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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

Flexural performance of FRP reinforced concrete beams

Kara, Ilker F., Ashour, Ashraf 04 1900 (has links)
yes / A numerical method for estimating the curvature, deflection and moment capacity of FRP reinforced concrete beams is developed. Force equilibrium and strain compatibility equations for a beam section divided into a number of segments are numerically solved due to the non-linear behaviour of concrete. The deflection is then obtained from the flexural rigidity at mid-span section using the deflection formula for various load cases. A proposed modification to the mid-span flexural rigidity is also introduced to account for the experimentally observed wide cracks over the intermediate support of continuous FRP reinforced concrete beams. Comparisons with experimental results show that the proposed numerical technique can accurately predict moment capacity, curvature and deflection of FRP reinforced concrete beams. The ACI-440.1R-06 equations reasonably predicted the moment capacity of FRP reinforced concrete beams but progressively underestimated the deflection of continuous ones. On the other hand, the proposed modified formula including a correction factor for the beam flexural rigidity reasonably predicted deflections of continuous FRP reinforced concrete beams. It was also shown that a large increase in FRP reinforcement slightly increases the moment capacity of FRP over-reinforced concrete beams but greatly reduces the defection after first cracking.
12

Floor Vibrations: Girder Effective Moment of Inertia and Cost Study

Warmoth, Francis James 14 February 2002 (has links)
Studies on the effective moment of inertia of girders that support concrete slabs using joist seats as the horizontal shear connections, and a cost efficiency analysis comparing composite and non-composite floor systems that meet vibrations design standards, were conducted. The first study was undertaken because over-prediction of girder effective moment of inertia was the suspected cause of several recent vibration problems in floors supported by widely spaced LH-series joists. Eight purpose-built floors of the type in question were subjected to experimental tests of girder effective moment of inertia and girder frequency. Frequencies were tested for two live loading cases. Three separate test configurations were made with each floor by changing the seat-to-girder connections between bolted, welded, and reinforced. In the study, 1) the accuracy of the current design practice is assessed, 2) a new relationship was proposed, and 3) suggestions for finite element modeling are made. In recent years, composite construction has been used to improve cost efficiency by reducing structural weight and in some cases by reducing story height. However, vibration problems are a design consideration in composite floors because lighter floors tend to be more lively. It is not clear if cost savings can be made with composite construction if vibrations are considered in the design. To compare the cost of composite and non-composite floors that satisfy AISC/CISC Design Guide criterion for walking excitation, four typical size bays were analyzed using commercial design software that finds the least expensive member configuration for a given bay size. All acceptable bay configurations of member sizes and spacing were evaluated for least non-composite and composite costs, then these results were compared. The findings show that composite construction can be more economical when initial dead load deflections do not control the design. / Master of Science
13

Design and Analysis of a Shock Absorber with a Variable Moment of Inertia Flywheel for Passive Vehicle Suspension

Xu, Tongyi 05 November 2013 (has links)
Conventional vehicle suspensions consist of a spring and a damper, while mass is rarely used. A mass, if properly used, can also create a damping-like effect. However, a mass has only one terminal which makes it difficult to be incorporated into a suspension. In order to use a mass to achieve the damping-like effect, a two-terminal mass (TTM) has to be designed. However, most of the reported TTMs are of fixed moment of inertia (TTM-CMI), which limits the further improvement of the suspension performance and responsiveness to changes in environment and driving conditions. In this study, a TTM-based vibration absorber with variable moment of inertia (TTM-VMI) is proposed. The main component of the proposed TTM absorber contains a hydraulic-driven flywheel with sliders. The moment of inertia changes with the positions of the sliders in response to the driving conditions. The performance of the proposed TTM-VMI absorber has been analyzed via dynamics modeling and simulation and further examined by experiments. The analysis results indicate that the TTM-VMI absorber outperforms the TTM-CMI design in terms of body displacement; and ride comfort, tire grip and suspension deflection for zero and impulse inputs with comparable performance for sinusoidal input.
14

Utilização do biospeckle laser na avaliação do potencial germinativo de sementes de ipê-roxo (Tabebuia heptaphylla) (Vellozo) Toledo / Application of the laser biospeckle in evaluation ipê-roxo (Tabebuia heptaphylla) (Vellozo) Toledo

