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":"物理学报","volume":"110 1","pages":""},"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":"物理学报","volume":"1 1","pages":""},"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 Yun, Wang Wen-Hai, He De-Jing, Zhou Yong-Zhuang, Shen Yong, Zou Hong-Xin
The first space optical clock (SOC) in the world developed in China, which is composed by five subsystems, including an optical unit, a physics unit, an electronic control unit, a space optical frequency comb, and an ultrastable laser, has been successfully launched with the Mengtian space laboratory into the China Space Station (CSS). Compact and stable lasers are key elements for the operation of the SOC. The optical unit consists of 5 lasers at 461 nm, 679 nm, 689 nm, 707nm, and 813 nm. With a synchronous-tuning-like scheme, high quality external cavity diode lasers (ECDL) have been developed as the seeds. The linewidth of the lasers is suppressed to the order of 100 kHz, and the mode-hop-free tuning range reaches 20 GHz, which meet the requirements of the SOC. With careful mechanical and thermal design, the stability of the lasers against vibration and temperature fluctuation has been sufficiently promoted to confront the challenge of rocket launching. While the power from the ECDL is sufficient for 679 nm and 707 nm repump lasers, additional injection lock is utilized for the 461 nm and 689 nm lasers to amplify the power of the seeds to more than 600 mW, so that efficient first and second stage Doppler cooling can be achieved. To generate an optical lattice with deep enough potential well, over 800 mW 813 nm lasers is required. Therefore, a semiconductor tapered amplifier is adopted to amplify the seed to more than 2 W, so as to cope with various losses of the coupling optics. The wavelength and output power of the 5 lasers are monitored and feedback-controlled by the electronic control unit. All the modules are designed and manufactured as orbital replaceable units, which can be easily replaced by astronauts in case failure occurs. Now the lasers are all turned on and operates normally in CSS. More data of the SOC will be obtained in the near future. At present stage, according to our evaluation, the continuous operation time of the SOC is limited by the injection locked lasers, which are relatively vulnerable to mode hopping. Hopefully this problem can be solved by improving the laser diode manufacturing technology, or developing fiber lasers with compact frequency conversion modules.
{"title":"Research progress on the laser system of the cold atomic clock in China Space Station","authors":"Liu Yun, Wang Wen-Hai, He De-Jing, Zhou Yong-Zhuang, Shen Yong, Zou Hong-Xin","doi":"10.7498/aps.72.20230412","DOIUrl":"https://doi.org/10.7498/aps.72.20230412","url":null,"abstract":"The first space optical clock (SOC) in the world developed in China, which is composed by five subsystems, including an optical unit, a physics unit, an electronic control unit, a space optical frequency comb, and an ultrastable laser, has been successfully launched with the Mengtian space laboratory into the China Space Station (CSS). Compact and stable lasers are key elements for the operation of the SOC. The optical unit consists of 5 lasers at 461 nm, 679 nm, 689 nm, 707nm, and 813 nm. With a synchronous-tuning-like scheme, high quality external cavity diode lasers (ECDL) have been developed as the seeds. The linewidth of the lasers is suppressed to the order of 100 kHz, and the mode-hop-free tuning range reaches 20 GHz, which meet the requirements of the SOC. With careful mechanical and thermal design, the stability of the lasers against vibration and temperature fluctuation has been sufficiently promoted to confront the challenge of rocket launching. While the power from the ECDL is sufficient for 679 nm and 707 nm repump lasers, additional injection lock is utilized for the 461 nm and 689 nm lasers to amplify the power of the seeds to more than 600 mW, so that efficient first and second stage Doppler cooling can be achieved. To generate an optical lattice with deep enough potential well, over 800 mW 813 nm lasers is required. Therefore, a semiconductor tapered amplifier is adopted to amplify the seed to more than 2 W, so as to cope with various losses of the coupling optics. The wavelength and output power of the 5 lasers are monitored and feedback-controlled by the electronic control unit. All the modules are designed and manufactured as orbital replaceable units, which can be easily replaced by astronauts in case failure occurs. Now the lasers are all turned on and operates normally in CSS. More data of the SOC will be obtained in the near future. At present stage, according to our evaluation, the continuous operation time of the SOC is limited by the injection locked lasers, which are relatively vulnerable to mode hopping. Hopefully this problem can be solved by improving the laser diode manufacturing technology, or developing fiber lasers with compact frequency conversion modules.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"1973 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90245015","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}
