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In commuting research the geographic area under investigation is of central importance. When examining commutes occurring in a region of interest, the selection and use of different city, county, or metropolitan region boundaries will have a large impact on analyses of travel times and distances, whether a transit network provides adequate access to jobs, levels of congestion, and so on. This research examines two cluster detection methods to delineate the commuter shed of Miami, Florida and Cincinnati, Ohio. These clusters are then compared to a series of government delineated boundaries often used in commuting research for a jobs-housing balance analysis of each. The results of the clustering methods are different for the two regions due to the differing urban forms of each. The results demonstrate that the decision of what boundary to use for research on commuting can lead to drastically different results. While there is not necessarily any correct boundary, one may be more appropriate and the rationale for such should be more thoroughly discussed.

Manufacturing plant closure has been the subject of much national concern, and an extensive literature principally focused on the developed world. This study extends the findings on plant closure w...

While urban structures have been delineated at the regional level, few works have explored the impact of urban structures on commuting at this same level. This article studies how urban structures affect commuting from 2000 to 2010. It applies a spatial statistical tool, standard deviation ellipses, to capture spatial patterns of jobs and residential workers for metropolitan statistical areas (MSAs). Two urban structure indexes are constructed to illustrate different decentralization levels of employment with reference to the distribution of residential workers; one illustrates the spatial decentralization of high job density nodes, while the other shows the spatial decentralization of moderate job density nodes. Commuting times of two modes by private cars and public transit are analyzed along with the number of commuters. The results highlight three findings: (1) MSAs become more compact in terms of employment distribution, (2) more decentralized high-density nodes lead to less total commuting times, and on the other hand, more decentralized moderate job density nodes contribute to longer commuting times, and (3) the decentralization of high job density nodes is associated with less commuting time of private cars, while they have insignificant effect on commuting time of public transit.

While urban planners and transportation geographers have long emphasized the importance of social influences on individual travel behavior, many challenges remain to bridge the gap between complex conceptual frameworks and operational behavioral models. Improving the ability of models to forecast activity-travel behavior can provide greater insights into urban planning issues. This paper proposes a new model framework by evaluating how individual travel behavior is influenced by inter- and intra-household interactions. The built environment, land-use mix, and social interactions influence household member choices among different transport modes. We propose a spatial multivariate Tobit specification that allows each individual to face a set of potential destinations and transport modes and takes into consideration the travel behavior of other household members and nearby neighbors. Using the Greater Cincinnati Household Travel Survey, we analyzed more than 37,000 trips made by 1968 individuals located in Hamilton County in Cincinnati, Ohio. Results reveal that social influences and the built environment have a strong impact on the willingness to walk and to cycle.

Understanding individual travel behavior is vital in travel demand management as well as in urban and transportation planning. New data sources including mobile phone data and location-based social media (LBSM) data allow us to understand mobility behavior on an unprecedented level of details. Recent studies of trip purpose prediction tend to use machine learning (ML) methods, since they generally produce high levels of predictive accuracy. Few studies used LSBM as a large data source to extend its potential in predicting individual travel destination using ML techniques. In the presented research, we created a spatio-temporal probabilistic model based on an ensemble ML framework named “Random Forests” utilizing the travel extracted from geotagged Tweets in 419 census tracts of Greater Cincinnati area for predicting the tract ID of an individual’s travel destination at any time using the information of its origin. We evaluated the model accuracy using the travels extracted from the Tweets themselves as well as the travels from household travel survey. The Tweets and survey based travels that start from same tract in the south western parts of the study area is more likely to select same destination compare to the other parts. Also, both Tweets and survey based travels were affected by the attraction points in the downtown of Cincinnati and the tracts in the north eastern part of the area. Finally, both evaluations show that the model predictions are acceptable, but it cannot predict destination using inputs from other data sources as precise as the Tweets based data.

