工业SO2及碳黑颗粒紫外成像遥感监测技术

为了准确有效监测工业烟囱排放,基于SO2及碳黑颗粒物的光学特性,设计并研制出一套双通道紫外成像遥感监测系统.该成像系统的两个光谱通道的中心波长分别定于310 nm和330 nm,利用两个通道的光学厚度之差反演SO2浓度图像,颗粒物浓度图像由330 nm通道获取,根据浓度图像结合光流法获取烟羽运动速度,进而计算得出SO2和碳黑颗粒物的排放速率.结果表明,该工业烟囱的SO2及碳黑颗粒物排放速率分别为72.48±3.16 kg/h和6.33±1.18 kg/h.实验采用紫外相机同时对工业烟囱排放的SO2及碳黑颗粒物进行监测,实验表明双通道紫外成像遥感监测兼具高时间分辨率与高空间分辨率,测量结果准确直观,在工业废气污染、船舶尾气污染以及火山喷发污染排放遥感监测中具有非常明显的技术优势及巨大的应用前景.     

Solvable model of quantum-optical feedback

A quantized optical cavity mode controlled by dissipation, two-photon source and feedback loop is studied. The feedback is activated by detections of photons leaving the cavity and consists of rapid phase shifts of the cavity field by π. The steady-state of the mode and first-order field correlation functions let analytical exploration. The feedback radically modifies the shape of the mode's spectrum - it gets asymmetry and its double-peaked structure manifests itself much more discernibly than in no-feedback case. Up to our knowledge, the present quantum feedback model is the first one which permits exact solution.     

Tunable electronic and optical properties of SnC/BAs heterostructure by external electric field and vertical strain

Based on the first-principles method, we investigate the electronic structure of SnC/BAs van der Waals (vdW) heterostructure and find that it has an intrinsic type-II band alignment with a direct band gap of 0.22 eV, which favors the separation of photogenerated electron–hole pairs. The band gap can be effectively modulated by applying vertical strain and external electric field, displaying a large alteration of band gap via the strain and experiencing an indirect-to-direct band gap transition. Moreover, the band gap of the heterostructure varies almost linearly with external electric field, and the semiconductor-to-metal transition can be realized in the presence of a strong electric field. The calculated band alignment and the optical absorption reveal that the SnC/BAs heterostructure could present an excellent light-harvesting performance. Our designed heterostructure is expected to have great potential applications in nanoelectronic devices and photovoltaics and optical properties.     

Physical properties of Pb doped ZnS thin films prepared by ultrasonic spray technique

In the present work, high quality Pb doped ZnS thin films were deposited on glass substrates at 450°C using spray ultrasonic technique. The dependence of the structural, morphological and optical properties of the films on the lead (Pb) doping amount was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis–NIR spectrophotometry, and four-point method. The improvement of the obtained Pb:ZnS thin films properties were discussed as a function of Pb concentration (0.5 to 2 at.%). The average crystallite size of Pb:ZnS was found in the range of 25–37 nm. The scanning electron microscopy (SEM) reveals that the films are continuous, homogeneous and dense. The UV–vis–NIR spectroscopy characterizations demonstrated that all the films exhibit good transmittance (60–70%) in the visible region and their optical band gap energy ($E_{\mathrm{g}}$) changes from 3.92 to 3.6 eV. The films electrical resistivity showed an apparent dependence on Pb content.     

Non-Abelian gauge potentials driven localization transition in quasiperiodic optical lattices

Derived from quantum waves immersed in an Abelian gauge potential, the quasiperiodic Aubry-André-Harper (AAH) model is a simple yet powerful Hamiltonian to study the Anderson localization of ultracold atoms. Here, we investigate the localization properties of ultracold atoms in quasiperiodic optical lattices subject to a non-Abelian gauge potential, which are depicted by non-Abelian AAH models. We identify that the non-Abelian AAH models can bear the self-duality. We analyze the localization of such non-Abelian self-dual optical lattices, revealing a rich phase diagram driven by the non-Abelian gauge potential involved: a transition from a pure delocalization phase, then to coexistence phases, and finally to a pure localization phase. This is in stark contrast to the Abelian counterpart that does not support the coexistence phases. Our results establish the connection between localization and gauge symmetry, and thus comprise a new insight on the fundamental aspects of localization in quasiperiodic systems, from the perspective of non-Abelian gauge potential.     

