Chinese Physics最新文献

{"title":"The mirror buckling analysis of freestanding graphene membranes based on the coarse-grained molecular dynamics method","authors":"None Xu Wenlong, None Kai Yue, None Zhang Kai, None Zheng Balin","doi":"10.7498/aps.72.20231120","DOIUrl":"https://doi.org/10.7498/aps.72.20231120","url":null,"abstract":"For now, just few researchers have analyzed the thermal-mechanical mirror buckling behavior of freestanding graphene membranes discovered in scan tunneling microscope experiments. Ones of the potential applies of the out-of-plane deformational behavior of graphene membranes are energy harvesting systems. Whatever in the experiments, or for energy harvesting systems, the graphene membranes are micron order. According to previous researches, traditional molecular dynamics method is an appropriate approach to express mirror buckling with nano scale. However, due to the limit of algorithm, when dealing with micro size model by molecular dynamics method, the problems of low computational efficiency and too long calculational time may arise. Therefore, for analyzing the mirror buckling of micro size graphene membranes, the coarse-grained molecular dynamics method is utilized in this paper. Graphene membranes with a fan-shaped cross section and various depth-span ratios are under mechanical or thermal loads. Influences of every factor on the mirror buckling are explored. The calculations indicated that for graphene membranes with various depth-span ratios under mechanical load mirror buckling could be observed. And the critical loading increases with the depth-span ratio. Under thermal load graphene membranes only with low depth-span ratios could totally overturn. For high depth-span ratio graphene, the center height decreases with temperature rise. However, it is hard to overturn completely. Understanding the influences of various factors on the mirror buckling phenomenon of graphene membranes provides theoretical guidance for the design of energy harvesting systems.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"2013 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":"135495742","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":"Mechanical stress-thermodynamic phase-field simulation of lithium dendrite growth in solid electrolyte battery","authors":"None Geng Xiao-Bin, None Li Ding-Gen, None Xu Bo","doi":"10.7498/aps.72.20230824","DOIUrl":"https://doi.org/10.7498/aps.72.20230824","url":null,"abstract":"Growth of lithium dendrites in solid state batteries is an important factor that disturbs their commercial applications. The growth of lithium dendrites at the interface of lithium metal anode will not only lead to the decrease of battery energy efficiency, but also cause combustion, explosion and other safety problems. In order to explore the factors and methods that inhibit the growth of lithium dendrites, the phase-field theory is used to simulate the growth of lithium dendrites in polymer solid electrolyte batteries, and a phase-field model of lithium dendrite growth coupled with mechanical stress and thermal field is established. The effects of key physical factors such as ambient temperature, solid electrolyte Young’s modulus and external stress on dendrite growth and their acting principles are discussed and analyzed. The results show that under the conditions of high temperature, high solid electrolyte Young’s modulus and external stress, the growth of lithium dendrites is slow, the number of long dendrites is small, and the electrodeposition is more uniform. In addition, the effects of Young’s modulus of solid electrolyte and ambient temperature on the growth of lithium dendrites in a common range are compared with each other. It is found that the inhibition effect of changing Young’s modulus of solid electrolyte on the maximum length of lithium dendrites is 19% higher than that caused by the change of ambient temperature.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"29 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":"135496014","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":"Large scale and quantum accurate molecular dynamics simulation: liquid iron under extreme condition","authors":"Qi-Yu Zeng, Bo Chen, Dong-Dong Kang, Jia-Yu Dai","doi":"10.7498/aps.72.20231258","DOIUrl":"https://doi.org/10.7498/aps.72.20231258","url":null,"abstract":"Liquid iron is the major component of planetary cores. Its structure and dynamics under high pressure and temperature is of great significance in studying geophysics and planetary science. However, for experimental techniques, it is still difficult to generate and probe such a state of matter under extreme conditions, while for theoretical method like molecular dynamics simulation, the reliable estimation of dynamic properties requires both large simulation size and <i>ab initio</i> accuracy, resulting in unaffordable computational costs for traditional method. Owing to the technical limitation, the understanding of such matters remains limited. In this work, combining molecular dynamics simulation, we establish a neural network potential energy surface model to study the static and dynamic properties of liquid iron at its extreme thermodynamic state close to core-mantle boundary. The implementation of deep neural network extends the simulation scales from one hundred atoms to millions of atoms within quantum accuracy. The estimated static and dynamic structure factor show good consistency with all available X-ray diffraction and inelastic X-ray scattering experimental observations, while the empirical potential based on embedding-atom-method fails to give a unified description of liquid iron across a wide range of thermodynamic conditions. We also demonstrate that the transport property like diffusion coefficient exhibits a strong size effect, which requires more than at least ten thousands of atoms to give a converged value. Our results show that the combination of deep learning technology and molecular modelling provides a way to describe matter realistically under extreme conditions.