基于结构性信息的纹理合成与图像修复

纹理合成与图像修复是计算机图形学中的一个研究热点,具有广泛的应用前景．提出了一种基于结构性信息的判断纹理块匹配误差的新方法：颜色-结构差异算法．该方法同时考虑了纹理块之间颜色误差和结构误差对纹理块的相似性的影响,弥补了单纯考虑颜色误差的不足,保证了图像间结构信息的连贯性,从而确保合成后的纹理及修复后的图像在视觉上的连贯性．     

甲烷浓度对CVD自支撑金刚石薄膜残余应力的影响

根据唯像理论研究了化学气相沉积自支撑金刚石薄膜中织构和弹性性能之间的关系,揭示了晶体取向和织构对残余应变和残余应力的影响.织构使CVD金刚石薄膜杨氏模量和宏观残余应变呈现各向异性,而且两者呈现相反的分布规律.织构和杂质都能影响金刚石薄膜的弹性模量和残余应变,但是织构的影响是主要的.实验中测量的残余应变很好的符合了根据薄膜织构计算得到的弹性模量值.因此可以借助改变薄膜织构来调节薄膜的残余应力.     

田间行走式测定的红外光谱数据与土壤质地之间的相关性研究

近红外光谱是利用漫反射来分析物质的某些化学性质,已在农业及其他许多领域得到广泛应用。尽管在实验室条件下,研究证明可以应用近红外光谱分析技术来快速、方便地测定土壤参数,但在田间大范围内应用红外光谱快速测定来分析土壤性质,仍然缺乏研究;该研究以田间行走式设备获取的红外光谱数据为基础,分析和比较了不同数据处理技术下红外光谱信息与土壤质地之间的相关性,发现应用基于算术运算的波段组合技术可以明显地提高红外光谱信息与土壤质地之间的相关性,为田间光谱数据的分析处理与应用提供了依据。     

一种基于胸部CT图像感兴趣区域提取的检索技术

探索高效的医学图像检索技术,可以方便医务人员快速高效地查找相似的图像．针对胸部CT图像,提出一种采用改进的区域生长法提取感兴趣区域,在此基础上再提取纹理特征作为图像的特征向量,并以特征向量作为图像检索的依据来进行检索．实验结果表明：在有效提取出病灶区域之余,针对该区域提取图像特征起到了良好的检索效果．将此方法应用于医学图像检索系统可有助于提高医生的诊断效率．     

Tightly bound soil water introduces isotopic memory effects on mobile and extractable soil water pools

Cryogenic vacuum extraction is the well-established method of extracting water from soil for isotopic analyses of waters moving through the soil–plant–atmosphere continuum. We investigate if soils can alter the isotopic composition of water through isotope memory effects, and determined which mechanisms are responsible for it. Soils with differing physicochemical properties were re-wetted with reference water and subsequently extracted by cryogenic water distillation. Results suggest some reference waters bind tightly to the soil and not all of this tightly bound water is removed during cryogenic vacuum extraction. Kinetic isotopic fractionation occurring when reference water binds to the soil is likely responsible for the ¹⁸O-depletion of re-extracted reference water, suggesting an enrichment of the tightly bound soil water pool. Further re-wetting of cryogenically extracted soils indicates an isotopic memory effect of tightly bound soil water on water added to the soil. The data suggest tightly bound soil water can influence the isotopic composition of mobile soil water. Findings show that soils influence the isotope composition of soil water by (i) kinetic fractionation when water is bound to the soil and (ii) equilibrium fractionation between different soil water pools. These findings could be relevant for plant water uptake investigations and complicate ecohydrological and paleohydrological studies.     

具有面内四极磁场的旋转玻色-爱因斯坦凝聚体的基态结构研究

通过虚时演化方法研究了具有面内四极磁场的旋转玻色-爱因斯坦凝聚体的基态结构.结果发现:面内四极磁场和旋转双重作用可导致中央Mermin-Ho涡旋的产生;随着磁场梯度增强,Mermin-Ho涡旋周围环绕的涡旋趋向对称化排布;在四极磁场下,密度相互作用和自旋交换相互作用作为体系的调控参数,可以控制Mermin-Ho涡旋周围的涡旋数目;该体系自旋结构中存在双曲型meron和half-skyrmion两种拓扑结构.     

