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Thomas Welch Gillespie Stephanie Pincetl Shea Brossard Jenny Smith Sassan Saatchi Diane Pataki Jean-Daniel Saphores 《Urban Ecosystems》2012,15(1):233-246
There has been an increasing interest in the evolution of urban forests. This research uses historic and digital aerial photography
to quantify changes in tree density in Los Angeles, California since the 1920’s. High-resolution geographic information system
analysis (4 to 6 time periods) of three regions (San Fernando Valley, Hollywood, Los Angeles Basin) of Los Angeles reveals
that there has not always been an increase in tree density with time. Tree densities on public and private land were highest
in the 1940’s in Hollywood, while the San Fernando Valley and Los Angeles Basin experienced a near linear increase in tree
density on both private and public land since the 1920’s. When historic tree density reconstructions were examined for the
15 Los Angeles city council districts from the 1920’s, 1950’s and 2006, most districts in Los Angeles have experienced a significant
increase in tree density, however, there has been wide variation in tree densities among city council districts. Trees densities
have generally been higher on private land since the 1920’s and currently tree densities on private land are significantly
higher than on public land. Results suggest the evolution of urban forests in Los Angeles mirrors the dynamics of urban forests
in desert and grassland cities. It is possible to reconstruct the development of urban forests in sections of cities using
historic and contemporary aerial photography. We estimated that Los Angeles averages approximately 104 trees per hectare (82
private land, 22 public land) based on 2006 imagery at 0.3 m resolution, however, field validation suggests that we identified
only 73% of trees. Although there is still space to plant trees on public land, private land owners will need to be heavily
involved in order to achieve the goals of Los Angeles’ Million Tree Initiative. 相似文献
3.
Quantifying urban forest structure,function, and value: the Chicago Urban Forest Climate Project 总被引:22,自引:4,他引:18
McPherson E. Gregory Nowak David Heisler Gordon Grimmond Sue Souch Catherine Grant Rich Rowntree Rowan 《Urban Ecosystems》1997,1(1):49-61
This paper is a review of research in Chicago that linked analyses of vegetation structure with forest functions and values. During 1991, the regions trees removed an estimated 5575 metric tons of air pollutants, providing air cleansing worth 9.2 million. Each year they sequester an estimated 315 800 metric tons of carbon. Increasing tree cover 10% or planting about three trees per building lot saves annual heating and cooling costs by an estimated 50 to 90 per dwelling unit because of increased shade, lower summertime air temperatures, and reduced neighborhood wind speeds once the trees mature. The net present value of the services trees provide is estimated as 402 per planted tree. The present value of long-term benefits is more than twice the present value of costs. 相似文献
4.
Urban forest fragments can potentially be ‘habitat islands’ for native birds, but pedestrian traffic could influence the composition
and conservation value of their bird assemblages by reducing the representation of disturbance-sensitive species. Winter bird
assemblages and pedestrian traffic rates were documented in twelve forested parks in suburban Melbourne, Australia. Native
birds comprised 87% of sightings, but two exotic species were common. Bird species' distribution among the parks was significantly
nested. However, park rank orders for bird assemblage nestedness and mean pedestrian traffic rate were not correlated and
only one species' distribution was nested with respect to this variable. The observed correlation between park area and bird
assemblage nestedness may have been partly due to passive sampling. Degree of isolation of parks influenced nestedness less
than park area. Forested parks provided habitat for species that occur at intermediate to low densities in other suburban
habitats and for ecological specialists otherwise rare in suburbia. Larger parks contained more species than, and many of
the native species found in, smaller parks. However, smaller parks each had 25% of the native bird species inhabiting the
suite of fragments and thus had both aesthetic value and some potential to enhance city-dwellers' awareness about biodiversity
conservation. 相似文献
5.
