Flow Structures Around Micro-bubbles During Subcooled Nucleate Boiling

The flow structures were investigated around micro bubbles on extremely thin wires during subcooled nucleate boiling.Jet flows emanating from the bubbles were observed visually with the fluid field measurement using high-speed photography and a PIV system.The jet flows induced a strong pumping effect around a bubble.The multi-jet structure was further observed experimentally, indicating the evolution of flow structure around micro bubbles.Numerical simulations explore that the jet flows were induced by a strong Marangoni effect due to high temperature gradients near the wire.The bubble interface with multi-jet structure has abnormal temperature distribution such that the coolest parts were observed at two sides of a bubble extending into the subcooled bulk liquid rather than at the top.Evaporation and condensation on the bubble interface play important roles not only in controlling the intensity of the jet flow,but also in bringing out the multi-jet structure.     

RIBLL终端LASCAR闪烁体阵列探测器研制进展

介绍了RIBLL终端LASCAR闪烁体阵列探测器的工作原理和结构特点. 描述了为满足放射性核束实验的要求而对阵列所作的重要改进. 给出了LASCAR构型优化改造的工作设想和实施步骤. The principles and structure characteristics of LASCAR scintillator array detector at RIBLL terminal are described. Special emphases are laid upon the latest progress for the development of LASCAR array detector to meet the requirements of the RIB experiments. The working plan and steps for optimizing configuration of the LASCAR multi unit neutron scintillator array detector are also presented.     

3 ω线法测量液体热参数影响因素分析

首先给出基于谐波探测技术测量液体导热系数和热扩散系数的3ω线法的基本原理.采用实验和理论分析相结合的方法,分析了加热丝结构参数和自身热参数对温度波动和测量结果的影响.给出了加热丝直径和长度的合理范围.液体导热系数比较小时可以利用三次谐波的实部和虚部的交点测量液体的比热容.     

反相电极聚合物定向耦合电光开关的优化设计

为了消除单节电极定向耦合电光开关的工艺误差对器件性能的不良影响,应用耦合模理论、电光调制理论、保角变换及镜像法,优化设计了一种两节交替反相电极聚合物定向耦合电光开关.模拟结果表明,该器件具有良好的开关性能:在1 550 nm的工作波长下,器件耦合区的长度为4 753.5 μm,交叉态电压为1.22 V,直通态电压为2.65 V,插入损耗小于2.21 dB,串扰小于-30 dB.通过微调状态电压,可以很容易地消除工艺误差对器件性能产生的不良影响.本文方法的设计结果与光束传播法的仿真结果符合得很好.     

Efficiency enhancement of InGaN based blue light emitting diodes with InGaN/GaN multilayer barriers

The advantages of InGaN based light-emitting diodes with InGaN/GaN multilayer barriers are studied.It is found that the structure with InGaN/GaN multilayer barriers shows improved light output power,lower current leakage,and less efficiency droop over its conventional InGaN/GaN counterparts.Based on the numerical simulation and analysis,these improvements on the electrical and the optical characteristics are mainly attributed to the alleviation of the electrostatic field in the quantum wells(QWs) when the InGaN/GaN multilayer barriers are used.     

2-(3’,4’-二羧基苯氧基)苯甲酸配体桥联的锌(Ⅱ)配合物的合成、结构及荧光性质

以2-(3’,4’-二羧基苯氧基)苯甲酸(H3DPBA)和1,3-二(4-吡啶基)-丙烷(bpp)为配体,与Zn(Ac)2通过水热反应,获得了一维链状配合物Zn(DPBA)(bpp)。该配合物的一个不对称单元包括一个Zn(Ⅱ)离子,一个DPBA配体和一个bpp配体。Zn(Ⅱ)离子与四个氧原子及一个氮原子配位,其配位数为5。固态配合物在375nm处出现强的发射峰,来自于配体的π~*—π跃迁。与配体的荧光发射光谱比较,配合物的荧光发射峰发生了蓝移,而且配合物的荧光发射强度有大幅度增强。讨论了配合物在常见溶剂中和金属阳离子中的荧光性质。实验结果表明不同有机小分子或不同金属阳离子对配合物的荧光强度有不同程度的影响,有机小分子硝基苯和Fe~(3+)使配合物荧光猝灭,该Zn(Ⅱ)-配合物可用于硝基苯的检测以及水和乙醇体系中Fe~(3+)的检测。     

等离子体纳米结构中的Fano共振效应及其应用

Fano共振效应是一种具有非对称线型的共振散射现象,起源于共振过程和非共振过程的量子干涉效应。近年来,在等离子体纳米结构中Fano共振现象也被发现,并成为纳米光子学的一个研究热点。等离子体Fano共振通常具有较窄的光谱线宽,且不能直接与入射光耦合,只能局域在近场,强的近场局域特性可以获得巨大的表面电磁场增强。由于等离子体Fano共振独特的光学特性,已经被应用到单分子探测、高灵敏度传感、增强光谱、完美吸收、电磁诱导透明和慢光光子学器件等众多领域当中。     

基于超材料实现等离激元诱导透明

电磁诱导透明是在介质中由不同的入射光诱导产生的量子干涉效应。它以其独特的物理现象,在量子通信和非线性光学应用中具有重要的地位。近年来,人工超材料发展十分迅速,并成为等离子体学领域的一个研究热点。超材料可以很好地调控其物理结构和特性,而且降低了对电磁诱导透明实验条件的要求,模拟出类似于电磁诱导透明的现象即等离激元诱导透明。本文介绍等离激元诱导透明的工作原理,总结实现等离激元诱导透明的几种结构,以及等离激元诱导透明的研究现状,为微型传感器的应用以及等离激元诱导透明结构的设计提供依据。     

Time-varying networks based on activation and deactivation mechanisms

A class of models for activity-driven networks is proposed in which nodes vary in two states: active and inactive.Only active nodes can receive links from others which represent instantaneous dynamical interactions. The evolution of the network couples the addition of new nodes and state transitions of old ones. The active group changes with activated nodes entering and deactivated ones leaving. A general differential equation framework is developed to study the degree distribution of nodes of integrated networks where four different schemes are formulated.     

Flow characterization and dilution effects of N_2 and CO_2 on premixed CH_4/air flames in a swirl-stabilized combustor

Numerically-aided experimental studies are conducted on a swirl-stabilized combustor to investigate the dilution effects on flame stability, flame structure, and pollutant emissions of premixed CH4/air flames. Our goal is to provide a systematic assessment on combustion characteristics in diluted regimes for its application to environmentally-friendly approaches such as biogas combustion and exhanst-gas recirculation technology. Two main diluting species, N2 and CO2, are tested at various dilution rates. The results obtained by means of optical diagnostics show that five main flame regimes can be observed for Nz-diluted flames by changing excess air and dilution rate. CO2-diluted flames follow the same pattern evolution except that all the domains are shifted to lower excess air. Both N2 and CO2 dilution affect the lean blow- out （LBO） limits negatively. This behavior can be counter-balanced by reactant preheating which is able to broaden the flammability domain of the diluted flames. Flame reactivity is degraded by increasing dilution rate. Meanwhile, flames are thickened in the presence of both diluting species. NOx emissions are significantly reduced with dilution and proved to be relevant to flame stability diagrams： slight augmentation in NOx emission profiles is related to transitional flame states where instability occurs. Although dilution results in increase in CO emissions at certain levels, optimal dilution rates can still be proposed to achieve an ideal compromise.