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高线密度X光透射光栅衍射效率 被引量:2
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作者 张文海 曹磊峰 +2 位作者 朱效立 谢常青 刘慎业 《强激光与粒子束》 EI CAS CSCD 北大核心 2012年第10期2347-2350,共4页
高线密度X光透射光栅是各种高分辨光栅摄谱仪的核心色散元件,为了获得较高的光谱分辨率,工作在2~5keV能区的光谱仪需要使用5000l/mm的X射线透射光栅。为了获得光栅的绝对衍射效率,采用同步辐射光在多个能点对5000l/mm的X光透射光栅进... 高线密度X光透射光栅是各种高分辨光栅摄谱仪的核心色散元件,为了获得较高的光谱分辨率,工作在2~5keV能区的光谱仪需要使用5000l/mm的X射线透射光栅。为了获得光栅的绝对衍射效率,采用同步辐射光在多个能点对5000l/mm的X光透射光栅进行衍射效率实验标定,通过光栅相对衍射效率拟合获得了光栅结构参数,与光栅结构测量结果非常接近。然后,采用衍射效率的矩形栅线模型,计算得到了光栅的绝对衍射效率。 展开更多
关键词 透射光栅 衍射效率 实验标定 高线密度
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高线密度胶原蛋白/PVA共混纤维的制备及其结构性能 被引量:2
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作者 吴炜誉 王雪娟 +1 位作者 徐建军 叶光斗 《合成纤维》 CAS 北大核心 2008年第9期29-34,共6页
在胶原蛋白与聚乙烯醇(PVA)共混溶液中,改变原液中胶原蛋白和聚乙烯醇的组成,由湿法纺丝得到初生纤维,经热拉伸、热定形、缩醛化反应制得线密度大于25dtex的胶原蛋白/PVA共混纤维。共混纤维横截面呈圆形,纤维内部无孔洞及裂纹,表面光滑... 在胶原蛋白与聚乙烯醇(PVA)共混溶液中,改变原液中胶原蛋白和聚乙烯醇的组成,由湿法纺丝得到初生纤维,经热拉伸、热定形、缩醛化反应制得线密度大于25dtex的胶原蛋白/PVA共混纤维。共混纤维横截面呈圆形,纤维内部无孔洞及裂纹,表面光滑,断裂强度和初始模量分别达到4.63cN/dtex和160.2cN/dtex,断裂伸长率为25.4%,结晶度为48.6%,水中软化点和回潮率分别为104℃和13.67%。 展开更多
关键词 胶原蛋白 聚乙烯醇 共混纤维 高线密度 制备 结构 性能
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光纤激光精密切割高线密度不锈钢支架 被引量:1
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作者 杨莉 苏志辉 +1 位作者 农登 王海艳 《材料研究与应用》 CAS 2009年第4期276-280,共5页
实验选用波长1090nm、峰值功率50W的光纤激光器,切割直径2mm、厚0.13mm的316L不锈钢管材以获得理想的心血管支架.实验结果表明:激光切割质量主要与激光聚焦、激光切割频率、激光切割速率和脉冲宽度等因素有关.在激光切割频率2000 Hz、... 实验选用波长1090nm、峰值功率50W的光纤激光器,切割直径2mm、厚0.13mm的316L不锈钢管材以获得理想的心血管支架.实验结果表明:激光切割质量主要与激光聚焦、激光切割频率、激光切割速率和脉冲宽度等因素有关.在激光切割频率2000 Hz、激光平均功率50W、脉宽0.06~0.2ms、典型值0.1ms、切割速率100mm/min、焦距50mm、氧压(同轴)0.6~1MPa的条件下,获得了切口表面光滑、切缝垂直度好、筋宽为(100±10)μm的血管支架.其延伸率δ≥40%,抗拉强度σ≥480 MPa,综合性能能够满足使用要求. 展开更多
关键词 激光精密切割 不锈钢支架 光纤激光 高线密度
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拉伸方法对高强高线密度PVA纤维结构性能的影响
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作者 卢晓轶 赵天宝 +2 位作者 许远远 叶光斗 徐建军 《广州化工》 CAS 2009年第2期140-142,共3页
聚乙烯醇经干湿法凝胶纺丝制得初生纤维后,采用不同的两级后拉伸方法,制得单纤线密度在200~300 dtex的高线密度PVA纤维。探讨了两级不同拉伸条件对PVA纤维结构和性能的影响。结果表明:一级拉伸热定型,有利于折叠链晶体的完善,一级拉伸... 聚乙烯醇经干湿法凝胶纺丝制得初生纤维后,采用不同的两级后拉伸方法,制得单纤线密度在200~300 dtex的高线密度PVA纤维。探讨了两级不同拉伸条件对PVA纤维结构和性能的影响。结果表明:一级拉伸热定型,有利于折叠链晶体的完善,一级拉伸后再经二级拉伸定型,纤维结晶更完善,水中软化点和纤维断裂强度分别达到116℃和11.5 cN/dtex。 展开更多
关键词 高线密度聚乙烯醇纤维 两级拉伸 热定型时间 水中软化点
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基于密度等高线法的柔顺机构轮廓提取算法 被引量:7
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作者 裴灵 郭为忠 《上海交通大学学报》 EI CAS CSCD 北大核心 2009年第5期811-815,共5页
利用连续的密度函数逼近柔顺机构拓扑优化结果,采用共轭梯度法优化密度误差,对不同等高线对应的机构轮廓进行分析,得到柔顺机构输出位移误差,用插值法获得最小误差值及其对应的等高线值.数值分析结果表明,轮廓提取后机构的输出位移误差... 利用连续的密度函数逼近柔顺机构拓扑优化结果,采用共轭梯度法优化密度误差,对不同等高线对应的机构轮廓进行分析,得到柔顺机构输出位移误差,用插值法获得最小误差值及其对应的等高线值.数值分析结果表明,轮廓提取后机构的输出位移误差得到较大改善,但轮廓的光滑性与加工要求之间仍然存在一定距离. 展开更多
关键词 柔顺机构 轮廓提取 密度高线
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基于密度等高线的原型初始化方法 被引量:1
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作者 郑金彬 欧阳利军 《南华大学学报(自然科学版)》 2007年第1期38-41,45,共5页
对于FCM类算法而言,种子的初始化是保证算法不陷入局部最优值和减少计算时间的关键.本文中提出根据密度分布特性的密度等高线来确定种子的选取不仅可以确定种子的个数,同时可以加快FCM算法的执行.
关键词 密度高线 聚类 种子初始化 FCM
