Model averaging for linear models with responses missing at random

Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the...     

On the existence and uniqueness of classical global solution to a type of Boussinesq equations

The existence and uniqueness of classical global solutions to a type of Boussinesq equations with initial and boundary values are studied in this paper. The existence of such solutions is proved by means of compactness theorem and Schauders fixed point theorem, and its uniqueness by the so called energy method.Projects Supported by the Science Fund of the Chinese Academy of Sciences.     

卡尔曼滤波分光光度法同时测定钢样中的硅、磷、砷

研究了在聚乙烯醇存在下,硅、磷、砷钼杂多酸与罗丹明6G形成离子缔合物的反应,建立了能同时测定硅、磷、砷的卡尔曼滤波分光光度法。用于钢样中微量硅、磷、砷的同时测定,操作简便快速,相对误差小于8％。     

乳状液法制备憎液溶胶Ⅰ.BaCO_3均匀粒子的制备

均匀胶体粒子的形成，除与反应条件（反应物浓度、陈化时间和温度、介质种类等）有关外，反应体系的环境也影响最终产物的形态，《至结晶结构．气溶胶法和微乳液法正是利用微环境中的‘水池效应”；分别制备出球形亚微米和纳米级的均匀粒子［‘－‘］、这些方法与水解法和相转化法等方法比较，反应物浓度要大几个数量级，而反应时间却短很多，因而受到研究人员的关注．乳状液也能提供亚微米、微米及以上级的微环境，因此，可以应用O／W乳状液乳液中的聚合反应制备亲液的分散体系．然而，极少有关利用w／O乳状液制备僧液溶胶的报导问；最近…     

非对称碰撞约束下形状记忆合金梁的随机响应与分岔

形状记忆合金(SMA)是二十一世纪具有形状记忆效应的新型智能材料.针对具有非对称约束的SMA梁,本文构造了碰撞振动系统.在无碰撞和有碰撞两种情况下,利用随机平均法给出了近似解析结果.数值模拟作为验证解析结果的工具.结果表明,系统能量的概率响应曲线具有非光滑特性.当约束位置发生变化时,系统会出现随机P分岔和D分岔.     

Single Atoms of Iron on MoS2 Nanosheets for N2 Electroreduction into Ammonia

Efforts have been devoted to achieving a highly efficient artificial synthesis of ammonia (NH₃). Reported herein is a novel Fe-MoS₂ catalyst with Fe atomically dispersed onto MoS₂ nanosheets, imitating natural nitrogenase, to boost N₂ electroreduction into NH₃ at room temperature. The Fe-MoS₂ nanosheets exhibited a faradic efficiency of 18.8 % with a yield rate of 8.63 μg mg_cat.⁻¹ h⁻¹ for NH₃ at −0.3 V versus the reversible hydrogen electrode. The mechanism study revealed that the electroreduction of N₂ was promoted and the competing hydrogen evolution reaction was suppressed by decorating the edge sites of S in MoS₂ with the atomically dispersed Fe, resulting in high catalytic performance for the electroreduction of N₂ into NH₃. This work provides new ideas for the design of catalysts for N₂ electroreduction and strengthens the understanding about N₂ activation over Mo-based catalysts.     

H-Bonding Room Temperature Phosphorescence Materials via Facile Preparation for Water-Stimulated Photoluminescent Ink

Pure organic room-temperature phosphorescence (RTP) materials built upon noncovalent interactions have attracted much attention because of their high efficiency, long lifetime, and stimulus-responsive behavior. However, there are limited reports of noncovalent RTP materials because of the lack of specific design principles and clear mechanisms. Here, we report on a noncovalent material prepared via facile grinding that can emit fluorescence and RTP emission differing from their components’ photoluminescent behavior. Exciplex can be formed during the preparation process to act as the minimum emission unit. We found that H-bonds in the RTP system provide restriction to nonradiative transition but also enhance energy transformation and energy level degeneracy in the system. Moreover, water-stimulated photoluminescent ink is produced from the materials to achieve double-encryption application with good resolution.     

