pH represents solution acidity and plays a key role in many life events that are associated with human diseases. For instance, the β-site amyloid precursor protein cleavage enzyme, BACE1, which is a major therapeutic target of treating Alzheimer’s disease, functions within a narrow pH region around 4.5. In addition, the sodium-proton antiporter NhaA from Escherichia coli is activated only when the cytoplasmic pH is higher than 6.5 and the activity reaches the maximal around pH 8.8. To explore the molecular mechanism of a protein regulated by pH, it’s of importance to measure, typically by NMR, the binding affinities of protons to ionizable key residues, namely pKa’s, which determine the deprotonation equilibria under a pH condition. However, web-lab experiments are often expensive and time consuming. In some cases, due to the structural complexity of a protein, pKa measurements become difficult, making theoretical pKa predictions in a try lab more advantageous.In the past thirty years, many efforts had been made for accurate and fast protein pKa predictions with physics-based methods. Theoretically, constant pH molecular dynamics (CpHMD) methods that take conformational fluctuations into account give the most accurate predictions, especially the explicit-solvent CpHMD model proposed by Huang and coworkers (J. Chem. Theory Comput. 2016, 12, 5411-5421) which in principle is applicable to any system that a force field can describe. However, lengthy molecular simulations are usually necessary for extensive sampling in conformation. In particular, the computational complexity increases significantly if water molecules are included explicitly in the simulation systems. Thus, CpHMD is not suitable for high-throughout computing requested in industry. To accelerate pKa prediction, Poisson-Boltzmann (PB) or empirical equation-based schemes, such as H++ and PropKa, have been developed and widely applied where pKa’s are obtained via one-structure calculations. Recently, artificial intelligence (AI) is applied to the area of protein pKa prediction, which leads to the development of DeepKa by Huang lab (ACS Omega 2021, 6, 34823-34831), the first AI-driven pKa predictor. In this paper, we review the advances in protein pKa prediction contributed mainly by CpHMD methods, PB or empirical equation-based schemes, and AI models. Notably, the modeling hypotheses explained in the review would shed light on future developments of more powerful protein pKa predictors.
{"title":"Progress in protein pK<sub>a</sub> prediction","authors":"None Fangfang Luo, None Zhitao Cai, None Yandong Huang","doi":"10.7498/aps.72.20231356","DOIUrl":"https://doi.org/10.7498/aps.72.20231356","url":null,"abstract":"pH represents solution acidity and plays a key role in many life events that are associated with human diseases. For instance, the β-site amyloid precursor protein cleavage enzyme, BACE1, which is a major therapeutic target of treating Alzheimer’s disease, functions within a narrow pH region around 4.5. In addition, the sodium-proton antiporter NhaA from <i>Escherichia coli</i> is activated only when the cytoplasmic pH is higher than 6.5 and the activity reaches the maximal around pH 8.8. To explore the molecular mechanism of a protein regulated by pH, it’s of importance to measure, typically by NMR, the binding affinities of protons to ionizable key residues, namely pK<sub>a</sub>’s, which determine the deprotonation equilibria under a pH condition. However, web-lab experiments are often expensive and time consuming. In some cases, due to the structural complexity of a protein, pK<sub>a</sub> measurements become difficult, making theoretical pK<sub>a</sub> predictions in a try lab more advantageous.In the past thirty years, many efforts had been made for accurate and fast protein pK<sub>a</sub> predictions with physics-based methods. Theoretically, constant pH molecular dynamics (CpHMD) methods that take conformational fluctuations into account give the most accurate predictions, especially the explicit-solvent CpHMD model proposed by Huang and coworkers (<i>J. Chem. Theory Comput.</i> 2016, 12, 5411-5421) which in principle is applicable to any system that a force field can describe. However, lengthy molecular simulations are usually necessary for extensive sampling in conformation. In particular, the computational complexity increases significantly if water molecules are included explicitly in the simulation systems. Thus, CpHMD is not suitable for high-throughout computing requested in industry. To accelerate pK<sub>a</sub> prediction, Poisson-Boltzmann (PB) or empirical equation-based schemes, such as H++ and PropKa, have been developed and widely applied where pK<sub>a</sub>’s are obtained via one-structure calculations. Recently, artificial intelligence (AI) is applied to the area of protein pK<sub>a</sub> prediction, which leads to the development of DeepKa by Huang lab (<i>ACS Omega</i> 2021, 6, 34823-34831), the first AI-driven pK<sub>a</sub> predictor. In this paper, we review the advances in protein pK<sub>a</sub> prediction contributed mainly by CpHMD methods, PB or empirical equation-based schemes, and AI models. Notably, the modeling hypotheses explained in the review would shed light on future developments of more powerful protein pK<sub>a</sub> predictors.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135495729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Li Wen-Wen, None Hui Ning-Jv, None Li Cun-Xia, None Liu Yang-He, None Fang Yan, None Li Ling-Qing, None Wang Yan-Long, None Tang Yuan-He
