超声波流量检测系统误差的温度修正研究

介绍时差法超声波流量检测液压系统的工作原理,针对液压系统工作过程中温度变化影响系统测量精度的问题,通过在实验室中建立温度—声速模型检测两种常用液压油的工作特性,采用多次测量取平均值的方法记录实验结果,根据实验数据利用非线性回归分析理论推导出两种常用液压油的温度—声速关系,为降低温度变化对超声波流量检测系统的影响、提高系统测量精度提供一种参考。

Ultrasonic elastic characteristics of five kinds of metamorphic deformed coals under room temperature and pressure conditions

The calibration of the elastic characteristics of deformed coals is essential for seismic inversion of such units, because the prediction of coal deformation is essential for both mining safety and methane production. Therefore, many samples of broken and mylonitic deformed coal were tested with ultrasonic waves in the laboratory. These samples came from four mining areas: the Huainan, Pingdingshan, Hebi and Jiaozuo coal mines, which present five different metamorphic ranks shown as cylinders striking across circular limits of steel. Under normal pressures and temperatures, ultrasonic P- and S-wave tests show that the velocities, quality factors, and elastic moduli of the deformed coals were greatly reduced compared with undeformed coals. Also, some correlation was found between the P- and S-wave velocities in the deformed coals. However, there is no evidence of linear correlations between velocity and density, velocity and quality factor, or the quality factors of P- and S-waves. Compared with the elastic characteristics of undeformed coals, such as P- and S-wave velocity ratios or Poisson's ratio, those of deformed coals generally decrease and the P-wave quality factors are less than those of S-waves. Moreover, the analysis of the relationship between pore structure and elastic modulus shows a better correlation between the P- and S-wave velocities and effective porosity, pore volume and specific surface area. Also, there are similar relationships between the pore structure and the Young's and shear moduli. However, there are no such correlations with other moduli. Correlations between these elastic moduli, pore structure, coal rank and density were not found for the various samples of deformed coals, which is consistent with only structural destruction occurring in the deformed coals with other physical properties remaining unchanged. The experimental results show that it is possible to predict the deformation of coals with multi-component seismic elastic inversion.

Improved Speed and Shape of Ion-Acoustic Waves in a Warm Plasma

The basic set of fluid equations can be reduced to the nonlinear Kortewege-de Vries(KdV)and nonlinear Schro¨dinger(NLS)equations.The rational solutions for the two equations has been obtained.The exact amplitude of the nonlinear ion-acoustic solitary wave can be obtained directly without resorting to any successive approximation techniques by a direct analysis of the given field equations.The Sagdeev’s potential is obtained in terms of ion acoustic velocity by simply solving an algebraic equation.The soliton and double layer solutions are obtained as a small amplitude approximation.A comparison between the exact soliton solution and that obtained from the reductive perturbation theory are also discussed.

Effects of chemical,mineralogical,and temperature variations on the density and bulk sound velocity of the bottom lower mantle

In this study, we have modeled the density （p） and bulk sound velocity （V.） profiles of the bottom lower mantle using the experimental thermal equation of state （EoS） parameters of lower-mantle minerals, including bridgmanite, ferropericlase, CaSiO3-perovskite, and post-perovskite. We re-evaluated the literature pressure-volume-temperature relationships of these minerals using a self-consistent pressure scale in order to avoid the long-standing pressure scale problem and to provide more reliable constraints on the thermal EoS parameters. With the obtained thermal EoS parameters, we have constructed the p and V. profiles of the bottom lower mantle in different composition, mineralogy, and temperature models. Our modelling results show that the variations of chemistry, mineralogy, and temperature and AI enrichment at the bottom lower mantle can cause an increase have different seismic signatures from each other. The Fe in p but greatly lower V.. A change in mineralogy needs to be considered with the lateral variation in temperature. The cold slabs will be shown as denser regions compared to the normal mantle because of the combined effect of a lower temperature and the presence of a denser post-perovskite at a shallower depth, whereas the hot regions will have a 1-2% lower p than the normal mantle. V, of both cold slabs and hot regions will he lower than the normal mantle when bridgmanite is the dominant phase in the normal mantle, yet they will be greater once bridgmanite transforms into post-perovskite in the normal mantle. Our modeling also shows that the presence of a （Fe, Al）-enriched bridgmanite thermal pile above the core-mantle boundary will exhibit a seismic signature of enhancedp and V., but a reduced Vs, which is consistent with the observed seismic anomalies in the large-low-shear-velocity-provinces （LLSVPs）. The existence of such a （Fe, A1）-enriched bridgmanite thermal pile thus can help to understand the origin of the LLSVPs. These results provide new insights for the chemical and structure of the deepest lower mantle.