Micro pore characteristics of Luohe aquifer sandstone in Binchang Mining Area typical roof water hazard mines

The mining of Huanglong Coalfield faces a serious threat from roof sandstone water disaster of the extremely thick Luohe Formation. A laboratory study on the microscopic pore characteristics of the sandstone of the Luohe Formation in the Gaojiapu Coal Mine, Binchang Mining Area were carried out using various methods. XRD diffraction, casting thin sections, and scanning electron microscopy were combined to study the pore types of the sandstone particles. Overburden porosimeter was used to illustrate the variation characteristics of porosity and permeability under different confining pressures. High-pressure mercury injection and nuclear magnetic resonance techniques were used to characterize the pore-throat radius of the sandstone core, and X-ray three-dimensional CT scanning was used to quantitatively characterize sandstone pores larger than 9 μm. The results show that, ①the sandstone particles of medium-grained sandstone are larger, and the pore types are mainly residual intergranular pores with a small amount of intergranular dissolved pores, while the particles of fine-grained sandstone are smaller, and the intergranular pores are mostly filled with clay minerals, secondary dissolution intergranular pores, and a smaller degree of pore development.; ②The pore throat radius of large pores in medium-grained sandstone ranges from 0.61 to 4.94 μm, with a cumulative distribution frequency of 48%, while in fine-grained sandstone, the pore-throat radius ranges from 0.188 to 0.683 um, with a cumulative distribution frequency of 47%, indicating that medium-grained sandstone has larger pore-throat radius, which are more conducive to groundwater storage and migration.; ③CT scanning shows that the average surface porosity of medium-grained sandstone is 7.081%, and that of fine grained sandstone is 2.032%. The highly developed macropores (equivalent pore diameter > 180 μm) and micropores contribute to a higher surface porosity. Combined with a larger pore throat radius, the medium-grained sandstone presents a higher permeability. The microscopic pore characteristics of the two types of sandstone are consistent with the on-site evaluation result of the water yield propertyof the corresponding aquifer. The research findings can provide a basic reference for the prevention and control of water disasters from the sandstone roof of the Luohe Formation

A new post-frac evaluation method for shale gas wells based on fracturing curves

AbstractPost-fracturing evaluation by using limited data is of great significance to continuous improvement of the fracturing programs. In this paper, a fracturing curve was divided into two stages (i.e., prepad fluid injection and main fracturing) so as to further understand the parameters of reservoirs and artificial fractures. The brittleness and plasticity of formations were qualitatively identified by use of the statistics of formation fracture frequency, and average pressure dropping range and rate during the prepad fluid injection. The composite brittleness index was quantitatively calculated by using the energy zones in the process of fracturing. It is shown from the large-scale true triaxial physical simulation results that the complexity of fractures is reflected by the pressure fluctuation frequency and amplitude in the main fracturing curve, and combined with the brittleness and plasticity of formations, the fracture morphology far away from the well can be diagnosed. Well P, a shale gas well in SE Chongqing, was taken as an example for post-fracturing evaluation. It is shown that the shale beds are of stronger heterogeneity along the extension directions of horizontal wells, and with GR 260 API as the dividing line between brittleness and plasticity in this area, complex fracture systems tend to form in brittleness-prone formations. In Well P, half of the fractures are single fractures, so it is necessary to carry out fine subsection and turnaround fracturing so as to improve development effects. This paper provides a theoretical basis for improving the fracturing well design and increasing the effective stimulated volume in this area

SAM: a unified self-adaptive multicompartmental spiking neuron model for learning with working memory

Working memory is a fundamental feature of biological brains for perception, cognition, and learning. In addition, learning with working memory, which has been show in conventional artificial intelligence systems through recurrent neural networks, is instrumental to advanced cognitive intelligence. However, it is hard to endow a simple neuron model with working memory, and to understand the biological mechanisms that have resulted in such a powerful ability at the neuronal level. This article presents a novel self-adaptive multicompartment spiking neuron model, referred to as SAM, for spike-based learning with working memory. SAM integrates four major biological principles including sparse coding, dendritic non-linearity, intrinsic self-adaptive dynamics, and spike-driven learning. We first describe SAM’s design and explore the impacts of critical parameters on its biological dynamics. We then use SAM to build spiking networks to accomplish several different tasks including supervised learning of the MNIST dataset using sequential spatiotemporal encoding, noisy spike pattern classification, sparse coding during pattern classification, spatiotemporal feature detection, meta-learning with working memory applied to a navigation task and the MNIST classification task, and working memory for spatiotemporal learning. Our experimental results highlight the energy efficiency and robustness of SAM in these wide range of challenging tasks. The effects of SAM model variations on its working memory are also explored, hoping to offer insight into the biological mechanisms underlying working memory in the brain. The SAM model is the first attempt to integrate the capabilities of spike-driven learning and working memory in a unified single neuron with multiple timescale dynamics. The competitive performance of SAM could potentially contribute to the development of efficient adaptive neuromorphic computing systems for various applications from robotics to edge computing

