The lunar magma ocean hypothesis suggests that the primordial KREEP(an acronym of potassium(K),rare earth element(REE),and phosphorus(P))was the final product of fractional crystallization.However,the primordial KREEP...The lunar magma ocean hypothesis suggests that the primordial KREEP(an acronym of potassium(K),rare earth element(REE),and phosphorus(P))was the final product of fractional crystallization.However,the primordial KREEP(a.k.a.urKREEP)has never been identified in previous lunar samples or meteorites.The Moon is the focus of many countries’and agencies’space exploration plans,and with the advancement of technology,crewed missions have been proposed.We propose two candidate landing sites,located respectively in the northwest(9.5°W,0.9°S)and southeast(11.1°W,6.2°S)of Lalande crater(8.6°W,4.5°S),for future crewed missions,with the primary goal of sampling the speculated urKREEP.Both sites are situated on the Th-(a critical marker of KREEP)and silica-rich Lalande ejecta in the Mare Insularum and Mare Nubium,respectively.Their geolocations at the low latitude on the lunar nearside,the flat surface,and the low rock abundance suggest the sites are safe for landing and meet the needs of real-time Earth-Moon communication.The astronauts could perform many extravehicular activities,such as collecting KREEP-rich samples,screening clast samples,and drilling regolith cores,to gather a variety of samples,such as Lalande ejecta,basalts,Copernicus ejecta,and regolith.The returned samples are valuable to explore the speculated urKREEP,to reveal the relationship between heat-producing elements and volcanism,to refine the lunar cratering chronology function,and to investigate volatiles in the regolith.展开更多
On 5 June 2024,after many delays,Boeing(Arlington,VA,USA)launched the inaugural crewed flight of its conical Starliner space-craft(Fig.1)[1].But the mission did not finish as planned.Multiple technical problems emerge...On 5 June 2024,after many delays,Boeing(Arlington,VA,USA)launched the inaugural crewed flight of its conical Starliner space-craft(Fig.1)[1].But the mission did not finish as planned.Multiple technical problems emerged,and the National Aeronautics and Space Administration(NASA)three months later had the spacecraft return from the International Space Station(ISS)empty,further stranding its crew of two astronauts at the orbital outpost until they could be rescued with another craft.展开更多
As we look ahead to future lunar exploration missions, such as crewed lunar exploration and establishing lunar scientific research stations, the lunar rovers will need to cover vast distances. These distances could ra...As we look ahead to future lunar exploration missions, such as crewed lunar exploration and establishing lunar scientific research stations, the lunar rovers will need to cover vast distances. These distances could range from kilometers to tens of kilometers, and even hundreds and thousands of kilometers. Therefore, it is crucial to develop effective long-range path planning for lunar rovers to meet the demands of lunar patrol exploration. This paper presents a hierarchical map model path planning method that utilizes the existing high-resolution images, digital elevation models and mineral abundance maps. The objective is to address the issue of the construction of lunar rover travel costs in the absence of large-scale, high-resolution digital elevation models. This method models the reference and semantic layers using the middle- and low-resolution remote sensing data. The multi-scale obstacles on the lunar surface are extracted by combining the deep learning algorithm on the high-resolution image, and the obstacle avoidance layer is modeled. A two-stage exploratory path planning decision is employed for long-distance driving path planning on a global–local scale. The proposed method analyzes the long-distance accessibility of various areas of scientific significance, such as Rima Bode. A high-precision digital elevation model is created using stereo images to validate the method. Based on the findings, it can be observed that the entire route spans a distance of 930.32 km. The route demonstrates an impressive ability to avoid meter-level impact craters and linear structures while maintaining an average slope of less than 8°. This paper explores scientific research by traversing at least seven basalt units, uncovering the secrets of lunar volcanic activities, and establishing ‘golden spike’ reference points for lunar stratigraphy. The final result of path planning can serve as a valuable reference for the design, mission demonstration, and subsequent project implementation of the new manned lunar rover.展开更多
