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Interannual variability analysis of utility-scale solar photovoltaic and wind power resources in Arizona and New Mexico
No full textInterannual variability (IAV) of wind and solar resources impacts multi-million-dollar power
system decisions related to operations, planning, and investments. Decisions pertaining to power
systems are usually made based on a limited number of years where the consequences of
interannual variability are often neglected or reduced. As the electric sector transitions to a
renewable energy future, larger shares of wind and solar will introduce more variability to the
operation of the power system. Consequently, we use the National Radiation Database (1998-
2015) as well as the WIND Toolkit (2007-2013) to create wind and solar photovoltaic power time
series using NREL’s System Advisor Model (SAM), and study the interannual variability of wind
and solar resources in Arizona and New Mexico. We define IAV as half of the ratio between the
range of capacity factor (CF) and the long-term mean in the time frame of interest, expressed as a
percentage. Results show a ±3-4% IAV of annual solar CF and ±7-8% IAV of annual wind CF.
IAV of annual wind CF is significantly impacted by geographical location, with larger IAV values
in the Great Plains and southern Rocky Mountains. IAV of seasonal wind CF is calculated on the
order of ±11-26%, whereas IAV of seasonal solar CF was found to range from ±6% to ±16%. In
both cases, IAV of wind and solar seasonal CF showed lower IAV values in summer and larger in
winter. Extreme ramping events in aggregated wind and solar power time series are also studied.
It is shown that extreme events can increase as much as 40% from year to year. Impacts on
generation, transmission, and storage investments as well as impacts on operating reserves,
transmission congestion, maintenance and seasonal storage scheduling are discussed
Metabolic implications of single-unit avian intrapulmonary CO2 chemoreceptor (IPC) responses to sustained anoxia and normoxic recovery
No full textPilarski (et al., 2009) reported that both tonic and phasic IPC CO2 transduction are strongly inhibited by mitochondrial electron transport system (ETS) inhibitor rotenone and glycolysis inhibitor iodoacetate, while ETS uncoupler 2,4-DNP inhibited only tonic CO2 transduction. They suggested that glycolysis may provide sufficient ATP to power phasic IPC transduction, but could not sustain tonic CO2 transduction. To investigate further, we separately ventilated and perfused the right (R) and left (L) lungs of anesthetized mallard ducks, and recorded L lung IPC responses to CO2 in 12 IPC. Ten (10) min of complete L lung anoxia produced by ligating the L pulmonary artery (LPA) and ventilating the L lung with N2 and CO2 significantly reduced mean IPC discharge CO2 responses (to 36% of control, p 10 min). Inhibition may have been due to accumulation of lactate causing intracellular acidosis, formation of reactive oxygen species (ROS), and disruption of transmembrane ionic gradients. Previous work has shown that decreased intracellular pH inhibits IPC (Bebout and Hempleman, 1999 Hempleman et. al, 2000). Ischemia and the subsequent formation of ROS can also increase intracellular calcium [Ca++]i (Kristian et. al., 1998; Turrens, 2003), which is a known depressant of IPC excitability (Hempleman et al., 2006). The inhibitory effect of 10 min anoxia on IPC CO2 transduction was entirely reversible
Abiotic and biotic mediation of grazing impacts on soil carbon in Northern Arizona
Get PDFSoil, the largest terrestrial carbon reservoir, has the ability to sequester carbon, however numerous variables influence its storage potential. Livestock management practices, precipitation, plant species composition, and soil parent material may all influence the potential for carbon to be stored in the soil. There is little empirical evidence measuring these effects in arid and semi-arid environments which motivated this study to sample across the Diablo Trust in northern Arizona. Stratified random sites were selected based on the locations of fence-lines or grazing exclosures that have excluded livestock for at least 20 years. Soil samples were collected from grazed and adjacent ungrazed sides of the fences across five distinct soil series and along a precipitation gradient ranging from 230 mm – 623 mm at the surface (0-5 cm) and subsurface (20-25 cm). The sites were measured for soil texture, precipitation, plant community composition, root biomass, soil organic carbon, and soil inorganic carbon. Results from the general linear models and the structural equation model found that the abiotic factors of precipitation and soil texture were the main drivers in soil organic and inorganic carbon. Grazing did not have a significant direct effect on soil organic or inorganic carbon, although there were significantly more C4 grasses under the grazed treatments. Surprisingly, roots, especially C4 roots, had a greater effect on soil inorganic carbon than organic carbon. More research is needed to better understand the mechanisms driving this interaction, but could be crucial to understand if this drives more carbon to be released into the atmosphere in semi-arid and arid environments. Overall, the results from this study show that the abiotic factors of soil texture and precipitation were the main drivers in soil organic and inorganic carbon across this semi-arid rangeland. This may be explained through the theoretical framework provided by the state-and-transition model which incorporates both equilibrium and non-equilibrium models. Arid and semi-arid environments have more stochastic rainfall patterns compared to mesic environments, driving net primary production, which increases with timely precipitation. Along the continuum of the state-and-transition model, semi-arid rangelands fall more along the non-equilibrium systems. If the non-equilibrium model explains more of the ecological dynamics within system in this semi-arid rangeland, then predictable sequestration of carbon is complex through management and it may not be appropriate to include management practices within protocols in the voluntary carbon market. More research is needed to better understand grazing’s impact on soil carbon storage across various precipitation gradients. The research from this study shows that grazing had a minimal impact on soil carbon storage across a landscape scale and that there are biotic interactions with inorganic carbon that can no longer be ignored
The design and testing of a powered exoskeleton to reduce the metabolic cost of walking in individuals with cerebral palsy
Get PDFCerebral palsy (CP) is the most common form of motor impairment in children. Although CP is a non-progressive neurodevelopmental disorder, its secondary effects can lead to a decline in mobility over time. Eventually, individuals with CP may lose all ambulatory function. Interventions for CP, such as surgery and physical therapy, seek to delay the decline and improve mobility. Research into alternative interventions attempt to find improved outcomes over the traditional treatments. Robot-assistive devices are one such intervention that makes use of powered actuation, sensing, and control to help individuals with CP to retain and improve mobility.