Shu-Peng Sun, Yongzhi Cheng, Hui Luo, Fu Chen, Xiangcheng Li
In this paper, a compact broadband bandpass filter with wide out-of-band rejection characteristics based on halberd-shaped spoof surface plasmon polariton (SSPP) is proposed. The filtering structure is achieved by etching a periodic halberd-shaped groove at the bottom of the substrate and a microstrip-to-slot line transition with a crescent-shaped patch at the top. Compared with the traditional dumbbell-shaped SSPP, the halberd-shaped SSPP has good slow-wave property, and the designed bandpass filter based on halberd-shaped SSPP can achieve a more compact size. The upper cutoff frequency and lower cutoff frequency of the passband can be adjusted by regulating the SSPP structure and the transition structure from microstrip-to-slot line, respectively. The simulation results show that the center frequency of broadband bandpass filter is 2.85 GHz, with the relative bandwidth of 130%, and the return loss in the passband is better than –10 dB, and the extreme strong out-of-band rejection of –40 dB from 5.6 GHz to 20 GHz. The size of the broadband bandpass filter is compact, only 1.08λg×0.39λg, where λg is the wavelength at the center frequency. In order to verify the effectiveness of the wideband bandpass filter, the traditional printed circuit board technology is used to fabricate the wideband bandpass filter. The measurement results are in good agreement with the simulation results, verifying the feasibility of the design. The proposed broadband bandpass filter shows promising prospects for developing SSPP functional devices and circuits at microwave frequencies.
{"title":"Compact broadband bandpass filter with wide stopband based on halberd-shaped spoof surface plasmon polariton","authors":"Shu-Peng Sun, Yongzhi Cheng, Hui Luo, Fu Chen, Xiangcheng Li","doi":"10.7498/aps.72.20222291","DOIUrl":"https://doi.org/10.7498/aps.72.20222291","url":null,"abstract":"In this paper, a compact broadband bandpass filter with wide out-of-band rejection characteristics based on halberd-shaped spoof surface plasmon polariton (SSPP) is proposed. The filtering structure is achieved by etching a periodic halberd-shaped groove at the bottom of the substrate and a microstrip-to-slot line transition with a crescent-shaped patch at the top. Compared with the traditional dumbbell-shaped SSPP, the halberd-shaped SSPP has good slow-wave property, and the designed bandpass filter based on halberd-shaped SSPP can achieve a more compact size. The upper cutoff frequency and lower cutoff frequency of the passband can be adjusted by regulating the SSPP structure and the transition structure from microstrip-to-slot line, respectively. The simulation results show that the center frequency of broadband bandpass filter is 2.85 GHz, with the relative bandwidth of 130%, and the return loss in the passband is better than –10 dB, and the extreme strong out-of-band rejection of –40 dB from 5.6 GHz to 20 GHz. The size of the broadband bandpass filter is compact, only 1.08λg×0.39λg, where λg is the wavelength at the center frequency. In order to verify the effectiveness of the wideband bandpass filter, the traditional printed circuit board technology is used to fabricate the wideband bandpass filter. The measurement results are in good agreement with the simulation results, verifying the feasibility of the design. The proposed broadband bandpass filter shows promising prospects for developing SSPP functional devices and circuits at microwave frequencies.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"38 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90347562","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}
Active matter is a new and challenging field of physics. Chiral active particle experiences a constant torque and performs circular motion due to the self-propulsion force not aligning with the propulsion direction. Recently, most of studies of the active particle systems focused on constant temperature, but did not take into consideration the constraints by the barriers. In our work, the rectification of a ring containing chiral active particles with transversal temperature difference is numerically investigated in a two-dimensional periodic channel. It is found that the ring powered by chiral active particles can be rectified by the transversal temperature difference and the direction of the transport is determined by the chirality of active particles. The average velocity is a peaked function of angular velocity, the temperature of the lower wall or temperature difference. The transport behaviors of the ring containing one chiral active particle is qualitatively