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Comparison of Compact Formulations for the Electric Vehicle Routing Problem
No full textThe electric vehicle routing problem is an extension of the capacitated vehicle routing problem, where en-route recharging needs to be addressed due to the limited driving range of electric vehicles. In this study, we compare four compact formulations that differ in the way they model the battery consumption. The first two formulations use Miller–Tucker–Zemlin’s approach, while the last two use single-commodity flows for this purpose. Within each approach, the two formulations have distinct ways of dealing with the fact that recharging stations may be visited more than once. In particular, two formulations make use of arcs that correspond to two-leg paths with a recharging station in the middle, whereas the other two formulations use copies of recharging stations, as suggested in the literature. We compare the linear programming bounds of these four formulations as well as the existing formulations from a theoretical point of view. Then, we analyze the performance of the new and existing formulations using six sets of benchmark instances. The computational results show that our formulations tighten the linear programming bounds and require less computation time to prove optimality.sponsorship: This work was supported by R&D Program of Beijing Municipal Education Commission, China (KM202411417005); the Academic Research Projects of Beijing Union University, China (No.12213611615-012); and the China Scholarship Council (202007090061). (R&D Program of Beijing Municipal Education Commission, China|KM202411417005, Academic Research Projects of Beijing Union University, China|12213611615-012, China Scholarship Council|202007090061)status: Publishe
Essays on real estate economics: dynamics of pricing and demand
No full textThe doctoral research, which is connected to The Policy Research Centre Housing, is situated in the research field of Real Estate and Urban Economics. The focus of the research is on search behavior, and price and demand dynamics in the housing market.status: Publishe
Understanding the Behavioral Determinants of First Responder App Adoption by Integrating Perspectives From the Unified Theory of Acceptance and Use of Technology and Health Belief Model: Cross-Sectional Survey
No full textBACKGROUND: Out-of-hospital cardiac arrests (OHCAs) are a leading cause of death worldwide, yet first responder apps can significantly improve outcomes by mobilizing citizens to perform cardiopulmonary resuscitation before professional help arrives. Despite their importance, limited research has examined the psychological and behavioral factors that influence individuals' willingness to adopt these apps. OBJECTIVE: Given that first responder app use involves elements of both technology adoption and preventive health behavior, it is essential to examine this behavior from multiple theoretical perspectives. Building on the unified theory of acceptance and use of technology (UTAUT) and health belief model (HBM), this study therefore developed an integrative framework to explain which behavioral determinants and demographic and health-related factors drive an individual's willingness to install a first responder app for OHCA. METHODS: We conducted a web-based cross-sectional survey (N=3660; mean age 49.95, SD 16.75 years; n=1909, 52.2% women) in June 2024 among Belgian adults. Behavioral determinants (UTAUT and HBM constructs), demographic (eg, age), and health-related (eg, cardiopulmonary resuscitation training experience) variables were measured using (multi-item) scales. Willingness to install the app served as the outcome variable. We developed a structural equation model using the Lavaan package in R and specified regression paths, on the one hand, between the behavioral determinants and willingness to install the app, and on the other hand, between the demographic and health-related factors and the behavioral determinants. Additionally, we conducted multiple group analyses to examine the moderating role of demographic and health-related factors on the relationships between the behavioral determinants and the willingness to install the app. RESULTS: Our results revealed that 2 UTAUT variables (ie, facilitating conditions: β=.07; P=.003 and social influence: β=.16; P<.001) and 3 HBM variables (ie, perceived susceptibility: β=.06; P=.003, perceived barriers: β=-.29; P<.001, and perceived benefits: β=.38; P<.001) were associated with willingness to install a first responder app for OHCA. Additionally, most demographic and health-related factors were indirectly related to willingness via behavioral determinants, with age being the sole moderator. Specifically, a negative association between perceived severity and willingness was only observed among older adults. In addition, the positive relationship between perceived benefits and willingness was stronger for older adults compared to younger ones. CONCLUSIONS: Overall, the results of this study have both theoretical and practical implications. Theoretically, this study finds its relevance in extending the UTAUT and HBM to altruistic mobile health apps and advancing our understanding of technology adoption in health contexts. Practically, the study's findings could inform real-life health campaigns aimed at enhancing citizen participation in first responder systems.sponsorship: Generative artificial intelligence (ChatGPT) was used to improve the language and clarity of certain sections, as all authors are nonnative English speakers. However, it was not used to generate original content, ideas, or code. This work was supported by grants from Interne Fondsen KU Leuven (Internal Funds KU Leuven; CITSC/24/012). The authors thankfully acknowledge their support. (Interne Fondsen KU Leuven (Internal Funds KU Leuven)|CITSC/24/012)status: Publishe
D. R. Bereskin (ed.), Trademark Dilution and Free Riding, in Elgar Intellectual Property Law and Practice series
No full textstatus: Publishe
Computational modeling of endogenous tissue restoration in biodegradable implants: Bridging scaffold degradation and neo-tissue adaptation.
