Ports operating in the same geographical range face significant competition among them. In such setting, less competitive ports may continually lose patronage of shippers （indigenous to them） to adjacent ones with b...Ports operating in the same geographical range face significant competition among them. In such setting, less competitive ports may continually lose patronage of shippers （indigenous to them） to adjacent ones with better attributes. The extent of and determinants of inter-port competition in the West Africa＇s coast are of interest to port administrators/operators who risk losing significant portion of their domestic generated cargo traffic to competing neighbouring ports. In this paper, we explore the question of what port specific attributes serve as competitive basis for West Africa＇s coastal ports operating in proximity to the other. Through a survey, users of these ports were asked to identify port specific attributes which they consider when deciding which port to use for shipments making. To enrich our empirical model, data collected from the survey were augmented with secondary data （on the identified attributes） obtained from the respective ports. Statistical evidence from data analysis suggests that ports operating in proximity in the West Africa＇s coast compete on the basis of attributes that minimise costs for port users, viz： ships＇ pre-berthiig time, ship turnround time, crane efficiency and availability of cargo spaces （proxied by frequency of ship calls）. Policy implications of the findings were discussed.展开更多
Microwave precondition has been highlighted as a promising technology for softening the rock mass prior to rock breakage by machine to reduce drill bit/cutter wear as well as inverse production rate.To numerically exp...Microwave precondition has been highlighted as a promising technology for softening the rock mass prior to rock breakage by machine to reduce drill bit/cutter wear as well as inverse production rate.To numerically explore the effect of numerical parameters on rock static strength simulation,and determine the numerical mechanical parameters of microwave-treated basalts for future drilling and cutting simulations,numerical models of uniaxial compression strength(UCS)and Brazilian tensile strength(BTS)were established with the coupling of smoothed particle hydrodynamics and finite element method(SPH-FEM).To eliminate the large rock strength errors caused by microwave-induced damage,the cohesion and internal friction angle of microwave-treated basalt specimens with the same microwave treatment parameters were calibrated based on a linear Mohr-Coulomb theory.Based on parametric sensitivity analysis of SPH simulation of UCS and BTS,experimental UCS and BTS values were simultaneously captured according to the same set of calibrated cohesion and internal friction angle data,and the UCS modeling results are in good agreement with experimental tests.Furthermore,the effect of microwave irradiation parameter on the basalt mechanical behaviors was evaluated.展开更多
Most ports around the globe have adopted ICT in a bid to improve their operational performance and remain competitive in the industry. However,</span></span><span><span><span style="fon...Most ports around the globe have adopted ICT in a bid to improve their operational performance and remain competitive in the industry. However,</span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> ports in developing economies still grapple with challenges associated with manual terminal operation. This paper evaluated the level of application</span><span style="font-family:Verdana;"> and integration of Information and Communication Technologies (ICT) and fac</span><span style="font-family:Verdana;">tors limiting their use in terminal operations in Nigerian seaports. The data for the study were obtained from copies of structured Likert scaled questionnaire administered to a random sample of terminal operators, stevedores, </span><span style="font-family:Verdana;">shipping companies’ agents, Customs licensed Clearing and Forwarding</span><span style="font-family:Verdana;"> agents (C&F) operating in Apapa and Tincan Island ports in Nigeria. Specifically, opinion of these respondents was sought on extent of ICT application, inte</span><span style="font-family:Verdana;">gration and perceived constraints to ICT use in port terminal operations.</span><span style="font-family:Verdana;"> Based on our findings using statistical model tests of proportion, the respondents stated that significant level of ICT procedures and processes have been adopted in port terminal operations. In terms of ICT applications, we found that electronic data and communication exchange applications were available in the terminals for use by the respondents. There are also in place ICT applications for warehouses and storage facilities management and e-payment </span><span style="font-family:Verdana;">systems. However, significant constraining factors were found to be: low ICT</span><span style="font-family:Verdana;"> investment budgetary allocation, lack of e-skilled manpower and poor equipment maintenance culture. Other limiting factors were lack of integrated ICT facilities operated by other port stakeholders and absence of Port Community Systems network (PCS) linking all other relevant interests connected to terminal operations. Policy implications of our findings were discussed.展开更多
