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71.
The problem of scale in community resource management 总被引:1,自引:0,他引:1
Jefferson Fox 《Environmental management》1992,16(3):289-297
Scale is a fundamental variable in most community resource management programs. This is true both in terms of scale as a management
concept (i.e., local, regional, and national level management) as well as a mapping concept (i.e., units on the map per unit
on the ground). Julian Steward, the father of human ecology, recognized as early as 1950 that social scientists have failed
to develop methods for incorporating the effect of scale in their work. This article seeks to determine whether methods used
in plant and animal ecology for assessing the effects of scale are applicable to community resource management. The article
reviews hierarchy theory and multiple scales, two methods (one theoretical and the other practical) for dealing with problems
that span many scales. The application of these methods to community resource management programs is examined by way of an
example. 相似文献
72.
Thomas J. Wilbanks Jayant Sathaye 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):957-962
Integrating mitigation and adaptation (M&A) is a practical reality for climate change response policy, despite a range of
conceptual and methodological challenges. Based on the papers in this special issue, some preliminary findings about appropriate
integrated portfolios are offered, along with several implications for climate policy. 相似文献
73.
Fenton法处理卫生填埋渗滤液——从模型放大到中试的问题初探 总被引:4,自引:0,他引:4
在中试厂中进行了Fenton法处理卫生填埋渗滤液的试验,以检验根据小试结果得出的统计模型。对三种不同渗滤液的试验发现,COD去除率与模型推出的几种最佳操作条件无关,三种渗滤液的COD去除率分别为35.0±2.2%、42.1±1.0%及50.6±5.6%。这表明不仅中试结果和模型预测(>80%)之间存在较大的差异,而且不同渗滤液的处理程度也存在一定的差异,其中一个原因是各种渗滤液的组分各有差异,因此不能用一种渗滤液的处理结果去预测其它渗滤液。而中试时较低的反应温度是造成试验结果和模型之间存在差异的另一个原因。 相似文献
74.
H. Chanson 《Environmental Fluid Mechanics》2009,9(2):125-142
In hydraulic structures, free-surface aeration is commonly observed: i.e., the white waters. The air bubble entrainment may
be localised (hydraulic jumps, plunging jets) or continuous along an interface (water jets, chutes). Despite recent advances,
there are some basic concerns about the extrapolation of laboratory results to large size prototype structures. Herein the
basic air bubble entrainment processes are reviewed and the relevant dynamic similarities are discussed. Traditionally, physical
studies are conducted using a Froude similitude which implies drastically smaller laboratory Reynolds numbers than in the
corresponding prototype flows. Basic dimensional analyses are developed for both singular and interfacial aeration processes.
The results are discussed in the light of systematic investigations and they show that the notion of scale effects is closely
linked with the selection of relevant characteristic air–water flow properties. Recent studies of local air–water flow properties
highlight that turbulence levels, entrained bubble sizes and interfacial areas are improperly scaled based upon a Froude similitude
even in large-size models operating with the so defined Reynolds numbers ρ
w × q
w/μ
w up to 5 E+5. In laboratory models, the dimensionless turbulence levels, air–water interfacial areas and mass transfer rates
are drastically underestimated. 相似文献
75.
76.
介绍了腐殖酸钠(HAS)的阻垢机理,研究了HAS在石灰石湿法烟气脱硫系统中的阻垢效应,同时在相同的条件下与己二酸的阻垢效果作了对比实验.结果表明,HAS对pH在5.5~6.5、质量分数为3.5%的石灰石脱硫浆液有很好的缓冲作用;并在此浓度的脱硫浆液中,质量浓度为1.5g/L的HAS的阻垢效果达到最佳.石灰石浆液中挂片上的结垢量对比实验得出,添加最佳浓度己二酸时的结垢量,只比添加最佳浓度HAS时的结垢量平均少1.8×10-4g/cm2. 相似文献
77.
