The transient critical boundary of dynamic security region (DSR) can be approximated by a few hyper planes correlated with instability separation modes. A method to fast predict instability separation modes is propose...The transient critical boundary of dynamic security region (DSR) can be approximated by a few hyper planes correlated with instability separation modes. A method to fast predict instability separation modes is proposed for DSR calculation in power injection space. The method identifies coherent generation groups by the developed K-medoids algorithm, taking a similarity matrix derived from the reachability Grammian as the index. As an experimental result, reachability Grammian matrices under local injections are approximately invariant. It indicates that the generator coherency identifications are nearly consistent for different injections. Then instability separation modes can be predicted at the normal operating point, while average initial acceleration is considered as the measure of the critical generator group to amend the error. Moreover, based on these predicted instability separation modes, a critical point search strategy for DSR calculation is illustrated in the reduced injection space of the critical generators. The proposed method was evaluated using New England Test System, and the computation accuracy and speed in determining the practical DSR were improved.展开更多
Realized new break-through on the basis of existing security management theory, tentatively and creatively carried out ＂realizing management theory of mine security production＂ and proposed ＂bridge＂ mode of realiz...Realized new break-through on the basis of existing security management theory, tentatively and creatively carried out ＂realizing management theory of mine security production＂ and proposed ＂bridge＂ mode of realizing green management theory. Green management theory has an integrated system structure. The green management system of mine security production includes three parts, the foundation of green system, the supervision system of green system operation and the safeguard system of green system. The key of ＂bridge＂ mode is to analyze the existing insecurity factors in the process of security production and establish corresponding regulations.展开更多
Language security is an important part of national security,and in the current complex international environment,the issue of language security is becoming more and more prominent and has become an unignorable part of...Language security is an important part of national security,and in the current complex international environment,the issue of language security is becoming more and more prominent and has become an unignorable part of national security strategy.As the bridge and link of international communication,foreign language talents’language skills and the level of national security awareness directly affect our country’s international image and the effect of international communication.Therefore,the establishment of a foreign language talent cultivation mode based on the concept of language security is not only an important way to improve the quality of foreign language education but also a realistic need to safeguard national security and promote international exchanges.Starting from the influence of the language security concept on foreign language talent cultivation,this paper analyzes the foreign language talent cultivation mode based on the language security concept,with a view to providing new ideas and methods for the development of foreign language education.展开更多
Social security of migrant workers has been significant in dissolving social contradictions and achieving the economic and social development in China during the transitional period. The researches of domestic scholar...Social security of migrant workers has been significant in dissolving social contradictions and achieving the economic and social development in China during the transitional period. The researches of domestic scholar on social security of migrant workers can be classified into three categories. Firstly, theoretical analysis on social security of migrant workers, including researches on the appeal of social security and misunderstanding of recognition, theory-construction of rural worker social security, policy defects and equity construction in social security system of migrant workers. Secondly, real studies on social security of migrant workers, including researches on sequence of demand and influencing factors of social security of migrant workers as well as intrinsic motivation forming the perspective on social security. Lastly, road exploration of establishing social security system, including researches on the multi-level development of rural worker social security system, comparison of "Double-low method", "Guangdong Method" and "Shanghai Method" of the social security of migrant workers in Zhejiang Province and establishing multi-level social security system according to the hierarchy after the internal differentiation.展开更多
