To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its ...To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its stability is analyzed by using Lyapunov stability criterion.Secondly,according to the relationship among bus current,switching state and phase current,a single bus resistance sampling current reconstruction scheme without current sensors is adopted,which effectively reduces the cost of motor system.Finally,the feasibility and effectiveness of the proposed scheme are verified by simulation.展开更多
Reconstruction of experimental axisymmetric equilibria is an important part of tokamak data analysis. Fourier expansion is applied to reconstruct the vessel current distribution in EFIT code. Benchmarking and testing ...Reconstruction of experimental axisymmetric equilibria is an important part of tokamak data analysis. Fourier expansion is applied to reconstruct the vessel current distribution in EFIT code. Benchmarking and testing calculations are performed to evaluate and validate this algorithm. Two cases for circular and non-circular plasma discharges are presented. Fourier expansion used to fit the eddy current is a robust method and the real time EFIT can be introduced to the plasma control system in the coming campaign.展开更多
The degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization.EN data were analyzed using phase space reconstructio...The degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization.EN data were analyzed using phase space reconstruction theory.With the correlation dimensions obtained from the phase space reconstruction,the chaotic behavior of EN was quantitatively evaluated.The results show that both electrochemical potential noise (EPN) and electrochemical current noise (ECN) have chaotic properties.The correlation dimensions of EPN increase with corrosion extent,while those of ECN seem nearly unchanged.The increased correlation dimensions of EPN during the degradation process are associated with the increased susceptibility to local corrosion.展开更多
A method for the reconstruction of the plasma boundary in the sino-united spherical tokamak （SUNIST） based on the outer plasma magnetic diagnostics is reported. In SUNIST, the magnetic flux loop integral signals wer...A method for the reconstruction of the plasma boundary in the sino-united spherical tokamak （SUNIST） based on the outer plasma magnetic diagnostics is reported. In SUNIST, the magnetic flux loop integral signals were measured recently and the plasma boundary could be reconstructed well with a current filament （CF） model by setting 2 to 8 current filaments. There are three additional filament positional parameters in addition to the filament current to minimize the square root error in the CF model. The plasma configuration obtained with the CF method is consistent with the visible plasma image from the CCD camera. The average difference in the minor radii for the plasma boundary, by applying the CF model and EFIT code, is below 6 mm.展开更多
