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Jianxun Chen,Qizhong Huang 한국탄소학회 2006 Carbon Letters Vol.7 No.4
Carbon/Carbon composite was been manufactured by the technology of warmer-molding process of clutter chopped carbon fiber, using phenolic resin as an adhesive. The degree of graphitization, the microstructure and the friction properties were studied. The results show that the clutter chopped carbon fiber fully scatter in the Carbon/Carbon composite and the degree of graphitization of phenolic resin can reach up to 86.2%, this matrix carbon can form the continuous and stable graphitic thin film on the friction surface during braking process so that the composite has fine friction properties and low wear rate.
Criteria for evaluating working fluids in loop gravity-assisted heat systems
Chen Jianxun,Liu Jinping,Xu Xiongwen,Liang Lingjiao,Yu Yinhao 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.9
A loop gravity-assisted heat pipe (LGHP) is characterized by passive heat dissipation and extensive application prospect. Dissimilar working fluids give rise to noticeable differences in their working performance (Critical heat flux (CHF)). Consequently, it is of great significance to evaluate the performance of LGHP working fluid for its design. In accordance with the basic theories of CHF and hydrodynamics, the pressure drop models of laminar, smooth turbulence, and completely rough turbulence flows were established, and an extensible two-phase composite property parameter was obtained. On this basis, the physical property parameter of transitional rough turbulent flow was also derived. Finally, as persuasively illustrated by the experimental results, there was almost a linear association between CHFs and the derived physical parameter. As a result, the physical parameters derived in this paper can be employed as favorable criteria for the selection of LGHP working fluid.
Jianxun Chen,Xiang Xiong 한국탄소학회 2007 Carbon Letters Vol.8 No.1
The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.
pH-Responsive Drug Delivery Systems Based on Clickable Poly(L-glutamic acid)-Grafted Comb Copolymers
Jianxun Ding,Xuesi Chen,Chaoliang He,Chunsheng Xiao,Jie Chen,Xiuli Zhuang 한국고분자학회 2012 Macromolecular Research Vol.20 No.3
Five pH-responsive alkyne-poly(2-aminoethyl methacrylate)-graft-poly(L-glutamic acid) (alkyne-PAMA-g-PLGA) comb copolymers were synthesized through the ring-opening polymerization (ROP) of γ-benzyl-L-glutamate N-carboxyanhydride (BLG NCA) and the subsequent deprotection of benzyl group from BLG unit. The chemical structures of copolymers were confirmed by proton nuclear magnetic resonance spectra (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The pyrene-probe-based fluorescence technique and transmission electron microscopy (TEM) measurements revealed that the comb copolymers could spontaneously self-assemble into micellar or vesicular nanoparticles in phosphate buffered saline (PBS) at pH 7.4. Doxorubicin (DOX), an anthracycline anticancer drug, was loaded into nanoparticles as a model anticancer drug. The in vitro release results showed that the release behaviors could be altered by adjusting the composition of the comb copolymer and pH of the release medium. In vitro methyl thiazolyl tetrazolium (MTT) assays demonstrated that the copolymers were biocompatible,and DOX-loaded nanoparticles showed effective inhibition of cellular proliferation. Hemolysis tests indicated that the copolymers were also hemocompatible, and that the presence of the copolymers could reduce the hemolysis ratio (HR) of the DOX significantly. In addition, the comb copolymers could be modified through versatile Cu(I)-catalyzed “click chemistry” between the terminal alkyne group and azide-modified functional agents. These properties indicate that the pH-responsive clickable comb copolymers are promising candidates for multifunctional nanocarriers in cancer diagnosis and therapy.
Failure Mechanisms and Modes of Tunnels in Monoclinic and Soft-Hard Interbedded Rocks: A Case Study
Jianxun Chen,Weiwei Liu,Lijun Chen,Yanbin Luo,Yao Li,Haijiang Gao,Daochuan Zhong 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4
The issue of large deformation mechanism in soft rock tunnels has puzzled tunnel scholars for decades. Previous studies have not evolved a clear and common understanding. Therefore, detailed on-site measurement, full investigation and statistical analysis have been conducted on the instability and failure of Muzhailing Tunnel since its construction, whose length is beyond 15 km. The study aims at systematically analyzing the failure mechanisms and modes of Muzhailing Tunnel in monoclinic and soft-hard interbedded rock strata. Study results show that the angle between strata strike and tunnel axis greatly determines the magnitude of deformation, the dip direction significantly controls the bias direction and maximum deformation direction, and the dip angle deeply affects the deformation form. The failure modes of surrounding rock mainly include four types: spalling and overturning failure, bending failure, shear slip failure and buckling failure. Large deformation characteristics are summarized from six aspects: failure form, groundwater, sensitivity to influencing factors, deformation degree, deformation speed and deformation duration. The instability modes of primary lining include in-plane (transverse) instability and out-plane (longitudinal) instability. Finally, the causes of large deformation are analyzed from geological, structural, engineering and human factors.
Chen, Jianxun,Xiong, Xiang Korean Carbon Society 2007 Carbon Letters Vol.8 No.1
The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.
Chen, Jianxun,Huang, Qizhong Korean Carbon Society 2006 Carbon Letters Vol.7 No.4
Carbon/Carbon composite was been manufactured by the technology of warmer-molding process of clutter chopped carbon fiber, using phenolic resin as an adhesive. The degree of graphitization, the microstructure and the friction properties were studied. The results show that the clutter chopped carbon fiber fully scatter in the Carbon/Carbon composite and the degree of graphitization of phenolic resin can reach up to 86.2%, this matrix carbon can form the continuous and stable graphitic thin film on the friction surface during braking process so that the composite has fine friction properties and low wear rate.
Performance of Tunnel Feet-Lock Pipe (TFP) in Sharing Vertical Foundation Load
Lijun Chen,Jianxun Chen,Yao Li,Yanbin Luo,Yongjun Mu,Taotao Hu,Chuanwu Wang 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.3
During the tunnel construction in soft ground, the insufficient bearing capacity of tunnel foundation usually causes a series of settlement problems. Tunnel feet-lock pipe (TFP) has been widely used to take the vertical load acting at the foundation of a tunnel foot. However, the detailed bearing performance of TFP is still not clear, and there is a lack of quantitative research. In this paper, a simple analytical approach is adopted to evaluate the performance of the TFP, and the main parameters affecting the supporting performance of the TFP are analyzed. The results show that the ϕ42 − ϕ140 TFP with the angle of 10° can take 3.8% −40.4% of vertical load. TFP has an effective length of 1.7 m − 2.8 m, which is related to the relative stiffness between the TFP and the stratum. With the increase of the installation angle, the TFP shares more vertical load. This trend is more obvious when the angle of the TFP is greater than 20°. If the proportion coefficient of the subgrade reaction coefficient is doubled, the vertical load shared by the TFP can be increased by 34% − 38%. For every 10 cm increase in overbreak behind the steel rib, the vertical load shared by TFP is reduced by 16%.