Permeability evaluation for artificial single rock fracture according to geometric aperture variation using electrical resistivity

A convenient approach was proposed by which to evaluate and monitor the permeability of a rock fracture by verifying the quantitative correlation between the electrical resistivity and permeability at laboratory scale.For this purpose,an electrical resistivity measurement system was applied to the laboratory experiments using artificial cells with the shape of a single rock fracture.Sixty experiments were conducted using rock fractures according to the geometry,aperture sizes,wavelengths,and roughness amplitudes.The overall negative relationship between the normalized electrical resistivity values and the aperture sizes directly linked with the permeability,was well fitted by the power-law function with a large determination coefficient(≈0.86).The effects of wavelength and roughness amplitude of the rock fracture on the electrical resistivity were also analyzed.Results showed that the electrical resistivity was slightly increased with decreasing wavelength and increasing roughness amplitude.An empirical model for evaluating the permeability of a rock fracture was proposed based on the experimental data.In the field,if the electrical resistivity of pore groundwater could be measured in advance,this empirical model could be applied effectively for simple,quick monitoring of the fracture permeability.Although uncertainty may be associated with the permeability estimation due to the limited control parameters considered in this research,this electrical resistivity approach could be helpful to monitor the rock permeability in deep underground facilities such as those used for radioactive waste repositories or forms of energy storage.

Development of large acceptance multi-purpose spectrometer in Korea for symmetry energy

The Rare Isotope Accelerator complex for ONline experiments(RAON) is a new radioactive ion beam accelerator facility under construction in Korea. The large acceptance multi-purpose spectrometer(LAMPS) is one of the experimental devices for nuclear physics at RAON. It focuses on the nuclear symmetry energy at supra-saturation densities. The LAMPS Collaboration has developed and constructed various detector elements, including a time projection chamber(TPC) and a forward neutron detector array. From the positron beam test, the drift velocity of the secondary electrons in the TPC is 5:3±0:2 cm/ls with P10 gas mixture, and the position resolution for pads with dimensions of 4×15 mm^2 is in the range of$ 0.6–0.8 mm, depending on the beam position. From the neutron beam test, the energy resolution of the prototype neutron detector module is determined to be 3.4%, and theposition resolution is estimated to be better than 5.28 cm.At present, the construction of the LAMPS neutron detector system is in progress.

Low-temperature synthesis of Fe_(2)(MoO_(4))_(3) nanosheets: A cathode for sodium ion batteries with kinetics enhancement

Sodium ion batteries (SIBs) are alternatives to lithium ion batteries (LIBs), and offer some significant benefits such as cost reduction and a lower environmental impact;however, to compete with LIBs, further research is required to improve the performance of SIBs. In this study, an orthorhombic Na super ionic conductor structural Fe_(2)(MoO_(4))_(3) nanosheet with amorphous-crystalline core-shell alignment was synthesized using a facile low-temperature water-vapor-assisted solid-state reaction and applied as a cathode material for SIBs. The obtained material has a well-defined three-dimensional stacking structure, and exhibits a high specific capacity of 87.8 mAh·g^(−1) at a current density of 1 C = 91 mA·g^(−1) after 1,000 cycles, which is due to the considerable contribution of extra surface-related reaction such as the pseudo-capacitive process. This material shows significantly improved cycling and rated behavior as well as enhanced performance under high- and low-temperature conditions, as compared to the same materials prepared by the conventional high-temperature solid-state reaction. This enhancement is explained by the unique morphology in combination with the improved kinetics of the electrochemical reaction due to its lower charge transfer resistance and higher sodium ion conductivity.

Detection of damage locations and damage steps in pile foundations using acoustic emissions with deep learning technology

The aim of this study is to propose a new detection method for determining the damage locations in pile foundations based on deep learning using acoustic emission data.First,the damage location is simulated using a back propagation neural network deep learning model with an acoustic emission data set acquired from pile hit experiments.In particular,the damage location is identified using two parameters:the pile location(PL)and the distance from the pile cap(DS).This study investigates the influences of various acoustic emission parameters,numbers of sensors,sensor installation locations,and the time difference on the prediction accuracy of PL and DS.In addition,correlations between the damage location and acoustic emission parameters are investigated.Second,the damage step condition is determined using a classification model with an acoustic emission data set acquired from uniaxial compressive strength experiments.Finally,a new damage detection and evaluation method for pile foundations is proposed.This new method is capable of continuously detecting and evaluating the damage of pile foundations in service.