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Congzheng Liu

Publications and source records attributed to Congzheng Liu.

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Newsvendor Conditional Value-at-Risk Minimisation: a Feature-based Approach under Adaptive Data Selection

The classical risk-neutral newsvendor problem is to decide the order quantity that maximises the expected profit. Some recent works have proposed an alternative model, in which the goal is to minimise the conditional value-at-risk (CVaR), a different but very much important risk measure in financial risk management. In this paper, we propose a feature-based non-parametric approach to Newsvendor CVaR minimisation under adaptive data selection (NPC). The NPC method is simple and general. It can handle minimisation with both linear and nonlinear profits, and requires no prior knowledge of the demand distribution. Our main contribution is two-fold. Firstly, NPC uses a feature-based approach. The estimated parameters of NPC can be easily applied to prescriptive analytic to provide additional operational insights. Secondly, unlike common non-parametric methods, our NPC method uses an adaptive data selection criterion and requires only a small proportion of data (only data from two tails), significantly reducing the computational effort. Results from both numerical and real-life experiments confirm that NPC is robust with regard to difficult and large data structures. Using fewer data points, the computed order quantities from NPC lead to equal or less downside loss in extreme cases than competing methods.

math.OC

An integrated mixed integer program model for the two-level capacitated vehicle routing problem with extensions

This paper introduces the two-level capacitated vehicle routing problem (2S-CVRP). This problem combines the two-level bin packing problem and the vehicle routing problem into an integrated framework. The problem itself is an NP-hard problem and it can be seen as an extension to the traditional capacitated vehicle routing problem (CVRP). We propose this extension as it enable one to model more real-life applications in logistics. A mixed integer program (MIP) model is presented for the problem. Our MIP model includes an extensive set of constraints encountered in real-world applications. The validity of the model is tested on both artificial and real-life instances.

math.OC

Naive Newsvendor Adjustments: Are They Always Detrimental?

Newsvendor problems are an important and much-studied topic in stochastic inventory control. One strand of the literature on newsvendor problems is concerned with the fact that practitioners often make judgemental adjustments to the theoretically "optimal" order quantities. Although judgemental adjustment is sometimes beneficial, two specific kinds of adjustment are normally considered to be particularly naive: demand chasing and pull-to-centre. We discuss how these adjustments work in practice and what they imply in a variety of settings. We argue that even such naive adjustments can be useful under certain conditions. This is confirmed by experiments on simulated data. Finally, we propose a heuristic algorithm for "tuning" the adjustment parameters in practice.

math.OC