弛豫理论对离子交换毛细管电色谱中峰压缩现象的研究

在毛细管电色谱中,由于溶质在输运过程中所具有的电性质,常会产生一些特殊的现象。这些现象,如离子交换毛细管电色谱中产生超高柱效峰的现象,已经不能用一般的色谱理论加以解释。基于弛豫理论所建立的基本模型,在考虑溶质在两相中皆有可能发生正、反向迁移的情况下,得到了流出曲线一阶原点矩和二阶中心矩的理论表达式,并通过对溶质在两相中电扩散速率与电泳速率、电渗流速率关系的分析结果证实:溶质在固定相表面的电扩散行为可以使其保留变弱,出峰加快;而这种电扩散导致的超常柱效峰的出现具有不稳定性,只有在多方面因素综合影响匹配的情况下才可能出现。

高效液相色谱峰压缩中灵敏度增加值与峰压缩因子的关系研究

以从塔板理论得到的色谱流出曲线为基础,推导了高效液相色谱(HPLC)双流动相分离场中实现峰压缩时,峰压缩因子(峰压缩后的半峰宽与未进行峰压缩时的半峰宽的比值)和峰高表示的灵敏度变化(峰压缩后的峰高与未进行峰压缩时的峰高的比值)的关系,结果表明峰高表示的灵敏度增加值等于峰压缩因子的倒数。并用色氨酸、香豆素、苯和2-硝基酚在不同速率差实现堆积时的相关参数进行了验证。实验结果表明,这些化合物在各个峰压缩条件下的峰压缩因子倒数和实际灵敏度增加值相等,实验结果与理论推导结果一致。考察了该关系式在实际样品测定中的应用,结果表明灵敏度增加值等于峰压缩因子的倒数,这也与理论部分的结果一致。

高效液相色谱中的峰压缩技术

以苯甲醛和4-羟基喹啉为模型化合物,以不同流动相组成时化合物迁移速度差为基础,建立了双流动相体系中的峰压缩技术,并以峰压缩因子(峰压缩条件下的半峰宽与未进行峰压缩的半峰宽的比值)表征峰压缩技术.在本文实验的最佳峰压缩条件下,苯甲醛和4-羟基喹啉的峰压缩因子分别为0.19和0.13.该峰压缩技术可成功用于混合物体系,实现混合物体系中各个物质的峰压缩.将该峰压缩技术应用于通过测定产物苯甲醛的生成量来测定SSAO酶活性时,也能成功实现峰压缩,峰压缩后的峰高、塔板数和信噪比分别提高了4.94,19.3和5.74倍,说明该峰压缩技术可成功应用于实际样品测定.

基于压缩峰分解的柴油机着燃角的检测方法

提出了一种通过柴油机缸内压力变化率曲线分解的着燃角检测方法。在喷油燃烧信号中根据着火前的部分压缩峰曲线,通过曲线拟合推算出着燃点附近的压缩峰曲线,分离出喷油燃烧压力曲线,从而判断燃烧的开始时刻。这种方法与一般的基于压力变化率的处理方法相比有更高的精确度。

Compressive performance of innovative reinforced pillars in closed/abandoned mines

Pillar is closely related to the stability and reliability of underground spaces in closed/abandoned mines.The present research introduced a new technique to strengthen square cement mortar columns via fiber-reinforced polymer(FRP)strips to verify the strengthening effect of FRP on pillars.Compared to a fully wrapped FRP jacket,the advantages of FRP strip are cost-effective and easy-to-construct.A series of compression tests as well as theoretical analysis were carried out to explore the mechanical behavior of square cement mortar specimens partially strengthened with FRP strips.The results verified the effectiveness of FRP strips in enhancing the stress and strain of cement mortar.Different from unconfined cement mortar specimens,these FRP-strengthened cement mortar specimens are featured with the double-peaked behaviors,mainly attributed to the stress state transformation from a one-dimensional to a three-dimensional stress state.It also indicated that the enhancement of stress increased with the FRP strip width.Moreover,the brittle-ductile transition ductile failure characteristics were also observed in FRP-confined cement mortar specimens.The ultimate ductility of the cement mortar specimen decreases gradually with the growth of the FRP strip width.The main contribution of this research is to enrich the strengthening techniques for residual pillars.

Rice Crop Digital Image Compression Technology Based on Discrete Fourier Transform

[Objective] To study the digital image compression technology in rice monitoring system. [Method] A digital image compression technology program based on the discrete Fourier transform was proposed, and simulation experiments were carried out to compress the image at different compression ratios. [Result] When com- pression ratios were less than 30, the compression ratio, image entropy, average codeword length, coding efficiency and redundancy which reflected the quality of the coding, and the parameter PSNR which estimated the fidelity of the compressed im- age were all achieved good results that human eye could barely percept the differ- ence between the original image and decompressed image; and when the compres- sion ratios were more than 30, there was a certain distortion in the decompressed image. And when the compression ratio was 91.516 3, although the image had some distortion, the PSNR was still achieved to 21.528 2, and human eye could accept the decompressed image intuitively within the acceptable error range. [Conclusion] The results show that the proposed image compression program is a viable, effective, and better image compression technology which can satisfy the requirements of the crop monitoring system on image storage, transforming and transporting.

Application Research of Image Compression Technology in Monitoring System of Rape Crop in Areas of Qinling Mountains

[Objective] The aim was to present a proposal about a new image compression technology, in order to make the image be able to be stored in a smaller space and be transmitted with smaller bit rate on the premise of guaranteeing image quality in the rape crop monitoring system in Qinling Mountains. [Method] In the proposal, the color image was divided into brightness images with three fundamental colors, followed by sub-image division and DCT treatment. Then, coefficients of transform domain were quantized, and encoded and compressed as per Huffman coding. Finally, decompression was conducted through inverse process and decompressed images were matched. [Result] The simulation results show that when compression ratio of the color image of rape crops was 11.972 3∶1, human can not distinguish the differences between the decompressed images and the source images with naked eyes; when ratio was as high as 53.565 6∶1, PSNR was still above 30 dD,encoding efficiency achieved over 0.78 and redundancy was less than 0.22. [Conclusion] The results indicate that the proposed color image compression technology can achieve higher compression ratio on the premise of good image quality. In addition, image encoding quality and decompressed images achieved better results, which fully met requirement of image storage and transmission in monitoring system of rape crop in the Qinling Mountains.

Size effect of confined concrete subjected to axial compression

In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. Effects of key parameters such as size of specimens, tie configuration, transverse reinforcement ratio, and concrete cover were studied. The results show that for specimens with the same configuration and the same volumetric ratio of the transverse reinforcement, along with the increasing specimen size, the peak stress, peak strain and deformation of the post-peak show a down trend, however, the volumetric ratio of the transverse reinforcement is lowered, the decreasing of the peak stress is accelerated, but the decreasing of the deformation is slow down. For specimens with the same volumetric ratio but different configurations of transverse reinforcement, though the transverse reinforcement configuration becomes more complicated, the peak stress of the large size specimen does not improve more than that of the small size. However, the deformation occurs before the stress declines to 85% of peak stress, and the improvement with the grid pattern tie configuration is much greater due to size effect.

Mechanical properties and failure characteristics of fractured sandstone with grouting and anchorage

Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage,the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5–320.0%, 62.8–493.0%, and 31.6–181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile–shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure.