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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the rapid development of agricultural aviation, electric multi-rotor unmanned aerial vehicles (UAV) for planting protection are favored in plant protection operations due to their advantages of vertical take-off and landing, air hovering, and easy operation. However, because of its low aerodynamic efficiency, there are currently problems such as low loading mass and short battery life, and it is still necessary to optimize and improve it. The lift characteristics is one of the important parameters for the performance test of the multi-rotor UAV. However, few tests have been conducted on the lifting characteristics of multi-rotor UAV. How do we comprehensively evaluate the lifting characteristics of various types of multi-rotor UAV and make comparisons and judgments on the performance of multi-rotor UAV. At present, there are no standards to follow. Only by clearly defining the evaluation index for lift performance, and by standardizing the test methods and evaluation criteria, the performance of the multi-rotor UAV can be judged and the suggestions for optimization and improvement can be given. Based on the existing research results, this paper considered the functional effectiveness criteria of helicopters combining economy, weight reduction, and heat transfer. A method of test and evaluation for the lift characteristics of the semi-tethered multi-rotor UAV is proposed. It includes performance testing semi-tethered platform, lift characteristics test method and index, and lift characteristics evaluation method. In order to verify the feasibility of the method, the performance test of 3 different models (four-rotor, Type I; six-rotor, Type II; and eight-rotor, Type III) was carried out. The test results show that the 3 models have great difference in power load, weight efficiency and thermal efficiency ratio. Type III is the best in power load, 7.6 mN/W larger than the worst Type I. The best Type I is 0.33 larger than the worst Type Ⅱ in weight efficiency. The best Type III is 10.5 N/°C larger than the worst Type I in thermal efficiency ratio. It reflects the difference in motor and propeller selection and structure of the 3 models of aircraft during the design process, thus showing difference in the performance of the whole machine. On the basis of the above index test, combined with the mathematical model of multi-rotor UAV power system, a scoring method is put forward to evaluate the lift characteristics of the multi-rotor UAV using the power load, weight efficiency and thermal efficiency ratio. The results of the comprehensive score of the 3 types are as follows: Type III > Type I > Type II. The results show that the proposed evaluation method can effectively evaluate the lift characteristics of different types of multi-rotor UAV. It can more objectively and accurately assess the technical level of multi-rotor UAV and strengthen the management of multi-rotor UAV in use. The test and evaluation method presented in this paper can not only be used to evaluate the performance of the multi-rotor UAV, but also provide a reference for the further improvement of the model performance. Of course, in the performance evaluation of multi-rotor UAV, the improvement of power load, weight efficiency and thermal efficiency ratio cannot be excessively pursued, and the balance of technical performance, reliability performance, safety performance, and economical efficiency should be upheld. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rapid and accurate acquisition of evapotranspiration in field crops is an urgent issue to be solved in crop evapotranspiration researches. In this paper, the feasibility of estimating crop coefficient by unmanned aerial vehicle (UAV) remote sensing in maize under different water stresses was analyzed. The experiment was conducted in Zhaojun town Experimental Station in Dalate Qi, Inner Mongolia. Full irrigation (TR1) was designed as 50% of field water holding capacity based on previous research results and local situation, which was considered as the base. The water stress condition (80% of the base soil moisture) was designed in the fast growth stage for TR2-TR4. The 82% and 43% of the base soil moisture were also designed for the late growth stage of TR2 and TR3, respectively. In addition, in the middle growth stage, the water stress with 65% of the base soil moisture was designed for TR4. The maize was planted on May 20th,2017. The whole growth period lasted 110 days. The sprinkled irrigation was used for the experiment. The experimental area was partitioned into 4 regions for the different treatments. In each region, a squared area with the side length of 12 m was chosen for plant height and leaf area index measurements. The measurements were carried out every 2-5 days. Soil moisture at 30-cm depth was determined in each area as the surface soil moisture. Meanwhile, climatic parameters such as precipitation, air temperature, relative humidity and so on were collected from local meteorological station. Crop coefficient was calculated by dual crop coefficient method proposed by FAO56 based on meteorological parameters and plant height. The UAV multispectral monitoring system was to obtain the canopy spectral vegetation index of field maize under different water stress conditions. The UAS images were obtained at the same time with the plant height measurement. The simple ratio index was calculated based on reflectivity of red and near infrared band. The dynamic change of leaf area index, soil moisture, simple ratio index, and crop coefficient was analyzed. The results showed that the water stress heavily affected the leaf area index, the simple ratio index and the surface soil moisture was decreased in the late growth stage