Browsing by Subject "network analysis"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Coupling of ecological and water quality models for improved water resource and fish management(2009-05-15) Tillman, Dorothy HamlinIn recent years new ideas for nutrient management to control eutrophication in estuarine environments have been under consideration. One popular approach being considered in the Chesapeake Bay Program is called the ?top down? approach based on the premise that restoring algal predators, such as oysters and menhaden, will limit excess phytoplankton production and possibly eliminate costly nutrient control programs. The approach is being considered to replace or use in conjunction with the ?bottom up? approach of reducing nutrient loads. The ability to model higher trophic levels such as fish, as well as the eutrophication processes driving production of primary producers in an aquatic ecosystem is needed. CE-QUAL-ICM (ICM) and Ecopath were two models selected for this research. ICM is a time- and spatial-varying eutrophication model that uses nutrient loads to predict primary producers, while Ecopath is a static mass balance model representing an average time period (e.g., season or year) and uses values of primary producers and other groups to predict fish biomass. Linking the two models will provide the means of going up the food chain by trophic levels. The Chesapeake Bay was chosen as the study site since both models are in use there. Before coupling ICM and Ecopath, common links between the two models were found. Ten groups were identified with such variables as production rates, consumption rates, and unassimilated food/consumption. A post-processor/subroutine was developed for ICM to aggregate output data from 3-D to 0-D to be used in Ecopath. Two Ecopath runs were developed with data from ICM and the Chesapeake Bay (CB) Ecopath model to see how network interactions differed with data representing the same system. Four additional runs were made, creating perturbations (i.e., increased phytoplankton production) using the CB Ecopath model and replacing the primary producers with data from ICM. Final runs of ICM were conducted looking at adjusting three parameters to try to restore the Bay back to 1950 conditions. It was demonstrated that ICM data can be coupled with Ecopath to study management strategies in eutrophication. Because of model formulations there was no data exchange from Ecopath back to ICM.Item The Use of Interorganizational Network Analysis as a Tool for Evaluating Community-Based Coalitions and Partnerships(2014-04-11) Clark, Heather R.This dissertation presents a brief history of community-based interventions to improve health, the assumptions when working at the community level health, and a review of notable community-based interventions. When using community health development as a tool for organizing communities to build capacity, a primary focus is on building relationships. What occurs more often now than 30 years ago, is the evaluation of community-based interventions and partnerships. Common measures among partnership evaluation are participation, commitment, and leadership. This dissertation analyzes the use of social network analysis techniques to evaluate interorganizational relationships among community partnerships or coalitions. The first paper presents the results of a systematic review of the use of network analysis in evaluating community-based partnerships and coalitions. The second paper illustrates the use of network analysis in the evaluation of a community-based health partnership in a rural region of Central Texas. Finally, the third paper builds on partnership and coalition evaluation of relationships using an advanced network analysis technique, multiplexity, to analyze how the combinations of relationship types changed over time.Item Types and Gender Composition of Social Networks: Their Influence on Adolescent Substance Use(2015-01-22) Jacobs, Wuraola OThis dissertation presents three separate studies designed to examine how the different factors and determinants known to influence adolescent alcohol and tobacco use and the gender compositions of different adolescent network types are associated with alcohol and tobacco use among adolescents. Additionally, the similarities and/or differences in networks of adolescent substance users and non-users are also examined. First, a systematic review of empirical studies (n=48) employing social network analysis to examine adolescents? alcohol, tobacco, and other drugs (ATOD) use behavior will be presented discussing: (a) how this body of literature examined gender differences in ATOD use, (b) whether these network studies examine the gender composition of these adolescents? networks, and (c) what network affiliation types are used to characterize adolescent networks. Secondly, descriptive characteristics and network analysis of the social networks of 10th grade substance using and non-using adolescents will be presented. Employing a bounded whole network approach, data was collected from 1,707 10th graders in a school district in Los Angeles, California. The students were asked different network questions in order to generate different network types. The network types elicited from these network questions are: Friendship, Admiration, Succeed, Popularity, and Romantic networks. Attributes and network characteristics of users and non-users across these five different networks are presented and the commonalities and/or differences are described also. Lastly, using data from the same students, a quantitative analysis of the associations between interpersonal (e.g. age, gender) and interpersonal (e.g. parent and sibling substance use) factors, network measures, and gender composition of the networks and their alcohol and tobacco use will be discussed. These associations are then further examined across the five different types of networks mentioned above. Prior to this study, research studies employing social network analysis did not attempt to examine the gender composition of the networks in which adolescents are embedded; and only a few other studies used networks other than friendship networks to characterize adolescent social networks. Thus, this study represents the first step towards addressing these limitations associated with examining how adolescents? social networks facilitate or constrain their substance use behavior and filling these apparent conceptual gaps.