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991.
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Guo Pengju Chen XuedongGuan Weihe Cheng HuayunJiang Heng 《Journal of magnetism and magnetic materials》2011,323(20):2474-2477
The surface magnetic field intensity Hp(y) of low-carbon steel plate specimen was measured after tensile test and unloading; variation of Hp(y) was studied. It was found that Hp(y) signals first decreased with increase in stress, and then reversed to the initial field when the stress was greater than 160 MPa. Under yield stress, Hp(y) reached its maximum, and then decreased slightly with further increase in stress. The initial magnetic signals have great impact on the variation of magnetic field. 相似文献
994.
Functional magnetic resonance imaging (fMRI) research has revealed not only important aspects of the neural basis of cognitive and perceptual functions, but also important information on the relation between high-level brain functions and physiology. One of the central outstanding questions, given the features of the blood oxygenation level-dependent (BOLD) signal, is whether and how autonomic nervous system (ANS) functions are related to changes in brain states as measured in the human brain. A straightforward way to address this question has been to acquire external measurements of ANS activity such as cardiac and respiratory data, and examine their relation to the BOLD signal. In this article, we describe two conceptual approaches to the treatment of ANS measures in the context of BOLD fMRI analysis. On the one hand, several research lines have treated ANS activity measures as noise, considering them as nothing but a confounding factor that reduces the power of fMRI analysis or its validity. Work in this line has developed powerful methods to remove ANS effects from the BOLD signal. On the other hand, a different line of work has made important progress in showing that ANS functions such as cardiac pulsation, heart rate variability and breathing rate could be considered as a theoretically meaningful component of the signal that is useful for understanding brain function. Work within this latter framework suggests that caution should be exercised when employing procedures to remove correlations between BOLD data and physiological measures. We discuss these two positions and the reasoning underlying them. Thereafter, we draw on the reviewed literature in presenting practical guidelines for treatment of ANS data, which are based on the premise that ANS data should be considered as theoretically meaningful information. This holds particularly when studying cortical systems involved in regulation, monitoring and/or generation of ANS activity, such as those involved in decision making, conflict resolution and the experience of emotion. 相似文献
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《Communications in Nonlinear Science & Numerical Simulation》2014,19(4):1088-1096
The dependence of stochastic resonance in the feed-forward-loop neuronal network motifs on the noise and time delay are studied in this paper. By computational modeling, Izhikevich neuron model with the chemical coupling is used to build the triple-neuron feed-forward-loop motifs with all possible motif types. Numerical results show that the correlation between the periodic subthreshold signal’s frequency and the dynamical response of the network motifs is resonantly dependent on the intensity of additive spatiotemporal noise. Interestingly, the excitatory intermediate neuron could induce intermittent stochastic resonance, whereas the inhibitory one weakens its influence on the intermittent mode. More importantly, it is found that the increasing delays can induce the intermittent appearance of regions of stochastic resonance. Based on the effects of the time delay on the stochastic resonance, the reasons and conditions of such intermittent resonance phenomenon are analyzed. 相似文献
997.
线性正则变换是经典Fourier变换的广义形式,目前在非平稳信号的参数检测与估计方面取得了优异的应用效果,但线性正则变换理论体系还不完善.探讨了线性正则变换相关的复能量密度函数的基本概念,并详细推导研究了其基本的数学性质与特点,在上述理论的基础上,通过仿真实验来验证所得到结论的准确性.为其在实际应用中发挥更大的作用奠定了基础. 相似文献
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无线广播电视发射台作为国家重要的基础设施和宣传播出机构,与人民群众的政治、经济、文化、娱乐生活息息相关,是构建和谐社会的重要基石。发射台实时性能监测系统的建设是实现发射台安全播出、提高管理效率的重要环节,是确保广播电视无线覆盖效果的重要手段,是发射台技术发展和进步的必然趋势。 相似文献
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本文论述了在以便件为基础的环境下,沿时间轴对电视图像信号进行帧间变换(如压缩与还原、帧间有序排列等)及其控制方法-帧间编码技术。 相似文献