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Search Results: 1 - 10 of 5510 matches for " Ibrahim Yusuf "
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Analysis of Stochastic Reliability Characteristics of a Repairable 2-out-of-3 System with Minimal Repair at Failure  [PDF]
Ibrahim Yusuf, Fatima Salman Koki
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.48151
Abstract:

In this paper, we study the reliability and availability characteristics of a repairable 2-out-of-3 system. Failure and repair times are assumed exponential. The explicit expressions of reliability and availability characteristics such as mean time to system failure (MTSF), steady-state availability, busy period and profit function are derived using Kolmogorov’s forward equations method. Various cases are analyzed graphically to investigate the impact of system parameters on MTSF, availability, busy period and profit function.

Assessment of Profit of a Two-Stage Deteriorating Linear Consecutive 2-out-of-3 Repairable System  [PDF]
Ibrahim Yusuf, Fatima Salman Koki
Journal of Applied Mathematics and Physics (JAMP) , 2013, DOI: 10.4236/jamp.2013.13005
Abstract:

Most of the researches on profit and cost evaluation of redundant system focus on the effect of failure and repair on revenue generated. However, as these systems continue to work, their strength gradually deteriorates. Where such deterioration occurs, minor and major maintenance is employed to remedy the deterioration. Little or no attention is paid on the effect of deterioration on the impact of deterioration and their maintenance on the revenue generated. In this paper, we study the profit generated of two-stage deteriorating linear consecutive 2-out-of-3 system. Failure, repair and deterioration time are assumed exponential. The explicit expressions of availability, busy period of a repairman and profit function are derived using Kolmogorov’s forward equations method. Various cases are analyzed graphically to investigate the effect of deterioration parameters such as slow deterioration, fast deterioration, and their maintenance such as minor and major minimal maintenance on profit generated.

