Observing student working styles when using graphic calculators to solve mathematics problems

Some research studies, many of which used quantitative methods, have suggested that graphics calculators can be used to effectively enhance the learning of mathematics. More recently research studies have started to explore students’ styles of working as they solve problems with technology. This paper describes the use of a software application that records the keystrokes made by students as they use calculators, in order to enable researchers to gain better insights into students’ working styles. The recordings obtained from this software can be replayed to observe how students have actually used their calculator in tackling a problem. The paper describes three pilot studies from quite different contexts, in which the software reveals how the calculators have been used by the students. In all of these studies the software provides insights into the working that would have been very difficult to obtain without the record of the keystrokes provided by the software.     

New insights on the single machine total tardiness problem

Virtually all algorithmic studies on the single machine total tardiness problem use Emmons’ theorems that establish precedence relations between job pairs. In this paper, we investigate these theorems with a geometric viewpoint. This approach provides a compact way of representing Emmons’ theorems and promotes better insights into dominance properties. We use these insights to differentiate between certain classes of easy and hard instances.     

Optimal dividend and capital injection problem in the dual model with proportional and fixed transaction costs

In this paper we consider the dividend payments and capital injections control problem in a dual risk model. Such a model might be appropriate for a company that specializes in inventions and discoveries, which pays costs continuously and has occasional profits. The objective is to maximize the expected present value of the dividends minus the discounted costs of capital injections. This paper can be considered as an extension of Yao et al. (2010), we include fixed transaction costs incurred by capital injections in this paper. This leads to an impulse control problem. Using the techniques of quasi-variational inequalities (QVI), this optimal control problem is solved. Numerical solutions are provided to illustrate the idea and methodologies, and some interesting economic insights are included.     

负载均衡问题

自Ron Graham20世纪60年代发表第一篇负载均衡算法的论文以来,平行机排序作为组合优化近似算法理论的首个问题引起了学界的广泛兴趣,其本身研究的不断深化也一路见证了该领域的发展历程.介绍负载均衡问题的来龙去脉,特别是作者所在团队在相关问题的研究进展,从算法和复杂性不同的视角分析经典问题的计算本质,并对未来的研究提出一些建议.     

Operational Research and Innovation in Management Methods

This paper is an attempt to specify some of the conditions which would need to be met both in the staffing of a group and in its place in the organization, if operational research is to play a part in initiating change in the processes of decision-making. An analogy is drawn with the "planned change" of the behavioural sciences.The conflict inherent in the role is identified. To illustrate the kinds of insights the group would need to possess, into the structure of an organization, and the ways its control systems operate, examples of long-, medium- and short-term decision-making are given.Finally, an attempt is made to identify the characteristics which the group would need to possess for success in this innovative role, including its knowledge, attitudes and insights. The relationship between the group and the sponsor of work is discussed, and between the group and the parent organization in general. It is suggested that a participative style of organization would be the most appropriate for effective innovation in the methods of management by this means.     

OR as technology revisited

In this paper the issue of how OR is related to science and technology is revisited. An earlier argument that a modern view of science and technology offers a better explanation of this relationship than a traditional view is strengthened and developed. Using concepts drawn from the sociology of scientific knowledge (SSK) a new perspective on OR practice is introduced and shown to offer different insights into the work of OR practitioners and the way OR may be understood in relation to science and technology.     

Sizing initial stockpiles in a conventional military retrograde movement

The importance of stockpiles in waging and supporting war has long been recognized by the military. However, despite this recognition, very few theoretical attempts have been undertaken to incorporate stockpile considerations in land combat models. This paper describes a multicriteria optimization model to estimate the minimum stockpile required to sustain fighting a conventional mobile delaying land battle. By studying the post-optimality analysis, valuable insights on the relationships between the key governing parameters can be established.     

