Field emission from the structure of well-aligned TiO2/Ti nanotube arrays

Well-aligned TiO2/Ti nanotube arrays were synthesized by anodic oxidation of titanium foil in 0.5 wt.% HF in various anoclization voltages. The images of filed emission scanning electron microscopy indicate that the nanotubes structure parameters, such as diameter, wall thickness and density, can be controlled by adjusting the anoclization voltage. The peaks at 25.3 degrees and 48.0 degrees of X-ray diffraction pattern illuminate that the TiO2 nanotube arrays annealed at 500 degrees C are mainly in anatase phase. The filed emission (FE) properties of the samples were investigated. A turn-on electric field 7.8 V/mu m, a field enhancement factors approximately 870 and a highest FE current density 3.4 mA/cm(2) were obtained. The emission current (2.3 mA/cm(2) at 18.8 V/mu m) was quite stable within 480 min. The results show that the FE properties of TiO2/Ti have much relation to the structure parameters.

Synthesis and field emission of diamond-like carbon nanorods on TiO2/Ti nanotube arrays

Highly ordered TiO2/Ti nanotube arrays were fabricated by anodic oxidation method in 0.5 wt% HF. Using prepared TiO2/Ti nanotube arrays deposited Ni nanoparticles as substrate, high quality diamond-like carbon nanorods (DLCNRs) were synthesized by a conventional method of chemical vapor deposition at 750 degrees C in nitrogen atmosphere. DLCNRs were analyzed by filed emission scanning electron microscopy and Raman spectrometer. It is very interesting that DLCNRs possess pagoda shape with the length of 3-10 mu m. Raman spectra show two strong peaks about 1332 cm (1) and 1598 cm (1), indicating the formation of diamond-like carbon. The field emission measurements suggest that DLCNRs/TiO2/Ti has excellent field emission properties, a low turn-on field about 3.0 V/mu m, no evident decay at 3.4 mA/cm(2) in 480 min. (C) 2009 Elsevier B. V. All rights reserved.

Studies on the exotic structure of Al-23

The longitudinal momentum distribution (P-//) of fragments after one-proton removal from Al-23 and reaction cross sections (sigma(R)) for Al-23,Al-24 on carbon target at 74A MeV have been measured simultaneously. An enhancement in sigma(R) is observed for Al-23 compaxed with Al-24. The full width at half maximum of the P-// distribution for Mg-22 fragments has been determined to be 232 +/- 28 MeV/c. Analysis of P-// using the Few-Body Glauber Model indicates a dominant d-wave configuration for the valence proton in the ground state of Al-23. The exotic structure in Al-23 is discussed.

Isospin effect of projectile fragment yields

Isospin asymmetry is very important in the nuclear equation of state (EOS), isotope yield from the projectile fragments can give information of the reaction process. In this paper projectile fragment yields are measured in the collision Ar-36,Ar-40 + Ni-64 at incident energy 50 MeV/u with different isospin asymmetry project Ar-36,Ar-40, data analysis, particle identification and event selection are described. Isotope yields are compared in these two reactions, and axe also compared with the empirical parametrization of fragmentation cross-section calculated by EPAX.

Field emission from TiO2/Ti nanotube arrays with different morphologies

Well-aligned TiO2/Ti nanotube arrays were electrochemically formed in a HF solution for different anodization times. Field emission scanning electron microscopy (FE-SEM) images reveal that anodization time had a great influence on the morphology of TiO2/Ti nanotube arrays. The composition of resulting nanotubes was analyzed by X-ray photoelectron spectroscopy (XPS). Field emission properties of the prepared samples with different morphologies were investigated by the Fowler-Nordheim (F-N) theory. The results indicate that the morphology can affect field emission behaviors. TiO2/Ti nanotube arrays with clear, uniform, and short nanotubes display moderate field emission properties, and have the better turn-on field of 4.6 V/mu m and good field emission stability. (C) 2010 Elsevier B.V. All rights reserved.

PROJECTILE FRAGMENTATION OF Ar-36,Ar-40 INDUCED REACTIONS

Fragment yields for Z >= 5 from projectile fragmentation using primary beams of Ar-36,Ar-40 at 50 MeV/nucleon on Ni-64 target have been measured in RIBLL fragment separator. We compare the fragment cross sections with the predictions of the empirical EPAX parametrization of fragmentation cross-sections and Statistical Abration-Ablation model (SAA) by considering the RIBLL separator transmission rate. Isotope yield ratios between these two reactions were calculated and isoscaling parameters alpha and beta are extracted, their dependences on fragment atomic number Z and neutron number N were presented.

