6G Network Architecture Using FSO-PDM/PV-OCDMA System with Weather Performance Analysis

This paper presents a novel 160 Gbps free space optics (FSO) communication system for 6G applications. Polarization division multiplexing (PDM) is integrated with an optical code division multiple access (OCDMA) technique to form a PDM-OCDMA hybrid. There are two polarization states: one is X-polarization generated from adjusting the azimuthal angle of a light source at 0° while the other is Y-polarization which is generated by adjusting the azimuthal angle of a light source at 90°. Each polarization state is used for the transmission of four independent users. Each channel is assigned by permutation vector (PV) codes and carries 20 Gbps data. Four different weather conditions are considered for evaluating the performance of our proposed model. These weather conditions are clear air (CA), foggy conditions (low fog (LF), medium fog (MF), and heavy fog (HF)), dust storms (low dust storm (LD), moderate dust storm (MD), heavy dust storm (HD)), and snowfall (wet snow (WS) and dry snow (DS)). Bit error rate (BER), Q-factors, maximum propagation range, channel capacity, and eye diagrams are used for evaluating the performance of the proposed model. Simulation results assure successful transmission of 160 Gbps overall capacity for eight channels. The longest FSO range is 7 km which occurred under CA while the minimum is achieved under HD, which is 0.112 km due to large attenuation caused by HD. Within fog conditions, the maximum propagation distances are 1.525 km in LF, 1.05 km in MF, and 0.85 km in HF. Likewise, under WS and DS, the proposed system can support transmission distances of 1.15 km and 0.28 km, respectively. All these transmission distances are achieved at BER less than 10−5

Novel Thiazole Derivatives of Medicinal Potential: Synthesis and Modeling

This paper reports on the synthesis of new thiazole derivatives that could be profitably exploited in medical treatment of tumors. Molecular electronic structures have been modeled within density function theory (DFT) framework. Reactivity indices obtained from the frontier orbital energies as well as electrostatic potential energy maps are discussed and correlated with the molecular structure. X-ray crystallographic data of one of the new compounds is measured and used to support and verify the theoretical results

Flexible Bench-Scale Recirculating Flow CPC Photoreactor for Solar Photocatalytic Degradation of Methylene Blue Using Removable TiO 2

TiO2 immobilized on polyethylene (PET) nonwoven sheet was used in the solar photocatalytic degradation of methylene blue (MB). TiO2 Evonik Aeroxide P25 was used in this study. The amount of loaded TiO2 on PET was approximately 24%. Immobilization of TiO2 on PET was conducted by dip coating process followed by exposing to mild heat and pressure. TiO2/PET sheets were wrapped on removable Teflon rods inside home-made bench-scale recirculating flow Compound Parabolic Concentrator (CPC) photoreactor prototype (platform 0.7 × 0.2 × 0.4 m3). CPC photoreactor is made up of seven low iron borosilicate glass tubes connected in series. CPC reflectors are made of stainless steel 304. The prototype was mounted on a platform tilted at 30°N local latitude in Cairo. A centrifugal pump was used to circulate water containing methylene blue (MB) dye inside the glass tubes. Efficient photocatalytic degradation of MB using TiO2/PET was achieved upon the exposure to direct sunlight. Chemical oxygen demand (COD) analyses reveal the complete mineralization of MB. Durability of TiO2/PET composite was also tested under sunlight irradiation. Results indicate only 6% reduction in the amount of TiO2 after seven cycles. No significant change was observed for the physicochemical characteristics of TiO2/PET after the successive irradiation processes

Filling a niche in “ligand space” with bulky, electron-poor phosphorus (III) alkoxides