There exists the challenge of seeming lack of empirically determined cargo throughput benchmark models for the privatized West African port terminals particularly in Nigeria,as target benchmarks which terminal operato...There exists the challenge of seeming lack of empirically determined cargo throughput benchmark models for the privatized West African port terminals particularly in Nigeria,as target benchmarks which terminal operators and port authorities must drive towards to ensure that the current improvement in port productivity experienced in the post concession era is sustained.The study was therefore aimed at developing benchmarks for the cargo throughput performances of the privatized five Nigeria ports of Apapa(Lagos),Port-Harcourt,Onne,Warri and Calabar.Such benchmarks developed for each seaport must be higher than the pre-privatization cargo throughput performances of the seaport.This became important following the improvements observed in the cargo throughput performances of the various ports from the year 2006 after the privatization of the ports and the recent recession faced in the Country which seems to have retarded the cargo throughput performances and other measures of seaport performance in the various Nigeria ports.Using Cp1,CL1,Cw1,Co1,Cc1,to represent the base year 2006 cargo throughput performances of Port-Harcourt,Lagos,Warri,Onne and Calabar seaport respectively;and n,d,to represent the number of post privatization years covered in the study and common difference in cargo throughput performances;the study used a historical design approach in which time series data on cargo throughput performances of the ports were obtained from the Nigeria ports Authority(NPA)annual statistical reports were analyzed using the converging and diverging arithmetic series mathematical modeling tool and MATLAB software,to determine benchmark models,for ensuring that the improved cargo throughput performances of the various seaports,are sustained to remain higher that the pre-privatization cargo throughput performances.The study developed the following Cargo throughput benchmark models for each seaport as findings.Lagos port=CL1+(n–1)d≥15223340;Onne port=Co1+(n-1)d≥15820381;Port-Harcourt port=Cp1+(n-1)d≥28016979;Warri=Cw1+(n-1)d≥4643128;Calabar=Cc1+(n-1)d≥7963434.It was recommended that to improve port revenue which is a dependent factor on cargo throughput and vessel call rate,cargo throughput benchmarks model developed for the individual seaports should be used to empirically model quantum s of cargo throughput needed to economically sustain and improve the level of port operations.It should equally influence port marketing drives.This will ensure that the performance of the ports does not recede into the poor performance indices experienced in the pre-privatization era.展开更多
This paper evaluated performance of motor insurance companies in Nigeria. The objectives were to determine the following: 1) significant effects of claims settlements on motor insurance firms’ earned premium;2) diffe...This paper evaluated performance of motor insurance companies in Nigeria. The objectives were to determine the following: 1) significant effects of claims settlements on motor insurance firms’ earned premium;2) differences in managerial/technological capabilities among the companies and 3) effects of policy (or time effect) on insurance firms’ output within the study </span><span style="font-family:Verdana;">period. Panel data obtained for this study comprised operational data on</span><span style="font-family:Verdana;"> premium earned and direct claims settlement by these companies over a period </span><span style="font-family:Verdana;">of six (6) years. Using panel data statistical models, we found that direct</span><span style="font-family:Verdana;"> claims settlement negatively affected insurance companies’ earned premium. Also, </span><span style="font-family:Verdana;">significant differences in technological and managerial capabilities were </span><span style="font-family:Verdana;">found to exist among the companies, though only one company exhibited this heterogeneity. Besides, there were no policy impacts (or time effect) on vehicle insurance firms’ output in the study period. Policy implications of the results were discussed.展开更多
The maximum satisfiability problem (MAX-SAT) refers to the task of finding a variable assignment that satisfies the maximum number of clauses (or the sum of weight of satisfied clauses) in a Boolean Formula. Most loca...The maximum satisfiability problem (MAX-SAT) refers to the task of finding a variable assignment that satisfies the maximum number of clauses (or the sum of weight of satisfied clauses) in a Boolean Formula. Most local search algorithms including tabu search rely on the 1-flip neighbourhood structure. In this work, we introduce a tabu search algorithm that makes use of the multilevel paradigm for solving MAX-SAT problems. The multilevel paradigm refers to the process of dividing large and difficult problems into smaller ones, which are hopefully much easier to solve, and then work backward towards the solution of the original problem, using a solution from a previous level as a starting solution at the next level. This process aims at looking at the search as a multilevel process operating in a coarse-to-fine strategy evolving from k-flip neighbourhood to 1-flip neighbourhood-based structure. Experimental results comparing the multilevel tabu search against its single level variant are presented.展开更多
