Inventory models comparative analysis

Este trabalho é um estudo do problema de escolha entre modelos de estoque para a gestão de itens independentes em local único. Quatro modelos de estoque são considerados, sendo três deles reativos, que não utilizam previsão de demanda para a tomada de decisões, e um ativo, que decide com base em previsões. A medida de desempenho considerada é o custo de operação médio por período, que é obtida através de simulação da utilização dos modelos com base num histórico de vendas. O trabalho analisa o efeito da alteração de previsibilidade e da consideração de quantidades mínimas de compra no modelo ativo no desempenho relativo dos modelos analisados. A análise utiliza um modelo de busca acoplado a um simulador. O trabalho apresenta subsídios para a escolha e parametrização de modelos de estoque em empresas.This paper is an approach of the inventory models selection problem in single echelon system management with independent items. Four inventory models are considered, three reactive, which don't use demand forecasting for decision making, and one active model, that decides based on forecasting. Average operation cost per period is the performance measurement variable considered, calculated by using simulation of the models applied on sales temporal series. The paper analyses the effects, in the relative models performance, of the demand forecast accuracy and the use of minimum acquisition quantity in the active model. The analysis uses a search model jointly a simulator to optimize the parameters. The results present useful information for models selection and parameters determination in organizations environment

Modelo matemático e algoritmo de apoio para auxílio ao sequenciamento e à programação de lavra com alocação de equipamentos de carga

This paper focuses on the sequencing and scheduling problem of open pit mining,\ud with the allocation of loading equipment considering a medium-term horizon.\ud This study considers the existence of a heterogeneous loading equipment fleet and two\ud types of mineable material, namely ore or waste rock. For the mining of ore, the following\ud requirements are taken under consideration: the mixture quality, a crusher, the\ud processing plant capacity and a stockpile, called ROM stockpile. In this context, we\ud present a mathematical model in mixed integer linear programming, supported by an\ud algorithm that is responsible for moving the time horizon at each model run, aiming\ud to generate mining orders resolved with optimality. Together, these orders describe the\ud loading equipment mining plan.Esse trabalho tem seu foco no problema de sequenciamento e programação da\ud lavra em mina a céu aberto com a alocação de equipamentos de carregamento, considerando\ud um período de médio prazo. Nesse estudo, considera-se a existência de uma\ud frota heterogênea de equipamentos de carga e de dois tipos de materiais lavráveis,\ud sendo minério ou estéril. Para a lavra de minério, são contemplados requisitos de\ud qualidade da mistura, um britador, capacidade da usina de beneficiamento e uma pilha\ud de estoque, denominada pilha de ROM. Nesse contexto, apresenta-se um modelo\ud matemático em programação linear inteira mista, apoiado por um algoritmo responsável\ud por mover o horizonte de tempo, a cada execução do modelo, com intuito de\ud gerar ordens de lavra resolvidas com otimalidade. Juntas, essas ordens descreverão o\ud plano de lavra dos equipamentos de carga

The Effect of the Workload on Due Date Performance in Job Shop Scheduling

This paper provides a simulation model to study the effect of the work-in-process control on due date performance in job shop environment. The due date performance is measured by both the number of tardy jobs and the total tardiness. The simulation runs include different shop configurations (flow shop and general job shop), workloads and sequencing rules. As expected, the results reveal that due date performance is highly dependent on the work-in-process, particularly after the system reaches saturation. Nevertheless, the model is very useful to show job shop managers the effect of the work-in-process control in the due date meeting performance

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Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Effect of negative parameters in inventory models performance

This paper presents a comparative study of four inventory models. Three of them are reactive ones, the Order Up to Maximum Inventory Level, base Stock and Fixed Lot Size models which don’t use demand forecasting to quantify the acquisition decisions. One of them, referred as Requirement Planning, operates using demand forecast . The Requirement Planning and Base Stock models operate with minimal purchase order quantity parameter to improve their competitiveness.\ud Reorder Level and Safety Stock parameters are permitted to be negative. Average operation coast per period is the performance measurement considered, restricted to a minimum service level. The analysis uses a search model jointly a simulator to optimize the parameters. The paper analyses the effects, in the relative models performance, of the Purchase Cost and effectuates a sensibility analysis by testing four different Service Levels[org. within the] International Mediterranean and Latin American Modeling Multiconference, 5. 200

Avaliação do grau de prioridade e do foco do Planejamento e Controle da Produção (PCP): modelos e estudos de casos Assessment of the priority and focus of Production Planning and Control (PPC): models and case studies

Neste artigo propomos um modelo que sugere qual o grau de prioridade que a empresa deve dar à sua função Planejamento e Controle da Produção (PCP) e outro que sugere qual o foco decisório que deve ter o PCP [foco em planejamento, foco em programação ou foco em ambos (planejamento e programação)]. Ambos os modelos são validados por meio de estudos de casos em 10 importantes empresas industriais brasileiras.Two models are proposed in this paper: the first suggests the degree of priority a company should give to Production Planning and Control (PPC), while the second suggests the decision-making focus PPC should concentrate on, i.e., planning, scheduling, or both planning and scheduling. The two models are validated through case studies of ten major Brazilian manufacturers

Two-stage tactical planning model for the meat processing industry with divergent production flow

This work presents a two-stage production planning model for the meat processing industry in a divergent production flow with co-production. Besides the decisions about the production, inventory and workforce level at the processing plant, the model also has to take into consideration the decisions regarding livestock production flow and weight ranges in which animals have to be slaughtered. A vertically integrated medium size pork processor is studied in this work. The main challenge in planning is to deal with the divergent flow in attending the demand for the derived pork products with the available raw material (live hogs in diverse weight ranges) at each period and, at the same time, avoid overproduction of low demand products which ends up increasing inventory levels. A mixed integer programming model with a pattern generation program was developed and implemented in a solver and then applied to the company with consistent preliminary result