This study integrates pedestrian flow characteristics to formulate a mesoscopic cellular automata model tailored for simulating evacuations in large-scale scenarios. Departing from the conventional planar grid cell division, the model employs road cell segmentation, thereby physically enlarging the dimensions of individual cells. This augmentation accommodates an increased occupancy of individuals per cell, representing pedestrian flow parameters within each cell through state variables. The source loading cell facilitates the simulation of pedestrian behavior transitioning from buildings to roads during an actual evacuation event, while the unloading cell situated at the exit removes evacuees from the system. The continuity equation for state transitions comprehensively encapsulates the dynamics of pedestrians throughout the evacuation process. Potential challenges in actual evacuation processes are identified through the simulation, offering valuable insights for improvement. This research aims to contribute to a more effective and informed approach to evacuation planning and management.
{"title":"Simulation method of urban evacuation based on mesoscopic cellular automata","authors":"Lu Wei, Wang Jing-Hui, Fang Zhi-ming, Mao Dun","doi":"10.7498/APS.70.20210018","DOIUrl":"https://doi.org/10.7498/APS.70.20210018","url":null,"abstract":"This study integrates pedestrian flow characteristics to formulate a mesoscopic cellular automata model tailored for simulating evacuations in large-scale scenarios. Departing from the conventional planar grid cell division, the model employs road cell segmentation, thereby physically enlarging the dimensions of individual cells. This augmentation accommodates an increased occupancy of individuals per cell, representing pedestrian flow parameters within each cell through state variables. The source loading cell facilitates the simulation of pedestrian behavior transitioning from buildings to roads during an actual evacuation event, while the unloading cell situated at the exit removes evacuees from the system. The continuity equation for state transitions comprehensively encapsulates the dynamics of pedestrians throughout the evacuation process. Potential challenges in actual evacuation processes are identified through the simulation, offering valuable insights for improvement. This research aims to contribute to a more effective and informed approach to evacuation planning and management.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76105482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We generalize the gravitational form factor for chiral fermion in vacuum, which reproduces the well-known spin-vorticity coupling. We also calculate radiative correction to the gravitational form factors in quantum electrodynamics plasma. We find two structures in the form factors contributing to the scattering amplitude of fermion in vorticity field, one is from the fermon self-energy correction, pointing to suppression of spin-vorticity coupling in medium; the other strucutre comes from graviton-fermion vertex correction, which does not adopt potential interpretation, but corresponds to transition matrix element between initial and final states. Both structures contribute to chiral vortical effect. The net effect is that radiative correction enhances the chiral vortical effect. Our results claify the relation and difference between spin-vorticity coupling and chiral vortical effect from the perspective of form factors. We also discuss the application of the results in QCD plasma, indicating radiative correction might have an appreciable effect in spin polarization effect in heavy ion collisions.
{"title":"Medium Correction to Gravitational Form Factors","authors":"Shu Lin, Jiayuan Tian","doi":"10.7498/aps.72.20222473","DOIUrl":"https://doi.org/10.7498/aps.72.20222473","url":null,"abstract":"We generalize the gravitational form factor for chiral fermion in vacuum, which reproduces the well-known spin-vorticity coupling. We also calculate radiative correction to the gravitational form factors in quantum electrodynamics plasma. We find two structures in the form factors contributing to the scattering amplitude of fermion in vorticity field, one is from the fermon self-energy correction, pointing to suppression of spin-vorticity coupling in medium; the other strucutre comes from graviton-fermion vertex correction, which does not adopt potential interpretation, but corresponds to transition matrix element between initial and final states. Both structures contribute to chiral vortical effect. The net effect is that radiative correction enhances the chiral vortical effect. Our results claify the relation and difference between spin-vorticity coupling and chiral vortical effect from the perspective of form factors. We also discuss the application of the results in QCD plasma, indicating radiative correction might have an appreciable effect in spin polarization effect in heavy ion collisions.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88599214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liu Zhong-Lei, Cao Jin-Ming, Wang Zhi, Zhao Yu-Hong
The perovskite crystal structure determines the appearance of ferroelectricity and the determination of the polarization direction of ferroelectric ceramics. When the polarization direction has a certain order, different domain structures will combine to form a multiparticle system with a specific morphology, the topological structures that exist in ferroelectrics. In this study, the domain structure of potassium sodium niobate (K0.5Na0.5NbO3) thin films under different hysteresis electric fields and thicknesses was observed by the phase field method. According to the different switching paths of the domain structure under the electric field, the domain is divided into fast and slow switching process. Based on this, a method is proposed to first determine the domain switching state of the desired experiment and then conduct directional observation. Through the analysis of the domain structures combined with the polarization vector, a clear multi-domain combined vortex-antivortex pair topological structure was observed for the first time in K0.5Na0.5NbO3 films. The vortex structure was further analyzed for its switching process, and it was observed that this vortex topological microstructure can make the domain more likely to switch, so that more small-scale polarization vectors can be ordered to form the desired multiparticle system topology. This polarization vector ordering is similar to the microscopic phase boundary formed by the specific polarization directions on both sides of the morphotropic phase boundary (MPB) for the improvement of the dielectric properties of ferroelectric materials.
