This paper is a concept paper about a suggestion proposed by Nathan Forrester, in the last year conference to extend eigenvalue analysis to nonlinear models. His idea was to consider higher order terms of the Taylor series expansion when approximating nonlinear models. In this paper, we demonstrate the feasibility of Nathan's idea. The main contribution of this paper is to devise a pragmatic approach to solve the resulting equations of Taylor series expansion. This pragmatic approach is based on our novel concept of 'smoothed Jacobian' matrix, which is computed from both the ordinary Jacobian matrix and the set of Hessian matrices. Recall that the elements of the ordinary Jacobian matrix represent slopes of relationships, while the elements of the Hessian matrices represent curvatures of relationships. So by integrating the elements the ordinary Jacobian with the elements of the Hessian matrices, we are actually smoothing the slopes given the knowledge about curvatures. Consequently we are smoothing the time trajectories of eigenvalues and eigenvectors in nonlinear models.
This paper revisits the use of trend forecasting in driving policy in social systems by comparing it with
derivative control in classical control theory. While both processes involve use of trend to determine
policies for achieving reliable performance, the outcomes of the former have considerable variability while
those of the later can create improvement in performance with certainty. The similarities and differences
between the two processes are discussed and guidelines suggested for improving the efficacy of trend-
forecasting in policy design in social systems.
Elderly patients use more medications given the prevalence of co-morbidities putting them at risk of experiencing medication errors. A highly anticipated strategy is the implementation of health record solutions, namely a mix of shared electronic health records and personal health records. This intervention provides information for all individuals involved in the medication use system (patients, carer, doctors and pharmacists) and enables them to make more informed decisions throughout the medication use process (prescribing, dispensing, administering, monitoring of medications). However, it is difficult to direct the design of such an integrated health record solution that takes into consideration contextual factorsand its impact on, existing interventions and society. Traditional methods such as random controlled trials lack the capacity to capture the scale of the problem and are inadequate in terms of time frames, cost, resources required, and non-applicability of trial settings. Multi-scale simulations can represent the systems different spatial and temporal resolutions providing a logical and consistent framework for dynamic analysis and a means to design and test health record policies to cover a range of possible futures in a risk-free environment.
This paper elaborates the original theoretical law of capital accumulation that generates scenarios of macroeconomic evolution. The main variables are relative labour compensation, employment ratio, and gross unit rent, produced capital-output ratio, proved non-renewable reserves-output ratio, desired proved non-renewable reserves-output ratio, and depletion of non-renewable reserves per unit of net output.
Worsening profitability and declining employment ratio over the long term characterise an inertia scenario for the U.S. economy over 19912107. Excessive depletion of proved non-renewable reserves contributes to these disadvantageous tendencies.
A forward-looking investment policy based on proportional and derivative control over proved non-renewable reserves brings about their extension, raises profitability and employment over the long term in the first normative scenario in comparison with the inertia scenario.
The initial theoretical law is transformed into control law of capital accumulation. The operational application of this control law to the U.S. economy reveals and explains substantial lasting improvements in profitability, employment ratio, labour productivity and real labour compensation in the second normative scenario compared with the first normative scenario that are achieved together with extending proved non-renewable reserves due to excess income levy.
Keywords: Capital accumulation, proved reserves, long wave, closed loop control, excess income levy, the U.S. economy
This article presents the results of ongoing research on resilience in production systems. It refers to the term resilience as a way of dealing with uncertainty and disturbances. The proposed resilience analysis method, based on dynamic models, supports analysis of the production system in order to determine which structures and processes should be improved or reduced, and what resources preserved, in order to manage resilience. The application of the method is presented using results of the research project in Bombardier Transportation manufacturing plant in Poland. For the purpose of the analysis highly detailed discrete-event model and System Dynamics model were built. Both area of interest of both models complemented one another. In this paper the main focus is given to the System Dynamics model. In the course of the research project the System Dynamics approach proofed to be very useful for examining the impacts of various disturbances and possible solution policies. As a tool for the resilience analysis results dissemination, the dynamic model based simulator, was prepared.
Abstract.
This paper critically examines the challenges associated with demand for immunization, including the interplay of political, social, economic and technology forces that influence the level of immunization coverage. In an earlier paper by the same authors, system dynamics modeling and case study research methods are used to capture the complex and dynamic nature of the immunization process. This paper suggests a framework to capture the complex and dynamic nature of the immunization process and tests its effectiveness using a case study on Uganda healthcare provision. The results indicate in cases of developing nations, immunization demand outstrips immunization coverage. The paper suggests that the model and results could be used for theory building in immunization policy evaluation in developing countries.
Modeling and Analysis of Production System of A Steel Plant- A System Dynamics Approach
K.R.Divakar Roy
Department of Mechanical Engineering, A.U.College of Engineering (Autonomous)
Visakapatnam-530 003
Mail Id: divakarroy@rediff.com, krdroy@hotmail.com
Abstract
In the fast changing economic scenario world over, the economic strength of any company depends on the managements ability in improving quality, cutting production costs and providing better customer services to compete effectively in the global market. Even though every management aims at improving the productivity, there is a limitation on the part of various production facilities located in any plant as they cannot be stretched beyond a point. However, management can exploit the existing facilities to the maximum extent possible by introducing the latest state of art technology. Against this backdrop, present production scenario of a local integrated steel plant is described. The key variables considered for the simulation of steel plant production activities are: production of hot metal, liquid steel, prime blooms, bar mill products and wire rod products over a period of 20 years from 1994 to2013. The results obtained from the SD modeling are validated. Further, the model is utilized to explore alternative policies, which have been compared for their relative effectiveness.
This paper is about a group model building project at the Ministry of Justice in the Netherlands. The aim of the model is to gain insight into the combined effects of an increase in the case load and investments in different phases of criminal justice administration and contextual developments such as increased complexity of cases. A group of representatives from the police force, public prosecution, courts and sentence execution participated in constructing the model from January to August 2004. In this paper we report on reasons for starting the modeling effort and the process of model construction. We then compare the procedure followed to scripts small parts of modeling process that have been tested out in practice and serve as standard building blocks for a group model building project. Scripts specify a technique, the situations for which it is suited and the expected results, enabling a modeler to choose from the wide variety of available modeling techniques. By describing the process followed in this case and consistently relating it to well-established practices we hope to further clarify the modeling process, by contributing to the existing body of modeling techniques and the dissemination of process insights.
This paper is aimed at formalizing and testing a model for explaining the relations among supply chain design decisions (i.e. sourcing strategies, number of network stages, nodes capacity and localization) and the need for collaboration between the nodes of pull-based supply chain. As a consequence, a causal diagram which depicts such relations is built and its validation is performed by means of simulation techniques and statistical analyses (ANOVA and linear regression). In particular, since the magnitude of the relations is out of the scope of the paper, the validation is done in relative terms. The results obtained by running the simulation model of the supply chain which represents the base case are compared with the outputs of the models which simulates the original logistic network modified according to the above mentioned supply chain design elements. The statistical analyses allow the majority of the relations of the proposed causal diagram to be actually validated.
This paper examines the rising competition between computational and dynamic conceptualizations of complexity in economics. While computable economics views complexity as something rigorously defined based on concepts from probability, information, and computability criteria, dynamic complexity is based on whether a system endogenously and deterministically generates erratically dynamic behavior of certain kinds. One such behavior is the phenomenon of emergence, the appearance of new formes or structures at higher levels of a system from processes occurring at lower levels. While the two concepts can overlap, they represent substantially different perspectives. A competition of sorts between them my become more important as new, computerized market systems emerge and evolve to higher levels of complexity of both kinds.