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Sancho, Elena, Maya R. Vilá, Luis Sánchez-Pulido, Juan José Lozano, Rosanna Paciucci, Marga Nadal, Margaret Fox i in. "Role of UEV-1, an Inactive Variant of the E2 UbiquitinConjugating Enzymes, in In Vitro Differentiation and Cell Cycle Behavior of HT-29-M6 Intestinal Mucosecretory Cells". Molecular and Cellular Biology 18, nr 1 (1.01.1998): 576–89. http://dx.doi.org/10.1128/mcb.18.1.576.
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By means of differential RNA display, we have isolated a cDNA corresponding to transcripts that are down-regulated upon differentiation of the goblet cell-like HT-29-M6 human colon carcinoma cell line. These transcripts encode proteins originally identified as CROC-1 on the basis of their capacity to activate transcription of c-fos. We show that these proteins are similar in sequence, and in predicted secondary and tertiary structure, to the ubiquitin-conjugating enzymes, also known as E2. Despite the similarities, these proteins lack a critical cysteine residue essential for the catalytic activity of E2 enzymes and, in vitro, they do not conjugate or transfer ubiquitin to protein substrates. These proteins constitute a distinct subfamily within the E2 protein family and are highly conserved in phylogeny from yeasts to mammals. Therefore, we have designated them UEV (ubiquitin-conjugating E2 enzyme variant) proteins, defined as proteins similar in sequence and structure to the E2 ubiquitin-conjugating enzymes but lacking their enzymatic activity (HW/GDB-approved gene symbol, UBE2V). At least two human genes code for UEV proteins, and one of them, located on chromosome 20q13.2, is expressed as at least four isoforms, generated by alternative splicing. All human cell types analyzed expressed at least one of these isoforms. Constitutive expression of exogenous human UEV in HT-29-M6 cells inhibited their capacity to differentiate upon confluence and caused both the entry of a larger proportion of cells in the division cycle and an accumulation in G2-M. This was accompanied with a profound inhibition of the mitotic kinase, cdk1. These results suggest that UEV proteins are involved in the control of differentiation and could exert their effects by altering cell cycle distribution.
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Fayomi, Aisha, Amal S. Hassan i Ehab M. Almetwally. "Inference and quantile regression for the unit-exponentiated Lomax distribution". PLOS ONE 18, nr 7 (18.07.2023): e0288635. http://dx.doi.org/10.1371/journal.pone.0288635.
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In probability theory and statistics, it is customary to employ unit distributions to explain practical variables having values between zero and one. This study suggests a brand-new distribution for modelling data on the unit interval called the unit-exponentiated Lomax (UEL) distribution. The statistical aspects of the UEL distribution are shown. The parameters corresponding to the proposed distribution are estimated using widely recognized estimation techniques, such as Bayesian, maximum product of spacing, and maximum likelihood. The effectiveness of the various estimators is assessed through a simulated scenario. Using mock jurors and food spending data sets, the UEL regression model is demonstrated as an alternative to unit-Weibull regression, beta regression, and the original linear regression models. Using Covid-19 data, the novel model outperforms certain other unit distributions according to different comparison criteria.
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Tang, Zhanzhong, Zengxiang Zhang, Lijun Zuo, Xiao Wang, Xiaoli Zhao, Fang Liu, Shunguang Hu, Ling Yi i Jinyong Xu. "Spatial Evolution of Urban Expansion in the Beijing–Tianjin–Hebei Coordinated Development Region". Sustainability 13, nr 3 (2.02.2021): 1579. http://dx.doi.org/10.3390/su13031579.
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Against the background of coordinated development of the Beijing–Tianjin–Hebei region (BTH), it is of great significance to quantitatively reveal spatiotemporal dynamics of urban expansion for optimizing the layout of urban land across regions. However, the urban expansion characteristics, types and trends, and spatial coevolution (including urban land, GDP, and population) have not been well investigated in the existing research studies. This study presents a new spatial measure that describes the difference of the main trend direction. In addition, we also introduce a new method to classify an urban expansion type based on other scholars. The results show the following: (1) The annual urban expansion area (UEA) in Beijing and Tianjin has been ahead of that in Hebei; the annual urban expansion rate (UER) gradually shifted from the highest in megacities to the highest in counties; the high–high clusters of the UEA presented an evolution from a “seesaw” pattern to a “dumbbell” pattern, while that of the UER moved first from Beijing to Tianjin and eventually to Hebei. (2) Double high speed for both UEA and UER was the main extension type; most cities presented a U-shaped trend. (3) Qinhuangdao has the largest difference between the main trend direction of spatial distribution of urban land, GDP and population; the spatial distribution of GDP is closer to that of urban land than population. (4) The area and proportion of land occupied by urban expansion varied greatly across districts/counties. BTH experienced dramatic urban expansion and has a profound impact on land use. These research results can provide a data basis and empirical reference for territorial spatial planning.
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Feng, Lin Ping, Yu Qiang Wu, Shuang Pan i Xi Bin Wang. "FastSLAM Algorithm for Uninhabited Flying Vehicle". Applied Mechanics and Materials 347-350 (sierpień 2013): 3596–99. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.3596.
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For uninhabited flying vehicle, it is a key prerequisite of truly autonomous mobile vehicles to simultaneously localize and accurately map its surroundings. Kalman filter-based algorithms require time quadratic in the number of landmarks to incorporate each sensor observation. This paper presents an algorithm so called FastSLAM that recursively estimates the full posterior distribution over robot pose and landmark locations, but scales logarithmically with the number of landmarks in the map. FastSLAM factors the posterior into a product of conditional landmark distributions and a distribution over UAV paths. The algorithm has been tested in UAV environments. Experimental results demonstrate the advantages and disadvantages of the FastSLAM algorithm for UAV.
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Kaliszewski, Miron, Maksymilian Włodarski, Jarosław Młyńczak, Bartłomiej Jankiewicz, Lukas Auer, Bartosz Bartosewicz, Malwina Liszewska i in. "The Multi-Gas Sensor for Remote UAV and UGV Missions—Development and Tests". Sensors 21, nr 22 (16.11.2021): 7608. http://dx.doi.org/10.3390/s21227608.
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In this article, we present a versatile gas detector that can operate on an unmanned aerial vehicle (UAV) or unmanned ground vehicle (UGV). The device has six electrochemical modules, which can be selected to measure specific gases, according to the mission requirements. The gas intake is realized by a miniaturized vacuum pump, which provides immediate gas distribution to the sensors and improves a fast response. The measurement data are sent wirelessly to the operator’s computer, which continuously stores results and presents them in real time. The 2 m tubing allows measurements to be taken in places that are not directly accessible to the UGV or the UAV. While UAVs significantly enhanced the versatility of sensing applications, point gas detection is challenging due to the downwash effect and gas dilution produced by the rotors. In our work, we demonstrated the method of downwash effect reduction at aerial point gas measurements by applying a long-distance probe, which was kept between the UAV and the examined object. Moreover, we developed a safety connection protecting the UAV and sensor in case of accidental jamming of the tubing inside the examined cavity. The methods presented provide an effective gas metering strategy using UAVs.
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Rudge, Mitchel L. M., Shaun R. Levick, Renee E. Bartolo i Peter D. Erskine. "Modelling the Diameter Distribution of Savanna Trees with Drone-Based LiDAR". Remote Sensing 13, nr 7 (26.03.2021): 1266. http://dx.doi.org/10.3390/rs13071266.
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The diameter distribution of savanna tree populations is a valuable indicator of savanna health because changes in the number and size of trees can signal a shift from savanna to grassland or forest. Savanna diameter distributions have traditionally been monitored with forestry techniques, where stem diameter at breast height (DBH) is measured in the field within defined sub-hectare plots. However, because the spatial scale of these plots is often misaligned with the scale of variability in tree populations, there is a need for techniques that can scale-up diameter distribution surveys. Dense point clouds collected from uncrewed aerial vehicle laser scanners (UAV-LS), also known as drone-based LiDAR (Light Detection and Ranging), can be segmented into individual tree crowns then related to stem diameter with the application of allometric scaling equations. Here, we sought to test the potential of UAV-LS tree segmentation and allometric scaling to model the diameter distributions of savanna trees. We collected both UAV-LS and field-survey data from five one-hectare savanna woodland plots in northern Australia, which were divided into two calibration and three validation plots. Within the two calibration plots, allometric scaling equations were developed by linking field-surveyed DBH to the tree metrics of manually delineated tree crowns, where the best performing model had a bias of 1.8% and the relatively high RMSE of 39.2%. A segmentation algorithm was then applied to segment individual tree crowns from UAV-LS derived point clouds, and individual tree level segmentation accuracy was assessed against the manually delineated crowns. 47% of crowns were accurately segmented within the calibration plots and 68% within the validation plots. Using the site-specific allometry, DBH was modelled from crown metrics within all five plots, and these modelled results were compared to field-surveyed diameter distributions. In all plots, there were significant differences between field-surveyed and UAV-LS modelled diameter distributions, which became similar at two of the plots when smaller trees (<10 cm DBH) were excluded. Although the modelled diameter distributions followed the overall trend of field surveys, the non-significant result demonstrates a need for the adoption of remotely detectable proxies of tree size which could replace DBH, as well as more accurate tree detection and segmentation methods for savanna ecosystems.
