Search Results (396)

Accurate methane emission estimates are essential for climate policy, yet current field methods often struggle with spatial constraints and source complexity. Ground-based mobile approaches frequently miss key plume features, introducing bias and uncertainty in emission rate estimates. This study addresses these limitations by using small unmanned aerial systems equipped with precision gas sensors to measure methane alongside co-released tracers. We tested whether arc-shaped flight paths and alternative ratio estimation methods could improve the accuracy of tracer-based emission quantification under real-world constraints. Controlled releases using ethane and nitrous oxide tracers showed that (1) arc flights provided stronger plume capture and higher correlation between methane and tracer concentrations than traditional flight paths; (2) the cumulative sum method yielded the lowest relative error (as low as 3.3%) under ideal mixing conditions; and (3) the arc flight pattern yielded the lowest relative error and uncertainty across all experimental configurations, demonstrating its robustness for quantifying methane emissions from downwind plume measurements. These findings demonstrate a practical and scalable approach to reducing uncertainty in methane quantification. The method is well-suited for challenging environments and lays the groundwork for future applications at the facility scale. Full article

Green hydrogen will play a crucial role in the future of emission reduction in air traffic in the long-term, as it will completely eliminate CO₂ emissions and significantly reduce other pollutants such as contrails and nitrogen oxides. Hydrogen offers a promising alternative to kerosene for short- and medium-haul flights, particularly through direct combustion and hydrogen fuel cell technology in new aircraft concepts. Against the background of the immense capital-intensive infrastructure adjustments that are required at airports for this purpose and the simultaneously high future hydrogen demand for the shipping industry, this paper analyses the emission savings potential in Europe if airports near seaports would switch to hydrogen-powered flight connections. Full article

Aviation is widely recognised to have global-scale climate impacts through the formation of ozone (O₃) in the upper troposphere and lower stratosphere (UTLS), driven by emissions of nitrogen oxides (NO_X). Ozone is known to be one of the most potent greenhouse gases formed from the interaction of aircraft emission plumes with atmospheric species. This paper follows up on previous research, where a Photochemical Trajectory Model was shown to be a robust measure of ozone formation along flight trajectories post-flight. We use a combination of a global Lagrangian chemistry-transport model and a box model to quantify the impacts of aircraft NO_X on UTLS ozone over a five-day timescale. This work expands on the spatial and temporal range, as well as the chemical accuracy reported previously, with a greater range of NO_X chemistry relevant chemical species. Based on these models, route optimisation has been investigated, through the use of network theory and algorithms. This is to show the potential inclusion of an understanding of climate-sensitive regions of the atmosphere on route planning can have on aviation’s impact on Earth’s Thermal Radiation balance with existing resources and technology. Optimised flight trajectories indicated reductions in O₃ formation per unit NO_X are in the range 1–40% depending on the spatial aspect of the flight. Temporally, local winter times and equatorial regions are generally found to have the most significant O₃ formation per unit NO_X; moreover, hotspots were found over the Pacific and Indian Ocean. Full article

By assuming that both travel and departure time are normally distributed variables, a multi-objective stochastic optimization model for the multi-airport flight cooperative scheduling problem (MAFCSP) with CvaR of travel and departure time is firstly proposed. Herein, conflicts of flights from different airports at the same waypoint can be avoided by simultaneously assigning an optimal route to each flight between the airport and waypoint and determining its practical departure time. Furthermore, several real-world constraints, including the safe interval between any two aircraft at the same waypoint and the maximum allowable delay for each flight, have been incorporated into the proposed model. The primary objective is minimization of both total carbon emissions and delay times for all flights across all airports. A feasible set of non-dominated solutions were obtained using a two-stage heuristic approach-based NSGA-II. Finally, we present a case study of four airports and three waypoints in the Beijing–Tianjin–Hebei region of China to test our study. Full article

