ZrO2∶Er3+,Yb3+纳米晶的制备及Er3+离子能级在晶体场中的分裂

采用1,3-丁二醇低热结晶法制备了ZrO2∶Er3+,Yb3+纳米晶.常温下,用980nm的红外激光激发可以观察到很强的ZrO2∶Er3+,Yb3+纳米晶红光发射,用荧光光谱仪记录了该上转换光谱.X射线粉末衍射(XRD)结果表明,ZrO2∶Er3+,Yb3+纳米晶属于立方晶系.研究了纳米晶的上转换发光机理,根据晶体场理论对Er3+的2个上转换能级进行了Stark分裂计算,对2个能级之间的谱线进行了归属,进一步证实了980nm激发Er3+离子的上转换经历两个过程:一是连续吸收2个980nm光子的过程,二是吸收980nm光子,电子转移到亚稳态能级后,再吸收980nm光子的过程     

GC-14A气相色谱仪分流装置的故障排除

 介绍了日本岛津公司产GC-14A气相色谱仪中SPL- 14分流/不分流进样器的连接管引起的故障现象及排除方法。指出该公司产同类型带有分流/ 不分流装置的气相色谱仪,若长期分析高沸点油状化合物,则应定期清洗连接管,及时清除 堵塞物,以保证测试数据有较好的重现性。     

以“联合大作业”实践加强学生创新创业能力的培养

以联合大作业的实践项目,通过校企合作、项目驱动、兴趣引导、文献查阅、市场调研、实验研发等实践训练,激发学生的创新创业意识,加强课内外联动,培养学生的自主学习能力、团队协作能力和创新能力。改革实践教学模式和方法,构建产学研创新实践平台,探索符合社会转型发展需要的复合型、创新型人才课外培养的有效途径。     

原子力显微镜的基本原理及应用

先进的测试表征技术是认识微观世界的重要手段，对于尺度和维度观的培养具有重要意义。不同于传统光学显微镜和电子显微镜，原子力显微镜是通过其探针原子与样品的表面原子的作用力来实现对样品表面形貌观测的。简述了原子力显微镜的基本原理和基本构造，阐释了其核心部件及功能。原子力显微镜主要有4种工作模式，比较了它们的优劣及应用范围。最后对原子力显微镜在分析测试中的实际应用进行了简述，展现了原子力显微镜的优越性与广阔的应用前景。     

Radial Basis Function Neural Networks-Based Modeling of the Membrane Separation Process： Hydrogen Recovery from Refinery Gases

Membrane technology has found wide applications in the petrochemical industry, mainly in the purification and recovery of the hydrogen resources. Accurate prediction of the membrane separation performance plays an important role in carrying out advanced process control (APC). For the first time, a soft-sensor model for the membrane separation process has been established based on the radial basis function (RBF) neural networks. The main performance parameters, i.e, permeate hydrogen concentration, permeate gas flux, and residue hydrogen concentration, are estimated quantitatively by measuring the operating temperature, feed-side pressure, permeate-side pressure, residue-side pressure, feed-gas flux, and feed-hydrogen concentration excluding flow structure, membrane parameters, and other compositions. The predicted results can gain the desired effects. The effectiveness of this novel approach lays a foundation for integrating control technology and optimizing the operation of the gas membrane separation process.     

A structure-switchable aptasensor for aflatoxin B1 detection based on assembly of an aptamer/split DNAzyme

An ultrasensitive, colorimetric and homogeneous strategy for aflatoxin B1 (AFB1) detection, which uses a DNA aptamer and two split DNAzyme halves, has been developed. Split halves of a hemin-binding DNAzymes is combined with an AFB1 aptamer to generate a homogeneous colorimetric sensor that undergoes an AFB1 induced DNA structural change. In the absence of AFB1, the split probes have peroxidase mimicking DNAzyme activity associated with catalysis of a color change reaction. Specific recognition of AFB1 by the aptamer component leads to structural deformation of the aptamer-DNAzyme complex, which causes splitting of the DNAzyme halves and a reduction in peroxidase mimicking activity. Therefore, a decrease of colorimetric signal arising from the catalytic process takes place upon in the presence of AFB1 in a concentration dependent manner in the 0.1–1.0 × 10⁴ ng/mL range and with a colorimetric detection limit of 0.1 ng/mL. The new assay system exhibits high selectivity for AFB1 over other mycotoxins and can be employed detect the presence of AFB1 in ground corn samples. Overall, the strategy should serve as the basis for the development of rapid, simple and low-cost methods for detection of mycotoxins.     

Design of a Powerful and Compact THZ Oscillator

According to simulations, a Large Orbit Gyrotron with a 30 keV/1 A electron beam and magnetic field of 5 T can produce CW radiation with output power of 10²−10³ W at the frequencies of 0.4–0.5 THz.     

The first loop for daily bus operation

We study the basic behaviors of buses using bus route models (BRM) by introducing a special kind of noise induced by impacts of other vehicles. The peak where the maximum velocity of buses exists shrinks in low noise conditions, which is worth the further study. Furthermore, we extend the model to take into consideration more realistic and important parameters, such as the number of passengers, the capacity of buses, and the possibility of overtaking, for performing simulations of the first loop. Suggestions on the choice of the number of buses and the maximum velocity are provided for the practical operation.     

浅谈实验安全和实验事故的救助

安全事故发生的重要原因之一是人的不安全行为。不规范的操作,安全意识淡薄,从而引发实验事故。要高度重视安全,正确认识安全,加强安全防护,学会正确救助,确保实验安全,避免实验事故的发生     

The Pilot Application of Electrochemical Impedance Spectroscopy on Dynamic Proton Exchange Membrane Fuel Cell北大核心CSCD

By analyzing Electrochemical Impedance Spectroscopy (EIS) in applications of dynamic proton exchange membrane fuel cell (PEMFC), bottlenecks which restrict EIS tool development have been pointed out in this paper.Though the high-frequency resistance in EIS is largely accepted as cell inner-resistance, this can only be applied for cell with low current.The low-fre¬quency resistance is difficult to be realized due to its relation with mass transfer.Furthermore, the improved Randies equiva¬lent circuits are built up preliminarily, thus, penetrating into studies for mass transfer reaction, cell operation/degeneration, and high temperature fuel cell.Inspiringly, EIS is becoming an analyzing tool for stack and control core for electric-vehicle.Nevertheless, it is still pioneer challenge to make breakthrough towards transient EIS method based on multi-discipline con-vergence. © 2018 Journal of Electrochemistry. All rights reserved.