154092 research outputs found
Sort by
The selective multiple depot pickup and delivery problem with multiple time windows and paired demand
Get PDFA recurring challenge for transportation companies is the inefficiency of returning (partially) empty vehicles, or backhauling, after delivering orders. To address this issue, companies search on freight exchange platforms for profitable pickup and delivery orders, aiming to reduce the costs associated with empty return trips. The increasing reliance on freight exchange platforms presents both an opportunity and a challenge: while they offer access to profitable loads, effectively selecting the right combination of orders to maximize returns is challenging. This paper addresses this challenge by introducing the Selective Multiple Depot Pickup and Delivery Problem with Multiple Time Windows and Paired Demand (SMDPDPMTWPD). We formulate the SMDPDPMTWP as a Mixed-Integer Linear Program (MILP) to maximize profit and optimize freight selection for return trips. In addition to the main model, three problem extensions are proposed: (i) profit maximization including CO2 costs, (ii) soft time windows, and (iii) soft time windows including CO2 costs. Given the complexity of the problem, we develop an Adaptive Large Neighborhood Search (ALNS) metaheuristic to solve large instances within reasonable computing times and compare it with a Simulated Annealing (SA) heuristic. Results show that ALNS outperforms SA and finds the same optimal solutions as the MILP formulation for small instances. Furthermore, ALNS achieves an average improvement of 308.17% over the initial solutions for the profit maximization variant. The model variant with CO2 costs shows a slight sensitivity of the routing schedules to the CO2 emissions costs, whereas we observe a significant change when allowing soft time windows. Finally, soft time windows significantly increase the profits earned compared to the hard time windows (179.54% on average), due to the additional flexibility created when late arrivals are possible.</p
The two-tier multi-depot vehicle routing problem with robot stations and time windows
Get PDFThe deployment of sidewalk robots or automated guided vehicles (AGVs) offers significant potential to reduce traffic congestion and operational costs in last-mile logistics. Delivery systems using a two-layer structure, with trucks in the first layer and sidewalk robots at stations in the second, are modeled as Two-Tier Vehicle Routing Problems with Robot Stations (2T-VRP-RS). In this paper, we extend the 2T-VRP-RS to introduce the Two-Tier Multi-Depot Vehicle Routing Problem with Robot Stations and Time Windows (2T-MDVRP-RS-TW). We propose a Mixed-Integer Linear Programming (MILP) formulation and a Multi-Start Iterated Local Search metaheuristic with Crossover and Repair (MS-ILS-CR) operators. The MS-ILS-CR combines three strategies: a Multi-Start mechanism, a Crossover operator, and a Repair operator adapted from Variable Neighborhood Search, Genetic Algorithms, and Adaptive Large Neighborhood Search, respectively. We introduce new instance sets to study the 2T-MDVRP-RS-TW. Results showed that the MILP formulation is competitive for small instances of 10 customers. However, the metaheuristic consistently achieved better solution quality and lower computational times, with improvements of over 20% in the average objective values for instances of up to 30 customers. The MS-ILS-CR outperformed similar metaheuristic methods, improving its initial solutions by 66%. Furthermore, a sensitivity analysis showed a limited impact of time-window variations on the objective values. Nevertheless, a significant sensitivity was found to the depot configurations. Hence, increasing the number of depots from 1 to 3 improved the average objective values by 56%. Additionally, the MS-ILS-CR performance was further enhanced with more crossover iterations, but at the cost of higher computational times.</p
Automated vehicles’ safety:The multidimensionality of disengagement reports
Get PDFThe concerns around the safety of automated vehicles (AVs) persist. This study examines AV disengagements using reports from the California Department of Motor Vehicles, focusing on the multidimensional factors influencing disengagements during Level 3 AV testing. Multidimensional factors include technological, environmental, human, and organizational aspects. The findings reveal that disengagements are not solely due to technological failures but also involve complex interactions with human perceptions, environmental conditions, and organizational characteristics of testing entities. Notably, although technological and environmental disengagements have increased over time, human-related disengagements have decreased, implying that advancements in AV technology are pushing vehicles into more complex operational scenarios. This study highlights the need for a holistic, multidimensional approach to AV safety by integrating technological, social, and environmental perspectives to better understand and address disengagements. The contributions of this study are twofold. First, it empirically demonstrates the multidimensionality of disengagement reports, which can be perceived as the last hurdle to Level 4 AVs. Second, this paper demonstrates that technological innovations do not happen in a bubble. Instead, they are accompanied, triggered, or are themselves stimulated by social interactions and their environments. These implications are critical for designing responsible AV technologies and informing policy framework.</p
