On a problem of Katona on minimal separating systems

Let S be an n-element set. In this paper, we determine the smallest number f(n) for which there exists a family of subsets of S{A₁,A₂,…,A_f(n)} with the following property: Given any two elements x, y ∈ S (x ≠ y), there exist k, l such that A_k ∩ A_l= ?, and x ∈ A_k, y ∈ A_l. In particular it is shown that f(n)= 3 log₃n when n is a power of 3.     

On‐line surface enhanced Raman spectroscopic detection in a recyclable Au@SiO2 modified glass capillary

A facile method was developed to fabricate a high sensitive, reproducible and recyclable surface enhanced Raman spectroscopy (SERS) active glass capillary. The Au nanoparticles were synthesized through a seed‐mediated growth approach and then self‐assembled onto the inner wall of glass capillaries. The attached Au nanoparticles were homogeneously coated with thin silica shell by using the silane coupling agent to functionalize the Au surface. By using thiophenol (TP) as SERS probe molecules, the substrate exhibited robust SERS effects. The adsorbed SERS probe molecules could be rapidly and completely removed away by flowing sodium borohydride solution and thus to obtain a refresh Au@SiO₂ film‐coated substrate for the cyclic detection on different species. The on‐line detection of TP and malachite green (MG) with different concentrations was performed in the flowing system. The intensities of SERS signals were dependent on concentrations of the detected molecules. The results indicated that the SERS‐active substrate has potential applications on the on‐line qualitative and quasi‐quantitative analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

SiO_2溶胶的簇团特性及其对增透膜光学性能的影响

在碱性条件下制备的ＳｉＯ２溶胶,经旋转法镀膜,得到具有增透效果的膜层。结果表明随着与陈化温度和陈化时间密切相关的溶胶族团的粒度分布及交联行为直接影响膜层的增透效果,膜层增透效果与溶胶族团的特性间存在一定的内在规律。     

τ→π~±2π~0v结构函数的测量

首次对τ→π2π0v衰变的结构函数进行了模型无关的实验测量,并与KS模型、IMR模型和Feindt模型进行了比较,在误差范围内,三种理论模型与实验结果一致．与OPAL组测量的τ→3π±v道的结构函数相比,在0．5＜Q2＜2．75GeV2范围内未发现明显差异．     

用自聚焦透镜作平行光束与单模光纤的最佳耦合

本文提出一种用两片自聚焦透镜组合而成的耦合系统,可以实现平行光束与单模光纤的最佳耦合.文中给出了该耦合系统的参数计算公式,并进行了计算机数字式计算,最后推导给出了最佳结构参数计算的解析公式.表明给出的耦合系统具有唯一最佳结构参数解,并且这种解具有和谐的对称性.     

实现20Gbit/s的OTDM孤子信号56km色散位移光纤的传输

在国内最先采用孤子的方式将8×2.5Gb/s的OTDM信号在色散位移光纤中传输了56.1km,对8×2.5Gb/s的OTDM进行解复用后进行了误码测量,系统功率代价为2.9dB.系统采用增益开关半导体激光器作光孤子源,高Q电滤波方式提取时钟,非线性光学环路镜解复用。孤子脉冲最大半宽度为20ps,传输光纤平均色散1.2ps/nm/km。     

ITER 极向场磁体支撑U 型韧性夹焊接方案优化

利用试验及数值模拟技术研究了ITER 极向场磁体支撑U 型韧性夹的焊接变形规律,模拟和实际测量的比较验证了模拟的准确性,从而得到了U 型夹焊缝变形的基本规律,并改进现有夹具类型。基于验证好的热力边界条件以及优化的夹具,对三种焊接方案的U 型韧性夹的焊接变形进行了计算,从而提出了极向场磁体支撑制造的优化方案。优化后的焊接方案将焊接变形控制在0.6mm 以内。     

INCREASING TRANSVERSE STABILITY OF OPTICAL TWEEZERS BY USING DUAL-GAUSSIAN BEAM PROFILE

Trapping force was calculated with a homogeneous dielectric sphere model. Results indicate that the transverse trapping force of optical tweezers can be increased effectively through modifying laser beam profile while the axial stability of the system is still assured. This is quite important when optical tweezers are applied to the precise measurements for single biological molecule.     

Formation and crystal structure of metallic inclusions in a HPHT as-grown diamond single crystal

One of the most important characteristics associated with crystal growth technology is the entrapment of inclusions by the growing crystal. Diamond single crystals prepared under high temperature-high pressure (HPHT) usually contain metallic inclusions. In the present paper, metallic inclusions in a diamond grown from a Fe-Ni-C system using the HPHT method have been, for the first time, systematically examined by transmission electron microscopy (TEM). Energy dispersive X-ray spectrometry (EDS) , combined with selected area electron diffraction (SAD) patterns, has been used to identify the chemical composition and crystal structure of the metallic inclusions. The metallic inclusions were found to be composed mainly of cubic γ-(FeNi), face-centered cubic (FeNi)₂₃C₆, ortho-rhombic Fe₃C and hexagonal Ni₃C, which may have been formed through the entrapment of molten catalyst by the growth front or through reaction of the trapped melt with contaminants in the diamond. Received: 19 June 2000 / Accepted: 21 June 2000 / Published online: 16 August 2000     

高速通道压裂裂缝的高导流能力分析及其影响因素研究

高速通道压裂是近年在非常规致密油气资源开采中出现的新工艺, 已在世界范围内推广实施, 并取得了良好的增产效果. 该技术可使支撑剂在人工压裂缝中形成簇团式分布, 从而形成油气高速流动通道, 提高裂缝的导流能力. 但目前对于高速通道压裂裂缝高导流能力的形成机理及其影响因素尚不清楚. 对此, 本文从流体力学理论出发, 首先将高速通道压裂裂缝内形成的支撑剂簇团视为渗流区域, 簇团间的大通道视为自由流动区域; 然后基于Darcy-Brinkman方程建立了裂缝内的流动数学模型, 采用均匀化理论对该流动数学模型进行了尺度升级, 推导得到了高速通道压裂裂缝的渗透率, 揭示了其高导流能力的形成机理; 并以此为基础, 分析了不同支撑剂簇团形状、大小以及分布方式等因素对其导流能力的影响, 可为高速通道压裂工艺参数设计与优化提供基础.