Cuprum Metal-Organic-Framework and Polyacrylonitrile-Derived Cu-N-C Electrocatalyst for Application in Zinc-Air Batteries

Yajun Zhao,Jintao Chen,Xiaorui Li,Jiaqing Zhang,Yanan Li,Yajun Zhao,Liye Cao,Xiaoshi Jin 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.02

Cu-N-C electrocatalyst was successfully prepared with Cu-BTC and polyacrylonitrile as templates by electrospinning and in-situ growth method. The effect of various N-doped content on the electrochemical performance of the catalyst were investigated and the Cu-N-C-0.25 exhibited the best OER/ORRcatalytic activities. When it was applied to the cathode of the zinc-air batteries, the power density of Cu-N-C-0.25 was 209.1 mW cm -2, which exceeded that of the commercial Pt/C + IrO2 hybrid catalyst (157 mW cm -2). The excellent electrochemical performance may be attributed to large number of active sites and high specific surface area on Cu-N-C electrocatalyst. It will be a promising alternative to precious metal catalysts containing Pt, Ir or Ru and their oxides.

Wind-induced responses of supertall buildings considering soil-structure interaction

Yajun Huang,Ming Gu 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.4

In this study, a simplified three-dimensional calculation model is developed for the dynamic analysis of soil-pile group-supertall building systems excited by wind loads using the substructure method. Wind loads acting on a 300-m building in different wind directions and terrain conditions are obtained from synchronous pressure measurements conducted in a wind tunnel. The effects of soil-structure interaction (SSI) on the first natural frequency, wind-induced static displacement, root mean square (RMS) of displacement, and RMS of acceleration at the top of supertall buildings are analyzed. The findings demonstrate that with decreasing soil shear wave velocity, the first natural frequency decreases and the static displacement, RMS of displacement and RMS of acceleration increase. In addition, as soil material damping decreases, the RMS of displacement and the RMS of acceleration increase.

CO2 Capture on a Novel Porous Silicate Material from Coal Gangue: Equilibrium, Kinetic, and Thermodynamic Studies

Yajun Gao,Hong Du,Yu Wu,Kai Liu,Jianbin Zhang 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.2

The adsorption of CO2 on a novel porous silicate material (PSM) from coal gangue at T = (288.15, 303.15, and 318.15) K was thoroughly characterized, and the experimental results showed that the adsorption capacity increased with the increasing pressures. Furthermore, the isotherm data were well fitted to Double–Langmuir model, and the adsorption process was found to be exothermic in nature with a decrease in entropy. Meanwhile, thermodynamic results also showed that the adsorption occurred via a spontaneous and enthalpy driven process and controlled by physisorption. In addition, the adsorption performance was still stable after 10 times adsorption—desorption cycles, which indicated that the PSM had a positive regeneration performance.

Simulation of Nonstationary Process Using Ensemble Empirical Mode Decomposition and Empirical Envelope Methods

Yajun Zhao,Yuanming Dou 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.11

A simulation method for nonstationary process is proposed based on the ensemble empirical mode decomposition (EEMD) and the empirical envelope (EE) methods: the EEMD is used to decompose a nonstationary process into several mono-component signals, and then the EE method is utilized to calculate the instantaneous characteristics of these mono-component signals; a simulated process can be constructed based on the distributions of the instantaneous characteristics of the mono-component signals. An earthquake ground motion recorded in chi-chi earthquake and a nonstationary wind speed induced by typhoon Rammasun are utilized to verify the accuracy and efficacy of the newly-developed method. Results show that: the EE method performs much better than the Hilbert transform (HT)-based method in calculating the instantaneous frequency; the proposed method can successfully capture the global and transient energy distributions of a nonstationary process; the nonstationary wind speed can be modeled as a uniformly modulated nonstationary process, while the earthquake ground motion should be modeled as a non-uniformly modulated nonstationary process. The proposed method does not include any pre-assumed modulation function or inappropriate assumption such as piece-wise stationarity. The method is applicable to the simulation of various types of nonstationary processes, and it can be extended to simulate multivariate nonstationary processes.

