Target oriented dimensionality reduction of hyperspectral data by Kernel Fukunaga–Koontz Transform

Principal component analysis (PCA) is a popular technique in remote sensing for dimensionality reduction. While PCA is suitable for data compression, it is not necessarily an optimal technique for feature extraction, particularly when the features are exploited in supervised learning applications (Cheriyadat and Bruce, 2003) [1]. Preserving features belonging to the target is very crucial to the performance of target detection/recognition techniques. Fukunaga–Koontz Transform (FKT) based supervised band reduction technique can be used to provide this requirement. FKT achieves feature selection by transforming into a new space in where feature classes have complimentary eigenvectors. Analysis of these eigenvectors under two classes, target and background clutter, can be utilized for target oriented band reduction since each basis functions best represent target class while carrying least information of the background class. By selecting few eigenvectors which are the most relevant to the target class, dimension of hyperspectral data can be reduced and thus, it presents significant advantages for near real time target detection applications. The nonlinear properties of the data can be extracted by kernel approach which provides better target features. Thus, we propose constructing kernel FKT (KFKT) to present target oriented band reduction. The performance of the proposed KFKT based target oriented dimensionality reduction algorithm has been tested employing two real-world hyperspectral data and results have been reported consequently.     

A high dynamic range structured light means for the 3D measurement of specular surface

This paper presents a novel structured light approach for the 3D reconstruction of specular surface. The binary shifting strip is adopted as structured light pattern instead of conventional sinusoidal pattern. Based on the framework of conventional High Dynamic Range (HDR) imaging technique, an efficient means is first introduced to estimate the camera response function. And then, dynamic range of the generated radiance map is compressed in the gradient domain by introducing an attenuation function. Subject to the change of lighting conditions caused by projecting different structured light patterns, the structure light image with middle exposure level is selected as the reference image and used for the slight adjustment of the primary fused image. Finally, the regenerated structured light images with well exposing condition are used for 3D reconstruction of the specular surface. To evaluate performance of the method, some stainless stamping parts with strong reflectivity are used for the experiments. And the results showed that, different specular targets with various shapes can be precisely reconstructed by the proposed method.     

屋面光伏板风荷载特性数值分析

风荷载在屋面光伏阵列结构体系设计中起控制作用。采用计算风工程的方法分析讨论了屋面光伏板的风荷载特性。数值算法采用分离涡模拟方法。数值计算结果与现有风洞实验数据的比较,验证了本文方法的正确性。考虑影响光伏板风荷载的因素主要有光伏板在屋面上的安装位置、安装倾角、光伏阵列之间的距离和风向等。计算结果表明,屋面处脱落的涡对安装在不同位置的光伏阵列风荷载的影响较明显。当倾角由15°增加到45°时,电池板受到的风荷载随着倾角的增加而增大。在一定阵列间距范围内,光伏板风荷载主要表现为前排对下游光伏板的遮挡影响。本文方法与结果能为屋面光伏建筑结构设计提供重要参考。     

Novel Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites:High-efficiency and magnetic recyclable catalysts for organic dye degradation

A facile step-by-step approach is developed for synthesizing the high-efficiency and magnetic recyclable Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites.This method involves coating Fe_2O_3 nanorods with a uniform silica layer,reduction in 10%H_2/Ar atmosphere to transform the Fe_2O_3 into magnetic Fe_3O_4,and finally depositing Ag@Ni core-shell nanoparticles on the L-lysine modified surface of Fe_3O_4@SiO_2 nanorods.The fabricated nanocomposites are further characterized by x-ray diffraction,transmission electron microscopy,scanning electron microscope,Fourier transform infrared spectroscopy,and inductively coupled plasma mass spectroscopy.The Fe_3O_4@SiO_2@Ag@Ni trepang-like nanocomposites exhibit remarkably higher catalytic efficiency than monometallic Fe_3O_4@SiO_2@Ag nanocomposites toward the degradation of Rhodamine B(RhB) at room temperature,and maintain superior catalytic activity even after six cycles.In addition,these samples could be easily separated from the catalytic system by an external magnet and reused,which shows great potential applications in treating waste water.     

