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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.
11

Rozdíl mobility zápěstí u hráčů závodního a rekreačního tenisu / Difference wrist mobility with players racing and recreational tennis

Mertlík, Jakub January 2013 (has links)
Title: Difference wrist mobility with players racing and recreational tennis Objective: The aim of this work is to measure and compare the range of motion of the wrist in racing and recreational tennis players and both upper limbs (playing, not playing). To compare the values measured 2D electrogoniometry, by sex and game levels. Method: Research probands were divided into two groups, a total of 20 people. In one group, there were ten boys and ten girls aged 14-17 years who play tennis at competitive level and train four to five times a week for at least 4 years. The second group also consisted of 10 boys and 10 girls in the same age range, but tennis is played on a recreational level once maximum twice a week for at least 4 years. It was important that the criteria for selecting probands had several common denominators. These are gender, age, level of game, whether measured by an individual not had any injury, regeneration is not and should not do other activities besides tennis. Wrist probands were tested using an electric goniometer. Were measured in the frontal plane (radial and ulnar reduction) and sagittal plane (dorsal and palmar flexion). These data were measured by sitting electrogoniometry and subsequently were compared and statistically analyzed. Results: Measurements confirmed...
12

Crescimento e caracterização de heteroestruturas tensionadas de InxGa1-x-As/GaAs / Growth and characterization of stressed heterostructures of InxGa1-x-As/GaAs

Ceschin, Artemis Marti 17 December 1992 (has links)
Utilizando a técnica de epitaxia por feixe molecular (MBE), crescemos heteroestruturas tensionadas de InxGa1-xAs sobre substratos de GaAs (100). A composição de In, a espessura para a transição 2D-3D e a espessura crítica (hc) foram determinadas através da análise \"in situ\" pelo RHEED. Os valores da hc e da espessura para a transição 2D- 3D foram observadas ser funções da composição do In e da temperatura do substrato. Um estudo do efeito da desorientação do substrato de GaAs (100) de alguns graus sobre as qualidades ópticas (PL) de poços quânticos simples e múltiplos de InxGa1-xAs/GaAs também foi realizado. Microscopia eletrônica por transmissão (TEM) foi utilizada para a verificação da qualidade das interfaces dos poços quânticos de InxGa1-x/GaAs. Algumas estruturas de dupla barreira (AlGaAs/GaAs/InAs/GaAs/AlGaAs) foram crescidas e caracterizadas opticamente (PL) / InxGa1-xAs strained heterostructures were grown on GaAs (100) by Molecular Beam Epitaxy (MBE). Indium concentration (x), 2D-3D growth mode transition thickness and critical thickness (hc) were determined by \"in situ\" RHEED analysis. Hc and 2D-3D growth mode transition thickness values were verified to depend on In concentration and substrate temperature. The dependence of the InxGa1-xAs /GaAs simple and multiple quantum wells (SQW and MQW) PL optical quality on the GaAs (100) substrate misorientation was also studied. The SQW interfaces were investigated by Transmission Eletronic Microscopy (TEM). Some double-barrier structures (AlGaAs/GaAs/InAs/GaAs/AlGaAs was also grown and optically characterized
13

Acoustic Emission Sensing for Crack Monitoring in Prefabricated and Prestressed Reinforced Concrete Bridge Girders

Worley, Robert Lee, II 01 January 2019 (has links)
Prefabricated and pre-stressed reinforced concrete beams and girders are integral components of many highway structures, including those built by rapid construction techniques. Concerns exist regarding the development of cracks during curing, form removal, detensioning, transport, installation, and operation. Non-destructive, Acoustic Emission (AE) sensing techniques have the potential for detecting and locating cracking in prefabricated, pre-stressed concrete girders used as Prefabricated Bridge Elements and Systems (PBES) used in rapid construction practices as part of a Quality Assurance/Quality Control (QA/QC) program. AE sensing records transient elastic waves produced by the release of stored elastic energy resulting in plastic deformations (i.e., crack nucleation and growth) with an array of point sensors. The AE instrument system is relatively portable which can allow for it to be an option for both off-site fabrication QA/QC as well as on-site field QA/QC. This thesis presents a multi-stage research initiative on acoustic emission monitoring of prefabricated and pre-stressed reinforced concrete beams used in highway bridge construction during detensioning, craned removal from formwork and transport to bridge sites, along with supporting laboratory tests and numerical analysis. The specific objectives of this research were to: 1. Identify suitable instruments to monitor pre-stressed and/or post-tensioned concrete girders for cracking activity; 2. Design and develop a reusable instrumentation package; 3. Measure performance and condition of concrete girders during fabrication and transport; and 4. Identify test protocols and possible accept/fix/reject criteria for structural elements based on information from monitoring system. Presented are results from laboratory, full-scale girder fabrication, and transport monitoring, along with overall conclusions and recommendations for future research.
14

