Analysis of Seismic Anisotropy Parameters for Sedimentary Rocks and Strata

The most prominent feature of sedimentary basins is often its layered structure. The effective elastic properties of the layered media are anisotropic. Mudstones account for most of the volume of the sedimentary rocks, and the elastic properties are usually approximated by transverse isotropy. Therefore, seismic anisotropy is very important for exploration geophysics. Study of the relationships between the anisotropy parameters may supply very useful constraints for the estimation of the anisotropy parameters and be critically important for simplification of the problems in anisotropic-seismic-data processing and interpretation. Based on the theory of anisotropic elasticity and observation from the mechanical measurements on mudstones, tight physical constraints on c13 by c11, c33, and c66 are derived. The physical constraints on c13 are used to evaluate the quality control of the laboratory anisotropy-measurement data from the literature. It is found that there are significant uncertainties in the determination of c13 and delta. When the measurement data of bad quality control are identified and discarded, the intrinsic relationship between c13 and other TI elastic constants, and the relationship between delta and the other Thomsen parameters are revealed. Considering the difficulty and significant uncertainty in laboratory anisotropy-measurements, a practical and robust method for laboratory determination of c13 and delta is proposed. Based on laboratory ultrasonic-measurement data of sedimentary rocks and using Monte Carlo simulation and Backus averaging, the layering effects on seismic anisotropy are analyzed. If the sedimentary strata consist of fully brine-saturated isotropic rocks, delta is usually negative; and if the sedimentary strata are gas bearing, delta increases. For an effective TI medium consisting of isotropic layers, c13 can be determined by other TI elastic constants; and therefore, delta can be predicted from the other Thomsen parameters with confidence. The layering effects on seismic anisotropy at the high-frequency limit are compared with those at the low-frequency limit. Relative to the Backus averaging, ray theory usually underestimates the Thomsen parameters epsilon and gamma and overestimates delta. For the sedimentary strata consisting of isotropic layers, the differences are very significant.Earth and Atmospheric Sciences, Department o

Review of Aircraft Vibration Environment Prediction Methods

AbstractAircraft vibration response environment prediction, which is adopted in aircraft initial vehicle development, has not been got enough attention and wide application yet. This paper briefly reviews theoretical and engineering significance of aircraft vibration response environment prediction firstly. Then the paper summarizes the main aircraft vibration response environment prediction methods and indicates their advantages, disadvantages and applicability scopes, including extrapolation of similar structure, theory analysis and analytical solution of differential dynamical equation, statistical parameter modeling, simulation calculation modeling and machine learning. Finally, the paper points out that uncertainty and non-linear structures, nonstationary signal analysis and complex vibration environment response prediction are major problems for aircraft vibration response prediction and directions for future research work

Modeling of effective pressure effect on porous reservoir rocks

Summary Effective pressure effect on porous reservoir formation is one of the most important factors contributing to time-lapse seismic attribute changes. Our research shows that the existing commonly used models tend to overestimate effective pressure effect at high effective pressure, which might cause significant misinterpretation of 4D seismic data. Based on analysis of a large quantity of lab data, a new model that is simpler and has clearer physical meaning was brought up in this study. This new model should be sufficient to describe the effective pressure effect on various porous reservoir rocks

Human umbilical cord mesenchymal stem cells inhibit coronary artery injury in mice with Lactobacillus casei wall extract-induced kawasaki disease

Kawasaki disease (KD) is a serious threat to children’s physical and mental health. This study investigated the effect of human umbilical cord mesenchymal stem cells (hUC-MSCs) on KD coronary arteritis induced by Lactobacillus casei wall extract (LCWE) in an animal model. Sixty BALB/C mice were randomly assigned to three groups (n = 20 mice per group). Mice in the model and stem-cell groups were injected with LCWE, while the control-group mice were injected with phosphate-buffered saline (PBS) for 2 days. At day 16 of modeling, PBS was injected into the control and model-group mice, and hUC-MSCs were injected into the stem-cell group mice for 10 days. At days 4, 15, 26, and 32 of modeling, echocardiography and histopathology were performed to examine the cardiac structure and the morphological changes in the coronary arteries in each group. B-ultrasonography showed that 57.5% (23/40) of the mice had coronary artery lesions, of which 5% (2/40) had right coronary artery aneurysm, 27.5% (11/40) had coronary artery wall thickening, a widened inner diameter of the main artery of the left coronary artery, and thickened intima. Histopathology showed slight swelling of the epicardium of the aortic valve, mitral valve, right ventricle, and atrium, as well as scattered infiltration of a few neutrophils. Following hUC-MSCs intervention treatment, B-ultrasonography showed a decrease in the main coronary artery diameter, while histopathology showed no obvious vascular inflammatory reaction or other obvious abnormalities. These findings highlight that hUC-MSCs inhibit coronary artery injury in animal models of KD induced by LCWE

