| 1. |
- Wik, V. M., et al.
(författare)
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Castor Oil-based Polyurethanes Containing Cellulose Nanocrystals
- 2011
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 51:7, s. 1389-1396
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Tidskriftsartikel (refereegranskat)abstract
- Partially foamed and nanocellulose-reinforced polyurethanes (PU) based on castor oil (CO) were prepared and their different properties were measured and related to their structures. A castor oil-based polyol (COPO) was obtained by alcoholysis of CO with triethanolamine. The COPO was used in the preparation of partially foamed and solid PU. Cellulose nanofibrils (NC) in the range of the rheological percolation content were incorporated to the materials and the final mechanical properties of these nanocomposites were analyzed. The incorporated NC considerably affected the rheology of the suspensions, which presented solid-like behavior under frequency sweep tests with the addition of only 0.5 wt% of NC. By increasing the NC concentration the dispersion becomes increasingly difficult. The properties of the solid PU were also affected by the incorporation of NC and a significant increase of the tensile modulus was observed for the 0.5 wt% NC composite, compared to the unfilled solid PU. This behavior was associated to the incorporation of the rigid particle reinforcement and the interfacial bonding. As expected, the partially foamed PU showed lower modulus than the corresponding solid PU.
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| 2. |
- Casas-Ordaz, A., et al.
(författare)
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Enhancing image thresholding segmentation with a novel hybrid battle royale optimization algorithm
- 2024
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Ingår i: Multimedia tools and applications. - : Springer Nature. - 1380-7501 .- 1573-7721.
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Tidskriftsartikel (refereegranskat)abstract
- Accurate image segmentation is crucial in digital image processing, enabling efficient image analysis and robust vision systems. However, segmentation is a complex task as images vary in their characteristics, and the computational costs increase with the number of classes involved. To address these challenges, incorporating metaheuristic algorithms to guide the segmentation process presents an exciting opportunity for improvement. This research paper introduces a novel multilevel image segmentation approach that leverages a hybrid battle royale optimization algorithm. By combining opposition-based learning, highly disruptive polynomial mutation, differential evolution mutation, and crossover operators, the proposed method enhances the original battle royale optimization algorithm and effectively solves the segmentation problem. To evaluate the effectiveness of the proposed approach, the minimum cross-entropy criterion is applied to two sets of reference images that undergo multilevel thresholding with up to five thresholds. The results are compared with those obtained using nine other metaheuristic algorithms, employing various image quality metrics such as peak signal noise ratio, structural similarity index method, feature similarity index method, quality index based on local variance, Haar wavelet-based perceptual similarity index, and universal image quality index. The results are analyzed quantitatively, qualitatively, and statistically. The findings demonstrate the potential of the proposed approach in achieving high-quality multilevel thresholding image segmentation. Additionally, the hybrid battle royale optimization algorithm showcases its robustness and efficiency when compared to the other metaheuristic algorithms tested. Notable results are PSNR = 2.13E+01, SSIM = 8.41E-01, FSIM = 8.42E-01, QILV = 8.94E-01, HPSI = 6.52E-01, and UIQI = 9.78E-01.
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| 3. |
- Nunez, A. J., et al.
(författare)
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Toughening of wood particle composites - Effects of sisal fibers
- 2006
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 101:3, s. 1982-1987
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Tidskriftsartikel (refereegranskat)abstract
- Sisal fibers were added to wood particle composites to enhance their toughness. The selected matrix was a commercial styrene diluted unsaturated polyester thermoset resin. Fracture tests were carried out using single-edge notched beam geometries. Stiffness, strength, critical stress intensity factor K-IQ, and work of fracture W-f of notched specimens were determined. The incorporation of sisal fibers into wood particle composites significantly changed the fracture mode of the resulting hybrid composite. For the neat matrix and the wood particle composites, once the maximum load was reached, the crack propagated in a catastrophic way. For hybrid composites, fiber bridging and pull-out were the mechanisms causing increased crack growth resistance. Addition of a 7% wt of sisal fibers almost doubled the K-IQ value of a composite containing 12% wt of woodflour. Moreover, the W-f increased almost 10-fold, for the same sample. In general, the two composite toughness parameters K-IQ and W-f increased when the fraction of sisal fibers was increased.
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