{"title":"Exploring Ferroelectric Vortex Topology and morphotropic Phase Boundaries by Phase Field Method","authors":"Liu Zhong-Lei, Cao Jin-Ming, Wang Zhi, Zhao Yu-Hong","doi":"10.7498/aps.72.20221898","DOIUrl":"https://doi.org/10.7498/aps.72.20221898","url":null,"abstract":"The perovskite crystal structure determines the appearance of ferroelectricity and the determination of the polarization direction of ferroelectric ceramics. When the polarization direction has a certain order, different domain structures will combine to form a multiparticle system with a specific morphology, the topological structures that exist in ferroelectrics. In this study, the domain structure of potassium sodium niobate (K0.5Na0.5NbO3) thin films under different hysteresis electric fields and thicknesses was observed by the phase field method. According to the different switching paths of the domain structure under the electric field, the domain is divided into fast and slow switching process. Based on this, a method is proposed to first determine the domain switching state of the desired experiment and then conduct directional observation. Through the analysis of the domain structures combined with the polarization vector, a clear multi-domain combined vortex-antivortex pair topological structure was observed for the first time in K0.5Na0.5NbO3 films. The vortex structure was further analyzed for its switching process, and it was observed that this vortex topological microstructure can make the domain more likely to switch, so that more small-scale polarization vectors can be ordered to form the desired multiparticle system topology. This polarization vector ordering is similar to the microscopic phase boundary formed by the specific polarization directions on both sides of the morphotropic phase boundary (MPB) for the improvement of the dielectric properties of ferroelectric materials.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74000656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cheng Ai-Qiang, Wang Shuai, Xu Zu-Yin, He Jin, Zhang Tian-Cheng, Bao Hua-Guang, Ding Da-Zhi
With the rapid development of wireless communications, GaN HEMTs, which have various advantages of high power density, high electron mobility, and high breakdown threshold, have attracted increasing attention. Microwave power amplifiers based on GaN HEMTs are widely used in many fields, such as communication, medical, and detection instruments. In the accurate design of GaN microwave power amplifiers, reliable RF large signal models are vitally important. In this paper, a scalable large-signal model based on EEHEMT model is proposed to describe the properties of multifinger AlGaN/GaN high electrom mobility transistors (HEMTs) accurately. A series of scaling rules are established for the intrinsic parameters of the device, including drain-source current Ids, input capacitance Cgs and Cgd, which take into account both the gate width of a single finger and the number of gate fingers. With the proposed scalable large-signal model, the performances of the L-band GaN high-efficiency power amplifier with the length of gate of 14.4mm is analyzed. This amplifier demonstrates outstanding performance with the output power up to 46.5dBm and the drain efficiency of over 70% covering the entire frequency range from 1120MHz to 1340MHz. Great agreement between the simulations and experiments is achieved, demonstrating the excellent accuracy of the proposed model. Moreover, the proposed model can further predict the performance of high-order harmonics, providing an effective tool for the design of advanced high-power and high-efficiency microwave power amplifiers. Certainly, the EEHEMT model lacks the ability to characterize the dynamical behavior induced by trap and self-heating effects. Thus, for further consideration, scaling models for the thermal resistance and heat capacity will be investigated to broaden the applicability of the proposed model in the case of continuous waves.
