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نتیجه جستجو - لایه برداری

تعداد مقالات یافته شده: 3
ردیف عنوان نوع
1 Delamination analysis using cohesive zone model: A discussion on traction-separation law and mixed-mode criteria
تجزیه و تحلیل لایه لایه شدن با استفاده از مدل منطقه منسجم: بحث در مورد قانون جداسازی کشش و معیارهای حالت مختلط-2020
A discussion on cohesive zone model formulation for prediction of interlaminar damage in composite laminates is presented in this paper. The degradation of interlaminar mechanical properties is analysed from a physical point of view. Firstly, the damage evolution is evaluated according to the traction-separation law and it is demonstrated that if a linear elastic unloading/ reloading curve is assumed, the softening function must also be linear. Secondly, issues regarding damage onset and fracture criteria in mixed-mode loading are critically addressed and commented. A new set of criteria is proposed, and the limitations of existing criteria are discussed.
Keywords: Cohesive zone modelling | Fracture mechanics | Finite element analysis (FEA) | Delamination | Interface fracture
مقاله انگلیسی
2 A PAPR reduction scheme combining superimposed O-OFDM and M-law mapping for VLC-OFDM systems
یک طرح کاهش PAPR ترکیبی از نقشه برداری O-OFDM و لایه برداری قانون برای سیستم های VLC-OFDM-2020
Due to the high peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals, the inherent nonlinearity of light emitting diodes (LEDs) is a challenge for optical OFDM (O-OFDM) schemes in visible light communication (VLC) systems. In order to reduce PAPR to mitigate the effects of the nonlinearity of LEDs, and avoid the asymmetric clipping interference in the conventional hybrid OOFDM schemes, a novel superimposed O-OFDM scheme is proposed in this paper, which reduce the PAPR by combining the ????-law mapping and the superposition modulation. Moreover, at the transmitter, the hybrid O-OFDM components are superimposed in an interference-free way, the receiver does not require the operation of interference cancellation, and the symbols of each branch can be demodulated independently. Simulation results verify that the proposed scheme can significantly reduce the PAPR. At the same time, the comprehensive performance of the proposed scheme outperforms other competing schemes under the constraints of the nonlinearity and limited dynamic range of LEDs.
Keywords: Visible light communications | Optical orthogonal frequency division | multiplexing | Peak-to-average power ratio | M-law mapping | LED nonlinearity
مقاله انگلیسی
3 Acoustic emission monitoring of containment structures during posttensioning
نظارت بر انتشار صوتی ساختارهای مهار شده در زمان پس از فشار خون-2019
This paper introduces a method based on acoustic emission (AE) to monitor the onset of delamination in posttensioned concrete containment structures. The method is based on clustering AE occurring during post-tensioning and/or re-tensioning such structures. In particular, the investigation is focused on AE of a large-scale, curved concrete wall subject to monotonically increasing prestressing forces. This specimen is a representative of typical cylindrical concrete structures, such as water storage tanks, silos, bins, and nuclear containment structures. To analyze AE data, this paper uses both time-driven and hit-driven features extracted from AE. To this end, a novel approach is proposed to analyze and visualize hit-driven features. To detect and localize such defects, the proposed approach identifies an optimal number of clusters in AE data and interprets each cluster based on the physical mechanism that generates it. Such interpretations are compared with the state of stresses and modified Mohr–Coulomb failure criteria. The results show that the AE events are due to three categories of source mechanisms, micro shear cracking, micro tensile cracking, and macro delamination cracking. To validate the results, comparisons are made with through-thickness expansion measurements of the wall. The results demonstrate that the proposed approach can detect delamination defects and enable decision makers to take remedial and preventive actions.
Keywords: Acoustic emission | K-means clustering | Delamination | Containment structures | Pattern recognition | Concrete structures | Post-tensioning | Structural health monitoring
مقاله انگلیسی
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