Inventory control systems model for strategic capacity acquisition

Variation of installed industrial capacity has been found to follow a cyclic pattern. This paper discusses the application of control theory to the problem of the timely acquisition of extra production capacity. The control system based model presented here is compared with a System Dynamics model proposed by Sterman. Key differences are the method of implementing rational decisions about deployment of extra capacity and the use of a nonlinear APVIOBPCS inventory model. Benefits of this new model are a more measurable process and the ability to select parameter values to optimise capacity deployment. Simulation of the model indicates that the results found by Sterman underestimate the production backlog and time taken to reach equilibrium. The use of a Proportional, Integral, and Derivative (PID) controller in the capacity control loop model illustrates that it is possible not only to alter the backlog levels but at the same time to reduce the sales force and improve the revenue. The model also shows clearly that the impact of not increasing capacity promptly results in catastrophic failure of sales as a structural, rather than a business, problem. This model is simple enough to be implemented as a spreadsheet for use as a guide by managers

Inventory control systems model for strategic capacity acquisition

Variation of installed industrial capacity has been found to follow a cyclic pattern. This paper discusses the application of control theory to the problem of the timely acquisition of extra production capacity. The control system based model presented here is compared with a System Dynamics model proposed by Sterman. Key differences are the method of implementing rational decisions about deployment of extra capacity and the use of a nonlinear APVIOBPCS inventory model. Benefits of this new model are a more measurable process and the ability to select parameter values to optimise capacity deployment. Simulation of the model indicates that the results found by Sterman underestimate the production backlog and time taken to reach equilibrium. The use of a Proportional, Integral, and Derivative (PID) controller in the capacity control loop model illustrates that it is possible not only to alter the backlog levels but at the same time to reduce the sales force and improve the revenue. The model also shows clearly that the impact of not increasing capacity promptly results in catastrophic failure of sales as a structural, rather than a business, problem. This model is simple enough to be implemented as a spreadsheet for use as a guide by managers

Nonlinear oil price dynamics: a tale of heterogeneous speculators?

While some of the recent surge of oil prices can be attributed to robust global demand at a time of tight production capacities, commentators occasionally also blame the impact of speculators for part of the price pressure. We propose an empirical oil market model with heterogeneous speculators. Whereas trend-extrapolating chartists may tend to destabilize the market, fundamentalists exercise a stabilizing effect on the price dynamics. Using monthly data for WTI oil prices, our STR-GARCH estimates indicate that oil price cycles may indeed emerge due to the nonlinear interplay between different trader types. --oil price dynamics,endogenous bubbles,STR GARCH model

Symptoms of complexity in a tourism system

Tourism destinations behave as dynamic evolving complex systems, encompassing numerous factors and activities which are interdependent and whose relationships might be highly nonlinear. Traditional research in this field has looked after a linear approach: variables and relationships are monitored in order to forecast future outcomes with simplified models and to derive implications for management organisations. The limitations of this approach have become apparent in many cases, and several authors claim for a new and different attitude. While complex systems ideas are amongst the most promising interdisciplinary research themes emerged in the last few decades, very little has been done so far in the field of tourism. This paper presents a brief overview of the complexity framework as a means to understand structures, characteristics, relationships, and explores the implications and contributions of the complexity literature on tourism systems. The objective is to allow the reader to gain a deeper appreciation of this point of view.Comment: 32 pages, 3 figures, 1 table; accepted in Tourism Analysi

Valuing Ecosystem Services with Fishery Rents: A Lumped-Parameter Approach to Hypoxia in the Neuse River Estuary

Valuing ecosystem services with microeconomic underpinnings presents challenges because these services typically constitute nonmarket values and contribute to human welfare indirectly through a series of ecological pathways that are dynamic, nonlinear, and difficult to quantify and link to appropriate economic spatial and temporal scales. This paper develops and demonstrates a method to value a portion of ecosystem services when a commercial fishery is dependent on the quality of estuarine habitat. Using a lumped-parameter, dynamic open access bioeconomic model that is spatially explicit and includes predator-prey interactions, this paper quantifies part of the value of improved ecosystem function in the Neuse River Estuary when nutrient pollution is reduced. Specifically, it traces the effects of nitrogen loading on the North Carolina commercial blue crab fishery by modeling the response of primary production and the subsequent impact on hypoxia (low dissolved oxygen). Hypoxia, in turn, affects blue crabs and their preferred prey. The discounted present value fishery rent increase from a 30% reduction in nitrogen loadings in the Neuse is $2.56 million, though this welfare estimate is fairly sensitive to some parameter values. Surprisingly, this number is not sensitive to initial conditions.Open access, Predator-prey, Hypoxia, Habitat-dependent fisheries