In the past several decades, the use of all-terrain vehicles (ATVs) has proliferated in many Arctic communities in North America. One example is the village of Barrow, Alaska. This coastal community has only local roads, so all access to the interior utilizes off-road machines. These 4-wheel vehicles are the primary means of tundra traverse and transport in summer by hunters and berry-pickers, and by village residents accessing summer camps. Traveling cross-country is difficult due to the large number of thermokarst lakes, wetlands, and streams, and tundra trails tend to follow dryer higher ground while avoiding areas of high microrelief such as high-centered ice-wedge polygons. Thus, modern ATV trails tend to follow the margins of drained or partially drained thermokarst lake basins where it is flat and relatively dry, and these trails are heavily used. The deeply-ribbed tires of the heavy and powerful ATVs cause damage by destroying the vegetation and disturbing the underlying organic soil. Exposure of the dark soil enhances summer thaw and leads to local thermokarst of the ice-rich upper permafrost. The damage increases over time as vehicles continue to follow the same track, and sections eventually become unusable; this is especially true where the trail crosses ice-wedge troughs. Deep subsidence in the ponded troughs results in ATV users veering to avoid the wettest area, which leads to a widening of the damaged area. Helicopter surveys, site visits, and collection of ground penetrating radar data were combined with time series analysis of high-resolution aerial and satellite imagery for the period 1955–2014. The analysis reveals that there are 507 km of off-road trails on the Barrow Peninsula. About 50% of the total trail length was developed before 1955 in association with resource extraction, and an additional 40% were formed between 1979 and 2005 by ATVs. Segments of the more modern trail are up to 100 m wide. Damage to the tundra is especially pronounced in wet areas, such as ice-wedge troughs. Knowledgeable indigenous people are aware of the problem. Some remediation has been attempted by using heavy-duty PVC matting in areas of greatest damage, but this approach is prohibitively expensive on a large scale.

Spatial access to healthy foods has drawn growing attention regarding the relationship with people's health conditions and demographic and socioeconomic characteristics. Individuals' differences and the impact of travel behaviors on food accessibility, however, are rarely studied. This study incorporates mobility, time, and transportation mode components to measure each individual's access to healthy foods. We employed three activity space measures to estimate food accessibility: route network buffer, time-weighted standard deviational ellipse (SDE), and mode-weighted SDE. Food accessibility in three activity spaces shows similar variabilities. Geographic size and spatial access to healthy foods differ significantly by income and employment for all three activity space measures. People with higher incomes and those who are currently employed are likely to have larger activity spaces and higher food accessibility. As age increases, people tend to increase their size of activity spaces (in both SDE measures...

This paper investigates how individual activity–travel behaviors are influenced by interactions between household members in making decisions about their daily trips. Traditional discrete choice models mainly incorporate individual decision-making mechanisms ignoring the household context. In reality, each household member's travel choice often depends on the decision of the other members. We propose a new estimation method that assumes each travel decision depends on intra-household interactions. Using Bayesian estimation we develop a spatial multivariate tobit specification that allows for each individual facing a set of potential destinations to take into account the willingness to travel of other household members. Using a unique dataset containing more than 67,000 trips made by more than 3500 individuals in the area of Greater Cincinnati, we show that depending on the purpose of the trip, household members do interact and accommodate their travel decisions with respect to other household members.

Spatial access to healthy foods has drawn much attention due to its potential to facilitate healthy eating habits, and subsequently reduce the risk of chronic diseases. However, the associations of healthy food accessibility with grocery shopping patterns depending on various spatial contextual units remain little known. This study aimed to (1) compare healthy food accessibility among residential neighborhoods with varying buffer sizes and activity space; (2) examine the associations of grocery shopping patterns and healthy food accessibility in residential neighborhoods and activity space; (3) explore the differences in healthy food environment and the associations between healthy food accessibility and grocery shopping patterns by populations density depending on residential neighborhoods and activity space. Data came from GPS-based Household Interview Survey for the Cincinnati Ohio Region conducted during 2009–2010, of which final sample consisted of 1625 participants. The results illustrated that (1) healthy food accessibility in activity space had greater variability than in residential neighborhoods; (2) healthy food accessibility had significant associations with grocery shopping patterns across various spatial contextual units; and (3) healthy food accessibility and its associations with grocery shopping patterns differed significantly by population density in residential neighborhoods but not in activity space. This study provides a deeper insight into the relationships between grocery shopping patterns and healthy food accessibility by accounting for various spatial contextual units. It also improves nuanced understanding of the spatial heterogeneity in healthy food environment and its associations with grocery shopping patterns between more urbanized areas and more rural areas depending on residential neighborhoods and activity space. One implication is that improving healthy food exposures to people's residence and other routine activity destinations may encourage them to visit the healthy food stores for food purchase. Another implication is that future research should carefully consider the place effects in evaluating people's food environment in residential neighborhoods and its associations with grocery shopping behaviors.

