Direct drive servovalves are mostly restricted to low flow rate and low bandwidth applications due to the considerable flow forces.Current studies mainly focus on enhancing the driving force,which in turn is limited t...Direct drive servovalves are mostly restricted to low flow rate and low bandwidth applications due to the considerable flow forces.Current studies mainly focus on enhancing the driving force,which in turn is limited to the development of the magnetic material.Aiming at reducing the flow forces,a novel rotary direct drive servovalve（RDDV）is introduced in this paper.This RDDV servovalve is designed in a rotating structure and its axially symmetric spool rotates within a certain angle range in the valve chamber.The servovalve orifices are formed by the matching between the square wave shaped land on the spool and the rectangular ports on the sleeve.In order to study the RDDV servovalve performance,flow rate model and mechanical model are established,wherein flow rates and flow induced torques at different spool rotation angles or spool radiuses are obtained.The model analysis shows that the driving torque can be alleviated due to the proposed valve structure.Computational fluid dynamics（CFD）analysis using ANSYS/FLUENT is applied to evaluate and validate the theoretical analysis.In addition,experiments on the flow rate and the mechanical characteristic of the RDDV servovalve are carried out.Both simulation and experimental results conform to the results of the theoretical model analysis,which proves that this novel and innovative structure for direct drive servovalves can reduce the flow force on the spool and improve valve frequency response characteristics.This research proposes a novel rotary direct drive servovalve,which can reduce the flow forces effectively.展开更多
雷电感应过电压导致的10 k V配电线路跳闸事故十分频繁,需要合理计算线路雷电感应跳闸率并采取针对性防护措施。利用EMTP中的MODEL模块编程计算线路雷电感应过电压,建立线路模型考虑线路闪络跳闸情况,利用区间统计法求取配电线路雷电感...雷电感应过电压导致的10 k V配电线路跳闸事故十分频繁,需要合理计算线路雷电感应跳闸率并采取针对性防护措施。利用EMTP中的MODEL模块编程计算线路雷电感应过电压,建立线路模型考虑线路闪络跳闸情况,利用区间统计法求取配电线路雷电感应跳闸率,分析线路工频电压对感应跳闸率的影响,最后讨论安装避雷器的防护效果。分析结果表明:配电线路三相感应过电压波形较为类似,过电压幅值相差不大;雷击点距离线路越近,感应过电压可能引发的线路跳闸次数越多;线路工作电压对雷电感应跳闸率的影响很小,基本可以忽略。安装避雷器可以降低雷电感应跳闸率,每基杆塔安装避雷器的相数越多,避雷器安装间隔越密,防护效果越明显。展开更多
Electrochemical production of hydrogen from water requires the development ofelectrocatalysts that are active,stable,and low-cost for water splitting.To address these challenges,researchers are increasingly exploring ...Electrochemical production of hydrogen from water requires the development ofelectrocatalysts that are active,stable,and low-cost for water splitting.To address these challenges,researchers are increasingly exploring binder-free electrocatalytic integratedelectrodes (IEs) as an alternative to conventional powder-based electrode preparation methods,for the former is highly desirable to improve the catalytic activity and long-term stability for large-scale applications of electrocatalysts.Herein,we demonstrate a laser-inducedhydrothermal reaction (LIHR) technique to grow NiMoO4nanosheets on nickel foam,which is then calcined under H2/Ar mixed gases to prepare the IE IE-NiMo-LR.This electrode exhibits superior hydrogen evolution reaction performance,requiring overpotentials of 59,116 and143 mV to achieve current densities of 100,500 and 1000 mA·cm-2.During the 350 h chronopotentiometry test at current densities of 100 and 500 m A·cm-2,the overpotentialremains essentially unchanged.In addition,NiFe-layered double hydroxide grown on Ni foam is also fabricated with the same LIHR method and coupled with IE-NiMo-IR to achieve water splitting.This combination exhibits excellent durability under industrial current density.The energy consumption and production efficiency of the LIHR method are systematicallycompared with the conventional hydrothermal method.The LIHR method significantly improves the production rate by over 19 times,while consuming only 27.78%of the total energy required by conventional hydrothermal methods to achieve the same production.展开更多
