Browsing by Subject "productivity"
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Item Age Structure of Golden-cheeked Warblers in Areas of Low Abundance(2014-08-05) Pruett, Hannah LUnderstanding how habitat use and reproductive performance vary among age classes is important to understanding population structure and viability. Habitat conditions can affect occupancy and productivity of many songbirds, including golden-cheeked warblers (Setophaga chrysoparia). Thus, it is important to know which members of the population are using habitat of varying conditions. Existing demographic literature on golden-cheeked warblers focuses on populations where warblers occur in high abundance. I examined the age structure of golden-cheeked warblers in areas of low abundance to determine if there are patterns of differential habitat use based on age in this species. Over two breeding seasons, I monitored 13 low-density and 10 high-density study sites in central Texas for arrival dates and productivity. Males arrived to low density sites on average 6 days later (11 March) and those that established territories on those sites tended to be younger (62% Second-year, n = 8) than those males that established territories on high density sites (5 March, 32% SY, n = 22) although there were no differences in age structure by territory density. I aged 30 males on my study sites, 26 of which were territorial. Productivity did not vary between low and high-density sites; however, SY males had lower pairing and territory success than After Second-year (ASY) males. Understanding which portions of the warbler population are using patches of varying condition could lead to the detection of potential demographic drivers in habitat selection and could inform future management.Item Alleviation of effective permeability reduction of gas-condensate due to condensate buildup near wellbore(Texas A&M University, 2006-04-12) Carballo Salas, Jose GilbertoWhen the reservoir pressure is decreased below dew point pressure of the gas near the wellbore, gas-condensate wells start to decrease production because condensate is separated from the gas around the wellbore causing a decrease in gas relative permeability. This effect is more dramatic if the permeability of the reservoir is low. The idea proposed for reducing this problem is to eliminate the irreducible water saturation near the wellbore to leave more space for the gas to flow and therefore increase the productivity of the well. In this research a simulation study was performed to determine the range of permeabilities where the cylinder of condensate will seriously affect the well??s productivity, and the distance the removal of water around the wellbore has to be extended in order to have acceleration of production and an increase in the final reserves. A compositional-radial reservoir was simulated with one well in the center of 109 grids. Three gas-condensate fluids with different heptanes plus compositions ( 4, 8 and 11 mole %), and two irreducible water saturations were used. The fitting of the Equation of State (EOS) was performed using the method proposed by Aguilar and McCain. Several simulations were performed with several permeabilities to determine the permeabilities for which the productivity is not affected by the presence of the cylinder of condensate. At constant permeability, various radii of a region of zero initial water saturation around the wellbore were simulated and comparisons of the effects of removal of irreducible water on productivity were made. Reservoirs with permeabilities lower than 100 mD showed a reduction in the ultimate reserves due to the cylinder of condensate. The optimal radius of water removal depends on the fluid composition and the irreducible water saturation of the reservoir. The expected increase in reserves due to water removal varies from 10 to 80 % for gas production and from 4 to 30% for condensate production.Item Effects of Habitat Characteristics on Occupancy and Productivity of a Forest-Dependent Songbird in an Urban Landscape(2013-04-24) Robinson, Dianne HaliHabitat fragmentation and isolation can result in decreased occupancy and reproductive success within songbirds, particularly for species inhabiting urban environments where suitable habitat may be limited. The golden-cheeked warbler (Setophaga chrysoparia) is a federally endangered songbird that inhabits oak-juniper (Quercus spp.