Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351666
D. Gazzana, A. Bretas, G. Dias, M. Telló, Dave W. P. Thomas, C. Christopoulos
This paper presents a study about the effective length of a horizontal grounding electrode used to dissipate electrical current to the earth proceeding from a lightning surge. The work discusses the influence of the soil parameters in the scattering process considering fasts and slow wave shapes. Initially an introduction about the problem is made, with a brief description about the effective length concepts. An algorithm based on the Transmission Line Modeling Method in one dimension (TLM-1D), taking into account the soil ionization phenomenon, was developed in order to evaluate the transitory behavior of the grounding. The simulation results show that a significant part of the electrode is not effectively used for scattering the surge current to the soil and that the effective length of the conductor is dependent mainly on the soil resistivity and the wave shape.
{"title":"Effective length study of grounding electrod reached by lightning based on Transmission Line modelling Method","authors":"D. Gazzana, A. Bretas, G. Dias, M. Telló, Dave W. P. Thomas, C. Christopoulos","doi":"10.1109/ISEMC.2012.6351666","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351666","url":null,"abstract":"This paper presents a study about the effective length of a horizontal grounding electrode used to dissipate electrical current to the earth proceeding from a lightning surge. The work discusses the influence of the soil parameters in the scattering process considering fasts and slow wave shapes. Initially an introduction about the problem is made, with a brief description about the effective length concepts. An algorithm based on the Transmission Line Modeling Method in one dimension (TLM-1D), taking into account the soil ionization phenomenon, was developed in order to evaluate the transitory behavior of the grounding. The simulation results show that a significant part of the electrode is not effectively used for scattering the surge current to the soil and that the effective length of the conductor is dependent mainly on the soil resistivity and the wave shape.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127506773","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351685
N. LaSorte, Samer A. Rajab, H. Refai
Wireless coexistence is a growing concern, given the ubiquity of wireless technology. Although IEEE Standards have started to address this problem in an analytical framework, a standard experimental setup and process to evaluate wireless coexistence is lacking. Literature that reports experimental assessment of wireless coexistence places little emphasis on separation distance of wireless nodes under test or the spectrum occupancy of the interfering network, making comparisons difficult. This paper provides an extensive literature survey of 802.15.4 and 802.11 b/g/n wireless coexistence and demonstrates that in a higher wireless channel occupancy environment, ZigBee coexists with 802.11n better than with 802.11g. A reproducible, versatile, and practical test setup is presented to serve as a starting point toward establishing standard practice for wireless coexistence testing of wireless systems in general and wireless medical devices in particular. Experimental evaluations demonstrated consistency with results reported in the literature.
{"title":"Experimental assessment of wireless coexistence for 802.15.4 in the presence of 802.11g/n","authors":"N. LaSorte, Samer A. Rajab, H. Refai","doi":"10.1109/ISEMC.2012.6351685","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351685","url":null,"abstract":"Wireless coexistence is a growing concern, given the ubiquity of wireless technology. Although IEEE Standards have started to address this problem in an analytical framework, a standard experimental setup and process to evaluate wireless coexistence is lacking. Literature that reports experimental assessment of wireless coexistence places little emphasis on separation distance of wireless nodes under test or the spectrum occupancy of the interfering network, making comparisons difficult. This paper provides an extensive literature survey of 802.15.4 and 802.11 b/g/n wireless coexistence and demonstrates that in a higher wireless channel occupancy environment, ZigBee coexists with 802.11n better than with 802.11g. A reproducible, versatile, and practical test setup is presented to serve as a starting point toward establishing standard practice for wireless coexistence testing of wireless systems in general and wireless medical devices in particular. Experimental evaluations demonstrated consistency with results reported in the literature.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125175562","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351828
J. Gilbert, W. Radasky, E. Savage
This paper provides details of a computational technique used to calculate currents induced by geomagnetic storms on transmission lines and in transformers of a large power grid. In practice, this technique has been driven by three sets of input data - magnetometer data on an irregular grid, magnetic fields from storm models, and predictions of magnetic fields from satellite data. The technique employs a ground conductivity that varies in both the horizontal and vertical directions and a computationally efficient technique for performing the convolutions needed to obtain the horizontal electric field from the horizontal magnetic field. A quasistatic technique is used for circuit modeling of lines and transformers, and various transformer and core types may be included for modeling of the current flow and of the generation of reactive power demand. This technique has been implemented in the POWERCAST™ code.
