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Improving Models of Forest Carbon and Water Cycling: Revisiting Assumptions and Incorporating VariabilityWard, Eric Jason January 2012 (has links)
<p>This dissertation examines issues concerning sap flux scaled estimates of the canopy-averaged transpiration rate of trees per unit leaf area (E<sub>L</sub>) and stomatal conductance (G<sub>S</sub>), as well as their implications in the water and carbon balance of individuals and stands, with the final goal of an integrated assessment of 11 years of such data from two species (<italic>Pinus taeda</italic> and <italic>Liquidambar styraciflua</italic>) at the Duke Free Air Carbon dioxide Enrichment (Duke FACE) facility. These issues include (1) the effects of allometric relationships and xylem characteristics on the gas phase transport of water from leaves and the hydraulic supply of it, (2) consideration of the hydraulic capacitance in the inference of stomatal behavior from sap flux data and (3) the dynamic modeling of stomatal conductance to environmental drivers using Bayesian techniques. It is shown that a) for resolution of sap flux in conifers at the scale of minutes under dynamic conditions, time constants for both stomatal responses and hydraulic capacitance of sapwood must be considered, (b) nighttime conductance can lead to large errors in rates of sap flux measured under some conditions, (c) variation in allometry between <italic>P. taeda</italic> individuals can lead to different rates of transpiration and carbon assimilation per unit leaf area and that (d) hydraulic time constants for the stems of mature <italic>P. taeda</italic> at Duke FACE trees varied by the stem length considered and were on the order of 30-45 minutes for a 10-m segment. An analysis incorporating all these elements leads to the conclusions that (e) both elevated CO<sub>2</sub> (eCO<sub>2</sub>) and fertilization (FR) resulted in proportionally larger reductions in the E<sub>L</sub> and G<sub>S</sub> of P. taeda as soil moisture decreased with (f) eCO<sub>2</sub> having little to no effect in months of high soil moisture and (g) FR leading to ~14% reduction of GS under high soil moisture in absence of eCO<sub>2</sub>, while (h) both eCO<sub>2</sub> and FR led to reduced E<sub>L</sub> and G<sub>S</sub> of <italic>L. styraciflua</italic> across soil moisture conditions.</p> / Dissertation
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Performance Comparison of Public Bike Demand Predictions: The Impact of Weather and Air PollutionMin Namgung (9380318) 15 December 2020 (has links)
Many metropolitan cities motivate people to exploit public bike-sharing programs as
alternative transportation for many reasons. Due to its’ popularity, multiple types of research
on optimizing public bike-sharing systems is conducted on city-level, neighborhood-level,
station-level, or user-level to predict the public bike demand. Previously, the research on the
public bike demand prediction primarily focused on discovering a relationship with weather
as an external factor that possibly impacted the bike usage or analyzing the bike user trend
in one aspect. This work hypothesizes two external factors that are likely to affect public
bike demand: weather and air pollution. This study uses a public bike data set, daily
temperature, precipitation data, and air condition data to discover the trend of bike usage
using multiple machine learning techniques such as Decision Tree, Naïve Bayes, and Random
Forest. After conducting the research, each algorithm’s output is evaluated with performance
comparisons such as accuracy, precision, or sensitivity. As a result, Random Forest is an
efficient classifier for the bike demand prediction by weather and precipitation, and Decision
Tree performs best for the bike demand prediction by air pollutants. Also, the three class
labelings in the daily bike demand has high specificity, and is easy to trace the trend of the
public bike system.
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Detecting and Measuring Corruption and Inefficiency in Infrastructure Projects Using Machine Learning and Data AnalyticsSeyedali Ghahari (11182092) 19 February 2022 (has links)
Corruption is a social evil that resonates far and deep in societies,
eroding trust in governance, weakening the rule of law, impairing economic
development, and exacerbating poverty, social tension, and inequality. It is
a multidimensional and complex societal malady that occurs in various forms and
contexts. As such, any effort to combat corruption must be accompanied by a
thorough examination of the attributes that might play a key role in
exacerbating or mitigating corrupt environments. This dissertation identifies a number of attributes that
influence corruption, using machine learning techniques, neural network
analysis, and time series causal relationship analysis and aggregated data from
113 countries from 2007 to 2017. The results suggest that improvements in
technological readiness, human development index, and e-governance index have
the most profound impacts on corruption reduction. This dissertation discusses
corruption at each phase of infrastructure systems development and engineering
ethics that serve as a foundation for corruption mitigation. The dissertation then applies novel analytical
efficiency measurement methods to measure infrastructure inefficiencies, and to rank
infrastructure administrative jurisdictions at the state level. An efficiency frontier is
developed using optimization and the highest performing jurisdictions are
identified. The dissertation’s framework could serve as a
starting point for governmental and non-governmental oversight agencies to
study forms and contexts of corruption and inefficiencies, and to propose
influential methods for reducing the instances. Moreover, the framework can help
oversight agencies to promote the overall accountability of infrastructure
agencies by establishing a clearer connection between infrastructure investment
and performance, and by carrying out comparative assessments of infrastructure
performance across the jurisdictions under their oversight or supervision.
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Digital Soil Mapping of the Purdue Agronomy Center for Research and EducationShams R Rahmani (8300103) 07 May 2020 (has links)
This research work concentrate on developing digital soil maps to support field based plant phenotyping research. We have developed soil organic matter content (OM), cation exchange capacity (CEC), natural soil drainage class, and tile drainage line maps using topographic indices and aerial imagery. Various prediction models (universal kriging, cubist, random forest, C5.0, artificial neural network, and multinomial logistic regression) were used to estimate the soil properties of interest.
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