The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment(FFICC)of a truck-mounted howitzer during the artillery firing.This overpressure is the primary factor preventing personn...The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment(FFICC)of a truck-mounted howitzer during the artillery firing.This overpressure is the primary factor preventing personnel from firing artillery within the cab.To investigate the overpressure characteristics of the FFICC,a foreign trade equipment model was used as the research object,and a numerical model was established to analyze the propagation of muzzle blast from the muzzle to the interior of the crew compartment under extreme firing condition.For comparative verification,the muzzle blast experiment included overpressure data from both the flow field outside the crew compartment(FFOCC)and the FFICC,as well as the acceleration data of the crew compartment structure(Str-CC).The research findings demonstrate that the overpressure-time curves of the FFICC exhibit multi-peak characteristics,while the pressure wave shows no significant discontinuity.The enclosed nature of the cab hinders the dissipation of pressure wave energy within the FFICC,leading to sustained high-amplitude overpressure.The frameskin structure helps attenuate the impact of muzzle blast on the FFICC.Conversely,local high overpressure caused by the convex or concave features of the cab's exterior significantly amplifies the overpressure amplitude within the FFICC.展开更多
Motivated by a critical issue of airline planning process,this paper addresses a new two-stage scenario-based robust optimization in operational airline planning to cope with uncertainty and possible flight disruption...Motivated by a critical issue of airline planning process,this paper addresses a new two-stage scenario-based robust optimization in operational airline planning to cope with uncertainty and possible flight disruptions.Following the route network scheme and generated flight timetables,aircraft maintenance routing and crew scheduling are critical factors in airline planning and operations cost management.This study considers the simultaneous assignment of aircraft fleet and crew to the scheduled flight while satisfying a set of operational constraints,rules,and regulations.Considering multiple locations for airline maintenance and crew bases,we solve the problem of integrated Aircraft Maintenance Routing and Crew Rostering(AMRCR)to achieve the minimum airline cost.One real challenge to the efficiency of the planning results is the possible disruptions in the initial scheduled flights.Due to the fact that disruption scenarios are expressed discretely with a specified probability,and we provide adjustable decisions under disruption to deal with this disruption risk,we provide a Two-Stage Scenario-Based Robust Optimization(TSRO)model.In this model,here-and-now or first-stage variables are the initial resource assignment.Furthermore,to adapt itself to different disruption scenarios,the model considers some adjustable variables,such as the decision to cancel the flight in case of disruption,as wait-and-see or second-stage variables.Considering the complexity of integrated models,and the scenario-based decomposable structure of the TRSO model to solve it with better computational performance,we apply the column and row generation(CRG)method that iteratively considers the disruption scenarios.The numerical results confirm the applicability of the proposed TSRO model in providing the AMRCR problem with an integrated and robust solution with an acceptable level of computational tractability.To evaluate the proposed TSRO model,which solves the AMRCR problem in an integrated and robust manner,five Key Performance Indicators(KPIs)like Number of delayed/canceled flights,Average delay time,and Average profit are taken into account.As key results driven by conducting a case study,we show the proposed TSRO model has substantially improved the solutions at all indicators compared with those of the sequential/non-integrated and nominal/non-robust models.The simulated instances used to assess the performance of the proposed model and CRG method reveal that both CPLEX and the CRG method exhibit comparable and nearly optimal performance for small-scale problems.However,for large-scale instances the proposed TSRO model falls short in terms of computational efficiency.Conversely,the proposed CRG method is capable of significantly reducing computational time and the optimality gap to an acceptable level.展开更多
工作场所无礼行为不仅会给员工带来一系列消极影响,还会导致员工"以牙还牙,加倍奉还",引起行为的恶化升级,严重污染组织环境。而文明行为则有利于组织中人际关系的和谐发展,带给员工众多积极影响。梳理无礼行为恶化升级的相...工作场所无礼行为不仅会给员工带来一系列消极影响,还会导致员工"以牙还牙,加倍奉还",引起行为的恶化升级,严重污染组织环境。而文明行为则有利于组织中人际关系的和谐发展,带给员工众多积极影响。梳理无礼行为恶化升级的相关研究,从受害者和旁观者的角度详细分析无礼行为恶化升级的多条途径和原因;并基于情绪的认知评价理论,从评价和情绪入手,对无礼行为恶化升级的详细机制和影响因素进行解析,构建无礼行为的恶化升级模型。与此同时,着眼于促进无礼行为的积极转化,对文明行为的CREW干预(Civility,Respect and Engagement in the Workforce)的研究进行总结,并分析个体水平的文明行为和组织水平的文明气氛的积极作用。展开更多
The normal operation of aircraft and flights can be affected by various unpredictable factors,such as severe weather,airport closure,and corrective maintenance,leading to disruption of the planned schedule.When a disr...The normal operation of aircraft and flights can be affected by various unpredictable factors,such as severe weather,airport closure,and corrective maintenance,leading to disruption of the planned schedule.When a disruption occurs,the airline operation control center performs various operations to reassign resources(e.g.,flights,aircraft,and crews)and redistribute passengers to restore the schedule while minimizing costs.We introduce different sources of disruption and corresponding operations.Then,basic models and recently proposed extensions for aircraft recovery,crew recovery,and integrated recovery are reviewed,with the aim of providing models and methods for different disruption scenarios in the practical implementation of airlines.In addition,we provide suggestions for future research directions in these topics.展开更多
