STABILITY AND BIFURCATION ANALYSIS FOR A TWO-COMPETITOR/ONE-PREY SYSTEM WITH TWO DELAYS

Cui, Guo-Hu,Yany, Xiang-Ping Korean Mathematical Society 2011 대한수학회지 Vol.48 No.6

The present paper is concerned with a two-competitor/oneprey population system with Holling type-II functional response and two discrete delays. By linearizing the system at the positive equilibrium and analyzing the associated characteristic equation, the asymptotic stability of the positive equilibrium and existence of local Hopf bifurcations are investigated. Particularly, by applying the normal form theory and the center manifold reduction for functional differential equations (FDEs) explicit formulae determining the direction of bifurcations and the stability of bifurcating periodic solutions are derived. Finally, to verify our theoretical predictions, some numerical simulations are also included at the end of this paper.

Effects of acid vapour mediated oxidization on the electrochemical performance of thermally exfoliated graphene

Yan, Y.,Kuila, T.,Kim, N.H.,Lee, J.H. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.74 No.-

The surface modification of thermally exfoliated graphene (TEG) is an important technique for alteration of its hydrophobic nature and the resolution of its limited dispersibility. We have developed an easy acid-vapour-mediated method to functionalize the inert TEG surface with oxygen functional groups. The effects of oxygen functional groups on the capacitive performances of TEG were investigated with various reaction times. Ultraviolet-visible, Fourier transform infrared and Raman spectroscopy analyses demonstrated that the dispersibility of TEG was improved due to defect augmenting as the extent of oxidation progressed. Quantitative analyses of functional groups of the oxidized TEG samples (O-TEGs) were performed by thermogravimetric analysis and X-ray photoelectron spectroscopic studies. Physisorption surface analysis showed that the pore volumes of O-TEGs were greater than that of the pristine TEG, whereas the specific surface areas of O-TEGs were lower than that of pristine TEG. Electrochemical performances of the O-TEG samples were measured through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy analysis. A maximum specific capacitance of 175.2Fg<SUP>-1</SUP> was recorded at a current density of 1Ag<SUP>-1</SUP> for the O-TEG oxidized for 2h. Retention of specific capacitance for the sample was ~97% after 5000 charge-discharge cycles.

Assembling pore-rich FeP nanorods on the CNT backbone as an advanced electrocatalyst for oxygen evolution

Yan, Y.,Zhao, B.,Yi, S.,Wang, X. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.33

<P>Electrocatalytic water splitting is a promising means for clean energy production. There is a great need to develop low cost, efficient and durable electrocatalysts for such purposes. Herein, we report a novel hierarchical nanostructure composed of FeP porous nanorods on CNT backbones. The directed growth of alpha-FeO(OH) nanospindles on CNTs was first realized via a bottom-up assembly, followed by phosphorization transformation. When evaluated for the electrocatalytic water splitting reaction, these hierarchical structures exhibited superior oxygen evolution performance due to their advantageous structural features.</P>

N-doped carbon layer coated thermally exfoliated graphene and its capacitive behavior in redox active electrolyte

Yan, Y.,Kuila, T.,Kim, N.H.,Lee, S.H.,Lee, J.H. Pergamon Press ; Elsevier Science Ltd 2015 Carbon Vol.85 No.-

A nitrogen-doped carbon layer coated thermally exfoliated graphene (NC-TEG) is prepared by in-situ polymerization of p-phenylene diamine (PD) with thermally exfoliated graphene (TEG) and subsequent high temperature pyrolysis (600<SUP>o</SUP>C for 1h in argon gas environment). Fourier transfer infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy confirm the formation of poly-(p-phenylene diamine) layers on the TEG surfaces with a nitrogen doping level of ~6.1%. Physisorption analysis indicates that NC-TEG not only has the enlarged surface area, but also forms hierarchical three dimensional structures with several micro and meso-pores compared to pristine TEG. Due to the synergic effect of nitrogen atoms in the carbon structures and augmented surface area, the capacitance measured from cyclic voltammetry and galvanic charge-discharge increases to 282.5Fg<SUP>-1</SUP> from the 95.1Fg<SUP>-1</SUP> of TEG. Moreover, the PD monomer acts as a reversible faradaic agent. The capacitive performance of the NC-TEG electrode is investigated in different mixed electrolytes. The specific capacitance is significantly increased to 635.6Fg<SUP>-1</SUP> in a mixed electrolyte of 0.025M PD and 2M KOH. After 10,000 cycles, the capacitive retention shows remarkable stability as high as 87.4%.