Kevin A. Harrigan Mike Dixon 《Journal of gambling studies / co-sponsored by the National Council on Problem Gambling and Institute for the Study of Gambling and Commercial Gaming》2010,26(1):159-174
In Ontario, Canada, the regulator approves identical looking slot machine games with different payback percentages. We gained
access to the design documents (called PAR Sheets) used to program these different versions of the same slots game and ran
Gambler’s Ruin simulations of 2,000 first-time players who each arrived with a $100 bankroll and played either the 85 or 98%
version of the same game until broke. Simulations revealed that the typical (median) player’s experience did not differ significantly
between versions. However the payback percentage affected the experience of players in the upper tails of the distributions
with those in the 98% version having dramatically more total spins, winning spins, entries into the “bonus mode”, and “hand
pays” (a win of $100 bankroll and played either the 85 or 98%
version of the same game until broke. Simulations revealed that the typical (median) player’s experience did not differ significantly
between versions. However the payback percentage affected the experience of players in the upper tails of the distributions
with those in the 98% version having dramatically more total spins, winning spins, entries into the “bonus mode”, and “hand
pays” (a win of 125 or more on a given spin). Most importantly, the number of simulated players who had a maximum peak balance
in excess of $1,000 rose tenfold—from 5 in the 85% version to 54 in the 98% version. The results are discussed in terms of
the Pathways Model of Problem and Pathological Gambling especially in terms of behavioural conditioning, cognitive beliefs,
and early big wins. It may well be that those machines that are on the surface the “fairest” to the gambler, actually pose
the most risk for ensuing gambling problems. 相似文献
6.
Masashi Umezawa 《Social Choice and Welfare》2012,38(2):211-235
This article considers the provision of two public goods on tree networks where each agent has a single-peaked preference.
We show that if there are at least four agents, then no social choice rule exists that satisfies efficiency and replacement-domination. In fact, these properties are incompatible, even if agents’ preferences are restricted to a smaller domain of symmetric
single-peaked preferences. However, for rules on an interval, we prove that Miyagawa’s (Soc Choice Welf 18:527–541, 2001) characterization that only the left-peaks rule and the right-peaks rule satisfy both of these properties also holds on the
domain of symmetric single-peaked preferences. Moreover, if agents’ peak locations are restricted to either the nodes or the
endpoints of trees, rules exist on a subclass of trees. We provide a characterization of a family of such rules for this tree
subclass. 相似文献
7.
Richard J. Smithers Kieron J. Doick Aaron Burton Raphael Sibille David Steinbach Rachel Harris Lisa Groves Malgorzata Blicharska 《Urban Ecosystems》2018,21(5):851-862
Increasing urbanisation poses numerous challenges to human quality of life. Cities are particularly vulnerable to the urban heat-island effect, which will be amplified by climate change. Increasing tree cover may be one of the most cost-effective ways of moderating urban temperatures. Trees cool their surroundings by casting shade, reflecting solar radiation, transpiring, and intercepting rainfall that subsequently evaporates. However, the potential of trees to reduce the urban heat-island effect is underutilised. The aim of this study was to synthesise understanding of the relative abilities of different tree species to provide urban cooling in temperate regions of the world and thereby develop a pragmatic approach for choosing those trees that have greatest potential in that regard. Based on a literature review and semi-structured interviews with leading experts, we developed a series of scenarios to illustrate the impacts of a tree’s cooling mechanisms and tree species’ attributes on components of the surface-energy balance equation. This enabled us to select parameters and propose simple equations that can be used to compare the relative abilities of tree species in relation to each of the cooling mechanisms. The parameters selected were for: transpiration – crown diameter, Leaf Area Index (LAI), canopy aspect ratio, and stomatal conductance or growth rate; reflection – albedo, crown diameter and LAI; shading – canopy aspect ratio, crown diameter, LAI and tree height. The approach is intended for use by urban planners and managers who wish to make informed decisions about which tree species to select for planting to counter the urban heat-island effect. 相似文献
8.
Excess exposure to ultraviolet radiation (UV) from the sun, particularly the ultraviolet B (UVB), is cited as a cause or contributing factor for deleterious effects on human health, including skin cancers and cataracts. Rates of skin cancer have increased greatly in recent years, and increased UVB caused by reductions in stratospheric ozone may be responsible for some of the increase in rates, though quantified estimates of the effect of the UVB changes on health have low certainty. UVB exposure also affects the function of the immune system, and the potential resulting effects on infectious diseases and immunizations are a concern. Epidemiological considerations suggest that peoples' routine exposure to UV in urban areas can be significant in adverse health effects, particularly for young children. Projected trends of ozone indicate that agreements to limit ozone-depleting substances are slowing the UVB increase, but high levels will continue and apparently impact health to the middle of the current century. Urban trees greatly reduce ultraviolet irradiance in their shade when they obscure both the sun and sky. Where trees or other structures obscure only the sun, leaving much of the sky in view, UVB irradiance will be greater than suggested by the visible shade. Since air pollutants influence the UVB above the canopy, and the overlying atmosphere is usually more polluted in urban than rural areas, additional above-canopy monitoring of UV in urban areas is needed for comparison to existing rural monitoring sites. Such monitoring would facilitate the development of computer models of urban effects on UV, which are needed for epidemiological investigations, public education, and urban planning. 相似文献
9.
