Electrochemical Deposition of γ-MnO2 on Ag/rGO Hybrid Films as Flexible Electrode Materials for Asymmetric Supercapacitor

Shiqing Sun,Yongkun Liu,Guohua Jiang,Bo Yu,Uwamahoro Evariste,Pianpian Ma 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.3

The fl exible electrodes are the essential components for fabricating modern fl exible supercapacitors. In this study, a compositehybrid fi lm integrated with silver nanoparticles (Ag NPs), reduced graphene oxide (rGO) and γ-MnO 2 nanorods asa fl exible electrode has been developed by the electrochemical deposition method. The substrate (rGO) of the electrode notonly provides mechanical stability but also ensures fast electron transfer during charge–discharge. The Ag NPs distributedin electrode provide the electronic channel to enhance the electric conductivity. The γ-MnO 2 electroplated on the surface ofhybrid fi lms further improved the electrochemical performance of them. The resultant γ-MnO 2 /Ag/rGO hybrid fi lms exhibita high specifi c capacitance of 1090.3 F g −1 at current density of 0.3 A g −1 . The asymmetric supercapacitor (ASC) deviceswere further fabricated by γ-MnO 2 /Ag/rGO fi lms as anode and AC/rGO fi lms as cathode electrodes within a wide operatingvoltage of 0–1.7 V. The energy density of obtained ASC devices was 71.8 Wh kg −1 at a power density of 279.4 W kg −1 .

DEPOSITION AND CHARACTERIZATION OF YN THIN FILMS

Xiao, Shiqing,Takai, Osamu 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.2 No.4

YNx films were prepared by the rf reactive ion plating method. The composition of the films were altered by changing the rf power and Ar/$N_2$ ratio. The films exhibited metallic and semiconductive electrical conductive behavior depending on the film composition. The hardness of the films reached HD900, which meant that the films were harder than sodalime glass. The XPS result revealed the chemical shifts of 2.6eV for the Y 3d peak and -1.9eV for the N ls peak by the formation of Y-N bonds.

MicroRNA-21 promotes epithelial-mesenchymal transition and migration of human bronchial epithelial cells by targeting poly (ADP-ribose) polymerase-1 and activating PI3K/AKT signaling

Zhang, Shiqing,Sun, Peng,Xiao, Xinru,Hu, Yujie,Qian, Yan,Zhang, Qian The Korean Society of Pharmacology 2022 The Korean Journal of Physiology & Pharmacology Vol.26 No.4

Epithelial-mesenchymal transition (EMT) is known to be involved in airway remodeling and fibrosis of bronchial asthma. However, the molecular mechanisms leading to EMT have yet to be fully clarified. The current study was designed to reveal the potential mechanism of microRNA-21 (miR-21) and poly (ADP-ribose) polymerase-1 (PARP-1) affecting EMT through the PI3K/AKT signaling pathway. Human bronchial epithelial cells (16HBE cells) were transfected with miR-21 mimics/inhibitors and PARP-1 plasmid/small interfering RNA (siRNA). A dual luciferase reporter assay and biotin-labeled RNA pull-down experiments were conducted to verify the targeting relationship between miR-21 mimics and PARP-1. The migration ability of 16HBE cells was evaluated by Transwell assay. Quantitative real-time polymerase chain reaction and Western blotting experiments were applied to determine the expression of Snail, ZEB1, E-cadherin, N-cadherin, Vimentin, and PARP-1. The effects of the PI3K inhibitor LY294002 on the migration of 16HBE cells and EMT were investigated. Overexpression of miR-21 mimics induced migration and EMT of 16HBE cells, which was significantly inhibited by overexpression of PARP-1. Our findings showed that PARP-1 was a direct target of miR-21, and that miR-21 targeted PARP-1 to promote migration and EMT of 16HBE cells through the PI3K/AKT signaling pathway. Using LY294002 to block PI3K/AKT signaling pathway resulted in a significant reduction in the migration and EMT of 16HBE cells. These results suggest that miR-21 promotes EMT and migration of HBE cells by targeting PARP-1. Additionally, the PI3K/AKT signaling pathway might be involved in this mechanism, which could indicate its usefulness as a therapeutic target for asthma.

