Available safety egress time under ship fire (SFAT) is critical to ship fire safety assessment, design and emergency rescue. Although it is available to determine SFAT by using fire models such as the two-zone fire ...Available safety egress time under ship fire (SFAT) is critical to ship fire safety assessment, design and emergency rescue. Although it is available to determine SFAT by using fire models such as the two-zone fire model CFAST and the field model FDS, none of these models can address the uncertainties involved in the input parameters. To solve this problem, current study presents a framework of uncertainty analysis for SFAT. Firstly, a deterministic model estimating SFAT is built. The uncertainties of the input parameters are regarded as random variables with the given probability distribution functions. Subsequently, the deterministic SFAT model is employed to couple with a Monte Carlo sampling method to investigate the uncertainties of the SFAT. The Spearman's rank-order correlation coefficient (SRCC) is used to examine the sensitivity of each input uncertainty parameter on SFAT. To illustrate the proposed approach in detail, a case study is performed. Based on the proposed approach, probability density function and cumulative density function of SFAT are obtained. Furthermore, sensitivity analysis with regard to SFAT is also conducted. The results give a high-negative correlation of SFAT and the fire growth coefficient whereas the effect of other parameters is so weak that they can be neglected.展开更多
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
The optimal imaging time selection of ship targets for shore-based inverse synthetic aperture radar (ISAR) in high sea conditions is investigated. The optimal imaging time includes opti- mal imaging instants and opt...The optimal imaging time selection of ship targets for shore-based inverse synthetic aperture radar (ISAR) in high sea conditions is investigated. The optimal imaging time includes opti- mal imaging instants and optimal imaging duration. A novel method for optimal imaging instants selection based on the estimation of the Doppler centroid frequencies (DCFs) of a series of images obtained over continuous short durations is proposed. Combined with the optimal imaging duration selection scheme using the image contrast maximization criteria, this method can provide the ship images with the highest focus. Simulated and real data pro- cessing results verify the effectiveness of the proposed imaging method.展开更多
The characteristics of frequency correlation and group time delay of ambient noise and ship radiated-noise in the sea are studied. The theoretical and experimental results show that the frequency correlation of ship r...The characteristics of frequency correlation and group time delay of ambient noise and ship radiated-noise in the sea are studied. The theoretical and experimental results show that the frequency correlation of ship radiated-noise is much greater than that of ambient noise,and the frequency correlation of ship radiated-noise at long distance has obvious group time delay展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50909058)"Chen Guang" Project of Shanghai Municipal Education Commission and Shanghai Education Development Foundation Science & Technology(Grant No. 10CG51)the Innovation Program of Shanghai Municipal Education Commission (Grant No.11YZ133)
文摘Available safety egress time under ship fire (SFAT) is critical to ship fire safety assessment, design and emergency rescue. Although it is available to determine SFAT by using fire models such as the two-zone fire model CFAST and the field model FDS, none of these models can address the uncertainties involved in the input parameters. To solve this problem, current study presents a framework of uncertainty analysis for SFAT. Firstly, a deterministic model estimating SFAT is built. The uncertainties of the input parameters are regarded as random variables with the given probability distribution functions. Subsequently, the deterministic SFAT model is employed to couple with a Monte Carlo sampling method to investigate the uncertainties of the SFAT. The Spearman's rank-order correlation coefficient (SRCC) is used to examine the sensitivity of each input uncertainty parameter on SFAT. To illustrate the proposed approach in detail, a case study is performed. Based on the proposed approach, probability density function and cumulative density function of SFAT are obtained. Furthermore, sensitivity analysis with regard to SFAT is also conducted. The results give a high-negative correlation of SFAT and the fire growth coefficient whereas the effect of other parameters is so weak that they can be neglected.
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supported by the Innovation Foundation for Scientific Research Base(NJ20140008NJ20150018)+1 种基金the Aeronautical Science Foundation of China(20132052035)the National Defense Basic Scientific Research(B2520110008)
文摘The optimal imaging time selection of ship targets for shore-based inverse synthetic aperture radar (ISAR) in high sea conditions is investigated. The optimal imaging time includes opti- mal imaging instants and optimal imaging duration. A novel method for optimal imaging instants selection based on the estimation of the Doppler centroid frequencies (DCFs) of a series of images obtained over continuous short durations is proposed. Combined with the optimal imaging duration selection scheme using the image contrast maximization criteria, this method can provide the ship images with the highest focus. Simulated and real data pro- cessing results verify the effectiveness of the proposed imaging method.
文摘The characteristics of frequency correlation and group time delay of ambient noise and ship radiated-noise in the sea are studied. The theoretical and experimental results show that the frequency correlation of ship radiated-noise is much greater than that of ambient noise,and the frequency correlation of ship radiated-noise at long distance has obvious group time delay