Volume and Issue Articles
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September-October 2013
Analysis of Rainfall Variability in Ghana
Abstract: Understanding the decadal and/or annual variability and distributions of rainfall of a region is important and useful especially for agricultural activities. Rainfall data from 77 stations were analysed to determine the mean annual and inter- decadal rainfall variability and distribution in Ghana for the period 1981-2010. The ArcView GISTM (version 3.2) software was the tool used to analyse the temporal variability of the decadal mean rainfall for the periods 1981-1990, 1991-2000 and 2001- 2010. The study shows variation on high and low rainfall distributions in the country. With respect to previous studies, results showed a general decline in mean annual rainfall for the period 1981-2010 with high rainfalls shifting to the South-western corner of the country. However, it could be deduced that mean decadal rainfall amounts in Ghana is on a gradual increase from 1981 to 2010, though the rate at which it is increasing is on a decline, i.e. from 8.6 % in 1991-2000 to 2.6 % in 2001-2010. We recommend that the agro-meteorological sub-department of the GMET studies the inter-annual and/or inter-decadal rainfall variability and distribution in the country and appropriately inform farmers of the same in order to avoid total crop failure. We also recommend that studies on rainfall variability in Ghana be carried out in a continuous manner as and when new rainfall data is available.
A Novel Network Coding Based Privacy Safeguarding Scheme against Traffic Analysis
Abstract: Wireless access networks have been extensively deployed due to their ease, portability, and low cost. For expanding the radio coverage range of the accessible wireless networks, a Multi-hop Wireless Networks (MWNs) are considered as extremely capable solution and they can also be used to get enhance the system reliability through multi-path packet forwarding. However, due to the open wireless medium, MWNs are vulnerable to a variety of attacks, such as eavesdropping, data alteration and node compromising. Due to the open wireless medium attacks the traffic analysis and flow tracing can be easily initiated by a hateful adversary as privacy hazard is one of the significant issues in multihop wireless networks. Since the network coding has the potential to prevent these attacks as the coding operation is encouraged at intermediate nodes. However, the simple consumption of network coding cannot accomplish the goal once adequate packets are collected by the adversaries. On the other hand, the coding nature averts the possibility of employing the available privacy safeguarding methods, such as Onion Routing. A novel network coding based privacy safeguarding scheme against traffic analysis in multi-hop wireless networks is proposed in this paper. The proposed scheme offers two important privacy preserving features with homomorphic encryption on Global Encoding Vectors (GEVs). The packet flow un-traceability and message content confidentiality are two features for resourcefully preventing the traffic analysis attacks.
Developing Short Duration Rainfall Intensity Frequency Curves for Accra in Ghana
Abstract: Estimation of rainfall Intensity-Duration-Frequency (IDF) is commonly required for the design of hydraulic control structures and for water resources engineering planning and development. The relationship between rainfall intensity, duration and the return period of a certain rainfall amount can be determined through statistical analysis of rainfall data. Rainfall data collected from the four meteorological stations in the Greater Accra Region of Ghana were used to develop the rainfall intensity duration frequency curves with return periods ranging from 2 to 100 years and using the Gumbel distribution for rainfall intensity values for durations of 15, 30, 60, 120, 240 and 360 minutes. The rainfall intensity duration frequency curves developed for these stations are recommended for the prediction of rainfall intensities for Accra.
Efficient deployment of heterogeneous sensors for tracking moving objects: An algorithmic approach
Abstract: Detecting a moving object inside an irregular region is one of the most fundamental challenges of Wireless Sensor Networks. The performance of an effective and efficient sensor network for detecting moving object is highly related to the proper deployment of the sensors. In this paper we have addressed the problem of deploying heterogeneous sensors in a regular space with a grid-based routing model which may further be extended to an irregular one. We have also considered clustered energy model to detect and replace of a dead node if exist in the network. The simulation shows that with the increase number of deploying nodes for larger space, this model has more than 50% gain with guaranteed shortest path than that of the existing broadcast techniques. More over, the worst case of this deployment algorithm is compare to the average case with existing one.
Electrical Interconnections Limits and Optical Interconnections Solutions to Signal Propagation delay for On Chip Data Path Ahmed Nabih Zaki Rashed Electronics and Electrical Communications Engineering Department
Abstract: Optical interconnection is a promising solution for high speed interconnects between chips or boards to solve the inherent limits of electrical interconnects in speed, crosstalk, and power dissipation. It is believed that the concept of integrated optical interconnect is a potential technological solution to alleviate some of the ever more pressing issues involved in exchanging data between cores in optical communication architectures (inter-line crosstalk, latency, connectivity and power consumption). This paper has presented optical interconnects that bring advantage of high data rate density, i.e. large bandwidth with small physical dimensions, as well as large bandwidth x distance product. High data rate density enables tight integration of many optical channels with electronic chips.
