Space range estimate for battery-powered vertical take-off and landing aircraft

A novel method for estimating the space range of battery-powered vertical take-off and landing(VTOL) aircraft is presented. The method is based on flight parameter optimization and numerical iteration. Subsystem models including required thrust, required power and battery discharge models are presented. The problem to be optimized is formulated, and then case study simulation is conducted using the established method for quantitative analysis. Simulation results show that the space range of battery-powered VTOL aircraft in a vertical plane is an oblate curve, which appears horizontally long but vertically short, and the peak point is not located on the vertical climb path. The method and results are confirmed by parameter analysis and validations.

Problems and Barriers Impeding the Implementation of MagLev Assisted Aircraft Take-Off and Landing Concept

Nowadays, the success of the new technology development and deployment process depends not only on technical, technological solutions, but also on solving the non-technological problems and crossing the societal and psychological barriers. A large international European projects, GABRIEL1 had developed a maglev assisted aircraft take-off and landing, that was applied to conceptual design of aircraft and required on-board and ground systems, had analysed all impacts (effects of concept deployment on effectiveness, safety, security, noise, emissions) and had demonstrated the safe applicability by concept validation. The applied methodology, used methods and the results of the Gabriel projects had been described and discussed by 55 project deliverables. This paper has a special goal: investigating the problems and barriers of possible implementing of the radically new technology, aircraft MagLev assisted take-off and landing. The study was started by identification and classification of the problems and barriers. After it, the problems were systematically analysed by use of special methodology containing the understanding (description) of the problems, investigation of the possible solutions and discussing their applicability (mainly by use of the Gabriel project results). The paper has three major sections: 1) description of the Gabriel concept and project results, 2) introducing some related thoughts on general aspects of new technology developments, and 3) discussion on the problems and their solutions. The major classes of the problems are the 1) technical, technological problems as developing a radically new solution, landing the undercarriage-less aircraft on the magnetic tracks, 2) stakeholders’ problems as decision makers kicking against supporting the developments of so radically new technologies and 3) society barriers like society worrying on and fear of future passengers on flying by aircraft have not conventional undercarriage systems. The paper will show that these problems have safe and cost-effective solutions.

Trajectory Tracking of Vertical Take-off and Landing Unmanned Aerial Vehicles Based on Disturbance Rejection Control

We investigate the trajectory tracking problem of vertical take-off and landing (VTOL) unmanned aerial vehicles (UAV), and propose a practical disturbance rejection control strategy. Firstly, the nonlinear error model is established completely by the modified Rodrigues parameters, while considering dynamics of the servo actuators. Then, a hierarchical control scheme is applied to design the translational and rotational controllers based on the time-scale property of each subsystem, respectively. And the linear extended state observer and auxiliary observer are used to deal with the uncertainties and saturation. At last, global stability of the closed-loop system is analyzed based on the singular perturbation theory. Simulation results show the effectiveness of the proposed control strategy. © 2014 Chinese Association of Automation.

The Influence of Climate Change and Variability on Aircraft Take-off and Landing Performance;a Case Study of the Abeid Amani Karume International Airport-Zanzibar

Climate change (CC) and variability have been world widely reported to pose number of risks in aviation industry including accidents, astray, and other operational difficulties. The impact of weather on landing and take-off performances has been several times experienced at Abeid Amani Karume International Airport (AAKIA);however, the influence of climate change and variability to the aircraft performance needs to be assessed. Thus, this study investigated the influence of climate change and variability on aircrafts take-off and landing performances. Specifically, the study investigated;i) the influence of climate change on Take-off Distance Required (TODR) and Maximum Take-off Mass (MTOM) for different types of aircraft;ii) the influence of climate variability to the aircraft landing performance on light, medium and heavy aircraft and lastly, iii) the study investigated the seasonal and annual variability on aircraft landing performance due to climate variability. The datasets used in this study include the eight years (2014-2021), aircraft operational records (diversion and missed approach events) and Aviation Routine Weather Reports (METAR) records which were utilized as the indicators for landing performance, the long-term (1990-2020) annual maximum temperatures (Tmax) which was used to determine the TODR and MTOM. Statistical tools including mean, percentage changes, correlations, regression, and the chi-square test were used for analysis and hypotheses testing. The results revealed that light and medium aircraft categories were significantly most affected on diversion events as compared to the heavy categories;however, for the missed approach events the impact was vice versa. Moreover, the seasonal and annual variability on diversion and missed approach events were significantly different (at p ≤ 0.001). As for the take-off performance, results show that the TODR and MTOM were significantly increasing and decreasing (at p ≤ 0.001), based on increasing air temperatures. Therefore, the study concludes that the changing climate has significantly affected aircraft by increasing the TODR and decreasing the MTOM, while the climate variability has significantly affected landing performance by influencing the diversion and missed approach events. Thus, the study recommends (i) further research works including the feasibility study on runway extension for the safety of future aircraft operations at the AAKIA and (ii) proper maintenance and improvement of the Instrumental Landing Systems (ILS) as an adaptation measures to the landing aircraft during bad weather events.

