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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.
1

Musik-En starkare kundupplevelse / Music- A source for a stronger customer experience

Willén, Fredrik January 2014 (has links)
Musikens tempo kan som en del av servicescape påverka individen i samband med styrketräning på gym. Den kan bidra till hur en konsument känner under sin vistelse hos ett tjänsteföretag, vilket tar sig i uttryck genom ett närmande- eller undvikande beteende hos konsumenten gentemot tjänsteföretaget. Syftet med detta arbete var att undersöka hur musikens tempo påverkar individens upplevelse i samband med styrketräning på gym, något som påverkar hur motiverad individen är att återvända till gymmet. / As a part of servicescape music tempo can influence individuals during weight training at the gym.  The tempo of music can affect the customer emotionally and contribute to their service experience.  The customer’s internal response to the servicescape will consequently influence their outward behaviour towards the company. The behaviour can be classified into two dimensions, either an approach or avoidance behaviour. The purpose of this study was to examine how music tempo influences the individual during weight training at the gym and affect the external behaviour towards the company.
2

Analysis of flexure pivot tilting pad gas bearings with different damper configurations

Rimpel, Aaron Michael 15 May 2009 (has links)
Hydrodynamic flexure pivot tilting pad gas bearings (FPTPGBs) can enable successful operation of oil-free microturbomachinery. This work presents the experimental and analytical study of such bearings with different damper configurations. A test rig was constructed that could safely operate a ~28.6 mm, 0.8 kg rotor beyond 120 krpm. A time domain orbit simulation, which integrates nonlinear equations of motion for the rotor-bearing elements, was implemented as the primary analysis tool to predict rotor-bearing responses to imbalance, the presence and location of critical speeds, etc. Complementary analyses were also performed with a model that uses linear bearing impedance coefficients to predict system natural frequencies. Imbalance response testing verified that the rotor-bearing system behaved linearly in the region above the critical speed, and orbit simulations predicted the response to a calibrated imbalance with notable agreement. Viscoelastic dampers added behind the FPTPGB pads delayed the onset of subsynchronous vibrations (from 43 krpm without damper to above 50 krpm with damper) of the system with bearing clearance increased by shims. Midrange subsynchronous vibrations initiated at ~20 krpm were eventually suppressed by ~25 krpm due to the stabilizing effect of rotor centrifugal growth. The viscoelastic dampers had a negligible effect on suppressing these midrange subsynchronous vibrations in experiments, but this was not demonstrated in simulations, presumably due to much lower stiffness contribution of the damper at lower frequencies. The ideal, perfectly aligned models in the simulations were able to tolerate shims up to only 10% of nominal clearance, but the test rig exhibited surprising stability with shims as much as 200% of nominal clearance; this increase may be caused by imposed eccentricities due to misalignments in the test rig. FPTPGBs supported by compliant bump foils can have the ability to tolerate rotor misalignments and shock loading like foil gas bearings. Simulation studies on imbalance response characteristics for several bearing shell mass and support stiffness configurations present initial design guidelines for the application. Namely, results showed that FPTPGBs favored large bearing shell mass and large support stiffness, while FPTPGBs with radial compliance favored small bearing shell mass with large support stiffness.
3

Contribution to Development of Copper Free Automotive Brake Pad

Lee, Lin 01 August 2013 (has links)
When passenger vehicle drivers hit the brakes of their cars, the friction releases airborne wear particles from the contact between rotor and brake pad onto the road which are eventually washed down storm drains and into rivers. The wear particles includes copper, which functions as solid lubricant for increasing thermal heat fade as well as increasing friction coefficient for the brake pad. Nevertheless, copper not only endangers aquatic life, but it also directly affects the economy by lowering the supply of salmon. Copper is toxic to most aquatic life and is especially harmful to the sensory systems of salmon. Copper impairs salmon's sense of smell, thus reducing their ability to escape from predators. Up to half of the copper found in waterways from urban areas are from copper brake pads and is a key factor in the reduction of salmon population. In 2010, Washington and California each passed laws to ban production of brake pads containing more than 0.5% copper which will be effective in 2025. Since then, several other states including New York, Rhode Island, and Oregon have all introduced similar bills to ban copper brake pads. The raw materials that were added to the newly developed copper free sample brake pads are geopolymers; they are synthetic mineral products that combine properties of polymers, ceramics and cements. Geopolymers have the characteristic of behaving as adhesive rubber in order to replace phenolic resin matrix in the brake materials also it can be harden at room temperature which can increase friction coefficient of the brake pad. Sample brake pads manufactured on site with known constituents were tested with friction assessment and screening test machine, which measured and recorded the friction coefficient and wear of the brake pad. According to the experience in the past, the sample brake pads will be analyzed with density test and Shore Durometer test. The results presented in this report shows that geopolymers brake pad shows promising results for copper replacement for low-metallic friction material. Developed copper free friction sample shows promising result of coefficient of friction of 0.44 with thickness loss of 0.62 mm from friction assessment and screening test machine compare to commercial brake pad.
4

