Analytical time-domain model for radio over free space optical (RoFSO) systems considering the scintillation effect

This work was supported by the World-Class University (WCU) Program through the National Research Foundation of Korea (R31-10026), and Grant K20901000004-09E0100-00410 funded by the Ministry of Education, Science, and Technology (MEST).An analytical time-domain model is presented to analyze a radio over free space optical (RoFSO) system considering the scintillation effect with a log-normal distribution. This analytical model uses a dual-drive Mach-Zehnder modulator (DD-MZM) and photodetector (PD) for typical optical double sideband (ODSB) and single sideband (OSSB) signals. We show the output current of PD as a function of the summation of each frequency component in time domain. Finally, we calculate the received signal power with respect to the power spectral density (PSD) and derive a closed-form average bit error rate (BER) performance.Peer reviewedFinal Accepted Versio

Average BER analysis of SCM-based free-space optical systems by considering the effect of IM3 with OSSB signals under turbulence channels

© 2009 Optical Society of AmericaIn this paper, we derive the average bit error rate (BER) of subcarrier multiplexing (SCM)-based free space optics (FSO) systems using a dual-drive Mach-Zehnder modulator (DD-MZM) for optical single-sideband (OSSB) signals under atmospheric turbulence channels. In particular, we consider the third-order intermodulation (IM3), a significant performance degradation factor, in the case of high input signal power systems. The derived average BER, as a function of the input signal power and the scintillation index, is employed to determine the optimum number of SCM users upon the designing FSO systems. For instance, when the user number doubles, the input signal power decreases by almost 2 dBm under the log-normal and exponential turbulence channels at a given average BER.Peer reviewe

BER performance analysis of radio over free-space optical systems considering laser phase noise under Gamma-Gamma turbulence channels

This paper analytically investigates a bit error rate (BER) performance of radio over free space optical (FSO) systems considering laser phase noise under Gamma-Gamma turbulence channels. An external modulation using a dual drive Mach-Zehnder modulator (DD-MZM) and a phase shifter is employed because a DD-MZM is robust against a laser chirp and provides high spectral efficiency. We derive a closed form average BER as a function of different turbulence strengths and laser diode (LD) linewidth, and investigate its analytical behavior under practical scenario. As a result, for a given average SNR with normalized perturbation, it is shown that the difference of average BER corresponding to two LDs (with linewidth of 624MHz and 10MHz) under weak turbulence is almost 3 times larger than that under strong turbulencePeer reviewe

Mildly oxidized porous covalent triazine frameworks with rapid and high adsorption capability for aqueous organic micropollutants

Two microporous and amorphous covalent triazine-based frameworks (CTFs) were synthesized by the low-temperature Friedel–Craft reaction using phenanthrene and anthracene as monomers, and cyanuric chloride as a linker. The synthesized CTFs were then further functionalized by mild oxidation to obtain CTF derivatives (CTF-OXs) with amide and imine groups. The functionalized derivatives showed excellent maximum adsorption capacities for bisphenol A (BPA), bisphenol S (BPS), and 2-naphthol (247, 249, and 376 mg g−1, respectively), which are aqueous organic micropollutants. The maximum adsorption capacities were estimated using the Langmuir and Jovanovic isotherm models, and the adsorption kinetics could be well fitted by the pseudo-second-order kinetics model. The extremely high association constants between the pollutants and the mildly oxidized CTFs surface, calculated by the Langmuir isotherm model, showed a 1:1 complex formation between micropollutants (BPA, BPS, and 2-naphthol) and CTF-OXs. This suggests excellent binding properties for the removal of the selected micropollutants at any concentration level. The thermodynamics parameters for the removal of BPA, BPS, and 2-naphthol showed the adsorption process is feasible and involves physisorption. Hence, CTF-OXs have significant potential for use as effective adsorbents for water decontamination. © 2022 The Korean Society of Industrial and Engineering ChemistryFALS

Electrically Healable and Mechano‐Sensitive Gel Composites of Carbon Nanotubes and Conducting Polymers

We performed a one-pot mechanosynthesis of adaptive conducting gels using carbon nanotubes (CNTs) and a non-volatile eutectic liquid (EL) of diphenylamine (DP) with benzophenone (BP). Upon further mixing with ammonium persulfate (APS), oxidative polymerization of DPs enabled the generation of electrically healable conductors containing poly(diphenylamine) (PDPA) as an adaptive matrix. The resulting composite gels were created through a synergistic combination of CNTs and PDPAs, which exhibited printable and conductive characteristics. Thus, after printing on an elastic substrate, the conducting ink composite displayed excellent electromechanical sensory properties. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim1

Light-Induced Transport of Water and Guest Molecules in Mesoporous Silica Nanocontainer Interface

[No abstract available]1

Supramolecular Engineering of Amorphous Porous Polymers for Rapid Adsorption of Micropollutants and Solar-Powered Volatile Organic Compounds Management

Freshwater shortage is becoming one of the most critical global challenges owing to severe water pollution caused by micropollutants and volatile organic compounds (VOCs). However, current purification technology shows slow adsorption of micropollutants and requires an energy-intensive process for VOCs removal from water. In this study, a highly efficient molecularly engineered covalent triazine framework (CTF) for rapid adsorption of micropollutants and VOC-intercepting performance using solar distillation is reported. Supramolecular design and mild oxidation of CTFs (CTF-OXs) enable hydrophilic internal channels and improve molecular sieving of micropollutants. CTF-OX shows rapid removal efficiency of micropollutants (>99.9% in 10 s) and can be regenerated several times without performance loss. Uptake rates of selected micropollutants are high, with initial pollutant uptake rates of 21.9 g mg(-1) min(-1), which are the highest rates recorded for bisphenol A (BPA) adsorption. Additionally, photothermal composite membrane fabrication using CTF-OX exhibits high VOC rejection rate (up to 98%) under 1 sun irradiation (1 kW m(-2)). A prototype of synergistic purification system composed of adsorption and solar-driven membrane can efficiently remove over 99.9% of mixed phenol derivatives. This study provides an effective strategy for rapid removal of micropollutants and high VOC rejection via solar-driven evaporation process.FALS

Mechanochemical synthesis and interfacial engineering of photothermal polymer composites for solar‐driven water evaporation

Freshwater generation has been extensively studied to address the global freshwater scarcity issue, although designing a simple, inexpensive system with high efficiency and sustainability is complicated. Solar-driven water evaporation is a promising, highly efficient water purification strategy. This paper reports the synthesis of a hydrophilic conductive polymer and its carbon nanotube (CNT) composites for efficient solar-driven water evaporation via a quick mechanochemical process. Doped polydiphenylamine (PD) and its CNT composites were obtained by the simple grinding of an inexpensive eutectic-phase monomer with oxidants, doping agents, and oxidized CNTs. The obtained composites exhibited high photothermal efficiency (89.9%) and water evaporation rate (1.41 kg m−2 h−1) under 1 sun irradiation. Dual doping and introducing oxidized CNTs into PD enhanced the wettability, photothermal efficiency, and water evaporation performance. This study provides an effective strategy for the fast and facile fabrication of photothermal membranes for solar-driven freshwater generation. © 2023 Korean Chemical Society, Seoul & Wiley-VCH GmbH.FALS