In underwater wireless networks (UWNs), conventionally there is no direct communication between an underwater node and a remote command center. A floating base-station is often used to serve as an interface to a UWN; such a base-station would typically have both acoustic and radio modems to communicate with underwater nodes and offshore centers, respectively. Although employing an airborne base-station would avoid the logistically-complicated surface nodes deployment, communication across the air-water interface becomes the main challenge since it involves two mediums. This paper promotes a novel way to interconnect UWNs to airborne base-stations through visible light communication (VLC) links. The paper analyzes the viability of VLC across the air-water interface by determining the coverage area and intensity inside the water for a light transmitter placed in the air. We show that enough intensity can be achieved for VLC communication even in the presence of a wavy water surface. We then provide guidelines for using single and multiple light sources to establish robust VLC links under rough environmental conditions like high water current and turbidity. Our approach is validated using simulation and a lab experiment is done to validate the simulation result for flat water surfaces.
Atomic layer deposition (ALD) is a versatile technique to functionalize textile substrates due to its ability to create conformal films on the fibers’ surface. Photocatalytic activity and antibacterial activity of TiO2 and ZnO films deposited onto polyamide 66 fabrics were investigated. ALD coated fabrics were examined to eliminate Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria with ISO 20645 and AATCC 100 standard methods. Both materials were only slightly successful for the elimination of E. coli. However, ZnO films were more effective in killing S. aureus bacteria than TiO2 films independent of incubation conditions (i.e., under dark or ambient light). Deposited films were characterized using SEM, FTIR, UV-Vis, and XPS spectroscopy techniques. Furthermore, the samples’ photocatalytic activity was determined by measuring methylene blue degradation as a model organic molecule showing that ZnO films were better photocatalysts as deposited. The films’ antibacterial mechanism is mainly due to ions dissolving from the films into the bacterial solutions.
Cl− is found to be detrimental to the photodegradation of PNP. Hydrogen ion concentration of reaction mixture was found to increase continuously during photodegradation suggesting mineralization of PNP.
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