一类新疆民族风格的织物图案生成方法

独具文化内涵的新疆民族织物图案是中华民族艺术瑰宝的重要组成部分。为了生成一类具有民族特色或风格的新疆织物图案,如何自动分割织物图案提取风格特征是一个关键问题。论文以需求为驱动,提出了纹样基因的概念。首先利用连通区域标记法切割图案,提取分割区域特征,根据投票原则过滤获得纹样基因;然后设计六边形构型,嵌入纹样基因;按构型旋转变换生成具有民族风格的织物图案。以提取维吾尔族和哈萨克族两类民族织物图案纹样基因,利用六边形结构堆砌生成图案进行仿真实验,并对图案的风格相似度进行评价。结论是基于纹样基因的生成算法,不仅能够丰富图案风格化设计素材,而且为传承民族图案风格设计提供新途径。     

Growth of hexagonal selenium crystals: Observation of new growth morphologies

In this communication, we report the single crystal growth of selenium by the solution method. We have observed a new mesh-like growth pattern in hexagonal selenium for the first time. Crystals having hexagonal morphology are packed together like hay stick bunches.     

Fabrication of two-dimensional superposed microstructure by interference lithography

In this paper, we report the basic theory and method of single exposure interference lithography (IL) to fabricate two-dimensional (2D) superposed microstructures. Distribution of six-beam interference intensities with different azimuth angle is discussed, and 2D superposed microstructures with different periodic constants are obtained by computer simulations. The experiment results using CHP-C positive photoresist show a 2D superposed photonic crystal composed of a periodically repeated hexagonal pattern of hexagonal lattice cells, which is in close agreement with the computer simulation. Fabrication of a superposed structure by single exposure IL paves the way for studying 2D photonic crystal fabrication, surface lasing, optical waveguides, and so on.     

Compact sensor for measuring two-dimensional tilt using a two-dimensional transmission grating and the Talbot effect

This paper proposes a tilt sensor that measures the small two-dimensional tilt of a plane reflective object using the Talbot effect. It is an extension of a previously proposed one-dimensional tilt sensor. The light beam reflected from the object impinges on a hexagonal grating, and the intensity of the diffracted wave is detected on an image sensor located at a Talbot distance from the grating. The diffraction intensity displaces due to the tilt of the object. The displacement is calculated by the Fourier transform method to obtain the two-dimensional tilt. This sensor is very simple and compact. The principle of the sensor is explained for a grating with a general pattern. An experiment using a hexagonal grating shows its validity. Discussions are given for making it more practical.     

Application of generalized grating imaging to pattern projection in three-dimensional profilometry

The theory of generalized grating imaging for a one-dimensional grating is applied to a pattern projection system in pattern projection profilometry. Contrast of the projected grating image is calculated under various conditions. The results help to determine the conditions suitable for obtaining high contrast grating images in a large space. Although the gratings required for the profilometry are hexagonal, the theory for two-dimensional gratings is prohibitively complex. Therefore, the projection system was designed using the one-dimensional theory. The projection system using two-dimensional hexagonal gratings was constructed and experiments were done with it. The result agrees approximately with the theoretical calculations for one-dimensional gratings. This suggests that the one-dimensional theory may be used for estimating the approximated behavior for hexagonal gratings for use in pattern projection profilometry. Some discussions are given for the application of the projection system for profiling the mannequin or human body.     

Periodic ZnO nanorod arrays defined by polystyrene microsphere self-assembled monolayers

We demonstrate a low-cost and effective method to fabricate hexagonally patterned, vertically aligned ZnO nanorod arrays. Selective wet-etching is used to develop the catalyzing gold particle hexagonal pattern with the aid of a polystyrene microsphere self-assembled monolayer. The gold particles have tunable sizes independent of the polystyrene microsphere's diameter and are inherently round in shape. Each ZnO rod is grown individually from a catalyzing site via catalyst-initiated epitaxy, and the original hexagonal periodicity is well-preserved. The rods have flat ends, and the diameters of the rods can be controlled well by the amount of source materials. This method provides a promising way to create ZnO one-dimensional nanostructures for applications as two-dimensional photonic crystal, sensor arrays, nanolaser arrays, and optoelectronic devices.     

Flower-like Se nanorods synthesized via carbamide-assisted hydrothermal routes

Flower-like Se nanostructures consisting of clusters of nanorods with width of 40–100 nm and length of several 100 nm have been synthesized via a carbamide-assisted hydrothermal method. The optimal clusters are composed of nanorods protruding from a central point. FESEM and TEM demonstrate the flower-like morphology. The X-ray diffraction (XRD) pattern shows that the as-prepared flower-like Se nanostructures are of hexagonal phase.     

Hierarchical structural nanopore arrays fabricated by pre-patterning aluminum using nanosphere lithography

A highly ordered and hierarchical structural nanopore array is fabricated via anodizing a pre-patterned aluminum foil under an optimized voltage. A pre-patterned hexagonal nanoindentation array on an aluminum substrate is prepared via the nanosphere lithography method. This pattern leads to an elaborate nanochannel structure with seven nanopores in each nanoindentation after anodization treatment. The structure achieved in our study is new, interesting, and likely to be applied in photonic devices.     

