Multi-criteria decision making support tools for maintenance of marine machinery systems

PhD ThesisFor ship systems to remain reliable and safe they must be effectively maintained through a sound maintenance management system. The three major elements of maintenance management systems are; risk assessment, maintenance strategy selection and maintenance task interval determination. The implementation of these elements will generally determine the level of ship system safety and reliability. Reliability Centred Maintenance (RCM) is one method that can be used to optimise maintenance management systems. However the tools used within the framework of the RCM methodology have limitations which may compromise the efficiency of RCM in achieving the desired results. This research presents the development of tools to support the RCM methodology and improve its effectiveness in marine maintenance system applications. Each of the three elements of the maintenance management system has been considered in turn. With regard to risk assessment, two Multi-Criteria Decision Making techniques (MCDM); Vlsekriterijumska Optimizacija Ikompromisno Resenje, meaning: Multi-criteria Optimization and Compromise Solution (VIKOR) and Compromise Programming (CP) have been integrated into Failure Mode and Effects Analysis (FMEA) along with a novel averaging technique which allows the use of incomplete or imprecise failure data. Three hybrid MCDM techniques have then been compared for maintenance strategy selection; an integrated Delphi-Analytical Hierarchy Process (AHP) methodology, an integrated Delphi-AHP-PROMETHEE (Preference Ranking Organisation METHod for Enrichment Evaluation) methodology and an integrated Delphi-AHP-TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) methodology. Maintenance task interval determination has been implemented using a MCDM framework integrating a delay time model to determine the optimum inspection interval and using the age replacement model for the scheduled replacement tasks. A case study based on a marine Diesel engine has been developed with input from experts in the field to demonstrate the effectiveness of the proposed methodologies.Tertiary Education Trust Fund (TETFUND), a scholarship body of the Federal Republic of Nigeria for providing the fund for this research. My gratitude also goes to Federal University of Petroleum Resource, Effurun, Nigeria for giving me the opportunity to be a beneficiary of the scholarship

Current Trends In The Laboratory Diagnosis Of Tuberculosis

No Abstrac

Continuing Medical Education: Closing The Gap Between Medical Research And Practice

Continuing medical education (CME) has long been recognized as the key to updating and maintaining the knowledge and skill of health professionals.CME activities are well advocated, accepted and regulated in the developed world with sanctions for non-participation. In developing countries, including West Africa subregion, CME activities are less effective and no practical enforcement to compel individual’s participation. This review examined the importance, scope and regulation of CME activities and identified the barriers to effective CME in developing countries to include lack of motivation, time, finance and lack of access to CME facilities occasioned by underdevelopment in information and communication technology (ICT) and know-how. It is concluded with practical suggestions that; health professionals should embrace CME as a moral and ethical obligation; health organizations and institutions should provide incentives, adequate funding and protected time for CME activities; professional and regulatory bodies should enforce participation and impose sanctions if need be, as the way forward

Lassa virus persistence in body fluids after recovery from acute Lassa fever: a 2-year interim analysis of a prospective longitudinal cohort study

