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基于宽频阻抗谱BIS的XLPE电缆绝缘电树枝缺陷定位方法

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电工技术 2024年第13期 160-162页

作者：郑渠岸刘莹刘兆领国网天津市电力公司天津300010

提出了一种改进的宽频阻抗谱BIS方法来定位XLPE电缆中的电树枝缺陷。进行了不同温度下的电树枝实验,以启动不同类型的电树枝。利用矢量网络分析仪测试了电树枝生长过程中的高频电容特性。采用改进的定位算法计算了含有不同类型电树枝缺... 详细信息

提出了一种改进的宽频阻抗谱BIS方法来定位XLPE电缆中的电树枝缺陷。进行了不同温度下的电树枝实验,以启动不同类型的电树枝。利用矢量网络分析仪测试了电树枝生长过程中的高频电容特性。采用改进的定位算法计算了含有不同类型电树枝缺陷的20m长电缆的定位谱,结果表明切片样品的电容随着电树枝的生长而减小。丛林状电树对电容参数的影响大于松枝状电树枝。在丛林状电树枝的定位谱中发现了一个典型的双峰,在松枝状电树枝的光谱中发现了单个峰。

关键词： XLPE电缆电树枝劣化位置宽频阻抗谱分布参数

无人驾驶航空器系统工程专业建设——以创新就业为导向的教育改革研究

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教育教学论坛 2024年第29期 77-80页

作者：杨永刚杨正全中国民航大学交通科学与工程学院天津300300

随着社会的不断发展,我国无人机技术也在不断进步,近些年无人机在我国多个领域的应用变得越来越广泛,使得社会对无人驾驶航空器系统工程专业的人才需求变得越来越迫切。基于创新就业导向,探讨了无人驾驶航空器系统工程专业的建设以及教... 详细信息

随着社会的不断发展,我国无人机技术也在不断进步,近些年无人机在我国多个领域的应用变得越来越广泛,使得社会对无人驾驶航空器系统工程专业的人才需求变得越来越迫切。基于创新就业导向,探讨了无人驾驶航空器系统工程专业的建设以及教育改革的相关问题,并且从以下几个方面提出了相关建议,为无人机专业建设提供参考:聚焦行业需求,加强实践教学;积极推广校企合作,熟悉新型技术;提高教师实践水平,完善人才培养体系。

关键词：无人驾驶教育改革创新就业

Asymptotic Behavior of Global Classical Solutions to Quasilinear Hyperbolic Systems of Diagonal Form

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Journal of Mathematical Research and Exposition 2010年第1期30卷 29-40页

作者： quan zheng School of Mathematical Sciences Fudan University Shanghai 200433 P. R. China

This paper deals with the asymptotic behavior of global classical solutions to quasilinear hyperbolic systems of diagonal form with weakly linearly degenerate characteristic fields. On the basis of global existence and uniqueness of C^1 solution, we prove that the solution to the Cauchy problem approaches a combination of C^1 traveling wave solutions when t tends to the infinity.

关键词： quasilinear hyperbolic systems of diagonal form weak linear degeneracy global classical solution rich system traveling wave.

Control of surface wettability via strain engineering

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Acta Mechanica Sinica 2013年第4期29卷 543-549页

作者： Wei Xiong Jefferson Zhe Liu Zhi-Liang Zhang quan-Shui zheng Department of Engineering Mechanics and Center for Nano and Micro Mechanics Tsinghua University Department of Mechanical and Aerospace Engineering Monash University Department of Structural Engineering Norwegian University of Science and Technology (NTNU)

Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, we demon- strate that strain engineering can serve as an effective way to control the surface wettability. The contact angles 0 of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface （at zero strain）, the variation of 0 upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. In light of the inherent dependence of the contact an- gle on liquid-solid interfacial energy, we develop an analytic model to show the cos 0 as a linear function of the adsorption energy Eads of a single water molecule over the substrate sur- face. This model agrees with our molecular dynamic results very well. Together with the linear dependence of Eads on bi- axial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly ap- plying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promis- ing means to achieve the reversibly control of surface wetta- bility.

关键词： Wettability ~ Strain engineering ~ Molecular dy-namics simulation

Insights from metagenomic,metatranscriptomic,and molecular ecological network analyses into the effects of chromium nanoparticles on activated sludge system

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Frontiers of Environmental Science & Engineering 2020年第4期14卷 53-63页

作者： quan zheng Minglu Zhang Tingting Zhang Xinhui Li Minghan Zhu Xiaohui Wang Beijing Engineering Research Center of Environmental Material for Water Purification College of Chemical EngineeringBeijing University of Chemical TechnologyBeijing 100029China Key Laboratory of Cleaner Production and Integrated Resource Utilization of China National Light Industry Beijing Technology and Business UniversityBeijing 100048China

The objectives of this study were to investigate the influence of chromium nanoparticles(Cr NPs)on the nitrogen and phosphorus removal performance and the bacterial structures of an activated sludge(AS)***,we through molecular ecological networks(MENs)discussed the bacterial *** last we researched the change of the functional genes and their expression patterns related to nitrogen and phosphorus removaT in an AS *** results showed that long-term exposure to 1 mg/L Cr NPs significantly promoted the denitrifying process and phosphorus removal in the AS *** relative abundance of denitrifying and phosphorus removal microorganisms,such as Denitratisoma,Thauera,Dechloromonas,and Defluviicoccus,increased *** Accumulibacter,well-known as polyphosphate-accumulating organisms(PAOs),increased significantly;the relative abundance of Candidatus Competibacter,known as glycogen-accumulating organisms(GAOs),decreased ***,metagenomic and metatranscriptomic analysis revealed that most of the genera related to denitrifying and phosphorus removal had greatly increased,according to the quantities of denitrifying and phosphorus genes,and the corresponding transcription likewise greatly ***,MENs analysis showed that although the overall network became smaller and looser in the presence of Cr NPs,the microbial connections among members related to nitrogen and phosphorus removal were *** abundance increases of denitrifiers and PAOs,and their increased transcription of functional genes,together with the enhanced interactions may be associated with the promotion of the denitrifying process and phosphorus removal.

