Multiband and Broadband Absorption Enhancement of Monolayer Graphene at Optical Frequencies from Multiple Magnetic Dipole Resonances in Metamaterials

Liu, Bo,Tang, Chaojun,Chen, Jing,Xie, Ningyan,Tang, Huang,Zhu, Xiaoqin,Park, Gun-sik Springer US 2018 NANOSCALE RESEARCH LETTERS Vol.13 No.1

<P>It is well known that a suspended monolayer graphene has a weak light absorption efficiency of about 2.3% at normal incidence, which is disadvantageous to some applications in optoelectronic devices. In this work, we will numerically study multiband and broadband absorption enhancement of monolayer graphene over the whole visible spectrum, due to multiple magnetic dipole resonances in metamaterials. The unit cell of the metamaterials is composed of a graphene monolayer sandwiched between four Ag nanodisks with different diameters and a SiO<SUB>2</SUB> spacer on an Ag substrate. The near-field plasmon hybridizations between individual Ag nanodisks and the Ag substrate form four independent magnetic dipole modes, which result into multiband absorption enhancement of monolayer graphene at optical frequencies. When the resonance wavelengths of the magnetic dipole modes are tuned to approach one another by changing the diameters of the Ag nanodisks, a broadband absorption enhancement can be achieved. The position of the absorption band in monolayer graphene can be also controlled by varying the thickness of the SiO<SUB>2</SUB> spacer or the distance between the Ag nanodisks. Our designed graphene light absorber may find some potential applications in optoelectronic devices, such as photodetectors.</P>

Antibacterial Magnetic Nanoparticles Functionalized with N-Halamine/Quaternary Ammonium Polymer Coatings

Xiaoqin Chen,Qian Xiang,Chunyan Yong,Zu Liang Liu,Xiao Dong Xing 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.12

The bactericidal magnetic nanoparticles were prepared by modifying magnetic nanoparticles (MNPs) with N-halamine polymer coating and quaternary ammonium polymer coating via a two-step soap-free emulsion polymerization method. The success of the surface functionalization was confirmed by Fourier transform infrared (FT-IR), X-ray photoelectron spectra (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and zeta-potential measurement. The results of antibacterial tests showed that the functional MNPs exhibited excellent antibacterial efficiency against both Gram negative bacteria E. coli and Gram positive bacteria S. aureus. Meanwhile the nanoparticles could be removed easily from water by an external magnetic field after antibacterial tests.

Toward Understanding the Adsorption And Inhibition Mechanism of Cu‑MBTA Passivation Film on Copper Surface: A Combined Experimental and DFT Investigation

Mengrui Liu,Da Yin,Baimei Tan,Fan Yang,Xiaoqin Sun,Pengcheng Gao,Shihao Zhang,Yazhen Wang 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.1

The adsorption and passivation reactions of 5-methyl benzotriazole (MBTA) with different copper samples (as received, citricacid treated and citric acid and KIO4treated) were studied. The experiments were characterized by contact angle measurement,potentiodynamic polarization curve, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. The results showed that the adsorption behavior of MBTA on different treated surfaces was different and MBTA was preferentiallyadsorbed on the surface of citric acid treated copper. Based on the density functional theory, quantum chemicaldescriptors such as the frontier molecular orbital energies EHOMO,ELUMOand the energy gap between them, molecularelectrostatic potential, and Fukui function had been calculated and discussed. The adsorption mechanism of MBTA andcopper surface was further revealed, which had positive significance for the corrosion inhibition of copper surface in copperinterconnection CMP.

ZnO nanowire array ultraviolet photodetectors with self-powered properties

Zhiming Bai,Xiaoqin Yan,Xiang Chen,Hanshuo Liu,Yanwei Shen,Yue Zhang 한국물리학회 2013 Current Applied Physics Vol.13 No.1

A ZnO nanowire (NW) array ultraviolet photodetector (PD) with Pt Schottky contacts has been fabricated on a glass substrate. Under UV light illumination, this PD showed a high photo-to-dark current ratio of 892 at 30 V bias. Interestingly, it was also found that this PD had a high sensitivity of 475 without external bias. This phenomenon could be explained by the asymmetric Schottky barrier height (SBH) at the two ends causing different separation efficiency of photogenerated electronehole pairs, which resulted in the formation of photocurrent. It is anticipated to have potential applications in self-powered UV detection field.