different from those of the ring containing several particles. Especially, the ring radius can strongly affect the transport behaviors. For the ring containing one chiral active particle, the interaction between the particle and the ring facilitates the rectification of the ring when the circular trajectory radius of the chiral particle is large. The average velocity decreases with the increase of the ring radius because the propelling force to the ring by the particle is small. When the circular trajectory radius is small, the interaction between the particle and the ring suppresses the transport. The speed increases as the ring radius increases because the directional transport comes from the difference in temperature between the upper wall and the lower wall. For the ring containing several particles, the interaction between particles reduces the rectification of the ring. The average velocity increases with the increase of the ring radius due to the interaction between particles decreasing. Remarkably, the velocity of the ring decreases as the particle number increases when the ring radius is small, but is a peaked function when the ring radius is not small. Our results offer new possibilities for manipulating an active particle flow on a microscale, and can be applied practically to propelling carriers and motors by a bath of bacteria or artificial microswimmers, such as hybrid micro-device engineering, drug delivery, micro-fluidics, and lab-on-chip technology.
{"title":"Transport of closed ring containing chiral active particles under transversal temperature difference","authors":"Jing-Jing Liao, Qi Kang, Fei Luo, Fu-Jun Lin","doi":"10.7498/aps.72.20221772","DOIUrl":"https://doi.org/10.7498/aps.72.20221772","url":null,"abstract":"Active matter is a new and challenging field of physics. Chiral active particle experiences a constant torque and performs circular motion due to the self-propulsion force not aligning with the propulsion direction. Recently, most of studies of the active particle systems focused on constant temperature, but did not take into consideration the constraints by the barriers. In our work, the rectification of a ring containing chiral active particles with transversal temperature difference is numerically investigated in a two-dimensional periodic channel. It is found that the ring powered by chiral active particles can be rectified by the transversal temperature difference and the direction of the transport is determined by the chirality of active particles. The average velocity is a peaked function of angular velocity, the temperature of the lower wall or temperature difference. The transport behaviors of the ring containing one chiral active particle is qualitatively different from those of the ring containing several particles. Especially, the ring radius can strongly affect the transport behaviors. For the ring containing one chiral active particle, the interaction between the particle and the ring facilitates the rectification of the ring when the circular trajectory radius of the chiral particle is large. The average velocity decreases with the increase of the ring radius because the propelling force to the ring by the particle is small. When the circular trajectory radius is small, the interaction between the particle and the ring suppresses the transport. The speed increases as the ring radius increases because the directional transport comes from the difference in temperature between the upper wall and the lower wall. For the ring containing several particles, the interaction between particles reduces the rectification of the ring. The average velocity increases with the increase of the ring radius due to the interaction between particles decreasing. Remarkably, the velocity of the ring decreases as the particle number increases when the ring radius is small, but is a peaked function when the ring radius is not small. Our results offer new possibilities for manipulating an active particle flow on a microscale, and can be applied practically to propelling carriers and motors by a bath of bacteria or artificial microswimmers, such as hybrid micro-device engineering, drug delivery, micro-fluidics, and lab-on-chip technology.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"36 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90805052","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}
