Sustainable design of a closed-loop location-routing-inventory supply chain network under mixed uncertainty

Considering economic, environmental and social impacts, this paper presents a new sustainable closed-loop location-routing-inventory model under mixed uncertainty. The environmental impacts of CO₂ emissions, fuel consumption, wasted energy and the social impacts of created job opportunities and economic development are considered in this paper. The uncertain nature of the network is handled using a stochastic-possibilistic programming approach. Furthermore, for large-sized problems, a hybrid meta-heuristic algorithm and lower bounds are developed and discussed. Finally, a real case study is provided to demonstrate the applicability of the model in real-world applications, and several in-depth analyses are conducted to develop managerial implications.     

Analyzing tactical control strategies for aircraft arrivals at an airport using a queuing model

This paper proposes to analyze control strategies for arrival air traffic at an airport using a classical queuing model. The parameters of our model are estimated by means of a data-driven analysis of two years of radar tracks and flight plans for arrival flights at Tokyo International Airport from 2016 to 2017. Our results show that increasing the capacity with one or two more aircraft in the airspace up to 60 NM around the airport significantly mitigates arrival delays, even when assuming future, increased arrival traffic volumes. The outcomes of this study provide insights into the effectiveness of arrival control strategies and are seen as a means to recommend scenarios to be further analyzed with human-in-the-loop simulations.     

“I got it FIRST”: Antecedents of competitive consumption of a new product

When a new product of a well-known brand is released, consumers wait in line as early as possible to increase their chances of purchasing the product. This research investigated the two-stage competitive arousal model of a new product purchase competition. Results of a structural equation modeling with a multi-group analysis approach showed that competitive arousal was a central psychological state stimulated by product uniqueness, scarcity, popularity, need for uniqueness, and self-enhancement value, influencing the intention to queue in line. Practical insights in targeting the right consumers and promoting a new product to draw optimal attention from consumers were further discussed.     

The optimal disposition decision for product returns

We provide an analytic model for the optimal disposition decision for product returns. The manager decides which product returns to accept for processing at the remanufacturing facility, and which ones to sell immediately as-is at a salvage value. High congestion levels in the remanufacturing facility delay the sale of the remanufactured product at the secondary market, decreasing the value at which it can be sold; this may imply a more attractive salvaging option. This is particularly important for high-tech products with short life cycles, such as computers and printers. We propose a two-step policy. In the first step, the returned product’s random processing time is observed. In the second step, a disposition decision is made: if the processing time is larger than a threshold k* the product is salvaged; otherwise the product is remanufactured. We provide an approximate procedure to compute k* in industrial settings. Our numerical study demonstrates the superiority of our policy over the current industrial practice ignoring the time value of money.     

Internalisation by electronic FX spot dealers

Dealers in over-the-counter financial markets provide liquidity to customers on a principal basis and manage the risk position that arises out of this activity in one of two ways. They may internalise a customer's trade by warehousing the risk in anticipation of future offsetting flow, or they can externalise the trade by hedging it out in the open market. It is often argued that internalisation underlies much of the liquidity provision in the currency markets, particularly in the electronic spot segment, and that it can deliver significant benefits in terms of depth and consistency of liquidity, reduced spreads, and a diminished market footprint. However, for many market participants, the internalisation process can be somewhat opaque, data on it are scarcely available, and even the largest and most sophisticated customers in the market often do not appreciate or measure the impact that internalisation has on their execution costs and liquidity access. This paper formulates a simple model of internalisation and uses queuing theory to provide important insights into its mechanics and properties. We derive closed form expressions for the internalisation horizon and demonstrate—using data from the Bank of International Settlement's triennial FX survey—that a representative tier 1 dealer takes on average several minutes to complete the internalisation of a customer's trade in the most liquid currencies, increasing to tens of minutes for emerging markets. Next, we analyse the costs of internalisation and show that they are lower for dealers that are willing to hold more risk and for those that face more price-sensitive traders. The key message of the paper is that a customer's transaction costs and liquidity access are determined both by their own trading decisions as well as the dealer's risk management approach. A customer should not only identify the externalisers but also distinguish between passive and aggressive internalisers, and select those that provide liquidity compatible with their execution objectives.     

RPR三种优先级业务的时延吞吐量性能分析

弹性分组环(ResilientPacketRing,RPR)是IEEE802.17正在进行标准化主要用于城域网的新型MAC层协议,也是宽带IP光城域网技术的重要发展方向。RPR在结构上从属寄存器插入环,其时延性能为业界所关注。本文根据RPR包含3个传输缓存的完整模型,利用排队论,对两种转发缓存结构下RPR3种优先级业务的排队时延吞吐量性能进行深入分析并比较,得到最大吞吐量和节点数目的关系、单转发缓存和双转发缓存结构下RPR的3种优先级业务的排队时延吞吐量性能及其对比、排队时延和节点数目的关系等一系列极具参考价值的结果。     

Charging parking by the minute: What to expect from this parking pricing policy?

In the days when parking had to be charged by a person or a mechanical device, it made sense to charge by blocks of time. However, these days, computers are capable of charging by the minute (or second if an operator so chooses), so technically there is no need for block pricing and the pricing strategy can be a policy decision. Operators, in one hand, are unaware of the impact of this measure on parking turnover and may believe that daily income will be affected. Businesses, on the other hand, will want to know if the measure has an effect on whether or not trips motivated by non-social activities will be carried out, given that they are spontaneous and are directly related to a client's perception. Finally, practical implications in terms of client response have not been studied, since smaller charging blocks may be considered as a disincentive to make additions to stay duration; this has repercussions on turnover and consequently on wait time at the entrance. This paper covers the abovementioned topics based on a study carried out in Barcelona (Spain).     

Queues, not just mediocrity: Inefficiency in decentralized markets with vertical differentiation

We analyze a dynamic, decentralized market with endogenous entry, where in each period the active sellers supply one unit of an indivisible service at varying degrees of quality. The customers that have entered the market are randomly matched with the active sellers and prices are set by (complete information) pair-wise bargaining. In its unique steady state, the market leads to an excess diversity of quality and customers may have to suffer costly delays. Notably, efficiency is not regained as per period delay costs disappear. We also show that setting minimal quality standards, such as licensing rules by a professional college, will improve welfare (and even Consumer Surplus), relative to the free market, whenever the inefficiency is caused by a large enough excess supply.     

Endogenous control of service rates in stochastic and dynamic queuing models of airport congestion

Airport congestion mitigation requires reliable delay estimates. This paper presents an integrated model of airport congestion that combines a tactical model of capacity utilization into a strategic queuing model. The model quantifies the relationships between flight schedules, airport capacity and flight delays, while accounting for the way arrival and departure service rates can be controlled over the day to maximize operating efficiency. We show that the model estimates the average and variability of the delays observed at New York’s airports relatively well. Results suggest that delays can be extremely sensitive to even small changes in flight schedules or airport capacity.     

Multi-objective design of an organ transplant network under uncertainty

We propose a novel multi-period location–allocation model for the design of an organ transplant transportation network under uncertainty. The model consists of a bi-objective mathematical programming model that minimizes total cost and time, including waiting time in the queue for the transplant operation, while considering organs’ priorities. A fuzzy multi-objective programming based approach is presented to solve the small and medium size problems to optimality. For larger problems, we propose two meta-heuristics based algorithms. Lower bounds, and several numerical examples with managerial insights are discussed. A real case-study is provided, and the existing and the proposed optimal solutions are compared.