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Wan, Dai, Miao Zhao, Hengyi Zhou, Fei Qi, Xin Chen i Guanxuan Liang. "Analysis of UAV patrol inspection technology suitable for distribution lines". Journal of Physics: Conference Series 2237, nr 1 (1.03.2022): 012009. http://dx.doi.org/10.1088/1742-6596/2237/1/012009.
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Abstract With the continuous improvement of UAV manufacturing level, it is more and more widely used in various fields. In recent years, unmanned aerial vehicle (UAV) inspection technology has been widely used in transmission lines above 110kV voltage level, and achieved good application results. However, because the operation of 10kV distribution line is much more complex than that of high-voltage transmission line, and the standardization of distribution equipment is low, the application effect of UAV inspection technology on distribution line is always unsatisfactory. Although some power enterprises have made continuous attempts, they have never formed an efficient and applicable UAV inspection technology system for distribution lines. In this paper, the operation characteristics of distribution lines and the existing working mode of manual inspection are deeply analyzed. At the same time, combined with the technologies of UAV carrying, attitude sensing and front-end identification, a practical implementation strategy of UAV patrol inspection of distribution line is proposed. It has guiding significance for expanding the application field of UAV and improving the efficiency of distribution line inspection.
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Cantieri, Alvaro, Matheus Ferraz, Guido Szekir, Marco Antônio Teixeira, José Lima, André Schneider Oliveira i Marco Aurélio Wehrmeister. "Cooperative UAV–UGV Autonomous Power Pylon Inspection: An Investigation of Cooperative Outdoor Vehicle Positioning Architecture". Sensors 20, nr 21 (9.11.2020): 6384. http://dx.doi.org/10.3390/s20216384.
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Realizing autonomous inspection, such as that of power distribution lines, through unmanned aerial vehicle (UAV) systems is a key research domain in robotics. In particular, the use of autonomous and semi-autonomous vehicles to execute the tasks of an inspection process can enhance the efficacy and safety of the operation; however, many technical problems, such as those pertaining to the precise positioning and path following of the vehicles, robust obstacle detection, and intelligent control, must be addressed. In this study, an innovative architecture involving an unmanned aircraft vehicle (UAV) and an unmanned ground vehicle (UGV) was examined for detailed inspections of power lines. In the proposed strategy, each vehicle provides its position information to the other, which ensures a safe inspection process. The results of real-world experiments indicate a satisfactory performance, thereby demonstrating the feasibility of the proposed approach.
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Moon, Inseok, Le The Dung i Taejoon Kim. "Optimal 3D Placement of UAV-BS for Maximum Coverage Subject to User Priorities and Distributions". Electronics 11, nr 7 (25.03.2022): 1036. http://dx.doi.org/10.3390/electronics11071036.
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The usage of unmanned aerial vehicle (UAV) as a base station is in the spotlight to overcome the severe attenuation characteristics of short-wavelength radio in high-speed wireless networks. In this paper, we propose an optimal UAV deployment algorithm, considering the priority of ground nodes (GNs) in different wireless communication environments. Specifically, the optimal position of a UAV is determined so that as many high-priority GNs can be served rather than covering as many GNs as possible. The proposed optimization problem deals with two groups of GNs with different priorities and finds the optimal position of the UAV by solving the mixed-integer second-order cone problem (MISOCP). To verify the effectiveness of the proposed optimal UAV deployment algorithm, we conduct various evaluating scenarios with different urban environments and GN spatial distributions. We also compare the performance of the proposed algorithm with the conventional one. Simulation results show that the proposed scheme achieves superior coverage efficiency, throughput, and delay performance compared to the conventional algorithm, even when the environment and the spatial distribution of GNs are changed.
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Forer, A. "In ultraviolet microbeam irradiations, characteristics of the monochromator and lamp affect the spectral composition of the ultraviolet light and probably the biological results". Journal of Cell Science 98, nr 3 (1.03.1991): 415–22. http://dx.doi.org/10.1242/jcs.98.3.415.
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Biological conclusions recently published concerning ultraviolet (u.v.) microbeam irradiation of spindles are different from those we previously published. Several technical differences between the two sets of experiments were investigated. The spectral distributions in the light emitted from mercury-arc, xenon-mercury-arc, and xenon-arc lamps were measured, as were the spectral distributions after the light from these lamps passed through a monochromator that was set to various wavelengths and various half-band-widths. Both the source of the u.v. light and the half-band-width of the monochromator influence the spectral distribution of the light leaving the monochromator: depending on the conditions, the light leaving the monochromator is not necessarily of the same wavelength as that to which the monochromator is set. Differences in these aspects of the experiments could easily give rise to the different biological conclusions reached in the two sets of experiments.
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Tanveer, Muhammad Hassan, Antony Thomas, Waqar Ahmed i Hongxiao Zhu. "Estimate the Unknown Environment with Biosonar Echoes—A Simulation Study". Sensors 21, nr 12 (18.06.2021): 4186. http://dx.doi.org/10.3390/s21124186.
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Unmanned aerial vehicles (UAVs) have shown great potential in various applications such as surveillance, search and rescue. To perform safe and efficient navigation, it is vitally important for a UAV to evaluate the environment accurately and promptly. In this work, we present a simulation study for the estimation of foliage distribution as a UAV equipped with biosonar navigates through a forest. Based on a simulated forest environment, foliage echoes are generated by using a bat-inspired bisonar simulator. These biosonar echoes are then used to estimate the spatial distribution of both sparsely and densely distributed tree leaves. While a simple batch processing method is able to estimate sparsely distributed leaf locations well, a wavelet scattering technique coupled with a support vector machine (SVM) classifier is shown to be effective to estimate densely distributed leaves. Our approach is validated by using multiple setups of leaf distributions in the simulated forest environment. Ninety-seven percent accuracy is obtained while estimating thickly distributed foliage.
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Li, Li, Hong Zhan i Yongjing Hao. "The Online Path Planning Method of UAV Autonomous Inspection in Distribution Network". E3S Web of Conferences 256 (2021): 01047. http://dx.doi.org/10.1051/e3sconf/202125601047.
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In this paper, the problem of online path planning for autonomous inspection of distribution network lines by UAV is studied. Because the distribution lines are mostly distributed around cities, counties and mountainous areas, the lines and their surrounding environment are uncertain and dynamic. These factors will affect the safety of UAV inspection, making the off-line pre-planned path for UAV unavailable. This paper designs an improved iteration random tree algorithm (IRRT) algorithm, which can quickly plan the path of UAV in dynamic environment.
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OBANAWA, Hiroyuki, Katsuhisa KAWASHIMA, Takane MATSUMOTO, Tsutomu IYOBE i Hirokazu OHMAE. "Measurement of snow distribution using small UAV". Journal of the Japanese Society of Snow and Ice 78, nr 5 (2016): 317–28. http://dx.doi.org/10.5331/seppyo.78.5_317.
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Wang, Weijia, Chenying Jin i Bing Cui. "Research on emergency supplies distribution in 5G network environment based on TSP model". Highlights in Science, Engineering and Technology 12 (26.08.2022): 83–91. http://dx.doi.org/10.54097/hset.v12i.1409.
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Along with the improvement of technology and the gradual popularization of 5G network, the application of UAVs is becoming more and more widespread, and the delivery mode of "delivery vehicle + UAV" has gradually become a new and effective delivery method. In order to solve the real problem of emergency supplies to be delivered to the disaster area after the disaster and to improve the efficiency of emergency supplies delivery, this new and effective delivery mode is used to solve the delivery problem. In this paper, a TSP model based on Floyd algorithm and genetic algorithm is established and the optimal distribution scheme is given. In the delivery mode of "delivery vehicle + UAV", the individual evaluation function is improved, and the flight conditions of UAV are introduced, and the optimal delivery scheme is given by simulation selection, crossover and variation. In the mode of "delivery vehicle + UAV" and the delivery vehicle has a single weight limit of 500 kg, The optimal solution is given for single "delivery vehicle + UAV" and the optimal solution is given for a single "delivery vehicle + UAV" and a double "delivery vehicle + UAV".
