饼干状二硫化钨纳米片的制备与结构表征

以钨粉、硫粉为原料,以K2HPO4为矿化剂,在500℃的密闭条件下,利用固相法合成了WS2纳米微粒;采用X射线衍射仪、扫描电子显微镜等表征了产物的结构,分析了矿化剂对WS2尺寸和形貌的影响.结果表明,当反应体系中存在适量的K2HPO4时,合成的WS2晶体呈饼干状,厚度约50nm,且结晶性良好.研究发现,在高温条件下,WS2晶粒在熔融K2HPO4中的形成和生长受到抑制,从而有利于其形貌和尺寸的控制.     

Application of artificial neural networks for unfolding neutron spectra by using a scintillation detector

The unfolding of neutron spectra from the pulse height distribution measured by a BC501A scintillation detector is accomplished by the application of artificial neural networks (ANN). A simple linear neural network without biases and hidden layers is adopted. A set of monoenergetic detector response functions in the energy range from 0.25 MeV to 16 MeV with an energy interval of 0.25 MeV are generated by the Monte Carlo code O5S in the training phase of the unfolding process. The capability of ANN was demon...     

机械泵驱动两相回路的实时动态模型分析

在航空航天领域,为了加速系统设计及测试进度,通常需要进行半实物实时仿真,即控制器用实物,受控对象采用数学模型。本文开发出了基于Matlab/Simulink的两相传热模块,并用其搭建了某机械泵驱动两相回路的实时动态模型。通过与实验的对比,验证了模型的可靠性,表明该模型满足实时要求,可以在下一步用于半实物仿真。     

Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate（MMDS） as electrolyte additive and its acting mechanism

The effects of methylene methanedisulfonate(MMDS) on the high-temperature(~50℃) cycle performance of LiMn_2O_4/graphite cells are investigated.By addition of 2 wt%MMDS into a routine electrolyte,the high-temperature cycling performance of LiMn204/graphite cells can be significantly improved.The analysis of differential capacity curves and energy-dispersive X-ray spectrometry(EDX) indicates that MMDS decomposed on both cathode and anode.The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells.It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn_2O_4 material,while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.     

Novel Access to Organostannane Compounds under Ultrasound Irradiation

A simple and efficient procedure has been developed for the synthesis of organostannane compounds by one-pot reaction of stannane halides, magnesium turnings and organic halides in the presence of 1,2-dibromoethane under ultrasound irradiation.     

Mechanism and Kinetics for the Reaction of NCS and OH Radicals

The mechanism and dynamical properties for the reaction of NCS and OH radicals have been investigated theoretically. The minimum energy paths (MEP) of the reaction were calculated using the density functional theory(DFT) at the B3LYP/6-311 G^** level, and the energies along the MEP were further refined at the QCISD(T)/6-311 G^** level. As a result, the reaction mechanism of the title reaction involves three channels, producing HCS NO and HNC SO products, respectively. Path Ⅰ and path Ⅱ are competitive, with some advantages for path Ⅰ in kinetics. As for path Ⅲ, it looks difficult to react for its high energy barrier. Moreover, the rate constant have been calculated over the temperature range of 8190-2500K using canonical variational transition-state theory (CVT). It was found that the rate constants for both path Ⅰ and path Ⅱ are negatively dependent on temperature, which is similarwith the experimental results for reactions of NCS with NO and NO2, and the variational effect for the rate constant calculation olavs an important role in whole temperature range.     

Synthesis and Characterization of Star-like Liquid Crystals Centered by Silicon

The synthesis and characterization of two new star-like liquid crystals are reported. They are made of a silicon core and four alkoxyazobenzene monomers in the periphery. Theirp hase behaviors and the structures are determined by infrared absorption spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), elemental analysis (EA), polarizing optical microscope (POM) and differential scanning calorimetry (DSC).     

Preparation of PO4^3-, P2O7^4- Anion-Pillared Nanocrystalline Mg-Al and Zn-Al Layered Double Hydroxides in Microwave Fields

Using nanocrystalline [Mg-Al-CO3] and [Zn-Al-CO3] as precursors, [Mg-Al-PO4],[Zn-Al-PO4], [Mg-Al-P2O7] and [Zn-Al-P2O7] have been successfully synthesized by a direct reaction with the free PO4^3- or P2O7^4- using the microwave techniques and the anion-exchange method. And the samples thus obtained were characterized by TEM, FT-IR and XRD. The results show that the initial interlayer carbonate ions can be completely replaced by the free PO4^3- or P2O7^4- under controlled microwave conditions employed for a short time.     

正交型光热偏转光谱法及其差分构型研究

本工作设计了一种新的差分式光热偏转光路构型，光路的优点是只使用单一的位置传感器，可随意调节样品池和参考池的距离，电学补偿和差分光路装置简单，容易调整，可以有效地消除溶剂空白吸收的影响和泵浦激光功率起伏的影响。文章还讨论了该差分构型的原理，差分响应公式和基本实验参数。获得的结晶紫和钴的检测下限分别为８．０×１０＾－１０ｍｏｌ／Ｌ和６０ｍｇ／ｍｌ，对应的最小吸光度分别为１．２×１０＾－８和５．４×１０     

红外光谱法研究聚脲氨酯的取向行为

利用红外二向色性研究了聚脲氨酯中软、硬段及界面层的取向行为。证明了软、硬段处于完全不同的结构形态中。在较低拉伸水平时,硬段主要垂直于拉伸方向取向;在较高拉伸水平时,则转到沿拉伸方向取向。软段和界面则始终沿拉伸方向取向。