Do cities with greater transformative governance capacity pursue more ambitious policies? Examining U.S. cities through the lens of climate resiliency
No full textMunicipalities face increasingly complex challenges from climate change-driven natural hazards that threaten health, infrastructure, and livelihoods. Addressing these risks requires ambitious climate policies that drive the societal transformations advocated in climate policy literature. This study examines factors enabling local governments to adopt ambitious flood risk management. Ambitious climate adaptation policies go beyond minimum regulatory requirements to reduce climate vulnerability and enhance resilience. They facilitate their community’s ability to bounce forward after confronting system disruptions and shocks. Given the dynamic nature of climate challenges, scholars emphasize the importance of having a capacity for transformation over achieving fixed outcomes. Accordingly, this study hypothesizes that city governments with higher Transformative Governance Capacity (TGC) are more likely to implement ambitious flood management strategies. TGC is characterized by behavioural qualities such as being learning-focused, proactive, and risk-accepting. Using survey data from 386 U.S. cities, we operationalize and quantify local governments’ TGC and analyze its association with ambitious flood management practices, as proxied by participation in the Community Rating System (CRS)–a voluntary programme that incentivizes communities to exceed national flood mitigation standards. The findings support the hypothesis that greater TGC is associated with higher levels of involvement in the CRS and higher CRS scores, underscoring the importance of this distinct type of behavioural capacity in addressing escalating climate threats.</p
DNA-poli:Design and development of a digital platform for family communication support and predictive genetic counseling on inherited diseases
Get PDFObjectives: By developing a digital platform (“DNA-poli”) we aim to improve the uptake and efficiency of predictive genetic counseling and cascade testing for relatives at-risk of inherited conditions. This is crucial for reducing disease morbidity and mortality while meeting the growing demand for genetic counseling. We outline the design, development, and final concept and prototype of DNA-poli and discuss the challenges faced and how these were addressed. Methods: We followed an approach based on the Design Thinking and Human-Centered Design methods, which entails four stages: 1) Discover/Define, 2) Design, 3) Develop, and 4) Deliver. Stakeholders were actively involved through interviews, focus groups, and sounding board consultations. Two inherited cardiac conditions (hypertrophic cardiomyopathy and dilated cardiomyopathy) served as the first use case. Results: The DNA-poli prototype is a digital outpatient clinic for predictive counseling on inherited conditions and cascade testing. It facilitates both pre-test and post-test genetic counseling, including information provision on specific conditions and tests, decision support, collecting medical information from a counselee, and return of results. ARRs can process relevant information online at their convenience and can request genetic tests locally after a short teleconsultation with a healthcare professional. A conversational agent is incorporated to answer questions and collect patient characteristics. Conclusions: DNA-poli is the first digital cardiogenetics platform to encompass the full genetic care pathway for family communication and predictive genetic counseling. Development challenges related to logistical implementation, ethical and legal considerations, and ensuring quality of care standards. Practice implications: DNA-poli allows timely, efficient, and flexible access to predictive counseling, supporting probands with informing their ARRs. ARRs have access to personalized information and modules to support decision-making at their convenience.</p
Eye contact during virtual storytelling:Enhancing social evaluation through pupil mimicry
Get PDFThe human eye plays a crucial role in shaping social judgments; for instance, maintaining eye contact enhances social interactions and influences how others perceive us. At a more subtle level, the pupils also play an important role; recent research shows that pupil mimicry fosters trust. In our digitizing world, people frequently interact with virtual agents. Therefore, it is of crucial importance to investigate whether the positive effects of eye gaze and pupil mimicry generalize to virtual interactions. In the current study, we investigated whether eye contact and pupil dilation mimicry influence the evaluation of virtual humans and whether these effects vary with the participants’ levels of social anxiety. Six virtual humans told a story which participants watched on a monitor screen. Three of them were programmed to mimic the participants’ pupil size at moments when participants displayed natural pupil dilation, while the other three did not mimic these instances and instead, their pupil sizes dilated at random moments. After each story, we assessed how the virtual human was perceived by taking multiple social evaluation measures. The results show that the more the participants made eye contact, the more positively they evaluated the virtual human, especially during trials where the virtual humans mimicked the spontaneous instances of pupil dilation in participants’ eyes. Social anxiety levels did not influence the results. This study demonstrates that the cumulative positive effects of eye contact and pupil dilation mimicry generalize to interactions with virtual agents, which may inspire potential applications.</p
Tuning the Enzymatic Activity of Aqueous Phase Separation-Based PEI-PSS Membranes
Get PDFAqueous phase separation (APS), a highly sustainable method of membrane production, has already been successfully applied to prepare biocatalytic membranes. In this work, membranes were prepared by APS through the complexation of polyethyleneimine (PEI) and poly(sodium 4-styrene sulfonate) (PSS). Lysozyme and laccase were successfully introduced to give enzymatic function to the membranes at room temperature. Changing the PEI:PSS mixing ratio affected the membrane structure and thereby also the resulting enzymatic activity. The optimum PEI:PSS mixing ratio, in terms of enzymatic activity and mechanical properties, was found to be 1.9:1, and this ratio was subsequently used to study the influence of enzyme concentration. PEI-PSS membranes showed a linear increase in activity with enzyme concentration, with an optimum activity of 3.0 ± 0.2 U·cm−2 for a casting solution with 0.25 wt.% lysozyme. Above this concentration, activity decreased, likely due to enzyme aggregation. For laccase functionalized membranes, it was demonstrated to be possible to oxidize syringaldazine during active filtration, while a higher enzyme loading was found compared to lysozyme. This work demonstrates the possibility of tuning the enzymatic activities of APS-produced membranes by changing the polyelectrolyte mixing ratio and enzyme concentration. Moreover, the incorporation of laccase demonstrates the versatility of the APS approach and its potential to degrade organic pollutants in wastewater treatment.</p
Improving the fixed charge density of sustainably produced saloplastic anion exchange membranes
Get PDFRecent studies have shown that sustainable ion exchange membranes can be fabricated by hot-pressing polyelectrolyte complexes (PECs), resulting in saloplastic membranes. Among these, the anion exchange membrane (AEM) formed from the strongly charged polyelectrolyte pair, poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyl-dimethylammonium chloride) (PDADMAC) stands out due to its excellent chemical stability. However, the performance of this membrane is limited by its comparatively low fixed charge density. To address this limitation, we aimed to enhance the fixed charge density through incremental PDADMAC overcharging during the complexation step, followed by optimisation of hot-pressing conditions to produce dense, freestanding films. This approach allows for precise control over membrane charge and improves the reproducibility of films, thereby overcoming challenges in the processing and handling of non-stoichiometric PECs. NMR spectroscopy was used to quantify the fixed charge of the saloplastic AEMs before and after testing, providing a reliable and time-efficient method for assessing stability. Our results showed that a PDADMAC overcompensation of ∼30 mol% optimised the fixed charge density without compromising membrane stability. The enhanced membrane exhibited an 84% improvement in ionic conductivity (4.3 ± 0.3 mS cm−1 in 0.5 M KCl) compared to the original membrane. Notably, all membranes displayed excellent permselectivity (>90%) in 0.1 M KCl, and at higher electrolyte concentrations, a moderate improvement in permselectivity was observed with the increase in fixed charge density. Overall, this study presents a simple yet effective methodology for quantifying and optimising the fixed charge density of saloplastic membranes, resulting in significantly improved performance.</p
Second-Order Flows for Approaching Stationary Points of a Class of Nonconvex Energies via Convex-Splitting Schemes
No full textThis paper contributes to the exploration of a recently introduced computational paradigm known as second-order flows, which are characterized by novel dissipative hyperbolic partial differential equations extending accelerated gradient flows to energy functionals defined on Sobolev spaces, and exhibiting significant performance particularly for the minimization of nonconvex energies. Our approach hinges upon convex-splitting schemes, a tool which is not only pivotal for clarifying the well-posedness of second-order flows, but also yields a versatile array of robust numerical schemes through temporal (and spatial) discretization. We prove the convergence to stationary points of such schemes in the semidiscrete setting. Further, we establish their convergence to time-continuous solutions as the timestep tends to zero. Finally, these algorithms undergo thorough testing and validation in approaching stationary points of representative nonconvex variational models in scientific computing.</p