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Dong, Luying, Shuhan Ma, Yajuan Han i Yipeng Zhou. "Split delivery scheme for vehicle supported UAV". MATEC Web of Conferences 355 (2022): 02065. http://dx.doi.org/10.1051/matecconf/202235502065.
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The traditional demand split logistics distribution schemes are mainly based on vehicle distribution. In recent years, with the rapid development of civil UAVs, the use of UAVs for distribution will be more efficient and economical in some specific conditions. In this paper, through the analysis of the advantages of UAV distribution, we simulate the demands and distribution schemes in real scene, especially in remote mountainous areas. And then, we propose to define a demand-splitting distribution scheme of vehicle-supported UAV, which ensures the customer point will be satisfy demand when the loading capacity of the UAV is exceeded. This scheme aims to provides a realizable distribution scheme for the customers point in mountainous areas with large demand.
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Fang, Tao, Hua Tian, Xiaobo Zhang, Xueqiang Chen, Xinhong Shao i Yuli Zhang. "Context-Aware Caching Distribution and UAV Deployment: A Game-Theoretic Approach". Applied Sciences 8, nr 10 (17.10.2018): 1959. http://dx.doi.org/10.3390/app8101959.
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This paper investigates the problem of the optimal arrangement for both unmanned aerial vehicles’ (UAVs’) caching contents and service locations in UAV-assisted networks based on the context awareness, which considers the influence between users and environment. In the existing work, users within the coverage of UAVs are considered to be served perfectly, which ignores the communication probability caused by line-of-sight (LOS) and non-line-of-sight (NLOS) links. However, the links are related to the deployment of UAVs. Moreover, the transmission overhead should be taken into account. To balance the tradeoff between these two factors, we design the ratio of users’ probability and transmission overhead as the performance measure mechanism to evaluate the performance of UAV-assisted networks. Then, we formulate the objective for maximizing the performance of UAV-assisted networks as a UAV-assisted caching game. It is proved that the game is an exact potential game with the performance of UAV-assisted networks serving as the potential function. Next, we propose a log-linear caching algorithm (LCA) to achieve the Nash equilibrium (NE). Finally, related simulation results reflect the great performance of the proposed algorithm.
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MacRae, Andrew R., H. Allen Gardner, Lynn C. Allen, Sonya Tokmakejian i Nathalie Lepage. "Outcome Validation of the Beckman Coulter Access Analyzer in a Second-Trimester Down Syndrome Serum Screening Application". Clinical Chemistry 49, nr 1 (1.01.2003): 69–76. http://dx.doi.org/10.1373/49.1.69.
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Abstract Background: Mid-trimester maternal serum α-fetoprotein (AFP) and unconjugated estriol (uE3) are 30% lower and human chorionic gonadotropin (hCG) is twofold higher in Down syndrome pregnancies compared with unaffected pregnancies. In maternal serum screening, patient-specific risks are calculated using published gaussian frequency distribution parameters for these three markers obtained with previously available immunoassays. New immunoassays must generate similar distribution parameters if the accuracy of assigned risks and overall performance of prenatal screening are to be maintained. Methods: Agreement between the Beckman Coulter Access and the Bayer Immuno 1 assays for AFP and hCG and the Amersham Amerlex-M RIA for uE3 was assessed in 558 fresh sera. Precision was measured over 6 weeks. Median concentrations were calculated by regression of 568 Caucasian singleton pregnancy samples against gestational age in days. Frozen mid-trimester sera from 44 confirmed Down syndrome singleton pregnancies (cases) were selected without conscious bias for reanalysis, and each case was matched with five control specimens from unaffected pregnancies. Serum markers were expressed as the multiple of the median (MoM) concentration derived from the control samples, cor-rected for maternal weight and converted to their log-equivalent values. Normality was assessed using probability plots and the Shapiro–Wilk W-test. Gaussian distribution parameters were compared with established values, and Down syndrome risk calculations were assessed with a commonly used risk algorithm. Results: The Access AFP and hCG assays had consistent proportional agreement with the established assays, whereas agreement between the uE3 methods was less consistent. Analytical imprecision was 3–6% at mid-trimester concentrations. Normal distributions were obtained for the log MoM values of all three markers in both the Down syndrome and unaffected populations, and their gaussian distribution parameters compared well with established values. The performance of the Access assays in an established trivariate risk algorithm for Down syndrome was equal to the performance exhibited by traditional methods. Conclusion: The Beckman Coulter Access analyzer provides valid mid-trimester serum AFP, uE3, and hCG results and risk assessments when applied in a prenatal Down syndrome screening service.
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Shen, Jinxing, Xuejun Feng, Kai Zhuang, Tong Lin, Yan Zhang i Peifang Wang. "Vertical Distribution of Particulates within the Near-Surface Layer of Dry Bulk Port and Influence Mechanism: A Case Study in China". Sustainability 11, nr 24 (12.12.2019): 7135. http://dx.doi.org/10.3390/su11247135.
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Knowing the vertical distribution of ambient particulate matter (PM) will help port authorities choose the optimal dust-suppression measures to reduce PM concentrations. In this study, we used an unmanned aerial vehicle (UAV) to assess the vertical distribution (0–120 m altitude) of PM in a dry bulk port along the Yangtze River, China. Total suspended particulates (TSP), PM10, and PM2.5 concentrations at different altitudes were measured at seven sites representing different cargo-handling sites and a background site. Variations in results across sites make it not suitable to characterize the vertical distribution of PM concentration at this port using simple representative distributions. Bulk cargo particle size, fog cannon use, and porous fence all affected the vertical distribution of TSP concentrations but had only minor impacts on PM10 and PM2.5 concentrations. Optimizing porous fence layout according to weather conditions and cargo demand at port have the most potential for mitigating PM pollution related to port operation. As ground-based stations cannot fully measure vertical PM distributions, our methods and results represent an advance in assessing the impact of port activities on air quality and can be used to determine optimal dust-suppression measures for dry bulk ports.
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Wang, Qiuming, Liang Shi, Xu Zhao i Jun Fan. "Effects of Biomass and Soil Water Content Distribution on Cosmic Ray Neutron Probe Measurement". Water 15, nr 15 (30.07.2023): 2766. http://dx.doi.org/10.3390/w15152766.
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Cosmic ray neutron probes (CRNPs) provide continuous monitoring of average near-surface soil water content (SWC) on hectometer scales. However, the performance of CRNPs on surfaces of highly heterogeneous vegetation and SWC remains uncertain. This study evaluated three vegetation calibration methods with the correction of vegetation distribution developed for a CRNP on the Loess Plateau of China. Three plots with different vegetation distributions were selected and equipped with CRNPs and SWC sensors, and their biomass as well as distribution were measured by an unmanned aerial vehicle (UAV) equipped with a RedEdge multispectral camera. We found that the parameter N0, which is neutron flux in dry soil, was best represented by the biomass at average growth conditions of the monitoring period, yielding the lowest RMSE (0.068). The Veg–N0 vegetation calibration method reduced the RMSE the most between the CRNP SWC and the Kriging-weighted SWC, and the correction of the spatial distribution of the vegetation further reduced the RMSE. The cooperation between the CRNP and the UAV could obtain the regional averaged SWC accurately. This study makes up for the lack of vegetation calibration for the CRNP on the Loess Plateau, which should help develop sustainable vegetation management and ecohydrological management strategies on the Loess Plateau, so as to protect water security in the region.
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Chung, Chih-Hsin, Jonathan Wang, Shu-Lin Deng i Cho-ying Huang. "Analysis of Canopy Gaps of Coastal Broadleaf Forest Plantations in Northeast Taiwan Using UAV Lidar and the Weibull Distribution". Remote Sensing 14, nr 3 (30.01.2022): 667. http://dx.doi.org/10.3390/rs14030667.
