743 research outputs found

    HySST: hyper-heuristic search strategies and timetabling

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    9th International Conference on the Practice and Theory of Automated Timetabling, Son, Norway, 28-31 August 201

    Heuristic generation via parameter tuning for online bin packing

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    Online bin packing requires immediate decisions to be made for placing an incoming item one at a time into bins of fixed capacity without causing any overflow. The goal is to maximise the average bin fullness after placement of a long stream of items. A recent work describes an approach for solving this problem based on a ‘policy matrix’ representation in which each decision option is independently given a value and the highest value option is selected. A policy matrix can also be viewed as a heuristic with many parameters and then the search for a good policy matrix can be treated as a parameter tuning process. In this study, we show that the Irace parameter tuning algorithm produces heuristics which outperform the standard human designed heuristics for various instances of the online bin packing problem

    Design of Industrial Workplaces to relieve Workers when Interacting with Joint-Arm-Robots

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    A comprehensive understanding of the needs of the user is required to design adequate workplace systems in general, but especially in the highly digitised area of industry where operators are interacting with autonomously operating machines. There is little knowledge in design criteria for professionals to enable adequate developments of system design for Human-Machine Interaction, e.g. Human-Robot Collaboration regarding the effects of design decisions to all three levels of Human Factors, i.e. physiological, cognitive and organisational limitations. Moreover, there is little known about objective measurement procedures that evaluate whether the operator subjectively perceives the workplace system design as assistance and improvement. The research presented in the following is affiliated with the scientific discipline of Human Factors Engineering and focuses on the evaluation of Human Factor issues within the digitised industry. Based on broad theoretical and empirical investigations, the results of this research extend our knowledge of adequate Human-Centred Design by providing reliable, powerful design criteria for workplaces where operators interact with machines/collaborate with robots, but also an overall technique, the Objective Workload Detection Method, for evaluation of the effectiveness of design investigation focusing on cognitive stress relief. Through the application of this method within a controlled experiment, the validation of the derived design criteria was confirmed. The study significantly shows how the cognitive workload can be relieved by an assisting environment. This work also gives one best-practice design example of a self-adapting workplace system for hybrid Human-Robot Teams. Following the Human-Centred Design method, the concept of Assisting Industrial Workplace System for Human-Robot Collaboration has been successfully developed as a flexible hybrid unit design. The prototype is related to a real-world scenario from the aerospace industry and the demonstrator was implemented within a laboratory set-up. This work seamlessly applies techniques from interdisciplinary science fields, e.g. Engineering, Neuroscience, Gestalt theory, and Design. Equally, the design criteria and the evaluation method will support professionals from varied disciplines to succeed in the creation process of future system-designs by giving a clear indication of future Human-Centred Design research

    Concept of a Self-Learning Workplace Cell for Worker Assistance While Collaboration with a Robot Within the Self-Adapting-Production-Planning-System

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    For some time, the focus of past research on industrial workplace designs has been the optimization of processes from the technological point of view. Since human workers have to work within this environment the design process must regard Human Factor needs. The operators are under additional stress due to the range of high dynamic processes and due to the integration of robots and autonomous operating machines. There have been few studies on how Human Factors influence the design of workplaces for Human-Robot Collaboration (HRC). Furthermore, a comprehensive, systematic and human-centred design solution for industrial workplaces particularly considering Human Factor needs within HRC is widely uncertain and a specific application with reference to production workplaces is missing. The research findings described in this paper aim the optimization of workplaces for manual production and maintenance processes with respect to the workers within HRC. In order to increase the acceptance of integration of human-robot teams, the concept of the Assisting-Industrial-Workplace-System (AIWS) was developed. As a flexible hybrid cell for HRC integrated into a Self-Adapting-Production-Planning-System (SAPPS) assists the worker while interaction

    Prediction of the annuloplasty ring size in patients undergoing mitral valve repair using real-time three-dimensional transoesophageal echocardiography