Improved Stretchable and Sensitive Fe Nanowire-Based Strain Sensor by Optimizing Areal Density of Nanowire Network

Flexible strain sensors, when considering high sensitivity and a large strain range, have become a key requirement for current robotic applications. However, it is still a thorny issue to take both factors into consideration at the same time. Here, we report a sandwich-structured strain sensor based on Fe nanowires (Fe NWs) that has a high GF (37–53) while taking into account a large strain range (15–57.5%), low hysteresis (2.45%), stability, and low cost with an areal density of Fe NWs of 4.4 mg/cm². Additionally, the relationship between the contact point of the conductive network, the output resistance, and the areal density of the sensing unit is analyzed. Microscopically, the contact points of the conductive network directly affect the sensor output resistance distribution, thereby affecting the gauge factor (GF) of the sensor. Macroscopically, the areal density and the output resistivity of the strain sensor have the opposite percolation theory, which affects its linearity performance. At the same time, there is a positive correlation between the areal density and the contact point: when the stretching amount is constant, it theoretically shows that the areal density affects the GF. When the areal density reaches this percolation threshold range, the sensing performance is the best. This will lay the foundation for rapid applications in wearable robots.     

基于有机羧酸配体的Co(Ⅲ)/Cu(Ⅱ)配合物的合成、结构及表征

在溶剂热条件下,以含卤素有机羧酸3-溴-吡啶-2,6-二甲酸(H₂L)为配体,以硝酸钴、硝酸铜为金属源,合成了两例配合物:[Co(L′)₃](1)和[Cu(L′)₂]_n(2)(HL′=5-溴-吡啶-2-甲酸),通过元素分析(EA)、X射线单晶衍射(SXRD)、X射线粉末衍射(PXRD)、红外光谱(IR)和热重分析(TGA)进行结构表征。X射线单晶衍射结果表明,配体H₂L在反应过程中发生脱羧现象,生成单羧酸配体5-溴-吡啶-2-甲酸。在配合物1中,每个Co(Ⅲ)都位于略微扭曲的八面体几何构型中,不对称单元中含有两个单核单元,单核单元通过C—H…O氢键形成三维超分子结构。配合物2的不对称单元中含有一个Cu(Ⅱ),两个脱质子的L′^-配体,每个Cu(Ⅱ)都是六配位的,位于扭曲的八面体几何构型中。Cu(Ⅱ)由配体连接生成1D链结构,通过C—H…O氢键形成三维超分子结构。此外,研究了两例配合物的热稳定性能。     

Recent Progress in Iron-Based Microwave Absorbing Composites: A Review and Prospective

With the rapid development of communication technology in civil and military fields, the problem of electromagnetic radiation pollution caused by the electromagnetic wave becomes particularly prominent and brings great harm. It is urgent to explore efficient electromagnetic wave absorption materials to solve the problem of electromagnetic radiation pollution. Therefore, various absorbing materials have developed rapidly. Among them, iron (Fe) magnetic absorbent particle material with superior magnetic properties, high Snoek’s cut-off frequency, saturation magnetization and Curie temperature, which shows excellent electromagnetic wave loss ability, are kinds of promising absorbing material. However, ferromagnetic particles have the disadvantages of poor impedance matching, easy oxidation, high density, and strong skin effect. In general, the two strategies of morphological structure design and multi-component material composite are utilized to improve the microwave absorption performance of Fe-based magnetic absorbent. Therefore, Fe-based microwave absorbing materials have been widely studied in microwave absorption. In this review, through the summary of the reports on Fe-based electromagnetic absorbing materials in recent years, the research progress of Fe-based absorbing materials is reviewed, and the preparation methods, absorbing properties and absorbing mechanisms of iron-based absorbing materials are discussed in detail from the aspects of different morphologies of Fe and Fe-based composite absorbers. Meanwhile, the future development direction of Fe-based absorbing materials is also prospected, providing a reference for the research and development of efficient electromagnetic wave absorbing materials with strong absorption performance, frequency bandwidth, light weight and thin thickness.