The purpose of this research was to develop and test a robot-assistive device that reduces the metabolic cost of walking in children and young adults with CP. Our device consisted of an actuator-and-control module worn on the back, and two custom ankle-foot orthotics (AFOs). The control module contained brushless DC motors, electronics to control actuation, and a power supply. Plantarflexion, or “push-off”, assistive torque was transferred from the motors to the orthotics using Bowden cables. 32-Bit ARM microcontrollers operated the system with inputs from force sensitive resistors (FSR) placed under the ball of each foot, and torque sensors aligned with each ankle joint. Proportional gain control was used to control motor output torque. We implemented a two-state Finite State Machine (FSM) to control the timing of assistance.
We completed a pilot study with three participants with CP. We used indirect calorimetry to estimate metabolic cost. The study participants walked under three conditions: baseline, zero-torque, and powered assist. During the baseline condition, participants walked using their own shoes/AFOs and not our device. During the zero-torque condition, participants wore the device and the motors actively maintained a zero-torque reading at the ankle. During the assisted condition, participants wore the device while the motors gave plantarflexion assistance during late stance. Two participants had a decrease in metabolic cost between baseline and assisted conditions, an average of 16.5%. All participants showed an average reduction in the metabolic cost of walking of 40% between the zero-torque condition and the assisted condition, on average. Our youngest and lightest participant (5 years old, 16 kg) did not show a net decrease in metabolic cost between baseline and assisted walking, a result likely due to our device being a large percentage of their total mass, 12.5% as opposed to 7.5% and 4.4%.
We conclude that our device shows a strong potential for clinically-relevant applications. Further studies may show that robotic-assistance can improve mobility and quality of life in individuals with CP
Spatio-temporal variability and demographic characteristics of transit-based job accessibility: a GIS assessment of the public transit system in Flagstaff, Arizona
Get PDFAccessibility measures the ease at which an individual can access a desired location. It is a major aspect in transportation planning, and transit systems are extensively used to improve accessibility. Well-designed public transit systems enable a high level of access to socioeconomic opportunities. This is especially important to socially disadvantaged populations due to their higher need for transit services to maintain a basic level of mobility. Increased transit-based accessibility can potentially diminish social exclusion rates and improve the well-being of these population groups. This research analyzes the spatio-temporal variability and the socio-demographic characteristics of transit-based job accessibility in Flagstaff, Arizona. This study employs a temporally-enabled schedule-aware simulation based on the transit system’s General Transit Feed Specification and the city’s street network. Gravity-based measurements were used in the calculation of accessibility from origin locations to job opportunities. This accessibility calculation considers the supply and demand location characteristics, the travel time impedance between them, and temporal variations in transit service frequency and availability. Statistical analyses were used to measure the relationship between accessibility and the individual socioeconomic attributes. The results served as the quantitative basis for discussing the social aspects of the city’s transportation system
Co-trajectories in delinquency and attachment with non-resident fathers among low-income adolescents
Get PDFFamilies that reside in low income communities have higher rates of non-resident, biological fathers. Although there is a substantial body of literature on attachment in adolescence, much less is known about both attachment quality and trajectories across adolescence with non-resident, biological fathers. Using longitudinal data from a sample of over 2,000 low income families from the Welfare, Children, and Families: A Three City Study, the current study will investigate trajectories of attachment quality between adolescents and their non-resident, biological father and delinquency across adolescence, as well as how the two constructs co-vary. Results indicated that on average, feelings of trust and communication declined across adolescence, rates of delinquency increased, and feelings of anger and alienation remained stable, although there were individual differences in trajectories of each. After the addition of covariates into the model, the only the slopes of anger/alienation and delinquency remained significant (B = 0.15, SE = 0.05, p < 0.01), such that individuals who were changing in anger/alienation were also changing in delinquency. The results indicate that attachment between adolescents and their non-resident fathers is not a particularly influential predictor of delinquency above and beyond the effect of other ecological risk factors. While was found that individuals changing in anger/alienation were also changing in delinquency, this relationship was not clear enough to estimate the direction of the changes. Despite this, low-income, minority adolescents do appear to display unique attachment trajectories, and this should be noted in future research in to similar samples