No full textBiodegradable polymeric scaffolds produced by electrospinning offer an innovative alternative to conventional implants made from animal or synthetic materials. By promoting endogenous tissue restoration (ETR), these scaffolds solve problems such as limited durability, calcification, and thromboembolic complications. The concept of ETR is based on the idea that a biodegradable scaffold provides temporary structural support until it is gradually replaced by the body's own tissue through natural regeneration processes. This study investigates the underlying processes following implantation by introducing a computational modeling framework for ETR. Specifically, we focused on the gradual formation of neo-tissue that leads to the functional restoration of the degraded vessel wall. Our model focuses on implementing growth and remodeling to predict the in vivo evolution of ETR as well as the long-term behavior of a biodegradable conduit implant. This is accomplished by coupling the homogenized constrained mixture theory with a plasticity framework. The combination of both allowed us to model scaffold degradation and neo-tissue formation within the porous scaffold. A global sensitivity analysis was performed to assess the influence of uncertain model inputs and their interactions on the ETR process, thereby identifying the most influential parameters to reduce subsequent calibration effort. The computational model was then calibrated using 6-months data from an animal study in which biodegradable conduits were implanted into the carotid arteries of three sheep. Through a parallel twelve-month follow-up in three additional animals, we could subsequently assess the model's predictive capabilities. This study demonstrates the efficacy of the proposed ETR modeling framework in predicting the long-term outcomes of biodegradable conduit implants. By comparing the evolution of scaffold and neo-tissue mass densities and the inner diameter of the conduit over time, the framework provides a valuable tool to accelerate implant development and demonstrates how research can be translated into practical applications.sponsorship: Horizon 2020, Horizon 2020 Framework Programme|101017523, Research Foundation Flanders|SB1SE2125Nstatus: Published onlin
Optimalisatie van de preoperatieve diagnostiek en minimaal invasieve technieken in de gynaecologie
No full textMinimally invasive surgery is growing rapidly in various domains, including benign gynaecological surgery. This stems from the advantages for the patient, such as less morbidity, better postoperative quality of life and a shorter interval to regaining normal functioning. But also the societal burden diminishes by omitting or shortening the need for overnight hospitalisation, and by enhancing a quicker return to work. We strive to optimize already available as well as new techniques for benign gynaecologic operative interventions, focusing on surgical techniques, in need for high quality evidence. In particular, we will assess the outcome of these newly introduced procedures in terms of patient reported outcome measures (PROMs), patient reported experience measures (PREMs) and health economic impact. Pre-operative imaging (e.g. gynaecological ultrasonography) is essential in tailoring therapy for each individual patient. High-quality imaging helps to predict surgical difficulties, to choose the appropriate technique and to exclude underlying malignancy. We will specifically investigate the role of liquid biopsies and artificial intelligence to improve the subjective diagnosis by ultrasonography. This has been implemented in a growing number of fields, but rarely in gynaecology.status: Publishe
Design rules for 3D micro-extrusion of Cu
No full textsponsorship: This work was funded by VITO through a PhD scholarship for S. Kolli and by VLAIO through the SIM/Flux50 cSBO IAMHEX project (HBC.2021.0801). (VITO through a PhD scholarship, VLAIO through the SIM/Flux50 cSBO IAMHEX project|HBC.2021.0801)status: Published onlin
Influence of Quantized Magnetic Field on Electromagnetic Wave Propagation in Counter-Streaming Plasmas
No full textThe stability of transverse modes in a two-stream quantum magneto-plasma is re-examined by incorporating the effects of quantized magnetic Fermi pressure. Within the framework of Landau quantization, the linear propagation of electromagnetic (EM) waves is analyzed, revealing that the growth rate of the instability is significantly suppressed as a function of the quantizing magnetic field parameter eta. This decrease is primarily attributed to a reduction in the relative streaming velocities of the two counter-propagating beams. For a quantum magneto-plasma with a fixed density, the cut-o¤ wave number, beyond which the mode stabilizes, is found to be dependent on
