Determination of Stock for Sales Promotions

This paper describes the solution of the practical problems encountered by a Company when a product is made and sold for a limited promotional period only. The production and inventory control aspects are considered and a system aimed at the reduction of obsolescence costs is described which is based on a model of the demand pattern which uses a Gompertz exponential growth curve. Under pressure for an early improvement from the organisation, a system based on an empirical model was implemented, as an interim measure, which achieved a considerable improvement in performance. The Gompertz model has now been put into operation and the results of a simulation model are presented indicating that further improvements can be achieved.     

基于改进的多层次模糊综合评价模型的高校课堂教学质量评价研究

依据模糊数学的理论,构造了一种改进的多层次模糊综合评价模型.通过建立高校课堂教学质量评估指标体系,利用改进的多层次模糊综合评价模型对高校课堂教学质量进行综合评价.实证结果表明,模型具有较好的科学性和实用性,是一种有效地评估高校课堂教学质量的方法.     

Dynamical stability of a viscoelastic bar

In the paper the dynamic stability of a simply supported viscoelastic bar of the Zener material model is investigated. The bar is subjected to a parametric excitation of a periodic nature. The physical model of the system is of the continuous type. However, the proposed approach yields a transformation of the mathematical model from the partial differential equation to an ordinary one. Such a transformation is made possible by the use of an approximation function for the bending line of the bar. This way, the system is governed by a homogeneous, ordinary differential equation of the third order with periodic coefficients. For stability studies the Floquet theory is applied. A sensitivity analysis of a parametric periodic system is discussed, i.e. the influence of stiffness and damping coefficient of the Zener model on stability of the differential equation that describes the vibration of the viscoelastic bar. Furthermore the stabilization process of an unstable parametric system was realized. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

赤道东太平洋海气耦合振荡的非线性分析及ENSO循环的极限环理论

把赤道东太平洋地区大气对流层,海洋混合层看作是在定常热源（太阳辐射）驱动下的动力系统,利用一个局域平均的热力学气候模式,建立了海气耦合自激振荡模型,得到了一个封闭的自治的二次系统,对系统进行了线性和非线性分析．结合系统稳定的极限环解,对海气耦合的物理机制进行了探讨．和观测事实的比较表明,在赤道东太平洋区域平均的以500 hPa为代表的大气对流层的温度距平和海表温度距平,在相平面上和极限环解定性上很一致．这为研究热带海气相互作用的年际变化提供了一个理论模型．     

A pricing policy for a computer facility with congestion externalities

The paper proposes an adaptive pricing mechanism which allocates computer resources among the different consumers in an economically efficient manner. Users are charged a unit price designed to reflect the marginal congestion load each imposes upon the system. Some of the more common allocation schemes are described briefly followed by a discussion of the desirable properties of an efficient allocative system. These properties are incorporated into a model of a computer facility, and a number of propositions regarding the behavior of this model are proposed. In order to test empirically the behavior of this system under conditions approximating those which would prevail in an actual computer center, the pricing mechanism was analyzed by a simulation model of a computer center, using data obtained from a survey of customers at the computer center of a university (Technion, Israel Institute of Technology at Haifa, Israel). A few suggestions regarding the implementation of the proposed pricing policy conclude the paper.     

N.E.W.S.: A model for the evaluation of non-life insurance companies

This paper describes a model which can be used by the Dutch insurance supervisor to determine the priority a non-life insurer should have for further examination. This model combines a traditional statistical technique (an ordered logit model) with artificial intelligence techniques (a neural network and an expert system). The output of the model consists of the priority for further examination (high, medium, or low), and a report which summarizes the main findings of the model. The model was able to adequately classify 93% of the companies in a 1993 data set.     

A prolog-based decision support system for computer capacity planning

This paper describes a project to implement a decision support system for computer capacity planning. The system provides an intelligent interface to the various models needed for this type of planning by assisting the user in model formulation, data manipulation, model execution, interpretation and manipulation of results. The implementation strategy is based on the integration of relational model and database management with logic. A modified version of a Prolog interpreter is utilized as the vehicle for this integrated strategy.This research was supported by Sandia National Laboratories Grant No. 56-3737. Sandia is managed by AT&T Technologies for the U.S. Department of Energy.     

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.     