Ce掺杂6H-SiC电子结构和光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理计算方法,对未掺杂及Ce掺杂6H-SiC的电子结构和光学性质进行理论计算.计算结果表明,未掺杂6H-SiC是间接带隙半导体,其禁带宽度为2.045 eV,掺杂Ce元素,带隙宽度下降为0.812 eV.未掺杂6H-SiC在价带的低能区,Si-3s、C-2s电子轨道对态密度的贡献较大,在价带的高能区,主要是由Si-3p、Si-3s、C-2p态组成.掺杂后Ce原子的4f轨道主要贡献在导带部分,掺杂后电导率提高.未掺杂时,只有一个介电峰,是价带电子跃迁到导带电子所致,掺杂后有两个介电峰,第一个介电峰是由于导带电子跃迁到Ce原子4f轨道上产生,第二个峰是价带电子向导带电子跃迁产生.未掺杂6H-SiC,在能量为10.31 eV处吸收系数达到最大值,掺杂后在能量为6.57 eV处,吸收系数达到最大值.     

Optical diffusers based on uniform nano-sized polymer balls/nematic liquid crystals composite films

ABSTRACT

Optical diffusers are promising diffusing materials in the optical devices such as monitors, projectors, fibre optics, light-emitting diode (LED) systems and liquid crystal displays (LCDs). We report optical diffusers comprising uniformly distributed nano-sized polymer balls/nematic liquid crystals (LCs) by ultraviolet (UV) click reaction of ene monomer and thiol monomer. By optimising the mass ratio 1:1 of ene and thiol, of which the average diameter of the corresponding nano-sized polymer balls is about 900 nm, relatively high optical transmission and haze with 88.99% and 94.49% are yielded, respectively. Furthermore, by controlling the curing time, the average diameter of nano-sized polymer balls can be reduced to 810 nm, and the developed film exhibits high transmission (98.49%) without sacrificing the high haze (91.77%). This paper demonstrates that UV click reaction is an economical approach to fabricate optical diffusers in a controllable manner.     

Curing behavior and properties of high biosourced epoxy resin blends based on a triepoxy monomer and a tricarboxylic acid hardener from 10-undecenoic acid

Renewable propane-1,2,3-triyl tris(9-(oxiran-2-yl) nonanoate) (EGU, 100 wt% biogenic) and a tricarboxylic acid triglyceride (CGTU) hardener (85.7 wt% biogenic) were synthesized from 10-undecenoic acid (10-UDA) and used to produce epoxy resins with 52–92 wt% biobased carbon. CGTU was prepared by thermally activated thiol-ene coupling of thioglycolic acid onto propane-1,2,3-triyl tris(undec-10-enoate), (GUD) in the absence of solvent. The characterized CGTU was used as a green hardener of blends based on EGU and a conventional bisphenol A-based epoxy pre-polymer (DGEBA) at various mass percentages (0–100 wt%) with an stoichiometric epoxy/acid equivalent ratio. Calorimetric studies revealed higher peak temperature, lower reaction heats, and longer gelation times in resins with high EGU proportion, evidencing the lower reactivity of aliphatic EGU compared with aromatic DGEBA. Cured resins were yellowish transparent rubber-like materials with glass transition temperatures (Tg) varying from −14 °C to −42 °C and tensile strength in the range of 1750 kPa–790 kPa, for 0 and 100 wt % EGU, respectively. The soluble fraction of all resins was less than 4.3%, reflecting a high level of crosslinking. Thermosets with high biobased content showed both UV-light protection and visible light transparency.