Characterizing human mobility patterns is essential for understanding human behaviors and the interactions with socioeconomic and natural environment, and plays a critical role in public health, ...urban planning, transportation engineering and related fields. With the widespread of location-aware mobile devices and continuing advancement of Web 2.0 technologies, location-based social media (LBSM) have been gaining widespread popularity in the past few years. With an access to locations of hundreds of million users, profiles and the contents of the social media posts, the LBSM data provided a novel modality of data source for human mobility study. By exploiting the explicit location footprints and mining the latent demographic information implied in the LBSM data, the purpose of this paper is to investigate the spatiotemporal characteristics of human mobility with a particular focus on the impact of demography. To serve this purpose, we first collect geo-tagged Twitter feeds posted in the conterminous United States area, and organize the collection of feeds using the concept of space-time trajectory corresponding to each Twitter user. Commonly human mobility measures, including detected home and activity centers, are derived for each user trajectory. We then select a subset of Twitter users that have detected home locations in the city of Chicago as a case study, and apply name analysis to the names provided in user profiles to learn the implicit demographic information of Twitter users, including race/ethnicity, gender and age. Finally we explore the spatiotemporal distribution and mobility characteristics of Chicago Twitter users, and investigate the demographic impact by comparing the differences across three demographic dimensions (race/ethnicity, gender and age). We found that, although the human mobility measures of different demographic groups generally follow the generic laws (e.g., power law distribution), the demographic information, particular the race/ethnicity group, significantly affects the urban human mobility patterns.
•Spatiotemporal characteristics of urban human mobility were explored using Twitter posts.•Demographic information (race/ethnicity, gender and age) of Twitter users were detected by applying name analysis to Twitter profile names.•Differences of human mobility patterns were compared across different demographic groups.•Race/ethnicity has the largest and gender has the least impact on human mobility, in the three demographic factors of study.
Understanding the movement, direction, and shape of sand dunes can contribute to reducing their impact on infrastructure and the environment. The Rub’ al Khali desert has a distribution of dune ...types. This study aims to identify and map the different types of dunes within the Rub’ al Khali using a texture analysis method based on a digital elevation model (DEM). Statistical texture analysis methods (variance, skewness, and kurtosis) show three different textures of sand dune shapes, according to the geography of the dunes, using data contained in global DEMs. The analysis presented in this study focused on the use of DEMs to investigate the varied dune morphology within the Rub’ al Khali. The GMTED2010 and EarthEnv_DEM90 digital elevation models were compared. Spatial variability in dune height, spatial variability in dune texture, and profile graphs were created to examine dune surfaces in cross-section. The results provided six different dune types within the sand sea: giant compound linear dunes, simple linear dunes, simple transverse dunes, compound crescentic dunes (megabarchans), huge star dunes, and many transitional forms that defy classification. The results showed that the compound linear dune and simple linear dune were the dominant dune types, covering 41.61% and 31.7% of the total study area, respectively. The maps of variance, using either 10 × 10 and 30 × 30 focal blocks, produced a fairly sharp distinction in dune texture. It is hoped that future research in aeolian geomorphology will greatly benefit from these results, which could easily be expanded with the use of more sophisticated pattern recognition software, which clearly shows the value of using such an approach.
The Rub’ al Khali desert (or Empty Quarter) is the largest and perhaps most significant sand sea in the world. Located on the southern Arabian Peninsula, the dune field has remained largely ...unexplored owing to the harsh clime and difficult terrain. This study takes advantage of geospatial technology (interpolations, supervised classification, minimum focal statistic) to extract information from the data contained in global Digital Elevation Model (DEM)s, satellite imagery. The main objective here is to identify and map different dune forms within the sand sea, estimate the volume of sand and explore probable sources of sand. The analysis of dune color strongly suggests that the sand is not completely reworked and intermixed. If this is true, a spatial variability map of the mineral composition of the sand could be very revealing. The red sand is quite pronounced, the largest volume of sand (~36%) is associated with the yellow color class. Yellow sand covers most of the western part of the dunes field and seems to be a transitional color between red and white sand in the eastern part of the dune field. This suggests that the yellow sand might be derived from both local and regional sources, or it might be less oxidized, reworked, or have a different composition that represents a combination of red and white sand.
This study explores groundwater management policies and the effect of modeling assumptions on the projected performance of those policies. The study compares an optimal economic allocation for ...groundwater use subject to streamflow constraints, achieved by a central planner with perfect foresight, with a uniform tax on groundwater use and a uniform quota on groundwater use. The policies are compared with two modeling approaches, the Optimal Control Model (OCM) and the Multi‐Agent System Simulation (MASS). The economic decision models are coupled with a physically based representation of the aquifer using a calibrated MODFLOW groundwater model. The results indicate that uniformly applied policies perform poorly when simulated with more realistic, heterogeneous, myopic, and self‐interested agents. In particular, the effects of the physical heterogeneity of the basin and the agents undercut the perceived benefits of policy instruments assessed with simple, single‐cell groundwater modeling. This study demonstrates the results of coupling realistic hydrogeology and human behavior models to assess groundwater management policies. The Republican River Basin, which overlies a portion of the Ogallala aquifer in the High Plains of the United States, is used as a case study for this analysis.
