Fabrication and electrical properties of axial and radial GaAs nanowire pn junction diode arrays

We report on the fabrications and characterizations of axial and radial Ga As nanowire pn junction diode arrays.The nanowires are grown on n-doped Ga As（111）B substrates using the Au-catalyzed vapor–liquid–solid mechanism by metal–organic chemical vapor deposition（MOCVD）. Diethyl–zinc and silane are used as p- and n-type dopant precursors,respectively. Both the axial and radial diodes exhibit diode-like J–V characteristics and have similar performances under forward bias. Under backward bias, the axial diode has a large leakage current, which is attributed to the bending of the pn junction interface induced by two doping mechanisms in Au-catalyzed nanowires. The low leakage current and high rectification ratio make the radial diode more promising in electrical and optoelectronic devices.     

带控制片方柱绕流的非定常数值模拟

对高雷诺数下带控制片的方体(在方柱之前放置一小尺度的柱形薄片)非定常绕流进行了数值模拟。数值模拟方法采用RNG重整化群紊流模型，SIMPLE算法，在非定常计算中引入双重时间步方法，将方体和控制片区域作为求解域的一部分作整体求解。结果表明，控制片与方柱之间距离的不同，使得控制片所形成的涡被抑止或产生卡门涡街，从而对柱体侧面边界层的分离发生影响，产生三种典型的流态，柱体时均阻力系数相对于无控制片的情况迅速减小，当控制片偏离柱体轴心时，柱体升力系数迅速增大，偏心至柱体外壁面附近达到极大值。阻力系数达到最小值后将产生跳跃式的增大，而升力系数在达到最大值后也将产生跳跃式的减小。     

考虑非线性变形的航天器柔性附件建模方法

针对航天器的柔性附件,将其简化为常见的大范围运动空间柔性梁结构。根据柔性体的非线性变形原理,考虑了弯曲和扭转的非线性因素的影响,在柔性梁的三个变形方向上均考虑了变形的二次耦合项。利用有限元方法进行离散并用Lagrange方程建立了非线性变形模式下的动力学方程,包含了较为完全的刚度矩阵和各种耦合项。对一大范围运动的空间梁进行了仿真计算,表明在运动速度较大并且基座具有大范围运动时,一次耦合模型与本文模型有一定差异,且初始变形对两种模型也会产生影响。     

两个菲咯啉铜配合物的合成、晶体结构和催化性能

在醇溶剂中合成了2个铜配合物[Cu（Ⅱ）（phen）₂Br]₂[Cu（Ⅰ）₄Br₆]（1）和[Cu（Ⅱ）（phen）₂Br]Br·CH₃OH（2）（phen=菲咯啉）,并采用红外光谱、元素分析、热重和X射线单晶衍射对其进行了分析。1是Cu（Ⅰ）-Cu（Ⅱ）混价态化合物,并通过π-π作用和C-H…Br氢键作用形成了一个超分子网络结构。该化合物的结构单元包括2个[Cu（Ⅱ）（phen）₂Br]⁺阳离子和1个[Cu（Ⅰ）₄Br₆]^2-四核阴离子;阴离子中的4个铜原子组成四面体结构,而6个溴原子分别沿铜四面体的6个边桥联铜原子,形成八面体结构。2由[Cu（Ⅱ）（phen）₂Br]⁺、Br^-和CH₃OH组成,并通过π-π作用也形成了一个超分子网络结构。当它们催化甲醇氧化羰基化合成碳酸二甲酯（DMC）时,2仅显示了5.9的DMC转化数,而1中的[Cu（Ⅰ）₄Br₆]^2-阴离子能为甲醇的氧化羰基化反应提供适宜的合成环境,DMC的转化数达到54.7。     

N-乙基咔唑甲酰化衍生物的合成

以咔唑为原料,经烷基化和甲酰化反应合成了3-甲酰基-N-乙基咔唑和3,6-二甲酰基-N-乙基咔唑,其结构经1H NMR, IR和MS表征.重点研究了反应条件对甲酰化反应的影响.研究结果表明,甲酰化反应的较适宜条件为: 1 10 mmol, n(DMF) : n(1)=10 : 1, 1,2-二氯乙烷(25 mL)为溶剂,回流反应8 h～48 h.通过选择适当的反应条件,可以提高产率以及控制单乙酰化和双乙酰化产物的选择性.     

