scholarly journals Common power laws for cities and spatial fractal structures

2020 ◽  
Vol 117 (12) ◽  
pp. 6469-6475 ◽  
Author(s):  
Tomoya Mori ◽  
Tony E. Smith ◽  
Wen-Tai Hsu
Keyword(s):  
Spatial Scales ◽  
Power Laws ◽  
The United States ◽  
City Size ◽  
Size Distributions ◽  
Fractal Structures ◽  
Large Cities ◽  
Geographic Space ◽  
Wide Range ◽  
Using Data

City-size distributions are known to be well approximated by power laws across a wide range of countries. But such distributions are also meaningful at other spatial scales, such as within certain regions of a country. Using data from China, France, Germany, India, Japan, and the United States, we first document that large cities are significantly more spaced out than would be expected by chance alone. We next construct spatial hierarchies for countries by first partitioning geographic space using a given number of their largest cities as cell centers and then continuing this partitioning procedure within each cell recursively. We find that city-size distributions in different parts of these spatial hierarchies exhibit power laws that are, again, far more similar than would be expected by chance alone—suggesting the existence of a spatial fractal structure.

scholarly journals Urban Accounting and Welfare

2013 ◽  
Vol 103 (6) ◽  
pp. 2296-2327 ◽  
Author(s):  
Klaus Desmet ◽  
Esteban Rossi-Hansberg
Keyword(s):  
Large Population ◽  
The United States ◽  
Welfare Effects ◽  
City Size ◽  
Negative Effects ◽  
The Us ◽  
City Size Distribution ◽  
Using Data ◽  
Main Components ◽  
The City

We use a simple theory of a system of cities to decompose the determinants of the city size distribution into three main components: efficiency, amenities, and frictions. Higher efficiency and better amenities lead to larger cities but also to greater frictions through congestion and other negative effects of agglomeration. Using data on MSAs in the United States, we estimate these city characteristics. Eliminating variation in any of them leads to large population reallocations, but modest welfare effects. We apply the same methodology to Chinese cities and find welfare effects that are many times larger than those in the US. (JEL H71, O18, P25, R11, R23, R41)

scholarly journals The variability of tidewater-glacier calving: Origin of event-size and interval distributions

2014 ◽  
Vol 60 (222) ◽  
pp. 622-634 ◽  
Author(s):  
Anne Chapuis ◽  
Tom Tetzlaff
Keyword(s):  
Size Distribution ◽  
Power Laws ◽  
Size Distributions ◽  
Event Data ◽  
Model Data ◽  
Small Perturbations ◽  
Tidewater Glaciers ◽  
Glacier Terminus ◽  
Wide Range ◽  
Parameter Measuring

AbstractCalving activity at the termini of tidewater glaciers produces a wide range of iceberg sizes at irregular intervals. We present calving-event data obtained from continuous observations of the termini of two tidewater glaciers on Svalbard, and show that the distributions of event sizes and inter-event intervals can be reproduced by a simple calving model, focusing on the mutual interplay between calving and the destabilization of the glacier terminus. The event-size distributions of both the field and the model data extend over several orders of magnitude and resemble power laws. The distributions of inter-event intervals are broad, but have a less pronounced tail. In the model, the width of the size distribution increases with the calving susceptibility of the glacier terminus, a parameter measuring the effect of calving on the stress in the local neighborhood of the calving region. Inter-event interval distributions, in contrast, are insensitive to the calving susceptibility. Above a critical susceptibility, small perturbations of the glacier result in ongoing self-sustained calving activity. The model suggests that the shape of the event-size distribution of a glacier is informative about its proximity to this transition point. Observations of rapid glacier retreats can be explained by supercritical self-sustained calving.

scholarly journals THE SPATIAL MEANING OF PARETO'S SCALING EXPONENT OF CITY-SIZE DISTRIBUTIONS

Fractals ◽  
2014 ◽  
Vol 22 (01n02) ◽  
pp. 1450001 ◽  
Author(s):  
YANGUANG CHEN
Keyword(s):  
Fractal Dimension ◽  
The United States ◽  
City Size ◽  
Fractional Dimension ◽  
Scaling Exponent ◽  
Size Distributions ◽  
Pareto Exponent ◽  
New Interpretation ◽  
Map Scale ◽  
Dimension Ratio

