钛宝石飞秒激光振荡器的稳定性改善

对钛宝石飞秒激光器脉冲序列的强度和时间的稳定性进行了分析.实验比较了钛宝石飞秒激光器底板有无水冷的条件下,输出锁模脉冲序列的稳定性以及中心波长和光谱宽度的变化.结果表明对钛宝石飞秒激光器底板施加水冷可改善锁模脉冲的稳定性. 关键词： 钛宝石激光器 稳定性 飞秒脉冲     

3He spin-dependent cross sections and sum rules

We present a measurement of the spin-dependent cross sections for the 3He over -->(e over -->,e')X reaction in the quasielastic and resonance regions at a four-momentum transfer 0.1< or =Q2< or =0.9 GeV2. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt-Cottingham and extended Gerasimov-Drell-Hearn sum rules for the first time. The data are also compared to an impulse approximation calculation and an exact three-body Faddeev calculation in the quasielastic region.     

Particle-species dependent modification of jet-induced correlations in Au+Au collisions at sqrt[s_{NN}]=200 GeV

Measurements in Au+Au collisions at sqrt[s_{NN}]=200 GeV of jet correlations for a trigger hadron at intermediate transverse momentum (p_{T,trig}) with associated mesons or baryons at lower p_{T,assoc} indicate strong modification of the away-side jet. The ratio of jet-associated baryons to mesons increases with centrality and p_{T,assoc}. For the most central collisions, the ratio is similar to that for inclusive measurements. This trend is incompatible with in-vacuum fragmentation but could be due to jetlike contributions from correlated soft partons, which recombine upon hadronization.     

Characterization of transition shifts in perpendicular magnetic recording using 3D FEM

Transition shift can create serious timing problems for high density recording environments. However, it is possible to use techniques such as write precompensation to offset the timing error introduced if the magnitude and the behaviour of the transition shift are properly understood. This paper introduces a 3D finite element method (FEM) to analyse the transition shift in perpendicular magnetic recording (PMR) quantitatively, allowing the combinational effects of the transition shifts from non-linear transition shift (NLTS), HTS, and neighbourhood-induced transition shift (NITS) to be examined. The consideration of all contributing factors to the final written transition position is important in determining the precompensation scheme of magnetic data recording, and 3D FEM can facilitate such quantitative analysis.     

The acousto-optic Q-switched mode-locking Nd:YVO4 laser

Q-switched mode locking (QML) has been observed in acousto-optic Q-switched Nd:YVO₄ laser that contained no mode-locking components. It was found that QML was easily realized in a long cavity and the modulation depth was observed to increase with increased cavity length. The maximum modulation depth was as high as 90%. This phenomenon is explained by the introduction of gain-related effect in the gain medium. The longitudinal modes at higher frequency, than the central frequency of the gain profile, experience positive guiding, which results in mode locking of these modes.     

CFCl3的理论和紫外光电子能谱研究

采用紫外光电子能谱(PES)和量子化学方法,研究了以CFCl3化合物为代表的系列化合物(CFCl3、CF2Cl2、CF3Cl、CCl4)不同离子态的电子结构和性质。结果表明,四种化合物CF3Cl、CF2Cl2、CFCl3、CCl4的第一电离能依次下降。结合从头算自洽场分子轨道(abinitioSCFMO)和外壳层格林函数法(OVGF)计算对化合物的PES进行了分析和指认,表明化合物的外层轨道中Cl的孤对电子成分对电离能存在明显的影响;外层格林函数法计算得到电离能与实验吻合很好;同时发现在外壳层格林函数法计算结果中由于考虑相关能,得到的分子轨道存在能级顺序的交错。     

基于热管的自燃煤矸石山降温效应

为预防煤矸石山氧化发火,抑制矸石山自燃升温,基于热管相变传热原理,在煤矸石山现场开展热管降温效果的单管试验,研究煤矸石山温度分布规律和热管对其内部温度的冷却效果。研究结果表明,试验条件下,热管能够有效降低煤矸石山内部温度,达到抑制升温、预防自燃的目的。60 d内,降温最大值在深度4 m位置,最大值为27℃,平均降温0.45℃/d。水平方向上,矸石与热管距离越近,降温效果越明显,最大控温半径可达3 m,最佳控温半径为2 m;垂直方向上,降温效果随深度增加先增加后减小,蒸发段所在深度为降温效果最佳深度范围。     

断块油藏水平井提液参数优化

在断块油藏开发中水平井具有改善断块油藏连通能力的特点,并且提液作为一种重要的剩余油挖潜手段,具有降本增效的特点。为研究水平井提液参数优化,采用数理统计的方法,针对典型断块油藏的水淹模式进行总结,运用多元线性回归方法对水平井提液效果主控因素进行分析,并针对提液效果开展三参数的响应曲面研究。研究结果表明三个参数中注采比对提液效果的影响最大;快速水淹井晚期提液总体效果明显,并且提液时机越早,采出单位的水带出的油越少,水的处理费用越高;缓慢水淹井早期提液总体效果明显,其提液规律与快速类表现基本类似,不同之处在于,提液时机越晚,采出单位水带出来的油越少,水的处理费用越高;经过优化后,快速水淹井提液后累产油提高12.64×10⁴ m³,缓慢水淹井提液后累产油提高7.24×10⁴ m³。     

基于簇相似度的网络社团结构探测算法

社团结构对复杂系统的结构特性和动力学特性有重要影响.提出了一个度量社团相似度的模型,称为簇相似度.该模型能够度量两个社团的相似度大小,为研究社团间的作用机制提供帮助.而且基于该模型,设计了一个社团划分算法.算法采用层次聚类的思想,每次合并两个相似度最大的社团,并通过一个评价函数选择最优社团划分.数值实验以及与CNM,GN,EigenMod等主流算法做比较,表明本算法的精度和效率都比较高,尤其对于边密度较高的网络,性能非常理想.     

Compact and high-power broadband terahertz source based on femtosecond photonic crystal fiber amplifier

We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier.The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient.Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz.A strong saturation effect is observed,which is attributed to pump pulse absorption;a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm.A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy.