• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1157
  • 272
  • 249
  • 168
  • 147
  • 112
  • 25
  • 17
  • 16
  • 14
  • 11
  • 10
  • 10
  • 10
  • 6
  • Tagged with
  • 2848
  • 313
  • 273
  • 259
  • 256
  • 229
  • 201
  • 177
  • 153
  • 139
  • 133
  • 126
  • 124
  • 123
  • 122
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Will Oakland Burn Again: Understanding the Fire Hazard in an Urban Park System

Zambrano, Alessandra M 01 June 2021 (has links) (PDF)
Though almost thirty years have passed since the 1991 Tunnel Fire, the wildfire hazard is still present in the Oakland Hills. This study was conducted to determine if the vegetation in the Oakland Hills had reverted back to fuel conditions that contributed to the Tunnel Fire, examine how the fire hazard has changed since 1991, and evaluate planned wildfire mitigation. The goal was to determine how fuel conditions have changed since 1991 and compare potential fire behavior to that of the Tunnel Fire. Additionally, the study examined the effectiveness of the mitigation actions described in the East Bay Regional Park District’s Wildfire Hazard Reduction and Resource Management Plan on lowering extreme fire behavior. Through the use of remote sensing, historical aerial imagery, satellite imagery, and Landsat imagery the 1991 and 2018 fuel conditions were analyzed. ArcGIS Pro and FlamMap 6 were used to compare hectares of fuel and changed in fire behavior between the two year. Mitigation actions were modeled with FlamMap 6 and ArcGIS Pro and fire behavior was compared between untreated conditions and post treatment conditions. The vegetation in the Oakland Hills, in the absence of fire, returned to a mature state, similar to the 1991 conditions. However, there was a reduction in the overall hectares of fuel model 147 in 2018. Modeled fire behavior indicated an overall reduction in extreme fire behavior when comparing 1991 to 2018. This reduction varied on a park level with each park performing differently. When modeled, mitigation was able to lower extreme fire behavior across the landscape but success varied on an individual park basis. In conclusion, should ignition occur presently, under foehn wind conditions, a fire would still exhibit very extreme behavior with a high potential for catastrophic loss, and implantation of planned mitigation measures may be able to lower the degree of extreme fire behavior.
202

Administrative and Political Implications of GIS Implementation within the Fire Service: A Case Study of Norfolk, VA

Bloom, Paul Sean 04 May 1998 (has links)
The advent of faster, cheaper, and more powerful computer hardware has led to the widespread integration of GIS technologies into decision making processes within local governments. Most GIS literature has focused on the models and benefits that the technology can produce and not on the impacts that GIS has on the organization. This research explores the political and administrative implications of utilizing a GIS to address a resource allocation problem within the Fire Service Administration of the City of Norfolk, VA. A network model is employed to allocate rescue resources throughout the city in various configurations. The goal of NFPS (Norfolk Fire and Paramedical Services) is to be able to cover the entire City of Norfolk within five minutes of travel time. City and NFPS administrators evaluate various models based upon a provided questionnaire that focuses on the administrative and political viability of each of the models produced. / Master of Science
203

Population genetics study of the imported fire ants (Formicidae: Solenopsis spp.)