Indexing Kossel patterns

Procedures for the indexing of Kossel patterns are fully explained with reference to the use of pattern symmetry, diffraction curve intensity, line curvature and Kossel curve intersections. The indexing methods are illustrated by analysis of a face centred cubic pattern. General application of the concepts described here to the more difficult indexing problems experienced with hexagonal and orthorhombic crystal structures is included.     

CdS及其稀土掺杂纳米带的制备与发光性质的研究

采用热蒸发法制备CdS及其稀土掺杂的纳米带(CdS∶Ce3+、CdS∶Er3+)。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和荧光光谱仪(PL)对纳米带的形貌、晶体结构和发光性质进行了表征和分析。结果表明,所制备的纳米带的外形规则,表面光滑、平整,纳米带的厚度大约在20～60nm范围内;纳米带具有六方结构,晶格常数a=0.414nm、c=0.671nm;CdS纳米带的光致发光谱的谱峰位于405nm左右;CdS∶Ce3+纳米带的光致发光谱的谱峰位于523和535nm处;CdS∶Er3+纳米带的光致发光谱中观察到3个强的发光峰,分别位于525、556和582nm处。     

Image structure from mirrors with print-through undulations: theoretical analysis

The image structure produced by a periodic hexagonal pattern of mirror surface undulations has been analyzed. Such undulations form a two-dimensional phase grating that can result from the polishing of honeycomb mirrors or, for example, meniscus mirrors with a hexagonal pattern of axial supports. For monochromatic light of wavelength lambda, undulations having uniform peak-to-valley amplitude H ? lambda and period L cause a decrease in the central intensity of the point spread function (PSF), and a fraction, ~13(H/lambda)(2), of the total power is diffracted into an infinite hexagonal array of satellite images. These have angular separations of 2lambda/ radical3L and intensity profiles in the form of perfect diffraction limited PSF's, but with intensities decreasing with increasing diffraction order. The six innermost (first-order) satellites each have central intensities approximately 2(H/lambda)(2) times that of the central image. If the amplitudes of the surface bumps are of random size with a normal frequency distribution, then the intensity of the diffracted orders decreases, and an additional weak structure appears over the image plane; the positions and heights of the peaks in this grasslike structure depend on the particular two-dimensional distribution of the random bumps. When the input is polychromatic, the diffracted orders other than zero give images that are elongated radially and decrease outward in intensity with a 1/lambda(4) dependence.     

Generalized method for sorting Shack-Hartmann spot patterns using local similarity

The sensitivity and dynamic range of a Shack-Hartmann wavefront sensor is enhanced when the spots produced by the lenslet array are allowed to shift more than one lenslet radius from their on-axis positions. However, this presents the problem of accurately and robustly associating the spots with their respective subapertures. This paper describes a method for sorting spots that takes advantage of the local spot position distortions to unwrap the spot pattern. The described algorithm is both simple and robust and also applicable to any lenslet array geometry that can be described as a two-dimensional lattice, including hexagonal arrays, which are shown here to be more efficient than square arrays.     

Synthesis of flower-like CdS nanostructures by organic-free hydrothermal process and their optical properties

Flower-like CdS nanostructures consisting of sword-like nanorods have been prepared via organic-free hydrothermal method using thioacetamide (TAA) as sulfur source. X-ray diffraction pattern (XRD) shows that the obtained flower-like CdS nanostructures are of hexagonal phase. The selected area electron diffraction (SAED) pattern identifies that the flower-like CdS nanostructures are single crystalline in nature. Furthermore, the optical properties of flower-like CdS nanostructures have been characterized by ultraviolet-vis (UV-vis) and photoluminescence (PL) spectra. Finally, the investigation on the mechanism indicates that the internal structure and sulfur mass transport controlled by TAA play the critical role in the formation of flower-like CdS nanostructures.     

影响区形状对砂井地基固结性状的影响

为研究现有砂井固结解析理论中将砂井多边形影响区简化为圆形所带来的影响,考虑了影响区为正六边形的梅花形布置砂井的两种计算模型,即将砂井及其涂抹区假定为正六边形的模式1和考虑真实砂井横截面的模式2。根据等应变假定和Carrillo定理分别得到固结基本方程,引入边界和初始条件,结合现有理论结果,给出了两种模式下平均超静孔压和地基总平均固结度的解答。分析了3个无量纲参数对固结性状的影响,结果表明,两种模式得到的固结曲线呈现的规律一致。最后与现有理论进行对比,发现相同条件下模式1计算的固结度最大,而模式2的解答与现有理论结果十分接近。     

Nucleation of cracks in two-dimensional periodic cellular materials

This paper describes the nucleation and propagation of cracks in brittle cellular material. Four basic patterns with triangular, square, hexagonal and kagome-type cells are considered. The cracks propagate by sequential failure of critical elements. The analysis technique hinges on the combined use of the structural variation method and the representative cell method. While the latter allows for the analysis of periodic structures under arbitrary loads, by means of the discrete Fourier transform, the former analyzes modified structures (the cracked lattices) on the basis of analysis of the pristine structure (the periodic lattices). Within the assumptions of Bernoulli–Euler beam theory the suggested method for the analysis of infinite cracked lattices is exact. Although most cracks follow intuitive paths it was found that the microstructure of cellular materials has a significant influence on the crack pattern.     

