| 1. |
- Barack, Leor, et al.
(author)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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In: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Research review (peer-reviewed)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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| 2. |
- Qian, Cheng, et al.
(author)
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Calibration of the ISO tapping machine for finite-element prediction tool on a wooden-base floor
- 2019
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In: Building Acoustics. - 1351-010X. ; 26:3, s. 157-167
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Journal article (peer-reviewed)abstract
- One important challenge of the wooden constructions is to achieve a high quality of acoustic insulation, especially decreasing the impact noise in the low-frequency range. In order to avoid over-designed solutions and expensive experimental tests in the design phase, reliable prediction tools are called for. This article is an initial investigation of modeling the ISO standardized tapping machine on a cross-laminated timber floor, using finite element method. The wooden-based floor was first calibrated in terms of its dynamic properties. The influence of the material properties of the cross-laminated timber floor was discussed. The force generated by the tapping machine was then introduced in the established cross-laminated timber model. The model was finally validated by comparing the simulation results with the measured accelerations.
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| 3. |
- Qian, Cheng, et al.
(author)
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Development of a vibroacoustic stochastic finite element prediction tool for a CLT floor
- 2019
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In: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 9:6
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Journal article (peer-reviewed)abstract
- Low frequency impact sound insulation is a challenging task in wooden buildings. Low frequency prediction tools are needed to access the dynamic behavior of a wooden floor in an early design phase to ultimately reduce the low frequency impact noise. However, due to the complexity of wood and different structural details, accurate vibration predictions of wood structures are difficult to attain. Meanwhile, a deterministic model cannot properly represent the real case due to the uncertainties coming from the material properties and geometrical changes. The stochastic approach introduced in this paper aims at quantifying the uncertainties induced by material properties and proposing an alternative calibration method to obtain a relative accurate result instead of the conventional manual calibration. In addition, 100 simulations were calculated in different excitation positions to assess the uncertainties induced by material properties of cross-laminated-timber A comparison between the simulated and measured results was made in order to extract the best combination of Young's moduli and shear moduli in different directions of the CLT panel.
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| 4. |
- Qian, Cheng, et al.
(author)
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Development of stochastic finite prediction element model for CLT floors
- 2019
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Conference paper (other academic/artistic)abstract
- One of the important challenges for wooden construction is to assure good sound insulation in low-frequency range. To that end, it is important to establish reliable prediction tools to reduce the number of experimental tests and the costs. The study reported here is a first investigation aiming at developing a reliable numerical model to predict the vibration behavior of a cross-laminated timber (CLT) floor in low-frequency range. More specifically, and in order to give more meaningful and useful inputs, stochastic simulations were applied to the CLT finite-element (FE) model, in using the measurement data as the canonical reference. A comparison between the conventional manual calibration and the stochastic calibration by tuning the material properties of the target modeling was subsequently made to evaluate the performance of the stochastic method employed. It was shown that this stochastic method gives an alternative to mimic the dynamic behavior of wooden construction elements without tedious manual calibrations when the data base of the material properties is missing. Meanwhile, the stochastic method included in the FE model also allows to take into account the uncertainties of the wooden materials which are not always under control because of the diversity and nature of wood.
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