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31.
32.
水平台阶式丰水梨冠层结构特点及其与果实品质的关系 总被引:2,自引:0,他引:2
以大冠疏散分层形为对照,连续多年对丰水梨采取水平台阶武整形修剪,应用W inSCANOPY2005a冠层分析仪研究了该树形的冠层结构特点,分析了与其品质的关系,结果表明:水平台阶式丰水梨的冠层开度、树冠下散射光合光量子通量密度、平均叶倾角均显著高于疏散分层形;树冠下直射光合光量子通量密度和总光合光量子通量密度分别是疏散分层形的1.83和1.76倍;而水平台阶式梨叶面积系数极显著低于疏散分层形.水平台阶式丰水梨果实平均单果重、可溶性固形物、总糖、糖酸比值分别比疏散分层形的高23.39%、20.20%、18.75%和29.78%;总酸低8.50%. 相似文献
33.
电子示波器是常用的电子测量仪器,它可以用来测量各种电信号的电压、电流、周期、频率、相位等参量.电子示波器也是调试、检验、修理和制作各种电子仪表设备时所不可缺少的工具.因此,示波器在生产、科研、教育等各部门都有广泛的应用.本文就示波器在实验中的基本测量进行简要的介绍. 相似文献
34.
Stuart W. Bunting 《Aquaculture International》2008,16(2):153-169
Horizontal integration represents a technically viable opportunity for aquaculture producers to reduce environmental impacts
whilst apparently enhancing production efficiency and gaining from economies of integration. Despite significant research,
pilot-scale developments and recommendations advocating adoption by producers, uptake has been limited. Consequently, research
was undertaken, invoking the iterative Delphi methodology, to explore consensus amongst a multidisciplinary stakeholder panel
concerning the nature and significance of constraints and opportunities associated with horizontal integration. Round 1 participants
(n = 24) submitted 84 and 94 statements identifying constraints and opportunities, respectively, within physical, environmental,
managerial, institutional, economic and social subcategories; aggregating similar statements produced 29 distinct constraints
and 27 opportunities for subsequent evaluation. Friedman’s randomised block analysis indicated similar rank patterns (P < 0.001, two-tailed) in the distribution of weights assigned to opportunities and constraints by panel members after round
3. Kendall’s coefficient of concordance (W) indicated that agreement on constraints was ‘strong’ and confidence in rank patterns ‘high’; agreement was ‘very strong’
and confidence ‘high’ to ‘unusually high’ concerning opportunities. Agreement within subcategories ranged from ‘unusually
high’ for physical and environmental constraints and opportunities to ‘moderate’ for institutional and social constraints.
Economic, physical and managerial constraints were ranked highest, as compared with environmental and physical opportunities.
These findings confirm that constraints and opportunities associated with horizontal integration are multifaceted and that
a multidisciplinary, systems-based approach to aquaculture development is critical. Furthermore, the stakeholder Delphi constitutes
a promising approach to facilitating constructive dialogue and consensus-building amongst diverse, antagonistic and hierarchical
stakeholder groups frequently associated with aquaculture development. 相似文献
35.
全面推进农村饮水安全工程建设,保证农村居民的饮水安全是关系农村可持续发展、城乡一体化建设的重要举措.该文在详细了解国内农饮工程水泵机组布置现状的基础上,结合蒙城县立仓镇的工程实例,对水泵机组的布置优化提出新的建议. 相似文献
36.
Éric Niqueux Jean-Paul Picault Michel Amelot Chantal Allée Josiane Lamandé Carole Guillemoto Isabelle Pierre Pascale Massin Guillaume Blot François-Xavier Briand Nicolas Rose Véronique Jestin 《Veterinary microbiology》2014
EU annual serosurveillance programs show that domestic duck flocks have the highest seroprevalence of H5 antibodies, demonstrating the circulation of notifiable avian influenza virus (AIV) according to OIE, likely low pathogenic (LP). Therefore, transmission characteristics of LPAIV within these flocks can help to understand virus circulation and possible risk of propagation. This study aimed at estimating transmission parameters of four H5 LPAIV (three field strains from French poultry and decoy ducks, and one clonal reverse-genetics strain derived from one of the former), using a SIR model to analyze data from experimental infections in SPF Muscovy ducks. The design was set up to accommodate rearing on wood shavings with a low density of 1.6 ducks/m2: 10 inoculated ducks were housed together with 15 contact-exposed ducks. Infection was monitored by RNA detection on oropharyngeal and cloacal swabs using real-time RT-PCR with a cutoff corresponding to 2–7 EID50. Depending on the strain, the basic reproduction number (R0) varied from 5.5 to 42.7, confirming LPAIV could easily be transmitted to susceptible Muscovy ducks. The lowest R0 estimate was obtained for a H5N3 field strain, due to lower values of transmission rate and duration of infectious period, whereas reverse-genetics derived H5N1 strain had the highest R0. Frequency and intensity of clinical signs were also variable between strains, but apparently not associated with longer infectious periods. Further comparisons of quantitative transmission parameters may help to identify relevant viral genetic markers for early detection of potentially more virulent strains during surveillance of LPAIV. 相似文献
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38.
紫茎泽兰(Eupatorium adenophorum Spreng)是一种外来入侵物种,干枯的紫茎泽兰植株具有较好的易燃性,并且紫茎泽兰植株枯死期正是昆明地区的森林防火期,对森林防火具有重要的影响。在昆明周边的林区内进行外业调查、采集紫茎泽兰样品,并在可控条件的实验室内利用热电偶等测定紫茎泽兰的燃烧火行为特征(包括点燃时间、辐射热、火焰高度和蔓延时间等)。结果表明:(1)垂直燃烧的平均点燃时间、蔓延时间和火焰最大高度都大于水平燃烧(31、1 s;3.50、1.67 min;300、120 cm)。(2)水平燃烧的平均火焰最高温度大于垂直燃烧(761、611℃);(3)水平燃烧和垂直燃烧的平均热辐射没有明显差异。紫茎泽兰水平燃烧和垂直燃烧时的温度高,释放能量大,热辐射强,是地表火垂直转换为树冠火的重要介质,也是地表火水平快速蔓延的通道。紫茎泽兰垂直燃烧的火灾危险性较大,且燃烧后具有较大发生复燃的可能性。应在防火期来临前对紫茎泽兰进行清除,以减少森林火灾发生的频率和强度。 相似文献
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40.
从产业链角度分析我国生猪养殖业发展趋势 总被引:1,自引:0,他引:1
分析了猪肉食品产业链上的各个环节,在整条产业链中考虑提高生猪养殖业产业化和集中度的问题。并且以国外经验为借鉴,结合我国实际情况,分析生猪养殖业整合的主体和方式。 相似文献