Structure and photoluminescence of S-doped ZnO nanorod arrays

Vertically aligned S-doped ZnO nanorod arrays have been successfully synthesized by hydrothermal method at 90 °C for 2 h. The obtained nanorod is ～ 70 nm in diameter and 1.2 μm in length. The XRD pattern and the Raman spectra indicate that the S-doped nanorod arrays are orientated at [001] and are single crystals with hexagonal wurtzite structure. The photoluminescence (PL) spectra show that S-doped ZnO nanorod arrays exhibit a relative weak ultraviolet (UV) emission, a violet emission and a strong green emission. The effects of S-doping on the structure and photoluminescence of ZnO nanorod arrays are discussed in detail.     

A template-based electrochemical method for the synthesis of high dense nickel nanotube arrays

High dense Ni nanotube arrays have been successfully fabricated using electrochemical method with the assistance of anodic aluminum oxide (AAO) template from NiSO4 aqueous solution without any additive. Field emission scanning electron microscope (FE-SEM) results indicate that the pores of AAO template are high uniform and all the pores are filled with Ni nanotubes. Transmission electron microscope (TEM) results demonstrate that the diameter of Ni nanotubes is about 65 nm. The electron diffraction (ED) pattern results show that the Ni nanotubes are polycrystalline. X-ray diffraction (XRD) pattern shows that the electrodeposited nickel is hexagonal crystal structure.     

Use of circular cylinders as surrogates for hexagonal pristine ice crystals in scattering calculations at infrared wavelengths

We investigate the errors associated with the use of circular cylinders as surrogates for hexagonal columns in computing the optical properties of pristine ice crystals at infrared (8-12-microm) wavelengths. The equivalent circular cylinders are specified in terms of volume (V), projected area (A), and volume-to-area ratio that are equal to those of the hexagonal columns. We use the T-matrix method to compute the optical properties of the equivalent circular cylinders. We apply the finite-difference time-domain method to compute the optical properties of hexagonal ice columns smaller than 40 microm. For hexagonal columns larger than 40 microm we employ an improved geometric optics method and a stretched scattering potential technique developed in previous studies to calculate the phase function and the extinction (or absorption) efficiency, respectively. The differences between the results for circular cylinders and hexagonal columns are of the order of a few percent. Thus it is quite reasonable to use a circular cylinder geometry as a surrogate for pristine hexagonal ice columns for scattering calculations at infrared (8-12-microm) wavelengths. Although the pristine ice crystals can be approximated as circular cylinders in scattering calculations at infrared wavelengths, it is shown that optical properties of individual aggregates cannot be well approximated by those of individual finite columns or cylinders.     

Lidar inelastic multiple-scattering parameters of cirrus particle ensembles determined with geometrical-optics crystal phase functions

Multiple-scattering correction factors for cirrus particle extinction coefficients measured with Raman and high spectral resolution lidars are calculated with a radiative-transfer model. Cirrus particle-ensemble phase functions are computed from single-crystal phase functions derived in a geometrical-optics approximation. Seven crystal types are considered. In cirrus clouds with height-independent particle extinction coefficients the general pattern of the multiple-scattering parameters has a steep onset at cloud base with values of 0.5-0.7 followed by a gradual and monotonic decrease to 0.1-0.2 at cloud top. The larger the scattering particles are, the more gradual is the rate of decrease. Multiple-scattering parameters of complex crystals and of imperfect hexagonal columns and plates can be well approximated by those of projected-area equivalent ice spheres, whereas perfect hexagonal crystals show values as much as 70% higher than those of spheres. The dependencies of the multiple-scattering parameters on cirrus particle spectrum, base height, and geometric depth and on the lidar parameters laser wavelength and receiver field of view, are discussed, and a set of multiple-scattering parameter profiles for the correction of extinction measurements in homogeneous cirrus is provided.     

六边形蜂窝芯异面类静态压缩力学行为的仿真分析

目的研究六边形蜂窝芯材异面类静态压缩载荷的数值模拟方法及相关力学行为。方法基于蜂窝单元阵列的方法,构筑了单双壁厚六边形蜂窝芯材异面类静态压缩有限元数值计算模型和分析方法。结果借助于该模拟方法,分析计算了不同结构参数条件下单双壁厚六边形蜂窝芯材的异面变形模式、变形曲线和类静态峰应力值,并绘制了相应的图、压缩力位移曲线和数据表格。结论将计算结果与现有的实验和理论计算结果作对比分析可知,计算结果与已有结果吻合较好,证明了所提出的有限元分析方法的可靠性。