
GB/T 138632011激光辐射功率和功率不稳定度测试方法Test methods for laser radiation power and its instability
本标准规定了连续和准连续激光器的激光辐射连续功率以及连续激光器的输出功率不稳定度的测试方法。<br>本标准适用于各种连续和准连续激光器的激光辐射连续功率以及连续激光器输出功率不稳定度的测试。...
20220615 09:11:48浏览：4
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Laboratory study and analysis of the instability of alongshore currents
A laboratory experiment on the instability of alongshore currents was conducted on a plane beach with slope 1:40. Lowfrequency fluctuations of alongshore currents with the period of approximately 100 s were observed. The dominant frequency and amplitudes of the oscillations of alongshore currents were determined using the maximum entropy method and the regression method of trigonometric function. The variations across the beach crosssection of the oscillation amplitudes of the alongshore current were given. The linear shear instability theory was used to analyze the mechanism of the oscillation, and the calculated results agreed with measurements. This confirms that the observed fluctuation of alongshore currents is due to the shear instability of alongshore currents....
20201206 21:11:24浏览：31
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EXPERIMENTAL STUDY ON THE MECHANISM OF THE RICHTMYERMESHKOV INSTABILITY AT A GASLIQUID INTERFACE
The mechanism of the RichtmyerMeshkov instability was experimentally studied in a vertical rectangular shock tube. The velocity of the interface driven by the shock wave was measured by a selfdesigned measurement system, which consists of semiconductor lasers, signal amplification circuits, digital oscilloscope and computer. Tests were carried out at several shock wave Mach numbers. In addition, the movement of the interface and the variation of the mixed zone width with time were recorded by highspeed photography. The experimental results show that the interface velocity increases with the increase of the Mach number, and the distance of the interface's movement and the width of the mixed zone vary with time in a linear relationship....
20200915 12:28:59浏览：25
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Stability of stratified flow and slugging in horizontal gasliquid flow
A transient onedimensional twofluid model is proposed to investigate numerically the interfacial instability and the onset of slugging for liquidgas flow in a horizontal duct. In the present model, the effects of surface tension and transverse variations in dynamic pressure are taken into account. The evolution of interfacial disturbances is displayed and compared with the linear viscous KelvinHelmholtz stability analyses. It shows that interfacial wave is more instable due to the nonlinear effect. The model predicts well the stability limit of stratified flow in comparison with the experimental data, and also automatically tracks the onset of slugging. The results show that the initiation of hydrodynamic slugging is related to local interfacial instability. Based on the cycle of slugging, a model for slug frequency is presented, which predicts the trends of slug frequencies with gas/liquid flow rate well in comparison with the available data. The effects of physical properties on slugging have been examined. It is found that with the increase in the gas viscosity and liquid density the slugging would be inhibited, whereas, with the increase in liquid viscosity and gas density, the slugging can be promoted....
20200915 12:28:59浏览：28
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Instability of Two Interacting QuasiMonochromatic Waves in Shallow Water
The nonlinear interactions of waves with a doublepeaked power spectrum have been studied in shallow water. The starting point is the prototypical equation for nonlinear unidirectional waves in shallow water,i.e. The Korteweg de Vries equation. By means of a multiplescale technique two defocusing coupled Nonlinear Schr(o)dinger equations are derived. It is found analytically that plane wave solutions of such a system are unstable for small perturbations, showing that the existence of a new energy exchange mechanism which can influence the behavior of ocean waves in shallow water....
20200708 21:52:19浏览：31
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Analysis of the Harmfulness of WaterInrush from Coal Seam Floor Based on Seepage Instability Theory
A theory of seepage instability was used to estimate the harmfulness of waterinrush from a coal seam floor in a particular coal mine of the Mining Group, Xuzhou.Based on the stratum column chart in this coal mine, the distribution of stress in mining floors when the longwall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D).The permeability parameters of the coal seam floor are described given the relationship between permeability parameters.Strain and the waterinrushindices were calculated.The waterinrushindex was 67.2% when the working face was pushed to 100 m, showing that waterinrush is possible and it was 1630% when the working face was pushed to 150 m, showing that waterinrush is quite probable.The results show that as longwall mining is pushed along, the failure zone is enlarged, the strain increased, and fissures developed correspondingly, resulting in the formation of waterinrush channels.Accompanied by the failure of the strata, the permeability increased exponentially.In contrast, the nonDarcy flow β factor and the acceleration coefficient decreased exponentially, while the increase in the waterinrushindex was nearly exponential and the harmfulness of waterinrush in the coal mine increased accordingly....
20200612 16:18:35浏览：1388
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Catastrophic mechanism of coal and gas outbursts and their prevention and control
Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal bodies.We studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of inplane load and normal load,by using the catastrophe theory.The total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point (P,q) in the control space on the stability of rock plate is analyzed.The study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the inplane load and the normal load.When the gas in the coal bodies ahead of the mining face is predrained,the gas pressure can be reduced and the normal load q can be lowered.Consequently,disasters such as coal and gas outbursts can be effectively prevented....
20200612 16:16:37浏览：1380
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