1 On a Sunday morning,Zheng Shiying drove 130 kilometers to a village on the outskirts of Beijing,not for a hike or a hot spring,but for a cup of coffee.Housed in an old stone building that looks untouched by time,by ...1 On a Sunday morning,Zheng Shiying drove 130 kilometers to a village on the outskirts of Beijing,not for a hike or a hot spring,but for a cup of coffee.Housed in an old stone building that looks untouched by time,by the time Zheng arrived,the caféwas already packed with weekend visitors,and finding a seat was a bit of a challenge.展开更多
Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of in...Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of intelligent factories,constantly face dynamic disturbances during the production process,including machine failures and urgent orders.This paper discusses the basic models and research methods of job shop scheduling,emphasizing the important role of dynamic job shop scheduling and its response schemes in future research.A multi-objective flexible job shop dynamic scheduling mathematical model is established,highlighting its complex and multi-constraint characteristics under different interferences.A classification discussion is conducted on the dynamic response methods and optimization objectives under machine failures,emergency orders,fuzzy completion times,and mixed dynamic events.The development process of traditional scheduling rules and intelligent methods in dynamic scheduling are also analyzed.Finally,based on the current development status of job shop scheduling and the requirements of intelligent manufacturing,the future development trends of dynamic scheduling in flexible job shops are proposed.展开更多
To address the issue that hybrid flow shop production struggles to handle order disturbance events,a dynamic scheduling model was constructed.The model takes minimizing the maximum makespan,delivery time deviation,and...To address the issue that hybrid flow shop production struggles to handle order disturbance events,a dynamic scheduling model was constructed.The model takes minimizing the maximum makespan,delivery time deviation,and scheme deviation degree as the optimization objectives.An adaptive dynamic scheduling strategy based on the degree of order disturbance is proposed.An improved multi-objective Grey Wolf(IMOGWO)optimization algorithm is designed by combining the“job-machine”two-layer encoding strategy,the timing-driven two-stage decoding strategy,the opposition-based learning initialization population strategy,the POX crossover strategy,the dualoperation dynamic mutation strategy,and the variable neighborhood search strategy for problem solving.A variety of test cases with different scales were designed,and ablation experiments were conducted to verify the effectiveness of the improved strategies.The results show that each improved strategy can effectively enhance the performance of the IMOGWO.Additionally,performance analysis was conducted by comparing the proposed algorithm with three mature and classical algorithms.The results demonstrate that the proposed algorithm exhibits superior performance in solving the hybrid flow-shop scheduling problem(HFSP).Case validations were conducted for different types of order disturbance scenarios.The results demonstrate that the proposed adaptive dynamic scheduling strategy and the IMOGWO algorithm can effectively address order disturbance events.They enable rapid response to order disturbance while ensuring the stability of the production system.展开更多
Objective:To assess the food safety knowledge and practices in meat handling,and to determine microbial load and pathogenic organisms in meat at Mekelle city.Methods:A descriptive survey design was used to answer ques...Objective:To assess the food safety knowledge and practices in meat handling,and to determine microbial load and pathogenic organisms in meat at Mekelle city.Methods:A descriptive survey design was used to answer questions concerning the current status of food hygiene and sanitation practiced in the abattoir and butcher shops.Workers from the abattoir and butcher shops were interviewed through a structured questionnaire to assess their food safety knowledge.Bacterial load was assessed by serial dilution method and the major bacterial pathogens were isolated by using standard procedures.Results:15.1%of the abattoir workers had no health certificate and there was no hot water,sterilizer and cooling facility in the abattoir.11.3%of the butchers didn’t use protective clothes.There was a food safety knowledge gap within the abattoir and butcher shop workers.The mean values of bacterial load of abattoir meat,butcher shops and street meat sale was found to be 1.1×10~5,5.6×10~5and 4.3×10~6 cfu/g,respectively.The major bacterial pathogens isolated were Escherichia coli,Staphylococcus aureus and Bacillus cereus.Conclusions:The study revealed that there is a reasonable gap on food safely knowledge by abattoir and butcher shop workers.The microbial profile was also higher compared to standards set by World Health Organization.Due attention should be given by the government to improve the food safety knowledge and the quality standard of meat sold in the city.展开更多
