园林种植容器的发展及应用现状     

谷亚琴  马涛 《安徽农业科学》2016,(11):184-185

综述了国内外园林种植容器的发展史及应用现状,并总结出园林种植容器的设计要素及应用原则,最后对种植容器的发展进行展望。  相似文献   

Simulation of future dissolved oxygen distribution in pond culture based on sliding window-temporal convolutional network and trend surface analysis     

《Aquacultural Engineering》2021

Dissolved oxygen (DO) is a key ecological factor to measure the quality of water in the aquaculture. As the pond water body is affected by the breeding environment, the spatial distribution of DO shows a certain law in the entire pond. Therefore, to simulate the distribution of DO in aquaculture waters and grasp the temporal and spatial variation of DO is the key to achieving precise regulation of DO. For this purpose, this paper proposed a method for simulating the temporal and spatial distribution of DO in pond culture based on a sliding window-temporal convolutional network together with trend surface analysis (SW-TCN-TSA). This paper first utilized SW to construct DO data sets with different prediction durations, and then used the improved TCN model to realize one-dimensional time series prediction for DO at single monitoring point. Based on the prediction results of DO, a TSA method was performed on the predicted values of DO at the extreme moments of all discrete monitoring points, so as to realize the simulation of the temporal and spatial distribution of DO in the pond. Experimental results show that the SW-TCN model has better prediction performance for one-dimensional time series prediction of DO. Compared with traditional deep networks, such as CNN, GRU, LSTM, CNN-GRU and CNN-LSTM, the values of evaluation indicators (MSE, MAE and RMSE) have been greatly improved. In the process of trend surface fitting, all fitting R² of DO at different water depths are higher than 0.9, indicating that the TSA can accurately reflect the temporal and spatial distribution of DO. This method can provide a basis for the prediction and early warning of DO in the three-dimensional space of the pond and has high practicability in aquaculture.  相似文献   

金融时间序列指标判别框架：以特质波动率为例     

汤胤  毛景慧 《湖南农业大学学报(自然科学版)》2016,(3):35-39

基于拐点集合判别的TBUD方法主要思路是分析拐点集合间的关系，并在高维空间进行划分，从而搭建判别模型，并将分析框架应用在特质波动率等若干指标上，利用实证数据得到结论。应用TBUD判别框架可以发现，特质波动率等指标无法对拐点集合进行清晰划分，因而并不具有预测能力。  相似文献   

冀、京、津产麦区小麦赤霉病菌原体形成期的气象要素演变特征与分析   总被引：1，自引：0，他引：1  

袁淑杰 梁平武文辉  徐大红杨昌银韩俊玲  李智慧 《华北农学报》2007,22(B10):220-224

根据河北省、北京市、天津市22个代表站1960—2000年逐日平均气温、降雨量、相对湿度以及日照时数等资料，运用统计学方法，分析了京、津、冀地区小麦赤霉病菌原体形成期各相关气象因子的年际、年代际变化及空间分布。结果表明，日平均气温≥12℃日数大部地区呈弱增加趋势，降雨量和雨日呈减少趋势，中部以南地区的日照条件向降低小麦抗病能力的方向转化；贴近度分析表明，塘沽一天津一保定以南地区秋季小麦赤霉病菌原体形成期的气候条件是最适宜或适宜小麦赤霉病发生。  相似文献   

自吸泵研究现状及发展趋势   总被引：3，自引：8，他引：3  

吕智君  兰才有  王福军 《排灌机械》2005,23(3):1-5

自吸泵广泛用于喷灌、消防等场合。全面总结和分析了自吸泵的发展史，归纳了自吸泵自吸时间和最大自吸高度的计算模型，总结了自吸性能影响因素研究现状，介绍了回流孔大小、位置的计算公式，以及隔舌间隙及泵内储水容积和气液分离室容积的控制；阐明了轴封的气密性、吸入管路的气密性、浸入液面下的管路深度和入口管路的容积这些外部因素对自吸性能的影响机理；指出了自吸泵进一步发展的趋势和方向，为后续研究工作提供了指导性建议。  相似文献   

