| 1. |
- Mahajan, Anubha, et al.
(författare)
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Multi-ancestry genetic study of type 2 diabetes highlights the power of diverse populations for discovery and translation
- 2022
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Ingår i: Nature Genetics. - : Springer Nature. - 1061-4036 .- 1546-1718. ; 54:5, s. 560-572
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Tidskriftsartikel (refereegranskat)abstract
- We assembled an ancestrally diverse collection of genome-wide association studies (GWAS) of type 2 diabetes (T2D) in 180,834 affected individuals and 1,159,055 controls (48.9% non-European descent) through the Diabetes Meta-Analysis of Trans-Ethnic association studies (DIAMANTE) Consortium. Multi-ancestry GWAS meta-analysis identified 237 loci attaining stringent genome-wide significance (P < 5 x 10(-9)), which were delineated to 338 distinct association signals. Fine-mapping of these signals was enhanced by the increased sample size and expanded population diversity of the multi-ancestry meta-analysis, which localized 54.4% of T2D associations to a single variant with >50% posterior probability. This improved fine-mapping enabled systematic assessment of candidate causal genes and molecular mechanisms through which T2D associations are mediated, laying the foundations for functional investigations. Multi-ancestry genetic risk scores enhanced transferability of T2D prediction across diverse populations. Our study provides a step toward more effective clinical translation of T2D GWAS to improve global health for all, irrespective of genetic background. Genome-wide association and fine-mapping analyses in ancestrally diverse populations implicate candidate causal genes and mechanisms underlying type 2 diabetes. Trans-ancestry genetic risk scores enhance transferability across populations.
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| 2. |
- Surendran, Praveen, et al.
(författare)
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Discovery of rare variants associated with blood pressure regulation through meta-analysis of 1.3 million individuals
- 2020
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 52:12, s. 1314-1332
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Tidskriftsartikel (refereegranskat)abstract
- Genetic studies of blood pressure (BP) to date have mainly analyzed common variants (minor allele frequency > 0.05). In a meta-analysis of up to similar to 1.3 million participants, we discovered 106 new BP-associated genomic regions and 87 rare (minor allele frequency <= 0.01) variant BP associations (P < 5 x 10(-8)), of which 32 were in new BP-associated loci and 55 were independent BP-associated single-nucleotide variants within known BP-associated regions. Average effects of rare variants (44% coding) were similar to 8 times larger than common variant effects and indicate potential candidate causal genes at new and known loci (for example, GATA5 and PLCB3). BP-associated variants (including rare and common) were enriched in regions of active chromatin in fetal tissues, potentially linking fetal development with BP regulation in later life. Multivariable Mendelian randomization suggested possible inverse effects of elevated systolic and diastolic BP on large artery stroke. Our study demonstrates the utility of rare-variant analyses for identifying candidate genes and the results highlight potential therapeutic targets.
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| 3. |
- Afzal, Mohammad, 1987-, et al.
(författare)
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Adaptive control of normal load at the friction interface of bladed disks using giant magnetostrictive material
- 2020
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Ingår i: Journal of Intelligent Materials Systems and Structures. - : SAGE Publications. - 1045-389X .- 1530-8138. ; 31:8, s. 1111-1125
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Tidskriftsartikel (refereegranskat)abstract
- A novel application of magnetostrictive actuators in underplatform dampers of bladed disks is proposed for adaptive control of the normal load at the friction interface to achieve the desired friction damping in the structure. Friction damping in a bladed disk depends on operating parameters, such as rotational speed, engine excitation order, nodal diameter normal contact load, and contact interface parameters, such as contact stiffness and friction coefficient. The operating parameters have a fixed value, whereas the contact interface parameters vary in an unpredictable way at an operating point. However, the ability to vary some of these parameters such as the normal contact load in a controlled manner is desirable to attain an optimum damping in the bladed disk at different operating conditions. Under the influence of an external magnetic field, magnetostrictive materials develop an internal strain that can be exploited to vary the normal contact load at the friction interface, which makes them a potentially good candidate for this application. A commercially available magnetostrictive alloy, Terfenol-D is considered in this analysis that is capable of providing magnetostrain up to 2 × 10-3 under prestress and a blocked force over 1500 N. A linearized model of the magnetostrictive material, which is accurate enough for a direct current application, is employed to compute the output force of the actuator. A nonlinear finite element contact analysis is performed to compute the normal contact load between the blade platform and the underplatform damper as a result of magnetostrictive actuation. The nonlinear contact analysis is performed for different actuator mounting configurations and the obtained results are discussed. The proposed solution is potentially applicable to adaptively control vibratory stresses in bladed disks and consequently to reduce failure due to high-cycle fatigue. Finally, the practical challenges in employing magnetostrictive actuators in underplatform dampers are discussed.