No-wait job-shop scheduling (NWJSS) problem is one of the classical scheduling problems that exist on many kinds of industry with no-wait constraint, such as metal working, plastic, chemical, and food industries. Seve...No-wait job-shop scheduling (NWJSS) problem is one of the classical scheduling problems that exist on many kinds of industry with no-wait constraint, such as metal working, plastic, chemical, and food industries. Several methods have been proposed to solve this problem, both exact (i.e. integer programming) and metaheuristic methods. Cross entropy (CE), as a new metaheuristic, can be an alternative method to solve NWJSS problem. This method has been used in combinatorial optimization, as well as multi-external optimization and rare-event simulation. On these problems, CE implementation results an optimal value with less computational time in average. However, using original CE to solve large scale NWJSS requires high computational time. Considering this shortcoming, this paper proposed a hybrid of cross entropy with genetic algorithm (GA), called CEGA, on m-machines NWJSS. The results are compared with other metaheuritics: Genetic Algorithm-Simulated Annealing (GASA) and hybrid tabu search. The results showed that CEGA providing better or at least equal makespans in comparison with the other two methods.展开更多
Aim of this research is to minimize makespan in the flexible job shop environment by the use of genetic algorithms and scheduling rules. Software is developed using genetic algorithms and scheduling rules based on cer...Aim of this research is to minimize makespan in the flexible job shop environment by the use of genetic algorithms and scheduling rules. Software is developed using genetic algorithms and scheduling rules based on certain constraints such as non-preemption of jobs, recirculation, set up times, non-breakdown of machines etc. Purpose of the software is to develop a schedule for flexible job shop environment, which is a special case of job shop scheduling problem. Scheduling algorithm used in the software is verified and tested by using MT10 as benchmark problem, presented in the flexible job shop environment at the end. LEKIN software results are also compared with results of the developed software by the use of MT10 benchmark problem to show that the latter is a practical software and can be used successfully at BIT Training Workshop.展开更多
The rent of shops in commercial complex reflects consumers’ preferences to some extent, and provides references for urban planning and the construction and operation of commercial complex. In this paper, Sea World Co...The rent of shops in commercial complex reflects consumers’ preferences to some extent, and provides references for urban planning and the construction and operation of commercial complex. In this paper, Sea World Commercial Complex in Nanshan District of Shenzhen City is taken as the research object, and correlation and variability analysis on 41 groups of shop data are conducted. It is found that rent of shops in the same commercial complex is affected by location, visibility and area of outdoor stall, while the influence of shop area on rent is not obvious. Additionally, there is no significant correlation between the accessibility to traffic stations and the rent of shops in pedestrian business district.展开更多
A cross-sectional study was conducted from November 2008 to May 2009 to estimate the prevalence of Salmonella in retail meat shops in Kathmandu. The methods followed were ISO 18593：2004 for swab sample collection, IS...A cross-sectional study was conducted from November 2008 to May 2009 to estimate the prevalence of Salmonella in retail meat shops in Kathmandu. The methods followed were ISO 18593：2004 for swab sample collection, ISO 6579：2002 for Salmonella isolation and manufacturer＇s instructions （SIFIN, Germany） for serotype identification. A questionnaire was used to collect information on some of the risk factors of shops likely to be associated with Salmonella identification. A total of 492 environmental swab samples （164 chopping board samples, 164 knife samples and 164 table samples） from 82 retail meat shops were analyzed. The prevalence of Salmonella positive shops was 40.2% （95% CI： 29-51）. The isolation rates of Salmonella from chopping boards （36.0%）, knives （32.9%） and tables （25.0%） were not significantly different （P 〉 0.05）. Retail meat shops were 1.9 times more likely to yield Salmonella in the evening （38.2%） as compared to the morning （24.4%） （P = 0.001）. S. Typhimurium （54.5%） was the most common serotype found in retail meat shops followed by S. Enteritidis （16.9%）, S. Haifa （13.6%）, S. Virchow （10.4%）, S. Agona （3.9%） and S. enterica （0.6%）. Among the risk factors examined, ＂hygiene status of shop＂, ＂type of shops＂, ＂number of person handling meats＂, ＂number of knives used＂, ＂number of kinds of meat sold＂ and ＂number of kinds of meat sold using different numbers of knives＂ were individually significantly （P 〈 0.05） associated with Salmonella contamination in the retail meat shops. After univariate analysis of these risk factors, a final logistic regression model with Salmonella yes or no category of shops as outcome variable identified four significant predictors. Odds ratios, indicating the likelihood increase of a shop to achieve Salmonella positivity status were 10.17 for multiple persons rather than a single person involved, 7.66 for open rather than closed shops, 9.44 for use of several knives rather than one knife and 5.18 for single kind of meat using several knives. The results of this investigation revealed that retail meat shops to a noticeable extent are Salmonella contaminated, with a considerable degree of cross-contamination between meats and personnel and equipment used during a day in processing of meats.展开更多
A modified shifting bottleneck algorithm was proposed to solve scheduling problems of a large-scale job shop.Firstly,a new structured algorithm was employed for sub-problems so as to reduce the computational burden an...A modified shifting bottleneck algorithm was proposed to solve scheduling problems of a large-scale job shop.Firstly,a new structured algorithm was employed for sub-problems so as to reduce the computational burden and suit for large-scale instances more effectively.The modified cycle avoidance method,incorporating with the disjunctive graph model and topological sort algorithm,was applied to guaranteeing the feasibility of solutions with considering delayed precedence constraints.Finally,simulation experiments were carried out to verify the feasibility and effectiveness of the modified method.The results demonstrate that the proposed algorithm can solve the large-scale job shop scheduling problems(JSSPs) within a reasonable period of time and obtaining satisfactory solutions simultaneously.展开更多
Do you enjoy art?Maybe you like to draw or color.If you want to do those things,you need supplies.You can go to an art store to buy them.You can buy colored pencils,markers or crayons.You can buy paper to draw picture...Do you enjoy art?Maybe you like to draw or color.If you want to do those things,you need supplies.You can go to an art store to buy them.You can buy colored pencils,markers or crayons.You can buy paper to draw pictures on.You can also buy coloring books.If you want to make things out of paper,you can buy colorful paper,too.Are you a painter?You can buy many different kinds of paint at an art store.展开更多
In this paper the scheduling problem to minimize the expected makespan is discussed on two-machine flow shops with random disturbance on job processing times. The problem is represented by a stochastic programming mod...In this paper the scheduling problem to minimize the expected makespan is discussed on two-machine flow shops with random disturbance on job processing times. The problem is represented by a stochastic programming model. We approximate the stochastic problem by a deterministic problem which can be solved by Johnson's rule. The estimation of approximation error is also discussed by analyzing the stochastic model and its approximate LP model.展开更多
Duty-free shops play a very important role in tourism. In particular, overseas tourist souvenirs are related to the export of domestic products. Foreign tourists' spending on souvenirs is equivalent to buying fore...Duty-free shops play a very important role in tourism. In particular, overseas tourist souvenirs are related to the export of domestic products. Foreign tourists' spending on souvenirs is equivalent to buying foreign currency, so it directly affects the national economy. Duty-free shops are a kind of tourist destination where purchases take place. The products sold cannot flow into the home economy at duty-free prices, so they are treated as exports. This increases the acquisition of foreign currency and helps to improve the balance of payments, thus creating a higher value added than exports, whose importance lies in creation.展开更多
She clambers up a rock, reaches both hands onto comers of the shabby cement wall and heaves herself up, being careful not to catch her school bag on the protruding bricks. She straddles the top and then jumps gingerly...She clambers up a rock, reaches both hands onto comers of the shabby cement wall and heaves herself up, being careful not to catch her school bag on the protruding bricks. She straddles the top and then jumps gingerly down onto the pebbled ground beside the railway line.展开更多