Fracarolli, Juliana Aparecida, 1984- 17 August 2018 (has links)
Orientadores: Inacio Maria Dal Fabbro, Leila Martins / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-17T22:21:55Z (GMT). No. of bitstreams: 1 Fracarolli_JulianaAparecida_M.pdf: 1740641 bytes, checksum: 3b58affa12601dc23d779d12bd0a1f66 (MD5) Previous issue date: 2011 / Resumo: O ipê-roxo (Tabebuia heptaphylla (Vellozo) Toledo) é uma espécie de alto valor econômico, ornamental e medicinal, pertencente à família Bignoniaceae, cuja multiplicação ocorre prioritariamente por sementes. Há considerável necessidade de estudos sobre o desempenho fisiológico das unidades de dispersão dessa e de outras espécies florestais. O objetivo desse trabalho foi avaliar a potencialidade do biospeckle, técnica baseada no fenômeno óptico de interferência, como ferramenta de caracterização do potencial germinativo das sementes de ipê-roxo. A quantificação do biospeckle foi expressa através do cálculo do Momento de Inércia (MI). Foram utilizados laser vermelho (632 nm de comprimento de onda) e 10 mW de potência, câmera filmadora digital e computador. Foram realizados cinco experimentos, a saber: (1) Avaliação de danos térmicos em sementes através do biospeckle; (2) Avaliação da interferência do tegumento na sensibilidade do biospeckle; (3) Diferenciação entre sementes germinadas e não germinadas através do biospeckle; (4) Determinação da faixa de umidade das sementes para a melhor interação entre o laser e a semente para o biospeckle; (5) Avaliação de sementes de ipê-roxo submetidas ao envelhecimento acelerado através do biospeckle. Para os experimentos 1, 2, 3 e 4 as sementes foram hidratadas até atingirem grau de umidade de 69%, divididas em quatro sub-amostras sendo que duas delas foram submetidas ao congelamento. Em seguida as sub-amostras foram separadas em 5 níveis de umidade (28, 35, 54, 63, 69%) e iluminadas com laser. Nesses ensaios foram planejados quatro tratamentos: (1) sementes sem tegumento; (2) sementes com tegumento; (3) sementes sem tegumento submetidas a congelamento a 0°C e (4) sementes com tegumento submetidas ao congelamento a 0°C. Os resultados permitem afirmar que é possível diferenciar as sementes que sofreram dano térmico daquelas que não sofreram através do biospeckle. A presença do tegumento interfere na sensibilidade do biospeckle. É possível diferenciar as sementes viáveis das inviáveis através do biospeckle. Do experimento 4 obteve-se uma correlação positiva entre os valores de MI e de umidade das sementes. Verificou-se também que a faixa de teor de água para a melhor interação entre o laser e a semente de ipê-roxo está entre 28 e 54%. Esta faixa de umidade das sementes foi utilizada como referência para o experimento 5. No experimento 5 as sementes foram submetidas ao envelhecimento acelerado (42°C e umidade relativa do ar de 100 % durante 24, 48, 72, 96 e 120 horas) e avaliadas através da técnica do biospeckle e teste de germinação. Obteve-se que é possível detectar a redução de viabilidade e vigor das sementes de T. heptaphylla ocasionada pelo envelhecimento acelerado. Dessa forma, o biospeckle é uma técnica que vem sendo desenvolvida e apresenta-se como uma ferramenta possível para avaliar o potencial germinativo das sementes de ipê-roxo / Abstract: Ipê-roxo (Tabebuia heptaphylla (Vellozo) Toledo) is considered of very important economical, ornamental, as well as medicinal value which is included in the Bignoniaceae botanical family which multiplication is quite solely carried by seeds. Forest dispersion elements, i.e., the seeds, deserve a deep understanding of their physiological performance. The objective of this research work was to evaluate a biospeckle method potential in testing seed viability, which is based on the laser interferometry. The biospeckle phenomenon quantification was carried by means of the Moment of Inertia (MI) which formula resembles its mechanical counterpart. The equipment employed in the experimental setup included a 632 nm red diode laser of 10mW, a digital movie camera as well as a PC. The five tests carried were (1) thermal damage evaluation on seeds, (2) biospeckle sensitivity to the tegument interference, (3) differentiation between non germinated and germinated seeds evaluation by the biospeckle, (4) determination of the best seed moisture content to laser interaction and (5) evaluation of accelerated aging ipê-roxo seeds through the biospeckle. In tests 1, 2, 3 and 4 seeds were hydrated to the value of 69% and divided into four sub samples from which two of them were forwarded to freezing. Following the four sub samples were separated into five moisture level groups (28, 35, 54, 63, 69%) and exposed to the laser. Four treatments have been imposed to the experimental tests, named (1) seeds without teguments, (2) seeds with tegument, (3) frozen at 0° C seeds without teguments and (4) frozen at 0° C seeds with teguments. Results from biospeckle tests confirm the possibility of differentiating seeds with thermal damage from those without thermal damage. When the tegument is covering the seed, the sensitivity of biospeckle is affected.?It's possible to differentiate viable seeds from non viable seeds using biospeckle technique. From test (4) it is obtained a positive correlation between MI and seeds moisture content. It was also verified that seed moisture content between 28% and 54% showed better interaction with laser. That moisture content range was adopted for the test (5). Seeds were submitted to accelerated aging process in the test (5) (42°C and 100% of relative humidity for 24, 48, 72, 96 and 120 hours) following by biospeckle evaluation and germination tests. It was concluded that viability reduction of T. heptaphylla as generated by accelerated aging can be detected by the biospeckle test. Thus, the biospeckle is a technique that has been developed and is presented as a possible tool to assess the germination potential of ipê-roxo seeds / Mestrado / Maquinas Agricolas / Mestre em Engenharia Agrícola
15

