Three-dimensional multi-constraint route planning of unmanned aerial vehicle low-altitude penetration based on coevolutionary multi-agent genetic algorithm

To address the issue of premature convergence and slow convergence rate in three-dimensional (3D) route planning of unmanned aerial vehicle (UAV) low-altitude penetration,a novel route planning method was proposed.First and foremost,a coevolutionary multi-agent genetic algorithm (CE-MAGA) was formed by introducing coevolutionary mechanism to multi-agent genetic algorithm (MAGA),an efficient global optimization algorithm.A dynamic route representation form was also adopted to improve the flight route accuracy.Moreover,an efficient constraint handling method was used to simplify the treatment of multi-constraint and reduce the time-cost of planning computation.Simulation and corresponding analysis show that the planning results of CE-MAGA have better performance on terrain following,terrain avoidance,threat avoidance (TF/TA2) and lower route costs than other existing algorithms.In addition,feasible flight routes can be acquired within 2 s,and the convergence rate of the whole evolutionary process is very fast.

Occurrence Regularity of Tobacco Cutworm Moth (Spodoptera Litura) in Low-Altitude Tobacco Cultivation Areas in Lincang

[ Objective ] The paper was to study the occurrence and damage regularity of tobacco cutworm moth （Spodoptera Litura Fabricius） in low-altitude area in Lincang city. [ Method] The adult sex attractant monitoring, field investigation of occurrence and damage, and observation of continuous generation development of natural populations were carried out in natural flue-cured tobacco fields. [ Result] In field growth period of flue-cured tobacco under low-altitude of 1 000 - 1300 m, tobacco cutworm moth occurred for 4 generations, the duration of each generation was about 33 d, and the main injurious generation was the third generation. [ Conclusion] The paper provided reference for comprehensive control of tobacco cutworm moth in the low altitude areas.

Analysis of Low-Altitude Inversion Characteristics of Coal-Fired Power Projects Based on Tethered Balloon Observation

Atmospheric inversion phenomenon directly affects the vertical movement of air, which causes the cooling heat of the cooling tower in the power plant to be blocked. Therefore, it is necessary to analyze the atmospheric inversion characteristics of the research project during the design of the air cooling system. Using the low-altitude observing system of the tethered balloon, the on-site observation of the temperature below 300 m in summer is carried out for a coal-fired power integration project in Yulin, Shaanxi, China. Observations were made at 10 fixed times per day, with a cumulative observation of 46 days and 247 effective detections. The data were quality-controlled, and then linearly interpolated. According to the requirements of the project designer, the temperature data of 20, 50, 100, 150, 200, 250, 300 m was used for low-temperature inversion analysis. The research shows that the grounding inversion and low-altitude inversion can be observed at the same time. In the time and space changes, the grounding inversion temperature and intensity are significantly higher than the low-altitude inversion. The maximum inversion of grounding inversion and low-altitude inversion is 2.3?C/hm, 1.0?C/hm. Grounding inversion temperature occurs every time, the frequency is the highest at 20 o’clock, the average intensity is maximum at 17 o’clock, and the average height, maximum intensity and maximum height are maximum at 7 o’clock. When the low-altitude inversion temperature is 18 o’clock, other times can occur, and the frequency is the highest at 15 o’clock, but the inversion layer is shallow, the bottom is high and the intensity is small. Grounding inversion and low-altitude inversion can occur in all levels, and as the height increases, the grounding inversion decreases and the low-temperature inversion increases. The design of the project air cooling tower needs to fully consider the impact caused by the inverse temperature below 300 m.

Application of 3D Digital Modeling Technology in the Construction of Digital Cities

The concepts of “digital twins”, “3D real scene”, “metacosm” and others were the technical paths for building digital cities with the development of emerging surveying and mapping science and technology, which was to build a digital and virtualized city that matched the real physical world, to achieve a one-to-one correspondence between all elements of the physical world and the digital virtual world. And one of its basic geographic information data was a highly similar, virtual simulation of the 3D real scene. After exploring the traditional manual 3DsMax modeling, UAV low-altitude digital oblique photogrammetry modeling, airborne laser scanning modeling and other single modeling technologies, this paper discussed the 3D digital modeling technology used by the UAV airborne laser scanning point cloud and low-altitude digital oblique photogrammetry for complementary integration, constructing the 3D scene of the digital city. This paper expounded the technical route and production process of 3D digital modeling, in order to provide technical references for related projects.

