共查询到19条相似文献,搜索用时 125 毫秒
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本文首先导出四探针处于平面上任意位置时求算电阻率的公式,并由此出发获得一包括横向及纵向游移在内的游移误差普遍公式,用此公式可计算出直线探针及方形探针游移误差的大小。此外,还计算出了这两种探针用来测量薄片样品时的探针游移误差。研究指明在作精确测量时游移误差是不容忽视的。最后并讨论到消除或减少深针游移误差的方法。 相似文献
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测量电阻率的四探针法公式中,要求是点接触而且探针的排列有一定的形状。实际上,接触总有一定的大小。本文考虑到接触面积大小的影响,并让四根探针排列成任意形状,导出了测量电阻率和薄层电阻的关系式。而直线四探针、方形四探针只不过是本公式的两个特例。
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对四探针测试半导体薄层电阻中二维电流场的电势分布采用有限元法(FEM)数值计算,并提出了计算模型。对几种常用的测试结构进行计算其电势分布证明了有限元方法的正确性。与以前所采用的镜像源法和图形变换法相比,该方法具有对任意形状的样品和任意放置探针具有同样简单和计算通用的特点。 相似文献
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介绍了微束微区X荧光探针分析仪的工作原理,该探针分析仪能够对样品表面约50μm范围内进行多元素定性与定量分析.在定量分析中,建立线性校准方程,采国家标准样品对微束微区X荧光该探针分析仪进行校准曲线的系数标定.以Fe、As和Ti元素所制定的校准曲线为例,定量分析出的元素含量与标准含量相对误差低于9.62%.结果显示微束微区X荧光探针分析仪具有较高的能量的分辨率,可以快速鉴定矿石的物质成分.定量分析结果的准确度低于地质样品分析的误差标准.表明该探针分析仪可以应用于野外条件下矿石微区成分的定性与定量分析. 相似文献
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研制了实用的高温超导材料电阻-温度特性测试设备.该设备利用液氮容器梯度温度法控制温度,釆用四探针法利用温差电偶测试超导的转变温度,最后利用计算机采集与样品相连的电压表和与温差电偶相连的电压表数值,最终实现超导材料的电阻-温度特性的测量. 相似文献
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为克服既有原子力显微镜(AFM)悬臂式探针的谐振频率难以超过3.5 MHz,Q值低、成像速度低及在液体中成像效果欠佳等缺点,设计并制作了一种基于微机电系统(MEMS)谐振器的I2形探针,并成功实现了成像实验。为更进一步提高I2形探针的力灵敏度,从结构设计和检测方法入手,对原有探针进行改进。设计了简单有效的电阻差分检测方法,成功去处了输入端与输出端的耦合现象;采用局部离子注入的方法,提高了压阻敏感的传输效率。实验结果显示,在输入信号相同的条件下,改进后探针的输出信号与原有探针相比,输出信号得到了明显提高。计算结果表明,采用新方法制作的探针可使力灵敏度提高10倍以上。 相似文献
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提出和发展了基于毛细管-微球组合探针的任选区、 高分辨显微成像新方法. 建立了微球显微成像的物理模型, 利用成像理论,推导出微球成像的放大倍率; 采用3.0, 4.4, 5.6, 7.5, 10.0 μm等不同直径的SiO2微球, 对未经刻录的DVD光盘进行了微球显微成像实验, 可以观察到DVD光盘的微纳米结构被明显放大且对比度显著提高, 与理论计算结果相符合; 采用毛细管微探针操纵微球的方法, 实现了基于微球透镜阵列的样品微纳米结构的高分辨显微成像; 在此基础上, 进一步将毛细管微探针与微球组合, 制备出毛细管-微球组合型探针, 首次实现了基于微球透镜的样品任意区域高分辨显微成像. 相似文献
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In this study, a DNA colorimetric detection system based on gold nanoparticles functionalized with L-shaped DNA probes was prepared and evaluated. We investigated the hybridization efficiency of the L-shaped probes and studied the effect of nanoparticle size and the L-shaped DNA probe length on the performance of the as-prepared system. Probes were attached to the surface of gold nanoparticles using an adenine sequence. An optimal sequence of 35S rRNA gene promoter from the cauliflower mosaic virus, which is frequently used in the development of transgenic plants, and the two complementary ends of this gene were employed as model target strands and probe molecules, respectively. The spectrophotometric properties of the as-prepared systems indicated that the large NPs show better changes in the absorption spectrum and consequently present a better performance. The results of this study revealed that the probe/Au-NPs prepared using a vertical spacer containing 5 thymine oligonucleotides exhibited a stronger spectrophotometric response in comparison to that of larger probes. These results in general indicate the suitable performance of the L-shaped DNA probe-functionalized Au-NPs, and in particular emphasize the important role of the gold nanoparticle size and length of the DNA probes in enhancing the performance of such a system. 相似文献
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An experimental dynamic calibration technique of reliable, rugged, low-cost, and fast-response coaxial temperature probes is presented. These probes were successfully designed and fabricated in-house, in conjunction with its signal processing circuit, which can be used for transient heat transfer measurements in a hypersonic testing facility. These probes have a response time less than 50 μs with a rise time less than 0.3 μs. Two types of scratches were used, mainly abrasive papers with different grit sizes and scalpel blades with different thicknesses to form the probe junction. The effect of the scratch technique on the probe's thermal product is investigated. The probes were tested and calibrated in the test section and end wall of the UNITEN shock tube facility at different axial and radial locations. The effects of placing the coaxial temperature probe at different axial and radial distances, different working fluids, and different Mach numbers on the transient surface temperature rise were examined. It was observed from the dynamic calibration results that the thermal product of a particular coaxial temperature probe depends on Mach number, junction scratch technique, and junction location, as well as on the enthalpy conditions. It was also noticed that the calibrated coaxial temperature probe using the scalpel blade technique with a particular blade size gives consistent thermal product values. Thus, it does not require an individual calibration. However, for a coaxial temperature probe whose junction was created using the abrasive paper technique with different grit sizes, a calibration for each coaxial temperature probe is likely to be needed. 相似文献
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In a previous paper we proposed a modification of metal-coated tapered-fibre aperture probes for scanning near-field optical