DEFORMATION OF BEARING PADS WHILE UNDER SERVICE LOADS

Suits, Chris Allen 01 May 2013 (has links)
Bearing pads undergo deformation while under service loads of any bridge. The pad translates the load to the support structure, and allows for movement of the superstructure. The deformation of bearing pads is an important element to consider when designing both the super and sub structures of the bridge. The Federal Highway Administration provides a guide for the design of steel brigdes, and Step 6 of this guide covers the design of bearing pads. The purpose of this study is to analyze the deformation of bearing pads using a finite element analysis software. This study will analyze two separate models, one ignoring the steel plates in a bearing pad and ignoring friction, while the other will take into account the steel plates as well as friction during the analysis. Once the linear analysis is run the models that are built can be compared with the FHWA design examples to compare and verify the results. This will facilitate the possible improvement of current design examples and allow for a more realistic result for designers to use. This study also looks at the internal testing results provided by a bearing pad manufacturing company. These internal results will provide a real world model for the linear analysis models to be compared to as well. Once all factors are taken into account, the validity of the current standards can be evaluated.
5

Measured and predicted rotordynamic coefficients and static performance of a rocker-pivot, tilt pad bearing in load-on-pad and load-between-pad configurations

Carter, Clint Ryan 02 June 2009 (has links)
This thesis presents the static and dynamic performance data for a 5 pad tilting pad bearing in both the load-on-pad (LOP) and the load-between-pad (LBP) configurations over a variety of different loads and speeds. The bearing tested was an Orion Advantage with direct lubrication exhibiting these specifications: 5 pads, .282 preload, 60% offset, 57.87° pad arc angle, 101.587 mm (3.9995 in) rotor diameter, .1575 mm (.0062 in) diametrical clearance, 60.325 mm (2.375 in) pad length. Dynamic tests were performed over a range of frequencies to observe any frequency effects on the dynamic stfffnesses. It was found that under most test conditions the direct real part of the dynamic stiffnesses could be approximated as quadratic functions of the excitation frequency. This frequency dependency is caused by pad inertia, pad flexibility, and fluid inertia. The observed frequency dependency can be accounted for with the addition of an added mass matrix to the conventional [K][C] matrix model to produce a frequency independent [K][C][M] model. This method eliminates the often debated question over whether a stability analysis should be performed at the running speed or at the first natural frequency. Substantially large added mass terms in the loaded direction were found that approached 60 kg. Some conditions for the LBP bearing exhibited unloaded direct mass coefficients that were at or near zero, which would lead to a frequency dependent [K][C] model to be used instead. The whirl frequency ratio was found to be zero at all test conditions. Static data were also recorded which included pad temperatures, attitude angle, eccentricity, static stiffness and power loss. Some cross coupling in the form of deviation from the loaded axis was evident from the locus plots; however, the cross coupled stiffness coefficients were found to be very small relative to the direct stiffness coefficients. Both static and dynamic experimental results were compared to theoretical predictions via a bulk flow analysis. Most parameters were modeled well including the static eccentricity e dynamic direct stiffness coefficients Kxx and Kyy, which were slightly over predicted. However, the direct damping coefficients Cxx and Cyy were significantly over predicted.
6

Measured and predicted rotordynamic coefficients and static performance of a rocker-pivot, tilt pad bearing in load-on-pad and load-between-pad configurations