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黄河粗泥沙集中来源区区域地形因子比较研究 被引量:6
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作者 高云飞 李智广 +1 位作者 杨胜天 曹炜 《水土保持通报》 CSCD 北大核心 2012年第1期111-114,共4页
在黄河粗泥沙集中来源区的清水川流域,以1∶10 000比例尺地形图上的小流域为基本单元,在1∶250 000比例尺DEM上提取地表起伏度、高程变异系数和等高线密度等区域土壤侵蚀地形因子,以1∶10 000比例尺计算的地形因子为真值,拟合各区域土... 在黄河粗泥沙集中来源区的清水川流域,以1∶10 000比例尺地形图上的小流域为基本单元,在1∶250 000比例尺DEM上提取地表起伏度、高程变异系数和等高线密度等区域土壤侵蚀地形因子,以1∶10 000比例尺计算的地形因子为真值,拟合各区域土壤侵蚀地形因子的计算方法。结果表明,等高线密度是合适的区域土壤侵蚀地形因子计算指标。应用该方法在皇甫川下游进行检验,模拟结果误差小于10%,效果良好,可作为土壤侵蚀区域地形因子计算时指标选择的参考。 展开更多
关键词 USLE 地形因子 粗泥沙集中来源区 高线密度
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稀疏信号的参数分析 被引量:3
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作者 傅予力 谢胜利 何昭水 《武汉大学学报(工学版)》 CAS CSCD 北大核心 2006年第6期101-104,121,共5页
对于服从广义高斯分布(Generalized Gaussian distribution,GGD)的稀疏信号进行了参数分析.首先给出了广义高斯分布信号的一些性质,通过对信号等高线的分析,导出了计算稀疏性参数的公式,通过该公式的计算可以得到,对Laplace信号稀疏性... 对于服从广义高斯分布(Generalized Gaussian distribution,GGD)的稀疏信号进行了参数分析.首先给出了广义高斯分布信号的一些性质,通过对信号等高线的分析,导出了计算稀疏性参数的公式,通过该公式的计算可以得到,对Laplace信号稀疏性参数为1,对Gauss信号为2.参照Laplace信号和Gauss信号,对于给定的服从广义高斯分布的信号,通过稀疏度量的计算可以直观地知道它究竟多么稀疏.实例表明只有当信号充分稀疏时才能通过稀疏表示方法实现欠定盲源分离. 展开更多
关键词 广义高斯分布 盲源分离 独立元分析 概率密度高线 散点图
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Experiments on excitation and data processing of low-frequency vibroseis in permafrost area of the tibetan plateau
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作者 Tian Yu-Kun Kang Hai-xia +3 位作者 Cao Jie Li Juan Zhou Hui Ma Yan-Yan 《Applied Geophysics》 SCIE CSCD 2020年第5期834-843,904,共11页
Few seismic exploration work was carried out in Tibetan Plateau due to the characteristics of alpine hypoxia and harsh environmental protection needs.Complex near surface geological conditions,especially the signal sh... Few seismic exploration work was carried out in Tibetan Plateau due to the characteristics of alpine hypoxia and harsh environmental protection needs.Complex near surface geological conditions,especially the signal shielding and static correction of permafrost make the quality of seismic data is not ideal,the signal to noise ratio(SNR)is low,and deep target horizon imaging is difficult.These data cannot provide high quality information for oil and gas geological survey and structural sedimentary research in the area.To solve the issue of seismic exploration in Tibetan Plateau,this test used low frequency vibroseis wide-line and high-density acquisition scheme.In view of the actual situation of the study area,the terrain,the source and the diff erent observation system were simulated,and the processing technique was adopted to improve the quality of seismic data.Low-frequency components with a minimum of 1.5Hz of vibroseis ensure the deep geological target imaging quality in the area,the seismic profi le wave group is clear,and the SNR is relatively high,which can meet the needs of oil and gas exploration.Seismic data can provide the support for the development of oil and gas survey in the Tibet plateau. 展开更多
关键词 Tibetan Plateau permafrost region low frequency vibroseis wide-line and high-density 2D seismic static correction noise attenuation
