检索结果-南通市图书馆

Research on the principle of space high-precision temperature control system of liquid crystals based Stokes polarimeter

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第1期21卷 97-104页

作者： Xin-Wei Zhang Yang Zhang jia-ben lin Jun-Feng Hou Yuan-Yong Deng Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 101408China

The magnetic field is one of the most important parameters in solar physics,and a polarimeter is the key device to measure the solar magnetic *** crystals based Stokes polarimeter is a novel technology,and will be applied for magnetic field measurement in the first space-based solar observatory satellite developed by China,Advanced Space-based Solar ***,the liquid crystals based Stokes polarimeter in space is not a mature ***,it is of great scientific significance to study the control method and characteristics of the *** retardation produced by a liquid crystal variable retarder is sensitive to the temperature,and the retardation changes 0.09°per 0.10℃.The error in polarization measurement caused by this change is 0.016,which affects the accuracy of magnetic field *** order to ensure the stability of its performance,this paper proposes a high-precision temperature control system for liquid crystals based Stokes polarimeter in *** order to optimize the structure design and temperature control system,the temperature field of liquid crystals based Stokes polarimeter is analyzed by the finite element method,and the influence of light on the temperature field of the liquid crystal variable retarder is analyzed *** analyzing the principle of highprecision temperature measurement in space,a high-precision temperature measurement circuit based on integrated operational amplifier,programmable amplifier and 12 bit A/D is designed,and a high-precision space temperature control system is developed by applying the integral separation PI temperature control algorithm and PWM driving heating *** experimental results show that the effect of temperature control is accurate and stable,whenever the liquid crystals based Stokes polarimeter is either in the air or *** temperature stability is within±0.0150℃,which demonstrates greatly improved stability for the liquid crystals based Stokes polarim

关键词： liquid crystals based Stokes polarimeter high-precision temperature measurement space high-precision temperature control temperature field analysis PID control

Evolution of isolated G-band bright points: size, intensity and velocity

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2014年第6期14卷 741-752页

作者： Yun-Fei Yang jia-ben lin Song Feng Kai-Fan Ji Hui Deng Feng Wang Faculty of Information Engineering and Automation/Yunnan Key Laboratory of Computer Technology Application Kunming University of Science and Technology Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Key Laboratory of Modern Astronomy and Astrophysics Nanjing University Ministry of Education

We study the evolution pattern of isolated G-band bright points （GBPs） in terms of their size, intensity and velocity. Using a high resolution image sequence taken with the Hinode/Solar Optical Telescope （SOT）, we detect GBPs in each image by the Laplacian and Morphological Dilation algorithm, and track their evolutions by a 26-adjacent method in a three-dimensional space-time cube. For quantifying the evolution, we propose a quantification method based on lifetime normalization which aligns the different lifetimes to common stages. The quantification results show that, on average, the diameter of isolated GBPs changes from 166 to 173 km, then down to 165 km; the maximum intensity contrast changes from 1.012 to 1.027, then down to 1.011; however, the velocity changes from 1.709 to 1.593 km s-1, then up to 1.703 km s-i. The results indicate that the evolution follows a pattern such that the GBP is small, faint and fast-moving at the birth stage, becomes big, bright and slow-moving at the middle stage, then gets small, faint and fast-moving at the decay stage until disappearance. Although the differences are very small, a two-sample t-test is used to demonstrate there are significant differences in means between the distri- butions of the different stages. Furthermore, we quantify the relationship between the lifetimes of GBPs and their properties. It is found that there are positive correlations between the lifetimes and their sizes and intensities with correlation coefficients of 0.83 and 0.65, respectively; however, there is a negative correlation between the life- times and velocities with a correlation coefficient of-0.49. In summary, the longer the GBP persists, the bigger, brighter and slower it will be.

关键词： techniques: image processing -- Sun: photosphere -- methods: dataanalysis -- methods: statistical

Characterizing motion types of G-band bright points in the quiet Sun

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2015年第4期15卷 569-582页

作者： Yun-Fei Yang Hui-Xue Qu Kai-Fan Ji Song Feng Hui Deng jia-ben lin Feng Wang Faculty of Information Engineering and Automation / Yunnan Key Laboratory of Computer Technology Application Kunming University of Science and Technology Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of Sciences Key Laboratory of Modern Astronomy and Astrophysics Nanjing UniversityMinistry of Education Yunnan Observatories Chinese Academy of Sciences