不同温度下氦离子辐照316L不锈钢氦泡形成的研究

本工作用2.5MeV的~4He~+分别在室温、500 ℃和600 ℃对经过固溶和冷扎处理的316L不锈钢进行了辐照，辐照剂量为2.7 × 10~(17)ions／cm~2，剂量率在3.6 × 10~(11) - 2.6 × 10~(12)ions／cm~2·s之间。用扫描电镜（SEM）观察样品表面形貌的变化，发现600 ℃时，辐照样品的表面出现许多形状不规则的小坑和类似颗粒的东西。用透射电镜（TEM）结合横截面制样技术观察样品内部氦泡的特征，发现室温和500 ℃下氦泡呈圆形，在600 ℃下氦泡呈多面体形状。温度由室温上升到500 ℃，氦泡的大小、数密度的变化比较小，当温度上升到600 ℃，氦泡直径迅速增大、数密度减小，估计在500 ℃和600 ℃之间存在一个氦泡演变转折点。对室温和600 ℃辐照样品中氦泡大小、数密度随深度的变化做定量测量，发现室温下氦泡的形核、长大主要依赖于氦原子的沉积浓度，而600 ℃下氦泡的形核、长大主要依赖于氦引进过程中产生的离位损伤（dpa）。另外，不同晶界处氦泡的特征也不同，大角晶界处氦泡优先生长；小角晶界处不存在氦泡的优先生长。在同一温度下，CW样品中氦泡的数密度比SA样品中氦泡的数密度大、直径小，对应氦泡产生的肿胀比SA样品的小

Theoretical study on the mechanism of the reaction of CH4+MgO

The reactions of (1) CH4 + MgO --> MgOH. + CH3. and (2) CH4 + MgO --> Mg + CH3OH have been studied on the singlet spin state potential energy surface at the MP2/6-311+G(2d,2p) level. These two reaction channels, both involving intermediates and transition states, have been rationalized by the structures of the species involved, natural bond orbital (NBO), and vibrational frequency analysis. We have considered two initial interacting models between CH4 and MgO: a collinear C-H approach to the O end of the MgO forming the MgOCH4 complex with C-3nu symmetry and three hydrogen atoms of the methane point to the Mg end of the MgO forming the OMgCH4 complex with C-1 symmetry. The calculations predict that reactions 1 and 2 are exothermic by 39.8 and 86.5 kJ mol(-1), respectively. Also, the former reaction proceeds more easily than the latter, and the complex HOMgCH3 is energetically preferred in the reaction of MgO + CH4.

实时数据流系统降载方法研究

随着信息技术的发展，出现了大量的数据流应用，如传感器数据处理、网络监控、金融数据分析等。在这些应用中，数据是一种连续、时变、有序、无限的序列，查询大多数都是采用连续查询方式。这种数据和查询的连续性对管理系统的资源需求很大。当系统资源不能满足查询处理要求，即查询处理任务超过系统的最大处理能力，用户的查询将得不到及时、正确地处理。同时，如果查询处理时间超过了查询截止期需求，查询结果就没有意义，甚至会造成灾难性后果。目前，很多研究都集中于数据流系统的降载，对支持实时查询处理的实时数据流系统降载的研究比较少。 本论文主要研究支持实时查询处理的实时数据流管理系统中的降载方法，主要包括如下三个方面：随机降载方法、语义降载方法与共享滑动窗口连接操作的降载方法。最后，通过实时数据流管理系统测试平台验证了所提出算法在提高系统吞吐量与降低截止期错失率方面表现出良好的性能。 针对实时数据流应用需求，提出了一种适合实时查询的数据流处理框架结构RT-DSPA和相应的多层过载处理策略MLOHS，为降载方法的研究提供一个框架基础。RT-DSPA分为用户层、DSMS层以及数据源层多个功能模块，具有多层性、可扩展性、健壮性以及可配置性的特点。 在随机降载方面，提出了一种基于数据流流速的负载估计算法；在实时数据流处理框架与负载估计算法的基础上，提出了一种截止期敏感的随机降载算法RLS-EDA。由于系统负载经常波动较大，该算法利用截止期的特点，使用暂存所丢弃元组技术充分地利用CPU空闲资源，使降载执行后系统的吞吐量得到提高，进而尽可能地降低查询截止期错失率；最后，讨论了降载过程中的队列维护策略、含共享操作符查询网络中的降载位置以及降载操作符插入查询网络的算法。实验结果表明，在系统负载波动较大的情况下，RLS-EDA算法表现出良好的性能。 在充分了解数据流及查询特征的情况下，语义降载表现出更好的降载效果。为明确语义降载时使用到的语义，提出了元组价值、价值等级的概念，给出价值等级划分时发生冲突的解决方法。设计了适合实时数据流管理系统的价值等级–执行开销优先级表和截止期–价值密度优先级表，其在确定优先级时可考虑多维因素。基于这两种优先级表设计，提出了相对应的语义降载算法SLS-PT-VD&EC和SLS-PT-D&TVD。基于优先级表的语义降载算法能够灵活地满足用户的不同需求，同时提高系统降载时的性能。 最后，针对共享滑动窗口连接操作符的过载情况，利用查询截止期的特点，提出了一种基于暂存丢弃元组技术的共享滑动窗口连接的降载算法LS-SJRT；为减小LS-SJRT算法的降载开销，提出了一种改进的基于调节滑动窗口宽度的共享滑动窗口连接降载算法LS-SJRT-CW。实验结果显示这两种算法在共享连接操作符过载时都能够表现出较好的性能。

