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51.
机器视觉技术在精细农业中的研究进展 总被引:2,自引:0,他引:2
精细农业以节约投入、增加产出、提高投入物利用率、减少环境污染为目的.快速、准确地采集各种农田信息,有效地监测农业对象是实施精细农业的重要基础.机器视觉技术由于其非破坏性、精度高、成本效率高、信息量大、灵活等特点,在精细农业中得到了广泛的应用.为此,通过对大量参考文献进行分析,发现机器视觉在精细农业中的主要研究方向集中在农业机械自动导航、作物生长信息检测、变量控制等方面.同时,对机器视觉技术在上述领域中的研究情况进行分析和总结,并讨论了未来机器视觉技术在精细农业中应用存在的问题以及发展前景. 相似文献
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L.S. Pereira M.J. Calejo N. Lamaddalena A. Douieb R. Bounoua 《Irrigation and Drainage Systems》2003,17(4):305-324
Low-pressure pipe distribution systems forsurface irrigation provide both off- andon-farm recognized environmental benefits.However, expected benefits can only beattained when adequacy, dependability andequity of systems are high enough tosupport appropriate conditions for wateruse on the farm. An innovative methodologyfor design and analysis is proposed anddescribed, which includes the generation ofthe demand at the scale of the distributionsystem and, consequently, the generation ofthe flow regimes expected during a givenperiod of time, generally the peak month.These flow regimes are utilized for theoptimization of pipe sizes using theiterative discontinuous method for severalflow regimes. The performance analysis isdeveloped through the system simulationwith several flow regimes, which allow thecomputation of the system adequacy,dependability and equity. An application toone sector of the Sorraia irrigation systemillustrates the usefulness of themethodology proposed. 相似文献
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介绍了黑龙江垦区的几个发展阶段,分析了改革前垦区农业机械状况,指出了改革后星区农业机械化的发展方向。 相似文献
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选择了4种家鱼作指示生物,用紫外分光光度法测定其白肌中RNA和DNA的含量。结果表明:同种鱼,污染区的RNA含量显著低于对照区,白鲢和鳊鱼白肌中RNA/DNA低于对照区;不同种的鱼,污染区鱼肌核酸比对照区下降的程度有鳊鱼>白鲢>鲫鱼和鲤鱼的趋势。鱼肌核酸下降同水体重金属污染有一定联系,RNA是比RNA/DNA更合适的指标,鳊鱼和白鲢是比鲫鱼和鲤鱼更敏感的指示生物。 相似文献
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The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in cross-section, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar. 相似文献
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The dispersal ecology of most stream fishes is poorly characterised, complicating conservation efforts for these species. We used microsatellite DNA marker data to characterise dispersal patterns and effective population size (Ne) for a population of Roanoke logperch Percina rex, an endangered darter (Percidae). Juveniles and candidate parents were sampled for 2 years at sites throughout the Roanoke River watershed. Dispersal was inferred via genetic assignment tests (ATs), pedigree reconstruction (PR) and estimation of lifetime dispersal distance under a genetic isolation‐by‐distance model. Estimates of Ne varied from 105 to 1218 individuals, depending on the estimation method. Based on PR, polygamy was frequent in parents of both sexes, with individuals spawning with an average of 2.4 mates. The sample contained 61 half‐sibling pairs, but only one parent–offspring pair and no full‐sib pairs, which limited our ability to discriminate natal dispersal of juveniles from breeding dispersal of their parents between spawning events. Nonetheless, all methods indicated extensive dispersal. The AT indicated unrestricted dispersal among sites ≤15 km apart, while siblings inferred by the PR were captured an average of 14 km and up to 55 km apart. Model‐based estimates of median lifetime dispersal distance (6–24 km, depending on assumptions) bracketed AT and PR estimates, indicating that widely dispersed individuals do, on average, contribute to gene flow. Extensive dispersal of P. rex suggests that darters and other small benthic stream fishes may be unexpectedly mobile. Monitoring and management activities for such populations should encompass entire watersheds to fully capture population dynamics. 相似文献
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Multiple watershed alterations influence fish community structure in Great Plains prairie streams 下载免费PDF全文
Joshuah S. Perkin Matthew J. Troia Dustin C.R. Shaw Joseph E. Gerken Keith B. Gido 《Ecology of Freshwater Fish》2016,25(1):141-155
Stream fish distributions are commonly linked to environmental disturbances affecting terrestrial landscapes. In Great Plains prairie streams, the independent and interactive effects of watershed impoundments and land cover changes remain poorly understood despite their prevalence and assumed contribution to declining stream fish diversity. We used structural equation models and fish community samples from third‐order streams in the Kansas River and Arkansas River basins of Kansas, USA to test the simultaneous effects of geographic location, terrestrial landscape alteration, watershed impoundments and local habitat on species richness for stream‐associated and impoundment‐associated habitat guilds. Watershed impoundment density increased from west to east in both basins, while per cent altered terrestrial landscape (urbanisation + row‐crop agriculture) averaged ~50% in the west, declined throughout the Flint Hills ecoregion and increased (Kansas River basin ~80%) or decreased (Arkansas River basin ~30%) to the east. Geographic location had the strongest effect on richness for both guilds across basins, supporting known zoogeography patterns. In addition to location, impoundment species richness was positively correlated with local habitat in both basins; whereas stream‐species richness was negatively correlated with landscape alterations (Kansas River basin) or landscape alterations and watershed impoundments (Arkansas River basin). These findings suggest that convergences in the relative proportions of impoundment and stream species (i.e., community structure) in the eastern extent of both basins are related to positive effects of increased habitat opportunities for impoundment species and negative effects caused by landscape alterations (Kansas River basin) or landscape alterations plus watershed impoundments (Arkansas River basin) for stream species. 相似文献