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  • 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.
581

Effects of Support Fluid Type on Concrete Integrity and Durability in Drilled Shafts

Mobley, Sarah J. 02 July 2019 (has links)
Until recently, concrete flow in tremie-placed drilled shafts has been mischaracterized as rising uniformly with laitance formation occurring only at the top of the rising concrete in the shaft. In actuality, concrete first fills a portion of the reinforcement cage to a sufficient height to promote radial flow into the cover region. Depending on support fluid type, the radial flow can produce laitance-filled creases/channels projecting the reinforcing cage configuration to the side of shaft surface. The flow pattern (and creases) can affect filter cake thickness, cover quality and propensity for corrosion. This research examines 52 tremie-placed laboratory drilled shaft specimens constructed using bentonite, polymer or natural support fluid to identify correlations between support fluid type and laitance channel formation. The extent of the laitance channel effect was quantified with surface texture, corrosion potential, and strength distribution methods. A direct correlation between the use of bentonite support fluid and laitance channel formation was identified which showed a high propensity for corrosion and lower concrete strengths.
582

Building models of Wireless Local Area Network coverage

Fu, Qiang January 2007 (has links)
Wireless LANs are becoming more and more popular because they can provide high data rate network access to computer users without the tradition cable. Additionally mobile devices allow people to have connectivity, even when moving from place to place, additionally they are small in size and light in weight. While such devices only offer some of the capabilities of PC they are more convenient to use than a desktop PC when traveling. Cellular phone and smart phones have more function than before, with some newer models phone having an embedded GPS receiver. This GPS receiver can provide user with new services, in addition to location information. Many of these handheld devices include wireless LAN functionality, enabling people to walk from one place to another with a continuous network access, via either the WLAN or the cellular network. By using voice over IP, a wireless enabled hand device becomes a Virtual Cell Phone enabling low cost calls via the WLAN when the user is within coverage of an access point which will give them access, or via the normal cellular phone network (when with in coverage). Because the WLAN coverage is not ubiquitous, it is important to build a Wireless Network Coverage model to enable every user to see where there is WLAN network coverage. Present methods to create such a coverage map require a lot of work to collect data, both indoors and outdoors. Currently a lot of human effort is needed to collect, process, and format this data. The method proposed her could provide an easier way of gathering data from the field and be simple enough that even a normal user could collect data and contribute it to help generate a coverage model of areas where they visit. The measurements reported indicate that it is possible to combine data from multiple devices of the same and different types, but only when the signal strength is high. Fortunately, it is just these areas where the signal quality is good which are of interest to users. The thesis also shows one way of presenting this data in an easy to understand visual manner as an overlay on Google Earth. / Trådlös LANs blir mer och mer populär emedan de kanna skaffa hög datanhastighet nätverken tillträde till computern förbrukaren utantraditionen kabel. Ytterligare rörlig anordningen tillåta folk tillhar connectivity, jämn när flyttanden från ställe till ställe, ochblir liten i storlek och ljus i vikt. Fördriva tiden sådan anordningenbara erbjudande något om anlagen av PC de er mer bekväm till användaän en desktopen PC när resande. Cellular telefonerna och "smart"telefonerna har mer funktion än framför, med något nye modellernatelefonerna har inbyggd GPS. Den här GPS ta emot kanna skaffaförbrukaren med ny tjänsten, dessutom till läge informationen. Mångaav de här handheld omfatta trådlös LAN funktionellitet, sättande istånd till folk till gå från en ställe till en annan med enkontinuerlig nätverken tillträde, via WLAN eller den cellularnätverken. Vid användande röst över IP, en trådlös sättet i stånd tillhand anordning blir en Verklig cellular telefonerna sättande i ståndtill låg kostnad telefonsamtalen via den WLAN när förbrukaren ertäckningenhåll av en tillträde punkt vilken vilja ger dem tillträde,eller via den normal cellular telefonerna nätverken (när i täckningenhåll). Emedan den WLAN täckningen är inte allmänt utbredd, den er viktig tillbygga en Trådlös Nätverken Täckningen modell till möjliggöra varjeförbrukaren till se var där er WLAN nätverken täckningen. Föreställametoderna till skapa sådan en täckningen karta behöva mycket verk tillsamla datan, båda indoors och utomhus. Just nu en masse mänskligansträngning är behövde till samla, förlopp, och formaten den härdatan. Metoden föreslå här kunde skaffa en lättare väg av samlingendatan från fält och bli enkel nog så pass jämn en normal förbrukarenkunde samla datan och bidra med den till hjälp generera en täckningenmodell av områdena var de besöka. Måtten rapportera ange så pass den er möjlig till kombinera datan frånmångfaldig anordningen om det lika och olik typen, utom bara närsignalen styrka är hög. Lyckligtvis, den er rättvis de här områdenavar signalen kvalitet är god vilken är om intresse tillförbrukaren. Theses också visar en väg av presenterande den här datani en lätt till förstå visuell sätt så en täcka över på GoogleEarth.
583