Rhein lysinate inhibits monocyte adhesion to human umbilical vein endothelial cells by blocking p38 signaling pathway

Yajun Lin,Yongzhan Zhen,Jiang Liu,Jie Wei,Ping Tu,Gang Hu 대한약학회 2013 Archives of Pharmacal Research Vol.36 No.11

The objective of this study was to investigate theeffect of rhein lysinate (RHL) on monocyte adhesion and itsmechanism. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay was used to determine thegrowth inhibition by drugs. The monocyte chemoattractantprotein (MCP)-1 levels were assayed using MCP-1 ELISA. The expression of proteins was detected by Western blottinganalysis. The results indicated that RHL inhibited monocyteadhesion in a dose- and time-dependent manner. RHL(\20 lmol/L) and lipopolysaccharide (LPS) had no effecton viability of human umbilical vein endothelial cells. Therefore, 20 lmol/L RHL was selected for this study. RHLinhibited secretion ofMCP-1 induced by LPS and expressionof intercellular adhesion molecule (ICAM)-1 and vascularcell adhesion molecule (VCAM)-1. In the meantime, bothRHL and p38 inhibitor (SB203580) inhibited phosphorylationof p38 and mitogen-activated protein kinase-activatedprotein kinase-2 (MAPKAPK-2) and transcription andexpression of ICAM-1 and VCAM-1. In conclusion, RHLinhibits the transcription and expression of ICAM-1 andVCAM-1 by the p38/MAPKAPK-2 signaling pathway, andthe effect ofRHLon transcription and expression of ICAM-1and VCAM-1 is similar to p38 inhibitor. RHL could be aprophylactic drug for atherosclerosis.

Bacterial Community Shift during the Startup of a Full-Scale Oxidation Ditch Treating Sewage

( Yajun Chen ),( Lin Ye ),( Fuzheng Zhao ),( Lin Xiao ),( Shupei Cheng ),( Xu-xiang Zhang ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.1

The oxidation ditch (OD) is one of the most widely used processes for treating municipal wastewater. However, the microbial communities in the OD systems have not been well characterized, and little information about the shift of bacterial community during the startup process of the OD systems is available. In this study, we investigated the bacterial community changes during the startup period (over 100 days) of a full-scale OD. The results showed that the bacterial community dramatically changed during the startup period. Similar to the activated sludge samples in other studies, Proteobacteria (accounting for 26.3%-48.4%) was the most dominant bacterial phylum in the OD system, but its relative abundance declined nearly 40% during the startup process. It was also found that Planctomycetes proliferated greatly (from 4.79% to 13.5%) and finally replaced Bacteroidetes as the second abundant phylum in the OD system. Specifically, some bacteria affiliated with genus Flavobacterium exhibited remarkable decreasing trends, whereas bacterial species belonging to the OD1 candidate division and Saprospiraceae family were found to increase during the startup process. Despite of the bacterial community shift, the organic matter, nitrogen, and phosphorus in the effluent were always in low concentrations, suggesting the functional redundancy of the bacterial community. Moreover, by comparing with the bacterial community in other municipal wastewater treatment bioreactors, some potentially novel bacterial species were found to be present in the OD system. Collectively, this study improved our understandings of the bacterial community structure and microbial ecology during the startup of a full-scale wastewater treatment bioreactor.

Deposition and evaluation of MoNx films deposited by magnetron sputtering

Yajun Ma,Shenghua Li,Yuansheng Jin,Guoshun Pan,Yucong Wang,Simon C. Tung 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10

Molybdenum Nitrided (MoNx) films were deposited by DC planar magnetron sputtering. Silicon wafers and real nitrided stainless steel piston rings are employed as substrates. 12 different combinations of nitrogen and argon partial pressure, from 1:7 to 7:1, were applied to deposit MoNx films. X-ray diffraction (XRD) was used to determine the phase structures of films. When nitrogen vs. argon partial pressure is 1:7, the film is mainly MO₂N phase. With increase of nitrogen partial pressure, MoN phase emerges, but MO₂N phase still exists. Composition analysis with atomic emission spectrometry (AES) also agreed with this. The films have very high nanohardness (max 2400Hv) and good adhesion to the substrates.

