图像三维重构在叶片表面压力测量的应用

PSP(Pressure Sensitive Paint)图像的三维重构即将PSP处理所得二维压力图谱转变为叶片三维模型上的压力分布,其有助于PSP实验结果的分析和压力信息的定量提取。以某叶栅的PSP压力图像为对象进行图像的三维重构,得到了三维叶片模型表面的压力分布,并对三维重构图像进行了误差分析。结果表明:1)将PSP图像进行三维重构以后可以方便压力信息的分析及读取;2)标记点的数量及位置分布对PSP图像的三维重构精度有影响。     

Fast calibration methods using cosmic rays for a neutron detection array

An overall irradiation and calibration technique was introduced and applied to a test scintillation detector array. An integral conversion method was used to reduce the nonlinearity of the time difference spectrum, and to improve the position determination especially for positions close to the two ends of a long scintillation bar. An overall position resolution of about 3.0 cm (FWHM) was extracted from the residual analysis method and verified by a direct measurement. Energy calibration was also realized by selecting cosmic rays at different incident angles. The bulk light attenuation lengths for the four test bars were also determined. It is demonstrated that these methods are especially efficient for calibrating large and complex detector arrays.     

The beam-based calibration of an X-ray pinhole camera at SSRF

A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The electron beam size is derived by unfolding the radiation image and the point spread function (PSF) with deconvolution techniques. The performance of the pinhole is determined by the accuracy of the PSF measurement. This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes. Applying this method at SSRF, the PSF value of the pinhole is revised from 37 to 44 μm. The deviation in beam size between the theoretical value and the measured value is minimized to 4% after calibration. This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5 μm.     

Facile Iron‐Mediated AGET ATRP for Water‐Soluble Poly(ethylene glycol) Monomethyl Ether Methacrylate in Water

An environmentally friendly iron catalyst system was successfully developed in water for the AGET ATRP (activator generated by electron transfer for atom transfer radical polymerization) of water‐soluble monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) for the first time. A kinetic study indicated that the polymerization was a living/controlled process in which molecular weight increased linearly with monomer conversion. A lower molecular weight distribution ( / < 1.5) was maintained. The nontoxic and biocompatible characteristics of the iron catalyst facilitate its mediated polymerization to be used in the preparation of functional polymer materials for biomedical use.     

Crystallization kinetics and magnetic properties of Fe63.5Co10Si13.5B9Cu1Nb3 nanocrystalline powder cores

Amorphous ribbons of the alloy Fe_63.5Co₁₀Si_13.5B₉Cu₁Nb₃ were prepared by the standard single copper wheel melt spinning technique in air and their crystallization kinetics was analyzed by non-isothermal differential scanning calorimetry (DSC) measurements. The crystallization activation energies (E_x, E_a1 and E_a2) of amorphous ribbons calculated from Kissinger model were 448, 385 and 396 kJ/mol for the first and the second crystallizations, respectively. The Avrami exponent n was calculated from the Johnson–Mehl–Avrami (JMA) equation and was used to identify the crystallization mechanism for the amorphous ribbons. The ribbons were milled into different sized flakes, which were molded subsequently to cores using 3 wt.% epoxy as a binder. The effective permeability of the cores showed high frequency stability and increased with the size of the flakes. For the cores made from small sized flakes (? 75 μm), the quality factor was increased at high frequencies, which was attributed to the reduction in the eddy current loss.     

Growth imperfections in oriented grown KDP crystals by X‐ray topographic analysis

Potassium dihydrogen phosphate (KDP) crystals were restrained to grow in two dimensions only, using a specially designed platform. This enables us to grow the blanks of frequency conversion elements that satisfy type‐II phase matching direction out of a type‐II phase‐matched seed crystal. Synchrotron radiation topography was used to study the growth mechanism of these profiling grown KDP crystals. It is found that both dislocation growth mechanism and layer growth mechanism were involved in the growing process. Inclusions, growth striations and dislocations were the main defects that influenced the crystalline quality of these crystals. High‐resolution X‐ray diffraction was employed to study the lattice integrality of the crystal.     

微波水热温度对合成Bi2MoO6微晶形貌和光学性能的影响

以硝酸铋和钼酸钠为起始原料,采用微波水热法制备了片状的Bi2MoO6微晶。利用X射线衍射仪(XRD)、透射电子显微镜(TEM)和紫外-可见吸收光谱(UV-vis)分别对产物的物相组成、形貌和光学性能进行分析。结果表明:随着微波水热温度的升高,衍射峰的强度增强,产物的结晶程度逐渐提高,晶粒尺寸逐渐增大,Bi2MoO6微晶由不规则的形状转变成规则的片状结构;紫外-可见吸收光谱分析表明,Bi2MoO6微晶在紫外光区具有优异的吸收性能,且随微波水热温度的降低,其吸收边出现略微蓝移,禁带宽度逐渐增大。     

Effective control of photoluminescence from ZnO nanowires by a-SiN_x:H decoration

The a-SiN_x:H with a large bandgap of 3.8 eV was utilized to decorate ZnO nanowires. The UV emission from the a-SiN_x:H-decorated ZnO nanowires are greatly enhanced compared with the undecorated ZnO nanowire. The deep-level defect emission has been completely suppressed even though the sample was annealed at temperatures up to 400 °C. The incorporation of H and N is suggested to passivate the defect states at the nanowire surface and thus result in the flat-band effect near ZnO surface as well as reduction of the nonradiative recombination probability.     

Bragg gratings in rectangular microfiber for temperature independent refractive index sensing

We present fiber Bragg grating fabricated in rectangular microfiber for temperature-independent refractive index (RI) measurement. The grating has two Bragg peaks due to the high geometrical birefringence of the rectangular microfiber. The two peaks present different RI responses because the modes along the orthogonal polarizations have different energy fractions in terms of evanescent field outside the silica microfiber and hence the light/liquid interaction strength are different. In contrast, they exhibit identical temperature sensitivities because most mode energy is confined in the microfiber and the thermal-optic effect of silica dominantly determines the temperature response. As a result, temperature-independent RI sensing can be realized by monitoring the wavelength separation between the two peaks.