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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.
711

Strength grading and selected strength properties of European hardwoods

Schlotzhauer, Philipp 13 September 2018 (has links)
No description available.
712

Vybrané kondiční aspekty profesionálních hasičů soutěžících v požárním sportu a TFA / Selected fitness aspects of professional firefighters competing in fire sport and TFA

Miřátský, Petr January 2018 (has links)
Title: Selected fitness aspects of professional firefighters competing in fire sport and TFA Objectives: The aim of the thesis was to find out the level and the difference in the parameters of body constitution, postural stability and muscular and explosive force of lower limbs with groups of professional firemen competing in fire sport and TFA Methods: The research sample was represented by two groups of professional firemen (17 fire sportsmen and 17 TFA competitors). We assessed chosen parameters of body constitution (Tanita MC-980MA), postural stability (RS Footscan), explosive force (Kistler) and muscular force (Cybex Humac Norm). Assessed parameters of body constitution were percentage of body fat and fatless matter. In the tests of postural stability we assessed total travel way of the centre of pressure (TTW), narrow stand (open and closed eyes) and one-leg stand (right, left). When testing explosive force, overall produced maximal force and height of the leap were assessed. Muscular force was assessed with the help of muscular force moment in concentric muscle activity with angular velocity 60ř·s-1. Results: We found out a significant difference between the two groups in the tests of postural stability - narrow stand with open and closed eyes (F1,32 = 9,94, p<0,01), in the tests of...
713

Investigation on static strength of welded joints

Akbarnejad, Shahin January 2012 (has links)
Although high strength steels represent yield strength up to 1300 MPa, welded structures reveal lowerstrength values. The strongest commercially available electrode provides the yield strength of about900 MPa. Therefore, in welded steels with strength above this type of filler metal, achieving anacceptable global strength is a crucial issue. In this master thesis, affects of different welding procedures on static strength of welded jointsof Weldox 960 and Weldox 1100 steels, were studied. These steels are produced by SSAB inOxelösund. Meanwhile, finite element method analyses were applied in order to investigatethe static strength behavior of such weldments under uniaxial tension. The welding parameters which were selected as variables are:  Heat input Weld joint geometry Filler metal When weld metal is undermatching in strength levels than the base material, by applyingtension the soft weld metal begins to deform before parent metal. At that point thedeformation of resulted soft zone, including the weld metal and the heat affected zone, ishindered by high strength parent metal. Thus, uniaxial stress caused by uniaxial load isconverted to multiaxial stress. This conversion in tension results in increase in the staticstrength of weldment. The increase in strength is emphasized by increase in the width of thewelded joint while the thickness of the plate is kept as constant. After experiments and performing FEM studies, it was revealed that the static strength ofWeldox 960 welded joints approaches towards the tensile strength of parent metal by increasein the width of the weldment. In Weldox 1100 joints; a slight increase in tensile properties ofthe weldments, when the width of the sample increases, was observed.
714

Feasibility of Using a Non-Counter Movement Squat to Assess Lower Body Strength in Adults Ages 20-70 years.

January 2019 (has links)
abstract: The purpose of this study was to investigate the Feasibility of Using a Non-Counter Movement Squat to Assess Lower Body Strength in Adults ages 20-70 years. Feasibility was tested by measuring five feasibility metrics described by Bowen et al. (Bowen et al., 2009): Acceptability, Demand, Implementation, Practicality, and Limited Efficacy. Seven male subjects and fifteen female subjects participated in the study. The subjects had their height, weight, body fat percentage by bioelectrical impedance analysis (BIA), and grip strength measured. Subjects performed a warm-up on a cycle ergometer, a Non-Counter Movement Squat Test (NCMST) 1-repetition maximal strength test using a Smith machine, and a cool down on a treadmill. Each subject then completed a post-participation questionnaire used to measure acceptability, Demand was measured by subjects who agreed to participate, implementation was measured by subjects who completed the protocol, practicality was measured by an administrator survey, and limited efficacy was measured by distribution of strength results by age and for all subjects by sex. Results showed acceptance of hypotheses of acceptability, demand, implementation and practicality for both males and females. Limited efficacy was inconclusive for both males and females resulting in rejection of hypothesis. The findings of this study show that further research is needed to compare the NCMST to other lower body muscular strength tests to determine the validity of the NCMST. / Dissertation/Thesis / Masters Thesis Healthcare Innovation 2019
715

