Simulation in manufacturing and business: A review

This paper reports the results of a review of simulation applications published within peer-reviewed literature between 1997 and 2006 to provide an up-to-date picture of the role of simulation techniques within manufacturing and business. The review is characterised by three factors: wide coverage, broad scope of the simulation techniques, and a focus on real-world applications. A structured methodology was followed to narrow down the search from around 20,000 papers to 281. Results include interesting trends and patterns. For instance, although discrete event simulation is the most popular technique, it has lower stakeholder engagement than other techniques, such as system dynamics or gaming. This is highly correlated with modelling lead time and purpose. Considering application areas, modelling is mostly used in scheduling. Finally, this review shows an increasing interest in hybrid modelling as an approach to cope with complex enterprise-wide systems.     

Introducing system dynamics to the BBC World Service: an insider perspective

The paper relates the story of the encounter between system dynamics modelling and the BBC World Service told from the perspective of a manager who was also championing the approach inside the World Service. The outcome provides interesting lessons and useful ideas on the contribution to organisational change that can and cannot be expected from a system dynamics project. The paper opens with a review of the published literature on the impact of system dynamics within organisations. The BBC World Service organisation and culture are then briefly described, with particular reference to potential fits and misfits with the system dynamics approach. The process of building a World Service model is described, both in terms of historical and technical stages. The project's impact on the organisation is reported, whether the impact arose by design or default. This appraisal covers the model building process, the analysis of simulations and finally the development of a microworld or gaming simulator. The paper concludes with comments on the merits of system dynamics to an organisation like the BBC World Service, pinning down the tangible and less tangible benefits delivered, and making suggestions to encourage acceptability of the approach.     

A survey of business failures with an emphasis on prediction methods and industrial applications

The considerable interest in the prediction of business failures is reflected in the large number of studies presented in the literature. Various methods have been used to construct prediction models. This paper provides a review of the literature and a framework for the presentation of this information. Articles can be classified according to the country, industrial sector and period of data, as well as the financial ratios and models or methods employed. Relationships and research trends in the prediction of business failure are discussed.     

求解洛伦兹力系统的一个任意高阶的能量守恒格式

本文旨在提出一种求解带电粒子系统的任意高阶能量守恒格式.在使用能量不变二次化方法将原始哈密顿能量泛函转化为一个二次形式后,辛龙格-库塔方法被用来构造了一种新的能量守恒格式来求解洛伦兹力系统.新格式不仅能保持能量守恒,而且可以达到任意高阶.通过与经典的Boris方法和另一个二阶能量守恒方法对比,数值实验验证了所提算法的显著优越性.     

Modelling a sector undergoing structural change: The case of Danish energy supply

This paper examines structural change in the power and heat producing sector (energy supply) and its implications for the economy. An integrated approach is used to describe the interactions between this sector and the rest of the economy. Thus, a very detailed model of the sector for Denmark has been linked to a macroeconometric model of the Danish economy. It is argued that analysing sectors that undergo radical changes, for example the energy supply sector, should be undertaken by using a model that describes the technological and organisational changes in production along with implications for the demand of the produced goods. Environmental priorities and targets for emission reductions are important for defining energy policy in Denmark. As the energy supply sector at present is a major contributor to emissions of CO₂ and SO₂, knowledge of this sector is vital for reducing these emissions. It is shown that quite substantial emission reductions are possible without encountering a substantial negative impact on the economy. The reduction potential through such economic incentives as fuel taxes is shown to be very sensitive to the technology used at present and in the future. This study also emphasises that the large reduction potential of emissions from the energy supply sector is a one-time gain. Fuel switching and increasing use of wind power cannot be repeated. Scenarios carried out with the combined model show that emission reduction in the energy supply sector will decrease the share of this sector in total emissions remarkably, and that the importance of the sector as a key element in any overall emission reduction strategy will decline. This revised version was published online in June 2006 with corrections to the Cover Date.     

Self-organization and social science

Complexity science and its methodological applications have increased in popularity in social science during the last two decades. One key concept within complexity science is that of self-organization. Self-organization is used to refer to the emergence of stable patterns through autonomous and self-reinforcing dynamics at the micro-level. In spite of its potential relevance for the study of social dynamics, the articulation and use of the concept of self-organization has been kept within the boundaries of complexity science and links to and from mainstream social science are scarce. These links can be difficult to establish, even for researchers working in social complexity with a background in social science, because of the theoretical and conceptual diversity and fragmentation in traditional social science. This article is meant to serve as a first step in the process of overcoming this lack of cross-fertilization between complexity and mainstream social science. A systematic review of the concept of self-organization and a critical discussion of similar notions in mainstream social science is presented, in an effort to help practitioners within subareas of complexity science to identify literature from traditional social science that could potentially inform their research.     

