Transport of an underdamped Brownian particle in a one-dimensional asymmetric deformable potential is investigated in the presence of both an ac force and a static force,respectively.From numerical simulations,we obta...Transport of an underdamped Brownian particle in a one-dimensional asymmetric deformable potential is investigated in the presence of both an ac force and a static force,respectively.From numerical simulations,we obtain the current average velocity.The current reversals and the absolute negative mobility are presented.The increasing of the deformation of the potential can cause the absolute negative mobility to be suppressed and even disappear.When the static force is small,the increase of the potential deformation suppresses the absolute negative mobility.When the force is large,the absolute negative mobility disappears.In particular,when the potential deformation is equal to0.015,the two current reversals present with the increasing of the force.Remarkably,when the potential deformation is small,there are three current reversals with the increasing of the friction coefficient and the average velocity presents a oscillation behavior.展开更多
The mechanisms of influence of physiotherapy procedures in ozokeriteparaffin therapy are considered in this paper.It is shown that microwave electromagnetic radiation formed by heated ozokerite-paraffin mixture is an ...The mechanisms of influence of physiotherapy procedures in ozokeriteparaffin therapy are considered in this paper.It is shown that microwave electromagnetic radiation formed by heated ozokerite-paraffin mixture is an important component of physiotherapy procedures.Using the experimental setup developed by the authors,the radiative abilities of ozokerite,paraffin and their mixtures in the microwave range were investigated.It was found that in the process of cooling the ozokerite-paraffin mixture,during the procedure,negative microwave fluxes occur,affecting the inflammatory processes in the patient’s body.The dependences of the microwave radiation level on the composition of the ozokerite-paraffin mixture are investigated.The results of experimental studies allowed us to evaluate the interaction of electromagnetic radiation of ozokerite-paraffin mixtures with human own electromagnetic radiation and to approach the choice of modes of therapeutic interaction more carefully.展开更多
Voltage sag is one of the most common power quality disturbances in industry,which causes huge inrush currents in stator windings of induction motors,and adversely impacts the motor secure operation.This paper firstly...Voltage sag is one of the most common power quality disturbances in industry,which causes huge inrush currents in stator windings of induction motors,and adversely impacts the motor secure operation.This paper firstly introduces a 2D Time-Stepping multi-slice finite element method(2D T-S multi-slice FEM)which is used for calculating the magnetic field distribution in induction motors under different sag events.Then the paper deduces the transient analytical expression of stator inrush current based on the classical theory of AC motors and presents a separation method for the positive,negative and zero sequence values based on instantaneous currents.With this method,the paper studies the influences of voltage sag amplitude,phase-angle jump and initial phase angle on the stator positive-and negative-sequence peak currents of 5.5 kW and 55 kW induction motors.This paper further proposes a motor protection method under voltage sag condition with the stator negative-sequence peak currents as the protection threshold,so that the protection false trip can be avoided effectively.Finally,the calculation and analysis results are validated by the comparison of calculated and measured stator peak value of the 5.5 kW induction motor.展开更多
An intelligent power factor correction scheme is presented for three phase low power factor loads. This new scheme is able to perform individual phase sensing of parameters by monitoring at all times to sense a change...An intelligent power factor correction scheme is presented for three phase low power factor loads. This new scheme is able to perform individual phase sensing of parameters by monitoring at all times to sense a change in system parameters and affects individual phase correction by applying the exact amount of reactive components needed for each phase, and can also reduce negative sequence current caused by the load to improve system balance. An optimization criterion is used for the proper calculation of reactive power steps in a power compensation installation of capacitor banks. The criterion is enabled by sampling measurements performed on the electrical plant examined within specific interval of time.展开更多