{"title":"A large signal scaling model of high power GaN microwave device","authors":"Cheng Ai-Qiang, Wang Shuai, Xu Zu-Yin, He Jin, Zhang Tian-Cheng, Bao Hua-Guang, Ding Da-Zhi","doi":"10.7498/aps.72.20230440","DOIUrl":"https://doi.org/10.7498/aps.72.20230440","url":null,"abstract":"With the rapid development of wireless communications, GaN HEMTs, which have various advantages of high power density, high electron mobility, and high breakdown threshold, have attracted increasing attention. Microwave power amplifiers based on GaN HEMTs are widely used in many fields, such as communication, medical, and detection instruments. In the accurate design of GaN microwave power amplifiers, reliable RF large signal models are vitally important. In this paper, a scalable large-signal model based on EEHEMT model is proposed to describe the properties of multifinger AlGaN/GaN high electrom mobility transistors (HEMTs) accurately. A series of scaling rules are established for the intrinsic parameters of the device, including drain-source current Ids, input capacitance Cgs and Cgd, which take into account both the gate width of a single finger and the number of gate fingers. With the proposed scalable large-signal model, the performances of the L-band GaN high-efficiency power amplifier with the length of gate of 14.4mm is analyzed. This amplifier demonstrates outstanding performance with the output power up to 46.5dBm and the drain efficiency of over 70% covering the entire frequency range from 1120MHz to 1340MHz. Great agreement between the simulations and experiments is achieved, demonstrating the excellent accuracy of the proposed model. Moreover, the proposed model can further predict the performance of high-order harmonics, providing an effective tool for the design of advanced high-power and high-efficiency microwave power amplifiers. Certainly, the EEHEMT model lacks the ability to characterize the dynamical behavior induced by trap and self-heating effects. Thus, for further consideration, scaling models for the thermal resistance and heat capacity will be investigated to broaden the applicability of the proposed model in the case of continuous waves.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75861189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The optimal selection of parameters in practical quantum key distribution can greatly improve the key generation rate and maximum transmission distance of the system. Due to the high cost of global search algorithm, local search algorithm is widely used. However, there are two vulnerabilities in local search algorithm, one is that the solution obtained is not always the global optimal solution, the other is that the effectiveness of the algorithm is greatly dependent on the choice of initial value. It is different from the previous article that this paper uses the Monte Carlo method to prove whether the key generation rate function is convex, and also simulates and analyzes the projection of key generation rate function on each dimension of the parameter. In order to eliminate the effect of the initial value, this paper proposes the particle swarm local search optimization algorithm which is combining particle swarm optimization algorithm and local search algorithm. The first step is using the particle swarm optimization to find a valid parameter which leads to nonzero key generation rate, the second step is using the parameter as the initial value of local search algorithm to derive the global optimal solution. Then, the two algorithms are simulated and compared. The results show that the key generation rate function is non-convex because it does not satisfy the definition of a convex function, however, since the key generation rate function has only one non-zero stagnation point, the LSA algorithm can still obtain the global optimal solution with a proper initial value, when the transmission distance is relatively long, the local search algorithm is invalid because it is difficult to obtain an effective initial value by random value method. Particle swarm optimization algorithm can overcome this shortcoming and improve the maximum transmission distance of the system at the cost of slightly increasing the complexity of the algorithm.
