Abstract

Most of Arabic countries are located within the arid and semi-arid zones, which are characterised by the scarcity and the high spatial and temporary variability of rainfall .The influence of rainfall patterns on natural vegetation cover is significant and can be monitored and assessed using NDVI indices derived from remote sensing data. The literature stresses on the wide use of NDVI to study the changes in vegetation cover, because of the sensitivity of vegetation to the Red and Infra-red spectrum. In this paper the SPOT Apparent Green Cover Percentage data and MODIS Vegetation index are used to monitor the vegetation cover change in North western Libya. The aim of this study is to establish the spatial and temporal changes in vegetation cover and their relation to the rainfall pattern. The data and method: The utilized data for research included multi-temporal remotely sensed data (Spot, MODIS, and Landsat ETM), climatic data (ground stations and satellite data) and digital maps (DEM, slope, flow direction and basins). The satellite images were firstly pre-processed. This included the importing of different format images into a standard format of the ERDAS IMAGINE 9.1. Then the dataset were geometrically corrected into the WGS84 latitude/longitude geographic co-ordinate system. The study area was then subseted using a vector file representing the area boundary (AOI). The multibands were stacked to create time series, the NDVI equation was used to convert the DN values into NDVI values. 

This study is part of a larger study that explores societal and organizational culture factors that influence the adoption of information systems (IS) in Libya’s Oil and Banking sectors (Twati & Gammack, 2004; 2006). Using a structured survey questionnaire based on the work of Geert Hofstede’s Value Survey Module (VSM 94), 400 questionnaires were administrated to middle and top management employees in more than 15 government and public organizations in the two named industry sectors. The findings showed that there is a direct positive relationship between Hofstede’s (1980) societal culture dimensions and the adoption of IS. The findings also showed that there are no differences in the societal culture dimensions between the two sectors covered in this study. This implies that the adoption of IS is influenced by societal culture and other factors, which are worthy of investigating. The future implications of this research are also discussed

As software systems grow, their complexity augments dramatically. In consequence their understandability and evolvability are becoming a difficult task, therefore a way to describe the architecture of software systems is becoming a must. The architecture of a software system can be described using either an architecture description language (ADL) or an object-oriented modeling language. In this article, we show how we can build a hybrid model, based on the two approaches, to describe the architecture of software systems. This approach profits from the advantages of the two approaches, i.e. the explicit presentation of functional aspects in object-oriented modeling and the explicit separation of competition (components) from interactions (connectors) in architectural description.

Significant challenges has been introduced for IP networks with the advent of new emerging applications, such as VOIP and E-Commerce, that require delivering quality guarantees. However, IP networks were originally designed to support best effort delivery only. Two Quality of Service (QoS) standard models, IntServ, DiffServ have been standardized by the Internet Engineering Task Force (IETF). Although these methods guarantee delivery, they have drawbacks such as complexity, restrictions of predefined classes and higher end-to-end delay. In this paper, a new QoS mathematical model has been proposed. This model is based on the principles of Network Calculus in which an incoming traffic flow is regulated by an arrival curve that upper bounds its rate. Then, this traffic flow is lower bounded and delayed by a service latency time at each node on its way to the destination node. The worst case end-to-end delay is derived and illustrated by a numerical example. The proposed model has achieved acceptable end-to-end delay compared with the other models.

Abstract

This paper presents the effect of corrugation geometry on the crushing behavior, energy absorption, failure mechanism, and failure mode of woven roving glass fibre/epoxy laminated composite tube. Experimental investigations were carried out on three geometrical different types of composite tubes subjected to axial and lateral compressive loadings. On the addition to a radial corrugated composite tube, cylindrical composite tube, and corrugated surrounded by cylindrical tube were fabricated and tested under the same condition in order to know the effect of corrugation geometry. The results showed that the loading carrying capability is significantly influenced by corrugation geometry in axial crushing. However, no affect of corrugation geometry was observed for lateral crushing. Load–displacement curve was plotted for all conducted tests, thus clear comparison between different specimen's geometry was achieved. It is also found that radial corrugation could significantly applicable as a stable and effective energy absorber.