Based on the fractional order theory and sliding mode control theory,a model prediction current control(MPCC)strategy based on fractional observer is proposed for the permanent magnet synchronous motor(PMSM)driven by ...Based on the fractional order theory and sliding mode control theory,a model prediction current control(MPCC)strategy based on fractional observer is proposed for the permanent magnet synchronous motor(PMSM)driven by three-level inverter.Compared with the traditional sliding mode speed observer,the observer is very simple and eases to implement.Moreover,the observer reduces the ripple of the motor speed in high frequency range in an efficient way.To reduce the stator current ripple and improve the control performance of the torque and speed,the MPCC strategy is put forward,which can make PMSM MPCC system have better control performance,stronger robustness and good dynamic performance.The simulation results validate the feasibility and effectiveness of the proposed scheme.展开更多
In this paper, a voltage oriented control strategy for three-level PWM rectifier based on Sliding Mode Control (SMC) is introduced in order to obtain fast and accurate response of dc-bus voltage. To verify the validit...In this paper, a voltage oriented control strategy for three-level PWM rectifier based on Sliding Mode Control (SMC) is introduced in order to obtain fast and accurate response of dc-bus voltage. To verify the validity of the analysis and the feasibility of the proposed control method a set of simulation tests have been conducted using Matlab/Simulink. The simulation results show that compared to the conventional PI controller, the SMC can reduce drastically the three-level rectifier’s voltage fluctuation and improve the dynamic response of dc-bus significantly.展开更多
The solid state transformer(SST) can be viewed as an energy router in energy internet. This work presents sliding mode control(SMC) to improve dynamic state and steady state performance of a three-stage(rectifier stag...The solid state transformer(SST) can be viewed as an energy router in energy internet. This work presents sliding mode control(SMC) to improve dynamic state and steady state performance of a three-stage(rectifier stage, isolated stage and inverter stage) SST for energy internet. SMC with three-level hysteresis sliding functions is presented to control the input current of rectifier stage and output voltage of inverter stage to improve the robustness under external disturbance and parametric uncertainties and reduce the switching frequency. A modified feedback linearization technique using isolated stage simplified model is presented to achieve satisfactory regulation of output voltage of the isolated stage. The system is tested for steady state operation, reactive power control, dynamic load change and voltage sag simulations, respectively. The switching model of SST is implemented in Matlab/ Simulink to verify the SST control algorithms.展开更多
In recent years, cyber attacks have posed great challenges to the development of cyber-physical systems. It is of great significance to study secure state estimation methods to ensure the safe and stable operation of ...In recent years, cyber attacks have posed great challenges to the development of cyber-physical systems. It is of great significance to study secure state estimation methods to ensure the safe and stable operation of the system. This paper proposes a secure state estimation for multi-input and multi-output continuous-time linear cyber-physical systems with sparse actuator and sensor attacks. First, for sparse sensor attacks, we propose an adaptive switching mechanism to mitigate the impact of sparse sensor attacks by filtering out their attack modes. Second, an unknown input sliding mode observer is designed to not only observe the system states, sensor attack signals, and measurement noise present in the system but also counteract the effects of sparse actuator attacks through an unknown input matrix. Finally, for the design of an unknown input sliding mode state observer, the feasibility of the observing system is demonstrated by means of Lyapunov functions. Additionally, simulation experiments are conducted to show the effectiveness of this method.展开更多
Ecological security of tourism destination is an important factor for the sustainable development of tourism industry, and many tourism destinations are threatened by various ecological problems. A complete understand...Ecological security of tourism destination is an important factor for the sustainable development of tourism industry, and many tourism destinations are threatened by various ecological problems. A complete understanding of eco-security situation is the foundation of maintaining sustainable development for tourism destinations. However, study on tourism destination eco-security has remained in the initial stage, based on domestic and international researches, the connotations and dynamic characteristics of tourism destination eco-security were discussed. Then, evaluation method of tourism destination eco-security and standard system were proposed, also dynamic evaluation method of tourism destination eco-safety based on the situation evaluation and trend was analyzed.展开更多
Security is a serious concern, whether it may be the security of assets, data and human life. Providing humans with security and safety for their belongings and items is an important need. A smart lock door project/ w...Security is a serious concern, whether it may be the security of assets, data and human life. Providing humans with security and safety for their belongings and items is an important need. A smart lock door project/ with different types of methods for entry, like fingerprint and authentication PIN code is suggested with an unnoticeable face tracking camera capturing a photo in case of error data entry. It is to be controlled via the user’s smartphone using Blynk with the implementation of IoT. This technology is made with two microcontrollers. ESP32 is used to control the solenoid lock, fingerprint sensor and keypad. ESP32-CAM is used to capture a photo and send it to the owner’s smartphone to be viewed on Telegram application. Many conclusions are extracted from system results, as well as suggested ideas for future work.展开更多