Facing with the increasing capacity requirements of on-chip optical interconnects, mode division multiplexing technology (MDM), which leverages the different spatial eigenmodes at the same wavelength as independent channels to transmit optical signals, has attracted tremendous interest. Mode-order converters that can convert the fundamental mode to high-order modes are key components in MDM systems. However, it is still very challenging to achieve compact mode-order converters with high performances. Subwavelength grating (SWG) can be equivalent to homogenous material, which has the prominent advantages such as control over birefringence, dispersion and anisotropy, enabling photonic devices with high performance. Wheras the conventional SWG only needs single-etch step, but the implementation of SWG structure usually requires a fabrication resolution of the order of 100 nm and below, which is difficult for current wafer-scale fabrication technology. The anisotropic response of SWG can be further engineered by introducing bricked topology structure, providing an additional degree of freedom in the design. Meanwhile, the requirement of fabrication resolution can also be reduced (>100 nm). In this work, we experimentally demonstrate compact TE0-TE1 and TE0-TE2 mode-order converters using bricked subwavelength grating (BSWG) based on silicon-on-insulator (SOI) with the minimum feature size of the BSWG is 145 nm. In the proposed mode-order converter, a quasi-TE0 mode is generated in the BSWG region, which can be regarded as an effective bridge between the two TE modes to be converted. Flexible mode conversion can be realized by only choosing appropriate structural parameters for specific mode transitions between input/output modes and the quasi-TE0 mode. By combing 3D finite difference time domain (FDTD) and particle swarm optimization (PSO) method, TE0-TE1 and TE0-TE2 mode-order converters are optimal designed. It can convert TE0 mode into TE1 and TE2 mode with conversion length of 9.39 μm and 11.27 μm. The simulation results show that the insertion loss of <1 dB and crosstalk of < ‒ 15 dB are achieved for both TE0-TE1 and TE0-TE2 mode-order converters, the corresponding working bandwidth are 128 nm (1511~1639 nm) and 126 nm (1527~1653 nm), respectively. The measurement results indicate that insertion loss and crosstalk are less than 2.5 dB and -10 dB in a bandwidth of 68 nm (1512~1580 nm, limited by the laser tuning range and grating coupler).
{"title":"A compact silicon-based mode converter using bricked subwavelength grating","authors":"Lu Meng-jia, Yun Bin-Feng","doi":"10.7498/aps.72.20230673","DOIUrl":"https://doi.org/10.7498/aps.72.20230673","url":null,"abstract":"Facing with the increasing capacity requirements of on-chip optical interconnects, mode division multiplexing technology (MDM), which leverages the different spatial eigenmodes at the same wavelength as independent channels to transmit optical signals, has attracted tremendous interest. Mode-order converters that can convert the fundamental mode to high-order modes are key components in MDM systems. However, it is still very challenging to achieve compact mode-order converters with high performances. Subwavelength grating (SWG) can be equivalent to homogenous material, which has the prominent advantages such as control over birefringence, dispersion and anisotropy, enabling photonic devices with high performance. Wheras the conventional SWG only needs single-etch step, but the implementation of SWG structure usually requires a fabrication resolution of the order of 100 nm and below, which is difficult for current wafer-scale fabrication technology. The anisotropic response of SWG can be further engineered by introducing bricked topology structure, providing an additional degree of freedom in the design. Meanwhile, the requirement of fabrication resolution can also be reduced (>100 nm). In this work, we experimentally demonstrate compact TE0-TE1 and TE0-TE2 mode-order converters using bricked subwavelength grating (BSWG) based on silicon-on-insulator (SOI) with the minimum feature size of the BSWG is 145 nm. In the proposed mode-order converter, a quasi-TE0 mode is generated in the BSWG region, which can be regarded as an effective bridge between the two TE modes to be converted. Flexible mode conversion can be realized by only choosing appropriate structural parameters for specific mode transitions between input/output modes and the quasi-TE0 mode. By combing 3D finite difference time domain (FDTD) and particle swarm optimization (PSO) method, TE0-TE1 and TE0-TE2 mode-order converters are optimal designed. It can convert TE0 mode into TE1 and TE2 mode with conversion length of 9.39 μm and 11.27 μm. The simulation results show that the insertion loss of <1 dB and crosstalk of < ‒ 15 dB are achieved for both TE0-TE1 and TE0-TE2 mode-order converters, the corresponding working bandwidth are 128 nm (1511~1639 nm) and 126 nm (1527~1653 nm), respectively. The measurement results indicate that insertion loss and crosstalk are less than 2.5 dB and -10 dB in a bandwidth of 68 nm (1512~1580 nm, limited by the laser tuning range and grating coupler).","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"59 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90868198","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}
Dan Min, 金凡亚, Chen Lun-Jiang, He Yan-Bin, Wan Jun-Hao, Zhang Hong, Zhang Ke-Jia, Yang Yin, Jin Fan-Ya