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Minimizing crosstalk for high-speed and high-density bus systems using the sample-decision method
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作者 王亚飞 Chen Yinchao +2 位作者 Yang Shuhui Yang Hongwen Li Xuehua 《High Technology Letters》 EI CAS 2014年第1期16-21,共6页
This paper presents a method based on a sample-decision(SD) circuit to suppress crosstalk and noise for a high-speed and high-density bus system.A method to count the number of times of SD for different length of tran... This paper presents a method based on a sample-decision(SD) circuit to suppress crosstalk and noise for a high-speed and high-density bus system.A method to count the number of times of SD for different length of transmission lines is presented and a bit error rates(BERs) formula is given by the SD circuit.It is shown that for long transmission line systems,multiple SD circuits can improve the BERs significantly.Circuits simulation for single SD method is also done,it is found that when the amplitude peak values of the superposed crosstalk and noise are less than half of the corresponding signal ones,they will be eliminated completely for the cases investigated. 展开更多
关键词 CROSSTALK transmission line sample-decision high-speed and high-density circuits
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A Mechanism for Biological Control-Tempo-Spatial Synchronization of Natural Enemy and Insect Pest Population Dynamics at the Peak by Increase of Biodiversity
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作者 Long Zhang Xiangyong Li 《Journal of Environmental Science and Engineering(B)》 2015年第10期538-546,共9页
To reveal the mechanism of control of the Woolly Apple Aphid (Eriosoma lanigerum Hausm, WAA) by increase of biodiversity in the apple orchard, a consecutive two-year field trials were conducted in Yurman province, C... To reveal the mechanism of control of the Woolly Apple Aphid (Eriosoma lanigerum Hausm, WAA) by increase of biodiversity in the apple orchard, a consecutive two-year field trials were conducted in Yurman province, China. The results showed that the peak of natural enemy density curve in the cover cropping orchard was well temporally synchronized with that of the WAA density on trees, but did not synchronize with that of WAA density on trees in clean orchard. In addition, the frequency of natural enemies and WAA within a same sample in cover cropping orchard was obviously higher than that in clean cultivated orchard during the peak of population curves, indicating that natural enemies spatially synchronized with aphids. The density of WAA for the whole growing season in cover cropping orchard was much less than that in clean orchard. Therefore, the temporal-spatial synchrony of natural enemy and aphid populations was proposed as one of the mechanisms for aphid control in cover cropped orchards. 展开更多
关键词 Synchrony natural enemies APHID Eriosoma lanigerum cover crops apple orchard biological control temporal-spatialdynamics.