The article describes the layered model of physical network and information security,and the establishment of the mobile Internet’s security framework based on its network architecture.The mobile Internet has three p...The article describes the layered model of physical network and information security,and the establishment of the mobile Internet’s security framework based on its network architecture.The mobile Internet has three parts,i.e.terminal,network and service system,each of which can be studied in four layers of the network and information security,namely,the equipment/environment security layer,the service and application security layer,the information security layer and the information content security layer.展开更多
The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as describ...The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.展开更多
The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as describ...The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.展开更多
This paper proposes a novel adaptive sliding mode control(SMC) method for synchronization of non-identical fractional-order(FO) chaotic and hyper-chaotic systems. Under the existence of system uncertainties and extern...This paper proposes a novel adaptive sliding mode control(SMC) method for synchronization of non-identical fractional-order(FO) chaotic and hyper-chaotic systems. Under the existence of system uncertainties and external disturbances,finite-time synchronization between two FO chaotic and hyperchaotic systems is achieved by introducing a novel adaptive sliding mode controller(ASMC). Here in this paper, a fractional sliding surface is proposed. A stability criterion for FO nonlinear dynamic systems is introduced. Sufficient conditions to guarantee stable synchronization are given in the sense of the Lyapunov stability theorem. To tackle the uncertainties and external disturbances, appropriate adaptation laws are introduced. Particle swarm optimization(PSO) is used for estimating the controller parameters. Finally, finite-time synchronization of the FO chaotic and hyper-chaotic systems is applied to secure communication.展开更多
This paper deals with the synchronization of chaotic systems with structure or parameters difference. Nonlinear differential geometry theory was applied to transform the chaotic discrepancy system into canonical form....This paper deals with the synchronization of chaotic systems with structure or parameters difference. Nonlinear differential geometry theory was applied to transform the chaotic discrepancy system into canonical form. A feedback control for synchronizing two chaotic systems is proposed based on sliding mode control design. To make this controller physically realizable, an extended state observer is used to estimate the error between the transmitter and receiver. Two illustrative examples were carried out: (1) The Chua oscillator was used to show that synchronization was achieved and the message signal was recovered in spite of parametric variations; (2) Two second-order driven oscillators were presented to show that the synchronization can be achieved and that the message can be recovered in spite of the strictly different model.展开更多
A new finite-time sliding mode control approach is presented for synchronizing two different topological structure chaotic systems. With the help of the Lyapunov method, the convergence property of the proposed contro...A new finite-time sliding mode control approach is presented for synchronizing two different topological structure chaotic systems. With the help of the Lyapunov method, the convergence property of the proposed control strategy is discussed in a rigorous manner. Furthermore, it is mathematically proved that our control strategy has a faster convergence speed than the conventional finite-time sliding mode control scheme. In addition, the proposed control strategy can ensure the finite-time synchronization between the master and the slave chaotic systems under internal uncertainties and external disturbances. Simulation results are provided to show the speediness and robustness of the proposed scheme. It is worth noticing that the proposed control scheme is applicable for secure communications.展开更多
With the low cost and low hardware complex considerations,cooperative systems are a tendency in the future communications.This work considers the secure cooperative communications systems.For a practical situation in ...With the low cost and low hardware complex considerations,cooperative systems are a tendency in the future communications.This work considers the secure cooperative communications systems.For a practical situation in the system,the scenario includes multiple source stations,multiple relay stations,multiple destination stations,and eavesdroppers.To analyze the optimal relay selection in the system,we begin with the performance analysis for a single source station and a single destination station.By applying two cooperative models,the amplify-andforward（AF） mode and decode-and-forward（DF）mode,the secrecy capacity is derived.Then,we apply the derived results to the considered environment to find the optimal relay assignment.By the way,the relay selection can be obtained by the exhaustive search algorithm.However,there are a lot of steps needed if the number of source stations is large.Hence,applying the characters of the cooperative modes in the relay selection,the pre-selection step is proposed with a mathematical derivation.It could be used for the practical situation without a long-time calculation.展开更多