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| 4. |
- Blanco, B., et al.
(författare)
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On the correction of rail accelerations predicted by numerical track models based on Timoshenko beam theory
- 2021
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 0042-3114 .- 1744-5159. ; , s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Rail accelerations can be used on the defect detection and health monitoring of railway vehicle and track components; therefore, mathematical models that predict this response are of interest for reproducing its behaviour in a wide range of situations. The numerical track models based on the Timoshenko beam theory introduce a non-physical response, which is especially noticeable in the rail accelerations. It is due to the lack of dynamic convergence of the Timoshenko finite element (FE). This paper addresses this phenomenon employing an enhanced formulation of the Timoshenko FE that includes internal degrees of freedom (iDoF). The iDoF shape functions are derived from the Timoshenko beam dynamic governing equations. Firstly, the formulation is presented, and its performance is compared with a similar Timoshenko FE formulation. Secondly, the proposal is assessed in the dynamic modelling of railway track structures. The use of iDoF efficiently corrects the non-physical response of rail accelerations by improving the FE dynamic convergence. Subsequently, a filtering criterion for accelerations is proposed, which removes the remaining non-physical response while guaranteeing the conservation of coherent frequency content. Finally, practical cases are simulated for which the proposed methodology is proved to be more efficient and reliable than the standard approach.
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| 5. |
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| 6. |
- Coja, Michael, et al.
(författare)
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Using Waveguides to Model the Dynamic Stiffness of Pre-Compressed Natural Rubber Vibration Isolators
- 2021
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- A waveguide model for a pre-compressed cylindrical natural rubber vibration isolator is developed within a wide frequency range-20 to 2000 Hz-and for a wide pre-compression domain-from vanishing to the maximum in service, that is 20%. The problems of simultaneously modeling the pre-compression and frequency dependence are solved by applying a transformation of the pre-compressed isolator into a globally equivalent linearized, homogeneous, and isotropic form, thereby reducing the original, mathematically arduous, and complex problem into a vastly simpler assignment while using a straightforward waveguide approach to satisfy the boundary conditions by mode-matching. A fractional standard linear solid is applied as the visco-elastic natural rubber model while using a Mittag-Leffler function as the stress relaxation function. The dynamic stiffness is found to depend strongly on the frequency and pre-compression. The former is resulting in resonance phenomena such as peaks and troughs, while the latter exhibits a low-frequency magnitude stiffness increase in addition to peak and trough shifts with increased pre-compressions. Good agreement with nonlinear finite element results is obtained for the considered frequency and pre-compression range in contrast to the results of standard waveguide approaches.
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| 7. |
- Cronhjort, Mikael, et al.
(författare)
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Nationellt erfarenhetsutbyte och utmaningar för civilingenjörsutbildning
- 2020
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Ingår i: Proceedings of 7:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar. ; , s. 231-232
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Konferensbidrag (refereegranskat)abstract
- Vi vill i en workshop identifiera behovoch intresse för att bilda ett nätverk för civilingenjörsutbildningar i Sverige. Vi tror att det kan finnas ett behov av etteget forum för att diskutera utmaningar som är specifika förcivilingenjörsutbildningar. Vi presenterar här några förslag påområden som vi på KTH tror att kan vara intressanta att ta uppi ett sådant nätverk, men vi är mycket intresserade av att läraoss om vilka utmaningar som uppfattas som intressanta ochviktiga på andra lärosäten.
