Exploring age and gender differences of computational thinkers in primary school: A developmental perspective

Over the past decade, the call to foster computational thinking (CT) in every child has received considerable attention. However, there is little understanding of whether children are developmentally ready to think computationally and what specific CT concepts and skills can be developed at various ages. This study explored the developmental and gender differences in CT skills of 197 Grade 4–6 students (aged 9–13) before being exposed to instruction and investigated the age–gender interaction effects on their CT acquisition in an intervention combining both programming and non-programming (unplugged) activities. Results show that students' CT skills followed a developmental progression before instruction. Gender difference across ages was insignificant in conditionals, logical operators, pattern recognition and generalization skills. Additionally, students of different ages developed CT differently during the intervention, and their CT acquisition was unaffected by gender. Implications for practice and research in CT education were discussed.     

Personalized Convolution for Face Recognition

International Journal of Computer Vision - Face recognition has been significantly advanced by deep learning based methods. In all face recognition methods based on convolutional neural network...     

水资源缺乏地区地表水环境承载现状研究——以京津冀和西北五省(自治区)为例

本研究以主体功能区划作为控制单元进行划分,以水功能区纳污能力作为环境容量基础数据,结合国家环境保护部污染物排放统计数据,分析京津冀和西北五省(自治区)的不同主体功能区的地表水环境容量超载情况。结果显示,在水资源缺乏的京津冀和西北五省(自治区)地区,其重点开发区的氨氮排放入河量均已超出水环境容量,城镇生活污水排放是水环境氨氮容量超载的主要贡献因子。对于农产品主产区和重点生态功能区,京津冀地区水环境的化学需氧量(COD)和氨氮排放量普遍超载,而西北五省(自治区)还有19%~73%的水环境容量剩余。不同主体功能区的环境和产业政策取决于主体功能区的类型和水环境容量的超载情况。     

A Method for Performance Degradation Modeling Based upon the Accelerated Experiment

Performance degradation modeling plays an important role in prognostics and health management of mechanical system. Influenced by the complex structure of the hydraulic pump and the limited experiment standards, it is hard to establish an appropriate performance degradation model. To fulfill current requirements, a method for establishing the performance degradation model based on accelerated experiment is proposed. In order to describe the general trend of the degradation, the double-stress exponential model is firstly established as the theoretical degradation model. On this basement, combined with the characteristics of the experiment, the accelerating coefficient is settled; meanwhile, the procedures for assuring the model parameters are presented. Furthermore, based on the accelerated experiment of the hydraulic pump under various stresses, the performance degradation model is finally established. Result of the experimental analysis indicates that the proposed method is applicable and the presented model is effective to measure the performance degradation of pump.     

提高工艺安全性的FOX-7合成方法?

为了提高合成工艺的安全性,提出了一锅法制备1,1-二氨基-2,2-二硝基乙烯(FOX-7)的方法。控制反应体系温度在15℃左右,采用蠕动泵将浓硫酸连续地加入到2-甲基-4,6-二羟基嘧啶与二氯甲烷的悬浮液中,固体原料溶解后,再将发烟硝酸滴加到反应物料中,进行硝化反应;然后连续滴加水到反应器中,进行水解开环反应;再经过固液分离、洗涤和干燥,得到FOX-7。探讨了硝化剂的加料方式对收率和工艺安全性的影响。结果表明:惰性溶剂的引入,分散了反应物,硝化反应释放的热量可以及时扩散,物料温度控制更平稳,消除了物料团聚现象,而且与硝硫混酸加料相比,采用浓硫酸与发烟硝酸分步加料的方式,升温速率可降低51.0%,FOX-7的收率由63.0%提高到了82.6%,工艺的安全性显著提升。     

体外模拟胶原纤维矿化的研究进展

矿化胶原纤维是天然骨的主要成分,掌握胶原纤维的生物矿化过程、原理和调控机制对于骨修复材料的设计及骨组织的再生修复发展有重要意义。综述了体外模拟胶原纤维矿化的研究进展,主要包括胶原纤维内矿化机理和非胶原蛋白对胶原生物矿化的调控作用,以期为胶原生物矿化机理的探讨及骨组织再生修复的研究提供借鉴。     

柠檬酸根对纳米Fe_3O_4/PVA磁性复合膜性能的影响

采用化学共沉淀法制备了添加柠檬酸根前后的纳米Fe_3O_4粉体材料,用流延成膜法制备了添加柠檬酸根前后的Fe_3O_4/聚乙烯醇(PVA)复合膜。用红外光谱分析仪、古埃磁天平法、振动样品磁强计、自制磁致变形设备、发射扫描电子显微镜对添加柠檬酸根前后的纳米Fe_3O_4/PVA复合膜的结构及性能进行了表征和分析。结果表明:添加柠檬酸根纳米Fe_3O_4制备的Fe_3O_4/PVA复合膜磁化率更大、磁性能更好、磁致变形性能更大、分散性好。