Mapping the Internet using GIS: The death of distance hypothesis revisited

This paper revisits the death of distance hypothesis. To explore the role of distance in the information age, three methods – web scan, hyperlink, and trace-route – are used to map the Internet for the US educational network. Statistical analysis is conducted to evaluate whether physical distance has any impact on the Internet information access. The cartographic and statistical results indicate that geography in general and distance in particular are still important factors in shaping the spatial pattern of Internet activities. For the most popular fifty-three US educational web sites, the physical distance within one thousand miles has positive effects on Internet access while access to international hosts heavily depends on the response time, link speed and other Internet infrastructures and interconnections such as the availability of domain name servers, network access points, backbones, etc. Implications of absolute, relative, and virtual distance in mapping the Internet are discussed. It is concluded that the death of distance hypothesis is premature, even misguided in most cases.     

Karst depressions in a time context

A study of karst depression enlargement through time on the Western Highland Rim (physiographic province), based on two sets of aerial photography (1937, 1972) and field work, indicates that areal growth rates (dA/dt, m²/a) depend upon the surficial geologic setting. Areal growth rates were calculated from rates of long axis (dL/dt) and mean width (dW/dt) enlargement assuming an elliptical plan shape. Areal growth rates averaged 40, 70, and 100 m²/century for loessial, clayey residual, and silty colluvial surficial material, respectively. Estimates of average apparent age of karst depressions in each of the three surficial materials, based on linear growth rates, varied from 25,000 to 65,000 years B.P. An occurrence of mastodon (Mammut americanum) and ground sloth (Megalonyx jeffersoni) from the Darks Mill depression as well as a pollen record from another depression dating from the Late Wisconsin glacial maximum in the same geomorphic setting yielded dates compatible with estimates of depression age.     

Carbon-13 NMR spectra of macerals separated from individual coals

The density gradient centrifugation technique has recently been applied to the separation of macerals from whole coals. Sufficient quantities have been separated to permit examination of pure exinite, vitrinite and inertinite fractions by combined cross polarization and magic angle sample spinning (CP/MASS) carbon-13 NMR techniques. The similarities and differences observed in the maceral groups of two coals are discussed. Diversity in precursors or in differential chemical maturation or a combination of both of these factors can be used to account for subtle spectral differences in the two coals and macerals studied even though the gross spectral features are very similar for a given maceral type. The data show that CP/MASS is a technique that can address such interesting geochemical questions.     

3D Geographic Reconstruction and Visualization Techniques Applied to Land Resource Management

Optimized land resource management depends on reliable and detailed information describing the spatial distribution of soils, geology, topography, and land use. Soil–landscapes are three–dimensional (3D) systems commonly represented using 2D maps utilizing geographic information systems. Addressing 3D soil–landscape reality is crucial for land resource management in terms of crop growth and transport processes (e.g. nitrate leaching) that are driving soil and water quality. Our objective was to investigate the usefulness of 3D geographic information technology (GIT) applied to land resource management. Our approach is based on 2D and 3D ordinary kriging interpolating surface and subsurface attributes to reconstruct soil–landscapes. We used Virtual Reality Modeling Language, which is a web–based 3D graphics language, to visualize objects (e.g. voxels, polyhedrons) representing soil and landscape attributes. We produced a 3D block model showing the spatial distribution of bulk densities and relief for a site in southern Wisconsin and a 3D stratigraphic model showing the spatial distribution of soil horizons and relief for a site in northern Florida. Emerging GIT was used to develop 3D soil–landscape models describing continuous changes of soil and landscape attributes. Combining multimedia elements (e.g. WWW, 3D visualization, and interactivity) can produce insight that would not arise from use of the elements alone. Three–dimensional scientific visualization is a powerful tool to help us see what is invisible from above the ground.     

The use of X-ray computer tomography to investigate particulate interactions within opencast coal mine backfills

Restoration of opencast coal sites frequently involves the controlled compaction of heterogeneous arisings, and accurate prediction of the settlements associated with such backfill is difficult. Attention has previously focussed on improving the specifications used to control backfilling as a way of both reducing the magnitude of the settlements and improving their predictability. However, there still exists a large degree of uncertainty about the fundamental particulate interactions that occur within a fill. The range of mechanisms previously considered to be influential on creep behaviour is described.

A current research programme is investigating the use of X-ray computer tomography (CT) as a means of nondestructively observing particle interactions during settlement, in conjunction with both long-term creep tests and short-term compressibility tests. The principles of this radiographic technique, which is relatively new to geotechnical engineering, are described, and findings are presented that illustrate the potential of the method.

Interim findings indicate that large particles are distributed on an apparently random basis within a fill, and the nonuniform distribution of voids is clearly demonstrated. Moreover, the results presented conflict to some degree with the general consensus of opinion that particle crushing is a major mechanism in the settlement process. Rather, local collapse into small voids left by compaction, and relative sliding and rotation of particles, seem to be the dominant factors for a range of compaction efforts. Particle splitting is discernible on some sections, but this mechanism appears to be less significant than others. Research is continuing into the time dependency of the observed mechanisms, the effects of moisture content changes and the effects of heterogeneous initial particle strengths.     

Growing up with rivers? Rivers in London children's worlds

This paper presents the results from exploratory research which set out to investigate London children's perceptions and uses of river environments. Mainly qualitative, multi-method research was carried out in four primary schools with children aged 9–11, focusing on two rivers near to the schools. Rivers were found to be marginal to the children's everyday lives and outdoor play, being perceived as polluted, neglected, and initially dangerous places. However, when experienced on visits observed as part of the research, some of these perceptions changed and rivers were also found to afford many special activities and experiences for the children. The visits were generally seen to have a positive effect on the children's perceptions of rivers, at least in the short term. This suggests that, if managed appropriately, rivers could be potentially rewarding play areas for children. Moreover, children could provide valuable input for river managers in suggesting ways of improving suitable local rivers for increased recreational uses.     

Soil-pile-structure interaction effects on the seismic response of a cooling tower

A study of the effects of soil-pile-structure interaction on the response of rotational shell structures supported by a group of vertical piles is presented. The interaction effects are included in the dynamic analysis through the development of a frequency dependent boundary system at the interface between the shell and the underlying foundation. The substructure method is used to simplify the connection problem between the shell and the pile foundation. A free vibration analysis of a cooling tower is carried out to investigate the dynamic properties of rotational shells with four different foundation stiffnesses. The effects of soil-pile-structure interaction on the response in the shell are demonstrated by a complex response analysis of a cooling tower.