Stability Analysis of Nonlinear Models of Nose Landing Gear Shimmy

Shimmy can reduce the service life of the nose landing gear, affect ride comfort, and even cause fuselage damage leading to aircraft crashes. Taking a light aircraft as the research object, the torsional freedom of landing gear around strut axis and lateral deformation of tire are considered. Since the landing gear shimmy is a nonlinear system, a nonlinear mechanical model of the front landing gear shimmy is established. Sobol index method is proposed to analyze the influence of structural parameters on the stability region of the nose landing gear, and Routh-Huritz criterion is used to verify the reliability of the analysis results of Sobol index method. We analyse the effect of torsional stiffness of strut, caster length, rated initial tire inflation pressure, rake angle, and vertical force on the stability region of theront landing gear. And the research shows that the optimization of the torsional stiffness of the strut and the caster length of the nose landing gear should be emphasized, and the influence of vertical force on the stability region of the nose landing gear should be paid attention to.

A multi-strategy pigeon-inspired optimization approach to active disturbance rejection control parameters tuning for vertical take-off and landing fixed-wing UAV

In this paper.Active Disturbance Rejection Control(ADRC)is utilized in the pitch control of a vertical take-off and landing fixed-wing Unmanned Aerial Vehicle(UAV)to address the problem of height fluctuation during the transition from hover to level flight.Considering the difficulty of parameter tuning of ADRC as well as the requirement of accuracy and rapidity of the controller,a Multi-Strategy Pigeon-Inspired Optimization(MSPIO)algorithm is employed.Particle Swarm Optimization(PSO),Genetic Algorithm(GA),the basic Pigeon-Inspired Optimization(PIO),and an improved PIO algorithm CMPIO are compared.In addition,the optimized ADRC control system is compared with the pure Proportional-Integral-Derivative(PID)control system and the non-optimized ADRC control system.The effectiveness of the designed control strategy for forward transition is verified and the faster convergence speed and better exploitation ability of the proposed MSPIO algorithm are confirmed by simulation results.

Development of a Bird-like Flapping-wing Aerial Vehicle with Autonomous Take-off and Landing Capabilities

The lack of autonomous take-off and landing capabilities of bird-like flapping-wing aerial vehicles(BFAVs)seriously restricts their further development and application.Thus,combined with the current research results on the autonomous take-off and landing technology of unmanned aerial vehicles,four types of technologies are studied,including jumping take-off and landing technology,taxiing take-off and landing technology,gliding take-off and landing technology,and vertical take-off and landing(VTOL)technology.Based on the analytic hierarchy process(AHP)-comprehensive evaluation method,a fuzzy comprehensive evaluation model for the autonomous take-off and landing scheme of a BFAV is established,and four schemes are evaluated concretely.The results show that under the existing technical conditions,the hybrid layout VTOL scheme is the best.Furthermore,the detailed design and development of the prototype of a BFAV with a four-rotor hybrid layout are carried out,and the vehicle performance is tested.The results prove that through the four-rotor hybrid layout design,the BFAV has good autonomous take-off and landing abilities.The power consumption analysis shows that for a fixed-point reconnaissance mission,when the mission radius is less than 3.38 km,the VTOL type exhibits longer mission duration than the hand-launched type.

New stabilization design for planar vertical take-off and landing aircrafts

This paper presents a new stabilizing control law for a planar vertical take-off and landing aircraft.The model is first transformed into an equivalent form,and then a control law consisting of a linear term and a saturated term is given for a related subsystem,with the saturation levels being assigned as large as possible.Compared to the existing saturation scheme in which all states are restricted by saturations,the design brings about a relatively fast convergence.The effectiveness and advantage of the design are validated by numerical simulations.

