第1页共7页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第1页共7页Schedulingofmanufacturingsystemsunderdual-resourceconstraintsusinggeneticalgorithmsOriginalResearchArticleJournalofManufacturingSystemsSchedulingbelongstothespecialclassofNP-hardproblemsforwhichnopolynomialtimealgorithmhasbeenfound.Therefore,aschedulethatisthebestpossiblenear-optimalsolutionisoftenacceptable.Thispaperpresentsaschedulingapproach,basedonGeneticAlgorithms(GAs),developedtoaddresstheschedulingprobleminmanufacturingsystemsconstrainedbybothmachinesandworkers.Thisgeneticalgorithmutilizesanewchromosomerepresentation,whichtakesintoaccountmachineandworkerassignmentstojobs.Asetofexperimentsfordeterminingthebeststaffinglevelandmachineandworkerassignmenttojobswasperformed.Astudywasconductedusingdispatchingruleswithvariousperformancemeasuresfortwotypesofshopcharacteristics:(i)dual-resource(machinesandworkers)constrained,and(ii)single-resourceconstrained(machinesonly).Anexampleisusedforillustrationandcomparison.Theresultingschedulingmethodologyiscapableofdeterminingthebeststaffinglevelanddispatchingrulesforthechosenperformancemeasureinbothsingleanddual-resourceconstrainedshops.Decisionstoadopttheprescribedstaffingstrategytoimprovetheprimaryperformancemeasuressuchasmeanflowtime,meantardiness,andmeanwaitingtimemustbebalancedbymanagersagainstthepotentialincreaseindirectcost.Thedevelopedschedulingapproachandformulationprovedtobeveryusefulforoptimizingproductionperformanceundertherealisticconditionsimposedbybothmachineandworkeravailabilityconstraints.Suchatoolshouldbeusedtodefineapriorithebestdispatchingrulesandschedulesforagivensetofproductionrequirementsandobjectives.MicrobialcontaminationoffoodrefrigerationequipmentOriginalResearchArticleJournalofFoodEngineeringRefrigerationsystemsinchilledroomsin15plantsprocessingavarietyoffoodswerestudied.Theseincludedplantsprocessingrawmeatandsalads,Chinesereadymeals,dairyproducts,slicingandpackingofcookedmeatsandcateringestablishments.Aninitialsurveyoftotalnumbersofmicrobesatatotalof891sitesonevaporators,driptraysandchilledroomwallswasfollowedupwithamoredetailedexaminationof336siteswithhighcounts,selectingforListeriaspp.,coliforms,enterococci,StaphylococcusaureusandBacilluscereus.Temperatures(particularlyaironandairoff,maximumandneardefrostheaters)relativehumidity,airflow,layoutandcleaningregimesweresurveyed.Ingeneral,nocorrelationcouldbefoundbetweenanyofthephysicalmeasurementsandthenumbersandtypesofbacteriadetected.Maximummeantemperaturesinthechilledroomsvariedfrom−1to+16.9°Candfewchilledunitswereregularlycleaned.Twentyfivepercentofsitesexaminedhadmorethan105colony-formingunitspercm2,although,veryfewpathogensorfaecalindicatorbacteriawere第2页共7页第1页共7页编号：时间：2021年x月x日书山有路勤为径，学海无涯苦作舟页码：第2页共7页detected.Listeriaspp.werenotfoundandcoliformswerefoundonlyonce,inlownumbers.LownumbersofS.aureusorB.cereuswerepresentin9ofthe15plants,B.cereuswasfoundonevaporatorsandassociateddriptraysintwocateringplantsandtwoplantsprocessingcookedmeat.EnterococciandS.aureuswerefoundmostfrequentlyinarawredmeatslaughterhouse(alwaysinlownumbers).Ingeneral,microbialcontaminationwaslowerinroomswherewrappedratherthanunwrappedproductswerestored.Thetypeofproductalsoaffectedthedegreeofcontamination,withrawredmeatandpoultryordryingredientsgivinghighestcoun...