The scaling exponent of a hierarchy of cities used to be regarded as a fractional dimension. The Pareto exponent was treated as the fractal dimension of size distribution of cities, while the Zipf exponent was considered to be the reciprocal of the fractal dimension. However, this viewpoint is not exact. In this paper, I will present a new interpretation of the scaling exponent of rank-size distributions. The ideas from fractal measure relation and the principle of dimension consistency are employed to explore the essence of Pareto's and Zipf's scaling exponents. The Pareto exponent proved to be a ratio of the fractal dimension of a network of cities to the average dimension of city population. Accordingly, the Zipf exponent is the reciprocal of this dimension ratio. On a digital map, the Pareto exponent can be defined by the scaling relation between a map scale and the corresponding number of cities based on this scale. The cities of the United States of America in 1900, 1940, 1960, and 1980 and Indian cities in 1981, 1991, and 2001 are utilized to illustrate the geographical spatial meaning of Pareto's exponent. The results suggest that the Pareto exponent of city-size distributions is a dimension ratio rather than a fractal dimension itself. This conclusion is revealing for scientists to understand Zipf's law on the rank-size pattern and the fractal structure of hierarchies of cities.

scholarly journals Enhancing Drought Monitoring and Early Warning for the United Kingdom through Stakeholder Coinquiries

2018 ◽  
Vol 11 (1) ◽  
pp. 49-63 ◽  
Author(s):  
Jamie Hannaford ◽  
Kevin Collins ◽  
Sophie Haines ◽  
Lucy J. Barker
Keyword(s):  
Decision Making ◽  
United Kingdom ◽  
Early Warning ◽  
Spatial Scales ◽  
The United States ◽  
Drought Monitoring ◽  
The United Kingdom ◽  
Wide Range ◽  
Drought Preparedness ◽  
Monitoring And Early Warning

Abstract Drought is widely written about as a complex, multifaceted phenomenon, with complexity arising not just from biophysical drivers, but also human understanding and experiences of drought and its impacts. This has led to a proliferation of different drought definitions and indicators, creating a challenge for the design of drought monitoring and early warning (MEW) systems, which are a key component of drought preparedness. Here, we report on social learning workshops conducted in the United Kingdom aimed at improving the design and operation of drought MEW systems as part of a wider international project including parallel events in the United States and Australia. We highlight key themes for MEW design and use: “types” of droughts, indicators and impacts, uncertainty, capacity and decision-making, communications, and governance. We shed light on the complexity of drought through the multiple framings of the problem by different actors, and how this influences their needs for MEW. Our findings suggest that MEW systems need to embrace this complexity and strive for consistent messaging while also tailoring information for a wide range of audiences in terms of the drought characteristics, temporal and spatial scales, and impacts that are important for their particular decision-making processes. We end with recommendations to facilitate this approach.

scholarly journals Spatial Pattern and City Size Distribution

2020 ◽  
Author(s):  
Tomoya Mori
Keyword(s):  
Spatial Pattern ◽  
Size Distribution ◽  
Spatial Patterns ◽  
Regional Economics ◽  
Size Variation ◽  
Power Laws ◽  
City Size ◽  
Industrial Composition ◽  
Large Cities ◽  
Economic Agglomeration

Many large cities are found at locations with certain geographic and historical advantages, or the first nature advantages. Yet those exogenous locational features may not be the most potent forces governing the spatial pattern and the size variation of cities. In particular, population size, spacing, and industrial composition of cities exhibit simple, persistent, and monotonic relationships that are often approximated by power laws. The extant theories of economic agglomeration explain some aspects of this regularity as a consequence of interactions between endogenous agglomeration and dispersion forces, or the second nature advantages. To obtain results about explicit spatial patterns of cities, a model needs to depart from the most popular two-region and systems-of-cities frameworks in urban and regional economics in which the variation in interregional distance is assumed away in order to secure analytical tractability of the models. This is one of the major reasons that only few formal models have been proposed in this literature. To draw implications about the spatial patterns and sizes of cities from the extant theories, the behavior of the many-region extension of the existing two-region models is discussed in depth. The mechanisms that link the spatial pattern of cities and the diversity in size as well as the diversity in industrial composition among cities are also discussed in detail, thought the relevant theories are much less available. For each aspect of the interdependence among spatial patterns, size distribution and industrial composition of cities, the concrete facts are drawn from Japanese data to guide the discussion.