The equilibrium reconstruction is important to study the tokamak plasma physical processes.To analyze the contribution of fast ions to the equilibrium,the kinetic equilibria at two time-slices in a typical H-mode disc...The equilibrium reconstruction is important to study the tokamak plasma physical processes.To analyze the contribution of fast ions to the equilibrium,the kinetic equilibria at two time-slices in a typical H-mode discharge with different auxiliary heatings are reconstructed by using magnetic diagnostics,kinetic diagnostics and TRANSP code.It is found that the fast-ion pressure might be up to one-third of the plasma pressure and the contribution is mainly in the core plasma due to the neutral beam injection power is primarily deposited in the core region.The fast-ion current contributes mainly in the core region while contributes little to the pedestal current.A steep pressure gradient in the pedestal is observed which gives rise to a strong edge current.It is proved that the fast ion effects cannot be ignored and should be considered in the future study of EAST.展开更多
利用可再生能源发电,并通过低温电解水技术生产氢气,被认为是一种环保且可持续的制氢途径,是未来氢能发展的重要方向之一.采用该方法生产的氢气因其环保特性而被称为“绿氢”.然而,目前绿氢高昂的生产成本限制了电解水制氢技术的大规模...利用可再生能源发电,并通过低温电解水技术生产氢气,被认为是一种环保且可持续的制氢途径,是未来氢能发展的重要方向之一.采用该方法生产的氢气因其环保特性而被称为“绿氢”.然而,目前绿氢高昂的生产成本限制了电解水制氢技术的大规模应用.因此,开发先进的非贵金属催化剂和电催化体系以降低电解水制氢成本具有重要意义.界面工程是一种提升非贵金属催化剂电解水性能的有效策略,但目前对其催化活性位点的识别及活性提升机制的研究仍然不足.本文采用简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF催化剂,并研究了其在电解水过程中的催化活性位点及这些位点在提升催化能力方面的协同作用.采用扫描电镜(SEM)证明了Ni_(2)P/CoP/FeP_(4)/IF催化剂呈现纳米线网络结构,这种结构不仅有利于增加催化剂的电化学活性位点和加速反应动力学,而且促进了连续产生的气泡从活性位点逃逸,从而提高了催化剂的机械稳定性.电化学研究结果表明,所制备Ni_(2)P/CoP/FeP_(4)/IF催化剂在1.0 mol L^(‒1)KOH溶液中表现出较好的析氧反应(OER)和析氢反应(HER)活性,分别仅需218和127 mV的过电位,即可达到100 mA cm^(‒2)的电流密度.将Ni_(2)P/CoP/FeP_(4)/IF分别作为阴极和阳极构建双电极电解槽,该装置产生100和500 mA cm^(‒2)的电流密度分别仅需1.68和2.05 V的电压,这一性能优于大多数已报道的自支撑过渡金属磷化物催化剂.多步计时电位测试结果进一步证实了Ni_(2)P/CoP/FeP_(4)/IF作为阳极和阴极材料在水分解过程中具有较好的长期耐久性.X射线光电子能谱和差分电荷分析表明,电子从富电子的FeP_(4)向缺电子的Ni_(2)P和CoP转移,这促使Ni_(2)P和CoP上的电子积累和FeP_(4)上的空穴积累,有利于优化反应中间体的吸附和脱附自由能,提升OER和HER催化性能.结合X射线衍射、扫描电镜、透射电镜、X射线光电子能谱和原位拉曼光谱结果发现,催化剂重构后形成的特定(氧)氢氧化物结构,是OER反应真正的关键活性位点.原位拉曼光谱进一步证实了异质界面促进了OER过程中Ni_(2)P/CoP/FeP_(4)/IF的快速重构.此外,利用密度泛函理论分析了催化剂的HER反应机理.计算结果表明,H2O优先吸附在Fe位点并发生水解,随后产生的H*吸附在Ni位点上并发生解吸,从而促进了催化剂中Fe和Ni活性位点的高效利用.同时,CoP的引入提高了Ni_(2)P/CoP/FeP_(4)/IF催化剂的水吸附和解离能力,进一步提升了其HER活性.综上所述,本文通过简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF过渡金属磷化物纳米线网络催化剂,并将其用于碱性水分解.通过多种表征技术及理论计算结果分析,识别了电解水过程中的关键催化活性位点,即催化剂重构后形成的特定(氧)氢氧化物结构,并揭示了其在OER和HER反应中的催化机制.本研究可为高性能碱性电解水催化剂的理性设计和开发提供参考.展开更多
电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍...电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍铁羟基/氢氧化物(NiFe(oxy)hydroxides)是近期研究的热点,其在碱性条件下具有极低的OER过电位,部分材料性能甚至超过了贵金属基催化剂,如IrO_(2)和RuO_(2).然而,NiFe(oxy)hydroxides的长期催化稳定性,尤其是在大电流下的长期催化稳定性,成为限制其实际应用的主要问题,这主要是由于铁元素的严重流失导致的.因此,如何有效控制和利用电化学溶解/沉积动力学成为稳定铁位点的关键.为克服该挑战,本文提出了一种大电流极化重构方法来固定活性铁位点.通过在大电流(1.5 A cm^(-2))下对材料进行表面快速极化重构,成功制备了FeOOH@NiOOH(eFNO_(L))电催化剂.eFNO_(L)不仅具有稳定的铁位点,还暴露出高指数晶面,因此eFNO_(L)同时展现出较好的OER催化活性和稳定性.同时,密度泛函理论计算结果表明,与具有低指数晶面的FeNiOOH相比,大电流极化工程制备的分相eFNO_(L)对铁位点表现出更高的结合能,可以有效抑制OER过程中的铁流失,且高指数晶面在改变速率决定步骤和减少吸附能垒上具有更大的优势.电化学测试结果表明,经过优化后的eFNO_(L)催化剂在产生100和500 mA cm^(-2)大电流密度仅需234和27 mV的过电位,并且具有较小的Tafel斜率(35.2 mV dec^(-1)).由于铁位点结合能的提高,eFNO_(L)催化剂在500 mA cm^(-2)的电流密度下能够稳定催化超过100 h,且仅有1.5%的性能衰减,优于近期报道的大多数镍铁基OER催化剂.综上,本文为开发高活性和高稳定性能的催化剂提供了一种有效的大电流电化学重构策略,在电解水制氢领域实现其工业化的大规模应用方面显示出巨大潜力,有望降低可持续电解水制氢成本.展开更多
文摘To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its stability is analyzed by using Lyapunov stability criterion.Secondly,according to the relationship among bus current,switching state and phase current,a single bus resistance sampling current reconstruction scheme without current sensors is adopted,which effectively reduces the cost of motor system.Finally,the feasibility and effectiveness of the proposed scheme are verified by simulation.
