Matching Items (36)
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Description

Disparities in access to healthy food are a key public health concern in the United States (U.S.) Food access is considered as a critical element of food insecurity. Food insecurity can often be prevalent in a region due to lack of healthy food outlets as well as inequitable access to

Disparities in access to healthy food are a key public health concern in the United States (U.S.) Food access is considered as a critical element of food insecurity. Food insecurity can often be prevalent in a region due to lack of healthy food outlets as well as inequitable access to healthy food outlets. A large body of literature pertaining to access to healthy food has reported that conventional food outlets such as supermarkets and large grocery stores may not be equitably distributed across different neighborhoods in a region. There has been limited research on local food access patterns. Despite the few studies focused on access to individual types of local food outlets, such as farmers markets, little is known about whether such access varies among different types of local food outlets and how such access patterns compare with the uneven access to conventional food outlets. This study uses Maricopa County, one of the largest counties in Arizona, as a case study to examine the spatial patterns of access to conventional food markets (i.e. supermarkets or large grocery stores) and four different types of local food outlets, including farmers market, community garden, community supported agriculture (CSA) and mobile food markets. By analyzing the association between healthy food access and neighborhood characteristics, the study suggests that the local food system has a great potential in providing healthy food access to low-income and minority populations of the County than conventional food outlets. The study provides important insights into the way different types of local food outlets offer their availability in space and whether they are more equitable in serving underserved neighborhoods. The findings from this study can assist both government agencies and city planner formulate strategies to improve access to healthy food in disadvantaged neighborhoods.

ContributorsSafayet, Mastura (Author) / Tong, Daoqin (Thesis advisor) / Pijawka, David (Thesis advisor) / McGregor, Joan (Committee member) / Arizona State University (Publisher)
Created2020
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Description
Urban community gardens hold the potential to serve as a form of multifunctional green infrastructure to advance urban sustainability goals through the array of ecosystem services they afford. While a substantial body of literature has been produced that is dedicated to the study of these services (e.g., providing fresh produce,

Urban community gardens hold the potential to serve as a form of multifunctional green infrastructure to advance urban sustainability goals through the array of ecosystem services they afford. While a substantial body of literature has been produced that is dedicated to the study of these services (e.g., providing fresh produce, promoting socialization, and enhancing urban biodiversity), less attention has been paid to the strategic planning of urban community gardens, particularly in an expansive urban setting, and in the context of the co-benefit of mitigating extreme heat. The research presented in this dissertation explores the potential of community gardens as a form of multifunctional green infrastructure and how these spaces can be planned in a manner that strives to be both systematic and transparent. It focuses on methods that can (1) be employed to identify vacant or open land plots for large metropolitan areas and (2) explores multicriteria decision analysis and (3) optimization approaches that assist in the selection of “green” spaces that serve as both provisioning (a source of fresh fruits and vegetables) and regulating (heat mitigation) services, among others. This exploration involves three individual studies on each of these themes, using the Phoenix metropolitan area as its analytical backdrop. The major lessons from this piece are: (1) remotely sensed data can be effectively paired with cadastral data to identify thousands of vacant parcels for potential greening at a metropolitan scale; (2) a stakeholder-weighted multicriteria decision analysis for community garden planning can serve as an effective decision support tool, but participants' conceptualization of garden spaces resulted in social criteria being prioritized over physical-environmental factors, potentially influencing the provisioning of co-benefits; and (3) optimized urban community garden networks hold the potential to synergistically distribute co-benefits across a large metropolitan area in a manner that systematically prioritizes high-need neighborhoods. The methods examined are useful for all metropolises with a preponderance of open or vacant land seeking to advance urban sustainability goals through green infrastructure.
ContributorsSmith, Jordan Paul (Author) / Turner, Billie L (Thesis advisor) / Meerow, Sara (Committee member) / Tong, Daoqin (Committee member) / Grebitus, Carola (Committee member) / Arizona State University (Publisher)
Created2021
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Description
Biodiversity has been declining during the last decades due to habitat loss, landscape deterioration, environmental change, and human-related activities. In addition to its economic and cultural value, biodiversity plays an important role in keeping an environment’s ecosystem in balance. Disrupting such processes can reduce the provision of natural resources such