In order to further improve the superconducting current carrying capacity of REBCO coated conductor under strong magnetic field, ion irradiation is used to generate the pinning center of introduced magnetic flux in the REBCO coated conductor. In this paper, the H-ion irradiation of REBCO second generation high temperature superconductor strip was carried out by using the 320kV high charge state ion synthesis research platform. DB-SPBA combined with Raman spectroscopy was used to measure the change of microstructure in YBCO samples irradiated by H+ions within the range of 5.0×1014~1.0×1016. The positron annihilation parameters in YBCO before and after irradiation were analyzed. It is found that after 100 keV H+ion irradiation, a large number of defects including vacancy, vacancy group or dislocation group are produced in the superconducting layer. The larger the irradiation dose, the more vacancy type defects are produced, the more complex the defect types are, and the annihilation mechanism of positrons in the defects changes. Raman spectroscopy results show that with the increase of H+ion irradiation dose, the oxygen atoms in the coating rearrange, the plane spacing increases, the orthogonal phase structure of the coating is destroyed, and the degree of order decreases. The defects produced by such ion irradiation lay a foundation for the introduction of flux pinning centers. Further research can be carried out in combination with X-ray diffractometer, transmission electron microscope, superconductivity and other testing methods to provide theoretical and practical reference for the optimization of material properties.
{"title":"Defect Evolution in Y0.5Gd0.5Ba2Cu3O7-δ Layer by H Ion Irradiation","authors":"Dan Min, 金凡亚, Chen Lun-Jiang, He Yan-Bin, Wan Jun-Hao, Zhang Hong, Zhang Ke-Jia, Yang Yin, Jin Fan-Ya","doi":"10.7498/aps.72.20221612","DOIUrl":"https://doi.org/10.7498/aps.72.20221612","url":null,"abstract":"In order to further improve the superconducting current carrying capacity of REBCO coated conductor under strong magnetic field, ion irradiation is used to generate the pinning center of introduced magnetic flux in the REBCO coated conductor. In this paper, the H-ion irradiation of REBCO second generation high temperature superconductor strip was carried out by using the 320kV high charge state ion synthesis research platform. DB-SPBA combined with Raman spectroscopy was used to measure the change of microstructure in YBCO samples irradiated by H+ions within the range of 5.0×1014~1.0×1016. The positron annihilation parameters in YBCO before and after irradiation were analyzed. It is found that after 100 keV H+ion irradiation, a large number of defects including vacancy, vacancy group or dislocation group are produced in the superconducting layer. The larger the irradiation dose, the more vacancy type defects are produced, the more complex the defect types are, and the annihilation mechanism of positrons in the defects changes. Raman spectroscopy results show that with the increase of H+ion irradiation dose, the oxygen atoms in the coating rearrange, the plane spacing increases, the orthogonal phase structure of the coating is destroyed, and the degree of order decreases. The defects produced by such ion irradiation lay a foundation for the introduction of flux pinning centers. Further research can be carried out in combination with X-ray diffractometer, transmission electron microscope, superconductivity and other testing methods to provide theoretical and practical reference for the optimization of material properties.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"15 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87584065","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}
Keda Liang, Tengfei Liu, Zhe Chang, Meng Zhang, ZhiXin Li, Songsong Huang, Jing Wang
The propagation speed is one of the important parameters of the internal solitary waves(ISWs). How to obtain the ISWs speed through optical remote sensing images accurately and quickly is an important problem to be solved. In this paper, we simulate ISWs optical remote sensing imaging and obtain an experimental database and build the ISWs speed inversion models based on a single-scene optical remote sensing image by using the least squares method and the support vector machine. The accuracy of the ISW speed inversion models were tested by using MODIS Image and GF-4 image data of the South China Sea. The study results show that: The least squares ISW speed inversion model can give the regression equation, which is more intuitive and has less accuracy in the water depth range from 300 meters to 399 meters, while the support vector machine ISW speed inversion model has high accuracy in the water depth range from 400 meters to 1200 meters and from 83 meters to 299 meters. Therefore, the two kinds of ISW speed inversion models have different advantages, and can be applied to the inversion of the ISW speed in the real ocean.