In Reply: SARS-CoV-2 Vaccination Related, Pediatric Guillain-Barre Syndrome Requires the Same Management as in Adults

Pricilla Yani Gunawan(Pricilla Yani Gunawan ) 대한정신약물학회 2023 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.21 No.1

Guillain-Barre Syndrome Following SARS-CoV-2 Vaccination: A Case Report

Pricilla Yani Gunawan(Pricilla Yani Gunawan ),Pamela Tiffani(Pamela Tiffani ),Lilie Lalisang(Lilie Lalisang ) 대한정신약물학회 2022 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.20 No.4

After more than a year of Coronavirus disease 2019 pandemic, in 2021 Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccination have been made possible and vaccine was distributed globally. Since then, there have been reports of symptoms following SARS-CoV-2 vaccination, including neurological symptoms of ascending paralysis known as Guillain-Barre syndrome. In this report, we describe the first case of Guillain-Barre syndrome following vaccination in Indonesia. Symptoms of ascending paralysis were of late onset after the first dose, however, were full blown after receiving the second dose followed by left-sided facial paralysis.

Adsorption differences and mechanism of chitooligosaccharides with specific degree of polymerization on macroporous resins with different functional groups

Yanying Hou,Lujie Liu,Xingxing Zhang,Yuechao Zhu,Yongjun Qiu,Liming Zhao 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Ion exchange resins are promising materials for separating chitooligosaccharides (COSs) with differentdegrees of polymerization (DP). The adsorbent functional groups significantly determine the interactionswith COSs and affect their adsorption and separation efficiency. This study investigated the adsorptionbehaviors of COSs on macroporous cation exchange resins with different functional groups to clarifythe functional group effect on the adsorption of COSs with different DP, which can also help to providea theoretical basis for the selection of separation medium and optimization of the separation technicsof COSs. The results showed that the adsorption of COSs on sulfonic-acid type resin DX-10 andcarboxylic-acid type resin DC-10 were favorable, and the adsorption isotherms were in accord withthe Sips model. Adsorption thermodynamics showed that temperature had opposite effects on the tworesins’ equilibrium adsorption capacity of COSs. The diffusion coefficient of COSs on DX-10 resin wasgreater, and the affinity gap between COSs on DX-10 resin was larger than that of DC-10 resin, whichis beneficial for improving the separation resolution of COSs. In contrast, the interaction energy betweenCOSs with high DP and DC-10 resin was weaker compared with DX-10, which made the elution of COSswith high DP easier.

The Effect of Family Structure on Labor Supply of Married Women in China

Yani Cao, Chanyoung Lee 부산대학교 중국연구소 2019 Journal of China Studies Vol.22 No.3

Fundamental issues of applications of C/SiC composites for re-entry vehicles

Yani Zhang,Litong Zhang,Hui Mei,Qingqing Ke,Yongdong Xu,Laifei Cheng 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.3