When disruptions occur, the airlines have to recover from the disrupted schedule. The recovery usually consists of aircraft recovery, crew recovery and passengers' recovery. This paper focuses on the integrated re...When disruptions occur, the airlines have to recover from the disrupted schedule. The recovery usually consists of aircraft recovery, crew recovery and passengers' recovery. This paper focuses on the integrated recovery, which means above-mentioned two or more recoveries are considered as a whole. Taking the minimization of the total cost of assignment, cancellation and delay as an objective, we present a more practical model, in which the maintenance and the union regulations are considered. Then we present a so-called iterative tree growing with node combination method. By aggregating nodes, the possibility of routings is greatly simplified, and the computation time is greatly decreased. By adjusting the consolidating range, the computation time can be controlled in a reasonable time. Finally, we use data from a main Chinese airline to test the algorithm. The experimental results show that this method could be used in the integrated recovery problem.展开更多
Airline crew rostering is the assignment problem of crew members to planned rotations/pairings for certain month. Airline companies have the monthly task of constructing personalized monthly schedules (roster) for cre...Airline crew rostering is the assignment problem of crew members to planned rotations/pairings for certain month. Airline companies have the monthly task of constructing personalized monthly schedules (roster) for crew members. This problem became more complex and difficult while the aspirations/criterias to assess the quality of roster grew and the constraints increased excessively. This paper proposed the differential evolution (DE) method to solve the airline rostering problem. Different from the common DE, this paper presented random swap as mutation operator. The DE algorithm is proven to be able to find the near optimal solution accurately for the optimization problem. Through numerical experiments with some real datasets, DE showed more competitive results than two other methods, column generation and MOSI (the one used by the Airline). DE produced good results for small and medium datasets, but it still showed reasonable results for large dataset. For large crew rostering problem, we proposed decomposition procedure to solve it in more efficient manner using DE.展开更多
The area of operations management has had a substantial effect on the today’s air transportation management.Having moved with huge demand from management to obtain a competitive advantage in the market,the airlines a...The area of operations management has had a substantial effect on the today’s air transportation management.Having moved with huge demand from management to obtain a competitive advantage in the market,the airlines are utilizing advanced optimization techniques to develop decision support systems for operations management and control.In order to provide a service with high quality and low cost,airlines spend a tremendous amount of resources and effort to generate profitable and cost-effective fare classes,flight schedules,fleet plans,aircraft routes,crew scheduling,gate assignment,etc.In this paper,the techniques and operations management applications that are used in the air transportation industry are reviewed including demand forecasting,fleet assignment,aircraft routing,crew scheduling,runway scheduling problem and gate assignment.展开更多
Crew pairing is a sequence of flights beginning and ending at the same crewbase. Crew pairing planning is one of the primary processes in airline crew scheduling;it is also the primary cost-determining phase in airlin...Crew pairing is a sequence of flights beginning and ending at the same crewbase. Crew pairing planning is one of the primary processes in airline crew scheduling;it is also the primary cost-determining phase in airline crew scheduling. Optimizing crew pairings in an airline timetable helps minimize operational crew costs and maximize crew utilization. There are numerous restrictions that must be considered and just as many regulations that must be satisfied in crew pairing generation. The most important regulations—and the ones that make crew pairing planning a highly constrained optimization problem—are the the limits of the flight and the duty periods. Keeping these restrictions and regulations in mind, the main goal of the optimization is the generation of low cost sets of valid crew pairings which cover all flights in the airline’s timetable. For this research study, We examined studies about crew pairing optimization and used these previously existing methods of crew pairing to develop a new solution of the crew pairing problem using genetic algorithms. As part of the study we created a new genetic operator—called perturbation operator.Unlike traditional genetic algorithm implementations, this new perturbation operator provides much more stable results, an obvious increase in the convergence rate, and takes into account the existence of multiple crewbases.展开更多
