Browsing by Subject "Density"

Now showing 1 - 7 of 7
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    Density of Development in Newly Urbanized Areas Over Time
    (Elsevier, 2021-01-01) Ottensmann, John R.; School of Public and Environmental Affairs
    Initial significant development at the urban fringe is only the beginning of a period of development that continues for at least several decades. Two hypotheses are posited: The density of development in newly urbanized areas will increase over time, and the increase will be greater in urban areas that are growing more rapidly. The percent of housing in newly urbanized areas that is more dense — single-family attached and multifamily housing — is used as the measure of density. Percent more dense housing and its change were examined for the decades after urbanization in the areas newly urbanized from 1960 to 2010 for 59 large urban areas in the United States. Densities increased significantly in the 2 decades after those areas became urban and the increases were greater in faster growing urban areas.
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    Exploring Urban Density
    (Elsevier, 2021-07-01) Ottensmann, John R.; School of Public and Environmental Affairs
    Density in urban areas is not a simple concept. It can be defined in a variety of ways. This paper presents alternative measures of urban density and compares how they perform across a set of 59 large urban areas in the United States in 2010. Population and housing unit densities show similar patterns, though with differences for some areas with extreme population-housing unit ratios. The housing unit densities do perform better in the estimation of the negative exponential model of density decline. The conventional measure of total population divided by the total land area of an urban area differs from various measures of the density of residential areas. The absence of data precludes the calculation of residential densities for large numbers of urban areas, but using block data and excluding blocks that are completely or largely nonresidential makes possible alternative measures coming closer to residential density. When used to estimate the negative exponential model, these measures produce higher estimates of the parameters and a significantly greater goodness-of-fit. Weighted density calculated as the mean of the densities of small areas weighted by their population is another, completely different measure. These are higher than convention densities, with the differences being larger for those urban areas with greater internal variation in density, such as areas with high density cores and low density peripheries.
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    A Framework for Optimizing Process Parameters in Powder Bed Fusion (PBF) Process using Artificial Neural Network (ANN)
    (2019-08) Marrey, Mallikharjun; El-Mounayri, Hazim; Zhang, Jing; Tovar, Andres
    Powder bed fusion (PBF) process is a metal additive manufacturing process, which can build parts with any complexity from a wide range of metallic materials. Research in the PBF process predominantly focuses on the impact of a few parameters on the ultimate properties of the printed part. The lack of a systematic approach to optimizing the process parameters for a better performance of given material results in a sub-optimal process limiting the potential of the application. This process needs a comprehensive study of all the influential parameters and their impact on the mechanical and microstructural properties of a fabricated part. Furthermore, there is a need to develop a quantitative system for mapping the material properties and process parameters with the ultimate quality of the fabricated part to achieve improvement in the manufacturing cycle as well as the quality of the final part produced by the PBF process. To address the aforementioned challenges, this research proposes a framework to optimize the process for 316L stainless steel material. This framework characterizes the influence of process parameters on the microstructure and mechanical properties of the fabricated part using a series of experiments. These experiments study the significance of process parameters and their variance as well as study the microstructure and mechanical properties of fabricated parts by conducting tensile, impact, hardness, surface roughness, and densification tests, and ultimately obtain the optimum range of parameters. This would result in a more complete understanding of the correlation between process parameters and part quality. Furthermore, the data acquired from the experiments are employed to develop an intelligent parameter suggestion multi-layer feedforward (FF) backpropagation (BP) artificial neural network (ANN). This network estimates the fabrication time and suggests the parameter setting accordingly to the user/manufacturers desired characteristics of the end-product. Further, research is in progress to evaluate the framework for assemblies and complex part designs and incorporate the results in the network for achieving process repeatability and consistency.
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    Nonlinear Estimation of the Negative Exponential Model of Population Density Decline
    (Elsevier, 2022-05-19) Ottensmann, John R.; School of Public and Environmental Affairs
    The negative exponential model of the decline of density with distance from the center was estimated using census tract data for New York in the traditional manner, regressing the natural log of density on distance, log linear estimation. The predicted densities were plotted along with the actual densities and showed significant under prediction near the center, readily explained by the log transformation of density. Nonlinear estimation of the model produced more satisfactory results. The model was estimated using nonlinear and log linear estimation for 43 large urban areas in the United States using tract data for 1970 and 2010. The average log linear estimates of the density gradient and central density were lower than the nonlinear estimates, with some urban areas having very large differences. Comparison of the values obtained from regressing the predicted densities on the actual densities showed the nonlinear values to be either higher or similar to the log linear values. Considering the conclusions that might be drawn regarding changes over time, the mean results for percent change were similar for the nonlinear and log linear estimates, but differences for some individual urban areas were substantial. The conclusion is that nonlinear regression is superior for the estimation of the negative exponential model.
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    The Decline of the Density Gradient is Not a Good Measure of Decentralization
    (Elsevier, 2022-06-17) Ottensmann, John R.; School of Public and Environmental Affairs
    The decrease in the density gradient estimated assuming the negative exponential decline of density has been used as a measure of the decentralization of the population in urban areas. A definition of urban population decentralization is presented and a measure of centralization is developed. The density gradient and its change are compared with this index of centralization, first in a numerical model and then using data on the distribution of the population in 43 large urban areas in 1970 and 2010. The density gradient is only somewhat related to this index and is not a good measure of decentralization.
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    The Use (and Misuse) of Population-Weighted Density
    (Elsevier, 2021-11-01) Ottensmann, John R.; School of Public and Environmental Affairs
    During the past several decades, population-weighted density has come to be used in scholarly papers and other formal reports. It is a weighted average of the densities of smaller subareas that is an alternative to the traditional measure of density, total population divided by total area. The U.S. Census used it in a 2012 report resulting in increased attention in more informal pieces such as blog posts and pieces in popular media. Calculation of population-weighted densities and their reporting and inclusion in datasets occurred. The quality of the treatment of population-weighted density in all of these works has been uneven. Important information has not always been provided. This paper reviews these items and assesses the use of population-weighted density.
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    Unequal access: Tobacco Retail in the Indianapolis Metro Area
    (The Polis Center, Indiana University at Indianapolis, 2017-07) Comer, Karen; Davila, Kelly; Hollon, Deb; Nowlin, Matt
    Retail access to various smoking products is an important consideration when discussing community action to improve a community’s health. Studies show that tobacco outlet density and proximity are linked to tobacco use–particularly in poor areas. We used socioeconomic data culled from the SAVI community information system to examine the density and proximity of tobacco outlets relative to vulnerable communities in Marion County. The report serves as a companion piece to the IU Richard M. Fairbanks School of Public Health’s September 2016 Report on the Tobacco Epidemic in Marion County and Indiana.