Carbon fiber reinforced silicon carbide ceramic matrix composite materials (C/SiCs) are being tested for hot structures and thermal protection systems (TPS) of launch vehicles and spacecraft, and also for advanced friction system of aircraft and racing cars. A number of tribological and joining components are required in these applications, such as bushing and rolling contact bearings, nuts and bolts, which require excellent mechanical, physical and chemical properties at temperatures higher than 1650℃. This study summarizes preparation of C/SiC load-carrying bearings for hinge by the Chemical Vapor Infiltration (CVI) method and C/SiC bolts for joints by the CVI + PIP (Polymer Impregnation and Pyrolysis) methods. The hinge bearing and bolts were examined in a simulated re-entry environment. Stress-oxidation was investigated under different stress levels from 0 to 200MPa up to 1800℃. The friction behavior of the hinge bearing system was studied under high loads (up to 25 kN) and low rotating velocities. The mechanical properties of the bolts with a thread connection were conducted under tensile and shear fatigue at both room temperature and elevated temperature. The results show that the stress-oxidation behavior of 2D-C/SiC composites in a combustion environment is a combined effect of extremely high load, high temperature, and oxidation. The load and temperature influenced the crack openings and thus the oxidation of carbon fibers in the precracked composites. The combustion environment mainly determined the time to failure of the specimens by oxidation damage under a high applied stress. Reliable thermal load-carrying ability and stable friction performance of the hinge bearing is demonstrated in high-temperature combustion environments with extremely high loads. The oxidation products of SiO2 at high temperatures between surfaces played an important role to modifies the friction by providing a protective layer. The room temperature tensile and shear strength of the bolts made of needled C/SiC are 139 MPa and 83 MPa, respectively. Even at 1800℃ in a combustion environment, the strengths still retained about 116MPa with a maximum decrease of 13%. More importantly, the bolts did not suffer significant mechanical degradation after tension-tension fatigue at 1 Hz for 24 h. Carbon fiber reinforced silicon carbide ceramic matrix composite materials (C/SiCs) are being tested for hot structures and thermal protection systems (TPS) of launch vehicles and spacecraft, and also for advanced friction system of aircraft and racing cars. A number of tribological and joining components are required in these applications, such as bushing and rolling contact bearings, nuts and bolts, which require excellent mechanical, physical and chemical properties at temperatures higher than 1650℃. This study summarizes preparation of C/SiC load-carrying bearings for hinge by the Chemical Vapor Infiltration (CVI) method and C/SiC bolts for joints by the CVI + PIP (Polymer Impregnation and Pyrolysis) methods. The hinge bearing and bolts were examined in a simulated re-entry environment. Stress-oxidation was investigated under different stress levels from 0 to 200MPa up to 1800℃. The friction behavior of the hinge bearing system was studied under high loads (up to 25 kN) and low rotating velocities. The mechanical properties of the bolts with a thread connection were conducted under tensile and shear fatigue at both room temperature and elevated temperature. The results show that the stress-oxidation behavior of 2D-C/SiC composites in a combustion environment is a combined effect of extremely high load, high temperature, and oxidation. The load and temperature influenced the crack openings and thus the oxidation of carbon fibers in the precracked composites. The combustion environment mainly determined the time to failure of the specimens by oxidation damage under a high applied stress. Reliable thermal load-carrying ability and stable friction performance of the hinge bearing is demonstrated in high-temperature combustion environments with extremely high loads. The oxidation products of SiO2 at high temperatures between surfaces played an important role to modifies the friction by providing a protective layer. The room temperature tensile and shear strength of the bolts made of needled C/SiC are 139 MPa and 83 MPa, respectively. Even at 1800℃ in a combustion environment, the strengths still retained about 116MPa with a maximum decrease of 13%. More importantly, the bolts did not suffer significant mechanical degradation after tension-tension fatigue at 1 Hz for 24 h.

Modelling the multi-physics of wind-blown sand impacts on high-speed train

Yani Zhang,Chen Jiang,Xuhe Zhan 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.5

The wind-blown sand effect on the high-speed train is investigated. Unsteady RANS equation and the SST k–ω turbulent model coupled with the discrete phase model (DPM) are utilized to simulate the two-phase of air-sand. Sand impact force is calculated based on the Hertzian impact theory. The different cases, including various wind velocity, train speed, sand particle diameter, were simulated. The train’s flow field characteristics and the sand impact force were analyzed. The results show that the sand environment makes the pressure increase under different wind velocity and train speed situations. Sand impact force increases with the increasing train speed and sand particle diameter under the same particle mass flow rate. The train aerodynamic force connected with sand impact force when the train running in the wind-sand environment were compared with the aerodynamic force when the train running in the pure wind environment. The results show that the head car longitudinal force increase with wind speed increasing. When the crosswind speed is larger than 35m/s, the effect of the wind- sand environment on the train increases obviously. The longitudinal force of head car increases 23% and lateral force of tail increases 12% comparing to the pure wind environment. The sand concentration in air is the most important factor which influences the sand impact force on the train.