A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit....A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.展开更多
The low-intensity attack flows used by Crossfire attacks are hard to distinguish from legitimate flows.Traditional methods to identify the malicious flows in Crossfire attacks are rerouting,which is based on statistic...The low-intensity attack flows used by Crossfire attacks are hard to distinguish from legitimate flows.Traditional methods to identify the malicious flows in Crossfire attacks are rerouting,which is based on statistics.In these existing mechanisms,the identification of malicious flows depends on the IP address.However,the IP address is easy to be changed by attacks.Comparedwith the IP address,the certificate ismore challenging to be tampered with or forged.Moreover,the traffic trend in the network is towards encryption.The certificates are popularly utilized by IoT devices for authentication in encryption protocols.DTLShps proposed a new way to verify certificates for resource-constrained IoT devices by using the SDN controller.Based on DTLShps,the SDN controller can collect statistics on certificates.In this paper,we proposeCertrust,a framework based on the trust of certificates,tomitigate the Crossfire attack by using SDN for IoT.Our goal is threefold.First,the trust model is built based on the Bayesian trust system with the statistics on the participation of certificates in each Crossfire attack.Moreover,the forgetting curve is utilized instead of the traditional decay method in the Bayesian trust system for achieving a moderate decay rate.Second,for detecting the Crossfire attack accurately,a method based on graph connectivity is proposed.Third,several trust-based routing principles are proposed tomitigate the Crossfire attack.These principles can also encourage users to use certificates in communication.The performance evaluation shows that Certrust is more effective in mitigating the Crossfire attack than the traditional rerouting schemes.Moreover,our trust model has a more appropriate decay rate than the traditional methods.展开更多
Increasing railway traffic and energy utilization issues prompt electrified railway systems to be more economical,efficient and sustainable.As regenerative braking energy in railway systems has huge potential for opti...Increasing railway traffic and energy utilization issues prompt electrified railway systems to be more economical,efficient and sustainable.As regenerative braking energy in railway systems has huge potential for optimized utilization,a lot of research has been focusing on how to use the energy efficiently and gain sustainable benefits.The energy storage system is an alternative because it not only deals with regenerative braking energy but also smooths drastic fluctuation of load power profile and optimizes energy management.In this work,we propose a co-phase traction power supply system with super capacitor(CSS_SC)for the purpose of realizing the function of energy management and power quality management in electrified railways.Besides,the coordinated control strategy is presented to match four working modes,including traction,regenerative braking,peak shaving and valley filling.A corresponding simulation model is built in MATLAB/Simulink to verify the feasibility of the proposed system under dynamic working conditions.The results demonstrate that CSS_SC is flexible to deal with four different working conditions and can realize energy saving within the allowable voltage unbalance of 0.008%in simulation in contrast to 1.3%of the standard limit.With such a control strategy,the performance of super capacitor is controlled to comply with efficiency and safety constraints.Finally,a case study demonstrates the improvement in power fluctuation with the valley-to-peak ratio reduced by 20.3%and the daily load factor increased by 17.9%.展开更多
Software Defined Networking(SDN) provides a flexible and convenient way to support fine-grained traffic-engineering(TE). Besides, SDN also provides better Quality of Experience(QoE) for customers. However, the policy ...Software Defined Networking(SDN) provides a flexible and convenient way to support fine-grained traffic-engineering(TE). Besides, SDN also provides better Quality of Experience(QoE) for customers. However, the policy of the evolution from legacy networks to the SDNs overemphasizes the controllability of the network or TE while ignoring the customers' benefit. Standing in the customers' position, we propose an optimization scheme, named as Optimal Migration Schedule based on Customers' Benefit(OMSB), to produce an optimized migration schedule and maximize the benefit of customers. Not only the quality and quantity of paths availed by migration, but also the number of flows from the customers that can use these multi-paths are taken into consideration for the scheduling. We compare the OMSB with other six migration schemes in terms of the benefit of customers. Our results suggest that the sequence of the migration plays a vital role for customers, especially in the early stages of the network migration to the SDN.展开更多