{"title":"A technique for calculating the currents induced by geomagnetic storms on large high voltage power grids","authors":"J. Gilbert, W. Radasky, E. Savage","doi":"10.1109/ISEMC.2012.6351828","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351828","url":null,"abstract":"This paper provides details of a computational technique used to calculate currents induced by geomagnetic storms on transmission lines and in transformers of a large power grid. In practice, this technique has been driven by three sets of input data - magnetometer data on an irregular grid, magnetic fields from storm models, and predictions of magnetic fields from satellite data. The technique employs a ground conductivity that varies in both the horizontal and vertical directions and a computationally efficient technique for performing the convolutions needed to obtain the horizontal electric field from the horizontal magnetic field. A quasistatic technique is used for circuit modeling of lines and transformers, and various transformer and core types may be included for modeling of the current flow and of the generation of reactive power demand. This technique has been implemented in the POWERCAST™ code.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126855191","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351789
D. Oh
As I/O speed continues to increase; the contribution of device jitter to the overall timing error becomes increasingly significant in high-speed interfaces. Conventional deterministic jitter components, such as inter-symbol interference (ISI) and duty-cycle distortion (DCD), remain relatively constant in terms of bit time. Other uncorrelated jitter components, such as random jitter (RJ) and power supply noise induced jitter (PSIJ), become more critical, because they are relatively hard to reduce. To date, uncorrelated jitter has been primarily modeled at the device or component level. Little work has been done to characterize its impact at the system level. First, this paper illustrates the various system-level issues caused by uncorrelated jitter. Next, the concept of jitter amplification and cancellation, using a clock signal, is reviewed in detail. Then, we describe a statistical link-simulation methodology that can be used to analyze the system-level jitter behavior. (PSIJ is used to demonstrate the modelling of the jitter source and its propagation.) We conclude with the correlation between in-situ on-chip measurements, and the results of the simulation.
{"title":"System level jitter characterization of high speed I/O systems","authors":"D. Oh","doi":"10.1109/ISEMC.2012.6351789","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351789","url":null,"abstract":"As I/O speed continues to increase; the contribution of device jitter to the overall timing error becomes increasingly significant in high-speed interfaces. Conventional deterministic jitter components, such as inter-symbol interference (ISI) and duty-cycle distortion (DCD), remain relatively constant in terms of bit time. Other uncorrelated jitter components, such as random jitter (RJ) and power supply noise induced jitter (PSIJ), become more critical, because they are relatively hard to reduce. To date, uncorrelated jitter has been primarily modeled at the device or component level. Little work has been done to characterize its impact at the system level. First, this paper illustrates the various system-level issues caused by uncorrelated jitter. Next, the concept of jitter amplification and cancellation, using a clock signal, is reviewed in detail. Then, we describe a statistical link-simulation methodology that can be used to analyze the system-level jitter behavior. (PSIJ is used to demonstrate the modelling of the jitter source and its propagation.) We conclude with the correlation between in-situ on-chip measurements, and the results of the simulation.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116457001","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351825
T. Sekine, H. Asai, J. S. Lee
In this paper, we describe the modeling and simulation techniques of electrostatic discharge (ESD) events. First, the existing circuit models of the ESD generator are reviewed, and the improved model is proposed. Next, the target printed circuit board circuit is modeled, and a ground plane of the board is excited by the proposed ESD generator model. Finally, simulation of the whole circuit is performed using our models, and it is shown that our methodology is far superior to the conventional techniques.
{"title":"Unified circuit modeling technique for the simulation of electrostatic discharge (ESD) injected by an ESD generator","authors":"T. Sekine, H. Asai, J. S. Lee","doi":"10.1109/ISEMC.2012.6351825","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351825","url":null,"abstract":"In this paper, we describe the modeling and simulation techniques of electrostatic discharge (ESD) events. First, the existing circuit models of the ESD generator are reviewed, and the improved model is proposed. Next, the target printed circuit board circuit is modeled, and a ground plane of the board is excited by the proposed ESD generator model. Finally, simulation of the whole circuit is performed using our models, and it is shown that our methodology is far superior to the conventional techniques.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121922570","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351769
A. Mediano, D. C. Smith
Mobile phones using Time Division Multiple Access (TDMA) technology generate audio noise on audio systems using speakers, specially if long cables are used. In general, any RF amplitude modulated signal can interfere other electronic systems when entering the circuits and being rectified (“audio rectification”). In this paper a simple setup for troubleshooting a system for that audio rectification problem is described. An RF power amplifier and a coaxial antenna are described as key elements of the setup and the general ideas about the use of the system are included.
