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Predicting Moment and Rotation Capacity of Semi-rigid Composite Joints with Precast Hollowcore SlabsLam, Dennis, Fu, F., Ye, J. January 2009 (has links)
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Design provisions for autoclaved aerated concrete (AAC) infilled steel moment framesRavichandran, Shiv Shanker 27 May 2010 (has links)
In this dissertation, the seismic behavior and design of AAC-infilled steel moment frames are investigated systematically. The fundamental vehicle for this investigation is the ATC-63 methodology, which is intended for the establishment of seismic design factors for structural systems. The ATC-63 methodology is briefly reviewed, including the concepts of archetypical structures, design rules and mathematical models simulating the behavior of those archetypes. A limited experimental investigation on the hysteretic behavior of an AAC-infilled steel moment frame is developed, conducted, and discussed. Using the experimental results of that investigation, the draft infill design provisions of the Masonry Standards Joint Committee (MSJC) are extended to AAC infills, and a mathematical model is developed and calibrated to simulate the behavior of AAC infills under reversed cyclic loads. Prior to application of ATC-63 methodology to AAC-infilled steel moment frames, the methodology is applied to an example steel moment frame to demonstrate the methodology and verify understanding of it. Then, archetypical infilled frames to be evaluated by the ATC-63 methodology are developed using a series of pushover analyses. Infill configurations whose total lateral strength in a particular story exceeds about 35% of the lateral strength of the bare frame in that story are observed to provoke story mechanisms in the frame. Based on this observation, archetypical infilled frames are selected conforming to two infill configurations: uniformly infilled frames, and open ground story frames. Each infill configuration includes archetypes whose ratio of infill strength to bare-frame strength at each story is less than 35%, and archetypes whose ratio is greater than 35%. The former archetype is typical of steel moment frames infilled with AAC; the latter archetype is typical of steel moment frames infilled with conventional (clay or concrete) masonry. The ATC-63 methodology, specialized for application to infilled frames, is applied to the archetypical infilled frames developed above. The performance of those archetypical infilled frames is evaluated, and seismic design factors are proposed for AAC-infilled steel moment frames. The extension of this work to other types of infilled frames is discussed. / text
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Simulace procesů v buněčných membránách / Simulation of processes in cellular membranesTimr, Štěpán January 2013 (has links)
Probing orientations of fluorescent molecules embedded in or attached to cell membranes has a great potential to reveal information on membrane structure and processes occurring in living cells. In this thesis, we first describe one- and two-photon linear dichroism measurements on a fluorescent probe embedded in a phospholipid membrane with a well- defined lipid composition. On the basis of experimental data, we determine the distribution of the angle between the one-photon transition dipole moment of the probe and the membrane normal. At the same time, we perform molecular dynamics simulations of the fluorescent probe and quantum calculations of its one-photon and two-photon absorption properties. By comparing the orientational distribution gained from experiments with that predicted by simulations, we test the ability of linear dichroism measurements to report on the orientation of a fluorescent molecule in a lipid membrane. We also examine the applicability of molecular simulations as a basis for the interpretation of experimental data.
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Mechanická analýza vlivu výrobních odchylek na styk hlavice a jamky totální endoprotézy kyčelního kloubu / Mechanical Analysis of the Influence of Fabrication Tolerances on Contact Conditions between the Acetabular Cup and the Femoral Head in Total Hip ReplacementKoukal, Milan January 2010 (has links)
In endoprosthesis surgery there are typically a high percentage of implant defects, these can lead to failure of the whole prosthesis. One type of total hip replacement function loss is acetabular cup loosening from the pelvic bone. This disertation examines manufacture perturbations as one of the possible reasons for this kind of failure. Both dimension and geometry manufacturing perturbations of ceramic head and polyethylen cup were analyzed. We find that perturbations in the variables analysed here affect considered values of contact pressure and frictional moment. Furthermore, contact pressure and frictional moment are quantities affecting replacement success and durability. From obtained results it can be recommended to fit head and cup with a clearance of between 0 mm and 0.05 mm. It can not be recommend using interference type of fit because of strong deterioration of the contact conditions. Roundness perturbation of ceramic head should not exceed 0.025 mm.
