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- Andersson, Håkan, et al.
(författare)
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Simulation of leakage flow through dynamic sealing gaps in hydraulic percussion units using a co-simulation approach
- 2021
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Ingår i: Simulation (San Diego, Calif.). - : Elsevier B.V.. - 1569-190X .- 1878-1462. ; 111
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a previously developed co-simulation method has been expanded to also simulate the dynamic behaviour of sealing gap regions in hydraulic percussion units. This approach is based on a 1D system model representing the fluid components and a 3D finite element model representing the structural parts of a hydraulic hammer. The sealing gap is a fundamental feature of a percussion unit, where the reciprocating motion of the piston is generated by the valve mechanism of the sealing gap. When the gap is closed it will prevent fluid flow between regions of different pressure levels. However, a small leakage flow through the gap will always occur which size depends on the clearance and the position of the piston. The method proposed here will take the structural motion and deformation into consideration when calculating the leakage flow. The deformed state of the structure is approximated by a cylindrical surface, in a least square manner, and communicated through the co-simulation interface to the fluid simulation module, and then used when calculating the leakage flow. This method aims at a more accurate simulation of the leakage flow that will not only yield a more realistic description of the mechanism on the local level, but also a more accurate estimation of global parameters such as overall performance and efficiency. The results indicate that the simulated leakage flow will decrease when dynamic gaps are used in comparison to static gaps, which is a consequence of the deformed structure that will generate smaller clearances. The leakage flow for the dynamic gaps will even be lower than for the static perfectly concentric case, mainly due to the reduction of clearances. The results also indicate that the dynamic eccentricity does not have a major influence on the leakage flow. The outcome from this study highlights the potentials of the described co-simulation approach for analysing the dynamics of the sealing gaps in a hydraulic percussion unit (i.e. gap heights, eccentricity ratios, etc.) including the evaluation of leakage flows and its impact on the overall performance. © 2021
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- Andersson, Håkan, et al.
(författare)
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Validation of a co-simulation approach for hydraulic percussion units applied to a hydraulic hammer
- 2019
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Ingår i: Advances in Engineering Software. - : ELSEVIER SCI LTD. - 0965-9978 .- 1873-5339. ; 131, s. 102-115
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a previously developed co-simulation approach has been adopted to simulate the responses of an existing hydraulic hammer product. This approach is based on a 1D system model representing the fluid components and a 3D finite element model representing the structural parts of the hydraulic hammer. The simulation model was validated against four experiments with different running conditions. The corresponding set-ups were analysed using the co-simulation method in order to evaluate the overall responses. A parameter study was also performed involving the working pressure and the restrictor diameter, with the objective to validate that a parameter change in the simulation model will affect the input and output power in the same direction as in the experiments. The experimental responses used in the validation were time history data of fluid pressure, component position and acceleration, and structural stresses. The experiments result in high frequency and high amplitude excitations of the hydraulic hammer and thus require a model with a high resolution of the model dynamics. The conclusion of the validation is that the simulation model is able to replicate the experimental responses with high accuracy including the high frequency dynamics. The favourable outcome of the validation makes the described co-simulation approach promising as an efficient tool for a wide range of other applications where short time duration mechanisms need to be studied.
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- Lundin, M., et al.
(författare)
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Diffusely Increased Myocardial Extracellular Volume with or without Focal Late Gadolinium Enhancement: Prevalence and Associations with Left Ventricular Size and Function
- 2022
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Ingår i: Journal of Thoracic Imaging. - 0883-5993 .- 1536-0237. ; 37:1, s. 17-25
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Myocardial extracellular volume fraction (ECV) using cardiovascular magnetic resonance (CMR) can identify diffuse lesions not detected by late gadolinium enhancement (LGE). We aimed to determine the prevalence of increased ECV and its relation to other CMR findings. Materials and Methods: Consecutive patients (n=609, age median [interquartile range] 53 [39 to 66] y, 62% male) underwent CMR at 1.5 T. Focal lesions on LGE images were noted. ECV in regions without focal LGE findings defined diffuse changes. Pronounced increases in left ventricular (LV) end-diastolic volume index and LV mass index, and pronounced decreases in LV ejection fraction were defined as >3 SD from the sex-specific mean in healthy volunteers. Results: Of 609 patients without amyloidosis or hypertrophic cardiomyopathy, 8% had diffusely increased ECV and 5% of all patients had diffusely increased ECV without any focal LGE findings. Multivariate analysis showed that a pronounced increase in the LV end-diastolic volume index was associated with increased ECV (P=0.001), but not LGE (P=0.52). A pronounced decrease in LV ejection fraction was associated with the presence of LGE (P<0.001), but not with increased ECV (P=0.41). Conclusions: Eight percent of patients in this clinical cohort with known or suspected heart disease had diffusely increased ECV and 60% of these lacked focal LGE findings. LV size is independently associated with increased ECV, whereas systolic dysfunction is independently associated with LGE. This image-based clinical study demonstrates that ECV-CMR provides additional information negligibly related to the results of LGE imaging, and thereby increases the diagnostic yield of CMR. © 2020 Lippincott Williams and Wilkins. All rights reserved.