As one of the most classical scheduling problems,flexible job shop scheduling problems(FJSP)find widespread applications in modern intelligent manufacturing systems.However,the majority of meta-heuristic methods for s...As one of the most classical scheduling problems,flexible job shop scheduling problems(FJSP)find widespread applications in modern intelligent manufacturing systems.However,the majority of meta-heuristic methods for solving FJSP in the literature are population-based evolutionary algorithms,which are complex and time-consuming.In this paper,we propose a fast effective singlesolution based local search algorithm with an innovative adaptive weighting-based local search(AWLS)technique for solving FJSP.The adaptive weighting technique assigns weights to each operation and adaptively updates them during the exploration.AWLS integrates a Tabu Search strategy and the adaptive weighting technique to smooth the landscape of the search space and enhance the exploration diversity.Computational experiments on 313 well-known benchmark instances demonstrate that AWLS is highly competitive with state-of-the-art algorithms in terms of both solution quality and computational efficiency,despite of its simplicity.Specifically,AWLS improves the previous best-known results in the literature on 33 instances and match the best-known results on the remaining ones except for only one under the same time limit of up to 300 s.As a strongly non-deterministic polynomia(NP)-hard problem which has been extensively studied for nearly half a century,breaking the records on these classic instances is an arduous task.Nevertheless,AWLS establishes new records on 8 challenging instances whose previous best records were established by a state-of-the-art meta-heuristic algorithm and a famous industrial solver.展开更多
The distributed permutation flow shop scheduling problem(DPFSP)has received increasing attention in recent years.The iterated greedy algorithm(IGA)serves as a powerful optimizer for addressing such a problem because o...The distributed permutation flow shop scheduling problem(DPFSP)has received increasing attention in recent years.The iterated greedy algorithm(IGA)serves as a powerful optimizer for addressing such a problem because of its straightforward,single-solution evolution framework.However,a potential draw-back of IGA is the lack of utilization of historical information,which could lead to an imbalance between exploration and exploitation,especially in large-scale DPFSPs.As a consequence,this paper develops an IGA with memory and learning mechanisms(MLIGA)to efficiently solve the DPFSP targeted at the mini-malmakespan.InMLIGA,we incorporate a memory mechanism to make a more informed selection of the initial solution at each stage of the search,by extending,reconstructing,and reinforcing the information from previous solutions.In addition,we design a twolayer cooperative reinforcement learning approach to intelligently determine the key parameters of IGA and the operations of the memory mechanism.Meanwhile,to ensure that the experience generated by each perturbation operator is fully learned and to reduce the prior parameters of MLIGA,a probability curve-based acceptance criterion is proposed by combining a cube root function with custom rules.At last,a discrete adaptive learning rate is employed to enhance the stability of the memory and learningmechanisms.Complete ablation experiments are utilized to verify the effectiveness of the memory mechanism,and the results show that this mechanism is capable of improving the performance of IGA to a large extent.Furthermore,through comparative experiments involving MLIGA and five state-of-the-art algorithms on 720 benchmarks,we have discovered that MLI-GA demonstrates significant potential for solving large-scale DPFSPs.This indicates that MLIGA is well-suited for real-world distributed flow shop scheduling.展开更多
文摘1 On a Sunday morning,Zheng Shiying drove 130 kilometers to a village on the outskirts of Beijing,not for a hike or a hot spring,but for a cup of coffee.Housed in an old stone building that looks untouched by time,by the time Zheng arrived,the caféwas already packed with weekend visitors,and finding a seat was a bit of a challenge.
基金supported by the National Key Research and Development Program Project(No.2021YFB3301300).
文摘Intelligent production is an important development direction in intelligent manufacturing,with intelligent factories playing a crucial role in promoting intelligent production.Flexible job shops,as the main form of intelligent factories,constantly face dynamic disturbances during the production process,including machine failures and urgent orders.This paper discusses the basic models and research methods of job shop scheduling,emphasizing the important role of dynamic job shop scheduling and its response schemes in future research.A multi-objective flexible job shop dynamic scheduling mathematical model is established,highlighting its complex and multi-constraint characteristics under different interferences.A classification discussion is conducted on the dynamic response methods and optimization objectives under machine failures,emergency orders,fuzzy completion times,and mixed dynamic events.The development process of traditional scheduling rules and intelligent methods in dynamic scheduling are also analyzed.Finally,based on the current development status of job shop scheduling and the requirements of intelligent manufacturing,the future development trends of dynamic scheduling in flexible job shops are proposed.
