Chemical bond characteristics and infrared reflectivity spectrum of a novel microwave dielectric ceramic CaIn2O4 with near-zero τf

Orthorhombic-structured CaIn₂O₄ ceramics with a space group Pca2₁ were synthesized via a solid-state reaction method. A high relative density (95.6 %) and excellent microwave dielectric properties (ε_r ～11.28, Qf = 74,200 GHz, τ_f ～ ?4.6 ppm/°C) were obtained when the ceramics were sintered at 1375 °C for 6 h. The dielectric properties were investigated on the basis of the Phillips–Van Vechten–Levine chemical bond theory. Results indicated that the dielectric properties were mainly determined by the InO bonds in the CaIn₂O₄ ceramics. These bonds contributed more (74.65 %) to the dielectric constant than the CaO bonds (25.35 %). Furthermore, the intrinsic dielectric properties of the CaIn₂O₄ ceramics were investigated via infrared reflectivity spectroscopy. The extrapolated microwave dielectric properties were ε_r ～10.12 and Qf = 112,200 GHz. Results indicated that ion polarization is the main contributor to the dielectric constant in microwave frequency ranges.     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

硬石膏激发体系的激发效应研究

介绍了目前硬石膏改性研究的主要成果,并建立了对一种硬石膏具有良好激发效果的复合激发体系;对掺加一定量二水石膏的硬石膏混合物料进行煅烧,并添加激发矿渣和复合激发剂,可改变硬石膏的活性;在此基础上探讨了石膏种类与激发体系的相关关系.     

安庆铜矿深部特大型采场充填体稳定性研究

为论证安庆铜矿深部特大型矿柱开采过程中充填体的自立高度、可暴露面积,开展了安庆铜矿深部采场充填体稳定性研究,在充填体现场调查、充填体力学性质的现场测试和室内实验的基础上,采用3种理论计算方法分析了充填体的稳定性,为特大型矿柱回采方案设计提供了依据。     

大型运输机（VLTA）的消防保护

飞机救援与消防工作的主要目的就是抢救生命。设备的选择,人员的数量与挑选,以及所进行的培训都必须为这个目标服务。在飞机事故(或事件)后,或在救援过程中进行灭火的可能性和需要必须时刻加以认真地考虑。任何救援和消防服务都应该做到装备完善,训练有素,时刻准备应对预期抵达     

楼板挠度试验中支承条件和加载方式的影响

预应力混凝土空心楼板的挠度在不同的支承条件下以及在不同的加载方法下存在着明显差异，文章从楼板的支承条件和活荷载的加栽方法等方面进行详细的计算分析挠度的变化，得出有关结论。     

在存在和准存在之间--评说王晖及作品

相识 2000年，张永和和非常建筑作为中国的建筑师事务所首次被邀请参加威尼斯建筑双年展，开幕那天晚上，我和张永和夫妇以及合伙人王晖一起共进晚餐。王晖给我的印象是一条汉子，个子高高，有胡茬，戴着粗边眼镜，肯定是北方人。那时我还弄不清楚，作为合伙人的王晖才能有多少。     

改性沥青在漳诏高速公路中的应用

本文简单地对改性沥青及改性沥青混合料的性能进行评价,并通过漳诏高速公路路面工程实例,提出改性沥青的推广应用价值。     

谈结合城市设计概念的现代博物馆建筑设计--以连云港市新博物馆方案设计为例

城市设计概念在过去的二十年里逐渐成为建筑设计所关注的新热点,也为建筑设计提供了新的出发点和方法途径.博物馆建筑作为公共建筑的一种类型,与城市关系密切,又具有建筑类型自身的特点.本文试图通过笔者参与设计的连云港市新博物馆方案为例,重点探讨建筑创作中的城市设计维度问题以及博物馆建筑设计的发展趋势.