{"title":"Improved parameter optimization method for measurement device independent protocol","authors":"Zhou Jiang-Ping, Zhou Yuan-Yuan, Zhou Xue-Jun","doi":"10.7498/aps.72.20230179","DOIUrl":"https://doi.org/10.7498/aps.72.20230179","url":null,"abstract":"The optimal selection of parameters in practical quantum key distribution can greatly improve the key generation rate and maximum transmission distance of the system. Due to the high cost of global search algorithm, local search algorithm is widely used. However, there are two vulnerabilities in local search algorithm, one is that the solution obtained is not always the global optimal solution, the other is that the effectiveness of the algorithm is greatly dependent on the choice of initial value. It is different from the previous article that this paper uses the Monte Carlo method to prove whether the key generation rate function is convex, and also simulates and analyzes the projection of key generation rate function on each dimension of the parameter. In order to eliminate the effect of the initial value, this paper proposes the particle swarm local search optimization algorithm which is combining particle swarm optimization algorithm and local search algorithm. The first step is using the particle swarm optimization to find a valid parameter which leads to nonzero key generation rate, the second step is using the parameter as the initial value of local search algorithm to derive the global optimal solution. Then, the two algorithms are simulated and compared. The results show that the key generation rate function is non-convex because it does not satisfy the definition of a convex function, however, since the key generation rate function has only one non-zero stagnation point, the LSA algorithm can still obtain the global optimal solution with a proper initial value, when the transmission distance is relatively long, the local search algorithm is invalid because it is difficult to obtain an effective initial value by random value method. Particle swarm optimization algorithm can overcome this shortcoming and improve the maximum transmission distance of the system at the cost of slightly increasing the complexity of the algorithm.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74644463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xu Meng-min, Li Xiao-qing, Tang rong, Ji xiao-ling
The influence of thermal blooming on orbital angular momentum (OAM) and phase singularity of dual-mode vortex beams under different wind direction and wind speed has been studied in this paper. Due to the different symmetries of dual-mode vortex beams superimposed by different modes, the impact of thermal blooming on them not only depends on wind speed, but also on wind direction. Based on the scalar wave equation and the hydrodynamic equation, a 4D computer code to simulate the time-dependent propagation of dual-mode vortex beams in the atmosphere is devised by using the multiphase screen method and finite difference method. It is found that, for certain wind direction, the value of OAM increases with the decreasing wind speed because the thermal blooming becomes more serious, i.e., the thermal blooming effect promotes the OAM of dual-mode vortex beam growth. For an example, when the angle between the wind direction and the beam is 0＜θ＜50°, the OAM of the dual-mode vortex beams with a topological charge difference of 2 increases with decreasing wind speed, and there is an optimal angle (θ≈20°) to maximize OAM. Therefore, for certain wind direction and wind speed, the OAM of dual-mode vortex beam propagating in the atmosphere could be larger than that in free space, and could be larger than the OAM of single-mode vortex beam. The dual-mode vortex beam with higher modes requires smaller wind speed to make its OAM larger than the OAM in free space. In addition, the larger the topological charge difference between the two element beams of a dual-mode vortex beam is, the more stable the OAM of the dual-mode vortex beam is. On the other hand, the evolution of linear edge dislocation singularity under atmospheric thermal blooming are also investigated in this paper. When the wind direction is perpendicular to the dislocation line, the linear edge dislocation singularity disappears. If the wind direction is parallel to the dislocation line, the linear edge dislocation singularity always exists. At other angles, the linear edge dislocation singularity will evolve into optical vortex pairs. The results obtained in this paper are useful to laser propagating in the atmosphere and optical communication.