带刚性限位的双层隔振系统的离散随机模型

研究由多刚体组成的带刚性限位的双层隔振系统,对其冲击后受到周期性外激励和低强度噪声扰动共同作用下可能会产生的碰撞进行了分析．基于单向约束多体动力学理论,导出了此隔振系统的最大Poincaré映射,建立了其冲击后的零次近似随机离散模型和一次近似随机离散模型．通过对一MTU公司的柴油机隔振系统冲击作用后振动响应的调查指出,由于可能发生间歇性碰撞,该系统呈现复杂的非线性特性．零次近似模型和一次近似模型有较大的区别,低强度的噪声也会对系统产生较大的影响．得到的结果对如何正确设计带刚性限位的双层隔振系统提供了理论参考依据．     

Stability study of the human body-seat system into an autovehicle

The paper presents the study of the human body, as a mechanical system, seated inside an autovehicle and exposed under the vertical harmonic vibration action during the auto vehicle motion time. The human body may be roughly approximated by a linear lumped parameter at low frequencies and low vibration levels. Therefore, the model has 5 DOFs in translation, where 4 DOFs represents the human body and 1 DOF is for the seat cushion The mechanical model of the human body, in sitting position on the seat cushion of a vehicle seat, consists of four parts: pelvis, upper torso, viscera and head.. The eigenvalues for the human body – seat system and the damping ratio for the system was been calculate. The system stability analysis is given by the existence of a Lyapunov function for the system. The stability of a system can also be characterized by the eigenvalues of the system. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Research into Expert Systems to Aid Simulation Model Formulation

The widespread availability of inexpensive computing power and recent developments in machine intelligence now makes it possible to consider computer assistance in the formulation phase of a discrete-event simulation model. The goal is to speed up this process. With this in mind, a series of prototype expert systems (written in LISP and run on an APPLE II) have been produced. The first prototype system was built using the ‘MYCIN’ approach. In the second prototype system a more informal approach was used, and the resulting computer-aided system is a natural-language understanding system. This paper outlines the need for such research and discusses the system development by describing the two main models and explaining why the natural-language approach was adopted.     

An Operations Research Approach to the Problem of the Sugarcane Selection

Selection for superior clones is the most important aspect of sugar cane improvement programs, and is a long and expensive process. While studies have investigated different components of selection independently, there has not been a whole system approach to improve the process. This study observes the problem as an integrated system, where if one parameter changes the state of the whole system changes. A computer based stochastic simulation model that accurately represents the selection was developed. This paper describes the simulation model, showing its accuracy as well as how a combination of dynamic programming and branch and bound can be applied to the model to optimise the selection system, giving a new application of these techniques. The model can be directly applied to any region targeted by sugarcane breeding programs or to other clonally propagated crops.     

A dynamic unreliability assessment and optimal maintenance strategies for multistate weighted k‐out‐of‐n:F systems

In this paper, a dynamic evaluation of the multistate weighted k‐out‐of‐n:F system is presented in an unreliability viewpoint. The expected failure cost of components is used as an unreliability index. Using failure cost provides an opportunity to employ financial concepts in system unreliability estimation. Hence, system unreliability and system cost can be compared easily in order to making decision. The components' probabilities are computed over time to model the dynamic behavior of the system. The whole system has been assessed by recursive algorithm approach. As a result, a bi‐objective optimization model can be developed to find optimal decisions on maintenance strategies. Finally, the application of the proposed model is investigated via a transportation system case. Matlab programming is developed for the case, and genetic algorithm is used to solve the optimization model. Copyright © 2016 John Wiley & Sons, Ltd.     

Novel dynamics of a predator–prey system with harvesting of the predator guided by its population

A predator–prey model was extended to include nonlinear harvesting of the predator guided by its population, such that harvesting is only implemented if the predator population exceeds an economic threshold. The proposed model is a nonsmooth dynamic system with switches between the original predator-prey model (free subsystem) and a model with nonlinear harvesting (harvesting subsystem). We initially examine the dynamics of both the free and the harvesting subsystems, and then we investigate the dynamics of the switching system using theories of nonsmooth systems. Theoretical results showed that the harvesting subsystem undergoes multiple bifurcations, including saddle-node, supercritical Hopf, Bogdanov–Takens and homoclinic bifurcations. The switching system not only retains all of the complex dynamics of the harvesting system but also exhibits much richer dynamics such as a sliding equilibrium, sliding cycle, boundary node (saddle point) bifurcation, boundary saddle-node bifurcation and buckling bifurcation. Both theoretical and numerical results showed that, by implementing predator population guided harvesting, the predator and prey population could coexist in more scenarios than those in which the predator may go extinct for the continuous harvesting regime. They could either stabilize at an equilibrium or oscillate periodically depending on the value of the economic threshold and the initial value of the system.     

