Aperture Field Estimation in E Plane and H-Plane T-Junctions Using Field Theoretic Analysis

Wireless Personal Communications - This paper presents method of moment based analysis of E Plane and H-Plane T-junctions to find the field distributions on different transverse and longitudinal...     

A model for the performance analysis and design of waveguide p-i-n photodetectors

A model to investigate the frequency response of waveguide (WG) p-i-n photodetectors (PDs) is presented. The model is based on the 2-D position-dependent distribution of carriers in the device and the results show that the contribution to the total current mainly comes from a small length of the PD measured from its input end. The effect of carrier trapping at a heterointerface has also been considered to study the frequency dependence of the photocurrent at low-bias voltages. The frequency response and bandwidth obtained from the model are in good agreement with published experimental results. A simplified and approximate relation for the fiber-to-WG coupling efficiency has also been used to calculate the overall quantum-efficiency of WGPDs. Then, the effect of WG geometry on the bandwidth-quantum efficiency product has been analyzed and some results on the optimum design of a WG p-i-n PD for maximum bandwidth-quantum efficiency product have been tabulated.     

Mobility management for VoIP service: Mobile IP vs. SIP

Wireless Internet access has gained significant attention as wireless/mobile communications and networking become widespread. The voice over IP service is likely to play a key role in the convergence of IP-based Internet and mobile cellular networks. We explore different mobility management schemes from the perspective of VoIP services, with a focus on Mobile IP and session initiation protocol. After illustrating the signaling message flows in these two protocols for diverse cases of mobility management, we propose a shadow registration concept to reduce the interdomain handoff (macro-mobility) delay in the VoIP service in mobile environments. We also analytically compute and compare the delay and disruption time for exchanging signaling messages associated with the Mobile IP and SIP-based solutions.     

High extinction, broadband polarisers using long-period fibre gratings in few-mode fibres

Long-period fibre gratings in specially designed birefringent few-mode fibres are used to demonstrate spectrally flat polarisers with bandwidths of 10 nm and polarisation extinction levels of 20 dB. This is enabled by the special dispersive properties of few-mode fibres, yielding fibre polarisers with performance approaching that of bulk-optic devices.     

A review of reliability prediction methods for electronic devices

A wide range of reliability prediction methods is available today for electronic systems. This article classifies the commonly used and referred to reliability prediction methodologies into some categories easy to understand. A set of selected methods, which are of relevance to many industries, the aerospace industry among others, are reviewed and the possibility they offer to address the stated objectives is assessed. Their respective advantages and shortcomings are the basis for the recommendation we make to use the methods in a combined fashion (simultaneously or successively) along the product development process.     

COMPARATIVE LIMITING FLUX ANALYSIS OF BLACK LIQUOR AND POLYETHYLENE GLYCOL IN ULTRAFILTRATION

Ultrafiltration of black liquor was carried out using an asymmetric membrane and the results were compared with that of polyethylene glycol, a standard macromolecule, in a stirred batch cell. The effects of system parameters, e.g., pressure, concentration and stirrer speed on permeate flux and solute rejection were studied extensively for both the solutes.

An osmotic pressure model was used to analyze experimental results. To take into account the phenomena of concentration polarization, an extra resistance term, called the polarization layer resistance (R_p), was incorporated into the model. The polarization layer resistance was found to be a function of flow regime and concentration at the membrane. To correlate these, the following two types of relationship were examined and tested with the experimental results,

and

where a, b, c, a₁, b₁, are constants.     

AKH-NFIS: Adaptive Krill Herd Network Fuzzy Inference System for Mobile Robot Navigation

Wireless Personal Communications - Mobile robot navigation has been a current issue in the most recent two decades. Mobile robots are necessary to explore in obscure and dynamic situations. To...     

Irradiation of Transition Metal Dichalcogenides Using a Focused Ion Beam: Controlled Single‐Atom Defect Creation

Manipulation and structural modifications of 2D materials for nanoelectronic and nanofluidic applications remain obstacles to their industrial‐scale implementation. Here, it is demonstrated that a 30 kV focused ion beam can be utilized to engineer defects and tailor the atomic, optoelectronic, and structural properties of monolayer transition metal dichalcogenides (TMDs). Aberration‐corrected scanning transmission electron microscopy is used to reveal the presence of defects with sizes from the single atom to 50 nm in molybdenum (MoS₂) and tungsten disulfide (WS₂) caused by irradiation doses from 10¹³ to 10¹⁶ ions cm^?2. Irradiated regions across millimeter‐length scales of multiple devices are sampled and analyzed at the atomic scale in order to obtain a quantitative picture of defect sizes and densities. Precise dose value calculations are also presented, which accurately capture the spatial distribution of defects in irradiated 2D materials. Changes in phononic and optoelectronic material properties are probed via Raman and photoluminescence spectroscopy. The dependence of defect properties on sample parameters such as underlying substrate and TMD material is also investigated. The results shown here lend the way to the fabrication and processing of TMD nanodevices.     

Design and Implementation of Optical Signal Reinstatement Technique for High DPSK RZ Transceiver Scheme

Wireless Personal Communications - Optical signal reinstatement (OSR) is a common technique used in high-speed communication systems. OSR can be achieved using various techniques such as;...