{"title":"Troubleshooting setup with simple coaxial antenna for TDMA-GSM EMI/EMC in audio systems","authors":"A. Mediano, D. C. Smith","doi":"10.1109/ISEMC.2012.6351769","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351769","url":null,"abstract":"Mobile phones using Time Division Multiple Access (TDMA) technology generate audio noise on audio systems using speakers, specially if long cables are used. In general, any RF amplitude modulated signal can interfere other electronic systems when entering the circuits and being rectified (“audio rectification”). In this paper a simple setup for troubleshooting a system for that audio rectification problem is described. An RF power amplifier and a coaxial antenna are described as key elements of the setup and the general ideas about the use of the system are included.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129505782","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351791
C. Rostamzadeh, F. Canavero, F. Kashefi, M. Darbandi
Radiated emission (RE) compliance requirements of automotive sector demands one of the most difficult design challenges for EMC engineers as compared with those of FCC and military standard mandates. Recent revisions to EMC requirements has exasperated the RE compliance levels considerably. Automotive industry radiated emission requirements span over a wide frequency range (150 kHz-1.583 GHz). The European Long Wave (150 kHz-280 kHz) and global Medium Wave AM band (0.53 MHz-1.7 MHz) is the subject of this article. Onboard receivers in modern vehicle intended for the reception of the RF services, indicated as low frequency LW and MW audio broadcast, can be susceptible to unintended noise source(s). The modern vehicle is abundantly rich in noise source with a large number of electrical and electronics components. As a result of integration of electronics in modern vehicle, it hence creates the most demanding electromagnetic environment.
{"title":"Automotive AM-band radiated emission mitigation techniques, a practical approach","authors":"C. Rostamzadeh, F. Canavero, F. Kashefi, M. Darbandi","doi":"10.1109/ISEMC.2012.6351791","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351791","url":null,"abstract":"Radiated emission (RE) compliance requirements of automotive sector demands one of the most difficult design challenges for EMC engineers as compared with those of FCC and military standard mandates. Recent revisions to EMC requirements has exasperated the RE compliance levels considerably. Automotive industry radiated emission requirements span over a wide frequency range (150 kHz-1.583 GHz). The European Long Wave (150 kHz-280 kHz) and global Medium Wave AM band (0.53 MHz-1.7 MHz) is the subject of this article. Onboard receivers in modern vehicle intended for the reception of the RF services, indicated as low frequency LW and MW audio broadcast, can be susceptible to unintended noise source(s). The modern vehicle is abundantly rich in noise source with a large number of electrical and electronics components. As a result of integration of electronics in modern vehicle, it hence creates the most demanding electromagnetic environment.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129292871","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351679
G. Antonini, A. Ruehli
The solution of EM/Circuit problems is important for the EMC/SI/PI system designs. An essential issue today is the solution of larger problems without excessive memory and compute time requirements. In this paper, we show the potential for a new speed-up approach using the PEEC method. One source of the speed-up is due to the use of the waveform relaxation (WR) technique, which is very suitable for parallel processing. Importantly, the dense part of the partial inductance and potential matrices are sparsified by taking advantage of the rank deficiency of the dense parts of the MNA matrix. We show that both time as well as storage can be saved.
