One of my PhD students, for who I am a co-supervisor, has just finished the defense of her thesis titled “Methods for Sensor Based Farrowing Prediction and Floor-heat Regulation: The Intelligent Farrowing Pen“. I would like to congratulate Aparna with her PhD title and for a good thesis and presentation at the defense. I have included the thesis summary below.
The research paper “Ranking paths in stochastic time-dependent networks” have been accepted for publication in European Journal of Operational Research. In this paper we address optimal routing problems in networks where travel times are both stochastic and time-dependent. In these networks, the best route choice is not necessarily a path, but rather a time-adaptive strategy that assigns successors to nodes as a function of time. Nevertheless, in some particular cases an origin-destination path must be chosen a priori, since time-adaptive choices are not allowed. Unfortunately, finding the a priori shortest path is an NP-hard problem. We propose a solution method for the a priori shortest path problem, and we show that it can be easily extended to the ranking of the first K shortest paths. Our method exploits the solution of the time-adaptive routing problem as a relaxation of the a priori problem. Computational results are presented showing that, under […]
From 17-22 June 2013 I have been participating in MCDM 2013 in Malaga. The 22nd International Conference on Multiple Criteria Decision Making. The conference was held in a nice atmosphere and the city can be recommended. I coauthored a talk about the Bicriterion Stochastic Knapsack Problem which is a problem we currently are working on.
The research paper “Inventory control in a lost-sales setting with information about supply lead times” have been accepted for publication in International Journal of Production Economics. We consider a periodically reviewed single-item inventory system in a lost sales setting where at most one order can be outstanding at a time and compare the performance of an inventory model assuming informed lead times to a model assuming uninformed independent and identically distributed lead times.
This week I am participating in the EURO conference in Vilnius where I have a joint talk “Spare parts sharing with joint optimization of maintenance and inventory policies” with my college Christian Larsen.
The VeRoLog 2012 conference in Boglogna has just ended. I gave a talk about “Ranking shortest paths in Stochastic time-denpendent networks”. The conference had approximately 160 participants.
En populærvidenskabelig artikel er netop udkommet i OrBit omkring min MDP model for udskiftning af malkekvæg. “Det optimale udskiftningstidspunkt for en malkeko“, L.R. Nielsen and E. Jørgensen, OrBit, 17, 14-16 (2010).
The research paper “Quantifying walking and standing behaviour of dairy cows using a moving average based on output from an accelerometer” have been accepted for publication in Applied Animal Behaviour Science. It presents research from my time at DJF where we use a moving average to predict walking and standing behaviour of dairy cows.
I have written a small note about mapping a multidimensional index into a unique id. An unique id might be useful e.g. when having multiple state variables in an Markov decision process. Here each state at a stage may be identified using the id.
Two of my papers have been accepted for publication. “Optimal Replacement Policies for Dairy Cows Based on Daily Yield Measurements” have been published in Journal of Dairy Scienc. Abstract: Markov decision processes (MDP) with finite state and action space have often been used to model sequential decision making over time in dairy herds. However, the length of each stage has been at least 1 mo, resulting in models that do not support decisions on a daily basis. The present paper describes the first step of developing an MDP model that can be integrated into a modern herd management system. A hierarchical MDP was formulated for the dairy cow replacement problem with stage lengths of 1 d. It can be used to assist the farmer in replacement decisions on a daily basis and is based on daily milk yield measurements that are available in modern milking systems. Bayesian updating was used […]