Geochemical and S isotopic studies of pollutant evolution in groundwater after acid in situ leaching in a uranium mine area in Xinjiang

Liu Zhenzhong,Tan Kaixuan,Li Chunguang,Li Yongmei,Zhang Chong,Song Jing,Liu Longcheng 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.4

Laboratory experiments and point monitoring of reservoir sediments have proven that stable sulfate reduction (SSR) can lower the concentrations of toxic metals and sulfate in acidic groundwater for a long time. Here, we hypothesize that SSR occurred during in situ leaching after uranium mining, which can impact the fate of acid groundwater in an entire region. To test this, we applied a sulfur isotope fractionation method to analyze the mechanism for natural attenuation of contaminated groundwater produced by acid in situ leaching of uranium (Xinjiang, China). The results showed that δ34S increased over time after the cessation of uranium mining, and natural attenuation caused considerable, area-scale immobilization of sulfur corresponding to retention levels of 5.3%–48.3% while simultaneously decreasing the concentration of uranium. Isotopic evidence for SSR in the area, together with evidence for changes of pollutant concentrations, suggest that area-scale SSR is most likely also important at other acid mining sites for uranium, where retention of acid groundwater may be strengthened through natural attenuation. To recapitulate, the sulfur isotope fractionation method constitutes a relatively accurate tool for quantification of spatiotemporal trends for groundwater during migration and transformation resulting from acid in situ leaching of uranium in northern China.

Mechanical and Tribological Properties of Short Basalt Fiber-reinforced Polyoxymethylene Composites

Chenghe Liu,Chunguang Long,Lei Chen,Junpeng Liu,Taishan Cao,Jian Zhang 한국고분자학회 2016 폴리머 Vol.40 No.6

In this paper, short basalt fiber-reinforced polyoxymethylene (POM) composites were prepared by melt blending and injection molding. The mechanical and tribological properties of the composites were studied by an orthogonal experiment. It was found that the optimal combination of fiber length 4 mm, fiber content 20 wt% and treated with KH550 would result in a comprehensive property which is 27.45% higher tensile strength, 9.65% higher impact strength and 18.11% higher flexural strength with compared to that of pure POM. But its tribological properties would be worse with the addition of the basalt fibers. After incorporating 10 wt% of polytetrafluoroethylene (PTFE) into the composites, the tribological properties of the composites was improved, closed to that of pure POM, with an insignificant decrease to their mechanical properties. Moreover, the morphology of fracture surfaces and worn surfaces evaluated by scanning electron microscopy showed good agreement with the results of the literature.

Solidification of uranium mill tailings by MBS-MICP and environmental implications

Niu Qianjin,Li Chunguang,Liu Zhenzhong,Li Yongmei,Meng Shuo,He Xinqi,Liu Xinfeng,Wang Wenji,He Meijiao,Yang Xiaolei,Liu Qi,Liu Longcheng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10

Uranium mill tailing ponds (UMTPs) are risk source of debris flow and a critical source of environmental U and Rn pollution. The technology of microbial induced calcium carbonate precipitation (MICP) has been extensively studied on reinforcement of UMTs, while little attention has been paid to the effects of MICP on U & Rn release, especially when incorporation of metakaolin and bacillus subtilis (MBS). In this study, the reinforcement and U & Rn immobilization role of MBS -MICP solidification in different grouting cycle for uranium mill tailings (UMTs) was comprehensively investigated. The results showed that under the action of about 166.7 g/L metakaolin and ~50% bacillus subtilis, the solidification cycle of MICP was shortened by 50%, the solidified bodies became brittle, and the axial stress increased by up to 7.9%, and U immobilization rates and Rn exhalation rates decrease by 12.6% and 0.8%, respectively. Therefore, the incorporation of MBS can enhance the triaxial compressive strength and improve the immobilization capacity of U and Rn of the UMTs bodies solidified during MICP, due to the reduction of pore volume and surface area, the formation of more crystals general gypsum and gismondine, as well as the enhancing of coprecipitation and encapsulation capacity

Reliability analysis on flutter of the long-span Aizhai bridge

Liu, Shuqian,Cai, C.S.,Han, Yan,Li, Chunguang Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.27 No.3

