The hydrogenation/dehydrogenation thermodynamic properties of a Mg 50 Ni 50 alloy synthesized by mechanical alloying is measured by electrochemical method, and serious hydrogenation/dehydrogenation hysteresis...The hydrogenation/dehydrogenation thermodynamic properties of a Mg 50 Ni 50 alloy synthesized by mechanical alloying is measured by electrochemical method, and serious hydrogenation/dehydrogenation hysteresis characteristic was observed. The electrochemical impedance of the electrode discharge reaction of this electrode is mainly composed of charge transfer resistance R ct , hydrogen diffusion impedance Z w and surface H adsorption/desorption capacitance C ads . Electrochemical impedance analysis reveals that R ct is about one degree larger than the other impedance component. Thus it is reasonable to believe that discharge reaction is mainly dominated by the charge transfer reaction at the alloy surface, and the discharge hysteresis phenomenon is related to the factors that effect the charge transfer reaction. Hydroxides are present in the alloy surface before and after charging/discharging. These hydroxides would decrease the conductivity of the alloy surface and hinder the charge transfer process.展开更多
In the past,arms used in the fields of industry and robotics have been designed not to vibrate by increasing their mass and stiffness.The weight of arms has tended to be reduced to improve speed of operation,and decre...In the past,arms used in the fields of industry and robotics have been designed not to vibrate by increasing their mass and stiffness.The weight of arms has tended to be reduced to improve speed of operation,and decrease the cost of their production.Since the weight saving makes the arms lose their stiffness and therefore vibrate more easily,the vibration suppression control is needed for realizing the above purpose.Incidentally,the use of various smart materials in actuators has grown.In particular,a shape memory alloy(SMA)is applied widely and has several advantages:light weight,large displacement by temperature change,and large force to mass ratio.However,the SMA actuators possess hysteresis nonlinearity between their own temperature and displacement obtained by the temperature.The hysteretic behavior of the SMA actuators affects their control performance.In previous research,an operator-based control system including a hysteresis compensator has been proposed.The vibration of a flexible arm is dealt with as the controlled object;one end of the arm is clamped and the other end is free.The effectiveness of the hysteresis compensator has been confirmed by simulations and experiments.Nevertheless,the feedback signal of the previous designed system has increased exponentially.It is difficult to use the system in the long-term because of the phenomenon.Additionally,the SMA actuator generates and radiates heat because electric current passing through the SMA actuator provides heat,and strain on the SMA actuator is generated.With long-time use of the SMA actuator,the environmental temperature around the SMA actuator varies through radiation of the heat.There exists a risk that the ambient temperature change dealt with as disturbance affects the temperature and strain of the SMA actuator.In this research,a design method of the operator-based control system is proposed considering the long-term use of the system.In the method,the hysteresis characteristics of the SMA actuator and the temperature change around the actuator are considered.The effectiveness of the proposed method is verified by simulations and experiments.展开更多
To improve the logic stability of conventional multi-valued logic（MVL） circuits designed with a GaNbased resonate tunneling diode（RTD）, we proposed a GaN/InGaN/AlGaN multi-quantum well（MQW） RTD. The proposed RTD...To improve the logic stability of conventional multi-valued logic（MVL） circuits designed with a GaNbased resonate tunneling diode（RTD）, we proposed a GaN/InGaN/AlGaN multi-quantum well（MQW） RTD. The proposed RTD was simulated through solving the coupled Schrodinger and Poisson equations in the numerical non-equilibrium Green＇s function（NEGF） method on the TCAD platform. The proposed RTD was grown layer by layer in epitaxial technologies. Simulated results indicate that its current-voltage characteristic appears to have a wider total negative differential resistance region than those of conventional ones and an obvious hysteresis loop at room temperature. To increase the Al composite of AIGaN barrier layers properly results in increasing of both the total negative differential resistance region width and the hysteresis loop width, which is helpful to improve the logic stability of MVL circuits. Moreover, the complement resonate tunneling transistor pair consisted of the proposed RTDs or the proposed RTD and enhanced mode HEMT controlled RTD8 is capable of generating versatile MVL modes at different supply voltages less than 3.3 V, which is very attractive for implementing more complex MVL function digital integrated circuits and systems with less devices, super high speed linear or nonlinear ADC and voltage sensors with a built-in super high speed ADC function.展开更多
文摘The hydrogenation/dehydrogenation thermodynamic properties of a Mg 50 Ni 50 alloy synthesized by mechanical alloying is measured by electrochemical method, and serious hydrogenation/dehydrogenation hysteresis characteristic was observed. The electrochemical impedance of the electrode discharge reaction of this electrode is mainly composed of charge transfer resistance R ct , hydrogen diffusion impedance Z w and surface H adsorption/desorption capacitance C ads . Electrochemical impedance analysis reveals that R ct is about one degree larger than the other impedance component. Thus it is reasonable to believe that discharge reaction is mainly dominated by the charge transfer reaction at the alloy surface, and the discharge hysteresis phenomenon is related to the factors that effect the charge transfer reaction. Hydroxides are present in the alloy surface before and after charging/discharging. These hydroxides would decrease the conductivity of the alloy surface and hinder the charge transfer process.