{"title":"Speed-up of PEEC EM/Ckt solver using rank-reduced waveform relaxation","authors":"G. Antonini, A. Ruehli","doi":"10.1109/ISEMC.2012.6351679","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351679","url":null,"abstract":"The solution of EM/Circuit problems is important for the EMC/SI/PI system designs. An essential issue today is the solution of larger problems without excessive memory and compute time requirements. In this paper, we show the potential for a new speed-up approach using the PEEC method. One source of the speed-up is due to the use of the waveform relaxation (WR) technique, which is very suitable for parallel processing. Importantly, the dense part of the partial inductance and potential matrices are sparsified by taking advantage of the rank deficiency of the dense parts of the MNA matrix. We show that both time as well as storage can be saved.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125309710","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351680
Clayton G. Thomas, G. Wilkins
The Wavefront Topology System (WTS) is a novel algorithm which produces 3D grids in various coordinate systems. The mathematical procedure is identical for all coordinate geometries. The geometrical boundaries constrain the node insertion process for mesh topologies. In conjunction with local and global indexes, coordinates are simultaneously generated for arbitrary geometrical domains. This unique technique will demonstrate compatibility with existing finite element methods. Due to a universal approach for various coordinate systems and geometrical structures, the technique is useful in EMC modeling. For the exposition of EMC, the Laplace equation will provide a natural choice for analysis. The sparsity pattern will prove the efficiency of the algorithm. The computational complexity is also comparable to existing methods. The results will demonstrate an effective implementation of the algorithm.
{"title":"Wavefront Topology System & finite element method applied to orthogonal mesh structures","authors":"Clayton G. Thomas, G. Wilkins","doi":"10.1109/ISEMC.2012.6351680","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351680","url":null,"abstract":"The Wavefront Topology System (WTS) is a novel algorithm which produces 3D grids in various coordinate systems. The mathematical procedure is identical for all coordinate geometries. The geometrical boundaries constrain the node insertion process for mesh topologies. In conjunction with local and global indexes, coordinates are simultaneously generated for arbitrary geometrical domains. This unique technique will demonstrate compatibility with existing finite element methods. Due to a universal approach for various coordinate systems and geometrical structures, the technique is useful in EMC modeling. For the exposition of EMC, the Laplace equation will provide a natural choice for analysis. The sparsity pattern will prove the efficiency of the algorithm. The computational complexity is also comparable to existing methods. The results will demonstrate an effective implementation of the algorithm.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121458137","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}
Pub Date : 2012-11-12DOI: 10.1109/ISEMC.2012.6351667
Woojin Ahn, Sungkwan Jung, Wonkyum Lee, Sangsik Kim, Junseok Park, Jaegue Shin, Hongseok Kim, Kyoungchoul Koo
In this paper, we designed the magnetically coupled resonators for wireless power transfer to mobile devices using field shaping technique. Power transfer to mobile devices is normally sensitive to variation of distance and alignment between transmitters and receivers. The magnetic field shaping technique, which is applied by On-line Electric Vehicle (OLEV) system, is considered to compensate the sensitivity, to reduce electromagnetic fields (EMF) around the receivers, and also to improve efficiency of power transfer [1]. We developed miniaturized coupled resonators to cover mobile devices, and enhanced coupling effect with modified formation of coupled resonators. Also, the coupled resonators are designed to receive power stably, less sensitive to variation of distance and alignment. We present measurement results with s-parameter value of the amount of power transferred.
{"title":"Design of coupled resonators for wireless power transfer to mobile devices using magnetic field shaping","authors":"Woojin Ahn, Sungkwan Jung, Wonkyum Lee, Sangsik Kim, Junseok Park, Jaegue Shin, Hongseok Kim, Kyoungchoul Koo","doi":"10.1109/ISEMC.2012.6351667","DOIUrl":"https://doi.org/10.1109/ISEMC.2012.6351667","url":null,"abstract":"In this paper, we designed the magnetically coupled resonators for wireless power transfer to mobile devices using field shaping technique. Power transfer to mobile devices is normally sensitive to variation of distance and alignment between transmitters and receivers. The magnetic field shaping technique, which is applied by On-line Electric Vehicle (OLEV) system, is considered to compensate the sensitivity, to reduce electromagnetic fields (EMF) around the receivers, and also to improve efficiency of power transfer [1]. We developed miniaturized coupled resonators to cover mobile devices, and enhanced coupling effect with modified formation of coupled resonators. Also, the coupled resonators are designed to receive power stably, less sensitive to variation of distance and alignment. We present measurement results with s-parameter value of the amount of power transferred.","PeriodicalId":197346,"journal":{"name":"2012 IEEE International Symposium on Electromagnetic Compatibility","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134220561","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：