We examined the relationship between bat species activity and composition and the extent of forest cover and urbanization
in and adjacent to 11 U.S. National Park Service, National Capital Region Parks in Maryland, Virginia, West Virginia, and
Washington, D.C., from 2003–2004, using mist nets, harp traps, acoustical detectors, and visual observations in a variety
of habitats. Our efforts included 363 trap nights across 74 sites along with acoustical sampling at 362 sites. We captured
383 bats and identified 6,380 echolocation passes of 6 species. Both overall and species-specific activities were affected
more by forest fragmentation within parks than by urbanization adjacent to parks. With an ability to exploit anthropogenic
structures for day-roosts, big brown bats (Eptesicus fuscus) were the most ubiquitous and probably the most abundant species in NCR Parks, particularly in forested, urban parks. Northern
myotis (Myotis septentrionalis), and to a lesser extent, little brown myotis (Myotis lucifugus) were more prevalent in forested, rural parks of the Ridge and Valley and Blue Ridge than in eastern, less forested urban
parks of the Piedmont and Coastal Plain physiographic provinces. Retention of larger, residual forest tracts and day-roosting
habitat (i.e., trees and snags) would be beneficial to most species, as urban expansion continues throughout the region. 相似文献
10.
Gary Dean Jaworski 《The American Sociologist》1990,21(3):209-216
Within the context of a discussion of Robert K. Merton’s ideas on leadership in postwar America, the article examines the
nature and impact of Merton’s “sociological parables.” This term refers to short tales from social life from which sociological
lessons with moral implications can be drawn. These parables, such as the bank insolvency story told in “The Self-Fulfilling
Prophecy,” illustrate the manner in which Merton merged moral and sociological messages in his writings. Suggestions are made
along the lines that these parables, or at least the moral messages they contain, contributed to Merton’s postwar fame.
His most recent publications are “Simmel’s Contribution to Parsons’ Action Theory and Its Fate,” in Michael Kaern, ed.Georg Simmel and Contempory Sociology (Kluwer, 1990); and “Robert K. Merton’s Extension of Simmel’sUbersehbar” inSociological Theory, Spring 1990. 相似文献
11.
Geometric models of consistent judgement aggregation 总被引:1,自引:1,他引:0
Marcus Pivato 《Social Choice and Welfare》2009,33(4):559-574
Given a set of propositions with unknown truth values, a ‘judgement aggregation function’ is a way to aggregate the personal
truth-valuations of a group of voters into some ‘collective’ truth valuation. We introduce the class of ‘quasimajoritarian’
judgement aggregation functions, which includes majority vote, but also includes some functions which use different voting
schemes to decide the truth of different propositions. We show that if the profile of individual beliefs satisfies a condition
called ‘value restriction’, then the output of any quasimajoritarian function is logically consistent; this directly generalizes
the recent work of Dietrich and List (Majority voting on restricted domains. Presented at SCW08; see , 2007b). We then provide two sufficient conditions for value-restriction, defined geometrically in terms of a lattice ordering
or a metric structure on the set of individuals and propositions. Finally, we introduce another sufficient condition for consistent
majoritarian judgement aggregation, called ‘convexity’. We show that convexity is not logically related to value-restriction. 相似文献
12.
Bertil Tungodden 《Social Choice and Welfare》2005,25(1):75-84
The Foster–Greer–Thorbecke (FGT) family of poverty-measures is commonly used when comparing income distributions with respect
to poverty. Within this framework, the poverty ranking will be sensitive to the choice of poverty aversion parameter (defining
a particular FGT poverty-measure). If we content ourselves with applying a few specific parameter values, then we may demand
too little in order to claim robustness in our poverty comparisons. On the other hand, we may demand too much if we only work
with FGT poverty-measure quasi orderings established by considering every possible parameter value. An alternative approach
may be to report the number of parameter values representing possible reversal points in our poverty ranking—what we call
critical comparison values—and leave the final evaluative step to the relevant decision-makers. By applying a generalized version of Descartes’ Rule
of Signs, we show that the number of critical comparison values depends on the number of times the cumulative distribution
functions intersect.
