Current Search:  strength (x)

View All Items

  • CSV Spreadsheet
(1 - 20 of 21)

Pages

A STUDY OF THE STRENGTH OF PERVIOUS PAVEMENT SYSTEMS
Title
A STUDY OF THE STRENGTH OF PERVIOUS PAVEMENT SYSTEMS.
Creator
Uju, Ikenna, CHOPRA, MANOJ, University of Central Florida
Abstract / Description
This thesis presents a study on the strength properties of the different pervious pavement systems installed at the Stormwater Management Academy field laboratory at University of Central Florida (UCF), Orlando. The strength tests were performed both in the laboratory and in the field. Laboratory testing was conducted to determine the compressive strength and flexural strength of the various pavement surfaces. Evaluation of field pavement performance was performed by comparing the deflection...
Show moreThis thesis presents a study on the strength properties of the different pervious pavement systems installed at the Stormwater Management Academy field laboratory at University of Central Florida (UCF), Orlando. The strength tests were performed both in the laboratory and in the field. Laboratory testing was conducted to determine the compressive strength and flexural strength of the various pavement surfaces. Evaluation of field pavement performance was performed by comparing the deflection basins using the Falling Weight Deflectometer test on pervious concrete and porous asphalt with conventional impervious concrete and asphalt pavements of similar layer profile and thickness, respectively. From literature and previous work at the academy, it is evident that pervious pavements should not be used to withstand heavy traffic loading. They are mostly used in low traffic volume areas such as parking lots, driveways, walkways and some sub-divisional roads. This research studied the compressive strength and flexural moduli. Also it investigated the relationship between the compressive strength and void ratio, unit weight and volume by carrying out laboratory testing of different pervious pavements such as pervious concrete, porous asphalt, recycled rubber tires, recycled glass and porous aggregate. Different sizes of cylinders and beams were cast in place molds for these laboratory tests. Furthermore, the in-situ resilient moduli of the twenty four pavement sections in our research driveway were back calculated with Modulus 6.0 (Liu, et al., 2001) computer program. The calculated deflection basins were compared to the results obtained from a well known computer program called KENPAVE (Huang, 2004). The design of the requisite pavement layer thickness design was performed by doing hand calculations using American Association of State Highway Transportation Officials (AASHTO) method for flexible and rigid pavements and utilizing a Texas Transportation Institute (TTI) computer software known as FPS 19W (Liu, et al., 2006). The structural number for flexible pavements were calculated and tabulated for two different reliability levels (90% and 95%). Traffic loading was estimated in the absence of actual traffic count measurement devices at the field test site. Based on the laboratory testing, the maximum compressive strength of the cored pervious concrete was about 1730 psi. Backcalculated pervious concrete and porous asphalt moduli values were within the specified range discussed in literature. The in-situ modulus of elasticity range for pervious concrete is found to be 740 – 1350 ksi, for porous asphalt 300 – 1100 ksi, for permeable pavers 45 – 320 ksi, for recycled rubber tire 20 – 230 ksi, recycled glass pavement 850 ksi and porous aggregate 150 ksi. For low volume traffic loading, the minimum layer thickness was calculated for rigid pavements and it is presented in this study. In conclusion, this research summarizes the result of laboratory and field testing performed at the University of Central Florida Stormwater Management Academy Research laboratory to determine the strength related properties of pervious pavement systems.
Show less
Date Issued
2010
Identifier
CFE0003371, ucf:48472
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003371
MECHANICAL PROPERTIES OF CARBON NANOTUBE / METAL COMPOSITES
Title
MECHANICAL PROPERTIES OF CARBON NANOTUBE / METAL COMPOSITES.
Creator
Sun, Ying, Chen, Quanfang, University of Central Florida
Abstract / Description
Carbon nanotubes (CNTs) have captured a great deal of attention worldwide since their discovery in 1991. CNTs are considered to be the stiffest and strongest material due to their perfect atomic arrangement and intrinsic strong in-plane sp2ÂÂ--sp2 covalent bonds between carbon atoms. In addition to mechanical properties, CNTs have also shown exceptional chemical, electrical and thermal properties. All these aspects make CNTs promising candidates in the development of novel...
Show moreCarbon nanotubes (CNTs) have captured a great deal of attention worldwide since their discovery in 1991. CNTs are considered to be the stiffest and strongest material due to their perfect atomic arrangement and intrinsic strong in-plane sp2ÂÂ--sp2 covalent bonds between carbon atoms. In addition to mechanical properties, CNTs have also shown exceptional chemical, electrical and thermal properties. All these aspects make CNTs promising candidates in the development of novel multi-functional nanocomposites. Utilizing CNTs as fillers to develop advanced nanocomposites still remains a challenge, due to the lack of fundamental understanding of both material processing at the nanometer scale and the resultant material properties. In this work, a new model was developed to investigate the amount of control specific parameters have on the mechanical properties of CNT composites. The new theory can be used to guide the development of advanced composites using carbon nanotubes, as well as other nano-fibers, with any matrices (ceramic, metal, or polymer). Our study has shown that the varying effect based on changes in CNT dimensions and concentration fit the model predictions very well. Metallic CNT composites using both single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT), have been developed through a novel electrochemical co-deposition process. Copper and nickel matrix composites were developed by using pulse-reverse electrochemical co-deposition. Uniaxial tensile test results showed that a more than 300% increase in strength compared to that of the pure metal had been achieved. For example, the ultimate tensile strength of Ni/CNTs composites reached as high as about 2GPa. These are best experimental results ever reported within this field. The mechanical results are mainly attributed to the good interfacial bonding between the CNTs and the metal matrices and good dispersion of carbon nanotubes within the matrices. Experimental results have also shown that the strength is inversely dependent on the diameter of carbon nanotubes. In addition to the mechanical strength, carbon nanotube reinforced metallic composites are excellent multifunctional materials in terms of electrical and thermal conduction. The electrical resistivity of carbon nanotube/copper composites produces electrical resistivity of about 1.0~1.2 x10-6ohm-cm, which is about 40% less than the pure copper. The reduced electrical resistivity is also attributed to the good interfacial bonding between carbon nanotubes and metal matrices, realized by the electrochemical co-deposition.
Show less
Date Issued
2010
Identifier
CFE0003144, ucf:48652
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003144
National Collegiate Athletic Association Strength and Conditioning Coaches' Knowledge and Practices Regarding Prevention and Recognition of Exertional Heat Stroke
Title
National Collegiate Athletic Association Strength and Conditioning Coaches' Knowledge and Practices Regarding Prevention and Recognition of Exertional Heat Stroke.