The research and development of the next generation of supersonic transports (SSTs) meets economic and environmental problems. An SST encounters critical challenges, including the need for low fuel consumption, low noise, and low gas emissions. Currently, the feasibility of developing SSTs is increasing through the application of cutting-edge technologies, such as composite materials, advanced electric systems, sustainable aviation fuel, and innovative design methodologies. The object of this study was to perform the conceptual design of a 50-seat supersonic transport utilizing general conceptual design methods. In estimating weight and flight performance, statistical formulae were correlated with data from civil supersonic and subsonic jet transports. For wing sizing, carpet plots were created to explore the optimal combination of wing aspect ratio and wing loading. The results suggested that by utilizing advanced technologies, such as the use of a composite material for the structure, the maximum takeoff weight can potentially be reduced while still meeting design requirements. The constraint of climb gradient largely affects the maximum takeoff weight, and it is anticipated that flight performance at low speeds will be improved. Full article

While airlines can directly quantify carbon emissions based on flight-specific fuel burn data, such data, along with data on other gaseous emissions that do not scale linearly with fuel consumption, are often unavailable to external stakeholders, necessitating the reliance on estimation models. Emissions are thus approximated from known quantities, with most usually from the fuel burned and distance travelled. Emission approximators developed for the aviation industry thus involve some degree of approximation and assumptions, as well as different exogenous and endogenous factors. As a result, such solutions differ primarily due to the significant methodological variations they incorporate. This paper assesses carbon emission approximators developed to valorize emissions generated by flight operations. It reveals the significance and sources of the misestimation of emissions by focusing on the ICAO Carbon Emission Calculator (ICEC), ICAO CORSIA CO₂ Estimation and Reporting Tool (CERT) and EUROCONTROL’ Advanced Emission Model (AEM) and Small Emitters Tool (SET). Thereby, the main research findings indicate considerable estimation uncertainty among the reviewed solutions, ranging from 1.77% to 27.95% on average compared to the baseline, which translates to statistical confidence levels ranging from 15% to 77.50% on average with respect to a 95% confidence threshold. Full article

Pollen allergies represent a growing public health concern that necessitates enhancements to the network of instruments and modeling calculations in order to facilitate a more profound comprehension of pollen transportation. The Beenose instrument quantifies the light scattered by particles that traverse a laser beam at four angles. This methodology enables the differentiation of pollen particles from other particulate matter, predominantly mineral and carbonaceous in nature, thereby facilitating the retrieval of pollen concentrations. The Beenose instrument has been installed on the tourist balloon known as “Ballon de Paris” in a large park situated in the southwest of Paris, France. The measurement period is from April to November 2024, coinciding with the pollen seasons of trees and grasses. The balloon conducts numerous flights per day, reaching an altitude of 150 m when weather conditions are conducive, which occurs approximately 58% of the time during this period. The data are averaged to produce vertical profiles with a resolution of 30 m. Concentrations of the substance decrease with altitude, although a secondary layer is observed in spring. This phenomenon may be attributed to the presence of emissions from a proximate forest situated at a higher altitude. The average decrease in concentration of 11 ± 8% per 10 m is consistent with the findings of previous studies. The long-term implementation of Beenose measurements on this tourist balloon is intended to enhance the precision of the results and facilitate the differentiation of the various parameters that can influence the vertical transportation of pollen. Full article

The planthopper Pentastiridius leporinus, commonly called reed glass-winged cicada, transmits the pathogens “Candidatus Arsenophonus phytopathogenicus” and “Candidatus Phytoplasma solani”, which are infesting sugar beet and, most recently, also potato in the Upper Rhine valley area of Germany. They cause the “Syndrome Basses Richesses” associated with reduced yield and sugar content in sugar beet, leading to substantial monetary losses to farmers in the region. No effective solutions exist currently. This study uses statistical models to understand to what extent the abundance of cicadas depends on climate regions during the vegetation period (April–October). We further investigated what influence temperature and precipitation have on the abundance of the cicadas in sugar beet fields. Furthermore, we investigated the possible impacts of future climate on cicada abundance. Also, 22 °C and 8 mm/day were found to be the optimal temperature and precipitation conditions for peak male cicada flight activity, while 28 °C and 8 mm/day were the optimum for females. By the end of the 21st century, daily male cicada abundance is projected to increase significantly under the worst-case high greenhouse gas emission scenario RCP8.5 (RCP-Representative Concentration Pathways), with confidence intervals suggesting a possible 5–15-fold increase compared to current levels. In contrast, under the low-emission scenario RCP2.6, male cicada populations are projected to be 60–70% lower than RCP8.5. An understanding of the influence of changing temperature and precipitation conditions is crucial for predicting the spread of this pest to different regions of Germany and other European countries. Full article

