Despite of modern navigation devices, there are problems in navigation of vessels in waterways due to the geographical structures, disturbances in water, dynamic nature, and heavily environmental influenced sea traffi...Despite of modern navigation devices, there are problems in navigation of vessels in waterways due to the geographical structures, disturbances in water, dynamic nature, and heavily environmental influenced sea traffic. Even though all vessels are equipped with modern navigation devices, the accidents are reported caused by various reasons and mainly by human factor according to investigation. We propose an effective and efficient composition collision risk calculation method for finding the collision probability and avoiding the collision between ships in possible collision situations. The proposed composition collision risk calculation method at ship's position using combination of fuzzy and fuzzy comprehensive evaluation methods. The algorithm is straightforward to implement and is shown to be effective in automatic ship handling for ships involved in complex navigation situations. Experiments are carried out with indigenous data and the results show the effectiveness of the proposed approach.展开更多
In this paper, Noblesse's New Slender-Ship Wave-Making Theory was investigated numerically. Detailed expressions of zeroth and 1st order wave resistance have been derived and calculation programs have also been co...In this paper, Noblesse's New Slender-Ship Wave-Making Theory was investigated numerically. Detailed expressions of zeroth and 1st order wave resistance have been derived and calculation programs have also been compiled. In the single and double integral terms of Green function, the kernel function of wave resistance expression, special function expansion method and Chebyshev polynomials approach have been adopted respectively, which greatly simplify the calculation and increase the convergence speed.展开更多
Traditional intercept probability model has some drawbacks and can not meet the demands of command and control system. Aiming at this problem, a new calculation method based on search theory, terminal control area dis...Traditional intercept probability model has some drawbacks and can not meet the demands of command and control system. Aiming at this problem, a new calculation method based on search theory, terminal control area distribution function of anti-ship missile, target distribution function and missile's radar scan feature is proposed. Under the condition of common target distribution, an intercept probability model for present point attacking is determined. The simulation verifies its effectiveness and establishes the selecting model for aiming point when enemy ships evade in high speed.展开更多
The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow for...The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function.The code is fully developed in C++language with extensive use of the object-oriented paradigm.The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles.The hydrodynamic responses such as hydrodynamic coefficients,ship motions,the vertical shear force and the vertical bending moment are estimated.A benchmark container ship and an LNG carrier are selected for testing and validating the computer code.The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.展开更多
In this paper, the results of model tests of impact energy and forces and motions of moored ships from 20,000 dwt to 200,000 dwt in regular waves upon piers are synthetically analyzed. Based on the concept of wave ene...In this paper, the results of model tests of impact energy and forces and motions of moored ships from 20,000 dwt to 200,000 dwt in regular waves upon piers are synthetically analyzed. Based on the concept of wave energy transmission and the theory of vibration, a semi-empirical formula for evaluating impact energy and forces is proposed.展开更多
Purpose-The oversupply of college graduates and increasing competition in the Chinese urban labor market have forced college students to undertake internships much earlier and to a greater intensity in the hope of boo...Purpose-The oversupply of college graduates and increasing competition in the Chinese urban labor market have forced college students to undertake internships much earlier and to a greater intensity in the hope of boosting their employment prospects.It may be argued that the considerable time and energy thus spent on internships is deleterious to their university studies.The paper considers the factors that determine the intensity of an internship experience.Design/Approach/Methods-Building on a Cobb-Douglas utility function,the paper constructs a Prisoners’Dilemma game to model the internship behavior of Chinese college students,and then examines the determinants of internship using data from a 2011 survey of approximately 10,000 Chinese college students from 47 higher education institutions in the Beijing metropolitan area and multivariate regression analysis.Findings-Empirical results confirm three key hypotheses derived from our model:first,students’perceptions of higher differentials across available jobs in the labor market entice them to intern excessively;second,the improving quality of college teaching and the consequent benefit for knowledge acquisition mitigates the need for excessive internship;third,student preferences for fundamental knowledge acquisition also tilts the balance towards more study and less internship.Originality/Value-These findings suggest that in the context of a tight graduate labor market,improving the quality of college teaching provides a viable alternative to excessive internship by students.展开更多
Many studies have qualitatively explained that information and communication technology(ICT) has loosened the restrictions of distance and space on retailers' sales. Few empirical studies, however, have explored t...Many studies have qualitatively explained that information and communication technology(ICT) has loosened the restrictions of distance and space on retailers' sales. Few empirical studies, however, have explored the impact of shipping distance on online retailers' sales. This study examined the Maiyang(M-Y) store on Tmall in China as a case study to investigate the relationship between shipping distance and sales. The results showed that sales volume in 2014 at the county level did not strictly obey the distance decay law. The shipped distance of high-priced commodities may not be much longer than that of low-priced commodities. Within the scope of investigation, the relationships between income, cost, and net profit curves do not follow central place theory. Goods have neither thresholds nor ranges. The key factor in the spatial discrepancy of sales is the size of market. The impact of shipping distance on sales is not as strong as that of traditional retailers in Information Era.展开更多
Ship motion,with six degrees of freedom,is a complex stochastic process.Sea wind and waves are the primary influencing factors.Prediction of ship motion is significant for ship navigation.To eliminate errors,a path pr...Ship motion,with six degrees of freedom,is a complex stochastic process.Sea wind and waves are the primary influencing factors.Prediction of ship motion is significant for ship navigation.To eliminate errors,a path prediction model incorporating ship pitching was developed using the Gray topological method,after analyzing ship pitching motions.With the help of simple introduction to Gray system theory,we selected a group of threshold values.Based on an analysis of ship pitch angle sequences over 40 second intervals,a Grey metabolism GM(1,1) model was established according to the time-series which every threshold corresponded to.Forecasting future ship motion with the GM(1,1) model allowed drawing of the forecast curve with effective forecasting points.The precision of the test results show that the model is accurate,and the forecast results are reliable.展开更多
基金supported by ETRI through Maritime Safety & Maritime Traffic Management R&D Program of the MOF/KIMST (2009403, Development of Next Generation VTS for Maritime Safety)supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MEST) (No. 2011-0015009)
文摘Despite of modern navigation devices, there are problems in navigation of vessels in waterways due to the geographical structures, disturbances in water, dynamic nature, and heavily environmental influenced sea traffic. Even though all vessels are equipped with modern navigation devices, the accidents are reported caused by various reasons and mainly by human factor according to investigation. We propose an effective and efficient composition collision risk calculation method for finding the collision probability and avoiding the collision between ships in possible collision situations. The proposed composition collision risk calculation method at ship's position using combination of fuzzy and fuzzy comprehensive evaluation methods. The algorithm is straightforward to implement and is shown to be effective in automatic ship handling for ships involved in complex navigation situations. Experiments are carried out with indigenous data and the results show the effectiveness of the proposed approach.