In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due t...In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due to unequal voltage magnitudes at the fundamental frequency, phase angle deviations or unequal distribution of single phase loads. The voltage unbalance is a major power quality issue, because a small unbalance in the phase voltages can cause a larger unbalance in the phase currents. A completely balanced three-phase three wire system contains only positive sequence components of voltage, current and impedance, whereas unbalanced system contains both positive and negative sequence components of voltages and currents. The negative sequence component of current in the unbalanced system increases the temperature and losses in the equipments. Hence, it is necessary to mitigate this problem by supplying the negative sequence current to the load at the load side and keep the source side balanced. This paper proposes the shunt connected, current injecting Distribution Static Synchronous Compensator (DSTATCOM) with appropriate controller to mitigate the unbalanced load current. The symmetrical components based Hysteresis Current Controller (HCC) is designed for DSTATCOM to diminish the unbalances in a three-phase three-wire system. The performance of the controller is studied by simulating the entire system in the MATLAB/Simulink environment. The DSTATCOM with HCC is found to be better than other controllers because it is suitable for compensating both balanced and unbalanced loads.展开更多
When private electric vehicles(EVs),which will be the main part of the EVs’cluster in the future,are plugged in power system by single phase power line,can result to three-phase unbalance problem of distribution netw...When private electric vehicles(EVs),which will be the main part of the EVs’cluster in the future,are plugged in power system by single phase power line,can result to three-phase unbalance problem of distribution network.In this work,a phased-controlled coordinated charging method was put forward to solve this problem.Firstly,the impacts of charging load to distribution network was analyzed based on the equivalent circuit;and then an architecture of the control method and its corresponding optimal control model were introduced.The optimal model is a multi-objective optimization model,which includes minimizing load variance of each phase and minimizing the power asymmetrical degree of three-phase load;lastly,three scenarios considering balance and unbalance cases were envisioned to verify the reasonableness of this control method based on IEEE-37 distribution network.Results show that the phased-controlled coordinated charging method can minimize the load variance as well as the negative sequence current.展开更多
We present a fluctuation theorem for Floquet quantum master equations. This is a detailed version of the famous Gallavotti–Cohen theorem. In contrast to the latter theorem, which involves the probability distribution...We present a fluctuation theorem for Floquet quantum master equations. This is a detailed version of the famous Gallavotti–Cohen theorem. In contrast to the latter theorem, which involves the probability distribution of the total heat current, the former involves the joint probability distribution of positive and negative heat currents and can be used to derive the latter. A quantum two-level system driven by a periodic external field is used to verify this result.展开更多
Tunneling field effect transistors（TFETs） based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low...Tunneling field effect transistors（TFETs） based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here,we investigate the TFETs based on two different integration types： in-plane and vertical heterostructures composed of two kinds of layered phosphorous（β-P and δ-P） by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio（PVR）when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of - 10-6 and a steeper subthreshold swing（SS） of - 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of theβ-P and δ-P layers in the in-plane and vertical heterostructures.展开更多
基金Supported in part by the National Natural Science Foundation of China under Grant Nos.11575064 and 11175067the Natural Science Foundation of Guangdong Province under Grant No.2016A030313433
文摘Transport of an underdamped Brownian particle in a one-dimensional asymmetric deformable potential is investigated in the presence of both an ac force and a static force,respectively.From numerical simulations,we obtain the current average velocity.The current reversals and the absolute negative mobility are presented.The increasing of the deformation of the potential can cause the absolute negative mobility to be suppressed and even disappear.When the static force is small,the increase of the potential deformation suppresses the absolute negative mobility.When the force is large,the absolute negative mobility disappears.In particular,when the potential deformation is equal to0.015,the two current reversals present with the increasing of the force.Remarkably,when the potential deformation is small,there are three current reversals with the increasing of the friction coefficient and the average velocity presents a oscillation behavior.
文摘The mechanisms of influence of physiotherapy procedures in ozokeriteparaffin therapy are considered in this paper.It is shown that microwave electromagnetic radiation formed by heated ozokerite-paraffin mixture is an important component of physiotherapy procedures.Using the experimental setup developed by the authors,the radiative abilities of ozokerite,paraffin and their mixtures in the microwave range were investigated.It was found that in the process of cooling the ozokerite-paraffin mixture,during the procedure,negative microwave fluxes occur,affecting the inflammatory processes in the patient’s body.The dependences of the microwave radiation level on the composition of the ozokerite-paraffin mixture are investigated.The results of experimental studies allowed us to evaluate the interaction of electromagnetic radiation of ozokerite-paraffin mixtures with human own electromagnetic radiation and to approach the choice of modes of therapeutic interaction more carefully.