Received Signal Strength-Based Localization of Non-Collaborative Emitters in the Presence of Correlated Shadowing

Taylor, Ryan Charles 23 May 2013 (has links)
RSS-based localization is a promising solution for estimating the position of a non-collaborative emitter using a network of collaborative sensors. This paper examines RSS-based localization and differential RSS (DRSS) localization in the presence of correlated shadowing with no knowledge of the emitter's reference power.  A new non-linear least squares (NLS) DRSS location estimator that uses correlated shadowing information to improve performance is introduced. The existing maximum likelihood (ML) estimator and Cram\' er Rao lower bound (CRLB) for RSS-based localization given do not account for correlated shadowing. This paper presents a new ML estimator and CRLB for RSS-based localization that account for spatially correlated shadowing and imperfect knowledge of the emitter's reference power. The performance of the ML estimator is compared to the CRLB under different simulation conditions. The ML estimator is shown to be biased when the number of sensors is small or the shadowing variance is large. The effects of correlated shadowing on an RSS-based location estimator are thoroughly examined. It is proven that an increase in correlated shadowing will improve the accuracy of an RSS-based location estimator. It is also demonstrated that the ideal sensor geometry which minimizes the average error becomes more compact as correlation is increased. A geometric dilution of precision (GDOP) formulation is derived that provides a metric for the effect of the position of the sensors and emitter on the location estimator performance. A measurement campaign is conducted that characterizes the path loss at 3.4 GHz. The measurements are compared to the log-distance model. The errors between the model and the measurements, which should theoretically be Gaussian, have a Kurtosis value of 1.31. The errors were determined to be spatially correlated with an average correlation coefficient of 0.5 at a distance of 160 meters. The performance of the location estimators in simulation is compared to the performance using measurements from the measurement campaign. The performance is very similar, with the largest difference between the simulated and actual results in the ML estimator. In both cases, the new NLS DRSS estimator outperformed the other estimators and achieved the CRLB. / Master of Science
716

Identifikace, objektivizace a determinace kritérií výkonnostního hlediska u elitních hráčů fotbalu / Identification, objectification and determination of performance and health-prevention criteria in elite soccer players

Kunzmann, Egon January 2021 (has links)
Identification, objectification, and determination of performance criteria for elite soccer players. Aim: Identification of key point indicators (KPI) of young soccer players with a focus on objectifying and determining the possibility of achieving the highest level of performance. Methods: The study included 157 soccer players, who were then divided into five age groups (U21, U19, U18, U17 and U16) and three performance groups (Elite - 1st league players, Sub-elite - 2nd league players, Amateur - 3rd league and lower performance levels players). Within laboratory diagnostics, the following areas were evaluated: body composition (bioimpedance method), postural stability (using pressure plates), explosive power of the lower limbs (three types of vertical jumps), strength and power of knee extensors and flexors (using isokinetic dynamometry) and the value of the maximum aerobic capacity VO2max (using the pulmonary ventilation exercise test). Within the field diagnostics, the areas of acceleration time (sprint at 5 and 10 m), maximum speed (sprint at 20 m flight), time in the test of change of direction (Agility 505 test and K-test) and values of endurance ability (Yo- Yo intermittent recovery test level 1 and 2). The diagnosed data were then processed in the statistical program RStudio® (USA) using...
717

Investigation of the Effect of Nano SiO<sub>2</sub> on Porosity

Alrumaih, Mohammed Aulwai 30 May 2019 (has links)
No description available.
718

The application of modified linear elastic fracture mechanics (LEFM) and its implication for tear strength development of fibrous materials

