Preparation of fully cross‐linked CNBR/PP‐g‐GMA and CNBR/PP/PP‐g‐GMA thermoplastic elastomers and their morphology,structure and properties

Binary CNBR/PP‐g‐GMA and ternary CNBR/PP/PP‐g‐GMA thermoplastic elastomers were prepared by reactive blending carboxy nitrile rubber (CNBR) powder with nanometer dimension and polypropylene functionalized with glycidyl methacrylate (PP‐g‐GMA). Morphology observation by using an atomic force microscope (AFM) and TEM revealed that the size of CNBR dispersed phase in CNBR/PP‐g‐GMA binary blends was much smaller than that of the corresponding CNBR/PP binary blends. Thermal behavior of CNBR/PP‐g‐GMA and CNBR/PP blends was studied by DSC. Comparing with the plain PP‐g‐GMA, T_c of PP‐g‐GMA in CNBR/PP‐g‐GMA blends increased about 10 °C. Both thermodynamic and kinetic effects would influence the crystallization behavior of PP‐g‐GMA in CNBR/PP‐g‐GMA blends. At a fixed content of CNBR, the apparent viscosity of the blending system increased with increasing the content of PP‐g‐GMA. FTIR spectrum verified that the improvement of miscibility of CNBR and PP‐g‐GMA was originated from the reaction between carboxy end groups of CNBR and epoxy groups of GMA grafted onto PP molecular chains. Comparing with CNBR/PP blends, the tensile strength, stress at 100% strain, and elongation at break of CNBR/PP‐g‐GMA blends were greatly improved. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1042–1052, 2004     

Observation of signature inversion in the πh9/2?vi13/2 oblate band

High-spin states in ¹⁹⁰Tl have been studied via the ¹⁶⁰Gd(³⁵Cl, 5nγ) reaction. The level scheme, consisting of the πh _9/2⊗vi _13/2 oblate band and a cascade with character of single particle excitations, has been established. Spin values have been firmly assigned to the oblate band in ¹⁹⁰Tl, resulting in low-spin signature inversion in the πh _9/2⊗vi _13/2 oblate band for the first time. Based on the similarity of the level structure in doubly odd Tl nuclei, spin values for the oblate bands in ^192–200Tl should be re-assigned, and a consistent low-spin signature inversion has occurred in these oblate deformed nuclei. The low-spin signature inversion phenomena can be interpreted qualitatively by using the 2-quasiparticle plus rotor model including p-n residual interactions.     

电子束泵浦百焦耳级准分子激光实验研究

利用“闪光二号”相对论电子束加速器研制了百焦耳级ＸｅＣｌ和ＫｒＦ准分子激光器，激光器激活体积２４ｌ，输出口径２０×２０ｃｍ２，泵浦功率密度１．５～２．０ＭＷ／ｃｍ３。ＸｅＣｌ激光器最大能量１３６Ｊ，波长３０８ｎｍ，脉宽５０～１００ｎｓ，峰值功率１．５ＧＷ，采用虚共焦非稳腔技术，束散角达１．３ｍｒａｄ；ＫｒＦ激光最大能量１５７Ｊ，波长２４８ｎｍ，脉宽８０～１００ｎｓ，峰值功率２ＧＷ。     

A W-band Frequency Source with Low Spurs and Low Phase Noise

A W-band millimeter wave frequency source is developed by frequency multiplier chain and injection locking. The referenced crystal oscillator (CO) signal 120 MHz is multiplied 400 times to output 48 GHz signal. Then, it is used as a referenced source of fundamental-wave injection-locked harmonic Gunn oscillator with output power more than 10 mW at 96 GHz and spurious output less than −65 dBc. The measured phase noise is −97 and −105 dBc/Hz at 10 kHz and 200 kHz offset, respectively. At last, the influence of the flicker noise, provided by the frequency multipliers and amplifiers, is analyzed.     