Creator
Valdes, Anna, Hoffman, Jay, Boote, David, Fisher, Thomas, Mitchell, Debby, University of Central Florida
Abstract / Description
The purpose of this study was to assess and determine the current level of knowledge that National Collegiate Athletic Association (NCAA) Strength and Conditioning Coaches (SCCs) possess regarding exertional heat stroke (EHS) prevention and recognition and to determine if SCC certification type had any effect. Major findings of this study support the view that SCCs need more preparation, education and training to increase their competency in preventing and recognizing EHS. Research found that...
Show moreThe purpose of this study was to assess and determine the current level of knowledge that National Collegiate Athletic Association (NCAA) Strength and Conditioning Coaches (SCCs) possess regarding exertional heat stroke (EHS) prevention and recognition and to determine if SCC certification type had any effect. Major findings of this study support the view that SCCs need more preparation, education and training to increase their competency in preventing and recognizing EHS. Research found that there was no significant difference in scores on the EHS scale based on SCC certification (CSCS vs. SCCC) after accounting for experience, education or division but the CSCS certified professionals scored higher on all the factors as compared to SCCs without the CSCS.. The major key finding was that SCCs lacked essential knowledge to prevent or recognize EHS. Furthermore, the study defines relevant EHS prevention and recognition competencies that an undergraduate curriculum, graduate curriculum and professional certification providers, should include and emphasize in their preparation programs.
Show less
Date Issued
2013
Identifier
CFE0004766, ucf:49790
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004766
SLOPE STABILITY ANALYSIS OF CLASS I LANDFILLS WITH CO DISPOSAL OF BIOSOLIDS USING FIELD TEST DATA
Title
SLOPE STABILITY ANALYSIS OF CLASS I LANDFILLS WITH CO DISPOSAL OF BIOSOLIDS USING FIELD TEST DATA.
Creator
Vajirkar, Mrutyunjay, Chopra, Dr. Manoj, University of Central Florida
Abstract / Description
Land filling provides a major, safe, and economical disposal route for biosolids and sludges. With an expanding world, the demand for larger and higher capacity landfills is rapidly increasing. Proper analysis and design on such fills have pushed the boundaries of geotechnical engineering practice, in terms of proper identification and assessment of strength and deformation characteristics of waste materials. The engineering properties of Municipal Solid Waste (MSW) with co-disposal of...
Show moreLand filling provides a major, safe, and economical disposal route for biosolids and sludges. With an expanding world, the demand for larger and higher capacity landfills is rapidly increasing. Proper analysis and design on such fills have pushed the boundaries of geotechnical engineering practice, in terms of proper identification and assessment of strength and deformation characteristics of waste materials. The engineering properties of Municipal Solid Waste (MSW) with co-disposal of biosolids and sludges with regards to moisture characteristics and geotechnical stability are of utmost importance. Significant changes in the composition and characteristics of landfill may take place with the addition of sludges and biosolids. In particular, the stability of waste slopes needs to be investigated, which involves the evaluation of the strength properties of the mixture of the waste and biosolids. This thesis deals with impact of the addition of biosolids on the geotechnical properties of class I landfill as determined from field investigations. The geotechnical properties are evaluated using an in-situ deep exploration test, called the Cone Penetration Test (CPT). CPT provides a continuous log of subsurface material properties using two measuring mechanisms, namely, tip resistance and side friction. The areas receiving biosolids are compared with areas without, to evaluate the effect of landfilling of biosolids. The required geotechnical shear strength parameters (angle of internal friction and cohesion) of MSW and biosolids mixture are determined by correlation with CPT results similar to the procedure followed in evaluating soil properties. The shear strength parameters obtained from the CPT data are then used to study the stability of different slope configurations of the landfill. The slope stability analysis is conducted on the various landfill models using the computer software SLOPE/W. This software was designed for soils but was found to be suitable for modeling landfills, as the waste is assumed to act similar to a cohesionless soil. Based on the field investigations, the angle of internal friction was found to be about 29° and the determination of any cohesion was not possible. It was concluded that the most suitable practical solution to adding biosolids into the landfill was in the form of trenches. From the slope stability study, it was found that the factor of safety reduces significantly with the introduction of biosolids due to a reduction in shear strength and increase in the overall moisture content. From a parametric study, the stability of a 1:2 side slope with an angle of friction lower than about 20° was found to be less than the safe limit of 1.5. In addition, the factors of safety for landfills with trenches extending close to the edges of the slopes were also found to be unsafe and this situation needs to be avoided in practice.
Show less
Date Issued
2004
Identifier
CFE0000301, ucf:46313
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000301
ATTAINABLE COMPRESSIVE STRENGTH OF PERVIOUS CONCRETE PAVING SYSTEMS
Title
ATTAINABLE COMPRESSIVE STRENGTH OF PERVIOUS CONCRETE PAVING SYSTEMS.
Creator
Mulligan, Ann Marie, Chopra, Manoj, University of Central Florida
Abstract / Description
The pervious concrete system and its corresponding strength are as important as its permeability characteristics. The strength of the system not only relies on the compressive strength of the pervious concrete but also on the strength of the soil beneath it for support. Previous studies indicate that pervious concrete has lower compressive strength capabilities than conventional concrete and will only support light traffic loadings. This thesis investigated prior studies on the compressive...
Show moreThe pervious concrete system and its corresponding strength are as important as its permeability characteristics. The strength of the system not only relies on the compressive strength of the pervious concrete but also on the strength of the soil beneath it for support. Previous studies indicate that pervious concrete has lower compressive strength capabilities than conventional concrete and will only support light traffic loadings. This thesis investigated prior studies on the compressive strength on pervious concrete as it relates to water-cement ratio, aggregate-cement ratio, aggregate size, and compaction and compare those results with results obtained in laboratory experiments conducted on samples of pervious concrete cylinders created for this purpose. The loadings and types of vehicles these systems can withstand will also be examined as well as the design of appropriate thickness levels for the pavement. Since voids are supposed to reduce the strength of concrete 1% for every 5% voids(Klieger, 2003), the goal is to find a balance between water, aggregate, and cement in order to increase strength and permeability, two characteristics which tend to counteract one another. In this study, also determined are appropriate traffic loads and volumes so that the pervious concrete is able to maintain its structural integrity. The end result of this research will be a recommendation as to the water-cement ratio, the aggregate-cement ratio, aggregate size, and compaction necessary to maximize compressive strength without having detrimental effects on the permeability of the pervious concrete system. This research confirms that pervious concrete does in fact provide a lower compressive strength than that of conventional concrete; compressive strengths in acceptable mixtures only reached 1700 psi. Extremely high permeability rates were achieved in most all mixtures regardless of the compressive strength. Analysis of traffic loadings reinforce the fact that pervious concrete cannot be subjected to large numbers of heavy vehicle loadings over time although pervious concrete would be able to sustain low volumes of heavy loads if designed properly. Calculations of pavement thickness levels indicate these levels are dependent on the compressive strength of the concrete, the quality of the subgrade beneath the pavement, as well as vehicle volumes and loadings.