A RIF Based Mapping of RDB2RDF

Ying Chen,Zhuoming Xu,Yuyan Ni,Guangxu Cao,Shiqing Zhang 보안공학연구지원센터 2014 International Journal of Database Theory and Appli Vol.7 No.6

Mapping RDB to RDF (i.e., RDB2RDF) is the key to constructing the Semantic Web, hence has been an active research field during the last decade. Many technically heterogeneous RDB2RDF tools resulted in non-interchangeable and unreusable RDB2RDF mapping descriptions. In 2009, the W3C RDB2RDF Incubator Group Report once strongly suggested that the RDB2RDF mapping language be expressed in rules as defined by the W3C Rule Interchange Format (RIF) Working Group, because rules are an effective way to express mappings between information models, and RIF, as part of the infrastructure for the Semantic Web, is now a standard for exchanging rules among Web rule systems. This paper addresses the issue of RIF-based RDB2RDF mapping and proposes a database semantics-driven, RIF Production Rule Dialect (RIF-PRD) based mapping description approach. The work includes defining a set of generic RIF-PRD mapping rules for RDB2RDF, developing a prototype mapping engine called RIFD2RME (stands for RIF-based RDB2RDF Mapping Engine), and conducting case study experiments with the prototype. The experimental results indicate that the proposed mapping approach is achievable and effective.

A study of a new hybrid vibration energy harvester based on broadband-multimode

Bing Chen,Shiqing Li,Xiaolei Tang,Lijie Zhang 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.1

To improve the energy conversion efficiency and working frequency bandwidth of a single frequency piezoelectric vibration energy harvester, a new type of hybrid vibration energy harvester is developed which is combined with the mechanism of piezoelectric and electromagnetic energy conversion. The system comprises of a PZT cantilever beam, an elastic suspended magnetic mass, a magnet block attached to the end of the cantilever beam and a resonator. The addition of resonator can not only increase the mode, but also adjust the frequency of harvester flexibly. Nonlinear magnetic force of magnet block not only broadens the frequency band and improves the output performance of the system, but also changes the resonant frequency to make the harvester have better adjustable performance. On this basis, an improved electromechanical coupled analytical model of continuum is proposed which can be solved by the Runge-Kutta algorithm and the influence of different factors (the mass and spring stiffness of the resonator, as well as the electromechanical coupling coefficient, electromagnetic coupling coefficient, magnet mass and magnetic flux) on the output are analyzed. According to the prototype of the vibration energy harvester developed, an experimental system was built. The performance of the independent and hybrid energy harvesters is evaluated by experimental and analytical methods. The peak output voltage of the piezoelectric part was about 4 times that of the electromagnetic part. The peak output current of the electromagnetic part is about 30 times that of the piezoelectric part. The study results show that the proposed new hybrid vibration energy harvester can achieve a wider frequency range and multimodal vibration energy harvesting. In addition, the bandwidth and power of the harvester can be dynamically adjusted by changing the resonator or electromechanical coupling coefficient, and the bandwidth of the harvester can also be adjusted by changing the quality and characteristics of the magnet.

Running-in performance of 7075 aluminum alloy strengthened by burnishing technology

Cong Ding,Shiqing Feng,Zhizhao Qiao,Zhenyu Zhou,Zhongyu Piao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

A 2D ultrasonic burnishing technology was employed to strengthen 7075 aluminum alloy. The running-in experiments for original and burnished samples were implemented, and the running-in performance was explored qualitatively and quantitatively. The results show that the worn surface of an original sample exhibited the peelings, scratches, and abrasive particles, yet the wear form of a burnished sample was relatively single, mainly with scratches. The quantitative parameter “maximum distance between phase points d max ” was calculated. During the friction and wear process, the d max of friction coefficient signal displayed the variation of first decreasing and then stabilizing, which was consistent with the running-in and steadystate stages of the friction system. Compared with the original sample, the burnished sample had a less d max , which indicated that the phase trajectory had a more convergence, and the friction system had a better stability. This study can guide surface strengthening and running-in performance analysis.