scholarly journals Potential Utilization of Specific Attenuation for Rainfall Estimation, Mitigation of Partial Beam Blockage, and Radar Networking

2014 ◽  
Vol 31 (3) ◽  
pp. 599-619 ◽  
Author(s):  
Alexander Ryzhkov ◽  
Malte Diederich ◽  
Pengfei Zhang ◽  
Clemens Simmer
Keyword(s):  
Radial Profile ◽  
The United States ◽  
Rainfall Estimation ◽  
Differential Phase ◽  
Specific Attenuation ◽  
X Band ◽  
Wide Range ◽  
Drop Size Distributions ◽  
Using Data ◽  
Rain Rates

Abstract The potential utilization of specific attenuation A for rainfall estimation, mitigation of partial beam blockage, and radar networking is investigated. The R(A) relation is less susceptible to the variability of drop size distributions than traditional rainfall algorithms based on radar reflectivity Z, differential reflectivity ZDR, and specific differential phase KDP in a wide range of rain intensity. Specific attenuation is estimated from the radial profile of the measured Z and the total span of the differential phase using the ZPHI method. Since the estimated A is immune to reflectivity biases caused by radar miscalibration, attenuation, partial beam blockage, and wet radomes, rain retrieval from R(A) is also immune to the listed factors. The R(A) method was tested at X band using data collected by closely located radars in Germany and at S band for polarimetrically upgraded Weather Surveillance Radar-1988 Doppler (WSR-88D) radars in the United States. It is demonstrated that the two adjacent X-band radars—one of which is miscalibrated and another which is affected by partial beam blockage—produce almost indistinguishable fields of rain rate. It is also shown that the R(A) method yields robust estimates of rain rates and rain totals at S band, where specific attenuation is vanishingly small. The X- and S-band estimates of rainfall obtained from R(A) are in good agreement with gauges.

scholarly journals Demography and the emergence of universal patterns in urban systems

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Luís M. A. Bettencourt ◽  
Daniel Zünd
Keyword(s):  
Urban Areas ◽  
Small Towns ◽  
City Size ◽  
Zipf’S Law ◽  
Urban Systems ◽  
Size Distributions ◽  
Vital Rates ◽  
Zipf's Law ◽  
Large Cities ◽  
Population Sizes

Abstract Urban areas exist in a wide variety of population sizes, from small towns to huge megacities. No proposed form for the statistical distribution of city sizes has received more attention than Zipf’s law, a Pareto distribution with power law exponent equal to one. However, this distribution is typically violated by empirical evidence for small and large cities. Moreover, no theory presently exists to derive city size distributions from fundamental demographic choices while also explaining consistent variations. Here we develop a comprehensive framework based on demography to show how the structure of migration flows between cities, together with the differential magnitude of their vital rates, determine a variety of city size distributions. This approach provides a powerful mathematical methodology for deriving Zipf’s law as well as other size distributions under specific conditions, and to resolve puzzles associated with their deviations in terms of concepts of choice, symmetry, information, and selection.

scholarly journals A Classification of US Wildland Firefighter Entrapments Based on Coincident Fuels, Weather, and Topography

Fire ◽  
2019 ◽  
Vol 2 (4) ◽  
pp. 52
Author(s):  
Wesley G. Page ◽  
Patrick H. Freeborn ◽  
Bret W. Butler ◽  
W. Matt Jolly
Keyword(s):  
United States ◽  
Environmental Factors ◽  
Environmental Conditions ◽  
Spatial Scales ◽  
Canopy Cover ◽  
The United States ◽  
Fire Danger ◽  
Fire Environment ◽  
Wide Range ◽  
The Times