Schedule-induced posets

Schedules are a basic tool in the treatment of project networks and sequencing problems. For many questions, however, it is not the schedule itself but a partial order (poset) naturally induced on the set of activities that is really relied on. In fact, this correspondence of the usually uncountably many schedules to a finite system of posets was a key to many recent results in this field and constitutes the discrete character of the described problems, all the more so as additional properties of the respective schedules can very often be reflected in related properties of these induced posets.The present paper gives insights into the class of those posets that can be induced by schedules. An immediate observation is that schedule-induced posets are just the interval orders. More involved characterizations are concerned with the possible ‘local optimality’ of such structures. One such property is the existence of activity durations that will result in a project duration of the considered poset that is shorter (simultaneously) than the duration of all its extensions. A similar, related characterization for general regular cost functions (in particular tardiness cost) is also included, as are insights into ‘best’ activity durations with the mentioned properties.The paper closes with some remarks and numerical data on the considered class of posets as a whole.     

An economic order quantity model for deteriorating item in a purchasing system with multiple prepayments

In the classic economic order quantity model the purchasing cost of an order should be paid at the time of its receipt. Sometimes, retailers ask purchasers to pay all or a fraction of the purchasing cost in advance and sometimes allow them to divide the prepayment into several equal-sized parts. In this paper, economic order quantity model for a deteriorating product with and without shortage under consecutive prepayments are developed. Numerical examples illustrate the proposed models and solution method and sensitivity analysis provides some managerial insights for managers.     

OR as Technology: Some Issues and Implications

There has been a growing acceptance of the view that OR can be more appropriately understood as a technology rather than as a science. This view has, however, not been fully developed. This paper seeks to extend this area of investigation by addressing three issues: first, to consider why it is inappropriate to see OR as a science; second, if OR is to be seen as a technology, to ask what model of a technology, the classical or the modern, should be adopted; finally, to explore what implications for understanding OR are held by the most appropriate model of OR as technology. This paper shows that valuable insights might be gained for understanding and guiding the development of OR by seeing it as a technology.     

Towards user-friendly OR: a Chinese experience

In contemporary China, user-friendliness has become not only a necessity for the success of OR projects but also a must for the survival of OR workers. This paper presents an approach that, based upon insights from Chinese thought as well as OR/MS experience in the Chinese context since the 1950s, can be useful for improving user-friendliness in the OR process. The paper also reports a real-world project in which OR workers pursue the user-friendliness of their work under the guidance of these insights and approach. A cultural analysis suggests that, while user-friendly OR is a universal concern, the Eastern and Western ways of tackling the issue appear different. The paper concludes that, in reality, Chinese OR workers must enhance their vision and skills so as to solve sociotechnical problems with diverse methods and do so in a user-friendly manner.     

A branch-and-cut algorithm for the multi-compartment vehicle routing problem with flexible compartment sizes

Multi-compartment vehicle routing problems arise in a variety of problem settings in which different product types have to be transported separated from each other. In this paper, a problem variant which occurs in the context of glass waste recycling is considered. In this problem, a set of locations exists, each of which offering a number of containers for the collection of different types of glass waste (e.g. colorless, green, brown glass). In order to pick up the contents from the containers, a fleet of homogeneous disposal vehicles is available. Individually for each disposal vehicle, the capacity can be discretely separated into a limited number of compartments to which different glass waste types are assigned. The objective of the problem is to minimize the total distance to be travelled by the disposal vehicles. For solving this problem to optimality, a branch-and-cut algorithm has been developed and implemented. Extensive numerical experiments have been conducted in order to evaluate the algorithm and to gain insights into the problem structure. The corresponding results show that the algorithm is able to solve instances with up to 50 locations to optimality and that it reduces the computing time by 87% compared to instances from the literature. Additional experiments give managerial insights into the use of different variants of compartments with flexible sizes.

     

Local Structure of The Set of Steady-State Solutions to The 2d Incompressible Euler Equations

It is well known that the incompressible Euler equations can be formulated in a very geometric language. The geometric structures provide very valuable insights into the properties of the solutions. Analogies with the finite-dimensional model of geodesics on a Lie group with left-invariant metric can be very instructive, but it is often difficult to prove analogues of finite-dimensional results in the infinite-dimensional setting of Euler’s equations. In this paper we establish a result in this direction in the simple case of steady-state solutions in two dimensions, under some non-degeneracy assumptions. In particular, we establish, in a non-degenerate situation, a local one-to-one correspondence between steady-states and co-adjoint orbits.     

