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Ma, Junpeng,Fan, Jingbiao,Chen, Shang,Yang, Xinyue,Hui, Kwun Nam,Zhang, Hongwen,Bielawski, Christopher W.,Geng, Jianxin American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.14
<P>Lithium-sulfur (Li-S) batteries have received significant attention due to the high theoretical specific capacity of sulfur (1675 mA h g<SUP>-1</SUP>). However, the practical applications are often handicapped by sluggish electrochemical kinetics and the “shuttle effect” of electrochemical intermediate polysulfides. Herein, we propose an in-situ copolymerization strategy for covalently confining a sulfur-containing copolymer onto reduced graphene oxide (RGO) to overcome the aforementioned challenges. The copolymerization was performed by heating elemental sulfur and isopropenylphenyl-functionalized RGO to afford a sulfur-containing copolymer, that is, RGO-<I>g</I>-poly(S-<I>r</I>-IDBI), which is featured by a high sulfur content and uniform distribution of the poly(S-<I>r</I>-IDBI) on RGO sheets. The covalent confinement of poly(S-<I>r</I>-IDBI) onto RGO sheets not only enhances the Li<SUP>+</SUP> diffusion coefficients by nearly 1 order of magnitude, but also improves the mechanical properties of the cathodes and suppresses the shuttle effect of polysulfides. As a result, the RGO-<I>g</I>-poly(S-<I>r</I>-IDBI) cathode exhibits an enhanced sulfur utilization rate (10% higher than that of an elemental sulfur cathode at 0.1C), an improved rate capacity (688 mA h g<SUP>-1</SUP> for the RGO-<I>g</I>-poly(S-<I>r</I>-IDBI) cathode vs 400 mA h g<SUP>-1</SUP> for an elemental sulfur cathode at 1C), and a high cycling stability (a capacity decay of 0.021% per cycle, less than one-tenth of that measured for an elemental sulfur cathode).</P> [FIG OMISSION]</BR>
Acquired Localized Hypertrichosis Induced by Internal Fixation and Plaster Cast Application
Hui-Jun Ma,Yang Yang,Hui-Yong Ma,Chi-Yu Jia,Ting-Hui Li 대한피부과학회 2013 Annals of Dermatology Vol.25 No.3
Hypertrichosis refers to increased vellus hair growth and is independent to androgen excess. The acquired localized hypertrichosis (ALH) is one of the typical hypertrichosis,which mainly results from chronic irritation, inflammation,friction, and occlusion by plaster of Paris. Here, we report a young boy who had ALH on his right hand following a closed fracture with internal fixation and plaster cast application. The case is unusual because the hairy area is limited to the operative region of internal fixation. We suggest that the local vascular changes and skin inflammation induced by internal fixation and plaster cast application may be associated with ALH.
Characteristics of Gas- and Particle-phase Acids and NH₃at Urban and Rural Sites in Korea
Chang-Jin Ma(Chang-Jin Ma),Hui-Kang Kim(Hui-Kang Kim),Gong-Unn Kang(Gong-Unn Kang),Susumu Tohno(Susumu Tohno),Mikio Kasahara(Mikio Kasahara) 한국대기환경학회 2004 한국대기환경학회지 Vol.20 No.E1
To study the characteristics of ammonia and the related compounds, atmospheric aerosols and gases were collected using a triple filter pack sampler, a low volume air sampler, and a three-stage Andersen air sampler in Seoul and Kangwha Island, Korea from Dec. 1996 to Oct. 1997. Ammonia concentrations showed approximately two times higher in summer than in winter at both sites. The highest HNO₃ levels were generally observed in summertime at two sampling sites. The average mass concentration of PM_2.5 in heavily industrialized Seoul was about three times higher than that of Kangwha. In winter, the sum of NH₄^+ and its counter ions (such as CI^-, NO₃^-, and S0₄²^-) comprised 30-41% of PM_2.5 mass concentration at each sampling site. Temperature dependence of particulate nitrate was examined at the urban sampling site. The formation of the nitrate in the fine mode was dependent not only on the amount of precursors but also on the variation of temperature. (NH₄)S0₄and NH₄HS0₄coexisted with NH₄NO₃and NH₄Cl at each site. According to the summertime backward trajectory analysis. NO₃- showed higher level with air parcels transported from northeast Asian continent. On the other hand, the concentration of SO₄²- showed significantly higher level when air masses originated from Pacific Ocean, southern part of Japan. and Korea.