The effects of preventive training programs on shoulder injury, pain, and strength in overhead athletes – a review

Looft, Patrik January 2021 (has links)
Background Shoulder pain and injury is common in both the general population and among athletes. Overhead athletes, such as handball players, are at an even higher risk of shoulder injury. There is currently no consensus regarding how or if these injuries can be prevented.  Purpose The aim of this review was to examine whether preventive training programs reduce acute and/or overuse injuries in overhead athletes. Another aim was to examine if training programs increase the strength of the rotator cuff in overhead athletes.  Method Searches were made in PubMed, Cinahl, and Sport Discus in March and April 2021. Ten studies were included in the study. The PEDro-scale was used to assess methodological quality and GRADE was used to determine level of evidence.  Results The methodological quality was “moderate to high” for five of the studies. The remaining five studies were of lower quality. The level of evidence was “limited” for prevention and “inadequate” for rotator cuff strength.  Conclusion The evidence for prevention of shoulder injuries was “limited” and the evidence for rotator cuff strength was “inadequate”. A narrower focus on one sport might result in more robust evidence.  Keywords overhead athlete, prevention, shoulder, strength
584

Effect of internal erosion on the mechanical behaviour of soils

MacRobert, Charles John January 2017 (has links)
A thesis submitted to the Faculty of Engineering and Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy, 2017 / The effect of internal erosion on the mechanical behaviour of soils was investigated experimentally, using sodium chloride grains as an analogue for erodible soil grains. With this technique, the loss of controlled quantities of finer particles could be simulated under more realistic hydro-mechanical conditions than in previous research, but within practical experimental time scales. Two experimental programs were undertaken. The first looked at general changes in volume and shear strength using a large diameter oedometer adapted to perform a punch test following salt dissolution. The second program investigated particular changes in volume and shear strength following salt dissolution using an adapted direct shear box Previous studies have shown shear strength reductions following the loss of finer particles representing as little as 5 % of the total mass of the original soil. Findings here show shear strength can be largely unaffected if the erodible finer fraction (F) makes up less than a transition value (Ft) of approximately 10 – 15 % by mass of the original soil. This threshold represents F above which the coarser fabric is looser than at its minimum void ratio. As F increases further, finer particles increasingly hinder the coarser particles from achieving their densest packing, such that the coarser fabric remaining after finer particle loss is in a looser state than the original fabric, the remaining fabric reaching its maximum void ratio at a critical finer fraction (Fc) of approximately 25 – 35 %. For F < Fc, finer particle loss results in limited collapse of the coarser fabric and it was found that the state of this initial coarser fabric determines the shear behaviour of the soil following the loss of finer particles. The shear behaviour of initially dense specimens with F < Ft remained similar to that of a dense soil following finer particle loss, whereas shear behaviour of initially dense specimens with Ft < F < Fc approached that of a loose soil as F increased. Soils with higher internal filter ratios (D15c/D85f) were found to have higher values of Ft and Fc. Soils with F > Fc, settled and weakened significantly following finer particle loss, reflecting the load-bearing role finer particles play in this case. This load bearing nature of the finer particles in soils with F > Fc decreases the risk of internal erosion. / CK2018
585

