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State and tendency: an empirical study of deep learning question&answer topics on Stack Overflow

science China(information sciences) 2021年第11期64卷 131-153页

作者： Henghui ZHAO Yanhui LI Fanwei LIU Xiaoyuan XIE Lin CHEN State key laboratory for Novel Software technology Nanjing University School of Computer science Wuhan University

Deep learning has developed rapidly in recent years, attracting the attention of numerous researchers. Since a wide range of topics are covered in this field, we are wondering what topics researchers have concerned about. However, after investigation, we find that very few researchers have paid attention to this demand. In this paper, we conduct a large-scale study to analyze the questions faced by deep learning developers. We use Stack Overflow, one of the largest question&answer sites, as our data source, and extract32969 posts about deep learning as our studied dataset. After filtering, augmenting and pre-processing the post datasets from Stack Overflow, we use the latent Dirichlet allocation(LDA) topic model to summarize30 topics based on their text content. In addition, we measure the difficulty and popularity of each topic,compare the different issues faced by different deep learning frameworks, and analyze the development trend of each topic. Our main results are as follows:(1) developers ask a broad spectrum of questions about deep-learning, ranging from Data Shape to Object Detection;(2) Gradient Propagation is the most popular among all the topics and(3) Object Detection is the most difficult;(4) issues of Package Installation, Code Understanding and Method Introduction are common in the current different deep learning frameworks;(5) there are three trends in these topics, e.g., a significant rising trend is found in the number of discussion on Data Shape. Finally, based on our research findings, we make some targeted and valuable suggestions for developers, researchers, educators, and framework providers of deep learning.

关键词： topic model deep learning Stack Overflow question&answer

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Chemical Mechanical Polishing of Ge_(2)Sb_(2)Te_(5) Using Abrasive-Free Solutions of Iron Trichloride

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Chinese Physics Letters 2012年第3期29卷 243-246页

作者： YAN Wei-Xia WANG Liang-Yong ZHANG Ze-Fang HE Ao-Dong ZHONG Min LIU Wei-Li WU Liang-Cai SONG Zhi-Tang State key laboratory of Functional Materials for Informatics Laboratory of NanotechnologyShanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050

Chemical mechanical polishing(CMP)of amorphous Ge_(2)Sb_(2)Te_(5)(GST)is studied using aqueous solutions of iron trichloride(FeCl_(3))as possible abrasive-free *** polishing performance of abrasive-free solutions is compared with abrasive-containing(3wt% colloidal silica)slurry in terms of polishing rate and surface *** experimental results indicate that the abrasive-free solutions have a higher polishing rate and better surface *** order to further investigate the polishing mechanism,post-CMP GST films using the abrasive-free solutions and abrasive-containing slurry are characterized by x-ray photoelectron ***,it is verified that the abrasive-free solutions have no influence on the electrical property of the post-CMP GST films through the resistivity test.

关键词： spectroscopy resistivity verified

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Planning the obstacle-avoidance trajectory of mobile anchor in 3D sensor networks

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science China(information sciences) 2015年第10期58卷 109-118页

作者： SHU MingLei CUI HuanQing WANG YingLong WANG Cheng-Xiang School of information science and Engineering Shandong University Shandong Provincial key laboratory of Computer Networks Shandong Computer Science Center (National Supercomputer Center in Jinan) College of information science and Engineering Shandong University of Science and Technology Institute of Sensors Signals and Systems School of Engineering & Physical SciencesHeriot-Watt University

Localization plays an important role in many applications of wireless sensor networks. Recently,mobile anchor assisted localization methods become promising, and the moving trajectory planning of anchor is an interesting and basic issue in these methods. In this paper, an obstacle-avoidance trajectory planning method for three-dimensional wireless sensor networks is proposed. After dividing the network into grids, a depth-firstsearch algorithm with greedy strategy is proposed to get the approximately shortest path, and a trigonal function based localization method is presented to estimate the positions of the sensor nodes. Simulations show that this method can obtain almost the optimal path and localize almost all the sensor nodes.

