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Determination of Young's modulus by nanoindentation

Science china(Technological Sciences) 2004年第4期47卷 398-408页

作者： MA Dejun1, Chung Wo Ong2, LIU Jianmin1 & HE Jiawen3 1. Surface Engineering Research Institute, CMES, Beijing 100072, china 2. department of applied physics and Materials Research Center, The Hong Kong Polytechnic {4., Hong Kong, china 3. State Key Laboratory for Mechanical Behavior of Materials, xian jiaotong {4., xian 71004., china 1. Surface Engineering Research Institute CMES 100072 Beijing China 2. department of applied physics and Materials Research Center The Hong Kong Polytechnic University Hong Kong China 3. State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University 710049 Xi’an China

A methodology for determining Youngs modulus of materials by non-ideally sharp indentation has been developed. According to the principle of the same area-to-depth ratio, a non-ideally pyramidal indenter like a Berkovich one can be approximated by a non-ideally conical indenter with a spherical cap at the tip. By applying dimensional and finite element analysis to the non-ideally conical indentation, a set of approximate one-to-one relationships between the ratio of nominal hardness/reduced Youngs modulus and the ratio of elastic work/total work, which correspond to different tip bluntness, have been revealed. The nominal hardness is defined as the maximum indentation load divided by the cross-section area of the conical indenter specified at the maximum indentation depth. As a consequence, Youngs modulus can be determined from a nanoindentation test only using the maximum indentation load and depth, and the work done during loading and unloading processes. The new method for determining Youngs modulus is referred to as pure energy method. The validity of the method was examined by performing indentation tests on five materials. The experimental results and the standard reference values are in good agreement, indicating that the proposed pure energy method is a promising substitution for the most widely used analysis models at present.

关键词： Young's modulus, nanoindentation, nominal hardness, indentation work.

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矩形芯介质波导色散关系及定向耦合器耦合长度的加权余量法计算

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光学学报 1987年第6期7卷 544-551页

作者：佘守宪北方交通大学应用数理系

本文用加权余量法导出了用以计算各种条形介质波导色散关系,矩形芯双沟道耦合器耦合长度以及条载型波导色散关系的数学表达式,其精确度较其它近似方法高,且简便易行。

关键词：波导色散定向耦合器加权余量法

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Rapid dendritic growth of Al-Ge hypoeutectic alloy in a drop tube

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Progress in Natural Science:Materials International 2003年第2期 79-82页

作者： LIU xiangrong, CAO Chongde and WEI Bingbo(department of applied physics, Northwestern Polytechnical university, xi’an 710072,{4.) department of applied physics Northwestern Polytechnical University Xi'an 710072 China

Abstract Dendritic growth in Al-4.% Ge hypoeutectic alloy has been investigated during free fall in a 3 m drop tube. Calculationsindicate that the undercooling obtained for the falling Al-4.% Ge droplets ranges from 13 K to 201 K. The maximum undercooling attains0. 27 TL. With the increase of undercooling, the primary (Al) phase undergoes a "columnar dendrite to equiaxed dendrite" structural tran-sition. According to the current rapid dendritic growth theory, the growth of primary (Al) phase is always controlled by solute diffusion.

关键词： dendritic growth undercooling containerless processing Al-Ge alloy.

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利用长短期记忆神经网络的改进POD-Galerkin降阶模型及其在流场预测中的应用

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西安交通大学学报 2024年第2期58卷 12-21页

作者：张译文王志恒邱睿贤席光西安交通大学能源与动力工程学院西安710049

针对标准POD-Galerkin降阶模型在流场快速预测中存在误差而导致精度不高的问题,提出了一种利用长短期记忆神经网络的改进POD-Galerkin降阶模型。使用本征正交分解对流场进行降维,投影得到低维降阶模型,引入两个长短期记忆神经网络,建立... 详细信息