Carter, Clint Ryan 02 June 2009 (has links)
This thesis presents the static and dynamic performance data for a 5 pad tilting pad bearing in both the load-on-pad (LOP) and the load-between-pad (LBP) configurations over a variety of different loads and speeds. The bearing tested was an Orion Advantage with direct lubrication exhibiting these specifications: 5 pads, .282 preload, 60% offset, 57.87° pad arc angle, 101.587 mm (3.9995 in) rotor diameter, .1575 mm (.0062 in) diametrical clearance, 60.325 mm (2.375 in) pad length. Dynamic tests were performed over a range of frequencies to observe any frequency effects on the dynamic stfffnesses. It was found that under most test conditions the direct real part of the dynamic stiffnesses could be approximated as quadratic functions of the excitation frequency. This frequency dependency is caused by pad inertia, pad flexibility, and fluid inertia. The observed frequency dependency can be accounted for with the addition of an added mass matrix to the conventional [K][C] matrix model to produce a frequency independent [K][C][M] model. This method eliminates the often debated question over whether a stability analysis should be performed at the running speed or at the first natural frequency. Substantially large added mass terms in the loaded direction were found that approached 60 kg. Some conditions for the LBP bearing exhibited unloaded direct mass coefficients that were at or near zero, which would lead to a frequency dependent [K][C] model to be used instead. The whirl frequency ratio was found to be zero at all test conditions. Static data were also recorded which included pad temperatures, attitude angle, eccentricity, static stiffness and power loss. Some cross coupling in the form of deviation from the loaded axis was evident from the locus plots; however, the cross coupled stiffness coefficients were found to be very small relative to the direct stiffness coefficients. Both static and dynamic experimental results were compared to theoretical predictions via a bulk flow analysis. Most parameters were modeled well including the static eccentricity e dynamic direct stiffness coefficients Kxx and Kyy, which were slightly over predicted. However, the direct damping coefficients Cxx and Cyy were significantly over predicted.
7

Experimental frequency-dependent rotordynamic coefficients for a load-on-pad, high-speed, flexible-pivot tilting-pad bearing

Rodriguez Colmenares, Luis Emigdio 30 September 2004 (has links)
This thesis provides experimental frequency dependent stiffness and damping coefficient results for a high-speed, lightly loaded, flexible-pivot tilting-pad bearing, with a load-on-pad configuration. Test conditions include four shaft speeds (6000, 9000, 13000 and 16000 rpm), and bearing unit loads from 172 kPa to 690 kPa. The results show that the bearing stiffness is a quadratic function of the frequency of vibration; hence their frequency dependency can be modeled by added-mass terms. The additional degrees of freedom introduced by the pads and the influence of the inertial forces generated in the fluid film account for this frequency dependency. The conventional frequency-dependent stiffness and damping model for tilting-pad bearings is extended with an added-mass matrix to account for the frequency dependency. This approach allows the description of the bearing dynamic characteristics with frequency-independent stiffness, damping and added-mass matrices. Experimental results are compared with predictions from the Reynolds equation and from a bulk-flow Navier-Stokes model. Both models produce good predictions of the stiffness and damping coefficients. However, results show that the bulk-flow model is more adequate for predicting the direct added-mass terms because it accounts for the fluid inertial forces. A bulk-flow solution of the Navier-Stokes equations that includes the effects of fluid inertia should be used to calculate the rotordynamic coefficients of a flexible-pivot tilting-bearing. Static performance measurement results are also detailed. Results include pad metal temperatures, eccentricity-ratios and attitude-angle as a function of bearing load, and estimated power losses.
8

Pressão arterial em adolescentes durante teste de esforço com protocolo em rampa

de Moraes chaves Becker, Mônica January 2005 (has links)
Made available in DSpace on 2014-06-12T18:29:44Z (GMT). No. of bitstreams: 2 arquivo8034_1.pdf: 637147 bytes, checksum: afffa85939ad57ad75e1f441cfd8bad2 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / O teste de esforço é utilizado para avaliar o comportamento da pressão arterial, inclusive em crianças e adolescentes. Porém, não existe consenso dos valores normais de variação da pressão arterial com o exercício. Foi realizado estudo transversal de 218 adolescentes entre 10 e 19 anos (131 do sexo masculino), onde são descritos FC máxima, tempo de exercício, VO2 máximo e PA sistólica e diastólica de repouso, no esforço máximo e aos seis minutos da recuperação, durante teste de esforço com protocolo em rampa. A FC máxima foi semelhante em ambos os sexos, com média de 192 + 08 bpm. O tempo de exercício e o VO2 max foram maiores no sexo masculino. No repouso, a PA sistólica teve valores maiores no sexo masculino e a PA diastólica não mostrou diferença entre os sexos, porém ambas aumentaram com a idade. No exercício ocorreu elevação da PAS e queda da PAD em ambos os sexos. A variação da PAS foi maior no sexo masculino, principalmente acima dos 14 anos. A análise dos resultados demonstrou que a PAS durante o exercício tem relação direta com idade, peso, altura e IMC do indivíduo e a PAD guardou relação apenas com a idade
9

i-Nitrite Therapy for Treatment of Peripheral Arterial Disease

Maan, Neeti 27 August 2012 (has links)
No description available.
10

Measured and Predicted Rotor-Pad Transfer Functions for a Rocker-Pivot Tilting-Pad Journal Bearing

