Responsible Inventory Models for Operation and Logistics Management

The industrialization and the subsequent economic development occurred in the last century have led industrialized societies to pursue increasingly higher economic and financial goals, laying temporarily aside the safeguard of the environment and the defense of human health. However, over the last decade, modern societies have begun to reconsider the importance of social and environmental issues nearby the economic and financial goals. In the real industrial environment as well as in today research activities, new concepts have been introduced, such as sustainable development (SD), green supply chain and ergonomics of the workplace. The notion of “triple bottom line” (3BL) accounting has become increasingly important in industrial management over the last few years (Norman and MacDonald, 2004). The main idea behind the 3BL paradigm is that companies’ ultimate success should not be measured only by the traditional financial results, but also by their ethical and environmental performances. Social and environmental responsibility is essential because a healthy society cannot be achieved and maintained if the population is in poor health. The increasing interest in sustainable development spurs companies and researchers to treat operations management and logistics decisions as a whole by integrating economic, environmental, and social goals (Bouchery et al., 2012). Because of the wideness of the field under consideration, this Ph.D. thesis focuses on a restricted selection of topics, that is Inventory Management and in particular the Lot Sizing problem. The lot sizing problem is undoubtedly one of the most traditional operations management interests, so much so that the first research about lot sizing has been faced more than one century ago (Harris, 1913). The main objectives of this thesis are listed below: 1) The study and the detailed analysis of the existing literature concerning Inventory Management and Lot Sizing, supporting the management of production and logistics activities. In particular, this thesis aims to highlight the different factors and decision-making approaches behind the existing models in the literature. Moreover, it develops a conceptual framework identifying the associated sub-problems, the decision variables and the sources of sustainable achievement in the logistics decisions. The last part of the literature analysis outlines the requirements for future researches. 2) The development of new computational models supporting the Inventory Management and Sustainable Lot Sizing. As a result, an integrated methodological procedure has been developed by making a complete mathematical modeling of the Sustainable Lot Sizing problem. Such a method has been properly validated with data derived from real cases. 3) Understanding and applying the multi-objective optimization techniques, in order to analyze the economic, environmental and social impacts derived from choices concerning the supply, transport and management of incoming materials to a production system. 4) The analysis of the feasibility and convenience of governmental systems of incentives to promote the reduction of emissions owing to the procurement and storage of purchasing materials. A new method based on the multi-objective theory is presented by applying the models developed and by conducting a sensitivity analysis. This method is able to quantify the effectiveness of carbon reduction incentives on varying the input parameters of the problem. 5) Extending the method developed in the first part of the research for the “Single-buyer” case in a "multi-buyer" optics, by introducing the possibility of Horizontal Cooperation. A kind of cooperation among companies in different stages of the purchasing and transportation of raw materials and components on a global scale is the Haulage Sharing approach which is here taken into consideration in depth. This research was supported by a fruitful collaboration with Prof. Robert W. Grubbström (University of Linkoping, Sweden) and its aim has been from the beginning to make a breakthrough both in the theoretical basis concerning sustainable Lot Sizing, and in the subsequent practical application in today industrial contexts

Grocery omnichannel perishable inventories: performance measures and influencing factors

Purpose- Perishable inventory management for the grocery sector has become more challenging with extended omnichannel activities and emerging consumer expectations. This paper aims to identify and formalize key performance measures of omnichannel perishable inventory management (OCPI) and explore the influence of operational and market-related factors on these measures. Design/methodology/approach- The inductive approach of this research synthesizes three performance measures (product waste, lost sales and freshness) and four influencing factors (channel effect, demand variability, product perishability and shelf life visibility) for OCPI, through industry investigation, expert interviews and a systematic literature review. Treating OCPI as a complex adaptive system and considering its transaction costs, this paper formalizes the OCPI performance measures and their influencing factors in two statements and four propositions, which are then tested through numerical analysis with simulation. Findings- Product waste, lost sales and freshness are identified as distinctive OCPI performance measures, which are influenced by product perishability, shelf life visibility, demand variability and channel effects. The OCPI sensitivity to those influencing factors is diverse, whereas those factors are found to moderate each other's effects. Practical implications- To manage perishables more effectively, with less waste and lost sales for the business and fresher products for the consumer, omnichannel firms need to consider store and online channel requirements and strive to reduce demand variability, extend product shelf life and facilitate item-level shelf life visibility. While flexible logistics capacity and dynamic pricing can mitigate demand variability, the product shelf life extension needs modifications in product design, production, or storage conditions. OCPI executives can also increase the product shelf life visibility through advanced stock monitoring/tracking technologies (e.g. smart tags or more comprehensive barcodes), particularly for the online channel which demands fresher products. Originality/value- This paper provides a novel theoretical view on perishables in omnichannel systems. It specifies the OCPI performance, beyond typical inventory policies for cost minimization, while discussing its sensitivity to operations and market factors

Scholarly Research Trends of State Universities of Gujarat: A bibliometric Study

The paper is describing bibliometric analysis of research publications of six state government universities of Gujarat during the year 2015-2019 indexed in SCOPUS database. The study exploring the various aspects of bibliometric analysis i.e. Number of publications and citation of the universities, the most productive author, the most productive publication source, the most preferred type of publication, the highest cited paper, and authorship pattern of 3825 bibliographic records. Analysis of the study is helpful to understand research output of the universities and which university has to do more effort to promote research activities and need to focus more on research productivity

