Influence of boundary masks on dimensions and surface roughness using segmented exposure in ceramic 3D printing

Mask projection stereolithography can be used to fabricate complex ceramic parts layer by layer through the photopolymerisation of ceramic suspensions. The broadening or lateral overcure of the curing shape occurs because of light scattering effects. Achieving a better dimension and strength quality by adjusting light energy delivery in the boundary mask area has been insufficiently investigated thus far. In this study, the conventional mask was segmented into boundary and interior masks. The exposure time and power of the boundary mask (two pixels wide) were varied to investigate the effects of segmented exposure. The segmented exposure constrained the dimension errors to a width of within two pixels for a feature dimension of less than 1200?µm. It further smoothed the lateral surface of the green part to achieve Ra values of below 6?µm. Moreover, enhancing the boundary mask increased the flexural strength and Weibull modulus to 248?MPa and 11.1, respectively. The results indicate that segmented exposure can potentially be used in complex lattice ceramic structures.     

7.00R16LT 14PR公路型全钢轻型载重子午线轮胎的开发

介绍7.00R16LT 14PR公路型全钢轻型载重子午线轮胎的开发。结构设计:外直径768 mm,断面宽198 mm,行驶面宽度148 mm,行驶面弧度高4.8 mm,胎圈着合直径404.1 mm,胎圈着合宽度152 mm,断面水平轴位置(H₁/H₂)0.9907;采用有限元分析方法,通过调整轮胎外轮廓曲线解决冠部花纹异常磨损问题;花纹沟壁采用单边双层设计,花纹沟底采用偏心设计,可有效改善花纹沟夹石子问题。施工设计:胎体采用3×0.22/9×0.20CCHT钢丝帘线,带束层采用2层2+7×0.30ST超高强度钢丝帘线,以提升轮胎的高速性能和承载性能;胎面配方优化设计后可提高轮胎的耐磨及抗刺扎性能。成品轮胎性能试验结果表明,成品轮胎充气外缘尺寸及强度、耐久和高速性能均符合设计要求。     

A novel randomly textured phosphor structure for highly efficient white light-emitting diodes

We have successfully demonstrated the enhanced luminous flux and lumen efficiency in white light-emitting diodes by the randomly textured phosphor structure. The textured phosphor structure was fabricated by a simple imprinting technique, which does not need an expensive dry-etching machine or a complex patterned definition. The textured phosphor structure increases luminous flux by 5.4% and 2.5% at a driving current of 120 mA, compared with the flat phosphor and half-spherical lens structures, respectively. The increment was due to the scattering of textured surface and also the phosphor particles, leading to the enhancement of utilization efficiency of blue light. Furthermore, the textured phosphor structure has a larger view angle at the full width at half maximum (87°) than the reference LEDs.     

Characterization of poly(N-vinyl-2-pyrrolidone)s with broad size distributions

We report on the characterization of the solution structure of poly(N-vinyl-2-pyrrolidone)s (PVP) by small-angle X-ray scattering (SAXS) and by online coupling of asymmetrical flow field-flow fractionation (A4F), SAXS and dynamic light scattering (DLS). The commercial products PVP K30 and PVP K90 with nominal molar masses of 40 × 10³ and 360 × 10³ g mol⁻¹, respectively, were investigated separately and as binary mixture. Detailed information for all polymer fractions is available on the polymer contour lengths and the diffusion coefficients. Key areas of applications for the A4F-SAXS-DLS coupling are seen in comparison to static light scattering for polymers with radii of gyration smaller than 10 nm, for which only SAXS produces precise analytical results on the size of the polymers in solution.     