eta, mainly through its influence on the magnetic Fermi velocity. Furthermore, a novel nonlinear theory is proposed to explain the generation of magnetic fields via the ponderomotive force. This force arises due to the nonlinear propagation of high-amplitude EM waves within the plasma under consideration. In a fixed-density two-stream quantum plasma, the effective quantum frequency omega* varies as a function of eta, allowing it to compete with the mode frequency, ultimately leading to the amplification of the induced magnetic field. These findings provide valuable insights into the influence of strong magnetic fields on the stability of transverse wave propagation. Additionally, the results may enhance our understanding and control of magnetic field dynamics in solid-density plasmas, laser-driven systems, and astrophysical environments, particularly those associated with intense X-ray emissions, such as pulsar surfaces.sponsorship: KU Leuven|C16/24/010, Fonds Wetenschappelijk Onderzoek|G0B5823N, Fonds Wetenschappelijk Onderzoek|G002523N, ESA Prodex|4000145223, ERCEA|101141362, KU Leuven|NF/24/003status: Publishe
De MARVEL exoplaneet-array: Technologieën voor hoge precisie detectie van exoplaneten met radiale snelheid
No full textThis thesis presents the design and development of key technological components for high-precision radial velocity measurements of exoplanets, focusing on the Mercator Array for Radial VELocities (MARVEL), a dedicated four-telescope facility targeting 1 m/s radial velocity precision for follow-up of exoplanet candidates from ESA's PLATO mission.
I detail the optical design of the MARVEL spectrograph, a cross-dispersed white pupil relay echelle spectrograph covering 380-950nm at spectral resolutions of R=90,000 and R=135,000. The design philosophy prioritizing stability and risk minimization is outlined, with comprehensive tolerance analyses establishing manufacturing and alignment specifications.
I also present the design and development of the MARVEL telescope units\textemdash the optical assemblies that provide atmospheric dispersion correction, guiding, calibration injection, and fibre coupling at each of MARVEL's four 0.8m telescopes. These units incorporate a fast tip-tilt mirror, a high-performance atmospheric dispersion corrector, and a modular design suitable for deployment across multiple telescopes.
Additionally, I describe the development of a Fabry-Pérot etalon-based wavelength calibration system for another radial velocity facility, the Keck Planet Finder spectrograph. I describe numerical simulations of Gaussian beam propagation within etalon cavities, the system's design and its installation, and first results from the analysis of calibration spectra. This system enables critical drift correction for the Keck Planet Finder spectrograph, and offers insights into calibration strategies for MARVEL, which will use a near-identical system.
The technologies presented address a number of the fundamental challenges in precision radial velocity measurements, including optical stability, efficient fibre coupling, and wavelength calibration. Upon completion, MARVEL will be a key northern hemisphere facility for exoplanet characterization.status: Publishe
Design, steekproefgrootteplanning en preprocessen van experience sampling methode studies
No full textPlenty of research focuses nowadays on understanding how psychological processes dynamically evolve within persons. To capture these processes, data are collected through intensive longitudinal designs (ILD) and modeled with time series approaches. A popular approach is Vector Autoregressive (VAR(1)) modeling of order 1, in which observations at the current measurement occasion are modeled as a function of the observations at the previous occasion. To interpret VAR(1) parameters using hypothesis tests, it is crucial to perform rigorous sample size planning to ensure sufficient statistical power. Sample size planning methods are largely lacking and existing methods for cross-sectional data are invalid as they ignore the serial dependence in the data. This project aims to develop simulation-based techniques to perform sample size planning for ILD, focusing on VAR(1) and its multilevel extensions. We will first study how to optimally select the number of measurement occasions for a single individual. Next, we will compare event- and time-contingent sampling schemes in terms of power. Third, when simultaneously studying multiple persons, we will investigate the optimal trade-off between the number of persons and measurement occasions. Fourth, we will inspect if an alternative statistical quality measure, predictive accuracy, can adequately inform about sample size planning. Finally, we will disseminate the new techniques by building freely available software.status: Publishe