Effect of Water Saturation on Gas-Accessible Effective Pore Space in Gas Shales

AbstractThe existence and content of water will certainly affect the effective pore space of shales and therefore is a key point for the evaluation of in-situ gas content and gas flow capacity of shale reservoirs. In order to reasonably evaluate the gas storage and flow capacities of water-bearing shale reservoirs, the effect of water on the effective pore space of shales needs to be understood. In this study, the Upper Permian Longtan shale in the southeastern Sichuan Basin, China, was selected as an example to conduct nuclear magnetic resonance cryoporometry (NMRC) measurements under different water saturation levels. The gas-accessible effective pore spaces in shales under different water saturation levels were quantified, and the effect of water saturation on gas-accessible effective pore space in shales was investigated. The results show that water plays an important role in the gas-accessible effective pore space of shales. When the Longtan shale increases from a dry state to a water saturation of 65%, 75%, and 90%, the gas-accessible effective pore volume decreases by 35%-60% (average 46.3%), 50%-70% (average 58.8%), and 65%-82% (average 75.8%), respectively. Water has an effect on the gas-accessible effective pore space regardless of pore size, and the effect is the strongest in the 4-100 nm range, which may be mainly due to the high content of clay minerals in the Longtan shale. Our studies are of important theoretical significance and application prospects for accurately evaluating the gas-accessible effective pore space of gas shales under actual geological conditions

An Improved Discriminative Tracking Algorithm Based on Spatial Information and Model Updating

Tracking object occluded partially is a difficult problem in video surveillance. Many previous tracking methods fail to track occlusion objects robustly. In this paper, we propose an improved discriminative tracking algorithm based on bag of patches to cope with the partial occlusion as well as drift. In the proposed method, the spatial information is introduced to build the object appearance model and construct the confidence map from three different aspects, which directly determine the ultimate tracking effect. In addition, the context information of the small image patches is also applied. In order to adapt to the variance of the environment, an online model updating strategy is proposed. Contrasting experimental results on several real world scenarios show that our proposed approach can handle partial occlusion and recover from drift. Comparing with four stat-of-the-art tracking methods, our proposed method has better tracking performance

Survey on the hunting stability of High-speed Trains

The long-term service safety and reliability of high-speed trains are the primary guarantee for the construction of high-speed trains. Self-excited hunting movement is a unique form of instability for rail vehicles. In order to guarantee the hunting stability, high speed and safety traffic of high speed trains, on the basis of the theoretical research methods of high speed train hunting unstability, the main research methods and their deficiency are summarized, as well as the recent research hotspots. The research of non-smooth bifurcation and asymmetric operation stability is prospected. Without considering the nonlinear characteristics of the vehicle, the characteristic root method, the routh-hurwitz criterion method and the minimum damping coefficient can be used to analyze the certainty stability of high speed trains. When the wheel-rail contact and the nonlinear characteristics of the suspension system must be considered, the method of eigenvalue change, QR algorithm, binary method, center manifold method, shooting method and continuation algorithm can be used. In addition, stochastic nonlinear dynamics hamilton theory, monte-carlo method, semi-implicit milstein stochastic numerical simulation and small data quantity can be used to analyze random stability, random bifurcation and its types. Generally speaking, stochastic stability and random bifurcation can get closer to the real conditions of the critical speed of instability because of considering their own structure parametric excitation and wheeltrack contact irregularity excitation. This aspect of theoretical research and experimental research has been paid more attention to by researchers, and has become a hot topic of the hunting stability of high speed trains

A new method for high speed and smooth transfer of robot motion trajectory

In the process of the robot practical working, the change of motion direction of trajectory is inevitable. When the direction changes dramatically, the sharp angle between adjacent trajectories, which can generate the vibration of robot, affects the service life of the robot. In order to deal with the sharp angle between adjacent trajectories, we propose a method which can deal with the sharp angle transferring by inserting transition arc, which is called position level, to solve the trajectory speed control problem. We analyze three basic analytic trajectories—space line, space arc, and space parabola—and present the formula for calculating the parameters of circular-arc-related parameters and propose the implementation process of algorithm of robot system. Through the simulation and experiment, this method can solve the sharp angle trajectory transfer problem effectively, increase the transfer speed dramatically, and reduce the vibration of robot’s mechanical structure

Target reliability indices for long geotechnical embankment slopes

10.1080/19648189.2020.1722247European Journal of Environmental and Civil Engineering2641622-163

Ion-Radical Mediated Multi-Color Ultra-Long Afterglow Materials

Pure organic persistent room temperature phosphorescence (RTP) has shown great potential in numerous applications, ranging from information encryption and display technologies to bio-applications and beyond. In this work, a suite of multi-color long-lived RTP materials featuring distinct afterglow emissions was constructed using an ion-radical mediated approach. b[c]p/MeBPO emitted a vivid yellow afterglow centered at 560 nm with an impressively long lifetime of 860.01 ms. While compound b[a]a exhibited a near-infrared (NIR) afterglow (τ = 215.96 ms) after doping into the matrix. The transient absorption spectroscopy investigations disclosed that the observed afterglow phenomenon was fundamentally tied to the generation of radical ions rather than the exciplex. These radical ions resulted from the reduction quenching process of the triplet excited state of compound BPO by the ground state of the doping agent. A novel evaluation methodology was devised, rooted in Marcus theory, to gauge the potential of a specific dopant-matrix combination towards generating pronounced afterglow. According to this framework, the enhancement of the afterglow is directly proportional to the decrease in the activation energy (ΔG≠) associated with the electron transfer reaction occurring between the dopant and the matrix. Notably, when the ΔG≠ surpasses 30 kcal/mol, no observable afterglow occurs, as higher ΔG≠ values significantly impede the electron transfer reaction between the two components. Furthermore, the system exhibits exceptional sensitivity, with the dopant as low as 0.02‰ molar ratio between the dopant and the host material. This remarkable dependence of afterglow intensity on the dopant concentration renders the bi-component RTP system highly promising for applications requiring ultra-high sensitivity and broad-spectrum detection capabilities