聚合物流动行为的光散射表征

简要地介绍了光散射原理及目前光散射技术在聚合物流变学的中的应用，归纳并分析了前人的一些主要工作成果。对于一些至今难以解释的实验现象提出了自己的一些认识，并对仍未有人涉足的振动力场下聚合物复杂流动光散射表征提出了新的设想。     

Light‐scattering capacity of ethylene–vinyl acetate copolymers in polypropylene: Toward high haze and transmittance

Light‐scattering materials were fabricated by the melt blending of polypropylene with an ethylene–vinyl acetate copolymer (EVA) to prevent the glare effect of light‐emitting diodes. The results show that the light‐scattering capacity was remarkably dependent on the phase morphologies of EVA. (1) When EVA was dispersed as spherical droplets, the transmittance and haze gradually increased with the enrichment of EVA, and the half‐peak width of the light‐scattering pattern reached a maximum when 30 wt % EVA was loaded. On the basis of the analysis of Mie scattering theory, the enlargement of scattering particles promoted light transmittance, and more incoming light was deflected at the arclike interfaces. This induced a distinct antiglare effect. (2) When scattering particles deformed and expanded vertically in the light‐transmitting direction, the light‐scattering capacity turned out to be weakened by further enrichment of the EVA phase. The planelike interfaces reduced the deflection of incoming light, and this led to decreases in the scattering angles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42844.     

Investigating polymer crystallization by time-dependent light scattering: a direct approach in the data analysis applied for s-polypropylene

We developed a procedure for a direct evaluation of light scattering patterns registered during an isothermal crystallization of s-polypropylene. Analysis is based on the determination of three parameters of the scattering curve for both, polarized and depolarized measuring conditions: (i) the forward scattering intensity I(q→0) (ii) the width Δq of the intensity distribution (iii) the integral intensity in the registration plane, Q₂. We derive equations for these parameters and relate them to the size and the inner structure of the hedrites which develop in s-polypropylene during a crystallization.     

Synthesis of hypergrafted poly[4-(N,N-diphenylamino)methylstyrene] through tandem anionic-radical polymerization of radical-inimer

In this paper, we present a tandem anionic-radical approach for synthesizing hypergrafted polymers. We prepared 4-(N,N-diphenylamino)methylstyrene (DPAMS) as a new radical-based inimer. Linear PDPAMS was prepared through anionic polymerization. Hypergrafted PDPAMS was synthesized through the self-condensing vinyl polymerization of DPAMS with linear PDPAMS. The linear backbone of PDPAMS, which incorporated latent radical initiating sites, served as a ‘hyperlinker’ to link hyperbranched side chains. The molecular weights of hypergrafted polymers increased as the length of the linear backbone chain increased. The hypergrafted structure of the resulting polymer was confirmed using a conventional gel permeation chromatograph apparatus equipped with a multiangle light scattering detector, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. This strategy can be applied to synthesize other complex architectures based on hyperbranched polymers by changing the structure of a polymer backbone through anionic polymerization.     

Ni掺杂ZnO电子结构理论的研究

应用第一性原理、电子密度泛函理论作为研究的理论基础,通过计算来研究Ni掺杂ZnO晶体的几何结构、电子内部结构和光学性质。由结构图、能带图、光吸收曲线相互分析其几何结构、电子内部结构和光学性质的形成原因。对图形进行分析,结果表明Ni掺杂使ZnO的价带上移,禁带宽度小于纯ZnO,其光吸收曲线发生红移,提高了ZnO对可见光的利用率,这一结果可为进一步研究Ni掺杂ZnO实验奠定基础。     

Investigation of aggregation, breakage and restructuring kinetics of colloidal dispersions in turbulent flows by population balance modeling and static light scattering

Quantitative modeling of aggregating colloidal systems is the underlying problem in many industrial processes, such as micro and nanoparticle processing, crystallization or flocculation. Population balance models with various aggregation and breakage kernels have been proposed in order to describe aggregating systems, but they have been rarely validated against appropriate experimental data. Typically, model parameters are fitted against a single measured moment of the cluster distribution which can usually be equivalently described using several variations of the set of parameters underlying the relevant aggregation, breakage and restructuring kernels. In order to discriminate among alternative models we propose an approach based on measurement and quantitative modeling of multiple moments of the cluster mass distribution, such as those obtained from static light scattering measurements. This approach is applied to aggregation processes in turbulent conditions in order to test alternative kernels for aggregation, breakage, and restructuring kinetics. We present a detailed study on the sensitivity of measurables from static light scattering with respect to commonly used aggregation and breakage kinetic models. In particular, we analyze the dynamic and steady state behavior of two measurables: the average radius of gyration and the average zero angle intensity which represent two independent moments of the cluster mass distribution. In addition, we discuss the effect of cluster structure and mass distribution on the average structure factor and the apparent fractal dimension measured by static light scattering, in order to assess what structural information can be reliably extracted from such measurements.     