КОРПОРАТИВНАЯ ДИНАМИКА СИСТЕМ ЛОГИСТИЧЕСКИХ УРАВНЕНИЙ С ЗАПАЗДЫВАНИЕМ И С БОЛЬШИМ ЗАПАЗДЫВАЮЩИМ УПРАВЛЕНИЕМ

A system of two logistic equations with delay coupled by delayed control is considered. It is shown that in the case of a sufficiently large delay control coefficient the problem of the dynamics of the initial systems is reduced to studying the non-local dynamics of special families of partial differential equations that do not contain small and large parameters. New interesting dynamic phenomena were discovered on the basis of the results of numerical analysis. Systems of three logistic delay equations with two types of ”diffusion” relation were considered. Special families of partial differential equations that do not contain small and large parameters were also constructed for each of these systems. The results of the study of the original equations dynamic properties are presented. It is shown that the difference in the dynamics of the considered systems of three equations may be of a fundamental nature.Рассматривается система двух логистических уравнений с запаздыванием, связанных через запаздывающее управление. Показано, что при достаточно большом коэффициенте запаздывающего управления задача о динамике исходных систем сводится к исследованию нелокальной динамики специальных семейств уравнений с частными производными, не содержащих малые и большие параметры. На основе представленных результатов численного исследования таких уравнений обнаружен ряд новых и интересных динамических явлений. Рассмотрены системы из трех логистических уравнений с запаздыванием с двумя типами «диффузионных» связей. Для каждой из этих систем были так же построены специальные семейства уравнений с частными производными, не содержащие малых и больших параметров. Приведены результаты исследования динамических свойств исходных уравнений. Показано, что различие в динамике рассмотренных систем трех уравнений может носить принципиальных характе

Supply Chain

Traditionally supply chain management has meant factories, assembly lines, warehouses, transportation vehicles, and time sheets. Modern supply chain management is a highly complex, multidimensional problem set with virtually endless number of variables for optimization. An Internet enabled supply chain may have just-in-time delivery, precise inventory visibility, and up-to-the-minute distribution-tracking capabilities. Technology advances have enabled supply chains to become strategic weapons that can help avoid disasters, lower costs, and make money. From internal enterprise processes to external business transactions with suppliers, transporters, channels and end-users marks the wide range of challenges researchers have to handle. The aim of this book is at revealing and illustrating this diversity in terms of scientific and theoretical fundamentals, prevailing concepts as well as current practical applications

Pseudo Phase Plane and Fractional Calculus Modelling of Western Global Economic Downturn

This paper applies Pseudo Phase Plane (PPP) and Fractional Calculus (FC) mathematical tools for modeling world economies. A challenging global rivalry among the largest international economies began in the early 1970s, when the post-war prosperity declined. It went on, up to now. If some worrying threatens may exist actually in terms of possible ambitious military aggression, invasion, or hegemony, countries’ PPP relative positions can tell something on the current global peaceful equilibrium. A global political downturn of the USA on global hegemony in favor of Asian partners is possible, but can still be not accomplished in the next decades. If the 1973 oil chock has represented the beginning of a long-run recession, the PPP analysis of the last four decades (1972–2012) does not conclude for other partners’ global dominance (Russian, Brazil, Japan, and Germany) in reaching high degrees of similarity with the most developed world countries. The synergies of the proposed mathematical tools lead to a better understanding of the dynamics underlying world economies and point towards the estimation of future states based on the memory of each time series

Parameter Estimation of Cancer Cell Dynamics

The goal of this project is to model cancer cell dynamics and their sensitivity to cancer drugs, and use parameter estimation techniques to provide experimental insights. We introduce several variations of a model developed by our team to capture the interactions between cancer cells and different drugs, as well as the methods utilized for parameter estimation. All variations of our model include a natural growth rate, cell-induced and drug-induced death rates, which are immeasurable and potentially time-varying. We utilize the Ensemble Kalman Filter for estimation as it accommodates noisy data noise by producing distribution estimations. Long term, estimation of parameters may lead to insight with regards to the drug-induced cell death mechanisms and proper data collection methods

The global vulnerability discovery and disclosure system: a thematic system dynamics approach

Vulnerabilities within software are the fundamental issue that provide both the means, and opportunity for malicious threat actors to compromise critical IT systems (Younis et al., 2016). Consequentially, the reduction of vulnerabilities within software should be of paramount importance, however, it is argued that software development practitioners have historically failed in reducing the risks associated with software vulnerabilities. This failure is illustrated in, and by the growth of software vulnerabilities over the past 20 years. This increase which is both unprecedented and unwelcome has led to an acknowledgement that novel and radical approaches to both understand the vulnerability discovery and disclosure system (VDDS) and to mitigate the risks associate with software vulnerability centred risk is needed (Bradbury, 2015; Marconato et al., 2012). The findings from this research show that whilst technological mitigations are vital, the social and economic features of the VDDS are of critical importance. For example, hitherto unknown systemic themes identified by this research are of key and include; Perception of Punishment; Vendor Interactions; Disclosure Stance; Ethical Considerations; Economic factors for Discovery and Disclosure and Emergence of New Vulnerability Markets. Each theme uniquely impacts the system, and ultimately the scale of vulnerability based risks. Within the research each theme within the VDDS is represented by several key variables which interact and shape the system. Specifically: Vender Sentiment; Vulnerability Removal Rate; Time to fix; Market Share; Participants within VDDS, Full and Coordinated Disclosure Ratio and Participant Activity. Each variable is quantified and explored, defining both the parameter space and progression over time. These variables are utilised within a system dynamic model to simulate differing policy strategies and assess the impact of these policies upon the VDDS. Three simulated vulnerability disclosure futures are hypothesised and are presented, characterised as depletion, steady and exponential with each scenario dependent upon the parameter space within the key variables