Semi-supervised Cross-media Feature Learning via Efficient L_2,q Norm

( Zhikai Zong ),( Aili Han ),( Qing Gong ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.3

With the rapid growth of multimedia data, research on cross-media feature learning has significance in many applications, such as multimedia search and recommendation. Existing methods are sensitive to noise and edge information in multimedia data. In this paper, we propose a semi-supervised method for cross-media feature learning by means of L_2,q norm to improve the performance of cross-media retrieval, which is more robust and efficient than the previous ones. In our method, noise and edge information have less effect on the results of cross-media retrieval and the dynamic patch information of multimedia data is employed to increase the accuracy of cross-media retrieval. Our method can reduce the interference of noise and edge information and achieve fast convergence. Extensive experiments on the XMedia dataset illustrate that our method has better performance than the state-of-the-art methods.

Rapid Identification of the Layer Number of Large-Area Graphene on Copper

Qi, Zhikai,Zhu, Xudong,Jin, Hongchang,Zhang, Tiezhu,Kong, Xianghua,Ruoff, Rodney S.,Qiao, Zhenhua,Ji, Hengxing American Chemical Society 2018 Chemistry of materials Vol.30 No.6

<P>Chemical vapor deposition (CVD) on Cu foils emerged as an important method for preparing high-quality and large-area graphene films for practical applications. However, to date it remains challenging to rapidly identify the structural features, especially the layer numbers, of CVD-graphene directly on Cu substrate. Herein, we report an O<SUB>2</SUB>-plasma-assisted approach for identifying the coverage, wrinkles, domain size, and layer number of large-area graphene films on Cu foils by optical microscopy. The wrinkles and grain boundaries of five-layer graphene can be observed with a grayscale increment of ∼23.4% per one graphene layer after O<SUB>2</SUB>-plasma treatment for only 15 s, which allows for checking graphene on Cu foils with a sample size of 17 cm × 20 cm in a few minutes. The Raman spectroscopy and X-ray photoelectron spectroscopy presents a strong layer number dependence of both the plasma induced graphene defects and Cu oxides, which, as indicated by molecular dynamic simulation, is responsible for the improved image contrast as a result of the interaction between O-ions and graphene with different layer numbers. We expect that this O<SUB>2</SUB>-plasma-assisted method would be applied to meter-scale samples if atmospheric-pressure plasma is used and therefore will be beneficial for the fast evaluation of CVD-graphene in both laboratory and industry.</P> [FIG OMISSION]</BR>

Chemical Vapor Deposition Growth of Bernal-Stacked Bilayer Graphene by Edge-Selective Etching with H₂O

Qi, Zhikai,Shi, Haohao,Zhao, Mingxing,Jin, Hongchang,Jin, Song,Kong, Xianghua,Ruoff, Rodney S.,Qin, Shengyong,Xue, Jiamin,Ji, Hengxing American Chemical Society 2018 Chemistry of materials Vol.30 No.21

<P>Bernal-stacked bilayer graphene is uniquely suited for application in electronic and photonic devices because of its tunable band structure. Even though chemical vapor deposition (CVD) is considered to be the method of choice to grow bilayer graphene, the direct synthesis of high-quality, large-area Bernal-stacked bilayer graphene on Cu foils is complicated by overcoming the self-limiting nature of graphene growth on Cu. Here, we report a facile H<SUB>2</SUB>O-assisted CVD process to grow bilayer graphene on Cu foils, where graphene growth is controlled by injecting intermittent pulses of H<SUB>2</SUB>O vapor using a pulse valve. By optimizing CVD process parameters fully covered large area graphene with bilayer coverage of 77 ± 3.6% and high AB stacking ratio of 93 ± 3% can be directly obtained on Cu foils, which presents a hole concentration and mobility of 4.5 × 10<SUP>12</SUP> cm<SUP>-2</SUP> and 1100 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, respectively, at room temperature. The H<SUB>2</SUB>O selectively etches graphene edges without damaging graphene facets, which slows down the growth of the top layer and improves the nucleation and growth of a second graphene layer. Results from our work are important both for the industrial applications of bilayer graphene and to elucidate the growth mechanism of CVD-graphene.</P> [FIG OMISSION]</BR>