of maize, and the crop coefficient was low in the late growth stage. The correlation analysis between the crop coefficient, simple ratio index, leaf area index and surface soil moisture showed that the surface soil moisture had the highest correlation with the crop coefficient for the treatment of TR1, TR2 and TR4 but the leaf area index was highly correlated with the crop coefficient in the TR3. By stepwise regression analysis, the 3-variable model had the highest accuracy with the adjusted determination coefficient of 0.63, root mean square error of 0.21 and the normalized root mean square of error of 25.16%. The validation showed the determination coefficient of 0.60, root mean square error of 0.21 and the normalized root mean square of error of 23.35%. It indicated that the 3-variable model was well to estimate crop coefficient. The results provide a method support for crop coefficient estimation by UAV. [ABSTRACT FROM AUTHOR]

Recently, multi-rotor unmanned aerial vehicle (UAV) becomes more and more irreplaceable in the field of plant protection. Multi-rotor unmanned plant protection machine has been widely used in pesticide spraying, pollination operation, and so on, however, the unclearness of wind field distribution leads to non-uniform deposition problem. In this paper, the influence of the down wash flow on the motion distribution of droplet group was studied for the multi-rotor UAV in hovering state. Based on the N-S equation and realizable k-ε turbulence model, the three-dimensional numerical model was established for six-rotor unmanned plant protection machine under 3 kg load condition. In the numerical calculation, 12 observation points were set at 2 heights directly below each rotor, and the wind velocity value at each point was observed. When the computing time reached 2.28 s, the wind velocity tended to be stable, and the 12 stable wind velocity pulsation values were obtained. The wind velocity of the down wash flow was tested one by one at the 12 observation points for the multi-rotor UAV in hovering state. Comparative analysis showed that the relative error of the velocity at the z direction between the experimental measurement and numerical simulation for characteristic points was less than 9% when the down wash flow was stable, and the reliability of the wind field numerical calculation was verified. Under the rotation of airfoil and the extrusion of the external atmospheric pressure, the “shrinkage-expansion-shrinkage” phenomenon appeared in the longitudinal main section; under the influence of wing interference caused by the opposite velocity of adjacent rotor, the turbulent effect of down wash flow was obvious, and the “airflow inlet” and “airflow outlet” region appeared between the wings area at the cross section. Droplet discrete phase was introduced to N-S equation, the momentum and energy equations were also corrected for continuous phase to establish two-phase flow model, then the two-phase flow model with droplet discrete phase was established for the nozzle, and the feasibility and validity of the two-phase flow model to calculate the trajectory of the droplets were also verified combined with the spray test. The advantages of easy boundary setting in numerical computation were used to discuss the influence law of droplet size on droplet motion for the atomization nozzle. Numerical results showed that the droplet distribution was basically circular, and the area of droplets with the highest concentration was the medium-sized droplet sedimentation area, which had the maximum differential ratio. Moreover, the numerical simulation results also showed that the smaller the droplet size, the smaller the droplet spray amplitude; the larger the droplet size of the droplet, the larger the final sub-velocity value at the vertical direction. Then the three-dimensional two-phase flow model was established for six-rotor unmanned plant protection machine, and the analysis showed that droplets were mainly distributed in the 3 “airflow inlet” areas and 3 “airflow outlet” areas where wing interference was obvious. The droplets in the inner side of down wash area were interlaced, and the horizontal travel of large particles was greater and they were distributed in the outside periphery of down wash area. When the diameter was less than 200 m, the droplet movement range could not cover all the “airflow inlet” area, and the droplets were mostly distributed in the center down wash area. When the diameter was greater than 250 m, the droplet motion region gradually covered all the “airflow inlet” and “airflow outlet”. The result can lay a foundation for the research of drifting and deposition of droplets under the disturbance of vertical wind flow, down wash flow and instantaneous transverse wind during the flight spraying. [ABSTRACT FROM AUTHOR]

For the sustainable development and the accurate monitoring and information-based management of forestry resources, in this paper, we constructed a forest resource inventory system for forestry investigation and management. This research was based on the unmanned aerial vehicle (UAV) images data with the help of photogrammetric technique, UAV image post-processing technology and geographic information system technology, etc. In the system, we used C# programming language and fully used ArcGIS Engine10.2 embedded component technology. We also used UAV images to achieve efficient functions, such as forest spatial division, area adjustment and forest sub-compartment investigation, vegetation information extraction in high-precision and large-scale. The system can timely update resource database, greatly shorten the traditional investigation period, and achieve the scientific management of forest resources. The extraction of landform factors by software is based on UAV image data, DEM data, and spatial data