面团的形成是面制品生产过程中的重要工序，它的质量直接影响面制品的品质。核磁共振（Nuclear Magnetic Resonance，NMR）技术能直观、快速、精确地反映和体现面团在搅拌过程中水分迁移变化，通过磁共振成像（Magnetic Resonance Imag...面团的形成是面制品生产过程中的重要工序，它的质量直接影响面制品的品质。核磁共振（Nuclear Magnetic Resonance，NMR）技术能直观、快速、精确地反映和体现面团在搅拌过程中水分迁移变化，通过磁共振成像（Magnetic Resonance Imaging，MRI）技术观察面团面筋网络的形成和破坏过程，采用多成分模型分析质子弛豫曲线，将面团中的水分划分为三部分，具有各自不同的自旋-自旋弛豫时间，分别为T21、T22和T23。随着和面时间的延长，面团的他值和质子信号幅度（A）发生相应的变化。研究结果发现，面团的NMR弛豫参数的变化规律，以及面团形成过程的所体现的MR图像对指导和评价工业化面团形成所需要的最佳搅拌时间具有重要意义。实验结果表明：当中速搅拌，水分添加量为面粉的45％，其水温为30℃时，低筋粉的和面时间为15～25min，其面团的质量最佳。展开更多
For the most coastal areas where the air is very humid,study on the effect of humidity on the performance of asphalt has its practical significance.However,limited research has been done to investigate the effect of h...For the most coastal areas where the air is very humid,study on the effect of humidity on the performance of asphalt has its practical significance.However,limited research has been done to investigate the effect of humidity on rheological properties of asphalt.In this study,asphalt binders were aged in the pressure aging vessel(PAV)under different conditions of moisture and aging time.Then Dynamic Shear Rheometer(DSR)and Bending Beam Rheometer(BBR)measurements were conducted to obtain the parameters relating to the complex modulus,phase angle,failure temperature,and creep stiffness.It was found that the low temperature performance decreased as evidenced by the results of the creep stiffness.While there were no significant differences among conditioned binders based on complex modulus G*and phase angleδ,it was found that theδvalue increased when the humidity increased from 0% to 80% ,and then theδvalue decreased when the humidity increased to 100% .In addition,the results of the failure temperature indicated that the humidity of 80% would be a critical point for the high temperature performance of the asphalt binders.展开更多
To analyze the interaction between wind turbines and the atmospheric boundary layer, we integrated a large-eddy simulation with an actuator line model and examined the characteristics of wind-turbine loads and wakes w...To analyze the interaction between wind turbines and the atmospheric boundary layer, we integrated a large-eddy simulation with an actuator line model and examined the characteristics of wind-turbine loads and wakes with reference to a corresponding experiment in Gansu. In the simulation, we set the wind turbine to have a rotor diameter of 14.8 m and a tower height of 15.4 m in the center of an atmospheric boundary layer with a 10.6° yaw angle. The results reveal an obviously skewed wake structure behind the rotor due to the thrust component normal to the flow direction. The power spectra of the inflow fluctuation velocity exhibit a region of-5/3 slope, which confirms the ability of large-eddy simulations to reproduce the energy cascade from larger to smaller scales. We found there to be more energy in the power spectrum of the axial velocity, which shows that coherent turbulence structures have more energy in the horizontal direction. By the conjoint analysis of atmospheric turbulence and windturbine loads, we found that when the inflow wind direction changes rapidly, the turbulence kinetic energy and coherent turbulence kinetic energy in the atmospheric turbulence increase, which in turn causes fluctuations in the wind turbine load.Furthermore, anisotropic atmospheric turbulence causes an asymmetric load cycle, which imposes a strike by the turbine blade on the shaft, thereby increasing the fatigue load on the shaft. Our main conclusion is that the atmospheric boundary layer has a strong effect on the evolution of the wake and the structural response of the turbine.展开更多
文摘面团的形成是面制品生产过程中的重要工序，它的质量直接影响面制品的品质。核磁共振（Nuclear Magnetic Resonance，NMR）技术能直观、快速、精确地反映和体现面团在搅拌过程中水分迁移变化，通过磁共振成像（Magnetic Resonance Imaging，MRI）技术观察面团面筋网络的形成和破坏过程，采用多成分模型分析质子弛豫曲线，将面团中的水分划分为三部分，具有各自不同的自旋-自旋弛豫时间，分别为T21、T22和T23。随着和面时间的延长，面团的他值和质子信号幅度（A）发生相应的变化。研究结果发现，面团的NMR弛豫参数的变化规律，以及面团形成过程的所体现的MR图像对指导和评价工业化面团形成所需要的最佳搅拌时间具有重要意义。实验结果表明：当中速搅拌，水分添加量为面粉的45％，其水温为30℃时，低筋粉的和面时间为15～25min，其面团的质量最佳。
基金supported by the National Natural Science Fund Project of China(NSFC)(No.:51278173)the Natural Science Fund Project of Jiangsu Provincial Communications Department(No.:SBK201120606)
文摘For the most coastal areas where the air is very humid,study on the effect of humidity on the performance of asphalt has its practical significance.However,limited research has been done to investigate the effect of humidity on rheological properties of asphalt.In this study,asphalt binders were aged in the pressure aging vessel(PAV)under different conditions of moisture and aging time.Then Dynamic Shear Rheometer(DSR)and Bending Beam Rheometer(BBR)measurements were conducted to obtain the parameters relating to the complex modulus,phase angle,failure temperature,and creep stiffness.It was found that the low temperature performance decreased as evidenced by the results of the creep stiffness.While there were no significant differences among conditioned binders based on complex modulus G*and phase angleδ,it was found that theδvalue increased when the humidity increased from 0% to 80% ,and then theδvalue decreased when the humidity increased to 100% .In addition,the results of the failure temperature indicated that the humidity of 80% would be a critical point for the high temperature performance of the asphalt binders.
基金supported by the National Basic Research Program of China（Grant No.2014CB046201） the National Natural Science Foundation of China（Grant Nos.51465033,51766009,and 51479114）+2 种基金 the Thousand Talents Program,NSFC-RCUK_EPSRC,the platform construction of ocean energy comprehensive supporting service（2014）（Grant No.GHME2014ZC01） the High-tech Ship Research Projects Sponsored by MIITC Floating Support platform project（Grant No.201622） the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University
文摘To analyze the interaction between wind turbines and the atmospheric boundary layer, we integrated a large-eddy simulation with an actuator line model and examined the characteristics of wind-turbine loads and wakes with reference to a corresponding experiment in Gansu. In the simulation, we set the wind turbine to have a rotor diameter of 14.8 m and a tower height of 15.4 m in the center of an atmospheric boundary layer with a 10.6° yaw angle. The results reveal an obviously skewed wake structure behind the rotor due to the thrust component normal to the flow direction. The power spectra of the inflow fluctuation velocity exhibit a region of-5/3 slope, which confirms the ability of large-eddy simulations to reproduce the energy cascade from larger to smaller scales. We found there to be more energy in the power spectrum of the axial velocity, which shows that coherent turbulence structures have more energy in the horizontal direction. By the conjoint analysis of atmospheric turbulence and windturbine loads, we found that when the inflow wind direction changes rapidly, the turbulence kinetic energy and coherent turbulence kinetic energy in the atmospheric turbulence increase, which in turn causes fluctuations in the wind turbine load.Furthermore, anisotropic atmospheric turbulence causes an asymmetric load cycle, which imposes a strike by the turbine blade on the shaft, thereby increasing the fatigue load on the shaft. Our main conclusion is that the atmospheric boundary layer has a strong effect on the evolution of the wake and the structural response of the turbine.