The DASH (Doppler Asymmetric Spatial Heterodyne) is used to detect the upper atmospheric wind velocity by its imaging Fizeau interference fringes. There are two wind measurement methods: Fourier series method (FSM) and popular Fourier transform method (FTM). However, the wind measurement accuracy of FTM is greatly influenced by window function, and the calculation amount is relatively complicated. The Four-point algorithm (FPA) for DASH’ s wind measurement is proposed in this paper. The contents of wind measurement principle, forward modeling, noise and inversion by the FSM, FTM and FPA are wholly compared and researched. The three wind measurement methods are all derived from the phase difference transformation of DASH Fizeau interference fringes. The Fizeau interference fringes with wind speed of 0-100m/s at the interval of 10m/s is simulated, and the forward wind speed is obtained by FSM, FTM and FPA, and the corresponding wind measurement errors are 2.93%, 4.67% and 3.00%,respectively. After artificially adding Gaussian noise with a mean value of 0 and a standard deviation of 0.1, FSM, FTM and FPA are used to forward the Fizeau interference fringes after flat field, and the corresponding relative errors are 2.30%, 11.66% and 2.27% respectively. After artificially adding Gaussian noise, the Fizeau interference fringes of wind speeds of 31-39m/s with 1m/s interval and 30.1-30.9m/s with 0.1m/s interval are simulated, and the forward wind speeds are obtained by FSM and FPA. In both cases, the wind measurement errors of FSM are 3.55% and 4.15% higher than those of FPA. The O(1S)557.7nm airglow at peak altitude of 98 km was photographed by our GBAII (Ground based airglow imaging interferometer)-DASH, and the imaging interferograms with zenith angles of 0 ° and 45 ° were obtained. Then by the methods of Fourier series, Fourier transform and FPA were used to obtain the inversion wind speed of 32.21m/s, 43.55m/s and 32.17m/s, respectively. From the forward and inversion results of DASH, we can see that the FPA has a better results for detecting the upper atmospheric wind, for its simple calculation and smaller wind measurement error.
{"title":"A comparative study of three methods to detect the upper atmospheric wind by DASH","authors":"None Li Wen-Wen, None Hui Ning-Jv, None Li Cun-Xia, None Liu Yang-He, None Fang Yan, None Li Ling-Qing, None Wang Yan-Long, None Tang Yuan-He","doi":"10.7498/aps.72.20231292","DOIUrl":"https://doi.org/10.7498/aps.72.20231292","url":null,"abstract":"The DASH (Doppler Asymmetric Spatial Heterodyne) is used to detect the upper atmospheric wind velocity by its imaging Fizeau interference fringes. There are two wind measurement methods: Fourier series method (FSM) and popular Fourier transform method (FTM). However, the wind measurement accuracy of FTM is greatly influenced by window function, and the calculation amount is relatively complicated. The Four-point algorithm (FPA) for DASH’ s wind measurement is proposed in this paper. The contents of wind measurement principle, forward modeling, noise and inversion by the FSM, FTM and FPA are wholly compared and researched. The three wind measurement methods are all derived from the phase difference transformation of DASH Fizeau interference fringes. The Fizeau interference fringes with wind speed of 0-100m/s at the interval of 10m/s is simulated, and the forward wind speed is obtained by FSM, FTM and FPA, and the corresponding wind measurement errors are 2.93%, 4.67% and 3.00%,respectively. After artificially adding Gaussian noise with a mean value of 0 and a standard deviation of 0.1, FSM, FTM and FPA are used to forward the Fizeau interference fringes after flat field, and the corresponding relative errors are 2.30%, 11.66% and 2.27% respectively. After artificially adding Gaussian noise, the Fizeau interference fringes of wind speeds of 31-39m/s with 1m/s interval and 30.1-30.9m/s with 0.1m/s interval are simulated, and the forward wind speeds are obtained by FSM and FPA. In both cases, the wind measurement errors of FSM are 3.55% and 4.15% higher than those of FPA. The O(<sup>1</sup>S)557.7nm airglow at peak altitude of 98 km was photographed by our GBAII (Ground based airglow imaging interferometer)-DASH, and the imaging interferograms with zenith angles of 0 ° and 45 ° were obtained. Then by the methods of Fourier series, Fourier transform and FPA were used to obtain the inversion wind speed of 32.21m/s, 43.55m/s and 32.17m/s, respectively. From the forward and inversion results of DASH, we can see that the FPA has a better results for detecting the upper atmospheric wind, for its simple calculation and smaller wind measurement error.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135594445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Preface to the special topic: The 70 th anniversary of National University of Defense Technology","authors":"","doi":"10.7498/aps.72.180101","DOIUrl":"https://doi.org/10.7498/aps.72.180101","url":null,"abstract":"摘要 国防科技大学物理学科起源于哈军工时期的物理教授会和原子工程系, 专业积淀深厚、军事特色鲜明. 七十年传承, 始终面向国家重大战略特别是国防科技战略, 为我国相关领域培养了一大批优秀人才. 围绕国防高科技武器基础原理和新概念武器开展特色研究, 在极端条件物态物性、强场超快、聚变能源、量子技术、武器物理等方面形成优势, 孵化了核科学与技术、光学工程一级学科和量子信息、高能量密度物理等交叉学科, 形成了基础研究与军事应用紧密结合、前沿探索与高水平人才培养有机统一、自主创新与开放合作相得益彰的鲜明特色, 建成了一流的拔尖人才培养基地和前沿创新科研平台. 