粗糙表面镜向散射光强统计

粗糙表面散射可分为镜向散射和非镜向散射,镜向散射光强的分析不仅具有理论上的简洁性,而且能够给出粗糙表面散射的一些重要特性。论文根据相干散射和傅里叶光学理论,对粗糙表面的镜向散射光场进行了理论分析和推导,结果表明:镜向散射光场的主要特征由粗糙表面高度分布的傅里叶变换和入射光场的傅里叶变换共同决定。对于均匀平行光照射高斯表面情形,镜向散射光强是有效粗糙度的高斯函数,镜向散射光强在焦平面的分布为sinc平方函数。

基于光场扫描的真三维立体显示系统的开发

近年来,计算机视觉领域出现了一种新型的三维显示技术,即光场三维显示技术。基于光场扫描的真三维立体显示系统通过重构物体光强的空间分布,减少了信息冗余,采用高速投影仪、定向散射反射镜和高速旋转马达等设计而成。通过分析光场三维显示原理和系统工作原理、显示系统架构和立体成像原理等,详细论述了显示系统开发的可行性,并通过实验证明了当达到一定投影输出功率和马达旋转功率时可实现立体成像。观测者可360度裸眼观测立体图像,并且无需佩戴任何辅助工具。

TCL王牌HiD系列背投电视

85Hz快速高频逐行扫描,60Hz/85Hz逐行扫描精密显像TCL HiD背投采用快速高频逐行扫描技术,将普通电视的隔行信号转为逐行扫描输出,垂直的扫描密度提高2倍,避免了传统背投的百叶窗现象。针对常用的PAL制节目,还具备60Hz/85Hz两种逐行扫描模式,消除画面闪烁现象。图像的闪烁与抖动现象通常是由于图像刷新频率较低所致。TCL HiD背投采用最新的精密显像技术。

Design of supercontinuum source for coherent anti-Stokes Raman scattering microscopy

A new method to obtain supercontinuum(SC) source for multiplex coherent anti-stokes Raman scattering (CARS) microscopy is proposed. The nonlinear propagation in photonic-crystal fibers (PCF) of femtosecond pulse laser with central wavelength at 800.9 nm is studied with scalar wave theory. Based on the incident laser power and dispersion of PCF, super broadband source for multiplex CARS microscopy is designed.

A yttrium-containing high-temperature titanium alloy additively manufactured by selective electron beam melting

A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.

非线性光学器件

O437 99020981受激布里渊散射相位共轭镜产生高质量短脉冲XeCl激光=Phase-conjugate mirror for generation ofhigh quality and short pulse XeCl laser[刊,中]/周卫东,余吟山,洪玲,季明,高晓明,张为俊(中国科学院安徽光机所.安徽,合肥(230031))//光学学报.—1998,18(7).

Influence of exfoliation corrosion on tensile properties of a high strength Al-Zn-Mg-Cu alloy

The influence of exfoliation corrosion on the tensile properties of a high strength Al-Zn-Mg-Cu alloy was investigated by ambient temperature tensile testing, optical microscopy, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and electron backscatter diffraction （EBSD）. After exfoliation corrosion immersion, blisters and corrosion pits can be seen on the sheet surface, which lead to loss of materials and notches. A number of intergranular cracks are observed to initiate at the bottom of the corrosion-induced notches and propagate rapidly into the bulk materials during tensile. Consequently, exfoliation corrosion results in significant loss of strength and brittle fracture. EBSD results show that the crack propagation path is primarily along the grain boundaries with misorientation of-45°, and coincidence site lattice （CSL） boundaries are slightly more resistant to crack.

Performance of engineered cementitious composite containing stone slurry powder waste

Most of the materials used in engineered cementitious composite are fine in size to achieve ductile nature.Stone slurry powder(SSP)is an inert material obtained from stone industries as by-product which may cause hazardous impact on environment.In this research work,partial replacement of silica sand(SS)and fine sand(FS)by SSP with different contents(25%and 50%each)for making engineered cementitious composite has been explored.The performance was evaluated on the basis of strength,tensile strain,mid span deflection capacity,ultra-sonic pulse velocity and microstructure.Mechanical strength was found to be increased at 25%SSP in both replacements;whereas,strength decreased slightly at 50%replacement.Tensile strain,mid span deflection and quality of concrete were enhanced with increase in SSP content.Using SSP formed denser cementitious composite can help to save the natural resources and contribute in making green cementitious composite.

Synthesis of Silica-Dispersed NiMo Hydrodesulfurization Catalysts

Silica-dispersed NiMo hydrodesulfurization catalysts were synthesized by the deposition-precipitation method. For comparative purposes, bulk NiMo catalysts were obtained by co-precipitation. The silica-dispersed NiMo catalyst had highly active metals content. Silica was employed to disperse active metals for full utilization of active components. The BET analysis showed that the silica-dispersed NiMo catalysts had a high surface area （147.0 m2/g） and pore volume （0.27 mL/g）, whereas the bulk NiMo catalysts exhibited a very low surface area （87.5 m2/g）. Transmission electron microscopy results proved that the active components were dispersed on the SiO2 substrate. X-ray diffraction patterns of the silicadispersed NiMo catalyst and the bulk NiMo catalyst were indexed to NiMoO4. The hydrodesulfurization activity of silicadispersed NiMo catalysts was much higher than that of reference catalysts and could be up to twice greater than those of commercial NiMo alumina-supported systems per gram of catalyst. The activity testing results also demonstrated that the silica-dispersed NiMo catalyst was an effective hydrodesulflarization catalyst.