Background: There is anecdotal evidence for Lassa virus persistence in body fluids. We investigated various body fluids after recovery from acute Lassa fever and describe the dynamics of Lassa virus RNA load in seminal fluid. The primary objective of this study was to quantitatively describe virus persistence and clearance and assess the infectivity of seminal fluid. Methodology: In this prospective, longitudinal, cohort study, we collected plasma, urine, saliva, lacrimal, vaginal and seminal fluids from Lassa fever survivors at Irrua Specialist Teaching Hospital in Edo State, Nigeria. Inclusion criteria for participants were RT-PCR-confirmed Lassa fever diagnosis and age 18 years and above. Samples were taken at discharge from hospital (month 0) and at months 0·5, 1, 3, 6, 9, 12, 18, and 24 after discharge. Lassa virus RNA was detected using real-time RT-PCR. Infectivity was tested in cell culture and immunosuppressed mice. We used a linear mixed-effect model to analyse the dynamics of virus persistence in seminal fluid over time. Results: Between Jan 31, 2018, and Dec 11, 2019, 165 participants were enrolled in the study, of whom 159 were eligible for analysis (49 women and 110 men). Low amounts of Lassa virus RNA were detected at month 0 in plasma (45%, n=49/110), urine (34%, 37/110), saliva (5%, 5/110), lacrimal fluid (9%, 10/110), and vaginal fluid (21%, n=7/33 female participants). Virus RNA was cleared from these body fluids by month 3. However, 35 (80%) of 44 male participants had viral RNA in seminal fluid at month 0 with a median cycle threshold of 26·5. Lassa virus RNA remained detectable up to month 12 in seminal fluid. Biostatistical modelling estimated a clearance rate of 1·19 log₁₀ viral RNA copies per month and predicted that 50% of male survivors remain Lassa virus RNA-positive in seminal fluid for 83 days after hospital discharge, and 10% remain positive in seminal fluid for 193 days after discharge. Viral RNA persistence in seminal fluid for 3 months or more was associated with higher viraemia (p=0·006), more severe disease (p=0·0075), and longer hospitalisation during the acute phase of Lassa fever (p=0·0014). Infectious virus was isolated from 48 (52%) of 93 virus RNA-positive seminal fluid samples collected between month 0 and 12. Conclusion: Lassa virus RNA is shed in various body fluids after recovery from acute disease. The persistence of infectious virus in seminal fluid implies a risk of sexual transmission of Lassa fever

Machinery/service system Scheduled Replacement time determination: A combine Weighted Aggregated Sum Product Assessment, Additive Ratio Assessment and Age Replacement Model approach

The productivity of manufacturing/service industries greatly depend on the safety and reliability of the machinery/service system use for production/service delivery. The safety and reliability of the system can only be guaranteed through efficient maintenance. Scheduled replacement is an integral element of maintenance strategies. The major challenge of the maintenance policy is the determination of the optimum interval for carrying out replacement of equipment item of machinery/service system. A number of approaches have been applied in the literature in addressing this problem but these techniques have one limitation or another. In this paper, an MCDM approaches which avoid these limitations is proposed. The proposed Multi-Criteria Decision Making (MCDM) techniques combined weighted Aggregated Sum Product Assessment (WASPAS) and Additive Ratio Assessment (ARAS) with Age Replacement Model (ARM) for the determination optimum scheduled replacement time interval. The ARM for cost, reliability and downtime are aggregated using WASPAS and ARAS methods in order to rank alternative time intervals. The WASPAS and ARAS methods outputs are compared with another well-known technique in literature. To demonstrate the applicability of the proposed approaches a numerical example was applied. The result of the analysis revealed that, WASPAS and ARAS produces similar ranking for alternatives when compared with that of TOPSIS technique in the literature which is more computationally intensive, thereby validating the suitability of the proposed approaches

Knowledge, attitude and practice of Human Immunodeficiency Virus infection post-exposure prophylaxis among resident doctors in a tertiary hospital, Benin City, Nigeria

Infection with HIV is an occupational risk to health care workers, especially doctors, during treatment of patients. HIV post-exposure prophylaxis (PEP) is effective in preventing potential HIV infection following accidental exposure. The objective of this study was to assess the knowledge,  attitude and practice of HIV post-exposure prophylaxis among resident doctors at the University of Benin Teaching Hospital (UBTH). A cross-sectional survey was conducted on 187 resident doctors at UBTH. Using a self- administered questionnaire, data was collected on socio demographic characteristics, attitude, and practice of HIV-PEP. Descriptive statistics were employed to analyzed data. Majority (66%) of respondents had good knowledge of HIV-PEP. Ninety five percent agreed they wound recommend HIV-PEP, 85% reported they would take PEP if accidentally exposed; 10.2% reported history of accidental exposure; and 47.4% of exposed  respondents took PEP. Reasons for not taking PEP included lack of information about existing HIV-PEP policy and fear of stigmatization. The respondents had good knowledge of HIV-PEP, but poor practice. Thus, there is the need to reinforce education and training of doctors and otherhealthcare workers on HIV-PEP. Health care policy makers and employee should create more awareness by public display of HIV-PEP protocol and guidelines in the work place.Key words: HIV, Post-exposure prophylaxis, Attitude, Knowledge, Practice, Health care workers