Changes in the global atmospheric budget of platinum reportedly correspond to explosive volcanic eruptions. Using inductively coupled plasma mass spectrometry (ICP-MS) elemental analysis we examined eight widely separated stratified sites to evaluate the geographic extent of three late Holocene high magnitude volcanic events. We found characteristic Pt anomalies across the Western Hemisphere dating to the Laki, Iceland (CE 1783–1784), Kuwae, Vanuatu (CE 1452–1453), and Eldgjá, Iceland (CE 934) explosive volcanic eruptions. Pt anomalies in sediments over a broad geographic area indicate distinctive time-correlative atmospheric deposition rates of platinum-rich volcanic ash. These anomalies provide new chronostratigraphic markers for these late Holocene high magnitude volcanic eruptions, which are especially valuable in the Western Hemisphere in strata with limited chronometric control. Pt anomalies provide an important tracer for the age of these volcanic events and ultimately a new chronostratigraphic marker in archaeological, geological, palynological, and paleontological sediments.

In recent years, recognition of the importance of neighborhood context has produced a growing body of geographic research. When making their activity–travel decisions, individuals are restricted in different ways. In particular, individual choice behavior is often influenced by a neighborhood environment and a built environment. This study using the 2010 household trip survey demonstrated the effectiveness of incorporating multilevel mechanisms in various contexts of activity–travel behavior by comparing with traditional models. The analysis shows that one individual's activity participation patterns with respect to mode choice, trip count, trip distance, and trip time, under a variety of spatio-temporal constraints, tend to be affected by shared characteristics of neighborhoods. The results also imply that neighborhood travel behaviors are significantly influenced by neighborhood characteristics requiring policy makers to consider not only individual characteristics but surrounding environment.

The recent increase in demand and transportation security highlights the importance of the public transit system in the United States. This study explores how potential failures on nodal disruptions affect transit system flows and examines the change in the reliability of transit systems with a case study of the Greater Metropolitan Area of Washington, DC. For methodology, we employ network reliability and system flow loss and assess the criticality of stations under a variety of simulated nodal disruptions. We evaluate network resilience by identifying the best and worst geographical impact scenarios on networks.

Automated forest fire monitoring systems can be constructed using forest fire watchtowers equipped with laser night vision cameras or high-definition video cameras. In order to minimize the construction cost and to maximize the monitoring coverage of forest fires, efficiently placing the watchtowers is critical. This paper examines efficient watchtower locations by integrating visibility analysis and location-allocation models. Specifically, based on the classical location set covering problem and maximum covering location problem, three optimization models are developed to satisfy three kinds of requirements of forest fire monitoring in practice: minimizing cost with full coverage, maximizing coverage with a fixed budget, and maximizing coverage while minimizing the cost. The models are tested using integer programming and a multi-objective genetic algorithm, with an application in a forest park in Guangzhou, China. The results suggest that this model-based optimization approach to watchtower location can be used to improve the efficiency of forest fire alarm systems.

Regional economists are increasingly adopting spatial analytical and spatial econometric perspectives to study questions related to local versus global spatial spillover effects. Recent studies have shown that blindly adopting traditional spatial econometric models to measure those externalities might not be relevant. Explicitly accounting on how closely related groups of economic agents such as individuals or firms interact across space can be of great benefit for researchers working at the interface of social economics and geography. Recent development in economic theory has provided new ways to incorporate a range of spillover effects into a variety of economic models (Bramoulle et al., Am Econ Rev 104:898–930, 2014). The newly redefined concept of local spillover in the socio-economic literature involves a more complex interaction structure that includes feedback effects, resulting from impact passing through neighboring observations and coming back to the original location, as typically observed for global interaction models. However, the spatial magnitude of those local externalities is more limited across space.

Airline mergers and acquisitions (MAs) are on the rise across the globe and have been a growing trend in the U.S. aviation industry in the last few years. MAs are taking several factors into consideration, such as cost efficiency, competition, and geographic coverage. For airlines, these transactions can eliminate overlapping routes and help reduce competition, leading airlines to achieve higher operating margins. For travelers, MAs often lead to lesser flight frequency, higher airfares or longer travel miles. To explore spatial-temporal variations from airline and passenger perspectives, this paper focuses on 55 major airports in the 50 largest cities between 2000 and 2010. The detailed results of passenger flow patterns suggest that some airports have more spatial imbalance than others in terms of passenger travel distances. Further, the findings indicate that the MAs have different effects on passenger flows and traveled distances, and the effect is complexly related to the airport’s spatial status.