Design and Analysis of a Shock Absorber with a Variable Moment of Inertia Flywheel for Passive Vehicle Suspension

Xu, Tongyi January 2013 (has links)
Conventional vehicle suspensions consist of a spring and a damper, while mass is rarely used. A mass, if properly used, can also create a damping-like effect. However, a mass has only one terminal which makes it difficult to be incorporated into a suspension. In order to use a mass to achieve the damping-like effect, a two-terminal mass (TTM) has to be designed. However, most of the reported TTMs are of fixed moment of inertia (TTM-CMI), which limits the further improvement of the suspension performance and responsiveness to changes in environment and driving conditions. In this study, a TTM-based vibration absorber with variable moment of inertia (TTM-VMI) is proposed. The main component of the proposed TTM absorber contains a hydraulic-driven flywheel with sliders. The moment of inertia changes with the positions of the sliders in response to the driving conditions. The performance of the proposed TTM-VMI absorber has been analyzed via dynamics modeling and simulation and further examined by experiments. The analysis results indicate that the TTM-VMI absorber outperforms the TTM-CMI design in terms of body displacement; and ride comfort, tire grip and suspension deflection for zero and impulse inputs with comparable performance for sinusoidal input.
16

Měření momentů setrvačnosti vozidla / Measurement of vehicle moments of inertia

Grác, David January 2014 (has links)
This diploma thesis is concerned with selecting the appropriate method for determining the moment of inertia to the vertical, lateral and longitudinal axis through the centre of gravity of the vehicle. Using the special mechanical device, constructed on IAE was carried out repeated measurements of known mass properties in each axis. With the aid of obtained data was calculated measurement error. To compare the resulting values was created MBS model.
17

Zařízení pro měření výškové polohy těžiště vozidla / Device for Vehicle CG Height Position Measurement

Toman, Josef January 2014 (has links)
This diploma thesis deals with measurement of vehicle centre of gravity height position. In the first part is created summary of methods used for measuring centre of gravity position and moment of inertia of the vehicle. In the other parts are designed and analyzed two dynamics method of measuring centre of gravity height position. This thesis presents analysis of the errors of the proposed methods, results of measurements and design of the construct adjustments device for measuring of the moments of inertia enabling its used for measuring centre of gravity height position. Some components are through analyse of tension.
18

Bewegungsdesign unter Berücksichtigung des reduzierten Massenträgheitsmoments

Schulze, Sören 22 July 2016 (has links) (PDF)
Das Bewegungsdesign stellt einen wichtigen Aspekt beim Betrieb von ungleichmäßig übersetzenden Mechanismen dar. Durch Minimierung von Bewegungsparametern wie der Geschwindigkeit und Beschleunigung ist die Verringerung von Schwingungsamplituden sowie Bauteildeformationen infolge kinetostatischer Kräfte erzielbar. Weiterhin kann hierdurch der Verlauf des Antriebsmoments des Motors beeinflusst werden. Das reduzierte Massenträgheitsmoment J(φ) eines nichtlinear übersetzenden Mechanismus ist stellungsabhängig definiert durch die generalisierte Koordinate φ. Daher stellt die Minimierung von Beschleunigung und Geschwindigkeit mittels konstanter Grenzen über den gesamten Antriebsbereich eine Vereinfachung dar, welche die stellungsabhängige Trägheit außer Acht lässt. Der Beitrag stellt eine Möglichkeit zur Generierung der Grenzwerte für die Beschleunigung und Geschwindigkeit aus den Verläufen des reduzierten Massenträgheitsmoments J(φ) sowie dessen Ableitung nach der generalisierten Koordinate J‘(φ) vor. Die ermittelten Ober- und Untergrenzen dienen als Parameter für einen Optimierungsalgorithmus. Dieser nutzt den Ansatz der harmonischen Synthese um mit Hilfe der linearen Programmierung die Bewegungsfunktion zu generieren. Für einen Mechanismus mit einem Freiheitsgrad wird mittels eines herkömmlichen Ansatzes und mit dem neu vorgestellten Verfahren das optimale Bewegungsgesetz ermittelt. Mittels einer Mehrkörpersimulation werden neben Geschwindigkeit und Beschleunigung auch das resultierende Antriebsmoment und der Energiebedarf bilanziert.
19