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    Aims We sought to investigate the additional value of real-time three-dimensional transoesophageal echocardiography (RT 3D TOE)-guided sizing for predicting annuloplasty ring size during mitral valve repair. Methods and results In 53 patients undergoing elective mitral valve repair, an RT 3D TOE was performed pre- and post-operatively. The digitally stored loops were imported into a software for mitral valve assessment. The annuloplasty ring size was predicted by superimposing computer-aided design (CAD) models of annuloplasty rings onto Live 3D zoom loops, measurement of the intercommissural distance, or the height of the anterior mitral leaflet. The surgeon implanted the annuloplasty ring according to the usual surgical technique and was blinded to the echocardiographic measurement results. Pre-operative correlation between the selected ring size with mitral valve assessment and the actual implanted annuloplasty ring size was 0.91. The correlation for measurement of the intercommissural distance was 0.55 and for measurement of the height of the anterior mitral leaflet 0.75. The post-operative correlation with the actual implanted ring size was 0.96 for mitral valve assessment, 0.92 for intercommissural distance, and 0.79 for the anterior mitral leaflet height. Conclusion Superimposition of annuloplasty ring CAD models on the Live 3D zoom loops of the mitral valve using mitral valve assessment is superior to two-dimensional measurements of the intercommissural distance or the height of the anterior mitral leaflet in predicting correct annuloplasty ring size

    Near-infrared Spectroscopy Monitoring of the Collateral Network Prior to, During, and After Thoracoabdominal Aortic Repair: A Pilot Study

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    ObjectiveThe aim of this study was to evaluate the feasibility of non-invasive monitoring of the paraspinous collateral network (CN) oxygenation prior to, during, and after thoracoabdominal aortic repair in a clinical series.MethodsNear-infrared spectroscopy optodes were positioned bilaterally—over the thoracic and lumbar paraspinous vasculature—to transcutaneously monitor muscle oxygenation of the CN in 20 patients (age: 66 ± 10 years; men = 11) between September 2010 and April 2012; 15 had open thoracoabdominal aortic repair (Crawford II and III), three had thoracic endovascular aortic repair (TEVAR; Crawford I), and two had a hybrid repair (Crawford II). CN oxygenation was continuously recorded until 48 hours postoperatively.ResultsHospital mortality was 5% (n = 1), 15% suffered ischemic spinal cord injury (SCI). Mean thoracic CN oxygenation saturation was 75.5 ± 8% prior to anesthesia (=baseline) without significant variations throughout the procedure (during non-pulsatile cooling on cardiopulmonary bypass and with aortic cross-clamping; range = 70.6–79.5%). Lumbar CN oxygenation (LbS) dropped significantly after proximal aortic cross-clamping to a minimum after 11.7 ± 4 minutes (74 ± 13% of baseline), but fully recovered after restoration of pulsatile flow to 98.5% of baseline. During TEVAR, stent-graft deployment did not significantly affect LbS. Three patients developed relevant SCI (paraplegia n = 1/paraparesis n = 2). In these patients LbS reduction after aortic cross-clamping was significantly lower compared with patients who did not experience SCI (p = .041).ConclusionsNon-invasive monitoring of CN oxygenation prior to, during, and after thoracoabdominal aortic repair is feasible. Lumbar CN oxygenation levels directly respond to compromise of aortic blood circulation

    Variability of Manual Segmentation of the Prostate in Axial T2-weighted MRI: A Multi-Reader Study

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    Purpose To evaluate the interreader variability in prostate and seminal vesicle (SV) segmentation on T2w MRI. Methods Six readers segmented the peripheral zone (PZ), transitional zone (TZ) and SV slice-wise on axial T2w prostate MRI examinations of n = 80 patients. Twenty different similarity scores, including dice score (DS), Hausdorff distance (HD) and volumetric similarity coefficient (VS), were computed with the VISCERAL EvaluateSegmentation software for all structures combined and separately for the whole gland (WG = PZ + TZ), TZ and SV. Differences between base, midgland and apex were evaluated with DS slice-wise. Descriptive statistics for similarity scores were computed. Wilcoxon testing to evaluate differences of DS, HD and VS was performed. Results Overall segmentation variability was good with a mean DS of 0.859 (±SD = 0.0542), HD of 36.6 (±34.9 voxels) and VS of 0.926 (±0.065). The WG showed a DS, HD and VS of 0.738 (±0.144), 36.2 (±35.6 vx) and 0.853 (±0.143), respectively. The TZ showed generally lower variability with a DS of 0.738 (±0.144), HD of 24.8 (±16 vx) and VS of 0.908 (±0.126). The lowest variability was found for the SV with DS of 0.884 (±0.0407), HD of 17 (±10.9 vx) and VS of 0.936 (±0.0509). We found a markedly lower DS of the segmentations in the apex (0.85 ± 0.12) compared to the base (0.87 ± 0.10, p < 0.01) and the midgland (0.89 ± 0.10, p < 0.001). Conclusions We report baseline values for interreader variability of prostate and SV segmentation on T2w MRI. Variability was highest in the apex, lower in the base, and lowest in the midgland
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