Browsing by Subject "strength"
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Item Carbon nanotube and nanofiber reinforcement for improving the flexural strength and fracture toughness of portland cement paste(2012-07-16) Tyson, Bryan MichaelThe focus of the proposed research will be on exploring the use of nanotechnology-based nano-filaments, such as carbon nanotubes (CNTs) and nanofibers (CNFs), as reinforcement in improving the mechanical properties of portland cement paste as a construction material. Due to their ultra-high strength and very high aspect ratios, CNTs and CNFs have been used as excellent reinforcements in enhancing the physical and mechanical properties of polymer, metallic, and ceramic composites. Very little attention has been devoted on exploring the use of nano-filaments in the transportation industry. Therefore, this study aims to bridge the gap between nano-filaments and transportation materials. This will be achieved by testing the integration of CNTs and CNFs in ordinary portland cement paste through state-of-the-art techniques. Different mixes in fixed proportions (e.g. water-to-cement ratio, air content, admixtures) along with varying concentrations of CNTs or CNFs will be prepared. Different techniques commonly used for other materials (like polymers) will be used in achieving uniform dispersion of nano-filaments in the cement paste matrix and strong nano-filaments/cement bonding. Small-scale specimens will be prepared for mechanical testing in order to measure the modified mechanical properties as a function of nano-filaments concentration, type, and distribution. With 0.1 percent CNFs, the ultimate strain capacity increased by 142 percent, the flexural strength increased by 79 percent, and the fracture toughness increased by 242 percent. Furthermore, a scanning electron microscope (SEM) is used to discern the difference between crack bridging and fiber pullout. Test results show that the strength, ductility, and fracture toughness can be improved with the addition of low concentrations of either CNTs or CNFs.Item From Pain to Peace: An African American Woman Finding Voice in Black Womanist Theology(2014-12-12) Abney, AngelaThis was an autoethnographic study designed to assist me to understand my journey as daughter, mother, wife, teacher, and leader. Autoethnography was used as an examination of the author?s perspective as the researcher, through a detailed examination of African American women in leadership and mothering, as a subject. This study examined the lived experiences of two focus groups compromised of four African American Young mothers and four Older African American mothers. Additionally the study also examined the lived experiences of my father, husband, three aunts, and my three daughters. The objective was to gain an understanding of their perspectives on African American women as mothers and leaders. The data were collected using reflexive journaling, interviews, and family photos. The data were analyzed using Nvivo for transcript analysis where reoccurring themes simulated to allow dominant themes to emerge. The study confirmed findings that 1) African American women as mothers show love in many ways, 2) African American women pass strength on as a legacy, 3) African American women rely on church and God in their leadership, and 4) African American women?s views on education are paramount in the African American community. The most insightful conclusions from the discussions were with the African American women and men were the emergence of my voice in Black Womanist Theology.Item Inheritance of Cotton Fiber Length and Strength(2014-04-23) Joy, Kolbyn SethThe U.S. cotton industry has become predominantly an export market which requires a higher standard of fiber quality than does the domestic market. To remain competitive, U.S. cotton must meet the quality standards demanded by the consumers of raw cotton whether domestic or abroad. Diallel and generation means analyses (GMA) were conducted on fiber quality data of nine and five parental genotypes, respectively, to gain a better understanding of the genetic control of cotton fiber length and strength as well as to ascertain the value of the reported genotypes toward the improvement of fiber quality. Parental genotypes included extra-long staple uplands (Gossypium hirsutum, L.), EMS mutated uplands, high strength uplands, and interspecific hybrids. General combining ability (GCA) and specific combining ability (SCA) were estimated according to Griffing?s diallel Model I, Method 4 for lint percent, high volume instrument (HVI) upper half mean length (UHML), fiber bundle strength (Str), uniformity index, elongation, micronaire, advanced fiber information system (AFIS) upper quartile length on a weight basis, mean length on a number basis, short fiber content on a number basis, immature fiber content, maturity ratio, and standard fineness. Estimates of GCA were significant across environments for all traits. SCA effects were significant for most traits but accounted for a smaller proportion of the variability in comparison to GCA effects. TAM B182-33 ELS would be the parent of choice to simultaneously improve fiber length and Str. The GMA was conducted on the parental, F_(1), F_(2), and backcross generations. Low levels of transgressive segregation for both UHML and Str were observed for some populations. Broad sense heritability ranged from 