Extreme weather events pose increasing risks to air transport operations, affecting flight safety, scheduling, and infrastructure resilience. This paper provides a comprehensive bibliometric analysis of scientific literature addressing the impacts of extreme weather on aviation, based on 1000 documents retrieved from the Web of Science Core Collection (2010–2024). Using VOSviewer software, keyword co-occurrence, overlay visualization, co-authorship networks, and citation analyses were conducted. Results revealed a clear thematic shift from environmental impact assessments toward research emphasizing operational resilience, technological adaptation, and mitigation strategies. Collaboration networks highlighted strong international cooperation, particularly among institutions in the United States, Germany, and the United Kingdom, with growing contributions from emerging research regions. Highly cited studies predominantly focused on emissions modeling and operational mitigation measures. Despite notable advances, the field remains fragmented and geographically uneven, underscoring the need for broader interdisciplinary integration and empirical validation of adaptation strategies. This paper offers a systematic overview of the evolving research landscape and identifies critical directions for future efforts to enhance the resilience and sustainability of global air transport systems under increasing climatic volatility. Full article

This study developed a neutron-beam-focusing supermirror for grazing-incidence small-angle neutron scattering (GISANS) measurements. We adopted point-to-point beam focusing based on an ellipse whose two foci correspond to a virtual point source and a spot on the detector surface. The focusing supermirror was fabricated by depositing NiC/Ti supermirror film with ion-beam sputtering on a precise elliptic surface of fused quartz figured using the elastic emission machining technique. Neutron measurements at the pulsed neutron reflectometer BL17 of the MLF, J-PARC, successfully demonstrated that the focusing supermirror enhances the beam intensity twentyfold compared with an optimally collimated beam, achieving a signal-to-background ratio of the focal spot as high as 500. The mirror can be readily installed and used at BL17 for time-of-flight GISANS measurements. Full article

This study aimed to evaluate the characteristics of short acquisition times using the Clear adaptive Low-noise Method (CaLM) and Advanced intelligent clear-IQ engine (AiCE) reconstructions in a semiconductor-based positron emission tomography (PET)/computed tomography system. PET data were acquired for 30 min in list mode and resampled into time frames ranging from 15 to 120 s. Images were reconstructed using three-dimensional ordinary Poisson ordered-subset expectation maximization (OSEM) with time of flight (TOF) and OSEM with TOF and point spread function modeling (PSF) algorithms, with OSEM iterations adjusted from 1 to 20 and CaLM applied under Mild, Standard, and Strong settings. AiCE reconstruction allows for the modification of only the acquisition time. The images were evaluated based on the coefficient of variation, recovery coefficient, % background variability (N_10mm), % contrast-to-% background variability ratio (Q_H10mm/N_10mm), and contrast-to-noise ratio. While OSEM with TOF reconstruction did not significantly reduce the acquisition time, the addition of PSF correction suggested the potential for further reduction. Given that the AiCE characteristics may vary depending on the equipment used, further investigation is required. Full article

The effective management of landfills requires advancements in techniques for rapid data collection and analysis of gas emissions. This work aims to refine methane (CH₄) emission data acquired from landfills by applying a robust geostatistical method to drone-collected measurements. Specifically, we use UAV-mounted laser spectrophotometer technology (TDLAS-UAV) to gather rapid, high-resolution data, which can sometimes be noisy due to atmospheric variations and sensor drift. For data handling, the key innovation is the application of the local indicator of spatial association (LISA), a technique that typically provides p-values to assess the statistical significance of observed spatial clusters. This approach was applied both on an areal basis and on a linear basis, following the order of data acquisition, and it produced comparable results. Very low p-values are considered indicative of non-random clustering, suggesting the influence of an underlying spatial control factor. These results were subsequently validated through independent flux chamber surveys. This validation confirms the reliability and objectivity of our geostatistical method in improving drone-based methane emission assessments. The research highlights the need to optimize drone flight paths to ensure a uniform spatial distribution of data and reduce edge effects. It notes that many CH₄ flux measurements often yield non-detectable results, suggesting a review of detection limits. Future work should refine UAV flight patterns and data processing with semi-controlled experiments—using known methane sources—to determine optimal acquisition parameters, such as flight height, sampling frequency, grid resolution, and wind influence. Full article

