Formula manipulation in the bond graph modelling and simulation of large mechanical systems

A multibond graph element for a general single moving body is derived. A multibody system can easily be described as an interconnection of these elements. 3-D mechanical systems usually contain dependent inertias having both differential and integral causality. A method is described for the transformation of inertias with differential causality to an integral form, using formula manipulation. The program also helps to find experimentally the optimal choice for the generalized coordinates. The resulting explicit differential equation may be solved using a standard integration routine or simulation program

REPRESENTATION SCHEMES FOR MATHEMATICAL PROGRAMMING MODELS

Because of the difficulties often experienced in formulating and understanding large scale models, much current research is directed towards developing systems to support the construction and understanding of management science models. This paper discusses six different methods for representing mathematical programming models during the formulation phase of the modeling process. The approaches discussed in the paper include algebra, three different kinds of graphical schemes, a database-oriented approach and Structured Modeling. We emphasize representations that have graphical elements suitable for incorporation in the interface to a modeling system. The different methods are compared using a common example and conclusions are drawn as to their suitability for various modeling tasks and situations.Information Systems Working Papers Serie

REPRESENTATION SCHEMES FOR MATHEMATICAL PROGRAMMING MODELS

Because of the difficulties often experienced in formulating and understanding large scale models, much current research is directed towards developing systems to support the construction and understanding of management science models. This paper discusses seven different methods for representing mathematical programming models during the formulation phase of the modeling process. The approaches discussed are block-schematic, algebraic, three different kinds of graphical schemes, a database-oriented approach and Structured Modeling. We emphasize representations that have graphical elements suitable for incorporation in the interface to a modeling system. The different methods are compared using a common example and the transformations that allow one to go from one representation to another are discussed.Information Systems Working Papers Serie

REPRESENTATION SCHEMES FOR MATHEMATICAL PROGRAMMING MODELS

Because of the difficulties often experienced in formulating and understanding large scale models, much current research is directed towards developing systems to support the construction and understanding of management science models. This paper discusses six different methods for representing mathematical programming models during the formulation phase of the modeling process. The approaches discussed in the paper include algebra, three different kinds of graphical schemes, a database-oriented approach and Structured Modeling. We emphasize representations that have graphical elements suitable for incorporation in the interface to a modeling system. The different methods are compared using a common example and conclusions are drawn as to their suitability for various modeling tasks and situations.Information Systems Working Papers Serie

An Expanded Database Structure for a Multi-Period, Optimization Model

We describe a generic database structure of a multi-period two-stage stochastic optimization based decision support system. The model is an extension of earlier work (Dutta & Fourer; 2004). The model could be used with no or little knowledge of OR/MS. The model maximizes expected contribution subject to material balance, facility capacity, facility input, facility output, storage inventory balance, storage area constraints. The model also considers non-anticipativity constraints for first stage decision variables

Modeling Product Reconfiguration At Distribution Center Level

Scope and method of study: This study focused on recognizing, understanding, and modeling product reconfiguration. Product reconfiguration is a process by which an in-stock product is reconfigured to meet the demand of an out-of-stock product with which it shares common parts or kits. The donor product consumes in-stock service-kit(s) for the reconfiguration process and releases kit(s) that can be used in other reconfigurations. Product reconfiguration can be employed by enterprises striving for mass customization with off-shore manufacturing facilities and local-to-demand Distribution Centers (DC). We modeled the reconfiguration process using single period Network Flow based and Integer Programming (IP) formulations and developed a prototype Decision Support System (DSS) that interfaces with the optimization models. Product reconfiguration is a relatively new field and published literature is limited. Our modeling approaches contribute to this field by providing insight into the product reconfiguration process at DC level.Findings and Conclusions: The models aid in making reconfiguration decisions by optimally deciding which product is to be reconfigured to which other product and by consuming which kit(s). The IP formulation is an aggregate planning model and the network flow based formulation specifies which kit inventory to consume. Post processing algorithms were necessary to construct reconfiguration decisions from the solution to the network flow model. The DSS acts as an interface between the model data and optimization software; final reconfiguration decision from the network model is also displayed in the DSS. This research has established the need for and the applicability of optimization models in the product reconfiguration context; it has also highlighted the importance of a DSS in supporting reconfiguration operations and in developing and refining the underlying decision-making models.Industrial Engineering & Managemen