基金funded by National Key Research and Development Program Projects of China under Grant No.2020YFB1713500.
文摘To address the issue that hybrid flow shop production struggles to handle order disturbance events,a dynamic scheduling model was constructed.The model takes minimizing the maximum makespan,delivery time deviation,and scheme deviation degree as the optimization objectives.An adaptive dynamic scheduling strategy based on the degree of order disturbance is proposed.An improved multi-objective Grey Wolf(IMOGWO)optimization algorithm is designed by combining the“job-machine”two-layer encoding strategy,the timing-driven two-stage decoding strategy,the opposition-based learning initialization population strategy,the POX crossover strategy,the dualoperation dynamic mutation strategy,and the variable neighborhood search strategy for problem solving.A variety of test cases with different scales were designed,and ablation experiments were conducted to verify the effectiveness of the improved strategies.The results show that each improved strategy can effectively enhance the performance of the IMOGWO.Additionally,performance analysis was conducted by comparing the proposed algorithm with three mature and classical algorithms.The results demonstrate that the proposed algorithm exhibits superior performance in solving the hybrid flow-shop scheduling problem(HFSP).Case validations were conducted for different types of order disturbance scenarios.The results demonstrate that the proposed adaptive dynamic scheduling strategy and the IMOGWO algorithm can effectively address order disturbance events.They enable rapid response to order disturbance while ensuring the stability of the production system.
基金Supported by the Tigray Regional National State,Science and Technology Agency(Grant No.TSTA/08/2010)
文摘Objective:To assess the food safety knowledge and practices in meat handling,and to determine microbial load and pathogenic organisms in meat at Mekelle city.Methods:A descriptive survey design was used to answer questions concerning the current status of food hygiene and sanitation practiced in the abattoir and butcher shops.Workers from the abattoir and butcher shops were interviewed through a structured questionnaire to assess their food safety knowledge.Bacterial load was assessed by serial dilution method and the major bacterial pathogens were isolated by using standard procedures.Results:15.1%of the abattoir workers had no health certificate and there was no hot water,sterilizer and cooling facility in the abattoir.11.3%of the butchers didn’t use protective clothes.There was a food safety knowledge gap within the abattoir and butcher shop workers.The mean values of bacterial load of abattoir meat,butcher shops and street meat sale was found to be 1.1×10~5,5.6×10~5and 4.3×10~6 cfu/g,respectively.The major bacterial pathogens isolated were Escherichia coli,Staphylococcus aureus and Bacillus cereus.Conclusions:The study revealed that there is a reasonable gap on food safely knowledge by abattoir and butcher shop workers.The microbial profile was also higher compared to standards set by World Health Organization.Due attention should be given by the government to improve the food safety knowledge and the quality standard of meat sold in the city.
文摘No-wait job-shop scheduling (NWJSS) problem is one of the classical scheduling problems that exist on many kinds of industry with no-wait constraint, such as metal working, plastic, chemical, and food industries. Several methods have been proposed to solve this problem, both exact (i.e. integer programming) and metaheuristic methods. Cross entropy (CE), as a new metaheuristic, can be an alternative method to solve NWJSS problem. This method has been used in combinatorial optimization, as well as multi-external optimization and rare-event simulation. On these problems, CE implementation results an optimal value with less computational time in average. However, using original CE to solve large scale NWJSS requires high computational time. Considering this shortcoming, this paper proposed a hybrid of cross entropy with genetic algorithm (GA), called CEGA, on m-machines NWJSS. The results are compared with other metaheuritics: Genetic Algorithm-Simulated Annealing (GASA) and hybrid tabu search. The results showed that CEGA providing better or at least equal makespans in comparison with the other two methods.