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3333lp/mm X射线透射光栅的研制 被引量:11
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作者 朱效立 马杰 +5 位作者 谢常青 叶甜春 刘明 曹磊峰 杨家敏 张文海 《光学学报》 EI CAS CSCD 北大核心 2008年第6期1026-1030,共5页
针对X射线透射光栅摄谱仪中的高线密度光栅,研究了采用电子束曝光和X射线曝光技术结合制作高线密度X射线透射光栅的工艺技术。首先利用电子束曝光和微电镀技术在镂空的薄膜上制备母光栅X射线掩模版,然后利用X射线曝光和微电镀技术小批... 针对X射线透射光栅摄谱仪中的高线密度光栅,研究了采用电子束曝光和X射线曝光技术结合制作高线密度X射线透射光栅的工艺技术。首先利用电子束曝光和微电镀技术在镂空的薄膜上制备母光栅X射线掩模版,然后利用X射线曝光和微电镀技术小批量复制光栅。在国内首次完成了3333lp/mm X射线透射光栅的研制,栅线宽度为150nm,周期为300nm,金吸收体厚度为500nm。衍射效率标定的结果表明,该光栅的占空比合理、侧壁陡直,具有良好的色散特性,能够满足空间探测、同步辐射和变等离子诊断等多个领域的应用。 展开更多
关键词 X射线透射光栅 电子束光刻 X射线光刻 高线密度光栅
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Sodium iron hexacyanoferrate with high Na content as a Na-rich cathode material for Na-ion batteries 被引量:27
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作者 Ya You Xiqian Yu +2 位作者 Yaxia Yin Kyung-Wan Nam Yu-Guo Guo 《Nano Research》 SCIE EI CAS CSCD 2015年第1期117-128,共12页
Owing to the worldwide abundance and low-cost of Na, room-temperature Na-ion batteries are emerging as attractive energy storage systems for large- scale grids. Increasing the Na content in cathode materials is one of... Owing to the worldwide abundance and low-cost of Na, room-temperature Na-ion batteries are emerging as attractive energy storage systems for large- scale grids. Increasing the Na content in cathode materials is one of the effective ways to achieve high energy density. Prussian blue and its analogues (PBAs) are promising Na-rich cathode materials since they can theoretically store two Na+ ions per formula unit. However, increasing the Na content in PBAs cathode materials remains a major challenge. Here we show that sodium iron hexacyanoferrate with high Na content can be obtained by simply controlling the reducing agent and reaction atmosphere during synthesis. The Na content can reach as high as 1.63 per formula, which is the highest value for sodium iron hexacyanoferrate. This Na-rich sodium iron hexacyanoferrate demonstrates a high specific capacity of 150 mAh·g^-1 and remarkable cycling performance with 90% capacity retention after 200 cycles. Furthermore, the Na intercalation/ de-intercalation mechanism has been systematically studied by in situ Raman spectroscopy, X-ray diffraction and X-ray absorption spectroscopy analysis for the first time. The Na-rich sodium iron hexacyanoferrate can function as a plenteous Na reservoir and has great potential as a cathode material for practical Na-ion batteries. 展开更多
关键词 sodium iron hexacyanoferrate Na-rich cathode sodium-ion batteries Prussian blue analogues
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The way to improve the energy density of supercapacitors:Progress and perspective 被引量:6
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作者 Yu Wu Chuanbao Cao 《Science China Materials》 SCIE EI CSCD 2018年第12期1517-1526,共10页
Compared with other energy storage devices, supercapacitors have superior qualities,including a long cycling life,fast charge/discharge processes,and a high safety rating.The practical use of supercapacitor devices is... Compared with other energy storage devices, supercapacitors have superior qualities,including a long cycling life,fast charge/discharge processes,and a high safety rating.The practical use of supercapacitor devices is hindered by their low energy density.Here,we briefly review the factors that influence the energy density of supercapacitors.Furthermore,possible pathways for enhancing the energy density via improving capacitance and working voltage are discussed. In particular,we offer our perspective on the most exciting developments regarding high-energy-density supercapacitors, with an emphasis on future trends.We conclude by discussing the various types of supercapacitors and highlight crucial tasks for achieving a high energy density. 展开更多
关键词 energy materials SUPERCAPACITOR CAPACITANCE working voltage energy storage
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Investigation of the hydrogen adsorbed density inside the pores of MOF-5 from path integral grand canonical Monte Carlo at supercritical and subcritical temperature 被引量:3
