The dynamic process of how fast a spintronic device can be switched from one state to another is characterized by the Gilbert damping parameter. It has been found that the Gilbert damping along with other intrinsic properties in permalloy, can be tuned by different dopants and doping concentration. Therefore, a study of intrinsic magnetic properties with emphasis on the dependence of the Gilbert damping parameter from first principles calculations is investigated. It is aimed at to give an insight of the microscopic understanding originated from electronic structure and to provide a guideline in the practical spintronic design. The topic of the present thesis is to investigate, by means of first principle calculations, how the variation of the Gilbert damping parameter depends upon the electronic structure of pure and doped permalloy. We show that the Gilbert damping has a monotonic increase with the doping concentration due to an increasing amount of scattering processes. The dopants of the 5d transition metal give rise to a much larger impact than the 4d, as the spin orbit coupling effect is more pronounced in the heavy elements. Our results are in satistying agreement with experiment. / <p>QC 20150629</p>

No description available.

No description available.

The effect of different vertical support stiffness of a frame railway bridge is investigated in this study. Due to the dynamic loads of the high speed trains that run over the railway bridges, the response of these structures is far from the static effects. The frame bridge chosen for this study is the Rössjö bridge, located on the Bothnia Line, the first high speed railway built in Sweden. Using a theoretical model of this bridge, the eigenfrequencies of the structure and the vertical accelerations of the deck are evaluated. Not only different vertical support stiffness, but also different trains and train speeds are studied. Finally, some real in-situ measurements are compared with the results from the theoretical model.

Cross Laminated Timber (CLT) has in recent years become a more important building material. This means that the demand for accurate calculation methods in building standards such as Eurocode 5 has increased. There is limited knowledge about the connections in CLT buildings which is an important part of a CLT structure. This thesis was therefore focused on investigating a wall-floor-wall type connection commonly found in platform type buildings.  An experimental and numerical study on typical wall-floor-wall connections was carried out in this thesis. In the experimental part 60 tests with 8 different configurations were conducted to investigate the influence of different parameters on the connection, moment capacity and rotational stiffness. During the tests the deformation of the specimens under four load levels were investigated. Compression tests were also performed on the specimens to determine the compressive strength and stiffness of the elements. In the numerical part two different models for the connection were created. One simplified model with rotational springs and one more complex model with compression springs. With these models the influence from the number of stories, span and thickness of the wall on the global behavior of a structure was investigated.  The result from this thesis shows that there is both moment capacity and rotational stiffness in the wall-floor-wall type connection that can be utilized in the design phase of a structure. This was proven by both the experimental and the numerical study. The parameters that influence the behavior of the connection most were the load level applied on the wall and the wall thickness. The model created in the numerical study showed great potential regarding the replication of the connection behavior observed in the experimental study.

Research in damage detection and structural health monitoring in engineering systems during their service life has received increasing attention because of its importance and benefits in maintenance and rehabilitation of structure. Though the concept of vibration-based damage detection has been in existence for decades, and several procedures have been proposed to date, its practical applications remain limited, considering the increased utilization of sensors to measure structural response at multiple points. In this thesis, use of acceleration response of the structure as a method of global damage detection is explored using instantaneous frequency and stiffness degradation methods. Instantaneous frequency was estimated using continuous wavelet transform of measured acceleration response of the structure subjected to ground motion. Complex Morlet Wavelet was used in the time-frequency analysis due to its ability to provide sufficient resolution in both time and frequency domains. This ability is important in analyzing nonstationary signals like earthquake response of structure containing sharp changes in the signal. The second method, called the stiffness degradation analysis, is based on estimating the time-varying stiffness. This estimation is done by fitting a moving least-square line to the force-displacement loop for the duration of the ground motion.A four-story shear building is used as the model structure for numerical analysis. Two damage scenarios are considered: single damage instant and multiple damage instants. Both scenarios assume that the damage occurs at a single location. In the numerical simulations, damage was modeled as a reduction in the stiffness of the first floor, and accelerations were computed at floor levels using state-space model. The two methods were compared in terms of their damage detection ability and it was shown that both methods can be used in detecting damage and the time at which the damage occurs. These methods can later be extended by simultaneously considering the correlations of responses at all floor levels. This extension may enable locating the damage and quantifying the severity of the damage.

No description available.