文摘In the past,arms used in the fields of industry and robotics have been designed not to vibrate by increasing their mass and stiffness.The weight of arms has tended to be reduced to improve speed of operation,and decrease the cost of their production.Since the weight saving makes the arms lose their stiffness and therefore vibrate more easily,the vibration suppression control is needed for realizing the above purpose.Incidentally,the use of various smart materials in actuators has grown.In particular,a shape memory alloy(SMA)is applied widely and has several advantages:light weight,large displacement by temperature change,and large force to mass ratio.However,the SMA actuators possess hysteresis nonlinearity between their own temperature and displacement obtained by the temperature.The hysteretic behavior of the SMA actuators affects their control performance.In previous research,an operator-based control system including a hysteresis compensator has been proposed.The vibration of a flexible arm is dealt with as the controlled object;one end of the arm is clamped and the other end is free.The effectiveness of the hysteresis compensator has been confirmed by simulations and experiments.Nevertheless,the feedback signal of the previous designed system has increased exponentially.It is difficult to use the system in the long-term because of the phenomenon.Additionally,the SMA actuator generates and radiates heat because electric current passing through the SMA actuator provides heat,and strain on the SMA actuator is generated.With long-time use of the SMA actuator,the environmental temperature around the SMA actuator varies through radiation of the heat.There exists a risk that the ambient temperature change dealt with as disturbance affects the temperature and strain of the SMA actuator.In this research,a design method of the operator-based control system is proposed considering the long-term use of the system.In the method,the hysteresis characteristics of the SMA actuator and the temperature change around the actuator are considered.The effectiveness of the proposed method is verified by simulations and experiments.
基金Project supported by the National Natural Science Foundation of China(Nos.61302009,61571171)
文摘To improve the logic stability of conventional multi-valued logic（MVL） circuits designed with a GaNbased resonate tunneling diode（RTD）, we proposed a GaN/InGaN/AlGaN multi-quantum well（MQW） RTD. The proposed RTD was simulated through solving the coupled Schrodinger and Poisson equations in the numerical non-equilibrium Green＇s function（NEGF） method on the TCAD platform. The proposed RTD was grown layer by layer in epitaxial technologies. Simulated results indicate that its current-voltage characteristic appears to have a wider total negative differential resistance region than those of conventional ones and an obvious hysteresis loop at room temperature. To increase the Al composite of AIGaN barrier layers properly results in increasing of both the total negative differential resistance region width and the hysteresis loop width, which is helpful to improve the logic stability of MVL circuits. Moreover, the complement resonate tunneling transistor pair consisted of the proposed RTDs or the proposed RTD and enhanced mode HEMT controlled RTD8 is capable of generating versatile MVL modes at different supply voltages less than 3.3 V, which is very attractive for implementing more complex MVL function digital integrated circuits and systems with less devices, super high speed linear or nonlinear ADC and voltage sensors with a built-in super high speed ADC function.