Hui Ma,Yanan Wu,Cheng Huang,Yanli Zhao 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.4
To study the axial compression behavior of carbon fiber reinforced plastics (CFRP) confined steel reinforced recycled concrete (CSRRC) columns, 11 specimens of CSRRC columns were manufactured and tested under axial compression loading. The design variables in the experiments included the replacement percentage of recycled coarse aggregate (RCA), layers of CFRP, strength of recycled aggregate concrete (RAC), profile steel ratio and slenderness ratio. Subsequently, the failure process and modes, load-displacement curves, stress-strain curves, transverse deformation coefficient and stiffness degradation of the specimens were obtained and analyzed in detail. The experimental results showed that the profile steel yielded before the steel rebars in the columns, then the RAC was crushed, and finally the CFRP broke under axial compression loading. The axial bearing capacity of CSRRC columns decreased with the increase of replacement percentage of RCA and slenderness ratio, respectively. However, the CFRP can give full play to its high-strength confinement performance and effectively improve the axial bearing capacity and deformability of columns. Moreover, the profile steel ratio and strength of RAC have significant effects on the initial stiffness of CSRRC columns, and the stiffness degradation rate of columns decreases with the increase of these parameters. Overall, the CSRRC columns exhibit high axial bearing capacity and good ductility deformation ability. Based on ACI 440.2R-08, the modified formula on the nominal axial bearing capacity of CSRRC columns was proposed in this study. The accuracy on the modified formulae was evaluated by the comparison between the calculated values and test values.
Compressive performance of RAC filled GFRP tube-profile steel composite columns under axial loads
Ma, Hui,Bai, Hengyu,Zhao, Yanli,Liu, Yunhe,Zhang, Peng Techno-Press 2019 Advances in concrete construction Vol.8 No.4
To investigate the axial compressive performance of the recycled aggregate concrete (RAC) filled glass fiber reinforced polymer (GFRP) tube and profile steel composite columns, static loading tests were carried out on 18 specimens under axial loads in this study, including 7 RAC filled GFRP tube columns and 11 RAC filled GFRP tube-profile steel composite columns. The design parameters include recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, slenderness ratio and RAC strength. The failure process, failure modes, axial stress-strain curves, strain development and axial bearing capacity of all specimens were mainly analyzed in detail. The experimental results show that the GFRP tube had strong restraint ability to RAC material and the profile steel could improve the axial compressive performance of the columns. The failure modes of the columns can be summarized as follow: the profile steel in the composite columns yielded first, then the internal RAC material was crushed, and finally the fiberglass of the external GFRP tube was seriously torn, resulting in the final failure of columns. The axial bearing capacity of the columns decreased with the increase of RCA replacement percentage and the maximum decreasing amplitude was 11.10%. In addition, the slenderness ratio had an adverse effect on the axial bearing capacity of the columns. However, the strength of the RAC material could effectively improve the axial bearing capacity of the columns, but their deformability decreased. In addition, the increasing profile steel ratio contributed to the axial compressive capacity of the composite columns. Based on the above analysis, a formula for calculating the bearing capacity of composite columns under axial compression load is proposed, and the adverse effects of slenderness ratio and RCA replacement percentage are considered.
Research on Carried-Based PWM with Zero-Sequence Component Injection for Vienna Type Rectifiers
Hui Ma,Mao Feng,Yu Tian,Xi Chen 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2
This paper studies the inherent relationship between currents and zero-sequence components. Then a precise algorithm is proposed to calculate the injected zero-sequence component to control the DC-Link neutral-point voltage balance, which can result in a more efficient and flexible neutral point voltage balance with a desirable performance. In addition, it is shown that carried-based PWM with the calculated zero-sequence component scheme can be equivalent to space-vector pulse-width modulation (SVPWM). Based on the proposed method, the optimal zero-sequence component of the feasible modulation indices is analyzed. In addition, the unbalanced load limitation of the DC-Link neutral-point voltage balance control is also revealed. Simulation and experimental results are shown to verify the validity and practicality of the proposed algorithm.
Research on Carried-Based PWM with Zero-Sequence Component Injection for Vienna Type Rectifiers
Ma, Hui,Feng, Mao,Tian, Yu,Chen, Xi The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2
This paper studies the inherent relationship between currents and zero-sequence components. Then a precise algorithm is proposed to calculate the injected zero-sequence component to control the DC-Link neutral-point voltage balance, which can result in a more efficient and flexible neutral point voltage balance with a desirable performance. In addition, it is shown that carried-based PWM with the calculated zero-sequence component scheme can be equivalent to space-vector pulse-width modulation (SVPWM). Based on the proposed method, the optimal zero-sequence component of the feasible modulation indices is analyzed. In addition, the unbalanced load limitation of the DC-Link neutral-point voltage balance control is also revealed. Simulation and experimental results are shown to verify the validity and practicality of the proposed algorithm.