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"48 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":"135501946","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":"Mott physics — one of main themes in quantum materials","authors":"Dong-Lai Feng","doi":"10.7498/aps.72.20231508","DOIUrl":"https://doi.org/10.7498/aps.72.20231508","url":null,"abstract":"<sec>The competition and cooperation between the itinerancy behavior and localization behavior of electrons in correlated quantum materials, known as Mott physics, is the physical mechanism behind the diverse states of many quantum materials. This article reviews the manifestation of Mott physics in various quantum materials and establishes it as one of the main themes of quantum materials. Finding and understanding its ever-changing ways of manifestation is one of the central tasks of experimental research on condensed matter physics.</sec><sec>Specifically, the filling-control route of Mott transition is illustrated by exampling the surface K-dosed Sr₂IrO₄, which exhibits d-wave gap, pseudogap behavior in underdoped regime, and phase separation with inhomogeneous electronic state distribution. All of these show strong resemblances to the doped cuprate superconductors, another prototypical filling-control type of Mott transition case. On the other hand, the bandwidth-control route of Mott transition could be found in NiS_2–<i>x</i>Se_<i>x</i>, where its bandwidth continuously decreases with Se concentration decreasing, until it becomes an insulator. In addition, the essence of various ways of doping in iron-based superconductors is to change their bandwidths. The superconductivity shows up at intermediate bandwidth with moderate correlations, and it diminishes when the bandwidth is large and the electron correlations are weak. For heavily electron-doped iron-selenides, there is even a Mott insulator phase with strong correlations.</sec><sec>For carbon based materials, the phase transition between the antiferromagnetic insulator and superconducting state of A15 Cs₃C₆₀ as the volume of fullerene anions decreases could be understood in terms of a bandwidth-control Mott transition; the insulator-superconductor transition discovered in electrically gated twisted-angle bilayer graphene could be understood as a filling-control Mott transition.</sec><sec>For f electron systems, the interplay between itinerancy and localization dominates the heavy fermion behavior and their ground states. The behaviors of the f electrons are demonstrated by using the angle-resolved photoemission data of CeCoIn₅, whose f electron band becomes more coherent with temperature decreasing, and the c-f hybridization is thus enhanced and the band mass of conduction band continuously increases. The c-f hybridization behaviors of CeCoIn_5, CeIrIn₅, and CeRhIn₅ are compared with each other, and the differences in hybridization strength put their ground states into different regimes of the Doniach phase diagram. Similarly, the Skutterudites 4f² Kondo lattice system PrOs₄Sb₁₂ and its sibling 4f¹ system CeOs₄Sb₁₂ also have different ground states due to a slight difference in their c-f hybridization strengths.</sec","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"38 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":"135659105","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":"Floquet engineering in quantum materials","authors":"None Changhua Bao, None Benshu Fan, None Peizhe Tang, None Wenhui Duan, None Shuyun Zhou","doi":"10.7498/aps.72.20231423","DOIUrl":"https://doi.org/10.7498/aps.72.20231423","url":null,"abstract":"Floquet engineering based on the strong light-matter interaction is expected to drive quantum materials into nonequilibrium states on an ultrafast timescale, thereby engineering their electronic structure and physical properties, and achieving novel physical effects which has no counterpart in equilibrium states. In recent years, Floquet engineering has attracted a lot of research interest, and there have been numerous rich theoretical predictions. In addition, important experimental research progress has also been made in several representative materials such as topological insulators, graphene, and black phosphorus. Here, we briefly introduce the important theoretical and experimental progress in this field, and prospects the research future, experimental challenges, and development directions.","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":"135758464","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":"Thermodynamic phase transition driven by topological excitations and their tensor network approach","authors":"None Song Feng-Feng, None Zhang Guang-Ming","doi":"10.7498/aps.72.20231152","DOIUrl":"https://doi.org/10.7498/aps.72.20231152","url":null,"abstract":"The fundamental concepts of phases and phase transitions constitute the cornerstone of our understanding of the physical universe. The historical development of the phase transition theory from Landau's spontaneous symmetry breaking paradigm to modern topological phase transition theories represents a major milestone in the evolution of numerous scientific disciplines. From the perspective of emergent philosophy, the interplay of topological excitations leads to enriched physical phenomena. One prominent prototype is the Berezinskii-Kosterlitz-Thouless (BKT) phase transition, where unbinding of integer vortices occurs in the