文摘Aim of this research is to minimize makespan in the flexible job shop environment by the use of genetic algorithms and scheduling rules. Software is developed using genetic algorithms and scheduling rules based on certain constraints such as non-preemption of jobs, recirculation, set up times, non-breakdown of machines etc. Purpose of the software is to develop a schedule for flexible job shop environment, which is a special case of job shop scheduling problem. Scheduling algorithm used in the software is verified and tested by using MT10 as benchmark problem, presented in the flexible job shop environment at the end. LEKIN software results are also compared with results of the developed software by the use of MT10 benchmark problem to show that the latter is a practical software and can be used successfully at BIT Training Workshop.
文摘The rent of shops in commercial complex reflects consumers’ preferences to some extent, and provides references for urban planning and the construction and operation of commercial complex. In this paper, Sea World Commercial Complex in Nanshan District of Shenzhen City is taken as the research object, and correlation and variability analysis on 41 groups of shop data are conducted. It is found that rent of shops in the same commercial complex is affected by location, visibility and area of outdoor stall, while the influence of shop area on rent is not obvious. Additionally, there is no significant correlation between the accessibility to traffic stations and the rent of shops in pedestrian business district.
文摘A cross-sectional study was conducted from November 2008 to May 2009 to estimate the prevalence of Salmonella in retail meat shops in Kathmandu. The methods followed were ISO 18593：2004 for swab sample collection, ISO 6579：2002 for Salmonella isolation and manufacturer＇s instructions （SIFIN, Germany） for serotype identification. A questionnaire was used to collect information on some of the risk factors of shops likely to be associated with Salmonella identification. A total of 492 environmental swab samples （164 chopping board samples, 164 knife samples and 164 table samples） from 82 retail meat shops were analyzed. The prevalence of Salmonella positive shops was 40.2% （95% CI： 29-51）. The isolation rates of Salmonella from chopping boards （36.0%）, knives （32.9%） and tables （25.0%） were not significantly different （P 〉 0.05）. Retail meat shops were 1.9 times more likely to yield Salmonella in the evening （38.2%） as compared to the morning （24.4%） （P = 0.001）. S. Typhimurium （54.5%） was the most common serotype found in retail meat shops followed by S. Enteritidis （16.9%）, S. Haifa （13.6%）, S. Virchow （10.4%）, S. Agona （3.9%） and S. enterica （0.6%）. Among the risk factors examined, ＂hygiene status of shop＂, ＂type of shops＂, ＂number of person handling meats＂, ＂number of knives used＂, ＂number of kinds of meat sold＂ and ＂number of kinds of meat sold using different numbers of knives＂ were individually significantly （P 〈 0.05） associated with Salmonella contamination in the retail meat shops. After univariate analysis of these risk factors, a final logistic regression model with Salmonella yes or no category of shops as outcome variable identified four significant predictors. Odds ratios, indicating the likelihood increase of a shop to achieve Salmonella positivity status were 10.17 for multiple persons rather than a single person involved, 7.66 for open rather than closed shops, 9.44 for use of several knives rather than one knife and 5.18 for single kind of meat using several knives. The results of this investigation revealed that retail meat shops to a noticeable extent are Salmonella contaminated, with a considerable degree of cross-contamination between meats and personnel and equipment used during a day in processing of meats.
基金National Natural Science Foundations of China(Nos.71471135,61273035)
文摘A modified shifting bottleneck algorithm was proposed to solve scheduling problems of a large-scale job shop.Firstly,a new structured algorithm was employed for sub-problems so as to reduce the computational burden and suit for large-scale instances more effectively.The modified cycle avoidance method,incorporating with the disjunctive graph model and topological sort algorithm,was applied to guaranteeing the feasibility of solutions with considering delayed precedence constraints.Finally,simulation experiments were carried out to verify the feasibility and effectiveness of the modified method.The results demonstrate that the proposed algorithm can solve the large-scale job shop scheduling problems(JSSPs) within a reasonable period of time and obtaining satisfactory solutions simultaneously.
文摘Do you enjoy art?Maybe you like to draw or color.If you want to do those things,you need supplies.You can go to an art store to buy them.You can buy colored pencils,markers or crayons.You can buy paper to draw pictures on.You can also buy coloring books.If you want to make things out of paper,you can buy colorful paper,too.Are you a painter?You can buy many different kinds of paint at an art store.