Garlapati, Rajesh Babu 08 August 2009 (has links)
The study was divided into three main sections. In the first section, temporal stability of genetic structure of red imported fire ant populations and effective population sizes were assessed with the help of microsatellites. The second part of the study was focused on the development of new microsatellite markers for the population genetics study of fire ants. The third part of the study was aimed at describing the association of phenotypic and genotypic characters of polygyne hybrid (Solenopsis invicta x richteri) fire ant in a colony and identifying the origin of polygyny in hybrid imported fire ant colony. Meridian, Yazoo City and Crystal Springs in Mississippi and Mobile, Alabama were selected for conducting the study. The overall FST estimates and the pairwise FST estimates between the populations of study, indicated little genetic differentiation and low spatial variation in the nuclear genetic structure of red imported fire ant. Gene flow estimates indicated that there is extensive movement between these populations. From 2006 to 2008 the FST estimates decreased and gene flow estimates increased, indicating that there is no equilibrium between genetic drift and migration in the populations studied. Effective population sizes ranged from 10 -17 in these populations.We have isolated and characterized an additional 11 polymorphic microsatellite loci in the invasive ant S. invicta from a population in Lauderdale County, Mississippi. The observed and effective number of alleles ranged from two to six (average 3.1818 ± S. E. 0.0486). Probability tests indicated significant deviations from the Hardy-Weinberg equilibrium at three loci. The polymorphism information content of the microsatellites ranged from 0.1482 to 0.6208.Identifying multiple inseminated queens in a colony and sequencing the critical region of Gp-9 locus (1600 base pairs) in individuals with the polygyne allele strongly indicate the association of phenotypic and genotypic characters of polygyny in a hybrid imported fire ant colony. A 100% match of Gp-9B and Gp-9b alleles and concordance in the critical amino acid substitutions of the Gp-9 locus in the hybrid fire ant with S. invicta Buren provides the evidence that polygyny in the hybrid imported fire ant colony is derived from S. invicta.
204

Synthesis and Characterization of Phosphorus Containing Poly(arylene ether)s

Riley, Daniel J. 28 February 1997 (has links)
The synthesis and characterization of phosphorus containing poly(arylene ether)s were investigated to determine the effect of phosphorus upon the thermal stability, mechanical strength, and fire resistance of thermoplastics. Phosphorus containing activated aromatic dihalides and bisphenols were synthesized in high purity. These monomers were successfully polymerized via nucleophilic aromatic substitution to afford high molecular weight polymers. It was determined that by incorporating the phosphine oxide moiety into the polymer backbone certain properties of the resulting poly(arylene ether)s were substantially improved, such as an increase in T<sub>g</sub>, thermal stability in air, modulus, and char yield, compared with control poly(arylene ether sulfone)s. The high char yields obtained for these polymers in air, along with observed intumescence indicates that these materials have improved fire resistance. Preliminary cone calorimetry measurements support this conclusion. In addition, the phosphine oxide group in the backbone was reduced to a phosphine and successfully converted to a phosphonium bromide ionomer. The resulting system was further chemically modified to ionically bond second-order nonlinear optical chromophores to the backbone of selected poly(arylene ether)s. Initial results on corona poling of cast film at low temperature produced stable second harmonic generation in these materials, indicating that they may have promise in nonlinear optical applications. / Ph. D.
205