Show less
Date Issued
2005
Identifier
CFE0000634, ucf:46539
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000634
RAMAN SPECTROSCOPY OF THE SKELETON OF THE CORAL ACROPORA CERVICORNIS
Title
RAMAN SPECTROSCOPY OF THE SKELETON OF THE CORAL ACROPORA CERVICORNIS.
Creator
Shepard, Zachary C, Orlovskaya, Nina, University of Central Florida
Abstract / Description
Coral reefs are an important element of marine ecosystem that are critical to maintain a healthy environment. Unfortunately, in recent years coral reefs are doing poorly and many in parts of the ocean are simply dying. Therefore, study of coral's structural response to external loads could answer what will happen with their structures, while they exhibit different types of loading. Therefore, the proposition of using in-situ micro-Raman spectroscopy to study skeletons of Acropora cervicornis...
Show moreCoral reefs are an important element of marine ecosystem that are critical to maintain a healthy environment. Unfortunately, in recent years coral reefs are doing poorly and many in parts of the ocean are simply dying. Therefore, study of coral's structural response to external loads could answer what will happen with their structures, while they exhibit different types of loading. Therefore, the proposition of using in-situ micro-Raman spectroscopy to study skeletons of Acropora cervicornis was used. Coral skeleton samples I subjected to mechanical loading studied their vibrational properties by exciting the material with 532nm visible light. A uniaxial compressive load I applied using a MTS universal testing machine and then using the Raman Spectroscopy to study the vibrational response of coral skeletons. Indentations used Vickers Hardness tester and performed 2D mapping of the coral structure around the indentation. If it's expected that as a result of the proposed research the better understanding of structural stability of the Acropora Cervicornis coral skeletons will be achieved.
Show less
Date Issued
2018
Identifier
CFH2000398, ucf:45856
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH2000398
EFFECT OF NEUTRON RADIATION ON THE MECHANICAL PROPERTIES OF B4C
Title
EFFECT OF NEUTRON RADIATION ON THE MECHANICAL PROPERTIES OF B4C.
Creator
Xia, Zichao, Orlovskaya, Nina, University of Central Florida
Abstract / Description
B4C is an important engineering ceramic used in a number of different applications. One of the promising applications of B4C is in the nuclear industry. B4C has a high neutron absorption cross-section (600 barns) and that is why it can absorb neutrons without forming long lived radio nuclides. As a result, B4C is extensively used as control rods, shielding material and as neutron detectors in nuclear reactors. During the reactor's operation, the B4C undergoes severe neutron radiation and...
Show moreB4C is an important engineering ceramic used in a number of different applications. One of the promising applications of B4C is in the nuclear industry. B4C has a high neutron absorption cross-section (600 barns) and that is why it can absorb neutrons without forming long lived radio nuclides. As a result, B4C is extensively used as control rods, shielding material and as neutron detectors in nuclear reactors. During the reactor's operation, the B4C undergoes severe neutron radiation and defects, such as vacancies and helium bubbles, are generated in the structure. These defects are responsible for the degradation of mechanical performance of B4C and can make this material unsuitable for further exploitation. Therefore, both crystal structure and mechanical properties of B4C were studied before and after radiation, as well as for the case when irradiated by neutrons B4C samples has been annealed in order to heal the defects introduced by the radiation. Fully dense B4C ceramics were produced by hot pressing at 2100ºC, 30MPa, and 45 minutes dwell time. 120 small bars of 2—2.5—25mm were machined according to the MOR bar standard. 40 bars after machining were tested as they were, 80 bars were irradiated with neutrons in neutron source for 3.5 months. 40 out of the 80 irradiated bars were annealed at 400ºC for 1 hour with an attempt to heal the defects possibly introduced by the irradiation. 4-point bending strength, SEVNB fracture toughness, and Vickers hardness have been measured on as received B4C, B4C after radiation, and B4C after radiation and annealing. The Weibull parameters were determined for each set of the conditions. The fracture surfaces of the B4C samples before and after radiation as well as after radiation and annealing have also been analyzed using SEM. X-ray diffractometer was used to collect diffraction pattern of the B4C, and Raman spectrometer was used to evaluate the vibrational response of B4C. Thus the effect of neutron radiation and annealing on the mechanical performance and structure of B4C has been analyzed.
Show less
Date Issued
2011
Identifier
CFE0003654, ucf:48823
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003654
Strengths of Secondary School Principals in One Large Florida School District, and Achievement of Adequate Yearly Progress in 2010-2011
Title
Strengths of Secondary School Principals in One Large Florida School District, and Achievement of Adequate Yearly Progress in 2010-2011.
Creator
Paduano, Kelly, Taylor, Rosemarye, Pawlas, George, Doherty, Walter, Baldwin, Lee, University of Central Florida
Abstract / Description
Increased accountability has led to increased pressure on administrators to meet AYP. By identifying strengths that are present in successful administrators, superintendents will be better equipped to make well-informed selections and administrators can target specific areas for professional growth.This study used a self-assessment created from the Clifton StrengthsFinder Assessment to analyze the strengths of principals and the commonalities in those strengths based on (a) percentage of...
Show moreIncreased accountability has led to increased pressure on administrators to meet AYP. By identifying strengths that are present in successful administrators, superintendents will be better equipped to make well-informed selections and administrators can target specific areas for professional growth.This study used a self-assessment created from the Clifton StrengthsFinder Assessment to analyze the strengths of principals and the commonalities in those strengths based on (a) percentage of adequate yearly progress (AYP) achieved, (b) grade levels served (middle school or high school) and (c) community served (urban or suburban). It is important to note that community served is not meant to indicate the socio-economic status of a school, but instead whether schools reside within census defined urban areas.It was found that there was a statistically significant difference in the ranking of principal strength of input based on the adequate yearly progress achievement of the school. There was also a statistically significant difference between the principals' ranking of both the strengths of communication and harmony based on grade level served and strengths of achiever and responsibility based on community served. While other strengths did not show statistically significant differences among various groups, their overall rankings are provided and discussed.
