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Very-low-level U-space Conflict Detection and Resolution: Focused Developments, Analysis, and Future Prospects
Full text linkA safe and efficient integration of U-space operations necessitates robust conflict detection and resolution (CD&R) mechanisms, particularly for very-low-level (VLL) operations in constrained urban airspace. Research has focused on the development of navigation and traffic management concepts suitable for such operations that aim to mitigate the challenges posed by this novel environment. However, the current research landscape is fragmented, with CD&R methods still needing to be integrated within a more unified framework. In this paper, we present an overview of our approach towards air traffic management for VLL U-space operations and analyse their limitations compared to other work. Then, based on the conclusions of other existing work, we identify key areas for improvement and propose recommendations for future research and development for VLL airspace structure design, conflict detection and resolution, and U-space operations simulations. We conclude that a unified approach should be used towards integrating and investigating the interdependencies of U-space services within a standardised verification and validation framework
Reviews and Responses for Open Machine Learning Models for Actual Takeoff Weight Prediction
Full text linkDetailed reviews and responses can be found in the PDF and HTML versions of this document.
The DOI for the original paper is https://doi.org/10.59490/joas.2025.7963
Who influences risk management standardisation processes? The example of risk management standards
No full textThe use of standards has permeated virtually all aspects of modern society. Standards should be seen as the combined result of the standardisers’ expertise and the effects of the dynamics of the standardisation process itself. This article explores why some participants are more influential in standards development than others. Using an insider perspective, observations are gathered from almost a hundred activities and three hundred hours spent with international and national standardisation workgroups related to risk management. Discussing power relations, this study exposes the high influence of individuals in standardisation. By knowing and using the rules of the game, individual participants may significantly impact the process and the output. The empirical examples also show that people with high proficiency in English interact more in international standardisation activities than participants with a lower command of English. The challenges of inadequate participation, particularly from the risk science community, and unbalanced representation in standardisation activities are also discussed in the article
City character and standardisation – A historical perspective – The case of Delft
Full text linkThis paper explores the relation between a city’s character and standardisation activities in that city, taking the case of the Dutch city of Delft. In Delft’s 2000 years of history, and in the current situation, many cases of standards development and use can be found. The analysis shows that these show a huge variety. Several cases go beyond ‘normal,’ and had or have substantial impact. This strong standardisation profile is in line with the city’s character expressed in its branding. However, causal relationships cannot be found. The paper seeks for alternative explanations for the correlations. Future research may deepen this study and replicate it in other cities
Towards transition pathways in agriculture and livestock in the Vietnamese Mekong Delta from an agricultural water management perspective
No full textThe Vietnamese Mekong Delta (VMD) is the main agricultural production region in Vietnam producing rice, fruits, shrimps, livestock among a variety of crops. The current VMD agricultural production system (APS) is under threat from sea level rise aggravated by climate change causing further inland salinity intrusion. Transition pathways towards increased salinity adaptation in APSs are therefore required to maintain food security. This study assesses the present water sources usage for APSs and associated quality, quantity and food safety issues. Water-related stresses observed by farmers in the coastal Tra Vinh region are described based on a focus group discussion and in-depth household interviews. Multiple water sources were described for agricultural practices (e.g., surface water, deep well, rainwater) which differed per season. Also, farmers reported to be affected by salinity (67.3%) and groundwater shortages (28.8%) hampering current agricultural production. Solutions and adaptations foreseen vary from more efficient irrigation, dropping crops and new practices and in a lesser brackish water farming systems or moving to new places and transfer to new jobs. Subsequently, transition pathways focusing on salinity adaptation to maintain food security are proposed from a water- and soil management perspective and include i) irrigation innovations to produce crops under more scarce fresh water availability, ii) freshwater storage as a buffer in dry season; iii) basic water treatment options to make water brackish/saline water suitable for livestock and iv) increase soil organic content which can improve soil water retention and reduce impacts of salinity on crops. It is recommended to test multiple transition pathways on farm level in representative regions in the VMD through living labs or demonstration farms
Implications of simplified policy indicators on water security outcomes for vulnerable households in Irbid, Jordan
No full textThis paper investigates the prevalence of water scarcity discourse in Jordan’s policy indicators and examines potential implications of such metrics on the achievement of sufficient, clean water for household needs. The research utilises concepts of household water security and indicator bias to unpack policy-related assessments of domestic water allocation performance and compare them with end-user experiences of system outcomes. Stakeholder perspectives were collected in two northwestern districts, Irbid Qasaba and Ramtha, with a focus on vulnerable Syrian refugee and Jordanian households. The study reveals that the indicators used in policymaking measure allocation performance based on average supply per capita at the governorate level, which inaccurately presumes accessibility and equitability of service across the studied districts and individual households. Syrian refugee and Jordanian end-users in Irbid reported significant variations in their experiences of household water security, highlighting the importance of factors such as frequency of network delivery, tank storage capacity, and assets for alternative sources like private tanker trucks. These point-of-access differentiators are found to be largely unrepresented in policymakers’ data and unaddressed in national or regional management strategies. Instead, simplified indicators in Jordan’s water policies appear to reinforce the national discourse of water scarcity and prioritize supply-driven management practices that insufficiently alleviate insecurities of vulnerable Syrian refugee and Jordanian end-users. The paper emphasizes the need for critical reflection on scarcity data and indicators, urging a shift towards more inclusive and accurate representations of household water access in policymaking processes
Reviews and Responses for Enhancing Aircraft Ground Trajectories through Map-Matching and Stochastic Pavement Roughness Modeling
Full text linkDetailed reviews and responses can be found in the PDF and HTML versions of this document.