Porous Structure, Salt Component Distribution and Catalytic Preference of Zinc Acetate Catalysts for Vinylacetate Synthesis on Modified Carbon Supports

The main problem in an efficient Zn（CH3COO）2/AC （AC-activated carbon） catalyst preparation is the achievement of uniform distribution of highly dispersed salt component on the activated carbon （AC） surface. The solution of this problem is modification of the AC by hydrogen peroxide （H202） oxidation of the surface and treatment of AC with acetic acid as well as special methods of salt deposition and catalyst drying. The investigations of these ways of AC surface modification （treatment of AC with acetic acid and H2O2） have demonstrated the obtained AC to have both an increased adsorption capacity as to Zn（OAc）2 and optimum volumes of meso- and micro-pores as well as high catalyst activity in vinyl acetate （VA） synthesis. The characteristics of supports and catalysts were found out by benzene, water and acetic acid vapors adsorption. The distribution of the salt on the AC surface was studied by small-angle X-ray scattering （SAXS）, by scanning electron microscopy （SEM） and X-ray micro-analysis （XMA）. The catalysts were tested in vinyl acetate synthesis in flow-bed isothermal reactor by cyclic method at 175, 205 and 230℃.

The preparation of high concentration alkaline silica sol with the method of vacuum distillation

High concentration alkaline silica sol has been prepared by the method of vacuum distillation, which shows that the stable and high concentration silica sol can be obtained under conditions as follows： 70℃, vacuum degree of 0.095Mpa and dispersant of SDS. The experimental results show that the sol particles size decreases with mass concentration first and then increase, sol viscosity increases with mass concentration during the concentrating process. The TEM method was used to study the dispersion behavior of sol particles, its result showed that sol particles dispersed more uniformly after concentrating process than before concentrating distinctly. It could be concluded that the disperse degree of alkaline silica sol could be increased by addition of right dispersant. The dispersion mechanism of dispersant in alkaline silica sol was also discussed.

A new method for storing Ag nanoparticles

Silver nanoparticles were obtained by reduction method. Various techniques, such as UV-Vis spectroscopy, transmission electron microscopy （TEM） and light-scattering spectroscopy, were used to characterize nanoparticles. Sodium borohydride or sodium citrate was adopted as reduction regent, and polyvinyl alcohol or polyethylene glycol was adopted as stabilizing regent. An experimental condition was studied in detail. After the water was eliminated, the silver nanoparticle was fixed in the solid polymer. The silver nanoparticle in polymer could be re-dissolved in water. It was found that light scattering characteristic of silver nanoparticle storied in polymer was not changed. A new method of storing silver nanoparticles in solid polymer was given in this paper.

Sharp scattering spectra induced brilliant and directional structural colors

Structural color materials,which generate colors through the interaction between light and nano-microstructures,have always been research hotspots in the fields of display,anticounterfeiting and stimuli-responsive materials.Structural colors based on scattering have received increasing attention due to their wider viewing angles than that originating from the specular reflection of photonic crystals.However,the wide scattering spectrum of an amorphous structure leads to lower purity and brightness of the appeared colors.Few researchers have focused on the scattering of ordered structures due to their strong reflection and diffraction in the visible regions.In this work,by building ordered films(OFs)using SiO2 spheres(refractive index n=1.46)with a diameter of 300–500 nm,for the first time,sharp scattering spectra with narrow full width at half-maximum(FWHM,24 nm)were generated.Importantly,under ambient light,brilliant colors covering the entire visible region can be observed,and a formula was proposed to calculate the scattering spectra of OFs.Moreover,rainbow structural color was realized under irradiation of the nonparallel light,and full-spectrum structural color patterns were fabricated using building blocks with a single particle size by a spraying method.Finally,a composite structure was constructed to explore possibilities in the field of flexible transparent displays.

Evolution of microstructure and texture of cold-drawn polycrystalline Ag with low stacking fault energy

The evolution of microstructure and texture for drawn polycrystalline Ag was investigated by transmission electron microscopy and electron backscattering diffraction.The results show that there are deformation twins and some un-tangled discrete dislocations at low strains.When the strain is increased to 0.58,a lot of high density dislocation walls and microbands come into being.At the same time,some twins lose the twinning relationship of 60°<111>.At a strain of 0.94,both dislocation boundaries and twin boundaries will rotate to the axis direction of wires and the shear bands start to appear.When the strain is higher than 1.96,most of the boundaries are parallel to the drawn direction.Texture analysis indicates that with the strain increasing,the volume fraction of complex texture component decreases,but<111>and<100>texture components increase.However,the variation in the volume fraction of each texture component as strains is not evident when the strains are higher than 0.58.For polycrystalline Ag with low stacking fault energy,complex texture components are easily formed.

