基于信任算法的分布式农产品交易系统设计

针对分布式农产品交易系统里的主机和网络通信容易受到安全威胁的现状,提出一种基于信任的安全算法.首先,使用移动代理对用户交易记录进行综合统计并计算出行为信任值;然后对用户反馈进行分析筛选,计算出推荐信任值;最后对各种信任值进行分析,得出综合信任值.使用该算法的分布式农产品交易系统运行正常,能较好地保障网络交易安全.     

重庆市不同规模灌区农灌水有效利用系数测算与对比研究

通过对重庆市不同规模灌区农田灌溉用水有效利用系数计算结果的比较研究,对出现的中型灌区农田灌溉用水有效利用系数大于小型灌区的结果进行合理性分析,并为重庆市农田灌溉用水有效利用系数的进一步提高,提出相关建议,为政府相关部门的科学决策提供参考.综合考虑重庆的地形、气候、土壤等因素.根据选定灌区的实测数据,采用首尾测算法计算2017年重庆市不同规模灌溉农田灌溉水的有效利用系数,采用单因素和主成分分析法,分析影响农田灌溉水有效灌溉系数的主要因素. 1)通过测算, 2017年重庆市中型灌区农田灌溉水有效利用系数为0.499,小型灌区为0.487,推算全市为0.495; 2)在影响农田灌溉水有效利用系数的主要因素中,当地的节水工程和管理状况所占的比例大于自然因素; 3)中型灌区在节水工程的投资、管理和维护等方面均优于小型灌区; 4)自然因素中,降水量对农田灌溉水有效利用系数具有一定的负面影响.     

Early pathogen detection under different water status and the assessment of spray application in vineyards through the use of thermal imagery

Remote detection using thermal imagery has potential for use in the pre-symptomatic diagnosis of abiotic stress or of early disease detection. The latter is an issue of great importance since late detection of fungus attacks or poor spray coverage are major factors contributing to weak disease control affecting fruit quality or reducing yield in grapes. In greenhouse experiments the effects on spatial and temporal variability of leaf temperature of grapevine (Vitis vinifera L. cv. Riesling) leaves inoculated with a fungal pathogen (Plasmopara viticola (Berk. & Curt. Ex de Bary) were studied in either well-irrigated or non-irrigated potted plants. Due to the high sensitivity of leaf temperature to the amount of water transpired, infra-red thermography can be used to monitor irregularities in temperature at an early stage of pathogen development. Evidence for characteristic thermal responses in grapevines was apparent well before visible symptoms appeared. Contrasting thermal effects due to the pathogen attack were found between measurements on well-irrigated and water-stressed plants. Furthermore, from a technical point of view, thermal imagery has the potential to assess the evenness of spray coverage within a canopy, hence optimizing pesticide application efficiency.     

基于上部叶片SPAD值估算小麦氮营养指数

快速、准确的监测诊断小麦氮营养状态对于评价小麦长势、指导氮肥运筹并预测籽粒产量均具有重要的意义.基于2009-2011年的大田试验,系统分析了小麦上部4张单叶不同叶位的SPAD值和归一化SPAD指数(NDSPADij)与氮营养指数的定量关系,通过简单分组线性回归筛选出在不同年际和不同品种间表现稳定的氮营养指数(NNI)定量方程.结果表明,小麦上部不同叶位SPAD值和NNI随施氮量提高而提高,而NDSPADij随施氮量的提高而降低.小麦单叶SPAD值与NNI的关系呈显著正相关,但这种关系在品种或年份之间不稳定,对小麦氮素诊断存在风险;除NDSPAD12外,NDSPADij与NNI之间呈显著负相关,经简单分组线性分析发现NDSPAD14与NNI之间在年份和品种之间表现最稳定,能够较好的定量估算氮营养指数,从而快速诊断小麦氮素是否亏缺.     