基金supported by National Natural Science Foundation of China (No. 10725523)
文摘Reconstruction of experimental axisymmetric equilibria is an important part of tokamak data analysis. Fourier expansion is applied to reconstruct the vessel current distribution in EFIT code. Benchmarking and testing calculations are performed to evaluate and validate this algorithm. Two cases for circular and non-circular plasma discharges are presented. Fourier expansion used to fit the eddy current is a robust method and the real time EFIT can be introduced to the plasma control system in the coming campaign.
基金Supported by Major State Basic Research Program of China ("973" Program,No. 2011CB610505)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20120032110029)
文摘The degradation process of organosol coated tinplate in beverage was investigated by electrochemical noise (EN) technique combined with morphology characterization.EN data were analyzed using phase space reconstruction theory.With the correlation dimensions obtained from the phase space reconstruction,the chaotic behavior of EN was quantitatively evaluated.The results show that both electrochemical potential noise (EPN) and electrochemical current noise (ECN) have chaotic properties.The correlation dimensions of EPN increase with corrosion extent,while those of ECN seem nearly unchanged.The increased correlation dimensions of EPN during the degradation process are associated with the increased susceptibility to local corrosion.
基金supported by National Natural Science Foundation of China (Nos.10775177, 10535020)the Major State Basic Research Development Program of China (Program 973) (No.2008CB717804)
文摘A method for the reconstruction of the plasma boundary in the sino-united spherical tokamak （SUNIST） based on the outer plasma magnetic diagnostics is reported. In SUNIST, the magnetic flux loop integral signals were measured recently and the plasma boundary could be reconstructed well with a current filament （CF） model by setting 2 to 8 current filaments. There are three additional filament positional parameters in addition to the filament current to minimize the square root error in the CF model. The plasma configuration obtained with the CF method is consistent with the visible plasma image from the CCD camera. The average difference in the minor radii for the plasma boundary, by applying the CF model and EFIT code, is below 6 mm.
基金supported by National Key R&D Program of China under Grant No.2017YFE0300400National Natural Science Foundation of China under Grant Nos.11475220,11405218,11575248+1 种基金the National Magnetic Confinement Fusion Science Program of China under Contracts No.2014GB106001sponsored in part by Youth Innovation Promotion Association Chinese Academy of Sciences (Grant No.2016384)
文摘The equilibrium reconstruction is important to study the tokamak plasma physical processes.To analyze the contribution of fast ions to the equilibrium,the kinetic equilibria at two time-slices in a typical H-mode discharge with different auxiliary heatings are reconstructed by using magnetic diagnostics,kinetic diagnostics and TRANSP code.It is found that the fast-ion pressure might be up to one-third of the plasma pressure and the contribution is mainly in the core plasma due to the neutral beam injection power is primarily deposited in the core region.The fast-ion current contributes mainly in the core region while contributes little to the pedestal current.A steep pressure gradient in the pedestal is observed which gives rise to a strong edge current.It is proved that the fast ion effects cannot be ignored and should be considered in the future study of EAST.
