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mean and fluctuating velocity fields of a diamond turbulent jet

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Chinese physics B 2013年第3期22卷 344-351页

作者：徐敏义张健鹏米建春 Nathan G.J. kalt p.a.m. State Key Laboratory of Turbulence & Complex Systems College of EngineeringPeking University marine Engineering College Dalian Maritime University Centre for Energy Technology and School of mechanical Engineering University of AdelaideSA 5005Australia

The present paper reports the first investigation on a turbulent jet issuing from a diamond orifice（hereafter termed a ＂diamond jet＂） with an aspect ratio of *** measurements were conducted in the transitional region,and the exit Reynolds number of the jet was *** comparison,a round jet with identical normalized boundary conditions was also *** is shown that the diamond jet decays and spreads faster than the round jet does over the measured flow *** axis-switching phenomenon is observed in the diamond *** both jets disp.ay primary coherent structures in the near field,these structures are found to break down more rapidly in the diamond jet,due to the higher three-dimensionality of the ***,the streamwise components of the Reynolds normal stress and all the shear stresses reach their maxima around the location of the maximal mean shear while the maxima of the lateral components of the Reynolds normal stresses occur around the centreline of the jet.

关键词： turbulent jet non-circular jet pIV measurement jet entrainment

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Effect of noncircular orifice p.ates on the near flow field of turbulent free jets

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Chinese physics B 2014年第12期23卷 298-306页

作者：徐敏义童杏清岳丹婷张健鹏米建春 Nathan G.J. kalt p.a.m. marine Engineering College Dalian Maritime University State Key Laboratory of Turbulence & Complex Systems College of Engineering Peking University Centre for Energy Technology and School of mechanical Engineering University of Adelaide

In this paper, we experimentally investigate the near-field flow characteristics of turbulent free jets respectively issued from circular, triangular, diamond, rectangular, and notched-rectangular orifice p.ates into air surroundings. All the orifice p.ates have identical opening areas or equivalent diameters（De） and their aspect ratios（AR） range from 1 to 6.5. p.anar particle image velocimetry（pIV） is used to measure the velocity field at the same Reynolds number of Re = 5 × 10^4,where Re = Ue De/ν with Ue being the exit bulk velocity and ν the kinematic viscosity of fluid. The mean and turbulent velocity fields of all the five jets are compared in detail. Results show that the noncircular jets can enhance the entrainment rate, reflected by the higher acceleration rates of mean velocity decay and spread, shorten the length of the unmixed core,expedite the increase of turbulent intensity compared with the circular counterpart shortened unmixed core, and increase turbulent intensity comparing to the circular counterpart. Among the five jets, the rectangular jet（AR = 6.5） produces the greatest decay rate of the near-field mean velocity, postpones the position at which the 鈥榓xis-switching鈥檖henomenon occurs. This supports that axis switching phenomenon strongly depends on jet initial conditions. In addition, the hump in the centerline variation of the turbulence intensity is observed in the rectangular and triangular jets, but not in the circular jet, nor in diamond jet nor in notched-rectangular jet.

关键词： noncircular jet free jet turbulence mixing axis-switching

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A multi-photon(7×7)-focus 3D laser printer based on a 3D-printed diffractive optical element and a 3D-printed multi-lens array

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Light(Advanced manufacturing) 2024年第1期5卷 26-39页

作者： pascal Kiefer Vincent Hahn Sebastian kalt Qing Sun Yolita m.Eggeler martin Wegener Dmm2O-Cluster of Excellence Karlsruhe Institute of Technology(KIT)and Heidelberg University76128 KarlsruheGermany Institute of Applied physics(ApH) Karlsruhe Institute of Technology(KIT)76128 KarlsruheGermany Institute of Nanotechnology(INT) Karlsruhe Institute of Technology(KIT)76128 KarlsruheGermany Laboratory for Electron microscopy(LEm) Karlsruhe Institute of Technology(KIT)76128 KarlsruheGermany

One of the challenges in the field of multi-photon 3D laser printing lies in further increasing the print speed in terms of voxels/***,we present a setup based on a 7×7 focus array(rather than 3×3 in our previous work)and using a focus velocity of about 1 m/s(rather than 0.5 m/s in our previous work)at the diffraction limit(40×/NA1.4 microscope objective lens).Combined,this advance leads to a ten times increased print speed of about 108 voxels/*** demonstrate polymer printing of a chiral metamaterial containing more than 1.7×10^(12) voxels as well as millions of printed microparticles for potential p.armaceutical *** critical high-quality micro-optical components of the setup,namely a diffractive optical element generating the 7×7 beamlets and a 7×7 lens array,are manufactured by using a commercial two-photon grayscale 3D laser printer.

关键词： 3D laser printing Direct laser writing multi-photon absorption multi-focus optics Diffractive optical element Lens array

用p.ason Ⅲ型曲线拟合菜蚜种群空间分布型的初步研究

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生态学报 1985年第4期5卷 364-372页

作者：沈佐锐管致和 p.Dagnelie J.Deltour 北京农业大学植保系比利时Gembloux农学院

为寻求某些研究r-对策昆虫种群在其生境空间的概率分布的方法,我们用pesson Ⅲ型曲线(简称p-Ⅲ分布)拟合了菜蚜种群的9批抽样数据,它们是1981年在菜蚜种群发生期的不同日期抽取于北京郊区的秋白菜田间。我们可以通过mTLK方案将p-Ⅲ分... 详细信息

为寻求某些研究r-对策昆虫种群在其生境空间的概率分布的方法,我们用pesson Ⅲ型曲线(简称p-Ⅲ分布)拟合了菜蚜种群的9批抽样数据,它们是1981年在菜蚜种群发生期的不同日期抽取于北京郊区的秋白菜田间。我们可以通过mTLK方案将p-Ⅲ分布用于拟含9批样本中经过初步判断具有可拟性的3批数据: m——初值估计采用矩法,即以矩法估计p-Ⅲ分布的三个基本参数:平均数Ex,离势系数Cv和偏差系数Cs,做为下面将要进行的适线法之初始值。 T——p-Ⅲ分布的累积概率值p是由数表给出,具体做法是由给定的Cs值和抽样数据x的标准化变量φ值在数表中查得p值。 L——以适线法实现良好的拟合,该法是在计算机上通过一项最优化技术,即在Cv-Cs直角坐标系中产生一组正三角形(简称GRT法),以自动得到拟合的良好结果。 K——对拟合优度采用柯尔莫哥洛夫检验。拟合结果,3批样本中有两批可理论地拟合。该p-Ⅲ分布的概率密度函数为f(x)=βα/г(α)(x-b)α-1*exp(-β*(x-b)),(b≤x<∞)其中b=Ex*(1-2*Cv/Cs),α=4/Cs~2,β=2/(Ex*Cv*Cs),经过拟合后,b、α和β的取值便更加适合了。本文得出的结论是: 1.连续型概率分布可以被用来拟合某些r-对策昆虫种群的田间抽样数据,这是与传统的方法不同的。这里所谓传统的方法是指用于拟合k-对策昆

关键词：样本数据初步研究昆虫种群矩法估计矩法曲线拟合数值分析 p.ason 抽样数据空间分布型菜蚜