With the continuous increase of span lengths, modern bridges are becoming much more flexible and more prone to flutter under wind excitations. A reasonable probabilistic flutter analysis of long-span bridges involving random and uncertain variables may have to be taken into consideration. This paper presents a method for estimating the reliability index and failure probability due to flutter, which considers the very important variables including the extreme wind velocity at bridge site, damping ratio, mathematical modeling, and flutter derivatives. The Aizhai Bridge in China is selected as an example to demonstrate the numerical procedure for the flutter reliability analysis. In the presented method, the joint probability density function of wind speed and wind direction at the deck level of the bridge is first established. Then, based on the fundamental theories of structural reliability, the reliability index and failure probability due to flutter of the Aizhai Bridge is investigated by applying the Monte Carlo method and the first order reliability method (FORM). The probabilistic flutter analysis can provide a guideline in the design of long-span bridges and the results show that the structural damping and flutter derivatives have significant effects on the flutter reliability, more accurate and reliable data of which is needed.

Reliability analysis on flutter of the long-span Aizhai bridge

Shuqian Liu,C.S. Cai,Yan Han,Chunguang Li 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.3

With the continuous increase of span lengths, modern bridges are becoming much more flexible and more prone to flutter under wind excitations. A reasonable probabilistic flutter analysis of long-span bridges involving random and uncertain variables may have to be taken into consideration. This paper presents a method for estimating the reliability index and failure probability due to flutter, which considers the very important variables including the extreme wind velocity at bridge site, damping ratio, mathematical modeling, and flutter derivatives. The Aizhai Bridge in China is selected as an example to demonstrate the numerical procedure for the flutter reliability analysis. In the presented method, the joint probability density function of wind speed and wind direction at the deck level of the bridge is first established. Then, based on the fundamental theories of structural reliability, the reliability index and failure probability due to flutter of the Aizhai Bridge is investigated by applying the Monte Carlo method and the first order reliability method (FORM). The probabilistic flutter analysis can provide a guideline in the design of long-span bridges and the results show that the structural damping and flutter derivatives have significant effects on the flutter reliability, more accurate and reliable data of which is needed.

Flutter stability of a long-span suspension bridge during erection

Han, Yan,Liu, Shuqian,Cai, C.S.,Li, Chunguang Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.21 No.1

The flutter stability of long-span suspension bridges during erection can be more problematic and more susceptible to be influenced by many factors than in the final state. As described in this paper, numerical flutter stability analyses were performed for the construction process of Zhongdu Bridge over Yangtze River using the commercial FE package ANSYS. The effect of the initial wind attack angle, the sequence of deck erection, the stiffness reduction of stiffening girders, the structural damping, and the cross cables are discussed in detail. It was found that the non-symmetrical sequence of deck erection was confirmed to be aerodynamically favourable for the deck erection of long-span suspension bridges and the best erection sequence should be investigated in the design phase. While the initial wind attack angle of $-3^{\circ}$ is advantageous for the aerodynamic stability, $+3^{\circ}$ is disadvantageous compared with the initial wind attack angle of $0^{\circ}$ during the deck erection. The stiffness reduction of the stiffening girders has a slight effect on the flutter wind speed of the suspension bridge during erection, but structural damping has a great impact on it, especially for the early erection stages.

Flutter stability of a long-span suspension bridge during erection

Yan Han,Shuqian Liu,C.S. Cai,Chunguang Li 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.1

The flutter stability of long-span suspension bridges during erection can be more problematic and more susceptible to be influenced by many factors than in the final state. As described in this paper, numerical flutter stability analyses were performed for the construction process of Zhongdu Bridge over Yangtze River using the commercial FE package ANSYS. The effect of the initial wind attack angle, the sequence of deck erection, the stiffness reduction of stiffening girders, the structural damping, and the cross cables are discussed in detail. It was found that the non-symmetrical sequence of deck erection was confirmed to be aerodynamically favourable for the deck erection of long-span suspension bridges and the best erection sequence should be investigated in the design phase. While the initial wind attack angle of -3o is advantageous for the aerodynamic stability, +3o is disadvantageous compared with the initial wind attack angle of 0o during the deck erection. The stiffness reduction of the stiffening girders has a slight effect on the flutter wind speed of the suspension bridge during erection, but structural damping has a great impact on it, especially for the early erection stages.

