The influence of Mozart's sonata K.448 on visual attention: An ERPs study

In the present study, the effects of Mozart's sonata K.448 on voluntary and involuntary attention were investigated by recording and analyzing behavioral and event-related potentials (ERPs) data in a three-stimulus visual oddball task. P3a (related to inv

高产节水春小麦新品种--高原448

高原448是中国科学院西北高原生物研究所采用有性杂交方法选育而成的,其系谱是:青春533/高原602.原代号为94-448,1999年11月通过青海省农作物品种审定委员会审定,定名为高原448.该品种现已成为青海省灌区种植的主要品种之一,是青海省农作物品种审定委员会指定的全省灌区小麦区域试验和生产试验的对照品种.

承受弯曲的板在裂纹顶端附近的应力和变形

<正> 1.引言板壳结构是工程中常用的一种受力结构元件,对于有裂纹板的弯曲问题已经发表了一批著作,绝大部分是采用了克希霍夫经典板理论,应用此理论进行断裂分析在理论上是有重大缺陷的。这是由于经典板理论对于裂纹面边界条件只是近似地满足,因此不能正确反映裂纹尖端附近的力学性质。对于Reissner理论的分析工作从六十年代以来就开始了。由于问题的复杂性,长期进展不快。有代表性的是Knowlts和Wang以及Hartranft和Sih的工作,他们用积分变换的方法求解问题,他们得到了问题的首项表达式。这是一个近似的形式。为了更好的了解有裂纹情况下板的力学性能以及更可靠的进行近似分析和计算应力强度因子的目的,类似于平面问题的Williams展开,

K418高温合金和42CrMo合金钢的激光焊接

进行了K418高温合金和42CrMo钢的激光焊接实验，分别采用OM、SEM、XRD和EDS等手段分析了焊缝的金相组织和物相组成，评价了焊缝的显微硬度和拉伸强度。结果表明：焊缝主要由树枝状非平衡凝固的FeCrNiC（力固溶体组成，此外，还有少量细小、弥散的Ni_3Al（γ′）相、Laves颗粒和少量MC碳化物分布在树枝晶间区域。由于主要强化相γ′在激光辐照后的部分溶解和随后快速凝固的抑制作用，焊缝的硬度虽分布较均匀但低于母材。由于没有获得穿透的焊接接头，焊接接头的强度约只有母材的88．5％，焊缝的断裂机制是塑性和脆性断裂的混合机制。由于在焊缝中存在一些Laves颗粒，这促进了微裂纹和微孔的形成和扩展，降低了焊接接头的抗拉强度。

基于自由型曲面的贴体网格生成

建立了基于自由型曲面的曲面网格生成的数学模型，生成了曲面网格，把它作为三维Dirichlet问题的边界条件，求解三维Poisson方程，获得了满足数值模拟要求的三维贴体网格。采用上述方法，完成了基于自由型曲面的某直升机空调座舱三维贴体网格的生成，结果令人满意。

适宜海水钻井液体系新前置液实验和现场试验

前置液是影响固井质量的重要因素之一,对于海水钻井液体系,如何选用前置液是一个新的课题.提出了一种适宜于海水钻井液体系的新型前置液,对其在固井过程中的各种性能进行了室内实验研究,结果表明:新型前置液与海水钻井液、固井水泥浆及盐水等环境流体有良好的相容性,对井壁具有稳定作用,其中的固体颗粒及表面活性剂有利于冲刷海水钻井液形成的泥饼.在此基础上,将新型前置液应用于胜利油田的固井作业,进行现场试验,发现:应用新型前置液后,环空水泥浆界面清晰,混浆段长度缩短,第2界面的胶结质量有明显提高.

混浊介质中光子传播路径的蒙特卡罗模拟研究

发展了一种新的蒙特卡罗方法用于研究超短激光脉冲进入混浊介质后的光子传播路径。这种方法可以获得任一时刻的光子最可几传播路径，研究了混浊介质的光学参数如何影响光子的最可几传播路径，发现吸收系数不影响光子的最可几传播路径。

Laser ranging based on electro-optic switch

Based on electro-optic switch effect in crystal, a novel laser ranging method is proposed. CW-laser emitted by laser transmitter propagates forward to the measured target, after being reflected by the target, and then goes back to the transmitter. Close to the transmitter, a special mono-block LiNbO3 crystal is added into the round-trip light beams. High-voltage pulses with the sharp enough changes in rising edges are loaded on the crystal. Based on electro-optic effect, double refraction and internal double reflection effect in crystal, the crystal cuts off the round-trip light beams, and reflects a light pulse cut out by the crystal to a detector aside from the original beam path. The pulse width T is the period that laser propagates forward and back between the crystal and the target. The feasibility of the new idea is proved by our experiments and a brand-new way for the laser ranging is provided. (c) 2005 Elsevier GmbH. All rights reserved.

Optical transitions of Er3+ and Yb3+ ions in novel oxyfluoride bismuth-germanium glass: Observation of up-conversion

Er3+/Yb3+-codoped novel oxyfluoride bismuth-germanium glass was prepared and its up-conversion fluorescence property under 975 nm excitation has been studied. Intense green and weak red emissions centered at 525, 546, and 657 nm, corresponding to the transitions 2H(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. The possible up-conversion mechanism was also evaluated. The optimal Yb3+-Er3+ concentration ratio is found based on the direct lifetime measurements of excited levels for Er3+ ion. The structure of this novel oxyfluoride bismuth-germanium glass has been investigated by peak-deconvolution of FT-Raman spectrum, and the structural information was obtained from the peak wavenumbers. This novel oxyfluoride bismuth-germanium glass with relatively lower maximum phonon energy (similar to 731 cm(-1)) can be used as potential host material for up-conversion lasers. (c) 2005 Elsevier B.V. All rights reserved.

液相外延法制备β-BBO薄膜

采用液相外延法在掺Sr^2＋的Q—BBO（001）衬底上制备了β-BBO薄膜，研究了制备条件对薄膜质量的影响．结果表明：当生长温度为810℃时，转速为300r／min生长的外延膜具有较高的结晶质量，且随着生长时间的延长，外延膜的结晶质量有所提高．β—BBO薄膜呈C轴高度择优取向，薄膜的双晶摇摆曲线半峰宽值FWHM仅为676．6”，表明β-BBO薄膜较好的结晶质量；在不具备相位匹配的条件下，β—BBO外延膜也能够实现二次谐波输出．

Laser-induced damage morphology of high-reflective optical coatings

Two different kinds of 1064 nm high-reflective (HR) coatings, with and without SiO2 protective layer, were prepared by electron beam evaporation. Three-dimensional damage morphology, caused by a Nd:YAG pulsed laser, was investigated for these HR coatings. Development of laser-induced damage on HR coatings was revealed by both temperature field calculation and discrete meso-element simulation. Theoretical results met experimental very well. (C) 2004 Elsevier B.V. All rights reserved.