With increasing availability of spatio-temporal data and the democratization of Geographical Information Systems (GIS), there has been a demand for novel statistical and visualization techniques which can explicitly integrate space and time. The paper discusses the nature of spatio-temporal data, the integration of time within GIS and the flourishing availability of spatial and temporal-explicit data over the Internet. The paper attempts to answer the fundamental question on how these large datasets can be analyzed in space and time to reveal critical patterns. The authors further elaborate on how spatial autocorrelation techniques are extended to deal with time, for point, linear, and areal features, and the impact of parameter selection, such as critical distance and time threshold to build adjacency matrices. The authors also discuss issues of space-time modeling for optimization problems.

When comparing accessibility, the interpretation of results is complex because of lack of standard or universal norm. This uncertainty issue of the distinction from the lack of standard can be solved using the multi-level approach of fuzzy set: universal, relative, and absolute index. Since a fuzzy set approach deals with the vagueness and indiscernibility of accessibility index, the proposed approach suggests a better solution to classify the index than a crisp set or even a single-level fuzzy set approach. In this study, we evaluate job accessibility of locations in the Columbus MSA in Ohio, USA for 18 worker groups. The uncertain distinction between strong/weak, rich/poor, and higher/lower accessibility is improved by the multi-level approach. Moreover, this study attempts to enhance our understanding of spatial structure of job accessibility disaggregated by occupation type and gender.

This research examines the crime prevention effects of open-street closed circuit televisions (CCTVs), installed in the city of Chuncheon, South Korea on serious crimes and disorder crimes. After controlling for the length of the month, season and temporal trend, we applied a mixed linear model for repeated measurements. We also used a Weighted Displacement Quotient (WDQ) to analyze the crime-reduction effects of each open-street CCTV location. The results of a mixed linear model showed that, on average, open-street CCTV did not show a statistically significant effect on the reduction of serious crimes or disorder crimes. However, the analysis of a WDQ showed that the crime-reduction effect of open-street CCTV location depends on the characteristics of the locations. The results also showed that the effects of a diffusion of benefits were higher in serious crimes than in disorder crimes. Results are similar to findings in European and North-American contexts.

Although data for temporal spring river ice breakup are available for a number of Arctic rivers, there is a paucity of information related to the type of breakup. The Arctic Climate Impact Assessment (ACIA) of 2005 predicted a transition from mechanical to thermal spring breakup of ice cover on arctic rivers, with this shift being greatest in exclusively Arctic watersheds where observed warming is most pronounced. We describe a rare instance of an entirely Arctic river with limited but well documented historical and recent data regarding the type of breakup. Time-series ground imagery of spring breakup from 1966, 1975, 1978, 2009, 2010 and 2012, in combination with interviews of local inhabitants, documents a shift from predominantly mechanical to predominantly thermal breakup after spring 1978 and by spring 2009 within the context of a locally and regionally warming Arctic. The resultant shift from predominantly mechanical to predominantly thermal breakup is predicted to result in significant changes to water, sediment, nutrient and organic carbon fluxes, as well as riparian ecology and human activities.

Spatial interaction models are frequently used to predict and explain interregional commodity flows. Studies suggest that the effects of spatial structure significantly influence spatial interaction models, often resulting in model misspecification. Competing destinations and intervening opportunities have been used to mitigate this issue. Some recent studies also show that the effects of spatial structure can be successfully modeled by incorporating network autocorrelation among flow data. The purpose of this paper is to investigate the existence of network autocorrelation among commodity origin–destination flow data and its effect on model estimation in spatial interaction models. This approach is demonstrated using commodity origin–destination flow data for 111 regions of the United States from the 2002 Commodity Flow Survey. The results empirically show how network autocorrelation affects modeling interregional flows and can be successfully captured in spatial autoregressive model specifications.

