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A Novel Multi-Objective Model for Data-Driven Scattered Storage Assignment in Warehouses
No full textA Novel Multi-Objective Model for Data-Driven Scattered Storage Assignment
Today’s competitive retail market is faced with high expectations from customers on both delivery (time) and price (cost). This situation has led retailers such as Amazon and Zalando to improve their replenishment and picking strategies at their distribution centers to achieve a higher degree of efficiency [1]. One of these replenishment strategies is Scattered Storage Assignment (SSA). The underlying idea behind SSA is to unbundle each received Stock-Keeping Unit (SKU) and spread it within different positions in the warehouse. As the distance traveled by pickers to retrieve items is a crucial issue in warehouse operations management, SSA increases the average adjacency of pickers to SKUs, irrespective of his/her actual position, which leads to less travel distance in the warehouse [2].
To the extent of our review, the prevalent definition and measure used in literature for scatteredness is based on [3]. We present a new data-driven scatteredness measure which extends the concept of scatteredness to include more real-world requirements and takes customer order data into account. To do so, a novel multi-objective mathematical model is proposed in this study. This model aims to (a) maximize the scatteredness; (b) minimize splitting order-lines by aiming to collect all items of an order-line from the same location; (c) maximize order correlation of items close to each other by reducing the distance between items which are frequently ordered together and (d) maximize adjacency of frequently-ordered items to the depot. This proposed model has several benefits.
Firstly, as order frequency of items is not identical, their degree of scatteredness is weighted differently. Therefore, association rules which describe customer order behavior, are included in the proposed scatteredness measure. Secondly, as mentioned by [4], balanced dispersion of each SKU through the warehouse is important. In other words, if 18 units of an SKU are located in three different locations with the inventory of (6, 6, 6), it is more balanced than (5, 1, 12). Consequently, this characteristic is also embedded in the proposed measure. Thirdly, pairwise distance between various locations of an SKU is taken into account. Namely, if 2 units of an SKU are located in two different locations where their pairwise distance is 30 meters, they are more scattered than the situation where their pairwise distance is 5 meters. Fourthly, in contrast to existing SSA measures that allow a single SKU in each position, the proposed measure in this study allows multiple SKUs in a position which can have different spatial capacities. Fifthly, previous research requires a pre-defined degree of scatteredness [5], while our proposed multi-objective SSA model determines the optimal storage location without needing pre-calculation of a fitted scatteredness degree. Like this, the provided approach in this study not only scatters the inventory fit to the context of corresponding business but also tries to keep the inventory level of each SKU in each location in a way that minimizes splitting order-lines.
In order to avoid having to find the Pareto frontier which affects solution time, lower and upper bounds of each criterion are calculated. Second, a data-driven method for assigning the weight of each objective is introduced in this study. Finally, as the proposed model is both non-linear and non-differentiable, a meta-heuristic solution algorithm based on Differential Evolution [6] is developed. It is notable that the authors are working on testing the model and the algorithm on problems of different scale.
References
1. Boysen, N., R. De Koster, and F. Weidinger, Warehousing in the e-commerce era: A survey. European Journal of Operational Research, 2019. 277(2): p. 396-411.
2. Weidinger, F. A precious mess: on the scattered storage assignment problem. in Operations Research Proceedings 2016: Selected Papers of the Annual International Conference of the German Operations Research Society (GOR), Helmut Schmidt University Hamburg, Germany, August 30-September 2, 2016. 2018. Springer.
3. Weidinger, F., Picker routing in rectangular mixed shelves warehouses. Computers & Operations Research, 2018. 95: p. 139-150.
4. Pawar, N.S., S.S. Rao, and G.K. Adil, A New Measure for Scattering of Stocks in E-commerce Warehouses. IFAC-PapersOnLine, 2022. 55(10): p. 1357-1362.
5. Albán, H.M.G., T. Cornelissens, and K. Sörensen, Scattered storage assignment: Mathematical model and valid inequalities to optimize the intra-order item distances. Computers & Operations Research, 2023. 149: p. 106022.