Blends of Polypropylene and Syndiotactic 1,2-Polybutadiene: Morphology, Crystallization Behaviors and Mechanical Properties

Morphologies, crystallization behavior and mechanical properties of polypropylene(PP)/syndiotactic 1,2-polybutadiene(s-1,2 PB) blends were investigated. Morphology observation shows the well dispersed domains of s-1,2 PB in PP matrix with the rather small domain sizes from 0.1 to 0.5 mu m when the s-1,2 PB content increases from 5% to 20% (mass fraction) in the blends, and the phase structure tends to become co-continuous as s-1,2 PB content further increases.

Vulcanization of polybutadiene latex induced by Co-60 gamma radiation

Polybutadiene latex (PBL) vulcanization induced by Co-60 radiation and the influence of dose on crosslinking were investigated. Morphology and particle size distribution were examined by AFM and a particle size analyzer. The casting films were characterized for their swelling and mechanical properties as a function of dose.

Novel temperature- and pH-responsive graft copolymers composed of poly(L-glutamic acid) and poly(N-isopropylacrylamide)

A series of novel temperature- and pH-responsive graft copolymers, poly(L-glutamic acid)-g-poly(N-isopropylacrylamide), were synthesized by coupling amino-semitelechelic poly(N-isopropylacrylamide) with N-hydroxysuccinimide-activated poly(L-glutamic acid). The graft copolymers and their precursors were characterized, by ESI-FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (H-1 NMR). The phase-transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering.

Novel pH- and temperature-responsive block copolymers with tunable pH-responsive range

A series of novel pH- and temperature-responsive diblock copolymers composed of poly(N-isopropylacrylamide) (PNIPAM) and poly[(L-glutamic acid)-co-(gamma-benzyl L-glutamate)] [P(GA-co-BLG)] were prepared. The influence of hydrophobic benzyl groups on the phase transition of the copolymers was studied for the first time. With increasing BLG content in P(GA-co-BLG) block, the thermal phase transition of the diblock copolymer became sharper at a designated pH and the critical curve of phase diagram of the diblock copolymer shifted to a higher pH region.

Improved Melting Strength of Polypropylene by Reactive Compounding With Ultrafine Full-Vulcanized Polybutadiene Rubber (UFBR) Particles

Ultrafine full-vulcanized polybutadiene rubber (UFBR) in particle sizes of ca. 50-100 nm has been used for modifying mechanical and processing performances of polypropylene (PP), and PP-g-maleic anhydride (PP-MA) has been used as a compatibilizer for enhancing the interfacial adhesion between the two components. The results show that PP/UFBR possesses rheological behaviors such as highly branched PP when UFBR content in blends reaches 10 wt%, while in contrast, the much low content of UFBR combining small amount of PP-MA endows the material with rheological characteristics of high melt strength materials like highly branched PP.

Novel Method for Preparation of Polypropylene Blends with High Melt Strength by Reactive Compounding

Ultrafine full-vulcanized polybutadiene rubber(UFBR) with particle sizes of ca. 50-100 nm were used for modifying mechanical and processing performances of polypropylene(PP) with PP-g-maleic anhydride(PP-g-MA) as a compatibilizer for enhancing the interfacial adhesion between the two components. The morphology, dynamical rheology response and mechanical properties of the blends were characterized by means of SEM, rheometer and tensile test, respectively.