轻烃芳构化与催化重整技术比较

轻烃芳构化技术是近年来发展起来的一种生产芳烃的新工艺。尝试通过从技术发展、反应原理与催化剂、装置与工艺等几个方面与传统的催化重整技术进行对比,分析轻烃芳构化技术特点。归纳轻烃芳构化技术的优缺点,并结合技术特点提出了该技术的适用建议。     

Optically and electrically excited emissions from organic semiconducting oligomer crystals

This paper reviews optically and electrically excited emissions from organic semiconducting oligomers in the form of their single crystals. Of the semiconducting oligomers, the review focuses on thiophene/phenylene co‐oligomers (TPCOs). The topics cover crystal growth and laser oscillation along with related spectrally narrowed emissions of TPCO crystals. Aside from the strong excitation with a laser beam, weak excitation using a mercury lamp produces optical fringes superimposed on broadband emission spectra. The laser oscillation spectra accompanied by longitudinal multimode and optical fringes observed from the weak excitation have the same origin. This enables us to determine optical constants (i.e. refractive indices) and their dispersion of the crystals and provides sufficient information for the construction of optoelectronic devices based on the organic crystals. As a typical example, the review outlines the improved device constitution and performance as well as device operation methods with light‐emitting field‐effect transistors (LEFETs), because the device configuration is suited for cutting‐edge devices including lasers. Finally the review presents device performance of LEFETs having a diffraction grating. These devices are suited for exploring the possibility of constructing a next‐generation current‐injected laser device. © 2016 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Effects of molecular weight on dual light‐ and thermo‐responsive behaviors of homopolymers with azobenzene units and terminal oligo(ethylene glycol) units

A series of water‐soluble dual light‐ and thermo‐responsive homopolymers bearing azobenzene units and terminal oligo(ethylene glycol) units with well‐defined molecular weight (M _n = 0.69 × 10⁴ to 4.60 × 10⁴ g mol^?1) were synthesized via reversible addition–fragmentation chain transfer polymerization. All the homopolymers exhibited reversible photoisomerization and their lower critical solution temperatures showed an unusual increase with increasing molecular weight. Interestingly, by increasing the molecular weight, the aggregate morphology of these polymers was found to evolve from a spherical to a cylindrical shape. © 2017 Society of Chemical Industry     

聚丙烯单丝用抗老化剂浅述

简述了聚丙烯的老化机制,着重介绍了在光氧作用下的老化及添加抗老化剂的措施,分别从添加紫外线吸收剂、氢过氧化物分解剂、激发态猝灭剂和自由基捕获剂、光屏蔽剂六种助剂出发,研究其作用机制、性能优势并综述当前的研究进展。研究了在水和金属离子以及力的作用等不同环境因素影响下聚丙烯的老化过程,最后简要介绍了目前的复合抗老化剂。     

A first-principles study of the electronic,structural, and optical properties of CrN and Mo:CrN clusters

CrN, one of the most investigated transition metal nitrides, is noted for its wear, corrosion, and oxidation resistance. It also has many other unique chemical and mechanical properties. In the present study, we conducted a density functional theory (DFT) analysis to probe the structural, electronic, and optical properties of pristine and Mo-doped CrN structures in non-crystalline phases using different combinations in which one or two Cr and/or N atoms were substituted by Mo. This study found that the Cr₄Mo₂N₂ structure was chemically and energetically the most stable species among the six considered clusters (Cr₄N₄, Cr₃Mo₂N₃, Cr₄Mo₂N₂, Cr₂Mo₂N₄, Cr₄MoN₃, and Cr₃MoN₄). The DFT-derived electronic structure predicted that the Cr₃Mo₂N₃ and Cr₄MoN₃ clusters possess magnetic susceptibility. Computed infrared (IR), Raman, and ultraviolet–visible (UV–Vis) analyses indicated that the Cr₄N₄ and Cr₄Mo₂N₂ clusters were naturally stable. This should enable these clusters to serve as light-harnessing materials for strategic applications in solar selective surfaces.     

