原子激发态在高频强激光作用下的光电离研究

本文通过数值求解动量空间的三维含时薛定谔方程, 研究了原子高激发态在高频激光脉冲作用下, 在电离阈值附近的光电子能谱和两维动量角分布. 研究结果表明: 在该能量范围内, 单光子电离过程的贡献是最主要的. 体系初态的主量子数可以由光电子能谱峰值的位置来确定; 体系初态的角量子数可以通过光电子的两维动量角度分布确定. 在比较宽泛的参数范围内, 这一规律不随入射激光的强度和脉冲时间宽度的改变而改变, 因此原则上可以利用它对原子的初态进行识别. 此外, 还研究了体系的初态为相干叠加态, 光电子动量谱随着叠加态相对相位的变化规律. 关键词： 阈上电离 激发态 高频激光脉冲 两维动量角度分布     

近玻尔速度Ne2+离子穿过碳膜引起的电子发射

本文测量了入射能为2–25 keV/u的Ne²⁺离子穿过不同厚度碳膜诱导的前向、后向 (分别对应出射表面和入射表面) 电子发射产额. 实验中通过改变炮弹离子的能量, 系统的研究了势能沉积、电子能损以及反冲原子对前向、后向电子发射产额的贡献. 结果表明, 离子的势能沉积只对后向电子发射有贡献, 前向、后向电子发射产额分别与Ne²⁺离子在薄膜出射、入射表面的电子能损近似成正比关系, 其中电子能损很低 (对应于离子能量很低) 的时候, 反冲原子对电子发射的贡献不能忽略. 关键词： 近玻尔速度 电子发射 电子能损 反冲原子     

TiO2 Nanotube Array/Monolayer Graphene Film Schottky Junction Ultraviolet Light Photodetectors

Schottky junctions made from a titanium dioxide nanotube (TiO₂NT) array in contact with a monolayer graphene (MLG) film are fabricated and utilized for UV light detection. The TiO₂NT array is synthesized by the anodization and the MLG through a simple chemical vapor deposition process. Photoconductive analysis shows that the fabricated Schottky junction photodetector (PD) is sensitive to UV light illumination with good stability and reproducibility. The corresponding responsivity (R), photoconductive gain (G), and detectivity (D*) are calculated to be 15 A W^?1, 51, and 1.5 × 10¹² cm Hz^1/2 W^?1, respectively. It is observed that the fabricated PD exhibits spectral sensitivity and a simple power‐law dependence on light intensity. Moreover, the height of the Schottky junction diode is derived to be 0.59 V by using a low temperature I–V measurement. Finally, the working mechanism of the TiO₂NT array/MLG film Schottky junction PD is elucidated.     

含磁控和荷控两种忆阻器的混沌电路设计与仿真

利用惠普实验室荷控和磁控两种忆阻器模型设计了一个五阶混沌电路. 数值仿真结果表明该电路在参数变化情况下能产生Hopf分岔和反倍周期分岔两种分岔行为,并能产生双涡卷、单涡卷、周期态等不同相轨道. 为了验证电路的混沌行为,利用基本元器件设计了惠普实验室荷控和磁控忆阻器模拟器,并将其应用到对所设计电路中进行Pspice仿真,电路仿真结果验证了理论分析的正确性. 关键词： 混沌电路 HP忆阻器 模拟器 Pspice仿真     

周期性纳米洞内边缘氧饱和石墨烯纳米带的电子特性

利用基于密度泛函理论的第一性原理方法,研究了内边缘氧饱和的周期性凿洞石墨烯纳米带（G NR）的电子特性. 研究结果表明：对于凿洞锯齿形石墨烯纳米带（ZGNRs）,在非磁性态时不仅始终为金属,且金属性明显增强;反铁磁态（AFM）时为半导体的ZGNR,凿洞后可能成为金属;但铁磁态（FM）为金属的ZGNR,凿洞后一般变为半导体或半金属. 而对于凿洞的扶手椅形石墨烯（AGNRs）,其带隙会明显增加. 深入分析发现：这是由于氧原子对石墨烯纳米带边的电子特性有重要的影响,以及颈次级纳米带（NSNR）及边缘次级纳米带（ESNR）的不同宽度及边缘形状（锯齿或扶手椅形）能呈现出不同的量子限域效应. 这些研究对于发展纳米电子器件有重要的意义. 关键词： 石墨烯纳米带 纳米洞 内边缘氧饱和 电子特性     

Thermal and Thermo-Oxidative Degradation of Biodegradable Poly(Ester Urethane) Containing Poly(L-Lactic Acid) and Poly(Butylene Succinate) Blocks