Evaluation of Reliability and Availability Characteristics of a Repairable System with Active Parallel Units  [PDF]
Ibrahim Yusuf, Fatima Salman Koki
Open Journal of Applied Sciences (OJAppS) , 2013, DOI: 10.4236/ojapps.2013.35044
Abstract: In this paper, we study the reliability and availability characteristics of a repairable system consisting of two subsystems A and B in series. Subsystem A consists of two units A1 and A2 operating in active parallel while subsystem B is a single unit. Failure and repair times are assumed exponential. The explicit expressions of reliability and availability characteristics like mean time to system failure (MTSF), system availability, busy period and profit function are derived using Kolmogorov forward equations method. Various cases are analyzed graphically to investigate the impacts of system parameters on MTSF, availability, busy period and profit function.
Evaluation of reliability characteristics of two dissimilar network flow systems
Ibrahim Yusuf,Bashir Yusuf
Applied Mathematical Sciences , 2013,
Abstract: This paper presents a study on reliability characteristics of two dissimilar systems.System I consist of two paths while system II consist of three paths. A signal flowfrom the source to the terminal through the paths. Failure times and service times ofeach system are assumed to be exponentially distributed. The failure and repair timesassumed exponentially distributed. Using Kolmogorov’s forward equations method,derivations for availability, busy period and profit function are presented in thispaper. Also numerical illustrations for the two systems are presented. Comparisonsare made based on assumed numerical values for the two systems.
Reliability Modelling and Analysis of Redundant Systems Connected to Supporting External Device for Operation Attended by a Repairman and Repairable Service Station  [PDF]
Ibrahim Yusuf, Rabia Salihu Said, Fatima Salman Koki, Mansur Babagana
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.213145
Abstract: In this paper, probabilistic models for three redundant configurations have been developed to analyze and compare some reliability characteristics. Each system is connected to a repairable supporting external device for operation. Repairable service station is provided for immediate repair of failed unit. Explicit expressions for mean time to system failure and steady-state availability for the three configurations are developed. Furthermore, we compare the three configurations based on their reliability characteristics and found that configuration II is more reliable and efficient than the remaining configurations.
Availability and Profit Optimization of Series-Parallel System with Linear Consecutive Cold Standby Units  [PDF]
Muhammad Sagir Aliyu, Ibrahim Yusuf, U. A. Ali
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.62032
Abstract: In this paper, we study availability and profit optimization of a series-parallel system consisting of three subsystems A, B and C in which A and B are cold standby. Subsystem A consists of linear consecutive k-out-of-n units while subsystems B and C consist of a single unit each. The system works if any of A or B and C work. The objective of this study is to maximize the steady-state availability and profit. To solve the optimization problem, different numbers of units for n = 2, 3, 4, 5 in subsystem A are considered. Explicit expressions for busy period of repairmen, steady-state availability and profit function are derived using linear first order differential equations. Several cases are analyzed graphically for n = 2, 3, 4, 5 to investigate the effects of various system parameters on availability and profit. The paper also presents graphical comparison for specific values of system parameters and finds that the optimal system configuration is when n = 5.
Gastro-Intestinal Parasites of Camels (Camelus dromedarius) from Mogadishu, Somalia  [PDF]
Abdalla M. Ibrahim, Ahmed A. H. Kadle, Abdulkarim A. Yusuf
Open Journal of Veterinary Medicine (OJVM) , 2016, DOI: 10.4236/ojvm.2016.67015
Abstract: Somalia has the largest dromedary (Camelus dromedarius) population in the world. However, scientific research and camel diseases investigation in the country were lacking since 1980s. A total of 167 camels (131 semi-intensive dairy camels system and 36 free grazing systems) were sampled from three districts in Mogadishu citybetween December 2015 and March 2016 to investigate the prevalence rate of gastro-intestinal parasites in camels from Mogadishu city using different coprological techniques. The overall prevalence of camel gastro-intestinal parasites was 50.3%. The prevalence rate were significantly varies between the extensive and semi-intensive production systems (p = 0.000) and between the different districts (p = 0.000). Nematodes revealed higher prevalence rate (47.9%) than Cestodes (6.0%), Trematodes (4.2%) and Coccidia (0.65%). Eggs of eight genera of nematodes, two genera of trematodes and two genera of cestodes as well as Eimeria sp. Oocysts were identified in this study. Dictyocaulus sp. and Trichostrongylus sp. were the most prevalent followed by Parascaris equorum and Strongyloides sp. About 56.0% of the infected camels revealed mix-infection of up to five different parasite species. Moreover, 35.7% of these animals revealed heavy infection. The important role of the camel has inspired investigators and researchers to look for diseases that may threaten camel health and production. However, in Somalia in spite of having the largest counts of camels but in depth scientific data are not available. Therefore, the present paper was to be the first detailed data on camel gastro-intestinal parasites in Mogadishu area and may be in whole Somalia. We came to conclude that gastrointes-tinal parasites were highly prevalent in camels from Mogadishu particularly in nomadic herds of camels. Studies on the effect of gastro-intestinal parasites on camel production and productivity are recommended. Moreover, the intensive system of camel production should be encouraged.
A comparative study of diagonal updating Newton methods for systems of nonlinear equations with singular Jacobian
Mohammed waziri Yusuf,Ibrahim Saidu
Journal of Engineering and Applied Sciences , 2010,
Abstract: We have compared the efficiency of two diagonal updating Newton methods for solving systems of nonlinear equations with singular Jacobian. Due to the fact that, the quadratic rate of convergence of Newton method for solving nonlinear systems of equations depends on when the Jacobian is nonsingular in the neighborhood of the solution. Contrary to this condition, i.e. the Jacobian to be singular the convergence is very slow and may even vanished. The two approaches are simple and straight forward to implement. We report on numerous numerical experiments which show that, the proposed algorithms are very efficient and reliable.
Caesarian Section for Placenta Praevia: Does Booking Status Affect Maternofetal Outcome?  [PDF]
Oshodi Yusuf Abisowo, Akinola Oluwarotimi Ireti, Fabamwo Adetokunbo Olusegun, Olaifa Ibrahim Adeniyi, Oyedele Yekeen Oyedokun
Open Journal of Obstetrics and Gynecology (OJOG) , 2016, DOI: 10.4236/ojog.2016.65039
Abstract: Background: Placenta praevia accounts for significant maternal morbidity and perinatal morbidity and mortality. Despite advances in blood transfusion technique and surgical procedure, abnormal placentation still remains a difficult challenge for obstetricians. Objective: To determine the influence of booking status on the fetal and maternal outcome among parturients with placenta praevia that underwent caesarian delivery. Methodology: This was a comparative and retrospective study between booked and unbooked subjects with significant placenta praevia that were delivered by caesarian section between January 1st 2004 and December 31st 2008 with respect to maternal and fetal outcome. Result: Out of 14,344 deliveries during study period, 123 cases of placenta praevia that underwent caesarian delivery were identified giving a prevalence rate of 0.86%. 49 subjects were booked while 74 were unbooked. There was no statistically significant difference between booked and unbooked cases with respect to risk factors (30.6% of booked and 23% of unbooked), X2(4) = 7.203, P = 0.126 and the mean blood loss at surgery (870.4 ± 486.9 ml in booked versus 779.7 ± 380.96 ml in unbooked), X2(1) = 0.202, P = 0.653. However, antepartum transfusion (12.2% booked versus 34.7% unbooked) and postpartum transfusion (51% booked versus 72% unbooked) showed statistically significant difference, X2(1) = 9.744, P = 0.002. One maternal death occurred amongst the unbooked cases and none among the booked cases. Statistically significant differences were also noted in the apgar score at 1 minute X2(3) = 15.528, P = 0.001 and 5 minutes X2(3) = 12.912, P = 0.005 respectively. More babies died in the unbooked group (19) compared to two (2) in the booked mothers. Conclusion: Unbooked status in placenta previa significantly
Evaluation of Economic Importance of Locally Produced Manure over Inorganic Fertilizer for Maize Production: Vegetative Performance and Cost Implication  [PDF]
Fatima Aliyu Deba, Safiya Isma’il, Muhammed Rabiu Sahal, Ibrahim Yusuf Okpanachi
American Journal of Molecular Biology (AJMB) , 2019, DOI: 10.4236/ajmb.2019.92006
Abstract:
Background: Crops of economic importance like Maize are preferred to other crops with capacity of giving the highest yields, having the ability to help alleviate poverty within the African continent. The consistent use of inorganic fertilizers has great adverse effect on soil structure. The quest to seek alternative method of boosting maize production is imminent to avoid further soil degradation. Most plants form symbiotic relationships with mycorrhizae and improve nutrients uptake by host plants. Objectives: The aim of this study is to examine the effect of mycorrhizae in local manure production on development of maize, in comparison with inorganic fertilizer application and its cost implication. Methods: The experiment involved samples of starter soil from 7 local governments. Organic waste was added to starter soil, each having three replicates. Nine other replicates served as non-inoculated controls and nine served for fertilizer application at 50 g, 100 g and 150 g. One [1] gram of Maize sown in 50 ml pot contains soil at different treatment levels 50 g, 100 g, and 150 g. After two weeks, samples were transplanted in an open field. Results: The result showed plots treated with locally produced fertilizer, significantly influenced plant height, culm diameter, number of leaves and leaf broadness in comparison to inorganic fertilizer, which showed 53%, 47% respectively. Conclusion: Cost production of a bag of organic fertilizer was one-fourth cheaper compared to an inorganic fertilizer price from an open market.
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