The Orienteering Problem under Uncertainty Stochastic Programming and Robust Optimization compared

The Orienteering Problem (OP) is a generalization of the well-known traveling salesman problem and has many interesting applications in logistics, tourism and defense. To reflect real-life situations, we focus on an uncertain variant of the OP. Two main approaches that deal with optimization under uncertainty are stochastic programming and robust optimization. We will explore the potentialities and bottlenecks of these two approaches applied to the uncertain OP. We will compare the known robust approach for the uncertain OP (the robust orienteering problem) to the new stochastic programming counterpart (the two-stage orienteering problem). The application of both approaches will be explored in terms of their suitability in practice

U–Pb zircon-rutile dating of the Llangynog Inlier, Wales: constraints on an Ediacaran shallow marine fossil assemblage from East Avalonia

The Llangynog Inlier of south Wales contains an assemblage of Ediacaran macrofossils from a shallow-marine environment, including discoidal morphs of Aspidella and rare examples of Hiemalora, Palaeopascichnus and Yelovichnus. These are taxa found in other sites in the Avalonian microcontinent (e.g. Charnwood Forest and eastern Newfoundland) and in the younger White Sea Ediacaran assemblages. As the Charnwood fossils reflect a deep-water environment, and no macrofossils have been found in the Ediacaran rocks of the Long Mynd, the fossils of the Llangynog Inlier represent a unique glimpse of shallow marine life in southern Britain (East Avalonia). However, the lack of absolute age constraints has hampered direct comparison with other assemblages. Here, we report in-situ zircon and rutile U–Pb dates from a rhyolitic ash-flow layer of the Coed Cochion Volcaniclastic Member, Llangynog Inlier, which constrains the age of the fossiliferous strata. A weighted mean single grain zircon ID-TIMS U–Pb age of 564.09 ± 0.70 Ma is interpreted as the rhyolite's crystallisation age. This age is consistent with in-situ LA-ICPMS zircon and rutile U–Pb dating. The Llangynog age temporally correlates these fossils to dated horizons within East Avalonia at the Beacon Hill Formation, Charnwood (565.22 ± 0.89 Ma), and the Stretton Shale Formation, Long Mynd (566.6 ± 2.9 Ma). Correlations to West Avalonia include the time-equivalent Fermeuse Formation, St John’s Group, eastern Newfoundland (564.13 ± 0.65 Ma). The data presented here establish the biota of the Llangynog Inlier as a lateral equivalent to the similarly shallow marine, tidally influenced ecosystem of the upper Fermeuse Formation. Intra-terrane depositional environmental variability also affects what is preserved in Avalonian fossil sites. Further, time-constrained geochemical data reinforce the Llangynog Inlier's classification within the Wrekin Terrane

An expanding culture of control? The municipal administrative sanctions Act in Belgium

This article provides an in-depth study of the Act on Municipal Administrative Sanctions 1999 (MAS), which is the first major piece of legislation regulating antisocial behaviour in Belgium. MAS provides municipalities with an instrument to sanction antisocial behaviour and conduct perceived to disturb public order. The article uses Garland’s(2001) thesisonthecultureofcontroltoanalysewhetherMAShasledtoincreasedgovernmentcontrol and the exclusion of significant groups of the population. The research is based on a multiple case study in which the application of MAS was analysed over a 25-year period of security policies in Belgium (1985–2010). The Act’s implementation was studied in the two Belgian cities of Antwerp and Liège in order to consider the influence of the Flemish government and the Walloon government, respectively, in this policy area. The article uses insights from this comparison to revisit the culture of control thesis and its limitations in understanding the political competition that exists over the formulation of policies on antisocial behaviour. Effective Protection of Fundamental Rights in a pluralist worl

On Maximum Weight Clique Algorithms, and How They Are Evaluated

Maximum weight clique and maximum weight independent set solvers are often benchmarked using maximum clique problem instances, with weights allocated to vertices by taking the vertex number mod 200 plus 1. For constraint programming approaches, this rule has clear implications, favouring weight-based rather than degree-based heuristics. We show that similar implications hold for dedicated algorithms, and that additionally, weight distributions affect whether certain inference rules are cost-effective. We look at other families of benchmark instances for the maximum weight clique problem, coming from winner determination problems, graph colouring, and error-correcting codes, and introduce two new families of instances, based upon kidney exchange and the Research Excellence Framework. In each case the weights carry much more interesting structure, and do not in any way resemble the 200 rule. We make these instances available in the hopes of improving the quality of future experiments

Mobilise-D insights to estimate real-world walking speed in multiple conditions with a wearable device

This study aimed to validate a wearable device’s walking speed estimation pipeline, considering complexity, speed, and walking bout duration. The goal was to provide recommendations on the use of wearable devices for real-world mobility analysis. Participants with Parkinson’s Disease, Multiple Sclerosis, Proximal Femoral Fracture, Chronic Obstructive Pulmonary Disease, Congestive Heart Failure, and healthy older adults (n = 97) were monitored in the laboratory and the real-world (2.5 h), using a lower back wearable device. Two walking speed estimation pipelines were validated across 4408/1298 (2.5 h/laboratory) detected walking bouts, compared to 4620/1365 bouts detected by a multi-sensor reference system. In the laboratory, the mean absolute error (MAE) and mean relative error (MRE) for walking speed estimation ranged from 0.06 to 0.12 m/s and − 2.1 to 14.4%, with ICCs (Intraclass correlation coefficients) between good (0.79) and excellent (0.91). Real-world MAE ranged from 0.09 to 0.13, MARE from 1.3 to 22.7%, with ICCs indicating moderate (0.57) to good (0.88) agreement. Lower errors were observed for cohorts without major gait impairments, less complex tasks, and longer walking bouts. The analytical pipelines demonstrated moderate to good accuracy in estimating walking speed. Accuracy depended on confounding factors, emphasizing the need for robust technical validation before clinical application. Trial registration: ISRCTN – 12246987

A two-stage approach to the orienteering problem with stochastic weights

The Orienteering Problem (OP) is a routing problem which has many interesting applications in logistics, tourism and defense. The aim of the OP is to find a maximum profit path or tour, which is feasible with respect to a capacity constraint on the total weight of the selected arcs. In this paper we consider the Orienteering Problem with Stochastic Weights (OPSWs) to reflect uncertainty in real-life applications. We approach this problem by formulating a two-stage stochastic model with recourse for the OPSW where the capacity constraint is hard. The model takes into account the effect that stochastic weights have on the expected total profit value to be obtained, already in the modeling stage. Since the expected profit is in general non-linear, we introduce a linearization that models the total profit that can be obtained for a given tour and a given scenario of weight realizations. This linearization allows for the application of Sample Average Approximation (SAA). The SAA solution asymptotically converges to the optimal solution of the two-stage model, but is computationally expensive. Therefore, to solve large instances, we developed a heuristic that exploits the problem structure of the OPSW and explicitly takes the associated uncertainty into account. In our computational experiments, we evaluate the benefits of our approach to the OPSW, compared to both a standard deterministic approach, and a deterministic approach that is extended with utilization of real-time information. © 2013 Elsevier Ltd