The effects of body composition on setpoint based weight loss

The setpoint model of human metabolic adaption to diet-induced weight loss has been introduced and examined considering a constant energy density in the body weight lost. Body composition analysis indicates that the ratio of fat and nonfat lost is constant for an individual but is dependent on the initial percent body fat, producing an energy density varying from individual to individual. In this study, body composition and the setpoint model are used to examine weight loss dynamics. Comparison is made to a Harris-Benedict (HB) based model using a nominal energy density (3500 calories/lb). Conclusions: the weight dynamics for a given reduction in calorie intake are completely determined by the initial percentage of body fat. The HB model is predicted to accurately track the weight loss for the very obese who experience little metabolic adaption and whose energy density is close to the nominal value. However, for subjects with decreased initial body fat percentage, the HB model first underestimates then overestimates the weight loss. The crossover time and the maximum overestimate is dependent on the initial body fat percent and the percent dietary calorie reduction. A characteristic time and an energy density ratio are defined and used to calculate a maximum rate of weight loss for a given calorie reduction.     

Inventory models with lateral transshipments: A review

Lateral transshipments within an inventory system are stock movements between locations of the same echelon. These transshipments can be conducted periodically at predetermined points in time to proactively redistribute stock, or they can be used reactively as a method of meeting demand which cannot be satisfied from stock on hand. The elements of an inventory system considered, e.g. size, cost structures and service level definition, all influence the best method of transshipping. Models of many different systems have been considered. This paper provides a literature review which categorizes the research to date on lateral transshipments, so that these differences can be understood and gaps within the literature can be identified.     

Dynamics and chaos control in nonlinear electrostatic transducers

In this paper, we analyze the dynamics of a system consisting of two coupled nonlinearly Duffing oscillators, obtained from a nonlinear electrostatic device which is a prototype of emitters and receivers in communication engineering. Inverse or backward period doubling cascades and sudden transition to chaos are observed. A sliding mode controller is applied to control the electrostatic transducers system. The sliding surface used is one dimension higher than the traditional surface and guarantees its passage through the initial states of the controlled system. By means of the design of sliding mode dynamics characteristics, the controlled system performance is arbitrarily determined by assigning the switching gain of the sliding mode dynamics. Therefore, using the characteristic of this sliding mode we aim to design a controller that can meet the desired specification and use less control energy by comparing with the result in the current literature. The results show that the proposed controller can steer electrostatic transducers to the desired reference trajectory without chattering phenomenon and abrupt state change.     

Modelling replenishment and transshipment decisions in periodic review multilocation inventory systems

Effective models of key operational decisions in multilocation inventory systems are important for a successful retail sector. This paper argues that much of the existing research in this area is not applicable to a highly competitive retail environment, particularly if periodic review replenishment policies are used. The paper develops a model of a periodic review multilocation inventory system that is suitable for this environment and investigates the characteristics of optimal replenishment and transshipment decisions. This motivates the development of three simple heuristic transshipment policies that are practical for systems with many locations. The results of a numerical study involving systems with five locations suggest that the performance of these heuristic policies is often close to optimal and can be considerably better than the performance of commonly used policies.     

Energy crop supply in France: a min-max regret approach

This paper attempts to estimate energy crop supply using a linear programming (LP) model comprising hundreds of representative farms of the arable cropping sector in France. In order to enhance the predictive ability of such a model and to provide an analytical tool useful to policy makers, interval linear programming is used to formalize bounded rationality conditions. In the presence of uncertainty related to yields and prices, it is assumed that the farmer may adopt a min-max regret (MMR) criterion as an alternative to the classic profit maximization criterion. Recent advances in operational research are exploited, permitting an efficient implementation of the min-max criterion within an LP model. Model validation based on observed activity levels suggests that about 40% of the farms adopt the MMR criterion. Energy crop supply curves generated by the MMR model prove to be upward-sloped, like classic LP supply curves.     