Complex mullite structures fabricated via digital light processing of a preceramic polysiloxane with active alumina fillers

By taking advantage of the multi-functional properties of preceramic polymers, their transformation into ceramic material at low sintering temperatures and the processing capabilities of polymer manufacturing processes, mullite components were fabricated by additive manufacturing. A photocurable silicone preceramic polymer resin containing alumina particles was shaped into complex structures via Digital Light Processing. Dense and crack-free, highly complex porous mullite ceramics were produced by firing a mixture of a commercially available photosensitive polysiloxane as the silica source, containing alumina powder as active filler, in air at a low sintering temperature (1300 °C). In particular, the developed formulations, coupled with the additive manufacturing approach, allow for precise control of the architecture of the porous ceramic components, providing better properties compared to parts with stochastic porosity.     

Importance of the color of light for the illumination of urban squares

The objective of this article was to establish the significance of parameters relevant for urban square illumination, particularly those related with the color of light. Performed using a questionnaire and with 154 architecture students as respondents, the survey showed that the 18 parameters can be divided into two groups. The first group of 13 parameters refers to the overall impression, influencing the basic and most important lighting aims like safety, security, orientation, visual comfort, and amenity, whereas the second group includes parameters related to lighting features which may negatively influence the overall impression. The four parameters directly linked to the color of light were evaluated lower than expected, indicating that architecture students were probably translating their attitude toward color in architecture to color of light, thus underestimating this lighting parameter. The survey results also showed that female respondents are more sensitive to parameters, which affect safety and security.     

Study on metamerism degree evaluation based on wavelength sensitive cone weighting algorithm

Metamerism phenomenon can be used in illuminant detection to ensure the accuracy of light source. A method based on Long‐, Middle‐, Short‐ wavelength cones(LMS) weighting algorithm to evaluate metamerism degree is proposed. The chromatic relationship between the degree of metamerism mismatch and the light source is studied. Herein, the consistency between the metameric indices (MIs) and CIE1976 L*a*b* color difference ranking is analyzed by SRCC, KRCC, PLCC and RMSE. A statistically sampling method to obtain practical LMS cone fundamentals to evaluate metamerism degree is employed. The analysis results obtained show that the method based on LMS weighting algorithm has good evaluation ability and stability in simulation experiments and statistically sampling experiments, which are in line with visual characteristics of human. Proposed method meets the requirements of selecting metameric pairs used in light source detection. The analysis results have certain guiding significance.     

Phase structure analysis and pyroelectric energy harvesting performance of Ba(HfxTi1-x)O3 ceramics

Ba(Ti_1-xHf_x)O₃ ceramics were synthesized by a solid-state reaction process. The evolution of the phase structure was identified by XRD spectrum, dielectric spectroscopy, and temperature-dependent Raman spectroscopy for the Ba(Ti_1-xHf_x)O₃ ceramics. In addition, pyroelectric energy harvesting properties based on the Olsen cycle were investigated for the first time. A maximum pyroelectric energy harvesting density value of N_D = 491.30 kJ/m³ (ΔT = 120°C, E_H = 50 kV/cm) was achieved in the Ba(Hf_0.05Ti_0.95)O₃ ceramic. Compared with those of BT, the values of N_D more than doubled in the temperature range from ΔT = 60°C to ΔT = 100°C in the Ba(Hf_0.05Ti_0.95)O₃ ceramic and even increased 3.2 times at ΔT = 80°C near the Curie temperature (T_C) of the Ba(Hf_0.05Ti_0.95)O₃ sample. In addition, a larger pyroelectric energy harvesting density value of N_D = 367.10 kJ/m³ (ΔT = 120°C, E_H = 50 kV/cm) was acquired in the Ba(Hf_0.12Ti_0.88)O₃ ceramic. Values of N_D-BHT5/N_D-BT and N_D-BHT12/N_D-BT were analyzed in the Ba(Ti_1-xHf_x)O₃ ceramics. The optimal pyroelectric properties can be obtained in the vicinity of the ferroelectric to paraelectric phase-transition region.