Control of the VIV of a cantilevered square cylinder with free-end suction

Li Ying,Li Shiqing,Zeng Lingwei,Wang Hanfeng 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.1

A steady slot suction near the free-end leading edge of a finite-length square cylinder was used to control its aerodynamic forces and vortex-induced vibration (VIV). The freestream oncoming flow velocity (U∞) was from 3.8 m/s to 12.8 m/s. The width of the tested cylinder d = 40 mm and aspect ratio H/d = 5, where H was the height of the cylinder. The corresponding Reynolds number was from 10,400 to 35,000. The tested suction ratio Q, defined as the ratio of suction velocity (Us) at the slot over the oncoming flow velocity at which the strongest VIV occurs (Uv), ranged from 0 to 3. It was found that the free-end slot suction can effectively attenuate the VIV of a cantilevered square cylinder. In the experiments, the RMS value of the VIV amplitude reduced quickly with Q increasing from 0 to 1, then kept approximately constant for Q ≥ 1. The maximum reduction of the VIV occurs at Q = 1, with the vibration amplitude reduced by 92% , relative to the uncontrolled case. Moreover, the overall fluctuation lift of the finite-length square cylinder was also suppressed with the maximum reduction of 87%, which occurred at Q = 1. It was interesting to discover that the free-end shear flow was sensitive to the slot suction near the leading edge. The turbulent kinetic energy (TKE) of the flow over the free end was the highest at Q = 1, which may result in the strongest mixing between the high momentum free-end shear flow and the near wake.

상장지수펀드의 주식소유비중과 변동성에 관한 검정

최병호(Byoungho Choi),김시청(Shiqing Jin),한재훈(Jaehoon Hahn) 한국경영학회 2021 한국경영학회 통합학술발표논문집 Vol.2021 No.8

본 연구는 상장지수펀드가 보유하고 있는 개별 주식에 대한 소유비중이 해당 주식의 변동성에 영향을 미치는지 검정하였다. 코스피200을 기초자산으로 추종하는 상장지수펀드와 이들이 보유한 주식을 바탕으로 소유비중과 변동성 간의 관계를 검정한 결과, 내생성을 고려하지 않은 분석에서는 상장지수펀드의 소유비중과 주식의 변동성 간 음의 상관관계를 보였다. 하지만 코스피200 구성종목에 대한 편입 및 탈락 여부를 도구변수로 사용한 2단계 최소자승 회귀분석에서는 상장지수펀드의 소유비중이 높아질수록 주식의 변동성도 유의적으로 높아지는 현상을 발견하였다. 이러한 변동성 증가는 상장지수펀드의 소유 비중이 올라갈수록 기관투자자와 외국인투자자의 거래빈도와 매수-매도 불균형이 유의적으로 증가하기 때문인 것으로 나타났다. 반면, 개인투자자의 거래데이터에서는 상장지수펀드의 소유비중이 거래 행위에 영향을 미친다는 증거를 찾을 수 없었다. 본 논문은 최근 급성장하고 있는 상장지수펀드가 간접투자의 활성화라는 본래 목적과는 다르게 기업가치와 무관한 변동성 증가라는 의도하지 않은 결과를 초래할 수 있음을 밝혔다는 점에서 의의가 있다. This paper investigates the volatility-increasing effect of exchange-traded funds (ETFs) ownership on individual stocks in Korean stock market: The value deviation of ETF from the net asset value triggers institutional investors’ arbitrage and eventually elevates stock volatility at static level. Using the monthly sample of ETFs tracking KOSPI200 as an underlying asset, we find a negative correlation between its ownership and stock volatility. There exists, however, an endogeneity that large, mature, and stable stocks are likely to be owned by exchange-traded funds because it is inherently constructed to follow the market returns. In order to estimate the exogeneous ETF ownership, we take the two stage least squares (2SLS) approach employing the KOSPI200 reconstitution event as an instrument variable. This endogeneity-controlled regression results show that the ETF ownership significantly increases the stock volatility. We additionally explore whether the arbitrage behavior co-moves with the exogeneous ETF ownership. As a result, the arbitrage trading of institutional and foreign traders is significantly moving together with the ETF ownership. But we cannot find any meaningful change in the trading behavior of individual investors, who are fundamentally limited in arbitrage trading in Korean ETF market. Our paper timely raises a problem of its unintended result of ETFs, volatility-increasing effect, despite original purpose of activating indirect investment. This empirical fact provides financial regulators with useful implications needed to establish relevant policies and allows investors to manage their portfolio risks within more sophisticated scopes.