absence of spontaneous breaking of continuous <i>U</i>(1) symmetry. Using the state-of-the-art tensor network methods, we express the partition function of the two-dimensional <i>XY</i>-related system in terms of a product of one-dimensional transfer operators. From the singularities of the entanglement entropy of the one-dimensional transfer operator, we accurately determine the complete phase diagram. This method provides new insights into the emergent phenomenon driven by topological excitations, and sheds new light on future studies of 2D systems with continuous symmetries.","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":"135400644","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":"Finite-key analysis of decoy model Semi-quantum key distribution based on four-state protocol","authors":"None Zhan Shao-Kang, None Wang Jin-Dong, None Dong Shuang, None Huang Si-Ying, None Hou Qing-Cheng, None Mo Nai-Da, None Mi Shang, None Xiang Li-Bing, None Zhao Tian-Ming, None Yu Ya-Fei, None Wei Zheng-Jun, None Zhang Zhi-Ming","doi":"10.7498/aps.72.20230849","DOIUrl":"https://doi.org/10.7498/aps.72.20230849","url":null,"abstract":"Semi-quantum key distribution allows a full quantum user Alice and a classical user Bob to share a pair of security keys guaranteed by physical principles. Semi-quantum key distribution is proposed while verifying its robustness. Subsequently, its unconditional security of semi quantum key distribution system is verified theoretically. In 2021, the feasibility of semi quantum key distribution system based on mirror protocol was verified experimentally. However, the feasibility experimental system still uses the laser pulse with strong attenuation. It has been proved in the literature that the semi-quantum key distribution system still encounters the risk of secret key leakage under photon number splitting attack. Therefore, the actual security of key distribution can be further reasonably evaluated by introducing the temptation state and conducting the finite-key analysis in the key distribution process. In this work, for the model of adding one-decoy state only to Alice at the sending based on a four state semi-quantum key distribution system, the length of the security key in the case of finite-key is analyzed by using Hoeffding inequality, and then the formula of the security key rate is obtained. It is found in the numerical simulation that when the sample size is <inline-formula><tex-math id=\"M3\">begin{document}$ {10}^{5} $end{document}</tex-math><alternatives><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20230849_M3.jpg\"/><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20230849_M3.png\"/></alternatives></inline-formula>, the security key rate of <inline-formula><tex-math id=\"M4\">begin{document}$ {10}^{-4} $end{document}</tex-math><alternatives><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20230849_M4.jpg\"/><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20230849_M4.png\"/></alternatives></inline-formula>, which is close to the security key rate of the asymptotic limits, can be obtained in the case of close range, It is very important for the practical application of semi quantum key distribution system.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"74 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":"135401836","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":"Effects of radial electric field on ion-temperature gradient driven mode stability","authors":"None Chen Ning-Fei, None Wei Guang-Yu, None Qiu Zhi-Yong","doi":"10.7498/aps.72.20230798","DOIUrl":"https://doi.org/10.7498/aps.72.20230798","url":null,"abstract":"To understand the effects of given radial electric field on ion-temperature gradient driven mode (ITG) stability in tokamak plasmas, the eigenmode equation for ITG including the poloidal rotation and density modulation associated with radial electric field is derived using nonlinear gyrokinetic theory. The equation is solved for eigenfrequency, growth rate and parallel mode structure of ITG both in short- and long-wavelength limit with energetic-particle-induced geodesic acoustic mode (EGAM) as a specific form. The eigenmode equation is not only solved analytically, but also solved numerically to validate the analytic solutions. It is found that, radial electric field induced poloidal rotation can significantly stabilize ITG, while the density perturbation of the radial electric field may slightly distort the ITG parallel mode structure, but has little effect on ITG stability. The result is consistent with common picture of turbulence suppression by poloidal shear flow. The general model is also applicable to the investigation of the indirect interaction of ITG and energetic particle driven Alfvén instabilities via zonal structures generation, by means of introducing poloidal rotation and density modulation associated with zonal structures spontaneously excited by Alfvén instabilities. The indirect channel is supplement to the direct interaction of microturbulences and energetic particle driven Alfvén instabilities.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"242 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":"136259598","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":"Modulation of photocurrent response in WS&lt;sub&gt;2&lt;/sub&gt; optoelectronic devices with Li intercalation","authors":"None Song Yu-Xin, None Li Yu-Qi, None Wang Ling-Han, None Zhang Xiao-Lan, None Wang Chong, None Wang Qin-Sheng","doi":"10.7498/aps.72.20231000","DOIUrl":"https://doi.org/10.7498/aps.72.20231000","url":null,"abstract":"Transition metal dichalcogenides have emerged as a prominent class of two-dimensional layered materials, capturing sustained attention from researchers due to their unique structures and properties. These distinctive characteristics render transition metal dichalcogenides highly versatile in numerous fields, including optoelectronics, nanoelectronics, energy storage devices, and electrocatalysis. In particular, the ability to modulate the doping characteristics of these materials plays a crucial role in improving the photoelectric response performance of devices, making it imperative to investigate and understand such effects.