利用“神光-Ⅱ”激光装置多路光束叠加直接驱动下的冲击波平面性及稳定性

利用“神光-Ⅱ”的3路基频光输出及小透镜列阵束匀滑技术,通过优化设计和合理地选择光路组合,实现了多路叠加斜入射的驱动激光, 在靶材料中产生一个650~750μm范围内平面性良好的冲击波,有效地提高了“神光-Ⅱ”输出光束的利用率。同时,利用斜面靶进行的冲击稳定性实验表明,在靶面功率密度分别为3.26×1014及2.56×1014W/cm2时,冲击波至少在28.38~55.82和22.13~35.07μm的Al样品厚度内是稳定传播的。     

屯田余绪中的近世边疆社会嬗变—以1719至1949年间甘肃省金塔县水利事务为中心的研究

以公元1719至1949年间甘肃金塔县水利事务为主线,可以分析这一因屯田而兴起的边疆社会在两百余年间的演化特征。清代屯田时期,金塔县水利事务完全由政府控制,屯田结束后逐渐转向民间自行管理;但政府却出于对边疆地区民众领袖易引发社会不稳定的成见,刻意将士绅集团排斥于水利管理事务之外。民国时期随着外源性水利危机的爆发,向外部“争水”成为决定区域社会生死存亡的头等大事,政府转而支持士绅阶层积极“争水”,士绅由此控制了全县水利事务。“争水”成功的士绅阶层很快涣散并劣化,致使金塔内部水利逐渐废弛、社会矛盾重重,并非迫切的“对外争水”成为凝聚区域社会的唯一共识。从屯田到争水,金塔社会在近世大多数时间中始终为单一维度社会管制目标所牵引,并未走上繁荣、有序、富于活力的发展之路。这其中涉及政治、环境等复杂因素的交相作用,但自屯田时代所遗留的制度化要素扮演了重要角色。短时期的屯田活动,造就了长时期存在于边疆区域的“屯田社会”,其流风余绪影响至今。     

基于MODIS数据的卫星辐射特性研究

本文提出了一种结合MODIS数据产品和MODTRAN模型的典型地形条件空间目标红外辐射特性计算方法.考虑了地形条件和大气环境对空间目标的红外辐射特性影响,应用MODIS 3级陆地,海洋,冰雪圈数据产品得到全球温度分布,地形特征分布,将温度及地形条件代入MODTRAN计算得到地表-目标的辐亮度,进而计算目标的外热流以及表...     

Observation of defect clustering in Gd-doped calcium fluoride

Abstract

Solid solutions Ca_1-xGd_xF_2+x for 3 × 10^?7≤ x ≤10^?1 have been studied by electron paramagnetic resonance (EPR) and ionic thermal currents (ITC). The EPR experiments show the presence of two single-ion sites a cubic and a tetragonal Gd³⁺ center which co-exist with comparable abundances for intermediate impurity concentrations. The cubic center predominates at very low and high concentrations. Seven different relaxation processes have been identified from the ITC spectra and the variation of their intensity vs. x was measured. The absolute concentrations of the cubic and nn Gd³⁺ dipoles were calculated. The scavenging of interstitial fluorines by the neutral clusters explains both the abundance of cubic sites at high concentration and the variety of orientable clusters detected by ITC.     

Influence of Control Parameters on the Competition Between Spiral Waves and Target Waves

In this paper we systematically investigate the influence of control parameters on the competition results between spiral waves and target waves. Driving frequency f , amplitude A and injection area n of the input signals are three important parameters and the competition results between spiral waves and target waves are influenced by these three parameters remarkably. Based on these understandings we can control spiral waves effectively by suitable combination these parameters to generate faster target waves. And the effective controllable parameter regions are also studied.     

室内环境中脑控轮椅的路径跟踪控制

为了实现室内环境中脑控轮椅的自主导航,提出了一种简单有效的路径跟踪控制方法。给定的路径通常被表示为一系列离散点,根据这一特点,提出了分段直线路径跟踪方法,即依次跟踪由前后两个路径点构成的直线路径到达目标点。基于预瞄点技术并结合模糊算法和传统的PID控制方法设计控制器,完成各分段直线路径的跟踪,并给出了有效的切换条件。实验结果表明,本文提出的路径跟踪控制方法能够使脑控轮椅在室内环境中精确地跟踪给定路径。     

Rapid analysis of phthalic acid esters in environmental water using fast elution gas chromatography with mass spectrometry and adaptive library spectra

A method for the fast determination of the components in a complex sample by using gas chromatography with mass spectrometry was developed and used for the quantitative analysis of phthalic acid esters in environmental water. In the method, the adaptively corrected mass spectra were used to compensate for the differences between the library spectra and the measured ones in the experiment. The correction was obtained by the iterative transformation of the library spectra using iterative target transformation factor analysis, and the resolution was performed by non‐negative immune algorithm using the corrected spectra. Rapid analysis of 16 phthalic acid esters in water samples was achieved using fast elution gas chromatography with mass spectrometry measurements. The results show that the mass spectra and chromatographic profiles of the phthalic acid esters can be obtained from the overlapping signal of 13 min elution, and accurate quantitative analysis can be obtained. The recoveries of the phthalic acid esters obtained by standard addition are between 90.3 and 107.4%, and the relative standard deviations obtained in repeated measurements are less than 9%.     

Differentiating bulk nanobubbles from nanodroplets and nanoparticles

History has shown that it is not as easy as one might think to differentiate between bulk nanobubbles and nanodroplets or nanoparticles. It is generally easy to detect colloids (i.e. something that looks different, e.g. scatters light differently than its surrounding solvent), but less easy to determine the nature of these colloids. This has led to misinterpretations in the literature, where nanodroplets or nanoparticles have mistakenly been assumed to be nanobubbles. In this paper, we review a multitude of experimental methods and approaches to prove the existence of bulk nanobubbles. We conclude that combinations of optical detection with physical perturbations such as pressure or ultrasound, or phase-sensitive holographic methods are the most promising and convenient approaches.