The shear thinning and shear thickening rheological properties of PCC/PEG suspension were investigated with the increase of oscillatory amplitude stress at different constant frequencies. The results show that the com...The shear thinning and shear thickening rheological properties of PCC/PEG suspension were investigated with the increase of oscillatory amplitude stress at different constant frequencies. The results show that the complex viscosity was initially independent of stress amplitude and obvious shear thinning occurred, then dramatic shear thickening took place after reaching the minimum viscosity. Typically, in a constant frequency of 5 rad/s, the elastic modulus, viscous modulus, and tanδ （δ is the out-of-phase angle） vs. the stress amplitude was investigated. It is found that the elastic modulus initially appeared to be independent of stress amplitude and then exhibited a rapid decrease, but the viscous modulus was independent of amplitude stress at lower amplitude stress. After reaching the minimum value the viscous modulus showed a rapid increase. On the other hand, tanδ increased from 0.6 to 92, which indicates that the transition from elastic to viscous had taken place and tanδ showed a steep increase when shear thickening occurred. Lissajous plots are shown for the dissipated energy vs. different maximum stress amplitude in the shear thinning and shear thickening regions. The relationship of dissipated energy vs. maximum stress amplitude was determined, which follows a power law. In the shear thinning region the exponent was 1.91, but it steeply increases to 3.97 in the shear thickening region.展开更多
Vocal communication plays an important role for individual recognition and male-female interaction during mating in greater horseshoe bats,especially in respect to mate fidelity,which ensures that the bats can maintai...Vocal communication plays an important role for individual recognition and male-female interaction during mating in greater horseshoe bats,especially in respect to mate fidelity,which ensures that the bats can maintain a stable social organization.Few studies,however,have addressed the calling behavior during copulating in bats.Here,we initially report the copulation vocalizations and behaviors of both male and female greater horseshoe bats.During copulation,the male assumed a dorsal position and arched his back,arming around the female using his feet and thumbs.The male repeatedly produced very short constant frequency(SCF) syllables with high intensity and repetition rate(male 1:16.48±4.8 ms,male 2:17.79±4.03 ms) when he tried to insert the penis into the female,and then long syllables(male 1:42.08±12.67 ms,male 2:43.02±11.44 ms) after penile insertion.The female bats sometime refused the male bats in the early phase of copulations as emitting noise bursts and broad-band vocalizations,but kept silence during actual copulation.We also found that the SCF copulation calls of one male remained stable peak frequencies on different copulation days although its echolocation call frequency varied each day.Moreover,different male individuals maintained their own "private frequency" in the SCF copulation calls.Therefore,we predicted that the SCF copulation calls may serve as an indicator for female greater horseshoe bats to recognize the mating males in order to maintain mate fidelity because horseshoe bats exhibit sexual segregation before mating.Our results stipulate further studies on mating system and copulation strategies in polygynous bats.Such work may also aid in promoting the preservation of greater horseshoe bats.展开更多
The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flo...The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flow exponent N of suspensions with different volume fractions were determined. The shear-thinning and the discontinuous shear-thickening behavior were observed at different constant frequencies from 10 to 100 rad/s. The relationship between the complex viscosity and the constant frequency were determined. As the volume fraction increases,flow exponent N shows a rapid increase,and it increases dramatically when the discontinuous shear-thickening takes place,while consistency index K decreases. Dynamic oscillatory shear experiments were conducted at constant strain amplitude and constant frequency,respectively. For the frequency sweep,the system shows viscous property in entire range of the frequency investigated,and the complex viscosity shows discontinuous jump at a critical frequency of 10 rad/s. For the strain sweep,on the other hand,at low strain the elastic modulus is strongly dependent on the strain,and the viscous modulus is independent of the strain. But at the critical strain point both of the moduli show an abrupt jump and the system transits from elastic to viscous at a strain of 0.1.展开更多
对动态电压调节(Dynamic Voltage Scaling,DVS)开关变换器的定频导通时间(Constant Frequency Turn-On Time,CFOT)控制技术进行了研究,在恒定导通时间(Constant On-Time,COT)基础上,通过引入输入电压前馈和输出参考电压反馈环路,实现不...对动态电压调节(Dynamic Voltage Scaling,DVS)开关变换器的定频导通时间(Constant Frequency Turn-On Time,CFOT)控制技术进行了研究,在恒定导通时间(Constant On-Time,COT)基础上,通过引入输入电压前馈和输出参考电压反馈环路,实现不同输入、输出电压条件下DVS开关变换器保持开关频率恒定。研究结果表明,CFOT控制不仅继承了传统COT控制环路设计简单、无需误差放大器及其相应的补偿网路、瞬态响应快的优点,而且消除了输入、输出电压变动对开关频率的影响。展开更多
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.50774096 and No.50604017）.