Raman spectroscopy of stressed samples of oriented poly(ethylene terephthalate)

Measurements of the shift and change of shape of the 1616 cm⁻¹ Raman scattering peak of two moderately oriented samples of poly(ethylene terephthalate) (PET) under tensile loads of up to 0.2 GPa are reported, together with the corresponding strains. To obtain reproducible results load cycling procedures were adopted similar to those established for the study of viscoelastic behaviour. The Raman scattering was observed with polarized incident and scattered light, with the polarization directions either both parallel or both perpendicular to the draw direction in the samples. The results showed that for both samples the Raman shift was linearly related to the applied stress below the yield point. Up to the yield point very little change of line width was observed but above the yield point the width increased significantly. Differences in both widths and shifts were observed for the two polarization directions at the same stress level. The results are discussed in terms of the usual assumptions that the shift of the line gives a measure of the average stress in those chains which predominantly contribute to the peak and that the width and shape of the line give information about the spread of stresses. It is concluded that the technique can give useful information about the molecular stress distribution in thick samples of moderately oriented PET under load, including information about the different stress distributions on chains at different angles to the draw direction.     

Lattice Model for Estimating the Opacity of White Coatings

White pigments impart opacity to films and coatings by virtue of their ability to scatter incident light. This study considers a homogeneous coating that contains a low concentration of randomly dispersed, monodisperse pigment particles. The optical properties are determined using a lattice model with cell size defined by the diameter ( d ) of the particles. For pure scattering, the contrast ratio (CR) is an algebraic function of the scattering coefficient (κ), pigment volume fraction (φ), and coating layer thickness ( L ), as follows: [formula omitted]When tested against literature data for white films opacified with titanium dioxide, an empirical expression with a single adjustable constant provides a better interpolation formula than the above equation. This discrepancy is attributed to the contribution of a minor amount of absorption to the measured opacity.     

尼龙斜交轮胎“充气平衡内轮廓”设计浅析

通过分析影响斜交轮胎结构设计的３个主要因素（即充气后胎里半径、充气后断面宽最宽点半径和胎冠角度），研讨了内轮廓伸张值的确定方法。认为以“静态充气平衡理论”为设计依据，可把轮胎静态形状和柔性复合材料性能等有机地联系起来，对轮胎进行优化设计。     

环烷基轻质油为介质的25%丙环唑乳油配方

环烷基轻质油作为新型有机溶剂应用于丙环唑乳油的研发中.主要利用优化组合法对多种阴离子和非离子表面活性剂的复配体系及其他助剂进行筛选,确定25%丙环唑乳油最佳配方:丙环唑25%,脂肪醇聚氧乙烯醚6.5%,十二烷基苯磺酸钙1.5%,异丙醇与环烷基轻质油B复合溶剂67%.该乳油的乳化分散性、乳液稳定性和冷、热贮稳定性均符合国家标准.热贮后的气相色谱分析结果表明此配方中丙环唑分解率为2.3%.     

Phase separation kinetics of rigid-rod polymers during coagulation

Kinetics of phase separation of poly(p-phenylenebenzobisoxazole) (PBO) in methanesulfonic acid are examined by the time-resolved small angle light scattering and turbidity measurements. Thin films of polymer solutions are spin-coated on microscope slides and observed in a controlled environment light scattering cell. These solutions appear to undergo a spinodal decomposition-like phase separation, following Cahn-Hilliard type phase separation kinetics upon exposure to water vapor. An exponential increase in the scattered light intensity at short times is found. Transmittance measurements are used to determine the effects of molecular weight and coagulation medium on the rate of coagulation.     