- Juniperus spp.) across central Texas. Past research on this warbler has indicated decreased patch occupancy near urban areas and negative reproductive effects associated with decreased distance to edge and decreased canopy cover. A rural study indicated warblers occupy patches ?3 ha, and warblers in patches ?20 ha are more likely to successfully fledge young. There are no thresholds yet identified for this warbler within urban environments, where effects of habitat fragmentation on reproductive success are more pronounced than within rural environments. I monitored patch occupancy, territory establishment, pairing success, and fledging success of warblers in an urban environment. I determined minimum patch-size thresholds for productivity measurements, and also monitored effects on productivity from canopy cover, woodland composition, distance to and size of the nearest habitat patch, and distance to the nearest habitat patch >100 ha. I compared my results to those from a similar study conducted in a rural system. I compared territory size and territory density between an urban and rural system. Warblers occupied 24% (n = 63) patches surveyed; the smallest patch occupied was 3.5 ha. The smallest patch with an established territory was 10.7 ha, and 10% (n = 63) of habitat patches had at least one established territory. Warblers successfully fledged young in 3 patches, the smallest of which was 26.5 ha. I found patch-size was predictive for territory establishment and pairing success with warblers requiring 13 ha (95% CI: 10.0 ? 16.8 ha) and 19 ha (95% CI: 15.7 ? 22.6 ha) habitat patches, respectively. I found a minimum threshold of approximately 66% canopy cover (95% CI: 65.2 ? 66.4%) required for patch occupancy, and found no warblers established a territory in a habitat patch >25 m from the next nearest patch. I found higher minimum thresholds within an urban system for territory establishment and pairing success than those seen within a rural system. I suggest preserving warbler habitat patches >22 ha that are in close proximity to other habitat patches. This will help to enhance warbler habitat within urban areas and maintain reproductively viable habitat patches, while not halting development completely.Item Essays in International Macroeconomics and Forecasting(2012-10-19) Bejarano Rojas, Jesus AntonioThis dissertation contains three essays in international macroeconomics and financial time series forecasting. In the first essay, I show, numerically, that a two-country New-Keynesian Sticky Prices model, driven by monetary and productivity shocks, is capable of explaining the highly positive correlation across the industrialized countries' inflation even though their cross-country correlation in money growth rate is negligible. The structure of this model generates cross-country correlations of inflation, output and consumption that appear to closely correspond to the data. Additionally, this model can explain the internal correlation between inflation and output observed in the data. The second essay presents two important results. First, gains from monetary policy cooperation are different from zero when the elasticity of substitution between domestic and imported goods consumption is different from one. Second, when monetary policy is endogenous in a two-country model, the only Nash equilibria supported by this model are those that are symmetrical. That is, all exporting firms in both countries choose to price in their own currency, or all exporting firms in both countries choose to price in the importer's currency. The last essay provides both conditional and unconditional predictive ability evaluations of the aluminum futures contracts prices, by using five different econometric models, in forecasting the aluminum spot price monthly return 3, 15, and 27-months ahead for the sample period 1989.01-2010.10. From these evaluations, the best model in forecasting the aluminum spot price monthly return 3 and 15 months ahead is followed by a (VAR) model whose variables are aluminum futures contracts price, aluminum spot price and risk free interest rate, whereas for the aluminum spot price monthly return 27 months ahead is a single equation model in which the aluminum spot price today is explained by the aluminum futures price 27 months earlier. Finally, it shows that iterated multiperiod-ahead time series forecasts have a better conditional out-of-sample forecasting performance of the aluminum spot price monthly return when an estimated (VAR) model is used as a forecasting tool.Item Exploring the Effectiveness of LEED Certification in LEED Certified Healthcare Settings in Climate Zone 2 and 3(2012-10-19) Xuan, XiaodongMost LEED (Leadership in Energy and Environmental Design) certified buildings are commercial office buildings and multi-use buildings. As of October 2009, 35,000 projects were registered in the LEED system, "comprising over 4.5 billion square feet of construction space in all 50 states and 91 countries." However, as of April 30, 2009, only 43 healthcare projects had achieved LEED certification. Currently, most studies focus on the economic benefits and energy consumption of LEED certified buildings, rather than human factors. A small gain in productivity can result in a heftier financial gain. Even modest improvements in productivity and absenteeism can substantially outweigh the energy cost. This study surveyed 164 staff in the two healthcare settings for case study, and 146 staff in the six LEED certified healthcare settings for the main study in climate zone 2 and 3. Telephone