Show less
Date Issued
2012
Identifier
CFE0004335, ucf:49457
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004335
MICROSTRUCTURAL INVESTIGATION OF PRECIPITATION HARDENED CUNI2SI+ZR ALLOYS FOR ROTOR APPLICATIONS
Title
MICROSTRUCTURAL INVESTIGATION OF PRECIPITATION HARDENED CUNI2SI+ZR ALLOYS FOR ROTOR APPLICATIONS.
Creator
Vega-Garcia, Jean-Paul, Sohn, Yong-Ho, University of Central Florida
Abstract / Description
Industrial generator components experience high stresses and electrical fields during their service life. Material integrity is key in guaranteeing component performance. CuNi2SiZr, used as rotor wedges in generators, serve to maintain rotor slot content in place while experiencing high centrifugal stresses and low cycle fatigue during start and stop at elevated temperature. The quality and integrity of this material in service can be directly related to its microstructure, which is...
Show moreIndustrial generator components experience high stresses and electrical fields during their service life. Material integrity is key in guaranteeing component performance. CuNi2SiZr, used as rotor wedges in generators, serve to maintain rotor slot content in place while experiencing high centrifugal stresses and low cycle fatigue during start and stop at elevated temperature. The quality and integrity of this material in service can be directly related to its microstructure, which is determined by the processing procedures of the wedges. In this study, the microstructure development in this material is evaluated to eliminate grain boundary defects by optimizing processing parameters, determining the best temperature/time combination for precipitation hardening, and determining cold work effect on aging parameters. Two chemistries containing Nickel-to-Silicon ratios of 3.2 and 3.8 were selected for analysis. Cast samples were hot extruded, cold worked, and precipitation hardened. Parameters were varied at each processing step. Five different levels of cold work (4, 5, 7, 10 and 13%) were evaluated using 5 different aging temperatures (450, 460, 470, 490 and 500°C). Each processing parametersÂÂÂÂÂÂÂÂ' effect on microstructure and subsequently on hardness, conductivity, and tensile strength was recorded to assess material performance and identify grain boundary defects origination. Finding of this study identified observed grain boundary defects, using Transmission Electron Analysis, as voids/micro-tears. These defects on grain boundary are detrimental to low cycle fatigue, creep rupture and tensile strength properties and important aspects of the material performance. Grain boundary defects were observed at all levels of cold work, however, origination of defects was only observed in grain sizes larger than 50µm. The strengthening phases for the CuNi2Si+Zr alloy system were identified as Ni2Si and Cr3Si. The Nickel-to-Silicon ratio had an evident effect on the electrical conductivity of the material. However, aging benefits were not clearly established between the two Nickel-to-Silicon ratios.
Show less
Date Issued
2010
Identifier
CFE0003350, ucf:48467
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003350
An Exploratory Study of the Strengths of Islamic School Principals in California, Texas, New York, Florida, and Illinois
Title
An Exploratory Study of the Strengths of Islamic School Principals in California, Texas, New York, Florida, and Illinois.
Creator
Qadri, Kamran, Taylor, Rosemarye, Baldwin, Gordon, Mitchell, Paul, Eriksson, Gillian, University of Central Florida
Abstract / Description
As the focal point of the school, the principal's leadership is integral to its effective functioning. This study used a self-assessment to analyze the self-identified strengths of principals in Islamic schools within the five most populated states in the United States (which also have the largest number of mosques) and the commonalities in those strengths based on (a) the enrollment of the school; (b) year school was established; (c) the gender of the principal; (d) the principal's...
Show moreAs the focal point of the school, the principal's leadership is integral to its effective functioning. This study used a self-assessment to analyze the self-identified strengths of principals in Islamic schools within the five most populated states in the United States (which also have the largest number of mosques) and the commonalities in those strengths based on (a) the enrollment of the school; (b) year school was established; (c) the gender of the principal; (d) the principal's professional preparation, e.g., degree in education vs. other fields and years of experience; and (e) geographic location. While only a small amount of statistical significance was evident (p (<) .05) in exploring the differences between groups, several conclusions were made. In analyzing the strengths of the principals, the least selected strength was Significance and the most was Analytical, which had the highest proportion of affirmatively responding principals as compared to any of the other strengths. Additionally, the relationship between principal strength and school enrollment resulted in for the strengths of Command and Developer at a significance level that was less stringent than the p = .002 dictated by the study; principals at schools that have a student enrollment of 151-200 ranked Command higher as compared to principals in schools of other sizes, whereas those with an enrollment of 150 or fewer students ranked Developer as a more preferred strength. In addressing principal strengths and gender, the results showcased males ranking Self-assuredness as their preferred trait more frequently than their female counterparts, who preferred Futuristic. Furthermore, the relationship of principal strengths and area of education resulted in the strengths of Activator, Maximizer, and Positivity as being ranked higher for principals who had a degree in education at the p = .05 level. The strengths of Empathy, Harmony, and Responsibility (p (<) .05) and Deliberative (p (<) .01) were ranked higher by principals who did not have a degree in education. Also, based on the average rankings of principal strengths, Achiever indicated the strongest association for principals with a degree in education and Deliberative for principals who did not. The results of the mean ranking of the strengths among principals of differing years of experience resulted in the ranking of Focus and Includer at higher levels for principals with 3-6 years of experience (p (<) .01). Furthermore, the average rankings showcased the strength of Achiever as the most strongly rated for principals with less than 3 years of experience, Focus for principals with 3-6 years of experience, and Analytical for principals with more than 6 years. Examination of principal strengths based on geographic location was conducted descriptively due to small group sizes. Among the five states of focus, average rankings of strengths indicated that Deliberative was the most preferred among California principals, Includer among Florida principals, Activator among Illinois respondents, Command among New York principals, and Analytical in Texas.
Show less
Date Issued
2014
Identifier
CFE0005235, ucf:50601
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005235
The impact of a strengths-based group counseling intervention on LGBTQ+ young adult's coping, social support, and coming out growth
Title
The impact of a strengths-based group counseling intervention on LGBTQ+ young adult's coping, social support, and coming out growth.
Creator
Ali, Shainna, Lambie, Glenn, Barden, Sejal, Clark, M. H., Vaughan, Michelle, University of Central Florida
Abstract / Description
Lesbian, gay, bisexual, transgender, and queer individuals, and those who otherwise identify as a minority in terms of affectional orientation and gender expression identity (LGBTQ+) have a higher rate of mental health concerns than their heterosexual and cisgender counterparts (Meyer, 2003). Young adulthood is a difficult time for individuals who identify as LGBTQ+ as internal identity development processes coincide with stressors from the outside world. The conflict between intrapersonal...