Transcriptome analysis of response strategy in Hemerocallis fulva under drought stress

Cai Xiaoteng,Liu Jialin,Zhao Fukuan,Wang Xiaoqin 한국유전학회 2023 Genes & Genomics Vol.45 No.5

Background Hemerocallis fulva is an important ground cover plant widely used in urban greening. The analysis of the molecular mechanism underlying the drought response of H. fulva can lay a foundation for improving its adaptability and expanding its planting area. Objective To reveal the drought response mechanisms of H. fulva, identify candidate unigenes associated with drought response, and lay a foundation for further unigenes functional study and drought resistance improvement of H. fulva via genetic engineering. Methods RNA was isolated from H. fulva under different experimental conditions. De novo transcriptomic analysis of the samples was performed to screen drought response unigenes. The transcriptional changes of candidate drought response unigenes were verified by quantitative real-time PCR. Results The differentially expressed unigenes and their functions were analyzed after H. fulva treated by PEG-simulated drought stress and rewatering. The candidate unigenes, associated with H. fulva drought response, were identified after transcriptome analysis. Then, the transcription level of drought response unigenes of H. fulva under different conditions was further verified. Abscisic acid, protein phosphorylation, sterol biosynthesis and ion transport were involved in drought response with quick restore in H. fulva. The response unigenes, involved in hormone (ABA, JA, CK and GA) signaling pathways, defense response, high light response, karrikin response and leaf shaping, can maintain at changed expression levels even after stress withdraw. Conclusion Hemerocallis fulva has unique drought response mechanism. Negative regulation mechanism may play more important roles in drought response of H. fulva. The analysis of candidate unigenes, associated with drought response, lays a foundation for further drought resistance improvement of H. fulva.

Effects of gear eccentricity on time-varying mesh stiffness and dynamic behavior of a two-stage gear system

Xiuzhi He,Xiaoqin Zhou,Zhen Xue,Yixuan Hou,Qiang Liu,Rongqi Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

Gear eccentricity, one of the most common defects of gear systems, affects not only dynamic behavior but also mesh stiffness. Accurate mesh stiffness under defect conditions is vital for the dynamic simulation and fault diagnosis of gear systems. Hence, the timevarying mesh stiffness affected by gear eccentricity, which is commonly neglected in most studies, is incorporated in the proposed twostage spur gear dynamic model and calculated by a novel gear mesh model with an improved potential energy method. The effects of mesh stiffness with and without gear eccentricity on the gear system are compared on the basis of the constructed dynamic model. The influences of gear eccentricity on dynamic transverse and torsional responses, as well as dynamic transmission errors, are also quantitatively studied. Some helpful analytical results are then presented.

Multi-objective optimum design of fast tool servo based on improved differential evolution algorithm

Zhiwei Zhu,Xiaoqin Zhou,Qiang Liu,Shaoxin Zhao 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12

The flexure-based mechanism is a promising realization of fast tool servo (FTS), and the optimum determination of flexure hinge parameters is one of the most important elements in the FTS design. This paper presents a multi-objective optimization approach to optimizing the dimension and position parameters of the flexure-based mechanism, which is based on the improved differential evolution algorithm embedding chaos and nonlinear simulated anneal algorithm. The results of optimum design show that the proposed algorithm has excellent performance and a well-balanced compromise is made between two conflicting objectives, the stroke and natural frequency of the FTS mechanism. The validation tests based on finite element analysis (FEA) show good agreement with the results obtained by using the proposed theoretical algorithm of this paper. Finally, a series of experimental tests are conducted to validate the design process and assess the performance of the FTS mechanism. The designed FTS reaches up to a stroke of 10.25 μm with at least 2 kHz bandwidth. Both of the FEA and experimental results demonstrate that the parameters of the flexure-based mechanism determined by the proposed approaches can achieve the specified performance and the proposed approach is suitable for the optimum design of FTS mechanism and of excellent performances.

