排序方式: 共有29条查询结果,搜索用时 15 毫秒
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森林冠层地面叶面积指数光学测量方法研究进展 总被引:7,自引:1,他引:6
作为表征植被冠层结构的核心参数之一,叶面积指数(LAI)控制着植被冠层的多种生物物理和生理过程,如光合、呼吸、蒸腾、碳循环、降水截获、能量交换等.本文首先阐述了森林冠层地面LAI光学测量方法的理论基础和数学模型;其后介绍了目前主流光学测量方法的测量原理及其优缺点;归纳了LAI光学测量方法的主要误差来源(聚集效应、非光合作用组分、观测条件和地形效应),并分析总结了聚集效应、非光合作用组分和地形效应的定量评估现状;最后展望了森林冠层地面LAI光学测量方法的未来发展方向. 相似文献
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Optimal experimental design is important for the efficient use of modern highthroughput technologies such as microarrays and proteomics. Multiple factors including the reliability of measurement system, which itself must be estimated from prior experimental work, could influence design decisions. In this study, we describe how the optimal number of replicate measures (technical replicates) for each biological sample (biological replicate) can be determined. Different allocations of biological and technical replicates were evaluated by minimizing the variance of the ratio of technical variance (measurement error) to the total variance (sum of sampling error and measurement error). We demonstrate that if the number of biological replicates and the number of technical replicates per biological sample are variable, while the total number of available measures is fixed, then the optimal allocation of replicates for measurement evaluation experiments requires two technical replicates for each biological replicate. Therefore, it is recommended to use two technical replicates for each biological replicate if the goal is to evaluate the reproducibility of measurements. 相似文献
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肉用性能表型特征直接决定了羊肉的产量和品质,肉用相关性状鉴定技术的进步有助于挖掘优异肉羊种质资源,培育优良肉羊品种,促进肉羊遗传改良.目前,肉用性能表型鉴定方法多以人工测量方式为主,存在耗时、费力、低通量等不足.随着机器视觉、光谱成像、人工智能等前沿技术的进步,肉用性能表型鉴定方法已向非接触式自动测量模式转变,逐渐实现了表型高通量精准鉴定.同时,数据信息量大、图像算法处理复杂等问题成为智能表型鉴定方法的重要挑战.本文主要介绍了羊肉用性能表型鉴定内容以及表型鉴定方法现状,以期为合理选用羊肉用性能表型鉴定方法提供参考. 相似文献
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现代口腔医学中人体头面部测量方法 总被引:5,自引:1,他引:4
本文对现代口腔医学中所使用的人体头面部测量方法,包括三维坐标测量、立体摄影测量、云纹影象测量,X线头影测量等原理和应用予以简介。这些近年来随计算机技术发展而出现的新的测量方法,使传统的颅测量和面部测量大大改观。 相似文献
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全球气候变化与森林生态系统碳循环息息相关,定量评估森林碳收支是生态系统与全球变化研究的重要任务。30年来森林生态系统碳循环研究已经取得了长足的进展,但全球和区域森林碳收支仍然存在很大的不确定性。这一方面与森林生态系统本身的复杂性有关,另一方面也与具体研究方法有关。评述了森林生态系统碳循环的基本概念和主要野外测定方法,为我国森林生态系统碳循环研究提供可参考的方法论。从生态系统碳浓度、密度、通量、分配和周转5个方面回顾了碳循环相关概念,指出碳浓度和碳储量是对碳库的静态描述,而碳通量和碳周转是对碳库的动态描述。净初级生产力是测量最普遍的碳通量组分,但大多数情况下因忽略了一些细节而被系统低估。普遍使用的净生态系统生产力,由于没有包含非CO2形式的水文、气象和干扰过程产生的碳通量,通常情况下高于生态系统净碳累积速率。在详细介绍碳通量组分的基础上,改进了森林生态系统碳循环的概念模型。重点讨论了碳通量的3种地面实测方法:测树学方法、箱法和涡度协方差法,并指出了其注意事项和不确定性来源。针对当前碳循环研究的突出问题,建议从4个方面减小碳循环测定的不确定性:(1)恰当运用生物量方程估算乔木生物量;(2)尽可能全面测定生态系统碳组分;(3)给出碳通量估算值的不确定性;(4)多种途径交互验证。 相似文献
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Application of Non-invasive Microsensing System to Simultaneously Measure Both H^+ and O2 Fluxes Around the Pollen Tube 总被引:3,自引:0,他引:3
Yue Xu Tong Sun Li-Ping Yin 《植物学报(英文版)》2006,48(7):823-831
Various Ionic and molecular activities in the extraceUular environment are vital to plant cell physiological processes. A noninvasive microsensing system (NMS) based on either the scanning ion-selective electrode technique (SIET) or the scanning polarographlc electrode technique (SPET) is able to obtain information regarding the transportation of various Ions/molecules in Intact samples under normal physiological conditions. The two-probe simultaneous test system (2STS) Is an Integrated system composed of SIET, SPET, and a Xu-Kunkel sampling protocol. In the present study, 2STS was able to simultaneously measure fluxes of H^+ and O2 of the Uly (Lillum Iongiflorum Thunb. cv. Ace) pollen tube while avoiding interference between the two probes. The results Indicate that the proton fluxes were effluxes, whereas the oxygen fluxes were Influxes, and they were closely correlated to each other surrounding the constitutive alkaline band region. Specifically, when the proton effluxes increased, the oxygen Influxes also increased. Therefore, the hypothesis of condensed active mitochondria existing in the alkalized area of the pollen tube proposed by Hepler's group is supported. 相似文献