Show moreLesbian, gay, bisexual, transgender, and queer individuals, and those who otherwise identify as a minority in terms of affectional orientation and gender expression identity (LGBTQ+) have a higher rate of mental health concerns than their heterosexual and cisgender counterparts (Meyer, 2003). Young adulthood is a difficult time for individuals who identify as LGBTQ+ as internal identity development processes coincide with stressors from the outside world. The conflict between intrapersonal and interpersonal pressures may evoke a multitude of negative emotions such as anxiety, loneliness, isolation, fear, anger, resentment, shame, guilt, and fear. One difficult task that triggers these depreciating sentiments is the task of managing the process of coming out during LGBTQ+ young adulthood. The tumultuous, transformative coming out process prompts stressors that may cause the increase of mental health concerns for the LGBTQ+ population. Although counselors recognize the need and lack of counselor competency to assist LGBTQ+ individuals, there is limited (a) client-based outcome research and (b) intervention research to assert the efficacy of methods to assist LGBTQ+ young adults during the coming out process. Specifically, no studies were found that examined the efficacy of a group counseling intervention to assist LGBTQ+ young adults through the coming out process.The purpose of this study was to investigate the impact of a strengths-based coming out group counseling intervention on LGBTQ+ young adults' (ages 18-24) levels of coping, appraisal of social support, and coming out growth. In an effort to contribute to the knowledgebase in the fields of counseling and counselor education, the researcher examined (a) if a strengths-based group counseling intervention influences LGBTQ+ young adults' levels of coping (as measured by the Brief COPE [Carver, 1997]), social support (as measured by the Social Support Questionnaire-6 [Sarason, Sarason, Shearin, (&) Pierce, 1987]), and coming out growth (as measured by the Coming Out Growth Scale [Vaughan (&) Waehler, 2010]) over time; (b) the potential relationship between the outcome variables and group therapeutic factors (Therapeutic Factors Inventory(-)Short Form [TFI-S]; Joyce et al., 2011); and (c) the potential relationship between the outcome variables and the participants' demographic data (e.g., age, affectional orientation, level of outness).A one-group, pretest-posttest quasi-experimental design was utilized in this study. Participants received an eight-hour group counseling intervention divided in to four two-hour sessions. The counseling groups were offered at the University of Central Florida's Community Counseling and Research Center (CCRC). There were three data collection points: (a) prior to the first session, (b) after the second session, and (c) at the end of the last session. The final sample size included 26 LGBTQ+ participants. The research questions were examined using: (a) Repeated Measures Multivariate Analysis of Variance (RM-MANOVA), (b) MANOVA, (c) Canonical correlation, (d) Analysis of Variance (ANOVA), (e) Pearson Product Moment Correlations, and (f) Cronbach's alpha reliability analysis.The RM-MANOVA results identified a multivariate within-subjects effect across time (Wilks' ? = .15; F (12, 14) = 6.77, p (<) .001) and 84% of the variance was accounted for by this effect. Analysis of univariate tests indicated that Social Support Number (F [1.63, 68.18] = 13.94, p (<) .01; partial ?(&)#178; = .25), Social Support Satisfaction (F [2, 50] = 10.35, p (<) .001; partial ?(&)#178; = .29), Individualistic Growth (F [2, 50] = 8.22, p (<) .01; partial ?(&)#178; = .25), and Collectivistic Growth (F [2, 50] = 9.85, p (<) .001; partial ?(&)#178; = .28) exhibited change over time. Additionally, relationships were identified between the outcome variables of Individualistic Growth, Adaptive Coping, and Collectivistic Growth and the group therapeutic factors of Secure Emotional Expression, Awareness of Relational Impact, and Social Learning. Furthermore, age of questioning was positively correlated with Collectivistic Growth.In addition to a literature review, the research methods and statistical results are provided. Results of the investigation are reviewed and compared to previous research findings. Further, areas for future research, limitations of the study, and implications for the counseling and counselor education are presented. Implications of the study's findings include: (a) support for the use of a strengths-based group counseling intervention in order to increase social support and coming out growth in LGBTQ+ young adults, (b) empirical evidence of a counseling strategy promoting positive therapeutic outcomes with LGBTQ+ college age clients, and (c) verification of the importance of group therapeutic factors in effective group counseling interventions.
Show less
Date Issued
2016
Identifier
CFE0006066, ucf:50991
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006066
Mechanistic Behavior of UHPC and UHPC Composite Structural Components
Title
Mechanistic Behavior of UHPC and UHPC Composite Structural Components.
Creator
Al-Ramahee, Munaf, Mackie, Kevin, Makris, Nicos, Nam, Boo Hyun, Gou, Jihua, University of Central Florida
Abstract / Description
The resistance of reinforced concrete is mobilized through the composite action of two materials with different mechanical behaviors and physical features. Enabling the composite action requires a transfer mechanism between the concrete and the reinforcement which is referred to as bond. The bond model can be defined as a traction-slip relation tangent to the interface. The bond strength between different types of concrete, internal reinforcement, and external reinforcement has been of...
Show moreThe resistance of reinforced concrete is mobilized through the composite action of two materials with different mechanical behaviors and physical features. Enabling the composite action requires a transfer mechanism between the concrete and the reinforcement which is referred to as bond. The bond model can be defined as a traction-slip relation tangent to the interface. The bond strength between different types of concrete, internal reinforcement, and external reinforcement has been of interest to structural engineers for decades. Experimental tests have been carried out to validate the existing bond models and introduce new bond models for special cases of concrete or reinforcement. The effect of various parameters on the bond stress, such as bar diameter, concrete compressive strength, presence of fibers, cyclic loading, etc. have been investigated. However, little attention has been directed to the contribution of normal (to the interface) stress and state of stress of the substrate layer on the mechanical response of the interface. Since the state of stress (tangential, normal, and substrate) within each type of experimental test is different, the resulting bond models are not consistent.Behavior of ultra-high performance concrete (UHPC) composite flexural members are studied using experimental, analytical, and numerical approaches in this research. A new bond-slip model is proposed that contains an explicit representation of the normal stress and constitutive model of the substrate. The parameters of the model were calibrated from beam and pullout tests using UHPC and HSS. The calibrated results showed consistency in the material point behavior between the pullout and beam test although the states of stress were different. The effect of the normal force was verified throughout a numerical model compared with experimental flexural tests. Single and double lap shear tests were carried out for UHPC and FRP, and parameters of the bilinear model were calibrated and used in the finite element model of the new composite deck.A new lightweight composite deck system is proposed that uses fiber reinforced polymers (FRP) bonded to UHPC using vacuum-assisted resin transfer molding. The high-performance deck system has application in deck design and replacement for bridges with weight restrictions as well as for accelerated bridge construction. Results show the deck satisfies strength and serviceability criteria under monotonic load. The bond strength between the UHPC and the glass fiber reinforced polymers (GFRP) plays a significant role in the performance of the proposed deck and controls the behavior of the system. However, live loads on bridges are inherently cyclic and therefore research on serviceability and fatigue behavior of UHPC and UHPC composite members were carried out. The UHPC beams were strengthened using glass GFRP plates on compression side to obtain data that could be utilized for the future design. The effect of fatigue loading on the interfacial shear stress between UHPC and GFRP was also investigated and it is found to be minor under low load level. However, a noticeable progression in the interfacial shear stress was found for the higher load ratio.