Instrumentation on Multi-Scaled Scattering of Bio-Macromolecular Solutions

The design, construction and initial tests on a combined laser light scattering and synchrotron X-ray scattering instrument can cover studies of length scales from atomic sizes in Angstroms to microns and dynamics from microseconds to seconds are presented. In addition to static light scattering (SLS), dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD), the light scattering instrument is being developed to carry out studies in mildly turbid solutions, in the presence of multiple scattering. Three-dimensional photon cross correlation function (3D-PCCF) measurements have been introduced to couple with synchrotron X-ray scattering to study the structure, size and dynamics of macromolecules in solution.     

A Novel Method for Estimating Light-Scattering Properties of Soot Aerosols Using a Modified Single-Particle Soot Photometer

A Single-Particle Soot Photometer (SP2) detects black refractory or elemental carbon (EC) in particles by passing them through an intense laser beam. The laser light heats EC in particles causing them to vaporize in the beam. Detection of wavelength-resolved thermal radiation emissions provides quantitative information on the EC mass of individual particles in the size range of 0.2–1 μm diameter. Non-absorbing particles are sized based on the amount of light they scatter from the laser beam. The time series of the scattering signal of a non-absorbing particle is a Gaussian, because the SP2 laser is in the TEM00 mode. Information on the scattering properties of externally and internally mixed EC particles as detected by the SP2 is lost in general, because each particle changes size, shape, and composition as it passes through the laser beam. Thus, scattered light from a sampled EC particle does not yield a full Gaussian waveform. A method for determining the scattering properties of EC particles using a two-element avalanche photodiode (APD) is described here. In this method, the Gaussian scattering function is constructed from the leading edge of the scattering signal (before the particle is perturbed by the laser), the Gaussian width, and the location of the leading edge in the beam derived from the two-element APD signal. The method allows an SP2 to determine the scattering properties of individual EC particles as well as the EC mass. Detection of polystyrene latex spheres, well-characterized EC particles with and without organic coatings, and Mie scattering calculations are used to validate the method.     

光散射测量技术在聚合物共混体系中的应用

首先介绍了聚合物共混体系混炼效果的传统表征方法,并分析了其局限性,在此基础上,对近年来逐步应用于聚合物多组分流变行为表征的光散射理论作了简要说明,概述了光散射在共混体系中相分离机理、相图以及形态学方面的应用,归纳分析了前人的一些主要工作成果,并对利用光散射测量振动力场下聚合物的混炼效果提出了自己的设想.     

Pore Structure Control of Silica Gels Based on Phase Separation

In the alkoxy-derived sol-gel system, various macroporous morphologies can be obtained by inducing the phase separation parallel to the sol-gel transition. This principle of macroporous morphology control can be best applied to pure silica and silica-based multicomponent oxide systems. The earlier the phase separation takes place than the sol-gel transition, the larger the characteristic sizes of pores and gel skeletons become. The time resolved light scattering measurements revealed that the morphology formation process exhibits the features of spinodal decomposition and that the final gel morphology is determined by the competitive kinetics between the domain coarsening and the structure freezing by sol-gel transition. The mesopore structure of such macroporous gel skeletons could be easily tailored by the solvent exchange procedures. Silica gels with controlled macropores and mesopores were successfully applied as a material for the continuous rod type column for high performance liquid chromatography.     

茜素红共振散射法测定硫酸庆大霉素

在pH5.5的Britton-Robinson介质中,茜素红和硫酸庆大霉素(GEN)相互作用形成缔合物,使体系的共振散射信号(RLS)增强,最大散射峰位于312 nm处,且增强的RLS强度与GEN浓度成正比,据此建立了一种测定硫酸庆大霉素含量的新方法。测定硫酸庆大霉素的线性范围是0.15~1.5 U/mL,检出限为0.029 U/mL。将方法用于硫酸庆大霉素注射液中硫酸庆大霉素含量的测定,结果满意。