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Böjprovning av spikplåtsskarvad träbalkKorkmaz, Ebubekir, Lundstöm, Jerry January 2019 (has links)
This thesis examines the bearing capacity, stiffness, shear and moment force of a continuous wooden beam and how the parameters of the beam changes when the beam is spliced with nail plate. A literature study has been conducted to examine which studies have been carried out in this field. Construction timber is the most common wooden element for wooden constructions but has limitations in available lengths since the maximum length manufactured is 5400 mm. If larger lengths are required, splicing must occur or use of other materials. The study examines a 2 series, a 3-point series (moment and shear) and a 4-point series (moment). Each series consists off 3 trials in each series to see how shear and moment force affect the strength. The study also shows which off the joints that gives the least strength. The samples are tested in a draw and pressure machine lying on 2 supports and with a point load for the 3-point method and 2-point loads for the 4-point method. In the trials pressure is applied until the beams break. The study investigates the lab results, fracture state and use state for the wooden beams being tested. The result of the study shows that a splicing will lower the wood's carrying capacity between 21-60% compared to a non-spliced beam for the 3-point method and a reduction of 40-66% compared to a non-spliced beam for the 4-point method. Despite the lowered bearing capacity all the experiments are still within the characteristic value and approved for use. A larger dimension on the nail plate would probably have given a better value. / Detta examensarbete undersöker bärförmåga, styvhet, moment- och tvärkrafts påverkan hos en kontinuerlig träbalk och hur parametrarna för balken ändras då balken skarvas med spikplåt. En litteraturstudie har genomförts för att undersöka vilka studier som utförts på området. Konstruktionsvirke är det vanligaste träelementet vid träkonstruktioner men har begränsningar i tillgängliga längder då maxlängden som tillverkas är 5400mm. Vid behov av större längder måste skarvning förekomma eller användning av andra material. I studien undersöks två serier, en 3-punktsserie (moment och tvärkraft) samt en 4-punktsserie (moment). Varje serie består av 3 försök för att se hur moment och tvärkraft påverkar hållfastheten. Studien visar även vilken typ av skarv som ger minst hållfasthet. Proverna testas i en drag-tryck-maskin liggandes på 2 upplag med 1 punktlast anbringad för 3-punktsmetoden och 2 punktlaster för 4-punktsmetoden. I försöken anbringas kraft på balkarna tills de går i brott. Studien undersöker labbvärdet, brottstadiet och bruksstadiet för balkarna som testas. Analysen av försöken visar att en skarvning kommer sänka balken bärförmåga med mellan 21–60% gentemot en ren träbalk för trepunktsmetoden och en minskning på mellan 40–66% gentemot en ren träbalk för fyrpunktsmetoden. Trots den sänkta bärförmågan för balken i testerna är alla försöken inom det karaktäristiska värdet och godkända att användas. En större dimension på spikplåten hade antagligen gett ett bättre värde.
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Etude de la structure nucléaire de noyaux exotiques à ALTO : développements et résultats de deux nouvelles installations / Study of the nuclear structure of exotic nuclei at ALTO : developments and results of two new experimental setupsÉtilé, Asénath 10 December 2014 (has links)
ALTO (Accélérateur Linéaire et Tandem d’Orsay) est une installation équipée de deux accélérateurs pour la recherche et les applications industrielles (un tandem de 15 MV et une accélérateur linéaire). Mon travail de thèse consiste à l’instrumentation pour la recherche fondamentale de la partie accélérateur linéaire d’ALTO qui fournir des faisceaux de noyaux radioactifs. Les faisceaux de noyaux radioactifs riches en neutrons sont produits par la technique de séparation isotopique en ligne (ISOL). Cette méthode de production permet trois types d’expérience : la mesure de masse, l’orientation nucléaire et les expériences de décroissances radioactives. Parmi ces trois types d’expériences, j’ai participé aux développements de deux nouvelles plateformes expérimentales dans le cadre du projet de l’instrumentation de l’installation ISOL d’ALTO. Le premier, BEDO (BEta Decay studies in Orsay) est un ensemble de détecteurs dédié à la spectroscopie β-γ des noyaux décroissants par désintégration β produits par ALTO. Je présente ici, la mise en fonctionnement de cette plateforme expérimentale, ses caractéristiques techniques et les développements d’outils permettant d’aboutir aux premiers résultats. Pour cette expérience un faisceau de la masse 82 a été produit, saisissant cette opportunité, une ré-investigation de la décroissance de ⁸²Ge vers ⁸²As a permis d’établir un nouveau schéma de niveaux pour ⁸²As et de donner les premières indications de la présence d’états issus de configurations intruses dans les isotones impair-impair N=49. Le second projet développé est POLAREX (POLARization of EXotic nuclei), il s’agit d’une plateforme expérimentale dédiée aux expériences d’orientation nucléaire. Mon travail traite ici de l’entière réhabilitation du cryostat à dilution ³He-⁴He (élément principal et le plus complexe de l’installation) et des développements techniques et R&D apportés à l’ensemble de la plateforme. L’ensemble de ces contributions a permis la validation du fonctionnement de l’installation avec les premières mesures physiques sur les noyaux de ⁵⁴Mn, ⁵⁶Co, ⁵⁷Co créés par activation d’une feuille de Fer avec des deutons produits par le Tandem. / ALTO (Accélérateur Linéaire et Tandem d’Orsay) is a facility composed of two accelerators dedicated to research and industrial applications. There is a 15 MV tandem and a linear accelerator. My PhD work was to develop the instrumentation of the linear accelerator part of ALTO which provides radioactive beams for fundamental research. These radioactive beams are produced using the Isotope Separation On-Line method (ISOL). This technique allows three kinds of experiments: mass measurement, nuclear orientation and radioactivity experiments. Among those three types of experiments, I worked on the development of two new experimental platforms for the ALTO instrumentation. The first one, BEDO (BEta Decay studies in Orsay) is an ensemble of detectors dedicated to β-γ spectroscopy of β-decaying nuclei produced by ALTO. I present in this thesis, the commissioning of this new experimental set-up, its technical characteristics and the tools development leading to the first results. For this commissioning experiment a mass 82 radioactive beam was produced, taking this opportunity the ⁸²Ge vers ⁸²As decay was re-investigated allowing to establish a new level scheme for ⁸²As and giving the first evidences for the presence of intruder states in the N=49 odd-odd isotones. The second project, which is developed, is POLAREX (POLARization of EXotic nuclei), a new facility for nuclear orientation experiments. My thesis deals with the entire reconditioning of a ³He-⁴He dilution refrigerator (major and most complex element of the facility) and R&D and technical developments of the platform. These contributions allowed the successful commissioning of the new experimental platform with the first physical measurements on ⁵⁴Mn, ⁵⁶Co, ⁵⁷Co created by activation of an iron foil with deuterons produced by the Tandem.
