Segmentation of synthetic aperture radar image using multiscale information measure-based spectral clustering

A multiscale information measure （MIM）, calculable from per-pixel wavelet coefficients, but relying on global statistics of synthetic aperture radar （SAR） image, is proposed. It fully exploits the variations in speckle pattern when the image resolution varies from course to fine, thus it can capture the intrinsic texture of the scene backscatter and the texture due to speckle simultaneously. Graph spectral segmen- tation methods based on MIM and the usual similarity measure are carried out on two real SAR images. Experimental results show that MIM can characterize texture information of SAR image more effectively than the commonly used similarity measure.     

中药黄柏主要活性成分的光谱成像检测技术

为了实现中药主要活性成分的在体检测,运用光谱成像技术检测中药活性成分.使用自行开发的液晶光谱成像装置对中药黄柏的主要活性成分盐酸小檗碱进行了在体检测,选取紫外光源波长254 nm,获取了检品480～700 nm之间的连续荧光光谱图像.在分析检品光谱剖面图的基础上,以中国药品生物制品检定所提供的盐酸小檗碱标准品的光谱剖面图为依据,设计了高通滤波器得到了检品的特征光谱数据.对八种不同来源的市售黄柏饮片特征光谱,以及黄柏与其同科植物黄皮特征光谱的比较显示,使用本方法对中药进行定性、定量的检测,样品无需特殊处理,可在原生态的情况下进行;检测过程无损、实时;检测结果指纹特征明显.     

用于木材水分检测的单边核磁共振传感器设计

为了实现对木材水分的无损检测,设计了一种单边核磁共振（unilateral nuclear magnetic resonance,UMR）传感器,该传感器由单边磁体、抗涡流板、射频线圈、阻抗匹配和调谐电路构成．在距离传感器表面上方75 mm处的50 mm×50 mm的平面内,建立了71.1 mT（共振频率为3.027 MHz）的静态磁场．本文详细介绍了该传感器的设计思路和实现方法,并开展了初步的木材水分无损测量实验．对圆柱形树桩的径向水分分布进行了一维扫描测量,观察了水分由树皮向树芯逐步深入过程中横向弛豫时间（T₂）的变化规律,还使用UMR仪对木材干燥过程中水分的挥发进行了测量.实验结果表明,随着干燥的加剧,被测样品T₂谱的长T₂波峰明显左移、积分面积渐减,而且积分面积与木材样品含水率呈正比．本文为木材研究提供了一种便携的NMR测量设备设计方案,且可以实现野外活体树木的无损测量．     

Characteristics of deep penetration laser welding of dissimilar metal Ni-based cast superalloy K418 and alloy steel 42CrMo

Experimental trials of autogenous deep penetration welding between dissimilar cast Ni-based superalloy K418 and alloy steel 42CrMo flat plates with 5.0 mm thickness were conducted using a 3 kW continuous wave (CW) Nd:YAG laser. The influences of laser output power, welding velocity and defocusing distance on the morphology, welding depth and width as well as quality of the welded seam were investigated. Results show that full keyhole welding is not formed on both K418 and 42CrMo side, simultaneously, due to the relatively low output power. Partial fusion is observed on the welded seam near 42CrMo side because of the large disparity of thermal–physical and high-temperature mechanical properties of these two materials. The microhardness of the laser-welded joint was also examined and analyzed. It is suggested that applying negative defocusing in the range of Raylei length can increase the welding depth and improve the coupling efficiency of the laser materials interaction.     

一维光子晶体缺陷模的偏振特性研究

利用周期结构的布洛赫定理推导了一维无限光子晶体缺陷模方程,研究了缺陷模的偏振特性,以及在不同入射角和缺陷层厚度下缺陷模位置的变化.利用传输矩阵方法对有限周期数光子晶体也进行了研究,分别对应一维无限光子晶体和有限周期数光子晶体给出了数值计算结果.通过比较这两者的数值结果得出了缺陷模随入射角和缺陷层厚度变化的一般规律.     

Geometric phase in a composite system subjected to decoherence

In this paper, we investigate the geometric phase of a composite system which is composed of two spin- particles driven by a time-varying magnetic field. Firstly, we consider the special case that only one subsystem driven by time-varying magnetic field. Using the quantum jump approach, we calculate the geometric phase associated with the adiabatic evolution of the system subjected to decoherence. The results show that the lowest order corrections to the phase in the no-jump trajectory is only quadratic in decoherence coefficient. Then, both subsystem driven by time-varying magnetic field is considered, we show that the geometric phase is related to the exchange-interaction coefficient and polar angle of the magnetic field.     

基于在聚合物中掺杂染料DCJTB的白色有机电致发光器件

将Alq₃和DCJTB作为掺杂物与基质PVK按照不同比例混合共溶,旋涂成膜,制备了PVK∶Alq₃∶DCJTB为发光层的结构为ITO/ PVK∶Alq₃∶DCJTB/ BCP/Alq₃/LiF/Al的器件,其中Alq₃和BCP分别用作电子传输层和空穴阻挡层,PVK用作蓝光发光层和空穴传输层。保持PVK和DCJTB的质量比为100∶1不变,改变PVK和 Alq₃的质量比,当PVK和Alq3的质量比为20∶1时,得到了效果较好的白光。器件在电压为14 V时,色坐标达到(0.33,0.36),在10～14 V范围内变化甚微。     

Photolyses of mammalian carboxy-hemoglobin studied by photoacoustic calorimetry

The enthalpy and conformational volume changes in the photolyses of carboxy-hemoglobin (HbCO) of human, bovine, pig, horse and rabbit are investigated by photoacoustic calorimetry. Considering the time scales of the exciting laser pulse and the receiving ultrasound transducers (PVDF films and PZT ceramics), as well as the reaction lifetimes in the photolysis processes of HbCO, the measured results are related to the geminate recombination and tertiary relaxation in photolyses of HbCO. Moreover, the quantum yields of the five mammals are also measured by laser pump-probe technique. The results show that the dynamic parameters, such as enthalpy and conformational volume changes, differ between the processes of the geminate recombination and tertiary relaxation. Also, the dynamic parameters differ among the five mammals although some of them may be consistent with each other.     

Investigation of Bessel beam propagation in scattering media with scalar diffraction method

Bessel beam propagation in scattering media is simulated using the angular spectrum method combined with slice-by-slice propagation model. Generating Bessel beams with a spatial light modulator, which provides a means to adjust flexibly the parameters of the Bessel beam, allows us to validate the simulation results experimentally. The study reveals that the self-reconstructing length changes oppositely with the axicon angle （i.e., the larger the axieon angle, the shorter the self-reconstructing length）. The radius of the incident beam has little influence on the self-reconstruction of the Bessel beam central lobe.     

Theoretical study of LiCl− and LiBr− molecular ions

The molecular structures and spectroscopic constants of the ground electronic states of LiCl^? and LiBr^? are investigated with the coupled-cluster method. To improve the accuracy of our calculations, we have employed the extrapolation schemes as well as corrections of the core–valence correlation and scalar relativistic effect. The equilibrium parameters, potential energy curves, force constants, vibrational energy levels and spectroscopic parameters of both molecular ions are derived, in which those of LiBr^? are reported for the first time. The electron affinities and vertical detachment energies of neutral and anionic LiCl and LiBr are also evaluated.