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Canopy gaps are pivotal for monitoring forest ecosystem dynamics. Conventional field methods are time-consuming and labor intensive, making them impractical for regional mapping and systematic monitoring. Gaps may be delineated using airborne lidar or aerial photographs acquired from a manned aircraft. However, high cost in data acquisition and low flexibility in flight logistics significantly reduce the accessibility of the approaches. To address these issues, this study utilized miniature light detection and ranging (lidar) onboard an unmanned aircraft vehicle (UAVlidar) to map forest canopy gaps of young and mature broadleaf forest plantations along the coast of northeastern Taiwan. This study also used UAV photographs (UAVphoto) for the same task for comparison purposes. The canopy height models were derived from UAVlidar and UAVphoto with the availability of a digital terrain model from UAVlidar. Canopy gap distributions of the forests were modeled with the power-law zeta and Weibull distributions. The performance of UAVlidar was found to be superior to UAVphoto in delineating the gap distribution through ground observation, mainly due to lidar’s ability to detect small canopy gaps. There were apparent differences of the power-law zeta distributions for the young and mature forest stands with the exponents λ of 1.36 (1.45) and 1.71 (1.61) for UAVlidar and UAVphoto, respectively, suggesting that larger canopy gaps were present within the younger stands. The canopy layer of mature forest stands was homogeneous, and the size distributions of both sensors and methods were insensitive to the spatial extent of the monitored area. Contrarily, the young forests were heterogeneous, but only UAVlidar with the Weibull distribution responded to the change of spatial extent. This study demonstrates that using the Weibull distribution to analyze canopy gap from high-spatial resolution UAVlidar may provide detailed information of regional forest canopy of coastal broadleaf forests.
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Zhang, Zilun, Mingmin Bao, Nanxuan Qiao i Tielin Ma. "Design of Ducted Fan Based on Optimal Circulation Distribution". Journal of Physics: Conference Series 2280, nr 1 (1.06.2022): 012015. http://dx.doi.org/10.1088/1742-6596/2280/1/012015.
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Abstract The ducted fan lift system has been widely used in vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV). According to the overall design requirements of a VTOL UAV, based on the optimal circulation distribution condition without blade element drag and combined with strip theory, the blade torsion angle distribution and chord length distribution are given. The parameters of ducted fan are designed, and the preliminary design of ducted fan lift system of this UAV is completed. The aerodynamic characteristics of the isolated fan and the ducted fan are compared by numerical simulation method, and the thrust characteristics of the ducted fan at different flight speeds are calculated. The results show that the duct increases the induced velocity at the propeller. Compared with the isolated fan, the power load and hover efficiency of the ducted fan are increased by 36.8% and 36.3% respectively. The hovering efficiency of the ducted fan designed by this method reaches 83%, which meets the design requirements and proves the effectiveness of the design method.
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Zhang, Zilun, Mingmin Bao, Nanxuan Qiao i Tielin Ma. "Design of Ducted Fan Based on Optimal Circulation Distribution". Journal of Physics: Conference Series 2280, nr 1 (1.06.2022): 012015. http://dx.doi.org/10.1088/1742-6596/2280/1/012015.
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Abstract The ducted fan lift system has been widely used in vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV). According to the overall design requirements of a VTOL UAV, based on the optimal circulation distribution condition without blade element drag and combined with strip theory, the blade torsion angle distribution and chord length distribution are given. The parameters of ducted fan are designed, and the preliminary design of ducted fan lift system of this UAV is completed. The aerodynamic characteristics of the isolated fan and the ducted fan are compared by numerical simulation method, and the thrust characteristics of the ducted fan at different flight speeds are calculated. The results show that the duct increases the induced velocity at the propeller. Compared with the isolated fan, the power load and hover efficiency of the ducted fan are increased by 36.8% and 36.3% respectively. The hovering efficiency of the ducted fan designed by this method reaches 83%, which meets the design requirements and proves the effectiveness of the design method.
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Udris, Dainius, Domantas Bručas i Raimondas Pomarnacki. "Reliability Improvement of Power Distribution System for UAV". Electronics 8, nr 6 (5.06.2019): 636. http://dx.doi.org/10.3390/electronics8060636.
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Unmanned aerial vehicles (UAV), like other complex mechatronics systems, use servomechanisms for the accurate positioning of construction elements. Servomechanisms are stable, reliable and easy to control. However, occasionally they fail and cause issues for the electrical system. In this paper, the authors present a full analysis of the system operations after a specific fault and the consequences of it. The authors propose a test bench and show the experimentation results that contain servo motor electrical parameters at loaded and idle states, the relations to the manufacturer technical specifications, and possible fault detection and elimination solutions. The obtained results could be implemented into existing popular UAV control systems to improve reliability and fault tolerance of commercial products.
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Yamagata, T., i Y. Yoshii. "Vertical Metallicity Gradient of the Galaxy Based on UBV Starcount Data". Symposium - International Astronomical Union 161 (1994): 420–22. http://dx.doi.org/10.1017/s0074180900047768.
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The spatial distribution of metal abundance in the Galaxy has been analyzed using the UBV starcount data recently obtained in two high-latitude regions of the North Galactic Pole (NGP) and Selected Area 54 (SA54). A least-squares analysis was performed to determine the vertical metallicity gradient for each of the thin and thick disk components that gives a reasonable fit to the observed U-B and B-V colour distributions to V = 18 mag. The most probable value of the vertical gradient is obtained as d[Fe/H]/dz = −0.5 kpc−1 for the thin disk, and −0.1 kpc−1 for the thick disk.
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Li, Jianxun, Hao Liu, Kin Keung Lai i Bhagwat Ram. "Vehicle and UAV Collaborative Delivery Path Optimization Model". Mathematics 10, nr 20 (12.10.2022): 3744. http://dx.doi.org/10.3390/math10203744.
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In the context of frequent public emergencies, emergency logistics distribution is particularly critical, and because of the unique advantages of unmanned aerial vehicles (UAVs), the model of coordinated delivery of vehicles and UAVs is gradually becoming an essential form of emergency logistics distribution. However, the omission of start-up costs prevents the cost of UAV battery replacement and the sorting, assembly and verification of packages from being factored into the total cost. Furthermore, most existing models focus on route optimization and delivery cost, which cannot fully reflect the customer’s desire for service satisfaction under emergency conditions. It is necessary to convert the unsatisfactory degree of time window into a penalty cost rather than a model constraint. Additionally, there is a lack of analysis on the mutual waiting cost between vehicles and UAVs when one of them is performing delivery tasks. Considering the effects of the time window, customer demand, maximum load capacity, and duration of distribution benefits, we propose a collaborative delivery path optimization model for vehicles and UAVs to minimize the total distribution cost. A genetic algorithm is used to obtain the model solution under the constraints of distribution subloops, distribution order, and take-off and landing nodes. To assess the efficacy of the vehicle and UAV collaborative delivery path optimization model, this paper employs a county-level district in Xi’an city as a pilot area for an emergency delivery. Compared with the vehicle-alone delivery model, the UAV-alone delivery model and vehicle-UAV collaborative delivery model, this model can significantly reduce the utilization of distribution vehicles while also significantly lowering the start-up cost, waiting cost and penalty cost. Thus, the model can effectively improve delivery timeliness and customer satisfaction. The total cost of this model is 39.2% less than that of the vehicle-alone delivery model and 16.5% less than that of the UAV-alone delivery model. Although its delivery cost is slightly higher than the vehicle-UAV collaborative delivery model, the reduction in the start-up cost and penalty cost decrease the overall cost of distribution by 11.8%. This suggests that to cut costs of all sizes and conserve half of the resources used by vehicles, employing the vehicle-UAV collaborative delivery model for emergency distribution is preferable. Moreover, the model integrating the start-up cost, penalty cost, waiting cost, etc., can more effectively express the requirements of timeliness for UAV delivery under emergency conditions.
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Weinberg, Graham V., i Mitchell M. Kracman. "Swarm UAV Defeat Modelling through Lifetime Distribution Analysis". Progress In Electromagnetics Research Letters 111 (2023): 71–78. http://dx.doi.org/10.2528/pierl23022808.
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Wen, Ding, Lei Su, Yuanman Hu, Zaiping Xiong, Miao Liu i Yingxian Long. "Surveys of Large Waterfowl and Their Habitats Using an Unmanned Aerial Vehicle: A Case Study on the Siberian Crane". Drones 5, nr 4 (23.09.2021): 102. http://dx.doi.org/10.3390/drones5040102.
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Waterfowl surveys, especially for endangered waterfowl living in wetlands, are essential to protect endangered waterfowl and to create a management scenario of their habitats. Unmanned aerial vehicles (UAVs) are powerful new tools for waterfowl surveys. In this paper, we propose one method for a habitat survey and another for a waterfowl species distribution survey. The habitat survey method obtained the waterfowl’s habitat and spatial distribution with a UAV automatic flight plan in the aggregation area. The waterfowl species distribution survey was used to detect and identify waterfowl species with high-spatial-resolution images from a free UAV flight plan in the aggregation area or areas where individuals were suspected to be present. The UAV-based data showed not only the area where waterfowl were found, but also additional ground surveys. The results showed that the species and locations of the waterfowl were recorded more accurately and efficiently using the distribution method based on the images from the UAV. The waterfowl habitat type and the number of waterfowl were obtained in detail using the habitat survey method. UAV-derived counts of waterfowl were greater (+37%) than ground counts. The results indicated the feasibility and advantages of using a low-cost UAV survey of large waterfowl in wetland regions with complex vegetation. This study provides one case study of large waterfowl numbers and habitat surveys. The UAV-based methods also provide a feasible and scientific way to obtain basic data for the protection and management of waterfowl.
