Simulation of dissolved nitrogen pollution in Xiaojiang river basin of Three Gorges reservoir     

LONG Tian yu  WU Lei  LIU La mei  LI Chong ming 《保鲜与加工》2009,(10):1181-1186

Xiao Jiang River is the largest tributary on the north of the middle part in Three Gorges reservoir area, because of predominant hilly cropland with purple soil, the dissolved nitrogen from surface and subsurface runoff caused by raining accounts for most part of the nitrogen pollution in water. This paper develops the annual pollution models based on the characteristics of topography and soil, etc., of the basin in order to study dissolved nitrogen pollution, and introduces a Semi distributed Land Use based Runoff Processes (SLURP) hydrological model into the surface and subsurface runoff simulation which is an important part of non point source pollution modeling. Integrated with the geography information system technology, the annual temporal spatial distribution of the dissolved nitrogen in the basin is simulated and the load at the watershed outlet is estimated from 2000 to 2007. The results show that the load from cropland is up to 68.3~76.8of the total load, in which over 85 from croplands and then rural settlement is 23.2~31.7.  相似文献   

Pollution characteristics of mercury in incineration fly ash of municipal solid waste in Three Gorges region     

DING Shi min  LIU Yuan yuan  WANG Li ao  SHEN Yue hui  JIANG Xue mei  FENG Xiang hua  HU Wu hong 《保鲜与加工》2009,(10):1197-1201

This study investigates the mercury distribution characteristics at different particle sizes, leaching characteristics with different impact factor such as the different time, the different ratio of liquid to solid and the different acidity, leaching toxicity and speciation of mercury in Municipal Solid Waste Incineration (MWSI) fly ash in Three Gorges area. The results show that the average content of mercury in the fly ash is 8.52 mg·kg1. The content of mercury in the fly ash is higher at the particle size of 100 μm, and which increases with the decreas of the ash particle size. Mercury leaching content closely relates to environmental conditions. The leaching content of mercury increases with the increase of pH and L/S, while it decreases with the leaching time. The content of mercury at oxidable form and the residue form are high, and whith at exchangeable form and reducible form is relatively low.  相似文献   

A contour extraction algorithm for digital images based on water balloons snake model     

LUO Xiao gang  HUANG Qian  PEN Cheng lin  LIU Ting  YIN Peng  WEN Li  GAO Yun hua 《保鲜与加工》2009,(1):116-120

Due to weak edges and low contrast areas in digital images, such as a left ventricle in Magnetic Resonance Imaging (MRI) images, a deformation curve may leak from the outer boundary when images are segmented using the traditional snake model. An improved algorithm based on the water balloons snake model is introduced to solve this problem. Firstly, the barycenter and the boundary shape area of the left ventricle in a digital MRI image are obtained through mathematical morphology. The left ventricular watershed line is obtained next using a watershed transform algorithm, which is taken as the initial deformation curve in a balloon snake model to capture the contour. Different snake models are tested to digitally tagged MRI images of left ventricles of small pigs. Contrast results indicate that the water balloons snake model can solve the leakage problem in traditional snake and balloon snake models. In addition, the processing speed is improved significantly.  相似文献   

An aeroelastic model design of ultra high voltage power transmission line systems     

LIANG Zheng ping  LI Zheng liang 《保鲜与加工》2009,(2):131-136

We present an aeroelastic model design and method creation based on the case of an ±800 kV ultra high voltage (UHV) power transmission line from Xiang Jiaba to Shanghai, P. R. Chin, Both the centralized and discreted stiffness modeling methods are unsuitable for tower aeroelastic modeling. Taking these stiffness and aerodynamic characteristics into account, we introduce a new method to create an aeroelastic model that includes a semi rigid model segment and U shaped springs. Because the span of this transmission line is too long to fit within the wind tunnel in the same proportions as the tower, the proportions of the line model is condensed further. Aeroelastic test requirements can be satisfied by comparing theoretical analysis and actual measurements of the system model dynamics.  相似文献   

Influence of fine aggregate on initial shrinkage of high performance concrete     

YE Jian xiong  LIAO Jia qing  YANG Chang hui 《保鲜与加工》2009,(2):168-172

The type and percentage of sand affect the gradation of coarse fine aggregate and the amount of spare mortar in concrete, which further affects the resistance of fresh concrete to initial plastic shrinkage. Taking into account the engineering characteristics of sand in the area of Chongqing, P. R. China, three fine aggregates composed of superfine, medium, mixed and manufactured sand, are used to prepare high performance concrete (HPC). The effects of these three fine aggregates on initial plastic shrinkage crack are investigated. The results show that the HPC prepared with superfine sand possesses a higher initial shrinkage value than HPC prepared with mixed or medium sand. An optimal sand percentage is necessary to reduce the initial shrinkage cracking of HPC prepared with mixed or medium sand.  相似文献   

