基于双阈值视觉注意模型的图像关注焦点检测

 图像关注焦点（FOA）检测是基于人眼视觉关注模型的图像感兴趣区提取的关键技术。为了更加精确、合理地搜索图像关注焦点,提出一种基于双阈值视觉关注模型的FOA检测算法。算法首先提取图像的亮度、颜色、方向和离散矩变换（DMT）特征,生成各个特征对应的特征图;然后将各特征图合并为一张包含多种特征的显著图;最后根据显著图的灰度直方图建立静态阈值与动态阈值,确定图像关注焦点的位置与数量。实验结果表明：新算法在图像关注焦点检测的准确性上较Itti模型有更为优秀的表现,更符合人眼视觉的关注习惯。     

酚羟基对木质素吸附层致密程度的影响

研究了酚羟基对木质素在固液界面上形成的吸附层致密程度的影响及作用机理.通过对碱木质素(AL)进行乙酰化处理制备了酚羟基含量显著减少的乙酰化木质素(ACAL).借助耗散型石英晶体微天平(QCM-D)研究了溶液环境中AL和ACAL所形成的单层吸附膜致密程度的差异,结合紫外-可见光光谱仪(UV)和原子力显微镜(AFM)研究了AL和ACAL分别与聚二烯丙基二甲基氯化铵(PDAC)交替自组装所形成的多层吸附膜的致密程度在干燥状态下的差异.结果都表明,酚羟基的存在会使木质素吸附层致密程度降低.分析认为,酚羟基的存在不利于木质素中的芳香环形成共面结构,酚羟基含量降低后会引起芳香环间的共面性增强,促进形成致密的π-π堆积,从而使得木质素吸附层致密程度增大.     

热熔型反光道路标线涂料的红外光谱三级鉴定

为了能从交通事故现场的微量物证中检测出道路标线涂料,并进一步区分其厂牌,选取国内三个不同厂牌的热熔型反光道路标线涂料及其配方原料,利用一维红外光谱(FTIR)、二阶导数光谱(SD-IR)、二维相关光谱(2D-IR)进行三级鉴定研究。实验结果表明,三个厂牌的涂料在一维谱图上峰形相似度很高,只是吸收峰波数有一定的差异,在1 435 cm-1附近都有宽强吸收峰,879,2 955,2 919,2 870 cm-1附近也有较强吸收峰,经过分区域局部放大并与每种配方原料图谱比对分析,可将三个厂牌涂料加以区分,700～970和1 370～1 660 cm-1区域内主要反映出三厂牌涂料的重质碳酸钙相对含量不同,2 800～2 960 cm-1区域内主要反映出聚乙烯蜡(PE蜡)、乙烯醋酸乙烯树脂(EVA)、邻苯二甲酸二辛酯(DOP)的相对含量不同。二阶导数谱图不仅验证了一维光谱分析的结果,而且进一步扩大微观差异,并在512～799 cm-1区域内反映出石英砂相对含量的不同。在1 351～1 525 cm-1范围内的二维红外相关光谱中,自动峰出现的位置和个数有着更为显著的差异。因此,红外光谱三级鉴定是一种快速有效识别、区分热熔型反光道路标线漆的方法,并且表观分辨率逐级提高。     

BrCN分子的电子碰撞离子对解离

离子对解离是一类重要的分子过程,常发生于分子被激发到超激发态. 与光激发的离子对解离实验研究不同,电子碰撞的相关过程研究尚存在实验挑战,特别是在测定其阈值方面. 本文报道了相关的利用单色化电子碰撞分子的实验研究进展. 以BrCN→Br^-+CN⁺离子对解离为例,根据CN⁺离子出现能测定其解离阈值为13.78 eV,同时在16.09 eV获得了CN⁺离子的时间切片速度影像且显示出动量分布的各向异性.     

亚轨道可重复使用飞行器轨迹/总体参数一体化优化方法

针对亚轨道可重复使用运载器(SRLV)的应用需求,在将卫星投送到预定轨道同时确保SRLV安全返回的前提下,对基于记忆原理的轨迹/总体参数一体化优化方法进行了研究。记忆优化算法是一种具有全局收敛性的随机搜索方法,每次搜索的试探解优劣状态由记忆元来存储。利用记忆原理的记忆增强和遗忘规律来衡量优化搜索过程中试探解的状态,并以燃料最省作为优化指标。同时采用三种不同的搜索策略,实现对试探解的随机搜索,避免陷入局部极小问题,并以此来提高搜索速度。仿真表明:卫星入轨速度偏差小于2 m/s,高度偏差小于10 m,轨道倾角偏差小于0.000 1°。SRLV最终与着陆场的位置偏差小于100 m,速度偏差小于5 m/s。相较于传统的轨迹优化方法,新方法适用于复杂的轨迹/参数一体化优化问题,搜索速度快,求解精度高,有利于算法在工程实际中的应用与推广。     