在国防科技大学70年校庆之际, 在国内对基础学科发展前所未有重视之时, 国防科技大学对物理学科的支持力度也进入了全新的时期, 学科发展进入快车道, 高水平成果不断涌现. Abstract 作者及机构信息 Authors and contacts 文章全文 : translate this paragraph 参考文献 施引文献","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135595748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Compared with two-electrode gas spark switch, three-electrode gas spark switch has the advantages of lower operating voltage, higher reliability and less discharge jitter, so it has been widely used in pulse power systems. However, due to the characteristics of pulse power technology, the gas spark switch is easy to cause ablation on the electrode surface during use, and the metal particles generated by ablation will significantly affect the stability and reliability of the switch. This paper first simulated the discharge process of the three-electrode gas spark switch under atmospheric pressure nitrogen environment. In this model, the ionization coefficient near the trigger electrode is modified to compensate for the shortcomings of the local field approximation, and the relevant mathematical derivation process is given. The formation of the initial electron is described by the field electron emission phenomenon, and the development process of electron collapse into the streamer is obtained. The physical mechanism of switch on is investigated, and the development process of each stage of switch discharge is described in detail. Then, the discharge process of the switch is studied when there is metal particle near the trigger. The study shows that the presence of metal particles enhances the electric field near the trigger and accelerates the formation of the initial electron cloud. In addition, in the presence of metal particles, the metal particles and the trigger will first break down, forming a high-density plasma channel after the breakdown, and becoming the source of the subsequent flow development. At the same time, because the metal particles on the channel have an obstructing effect on the streamer development, the streamer generates a discharge branch after contact with metal particle. In the end, this paper discusses the influence of metal particles of different shapes and sizes on the discharge process. The results show that metal particle with sharp shapes has stronger electric field distortion near it, when the electric field intensity is large enough, it may cause field emission on the surface of metal particle. And it also make clearly that the size of metal particle is small, the obstruction to the development path of streamer is small, the streamer quickly converge behind the particles.
{"title":"Simulation of the effect of metal particles on the breakdown process of gas spark switches","authors":"None Zhou Xin-Miao, None Zhang Bo-Ya, None Chen Li, None Li Xing-Wen","doi":"10.7498/aps.73.20231283","DOIUrl":"https://doi.org/10.7498/aps.73.20231283","url":null,"abstract":"Compared with two-electrode gas spark switch, three-electrode gas spark switch has the advantages of lower operating voltage, higher reliability and less discharge jitter, so it has been widely used in pulse power systems. However, due to the characteristics of pulse power technology, the gas spark switch is easy to cause ablation on the electrode surface during use, and the metal particles generated by ablation will significantly affect the stability and reliability of the switch. This paper first simulated the discharge process of the three-electrode gas spark switch under atmospheric pressure nitrogen environment. In this model, the ionization coefficient near the trigger electrode is modified to compensate for the shortcomings of the local field approximation, and the relevant mathematical derivation process is given. The formation of the initial electron is described by the field electron emission phenomenon, and the development process of electron collapse into the streamer is obtained. The physical mechanism of switch on is investigated, and the development process of each stage of switch discharge is described in detail. Then, the discharge process of the switch is studied when there is metal particle near the trigger. The study shows that the presence of metal particles enhances the electric field near the trigger and accelerates the formation of the initial electron cloud. In addition, in the presence of metal particles, the metal particles and the trigger will first break down, forming a high-density plasma channel after the breakdown, and becoming the source of the subsequent flow development. At the same time, because the metal particles on the channel have an obstructing effect on the streamer development, the streamer generates a discharge branch after contact with metal particle. In the end, this paper discusses the influence of metal particles of different shapes and sizes on the discharge process. The results show that metal particle with sharp shapes has stronger electric field distortion near it, when the electric field intensity is large enough, it may cause field emission on the surface of metal particle. And it also make clearly that the size of metal particle is small, the obstruction to the development path of streamer is small, the streamer quickly converge behind the particles.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136201920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Kong Meimei, None Xue Yinyan, None Xu Chunsheng, None Dong Yuan, None Liu Yue, None Pan Shicheng, None Zhao Rui
In this paper, based on the research of zoom liquid lens with parallel plate electrode and the principle of dielectrophoresis, a model of the biconvex liquid lens with circular hole plate electrode structure is proposed, which is a novel three-layer liquid lens structure. The dielectrophoretic effect refers to the phenomenon that free dielectric molecules will be polarized and moved by the force in a non-uniform electric field, thus deforming the dielectric liquid. In the dielectrophoretic liquid lens, only two insulating liquid materials with large refractive index difference and dielectric constant difference need to be selected, which can increase the selection range of liquid materials. The liquid lens structure mainly consists of a piece of double-sided conductive flat plate ITO glass with a circular hole and two pieces of single-sided conductive flat plate ITO glass, which respectively form two sets of flat electrode structures to control the upper and lower interfaces of the liquid droplet. In this structure, the influence of the intermediate glass plate on the focus and imaging is reduced by using the flat plate electrode with circular hole. The theoretical analysis of the structure is carried out with simulation software. Firstly, the models of the biconvex liquid lens with circular hole plate electrode under different voltages are built with Comsol software, the data of upper and lower interfaces of the liquid droplet are exported. Then by using Matlab, the surface shapes of the upper and lower interfaces of the droplet are fitted and the corresponding aspheric coefficients are obtained. Finally, the optical models are built with Zemax software, the imaging optical paths and the variation range of focal length under different voltages are analyzed. On the basis of the simulation, the corresponding device is manufactured, and the specific experimental analysis is carried out. The surface pattern of the upper and lower interfaces of the droplet of the biconvex liquid lens under different voltages are recorded, the focal length and imaging resolution of the liquid lens are measured. When the operating voltage is 0V-260V, the focal length varies from 23.8mm to 17.5mm, which is basically consistent with the simulation results(22.6mm-15.9mm). The feasibility of the structure of the biconvex liquid lens with circular hole plate electrode structure is verified by experiments. The imaging resolution can reach 45.255 lp/mm. The results show that this proposed novel three-layer liquid structure of the biconvex liquid lens has the characteristics of simple structure, easy to realize and good imaging quality. Therefore, the research of this biconvex liquid lens can provide a new idea for expanding the high-resolution imaging research of liquid lenses and their applications.
{"title":"Design and analysis of the biconvex liquid lens with circular hole plate electrode structure","authors":"None Kong Meimei, None Xue Yinyan, None Xu Chunsheng, None Dong Yuan, None Liu Yue, None Pan Shicheng, None Zhao Rui","doi":"10.7498/aps.72.20231291","DOIUrl":"https://doi.org/10.7498/aps.72.20231291","url":null,"abstract":"In this paper, based on the research of zoom liquid lens with parallel plate electrode and the principle of dielectrophoresis, a model of the biconvex liquid lens with circular hole plate electrode structure is proposed, which is a novel three-layer liquid lens structure. The dielectrophoretic effect refers to the phenomenon that free dielectric molecules will be polarized and moved by the force in a non-uniform electric field, thus deforming the dielectric liquid. In the dielectrophoretic liquid lens, only two insulating liquid materials with large refractive index difference and dielectric constant difference need to be selected, which can increase the selection range of liquid materials. The liquid lens structure mainly consists of a piece of double-sided conductive flat plate ITO glass with a circular hole and two pieces of single-sided conductive flat plate ITO glass, which respectively form two sets of flat electrode structures to control the upper and lower interfaces of the liquid droplet. In this structure, the influence of the intermediate glass plate on the focus and imaging is reduced by using the flat plate electrode with circular hole. The theoretical analysis of the structure is carried out with simulation software. Firstly, the models of the biconvex liquid lens with circular hole plate electrode under different voltages are built with Comsol software, the data of upper and lower interfaces of the liquid droplet are exported. Then by using Matlab, the surface shapes of the upper and lower interfaces of the droplet are fitted and the corresponding aspheric coefficients are obtained. Finally, the optical models are built with Zemax software, the imaging optical paths and the variation range of focal length under different voltages are analyzed. On the basis of the simulation, the corresponding device is manufactured, and the specific experimental analysis is carried out. The surface pattern of the upper and lower interfaces of the droplet of the biconvex liquid lens under different voltages are recorded, the focal length and imaging resolution of the liquid lens are measured. When the operating voltage is 0V-260V, the focal length varies from 23.8mm to 17.5mm, which is basically consistent with the simulation results(22.6mm-15.9mm). The feasibility of the structure of the biconvex liquid lens with circular hole plate electrode structure is verified by experiments. The imaging resolution can reach 45.255 lp/mm. The results show that this proposed novel three-layer liquid structure of the biconvex liquid lens has the characteristics of simple structure, easy to realize and good imaging quality. Therefore, the research of this biconvex liquid lens can provide a new idea for expanding the high-resolution imaging research of liquid lenses and their applications.