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31.
32.
Madhab Chandra Tripathy Debasmita Mondal Karabi Biswas Siddhartha Sen 《International Journal of Circuit Theory and Applications》2015,43(6):776-792
The present work reports the realization of an analog fractional‐order phase‐locked loop (FPLL) using a fractional capacitor. The expressions for bandwidth, capture range, and lock range of the FPLL have been derived analytically and then compared with the experimental observations using LM565 IC. It has been observed that bandwidth and capture range can be extended by using FPLL. It has also been found that FPLL can provide faster response and lower phase error at the time of switching compared to its integer‐order counterpart. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
33.
随着我国石油需求量不断增加,致密油藏的开发也愈发重要。如何高效开发致密油藏是一项重点难点,其中致密油藏注天然气提高采收率是一个极具潜力的研究方向。因此,本文着重介绍以天然气作为能量补充介质在国内外的研究现状和应用现状,并且从两相特征等方面总结了理论研究中的一些机理,对致密油藏注天然气提高采收率的发展前景进行了一定的展望。 相似文献
34.
以钙系生料釉为基础,引入结晶剂CuO、MnO2制备无铅CuO-MnO2系金属光泽釉;结合XRD、SEM-EDS进行物相组成定性分析和显微结构表征,系统探究外加TiO2、V2O5以及玻璃粉对金属光泽釉釉面分相的影响。研究表明:一定量的TiO2、V2O5引入能有效促进釉面的分相,将玻璃粉部分替换基础釉中的钾长石能使得釉熔体的高温粘度降低,并进一步加剧釉面分相,促进CuMn2O4铜锰尖晶石在釉层表面的析出和富集;当TiO2引入量为2%,V2O5引入量为1%,玻璃粉引入量为25%(同为质量分数)时,金属光泽釉釉面效果最佳。 相似文献
35.
新疆卤水硝酸盐矿主要含有Na+、K+、Mg2+、Cl-、NO3-、SO42-六种离子,属于高元复杂体系,其合理利用和开发需要不同温度下的相平衡研究作为理论支撑。采用等温溶解平衡法,对Na+, K+, Mg2+//Cl-, NO3-, SO42--H2O体系在-15℃、NaCl·2H2O饱和条件下的相平衡进行了研究,并构建了相图。相图中有六个零变量点和八个两盐结晶区,只存在一种复盐KCl·MgCl2·6H2O。八个两盐结晶区,分别对应于NaCl·2H2O+Na2SO4·10H2O、NaCl·2H2O+NaNO3、NaCl·2H2O+KCl、NaCl·2H2O+KNO3、NaCl·2H2O+MgSO4·7H2O、NaCl·2H2O+MgCl2·8H2O、NaCl·2H2O+Mg(NO3)2·6H2O和NaCl·2H2O+KCl·MgCl2·6H2O,其中NaCl·2H2O+Na2SO4·10H2O共晶区最大,在低温时,硫酸钠的溶解度最小,降温过程中较易结晶析出。与该体系在25℃下的相图相比,复盐种类减少5种,零变量点减少19个,相关系得以极大简化。 相似文献
36.
《Ceramics International》2020,46(7):8675-8681
The dielectric properties and bipolar polarization-electric field (P-E) and strain-electric field (S-E) dynamic hysteresis of a relaxor [001]c 0.73Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 (PMN-0.27PT) single crystal were investigated to reveal more details of the temperature-induced phase transitions. Different linear scaling relations for ferroelectric hysteresis area <A>, coercive field Ec, saturation polarization Ps and remnant polarization Pr versus temperature τ were measured in different temperature regions. For each measurement frequency f, all hysteresis parameters were found to decrease linearly with temperature in the temperature range of the single rhombohedral (R) phase or tetragonal (T) phase, and the rate of decrease in the T phase was observed to be much larger than the corresponding rate in the R phase. In the temperature range near the R-T phase transition, the exponent α in the power law <A>∝f α for the R phase was found to be smaller than that for the T phase, and the magnitude of α depended strongly on temperature when the crystal was in the R-T coexisting phase state. Our experimental and theoretical results indicate that the difference in the activation energy and dipole moment in the R and T phases may lead to the observed discrepancy for the P-E and S-E hysteresis behaviour in different temperature regions. 相似文献
37.
In this paper, we propose a novel change detection method for synthetic aperture radar images based on unsupervised artificial immune systems. After generating the difference image from the multitemporal images, we take each pixel as an antigen and build an immune model to deal with the antigens. By continuously stimulating the immune model, the antigens are classified into two groups, changed and unchanged. Firstly, the proposed method incorporates the local information in order to restrain the impact of speckle noise. Secondly, the proposed method simulates the immune response process in a fuzzy way to get an accurate result by retaining more image details. We introduce a fuzzy membership of the antigen and then update the antibodies and memory cells according to the membership. Compared with the clustering algorithms we have proposed in our previous works, the new method inherits immunological properties from immune systems and is robust to speckle noise due to the use of local information as well as fuzzy strategy. Experiments on real synthetic aperture radar images show that the proposed method performs well on several kinds of difference images and engenders more robust result than the other compared methods. 相似文献
38.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
39.
《Ceramics International》2020,46(8):11846-11853
Cr2AlC and its composites containing α-Al2O3 (6.1 and 15.2 wt %) were prepared by hot pressing and their corrosion behaviors in air-saturated 3.5 wt % NaCl aqueous solution were investigated by electrochemical testing methods. It was revealed that the secondary phase of Al2O3 particles mainly distributed along grain boundaries of Cr2AlC matrix. The potentiodynamic polarization measurements showed that the corrosion current densities of these Cr2AlC composites were lower than that of the pure Cr2AlC. The Aluminum in Cr2AlC was prone to be attacked more easily. When immersed at open circuit potential (OCP), Al readily slipped out from Cr2AlC matrix into NaCl solution in the form of dissoluble species. But in the case of polarization, regardless of potentiostatic polarization or potentiodynamic polarization, more de-intercalated Al, reacted with the electrolyte to form corrosion products of Al2O3 and/or AlOOH and deposited on the sample surface. For Cr2AlC/α-Al2O3 composites, the presence of Al2O3 weakened the corrosion along grain boundaries by partly blocking the permeation of electrolyte and inhibiting the anodic dissolution process. 相似文献
40.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献