The scope of this article is to screen thesymptoms of Post-Traumatic Stress Disorder （PTSD） among the professionals of health and public safety securi~ who providedhumanitarian aid fbr the population of Madeira afte...The scope of this article is to screen thesymptoms of Post-Traumatic Stress Disorder （PTSD） among the professionals of health and public safety securi~ who providedhumanitarian aid fbr the population of Madeira after the 2010 alluvium. It involves a cross-sectional study. The list of life events （LAV） and theperi-traumaticexperiences questionnaire （PTSB）--adult versionwere used for screening symptoms.The participants included 405 professionalson the emergency crews （mean age = 34.51）. Most are male （83.5%） and was in his residence （52.8%） at the time of the event.The results showed that there are significant differences between the profession and the response to the event （P 〈 0.001）, as well as in relation to Post Traumatic Stress Disorder （PTSD）, being most evident in the group of firemen and military （P 〈 0.001） of developing PTSD.Therefore, the mental health care of the professionals should suggest the vital need for specific training and the prevention of psychological disorders.展开更多
A ship＇s crew plays an important role in the maritime transportation sector and their performance is paramont in the shipping industry. On this account, an impartial evaluation of the crew＇s performance is an import...A ship＇s crew plays an important role in the maritime transportation sector and their performance is paramont in the shipping industry. On this account, an impartial evaluation of the crew＇s performance is an important issue. In this paper, the ship officer＇s performance evaluation problem is studied. The performance evaluation criteria that shipping companies take into account are determined and a performance evaluation process is modelled by using the FAHP （Fuzzy Analytic Hierarchy Process） based on Chang＇s Algorithm. Linguistic variables and fuzzy numbers are used in the assessment process. The results of the proposed model demonstrate that the FAHP method is effective and helps managers make better and more reliable decisions under fuzzy circumstances.展开更多
An open source Direct Simulation Monte Carlo (DSMC) code, called as dsmcFoam in OpenFOAM, is used to study a blunt body with the shape of a space crew capsule return vehicle. The rarefied gas has the Knudsen number wi...An open source Direct Simulation Monte Carlo (DSMC) code, called as dsmcFoam in OpenFOAM, is used to study a blunt body with the shape of a space crew capsule return vehicle. The rarefied gas has the Knudsen number with 0.03. The flow with a Mach number 4.35 over the capsule was simulated by DSMC. The distributions of velocity field and temperature around the capsule were calculated. This study may provide some useful information for the reentry of the return vehicle.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0503104)the National Natural Science Foundation of China(Grant Nos.42241111,62227901,and 42441826)+1 种基金the Macao Young Scholars Program(Grant No.AM201902)the Key Research Program of the Institute of Geology and Geophysics,Chinese Academy of Sciences(Grant No.IGGCAS-202401).
文摘The lunar magma ocean hypothesis suggests that the primordial KREEP(an acronym of potassium(K),rare earth element(REE),and phosphorus(P))was the final product of fractional crystallization.However,the primordial KREEP(a.k.a.urKREEP)has never been identified in previous lunar samples or meteorites.The Moon is the focus of many countries’and agencies’space exploration plans,and with the advancement of technology,crewed missions have been proposed.We propose two candidate landing sites,located respectively in the northwest(9.5°W,0.9°S)and southeast(11.1°W,6.2°S)of Lalande crater(8.6°W,4.5°S),for future crewed missions,with the primary goal of sampling the speculated urKREEP.Both sites are situated on the Th-(a critical marker of KREEP)and silica-rich Lalande ejecta in the Mare Insularum and Mare Nubium,respectively.Their geolocations at the low latitude on the lunar nearside,the flat surface,and the low rock abundance suggest the sites are safe for landing and meet the needs of real-time Earth-Moon communication.The astronauts could perform many extravehicular activities,such as collecting KREEP-rich samples,screening clast samples,and drilling regolith cores,to gather a variety of samples,such as Lalande ejecta,basalts,Copernicus ejecta,and regolith.The returned samples are valuable to explore the speculated urKREEP,to reveal the relationship between heat-producing elements and volcanism,to refine the lunar cratering chronology function,and to investigate volatiles in the regolith.
