联合概率密度函数的一个性质

本文引进n元实变函数的广义n阶导数,证明:若n元分布函数F(x_1,…,x_n)有概率密度函数f(x_1,…,x_n)且f(x_1,…,x_n在点(x_1,…,x_n)处连续,则f(x_1,…,x_n)等于F(x_1,…,x_n)在点(x_1,…,x_n)处的广义n阶导数,但当n≥2时,f(x_1,…,x_n)并不总等于F(x_1,…,x_n)在点(x_1,…,x_n)处的n阶混合偏导数?~nF(x_1,…,x_n)/?x_1…?x_n     

CRYSTAL STRUCTURE AND MORPHOLOGY OF NASCENT SAMPLES OF SYMMETRIC AROMATIC POLYESTERS——Ⅱ. POLY(p-PHENYLENE 2,6-NAPHTHALATE)

Confined thin film melt polymerization (CTFMP) of naphthalene chloride/hydroquinone (NCMQ, 1/1, molar)mixtures at polymerization temperatures (T_p) below ca. 300℃ resulted in relatively thick, elongated crystals. Polymerizationof NC/HQ above 300℃ between glass yielded well-formed lamellar crystals ca. 100 A thick. Phase Ⅰ and Ⅱ [001] EDpatterns were obtained for all T_p, the relative amount of phase Ⅰ increasing with T_p. Polymerization of naphthalenedicarboxylic acid/hydroquinione diacetate 1/1 mixtures at high T_p also yielded lamellar crystals that "curled up" off of thesubstrate. When the high temperature CTFMP polymerization was conducted between mica, aggregates of lamellae on-edgedeveloped but epitaxial growth did not occur. Epitaxial growth of lamellae between mica could be obtained, however, byconfined thin film solution polymerization, with both of the latter samples yielding apparently related ED patterns from adifferent unit cell than phase Ⅰ or Ⅱ. Fiber patterns, obtained from sheared samples, indicated considerably greater crystaldisorder than in the nascent crystals. Refinement of the phase Ⅰ unit cell parameters, based on the [001] and [01 1] EDpatterns, with modeling based on Cerius~2, suggests a monoclinic phase Ⅰ unit cell with a = 7.76, b = 5.71, c = 14.99 A, α = γ= 90°, β= 99.7°, ρ = 1.47 g/cm~3, space group P12_1/al.     

碰撞问题浅谈

碰撞是一个重要的物理模型，但同学们对此模型的认识和理解有些困难，下面对此问题进行讨论．     

Generation of high energy and good beam quality pulses with a master oscillator power amplifier

A high efficiency and high peak power laser system with short-pulse and good beam quality has been demonstrated by using a master oscillator power amplifier with two-pass amplification configuration. The master oscillator, end-pumped with a fiber-coupled laser diode array, provides low power but excellent beam quality pulses, and the amplifier boosts the pulse energy by orders without significant beam quality degradation. Short pulses of 8.5 ns with energy up to 130 mJ and approximately diffraction limited beam quality have been demonstrated.     

原子核的单粒子共振态

采用基于相对论平均场的耦合常数解析延拓方法研究球形核的单粒子共振态.具体计算了Zr同位素链中巨晕核的核芯核122Zr阈值附近的中子共振态的能量、宽度和波函数,其结果同相应的散射相移法的结果一致. Using analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean field (RMF) theory, the energies, widths and wave functions for single-particle resonant states close to the continuum threshold are evaluated. Predictions are also compared with corresponding results obtained by the scattering phase shift method.     

热处理对V-4Ti合金氦的滞留与热解吸行为的影响

钒合金由于其低中子诱导的放射性和良好的高温性能被认为是未来聚变堆很有希望的第一壁和结构材料。因为氦可以通过放电清洗和中子嬗变产生，氦的滞留与热释放行为将是钒合金在聚变堆应用的重要课题。A．V．Veen领导的研究小组用1keV的氦离子注入到10^13-10^14He／cm^2的剂量研究了钒合金的氦俘获和热解吸机理以及预退火处理的影响。两群热解吸峰被发现，他们认为一个对应于氦，空位一杂质链，另一个对应于氦，带有钒合金原有的缺陷，如细小的析出物所俘获。既然钒合金原有的缺陷与退火处理有关，热处理对氦在钒合金中的滞留的影响是可以预期的，并且已被实验所证实。     

Mid—Infrared Optical Parametric Oscillator Based on All—Solid—State—Pumped Periodically Poled LiNbO

We report the tunable mid-infrared generation with a periodically poled LinbO3(PPLN).Using an all-solid-state pumped Nd:YVO4 laser as the pump source and a PPLN nonlinear crystal with grating periods of 28.2-30.8μm,we have achieved wavelength conversion in the 2.90-4.05μm spectral range by period tuning.The use of confocal cavity design has brought a compact,all-solid-state configuration with an average output powers of idler up to -200mW.The maximum power of 277mW was obtained at the wavelength of 3.35um.     

高分辨电感耦合等离子质谱测定黄连中的微量元素

文章采用高分辨电感耦合等离子体质谱(HR-ICP-MS)的方法,测定了中草药中四种黄连——味连、雅连、马尾连和胡黄连中的微量元素。结果表明:在所有16种稀土元素中,La,Ce,Nd,Gd,Sm,Sc含量较高,胡黄连的稀土总量为5.18μg·g~(-1),是所有四种黄连的最高者,其次是雅连和马尾连,最低的是味连(1.26μg·g~(-1))。而对于与清热解毒有关的金属无素如Mg,Mn,Zn,Ca和Fe元素,雅连中Mg,Mn,Zn的含量最高。高Fe和Ca的含量存在于马尾连和胡连之中。在测定不同提取方法的提取物中发现,只有部分的稀土元素能被醇和水所提取,它们分别是31.6％和4.1％。清热解毒元素的提取率明显高于稀土元素。     

Aligned ZnO Nanofibre Array Prepared by Vapour Transport in Air

An aligned zinc oxide nanofibre array has been fabricated by heating the mixture of ZnO, Ga2Oa, and graphite powders in atmosphere. The ZnO nanofibre showed a uniform size of about 150nm in diameter and 50μm in length. The nanofibres grew predominantly along one direction. Both x-ray diffraction (XRD) and Raman shift spectra show that the product is composed of ZnO with the typical hexagonal structure. The good crystallinity of these ZnO nanofibres has been verified by photoluminescence spectra with strong UV emission at 287nm and weak green band emission observed at room temperature. The component of the product was analysed by XRD,Raman shift spectrum, x-ray energy dispersion (EDX) and x-ray photoelectronic energy spectroscopy (XPS). The growth process and the characteristics can be interpreted by vapour-liquid-solid mechanism.     

基于Delaunay三角法的电压门控钾离子通道的分类和拓扑结构识别

本文构建了一个Delaunay模型对电压门控钾离子(Kv)通道进行预测。该方法通过建立一系列带有隐含变量的单纯形来分类电压门控钾离子通道,然后通过未知序列在主成分空间里面的投影来预测结构。结果表明该模型无论是在分类和结构预测上均可以得到很好的结果。