Dielectric characteristics of HTS cables based on partial discharge measurement

Hayakawa, N., Nagino, M., Kojima, H., Goto, M., Takahashi, T., Yasuda, K., Okubo, H. 06 1900 (has links)
No description available.
15

Determination of Longitudinal Stress in Rails

Djayaputra, Ferdinand 2010 December 1900 (has links)
The objective of this research is to determine the longitudinal stress in rails by using the polarization of Rayleigh waves. Analytical models are developed to describe the effect of applied stress on wave speed and on the polarization of Rayleigh waves. A numerical simulation is performed to find the effect of applied stress on wave velocity and Rayleigh wave polarization. The effect of uncertainties in material properties on wave velocity and polarization of Rayleigh wave is also examined in the simulation. The experiment uses a laser Doppler vibrometer (LDV) to measure the particle velocities. The in-plane and out-of-plane velocity components are obtained from the measured particle velocities. The polarization of Rayleigh wave, which is defined as the ratio between the in-plane and out-of-plane displacements, is calculated. Furthermore, the polarization of the Rayleigh wave is considered as a measure to identify applied stress. The experiment is performed on unstressed and stressed rail specimen. Thus, Rayleigh wave polarization is obtained as a function of applied stress. The experimental results are compared with the analytical model. The result shows a good agreement with the theoretical values for unstressed rail.
16

Formation of Silica Microstructures between Inundated Stressed Silica Grains: Effect on Intergranular Tensile Strength

Guo, Rui January 2014 (has links)
<p>Laboratory tests on microscale are reported in which amorphous silica grains were compressed in a liquid environment, namely in solutions with different silica ion concentrations for up to four weeks. Such an arrangement represents an idealized representation of two sand grains. The grain surfaces and asperities were examined in Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for fractures, silica polymer growth, and polymer strength. Single chains of silica polymers are found to have a failure pulling force of 330 - 450 nN. </p><p>A chain of observations are reported for the first time, using Pneumatic Grain Indenter and Grain Indenter-Puller apparatuses, confirming a long-existing hypothesis that a stressed contact with microcracks generates dissolved silica in the contact (asperity) vicinity, which eventually polymerizes, forming a structure between the grains on a timescale in the order of weeks. Such structure exhibits intergranular tensile force of 1 - 1.5 mN when aged in solutions containing silica ion concentrations of 200- to 500 ppm. Stress appears to accelerate the generation of silica polymers around stressed contact regions, so does mica-silica contacts. The magnitude of intergranular tensile force is 2 to 3 times greater than that of water capillary effect between grains.</p> / Dissertation
17

Crescimento e caracterização de heteroestruturas tensionadas de InxGa1-x-As/GaAs / Growth and characterization of stressed heterostructures of InxGa1-x-As/GaAs