6. Storn, R. and K. Price, Differential evolution–a simple and efficient heuristic for global optimization over continuous spaces. Journal of global optimization, 1997. 11: p. 341-359
Telomere Length in Neonatal Dairy Calves in Relation to Lifetime Parameters
No full textTelomere length (TL) has gained attention as a biomarker for longevity and productivity in dairy cattle. This study explored the association between neonatal TL in Holstein calves and lifetime parameters (lifespan, milk production, and reproduction). Blood samples were collected from 210 calves (≤10d old) across four dairy farms in Flanders, Belgium. Telomere length was measured using qPCR and analyzed as a continuous variable and across three groups: the 10% shortest, the 10% longest, and the remaining 80%. Survival analyses showed no association between TL and lifespan (p = 0.1) or TL groups (p = 0.8). Similarly, TL showed no significant association with production traits. However, categorical analyses revealed that calves with the longest TL had lower lifetime fat (p = 0.01) and protein yields (p = 0.01) than those with the shortest TL. Reproductive analyses showed cows in the long TL group required fewer inseminations per lactation (p = 0.02) and exhibited longer calving intervals (p = 0.05). These findings suggest that while neonatal TL may not predict productive lifespan, it may provide insight into reproductive efficiency. Future studies should prioritize longitudinal assessments of TL dynamics to better understand their interactions with management practices and application in herd improvement.Funding
The present study was funded by a PhD grant from the Research Foundation—Flanders (FWO grant 1SH5N24N). Dries S. Martens holds a postdoctoral grant from the Research Foundations Flanders (FWO grant 12X9623N). This research did not receive any specific grant from other funding agencies in the public, commercial, or not-for-profit sectors.
Acknowledgments
The authors acknowledge the University of Ghent and the University of Hasselt for providing computational resources and support that have contributed to obtaining the research results reported in the present publication. The authors gratefully acknowledge the Research Foundation—Flanders (FWO) for the funding
Decoding specialisation patterns in global value chains: the role of multinationals and domestic firms
No full textThis paper examines the role of multinationals (MNEs) and domestic firms and their exporting channels—direct/indirect— in explaining functional specialisation (FS) patterns. In particular, we consider R&D and fabrication value chain functions. To identify the FS pattern, we apply the FDI-based approach proposed by Stöllinger (2021). The export intensity of domestically and foreign-owned firms is assessed by decomposing the OECD AMNE database. We employ a Generalised Structural Equation Model in the form of the 3-equation recursive system to evaluate the relation between FS and the exporting channels of MNEs and domestic firms. In this paper, we draw on data for the EU countries, with a particular focus on the Central and Eastern European (CEE) economies from 2003 to 2018. The results indicate different roles of MNEs and domestic firms in supporting GVC activities. The direct export intensity of domestic firms is positively related to FS in production, while the direct export intensity of MNEs supports specialisation in R&D. More detailed analyses for the EU15 and CEE countries indicate two different types of firms and their different export channels supporting specialisation in R&D activities. For EU15 countries, it is the direct export of MNEs, whereas CEE countries strengthen the R&D function through the indirect export of their domestic firms. Our findings suggest that EU countries should consider more flexible, task-specific FDI incentives, particularly for R&D, rather than targeting specific sectors. For CEE countries, promoting the indirect export of domestic firms by facilitating matchmaking with local exporters could enhance specialisation in R&D
The Oxygen Cascade According to HFpEF Likelihood A Focus on Sex Differences
No full textBACKGROUND Women are at greater risk for heart failure with preserved ejection fraction (HFpEF). OBJECTIVES The aim of the study was to compare sex differences in the pathophysiology of exertional breathlessness in patients with high vs low HFpEF likelihood. METHODS This cohort study evaluated consecutive patients (n = 1,936) with unexplained dyspnea using cardiopulmonary exercise testing and simultaneous echocardiography and quantified peak oxygen uptake (peak VO2) and its determinants. HFpEF was considered likely when the H2FPEF or HFA-PEFF score was >= 6 or >= 5, respectively. Sex differences were evaluated with the Student's t-test or Mann-Whitney U test and determinants of exercise capacity with a multivariable linear regression. RESULTS The cohort included 1,963 patients (49% women and 28% [n = 555] with a high HFpEF likelihood). HFpEF likelihood did not impact the magnitude of sex differences in peak VO2 and its determinants. Overall, women had lower peak VO2 (mean difference-4.4 mL/kg/min [95% CI:-3.7 to-5.1 mL/kg/min]) secondary to a reduced O(2 )delivery (-0.5 L/min [95% CI:-0.4 to-0.6 L/min]) and less oxygen extraction (-2.9 mL/dL [95% CI:-2.5 to-3.2 mL/dL]). Reduced O2 delivery was due to lower hemoglobin (-1.2 g/dL [95% CI:-0.9 to-1.5 g/dL]) and smaller stroke volume (-15 mL [95% CI:-14 