Nirupam Julka

Distributed Supply Chain Simulation as a Decision Support Tool for the Semiconductor Industry

The need for better understanding, control, and optimization of supply chains is being recognized more than ever in the new economy. Simulation holds a great potential in portraying the dynamic evolution of supply chains and providing appropriate decision support to address challenges arising from high variability and stochastic uncertainty. Realizing high-fidelity supply chain simulation will require integration of individual supply chain component simulation models and planning systems, shielding to prevent sensitive data from being shared indiscriminately, and even the geographical distribution of the supply chain component models. The authors discuss various conceptual and technical issues that have been successfully addressed to realize a prototype of distributed semiconductor supply chain simulation as well as implementation approaches that can be pursued. The prototype emulates a semiconductor supply chain consisting of two wafer fabs, an assembly and test facility, a distribution center, a warehouse, a supply chain planning module, a logistics provider, and customers.

An integrated and adaptive decision-support framework for high-tech manufacturing and service networks

This article gives an update on a major international collaborative project under the integrated manufacturing and service systems initiative pursued by the Agency for Science, Technology and Research in Singapore. The objective of the project is to investigate how design, analysis, enhancement and implementation of critical business processes in a manufacturing and service network can be realized using one single simulation/application framework. The overall architecture of the framework outlines how commercial simulation packages and web service-based business process application components can be connected through a commercial application framework to achieve maximum leverage and re-usability of the application components involved. The project also addresses research issues with regard to mechanisms for interoperation between commercial simulation packages, symbiotic interaction between simulation-based decision support components and physical systems, and simulation speed-up through multi-objective optimal computing budget allocation techniques on a grid/cluster infrastructure.

Making use of prognostics health management information for aerospace spare components logistics network optimisation

Although research has evolved significantly over the last decade, there are still a large number of Grand Challenges confronting modelling, model deployment, and model-based decision making of large-scale complex Discrete Event Logistics Systems (DELS) to be tackled, as identified and reviewed during a Dagstuhl workshop in March 2010. This paper illustrates how several of these challenges are already being addressed, based on a series of case studies from the Aerospace Spare Components Logistics domain, where consolidated operational Prognostics and Health Management (PHM) information can be used for tactical planning and optimisation of spare components logistics networks. In this setting, the growing potential of PHM technology to facilitate the maintenance and support of commercial and military aircraft emphasises the need for tools to determine the impacts and benefits of a PHM system. To achieve this, the prognostics parameters and related logistics policies were identified, modelled, and subsequently incorporated into a simulation-based decision support framework.

Alternative Solutions for Distributed Simulation Cloning

Simulation cloning is designed to satisfy the requirement of examining alternative scenarios concurrently. This article discusses the issues involved in cloning distributed simulations based on the High Level Architecture (HLA) and proposes tentative solutions. Alternative solutions are compared from both the qualitative and quantitative point of view. In terms of federation organization, candidate solutions can be classified into the single-federation and the multiple-federation categories. To guarantee the correctness and optimize the performance of the whole cloning-enabled distributed simulation, the single-federation solution requires an additional mechanism to isolate the interactions among alternative executions. Data distribution management (DDM) is one of the candidate approaches. To measure the trade-off between complexity and efficiency, the authors introduce a series of experiments to benchmark various solutions at the runtime infrastructure (RTI) level. The benchmark results indicate that the single-federation solution provides encouraging performance when using DDM.

Evaluating alternative solutions for cloning in distributed simulation

Simulation cloning is designed to satisfy the requirement of examining alternative scenarios concurrently. This paper discusses the issues involved in cloning distributed simulations based on the high-level architecture (HLA) as well as proposing tentative solutions. Alternative solutions are compared from both the qualitative and quantitative point of view. In terms of federation organization, candidate solutions can be classified into the single-federation and the multiple-federation categories. In order to guarantee the correctness and optimize the performance of the whole cloning-enabled distributed simulation, the single-federation solution requires an additional mechanism to isolate the interactions amongst alternative executions. Data distribution management (DDM) is one of the candidate approaches. To measure the trade-off between complexity and efficiency, we introduce a series of experiments to benchmark various solutions at the RTI level. The benchmark results indicate that the single-federation solution provides encouraging performance when using DDM.

Unlocking value from component exchange contracts in aviation using simulation-based optimisation

Motivated by the entry into service of new aircraft such as the Airbus A380 as well as the pressure to operate existing fleets at lower cost, not only in civil but also in military aviation, a new industry paradigm has emerged where MRO (Maintenance, Repair and Overhaul) service providers or OEMs (Original Equipment Manufacturers) supply spare parts to airline operators on a maintenance-by-the-hour basis. As a consequence, the associated logistics networks have reached unprecedented complexity: Component exchange commitments are now made to multiple operators, not only at their main bases but also at outstations. In this setting, the limitations of conventional Initial Provisioning methods can be overcome with high-fidelity simulation-based optimisation techniques. In particular, this paper discusses how value can be unlocked from new logistics policies for spare parts management in aviation.

Analysis and enhancement of planning and scheduling applications in a distributed simulation testbed

Planning and scheduling applications and operations simulation models jointly represent the manufacturing activities of an enterprise. This paper relates to a framework that enables integration of both into a unified model and allows improvement of their performance with discrete event simulation (DES) technology. The high level architecture, which is the IEEE standard for interoperability of simulations, forms the backbone of this framework in which business applications can be reused with operations simulation models to generate an integrated simulation model. This enables a company to optimise not only operational processes such as shop floor or warehouse operations but also business processes such as planning, order management and scheduling through simulation using the same software infrastructure. A case study to demonstrate the feasibility of this framework is included and ongoing work on implementation of this framework in an industrial environment is presented.