By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the earl...By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process.With the curves of the T_(2)signals and hydration time obtained,the hydration process could be divided into four typical periods using the null points of the second derivative curve,and the influences of water-cement ratio(w/c)and hydration heat regulating materials(HHRM)on hydration process were analyzed.The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c.Compared to pure cement paste,the addition of HHRM extended all four periods,and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period.Finally,according to the LFNMR test results,the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.展开更多
Wireless power transfer (WPT) from a transmitter resonator on the ground to an electrically powered miniature heli-copter was attempted to demonstrate WPT using magnetic resonance coupling to an object moving in 3D sp...Wireless power transfer (WPT) from a transmitter resonator on the ground to an electrically powered miniature heli-copter was attempted to demonstrate WPT using magnetic resonance coupling to an object moving in 3D space. The transmission efficiency was optimized by automatic impedance matching for different flight attitudes: a maximum flight altitude of 590 mm was achieved. Furthermore, an estimation method of transmission efficiency using only the properties on the transmitter side was proposed, with transmission power regulated as constant against the change in the coupling coefficient.展开更多
We investigate two different kinds of resonant current regulators for a doubly fed induction generator(DFIG) under distorted grid voltage conditions: proportional integral resonant(PIR) regulator with traditional reso...We investigate two different kinds of resonant current regulators for a doubly fed induction generator(DFIG) under distorted grid voltage conditions: proportional integral resonant(PIR) regulator with traditional resonant part and vector proportional integral(VPI) regulator with VPI resonant part. Based on the mathematical model of DFIG under distorted grid voltage, the transfer function and frequency response characteristics of the two current regulators are analyzed and compared. The superiority of the VPI current regulator over the PIR regulator is pointed out, and the influence of discretization methods on the performance of the resonant current regulator is studied. All the results are validated by MATLAB simulation and experiments.展开更多
Functional MRI was used to map the brains of subjects on-line during the process of media training for the acquisition and improvement of self-regulation mechanisms. The temporal and spatial dynamics of the new neural...Functional MRI was used to map the brains of subjects on-line during the process of media training for the acquisition and improvement of self-regulation mechanisms. The temporal and spatial dynamics of the new neural network formation were studied in real and simulated (false) biofeedback game, and their qualitative characteristics were discussed. It has been shown that immersion into a virtual competitive game, controlled by physiological responses, causes a wide involvement of the cortices, characterized by a high volume of activation in the mid-temporal, occipital and frontal areas, the cuneus and the precuneus. In both forms of media training, high values of activation volume were identified in the cerebellar structures.展开更多
目的探索Jurkat T细胞中胞外调节蛋白激酶(extracellular regulated protein kinases,ERK)活性动力学以及基质刚度对ERK活性的影响。方法利用荧光共振能量转移(fluorescence resonance energy transfer,FRET)技术实时观测Jurkat细胞中ER...目的探索Jurkat T细胞中胞外调节蛋白激酶(extracellular regulated protein kinases,ERK)活性动力学以及基质刚度对ERK活性的影响。方法利用荧光共振能量转移(fluorescence resonance energy transfer,FRET)技术实时观测Jurkat细胞中ERK活性的变化,或细胞处于I型胶原基质胶中检测其影响。结果部分Jurkat细胞中存在ERK活性脉冲现象,频率约为3次/h,FRET振幅变化约为20%。在抗体激活T细胞抗原受体(T-cell receptor,TCR)的条件下,ERK脉冲依然存在,频率和振幅无显著变化。当细胞处于I型胶原水凝胶中,随着胶基质刚度增加,脉冲频率有所下调。结论Jurkat T细胞中存在自发的ERK活性脉冲现象,初步实验显示其频率受基质刚度影响。而该信号波动的生理意义和分子机制仍有待探索。展开更多
海马在情绪调节过程中发挥关键作用,针对海马的实时功能磁共振成像(real-time functional Magnetic Resonance Imaging,rtfMRI)神经反馈训练能够有效增强健康人的情绪、记忆功能。脑网络是空间位置不同的脑区通过功能联系整合形成的网...海马在情绪调节过程中发挥关键作用,针对海马的实时功能磁共振成像(real-time functional Magnetic Resonance Imaging,rtfMRI)神经反馈训练能够有效增强健康人的情绪、记忆功能。脑网络是空间位置不同的脑区通过功能联系整合形成的网络模式,情绪调节涉及多个脑网络之间信息的协同交互,脑网络间连接特性的变化能够反映大脑情绪功能的改变。针对海马体的神经反馈情绪调节训练,从静息态脑网络的动态特性出发,提取被试与情绪调节相关的默认模式网络(Default Mode Network,DMN)、执行控制网络(Executive Control Network,ECN)和突显网络(Salience Network,SN)等高级认知网络,并分析这些高级认知网络的功能连接特征在神经反馈训练前后的差异。结果表明通过神经反馈训练,健康被试前突显网络与背侧默认模式网络、左侧执行控制网络之间的功能连接显著增强,而左侧执行控制网络与楔前叶网络之间的功能连接显著下降。结果验证了针对海马体的rtfMRI神经反馈情绪调节训练的有效性,并且情绪调节相关的脑网络间功能连接的变化与临床精神病学研究结果一致,或可作为评估神经反馈训练效果的影像学标记。展开更多
基金Funded by National Natural Science Foundation of China(Nos.U1965105,51878245)National Key R&D Program of China(No.2021YFF0500802)。
文摘By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process.With the curves of the T_(2)signals and hydration time obtained,the hydration process could be divided into four typical periods using the null points of the second derivative curve,and the influences of water-cement ratio(w/c)and hydration heat regulating materials(HHRM)on hydration process were analyzed.The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c.Compared to pure cement paste,the addition of HHRM extended all four periods,and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period.Finally,according to the LFNMR test results,the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.
