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Humidity sensor and ultraviolet photodetector based on carrier trapping effect and negative photoconductivity in graphene quantum dots

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Science China(Physics,Mechanics & Astronomy) 2018年第1期61卷 51-56页

作者： ShenDong Zhuang Yan Chen WeiChao Zhang Zhuo Chen zhenlin wang School of Physics and National Laboratory of Solid State Microstructures Nanjing University College of Engineering and Applied Sciences Nanjing University

We report on the experimental realization of a graphene quantum dots （GQD）-based htunidity sensor and ultraviolet （UV） photodetector. We demonstrate that the conductance of the GQD increases linearly with increasing relative humidity （RH） of the surrounding environment due to the carrier trapping effect, which forms the basis of a humidity sensor. When the sensor is operated in the dark state, the sensitivity can reach as high as 0.48 nS RH-^1. The GQD are also found to exhibit light intensity dependent negative photoconductivity under the UV irradiation, which can be exploited for UV detection. As a result of these carrier trapping and de-trapping processes, the performance of the photodetector can be significantly improved with the increasing RH, and the photoresponsivity can reach a high value of-418.1 μA W^-1 in the high humid state of RH=90%.

关键词： graphene quantum dots carrier trapping effect negative photoconductivity

Huge Page Friendly Virtualized Memory Management

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Journal of Computer Science & Technology 2020年第2期35卷 433-452页

作者： Sai Sha Jing-Yuan Hu Ying-Wei Luo Xiao-Lin wang zhenlin wang School of Electronics Engineering and Computer Science Peking UniversityBeijing 100871China Peng Cheng Laboratory Shenzhen 518052China Shenzhen Key Laboratory for Cloud Computing Technology&Applications School of Electronic and Computer EngineeringPeking University ShenzhenShenzhen 518000China Department of Computer Science Michigan Technological UniversityMichigan 49246U.S.A.

With the rapid increase of memory consumption by applications running on cloud data centers,we need more efficient memory management in a virtualized *** huge pages becomes more critical for a virtual machine's performance when it runs large working set size *** with large working set sizes are more sensitive to memory allocation,which requires us to quickly adjust the virtual machine's memory to accommodate memory phase *** would be much more efficient if we could adjust virtual machines'memory at the granularity of huge ***,existing virtual machine memory reallocation techniques,such as ballooning,do not support huge *** addition,in order to drive effective memory reallocation,we need to predict the actual memory demand of a virtual *** find that traditional memory demand estimation methods designed for regular pages cannot be simply ported to a system adopting huge *** to adjust the memory of virtual machines timely and effectively according to the periodic change of memory demand is another challenge we *** paper proposes a dynamic huge page based memory balancing system(HPMBS)for efficient memory management in a virtualized *** first rebuild the ballooning mechanism in order to dispatch memory in the granularity of huge *** then design and implement a huge page working set size estimation mechanism which can accurately estimate a virtual machine's memory demand in huge pages *** these two mechanisms,we finally use an algorithm based on dynamic programming to achieve dynamic memory *** show that our system saves memory and improves overall system performance with low overhead.

关键词： virtualization huge page ballooning memory balancing

Dynamic cache partitioning based on hot page migration

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Frontiers of Computer Science 2012年第4期6卷 363-372页

作者： Xiaolin wang Xiang WEN Yechen LI zhenlin wang Yingwei LUO Xiaoming LI Department of Computer Science Peking UniversityBeijing 100871China Department of Computer Science Michigan Technological UniversityHoughtonMI 49931USA The Shenzhen Key Lab for Cloud Computing Technology and Applications Peking University Shenzhen Graduate SchoolShenzhen 518055China

Static cache partitioning can reduce inter- application cache interference and improve the composite performance of a cache-polluted application and a cache- sensitive application when they run on cores that share the last level cache in the same multi-core processor. In a virtu- alized system, since different applications might run on dif- ferent virtual machines （VMs） in different time, it is inappli- cable to partition the cache statically in advance. This paper proposes a dynamic cache partitioning scheme that makes use of hot page detection and page migration to improve the com- posite performance of co-hosted virtual machines dynami- cally according to prior knowledge of cache-sensitive appli- cations. Experimental results show that the overhead of our page migration scheme is low, while in most cases, the com- posite performance is an improvement over free composition.