基金Supported by National Natural Science Foundation of China (No.50595413)Special Fund of the National Fundamental Research of China(No.2004CB217904)+4 种基金US EPRI under Agreement EP-P29464/C9966Foundation for the Author of National Excellent Doctoral Disserta-tion (No.200439)Key Project of Ministry of Education of China(No.105047)Program for New Century Excellent Talents in University,Fok Ying Tung Education Foundation (No.104019)Innovation Fund of Tianjin Municipal (2006-09)
文摘The transient critical boundary of dynamic security region (DSR) can be approximated by a few hyper planes correlated with instability separation modes. A method to fast predict instability separation modes is proposed for DSR calculation in power injection space. The method identifies coherent generation groups by the developed K-medoids algorithm, taking a similarity matrix derived from the reachability Grammian as the index. As an experimental result, reachability Grammian matrices under local injections are approximately invariant. It indicates that the generator coherency identifications are nearly consistent for different injections. Then instability separation modes can be predicted at the normal operating point, while average initial acceleration is considered as the measure of the critical generator group to amend the error. Moreover, based on these predicted instability separation modes, a critical point search strategy for DSR calculation is illustrated in the reduced injection space of the critical generators. The proposed method was evaluated using New England Test System, and the computation accuracy and speed in determining the practical DSR were improved.
文摘Realized new break-through on the basis of existing security management theory, tentatively and creatively carried out ＂realizing management theory of mine security production＂ and proposed ＂bridge＂ mode of realizing green management theory. Green management theory has an integrated system structure. The green management system of mine security production includes three parts, the foundation of green system, the supervision system of green system operation and the safeguard system of green system. The key of ＂bridge＂ mode is to analyze the existing insecurity factors in the process of security production and establish corresponding regulations.
基金Heilongjiang Province Undergraduate University’s First Batch of Foreign Language Education Reform and Innovation Project:“Practical Research on Foreign Language Talent Cultivation Based on the Concept of Language Security in the Context of New Liberal Arts”(HWX2022018-B)Heilongjiang Province Higher Education Teaching Reform Project:A Mixed Training Study on the“Interdisciplinary Integration”Ability of University Foreign Language Teachers in the Context of New Liberal Arts(SJGY20220444)。
文摘Language security is an important part of national security,and in the current complex international environment,the issue of language security is becoming more and more prominent and has become an unignorable part of national security strategy.As the bridge and link of international communication,foreign language talents’language skills and the level of national security awareness directly affect our country’s international image and the effect of international communication.Therefore,the establishment of a foreign language talent cultivation mode based on the concept of language security is not only an important way to improve the quality of foreign language education but also a realistic need to safeguard national security and promote international exchanges.Starting from the influence of the language security concept on foreign language talent cultivation,this paper analyzes the foreign language talent cultivation mode based on the language security concept,with a view to providing new ideas and methods for the development of foreign language education.
文摘Social security of migrant workers has been significant in dissolving social contradictions and achieving the economic and social development in China during the transitional period. The researches of domestic scholar on social security of migrant workers can be classified into three categories. Firstly, theoretical analysis on social security of migrant workers, including researches on the appeal of social security and misunderstanding of recognition, theory-construction of rural worker social security, policy defects and equity construction in social security system of migrant workers. Secondly, real studies on social security of migrant workers, including researches on sequence of demand and influencing factors of social security of migrant workers as well as intrinsic motivation forming the perspective on social security. Lastly, road exploration of establishing social security system, including researches on the multi-level development of rural worker social security system, comparison of "Double-low method", "Guangdong Method" and "Shanghai Method" of the social security of migrant workers in Zhejiang Province and establishing multi-level social security system according to the hierarchy after the internal differentiation.
