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- 저자 : Heming Chen (검색결과 5 건)
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A High Birefringent Polymer Terahertz Waveguide: Suspended Elliptical Core Fiber
Jingli Wang,Heming Chen,Weihua Shi 한국광학회 2014 Current Optics and Photonics Vol.18 No.5
A novel high birefringent polymer terahertz (THz) fiber with a suspended elliptical core is proposed in this paper. The introduction of an elliptical core can enhance asymmetry to realize high mode birefringence, and a large porous outer cladding effectively isolates the core-guided mode from interacting with the surrounding environment. A full-vector finite element method(FEM) is used to analyze the characteristics of the THz fiber. Simulation results show that the suspended elliptical fiber exhibits high mode birefringence on a level of 10-2 over a wide frequency range, and an extremely large mode birefringence(≈0.06226) is obtained when ellipticity is 0.2. Moreover, a suspended hollow elliptical core fiber is also discussed for the purpose of lower loss, however high mode birefringence and low relative absorption loss can not coexist in such a kind of fiber.
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Preparation and electrochemical performance of porous carbon derived from polypyrrole
Wu Lili,Chen Xinguo,Ding Chang,Wang Pitao,Luo Heming 한국탄소학회 2023 Carbon Letters Vol.33 No.2
Supercross-linked polymers are widely used as carbon precursor materials due to their abundant carbon sources and low cost. In this paper, a supercross-linked polymer was prepared by the solvothermal method. The supercross-linked polymer as a precursor and the PPyC-800-A was synthesized by activating this with KOH. The microstructure, structure, and electrochemical performances of porous carbon PPyC-800-A were studied at different of temperature and carbon alkali ratio. According to the results, the porous carbon PPyC-800-1:2 is mainly composed of a stack of spherical particles with a high surface area of 1427.03 m2 g−1, an average pore diameter of 2.32 nm, and a high specific capacitance of 217.7 F g−1 at a current density of 1.0 A g−1 in a 6 M KOH electrolyte. It’s retention rate is 97.58% after 5000 constant current charges and discharges. With a specific capacitance decay rate of 21.91 percent, an energy density of 11.96 Wh kg−1, and a power density of 500.0 W kg−1, the current density rises from 1.0 A g−1 to 10.0 A g−1, exhibiting remarkable electrochemical properties, cycling stability, and energy production performance This study contributes experimental ideas to the field of supercross-linked polymer-derived carbon materials and energy storage.
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Wu Lili,Wang Pitao,Chen Xinguo,Zhang Jianqiang,Luo Heming 한국탄소학회 2022 Carbon Letters Vol.32 No.3
Hypercrosslinked polymers HCPs have been widely used as precursors to prepare porous carbon materials because of their highly ordered porous structure and large specific surface area. In this paper, we used a solvothermal method to prepare a hypercrosslinked polymer, and the HCPC-700-A was prepared using an activation method with the hypercrosslinked polymer as the precursor. The effects of different carbon–alkali ratios on the microstructure, composition and electrochemical properties of porous carbon HCP were studied. The results show that the surface of porous carbon HCPC-700-A presents a relatively regular geometric shape, and a large number of pore structures are mainly micro- and mesopores. The specific surface area is 2074.53 m2 g−1, and the average pore size is between 1.29 and 1.93 nm. Porous carbon HCPC-700-1:2 has excellent electrochemical performance in 1 M H2SO4, and the specific capacitance is up to 464.4 F g−1 at a current density of 1 A g−1. The specific capacitance decay rate is 29.72% when the current density is increased from 1 A g−1 to 8 A g−1. After 5000 cycles, the capacitance retention rate is 91.16% at a current density of 2 A g−1, showing excellent electrochemical performance, good cycle stability and perfect energy storage performance. This research provides new experimental ideas for HCPs in the electrochemical energy storage field.
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Ke Ji,Wen Zhou,Heming Chen 한국광학회 2014 Current Optics and Photonics Vol.18 No.5
Terahertz (THz) communication has important applications in high-speed and ultra broadband wireless access networks. The THz modulator is one of the key devices in a THz communications system. Wavelength division multiplexing (WDM) can expand the capacity of THz communications systems, so research on multi wavelength THz modulators has significant value. By combining photonic-crystal and THz technology, a novel type of multi wavelength THz modulator based on a triple-lattice photonic crystal is proposed in this paper. Compared to a compound-lattice photonic crystal, a triple-lattice photonic crystal has a larger gap width of 0.196. Simulation results show that six beams of THz waves can be modulated simultaneously with high performance. This modulator’s extinction ratio is as large as 34.25 dB, its insertion loss is as low as 0.147 dB, and its modulation rate is 2.35 GHz.
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Removal of methylene blue from aqueous solution by a carbon-microsilica composite adsorbent
Deyi Zhang,Ying Ma,Huixia Feng,Heming Luo,Jiao Chen,Yuan Hao 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.6
Microsilica, one kind of industrial solid waste material, was utilized firstly to prepare a carbon-microsilica composite adsorbent (CMS). The prepared adsorbent was characterized with XPS, SEM and Gas sorption experiments. The results indicated the SO3H groups, which are very effective in capturing cationic organic dye, were introduced onto the surface of CMS; the Brunauer-Emmett-Teller (BET) surface area (SBET) and total pore volume (Vtotal) of CMS reach 51m2/g and 0.045 cm3/g, respectively. Meanwhile, the possibility of the utilization of the adsorbent for removal of methylene blue (MB) from aqueous solution was investigated. The effect of pH, contact time and initial MB concentration for MB removal were studied. Equilibrium data were modeled using the Langmuir, Freundlich and Dubinin-Radushkevich equations to describe the equilibrium isotherms. It was found that data fit to the Langmuir equation better than the Freundlich equation. Maximum monolayer adsorption capacity was calculated at different temperatures (298,308, and 318 K) reach 251.81, 283.76 and 309.70 mg/g, respectively. It was observed that adsorption kinetics obeys the pseudo- first-order equation.
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