In this paper, we propose a new modulation classification method based on the combination of clustering and neural network, in which a new algorithm is introduced to extract key features. In order to recognize modulat...In this paper, we propose a new modulation classification method based on the combination of clustering and neural network, in which a new algorithm is introduced to extract key features. In order to recognize modulation types based on the constellation diagram such as phase shift keying （PSK） and quadrature amplitude modulation （QAM）, fuzzy C-means （FCM） clustering is adopted for recovering the constellation under different number of clusters. Then cluster validity measure is applied to extract key features which discriminate between different modulation types. The features are sent to neural network so that modulation types can be recognized. In order to conquer the disadvantages of standard back propagation （BP） neural network, conjugate gradient learning algorithm of Polak-Ribiere update is employed to improve the speed of convergence and the performance of modulation recognition. Simulation results show that classification rates of the algorithm proposed in this paper are much higher than those of clustering algorithm.展开更多
Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognitio...Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognition method is proposed in this paper. Because of the better noise suppression ability of the GAR model and the powerful pattern classification capacity of the MLP neural network classifier, the new method can significantly improve the recognition performance in lower SNR with better robustness. To assess the performance of the new method, computer simulations are also performed.展开更多
Objectives The purpose of this study is to examine the effects of applying anodal tDCS(2 mA for 20 min)over the scalp from T3(anodal-tDCS)to Fp2(cathodal-tDCS)on the perceptual,physiological and performance responses ...Objectives The purpose of this study is to examine the effects of applying anodal tDCS(2 mA for 20 min)over the scalp from T3(anodal-tDCS)to Fp2(cathodal-tDCS)on the perceptual,physiological and performance responses during maximal incremental and constant-load exercise(CLE)in trained cyclists.Methods Eleven male cyclists performed maximal incremental exercise(MIE)on a cycle ergometer under either tDCS or sham,with power output,heart rate(HR),oxygen uptake(V̇O_(2)),ratings of perceived exertion(RPE)assessed throughout,and blood samples collected before and after MIE.On two separate occasions,nine subjects performed CLE at 62%of the peak power output followed by a 15 km time trial under either tDCS or sham(n=8 for the time trial).Results HR,V̇O_(2),RPE and blood samples were collected at regular intervals.There were no differences between tDCS and sham in any variable during the MIE.tDCS elicited a decreased HR(F_(4,8)=9.232;p=0.016;η_(p)^(2)=0.54),increased V̇O_(2)(F_(4,8)=8.920;p=0.015;η_(p)^(2)=0.50)and increased blood non-esterified fatty acids(F_(6,8)=11.754;p=0.009;η_(p)^(2)=0.60)and glycerol(F_(6,8)=6.603;p=0.037;η_(p)^(2)=0.49)concentrations during the CLE when compared to sham.tDCS also improved 15 km time trial performance by 3.6%(p=0.02;d=0.47)without affecting RPE,HR and blood lactate.Conclusions The application of tDCS over the temporal cortex in trained cyclists improved cycling performance during a self-paced time trial but did not enhance performance during maximal incremental exercise.These results are encouraging and merit further investigation of the ergogenic effects of tDCS in trained athletes.展开更多
前列腺素E2(prostaglandin E2,PGE2)作为体内一种重要的生物活性物质,通过作用于前列腺素E受体(prostaglandin E receptor,EP),参与内环境稳态的维持。PGE2在骨代谢调控中发挥重要作用,在骨重建的过程中,调控成骨细胞介导的骨形成与破...前列腺素E2(prostaglandin E2,PGE2)作为体内一种重要的生物活性物质,通过作用于前列腺素E受体(prostaglandin E receptor,EP),参与内环境稳态的维持。PGE2在骨代谢调控中发挥重要作用,在骨重建的过程中,调控成骨细胞介导的骨形成与破骨细胞介导的骨吸收,维持动态平衡。在骨形成方面,PGE2/EP轴通过神经调控、机械负荷调控、与体内其他细胞分子间的交互作用,促进成骨细胞增殖分化,维持骨稳态。因此,PGE2在以骨量异常为特征的疾病中发挥关键作用,可能是潜在的治疗靶点。本文对近年来PGE2在骨形成中的调控机制进行综述,并总结现有的临床应用。展开更多
基金supported by the National Basic Research Program of China (2007CB310607)the National Natural Science Foundation of China (60772062)the National Science and Technology Key Project (2011ZX03001-006-02,2011ZX03005-004-03)
文摘In this paper, we propose a new modulation classification method based on the combination of clustering and neural network, in which a new algorithm is introduced to extract key features. In order to recognize modulation types based on the constellation diagram such as phase shift keying （PSK） and quadrature amplitude modulation （QAM）, fuzzy C-means （FCM） clustering is adopted for recovering the constellation under different number of clusters. Then cluster validity measure is applied to extract key features which discriminate between different modulation types. The features are sent to neural network so that modulation types can be recognized. In order to conquer the disadvantages of standard back propagation （BP） neural network, conjugate gradient learning algorithm of Polak-Ribiere update is employed to improve the speed of convergence and the performance of modulation recognition. Simulation results show that classification rates of the algorithm proposed in this paper are much higher than those of clustering algorithm.