Show less
Date Issued
2016
Identifier
CFE0006431, ucf:51464
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006431
Modeling Mass Transfer and Assessing Cost and Performance of a Hollow Fiber Nanofiltration Membrane Process
Title
Modeling Mass Transfer and Assessing Cost and Performance of a Hollow Fiber Nanofiltration Membrane Process.
Creator
Yonge, David, Duranceau, Steven, Sadmani, A H M Anwar, Lee, Woo Hyoung, Clausen, Christian, University of Central Florida
Abstract / Description
Bench-scale water treatment testing of three next generation hollow-fiber (HF) nanofiltration (NF) membranes was conducted to characterize divalent ion rejection capabilities and investigate removal mechanisms. Existing mathematical models were investigated to describe solute transport using synthetic magnesium sulfate solutions including the size exclusion model, homogenous solution diffusion (HSD) model, dimensional analysis, and the HSD model incorporating film theory. Solute transport for...
Show moreBench-scale water treatment testing of three next generation hollow-fiber (HF) nanofiltration (NF) membranes was conducted to characterize divalent ion rejection capabilities and investigate removal mechanisms. Existing mathematical models were investigated to describe solute transport using synthetic magnesium sulfate solutions including the size exclusion model, homogenous solution diffusion (HSD) model, dimensional analysis, and the HSD model incorporating film theory. Solute transport for two of the membranes were described by HSD theory and were predictive of their 90% divalent ion removal. A third membrane was more accurately modeled using size exclusion and was found to be predictive of its 40% divalent ion rejection. Feed ionic strength variation was shown to significantly impact rejection. In this work, semi-empirical models were developed to describe solute transport under varying feed ionic strength conditions. Bench-scale testing of aerated groundwater confirmed the HFNF membrane divalent ion rejection capabilities. Pilot testing of a commercially available HFNF membrane was shown to remove divalent ions and dissolved organic carbon (DOC) by 10% and 25%, respectively. Financial evaluations indicated that HFNF offered cost savings over traditional spiral-wound (SW) NF, $0.60/kgal versus $0.85/kgal operating costs, respectively. Traditional SWNF membranes produced superior water quality achieving 90% divalent ion removal and 96% DOC removal but required media and membrane filtration pretreatment. When considering the costs of constructing a new 2 million gallon per day (permeate) HFNF process, conceptual cost comparisons revealed that HFNF technologies could reduce capital costs by approximately $1 million, and operating costs by $0.27/kgal for an 85% recovery plant.
Show less
Date Issued
2016
Identifier
CFE0006549, ucf:51346
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006549
Phosphatidic Acid Increases Lean Body Tissue and Strength In Resistance Trained Men
Title
Phosphatidic Acid Increases Lean Body Tissue and Strength In Resistance Trained Men.
Creator
Williams, David, Hoffman, Jay, Fragala, Maren, Stout, Jeffrey, University of Central Florida
Abstract / Description
ABSTRACTPhosphatidic Acid (PA) is a natural phospholipid compound derived from lecithin which is commonly found in egg yolk, grains, fish, soybeans, peanuts and yeast. It has been suggested that PA is involved in several intracellular processes associated with muscle hypertrophy. Specifically, PA has been reported to activate protein synthesis through the mammalian target of rapamycin (mTOR) signaling pathway and thereby may enhance the anabolic effects of resistance training. To our...
Show moreABSTRACTPhosphatidic Acid (PA) is a natural phospholipid compound derived from lecithin which is commonly found in egg yolk, grains, fish, soybeans, peanuts and yeast. It has been suggested that PA is involved in several intracellular processes associated with muscle hypertrophy. Specifically, PA has been reported to activate protein synthesis through the mammalian target of rapamycin (mTOR) signaling pathway and thereby may enhance the anabolic effects of resistance training. To our knowledge, no one has examined the effect of PA supplementation in humans while undergoing a progressive resistance training program. To examine the effect of PA supplementation on lean soft tissue mass (LM) and strength after 8 weeks of resistance training.Fourteen resistance-trained men (mean (&)#177; SD; age 22.7 (&)#177; 3.3 yrs; height: 1.78 (&)#177; 0.10m; weight: 89.3 (&)#177; 16.3 kg) volunteered to participate in this randomized, double-blind, placebo-controlled, repeated measures study. The participants were assigned to a PA group (750mg/day; Mediator(&)#174;, ChemiNutra, MN, n=7) or placebo group (PL; rice flower; n=7), delivered in capsule form that was identical in size, shape and color. Participants were tested for 1RM strength in the bench press (BP) and squat (SQ) exercise. LM was measured using dual-energy X-ray absorptiometry. After base line testing, the participants began supplementing PA or PLfor 8 weeks during a progressive resistance training program intended for muscular hypertrophy. Data was analyzed using magnitude-based inferences on mean changes for BP, SQ and LM. Furthermore, the magnitudes of the inter-relationships between changes in total training volume and LM were interpreted using Pearson correlation coefficients, which had uncertainty (90% confidence limits) of approximately +0.25.In the PA group, the relationship between changes in training volume and LM was large(r=0.69, +0.27; 90%CL), however, in the PL group the relationship was small (r=0.21, +0.44; 90%CL). PA supplementation was determined to be likely beneficial at improving SQ and LM over PL by 26% and 64%, respectively. The strong relationship between changes in total training volume and LM in the PA group suggest that greater training volume most likely lead to the greater changes in LM, however, no such relationship was found with PL group. For the BP data, the PA group resulted in a 42% greater increase in strength over PL, although the effect was considered unclear. While more research is needed to elucidate mechanism of action; the current findings suggest that in experienced resistance trained men supplementing 750mg PA per day for 8 weeks may likely benefit greater changes in muscle mass and strength compared with resistance training only. ?
