Current Issue : October-December Volume : 2024 Issue Number : 4 Articles : 5 Articles
Civil infrastructures require a permanent attention and maintenance from the moment of commissioning to moment of demolition. One important aspect which is mandatory to be taken into consideration is crack detection. Cracks can appear during the lifetime of the civil infrastructure and require specialized personal for assessment. Depending of the civil infrastructure, this operation can require specialized skills (such as climbing). To overcome this issue with regards to specialized manpower, image processing is used. Nowadays, images can be easily acquired using an unmanned aircraft vehicle system known also as a drone. The main advantages of a drone for civil infrastructure image acquisition are: i) it can be operated at different heights, ii) rapid data collection, iii) cost and time savings, iv) user-friendly interface.The main purpose of our paper resides in improving the accuracy of the pre-trained neural networks when noisy images are used in civil works. Throughout our research, we used a dataset which contains three classes of images: with cracks, without cracks and with noise. To remove the noise presented in images mathematical morphology operators (MMO) are used. Our results reveal that using opening operator filter on a dataset of images which present civil infrastructure cracks outperform the results obtained using only pre-trained neural networks. In addition, the computation time is reduced....
The paper explores the linear and nonlinear dynamic interaction between the reactor and the auxiliary buildings of an idealized Nuclear Power Plant (NPP) on a realistic layered soil profile, aiming to exemplify the significance of structure–soil–structure interaction (SSSI) modelling in designing or re-evaluating critical structures, such as NPPs. Based on realistic geometrical assumptions, high-fidelity 3D finite element (FE) models of increasing sophistication are created in the Real-ESSI Simulator. Starting with elastic soil conditions and assuming tied soil–foundation interfaces, it is shown that the rocking vibration mode of the soil–reactor building system is amplified by the presence of the auxiliary building through a detrimental out-of-phase rotational interaction mechanism. Adding nonlinear interfaces, which allow for soil–foundation detachment during seismic shaking, introduces higher excitation frequencies (above 10 Hz) in the foundation of the reactor building, leading to amplification effects in the resonant vibration response of the biological shield wall inside the reactor building. A small amount of sliding at the soil–foundation interface of the auxiliary building slightly decreases its response, thus reducing its aforementioned negative effects on the reactor building. When soil nonlinearity is accounted for, the rocking vibration mode of the soil–reactor building system almost vanishes, due to the local nonlinear response of the underlying soil. This leads to a beneficial out-of-phase horizontal interaction mechanism between the two buildings that reduces the spectral accelerations at critical points inside the reactor building by up to 55 % for frequencies close to the resonant vibration frequency of the auxiliary building. This showcases the key role of SSSI modelling, and essentially implies that the neighboring buildings could offer mutual seismic protection to each other, in a similar way to the recently emerged seismic resonant metamaterials, provided that they are properly tuned during the design phase, accounting for soil and soil–foundation interface nonlinearities....
Ceramic materials have a very long tradition of use in construction. Their durability is related to the surface of the material and the action of the corrosive environment. One of the corrosive factors acting on ceramic materials is microorganisms. They can contribute to the deterioration of the technical and performance properties of building materials. Aesthetic, physical, and chemical deterioration are considered to be the main destructive processes in ceramic materials. This work shows how the different types of the most commonly used ceramic materials, i.e., brick and tiles, are damaged. Each of these types is susceptible to microbial growth. Most microorganisms that occur on ceramic materials produce staining substances and thus form coloured biofilms. The direct action of metabolic products secreted by organisms on inorganic substrates is the main cause of chemical biodeterioration. Therefore, this work presents the impact of microorganisms on ceramic building materials....
Al4SiC4 is a ternary wide-band-gap semiconductor with a high strength-to-weight ratio and excellent oxidation resistance. It consists of slabs of Al4C3 separated by SiC layers with the space group of P63mc. The space group allows Si to occupy two different 2a Wykoff sites, with previous studies reporting that Si occupies only one of the two sites, giving it an ordered structure. Another hitherto unexplored possibility is that Si can be randomly distributed on both 2a sites. In this work, we revisit the published ordered crystal structure using experimental methods and density functional theory (DFT). Al4SiC4 was synthesized by high-temperature sintering at 1800 °C from a powder mixture of Al4C3 and SiC. Neutron diffraction confirmed that Al4SiC4 crystallized with the space group of P63mc, with diffraction patterns that could be fitted to both the ordered and the disordered structures. Scanning transmission electron microscopy, however, provided clear evidence supporting the latter, with DFT calculations further confirming that it is 0.16 eV lower in energy per Al4SiC4 formula unit than the former. TEM analysis revealed Al vacancies in some of the atomic layers that can introduce p-type doping and direct band gaps of 0.7 and 1.2 eV, agreeing with our optical measurements. Finally, we propose that although the calculated formation energy of the Al vacancies is high, the vacancies are stabilized by entropy effects at the high synthesis temperature. This indicates that the cooling procedure after high-temperature synthesis can be important in determining the vacancy content and the electronic properties of Al4SiC4....
Loess has unique water sensitivity due to its distinct formation environment. The structure of loess is undercompactness, weak cementation, and porousness. The water sensitivity of loess directly leads to many environmental problems and geological hazards, including subgrade subsidences, slope collapse or failures, and building cracking. To reveal the relationship between water sensitivity and loess structure, confined-compression collapsibility tests and triaxial-collapsibility tests were performed on loess in different areas. The collapsibility coefficient, porosity ratio, and collapsibility rate were analyzed. Results show that the collapsibility process of loess can be divided into three stages: wetting, softening, and settling. The collapsibility sensitivity of loess is determined primarily by its structural and hydraulic state....
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