Excessive vibration and noise radiation of the track structure can be caused by the operation of high speed trains.Though the track structure is characterized by obvious periodic properties and band gaps,the bandwidth...Excessive vibration and noise radiation of the track structure can be caused by the operation of high speed trains.Though the track structure is characterized by obvious periodic properties and band gaps,the bandwidth is narrow and the elastic wave attenuation capability within the band gap is weak.In order to effectively control the vibration and noise of track structure,the local resonance mechanism is introduced to broaden the band gap and realize wave propagation control.The locally resonant units are attached periodically on the rail,forming a new locally resonant phononic crystal structure.Then the tuning of the elastic wave band gaps of track structure is discussed,and the formation mechanism of the band gap is explicated.The research results show that a new wide and adjustable locally resonant band gap is formed after the resonant units are introduced.The phenomenon of coupling and transition can be observed between the new locally resonant band gap and the original band gap of the periodic track structure with the band gap width reaching the maximum at the coupling position.The broader band gap can be applied for vibration and noise reduction in high speed railway track structure.展开更多
基于算法学习数据内部规律,进而对同类数据进行预测和判断的过程为机器学习。在体外受精-胚胎移植技术领域,基于机器学习算法建立的模型不仅可预测周期助孕结局,也可帮助胚胎学家挑选优质胚胎。本文共筛选出基于机器学习算法的周期结局...基于算法学习数据内部规律,进而对同类数据进行预测和判断的过程为机器学习。在体外受精-胚胎移植技术领域,基于机器学习算法建立的模型不仅可预测周期助孕结局,也可帮助胚胎学家挑选优质胚胎。本文共筛选出基于机器学习算法的周期结局预测模型和胚胎质量评估模型30个,其中基于传统机器学习算法模型28个,基于深度学习模型2个。采用受试者工作特征曲线的曲线下面积(area under curve,AUC)评价模型效果,基于传统机器学习算法的模型效果多不理想(0.60<AUC<0.86),深度学习算法准确率则较高(AUC>0.90)。完善的预测和评估模型有望提高助孕周期效率、标准化胚胎选择流程。展开更多
The multi-source and single-sink(MSSS) topology in wireless sensor networks(WSNs) is defined as a network topology,where all of nodes can gather,receive and transmit data to the sink.In energy-constrained WSNs with su...The multi-source and single-sink(MSSS) topology in wireless sensor networks(WSNs) is defined as a network topology,where all of nodes can gather,receive and transmit data to the sink.In energy-constrained WSNs with such a topology,the joint optimal design in the physical,medium access control(MAC) and network layers is considered for network lifetime maximization(NLM).The problem of integrating multi-layer information to compute NLM,which involves routing flow,link schedule and transmission power,is formulated as a nonlinear optimization problem.Specially under time division multiple access(TDMA) scheme,this problem can be transformed into a convex optimization problem.To solve it analytically we make use of the property that local optimization is global optimization in convex problem.This allows us to exploit the Karush-Kuhn-Tucker (KKT) optimality conditions to solve it and obtain analytical solution expression,i.e.,the globally optimal network lifetime(NL).NL is derived as a function of number of nodes,their initial energy and data rate arrived at them. Based on the analysis of analytical approach,it takes the influence of data rates,link access and routing method over NLM into account.Moreover,the globally optimal transmission schemes are achieved by solution set during analytical approach and applied to algorithms in TDMA-based WSNs aiming at NLM on OMNeT++ to compare with other suboptimal schemes.展开更多
基金Project(2016YFE0205200)supported by the National Key Research and Development Program of ChinaProjects(51425804,51508479)supported by the National Natural Science Foundation of China+1 种基金Project(2016310019)supported by the Doctorial Innovation Fund of Southwest Jiaotong University,ChinaProject(2017GZ0373)supported by the Research Fund for Key Research and Development Projects in Sichuan Province,China
文摘Excessive vibration and noise radiation of the track structure can be caused by the operation of high speed trains.Though the track structure is characterized by obvious periodic properties and band gaps,the bandwidth is narrow and the elastic wave attenuation capability within the band gap is weak.In order to effectively control the vibration and noise of track structure,the local resonance mechanism is introduced to broaden the band gap and realize wave propagation control.The locally resonant units are attached periodically on the rail,forming a new locally resonant phononic crystal structure.Then the tuning of the elastic wave band gaps of track structure is discussed,and the formation mechanism of the band gap is explicated.The research results show that a new wide and adjustable locally resonant band gap is formed after the resonant units are introduced.The phenomenon of coupling and transition can be observed between the new locally resonant band gap and the original band gap of the periodic track structure with the band gap width reaching the maximum at the coupling position.The broader band gap can be applied for vibration and noise reduction in high speed railway track structure.
文摘基于算法学习数据内部规律,进而对同类数据进行预测和判断的过程为机器学习。在体外受精-胚胎移植技术领域,基于机器学习算法建立的模型不仅可预测周期助孕结局,也可帮助胚胎学家挑选优质胚胎。本文共筛选出基于机器学习算法的周期结局预测模型和胚胎质量评估模型30个,其中基于传统机器学习算法模型28个,基于深度学习模型2个。采用受试者工作特征曲线的曲线下面积(area under curve,AUC)评价模型效果,基于传统机器学习算法的模型效果多不理想(0.60<AUC<0.86),深度学习算法准确率则较高(AUC>0.90)。完善的预测和评估模型有望提高助孕周期效率、标准化胚胎选择流程。
文摘The multi-source and single-sink(MSSS) topology in wireless sensor networks(WSNs) is defined as a network topology,where all of nodes can gather,receive and transmit data to the sink.In energy-constrained WSNs with such a topology,the joint optimal design in the physical,medium access control(MAC) and network layers is considered for network lifetime maximization(NLM).The problem of integrating multi-layer information to compute NLM,which involves routing flow,link schedule and transmission power,is formulated as a nonlinear optimization problem.Specially under time division multiple access(TDMA) scheme,this problem can be transformed into a convex optimization problem.To solve it analytically we make use of the property that local optimization is global optimization in convex problem.This allows us to exploit the Karush-Kuhn-Tucker (KKT) optimality conditions to solve it and obtain analytical solution expression,i.e.,the globally optimal network lifetime(NL).NL is derived as a function of number of nodes,their initial energy and data rate arrived at them. Based on the analysis of analytical approach,it takes the influence of data rates,link access and routing method over NLM into account.Moreover,the globally optimal transmission schemes are achieved by solution set during analytical approach and applied to algorithms in TDMA-based WSNs aiming at NLM on OMNeT++ to compare with other suboptimal schemes.
