The LTE and LTE-Advanced systems are supposed to be the most popular cellular network in 4Gnetworks. Relay technology is one of the most preferred technologies proposed in LTE-Advanced standardization to improve the c...The LTE and LTE-Advanced systems are supposed to be the most popular cellular network in 4Gnetworks. Relay technology is one of the most preferred technologies proposed in LTE-Advanced standardization to improve the capacity and coverage. This paper analyses the handover outage probability through relay deployment, and proposes some proofs and suggestions for relay deployment to minimize the handover outage probability in high speed scenarios.展开更多
In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue ...In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue life are deduced. And then, the fatigue damage probability densities of the Miner and Chaboche-Zhao models are deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of the two models can be obtained, considering different stress ratios. Finally, substituting load cycles into them, the change law of cement concrete fatigue reliability about load cycles can be acquired. The results show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines from almost 100% to 0% gradually. No matter under what stress ratio, during the initial stage of the load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the stable phase gradually shortens and the load cycle corresponding to the reliability of 0% also decreases. In the descent phase of reliability, the higher the stress ratio is, the lower the concrete reliability is for the same load cycle. Besides, compared with the Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.展开更多
In this paper,the problem of online distributed optimization subject to a convex set is studied via a network of agents.Each agent only has access to a noisy gradient of its own objective function,and can communicate ...In this paper,the problem of online distributed optimization subject to a convex set is studied via a network of agents.Each agent only has access to a noisy gradient of its own objective function,and can communicate with its neighbors via a network.To handle this problem,an online distributed stochastic mirror descent algorithm is proposed.Existing works on online distributed algorithms involving stochastic gradients only provide the expectation bounds of the regrets.Different from them,we study the high probability bound of the regrets,i.e.,the sublinear bound of the regret is characterized by the natural logarithm of the failure probability's inverse.Under mild assumptions on the graph connectivity,we prove that the dynamic regret grows sublinearly with a high probability if the deviation in the minimizer sequence is sublinear with the square root of the time horizon.Finally,a simulation is provided to demonstrate the effectiveness of our theoretical results.展开更多
随着大量新能源场站接入交直流混联电网,系统的静态电压稳定裕度(static voltage stability margin,SVSM)水平具有很大的不确定性,需要研究考虑新能源场站高阶不确定性的交直流混联电网SVSM计算方法。针对此问题,首先建立了交直流混联电...随着大量新能源场站接入交直流混联电网,系统的静态电压稳定裕度(static voltage stability margin,SVSM)水平具有很大的不确定性,需要研究考虑新能源场站高阶不确定性的交直流混联电网SVSM计算方法。针对此问题,首先建立了交直流混联电网SVSM计算模型,模型中考虑了直流换流站控制方式随负荷增长的切换;采用概率盒模型描述风速与光照强度的随机波动,提出了改进区间半不变量法以获得更准确的SVSM概率盒,该方法通过K-means++聚类算法将随机变量样本划分为多个波动范围较小的样本集,以降低半不变量的线性化计算带来的误差;并结合Gram-Charlier级数展开和概率加权和计算得到考虑新能源场站高阶不确定性的系统SVSM概率盒。通过对修改的IEEE-39节点交直流系统和南方电网两个算例的分析,并与区间半不变量法和双层蒙特卡洛法比较,验证了所提出方法获得的SVSM概率盒具有较高的计算精度和效率。展开更多
随着“双碳”目标的提出,我国的新能源建设正处于新一轮的发展阶段,但是高渗透率新能源的随机性、波动性也给电力系统静态电压稳定性分析带来了挑战。与此同时,电力电子技术的发展使得柔性交流输电系统(flexible AC transmission system...随着“双碳”目标的提出,我国的新能源建设正处于新一轮的发展阶段,但是高渗透率新能源的随机性、波动性也给电力系统静态电压稳定性分析带来了挑战。与此同时,电力电子技术的发展使得柔性交流输电系统(flexible AC transmission system,FACTS)在调节线路潮流、改善电力系统静态电压稳定性方面得到广泛应用。提出了一种考虑新能源不确定性的含分布式静止同步串联补偿器(distributed static series compensator,DSSC)的电力系统静态电压稳定性概率评估方法。首先分析了新能源并网系统的静态电压稳定机理。然后阐述了DSSC的工作原理,建立了DSSC的等效功率注入模型,并基于此模型推导出含DSSC的潮流方程。其次基于潮流计算方程提出了一种能映射新能源不确定性的静态电压稳定性指标,并采用蒙特卡洛模拟法实现了系统静态电压稳定性指标概率评估。最后通过算例分析验证了高渗透率新能源的不确定性导致系统静态电压稳定指标分布范围变大,系统失稳概率增加,合理配置DSSC能够有效提升电力系统静态电压稳定性,所提方法能够准确反映新能源不确定性对电网稳定性的影响,具有一定的工程应用价值。展开更多
文摘The LTE and LTE-Advanced systems are supposed to be the most popular cellular network in 4Gnetworks. Relay technology is one of the most preferred technologies proposed in LTE-Advanced standardization to improve the capacity and coverage. This paper analyses the handover outage probability through relay deployment, and proposes some proofs and suggestions for relay deployment to minimize the handover outage probability in high speed scenarios.