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Transition state is the key concept for chemists to understand and fine-tune the conformational changes of large biomolecules. Due to its short residence time, it is difficult to capture a transition state via experimental techniques. Characterizing transition states for a conformational change therefore is only achievable via physics-driven molecular dynamics simulations. However, unlike chemical reactions which involve only a small number of atoms, conformational changes of biomolecules depend on numerous atoms and therefore their coordinates in our 3D space. The searching of transition states for them will inevitably encounter the curse of dimensionality, i.e. the reaction coordinate problem, which invoked the invention of various algorithms for solution. Recent years have witnessed a rapid emergence of new machine learning techniques and the incorporation of some of them into the transition state searching methods. Here, we first review the design principle of representative transition state searching algorithms, including the collective-variable(CV)-dependent Gentlest Ascent Dynamics (GAD), Finite Temperature String, Fast Tomographic, Travelling-salesman based Automated Path Searching (TAPS) and the CV-independent Transition Path Sampling (TPS). Then, we focus on the new version of TPS that incorporates reinforcement learning for efficient sampling and clarify the suitable situation for its application. Finally, we propose a new paradigm for transition state searching-invent new dimensionality reduction techniques that preserve transition state information and combine them with GAD.
{"title":"Machine Learning in Transition State Searching for Complex Biomolecules","authors":"None Yang Jian-Yu, None Xi Kun, None Zhu Li-Zhe","doi":"10.7498/aps.72.20231319","DOIUrl":"https://doi.org/10.7498/aps.72.20231319","url":null,"abstract":"Transition state is the key concept for chemists to understand and fine-tune the conformational changes of large biomolecules. Due to its short residence time, it is difficult to capture a transition state via experimental techniques. Characterizing transition states for a conformational change therefore is only achievable via physics-driven molecular dynamics simulations. However, unlike chemical reactions which involve only a small number of atoms, conformational changes of biomolecules depend on numerous atoms and therefore their coordinates in our 3D space. The searching of transition states for them will inevitably encounter the curse of dimensionality, i.e. the reaction coordinate problem, which invoked the invention of various algorithms for solution. Recent years have witnessed a rapid emergence of new machine learning techniques and the incorporation of some of them into the transition state searching methods. Here, we first review the design principle of representative transition state searching algorithms, including the collective-variable(CV)-dependent Gentlest Ascent Dynamics (GAD), Finite Temperature String, Fast Tomographic, Travelling-salesman based Automated Path Searching (TAPS) and the CV-independent Transition Path Sampling (TPS). Then, we focus on the new version of TPS that incorporates reinforcement learning for efficient sampling and clarify the suitable situation for its application. Finally, we propose a new paradigm for transition state searching-invent new dimensionality reduction techniques that preserve transition state information and combine them with GAD.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, a modified Mott-Gurney differential equation set was built by Arrhenius' law and the overpotential theory of ionic motion in bipolar ECM resistive devices. The average displacement of ions was solved by the modified Mott-Gurney equation. Then, the relation between the average displacement and the growth length of the conductive filament was obtained by a geometric model based on cells. The applied voltage versus Forming/Set time equation and the length of the conductive filament growth versus time equation have been deduced by using this relation. This article proposed also an algorithm for extracting kinetic parameters of ions in bipolar ECM devices. By using this algorithm, the characteristics of the applied voltage versus Forming/Set time for Ag/γ-AgI/Pt, Ag/TiO2/Pt, Ag/GeS2/W, and Cu/SiO2/Au devices were calculated and the calculative results were consistent with experimental data. We found that in the Forming/Set process, the jump step of silver ions is the lattice constant along c direction of a unit cell of the crystal for TiO2 and the jump step is equal to the lattice constant of the cubic, a, for γ-AgI. These results are explained as followings. In a unit cell of the two crystals there are some tetrahedral and octahedral interstitial sites. The cationic motion paths consist of alternating octahedral and tetrahedral sites or some octahedral sites. The cations jump from tetrahedron to octahedron to tetrahedron etc. in the γ-AgI with coplanar polyhedron and octahedron to octahedron in the TiO2 with edge shared octahedron. In GeS2 crystal, we have found that the jump step of silver ions was the lattice constant in the c direction of a unit cell. Due to the periodicity of the lattice, the pathway of the ion motion in the three materials can be expressed by a periodic potential barrier. There had been calculated for the jump situation of the copper ion in amorphous SiO2, the jump step of copper ions was 1.57 times of the length of the O-O bond, and the jump pathway could be also explained by a periodic potential barrier. By introducing the cosine potential barrier, the ionic activation frequency, potential barrier height, ionic mobility & diffusion coefficient, and characteristics of the conductive filament growth versus time in several devices were calculated. The criteria of selecting dielectric materials for bipolar ECM devices was discussed by using these data. It was found that the standard for selecting dielectric materials of bipolar ECM devices is the ion activation energy ≤ 0.5eV, preferably between 0.1-0.2eV, and the DC conductivity as close as possible to 10‒4 (Ω cm)‒1.
