The kinetics and mechanism of methylene blue (MB) adsorption onto activated carbon fibers (ACFs) have been studied. The effects of various experimental parameters, such as the initial MB concentration and the ACF mass...The kinetics and mechanism of methylene blue (MB) adsorption onto activated carbon fibers (ACFs) have been studied. The effects of various experimental parameters, such as the initial MB concentration and the ACF mass, on the adsorption rate were investigated. Equilibrium data were fit well by a Freundlich isotherm equation. Adsorption measurements show that the process is very fast. The adsorption data were modeled using first- and second-order kinetic equations and intra–particle diffusion models. It was found that the first-order kinetic equation could best describe the adsorption kinetics. The adsorption process was found to be complex and controlled by both surface and pore diffusion with surface diffusion at the earlier stages, followed by pore diffusion at the later stages. The thermodynamic parameters △G0, △S0 and △H0, have been calculated. The thermodynamics of the MB-ACF system indicate that the adsorption process is spontaneous.展开更多
针对在反激式变换器中,变压器漏感导致开关管需要承受较大应力、能量损耗大、漏感能量无法回收以及电源工作效率偏低等问题,文中研究了反激式变换器的有源钳位技术,分析了反激式变换器中有源钳位电路的工作原理和各阶段工作过程,阐述了...针对在反激式变换器中,变压器漏感导致开关管需要承受较大应力、能量损耗大、漏感能量无法回收以及电源工作效率偏低等问题,文中研究了反激式变换器的有源钳位技术,分析了反激式变换器中有源钳位电路的工作原理和各阶段工作过程,阐述了在反激变换器中引入有源钳位技术的优势。以反激式变换器设计方法为基础,梳理有源钳位反激变换器(Active Clamp Flyback,ACF)的设计过程,给出有源钳位反激变换器的设计案例,并制作样机进行测试。测试结果表明,样机的原边开关管在工作过程中实现了零电压开通(Zero Voltage Switching,ZVS),对比无源钳位反激电路效率提升了约3%。研究结果表明,在反激变换器中引入有源钳位技术能有效改善由于变压器漏感造成的电压尖峰、能量损耗问题,降低了开关管电压应力,实现了ZVS,有效提高了电源系统的效率和稳定性。展开更多
超级电容器作为一种绿色的储能装置,对实现“可持续发展”、“绿色中国”的战略目标具有重要意义。然而,对于超级电容器而言,电极材料性能的优劣决定着超级电容器的容量的高低以及循环寿命的长短。在本研究中,根据镍钴硫化物与氢氧化物...超级电容器作为一种绿色的储能装置,对实现“可持续发展”、“绿色中国”的战略目标具有重要意义。然而,对于超级电容器而言,电极材料性能的优劣决定着超级电容器的容量的高低以及循环寿命的长短。在本研究中,根据镍钴硫化物与氢氧化物的溶解度差异,采用绿色环保的室温硫化法(room temperature sulfide,RTS),通过控制反应条件,制备不同形貌的以活性炭纤维(ACF)为核,NiCo_(2)S_(4)为壳的超级电容器电极材料(ACF/NiCo_(2)S_(4)),进行了一系列电化学测试。结果表明,孔隙丰富和蜂窝状材料表现出更大的比电容、更小的阻抗、更稳定的倍率性能。当电流密度为1 A/g时,其比电容值高达1682 F/g,是一种具有广阔应用前景的电极材料。展开更多
The fundamental frequency plays a significant part in understanding and perceiving the pitch of a sound. The pitch is a fundamental attribute employed in numerous speech-related works. For fundamental frequency extrac...The fundamental frequency plays a significant part in understanding and perceiving the pitch of a sound. The pitch is a fundamental attribute employed in numerous speech-related works. For fundamental frequency extraction, several algorithms have been developed which one to use relies on the signal’s characteristics and the surrounding noise. Thus, the algorithm’s noise resistance becomes more critical than ever for precise fundamental frequency estimation. Nonetheless, numerous state-of-the-art algorithms face struggles in achieving satisfying outcomes when confronted with speech recordings that are noisy with low signal-to-noise ratio (SNR) values. Also, most of the recent techniques utilize different frame lengths for pitch extraction. From this point of view, This research considers different frame lengths on male and female speech signals for fundamental frequency extraction. Also, analyze the frame length dependency on the speech signal analytically to understand which frame length is more suitable and effective for male and female speech signals specifically. For the validation of our idea, we have utilized the conventional autocorrelation function (ACF), and state-of-the-art method BaNa. This study puts out a potent idea that will work better for speech processing applications in noisy speech. From experimental results, the proposed idea represents which frame length is more appropriate for male and female speech signals in noisy environments.展开更多
The selective catalytic reduction(SCR) of NOx using MnOx and CeO2 supported on viscose-based active carbon fibers(ACF) at 120 ℃～270 ℃ relatively lower than the temperature when using V2O5/TiO2-anatase catalyst was ...The selective catalytic reduction(SCR) of NOx using MnOx and CeO2 supported on viscose-based active carbon fibers(ACF) at 120 ℃～270 ℃ relatively lower than the temperature when using V2O5/TiO2-anatase catalyst was studied.As a result,CeO2/ACF shows a better catalysis than MNOx/ACF,which is not affected by the reaction temperature. NO conversion of 85% is reached with the 10%-CeO2/ACF catalyst at the whole temperature window.Furthermore,a series of MnOx-CeO2/ACF composite catalysts were studied.The results show that the loading method of catalyst affects its activity.展开更多