Biodiversity has been declining during the last decades due to habitat loss, landscape deterioration, environmental change, and human-related activities. In addition to its economic and cultural value, biodiversity plays an important role in keeping an environment’s ecosystem in balance. Disrupting such processes can reduce the provision of natural resources such as food and water, which in turn yields a direct threat to human health. Protecting and restoring natural areas is fundamental to preserve biodiversity and to mitigate the effects of ongoing environmental change. Unfortunately, it is impossible to protect every critical area due to resource limitations, requiring the use of advanced decision tools for the design of conservation plans. This dissertation studies three problems on the design of wildlife corridors and reserves that include patch-specific conservation decisions under spatial, operational, ecological, and biological requirements. In addition to the ecological impact of each problem’s solution, this dissertation contributes a set of formulations, valid inequalities, and pre-processing and solution algorithms for optimization problems with spatial requirements. The first problem is a utility-based corridor design problem to connect fragmented habitats, where each patch has a utility value reflecting its quality. The corridor must satisfy geometry requirements such as a connectivity and minimum width. We propose a mix-integer programming (MIP) model to maximize the total utility of the corridor under the given geometry requirements as well as a budget constraint to reflect the acquisition (or restoration) cost of the selected patches. To overcome the computational difficulty when solving large-scale instances, we develop multiple acceleration techniques, including a brand-and-cut algorithm enhanced with problem-specific valid inequalities and a bound-improving heuristic triggered at each integer node in the branch-and-bound exploration. We test the proposed model and solution algorithm using large-scale fabricated instances and a real case study for the design of an ecological corridor for the Florida Panther. Our modeling framework is able to solve instances of up to 1500 patches within 2 hours to optimality or with a small optimality gap. The second problem introduces the species movement across the fragmented landscape into the corridor design problem. The premise is that dispersal dynamics, if available, must inform the design to account for the corridor’s usage by the species. To this end, we propose a spatial discrete-time absorbing Markov chain (DTMC) approach to represent species dispersal and develop short- and long-term landscape usage metrics. We explore two different types of design problems: open and closed corridors. An open corridor is a sequence of landscape patches used by the species to disperse out of a habitat. For this case, we devise a dynamic programming algorithm that implicitly enumerates possible corridors and finds that of maximum probability. The second problem is to find a closed corridor of maximum probability that connects two fragmented habitats. To solve this problem variant, we extended the framework from the utility-based corridor design problem by blending the recursive Markov chain equations with a network flow nonlinear formulation. The third problem leverages on the DTMC approach to explore a reserve design problem with spatial requirements like connectivity and compactness. We approximate the compactness using the concept of maximum reserve diameter, i.e., the largest distance allowed between two patch in the reserve. To solve this problem, we devise a two-stage approach that balances the trade-off between reserve usage probability and compactness. The first stage's problem is to detect a subset of patches of maximum usage probability, while the second stage's problem imposes the geometry requirements on the optimal solution obtained from the first stage. To overcome the computational difficulty of large-scale landscapes, we develop tailored solution algorithms, including a warm-up heuristic to initialize the branch-and-bound exploration, problem-specific valid inequalities, and a decomposition strategy that sequentially solves smaller problems on landscape partitions.
ContributorsWang, Chao (Author) / Sefair, Jorge A. (Thesis advisor) / Mirchandani, Pitu (Committee member) / Pavlic, Theodore (Committee member) / Tong, Daoqin (Committee member) / Arizona State University (Publisher)
Created2021
Food insecurity and food assistance program participation in the U.S.: One year into the COVID-19 pandemic
Description

Beginning in March 2020, the COVID-19 pandemic triggered a sudden and severe economic downturn and led to disruptions in domestic and international food systems and supply chains. Over the first few months of the pandemic, in the United States, many stores had empty shelves, bars and restaurants closed, and children

Beginning in March 2020, the COVID-19 pandemic triggered a sudden and severe economic downturn and led to disruptions in domestic and international food systems and supply chains. Over the first few months of the pandemic, in the United States, many stores had empty shelves, bars and restaurants closed, and children could no longer go to school. The unemployment rate increased from 3.5% in February 2020 to 14.8% in April 2020, leading to economic instability for many households. As a result, household food insecurity, defined as having limited or inconsistent access to nutritious and affordable food, increased rapidly.

