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1,213 results on '"Li, Changjun"'

111. Numerical simulation of high-pressure tritium leakage based on AN-EOS model

Author

LI Changjun, CAI Xingfu, XIAO Mingqing, WANG Fei, and CAO Xiaoyan

Subjects
tritium leakage, an-eos, transient behavior, numerical simulation, Nuclear engineering. Atomic power, TK9001-9401
Abstract

BackgroundTritium leakage is a typical nuclear accident scene, which is harmful to human and environment. Therefore, numerical simulation of tritium leakage is of significance to nuclear accident emergency decision making.PurposeThis study aims at the numerical simulation of high-pressure tritium leakage.MethodsA numerical simulation method based on AN-EOS model was proposed to solve the problem of tritium leakage from high pressure storage vessels. The AN-EOS model embedded into Fluent by user defined functions was used to describe the tritium leakage transient behavior. The leakage process of tritium and variation rule of concentration were simulated in closed and ventilated environment based on Fluent.ResultsThe results show that the concentration of tritium increases rapidly when the leakage occurs. After stopping leakage, the concentration of tritium in a closed environment increases first and then stabilizes, and gradually decreases in ventilated environment.ConclusionsVentilation has a significant effect on the diffusion of tritium gas, which can effectively achieve the purpose of tritium removal.

Published
2022
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113. Test Map and Discreteness Criteria for Subgroups in PU(1,n;C)

Author

Li, ChangJun and Zhang, XiaoYan

Subjects
Mathematics - Complex Variables
Abstract

We study the discreteness for non-elementary subgroup G in PU(1, n;C), under the assumption that G satisfies Condition A. Mainly, we present that one can use a test map, which need not to be in G, to examine the discreteness of G, and also show that G is discrete, if every two-loxodromic-generator subgroup of G is discrete., Comment: 9 pages

Published
2011

139. Perylene diimide covalent organic frameworks super-reductant for visible light-driven reduction of aryl halides

Author

Jin, Yucheng, Liu, Xiaolin, Qu, Chen, Li, Changjun, Wang, Hailong, Zhan, Xiaoning, Cao, Xinyi, Li, Xiaofeng, Yu, Baoqiu, Zhang, Qi, Qi, Dongdong, and Jiang, Jianzhuang

Abstract

In recent years, there has been a growing interest in the utilization of molecular photocatalysts in their radical ionic forms, especially as visible-light super-reductants. These catalysts exhibit remarkable capabilities in facilitating otherwise inert high-potential organic reactions, such as the reduction of aryl halides to aryl radicals. However, the development of heterogeneous super-reductants has lagged behind due to the deactivation effect caused by molecular aggregation. This study presents a novel approach to address this limitation by heterogenizing perylene diimides (PDIs) super-reductants with a consecutive photo-induced electron transfer mechanism into two-dimensional donor-acceptor (D-A) covalent organic frameworks (COFs). Both COFs, possessing D-A electronic structures and photothermal effects, demonstrated superior visible-light photocatalytic performance compared to their homogeneous counterparts. They achieved up to 99% conversion in the dehalogenation of aryl halides, primarily through a hydrogen atom trapping aryl radical mechanism. Additionally, we conducted a comparative investigation of the excited states of radical anionic D-A-type COFs and DPPDI using femtosecond transient absorption spectroscopy. Notably, the lifetimes of COFs were significantly prolonged, measuring 210 and 260 ps, respectively, compared to the 150 ps lifetime of (DPPDI•−). This study offers valuable insights into the design of efficient free radical ion-type photocatalysts, with potential applications in various chemical transformations.

Published
2024
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140. A low-Reynolds-number k–εmodel for polymer drag-reduction prediction in turbulent pipe flow

Author

Chen, Yang, Zhang, Meiyu, Valeev, A. R., Li, Changjun, Nechval, A. M., and Yang, Peng

Abstract

Pipeline transport at high Reynolds number can result in significant turbulent losses. One of the most effective methods for turbulent drag reduction is adding a very small amount of polymer drag-reducing agent to the pipeline. However, due to the complex interaction between polymers and turbulence, turbulence models incorporating polymer additives remain to be studied and developed. In the present work, we investigated the turbulence model using Reynolds averaged numerical simulation (RANS) to describe polyacrylamide drag reduction flow. A low-Reynolds-number k–εmodel in turbulent flow has been developed by considering the concentration and type of polymers, which can be applied for polymer drag reduction prediction in the pipe. Mean velocity profile Uf, turbulent intensity, turbulent kinetic energy k, and turbulent dissipation rate εin the regions of viscous sublayer, buffer layer and logarithmic layer have been predicted with various concentration θ, Reynolds number Re, degradation degrees, and changing laws of these factors have been revealed with wall distance. The developed turbulence model showed a good capability to qualitatively forecast mean velocity profile, turbulent intensity, turbulent kinetic energy, and turbulent dissipation rate, and the prediction error between the experimental and simulated values falls along the y= xcurve, which can be used for the investigation and prediction of varies water-soluble, oil-soluble polymers in turbulent drag reduction flow in pipes with other parameters such as pipe diameter, pipe length, and the Reynolds number.

Published
2024
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145. Improvements to the CIELUV color space.

Author

Wang, Ling, Li, Changjun, Xu, Yang, Melgosa, Manuel, Xiao, Kaida, and Gao, Cheng

Subjects
*COLOR space, *VIDEO monitors, *UNIFORM spaces, *CHROMATICITY, *SUM of squares
Abstract

Three new approximately uniform color spaces named MLUV, MLUV1, and MLUV2 were developed by modifying CIELUV lightness, u′v′ chromaticity coordinates, and u*v* color coordinates, respectively. Performance tests using the combined and four individual datasets employed at CIEDE2000 development showed that MLUV, MLUV1 and MLUV2 were significantly better than CIELUV. Using values of Standardized Residual Sum of Squares (CIE 217:2016) for predictions of the four individual datasets the ranking (from best to worst) was MLUV, MLUV2 and MLUV1, but for predictions of two ellipses datasets the ranking (from best to worst) was MLUV2, MLUV, and MLUV1. Overall, the MLUV2 space was found to be the best. Hence, it is expected that MLUV2 could be used for color specification and color difference evaluations, especially in industrial applications that depend on additive light mixing, such as color TV sets, video monitors, and lighting. [ABSTRACT FROM AUTHOR]

Published
2023
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146. Vibration control of a thin rectangular plate subjected to moving masses using an adaptive sliding mode control method.

Author

Pi, Yangjun, Yu, Rui, Li, Changjun, Yang, Bo, and Luo, Jun

Subjects
RECTANGULAR plates (Engineering), SLIDING mode control, ADAPTIVE control systems
Abstract

This study investigates the vibration control of a plate subjected to moving masses. The plate model reflects the dynamic behavior more accurately than the beam model which is usually used in the existing literature. However, the vibration control of plates subjected to moving masses is also more challenging as more degrees of freedom need to be taken into account. In addition, the measurement of system status and uncertainty problems in practical application is another nodus. In this paper, combining an adaptive sliding‐mode control (ASMC) strategy and a modal coordinate reconstruction (MCR) method, the MCR‐ASMC method is proposed. The MCR method is employed to capture the plate dynamic behavior for feedback to the ASMC. The ASMC strategy realizes vibration control through the adaptive updating of parameters. Numerical results demonstrate the effectiveness of the proposed method and excellent control performance in vibration suppression of moving mass problems. [ABSTRACT FROM AUTHOR]

Published
2023
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