户营小型拖拉机难以更新的机理探讨     

陈秉钧  陈丽能 《农业机械学报》1994,25(2):92-97

在分析农户使用、更新小型拖拉机经济行为的基础上，推证并建立了户营小型拖拉机的作业成本随使用年限增加而变化的规律，进一步提出户营小型拖拉机在作业量充足条件下的“成本均等理论”和在作业量欠充足条件下的“成本递减理论”，并通过实地采样加以验证。据此阐述了户营小型拖拉机难以更新的机理，得出在经济欠发达地区户营小型拖拉机基本上不存在最佳更新期的结论。  相似文献   

Transferring water from irrigation to higher valued uses: a case study of the Zhanghe irrigation system in China     

R. Loeve  B. Dong  L. Hong  C. D. Chen  S. Zhang  R. Barker 《Paddy and Water Environment》2007,5(4):263-269

The Zhanghe irrigation system (ZIS) is located in the Yangtze River Basin approximately 200 km west of Wuhan in Hubei Province. The reservoir was designed for multiple uses—irrigation, flood control, domestic water supply, industrial use, aquaculture, and hydropower. Over a period of more than 30 years a steadily increasing amount of water has been transferred from irrigation to other uses. Activities on the part of government, irrigation system managers, and farmers made this transfer possible with only modest decline in rice production. Most important factor was the steady increase in rice yields. The water pricing system provided an incentive for ZIS to reduce irrigation releases. With the steady decline in releases, farmers were forced to find ways to save water. Farmers improved existing ponds and built new ones to store water (improved infrastructure). Access to pond water on demand facilitated the adoption of alternate wetting and drying (technology) particularly in dry years. The establishment of volumetric pricing (price policy) and water user associations (institutions) may also have provided incentives for adoption of AWD, but more research is needed to establish their impact. These activities taken together can be seen as potentially complementary measures. Farmers received no direct compensation for the transfer of water, but recently farm taxes have been reduced or altogether abolished. Further reduction in water releases from the ZIS reservoir could adversely affect rice production in normal or dry years.  相似文献   

潮土区土壤有机质含量的趋势演变研究——以禹城市为例   总被引：10，自引：1，他引：10  

杨玉建  杨劲松 《土壤通报》2005,36(5):647-651

通过分析山东省禹城市100个采样点1980年和2003年耕层土壤的有机质含量,研究了土壤有机质的时空变异特征,探讨了潮土区有机质含量的变化,形成了研究区1980年和2003年有机质含量空间分布图及1980~2003年有机质含量的空间变化图。分析了研究区有机质含量增加的原因。研究结果表明,该市目前土壤有机质含量平均为14.68g kg-1,比1980年的6.0g kg-1增加了8.68 g kg-1,年均提高0.38g kg-1。土壤表层含盐量的降低为土壤养分含量提高提供了条件。  相似文献   

基于农业气象模型的农作物单产预测系统   总被引：7，自引：1，他引：7  

范锦龙  孟庆岩  吴炳方  周心铁 《中国农业气象》2003,24(2):46-48,51

基于农作物单产可以分解为趋势产量和气象产量的原理。采用面向对象的开发方法，在Windows 32位操作系统环境下，用VB与MO作为开发工具，成功开发了Client／Server结构的农作物单产预测系统。系统将数据库技术、组件化GIS技术集成在一起，各模块之间实现了无缝连接。系统运行表现出良好的性能。  相似文献   

我国生物质能源发展现状与思考   总被引：30，自引：5，他引：30  

吴创之  周肇秋  阴秀丽  易维明 《农业机械学报》2009,40(1):91-99

分析了我国生物质能源技术的现状、发展趋势和存在问题,提出了发展对策和建议.我国生物质资源开发以有机废弃物和利用边际性土地种植的能源植物作为主要原料来源,从长远看,能源农业和能源林业是未来发展生物质能源的基础.我国生物质能现代技术研究和应用起步较晚,目前的开发利用总体水平较低,各种技术的成熟度和商业化水平极不均衡,必须坚持自主开发与引进消化吸收相结合的技术路线,充分掌握相关的核心技术,在一些关键性技术上取得突破.发展生物质能产业,我国应当走原料与产品多元化的道路,针对不同的技术路线和工艺过程,加强多学科交叉研究.  相似文献