Journal of Engineering and Thermal Sciences
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Prestressed concrete continuous bridge girders: comparison of the Chinese and Southern African codes
Get PDFTo provide a reference for designers, taking a 30 m + 40 m + 30 m prestressed concrete continuous beam bridge as an example, this paper compares the differences between Chinese Codes and Southern African Codes in terms of load effect, prestressing requirements and design safety. The results show that the actual number of prestressed strands required by the Southern African Code in the mid-span section is 11.63 %-12.50 % larger than that required by the Chinese Code. The actual number of prestressed strands required by the Southern African Code in the fulcrum section is 16.33 %-30.00 % lower than that required by the Chinese Code. The safety margin factor of the section designed by the Southern African Code is higher than that of the Chinese Code, and has a higher safety reserve
Binary rat swarm optimizer algorithm for computing independent domination metric dimension problem
Get PDFIn this article, we look at the NP-hard problem of determining the minimum independent domination metric dimension of graphs. A vertex set B of a connected graph G(V,E) resolves G if every vertex of G is uniquely recognized by its vector of distances to the vertices in B. If there are no neighboring vertices in a resolving set B of G, then B is independent. Every vertex of G that does not belong to B must be a neighbor of at least one vertex in B for a resolving set to be dominant. The metric dimension of G, independent metric dimension of G, and independent dominant metric dimension of G are, respectively, the cardinality of the smallest resolving set of G, the minimal independent resolving set, and the minimal independent domination resolving set. We propose the first attempt to use a binary version of the Rat Swarm Optimizer Algorithm (BRSOA) to heuristically calculate the smallest independent dominant resolving set of graphs. The search agent of BRSOA are binary-encoded and used to identify which one of the vertices of the graph belongs to the independent domination resolving set. The feasibility is enforced by repairing search agent such that an additional vertex created from vertices of G is added to B, and this repairing process is repeated until B becomes the independent domination resolving set. Using theoretically computed graph findings and comparisons to competing methods, the proposed BRSOA is put to the test. BRSOA surpasses the binary Grey Wolf Optimizer (BGWO), the binary Particle Swarm Optimizer (BPSO), the binary Whale Optimizer (BWOA), the binary Gravitational Search Algorithm (BGSA), and the binary Moth-Flame Optimization (BMFO), according to computational results and their analysis
An effective simulation scheme for the prediction of aerodynamic environment under hypersonic conditions characterized by NACA0012
Get PDFCurrently, aerodynamic environment prediction research into scramjet-propelled vehicles characterized by NACA0012 under hypersonic conditions is relatively sparse. Two-dimensional external flow field models are established, and then through validation tests, we perform a systematic investigation between simulation parameters and prediction accuracy, and an effective aerodynamic environment prediction simulation scheme under hypersonic conditions is proposed. Unlike under incompressible conditions, the maximum accuracy decline could be attributed to the inappropriate choice of the sharp trailing edge modeling method, but the definition formula is still preferred. In particular, for the two modeling data point sources, Airfoil tools and NACA4, the numerical performance of the latter is better than the former, and the calculation accuracy negatively correlates with the number of data points offered by both of them. Moreover, for the mesh cells near the shock, the cell Reynolds number and aspect ratio values should be no smaller than 16 and not exceed 380, respectively, and the recommended values for the far field distance, the turbulence model and flux type are 16L, Spalart-Allmaras, and ROE flux type. Under hypersonic conditions, the aerodynamic environment characterized by NACA0012 predicts a maximum temperature of approximately 1856.85 °C, with an average temperature change rate of 77 °C/s. Meanwhile, the top sound pressure level and the vibration acceleration could reach up to 145 dB and 182 g, respectively
Fault diagnosis of rolling bearing based on hierarchical discrete entropy and semi-supervised local Fisher discriminant analysis
Get PDFThis paper addresses challenges in extracting effective information from rolling bearing fault signals and handling strong correlations and information redundancy in high-dimensional feature samples post-extraction. A rolling bearing fault diagnosis method is proposed on the basis of hierarchical discrete entropy (HDE) combined with semi-supervised local Fisher discriminant analysis (SELF). Firstly, hierarchical discrete entropy is extracted from signals preprocessed via variational mode decomposition. We assess entropy stability under different parameters using the coefficient of variation and select optimal parameters accordingly. Secondly, we employ the SELF method to remap the multidimensional feature sample set extracted, performing dimensionality reduction. Finally, a fault diagnosis model classifies the dimensionality-reduced feature samples for fault identification. Experimental results demonstrate that entropy samples extracted via HDE achieve higher diagnostic accuracy after dimensionality reduction with the SELF method. Specifically, accuracy rates of 100 % and 98.2 % are achieved for two types of fault samples, respectively, validating the feasibility and effectiveness of our approach
YOLOv3-MSSA based hot spot defect detection for photovoltaic power stations
Get PDFWith the continuous development of the energy industry, photovoltaic power generation is gradually becoming one of the main power generation methods. However, detecting hot spot defects in photovoltaic power stations is challenging. Therefore, enhancing detection efficiency using information technology has become a crucial aspect. The study presents a defect detection model for PV power stations using the YOLOv3 (You Only Look Once v3) algorithm. The model incorporates coordinate attention module (CAM) and self-attention module (SAM) to improve feature extraction in low-resolution conditions. The Multi objective Sparrow is employed to achieve multiple objectives. It is very contributing in the detection of low-resolution features. It shows that the research method can reduce the loss value to 0.009 after 400 iterations of the loss curve test. The precision-recall (P-R) curve generated by the research method only starts to drop sharply when the Recall value reaches 0.96. The number of parameters generated by the research method is 3.46×106. The detection accuracy of the research method reaches 98.86 % when there are five defective fault types. The results indicate that the proposed research method offers improved detection speed and higher accuracy in identifying hot spot defects in PV power stations. This technology provides valuable support for hot spot defect detection and presents new opportunities for the field
