Facilitating the analysis of a UK national blood service supply chain using distributed simulation

In an attempt to investigate blood unit ordering policies, researchers have created a discrete-event model of the UK National Blood Service (NBS) supply chain in the Southampton area of the UK. The model has been created using Simul8, a commercial-off-the-shelf discrete-event simulation package (CSP). However, as more hospitals were added to the model, it was discovered that the length of time needed to perform a single simulation severely increased. It has been claimed that distributed simulation, a technique that uses the resources of many computers to execute a simulation model, can reduce simulation runtime. Further, an emerging standardized approach exists that supports distributed simulation with CSPs. These CSP Interoperability (CSPI) standards are compatible with the IEEE 1516 standard The High Level Architecture, the defacto interoperability standard for distributed simulation. To investigate if distributed simulation can reduce the execution time of NBS supply chain simulation, this paper presents experiences of creating a distributed version of the CSP Simul8 according to the CSPI/HLA standards. It shows that the distributed version of the simulation does indeed run faster when the model reaches a certain size. Further, we argue that understanding the relationship of model features is key to performance. This is illustrated by experimentation with two different protocols implementations (using Time Advance Request (TAR) and Next Event Request (NER)). Our contribution is therefore the demonstration that distributed simulation is a useful technique in the timely execution of supply chains of this type and that careful analysis of model features can further increase performance

Advancing Cost-Effective Readiness by Improving the Supply Chain Management of Sparse, Intermittently-Demanded Parts

Many firms generate revenue by successfully operating machines such as welding robots, rental cars, aircraft, hotel rooms, amusement park attractions, etc. It is critical that these revenue-generating machines be operational according to the firm s target or requirement; thus, assuring sustained revenue generation for the firm. Machines can and do fail, and in many cases, restoring the downed machine requires spare part(s), which are typically managed by the supply chain. The scope of this research is on the supply chain management of the very sparse, intermittently-demanded spare parts. These parts are especially difficult to manage because they have little to no lead time demand; thus, modeling via a Poisson process is not viable. The first area of our research develops two new frameworks to improve the supply chain manager s stock policy on these parts. The stock polices are tested via case studies on the A-10C attack aircraft and B1 bomber fleets. Results show the AF could save $10M/year on the A10 and improve support to the B1 without increasing inventory. The second area of our research develops a framework to integrate the supply chain processes that generate these service parts. With the integrated framework, we establish two new forward-looking metrics. We show examples how these forward-looking metrics can advance the supply chain manager s desire to know what proactive decisions to make to improve his/her supply chain for the good of the firm

SURROGATE SEARCH: A SIMULATION OPTIMIZATION METHODOLOGY FOR LARGE-SCALE SYSTEMS

For certain settings in which system performance cannot be evaluated by analytical methods, simulation models are widely utilized. This is especially for complex systems. To try to optimize these models, simulation optimization techniques have been developed. These attempt to identify the system designs and parameters that result in (near) optimal system performance. Although more realistic results can be provided by simulation, the computational time for simulator execution, and consequently, simulation optimization may be very long. Hence, the major challenge in determining improved system designs by incorporating simulation and search methodologies is to develop more efficient simulation optimization heuristics or algorithms. This dissertation develops a new approach, Surrogate Search, to determine near optimal system designs for large-scale simulation problems that contain combinatorial decision variables. First, surrogate objective functions are identified by analyzing simulation results to observe system behavior. Multiple linear regression is utilized to examine simulation results and construct surrogate objective functions. The identified surrogate objective functions, which can be quickly executed, are then utilized as simulator replacements in the search methodologies. For multiple problems containing different settings of the same simulation model, only one surrogate objective function needs to be identified. The development of surrogate objective functions benefits the optimization process by reducing the number of simulation iterations. Surrogate Search approaches are developed for two combinatorial problems, operator assignment and task sequencing, using a large-scale sortation system simulation model. The experimental results demonstrate that Surrogate Search can be applied to such large-scale simulation problems and outperform recognized simulation optimization methodology, Scatter Search (SS). This dissertation provides a systematic methodology to perform simulation optimization for complex operations research problems and contributes to the simulation optimization field

Framework For Cost Modeling A Supply Chain

Researchers are interested in value chain analysis to identify the different opportunities for cost savings. The literature have been narrow in scope and addressed specific problems; however none has addressed the need for a general framework that can be used as a standard template in the supply chain cost management and optimization, though Dekker and Goor (2000) said that the goal was to develop a model that would allow direct comparison of specific activities between firms, such as warehousing activities costs. There was no indication in the literature of a cost model that can identify all costs and cost drivers through the supply chain. Some firms built models to analyze the effect of changes in activities but only with limited activities such as logistics. The purpose of this research is to create a general framework that can express the cost data for the partners of the supply chain in similar terms. The framework will layout the common activities identified within the firm and the relationship of these activities between the partners of the supply chain, and the framework will identify the effect of changes in activities on other partners within the supply chain. Cost information will help in making decisions about pricing, outsourcing, capital expenditures, and operational efficiency. The framework will be able to track cost through the chain, which will improve the flexibility of the supply chain to respond to rapidly changing technology. The framework will help in developing product strategy paradigms that encompass the dynamics of the market, in particular with respect to the technology adoption lifecycle