Analysis of Total Harmonic Distortion for PV- Battery Hybrid System with Multilevel Inverter
Abstract: This paper presents the control of a multilevel inverter supplied by a Photovoltaic (PV) panel and a batteries bank. It is well known that the power quality of multilevel inverter signals depends on their number of levels. However, the question that arises is whether there is a limit beyond which it is not necessary to increase the number of level. This question is addressed in this paper seven -level converters are studied. The harmonics content of the output signals are analyzed. A simplified Pulse Width Modulation (SPWM) method for a multilevel inverter that supplied an induction motor is developed. The controller equations are such that the SPWM pulses are generated automatically for any number of levels. The effectiveness of the propose method is evaluated in simulation. Matlab/Simulink is used to implement the control algorithm and simulate the system.
Analysis on the Critical Issues of UV Light Induced Corneal Cross Linking
Abstract: A dynamic model of UV light photoinitiated cross linking in corneal collagen is presented to analyze the critical issues involved in the procedure. These issues include the dynamics of the UV light penetration and the safety depth margin (z*), the roles of the UV light intensity, concentration and extinction coefficient of the initiator. Analytic formulas are developed to show that z* is a decreasing function of the extinction coefficient and the concentration of the initiator, but it is a nonlinearly increasing function of the light intensity and irradiation time. Our analytic formulas are used to analyze the measured data showing the dynamic feature of the light intensity. Finally, a new protocol is suggested based on our theoretical and experimental finding.
A Focused UV laser for Optimal Photo- polymerization in Thick Medium
Abstract: Modeling of a focused UV laser photoinitiated polymerization in thick polymer absorbing medium is presented. Optimal focusing offers more uniform polymerization and larger volume than the collimated or non-optimal cases. A scaling law governed by f*=1.6/S is derived numerically, where S is the product of the extinction coefficient and concentration of the initiator. The focusing technique and analytic formulas developed provide useful guidance for further experimental study and system design for efficient photoinitiated polymerization, particularly for thick medium.
Single Feed Dual band dual Polarized Micro-strip Patch antenna
Abstract: This paper covers some aspects of Microstrip antenna designs. The design and analysis of single feed Dual band and Dual polarized rectangular Microstrip antenna which operates at the central frequency of 2.23 GHz & 2.78 GHz. Radiation at frequency 2.23 GHz is Linear polarized & at frequency 2.78 GHz is circular polarized . . Basically, transmission line and cavity model have been used to model both antennas. First, the design parameters for dual band and dual polarized of rectangular patch antenna have been calculated from the transmission line model equation. The antenna design is extended to enhancement of bandwidth of multi- frequncy and multi-polarization rectangular Microstrip patch antenna using the slots at radiating edges.
A Study of Behavior-based and Role-based Autonomous Multi-Robot Exploration and
Abstract: The autonomous multi-robot exploration and coverage is a well-addressed problem in the field of robotics. Exploration and coverage is the task of guiding robots in such a way that they cover the environment in an efficient and effective manner. The Behaviour-based system and Role-based system for multi-robot control is popular in autonomous multi- robot exploration, because they are robust to the dynamic interactions inherent in any multi-robot systems. In this paper, the existing Multi-Robot exploration and coverage systems under the characterization of behaviour-based and role-based are identified and their strengths and shortcomings discussed. Existing solutions to this problem differ primarily by the type of coordination that exists between the robots. The level of coordination depends on the type of communication the robots are expected to share. Key words: autonomous mobile multi-robot, behaviour-based exploration, role-based exploration, navigation behaviour, path- planning behaviour.
Performance Enhancements for Pre-emptive Ad- Hoc On-demand Multipath Distance Vector
Abstract: An ad-hoc network will often change rapidly in topology, this courses for routes in the network to often disappear and new to arise. The Ad-hoc On-Demand Distance Vector Routing Protocol (AODV), is based on the principle of discover routes as needed. In this paper we will extend the definition of AODV with the ability to discover multiple routes to a host and switch between them, if an active route is becoming weak and there is a risk that it will disappear. We will refer to it as "pre- emptive AOMDV". We will show that the performance of pre-emptive AOMDV do handle changes in topology better than AODV itself. To show the effect of extending AODV, the suggested protocol is implemented in a simulator. Performance enhancements will be presented from different scenarios, to compare pre-emptive AOMDV with the ordinary AODV.
