Izaddeen Kabir Yakasai

A simple hexagonal lattice photonic crystal fiber model with liquid-infiltrated core for different liquids: water, ethanol and benzene, has been proposed. In the proposed structure, three air hole rings are present in the cladding and three equal sized air holes are present in the core. Numerical investigation of the proposed fiber has been performed using full vector finite element method with anisotropic perfectly match layers, to show that the proposed simple structure exhibits high relative sensitivity, high power fraction, relatively high birefringence, low chromatic dispersion, low confinement loss, small effective area, and high nonlinear coefficient. All these properties have been numerically investigated at a wider wavelength regime 0.6–1.8 μm within mostly the IR region. Relative sensitivities of water, ethanol and benzene are obtained at 62.60%, 65.34% and 74.50%, respectively, and the nonlinear coefficients are 69.4 W⁻¹ km⁻¹ for water, 73.8 W⁻¹ km⁻¹ for ethanol and 95.4 W⁻¹ km⁻¹ for benzene, at 1.3 µm operating wavelength. The simple structure can be easily fabricated for practical use, and assessment of its multiple waveguide properties has justified its usage in real liquid detection.

The liquid‐infiltrated photonic crystal fibre (LI‐PCF) is proposed for guiding terahertz radiation. Geometrical asymmetry is achieved by introducing a large ellipse in the core. By filling the ellipse with liquid cocaine, the optical properties of the photonic crystal fibre (PCF) are theoretically examined using finite element method‐based COMSOL multiphysics software. At an operating frequency of 1 THz, the proposed LI‐PCF demonstrates a sensitivity of 87.02% and confinement loss in the order of 10 ⁻⁴ cm ⁻¹ . The PCF also demonstrates extremely low effective material loss −1 , a birefringence of 0.018, large effective mode area of 1.11 × 10 ⁵ µm ² , a high numerical aperture of 0.45 and near‐zero ultra‐flattened chromatic dispersion of 1.4351 ± 0.5883 ps/THz/cm. The design simplicity and high sensitivity, strong confinement factor, low material losses and high birefringence of the fibre suggest that the proposed fibre may be convenient for PCF‐based cocaine sensing, for application in the security and defence industries.

The World Wide Web (www) has become an interactive medium for millions of Internet users across the world, daily visiting occur for various purposes. However, their behavior could be monitored by various service providers or company’s website they visited for several purposes. Thus, we can see that if certain data pre-processing techniques are practiced correctly, results will be of high quality and in turn provide substantial evidence of the user and its web session. This paper provides a way of knowing user behavior on the web. It explains the use of cookies: Cookies allow you to do many things such as log on to Internet Banking, have us 'remember' your log-in preferences, when logging on, a pop-up window appears stating the service is not available and to try later. A misspelled domain name in the address line. Lotteries that charge a fee to collect your winnings, apply for products and services online, and use financial tools like our ‘find and compare’ mortgage calculators., servers, and proxy logs with some scripting to be able not only to get a user’s IP address but also get personal information like age, identity, and any other credential as long as the user puts them down while using the web.

A thorough modal characterization, centred on the full vectorial finite element method (FEM) has been used to model and numerically investigate a porous core photonic crystal fibre (PC-PCF), which may potentially be integrated into Terahertz (1012 Hz) compact systems. The proposed fibre consists of a rotated hexagonal core surrounded by a conventional hexagonal cladding. It has been shown that effective material loss (EML), core power fraction and dispersion profile are 0.019 cm-1, 51.7% and 0.5 ± 0.04 ps/THz/cm within 1 THz bandwidth, respectively. Based on simulated results and noncomplex design, it is envisaged that the proposed fibre can be realised for industrial THz applications.

A novel liquid‐core photonic crystal fibre (LC‐PCF) based on the Zeonex substrate has been proposed for sensing the varying concentration of kerosene in petrol and diesel fuels in terahertz frequencies. Fuel sample infiltration is achieved by designing a single hexagon in the porous core region. The LC‐PCF has been numerically studied using a finite element method. By filling the core hexagon with different petrol–kerosene and diesel–kerosene concentrations, sensitivity and transmission profiles of the proposed LC‐PCF have been examined. The impact of different design parameters of the fibre on its performance has been analysed, allowing the optimum design parameter set to be selected for further analysis. The proposed fibre shows relative sensitivities above 96% and effective material losses in the order of 10 ⁻³ . With negligible confinement losses, the proposed fibre demonstrates near‐zero ultra‐flattened group velocity dispersion profiles within 1–1.6 THz. It is envisaged that the proposed fibre may be fabricated easily due to its simple design, and thus, serving as a significant step towards understanding THz pulse interaction with liquid petrochemical products.

Deployment of mini macrocell base stations can also be referred to as femtocells improve quality of service of indoor and outdoor users. Nevertheless, mobility management remains a key issue with regards to their deployment. This paper is leaned towards this issue, with in-depth focus on the most important aspect of mobility management - handover. In handover management, making a handover decision in the LTE two-tier macrocell femtocell network is a crucial research area. Decision algorithms in this research, are classified and comparatively analyzed according to received signal strength, user equipment speed, cost function and interference. However, it was observed that most of the discussed decision algorithms fail to consider cell selection with hybrid access policy in a single macrocell multiple femtocell scenario, another observation was a majority of these algorithms lack the incorporation of user equipment residence parameter. Not including this parameter boosts the number of unnecessary handover occurrence. To deal with these issues, a sophisticated handover decision algorithm is proposed. The proposed algorithm considers the user’s velocity, received signal strength, residence time as well as the femtocell base station’s access policy. Simulation results have shown that the proposed algorithm reduces the number of unnecessary handovers when compared to conventional received signal strength based handover decision algorithm.

A highly birefringent photonic crystal fibre with elliptical air holes in the core has been proposed and simulated for terahertz wave propagation. Using finite element method with anti-reflective perfectly matched layer, it is shown that the three elliptical air holes in the core are sufficient to produce extremely high birefringence, high power fraction and low transmission losses.

A novel photonic crystal fiber has been proposed for sensing liquid cocaine in terahertz frequencies. By varying the fiber's core ellipse height, simulation results have shown a high relative sensitivity above 85%, high birefringence of 0.018 and extremely low transmission effective material loss at 1 THz.