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- Micheal Raj, Pushparani, et al.
(författare)
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Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies
- 2021
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:47, s. 29859-29869
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Tidskriftsartikel (refereegranskat)abstract
- Some of the most fundamental chemical building blocks of life on Earth are the metal elements. X-ray absorption spectroscopy (XAS) is an element-specific technique that can analyse the local atomic and electronic structure of, for example, the active sites in catalysts and energy materials and allow the metal sites in biological samples to be identified and understood. A microfluidic device capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions is presented in this work. The device is evaluated at the K-edges of iron and bromine and the L-3-edge of lead, in both transmission and fluorescence mode detection and in a wide range of sample concentrations, as low as 0.001 M. The device is fabricated in silicon and glass with plasma etched microchannels defined in the silicon wafer before anodic bonding of the glass wafer into a complete device. The device is supported with a well-designed printed chip holder that made the microfluidic device portable and easy to handle. The chip holder plays a pivotal role in mounting the delicate microfluidic device on the beamline stage. Testing validated that the device was sufficiently robust to contain and flow through harsh acids and toxic samples. There was also no significant radiation damage to the device observed, despite focusing with intense X-ray beams for multiple hours. The quality of X-ray spectra collected is comparable to that from standard methods; hence we present a robust microfluidic device to analyse liquid samples using synchrotron XAS.
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- Raj, Pushparani, et al.
(författare)
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Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies
- 2021
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Ingår i: RSC Advances. - Cambridge : RSC Publishing. - 2046-2069. ; 11:47, s. 29859-29869
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Tidskriftsartikel (refereegranskat)abstract
- Some of the most fundamental chemical building blocks of life on Earth are the metal elements. X-ray absorption spectroscopy (XAS) is an element-specific technique that can analyse the local atomic and electronic structure of, for example, the active sites in catalysts and energy materials and allow the metal sites in biological samples to be identified and understood. A microfluidic device capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions is presented in this work. The device is evaluated at the K-edges of iron and bromine and the L3-edge of lead, in both transmission and fluorescence mode detection and in a wide range of sample concentrations, as low as 0.001 M. The device is fabricated in silicon and glass with plasma etched microchannels defined in the silicon wafer before anodic bonding of the glass wafer into a complete device. The device is supported with a well-designed printed chip holder that made the microfluidic device portable and easy to handle. The chip holder plays a pivotal role in mounting the delicate microfluidic device on the beamline stage. Testing validated that the device was sufficiently robust to contain and flow through harsh acids and toxic samples. There was also no significant radiation damage to the device observed, despite focusing with intense X-ray beams for multiple hours. The quality of X-ray spectra collected is comparable to that from standard methods; hence we present a robust microfluidic device to analyse liquid samples using synchrotron XAS.
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- Ramos, J. G., et al.
(författare)
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Comprehensive Cardiovascular Magnetic Resonance Diastolic Dysfunction Grading Shows Very Good Agreement Compared With Echocardiography
- 2020
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Ingår i: Jacc-Cardiovascular Imaging. - : Elsevier BV. - 1936-878X .- 1876-7591. ; 13:12, s. 2530-2542
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES The aims of this study were to develop a comprehensive cardiovascular magnetic resonance (CMR) approach to diastolic dysfunction (DD) grading and to evaluate the accuracy of CMR in the diagnosis of DD compared with echocardiography. BACKGROUND Left ventricular DD is routinely assessed using echocardiography. METHODS Consecutive clinically referred patients (n = 46; median age 59 years; interquartile range: 46 to 68 years; 33% women) underwent both conventional echocardiography and CMR. CMR diastolic transmitral velocities (E and A) and myocardial tissue velocity (e0) were measured during breath-hold using a validated high-temporal resolution radial sector-wise golden-angle velocity-encoded sequence. CMR pulmonary artery pressure was estimated from 4-dimensional flow analysis of blood flow vortex duration in the pulmonary artery. CMR left atrial volume was measured using the biplane long-axis area-length method. Both CMR and echocardiographic data were used to perform blinded grading of DD according to the 2016 joint American and European recommendations. RESULTS Grading of DD by CMR agreed with that by echocardiography in 43 of 46 cases (93%), of which 9% were normal, 2% indeterminate, 63% grade 1 DD, 4% grade 2 DD, and 15% grade 3 DD. There was a very good categorical agreement, with a weighted Cohen kappa coefficient of 0.857 (95% confidence interval: 0.73 to 1.00; p < 0.001). CONCLUSIONS A comprehensive CMR protocol for grading DD encompassing diastolic blood and myocardial velocities, estimated pulmonary artery pressure, and left atrial volume showed very good agreement with echocardiography. (C) 2020 by the American College of Cardiology Foundation.
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