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1.
Yugong Wu Huili Zhang Yue Zhang Jinyi Ma Daohua Xie 《Journal of Materials Science》2003,38(5):987-994
Compositions in (Na1/2Bi1/2)TiO3 based ternary system, (0.97 – x) (Na1/2Bi1/2)TiO3-0.03NaNbO3-xBaTiO3 (x = 0, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08) are synthesized using conventional solid state reaction method. Influence of BaTiO3 on crystal structure, dielectric and piezoelectric properties are investigated. All compositions can form single perovskite phase. Powder x-ray diffraction patterns can be indexed assuming a pseudo-cubic structure. Lattice constant increases with the increase of BaTiO3 concentration. Rhombohedral distortion is observed in poled samples with BaTiO3 concentration up to 6 mol%. Temperature dependence of dielectric constant and dissipation factor measurement reveals that all compositions experience two phase transitions: from ferroelectric to antiferroelectric and from antiferroelectric to paraelectric. Both transition temperatures, T
c and T
f, are lowered due to introduction of BaTiO3. Ferroelectric to antiferroelectric phase transition has relaxor characteristics. Piezoelectric properties have relatively higher value around 1 mol% to 4 mol% BaTiO3. In ceramics with x = 0.02, thickness electromechanical coupling factor (k
t) of 0.51 and piezoelectric charge constant (d
33) of 110 × 10–12 C/N are obtained. Addition of small amount of BaTiO3 (x = 0.01, 0.02) improves piezoelectric properties compared to NBT-NN binary system, while T
f remains above 140°C, higher than that of NBT-BT binary system composition with similar piezoelectric properties. This is in favor of the possible application of them as lead-free piezoelectric ceramics. 相似文献
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将传统的汽车同步器齿套倒锥及滑块槽的几种加工方法,与用摆线逼近法加工汽车同步器齿套倒锥及滑块槽的加工方法加以比较,阐明了这种新方法产生的背景和优势;介绍了用摆线加工滑块槽的原理;在此基础上设计了汽车同步器齿套摆线加工数控机床的总体结构;给出了机床的主要动力和运动参数,最后展望了这种方法的应用前景。 相似文献
5.
台风灾害会造成配电系统多个元件同时故障而导致大面积用户停电。为研究台风灾害对于配电系统的破坏影响,提出台风灾害下配电系统受损情况评估方法。为描述台风特征对元件故障概率的影响,基于台风影响历史数据,使用随机森林算法建立元件脆弱性曲线。在元件模型建立后,使用时序蒙特卡洛模拟法评估配电系统的实时和累计电量及用户损失。为提升评估效率,引入故障模式后果分析法,使用最小路法生成故障影响报表,更快地确定失电负荷节点。最后通过RBTS-BUS6测试系统和广州地区的实际系统进行算例分析,验证了所提算法的有效性。结果表明:台风对配电网的影响具有延时性,配电系统受损情况与元件维修时间和维修资源数量相关。 相似文献
6.
Toughening modification of poly(l -lactide) (PLLA) with rubber particles is often realized at the cost of transparency, mechanical strength, and modulus because high rubber loadings are generally required for toughening. In this work, a promising strategy to simultaneously improve the transparency and stiffness–toughness performance of poly(butyl acrylate)-poly(methyl methacrylate) (BAMMA) core-shell rubber nanoparticles toughened PLLA blends by utilizing the stereocomplex (SC) crystallization between PLLA and poly(d -lactide) (PDLA) is devised. The results reveal that the construction of SC crystallites in PLLA matrix via melt-mixing PLLA/BAMMA blends with PDLA can prevent BAMMA nanoparticles from aggregation and promote them to form network-like structure at lower contents. As a result, not only higher toughening efficiency with less rubber contents but also superior transparency is achieved in the PLLA/PDLA/BAMMA blends as compared with the PLLA/BAMMA ones where large aggregated BAMMA clusters are formed. Moreover, the outstanding reinforcement of SC crystallites network for PLLA can impart an enhanced tensile strength and modulus to PLLA/PDLA/BAMMA blends, thus improving the stiffness–toughness performance of PLLA/PDLA/BAMMA blends to a higher degree. This work demonstrates that SC crystallization is a promising solution to solve the contradiction between transparency and mechanical properties and then obtain superior comprehensive performances in rubber toughened PLLA blends. 相似文献
7.
通过简要介绍利用声学多普勒水流剖面仪(ADCP)回波强度估算悬移质含沙量的基本原理,结合梧州水文站的应用实例,利用ADCP的回波强度数据和现场采集的水样含沙量建立相关关系,根据相关关系由回波强度反演估算的水体悬移质含沙量验证了利用ADCP的回波强度估算悬移质含沙量的可行性。应用于梧州水文站的实践表明,左河道推算的系统误差为-0.1%,右河道推算的系统误差为1.5%。这种方法具有不扰动流场、测量剖面同步性较好、数据空间分辨率较高的优点,与传统的取样过滤称量法相比,计算效率显著提高。 相似文献
8.
Huili Chen Yanbo Wu Yunfei Cheng Hong Yang Fuyou Li Pin Yang Chunhui Huang 《Inorganic chemistry communications》2007,10(12):1413-1415
Spectroscopic studies revealed that the compound [N,N′-di(quinoline-2-methylene) -1,2-phenylenediimine] (1) exhibited a rather high selectivity toward Zn2+ over other metal ions, even Cd2+. In acetonitrile, the red shift of fluorescent emission from 396 nm to 426 nm upon zinc binding is due to the formation of a 1:1 metal/ligand complex. 相似文献
9.
LIHuili LINan WEIYaowu 《中国耐火材料》2003,12(3):30-33
The effects of refractories of quarz-corundum consisting of 45 mass% quartz and 55 mass% corundum,fused corundum and fused magnesia on the total axygen content(TOC) and the composition of inclusions in intersitital free(IF) steel were studied,3 mass% microsilica was added into the three refractories as binder.The refractories were shaped as lining of the graphite crucible by castable method IF steel was placed in the crucibles,then they were heated at 1600℃ for 90min and 45min respectively.Oxygen contents of the steel samples were obtained by axygen determinator.Inclusions were analyzed by SEM and EDS.The results show that the TOC of steel increase with ncrease of Index of Oxygen Potetial (IOP) of the refractories.The steel sample coped with MgO refractories having the lowest IOP has the lowest TOC. 相似文献
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