基金National Natural Science Foundation of China(No.61463025)Opening Foundation of Key Laboratory of Opto-Technology and Intelligent Control(Lanzhou Jiaotong University),Ministry of Education(No.KFKT2018-8)。
文摘Based on the fractional order theory and sliding mode control theory,a model prediction current control(MPCC)strategy based on fractional observer is proposed for the permanent magnet synchronous motor(PMSM)driven by three-level inverter.Compared with the traditional sliding mode speed observer,the observer is very simple and eases to implement.Moreover,the observer reduces the ripple of the motor speed in high frequency range in an efficient way.To reduce the stator current ripple and improve the control performance of the torque and speed,the MPCC strategy is put forward,which can make PMSM MPCC system have better control performance,stronger robustness and good dynamic performance.The simulation results validate the feasibility and effectiveness of the proposed scheme.
文摘In this paper, a voltage oriented control strategy for three-level PWM rectifier based on Sliding Mode Control (SMC) is introduced in order to obtain fast and accurate response of dc-bus voltage. To verify the validity of the analysis and the feasibility of the proposed control method a set of simulation tests have been conducted using Matlab/Simulink. The simulation results show that compared to the conventional PI controller, the SMC can reduce drastically the three-level rectifier’s voltage fluctuation and improve the dynamic response of dc-bus significantly.
基金Projects(61403404,71571187)supported by the National Natural Science Foundation of China
文摘The solid state transformer(SST) can be viewed as an energy router in energy internet. This work presents sliding mode control(SMC) to improve dynamic state and steady state performance of a three-stage(rectifier stage, isolated stage and inverter stage) SST for energy internet. SMC with three-level hysteresis sliding functions is presented to control the input current of rectifier stage and output voltage of inverter stage to improve the robustness under external disturbance and parametric uncertainties and reduce the switching frequency. A modified feedback linearization technique using isolated stage simplified model is presented to achieve satisfactory regulation of output voltage of the isolated stage. The system is tested for steady state operation, reactive power control, dynamic load change and voltage sag simulations, respectively. The switching model of SST is implemented in Matlab/ Simulink to verify the SST control algorithms.
基金supported by the National Science Foundation of China(Nos.62271293,61903238)the Natural Science Foundation of Shandong Province,China(No.ZR2021MF035)the Social Science Planning Project of Shandong Province,China(No.22CYYJ13).
文摘In recent years, cyber attacks have posed great challenges to the development of cyber-physical systems. It is of great significance to study secure state estimation methods to ensure the safe and stable operation of the system. This paper proposes a secure state estimation for multi-input and multi-output continuous-time linear cyber-physical systems with sparse actuator and sensor attacks. First, for sparse sensor attacks, we propose an adaptive switching mechanism to mitigate the impact of sparse sensor attacks by filtering out their attack modes. Second, an unknown input sliding mode observer is designed to not only observe the system states, sensor attack signals, and measurement noise present in the system but also counteract the effects of sparse actuator attacks through an unknown input matrix. Finally, for the design of an unknown input sliding mode state observer, the feasibility of the observing system is demonstrated by means of Lyapunov functions. Additionally, simulation experiments are conducted to show the effectiveness of this method.
基金Supported by Project of National Key Technology R & D (2012BAC16B04)
文摘Ecological security of tourism destination is an important factor for the sustainable development of tourism industry, and many tourism destinations are threatened by various ecological problems. A complete understanding of eco-security situation is the foundation of maintaining sustainable development for tourism destinations. However, study on tourism destination eco-security has remained in the initial stage, based on domestic and international researches, the connotations and dynamic characteristics of tourism destination eco-security were discussed. Then, evaluation method of tourism destination eco-security and standard system were proposed, also dynamic evaluation method of tourism destination eco-safety based on the situation evaluation and trend was analyzed.
