基于多源数据的华北平原夏玉米种植区划研究

精准识别农业生产环境信息和农业生产特征,对气象、土壤和作物等多源数据进行综合分类,是提高农业资源利用效率和优化农业种植结构的基础。本研究基于近20年(1998年~2017年)气象数据和华北五省的玉米单产统计数据,首先构建了华北平原气候资源和玉米生产时空分布特征数据库,研究区降雨量、活动积温、日照时数、太阳辐射和玉米单产均存在显著的时空变化;利用作物精细种植区划方法,将华北平原夏玉米种植区分为极不适应区、不适宜区、较适宜区、适宜区、极适宜区五大类,各类面积分别占总体的比例约为10%、11%、25%、30%、24%;进一步通过环境类别归属度分析方法,将每一大类分为5小类,概率大于75%的相对稳定区域约占总面积的63%,小于75%的波动区域约占37%;极不适宜区、不适宜区和较适宜区,三类时空分布比较稳定,隶属度为100%分别占各类面积的87.67%、70.41%和84.28%,波动区主要发生在极适宜区和适宜区,以及适宜区和较适宜区之间。本研究构建的华北平原夏玉米精细区划结果,对提高研究区资源利用效率和优化玉米产业布局具有重要的指导意义。

Grading method for tomato multi-view shape using machine vision

Owing to the requirements of a high yield and high-quality tomatoes, tomato grading is important-particularly for fruit morphology, and accuracy has become the focus of attention. Machine vision provides a fast and nondestructive manner to address this demand. In this study, the gamma correction method was used for preprocessing to enhance the edge information of tomatoes, and Otsu’s method was used to eliminate the tomato-image background in the A-component image under the LAB color model. On this basis, two levels of exploration were conducted. First, new evaluation indices were proposed for tomato shapes from different views. For the top view, two shape-evaluation indices were established: the area ratio of the maximum inscribed circle to the maximum circumscribed circle and the dispersion of the contour centroid distance (range and coefficient of variation), the highest accuracy was 94%. For the side view, the difference between the maximum and minimum centroid distances in the contour was established as a shape index, the highest accuracy was 91.91%. Second, an evaluation method based on multi-view fusion was developed by combining the advantage indices for different views. The classification accuracy reached 96%, with the highest identification accuracy of unqualified tomatoes. The results show that the proposed evaluation method combining top views (dispersion of centroid distance) with side views (difference between maximum and minimum centroid distances) is effective for classifying tomatoes.

Design and optimization on rootstock cutting mechanism of grafting robot for cucurbit

Cutting mechanisms in existing grafting machines are unable to completely cut through the rootstock growth point and can easily damage seedlings.During the mechanical operation of splice grafting,the cutting angle of the rootstock is an essential factor for ensuring the quality and survival rate of grafting seedlings and a stable process for grafting robots.Therefore,in this study,commonly used grafting rootstocks,e.g.,cucurbita moschata,and calabash gourd were used as research objects for studying and analyzing the cutting angle of a splice grafting method.The morphological and structural parameters of the rootstock and scion were measured,and a structural model of the internal cavity of the rootstock was constructed using an image analysis method.The critical cutting angles for the cucurbita moschata and calabash gourd seedlings were obtained.According to the analysis,the grafting cutting angles for cucumber seedlings matching with cucurbita moschata seedlings were 20°and 25°,respectively,and the fitting rate of the cutting surface of the rootstock and scion was 99.04%.A cutting mechanism for the rootstock growth point and geometric model of the cutting operation were established,and the structural parameters of the mechanism and cutting angle adjustment were optimized.A cutting performance test showed that the success rate of the pressing the cotyledons of cucurbita moschata seedlings was 96.67%,and the success rate of cutting was 98%.The cutting accuracy was 96.8%,and the cutting surface fitting rate of the rootstock and scion was 98.61%.The latter differed by 0.43%from the theoretical rate but met the requirements for the splice grafting method.Thus,this study can provide a reference for the design of a cutting mechanism for a grafting robot.

