Annals of Operations Research最新文献

The Production Routing Problem (PRP) seeks optimal production and distribution planning that minimises costs and fulfils customer orders. Yet, existing literature often overlooks the potential impact on profitability. Achieving optimal profit does not necessarily imply meeting all customer orders. The cost-to-profit ratio should be considered when serving customer orders, as there are circumstances where it might be more profitable to cancel or backorder certain orders. Thus, this paper proposes, for the first time, a novel extension of PRP that maximises profit where demand is price-sensitive and allows order cancellation and backorders under service level targets. From on-field observations, price is inherently subject to uncertainty; thus, we propose a robust mathematical model for the problem that optimises the worst-case profit. To solve the problem, the paper proposes a decomposition algorithm that splits the problem into a master problem and a set of subproblems, enhanced by valid inequalities and warming up lower bounds to alleviate the model complexity. Through a series of computational tests, we prove the ability of the proposed algorithm to tighten the optimality gaps and alleviate computational time. An additional economic study is conducted to investigate how parameter variation affects profit and how sensitive it is to service level targets.

One examines and discusses proposals on whether riders could be replaced in a team during multi-stage races, and how much a team final time at the end of the race would change (be "adjusted") if only the riders having completed the race are taken into account for ranking teams. A few results of the two main multi-stage races, the men Tour de France and the Giro d’Italia, are used as case studies. The impact of disqualification later on, due to doping, much after the end of such a race, is also examined in the case of two Tour de France. The statistical discussion is based on the Kendall-(tau ) coefficients for comparing team ranks at the end of these multi-stages races cases. One observes that there are significant differences in the results of the discussed measures. It is shown that there is much variety in results significance, whence demonstrating many interests of the "adjusted indicators". Moreover, it is argued that the "adjusted" rank indicator would promote more competitive and more attractive daily stages and lead to more valuable race management.

Within service systems, tasks can encompass diverse functionalities. In a two-phase queuing model featuring two customer priority classes, our study discerns two distinct task functionalities executed by the first-phase server (referred to as the auxiliary server). These tasks aim to facilitate priority-based service by the second-phase server (referred to as the expert). Load-balancing tasks aim to alleviate the expert’s workload, while differentiation tasks seek to enhance accurate customer prioritization in the second phase by reducing misclassifications. With customers queuing for both the auxiliary server and the expert in tandem, our investigation focuses on determining the optimal allocation of the auxiliary server’s time between these load-balancing and differentiation tasks. Through queuing optimization, we aim to minimize customers’ expected total delay cost. In scenarios where the auxiliary server is allowed to perform only one task type (either load-balancing or differentiation), we delineate the optimal solutions based on specific functional forms dictating the server’s efficiency in executing each task type. These solutions strike a balance between excess phase capacities and the square root of marginal cost-to-saving ratios arising from each task type. Additionally, we partially characterize the optimal solution in scenarios permitting both load-balancing and differentiation tasks. Notably, under high system loads, executing load-balancing tasks proves more efficient than differentiation tasks. However, the relationship between the optimal task durations and system load showcases a non-monotonic pattern. As AI decision support products increasingly enable expert providers to delegate “routine” tasks to mid-level providers, our study sheds light on the efficient allocation of different tasks to different provider types to minimize delay costs in service systems.

The aim of this paper is to establish a necessary and sufficient condition for the non-emptiness of the core in NTU games in partition function form, given an externality scheme ( f in textsf{Ex}(N) ). We extend the notion of convexity to incorporate externality effects. By introducing a new concept of rationality, called collective rationality, we demonstrate the efficiency of the grand coalition ( N ). We also identify a sufficient condition for the efficiency of the grand coalition using the property of individual superadditivity.

Over the past 150 years, life expectancy doubled and healthy life expectancy increased. Expectations reveal nothing about variability, so we present a stochastic analysis to investigate changes over time, age and gender of variation, among individuals, in healthy lifespan, for different levels of country income. To complement health-adjusted life expectancy (HALE) data from the Global Burden of Disease Study, we use a stochastic model to compute the standard deviation of healthy life (SDHL). The model is a finite-state absorbing Markov chain with rewards. It includes stochastic survival, mortality, and loss of good health status. An individual surviving from one age to the next gains, as a "reward," a year of good health. This method provides all the moments of healthy longevity. The mean healthy longevity is exactly the HALE. As a measure of variation, here we focus on the standard deviation of healthy longevity. From 1990 to 2019, HALE increased, with greater increases at younger ages. At the same time, SDHL at younger ages decreased and at older ages increased. The most significant changes at birth occurred in low- and lower-middle-income countries. High- and upper-middle-income countries saw notable increases at old ages. Women generally have longer HALE and higher SDHL, but the overall HALE increase was greater for men. The reduction in SDHL over time suggests that more individuals benefit from increased longevity, particularly in low-income countries closing the gap with high-income countries. However, improvements in healthy survival at older ages appear unevenly distributed among individuals in high-income countries.