文摘On 5 June 2024,after many delays,Boeing(Arlington,VA,USA)launched the inaugural crewed flight of its conical Starliner space-craft(Fig.1)[1].But the mission did not finish as planned.Multiple technical problems emerged,and the National Aeronautics and Space Administration(NASA)three months later had the spacecraft return from the International Space Station(ISS)empty,further stranding its crew of two astronauts at the orbital outpost until they could be rescued with another craft.
基金co-supported by the National Key Research and Development Program of China(No.2022YFF0503100)the Youth Innovation Project of Pandeng Program of National Space Science Center,Chinese Academy of Sciences(No.E3PD40012S).
文摘As we look ahead to future lunar exploration missions, such as crewed lunar exploration and establishing lunar scientific research stations, the lunar rovers will need to cover vast distances. These distances could range from kilometers to tens of kilometers, and even hundreds and thousands of kilometers. Therefore, it is crucial to develop effective long-range path planning for lunar rovers to meet the demands of lunar patrol exploration. This paper presents a hierarchical map model path planning method that utilizes the existing high-resolution images, digital elevation models and mineral abundance maps. The objective is to address the issue of the construction of lunar rover travel costs in the absence of large-scale, high-resolution digital elevation models. This method models the reference and semantic layers using the middle- and low-resolution remote sensing data. The multi-scale obstacles on the lunar surface are extracted by combining the deep learning algorithm on the high-resolution image, and the obstacle avoidance layer is modeled. A two-stage exploratory path planning decision is employed for long-distance driving path planning on a global–local scale. The proposed method analyzes the long-distance accessibility of various areas of scientific significance, such as Rima Bode. A high-precision digital elevation model is created using stereo images to validate the method. Based on the findings, it can be observed that the entire route spans a distance of 930.32 km. The route demonstrates an impressive ability to avoid meter-level impact craters and linear structures while maintaining an average slope of less than 8°. This paper explores scientific research by traversing at least seven basalt units, uncovering the secrets of lunar volcanic activities, and establishing ‘golden spike’ reference points for lunar stratigraphy. The final result of path planning can serve as a valuable reference for the design, mission demonstration, and subsequent project implementation of the new manned lunar rover.
基金supported by the National Natural Science Foundation of China(Grant No.U2341269)。
文摘The muzzle blast overpressure induces disturbances in the flow field inside the crew compartment(FFICC)of a truck-mounted howitzer during the artillery firing.This overpressure is the primary factor preventing personnel from firing artillery within the cab.To investigate the overpressure characteristics of the FFICC,a foreign trade equipment model was used as the research object,and a numerical model was established to analyze the propagation of muzzle blast from the muzzle to the interior of the crew compartment under extreme firing condition.For comparative verification,the muzzle blast experiment included overpressure data from both the flow field outside the crew compartment(FFOCC)and the FFICC,as well as the acceleration data of the crew compartment structure(Str-CC).The research findings demonstrate that the overpressure-time curves of the FFICC exhibit multi-peak characteristics,while the pressure wave shows no significant discontinuity.The enclosed nature of the cab hinders the dissipation of pressure wave energy within the FFICC,leading to sustained high-amplitude overpressure.The frameskin structure helps attenuate the impact of muzzle blast on the FFICC.Conversely,local high overpressure caused by the convex or concave features of the cab's exterior significantly amplifies the overpressure amplitude within the FFICC.
