目的探讨在彩色多普勒引导下经外周静脉置入中心静脉导管(peripherally inserted central catheter,PICC)置管穿刺过程中,采用平面内技术与平面外技术的应用效果。方法选取2015年1-12月在我院行超声引导下PICC置管患者130例,经患者知情...目的探讨在彩色多普勒引导下经外周静脉置入中心静脉导管(peripherally inserted central catheter,PICC)置管穿刺过程中,采用平面内技术与平面外技术的应用效果。方法选取2015年1-12月在我院行超声引导下PICC置管患者130例,经患者知情同意,按数字表法随机分为2组:超声引导下平面内技术组和平面外技术组,每组65例。观察2组穿刺用时和一针穿刺成功率。结果彩色多普勒引导下PICC置管穿刺过程中,平面内技术组穿刺时间为(180.0±35.0)s,平面外技术组为(98.0±24.1)s,2组比较差异有统计学意义(P<0.05);平面内技术组一针穿刺成功率为66.2%,平面外技术组为96.9%,2组比较差异有统计学意义(P<0.05)。结论超声引导下PICC置管平面外技术穿刺用时短,一针穿刺成功率高,适于在临床推广。展开更多
An experimental investigation on the properties of the near wake behind the rotor of a Horizontal-Axis Wind Turbine （HAWT） was carried out at model scale. Measurements were made with a stationary slanted hot-wire an...An experimental investigation on the properties of the near wake behind the rotor of a Horizontal-Axis Wind Turbine （HAWT） was carried out at model scale. Measurements were made with a stationary slanted hot-wire anemometer using the technique of phase-locked averaging. The primary aim is to study the formation and development of the three-dimensional wake. Five axial locations were chosen within four chord lengths of the blades over a range of tip speed ratios. The results show that during the downstream developmerit of the wake, the wake centre traces a helical curve with its rotation direction opposite to that of the rotor. The distribution of mean velocity behind the HAWT rotor reveals an expansion and a decay of the three-dimensional wake. The shapes of the mean velocity distribution are similar along the blades span at the same downstream axial location. It is shown that the turbulence levels in the wake are higher than those in the non-wake region. The circumferential component and the radial component of the turbulence intensity are higher than the axial component. Our study offers some food of thought for better understanding of the physical features of the flow field as well as the performance of HAWT.展开更多
In recent years, there has been a rapid development of the wind farms in Japan. It becomes very important to investigate the wind turbine arrangement in wind farm, in order that the wake of one wind turbine does not t...In recent years, there has been a rapid development of the wind farms in Japan. It becomes very important to investigate the wind turbine arrangement in wind farm, in order that the wake of one wind turbine does not to interfere with the flow in other wind turbines. In such a case, in order to achieve the highest possible efficiency from the wind, and to install as many as possible wind turbines within a limited area, it becomes a necessity to study the mutual interference of the wake developed by wind turbines. However, there is no report related to the effect of the turbulence intensity of the external flow on the wake behind a wind turbine generated in the wind tunnel. In this paper, the measurement results of the averaged wind profile and turbulence intensity profile in the wake in the wind tunnel are shown when the turbulence intensity of the external wind was changed. The wind tunnel experiment is performed with 500mm-diameter two-bladed horizontal axis wind turbine and the wind velocity in wake is measured by an I-type hot wire probe. As a result, it is clarified that high turbulence intensities enable to the entrainment of the main flow and the wake and to recover quickly the velocity in the wake.展开更多
In order to improve the accuracy of auto parts production and processing,and reduce the error of parts manufacturing,a 3D scanning modelling of auto parts for intelligent driving is designed in this paper.With the hel...In order to improve the accuracy of auto parts production and processing,and reduce the error of parts manufacturing,a 3D scanning modelling of auto parts for intelligent driving is designed in this paper.With the help of the structured light projection method,the auto parts image is obtained,and its horizontal axis grey value and stripe pixel value are analysed.The contour parameters are determined by k-frame strategy,and the width,length and height parameters of the external contour of vehicle parts are obtained.The basic principle of 3D scanning technology is analysed,its scanning process is designed,and the modelling of auto parts is realised with the help of 3D scanning technology.The experimental results show that the modelling method can effectively improve the machining accuracy and reduce the manufacturing error of the auto parts.展开更多
Determination of the aerodynamic configuration of wake is the key to analysis and evaluation of the rotor aerodynamic characteristics of a horizontal-axis wind turbine. According to the aerodynamic configuration, the ...Determination of the aerodynamic configuration of wake is the key to analysis and evaluation of the rotor aerodynamic characteristics of a horizontal-axis wind turbine. According to the aerodynamic configuration, the real magnitude and direction of the onflow velocity at the rotor blade can be determined, and subsequently, the aerodynamic force on the rotor can be determined. The commonly employed wake aerodynamic models are of the cylindrical form instead of the actual expanding one. This is because the influence of the radial component of the induced velocity on the wake configuration is neglected. Therefore, this model should be called a "linear model". Using this model means that the induced velocities at the rotor blades and aerodynamic loads on them would be inexact. An approximately accurate approach is proposed in this paper to determine the so-called "nonlinear" wake aerodynamic configuration by means of the potential theory, where the influence of all three coordinate components of the induced velocity on wake aerodynamic configuration is taken into account to obtain a kind of expanding wake that approximately looks like an actual one. First, the rotor aerodynamic model composed of axial (central), bound, and trailing vortexes is established with the help of the finite aspect wing theory. Then, the Biot-Savart formula for the potential flow theory is used to derive a set of integral equations to evaluate the three components of the induced velocity at any point within the wake. The numerical solution to the integral equations is found, and the loci of all elementary trailing vortex filaments behind the rotor are determined thereafter. Finally, to formulate an actual wind turbine rotor, using the nonlinear wake model, the induced velocity everywhere in the wake, especially that at the rotor blade, is obtained in the case of various tip speed ratios and compared with the wake boundary in a neutral atmospheric boundary layer. Hereby, some useful and referential conclusions are offered for the aerodynamic c展开更多
文摘目的探讨在彩色多普勒引导下经外周静脉置入中心静脉导管(peripherally inserted central catheter,PICC)置管穿刺过程中,采用平面内技术与平面外技术的应用效果。方法选取2015年1-12月在我院行超声引导下PICC置管患者130例,经患者知情同意,按数字表法随机分为2组:超声引导下平面内技术组和平面外技术组,每组65例。观察2组穿刺用时和一针穿刺成功率。结果彩色多普勒引导下PICC置管穿刺过程中,平面内技术组穿刺时间为(180.0±35.0)s,平面外技术组为(98.0±24.1)s,2组比较差异有统计学意义(P<0.05);平面内技术组一针穿刺成功率为66.2%,平面外技术组为96.9%,2组比较差异有统计学意义(P<0.05)。结论超声引导下PICC置管平面外技术穿刺用时短,一针穿刺成功率高,适于在临床推广。
基金Project supported by the National Natural Science Foundation of China(Grant No.50706025)the Shanghai Municipal Education Commission of China(Grant No.07ZZ144).