关键词： Chromium nanoparticles(Cr NPs) Metagenomic analysis Metatranscriptomic analysis Molecular ecological networks(MENs) Nitrogen and phosphorus removal

A study of sea level variability and its long-term trend in the South China Sea

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Acta Oceanologica Sinica 2016年第9期35卷 22-33页

作者： XU Ying LIN Mingsen zheng quan'an SONG Qingtao YE Xiaomin College of Information Science and Engineering Ocean University of China National Satellite Ocean Application Service State Oceanic Administration Key Laboratory of Space Ocean Remote Sensing and Application State Oceanic Administration Department of Atmospheric and Oceanic Science University of MarylandCollege Park

On the basis of the satellite maps of sea level anomaly（MSLA） data and in situ tidal gauge sea level data,correlation analysis and empirical mode decomposition（EMD） are employed to investigate the applicability of MSLA data,sea level correlation,long-term sea level variability（SLV） trend,sea level rise（SLR） rate and its geographic distribution in the South China Sea（SCS）.The findings show that for Dongfang Station,Haikou Station,Shanwei Station and Zhapo Station,the minimum correlation coefficient between the closest MSLA grid point and tidal station is *** suggests that the satellite altimeter MSLA data are effective to observe the coastal SLV in the *** the monthly scale,coastal SLV in the western and northern part of SCS are highly associated with coastal *** the seasonal scale,SLV of the coastal area in the western part of the SCS is still strongly influenced by the coastal current system in summer and *** Pacific change can affect the SCS mainly in winter rather than summer and the affected area mostly concentrated in the northeastern and eastern parts of the ***,the average SLR in the SCS is 90.8 mm with a rising rate of（5.0±0.4） mm/a during1993–*** SLR rate from the southern Luzon Strait through the Huangyan Seamount area to the Xisha Islands area is higher than that of other areas of the SCS.

关键词： South China Sea sea level variability correlation analysis empirical mode decomposition

Embrittlement Mechanism due to Slow Cooling During Quenching for M152 Martensitic Heat Resistant Steel

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Journal of Iron and Steel Research International 2010年第6期17卷 60-66页

作者： YANG Gang WANG Chang LIU Xin-quan LIU zheng-dong Central Iron and Steel Research Institute Beijing 100081 China

The mechanism of brittleness of M152 martensitic heat resistant steel due to slow cooling during quenching was experimentally investigated. The mechanical property tests and microstructure observation were conducted by TEM and XRD. The results showed that the presence of irreversible brittleness during slow cooling of quenching for M152 steel is attributed to the continuous M23C6 precipitation along prior austenite grain boundaries and M2C along prior residual austenite film. The residual austenite in the steel was unstable and decomposed after the precipitation of second phase during the process of slow cooling of quenching. The low cooling rate within the temperature range from 820 ℃ to 660 ℃ plays a key role in impact toughness, and the precipitation of second phase in the same temperature range results in irreversible brittleness.

关键词： M152 martensitic heat resistant steel brittleness carbides decomposition residual austenite

quantum Tunneling Radiation of Reissner-Nordstrom de Sitter Black Hole with a Global Monopole

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Communications in Theoretical Physics 2006年第3期45卷 457-460页

作者： JIANG Qing-quan YANG Shu-zheng LI Hui-Ling Institute of Theoretical Physics West China Normal University Nanchong 637002 China

Applying Parikh＇s quantum tunneling model, we study the quantum tunneling radiation of Reissne- Nordstrom de Sitter black hole with a global monopole. The result shows that the tunneling rates at the event horizon and the cosmic horizon are related to Bekenstein-Hawking entropy if we take the energy conservation into consideration, and the true radiate spectrum is not precisely thermal.

关键词： Reissner-Nordstrom de Sitter black hole global monopole energy conservation tunneling rate

QoE-Driven DASH Multicast Scheme for 5G Mobile Edge Network

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Journal of Communications and Information Networks 2021年第2期6卷 153-165页

作者： Xiaobin Tan Lei Xu quan zheng Simin Li Bei Liu Laboratory for Future Networks the University of Science and Technology of ChinaHefei 230027China The 54th Research Institute of China Electronic Technology Corporation Shijiazhuang 050081.China

Dynamic adaptive streaming over HTTP(DASH)can adaptively select the appropriate video bitrate for mobile *** edge computing(MEC)scenario is of great benefit to improve the performance of mobile networks by providing computing and storage *** the utilization of spectrum resources can be improved by multicast transmission,but the performance of the multicast transmission will be directly affected by the selected grouping algorithm and resource allocation *** order to improve the quality of experience(QoE)of video users in the 5G MEC scenario,this paper proposes a QoE-driven DASH multicast scheme,which mainly covers the grouping algorithm and the adaptive bitrate(ABR)*** of all,we take the optimized target QoE as the basis for grouping and propose an adaptive grouping algorithm that can dynamically adjust the grouping ***,we design a joint optimization ABR algorithm based on the prediction of QoE,which comprehensively considers the process of resource allocation and bitrate decision-making based on the prediction of QoE of video segments in a certain forward-looking field of *** simulation results show that the proposed DASH multicast scheme performs well in QoE and fairness.

关键词： DASH mobile edge computing multicast quality of experience adaptive bitrate algorithm