Search Results (3)

The goal of this paper is to optimize mission schedules for vertical airports (vertiports in short) to satisfy the different needs of stakeholders. We model the problem as a resource-constrained project scheduling problem (RCPSP) to obtain the best resource allocation and schedule. As a new approach to solving the RCPSP, we propose answer set programming (ASP). This is in contrast to the existing research using MILP as a solution to the RCPSP. Our approach can take complex scheduling restrictions and stakeholder-specific requirements. In addition, we formalize and include stakeholder needs using a knowledge representation and reasoning framework. Our experiments show that the proposed method can generate practical schedules that reflect what stakeholders actually need. In particular, we show that our approach can compute optimal schedules more efficiently and flexibly than previous approaches. We believe that this approach is suitable for the dynamic and complex environments of vertiports. Full article

Recently, urban air mobility (UAM), a new transportation system that can expand urban mobility from 2D to 3D, has been in the spotlight all over the world. For successful implementation of UAM, not only eVTOL aircraft development but also various systems such as UAM traffic management are required; however, research on these areas is still insufficient. Based on the BQA model, in this study, we introduce the balanced branch queuing approach (BBQA) model as a new approach control model that can improve operational efficiency by enabling the landing order to be changed more easily. Through simulation, its effectiveness was verified. The proposed BBQA achieved the identical airspace safety as the BQA model, in addition to showing a superior result to the SBA model in on-time performance (OTP). The vertiport airspace blueprint concept and approach control model proposed in this study are expected to play an important role in future studies in the area of air traffic management in UAM. Full article

Increased anthropogenic carbon dioxide (CO₂) in the atmosphere can enter surface waters and depress pH. In marine systems, this phenomenon, termed ocean acidification (OA), can modify a variety of physiological, ecological, and chemical processes. Shell-forming organisms are particularly sensitive to this chemical shift, though responses vary amongst taxa. Although analogous chemical changes occur in freshwater systems via absorption of CO₂ into lakes, rivers, and streams, effects on freshwater calcifiers have received far less attention, despite the ecological importance of these organisms to freshwater systems. We exposed four common and widespread species of freshwater calcifiers to a range of pCO₂ conditions to determine how CO₂-induced reductions in freshwater pH impact calcium carbonate shell formation. We incubated the signal crayfish, Pacifastacus leniusculus, the Asian clam, Corbicula fluminea, the montane pea clam, Pisidium sp., and the eastern pearlshell mussel, Margaritifera margaritifera, under low pCO₂ conditions (pCO₂ = 616 ± 151 µatm; pH = 7.91 ± 0.11), under moderately elevated pCO₂ conditions (pCO₂ = 1026 ± 239 uatm; pH = 7.67 ± 0.10), and under extremely elevated pCO₂ conditions (pCO₂ = 2380 ± 693 uatm; pH = 7.32 ± 0.12). Three of these species exhibited a negative linear response to increasing pCO₂ (decreasing pH), while the fourth, the pea clam, exhibited a parabolic response. Additional experiments revealed that feeding rates of the crayfish decreased under the highest pCO₂ treatment, potentially contributing to or driving the negative calcification response of the crayfish to elevated pCO₂ by depriving them of energy needed for biocalcification. These results highlight the potential for freshwater taxa to be deleteriously impacted by increased atmospheric pCO₂, the variable nature of these responses, and the need for further study of this process in freshwater systems. Full article