Built-up Surface Research Articles

Built-Up Encroachment and the Urban Field: A Comparison of Forty European Cities

We define the urban field as the spatial organisation of urban densities according to decreasing gradients from centre to periphery. This urban field can be estimated from the encroachment of built-up areas. The CORINE Land Cover database enables the measurement of the gradient values for the spatial distribution of built-up areas in European cities. Instead of the exponential or power functions, which usually provide the best fit for the distributions of population densities, we find that two linear functions strongly differentiating a central and a peripheral gradient provide the best fit for built-up surfaces. The comparison between the 1990 and 2000 CORINE images demonstrates a convergence in the trend of urban spread between Northern and Southern European cities. However, it is still difficult from the data to decide which of the models of urban field is winning: will the steeper central gradient become diluted into the less dense periphery, or are the closer fringes of the central parts becoming integrated into the ordered pattern of the urban central agglomerations?

Fractal dimension versus density of built-up surfaces in the periphery of Brussels

Abstract. This paper tries to demonstrate the usefulness of a fractal analysis for characterising the morphology of built‐up areas within the peri‐urban fringe. Methodology and expectations are discussed theoretically and geometrically. An empirical analysis is then performed on the southern periphery of Brussels. The effect of the size and shape of the windows is evaluated; this leads to a methodological discussion about the real meaning of fractality and its relationship to density. These analyses confirm the usefulness and limits of the fractal approach: it is a promising tool for describing the morphology of cities and for simulating the growth and development of this field of research.Abstract. Este artículo pretende demostrar la utilidad de un análisis fractal para caracterizar la morfología de áreas urbanizadas dentro del área peri urbana. La metodología y expectativas se discuten teórica y geométricamente. A continuación se realiza un análisis empírico en la periferia del sur de Bruselas. Se evalúa el efecto del tamaño y forma de las ventanas; esto lleva a una discusión metodológica sobre el verdadero significado de la fractalidad y su relación con la densidad. Estos análisis confirman la utilidad y limites del enfoque fractal: Es una herramienta promisoria para describir la morfología de ciudades y para simular el crecimiento y desarrollo de este campo de investigación.

Changes in urban built-up surface and population distribution patterns during 1986–1999: A case study of Cairo, Egypt

Landsat TM and ETM+ images were used to examine urban growth for the Greater Cairo area, Egypt, between 1986 and 1999, assisted by fieldwork and high spatial resolution images such as IRS, CORONA, and IKONOS. During the study period, urban land (collectively classified as built-up surface) increased significantly. Most of the increases in urban land came from the conversion of desert land and farmland on the Nile Delta. When changes in built-up surface were analyzed against census data of 1986 and 1996, it was found that population per unit area of built-up surface may serve as a good indicator of urbanization. This metric offers a different measure from the traditional calculation of population density and provides a measure of urban living environment by reflecting the dynamics of both population and urban land use growth. For the entire study area, population density increased by 26.8% from 7158 persons/km 2 to 9074 persons/km 2 during 1986–1999. In the mean time, the total built-up area increased by 33.7% from 344.4 km 2 to 460.4 km 2, while population per unit of urban land decreased from 27,188 persons/km 2 to 25,799 persons/km 2, indicating that urban land use growth in terms of construction and infrastructure may have outpaced population growth in Cairo overall. However, such changes were not evenly distributed. While most increases in built-up surface were found in the outer margin of the greater Cairo area, population per unit built-up area increased most significantly in the suburbs and to the south of the city. Such changes reflected the nature of housing demand and the mechanisms that governed the urbanization process in the Greater Cairo area.

A parametric study of a blown powder laser cladding and alloying process using a two-dimensional conduction model

A two-dimensional model has been developed to predict the temperature field and melt pool shape during blown powder laser cladding. A finite volume method has been used to solve the two-dimensional energy equation for a body moving relative to a stationary laser heat source. A boundary fitted coordinate system has been employed as the built-up surface geometry is complex. Important dimensionless groups representing laser parameters power ( P) and scanning speed ( U) and the process parameters built-up height and average dilution are identified. The effect of laser parameters on process parameters is investigated. For cladding P/U should always be kept low (less than 1) to reduce the average dilution, and in order to achieve the desired clad height the power level P should be controlled.