The chemistry of phosphorus(III) ligands, which are of key importance in coordination chemistry, organometallic chemistry and catalysis, is dominated by relatively electron-rich species. Many of the electron-poor P(III) ligands that are readily available have relatively small steric profiles. As such, there is a significant gap in “ligand space” where more sterically bulky, electron-poor P(III) ligands are needed. This contribution discusses the coordination chemistry, steric and electronic properties of P(III) ligands bearing highly fluorinated alkoxide groups of the general form PRn(ORF)3-n, where R = Ph, RF = C(H)(CF3)2 and C(CF3)3; n = 1-3. These ligands are simple to synthesize and a range of experimental and theoretical methods suggest that their steric and electronic properties can be “tuned” by modification of their substituents, making them excellent candidates for large, electron-poor ligands

Enhanced Spectral Amplitude Coding OCDMA System Utilizing a Single Photodiode Detection

In this paper, the performance of a spectral amplitude coding-optical code division multiple access (SAC-OCDMA) system is investigated utilizing a single photodiode (SPD) detection technique. The proposed system uses enhanced double weight (EDW) codes as signature codes with three simultaneous users to overcome both phase-induced intensity noise (PIIN) and multiple access interference (MAI). In addition, a dispersion compensating fiber (DCF) is used in order to decrease the group velocity dispersion (GVD) caused in the single mode fiber. An erbium-doped fiber amplifier (EDFA) is used to overcome the attenuation. The use of both DCF and EDFA leads to an appreciable enhancement in the system performance. The system performance is evaluated through its bit error rate (BER), Q-factor, and received power. A comparison between the EDW codes and modified double weight (MDW) codes on the SAC-OCDMA system is demonstrated. Simulation is carried out through Optisystem ver. 7. The simulation results show that: (a) using an avalanche photodiode (APD) over PIN photodiode allows data transmission over longer distances; (b) the use of DCF improves the system BER;(c) using MDW codes gives better BER than using EDW codes

Electronic Structure of Solvent-Polarity Indicators. Solvatochromism and Tautomeric Epuilibria of Styryl-Merocyanines

AbstractSolvatochromic and halochromic behaviour of two unsymmetrical merocyanine-type dyes, namely 2-[2′- and 4′-hydroxystyryl]-pyridinium methiodide, are studied.In alcoholic and hydrogen-bond-acceptor (HBA) solvents their visible absorption spectra exhibit an additional long-wavelength band suggesting the existence of tautomeric equilibria in their solutions. The tautomeric equilibrium constants in triethanolamine-acetone mixed solvents are determined.Quantum mechanical MO method PPP-π-SCF-CI is used to calculate the electronic spectra and the underlying keto-enol-tautomeric stability. Deprotonation of the OH group is shown to provide destabilization in binding energy in excess of 5 eV in agreement with the experimental results indicating that these indicators exist mainly as protonated species (enol form) in their solutions.Furthermore, solvent-induced changes in the ground-state electronic structures are examined by means of 1H-NMR spectroscopy and the PPP calculations

The interaction and photostability of some xanthenes and selected azo sensitizing dyes with TiO2 nanoparticles

We have tested simple Graetzel-type solar cells using semiconductor thin films consisting of TiO2 nanoparticles and some electron injecting dyes. The possibility of using xanthenes (rhodamine 101, fluorescein and 5(6)-carboxyfluorescein) and selected azo dyes (alizarin yellow R, alizarin yellow 2G and carboxyaesenazo) as sensitizers has been explored. Fluorescence and electronic absorption measurements revealed complex formation between the chosen dyes and the surface of the colloidal TiO2. The apparent association constants (Kapp) of the surface complexes have been estimated and are correlated with the dyeinduced negative shifts of the reduction potential of colloidal TiO2 nanoparticles. Moreover, due to its utmost importance, photostability of the organic dyes in absence and presence of colloidal TiO2 nanoparticles and the influence of the used electrolyte have been examined. The results point to a remarkable enhancement of photostability in the presence of the electrolyte (I3−/I−), which is attributed to fast regeneration of the neutral dye via the redox couple of the electrolyte. Furthermore, photocurrent action spectrum of the fabricated and tested DSC shows the origin of photoelectric output to be optical absorption of the dye used