基于水印技术的大容量信息隐藏算法研究

为了在普通的通信环境中传递保密信息,提出了基于水印嵌入技术原理的信息隐藏算法。算法设计中以模运算为基础,将待隐藏的信息嵌入至原始图片的DCT系数中,采用率失真最优化的分析方法,控制信息隐藏过程中对原始图片的变形影响,尽可能地在一个图片中嵌入更多的隐藏信息。经过测试分析表明:在视觉允许的失真条件下,每个DCT数据块可以嵌入1个字节的数据量。     

基于模糊专家系统的鱼疾病诊断方法

为实现鱼疾病的快速高效诊断,根据鱼疾病的模糊特性,建立多层次的知识库,并采用正向推理和反向推理相结合的模糊推理机。该系统采用Visual Basic6.0进行编程,在Windows2000平台上运行,其友好的人机交互操作界面,使鱼病诊断更为容易、形象、直观。     

基于图像规则的玉米病害诊断系统的设计与实现

针对传统病害诊断系统在病症推理过程中借助语言文字描述规则诊断病害让农户难以理解和应用的问题,将图像指认方法与传统文字规则推理技术相结合,建立的病害诊断系统更适合于农户使用,并改善了专家系统的应用效果,利于其在玉米生产中的应用。介绍了基于图像规则的玉米病害诊断系统的设计思想、功能特点和实现方法。     

用生物素标记寡核苷酸DNA探针快速检测鱼传染性胰脏坏死病病毒IPNV

研究了用生物素标记的寡核苷酸ＤＮＡ探针快速检测鱼传染性胰脏坏死病病毒ＩＰＮＶ，取得了较好的结果。对探针的灵敏度，特异性进行了灵敏度、特异性进行了测定，并与其它快速检测技术作了比较。     

Quantification of Flavobacterium psychrophilum in rainbow trout, Oncorhynchus mykiss (Walbaum), tissues by qPCR

A qPCR assay was developed for rapid and sensitive detection of Flavobacterium psychrophilum, the aetiological agent of bacterial cold-water disease and rainbow trout fry syndrome in salmonid fish worldwide. A set of F. psychrophilum-specific primers based on 16S rRNA gene sequences was designed and validated for specific detection and quantification of DNA isolated from representative strains of F. psychrophilum. The qPCR assay exhibited a high specificity for the 16S rRNA gene of F. psychrophilum (from 4 × 10(8) down to 11 copies per reaction) but not for other Flavobacterium species or other bacteria including fish pathogens. This qPCR-based method proved to be useful in the quantification of the F. psychrophilum titre present within organs dissected out from diseased fish. As the F. psychrophilum genome contains six copies of the 16S rRNA gene, we could infer a limit of detection corresponding to two bacteria per reaction, corresponding to 800 bacteria per fish tissue sample, and therefore 20 F. psychrophilum cells mg(-1) of tissue (for sample weighing 40 mg). The qPCR assay reported here could be a useful tool for veterinary diagnostic laboratories to monitor the F. psychrophilum infection level in fish farms.     

Antibody-coated gold nanoparticles immunoassay for direct detection of Aeromonas salmonicida in fish tissues

Aeromonas salmonicida is the causative agent of furunculosis, a disease that affects both salmonid and non‐salmonid fish. Detection of A. salmonicida can be labour intensive and time consuming because of the difficulties in distinguishing the bacterium from other species given the wide variety of existing biochemical profiles and the slow growth characteristics which allow other organisms to overgrow the A. salmonicida. Herein, we report the development of a specific immunoassay using gold‐conjugated polyclonal antibodies for the rapid detection of A. salmonicida in fish tissues. Monodispersible 13‐nm gold nanoparticles were coated with polyclonal antibodies specific to A. salmonicida. Reddish purple agglutination of gold particles indicated the presence of A. salmonicida in samples. Positive reactions were detected visually with the naked eye. No agglutination was observed when A. salmonicida antibody‐coated gold nanoparticles were tested with other common bacterial fish pathogens, thereby verifying the specificity of the assay. The assay could detect A. salmonicida in fish tissues down to 1 × 10⁴ CFU mL^?1, and results were obtained within 45 min. The antibody‐coated gold nanoparticles were stable for at least 2 months at 4°C. The immunoassay using antibody‐coated gold nanoparticles represents a promising tool for the rapid and specific detection of A. salmonicida in fish tissues.