Numerical investigation on effects of side curtain opening behavior on indoor climate of naturally ventilated dairy buildings

The side-curtain is popular in cattle buildings to regulate indoor climates and ventilation rates by adjusting the opening ratio.It normally had three different adjusting strategies relate to the position of rollers,i.e.central roller(S1),top roller(S2)and bottom roller(S3),which result in different opening behaviors to generate the same opening ratio but different opening positions in the side wall for a full-curtain house.Numerical simulations were conducted using computational fluid dynamics(CFD)to investigate the effects of the eight potential opening behaviors of side curtains on the indoor climates and airflow rates in winter for a typical naturally ventilated dairy house in China when the opening ratio were 8.5%and 17%.Airflow patterns,wind chilled temperature(WCT)and age of air were analyzed in the animal occupied zone(AOZ)by taking reference planes.Openings at the very bottom of side walls had more efficient ventilation due to the younger air age,more effective air disturbing,more uniformly distributed indicators in AOZ.However,it will result in a lower WCT in AOZ although a lower ventilation rate was observed in this case.Openings on the very top of side wall would generate a better thermal comfort in AOZ but with very poor air quality and nonuniformly distributed airflows in the dairy house.S1 was not recommended to the practical application due to the poor indoor climate and the higher cost of the mechanical structure.Based on the comprehensive evaluations of the analytic hierarchy process,the most satisfaction opening positions were at the bottom of the side curtains and the optimized adjusting strategy is S2.

Automatic diagnosis of strawberry water stress status based on machine vision

Water stress status of plants is very important for irrigation scheduling.However,plant water stress status monitoring has become the bottleneck of irrigation scheduling.In this study,an automatic water stress status monitoring method for strawberry plant was proposed and realized using combined RGB and infrared image information.RGB image and infrared images were obtained using RGB digital camera and infrared thermal camera,which were placed in a fixed shell in parallel.In the first experimental stage,three kinds of water stress treatments were carried out on three groups of strawberry plants,and each group includes three repetitions.Single point plant temperature,dry surface temperature,wet surface temperature were measured.In the second experimental stage,the infrared and visible light images of the canopy leaves were obtained.Meanwhile,plant temperature,dry surface temperature,wet surface temperature,and stomatal conductance were measured not only for single point but also for plant area temperature measurement.Fusion information of infrared image and visible light image was analyzed using image processing technology,to calculate the average temperature of plant areas.Based on single point temperature,area temperature,dry surface temperature and wet surface temperature of the plant,single point crop water stress index(CWSI)and area CWSI were calculated.Through analysis of variance(ANOVA),the experimental results showed that CWSI measured for plants under different treatments,were significantly different.Through correlation analysis,the experimental results showed that,determination coefficient between area CWSI and the corresponding stomatal conductance of three strawberry groups were 0.8834,0.8730 and 0.8851,respectively,which were larger than that of single-point CWSI and stomatal conductance.The results showed that area CWSI is more suitable to be used as the criteria for automatic diagnosis of plants.

Design and experiment on scion cutting mechanism of grafting robot for cucurbit

The scion cutting mechanism of the traditional grafting machine cannot correct the bending degree of the scion seedling stem so that the cutting angle of the scion seedling is not standard and the survival rate of the grafted seedling is affected.In this study,cucumber seedlings and watermelon seedlings were taken as experimental objects.Based on the analysis of the geometric parameters and mechanical characteristics of scion seedlings,a scion cutting mechanism with holding seedling applied to cucumber seedlings and watermelon was designed and developed.The main structure and operating parameters of V-shaped holding seedling block and cutting unit were determined,and holding seedling and cutting performance tests were carried out.The test results showed that compared with the common arc clamp,the V-shaped holding seedling block had a better guiding and centering effect on the scion seedling,could better correct the bending state of the scion seedling stem,and the success rate of holding seedling of the V-shaped holding block reached 98.33%,which was increased by 13.33%compared with the arc-shaped clamp,and the seedling injury rate was only 1.67%.The upper and lower two-point positioning of scion stem by clamping hand and holding seedling block can improve the cutting performance effectively.The cutting accuracy rate of the scion was 97.75%,and the cutting success rate was 98.67%.The cutting performance was closely related to the holding seedling effect.The research results can provide a reference for the design of cutting mechanisms of melon grafting robots.