家禽是长日照动物,科学合理的光照程序对蛋鸡的生长发育、性成熟、开产日龄、产蛋高峰等都有显著影响,在诱导换羽的禁食和恢复采食的不同阶段,设定相应的光照程序对于提升诱导换羽效果具有重要的意义。该研究选用529日龄体重相近、产蛋...家禽是长日照动物,科学合理的光照程序对蛋鸡的生长发育、性成熟、开产日龄、产蛋高峰等都有显著影响,在诱导换羽的禁食和恢复采食的不同阶段,设定相应的光照程序对于提升诱导换羽效果具有重要的意义。该研究选用529日龄体重相近、产蛋率约为60%的贵妃蛋鸡为试验材料,根据禁食诱导换羽的不同时期,将光照制度的变化分4个阶段,并于第Ⅰ阶段(16 h L/8 h D,禁食前)、第Ⅱ阶段(8 h L/16 h D持续3 d)、第Ⅲ阶段(10 h L/14 h D持续13 d)的最后1天(F 0、F 3、F 16)和第Ⅳ阶段(逐渐增加光照0.5 h/d至恢复到16 h L/8 h D)的第6、32天(R 6、R 32)5个不同时期屠宰采样,通过卵泡数量、卵巢抗氧化指标、KIT-PI3K-PTEN-AKT信号通路和GDF9基因表达量等来探究光照程序在禁食诱导换羽过程的作用。结果表明,缩短光照蛋鸡血清中生殖激素FSH、LH、E 2和P 4的水平降低(P<0.001),超氧化物歧化酶(P<0.05)、谷胱甘肽过氧化酶(P<0.001)活力增强,在此过程中原始卵泡可能被激活,使小黄卵泡(P<0.01)、大白卵泡(P>0.05)的数量增多;逐渐恢复光照时长过程中KIT和PI3K处于持续高表达状态(P<0.001),PTEN相对表达量降低(P<0.01),而AKT相对表达量基本不变(P>0.05),且血清中生殖激素水平和卵巢抗氧化水平恢复到初始状态,但整体卵泡数量有所上升。该结果表明在禁食换羽过程中科学合理的光照程序对卵巢功能的重塑具有辅助作用。展开更多
Larger amount of austenite could be retained in an intercritically heat-treated bainite- transformed steel. The elongation and the strength-ductility balance of the steel could be enhanced considerably due to strain-i...Larger amount of austenite could be retained in an intercritically heat-treated bainite- transformed steel. The elongation and the strength-ductility balance of the steel could be enhanced considerably due to strain-induced martensite transformation and transformation- induced plasticity (TRIP) of retained austenite. The effects of test temperature and strain rate on the mechanical properties and strain induced transformation behavior of retained austenite in the steel were investigated. Total elongation and strength-ductility balance of the specimen reached maximum when it strained at a strain rate of 2.8×10-4s-1 and at 350℃. The relation between test temperature and tensile properties showed the same tendency at three kinds of strain rates. Flow stress increased considerably with decreasing the strain rate.展开更多
Microstructure evolutions of the medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V (in wt.%) with stacking-fault energy of 22 mJ m-2 during deformation at strain rate ranging of 10^-2-1 s^-1 were analyzed by ...Microstructure evolutions of the medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V (in wt.%) with stacking-fault energy of 22 mJ m-2 during deformation at strain rate ranging of 10^-2-1 s^-1 were analyzed by means of X-ray diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results indicate that the twinning-induced plasticity effect is the main strengthening mechanism of the studied steel, whilst the transformation-induced plasticity effect only occurs at high strain rate. With an increase in strain rate, volume fraction of the deformation twins, in particular that of the secondary twins, increases significantly along with decreasing average size. When applied strain rate is higher than 10^-1 s^-1, the parallel deformation twins are turned into a crossing morphology, and the original straight twin boundaries exhibit a ladder feature, which is attributed to the interactions between regular dislocations and twin dislocations at the twin boundary. The critical strain, a key indicator of the initiation of deformation twin, decreases with increasing strain rate. In addition, the ductility and strength of medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V are mainly determined by the shape and volume fraction of deformation twins.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51375363)Xi’an Municipal Science and Technology Planning Project of China(Grant No.CX12504)Guangdong Provincial Key Technology Project on Emerging Industries of Strategic Importance of China(Grant No.2012A090100010)
