近红外光谱技术快速预测泡桐活立木年轮密度

应用近红外光谱分析技术主要对兰考泡桐活立木年轮密度进行了研究。取样时采用无损的方式,即不伐木,只从样木胸径处钻取直径为5 mm的木芯;用近红外光谱仪采用自动进级式采集样品光谱,波谱范围为350～2 500 nm;密度值采用水银体积仪测量;校正模型和预测模型建立与分析采用偏最小二乘和完全交互验证法。研究结果表明,中径级和大径级泡桐所选年轮数与近红外光谱值之间均存在很好的相关关系,预测模型相关系数分别达0.88和0.91;中径极的泡桐年轮密度与近红外光谱的校正模型和预测模型相关系数分别达到0.90和0.83,校正标准误差(SEC)和预测标准误差(SEP)分别为0.012和0.016。由此可见,该法可简单、快速、无损的预测中径级即接近采伐龄泡桐活立木的年轮密度。     

双泡模型共振频率的超声空化动力学研究

该研究旨在研究双泡模型的自然共振频率对超声空化的影响,通过理论计算研究了自然共振频率的影响因素,以及单频超声和双频超声与自然共振频率的关系。研究结果表明：气泡初始半径是影响自然共振频率的主要因素;低频驱动下的非线性波动程度会比高频的更加剧烈,当驱动频率等于气泡自然共振频率时,超声空化的效果更好;双频超声取气泡自然共振频率时超声空化效果远远优于单频超声驱动。该研究在超声医学和理解超声空化特性方面有着重要的意义。     

Accurate Phase Shift Extraction for Generalized Phase-Shifting Interferometry

An accurate phase shift extraction method for generalized phase-shifting interferometry is suggested. Based on the nearly random phase distribution of the diffraction field of the object, a singular formula is derived to calculate the unknown phase shift without the requirements of an iteration process or the selection of the correct value from two or more possible phase shift solutions as needed before. This method can be used in the cases of two or more frames with both smooth and diffusing object surfaces. Computer simulations and optical experiments have satisfactorily verified the efficiency and accuracy of this method.     

原子转移自由基聚合引发体系的最新研究进展

本文介绍了关于原子转移自由基聚合（ATRP）引发-活化-失活过程的最新研究情况,包括RATRP、SR&NI ATRP、AGET ATRP、ARGET ATRP以及ICAR ATRP等新型ATRP引发体系。这些新型ATRP体系逐渐克服了通常ATRP体系的局限性,尤其是后两种体系仅需微量（1～50 ppm）价态稳定的过渡金属络合物调控聚合,大大简化了ATRP方法的工业化生产程序;本文同时介绍了杂化及双金属ATRP催化体系,这两种新型催化体系具有较高的催化活性和对聚合反应的调控能力,而且通过简单地过滤或沉降就可从聚合产物当中脱除。     

数字同轴全息颗粒场检测中的颗粒分割识别与独立聚焦

针对数字同轴全息颗粒场检测中不同层面颗粒的自动聚焦问题,通过分析颗粒场数字同轴全息记录与再现的特点,提出一种颗粒分割识别与独立聚焦方法.给出了对单个颗粒进行聚焦判断的独立聚焦判据函数、以及实现颗粒分割识别和独立聚焦的方法.通过单层单个、两层两个及多层多个颗粒场的实验,验证了所提出方法的正确性.     

机理转移法合成星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯共聚物的研究

结合活性负离子聚合与原子转移自由基聚合(ATRP),采用机理转移法制备了一系列窄分布且分子量可控的星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯接枝共聚物(SC-(PB-g-PMMA)).首先通过阴离子聚合,制备星形聚丁二烯,后经甲酸-过氧化氢原位环氧化对链中部分双键进行环氧化,再与原位生成2-溴异丁酸发生酯化反应,得到具有链中活性溴的星形大分子引发剂(SPB-Brn).然后,利用该大分子引发剂,采用CuCl/CuCl2/PMDETA催化体系,通过ATRP聚合单体MMA,合成出星形梳状SC-(PB-g-PMMA)聚合物.通过GPC,1H-NMR和FTIR等分析手段对合成的星形大分子引发剂及星形梳状聚合物进结构表征,证实得到目标产物,并同时研究了聚合物的热力学性质与溶液性质.     

Multiple-image encryption by two-step phase-shifting interferometry and spatial multiplexing of smooth compressed signal

A multiple-image encryption method based on two-step phase-shifting interferometry(PSI) and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing(CS)and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme,only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.