An Improved Flux Estimator for Gap Flux Orientation Control of DC-Excited Synchronous Machines

Yajun Xu,Jianguo Jiang 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.2

Flux estimation is a significant foundation of high-performance control for DC-excited synchronous motor. For almost all flux estimators, such as the flux estimator based on phase locked loop (PLL), DC drift causes fluctuations in flux magnitude. Furthermore, significant dynamic error may be introduced at transient conditions. To overcome these problems, this paper proposes an improved flux estimator for the PLL-based algorithm. Filters based on the generalized integrator are used to avoid flux fluctuation problems caused by the DC drift at the back electromotive force. Programmable low-pass filters are employed to improve the dynamic performance of the flux estimator, and the cutoff frequency of the filter is determined by the dynamic factor. The algorithm is verified by a 960V/1.6MW industrial prototype. Simulation and experimental results show that the proposed estimator can estimate the flux more accurately than the PLL-based algorithm in a cycloconverter-fed DC-excited synchronous machine vector control system.

Study on Forage Oat in Qinghai Alpine Region

Yajun Ji,Qingping Zhou,Hongbo Yan,Wenhui Liu 한국초지조사료학회 2009 한국초지조사료학회 학술대회논문집 Vol.2009 No.08

The cultivation of oat in China could be traced back to 2500 B.C. while the Qinghai province, which located in the North-East of the Qinghai-Tibetan Plateau, has been the major region for oat production due to its high quality caused by the unique climate say long sun-shine hours and large temperature discrepancy between days and nights that is beneficial to the accumulation of nutrients in oat plant. Oat has been grown in the Qinghai alpine region on the altitude ranging from 1600m to 3600m and regarded as an ideal forage plant due to its resistance to environment. The role of oat drew more attention in 1980s along with the implementing of so called four-matched policy, which compounds establishment of fenced rangeland, animal bars, fodder production base and settled living place for local herdsmen who used to be nomadic around the region. To make a full use of the oat resource in Qinghai province, a great deal research and extension with respect of oat had been engaged in the region. The author overviewed researches accomplished in Qinghai province on oat germplasm collection, breeding of fine oat variety, cultivate techniques, oat base establishment and production and marketing system establishment as well in terms of projects completed.

Structural characterization and applications of ITS2 from rice leaffolders Cnaphalocrocis medinalis and Marasmia patnalis (Lepidoptera: Pyralidae)

Yajun Yang,ZhihongWu,Xu-Song Zheng,Zhong-Xian Lu,Hong-Xing Xu 한국응용곤충학회 2017 Journal of Asia-Pacific Entomology Vol.20 No.2

Cnaphalocrocis medinalis and Marasmia patnalis are important rice insect pests in Asia and have similarmorphologic features and same feeding patterns. Understanding the molecular difference of the two leaffolders is helpful to their identification and clarification of their phylogenetic class in the Pyraloidea. In this study, we determined and analyzed the nucleotide sequences of nuclear rDNA internal transcribed spacer 2 (ITS2) in the two rice leaffolders from 9 populations (six C. medinalis populations collected from China, Philippine, Thailand, and Vietnam, and threeM. patnalis populations from Philippine, Thailand, and Vietnam) and compared interspecies variation of IST2 among different geographic populations and intraspecies variation of ITS2 from Pyraloidea. Phylogenetic trees were constructed on the two leaffolders and other Pyraloidea species using Maximum Parsimony method. Results showed that the ITS2 sequences differed in the two leaffolders. Compared to C. medinalis, ITS2 ofM. patnalis had small deletion at the sites of 41, 72, 81, 304 and an insertion at the site of 337. Interspecies variation results showed that three C. medinalis populations fromSoutheast Asia (VN, PH, and TH) arewith small divergence compared to NJ andHZ, and small divergencewas observed among threeM. patnalis populations (VN, PH, and TH). Intraspecies variation results showed that two leaffolderswere with close relationship compared to the other Pyraloidea. Phylogenetic trees showed that two leaffolderswere grouped togetherwithMaruca vitrata. These results indicated that the ITS2 sequences differed in the two leaffolders could potentially be used in the distinguishing of the two rice leaffolders and the determination on the phylogeny of species.