6H-SiC单晶的激光刻蚀及光谱分析

激光微加工是半导体精密加工的一个有效方法。对于碳化硅(SiC)单晶,使用紫外波段激光可以获得对入射能量最大的吸收效率。使用355 nm全固态激光器对6H-SiC单晶进行刻蚀。同时将样品置于不同的介质下以探究最优加工条件。使用拉曼光谱表征激光刻蚀后的SiC表面。刻蚀后表面主要由无定形硅及纳米晶石墨组成,对于空气下刻蚀的SiC晶片,无定形硅主要分布于刻蚀坑的周围,刻蚀坑内较少。而在液体下刻蚀的样品,无定形硅的空间分布相反。通过分析残留在表面的物质,在另一角度研究了激光刻蚀的反应机理。对于液体辅助的激光加工,以往的研究主要关注液层的厚度及粘度,对液体还原性的研究很少。为确定液体还原性的影响,使用共聚焦激光扫描显微镜及能量色散谱检测了不同液体辅助加工样品的表面形貌及氧含量。结果表明,液体还原性在激光刻蚀过程中有着较大的影响,使用有着还原性的液体作为介质可以有效减少表面氧化并获得更规则的表面形貌。     

A posteriori error estimates for optimal control problems constrained by convection-diffusion equations

We propose a characteristic finite element discretization of evolutionary type convection-diffusion optimal control problems. Nondivergence-free velocity fields and bilateral inequality control constraints are handled. Then some residual type a posteriori error estimates are analyzed for the approximations of the control, the state, and the adjoint state. Based on the derived error estimators, we use them as error indicators in developing efficient multi-set adaptive meshes characteristic finite element algorithm for such optimal control problems. Finally, one numerical example is given to check the feasibility and validity of multi-set adaptive meshes refinements.     

Growth and characterization of a nonlinear optical crystal: l-histidine trifluoroacetate

A novel organic nonlinear optical crystal, l-histidine trifluoroacetate (LHTF), has been prepared, and single crystals had been grown by the controlled evaporation of the aqueous solution. Its solubility curve was determined gravimetrically. The structural, physicochemical properties of the grown crystals were characterized by X-ray powder diffraction, infrared spectroscopy and thermal analysis. Density functional theory at the B3LYP/6-31G (d, p) level had been used to compute the first-order hyperpolarizability of LHTF. The optical transmission spectrum and second-harmonic generation were investigated to study its linear and nonlinear optical properties.     

A facile route to prepare boron nitride hollow particles at 450 °C

Hexagonal boron nitride (h-BN) particles including hollow spheres (with a proportion of ~30–40%) and nanotubes (10%) have been synthesized by using sodium fluoroborate and sodium azide at 450 °C for 20 h. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) studies show that the as-obtained BN hollow particles are crystalline. The total specific surface area of the product calculated from Brunauer–Emmentt–Teller (BET) absorption measurement is 89.79 m²/g, indicating that it may be utilized as a promising candidate for hydrogen storage container or catalyst. Thermal gravimetric analysis (TGA) result reveals its excellent thermal stability below 800 °C. Its possible growth mechanism and the effects of reaction parameters were also briefly discussed.     

Preparation, phase transformation and microstructure of ZrxTi1−xO2 (x = 0.1-0.9) fine fibers

Zr_xTi_1−xO₂ (x = 0.1-0.9) fibers were prepared by the sol-gel dry-spinning method. Polyacetylacetonatozirconium (PAZ) and tetrabutyl titanate (C₁₆H₃₆O₄Ti) were used as raw materials. The green fibers were obtained from the amorphous spinnable solution and then heat-treated to convert into polycrystalline fibers. The main phase changes from TiO₂ to zirconium titanate (ZT) and then tetragonal ZrO₂ with increasing ZrO₂ content. The crystallization temperature varied with the molar ratio of Zr:Ti. The heat-treated fibers at 1050 °C have few pores and no cracks with diameters of 10-20μm and lengths of 1-5 cm.     

Carbon-based single atom catalyst: Synthesis,characterization, DFT calculations

Carbon-based single-atom catalysts(SACs) with atomic sizes of active sites have become the promising candidates for a variety of catalytic systems because of their high atom utilization, and unique electronic structures. Different types of single-atom sites can be fabricated via multiple preparation strategies, which would demonstrate distinct different coordination configurations and electronic features, and ultimately affected the structure-catalysis relationship of SACs in targeted reactions....