文摘In this paper, Noblesse's New Slender-Ship Wave-Making Theory was investigated numerically. Detailed expressions of zeroth and 1st order wave resistance have been derived and calculation programs have also been compiled. In the single and double integral terms of Green function, the kernel function of wave resistance expression, special function expansion method and Chebyshev polynomials approach have been adopted respectively, which greatly simplify the calculation and increase the convergence speed.
文摘Traditional intercept probability model has some drawbacks and can not meet the demands of command and control system. Aiming at this problem, a new calculation method based on search theory, terminal control area distribution function of anti-ship missile, target distribution function and missile's radar scan feature is proposed. Under the condition of common target distribution, an intercept probability model for present point attacking is determined. The simulation verifies its effectiveness and establishes the selecting model for aiming point when enemy ships evade in high speed.
文摘The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function.The code is fully developed in C++language with extensive use of the object-oriented paradigm.The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles.The hydrodynamic responses such as hydrodynamic coefficients,ship motions,the vertical shear force and the vertical bending moment are estimated.A benchmark container ship and an LNG carrier are selected for testing and validating the computer code.The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.
文摘In this paper, the results of model tests of impact energy and forces and motions of moored ships from 20,000 dwt to 200,000 dwt in regular waves upon piers are synthetically analyzed. Based on the concept of wave energy transmission and the theory of vibration, a semi-empirical formula for evaluating impact energy and forces is proposed.
基金The work was funded by grant#71473005 from the National Natural Science Foundation of China.All errors remain our own.
文摘Purpose-The oversupply of college graduates and increasing competition in the Chinese urban labor market have forced college students to undertake internships much earlier and to a greater intensity in the hope of boosting their employment prospects.It may be argued that the considerable time and energy thus spent on internships is deleterious to their university studies.The paper considers the factors that determine the intensity of an internship experience.Design/Approach/Methods-Building on a Cobb-Douglas utility function,the paper constructs a Prisoners’Dilemma game to model the internship behavior of Chinese college students,and then examines the determinants of internship using data from a 2011 survey of approximately 10,000 Chinese college students from 47 higher education institutions in the Beijing metropolitan area and multivariate regression analysis.Findings-Empirical results confirm three key hypotheses derived from our model:first,students’perceptions of higher differentials across available jobs in the labor market entice them to intern excessively;second,the improving quality of college teaching and the consequent benefit for knowledge acquisition mitigates the need for excessive internship;third,student preferences for fundamental knowledge acquisition also tilts the balance towards more study and less internship.Originality/Value-These findings suggest that in the context of a tight graduate labor market,improving the quality of college teaching provides a viable alternative to excessive internship by students.
基金Under the auspices of the National Planning Office of Philosophy and Social Science(No.17BRK010)National Natural Science Foundation of China(No.41601161)+1 种基金Natural Science Foundation of Guangdong Province(No.2017A030313224)Guangdong Planning Office of Philosophy and Social Science(No.2017GZZK16)
文摘Many studies have qualitatively explained that information and communication technology(ICT) has loosened the restrictions of distance and space on retailers' sales. Few empirical studies, however, have explored the impact of shipping distance on online retailers' sales. This study examined the Maiyang(M-Y) store on Tmall in China as a case study to investigate the relationship between shipping distance and sales. The results showed that sales volume in 2014 at the county level did not strictly obey the distance decay law. The shipped distance of high-priced commodities may not be much longer than that of low-priced commodities. Within the scope of investigation, the relationships between income, cost, and net profit curves do not follow central place theory. Goods have neither thresholds nor ranges. The key factor in the spatial discrepancy of sales is the size of market. The impact of shipping distance on sales is not as strong as that of traditional retailers in Information Era.
文摘Ship motion,with six degrees of freedom,is a complex stochastic process.Sea wind and waves are the primary influencing factors.Prediction of ship motion is significant for ship navigation.To eliminate errors,a path prediction model incorporating ship pitching was developed using the Gray topological method,after analyzing ship pitching motions.With the help of simple introduction to Gray system theory,we selected a group of threshold values.Based on an analysis of ship pitch angle sequences over 40 second intervals,a Grey metabolism GM(1,1) model was established according to the time-series which every threshold corresponded to.Forecasting future ship motion with the GM(1,1) model allowed drawing of the forecast curve with effective forecasting points.The precision of the test results show that the model is accurate,and the forecast results are reliable.