Fueled by the explosive growth of ultra-low-latency and real-time applications with specific computing and network performance requirements,the computing force network(CFN)has become a hot research subject.The primary...Fueled by the explosive growth of ultra-low-latency and real-time applications with specific computing and network performance requirements,the computing force network(CFN)has become a hot research subject.The primary CFN challenge is to leverage network resources and computing resources.Although recent advances in deep reinforcement learning(DRL)have brought significant improvement in network optimization,these methods still suffer from topology changes and fail to generalize for those topologies not seen in training.This paper proposes a graph neural network(GNN)based DRL framework to accommodate network trafic and computing resources jointly and efficiently.By taking advantage of the generalization capability in GNN,the proposed method can operate over variable topologies and obtain higher performance than the other DRL methods.展开更多
Dear Editor,Ovarian cancer remains the deadliest among all gynecological cancers.Although most patients at advanced stage respond to initial treatment,the majority experience recurrence[1].It was estimated that 55,342...Dear Editor,Ovarian cancer remains the deadliest among all gynecological cancers.Although most patients at advanced stage respond to initial treatment,the majority experience recurrence[1].It was estimated that 55,342 new cases and 37,519 deaths from ovarian cancer occurred in China annually[2].Contemporarily,the treatment landscape has changed rapidly since the role of poly(adenosine diphosphate-ribose)polymerase inhibitors(PARPi)in ovarian cancer treatmentwas explored.Based on data from the PRIMA/ENGOT-OV26/GOG-3012[3]and ENGOTOV16/NOVA trials[4],niraparib has been approved globally as maintenance therapy for newly diagnosed and platinum-sensitive recurrent ovarian cancer.The indication of niraparib for salvage treatment was based on the results of the QUADRA(NCT02354586)trial[5].Although niraparib has been tested in prospective randomized clinical trials(RCTs),no multicenter study on its real-world application in China had been conducted.Considering the differences in population,accessibility and affordability of drugs,the results of the real-world settings may differ from those of RCTs.Therefore,we conducted this multicenter,non-interventional study at 8 hospitals.展开更多
Aiming at the lack of classification and good standard corpus in the task of joint entity and relationship extraction in the current Chinese academic field, this paper builds a dataset in management science that can b...Aiming at the lack of classification and good standard corpus in the task of joint entity and relationship extraction in the current Chinese academic field, this paper builds a dataset in management science that can be used for joint entity and relationship extraction, and establishes a deep learning model to extract entity and relationship information from scientific texts. With the definition of entity and relation classification, we build a Chinese scientific text corpus dataset based on the abstract texts of projects funded by the National Natural Science Foundation of China(NSFC) in 2018–2019. By combining the word2vec features with the clue word feature which is a kind of special style in scientific documents, we establish a joint entity relationship extraction model based on the Bi LSTM-CNN-CRF model for scientific information extraction. The dataset we constructed contains 13060 entities(not duplicated) and 9728 entity relation labels. In terms of entity prediction effect, the accuracy rate of the constructed model reaches 69.15%, the recall rate reaches 61.03%, and the F1 value reaches 64.83%. In terms of relationship prediction effect, the accuracy rate is higher than that of entity prediction, which reflects the effectiveness of the input mixed features and the integration of local features with CNN layer in the model.展开更多
Background：Green tea has been shown to improve cholesterol metabolism in animal studies,but the molecular mechanisms underlying this function have not been fully understood.Long non-coding RNAs （lncRNAs） have recen...Background：Green tea has been shown to improve cholesterol metabolism in animal studies,but the molecular mechanisms underlying this function have not been fully understood.Long non-coding RNAs （lncRNAs） have recently emerged as a major class of regulatory molecules involved in a broad range of biological processes and complex diseases.Our aim was to identify important lncRNAs that might play an important role in contributing to the benefits of epigallocatechin-3-gallate （EGCG） on cholesterol metabolism.Methods：Microarrays was used to reveal the lncRNA and mRNA profiles in green tea polyphenol（-）-epigallocatechin gallate in cultured human liver （HepG2） hepatocytes treated with EGCG and bioinformatic analyses of the predicted target genes were performed to identify lncRNA-mRNA targeting relationships.RNA interference was used to investigate the role of lncRNAs in cholesterol metabolism.Results：The expression levels of 15 genes related to cholesterol metabolism and 285 lncRNAs were changed by EGCG treatment.Bioinformatic analysis found five matched lncRNA-mRNA pairs for five differentially expressed lncRNAs and four differentially expressed mRNA.In particular,the lncRNA4 T102202 and its potential targets mRNA-3-hydroxy-3-methylglutaryl coenzyme A reductase （HMGCR） were identified.Using a real-time polymerase chain reaction technique,we confirmed that EGCG down-regulated mRNA expression level of the HMGCR and up-regulated expression ofAT102202.After AT102202 knockdown in HepG2,we observed that the level of HMGCR expression was significantly increased relative to the scrambled small interfering RNA control （P 〈 0.05）.Conclusions：Our results indicated that EGCG improved cholesterol metabolism and meanwhile changed the lncRNAs expression profile in HepG2 cells.LncRNAs may play an important role in the cholesterol metabolism.展开更多
Dear Editor,Noroviruses(No Vs)are second only to the rotaviruses as etiologic agents of acute fulminant gastroenteritis in infants and young children worldwide,with an estimated 200,000deaths per year in children youn...Dear Editor,Noroviruses(No Vs)are second only to the rotaviruses as etiologic agents of acute fulminant gastroenteritis in infants and young children worldwide,with an estimated 200,000deaths per year in children younger than 5 years of age in developing countries(Patel et al.2008).No Vs are classified within the genus Norovirus of the family Caliciviridae with Norwalk virus as its prototype member(ICTV 2017).The virions are small(38–40 nm in diameter)nonenveloped,with an icosahedral capsidanda linear,positive-展开更多
Emerging economies provide interesting scenarios for examining how institutional context influences the financing behavior of firms. In this study, we examine the capital structure of Chinese listed firms following th...Emerging economies provide interesting scenarios for examining how institutional context influences the financing behavior of firms. In this study, we examine the capital structure of Chinese listed firms following the SplitShare Structure Reform of 2005. This reform allowed a reduction of government ownership by making government shares tradable. We find that the impact of government ownership on leverage is dependent on whether the government is the largest shareholder in a firm and whether the government ownership is through a parent state-owned enterprise. In addition, we document that the largest non-government shareholder positively influences leverage.Overall, our results reveal that the largest controlling shareholder, either government or non-government, has a significant impact on the capital structure of Chinese firms.展开更多
基金This research was supported by the Science and Technology Plan Project of Sichuan Province(No.21YYJC3324)the Science and Technology Plan Project of Sichuan Province(No.2022YFQ0104).
文摘A novel three-phase traction power supply system is proposed to eliminate the adverse effects caused by electric phase separation in catenary and accomplish a unifying manner of traction power supply for rail transit.With the application of two-stage three-phase continuous power supply structure,the electrical characteristics exhibit new features differing from the existing traction system.In this work,the principle for voltage levels determining two-stage network is dissected in accordance with the requirements of traction network and electric locomotive.The equivalent model of three-phase traction system is built for deducing the formula of current distribution and voltage losses.Based on the chain network model of the traction network,a simulation model is established to analyze the electrical characteristics such as traction current distribution,voltage losses,system equivalent impedance,voltage distribution,voltage unbalance and regenerative energy utilization.In a few words,quite a lot traction current of about 99%is undertaken by long-section cable network.The proportion of system voltage losses is small attributed to the two-stage three-phase power supply structure,and the voltage unbal-ance caused by impedance asymmetry of traction network is less than 1‰.In addition,the utilization rate of regenerative energy for locomotive achieves a significant promotion of over 97%.
基金supported by Joint Funds of the National Natural Science Foundation of China and Xinjiang under Project U1603261.
文摘The low-intensity attack flows used by Crossfire attacks are hard to distinguish from legitimate flows.Traditional methods to identify the malicious flows in Crossfire attacks are rerouting,which is based on statistics.In these existing mechanisms,the identification of malicious flows depends on the IP address.However,the IP address is easy to be changed by attacks.Comparedwith the IP address,the certificate ismore challenging to be tampered with or forged.Moreover,the traffic trend in the network is towards encryption.The certificates are popularly utilized by IoT devices for authentication in encryption protocols.DTLShps proposed a new way to verify certificates for resource-constrained IoT devices by using the SDN controller.Based on DTLShps,the SDN controller can collect statistics on certificates.In this paper,we proposeCertrust,a framework based on the trust of certificates,tomitigate the Crossfire attack by using SDN for IoT.Our goal is threefold.First,the trust model is built based on the Bayesian trust system with the statistics on the participation of certificates in each Crossfire attack.Moreover,the forgetting curve is utilized instead of the traditional decay method in the Bayesian trust system for achieving a moderate decay rate.Second,for detecting the Crossfire attack accurately,a method based on graph connectivity is proposed.Third,several trust-based routing principles are proposed tomitigate the Crossfire attack.These principles can also encourage users to use certificates in communication.The performance evaluation shows that Certrust is more effective in mitigating the Crossfire attack than the traditional rerouting schemes.Moreover,our trust model has a more appropriate decay rate than the traditional methods.
