An MILP-based heuristic for staff scheduling problems with acceptance levels

We present a real-world staff-assignment problem that was reported to us by a provider of an online workforce scheduling software. The problem consists of assigning employees to work shifts subject to a large variety of requirements related to work laws, work shift compatibility, workload balancing, and personal preferences of employees. A target value is given for each requirement, and all possible deviations from these values are associated with acceptance levels. The objective is to minimize the total number of deviations in ascending order of the acceptance levels. We present an exact lexicographic goal programming MILP formulation and an MILP-based heuristic. The heuristic consists of two phases: in the first phase a feasible schedule is built and in the second phase parts of the schedule are iteratively re-optimized by applying an exact MILP model. A major advantage of such MILP-based approaches is the flexibility to account for additional constraints or modified planning objectives, which is important as the requirements may vary depending on the company or planning period. The applicability of the heuristic is demonstrated for a test set derived from real-world data. Our computational results indicate that the heuristic is able to devise optimal solutions to non-trivial problem instances, and outperforms the exact lexicographic goal programming formulation on medium- and large-sized problem instances.

Efficient list-generation techniques for scheduling assessment centers

Human resources managers often conduct assessment centers to evaluate candidates for a job position. During an assessment center, the candidates perform a series of tasks. The tasks require one or two assessors (e.g., managers or psychologists) that observe and evaluate the candidates. If an exercise is designed as a role-play, an actor is required who plays, e.g., an unhappy customer with whom the candidate has to deal with. Besides performing the tasks, each candidate has a lunch break within a prescribed time window. Each candidate should be observed by approximately half the number of the assessors; however, an assessor may not observe a candidate if they personally know each other. The planning problem consists of determining (1) resource-feasible start times of all tasks and lunch breaks and (2) a feasible assignment of assessors to candidates, such that the assessment center duration is minimized. We present a list-scheduling heuristic that generates feasible schedules for such assessment centers. We propose several novel techniques to generate the respective task lists. Our computational results indicate that our approach is capable of devising optimal or near-optimal schedules for real-world instances within short CPU time.

Collecting the Painted Netherlands: The Art Collection of Ernest of Austria in Brussels

The (art) collection of Archduke Ernest of Austria (1553-1595) is widely unknown when it comes to early-modern Habsburg collections. Ernest, younger brother of Emperor Rudolf II (b. 1552) and educated at the Madrid court, was appointed Governor-General of the Netherlands by King Philip II of Spain, his uncle, in summer 1593. Ernest relocated his court from Vienna to Brussels in early 1594 and was welcomed there with lavish festivities: the traditional Blijde Inkomst, Joyous Entry, of the new sovereign. Unfortunately, the archduke died in February 1595 after residing in Brussels for a mere thirteen months. This investigation aims to shed new light on the archduke and his short-lived collecting ambitions in the Low Countries, taking into account that he had the mercantile and artistic metropolis Antwerp in his immediate reach. I argue, that his collecting ambitions can be traced back to one specific occasion: Ernest’s Joyous Entry into Antwerp in June 1594. There the archduke received a series of six paintings of Pieter Bruegel the Elder (1525/30-1569) known as The Months (painted in 1565), hanging today in separate locations in Vienna, New York and Prague. These works of art triggered Ernest’s collecting ambitions and prompted him to focus mainly on works of art and artefacts manufactured at or traded within the Netherlands during the last eight months of his lifetime. Additionally, it will be shown that the archduke was inspired by the paintings’ motifs and therefore concentrated on acquiring works of art depicting nature and landscape scenes from the 1560s and 1590s. On the basis of the archduke’s recently published account book (Kassabuch) and of the partially published inventory of his belongings, it becomes clear that Ernest of Austria must be seen in line with the better-known Habsburg collectors and that his specific collection of “the painted Netherlands” can be linked directly to his self-fashioning as a rightful sovereign of the Low Countries.

The Forgotten Archduke: The Funeral Monument for Ernest of Austria in Brussels

Archduke Ernest of Austria (1553–1595), second son of Emperor Maximilian II and younger brother of Emperor Rudolf II, was in his youth a possible candidate for the thrones of the Empire or the Spanish Kingdom. Instead, he became Governor-General of the Netherlands in 1593 and relocated to Brussels in 1594 where he was welcomed with lavish festivities as the bearer of hope and prosperity. Unfortunately, Ernest died only thirteen months later without having achieved any political success. His brother and successor Albert of Austria commissioned the funeral monument for Ernest in 1600 after it was settled that he would be buried in Brussels and not Vienna. Focusing on this monument, which draws stylistically from various dynasty-related models, it will be shown that Albert intended to use this monument – and thus his brother’s memoria – to make the Brussels Cathedral the primary location of Habsburg dynastic memory in the Low Countries.

Enhanced Caching Strategies At the Edge of LTE Mobile Networks

With a boom in the usage of mobile devices for traffic-heavy applications, mobile networks struggle to deliver good performance while saving resources to support more users and save on costs. In this paper, we propose enhanced strategies for the preemptive migration of content stored in Information-Centric Networking caches at the edge of LTE mobile networks. With such strategies, the concept of content following the users interested in it becomes a reality and content within caches is more optimized towards the requests of nearby users. Results show that the strategies are feasible, efficient and, when compared to default caching strategies, ensure that content is delivered faster to end users while using bandwidth and storage resources more efficiently at the core of the network.