associated synchronized switching devices. The general role of the multilevel inverter is to synthesize a desired voltage from several levels of dc voltages for these reason multilevel inverters can simply provide the high power required of a large electric drives. The proposed inverter system gives superior voltage regulation, smooth results and efficiency compared to multi-level inverters. The inverter is capable of producing thirteen levels of output voltage levels (Vpv, 5Vpv/6, 4Vpv/6, 3Vpv/6, 2Vpv/6, Vpv/6, 0, -Vpv/6, -2Vpv/6, -3Vpv/6, -4Vpv/6, -5Vpv/6, -Vpv). The proposed inverter was demonstrated by using simulation of MATLAB/SIMULINK software