排序方式: 共有31条查询结果,搜索用时 15 毫秒
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全面对电镜真空系统的检查、分析,证实扩散泵向镜筒返油导致DXB2—12型速射电镜高真空故障,通过采用延时电路制止扩散泵油返入镜筒,排除了电镜高真空故障。 相似文献
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利用相关性分析法选取了影响可燃物含水率变化的影响因子和延迟时间,同时说明气温、相对湿度和风速等影响因子对可燃物含水率变化的影响有滞后性,并通过微分方程理论推导,建立了具有时滞的可燃物含水率预测模型,给出了模型中各影响因子的取值范围。结果表明:所建模型的精度达到96.0%,说明在研究森林可燃物含水率变化规律时考虑时滞因素是正确的。 相似文献
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采后热空气处理对金冠苹果后熟衰老及病害的影响 总被引:2,自引:1,他引:2
金冠苹果采用38℃,72h或96h热空气处理,可降低0℃贮藏中果实的呼吸强度和乙烯释放量,延缓非溶性果胶的降解,维持较高的硬度、脆度,同时也会加速果皮的褪绿变黄和固酸比的上升,尤其是38℃96h处理的作用效果更为明显,显著提高了货架期后(20℃7d)苹果的质地品质和可接受程度,延缓衰老。苹果分别接种扩展青霉、灰葡萄孢霉,0℃和20℃条件下其病害发生率和腐烂均很严重,采用38℃96h热空气处理可以完全控制病害的发生,避免腐烂。可见,热空气处理一方面能延缓金冠苹果的后熟衰老,另一方面还能控制贮期病害的发生。 相似文献
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[目的]控制连翘、迎春的花期,满足晚春木本切花需求。[方法]选取枝条至少在10个花蕾以上的迎春、连翘当年生枝做切枝(20~25cm长)和冷藏(0~2℃)处理,通过低温冷藏延迟迎春和连翘的花期,研究迎春、连翘切枝冷藏延迟开花的技术措施,提高开花质量和效果。[结果]经过冷藏处理,迎春、连翘切枝的开花期延迟了1个月,迎春冷藏1~30d效果比较好,连翘冷藏1~20d效果比较好。迎春花期持续时间长,而连翘开花时间集中。冷藏后的花期曲线大都呈单峰曲线状态。冷藏5~25d的开花效果比较好。[结论]连翘、迎春含苞枝条在0~2℃冷藏5~25d后可以正常开放。 相似文献
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This study investigated whether four horses could recall the location of a food objective in a two-choice delayed response test. During testing, horses stood unrestrained in a station where they observed the delivery of 30 g of grain into one of two containers. They were then released and allowed to go toward a container under the following contexts: immediate release or delayed release of 5, 10, 15, 20, or 30 seconds. Results showed that horses remembered the correct objective not only under the immediate release condition but also for all delayed release conditions tested. Observational data were also collected to determine whether the horses were indeed relying on memory to solve the delayed response problems or whether they were using orienting cues to maintain focus on the correct container. These data showed that the horses did not maintain visual contact with the objective during many of the trials; instead, they attended to an assortment of distractions in the surrounding area. Contrary to a previous report in which horses could not accurately respond in a similar situation after 10-second delays, these findings suggest that at least some horses are not as limited with respect to their ability to recall things and have an adequate spatial short-term memory. Experimental design seems to play a significant role in the outcome of this type of research. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(8):835-853
Abstract Mixed opinions exist on the effect of organic matter on nitrification in soils as well as the lack of data on the effect of fulvic (FA) and humic (HA) acids on this biochemical process. This in vitro investigation was conducted to study the effect of FA and HA on oxidation of NH+ 4 and NO‐ 2 by soil nitrifiers and on the delay period (t') and maximum nitrification rate (Kmax). Soil extracts containing an ammonium‐oxidizer population were incubated in vitro for 3 weeks at 25C in the presence of (NH4)2SO4and 0 to 320 mg FA or HA/L at pH 7.0 or 8.0. A similar experiment was conducted with soil extracts containing a nitrite‐oxidizer population, but with KNO2 as the N source. An additional experiment was conducted with the nitrite‐oxidizer extracts for the determination of t’ and Kmax values. Nitrite production tended to increase linearly as a result of FA and HA treatments from 0 to 320 mg/L at pH 7.0 or 8.0. Fulvic acid appeared to be more effective than HA in increasing the oxidation process. Differences in pH had only a slight effect. On the other hand, nitrate production was decreased linearly by FA or HA treatments from 0 to 320 mg/L which provided some justification for reports of lower nitrate, but higher nitrite concentrations in soils high in organic matter content. Humic acid treatments increased the delay period (t1), and at the same time decreased the maximum nitrification rate (Kmax). The latter suggests that in the presence of HA more time is required to reach a maximum nitrification rate. 相似文献
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以滞量为参数,讨论昼夜节律起搏器模型线性部分特征方程根的分布情况,得到该系统的稳定性和Hopf分支产生的条件。研究了时滞昼夜节律起搏器模型的动力学性质,为时间生物学的应用提供理论依据。 相似文献