Wilkes, Jason Christopher 2011 December 1900 (has links)
Many researchers have compared predicted stiffness and damping coefficients for tilting-pad journal bearings (TPJBs) to measurements. Most have found that direct damping is consistently overpredicted. The thrust of this research is to explain the difference between measured and predicted stiffness and damping coefficients for TPJBs, and to provide some confidence to designers that TPJB dynamic coefficients can be accurately predicted. Most analytical models for TPJBs are based on the assumption that explicit dependence on pad motion can be eliminated by assuming harmonic rotor motion such that the amplitude and phase of pad motions resulting from radial and transverse rotor motions are predicted by rotor-pad transfer functions. In short, these transfer functions specify the amplitude and phase of pad motion (angular, radial, translational, etc.) in response to an input rotor motion. A new pad perturbation model is developed including the effects of angular, radial, and circumferential pad motion and changes in pad clearance due to pad bending compliance. Though all of these pad variables have previously been included in different analyses, there are no publications containing perturbations of all four variables. In addition, previous researchers have only perturbed the journal, while both the bearing and journal motions are perturbed in the present analysis, and the applicability of comparing rotor-perturbed bearing impedance predictions to impedances measured on a bearing-perturbed test rig is discussed. This perturbation model was implemented in a Reynolds-based TPJB code to predict the frequency-dependent bearing impedances and rotor-pad transfer functions. Direct measurements of pad motion during test excitation were recorded to produce measured transfer functions between rotor and pad motion, and a comparison between these measurements and predictions is given. Motion probes were added to the loaded pad (having the static load vector directed through its pivot) of a 5-pad TPJB to obtain accurate measurement of pad radial and tangential motion, as well as tilt, yaw, and pitch. Strain gages were attached to the side of the loaded pad to measure static and dynamic bending strains, which were then used to determine static and dynamic changes in pad curvature (pad clearance). Good agreement was found between the amplitude of the measured and predicted transfer functions concerning radial and transverse pad motions throughout the range of speeds and loads tested, while pad tilt was moderately underpredicted. For the bearing investigated, radial pad motions resulting from pivot compliance were as large as 60% of the radial component of shaft motion when operating at 4400 rpm under heavily loaded conditions. Hence, if a dynamic load applied to the shaft resulted in a shaft displacement of 25 microns (1 mil), the pad would displace radially 15 microns (0.6 mils), and the fluid film height would only decrease by 10 microns (0.4 mils). The consequence of this pad motion is that fluid film stiffness and damping forces produced by relative rotor-pad motions are significantly reduced, resulting in a bearing having significantly less direct stiffness and damping than predicted. A similar effect occurs when shaft motions produce significant changes in pad clearance due to pad compliance. For the pad tested here, the measurements show that predicting TPJB stiffness and damping coefficients without accounting for pad and pivot compliance will produce large errors, and is not advised. Transverse pad motion was predicted and observed. Based on phase measurements, this motion is lightly damped, and appears to be caused by pivot deflection instead of slipping. Despite observing a lightly damped phase change, an increase in magnitude at this natural frequency was not observed. Predicted direct stiffness and damping for unit loads from 0-3200 kPa (0-450 psi) fit through 1.5× running speed are within 18% of measurements at 4400 rpm, while predictions at 10200 rpm are within 10% of measurements. This is a significant improvement on the accuracy of predictions cited in literature. Comparisons between predictions from the developed bearing model neglecting pad, pivot, and pad and pivot flexibility show that predicted direct stiffness and damping coefficients for a model having a rigid pad and pivot are overestimated, respectively, by 202% and 811% at low speeds and large loads, by 176% and 513% at high speeds and high loads, and by 51% and 182% at high speeds and light loads. While the reader is likely questioning the degree to which these predictions are overestimated in regard to previous comparisons, these predictions are based on measured operating bearing clearances, which are 20-30% smaller than the cold bearing clearances that previous comparisons were based on. The effect of employing a full bearing model (retaining all of the pad degrees of freedom) versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability. This overestimation of stability is due to an increase in predicted direct damping at the synchronous frequency over the subsynchronously reduced value. This increase in direct damping with excitation frequency was also seen in highly loaded test data at frequencies below approximately 2×running speed, after which direct damping decreased with increasing excitation frequency. This effect was more pronounced in predictions, occurring at all load and speed combinations. The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies at 10200 rpm. It was found that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping. This outcome contrasts with the comparison between models using synchronously and subsynchronously reduced impedance predictions, which showed the subsynchronously reduced model to be the most conservative. This contrast results from a predicted increase in damping with increasing excitation frequency at all speeds and loads, while this increase in damping with increasing excitation frequency was only measured at the most heavily loaded conditions.

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