The need to mitigate downtime in<span style="font-family:;" "=""> </span><span style="font-family:Verdana;">marine vessels arising </span><span style="...The need to mitigate downtime in<span style="font-family:;" "=""> </span><span style="font-family:Verdana;">marine vessels arising </span><span style="font-family:Verdana;">from propulsion system failures has led ship operating companies to devote enormous resources for</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">research based solutions. This paper applied duration models to determine</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">failure probabilities of shaft and gearbox systems in service boats. Using dockyard’s event history data on boat</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">repairs and maintenance, we applied Kaplan Meier hazard and survival curves to analyse</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">probability of failure</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">of shaft and gearbox</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">systems in supply, crew and tug boats. We found that average time to shaft and gearbox failure was 8.33, 5.23 and 5.21 months for tug, supply and crew boats respectively. The hazard plots however, showed that supply boats had higher probability of failure than crew boats and then tug boats in that order. Further analysis using Cox regression model showed that </span><span style="font-family:Verdana;">t</span><span style="font-family:Verdana;">he boats’ shaft and gearbox system failures were significantly affected by level of lubrication oil, stress corrosion cracking and impacts on the propul</span><span style="font-family:Verdana;">sion system’s components. The paper proposes that</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">design of maintenan</span><span style="font-family:;" "=""><span style="font-family:Verdana;">ce </span><span style="font-family:Verdana;">schedules for service boats should take the following into consideration: </span><span style="font-family:Verdana;">1)</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">estimated survival limits or failure times of propulsion system’s shaft and gearboxes</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> 2) significant risk factors that affect failure mode of</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">the propulsion system components.</span>展开更多
In this paper, we developed performance assessment criteria to evaluate effects of compliance to ISPS Code＇s requirements on port/terminal operation in Nigeria. The primary data for the study were obtained from copie...In this paper, we developed performance assessment criteria to evaluate effects of compliance to ISPS Code＇s requirements on port/terminal operation in Nigeria. The primary data for the study were obtained from copies ofsurvey questionnaires administered to random sample of port users stratified by areas of specialisation. Hypotheses governing this study were based on the premise that additional port facilities provided and security measures adopted in compliance to ISPS code＇s requirements would have positive spillover effects on port operations. Evidence from data analysis indicated that compliance to ISPS code had positive effects on performance of operational performance of Nigeria ports. Similar effects were also observed inport users＇ satisfaction and profitability. The paper contributes by providing decision support framework for ports and terminals. monitoring and gauging outcomes of ISPS code administration in展开更多
Mitigation of blast pressure using water in a walled container was evaluated. A PETN （pentaerythritol tetranitrate） pellet of 1.4 g near the model wall was detonated on a steel plate. A water-filled container was pl...Mitigation of blast pressure using water in a walled container was evaluated. A PETN （pentaerythritol tetranitrate） pellet of 1.4 g near the model wall was detonated on a steel plate. A water-filled container was placed between the explosive and the wall. The pressure histories at six points, which corresponded to Hopkinson scaled distance of from 3.6 m·kg^-1/3 to 21.7 m·kg^-1/3 were evaluated along with dependence of mitigation effects on the amount of water and the position of the container. The presence of the water and the wall mitigated the peak overpressure near the explosion points and the positive impulse along all points. The mitigation effect was equivalent to 20-30% reduction of explosive weight based on discussion of the equivalent ratio. The presence of the water along the wall （not very close to the explosive） also mitigated the blast pressure.展开更多
