Structural Integration of Tellurium Oxide into Mixed-Network-Former Glasses: Connectivity Distribution in the System NaPO3–TeO2

FSodium phosphate tellurite glasses in the system (NaPO3)(x)(TeO2)(1-x) were prepared and structurally characterized by thermal analysis, vibrational spectroscopy, X-ray photoelectron spectroscopy (XPS) and a variety of complementary solid-state nuclear magnetic resonance (NMR) techniques. Unlike the situation in other mixed-network-former glasses, the interaction between the two network formers tellurium oxide and phosphorus oxide produces no new structural units, and no sharing of the network modifier Na2O takes place. The glass structure can be regarded as a network of interlinked metaphosphate-type P(2) tetrahedral and TeO4/2 antiprismotic units. The combined interpretation of the O 1s XPS data and the P-31 solid-state NMR spectra presents clear quantitative evidence for a nonstatistical connectivity distribution. Rather the formation of homootomic P-O-P and Te-O-Te linkages is favored over mixed P-O-Te connectivities. As a consequence of this chemical segregation effect, the spatial sodium distribution is not random, as also indicated by a detailed analysis of P-31/No-23 rotational echo double-resonance (REDOR) experiments. ACHTUNGTRENUNG(TeO2)1 x were prepared and structurally characterized by thermal analysis,vibrat ional spectroscopy,X-ray photoelectron spectroscopy (XPS) and a variety of complementary solid-state nuclear magnetic resonance (NMR) techniques. Unlike the situation in other mixed-network-former glasses,the interaction between the two network formers tellurium oxide and phosphorus oxide produces no new structural units,and no sharing of the network modifier Na2O takes place. The glass structure can be regarded as a network of interlinked metaphosphate-type P(2) tetrahedral and TeO4/2 antiprismatic units. The combined interpretation of the O 1s XPS data and the 31P solid-state NMR spectra presents clear quantitative evidence for a nonstatistical connectivity distribution. Rather,the formation of homoatomic P O P and Te O Te linkages is favored over mixed P O Te connectivities. As a consequence of this chemical segregation effect,the spatial sodium distribution is not random,as also indicated by a detailed analysis of 31P/23Na rotational echo double-resonance (REDOR) experiments.

基于Kappa系数的景观变化测度——以辽宁省中部城市群为例

分析了辽宁省中部城市群1988～1998年间的景观变化,结果表明沼泽地从景观中完全消失,沙地的变化弹性最大,耕地的变化最小。优势景观类型(耕地)的转化方向较多,非优势景观类型(沙地)转化的方向少。某些景观类型之间较稳定地相互转化(林地和耕地) ,但某些景观类型之间转化极不稳定(耕地和沼泽地)。总体上,景观的变化趋势是:居住用地面积增加,占居了周围的耕地,促进了耕地向菜地的转化。面积大的景观类型变化小(林地和耕地) ,相反,面积小的类型变化大。Kappa系数分析结果表明,位置、数量、随机和标准Kappa系数都降低,即景观在数量上丢失3.86 %的信息,位置上丢失5 .95 %的信息,丢失的综合信息为6 .89%。而且建议进行综合信息评价时用随机Kappa系数,因为它既不考虑数量,又不考虑位置的影响。虽然Kappa系数从位置、数量和综合信息方面揭示了景观变化,但是这些分析是单方面的,而且没有说明在整个图的一致率中由于空间位置、数量和偶然因子所引起的一致率和变化率。景观变化过程中,不考虑空间位置和数量的情况下,景观在空间上随机分布,某个象元属于某个类型的概率等于1/ J(J=类型总数) (8% )。随景观中类型数量的减少,偶然一致率所占的比重增加,因此建议对单个类型不要进行一致性分析。位置一致率在整个一致率中

用空间多样性指数分析辽河三角洲野生动物生境的格局变化

在利用遥感 (RS)和地理信息系统 (GIS)对辽河三角洲土地覆被变化进行研究的基础上 ,引用空间多样性指数 (Sd)对本区野生动物的生境格局进行了定量描述 ,并分析了其 1988～ 1998年间的生境格局变化 .结果表明 ,研究区野生动物生境格局受人为和自然干扰的双重影响而发生了较明显的变化 ,整体趋势是生境适宜性逐渐降低 ,适宜生境和较适宜生境 (Sd≥ 0 .35 )的面积 10年间减少 76 37hm2 ,且破碎化程度加深 ,在空间上呈现由北向南推进、由东向西压缩之势 ,生境质量呈下降趋势 .同时 ,空间多样性指数能够定量地反映野生动物生境的适宜程度 ,并能直观地描述生境的空间格局 ,为进一步揭示生境格局的变化规律及原因提供了有效措施和依据 ,对于协调区域经济发展与生物多样性保护具有重要意义