Artemis Marti Ceschin 17 December 1992 (has links)
Utilizando a técnica de epitaxia por feixe molecular (MBE), crescemos heteroestruturas tensionadas de InxGa1-xAs sobre substratos de GaAs (100). A composição de In, a espessura para a transição 2D-3D e a espessura crítica (hc) foram determinadas através da análise \"in situ\" pelo RHEED. Os valores da hc e da espessura para a transição 2D- 3D foram observadas ser funções da composição do In e da temperatura do substrato. Um estudo do efeito da desorientação do substrato de GaAs (100) de alguns graus sobre as qualidades ópticas (PL) de poços quânticos simples e múltiplos de InxGa1-xAs/GaAs também foi realizado. Microscopia eletrônica por transmissão (TEM) foi utilizada para a verificação da qualidade das interfaces dos poços quânticos de InxGa1-x/GaAs. Algumas estruturas de dupla barreira (AlGaAs/GaAs/InAs/GaAs/AlGaAs) foram crescidas e caracterizadas opticamente (PL) / InxGa1-xAs strained heterostructures were grown on GaAs (100) by Molecular Beam Epitaxy (MBE). Indium concentration (x), 2D-3D growth mode transition thickness and critical thickness (hc) were determined by \"in situ\" RHEED analysis. Hc and 2D-3D growth mode transition thickness values were verified to depend on In concentration and substrate temperature. The dependence of the InxGa1-xAs /GaAs simple and multiple quantum wells (SQW and MQW) PL optical quality on the GaAs (100) substrate misorientation was also studied. The SQW interfaces were investigated by Transmission Eletronic Microscopy (TEM). Some double-barrier structures (AlGaAs/GaAs/InAs/GaAs/AlGaAs was also grown and optically characterized
18

Energy harvesting from walking using piezoelectric cymbal and diaphragm type structures

Palosaari, J. (Jaakko) 01 December 2017 (has links)
Abstract Many electrical devices already surround us in our everyday life. Some devices monitor car performance and traffic while others exist in handheld devices used by the general public. Electrical devices also control manufacturing processes and protect workers from exposure to hazardous working environment. All these devices require electricity to operate. This exponential growth of low power electronic devices in industry, healthcare, military, transportation and in portable personal devices has led to an urgent need for system integrated energy sources. Many energy harvesting technologies have been developed to serve as a power source in close proximity to the electrical device itself. Solar and magnetic energy harvesters are the most common solutions when conditions are suitable. A more recent technique, called piezoelectric energy harvesting, has raised significant interest among scientists and in industry. Through piezoelectric (ceramic) material mechanical energy can be harvested and converted to electrical energy. This method requires accurate analysis of the kinetic energy experienced by the piezoelectric material so that the mechanics can be suitably designed. At the same time the mechanical design has to protect the piezoelectric material from intense forces that might cause cracks, while still transmitting the kinetic energy efficiently. These requirements usually mean a specific energy harvest design for each ambient energy source at hand. This thesis is focused on energy harvesting from low frequency compressions using piezoelectric ceramic materials. The objective was to manufacture, measure and implement structures that could sustain the forces experienced under the heel of a foot and maximize the harvested energy amount and efficiency. Two different construction designs were developed and optimised with an iterative process. The kinetic energy impulse under the heel part of the foot was studied by measuring the electrical output of the harvester during walking and then analysed with modelling software. The results were used to create a walking profile for a computer controlled piston to study the input energy phase, speed and force influence on the amount of the harvested energy and the efficiency of the harvesting process. Finally, the functionality of the concept was tested in a real environment with an energy harvester inserted inside a running shoe. The developed harvester showed the highest energy density reported in this frequency region. / Tiivistelmä Monet elektroniset laitteet ympäröivät meitä jokapäiväisessä elämässä. Ne tarkkailevat auton toimintaa tai liikennettä ja toiset toimivat aina mukana kulkevissa kannettavissa laitteissa. Töissä ne valvovat valmistusprosesseja tai varoittavat työntekijöitä vaarallisista työolosuhteista. Kaikki nämä laitteet tarvitsevat sähköä toimiakseen. Pienitehoisten elektronisten laitteiden eksponentiaalinen kasvu teollisuudessa, terveyssektorilla, puolustusteollisuudessa, kulkuneuvoissa sekä kannettavassa kulutuselektroniikassa on johtanut suureen tarpeeseen kehittää järjestelmiin integroituja energialähteitä. Monia energiankeräystekniikoita on kehitetty toimimaan elektronisten laitteiden läheisyydessä. Aurinkopaneelit ja magneettiset energiankeräysmenetelmät ovat yleisimpiä ratkaisuja, jos olosuhteet antavat siihen mahdollisuuden. Pietsosähköinen energiankeräys on uudempi tekniikka, joka on herättänyt kasvavaa huomiota tutkimusyhteisössä sekä teollisuudessa. Pietsosähköisen materiaalin avulla mekaaninen energia voidaan muuntaa suoraan sähköiseksi energiaksi. Tässä tekniikassa kineettinen energia tulee analysoida tarkasti mekaniikka suunnittelua varten, jotta se saadaan kohdistettua tehokkaasti pietsosähköiseen materiaaliin. Lisäksi mekaniikan tulee suojata materiaalia voimilta, jotka voivat johtaa murtumiin. Näistä vaatimuksista johtuen jokainen ulkoinen energialähde vaatii yleensä yksilöllisen energiankeräysrakenteen. Tämä väitöstyö keskittyy pietsosähköisten keraamien hyödyntämiseen energiankeräyksessä matalataajuisista mekaanisista voimista. Tarkoituksena oli suunnitella, valmistaa, mitata ja asentaa rakenteita, jotka kestävät kantapäähän kohdistuvia voimia kävelyn ja juoksun aikana sekä maksimoida talteen saatava energia ja hyötysuhde. Kaksi erilaista rakennetta suunniteltiin, valmistettiin ja optimoitiin energiankeräystä varten. Kantapäähän kohdistuva kineettinen energia analysoitiin mallinnusohjelmistolla ja mittaamalla sähköinen vaste energiakeräys rakenteesta. Tuloksien avulla suunniteltiin kävelyprofiilia imitoiva mekaaninen männän liike, jonka avulla tutkittiin kohdistettavan voiman nopeuden, vaiheen ja suuruuden vaikutusta energiankeräyksen hyötysuhteeseen ja saatavaan tehoon. Viimeisenä energiankeräysrakenteen toimivuutta testattiin oikeassa ympäristössä asentamalla se juoksukenkään. Kehitetyllä pietsosähköisellä energiakeräimellä saavutettiin korkeimmat raportoidut energiatiheydet käytetyllä taajuusalueella.
19