Initial Analysis on the Effect of High-low Altitude Jet Stream on Heavy Precipitation in Guangxi

By using the routine observation data,a heavy precipitation process which happened in Guangxi on May 27,2006 was analyzed.The results that this heavy precipitation occurred in the common coordination weather system which included the high-altitude trough,the shear line and the ground cold front.The ascent branch of subtropical longitude circle circulation and the polar front jet stream longitude circle circulation had the important role for the formation of rainstorm area.The coupling effect of southerly jet,low-altitude westerly jet and high-altitude westerly jet in the boundary layer was the important reason of rainstorm occurrence.

Development and evaluation of low-altitude remote sensing systems for crop production management

Precision agriculture accounts for within-field variability for targeted treatment rather than uniform treatment of an entire field.It is built on agricultural mechanization and state-of-the-art technologies of geographical information systems(GIS),global positioning systems(GPS)and remote sensing,and is used to monitor soil,crop growth,weed infestation,insects,diseases,and water status in farm fields to provide data and information to guide agricultural management practices.Precision agriculture began with mapping of crop fields at different scales to support agricultural planning and decision making.With the development of variable-rate technology,precision agriculture focuses more on tactical actions in controlling variable-rate seeding,fertilizer and pesticide application,and irrigation in real-time or within the crop season instead of mapping a field in one crop season to make decisions for the next crop season.With the development of aerial variable-rate systems,low-altitude airborne systems can provide high-resolution data for prescription variable-rate operations.Airborne systems for multispectral imaging using a number of imaging sensors(cameras)were developed.Unmanned aerial vehicles(UAVs)provide a unique platform for remote sensing of crop fields at slow speeds and low-altitudes,and they are efficient and more flexible than manned agricultural airplanes,which often cannot provide images at both low altitude and low speed for capture of high-quality images.UAVs are also more universal in their applicability than agricultural aircraft since the latter are used only in specific regions.This study presents the low-altitude remote sensing systems developed for detection of crop stress caused by multiple factors.UAVs,as a special platform,were discussed for crop sensing based on the researchers'studies.

Estimation of carbon and nitrogen contents in citrus canopy by low-altitude remote sensing

The study aimed to investigate the fast and nondestructive method for detecting carbon and nitrogen content in citrus canopy.The multispectral imagery of Tarocco blood orange(Citrus sinensis L.Osbeck)plant canopy was obtained by a multispectral camera array mounted at an eight-rotor unmanned aerial vehicle(UAV)flying at an altitude of 100 m above the canopy in Wanzhou District of Chongqing Municipality,China.Average spectral reflectance data of the whole canopy,mature leaf areas and young leaves areas were extracted from the imagery.Two spectral pre-processing methods,multiplicative scatter correction(MSC)and standard normal variable(SNV),and two modeling methods,the partial least squares(PLS)and the least squares support vector machine(LS-SVM),were adopted and compared for their prediction accuracy of total content of nitrogen,soluble sugar and starch in the leaves.The results showed that,based on the spectral data extracted from the mature leaves in the multispectral imagery,the PLS model based on the original spectrum obtained a Rp(correlation coefficient)of 0.6469 and RMSEP(root mean squares error of prediction)of 0.1296,suggested that it was the best for the prediction of total nitrogen content;the PLS model based on MSC(multiplicative scatter correction)spectrum pre-processing was the best for predicting total soluble sugar content(Rp=0.6398 and RMSEP=8.8891);and the LS-SVM model based on MSC was the best for the starch content prediction(Rp=0.6822 and RMSEP=14.9303).The prediction accuracy for carbon and nitrogen contents based on the spectral data extracted from the whole canopy and the young leaves were lower than that from the mature leaves.The results indicate that it is feasible to estimate the carbon and nitrogen contents by low-altitude airborne multispectral images.

Close up observation and inversion of low-altitude ENA emissions during a substorm event

During a series of substorm events on November 12 2004, the Neutral Atom Detector Unit(NUADU) flying onboard the TC-2 spacecraft observed, close to perigee, bright low-altitude Energetic Neutral Atom(ENA) emissions from both north and south poles. Through utilizing high temporal and spatial resolution data inversion techniques we present here a global view the associated processes of energetic ion deposition and injection at the uniquely high temporal resolution of a few minutes. It is demonstrated that the ENA emissions observed came mainly from the, low-altitude, high magnetic latitude polar region. Since precipitating ions follow magnetic field lines and have more chance to produce ENA emissions through charge exchange there.Therefore, the employment of a low-orbit satellite to record at high temporal and spatial resolution ENA image data is inferred to be the best way to monitor those dynamic ring current variations that occur during geomagnetic activity.