相似文献
Bertil TungoddenEmail: |
13.
The object of this paper is to propose a consistency test for an individual involved in collective choice process. Collective choice processes considered in the paper are those that
transform individuals ‘tastes’– which reflect the self-interested view point of the individuals – into (social) ranking of alternatives. In addition to
her tastes, an individual has values about the way by which collective decision should be made. We distinguish two categories of such values. First, there are
end-values that restrict the class of social rankings that the individual considers ethically acceptable. Second there are aggregation-values that specify the way by which the social ranking should depend upon the individuals tastes. The consistency test stands on
an hypothetical operation of universalization of the individual tastes to everyone. Five illustrations of the potential usefulness of our approach for interpreting social
choice theory and welfare economics are proposed. These illustrations deal with utilitarian aggregation in the presence of
income inequality aversion, the so-called ‘ethics of responsibility’ and the aggregation of individual ranking of opportunity
sets based on their freedom of choice. A discussion of the relevance of the consistency test for addressing the problem of
‘laundering’ individual preferences is also provided.
Received: 25 June 1998/Accepted: 16 March 1999 相似文献
14.
Andranik Tangian 《Social Choice and Welfare》2010,35(1):129-161
The article is based on three findings. The first one is the interrelation between Arrow’s (Social choice and individual values,
Wiley, New York, 1951) social choice model and the mathematical theory of democracy discussed by Tangian (Aggregation and
representation of preferences, Springer, Berlin, 1991; Soc Choice Welf 11(1):1–82, 1994), with the conclusion that Arrow’s
dictators are less harmful than commonly supposed. The second finding is Quesada’s (Public Choice 130:395–400, 2007) estimate
of their power as that of two voters, implying that Arrow’s dictators are not more powerful than a chairperson with an additional
vote. The third is the model of Athenian democracy (Tangian, Soc Choice Welf 31:537–572, 2008), where indicators of popularity
and universality are applied to representatives and representative bodies. In this article, these indicators are used to computationally
evaluate the representativeness/non-representativeness of Arrow’s dictators. In particular, it is shown that there always
exist Arrow’s dictators who on the average share opinions of a majority, being rather representatives. The same holds for
dictators selected by lot, which conforms to the practice of selecting magistrates and presidents by lot in ancient democracies
and medieval Italian republics. Computational formulas are derived for finding the optimal “dictator–representatives”. 相似文献
15.
Several environmental factors influence tree growth at any site. The objective of this study was to examine the relationship between biotic and abiotic factors and tree growth rate (mean ring width averaged over the last 10 years) in settings ranging from urban to rural. Six clusters, each with five communities and two rural parks, were sampled in Illinois, Iowa, Minnesota, Missouri, and Wisconsin, for a total sample of 320 trees. Within each community, trees in parks, and along residential and commercial streets were sampled. Five species were sampled: silver maple (Acer saccharinum L.), honeylocust, (Gleditisia triacanthos L.), hackberry (Celtis occidentalis L.), black maple (Acer nigrum Michx F.), and basswood (Tilia americana L.). Factors were investigated for three scenarios: (i) all trees sampled in all clusters, (ii) a single species, all clusters, and (iii) all species, a single cluster.Baseline variables (cluster, place population, site, species, and age) accounted for 49–71% of observed variation in growth rate. Combined biotic factors accounted for 5 to 6% of observed variation. For all species in a single cluster, combined abiotic factors accounted for 11% of observed variation. Biotic factors related to growth rate detected using multivariate analyses included number of other trees within 9 m, presence of disease and insects, and human-induced mechanical injury. Abiotic factors that were related to tree growth included presence of pavement and core bulk density. For trees in rural parks, number of other trees within 20 m, and for trees in both rural and community parks, number of other trees within 9 m of sample trees were associated with decreased growth rate. 相似文献
16.
Increased density, increased intraspecific aggression, and a reduced fear of humans have been suggested as the more observable
and frequently described characteristics of wildlife species undergoing synurbization, the process of becoming urbanized.