<br>In recent years, the electrochemical ion intercalation technique has emerged as a novel approach for precise doping control of two-dimensional materials. Building upon this advancement, this paper aims to demonstrate the effective doping control of transition metal dichalcogenides devices by utilizing the electrochemical ion intercalation method specifically on thick WS₂ layers. The results reveal a remarkable enhancement in electrical conductivity, approximately 200 times higher than the original value, alongside the achievement of efficient and reversible control over the photoelectric response performance through the manipulation of gate voltage. One of the key findings of this paper is the successful demonstration of the reversible cyclic control of the photoelectric response in WS₂ devices through ion intercalation, regulated by the gate voltage. This dynamic control mechanism showcases the potential for finely tuning and tailoring the performance of photoelectric devices made from two-dimensional materials. The ability to achieve reversible control is especially significant as it allows for a versatile range of applications, enabling devices to be adjusted according to specific requirements and operating conditions.<br>The implications of this work extend beyond the immediate findings and present a foundation for future investigations into response control of photoelectric devices constructed using two-dimensional materials through the utilization of the ion intercalation method. By establishing the feasibility and efficacy of this technique in achieving controlled doping and precise modulation of photoelectric response, researchers can explore its potential applications in various technological domains. Furthermore, this research serves as a stepping stone for the development of advanced doping strategies, enabling the design and fabrication of high-performance devices with enhanced functionalities.<br>In summary, this work showcases the significance of doping control in transition metal dichalcogenide devices and demonstrates the potential of the electrochemical ion intercalation method for achieving precise modulation of their photoelectric response performance. The observed enhancements in electrical conductivity and the ability to reversibly control the photoelectric response highlight th","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"26 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":"135212838","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":"Suppression of scattering clutter in underwater LiDAR based on CEEMDAN-wavelet threshold denoising algorithm","authors":"None Fan Chao-Yang, None Li Chao-Feng, None Yang Su-Hui, None Liu Xin-Yu, None Liao Ying-Qi","doi":"10.7498/aps.72.20231035","DOIUrl":"https://doi.org/10.7498/aps.72.20231035","url":null,"abstract":"<sec>The echo of underwater lidar often contains a significant quantity of scattering clutters. In order to effectively suppress this scattering clutter and improve the ranging accuracy of underwater lidar, a novel denoising method based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and wavelet threshold denoising is proposed.</sec><sec>The CEEMDAN-wavelet threshold denoising algorithm uses the correlation coefficient to select intrinsic mode function (IMF) components obtained from the CEEMDAN decomposition. The IMFs, which are more closely related to the original signal, are selected. Then, the wavelet thresholding denoising algorithm is applied to each of the selected IMFs to perform additional denoising. For each IMF component, specific threshold values are calculated based on their frequency and amplitude characteristics. Subsequently, the wavelet coefficients of the IMF components are processed by using these threshold values. Finally, the denoised IMF components are combined and reconstructed to obtain the final denoised signal. Applying the wavelet threshold denoising algorithm to IMF components can effectively remove noise components that cannot be removed by traditional CEEMDAN partial reconstruction methods. By using the threshold value calculated based on the characteristics of each IMF component, the wavelet thresholding denoising process is improved in comparison with directly using a single threshold value. This approach enhances the algorithm’s adaptability and enables more effective removal of noise from the signal.</sec><sec>We apply the proposed method to underwater ranging experiments. A 532 nm intensity-modulated continuous wave laser is used as a light source. Ranging is performed for a target in water with varying attenuation coefficients. A white polyvinyl chloride (PVC) reflector is used as a target. When the correlation extreme value is directly used to determine the delay at a distance of 3.75 attenuation length, it results in a ranging error of 19.2 cm. However, after applying the proposed method, the ranging error is reduced to 6.2 cm, thus effectively improving the ranging accuracy. These results demonstrate that the method has a significant denoising effect in underwater lidar system.</sec>","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":"231 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":"135400417","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}