Sino-South Korean Scientific Collaboration Based On Co-Authored SCI Papers

Sun, Junwei,Jiang, Chunlin Korea Institute of Science and Technology Informat 2014 Journal of Information Science Theory and Practice Vol.2 No.1

Using statistic and bibliometric methods to characterize scientific cooperation between China (excluding Hong Kong, Macao, and Taiwan) and South Korea through their bilateral co-authored papers covered by the Science Citation Index CD-ROM, 1991-2010, in our paper we exploit the feature of their cooperation in four levels: time sequence, academic community, key fields, and institution distribution. From the time sequence we know that collaboration between China and Korea starts in 1991, reaching the first peak during 2004-2007. As for the academic community, the number of Chinese corresponding authors (2414) is slightly lower than that of Korea (2700). Regarding the 27 high yield authors, there are only 4 coming from China. Korea has a higher active level than Chinese authors. China and Korea tend to cooperate with each other on strong disciplines such as physics, chemistry, material science, engineering, mathematics, pharmaceutical, computer science and biology. Furthermore, they also attach great importance to basic research and high-tech cooperation. Besides, Chinese Academy of Sciences ranks at the top 1 among the distribution of institutions. As a majority of the collaborative institutions are universities, the participation of non-university institutions is relatively low. There are 7 Korean universities among the top ten institutions, while Yanbian University and Tsinghua University in China rank respectively as third and fourth. Seoul National University, accompanied by Korea University and Yonsei University as the three top Korean universities, is also among the top among the cooperating institutions.

Dynamical Analysis of Memcapacitor Chaotic System and Its Image Encryption Application

Junwei Sun,Gaoyong Han,Yanfeng Wang 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.5

The prospective studies on memcapacitor models and potential applications are of importance due to its dynamical behavior. For this purpose, a memcapacitor model and a corresponding circuit model have been designed, whose characteristics have been investigated theoretically and experimentally. Based on the unique space conformation of DNA molecules and their unique information storage and processing ability, a memcapacitor chaotic image encryption algorithm combining with DNA sequence operations is proposed in the first time. DNA sequence operations and memcapacitor chaos iterations are used in the encryption process to strengthen the confusion and diffusion properties of the scheme. The simulation results and theoretical analysis show that the algorithm improves the sensitivity of key and the security of data transmission, and has better ability of the hacker attacks.

Preparation of an Early Strengthening Agent for Concrete under Low-Temperature Conditions and Evaluation of Its Reaction Mechanism

Bao, Junwei,Ren, Qifang,Sun, Lei,Ding, Yi,Oh, Won-Chun Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.4

To solve the common problems of concrete preparation in low-temperature environments, calcium formate (C₂H₂O₄Ca), anhydrous sodium sulfate (Na₂SO₄), triethanolamine (C₆H₁₅O₃N), calcium bromide (CaBr₂), and triisopropanolamine (C₉H₂₁NO₃) are selected as early strength agents and mixed with C40 concrete in different dosages under low-temperature environments of 5 ℃ and 10 ℃ to develop a high-efficiency low-temperature compound early strength agent based on the effect of single-doped early strength agents. The effects of the compound early strength agent on the early strength of the concrete, the cement paste setting time, and cement fluidity at 5 ℃ and 10 ℃ are investigated, and the corresponding reaction mechanism is discussed from the perspective of micro-products. The best compound early strength agent ratio is found to be 2 % of calcium formate + 0.08 % of TEA (C₆H₁₅O₃N). The compound early strength agent effectively promotes the formation of hydration products, such as Ca(OH)₂ and C-S-H gel. In comparison with the control group, the strength of the concrete cured for 18 h, 1 d, 3 d, and 7 d under simulated natural conditions at 5 ℃ increases by 700 %, 540 %, 11.4 % and 10 %, respectively, whereas at 10 ℃, the corresponding values are 991 %, 400 %, 19.6 % and 11 %, respectively. The strength of the concrete at each age is close to the normal temperature standard of the curing strength. The addition of the compound early strength agent causes a reduction in cement fluidity and initial and final setting times, and also yields a good effect on the porosity of the early concrete.

Workspace and Structural Parameter Analysis for a Novel 3-PRS Parallel Mechanism

Fuwei Sun,Junwei Zhao,Guoqiang Chen 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.12

The working space is one of the important indexes to measure the working capability of parallel mechanism. In this paper, the working space of a new type of 3-PRS parallel mechanism is studied. In the beginning, a novel 3-PRS parallel mechanism is proposed with the kinematics analyzed, and then the working space and volume are obtained by search algorithm, and the working space is drawn using MATLAB. Finally, the influence of the structural parameters on the working space is discussed, which provide theoretical basis for parameter optimization.

