Exponential Log-Periodic Antenna Design Using Improved Particle Swarm Optimization with Velocity Mutation

An improved particle swarm optimization (PSO) method applied to the design of a new wideband log-periodic antenna (LPA) geometry is introduced. This new PSO variant, called PSO with velocity mutation (PSOvm), induces mutation on the velocities of those particles that cannot improve their position. The proposed LPA consists of wire dipoles with lengths and distances varied according to an exponential rule, which is defined by two specific parameters called length factor and spacing factor. The LPA is optimized for operation in 790-6000MHz frequency range, in order to cover the most usual wireless services in practice, and also to provide in this range the highest possible forward gain, gain flatness below 2dB, secondary lobe level below –20dB with respect to the main lobe peak, and standing wave ratio below 2. To demonstrate its superiority in terms of performance, PSOvm is compared to well-known optimization methods. The comparison is performed by applying all the methods on several test functions and also on the LPA optimization problem defined by the above-mentioned requirements. Furthermore, the radiation characteristics of the PSOvm-based LPA give prominence to the effectiveness of the proposed exponential geometry compared to the traditional Carrel’s geometry

1.62 GHz Circularly Polarized Pin-Fed Notched Circular Patch Antenna

This paper studies a circular patch antenna which is fed by using a coaxial pin, which is a suitable antenna design for applications where small size is of importance. Such applications are wearable antenna designs. The main purpose of this paper is to design an antenna with wearable capabilities and adequate radiation characteristics for satellite communications and more specifically for the Iridium satellite constellation. The goals for the radiation characteristics of the antenna are the tuning of the antenna to 1.62GHz which is the Iridium's frequency, maximum boresight gain for this frequency, as well as circular polarization

An Efficient Algorithm for Partial Discharge Localization in High-Voltage Systems Using Received Signal Strength

The term partial discharge (PD) refers to a partial bridging of insulating material between electrodes that sustain an electric field in high-voltage (HV) systems. Long-term PD activity can lead to catastrophic failures of HV systems resulting in economic, energy and even human life losses. Such failures and losses can be avoided by continuously monitoring PD activity. Existing techniques used for PD localization including time of arrival (TOA) and time difference of arrival (TDOA), are complicated and expensive because they require time synchronization. In this paper, a novel received signal strength (RSS) based localization algorithm is proposed. The reason that RSS is favoured in this research is that it does not require clock synchronization and it only requires the energy of the received signal rather than the PD pulse itself. A comparison was made between RSS based algorithms including a proposed algorithm, the ratio and search and the least squares algorithm to locate a PD source for nine different positions. The performance of the algorithms was evaluated by using two field scenarios based on seven and eight receiving nodes, respectively. The mean localization error calculated for two-field-trial scenarios show, respectively, 1.80 m and 1.76 m for the proposed algorithm for all nine positions, which is the lowest of the three algorithms

Comparison of evolutionary algorithms for LPDA antenna optimization

A novel approach to broadband log-periodic antenna design is presented, where some of the most powerful evolutionary algorithms are applied and compared for the optimal design of wire log-periodic dipole arrays (LPDA) using Numerical Electromagnetics Code. The target is to achieve an optimal antenna design with respect to maximum gain, gain flatness, front-to-rear ratio (F/R) and standing wave ratio. The parameters of the LPDA optimized are the dipole lengths, the spacing between the dipoles, and the dipole wire diameters. The evolutionary algorithms compared are the Differential Evolution (DE), Particle Swarm (PSO), Taguchi, Invasive Weed (IWO), and Adaptive Invasive Weed Optimization (ADIWO). Superior performance is achieved by the IWO (best results) and PSO (fast convergence) algorithms.NATO's Public Diplomacy Division in the framework of “Science for Peace”. Grant Number: SfP-984409 ORC

Detecting and manipulating compressed alternate data streams in a forensics investigation

Data hiding technique through Alternate Data Streams in compressed form is poorly documented and less known among Forensic experts. This paper deals with the documentation of Compressed ADS and their attributes concerning hiding information, provides a simple technique of creating compressed ADS and using it in a malicious manner. Finally a method is presented in order to detect and manipulate ADS in a proper way, complying with the Computer Forensic techniques. © 2008 IEEE

User authentication method and implementation using a three-axis accelerometer

The rapid growth of accelerometer use on consumer electronics has brought an opportunity for unique user authentication. We present an efficient recognition algorithm for such interaction using a single three-axis accelerometer. Unlike common user authentication methods which require memorizing complex phrases and are prone to physical attacks, our method requires a single training sample for a gesture pattern which allows users to authenticate themselves in a fast and secure manner. Our work imitates the use of physical handwritten signatures, which are a common authentication technique and tries to integrate them in a digital form. The presented method aims at providing easy to remember personalized gesture passwords through the muscle memory ability of the human body. An implementation using the wii remote sensor, along with identification results for different users is presented as a proof of concept. © 2010 Institute for Computer Sciences, Social Informatics and Telecommunications Engineering

A framework for secure data delivery in wireless sensor networks

Typical sensor nodes are resource constrained devices containing user level applications, operating system components, and device drivers in a single address space, with no form of memory protection. A malicious user could easily capture a node and tamper the applications running on it, in order to perform different types of attacks. In this paper, we propose a 3-layer Security Framework composed by physical security schemes, cryptography of communication channels and live forensics protection techniques that allows for secure WSN deployments. Each of the abovementioned techniques maximizes the security levels leading to a tamper proof sensor node. By applying the proposed security framework, secure communication between nodes is guaranteed, identified captured nodes are silenced and their destructive effect on the rest of the network infrastructure is minimized due to the early measures applied. Our main concern is to propose a framework that balances its attributes between robustness, as long as security is concerned and cost effective implementation as far as resources (energy consumption) are concerned. © 2012 IFSA

Lightweight steganalysis based on image reconstruction and lead digit distribution analysis

This paper presents a novel method of JPEG image Steganalysis, driven by the need for a quick and accurate identification of stego-carriers from a collection of files, where there is no knowledge of the steganography algorithm used, nor previous database of suspect carrier files created. The suspicious image is analyzed in order to identify the encoding algorithm while various meta-data is retrieved. An image file is then reconstructed in order to be used as a measure of comparison. A generalization of the basic principles of Benford's Law distribution is applied on both the suspicious and the reconstructed image file in order to decide whether the target is a stego-carrier. The authors demonstrate the effectiveness of the technique with a steganalytic tool that can blindly detect the use of JPHide/JPseek/JPHSWin, Camouflage and Invisible Secrets. Experimental results show that the steganalysis scheme is able to efficiently detect the use of different steganography algorithms without the use of a time consuming training step, even if the embedding data rate is very low. The accuracy of the detector is independent of the payload. The method described can be generalized in order to be used for the detection of different type images which act as stego-carriers. Copyright © 2011, IGI Global