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Electrically switchable light transmittance of epoxy-mercaptan polymer/nematic liquid crystal composites with controllable microstructures
摘要： In this paper, we report the design, preparation and properties of epoxy-mercaptan polymer/nematic liquid crystal (LC) composites with electrically switchable optical transmittance. It is found that the polymer microstructure can be regulated from porous structure to microspheres or beads by appropriately modulating the curing temperature, the molecular structure of mercaptan, as well as the compositions of epoxy, mercaptan and nematic LC host. Under an external electric field, the thin films based on such composites can switch from opaque to transparent. The electro-optical performance is found to be highly dependent on the polymer microstructures and the optimum characteristics can be achieved in the composite with a microstructure of smaller microspheres. The possible mechanism for the formation of polymer microspheres and the effects of the microstructures on the electro-optical characteristics of the composites are also discussed. This work is expected to provide an efficient way to control the microstructure of epoxy/mercaptan polymer and develop the composites with switchable optical transmittances for both civil and military applications.
关键词： epoxy,microstructure,mercaptan,liquid crystal,electro-optical performance
更新于2025-09-10 09:29:36
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A novel modulation format identification based on amplitude histogram space
摘要： In this paper, we proposed a novel modulation format identification method for square M-quadrature amplitude modulation (M-QAM) signals which is based on amplitude histogram space of the incoming data after analog-to-digital conversion, chromatic dispersion compensation at the receiver. We demonstrated the identification of quadrature phase-shift keying (QPSK), 16-QAM, 64-QAM formats with an amplitude histogram space. Simulation results show that it achieve 100% identification accuracy when the incoming signal OSNR is 14 dB to identify the modulation format of QPSK, 16-QAM, and 64-QAM signals in digital coherent systems. The method has low complexity and small delay.
关键词： amplitude histogram space,high-order modulation format,optical performance monitoring,modulation format identification (MFI)
更新于2025-09-10 09:29:36
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A novel approach to prepare one-pot Fe/PPy nanocomposite and evaluation of its microwave, magnetic, and optical performance
摘要： The aim of this study was preparation of Fe/Fe2O3/Fe3O4 (Fe)/polypyrrole (PPy) nanocomposite using reductive method and investigation of its microwave absorbing properties using polymethylmethacrylate (PMMA) medium. Firstly, PPy was prepared by an oxidative polymerization method with Fe3+ as a doping agent. Next, the Fe/PPy nanocomposite was formed by insitu reduction of Fe2+ and remained Fe3+ with sodium borohydride solution under an inert nitrogen atmosphere. Finally, PPy and Fe/PPy nanostructures were separately suspended within the PMMA matrix to examine their microwave absorbing characteristics. The prepared PPy and Fe/PPy nanostructures were studied using the Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The diffuse reflection spectroscopy (DRS) analysis presented a 1.79 eV band gap for the Fe/PPy nanocomposite based on the Kubelka–Munk theory. The vibrating sample magnetometer (VSM) revealed that magnetic properties were reinforced in the Fe/PPy nanocomposite. According to the results obtained by vector network analyzer (VNA), the maximum reflection loss of Fe/PPy/PMMA nanocomposite was -76.02 dB at 8.96 GHz with a thickness of 3.2 mm, absorbing all of the x-band frequency more than 12.72 dB with a thickness of 2.8 mm. Interestingly, the Fe/PPy/PMMA nanocomposite demonstrated a bandwidth > 3.4 GHz more than 10 dB from 2.2 to 3.2 mm at the x-band frequency.
关键词： Optical performance,Magnetic properties,Fe/PPy/PMMA,Microwave absorption
更新于2025-09-09 09:28:46
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Optical performance analysis of an innovative linear focus secondary trough solar concentrating system
摘要： The parabolic trough solar concentrating system has been well developed and widely used in commercial solar thermal power plants. However, the conventional system has its drawbacks when connecting receiver tube parts and enhancing the concentration ratio. To overcome those inherent disadvantages, in this paper, an innovative concept of linear focus secondary trough concentrating system was proposed, which consists of a fixed parabolic trough concentrator, one or more heliostats, and a fixed tube receiver. The proposed system not only avoids the end loss and connection problem on the receiver during the tracking process but also opens up the possibility to increase the concentration ratio by enlarging aperture. The design scheme of the proposed system was elaborated in detail in this paper. Besides, the optical performance of the semi and the whole secondary solar trough concentrator was evaluated by using the ray tracing method. This innovative solar concentrating system shows a high application value as a solar energy experimental device.
关键词： secondary parabolic trough solar concentrator,optical performance,concentration ratio,linear focus,ray tracing method
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Second generation linear focus sun simulator to test optical performance of parabolic trough receivers - OptiRec
摘要： This paper presents results from a characterization of DLR’s second generation sun simulator test facility (OptiRec) for determining the optical performance of parabolic trough receivers. The configuration of the test bench is an elliptical mirror trough with flat end mirrors. Solar simulator lamps are situated in one focal line, the receiver in the other focal line. Water at ambient temperature flows through the receiver and allows for a calorimetric measurement of the absorbed power. Compared to the first generation test bench (ElliRec) the mirror material is changed from aluminum to glass, the ellipse size is changed and the handling is improved. Based on 34 measurements of the absorbed power the repeatability for OptiRec measurements is measured to 0.13% (1σ), compared to 0.2% in the ElliRec. Seven receivers from different manufacturers are measured in both test benches yielding consistent relative optical efficiency with <1.1% deviation. Particular differences are larger than the repeatability, which are attributed to differences in spectra and incidence angles between both test benches.
关键词： sun simulator,optical performance,calorimetric measurement,parabolic trough receivers,repeatability
更新于2025-09-04 15:30:14