针对标准POD-Galerkin降阶模型在流场快速预测中存在误差而导致精度不高的问题,提出了一种利用长短期记忆神经网络的改进POD-Galerkin降阶模型。使用本征正交分解对流场进行降维,投影得到低维降阶模型,引入两个长短期记忆神经网络,建立从POD-Galerkin降阶模型到实际POD模态时间系数之间的修正映射、低阶模态时间系数与高阶模态时间系数之间的扩展映射,分别用于消除标准POD-Galerkin降阶模型的误差累积和扩展降阶模型的阶数,从而实现物理驱动与数据驱动混合的流动降阶模型的构建。将改进POD-Galerkin降阶模型应用于二维圆柱绕流的流场预测,通过与原始标准POD-Galerkin降阶模型的对比,分析了所提模型的精度和计算速度。结果表明:添加神经网络修正项后的降阶模型相较于标准POD-Galerkin降阶模型,有效提升了降阶模型的精度,预测各阶模态时间系数的均方根误差能够减小1~2个数量级,预测的流场更接近原始流场;在预测相同阶数的情况下,计算时间显著减小,基于4.和6阶扩展的8阶改进降阶模型相较于原始8阶POD-Galerkin降阶模型预测速度分别提高了约56%和25%。

关键词：本征正交分解降阶模型神经网络流场预测

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Investigation of semi-insulating GaAs photoconductive switches triggered by semiconductor lasers

Investigation of semi-insulating GaAs photoconductive switch...

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2007亚洲光电子会议半导体激光器及应用分会场

作者： SHI Wei* LIAO Xue LIU Zheng MA Deming applied physics department xi’an university of Technology xi’an {4. china

The experiment result of semi-insulating GaAs photoconductive semiconductor switch（PCSS）with different electrode gaps triggered by semiconductor laser is reported. With the biased voltage of 500V, the semi-insulating GaAs PCSS with 2mm electrode gap is triggered by laser pulse with 5ns pulse width and repetition rate of 15 kHz, then two groups of electrical pulse samples indicate that laser pulse is instable when laser energy is very low. With the biased voltage of 210V, the GaAs PCSS with 0.5mm electrode gap is triggered by the laser pulse in several dozens nanoseconds at 905nm with a repetition rate of 2 kHz. A stable linear electrical pulse is observed. When the energy of the laser increases, the amplitude and the width of the electrical pulse also increase. It indicates that a stable electrical pulse is obtained while laser energy is high. With the biased voltage of 24.0V, the GaAs PCSS with 1mm electrode gap is triggered by laser pulse about 100nJ in 4.ns at 904.m. The GaAs PCSS switches a electrical pulse with a voltage up to 1700V. Carriers accumulation effect is discussed and the critical value of carriers accumulation effect is given. The relation of the biased voltage, electrode gap and carriers accumulation effect is also discussed. The concentration of deep EL2 traps in GaAs has a certain effect on nonlinear mode of GaAs PCSS.

关键词： photoconductive switch laser pulse semi-insulating GaAs linear mode nonlinear mode lock-on effect carriers accumulation light triggering semiconductor lasers EL2 traps

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SrGa_2S_4.Ce blue TFEL in new structure

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Chinese Science Bulletin 1998年第7期43卷 603-605页

作者： XU Chunxiang+1, LOU Zhidong+2, XU Zheng+3 and XU Xurong+31. National Laboratory of Molecular and Biomolecular Electronics, Southeast university, Nanjing 210096, china 2. department of applied {4., Tianjin university, Tianjin 300031, china 3. Institu National Laboratory of Molecular and Biomolecular Electronics Southeast University Nanjina China department of applied physics Tianjin University Tianjin China Institute of Photoelectronic Technology Northern Jiaotong University Beijing China

SrGa-2S-4.Ce blue TFEL device with a novel structure was prepared by electron beam evaporation. The dielectric constant of insulator layer in this structure is far less than that in the conventional structure, so the hot-electrons can be accelerated in SiO-2 layers. The stable TFEL with good chromaticity was achieved and the basic characteristics were investigated.

关键词： SrGa-2S-4.Ce bule TFEL low dielectric constant insulator layer.

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Effects of Quantum Interference on the Profile of Excitation Spectra in the Atomic Sodium D1

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Chinese Journal of Lasers 2002年第1期11卷 15-19页

作者： LI Yongfang 1,2 ZHANG xiangyang 2 SUN Jianfeng 2 ZHANG Yanliang 3 ZHAO Yongmei 3 WANG Yongchang 1 DING Liang’en 3 WANG Zugeng 3 ( 1Institute of Modern physics, department of applied physics,{4., xi’an 71004. Institute of Modern physics Department of Applied Physics Xi'an Jiaotong University Xi'an 710049 College of Physical and Information Technology Shaanxi Normal University Xi'an 710062 Joint Lab. for Quantum Optics Shanghai Institute of Optics and Fine Mechanics and East China Normal University Lab. for Quantum Optics National Education Commission 上海 200062 Joint Lab. for Quantum Optics Shanghai Institute of Optics and Fine Mechanics and East China Normal University Lab. for Quantum Optics National Education Commission 上海 200062

