Ultrasonic guided wave inspection with array sensors

Ultrasonic guided wave becomes one of promising tool for monitoring various types of structures such as large steel plates, vessels, and pipes in oil, chemical or nuclear industry, because guided waves have ability to travel wide range of the target structure in a single position. However, analysis of guided wave signals acquired from structure is difficult on account of low S/N ratio and its dispersive nature. To improve S/N ratio and overcome dispersion effect, focusing techniques for guided waves are needed. Thus, in this study, focusing techniques for guided waves were developed in order to improve long range inspection ability, and performance of the developed techniques was verified by experiments.     

A method for detecting target echo in reverberation based on fractional Fourier transform

A method for detecting the target echo in reverberation was proposed based on fractional Fourier transform theory when the transmitted signal is linear frequency modulation signal. The slow time-varying envelope of reverberation is computed to process reverberation to be stationary. The stationary reverberation is cut into blocks using a sliding window. A narrow-band filter is applied in FrFT domain for each block and the signal is recovered through inverse FrFT. Output of the system is the energy of the recovered signal. When the target echo is included in one of the blocks, the reverberation noise is reduced, and the output is the energy of the target echo. All the simulation and lake experiment results show that the detection performance of the present method is better than that of the matched filter.     

第三方检测市场入侵条件下乳品供应链网络均衡研究

构建包含生鲜乳供应商、第三方检测机构、乳品制造商以及需求市场的乳品供应链网络均衡模型，揭示第三方检测机构入侵下，生鲜乳检测技术革新投入水平变化对乳品供应链各层级均衡决策的影响。研究结果表明：第三方检测机构承担生鲜乳检测技术投入，有利于供应链检测质量水平的提升，行业风险规避能力加强，供应链整体获利增加，是实现乳品供应链治理的有益尝试；生鲜乳供应商应在质量控制上占据主导地位，通过价格传导机制，促使乳制品制造商分担部分检测费用；政府在第三方检测环境下扮演监管角色，通过补贴与惩罚举措提升第三方检测机构的公平性及公正性，并通过策略调整来推动第三方检测的市场化运作。     

核酸的分子结构--脱氧核糖核酸的结构

我们希望提出脱氧核糖核酸盐 (DNA)的一种结构模式 ,该结构模式将具有十分重要的生物学意义 .泡令 (Pauling)和科里 (Corey)已经提出过一种核酸结构并在稿件正式发表之前很友善地供我们参考[1] .他们的模型含有 3股相互缠绕的长链 ,核酸分子中的磷酸基团都位于中心轴的内侧 ,碱基排布于外侧 .我们认为该模型是不能令人满意的 ,理由如下 :(1)我们相信 ,产生X射线衍射图的是盐 ,而不是自由核酸 .在没有呈酸性的氢原子、尤其是在相互排斥的、带负电荷的磷酸基团都位于DNA长链中心轴附近的情况下 ,究竟靠什么力量将这种结构保持在一起呢 ?(2…     

双功能化合物-二氯荧光素二丙烯酸酯的合成与生物活性

荧光素主要用于生物细胞染色。本文合成了二氯荧光素二丙烯酸酯,并用元素分析,核磁共振,红外、紫外、荧光光谱进行表征,考察发现它对人体外培养肿瘤细胞L1210有很强的瞬时杀伤作用;对人体胃腺癌(SGC 7901)细胞增殖有很强的抑制作用;并可用于鉴定蚕豆花粉细胞的生活力和生活状态。1　实验部分1 1　试剂与仪器荧光素(上海医药化工试剂采购供应站)、丙烯酸、氯化亚砜(A R)。细胞由中科院上海药物研究所提供。意大利1106型元素分析仪,NICOLETFT IR170SX型IR仪(KBr压片),FT Ac80型核磁共振仪,KOFLER熔点仪(温度计未校正)。1 2　…     

生物固体核磁共振探头最新技术突破

美国瓦里安公司与诺伊大学香槟分校（UIUC）合作研制出最新的生物固体核磁共振探头[Bio-MAS（TM）]，该探头主要应用于固态蛋白或其它固态生物分子的结构鉴定。Bio—MAS（TM）采用了卷形线圈设计技术，从而使得Bio—MAS（TM）的发热量较之常规探头降低了3倍。