Light-scattering model for aerosol particles with irregular shapes and inhomogeneous compositions using a parallelized pseudo-spectral time-domain technique

To improve the modeling accuracy of radiative transfer, the scattering properties of aerosol particles with irregular shapes and inhomogeneous compositions should be simulated accurately. To this end, a light-scattering model for nonspherical particles is established based on the pseudo-spectral time domain(PSTD) technique. In this model, the perfectly matched layer with auxiliary differential equation(ADE-PML), an excellent absorption boundary condition(ABC) in the finite difference time domain generalized for the PSTD, and the weighted total field/scattered field(TF/SF) technique is employed to introduce the incident light into 3 D computational domain. To improve computational efficiency, the model is further parallelized using the Open MP technique. The modeling accuracy of the PSTD scheme is validated against Lorenz–Mie, Aden–Kerker, T-matrix theory and DDA for spheres, inhomogeneous particles and nonspherical particles, and the influence of the spatial resolution and thickness of ADE-PML on the modeling accuracy is discussed as well. Finally, the parallel computational efficiency of the model is also analyzed. The results show that an excellent agreement is achieved between the results of PSTD and well-tested scattering models, where the simulation errors of extinction efficiencies are generally smaller than 1%, indicating the high accuracy of our model. Despite its low spatial resolution, reliable modeling precision can still be achieved by using the PSTD technique, especially for large particles. To suppress the electromagnetic wave reflected by the absorption layers, a six-layer ADE-PML should be set in the computational domain at least.     

Characterization of barrier-tunable radio-frequency-SQUID for Maxwell's demon experiment

We present the design, fabrication, and characterization of a barrier-tunable superconducting quantum interference device(SQUID) qubit for the study of Maxwell's demon experiment. In this work, a compound Josephson junction(CJJ)radio-frequency(RF)-SQUID qubit with an overdamped resistively shunted direct-current(DC)-SQUID magnetometer is used to continuously monitor the state of the qubit. The circuit is successfully fabricated with the standard Nb/Al-Al Ox/Nb trilayer process of our laboratory and characterized in a low noise measurement system, which is capable of measuring coherent dynamics of superconducting qubits, in an Oxford dilution refrigerator. All circuit parameters are determined accurately by fitting experimental data to theoretical analysis and simulation, which allows us to make a quantitative comparison between the results of the experiment and theory.     

Optical total reflection and transmission with mode control in a dielectric subwavelength nanorod chain

We report a polarization dependent reflection phenomenon beyond the normal incidence with a subwavelength nanorod chain.Light waves of the transverse electric mode will be totally reflected while those of the transverse magnetic mode will transmit through.The total reflection or transmission phenomenon can be seen as a constructive or destructive interference of the incident field with the transverse mode field of the chain.With the low-loss feature and the ultra-compact characteristic,this structure may find applications in photonic circuits.     

拟合橡胶类材料非等双轴变形数据的显式超弹性势

基于样条插值的直接方法,构造精确符合单轴和等双轴拉伸数据以及剪切数据的大变形超弹性势,给出显式表达式,避免了现有各方法寻求待定参数组达到近似拟合的复杂计算过程;推导了一般变形情形下的应力应变关系,对非等双轴拉伸实验进行了预测,并与Rivlin和Saunders的非等双轴拉伸实验数据进行了对比,预言结果与实验数据一致．     

基于三角波瓣混合器的超声速流场精细结构和掺混特性

在超声速吸气式混合层风洞中,采用基于纳米粒子的平面激光散射(NPLS)技术对平板混合层和三角波瓣混合器诱导的混合层流场精细结构进行了对比实验研究.上下两层来流的实测马赫数分别为1.98和2.84,对流马赫数为0.2.NPLS图像清晰地展示了Kelvin-Helmholtz涡、流向涡、波系结构以及大尺度涡结构的配对合并过程.通过对比分析时间相关的NPLS流场图像,发现了大尺度拟序结构随时间发展演化的非定常特性.基于流动显示结果,采用分形维数和间歇因子指标对流场结构和混合特性进行了定量分析.实验研究表明,三角波瓣混合器诱导的流向涡结构显著提高了上下两层来流的掺混效率,其流动远场的分形维数突破了平板混合层中完全湍流区的分形维数值,达到了1.88,流场结构表现出明显的破碎性,有利于流动在标量层面的扩散和掺混.流动间歇性分析表明,流向涡与展向涡的相互剪切作用主导着混合层的掺混特性,同时由于流向涡的卷吸作用,三角波瓣混合器诱导的混合层混合区域更大,更多的流质被卷入混合区完成混合.