新型锂电池正极材料多硫化碳炔的研究

为克服锂/硫电池的正极材料单质硫的导电性差、放电产物的部分溶解导致电池性能下降等问题,设计并制备了一种新型正极材料多硫化碳炔。通过核磁共振、拉曼光谱、X-射线及SEM等手段对其进行了研究,并得到其形态及结构信息,证明材料具有“主链导电、侧链储能”的结构。通过充放电性能测试及循环伏安测试对其电化学性能进行了研究,结果表明该材料具有较高的充放电效率与良好的循环性能,0.4mA/cm²的放电条件下60次循环后比容量可以达到400mAh/g,充放电效率接近100%。     

Synthesis and photo-responsive behaviors of hollow polyazobenzene micro-spheres

By means of distillation precipitation polymerization, the silica-hybrid particles with polyazobenzene shell (PAzo@SiO₂) micro-spheres were prepared with 6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate (Azo-M) as monomer, divinylbenzene (DVB) as cross-linker, and ~250 nm vinylated sol-gel silica particles as template. Hollow polyazobenzene microspheres were further developed after selective removal of the silica cores with HF solution. When the content of DVB related to Azo-M is 20 wt%, the acetonitrile is 200 mL, and the polymerization time is 4.5 h, the hollow PAzo microspheres with about 20 nm shell are successfully fabricated. These hollow PAzo microspheres have excellent reversible photoisomerization, and their first-order rate constant of trans-cis isomerization only decreases 11.8% compared with homopolymer of azobenzene (Homo-PAzo).     

辽西建昌玲珑塔地区侏罗纪地层的离子探针锆石U-Pb定年:对最古老带羽毛恐龙的年代制约

辽西建昌玲珑塔地区髫髻山组火山-沉积岩地层中富含燕辽生物群(又称道虎沟生物群)的重要化石,并记录了若干重要的生物演化事件,特别是对研究鸟类的起源以及最早鸟类和恐龙祖先的分化均具有关键的意义,因而其地层时代问题备受关注.本文对建昌玲珑塔大西山含化石沉积层中的3个凝灰岩样品进行了详细的SIMS锆石U-Pb定年,获得了160.7±1.7,159.5±2.3和158.9±1.7Ma的年龄结果.根据近年广泛使用的地质年表GTS2004和新近修订的地质年表GTS2012,由侏罗兽和近鸟龙等构成的燕辽生物群生存于晚侏罗世早期,从而为最早哺乳动物和最早带毛恐龙的出现年代提供了确凿的同位素年代学证据.     

关于Padé样条的两种算法

在本文中,我们利用QD-算法及正交多项式给出了两种计算Pade样条的算法。它们均具有快速、简便及精度高的特点。     

Hydrodynamic process of Tibetan Plateau lake revealed by grain size: Case study of Pumayum Co

Under the background of global warming,some lakes on the Tibetan Plateau(TP) are potentially sensitive to temperature change.With a case study of Pumayum Co,where glacier meltwater is important to supply(we call this a glacier-fed lake hereafter),we analyze the sensitivity of lake sediment grain size to temperature change.This is done by resolving the modern hydrodynamic process,coupled with comparison of paleoclimatic proxies.According to the spatial distributions of parameters,percentage of grain size and the grain size frequency distribution curve,hydrodynamic processes are analyzed.Five clastic sedimentation types are thereby discriminated.In the open lake area,suspended load transport is the main transport agent.Grain Size Trend Analysis(GSTA),a sediment dynamics model,reveals a trend toward eastward transport.This indicates that the largest and glacier-fed river,the Jiaqu River,influences the entire lake(not just the subsurface alluvial fan),and that lake sediment grain size may serve as a temperature indicator.Time series comparison between grain size of a short core from the central lake and meteorological data confirms this temperature indication,which in turn shows reliability of the method discriminating the hydrodynamic process.This case study will improve the ability of paleoclimatic reconstruction using lake sediment in glacier-fed lakes on the Tibetan Plateau.     

单个大气超细颗粒物源特征的同步辐射光源X射线探针初步研究

研究了单个大气超细颗粒分析靶样的制备方法, 在美国阿贡国家实验室APS同步光源的13-ID-C试验站, 用束斑为2 μm的X射线探针分析了不同污染源超细颗粒物, 得到了单个超细颗粒物的特征X射线谱. 实验结果表明, 来自不同污染源的超细单颗粒具有不同的特征X射线能谱. 这为单颗粒分析方法识别大气超细颗粒物来源提供了依据. 超细含铅颗粒物的分析暗示, 大气颗粒物中的铅污染是多源的, 除燃烧加铅汽油外, 燃煤和钢铁工业也是大气铅污染的排放源. 来自燃煤排放的超细颗粒分析提示, 燃煤超细颗粒物对人体健康具有更大的潜在危害.     

Dynamic memory mapping delivers additional flexibility to virtual resource management

The Department of Computer Science and Technology, Peking University, Beijing, China, has shown that a novel Dynamic Memory Mapping (DMM) model brings about additional flexibility to virtual resource management, leading to the feature-adjustable design of a virtual machine monitor (VMM). The study is reported in Issue 53 (June, 2010) of SCIENCE CHINA Information Sciences because of its significant research value.
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一种基于特征空间的月球撞击坑自动识别算法

撞击坑不仅是月球表面常见的一种地质单元,也是研究月表地质年龄的一个重要因素,所以准确的识别撞击坑就很重要．本文提出了一种基于特征空间的对撞击坑进行自动识别的算法．新算法先将CCD图像转换成特征空间图像,在特征空间中通过自适应的区域检测寻找撞击坑候选区域．再对候选的区域进行椭圆拟合以进一步确认撞击坑,最后统计得到撞击坑个数．新算法在嫦娥一号采集的月球CCD图像上进行测试,测试结果显示该算法对月球中小撞击坑有较高的识别能力．     

下转换发光粉体SrAl2O4:Eu2,Dy3+在硅太阳能电池中的应用

采用化学共沉淀法结合水热处理方法制备了颗粒尺寸约为40 nm的发光粉体SrAl2O4:Eu2+,Dy3+。荧光光谱测试显示,该粉体在受到250～450 nm紫外光激发后可发射出约510 nm的可见光,且发射光与激发光强接近,因此该粉体具有下转换功能特性。将质量分数10%的SrAl2O4:Eu2+,Dy3+与聚甲基丙烯酸甲酯(PMMA)在N,N-二甲基甲酰胺溶剂中充分混合后,采用丝网印刷技术将其涂覆于市售硅太阳能电池板上形成覆盖下转换薄膜的太阳能电池,对涂覆和未涂覆下转换材料的太阳能电池进行了光电性能测试,结果表明涂覆下转换材料的太阳能电池的开路电压和短路电流均得到提高,并且电池的光电转化效率从7.96%提高至8.96%,提高了1%。     

DMP brings about new design space for virtualization technology

Professors Wang and Luo and their group in the Department of Computer Science and Technology, Peking University (PKU), have recently introduced a new memory virtualization technique called Dynamic Memory Paravirtualization (DMP). With DMP, binary code in the guest operating system can be dynamically patched by the hypervisor for improved performance. Their study is published in Issue 53 (January 2010) of SCIENCE CHINA Information Sciences and is a significant contribution to system virtualization technology.