文摘Motivated by a critical issue of airline planning process,this paper addresses a new two-stage scenario-based robust optimization in operational airline planning to cope with uncertainty and possible flight disruptions.Following the route network scheme and generated flight timetables,aircraft maintenance routing and crew scheduling are critical factors in airline planning and operations cost management.This study considers the simultaneous assignment of aircraft fleet and crew to the scheduled flight while satisfying a set of operational constraints,rules,and regulations.Considering multiple locations for airline maintenance and crew bases,we solve the problem of integrated Aircraft Maintenance Routing and Crew Rostering(AMRCR)to achieve the minimum airline cost.One real challenge to the efficiency of the planning results is the possible disruptions in the initial scheduled flights.Due to the fact that disruption scenarios are expressed discretely with a specified probability,and we provide adjustable decisions under disruption to deal with this disruption risk,we provide a Two-Stage Scenario-Based Robust Optimization(TSRO)model.In this model,here-and-now or first-stage variables are the initial resource assignment.Furthermore,to adapt itself to different disruption scenarios,the model considers some adjustable variables,such as the decision to cancel the flight in case of disruption,as wait-and-see or second-stage variables.Considering the complexity of integrated models,and the scenario-based decomposable structure of the TRSO model to solve it with better computational performance,we apply the column and row generation(CRG)method that iteratively considers the disruption scenarios.The numerical results confirm the applicability of the proposed TSRO model in providing the AMRCR problem with an integrated and robust solution with an acceptable level of computational tractability.To evaluate the proposed TSRO model,which solves the AMRCR problem in an integrated and robust manner,five Key Performance Indicators(KPIs)like Number of delayed/canceled flights,Average delay time,and Average profit are taken into account.As key results driven by conducting a case study,we show the proposed TSRO model has substantially improved the solutions at all indicators compared with those of the sequential/non-integrated and nominal/non-robust models.The simulated instances used to assess the performance of the proposed model and CRG method reveal that both CPLEX and the CRG method exhibit comparable and nearly optimal performance for small-scale problems.However,for large-scale instances the proposed TSRO model falls short in terms of computational efficiency.Conversely,the proposed CRG method is capable of significantly reducing computational time and the optimality gap to an acceptable level.
文摘工作场所无礼行为不仅会给员工带来一系列消极影响,还会导致员工"以牙还牙,加倍奉还",引起行为的恶化升级,严重污染组织环境。而文明行为则有利于组织中人际关系的和谐发展,带给员工众多积极影响。梳理无礼行为恶化升级的相关研究,从受害者和旁观者的角度详细分析无礼行为恶化升级的多条途径和原因;并基于情绪的认知评价理论,从评价和情绪入手,对无礼行为恶化升级的详细机制和影响因素进行解析,构建无礼行为的恶化升级模型。与此同时,着眼于促进无礼行为的积极转化,对文明行为的CREW干预(Civility,Respect and Engagement in the Workforce)的研究进行总结,并分析个体水平的文明行为和组织水平的文明气氛的积极作用。
基金This study is supported by the National Natural Science Foundation of China(71825001 and 71890973).
文摘The normal operation of aircraft and flights can be affected by various unpredictable factors,such as severe weather,airport closure,and corrective maintenance,leading to disruption of the planned schedule.When a disruption occurs,the airline operation control center performs various operations to reassign resources(e.g.,flights,aircraft,and crews)and redistribute passengers to restore the schedule while minimizing costs.We introduce different sources of disruption and corresponding operations.Then,basic models and recently proposed extensions for aircraft recovery,crew recovery,and integrated recovery are reviewed,with the aim of providing models and methods for different disruption scenarios in the practical implementation of airlines.In addition,we provide suggestions for future research directions in these topics.
文摘When disruptions occur, the airlines have to recover from the disrupted schedule. The recovery usually consists of aircraft recovery, crew recovery and passengers' recovery. This paper focuses on the integrated recovery, which means above-mentioned two or more recoveries are considered as a whole. Taking the minimization of the total cost of assignment, cancellation and delay as an objective, we present a more practical model, in which the maintenance and the union regulations are considered. Then we present a so-called iterative tree growing with node combination method. By aggregating nodes, the possibility of routings is greatly simplified, and the computation time is greatly decreased. By adjusting the consolidating range, the computation time can be controlled in a reasonable time. Finally, we use data from a main Chinese airline to test the algorithm. The experimental results show that this method could be used in the integrated recovery problem.