The DOI for the original paper is https://doi.org/10.59490/joas.2024.789
Spectres: Architectural Theory as Hauntology
Full text linkThe contemporary sensibility seems increasingly accustomed to observing the blind spots of reality. Architecture, less interested in drawing future visions, channels its utopian tension into scrutinising the past, laying bare in its investigations those absent from History, the lesser stories, what has been forgotten, and what remains unresolved. Following the clues scattered in sociologist Avery Gordon’s book Ghostly Matters: Haunting and the Sociological Imagination, I will refer to this mode of work as ‘hauntology’ to examine the operational strength of architectural design theory in the present era. The essay, that, essentially seeks to bring Gordon’s social theories into the discipline of architectural theory, suggesting the need to restore the relation between architecture and society, is structured as a theory-fiction about architecture. The first part builds the premises for the subsequent ones, defining words ‘theory’ and ‘spectre’ and the results of their crash. The second part observes a concrete case in which a piece of a city has disappeared while remaining in place. The third part concerns the architectural element ‘space’ that re-emerges when considering architectural theory as an observation of the intangible. Finally, the conclusions will leave the essay somewhat suspended, opening up the necessity for a spectrology of architecture
Validation of Lagrangian particle movement in CFD for simulating passive object transport over weirs
Full text linkValidated numerical models can facilitate the investigation of passive object transport over hydraulic structures. This study aims to validate the movement of Lagrangian particles in a numerical simulation using the two-phase OpenFOAM solver interFoam, modified to include particle tracking. A simplified weir overflow was modelled both numerically and physically, and the movement of spherical particles was analysed across three scenarios with varying tailwater levels.
The validation focused on particle collisions immediately after weir passage, residence times within the study area, and upstream movements in recirculation zones such as the hydraulic jump and the water cushion between the weir and the nappe. These parameters were selected because the method is intended to contribute to a better assessment of downstream fish passage over weirs. Results from the numerical and laboratory models showed a high level of agreement. Collision counts and positions, as well as particle residence times and upstream movements, exhibited consistent trends across all three scenarios. The most significant deviation was observed in the number of particles entering the water cushion. This discrepancy is attributed to limitations of the Volume of Fluid (VOF) method, particularly the smearing of the air–water interface. Thus, when employing this methodology, it is essential to account for the inherent limitations of the applied numerical simulation approach. While a perfect replication of fish passage over a weir is not achievable, the method enables reliable qualitative comparisons across different configurations. It may therefore serve as a useful tool for evaluating hydraulic conditions relevant to fish passage
Guidelines on wave overtopping discharges at rubble mound breakwaters including slope angle effects
Full text linkMean wave overtopping discharges at rubble mound breakwaters were measured in a wave flume for various rock-armoured slopes. In the physical model tests, the structure slope was varied: 1:1.5, 1:2, 1:4, 1:6 and 1:8 slopes were studied. The mean wave overtopping discharges appeared to be strongly dependent on the structure slope for both “breaking waves” and for “non-breaking waves”. Existing expressions that also account for friction, a berm (if present), a protruding crest wall (if present), and the angle of wave attack, were extended by incorporating both the slope angle and the wave steepness of the incident waves at the toe. The match between the empirical equations and the data (new and earlier tests) is good. The guidelines to estimate wave overtopping discharges as presented here perform much better than existing guidelines since most existing guidelines for rubble mound breakwaters ignore the explicit influence of the structure slope and the wave steepness. Both for “breaking waves” and for “non-breaking waves”, the structure slope and the wave steepness clearly affect wave overtopping discharges, and therefore expressions that ignore these effects should not be used if accurate estimates of mean wave overtopping discharges are required