文摘Based on the features extracted from generalized autoregressive (GAR) model parameters of the received waveform, and the use of multilayer perceptron(MLP) neural network classifier, a new digital modulation recognition method is proposed in this paper. Because of the better noise suppression ability of the GAR model and the powerful pattern classification capacity of the MLP neural network classifier, the new method can significantly improve the recognition performance in lower SNR with better robustness. To assess the performance of the new method, computer simulations are also performed.
文摘帕金森病(Parkinson disease,PD)是一种病因尚未完全明确的神经退行性疾病,其发生和进展与异常的神经振荡紧密相关,这些异常振荡已作为评价PD的生物标志物之一。积极探索神经振荡与PD的相互联系,并有针对性地精准调控PD患者异常的神经振荡是目前研究的热点,为寻找治疗PD提供了新方向。经颅交流电刺激(transcranial alternating current stimulation,tACS)作为一种新兴的非侵入性脑刺激技术,通过施加双相和正弦电流来影响大脑的神经元活动,显示出调控PD异常神经振荡的潜力。现对PD中常见的神经振荡、tACS调控PD神经振荡的工作机制以及tACS在PD中的应用研究进展进行综述,并探讨该领域的现存问题和未来发展趋势,旨在为PD的治疗和临床研究提供新思路。
文摘Objectives The purpose of this study is to examine the effects of applying anodal tDCS(2 mA for 20 min)over the scalp from T3(anodal-tDCS)to Fp2(cathodal-tDCS)on the perceptual,physiological and performance responses during maximal incremental and constant-load exercise(CLE)in trained cyclists.Methods Eleven male cyclists performed maximal incremental exercise(MIE)on a cycle ergometer under either tDCS or sham,with power output,heart rate(HR),oxygen uptake(V̇O_(2)),ratings of perceived exertion(RPE)assessed throughout,and blood samples collected before and after MIE.On two separate occasions,nine subjects performed CLE at 62%of the peak power output followed by a 15 km time trial under either tDCS or sham(n=8 for the time trial).Results HR,V̇O_(2),RPE and blood samples were collected at regular intervals.There were no differences between tDCS and sham in any variable during the MIE.tDCS elicited a decreased HR(F_(4,8)=9.232;p=0.016;η_(p)^(2)=0.54),increased V̇O_(2)(F_(4,8)=8.920;p=0.015;η_(p)^(2)=0.50)and increased blood non-esterified fatty acids(F_(6,8)=11.754;p=0.009;η_(p)^(2)=0.60)and glycerol(F_(6,8)=6.603;p=0.037;η_(p)^(2)=0.49)concentrations during the CLE when compared to sham.tDCS also improved 15 km time trial performance by 3.6%(p=0.02;d=0.47)without affecting RPE,HR and blood lactate.Conclusions The application of tDCS over the temporal cortex in trained cyclists improved cycling performance during a self-paced time trial but did not enhance performance during maximal incremental exercise.These results are encouraging and merit further investigation of the ergogenic effects of tDCS in trained athletes.
文摘前列腺素E2(prostaglandin E2,PGE2)作为体内一种重要的生物活性物质,通过作用于前列腺素E受体(prostaglandin E receptor,EP),参与内环境稳态的维持。PGE2在骨代谢调控中发挥重要作用,在骨重建的过程中,调控成骨细胞介导的骨形成与破骨细胞介导的骨吸收,维持动态平衡。在骨形成方面,PGE2/EP轴通过神经调控、机械负荷调控、与体内其他细胞分子间的交互作用,促进成骨细胞增殖分化,维持骨稳态。因此,PGE2在以骨量异常为特征的疾病中发挥关键作用,可能是潜在的治疗靶点。本文对近年来PGE2在骨形成中的调控机制进行综述,并总结现有的临床应用。