{"title":"Research on inversion models of internal solitary wave propagation speed in ocean based on least square method and support vector machine","authors":"Keda Liang, Tengfei Liu, Zhe Chang, Meng Zhang, ZhiXin Li, Songsong Huang, Jing Wang","doi":"10.7498/aps.72.20221633","DOIUrl":"https://doi.org/10.7498/aps.72.20221633","url":null,"abstract":"The propagation speed is one of the important parameters of the internal solitary waves(ISWs). How to obtain the ISWs speed through optical remote sensing images accurately and quickly is an important problem to be solved. In this paper, we simulate ISWs optical remote sensing imaging and obtain an experimental database and build the ISWs speed inversion models based on a single-scene optical remote sensing image by using the least squares method and the support vector machine. The accuracy of the ISW speed inversion models were tested by using MODIS Image and GF-4 image data of the South China Sea. The study results show that: The least squares ISW speed inversion model can give the regression equation, which is more intuitive and has less accuracy in the water depth range from 300 meters to 399 meters, while the support vector machine ISW speed inversion model has high accuracy in the water depth range from 400 meters to 1200 meters and from 83 meters to 299 meters. Therefore, the two kinds of ISW speed inversion models have different advantages, and can be applied to the inversion of the ISW speed in the real ocean.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"99 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88415916","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}
Large-size conductive targets or coated targets are difficult issues in computational electromagnetics. In general, such targets can be classified as multi-scale problems. Multi-scale problems usually consume a large number of computational resources. Researchers are devoted to seeking fast methods for these problems. When the skin depth is less than the size of a conductive target, the tangential components of the electric and magnetic fields over the surface of the target can be correlated by the surface impedance Ẑ. Ẑ is usually a complex function of the frequency, and it can be used to formulate an impedance boundary condition (IBC) to describe iterative equations in time domain methods to avoid the volumetric discretization of the target to improve computational efficiency. This condition is commonly known as the surface impedance boundary condition (SIBC). Similarly, for a conductor with thickness on the order or less than the skin depth, it also has high resource requirements if the target is straightforward volumetric discretization. The transmission impedance boundary condition (TIBC) can be applied to replace a coated object to reduce resource requirements. Thus, volumetric discretization is not required. There are few studies on the IBC scheme in the DGTD method. P. Li discussed the IBC scheme in DGTD, which involves complex matrix operations in the processing of IBC. In the DGTD method, numerical flux is used to transmit data between neighboring elements, and the key to the IBC scheme in DGTD is how to handle numerical flux. We hope to propose a DGTD method with a simple form and matrix-free IBC scheme. The key in dealing with IBC in DGTD is numerical flux. Unlike the literature, the impedance ẐR is not approximated by rational functions in our study. A specfic function ẐR obtained after the derivation in this paper is approximated by rational functions in the Laplace domain using the vector-fitting (VF) method, and its time-domain iteration scheme is given. This approach avoids matrix operations. The TIBC and SIBC processing schemes are given in section 4. The proposed method's advantage is that the upwind flux's standard coefficients are retained, and the complex frequency-time conversion problem is implemented by the vector-fitting method. The one-dimensional and three-dimensional examples also show the accuracy and effectiveness of our work in this paper.