Estimating Heat Tolerance of Tree Buds in the Southeastern United States

McClure, Adam Blake 11 January 2021 (has links)
Tree diameter, bark thickness and texture, litter bulk density and chemistry, and sprouting ability are a few, species-specific adaptations and properties that may be related to an individual tree stem's potential fire resistance. Based upon these features and others, trees exhibiting similar characteristics have been broadly classified as pyrophytic or pyrophobic. To our knowledge, few if any, research studies have been conducted to determine if tree buds may exhibit speciesspecific fire or heat tolerance. Understanding potential relationships between bud characteristics and fire tolerance may assist prescribed fire managers as they target control of specific undesired tree species while promoting desired tree species. Buds of six common hardwood species in the southeastern U.S. were harvested and exposed to different heat dosages using a propane gas tube burner: red maple (Acer rubrum L.), yellow-poplar (Liriodendron tulipifera L.), American beech (Fagus grandifolia Ehrh.), mockernut hickory (Carya tomentosa Lam.), scarlet oak (Quercus coccinea Münchh.), and chestnut oak (Quercus montana Willd.). These species are commonly categorized as pyrophobic (American beech, red maple, yellow-poplar) and pyrophytic (chestnut oak, mockernut hickory, scarlet oak). Using electrolyte leakage of heated and unheated buds, the mean difference in bud percent mortality between heated and unheated buds was compared by species, functional group, and differing heat dosages. The mean difference in bud percent mortality differed between the heated and unheated buds by species (p < 0.0001). Heated buds of yellow-poplar, mockernut hickory, and chestnut oak displayed similar percent mortality; however, the presumed pyrophytic species had greater heated bud percent mortality (34.0 %) than the pyrophobic species (26.8 %) (p = 0.0003). Heated bud percent mortality differed based upon differing heat dosage levels (height above the propane burner and heat exposure time) and their species-specific interactions. Fire tolerance, as assigned and assessed by features such as bark texture and thickness, may not be directly related to mid-story tree bud physical properties (i.e. length, mass, and diameter) or fire tolerance. Research including additional species, heat dosages, and different sampling times (i.e. late fall vs. late winter) would be valuable for investigating these dynamics further. Deploying a similar, field-scale experiment before and after prescribed burns would be useful to determine how tree buds may respond to different heat dosages that could be exacted during prescribed burns. / Master of Science / Prescribed fire is utilized on millions of acres per year in the southeastern United States. These burns are conducted for a variety of reasons, including: wildlife habitat establishment, restoration, and maintenance; aesthetics; hazardous fuel reduction; and the control of undesired vegetative species. Factors that may influence an individual species' response to fire include, but are not limited to: bark thickness and texture, litter bulk density and chemistry, and resprouting strategy. These traits may differ by species and by the age of a given stem. Few studies have investigated these characteristics in younger tree stems within the southeastern United States. Additionally, few research studies in any ecosystem have investigated potential species-specific tree bud responses to increased heat. Determining if undesired tree species respond differently to heating than desired tree species may provide additional information to assist prescribed fire managers in many locations where vegetation control is a management objective. As a result of this knowledge gap, a research study was designed to investigate these dynamics in the southeastern United States for six common, hardwood tree species: red maple (Acer rubrum L.), yellow-poplar (Liriodendron tulipifera L.), American beech (Fagus grandifolia Ehrh.), mockernut hickory (Carya tomentosa Lam.), scarlet oak (Quercus coccinea Münchh.), and chestnut oak (Quercus montana Willd.). The results suggested that percent bud mortality may be species-specific, but few relationships appeared to be present to relate bud physical characteristics to bud mortality. Additionally, supposed heat tolerance groups assigned to older tree stems based upon traits, such as bark thickness and texture, did not provide a valid assessment of bud mortality. Additional research is needed to understand these dynamics further, including burning under different heat dosages, evaluating additional tree species, and assessing bud mortality resulting from in-the-field prescribed fires.
206

Forest dynamics of pine- and oak-dominated communities on southeastern-facing slopes of Warm Springs Mountain, Virginia

Sams, Brent Shipley 23 July 2012 (has links)
Warm Springs Mountain (WSM), a priority conservation area for The Nature Conservancy in Bath County, Virginia, is home to a rare montane pine barren and large tracts of uninterrupted mixed pine and deciduous forest extending east into the George Washington National Forest. Limited documentation of past disturbances and their influence on WSM forests presents challenges for land managers desiring to understand historic conditions for these ecosystems. The only formal study of vegetation dynamics on WSM noted an absence of pitch pine (Pinus rigida Mill.) regeneration and an increase in fire-intolerant species during recent decades in the pine barren community that is probably linked to fire suppression. Dendrochronological studies of disturbance history in the central and southern Appalachians have mostly focused on ridgetop and southwestern-facing slopes. This study examines long-term forest dynamics in the pine- and oak-dominated forests on southeastern slopes of Warm Springs Mountain and downslope from the higher elevation pine barren using dendrochronology and vegetation analysis. We studied trees in six 20 x 50 m plots to develop a tree ring chronology and document changes in stand composition and structure through time. We found an increase in fire-intolerant species and decline in fire-dependent pines and oaks through time. Pitch pines have not recruited since 1954 in our sites due to a lack of burning, while Acer rubrum L. has produced high numbers of seedlings in recent years. This study of vegetation dynamics over space and time will provide insights for land managers and inform fire restoration practices. / Master of Science
207

