Weibull modulus for diverse strength due to sample-specificity

By sample specificity it is meant that specimens with the same nominal material parameters and tested under the same environmental conditions may exhibit different behavior with diversified strength. Such an effect has been widely observed in the testing of material failure and is usually attributed to the heterogeneity of material at the mesoscopic level. The degree with which mesoscopic heterogeneity affects macroscopic failure is still not clear. Recently, the problem has been examined by making use of statistical ensemble evolution of dynamical system and the mesoscopic stress re-distribution model (SRD). Sample specificity was observed for non-global mean stress field models, such as the duster mean field model, stress concentration at tip of microdamage, etc. Certain heterogeneity of microdamage could be sensitive to particular SRD leading to domino type of coalescence. Such an effect could start from the microdamage heterogeneity and then be magnified to other scale levels. This trans-scale sensitivity is the origin of sample specificity. The sample specificity leads to a failure probability Phi (N) with a transitional region 0 < (N) < 1, so that globally stable and catastrophic modes could co-exist. It is found that the scatter in strength can fit the Weibull distribution very well. Hence, the Weibull modulus is indicative of sample specificity. Numerical results obtained from the SRD for different non-global mean stress fields show that Weibull modulus increases with increasing sample span and influence region of microdamage.

Heating, current drive and confinement regimes with the JET ICRH and lhcd systems

During its 1990 operation, 2 large RF systems were available on JET. The Ion Cyclotron Resonance Heating (ICRH) system was equipped with new beryllium screens and with feedback matching systems. Specific impurities generated by ICRH were reduced to negligible levels even in the most stringent H-mode conditions. A maximum power of 22 MW was coupled to L-mode plasmas. High quality H-modes (tau-E greater-than-or-equal-to 2.5 tau-EG) were achieved using dipole phasing. A new high confinement mode was discovered. It combines the properties of the H-mode regime to the low central diffusivities obtained by pellet injection. A value of n(d) tau-E T(i) = 7.8 x 10(20) m-3 s keV was obtained in this mode with T(e) approximately T(i) approximately 11 keV. In the L-mode regime, a regime, a record (140 kW) D-He-3 fusion power was generated with 10 - 14 MW of ICRH at the He-3 cyclotron frequency. Experiments were performed with the prototype launcher of the Lower Hybrid Current Drive (LHCD) systems with coupled power up to 1.6 MW with current drive efficiencies up to < n(e) > R I(CD)/P = 0.4 x 10(20) m-2 A/W. Fast electrons are driven by LHCD to tail temperatures of 100 keV with a hollow radial profile. Paradoxically, LHCD induces central heating particularly in combination with ICRH. Finally we present the first observations of the synergistic acceleration of fast electrons by Transit Time Magnetic Pumping (TTMP) (from ICRH) and Electron Landau Damping (ELD) (from LHCD). The synergism generates TTMP current drive even without phasing the ICRH antennae.

Investigation of the influence of the aberration induced by a plane interface on STED microscopy

The structure of the inhibition patterns is important to the stimulated emission depletion (STED) microscopy. Usually, Laguerre-Gaussian (LG) beam and the central zero-intensity patterns created by inserting phase masks in Gaussian beams are used as the erase beam in STED microscopy. Aberration is generated when focusing beams through an interface between the media of the mismatched refractive indices. By use of the vectorial integral, the effects of such aberration on the shape of depletion patterns and the size of fluorescence emission spot in the STED microscopy are studied. Results are presented as a comparison between the aberration-free case and the aberrated cases. (C) 2009 Optical Society of America

Ultrabroad infrared luminescences from Bi-doped alkaline earth metal germanate glasses

We report on ultrabroad infrared (IR) luminescences covering the 1000-1700-nm wavelength region, from Bi-doped 75GeO(2) 20RO-5Al(2)O(3) 1B(2)O(3) (R = Sr, Ca, and Mg) glasses. The full width at half-maximum of the IR luminescences excited at 980 nm increases (315 -> 440 -> 510 nm) with the change of alkaline earth metal (Mg2+ -> Ca2+ -> Sr2+). The fluorescence lifetime of the glass samples is 1725, 157, and 264 mu s when R is Sr, Ca, and Mg, respectively. These materials may be promising candidates for broad-band fiber amplifiers and tunable laser resources.