基金Projects 20676110 supported by the National Natural Science Foundation of China20070421103 by the China Postdoctoral Science Foundation+1 种基金2006CB202202 by the National Basic Research Program of China06jk244 by the Special Fund of Shaanxi Education Department
文摘The kinetics and mechanism of methylene blue (MB) adsorption onto activated carbon fibers (ACFs) have been studied. The effects of various experimental parameters, such as the initial MB concentration and the ACF mass, on the adsorption rate were investigated. Equilibrium data were fit well by a Freundlich isotherm equation. Adsorption measurements show that the process is very fast. The adsorption data were modeled using first- and second-order kinetic equations and intra–particle diffusion models. It was found that the first-order kinetic equation could best describe the adsorption kinetics. The adsorption process was found to be complex and controlled by both surface and pore diffusion with surface diffusion at the earlier stages, followed by pore diffusion at the later stages. The thermodynamic parameters △G0, △S0 and △H0, have been calculated. The thermodynamics of the MB-ACF system indicate that the adsorption process is spontaneous.
文摘针对在反激式变换器中,变压器漏感导致开关管需要承受较大应力、能量损耗大、漏感能量无法回收以及电源工作效率偏低等问题,文中研究了反激式变换器的有源钳位技术,分析了反激式变换器中有源钳位电路的工作原理和各阶段工作过程,阐述了在反激变换器中引入有源钳位技术的优势。以反激式变换器设计方法为基础,梳理有源钳位反激变换器(Active Clamp Flyback,ACF)的设计过程,给出有源钳位反激变换器的设计案例,并制作样机进行测试。测试结果表明,样机的原边开关管在工作过程中实现了零电压开通(Zero Voltage Switching,ZVS),对比无源钳位反激电路效率提升了约3%。研究结果表明,在反激变换器中引入有源钳位技术能有效改善由于变压器漏感造成的电压尖峰、能量损耗问题,降低了开关管电压应力,实现了ZVS,有效提高了电源系统的效率和稳定性。
文摘超级电容器作为一种绿色的储能装置,对实现“可持续发展”、“绿色中国”的战略目标具有重要意义。然而,对于超级电容器而言,电极材料性能的优劣决定着超级电容器的容量的高低以及循环寿命的长短。在本研究中,根据镍钴硫化物与氢氧化物的溶解度差异,采用绿色环保的室温硫化法(room temperature sulfide,RTS),通过控制反应条件,制备不同形貌的以活性炭纤维(ACF)为核,NiCo_(2)S_(4)为壳的超级电容器电极材料(ACF/NiCo_(2)S_(4)),进行了一系列电化学测试。结果表明,孔隙丰富和蜂窝状材料表现出更大的比电容、更小的阻抗、更稳定的倍率性能。当电流密度为1 A/g时,其比电容值高达1682 F/g,是一种具有广阔应用前景的电极材料。
文摘The fundamental frequency plays a significant part in understanding and perceiving the pitch of a sound. The pitch is a fundamental attribute employed in numerous speech-related works. For fundamental frequency extraction, several algorithms have been developed which one to use relies on the signal’s characteristics and the surrounding noise. Thus, the algorithm’s noise resistance becomes more critical than ever for precise fundamental frequency estimation. Nonetheless, numerous state-of-the-art algorithms face struggles in achieving satisfying outcomes when confronted with speech recordings that are noisy with low signal-to-noise ratio (SNR) values. Also, most of the recent techniques utilize different frame lengths for pitch extraction. From this point of view, This research considers different frame lengths on male and female speech signals for fundamental frequency extraction. Also, analyze the frame length dependency on the speech signal analytically to understand which frame length is more suitable and effective for male and female speech signals specifically. For the validation of our idea, we have utilized the conventional autocorrelation function (ACF), and state-of-the-art method BaNa. This study puts out a potent idea that will work better for speech processing applications in noisy speech. From experimental results, the proposed idea represents which frame length is more appropriate for male and female speech signals in noisy environments.
文摘The selective catalytic reduction(SCR) of NOx using MnOx and CeO2 supported on viscose-based active carbon fibers(ACF) at 120 ℃～270 ℃ relatively lower than the temperature when using V2O5/TiO2-anatase catalyst was studied.As a result,CeO2/ACF shows a better catalysis than MNOx/ACF,which is not affected by the reaction temperature. NO conversion of 85% is reached with the 10%-CeO2/ACF catalyst at the whole temperature window.Furthermore,a series of MnOx-CeO2/ACF composite catalysts were studied.The results show that the loading method of catalyst affects its activity.
