声波团聚净化尿素造粒塔尾气实验研究*

尿素造粒塔大多采用水洗工艺处理尾气粉尘,存在较为严重的细颗粒粉尘溢出和水汽拖尾问题,因此深入探究声波团聚技术在造粒塔尾气处理方面的应用。通过实验研究了声波与喷雾对除尘效率的影响,发现声波单独作用时在3500 Hz达到最佳除尘效率,为74.49%,协同喷雾时2600 Hz即可实现相近的除尘效率,为73.83%。进一步探究其中机理,采用以粒径测试为依据的团聚效率作为评价指标,结果显示,2600 Hz声波与喷雾单独作用时团聚效率分别为30.37%和28.82%,协同作用时团聚效率大幅提升至57.95%。该研究可为后续造粒塔工程改造提供理论与数据支持。     

GOSs-稀土配合物紫外增强材料的光谱分析与稳定性研究

氧化石墨烯薄片(GOSs)作为一种新型的二维片状材料,具有较高的比表面积、丰富的表面含氧官能团以及良好的光热稳定性。而稀土配合物通过无机稀土元素与有机配体的结合表现出优异的荧光特性。为了将两类材料具有的物化特性结合起来应用于紫外光谱探测领域。选取了合适的有机配体啉菲罗啉(1,10-邻二氮杂菲,phen)、2’2-联嘧啶(bpm)作为桥联分子,把氧化石墨烯(GOSs)与稀土配合物通过氢键自组装作用进行复合,制备了高效稳定可调的GOSs-稀土配合物复合荧光材料GOSs-Eu(BA)3phen和GOSs-Eu(TTA)3bpm,并且制备了相应的聚乙烯醇(PVA)共混紫外增强薄膜,对其光谱特性与稳定性进行了深入的研究。采用红外光谱、扫描电镜和金相显微镜等方法,对紫外增强材料进行了性能表征。采用吸收光谱,荧光光谱等方法,对紫外增强薄膜进行了性能表征。此外,通过热重测试(TGA)表征了GOSs氢键复合前后紫外增强材料的热稳定性,通过荧光强度-紫外光照次数表征了GOSs氢键复合前后紫外增强薄膜的光稳定性。红外光谱分析发现,进行配位前后有机配体的特征峰产生了频移,表明稀土配合物中Eu 3+与配体之间存在着明显的配位作用。在进行复合之后,桥联配体的特征峰也产生了偏移,表明GOSs与稀土配合物通过桥联分子的氢键作用进行了进行复合。吸收光谱与荧光光谱测定结果表明增强薄膜吸收峰在200~400 nm,荧光主峰在612 nm左右,为Eu 3+特征红色荧光峰,且不同配体可以实现不同范围的吸收产生差异化的荧光表现。扫描电镜和金相显微镜清晰地展示了稀土配合物复合前后的微观形貌,即颗粒状稀土配合物附着在石墨烯薄片上。光稳定性测试表明经过GOSs氢键复合之后,Eu(BA)3phen和Eu(TTA)3bpm稀土配合物荧光材料在进行25次荧光强度测试后光漂白程度分别下降了4.26%和6.41%,提高了其光稳定性。热重测试也表明在经过GOSs氢键复合之后,稀土配合物的热稳定性有了很大提高。总之,得益于GOSs和稀土配合物的特性结合,所制备的紫外增强材料表现出优异的荧光特性与稳定性,必将在紫外探测方面有着广阔的应用前景。     

基于三支决策的灰色可能度聚类方法及应用

针对经典的灰色可能度聚类评估模型难以判定决策对象的灰类归属和过度聚类等问题,利用三支决策的思想和方法,通过引入三支灰类的概念描述决策对象和灰类之间的不确定聚类关系;将其代替灰色定权聚类中的灰类和严格的聚类关系,构建基于三支决策的灰色可能度聚类方法,并采用决策粗糙集中的贝叶斯推理确定聚类阈值;最后,以案例验证所提方法的有效性和合理性。结果表明：本文所构建的模型是经典灰色可能度聚类评估模型的拓展和泛化,可以有效避免过度聚类,降低决策风险,提高聚类可靠性。     

二维平板光子晶体直波导的制备和光传输特性的测量

利用聚焦离子束刻蚀的方法在SOI(silicon on insulator)基片上制备了W3型二维光子晶体直波导.观察并测量了近红外激光通过光子晶体波导的散射图形和透过谱.实验结果说明，激光在有引入引出脊形波导的光子晶体直波导中具有很好的传输特性. 关键词： 光子晶体波导 光子带隙 脊型波导     

Complete Band-Gap in Two-Dimensional Quasiperiod Photonic Crystals with Hollow Cylinders

The transmission properties of quasiperiodic photonic crystals (QPCs) based on the random square-triangle tiling system are investigated by the multiple scattering method. The hollow cylinders are introduced in our calculation. It is found that QPCs with hollow cylinders also possess a complete band gap common to s- and p-polarized waves when the inner radius of hollow cylinders is larger than a certain value. The QPCs possessing the complete band gap can be applied to the fields of light emitting, wave-guides, optical filters, high-Q resonators and antennas.     

