In the process of membrane absorption,spontaneous wetting of hydrophobic microporous membrane causes membrane modification and increases membrane phase mass transfer resistance,which have attracted wide interest.Howev...In the process of membrane absorption,spontaneous wetting of hydrophobic microporous membrane causes membrane modification and increases membrane phase mass transfer resistance,which have attracted wide interest.However,due to the limitations of previous testing methods,the study of the spontaneous membrane wetting process is limited.Herein,we present a method for monitoring spontaneous membrane wetting by measuring its alternating current(AC)impedance.The impedance tests of the PVDF flat membranes and hollow fiber membranes were conducted in a two-electrode system.The results of equivalent circuit fitting indicate that the impedance value of the unwetted membrane is about 1.02×10^(10)Ω,which is close to the theoretical value of 1.4×10^(10)Ω,and this method can quantify the electrochemical impedance value of membranes with different degrees of spontaneous wetting.In addition,a method of impedance test for real-time monitoring of spontaneous wetting was designed.During the experiment,the timeliness and continuity of this method are confirmed with exact judgment under different conditions.In future work,the impedance data will be used to build model to predict the percentage of membrane wetting degree.展开更多
Aim of this work is to try to explain, on a Rational basis, some equations of Electro-Magnetism, which are based on Experimental data. Any Electric Field can produce a Field of many small Electric Dipoles, continuousl...Aim of this work is to try to explain, on a Rational basis, some equations of Electro-Magnetism, which are based on Experimental data. Any Electric Field can produce a Field of many small Electric Dipoles, continuously distributed in space. In a region, where the Electric Field is constant, in direction and magnitude, all the small Dipoles are parallel to the Electric Field, and are represented by a single, long, parallel to them, fixed in space, Electric Dipole, which is here called Compass. An Alternating current, in a straight Conductor, is studied, by a simple, short computer program, for step-by-step nonlinear dynamic analysis. It is found that, only an Alternating current, not a direct current, can produce an Electric Dipole, in a straight Conductor. The two above Dipoles (Compass-Conductor) are assumed with equal lengths ℓ, lying on two skew lines, perpendicular to each other, at a distance ℓ√2, thus forming, by their four ends, a Regular Tetrahedron, with side length ℓ. Repulsion, between Like Charges, obeys the simple Coulomb Electro-Static law. Whereas Interaction (Attraction or Repulsion), between Unlike Charges, obeys a more accurate Lennard-Jones law. The analysis of Dipole-Dipole (Compass-Conductor) Interaction is performed by hand calculator. The only out-of-balance forces, in the regular Tetrahedron, acting on the Rigid Conductor, are the so-called magnetic forces. Their direction is found, in a simple Rational way, with help of Regular Tetrahedron, without recoursing to a “right-hand-rule”. The proposed model is applied to 1) The force acting on an Electric Charge moving in a magnetic field. 2) The force acting on a Current carrying straight Conductor, due to a magnetic field. 3) The magnetic fields created around a Current carrying straight Conductor. In these applications, proposed model gives reasonable results. Particularly, in third application, results, obtained by proposed model, are found in satisfactory approximation with corresponding ones, obtained by an empirical formula, based on relevant Experimental observations of H.-C. Oersted and A.-M. Ampère. So, the reliability of proposed model is checked. Position and direction of magnetic field vector coincide with those of a corresponding fixed Compass of a constant Electric Field. Main point of present work is that, without introducing the concept of a magnetic field vector, by combining field of dipoles, produced by an electric field, with dipole of an alternating current carrying conductor, the magnetic forces can be determined.展开更多