Possible activities facilitating solving processes: a lesson from a stuck state

States where solvers are stuck are important points in mathematical problem-solving processes. The purpose of this paper is to examine such states from the viewpoint of how a solver sees a problem situation and to obtain some insights into the kinds of activities which help solvers overcome such states. For this purpose, the information the solver has before the stuck state will be analysed closely. While the gap between such information and a typical solution will be checked, the opportunities the solver could have had in his/her solving process to bridge this gap will be identified based on the analysis of the process. Such discussion will show the importance of investigating problem situations and gathering information about them. A relation between such activity and heuristics will be also discussed.     

A computational analysis of lower bounds for big bucket production planning problems

In this paper, we analyze a variety of approaches to obtain lower bounds for multi-level production planning problems with big bucket capacities, i.e., problems in which multiple items compete for the same resources. We give an extensive survey of both known and new methods, and also establish relationships between some of these methods that, to our knowledge, have not been presented before. As will be highlighted, understanding the substructures of difficult problems provide crucial insights on why these problems are hard to solve, and this is addressed by a thorough analysis in the paper. We conclude with computational results on a variety of widely used test sets, and a discussion of future research.     

Solutions to Painleve III and other nonlinear equations by a generalized Cole–Hopf transformation

In this paper, we introduce a generalized form of Cole‐Hopf transformation and apply it to find new closed‐form (analytic) solutions to Painleve III equation. The same transformation is used then to find analytic solutions for the van der Pol and other nonlinear convective equations. These solutions provide analytic insights to some practical problems and might be used also to test the accuracy of numerical solutions. Copyright © 2017 John Wiley & Sons, Ltd.     

Simulation techniques for the sensitivity analysis of multi-criteria decision models

This paper presents a simulation approach for high dimensional sensitivity analysis of the weights of multi-criteria decision models. This approach allows simultaneous changes of the weights and generates results that can easily be analyzed statistically to provide insights into multi-criteria model recommendations. In this study we consider three cases: no information, order information, and partial information regarding the weights. Our approach also allows investigation of sensitivity to the form of multi-criteria decision models. The simulation procedures we propose can also be used to aide in the actual decision process, particularly when the task is to select a subset of superior alternatives.     

Inventory and investment in setup and quality operations under Return On Investment maximization

In this paper, we construct and analyze a Return On Investment (ROI) maximization model for inventory and capital investment in setup and quality operations under an investment budget constraint. Specifically, we show how such an ROI maximization model can be formulated and derive analytical results such as the conditions under which the inventory is reduced and for the determination of the unique global optimal solution. In addition, by applying the Reformulation-Linearization Technique (RLT), we show via numerical examples how this nonconvex optimization model can be solved effectively and how RLT may produce superior results to those from the conventional Cut Across the Board Rule (CABR). Various managerial insights are provided throughout the paper. For example, as the investment budget increases (or decreases), a fundamental shift of investment strategies (setup cost reduction vs. quality improvement) may be necessary so as to maximize ROI.     

Profit oriented supply chain network optimization

This paper proposes a novel mixed integer linear programming model to solve a supply chain network design problem. The proposed model deals with major issues for supply chains; product quality and cost. These issues are usually solved separately, but in this paper, we investigate effects of product quality on supply chain design and transportation flow. A trade-off between raw material quality, its purchasing and reprocessing costs was considered. Assuming decision maker (DM) wishes to work with a supplier which serves a low quality raw material; this raw material should be in need of reprocessing. To avoid the reprocessing costs, a supplier which serves a high quality raw material should be chosen but at this time the DM has to face a high purchasing cost. A supply chain network which consists of multiple suppliers, manufacturers, distribution centers and retailers is tried to be designed to accomplish aforementioned above trade-offs. The paper examines and discusses the relationship between product quality and supply chain design and offers several managerial insights.