Back Analysis of Rock Hydraulic Fracturing by Coupling Numerical Model and Computational Intelligent Technology

Hydraulic fracturing is widely used to determine in situ stress of rock engineering. In this paper we propose a new method for simultaneously determining the in situ stress and elastic parameters of rock. The method utilizing the hydraulic fracturing numerical model and a computational intelligent method is proposed and verified. The hydraulic fracturing numerical model provides the samples which include borehole pressure, in situ stress, and elastic parameters. A computational intelligent method is applied in back analysis. A multioutput support vector machine is used to map the complex, nonlinear relationship between the in situ stress, elastic parameters, and borehole pressure. The artificial bee colony algorithm is applied in back analysis to find the optimal in situ stress and elastic parameters. The in situ stress is determined using the proposed method and the results are compared with those of the classic breakdown formula. The proposed method provides a good estimate of the relationship between the in situ stress and borehole pressure and predicts the maximum horizontal in situ stress with high precision while considering the influence of pore pressure without the need to estimate Biot’s coefficient and other parameters

Lateralization Value of Low Frequency Band Beamformer Magnetoencephalography Source Imaging in Temporal Lobe Epilepsy

Objective: In presurgical evaluation of temporal lobe epilepsy (TLE), selection of the resection side is challenging when bilateral temporal epileptiform discharges or structural abnormalities are present. We aim to evaluate the lateralization value of beamformer analysis of magnetoencephalography (MEG) in TLE.Methods: MEG data from 14 TLE patients were analyzed through beamformer analysis. We measured the hemispherical power distribution of beamformer sources and calculated the lateralization index (LI). We calculated the LI at multiple frequencies to explore the frequency dependency and at the delta frequency to define laterality. LI values ranging from −1 to −0.05 indicated right hemispheric dominance. LI values ranging from 0.05 to 1 indicated left hemispheric dominance. LI values ranging from −0.05 to 0.05 defined bilaterality. We measured the power of beamformer sources with a 9-s duration to explore time dependency.Results: The beamformer analysis showed that 10/14 patients had power dominance ipsilateral to resection. The delta frequency band had a higher lateralization value than other frequency bands. A time-dependent power fluctuation was found in the delta frequency band.Conclusions: MEG beamformer analysis, especially in the delta band, might efficiently provide additional information regarding lateralization in TLE

Back Analysis of Rock Hydraulic Fracturing by Coupling Numerical Model and Computational Intelligent Technology

Hydraulic fracturing is widely used to determine in situ stress of rock engineering. In this paper we propose a new method for simultaneously determining the in situ stress and elastic parameters of rock. The method utilizing the hydraulic fracturing numerical model and a computational intelligent method is proposed and verified. The hydraulic fracturing numerical model provides the samples which include borehole pressure, in situ stress, and elastic parameters. A computational intelligent method is applied in back analysis. A multioutput support vector machine is used to map the complex, nonlinear relationship between the in situ stress, elastic parameters, and borehole pressure. The artificial bee colony algorithm is applied in back analysis to find the optimal in situ stress and elastic parameters. The in situ stress is determined using the proposed method and the results are compared with those of the classic breakdown formula. The proposed method provides a good estimate of the relationship between the in situ stress and borehole pressure and predicts the maximum horizontal in situ stress with high precision while considering the influence of pore pressure without the need to estimate Biot’s coefficient and other parameters

Multimodal non‐invasive evaluation in MRI‐negative epilepsy patients

Abstract Presurgical evaluation is still challenging for MRI‐negative epilepsy patients. As non‐invasive modalities are the easiest acceptable and economic methods in determining the epileptogenic zone, we analyzed the localization value of common non‐invasive methods in MRI‐negative epilepsy patients. In this study, we included epilepsy patients undergoing presurgical evaluation with presurgical negative MRI. MRI post‐processing was performed using a Morphometric Analysis Program (MAP) on T1‐weighted volumetric MRI. The relationship between MAP, magnetoencephalography (MEG), scalp electroencephalogram (EEG), and seizure outcomes was analyzed to figure out the localization value of different non‐invasive methods. Eighty‐six patients were included in this study. Complete resection of the MAP‐positive regions or the MEG‐positive regions was positively associated with seizure freedom (p = 0.028 and 0.007, respectively). When an area is co‐localized by MAP and MEG, the resection of the area was significantly associated with seizure freedom (p = 0.006). However, neither the EEG lateralization nor the EEG localization showed statistical association with the surgical outcome (p = 0.683 and 0.505, respectively). In conclusion, scalp EEG had a limited role in presurgical localization and predicting seizure outcome, combining MAP and MEG results can significantly improve the localization of epileptogenic lesions and have a positive association with seizure‐free outcome. Plain Language Summary Due to the lack of obvious structure abnormalities on neuroimaging examinations, the identification of epilepsy lesions in MRI‐negative epilepsy patients can be difficult. In this study, we intended to use non‐invasive examinations to explore the potential epileptic lesions in MRI‐negative epilepsy patients and to determine the results accuracy by comparing the neuroimaging results with the epilepsy surgery outcomes. A total of 86 epilepsy patients without obvious structure lesions on MRI were included, and we found that the combinations of different non‐invasive examinations and neuroimaging post‐processing methods are significantly associated with the seizure freedom results of epilepsy surgery

Three-Dimensional Nitrogen-Doped Carbon Nanoskeleton Cladded with a Graphitic C₃N₅ Nanolayer as a Sulfur Host for Lithium–Sulfur Batteries

Active site and morphology engineering are essential for the electrochemical performance of carbon-based nanomaterials. In this study, we proposed a three-dimensional (3D) N-doped carbon skeleton cladded with a g-C3N5 nanolayer (denoted as CS/U–C3N5–K) as a sulfur host for lithium–sulfur batteries (LSBs). A 3D N-doped carbon nanoskeleton (CS/U) was presynthesized by carbonizing mixed precursors composed of chitosan and urea. The g-C3N5 nanolayer was cladded over the carbon nanoskeleton via pyrolyzing a mixture of CS/U and 3-amino-1,2,4-triazole. KOH was also introduced into the mixture to generate additional intrinsic carbon defects in CS/U–C3N5–K. The porous graphitic carbon nanoskeleton ensured good electrical conductivity and sulfur-based species penetration. The abundant nitrogen-based moieties in the carbon nanoskeleton and g-C3N5 nanolayer, as well as intrinsic carbon defects, can redistribute the electrons and offer massive active sites for the sulfur redox reaction process. The as-obtained CS/U–C3N5–K nanocomposite delivered ameliorative sulfur redox reaction kinetics, including reduced charge transfer resistance, reasonable redox polarization, enhanced LiPS chemisorption and trapping capability, and a smaller potential difference for Li2S nucleation/activation. The LSB with CS/U–C3N5–K as a sulfur host material exhibited capacities of 1076.1 and 696.8 mAh g–1 at 0.2 for the initial and 200th cycles, respectively. The CS/U–C3N5–K cathode also exhibited capacities of 624.9 and 402.9 mAh g–1 at 2C for the initial and 1000th cycles, respectively. This work offers a feasible strategy for the engineering of active sites and morphology of metal-free carbon-based nanomaterials in electrochemical energy conversion and storage fields