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Structure and Tribological Properties of CrTiAlN Coatings Deposited by Multi-Arc Ion Plating

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Plasma Science and Technology 2011年第1期13卷 55-60页

作者：田灿鑫杨兵何俊王红军王泽松王广甫付德君 Accelerator laboratory and key laboratory of artificial Materials and Microstructures of ministry of education Wuhan University key laboratory of Beam Technology and Material Modication of ministry of education Beijing Normal University School of Power & Mechanical Engineering Wuhan University

CrTiAIN coatings were prepared by using a home-made industrial scale multi-arc ion plating system. The coatings were found to be composites of face-center-cubic CrN and TiN. The surface roughness, microhardness, and tribological properties of the films were significantly affected by the nitrogen pressure and dc-pulsed bias voltage applied to the substrate. The CrTiA1N coatings with the smoothest surfaces were obtained at optimum conditions of nitrogen pressure of 5.0 Pa and bias voltage of -200 V. The samples were found to exhibit a hardness of 2900 HV0.05 with an average friction coefficient of 0.16 and wear rate of 1.5× 10^-16 m^3/N.m against cemented carbide.

关键词： multi-arc ion plating CrTiAIN microhardness surface morphology friction coellicient wear rate

Triblock copolymer-assisted construction of 20 nm-sized ytterbium-doped TiO_2 hollow nanostructures for enhanced solar energy utilization efficiency

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Science China Chemistry 2015年第5期58卷 850-857页

作者： Lin Cheng Xuefeng Xu Yuyan Fang Yan Li Jiaxi Wang Guojia Wan Xueying Ge Liangjie Yuan Keli Zhang Lei Liao Quan Yuan key laboratory of Analytical Chemistry for Biology and Medicine Ministry of Education College of Chemistry and Molecular Sciences Wuhan University key laboratory of artificial Micro- and Nano-structures Ministry of Education Department of Physics Wuhan University

Rare-earth doped titania single-crystalline hollow nanoparticles of 20 nm are constructed via a simple sol-gel process. Amphiphilic ABA tri-block copolymers played a key role in assisting the formation of hollow structure, for which a hollow nanostructure growth mechanism is proposed. By introducing rare earth into the synthesis process, the as-prepared nanoparticles exhibit near-infrared light absorption properties. Photo-decomposition efficiency of Orange II azo dye can be successfully evaluated when using Yb3+-doped Ti O2 hollow nanoparticles as photocatalysts; it is more than two times higher than the pure Ti O2 hollow nanoparticles. The hollow nanostructured Yb3+-doped Ti O2 samples are exploited as photoanodes in N719- sensitized solar cells and prove able to improve the photoelectric conversion efficiency by measuring the solar cell parameters of dye-sensitized solar cells(DSSCs) under simulative sunlight.

关键词： rare earth hollow nanostructure titania single-crystalline copolymer

Preparation of graphene on Cu foils by ion implantation with negative carbon clusters

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Chinese Physics B 2015年第1期24卷 528-530页

作者：李慧尚艳霞张早娣王泽松张瑞付德君 School of Physics and Technology and key laboratory of artificial Micro- and Nano-Materials of ministry of education Wuhan University

We report on few-layer graphene synthesized on Cu foils by ion implantation using negative carbon cluster ions,followed by annealing at 950？C in vacuum. Raman spectroscopy reveals IG/I2 Dvalues varying from 1.55 to 2.38 depending on energy and dose of the cluster ions, indicating formation of multilayer graphene. The measurements show that the samples with more graphene layers have fewer defects. This is interpreted by graphene growth seeded by the first layers formed via outward diffusion of C from the Cu foil, though nonlinear damage and smoothing effects also play a role. Cluster ion implantation overcomes the solubility limit of carbon in Cu, providing a technique for multilayer graphene synthesis.

关键词： ion implantation carbon clusters graphene copper foil

Synthesis and Optical Responses of Ag@Au/Ag@Au Double Shells

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Chinese Physics Letters 2015年第2期32卷 70-73页

作者：李颖颖刘晓丽杨大杰郝中华王取泉 key laboratory of artificial Micro- and Nano-structures(ministry of education) and School of Physics and TechnologyWuhan University

We synthesize hollow-structured Ag@Au nanoparticles with single porous shell and Ag@Au/Ag@Au double shells by using the galvanic replacement reaction and investigate their linear and nonlinear optical properties. Our results show that the surface plasmon resonance wavelength of the hollow porous nanoparticles could be easily tuned in a wide range in the visible and near infrared region by controlling the volume of HAuCl4. The nonlinear optical refraction of the double-shelled Ag@Au/Ag@Au nanoparticles is prominently enhanced by the plasmon resonance. Our findings may find applications in biosensors and nonlinear optical nanodevices.

关键词： Ag Synthesis and Optical Responses of Ag@Au/Ag@Au Double Shells

A novel method of constructing high-dimensional digital chaotic systems on finite-state automata

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Chinese Physics B 2020年第9期29卷 233-243页

作者： Jun Zheng Han-Ping Hu School of artificial intelligence and Automation Huazhong University of Science and TechnologyWuhan 430074China key laboratory of Image Information Processing and Intelligent Control Ministry of EducationWuhan 430074China

When chaotic systems are implemented on finite precision machines, it will lead to the problem of dynamical degradation. Aiming at this problem, most previous related works have been proposed to improve the dynamical degradation of low-dimensional chaotic maps. This paper presents a novel method to construct high-dimensional digital chaotic systems in the domain of finite computing precision. The model is proposed by coupling a high-dimensional digital system with a continuous chaotic system. A rigorous proof is given that the controlled digital system is chaotic in the sense of Devaney's definition of chaos. Numerical experimental results for different high-dimensional digital systems indicate that the proposed method can overcome the degradation problem and construct high-dimensional digital chaos with complicated dynamical properties. Based on the construction method, a kind of pseudorandom number generator (PRNG) is also proposed as an application.