文摘Direct drive servovalves are mostly restricted to low flow rate and low bandwidth applications due to the considerable flow forces.Current studies mainly focus on enhancing the driving force,which in turn is limited to the development of the magnetic material.Aiming at reducing the flow forces,a novel rotary direct drive servovalve（RDDV）is introduced in this paper.This RDDV servovalve is designed in a rotating structure and its axially symmetric spool rotates within a certain angle range in the valve chamber.The servovalve orifices are formed by the matching between the square wave shaped land on the spool and the rectangular ports on the sleeve.In order to study the RDDV servovalve performance,flow rate model and mechanical model are established,wherein flow rates and flow induced torques at different spool rotation angles or spool radiuses are obtained.The model analysis shows that the driving torque can be alleviated due to the proposed valve structure.Computational fluid dynamics（CFD）analysis using ANSYS/FLUENT is applied to evaluate and validate the theoretical analysis.In addition,experiments on the flow rate and the mechanical characteristic of the RDDV servovalve are carried out.Both simulation and experimental results conform to the results of the theoretical model analysis,which proves that this novel and innovative structure for direct drive servovalves can reduce the flow force on the spool and improve valve frequency response characteristics.This research proposes a novel rotary direct drive servovalve,which can reduce the flow forces effectively.
文摘雷电感应过电压导致的10 k V配电线路跳闸事故十分频繁,需要合理计算线路雷电感应跳闸率并采取针对性防护措施。利用EMTP中的MODEL模块编程计算线路雷电感应过电压,建立线路模型考虑线路闪络跳闸情况,利用区间统计法求取配电线路雷电感应跳闸率,分析线路工频电压对感应跳闸率的影响,最后讨论安装避雷器的防护效果。分析结果表明:配电线路三相感应过电压波形较为类似,过电压幅值相差不大;雷击点距离线路越近,感应过电压可能引发的线路跳闸次数越多;线路工作电压对雷电感应跳闸率的影响很小,基本可以忽略。安装避雷器可以降低雷电感应跳闸率,每基杆塔安装避雷器的相数越多,避雷器安装间隔越密,防护效果越明显。
基金financial support from The University of Manchester to cover his PhD tuition fees for him to carry out this workChina National High-end Foreign Experts Recruitment Plan Project (G2023018001L) for partially supporting the work。
文摘Electrochemical production of hydrogen from water requires the development ofelectrocatalysts that are active,stable,and low-cost for water splitting.To address these challenges,researchers are increasingly exploring binder-free electrocatalytic integratedelectrodes (IEs) as an alternative to conventional powder-based electrode preparation methods,for the former is highly desirable to improve the catalytic activity and long-term stability for large-scale applications of electrocatalysts.Herein,we demonstrate a laser-inducedhydrothermal reaction (LIHR) technique to grow NiMoO4nanosheets on nickel foam,which is then calcined under H2/Ar mixed gases to prepare the IE IE-NiMo-LR.This electrode exhibits superior hydrogen evolution reaction performance,requiring overpotentials of 59,116 and143 mV to achieve current densities of 100,500 and 1000 mA·cm-2.During the 350 h chronopotentiometry test at current densities of 100 and 500 m A·cm-2,the overpotentialremains essentially unchanged.In addition,NiFe-layered double hydroxide grown on Ni foam is also fabricated with the same LIHR method and coupled with IE-NiMo-IR to achieve water splitting.This combination exhibits excellent durability under industrial current density.The energy consumption and production efficiency of the LIHR method are systematicallycompared with the conventional hydrothermal method.The LIHR method significantly improves the production rate by over 19 times,while consuming only 27.78%of the total energy required by conventional hydrothermal methods to achieve the same production.
