超声波辅助提取柿子树叶单宁的研究

以70%的丙酮溶液为提取溶剂,采用超声波辅助提取野柿叶中的单宁,考察了超声波的功率、提取温度、提取时间等因素对单宁提取量的影响.采用响应面法对提取条件进行优化,并建立了二次回归模型.实验结果显示:当提取温度为52℃、超声波功率为80 W、提取时间为42 min,在此条件下单宁的提取量为203.15 mr/g,比无超声波...     

快速溶剂萃取-气相色谱/质谱联用测定塑料桌布中的邻苯二甲酸酯

采用快速溶剂萃取-气相色谱/质谱联用法(ASE-GC/MS)和超声波萃取-气相色谱/质谱联用法(USE-GC/MS)测定了塑料桌布中的邻苯二甲酸酯.结果表明:ASE-GC/MS的测量精度优于USE-GC/MS,后者测量值大约为前者的五分之四;ASE-GC/MS的回收率为89.0%～95.5%,相对标准偏差为4.3%～1...     

EFFECT OF DAMAGE EVOLUTION ON POISSON’S RATIO OF CONCRETE UNDER SULFATE ATTACK

Experimental results about concrete under sulfate attack are summarized,which include the variation of mass density of samples and velocity of ultrasonic wave propagating in samples.The evolution damage is analyzed in terms of the experimental results,and close attention is paid to the effect of damage evolution on Poisson’s ratio.This study shows that Poisson’s ratio is significantly affected by the concentration of solution and water-cement ratio.Poisson’s ratio of concrete changes very little when the water-cement ratio is selected as 0.6 or 0.8,so that such change may be neglected.If water-cement is 0.4,however,the Poisson’s ratio of the sample significantly changes.When the concrete sample of 0.4 water-cement ratio is immersed in sodium sulfate solution of 8% concentration for 285 days,Poisson’s ratio increase 10.14% compared with its initial value.There exist a sensitive region and a non-sensitive region for the change rate of Poisson’s ratio with respect to corrosion time.The change rate of Poisson’s ratio monotonously decreases with corrosion time in the sensitive region;in the non-sensitive region,the change rate of Poisson’s ratio is almost equal to zero.     

Probing the nature of the contact between fine particles by using ultrasound propagation

The propagation velocity (vs) of an ultrasonic signal through a granular material depends on the type of interparticle contact. For noncohesive glass beads, a power law behavior for consolidation stresses applied (σc) above 1 MPa has been measured in previous work. This equation is compatible with Hertz's interaction law between elastic solids. In the present work, we have tested the propagation velocity of ultrasound signals through a sample of fine powder. The tensile strength and compactivity of the powder were previously measured by means of the Seville powder tester (SPT), indicating plastic deformation of the surface asperities in contact for small to moderate consolidation stresses. However, the measurements of ultrasound propagation at high consolidations presented here are compatible with Hertz's law. This finding suggests that for high consolidation stresses, surface asperities are flattened, and it is therefore the elastic deformation of the bulk of the particles that determines the transmission of ultrasonic pulses.     

基于优选NIR光谱波数的绿豆产地无损检测方法

产地是影响农作物生产的重要环境因素,产地溯源对于食品安全具有重要意义。针对传统农产品产地检测一般采用化学分析法,其操作繁琐且存在破坏性和耗时较长等不足的问题,以北方寒地绿豆为研究对象,分别在白城、杜蒙、泰来等优质绿豆主产区,获取绿豆的籽粒和粉末两种状态的近红外光谱数据（NIR）,利用优选NIR光谱特征波数,建立了绿豆产地无损检测的新方法。首先在吸光度值较强的10 105.37~4 078.655 cm-1波数范围内,采用多元散射校正法（MSC）,对不同产地的绿豆原始光谱数据进行预处理,以消除光谱干扰信息。应用竞争性自适应重加权采样算法（CARS）,优选不同产地绿豆籽粒和粉末状态的光谱特征波数,以减少光谱曲线的特征向量维度。最后利用前馈神经网络（BP）自适应推理机制,建立了绿豆产地与其光谱特征波数之间非线性映射模型,并将网络输出的编码向量解析至产地名称,作为绿豆产地检测的输出结果。研究结果表明：（1）原始光谱经过多元散射校正预处理后,绿豆粉末光谱曲线的误差从12.87降到3.20,绿豆籽粒光谱曲线的误差从153.04降到27.73,提供有效可靠的光谱数据。（2）通过竞争性自适应重加权采样算法,提取绿豆光谱曲线的重要特征波数,从籽粒和粉末状态原始2 114个波数中,分别优化为61个和107个特征波数,波段总数目减少了94.94%以上,并将其作为绿豆产地识别的特征指标。（3）创新性提出了MSC-CARS-BP绿豆产地检测模型,以优选出的光谱特征波数为定量依据,分别对绿豆籽粒和粉末进行产地检测,预测集准确率为92.59%和98.63%,相关系数均达到0.99以上。该方法能够利用近红外光谱处理技术,实现绿豆产地无损检测的目标,为农产品产地自动快速溯源提供了技术支持和参考。     

基于LMS自适应时延估计和FPGA的超声波测风系统研究

利用超声波传感器进行风速测量时,温度对超声波传播有很大影响,时延估计对超声波测风系统的精度起到很大的作用。本超声波测风系统为避免温度对风速测量中的影响,采用了基于时差法的测量原理,为了提高时延估计值的精度,提出了基于最小均方(LMS)自适应时延估计的测量方法,研制了以单片机Atmega128和现场可编程门阵列(FPGA)为核心的硬件系统。仿真和实际测试的结果表明,该超声波测风系统的时延估计值精确度较高,具有很高的应用价值。     

物质密度分布的数值回归计算

由物体的万有引力场分布，回归计算其密度分布。     

大面积高温超导薄膜的Jc的无损伤测量

本报告了采用单线圈感应法对大面积高温超导薄膜的临界电流密度进行无损伤测定的情况。此法为研究Ｊｃ及磁通钉扎提供了新手段。我们从理论上推导了电流比常数值，并将由此算得的Ｊｃ值与传统的输运法Ｊｃ结果进行了比较，然后开展了一些讨论。     

薄板声谐振子扰动的声学特征检测研究

为进行快速ＮＤＴ，研究了薄板声谐振子扰动和声学特征变化的关系，用有限元方法分析在睡无缺陷薄板的振动频率和振型。利用数字信号处理技术，实验研究了样品中缺陷对声学特征的影响。实现和理论分析结果一致性很好。研究结果有助于正确利用样品声学特征进行无损检测。     

我国超声波疗法的临床应用进展

本文通过对第三届全国超声治疗学术会议（１９９５年１０月３１日－１１月４日于贵阳市）论文的综合介绍，显示了我国超声波疗法在临床应用方面所取得的成就。