High-accuracy continuous measurements of atmospheric concentrations of CO2 were made from May 2016 to December 2017 using the Picarro G2301 analyzer at Xinglong station(40°24′N,117°30′E,940 MSL),150 km nor...High-accuracy continuous measurements of atmospheric concentrations of CO2 were made from May 2016 to December 2017 using the Picarro G2301 analyzer at Xinglong station(40°24′N,117°30′E,940 MSL),150 km northeast of Beijing.The near-ground CO2 measurements were calibrated by standards based on WMO procedures.The regional background measurements were ltered by the robust extraction of baseline signal method to study the seasonal and diurnal cycles.The regional background CO2 concentrations were low in summer.The maximum diffierence between the local sources and regional background CO2 concentrations occurred in summer and autumn,indicating a strong in uence from local sources.Cluster analysis and potential source contribution function analysis showed that the long-distance transport of anthropogenic emissions in the Beijing Tianjin Hebei metropolitan area in uenced the CO2 concentrations in Xinglong,espe-cially in summer.The diurnal variation of CO2 was mainly in uenced by the various vertical transport conditions of the tropospheric atmosphere in a day.展开更多
The Level-2 probabilistic safety assessment(PSA) of pressurized water reactors studies the possibility of creep rupture for major reactor coolant system components during the course of high pressure severe accident se...The Level-2 probabilistic safety assessment(PSA) of pressurized water reactors studies the possibility of creep rupture for major reactor coolant system components during the course of high pressure severe accident sequences. The present paper covers this technical issue and tries to quantify its associated phenomenological uncertainties for the development of Level-2 PSA. A framework is proposed for the formal quantification of uncertainties in the Level-2 PSA model of a PWR type nuclear power plant using an integrated deterministic and PSA approach. This is demonstrated for estimation of creep rupture failure probability in station blackout severe accident of a 2-loop PWR, which is the representative case for high pressure sequences. MELCOR 1.8.6 code is employed here as the deterministic tool for the assessment of physical phenomena in the course of accident. In addition, a MATLAB code is developed for quantification of the probabilistic part by treating the uncertainties through separation of aleatory and epistemic sources of uncertainty.The probability for steam generator tube creep rupture is estimated at 0.17.展开更多
The Device-to-Device(D2D)communication underlaying cellular networks is considered in this study.The D2D transmitter in the D2D mode can directly transmit messages to a receiver,but it may interfere with the transmiss...The Device-to-Device(D2D)communication underlaying cellular networks is considered in this study.The D2D transmitter in the D2D mode can directly transmit messages to a receiver,but it may interfere with the transmission of another cellular user who shares the same uplink channel.The transmitter can also operate in a cellular mode in which no interference to another cellular user occurs.We propose a mode selection scheme that aims to minimize the transmission power of the D2D transmitter subject to constraints on the minimum required data rate and maximum interference to other cellular users.The proposed scheme is based on bounds for transmission power and is less complex than the optimal scheme.Furthermore,it requires only a few statistics and does not need a fading channel distribution.The performance of the scheme is close to optimum when the number of Base Station(BS)antennas is large,and the mean absolute deviation of the fading terms is small.We verify this with numerical results of the Rician and Rayleigh fading channels by assuming that the BS antennas are independent.The simulation results for the two correlated BS antennas are presented herein.展开更多
In this paper Pi2 pulsations at Zhongshan Station of Antarctica are analyzed from October 1 - 31, 1996. Their characteristics e. g. occurrence frequency,frequency, and polarization are studied. The characteristics of ...In this paper Pi2 pulsations at Zhongshan Station of Antarctica are analyzed from October 1 - 31, 1996. Their characteristics e. g. occurrence frequency,frequency, and polarization are studied. The characteristics of Pi2 pulsations are summerized as follows: (1 ) Pi2 pulsations at Zhongshan Station usually take place from 2000 MLT to 0200 MLT; the main frequencies are between 6. 79 mHz and 13. 58mHZ; (2 ) Pi2 pulsations with low frequencies are dominent. The range of main frequencies becomes narrow at midnight; (3) The Polarization of Pi2 pulsations are almost linear; (4) About the orientation of major axes the NW-SE direction is dominent before 2200 MLT and NE-SW is dominent after 2200 MLT. The generation mechanism of Pi2 pulsations at Zhongshan Station is discussed theoretically.展开更多
In this paper, we study the coexistence of two key technologies in the same fifth-generation network, namely D2D (Device-to-Device) communication and MEC (Multi-Access Edge Computing) technology. These two promising t...In this paper, we study the coexistence of two key technologies in the same fifth-generation network, namely D2D (Device-to-Device) communication and MEC (Multi-Access Edge Computing) technology. These two promising technologies each have important roles to play in future telecommunications networks. D2D communication is a technology that aims to improve communication efficiency, increase overall throughput, and decrease latency. Multi-Access Edge Computing, a promising new concept, overcomes the burden of core cloud servers. This makes it possible to provide large storage, compute, and resource capacities to mobile edge nodes. With its closest deployment to users, it significantly reduces end-to-end transmission time. Our architecture consists of an access network and a central network, a base station (gNodeB), users, an MEC server and a gateway (UPF) to connect it to the RAN (Radio Access Network) of the core network. The base station controls communication by managing signaling and interference. The MEC server is placed next to the BS to provide data to the devices. It plays the role of the cloud that is located in the core network and allows you to store data and then do calculations for good communication between devices. Finally, we did a simulation using the OMNeT software. The results showed us that the data transmission passed well between the end devices, the antennas and the MEC server with very low latency and reliability.展开更多
The rapid development of the“Internet+”has ushered in a new era of global digital technology innovation.Concurrent with the deepening trends of economic globalization and integration,international trade is progressi...The rapid development of the“Internet+”has ushered in a new era of global digital technology innovation.Concurrent with the deepening trends of economic globalization and integration,international trade is progressively undergoing extensive digitization,with cross-border e-commerce emerging as a significant manifestation of this transformation.Within this landscape,the cross-border e-commerce B2B platform is anticipated to become a pivotal driver for China’s cross-border trade growth,representing a strategic opportunity for trade transformation.This paper provides a comprehensive examination of the concepts,characteristics,and development status of cross-border e-commerce and B2B platforms,considering both global and Chinese perspectives.Focusing on a prominent case study,Alibaba International Station,a B2B cross-border e-commerce platform,the paper delves into its business model and core competencies,offering a thorough analysis of its role in the intricacies of international e-commerce and its contribution to the field.Drawing on insights gained,the paper concludes by presenting targeted recommendations from both the platform and government perspectives.These suggestions are informed by a nuanced understanding of the development opportunities and challenges facing China’s cross-border e-commerce B2B platforms.展开更多
基金funded by the National Key Research and Development Program of China [grant numbers2017YFB0504000 and 2017YFC1501701]the National Natural Science Foundation of China [grant number 41575034]
文摘High-accuracy continuous measurements of atmospheric concentrations of CO2 were made from May 2016 to December 2017 using the Picarro G2301 analyzer at Xinglong station(40°24′N,117°30′E,940 MSL),150 km northeast of Beijing.The near-ground CO2 measurements were calibrated by standards based on WMO procedures.The regional background measurements were ltered by the robust extraction of baseline signal method to study the seasonal and diurnal cycles.The regional background CO2 concentrations were low in summer.The maximum diffierence between the local sources and regional background CO2 concentrations occurred in summer and autumn,indicating a strong in uence from local sources.Cluster analysis and potential source contribution function analysis showed that the long-distance transport of anthropogenic emissions in the Beijing Tianjin Hebei metropolitan area in uenced the CO2 concentrations in Xinglong,espe-cially in summer.The diurnal variation of CO2 was mainly in uenced by the various vertical transport conditions of the tropospheric atmosphere in a day.
文摘The Level-2 probabilistic safety assessment(PSA) of pressurized water reactors studies the possibility of creep rupture for major reactor coolant system components during the course of high pressure severe accident sequences. The present paper covers this technical issue and tries to quantify its associated phenomenological uncertainties for the development of Level-2 PSA. A framework is proposed for the formal quantification of uncertainties in the Level-2 PSA model of a PWR type nuclear power plant using an integrated deterministic and PSA approach. This is demonstrated for estimation of creep rupture failure probability in station blackout severe accident of a 2-loop PWR, which is the representative case for high pressure sequences. MELCOR 1.8.6 code is employed here as the deterministic tool for the assessment of physical phenomena in the course of accident. In addition, a MATLAB code is developed for quantification of the probabilistic part by treating the uncertainties through separation of aleatory and epistemic sources of uncertainty.The probability for steam generator tube creep rupture is estimated at 0.17.
