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61.
李晨阳  蒙凤群 《植物保护》2023,49(4):108-114
了解我国松毛虫发生的空间分布格局及其驱动因子, 对松毛虫暴发的预防?控制和治理具有重要意义?本研究基于我国各行政区2004年-2012年间每年松毛虫发生面积及其寄主植物面积, 使用一般线性模型分析气候因子是否以及如何驱动我国松毛虫发生的空间分布格局?结果表明:在全国尺度上, 最暖季降水量是松毛虫发生的主要气候驱动因子, 松毛虫平均发生率与最暖季降水量显著正相关?在最暖季降水量的作用下, 我国松毛虫的发生呈现明显的空间分布格局, 最暖季降水量较高的南方和北方部分地区松毛虫发生率较高, 而降水量较低的西北和青藏地区松毛虫发生率较低?我们的研究结果可为松毛虫暴发的预防和管理工作提供指导?  相似文献   
62.
The associations between feeding activities and environmental variables inform animal feeding tactics that maximize energetic gains by minimizing energy costs while maximizing feeding success. Relevant studies in aquatic animals, particularly marine mammals, are scarce due to difficulties in the observation of feeding behaviors in aquatic environments. This data scarcity concurrently hinders ecosystem-based fishery management in the context of small toothed-cetacean conservation. In the present study, a passive acoustic monitoring station was deployed in an East Asian finless porpoise habitat in Laizhou Bay to investigate potential relationships between East Asian finless porpoises and their prey. The data revealed that porpoises were acoustically present nearly every day during the survey period. Porpoise detection rates differed between spring and autumn in concert with activities of fish choruses. During spring, fish choruses were present throughout the afternoon, and this was the time when porpoise vocalizations were the most frequently detected. During autumn, when fish choruses were absent, porpoise detection rates decreased, and diurnal patterns were not detected. The close association between fish choruses and finless porpoise activities implies an “eavesdropping” feeding strategy to maximize energetic gains, similar to other toothed cetaceans that are known to engage similar feeding strategies. Underwater noise pollution, particularly those masking fish choruses, could interrupt finless porpoises’ feeding success. Fisheries competing soniferous fishes with finless porpoise could impact finless porpoise viability through ecosystem disruption, in addition to fishing gear entanglement.  相似文献   
63.
以乌苏1号无芒雀麦为材料,设置2个生长环境(荒漠绿洲区、高海拔地带),通过观测幼穗分化进程及开花习性,探究生境对无芒雀麦幼穗分化及生殖格局的影响。结果表明,无芒雀麦幼穗分化从分蘖期开始至抽穗期结束,分为初生期、伸长期、结节期、小穗原基分化期、小花原基分化期、雌雄蕊原基分化期、雌雄蕊形成期和完穗期8个时期。幼穗分化是从生长锥顶端第1枝梗原基与小花原基开始分化,相同小枝梗上原基与小花原基均是自下逐渐向上发育;整穗是从顶部向下逐渐开花,下部枝梗开花时间小于上部枝梗;小穗上的小花由下向上逐步开花。与荒漠绿洲区相比,高海拔地带的无芒雀麦幼穗分化时间晚,周期缩短,穗部赤霉素(GA)、脱落酸(ABA)及叶片可溶性蛋白含量相对较高,细胞分裂素(CTK)含量和种子千粒重较低,但高海拔地带单穗成熟种子粒数与单位面积内种子产量高,更适合无芒雀麦种子生产。  相似文献   
64.
试验表明,三道湾水电站原设计存在以下问题:泄洪排沙洞单独全开运行工况下,其进口上方存在贯通性吸气漏斗漩涡;正常溢洪洞进口侧收缩十分严重,泄流量不足,闸后存在水翅、折冲波等不良流态,下游消能效果不佳;针对实际情况,试验通过在泄洪排沙洞进口增设消涡格栅,在正常溢洪洞进口设置椭圆形导墙、延长闸后收缩段,下游采用扩散挑流消能等措施,很好地解决了上述问题。  相似文献   
65.
海河二道闸和防潮闸优化调度研究   总被引:1,自引:0,他引:1  
汛期为腾空海河河道并保证二道闸下咸水不致上溯,二道闸闸下水位应控制在1.0m左右。利用一维非恒定流模型对海河自西河闸至入海口河段进行数值模拟,研究了西河闸分流量为80、100、120m3/s3种情况下,海河防潮闸和二道闸优化调度结果。  相似文献   
66.
In order to analyze the reason why the Spiral Up-flow Reactor system has excellent removal effect of COD, N and P, the authors use PHOENICS, a computational fluid dynamics program, to investigate the hydraulic characteristics and flow model of the anaerobic part of Spiral uP-flow reactor. The result shows that the fluid in the reactor unit flowed upward by the spiral way, and that flow pattern was combined by plug flow and complete-mix flow, and that the percentage of plug flow was about sixty-five percent. Spiral Up-flow Reactor units the Characteristics of PFR and CSTR, which makes it work well.  相似文献   
67.
68.
This paper studies the tactics choice and its improvement in the development of economy by means of Markovian Decision Programming. An optimal decision and the maximum expected revenue can be obtained. The . paper also presents the procedures and formulas of numerical evaluation.  相似文献   
69.
According to the character of PD in GIS, the authors design four kinds of GIS defection models. The GIS gray intensity images are constructed based on mass specimens gathered by the ultra - high frequency and high speeds systems, Aiming at the PD characteristics and its defections, A PCA-FDA method is put forward based on PD images. The principal component analysis is employed to condense the dimension of PD images, then the optimal sets of statistically uncorrelated discriminant vectors are extracted, and the minimum distance classifier is constructed as classifier. The identified results show that this method can effectively elevated the discrimination of the four kinds of defects in GIS PD.  相似文献   
70.
In this paper, a kind of grey linear programming with grey interval coefficients is discussed,the definitions of the first and second whitenized linear programmlngs and the grey dual linear programmings are presented, the relationships between the solutions of the above three kinds of programming and the solution of the primal programming are explored, and some new conclusions are obtained.  相似文献   
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