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Pasichnyk, N., О. Opryshko i O. Tarariko. "Remote sensing of agrophytocenoses from the UAV platform to assess the level of plant nutrition". Agroecological journal, nr 4 (28.10.2021): 75–81. http://dx.doi.org/10.33730/2077-4893.4.2021.252958.
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Unmanned (remotely controlled) aircrafts (UAVs) are innovative equipment for monitoring fields that are free from a lot of the disadvantages of satellites such as availability, low cost, and high image resolution. However, the quality, reproducibility and suitability of spectral monitoring data of plantations for crop management processes remain topical issues. Since spectral monitoring is a necessary component in the concept of crop management, the development of a methodology for assessing the suitability of remote monitoring spectral data for the calculation of agrochemical practices was the purpose of the work. According to the publications, the dependence of the number of pixels on the values of the intensity of color components for plants and soil is described by the Gaussian distribution. Deviation from such distribution is caused by the imposing of distributions from various objects fixed on a photo. The experimental test was carried out on the basis of wheat, using the results obtained during 2017–2020 when considering the stresses of nutrient deficiency. UAVs with a specialized Slantrange spectral complex with standard Slantview software and an FC200 visible spectrum camera (from the Phantom 2 UAV) were used for monitoring. The investigation found experimental evidence that the pixel distribution of plantations on the example of the wheat crop is described by the Gaussian distribution. It was found that the analysis of the correspondence of the nature of the distribution on the spectral channels, namely the presence of several max peaks that affects the value of the distribution maximum may indicate the presence of foreign inclusions or a transitional stage of vegetation. The suitability of the data can be assessed on the basis of the reference values of the width of the distribution on the spectral channels. This determines the feasibility of introducing in the sets of regular vegetation indices of geographic information systems additional packages that reflect the spectral channels.
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Merik, Tania M., i John R. Slate. "Instructional Leadership Expenditures at Texas Schools: A Multiyear, Statewide Analysis". UMT Education Review 5, nr 2 (19.12.2022): 22–45. http://dx.doi.org/10.32350/uer.52.02.
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This study was conducted to determine the degree to which differences were present in the distribution of Instructional Leadership dollars spent per student at the elementary, middle, and high school levels for the 2009-2010 through the 2018-2019 school years in Texas. Texas statewide data for all public schools were obtained from the Texas Education Agency. Because archival data were analyzed, a causal-comparative research design was present. To determine whether statistically significant differences were present in Instructional Leadership dollars spent by school level, inferential statistical procedures were calculated for each school year. Statistically significant differences were established for each school year. The amount of Instructional Leadership dollars spent per pupil were highest at the high school level, followed by the middle school level, and were lowest at the elementary school level. From the 2009-2010 school year through the 2018-2019 school year, expenditures for elementary, middle, and high schools across the State of Texas increased by only $42, $40, and $48, respectively. As such, the Instructional Leadership funding did not keep up with the rate of inflation in this time period.Implications and recommendations for future research were discussed.
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Kattenborn, T., J. Hernández, J. Lopatin, G. Kattenborn i F. E. Fassnacht. "PILOT STUDY ON THE RETRIEVAL OF DBH AND DIAMETER DISTRIBUTION OF DECIDUOUS FOREST STANDS USING CAST SHADOWS IN UAV-BASED ORTHOMOSAICS". ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-1 (26.09.2018): 93–99. http://dx.doi.org/10.5194/isprs-annals-iv-1-93-2018.
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<p><strong>Abstract.</strong> One fundamental metric to characterize trees and forest stands is the diameter at breast height (DBH). However, the vertical geometry of tree stems hampers a direct measurement by means of orthographic aerial imagery. Nevertheless, the DBH in deciduous forest stands could be measured from UAV-based imagery using the width of a stem´s cast shadow projected on the ground. Here, we compare in-situ measured DBH of 100 trees with the DBH visually interpreted from cast-shadows derived in UAV-based aerial imagery. Then, based on simulated datasets, we determine suitable DBH sampling sizes for a robust and efficient retrieval of stand diameter distributions. The UAV-based DBH estimation resulted in an r<sup>2</sup> of 0.74, RMSE of 7.61<span class="thinspace"></span>cm, NRMSE of 12.8<span class="thinspace"></span>% and approximately unbiased results. According to our simulations it can be assumed that a sample size of 25&ndash;50 individual DBH measurements per forest stand allows estimating reliable diameter distributions. The presented pilot study gives a first insight on the potential of such an approach for operational assessments of diameter distribution in deciduous forest stands and might be particularly interesting for stands in difficult terrain situations. The presented approach can be extended to estimate the basal area, timber stock or biomass.</p>
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Abdurrahman, Umar, Indrawan Fadhil Pratyaksa, Totok Suprijo i Hansan Park. "Beach slope distribution mapping using UAV in the Cirebon coastal area". E3S Web of Conferences 324 (2021): 01006. http://dx.doi.org/10.1051/e3sconf/202132401006.
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The beach slope is usually estimated using the conventional ground survey, causing the availability of this parameter data to be limited in some areas. Meanwhile, this parameter is considered crucial in the study of shoreline changes and coastal area protection as well as other coastal morphodynamic research. The aim of this study is to demonstrate an efficient technique to calculate the beach slope as well as its distribution in an area. In the daily intertidal period, the beach profile is assumed to be a static planar beach state which does not change due to the insignificant effect of erosion and accretion process. First, the shoreline data set was delineated from the tidal-varied orthomosaic using the UAV. The beach slope is then calculated by comparing the difference in tide level with the difference in the horizontal distance of shoreline points along a cross-shore transect at different times. The utilization of UAV allows mapping the shoreline in an area in several different tidal conditions, allowing the distribution of the beach slope also be mapped. This technique was then applied in the Cirebon Coastal Area and found an average beach slope of 0.105 with 0.100 being the slope class with the highest number of distributions. It was also found that due to the presence of mangroves and coastal structures, no slope conditions dominated this area. The result of beach slope calculation using this technique shows suitability with other studies and reveals UAVs’ potential in mapping the beach slope distribution more efficiently.
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Wang, Yi, Yong Wang, Lei Zhang, Siyuan Liu i Quan Li. "Research on Visual Inspection System of Distribution Network Based on Unmanned Aerial Vehicle". Journal of Physics: Conference Series 2427, nr 1 (1.02.2023): 012027. http://dx.doi.org/10.1088/1742-6596/2427/1/012027.
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Abstract The increasing data acquisition information in the distribution network brings new challenges to the monitoring and management of the distribution network. Therefore, this paper proposes a visual inspection system of a distribution network based on UAVs. The overall system hardware and UAV flight control power supply hardware are designed. The distance between the UAV and the obstacles is calculated by detecting the duration of laser signal reception. The visual inspection of the UAV obstacle avoidance power distribution network is carried out. The visible light, infrared, and laser data are fused, multi-source data are processed cooperatively, and the visual inspection information is collected and summarized. The test results show that the system has high efficiency and can provide accurate information for power system operators and managers in a relatively timely manner.
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Huo, Mengzhen, Haibin Duan i Yanming Fan. "Pigeon-Inspired Circular Formation Control for Multi-UAV System with Limited Target Information". Guidance, Navigation and Control 01, nr 01 (marzec 2021): 2150004. http://dx.doi.org/10.1142/s2737480721500047.
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The problem of cooperative circular formation with limited target information for multiple Unmanned Aerial Vehicle (UAV) system is addressed in this paper. A pigeon-inspired circular formation control method is proposed to form the desired circular distribution in a plane based on the intelligent pigeon behavior during hovering. To reach the goal of prescribed radius and angular distribution, the controller is designed consisting of a circular movement part and a formation distribution part. Therein, the circular movement part is designed to make each UAV rotate around the specified circle at the same angular speed only using the relative position between the UAV and the target. The formation distribution part could adjust the angular distance between each UAV and its neighbors with the jointly connected network to reduce communication cost. To smooth the speed variation, nonlinear PID-type method is delivered throughout the evolution of the system. The convergence analysis of the proposed control protocol is presented using Lyapunov theory and graph tools. The effectiveness of the proposed control strategies is demonstrated through numerical simulations.
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Liu, Wusheng, Wang Li, Qing Zhou, Qian Die i Yan Yang. "The optimization of the "UAV-vehicle" joint delivery route considering mountainous cities". PLOS ONE 17, nr 3 (21.03.2022): e0265518. http://dx.doi.org/10.1371/journal.pone.0265518.