SYSTEM POWER LOSS OPTIMIZATION OF ELECTRIC VEHICLE DRIVEN BY FRONT AND REAR INDUCTION MOTORS

Binbin Sun,Song Gao,Chao Ma,Junwei Li 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.1

Power loss optimization aiming at the high-efficiency drive of front-and-rear-induction-motor-drive electric vehicle (FRIMDEV) as an effective way to improve energy efficiency and extend driving range is of high importance. Different from the traditional look-up table method of motor efficiency, power loss optimization of the dual- motor system based on the loss mechanism of induction motor (IM) is proposed. First of all, based on the power loss characteristic of FRIMDEV from battery to wheels, the torque distribution optimization model aiming at the minimum system power loss is put forward. Secondly, referring to d-q axis equivalent model of IM, the power loss functions of the dual-IM system are modeled. Then, the optimal torque distribution coefficient (βo) between the two IMs is derived, and the theoretical switching condition (Tsw) between the single- and dual-motor-drive mode (SMDM and DMDM) is confirmed. Finally, a dual-motor test platform is developed. The derived torque distribution strategy is verified. The influence of motor temperature on βo and Tsw are tested, and the correction models based on temperature difference are proposed. Based on the system power loss analysis, it can be confirmed that, under low load conditions, the SMDM takes priority over the DMDM, and the controller of the idling motor should be shut down to avoid the additional excitation loss. While under middle to high load conditions, even torque distribution (βo = 0.5) is preferred if the temperature difference between the two IMs is small; otherwise, βo should be corrected based on dual-motor temperatures. The theoretical Tsw derived without dealing with temperature difference is a function only of motor speed, while temperature difference correction of it should be conducted in actual operations based on motor resistance changing with temperature.

Five Inputs Code Lock Circuit Design Based on DNA Strand Displacement Mechanism

Jixiang Li,Yurong Li,Junwei Sun,Yanfeng Wang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.11

In recent years, the development of biological computers is becoming faster and faster, in order to make the logical operation algorithms of biological computers more mature and stable, a new idea for the code lock logic circuit is proposed based on DNA strand displacement by using the dual-rail method. The code lock is designed by four input signals and one conversion input signal. Only when the four input codes are correct and the conversion signal code is turned on, the password lock will be in open state, otherwise the password lock will produce an alarm signal, stopping outside invasion timely. The information of key is processed to obtain the correct password; finally, the experimental simulation results are obtained by Visual DSD software. The results analysis show that the designed code lock circuit is effective, which may provide a good technical support and a good theoretical basis in biological computers development.

Effect of Scale-Dependent Viscosity and Transesterification on Filling Behavior of Polycarbonate/Poly(ethylene terephthalate) Blends in Micro-Injection Molding

Bozhi Cai,Jing Jiang,Yongjun Cao,Junwei Sun,Ning Zhang,Qian Li 한국고분자학회 2022 Macromolecular Research Vol.30 No.3

This study introduces a new scale-dependent viscosity model, in which transesterification reaction of polycarbonate/poly(ethylene terephthalate) (PC/PET) blends with various phase morphologies and micro-scale effects have been taken into account. It is found that a Power-law model can be used to quantitatively describe the relationship between the degree of transesterification and shear rate employed during compounding of PC and PET. A micro-scale viscosity model, which incorporates the micro-scale effects, has been developed by characterizing the flow using a double-barrel capillary rheometer with different microscale channels. For both neat PC and PC/PET blends, under the conditions of the constant shear rate and melt temperature, the shear viscosity dropped with decreasing capillary diameter because of the wall-slip effect. The proposed viscosity model based on the Cross equation can describe the variation of shear viscosity for PC/PET blends under both macro- and micro-scale conditions. Less than 7% average error is obtained between the model predictions and rheological experimental data. Filling simulation and micro-injection molding (μIM) short-shot experiments were conducted to validate the accuracy of the proposed viscosity model. For all the L9(34) design of experiment (DOE) molding trials, the average relative error under the micro-scale condition was 4.5±1.1%, which is much smaller than that of the average relative error under the macro-scale condition at 11.4±2.7%.

Macrokinetic Model for Gluconobacter oxydans in 2-keto-L-gulonic Acid Mixed Culture

Zhixiong Zhang,Xinjie Zhu,Ping Xie,Junwei Sun,Jingqi Yuan 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.5

A set of kinetic models have been developed for the production of 2-keto-L-gulonic acid from L-sorbose by a mixed culture of Gluconobacter oxydans and Bacillus megaterium. A metabolic pathway is proposed for Gluconobacter oxydans, and a macrokinetic model has been developed for Gluconobacter oxydans, where the balances of some key metabolites, ATP and NADH are taken into account. An unstructured model is proposed for concomitant bacterium Bacillus megaterium. In the macrokinetic model and unstructured model, the mechanism of interaction between Gluconobacter oxydans and Bacillus megaterium is investigated and modeled. The specific substrate uptake rate and the specific growth rate obtained from the macrokinetic model are then coupled into a bioreactor model such that the relationship between the substrate feeding rate and the main state variables, such as the medium volume, the biomass concentrations, the substrate,and the is set up. A closed loop regulator model is introduced to approximate the induction of enzyme pool during lag phase after inoculation. Experimental results demonstrate that the model is able to describe 2-keto-Lgulonic acid fermentation process with reasonable accuracy.

Fluorine-doped porous carbon-decorated Fe₃O₄-FeF₂ composite versus LiNi_0.5Mn_1.5O₄ towards a full battery with robust capability

Ming, Hai,Ming, Jun,Kwak, Won-Jin,Yang, Wenjing,Zhou, Qun,Zheng, Junwei,Sun, Yang-Kook Elsevier 2015 ELECTROCHIMICA ACTA Vol.169 No.-

<P><B>Abstract</B></P> <P>A new fluorine-doped porous carbon-decorated Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB> composite, referred to as Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB>, was prepared for the first time. The formation mechanism is discussed, and a new concept of introducing double layers of FeF<SUB>2</SUB> and CF<SUB>x</SUB> into the oxide-based anode is presented for lithium ion batteries. Varying the amount of fluorine precursor, derivatives of Fe<SUB>3</SUB>O<SUB>4</SUB>@CF<SUB>x</SUB> and FeF<SUB>2</SUB>@CF<SUB>x</SUB> were further obtained, allowing an original analysis of their electrochemical behaviors. As-prepared Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB> can deliver a high capacity of 718mAhg<SUP>−1</SUP> at 50mAg<SUP>−1</SUP>. Under a hash rate of 1600mAg<SUP>−1</SUP>, the capacity of Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB> (around 338mAhg<SUP>−1</SUP>) is higher than that (200mAhg<SUP>−1</SUP>) of FeF<SUB>2</SUB>@CF<SUB>x</SUB>. Further, its capacity retention of 97% over 100 cycles is much better than the 59.4% observed for Fe<SUB>3</SUB>O<SUB>4</SUB>@CF<SUB>x</SUB>. The positive effect of the CF<SUB>x</SUB> layer on the electronic conductivity and ionic diffusion ability was confirmed. The role of FeF<SUB>2</SUB> in the stabilization of the structure of CF<SUB>x</SUB> and Fe<SUB>3</SUB>O<SUB>4</SUB> is also discussed. Further, a new battery composed of Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB>/LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> with a robust rate capability was assembled and delivered a reversible capacity of 565mAhg<SUP>−1</SUP> (<I>vs.</I> anode) at 100mAg<SUP>−1</SUP> with a high potential of 3.3V and a capacity retention of 81.5% over 50 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new anode of fluorine-doped porous Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB> composite is readily prepared. </LI> <LI> The CF<SUB>x</SUB> layer enhances the conductivity of Fe<SUB>3</SUB>O<SUB>4</SUB> and ensures a fast Li<SUP>+</SUP> diffusion. </LI> <LI> The FeF<SUB>2</SUB> can stabilize the structure of Fe<SUB>3</SUB>O<SUB>4</SUB> during the (dis) charge process. </LI> <LI> The Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB> can deliver a high capacity with a robust rate capability. </LI> <LI> A full cell of Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB>/LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> with high performance is assembled. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>A new anode of fluorine doped porous Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB> composite with double layers of FeF<SUB>2</SUB> and CF<SUB>x</SUB> was presented for the first time, and a high rate capability was obtained in lithium ion battery. Besides, a new full battery of Fe<SUB>3</SUB>O<SUB>4</SUB>-FeF<SUB>2</SUB>@CF<SUB>x</SUB>/LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> with a high capacity of 565mAhg<SUP>−1</SUP> (<I>vs</I>. anode) at the current density of 100mAg<SUP>−1</SUP> was successfully introduced. It demonstrated a robust rate capability, high operating potential of 3.3V and fine cycle ability over 50 cycles with capacity retention of 81.5%.</P> <P>[DISPLAY OMISSION]</P>

The binder effect on an oxide-based anode in lithium and sodium-ion battery applications: the fastest way to ultrahigh performance

Ming, Jun,Ming, Hai,Kwak, Won-Jin,Shin, Changdae,Zheng, Junwei,Sun, Yang-Kook The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.87

<P>A positive effect of the polyacrylic acid (PAA)–carboxymethyl cellulose (CMC) binder to enhance the performance of an oxide-based anode was reported in batteries. A series of super high capacity and cycling ability oxide powders rarely achieved before was obtained, particularly most of them without any specific carbon modification and/or morphology control.</P> <P>Graphic Abstract</P><P>A positive effect of the polyacrylic acid–carboxymethyl cellulose binder to enhance the performance of an oxide-based anode was reported in batteries. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cc02657h'> </P>