Prediction of Prostate Cancer Risk Stratification Based on A Nonlinear Transformation Stacking Learning Strategy

Xinyu Cao,Yin Fang,Chunguang Yang,Zhenghao Liu,Guoping Xu,Yan Jiang,Peiyan Wu,Wenbo Song,Hanshuo Xing,Xinglong Wu 대한배뇨장애요실금학회 2024 International Neurourology Journal Vol.28 No.1

Purpose: Prostate cancer (PCa) is an epithelial malignancy that originates in the prostate gland and is generally categorized into low, intermediate, and high-risk groups. The primary diagnostic indicator for PCa is the measurement of serum prostate-specific antigen (PSA) values. However, reliance on PSA levels can result in false positives, leading to unnecessary biopsies and an increased risk of invasive injuries. Therefore, it is imperative to develop an efficient and accurate method for PCa risk stratification. Many recent studies on PCa risk stratification based on clinical data have employed a binary classification, distinguishing between low to intermediate and high risk. In this paper, we propose a novel machine learning (ML) approach utilizing a stacking learning strategy for predicting the tripartite risk stratification of PCa. Methods: Clinical records, featuring attributes selected using the lasso method, were utilized with 5 ML classifiers. The outputs of these classifiers underwent transformation by various nonlinear transformers and were then concatenated with the lasso-selected features, resulting in a set of new features. A stacking learning strategy, integrating different ML classifiers, was developed based on these new features. Results: Our proposed approach demonstrated superior performance, achieving an accuracy of 0.83 and an area under the receiver operating characteristic curve value of 0.88 in a dataset comprising 197 PCa patients with 42 clinical characteristics. Conclusions: This study aimed to improve clinicians’ ability to rapidly assess PCa risk stratification while reducing the burden on patients. This was achieved by using artificial intelligence-related technologies as an auxiliary method for diagnosing PCa.

Adaptive virtual impedance control based on second-order generalized integral for circulating current suppression

Zhang, Baifu,Han, Xiaoqing,Meng, Runquan,Ren, Chunguang,Wang, Lei,Song, Tianhao,Liu, Yizhao The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.1

The redundant design of multi-paralleled bidirectional power converters (BPCs) provides technical support for hybrid microgrid systems to consume more distributed generations (DGs) and DC loads. However, the multi-BPCs also provide paths for circulating current. In addition, the AC sub-grid may operate under unbalanced conditions due to the consumption of single-phase loads and power electronic devices. In addition, unbalanced three-phase voltage deteriorates the generation of circulating current. In this paper, an adaptive virtual impedance control method based on second-order generalized integration (SOGI) is proposed to suppress circulating current on the basic analysis of circulating current generation mechanism, the equivalent model establishment, and the suppression principle. The virtual impedance is dynamically adjusted in real-time based on the power oscillation caused by unbalanced voltage. Moreover, an integral term is added to the reactive power droop control to realize the tracking of voltage without static error. Finally, the effectiveness and feasibility of the proposed control algorithm are verified by experiments. The research results show that the proposed control method can optimize the damping characteristics, reduce the voltage difference between the BPCs, and improve the current sharing effect.

Photocatalyst TiO2/WO3/GO nano-composite with high efficient photocatalytic performance for BPA degradation under visible light and solar light illumination

Xiaoyan Hao,Man Li,Li Zhang,Kuokuo Wang,Chunguang Liu 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.55 No.-

A high efficient photocatalyst (TiO2/WO3/GO) was developed with tungsten trioxide doping and graphene oxide hybridization. XRD and SEM indicate the formation of crystalline anatase/rutile TiO2 and hexagonal and cubic WO3. UV–vis spectroscopy shows the excellent visible-light-responsive performance. The photocatalyst exhibits excellent photocatalytic performance for bisphenol A degradation under visible light and sunlight irradiations. Transformation by-products were identified and main degradation pathways were proposed. The photocatalytic mechanism is also proposed on the basis of the fact that charge separation is facilitated owing to photo-generated electrons transfer from TiO2 to WO3 to GO and photogenerated holes transfer from WO3 to TiO2.