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Parameters Estimation of Generalized Linear Failure Rate Semi-Markov Reliability Models
El-Gohary, A.,Al-Khedhair, A. The Korean Reliability Society 2010 International Journal of Reliability and Applicati Vol.11 No.1
In this paper we will discuss the stochastic analysis of a three state semi-Markov reliability model. Maximum likelihood procedure will be used to obtain the estimators of the parameters included in this reliability model. Based on the assumption that the lifetime and repair time of the system units are generalized linear failure rate random variables, the reliability function of this system is obtained. Also, the distribution of the first passage time of this system will be derived. Some important special cases are discussed.
A Multivariate Mixture of Linear Failure Rate Distribution in Reliability Models
EI-Gohary A wad The Korean Reliability Society 2005 International Journal of Reliability and Applicati Vol.6 No.2
This article provides a new class of multivariate linear failure rate distributions where every component is a mixture of linear failure rate distribution. The new class includes several multivariate and bivariate models including Marslall and Olkin type. The approach in this paper is based on the introducing a linear failure rate distributed latent random variable. The distribution of minimum in a competing risk model is discussed.
Estimation of parameters including a quadratic failure rate semi-Markov reliability model
El-Gohary, A.,Alshamrani, A. The Korean Reliability Society 2011 International Journal of Reliability and Applicati Vol.12 No.1
This paper discusses the stochastic analysis and the statistical inference of a quadratic failure rate semi-Markov reliability model. Maximum likelihood procedure will be used to obtain the estimators of the parameters included in this reliability model. Based on the assumption that the lifetime and repair time of the system units are random variables with quadratic failure rate, the reliability function of this system is obtained. Also, the distribution of the first passage time of this system is derived. Many important special cases are discussed.
Utilization of alternative marine fuels for gas turbine power plant onboard ships
El Gohary, M. Morsy,Seddiek, Ibrahim Sadek The Society of Naval Architects of Korea 2013 International Journal of Naval Architecture and Oc Vol.5 No.1
Marine transportation industry is undergoing a number of problems. Some of these problems are associated with conventional marine fuel-oils. Many researchers have showed that fuel-oil is considered as the main component that causes both environmental and economic problems, especially with the continuous rising of fuel cost. This paper investigates the capability of using natural gas and hydrogen as alternative fuel instead of diesel oil for marine gas turbine, the effect of the alternative fuel on gas turbine thermodynamic performance and the employed mathematical model. The results showed that since the natural gas is categorized as hydrocarbon fuel, the thermodynamic performance of the gas turbine cycle using the natural gas was found to be close to the diesel case performance. The gas turbine thermal efficiency was found to be 1% less in the case of hydrogen compared to the original case of diesel.
Estimation of Parameters in a Generalized Exponential Semi-Markov Reliability Models
El-Gohary Awad The Korean Reliability Society 2005 International Journal of Reliability and Applicati Vol.6 No.1
This paper deals with the stochastic analysis of a three-states semi-Markov reliability model. Using both the maximum likelihood and Bayes procedures, the parameters included in this model are estimated. Next, assuming that the lifetime and repair time are generalized exponential random variables, the reliability function of this system is obtained. Then, the distribution of the first passage time of this system is discussed. Finally, some of the obtained results are compared with those available in the literature.
STUDY ON AFLATOXINS IN SOME FOODSTUFFS WITH SPECIAL REFERENCE TO PUBLIC HEALTH HAZARD IN EGYPT
EL-GOHARY, A.H. Asian Australasian Association of Animal Productio 1995 Animal Bioscience Vol.8 No.6
A total of 455 food samples representing 22 different food types were collected from several localities at Alexandria province in Egypt. Aflatoxin B1 and aflatoxin M1 were detected in 5 out of 455 (1.1%) of these food samples. From the same samples 206 fungal isolates were obtained. Thirty two of these isolates (15.5%) were found to be aflatoxin producers. Aspergillus flavus was the dominant isolate, while Aspergillus parasaticus was also isolated from a few other food samples. Among locally consumed foodstuffs. Peanut (7.5%) and Milk powder (6.6%) were found to be a suitable substrates for aflatoxin production. The hygienic and public health significance of the isolated aflatoxigenic strains were discussed.