Previous findings support that distance matters for job access. Typically, long distances act negatively on job access either due to the lack of information about the opportunities or the cost (time, transportation, etc.). Disparities in job access are explained with the workers’ demographic and socioeconomic characteristics and their spatial condition. Nevertheless, job access was not fully explored in multi-dimensional ways because of data and computational limitations. Recently, the wealth of commuting data, combined with the growing capacity of computation and methodological development, enables us to examine more commuting pattern details than what existing data provide at an aggregate level. This study uses a disaggregate journey-to-work model on 2000 Census Transportation Planning Package (CTPP) commuting data to investigate access to job by gender and occupation, in a more localized context. To explore this varying degree of job access and associated explanation, we analyzed disaggregate commuting flows and ran a regression model on them. This study has three main objectives: (1) to disaggregate journey-to-work flows by gender and occupation to estimate the number of commute trips between census tracts, (2) to explore the variations in job access by gender and occupation, and (3) to draw relationships between job access and various worker’s situations. The results show the details of commuting patterns, suggesting that some occupations have more gender imbalance than others. Further, the findings indicate that the same demographic, socioeconomic and spatial conditions have different effects on workers, and the effect is related to the workers’ demographic-socioeconomic status in complex ways. Unlike conventional research in which a particular worker group is compared to a control group of opposite characteristics, our methodology makes it possible to examine an overview of all the job and gender groups, providing advantages in 2-way comparisons between gender and occupation groups beyond a conventional comparison between two groups. Therefore, our study adds an additional dimension to the conventional comparison.

A traditional knowledge “Inupiaq Web GIS”, based on a five-year study and containing observations and environmental knowledge of Inupiat communities indigenous to Arctic Alaska, was incorporated into a Web-based platform. The website, “Arctic Cultural Cartography,” was created to be an open portal through which the password-protected “Inupiaq Web GIS” could be accessed. We discuss the process of developing the web GIS including the incorporation of user-friendly features such as links to interactive maps, video clips of interviews, discussion boards, and the integration of popular web interfaces such as Facebook. We also discuss short- and long-term goals for the further development of the GIS, its potential as a sustainable, participatory online database for sharing pertinent ecological knowledge, and challenges in achieving optimal community involvement given constraints imposed by remote locations with limited bandwidth.

In the present study, the corrosion and stress corrosion cracking (SCC) behavior of equal channel angular pressed (ECAPed) oxygen-free copper was examined in 3.5% NaCl solution. The specimen with two ECAP process cycles was found to have the greatest resistance to corrosion and SCC in 3.5% NaCl solution among the specimens studied, while the resistance varied in a complex manner with different number of ECAP process cycles. Micrographic observation and differential scanning calorimeter study suggested that both corrosion and SCC behavior of ECAPed copper was strongly dependent on the microstructural evolution, including the change in grain size and dislocation density, during ECAP process.

This study proposes a methodology through which transportation analysts and policy makers can use spatial optimization to support strategic planning, with the goal of extending existing service networks. Based on modeling objectives common to many service industries, an approach is developed for integrating geographic information systems (GIS) and spatial optimization modeling in order to extend an existing transit system through prioritizing route and stop additions. Development of a strategic methodology such as this is vital for agencies interested in extending transit networks to accommodate urban growth and development. This is especially true in public transit applications, such as bus route planning, as the future of bus-based public transportation depends on the success of route expansion and modification. The developed approach is applied to the transit system in Columbus, Ohio.

In the present study, the tensile behavior of nanograin-sized, pure copper produced by the equal channel angular pressing (ECAP) process, which is at present one of the most popular methods for producing nanograined bulk material, was examined as related to the microstructural evolution. It was found that the yield and tensile strength values of 99.99 pct pure, oxygen-free copper increased with the increasing number of ECAP cycles due to the strain hardening in the initial stage. Further ECAP process promoted the formation of equiaxed grains accompanied with the gradual decrease in dislocation density. Once the equiaxed grain formed, the decrease in dislocation density would be further accelerated due to the extremely high rate of dynamic recovery with the grain boundary area acting as a dislocation sink. The strain hardening mechanism would then stop to operate and the fine grain boundary hardening mechanism would begin to dominate after the forth cycle of the ECAP process, resulting in an increase in the tensile ductility without sacrificing the strength.

