Eajal A.A.,University of Tripoli |
El-Hawary M.E.,Dalhousie University
IEEE Transactions on Power Delivery | Year: 2010
Shunt capacitors installation in distribution systems requires optimal placement and sizing. More harmonics are being injected into distribution systems. Adding shunt capacitors may lead to high distortion levels. The capacitor placement and sizing problem is a nonlinear integer optimization problem, with locations and ratings of shunt capacitors being discrete values. The goal is to minimize the overall cost of the total real power loss and that of shunt capacitors while satisfying operating and power quality constraints. This paper proposes to solve the problem using particle swarm optimization (PSO). A discrete version of PSO is combined with a radial distribution power flow algorithm (RDPF) to form a hybrid PSO algorithm (HPSO). The former is employed as a global optimizer to find the global optimal solution, while the latter is used to calculate the objective function and to verify bus voltage limits. To include the presence of harmonics, the developed HPSO was integrated with a harmonic power flow algorithm (HPF). The proposed (HPSO-HPF)-based approach is tested on an IEEE 13-bus radial distribution system (13-Bus-RDS). The findings clearly demonstrate the necessity of including harmonics in optimal capacitor placement and sizing to avoid any possible problems associated with harmonics. © 2010 IEEE.
Husien W.,University of Tripoli |
El-Osta W.,Center for Solar Energy Studies |
Dekam E.,University of Tripoli
Renewable Energy | Year: 2013
This study deals with the modeling of the wake effect on the energy extracted from the wind farms. It covers the wake effect of the interaction of the upstream wind rotor with/without the upstream right and/or upstream left wind rotor. A mathematical model representing a single wake model based on the linear description of the wake is developed in order to predict the wind speed inside the wake region at any downstream distance within the wind farm. Two different types of turbines with diameters of 62 m and 100 m are considered. Accordingly the effect of the wake on the energy produced from the wind farms is estimated.A number of different wind farm layouts are studied. Case studies including 3 × 3, 4 × 4, 6 × 6, 1 × 16, 16 × 1, 2 × 8, and 8 × 2 layouts are considered. Extracted energy is calculated in each case and an optimum layout is determined from different layouts. The effectiveness of the other layouts with respect to the optimum is obtained. The results showed that there is a drop in the annual extracted energy from the above mentioned layouts depending on the W.T. distances separating the W.T.'s. The wind speed was assumed to be 15 m/s with 10. D downstream distances. The losses are estimated to be 20% for 3 × 3 (rows × column), 32% for 4 × 4, 46% for 6 × 6, 12.8% for 16 × 1, 23.3% for 2 × 8, and 29% for 8 × 2 when these layouts are compared to 1 × 16 layout as an optimum layout. © 2012.
Nasrallah N.F.,University of Tripoli
Physical Review C - Nuclear Physics | Year: 2013
QCD sum rules using polynomial kernels are used to evaluate the strong part of the proton-neutron mass difference δMnp in a model independent fashion. The result for the mass difference turns out to depend sensitively on the value of the four-quark condensate (q̄q) 2 and reproduces the experimental value of δMnp for (q̄q)2 q̄q2. © 2013 American Physical Society.
O'Connor A.J.,Trinity College Dublin |
Kenshel O.,University of Tripoli
Journal of Bridge Engineering | Year: 2013
This paper provides experimentally determined estimates of the scale of fluctuation of the principal variables employed in modeling chloride-induced corrosion for reinforced concrete; i.e., the surface chloride content (Cs) and apparent diffusion coefficient (Dapp). The estimation of the scale of fluctuation, θ, is based on the analysis of experimental data recorded on a bridge in South East Ireland prior to its extensive rehabilitation in 2007. In determining the scale of fluctuation the paper considers two commonly used methods; i.e., the maximum likelihood method and the autocorrelation curve-fitting method. The reliability of both methods is discussed. Introduction of the kriging statistical interpolation method is demonstrated to improve the reliability of the estimates of the scale of fluctuation. The results obtained from the analysis are compared with values in the literature proffered by other researchers. © 2013 American Society of Civil Engineers.
Taher Y.A.,University of Tripoli
Libyan Journal of Medicine | Year: 2012
Background: Mentha piperita L. (Labiatae) is an herbaceous plant, used in folk medicine for the treatment of several medical disorders. Methods and Results: In the present study, the aqueous extract of Mentha piperita leaf, at the i.p doses 200 and 400 mg/kg, showed significant analgesic effects against both acetic acid-induced writhing and hot plateinduced thermal stimulation in mice, with protection values of 51.79% and 20.21% respectively. On the contrary, the Mentha piperita leaf aqueous extract did not exhibit anti-inflammatory activity against carrageenan induced paw oedema. Conclusion: These findings indicate that Mentha piperita has a potential analgesic effect that may possibly have mediated centrally and peripherally, as well as providing a pharmacological evidence for its traditional use as a pain reliever. © 2012 Yousef A. Taher.