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As a new transportation tool, unmanned aerial vehicle (UAV), has a broad application prospect in logistics distribution, especially for mountainous cities with complex terrain. Due to the limited delivery conditions of UAV, considering the advantages of traditional vehicle delivery, this paper proposes a joint delivery mode of UAV and vehicle, and designs three steps for the joint delivery problem of single UAV and single vehicle: first, mark all special nodes; Secondly, the route of UAV and vehicle is planned; Finally, the total delivery route is optimized to minimize the total delivery distance. Genetic algorithm and single distribution terminal optimization are used to solve the problem, and the joint delivery in this paper is compared with the traditional vehicle delivery and the independent delivery of UAV and vehicle. The results show that UAV and vehicle can cooperate with each other to complete the delivery of all customer demand nodes, and the joint delivery of UAV and vehicle can effectively reduce the total delivery distance. Finally, the sensitivity analysis of UAV’s maximum load, maximum flight distance, relative speed between UAV and vehicle, and road impedance coefficient is carried out. By relaxing the restrictions of UAV, the UAV can deliver more customers at a single time, and it complete the delivery task with vehicles efficiently.
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Radhakrishnan, Varsha, i Wenyan Wu. "Energy Efficient Communication Design in UAV Enabled WPCN Using Dome Packing Method in Water Distribution System". Energies 15, nr 10 (23.05.2022): 3844. http://dx.doi.org/10.3390/en15103844.
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The water distribution system has deployed several low-power IoT devices on an uneven surface where battery power is a major concern. Therefore, this paper focuses on using a UAV-enabled wireless powered communication network capable of directing energy to a target location and using it for communication, thereby reducing battery issues. In this paper, a static optimization was applied to find the initial height values using 3D clustering and beamforming method and dynamic optimization using extremum seeking method was applied to find the optimized height. The optimized height values were calculated and Travelling Salesman Problem (TSP) was applied to create the trajectory of the UAV. The overall energy consumption of the UAV was minimized by integrating dynamic optimization and dome packing method, which can find an optimal position and trajectory where the UAV will be hovering to direct energy and collect data. Moreover, we also minimized the total flight time of the UAV.
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Tan, Qichen, Haoyu Bian, Siyang Zhong i Xin Zhang. "Simulation of multi-rotor powered urban aerial mobility noise for environmental assessment". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, nr 3 (1.08.2021): 3854–60. http://dx.doi.org/10.3397/in-2021-2541.
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The operation of the rapidly growing unmanned aerial vehicles (UAV) and the promising urban aerial mobility (UAM) could have a significant noise impact on the environment. In this work, we developed a cloud-based noise simulator to efficiently assess the environmental impact of UAM and UAV. The noise sources and long-distance propagation are computed by the propeller noise prediction models and an advanced Gaussian beam tracing method, respectively, in local high-performance computers. Users can define the working conditions and vehicle layer through a platform with a user-friendly graphical interface. In addition, the noise level distribution at the observers of interest such as the buildings can be visualized. By employing advanced interpolation methods or autonomous learning algorithms, the computations are efficiently accelerated such that the noise distributions are simultaneously displayed during flights of the vehicles. To better measure the noise impact on human perception, various noise metrics will be output for further analysis. By conducting the virtual flights using the simulator, the noise impact in each flight state and atmospheric condition of different vehicles can be predicted, which will then facilitate the low-noise flights for both UAV and UAM.
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Yin, Shiyun, Kai Zhou, Lin Cao i Xin Shen. "Estimating the Horizontal and Vertical Distributions of Pigments in Canopies of Ginkgo Plantation Based on UAV-Borne LiDAR, Hyperspectral Data by Coupling PROSAIL Model". Remote Sensing 14, nr 3 (2.02.2022): 715. http://dx.doi.org/10.3390/rs14030715.
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Pigments are the biochemical material basis for energy and material exchange between vegetation and the external environment, therefore quantitative determination of pigment content is crucial. Unmanned Aerial Vehicle (UAV)-borne remote sensing data coupled with radiative transfer models (RTM) provide marked strengths for three-dimensional (3D) visualization, as well as accurate determination of the distributions of pigment content in forest canopies. In this study, Light Detection and Ranging (LiDAR) and hyperspectral images acquired by a multi-rotor UAV were assessed with the PROSAIL model (i.e., PROSPECT model coupled with 4SAIL model) and were synthetically implemented to estimate the horizontal and vertical distribution of pigments in canopies of Ginkgo plantations in a study site within coastal southeast China. Firstly, the fusion of LiDAR point cloud and hyperspectral images was carried out in the frame of voxels to obtain fused hyperspectral point clouds. Secondly, the PROSAIL model was calibrated using specific model parameters of Ginkgo trees and the corresponding look-up tables (LUTs) of leaf pigment content were constructed and optimally selected. Finally, based on the optimal LUTs and combined with the hyperspectral point clouds, the horizontal and vertical distributions of pigments in different ages of ginkgo trees were mapped to explore their distribution characteristics. The results showed that 22-year-old ginkgo trees had higher biochemical pigment content (increase 3.37–55.67%) than 13-year-old ginkgo trees. Pigment content decreased with the increase of height, whereas pigment content from the outer part of tree canopies showed a rising tendency as compared to the inner part of canopies. Compared with the traditional vegetation index models (R2 = 0.25–0.46, rRMSE = 16.25–19.37%), the new approach developed in this study exhibited significant higher accuracies (R2 = 0.36–0.60, rRMSE = 13.53–16.86%). The results of this study confirmed the effectiveness of coupling the UAV-borne LiDAR and hyperspectral image with the PROSAIL model for accurately assessing pigment content in ginkgo canopies, and the developed estimation methods can also be adopted to other regions under different conditions, providing technical support for sustainable forest management and precision silvicuture for plantations.
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Martinez Bueno, Patricia, Marcias Martinez, Calvin Rans i Rinze Benedictus. "Strain Monitoring Using a Rayleigh Backscattering System for a Composite UAV Wing Instrumented with an Embedded Optical Fiber". Advanced Materials Research 1135 (styczeń 2016): 1–19. http://dx.doi.org/10.4028/www.scientific.net/amr.1135.1.
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The primary objective of this research study was to evaluate the capabilities for measuring strain of a composite UAV wing with an embedded optical fiber connected to a Rayleigh backscattering distributed sensing system. This research paper summarizes the manufacturing procedure used during the instrumentation of the composite UAV wing. In addition, a Finite Element Model was developed in order to verify the strain distribution of this complex structure under static and dynamic loading conditions. The use of strain gauge data as a means for verification is presented as part of this research. Finally, fatigue tests were carried out to determine the longevity of the embedded fiber during the design life of the structure. The results demonstrate the ability of a distributed sensing system to obtain complex and accurate strain distributions on a single non-grated fiber. In addition, the findings demonstrate current limitations of the system for capturing accurate strain profiles in dynamic loading test cases.
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Yang, Yin, Dawei Liu i Lianshan Lu. "A Study of Wind Shear Influences on the Aerodynamic Performances of a UAV Airfoil". Applied Sciences 13, nr 6 (15.03.2023): 3764. http://dx.doi.org/10.3390/app13063764.
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In order to study the flight strategies of birds in shear wind and realize the long-range flight of an unmanned aerial vehicle (UAV), the aerodynamic performances of a UAV’s airfoil under different shear wind are studied using numerical methods. The results are calculated using the RANS method in shear wind with a linear and logarithmic distribution of velocity. The results show that the slope of the lift curve, the maximum lift coefficient and the stall angle decrease when the velocity gradient is positive or increasing, conversely, they increase at a negative gradient compared to gradient-free wind fields. A positive gradient of wind significantly increased the maximum lift-drag ratio and the effective angle of attack. Compared with linear distributed shear wind with the same velocity at both the lowest and highest points of the flow field, logarithmic distribution decreases the slope of the lift curve, the maximum lift coefficient and the maximum lift-drag ratio and the effective angle of attack. Therefore, a shear wind with a positive gradient is beneficial to the increase of lift-drag ratio and more conducive to cruise flight, and a negative gradient is beneficial for increased lift and more conducive to take-off and landing of UAVs. The velocity distributions influence the aerodynamic performances of the airfoil which is related to the speed and gradient distribution of shear wind.
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Meng, Yanhua, Yan Ma, Zhiguo Wang i Hongyan Hu. "Droplet distribution in cotton canopy using single-rotor and four-rotor unmanned aerial vehicles". PeerJ 10 (14.06.2022): e13572. http://dx.doi.org/10.7717/peerj.13572.
