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71.
Phase‐shifting differential interference contrast microscope with Savart shear prism and rotatable analyser 下载免费PDF全文
A novel differential interference contrast microscope (DICM) is proposed in this research. It is constituted by inserting a Savart shear prism between the objective and sample of a polarising microscope having a rotatable analyser as the phase‐shifter, and it is with the ability to enhance image contrast using the principle of shearing interferometry. This letter is to introduce the configuration, interpret the interference patterns and present the experimental setup of the DICM. In addition, this letter is to display the experimental results from the uses of the setup; the results demonstrate the validity and ability of the DICM. 相似文献
72.
桥梁移动荷载识别技术的适用性是决定其能否直接应用于现场桥梁荷载在线识别的关键因素。基于矩量法和移动荷载识别理论,采用整域基函数表达桥面移动车载,提出了一种时域移动荷载识别改进方法(ITDM)。分别选用正交勒让德多项式和傅立叶级数作为基函数,形成两种改进算法(LITDM和FITDM),通过仿真及试验验证所提方法的正确性及可行性,并从基函数数量和运行时间两方面与时域法(TDM)进行对比研究。仿真及试验研究结果表明:LITDM、FITDM性能与TDM相近,但ITDM灵活性更强,其中以FITDM计算效率最高,适用性最强,LITDM次之,这对于桥梁移动荷载的现场在线准确识别非常有利。 相似文献
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Thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane, which is the main component of shale gas, were simulated. The temperature and velocity distributions were calculated according to the type of discharge gases and arc current level by a self-developed magnetohydrodynamics (MHD) code and a commercial ANSYS-FLUENT code; the transport of chemical species was analyzed as including the chemical reactions of methane conversion. The simulated results were verified by the comparison of calculated and measured arc voltages with permissible low error as under 4%. Three C2 hydrocarbon gases with ethane (C2H6), ethylene (C2H4), and acetylene (C2H2) were selected as the converted species of methane from experimental data. The mass fraction of C2 hydrocarbons and hydrogen as the product of the conversion reaction at the reactor was also calculated. Those values show good agreement with the actual experimental results in that the major conversion reaction occurred in C2H2 and hydrogen, and the conversions to C2H6, C2H4, and hydrogen were minor reactions of methane pyrolysis conversion. 相似文献
75.
Sintered silicon carbide (SiC) was etched by a dielectric barrier discharge source. A high voltage bipolar pulse was used with helium gas for the plasma generation. One stable filament plasma was generated and could be used for SiC etching. As the processing gas (NF3) mixing rate increased, the width and depth of the etching profile became narrower and deeper. The differentiated V–Q Lissajous method was used for measuring the capacitances (Ceq) of the electrode after the plasma turned on. The width of the etching profile was proportional to Ceq. As the current peak value Ismx of the substrate current increased, the volume removal rate of SiC increased. The etch depth was proportional to the ratio of Ismx to Ceq. Additionally, because of the different characteristics of the plasma disks on SiC substrate by the voltage polarity, the etching profile was unstable. However, in high NF3 mixing process, the etching profile became stable and deeper. 相似文献
76.
Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has a
negative effect on the global environment owing to its high global warming potential (GWP) value.
An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventional
perfluorocarbon etching gases such as CHF3 with C6F12O, which has a low GWP and is in a liquid
state at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched using
inductively coupled CF4 +C6F12O+O2 mixed plasmas. Subsequently, the etching characteristics
of the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated.
A double Langmuir probe was used and optical emission spectroscopy was performed for plasma
diagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were used
to confirm the change in the surface properties of the etched SiON film surface. Consequently, the
etching characteristics of the C6F12O mixed plasma exhibited a lower etching rate, higher SiON/Si
selectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF3 mixed plasma. In addition, the C6F12O gas can be recovered in the liquid state, thereby decreasing
global warming. These results confirmed that the C6F12O precursor can sufficiently replace the
conventional etching gas. 相似文献
77.
Application of a Novel Method for Machine Performance Degradation Assessment Based on Gaussian Mixture Model and Logistic Regression 总被引:1,自引:0,他引:1
LEE Jay 《机械工程学报(英文版)》2011,(5):879-884
The currently prevalent machine performance degradation assessment techniques involve estimating a machine’s current condition based upon the recognition of indications of failure features,which entail complete data collected in different conditions.However,failure data are always hard to acquire,thus making those techniques hard to be applied.In this paper,a novel method which does not need failure history data is introduced.Wavelet packet decomposition(WPD) is used to extract features from raw signals,principal component analysis(PCA) is utilized to reduce feature dimensions,and Gaussian mixture model(GMM) is then applied to approximate the feature space distributions.Single-channel confidence value(SCV) is calculated by the overlap between GMM of the monitoring condition and that of the normal condition,which can indicate the performance of single-channel.Furthermore,multi-channel confidence value(MCV),which can be deemed as the overall performance index of multi-channel,is calculated via logistic regression(LR) and that the task of decision-level sensor fusion is also completed.Both SCV and MCV can serve as the basis on which proactive maintenance measures can be taken,thus preventing machine breakdown.The method has been adopted to assess the performance of the turbine of a centrifugal compressor in a factory of Petro-China,and the result shows that it can effectively complete this task.The proposed method has engineering significance for machine performance degradation assessment. 相似文献
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80.
1 问题的提出
ND5型内燃机车的7FDL-16型柴油机,自大修换装国产凸轮轴和滚轮以来,凸轮型面经常发生损坏.根据ND5型机车检修工艺要求:凸轮轴凸形面和滚轮表面不许有剥离、麻点,凸形面磨耗不能大于0.25 mm,剥离面积不大于10 mm2. 相似文献