文摘The shear thinning and shear thickening rheological properties of PCC/PEG suspension were investigated with the increase of oscillatory amplitude stress at different constant frequencies. The results show that the complex viscosity was initially independent of stress amplitude and obvious shear thinning occurred, then dramatic shear thickening took place after reaching the minimum viscosity. Typically, in a constant frequency of 5 rad/s, the elastic modulus, viscous modulus, and tanδ （δ is the out-of-phase angle） vs. the stress amplitude was investigated. It is found that the elastic modulus initially appeared to be independent of stress amplitude and then exhibited a rapid decrease, but the viscous modulus was independent of amplitude stress at lower amplitude stress. After reaching the minimum value the viscous modulus showed a rapid increase. On the other hand, tanδ increased from 0.6 to 92, which indicates that the transition from elastic to viscous had taken place and tanδ showed a steep increase when shear thickening occurred. Lissajous plots are shown for the dissipated energy vs. different maximum stress amplitude in the shear thinning and shear thickening regions. The relationship of dissipated energy vs. maximum stress amplitude was determined, which follows a power law. In the shear thinning region the exponent was 1.91, but it steeply increases to 3.97 in the shear thickening region.
基金supported by the National Natural Science Foundation of China (31030011 and 30900166)the Ministry of Education of China(MS2011DBSF023)+1 种基金Jilin Provincial Science and Technology Department (20100148)NIH grant to Metzner Walter (dc5400)
文摘Vocal communication plays an important role for individual recognition and male-female interaction during mating in greater horseshoe bats,especially in respect to mate fidelity,which ensures that the bats can maintain a stable social organization.Few studies,however,have addressed the calling behavior during copulating in bats.Here,we initially report the copulation vocalizations and behaviors of both male and female greater horseshoe bats.During copulation,the male assumed a dorsal position and arched his back,arming around the female using his feet and thumbs.The male repeatedly produced very short constant frequency(SCF) syllables with high intensity and repetition rate(male 1:16.48±4.8 ms,male 2:17.79±4.03 ms) when he tried to insert the penis into the female,and then long syllables(male 1:42.08±12.67 ms,male 2:43.02±11.44 ms) after penile insertion.The female bats sometime refused the male bats in the early phase of copulations as emitting noise bursts and broad-band vocalizations,but kept silence during actual copulation.We also found that the SCF copulation calls of one male remained stable peak frequencies on different copulation days although its echolocation call frequency varied each day.Moreover,different male individuals maintained their own "private frequency" in the SCF copulation calls.Therefore,we predicted that the SCF copulation calls may serve as an indicator for female greater horseshoe bats to recognize the mating males in order to maintain mate fidelity because horseshoe bats exhibit sexual segregation before mating.Our results stipulate further studies on mating system and copulation strategies in polygynous bats.Such work may also aid in promoting the preservation of greater horseshoe bats.
基金Projects (50774096, 50606017) supported by the National Natural Science Foundation of China
文摘The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG) were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flow exponent N of suspensions with different volume fractions were determined. The shear-thinning and the discontinuous shear-thickening behavior were observed at different constant frequencies from 10 to 100 rad/s. The relationship between the complex viscosity and the constant frequency were determined. As the volume fraction increases,flow exponent N shows a rapid increase,and it increases dramatically when the discontinuous shear-thickening takes place,while consistency index K decreases. Dynamic oscillatory shear experiments were conducted at constant strain amplitude and constant frequency,respectively. For the frequency sweep,the system shows viscous property in entire range of the frequency investigated,and the complex viscosity shows discontinuous jump at a critical frequency of 10 rad/s. For the strain sweep,on the other hand,at low strain the elastic modulus is strongly dependent on the strain,and the viscous modulus is independent of the strain. But at the critical strain point both of the moduli show an abrupt jump and the system transits from elastic to viscous at a strain of 0.1.
文摘对动态电压调节(Dynamic Voltage Scaling,DVS)开关变换器的定频导通时间(Constant Frequency Turn-On Time,CFOT)控制技术进行了研究,在恒定导通时间(Constant On-Time,COT)基础上,通过引入输入电压前馈和输出参考电压反馈环路,实现不同输入、输出电压条件下DVS开关变换器保持开关频率恒定。研究结果表明,CFOT控制不仅继承了传统COT控制环路设计简单、无需误差放大器及其相应的补偿网路、瞬态响应快的优点,而且消除了输入、输出电压变动对开关频率的影响。