During the first months of 2021, vaccinations began rolling out, more individuals returned to in-person work, children to schools, and restrictions were gradually phased out. Unemployment has decreased since the April 2020 peak to 5.4% in July 2021, but remains above pre-pandemic levels. This brief describes the prevalence of household food insecurity, job disruptions, and food-related behaviors as reported by a nationally representative sample of 1,643 U.S. adults, both in the year prior to the COVID-19 pandemic (March 2019 – March 2020) and during the first four months of 2021 (January – April 2021), a period representing approximately one year since the onset of the pandemic.

Created2021-08
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Description

Background: Food access is a global issue, and for this reason, a wealth of studies are dedicated to understanding the location of food deserts and the benefits of urban gardens. However, few studies have linked these two strands of research together to analyze whether urban gardening activity may be a

Background: Food access is a global issue, and for this reason, a wealth of studies are dedicated to understanding the location of food deserts and the benefits of urban gardens. However, few studies have linked these two strands of research together to analyze whether urban gardening activity may be a step forward in addressing issues of access for food desert residents.

Methods: The Phoenix, Arizona metropolitan area is used as a case to demonstrate the utility of spatial optimization models for siting urban gardens near food deserts and on vacant land. The locations of urban gardens are derived from a list obtained from the Maricopa County Cooperative Extension office at the University of Arizona which were geo located and aggregated to Census tracts. Census tracts were then assigned to one of three categories: tracts that contain a garden, tracts that are immediately adjacent to a tract with a garden, and all other non-garden on-adjacent census tracts. Analysis of variance is first used to ascertain whether there are statistical differences in the demographic, socio-economic, and land use profiles of these three categories of tracts. A maximal covering spatial optimization model is then used to identify potential locations for future gardening activities. A constraint of these models is that gardens be located on vacant land, which is a growing problem in rapidly urbanizing environments worldwide.

Results: The spatial analysis of garden locations reveals that they are centrally located in tracts with good food access. Thus, the current distribution of gardens does not provide an alternative food source to occupants of food deserts. The maximal covering spatial optimization model reveals that gardens could be sited in alternative locations to better serve food desert residents. In fact, 53 gardens may be located to cover 96.4% of all food deserts. This is an improvement over the current distribution of gardens where 68 active garden sites provide coverage to a scant 8.4% of food desert residents.

Conclusion: People in rapidly urbanizing environments around the globe suffer from poor food access. Rapid rates of urbanization also present an unused vacant land problem in cities around the globe. This paper highlights how spatial optimization models can be used to improve healthy food access for food desert residents, which is a critical first step in ameliorating the health problems associated with lack of healthy food access including heart disease and obesity.

ContributorsMack, Elizabeth A. (Author) / Tong, Daoqin (Author) / Credit, Kevin (Author) / College of Liberal Arts and Sciences (Contributor)
Created2017-10-16
Description
This paper details the process of implementing a schedule change for the Orbit Saturn, a neighborhood circulator bus in Tempe with poor on-time performance. It describes the methods used to estimate the true runtimes for the Saturn between timepoints, and measures the effectiveness of a schedule change that allows operators

This paper details the process of implementing a schedule change for the Orbit Saturn, a neighborhood circulator bus in Tempe with poor on-time performance. It describes the methods used to estimate the true runtimes for the Saturn between timepoints, and measures the effectiveness of a schedule change that allows operators more time to traverse between timepoints. Changes were implemented on October 23, 2023, upon which there was a statistically significant decrease in average deviation from schedule, as well as a significant increase in the proportion of trips classified as “on-time” by Valley Metro. Increased on-time performance does not appear to be due to outside factors, such as seasonal changes in traffic.
ContributorsMalzewski, Trevor (Author) / Kuby, Michael (Thesis director) / Tong, Daoqin (Committee member) / Stevenson, Sam (Committee member) / Barrett, The Honors College (Contributor) / Economics Program in CLAS (Contributor)
Created2024-05