The reassessment of ocean economy contribution of nations has become a new strategy for frontier states adjacent to the coastal region for the improvement of their position in the efficiency frontier curve. The contin...The reassessment of ocean economy contribution of nations has become a new strategy for frontier states adjacent to the coastal region for the improvement of their position in the efficiency frontier curve. The continuity of a coastal state to remain a leader in the production and efficiency frontier curve of modem day development will thus depend on their ability to sustainably develop their most strategic economic resource base such as the ocean economy. The major economic bases include sustainable fishing, offshore oil field developments, offshore biodiversity development and marine biotechnology, offshore mining of manganese nodules, offshore wind farm potentials, international shipping （marine transport） and adjoining corridor development, ship dry docking potentials, marine renewable energy as well as other potentials outlined in the definition of African Union strategy for the development of her blue economy. Adopting the regression analysis and analysis of variance analytical tools, the study found that about 90% association exist between the GDP （gross domestic product） of the West African state （Nigeria） and her GDP. It equally found that offshore oil and gas energy sector more significantly impact on the GDP of Nigeria than other ocean economy business clusters. Given the various contributing marine environment business cluster used in the work, the model depicting the influence of the ocean economy of Nigeria is： Y = 2295334779895 - 294733（1 ＋ 3436995749 - 59276863（2 ＋ e.展开更多
Maritime shipping has been a major facilitator of economic prosperity<span><span><span style="font-family:;" "=""> <span>throughout the world and it is likely to grow t...Maritime shipping has been a major facilitator of economic prosperity<span><span><span style="font-family:;" "=""> <span>throughout the world and it is likely to grow to meet continued and growing transport needs in both developed and developing countries. However, global emissions from maritime shipping ha</span></span></span></span><span><span><span style="font-family:;" "="">ve</span></span></span><span><span><span style="font-family:;" "=""> increased considerably, causing depletion of the ozone layer and most importantly posing threat to lives and coastal environment through air pollution. This study investigated the constituents of ambient air in Onne port’s environment in Rivers State of Nigeria. Six air pollutants (O<sub>3</sub> CO, NO<sub>2</sub>, PM<sub>2.5</sub>, PM<sub>10</sub>, and SO<sub>2</sub>) were critically monitored with hand-held mobile Aeroqual gas monitors, series 500, at strategic locations within the port’s environment and Eleme Junction (</span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">control). We found that mean concentration</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> (μg·m<sup>3</sup>) of the following pollutants: O<sub>3</sub> (71.776 ± 0.726), CO, (19.145 ± </span></span></span><span><span><span style="font-family:;" "="">0.275) NO<sub>2</sub> (28.145 ± 0.965) and SO<sub>2</sub> (36.913 ± 0.378) were significantly high. The particulates (PM<sub>10</sub>, PM<sub>2.5</sub>) also showed higher mean concentrations of 48.400 ± 0.197 and 29.676 ± 0.352 respectively. The observed values were found<span> to be significantly higher</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">than those observed in the control group and also exceeded the safe permissible limits for gaseous pollutants when compared to the World Health Organization’s (WHO) standards. This exceedance raises questions on Nigeria’s commitments to implementations of (Annex VI) International Maritime Organization’s (IMO) Convention for the Prevention of Marine Pollution (MARPOL</span></span></span><span><span><span style="font-family:;" "=""> 73/78</span></span></span><span><span><span style="font-family:;" "="">) from Ships. Again, the findings portend ecological hazards to residents, flora and fauna as elevated levels of these gaseous pollutants have been associated with chronic respiratory diseases. The policy implications of the findings were discussed.</span></span></span>展开更多
文摘Ports operating in the same geographical range face significant competition among them. In such setting, less competitive ports may continually lose patronage of shippers （indigenous to them） to adjacent ones with better attributes. The extent of and determinants of inter-port competition in the West Africa＇s coast are of interest to port administrators/operators who risk losing significant portion of their domestic generated cargo traffic to competing neighbouring ports. In this paper, we explore the question of what port specific attributes serve as competitive basis for West Africa＇s coastal ports operating in proximity to the other. Through a survey, users of these ports were asked to identify port specific attributes which they consider when deciding which port to use for shipments making. To enrich our empirical model, data collected from the survey were augmented with secondary data （on the identified attributes） obtained from the respective ports. Statistical evidence from data analysis suggests that ports operating in proximity in the West Africa＇s coast compete on the basis of attributes that minimise costs for port users, viz： ships＇ pre-berthiig time, ship turnround time, crane efficiency and availability of cargo spaces （proxied by frequency of ship calls）. Policy implications of the findings were discussed.