{"title":"Study on the kinetics of ions in the process of the conductive filament growth for the electrochemical metallization resistive memory","authors":"None Qing Ke, None Yuehua Dai","doi":"10.7498/aps.72.20231232","DOIUrl":"https://doi.org/10.7498/aps.72.20231232","url":null,"abstract":"In this paper, a modified Mott-Gurney differential equation set was built by Arrhenius' law and the overpotential theory of ionic motion in bipolar ECM resistive devices. The average displacement of ions was solved by the modified Mott-Gurney equation. Then, the relation between the average displacement and the growth length of the conductive filament was obtained by a geometric model based on cells. The applied voltage versus Forming/Set time equation and the length of the conductive filament growth versus time equation have been deduced by using this relation. This article proposed also an algorithm for extracting kinetic parameters of ions in bipolar ECM devices. By using this algorithm, the characteristics of the applied voltage versus Forming/Set time for Ag/γ-AgI/Pt, Ag/TiO<sub>2</sub>/Pt, Ag/GeS<sub>2</sub>/W, and Cu/SiO<sub>2</sub>/Au devices were calculated and the calculative results were consistent with experimental data. We found that in the Forming/Set process, the jump step of silver ions is the lattice constant along c direction of a unit cell of the crystal for TiO<sub>2</sub> and the jump step is equal to the lattice constant of the cubic, a, for γ-AgI. These results are explained as followings. In a unit cell of the two crystals there are some tetrahedral and octahedral interstitial sites. The cationic motion paths consist of alternating octahedral and tetrahedral sites or some octahedral sites. The cations jump from tetrahedron to octahedron to tetrahedron etc. in the γ-AgI with coplanar polyhedron and octahedron to octahedron in the TiO<sub>2</sub> with edge shared octahedron. In GeS<sub>2</sub> crystal, we have found that the jump step of silver ions was the lattice constant in the c direction of a unit cell. Due to the periodicity of the lattice, the pathway of the ion motion in the three materials can be expressed by a periodic potential barrier. There had been calculated for the jump situation of the copper ion in amorphous SiO<sub>2</sub>, the jump step of copper ions was 1.57 times of the length of the O-O bond, and the jump pathway could be also explained by a periodic potential barrier. By introducing the cosine potential barrier, the ionic activation frequency, potential barrier height, ionic mobility & diffusion coefficient, and characteristics of the conductive filament growth versus time in several devices were calculated. The criteria of selecting dielectric materials for bipolar ECM devices was discussed by using these data. It was found that the standard for selecting dielectric materials of bipolar ECM devices is the ion activation energy ≤ 0.5eV, preferably between 0.1-0.2eV, and the DC conductivity as close as possible to 10<sup>‒4</sup> (Ω cm)<sup>‒1</sup>.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Ran Pei-Lin, None Wu Kang, None Zhao En-Yue, None Wang Fang-Wei, None Wu Zhi-Min
Li-ion batteries(LIBs) are widely used in mobile devices and electric vehicles, but the traditional layered transition metal cathode material, LiTMO2(TM=Ni, Co, Mn, or Al), has a low energy density that cannot satisfy the demand of commercial applications, and Li-rich Mn-based layered oxides(LRLOs) are a strong competitor to the traditional layered cathode materials for their specific capacity of more than 200 mAh/g. Due to the high energy density and low cost, Li-rich Mn-based layered oxides(LRLO) have been a promising candidate cathode for next-generation Li-ion batteries. The anionic redox reaction(ARR) in LRLO destabilizes the lattice oxygen, leading to voltage degradation and capacity loss. Although iron-substituted cobalt-free Li-rich materials can achieve less voltage decay, they suffer from severe cation disorder and poor kinetics. Here, we developed a simple and feasible high-valent ion doping strategy by doping Mo into Li1.2Ni0.13Fe0.13Mn0.54O2(LNFMO), which expands the Li layer spacing, provides a broader channel for Li+ transport, improves the diffusion kinetics of Li+, effectively suppresses the cation disorder, and further stabilizes the layered structure. As a result, the Mo-doped LRLO exhibited significantly enhanced electrochemical performance, with an initial reversible capacity of 209.48 mAh/g at 0.2 C, and the initial specific capacity increased from 137.02 mAh/g to 165.15 mAh/g at 1 C. After 300 cycles, there is still a specific capacity of 117.49 mAh/g for the Mo-doped cathode, and the voltage decay is reduced from 2.09 mV/cycle to 1.66 mV/cycle. The Mo-doped LRLO are systematically characterized, and the mechanism of cycle stabilization is revealed, which provides an important reference for designing high performance Li-rich cathode.