중국 대학생 내권(内卷)행동과 취업준비행동 간의 취업소진의 조절효과

SHEN ZHIKAI,SUN ZHANFANG 학습자중심교과교육학회 2023 학습자중심교과교육연구 Vol.23 No.10

목적 본 연구에서는 내권(内卷)행동과 취업준비행동 간의 취업소진의 조절효과에 대해 알아보고자 하였다. 방법 이를 위해 중국 대학생 282명을 대상으로 내권행동, 취업준비행동, 취업소진을 조사하였다. 수집된 자료를 바탕으로 SPSS Statistics 26.0 프로그램을 이용하여 271명의 자료를 분석하였다. 상관분석과 위계적 회귀분석을 실시하여 내권행동과 취업준비행동 관계에서 취업소진의 조절효과를 살펴보았다. 결과 상관관계 분석 결과 내권행동은 취업소진, 취업준비행동과 모두 유의한 정적 상관이 있는 것으로 나타났다. 위계적 회귀분석 결과내권행동이 취업준비행동에 영향을 미치는 과정에서 취업소진이 조절효과를 갖는 것으로 나타났다. 그중에 취업소진의 하위요인인 탈진과 비인간화의 조절효과가 유의미하지 않았으며 반감, 무능감, 부정적 신념의 조절효과를 살펴본 결과, 조절효과를 확인할 수 있다. 결론 본 연구의 결과는 세 변수 간 관계에 대한 이해뿐 아니라 취업소진 전체 그리고 하위요인별 조절효과에 대한 이해를 돕고 더나아가 중국 대학생의 취업준비행동 촉진 방안 마련을 위한 기초자료로 활용될 것이다.

On-Chip Break Junctions and Period-Adjustable Grating Driven by Thermal Stress

Ling Wang,Zhikai Zhao,Dong Xiang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.11

"The investigation of the electron transport through single molecule needs an efficient method to generate stable molecular junctions. There are various techniques, such as mechanically controllable break junction (MCBJ) technique and electromigration technique, to generate stable nanogaps and stable molecular junctions. However, it is a great challenge for MCBJ technique to obtain on-chip molecular junctions because of the constraint of the push rod components, which do not make it facile to fabricate highly integrated molecular devices. Meanwhile, the gap size between electrodes is nonadjustable for the electromigration method, which leads to a low yield of molecular junctions. In this report, a thermally controllable break junction method, which can overcome the above problem, is proposed for the first time. The device is based on a double-V-shaped symmetrical structure and mechanically driven by thermal expansion, thus the push rod is not needed. Furthermore, we proposed that the thermally controlled double-V-shaped structure can be employed to precisely adjust the period of the metal grating with nanometer accuracy, which is unavailable in other methods. "

Analysis on Slope Stability Considering Seepage Effect on Effective Stress

Yuanzhan Wang,Xufei Liu,Zhikai Zhang,Panbo Yang 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.6

Interaction between seepage field and soil stress field influences soil effective stress in general consideration. In addition, water erosion in soil skeleton can also affect soil effective stress. The current studies conducted triaxial compression experiments with seepage, Duncan-Chang model analysis, ABAQUS numerical simulation and followed by a case study analysis. Experiments show that the water erosion in soil skeleton reduces effective stress strength of soil, which is quantitatively described by the reduction of equivalent confining pressure. Through analyzing the characteristics of soil stress-strain curves, the equivalent confining pressure is applied to improve Duncan-Chang model. Using the modified Duncan-Chang model as well as considering the interaction between seepage field and soil stress field, ABAQUS software package is employed to simulate triaxial compression experiments with seepage. This method is validated by comparing simulation and experimental results. Furthermore, this method is applied in the case study of the overall stability of bank slope under seepage effect and finds that the modified model is more conservative on safety assessment of slope stability. The studies provided evidences to prove the importance of considering soil skeleton eroded by water flow in slope stability analysis quantitatively and proposed a modified Duncan-Chang model for engineering application with consideration of seepage effect.