In the present study, the tensile anisotropy of age-hardened Cu-6Ni-2Mn-2Sn-2Al, Cu-6Ni-2Mn-2Sn-2Al, and Cu-6Ni-2Mn-5Al alloy sheets, either perpendicular or parallel to the rolling direction, was examined. It was found that age-hardened Cu-Ni-Mn-Sn-Al alloys have higher tensile strength along the T orientation than L orientation at high rolling ratios. Such a trend was most notable in the high Al containing Cu-6Ni-2Mn-5Al alloy among the alloys studied. At high rolling ratios, well-developed deformation bandlike structures were observed to be mostly aligned perpendicular to the rolling direction for each alloy. These deformation bandlike structures appeared to be responsible for the higher tensile strength along the T orientation. The transmission electron microscopy (TEM) examination demonstrated that the deformation bandlike structures consisted of tangled dislocation networks, which were further thickened with the addition of Al or the reduction of Sn. The stacking fault energy (SFE) of Al and Sn, as related to the ease of cross-slip, is believed to be responsible for the present observation.

Satellite radar and aircraft laser altimeter data and a volume budget comparison of total snow accumulation with total ice discharge give three independent estimates of the recent mass balance of parts of the Greenland ice sheet above ∼2000 m elevation. Results show the entire region, on average, to be in balance to within 10 mm yr−1, with very low rates of regional thickness change (dH/dt) in the northeast but high rates with large spatial variability in the south. Only the volume budget estimates show significant thinning in the northwest, but thinning in this area is also inferred from local measurements of ice vertical velocities down boreholes. South of latitude 68°N, there has been rapid thickening west of the ice divide, with equally rapid thinning in the southeast, but with large differences between the three estimates of dH/dt throughout this region. The radar data apply to the period 1978–1988, the laser data are for 1993/1994–1998/1999, and the volume budget calculations represent conditions over at least the last few decades. Consequently, many of the differences between results could be caused by temporal changes, particularly in snow accumulation rates, that occurred since the 1970s. However, taken with other information, our results suggest long-term thickening in the southwest and possibly quite recent onset of rapid thinning in the southeast.

Multivariate regression methods are applied toneasurements of accumulation covering much of the interior of the Greenland ice sheet to evaluate the important factors that describe the current distribution of accumulation. Predictor variables considered in the regressions are geographical coordinates and three independent factors describing the geometry of the ice sheet. The results indicate that most of the variance in the data is explained by the combined effect of large-scale atmospheric circulation and ice sheet topographyo This finding implies that climate change scenarios in which changes in accumulation are mostly associated with changes in temperature or some other parameter may only be correct if the pattern of atmospheric circulation remains unaltered. Comparison with values predicted with a precipitation retrieval model is favorable, suggesting that the model captures the most important features of Greenland precipitation. Approximately 80% of the total area of Greenland is ice cov- ered. The main ice sheet reaches thicknesses in excess of 3 km and contains enough water to raise global sea level by 7 m if all ice were to melt. The ice cover is nourished and maintained by snowfall at higher elevations, while mass is lost through surface ablation and subsequent meltwater runoff in the coastal regions, melting underneath floating tidal glaciers, and calving at glacier tmxnini. Redistribution of mass from the accumulation area to the marginal ablation zones is achieved through ice flow. The magnitude of each of these processes determines whether the ice sheet is in balance or whether it is growing or slu-inkingIn as- sessing the state of balance of the Greenland ice sheet, it is thus important to detexnine accurately each term in the mass budget. In this study, the source term of average accumulation in the inte- rior is considered. The interior is defined as the region where surface elevations are in excess of 1100 m above sea level. At these elevations the contributions to net accmnulation of mass as- sociated with evaporation, condensation, surface ablation and runoff, and, perhaps, snowdrift are small (Ohnura et al., 1999). Using observations from automated weather stations, Box and Steffen (this issue) estimate sublimation over the Greenland ice sheet. Their results indicate that annual sublimation loss occurs mostly in the ablation zone at lower elevations (

Introduction. Local environmental factors provide important contributions to bicycle safety. The purpose of this study was to characterize bicycle collisions by neighborhood in Cincinnati, Ohio. Background. The majority of prior bicycle safety research has focused on helmet use, especially among youth. Studies that have considered the neighborhood have centered on the built environment and its facilitation of bicycling (e.g., connectivity of roads and road conditions). Other broad conditions may be associated with injury beyond the use of protective equipment and the physical environment. Method. This study sought to determine spatial clustering, local patterning, temporal differences (time of day and season of year), and significant neighborhood-level predictors of bicycle collisions. Bicycle collision data were obtained from the Cincinnati, Ohio Police Department. Conclusions. This study showed that collisions occur at higher rates in the south-central and southwest neighborhoods of Cincinnati, Ohio. There were seasonal and time-of-day differences with respect to collision rates with summer and afternoon being the most common collision times. Neighborhood ethnicity, population density and presence of public transportation were all significant predictors of bicycle collisions. These findings will be disseminated to local city authorities and bicycle advocacy groups.