Work engagement, as conceptualized by the Utrecht Work Engagement Scale (UWES), is a work-related positive state of mind that is characterized by vigour, dedication and absorption; however, it still remains unclear how many dimensions work engagement comprises. This study tested the factorial validity of 11 different UWES factorial models that are available in the literature using a confirmatory factor analysis approach on a large sample of multi-occupational Polish employees (N?=?1420). The two-factor UWES-6, comprising vigour and dedication, was found to be reliable and remained invariant across samples drawn from four different organizational positions. It also presented a better fit than the three-factor UWES-9, which is a scale used as a standard in contemporary research on work engagement. The findings suggest that the three-factor UWES-9 might not be an optimal measure of work engagement in Poland. 相似文献
78.
Miaomiao Fan Linjun Li Jinsuo Lu Heliang Pang Zhiqiang Zhang Jing Yang Pengpeng Li Xiaoyu Yan 《环境科学学报(英文版)》2023,35(2):901-914
Scale not only affects the taste and color of water, but also increases the risks of osteoporosis and cardiovascular diseases associated with drinking it. As a popular beverage, tea is rich many substances that have considerable potential for scale inhibition, including protein, tea polyphenols and organic acids. In this study, the effect of tea brewing on scale formation was explored. It was found that the proteins, catechins and organic acids in tea leaves could be released when the green tea was brewed in water with sufficient hardness and alkalinity. The tea-released protein was able to provide carboxyl groups to chelate with calcium ions (Ca2+), preventing the Ca2+ from reacting with the carbonate ions (CO32−). The B rings of catechins were another important structure in the complexation of Ca2+ and magnesium ions (Mg2+). The carboxyl and hydroxyl groups on the organic acids was able to form five-membered chelating rings with Ca2+ and Mg2+, resulting in a significant decrease in Ca2+ from 100.0 to 60.0 mg/L. Additionally, the hydrogen ions (H+) provided by the organic acids consumed and decreased the alkalinity of the water from 250.0 to 131.4 mg/L, leading to a remarkable reduction in pH from 8.93 to 7.73. It further prevented the bicarbonate (HCO3−) from producing CO32− when the water was heated. The reaction of the tea constituents with the hardness and alkalinity inhibited the formation of scale, leading to a significant decrease in turbidity from 10.6 to 1.4 NTU. Overall, this study provides information to help build towards an understanding of the scale inhibition properties of tea and the prospects of tea for anti-scaling in industrial applications. 相似文献
79.
Simone?Ciuti Sara?Davini Siriano?Luccarini Marco?ApollonioEmail author 《Behavioral ecology and sociobiology》2004,56(6):552-564
Large-scale spatial segregation was assessed by means of radio-telemetry in 48 fallow deer studied for 4 years. Three hypotheses have traditionally been used to explain sexual segregation: (1) the predation risk hypothesis, (2) the forage selection hypothesis, (3) the activity budget hypothesis. The first of these seems to be a valid explanation of large-scale segregation in fallow deer at San Rossore, where the use by the two sexes of areas characterized by intense anthropic disturbance, during the day, was compared with other areas not affected by human pressure. Males showed a high use of disturbed areas, both during the day and the night, with the exception of the rutting period, when they reached more remote areas to mate. Females frequented disturbed areas only during the night, with the exception of the birth period, when sexual segregation peaked because females never used these areas, not even during the night. The forage selection hypothesis was invalid on a large scale, considering that no differences between the degree of day and night sexual segregation were to be expected. However, the predation risk hypothesis seems not to be a valid explanation of small-scale sexual segregation, when further subdivisions of disturbed areas are considered, because sexes proved to be segregated also during the night in the area they both used. This emphasizes both the importance of scale in understanding ecological processes, since a combination of many different factors may be responsible for the evolution of sexual segregation in ungulates, and the importance of human pressure in influencing deer behaviour.Communicated by T. Czeschlik 相似文献
80.
讨论了化工废石膏在矿物掺合物、粉煤灰、激发剂、外加剂等存在时,在不同配比下的力学性能、凝结时间、溶蚀率、软化系数和体积稳定性,并分析了该材料水化、硬化规律,硬化体结构及与性能的关系,试验结果表明,化工废石膏掺加量的多少将直接影响到各项性能指标,采用复合早强减水剂,对于粉煤灰活性激发,及加速胶结材料凝结水化、降低用量,有显著效果。 相似文献