Gallstones have been linked to dyslipidemia, metabolic syndrome and cardiovascular disease. Arterial stiffness is an indicator of subclinical atherosclerosis. The aim of this study was to prospectively examine the relationship between gallstone disease and arterial stiffness progression in 347 men and 454 women. These subjects were followed for 7 years. Arterial stiffness progression was measured based on increases in brachial-ankle pulse wave velocity. Changes in brachial-ankle pulse wave velocity during the study period were significantly greater in patients with gallstones than in subjects without gallstones. After adjusting for multiple risk factors, gallstone disease was found to be a significant and independent predictor of brachial-ankle pulse wave velocity progression (β=0.189; P<0.001). In conclusion, gallstone disease is an independent predictor of arterial stiffness progression, even after adjusting for other cardiovascular risk factors.

Laminated glass (LG) consists of two or more glass layers bonded by an elasto-polymeric layer, the most commonly used being PVB (Polyvinyl Butyral). LG has improved safety properties compared with single layer glass because the interlayer prevents large sharp pieces from spreading when the glass is broken by impact. Even if one of the layers breaks, the other layer(s) still contribute in carrying the load. Through proper understanding of the interaction between the interlayer and the glass LG could be used in engineering as a load bearing material to a larger extent. This study aims at gaining a deeper knowledge of the behaviour of laminated glass by experimental investigations and by numerical model simulation. To pursue the proposed study, three point bending test with simple support conditions were performed for single layer glass and laminated glass units with three different types of interlayer materials. Corresponding finite element numerical models were created in the software ABAQUS to fit the model with experiment to obtain the bending stiffness and shear stiffness of the interlayer material. The PVB tested showed viscos-elastic material properties, whereas other two interlayer materials, Solutia DG 41 and Sentry Glass, showed linear elastic properties. PVB is the least stiff interlayer material among the three types. Solutia DG 41 and Sentry Glass have similar stiffness, about 13 to 15 times stiffer than the PVB. The behaviour of laminated glass lies in general between the two limits of a layered glass unit with no interaction and a monolithic unit of the same total thickness, depending on the stiffness of the interlayer material. Failure tests of the specimens were also carried out. The obtained strength of glass from four specimens is 80 MPa to 92 MPa with a variation of about 15%. The number of more performed experiments would have better outcome for strength of glass. The bending stiffness of the laminated glass as estimated with the numerical model fitted well with the experimental results with an error of about 2%. Hence the experimentally and numerically obtained results show a good correlation and are thought be possible to use in future larger scale modelling.

Background: Biomechanical stiffness has been linked to risk of injury and found to be a measureable characteristic in musculoskeletal disorders. Specific identification of stiffness may clarify who is most likely to benefit from the trigger point dry needling (TDN). The purpose of this study is to investigate the reliability and concurrent validity of the MyotonPRO® to the criterion of shear wave ultrasound elastography for the measurement of biomechanical stiffness in the infraspinatus, erector spinae, and gastrocnemius of healthy subjects over increasing muscle contraction. Second purpose is to investigate the biomechanical effects of TDN to latent myofascial trigger points (MTrPs) in the infraspinatus, erector spinae, or gastrocnemius. Research Design and Method: The first phase of the study investigated 30 subjects who completed three levels of muscle contraction in standardized test positions for the infraspinatus, erector spinae and gastrocnemius. Biomechanical stiffness measures were collected using shear wave elastography and MyotonPRO®. The second phase of the study investigated 60 new subjects who were categorized into infraspinatus, erector spinae, or gastrocnemius group based on an identified latent MTrP. These subjects underwent TDN while monitoring biomechanical stiffness at baseline, immediately post TDN, and 24 hours later. Analysis: Discriminate ability, reliability, and correlations were calculated for measured stiffness variable across the three conditions of contraction in the first phase of the study. Differences between stiffness at baseline and after TDN were calculated in the second phase of the study. Results: Correlation of the two measurement methods in the three muscle regions was significant and strongest in the gastrocnemius. MyotonPRO reliability was excellent, and demonstrated ability to discriminate between the three levels of muscle contraction. In the second phase, immediate decreased stiffness was observed in the MTrP following TDN treatment. Significant decreased stiffness was found in in the erector spinae and gastrocnemius group who also demonstrated a localized twitch response during TDN. Stiffness returned to near baseline values after 24 hours. Discussion: The MyotonPRO® stiffness measurement was found to be reliable and discriminate across predefined muscle contraction intensities. TDN may cause an immediate change in stiffness but this change was not observed at 24 hours. It is not known whether these effects are present in a symptomatic population or related to improvements in other clinical outcomes. Future studies are necessary to determine if a decrease in biomechanical stiffness is an indication of patient improvement in pain and function.