Modelling of linguistic variables in multicriteria energy policy support

The climate change and the increasing complexity of the energy sector along with the prerequisite for sustainability have broadened the energy policy shaping field by bringing out new challenges. Decision support tools and methods, such as Multicriteria Decision Aid (MCDA), are necessary for energy policy, in the pursuit of appropriate approaches necessary to support the restructuring of the energy sector, concerning patterns of energy extraction, generation, transformation and use, from unsustainable to sustainable forms of development. Papers devoted to the investigation of MCDA models using linguistic variables for energy policy support seem to be not available in the international literature. The scope of this paper is to explore different linguistic representation and computational models in MCDA that are or can be applied to energy policy support and to establish a clear linkage between them. This paper argues that MCDA methodologies with direct computation on linguistic variables can support energy policy frameworks, bridging the gap between energy policy makers thinking, reasoning, representation and computing. Finally, current trends, open questions and prospects in this topic are pointed out.     

MODELING DYNAMICS OF FISHERY HARVEST REALLOCATIONS: AN ANALYSIS OF THE NORTH CAROLINA RED DRUM FISHERY

The interactive dynamics of red drum stock growth and two-sector harvest are modeled as a system of differential equations. The dynamic effects of commercial harvest restrictions on stock growth and recreational catch and effort are simulated. The simulation shows that a reallocation of the North Carolina red drum stock from the commercial sector to the recreational sector will not only increase benefits to the recreational sector, but will also be stock enhancing. Stock growth in the years immediately following the reallocation is quite rapid, with complete transition to the final steady-state taking between 23 and 46 years. Parameters important to the behavior of the system are identified through sensitivity analysis, and are used to establish critical areas for further research.     

Literature review on multi-appointment scheduling problems in hospitals

This paper presents a review of the literature on multi-appointment scheduling problems in hospitals. In these problems, patients need to sequentially visit multiple resource types in a hospital setting so they can receive treatment or be diagnosed. Therefore, each patient is assigned a specific path over a subset of the considered resources and each step needs to be scheduled. The main aim of these problems is to let each patient visit the resources in his or her subset within the allotted time to receive timely care. This is important because a delayed diagnosis or treatment may result in adverse health effects. Additionally, with multi-appointment scheduling, hospitals have the opportunity to augment patient satisfaction, allowing the patient to visit the hospital less frequently. To structure the growing body of literature in this field and aid researchers in the field, a classification scheme is proposed and used to classify the scientific work on multi-appointment scheduling in hospitals published before the end of 2017. The results show that multi-appointment scheduling problems are becoming increasingly popular. In fact, multi-appointment scheduling problems in hospitals are currently gaining progressively more momentum in the academic literature.     

Modeling the synergy level in a vertical collaborative supply chain through the IMP interaction model and DEA framework

This work develops a mathematical programming model that characterizes the main variables present in the interaction dynamics of each agent in a collaborative vertical logistical system, such as a supply chain, and measures the synergy level of such system. The model is based on the interaction model developed by the IMP (Industrial Marketing and Purchasing) group and also on the DEA (Data Envelopment Analysis) framework. The basics of these two approaches allow modeling of the characteristics of an agent as well as the collaborative relationships with other agents within the chain. The model was validated using information of supply chain of leather and its products, classified by DANE (Departamento Nacional de Estadistica—Colombia) as the sector CIIU323.     

The dynamic behavior of multiregional multisectoral models: A biregional application to the Italian economy

This paper deals with the dynamics of multiregional systems in which economic growth is strictly dependent on the capital accumulation process and multisectoral multiregional interactions evolve within a general equilibrium context. The input-output approach allows an analysis based on the structural properties of the matrices representing the linkages among the different parts of the multiregional economy. The singularity of the regional matrices of capital input coefficients is realistically imposed, and the forward-in-time projection of the model is made possible by a suitable partition of the system. Moreover, the existence and relative stability of a balanced growth path are discussed under the assumption that each sector in the economy requires, directly or indirectly, either some current flow or some capital input from all the other sectors operating in the same and in the other regions. The model is applied to the Italian economy at 1985 within a biregional framework.     

Approximating the larger eddies in fluid motion V: Kinetic energy balance of scale similarity models

We first review a classical scale-similarity model used to simulate the motion of large eddies in a turbulent flow. The kinetic energy balance of this model is very unclear in theory. Experiments with it often have reported that an additional Smagorinski type subgridscale term is needed. This term is not benign; it can alter significantly the predicted long term dynamics of the large eddies. However, we also show that the principal of scale-similarity (introduced in 1980 by Bardina, Ferziger and Reynolds) can also give rise to other scale similarity models which have the correct kinetic energy balance.