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作者 David Durette Pierre Benard +1 位作者 Renju Zacharia Richard Chahine 《Science Bulletin》 SCIE EI CAS CSCD 2016年第8期594-600,共7页
We examine the high density limit of the adsorption isotherms of hydrogen on MOF-5. The isotherms are calculated using quantum GCMC simulations over the pressure range: 0-150 atm (1 atm = 1.01325 ~ 105 Pa) in the s... We examine the high density limit of the adsorption isotherms of hydrogen on MOF-5. The isotherms are calculated using quantum GCMC simulations over the pressure range: 0-150 atm (1 atm = 1.01325 ~ 105 Pa) in the subcritical and supercritical state at 30, 50, 77, 113, 196 and 296 K. The fluid phase density in the pores for each temper- ature is calculated and shown to reach values higher than normal liquid density. The fluid phase density obtained at 30 K is observed to correspond to a highly compressed liquid. The radial distribution function of the adsorbed phase at 30 and 50 K are calculated. The adsorption isotherms are compared with available experimental data at 30, 50, 77 and 298 K. 展开更多
关键词 Hydrogen adsorption isotherms MOF-5 Metal-organic frameworks Path integralgrand canonical Monte Carlo Radial distributionfunction . Hydrogen storage Hydrogen energyapplications
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Fabrication of Large Area High Density, Ultra-Low Reflection Silicon Nanowire Arrays for Efficient Solar Cell Applications 被引量:6
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作者 Subramani Thiyagu B. Parvathy Devi Zingway Pei 《Nano Research》 SCIE EI CAS CSCD 2011年第11期1136-1143,共8页
High density vertically aligned and high aspect ratio silicon nanowire (SiNW) arrays have been fabricated on a Si substrate using a template and a catalytic etching process. The template was formed from polystyrene ... High density vertically aligned and high aspect ratio silicon nanowire (SiNW) arrays have been fabricated on a Si substrate using a template and a catalytic etching process. The template was formed from polystyrene (PS) nanospheres with diameter 30-50 nm and density 10^10/cm^2, produced by nanophase separation of PS-containing block-copolymers. The length of the SiNWs was controlled by varying the etching time with an etching rate of 12.5 nm/s. The SiNWs have a biomimetic structure with a high aspect ratio (-100), high density, and exhibit ultra-low reflectance. An ultra-low reflectance of approximately 0.1% was achieved for SiNWs longer than 750 nm. Well-aligned SiNW/poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) heterojunction solar cells were fabricated. The n-type silicon nanowire surfaces adhered to PEDOT:PSS to form a core-sheath heterojunction structure through a simple and efficient solution process. The large surface area of the SiNWs ensured efficient collection of photogenerated carriers. Compared to planar cells without the nanowire structure, the SiNW/PEDOT:PSS heterojunction solar cell exhibited an increase in short-circuit current density from 2.35 mA/cm^2 to 21.1 mA/cm^2 and improvement in power conversion efficiency from 0.4% to 5.7%. 展开更多
关键词 Ultra-low reflection silicon nanowire polystyrene nanosphere heterojunction solar cell
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Angular momentum density of a Gaussian vortex beam 被引量:1
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作者 ZHOU GuoQuan WANG XiaoGang +1 位作者 DAI ChaoQing CHU XiuXiang 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2014年第4期619-627,共9页
The Gaussian vortex beam is assumed to be linearly polarized.The analytical expression of the electric field of a linearly polarized Gaussian vortex beam propagating in free space is derived by using the vectorial Ray... The Gaussian vortex beam is assumed to be linearly polarized.The analytical expression of the electric field of a linearly polarized Gaussian vortex beam propagating in free space is derived by using the vectorial Rayleigh-Sommerfeld integral formulae.The propagating magnetic field of the linearly polarized Gaussian vortex beam is presented by taking the curl of the electric field.By employing the electromagnetic field of the linearly polarized Gaussian vortex beam beyond the paraxial approximation,the