to-17 mL]). Women demonstrated increased mean pulmonary artery pressure/cardiac output slope (+0.5 mm Hg/L/min [95% CI: 0.3-0.7 mm Hg/L/min]) and left ventricular ejection fraction (+1% [95% CI: 1%- 2%]), while they had smaller left ventricular end-diastolic volumes (-9 mL/m(2) [95% CI:-8 to-11 mL/m(2)]) and mass (-12 g/m(2) [95% CI:-9 to-14 g/m(2)]) and more often iron deficiency (55% vs 33%; P < 0.001). CONCLUSIONS Women with unexplained dyspnea had significantly lower peak VO2, regardless of HFpEF likelihood, attributed to both lower peak exercise O-2 delivery and extraction. This suggests that physiologic sex differences, and not HFpEF likelihood, are an important factor contributing to functional limitations in females with exertional breathlessness. (JACC Adv 2024;3:101039) (c) 2024 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).Dr Bekhuis has received funding through the Flanders Research Foundation (FWO-T004420N). Dr Haykowsky is funded by a Research Chair in Ageing and Quality of life in the faculty of Nursing, University of Alberta. Dr Falter has received funding through the Flanders Research Foundation FWO, file number 1SE1222N. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
The authors thank the cardiology fellows who have contributed to performing the exams in the dyspnea clinic of Jessa Hospital (Hasselt, Belgium) over the years. In addition, they are grateful to the nurses for their vital support in the clinic
Immobilisation of uranium-contaminated liquid waste in an alkali-activated material (AAM) and subsequent leaching behaviour
No full textWe present a two-step procedure for treating contaminated liquid waste generated during the processing of uranium, specifically residual uranium-contaminated liquid after precipitation. After precipitating U(IV) as sodium diuranate under alkaline conditions, the resulting solution was solidified by immobilising it in an alkali-activated material. Static leaching tests indicated excellent material stability in water. Exposing the material to aggressive chemical conditions (nitric acid) resulted in slow and incomplete dissolution of uranium (and of structural elements) from a thin superficial layer with further passivation. Characterisation of the solid phase was performed to assess the stability of the alkali-activated material under the tested conditions.The authors would like to thank Sarah Nourry and Christophe Nourry for their support, Tobias Hertel and Yiannis Pontikes (SREMat) for their help in the production of the slag, Britta Bergfeldt for conducting the XRF measurements in the lab for bulk analysis at the Institute for Technical Chemistry KIT. This work was realised with the collaboration of the European Commission Joint Research Centre under the Collaborative Doctoral Partnership Agreement No 35342
Effect of virtual reality-based upper limb training on activity of daily living and quality of life among stroke survivors: a systematic review and meta-analysis
No full textBackground Stroke is a leading cause of disability worldwide, significantly impairing upper limb (UL) function and reducing patients' ability to perform activities of daily living (ADL) and quality of life (QoL). Virtual reality (VR) has emerged as a promising tool; for UL rehabilitation, offering immersive and engaging environments for motor recovery. However, the effectiveness of VR, its integration with conventional therapy, and their efficacy across different stroke recovery stages remain unclear. Therefore, this systematic review and meta-analysis aimed to evaluate the effectiveness of VR-based UL interventions in improving ADL and QoL among stroke survivors. Method This study adhered to PRISMA guidelines and was registered on PROSPERO (CRD42023426256). A systematic search of PubMed, Scopus, and Web of Science identified randomized controlled trials (RCTs) published in English. Inclusion criteria focused on studies using immersive VR (IVR) and non-immersive VR (NIVR) interventions to assess ADL and QoL in stroke survivors. Data extraction and quality assessment were performed independently by two reviewers using the PEDro scale to assess quality. Meta-analyses were conducted to determine the efficacy. Subgroup analyses were performed to compare IVR and NIVR, VR combined with conventional therapy versus standalone VR, and potential differences between stroke recovery stages. Result Thirty RCTs, representing 1,661 participants, were included. Overall, VR interventions significantly improved ADL (SMD = 0.27, 95% CI [0.11; 0.43], p < 0.001) and QoL (SMD = 0.94 [0.09; 1.79], p = 0.035) compared to conventional therapy. IVR demonstrated superior outcomes for ADL compared to NIVR (SMD = 0.54 [0.13; 0.95] Vs. 0.17 [0.02; 0.36], p = 0.03). Subacute stroke survivors exhibited the most significant gains in ADL (SMD = 0.52 [0.16; 0.88], p = 0.004), compared to chronic (SMD = 0.05 [-0.36; 0.46]) or acute patients (SMD = 0.08 [-0.11; 0.27]). Conclusion VR interventions, particularly IVR and VR combined with conventional therapy, significantly enhance ADL and QoL in stroke survivors with moderate certainty of evidence. These findings underscore the value of VR in rehabilitation, especially during the subacute phase, but highlight the need for further research into long-term effects and implementation in low-resource settings.Funding
The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study was supported by the NASCERE program.
