Numerical and experimental analysis of the hydroelastic behavior of purse seine nets

The paper presents a general three dimensional hydro-elastic tool for the analysis of different types of fishing nets and aquaculture facilities. Flexible net strands are modeled by non-linear truss elements having two nodes. Hydrodynamic loads due to relative motion of the net with the surrounding fluid are computed using the Morison equation. The coupled hydrodynamic-elastodynamic equations are solved using finite element (FE) approximations. Furthermore, experimental data are presented for the drag resistance of a purse seine net, commonly used as fishing tool in the Mediterranean sea. The measurements were conducted in the towing tank of NTUA on a sample of a net. The net was tested in three configurations: vertical, horizontal and inclined at 451. The derived drag coefficients are compared to predictions of the FEM developed model. The vertical submergence behavior of the seine in calm water is also examined, both experimentally and theoretically. Moreover, the shooting phase of the purse-seine fishing is simulated with the aim to investigate the diving behavior of the net. The flow shading effect of neighboring strands is identified as a critical parameter for the consistent predictions of the diving behavior

Engineering of composite metallic microfibers towards development of plasmonic devices for sensing applications

The paper discusses the analysis of tapered hybrid composite microfibers based on a metal-core and dielectric-cladding composite material system. Its advantages over the pure metal tips conventionally used, are the inherent enhanced environmental robustness due to inert borosilicate cladding and the capability of multiple excitation of the tapered nanowire through the length of the fiber due to the enabled total internal reflection at the borosilicate/air interface. Simulations through finite element method (FEM) have demonstrated an improved field enhancement at the tapered region of such microfibers. Furthermore, experimental results on tapering in copper based microfibers together with light coupling and propagation studies will be demonstrated revealing the potential for the development of plasmonic devices for sensing applications

Design and implementation of fiber-embedded plasmonic structures in microwires

Plasmonic structures can dramatically enhance photonic devices functionality [1] by providing controllable field confinement and light nanofocussing which are crucial for imaging, diagnostic, and sensing applications. Pure metallic tips or metal coated optical fibers have been demonstrated as fiber-compatible efficient plasmonic devices [2] but with limited applicability in real applications due to fragility and limited environmental robustness.The proposed platform based on hybrid microwires composed of metal core and silicate glass cladding offers the required robustness and flexibility for engineering and developing plasmonic devices in all-fiber form [3]. The presence of the dielectric cladding offers continuous re-excitation of the plasmon modes due to repeated total internal reflection at the glass/air interface, which can dramatically reduce the high losses induced by the metal core and allow long propagation distances. This enables direct light coupling from the distal end of fiber instead of side excitation of the tip, allowing their integration in optical fiber or and planar integrated circuitry for hybrid architectures. By employing the heating and stretching thermal processing method for diameter tapering of microwires with gold core, high-quality all-fiber plasmonic tips with high field intensity at the tip apex have been fabricated. Furthermore, embedded metal microspheres, as seen in the figure, were controllably formed targeting to the development of in-fiber plasmonic resonators.Extensive theoretical and experimental investigations were necessary for the identification of appropriate tapering conditions and adiabatic metal tips development with well-defined geometrical characteristics. In this context, analytical studies and microfluidic simulations by Finite Element Method — FEM were performed for the understanding of the appropriate thermal processing conditions of microwires and their behaviour towards their diameter tapering without discontinuities and metal core breakage. Fabricated plasmonic tips performance was successfully related to simulation results by FEM, predicting high field enhancement factors up to 105. Furthermore, theoretical investigations of instabilities-driven formation of gold microspheres embedded in the glass cladding by heating the hybrid microfibers was also performed suggesting ways to control the spherical formed features.<br/