A route optimization methodology in the frame of an onboard decision support/guidance system for the ship＇s master has been developed and is presented in this paper. The method aims at the minimization of the fuel vo...A route optimization methodology in the frame of an onboard decision support/guidance system for the ship＇s master has been developed and is presented in this paper. The method aims at the minimization of the fuel voyage cost and the risks related to the ship＇s seakeeping performance expected to be within acceptable limits of voyage duration. Parts of this methodology were implemented by interfacing alternative probability assessment methods, such as Monte Carlo, first order reliability method （FORM） and second order reliability method （SORM）, and a 3-D seakeeping code, including a software tool for the calculation of the added resistance in waves of NTUA-SDL. The entire system was integrated within the probabilistic analysis software PROBAN. Two of the main modules for the calculation of added resistance and the probabilistic assessment for the considered seakeeping hazards with respect to exceedance levels of predefined threshold values are herein elaborated and validation studies proved their efficiency in view of their implementation into an on-board optimization system.展开更多
This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framewor...This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framework rests on non-linear, static seismic analysis. The formats can be used to ensure that the structural seismic design can be expected to satisfy specified probabilistic performance objectives, and perhaps （more novel） that it does so with a desired, guaranteed degree of confidence. Performance objectives are presumed to be expressed as the annual probability of exceeding a structural performance level. Structural performance levels are in turn defined as specified structural parameters （e.g., ductility, strength, maximum drift ratio, etc.） reaching a structural limit state （e.g. onset of yield, collapse, etc.）. The degree of confidence in meeting the specified performance objective may be quantified through the upper confidence bound on the （uncertain） probability. In order to make such statements, aleatory （random） uncertainty and epistemic （knowledge limited） uncertainty must be distinguished. The single seismic design foundation can be formatted into the alternative conventional design methods such as LRFD design and fragility-hazard design. Versions of the new developments reported here are already in place in recently completed seismic guidelines.展开更多
An analytical approach for probabilistic evaluation of transient stability of a power system incorporating a wind farm is presented in this study. Based on the fact that the boundary of practical dynamic security regi...An analytical approach for probabilistic evaluation of transient stability of a power system incorporating a wind farm is presented in this study. Based on the fact that the boundary of practical dynamic security region(PDSR) of a power system with double fed induction generators(DFIG) can be approximated by one or few hyper-planes in nodal power injection space, transient stability criterion for given configurations of pre-fault, fault-on and post-fault of a power system is to be expressed by certain expressions of linear combination of nodal injection vector and the transient stability probability(TSP) is further obtained with a much more simplified expression than the complex integral. Furthermore, considering uncertainties of nodal injection power including wind power and load, TSP is calculated analytically by Cornish-Fisher expansion, which can provide reliable evaluation results with high accuracy and much less computing time compared with Monte Carlo simulation. TSP and its visualization can further help operators and planners be aware of the degree of stability or instability and find critical components to monitor and reinforce. Test results on the New England 10-generators and 39-buses power system show the method's effectiveness and significance for probabilistic security assessment.展开更多
A new distribution for the fluctuation of materials＇ lifetime cumulative hazard rate is firstly proposed. The new distribution is extended from the Weibull distribution by adding a sine function. After that, the prop...A new distribution for the fluctuation of materials＇ lifetime cumulative hazard rate is firstly proposed. The new distribution is extended from the Weibull distribution by adding a sine function. After that, the properties of its hazard rate function, cumulative hazard rate function, probability density function and cumulative distribution function are studied. The analysis result shows this distribution can well model the lifetime with variable and periodic hazard rate. Finally, the new distribution is verified with two real data sets as examples to demonstrate its capability.展开更多
基金supported by DNV in the framework of the GIFT strategic R&D collaboration agreement between DNV and the School of Naval Architecture and Marine Engineering of NTUA-Ship Design Laboratory
文摘A route optimization methodology in the frame of an onboard decision support/guidance system for the ship＇s master has been developed and is presented in this paper. The method aims at the minimization of the fuel voyage cost and the risks related to the ship＇s seakeeping performance expected to be within acceptable limits of voyage duration. Parts of this methodology were implemented by interfacing alternative probability assessment methods, such as Monte Carlo, first order reliability method （FORM） and second order reliability method （SORM）, and a 3-D seakeeping code, including a software tool for the calculation of the added resistance in waves of NTUA-SDL. The entire system was integrated within the probabilistic analysis software PROBAN. Two of the main modules for the calculation of added resistance and the probabilistic assessment for the considered seakeeping hazards with respect to exceedance levels of predefined threshold values are herein elaborated and validation studies proved their efficiency in view of their implementation into an on-board optimization system.
文摘This paper presents an analytical foundation for probability-based formats for seismic design and assessment of structures. These formats are designed to be suitable for code and guideline implementation. The framework rests on non-linear, static seismic analysis. The formats can be used to ensure that the structural seismic design can be expected to satisfy specified probabilistic performance objectives, and perhaps （more novel） that it does so with a desired, guaranteed degree of confidence. Performance objectives are presumed to be expressed as the annual probability of exceeding a structural performance level. Structural performance levels are in turn defined as specified structural parameters （e.g., ductility, strength, maximum drift ratio, etc.） reaching a structural limit state （e.g. onset of yield, collapse, etc.）. The degree of confidence in meeting the specified performance objective may be quantified through the upper confidence bound on the （uncertain） probability. In order to make such statements, aleatory （random） uncertainty and epistemic （knowledge limited） uncertainty must be distinguished. The single seismic design foundation can be formatted into the alternative conventional design methods such as LRFD design and fragility-hazard design. Versions of the new developments reported here are already in place in recently completed seismic guidelines.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2013CB228204)the National Natural Science Foundation of China(Grant No.51407126)Tianjin Natural Science Foundation(Grant No.15JCQNJC07000)
文摘An analytical approach for probabilistic evaluation of transient stability of a power system incorporating a wind farm is presented in this study. Based on the fact that the boundary of practical dynamic security region(PDSR) of a power system with double fed induction generators(DFIG) can be approximated by one or few hyper-planes in nodal power injection space, transient stability criterion for given configurations of pre-fault, fault-on and post-fault of a power system is to be expressed by certain expressions of linear combination of nodal injection vector and the transient stability probability(TSP) is further obtained with a much more simplified expression than the complex integral. Furthermore, considering uncertainties of nodal injection power including wind power and load, TSP is calculated analytically by Cornish-Fisher expansion, which can provide reliable evaluation results with high accuracy and much less computing time compared with Monte Carlo simulation. TSP and its visualization can further help operators and planners be aware of the degree of stability or instability and find critical components to monitor and reinforce. Test results on the New England 10-generators and 39-buses power system show the method's effectiveness and significance for probabilistic security assessment.
基金supported by the National Natural Science Foundation of China under Grant Nos.11461051and 11361036the Natural Science Foundation of Inner Mongolia under Grant No.2014MS0112
文摘A new distribution for the fluctuation of materials＇ lifetime cumulative hazard rate is firstly proposed. The new distribution is extended from the Weibull distribution by adding a sine function. After that, the properties of its hazard rate function, cumulative hazard rate function, probability density function and cumulative distribution function are studied. The analysis result shows this distribution can well model the lifetime with variable and periodic hazard rate. Finally, the new distribution is verified with two real data sets as examples to demonstrate its capability.
