高温高压密闭溶样-电感耦合等离子体质谱法测定荧光粉中的杂质元素

提出了一种采用高温高压密闭溶样快速消解荧光粉晶体的前处理新方法。针对目前常用的稀土氧化物和稀土磷酸盐类、碱土金属铝酸盐类、碱土金属硅酸盐类四大类荧光粉,研究了消解时间、温度、消解溶剂种类和用量4个条件对样品消解程度的影响。采用电感耦合等离子体质谱法(ICP-MS)测定了最佳消解条件下消解的荧光粉中杂质元素Cu、Zn、Cd和Pb的含量。结果表明:稀土氧化物和稀土磷酸盐类荧光粉的最佳消解条件为 2 mL HCl溶剂中120℃下消解3 h;碱土金属铝酸盐类荧光粉的最佳消解条件为2 mL HCl溶剂中160℃下消解6 h;碱土金属硅酸盐类的最佳消解条件为2 mL HCl+0.5 mL HF溶剂中160℃下消解3 h。荧光粉中主要共存元素对所测杂质元素Cu、Zn、Cd和Pb的检测无干扰。该法线性范围宽、检出限低、灵敏度高,是荧光粉晶体中元素检测的较佳方法。     

2006—2015年湖北省城市相对收缩时空变化

城市收缩是中国新型城镇化建设面临的重大挑战。当前,经济社会转型的“流空间”效应导致城市相对收缩日益加剧。收缩型中小城市转型已上升至中国新型城镇化建设决策视野。然而,目前对有关城市相对收缩的认识明显不足。论文选取中小城市密集的典型地区——湖北省为案例区,构建城市相对收缩识别框架及面板数据回归模型,开展城市相对收缩格局动态及成因分析。结果表明：① 2006—2015年,湖北全省36个城市中有27个出现了相对收缩,其中,强相对收缩城市18个。相对收缩城市占比总体呈“东西高、中部低”的格局。“流空间”效应对湖北省中小城市收缩的影响显著。② 从“十一五”到“十二五”时期,除武汉市持续强相对扩张、襄阳市持续弱相对扩张外,相对收缩城市从21个增长到24个。③ 湖北省城市发展战略在推动鄂西地区城市发展方面取得了一定的实质性效果。但是,对于武汉城市圈及其外围150 km圈层区域而言,大中小城市协调发展效果不理想。④ 产业空间规模扩大及城市建设维护管理水平提升对于控制城市相对收缩具有重要的积极作用。最后,从推动湖北省城市协调发展、加强中小城市收缩管控方面探讨了政策建议。     

Urban vacant land in growing urbanization: An international review

Urban growth and shrinkage constitute the overall pattern of growing urbanization across the globe.Studies on urban vacant land(UVL)are few,and have proved to be mainly rudimentary and subjective.This paper first presents the definition of UVL based on bibliometric analysis.Typology,morphology,proximate causes,and the multiple functions of UVL are then analyzed at parcel,transect,city,and national levels based on an international review.Results show that UVL can be categorized by land cover,land usage,and land ownership.Worldwide,UVL has been widespread and extensive.For example,the occurrence probabilities of UVL in the cases of Guangzhou and New York are 8.46%-8.88%and 3.17%-5.08%,respectively.The average vacancy rate of residential land amounts to 11.48%in 65 U.S.cities.Generally,UVL shows fragmentation and irregular shape,and significant spatial differences exist at parcel,transect,city,and national levels.Proximate causes,such as excessive land division,irregularly shaped land parcels,decreases in resident population,deindustrialization,land speculation,insufficient investment,and environmental concerns,can all result in UVL.Currently,UVL has become a gray area of social,economic,and ecological space.However,it can also be considered a potential resource for enhancing urban sustainability.Policy implications to promote urban sustainability using monitoring,control,and differential revitalization of UVL are presented.