基金the National Natural Science Foundation of China (No. 51774323)the Natural Science Foundation of Hunan Province, China (No. 2020JJ4704)+1 种基金the Fundamental Research Funds for the Central Universities of Central South University, China (No. 2018zzts216) the financial support from the China Scholarship Councilthe support of the high-performance computer from Compute Canada
文摘Microwave precondition has been highlighted as a promising technology for softening the rock mass prior to rock breakage by machine to reduce drill bit/cutter wear as well as inverse production rate.To numerically explore the effect of numerical parameters on rock static strength simulation,and determine the numerical mechanical parameters of microwave-treated basalts for future drilling and cutting simulations,numerical models of uniaxial compression strength(UCS)and Brazilian tensile strength(BTS)were established with the coupling of smoothed particle hydrodynamics and finite element method(SPH-FEM).To eliminate the large rock strength errors caused by microwave-induced damage,the cohesion and internal friction angle of microwave-treated basalt specimens with the same microwave treatment parameters were calibrated based on a linear Mohr-Coulomb theory.Based on parametric sensitivity analysis of SPH simulation of UCS and BTS,experimental UCS and BTS values were simultaneously captured according to the same set of calibrated cohesion and internal friction angle data,and the UCS modeling results are in good agreement with experimental tests.Furthermore,the effect of microwave irradiation parameter on the basalt mechanical behaviors was evaluated.
文摘Most ports around the globe have adopted ICT in a bid to improve their operational performance and remain competitive in the industry. However,</span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> ports in developing economies still grapple with challenges associated with manual terminal operation. This paper evaluated the level of application</span><span style="font-family:Verdana;"> and integration of Information and Communication Technologies (ICT) and fac</span><span style="font-family:Verdana;">tors limiting their use in terminal operations in Nigerian seaports. The data for the study were obtained from copies of structured Likert scaled questionnaire administered to a random sample of terminal operators, stevedores, </span><span style="font-family:Verdana;">shipping companies’ agents, Customs licensed Clearing and Forwarding</span><span style="font-family:Verdana;"> agents (C&F) operating in Apapa and Tincan Island ports in Nigeria. Specifically, opinion of these respondents was sought on extent of ICT application, inte</span><span style="font-family:Verdana;">gration and perceived constraints to ICT use in port terminal operations.</span><span style="font-family:Verdana;"> Based on our findings using statistical model tests of proportion, the respondents stated that significant level of ICT procedures and processes have been adopted in port terminal operations. In terms of ICT applications, we found that electronic data and communication exchange applications were available in the terminals for use by the respondents. There are also in place ICT applications for warehouses and storage facilities management and e-payment </span><span style="font-family:Verdana;">systems. However, significant constraining factors were found to be: low ICT</span><span style="font-family:Verdana;"> investment budgetary allocation, lack of e-skilled manpower and poor equipment maintenance culture. Other limiting factors were lack of integrated ICT facilities operated by other port stakeholders and absence of Port Community Systems network (PCS) linking all other relevant interests connected to terminal operations. Policy implications of our findings were discussed.
文摘There exists the challenge of seeming lack of empirically determined cargo throughput benchmark models for the privatized West African port terminals particularly in Nigeria,as target benchmarks which terminal operators and port authorities must drive towards to ensure that the current improvement in port productivity experienced in the post concession era is sustained.The study was therefore aimed at developing benchmarks for the cargo throughput performances of the privatized five Nigeria ports of Apapa(Lagos),Port-Harcourt,Onne,Warri and Calabar.Such benchmarks developed for each seaport must be higher than the pre-privatization cargo throughput performances of the seaport.This became important following the improvements observed in the cargo throughput performances of the various ports from the year 2006 after the privatization of the ports and the recent recession faced in the Country which seems to have retarded the cargo throughput performances and other measures of seaport performance in the various Nigeria ports.Using Cp1,CL1,Cw1,Co1,Cc1,to represent the base year 2006 cargo throughput performances of Port-Harcourt,Lagos,Warri,Onne and Calabar seaport respectively;and n,d,to represent the number of post privatization years covered in the study and common difference in cargo throughput performances;the study used a historical design approach in which time series data on cargo throughput performances of the ports were obtained from the Nigeria ports Authority(NPA)annual statistical reports were analyzed using the converging and diverging arithmetic series mathematical modeling tool and MATLAB software,to determine benchmark models,for ensuring that the improved cargo throughput performances of the various seaports,are sustained to remain higher that the pre-privatization cargo throughput performances.The study developed the following Cargo throughput benchmark models for each seaport as findings.Lagos port=CL1+(n–1)d≥15223340;Onne port=Co1+(n-1)d≥15820381;Port-Harcourt port=Cp1+(n-1)d≥28016979;Warri=Cw1+(n-1)d≥4643128;Calabar=Cc1+(n-1)d≥7963434.It was recommended that to improve port revenue which is a dependent factor on cargo throughput and vessel call rate,cargo throughput benchmarks model developed for the individual seaports should be used to empirically model quantum s of cargo throughput needed to economically sustain and improve the level of port operations.It should equally influence port marketing drives.This will ensure that the performance of the ports does not recede into the poor performance indices experienced in the pre-privatization era.