Integrated Network Design and Demand Forecast for On-Demand Urban Air Mobility

Urban air mobility(UAM)is an emerging concept proposed in recent years that uses electric vertical takeoff and landing vehicles(eVTOLs).UAM is expected to offer an alternative way of transporting passengers and goods in urban areas with significantly improved mobility by making use of low-altitude airspace.In addition to other essential elements,ground infrastructure of vertiports is needed to transition UAM from concept to operation.This study examines the network design of UAM on-demand service,with a particular focus on the use of integer programming and a solution algorithm to determine the optimal locations of vertiports,user allocation to vertiports,and vertiport access-and egress-mode choices while considering the interactions between vertiport locations and potential UAM travel demand.A case study based on simulated disaggregate travel demand data of the Tampa Bay area in Florida,USA was conducted to demonstrate the effectiveness of the proposed model.Candidate vertiport locations were obtained by analyzing a three-dimensional(3D)geographic information system(GIS)map developed from lidar data of Florida and physical and regulation constraints of eVTOL operations at vertiports.Optimal locations of vertiports were determined to achieve the minimal total generalized cost;however,the modeling structure allows each user to select a better mode between ground transportation and UAM in terms of generalized cost.The outcomes of the case study reveal that although the percentage of trips that switched from ground mode to multimodal UAM was small,users choosing the UAM service benefited from significant time saving.In addition,the impact of different parameter settings on the demand for UAM service was explored from the supply side,and different pricing strategies were tested that might influence potential demand and revenue generation for UAM operators.The combined effects of the number of vertiports and pricing strategies were also analyzed.The findings from this study offer in-depth planning and managerial insights for municipal decision-makers and UAM operators.The conclusion of this paper discusses caveats to the study,ongoing efforts by the authors,and future directions in UAM research.

A new skeleton based flying bird detection method for low-altitude air traffic management

In low-altitude air traffic management, non-cooperation targets are the greatest threat to security of low-flying aircraft. Among various aviation fatalities, flying bird is the main factor with the highest risk and directs economic losses amounted to nearly 10 billion US dollars each year.Therefore, Flying Bird Detection(FBD) has attracted considerable attention in low-altitude air traffic management. In this paper, we propose a skeleton based FBD method via describing bird motion information with a set of key poses. To overcome the variability of birds, the skeleton feature is selected as a relatively fixed and common characteristic for the pose appearance of flying bird. Based on the geometric topology among some key parts of bird body, a set of key poses can be described by some extracted skeleton features, which are used to represent the bird motion information. Aimed at robustly handling with the pose variations, multiple pose-specific classifiers are individually trained to learn the representative poses of the flying bird. At the detection stage,the flying bird skeleton features are combined with extracted key-pose sets to perform the flying bird classification task from each image. Afterwards, the key-frame pose-change set and the consistency of the classification results from sequent images are employed to validate the final detection results.Experiments on flying bird datasets demonstrate the effectiveness and efficiency of the proposed method.

Application of UAV in Road Safety in Intelligent Areas

With the continuous development of remote sensing(RS)technology,the surface information can be collected conveniently and quickly by using the popular unmanned aerial vehicle(UAV).The application of UAV low altitude RS technology in road safety in intelligent area has certain practical significance.It can provide safety warning for most drivers,and provide auxiliary decision-making for the road supervision department.Through the collection,processing,calculation and analysis of the road image,the UAV can find out the road obstacles with potential safety hazards,identify the road pit,calculate the radius and depth of the road pit through the digital mapping system,predict the accident risk according to different speed and provide scientific basis for the road safety monitoring.At the same time,UAV can provide repair scheme for damaged roads,estimate the quantity of materials needed for repair,and achieve the target of resource saving and efficiency improvement.The experimental results show that the UAV can not only provide scientific prediction information for driving safety,but also provide relatively accurate material consumption for road repair.

Pangenome and multi-tissue gene atlas provide new insights into the domestication and highland adaptation of yaks