{"title":"Influence of wind-dominated thermal blooming on orbital angular momentum and phase singularity of dual-mode vortex beams","authors":"Xu Meng-min, Li Xiao-qing, Tang rong, Ji xiao-ling","doi":"10.7498/aps.72.20230684","DOIUrl":"https://doi.org/10.7498/aps.72.20230684","url":null,"abstract":"The influence of thermal blooming on orbital angular momentum (OAM) and phase singularity of dual-mode vortex beams under different wind direction and wind speed has been studied in this paper. Due to the different symmetries of dual-mode vortex beams superimposed by different modes, the impact of thermal blooming on them not only depends on wind speed, but also on wind direction. Based on the scalar wave equation and the hydrodynamic equation, a 4D computer code to simulate the time-dependent propagation of dual-mode vortex beams in the atmosphere is devised by using the multiphase screen method and finite difference method. It is found that, for certain wind direction, the value of OAM increases with the decreasing wind speed because the thermal blooming becomes more serious, i.e., the thermal blooming effect promotes the OAM of dual-mode vortex beam growth. For an example, when the angle between the wind direction and the beam is 0＜θ＜50°, the OAM of the dual-mode vortex beams with a topological charge difference of 2 increases with decreasing wind speed, and there is an optimal angle (θ≈20°) to maximize OAM. Therefore, for certain wind direction and wind speed, the OAM of dual-mode vortex beam propagating in the atmosphere could be larger than that in free space, and could be larger than the OAM of single-mode vortex beam. The dual-mode vortex beam with higher modes requires smaller wind speed to make its OAM larger than the OAM in free space. In addition, the larger the topological charge difference between the two element beams of a dual-mode vortex beam is, the more stable the OAM of the dual-mode vortex beam is. On the other hand, the evolution of linear edge dislocation singularity under atmospheric thermal blooming are also investigated in this paper. When the wind direction is perpendicular to the dislocation line, the linear edge dislocation singularity disappears. If the wind direction is parallel to the dislocation line, the linear edge dislocation singularity always exists. At other angles, the linear edge dislocation singularity will evolve into optical vortex pairs. The results obtained in this paper are useful to laser propagating in the atmosphere and optical communication.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74741807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The low-frequency Alfvénic fluctuations in the kinetic thermal-ion gap frequency range have been of research interest since they can interact with both thermal and energetic particles. In this work, linear wave properties of the low-frequency shear Alfvén waves excited by energetic and/or thermal particles observed in tokamak experiments with reversed magnetic shear are theoretically investigated and delineated in the theoretical framework of the generalized fishbone-like dispersion relation (GFLDR). Since these low-frequency shear Alfvén waves are closely related to the dedicated experiment of energetic ion-driven low-frequency instabilities conducted on DIII-D in 2019, this work demonstrates, by adopting the representative experimental equilibrium parameters of DIII-D, that the experimentally observed lowfrequency modes and beta-induced Alfvén eigenmodes (BAEs) are, respectively, the reactive-type and dissipative-type unstable modes with dominant Alfvénic polarization, thus the former being more precisely called low-frequency Alfvén modes (LFAMs). More specifically, due to diamagnetic and trapped particle effects, the LFAM can be coupled with the beta-induced Alfvén-acoustic mode (BAAE) in the low-frequency region (frequency much less than the thermal-ion transit and/or bounce frequency); or with the BAE in the high frequency region (frequency higher than or comparable to the thermal-ion transit frequency); resulting in reactive-type instabilities. Moreover, due to different instability mechanisms, the maximal drive of BAEs occurs, in comparison to LFAMs, when the minimum of the safety factor (qmin) deviates from a rational number. Meanwhile, the BAE eigenfunction peaks at the radial position of the maximum energetic particle pressure gradient, resulting in a large deviation from the qmin surface. The ascending frequency spectrum patterns of the experimentally observed BAEs and LFAMs can be theoretically reproduced by varying qmin and also be well interpreted based on the GFLDR. In particular, it is confirmed that the stability of the BAAE is not affected by energetic ions, which is consistent with the first-principle-based theory predictions and simulation results. The present analysis illustrates the solid predictive capability of the GFLDR and its practical usefulness in enhancing the interpretative capability of both experimental and numerical simulation results.