Roles of Maximal Strength and Rate of Force Development in Maximizing Muscular Power

Taber, Christopher, Bellon, Christopher, Abbott, Heather, Bingham, Garett E. 01 February 2016 (has links)
This brief review encompasses the role of maximal strength and rate of force development in the production of muscular power. It begins with the investigation of power output and its importance for sport. After this basis for power production, this review examines both maximal strength and rate of force development effects on the development of optimal power output. Finally, a rational why maximizing rate of force development during the competition season to achieve success in sport is provided.
586

A 10-Week Stretching Program Increases Strength in the Contralateral Muscle

Nelson, Arnold G., Kokkonen, Joke, Winchester, Jason B., Kalani, Walter, Peterson, Karen, Kenly, Michael S., Arnall, David A. 01 March 2012 (has links)
It was questioned whether a unilateral stretching program would induce a crosstraining effect in the contralateral muscle. To test this, 13 untrained individuals participated in a 10-week stretching program while 12 other untrained individuals served as a control group. For the experimental group, the right calf muscle was stretched 4 times for 30 seconds, with a 30-second rest between stretches, 3 d·wk -1 for 10 weeks. Strength determined via 1 repetition maximum (1RM) unilateral standing toe raise, and range of motion (ROM) were measured pre-post. In the treatment group, the stretched calf muscle had a significant (p < 0.05) 8% increase in ROM, whereas the nonstretched calf muscle had a significant 1% decrease in ROM. The 1 RM of the stretched calf muscle significantly increased 29%, whereas the 1RM of the nonstretched calf muscle significantly increased 11%. In the control group, neither 1RM nor ROM changed for either leg. The results indicate that 10 weeks of stretching only the right calf will significantly increase the strength of both calves. Hence, chronic stretching can also induce a crosstraining effect for strength but not for the ROM. This study also validates earlier findings suggesting that stretching can elicit strength gains in untrained individuals.
587

A Comparison of the Effects of 6 Weeks of Traditional Resistance Training, Plyometric Training, and Complex Training on Measures of Strength and Anthropometrics

MacDonald, Christopher J., Lamont, Hugh S., Garner, John C. 01 February 2012 (has links)
Complex training (CT; alternating between heavy and lighter load resistance exercises with similar movement patterns within an exercise session) is a form of training that may potentially bring about a state of postactivation potentiation, resulting in increased dynamic power (P max) and rate of force development during the lighter load exercise. Such a method may be more effective than either modality, independently for developing strength. The purpose of this research was to compare the effects of resistance training (RT), plyometric training (PT), and CT on lower body strength and anthropometrics. Thirty recreationally trained college-aged men were trained using 1 of 3 methods: resistance, plyometric, or complex twice weekly for 6 weeks. The participants were tested pre, mid, and post to assess back squat strength, Romanian dead lift (RDL) strength, standing calf raise (SCR) strength, quadriceps girth, triceps surae girth, body mass, and body fat percentage. Diet was not controlled during this study. Statistical measures revealed a significant increase for squat strength (p = 0.000), RDL strength (p = 0.000), and SCR strength (p = 0.000) for all groups pre to post, with no differences between groups. There was also a main effect for time for girth measures of the quadricepsmuscle group (p = 0.001), the triceps surae muscle group (p = 0.001), and body mass (p = 0.001; post hoc revealed no significant difference). There were main effects for time and group × time interactions for fat-free mass % (RT: p = 0.031; PT: p = 0.000). The results suggest that CT mirrors benefits seen with traditional RT or PT. Moreover, CT revealed no decrement in strength and anthropometric values and appears to be a viable training modality.
588

Endurance and Resistance Training Lowers C-Reactive Protein in Young, Healthy Females