Agina A.M.,University of Tripoli
Computers in Human Behavior | Year: 2012
The present study sought to examine the effect of nonhuman's external regulation on children's self-regulation to regulate their own process of learning and to what extent did children succeed in terms of application when they talk and think while act alone with nonhuman's external regulator. The Aginian's methodology (Agina, Kommers, & Steehouder, 2011a, 2011b, 2011c, 2011d, 2011e) that used an isolated, computer-based learning system and acts as a standalone learning environment with special set of tasks was used by hundred healthy preschool children. The results showed that young children were able to regulate their own process of learning and engage with their full free-will without the need of their real teacher's regulation. The conclusion provided evidence that the verbalization of thinking aloud should occur spontaneously by nature, the nonhuman's external regulation has a positive effect on young children's development when they act with their full free-will, and has a positive effect on their behavior either. © 2012 Elsevier Ltd. All rights reserved.
Agina A.M.,University of Tripoli
Computers in Human Behavior | Year: 2012
The present study was conducted to explore the effect of nonhuman's external regulation on children's natural development process of creative thinking, the degree of the manifested creative thinking, the influence of children's verbalization on their creative thinking, and the extent the stimulus material was usable for children during learning math tasks. The Aginian's methodology (Agina, Kommers, & Steehouder, 2011a, 2011b, 2011c, 2011d, 2011e) that relied on an isolated, computer-based learning system that acts as a standalone learning environment, with special child-simple-calculator was used by 100 healthy preschool children. The results showed that children were fluctuated between negative and positive creative thinkers, children's verbalization has no effect on their creative thinking, and the relation between the children's verbalization of thinking aloud and their creative thinking is a reverse relationship. The usability analysis concluded that, fun is not a key element of the usability as it can only be a feature that could facilitate usability. The mathematical analysis showed that the computer, as a nonhuman external regulator, can integrate the net signed of children's creative thinking through embedding mathematics integration. © 2012 Elsevier Ltd. All rights reserved.
Belgacem F.B.,University of Tripoli
Inverse Problems | Year: 2012
We are interested in the detection of a pointwise source in a class of semi-linear advectiondiffusionreaction equations of Fisher type. The source is determined by its location, which may be steady or unsteady, and its time-dependent intensity. Observations recorded at a couple of points are the available data. One observing station is located upstream of the source and the other downstream. This is a severely ill-posed nonlinear inverse problem. In this paper, we pursue an identifiability result. The process we follow has been developed earlier for the linear model and may be sharpened to operate for the semi-linear equation. It is based on the uniqueness for a parabolic (semi-linear) sideways problem, which is obtained by a suitable unique continuation theorem. We state a maximum principle that turns out to be necessary for our proof. The identifiability is finally obtained for a stationary or a moving source. Many applications may be found in biology, chemical physiology or environmental science. The problem we deal with is the detection of pointwise organic pollution sources in rivers and channels. The basic equation to consider is the one-dimensional biochemical oxygen demand equation, with a nonlinear power growth inhibitor and/or the MichaelisMenten reaction coefficient. © 2012 IOP Publishing Ltd.
Ahmeda S.S.,University of Tripoli
2011 IEEE 3rd International Conference on Communication Software and Networks, ICCSN 2011 | Year: 2011
Ad hoc networking allows portable devices to establish communication independent of a central infrastructure. The fact that there is no central infrastructure and that the devices can move randomly gives rise to various kind of problems, such as routing and security. Attacks on routing protocols can create various undesirable effects that defeat the objectives of ad-hoc routing, Ad hoc networks is much more vulnerable to malicious exploits than a wired network. Secure communication is an important aspect of any network environment. Therefore to provide secure ad hoc network: authentication, confidentiality, integrity, non repudiation and access control should be provided. Authentication comes in the first place to ensure secure network operation, since other services depend on the authentication of communication entities. In mobile ad hoc, there is possibility of nodes being compromise, therefore, the network should not have any central control but instead have distributed architecture; when avoiding central control it's more difficult to implement authentication protocol. In this paper, the recently developed identity based scheme with threshold secret sharing will be used in two different scenarios; in the first scenario the serving nodes have been assumed fixed nodes, in the second scenario the serving nodes have been assumed mobile nodes. The purpose of applying this scheme is to provide authentication, confidentiality, reduce computation cost, avoiding central control and find out the proper threshold value. The authentication protocol has been implemented, tested and compared with central serving control using computer simulator method. The simulator that has been used to simulate the ad hoc authentication protocol is a self developed simulator. © 2011 IEEE.
Ahmed M.O.,University of Tripoli
Euro surveillance : bulletin européen sur les maladies transmissibles = European communicable disease bulletin | Year: 2010
Brucellosis is a global zoonotic disease, endemic in North African countries and around the Mediterranean.A prospective study of Brucella seroprevalence was conducted in north-western Libya (western mountains region). Blood samples collected over 13 months in the period December 2006 to January 2008 from 561 animals (goats, sheep, cattle and camels) and 546 human volunteers were tested for Brucella using the Rose Bengal test, tube agglutination test and ELISA assays. Amongst livestock, 31% of goats and 42% of cattle were seropositive. Human samples showed a high seropositivity of 40%, with 95 (43%) of the 221 positive samples positive for IgM, indicating active or recent infection. Control measures are needed to reduce this high prevalence of brucellosis in Libya.