文摘This paper evaluated performance of motor insurance companies in Nigeria. The objectives were to determine the following: 1) significant effects of claims settlements on motor insurance firms’ earned premium;2) differences in managerial/technological capabilities among the companies and 3) effects of policy (or time effect) on insurance firms’ output within the study </span><span style="font-family:Verdana;">period. Panel data obtained for this study comprised operational data on</span><span style="font-family:Verdana;"> premium earned and direct claims settlement by these companies over a period </span><span style="font-family:Verdana;">of six (6) years. Using panel data statistical models, we found that direct</span><span style="font-family:Verdana;"> claims settlement negatively affected insurance companies’ earned premium. Also, </span><span style="font-family:Verdana;">significant differences in technological and managerial capabilities were </span><span style="font-family:Verdana;">found to exist among the companies, though only one company exhibited this heterogeneity. Besides, there were no policy impacts (or time effect) on vehicle insurance firms’ output in the study period. Policy implications of the results were discussed.
文摘The maximum satisfiability problem (MAX-SAT) refers to the task of finding a variable assignment that satisfies the maximum number of clauses (or the sum of weight of satisfied clauses) in a Boolean Formula. Most local search algorithms including tabu search rely on the 1-flip neighbourhood structure. In this work, we introduce a tabu search algorithm that makes use of the multilevel paradigm for solving MAX-SAT problems. The multilevel paradigm refers to the process of dividing large and difficult problems into smaller ones, which are hopefully much easier to solve, and then work backward towards the solution of the original problem, using a solution from a previous level as a starting solution at the next level. This process aims at looking at the search as a multilevel process operating in a coarse-to-fine strategy evolving from k-flip neighbourhood to 1-flip neighbourhood-based structure. Experimental results comparing the multilevel tabu search against its single level variant are presented.
文摘The need to mitigate downtime in<span style="font-family:;" "=""> </span><span style="font-family:Verdana;">marine vessels arising </span><span style="font-family:Verdana;">from propulsion system failures has led ship operating companies to devote enormous resources for</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">research based solutions. This paper applied duration models to determine</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">failure probabilities of shaft and gearbox systems in service boats. Using dockyard’s event history data on boat</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">repairs and maintenance, we applied Kaplan Meier hazard and survival curves to analyse</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">probability of failure</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">of shaft and gearbox</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">systems in supply, crew and tug boats. We found that average time to shaft and gearbox failure was 8.33, 5.23 and 5.21 months for tug, supply and crew boats respectively. The hazard plots however, showed that supply boats had higher probability of failure than crew boats and then tug boats in that order. Further analysis using Cox regression model showed that </span><span style="font-family:Verdana;">t</span><span style="font-family:Verdana;">he boats’ shaft and gearbox system failures were significantly affected by level of lubrication oil, stress corrosion cracking and impacts on the propul</span><span style="font-family:Verdana;">sion system’s components. The paper proposes that</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">design of maintenan</span><span style="font-family:;" "=""><span style="font-family:Verdana;">ce </span><span style="font-family:Verdana;">schedules for service boats should take the following into consideration: </span><span style="font-family:Verdana;">1)</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">estimated survival limits or failure times of propulsion system’s shaft and gearboxes</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> 2) significant risk factors that affect failure mode of</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">the propulsion system components.</span>
文摘In this paper, we developed performance assessment criteria to evaluate effects of compliance to ISPS Code＇s requirements on port/terminal operation in Nigeria. The primary data for the study were obtained from copies ofsurvey questionnaires administered to random sample of port users stratified by areas of specialisation. Hypotheses governing this study were based on the premise that additional port facilities provided and security measures adopted in compliance to ISPS code＇s requirements would have positive spillover effects on port operations. Evidence from data analysis indicated that compliance to ISPS code had positive effects on performance of operational performance of Nigeria ports. Similar effects were also observed inport users＇ satisfaction and profitability. The paper contributes by providing decision support framework for ports and terminals. monitoring and gauging outcomes of ISPS code administration in
文摘Mitigation of blast pressure using water in a walled container was evaluated. A PETN （pentaerythritol tetranitrate） pellet of 1.4 g near the model wall was detonated on a steel plate. A water-filled container was placed between the explosive and the wall. The pressure histories at six points, which corresponded to Hopkinson scaled distance of from 3.6 m·kg^-1/3 to 21.7 m·kg^-1/3 were evaluated along with dependence of mitigation effects on the amount of water and the position of the container. The presence of the water and the wall mitigated the peak overpressure near the explosion points and the positive impulse along all points. The mitigation effect was equivalent to 20-30% reduction of explosive weight based on discussion of the equivalent ratio. The presence of the water along the wall （not very close to the explosive） also mitigated the blast pressure.