An analysis of the relationship between spatial patterns of water quality and urban development in Shanghai, China

Recent urban development in Shanghai, the largest city in China, and its impact on the water environment are examined in this study. The area of built-up surface was obtained from the classification of the Landsat 7 ETM+ images of the year 2000 for Shanghai. The proportion of built-up surface and population density were extracted from buffer zones with radii ranging from 100 to 2000 m, and used in regression analysis against various water quality parameters at 44 water quality monitoring stations across metropolitan Shanghai. Results suggest that in most cases, the pattern of urban land use as represented by the built-up surface was a stronger predictor than population density in explaining spatial patterns of water quality parameters in Shanghai. The best models of most water quality parameters were found for buffer zones of 2000 m radius rather than for smaller buffers, indicating the regional nature of the factors that influence water quality in the study area. Evidence suggests that strong associations between land use, population density, and water quality result from the contribution of untreated domestic wastewater and non-point pollution sources to waterways in Shanghai. Such relationships should remain strong in the near future until measures to increase the capacity of wastewater treatment and control of non-point pollution sources are fully implemented.

Using Fractal Dimensions for Characterizing Intra‐urban Diversity: The Example of Brussels

The objective of this paper is to compare fractal‐based parameters calculated by different fractal methods for urban built‐up areas and to link the observed spatial variations to variables commonly used in urban geography, urban economics, or land‐use planning. Computations are performed on Brussels, Belgium. Two fractal methods (correlation and dilation) are systematically applied for evaluating the fractal dimension of built‐up surfaces; correlation is used to evaluate the fractal dimension of the borders (lines). Analyses show that while fractal dimension is ideal for distinguishing the morphology of Brussels, each estimation technique leads to slightly different results. Interesting associations are to be found between the fractal dimensions and rent, distance, income, and planning rules. Despite its limitations, fractal analysis seems to be a promising tool for describing the morphology of the city and for simulating its genesis and planning. The model is robust: it replicates the urban spatial regularities and patterns, and could hence fruitfully be integrated into intra‐urban simulation processes.

Using Fractal Dimensions for Characterizing Intra-urban Diversity: The Example of Brussels

The objective of this paper is to compare fractal-based parameters calculated by different fractal methods for urban built-up areas and to link the observed spatial variations to variables commonly used in urban geography, urban economics, or land-use planning. Computations are performed on Brussels, Belgium. Two fractal methods (correlation and dilation) are systematically applied for evaluating the fractal dimension of built-up surfaces; correlation is used to evaluate the fractal dimension of the borders (lines). Analyses show that while fractal dimension is ideal for distinguishing the morphology of Brussels, each estimation technique leads to slightly different results. Interesting associations are to be found between the fractal dimensions and rent, distance, income, and planning rules. Despite its limitations, fractal analysis seems to be a promising tool for describing the morphology of the city and for simulating its genesis and planning. The model is robust: it replicates the urban spatial regularities and patterns, and could hence fruitfully be integrated into intra-urban simulation processes.

Dispersion of a passive plume in an idealised urban convective boundary layer: A large-eddy simulation

This large-eddy simulation study investigates the effects of an idealised surface inhomogeneity of sensible heat flux on dispersion of a passive plume emitted from elevated sources into an urban convective boundary layer (UCBL). The results show that when Deardorff's translation is made to introduce a wind with its direction aligned with the centreline of park blocks, dispersion of such a passive plume is strongly affected by turbulent structure associated with the patchy pattern of surface heat flux. In comparison with a case with a homogeneous surface, when the point source is located above the central line across the park areas, the mean plume height Z c is lower, the vertical dispersal parameter S z is smaller, the surface concentration C 0 is generally higher, and pollutant is less dispersed in the vertical direction. When the point source is aligned with the built-up area, however, the opposite situation occurs. The difference in surface concentration at a same downwind distance can be as large as 100% among the cases over a homogeneous surface, the location above built-up surface and the location above park surface in the idealised urban area. The extent to which the patchy pattern of surface heat flux influences the plume dispersion depends on two parameters: d/ Z i and b/ p, where d is the distance between the centres of two adjacent parks, b is the width of built-up area, p is the size of park, and Z i is the UCBL height. This study suggests that dispersion of a passive plume in a UCBL has different behaviour from that for a homogeneous surface in the previous studies. Estimate of pollutant concentration by the existing methods or models that are based on observations over a homogeneous surface cannot distinguish such differences revealed by the results in this paper.