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Unmanned aerial vehicles (UAVs) are widely used as the sprayers for low-volume pesticide application in recent years. Droplet distribution characteristics of UAV spraying in the cotton canopy have notable effect on the biological control efficacy of the targets and the defoliation efficiency of the harvest aids. In this work, the influences on droplet distribution in the cotton canopy with respect to the flight height, forward mode, and spraying volume were evaluated by conducting the field trials during two cotton growth stages in 2020, respectively. The first field trial was performed in the cotton flowering stage and the second one was conducted in the early boll development stage. Two typical UAVs equipped with a single-rotor and four-rotor, respectively, were adopted as the spraying platforms in this work. Droplet deposition obtained by water sensitive papers (WSPs) clipped on the cotton leaves was considered as the observing metric. All cotton leaves in the canopy were divided into three groups (i.e., upper, middle, and bottom layers) in both trials. Furthermore, the cotton canopy was divided as eight directions to assess the droplet distribution in the canopy from different directions. The results showed that the droplet deposition varied remarkable between the treatments and in the same canopy within a treatment. The upper layer obtained higher droplet deposition than those of the middle and bottom layers and plants P4 to P8 accessed more droplets than those of the remaining sampling plants in most treatments of both trials for the two UAVs. The upper layer droplet deposition of the four-rotor UAV treatments outperformed that of the single-rotor treatments under the same operating parameters. The forward modes rarely affected the droplet distribution of the four-rotor UAV treatments but significantly influenced that of the single-rotor UAV treatments. For the single-rotor UAV spraying with “head forward”, the droplet distribution of the treatment with a flight height of 2 m was more even than that of the 1 and 3 m in the first trial. Under the same flight height, droplet deposition of the treatments with a spraying volume of 22.5 L ha−1 was remarkably higher than that of the 12 L ha−1 for both forward modes in the second trial. “Tail forward” of the single-rotor UAV treatment had better penetration at a flight height of 2 m in both trials. Therefore, for the single-rotor UAV, under a flight height of 2 m and a spraying volume of 22.5 L ha−1, “tail forward” was recommended for applying pesticides to control targets at the lower canopy and “head forward” was a better choice for harvest aid application. Four-rotor UAV was a suitable adoption for the harvest aid application and controlling the targets of the upper canopy. The results also indicate that the systemic pesticides are recommended for UAV spraying due to its uneven droplet distribution uniformity in the whole cotton canopy.
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Jiao, Songming, Haiyue Gao, Xiaokun Zheng i Dengpan Liu. "Fault Tolerant Control Algorithm of Hexarotor UAV". Journal of Robotics 2020 (4.08.2020): 1–16. http://dx.doi.org/10.1155/2020/8829329.
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As the best representative of the current cutting-edge technology, unmanned aerial vehicle (UAV) is widely used in various fields such as electric power inspection, agriculture, forestry and plant protection, fire rescue, and film and television shooting. With the rapid development of UAV, the safety work of UAV has become more important. In order to improve the safety of hexarotor UAV during flight, a fault-tolerant control scheme independent of basic control law and control distribution is designed in this paper. Firstly, the linear active disturbance rejection control (LADRC) was used as the basic control law for attitude control of hexarotor UAV. Secondly, in the case of actuator failure of hexarotor UAV, a fault observer was used to estimate fault information accurately. Then, on this basis, the control distribution matrix was adjusted to reduce the use of the faulty motor, and the purpose of fault-tolerant control was achieved. Finally, simulation experiments and actual flight experiments were carried out to verify the effectiveness of the proposed scheme. Experimental results show that the proposed scheme can improve the robustness of the control system and the flight safety of UAV.
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Li, Shan, Honghai Zhang, Zhuolun Li i Hao Liu. "An Air Route Network Planning Model of Logistics UAV Terminal Distribution in Urban Low Altitude Airspace". Sustainability 13, nr 23 (25.11.2021): 13079. http://dx.doi.org/10.3390/su132313079.
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Traditional terminal logistics distribution in urban areas is mainly concentrated on the ground, which leads to increasingly serious air pollution and traffic congestion. With the popularization of unmanned aerial vehicle (UAV) techniques and the reform of low altitude airspace, terminal logistics distribution is expected to be carried out by drones. Therefore, it is of great significance to construct a reasonable air route network for logistics UAV to ensure the safety and efficiency of operations. In this paper, a single route planning model and an air route network planning model for UAV were constructed by fully considering the complex urban low altitude environment, the flight performance of UAV and the characteristics of logistics tasks to regulate the flights of drones. Then, taking Jiangjun Road Campus of Nanjing University of Aeronautics and Astronautics as an example, the improved cellular automata (CA) was adopted to search for the optimal route between different waypoints, and the optimal spanning tree algorithm was used to construct the route network. The experimental results demonstrated that the improved CA could greatly reduce search time and obtain the optimal route while enhancing safety. With the satisfaction of the voyage, the needs of logistics and distribution constraints, a network that had smaller intersection points and redundancy was generated. The models and core ideas proposed in this paper can not only regulate operation of drones but also provide a solid foundation for the distribution of logistics UAV in the future.
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Yang, Biao, Xuanrui Xiong, He Liu, Yumei Jia, Yunli Gao, Amr Tolba i Xingguo Zhang. "Unmanned Aerial Vehicle Assisted Post-Disaster Communication Coverage Optimization Based on Internet of Things Big Data Analysis". Sensors 23, nr 15 (29.07.2023): 6795. http://dx.doi.org/10.3390/s23156795.
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The rapid development of Internet of Things (IoT) communication devices has brought about significant convenience. However, simultaneously, the destruction of communication infrastructure in emergency situations often leads to communication disruptions and challenges in information dissemination, severely impacting rescue operations and the safety of the affected individuals. To address this challenge, IoT big data analytics and unmanned aerial vehicle (UAV) technologies have emerged as key elements in the solution. By analyzing large-scale sensor data, user behavior, and communication traffic, IoT big data analytics can provide real-time communication demand prediction and network optimization strategies, offering decision support for post-disaster communication reconstruction. Given the unique characteristics of post-disaster scenarios, this paper proposes a UAV-assisted communication coverage strategy based on IoT big data analytics. This strategy employs UAVs in a cruising manner to assist in communication by partitioning the target area into multiple cells, each satisfying the minimum data requirements for user communication. Depending on the distribution characteristics of users, flight–communication or hover-communication protocols are selectively employed to support communication. By optimizing the UAV’s flight speed and considering the coverage index, fairness index, and average energy efficiency of the mission’s target area, the Inner Spiral Cruise Communication Coverage (IS-CCC) algorithm is proposed to plan the UAV’s cruising trajectory and achieve UAV-based communication coverage. Simulation results demonstrate that this strategy can achieve energy-efficient cruising communication coverage in regions with complex user distributions, thereby reducing energy consumption in UAV-based communication.
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Zhang, Suming, i Gengxing Zhao. "A Harmonious Satellite-Unmanned Aerial Vehicle-Ground Measurement Inversion Method for Monitoring Salinity in Coastal Saline Soil". Remote Sensing 11, nr 14 (18.07.2019): 1700. http://dx.doi.org/10.3390/rs11141700.
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Soil salinization adversely impacts crop growth and production, especially in coastal areas which experience serious soil salinization. Therefore, rapid and accurate monitoring of the salinity and distribution of coastal saline soil is crucial. Representative areas of the Yellow River Delta (YRD)—the Hekou District (the core test area with 140 sampling points) and the Kenli District (the verification area with 69 sampling points)—were investigated. Ground measurement data, unmanned aerial vehicle (UAV) multispectral imagery and Sentinel-2A multispectral imagery were used as the data sources and a satellite-UAV-ground integrated inversion of the coastal soil salinity was performed. Correlation analyses and multiple regression methods were used to construct an accurate model. Then, a UAV-based inversion model was applied to the satellite imagery with reflectance normalization. Finally, the spatial and temporal universality of the UAV-based inversion model was verified and the soil salinity inversion results were obtained. The results showed that the green, red, red-edge and near-infrared bands were significantly correlated with soil salinity and the spectral parameters significantly improved this correlation; hence, the model is more effective upon combining spectral parameters with sensitive bands, with modeling precision and verification precision of the best model being 0.743 and 0.809, respectively. The reflectance normalization yielded good results. These findings proved that applying the UAV-based model to reflectance normalized Sentinel-2A images produces results that are consistent with the actual situation. Moreover, the inversion results effectively reflect the distributions characteristic of the soil salinity in the core test area and the study area. This study integrated the advantages of satellite, UAV and ground methods and then proposed a method for the inversion of the salinity of coastal saline soils at different scales, which is of great value for real-time, rapid and accurate soil salinity monitoring applications.