The relationship among these variables and how they may be related to environmental variables that change with urbanization
is poorly understood. In this paper we explore the relationship between density, intraspecific aggression, and reduced fear
of humans in urban populations of gray squirrel. In the summer and fall of 2003 and 2004, we studied a park with a documented
high density of gray squirrels, Lafayette Park, Washington, DC, and six urban parks in Baltimore, MD with unknown squirrel
densities. We used linear regression (SAS Institute, SAS/STAT user’s guide. SAS Institute, Cary, NC, 2005) to determine if there was a relationship (P < 0.05) between squirrel density and intraspecific aggression, squirrel density and reduced fear of humans (wariness), and
squirrel density and habitat suitability. We found a positive association between density and intraspecific aggression (R
2 = 0.81, P < 0.00). A negative relationship between density and wariness (, P < 0.00). However, no relationship was evident between habitat suitability and squirrel density (, P = 0.437). 相似文献
17.
Based on the problems of Global Education Assistance to Africa (GEAA), and combined with China’s rationale and practice of
Education Assistance to Africa, this paper proposes a vision and assumption to improve the GEAA, that is, using the assistance
rationale of ‘Africa-based’, ‘equal-relationship’, and ‘mutual-benefits’, through ‘multi-stakeholders cooperation’, ‘multi-modes
operation’, and ‘multi-goals achievement’ to build one ‘harmonious world’. 相似文献
18.
《Public opinion quarterly》2006,70(3):413-415
19.
Estimates of air pollution mitigation with green plants and green roofs using the UFORE model 总被引:4,自引:0,他引:4
The purpose of this study was to investigate the effect of green roofs and green walls on air pollution in urban Toronto.
The research looked at the synergistic effects on air pollution mitigation of different combinations of vegetation by manipulating
quantities of trees, shrubs, green roofs and green walls in the study area. The effects of these manipulations were simulated
with the Urban Forest Effects (UFORE) model developed by the USDA Forest Service Northeastern Regional Station. While UFORE
contains several modules, Module—D quantifies the levels of air pollution for contaminants such as NO2, S02, CO, PM10 and ozone as well as hourly pollution removal rates and the economic value of pollutant removal. Six vegetation scenarios
were developed within the Toronto study area to compare different subsets of vegetation and their effect on air contaminants.
Results of the study indicate that grass on roofs (extensive green roofs) could augment the effect of trees and shrubs in
air pollution mitigation, placing shrubs on a roof (intensive green roofs) would have a more significant impact. By extension,
a 10–20% increase in the surface area for green roofs on downtown buildings would contribute significantly to the social,
financial and environmental health of all citizens.
相似文献
Brad BassEmail: |
20.
Parental religiosity and daughters’ fertility: the case of Catholics in southern Europe 总被引:1,自引:0,他引:1
Preferences, including preferences for children, are shaped during the formative years of childhood. It is therefore essential
to include exposure to religious practice during childhood in an attempt to establish a link between religiosity and fertility.
This path has not been explored in the documented literature that looks at the relationship between current religiosity and fertility. The International Social Survey Programme: Religion II (ISSP) provides the data base. It includes information
on maternal/paternal/own mass participation when the respondent was a child (nine levels each), as well as on his current
churchgoing (six levels) and prayer habits (eleven levels). These variables are included as explanatory variables in ‘fertility
equations’ that explain the number of children of Catholic women in Spain and Italy. The core findings are that exposure to
religiosity during the formative years of childhood, has a pronounced effect on women’s ‘taste for children’ that later on
translates into the number of her offspring. In Spain, the two parents have major opposite effects on women. Most striking
is the negative effect of the mother’s intensity of church attendance on her daughter’s fertility: Women who were raised by
an intensively practicing mother have on average one child less that their counterparts who were raised by a less religious
mother. On the other hand, an intensively practicing father encourages the daughter to have more children (by about 0.8, on
average). The Italian sample confirms the statistically significant negative effect of the mother’s religiosity. The father’s
religious conduct has apparently no effect on Italian women’s birth rates. Current religiosity seems to be irrelevant, both
in Spain and in Italy. It follows that religiosity and fertility are interrelated but the mechanism is probably different
from the simplistic causality that is suggested in the literature.
相似文献
Shoshana NeumanEmail: |