关键词： wireless sensor networks three-dimension localization mobile anchor path planning

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Fabrication of narrow pulse passively Q-switched self-stimulated Raman laser with c-cut Nd:GdVO_4

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Optoelectronics Letters 2016年第6期12卷 430-432页

作者：申高李祚涵韩鸣 Center for Medical Device Evaluation China Food and Drug Administration key laboratory of Luminescence and optical information of Ministry of Education Institute of Laser School of Science Beijing Jiaotong University

Combining the self-stimulated Raman scattering technology and saturable absorber of Cr^(4+):YAG, a 1.17 μm c-cut Nd:GdVO_4 picosecond Q-switched laser is demonstrated in this paper. With an incident pump power of 10 W, the Q-switched laser with average power of 430 mW for 1.17 μm, pulse width of 270 ps, repetition rate of 13 kHz and the first order Stokes conversion efficiency of 4.3% is obtained. The Q-switched pulse width can be the narrowest in our research. In addition, the yellow laser at 0.58 μm is also achieved by using the LiB_3O_5 frequency doubling crystal.

关键词： switched repetition absorber yellow doubling Stokes coated stimulated mirror narrow

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Formation and instability of spiral wave induced by Gaussian coloured noise

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Chinese Physics B 2008年第11期17卷 4047-4055页

作者：甘正宁马军张国勇陈勇 Institute of Theoretical Physics Lanzhou University College of Electronic and information Engineering Changsha University of Science & Technology Department of Physics Lanzhou University of Technology key laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou University

In this paper, we studied the effect of Gaussian coloured noise on the formation and instability of spiral waves described by one class of modified FitzHugh Nagumo equation. It was found that Gaussian coloured noise plays a constructive role in the formation, transition and instability of spiral wave. Too weak or too strong noise may act against the formation of spiral waves. At a certain noise level, spiral wave is maintained in a medium, in which spiral wave cannot be observed in the absence of the noise. It is difficult to make a stable spiral wave into unstable state by Gaussian coloured noise, unless the noise level is very high. The parameter regions of Gaussian coloured noise for spiral forming and spiral instability were given and discussed with numerical simulations.

关键词： spiral wave FitzHugh-Nagumo model Gaussian coloured noise

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Link prediction in social networks: the state-of-the-art

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science China(information sciences) 2015年第1期58卷 4-41页

作者： WANG Peng XU BaoWen WU YuRong ZHOU XiaoYu School of Computer science and Engineering Southeast University State key laboratory of Software Engineering Wuhan University State key laboratory for Novel Software technology Nanjing University

In social networks, link prediction predicts missing links in current networks and new or dissolution links in future networks, is important for mining and analyzing the evolution of social networks. In the past decade, many works have been done about the link prediction in social networks. The goal of this paper is to comprehensively review, analyze and discuss the state-of-the-art of the link prediction in social networks. A systematical category for link prediction techniques and problems is presented. Then link prediction techniques and problems are analyzed and discussed. Typical applications of link prediction are also addressed. Achievements and roadmaps of some active research groups are introduced. Finally, some future challenges of the link prediction in social networks are discussed.

关键词： social network link prediction dynamic network similarity metric learning model

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Transparent Thermally Tunable microwave Absorber Prototype Based on Patterned VO2 Film

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Engineering 2023年第10期29卷 198-206页

作者： Zhengang Lu Yilei Zhang Heyan Wang Chao Xia Yunfei Liu Shuliang Dou Yao Li Jiubin Tan Ultra-Precision optical and Electronic Instrument Engineering Center Harbin Institute of TechnologyHarbin 150001China key laboratory of Ultra-Precision Intelligent Instrumentation(Harbin Institute of technology) Ministry of Industry and Information TechnologyHarbin 150001China Center for Composite Material and Structure Harbin Institute of TechnologyHarbin 150001China

Transparent microwave absorbers that exhibit high optical transmittance and microwave absorption capability are ideal,although having a fixed absorption performance limits their ***,a simple,transparent,and thermally tunable microwave absorber is proposed,based on a patterned vanadium dioxide(VO_(2))*** calculations and experiments demonstrate that the proposed VO_(2)absorber has a high optical transmittance of 84.9%at 620 nm;its reflection loss at 15.06 GHz can be thermally tuned from–4.257 to–60.179 dB,and near-unity absorption is achieved at 523.750 *** only the patterned VO_(2)film duty cycle can change the temperature of near-unity *** VO_(2)absorber has a simple composition,a high optical transmittance,a thermally tunable microwave absorption performance,a large modulation depth,and an adjustable temperature tuning range,making it promising for application in tunable sensors,thermal emitters,modulators,thermal imaging,bolometers,and photovoltaic devices.

