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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,veryfewpathogensorfaecalindicatorbacteriaweredetected.Listeriaspp.werenotfoundandcoliformswerefoundonlyonce,inlownumbers.LownumbersofS.aureusorB.cereuswerepresentin9ofthe15plants,B.cereuswasfoundonevaporatorsandassociateddriptraysintwocateringplantsandtwoplantsprocessingcookedmeat.EnterococciandS.aureuswerefoundmostfrequentlyinarawredmeatslaughterhouse(alwaysinlownumbers).Ingeneral,microbialcontaminationwaslowerinroomswherewrappedratherthanunwrappedproductswerestored.Thetypeofproductalsoaffectedthedegreeofcontamination,withrawredmeatandpoultryordryingredientsgivinghighestcounts,andrawvegetablesandcookedproductslowest.Theworkdemonstratedthatbacteriawerepresentonevaporatorcoolingcoilsinallfactorycoldroomsvisited.Althoughevaporator-cleaningprocedureswerecarriedoutinsomefactoriesaspartofroutinemaintenancethesewerenotshowntobeeffectiveatmaintaininglowlevelsofbacteriaonevaporators.Tomaintainevaporatorhygieneitissuggestedthatmoreregularcleaningprocedures,possiblybymeansofautomatedcleansingsystems,shouldbeconsidered.ArticleOutline1.Introduction2.Materialsandmethods2.1.Physicalmeasurements2.2.Microbiologicalsampling3.Results3.1.Totalviablecounts(TVC)3.2.Specificbacteria3.3.Effectoftemperature,relativehumidityandairvelocity3.4.Cleaningprocedures4.DiscussionAcknowledgementsReferencesRDFproductionplants:IDesignandcostsOriginalResearchArticleAppliedThermalEngineeringMunicipalsolidwaste(MSW)managementcallsfortheintegrationofdifferentrecovery,recyclinganddisposaltechnologies.Amongthesepossibleoptions,MSWmaybetreatedinordertoobtainafueltobesoldtothirdpartyusersordirectlyutilizedtogenerateelectricityprovideditisofsufficientqualitytobeemployedinsteadoftraditionalfuels.Inthistwo-partpapertheproblemofproducingrefusederivedfuel(RDF)havingahighheatingvalue(LHV4000kcal/kg)hasbeenexaminedfromatechnicalandeconomicviewpoint.Inthefirstpartarticleatechnicalassessmentofproductionplantsiscarriedout.Differentproductionlineshavebeenthuscomparedintermsofmassefficiency,heatingvalueofproducedRDFandtreatmentcosthighlightinghowthechoiceofprocessequipmentaffectsthesystemperformances.Asaresulttheprocessplantconfigurationsenablingtomeettherequiredproductspecificationsareidentified.Theinfluenceofmixingahighcalorificwastesuchasscraptireswiththestreamofhouseholdwaste,inthelimitsallowedbycurrentregulation,hasbeenalsoanalyzedandfoundtobeaprerequisitetomeettheprescribedheatingvaluetarget.EconomicfeasibilityandfinancialriskofR