In this paper, an experiment in a sodium vapor cell with cw laser pumping is reported. Two dips in the excitation spectrum profile of the sodium D 1 line are observed. Theoretically excitation spectra in the three-level system are calculated in detail and results are identical with experiments. It is demonstrated that the appearance of the two dips in the excitation spectrum is close connected with quantum interference effect.

关键词： atomic sodium excitation spectrum profile quantum interference effects

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Nitrous Oxide and Methane Emissions as Affected by Water,Soil and Nitrogen

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Pedosphere 2007年第2期17卷 146-155页

作者： xiONG Zheng-Qin xiNG Guang-xi ZHU Zhao-Liang State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 （China）. department of physics Portland State University Portland Oregon 97207 （USA）

Specific management of water regimes, soil and N in china might play an important role in regulating N2O and CH4.emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources (15N-(NH4.2SO4.and 15N-labeled milk vetch) were applied to two contrasting paddies: one derived from xiashu loess (Loess) and one from Quaternary red clay (Clay). Both N2O and CH4.emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH4.emissions during the flooded season, over which the weighted average flux was 111 mg C m-2 h-1 and 2.2 mg C m-2 h-1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4.emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.

关键词： anaerobic oxidation of methane (AOM) dissimilatory nitrate reduction to ammonium (DNRA) greenhouse gasses lysimeter paddy soil

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Light-Induced Photorefractive Waveguides in Iron-Doped Lithium Niobate Crystals

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光学学报 2003年第S1期23卷 171-172页

作者： Jianlin Zhao Peng Zhang Dexing Yang Bili Li(department of applied physics, Northwestern Polytechnical university, xi’an 710072, P. R.{4., Tel: 86-29-84.5724. Fax: 86-29-84.3154. E-mail: jlzhao@***) department of applied physics Northwestern Polytechnical University Xi'an 710072 P. R. China

Waveguides were fabricated in lithium niobate crystals solely by light irradiation using binary optical masks and SLM-prepared optical masks. Arrayed-waveguides were also obtained by once or twice irradiations of an i... 详细信息

关键词： SLM on of et in Light-Induced Photorefractive Waveguides in Iron-Doped Lithium Niobate Crystals for CCD

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Electrorheological fluid of kaolinite-based ternary nanocomposite and its properties

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Science china Technological Sciences 2005年第5期 18-31页

作者： WANG Baoxiang, ZHAO xiaopeng & YAO Yuan Institute of Electrorheological Technology, department of applied physics, Northwestern Polytechnical university, xi’an 710072,{4.

According to the physical and chemical design, a kind of kaolinite /dimethylsulfoxide/carboxymethyl starch (CMS) ternary nanocomposite was prepared by the two-step composite method. Firstly, the polar liquid-dimethylsulfoxide (DMSO) was directly intercalated into the interlayer of kaolinite, and then the intercalated complex was composite with CMS by the solution method. The results showed that DMSO moderately intercalated the interlayer of kaolinite and the basal spacing of kaolinite was swollen from 0.715 to 1.120 nm. Under the electric fields of 5 kV mm-1 and volume fraction 30%, the static shear stress of kaolinite/DMSO/CMS ternary ERF could reach 17 kPa, which was 14.times and 4.25 times higher than that of pure kaolinite ERF and kaolinite/CMS ERF respectively. At the suitable component ratio (kaolinite:DMSO:CMS=1:0.75:0.6) of nanocomposite, a stronger synergetic effect and the optimum electrorheological effect could be attained. The ternary nanocomposite ERF also had good temperature effect and sedimentation properties. The sedimentation part of ternary nanocomposite ERF was only 9% after 30 days. The results of dielectric properties showed that the dielectric constant and conductivity of ternary nanocomposite ERF had been improved more enormously than that of the single component ERF and binary composite ERF. So the polarization and dielectric mismatch were strengthened, which was suitable to the enhancement of ER effect.

关键词： electrorheological fluid intercalation ternary system nanocomposite.

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