Ultrabroad infrared luminescence from Bi-doped aluminogermanate glasses

We report ultrabroad infrared luminescence from Bi-doped aluminogermanate glasses. The infrared luminescence almost covers the whole low loss wavelength region (1200-1650 nm) of silica glass fiber when excited by a diode laser at 980 nm. The full width at half maximum (FWHM) of the luminescence is 510 nm. The luminescence peak can be divided into three Gaussian peaks, and the fluorescence lifetime of the three emissions are 297 mu s, 470 mu s and 1725 mu s, respectively. These fluorescence properties indicate that the glasses are promising material for broadband optical amplifiers. (C) 2007 Elsevier Ltd. All rights reserved.

湖北中泥盆世一植物新属的研究

植物自晚志留世登陆以来，经过对恶劣的陆生环境长期而艰难的适应，在泥盆纪，特别是中上泥盆世开始其大规模的演化发展。在此其间，石松类、楔叶类、前蕨类、真蕨类以及前裸子植物等相继出现，使得陆生植物进入其第一个空前繁盛时期。 但是，也正是在这个介于陆地植物起源及其大规模发展的阶段，植物分类以及各植物之间的亲缘关系很不清楚。特别是前蕨类，它起源于三枝蕨类，并且被认为是真蕨类和前裸子植物的祖先，但目前对它是如何从三枝蕨类进化到真蕨类和前裸子植物却几乎一无所知。就如同一个黑匣子，有一个入口和两个出口，我们的任务就是打开这个黑匣子，弄清楚前蕨类中各植物的自然分类位置以及他们之间的亲缘关系。那么，有关早期陆地植物进化的一些悬而未决的问题也便迎刃而解了。 本论文正是为此目的而作。并且，植物新属变枝蕨的发现将无疑为最终达到这个目的做出很大的贡献。

兰科舌喙兰属的研究

对舌喙兰属的研究表明，该属具下列独特的特征：具一枚着生于茎基部的叶;叶片肉质、几平贴地表;花具硕大而伸出的蕊喙;药室基部延伸成花药管。该属花部器官在发育早期表现为典型的红门兰亚族特点，但在发育后期出现一些特有的性状。尽管舌喙兰属在植物体形态、花部形态和发育等方面表现出许多特化的性状，但染色体水平上与红门兰亚族东亚产的其他属并无明显差异。舌喙兰属植物一般喜欢在石灰岩地区生长，但有些各类也可在其他土壤中生长。野外观察表明扇唇舌喙兰通过食源性欺骗系统来吸引唯一的传粉者：芒康条蜂。其他各类虽亦有类似结构，但未进行观察。 ITS序列数据支持：1）舌喙兰属的6个种为单系类群;2）舌喙兰属、紫斑玉凤花和短距红门兰等植物体形态相似的类群构成关系较为密切的分支;3）主要分布于亚洲的无柱兰属和铣兜被兰属互为关系密切的姐妹群，它们与广布红门兰有较弱的联系。无柱兰－兜被兰类群和舌喙兰－紫斑玉凤花类群构成红门兰亚族中的一个分支;而二叶红门兰、西南手参、滇藏舌唇兰和欧洲产红门兰亚族的代表种类构成另一个分支。 总之，植物体形态，花部形态和发育、传粉模式、生态学特点以及分子数据，都表明舌喙兰属是一个特化的类群。 最后，对舌喙兰属进行了全面修订，确定该属具7个种，主要分布于中国，个别种类向南可达泰国和缅甸南部，向西可达不丹和尼泊尔。