Athletes face tremendous pressure to perform, and, when conventional means prove insufficient for performance improvement, some turn to performance enhancing drugs (PEDs). The present paper uses system dynamics to examine one example: the use of anabolic androgenic steroids in Major League Baseball (MLB), which operates in the United States and Canada. The authors provide an explanation of a detailed causal loop diagram of the problem, along with a stock and flow model, based on the Bass Diffusion Model, of part of the problem. They provide a few policy recommendations based on model runs.
This paper/poster explores the role and contribution of dynamic models in reverse logistics processes. The purpose of reverse logistics processes within a manufacturing supply chain is to disassemble or reutilize products, or their components, in order to generate value. The first part of the paper describes the general process involved in reverse logistics as found in the supply chain management literature. The second part of the paper presents three dynamic models that represent the main factors driving product returns: The green factor or consumer sensitivity towards environmental issues; the regulatory factor or governmental requirements; and the profit factor or business opportunities. The third part of the paper combines the three factors behind products returns in order to create a general dynamic model of reverse logistics. Emphasis is placed on two major issues: The non-linear relationships involved in reverse logistic processes and business opportunities as the main driver of reverse logistics. The last section of the paper centers on the similarities and differences of dynamic models that aim to simulate forward logistics and reverse logistics. While forward logistics are centered in concepts such as assembly and bullwhip effect, reverse logistics models emphasize disassembly and funnel-like behavior.
When final customer demand exceeds available supply, retailers often hedge against shortages by inflating orders to their suppliers. As several retailers compete for scarce supply, the amplification in orders lead to excess supplier capacity, high inventory variability, low capacity utilization, and financial and reputation losses for suppliers and retailers. While the amplification in orders caused by the competition for scarce resources has been described in the literature almost a century ago (Mitchell 1924), there is little research quantifying the impact of such order amplification by retailers.
The performance analysis of a general productioninventory control system under uncertain demand is presented. In the model, the production order releases are determined based on the information feedback on the forecasted demand, work-in-process discrepancy and inventory discrepancy. Stability conditions are obtained in terms of the control parameters that manage the rate at which the above discrepancies are corrected. The service and cost performances of the system in terms of order fill rate, item fill rate and average system cost are analyzed for various values of the control parameters within the stability region. Additional safety stock is considered to help achieve a desired level of service (desired order fill rate). Results based on numerical simulations are presented and their implications are discussed.
In this study, by using system dynamics approach we aim to investigate the profitability of a company if it is engaged in remanufacturing, which is the most advanced form of product recovery. Our motivation is to find out whether investing in remanufacturing is advantageous for a company/sector in terms of long term profitability and, what should be the quality and price levels of the remanufactured and newly manufactured products. The model shows that a company involved both in new and remanufactured versions of the same product, endogenously generates interesting customer-base dynamics. Different from the studies in the literature that deal with micro level models, we analyze the effects of being involved in remanufacturing of electronic products on the profitability of the firm at macro level, by taking into account the government incentives for the firms that perform product recovery.
Service operations depend intensively on human resources because of their interaction with customers and suppliers and thus, training becomes a must in order to ensure higher performance. Knowledge Management (KM) may be looked as a framework for training programs since it addresses knowledge conversion from explicit and tacit knowledge. This paper proposes that dynamic simulation might be used as a tool to analyze training programs effectiveness from a KM perspective. Thus, a SD model was built using data from a customer support service of a software-house in Brazil. Three scenarios were considered, relying on the number of trainings per month. The main contribution of this work lies on shedding light over the intangible effects of tacit and explicit knowledge that support the effectiveness of training programs over organizational performance.
This paper addresses the challenge of identifying adequate theoretical starting points for problem oriented simulation studies of socio-technical transitions towards near fossil free energy services e.g. for housing and transportation. The identification of adequate starting points for simulation studies is becoming increasingly important for the generalization of simulation results as well as for theory refinement. We found that the Multi-Level Perspective (MLP) offers a helpful language for a modelling experiment based in a feedback perspective. This allows scientific conceptualization of a socio-technical transition challenge departing from an inter-subjective and hence scientific starting point. In addition feedback modelling appears to be a promising mathematical analysis approach that helps to substantiate the MLP. We have seen that the insights of the simulation experiment corroborate basics assumptions of the MLP concerning multi-level alignment processes but also discriminates the decisive determinants and governance mechanism that explain radical innovation and subsequently the creation of path dependency.
Over the past few decades, many studies of corruption have been carried out. These studies have mainly focused on specific characteristics such as: economic issues, legal issues, and social propositions. In this article we have described the concept of modeling corruption in Pakistan using a Causal Loop Diagram (CLD). Corruption represents a very dangerous social phenomenon observed in many parts of the world. However, its manifestation in a developing country is an especially destructive agent against human development. The System Dynamics (SD) approach has been extended in the past several years through its application to new problems such as modeling state instability, supply chain management, and analysis of different nation building policies. The main objective of this study is to develop a theoretical framework which can be used to study corruption dynamics by means of SD. The methodology employed is a case study. Semi structured interviews with key stakeholders such as: government ministries, donor agencies, judiciary, police departments, non-governmental organizations and the general public are done. On the basis of literature and social theory we have developed three preliminary CLD models of corruption. The data for the qualitative system dynamics analysis comes from 30 interviews conducted in (Islamabad) Pakistan.
This paper explores the Agile software development methodology to discover the essence that has enabled it to prosper and grow since the declaration of the Manifesto for Agile Software Development in 2001. Examined is the role of feedback in the Agile methodology and its relationship to single and double loop learning.