XeCl激光触发气体开关的实验研究

通过实验研究了在自流工作状态下,XeCl准分子激光(λ=308nm,FWHM=21ns)对N_2和SF_6两种气体开关的触发特性。实验结果表明:(1)在p=0.1MPa,开关工作电压90％V_(SB)(V_(SB)为开关的自击穿电压)时,XeCl激光对N_2和SF_6两种气体开关的触发阈值约为10~8W/cm~2。(2)开关的触发延时和抖动随着激光能量和开关欠压比的增大而减小,当激光能量为33.8mJ,开关工作电压90％V_(SB)(V(SB)=36.5kV)时,充N_2开关的延时和抖动分别为85.5ns和400ps。相同欠压比下,SF_6气体开关(V_(SB)=52kV)的最小抖动度为2ns。(3)SF_6气体开关的触发延时与用T.H.Martin公式计算的结果一致。     

Investigation on microstructure and properties of CrAlN/AlON nanomultilayers

Artificially modulated CrAlN/AlON nanomultilayers were synthesized by direct current reactive magnetron sputtering. The microstructure and mechanical properties were evaluated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nano-indentation techniques. The crystallization of AlON layer and its influence on the mechanical property of the nanomultilayers were studied. The results revealed that, under the template effect of NaCl structural CrAlN layer, amorphous AlON was forced to crystallize and grew epitaxially with CrAlN layer when AlON layer thickness was below 0.9 nm, leading to an increase of hardness up to 32.8 GPa. With the further increase of the AlON layer thickness, AlON layer gradually transformed into amorphous structure and blocked epitaxial growth of the multilayers, resulting in the decrease of hardness. The effect of CrAlN layer thickness on hardness of CrAlN/AlON nanomultilayers was also investigated. With the decrease of CrAlN layer thickness, the hardness increased gradually. The maximum hardness was 34.7 GPa when CrAlN layer thickness of was 3.0 nm. The strengthen mechanism of CrAlN/AlON nanomultilayers was finally discussed.     

汉语语篇层级性对焦点声学表现的影响

采用实验语音学的方法,考察了语篇焦点的声学表现是否受到语篇修辞层级的调节.六位普通发音人朗读了32组实验材料,处于不同层级焦点词的时长、音域、高音点和低音点分别被提取出来做统计分析.结果发现,处于高层级的焦点词时长更长,音域更宽;同时,随着声调组合的变化,不同层级焦点词的高音点和低音点呈现不同的特征,具体体现在对于不含...     

音高和时长在语篇语句重音中的作用

本研究通过30篇自然叙事语篇,以韵律词为分析单位,对语篇中音高和时长在语句重音中的作用进行探讨,结果主要发现:(1)韵律词音域的相对宽窄对语句重音起着最主要的作用.(2)音高和时长在语句重音中的作用受到小句音域宽度和韵律词等级的交互影响.在正常韵律诃中,1级重音由音高和时长共同发挥作用来实现;2级重音主要靠音高起作用.在强化韵律词中,小句音域越窄,时长在语句重音中的作用越重要.(3)音高和时长之间的相关性主要受到韵律词强度的影响,在弱化、正常和强化韵律词中,音高和时长分别表现出普遍的正相关、不相关和负相关.     

高流强电子束在锥形SiO2毛细管中的导向效应

 研究了高流强电子束(1～10 μA)在单根锥形SiO₂毛细管中的导向效应,测量了出射电子的角分布,分析了入射能量对电子传输效率的影响。实验发现：出射电子呈高斯分布且时间稳定性好,随着入射能量增加,电子在毛细管中的传输效率降低,传输效率与入射能量呈负指数关系。实验结果与导向效应模型符合得很好。     

纳秒强激光诱导K9玻璃表面损伤实验

 使用脉宽约10 ns的Nd:YAG激光器,研究低加工缺陷条件下K9光学玻璃在单激光脉冲作用下的损伤形貌。利用软边光阑加长程衍射的方法实现光斑整形,利用微分干涉光学显微镜和扫描电镜对样品前后表面的损伤形貌进行观察和成像,对比研究了K9光学玻璃前后表面的损伤形貌,分析了损伤机制。研究结果显示：在红外纳秒激光辐照下,加工缺陷是K9光学玻璃产生初始损伤的主要诱因;前表面的损伤主要表现为微坑及高温等离子体产生的冲蚀变色和表面微裂纹;后表面出现了均匀的亚波长周期性光栅结构,这种周期性结构是后表面损伤增长的主要诱因。