Key Points
Detailed physical model was necessary to properly investigate policy instruments
Agent heterogeneity significantly affects policy instrument effectiveness
Both policy instruments benefit from a weighted system or an adaptive system
A methodology for clustering stresses on a groundwater system based on similarity of hydrologic response produced by the stress is presented. The method is relevant to the computationally efficient ...calculation of response matrixes for use in groundwater management and other applications. The procedure is presented for the case in which the impact of pumping withdrawals on streamflow is of interest. The method uses cluster analysis on multiple, transient responses and a simplified response matrix for the modeled system. It is demonstrated on a field scale hypothetical management problem applied to a portion of the Republican River basin in the High Plains Aquifer of the United States with a multi-decadal planning horizon that maximizes well withdrawal while requiring that minimum streamflows be maintained. For this case, the clustering approach both reduces the computational requirement and helps to produce response coefficients with meaningful precision. The effectiveness of the model reduction is tested by comparing the optimal solutions produced by a full scale formulation and two reduced size formulations.
•A methodology for clustering stresses based on similarity of hydrologic response.•For computationally efficient calculation of response matrixes.•For use in groundwater management and other applications.•Method uses cluster analysis on multiple, transient responses and a simplified response matrix.•May help produce response coefficients with meaningful precision.
This paper examines the relationship between unemployment and psychological well-being before and during the Great Recession across 249 UK local authority districts (LADs). Substantial evidence ...demonstrates that unemployment has a large negative effect on psychological well-being. However, unique social norms develop in geographical areas with high unemployment rates, which significantly reduce the negative impact of unemployment on well-being. Though the post-2007 Great Recession period was characterized by widespread unemployment, few studies have examined the impact of this crisis on well-being in high- and low-unemployment local areas. The analysis constructs a rich panel data set which follows 15,798 individuals from 1998 to 2014, and applies difference-in-differences fixed-effects and general method of moments estimators. The findings indicate that unemployment had a large negative impact on psychological well-being. However, the magnitude of this effect did not change (or was even slightly lower) during the Great Recession. Furthermore, the unemployment social norm also ceased to have any additional effect on well-being during the Great Recession in high-unemployment LADs, as opposed to the pre-recession period.
Müller's account of the way episodic emotions function depends on a contrast between these and what he calls cares, concerns and attachments and the claim that the latter are in several respects ...prior to the former. The account seems to attribute no normative features to the latter. But this is implausible. If a preference for liberty over social justice is a concern, it is justified if liberty really is more important than social justice.
Policy-makers at regional, national and European Union (EU) levels of governance use a variety of subsidy programmes to stimulate firm-level innovation. Against this backdrop, this paper investigates ...three important issues that have not received sufficient attention in the literature: (1) whether evaluating the impact of subsidies from each individual source is biased by ignoring firms that receive a mix of subsidies from different sources at the same point in time; (2) whether receiving a mix of subsidies from regional, national and EU sources crowds out firm-level innovation; and (3) if effective, whether subsidy mix stimulates forms of innovation with higher private or social returns. The findings demonstrate that ignoring subsidy mix significantly biases evaluations of subsidies from individual sources. Moreover, subsidy mix can be a highly effective means of stimulating forms of firm-level innovation with the highest social returns, precisely where market and systemic failures are most acute.
Sedimentation (primarily from human land use) is a major threat to runoff-fed wetlands of the Great Plains of North America (playas), but it is unknown how many playas are turbid, how prevalence of ...turbidity has changed over time, and how turbidity is related to surrounding land use. We used remotely sensed imagery to assess sedimentation in the waters of over 7700 playa basins in Texas on four dates during a 29-year span: 25 July 1986 (a regionally wet time), 3 May 2014 (during drought), 4 June 2014 (after the drought was broken), and 25 July 2015 (one year post-drought). Even on the wettest date examined, 64% of playa basins did not hold water. Turbidity varied over time, was already present in over half of the basins examined in 1986, and prevalence of turbidity was not simply proportional to overall wet playa abundance. There was an increase in total and irrigated cropland in our focal region and a statistically significant association between sedimentation and land use within 100 m of a playa: clear playas were associated with more urban development and pasture/grassland, and turbid playas were surrounded mostly by cropland.
A major dust event occurred on 15 December 2003 in the Chihuahuan Desert region of Texas and New Mexico (USA) and Chihuahua (Mexico) and in the Southern High Plains region of Texas and New Mexico. ...Using a MODIS satellite image, 146 individual small-scale sources (plumes) of dust were identified. These plumes merged to form the regional-scale dust storm. The point sources were characterized with respect to land use and land cover using a combination of field work and aerial photography. Fifty-eight of the sources are on cropland, mostly on the Southern High Plains. Forty-nine are on rangeland, from across the entire region. Thirty of the dust plumes originate within playa basins, mostly in the Chihuahuan Desert.
Point sources of dust only represent a small fraction of the total land surface at any given moment (i.e., the period when the image was acquired) because most of the land within the region was not subject to erosion during the event. In general, land use and soil characteristics of point sources matched those of adjacent areas that were not emitting dust at the time, suggesting that microscale variations in erodibility or meteorological factors may dictate the actual emission points of dust during individual events.
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