{"title":"Theoretical Studies of Low-frequency Shear Alfvén Waves in Reversed Shear Tokamak Plasmas","authors":"Ma Rui-Rui, Chen Liu, Qiu Zhi-Yong","doi":"10.7498/aps.72.20230255","DOIUrl":"https://doi.org/10.7498/aps.72.20230255","url":null,"abstract":"The low-frequency Alfvénic fluctuations in the kinetic thermal-ion gap frequency range have been of research interest since they can interact with both thermal and energetic particles. In this work, linear wave properties of the low-frequency shear Alfvén waves excited by energetic and/or thermal particles observed in tokamak experiments with reversed magnetic shear are theoretically investigated and delineated in the theoretical framework of the generalized fishbone-like dispersion relation (GFLDR). Since these low-frequency shear Alfvén waves are closely related to the dedicated experiment of energetic ion-driven low-frequency instabilities conducted on DIII-D in 2019, this work demonstrates, by adopting the representative experimental equilibrium parameters of DIII-D, that the experimentally observed lowfrequency modes and beta-induced Alfvén eigenmodes (BAEs) are, respectively, the reactive-type and dissipative-type unstable modes with dominant Alfvénic polarization, thus the former being more precisely called low-frequency Alfvén modes (LFAMs). More specifically, due to diamagnetic and trapped particle effects, the LFAM can be coupled with the beta-induced Alfvén-acoustic mode (BAAE) in the low-frequency region (frequency much less than the thermal-ion transit and/or bounce frequency); or with the BAE in the high frequency region (frequency higher than or comparable to the thermal-ion transit frequency); resulting in reactive-type instabilities. Moreover, due to different instability mechanisms, the maximal drive of BAEs occurs, in comparison to LFAMs, when the minimum of the safety factor (qmin) deviates from a rational number. Meanwhile, the BAE eigenfunction peaks at the radial position of the maximum energetic particle pressure gradient, resulting in a large deviation from the qmin surface. The ascending frequency spectrum patterns of the experimentally observed BAEs and LFAMs can be theoretically reproduced by varying qmin and also be well interpreted based on the GFLDR. In particular, it is confirmed that the stability of the BAAE is not affected by energetic ions, which is consistent with the first-principle-based theory predictions and simulation results. The present analysis illustrates the solid predictive capability of the GFLDR and its practical usefulness in enhancing the interpretative capability of both experimental and numerical simulation results.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74760861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Heng-Di Wen, Yue Liu, Liang Zhen, Yang Li, Cheng-Yan Xu
Two-dimensional material heterojunction device with unique photoelectric properties due to its nanoscale thickness and van der Waals contact surface. In this paper, a MoS2/MoTe2 vertical vdWs heterojunction device with Gate-tunable is constructed. The Kelvin probe force microscopy (KPFM) technology is combined with the electric transport measurement technology, which reveals the charge transport behavior of the MoS2/MoTe2 heterojunction under dark and light conditions, including the bipolarity characteristics of the transition from n-n+ junction to p-n junction. This paper comprehensively and systematically explains the charge transport mechanism of heterojunction, including the charge transmission process of n-n+ junction and p-n junction under positive and negative bias conditions, the transformation of nodule behavior with gate voltage, the influence of barriers on charge transmission, the different rectification characteristics between n-n+ junction and p-n junction, the major role of source and leakage bias voltage on band tunneling, and the influence of photogenerated carriers on electrical transmission. The method in this paper can be generalized to other two-dimensional heterojunction systems and provides an important reference and reference for improving the performance of two-dimensional semiconductor devices and their applications in the future.
