Incidence and timing of wild and escaped farmed Atlantic salmon (Salmo salar) in Norwegian rivers inferred from video surveillance monitoring

Run timing of escaped farmed Atlantic salmon Salmo salar vs. wild fish was compared by the use of video camera surveillance in 15 rivers over several years, covering 1600 km of the Norwegian coastline (from 58°N to 69°N). Annual runs of wild salmon varied among rivers from <200 fish to more than 10 000. During the surveillance period that for most rivers extended from late May to early October, larger‐sized salmon (fish ≥ 65 cm) generally entered the rivers earlier than small fish. The percentage of salmon identified as escaped farmed fish ranged from 0.1% to 17% across rivers with an average of 4.3%. Estimates of escapees are, however, assumed to represent minimum values because an unknown number of farmed fish passing the video cameras may have been misclassified as wild fish. By the use of a linear mixed model and generalised additive mixed models, it was found that the relationship between run timing and fish length differed significantly between farmed and wild salmon. While small‐sized farmed and wild fish (<65 cm) entered the river at about the same time, wild large salmon returned on average 1–2 weeks earlier than similarly sized escapees. The proportion of large‐sized farmed escapees also increased until late August and decreased thereafter. In contrast, there was a relatively constant and lower proportion of small‐sized escapees throughout the season. Within the surveillance period, there was no evidence of any exceptionally late runs of fish classified as escaped farmed salmon.     

逻辑经验主义何以产生及其实质

逻辑经验主义的产生是西方哲学史上的一次伟大转变,并成为现代科学哲学的发轫之端。其出现与整个西方哲学的发展紧密相关,是存在论传统发展到当时历史阶段而形成的一种伟大的哲思。逻辑经验主义的产生旨在寻求世界确定性的实质。     

基于茎直径变化的作物水分状况监测研究进展

对“利用茎直径变化监测作物水分”的研究进行了综述。自20世纪60年代开始,基于茎直径变化的作物水分状况监测指标体系研究经历了两个阶段,即茎直径变化与作物水势关系的定性研究阶段;考虑环境变化和植株正常生长的茎直径变化—作物水势之间动态量化阶段。此方法通过对作物体内水分的动态监测,并与计算机应用相配合,可以用于温室和大田条件下指导适时灌溉。     

Effect of Nitrogen Application Timing and Cutting Treatments on Phenology and Leaf Area of Three Brassica Cultivars

Brassica has potential as a grain and grazing option for mixed farming operations. The objectives of this experiment were to determine suitable nitrogen (N) application timing and Brassica cultivar for use as a dual-purpose crop. The field experiment was conducted at the Agricultural Research Farm of the Agricultural University, Peshawar, Pakistan, during winter 2009–2010 in a randomized complete block design with split-plot arrangement. The experiment consisted of three cultivars, three N application timings, and cutting treatments. Plant height and leaf area were greater at two and three split N applications. Likewise, leaf area was greater for N when applied in two split applications. Brassica cultivar Abasin-95 quickly emerged and attained more leaf area and leaf area index when compared to NIFA Raya and Dure-e-NIFA. Abasin-95 and Dure-e-NIFA took fewer days to mature when compared to NIFA Raya. NIFA Raya produced taller plants. Cutting significantly affected all parameters except days to maturity. Early flowering, taller plants, and greater leaf number, area, and leaf area index were noted for no-cut plots when compared to cut plots.     

Effects of fertilizer timing and placement on grain yield and leaf nutrients of sole‐crop cowpeas (V. unguiculata) in Sierra Leone

Abstract

Effects of fertilizer timing and placement on the grain yield and leaf nutrients of uninoculated sole‐crop cowpeas in two experiments during the minor cropping season on Njala upland soil of Sierra Leone were studied. Timing and placement and their interaction had no significant effects on grain yield. Placement affected highly significantly lamina Mg, Cu and Co and significantly lamina N and Ca. Placement and timing x placement interaction affected highly significantly petiole N and petiole P respectively. Timing affected highly significantly petiole N, which decreased as fertilizer application was delayed. The spectrum of nutrient distribution in both lamina and petiole was decidedly different. Multiple regression studies indicated that variability in only petiole Mg, Cu and Co significantly contributed to grain yield variability. By the introduction of 15 nutrients (6 lamina and 9 petiole) after examining the linear regression coefficients into a composite multiple regression study, lamina Ca, petiole Fe and petiole Co were selected as significant contributors to grain yield variability with marked improvement in R². Removal of the effects of the correlated variables produced significances in the effects of fertilizer placement and timing x placement interaction on grain yields.     

基于OPTIMUS的柴油机配气正时及喷油提前角的优化

柴油机的配气正时与喷油提前角对其性能影响很大,最佳的匹配参数能够形成缸内良好的空燃比及较佳的燃烧效率,从而获得较高的动力性及较低的燃油消耗率。为得到不同工况下配气正时与喷油提前角的最佳组合,该文将增压直喷柴油机工作过程的SIMULINK仿真模型导入OPTIMUS多学科优化平台;以进气迟后角和排气提前角以及喷油提前角为优化设计变量,以柴油机的经济性和动力性为设计目标进行优化计算。额定工况下该发动机的优化结果是:进气迟后角为42°CA,排气提前角为60°CA,喷油提前角为16°CA。仿真和试验结果表明:模型设计合理准确,优化后柴油机动力性和经济性均有所改善,该研究可为柴油机的改进和优化提供参考。     

交叉口的信号优化与仿真

以减小车均延误为目标,在调查交叉口交通流量和当前信号控制的基础上,采用韦伯斯特配时算法进行优化计算,并通过通行能力、交通流量比等指标来确定信号周期时长和各相位绿灯时间,改善相位饱和度,从而充分利用道路的通行能力。以建设大道新华路交叉口为例,基于实际数据对优化前后的交叉口利用vissim软件进行仿真,结果表明,优化后各相位的饱和度较优化前更为平均,没有出现很高或很低的极端情况,优化后的车均延误明显改善。     

时间序列分析关键问题研究

简要介绍了时间序列的定义、模型及型态,重点研究了时间序列分析的相关内容,最后对其未来发展方向进行了展望。     

玉米植株冠层遥感技术揭示N缺乏的空间变异特征

To evaluate the temporal patterns in N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with various rates (56, 112, and 168 kg N ha-1), timing (early and late applications) and placement (injected into soil and dribbled on soil surface) of N fertilization in a split-plot design. Relationships between canopy reflectance during the growing season and yield data at the end of growing season were studied for different treatments. Results showed significant variation in both grain yields and canopy reflectance among the three cornfields. The N fertilization made in early June resulted in low canopy reflectance in early July, but the differences disappeared as the season progressed. The effect of N rates on canopy reflectance was not significant in early July but it gradually became detectable in mid-July and thereafter. The fertilizer placement had a significant effect on grain yields only in one field but not on canopy reflectance in all three fields. These observations suggest that the deficiency of N developed under field conditions is a dynamic phenomenon, which adds complexity for accurately defining “N deficiency” and effectively developing management strategies for in-season correction. Remote sensing throughout the season helps collect information about important interactions that have not been given enough attention in the past.     

车用发动机性能影响因素研究

介绍了数值模拟技术在发动机研究过程中的重要作用,以捷达前卫发动机为基础,应用GT-POWER软件建立了发动机工作过程模型,通过实验验证了该模型的可靠性.在此基础上对配气正时进行了模拟计算,计算结果表明在高转速时适当增大进气迟闭角对提高发动机的性能有利,与理论分析一致.