基于调频信号发射的超声造影剂谐波成像方法

提出了一种能够提取超声造影剂回波中二次谐波的非线性成像方法,从数学原理、仿真计算和声学实验三个方面对造影剂血流灌注成像方法进行了研究。首次将调频信号发射技术用于医学超声造影剂谐波成像领域,仿真计算和声学实验结果表明:为了获得较好的图像质量,发射调频信号应该具有合适的包络;发射信号带宽与解码匹配滤波器带宽之间必须有一个带宽间隔;适当降低发射声压能够降低生物组织的谐波。应用编码发射方法和解码滤波器,得到了造影剂二次谐波图像,此图像具有较好的信号噪声比和造影剂组织比。声学实验结果和理论计算结果完全吻合。     

光照与彩陶俑表面色变关系的实验研究

本文以秦彩俑表面色彩为研究对象,通过光照实验与色彩变化的色度测量,分析了光照引起彩俑颜料色变的规律,为秦彩俑这一大型重点文物的色彩保护提供了科学理论依据.     

包膜超声造影微泡次谐波特性的优化设计与实验研究

基于包膜超声造影微泡在超声场中的理论振动模型,对其次谐波特性进行优化设计,从理论上计算和分析了微泡粒径、膜弹性及声压等对微泡次谐波响应的影响,以期获得其用于非破坏性次谐波成像的最佳条件。另外通过改变膜材料的配比, 制备了具有不同膜弹性的超声造影微泡,对其声学特性进行了体外声学实验测定。仿真计算和实验结果表明,在合适的膜材料配比条件下,制得的平均粒径为3μm左右的包膜微泡,可获得满意的次谐波响应,并且其用于非破坏性次谐波成像时的最佳工作声压约200-400 kPa。     

2-巯基苯并咪唑保护的铜纳米团簇的制备及银离子检测

以2-巯基苯并咪唑为保护剂,聚乙烯吡咯烷酮为稳定剂,水合肼为还原剂,“一锅法”合成2-巯基苯并咪唑保护的,高稳定性、强荧光、大斯托克斯位移的铜纳米团簇(Cu NCs),并用于检测水样中的银离子含量。采用透射电子显微镜(TEM)和X射线光电子能谱(XPS)对铜纳米团簇的结构进行表征,通过荧光光谱和紫外可见光谱对其光学性能进行研究。研究表明:该铜纳米团簇的最大激发和发射波长分别为340和558 nm,在日光灯和紫外灯下分别为无色和橙色。Cu NCs具有较高的分散性,尺寸大小为2~3 nm。在最佳反应条件下,铜纳米团簇可以选择性地被银离子猝灭,且灵敏度高,线性范围为1~40μmol/L,检测限为0.5μmol/L。该方法用于检测实际水样(自来水、湖水)中银离子的浓度,结果令人满意,表明在环境监测中有非常高的应用价值。     

Facile synthesis of 4″-O-alkyl-(–)-EGCG derivatives through regioselective deacetylative alkylation

Therapeutic potential of the D-ring methyl ethers of (–)-epigallocatechin-3-gallate [(–)-EGCG] warrants extensive structure–activity relationship study of various D-ring ethers of (–)-EGCG but, for this purpose, efficient synthetic strategy needs to be developed. In this study, efficient preparation of the 4″-O-alkyl-(–)-EGCGs (4a–e) was demonstrated using KI/K₂CO₃-promoted deacetylative alkylation of peracetyl (–)-EGCG, which could be broadly utilized for the preparation of various D-ring alkyl ethers of (–)-EGCG and thereby extensive structure–activity relationship study.     

Effective contrast enhancement method for color night vision

Image fusion refers to the techniques that integrate complementary information from multiple image sensors’ data in a way that makes the new images more suitable for human visual perception. The paper focuses on the low color contrast problem of linear fusion algorithms with color transfer method. Firstly, the contrast of infrared and visible images is enhanced using local histogram equalization and median filter. Then the two enhanced images are fused into the three components of a Lab image in terms of a simple linear fusion strategy. To enhance the color contrast between the target and the background, the scaling factor is introduced into the transferring equation in the b channel. Experimental results based on three different data sets show that the hot and cold targets are all popped out with intense colors while the background details present natural color appearance. Target detection experiments through target recognition area, detection rate, target-background discrimination also show that the presented method has a better performance than the former methods.     

Rational design of thermoelastic damping in microresonators with phase-lagging heat conduction law

The design of thermoelastic damping (TED) affected by the phase-lagging non-Fourier heat conduction effects becomes significant but challenging for enlarging the quality factor of widely-used microresonators operating in extreme situations, including ultra-high excitation frequency and ultra-low working temperature. However, there does not exist a rational method for designing the TED in the framework of non-Fourier heat conduction law. This work, therefore, proposes a design framework to achieve low thermoelastic dissipation of microresonators governed by the phase-lagging heat conduction law. The equation of motion and the heat conduction equation for phase-lagging TED microresonators are derived first, and then the non-Fourier TED design problem is proposed. A topology optimization-based rational design method is used to resolve the design problem. What is more, a two-dimensional (2D) plain-strain-based finite element method (FEM) is developed as a solver for the topology optimization process. Based on the suggested rational design technique, numerical instances with various phase lags are investigated. The results show that the proposed design method can remarkably reduce the dissipation of microresonators by tailoring their substructures.     

Synthesis of a Zn-salen resorcinarene-based cavitand and its fluorescence response to nitro compounds

The synthesis, spectroscopic characterisation, conformational switching and fluorescence quenching efficiency of a resorcinarene-based cavitand containing Zn-salen (Zn-Cav) are reported. Synthesis of Zn-Cav was accomplished by the condensation of a quinoxaline derivatised with Zn-salen and a resorcinarene-based cavitand containing three quinoxalines. ¹H NMR spectroscopy confirmed that in DMSO, chloroform and acetone Zn-Cav resides in the vase conformation. The molecular geometry of Zn-Cav selectively changes from vase to kite under acidic conditions. Detection by fluorescence quenching of nitro-containing molecules, such as 4-nitrotoluene, 2,4-dinitrotoluene and 2,3-dimethyl-2,3-dinitrobutane was explored by spectrofluorimetry. It was found that the fluorescence of Zn-Cav is efficiently quenched by nitroaromatic compounds.     

光学系统时间畸变和色时间滞后的研究

本文对皮秒和飞秒技术中瞬态现象测量系统所用的特殊光学系统校正时间畸变和压缩色时间滞后的问题进行了讨论。实验证明用该方法设计研制的光学系统校正效果显着。     

基于视频图像测量的母线折弯技术研究

现有折弯机在母线的角度测量中一般采用光栅尺或编码器,针对这种接触式检测方法存在的局限性,提出了基于视频技术的角度检测方法,这种非接触式测量方法不仅使角度的检测更加方便,而且增加了折弯机机头机械设计的灵活性.分析了母线在进行边缘检测时角度存在跳动的原因,提出了一种通过抑制伪边缘的方法来控制检测角度的不稳定性.以铜、铝母线...