文摘Security is a serious concern, whether it may be the security of assets, data and human life. Providing humans with security and safety for their belongings and items is an important need. A smart lock door project/ with different types of methods for entry, like fingerprint and authentication PIN code is suggested with an unnoticeable face tracking camera capturing a photo in case of error data entry. It is to be controlled via the user’s smartphone using Blynk with the implementation of IoT. This technology is made with two microcontrollers. ESP32 is used to control the solenoid lock, fingerprint sensor and keypad. ESP32-CAM is used to capture a photo and send it to the owner’s smartphone to be viewed on Telegram application. Many conclusions are extracted from system results, as well as suggested ideas for future work.
基金supported by the National HighTechnology Research and Development Programof China("863"Program)under Grant No.2008AA01A204
文摘The article describes the layered model of physical network and information security,and the establishment of the mobile Internet’s security framework based on its network architecture.The mobile Internet has three parts,i.e.terminal,network and service system,each of which can be studied in four layers of the network and information security,namely,the equipment/environment security layer,the service and application security layer,the information security layer and the information content security layer.
文摘The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.
文摘The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.
文摘This paper proposes a novel adaptive sliding mode control(SMC) method for synchronization of non-identical fractional-order(FO) chaotic and hyper-chaotic systems. Under the existence of system uncertainties and external disturbances,finite-time synchronization between two FO chaotic and hyperchaotic systems is achieved by introducing a novel adaptive sliding mode controller(ASMC). Here in this paper, a fractional sliding surface is proposed. A stability criterion for FO nonlinear dynamic systems is introduced. Sufficient conditions to guarantee stable synchronization are given in the sense of the Lyapunov stability theorem. To tackle the uncertainties and external disturbances, appropriate adaptation laws are introduced. Particle swarm optimization(PSO) is used for estimating the controller parameters. Finally, finite-time synchronization of the FO chaotic and hyper-chaotic systems is applied to secure communication.
基金Project (No. 20040146) supported by Zhejiang Provincial Edu-cation Department Foundation, China
文摘This paper deals with the synchronization of chaotic systems with structure or parameters difference. Nonlinear differential geometry theory was applied to transform the chaotic discrepancy system into canonical form. A feedback control for synchronizing two chaotic systems is proposed based on sliding mode control design. To make this controller physically realizable, an extended state observer is used to estimate the error between the transmitter and receiver. Two illustrative examples were carried out: (1) The Chua oscillator was used to show that synchronization was achieved and the message signal was recovered in spite of parametric variations; (2) Two second-order driven oscillators were presented to show that the synchronization can be achieved and that the message can be recovered in spite of the strictly different model.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51177117 and 51307130)the Creative Research Groups Fund of the National Natural Science Foundation of China(Grant No.51221005)
文摘A new finite-time sliding mode control approach is presented for synchronizing two different topological structure chaotic systems. With the help of the Lyapunov method, the convergence property of the proposed control strategy is discussed in a rigorous manner. Furthermore, it is mathematically proved that our control strategy has a faster convergence speed than the conventional finite-time sliding mode control scheme. In addition, the proposed control strategy can ensure the finite-time synchronization between the master and the slave chaotic systems under internal uncertainties and external disturbances. Simulation results are provided to show the speediness and robustness of the proposed scheme. It is worth noticing that the proposed control scheme is applicable for secure communications.
文摘With the low cost and low hardware complex considerations,cooperative systems are a tendency in the future communications.This work considers the secure cooperative communications systems.For a practical situation in the system,the scenario includes multiple source stations,multiple relay stations,multiple destination stations,and eavesdroppers.To analyze the optimal relay selection in the system,we begin with the performance analysis for a single source station and a single destination station.By applying two cooperative models,the amplify-andforward（AF） mode and decode-and-forward（DF）mode,the secrecy capacity is derived.Then,we apply the derived results to the considered environment to find the optimal relay assignment.By the way,the relay selection can be obtained by the exhaustive search algorithm.However,there are a lot of steps needed if the number of source stations is large.Hence,applying the characters of the cooperative modes in the relay selection,the pre-selection step is proposed with a mathematical derivation.It could be used for the practical situation without a long-time calculation.
