Structural and Optical Properties of Nonpolar m-Plane GaN and GaN-Based LEDs on γ-LiAlO_2

We report the structural and optical properties of nonpolar m-plane GaN and GaN-based LEDs grown by MOCVD on a 7-LiAlO2 （100） substrate. The TMGa, TMIn and NH3 are used as sources of Ga, In and N, respectively. The structural and surface properties of the epilayers are characterized by x-ray diffraction, polarized Raman scattering and atomic force microscopy （AFM）. The films have a very smooth surface with rms roughness as low as 2nm for an area of 10×10μm^2 by AFM scan area. The XRD spectra show that the materials grown on 7-LiAl02 （100） have （1 - 100） m-plane orientation. The EL spectra of the m-plane InGaN/GaN multiple quantum wells LEDs are shown. This demonstrates that our nonpolar LED structure grown on the 7-LiAlO2 substrate is indeed free of internal electric field. The current voltage characteristics of these LEDs show the rectifying behaviour with a turn on voltage of 1-3 V.     

光的反射与折射实验

九年义务教育课本初中物理（第一册）第十四章光的反射与折射，可把两个实验合二为一.取一玻璃水槽，内盛2／3体积的洁净的水，再取一块硬纸板一面涂有黑色，纸上开一道窄窄狭缝，实验时黑色纸面朝下，硬纸大小比槽口略大，只要用手电筒朝狭缝中照射便可见到两种现象.一是黑色纸面上有明亮光斑，这是光的反射结果；二是在水槽底看到一个明亮光斑，这是光从空气射入水折射的现象.很容易说明光的反射是在同一媒质中发生的，而光的折射是在光从一种媒质进入另一种媒质时发生的.实验须在这光设备良好的室内进行，也可把这个实验改为学生分组实验…     

固定干扰法测定ISE选择性系数实验方法的改进

固定干扰法测定ＩＳＥ选择性系数实验方法的改进黄超伦修荣刘辉任聚杰（河北医科大学药学院石家庄０５００１７）选择性系数（ＫＰｏｔｉ，ｊ）是离子选择电极（ＩＳＥ）重要的性能标志之一，商品电极及新研制的电极一般都要报告对有关干扰离子的ＫＰｏｔｉ，ｊ数据。实验...     

Molecular dynamics study of temperature-dependent ripples in monolayer and bilayer graphene on 6H—SiC surfaces

Using classical molecular dynamics and a simulated annealing technique,we show that microscopic corrugations occur in monolayer and bilayer graphene on 6H-SiC substrates.From an analysis of the atomic configurations,two types of microscopic corrugations are identified,namely periodic ripples at room temperature and random ripples at high temperature.Two different kinds of ripple morphologies,each with a periodic structure,occur in the monolayer graphene due to the existence of a coincidence lattice between graphene and the SiC terminated surface(Si-or C-terminated surface).The effect of temperature on microscopic ripple morphology is shown through analysing the roughness of the graphene.A temperature-dependent multiple bonding conjugation is also shown by the broad distribution of the carbon-carbon bond length and the bond angle in the rippled graphene on the SiC surface.These results provide atomic-level information about the rippled graphene layers on the two polar faces of the 6H-SiC substrate,which is useful not only for a better understanding of the stability and structural properties of graphene,but also for the study of the electronic properties of graphene-based devices.     

铀(Ⅵ)的二溴水杨醛缩二胺类双希夫碱及溶剂三元配合物的合成和表征

铀（Ⅵ）的二溴水杨醛缩二胺类双希夫碱及溶剂三元配合物的合成和表征郑庚修＊毕彩丰张家祥王秋芬张广友（山东建材学院应用化学系，济南２５００２２）关键词：硝酸铀双希夫碱三元配合物关于铀与希夫碱的配合物的结构、萃取等研究已有报道。结构研究发现：铀（Ⅵ）盐可以...     

巧用三角代换解无理方程

巧用三角代换解无理方程６２９１１１四川蓬溪群力中学邓甫修形如人呼万个人死万一。（ｍ＞０）型的无理方程，常用的解法是两次平方法，化为有理方程来解，运算量很大，且将产生高次方程．现介绍巧用三角代换来妙解这类方程，其方法是：令人ｘ）。ｍ’幻ｎ‘５，ｇ（ｘ）...     

Simultaneous Generation of Multi-Wavelength Laser from Nd:YAG Crystals in a Cruciform Cavity

A cruciform cavity is presented for multi-wavelength laser generation. On the basis of considering the optimal power ratio and good spatial overlap of the two fundamental beams, the maximum output power of 589 nm laser reaches 3.5 W when the pumping power of Nd：YAG A and Nd：YAG B are 311.5 W and 261.8 W, respectively. At the same time, the other wavelength lasers are also obtained with the output power distribution of 2.5 W at 66Onto, 15 W at 532nm, lOOmW at 1319nm and 240mW at 1064nm. The corresponding beam quality factors are M^2 x = 4.93, M^2 y = 5.01 at 589nm, M^2z = 4.51, M^2 y = 4.85 at 660hm, and M^2 x = 4.12, M^2 y = 3.96 at 532nm, respectively. The instabilities of the three visible lights are measured, which are also less than 2% within three hours.     

电子信息类工程技术人才培养研究与实践

针对目前电子信息类工程技术人才培养现状及社会需求,分析了目前我国工程教育存在的问题,提出了解决这些问题的方法和措施,并结合这些措施,介绍了具体的做法,即以项目为依托将工程设计与工程实践融入到教学中,基于校内实习平台强化实习环节,将"大学生创新、创业训练计划"常态化、多元化.经过实践,该措施初见成效,以待进一步推广.     

高效液相色谱-串联质谱法测定地表水样品中5种有机磷酸酯代谢物

将固相萃取(SPE)和高效液相色谱-串联质谱(LC-MS/MS)结合,建立了河水样品中5种有机磷酸酯(OPEs)代谢物的分析方法。样品过滤后,使用HLB固相萃取小柱进行富集净化,采用6 m L甲醇洗脱后氮吹定容。以Luna Phenyl-Hexyl色谱柱为分离柱,甲醇和50 mmol·L-1乙酸铵水溶液为流动相梯度洗脱,在电喷雾负离子模式下,采用多反应监测模式(MRM)进行测定。优化条件下,仪器测定限(IDL)为0.002~1.15μg·L~(-1),方法检出限(MDL)为0.15~4.48 ng·L~(-1),实际水样加标浓度为10 ng·L~(-1)和50 ng·L~(-1)时回收率分别为54.1%~83.6%和57.8%~102%,相对标准偏差(RSD)分别为5.3%~19.5%和2.8%~15.7%。考察了基质效应对5种化合物分析的影响,同时应用该方法对武汉7个湖水样品进行分析,除DEHP外其它4种OPEs代谢物均有检出。该方法具有良好的精密度和准确度,可用于有机磷酸酯代谢物的环境行为研究。