microscopes (SNOMs). The modification consists in radial corrugations of the metal-dielectric interface oriented inward the
core. Their purpose is to facilitate the excitation of surface plasmons, which increase the transport of energy beyond the
cut-off diameter and radiate a quasi-dipolar field from the probe output rim. An increase in energy output allows for reduction
of the apex diameter, which is the main factor determining the resolution of the microscope. In two-dimensional finite-difference
time-domain (FDTD) simulations we analyse the performance of the new type of SNOM probe. We admit, however, that the two-dimensional
approximation gives better results than expected from exact three-dimensional ones. Nevertheless, optimisation of enhanced
energy throughput in corrugated probes should lead to at least twice better resolution with the same sensitivity of detectors
available nowadays. 相似文献
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Siye Wu 《Letters in Mathematical Physics》1993,29(4):311-328
The integration of the exponential of the square of the moment map of the circle action is studied by a direct stationary phase computation and by applying the Duistermaat-Heckman formula. Both methods yield two distinct formulas expressing the integral in terms of contributions from the critical set of the square of the moment map. Certain cohomological pairings on the symplectic quotient are computed explicitly using the asymptotic behavior of the two formulas. 相似文献
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Vikram DS Ahmad R Pandian RP Petryakov S Kuppusamy P 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,193(1):127-132
The goal of the present study was to evaluate the temporal response of particulate-based EPR oximetry probes to changes in partial pressure of oxygen (pO(2)). In order to accurately evaluate the oxygen-response time, we developed a method for rapid modulation of pO(2) in a chamber containing the probe using an oscillator-driven speaker-diaphragm setup. The apparatus was capable of producing sinusoidal changes in pO(2) at frequencies up to 300 Hz or more. The pressure-modulation setup was used to evaluate the temporal response of some of the most commonly used phthalocyanine-based particulate probes. For validation, the time-response of the probes was compared to that of a high sensitivity pressure sensor. The results revealed that some particulate probes could respond to changes in pO(2) with a temporal response of 3.3 ms (300 Hz). The observations were interpreted in the light of their crystalline packing in favor of oxygen diffusion. The results of the present study should enable the selection of probes for oximetry applications requiring high temporal resolution. 相似文献
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We report the first real-time observations of the entire fully developed laminar secondary flow field of aqueous 2% Viscarin GP-209NF (a λ-carrageenan polysaccharide) in a square duct as made using a modest rheological NMR imaging (rheo-NMR) apparatus. Simulations using the Reiner-Rivlin constitutive equation verify the results. An included rheo-NMR flow rate quantification study assesses the measurement precision. Rheo-NMR resolves slow flows superimposed on primary flows about 300 times greater, making it a universally accessible technique by which full secondary flow field data may be systematically gathered. 相似文献
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Fiber optic probes are designed, developed and fabricated in the laboratories for remote fluorescence spectroscopic studies in various fields such as investigation of tissues, environmental monitoring, and analysis of samples in hostile environment. Optimized probe design is very much important for efficient transport and collection of photons, which ultimately helps in quantifying resultant emission and understanding light-matter interaction. Instead of the conventional ray optics, Monte Carlo technique has been used to optimize the design of fiber optic probes, comprising only of flat tipped fibers with and without focusing lenses, for remote fluorescence measurement in three different types of target media having different optical properties. Typical probe geometry consists of one excitation fiber surrounded by a ring of collection fibers. The effects of fiber parameters like fiber diameter, numerical aperture, core-clad ratio, arrangement of collection fibers around the excitation fiber and dead space between them, and optical properties of the medium on the performance of probes have been analysed and compared with the results of previous observations, wherever the data are available. The results show a significant difference between the collected emission with and without consideration of dead space, which plays a very significant role in probe design and is dependent on the number of collection fibers in the geometry, relative dimension of collection and excitation fibers and separation between the two. Introduction of a convex lens in the probe increases the amount of fluorescence signal for a given probe arrangement. 相似文献