164 research outputs found
Research on a safety evaluation system for railway-tunnel structures by fuzzy comprehensive evaluation theory
Long-term health detection of railway-tunnel is the development direction and trend of future railway tunnel research. Based on the actual engineering of a railway tunnel, this study developed a safety evaluation model for railway tunnel structures using a fuzzy comprehensive evaluation method and examined a health state evaluation method suitable for most railway tunnel structures. The results showed that the evaluation method comprehensively reflected the impact of various factors, which had strong practicality. The evaluation results were clear, accurate, and consistent with engineering practice. When using the safety factor index to study the stress of a railway tunnel structure, Midas/civil analysis showed that different levels of the surrounding rock structural vault in railway tunnels were in a tensile, control-bearing capacity state. When calculating safety factors, the range of a 60° central angle of a railway tunnel vault was calculated according to the tensile control-bearing capacity. Theoretical formulas of the range of the center angle φ0 of the vault tension zone were derived and then verified by experiments and numerical analysis
Shell-thickness-dependent photoinduced electron transfer from CuInS2/ZnS quantum dots to TiO2 films
We demonstrate the electron transfer (ET) processes from CuInS2/ZnS core/shell quantum dots (QDs) into porous anatase TiO2 films by time-resolved photoluminescence spectroscopy. The rate and efficiency of ET can be controlled by changing the core diameter and the shell thickness. It is found that the ET rates decrease exponentially at the decay constants of 1.1 and 1.4 nm–1 with increasing ZnS shell thickness for core diameters of 2.5 and 4.0 nm, respectively, in agreement with the electron tunneling model. This shows that optimized ET efficiency and QD stability can be realized by controlling the shell thickness
Longitudinal optical phonons in the excited state of CuBr quantum dots
The size dependence of the longitudinal optical (LO) phonons in the excited state of CuBr quantum dots (QD’s) in glass and NaBr crystals in the intermediate confinement regime was studied by means of persistent spectral hole burning spectroscopy. The phonon-exciton coupled states were clearly observed at a photon energy of about 2.993 eV when the LO phonon energy is close to the energy difference between the ground 1S and excited 1P states of CuBr QD’s in glass. The energies of the LO phonons observed in smaller CuBr QD’s in glass and NaBr crystals were determined to be about 18.6 and 17.6 meV, respectively, which are smaller than that of LO phonons in the bulk CuBr material. The energy softening of the LO phonons was explained in terms of the phonon renormalization
FluentSpeech: Stutter-Oriented Automatic Speech Editing with Context-Aware Diffusion Models
Stutter removal is an essential scenario in the field of speech editing.
However, when the speech recording contains stutters, the existing text-based
speech editing approaches still suffer from: 1) the over-smoothing problem in
the edited speech; 2) lack of robustness due to the noise introduced by
stutter; 3) to remove the stutters, users are required to determine the edited
region manually. To tackle the challenges in stutter removal, we propose
FluentSpeech, a stutter-oriented automatic speech editing model. Specifically,
1) we propose a context-aware diffusion model that iteratively refines the
modified mel-spectrogram with the guidance of context features; 2) we introduce
a stutter predictor module to inject the stutter information into the hidden
sequence; 3) we also propose a stutter-oriented automatic speech editing (SASE)
dataset that contains spontaneous speech recordings with time-aligned stutter
labels to train the automatic stutter localization model. Experimental results
on VCTK and LibriTTS datasets demonstrate that our model achieves
state-of-the-art performance on speech editing. Further experiments on our SASE
dataset show that FluentSpeech can effectively improve the fluency of
stuttering speech in terms of objective and subjective metrics. Code and audio
samples can be found at https://github.com/Zain-Jiang/Speech-Editing-Toolkit.Comment: Accepted by ACL 2023 (Findings
Bearing capacity and seismic performance of Y-shaped reinforced concrete bridge piers in a freeze-thaw environment
A quantitative study is performed to determine the performance degradation of Y-shaped reinforced concrete bridge piers owing to long-term freeze-thaw damage. The piers are discretized into spatial solid elements using the ANSYS Workbench finite element analysis software, and a spatial model is established. The analysis addresses the mechanical performance of the piers under monotonic loading, and their seismic performance under low-cycle repeated loading. The influence of the number of freeze-thaw cycles, axial compression ratio, and loading direction on the pier bearing capacity index and seismic performance index is investigated. The results show that freeze-thaw damage has an adverse effect on the ultimate bearing capacity and seismic performance of Y-shaped bridge piers in the transverse and longitudinal directions. The pier peak load and displacement ductility coefficient decrease with increasing number of freeze-thaw cycles. The axial compression ratio is an important factor that affects the pier ultimate bearing capacity and seismic performance. Upon increasing the axial compression ratio, the pier peak load increases and the displacement ductility coefficient decreases, the effects of which are more significant in the longitudinal direction
Construction and validation of prognostic scoring models to risk stratify patients with acquired immune deficiency syndrome-related diffuse large B cell lymphoma
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