基于Landsat影像的城市土地利用动态监测

土地是自然界不可或缺的资源,土地利用反映了人地关系。随着人口数量的持续增加和社会工业化、城市化的持续推进,如何科学地开发利用宝贵的土地资源越来越受到人们的重视。本文通过2013年和2023年的Landsat影像数据,结合遥感与GIS,对10年间合肥市土地资源进行监测与分析,结果表明,经过10年的城市发展,合肥市耕地面积减少了65707.92 hm 2,建设用地增长了39181.05 hm 2,林地减少了1728.27 hm 2,水域增加了28255.14 hm 2。

Phenomenology of plume-surface interactions and preliminary results from the Tianwen-1 landing crater on Mars

The plume-surface interaction(PSI)is a common phenomenon that describes the environment surrounding the landers resulting from the impingement of hot rocket exhaust on the regolith of planetary bodies.The PSI will cause obscuration,erosion of the planetary surface,and high-speed spreading of dust or high-energy ejecta streams,which will induce risks to a safe landing and cause damage to payloads on the landers or to nearby assets.Safe landings and the subsequent scientific goals of deep-space exploration in China call for a comprehensive understanding of the PSI process,including the plume flow mechanics,erosion mechanism,and ejecta dynamics.In addition,the landing crater caused by the plume provides a unique and insightful perspective on the understanding of PSI.In particular,the PSI can be used directly to constrain the composition,structure,and mechanical properties of the surface and subsurface soil.In this study,we conducted a systematic review of the phenomenology and terrestrial tests of PSI:we analyzed the critical factors in the PSI process and compared the differences in PSI phenomena between lunar and Martian conditions;we also reviewed the main erosion mechanisms and the evolution and development of terrestrial tests on PSI.We discuss the problems with PSI,challenges of terrestrial tests,and prospects of PSI,and we show the preliminary results obtained from the landing crater caused by the PSI of Tianwen-1.From analysis of the camera images and digital elevation model reconstructions,we concluded that the landing of Tianwen-1 caused the deepest crater(depth>40 cm)on a planetary surface reported to date and revealed stratigraphic layers in the subsurface of Martian soil.We further constrained the lower bounds of the mechanical properties of Martian soil by a slope stability analysis of the Tianwen-1 landing crater.The PSI may offer promising opportunities to obtain greater insights into planetary science,including the subsurface structure,mineral composition,and properties of soil.

Autonomous landing scene recognition based on transfer learning for drones

In this paper, we study autonomous landing scene recognition with knowledge transfer for drones. Considering the difficulties in aerial remote sensing, especially that some scenes are extremely similar, or the same scene has different representations in different altitudes, we employ a deep convolutional neural network(CNN) based on knowledge transfer and fine-tuning to solve the problem. Then, LandingScenes-7 dataset is established and divided into seven classes. Moreover, there is still a novelty detection problem in the classifier, and we address this by excluding other landing scenes using the approach of thresholding in the prediction stage. We employ the transfer learning method based on ResNeXt-50 backbone with the adaptive momentum(ADAM) optimization algorithm. We also compare ResNet-50 backbone and the momentum stochastic gradient descent(SGD) optimizer. Experiment results show that ResNeXt-50 based on the ADAM optimization algorithm has better performance. With a pre-trained model and fine-tuning, it can achieve 97.845 0% top-1 accuracy on the LandingScenes-7dataset, paving the way for drones to autonomously learn landing scenes.

Indirect contact matters:Mid-flight external trunk perturbation increased unilateral anterior cruciate ligament loading variables during jump-landings