文摘Increasing railway traffic and energy utilization issues prompt electrified railway systems to be more economical,efficient and sustainable.As regenerative braking energy in railway systems has huge potential for optimized utilization,a lot of research has been focusing on how to use the energy efficiently and gain sustainable benefits.The energy storage system is an alternative because it not only deals with regenerative braking energy but also smooths drastic fluctuation of load power profile and optimizes energy management.In this work,we propose a co-phase traction power supply system with super capacitor(CSS_SC)for the purpose of realizing the function of energy management and power quality management in electrified railways.Besides,the coordinated control strategy is presented to match four working modes,including traction,regenerative braking,peak shaving and valley filling.A corresponding simulation model is built in MATLAB/Simulink to verify the feasibility of the proposed system under dynamic working conditions.The results demonstrate that CSS_SC is flexible to deal with four different working conditions and can realize energy saving within the allowable voltage unbalance of 0.008%in simulation in contrast to 1.3%of the standard limit.With such a control strategy,the performance of super capacitor is controlled to comply with efficiency and safety constraints.Finally,a case study demonstrates the improvement in power fluctuation with the valley-to-peak ratio reduced by 20.3%and the daily load factor increased by 17.9%.
基金supported by Joint Funds of National Natural Science Foundation of China and Xinjiang under code U1603261the Research Fund of Ministry of Education-China Mobile under Grant No. MCM20160304the Fundamental Research Funds for the Central Universities
文摘Software Defined Networking(SDN) provides a flexible and convenient way to support fine-grained traffic-engineering(TE). Besides, SDN also provides better Quality of Experience(QoE) for customers. However, the policy of the evolution from legacy networks to the SDNs overemphasizes the controllability of the network or TE while ignoring the customers' benefit. Standing in the customers' position, we propose an optimization scheme, named as Optimal Migration Schedule based on Customers' Benefit(OMSB), to produce an optimized migration schedule and maximize the benefit of customers. Not only the quality and quantity of paths availed by migration, but also the number of flows from the customers that can use these multi-paths are taken into consideration for the scheduling. We compare the OMSB with other six migration schemes in terms of the benefit of customers. Our results suggest that the sequence of the migration plays a vital role for customers, especially in the early stages of the network migration to the SDN.
基金supported by the Beijing University of Posts and Telecommunications-China Mobile Research Institute Joint Innovation Center。
文摘Fueled by the explosive growth of ultra-low-latency and real-time applications with specific computing and network performance requirements,the computing force network(CFN)has become a hot research subject.The primary CFN challenge is to leverage network resources and computing resources.Although recent advances in deep reinforcement learning(DRL)have brought significant improvement in network optimization,these methods still suffer from topology changes and fail to generalize for those topologies not seen in training.This paper proposes a graph neural network(GNN)based DRL framework to accommodate network trafic and computing resources jointly and efficiently.By taking advantage of the generalization capability in GNN,the proposed method can operate over variable topologies and obtain higher performance than the other DRL methods.
基金funded by the National Natural Science Foundation of China(NSFC 81972431).
文摘Dear Editor,Ovarian cancer remains the deadliest among all gynecological cancers.Although most patients at advanced stage respond to initial treatment,the majority experience recurrence[1].It was estimated that 55,342 new cases and 37,519 deaths from ovarian cancer occurred in China annually[2].Contemporarily,the treatment landscape has changed rapidly since the role of poly(adenosine diphosphate-ribose)polymerase inhibitors(PARPi)in ovarian cancer treatmentwas explored.Based on data from the PRIMA/ENGOT-OV26/GOG-3012[3]and ENGOTOV16/NOVA trials[4],niraparib has been approved globally as maintenance therapy for newly diagnosed and platinum-sensitive recurrent ovarian cancer.The indication of niraparib for salvage treatment was based on the results of the QUADRA(NCT02354586)trial[5].Although niraparib has been tested in prospective randomized clinical trials(RCTs),no multicenter study on its real-world application in China had been conducted.Considering the differences in population,accessibility and affordability of drugs,the results of the real-world settings may differ from those of RCTs.Therefore,we conducted this multicenter,non-interventional study at 8 hospitals.
基金Supported by the National Natural Science Foundation of China (71804017)the R&D Program of Beijing Municipal Education Commission (KZ202210005013)the Sichuan Social Science Planning Project (SC22B151)。
文摘Aiming at the lack of classification and good standard corpus in the task of joint entity and relationship extraction in the current Chinese academic field, this paper builds a dataset in management science that can be used for joint entity and relationship extraction, and establishes a deep learning model to extract entity and relationship information from scientific texts. With the definition of entity and relation classification, we build a Chinese scientific text corpus dataset based on the abstract texts of projects funded by the National Natural Science Foundation of China(NSFC) in 2018–2019. By combining the word2vec features with the clue word feature which is a kind of special style in scientific documents, we establish a joint entity relationship extraction model based on the Bi LSTM-CNN-CRF model for scientific information extraction. The dataset we constructed contains 13060 entities(not duplicated) and 9728 entity relation labels. In terms of entity prediction effect, the accuracy rate of the constructed model reaches 69.15%, the recall rate reaches 61.03%, and the F1 value reaches 64.83%. In terms of relationship prediction effect, the accuracy rate is higher than that of entity prediction, which reflects the effectiveness of the input mixed features and the integration of local features with CNN layer in the model.
基金The present study was supported by a grant from the National Natural Science Foundation of China （No. 81241007）.
文摘Background：Green tea has been shown to improve cholesterol metabolism in animal studies,but the molecular mechanisms underlying this function have not been fully understood.Long non-coding RNAs （lncRNAs） have recently emerged as a major class of regulatory molecules involved in a broad range of biological processes and complex diseases.Our aim was to identify important lncRNAs that might play an important role in contributing to the benefits of epigallocatechin-3-gallate （EGCG） on cholesterol metabolism.Methods：Microarrays was used to reveal the lncRNA and mRNA profiles in green tea polyphenol（-）-epigallocatechin gallate in cultured human liver （HepG2） hepatocytes treated with EGCG and bioinformatic analyses of the predicted target genes were performed to identify lncRNA-mRNA targeting relationships.RNA interference was used to investigate the role of lncRNAs in cholesterol metabolism.Results：The expression levels of 15 genes related to cholesterol metabolism and 285 lncRNAs were changed by EGCG treatment.Bioinformatic analysis found five matched lncRNA-mRNA pairs for five differentially expressed lncRNAs and four differentially expressed mRNA.In particular,the lncRNA4 T102202 and its potential targets mRNA-3-hydroxy-3-methylglutaryl coenzyme A reductase （HMGCR） were identified.Using a real-time polymerase chain reaction technique,we confirmed that EGCG down-regulated mRNA expression level of the HMGCR and up-regulated expression ofAT102202.After AT102202 knockdown in HepG2,we observed that the level of HMGCR expression was significantly increased relative to the scrambled small interfering RNA control （P 〈 0.05）.Conclusions：Our results indicated that EGCG improved cholesterol metabolism and meanwhile changed the lncRNAs expression profile in HepG2 cells.LncRNAs may play an important role in the cholesterol metabolism.
基金supported by General Program of the National Natural Science Foundation of China (31572529)the National Key Basic Research and Development Program of China (2016YFC1200100)the Youth Innovation Fund of the Academy of Military Medical Science (2015CXJJ28)
文摘Dear Editor,Noroviruses(No Vs)are second only to the rotaviruses as etiologic agents of acute fulminant gastroenteritis in infants and young children worldwide,with an estimated 200,000deaths per year in children younger than 5 years of age in developing countries(Patel et al.2008).No Vs are classified within the genus Norovirus of the family Caliciviridae with Norwalk virus as its prototype member(ICTV 2017).The virions are small(38–40 nm in diameter)nonenveloped,with an icosahedral capsidanda linear,positive-
文摘Emerging economies provide interesting scenarios for examining how institutional context influences the financing behavior of firms. In this study, we examine the capital structure of Chinese listed firms following the SplitShare Structure Reform of 2005. This reform allowed a reduction of government ownership by making government shares tradable. We find that the impact of government ownership on leverage is dependent on whether the government is the largest shareholder in a firm and whether the government ownership is through a parent state-owned enterprise. In addition, we document that the largest non-government shareholder positively influences leverage.Overall, our results reveal that the largest controlling shareholder, either government or non-government, has a significant impact on the capital structure of Chinese firms.