Zhang, Ziyang 06 November 2020 (has links)
No description available.
719

Effects of Short‐Term Free‐Weight and Semi‐block Periodization Resistance Training on Metabolic Syndrome

South, Mark A., Layne, Andrew S., Triplett, N. Travis, Sands, William A., Mizuguchi, Satoshi, Hornsby, W. Guy, Kavanaugh, Ashley, Stone, Michael H. 01 October 2016 (has links)
The effects of short-term resistance training on performance and health variables associated with prolonged sedentary lifestyle and metabolic syndrome (MS) were investigated. Resistance training may alter a number of health-related, physiological, and performance variables. As a result, resistance training can be used as a valuable tool in ameliorating the effects of a sedentary lifestyle including those associated with MS. Nineteen previously sedentary subjects (10 with MS and 9 with nonmetabolic syndrome [NMS]) underwent 8 weeks of supervised resistance training. Maximum strength was measured using an isometric midthigh pull and resulting force-time curve. Vertical jump height (JH) and power were measured using a force plate. The muscle cross-sectional area (CSA) and type were examined using muscle biopsy and standard analysis techniques. Aerobic power was measured on a cycle ergometer using a ParvoMedics 2400 Metabolic system. Endurance was measured as time to exhaustion on a cycle ergometer. After training, maximum isometric strength, JH, jump power, and V_ O2peak increased by approximately 10% (or more) in both the metabolic and NMS groups (both male and female subjects). Over 8 weeks of training, body mass did not change statistically, but percent body fat decreased in subjects with the MS and in women, and lean body mass increased in all groups (p # 0.05). Few alterations were noted in the fiber type. Men had larger CSAs compared those of with women, and there was a fiber-specific trend toward hypertrophy over time. In summary, 8 weeks of semiblock free-weight resistance training improved several performance variables and some cardiovascular factors associated with MS
720

The Use of Nanonindentation to Determine Composite Interfacial Shear Strength and the Effects of Environmental Aging

Haeberle, David Claibourne 25 June 2001 (has links)
Fiber sizings are used to improve the performance of fiber-reinforced polymer composites made from low-cost fiber and matrix materials. Evaluation of three sizings, poly(vinylpyrrolidone) (PVP), a carboxyl modified polyhydroxyether (PHE), and a standard industrial sizing (G'), have revealed tremendous improvements in static mechanical and enviro-mechanical properties. The focus of this work is to determine if these improvements in performance can be ascertained from a micromechanical test for interfacial shear strength (IFSS) on as-processed materials. The accomplishment of this goal would create more information with fewer experiments and a need for less experimental materials. In this study, a nanoindenter uniquely outfitted with a blunt tip is effectively used to obtain microindentation results where the debond load is extracted directly from the experimental load-deflection curve. Shear lag and finite element analyses are used to evaluate the mechanics of the system, but both methods show limitations with regard to determining interfacial stresses in an experimental system. In the results obtained, the PHE and Gâ materials outperform the PVP in IFSS, but the bulk properties for PVP and PHE outperform the Gâ material, suggesting the presence of another dominant mechanism. Despite better retention of bulk properties after hygrothermal exposure, PHE experiences degradation in IFSS that PVP does not. The PHE loses 10% of its original IFSS after 576 hours of 65ºC moisture exposure, while PVP improves by 25%. The tensile strengths for PHE and PVP decrease 7% and 10% respectively at 576 hours exposure. Finite element modeling shows that matrix swelling due to moisture absorption increases interfacial shear stresses, a finding supported by a comparison of wet and dry specimens subjected to equivalent aging times. Matrix swelling is not, however, responsible for the increase in IFSS of the PVP material. The relationship between tensile strength and IFSS proves to be small as predicted by a tensile strength model, but processing defects and other failure processes that are not included in the tensile strength model appear to have strong influences over the experimental results. IFSS is important in composite materials, but in the case of the G', PHE and PVP materials, other factors dominate fiber direction tensile performance. Therefore, this one simple micromechanical test provides significant insight into the composite material behavior, but it does not provide the same magnitude of information as from bulk composite experiments. / Master of Science

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