基金This work was supported by Kasetsart University Research and Development Institute(KURDI)under the FY2016 Kasetsart University research grant,and the Royal Golden Jubilee Ph.D.program.
文摘The Device-to-Device(D2D)communication underlaying cellular networks is considered in this study.The D2D transmitter in the D2D mode can directly transmit messages to a receiver,but it may interfere with the transmission of another cellular user who shares the same uplink channel.The transmitter can also operate in a cellular mode in which no interference to another cellular user occurs.We propose a mode selection scheme that aims to minimize the transmission power of the D2D transmitter subject to constraints on the minimum required data rate and maximum interference to other cellular users.The proposed scheme is based on bounds for transmission power and is less complex than the optimal scheme.Furthermore,it requires only a few statistics and does not need a fading channel distribution.The performance of the scheme is close to optimum when the number of Base Station(BS)antennas is large,and the mean absolute deviation of the fading terms is small.We verify this with numerical results of the Rician and Rayleigh fading channels by assuming that the BS antennas are independent.The simulation results for the two correlated BS antennas are presented herein.
文摘In this paper Pi2 pulsations at Zhongshan Station of Antarctica are analyzed from October 1 - 31, 1996. Their characteristics e. g. occurrence frequency,frequency, and polarization are studied. The characteristics of Pi2 pulsations are summerized as follows: (1 ) Pi2 pulsations at Zhongshan Station usually take place from 2000 MLT to 0200 MLT; the main frequencies are between 6. 79 mHz and 13. 58mHZ; (2 ) Pi2 pulsations with low frequencies are dominent. The range of main frequencies becomes narrow at midnight; (3) The Polarization of Pi2 pulsations are almost linear; (4) About the orientation of major axes the NW-SE direction is dominent before 2200 MLT and NE-SW is dominent after 2200 MLT. The generation mechanism of Pi2 pulsations at Zhongshan Station is discussed theoretically.
文摘In this paper, we study the coexistence of two key technologies in the same fifth-generation network, namely D2D (Device-to-Device) communication and MEC (Multi-Access Edge Computing) technology. These two promising technologies each have important roles to play in future telecommunications networks. D2D communication is a technology that aims to improve communication efficiency, increase overall throughput, and decrease latency. Multi-Access Edge Computing, a promising new concept, overcomes the burden of core cloud servers. This makes it possible to provide large storage, compute, and resource capacities to mobile edge nodes. With its closest deployment to users, it significantly reduces end-to-end transmission time. Our architecture consists of an access network and a central network, a base station (gNodeB), users, an MEC server and a gateway (UPF) to connect it to the RAN (Radio Access Network) of the core network. The base station controls communication by managing signaling and interference. The MEC server is placed next to the BS to provide data to the devices. It plays the role of the cloud that is located in the core network and allows you to store data and then do calculations for good communication between devices. Finally, we did a simulation using the OMNeT software. The results showed us that the data transmission passed well between the end devices, the antennas and the MEC server with very low latency and reliability.
文摘The rapid development of the“Internet+”has ushered in a new era of global digital technology innovation.Concurrent with the deepening trends of economic globalization and integration,international trade is progressively undergoing extensive digitization,with cross-border e-commerce emerging as a significant manifestation of this transformation.Within this landscape,the cross-border e-commerce B2B platform is anticipated to become a pivotal driver for China’s cross-border trade growth,representing a strategic opportunity for trade transformation.This paper provides a comprehensive examination of the concepts,characteristics,and development status of cross-border e-commerce and B2B platforms,considering both global and Chinese perspectives.Focusing on a prominent case study,Alibaba International Station,a B2B cross-border e-commerce platform,the paper delves into its business model and core competencies,offering a thorough analysis of its role in the intricacies of international e-commerce and its contribution to the field.Drawing on insights gained,the paper concludes by presenting targeted recommendations from both the platform and government perspectives.These suggestions are informed by a nuanced understanding of the development opportunities and challenges facing China’s cross-border e-commerce B2B platforms.