Principle and Application of the Ball End Mill: Tool Radius Compensation for NURBS Curve Swept Surfaces Based on 3-Axis CNC Milling Machines

Zhaoqin Wang,Xiaorong Wang,Xiaoqin Liu,Yusen Wang,Chengyu Li,Tiesong Lin,Peng He 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.9

Common 3-axis CNC milling machines are generally equipped with 2D tool radius compensation (2D-TRC), which can realize TRC function for the contours in three basic planes when flat end mills are used. The 2D-TRC function makes engineers to program according to the actual contour of a part, and avoids over-cut phenomenon. Unfortunately, the 2D-TRC is unsuitable for ball end mills (BEMs), especially in the situation of milling complex curves or surfaces. In this work, a new TRC named BEM-TRC is used for milling NURBS curve swept surfaces using BEMs based on 3-axis CNC milling machines. In BEM-TRC, the TRC of a BEM involves radial and axial compensation. The cutting point (CP), which is the tangent point between a BEM and a NURBS curve, is considered as a calculation basis point. After obtaining a CP on a NURBS curve using the equi-arc length bisection interpolation method, the cutter center point of a BEM is calculated through off setting the CP the radius ( r ) distance of the BEM along its normal vector. Then the cutter location point of the BEM can be obtained according to the cutter center point. The CNC finishing program corresponding to the cutter location point can be obtained using Matlab software. The simulation based on VERICUT and machining based on a 3-axis milling machine verifies the effectiveness of the BEM-TRC. The over-cut phenomenon is avoided successfully when the BEM-TRC is used.

Acoustic localization of surface defect for low-speed large bearing with averaged generalized inverse beamforming

Xiang Guo,Xing Wu,Xiaoqin Liu,Linjiang Tang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

Using microphone array to detect the fault of rotating machinery is an effective method. Compared with the fault diagnosis based on vibration analysis, the advantage of this method is that it does not need the direct contact between the sensor and the machine. In addition, acoustic location can be realized by using microphone array, to accurately identify the sound radiation source on the machine surface. Conventional beamforming (CBF) is widely applied in noise source identification because of its fast speed. In the local reverberation environment, the conventional beamforming is disturbed by the image source, causing inaccurate judgment of the fault location and low imaging resolution. In this paper, an acoustic imaging method of averaged generalized inverse beamforming (AGIB) is proposed. Compared with CBF, generalized inverse beamforming (GIB) possess higher location accuracy. First, the spectral kurtosis (SK) can enhance the impact characteristics of fault signals. According to the center frequency and bandwidth estimated by the spectral kurtosis diagram, the impact information which adopt in beamforming location can be extracted in time domain and frequency domain by spectral kurtosis matched filter. Then the average amplitude and standard deviation of generalized inverse beamforming output at different positions are calculated. Finally, the normalized standard deviation is used for the beamforming output weighting of the central measurement position, so as to enhance the spatially invariant source contribution and effectively attenuate the ghost caused by the local reverberation environment. Through defect location of low-speed large bearing, compared with the averaged conventional beamforming (ACBF), AGIB can not only overcome the influence of local reverberation environment and accurately locate the fault location, but also improve the resolution significantly.

Transcriptomic analysis reveals the molecular mechanism of apoptosis induced by Muscovy duck reovirus

Quanxi Wang,Baocheng Wu,Mengxi Liu,Xiaoqin Yuan,Chunyan Li,Shiyi Chen,Yubin Zhuang,Yijian Wu,Yifan Huang 한국유전학회 2017 Genes & Genomics Vol.39 No.11

This study was to investigate the molecular mechanism underlying the apoptosis induced by Muscovy duck reovirus (MDRV) through a transcriptomic analysis. Muscovy ducklings were infected with MDRV strain YB and the apoptotic cells in their livers were examined with terminal-deoxynucleotidyl-transferase-mediated nick end labeling and flow cytometry. Genes differentially expressed in the livers of the MDRV-infected ducklings were screened by comparing them with those of uninfected ducklings and were analyzed with a transcriptomic method to illuminate the mechanism of MDRV infection. The results showed that MDRV infection strongly induced apoptotic cells in liver. Significant pathway enrichment determined by a Kyoto Encyclopedia of Genes and Genomes analysis showed that MDRV activated the death receptor family signaling pathway (Fas, TNFR1), the interleukin receptor signaling pathway (IL1, IL3), the phosphatidylinositol 3-kinase signaling pathway, NF-ҝB signaling pathway and calcium ions signaling pathway to induce apoptosis. This was verified by SYBR-Green-based fluorescence quantitative PCR. In conclusion, MDRV induce apoptosis by activation multi signaling pathways.