analytical expression of the angular momentum density of the linearly polarized Gaussian vortex beam is derived.The three components of the angular momentum density of a linearly polarized Gaussian vortex beam are demonstrated in the reference plane.The effects of the linearly polarized angle and the topological charge on the three components of the angular momentum density are investigated.To acquire the more longitudinal angular momentum density requires such an optimal choice that the linearly polarized angle is set to be zero and the topological charge increases.This research is useful to the optical trapping,the optical guiding,and the optical manipulation. 展开更多
关键词 Gaussian vortex beam angular momentum density linearly polarized angle topological charge
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Method for extracting geometrical characteristics of joint probability density based on contour lines
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作者 Shengli Chen Zhiqiang Wu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2022年第2期130-140,I0004,共12页
This paper presents a method for extracting geometrical features of the joint probability density function(PDF)of two-dimensional systems based on its contour lines,with particular interests given to the number and po... This paper presents a method for extracting geometrical features of the joint probability density function(PDF)of two-dimensional systems based on its contour lines,with particular interests given to the number and position of peaks and craters.In order to detect those two types of structures,a series of horizontal planes are applied to truncate the joint PDF with contour lines generated.Starting with the analysis of contour lines in a single plane,shape characteristics of the peak and the crater can be reflected on the contour lines in the aspects of gradient direction and inclusion relationship.Aided by the properties of PDF,the information about gradient direction and inclusion relationship of contour lines can be obtained simultaneously if the contour tree is built.According to the contour tree,the contour lines can be classified as two groups.Then the corresponding relation between contour lines in different planes is discussed.Based on the corresponding relation,clustering analysis about contour lines belonging to the same group but having different heights is performed.Two sets of contour lines are finally obtained as the simplest expression of geometrical characteristics of a joint PDF.They can be used to obtain the number and position of each peak and crater.Three oscillators of different types are chosen to test this method,which shows that this method can pave the way for numerical calculation about the stochastic P-bifurcation of multi-dimensional systems. 展开更多
关键词 Joint probability density function PEAK CRATER Contour lines Stochastic P-bifurcation
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High sensitive and ultrafast UV photodetector based on ZrO_2 single crystals 被引量:1
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作者 XING Jie GUO ErJia LU HuiBin 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2011年第8期1416-1419,共4页
The fast-response ultraviolet (UV) photoelectric effect in ZrO2 single crystals with interdigitated electrodes has been investigated experimentally at room temperature. The photovoltage of ZrO2 single crystals exhibit... The fast-response ultraviolet (UV) photoelectric effect in ZrO2 single crystals with interdigitated electrodes has been investigated experimentally at room temperature. The photovoltage of ZrO2 single crystals exhibits a linear dependence on applied bias and light power density. The photocurrent responsivity to the UV light with a wavelength of 253.65 nm is 9.8 mA/W. For the photovoltaic pulse, a rise time of 501 ps and a full width at half maximum of 1.5 ns have been obtained, when the ZrO2 single crystal is illuminated by a 266 nm pulsed laser. These results indicate that the ZrO2 single crystal is a promising candidate for UV photodetectors. 展开更多
关键词 photoelectric effect ultraviolet photodetector ZrO2 single crystals
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