大脉冲电流下钨铜电极水和空气中的烧蚀特性

针对水中、空气中脉冲放电条件下金属电极烧蚀速率及烧蚀机理差异,对脉冲大电流作用下水中、空气中钨铜电极的烧蚀特性进行了对比研究。在保证放电电流波形一致性的前提下,通过采用高精度天平测量并获取了水中、空气中钨铜电极的阴、阳极烧蚀速率及总烧蚀速率,并对电极表面进行了二次电子观察和背散射电子观察分析。结果表明,大脉冲电流作用下,水中钨铜电极烧蚀较空气中更为严重,钨铜电极的烧蚀主要是金属蒸发引起的汽相侵蚀。由于水介质较空气具有不可压缩性,水中放电电弧集中,电极表面电弧斑点处电流密度和电流作用时间较空气中更为严重,同时由于水中脉冲放电时发生的高温物理化学反应,是造成水中电极烧蚀要高于空气中的根本原因。     

A simple and comprehensive electromagnetic theory uncovering complete picture of light transport in birefringent crystals

Birefringence production of light by natural birefringent crystal has long been studied and well understood. Here, we develop a simple and comprehensive rigorous electromagnetic theory that allows one to build up the complete picture about the optics of crystals in a friendly way. This theory not only yields the well-known refraction angle and index of ellipse for birefringence crystal, but also discloses many relevant physical and optical quantities that are rarely studied and less understood. We obtain the reflection and transmission coefficient for amplitude and intensity of light at the crystal surface under a given incident angle and show the electromagnetic field distribution within the crystal. We derive the wavefront and energy flux refraction angle of light and the corresponding phase and ray refractive index. We find big difference between them, where the phase refractive index satisfies the classical index of ellipse and Snell's law, while the ray refractive index does not. Moreover, we disclose the explicit expressions for the zero-reflection Brewster angle and the critical angle for total internal reflection. For better concept demonstration, we take a weak birefringent crystal of lithium niobate and a strong birefringent crystal tellurium as examples and perform simple theoretical calculations. In addition, we perform experimental measurement upon z-cut lithium niobate plate and find excellent agreement between theory and experiment in regard to the Brewster angle. Our theoretical and experimental results can help to construct a clear and complete picture about light transport characteristics in birefringent crystals, and may greatly facilitate people to find rigorous solution to many light-matter interaction processes happening within birefringent crystals, e.g., nonlinear optical interactions, with electromagnetic theory.     

Energy Squeeze of Ultrashort Light Pulse by Kerr Nonlinear Photonic Crystals

Self-phase modulation can efficiently shape the spectrum of an optical pulse propagating along an optical material with Kerr nonlinearity. In this work we show that a one-dimensional Kerr nonlinear photonic crystal can impose anomalous spectrum modulation to a high-power ultrashort light pulse. The spectrum component at the photonic band gap edge can be one order of magnitude enhanced in addition to the ordinary spectrum broadening due to self-phase modulation. The enhancement is strictly pinned at the band gap edge by changing the sample length, the intensity or central wavelength of the incident pulse. The phenomenon is attributed to band gap induced enhancement of light-matter interaction.     

Negative Refraction and Near-Field Imaging of an Elliptical-Rod Photonic Crystal Slab in the Second Band

Negative refraction and imaging properties of the electromagnetic wave through a two-dimensional photonic crystal （PC） slab, which consists of a square lattice of elliptical dielectric rods immersed in the air background, is studied by the plane-wave expansion method and the finite-difference time-domain method. A point source placed in the vicinity of the PC slab can form a good-quality image spot through the PC slab for the incident frequencies within the second photonic band. The calculated result also shows that negative refraction occurs in this kind of PC slab.     

光子晶体集成光电子器件

文章简要介绍了利用光子晶体实现微纳尺度上光调控的物理原理和工作机制,重点讨论了如何利用光子晶体的缺陷态实现微纳尺度的各种集成光电子器件,并结合文章作者所在研究组的研究工作经验,简单回顾了各种类型的集成光电子器件的工作原理、物理实现和光学特性.