{"title":"A simple DGTD method with the impedance boundary condition","authors":"Yang Qian, Wei Bing, Li Linqian, Deng Haochuan","doi":"10.7498/aps.72.20222104","DOIUrl":"https://doi.org/10.7498/aps.72.20222104","url":null,"abstract":"Large-size conductive targets or coated targets are difficult issues in computational electromagnetics. In general, such targets can be classified as multi-scale problems. Multi-scale problems usually consume a large number of computational resources. Researchers are devoted to seeking fast methods for these problems. When the skin depth is less than the size of a conductive target, the tangential components of the electric and magnetic fields over the surface of the target can be correlated by the surface impedance Ẑ. Ẑ is usually a complex function of the frequency, and it can be used to formulate an impedance boundary condition (IBC) to describe iterative equations in time domain methods to avoid the volumetric discretization of the target to improve computational efficiency. This condition is commonly known as the surface impedance boundary condition (SIBC). Similarly, for a conductor with thickness on the order or less than the skin depth, it also has high resource requirements if the target is straightforward volumetric discretization. The transmission impedance boundary condition (TIBC) can be applied to replace a coated object to reduce resource requirements. Thus, volumetric discretization is not required. There are few studies on the IBC scheme in the DGTD method. P. Li discussed the IBC scheme in DGTD, which involves complex matrix operations in the processing of IBC. In the DGTD method, numerical flux is used to transmit data between neighboring elements, and the key to the IBC scheme in DGTD is how to handle numerical flux. We hope to propose a DGTD method with a simple form and matrix-free IBC scheme. The key in dealing with IBC in DGTD is numerical flux. Unlike the literature, the impedance ẐR is not approximated by rational functions in our study. A specfic function ẐR obtained after the derivation in this paper is approximated by rational functions in the Laplace domain using the vector-fitting (VF) method, and its time-domain iteration scheme is given. This approach avoids matrix operations. The TIBC and SIBC processing schemes are given in section 4. The proposed method's advantage is that the upwind flux's standard coefficients are retained, and the complex frequency-time conversion problem is implemented by the vector-fitting method. The one-dimensional and three-dimensional examples also show the accuracy and effectiveness of our work in this paper.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"1 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88862481","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}
ZEWEI LUO, GE WU, ZHI CHEN, CHINAN DANG, RONG WAN, Tao Yang, ZHENGFEI ZHUANG, AND TONGSHENG CHEN
The Structured Illumination (SI)-based Super Resolution Fluorescence Resonance Energy Transfer (SR-FRET) imaging technique, known as SISR-FRET, enables the investigation of molecular structures and functions in cellular organelles by resolving sub-diffraction FRET signals within living cells. FRET microscopy offers unique advantages for quantitatively detecting dynamic interactions and spatial distribution of biomolecules within living cells. The spatial resolution of conventional FRET microscopy is limited by the diffraction limit, and it can only capture the average behavior of these events within the resolution limits of conventional fluorescence microscopy. SISR-FRET performs sequential linear reconstruction of the three-channel SIM images followed by FRET quantitative analysis using a common localization mask-based filtering approach. This two-step process ensures the fidelity of the reconstructed SR-FRET signals while effectively removing false-positive FRET signals caused by SIM artifacts. However, the slow imaging speed resulting from the switching of excitation-emission channels in SISR-FRET imaging limits its application in fast imaging scenarios. To address this issue, this study proposes a dual-channel structured illumination super-resolution quantitative FRET imaging system and method. By incorporating a FRET dual-channel imaging and registration module into the imaging pathway, spatial switching and channel multiplexing of the SISR-FRET excitation-emission channels are achieved. Combining the image reconstruction algorithm with channel sub-pixel registration correction, the dual-channel SISR-FRET technique enhances the temporal resolution by 3.5 times while preserving the quantitative super-resolution FRET analysis. Experimental results were obtained using a multi-color SIM system to perform super-resolution imaging of living cells expressing mitochondria outer membrane FRET standard plasmids. These experiments validate the improved spatial and temporal resolution of dual-channel SISR-FRET and the fidelity of FRET quantification analysis. In summary, this research presents a novel dual-channel structured illumination super-resolution FRET imaging system and methodology. It overcomes the limitations of slow imaging speed in SISR-FRET by enabling spatial switching and channel multiplexing of excitation-emission channels. The proposed technique enhances the temporal resolution while maintaining quantitative analysis of super-resolution FRET. Experimental validation demonstrates the increased spatial and temporal resolution of dual-channel SISR-FRET and the accuracy of FRET quantification analysis. This advancement contributes to the study of molecular structures and functions in cellular organelles, providing valuable insights into the intricate mechanisms of living cells.