Design and Implementation of Pixel Level Medical Image Fusion
Abstract: Medical image fusion has become a common term used with in medical diagnostics and treatment. Image fusion means the combining of two images into a single image that has the maximum information content without producing details that are non-existent in the given images. The term is used when multiple patient images are registered and overlaid or merged to provide additional information. Fused images may be created by combining information from multiple modalities, such as magnetic resonance image (MRI), computed tomography (CT). For example, CT images are used to determine hard bone information while MRI images are typically used to visualize soft tissue information. In this paper, discrete wavelet transform (DWT) based technique for medical image fusion is presented. Firstly, the medical images to be fused are decomposed by the DWT. DWT coefficients from two input images are fused pixel-by pixel by choosing the average of the approximation coefficients. Then an inverse DWT is performed to obtain the fused image. For the same images we apply Discrete Multi Wavelet Transform (DMWT). Then we evaluate the fused image for various parameters like peak signal to noise ratio (PSNR), entropy, standard deviation (std dev) and quality for both the methods. The results indicate that multi-wavelet transform is superior as compare to wavelet transform.
An Analysis of Fuzzy Approach For Detecting Anomalous Behaviour with E-mail Traffic
Abstract: This paper investigates the use of fuzzy inference for detection of abnormal changes in email traffic communication behaviour. Several communication behaviour measures and metrics are defined for extracting information on the traffic communication behaviour of email users. The information from these behaviour measures is then combined using a hierarchy of fuzzy inference systems, to provide an abnormality rating for overall changes in communication behaviour of suspect email accounts. The use of fuzzy inference is then demonstrated with a case study investigating the email traffic behaviour of a person’s email accounts from the Enron email corpus.
Extending Database for Hiding Sensitive Frequent Data Items
Abstract: In this paper, we propose a novel, exact border-based approach that provides an optimal solution for the hiding of sensitive frequent item sets by 1) minimally extending the original database by a synthetically generated database part-the database extension, 2) formulating the creation of the database extension as a constraint satisfaction problem, 3) mapping the constraint satisfaction problem to an equivalent binary integer programming problem, 4) exploiting underutilized synthetic transactions to proportionally increase the support of non sensitive item sets, 5) minimally relaxing the constraint satisfaction problem to provide an approximate solution close to the optimal one when an ideal solution does not exist, and 6) using a partitioning in the universe of the items to increase the efficiency of the proposed hiding algorithm. Extending the original database for sensitive item set hiding is proved to provide optimal solutions to an extended set of hiding problems compared to previous approaches and to provide solutions of higher quality. Moreover, the application of binary integer programming enables the simultaneous hiding of the sensitive item sets and thus allows for the identification of globally optimal solutions Key words: knowledge hiding, association rule mining, binary integer programming.
A Review on Recent Trends in Cryptography
Abstract: Modern information protection methods can only be effective if an almost impossibly wide range of conditions is met. Proper cryptography is one of these conditions. This article reviews some recent cryptographic development, but focuses on understanding the cryptographic decision making process. Keyword: Cypher Text, Public Key Cryptography, Private Key Cryptography, DES, AES, RSA.
Detection and Mitigation DDoS Defence Techniques to Strengthen Intrusion Prevention
Abstract: Nowadays, guarantee of secure communication is as important as the traditional computer and information security assurance. Presently Distributed Denial of Service (DDoS) Attacks are causing billions of dollars losses by affecting the normal functioning of organizations. DDoS attackers are infiltrating large numbers of computers by exploiting software vulnerabilities. By the time specific countermeasures are developed to prevent DDoS attacks, attackers enhance existing DDoS attack tools, developing new and derivative DDoS attack tools and techniques. Organizations are trying their best to minimize their losses from these systems. However, most of the organizations widely use the Intrusion Prevention Systems (IPS) to observe and manage their networks. In this paper the Preventive, Detective and Mitigation DDoS Defence techniques and Mechanisms have been discussed to strengthen existing IPS concepts, which can help to develop a new and intelligent Network Intrusion Prevention System. A new technique for an intelligent and smart Intrusion Prevention system has been introduced on the basis of Captcha, IP addresses, MAC Addresses and Application_Id.