C/SiC纳米管异质结电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理计算,对扶手椅型(4,4)和(6,6)及锯齿型(8,0)和(10,0)C/SiC纳米管异质结的电子结构进行了研究.结果表明两类异质结结构都表现为半导体特性.扶手椅型纳米管异质结形成了Ⅰ型异质结,电子和空穴都限制在碳纳米管部分.锯齿型纳米管异质结中价带顶主要分布在碳纳米管部分及C/SiC界面处,而导带底均匀分布在整个纳米管异质结上.这两种异质结结构在未来纳米器件中具有潜在的应用价值. 关键词： C/SiC纳米管异质结 第一性原理 电子结构     

10位CMOS数模转换器在中子和γ混合环境下的综合辐射效应

研究了在反应堆中子和γ射线综合辐照环境下CMOS工艺10位数模转换器(DAC)的辐射效应。通过对DAC在γ辐射环境、中子辐射环境、中子和γ混合辐射环境以及中子预辐照后进行γ射线辐照下的效应对比发现,在中子和γ混合辐射环境下会产生电离总剂量效应加剧现象,即一定混合程度的中子和γ同时辐照会增强CMOS器件的辐射效应。     

Curvature measurement by using low-birefringence photonic crystal fiber based Sagnac loop

An optical fiber curvature sensor with low-birefringence photonic crystal fiber (PCF) based Sagnac loop is demonstrated experimentally. The low-birefringence PCF of about 40 cm long is inserted into Sagnac loop, and a section of it about 155 mm is used as the sensing element. The Sagnac output spectra under different curvatures are measured and analyzed. The results show that the wavelength shift of the transmission dip has a linear relationship with the curvature. The sensitivity of the curvature measurement of − 0.337 nm is achieved in the range of 0-9.92 m^− 1. And the temperature effect of the proposed sensor is also analyzed.     

Thermospin phenomena in a quantum dot attached to ferromagnetic leads: Role of asymmetry and alignment

We study the thermospin effects in a system consisting of a quantum dot coupled to ferromagnetic leads. It is shown that sign reversal and oscillation of spin Seebeck coefficient are indicated as a function of device parameters. When the magnetizations of the leads are formed in parallel alignment, the spin Seebeck coefficient and the spin-FOM have their maximum values for the symmetric dot-lead coupling case. However, in the antiparallel case, the optimal device parameters depend mainly on the strength of the magnetic field.     

Synthesis,crystal structures,and antitumor activity of three new organotin carboxylates

Three new organotin(IV) carboxylates of composition [(R)₂Sn(O₂CC₆H₄C‐OC₆H₄CH₃)₂] 1 , [(R)₂Sn(O₂CC₆H₄COC₆H₄‐C₂H₅)₂]₂ 2 , and R₃SnO₂ CC₆H₄COC₆H₄CH₃ 3 , were obtained by reactions of (R)₂SnO [R = o‐tolyl] with 2‐(4‐methyl benzoyl) benzoic acid and 2‐(4‐ethyl benzoyl) benzoic acid, and reaction of Cy₃SnOH [Cy = cyclohexyl] with 2‐(4‐methyl benzoyl) benzoic acid, respectively. The complexes 1 , 2 and 3 have been characterized by elemental analysis, infrared (IR), ¹HNMR, and X‐ray crystallography diffraction analyses. The complex 1 has two folded symmetrical structure; the tin atom in 1 is found to adopt a distorted toward skew‐trapezoidal bipyramidal geometry. Molecular structure of the complex 2 is centrosymmetric, and the internal tin atom is five‐coordinated and is in distorted trigonal bipyramidal geometry. The crystal structure of the complex 3 is found to exhibit distorted tetrahedral geometry. Pilot studies have indicated that the complexes 1 and 2 have shown good antitumor activities. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:304–313, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20614     

关于Hadamard定理的一个数值方法

对超弹性材料静力稳定性问题的Hadamard定理,利用Hadamard不等式中一些主子式是齐次函数的特点,引入球坐标系,将这些主子式正定性的判别转化为判别一个初等的二元函数在一个矩形区域上不小于零的问题．对于一个具体问题,只要平衡解的位移给出,则可判别超弹性体中任一点是否满足Hadamard不等式．因此,这种数值方法可以用于分析各种具体问题．该文还给出超弹性材料稳定性分析的一个算例．     

980 nm Yb-doped double-clad photonic crystal fiber amplifier and its frequency doubling

In this paper, we report on a large-mode-area double-clad 980 nm Yb-doped photonic crystal fiber (PCF) amplifier. In the experiment, an output power of 1.21 W at 980 nm with 2.5 nm bandwidth has been yielded when the PCF length was 40 cm. Through frequency doubling the 980 nm amplified laser with a BIBO crystal, an output power of 51 mW at 490 nm has been generated.     

Dynamic behavior monitoring and damage evaluation for arch bridge suspender using GFRP optical fiber Bragg grating sensors

Suspenders, as the main bearing components in an arch bridge, can only manage to serve for about tens of years, or even a few years due to the influences of corrosion and fatigue load. This paper proposes a method of testing the suspender dynamic behavior with optical fiber Bragg grating sensors embedded in the glass fiber reinforced polymer (GFRP–OFBGS). Firstly, layout method of FRP–OFBGS among the suspender and protection technology are studied, and the self-monitoring smart suspender is developed. Secondly, stretching experiments were carried out on the smart suspender. The test experimental results demonstrated that the whole procedure of the stretching test can be perfectly monitored. Finally, the self-monitoring smart suspender successfully was applied in Ebian Bridge to monitor the strain history of suspenders under traffic load, and traffic effect to suspenders with various lengths and to different steel strands of a single suspender. Based on the monitoring data, the arch bridge suspenders fatigue damage dynamic evaluation methods and calculation results were given. The field monitoring results demonstrated that, the self-monitoring smart suspender mentioned in this paper is capable of monitoring suspender dynamic response and possible fatigue damages.     

Magneto-optical fiber sensor based on magnetic fluid

A novel magnetic field fiber sensor based on magnetic fluid is proposed. The sensor is configured as a Sagnac interferometer structure with a magnetic fluid film and a section of polarization maintaining fiber inserted into the fiber loop to produce a sinusoidal interference spectrum for measurement. The output interference spectrum is shifted as the change of the applied magnetic field strength with a sensitivity of 16.7 pm/Oe and a resolution of 0.60 Oe. The output optical power is varied with the change of the applied magnetic field strength with a sensitivity of 0.3998 dB/Oe.     

A note on lower bound of centered L2-discrepancy on combined designs

This note provides a theoretical justification of optimal foldover plans in terms of uniformity. A new lower bound of the centered L ₂-discrepancy values of combined designs is obtained, which can be used as a benchmark for searching optimal foldover plans. Our numerical results show that this lower bound is sharper than existing results when more factors reverse the signs in the initial design.