Characteristics of the aerodynamic interference between two high-rise buildings of different height and identical square cross-section

Dongmei, Huang,Xue, Zhu,Shiqing, He,Xuhui, He,Hua, He Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.24 No.5

In this work, wind tunnel tests of pressure measurements are carried out to assess the global aerodynamic interference factors, the local wind pressure interference factors, and the local lift spectra of an square high-rise building interfered by an identical cross-sections but lower height building arranged in various relative positions. The results show that, when the interfering building is located in an area of oblique upstream, the RMS of the along-wind, across-wind, and torsional aerodynamic forces on the test building increase significantly, and when it is located to a side, the mean across-wind and torsional aerodynamic forces increase; In addition, when the interfering building is located upstream or staggered upstream, the mean wind pressures on the sheltered windward side turn form positive to negative and with a maximum absolute value of up to 1.75 times, and the fluctuating wind pressures on the sheltered windward side and leading edge of the side increase significantly with decreasing spacing ratio (up to a maximum of 3.5 times). When it is located to a side, the mean and fluctuating wind pressures on the leading edge of inner side are significantly increased. The three-dimensional flow around a slightly-shorter disturbing building has a great effect on the average and fluctuating wind pressures on the windward or cross-wind faces. When the disturbing building is near to the test building, the vortex shedding peak in the lift spectra decreases and there are no obvious signs of periodicity, however, the energies of the high frequency components undergo an obvious increase.

Effect of Low-Temperature Heat Treatment on PM2.5 Adsorption Properties of GO Films

Weiwu Zou,Baoshan Gu,Shiqing Sun,Shidong Wang,Xin Li,Haoqi Zhao,Peiyan Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.15 No.01

To explore the mechanism of GO acting on PM 2.5, a graphene oxide (GO) film was prepared via a spraying method for air purification. The effects of different media, temperature and heat treatment times on the adsorption of PM 2.5 on GO film were investigated. The morphology, composition and structure of GO materials were characterized by scanning electron microscopy (SEM), electron spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR) and Raman spectroscopy. When the vacuum heat-treatment temperature is below 80 ℃ and the atmospheric heat-treatment temperature is below 100 ℃, the air purification performance of the film does not change significantly. With the increase in the vacuum heat-treatment temperature, the removal efficiency of PM 2.5 by GO film decreases gradually from 95% to 83%. At different times, the vacuum heat treatment increases with time, and the film removal rate shows a downward trend. As the heat-treatment temperature and time increase, a certain redox reaction occurs in the GO, and the air purification performance decreases. At a temperature of 120 ℃ and a time of 8 h, the removal rate drops to 81.68%. The adsorption of PM 2.5 by GO film mainly relies on the action of oxygen-containing functional groups.