文摘In this paper the scheduling problem to minimize the expected makespan is discussed on two-machine flow shops with random disturbance on job processing times. The problem is represented by a stochastic programming model. We approximate the stochastic problem by a deterministic problem which can be solved by Johnson's rule. The estimation of approximation error is also discussed by analyzing the stochastic model and its approximate LP model.
文摘Duty-free shops play a very important role in tourism. In particular, overseas tourist souvenirs are related to the export of domestic products. Foreign tourists' spending on souvenirs is equivalent to buying foreign currency, so it directly affects the national economy. Duty-free shops are a kind of tourist destination where purchases take place. The products sold cannot flow into the home economy at duty-free prices, so they are treated as exports. This increases the acquisition of foreign currency and helps to improve the balance of payments, thus creating a higher value added than exports, whose importance lies in creation.
文摘She clambers up a rock, reaches both hands onto comers of the shabby cement wall and heaves herself up, being careful not to catch her school bag on the protruding bricks. She straddles the top and then jumps gingerly down onto the pebbled ground beside the railway line.
基金supported in part by the National Natural Science Foundation of China(NSFC)(62202192 and 72101094)the National Science Fund for Distinguished Young Scholars of China(51825502).
文摘As one of the most classical scheduling problems,flexible job shop scheduling problems(FJSP)find widespread applications in modern intelligent manufacturing systems.However,the majority of meta-heuristic methods for solving FJSP in the literature are population-based evolutionary algorithms,which are complex and time-consuming.In this paper,we propose a fast effective singlesolution based local search algorithm with an innovative adaptive weighting-based local search(AWLS)technique for solving FJSP.The adaptive weighting technique assigns weights to each operation and adaptively updates them during the exploration.AWLS integrates a Tabu Search strategy and the adaptive weighting technique to smooth the landscape of the search space and enhance the exploration diversity.Computational experiments on 313 well-known benchmark instances demonstrate that AWLS is highly competitive with state-of-the-art algorithms in terms of both solution quality and computational efficiency,despite of its simplicity.Specifically,AWLS improves the previous best-known results in the literature on 33 instances and match the best-known results on the remaining ones except for only one under the same time limit of up to 300 s.As a strongly non-deterministic polynomia(NP)-hard problem which has been extensively studied for nearly half a century,breaking the records on these classic instances is an arduous task.Nevertheless,AWLS establishes new records on 8 challenging instances whose previous best records were established by a state-of-the-art meta-heuristic algorithm and a famous industrial solver.
基金supported in part by the National Key Research and Development Program of China under Grant No.2021YFF0901300in part by the National Natural Science Foundation of China under Grant Nos.62173076 and 72271048.
文摘The distributed permutation flow shop scheduling problem(DPFSP)has received increasing attention in recent years.The iterated greedy algorithm(IGA)serves as a powerful optimizer for addressing such a problem because of its straightforward,single-solution evolution framework.However,a potential draw-back of IGA is the lack of utilization of historical information,which could lead to an imbalance between exploration and exploitation,especially in large-scale DPFSPs.As a consequence,this paper develops an IGA with memory and learning mechanisms(MLIGA)to efficiently solve the DPFSP targeted at the mini-malmakespan.InMLIGA,we incorporate a memory mechanism to make a more informed selection of the initial solution at each stage of the search,by extending,reconstructing,and reinforcing the information from previous solutions.In addition,we design a twolayer cooperative reinforcement learning approach to intelligently determine the key parameters of IGA and the operations of the memory mechanism.Meanwhile,to ensure that the experience generated by each perturbation operator is fully learned and to reduce the prior parameters of MLIGA,a probability curve-based acceptance criterion is proposed by combining a cube root function with custom rules.At last,a discrete adaptive learning rate is employed to enhance the stability of the memory and learningmechanisms.Complete ablation experiments are utilized to verify the effectiveness of the memory mechanism,and the results show that this mechanism is capable of improving the performance of IGA to a large extent.Furthermore,through comparative experiments involving MLIGA and five state-of-the-art algorithms on 720 benchmarks,we have discovered that MLI-GA demonstrates significant potential for solving large-scale DPFSPs.This indicates that MLIGA is well-suited for real-world distributed flow shop scheduling.
