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Search Results: 1 - 10 of 85833 matches for " Nabil W. Musa "
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Whirl Interaction of a Drill Bit with the Bore-Hole Bottom  [PDF]
Nabil W. Musa, V. I. Gulyayev, L. V. Shevchuk, Hasan Aldabas
Modern Mechanical Engineering (MME) , 2015, DOI: 10.4236/mme.2015.53005
Abstract: This paper deals with the theoretic simulation of a drill bit whirling under conditions of its contact interaction with the bore-hole bottom rock plane. The bit is considered to be an absolutely rigid ellipsoidal body with uneven surface. It is attached to the lower end of a rotating elastic drill string. In the perturbed state, the bit can roll without sliding on the bore-hole bottom, performing whirling vibrations (the model of dynamic equilibrium with pure rolling when maximum cohesive force does not exceed the ultimate Coulombic friction). To describe these motions, a nonholonomic dynamic model is proposed, constitutive partial differential equations are deduced. With their use, the whirling vibrations of oblong and oblate ellipsoidal bits are analyzed, the functions of cohesive (frictional) forces are calculated. It is shown that the system of elastic drill string and ellipsoidal bit can acquire stable or unstable whirl modes with approaching critical Eulerian values by the parameters of axial force, torque and angular velocity. The analogy of the found modes of motions with ones of the Celtic stones is established. It is shown that the ellipsoidal bits can stop their whirling vibrations and change directions of their circumferential motions in the same manner as the ellipsoidal Celtic stones do. As this takes place, the trajectories of the oblate ellipsoidal bits are characterized by more complicated paths and irregularities.
The Use of Genetic Approach to the Kinematics of Cutting  [PDF]
Nabil Wanas Musa
World Journal of Mechanics (WJM) , 2016, DOI: 10.4236/wjm.2016.610028
Abstract: This article deals with the use of an interdisciplinary approach to modelling and creation of a complex technical system of different physical nature in relation to the kinematics of cutting and shaping. The professor of the National Technical University of Ukraine, Kuznetcov Iu. N., proposed the approach based on generalization of knowledge, methodological basis of which is the theory of evolution of the systems and methods of genetic analysis and synthesis. For generalization of the knowledge in the fundamental sciences is based on the principles of a limited number of elementary generic structures with the introduction of the gene concept. The modelling and synthesis of kinematic cutting schemes are providing the efficiency and viability of genetic and morphological approach. The material point, which can interact with other ma-terial points in space and time, simulating anthropogenic system of different origin, is introduced as a material object.
Elastic Bending Deformation of the Drill Strings in Channels of Curve Wells  [PDF]
Nabil Wanas Musa
Modern Mechanical Engineering (MME) , 2017, DOI: 10.4236/mme.2017.71001
Abstract:
The problem about identification of elastic bending deformation of a drill string in a curve wells based on the theory of flexible curved rods and the direct inverse problems of drill string bending in the channels of curvilinear bore-holes is stated. The problem is solved which determines the resistance forces and moments during performing ascending-descending operations in curvilinear bore-holes with trajectories of the second order curve shapes. The sensitivity of the resistance forces relative to geometric parameters of the bore-hole axial line trajectories is analyzed.
Review of Avaren Ipsen, Sex Working and the Bible, London: Equinox 2009
Musa W. Dube
Religion and Gender , 2012,
Abstract:
Investigations of Oxidant/antioxidant Status and Hemoglobin Biophysical Properties in Buffalo Calves with Special Reference to Inferior Preweaning Vitality
W.M. Ahmed,Ghada M. Nabil
Pakistan Journal of Biological Sciences , 2007,
Abstract: The present study aimed to investigate oxidant/antioxidants status and some biophysical properties of hemoglobin in preweaning buffalo calves in relation to their vitality. A total number of 253 buffalo calves (2-3 months old) were clinically examined, the vitality of these animals were recorded and blood samples were collected for determination of some oxidant-antioxidant values, as well as some hemoglobin biophysical properties. Results indicated that 38.74% of the examined calves showed preweaning inferior vitality as indicated by dullness, low growth rate, rough coat and signs of scoring. Inferior vitality calves have high malondialdehyde (MDA, p<0.001) and nitric oxide (NO, p<0.001) and low catalase (CAT, p<0.001), superoxide dismutase (SOD, p<0.001), ascorbic acid (p<0.01), glutathione reduced (GSH, p<0.001), total antioxidant capacity (TAC, p<0.001), zinc (Zn, p<0.01), copper (Cu, p<0.01), iron (Fe, p<0.05) and selenium (Se, p<0.001) in their blood. The electrical conductivity and derivatives of hemoglobin non significantly changed due to calf vitality. In conclusion, there is a tight relationship between oxidant/antioxidant status of buffalo-calves and their preweaning vitality.
Improving Rule Base Quality to Enhance Production Systems Performance  [PDF]
Nabil Arman
International Journal of Intelligence Science (IJIS) , 2013, DOI: 10.4236/ijis.2013.31001
Abstract: Production systems have a special value since they are used in state-space searching algorithms and expert systems in addition to their use as a model for problem solving in artificial intelligence. Therefore, it is of high importance to consider different techniques to improve their performance. In this research, rule base is the component of the production system that we aim to focus on. This work therefore seeks to investigate this component and its relationship with other components and demonstrate how the improvement of its quality has a great impact on the performance of the production system as a whole. In this paper, the improvement of rule base quality is accomplished in two steps. The first step involves re-writing the rules having conjunctions of literals and producing a new set of equivalent rules in which long inference chains can be obtained easily. The second step involves augmenting the rule base with inference short-cut rules devised from the long inference chains. These inference short-cut rules have a great impact on the performance of the production system. Finally, simulations are performed on randomly generated rule bases with different sizes and goals to be proved. The simulations demonstrate that the suggested enhancements are very beneficial in improving the performance of production systems.
A Review of Some Protozoan Parasites Causing Infertility in Farm Animals
B. Y. Kaltungo,I. W. Musa
ISRN Tropical Medicine , 2013, DOI: 10.1155/2013/782609
Abstract: The paper reviews some protozoan parasites responsible for infertility in livestock with specific emphasis on neosporosis, sarcocystosis, toxoplasmosis, and trichomoniasis. It highlights the transmission, pathogenesis, clinical signs, diagnosis, prevention, control, and treatment of the individual parasite. It is concluded that these parasites are often overlooked during investigation into causes of abortion in livestock, and they may, however, be responsible for some infertilities in this group of animals which may result in severe economic losses. 1. Introduction Infertility is a major cause of economic losses and a major limitation to achievement of optimum efficiency in the livestock production system largely as a result of loss of milk production in the dairy sector and increase in culling rates. The causes of infertility can be numerous and complex [1]. They may relate to impairment in Graafian follicle development and maturation, onset of estrus, ovulation, successful coitus, fertilisation, implantation, and the development and delivery of the foetus and its membranes. Any temporary state interfering with these routines, such as disease conditions, malnutrition, inadequate herd management, hereditary and congenital factors, hormonal disturbances, or environmental changes, makes the animal infertile [2]. Parasitic infections are typically associated with poor and often marginalized communities in low-income countries [3]. Protozoan parasites are a significant cause of abortion and infertility in domestic ruminants. Toxoplasma gondii and Sarcocystis species are a common cause of extensive abortion in livestock and they both have a two-host life cycle. Carnivorous definitive hosts spread the infection through their feces and domestic ruminants are intermediate hosts. A similar, recently recognized protozoon, Neospora spp., has emerged as an important cause of reproductive disease, especially as an abortifacient in cattle. Neospora is presumed to also have a two-host life cycle, although the definitive host(s) has not been identified. The venereally transmitted Tritrichomonas foetus has also been reported to be an important cause of pregnancy loss in naturally bred cattle throughout the world [4]. 2. Neosporosis Neospora caninum is an obligate protozoan (Coccidian) parasite related to Toxoplasma gondii and was first associated with neuromuscular disease in dogs in the mid-1980s [5]. It is globally distributed and has been identified as a major cause of infertility in cattle resulting in considerable economic losses [6, 7]. The parasite has been
Pure Geometric Field Theory: Description of Gravity and Material Distribution
M. I. Wanas,Nabil L. Youssef,W. El Hanafy
Mathematics , 2014,
Abstract: A field theory is constructed in the context of parameterized absolute parallelism\linebreak geometry. The theory is shown to be a pure gravity one. It is capable of describing the gravitational field and a material distribution in terms of the geometric structure of the geometry used (the parallelization vector fields). Three tools are used to attribute physical properties to the geometric objects admitted by the theory. Poisson and Laplace equations are obtained in the linearized version of the theory. The spherically symmetric solution of the theory, in free space, is found to coincide with the Schwarzschild exterior solution of the general theory of relativity. The theory respects the weak equivalence principle in free space only. Gravity and material distribution are not minimally coupled.
Product Ethnicity between the Hammer of Identity and the Anvil of Globalization  [PDF]
Jeddi Nabil, Zaiem Imed
American Journal of Industrial and Business Management (AJIBM) , 2013, DOI: 10.4236/ajibm.2013.31011
Abstract:

With the globalization of markets, the multinational production made obvious great strides marked by the proliferation of hybrid or bi-national products. In this context which supported the dissolution of identity of several products’ categories and called in question the weight of origin labels about the consumer behavior purchase. Beyond these reflections, this article proposed to wonder about the relation between globalization and product ethnicity, by analyzing the apparent effects of the current context of globalization on the establishment of stereotypic country-products associations by the consumers. Also, the question which is directed to the development and the presentation of this research is the following one: to what extend does the current context of globalization enable us to call in question the phenomenon of product ethnicity?

On Slide Mode Control of Chaotic Rikitake Two-Disk Dynamo—Chaotic Simulations of the Reversals of the Earth’s Magnetic Field  [PDF]
Ahmad Harb, Nabil Ayoub
International Journal of Modern Nonlinear Theory and Application (IJMNTA) , 2014, DOI: 10.4236/ijmnta.2014.33015
Abstract:

The modern nonlinear theory, bifurcation and chaos theory are used in this paper to analyze the dynamics of the Rikitake two-disk dynamo system. The mathematical model of the Rikitake system consists of three nonlinear differential equations, which found to be the same as the mathematical model of the well-known Lorenz system. The study showed that under certain value of control parameter, the system experiences a chaotic behaviour. The experienced chaotic oscillation may simulate the reversal of the Earth’s magnetic field. The main objective of this paper is to control the chaotic behaviour in Rikitake system. So, a nonlinear controller based on the slide mode control theory is designed. The study showed that the designed controller was so effective in controlling the unstable chaotic oscillations.

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