Microstructure and texture evolution of cold drawing <110> single crystal copper

By means of electron backscattering diffraction and transmission electron microscopy the microstructure and texture of drawn single crystal copper with initial orientation （110） parallel to axial direction have been investigated in the present work. In or- der to analyze the effect of initial orientation on microstructure and texture of drawn copper, the results of the drawn （110） sin- gle crystal copper wires have been compared with （100） and （111） single crystal copper wires. It is found that the grain subdi- vision of （110） single crystal is more evident than that of （100） and （111）, and the textures consisting of （111） and （100） abruptly form in the drawn （110） single crystal. At high strains, due to shear strain, the distribution of fiber textures is imho- mogenous along the radial direction of drawn （110） single crystal copper wires. （100） is near the surface and （111） is at the center. The microstructure results of drawn （110） single crystal show that at low strains, it can be characterized as two kinds of geometrically necessary boundaries with noncrystalline character. At medium strains, S bands can be observed. At high strains, lamellar boundaries form. Mean misofientation and average spacing of dislocation boundary are larger in drawn （110） single crystal, as compared with （111） and （100）. In drawn （110） single crystal with high strains, the bimodal distribution forms at lower strains than in drawn （100） single crystal, which is because the dislocation boundaries with high angle are contributed by not only the boundary between （111） and （100） fiber textures but also the boundary in （111） or （100） texture.

The application of back-scattered electron imaging for characterization of pearlitic steels

The microstructures of pearlitic steel wire rods and steel wires are commonly characterized by secondary electron imaging (SEI)technique using scanning electron microscopy(SEM).In this work,a back-scattered electron imaging(BSEI)method is proposed to determine the microstructures of undeformed and deformed pearlitic steels with nanometer scale pearlite lamellae.The results indicate that BSEI technique can characterize the pearlite lamellas veritably and is effective in quantitative measurement of the mean size of pearlite interlamellar spacing.To some extent,BSEI method is more suitable than SEI technique for studying undeformed and not severely deformed pearlitic steels.

Pore structure of selected Chinese coals with heating and pressurization treatments

Pore structure of Chinese coals with heating and pressurization treatments was studied using small angle X-ray scattering （SAXS）, N2 adsorption/desorption isotherms and scanning electron microscope （SEM）. SAXS was performed for some sam- ples after heat treatment at seven elevated temperatures from 25 to 250℃ at 0 MPa and for other samples with hydrostatic pressure treatment at 0, 5, 10, 15 and 20 MPa at the room temperature. The results show that N2 adsorption isotherm together with SAXS could be a comprehensive method to evaluate the pore shape and the pore size distribution： the pore shapes are generally spherical for low rank coal and they are mainly ellipsoidal for high rank coal. All these measurements were then interpreted using the fractal theory to reveal relationship between surface fractals and coal rank, and the evolution of surface fractals under heating and pressurization treatments. The results show that surface fractal dimension （Ds） changes with different treating temperature and pressure and maximum vitrinite reflectance （Ro,m）. Especially in the bituminous stage, Ds shows an increasing trend with Ro,m under varied temperatures. Moreover, Ds shows an increasing trend with increasing temperature before 200℃, and a decreasing trend after 200℃. Furthermore, the results show that Ds has a more complex relationship with Ro.m under varied treating temperature than that under varied treating pressure.

Single Photon Scattering Properties in Coupled-Resonator Waveguide Coupling with a Nanocavity Interacting with an External Mirror

We investigate theoretically single photon transport properties in coupled-resonator waveguide coupling with a nanocavity interacting with an external mirror. By using the discrete coordinates approach, transmission and reflection amplitudes of the propagating single photon in the waveguide are obtained. The influence of the coupling strength between the nanocavity and the external mirror on the single photon scattering spectra is discussed. We also extend the results to the waveguide with linear and quadratic form dispersion relations.

Bimodal plate structures induced by pulsed laser in duplex-phase Zr alloy

A duplex-phase Zr-2.5Nb alloy was treated by pulsed laser, followed by careful microstructural characterization using field emission gun scanning electron microscope and attached electron backscatter diffraction. Beneath the modification zones with common uniform α-plate structures(UPS), a layer of unreported bimodal α-plate structures(BPS) featured by coarse(submicron)plates forming multiple cores surrounded by dense fine(nanoscale) plates was found. Presence of such BPS is attributed to non-equilibrium thermodynamic conditions induced by the pulsed laser treatments. Limited diffusion of Nb due to the short pulse during laser heating allows β phases with distinctly different Nb contents to be presented: Nb-enriched prior β films and Nb-depleted β phases, transforming into the fine and the coarse plates during cooling, respectively. Orientation analyses show that both types of plates in the BPS are aroused essentially from a single β orientation, suggesting epitaxial growth of the Nb-depletedβ phases from the preexisting β films.