Purpose:To determine the effect of unanticipated mid-flight medial-lateral external perturbation of the upper or lower trunk on anterior cruciate ligament(ACL)loading variable s during jump-landings.Methods:Thirty-two participants performed double-leg vertical jump-landings while bilateral kinematics and kinetics were collected under 6conditions(upper or lower trunk perturbation locations;no,left,or right perturbation directions).Two customized catapult apparatuses were created to apply pushing perturbation to participants near the maximal jump height.Results:The ball contacted participants near the center of mass for the lower-trunk conditions and approximately 23 cm above the center of mass for the upper-trunk conditions.Under upper-trunk perturbation,the contralateral leg demonstrated significantly smaller knee flexion angles at initial contact and greater peak knee abduction angles,peak vertical ground reaction forces,peak knee extension moments,and peak knee adduction moments compared to other legs among all conditions.Under lower-trunk perturbation,the contralateral leg showed significantly smaller knee flexion angles at initial contact and increased peak vertical ground reaction forces and peak knee extension moments compared to legs in the no-perturbation conditions.Conclusion:Mid-flight external trunk pushing perturbation increased ACL loading variables for the leg contralateral to the perturbation.The uppertrunk perturbation resulted in greater changes in ACL loading variables compared to the lower-trunk perturbation,likely due to trunk and ipsilateral leg rotation and more laterally located center of mass relative to the contralateral leg.These findings may help us understand the mechanisms of indirect-contact ACL injuries and develop jump-landing training strategies under mid-flight trunk perturbation to better prevent ACL injury.

Understanding the Relationship Between Shrinking Cities and Land Prices:Spatial Pattern,Effectiveness,and Policy Implications

Urban shrinkage has emerged as a widespread phenomenon globally and has a significant impact on land,particularly in terms of land use and price.This study focuses on 2851 county-level cities in China in 2005–2018(excluding Hong Kong,Macao,Taiwan,and‘no data’areas in Qinhai-Tibet Plateau)as the fundamental units of analysis.By employing nighttime light(NTL)data to identify shrinking cities,the propensity score matching(PSM)model was used to quantitatively examine the impact of shrinking cities on land prices,and evaluate the magnitude of this influence.The findings demonstrate the following:1)there were 613 shrinking cities in China,with moderate shrinkage being the most prevalent and severe shrinkage being the least.2)Regional disparities are evident in the spatial distribution of shrinking cities,especially in areas with diverse terrain.3)The spatial pattern of land price exhibits a significant correlated to the economic and administrative levels.4)Shrinking cities significantly negatively impact on the overall land price(ATT=–0.1241,P<0.05).However,the extent of the effect varies significantly among different spatial regions.This study contributes novel insights into the investigation of land prices and shrinking cities,ultimately serving as a foundation for government efforts to promote the sustainable development of urban areas.

Thermo-hydro-mechanical (THM) coupled simulation of the land subsidence due to aquifer thermal energy storage (ATES) system in soft soils

Aquifer thermal energy storage(ATES)system has received attention for heating or cooling buildings.However,it is well known that land subsidence becomes a major environmental concern for ATES projects.Yet,the effect of temperature on land subsidence has received practically no attention in the past.This paper presents a thermo-hydro-mechanical(THM)coupled numerical study on an ATES system in Shanghai,China.Four water wells were installed for seasonal heating and cooling of an agriculture greenhouse.The target aquifer at a depth of 74e104.5 m consisted of alternating layers of sand and silty sand and was covered with clay.Groundwater level,temperature,and land subsidence data from 2015 to 2017 were collected using field monitoring instruments.Constrained by data,we constructed a field scale three-dimensional(3D)model using TOUGH(Transport of Unsaturated Groundwater and Heat)and FLAC3D(Fast Lagrangian Analysis of Continua)equipped with a thermo-elastoplastic constitutive model.The effectiveness of the numerical model was validated by field data.The model was used to reproduce groundwater flow,heat transfer,and mechanical responses in porous media over three years and capture the thermo-and pressure-induced land subsidence.The results show that the maximum thermoinduced land subsidence accounts for about 60%of the total subsidence.The thermo-induced subsidence is slightly greater in winter than that in summer,and more pronounced near the cold well area than the hot well area.This study provides some valuable guidelines for controlling land subsidence caused by ATES systems installed in soft soils.

Modelling Land Use/Land Cover Change of River Rwizi Catchment, South-Western Uganda Using GIS and Markov Chain Model

Analysis of catchment Land use/Land cover (LULC) change is a vital tool in ensuring sustainable catchment management. The study analyzed land use/land cover changes in the Rwizi catchment, south western Uganda from 1989-2019 and projected the trend by 2040. Landsat images, field observations, key informant interviews and focus group discussions were used to collect data. Changes in cropland, forestland, built up area, grazing land, wetland and open water bodies were analyzed in ArcGIS version 10.2.2 and ERDAS IMAGINE 14 software and a Markov chain model. All the LULC classes increased in area except grazing land. Forest land and builtup area between 2009-2019 increased by 370.03% and 229.53% respectively. Projections revealed an increase in forest land and builtup area by 2030 and only built up area by 2040. LULCC in the catchment results from population pressure, reduced soil fertility and high value of agricultural products.

