Controllable Synthesis of Co-Doped Spinel LiMn2O4 Nanotubes as Cathodes for Li-Ion Batteries

Li-Xin Zhang,Yuan-Zhong Wang,Hong-Fang Jiu,Ya-Lei Wang,Yi-Xin Sun,Zhenzhong Li 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.2

Spinel Co-LiMn2O4 nanotubes have been synthesized via solid state reaction using α-MnO2 nanotubes as selftemplates. The as-prepared powders were investigated by XRD, TEM, and galvanostatic discharge/charge analysis. The optimal doping amount was confirmed by galvanostatic charge/discharge measurements. The results indicate that about 67% of initial capacity (115 mAh/g) of LiMn2O4 nanotubes can be retained after 50 cycles. For Co-LiMn2O4 nanotubes, the initial reversible capacity is 126.6 mAh/g and 100 mAh/g can be maintained after 50 cycles. The capacitance retention rate of Co-LiMn2O4 nanotubes is as high as 79%. These results indicate that the doping Co can effectively improve circle stability and electrochemical performance of LiMn2O4 nanotubes.

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.

Highly Efficient Biotransformation of Astragaloside IV to Cycloastragenol by Sugar-Stimulated β-Glucosidase and β-Xylosidase from Dictyoglomus thermophilum

( Qi Li ),( Tao Wu ),( Linguo Zhao ),( Jianjun Pei ),( Zhenzhong Wang ),( Wei Xiao ) 한국미생물 · 생명공학회 2019 Journal of microbiology and biotechnology Vol.29 No.12

β-Glucosidases and β-xylosidases are two categories of enzymes that could cleave out nonreducing, terminal β-D-glucosyl and β-D-xylosyl residues with release of D-glucose and Dxylose, respectively. In this paper, two functional β-glucosidase Dth3 and β-xylosidase Xln-DT from Dictyoglomus thermophilum were heterologously expressed in E.coli BL21 (DE3). Dth3 and Xln-DT were relatively stable at 75oC and were tolerant or even stimulated by glucose and xylose. Dth3 was highly tolerant to glucose with a Ki value of approximately 3 M. Meanwhile, it was not affected by xylose in high concentration. The activity of Xln-DT was stimulated 2.13- fold by 1 M glucose and 1.29-fold by 0.3 M xylose, respectively. Furthermore, the β- glucosidase Dth3 and β-xylosidase Xln-DT showed excellent selectivity to cleave the outer C-6 and C-3 sugar moieties of ASI, which established an effective and green method to produce the more pharmacologically active CAG, an exclusive telomerase activator. We measured temperature, pH and dosage of enzyme using a single-factor experiment in ASI biotransformation. After optimization, the optimal reaction conditions were as follows: 75oC, pH 5.5, 1 U of Dth3 and 0.2 U of Xln-DT, respectively. Under the optimized conditions, 1 g/l ASI was transformed into 0.63 g/l CAG with a corresponding molar conversion of 94.5% within 3 h. This is the first report to use the purified thermostable and sugar-tolerant enzymes from Dictyoglomus thermophilum to hydrolyze ASI synergistically, which provides a specific, environment-friendly and cost-effective way to produce CAG.

An efficient time-variant reliability-based design optimization method based on probabilistic feasible region

Zihao Wu,Zhenzhong Chen,Ge Chen,Xiaoke Li,Chen Jiang,Xuehui Gan,Haobo Qiu,Liang Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

Time-variant reliability-based design optimization (T-RBDO) issues are probabilistic design problems that assess the dependability of the design across time. The engineering situation is most closely resembled by it. The approaches to resolving T-RBDO problems, nevertheless, are convoluted and time-consuming. In this paper, an effective strategy for solving RBDO issues are extended to resolving TRBDO problems in order to increase efficiency. To solve T-RBDO challenges, the time-variant probabilistic feasible region (T-PFR) approach, which is based on the PFR method for resolving RBDO issues, was presented. The idea of the equivalent inverse most probable point (EIMPP) is put out in this methodology. Based on the EIMPP, the probabilistic feasible region is likewise developed for time-variant constraints. The effective tactic of the proposed method is to identify the non-active time-variant constraints using the probabilistic feasible region and to forego conducting time reliability analysis on them. Three mathematics and two engineering issues demonstrate that the suggested solution is viable and effective.