interviews with the six facility managers were used to verify the survey results and further examine the healthcare facilities? performance and the effectiveness of the LEED strategies from facility managers' perspectives. Independent t-test was used to examine the difference between the LEED and Non-LEED hospitals in one healthcare system and results showed that building performance were rated higher by staff in LEED certified hospital than Non-LEED hospital. MANOVA was conducted to compare the staff's ratings between Silver and Gold certification levels, male and female, and also explore the possibility of interaction effect. Multilevel regression modeling was used to test how the building performance variables affect the overall comfort and productivity. Study results showed that staff in the Gold certified hospital had significant higher ratings in most the performance variables. Gold certified healthcare settings were significant better in rated building overall, overall comfort and controllability than Silver certified healthcare settings. And males felt more comfortable in temperature than females in healthcare facilities. Regarding the overall comfort and productivity, building design, efficiency of the space use, temperature comfort and controllability over building system were significant predictors for staff overall comfort; and lighting comfort, temperature comfort and controllability over building system had significant positive relationship with perceived productivity. LEED certified healthcare settings appear to have a good environment and building performance for occupants. Controllability, lighting, temperature, use of space, building design were important factors in staff comfort and productivity.Item Session 2E | Carry On: One Digitization Lab’s Journey Through Temporary Displacement(Texas Digital Library, 2021-05-25) Pankonien, Allie; McIntosh, MarciaBefore COVID-19 pandemic made work-at-home arrangements a normality, the mechanical, electrical, and plumbing (MEP) upgrades at the University of North Texas Library required the displacement of the Digital Projects Lab staff and students from their lab for an estimated six weeks. With little access to digitization equipment, the lab planned to continue running during that period. By presenting the preparation and planning for the move, the logistics of the transition, and the results from the experience, the authors hope to share their strategies for digitization lab mobility and continued, off-site productivity.Item The Influence of Tree Species Composition on Songbird Abundance and Productivity(2014-08-08) Long, Ashley MarieMost avian habitat selection studies are conducted within small spatial and temporal scales and fail to link habitat selection decisions to reproductive success. This limits our understanding of avian demographic patterns across the full continuum of ecological conditions a species inhabits and may result in the application of inappropriate conservation strategies. The golden-cheeked warbler (Setophaga chrysoparia; hereafter warbler) is a federally endangered songbird that breeds in oak-juniper woodland of central Texas. Management guidelines indicate that mature, dense Ashe juniper cover is an attribute of high quality warbler breeding habitat, but few studies have examined warbler responses to Ashe juniper across the continuum of vegetation types they inhabit. I used data collected from 899 territories on 90 study sites (2009?2013) located across the warbler?s breeding range to investigate the influence of year, geographic location, various Ashe juniper metrics, and dominant oak species on warbler abundance and productivity. My results reiterate that vegetation utilized by warblers is highly variable and that warblers successfully breed in areas with vegetation characteristics outside current descriptions of warbler breeding habitat. Warbler territory density remained constant across the full range of percent Ashe juniper cover in woodland dominated by Lacey (Quercus laceyi), live (Q. fusiformis), and Texas oak (Q. buckleyi). Warbler territory density increased with increasing percent Ashe juniper cover in woodland dominated by post oak (Q. stellata) and in mixed oak woodland and warbler territory density decreased with increasing percent Ashe juniper cover in woodland stands dominated by shin oak (Q. sinuata). Territories were larger in oak-juniper woodland stands dominated by live oak than oak-juniper woodland stands dominated by all other species but post oak. Results regarding relationships between territory-scale metrics and territory size and pairing and fledging success varied, but indicate that prioritizing sites based on qualitative Ashe juniper metrics or managing sites to promote single-aged stands of mature Ashe juniper cover may not be the most effective strategy for warblers. Management and restoration efforts may be more effective if tailored to local vegetation characteristics associated with tree species composition.