Wide stall mining for optimal recovery of coal from a thick seam under surface features

The conventional method, splitting and stooking of a pillar, to optimise recovery of coal under built-up surface structures has limited scope for a multisection-developed thick seam under massive, immediate, roof strata and shallow depth cover. Taking advantage of the rapid increase of pillar strength with increase in its size, the conventional method to optimise recovery under built-up surface structures is replaced by widening of the existing galleries using the method called wide stall mining. The first field trial of the method was conducted under the geomining conditions of East Bhuggatdih colliery. Successful application of this method at East Bhuggatdih colliery provided nearly 42% coal from a multisection-developed 17 m thick coal seam without endangering the surface and subsurface structures. This paper describes the principles of wide stall mining together with the results of laboratory and field investigations.

Spectral Reflectance Properties of Different Types of Built-Up Surfaces

The spectral reflectance properties of features present on the Earth's surface play an important role in the interpretation and analysis of remote sensing data. Usually the surface materials and objects are characterized by their spectral reflectance properties, in optical remote sensing. This paper presents the results obtained from the ground-truth spectral reflectance measurements in the 450–900 nm wavelength range (i.e., in the visible and near-infrared wavelengths) for various built-up surfaces. These reflectance measurements are taken by using a multiband ground-truth radiometer, which gives satellite-simulated spectral reflectance data. The spectral reflectance data are collected over brick, mud and bituminous roads and bituminous airstrip surfaces, which are considered representative of different types of built-up surfaces in this investigation. The use of the reflectance properties of various types of built-up surfaces are discussed in the mapping, planning, and maintenance of these surfaces using remote sensing.

Modifications in the Si valence band after ion-beam-induced oxidation

The changes undergone by the Si surface after oxygen bombardment have special interest for acquiring a good understanding of the Si+-ion emission during secondary ion mass spectrometry (SIMS) analysis. For this reason a detailed investigation on the stoichiometry of the builtup surface oxides has been carried out using in situ x-ray photoemission spectroscopy (XPS). The XPS analysis of the Si 2p core level indicates a strong presence of suboxide chemical states when bombarding at angles of incidence larger than 30°. In this work a special emphasis on the analysis and interpretation of the valence band region was made. Since the surface stoichiometry or degree of oxidation varies with the angle of incidence, the respective valence band structures also differ. A comparison with experimentally measured and theoretically derived Si valence band and SiO2 valence band suggests that the new valence bands are formed by a combination of these two. This arises from the fact that Si–Si bonds are present on the Si-suboxide molecules, and therefore the corresponding 3p–3p Si-like subband, which extends towards the Si Fermi level, forms the top of the respective new valence bands. Small variations in intensity and energy position for this subband have drastic implications on the intensity of the Si+-ion emission during sputtering in SIMS measurements. A model combining chemically enhanced emission and resonant tunneling effects is suggested for the variations observed in ion emission during O+2 bombardment for Si targets.

Development of a workstation environment for the assessment of a stormwater drainage fee

The design and development of a workstation for the assessment of a stormwater drainage fee based on built-up surfaces is described. The work was performed under contract to the City and County of Denver, Colorado, USA. The requirement for such a system was prompted by the City's decision to institute a fee for the expansion and maintenance of the City's stormwater drainage system. This fee should be based on the total amount of impervious surfaces (i.e. buildings, driveways, sidewalks) on the different properties. To determine the impervious areas on a parcel by parcel basis a method was selected that employs aerial photography in combination with existing property boundaries available on hand drawn assessor maps. Project requirements, setup and organization, and the implementation of the user requirements are briefly described. Subsequently, the strengths and weaknesses of the chosen approach are reviewed followed by a discussion of the experiences gained after more than three years of operation at the user's site.

Complejo de oficinas Madrid/España

With the re-modelling of an old building of the XVIth century, the re-construction of another of the XlXth century and carrying out a third of new design, an interrelated complex has been made to house the annexes of the new site of the Banco de Urquijo. The group of buildings, with a built-up surface of about 40,000 m 2 , has received different treatments, in accord with the different characteristics of the three constructions. It was always possible to join the adequate flexibility of use with the integrated harmony of the complex, both among its own units and with the neighbouring buildings, arriving, in this sense, to a new organisation of the Plaza del Rey, the focal point for all the buildings.

Cavitation erosion of turbines in the lower Dnieper hydroelectric station

1. It is necessary to develop soundly-based criteria for the required immersion of turbines, with allowance for operating conditions. 2. When surfaces damaged by cavitation are being built up, strict control of the blade profiles is necessary. The built-up surfaces must be carefully treated, and polishing must be used in the last stage of the process.