An examination of food storage in Grand Canyon National Park and Grand Staircase-Escalante National Monument
Get PDFAncient occupation of the American Southwest was full of uncertainty. Precipitation was unreliable, and sufficient edible plants and animal resources were linked to the productivity of the environment. Communities had to be resourceful and flexible in the face of scarcity. To ensure reliable food sources, ancient peoples often stored crops and other plant foods in sealed masonry structures, or granaries, protected in alcoves high on canyon walls. This thesis research compares ancient methods for coping with scarcity by examining the presence of patterns in prehispanic granary construction in the Grand Canyon and the Fiftymile Mountain region of Grand Staircase-Escalante. Granaries in the two regions date between A.D. 1000 and A.D. 1250 and are associated with three main cultural groups: the Kayenta branch of the Ancestral Puebloans, the Virgin branch of the Ancestral Puebloans, and the Cohonina. Food storage practices are analyzed using adaptive concepts of optimization and risk minimization, adding to the understanding of the complex nature of human interaction with the environment. Although similar Ancestral Puebloan groups occupied the Grand Canyon and Grand Staircase-Escalante, the results of the research show variability in how granaries were incorporated into scarcity management
Revering the past: the analysis of terminus groups in the Maya Lowlands
Get PDFThe functions of terminus groups and their relations with site cores are a topic of continuous debate among Mesoamerican archaeologist. Terminus groups contain monumental structures that are constructed atop platforms that are connected to the site core of large polities via sacbes, “white road” in Maya, or causeways. Hypotheses concerning terminus groups suggested they served as ritual centers, elite residences, and marketplaces. The focus of my research is to analyze the function of a large terminus group, called the Zopilote Group, that is connected to the site core of Cahal Pech in the Cayo District of Western Belize. Excavations at Zopilote have been conducted periodically over the past twenty years, yielding crucial information regarding the function of this group during the Middle Preclassic (900-300 BC) to the Terminal Classic period (AD 600-900). We hypothesized that the Zopilote Group functioned as a ritual pilgrimage center where rituals of ancestor worship were taking place even after the collapse of the Cahal Pech site core in the Terminal Classic period
The impact of a structured english immersion model on English language learners’ reading achievement
Get PDFResearchers have estimated that by 2030, two of every five American public school students will be acquiring English as second language learners (Shah & Cavanagh, 2012). Providing adequate means by which ELLs can obtain both English language and academic proficiency will be paramount if they are to be successful, contributing members of their communities. Thus, this study was designed to explore the impact of Arizona’s current instructional mandates (Ariz. H.R. 2064 and Ariz. Rev. Stat. § 15-751 – 15-756) on the academic progress of English Language Learners (ELLs) in reading. Two administrations (2012 and 2014) of the reading subtest of the Arizona’s Instrument to Measure Standards (AIMS) annual assessment were used to compare the third and fifth grade reading achievement of ELLs to that of mainstream students. The sample was comprised of 322 fifth grade students from a southwest Arizona school district. The sample included 64 ELL students who were enrolled in the school district continuously from kindergarten through fifth grade and 258 mainstream students who were educated within the district for third through fifth grade. Results of the one-way Analyses of Variance (ANOVA) and subsequent post hoc analyses revealed statistically significant differences in student achievement. ELLs who participated in the Structured English Immersion (SEI) program for three years or more by grade 3 and four or more years by grade 5, respectively, scored significantly lower than mainstream students on both administrations. Thus, the current SEI model mandated by the state of Arizona is not sufficiently supporting all ELLs
In the Shadow of the Giant: Understanding the Role of Plaza G at Lower Dover, Belize
Get PDFSince 2010, the Belize Valley Archaeological Reconnaissance Project (BVAR) has conducted intensive research at the site of Lower Dover, located directly across the Belize River from the minor center of Barton Ramie. Project research questions at Lower Dover have focused both on the monumental architecture of the site core, and on plazuela groups in the periphery of the site’s epicenter. One such peripheral patio group, classified as Group G, consists of five mounds that enclose a small plaza just north of the center’s ballcourt. This thesis presents the results of my investigations on Group G at Lower Dover. Results of my research indicate that Group G is an intermediate elite household that developed before and during the construction of the Lower Dover site core(dates). I compare the development of this household with that of the site center and discuss the potential relationships between site cores and adjacent patio groups