关键词： cache partitioning hot page migration dynamic cache partitioning virtualization virtual machine monitor

A Novel Sensor Deployment Method Based on Image Processing and Wavelet Transform to Optimize the Surface Coverage in WSNs

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Chinese Journal of Electronics 2016年第3期25卷 495-502页

作者： YANG Hang LI Xunbo wang zhenlin YU Wenjie HUANG Bo School of Communication and Information Engineering University of Electronic Science and Technology of China School of Mechatronics Engineering University of Electronic Science and Technology of China

A novel sensor deployment method utilize Discrete wavelet transform(DWT) is proposed, and the DWT is used to calculate the sub-band energy entropy to ascertain the coverage cavities in Wireless sensor networks(WSNs). We address the problem of deploying a limit number of sensors to optimize the coverage ratio in 3D surface, while it is a complex surface in space and sensors can be deployed only onto it. Another novel aspect of this paper is that the method followed utilizes an Artificial bee colony algorithm with dynamic search strategy(ABC-DSS), which mimics the behavior of bees, and the new modified ABC-DSS algorithm matches the sensor deployment problems on 3D surface well. The extensive simulations illustrate that comparing with the deployment method based on Particle swarm optimization(PSO) and ABC, the ABC-DSS which utilizes the wavelet sub-band energy entropy is functional and efficient on 3D surface deployment problems.

关键词： Artificial bee colony with dynamic search strategy(ABC-DSS) Discrete wavelet transform(DWT) Image processing Wireless sensor networks(WSNs)

Large-area surface-enhanced Raman scattering-active substrates fabricated by femtosecond laser ablation

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Science China(Physics,Mechanics & Astronomy) 2013年第9期56卷 1806-1809页

作者： ZHU ZhiQing YAN ZhenDong ZHAN Peng wang zhenlin School of Physics and National Laboratory of Solid State Microstructures Nanjing University

A rapid and simple approach to fabricate large-area surface-enhanced Raman scattering-active(SERS-active) substrates is *** substrates are fabricated by using femtosecond laser(fs-laser) direct writing on Silicon wafers,followed by thin-film coating of metal such as *** substrates are demonstrated to exhibit signal homogeneity and good enhancement ability for *** maximum enhancement factor(EF) up to 3×10 7 of such SERS substrates for rhodamine 6G(R6G) at 785 nm excitation wavelength was *** technique could demonstrate a functional microchip with SERS capability of signal homogeneity,high sensitivity and chemical stability.

关键词： surface-enhanced Raman scattering femtosecond laser ablation metal microstructure

A Mechanically Tunable Plasmonic Structure Composed of a Monolayer Array of Metal-Capped Colloidal Spheres on an Elastomeric Substrate

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Nano Research 2010年第11期3卷 807-812页

作者： Xiaolong Zhu Lei Shi Xiaohan Liu Jian Zi zhenlin wang Department of Physics Key Laboratory of Micro and Nano Photonic Structures(Ministry of Education)and State Key Laboratory of Surface PhysicsFudan UniversityShanghai 200433China National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China

A highly stretchable plasmonic structure composed of a monolayer array of metal-capped colloidal spheres on an elastomeric substrate has been fabricated using simple and inexpensive self-assembly and transfer-printing *** composite structure supports coupled surface plasmons whose wavelengths are sensitive to the arrangement of the metal-capped colloidal *** stretching,the lattice of metal-capped colloidal spheres will be deformed,leading to a large wavelength shift of surface plasmon resonances and simultaneously an obvious color *** stretchable plasmonic structure offers a promising approach to tune surface plasmon resonances and might be exploited in realizing flexible plasmonic devices with tunability of mechanical strain.

关键词： Plasmonic structure metal-capped colloidal spheres elastomeric substrate tunable surface plasmon resonance

Autogenous inside-out versus standard vein and skeletal muscle-combined grafting for facial nerve repair

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Neural Regeneration Research 2010年第4期5卷 282-286页

作者： Yulu Li Zhiqiang Gao zhenlin wang Yonggang Liu Qiuhang Zhang Department of Otorhinolaryngology Head and Neck Surgery Capital Medical University Xuan wu Hospital Beijing 100053 China Department of Otorhinolaryngology Head and Neck Surgery Peking Union Medical College Hospital Chinese Academy of Medical Sciences Beijing 100731 China