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Stark Spectroscopy, Lifetimes and Coherence Effects in Diatomic Molecular SystemsHansson, Annie January 2005 (has links)
<p>In this dissertation is exemplified how different laser based methods are applied in high-resolution spectroscopic studies of internal properties of diatomic molecules.</p><p>A molecular beam apparatus assembly is described, where a laser ablation source is combined with a time-of-flight mass spectrometer. Compounds investigated with this equipment are hafnium sulfide and hafnium oxide. The molecules are excited and ionized applying the resonant two-photon ionization (R2PI) scheme, which is a sensitive absorption and detection technique for probing the population of an excited state.</p><p>By means of the DC Stark effect, permanent electric dipole moments of HfS in the <i>D</i> <sup>1</sup>Π state and HfO in the <i>b</i> <sup>3</sup>Π<sub>1</sub> state are determined while the molecules are exposed to a static electric field. Under field-free conditions low temperature rotationally resolved spectra are recorded, generating line positions from which molecular parameters are derived.</p><p>The R2PI method, modified with an adjustable delay time, is also used in lifetime measurements of individual rotational levels of the HfS <i>D</i><sup> 1</sup>Π and HfO<i> b</i> <sup>3</sup>Π<sub>1</sub> states. Oscillator strengths for transitions from the ground state are calculated, and in this connection basic concepts like Einstein coefficients, line strengths and Hönl-London factors, are surveyed. Theoretical calculation of lifetimes is discussed in view of the fact that a commonly available computer program (LEVEL 7.5 by Le Roy) gives erroneous output.</p><p>Some coherence and quantum interference related phenomena, such as electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting, are presented in the latter part of this thesis. Fundamental concepts and relations are introduced and explained. The driven three-level cascade system is elucidated, including some of its experimental applications to alkali metal dimers, Na<sub>2</sub> and Li<sub>2</sub>.</p><p>A triple resonance spectroscopy experiment is described in terms of a three-laser, four-level inverted-Y excitation scheme, implemented in Na<sub>2</sub>. The accompanying density matrix formalism, providing the basis for theoretical simulations, is accounted for. From analysis of the results an absolute value of the electric dipole moment matrix element (transition moment) is extracted, using the AC Stark effect.</p><p>Some recently reported unexpected experimental results and unforeseen features, occurring in Doppler broadened samples and related to the open character of molecular systems, are briefly commented.</p>
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Stark Spectroscopy, Lifetimes and Coherence Effects in Diatomic Molecular SystemsHansson, Annie January 2005 (has links)
In this dissertation is exemplified how different laser based methods are applied in high-resolution spectroscopic studies of internal properties of diatomic molecules. A molecular beam apparatus assembly is described, where a laser ablation source is combined with a time-of-flight mass spectrometer. Compounds investigated with this equipment are hafnium sulfide and hafnium oxide. The molecules are excited and ionized applying the resonant two-photon ionization (R2PI) scheme, which is a sensitive absorption and detection technique for probing the population of an excited state. By means of the DC Stark effect, permanent electric dipole moments of HfS in the D 1Π state and HfO in the b 3Π1 state are determined while the molecules are exposed to a static electric field. Under field-free conditions low temperature rotationally resolved spectra are recorded, generating line positions from which molecular parameters are derived. The R2PI method, modified with an adjustable delay time, is also used in lifetime measurements of individual rotational levels of the HfS D 1Π and HfO b 3Π1 states. Oscillator strengths for transitions from the ground state are calculated, and in this connection basic concepts like Einstein coefficients, line strengths and Hönl-London factors, are surveyed. Theoretical calculation of lifetimes is discussed in view of the fact that a commonly available computer program (LEVEL 7.5 by Le Roy) gives erroneous output. Some coherence and quantum interference related phenomena, such as electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting, are presented in the latter part of this thesis. Fundamental concepts and relations are introduced and explained. The driven three-level cascade system is elucidated, including some of its experimental applications to alkali metal dimers, Na2 and Li2. A triple resonance spectroscopy experiment is described in terms of a three-laser, four-level inverted-Y excitation scheme, implemented in Na2. The accompanying density matrix formalism, providing the basis for theoretical simulations, is accounted for. From analysis of the results an absolute value of the electric dipole moment matrix element (transition moment) is extracted, using the AC Stark effect. Some recently reported unexpected experimental results and unforeseen features, occurring in Doppler broadened samples and related to the open character of molecular systems, are briefly commented.