Study on the Impact of Positioning Errors on the Process Performance of Robotic Bonnet Polishing

Xuepeng Huang,Zhenzhong Wang,Lucheng Li 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.9

High-precision optical components are widely used in major fields such as strong lasers and astronomy, but the production cycle of components is greatly constrained by the difficulty of machining optical components and the high price of special polishing machines, so it is important to develop a high-efficiency and low-cost fast polishing system for optical components. By combining bonnet polishing technology with industrial robotics, we have developed an industrial robotics bonnet polishing system for optical components, and the effect of robot positioning errors on pad trimming and on the polishing of the entire surface is also analyzed. To verify the processing capability of the robotic bonnet polishing device, polishing pad dressing experiments and optical component surface correction polishing experiments were carried out. After the pad was dressed, the runout value was reduced from 182 to 23 μm with a convergence ratio of 7.9. After polishing the optical component twice, the PV and RMS values on the surface of the component decreased significantly, from 38.05 λ and 9.98 λ to 8.65 λ and 1.38 λ (λ = 632.8) respectively in the middle area of the component, with a convergence ratio of 4.4 and 7.2, proving that the robotic bonnet polishing system can be applied to the polishing process of optical components.

A novel probabilistic feasible region method for reliability-based design optimization with varying standard deviation

Zihao Wu,Zhenzhong Chen,Ge Chen,Xiaoke Li,Chen Jiang,Xuehui Gan,Haobo Qiu,Liang Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

An effective method for reliability-based design optimization (RBDO) problems taking uncertainties into account is the probabilistic feasible region (PFR) approach. The PFR approach is built around the fixed nature of the standard deviation in general RBDO problems. Therefore, the accuracy of the PFR approach will be affected when dealing with RBDO problems with varying standard deviation. To improve the accuracy of PFR method in solving the RBDO problems with varying standard deviation, a novel probabilistic feasible region strategy considering varying standard deviations (PFR-vstd) approach is suggested in this paper. In place of the initial probabilistic feasible region in standard normal space, a new probabilistic feasible region is established in original design space in this novel approach. The results of four applications demonstrate the high accuracy and sufficient efficiency of PFR-vstd method. The findings demonstrate that PFR-vstd method is capable of accurately resolving RBDO problems with varying standard deviation.

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

Multi-scale heat conduction models with improved equivalent thermal conductivity of TRISO fuel particles for FCM fuel

Wang Mouhao,Bu Shanshan,Zhou Bing,Li Zhenzhong,Chen Deqi 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.3

Fully Ceramic Microencapsulated (FCM) fuel is emerging advanced fuel material for the future nuclear reactors. The fuel pellet in the FCM fuel is composed of matrix and a large number of TRistructural- ISOtopic (TRISO) fuel particles which are randomly dispersed in the SiC matrix. The minimum layer thickness in a TRISO fuel particle is on the order of 105 m, and the length of the FCM pellet is on the order of 102 m. Hence, the heat transfer in the FCM pellet is a multi-scale phenomenon. In this study, three multi-scale heat conduction models including the Multi-region Layered (ML) model, Multi-region Non-layered (MN) model and Homogeneous model for FCM pellet were constructed. In the ML model, the random distributed TRISO fuel particles and coating layers are completely built. While the TRISO fuel particles with coating layers are homogenized in the MN model and the whole fuel pellet is taken as the homogenous material in the Homogeneous model. Taking the results by the ML model as the benchmark, the abilities of the MN model and Homogenous model to predict the maximum and average temperature were discussed. It was found that the MN model and the Homogenous model greatly underestimate the temperature of TRISO fuel particles. The reason is mainly that the conventional equivalent thermal conductivity (ETC) models do not take the internal heat source into account and are not suitable for the TRISO fuel particle. Then the improved ETCs considering internal heat source were derived. With the improved ETCs, the MN model is able to capture the peak temperature as well as the average temperature at a wide range of the linear powers (165 W/ cm~ 415 W/cm) and the packing fractions (20%e50%). With the improved ETCs, the Homogenous model is better to predict the average temperature at different linear powers and packing fractions, and able to predict the peak temperature at high packing fractions (45%e50%).

Ultrafast dynamics control on ablation of Cu using shaped femtosecond pulse trains

Deng Jiannan,Qi Hongxia,Liu Xinyi,Li Xiaoyi,Tong Qiunan,Lian Zhenzhong,Li Juan,Bo Jinqiu,Fei Dehou,Chen Zhou,Hu Zhan 한국물리학회 2021 Current Applied Physics Vol.26 No.-

The ablation processes of Cu film are investigated using temporal shaped femtosecond pulse trains. The depth is modulated by changing the number and interval of the sub-pulses. The underlying ultrafast dynamic processes are discussed based on plasma shielding and electron multiple heating mechanisms. When the sub-pulse interval is less than 0.4 ps electron multiple heating is the dominant mechanism, while the plasma shielding dominates the subsequent ablation processes when the sub-pulse interval is larger than 0.4 ps. The curve of depth obtained by three pulse trains shows more significant oscillation as the function of sub-pulse interval under the lowfluence. We propose that the oscillation of depth is due to the coherent phonon oscillation excited by the pulse train. The study provides a basis for giving insight into the ultrafast dynamics for improving micromachining and nano-fabrications using shaped femtosecond pulse trains.