This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be ...This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be divided into several operating zones on the basis of the marine current speed,the system control objectives are different for each zone.To deal with this issue,we develop a new control approach based on a linear quadratic regulator with variable generator torque.Our proposed approach enables the optimization of the rotational speed of the turbine,which maximizes the power extracted by the MCT and minimizes the transient loads on the drivetrain.The novelty of our study is the use of a real profile of marine current speed from the northern coasts of Morocco.The simulation results obtained using MATLAB Simulink indicate the effectiveness and robustness of the proposed control approach on the electrical and mechanical parameters with the variations of marine current speed.展开更多
In this work, the hydrogen storage properties of the Mg-based hydrides, i.e., Mgl-xMxH2 （M=Ti, V, Fe, 0≤ x ≤ 0.1）, are studied using the Korringa-Kohn-Rostoker （KKR） calculation with the coherent potential appro...In this work, the hydrogen storage properties of the Mg-based hydrides, i.e., Mgl-xMxH2 （M=Ti, V, Fe, 0≤ x ≤ 0.1）, are studied using the Korringa-Kohn-Rostoker （KKR） calculation with the coherent potential approximation （CPA） . In particular, the nature and concentrations of the alloying elements and their effects are studied. Moreover, the material＇s stability and hydrogen storage thermodynamic properties are discussed. In particular, we find that the stability and the temperature of desorption decrease without significantly affecting the storage capacities.展开更多
Doped/filled skutterudites are much studied materials due to their excellent thermoelectric performance.However,their synthesis and preparation is complicated.This work synthesized indium(In)doped cobalt triantimonide...Doped/filled skutterudites are much studied materials due to their excellent thermoelectric performance.However,their synthesis and preparation is complicated.This work synthesized indium(In)doped cobalt triantimonide(CoSb_(3))skutterudite thick films using a facile electrochemical deposition technique through chronoamperometric steps for 2 h.The nominal composition of In element is found in the range of 0.55e0.23 for a stoichiometric condition of In doped CoSb_(3)thick films.The early crystal growth of In doped films shows instantaneous nucleation and is controlled by the charge transfer process with diffusion coefficient,D of 10^(-5)cm^(2)/s.The incorporation of In into the interstitial sites of CoSb_(3)cages is evident from the lattice constant(a)expansion as observed in XRD.The optimum Seeback coefficient(S)of the 0.5 mmol In doped CoSb_(3)thick film is89.84 mV/K at 282 K,due to an increase in the carrier concentration(n~10^(20)cm^(-3)).The negative S is due to the electron donor behaviour of the In.Meanwhile,high electrical conductivity,s value(14.26 kS/m)contributes to a power factor(S2s)increment of 115.11 mW/(m$K2).The result shows a promising thermoelectric property of doped skutterudite synthesized by electrochemical deposition technique.展开更多
文摘This paper presents a contribution related to the control of nonlinear variable-speed marine current turbine(MCT)without pitch operating below the rated marine current speed.Given that the operation of the MCT can be divided into several operating zones on the basis of the marine current speed,the system control objectives are different for each zone.To deal with this issue,we develop a new control approach based on a linear quadratic regulator with variable generator torque.Our proposed approach enables the optimization of the rotational speed of the turbine,which maximizes the power extracted by the MCT and minimizes the transient loads on the drivetrain.The novelty of our study is the use of a real profile of marine current speed from the northern coasts of Morocco.The simulation results obtained using MATLAB Simulink indicate the effectiveness and robustness of the proposed control approach on the electrical and mechanical parameters with the variations of marine current speed.
文摘In this work, the hydrogen storage properties of the Mg-based hydrides, i.e., Mgl-xMxH2 （M=Ti, V, Fe, 0≤ x ≤ 0.1）, are studied using the Korringa-Kohn-Rostoker （KKR） calculation with the coherent potential approximation （CPA） . In particular, the nature and concentrations of the alloying elements and their effects are studied. Moreover, the material＇s stability and hydrogen storage thermodynamic properties are discussed. In particular, we find that the stability and the temperature of desorption decrease without significantly affecting the storage capacities.
基金supported by Universiti Malaya,Malaysia(GPF003A-2018).Part of this work is performed in Micro/Nanomachining Research Education Center(MNC)of Tohoku University,Japan under the Japan Student Services Organization(JASSO)scholarship.Nuur Syahidah Sabran would like to thank the Ministry of Education of Malaysia for the scholarship(MyPhD)awarded.
文摘Doped/filled skutterudites are much studied materials due to their excellent thermoelectric performance.However,their synthesis and preparation is complicated.This work synthesized indium(In)doped cobalt triantimonide(CoSb_(3))skutterudite thick films using a facile electrochemical deposition technique through chronoamperometric steps for 2 h.The nominal composition of In element is found in the range of 0.55e0.23 for a stoichiometric condition of In doped CoSb_(3)thick films.The early crystal growth of In doped films shows instantaneous nucleation and is controlled by the charge transfer process with diffusion coefficient,D of 10^(-5)cm^(2)/s.The incorporation of In into the interstitial sites of CoSb_(3)cages is evident from the lattice constant(a)expansion as observed in XRD.The optimum Seeback coefficient(S)of the 0.5 mmol In doped CoSb_(3)thick film is89.84 mV/K at 282 K,due to an increase in the carrier concentration(n~10^(20)cm^(-3)).The negative S is due to the electron donor behaviour of the In.Meanwhile,high electrical conductivity,s value(14.26 kS/m)contributes to a power factor(S2s)increment of 115.11 mW/(m$K2).The result shows a promising thermoelectric property of doped skutterudite synthesized by electrochemical deposition technique.