A novel biodegradable poly(ester urethane; PEU) was synthesized by chain extension reaction of dihydroxylated poly(L-lactic acid; PLLA) and poly(butylene succinate; PBS) using diisocyanate as a chain extender. The kinetics of thermal and thermo-oxidative degradation of PEU containing PLLA and PBS blocks were studied by thermogravimetric analysis (TGA). TGA results indicated that PEU was more stable in air than in nitrogen and went through a two-stage degradation process irrespective of the experimental atmosphere. Activation energy of each stage was calculated by means of Kissinger, Kim-Park, Friedman, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose methods. For the first stage, the activation energy value obtained in air was slightly higher than the corresponding value obtained in nitrogen; and for the second stage, the activation energy showed a much higher value in air than in nitrogen. The Coats-Redfern method was employed to study the degradation mechanism of each stage. The results indicated that the degradation of the first stage follows the P3/4 mechanism irrespective of the experimental atmosphere; the degradation of the second stage of PEU obeys the P1 mechanism in nitrogen while P3/2 in air.     

Graft Polymerization of Methyl Methacrylate- Acrylonitrile onto Poly(ethene-co-1-butene) and Its Toughening Effect on SAN Resin

Poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile (PEB-g-MAN) was prepared by suspension grafting copolymerization of methyl methacrylate (MMA) and acrylonitrile(AN) onto PEB. PEB-g-MAN/SAN resin blends (ABMS) were prepared by blending PEB-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of AN/(MMA+AN) feed ratio (f_AN), PEB/(PEB+MMA+AN) feed ratio (f_PEB) and benzoyl peroxide (BPO) dosage on the monomer conversion ratio (CR), rubber's grafting ratio (GR), grafting efficiency (GE) of the copolymerization and the toughening effect of PEB-g-MAN on the SAN resin were investigated. FTIR quantitative analysis showed that when the weight percent of AN unit in the unextracted product was 21.5 wt% with f_AN of 25 wt%, the toughening effect of unextracted PEB-g-MAN on SAN resin was the highest. Gel permeation chromatography (GPC) analysis showed that when f_AN was 25 wt%, the grafted copolymer had the lowest molecular weight and ABMS had highest toughness. Transmission electron microscopy (TEM) analysis showed that the highest toughness occurred when the phase structure of ABMS was cocontinuous with f_AN of 25 wt%. When f_AN was 25 wt% PEB-g-MAN domains have numerous small SAN domains in them, which was occlusion structure. Scanning electron microscopy (SEM) analysis indicated that the ABMS fracture surfaces had plastic flow visible, which looked like a craze fibers morphology, for the sample with highest impact strength (f_AN = 25 wt%). Dynamic mechanical thermal analysis (DMA) showed that the miscibility of the PEB phase and SAN phase improved after graft copolymerization of MMA and AN onto PEB.     

Preparation and Properties of Polyethylene Terephthalate (PET)/Near Infrared Reflective Pigment (NIR) Composites

A near infrared reflective (NIR, nickel antimony titanium yellow rutile) pigment filler was incorporated into a polyethylene terephthalate (PET) matrix via a melt blending approach to increase the infrared reflection of PET and limit the thermal heat accumulation in light of environmental and energy conservation concerns. Two different types of surface modifiers, polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB), were used to modify the NIR surface, as NIR–PEG and NIR–CTAB fillers, to investigate the surface modification effect. Fourier transform infrared spectroscopy (FTIR), a Zetasizer, and electron spectroscopy for chemical analysis (ESCA) results suggested a successful adsorption of the organic modifiers onto the NIR surface. Thermogravimetric analysis indicated a higher adsorption degree for the CTAB modifier than the PEG modifier due to the electronic interaction between CTAB and NIR. The thermal crystallization temperature (T_c) for neat NIR-filled samples decreased with increasing NIR content within the PET matrix at first, up to 9°C, but then tended to increase again up to a measurable difference of 6°C with respect to pure PEG, indicating the promotion of the crystallization kinetics of the neat NIR within the PET matrix. On the other hand, a decrease in T_c for all NIR-CTAB or NIR-PEG loadings was found, with the depression close to 10°C for all NIR-CTAB samples regardless of the loading. CTAB modified NIR gave the highest improvement in tensile strength and strain at break in comparison with NIR and NIR-PEG filled samples. The near infrared reflection values of modified PET were higher than those of neat PET. The reflection values appeared to be the highest for some concentrations of the NIR-CTAB filled samples, but were of similar orders of magnitude with those for NIR or NIR-PEG filled samples.     

Further results on the euler and Genocchi numbers

Summary We characterize the ordinary generating functions of the Genocchi and median Genocchi numbers as unique solutions of some functional equations and give a direct algebraic proof of several continued fraction expansions for these functions. New relations between these numbers are also obtained.     

可能性理论的推广方法及合理性研究

本文通过引入二维可能性分布函数的概念，将可能性测度推广到二维的情形。并给出了二维可能性测度的一些重要性质。文中还重点证明了该推广方法的合理性。