Dielectric Properties of ZnTiO3 Microwave Ceramics Consolidated with MgTiO3

STABILIZED ZNTIO, WAS PREPARED BY DOPING MAGNESIUM OXIDE THROUGH TRADITIONAL SOLID-STATE REACTION. THE EXPERIMENTAL RESULTS INDICATE THAT ZINC TITANATE CRYSTALS DOPED WITH MAGNESIUM OXIDE GROW WELL AND THE DECOMPOSITION INTO ZN2TIO4 AND TIO2 IS RESTRAINED THROUGH TRADITIONAL SOLID STATE REACTION. BY ADJUSTING MOLAR RATIO OF MGO, BETTER PROPERTIES CAN BE OBTAINED. THE DIELECTRIC PROPERTIES OF THE CERAMICS DOPED WITH 30% MGO( MOLAR PERCENTAGE) SINTERED AT 1 060 ℃ ARE AS FOLLOWS:THE VALUE OF QUALITY FACTOR IS GREATER THAN 20 000(6. 5 GHZ), THE TEMPERATURE COEFFICIENT OF RESONANCE FREQUENCY IS ABOUT 2 × 10-6/℃, THE DIELECTRIC CONSTANT RANGES FROM 18 TO 22. BESIDES, IT IS PROVED THAT HEAT TREATMENT CAN OPTIMIZE MICROSTRUCTURE AND THE VALUE OF QUALITY FACTOR, WHICH INCREASES FROM 23 833.93 TO 47 584.00 AFTER 2 H OF HEAT TREATMENT AT 1 040 ℃.     

BaTi1-x-yNbxMnyO3半导体陶瓷PTC效应的研究

采用固相法制备了施主杂质Nb和受主杂质Mn共掺的BaTiO3基半导体复合陶瓷.通过对比实验结果,详细地分析了施主杂质和受主杂质的参杂效应对于BaTiO3基PTC陶瓷的室温电阻率和升阻比的影响,得到了充分利用BaTiO3基半导体复合陶瓷PTC效应较为理想的掺杂浓度范围.同时,比较Heywan与Ihring模型对于PTC效应的不同解释,根据原子价控理论和铁电效应补偿理论进一步分析了PTC效应的微观机制,较为完备地解释了PTC效应.     

陶瓷艺术的特点及其教育功能

陶瓷艺术是人类文化的重要组成部分，它折射出人类丰富的文化历史及文明发展进程。它所具有的文化性、参与性、直观性、愉悦性、多变性等特点赋予了它独特的教育功能。在中小学中开展陶艺教育，能发挥学生的学习主体性，培养学生的创新精神，拓展智力及思维能力，养成良好的个体心理品质，以促进学生的素质教育。     

Ce3+掺杂铝酸锌微晶玻璃的制备与发光性能研究

采用溶胶-凝胶法成功制备Ce3+:ZnO - Al2O3 - SiO2(ZAS)微晶玻璃。通过X射线粉末衍射（XRD）、透射电镜（TEM）和荧光光谱仪（PL）系统研究了铈离子掺杂浓度与热处理温度对ZAS微晶玻璃的结构与发光性能的影响。结果表明,900℃热处理后在非晶基体中析出了平均晶粒尺寸为13nm的ZnAl2O4尖晶石纳米晶;ZAS微晶玻璃的荧光发射峰峰值位于381nm,属于Ce3+离子的5d→4f跃迁,当Ce3+掺杂浓度为3%时发光性能达到最佳。     

环境陶艺与校园景观建设研究

校园景观是校园文化建设,也是学校教育内容的重要组成部分。构建校园景现的要素包括自然景现要素和人文景观要素,环境陶艺作为一种人文景现形式,在现代校园景现建设中越来越受到广泛应用。     

葡萄牙帝国与早期近代世界贸易

葡萄牙帝国在海外探险和扩张的过程中延伸了旧大陆的贸易航线,把新大陆和旧大陆连接成一个全球贸易网络。与此同时,葡萄牙帝国的武装贸易和垄断贸易模式也深刻地影响了早期近代世界贸易的运行。     

Raising the achievement of Portuguese pupils in British schools: a case study of good practice

The aim of the research was to study the experiences of Portuguese heritage pupils in British schools. The main findings from empirical data suggest Portuguese children are underachieving at the end of primary education but the case study confirms that in good schools Portuguese pupils do well and have made huge improvements over the periods. The findings show that the case study schools have adopted a number of strategies to overcome some of the barriers to achievement including parental engagement, effective use of a more diverse workforce, developing an inclusive ethos and curriculum, effective English language support for Portuguese pupils, monitoring performance of Portuguese pupils and good and well‐coordinated targeted support through extensive use of teachers, teaching assistants, learning mentors and Portuguese classes. The study argues that the worryingly low‐achievement levels of many Portuguese pupils in British schools have been masked by Government statistics that fail to distinguish between European ethnic groups. Policy implications for all concerned with school improvement are highlighted in the final section.     

钙钛矿型铁电体的宏观效应及其应用

简要综述了铁电体的基本物理特性，并重点论述了钙铁矿型氧化物铁电体的介电响应、压电效应和热电效应，以及这些宏观功能效应使其作为相应的材料在电子、国防、医疗、航天等领域的应用。     

传统彩陶色彩文化与中国现代陶艺

论文以中国传统彩陶文化及色彩在现代陶艺的作品创作中的应用为基础,论述了中国彩陶传统装饰文化艺术与现代形态造型艺术的互补,揭示了传统彩陶艺术与现代社会人生往复流转、浑然一体、互依互生的关系。进一步阐明了把传统彩陶装饰元素当作陶瓷艺术造型主体精神的形式载体之一,创造出具有强烈民族特性的全新的中国现代陶艺作品,从而创立一种具有民族风格和独特个性的艺术语言表达形式,是中国现代陶艺家共同追求和探索的目标。     

Waves of (Dis)Satisfaction: Effects of the Numerus Clausus system in Portugal

Access to higher education in Portugal is governed by a quota system (numerus clausus). The purpose of this article is to answer two questions: First, how does the numerus clausus system shape the demand for medical studies? Second, how do non-enrolled medical candidates influence the global allocation system and generate waves of dissatisfaction? The results show that students who do not succeed in entering medicine register in other programmes, such as pharmacy, veterinary medicine and dental studies, generating a first wave of dissatisfaction. Because students who are not placed in medicine occupy a large share of the places available in those other programmes, the wave of dissatisfaction propagates, with students being pushed to other programmes, especially biology and biochemistry. This process has also been analysed from a spatial perspective. Apparently, when students are competing to obtain a study place in a programme with prestige and good professional career perspectives such as medicine moving to a more peripheral region becomes more frequent.