Effects of AlN and AlGaN Interlayer on Properties of InAlN/GaN Heterostructures

InAlN/GaN heterojunction structures are grown on two-inch c-face（0001） sapphire substrates by metalorganic chemical vapour deposition. AlN and AlGaN interlayers are intentionally inserted into the structure to improve the electrical properties. The lowest sheet resistance of 359 Ω/sq and the highest room-temperature two-dimensional electron gas （2DEG） mobility of 1051 cm2 V-1s-1 is obtained in the structure with AlN thickness of 1.3 nm. The structure with AlN thickness of 2 nm exhibits the highest 2DEG concentration of 1.84×1013 cm-2. The sample with an AlGaN interlayer gives a smoother surface morphology compared to the one using an AlN interlayer, indicating potential applications of this technique in device fabrication.     

非倍测度条件下Marcinkiewicz积分及其交换子在Morrey空间中的有界性

讨论了测度μ在满足非倍条件下,Marcinkiewicz积分算子及其与RBMO（μ）函数、Lipschitz函数生成的交换子的有界性,通过Marcinkiewica积分及该交换子在Lebesgue空间中的有界性,得到了该算子及交换子在非齐型空间上的Morrey空间中的有界性．     

非齐型空间中一类满足Hrmander条件的Marcinkiewicz交换子估计

记μ为R~d上的非负Radon测度,且仅满足对固定的C_0>0和n∈(0,d],及所有的x∈R~d和r>0,μ(B(x,r))≤C_0r~n.作者建立了一类核函数满足H(o|¨)rmander条件的Marcinkiewicz积分与Lip_β(μ)(0<β)函数生成的交换子由L~p(μ)到L~q(μ),由L~p(μ)到Lip_(β-n/p)(μ)及L~(n/β)(μ)到RBMO(μ)有界.部分结论对经典Marcink(?)ewicz积分也是新的.     

Phase Transition in CCI4 under Pressure： a Raman Spectroscopic Study

High-pressure Raman studies at room temperature are performed on CC14 up to 13 GPa. The Raman bands of the internal modes （v2, v4 and vl） show entirely positive pressure dependence. The slopes dω/dP of the internal modes exhibit two sudden changes at O. 73 GPa and 7.13 GPa, respectively. A new lower frequency mode （225 em-1） appears at 3.03 GPa, and the splitting of v2, v3 and v4 occurs at about 7.13 GPa. Moreover, Raman spectra of Fermi resonance show that the relative position of the v1 ＋ v4 combination and the v3 fundamental firstly interchanges corresponding to that at ambient pressure, then the v1 ＋ v4 combination disappears in the gradual process of compression. It is indicated that the pressure-induced phase transition from CC14 Ⅱ to CC14 Ⅲ occurs at 0.73 GPa, and CC14 Ⅲ undergoes a transition to CC14 IV below 3.03 GPa. Further CC14 Ⅳ transforms in a new high-pressure phase at about 7.13 GPa, and the symmetry of the new high-pressure phase is lower than that of CC14 Ⅳ. All the transitions are reversible during decompression.     

Precision Higgs physics at the CEPC

The discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics.The Higgs boson will be the subject of extensive studies of the ongoing LHC program.At the same time,lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC,with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson.The Circular Electron Positron Collider(CEPC)is one of such proposed Higgs factories.The CEPC is an e~+e~- circular collider proposed by and to be hosted in China.Located in a tunnel of approximately 100 km in circumference,it will operate at a center-of-mass energy of 240 GeV as the Higgs factory.In this paper,we present the first estimates on the precision of the Higgs boson property measurements achievable at the CEPC and discuss implications of these measurements.