Environmental analysis of present and future fuels in 2D simple model marine gas tubines
El Gohary, M. Morsy The Society of Naval Architects of Korea 2013 International Journal of Naval Architecture and Oc Vol.5 No.4
Increased worldwide concerns about fossil fuel costs and effects on the environment lead many governments and scientific societies to consider the hydrogen as the fuel of the future. Many researches have been made to assess the suitability of using the hydrogen gas as fuel for internal combustion engines and gas turbines; this suitability was assessed from several viewpoints including the combustion characteristics, the fuel production and storage and also the thermodynamic cycle changes with the application of hydrogen instead of ordinary fossil fuels. This paper introduces the basic environmental differences happening when changing the fuel of a marine gas turbine from marine diesel fuel to gaseous hydrogen for the same power output. Environmentally, the hydrogen is the best when the $CO_2$ emissions are considered, zero carbon dioxide emissions can be theoretically attained. But when the $NO_x$ emissions are considered, the hydrogen is not the best based on the unit heat input. The hydrogen produces 270% more $NO_x$ than the diesel case without any control measures. This is primarily due to the increased air flow rate bringing more nitrogen into the combustion chamber and the increased combustion temperature (10% more than the diesel case). Efficient and of course expensive $NO_x$ control measures are a must to control these emissions levels.
Oreochromis spp. and Clarias Lazera as a Source of Transmitting Encysted Metacercariae to Man
El-Gohary, A.H.,Samaha, I.A. Asian Australasian Association of Animal Productio 1997 Animal Bioscience Vol.10 No.4
A total of 135 freshwater fish samples (Oreochromis spp. <85> and Clarias lazera <50>) were collected from different localities (shops and fish markets) in Alexandria Province-Egypt and examined for the presence of parasitic larval stages. The obtained data found the overall mean of the infestation with encysted metacercariae was 71.1% in the examined fish. The rates of infestation with encysted metacercariae were 72.9% and 68.0% in the examined Oreochromis spp. and Clarias lazera, respectively. The highest prevalence of the encysted metacercariae was found in summer (81.8%) in case of Oreochromis spp. and in winter (92.3%) in case of Clarias lazera, all these seasonal differences are statistically significant. The rate of infestation of encysted metacercariae in the anterior third, middle third and posterior third of Oreochromis spp. was found to be 82.3%, 74.2% and 95.2%, respectively, while 88.2%, 88.2% and 91.2%, respectively, in Clarias lazera. Moreover, the rate of infestation of encysted metacercariae in eyes, gills, liver, kidney and branchial cavity of Oreochromis spp. was 91.9%, 70.9%, 20.9%, 46.8% and 32.2%, respectively. In Clarias lazera the infestation rate was found to be 47.1%, 70.6%, 8.8% and 38.2% in the gills, liver, spleen and kidney, respectively. The zoonotic and public health importance of the encysted metacercariae are causes severe visceral pain, abdominal discomfort, intermittent bloody diarrhoea and colic after consumption of inadequately cooked fish especially Tilapia spp. (Oreochromis spp.).
A Mixture of Multivariate Distributions with Pareto in Reliability Models
El-Gohary Awad The Korean Reliability Society 2006 International Journal of Reliability and Applicati Vol.7 No.1
This paper presents a new class of multivariate distributions with Pareto where dependence among the components is characterized by a latent random variable. The new class includes several multivariate and bivariate models of Marshall and Olkin type. It is found the bivariate distribution with Pareto is positively quadrant dependent and its mixture. Some important structural properties of the bivariate distributions with Pareto are discussed. The distribution of minimum in a competing risk Pareto model is derived.
Estimation of parameters including a quadratic failure rate semi-Markov reliability model
A. El-Gohary,A. Alshamrani 한국신뢰성학회 2011 International Journal of Reliability and Applicati Vol.12 No.1
This paper discusses the stochastic analysis and the statistical inference of a quadratic failure rate semi-Markov reliability model. Maximum likelihood procedure will be used to obtain the estimators of the parameters included in this reliability model. Based on the assumption that the lifetime and repair time of the system units are random variables with quadratic failure rate, the reliability function of this system is obtained. Also, the distribution of the first passage time of this system is derived. Many important special cases are discussed.