文摘Airline crew rostering is the assignment problem of crew members to planned rotations/pairings for certain month. Airline companies have the monthly task of constructing personalized monthly schedules (roster) for crew members. This problem became more complex and difficult while the aspirations/criterias to assess the quality of roster grew and the constraints increased excessively. This paper proposed the differential evolution (DE) method to solve the airline rostering problem. Different from the common DE, this paper presented random swap as mutation operator. The DE algorithm is proven to be able to find the near optimal solution accurately for the optimization problem. Through numerical experiments with some real datasets, DE showed more competitive results than two other methods, column generation and MOSI (the one used by the Airline). DE produced good results for small and medium datasets, but it still showed reasonable results for large dataset. For large crew rostering problem, we proposed decomposition procedure to solve it in more efficient manner using DE.
文摘The area of operations management has had a substantial effect on the today’s air transportation management.Having moved with huge demand from management to obtain a competitive advantage in the market,the airlines are utilizing advanced optimization techniques to develop decision support systems for operations management and control.In order to provide a service with high quality and low cost,airlines spend a tremendous amount of resources and effort to generate profitable and cost-effective fare classes,flight schedules,fleet plans,aircraft routes,crew scheduling,gate assignment,etc.In this paper,the techniques and operations management applications that are used in the air transportation industry are reviewed including demand forecasting,fleet assignment,aircraft routing,crew scheduling,runway scheduling problem and gate assignment.
文摘Crew pairing is a sequence of flights beginning and ending at the same crewbase. Crew pairing planning is one of the primary processes in airline crew scheduling;it is also the primary cost-determining phase in airline crew scheduling. Optimizing crew pairings in an airline timetable helps minimize operational crew costs and maximize crew utilization. There are numerous restrictions that must be considered and just as many regulations that must be satisfied in crew pairing generation. The most important regulations—and the ones that make crew pairing planning a highly constrained optimization problem—are the the limits of the flight and the duty periods. Keeping these restrictions and regulations in mind, the main goal of the optimization is the generation of low cost sets of valid crew pairings which cover all flights in the airline’s timetable. For this research study, We examined studies about crew pairing optimization and used these previously existing methods of crew pairing to develop a new solution of the crew pairing problem using genetic algorithms. As part of the study we created a new genetic operator—called perturbation operator.Unlike traditional genetic algorithm implementations, this new perturbation operator provides much more stable results, an obvious increase in the convergence rate, and takes into account the existence of multiple crewbases.
文摘The scope of this article is to screen thesymptoms of Post-Traumatic Stress Disorder （PTSD） among the professionals of health and public safety securi~ who providedhumanitarian aid fbr the population of Madeira after the 2010 alluvium. It involves a cross-sectional study. The list of life events （LAV） and theperi-traumaticexperiences questionnaire （PTSB）--adult versionwere used for screening symptoms.The participants included 405 professionalson the emergency crews （mean age = 34.51）. Most are male （83.5%） and was in his residence （52.8%） at the time of the event.The results showed that there are significant differences between the profession and the response to the event （P 〈 0.001）, as well as in relation to Post Traumatic Stress Disorder （PTSD）, being most evident in the group of firemen and military （P 〈 0.001） of developing PTSD.Therefore, the mental health care of the professionals should suggest the vital need for specific training and the prevention of psychological disorders.
文摘A ship＇s crew plays an important role in the maritime transportation sector and their performance is paramont in the shipping industry. On this account, an impartial evaluation of the crew＇s performance is an important issue. In this paper, the ship officer＇s performance evaluation problem is studied. The performance evaluation criteria that shipping companies take into account are determined and a performance evaluation process is modelled by using the FAHP （Fuzzy Analytic Hierarchy Process） based on Chang＇s Algorithm. Linguistic variables and fuzzy numbers are used in the assessment process. The results of the proposed model demonstrate that the FAHP method is effective and helps managers make better and more reliable decisions under fuzzy circumstances.
文摘An open source Direct Simulation Monte Carlo (DSMC) code, called as dsmcFoam in OpenFOAM, is used to study a blunt body with the shape of a space crew capsule return vehicle. The rarefied gas has the Knudsen number with 0.03. The flow with a Mach number 4.35 over the capsule was simulated by DSMC. The distributions of velocity field and temperature around the capsule were calculated. This study may provide some useful information for the reentry of the return vehicle.