Abstract

A numerical simulation of a two-stage reciprocating compressor has replicated the operations of the compressor under various conditions for the development of diagnostic features for predictive condition monitoring. The simulation involves the development of a mathematical model of five different physical processes: speed–torque characteristics of an induction motor, cylinder pressure variation, crankshaft rotational motion, flow characteristics through valves and vibration of the valve plates. Modelling both valve leakage and valve spring deterioration has also been achieved. The simulation was implemented in a MATLAB environment for an efficient numerical solution and ease of result presentation. For normal operating conditions, the simulated results are in good agreement with the test results for cylinder pressure waveforms and crankshaft instantaneous angular speed (IAS). It has been found that both the IAS fluctuation and pressure waveform are sensitive detection features for compressor faults such as valve leakage and valve spring deterioration. However, IAS is preferred because of its non-intrusive measurement nature. Further studies using the model and experiments are being undertaken in order to develop fault detection features for compressor driving motors and transmission systems.

This paper presents a novel cellular handset design with a bottom-mounted short loaded-whip antenna. This new handset design is modeled and simulated using a finite difference time-domain (FDTD)-based platform SEMCAD. The proposed handset is based on a current commercially available bar-phone type with a curvature shape, keypad positioned above the screen, and top-mounted antenna. The specific absorption rates (SARs) are determined computationally in the specific anthropomorphic mannequin (SAM) and anatomically correct model of a human head when exposed to the EM-field radiation of the proposed cellular handset and the handset with top-mounted antenna. The two cellular handsets are simulated to operate at both GSM standards, 900 MHz as well as 1800 MHz, having different antenna dimensions and intput power of 0.6 W and 0.125 W, respectively. The proposed human hand holding the two handset models is a semirealistic hand model consists of three tissues: skin, muscle, and bone. The simulations are conducted with handset positions based on the IEEE standard 1528-2003. The results show that the proposed handset has a significant improvement of antenna efficiency when it is hand-held close to head, as compared with the handset of top-mounted antenna. Also, the results show that a significant reduction of the induced SAR in the human head-tissues can be achieved with the proposed handset

This paper is intended to investigate intensely the impact of multipossible hand-hold positions on the electromagnetic (EM) interaction of handset antennas and a human by using a finite-difference time-domain (FDTD) method. Candy-bar handsets with different external and internal antenna positions operating in the GSM900, GSM1800/DCS, and UMTS/IMT-2000 bands are hereby simulated with configuration of the most parts in order to achieve the commercially available handset model design. Homogeneous and heterogeneous phantoms both are used to simulate the human head, whereas, a semirealistic model with three different tissues is designed to simulate a human hand holding a set. Both of the antenna performance including the total isotropic sensitivity (TIS) and the specific absorption rate (SAR) in tissues are examined for the different suggested applicable cases, where various positions of antenna, handset and hand are considered in simulations. This simulation study determines that both of the antenna performance and the SAR in tissues significantly alter owing to the positioning of the handset against user’s head at different hand levels; where a maximum alteration is observed due to the exposure of handset with internal antenna, as compared with the handset having external antenna.

This paper presents a through investigation into the effect of the external antenna and printed circuit board (PCB) positions in cellular hand-sets on the coupling between the handset and human-head at GSM-900 frequency standard. The antenna performance and the specific absorption rate (SAR) induced in a human head were computed using a Finite Difference Time-Domain based platform (SEMCAD). A numerical correct model of a European female head was adopted and a semi-realistic hand model was designed during the simulation. The results showed that the optimum position for the antenna and PCB in hand-set close to head is the far right-corner for the right-hand users and the far left-corner for the left-hand users, where a minimum SAR in head is achieved.