We study the motion of G-band bright points （GBPs） in the quiet Sun to obtain the characteristics of different motion types. A high resolution image sequence taken with the Hinode/Solar Optical Telescope （SOT） is used, and GBPs are automat- ically tracked by segmenting 3D evolutional structures in a space-time cube. After putting the GBPs that do not move during their lifetimes aside, the non-stationary GBPs are categorized into three types based on an index of their motion type. Most GBPs that move in straight or nearly straight lines are categorized as a straight mo- tion type, a few moving in rotary paths into rotary motion, and the others fall into a motion type we called erratic. The mean horizontal velocities are 2.18±0.08 km s-1, 1.63±0.09km s^-1 and 1.33±0.07 km s^-1 for straight, erratic and rotary motion types, respectively. We find that a GBP drifts at a higher and constant velocity during its whole life if it moves in a straight line. However, it has a lower and variational velocity if it moves on a rotary path. The diffusive process is ballistic-, super- and sub-diffusion for straight, erratic and rotary motion types, respectively. The corresponding diffusion index （γ） and coefficients （K） are 2.13±0.09 and 850±37km^2 s^-1, 1.82±0.07 and 331 ±24 km^2 s^-1, and 0.73±0.19 and 13±9 km^2 s^-1. In terms of direction of motion, it is homogeneous and isotropic, and usually persists between neighboring frames, no matter what motion type a GBP is classified as.

关键词： techniques: image processing -- Sun: photosphere -- methods: dataanalysis -- methods: statistical

Curcumin Interferes with TGF-β1-Induced Fibrosis in NRK-49F Cells by Reversing ADAMTS18 Gene Methylation

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Integrative Medicine 2024年第7期30卷 600-607页

作者： XU ben ZHANG jia-en YE lin YUAN Chang-wei Department of Urology Peking University First Hospital and Institute of UrologyPeking UniversityNational Urological Cancer CenterBeijing100034China

Objective To explore the molecular mechanism by which curcumin affects renal interstitial fibrosis(RIF)progression by regulating ADAM metallopeptidase with thrombospondin type 1 motif 18(ADAMTS18)*** NRK-49F cells RIF model were induced with transforming growth factorβ1(TGF-β1).Effects of different concentrations of curcumin(0,10,20,and 30μmol/L)on cell proliferation,cell cycle,cell apoptosis as well as cyclin D1 expression were analyzed by cell counting kit-8,flow cytometry and Western blot,***18 methylation levels were determined by methylation-specific polymerase chain ***18,fibronectin(FN),type I collagen(Col-I)and alpha-smooth muscle actin(α-SMA)mRNA and protein expressions were analyzed by real-time PCR(RT-PCR)and Western blot,***,cells were treated with 50 mmol/L 5-aza-2′-deoxycytidine(5-aza-dC,demethylation agent)for 72 *** of curcumin on extracellular matrix(ECM)deposition was evaluated by immunochemical staining and Western ***-49F cells were transfected with ADAMTS18 small interfering RNA and grouped into a normal control,ADAMTS18-knock-out(KO),and ADAMTS18-KO+30μmol/L curcumin groups,and whether curcumin can reverse the effect of ADAMTS18 knockdown on RIF was *** Compared with the control group,TGF-β1 significantly inhibited the proliferation of NRK-49F cells,blocked the G1/G0 phase,promoted cell apoptosis and inhibited cyclin D1 expression(P<0.01).Among the different concentrations of curcumin,30μmol/L curcumin significantly reversed these processes(P<0.01).Immunochemical staining and Western blot results showed that curcumin significantly inhibited the deposition of FN,Col-I andα-SMA(P<0.01).Curcumin and 5-zaz-dC had synergistic effects,promoting ADAMTS18 expression,removing ADAMTS18 methylation,and reducing ECM ***18 knockdown promoted ECM accumulation,and curcumin reversed this process(P<0.01).Conclusion TGF-β1-induced fibrosis in NRK-49F ***

关键词： renal fibrosis curcumin Chinese medicine ADAMTS18 methylation modification

在线全文

学校读者我要写书评

暂无评论

基于虚内键模型的三维均质岩石本构关系模拟

岩土力学 2017年第3期38卷 740-746页

作者：贾珺肖本林柯长仁湖北工业大学土木建筑与环境学院湖北武汉430068

基于虚内键模型,推导出三维条件下虚内键演化函数的四阶弹性张量,对虚内键密度演化函数中的两个参数进行研究,建立单轴压缩下岩石数值模型,得出两参数对岩石应力-应变全过程曲线影响的一般性规律,实现对均质大理岩试样应力-应变全过程... 详细信息

基于虚内键模型,推导出三维条件下虚内键演化函数的四阶弹性张量,对虚内键密度演化函数中的两个参数进行研究,建立单轴压缩下岩石数值模型,得出两参数对岩石应力-应变全过程曲线影响的一般性规律,实现对均质大理岩试样应力-应变全过程曲线的数值模拟。数值结果表明,基于虚内键模型的均质岩石应力-应变全过程曲线与力学试验结果较为吻合。从而证明了用虚内键模型探讨岩石材料本构关系的适用性与可行性,为研究岩石本构关系提供了一个新思路。

关键词：虚内键模型三维应力-应变曲线单轴压缩数值模拟

Ballistic performances of the hourglass lattice sandwich structures under high-velocity fragments

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第1期31卷 312-325页

作者： He-xiang Wu jia Qu lin-zhi Wu Key Laboratory of Advanced Ship Materials and Mechanics College of Aerospace and Civil EngineeringHarbin Engineering UniversityHarbin150001China School of Civil Engineering Northeast Forestry UniversityHarbin150040China

In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of *** is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of *** results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural *** this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.

