碳酸钠共沉淀法制备LaNi0.6Fe0.4O3粉体的研究

以碳酸钠为沉淀剂,采用共沉淀法制备了亚微米级LaNi0.6Fe0.4O3(以下简称LNFO)粉体.研究了溶液离子总浓度,沉淀剂溶液pH,沉淀反应温度,滴定速率,前驱体热处理温度以及分散剂等因素对制备LNFO粉体的影响.采用X射线衍射分析(XRD)、差热失重分析(DSC-TG)、扫描电镜(SEM)对样品结构和形貌进行了表征.结果表明:前期混合液离子总浓度为0.4 mol/L,沉淀剂溶液pH为10,沉淀温度范围为60 ～80℃,滴定速率为30 mL/min,以CTAB为分散剂,所得前驱体在700℃煅烧2h后可得结晶程度良好的LNFO粉体.     

微结构超疏水表面减阻特性数值研究

通过湍流状态下超疏水表面的数值模拟,研究超疏水表面湍流流动的速度和剪应力分布,分析其与减阻的内在关系,初步总结出微观结构与减阻率之间的基本规律.数值模拟采用非定常雷诺平均模型,气液两相流则采用VOF模型.结果表明:超疏水表面存在滑移流动和周期分布的剪应力,其不仅可以实现减阻也有可能导致增阻;微结构尺寸对减阻率有显著影响,为了尽可能增大减阻率,矩形微结构的深宽比应大于3:2,且凹槽间距应尽可能小,凹槽宽度应小于200微米.     

Incident particle range dependence of radiation damage in a power bipolar junction transistor

The characteristic degradations in silicon NPN bipolar junction transistors(BJTs) of type 3DD155 are examined under the irradiations of 25-MeV carbon(C),40-MeV silicon(Si),and 40-MeV chlorine(Cl) ions respectively.Different electrical parameters are measured in-situ during the exposure of heavy ions.The experimental data shows that the changes in the reciprocal of the gain variation((1/β)) of 3DD155 transistors irradiated respectively by 25-MeV C,40-MeV Si,and 40-MeV Cl ions each present a nonlinear behaviour at a low fluence and a linear response at a high fluence.The(1/β) of 3DD155 BJT irradiated by 25-MeV C ions is greatest at a given fluence,a little smaller when the device is irradiated by 40-MeV Si ions,and smallest in the case of the 40-MeV Cl ions irradiation.The measured and calculated results clearly show that the range of heavy ions in the base region of BJT affects the level of radiation damage.     

InP-based evanescently coupled high-responsivity photodiodes with extremely low dark current density integrated diluted waveguide at 1550 nm

In this paper, we have demonstrated a high performance waveguide photodiode integrated diluted waveguide serving as a fibre-to-waveguide coupler to achieve high coupling efficiency. High responsivity (> 1 A/W), high saturation power (> 45 mA) in the static state and extremely low dark current density (0.04 pA/μm²) with 3 dB bandwidth at 13.4 GHz have been achieved.     

大跨机库桁架屋盖结构原型动力特性的实验研究

通过对跨度为(100+150m)的机库桁架屋盖结构的现场环境激励结构动力特性测试,利用谱分析方法对实测数据进行了分析,得出了结构的自振频率和振型.采用结构分析软件Midas建立屋盖的空间模型,采用特征向量法,得到了该结构的动力固有特性.有限元计算结果与动力试验结果在前3阶基本周期有相同的差异,各自所对应的振型吻合较好.结果表明环境激励下识别出该屋盖的低阶模态,可作为该机库的有限元模型修正和健康监测的基础.     

Separability of Bipartite Superoperator Based on Witnes

Based on the isomorphic relation between operator space L（H） and Hilbert space H^2, Cirac et al. mapped the global superoperator to a mixed state E which has the same separability of the initial superoperator. Zhang et al. [Phys. Rev. A 76 （2007） 012334] provided a calculable lower bound for both the linear and nonlinear witness. We use this bound to detect the entanglement of E to judge the separability of the initial superoperator. With the help of local orthogonal observables, we directly describe the separable condition of superoperator by its each operator. Lastly, using the lower bound of the nonlinear witness, we provide a calculable entanglement factor of bipartite superoperator.     

Studies of a scintillator-bar detector for a neutron wall at an external target facility

To achieve a better time resolution of a scintillator-bar detector for a neutron wall at the external target facility of HIRFL-CSR, we have carried out a detailed study of the photomultiplier, the wrapping material and the coupling media. The timing properties of a scintillator-bar detector have been studied in detail with cosmic rays using a high and low level signal coincidence. A time resolution of 80~ps has been achieved in the center of the scintillator-bar detector.     

Effect of Quantum Point Contact Measurement on Electron Spin State in Quantum Dots

We study the time evolution of two electron spin states in a double quantum-dot system, which includes a nearby quantum point contact （QPC） as a measurement device. We find that the QPC measurement induced decoherence is in the microsecond timescale. We also find that the enhanced QPC measurement will trap the system in its initial spin states, which is consistent with the quantum Zeno effect.     

MgSiO_3钙钛矿高温高压特性的第一性原理研究

本文采用第一性原理方法,计算了MgSiO_3钙钛矿在零温和0～150 GPa静水压范围内的晶体结构和弹性模量,并利用准简谐近似Debye模型,拟合三阶Birch-Murnaghan物态方程得到了其高温高压下的热力学性质.通过与现有的理论和实验的结果数据比较,确认在0～2000 K的温度区间内,第一性原理计算结合Debye模型能够较可靠地模拟在下地幔压力范围内MgSiO_3钙钛矿的热力学性质.     

Chrystal不等式的一个推广及其应用

利用均值不等式给出Chrystal不等式的一个推广,并利用该推广证明一个猜想.