A House For A River Rat

Matthews, David Stansfield 24 January 2014 (has links)
This is a house situated by a river. It is a retreat, or a cabin, and is not occupied on a full time basis. Its form is an interpretation of a cube, and retains its general appearance. It is lifted off the ground to prevent damage when the river floods, and has a deep foundation to achieve stability on the loose floodplain soil. It has three levels, the first containing the main living areas, the second, a lofted space containing the bed and bath, and the third, a roof terrace. It is for two people, and so has a small footprint of about thirty two feet square. The footprint is subdivided into nine squares, with a fireplace and chimney occupying the center and habitable spaces surrounding the periphery. Its foundation is of a concrete two way flat slab supported by concrete caissons, its walls are of reinforced concrete masonry units, and its floors and ceilings are of small timber frame construction. / Master of Architecture
208

Fire Response of Loaded Composite Structures - Experiments and Modeling

Burdette, Jason A. 01 May 2002 (has links)
In this work, the thermo-mechanical response and failure of loaded, fire-exposed composite structures was studied. Unique experimental equipment and procedures were developed and experiments were performed to assess the effects of mechanical loading and fire exposure on the service life of composite beams. A series of analytical models was assembled to describe the fire growth and structural response processes for the system used in the experiments. This series of models consists of a fire model (to predict the heat flux to the fire-exposed beam), a thermal response model (to calculate the temperature distribution within the beam due to this heat flux), a stiffness-temperature model (to calculate the loss in stiffness at elevated temperatures), a mechanical response model (to compute the strain distribution within the loaded beam), and a material failure model (to calculate the strain at which the beam is expected to fail). Each of these models is independently validated by comparing predictions with experimental results. The models are then used to predict the times-to-failure for beams over a range of fire and loading conditions. The predicted failure times agree fairly well with experimental results, but it is expected that the agreement could be improved with improvements to the first model in the series - the fire model. / Master of Science
209

Dynamic evolution patterns of legislative efforts on forestry-prescribed fires

Perera, Welgamage Kalani Gayathri 10 May 2024 (has links) (PDF)
Forestry-prescribed fires have been essential for managing forestland and reducing the risk of catastrophic wildfires. However, the use of prescribed fires has also raised concerns about their potential environmental and social impacts, leading to the development of various statutes and regulations that govern their implementation. This study explores the evolving legislative efforts related to forestry prescribed fire in managing forests and reducing wildfire risks to assess their dynamic nature. Determinants behind these legislative patterns are examined using qualitative content analysis and a binary logit model. A total of 199 legislative bills related to forestry prescribed fire were identified from 1995 to 2023 across the United States. The Southern United States reported the highest number of legislative bills. The passing rate of those legislative bills stands at 46.7%. This study contributes to a comprehensive understanding of the legislative effort surrounding forestry prescribed fires and informs ongoing discussions on effective forest management practices.
210

Reducing Information Overload in Situated Visualization for Firefighting: A Human Factors Evaluation of User Interface Prototypes for Pre-Incident Planning

Kapalo, Katelynn 01 January 2020 (has links) (PDF)
High profile structure fires, like the Grenfell Tower tragedy, have demonstrated that the quality of the information provided to firefighters arriving on the scene of an emergency is a matter of life or death. It has been suggested that access to structural information such as electronic building plans or unmanned aerial vehicle footage may bridge the information gap to help first responders build situation awareness at the incident scene. However, these technologies have not been fully evaluated from a human performance perspective. The use of pre-incident plans (PIPs), information captured systematically about a facility prior to an emergency, provides a way for firefighters to leverage data about a structure, increasing their efficiency and effectiveness in managing a fire and ultimately reducing fatalities and property damage. However, no standard interface configuration currently exists for presenting and displaying PIP information to firefighters digitally. This dissertation investigates the human factors implications associated with leveraging emerging technology in the form of 3D models and situated visualization techniques for displaying PIP information to fireground incident commanders. Through a series of mixed-method (qualitative and quantitative) studies, this dissertation directly captures user requirements and human performance data from firefighters in the form of focus groups, field data, surveys, and user study data. Based on qualitative participant feedback and objective user study data, this series of studies evaluate the usability (efficiency, effectiveness, satisfaction) of three different user interface configurations. This data serves as a foundation for standardizing the way PIP information is presented to first responders. Further recommendations are suggested for how to effectively present and display PIP information to better support fireground incident commanders operating in dangerous and unpredictable environments.

Page generated in 0.085 seconds