1989—2018年国内作物连作障碍研究现状 ——基于CNKI的文献计量学分析和科学知识图谱研究

为介绍国内作物连作障碍的研究进展,基于1989—2018年中国知网数据库(CNKI)中连作障碍相关发文情况,通过文献计量学方法分析文献的年代、期刊、机构、基金、作者、研究对象和主题分布等基础信息,并采用CiteSpace V软件对关键词进行科学知识图谱研究.结果表明,连作障碍文献数量总体上与年度变化呈明显正相关关系;受...     

网络环境下专家与农民对接平台建设

专家如何与农民进行常年对接,一直是困扰农业科技服务业的一大难题。文章提出利用因特网建立专家与农民对接平台,突破地域、时间限制,及时解决农业生产难题。     

Gas exchange, biomass partition, and water relationships of three grass seedlings under water stress

Three grass species, switchgrass ( Panicum virgatum ), foxtail millet ( Setaria italica ), and Old World bluestem ( Bothriochloa ischaemum ), referred to as introduced, traditional, and indigenous species, respectively, in the Loess hilly gully region on Loess Plateau in China, were grown in a growth chamber. Water was withheld to let the soil gravimetric moisture content (SGMC) decline gradually from 14.92% for 15 days. The gas exchange characteristics, leaf water conditions, root and shoot growth, and water use efficiency (WUE) of the three grasses were compared. The SGMC of foxtail millet declined faster than that of switchgrass and Old World bluestem, and it maintained higher leaf water potential at a lower soil water content, indicating that it might have greater drought tolerance. During the process of soil drying, the stomatal conductance (Gs), photosynthesis rate, and transpiration rate (Tr) of foxtail millet and Old World bluestem declined linearly, whereas those of switchgrass declined parabolically. The Gs of each grass was significantly different between the stressed and well-watered (WW) conditions. When the SGMC declined to ≈ 11.0%, 9.5%, and 8.6%, respectively, the leaf water potential was significantly different between the two growing conditions, showing the appearance of non-hydraulic and hydraulic signals. As a result of greater stomatal adjustment ability and a smaller Gs, foxtail millet had a high WUE. Among the three grasses, switchgrass had a high Tr and root/shoot (R/S) ratio under both WW and stressed conditions, and water stress significantly improved its R/S ratio. The results showed that foxtail millet seedlings have the best drought adaptability in the flexible soil–water environment, whereas switchgrass seedlings have the worst, but a high R/S ratio might be advantageous under drought conditions once the seedlings are established.     

Grazing every month minimizes size but boosts photosynthesis in Stipa grandis in the steppe of Inner Mongolia,China

In order to explore the effects of grazing frequency on functional traits and to test whether Stipa gandis has compensatory photosynthesis during the frequent grazing period, we investigated morphological traits, biomass allocation, photosynthetic traits, and chlorophyll fluorescence parameters of the species in Inner Mongolia, China. The grazing frequency treatments included fencing(T_0), grazing in May and July(T_1, i.e., two months per year) and grazing from May to September(T_2, i.e., continuous five months per year). Results indicate that T_1 and T_2 treatments did not affect individual biomass, but T_2 treatment negatively affected individual size, i.e., plant height, stem length, and leaf length. Physiological traits of S. grandis were significantly affected by grazing, year, and their interaction. In July 2014(i.e., dry environment and low relative humidity), the photosynthetic rate, transpiration rate and water use efficiency were highest under T_2 treatment, which was caused by the increase in stomatal conductance. However, in July 2015(i.e., wet environment and high relative humidity), the photosynthetic rate and water use efficiency were higher under T_1 and T_2 treatments, which were caused by the increase in actual quantum efficiency and stomatal conductance. Our results implied that under frequent grazing treatment, S. grandis had small height and efficient compensatory photosynthesis, which promoted its resistance to severe grazing.     

具有余热回收功能的旋风分离器性能的数值分析

旋风分离器能够去除工业废气中的固体颗粒,但排出的气体仍然有大量余热,为了回收利用废气的余热,实现节能减排的目的,在旋风分离器壁面外侧安装不同直径换热管,并且通过数值模拟对比分析旋风分离器在安装不同直径换热管前后的分离效率和换热效果.研究结果表明:安装直径80,100 mm的换热管对旋风分离器的内流场影响较小,与无换热管...     

面向烘烤工艺的知识图谱构建与应用研究

为解决烟叶烘烤工艺知识存在多源、异构等问题,有效利用和管理烘烤工艺知识,可借助知识图谱的知识互联组织功能对烘烤工艺知识进行整合及可视化。通过结合烘烤工艺的知识特点以及需求,经过本体构建、数据收集、知识抽取、知识融合和知识存储等环节,初步构建了面向烟叶烘烤工艺的知识图谱。在此基础上进行应用研究,包括烟叶烘烤实体识别和智能问答,从而形成一个面向烟叶烘烤工艺领域的知识平台。研究结果验证了烟叶烘烤工艺知识图谱构建和应用的可行性。     

黏粒阳离子交换量估测模型的优化研究

为了优化土壤黏粒阳离子交换量估测模型,提升估测结果准确性,为土壤系统分类检索提供可靠数据支持,以江西省土壤为主要研究对象,根据有机质、粉粒阳离子交换量对现有估测模型的影响,将有机质含量低于6 g·kg–1的土壤样本定为低有机质样本,高于6 g·kg–1的土壤定为高有机质样本开展分类建模.高有机质样本中主要误差因子为有机...     

磁力搅拌法改进土壤阳离子交换量测定的研究

针对传统土壤阳离子交换量测定方法中的玻璃棒搅拌所存在的分析效率低的问题,开展了运用磁力搅拌替代玻璃棒搅拌的探索性研究。通过平行性实验、条件实验、实验室间对比和不同黏粒含量土壤的CEC测定结果检验,分析了磁力搅拌法的精准度、可操作性、稳定性和适用性。结果表明,磁力搅拌法测定土壤CEC的准确度、精密度均不低于甚至高于玻璃棒搅拌方法,土壤CEC测定值与土壤标准物质认定值吻合。当搅拌时间在1 min、搅拌速度850 r·min^–1以上时,延长搅拌时间和提高搅拌速度对分析结果无影响。不同实验室间测定结果相关性好、没有显著性差异。相比传统的玻璃搅拌法,磁力搅拌法具有操作简单、高效,测定结果稳定性好、精准度高等优点,非常适用于大批量土壤CEC的测定。     

高校图书馆实施知识管理的基本原则和策略

知识管理已经成为现代高校图书馆实行管理变革的重要理论指南.但高校图书馆实施知识管理,应该在遵循相应原则的基础上,制定详细的实施策略,并按部就班、循序渐进地进行.     

德庆贡柑生产知识库建设

文章通过分析国内外农业生产知识库研究现状和德庆贡柑产业发展需求,提出了德庆贡柑生产知识库的建设,并从知识库系统体系结构确定、贡柑知识获取和知识库知识分类等方面展开论述。贡柑生产知识库的建设,为提高贡柑生产效益、实现标准化生产、提升贡柑品质和增加果农经济收入等方面具有重要的意义。