Show less
Date Issued
2012
Identifier
CFE0004641, ucf:49897
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004641
STRUCTURAL CAUSES OF SOCIAL CONFLICT IN AFRICA
Title
STRUCTURAL CAUSES OF SOCIAL CONFLICT IN AFRICA.
Creator
Charland, Lucien, Dolan, Thomas, University of Central Florida
Abstract / Description
Social conflict, as opposed to armed conflict, has received less attention in the field of quantitative research. This paper investigates the structural causes of political violence in 35 African states using data from the Social Conflict in Africa dataset and the Beck and Katz panel corrected standard errors time series regression model. Theoretically, a closed political opportunity structure, combined with a weak state unable to provide public goods, should together produce high levels of...
Show moreSocial conflict, as opposed to armed conflict, has received less attention in the field of quantitative research. This paper investigates the structural causes of political violence in 35 African states using data from the Social Conflict in Africa dataset and the Beck and Katz panel corrected standard errors time series regression model. Theoretically, a closed political opportunity structure, combined with a weak state unable to provide public goods, should together produce high levels of social conflict. The independent variables attempt to operationalize these concepts from four different angles. In this analysis Access to Education and Infrastructure (AEI), Ethno Linguistic Fractionalization (ELF), Freedom in the World Political Rights (FIW), and National Material Capabilities (NMC) were all significant predictors of social conflict. This study found that as the level of ethnic fractionalization and material capabilities within states rose, the frequency of social conflict events also increased. However, as access to infrastructure and political rights declined, the number of social conflict events increased. Wald chi-square and R-square values suggest that the model is complete and has substantial explanatory power.
Show less
Date Issued
2014
Identifier
CFH0004663, ucf:45314
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH0004663
THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS
Title
THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS.
Creator
Venkataraman, Manoj, Kumar, Ranganathan, University of Central Florida
Abstract / Description
Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and...
Show moreAddition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.
Show less
Date Issued
2005
Identifier
CFE0000837, ucf:46676
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000837
Effects of Rest Position on Ultrasound-Derived Morphological Characteristics of the Vastus Lateralis and Lower-Body Force Production
Title
Effects of Rest Position on Ultrasound-Derived Morphological Characteristics of the Vastus Lateralis and Lower-Body Force Production.
Creator
Varanoske, Alyssa, Wells, Adam, Fukuda, David, Stout, Jeffrey, Mangine, Gerald, University of Central Florida
Abstract / Description
INTRODUCTION: Ultrasound assessment of the lower body typically encompasses 10-15 minutes of supine rest prior to examination because of the potential influence of gravitational fluid shifts on tissue size and composition. However, examination of the vastus lateralis (VL) muscle requires individuals to lay in the lateral recumbent position, and this change in position may influence muscle morphological characteristics and their ability to predict muscle function.PURPOSE: The purpose of this...
Show moreINTRODUCTION: Ultrasound assessment of the lower body typically encompasses 10-15 minutes of supine rest prior to examination because of the potential influence of gravitational fluid shifts on tissue size and composition. However, examination of the vastus lateralis (VL) muscle requires individuals to lay in the lateral recumbent position, and this change in position may influence muscle morphological characteristics and their ability to predict muscle function.PURPOSE: The purpose of this investigation was to examine the effect of rest position on ultrasound-derived morphological characteristics of the VL and to determine whether or not rest position affects the relationships between muscle morphological characteristics of the VL and lower-body force and power production. METHODS: Thirty-one resistance-trained males (age: 23.0 (&)#177; 2.1 years; height: 1.79 (&)#177; 0.08 m; body mass: 87.4 (&)#177; 11.7 kg) participated in this investigation. Muscle morphological characteristics, including cross-sectional area (CSA), muscle thickness (MT), pennation angle (PA), echo intensity (UnCorEI), subcutaneous adipose tissue thickness (SFT), and EI corrected for SFT (CorEI) of the VL were assessed in the dominant limb after 15 minutes of rest in 3 recumbent positions: supine (SUP), dominant lateral recumbent (DLR), non-dominant lateral recumbent (NDLR), as well as after 15 minutes of standing (ST) and immediately after laying down (IP). Following ultrasound assessments, participants completed unilateral performance assessments, including vertical jumps (UVJ), isometric/isokinetic testing, and a 1-repetition maximum (1-RM) leg press. RESULTS: A repeated-measures analysis of variance revealed significantly different (p (<) 0.05) CSA, MT, PA, UnCorEI, and SFT in ST compared to recumbent positions after 15 minutes of rest (NDLR, DLR, and SUP). Additionally, significant differences were observed between recumbent positions for CSA, CorEI, and UnCorEI; however, no differences were observed for MT, PA, and SFT. Different magnitudes of relationships were observed between muscle morphological characteristics measured after rest in different positions and performance variables. However, muscle morphology after IP generally appears to be the best predictor of performance for most variables, although utilizing the NDLR and DLR positions may provide comparable, or potentially stronger results for variables such as IsokPF. The relationship between muscle morphology and various performance variables in ST were weaker compared to the recumbent positions examined, specifically for IsokPF, 1-RM leg press, and for all UVJ variables, except total work.CONCLUSIONS: Muscle morphology differs depending on the rest position utilized prior to ultrasound analysis. These rest positions also affect the ability for muscle morphology to predict lower-body force production. Future research should consider evaluation of muscle morphology of the VL after IP in the prediction of muscle function; however, NDLR and DLR may also be used. SUP and ST provide significantly weaker relationships for some performance variables compared to the other recumbent positions.
Show less
Date Issued
2019
Identifier
CFE0007550, ucf:52610
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007550
Ultra-High Performance Concrete for Precast Seismic Bridge Column Connection
Title
Ultra-High Performance Concrete for Precast Seismic Bridge Column Connection.
Creator
Chan, Titchenda, Mackie, Kevin, Catbas, Necati, Chopra, Manoj, Bai, Yuanli, University of Central Florida
Abstract / Description
Accelerated bridge construction (ABC) utilizes prefabricated bridge elements constructed off-site, delivered, and assembled on-site to expedite construction time and reduce traffic disruption. ABC has been increasingly used for super- and sub-structure elements in low seismic regions. However, its application in medium and high seismic regions remain limited, particularly for precast columns where connections typically coincide with plastic hinge (PH) regions. Ultra-high performance concrete ...