新能源随机性使得电力系统潮流复杂多变,加之大量新能源需要远距离输送消纳,输电阻塞问题日益严重。动态热定值(dynamic line rating,DTR)技术能够提升既有架空线路的输电能力,充分发挥系统的灵活调节能力。特别是在N-1事故场景下,采用...新能源随机性使得电力系统潮流复杂多变,加之大量新能源需要远距离输送消纳,输电阻塞问题日益严重。动态热定值(dynamic line rating,DTR)技术能够提升既有架空线路的输电能力,充分发挥系统的灵活调节能力。特别是在N-1事故场景下,采用DTR技术提升线路输送能力,能够缓解严重输电阻塞。然而,传统方法在考虑N-1事故时存在维数灾难问题,因此应用DTR技术仍然存在挑战性。为此,提出了一种两阶段分布鲁棒优化(distributionally robust optimization,DRO)方法以提升架空线路的输电能力。首先,构建了架空线路暂态温度计算模型并做适当简化处理,从而保证后续优化模型的凸性。随后,建立了考虑DTR和N-1安全准则的两阶段DRO模型以避免N-1事故下的持续停电,考虑无功与网损的线性化交流潮流模型能够更准确地计算线路潮流。最后,使用IEEE-24节点系统和IEEE-118节点系统验证了所提方法的有效性。展开更多
Objective:We investigated changes in cortico–subcortical spatiotemporal dynamics to explore the treatment mechanisms oftranscranial alternating current stimulation(tACS)in patientswith Parkinson’s disease(PD).Method...Objective:We investigated changes in cortico–subcortical spatiotemporal dynamics to explore the treatment mechanisms oftranscranial alternating current stimulation(tACS)in patientswith Parkinson’s disease(PD).Methods:Resting-state functional magnetic resonance imaging(rs-fMRI)data were collected from 20 patients with PD and 20 normal controls(NC).Each patient with PD received successivemultidisciplinary intensive rehabilitation treatment and tACStreatment over a one-year interval.Individual functional brain network mapping and co-activation pattern(CAP)analysis were performed to characterize cortico–subcortical dynamics.Results:The same tACS electrode placement stimulated different proportions of functional brain networks across the participants.CAP analysis revealed that the visual network,attentional network,and default mode network co-activated with the thalamus,accumbens,and amygdala,respectively.The pattern characterized by thede-activation of the visual network and the activation of the thalamus showed a significantly low amplitude in the patients with PD than inNCs,and this amplitude increased after tACS treatment.Furthermore,the co-occurrence of cortico–subcortical CAPs was significantly higherin patients with PD than in NCs and decreased after tACS treatment.Conclusions:This study investigated cortico–subcortical spatiotemporaldynamics in patients with PD and further revealed the tACS treatmentmechanism.These findings contribute to understanding cortico–subcortical dynamics and exploring noninvasive neuromodulationtargets of cortico–subcortical circuits in brain diseases,such as PD,Alzheimer’s disease,and depression.展开更多
为提高电力系统静态电压的稳定性,提出将静止无功补偿器(static var compensator,SVC)与可控串联补偿装置(thyristor controlled series compensator,TCSC)相结合并作用于电力系统线路中,运用动态连续潮流法计算电力系统静态电压稳定裕...为提高电力系统静态电压的稳定性,提出将静止无功补偿器(static var compensator,SVC)与可控串联补偿装置(thyristor controlled series compensator,TCSC)相结合并作用于电力系统线路中,运用动态连续潮流法计算电力系统静态电压稳定裕度的新方法。首先建立SVC与TCSC的稳态模型;然后引入节点参数因子和支路参数因子的概念,运用模态分析法确定系统母线和支路的薄弱点,并联SVC对母线薄弱点进行无功补偿,串联TCSC优化薄弱线路功率分配;最后运用动态连续潮流法求出静态电压稳定裕度。以IEEE-14节点系统进行仿真计算,并对无灵活交流输电(flexible AC transmission system,FACTS)装置、单独安装SVC或TCSC、SVC和TCSC相结合情况下的系统静态电压稳定裕度值作比较,结果表明所提新方法能够快速、准确地提高电力系统静态电压稳定性。展开更多
基金Fanatical support from the National Natural Science Foundation of China(21576011)and the kind supply of electrochemical workstation from Prof。
文摘In the process of membrane absorption,spontaneous wetting of hydrophobic microporous membrane causes membrane modification and increases membrane phase mass transfer resistance,which have attracted wide interest.However,due to the limitations of previous testing methods,the study of the spontaneous membrane wetting process is limited.Herein,we present a method for monitoring spontaneous membrane wetting by measuring its alternating current(AC)impedance.The impedance tests of the PVDF flat membranes and hollow fiber membranes were conducted in a two-electrode system.The results of equivalent circuit fitting indicate that the impedance value of the unwetted membrane is about 1.02×10^(10)Ω,which is close to the theoretical value of 1.4×10^(10)Ω,and this method can quantify the electrochemical impedance value of membranes with different degrees of spontaneous wetting.In addition,a method of impedance test for real-time monitoring of spontaneous wetting was designed.During the experiment,the timeliness and continuity of this method are confirmed with exact judgment under different conditions.In future work,the impedance data will be used to build model to predict the percentage of membrane wetting degree.
文摘Aim of this work is to try to explain, on a Rational basis, some equations of Electro-Magnetism, which are based on Experimental data. Any Electric Field can produce a Field of many small Electric Dipoles, continuously distributed in space. In a region, where the Electric Field is constant, in direction and magnitude, all the small Dipoles are parallel to the Electric Field, and are represented by a single, long, parallel to them, fixed in space, Electric Dipole, which is here called Compass. An Alternating current, in a straight Conductor, is studied, by a simple, short computer program, for step-by-step nonlinear dynamic analysis. It is found that, only an Alternating current, not a direct current, can produce an Electric Dipole, in a straight Conductor. The two above Dipoles (Compass-Conductor) are assumed with equal lengths ℓ, lying on two skew lines, perpendicular to each other, at a distance ℓ√2, thus forming, by their four ends, a Regular Tetrahedron, with side length ℓ. Repulsion, between Like Charges, obeys the simple Coulomb Electro-Static law. Whereas Interaction (Attraction or Repulsion), between Unlike Charges, obeys a more accurate Lennard-Jones law. The analysis of Dipole-Dipole (Compass-Conductor) Interaction is performed by hand calculator. The only out-of-balance forces, in the regular Tetrahedron, acting on the Rigid Conductor, are the so-called magnetic forces. Their direction is found, in a simple Rational way, with help of Regular Tetrahedron, without recoursing to a “right-hand-rule”. The proposed model is applied to 1) The force acting on an Electric Charge moving in a magnetic field. 2) The force acting on a Current carrying straight Conductor, due to a magnetic field. 3) The magnetic fields created around a Current carrying straight Conductor. In these applications, proposed model gives reasonable results. Particularly, in third application, results, obtained by proposed model, are found in satisfactory approximation with corresponding ones, obtained by an empirical formula, based on relevant Experimental observations of H.-C. Oersted and A.-M. Ampère. So, the reliability of proposed model is checked. Position and direction of magnetic field vector coincide with those of a corresponding fixed Compass of a constant Electric Field. Main point of present work is that, without introducing the concept of a magnetic field vector, by combining field of dipoles, produced by an electric field, with dipole of an alternating current carrying conductor, the magnetic forces can be determined.
文摘新能源随机性使得电力系统潮流复杂多变,加之大量新能源需要远距离输送消纳,输电阻塞问题日益严重。动态热定值(dynamic line rating,DTR)技术能够提升既有架空线路的输电能力,充分发挥系统的灵活调节能力。特别是在N-1事故场景下,采用DTR技术提升线路输送能力,能够缓解严重输电阻塞。然而,传统方法在考虑N-1事故时存在维数灾难问题,因此应用DTR技术仍然存在挑战性。为此,提出了一种两阶段分布鲁棒优化(distributionally robust optimization,DRO)方法以提升架空线路的输电能力。首先,构建了架空线路暂态温度计算模型并做适当简化处理,从而保证后续优化模型的凸性。随后,建立了考虑DTR和N-1安全准则的两阶段DRO模型以避免N-1事故下的持续停电,考虑无功与网损的线性化交流潮流模型能够更准确地计算线路潮流。最后,使用IEEE-24节点系统和IEEE-118节点系统验证了所提方法的有效性。
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U20A20191,82071912,12104049,82202291)the Fundamental Research Funds for the Central Universities(Grant No.2021CX11011)the National Key Research and Development Program of China(Grant No.2020YFC2007305).
文摘Objective:We investigated changes in cortico–subcortical spatiotemporal dynamics to explore the treatment mechanisms oftranscranial alternating current stimulation(tACS)in patientswith Parkinson’s disease(PD).Methods:Resting-state functional magnetic resonance imaging(rs-fMRI)data were collected from 20 patients with PD and 20 normal controls(NC).Each patient with PD received successivemultidisciplinary intensive rehabilitation treatment and tACStreatment over a one-year interval.Individual functional brain network mapping and co-activation pattern(CAP)analysis were performed to characterize cortico–subcortical dynamics.Results:The same tACS electrode placement stimulated different proportions of functional brain networks across the participants.CAP analysis revealed that the visual network,attentional network,and default mode network co-activated with the thalamus,accumbens,and amygdala,respectively.The pattern characterized by thede-activation of the visual network and the activation of the thalamus showed a significantly low amplitude in the patients with PD than inNCs,and this amplitude increased after tACS treatment.Furthermore,the co-occurrence of cortico–subcortical CAPs was significantly higherin patients with PD than in NCs and decreased after tACS treatment.Conclusions:This study investigated cortico–subcortical spatiotemporaldynamics in patients with PD and further revealed the tACS treatmentmechanism.These findings contribute to understanding cortico–subcortical dynamics and exploring noninvasive neuromodulationtargets of cortico–subcortical circuits in brain diseases,such as PD,Alzheimer’s disease,and depression.
文摘为提高电力系统静态电压的稳定性,提出将静止无功补偿器(static var compensator,SVC)与可控串联补偿装置(thyristor controlled series compensator,TCSC)相结合并作用于电力系统线路中,运用动态连续潮流法计算电力系统静态电压稳定裕度的新方法。首先建立SVC与TCSC的稳态模型;然后引入节点参数因子和支路参数因子的概念,运用模态分析法确定系统母线和支路的薄弱点,并联SVC对母线薄弱点进行无功补偿,串联TCSC优化薄弱线路功率分配;最后运用动态连续潮流法求出静态电压稳定裕度。以IEEE-14节点系统进行仿真计算,并对无灵活交流输电(flexible AC transmission system,FACTS)装置、单独安装SVC或TCSC、SVC和TCSC相结合情况下的系统静态电压稳定裕度值作比较,结果表明所提新方法能够快速、准确地提高电力系统静态电压稳定性。