0.00 to 0.67 for UHML and from 0.22 to 0.82 for Str. Additive gene action was significant for all but three parental combinations for UHML and for all parental combinations for Str. Generally, the significance and magnitude of additive genetic effects were more consistent among parental combinations and years than were non-additive genetic effects for both UHML and Str. Dominance and epistatic genetic effects often were of a greater magnitude than additive genetic effects but in an inconsistent manner, and in both positive and negative directions.Item Intra-Set Rest Intervals in Hypertrophic Training: Effects on Hypertrophy, Strength, Power, and Myosin Heavy Chain Composition(2012-10-19) Oliver, JonathanThe purpose of this study was to compare the effects of intra-set rest intervals (ALT) and traditional resistance (STD) training in hypertrophic resistance training. 22 males (25 +/- 5yrs, 179.71 +/- 5.0cm, 82.1 +/- 10.6kg, 13.6 +/- 4.3% fat, 6.5 +/- 4.5yrs training) were matched according to baseline characteristics and randomly assigned to a STD or ALT 12 week hypertrophic training protocol. Body composition, strength (1RM bench and squat); power (60% 1RM bench and squat); and vertical jump were assessed at baseline, 4, 8, and 12 weeks. Muscle biopsy for myosin heavy chain (MHC) was performed pre and post training. A 2 x 4 (Group x Time) ANOVA was used to assess changes in body composition. A 2 x 4 (Group x Time) ANCOVA covaried by baseline performance measures was used to assess differences in strength and power characteristics. A 2 x 2 (Group x Time) ANCOVA covaried for baseline percentage MHC was used to determine differences pre and post training. Both groups experienced increases in FFM with no differences between groups (62.6 +/- 7.9, 63.4 +/- 7.6, 64.2 +/- 7.4, 64.2 +/- 7.5kg; p>0.05). No time effects were noted in percent fat (13.6 +/- 4.3, 14.1 +/- 4.7, 14.0 +/- 4.6, 14.3 +/- 4.6%fat; p>0.05). Increase in FFM was associated with a decrease in MHCIIX, (ALT, -37.9 +/- 24.1%; STD, -23.4 +/- 23.8%; p = 0.001) and an increase in MHCIIA (ALT, 32.0 +/- 28.8%; STD, 25.4 +/- 29.1%; p = 0.001) with no difference between groups. A significant interaction was observed with the ALT group experiencing greater gains in both 1RM bench (STD 104.1 +/- 27.6, 102.7 +/- 29.0, 107.0 +/- 25.3, 113.2 +/- 27.3; ALT 110.9 +/- 20.1, 117.5 +/- 23.7, 120.8 +/- 22.6, 126 +/- 22.8; p<0.05) and 1RM squat (STD 123.3 +/- 39.3, 139.6 +/- 38.8, 160.2 +/- 36.1, 171.8 +/- 34.5; ALT 130.1 +/- 25.1, 152.6 +/- 24.8, 179.8 +/- 24.5, 193.9 +/- 24.2kg; p<0.05). The ALT group experienced greater gains in power in both the bench (STD 560 +/- 122, 541 +/- 105, 572 +/- 122, 593 +/- 135W; ALT 575 +/- 102, 586 +/- 123, 646 +/- 103, 658 +/- 113W; p<0.05) and vertical jump (STD 1378 +/- 237, 1418 +/- 214, 1452 +/- 210, 1470 +/- 215W; ALT 1389 +/- 179, 1434 +/- 152, 1470 +/- 149, 1537 +/- 150W;p<0.05), with gains in squat power approaching significance (STD 625 +/- 245, 704 +/- 233, 723 +/- 227, 830 +/- 232W; ALT 632 +/- 171, 734 +/- 179, 783 +/- 188, 914 +/- 207W; p<0.10). The use of intra-set rest intervals in programs designed to elicit hypertrophy results in greater gains in strength and power with no significant difference in lean mass or MHC composition after a 12 week resistance training program designed to elicit hypertrophy.Item The effects of concurrent training on performance variables in previously untrained males(Texas A&M University, 2005-02-17) Glowacki, Shawn PhilipResearch has shown conflicting results involving interference of strength development with combined resistance and endurance training. Purpose: To examine if endurance training and resistance training performed concurrently would produce different performance and physiological results when compared to each type of training alone. Methods: Forty-five untrained males were recruited and randomly assigned to one of three 12 wk training groups. An endurance training (ET, N=12) group trained by running (2-3 days/week, 20-40 min, 65- 80% HRR), a resistance training (RT, N=13) group performed a resistance training program (2-3 days/week, 3 sets/8 exercises, 6-10 reps, 75-85% 1RM), and a concurrent training (CT, N=16) group performed both the endurance and resistance training programs (5 days/week, even # week 3 endurance/2 resistance workouts, odd # week 3 resistance/2 endurance workouts). All groups were tested for all the following variables prior to and following training: percent body fat, VO2max, isokinetic-maximal torque and avg. power at two speeds, 1RM leg press, 1 RM bench press, vertical jump, lower body power (as calculated by the Lewis formula) and 40-yard dash time. Results: Percent body fat was significantly (p≤.05) decreased in both the ET and CT groups. Only the ET group significantly improved VO2max (+8.24%). Minimal changes were found for any of the isokinetic measurements. The ET, RT, and CT groups demonstrated significant improvements in leg press (20.4, 40.8, and 39.4%) and bench press (7.5, 30.5 and 21.2%) 1 RM. RT and CT 1 RM improvements were similar and significantly greater than the ET group. Only the RT group significantly increased power. No group showed a significant change in vertical jump or 40-yard dash time. Conclusions: Findings indicate that endurance training does not interfere with strength development, but resistance training appears to hinder development of maximal aerobic capacity.