Spatiotemporal landscape pattern changes and their effects on land surface temperature in greenbelt with semi-arid climate:A case study of the Erbil City,Iraq

Urban expansion of cities has caused changes in land use and land cover(LULC)in addition to transformations in the spatial characteristics of landscape structure.These alterations have generated heat islands and rise of land surface temperature(LST),which consequently have caused a variety of environmental issues and threated the sustainable development of urban areas.Greenbelts are employed as an urban planning containment policy to regulate urban expansion,safeguard natural open spaces,and serve adaptation and mitigation functions.And they are regarded as a powerful measure for enhancing urban environmental sustainability.Despite the fact that,the relation between landscape structure change and variation of LST has been examined thoroughly in many studies,but there is a limitation concerning this relation in semi-arid climate and in greenbelts as well,with the lacking of comprehensive research combing both aspects.Accordingly,this study investigated the spatiotemporal changes of landscape pattern of LULC and their relationship with variation of LST within an inner greenbelt in the semi-arid Erbil City of northern Iraq.The study utilized remote sensing data to retrieve LST,classified LULC,and calculated landscape metrics for analyzing spatial changes during the study period.The results indicated that both composition and configuration of LULC had an impact on the variation of LST in the study area.The Pearson's correlation showed the significant effect of Vegetation 1 type(VH),cultivated land(CU),and bare soil(BS)on LST,as increase of LST was related to the decrease of VH and the increases of CU and BS,while,neither Vegetation 2 type(VL)nor built-up(BU)had any effects.Additionally,the spatial distribution of LULC also exhibited significant effects on LST,as LST was strongly correlated with landscape indices for VH,CU,and BS.However,for BU,only aggregation index metric affected LST,while none of VL metrics had a relation.The study provides insights for landscape planners and policymakers to not only develop more green spaces in greenbelt but also optimize the spatial landscape patterns to reduce the influence of LST on the urban environment,and further promote sustainable development and enhance well-being in the cities with semi-arid climate.

Review of coastal land transformation:Factors,impacts,adaptation strategies,and future scopes

Coastal land transformation has been identified as a topic of research in many countries around the world.Several studies have been conducted to determine the causes and impacts of land transformation.However,much less is understood about coupling change detection,factors,impacts,and adaptation strategies for coastal land transformation at a global scale.This review aims to present a systematic review of global coastal land transformation and its leading research areas.From 1,741 documents of Scopus and Web of Science,60 studies have been selected using the PRISMA-2020 guideline.Results revealed that existing literature included four leading focus areas regarding coastal land transformation:change detection,driving factors,impacts,and adaptation measures.These focus areas were further analyzed,and it was found that more than 80%of studies used Landsat imagery to detect land transformation.Population growth and urbanization were among the major driving factors identified.This review further identified that about 37%of studies included impact analysis.These studies identified impacts on ecosystems,land surface temperature,migration,water quality,and occupational effects as significant impacts.However,only four studies included adaptation strategies.This review explored the scope of comprehensive research in coastal land transformation,addressing change detection,factor and impact analysis,and mitigation-adaptation strategies.The research also proposes a conceptual framework for comprehensive coastal land transformation analysis.The framework can provide potential decision-making guidance for future studies in coastal land transformation.