Show moreAccelerated bridge construction (ABC) utilizes prefabricated bridge elements constructed off-site, delivered, and assembled on-site to expedite construction time and reduce traffic disruption. ABC has been increasingly used for super- and sub-structure elements in low seismic regions. However, its application in medium and high seismic regions remain limited, particularly for precast columns where connections typically coincide with plastic hinge (PH) regions. Ultra-high performance concrete (UHPC), characterized by high compressive and tensile strength, and superior bond properties, is a potential material that can mitigate PH damage and enhance load transfer. This research proposes a new and simple damage tolerant precast column connection for use in medium and high seismic regions. The connection laps the column longitudinal reinforcement with footing dowels using a short splice length, a practical concrete cover, no shear reinforcement, and the shifted PH concept to prevent footing damage. Two 0.42-scale precast columns with different shear span ratios were tested under reversed cyclic loading to investigate the proposed connection relative to previously tested cast-in-place specimens. Results showed the connection performed well in shear, developed column longitudinal bars, shifted PH formation above the UHPC connection, and exhibited high lateral capacity and ductility. Twenty-seven pullout and lap splice beams were tested to study the bond of reinforcement in UHPC under different parameters and stress states. Results indicated significant bond strength improvement and splice length reduction compared with conventional concrete. The pullout specimens were simulated using the OpenSees framework to propose reinforcing steel in UHPC bond-slip models where existing studies in the literature were limited. The models were incorporated into the numerical modeling of the precast columns using one-dimensional fiber-section and two-dimensional plane stress nonlinear analyses. Results from the two modeling methods showed good agreement with the experiments, with the calibrated bond-slip models providing a good representation of load transfer in the connection.
Show less
Date Issued
2019
Identifier
CFE0007610, ucf:52534
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007610
VIBRATIONAL AND MECHANICAL PROPERTIES OF 10 MOL % SC2O3-1 MOL % CEO2- ZRO2 ELECTROLYTE CERAMICS FOR SOLID OXIDE FUEL CELLS
Title
VIBRATIONAL AND MECHANICAL PROPERTIES OF 10 MOL % SC2O3-1 MOL % CEO2- ZRO2 ELECTROLYTE CERAMICS FOR SOLID OXIDE FUEL CELLS.
Creator
Lukich, Svetlana, Orlovskaya, Nina, University of Central Florida
Abstract / Description
Solid Oxide Fuel Cells (SOFCs) are emerging as a potential breakthrough energy conversion technology for clean and efficient production of electricity and heat from hydrogen and hydro-carbon fuels. Sc0.1Ce0.01ZrO2 electrolytes for Solid Oxide Fuel Cells are very promising materials because their high ionic conductivity in the intermediate temperature range 700oC-800oC. The vibration response of cubic and rhombohedral (β) 10 mol%Sc2O3 - 1 mol%CeO2 - ZrO2 (Sc0.1Ce0.01ZrO2 ) both at room...
Show moreSolid Oxide Fuel Cells (SOFCs) are emerging as a potential breakthrough energy conversion technology for clean and efficient production of electricity and heat from hydrogen and hydro-carbon fuels. Sc0.1Ce0.01ZrO2 electrolytes for Solid Oxide Fuel Cells are very promising materials because their high ionic conductivity in the intermediate temperature range 700oC-800oC. The vibration response of cubic and rhombohedral (β) 10 mol%Sc2O3 - 1 mol%CeO2 - ZrO2 (Sc0.1Ce0.01ZrO2 ) both at room and high-temperatures is reported. The in-situ heating experiments and ex-situ indentation experiments were performed to characterize the vibrational behavior of these important materials. A temperature and stress-assisted phase transition from cubic to rhombohedral phase was detected during in-situ Raman spectroscopy experiments. While heating and indentation experiments performed separately did not cause the transition of the cubic phase into the rhombohedral structure under the performed experimental conditions and only broadened or strained peaks of the cubic phase could be detected, the heating of the indented (strained) surface leaded to the formation of the rhombohedral Sc0.1Ce0.01ZrO2. Both temperature range and strained zone were estimated by in situ heating and 2D mapping, where a formation of rhombohedral or retention of cubic phase has been promoted. The mechanical properties, such as Young's modulus, Vickers hardness, indentation fracture resistance, room and high temperature four point bending strength and SEVNB fracture toughness along with the stress – strain deformation behavior in compression, of 10 mol% Sc2O3 – 1 mol % CeO2 - ZrO2 (ScCeZrO2) ceramics have been studied. The chosen composition of the ScCeZrO2 has very high ionic conductivity and, therefore, is very promising oxygen ion conducting electrolyte for the intermediate temperature Solid Oxide Fuel Cells. Therefore, its mechanical behavior is of importance and is presented in this study.
Show less
Date Issued
2009
Identifier
CFE0002914, ucf:52845
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002914
The Sacrament of Violence: Myth and War in C.S. Lewis's Ransom Trilogy
Title
The Sacrament of Violence: Myth and War in C.S. Lewis's Ransom Trilogy.
Creator
Engelhardt, Tanya, Campbell, James, Dandrow, Edward, Jones, Donald, University of Central Florida
Abstract / Description
My primary aim for this study is to illuminate the Ransom trilogy's inherent psychological and spiritual themes, as well as demonstrate how these themes clarify Lewis's philosophical and political goals for the text. Specifically, by investigating Lewis's mythic imagery and suffering motifs in light of psychoanalytic and theological literary criticisms, I elucidate the reasoning behind Lewis's unique(-)and at times, horrific(-)portrayal of fear, violence, and death. I also investigate how...
Show moreMy primary aim for this study is to illuminate the Ransom trilogy's inherent psychological and spiritual themes, as well as demonstrate how these themes clarify Lewis's philosophical and political goals for the text. Specifically, by investigating Lewis's mythic imagery and suffering motifs in light of psychoanalytic and theological literary criticisms, I elucidate the reasoning behind Lewis's unique(-)and at times, horrific(-)portrayal of fear, violence, and death. I also investigate how Lewis integrates his theology with the horrors of personal and intrapersonal suffering, as well as how he utilizes imagination and myth to explicate the practical (or political) implications of his theodicy. As a whole, I present a systematic study of the relationship between the Great War, myth, and the three Ransom novels, one which reveals how Lewis manipulates his personal traumatic experiences to fashion a romantic Christian understanding of evil and violence in the modern world.
Show less
Date Issued
2012
Identifier
CFE0004279, ucf:49503
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004279

Pages