基金This work was supported in part by the National Natural Science Foundation of China under Grant51307050。
文摘Voltage sag is one of the most common power quality disturbances in industry,which causes huge inrush currents in stator windings of induction motors,and adversely impacts the motor secure operation.This paper firstly introduces a 2D Time-Stepping multi-slice finite element method(2D T-S multi-slice FEM)which is used for calculating the magnetic field distribution in induction motors under different sag events.Then the paper deduces the transient analytical expression of stator inrush current based on the classical theory of AC motors and presents a separation method for the positive,negative and zero sequence values based on instantaneous currents.With this method,the paper studies the influences of voltage sag amplitude,phase-angle jump and initial phase angle on the stator positive-and negative-sequence peak currents of 5.5 kW and 55 kW induction motors.This paper further proposes a motor protection method under voltage sag condition with the stator negative-sequence peak currents as the protection threshold,so that the protection false trip can be avoided effectively.Finally,the calculation and analysis results are validated by the comparison of calculated and measured stator peak value of the 5.5 kW induction motor.
文摘An intelligent power factor correction scheme is presented for three phase low power factor loads. This new scheme is able to perform individual phase sensing of parameters by monitoring at all times to sense a change in system parameters and affects individual phase correction by applying the exact amount of reactive components needed for each phase, and can also reduce negative sequence current caused by the load to improve system balance. An optimization criterion is used for the proper calculation of reactive power steps in a power compensation installation of capacitor banks. The criterion is enabled by sampling measurements performed on the electrical plant examined within specific interval of time.
文摘In a three phase power system, the voltages at the generation side are in sinusoidal and equal in magnitude with 120? phase difference between the phases. However, at the load side voltages may become unbalanced due to unequal voltage magnitudes at the fundamental frequency, phase angle deviations or unequal distribution of single phase loads. The voltage unbalance is a major power quality issue, because a small unbalance in the phase voltages can cause a larger unbalance in the phase currents. A completely balanced three-phase three wire system contains only positive sequence components of voltage, current and impedance, whereas unbalanced system contains both positive and negative sequence components of voltages and currents. The negative sequence component of current in the unbalanced system increases the temperature and losses in the equipments. Hence, it is necessary to mitigate this problem by supplying the negative sequence current to the load at the load side and keep the source side balanced. This paper proposes the shunt connected, current injecting Distribution Static Synchronous Compensator (DSTATCOM) with appropriate controller to mitigate the unbalanced load current. The symmetrical components based Hysteresis Current Controller (HCC) is designed for DSTATCOM to diminish the unbalances in a three-phase three-wire system. The performance of the controller is studied by simulating the entire system in the MATLAB/Simulink environment. The DSTATCOM with HCC is found to be better than other controllers because it is suitable for compensating both balanced and unbalanced loads.
基金This work was supported by the national high technology research and development program of China(863 Program)(No.2011AA05A109).
文摘When private electric vehicles(EVs),which will be the main part of the EVs’cluster in the future,are plugged in power system by single phase power line,can result to three-phase unbalance problem of distribution network.In this work,a phased-controlled coordinated charging method was put forward to solve this problem.Firstly,the impacts of charging load to distribution network was analyzed based on the equivalent circuit;and then an architecture of the control method and its corresponding optimal control model were introduced.The optimal model is a multi-objective optimization model,which includes minimizing load variance of each phase and minimizing the power asymmetrical degree of three-phase load;lastly,three scenarios considering balance and unbalance cases were envisioned to verify the reasonableness of this control method based on IEEE-37 distribution network.Results show that the phased-controlled coordinated charging method can minimize the load variance as well as the negative sequence current.
基金supported by the National Science Foundation of China under Grants No. 11 174 025 and No. 11 575 016the support of the CAS Interdisciplinary Innovation Team, No. 2060 299。
文摘We present a fluctuation theorem for Floquet quantum master equations. This is a detailed version of the famous Gallavotti–Cohen theorem. In contrast to the latter theorem, which involves the probability distribution of the total heat current, the former involves the joint probability distribution of positive and negative heat currents and can be used to derive the latter. A quantum two-level system driven by a periodic external field is used to verify this result.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11604019,61574020,and 61376018)the Ministry of Science and Technology of China(Grant No.2016YFA0301300)+1 种基金the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications),Chinathe Fundamental Research Funds for the Central Universities,China(Grant No.2016RCGD22)
文摘Tunneling field effect transistors（TFETs） based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here,we investigate the TFETs based on two different integration types： in-plane and vertical heterostructures composed of two kinds of layered phosphorous（β-P and δ-P） by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio（PVR）when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of - 10-6 and a steeper subthreshold swing（SS） of - 23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of theβ-P and δ-P layers in the in-plane and vertical heterostructures.