文摘An experimental investigation on the properties of the near wake behind the rotor of a Horizontal-Axis Wind Turbine （HAWT） was carried out at model scale. Measurements were made with a stationary slanted hot-wire anemometer using the technique of phase-locked averaging. The primary aim is to study the formation and development of the three-dimensional wake. Five axial locations were chosen within four chord lengths of the blades over a range of tip speed ratios. The results show that during the downstream developmerit of the wake, the wake centre traces a helical curve with its rotation direction opposite to that of the rotor. The distribution of mean velocity behind the HAWT rotor reveals an expansion and a decay of the three-dimensional wake. The shapes of the mean velocity distribution are similar along the blades span at the same downstream axial location. It is shown that the turbulence levels in the wake are higher than those in the non-wake region. The circumferential component and the radial component of the turbulence intensity are higher than the axial component. Our study offers some food of thought for better understanding of the physical features of the flow field as well as the performance of HAWT.
基金A part of this study is funded by METI/NEDO in Research and Development Project of Next Generation Wind Turbine Generation Technology (R&D of Basic and Applied Technology)
文摘In recent years, there has been a rapid development of the wind farms in Japan. It becomes very important to investigate the wind turbine arrangement in wind farm, in order that the wake of one wind turbine does not to interfere with the flow in other wind turbines. In such a case, in order to achieve the highest possible efficiency from the wind, and to install as many as possible wind turbines within a limited area, it becomes a necessity to study the mutual interference of the wake developed by wind turbines. However, there is no report related to the effect of the turbulence intensity of the external flow on the wake behind a wind turbine generated in the wind tunnel. In this paper, the measurement results of the averaged wind profile and turbulence intensity profile in the wake in the wind tunnel are shown when the turbulence intensity of the external wind was changed. The wind tunnel experiment is performed with 500mm-diameter two-bladed horizontal axis wind turbine and the wind velocity in wake is measured by an I-type hot wire probe. As a result, it is clarified that high turbulence intensities enable to the entrainment of the main flow and the wake and to recover quickly the velocity in the wake.
文摘In order to improve the accuracy of auto parts production and processing,and reduce the error of parts manufacturing,a 3D scanning modelling of auto parts for intelligent driving is designed in this paper.With the help of the structured light projection method,the auto parts image is obtained,and its horizontal axis grey value and stripe pixel value are analysed.The contour parameters are determined by k-frame strategy,and the width,length and height parameters of the external contour of vehicle parts are obtained.The basic principle of 3D scanning technology is analysed,its scanning process is designed,and the modelling of auto parts is realised with the help of 3D scanning technology.The experimental results show that the modelling method can effectively improve the machining accuracy and reduce the manufacturing error of the auto parts.
基金Project supported by the National Basic Research Program of China(No.2014CB046201)the National Natural Science Foundation of China(Nos.51766009,51566011,and 51479114)
文摘Determination of the aerodynamic configuration of wake is the key to analysis and evaluation of the rotor aerodynamic characteristics of a horizontal-axis wind turbine. According to the aerodynamic configuration, the real magnitude and direction of the onflow velocity at the rotor blade can be determined, and subsequently, the aerodynamic force on the rotor can be determined. The commonly employed wake aerodynamic models are of the cylindrical form instead of the actual expanding one. This is because the influence of the radial component of the induced velocity on the wake configuration is neglected. Therefore, this model should be called a "linear model". Using this model means that the induced velocities at the rotor blades and aerodynamic loads on them would be inexact. An approximately accurate approach is proposed in this paper to determine the so-called "nonlinear" wake aerodynamic configuration by means of the potential theory, where the influence of all three coordinate components of the induced velocity on wake aerodynamic configuration is taken into account to obtain a kind of expanding wake that approximately looks like an actual one. First, the rotor aerodynamic model composed of axial (central), bound, and trailing vortexes is established with the help of the finite aspect wing theory. Then, the Biot-Savart formula for the potential flow theory is used to derive a set of integral equations to evaluate the three components of the induced velocity at any point within the wake. The numerical solution to the integral equations is found, and the loci of all elementary trailing vortex filaments behind the rotor are determined thereafter. Finally, to formulate an actual wind turbine rotor, using the nonlinear wake model, the induced velocity everywhere in the wake, especially that at the rotor blade, is obtained in the case of various tip speed ratios and compared with the wake boundary in a neutral atmospheric boundary layer. Hereby, some useful and referential conclusions are offered for the aerodynamic c