Detections of seven faint g-ray pulsars and constraints on neutron star moments of inertia with the Fermi–LAT / Détection de sept pulsars gamma faibles et contraintes sur le moment d'inertie des étoiles à neutrons avec le Fermi-LAT

Hou, Xian 18 December 2013 (has links)
Le Large Area Telescope (LAT) à bord du satellite Fermi, lancé le 11 Juin 2008, est sensible au rayonnement gamma de20 MeV à plus de 300 GeV. 148 pulsars gamma à ce jour ont été détectés avec le Fermi-LAT, dont 117 sont détaillés dansle Deuxième Catalogue de Pulsars gamma de Fermi (2PC). Les pulsars forment la plus grande classe de sources au GeVdans la Voie Lactée. Les études de pulsars gamma apportent des contraintes importantes sur les modèles d’émission gamma etpermettent des percées dans notre compréhension des pulsars.Cette thèse présente des détections de sept pulsars gamma faibles déjà connus en radio, dont quatre jeunes ou d’âgesmoyens et trois millisecondes (MSP). L’analyse spectrale et la caractérisation des courbes de lumiére sont décriteset comparées à la population de 2PC. Ces détections ont l’intérêt particulier de sonder et d’étendre l’espace desparamètres de la population actuelle. Elles illustrent la distorsion inhérente dans 2PC et marquent la transition de lapremière phase (pulsars brillants) à la seconde phase (pulsars faibles) d’opération de Fermi. Le développement desmodèles théoriques et un recensement complet de la population galactique des étoiles à neutrons bénéficieront de plusde détections de pulsars faibles dans les années à venir.Certains pulsars gamma dans 2PC manifestant de grande efficacité gamma sont étudiés dans cette thèse. L’examen desdifférents paramètres qui influencent l’efficacité conduit à quelques candidats pour lesquels un plus grand momentd’inertie est nécessaire afin de résoudre le paradoxe de grande efficacité. Les observations de Fermi en rayons gamma ontl’air à apporter des contraintes indépendantes sur le moment d’inertie et les équations d’état des étoiles à neutrons. / The Large Area Telescope (LAT) on board the Fermi satellite, launched on June 11 2008, is sensitive to g raysfrom 20 MeV to over 300 GeV. gamma-ray pulsations from 148 pulsars to date have been detected with the Fermi-LAT, 117are detailed in the Second Fermi-LAT Gamma-ray Pulsar Catalog (2PC). Pulsars are by far the largest GeV sourceclassin the Milky Way. Studies of the increasing gamma-ray pulsar sample bring important constraints on theoretical gamma-rayemission models and enable breakthroughs in our understanding of pulsars.This thesis presents detections of seven faint gamma-ray pulsars that are already known at radio wavelengths, includingfour young or middle aged pulsars and three millisecond pulsars (MSPs). Spectral analysis and light curve characterizationsare detailed and compared to the 2PC sample. These detections have the special interest of allowing us toprobe and extend the parameter space of the current population. They illustrate the inherent bias in 2PC and mark thetransition from the early part (bright pulsars) to the later part (faint pulsars) of the Fermi mission. Theoretical modeldevelopments and a complete census of Galactic neutron star populations will benefit from more detections of weakpulsars in the years to come.Some high gamma-ray efficiency pulsars in 2PC are studied in this thesis. Investigations on different parameters whichinfluence the efficiency result in a few candidates for which a large moment of inertia is necessary to cure the highefficiency paradox. Fermi gamma-ray observations seem to bring independent constraints on the moment of inertia andequations of state of neutron stars
20

EFFEKTEN AV VIKTMANIPULERAD UTRUSTNING PÅ DRAGSKOTTSHASTIGHET OCH GREPPSTYRKA I INNEBANDY : EN SEX VECKORS STUDIE PÅ MANLIGA 17-ÅRIGA INNEBANDYSPELARE / The effect on drag shot velocity and grip strength with weight manipulated equipment : A six week study on male 17-year old floorball players