A4. En tekst om å ville â og ikke ville være vanlig

People living outside conventional families have to grapple with the concept of ordinariness. If their lives are not seen as ordinary intimate lives, what life choices and narrative choices do they have in claiming and responding to this extraordinariness? The article explores ordinariness as a theoretical and cultural concept, and shows how both theoretical approaches and self-narratives can have very different as well as ambivalent attitudes towards ordinariness

Cloud Point Extraction for the Determination of Trace Amounts of Cobalt in Water and Food Samples by Flame Atomic Absorption Spectrometry

A cloud point extraction (CPE) procedure which was developed for the separation and preconcentration of trace amounts of cobalt is combined with �ame atomic absorption spectrometry (FAAS) to determine trace amounts of cobalt in water and food samples. e procedure is based on the formation of the hydrophobic complex between Co(II) and 4-methoxy-2-sulfobenzenediazoaminoazo-benzene (MOSDAA) followed by its extraction into a Triton X-114 surfactant-rich phase. e parameters such as pH of sample, concentrations of MOSDAA and Triton X-114, equilibrium temperature, and equilibrium time, which affect both complexation and extraction, are optimized. Under the selected optimum conditions, the preconcentration of 10.0 mL, 0.1 g mL −1 Co(II) solution results in a limit of detection of 0.47 ng mL −1 (3 ) and an enrichment factor of 19. A relative standard deviation of 2.78% ( , 1 g mL −1 ) for the determination of Co(II) is obtained. e proposed method was applied for the determination of trace amounts of cobalt in river water and millet samples with satisfactory results

Study on Strain Characterization and Failure Location of Rock Fracture Process Using Distributed Optical Fiber under Uniaxial Compression

A rock fracture test is a very important method in the study of rock mechanics. Based on the Mechanics Test System (MTS), the dynamic strain response of the failure process of cylindrical granite specimens under uniaxial compression was observed by using distributed optical fiber strain sensors. Two groups of tests were designed and studied for rock sample fracturing. The main comparison and analysis were made between the distributed optical fiber testing technology and the MTS testing system in terms of the circumferential strain response curve and the evolution characteristics of strain with time. The strain characterization of distributed optical fiber in the process of rock fracturing was obtained. The results show that the ring strains measured by the distributed optical fiber sensor and the circumferential strain gauge were consistent, with a minimum ring strain error of 1.27%. The relationship between the strain jump or gradient band of the distributed optical fiber and the crack space on the sample surface is clear, which can reasonably determine the time of crack initiation and propagation, point out the location of the rock failure area, and provide precursory information about rock fracture. The distributed optical fiber strain sensor can realize the linear and continuous measurement of rock mass deformation, which can provide some reference for the study of macro damage evolution and the fracture instability prediction of field engineering rock mass

Numerical Study of Damage to Rock Surrounding an Underground Coal Roadway Excavation

In coal mines, underground roadways are required to transport coal and personnel. Such tunnels can become unstable and hazardous. This study simulates deformation and damage in the rock surrounding a shallow coal seam roadway using particle flow code. A numerical model of particle flow in the surrounding rock was constructed based on field survey and drilling data. Microcharacteristic indices, including stress, displacement, and microcrack fields, were used to study deformation and damage characteristics and mechanisms in the surrounding rocks. The results show that the stress within the rock changed gradually from a vertical stress to a circumferential stress pattern. Stress release led to self-stabilizing diamond-shaped and X-shaped tensile stress distribution patterns after the excavation of the roadway. Cracking increased and eventually formed cut-through cracks as the concentrated stress transferred to greater depths at the sides, forming shear and triangular-shaped failure regions. Overall, the roof and floor were relatively stable, whereas the sidewalls gradually failed. These results provide a reference for the control of rock surrounding roadways in coal mines