{"title":"Enhanced reversible capacity and cycling stability of Li<sub>1.2</sub>Ni<sub>0.13</sub>Fe<sub>0.13</sub>Mn<sub>0.54</sub>O<sub>2</sub> via Mo-doped induced low Li/Ni site disorder","authors":"None Ran Pei-Lin, None Wu Kang, None Zhao En-Yue, None Wang Fang-Wei, None Wu Zhi-Min","doi":"10.7498/aps.73.20231361","DOIUrl":"https://doi.org/10.7498/aps.73.20231361","url":null,"abstract":"Li-ion batteries(LIBs) are widely used in mobile devices and electric vehicles, but the traditional layered transition metal cathode material, LiTMO<sub>2</sub>(TM=Ni, Co, Mn, or Al), has a low energy density that cannot satisfy the demand of commercial applications, and Li-rich Mn-based layered oxides(LRLOs) are a strong competitor to the traditional layered cathode materials for their specific capacity of more than 200 mAh/g. Due to the high energy density and low cost, Li-rich Mn-based layered oxides(LRLO) have been a promising candidate cathode for next-generation Li-ion batteries. The anionic redox reaction(ARR) in LRLO destabilizes the lattice oxygen, leading to voltage degradation and capacity loss. Although iron-substituted cobalt-free Li-rich materials can achieve less voltage decay, they suffer from severe cation disorder and poor kinetics. Here, we developed a simple and feasible high-valent ion doping strategy by doping Mo into Li<sub>1.2</sub>Ni<sub>0.13</sub>Fe<sub>0.13</sub>Mn<sub>0.54</sub>O<sub>2</sub>(LNFMO), which expands the Li layer spacing, provides a broader channel for Li<sup>+</sup> transport, improves the diffusion kinetics of Li<sup>+</sup>, effectively suppresses the cation disorder, and further stabilizes the layered structure. As a result, the Mo-doped LRLO exhibited significantly enhanced electrochemical performance, with an initial reversible capacity of 209.48 mAh/g at 0.2 C, and the initial specific capacity increased from 137.02 mAh/g to 165.15 mAh/g at 1 C. After 300 cycles, there is still a specific capacity of 117.49 mAh/g for the Mo-doped cathode, and the voltage decay is reduced from 2.09 mV/cycle to 1.66 mV/cycle. The Mo-doped LRLO are systematically characterized, and the mechanism of cycle stabilization is revealed, which provides an important reference for designing high performance Li-rich cathode.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136203337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In van der Waals systems, the interlayer van der Waals coupling between adjacent atomically thin layers renders the electronic wave function to reside on more than one specific layer, promoting the layer degree of freedom from a spatial object to a quantum mechanical pseudospin. The coupling of layer degree of freedom with the in-plane center-of-mass motion of electrons shapes nontrivial layer pseudospin structures in momentum space, leading to various new quantum geometric properties in an extended parameter space unique to lattice mismatched van der Waals systems. They underly a plenty of novel transport and optical effects, linear and nonlinear responses, and offer new pathways towards device applications, constituting the research frontiers of quantum layertronics. This article provided a brief review of this emerging research direction, and discussed possible developments in near future based on its crossings with other intensive research fields such as nonlinear electronics, twistronics and chiral electronics.
