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81.
圆锥形血管中的振荡发展流动 总被引:5,自引:2,他引:3
本文在小锥度角的假设下,研究了圆锥形血管的非定常振荡的发展流动问题.导得了相应的速度分布公式.分析表明,所有收缩的圆锥形血管的流动都是发展流动,而且锥度角对发展流动的影响随着锥度角的增大而增大. 相似文献
82.
This paper puts emphasis on the problem of the developing flows in the circular tube under oscillatory conditions. According
to the Navier-Stokes' equations and using the method of Bessel function of imaginary argument, a system of formulas is obtained.
Comparing the formulas obtained in this paper with Atabek's formulas, it may be seen that the former is simpler and more convenient.
When both the formulas obtained in this paper and Atabek's formulas are reduced to the representation of developed flows,
both of them are consistent. Numerical calculation results show that the computed results obtained in this paper are rather
consistent with both Atabek's computed results and the experimental results. 相似文献
83.
An experimental study on turbulent coherent structures near a sheared air-water interface 总被引:3,自引:0,他引:3
The turbulence structures near a sheared air-water interface were experimentally investigated with the hydrogen bubble visualization
technique. Surface shear was imposed by an airflow over the water flow which was kept free from surface waves. Results show
that the wind shear has the main influence on coherent structures under air-water interfaces. Low- and high- speed streaks
form in the region close to the interface as a result of the imposed shear stress. When a certain airflow velocity is reached,
“turbulent spots” appear randomly at low-speed streaks with some characteristics of hairpin vortices. At even higher shear
rates, the flow near the interface is dominated primarily by intermittent bursting events. The coherent structures observed
near sheared air-water interfaces show qualitative similarities with those occurring in near-wall turbulence. However, a few
distinctive phenomena were also observed, including the fluctuating thickness of the instantaneous boundary layer and vertical
vortices in bursting processes, which appear to be associated with the characteristics of air-water interfaces.
The project supported by the National Natural Science Foundation of China (Grant No.19672070) 相似文献
84.
85.
First total synthesis of (±)-13-hydroxyneocembrene ( 1 ), starting from 6-methyl-5-hepten-2-one ( 6 ) and geraniol ( 7 ), is described. The key steps are (i) the addition of sulfur-stabilized carbanion 12 to aldehyde 9 , (ii) the synthesis of 18 by using phase-transfer catalyzed coupling reaction, and (iii) low-valent titanium-induced intramolecular coupling of oxo aldehyde 3 to afford the target molecule after the final deprotection. 相似文献
86.
给定一自反的Banach空间X.在c∞函数芽环∈(X)中,任何在原点O∈X的实奇芽f,若其二阶Frechet导数f″(0)=T是一个Fredholm算子,则它同构于形如:1/2+g(v)的一个芽.如果代替g以一个与之同构的芽g1,显然得到一个与原来的芽同构的芽.然而,其逆是否真呢?本文将证明其逆命题亦真 相似文献
87.
Longchao Yao Chenyue Wu Yingchun Wu Linghong Chen Jun Chen Xuecheng Wu Kefa Cen 《Proceedings of the Combustion Institute》2019,37(3):2911-2918
Devolatilization is an important process in pulverized coal combustion because it affects the ignition, volatile combustion, and subsequent char burning and ash formation. In this study, high-speed digital in-line holography is employed to visualize and quantify the particle and volatile evolution during pulverized coal combustion. China Shanxi bituminous coal particles sieved in the range of 105–154 µm are entrained into a flat flame burner through a central tube for the study. Time-resolved observations show the volatile ejection, accumulation, and detachment in the early stage of coal combustion. Three-dimensional imaging and automatic particle extraction algorithm allow for the size and velocity statistics of the particle and stringy volatile tail. The results demonstrate the smaller particle generation and coal particle swelling in the devolatilization. It is found that the coal particles and volatiles accelerate due to the thermal buoyancy and the volatiles move faster than the coal particles. On average, smaller particles move faster than the larger ones while some can move much slower possibly because of the fragmentation. 相似文献
88.
选择藏族地区常用的四种藏药成方制剂安置精华散、当佐、仁青常觉和七十味珍珠丸作为研究对象,通过优化消化条件和测定条件,探索建立其铅、砷含量测定的湿法消化与流动注射氢化物发生-原子吸收光谱(FI-HAAS)联用分析方法,并对其铅砷含量进行精确测定。在优化的工作条件下,铅和砷的检出限分别为:0.067和0.012 μg·mL-1;定量限分别为:0.22和0.041 μg·mL-1;线性范围分别为:25~1 600 ng·mL-1(r=0.999 5),12.5~800 ng·mL-1(r=0.999 4);精密度(RSD)分别为:2.0%和3.2%;加标回收率范围分别为:98.00%~99.98%和96.67%~99.87%。四种藏药成方制剂的铅、砷含量测定结果如下,安置精华散中铅砷含量分别为:0.63~0.67和0.32~0.33 μg·g-1;当佐为:42.92~43.36和24.67~25.87 μg·g-1;仁青常觉为:1 611.39~1 631.36和926.76~956.52 μg·g-1;七十味珍珠丸为:1 102.28~1 119.27和509.96~516.87 μg·g-1。本研究建立了藏药成方制剂中铅、砷检测方法,并测定了四种藏药成方制剂中铅、砷含量,为其在临床安全有效使用提供了参考依据。 相似文献
89.
Y. Liu T. P. Chen M. Yang Z. H. Cen X. B. Chen Y. B. Li S. Fung 《Applied Physics A: Materials Science & Processing》2009,95(3):753-756
Electroluminescence (EL) from Al-rich AlN thin films grown on p-type Si substrate by radio frequency (RF) magnetron sputtering
has been observed at room temperature. The light-emitting structure based on the thin films can be driven by an electrical
pulse as short as 10−5 s. No obvious change in the light emission intensity was observed after 106 pulse cycles. It has been found that the light emission intensity increases with the Al concentration. It is shown that the
phenomenon is due to the enhancement of the percolative conduction via the Al nanocrystals distributed in the AlN matrix as
a result of the increase in Al concentration. 相似文献
90.
采用ZYGO MarkIII-GPI数字波面干涉仪对以K9玻璃为基底的电子束蒸发方法制备的HfO2薄膜中的残余应力进行了研究,讨论了沉积速率、氧分压这两种工艺参量对HfO2薄膜残余应力的影响.实验结果表明:在所有的工艺条件下,薄膜的残余应力均为张应力;随着沉积速率的升高,氧分压的减小,薄膜的堆积密度逐渐增大,而残余应力呈减小趋势.同时用X射线衍射技术测量分析了不同工艺条件下HfO2薄膜的晶体结构,探讨了HfO2薄膜晶体
关键词:
残余应力
2薄膜')" href="#">HfO2薄膜
沉积速率
氧分压 相似文献