Modelling and Determining Inventory Decisions for Improved Sustainability in Perishable Food Supply Chains

Since the introduction of sustainable development, industries have witnessed significant sustainability challenges. Literature shows that the food industry is concerned about its need for efficient and effective management practices in dealing with perishability and the requirements for conditioned storage and transport of food products that effect the environment. Hence, the environmental part of sustainability demonstrates its significance in this industrial sector. Despite this, there has been little research into environmentally sustainable inventory management of deteriorating items. This thesis presents mathematical modelling based research for production inventory systems in perishable food supply chains. In this study, multi-objective mixed-integer linear programming models are developed to determine economically and environmentally optimal production and inventory decisions for a two-echelon supply chain. The supply chain consists of single sourcing suppliers for raw materials and a producer who operates under a make-to-stock or make-to-order strategy. The demand facing the producer is non-stationary stochastic in nature and has requirements in terms of service level and the remaining shelf life of the marketed products. Using data from the literature, numerical examples are given in order to test and analyse these models. The computational experiments show that operational adjustments in cases where emission and cost parameters were not strongly correlated with supply chain collaboration (where suppliers and a producer operate under centralised control), emissions are effectively reduced without a significant increase in cost. The findings show that assigning a high disposal cost, limit or high weight of importance to perished goods leads to appropriate reduction of expected waste in the supply chain with no major cost increase. The research has made contributions to the literature on sustainable production and inventory management; providing formal models that can be used as an aid to understanding and as a tool for planning and improving sustainable production and inventory control in supply chains involving deteriorating items, in particular with perishable food supply chains.the Ministry of Science and Technology, the Royal Thai Government

Stok kontrolü ve ekonomik sipariş miktarı modellerinde yeni açılımlar: ödemelerde gecikmeye izin verilmesi durumu ve bir model önerisi

Stok kontrol modelleri, talebin kesin olarak bilinip bilinememesine göre deterministik ve olasılıklı modeller olarak ikiye ayrılmaktadır. Deterministik stok kontrol modelleri arasında en yaygın kullanılan modeller Klasik Ekonomik Sipariş ve Üretim Miktarı Modelleridir. Bu modellerde ele alınan varsayımların çoğu, gerçek hayatta geçerli olabilen değişik durumları veya içinde bulunulan ekonomik koşulları dikkate almamaktadır. Dolayısıyla, sözü edilen varsayımların gevşetilmesi veya ek yeni varsayımlar yardımıyla, gerçek yaşamla daha tutarlı ve geçerli ekonomik koşulları dikkate alan yeni modeller üretilmiştir. Örneğin, stoksuzluk, öğrenme, enflasyon ve paranın zaman değeri etkileri, stoktaki ürünlerin zamanla bozulması, kusurlu ürün, ödemelerde gecikmeye izin verilmesi gibi yeni açılımlar, bu alanda geniş bir çalışma yelpazesi oluşmasını sağlamıştır. Bu çalışmada, klasik ekonomik sipariş miktarı modellerinde geçerli olan varsayımlardan bazıları gevşetilerek gelen siparişlerin belli bir oranda kusurlu ürün içerdiği, stoksuzluğa ve ödemelerde belli bir süre gecikmeye izin verildiği durum için yeni bir ekonomik sipariş miktarı modeli elde edilmektedir. Modelde, ödemelerde izin verilen gecikme süresinin iki farklı durumu için optimal değerler ile izin verilen gecikme süresi ve kusurlu ürün oranı arasındaki ilişkiler belirlenmektedir. Ayrıca, geliştirilen model için sayısal örnekler verilmekte ve izin verilen gecikme süresi ve kusurlu ürün oranındaki değişimlerin etkileri duyarlılık analizi ile incelenmektedir. Yapılan analizler sonucu ödemelerde izin verilen gecikme süresi arttıkça sipariş miktarının azaldığı toplam karın ise azaldığı görülmektedir. Anahtar Kelimeler: Ekonomik Sipariş Miktarı, Kusurlu Ürün, Ödemelerde Gecikmeye İzin Verilmesi, Stoksuzluk.\ud Inventory control models are classified as deterministic and stochastic models upon the condition that the demand is definitely known, or not. Economic Order and Production Quantity models are among the most widely used techniques in deterministic inventory control models. As a result of many unrealistic assumptions embedded in these models, some real life situations and current economic circumstances are not considered. Therefore, by loosening these assumptions and introducing some extra hypotheses, many new models consistent with real life and consider current economic conditions were developed. A vast literature has occurred under these conditions which are known as new approaches such as shortage, effect of learning, inflation and time value of money, deterioration, defective items and permissible delay in payment. In this study, a new model is proposed in the case of defective items, permissible delay in payments and shortage by loosening some of the assumptions of classical Economic Order Quantity models. For two case of permissible delay in payments, the relationships between permissible delay time, rate of defective item and optimal values are determined. Furthermore, numerical examples are given and analyzed for the developed model. Changes in the optimal values with respect to the rate of defective item and permissible delay in payments are analyzed with sensitivity analysis. Result of the analysis show that while permissible delay of payment increases order quantity decreases and total profit increases. However when rate of defective items increases order quantity increases and total profit decreases. Keywords: Economic Order Quantity, Defective Items, Permissible Delay in Payments, Shortag