07. Efficiency in Chinese Kindergarten: Based on the Shandong Province Investigational Data

( Yuanyuan Zhang ),( Zhanmei Song ),( Zhikai Li ),( Eunju Choi ) 한국유아교육학회 2019 정기학술대회 논문집 Vol.2019 No.2

Generic Adaptive Sliding Mode Control for a Quadrotor UAV System Subject to Severe Parametric Uncertainties and Fully Unknown External Disturbance

Tianpeng Huang,Deqing Huang,Zhikai Wang,Xi Dai,Awais Shah 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.2

This paper aims to provide a generic robust controller that is able to manipulate all kinds of quadrotor unmanned aerial vehicle (UAV) systems automatically or adaptively in the presence of severe parametric uncertainties and fully unknown external disturbance. The dynamic model of the quadrotor is first obtained using Newton-Euler equations. Then, considering the underactuated and the strongly coupled characteristics of the quadrotor system, a nonlinear adaptive sliding mode control (ASMC) scheme is proposed. Meanwhile, additional adaptive laws are designed to estimate all the parameters of the quadrotor system, which in principle are difficult to be measured directly and accurately. Furthermore, to guarantee the asymptotic stability of the closed-loop system, the upper bound of the fully unknown external disturbance is estimated and adopted as the switching gain of the ASMC. Finally, simulations and experiments are carried out to illustrate the effectiveness and robustness of the proposed control scheme, where the superiority to linear quadratic control (LQR) and active disturbance rejection control (ADRC) has been demonstrated clearly.

A New Quinoline-Based Acylhydrazone for Highly Selective Fluorescence Recognition of Cu(II) and Sulfide in Aqueous Solution

Li-Jun Tang,Pei Zhou,Zhikai Qi,Zhenlong Huang,Jia Zhao,Mingjun Cai 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.8

A new quinoline-based acylhydrazone (1) has been synthesized and applied as a fluorescent probe. Probe 1 exhibits high selectivity and sensitivity to Cu2+ with fluorescence “ON-OFF” behavior in HEPES buffered (1‰ DMSO, HEPES 20 mM, pH = 7.4) solution. The on-site generated 1-Cu2+ complex displays excellent selectivity to sulfide ions with fluorescence “OFF-ON” performance through copper displacement approach.

Collateral Flow in Magnetic Resonance Angiography: Prognostic Value for Vertebrobasilar Stenosis With Stroke Recurrence

Long Yan,Ying Yu,Kaijiang Kang,Zhikai Hou,Min Wan,Weilun Fu,Rongrong Cui,Yongjun Wang,Zhongrong Miao,Xin Lou,Ning Ma 대한신경과학회 2022 Journal of Clinical Neurology Vol.18 No.5

Background and Purpose Intracranial vertebrobasilar atherosclerotic stenosis (IVBAS) is a major cause of posterior circulation stroke. Some patients suffer from stroke recurrence despite receiving medical treatment. This study aimed to determine the prognostic value of a new score for the posterior communicating artery and the P1 segment of the posterior cerebral artery (PCoA-P1) for predicting stroke recurrence in IVBAS. Methods We retrospectively enrolled patients with severe IVBAS (70%–99%). According to the number of stroke recurrences, patients were divided into no-recurrence, single-recurrence, and multiple-recurrences groups. We developed a new 5-point grading scale, with the PCoA-P1 score ranging from 0 to 4 based on magnetic resonance angiography, in which primary collaterals were dichotomized into good (2–4 points) and poor (0 or 1 point). Stroke recurrences after the index stroke were recorded. Patients who did not experience stroke recurrence were compared with those who experienced single or multiple stroke recurrences. Results From January 2012 to December 2019, 176 patients were enrolled, of which 116 (65.9%) had no stroke recurrence, 35 (19.9%) had a single stroke recurrence, and 25 (14.2%) had multiple stroke recurrences. Patients with single stroke recurrence (odds ratio [OR]= 4.134, 95% confidence interval [CI]=1.822–9.380, p=0.001) and multiple stroke recurrences (OR=6.894, 95% CI=2.489–19.092, p<0.001) were more likely to have poor primary collaterals than those with no stroke recurrence. Conclusions The new PCoA-P1 score appears to provide improve predictions of stroke recurrence in patients with IVBAS