Yüksek seviyeli mimari (HLA) temelli dağıtık imalat benzetimi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Benzetim, bir karar verme aracı olarak her zaman kullanılagelmiştir. Benzetimin en çok kullanıldığı alanların başında imalat gelmektedir. Ancak geleneksel benzetim teknikleri tek başına karmaşık dağıtık imalat problemlerini modellemeye yetmemektedir. Son yıllarda imalat süreci oldukça karmaşık hale geldiğinden ve çoğu zaman dağıtık ortamlarda gerçekleştirildiğinden dağıtık imalat benzetimi modellerine ihtiyaç duyulmaktadır. Farklı benzetim modellerini bir araya getirerek bilgi alışverişini gerçekleştirecek ortak mimariye olan ihtiyaç, başlangıçta askeri alanlarda ortaya çıkmıştır. Benzer ihtiyac, dağıtık imalat benzetiminde de hissedilmektedir. Böyle bir mimari benzetim modellerinin yeniden kullanılabilirlik ve karşılıklı işleyebilirlik özelliklerine sahip olmasını sağlayabilmelidir. Bununla birlikte, bilgi alışverişinde bulunacak olan benzetim modelleri farklı platformlarda, farklı ticari benzetim paketleriyle veya farklı uygulama yazılımları ile modellenmiş olabilmektedir. HLA, bu tür problemleri çözmekte kullanılabilecek dağıtık benzetim mimarisidir. Amerikan Savunma Bakanlığı tarafından askeri benzetim sistemlerinde kullanılmak üzere 1995'lerden itibaren geliştirilen bu mimari, imalatta ve diğer sivil alanlarda da uygulanmaktadır. 2000 yılında IEEE tarafından 1516 kodu ile dağıtık benzetim standardı olarak kabul edilmesiyle sivil alanlarda kullanımı yaygınlaşmıştır.Bu çalışmada HLA temelli dağıtık imalat benzetimi ele alınmıştır. Dağıtık imalat benzetiminin yararları, HLA'nın imalatta kullanım gerekçesi, HLA temelli dağıtık imalat benzetimi geliştirmek için neler yapılması gerektiği açıklanmıştır. Çeşitli HLA temelli dağıtık imalat tasarım örnekleri verilmiştir. Örnek bir uygulama ile HLA'nın pratik olarak dağıtık imalat benzetiminde nasıl uygulandığı ortaya konulmuştur.Manufacturing is one of the areas where simulation is used more widely as a decision making tool. But traditional simulation techniques are not capable to simulate complex manufacturing systems. Since manufacturing processes became more complex and mostly performed in distributed environments, distributed manufacturing simulation models are needed. So, a common framework is required to integrate and exchange information of different manufacturing simulation models. The framework should have the capability of reusability and interoperability since simulation models could be modeled at different environments with different application programming languages. HLA can meet all of the requirements mentioned above. HLA was developed by American Department of Defense (DoD) since 1995 for military simulations, and after it was accepted as an IEEE standart (No:1516) in year 2000, HLA is being used not only for military simulations but also for civil applications.In this study HLA based distributed manufacturing simulation is examined. The benefits of distributed manufacturing simulation, reasons why HLA is used in manufacturing, what sould be done in order to develop HLA based distributed manufacturing simulation is explained in the study. It will also be put forward how HLA is implemented practically in distributed manufacturing simulation through a given scenario

Modelling an End-to-End Supply Chain System Using Simulation

Supply chains (SCs) are an important part of today’s world. Many businesses operate in the global marketplace where individual companies are no longer treated as separate entities, but as a vital part of an end-to-end supply chain (E2E-SC) system. Key challenges and issues in managing E2E-SCs are duly attributed to their extended, complex and systemic nature. In the era of uncertainty, risks and market volatility, decision makers are searching for modelling techniques to be able to understand, to control, design or evaluate their E2E-SC. This research aims to support academics and decision makers by defining a generic simulation modelling approach that can be used for any E2E-SC. This study considers the challenges and issues associated with modelling complex E2E-SC systems using simulation and underlines the key requirements for modelling an E2E-SC. The systematic literature review approach is applied to provide a twofold theoretical contribution [a] an insightful review of various contributions to knowledge surrounding simulation methods within the literature on end-to-end supply chains and [b] to propose a conceptual framework that suggests generic elements required for modelling such systems using simulation. The research adopts a simulation methodology and develops a generic guide to an E2E-SC simulation model creation process. It is a mindful inquiry into the implications relative to a simulation model development process in presence of generic elements from the proposed conceptual framework. The conceptual framework is validated with industry experts and insightful remarks are drawn. In conclusion, it is acknowledged that modelling an E2E-SC system using simulation is a challenge, and this area is not fully exploited by the business. A guide to an E2E-SC simulation model development is a theoretical and practical contribution of this research, immensely sought by businesses, which are continuously tackling day to day issues and challenges, hence often lacking resources and time to focus on modelling. The conceptual framework captures generic elements of the E2E-SC system; however, it also highlights multiple challenges around simulation model development process such as technical constraints and almost impracticability of a true reflection of an E2E-SC system simulation model. The significant contribution of this thesis is the evaluation of the proposed generic guide to E2E-SC simulate model development, which provides the architecture for better strategic supply and demand balancing as new products, price fluctuations, and options for physical network changes can be dynamically incorporated into the model. The research provides an insightful journey through key challenges and issues when modelling E2E-SC systems and contributes with key recommendations for mindful inquiries into E2E-SC simulation models