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| 8. |
- Erenchun, Aitor, et al.
(författare)
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Effect of lubrication on the mechanical behavior of magnetorheological elastomers in compression mode
- 2022
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Ingår i: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 111
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the lubrication on the mechanical behavior of magnetorheological elastomers (MREs) in compression mode is experimentally studied. According to ISO 7743, there are two procedures to characterize specimens in compression mode. Differences in the properties of these materials between lubricated and nonlubricated conditions must be considered if devices such as vibration absorbers and isolators are to be developed. With lubrication, compression is said to be uniaxial and homogeneous, thus material properties can be obtained. Without lubrication, tests are easier to perform but results are strongly dependent on the piece shape. In this study isotropic and anisotropic MREs with iron particle volume concentrations of 10, 20, 30 and 40% are tested under different strain amplitudes, prestrain and magnetic fields for a frequency range up to 300 Hz, with and without lubrication. Important design parameters like amplitude, frequency and magnetic field dependency are showed to be dependent on lubrication.
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| 9. |
- Erenchun, A., et al.
(författare)
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Model of an elevator system to characterize the influence of the isolator on the vibration transmission
- 2020
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Ingår i: Proceedings International Conference on Noise and Vibration Engineering (ISMA2020) / International Conference on Uncertainty in Structural Dynamics (USD). - : KU Leuven. ; , s. 2715-2729
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Konferensbidrag (refereegranskat)abstract
- Vibrations are a common issue in elevator installations, where a drive machine that holds and pulls the cabin and the counterweight composes the electromechanical system. In order to reduce the space needed by the installation, nowadays the drive machine is usually mounted upon a frame that is fixed to the guide rails. Therefore, vibration transmission can occur through the machine to the cabin or even to the building. With the purpose of reducing this vibration transmission, the use of isolators under the machine is a widely employed solution. These isolators are often selected just taking into account the static loads, due to the lack of information about the dynamic behavior of the system. The present research develops a theoretical model of an elevator system to study the influence of the isolators on vibration transmission.
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| 10. |
- Gomez, Erik
(författare)
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Centrifugal pendulum vibration absorbers in heavy-duty truck powertrains : Modelling, simulation and experimental investigations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The heavy-duty vehicle industry is facing big challenges to reduce CO2 emissions. Although electrification is on the rise, the combustion engine will used for some time to come. Unfortunately, CO2 reduction methods, such as downspeeding, down-sizing and increased cylinder gas-pressure, result in increased torsional vibrations and noise which must be addressed. Conventional torsional vibration reduction methods alone, such as the clutch-damper, will not suffice. The centrifugal pendulum vibration absorber (CPVA) is a torsional vibration reduction device that has not conventionally been used in heavy-duty vehicles and is herein investigated.This work presents analytical, simulation and experimental investigations of the CPVA. First, a model of a centrifugal pendulum vibration absorber with a general suspension architecture is derived with Kane's method. The model allows for different pendulum paths and relative rotation of the pendulum body with respect to the rotor. A normal-force friction loss of the pendulum is developed together with a measurement method to determine the friction coefficient. The measurement method may also be used to validate the pendulum model parameters without any special test-apparatus other than standard accelerometers and a data acquisition system. The developed CPVA model is then included in a torsional model of the complete powertrain including gas-pressure based excitation from the engine model. The powertrain model is developed to simulate transient and quasi-steady state conditions in the time-domain. Also, a continuous model of the end-stops of the pendulum are implemented which also facilitates the simulation.It is concluded that it is important to include the system dynamics of the powertrain in the final design of the CPVA. Also, by exploiting the frequency veering property of the CPVA, powertrain resonances can be completely eliminated.
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