BACKGROUND： In the repair of nerve defects, collapse of the venous wall, as a result of vein grafting alone, could impede nerve regeneration. Therefore, vein lumens filled with muscle and nerve segments have been used to bridge nerve defects. OBJECTIVE： To compare the effects of autogenous, inside-out, vein-skeletal, muscle-combined grafting versus standard, vein-skeletal, muscle-combined grafting for the repair of facial nerve defects. DESIGN, TIME AND SETTING： A randomized, controlled, neuroanatomical, animal study was performed at the Animal Experimental Center and Laboratories of the Capital Medical University Xuanwu Hospital and the Peking Union Medical College Hospital from September 2007 to October ***： A total of 10 healthy, male, New Zealand rabbits, aged 6 months, were randomly assigned to inside-out, vein-skeletal, muscle-combined grafting and standard, vein-skeletal, muscle-combined grafting groups, with 5 rabbits in each group. METHODS： A 20-mm gap in the buccal branch of the right facial nerve was made in each animal, which was respectively repaired with inside-out, vein-skeletal, muscle-combined grafts or standard vein-skeletal muscle-combined *** OUTCOME MEASURES： At 6 months after implantation, evoked maximal compound muscle action potentials were recorded on bilateral facial nerves using electromyogram. Myelinated nerve fibers of the regenerating nerves were quantified using myelin sheath osmic acid staining. RESULTS： There was no significant difference between the groups in terms of ratios of bilateral amplitude and latency of compound muscle action potential （P 〉 0.05）. Moreover, morphology of regenerating nerves and quantity of myelinated nerve fibers were similar between the groups （P 〉 0.05）. CONCLUTION： Compared with standard vein grafting, the inside-out vein grafting did not significantly improve nerve regeneration. Therefore, it is not necessary to utilize inside-out vein grafting for the repair of nerve defects, in part

关键词： facial nerve peripheral nerve nerve repair vein graft skeletal muscle graft neural regeneration

A perspective on regression and Bayesian approaches for system identification of pattern formation dynamics

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Theoretical & Applied Mechanics Letters 2020年第3期10卷 188-194页

作者： zhenlin wang Bowei Wu Krishna Garikipati Xun Huan Department of Mechanical Engineering University of MichiganAnn ArborMI 48109USA Oden Institute for Computational Engineering and Sciences University of Texas at AustinAustinTX 78712USA Departments of Mechanical Engineering and Mathematics Michigan Institute for Computational Discovery&EngineeringUniversity of MichiganAnn ArborMI 48109USA

We present two approaches to system identification, i.e. the identification of partial differentialequations (PDEs) from measurement data. The first is a regression-based variational systemidentification procedure that is advantageous in not requiring repeated forward model solves andhas good scalability to large number of differential operators. However it has strict data typerequirements needing the ability to directly represent the operators through the available *** second is a Bayesian inference framework highly valuable for providing uncertaintyquantification, and flexible for accommodating sparse and noisy data that may also be indirectquantities of interest. However, it also requires repeated forward solutions of the PDE modelswhich is expensive and hinders scalability. We provide illustrations of results on a model problemfor pattern formation dynamics, and discuss merits of the presented methods.

关键词： Computational mechanics Materials physics Pattern formation Bayesian inference Inverse problem

Enhanced Fatigue Properties of 2219 Al Alloy Joints via Bobbin Tool Friction Stir Welding

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Acta Metallurgica Sinica(English Letters) 2023年第4期36卷 586-596页

作者： zhenlin wang Beibei wang Zhen Zhang Peng Xue Yunfei Hao Yanhua Zhao Dingrui Ni Guoqing wang Zongyi Ma Shi‑Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China China Academy of Launch Vehicle Technology Beijing 100076China Capital Aerospace Machinery Company Beijing 100076China

In the present study,2219-T87 Al alloy plates,4 mm in thickness,were subjected to bobbin tool friction stir welding(BTFSW)under relatively high welding speeds of 200 and 400 mm/min,with the aim to analyze the effect of welding speeds on fatigue properties of the *** results showed that the tension–tension high-cycle fatigue performance of the BT-FSW joints at room temperature was significantly enhanced compared to that of other joints of 2xxx series Al alloys *** at a high welding speed of 400 mm/min,the fatigue strength of the joint reached 78%of the base material together with a high tensile strength of 311 *** was found that the joint line remnants had no effects on the fatigue properties of the BT-FSW joints due to the elimination of root flaws under the action of the lower *** of the samples with the welding speed of 200 mm/min failed at the thermo-mechanical zone(TMAZ)during fatigue tests,attributable to the coarsened grains and precipitates,but all of the samples with high welding speed of 400 mm/min randomly failed at the nugget zone due to the improved hardness value in the TMAZ.

关键词： 2219 Al alloys Bobbin tool friction stir welding Microstructure Fatigue properties