Fabrication and Assessment of a Motorcycle Piston using the Traditional Sand Casting Method

The RX 100 motorcycle piston was fabricated from end-of-life automobile piston using the traditional sand casting method. The fabricated piston was subjected to thermal analysis using ANSYS R18.1 version software to ascertain its performance under thermal loads. The recycled EOL aluminium used in the fabrication of the piston was characterised using SEM-EDS to determine the composition and morphology of the material. Results obtained show that the EOL aluminium employed in the fabrication of the piston performed excellently under thermal loads, and the SEM-EDS indicates that the material is predominantly aluminium with beneficial alloying elements

Fuzzy Cost Modelling of Diving Chamber Control Measures under Uncertainties

The diving chamber is an important system needed for diving operations in the oil and gas industry. Divers use it for various purposes. Thus, the safety level of the diving chamber needs to be very high at all times and the system needs to be in a good state. To achieve this, various control measures such as control measures 1 and 2 can be adopted in preventing failures/hazards or mitigate their consequences. In this study, fuzzy cost algorithm is used to estimate the cost of using control measures 1 and 2 in ensuring optimal operational level for the diving chamber, while the preference degree approach is adopted in prioritizing the aforementioned cost of control measures 1 and 2. The result of the analysis indicated that control measure 2 is the most cost effective approach

Prioritising Alternative Solutions to Power Generation Problems Using MCDM Techniques: Nigeria as Case Study

The engine that energizes industrialization and which invariably result to improved standard of living of nations’ citizens is electric power. Hence a steady power supply is crucial for Nigeria to achieve her aim of becoming one of the most industrialised nation in the world. However the biggest challenge in Nigeria is electricity crisis, a crisis that had been without any visible end in sight. From the literature the problems of power generation in Nigeria ranges from improper maintenance of power generation infrastructure to militant activities. Although alternative solutions are available for addressing these problems but there is difficulty in selecting the optimal solution that will yield greater power output. This paper present a Multi-Criteria Decision Making (MCDM) tool for prioritising alternatives solutions to power generation problems. The tool uses a combination of entropy technique and Multi-Attribute Utility Theory (MAUT) method. To illustrate the suitability of the technique, two examples were utilised. Results of the analysis revealed that Reliability Centered Maintenance (RCM) and diplomatic approach are the optimal solutions for resolving problem of improper maintenance and militant activities respectively. The proposed tool will assist Government or electric power managers to use optimal solutions in solving power generation problems in order to maximise power plant output and consistently ameliorate power crisis.Â

Facilitating Improvement of Design for Safety and Operations of a Seaweed Harvester: A Hybrid Traditional Safety Method

Sea harvester is a vital marine vessel needed in sea safety and cleanliness. Reliability and safety of the operations of the vessel need to be ensured via identification of hazards/failures that tends to affect the system and prevent them from occurring and also mitigate their consequences. In this research, a traditional hybrid methodology is employed in ensuring the reliability and safety of a sea harvester. The methodology is a logical combination of preliminary hazard analysis (PHA), risk matrix approach (RMA) and event tree analysis (ETA). Fire, flood, machinery failure and capsize that pose to affect optimal operations of a sea harvester are identified using a PHA method. RMA is incorporated in application of the PHA method to estimate the risks associated with them. Due the fact that risks associated with fire, flood, machinery failure and capsize are classified as very high, identifying preventing measures becomes necessary. Furthermore, systems which by means of their operability and non-operability can mitigate fire, flood, machinery failure, capsize and grounding consequences are captured using an ETA method. Therefore, the traditional hybrid methodology developed is successfully applied in design for safety, construction and operation of a sea harveste