复杂媒质散射特性的FETI分析

在分析复杂媒质的电磁场散射特性时,引入有限元撕裂对接法,对包含复杂媒质在内的整个计算空间做区域分解,通过合理的代数运算,将一个三维问题转化为二维问题进行求解,减小计算的复杂度.使用Krylov求解器,避免在形成交界面系统方程时,系数矩阵中的求逆运算.两个算例结果表明有限元撕裂对接法在分析复杂媒质散射特性时的正确性和有效性.     

基于神经网络集合预报的台风路径预报优化

针对目前台风路径预报研究中存在的预报精度不高、预报时次高耦合等缺陷,提出了一种基于神经网络集合预报的台风路径预报优化模型。运用混合模式集合预报思想和反向传播的多层前馈训练机制,充分挖掘数据特征,解决了单集合预报的固化性问题和单神经网络预报模型的随机性问题,为现有台风数值预报方法和人工智能技术的结合提供了新思路。以2018年活动在西北太平洋、南海地区的台风为样本进行对比实验,结果表明,60 h内的预报精度均得到了提高,一定程度上反映了该模型的实际应用价值。     

基于HBase与静态多级格网索引的地表覆盖数据高效检索方法

地表覆盖是地理国情监测的重要对象,为地理国情分析评价模型提供了可靠的数据源.高效的地表覆盖数据检索方法是挖掘地表覆盖数据潜在价值的前提.由于地表覆盖数据体量庞大、更新频繁,要素分布密集且不均匀,传统的空间检索方法出现了扩展困难、检索能力不足等问题.提出了一种基于HBase与静态多级格网索引的地表覆盖数据空间检索方法,针对地表覆盖数据特征设计了基于HBase的静态多级格网索引,利用MapReduce实现索引并行构建,通过多级过滤的方式,提高了地表覆盖空间范围的查询效率.实验表明,该方法能快速完成大规模、密集分布的地表覆盖数据的空间索引构建,提升空间检索性能,并具有良好的扩展性,可为其他海量空间矢量数据的检索提供借鉴.     

Poly-3BCMU薄膜上光栅的制备

报道了利用光致漂白现象在Poly－3BCMU薄膜上制备光栅的方法。对于不同条件下制备的光栅的衍射效率进行了测量。并建立了简单的模型，对实验结果进行了解释。     

Electrosyntheses of freestanding poly (3-(4-fluorophenyl)thiophene) films in boron trifluoride diethyl etherate

High quality free-standing poly (3-(4-fluorophenyl)thiophene) (PFPT) films with conductivity of 10⁻¹ S/cm were electrosynthesized in boron trifluoride diethyl etherate (BFEE) by direct anodic oxidation of the monomer 3-(4-fluorophenyl)thiophene (FPT) on stainless steel sheet. As-formed flexible and shiny PFPT films can be cut into various shapes by a knife or a pair of scissors. The structure, thermal stability and morphology of PFPT films were studied by FT-infrared, UV-vis, Raman spectroscopy thermogravimetric analysis and scanning electron microscopy, respectively.     

A solution to one of Kano's conjectures concerningk-th maximal spanning trees

Let (G) be the collection of all spanning trees of a connected and weighted graphG, andF ₁,F ₂, ...,F _m the partition of (G) such thatF _n the set ofi-th maximal spanning trees ofG. Kano^[1] conjectured that for anyA F ₁ and every integerk, 1km, there existsT F _k such that |T/A|k–1. This paper gives the conjecture a very simple proof, and related results.     

基于改进遗传算法的无线传感网覆盖优化

为提高混合无线传感器网络(WSNs)的覆盖率,将改进的遗传算法应用到WSNs覆盖优化中,通过合理调整移动节点的位置来提高网络覆盖率。针对传统群体智能算法易“早熟”,最大迭代次数需试探设定等缺陷,提出了基于多个种群并行优化的改进遗传算法。多个种群之间并不独立,而是通过移民算子相互联系;分别利用人工选择算子与精华种群选择并记录各个种群每一代最优染色体;并利用精华种群中保存的最优染色体设计出新的进化终止条件。仿真结果表明,改进的遗传算法不仅无需设定最大迭代次数而且收敛速度快,更兼有效地提高了WSNs的覆盖率     

Colorimetric determination of BCR/ABL fusion genes using a nanocomposite consisting of Au@Pt nanoparticles covered with a PAMAM dendrimer and acting as a peroxidase mimic

A colorimetric assay is described for the detection of BCR/ABL fusion genes. Polyamidoamine (PAMAM) dendrimers were placed on peroxidase (POx) mimicking Au@Pt nanoparticles to form a nanocomposite of type Au@Pt-PAMAM. Capture DNA probe is a designed nucleic acid strand that specifically binds target DNA to the surface of the electrode. The capture probe was attached to magnetic beads via biotin and avidin interaction. The hairpin structure of the capture probe can only be opened by the complementary BCR/ABL DNA. This results in a highly specific assay. The POx-mimicking property of the Au@Pt-PAMAM causes the formation of a blue dye by reaction of H₂O₂ and 3,3,3′,3′-tetramethylbenzidine (TMB) which is measured by a microplate reader. Under optimum conditions, the absorbance increases linearly the 1 pM to 100 nM BCR/ABL concentration range, and the detection limit is as low as 190 fM. The method is highly selective and was successfully applied to the determination of fusion genes in spiked real samples. Conceivably, it possesses a large potential in clinical testing of patients suffering from chronic myeloid leukemia.

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Graphical abstract Au@PtNP, an efficient catalyst, is bound with polyamidoamine (PAMAM) dendrimer to amplify the colorimetric signal. With the introduction of streptavidin-magnetic beads to remove non-specific signals, a novel colorimetric sensor is constructed to detect BCR/ABL fusion genes.

     

Two 3D Rubidium Halide Organic–Inorganic Hybrid Perovskite Ferroelectrics Templated by Quasi-Spherical Organic Amine 1,4-Diazabicyclo[3.2.2]nonane

The emergence of (CH₃NH₃)PbI₃ has brought the development of three-dimensional (3D) organic-inorganic hybrid perovskite (OIHP) structures with ABX₃ type to a higher level; however, most 3D frameworks are constructed by corner-sharing of BX₆ octahedra. Herein, we substituted the spherical molecule 1,4-diazabicyclo[2.2.2]octane (2.2.2-dabco) with 1,4-diazabicyclo[3.2.2]nonane (1,4-3.2.2-dabcn) as a template to react with RbX (X=Br, I) in the corresponding HX acids under the consideration of reducing the molecular symmetry. Two 3D OIHP compounds [1,4-3.2.2-H₂dabcn]RbI₃⋅H₂O ( 1 ) and [1,4-3.2.2-H₂dabcn]RbBr₃ ( 2 ) crystallized in non-centrosymmetric point group mm2 before the phase transition point were isolated. Among them, the 3D inorganic framework of 1 is constructed by sharing the corner of [RbI₆] octahedra, while that of 2 is constructed by sharing the corner and face of [RbBr₆] octahedra to acquire large cavities to accommodate the organic amine cation [1,4-3.2.2-H₂dabcn]²⁺; this 3D framework type is unprecedented in the OIHPs. As expected, compounds 1 and 2 exhibit reversible phase transition, dielectric and second harmonic generation (SHG) and ferroelectric properties, in which the phase transition temperature of 2 at 374 K is much higher than compound 1 at 280 K.