Linke, Mats, Saarela, Tobias January 2011 (has links)
Innebandy är en växande idrott, som framför allt utövas i Sverige, Finland och Schweiz, men där väldigt lite forskning ännu finns publicerad. Tidigare studier inom ishockey och baseboll har visat att träning med viktmanipulerad utrustning förbättrat bland annat greppstyrka och svinghastigheten av slagträ i baseboll. Annan forskning har visat på att det är en förbättring i det neuromuskulära samspelet snarare än ökad muskelmassa som förbättrat prestationen vid dynamisk motståndsträning. Skotthastigheten anses vara en viktig faktor inom innebandy för prestationen och eftersom det inom baseboll har visats att viktmanipulerad utrustning kan förbättra svinghastigheten så vore det intressant att se om samma resultat kan uppnås inom innebandy. Syftet med studien var att undersöka effekten av innebandyträning med en viktmanipulerad innebandyklubba med avseende på dragskottshastighet och greppstyrka hos manliga innebandyspelare samt undersöka korrelationen mellan dragskottshastighet och greppstyrka. Även testpersonernas subjektiva uppfattning av träningen med den viktmanipuleradeutrustningen undersöktes. Testgruppen bestod av 13 stycken 17-åriga manliga innebandyspelare. Under en sex veckors period genomförde testpersonerna 30 minuter av sin vanliga innebandyträning med den viktmanipulerade klubban (40 gram tyngre) tre gånger i veckan. Dragskotten filmades med en höghastighetskamera (Casio Exilim EX-FH25) med 250 fps och analyserades sedan i Dartfish för att mäta hastigheten. För att fastställa greppstyrkan användes en handdynamometer (Jamar – Baseline Hydraulic Hand Dynamometer). Träningen resulterade i en signifikant skillnad hos testpersonernas greppstyrka i den nedre handen på klubban (p<0,05). Däremot hittades ingen signifikant skillnad för den övre handens greppstyrka eller dragskottshastigheten. Studien visade heller inte på någon korrelation mellan dragskottshastighet och greppstyrka hos testpersonerna. Testpersonerna hade olika åsikter kring hur den extra tyngden påverkade innebandytekniken.De funna resultaten indikerar att träning med viktmanipulerad utrustning i innebandy signifikant förbättrar spelarnas greppstyrka i den nedre handen. Den ökade kraftutvecklingen kan eventuellt förklaras av ett ökat neuromuskulärt samspel. Studien ger en ökad förståelse för hur dynamisk motståndsträning kan implementeras i den dagliga innebandyträningen, vilket kan tillämpas vid planeringen av träningsprogram. / Floorball is a sport with increasing number of participants, which has not been studied extensively according to the literature. Previous studies on ice hockey and baseball have shown that training with weight manipulated equipment improved grip strength and swing speed. Other research has shown that the increased performance with dynamic resistance training rather occurs from the improvements in the neuromuscular facilitation than an increase in muscle mass. In floorball shooting velocity is considered to be an important factor of the performance. Since it has been shown in baseball that training with weight manipulated equipment can improve the bat velocity, it would be interesting to see if the same results can be found in floorball. The purpose of this study was to investigate the effect of grip strength and drag shot velocity in floorball training with a weight manipulated floorball stick. The study also investigated the relationship between grip strength and drag shot velocity. The test subjects’ subjective perception about the training method was also investigated. Thirteen 17-year-old male floorball players participated in the study. During a six weeks period the subjects used the weight manipulated equipment during 30 minutes, three times per week during their regular team practice. 40 grams lead tape was attached to the player's equipment to increase the resistance. The drag shots were filmed with a high speed camera (Casio Exilim EX-FH25) at 250 fps. The drag shot velocity was analyzed in Dartfish. To assess grip strength a hand dynamometer (Jamar - Baseline Hydraulic Hand Dynamometer)was used. The training resulted in a significant increase for the subjects’ grip strength in the lower hand on the stick (p <0,05). The study found no significant difference for the upper hand grip strength or drag shot velocity. No correlation between drag shot velocity and handgripstrength among the subjects were found. Conclusion: The results found in this study indicate that training with weight manipulated equipment can significantly improve the player’s lower hand grip strength. The results can eventually be explained by more effective fiber recruitment in the muscles. Studying floorball can contribute to increase the interest in research on floorball and increase the understanding for how dynamic resistance training can be incorporated in daily floorball practice.

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