Cu-9Ni-6Sn alloy has been developed as a possible substitute for high-strength, precipitation-hardened Cu-Be Fig. 1—Macroscopic views of (a) 90 pct hot-swaged Cu-6Ni-2Mn-2Sn2Al alloy and (b) 10 pct hot-swaged Cu-9Ni-6Sn alloy. alloys in the various applications of electronic industry.[1–7] However, it is often impracticable to produce sheet products from Cu-9Ni-6Sn alloy due to the severe cracking during hot working. It has been previously reported that Sn-rich segregates formed during solidification are responsible for hot cracking.[8] There have been considerable research activities to solve the hot cracking problem, including the powder metallurgy (PM) technique and the lowering of Sn content.[9] Powder metallurgy processed high Sn-containing Cu-Ni-Sn alloys can be readily rolled down to 0.2mm-thick sheet, but they have an inherent problem of high production cost. The previous study conducted by the authors has suggested that Cu-6Ni-2Mn-2Sn-2Al alloy is hot workable with a reduced production cost and reasonable physical properties compared to Cu-9Ni-6Sn alloys. The Sn content of 2 pct in the Cu-6Ni-2Mn-2Sn-2Al alloy makes it possible to be hot rolled to produce the sheet products. The Mn is isomorphous to Cu and can partially replace expensive Ni that is beneficial to castability and tensile strength. The addition of Al, which is a strong solid solution strengthener in Cu, compensates the reduced tensile strength as a result of lower Sn content. In conducting research, it was found that the addition of a small amount of Zr further improved the hot workability of Cu-6Ni-2Mn2Sn-2Al alloy significantly. The objective of the present study therefore was to examine the effects of beneficial Zr addition on the hot workability of Cu-6Ni-2Mn-2Sn2Al alloy. Cu-6Ni-2Mn-2Sn-2Al alloys without and with Zr addition of 0.3 wt pct were prepared using permanent mold casting in the form of either 25 mm round bar or 25mm-thick plate, respectively. A round bar with a 25-mm diameter was hot swaged at 850 8C to 8-mm diameter rod and air cooled. A plate with a 25-mm-thick plate was also hot rolled to 1-mm-thick sheet at 850 8C. Some specimens were aged at either 400 8C or 450 8C, respectively, for 1 to 7 hours. Tensile tests and Vickers hardness tests were conducted for selected specimens. Either a flat or cylindrical specimen, respectively, with a gage length of 25.4 mm was prepared from the rolled sheet or the swaged bar products, respectively. Bending fatigue tests were performed according to ASTM B593, using a Krouse-type bending fatigue machine, at an R ratio of 21 and test frequency of 20 Hz. Scanning electron microscope (SEM) and optical

Fast frequency channel saturation is one of big challenges in open spectrum bands. System designers may easily come up with TPC (transmission power control) applied to the down-streams of a network, to increase the cell reuse factor, but this scheme alone is likely to encounter initial access issues where beacons are not either receivable or decodable inside the network's maximum transmission range. Such problems can be handled in two major approaches: first, relaying beacons in a distributed manner to statistically sweep out hidden areas; and second, explicit demand of beacons from a connecting device. The latter is called active scan (or sending probes) and can guarantee successful connections to the network if, and only if, appropriate mechanisms are provided to avoid interference to neighboring networks. In that context, we will explore a wide span of DSA (dynamic spectrum access) techniques and introduce a system, called DPA (discrete probe access)-OFDMA, where probe frames are transmitted with orthogonality maintained in the power and code domain. A group of cognitive techniques to boost the efficiency of active scans will be presented too.

Comparison of ice discharge from higher elevation areas of the entire Greenland Ice Sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades. On average, the region has been in balance, but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast. The north of the ice sheet shows less variability, with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest. These results agree well with those from repeated altimeter surveys, except in the extreme south, where we find substantially higher rates of both thickening and thinning.