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61.
利用五点采样法采集桂林市11个主要规范化管理桃园土壤样品,测定土壤理化性质,评价桃园土壤肥力、重金属与抗生素污染生态风险.所调查桃园土壤深度为0~20、20~40 cm的土壤pH值平均值分别为5.61、5.56.深度在0~20 cm的土壤有机质、全氮、有效磷、速效钾含量平均值分别为25.56 g/kg、1.33 g/kg、100.49 mg/kg、205.58 mg/kg,在20~40 cm的含量分别为20.50 g/kg、1.11 g/kg、64.81 mg/kg、151.58 mg/kg,随着土壤深度加深,土壤有机质、全氮、有效磷、速效钾含量呈下降趋势.深度在0~20 cm土壤样品达到《绿色食品产地环境质量》分级标准Ⅰ级、Ⅱ级、Ⅲ级的比例分别为72.73%、27.27%、0,在20~40 cm的比例分别为45.45%、45.46%、9.09%.深度在0~20 cm土壤As、Hg、Cr、Ni、Cu、Zn、Cd、Pb的平均含量分别为19.38、0.18、85.89、29.25、29.72、98.21、0.19、34.53 mg/kg,在20~40 cm平均含量分别为19.44、0.19、81.90、29.29、29.38、99.36、0.16、34.55 mg/kg,土壤不同深度重金属含量差异不大.土壤重金属中高等潜在风险、中等潜在风险、低潜在风险桃园占比分别为9.09%、63.64%、27.27%.所调查桃园有36.36%的土壤检测出抗生素.其中,罗红霉素(ROX)的检出率最高,为27.27%;诺氟沙星(NFC)、恩诺沙星(ENR)、环丙沙星(CFC)、土霉素(OTC)的检出率均为9.09%.抗生素风险评价结果显示,ROX在部分果园污染程度表现为中风险,其他被检出抗生素在被检果园污染程度表现均为低风险. 相似文献
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为提高啤酒花产业的品质和产量,针对于传统人工识别鉴定难度大,效率低和客观性不够,以及啤酒花病虫害识别无大型公开数据集等问题.本文提出一种基于软注意力机制的小样本啤酒花病虫害识别方法,对传统深度残差网络ResNet模型进行改进,并使用图像增强技术-直方图均衡化处理图片得到新的数据集.实验结果表明,在小样本情况下,相比于传... 相似文献
68.
CAO Xian lei HAO Ji ping CAO Zhi min ZHANG Tian guang ZHANG Yao LI Tian ji 《保鲜与加工》2009,(5):1-8
To analyze mechanical behavior of Q460 high strength single angle steel struts with an eccentric load at one end in transmission towers, experimental analysis and theoretical calculation were carried out to study the overall stability and local buckling of members. Spherical hinge bearing and double knife edge bearing were applied at axial end of specimens. Influence of some factors on bearing capacity of compression members with eccentricities at both ends was analyzed, such as the end supporting conditions and residual stresses. It was shown that whether spherical hinge bearing or double knife edge bearing was used at axial end, the mechanical behavior can be accurately presented and the residual stresses affected the ultimate load carrying capacity by about 5% or less. Compared with different methods, such as experiment method、finite element method, method in the Guide for American Design of Latticed Steel Transmission Structure(ASCE101997)and method in Chinese Technical Regulation of Design for Tower and Pole Structure of Overhead Transmission Line (DL/T51542002), it was found that the calculated strength of high strength steel member by standard calculation method in DL/T51542000 was over conservative. According to the research results, the revised formulas of ASCE were proposed with dividing actual material strength by the resistance coefficient of rR=1.111. Therefore, the experimental results can provide reference for designing high strength Q460 single angle steel members compressed eccentrically at one end. 相似文献
69.
Through coupling vibration analysis of the transmission system of a 1.5 MW wind turbine gearbox, a torsional vibration model of a gear drive system in wind turbines is established. The fourth order Runge Kutta integration method is applied to calculate the dynamic response of a gear system caused by wind loads, time varying meshing stiffness, and system damping. The harmonic balance method is used to find the analytic solution. Based on the solution, a mathematical model for optimum gear system design is established. The model aims at minimizing the vibration acceleration of the planet gear and the total mass of the gear transmission system. The optimization toolbox in MATLAB program is adopted to obtain the optimal solution. A calculated example shows that the primary natural frequency of the gear system has been raised, the dynamic properties of the gear train have been improved remarkably, and the total mass of the gear train has been decreased. 相似文献
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The surfaces of the Planar Spiral Antennas and Conical Spiral Antennas are analyzed with planar triangle. The surface currents of the antennas are solved by using the Method of Moment (MoM) based on the RWG basis function. The input impedance, directivity, gain, radiated power and radiation field of the antenna can be found. The results indicate that, in very wide frequency band, the value of the input impedance equals to the theoretical value of Self-Compensated antennas (in agreement with Babinet-booker' principle), which is,188.5 ohm , the half of the wave impedance of free space, while the directivity, gain and radiated power are stable within the frequency band. When the antenna is driven by the signal of derivative Gaussian pulse, the radiating electric field waveform is obtained by the Fourier transform. When the spiral antenna is used as the pulse radiation antenna, the waveform of the radiation electric field shows the characteristics of the Gaussian quadratic differential. 相似文献