排序方式: 共有45条查询结果,搜索用时 15 毫秒
1.
5.12汶川大地震诱发大型崩滑灾害动力特征初探 总被引:19,自引:2,他引:19
对乙炔氧气混合气体中爆轰波与激波的正面对撞现象的实验研究是以高速摄影获
取两波对撞的x-t纹影图,以烟迹板记录对撞中的爆轰胞格图案,并基于激波
理论和经典CJ爆轰理论求解了两波对撞的稳态解并探寻其规律. 研究发现透射波系包括一道激波和爆轰波,
以及紧随爆轰波后的稀疏波区,这一结果对应于一维理论分析中的CJ解. 透射波系基本不受
初始压强影响;初始温度也只成比例地改变流场整体速度,温度越高,速度越快;对波系起
实质影响作用的是入射激波强度,激波越强,则整个透射流场呈现偏向激波的趋势;理论分
析还指出,稀疏波区的出现不可避免,当激波强度趋于声波稀疏波区趋于消失,激波越强则
疏波区趋于扩大. 两波对撞存在一个有限的转变阶段,透射爆轰首先减缓,接着迅速迸发为
过驱爆轰,然后再逐渐平衡为CJ爆轰. 对于强不稳定的燃气,对撞后爆轰波在空间上的发展
极不均衡,一些区域发生火焰面与诱导激波的严重脱离,随后的火焰面失稳发展为诱导激波
区内的爆轰波,实验观察到了这种爆轰在烟迹板上留下的极为精细的迹线. 相似文献
2.
R. D. Davies 《Journal of separation science》1981,4(6):270-275
This contribution comprises two parts, the one covering some variables in the dry-packing of columns for liquid chromatography, the other the use of an automatic dry-packer in liquid chromatography. A high-pressure stainless steel column was dry-packed using a 20-44 μm size, irrregularly shaped, silica gel support. It was found that, when support was added in discrete amounts, lateral tapping produced a column of higher efficiency (HETP = 0.69 mm) than was the case for vertical tapping (HETP = 1.37 mm). Simultaneous vertical and lateral tapping produced an intermediate result. Bulk filling of the column followed by tapping was inferior to adding support in discrete amounts. An apparatus constructed to perform the vertical and lateral tapping operations automatically confirmed the above conclusions. It was concluded that commercially available dry-packing apparatus do not offer the best action for packing an efficient column since they involve predominantly vertical tapping. 相似文献
3.
4.
Ionic‐liquid‐based,manual‐shaking‐ and ultrasound‐assisted,surfactant‐enhanced emulsification microextraction for the determination of three fungicide residues in juice samples
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A novel manual‐shaking‐ and ultrasound‐assisted surfactant‐enhanced emulsification microextraction method was developed for the determination of three fungicides in juice samples. In this method, the ionic liquid, 1‐ethyl‐3‐methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, instead of a volatile organic solvent was used as the extraction solvent. The surfactant, NP‐10, was used as an emulsifier to enhance the dispersion of the water‐immiscible ionic liquid into an aqueous phase, which accelerated the mass transfer of the analytes. Organic dispersive solvent typically required in common dispersive liquid–liquid microextraction methods was not necessary. In addition, manual shaking for 15 s before ultrasound to preliminarily mix the extraction solvent and the aqueous sample could greatly shorten the time for dispersing the ionic liquid into aqueous solution by ultrasound irradiation. Several experimental parameters affecting the extraction efficiency, including type and volume of extraction solvent, type and concentration of surfactant, extraction time, and pH, were optimized. Under the optimized conditions, good linearity with the correlation coefficients (γ) higher than 0.9986 and high sensitivity with the limit of detection ranging from 0.4 to 1.6 μg/L were obtained. The average recoveries ranged from 61.4 to 86.0% for spiked juice, with relative standard deviations from 1.8 to 9.7%. The proposed method was demonstrated to be a simple, fast, and efficient method for the analysis of the target fungicides in juice samples. 相似文献
5.
There are always some local damages in spatial steel structures induced by strong earthquakes, such as welding cracks of steel nodes, anchor loose of supports etc. If these local damages of spatial steel structures occur, there will be serious dangers to the structural safety. In order to detect the position of local damage under earthquake quickly and accurately, the method of support damage diagnosis of spatial steel structures under earthquakes is studied by using wavelet packet decomposition, data fusion and cluster analysis. Furthermore, a scale model of spatial steel structure was tested on a seismic simulation shaking table to detect the position of damaged support. Results show that the damaged support position can be detected accurately by using the method proposed in this paper, which has practical applications to the damage detection of spatial steel structures. 相似文献
6.
7.
锁模脉冲波长连续可调谐光纤激光器 总被引:2,自引:1,他引:1
利用在腔内加入可调谐光纤光栅滤波器使“8”字形腔掺Yb3+光纤激光器在锁模状态下实现波长连续可调谐.实验中,在保证锁模状态稳定的情况下,通过调节可调谐光纤光栅滤波器,使激光器输出锁模脉冲的中心波长在1 047 nm~1 055 nm范围内连续调谐,重复频率稳定维持在4.9 MHz.在中心波长1 053 nm处,测得锁模脉冲输出平均功率为8.02 mW,光谱带宽1 nm,脉冲宽度为259.3 ps.这种“8”字形腔被动锁模光纤激光器在锁模状态下对波长连续可调谐,并可长时间稳定工作. 相似文献
8.
9.
10.
An efficient and low-cost protocol for the manual synthesis of Peptide Nucleic Acids is reported here. The protocol relies on coupling reactions carried out with 2.5 equiv of PNA monomers activated with HOBT/HBTU, in the presence of pyridine/NMM. The protocol has been tested on four PNA oligomers with a length ranging from 9 to 12 bases and a purine content up to 67%. 相似文献