文摘利用可再生能源发电,并通过低温电解水技术生产氢气,被认为是一种环保且可持续的制氢途径,是未来氢能发展的重要方向之一.采用该方法生产的氢气因其环保特性而被称为“绿氢”.然而,目前绿氢高昂的生产成本限制了电解水制氢技术的大规模应用.因此,开发先进的非贵金属催化剂和电催化体系以降低电解水制氢成本具有重要意义.界面工程是一种提升非贵金属催化剂电解水性能的有效策略,但目前对其催化活性位点的识别及活性提升机制的研究仍然不足.本文采用简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF催化剂,并研究了其在电解水过程中的催化活性位点及这些位点在提升催化能力方面的协同作用.采用扫描电镜(SEM)证明了Ni_(2)P/CoP/FeP_(4)/IF催化剂呈现纳米线网络结构,这种结构不仅有利于增加催化剂的电化学活性位点和加速反应动力学,而且促进了连续产生的气泡从活性位点逃逸,从而提高了催化剂的机械稳定性.电化学研究结果表明,所制备Ni_(2)P/CoP/FeP_(4)/IF催化剂在1.0 mol L^(‒1)KOH溶液中表现出较好的析氧反应(OER)和析氢反应(HER)活性,分别仅需218和127 mV的过电位,即可达到100 mA cm^(‒2)的电流密度.将Ni_(2)P/CoP/FeP_(4)/IF分别作为阴极和阳极构建双电极电解槽,该装置产生100和500 mA cm^(‒2)的电流密度分别仅需1.68和2.05 V的电压,这一性能优于大多数已报道的自支撑过渡金属磷化物催化剂.多步计时电位测试结果进一步证实了Ni_(2)P/CoP/FeP_(4)/IF作为阳极和阴极材料在水分解过程中具有较好的长期耐久性.X射线光电子能谱和差分电荷分析表明,电子从富电子的FeP_(4)向缺电子的Ni_(2)P和CoP转移,这促使Ni_(2)P和CoP上的电子积累和FeP_(4)上的空穴积累,有利于优化反应中间体的吸附和脱附自由能,提升OER和HER催化性能.结合X射线衍射、扫描电镜、透射电镜、X射线光电子能谱和原位拉曼光谱结果发现,催化剂重构后形成的特定(氧)氢氧化物结构,是OER反应真正的关键活性位点.原位拉曼光谱进一步证实了异质界面促进了OER过程中Ni_(2)P/CoP/FeP_(4)/IF的快速重构.此外,利用密度泛函理论分析了催化剂的HER反应机理.计算结果表明,H2O优先吸附在Fe位点并发生水解,随后产生的H*吸附在Ni位点上并发生解吸,从而促进了催化剂中Fe和Ni活性位点的高效利用.同时,CoP的引入提高了Ni_(2)P/CoP/FeP_(4)/IF催化剂的水吸附和解离能力,进一步提升了其HER活性.综上所述,本文通过简单的水热及低温磷化法制备了具有丰富异质界面的Ni_(2)P/CoP/FeP_(4)/IF过渡金属磷化物纳米线网络催化剂,并将其用于碱性水分解.通过多种表征技术及理论计算结果分析,识别了电解水过程中的关键催化活性位点,即催化剂重构后形成的特定(氧)氢氧化物结构,并揭示了其在OER和HER反应中的催化机制.本研究可为高性能碱性电解水催化剂的理性设计和开发提供参考.
文摘电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍铁羟基/氢氧化物(NiFe(oxy)hydroxides)是近期研究的热点,其在碱性条件下具有极低的OER过电位,部分材料性能甚至超过了贵金属基催化剂,如IrO_(2)和RuO_(2).然而,NiFe(oxy)hydroxides的长期催化稳定性,尤其是在大电流下的长期催化稳定性,成为限制其实际应用的主要问题,这主要是由于铁元素的严重流失导致的.因此,如何有效控制和利用电化学溶解/沉积动力学成为稳定铁位点的关键.为克服该挑战,本文提出了一种大电流极化重构方法来固定活性铁位点.通过在大电流(1.5 A cm^(-2))下对材料进行表面快速极化重构,成功制备了FeOOH@NiOOH(eFNO_(L))电催化剂.eFNO_(L)不仅具有稳定的铁位点,还暴露出高指数晶面,因此eFNO_(L)同时展现出较好的OER催化活性和稳定性.同时,密度泛函理论计算结果表明,与具有低指数晶面的FeNiOOH相比,大电流极化工程制备的分相eFNO_(L)对铁位点表现出更高的结合能,可以有效抑制OER过程中的铁流失,且高指数晶面在改变速率决定步骤和减少吸附能垒上具有更大的优势.电化学测试结果表明,经过优化后的eFNO_(L)催化剂在产生100和500 mA cm^(-2)大电流密度仅需234和27 mV的过电位,并且具有较小的Tafel斜率(35.2 mV dec^(-1)).由于铁位点结合能的提高,eFNO_(L)催化剂在500 mA cm^(-2)的电流密度下能够稳定催化超过100 h,且仅有1.5%的性能衰减,优于近期报道的大多数镍铁基OER催化剂.综上,本文为开发高活性和高稳定性能的催化剂提供了一种有效的大电流电化学重构策略,在电解水制氢领域实现其工业化的大规模应用方面显示出巨大潜力,有望降低可持续电解水制氢成本.