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Mohamed, Ehab Mahmoud. "LEO satellite assisted UAV distribution using combinatorial bandit with fairness and budget constraints". PLOS ONE 18, nr 8 (23.08.2023): e0290432. http://dx.doi.org/10.1371/journal.pone.0290432.
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In this paper, an integration between a low earth orbit satellite (LEO-Sat) and unmanned aerial vehicle (UAV) is proposed to assist users in post-disaster areas. In this scenario, multiple UAVs will be distributed to fully cover the victims and provide rescue services, while LEO-Sat provides backhaul links for UAVs to the ground base station (GBS). In this regard, we consider the problem of efficient UAVs distribution to maximize the total sum rate of the victims while assuring fairness in their coverage within the limited resources of UAVs batteries and LEO-Sat bandwidth. In this paper, UAV distribution problem is considered as a combinatorial multi-armed bandit (MAB) with arms’ fairness and limited UAVs battery budget (CMAB-FB) constraints. Additionally, the utilization of LEO-Sat bandwidth resources is optimized based on the average traffic demands of the LEO-UAV links by means of gradient decent algorithm. The results of numerical analysis indicate that the proposed approach outperforms other naïve ben chmarks.
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Lou, Zhaoxia, Fang Xin, Xiaoqiang Han, Yubin Lan, Tianzhu Duan i Wei Fu. "Effect of Unmanned Aerial Vehicle Flight Height on Droplet Distribution, Drift and Control of Cotton Aphids and Spider Mites". Agronomy 8, nr 9 (13.09.2018): 187. http://dx.doi.org/10.3390/agronomy8090187.
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Unmanned aerial vehicles (UAVs), as emerging plant protection machinery, have the advantages of high operational efficiency, high speed, and low drift. The current study aimed to elucidate the characteristics of droplet distribution and drift, control efficiency on cotton aphids and spider mites, and attachment and absorption of cotton leaves during UAV spraying. Kromekote card and filter paper are used as samplers to collect droplets, and the droplet density, coverage rate, deposition, and drift percentage are statistically analyzed. The pooled results showed that the droplet uniformity, the droplet coverage rate, the deposition, and the drifting ability are higher when the UAV flight height was 2 m. The control effects by UAV spraying on cotton aphids and spider mites were 63.7% and 61.3%, respectively. These values are slightly inferior to those obtained through boom spraying. Cotton leaf attachment and absorption of spirodiclofen after UAV spraying were slightly lower than those after boom spraying, therefore, the control efficiency of cotton pests is slightly different. According to the different flight height operations by the UAV sprayer, the drift capability of the droplets at 2 m flight height was large, and the droplet uniformity and deposition were satisfactory. The research results could provide the theoretical basis and technical support for UAV operation.
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Feng, Lei, Weikang Wu, Junmin Wang, Chu Zhang, Yiying Zhao, Susu Zhu i Yong He. "Wind Field Distribution of Multi-rotor UAV and Its Influence on Spectral Information Acquisition of Rice Canopies". Remote Sensing 11, nr 6 (13.03.2019): 602. http://dx.doi.org/10.3390/rs11060602.
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Unmanned aerial vehicles (UAV) are widely used as remote sensing platforms to effectively monitor agricultural conditions. The wind field generated by the rotors in low-altitude operations will cause the deformation of rice crops, and may affect the acquisition of the true spectral information. In this study, a low-altitude UAV remote sensing simulation platform and a triple-direction wind field wireless sensor network system were built to explore the wind field distribution law. Combined with the multi-spectral images of the rice canopy, the influence of wind field on the spectral information acquisition was analyzed through variance and regression analysis. The results showed that the Z-direction wind field of UAV rotors dominated along three directions (X, Y, and Z). The coefficient of determination (R2) of three linear regression models for Normalized Difference Vegetation Index (NDVI), Ratio Vegetation Index (RVI), and Canopy Coverage Rate (CCR) was 0.782, 0.749, and 0.527, respectively. Therefore, the multi-rotor UAV wind field had an impact on the spectral information acquisition of rice canopy, and this influence could eventually affect the assessment of rice growth status. The models established in this study could provide a reference for the revised model of spectral indices, and offer guidance for the actual operations of low-altitude multi-rotor UAV.
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Zhao, Licheng, Yun Shi, Bin Liu, Ciara Hovis, Yulin Duan i Zhongchao Shi. "Finer Classification of Crops by Fusing UAV Images and Sentinel-2A Data". Remote Sensing 11, nr 24 (14.12.2019): 3012. http://dx.doi.org/10.3390/rs11243012.
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Accurate crop distribution maps provide important information for crop censuses, yield monitoring and agricultural insurance assessments. Most existing studies apply low spatial resolution satellite images for crop distribution mapping, even in areas with a fragmented landscape. Unmanned aerial vehicle (UAV) imagery provides an alternative imagery source for crop mapping, yet its spectral resolution is usually lower than satellite images. In order to produce more accurate maps without losing any spatial heterogeneity (e.g., the physical boundary of land parcel), this study fuses Sentinel-2A and UAV images to map crop distribution at a finer spatial scale (i.e., land parcel scale) in an experimental site with various cropping patterns in Heilongjiang Province, Northeast China. Using a random forest algorithm, the original, as well as the fused images, are classified into 10 categories: rice, corn, soybean, buckwheat, other vegetations, greenhouses, bare land, water, roads and houses. In addition, we test the effect of UAV image choice by fusing Sentinel-2A with different UAV images at multiples spatial resolutions: 0.03 m, 0.10 m, 0.50 m, 1.00 m and 3.00 m. Overall, the fused images achieved higher classification accuracies, ranging between 10.58% and 16.39%, than the original images. However, the fused image based on the finest UAV image (i.e., 0.03 m) does not result in the highest accuracy. Instead, the 0.10 m spatial resolution UAV image produced the most accurate map. When the spatial resolution is less than 0.10 m, accuracy decreases gradually as spatial resolution decreases. The results of this paper not only indicate the possibility of combining satellite images and UAV images for land parcel level crop mapping for fragmented landscapes, but it also implies a potential scheme to exploit optimal choice of spatial resolution in fusing UAV images and Sentinel-2A, with little to no adverse side-effects.
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Zhao, Haoran, Wenjie Yang i Huibin Zhu. "Unmanned Aerial Vehicles Rescue System Design and Traffic Model Planning". Applied Sciences 11, nr 21 (8.11.2021): 10481. http://dx.doi.org/10.3390/app112110481.
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Unmanned Aerial Vehicles (UAV) are widely used in disaster relief and road exploration in recent years. This paper mainly studied the emergency response of UAVs after disasters. The UAV response system is mainly suitable for the distribution of necessities and road exploration after geological disasters and tsunamis in coastal areas. By analyzing the problem and making reasonable assumptions, the optimization model was established with the traffic planning theory, and MATLAB software was used to program and solve the problem. An optimal scheduling scheme was presented to solve these problems. The normalization method was used to select a highly capable UAV. Taking the minimum volume of idle space buffer material as the objective function and taking into account the constraints, such as payload of unmanned aerial vehicle, a single objective programming model was established. The results are as follows: Each International Standards Organization (ISO) cargo container has five UAVs B, one UAV C, one UAV F and one UAV H. It provides 188 days of relief requirements with ISO cargo containers’ space utilization of 71.4%. The research shows that the UAV response system has the functions of necessities distribution and road exploration after disasters, and can be used to deal with the emergency response after disasters in coastal areas, and has a wide range of applicability.
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Fedorova, Aleksandra, Viktar Beliautsou i Armin Zimmermann. "Colored Petri Net Modelling and Evaluation of Drone Inspection Methods for Distribution Networks". Sensors 22, nr 9 (29.04.2022): 3418. http://dx.doi.org/10.3390/s22093418.
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The UAV industry is developing rapidly and drones are increasingly used for monitoring industrial facilities. When designing such systems, operating companies have to find a system configuration of multiple drones that is near-optimal in terms of cost while achieving the required monitoring quality. Stochastic influences such as failures and maintenance have to be taken into account. Model-based systems engineering supplies tools and methods to solve such problems. This paper presents a method to model and evaluate such UAV systems with coloured Petri nets. It supports a modular view on typical setup elements and different types of UAVs and is based on UAV application standards. The model can be easily adapted to the most popular flight tasks and allows for estimating the monitoring frequency and determining the most appropriate grouping and configuration of UAVs, monitoring schemes, air time and maintenance periods. An important advantage is the ability to consider drone maintenance processes. Thus, the methodology will be useful in the conceptual design phase of UAVs, in monitoring planning, and in the selection of UAVs for specific monitoring tasks.