文摘The reassessment of ocean economy contribution of nations has become a new strategy for frontier states adjacent to the coastal region for the improvement of their position in the efficiency frontier curve. The continuity of a coastal state to remain a leader in the production and efficiency frontier curve of modem day development will thus depend on their ability to sustainably develop their most strategic economic resource base such as the ocean economy. The major economic bases include sustainable fishing, offshore oil field developments, offshore biodiversity development and marine biotechnology, offshore mining of manganese nodules, offshore wind farm potentials, international shipping （marine transport） and adjoining corridor development, ship dry docking potentials, marine renewable energy as well as other potentials outlined in the definition of African Union strategy for the development of her blue economy. Adopting the regression analysis and analysis of variance analytical tools, the study found that about 90% association exist between the GDP （gross domestic product） of the West African state （Nigeria） and her GDP. It equally found that offshore oil and gas energy sector more significantly impact on the GDP of Nigeria than other ocean economy business clusters. Given the various contributing marine environment business cluster used in the work, the model depicting the influence of the ocean economy of Nigeria is： Y = 2295334779895 - 294733（1 ＋ 3436995749 - 59276863（2 ＋ e.
文摘Maritime shipping has been a major facilitator of economic prosperity<span><span><span style="font-family:;" "=""> <span>throughout the world and it is likely to grow to meet continued and growing transport needs in both developed and developing countries. However, global emissions from maritime shipping ha</span></span></span></span><span><span><span style="font-family:;" "="">ve</span></span></span><span><span><span style="font-family:;" "=""> increased considerably, causing depletion of the ozone layer and most importantly posing threat to lives and coastal environment through air pollution. This study investigated the constituents of ambient air in Onne port’s environment in Rivers State of Nigeria. Six air pollutants (O<sub>3</sub> CO, NO<sub>2</sub>, PM<sub>2.5</sub>, PM<sub>10</sub>, and SO<sub>2</sub>) were critically monitored with hand-held mobile Aeroqual gas monitors, series 500, at strategic locations within the port’s environment and Eleme Junction (</span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">control). We found that mean concentration</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> (μg·m<sup>3</sup>) of the following pollutants: O<sub>3</sub> (71.776 ± 0.726), CO, (19.145 ± </span></span></span><span><span><span style="font-family:;" "="">0.275) NO<sub>2</sub> (28.145 ± 0.965) and SO<sub>2</sub> (36.913 ± 0.378) were significantly high. The particulates (PM<sub>10</sub>, PM<sub>2.5</sub>) also showed higher mean concentrations of 48.400 ± 0.197 and 29.676 ± 0.352 respectively. The observed values were found<span> to be significantly higher</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">than those observed in the control group and also exceeded the safe permissible limits for gaseous pollutants when compared to the World Health Organization’s (WHO) standards. This exceedance raises questions on Nigeria’s commitments to implementations of (Annex VI) International Maritime Organization’s (IMO) Convention for the Prevention of Marine Pollution (MARPOL</span></span></span><span><span><span style="font-family:;" "=""> 73/78</span></span></span><span><span><span style="font-family:;" "="">) from Ships. Again, the findings portend ecological hazards to residents, flora and fauna as elevated levels of these gaseous pollutants have been associated with chronic respiratory diseases. The policy implications of the findings were discussed.</span></span></span>
