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21.
The heating of solar coronal loops by the resonant absorption or phase-mixing of incident wave energy is investigated in the framework of 3D nonlinear magnetohydrodynamics (MHD) by means of numerical simulations. 相似文献
22.
Spectral emission lines created in the solar chromosphere — corona transition region show net red-shifts. It has been proposed that this may be the result of the return of spicular material. We simulate a spicule numerically using the rebound shock model and find that the resulting hydrodynamic evolution leads to a perceived up-flow in transition region spectral lines even though the average velocity in the line forming region is directed downward. The explanation for this apparent paradox is found in the correlation between density and velocity in the waves generated by the rebound shock spicule. 相似文献
23.
24.
Ni-Cu-Mn-Co高温钎料的工艺钎焊性分析 总被引:2,自引:0,他引:2
通过飞机导管高温钎焊时Ni-Cu-Mn-Co钎料传热特征的物理模拟,得到了钎焊间隙的控制要素。在运用经典电磁场理论进行热电磁耦合分析的基础上,制定了安装式感应钎焊工艺。 相似文献
25.
The formation of planetary systems is intimately tied to the question of the evolution of the gas and solid material in the
early nebula. Current models of evolution of circumstellar disks are reviewed here with emphasis on the so-called “alpha models”
in which angular momentum is transported outward by turbulent viscosity, parameterized by an dimensionless parameter α. A
simple 1D model of protoplanetary disks that includes gas and embedded particles is used to introduce key questions on planetesimal
formation. This model includes the aerodynamic properties of solid ice and rock grains to calculate their migration and growth.
We show that the evolution of the nebula and migration and growth of its solids proceed on timescales that are generally not
much longer than the timescale necessary to fully form the star-disk system from the molecular cloud. Contrary to a widely
used approach, planet formation therefore can neither be studied in a static nebula nor in a nebula evolving from an arbitrary initial condition. We propose a simple approach to both account for sedimentation
from the molecular cloud onto the disk, disk evolution and migration of solids.
Giant planets have key roles in the history of the forming Solar System: they formed relatively early, when a significant
amount of hydrogen and helium were still present in the nebula, and have a mass that is a sizable fraction of the disk mass
at any given time. Their composition is also of interest because when compared to the solar composition, their enrichment
in elements other than hydrogen and helium is a witness of sorting processes that occured in the protosolar nebula. We review
likely scenarios capable of explaining both the presence of central dense cores in Jupiter, Saturn, Uranus and Neptune and
their global composition.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
26.
刘雨棣 《西安航空技术高等专科学校学报》2003,21(1):17-19
介绍一种多功能CAN节点的电路结构及在工业中频感应加热设备控制现场总线中的应用。 相似文献
27.
28.
本文根据航天飞机防热瓦缝隙流动的特点,从二维定常不可压缩层流的 N-S方程出发,提出了一个简化流动模型,即缝隙的二维流动可近似当作两个准一维沟槽流动的线性迭加,由此给出了缝隙中的热流率与压力、压力梯度和缝隙宽度的变化规律,并利用现有的实验结果作了验证。 相似文献
29.
Ⅰ型极值分布的环境因子 总被引:1,自引:0,他引:1
本文通过对Ⅰ型极值分布的理论分析和环境因子的二因子法,分别得到了Ⅰ型极大值分布和Ⅰ型极小值分布的环境因子,它们与正态分布的环境因子^[1]具有相同的形式,对Ⅰ型极值分布的环境因子进行了点估计,提出了用环境因子进行数据转换和综合的步骤。 相似文献
30.