关键词： Hourglass lattice sandwich structures Ballistic performances high-velocity Finite element analysis

Grain refinement of 5A06 aluminum alloy welds caused by tungsten inert gas welding arc characteristics under Ar-He alternating gas supply conditions:a coupled method of water-cooled copper plate test/numerical simulation

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2024年第3期31卷 767-777页

作者： Hong-bin Dai jian Miao jia-xin lin School of Materials Science and Engineering Harbin University of Science and TechnologyHarbin 150040HeilongjiangChina

The welding arc,as a carrier for the conversion of electrical energy to thermal energy,has a direct impact on the quality of welding by its properties and *** the tungsten inert gas(TIG)welding process under the condition of Ar-He alternating gas supply,the arc is alternately converted between Ar arc and He arc with an alternating gas supply cycle,which has obvious arc change *** FLUENT software was used to numerically simulate the characteristics of the TIG arc under the condition of alternating gas supply,and the arc temperature field,arc pressure,electric potential and current density distribution under the condition of alternating gas supply were *** with the real-time data of arc pressure measured by the water-cooled copper plate with holes,it is proved that the TIG arc has obvious dynamic characteristics under the condition of Ar-He alternating gas *** unique dynamic TIG arc acts on the 5A06 aluminum alloy weld,causing the molten pool to stir,resulting in uniform microstructure and grain refinement at the weld,and thereby improving the mechanical properties of the welded joint.

关键词： Alternating gas supply Grain refinement Numerical simulation Tungsten argon arc morphology Microstructure Mechanical property

Machine Learning Security Defense Algorithms Based on Metadata Correlation Features

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第2期78卷 2391-2418页

作者： Ruchun jia jianwei Zhang Yi lin College of Computer Science Sichuan UniversityChengdu610065China

With the popularization of the Internet and the development of technology,cyber threats are increasing day by *** such as malware,hacking,and data breaches have had a serious impact on *** network security environment in the era of big data presents the characteristics of large amounts of data,high diversity,and high real-time *** security defense methods and tools have been unable to cope with the complex and changing network security *** paper proposes a machine-learning security defense algorithm based on metadata association *** control over unauthorized users through privacy,integrity,and *** user model is established and the mapping between the user model and the metadata of the data source is *** analyzing the user model and its corresponding mapping relationship,the query of the user model can be decomposed into the query of various heterogeneous data sources,and the integration of heterogeneous data sources based on the metadata association characteristics can be *** and classify customer information,automatically identify and perceive sensitive data,build a behavior audit and analysis platform,analyze user behavior trajectories,and complete the construction of a machine learning customer information security defense *** experimental results show that when the data volume is 5×103 bit,the data storage integrity of the proposed method is 92%.The data accuracy is 98%,and the success rate of data intrusion is only 2.6%.It can be concluded that the data storage method in this paper is safe,the data accuracy is always at a high level,and the data disaster recovery performance is *** method can effectively resist data intrusion and has high air traffic control *** can not only detect all viruses in user data storage,but also realize integrated virus processing,and further optimize the security defense effect of user big data.

关键词： Data-oriented architecture metadata correlation features machine learning security defense data source integration

Experimental,Numerical,and Analytical Studies on the bending of Mechanically lined Pipe

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Ocean Engineering 2024年第2期38卷 221-232页

作者： WEI Wen-bin YUAN lin ZHOU jia-sheng LIU Zheng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China School of Mechanical Engineering Tianjin UniversityTianjin 300072China

Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion *** installation and operation,the pipe may undergo severe bending deformation,which causes the liner to separate from the outer pipe and buckles,affecting the stability of the whole *** this paper,the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments,numerical simulation,as theoretical *** types of MLPs were manufactured with GB 45 carbon steel(SLP)and Al 6061(ALP)used as the outer pipe material,*** hydraulic expansion and bending experiments of small-scale MLPs are *** addition to the ovalized shape of the cross-section for the SLP specimens,the copper liner was found to wrinkle on the compressive *** contrast,the liner of ALP remains intact without developing any wrinkling and collapse *** addition,a dedicated numerical framework and theoretical models were also *** was found both the manufacturing and bending responses of the MLP can be well reproduced,and the predicted maximum moment and critical curvatures are in good agreement with the experimental results.

关键词： lined pipe bending nonlinear ring theory buckling plasticity