Previous attempts to identify the environmental factors associated with firefighter entrapments in the United States have suggested that there are several common denominators. Despite the widespread acceptance of the assumed commonalities, few studies have quantified how often entrapments actually meet these criteria. An analysis of the environmental conditions at the times and locations of 166 firefighter entrapments involving 1202 people and 117 fatalities that occurred between 1981 and 2017 in the conterminous United States revealed some surprising results. Contrary to general assumptions, we found that at broad spatial scales firefighter entrapments happen under a wide range of environmental conditions, including during low fire danger and on flat terrain. A cluster-based analysis of the data suggested that entrapments group into four unique archetypes that typify the common environmental conditions: (1) low fire danger, (2) high fire danger and steep slopes, (3) high fire danger and low canopy cover, and (4) high fire danger and high canopy cover. There are at least three important implications from the results of this study; one, fire environment conditions do not need to be extreme or unusual for an entrapment to occur, two, the region and site specific context is important, and, three, non-environmental factors such as human behavior remain a critical but difficult to assess factor in wildland firefighter entrapment potential.

scholarly journals Co-distribution of Light at Night (LAN) and COVID-19 Incidence in the United States

2021 ◽  
Author(s):  
Yidan Meng ◽  
Vincent Zhu ◽  
Yong Zhu
Keyword(s):  
United States ◽  
New York ◽  
Multiple Linear Regression Model ◽  
The United States ◽  
Circadian Disruption ◽  
Immune Functions ◽  
Human Immune System ◽  
Light At Night ◽  
Large Cities ◽  
Using Data

Abstract Background: Light at night (LAN) as a circadian disruption factor may affect the human immune system and consequently increase an individual’s susceptibility or the severity of infectious diseases, such as COVID-19. COVID-19 infections spread differently in each state in the United States (US). The current analysis aimed to test whether there is an association between LAN and COVID-19 cases in 4 selected US states: Connecticut, New York, California, and Texas.Methods: We analyzed clustering patterns of COVID-19 cases in ArcMap and performed a multiple linear regression model using data of LAN and COVID-19 incidence with adjustment for confounding variables including population density, percent below poverty, and racial factors. Results: Hotspots of LAN and COVID-19 cases are located in large cities or metro-centers for all 4 states. LAN intensity is associated with cases/1k for overall and lockdown durations in New York and Connecticut (P <0.001), but not in Texas and California. The overall case rates is significantly associated with LAN in New York (P <0.001) and Connecticut (P <0.001). Conclusions: We observed a significant positive correlation between LAN intensity and COVID-19 cases-rate/1k, suggesting that circadian disruption of ambient light may increase the COVID-19 infection rate possibly by affecting an individual's immune functions. Furthermore, differences in the demographic structure and lockdown policies in different states play an important role in COVID-19 infections.

scholarly journals Sex Differences in the Prevalence and Correlates of Handgun Carrying Among Adolescents in the United States

2017 ◽  
Vol 17 (1) ◽  
pp. 24-41 ◽  
Author(s):  
Michael G. Vaughn ◽  
Sehun Oh ◽  
Christopher P. Salas-Wright ◽  
Matt DeLisi ◽  
Katie J. Holzer ◽  
...  
Keyword(s):  
United States ◽  
Sex Differences ◽  
Juvenile Justice System ◽  
The United States ◽  
National Study ◽  
Risk Propensity ◽  
Delinquent Behaviors ◽  
Current Trends ◽  
Wide Range ◽  
Using Data

Handgun carrying is associated with a wide range of delinquent behaviors, but very little is known about sex differences in this behavior and current trends in handgun carrying in the United States. Using data from the 2002 to 2015 National Study of Drug Use and Health surveys, we found that the prevalence of handgun carrying among girls nearly doubled from 0.9% to 1.7% with most of this increase seen among non-Hispanic White and Hispanic girls. Although boys are more likely to carry handguns, approximately 20% of the total handgun carrying by adolescents in the United States occurs among girls. Both male and female adolescents who have carried a handgun in the past year evince a behavioral profile that is characterized by substance use, versatile delinquency, elevated risk propensity, and substantial school and family problems. However, adjusted odds ratios are consistently higher for females, suggesting that girls who engage in handgun carrying represent an important subgroup of potentially pernicious offenders that should be targeted for primary and tertiary prevention and juvenile justice system oversight.

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