关键词： high-dimensional digital chaotic system dynamical degradation anti-control pseudorandom number generator

WPIA: accelerating DNN warm-up in Web browsers by precompiling WebGL programs

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Frontiers of Computer Science 2024年第6期18卷 186211-186211页

作者： TIAN Deyu MA Yun HAN Yudong YANG Qi YANG Haochen HUANG Gang key laboratory of High Confidence Software Technologies (Peking University) ministry of education School of Computer Science Peking University Institute for artificial intelligence Peking University National key laboratory of Data Space Technology and System

In this paper, we study the long warm-up time of GPU acceleration of DNN inference in Web browsers. We analyzed the reason behind the long warm-up time through a measurement study and revealed that compiling WebGL programs takes most of the warm-up time. Inspired by this finding, we proposed WPIA, an approach that suggests precompiling WebGL programs on the server side to avoid compiling them in Web browsers. WPIA tackles the challenges of precompiling by merging WebGL programs and using a record-and-replay technique. Evaluation experiment results show that WPIA can accelerate the DNN warm-up time to an order of magnitude.

关键词： Web browsers

RNA structure prediction:Progress and perspective

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Chinese Physics B 2014年第7期23卷 88-97页

作者：时亚洲吴园燕王凤华谭志杰 Department of Physics and key laboratory of artificial Micro- and Nano-structures of ministry of education School of Physics and TechnologyWuhan University

Many recent exciting discoveries have revealed the versatility of RNAs and their importance in a variety of cellular functions which are strongly coupled to RNA structures. To understand the functions of RNAs, some structure prediction models have been developed in recent years. In this review, the progress in computational models for RNA structure prediction is introduced and the distinguishing features of many outstanding algorithms are discussed, emphasizing three- dimensional （3D） structure prediction. A promising coarse-grained model for predicting RNA 3D structure, stability and salt effect is also introduced briefly. Finally, we discuss the major challenges in the RNA 3D structure modeling.

关键词： RNA structure prediction secondary structure three-dimensional (3D) structure coarse-grainedmodel

All-optical scheme for detecting the possible Majorana signature based on QD and nanomechanical resonator systems

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Science China(Physics,Mechanics & Astronomy) 2015年第5期58卷 2-15页

作者： CHEN HuaJun ZHU KaDi key laboratory of artificial Structures and Quantum Control (ministry of education) Department of Physics and Astronomy Shanghai Jiao Tong University

Majorana fermions(MFs) are exotic particles that are their own anti-particles. Currently, the search for MFs occurring as quasiparticle excitations in condensed matter systems has attracted widespread interest, because of their importance in fundamental physics and potential applications in topological quantum computation based on solid-state devices. Motivated by recent experimental progress towards the detection and manipulation of MFs in hybrid semiconductor/superconductor heterostructures, in this review, we present a novel proposal to probe MFs in all-optical domain. We introduce a single quantum dot(QD), a hybrid quantum dot-nanomechanical resonators(QD-NR) system, and a carbon nanotube(CNT) resonator implanted in a single electron spin system with optical pump-probe technology to detect MFs, respectively. With this scheme, a possible Majorana signature is investigated via the probe absorption spectrum and nonlinear optical Kerr effect, and the coupling strength between MFs and the QD or the single electron spin is also determined. In the hybrid QD-NR system, vibration of the NR will enhance the nonlinear optical effect, which makes the MFs more sensitive for detection. In the CNT resonator with a single electron, the single electron spin can be considered as a sensitive probe, and the CNT resonator behaved as a phonon cavity is robust for detecting of MFs. This optical scheme will provide another method for the detection MFs and will open the door for new applications ranging from robust manipulation of MFs to quantum information processing based on MFs.

关键词： Majorana fermions QD nanomechanical resonator carbon nanotube resonator optical pump-probe technology

Residual diverse ensemble for long-tailed multi-label text classification

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Science China(Information Sciences) 2024年第11期67卷 92-105页

作者： Jiangxin SHI Tong WEI Yufeng LI National key laboratory for Novel Software Technology Nanjing University School of artificial intelligence Nanjing University School of Computer Science and Engineering Southeast University key laboratory of Computer Network and Information Integration Southeast UniversityMinistry of Education

Long-tailed multi-label text classification aims to identify a subset of relevant labels from a large candidate label set, where the training datasets usually follow long-tailed label distributions. Many of the previous studies have treated head and tail labels equally, resulting in unsatisfactory performance for identifying tail labels. To address this issue, this paper proposes a novel learning method that combines arbitrary models with two steps. The first step is the “diverse ensemble” that encourages diverse predictions among multiple shallow classifiers, particularly on tail labels, and can improve the generalization of tail *** second is the “error correction” that takes advantage of accurate predictions on head labels by the base model and approximates its residual errors for tail labels. Thus, it enables the “diverse ensemble” to focus on optimizing the tail label performance. This overall procedure is called residual diverse ensemble(RDE). RDE is implemented via a single-hidden-layer perceptron and can be used for scaling up to hundreds of thousands of labels. We empirically show that RDE consistently improves many existing models with considerable performance gains on benchmark datasets, especially with respect to the propensity-scored evaluation ***, RDE converges in less than 30 training epochs without increasing the computational overhead.

关键词： multi-label learning extreme multi-label learning long-tailed distribution multi-label text classification ensemble learning