基金The National Natural Science Foundation of China(No. 51008071 )the Natural Science Foundation of Jiangsu Province(No. BK2010413)
文摘In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue life are deduced. And then, the fatigue damage probability densities of the Miner and Chaboche-Zhao models are deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of the two models can be obtained, considering different stress ratios. Finally, substituting load cycles into them, the change law of cement concrete fatigue reliability about load cycles can be acquired. The results show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines from almost 100% to 0% gradually. No matter under what stress ratio, during the initial stage of the load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the stable phase gradually shortens and the load cycle corresponding to the reliability of 0% also decreases. In the descent phase of reliability, the higher the stress ratio is, the lower the concrete reliability is for the same load cycle. Besides, compared with the Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.
文摘In this paper,the problem of online distributed optimization subject to a convex set is studied via a network of agents.Each agent only has access to a noisy gradient of its own objective function,and can communicate with its neighbors via a network.To handle this problem,an online distributed stochastic mirror descent algorithm is proposed.Existing works on online distributed algorithms involving stochastic gradients only provide the expectation bounds of the regrets.Different from them,we study the high probability bound of the regrets,i.e.,the sublinear bound of the regret is characterized by the natural logarithm of the failure probability's inverse.Under mild assumptions on the graph connectivity,we prove that the dynamic regret grows sublinearly with a high probability if the deviation in the minimizer sequence is sublinear with the square root of the time horizon.Finally,a simulation is provided to demonstrate the effectiveness of our theoretical results.
文摘随着大量新能源场站接入交直流混联电网,系统的静态电压稳定裕度(static voltage stability margin,SVSM)水平具有很大的不确定性,需要研究考虑新能源场站高阶不确定性的交直流混联电网SVSM计算方法。针对此问题,首先建立了交直流混联电网SVSM计算模型,模型中考虑了直流换流站控制方式随负荷增长的切换;采用概率盒模型描述风速与光照强度的随机波动,提出了改进区间半不变量法以获得更准确的SVSM概率盒,该方法通过K-means++聚类算法将随机变量样本划分为多个波动范围较小的样本集,以降低半不变量的线性化计算带来的误差;并结合Gram-Charlier级数展开和概率加权和计算得到考虑新能源场站高阶不确定性的系统SVSM概率盒。通过对修改的IEEE-39节点交直流系统和南方电网两个算例的分析,并与区间半不变量法和双层蒙特卡洛法比较,验证了所提出方法获得的SVSM概率盒具有较高的计算精度和效率。
文摘随着“双碳”目标的提出,我国的新能源建设正处于新一轮的发展阶段,但是高渗透率新能源的随机性、波动性也给电力系统静态电压稳定性分析带来了挑战。与此同时,电力电子技术的发展使得柔性交流输电系统(flexible AC transmission system,FACTS)在调节线路潮流、改善电力系统静态电压稳定性方面得到广泛应用。提出了一种考虑新能源不确定性的含分布式静止同步串联补偿器(distributed static series compensator,DSSC)的电力系统静态电压稳定性概率评估方法。首先分析了新能源并网系统的静态电压稳定机理。然后阐述了DSSC的工作原理,建立了DSSC的等效功率注入模型,并基于此模型推导出含DSSC的潮流方程。其次基于潮流计算方程提出了一种能映射新能源不确定性的静态电压稳定性指标,并采用蒙特卡洛模拟法实现了系统静态电压稳定性指标概率评估。最后通过算例分析验证了高渗透率新能源的不确定性导致系统静态电压稳定指标分布范围变大,系统失稳概率增加,合理配置DSSC能够有效提升电力系统静态电压稳定性,所提方法能够准确反映新能源不确定性对电网稳定性的影响,具有一定的工程应用价值。