Theoretical validation of fluid substitution by Hashin-Shtrikman bounds

Summary In this study, we find that variation of Hashin-Shtrikman bounds caused by pore fluid change is governed by the Biot-Gassmann theory. Also, we have shown that it is generally valid to assume that the relative position of the effective moduli of a rock within the Hashin-Shtrikman bounds is not affected by pore fluid change. Thus HashinShtrikman bounds can be used as a valid fluid substitution tool. Comparing with Gassmann fluid substitution, the velocity predicted by Hashin-Shtrikman bounds generally fits better with the measured data since part of the dispersion is included, and it can be used as a more general pore infill substitution tool

Review of Statistical Induction Analysis Methods on Aircraft Vibration Test Data

AbstractThe development of reliability and environment vibration test conditions depends on the processing of vibration test data. Because of randomness of vibration sources and different purposes of reliability testing and environmental testing, testing data should be dealt with different methods. This paper summarizes various statistical induction analysis methods for aircraft vibration test data, and indicates their advantages, disadvantages and applicability scope. Statistical analysis method on small sample, time-varying structures, non-stationary data processing and vibration environment prediction are the further research directions

The Role of Gut Microbiota in the Skeletal Muscle Development and Fat Deposition in Pigs

Pork quality is a factor increasingly considered in consumer preferences for pork. The formation mechanisms determining meat quality are complicated, including endogenous and exogenous factors. Despite a lot of research on meat quality, unexpected variation in meat quality is still a major problem in the meat industry. Currently, gut microbiota and their metabolites have attracted increased attention in the animal breeding industry, and recent research demonstrated their significance in muscle fiber development and fat deposition. The purpose of this paper is to summarize the research on the effects of gut microbiota on pig muscle and fat deposition. The factors affecting gut microbiota composition will also be discussed, including host genetics, dietary composition, antibiotics, prebiotics, and probiotics. We provide an overall understanding of the relationship between gut microbiota and meat quality in pigs, and how manipulation of gut microbiota may contribute to increasing pork quality for human consumption

Stress transfer of single yarn drawing in soft fabric studied by micro Raman spectroscopy

The load transfer behavior of the Kevlar 49 soft fabric commonly used for bulletproof clothing in yarn drawing test was investigated by micro-Raman spectroscopy. The linear relationship between Raman shift and axial stress of single yarn was established. The axial stresses of warp yarn in soft fabric with and without preload condition were obtained by Raman measurement under tension, and they conform to the theoretical prediction using a yarn-drawing model with interface debonding. The experimental results show that the drawing load is transferred along the yarn from the beginning to the end. In the process of straightening the yarn, the interfacial friction shear stress caused by the yarn relative sliding remains almost constant, and the length of straightened yarn becomes longer as the external load increases. The preload plays a role in inhibiting the straightening of the yarn, which is helpful for the load transfer in the sliding friction section

A state-of-the-art review on passivation and biofouling of Ti and its alloys in marine environments

High strength-to-weight ratio, commendable biocompatibility and excellent corrosion resistance make Ti alloys widely applicable in aerospace, medical and marine industries. However, these alloys suffer from serious biofouling, and may become vulnerable to corrosion attack under some extreme marine conditions. The passivating and biofouling performance of Ti alloys can be attributed to their compact, stable and protective films. This paper comprehensively reviews the passivating and biofouling behavior, as well as their mechanisms, for typical Ti alloys in various marine environments. This review aims to help extend applications of Ti alloys in extremely harsh marine conditions