文摘Wireless power transfer (WPT) from a transmitter resonator on the ground to an electrically powered miniature heli-copter was attempted to demonstrate WPT using magnetic resonance coupling to an object moving in 3D space. The transmission efficiency was optimized by automatic impedance matching for different flight attitudes: a maximum flight altitude of 590 mm was achieved. Furthermore, an estimation method of transmission efficiency using only the properties on the transmitter side was proposed, with transmission power regulated as constant against the change in the coupling coefficient.
基金Project supported by the National High-Tech R&D Program(863)of China(No.2011AA050204)the National Natural Science Foundation of China(No.51277159)
文摘We investigate two different kinds of resonant current regulators for a doubly fed induction generator(DFIG) under distorted grid voltage conditions: proportional integral resonant(PIR) regulator with traditional resonant part and vector proportional integral(VPI) regulator with VPI resonant part. Based on the mathematical model of DFIG under distorted grid voltage, the transfer function and frequency response characteristics of the two current regulators are analyzed and compared. The superiority of the VPI current regulator over the PIR regulator is pointed out, and the influence of discretization methods on the performance of the resonant current regulator is studied. All the results are validated by MATLAB simulation and experiments.
文摘Functional MRI was used to map the brains of subjects on-line during the process of media training for the acquisition and improvement of self-regulation mechanisms. The temporal and spatial dynamics of the new neural network formation were studied in real and simulated (false) biofeedback game, and their qualitative characteristics were discussed. It has been shown that immersion into a virtual competitive game, controlled by physiological responses, causes a wide involvement of the cortices, characterized by a high volume of activation in the mid-temporal, occipital and frontal areas, the cuneus and the precuneus. In both forms of media training, high values of activation volume were identified in the cerebellar structures.
文摘目的探索Jurkat T细胞中胞外调节蛋白激酶(extracellular regulated protein kinases,ERK)活性动力学以及基质刚度对ERK活性的影响。方法利用荧光共振能量转移(fluorescence resonance energy transfer,FRET)技术实时观测Jurkat细胞中ERK活性的变化,或细胞处于I型胶原基质胶中检测其影响。结果部分Jurkat细胞中存在ERK活性脉冲现象,频率约为3次/h,FRET振幅变化约为20%。在抗体激活T细胞抗原受体(T-cell receptor,TCR)的条件下,ERK脉冲依然存在,频率和振幅无显著变化。当细胞处于I型胶原水凝胶中,随着胶基质刚度增加,脉冲频率有所下调。结论Jurkat T细胞中存在自发的ERK活性脉冲现象,初步实验显示其频率受基质刚度影响。而该信号波动的生理意义和分子机制仍有待探索。
文摘海马在情绪调节过程中发挥关键作用,针对海马的实时功能磁共振成像(real-time functional Magnetic Resonance Imaging,rtfMRI)神经反馈训练能够有效增强健康人的情绪、记忆功能。脑网络是空间位置不同的脑区通过功能联系整合形成的网络模式,情绪调节涉及多个脑网络之间信息的协同交互,脑网络间连接特性的变化能够反映大脑情绪功能的改变。针对海马体的神经反馈情绪调节训练,从静息态脑网络的动态特性出发,提取被试与情绪调节相关的默认模式网络(Default Mode Network,DMN)、执行控制网络(Executive Control Network,ECN)和突显网络(Salience Network,SN)等高级认知网络,并分析这些高级认知网络的功能连接特征在神经反馈训练前后的差异。结果表明通过神经反馈训练,健康被试前突显网络与背侧默认模式网络、左侧执行控制网络之间的功能连接显著增强,而左侧执行控制网络与楔前叶网络之间的功能连接显著下降。结果验证了针对海马体的rtfMRI神经反馈情绪调节训练的有效性,并且情绪调节相关的脑网络间功能连接的变化与临床精神病学研究结果一致,或可作为评估神经反馈训练效果的影像学标记。
