北半球环流系统季节内及年际以上振荡信号的信息传输

利用NCEP/NCAR月平均高度场再分析资料,分别提取季节内和年际以上振荡的基本特征和形式,运用信息传输理论分析这两种振荡信号的信息在低纬度与中高纬度间的传输.发现季节内振荡信号信息损失率较年际以上的偏大,且在特定地区这两种振荡信号的信息具有反向传输的特征;空间传输的水平分布上,两种振荡信号均表现为纬向上低纬度信息损失率大且海陆分布差异显著;空间传输的垂直分布上,年际以上振荡信号的低纬度高空信息损失率较大,中高纬度从对流层至平流层底信息损失率都较小,而季节内振荡信号则是低空信息损失率大,高空信息损失率小. 关键词： 滤波 高度场 信息损失率     

铕与4-(4-吡啶甲酰基)苯甲酸配合物的合成与荧光性能研究

以Eu3+为中心离子,4-(4-吡啶甲酰基)苯甲酸(HPFBA)、1,10-菲罗啉(Phen)和三苯基氧膦(TPPO)为配体,合成了新型配合物Eu(PFBA)3(H2O)4,Eu(PFBA)3Phen(H2O)3和Eu(PFBA)3TPPO(H2O)3(PFBA=4-(4-吡啶甲酰基)苯甲酸根).红外光谱表明,形成配合...     

Single- and multi-shot laser-induced damages of Ta_2O_5/SiO_2 dielectric mirrors at 1064 nm

Ta2O5/SiO2 dielectric mirrors deposited by ion beam sputtering (IBS) are studied. The multi-shot laserinduced damage threshold (LIDT) and its dependence on the number of shots are investigated, after which we find that the multi-shot LIDT is lower than that of single-shot. The accumulation effects of defects play an important role in the multi-shot laser damage. A simple model, which includes the conduction band electron production vsa multiphoton and impact ionizations, is presented to explain the experimental phenomena.     

Thermal resistance matrix representation of thermal effects and thermal design in multi-finger power heterojunction bipolar transistors

The thermal resistance matrix including self-heating thermal resistance and thermal coupling resistance is presented to describe the thermal effects of multi-finger power heterojunction bipolar transistors. The dependence of thermal resistance matrix on finger spacing is also investigated. It is shown that both self-heating thermal resistance and thermal coupling resistance are lowered by increasing the finger spacing, in which the downward dissipated heat path is widened and the heat flow from adjacent fingers is effectively suppressed. The decrease of self-heating thermal resistance and thermal coupling resistance is helpful for improving the thermal stability of power devices. Furthermore, with the aid of the thermal resistance matrix, a 10-finger power heterojunction bipolar transistor (HBT) with non-uniform finger spacing is designed for high thermal stability. The optimized structure can effectively lower the peak temperature while maintaining a uniformity of the temperature profile at various biases and thus the device effectively may operate at a higher power level.     

Scaffold-directed and traceless synthesis of tricyclic quinoxalinone imidazoles under microwave irradiation

Traceless synthesis of 2-aminoimidazoquinoxalinones has been performed on soluble polymer support under open-vessel microwave dielectric heating. The reaction progression is monitored directly by the conventional proton NMR which indicated no release of the substrate from the support. Fmoc-deprotected amino acid polymer conjugates react with 1,5-difluoro-2,4-dinitro benzene to yield polymer bound dinitro fluoro amines, which are further substituted by various primary amines to yield PEG-immobilized dinitrodiamines. Simultaneous reduction of aromatic meta-dinitro group leads to the traceless release of 2-quinoxalinones, followed by N-hetero cyclization with various isothiocyanates in the presence of mercury(II)chloride to furnish 2-aminoimidazoquinolinone rings with three points of diversity at rapid pace.     

Methoxycarbonyl-terminated hyperbranched poly(amine-ester) as templates for synthesis of silver nanoparticles

Highly stable and spherical silver nanoparticles, stabilized by methoxycarbonyl-terminated hyperbranched poly(amine-ester) (HPAE-COOCH₃), were synthesized in water with reducing AgNO₃/HPAE-COOCH₃ using two methods, viz. NaBH₄ and ultraviolet irradiation. HPAE-COOCH₃ was found to play a key role in the formation of nanoparticles. UV–visible absorption, Transmission electron microscopic (TEM), and Fourier transform infrared spectroscopy (FT-IR) had been used to study the structure and characterization of the silver nanoparticles. The absorption peaks of the silver nanoparticles appear at ~420 nm in UV–visible absorption spectra; average particle size reduced by NaBH₄ is ~30 nm, which is ~10 and ~15 nm, respectively, when ultraviolet irradiation time is 12 and 24 h. FT-IR spectra confirm that there is strong interaction between silver nanoparticles and HPAE-COOCH₃. And silver nanoparticles/HPAE-COOCH₃ aqueous solution can keep stable for more than 3 months.     

Theoretical study of the dynamics for the H + Li H ( v = 0, j = 0) $\to$ H2 + Li reaction and its isotopic variants

Quasi-classical trajectory (QCT) method is carried out to calculate the dynamics of the H + LiH (v = 0, j = 0) ?\to H₂ + Li reaction and its isotopic variants based on the potential energy surface of the lowest ²A￠^2A' electronic state reported by Prudente et al. [Chem. Phys. Lett. 474, 18 (2009)]. The reaction cross-section, product rotational alignment parameter áP₂\langle P_2 ([(j￠)\vec]\vec{j'} ·\cdot [(k)\vec])?\vec{k})\rangle and one generalized polarization-dependent differential cross-section (2π/σ)(ds₀₀d\sigma_{00}/d w_t\omega_t) are calculated. We found that different collision energies and mass factors show driving influence on the process of the reactions and product molecules H₂ (HD, D₂) polarization distribution, and the trend of the isotopic effects in the high collision energy range is different to that in the low collision energy range. The calculations are also interpreted in relation to the features of the underlying potential energy surface. A comparison between the title reactions and a barrier-less reaction F + HBr ?\to FH + Br has been discussed in detail.     

光学元件群延迟的直接测量

提出了一种测量群延迟的新方法,利用白光干涉仪产生的光谱干涉,通过时间频率联合分析直接得出群延迟,减小了传统相位差分方法产生的误差,并通过测量结果减去系统背景,进一步提高了光学元件色散测量的准确度. 该方法适合于具有复杂色散光学元件群延迟和色散的准确测量,也适合于慢光器件群速度延迟的测量. 关键词： 色散测量 白光干涉 时间频率分析 超快激光     

双轴压缩下颗粒物质剪切带的形成与发展

本文采用离散元方法,研究了双轴压缩的颗粒体系在刚性边界约束下,局部剪切带的形成和发展过程,注重分析了细观的体积分数、配位数、颗粒旋转角度等参数以及力链结构形态的演变.并从颗粒体系jamming 相图中J点附近的边壁压强和配位数随体积分数的标度规律出发,分析了剪切带内外的体积分数和配位数的变化.结果表明:剪切带形成于颗粒体系的塑性变形开始阶段,此时体系发生剪胀,颗粒体积分数减小,颗粒体系抵抗旋转的能力降低,开始出现细小剪切带,随着轴向应变的继续,细小剪切带发生连接,最终导致贯穿性优势剪切带形成 关键词： 颗粒物质 力链 双轴压缩 剪切带