Analýza dynamických vlastností pneumatického aktuátoru / Analysis of dynamic properties of pneumatic actuator

Hrivňák, Ján January 2013 (has links)
This thesis deas with dynamic analysis of pneumatic actuator which is used as regulation mechanis of turbochargers with Variable Nozzle Turbine (VNT) technology. The first part of work is focused on experimental modeling which goal is obtaining Frequency Response Function on specify frequency range by Frequency Response Function Analysis – FRFA. Dominant vibrations of pneumatic actuator active parts is expected on this specify frequency range. Results of experimental modeling will be used for gaining input parameters for numerical computation as well. The second part deal with Pre-Stressed Modal Analysis and subsequently Harmonic analysis. Obtained results with numerical and experimental analysis will be compared. This part of diploma thesis is solved in programmatic environment ANSYS Workbench.
20

Commonly Prescribed β-lactam Antibiotics Induce C.trachomatis Persistence/Stress in Culture at Physiologically Relevant Concentrations

Kintner, Jennifer, Lajoie, Dawn, Hall, Jennifer, Whittimore, Judy, Schoborg, Robert V. 01 April 2014 (has links)
Chlamydia trachomatis, the most common bacterial sexually transmitted disease agent worldwide, enters a viable, non-dividing and non-infectious state (historically termed persistence and more recently referred to as the chlamydial stress response) when exposed to penicillin G in culture. Notably, penicillin G-exposed chlamydiae can reenter the normal developmental cycle upon drug removal and are resistant to azithromycin-mediated killing. Because penicillin G is less frequently prescribed than other ß-lactams, the clinical relevance of penicillin G-induced chlamydial persistence/stress has been questioned. The goal of this study was to determine whether more commonly used penicillins also induce C. trachomatis serovar E persistence/stress. All penicillins tested, as well as clavulanic acid, induced formation of aberrant, enlarged reticulate bodies (RB) (called aberrant bodies or AB) characteristic of persistent/stressed chlamydiae. Exposure to the penicillins and clavulanic acid also reduced chlamydial infectivity by >95%. None of the drugs tested significantly reduced chlamydial unprocessed 16S rRNA or genomic DNA accumulation, indicating that the organisms were viable, though non-infectious. Finally, recovery assays demonstrated that chlamydiae rendered essentially non-infectious by exposure to ampicillin, amoxicillin, carbenicillin, piperacillin, penicillin V, and clavulanic acid recovered infectivity after antibiotic removal. These data definitively demonstrate that several commonly used penicillins induce C. trachomatis persistence/stress at clinically relevant concentrations.

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