关键词： Tunable microwave absorber VO_(2)film optical transparent Near unity absorption Large modulation depth

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Numerical study on pulse trapping in birefringent photonic crystal fibers

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Optoelectronics Letters 2011年第3期7卷 205-208页

作者：姚艳艳李曙光付博张磊张美艳 key laboratory on Metastable Material science and technology College of ScienceYanshan University

Using an adaptive split-step Fourier method,the coupled nonlinear Schrdinger equations have been numerically solved in this *** nonlinear propagation of an ultrashort optical pulse in the birefringent photonic crystal fibers is investigated *** is found that the phenomenon of pulse trapping occurs when the incident pulse is deviating from the principal axis of the fiber with some *** to the birefringence effect,the incident pulse can be regarded as two orthogonal polarized *** phenomenon of pulse trapping occurs because of the cross phase modulation(XPM) between the two *** a result,the bandwidth of the supercontinuum(SC) decreases compared with the case that the incident pulse is input along the principal *** the polarization direction of the incident pulse is parallel to the fast axis,the bandwidth of the supercontinuum is maximal.

关键词： Bandwidth Birefringence Crystal whiskers Numerical methods Phase modulation Photonic crystals

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Sub-diffraction-Limit Imaging in optical Hyperlens

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Chinese Physics Letters 2008年第12期25卷 4439-4441页

作者：胡继刚王沛鲁拥华明海陈春翀陈俊学 Department of Physics University of Science and Technology of China Hefei 230026 Anhui key laboratory of Optoelectronic science and technology University of Science and Technology of China Department of Physics Hefei University of Technology Hefei 230009

Sub-diffraction-limit imaging in the optical hyperlens based on cylindrical metamaterials is studied. Some parameters of hyperlens, such as the dispersive relation and the divergence angle of imaging, are numerically analysed with the ray trajectory method and effective medium theory. The dependence of imaging properties on dielectric constant is discussed. As a result, a 0° divergence angle is obtained for the best imaging effect. This work will be helpful for the design, structure fabrication and resolution improvement of the optical hyperlens.

关键词： field emission molybdenum dioxide enhancement factor

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Sub-30 fs Yb-fiber laser source based on a hybrid cascaded nonlinear compression approach

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Chinese Optics Letters 2022年第10期20卷 25-29页

作者： Youming Liu Bowen Liu Youjian Song Minglie Hu Ultrafast Laser laboratory Key Laboratory of Opto-electronic Information Science and Technology of Ministry of EducationSchool of Precision Instruments and Opto-electronics EngineeringTianjin UniversityTianjin 300072China

Ultrafast lasers with high repetition rate,high energy,and ultrashort pulse duration have enabled numerous applications in science and *** efficient route to generate such pulses is postcompression of high-power Yb-doped ***,we report on the generation of 24.5 fs pulses with an output energy of 1.6μJ and a repetition rate of 500 *** pulses are obtained by using a hybrid cascaded nonlinear compression of the pulses delivered by a Yb-based fiber chirped pulse amplification(CPA)*** the first stage,the initial 390 fs laser pulses are compressed to 100.7 fs based on spectral broadening in three fused silica *** the second stage,the pulses have been shortened to sub-30 fs by means of nonlinear compression in a hollow-core ***,we could achieve∼16 times temporal shortening with the proposed *** results show that our system can effectively generate few-cycle pulses at a relatively high repetition rate and high energy,which can benefit future possible applications.

关键词： multiple-plate medium hollow-core photonic crystal fiber pulse compression

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