{"title":"Charge transmission of MoS2/MoTe2 vertical heterojunction and it's modulation","authors":"Heng-Di Wen, Yue Liu, Liang Zhen, Yang Li, Cheng-Yan Xu","doi":"10.7498/aps.72.20221768","DOIUrl":"https://doi.org/10.7498/aps.72.20221768","url":null,"abstract":"Two-dimensional material heterojunction device with unique photoelectric properties due to its nanoscale thickness and van der Waals contact surface. In this paper, a MoS2/MoTe2 vertical vdWs heterojunction device with Gate-tunable is constructed. The Kelvin probe force microscopy (KPFM) technology is combined with the electric transport measurement technology, which reveals the charge transport behavior of the MoS2/MoTe2 heterojunction under dark and light conditions, including the bipolarity characteristics of the transition from n-n+ junction to p-n junction. This paper comprehensively and systematically explains the charge transport mechanism of heterojunction, including the charge transmission process of n-n+ junction and p-n junction under positive and negative bias conditions, the transformation of nodule behavior with gate voltage, the influence of barriers on charge transmission, the different rectification characteristics between n-n+ junction and p-n junction, the major role of source and leakage bias voltage on band tunneling, and the influence of photogenerated carriers on electrical transmission. The method in this paper can be generalized to other two-dimensional heterojunction systems and provides an important reference and reference for improving the performance of two-dimensional semiconductor devices and their applications in the future.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73092164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiang Xing-Cheng, Ma Hai-Bei, Wang Lei, Tian Da, Zhang Wei, Zhang Cai-Hong, Wu Jing-Bo, Fan Ke-Bin, Jin Biao-Bing, Chen Jian, Wu Pei-heng
A metamaterial sensor using sample traps based on terahertz electromagnetically-induced-transparency-like（EIT-like） effect is proposed. The basic unit structure of the sensor is composed of a metal wire and a pair of split-ring resonators(SRRs), which are coupled to produce EIT-like effect. A transparency peak with a full width at half maximum (FWHM) of 178 GHz is obtained at 1.067 THz, and the maximum transmittance of the transparency peak is 89.71%. The sensing characteristics of the structure are studied, and the sensitivity is 178 GHz/(RIU·mm3). It is found that the electric field at gaps of the SRRs on both sides is the strongest by analyzing electric field distribution at the resonant frequency point of the metamaterial. Sample traps are constructed at the gaps, where the electric field is strongest. The photoresist was filled into the sample traps as the object to be measured, and 50 GHz frequency offset was successfully measured, which verified that the sample trap structure can be applied to sensing. After research and analysis, by placing samples in the sample traps, the sample volume is reduced to the ultra-micro level, and the sensitivity is increased to 5538 GHz/(RIU·mm3), which is 31 times higher than before. The successful identification of water, human skin and rat skin samples shows that the metamaterial sensor using sample traps has potential application value in the field of ultra-micro detection.
{"title":"Ultramicro-sensing of terahertz metamaterials using sample traps","authors":"Xiang Xing-Cheng, Ma Hai-Bei, Wang Lei, Tian Da, Zhang Wei, Zhang Cai-Hong, Wu Jing-Bo, Fan Ke-Bin, Jin Biao-Bing, Chen Jian, Wu Pei-heng","doi":"10.7498/aps.72.20230080","DOIUrl":"https://doi.org/10.7498/aps.72.20230080","url":null,"abstract":"A metamaterial sensor using sample traps based on terahertz electromagnetically-induced-transparency-like（EIT-like） effect is proposed. The basic unit structure of the sensor is composed of a metal wire and a pair of split-ring resonators(SRRs), which are coupled to produce EIT-like effect. A transparency peak with a full width at half maximum (FWHM) of 178 GHz is obtained at 1.067 THz, and the maximum transmittance of the transparency peak is 89.71%. The sensing characteristics of the structure are studied, and the sensitivity is 178 GHz/(RIU·mm3). It is found that the electric field at gaps of the SRRs on both sides is the strongest by analyzing electric field distribution at the resonant frequency point of the metamaterial. Sample traps are constructed at the gaps, where the electric field is strongest. The photoresist was filled into the sample traps as the object to be measured, and 50 GHz frequency offset was successfully measured, which verified that the sample trap structure can be applied to sensing. After research and analysis, by placing samples in the sample traps, the sample volume is reduced to the ultra-micro level, and the sensitivity is increased to 5538 GHz/(RIU·mm3), which is 31 times higher than before. The successful identification of water, human skin and rat skin samples shows that the metamaterial sensor using sample traps has potential application value in the field of ultra-micro detection.