Synthesis of crystalline perovskite-structured SrTiO<Subscript>3</Subscript> nanoparticles using an alkali hydrothermal process

We report an experimental route for synthesizing perovskite-structured strontium titanate (SrTiO₃) nanocubes using an alkali hydrothermal process at low temperatures without further heating. Furthermore, we studied the influence of heating time (at 180℃) on the crystallinity, morphology, and perovskite phase formation of SrTiO₃. The SrTiO₃ powder, which is formed via nanocube agglomeration, transforms into cubic particles with a particle size of 120–150 nm after 6 h of hydrothermal sintering. The crystallinity and percentage of the perovskite phase in the product increased with heating time. The cubic particles contained 31.24at% anatase TiO₂ that originated from the precursor. By varying the weight ratio of anatase TiO₂ used to react with the strontium salt precursor, we reduced the anatase-TiO₂ content to 18.8at%. However, the average particle size increased when the anatase-TiO₂ content decreased.     

微分在经济活动中的应用——需求弹性分析

文中利用弹性概念就市场需求对价格变动的敏感程度进行了剖析,旨在市场经济环境中为经营者对商品进行价格决策及供求分析提供参考。     

Predicting multistage financial distress: Reflections on sampling,feature and model selection criteria

This research proposes a prediction model of multistage financial distress (MSFD) after considering contextual and methodological issues regarding sampling, feature and model selection criteria. Financial distress is defined as a three‐stage process showing different nature and intensity of financial problems. It is argued that applied definition of distress is independent of legal framework and its predictability would provide more practical solutions. The final sample is selected after industry adjustments and oversampling the data. A wrapper subset data mining approach is applied to extract the most relevant features from financial statement and stock market indicators. An ensemble approach using a combination of DTNB (decision table and naïve base hybrid model), LMT (logistic model tree) and A2DE (alternative N dependence estimator) Bayesian models is used to develop the final prediction model. The performance of all the models is evaluated using a 10‐fold cross‐validation method. Results showed that the proposed model predicted MSFD with 84.06% accuracy. This accuracy increased to 89.57% when a 33.33% cut‐off value was considered. Hence the proposed model is accurate and reliable to identify the true nature and intensity of financial problems regardless of the contextual legal framework.     

华南地块中三叠统巴东组红层磁倾角浅化效应

对华南地块中三叠统巴东组红层样品进行系统的岩石磁学和古地磁学研究, 采用高场等温剩磁各向异性(hf-AIR)方法, 识别出巴东组红层的磁倾角浅化因子f = 0.63。岩石磁学研究结果显示, 巴东组红层的主要载磁矿物为赤铁矿和少量磁铁矿; 磁化率和高场等温剩磁各向异性组构均指示其具有典型沉积组构特征, 表明未遭受后期构造应力改造。高温特征剩磁分量为碎屑赤铁矿所携带, 具有单一负极性, 并在95%置信水平上通过褶皱检验, 与前人在同一剖面不同位置获得的以正极性为主的古地磁方向一致。该特征剩磁方向在地层校正后的平均方向为D_s = 222.1°, I_s = ?27.2° (α₉₅ = 8.7°), 对应古地磁极为48.1°N, 215.5°E (A₉₅ = 8.4°)。对包括本文数据在内的华南中三叠世红层高质量古地磁极数据(Q≥5)用f = 0.63 进行统一校正后, 获得平均古地磁极为48.5°N, 207.6°E (A₉₅ = 10.7°)。对比华北地块同样经hf-AIR方法浅化校正后的早三叠世古地磁极, 两者在其东部参考点上的古纬度完全一致, 验证了前人提出的华南华北中生代剪刀式旋转拼合模型。     

扩散方程导数边界条件的一种数值处理

以一维和二维扩散方程为例,构造导数边界条件一种二阶处理方法,并数值验证了这种处理方法对数值解的影响.数值结果表明,这种处理方法不但简单.而且已有的二阶处理方法有明显的改进.     

Systemic Change in a Higher Education Institution: Inquiring into Organizational and Instructional Transformation

Systemic Practice and Action Research - Changes often occur in organizational systems due to the technology, new methods, new understandings and emerging needs. This study examined the reasons,...