Daray, Laura A., Henagan, Tara M., Zanovec, Michael, Earnest, Conrad P., Johnson, Lisa G., Winchester, Jason, Tuuri, Georgianna, Stewart, Laura K. 01 October 2011 (has links)
The purpose of this study was to determine whether endurance (E) or endurance + resistance (ER) training affects C-reactive protein (CRP) and if these changes are related to alterations in fitness and (or) body composition in young females. Thirty-eight females (aged 18-24 years) were assigned to 1 of 3 groups: (1) E, (2) ER or (3) active control (AC). The E and ER groups completed 15 weeks of marathon training. The ER group performed additional resistance training and the AC group maintained their usual exercise routine. Primary outcomes were measured pre- and post-training and included anthropometric indices, dual-energy x-ray absorption metry, plasma CRP, time to complete 1.5 miles (in minutes), and upper and lower body strength tests (i.e., 8 repetition max on bench and leg press (ER group only)). There were no differences in any variable among the groups at baseline. After training, the E group decreased time to complete 1.5 miles (p < 0.05). The AC group decreased percent and absolute body fat while the E group decreased percent body fat, absolute body fat, and android and gynoid body fat (p < 0.05). The ER group significantly improved strength (p < 0.001) and reduced plasma CRP from 2.0 ± 1.1 to 0.8 ± 0.3 mg ·L -1 (p = 0.03). No significant associations were observed between CRP and measures of body composition or aerobic capacity. Combined endurance and resistance training may be an effective modality for reducing plasma CRP in young adult females independent of changes in aerobic capacity or body composition.
589

Intergenerational Transmission of Family Strengths

Bee, John R. 01 May 1991 (has links)
The purpose of this research was to study several dimensions of family strengths in family systems and to determine to what degree these strengths are passed from one generation to the next . The sample consisted of 23 couples, constituting the married child generation, and each husband's father and each wife's mother, constituting the parent generation, for a total of 23 family systems and a total~ of 92 . Each person involved in the study had to be in their first marriage and have at least one child. A significant (alpha . 05) difference was found between the father and son generations on the relative and friend support and the professional support . The alpha levels for differences between mothers and daughters on these two dimensions were .146 (relative and friend support) and . 190 (professional support) . A factorial analysis of variance suggests these differences are between generations rather than between genders of family groups. Significant correlations were found between the fathers' family togetherness score and the sons' family flexibility score and between the fathers' quality of life and the sons' family confidence and family coping and coherence scores, at (r=.4876, p=.018), and (r=.4582, p=.028), respectively, and between the fathers' family discord and the sons' family discord scores at (r=.4381, p=037). Corresponding correlation values for the mothers and daughters were (r=.0367, p=.868); (r=-.2049, p=.348); (r=-.0234, p=916); and (r=.0011, p =.996). A significant correlation was found between mothers and daughters on the mothers' relative and friend support score and the daughters' family confidence score at (r=.4215, p=.045), while the corresponding coefficient for fathers and sons was (r=-.3911, p=.065). Significant correlations were found more often than were significant differences . The results also indicate that the males are more volatile than the females in terms of significant findings on the family strength measures.
590

Efficient Coupling of Micro/Macroscale Analyses with Stochastic Variations of Constituent Properties

McWilliams, James Keith 17 May 2014 (has links)
Full-domain multiscale analyses of unidirectional AS4/H3502 open-hole composite tensile specimens were performed to assess the effect of microscale progressive fiber failures in regions with large stress/strain gradients on macroscale composite strengths. The effect of model discretization at the microscale and macroscale on the calculated composite strengths and analysis times was investigated. Multiple sets of microscale analyses of repeating unit cells, each containing varying numbers of fibers with a distinct statistical distribution of fiber strengths and fiber volume fractions, were used to establish the microscale discretization for use in multiscale calculations. In order to improve computational times, multiscale analyses were performed over a reduced domain of the open-hole specimen. The calculated strengths obtained using reduced domain analyses were comparable to those for full-domain analyses, but at a fraction of the computational cost. Such reduced domain analyses likely are an integral part of efficient adaptive multiscale analyses of large all-composite air vehicles.

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