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Service på Internet – Hur service erbjuds av företag som säljer resor på Internet / Web based service – How service is being provided by companies that sell trips over the InternetBjörk, Carolina, Lengroth, Anna, Eggeborn, Sofie January 2010 (has links)
Business across the Internet has increased in recent years and most companies that are selling trips have increased their sales online. Many companies that are selling trips strive for customers to receive and experience a personal service online. The meeting between the client and a webpage service system on the Internet should work. Service encounters are an essential part of the contact between customer and company and play a big part in how the first impression is perceived by the customer. To understand how a service encounter works, meeting face to face, companies need to understand how customers perceive that meeting. Among other things, personnel and customers confront each other in a physical meeting and during the first few seconds is what Normann (2002) call the moment of truth. The purpose of this paper is to find out how service is working over the Internet. We also want to contribute with increased insight of the interaction between customer and provider over the Internet. To examine how service works over the Internet and how customers are treated. Theories that include e-CRM, Image concept and e-SERVQUAL have been used. Interviews took place with various actors within the tourism industry. Parasuraman, et al. (2002) and Kuo, et al. (2005) say that companies need to understand what the customer wants to do on their website and meet the needs of the customer and to exceed customers’ expectations.
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Investigation of an extremely flexible stowable rotor for micro-helicoptersSicard, Jérôme 12 July 2011 (has links)
This thesis describes the analysis, fabrication and testing of a rotor with extremely flexible blades, focusing on application to a micro-helicopter. The flexibility
of the rotor blades is such that they can be rolled into a compact volume and stowed inside the rotor hub. Stiffening and stabilization of the rotor is enabled by centrifugal forces acting on a tip mass. Centrifugal effects such as bifilar and propeller moments are investigated and the torsional equation of motion for a blade
with low torsional stiffness is derived. Criteria for the design of the tip mass are also derived and it is chosen that the center of gravity of each blade section must be located ahead of the aerodynamic center.
This thesis presents the design of 18-inch diameter two-bladed rotors having untwisted circular arc airfoil profile with constant chord. A systematic experimental
investigation of the effect of various blade parameters on the stability of the rotor is conducted in hover and forward flight. These parameters include blade flexibility in bending and torsion, blade planform and mass distribution. Accordingly, several
sets of blades varying these parameters are constructed and tested. It is observed that rotational speed and collective pitch angles have a significant effect on rotor stability. In addition, forward flight velocity is found to increase the blade stability.
Next, the performance of flexible rotors is measured. In particular, they are compared to the performance of a rotor with rigid blades having an identical planform
and airfoil section. It is found that the flexible blades are highly twisted during operation, resulting in a decreased efficiency compared to the rigid rotor blades. This induced twist is attributed to an unfavorable combination of tip body design
and the propeller moment acting on it. Consequently, the blade design is modified and three different approaches to passively tailor the spanwise twist distribution for
improved efficiency are investigated. In a first approach, extension-torsion composite material coupling is analyzed and it is shown that the centrifugal force acting on the tip mass is not large enough to balance the nose-down twist due to the propeller moment. The second concept makes use of the propeller moment acting on the tip mass located at an index angle to produce an untwisted blade in hover. It is constructed and tested. The result is an untwisted 18-inch diameter rotor whose maximum Figure of Merit is equal to 0.51 at a blade loading of 0.14. Moreover, this rotor is found to be stable for any collective pitch angle greater than 11 degrees. Finally, in a third approach, addition of a trailing-edge flap at the tip of the flexible rotor blade is investigated. This design is found to have a lower maximum Figure
of Merit than that of an identical flexible rotor without a flap. However, addition of this control surface resulted in a stable rotor for any value of collective pitch angle. Future plans for increasing the efficiency of the flexible rotor blades and for developing an analytical model are described. / text
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