偏振-高光谱多维光信息的番茄叶片营养诊断

以Venlo型温室中无土栽培模式下自行培育的25%,50%,75%,100%,150%五个梯度水平的氮、磷、钾营养胁迫样本为研究对象,利用高光谱成像系统以及课题组自行研发的偏振反射光谱测量分析系统分别采集不同氮磷钾营养水平番茄叶片的偏振光谱和高光谱数据。通过扫描电镜分析阐明营养胁迫叶片非光滑表面的凹凸和质地发生的一系列变化与偏振反射辐射之间具有一定的联系。由斯托克斯公式将偏振光谱换算成偏振度后,提取偏振度与氮磷钾实测值之间的各4个偏振度特征;同时将高光谱数据经过主成分分析降维并确定氮磷钾各4个特征波长,再通过相关分析法提取这4个特征波长下的各8个高光谱图像纹理特征。偏振度特征与高光谱纹理特征相加累计氮磷钾各12个特征作为支持向量回归(SVR)的输入变量。对这12个特征变量进行最大—最小值归一化后,采用SVR建立番茄氮磷钾营养水平的定量诊断模型,求得氮的相关系数r=0.961 8,均方根误差RMSE=0.451;磷的相关系数r=0.916 3,均方根误差RMSE=0.620;钾的相关系数r=0.940 6,均方根误差RMSE=0.494。研究结果表明采用偏振反射光谱结合高光谱的多维光信息融合技术能够建立精度较高的番茄营养水平预测模型,具有较好的诊断作用,对于提高模型的精度和专用仪器的开发具有一定的指导意义,为番茄养分含量的快速检测提供了新的思路。     

表面织构对界面接触参数影响的实验研究

机械接触表面的接触刚度和接触阻尼是直接影响界面振动水平的两个重要动力学参数。本文介绍了一种测试机械连接界面接触刚度和接触阻尼的实验装置和方法,并针对用两种不同加工方法(激光加工及线切割)加工出的具有不同尺寸织构的试样与光滑平面相接触的界面进行了测量,初步探索了平面接触刚度和接触阻尼的表面织构效应,并得出结论：织构及润滑对接触刚度会产生一定影响,而实验中均未观察到这两者对接触阻尼有明显影响。     

Propagation and scattering of ultrasonic waves in polycrystals with arbitrary crystallite and macroscopic texture symmetries

A general ultrasonic attenuation model for a polycrystal with arbitrary macroscopic texture and triclinic ellipsoidal grains is described with proper accounting for the anisotropic Green’s function for the reference medium. The texture and the ellipsoidal grain frames in the model are independent and the wave propagation direction is arbitrary. The attenuation coefficients are obtained in the Born approximation accompanied by the Rayleigh and stochastic asymptotes. The scattering model displays statistical anisotropy due to two independent factors: (1) shape of the oriented grains and (2) preferred crystallographic orientation of the grains leading to macroscopic anisotropy of the homogenized reference medium. The model is applicable to most single phase polycrystalline materials that may occur as a result of thermomechanical manufacturing processes leading to different macrotextures and elongated-shaped grains. It predicts the strength of ultrasonic scattering and its dependence on frequency and propagation direction as a function of grain shape, grain crystallographic symmetry and macroscopic texture parameters and provides the texture-induced dependence of macroscopic ultrasonic velocity on propagation angle. It considers proper wave polarizations due to macroscopic anisotropy and scattering-induced transformations of waves with different polarizations. Competing effects of grain shape and texture on the attenuation are observed. In contrast to the macroscopically isotropic case, where in the stochastic regime the attenuation is highest in the direction of the longest ellipsoidal axis of the grain, the wave attenuation in the elongation direction may be suppressed or amplified by the texture with different effects on the quasilongitudinal and quasitransverse waves. The frequency behavior is also interestingly affected by texture: a hump in the total attenuation coefficient is found for the fast quasitransverse wave which is purely the result of macroscopic anisotropy and the existence of two quasitransverse waves; this hump is not observed in the macroscopically isotropic case. Striking differences of the texture effect on the directional dependences of the attenuation coefficients are found at low versus high frequencies.     

表面织构对刀具切削性能及前刀面摩擦特性的影响

为了研究刀具表面织构对切削性能的影响,通过控制前刀面上微凹坑的直径、深度和面积占有率等参数制备了两组表面高度算术平均值Sa相同的织构刀具.使用Talysurf CCI Lite非接触式三维光学轮廓仪对织构表面进行测量,采用ISO25178参数对测量表面进行表征;通过SL200KS接触角测量仪测量织构刀具前刀面湿润性的变化;随后在CA6140车床上进行45钢切削试验,研究不同织构对切削力、前刀面摩擦特性、工件表面粗糙度和切屑形变的影响.结果表明:合理的表面织构能够改善刀具的切削性能;切削液在前刀面铺展较快的织构刀具获得了较好的切削性能;凹坑直径、深度和面积占有率的协同作用对改善刀具切削性能至关重要,为了协调这三个织构参数,进一步研究三维表征参数Sku、Ssk、Sv、Vvv、Vvc、Sdv、Sda、Spd与刀具切削性能的关联性,为刀具表面设计提供了基础.