单级电磁感应线圈发射器温升研究

同步感应式线圈型电磁发射器主要采用脉冲电流对线圈直接供电,其实际工作过程中电枢和线圈会产生温升,这是当前制约线圈发射器向小型化、高速发展的一个主要因素。本文通过建立电磁线圈的温升模型,对于单次触发的情况,分别利用Comsol和自编程序Coilgun进行计算,并搭建相应的试验平台进行验证。采用直接耦合方式的Comsol计算结果最为准确,也能考虑材料参数随温度的变化。仿真得到电枢的温升大约为4.2℃,线圈最大温升为7.7℃。由于热电偶温度传感器的测量延迟性与采样频率的限制,电枢温度试验曲线未能测量到仿真曲线中出现的温度最大值点,可记录到整个试验过程中温度变化曲线,其变化形势以及最终稳定的温度与仿真的基本一致,误差最大为6.1%,说明了仿真的准确性。为后续进行多级线圈连续发射奠定基础。     

Real-time observations on crystallization of gold nanorods into spiral or lamellar superlattices

Real-time observations on gold nanorods evolving into spiral or lamellar superlattices are demonstrated. 2D critical nuclei and screw dislocations initiate the crystallization process. Kinetics of the superlattice growth is determined to be similar to that of classical crystal growth, where three basic modes are involved: spiral, layer-by-layer and dendritic.     

Areal moments of inertia revisited: on the distinction between the principal directions

Three commonly used methods to determine the principal moments of inertia of a plane area and their directions are based on: (i) the stationarity condition for the axial moment of inertia, (ii) the eigenvalue analysis, and (iii) Mohr’s circle. In this paper we provide two new derivations, which are based on: (a) the matrix diagonalization and the invariant tensor properties, and (b) the conjugacy property of the moment of inertia vectors. A new general expression is derived which specifies the principal directions of inertia, as well as the directions of the maximum and minimum product of inertia. A comparative study of the five presented approaches is given, which is of interest from both conceptual and methodological points of view. The connection between the deviatoric part of the moment of inertia tensor and Land’s circle of inertia is also given. The presented analysis applies to any two-by-two symmetric second order tensor.     

制备型高效液相色谱法分离纯化川西獐牙菜提取物中的龙胆苦苷

龙胆苦苷(GPS)是龙胆类药材及其相关制品质量控制的指标成分。本研究利用制备型高效液相色谱从川西獐牙菜提取物中分离纯化龙胆苦苷对照品。对制备色谱的流动相组成、流速、进样量和检测波长等制备参数进行了优化。采用的色谱柱为C18柱(200 mm×50 mm, 5 μm),流动相为甲醇和0.1%乙酸水溶液(体积比为30:70),流速为75 mL/min,检测波长为254 nm,进样体积为500 μL。在30 min的运行时间内,龙胆苦苷与其他干扰成分得到了很好的分离,产品纯度达到了99%以上。此方法具有快速高效、产品纯度高的特点,可用于制备龙胆苦苷对照品和对龙胆苦苷制品的质量控制。     

Capillary zone electrophoresis for U(VI) and short chain carboxylic acid sorption studies on silica and rutile

Capillary zone electrophoresis was used to study the uranyl and short chain carboxylic acid sorption on silica and rutile. The separation and the simultaneous determination (in a single run) of a number of short chain carboxylic acids (oxalic, formic, acetic and propionic) and U(VI) with direct UV detection is developed for the analysis of solutions after the sorption experiments. The reverse polarity mode is used (the injection is performed at the negative end). The matrix effect of Si(IV) (possible silica dissolution product) and perchlorate (added for constant ionic strength in sorption experiments) on the separation of U(VI) and organic acids is investigated. The influence of methanol addition in carrier electrolyte on the separation selectivity of given analytes is also studied. Under the chosen conditions (carbonate buffer (ionic strength of 0.1 M), pH 9.8, 0.15 mM of tetradecyltrimethylammonium bromide, 25% (v/v) of methanol) the calibration curves are plotted. They are linear in two ranges of concentration from ∼1 × 10⁻⁵ to ∼1 × 10⁻³ M for oxalate, acetate, propionate, U(VI) and ∼1 × 10⁻⁴ to ∼1 × 10⁻³ for formate. The accuracy of the procedure is checked by the “added-found” method in simulation solutions. The relative standard deviations of the concentrations found are within the range of 1-10% and the recovery is in the range of 90-115%. This method is applied for the analysis of aqueous samples issued from sorption experiments on silica and rutile. The obtained results indicate that the given organic acids decrease uranium sorption both on silica and rutile. These experiments demonstrate that short chain carboxylic acids can influence the mobility and the chemistry of U(VI) in the environment.     

聚二甲基硅氧烷的折射率和线膨胀气压响应特性

聚二甲基硅氧烷(PDMS)是一种高分子有机硅化物,广泛应用于微流控芯片制备、生物、光学以及复合材料基体等不同的领域.通过结合PDMS与光纤结构构建了光纤干涉仪,利用光学传感技术研究了PDMS折射率和线膨胀的气压响应特性.实验结果表明,PDMS的折射率随气压的变化率为-2.1×10-2 RIU/MPa(RIU为折射率单位),线膨胀随气压的变化率为17.3 μm/MPa.采用光学测量的形式对PDMS的折射率和线膨胀气压响应进行研究,精确度和可靠性更高.     

化学链燃烧中LaNixFe1-xO3载氧体的性能研究

采用柠檬酸络合法制备了不同Ni含量的LaNixFe1-xO3系列复合氧化物载氧体。采用热分析、X射线衍射、程序升温还原和扫描电境等手段对载氧体进行了表征,并在化学链燃烧反应中进行性能评价。XRD表征结果表明不同Ni含量的LaNixFe1-xO3均能形成钙钛矿结构,TPR表征结果表明随Ni含量增加,LNixaFe1-xO3上氧数量增加,还原能力增强。在连续十次化学链燃烧反应中,95%一氧化碳在LaFe0.5Ni0.5O3上被氧化,扫描电境照片发现部分载氧体颗粒出现破碎、烧结现象。