Sulphonated Reduced Graphene Oxide: A High Performance Anode Material for Lithium Ion Battery

Haibo Li,Rui Niu,Sen Liang,Yulong Ma,Min Luo,Jin Li,Lijun He 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.4

In this work, the sulfonated reduced graphene oxide (SRGO) was synthesized and proposed as an enhanced anode material for lithium ion battery (LIB). The result shows that the SRGO has an improved battery performance (i.e., ~341.7 mAh/g and ~190.6 mAh/g corresponds to SRGO and RGO at the 100th cycle with a current density of 200 mA/g) and superior cycling stability compared with pristine reduced graphene oxide (RGO). These are attributed to the improved specific surface area (448.35 m2 /g) and conductivity (2.5 x 10-4 S/m). Further, the SRGO exhibits good rate capability and excellent energy density at various current densities ranging from 50 mAh/g to 2000 mAh/g, suggesting that SRGO could be a promising anode material for high capacity LIB.

The effect of HCP on the formation of twin boundaries and dislocations in Ni–Co alloys

Ma Rui-bo,Zhou Li-li,Liang Yong-chao,Chen Qian,Tian Ze-an,Liu Rang-su,Mo Yun-fei,Gao Ting-hong,Xie Quan 한국물리학회 2021 Current Applied Physics Vol.29 No.-

In this study, molecular dynamics (MD) was used to simulate the rapid solidification process of Ni47Co53 and Ni48Co52 alloys at a cooling rate of 1012 K/s. The effects of HCP on the formation of twin boundaries and dislocations in two Ni–Co alloys are studied. It is found that the difference of HCP clusters is the main effect that producing discrepancies on microstructure of two alloys. The number of HCP clusters accounted for 9.23% in Ni47Co53 alloy. They are regularly arranged to form the number of single-layer twin boundaries, and each twin boundary ends in a dislocation. The FCC and HCP structures coexist in the same atomic layers, which is easy to create dislocations. The relatively standard FCC crystal and only 0.32% HCP clusters are formed in Ni48Co52 alloy at 300 K. That small amount of HCP clusters are dispersed on the surface, and cause the formation of dislocation in the border with FCC clusters.

Manipulation of microdroplets at a T-junction: Coalescence and scaling law

Rui Ma,Qindan Zhang,Taotao Fu,Chunying Zhu,Kai Wang,Youguang Ma,Guangsheng Luo 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.65 No.-

The manipulation of a droplet at a microfluidic T-junction is achieved via adding reagents into the droplet with the same solution. Three types for droplet coalescence at the T-junction were observed: tail coalescence, slipping coalescence and unsteady coalescence behaviors with a new droplet formation. The final droplet size decreased (increased) with increasing the capillary number when the flow rate of the dispersed (continuous) phase was fixed. The final droplet size increased with increasing the capillary number of the added phase. The correlations for predicting the coalesced droplet size for tail and slipping coalescence were proposed.

Research on Voltage Stability Boundary under Different Reactive Power Control Mode of DFIG Wind Power Plant

Rui Ma,Zeyu Qin,Wencan Yang,Mo Li 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.6

A novel method is proposed to construct the voltage stability boundary of power system considering different Reactive Power Control Mode (RPCM) of Doubly-Fed Induction Generator (DFIG) Wind Power Plant (WPP). It can be used for reflecting the static stability status of grid operation with wind power penetration. The analytical derivation work of boundary search method can expound the mechanism and parameters relationship of different WPP RPCMs. In order to improve the load margin and find a practical method to assess the voltage security of power system, the approximate method of constructing voltage stability boundary and the critical points search algorithms under different RPCMs of DFIG WPP are explored, which can provide direct and effective reference data for operators.

필라테스 운동과 코어안정성 운동이 노년기 여성의 골밀도와 낙상위험요인에 미치는 영향

Rui Ma,김영훈,김태규 한국운동생리학회 2022 운동과학 Vol.31 No.3

PURPOSE: This study aimed to verify the effect of 8-week Pilates and core stability exercises on bone mineral density (BMD) and risk of falls in older adult women. METHODS: A total of 49 healthy women over 60 years of age were randomly classified into three groups: Pilates exercise group (PG, n=17), core stability exercise group (CSG, n=17), and control group (CON, n=12). Pilates and core stability exercise programs were applied in each group for 8 weeks. Before and after the two exercise programs, BMD, Tinetti Performance Oriented Mobility Assessment (Tinetti POMA), and balance ability were measured RESULTS: There were no differences in BMD among the three groups depending on the application of the exercise program. The balance scores of the Tinetti POMA and total Tinetti POMA scores in both the PG and CSG were higher after the 8-week exercise program. In particular, the gait score of the Tinetti POMA in the PG was higher than that in the CSG. Static and dynamic balance abilities improved in both the PG and CSG. CONCLUSIONS: These results suggest that Pilates and core stability exercises can be effective for improving balance ability, leading to the prevention of falls in older adult women.

MoTe₂ Lateral Homojunction Field-Effect Transistors Fabricated using Flux-Controlled Phase Engineering

Ma, Rui,Zhang, Huairuo,Yoo, Youngdong,Degregorio, Zachary Patrick,Jin, Lun,Golani, Prafful,Ghasemi Azadani, Javad,Low, Tony,Johns, James E.,Bendersky, Leonid A.,Davydov, Albert V.,Koester, Steven J. American Chemical Society 2019 ACS NANO Vol.13 No.7

<P>The coexistence of metallic and semiconducting polymorphs in transition-metal dichalcogenides (TMDCs) can be utilized to solve the large contact resistance issue in TMDC-based field effect transistors (FETs). A semiconducting hexagonal (2H) molybdenum ditelluride (MoTe<SUB>2</SUB>) phase, metallic monoclinic (1T′) MoTe<SUB>2</SUB> phase, and their lateral homojunctions can be selectively synthesized <I><I>in situ</I></I> by chemical vapor deposition due to the small free energy difference between the two phases. Here, we have investigated, in detail, the structural and electrical properties of <I>in situ</I>-grown lateral 2H/1T′ MoTe<SUB>2</SUB> homojunctions grown using flux-controlled phase engineering. Using atomic-resolution plan-view and cross-sectional transmission electron microscopy analyses, we show that the round regions of near-single-crystalline 2H-MoTe<SUB>2</SUB> grow out of a polycrystalline 1T′-MoTe<SUB>2</SUB> matrix. We further demonstrate the operation of MoTe<SUB>2</SUB> FETs made on these <I>in situ</I>-grown lateral homojunctions with 1T′ contacts. The use of a 1T′ phase as electrodes in MoTe<SUB>2</SUB> FETs effectively improves the device performance by substantially decreasing the contact resistance. The contact resistance of 1T′ electrodes extracted from transfer length method measurements is 470 ± 30 Ω·μm. Temperature- and gate-voltage-dependent transport characteristics reveal a flat-band barrier height of ∼30 ± 10 meV at the lateral 2H/1T′ interface that is several times smaller and shows a stronger gate modulation, compared to the metal/2H Schottky barrier height. The information learned from this analysis will be critical to understanding the properties of MoTe<SUB>2</SUB> homojunction FETs for use in memory and logic circuity applications.</P> [FIG OMISSION]</BR>

Research on Control Technology of Variable Curvature Bending Springback Based on Iterative Compensation Method

Rui Ma,Chao Ma,Ruixue Zhai,Jun Zhao 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.5

The springback control method is usually based on surface compensation to make the shape of the springback consistent with the target. At present, it is mainly realized by theoretical calculation or numerical simulation, but the difference between material model and theoretical model leads to unstable compensation accuracy. In this paper, a compensation mechanism which based on the iterative principle of implicit equation is proposed from the point of view of mathematical analysis. The final shape of the part converges to the target shape by means of finite compensation with the iterative method. In this paper, the iterative compensation mechanism is applied to the free bending and stretch-bending processes under plane stress state, and the uniform curvature and variable curvature are compensated iteratively. The next iteration compensation profile is predicted according to the convergence of the iterative principle. Experimental results show that the iterative compensation method can predict the next compensation value, and the error is less than the target value after 2–3 iterations. The error convergence of the method studied in this project is directional and the convergence speed is fast. The compensation value can be quantitatively predicted, which has theoretical significance and application value for engineering design, mold repair and numerical simulation.

Breakup dynamics of ferrofluid droplet in a microfluidic T-junction

Rui Ma,Taotao Fu,Qindan Zhang,Chunying Zhu,Youguang Ma,Huai Z. Li 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-

This paper investigated the breakup dynamics of ferrofluid droplet in a microfluidic T-junction with the magnetic field. Droplet breakup types with permanent obstruction, part obstruction and without obstruction were observed. The droplet breakup processes with permanent and part obstruction could be divided into squeezing, transition and pinch-off stages. The minimum width of droplet neck could be scaled as power-law relationships with time for squeezing stage and with remaining time for the last two stages. The droplet breakup process without obstruction has only last two stages. The results show that the magnetic field could affect the dynamics of droplet breakup.

Research on Voltage Stability Boundary under Different Reactive Power Control Mode of DFIG Wind Power Plant

Ma, Rui,Qin, Zeyu,Yang, Wencan,Li, Mo The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.6

A novel method is proposed to construct the voltage stability boundary of power system considering different Reactive Power Control Mode (RPCM) of Doubly-Fed Induction Generator (DFIG) Wind Power Plant (WPP). It can be used for reflecting the static stability status of grid operation with wind power penetration. The analytical derivation work of boundary search method can expound the mechanism and parameters relationship of different WPP RPCMs. In order to improve the load margin and find a practical method to assess the voltage security of power system, the approximate method of constructing voltage stability boundary and the critical points search algorithms under different RPCMs of DFIG WPP are explored, which can provide direct and effective reference data for operators.

Preparation of Lysine-Coated Magnetic Fe₂O₃ Nanoparticles and Influence on Viability of A549 Lung Cancer Cells

Ma, Yu-Hua,Peng, Hai-Ying,Yang, Rui-Xia,Ni, Fang Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.20

Objective: To explore the effect of lysine-coated oxide magnetic nanoparticles (Lys@MNPs) on viability and apoptosis of A549 lung cancer cells. Methods: Transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Zeta potentiometric analyzer were employed to characterize Lys@MNPs. Then Lys@MNPs and lung cancer A549 cells were co-cultured to study the effect of Lys@MNPs on cell viability and apoptosis. The pathway of Lys@MNPs entering A549 cells was detected by TEM and cell imaging by 1.5 T MRI. Results: Lys@MNPs were 10.2 nm in grain diameter, characterized by small size, positive charge, and superparamagnetism. Under low-dose concentration of Lys@MNPs (< $40{\mu}g/mL$), the survival rate of A549 cells was decreased but remained higher than 95% while under high-dose concentration ($100{\mu}g/mL$), the survival ratewas still higher than 80%, which suggested Lys@MNPs had limited influence on the viability of A549 cells, with good biocompatibility and and no induction of apoptosis. Moreover, high affinity for cytomembranes, was demonstrated presenting good imaging effects. Conclusion: Lys@MNPs can be regarded as a good MRI negative contrast agents, with promising prospects in biomedicine.