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.     

湘西地区开发建设中的主要环境问题及保护对策

简要介绍了湖南湘西地区开发建设的基本概况，开发建设中存在的主要环境问题及保护对策。     

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.     

一种高温矿井用局部供冷装置研究

通过对现有矿井降温技术的分析，研究了一种适合采掘工作面布置特点局部降温装置．该矿用局部供冷装置主要由设有内部换热盘管的储冰车、安装有潜水泵的储水车及空冷器组成．分析了该装置的主要特点及供冷工艺流程，给出了该装置的设计计算依据及相关设计参数；设计确定了储冰箱内换热盘管温降5℃、不同管内水流速下的管程。确定了不同规格矿车、不同管内水流速下的单管程回路根数；确定了不同条件下的储冷量、供冷量及可供冷时间及对应条件下的盘管水阻力；为该局部供冷装置的实施提供了理论依据．图1，表4，参9．     

浅议监理队伍素质对公路建设监理工作影响

浅议我国目前公路施工监理队伍现状,如何提高监理人员业务水平和素质,其素质高低直接影响公路建设监理工作质量,提高监理队伍素质具有重要现实意义.     

原地破碎浸出采矿技术的现状及其发展前景

原地破碎浸出采矿法是一门多学科交叉技术。阐述了现阶段国内外原地破碎浸出采矿技术的研究现状和应用，并提出了今后的发展方向。     

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。     

钢网构架混凝土复合墙体的试验研究

保持竖向轴压比一定的情况下，对由冷弯格构（塞尔玛）型钢、钢板网、混凝土构成的钢网构架混凝土墙体进行拟静力试验，描述了这种新型墙体的破坏形式，得出了墙体的抗剪承载能力并分析了其受力性能，对墙体的实际应用提出了一些构造要求。     

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