An intelligent system for prioritisation of organ transplant patient waiting lists using fuzzy logic

The objective of this paper is to investigate the effectiveness of using fuzzy logic in a complex decision-making capacity, and in particular, for the prioritisation of kidney transplant recipients. Fuzzy logic is an extension to Boolean logic allowing an element to have degrees of true and false as opposed to being either 100% true or 100% false. Thus, it can account for the ‘shades of grey’ found in many real-world situations. In this paper, two fuzzy logic models are developed demonstrating its effectiveness as a model for vastly improving the current prioritisation system used in the UK and abroad. The first model converts an element of the current kidney transplant prioritisation system used in the UK into fuzzy logic. The result is an improvement to the current system and a demonstration of fuzzy logic as an effective decision-making approach. The second model offers an alternative prioritisation system to overcome the limitations of the current system both in the UK and abroad, as brought up by research reviewed in this paper. The current UK transplant prioritisation system, adapted in the first model, uses objective criteria (age of recipient, waiting time, etc) as inputs into the decision-making process. This alternative model takes advantage of the facility for infinitely varying inputs into fuzzy logic and a system is developed that can handle subjective (humanistic) criteria (pain level, quality of life, etc) that are key to arriving at such important decisions. Furthermore, the model is highly flexible allowing any number of criteria to be used and the individual characteristics of each criterion to be altered. The result is a model that utilises the scope of fuzzy logic's flexibility, usability and effectiveness in the field of decision-making and a transplant prioritisation method vastly superior to the original system, which is constrained by its use of only objective criteria. The ‘humanistic’ model demonstrates the ability of fuzzy logic to consider subjective and complex criteria. However, the criteria used are not intended to be exhaustive. It is simply a template to which medical professionals can apply limitless additional criteria. The model is produced as an alternative to any current national system. However, the model can also be used by individual hospitals to decide initially whether a patient should be placed on the transplant or surgery waiting list. The model can be further adapted and used for the transplant of other organs or similar decisions in medicine. Concurrently with the research and work carried out to develop the two models the investigation focused on the constraints of the current systems used in the UK and the US and the seemingly impossible dilemmas experienced by those having to make the prioritisation decisions. By removing the parameters of objective-only inputs the ‘humanistic’ model eradicates the previous limitations on decision-making.     

一类新的含有垂直传染与脉冲免疫的时滞SEIR传染病模型的全局动力学行为

对一个带有有害时滞与垂直传染的SEIR传染病模型,在脉冲免疫接种条件下,分析了其动力学行为．运用离散动力系统的频闪映射,获得了一个‘无病’周期解,证明了当模型的一些参数在适当的条件下,该‘无病’周期解是全局吸引的．运用脉冲时滞泛函微分方程理论,获得了含有时滞的持久性的充分条件,并且证明了时滞、脉冲免疫与垂直传染对模型的动力学行为能够产生显著的影响．结论表明该时滞是“有害”时滞．     

Optimal maintenance scheduling for a complex manufacturing system subject to deterioration

We address the problem of determining inspection strategy and replacement policy for a deteriorating complex multi-component manufacturing system whose state is partially observable. We develop inspection and replacement scheduling models and other simple maintenance scheduling models via employing an imperfect repair model coupled with a damage process induced by operational conditions. The system state in performance of the imperfectly repaired system is modelled using a proportional intensity model incorporating a damage process and a virtual age process caused by repair. The system is monitored at periodic times and maintenance actions are carried out in response to the observed system state. Decisions to perform imperfect repair and replacement are based on the system state and crossing of a replacement threshold. The model proposed here aims at joint determination of a cost-optimal inspection and replacement policy along with an optimal level of maintenance which result in low maintenance cost and high operational performance and reliability of the system. To demonstrate the use of the model in practical applications a numerical example is provided. Solutions to optimal system parameters are obtained and the response of the model to these parameters is examined. Finally some features of the model are demonstrated. The approach presented provides a framework so that different scenario can be explored.     

A neural network system for solving an assortment problem in the steel industry

A neural network model for solving an assortment problem found in the iron and steel industry is discussed in this paper. The problem arises in the yard where steel plate is cut into rectangular pieces. The neural network model can be categorized as a Hopfield model, but the model is expanded to handle inequality constraints. The idea of a penalty function is used. A large penalty is applied to the network if a constraint is not satisfied. The weights are updated based on the penalty values. A special term is added to the energy function of the network to guarantee the convergence of the neural network which has this feature. The performance of the neural network was evaluated by comparison with an existing expert system. The results showed that the neural network has the potential to identify in a short time near-optimal solutions to the assortment problem. The neural network is used as the core of a system for dealing with the assortment problem. In building the neural networks system for practical use, there were many implementation issues. Some of them are presented here, and the fundamental ideas are explained. The performance of the neural network system is compared to that of the expert system and evaluated from the practical viewpoint. The results show that the neural network system is useful in handling the assortment problem.     

Queueing Theory in the Solution of a Transport Evaluation Problem

The problem of minimizing the overall cost of operating the internal transport system of a steelworks is examined. The paper describes the practical problem encountered by an OR team and the approach that was adopted in the subsequent study. This approach led to the development of a simple queueing model of the rail transport system, which accounted for 90 per cent of the weight of material moved within the steelworks complex. The model was used to evaluate alternative methods of operating and controlling the rail transport system. The findings of the study were implemented and some of the operational details are outlined in the paper. Savings of at least 10 per cent in operating costs were achieved by the study.Hence this paper presents a detailed case study of a comprehensive approach to a transport planning and evaluation problem.