Background The genetic diversity of yak,a key domestic animal on the Qinghai-Tibetan Plateau(QTP),is a vital resource for domestication and breeding efforts.This study presents the first yak pangenome obtained through the de novo assembly of 16 yak genomes.Results We discovered 290 Mb of nonreference sequences and 504 new genes.Our pangenome-wide presence and absence variation(PAV)analysis revealed 5,120 PAV-related genes,highlighting a wide range of variety-specific genes and genes with varying frequencies across yak populations.Principal component analysis(PCA)based on binary gene PAV data classified yaks into three new groups:wild,domestic,and Jinchuan.Moreover,we pro-posed a‘two-haplotype genomic hybridization model'for understanding the hybridization patterns among breeds by integrating gene frequency,heterozygosity,and gene PAV data.A gene PAV-GWAS identified a novel gene(Bos-Gru3G009179)that may be associated with the multirib trait in Jinchuan yaks.Furthermore,an integrated transcrip-tome and pangenome analysis highlighted the significant differences in the expression of core genes and the muta-tional burden of differentially expressed genes between yaks from high and low altitudes.Transcriptome analysis across multiple species revealed that yaks have the most unique differentially expressed m RNAs and lnc RNAs(between high-and low-altitude regions),especially in the heart and lungs,when comparing high-and low-altitude adaptations.Conclusions The yak pangenome offers a comprehensive resource and new insights for functional genomic studies,supporting future biological research and breeding strategies.

The exploration and practice of low-altitude airspace flight service and traffic management in China

Due to the inherent nature of being highly digitalized,networked and intelligent,Unmanned Aerial System(UAS)operations pose a huge challenge to traditional aviation regulation and technical systems.How to keep safe,efficient and integrated operation for different Airspace users has become a pressing issue faced by civil aviation around the world.This paper focuses on the main operational scenarios and characteristics of unmanned aviation development in China.New operational characteristics and associated challenges due to diverse low-altitude users are analyzed,including operation concepts,UAS traffic management,technological test and verification,and standards.Drawing light on the practices in Europe and the United States,this paper summarizes China's practices and progress in low-altitude operations management,and analyzes future technological development needs and trends,as well as feasible implementation pathways and measures based on actual needs.

UAV-based spatial pattern of three-dimensional green volume and its influencing factors in Lingang New City in Shanghai,China

Three-dimensional green volume(TDGV)reflects the quality and quantity of urban green space and its provision of ecosystem services;therefore,its spatial pattern and the underlying influential factors play important roles in urban planning and management.However,little is known about the factors contributing to the spatial pattern of TDGV.In this paper,TDGV and land use intensity(LUI)extracted from high spatial resolution(0.05 m)remotely sensed data acquired by an unmanned aerial vehicle(UAV),anthropogenic factors^(1))and natural factors^(2))were utilized to identify the spatial pattern of TDGV and the potential influencing factors in Lingang New City,a rapidly developed coastal town in Shanghai.The results showed that most of the TDGV was distributed in the western part of this new city and that its spatial variations were significantly axial.TDGV corresponded well with the chronologies of land formation,urban planning,and construction in the city.Generalized least squares(GLS)analysis of TDGV(grid cell size:100×100 m)and its influencing factors showed that the TDGV in this new city was significantly negatively correlated with both LUI and distance from roads and significantly positively correlated with land formation time and distance from water.Distance from buildings did not affect TDGV.Additionally,the degree of influence decreased in the following order:distance from water>land formation time>distance from roads>LUI.These results indicate that the spatial pattern of TDGV in this new town was mainly affected by natural factors(i.e.,the distance from water and land formation time)and that the artificial disturbances caused by rapid urbanization did not decrease the regional TDGV.The main factors shaping the spatial distribution of TDGV in this city were local natural factors.Our findings suggest that the improvement in local soil and water conditions should be emphasized in the construction of new cities in coastal areas to ensure the efficient provision of ecological services by urban green spaces.

The application of threshold empirical mode decomposition de-noising algorithm for battlefield ambient noise

The detection of the low-altitude acoustic target is an important way to compensate for the weakness of radar.Removing the noise mixed in acoustic signal as much as possible to retain the useful information is a challenging task.Inspired by the wavelet threshold,the de-noising method for low-altitude battlefield acoustic signal based on threshold empirical mode decomposition(EMD-T)is proposed in this paper.Firstly,the noisy signal is decomposed by empirical mode decomposition(EMD)to get the intrinsic mode functions(IMFs).Then the IMFs,whose actual energy exceeds its estimated energy,are processed by the EMD threshold.Finally,the processed IMFs are summed to reconstruct the de-noised signal.To evaluate the performance of the proposed method,extensive simulations are performed using helicopter sound corrupted with four types of typical low-altitude ambient noise under different signal-to-noise ratio(SNR)input values.The performance is evaluated in terms of SNR,root mean square error(RMSE)and smoothness index(SI).The simulations results reveal that the proposed method de-noising method has the perspective of the highest SNR,smallest RMSE and SI in de-noising low-altitude ambient noise compared to other methods,including the wavelet transform(WT)and conventional EMD.