文摘家禽是长日照动物,科学合理的光照程序对蛋鸡的生长发育、性成熟、开产日龄、产蛋高峰等都有显著影响,在诱导换羽的禁食和恢复采食的不同阶段,设定相应的光照程序对于提升诱导换羽效果具有重要的意义。该研究选用529日龄体重相近、产蛋率约为60%的贵妃蛋鸡为试验材料,根据禁食诱导换羽的不同时期,将光照制度的变化分4个阶段,并于第Ⅰ阶段(16 h L/8 h D,禁食前)、第Ⅱ阶段(8 h L/16 h D持续3 d)、第Ⅲ阶段(10 h L/14 h D持续13 d)的最后1天(F 0、F 3、F 16)和第Ⅳ阶段(逐渐增加光照0.5 h/d至恢复到16 h L/8 h D)的第6、32天(R 6、R 32)5个不同时期屠宰采样,通过卵泡数量、卵巢抗氧化指标、KIT-PI3K-PTEN-AKT信号通路和GDF9基因表达量等来探究光照程序在禁食诱导换羽过程的作用。结果表明,缩短光照蛋鸡血清中生殖激素FSH、LH、E 2和P 4的水平降低(P<0.001),超氧化物歧化酶(P<0.05)、谷胱甘肽过氧化酶(P<0.001)活力增强,在此过程中原始卵泡可能被激活,使小黄卵泡(P<0.01)、大白卵泡(P>0.05)的数量增多;逐渐恢复光照时长过程中KIT和PI3K处于持续高表达状态(P<0.001),PTEN相对表达量降低(P<0.01),而AKT相对表达量基本不变(P>0.05),且血清中生殖激素水平和卵巢抗氧化水平恢复到初始状态,但整体卵泡数量有所上升。该结果表明在禁食换羽过程中科学合理的光照程序对卵巢功能的重塑具有辅助作用。
基金the National Natural Science Foundation of China(No.50334010)the Doctor Degree Thesis Subsidization Item of Northeastern Universiry(No.200302).
文摘Larger amount of austenite could be retained in an intercritically heat-treated bainite- transformed steel. The elongation and the strength-ductility balance of the steel could be enhanced considerably due to strain-induced martensite transformation and transformation- induced plasticity (TRIP) of retained austenite. The effects of test temperature and strain rate on the mechanical properties and strain induced transformation behavior of retained austenite in the steel were investigated. Total elongation and strength-ductility balance of the specimen reached maximum when it strained at a strain rate of 2.8×10-4s-1 and at 350℃. The relation between test temperature and tensile properties showed the same tendency at three kinds of strain rates. Flow stress increased considerably with decreasing the strain rate.
基金The authors gratefully appreciate the financial support by the National Natural Science Foundation of China (Grant Nos. 51471048 and U1860201)the Basic Research Program of Key Laboratory of Liaoning Province (LZ2015035).
文摘Microstructure evolutions of the medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V (in wt.%) with stacking-fault energy of 22 mJ m-2 during deformation at strain rate ranging of 10^-2-1 s^-1 were analyzed by means of X-ray diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results indicate that the twinning-induced plasticity effect is the main strengthening mechanism of the studied steel, whilst the transformation-induced plasticity effect only occurs at high strain rate. With an increase in strain rate, volume fraction of the deformation twins, in particular that of the secondary twins, increases significantly along with decreasing average size. When applied strain rate is higher than 10^-1 s^-1, the parallel deformation twins are turned into a crossing morphology, and the original straight twin boundaries exhibit a ladder feature, which is attributed to the interactions between regular dislocations and twin dislocations at the twin boundary. The critical strain, a key indicator of the initiation of deformation twin, decreases with increasing strain rate. In addition, the ductility and strength of medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V are mainly determined by the shape and volume fraction of deformation twins.
