Electric ignition energy evaluation and the energy distribution structure of energy released in electrostatic discharge process

Ignition energy is one of the important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters(the maximum power, duration of discharge process) of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%–14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy.     

基于KMnF_3∶Yb~(3+),Er~(3+)纳米晶的红光聚合物平面光波导放大器

制作了基于KMnF_3∶Yb~(3+),Er~(3+)纳米晶材料的工作波长655 nm的聚合物平面光波导放大器。材料的吸收光谱表明,KMnF_3∶Yb~(3+),Er~(3+)纳米晶在980 nm附近有很强的吸收。在980 nm激光的激发下,由于Er~(3+)和Mn2+能级之间的能量传递,KMnF_3∶Yb~(3+),Er~(3+)纳米晶产生了很强的红色上转换发光。根据KMnF_3∶Yb~(3+),Er~(3+)纳米粒子的发光特性,制备了KMnF_3∶Yb~(3+),Er~(3+)NCs-PMMA复合材料,用其作为芯层设计了掩埋形结构光波导放大器,利用传统的半导体工艺完成器件制备。器件测试结果表明,当655 nm信号光功率为0.1 m W、980 nm泵浦功率为260 m W时,器件获得了2.7 d B的相对增益。     

聚变-裂变混合堆系统在能源战略中的地位及其设计中若干问题的分析

简要描述聚变-裂变混合堆在长期能源发展战略中的地位,着重计算分析具有不同类型的聚变堆芯和包层的混合堆生产电能和可裂变核燃料的能力,研究不同类型聚变-裂变混合堆与其支持的卫星堆(如压水堆)组合燃料循环系统生产电能的能力.指出以天然铀或贫化铀为燃料,水冷却的包层设计是一种经济可行、技术风险较小的设计方案.     

Effect of surface treatment of GaN based light emitting diode wafers on the leakage current of light emitting diode devices

To form low-resistance Ohmic contact to p-type GaN, InGaN/GaN multiple quantum well light emitting diode wafers are treated with boiled aqua regia prior to Ni/Au (5~nm/5~nm) film deposition. The surface morphology of wafers and the current--voltage characteristics of fabricated light emitting diode devices are investigated. It is shown that surface treatment with boiled aqua regia could effectively remove oxide from the surface of the p-GaN layer, and reveal defect-pits whose density is almost the same as the screw dislocation density estimated by x-ray rocking curve measurement. It suggests that the metal atoms of the Ni/Au transparent electrode of light emitting diode devices may diffuse into the p-GaN layer along threading dislocation lines and form additional leakage current channels. Therefore, the surface treatment time with boiled aqua regia should not be too long so as to avoid the increase of threading dislocation-induced leakage current and the degradation of electrical properties of light emitting diodes.     

Microstructure and strain analysis of GaN epitaxial films using in-plane grazing incidence x-ray diffraction

This paper investigates the major structural parameters,such as crystal quality and strain state of (001)-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition,using an in-plane grazing incidence x-ray diffraction technique.The results are analysed and compared with a complementary out-of-plane xray diffraction technique.The twist of the GaN mosaic structure is determined through the direct grazing incidence measurement of (100) reflection which agrees well with the result obtained by extrapolation method.The method for directly determining the in-plane lattice parameters of the GaN layers is also presented.Combined with the biaxial strain model,it derives the lattice parameters corresponding to fully relaxed GaN films.The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established,reaching to a maximum level of-0.89 GPa.     

Time delay in InGaN multiple quantum well laser diodes at room temperature

This paper reports that a long delay between the beginning of pumping current pulse and the onset of optical pulse is observed in InGaN laser diodes.The delay time decreases as the pumping current increases,and the speed of the delay time reduction becomes slower as the current amplitude increases further.Such delay phenomena are remarkably less serious in laser diodes grown on GaN substrate than those on sapphire.It attributes the delay to the traps which cause a large optical loss by saturable absorption and retard the laser action.The traps can be bleached by capturing injected carriers.The effect of GaAs laser irradiation on InGaN laser action demonstrates that the traps responsible for the delay are deep centres which can be filled by the photo-assisted processes.     

硝基甲烷异构化反应势能面的ab initio研究

在B3LYP/6-311+ +G(2d,2p)水平上,优化得到硝基甲烷CH3NO2的10种异构体和23个异构化反应过渡态,并用G2MP2方法进行了单点能计算.根据计算得到的G2MP2相对能量,探讨了CH3NO2势能面上异构化反应的微观机理.研究表明,反应初始阶段的CH3NO2异构化过程具有较高的能垒,其中CH3NO2的两个主要异构化反应通道,即CH3NO2→CH3ONO和CH3NO2→CH2N(O)OH的活化能分别为270.3和267.8 kJ/mol,均高于CH3NO2的C-N键离解能.因而,从动力学角度考虑, CH3NO2的异构化反应较为不利.     

沉痛悼念国际著名电化学家——ErnestB.Yeager教授

国际著名化学家 ,理论电化学奠基人 ,美国ＣａｓｅＷｅｓｔｅｒｎＲｅｓｅｒｖｅ大学 (ＣＷＲＵ )ＥｒｎｅｓｔＢ .Ｙｅａｇｅｒ教授于 2 0 0 2年 3月 8日不幸逝世 ,享年 77岁 .科学巨星殒落 !学界为之悲恸 !Ｙｅａｇｅｒ教授是国际上公认的电化学界权威 ,一生都贡献给科学事业 ,他把毕生的精力用于探索电化学基本过程的本质 ,在他近 5 0年的科研生涯中共发表学术论文 2 70篇 ,编写专著2 0部 ,为后人留下了非常宝贵的知识财富 .Ｙｅａｇｅｒ教授是开发燃料电池的先驱 ,早在 1 976年于美国国家能源问题与自然资源保护会议上 ,他就预言今后电…     

不同模拟体系中草酸钙结晶的比较研究

泌尿系结石是一种世界范围内的常见病及多发病 ,如深圳市的尿结石患病率高达 4.87%[1] ,其发病率呈上升趋势 .泌尿系结石在手术后复发率高 ,尤其是对结石的预防 ,目前尚无十分理想的方法 ,至今其形成机制未完全阐明 ,80 %以上的尿结石患者病因不清 [2 ] .草酸钙 (Ca C2 O4 )是泌尿系结石的主要成分 .体内 Ca C2 O4 结石的形成与热力学 (过饱和度 )和动力学 (成核、生长和聚集 )因素相关 .虽然在尿液中发现有二水草酸钙 (COD)晶体 ,但是热力学稳定的一水草酸钙 (COM)是尿石中最普遍的晶型[3 ] .在大多数的 Ca C2 O4 结石中 ,COM的发…     

海带多糖对草酸钙结晶过程中晶相的影响

采用X射线衍射(XRD)、红外光谱(FTIR)、扫描电子显微镜(SEM)和原子吸收光谱(AAS)等方法研究了从海带中提取的硫酸多糖(SPS)对尿结石主要成分草酸钙结晶的影响。SPS可以稳定热力学亚稳定的二水草酸钙(COD)晶体。随着SPS浓度从0增加到0.60 mg·mL-1,COD晶体的质量百分比从0增加到100％;亚稳溶液中草酸钙的相对过饱和度从1.0增加到19.6。SPS可以稳定COD晶体在溶液中的存在并增加可溶性Ca2+离子的浓度,这有利于防止草酸钙结石形成。结果表明,SPS是一种潜在的防止草酸钙尿结石形成的药物。