from spatial division. It can be divided into two steps. The first is to extract the topographical attributes among the UAV image of whole area; the second is to ultimately extract landform factors combined with spatial data to finish attribute tables of each division, which is based on the first step. The goal of the stand factor extraction module is to obtain and store the vegetation information such as sub-compartment volume, stand density, average crown diameter, average tree height, average DBH and canopy coverage. Due to the difficulties for UAV to extract canopy coverage information in the dense forest area, in the study, we divided stand factor extraction module into the sparse forest area and the dense forest area. In the dense forest area, canopy coverage information of each sub-compartment was manually interpreted with the help of pattern spot border, and the input data were directly stored in its corresponding attribute database. In the sparse forest area, based on UAV images and spatial data, the system allowed its users to circle a nearly round sample area within the sub-compartment border, collect information of each single tree in the circle, automatically store the statistical results of all sample information into the corresponding sub-compartment, namely its vegetation information. The empirical study of this forest resource investigation system has been conducted in Lao Tudingzi, Liaoning Province. The results have proven its simple interface, high automation and good interactivity on system operation. The relative error in extraction of slope and elevation were about 5.17% and 5.41% respectively. Before the stand factors were acquired, the relationship between crown diameter and DBH and the relationship between tree height and DBH in test area were fitted by 1stOpt software, then the evaluation indexes, such as coefficient of determination, standard error estimate and total relative error, were introduced to determine the optimal model. The stand factors of the test area have been extracted based on the optimal model with the statistical value of stand density and sub-compartment volume measurement. The results showed the relative error of stand density is 2.68%, and that of sub-compartment volume is 4.01%. [ABSTRACT FROM AUTHOR]

Weeds is one of the main harmful factors to the yield and quality of wheat and other main crops during seedling stage. Image processing technology is often used in weed recognition, but the method mainly cares about the weeds between different rows, which is always inefficient and wasteful for unmanned aerial vehicle (UAV) and machine spraying ways. In order to overcome the limitations above, this paper proposes a regional weed identification method, which takes advantage of properties of shearlets. Shearlets have attracted much attention in the field of image recognition because of its good sensitivity and fast computation in texture recognition. Meanwhile, it is a multi-scale analysis method with the characteristic of direction independence. Through the comparison of the regional images of the wheat and weed, it shows that the texture of the weed leaves is more complex while the wheat leaves are relatively regular. So we first choose 8 images including 4 wheat images and 4 weed images. Then we obtain shearlet transform coefficient (STC) at diverse scales and directions according to the different texture characteristics of wheat and weeds. In the STC images of different scales, the brightness from black to white represents different coefficient value. Moreover, the complexity of bright regional distribution represents the textural complexity, which can be used to distinguish wheat and weeds. Shearlets have self-adaptability because of different directions on these scales, so that obvious textural features in images taken from different angles can be detected. In our research, we take the self-adaptability of shearlets and the differences of STC images into account, and we choose the STC in the second scale of vertical cone to distinguish wheat weeds as experimental object. The result shows that the STC mean of wheat in the second scale is lower than that of weeds. Additionally, the fluctuation of STC mean of wheat is smaller than that of weeds. This study chooses 16 wheat images and 16 weeds images, aiming to distinguish weed and wheat more intuitively; we take a further statistical analysis on the mean and variance of coefficient matrixes of shearlets in the second scale of vertical cone. After normalization treatment, the distinction mean values and mean square error between wheat seedling and weeds are about 0.07 and 0.08 respectively. We randomly select 13 pictures of weeds and wheat seedling, and the recognition accuracy is 69.2%. The experimental results of contrast experiment show that the shearlet-transform method performs better than gray level co-occurrence matrix (GLCM) method to distinguish wheat seedling and weeds. We can get an explanation for the experimental results from the different theory of the shearlet-transform and GLCM. The theory of shearlet-transform shows that it can get different directions information adaptively. On the contrary, GLCM can only get the directions assigned, so the number of directions for image processing can't be changed. In addition, the method of splitting blocks of larger image gathered by UAV is used to realize the effective identification of non-wheat region. From the experimental results, we can see that the difference between wheat and weeds is based on effective shearlet-transform, and we can generalize our method to other image classification based on textural features. Furthermore, this method performs with high flexibility and stability and it has the potential for herbicide spraying in the field. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)