在线式玉米单粒种子检测分选装置设计与试验     

张晗  闫宁  吴旭东  王成  罗斌 《农业机械学报》2022,53(13):159-166

针对农业生产中种子精选的需求,设计了在线式单粒种子检测分选装置,实现流水线式种子上料、检测和分选。该装置由上料装置、检测单元、分选单元和控制系统组成。上料装置通过两级振动实现籽粒的平铺,配合传输带完成籽粒的单粒化。检测单元由高速工业相机实时获取种子图像,并传送至上位机检测分析。控制系统根据检测结果和种子在图像中的位置,控制分选单元完成分选。利用搭建的装置采集了1200粒正常种子、1200粒霉变种子和1200粒破损种子的图像,使用HALCON软件提取了单粒种子的18个颜色和12个形态特征,通过偏最小二乘判别分析法进行判别分析,分别构建了种子霉变和破损的检测模型,并利用搭建的装置和模型进行了验证试验。试验结果表明：在线式单粒种子检测分选装置分选速率大于300粒/min;其中霉变种子的分选准确率高于95%,破损种子分选的准确率高于89%。  相似文献   

微细铣削表面粗糙度预测与试验   总被引：6，自引：0，他引：6  

石文天  刘玉德  王西彬  蒋放 《农业机械学报》2010,41(1):211-215

分别采用正交试验回归分析法和基于正交旋转组合设计的二次响应曲面法(RSM)建立了微细铣削表面粗糙度预测模型,并在微小型车铣中心上对硬铝合金进行了试验研究,分析了铣削参数对表面粗糙度的影响.分别对两种预测模型进行了显著性检验并进行对比分析后发现:二阶响应曲面法的预测精度明显优于正交回归分析法.根据二次响应曲面法的试验结果,对回归方程中的回归系数进行了显著性检验,得出了铣削参数影响表面粗糙度的线性效应、二次效应和交互效应的显著性并进行了排序.试验结果表明:在试验采用的工艺参数范围内,对微细铣削表面粗糙度影响重要程度依次是铣削速度、每齿进给量、切削深度.  相似文献   

基于远程监控的农业气象自动采集系统设计   总被引：4，自引：1，他引：3  

武永峰  宫志宏  刘布春  李茂松  陆明 《农业机械学报》2010,41(10):174-179

针对传统农业气象观测和当前传感器技术系统、方法存在的不足,设计了一套基于远程监控的农业气象自动采集系统,其硬件设备由农田小气候信息采集前端、视频图像信息采集前端、数据采集装置、数据传输装置和供电设备组成。该系统实现了农田小气候和视频图像信息参数采集与传输的高度集成,自动采集降水量、气温、空气湿度、风速、风向、光合有效辐射、土壤温度、土壤湿度和农作物视频图像信息,并通过远程客户端软件实现各要素信息的实时动态显示和远程监控。通过在郑州市、鹤壁市、温江市和荆州市开展的采集试验和系统试运行表明,系统显示出较好的稳定性,农田小气候和视频图像要素数据的采集、传输、动态实时显示与远程监控等各项功能均可满足各级用户需求。  相似文献   

导向管喷动床中煤和稻秸粒混料的流动特性试验     

刘伟民  张建  刘军  王立群  赵如金  赵杰文 《农业机械学报》2010,41(10):107-111

将导向管喷动床改进为煤粒和稻秸粒混料气化设备,通过导向管喷动床内进行的稻秸粒与煤粒混合物料冷态流动特性试验,给出喷动的流体力学条件。研究了床层压降随表观风速的变化规律,稻秸粒和煤粒混合比例、喷口直径和导向管喷口间距3因素对床层压降与表观风速关系曲线的影响以及对物料循环速率与风量关系曲线的影响。进行了3因素12拟水平的均匀设计试验,采用SPSS软件进行回归分析,分别得到了物料循环速率、单位床高压降及单位有效功率的物料循环速率3个因变量各自与稻秸粒和煤粒混合比例、导向管喷口间距及喷口直径3个自变量之间关系的多元回归方程,用于预测稻秸煤粒混料在导向管喷动床中喷动时的流体力学参数。  相似文献   

农产品贮藏设施温控仪表温度漂移控制方法     

张道辉  赵红军  周广芳  宗晓娟  沈广宁  刘庆忠 《农业机械学报》2010,41(6):108-112

选择3种具有代表性的贮藏设施通用温控仪表,检测其温度漂移幅度和方向。根据仪表电路原理并结合测试,进行了针对性电路改进,使温控仪表温漂误差幅度由3.5℃下降到0.3℃,贮藏环境温度波动幅度由5.3℃下降到1.4℃。试验筛选出3种简易温度补偿法,可在不改造仪表电路的前提下抑制温漂。  相似文献