Unmanned aerial vehicles (UAVs) are becoming a major part of the civil and military aviation industries. They meet user needs for effective supply transportation and the real-time acquisition of accurate information during air operations. Recently, concerns about greenhouse gas (GHG) emissions have increased due to the use and depletion of fossil fuels, shifting attention toward the broader use of electric propulsion as a green technology in different sectors, including transportation. The long-term objective of this work is to build a prototype of a hybrid electric propulsion system (HEPS) dedicated to a multi-rotor unmanned aerial vehicle with a MTOW of 25 kg and an onboard electric voltage of 44.4 V. The main components and operating principles of the HEPS were defined. The main HEPS digital twin block modules and their operations were described. Using the developed digital twin structure and operational model, simulations were carried out. Based on the results, it can be demonstrated that the use of hybrid electric propulsion allows for a significant increase in the flight time of a multi-rotor UAV. The developed DT can be used as a tool for optimizing the operation of the HEPS prototype and for redefining mathematical models of individual components. Full article

Ice accumulation poses a significant hazard to aviation safety, particularly in cold weather conditions, as it can compromise aerodynamic performance, increase structural weight, and diminish lift, occasionally resulting in severe stall incidents. At present, such risks are managed through the use of energy-demanding active ice protection systems (IPSs), which operate either by inhibiting ice formation (anti-icing) or by removing existing ice (de-icing). Nonetheless, in the context of future sustainable aviation, there is a pressing need to develop IPSs with lower energy requirements. A promising approach involves hybrid IPSs that integrate conventional active systems with passive superhydrophobic or icephobic surface treatments, which are capable of preventing, delaying, or minimizing ice buildup. These systems offer the potential to substantially decrease the energy consumption and consequently the CO₂ emissions. Furthermore, in accordance with FAA regulations, active IPSs are not permitted to operate during takeoff and initial flight stages to prevent any reduction in engine thrust. These two reasons emphasize the critical importance of developing efficient coatings that, on the one hand, promote the mobility of water droplets, hereby preventing ice formation, as achieved by superhydrophobic surfaces, and on the other hand, facilitate ice detachment, as required for icephobic performance. In this context, the primary objective of the present work is to emphasize the icephobic properties of two superhydrophobic coatings. To achieve this, an extensive characterization is first conducted, including wettability, Surface Free Energy (SFE), and surface roughness, to confirm their superhydrophobic nature. This is followed by an assessment of their icephobic performance, specifically in terms of ice adhesion strength, with comparisons made against a commercial aeronautical coating. The results revealed a significant reduction in both the wettability and SFE of the developed coatings compared to the reference, along with a marked decrease in ice adhesion strength, thereby demonstrating their icephobic properties. Future activities will focus on the combination of coatings with active IPS in order to assess the energy efficiency under extensive icing conditions where both superhydrophobic and icephobic properties are required. Full article

The laser pulse detection probability of a scanning direct time-of-flight light detection and ranging (LiDAR) measurement is evaluated based on the optical signal distribution on a multipixel single photon avalanche diode (SPAD) array. These detectors intrinsically suffer from dead-times after the successful detection of a single photon and, thus, allow only for limited counting statistics when multiple returning laser photons are imaged on a single pixel. By blurring the imaged laser spot, the transition from single-pixel statistics with high signal intensity to multipixel statistics with less signal intensity is examined. Specifically, a comparison is made between the boundary cases in which (i) the returning LiDAR signal is focused through optics onto a single pixel and (ii) the detection is performed without lenses using all available pixels on the sensor matrix. The omission of imaging optics reduces the overall system size and minimizes optical transfer losses, which is crucial given the limited laser emission power due to safety standards. The investigation relies on a photon rate model for interfering (background) and signal light, applied to a simulated first-photon sensor architecture. For single-shot scenarios that reflect the optimal use of the time budget in scanning LiDAR systems, the lens-less and blurred approaches can achieve comparable or even superior results to the focusing system. This highlights the potential of fully solid-state scanning LiDAR systems utilizing optical phase arrays or multidirectional laser chips. Full article