Acknowledgements
The authors would like to express appreciation to all the NASCERE project coordinators and their teams, at Ghent University, Hasselt University and Jimma University, for the funding and other facilities
A Comparative Study of Bikeability Index and CycleRAP in Examining Urban Cycling Facilities
No full textThis study conducts a comparative analysis of the Bikeability Index (BI) and CycleRAP in assessing urban cycling infrastructure. The BI, developed in previous research, evaluates cycling conditions through a user-centric framework incorporating safety, comfort, attractiveness, directness, and coherence. In contrast, CycleRAP employs a data-driven methodology focusing on safety by assessing crash risks and severity across different cycling facilities. Using field data and online tools, this research applies both methods to bicycle infrastructure in Hasselt, Belgium, comparing their results and evaluating their alignment in identifying safety concerns and infrastructure needs. A significant correlation between BI and CycleRAP scores was observed, indicating that a higher bikeability score corresponds to reduced safety risks measured by CycleRAP. The study highlights the complementary nature of the two tools, emphasizing the broader insights of the BI and the focused safety evaluations of CycleRAP. The BI safety score extracted from the BI equation showed an even stronger correlation with CycleRAP, suggesting that despite using different methodologies, both indices can yield similar results. These findings provide meaningful guidance for urban planners seeking to enhance cycling infrastructure safety.This research received no external funding.
We acknowledge the Higher Education Commission (HEC) Pakistan for funding Tufail Ahmed’s research
Evaluation of Algorithmic Contributions to Business Process Management
No full textAlgorithms play an important role for business process management. Indeed, all of the 27 papers accepted for BPM 2023 refer to algorithms in one way or the other. Some of these research papers propose new algorithms, such as the paper on the Agent Miner [8], they compose analytical pipelines, such as the paper on process mining video data [5], or they discuss the evaluation of algorithms, such as the paper on sustainability dimensions [3]. So far, however, the BPM community has not developed explicit guidelines for evaluating algorithmic contributions.
This tutorial describes an overarching methodological framework of how algorithms can be researched. In turn, we discuss its foundations in three dimensions. First, we describe four ontological entities including real-world problem, algorithmic task, algorithm design, and algorithm implementations. Second, we distinguish knowledge contributions along two dimensions, that is a) knowledge relating to tasks and to designs and b) knowledge of and knowledge about. Third, we discuss how methodologically new or better knowledge is established. The objective of this tutorial is to present specific strategies how algorithms can be systematically researched for early career researchers. These are illustrated by good examples of BPM papers.The research of the author was supported by Einstei, Foundation Berlin under grant EPP-2019-524, by the German Federal Ministry of Education and Research under grant 16DII133, and by Deutsche Forschungsgemeinschaft under grant ME 3711/2-
Echoes of Soviet Identity. Visualising Soviet Heritage in Contemporary Art: Post-Soviet Nostalgia and the Interaction of History, Memory, and Identity.
No full textEchoes of Soviet Identity: Visualising Soviet Heritage in Contemporary Art is a doctoral project in the arts by Natalia Drobot that investigates post-Soviet nostalgia—often referred to as Ostalgie—and its influence on the visual culture of former Soviet and socialist countries. The research combines academic inquiry with an extensive body of original artworks, ranging from ceramics and sculpture to photography and installation.
Through this artistic research, Drobot examines how contemporary artists—including herself—revisit Soviet symbols, everyday relics, and collective memory. The project engages with themes such as the fate of Lenin monuments, the militarization of daily life, and the aesthetic traces of socialism in domestic objects. Drawing on the writings of Svetlana Boym and other theorists, the work distinguishes between reflective and restorative nostalgia, proposing a visual language to articulate the ongoing tensions between history and identity.
The accompanying exhibition offers a personal yet critical interpretation of Soviet heritage, shaped by the artist’s position as a Belarusian emigrant living in Belgium. By combining personal memory, theoretical framing, and artistic experimentation, Echoes of Soviet Identity opens a broader dialogue on how art can mediate historical trauma, longing, and cultural transformation in post-Soviet contexts