Clinical semiology guide for dentofacial deformities in early childhood
Get PDFDentofacial deformities can begin in a very subtle way, which is why there is a need for a well-defined diagnosis. To ascertain whether there is a consensus among specialists regarding the importance of identifying dentofacial deformities in children before they reach six years of age; and to develop and validate a screening tool to assist general dentists so that they can identify signs of craniofacial asymmetry, thereby directing preventive and minimally invasive approaches in children aged three to six years. The guide was created and validated by 37 specialist professionals, masters and doctors. The Delphi technique was used for data analysis, along with the content validity index (CVI) and Cronbach’s alpha. Among the evaluators, 81.08 % had completed their training more than 10 years ago and 78.38% had been working as dentists for more than 10 years; 2.16 % were specialists, 32.16 % had a master's degree and 5.41 % had a doctoral degree. The agreement between the evaluators through the CVI was 100 % and the average Cronbach's alpha was 0.7571, which was considered substantial or acceptable. The clinical semiology guide for detecting dentofacial deformities in children between 3 and 6 years of age was developed and validated
Case report of 2-year-old child with congenital torticollis and crossbite treated with functional orthopedics of the jaws
Get PDFSatisfactory chewing is performed by an alternating bilateral pattern that depends on occlusal balance, the absence of occlusal interference or premature contacts, stability, good functioning of the temporomandibular joints (TMJs) and neuromuscular maturation. If mandibular functional imbalances occur, discrepancies in maxillomandibular development and future facial asymmetries may occur. The objective of this work was to remove dental interferences that cause anterior and posterior crossbite, as well as those that prevent the good execution of symmetrical lateroprotrusive movements (right side/left side), through occlusal adjustment and subsequent correction of maxillary asymmetry using the device; encapsulated. Clinical case report of a two-year-old female patient, with unilateral crossbite on the right side (anterior/posterior), diagnosed with congenital torticollis, difficulty breastfeeding and difficulty performing alternating lateral movements. with follow-up until the complete deciduous dentition. The treatment was divided into three stages. The first step was to correct the unilateral crossbite (anterior and posterior), on the right side, by making occlusal adjustment using a grid, and later with the addition of Planas Direct Tracks resin. The second stage used an encapsulated device to correct maxillary asymmetry. The third stage was completed after the eruption of the deciduous second molars with the functional analysis of lateral movements plus occlusal adjustments using a grid. Correction of unilateral crossbite (anterior and posterior) on the right side, symmetrization of the maxilla and better execution of lateroprotrusive movements. The results obtained in this case report suggest that the occlusal adjustment removed the dental interferences that caused the anterior/posterior crossbite on the right side; the maxilla was symmetrized with the distalization of sector 63-65, and the removal of dental interferences that prevented lateral movements made it possible to perform lateroprotrusive movements (right/left side) after the complete eruption of the primary teeth
Adoption of metal additive manufacturing in nnpc limited: current state and challenges
Get PDFMetal additive manufacturing has emerged as a promising technology with vast potential in the oil and gas industry. The Nigerian National Petroleum Company (NNPC) Limited recognizes the significance of this technology and has initiated efforts to adopt metal additive manufacturing within its operations. This paper aims to provide an overview of the current state of metal additive manufacturing in the NNPC and highlight the challenges faced during its adoption process. The study goes on further to suggest strategies and future directions to ensure successful company-wide and industry-wide adoption and acceptance
Numerical modelling of the warping behaviour at the first layer-build plate interface in 3D-printed models produced via the fused deposition modelling process
Get PDFThe material structure of 3D-models printed via the fused deposition modelling (FDM) technique is mainly affected in the z-direction of the 3D-print as a result of the layer-by-layer approach which tend to exhibit a deformation behavior corresponding to a type of transversely orthotropic material. Moreover, uncontrolled parameters such as printing temperature and printing speed have been reported to adversely affect 3D-print quality leading to undesired effects such as distortion and warpage. The additive manufacturing process is a relatively new field in advanced manufacturing where further research and innovation are required to overcome the limited strength and structural performance observed in presently 3D-printed components. In line with the above, this study proposes the numerical investigation of the warping behavior in PLA (Polylactic acid) - based 3D printed models by considering the finite element method (FEM) software of LS-DYNA. The warping investigation was specifically centered on the cooling cycle prevailing between the layer-by-layer structures. The findings of this study showed that warpage would most likely occur in the thermal process model corresponding to abrupt change in temperature due to a buildup of strain between the bottom most layers of the 3D model and the build plate. The findings of this study, which shed light on the warping behaviour in 3D-models, has direct implications on the final quality of 3D-printed components
Problems of rutting on asphalt pavements
Get PDFIn the article, under field conditions (on the lane of a city road for public transport), using modeling and traffic flow analysis methods, the formation of ruts on an asphalt concrete pavement is studied. The maximum total rut depth on the road section under consideration reaches 110 mm. 715 buses and 25 trucks pass along a separate lane of the road per day, the relative rutting impact of which is from 5.68 to 16.41 compared to the design vehicle. The design of the road pavement on the experimental section with a total thickness of 48 cm is too weak for the actual traffic flow, which was the main reason for the premature failure of the road due to unacceptable rut sizes on the asphalt concrete pavement