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75252250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Parity-time (PT)symmetric is not a necessary condition for achieving a real spectrum and some studies about realizing real spectra in non-PT-symmetric systems with arbitrary gain–loss profiles have been presented recently. By tuning the free parameters in non-PT-symmetric potentials, phase transition could also be induced. Above phase transition point, discrete complex eigenvalues bifurcate out from continuous real eigenvalues in the interior of the continuous spectrum. In this work, we investgate the existence and stability of solitons in nonlocal nonlinear couplers with non-PT-symmetric complex potentials both below and above phase transition. There are several discrete eigenvalues in the linear spectra of the non-PT-symmetric system used here. With the square-operator iteration method, we find that different continuous families of solitions can bifurcate from different discrete linear eigenvalues. Moreover, linear-stability analysis collaborated with direct numerical propagation simulations demonstrates that the nonlocal solitions can be stable in a range of parameter values. we first address the cases below the phase transition. To be specific,when we fix the coupling coefficient and vary the degree of nonlocality, it’s found that fundamental solitons, dipole solitons, tripolar solitons, quadrupole solitons bifurcate from the largest,the second-largest, the third-largest and the fifth-largest discrete eigenvalue, respectively. These nonlocal solitons are all stable in the low power region. With an increase of the degree of nonlocality, the stability region shrinks for the fundamental solitons while it widens for the dipole and multiplole solitons. At the same time, the power of all the stable solitons increases with the increase of the degree of nonlocality. By varying the coupling coefficient, the arrangement of soliton families emerging in the discrete interval of the linear spectrum can be changed. For example, the dipole solitons bifurcate from the third-or fourth-largest discrete eigenvalue while the tripolar solitons bifurcate from the fifth largest discrete eigenvalue. Above phase transition,the fundamental solitons are unstable in the low and high power region but are stable in the moderate power region. The stability region shrinks with the increasing degree of nonlocality. We also find the the family of dipole solitons bifurcates from the second-largest discrete eigenvalue, but all the dipole solitons are unstable. In addition,we find that the eigenvalues in linear-stability spectra of solitons emerge as conjugation pairs.
{"title":"Nonlocal soliton in non-parity-time-symmetric coupler","authors":"Jiang Hong-Fan, Lin Ji, Hu Bei-Bei, Zhang Xiao","doi":"10.7498/aps.72.20230082","DOIUrl":"https://doi.org/10.7498/aps.72.20230082","url":null,"abstract":"Parity-time (PT)symmetric is not a necessary condition for achieving a real spectrum and some studies about realizing real spectra in non-PT-symmetric systems with arbitrary gain–loss profiles have been presented recently. By tuning the free parameters in non-PT-symmetric potentials, phase transition could also be induced. Above phase transition point, discrete complex eigenvalues bifurcate out from continuous real eigenvalues in the interior of the continuous spectrum. In this work, we investgate the existence and stability of solitons in nonlocal nonlinear couplers with non-PT-symmetric complex potentials both below and above phase transition. There are several discrete eigenvalues in the linear spectra of the non-PT-symmetric system used here. With the square-operator iteration method, we find that different continuous families of solitions can bifurcate from different discrete linear eigenvalues. Moreover, linear-stability analysis collaborated with direct numerical propagation simulations demonstrates that the nonlocal solitions can be stable in a range of parameter values. we first address the cases below the phase transition. To be specific,when we fix the coupling coefficient and vary the degree of nonlocality, it’s found that fundamental solitons, dipole solitons, tripolar solitons, quadrupole solitons bifurcate from the largest,the second-largest, the third-largest and the fifth-largest discrete eigenvalue, respectively. These nonlocal solitons are all stable in the low power region. With an increase of the degree of nonlocality, the stability region shrinks for the fundamental solitons while it widens for the dipole and multiplole solitons. At the same time, the power of all the stable solitons increases with the increase of the degree of nonlocality. By varying the coupling coefficient, the arrangement of soliton families emerging in the discrete interval of the linear spectrum can be changed. For example, the dipole solitons bifurcate from the third-or fourth-largest discrete eigenvalue while the tripolar solitons bifurcate from the fifth largest discrete eigenvalue. Above phase transition,the fundamental solitons are unstable in the low and high power region but are stable in the moderate power region. The stability region shrinks with the increasing degree of nonlocality. We also find the the family of dipole solitons bifurcates from the second-largest discrete eigenvalue, but all the dipole solitons are unstable. In addition,we find that the eigenvalues in linear-stability spectra of solitons emerge as conjugation pairs.","PeriodicalId":6995,"journal":{"name":"Acta Physica Sinica","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75299975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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