Land use change and its driving factors in the ecological function area:A case study in the Hedong Region of the Gansu Province,China

Land use and cover change(LUCC)is important for the provision of ecosystem services.An increasing number of recent studies link LUCC processes to ecosystem services and human well-being at different scales recently.However,the dynamic of land use and its drivers receive insufficient attention within ecological function areas,particularly in quantifying the dynamic roles of climate change and human activities on land use based on a long time series.This study utilizes geospatial analysis and geographical detectors to examine the temporal dynamics of land use patterns and their underlying drivers in the Hedong Region of the Gansu Province from 1990 to 2020.Results indicated that grassland,cropland,and forestland collectively accounted for approximately 99% of the total land area.Cropland initially increased and then decreased after 2000,while grassland decreased with fluctuations.In contrast,forestland and construction land were continuously expanded,with net growth areas of 6235.2 and 455.9 km^(2),respectively.From 1990 to 2020,cropland was converted to grassland,and both of them were converted to forestland as a whole.The expansion of construction land primarily originated from cropland.From 2000 to 2005,land use experienced intensified temporal dynamics and a shift of relatively active zones from the central to the southeastern region.Grain yield,economic factors,and precipitation were the major factors accounting for most land use changes.Climatic impacts on land use changes were stronger before 1995,succeeded by the impact of animal husbandry during 1995-2000,followed by the impacts of grain production and gross domestic product(GDP)after 2000.Moreover,agricultural and pastoral activities,coupled with climate change,exhibited stronger enhancement effects after 2000 through their interaction with population and economic factors.These patterns closely correlated with ecological restoration projects in China since 1999.This study implies the importance of synergy between human activity and climate change for optimizing land use via ecological patterns in the ecological function area.

Assessing Spatio-Temporal Land Cover Changes in Dhund River Basin, Eastern Rajasthan (India), Using Multi-Temporal Landsat Data

Land cover is an impression of natural cover on surface of earth such as bare soil, river, grass etc. and utilization of these natural covers for various human needs and purposes by mankind is defined as land use. Land cover identification, delineation and mapping is important for planning activities, resource management and global monitoring studies while baseline mapping and subsequent monitoring is done by application of land use to get timely information about quantity of land that has been used. The present study has been carried out in Dhund river watershed of Jaipur, Rajasthan which covers an area of about 1828 sq∙km. The minimum and maximum elevation of the area is found to be 214 m and 603 m respectively. Land use and land cover changes of three decades from 1991 to 2021 have been interpreted by using remotes sensing and GIS techniques. ArcGIS software (Arc map 10.2), SOI topographic map, Cartosat-1 DEM and satellite data of Landsat 5 and Landsat 8 have been used for interpretation of eleven classes. The study shows an increase in cultivated land, settlement, waterbody, open forest, plantation and mining due to urbanization because of increasing demands of food, shelter and water while a decrease in dense forest, river, open scrub, wasteland and uncultivated land has also been marked due to destruction of aforementioned by anthropogenic activities such as industrialization resulting in environmental degradation that leads to air, soil and water pollution.

Historical Changes and Multi-scenario Prediction of Land Use and Terrestrial Ecosystem Carbon Storage in China

Terrestrial carbon storage(CS)plays a crucial role in achieving carbon balance and mitigating global climate change.This study employs the Shared Socioeconomic Pathways and Representative Concentration Pathways(SSPs-RCPs)published by the Intergovernmental Panel on Climate Change(IPCC)and incorporates the Policy Control Scenario(PCS)regulated by China’s land management policies.The Future Land Use Simulation(FLUS)model is employed to generate a 1 km resolution land use/cover change(LUCC)dataset for China in 2030 and 2060.Based on the carbon density dataset of China’s terrestrial ecosystems,the study analyses CS changes and their relationship with land use changes spanning from 1990 to 2060.The findings indicate that the quantitative changes in land use in China from 1990 to 2020 are characterised by a reduction in the area proportion of cropland and grassland,along with an increase in the impervious surface and forest area.This changing trend is projected to continue under the PCS from 2020 to 2060.Under the SSPs-RCPs scenario,the proportion of cropland and impervious surface predominantly increases,while the proportions of forest and grassland continuously decrease.Carbon loss in China’s carbon storage from 1990 to 2020 amounted to 0.53×10^(12)kg,primarily due to the reduced area of cropland and grassland.In the SSPs-RCPs scenario,more significant carbon loss occurs,reaching a peak of8.07×10^(12)kg in the SSP4-RCP3.4 scenario.Carbon loss is mainly concentrated in the southeastern coastal area and the Beijing-TianjinHebei(BTH)region of China,with urbanisation and deforestation identified as the primary drivers.In the future,it is advisable to enhance the protection of forests and grassland while stabilising cropland areas and improving the intensity of urban land.These research findings offer valuable data support for China’s land management policy,land space optimisation,and the achievement of dual-carbon targets.