{"title":"Dual-channel structured illumination super-resolution quantitative FRET imaging","authors":"ZEWEI LUO, GE WU, ZHI CHEN, CHINAN DANG, RONG WAN, Tao Yang, ZHENGFEI ZHUANG, AND TONGSHENG CHEN","doi":"10.7498/aps.72.20230853","DOIUrl":"https://doi.org/10.7498/aps.72.20230853","url":null,"abstract":"The Structured Illumination (SI)-based Super Resolution Fluorescence Resonance Energy Transfer (SR-FRET) imaging technique, known as SISR-FRET, enables the investigation of molecular structures and functions in cellular organelles by resolving sub-diffraction FRET signals within living cells. FRET microscopy offers unique advantages for quantitatively detecting dynamic interactions and spatial distribution of biomolecules within living cells. The spatial resolution of conventional FRET microscopy is limited by the diffraction limit, and it can only capture the average behavior of these events within the resolution limits of conventional fluorescence microscopy. SISR-FRET performs sequential linear reconstruction of the three-channel SIM images followed by FRET quantitative analysis using a common localization mask-based filtering approach. This two-step process ensures the fidelity of the reconstructed SR-FRET signals while effectively removing false-positive FRET signals caused by SIM artifacts. However, the slow imaging speed resulting from the switching of excitation-emission channels in SISR-FRET imaging limits its application in fast imaging scenarios. To address this issue, this study proposes a dual-channel structured illumination super-resolution quantitative FRET imaging system and method. By incorporating a FRET dual-channel imaging and registration module into the imaging pathway, spatial switching and channel multiplexing of the SISR-FRET excitation-emission channels are achieved. Combining the image reconstruction algorithm with channel sub-pixel registration correction, the dual-channel SISR-FRET technique enhances the temporal resolution by 3.5 times while preserving the quantitative super-resolution FRET analysis. Experimental results were obtained using a multi-color SIM system to perform super-resolution imaging of living cells expressing mitochondria outer membrane FRET standard plasmids. These experiments validate the improved spatial and temporal resolution of dual-channel SISR-FRET and the fidelity of FRET quantification analysis. In summary, this research presents a novel dual-channel structured illumination super-resolution FRET imaging system and methodology. It overcomes the limitations of slow imaging speed in SISR-FRET by enabling spatial switching and channel multiplexing of excitation-emission channels. The proposed technique enhances the temporal resolution while maintaining quantitative analysis of super-resolution FRET. Experimental validation demonstrates the increased spatial and temporal resolution of dual-channel SISR-FRET and the accuracy of FRET quantification analysis. This advancement contributes to the study of molecular structures and functions in cellular organelles, providing valuable insights into the intricate mechanisms of living cells.","PeriodicalId":6995,"journal":{"name":"物理学报","volume":"20 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88924264","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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