{"title":"Quantum layertronics in van der Waals systems","authors":"None Xiao Cong, None Yao Wang","doi":"10.7498/aps.72.20231323","DOIUrl":"https://doi.org/10.7498/aps.72.20231323","url":null,"abstract":"In van der Waals systems, the interlayer van der Waals coupling between adjacent atomically thin layers renders the electronic wave function to reside on more than one specific layer, promoting the layer degree of freedom from a spatial object to a quantum mechanical pseudospin. The coupling of layer degree of freedom with the in-plane center-of-mass motion of electrons shapes nontrivial layer pseudospin structures in momentum space, leading to various new quantum geometric properties in an extended parameter space unique to lattice mismatched van der Waals systems. They underly a plenty of novel transport and optical effects, linear and nonlinear responses, and offer new pathways towards device applications, constituting the research frontiers of quantum layertronics. This article provided a brief review of this emerging research direction, and discussed possible developments in near future based on its crossings with other intensive research fields such as nonlinear electronics, twistronics and chiral electronics.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135101369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Kong Mei-Mei, None Dong Yuan, None Xu Chun-Sheng, None Liu Yue, None Xue Yin-Yan, None Pan Shi-Cheng, None Zhao Rui
Based on the principle of dielectrophoresis, an aspherical double-liquid lens based on parallel plate electrode is designed. In comparison with the liquid lenses based on patterned-electrode, the aspherical double-liquid lens structure uses continuous electrode, which has the advantages of simpler processing, lower cost, easier realization and more practicability. The droplet in the dielectric electrophoretic liquid lens is polarized in the electric field and move towards the direction of higher electric field intensity under the action of the dielectrophoretic forces. With the change of applied voltage, the dielectrophoretic forces are also changed, thus the contact angle of the droplet at the liquid-liquid interface is changed. Firstly, the models of aspherical double-liquid lenses under different voltages are established with Comsol software, and the data of interfacial profile are derived. Then using Matlab software, the derived interface surface data are fitted by polynomial, and the aspherical coefficients are obtained. Finally, the optical models are built with Zemax software, the variation range of focal length and RMS radius of aspherical double-liquid lens under different voltages are analyzed. In order to further research the characteristics of aspherical double-liquid lens, it is compared with spherical double-liquid lens model. The liquid material, cavity structure and droplet volume of spherical double-liquid lens are consistent with those of aspherical double-liquid lens. The corresponding spherical double-liquid lens model is established by Zemax software, the range of focal length and RMS radius of spherical double-liquid lens under different voltages are obtained. The results show that the focal length variation range of aspherical double-liquid lens is larger than that of spherical double-liquid lens, and the imaging quality of the former is better than that of the latter. The experimental preparation of the designed aspherical double-liquid lens device is carried out, and its focal length and imaging resolution are measured. When the operating voltage is 0V-280V, the focal length varies from 54.2391mm to 34.5855mm, which is basically consistent with the result of simulation. The feasibility of the liquid lens structure is verified by experiments. The imaging resolution can reach 45.255lp/mm. The designed aspherical double-liquid lens based on parallel plate electrode can provide a new scheme for the high-quality imaging of liquid lens and its application, and can expand the application of liquid lens.
{"title":"Simulation and experimental analysis of aspherical double-liquid lens based on parallel plate electrode","authors":"None Kong Mei-Mei, None Dong Yuan, None Xu Chun-Sheng, None Liu Yue, None Xue Yin-Yan, None Pan Shi-Cheng, None Zhao Rui","doi":"10.7498/aps.72.20230994","DOIUrl":"https://doi.org/10.7498/aps.72.20230994","url":null,"abstract":"Based on the principle of dielectrophoresis, an aspherical double-liquid lens based on parallel plate electrode is designed. In comparison with the liquid lenses based on patterned-electrode, the aspherical double-liquid lens structure uses continuous electrode, which has the advantages of simpler processing, lower cost, easier realization and more practicability. The droplet in the dielectric electrophoretic liquid lens is polarized in the electric field and move towards the direction of higher electric field intensity under the action of the dielectrophoretic forces. With the change of applied voltage, the dielectrophoretic forces are also changed, thus the contact angle of the droplet at the liquid-liquid interface is changed. Firstly, the models of aspherical double-liquid lenses under different voltages are established with Comsol software, and the data of interfacial profile are derived. Then using Matlab software, the derived interface surface data are fitted by polynomial, and the aspherical coefficients are obtained. Finally, the optical models are built with Zemax software, the variation range of focal length and RMS radius of aspherical double-liquid lens under different voltages are analyzed. In order to further research the characteristics of aspherical double-liquid lens, it is compared with spherical double-liquid lens model. The liquid material, cavity structure and droplet volume of spherical double-liquid lens are consistent with those of aspherical double-liquid lens. The corresponding spherical double-liquid lens model is established by Zemax software, the range of focal length and RMS radius of spherical double-liquid lens under different voltages are obtained. The results show that the focal length variation range of aspherical double-liquid lens is larger than that of spherical double-liquid lens, and the imaging quality of the former is better than that of the latter. The experimental preparation of the designed aspherical double-liquid lens device is carried out, and its focal length and imaging resolution are measured. When the operating voltage is 0V-280V, the focal length varies from 54.2391mm to 34.5855mm, which is basically consistent with the result of simulation. The feasibility of the liquid lens structure is verified by experiments. The imaging resolution can reach 45.255lp/mm. The designed aspherical double-liquid lens based on parallel plate electrode can provide a new scheme for the high-quality imaging of liquid lens and its application, and can expand the application of liquid lens.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136053209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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