Maintenance, Reliability and Condition Monitoring
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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
Simulation analysis of helicopter rotor blade based on fluid-structure coupling
Get PDFSince the helicopters are required to fulfil many different attitudes during actual flight and are exposed to low amplitude and high number of cycles of vibration loads for a long period of time, the stresses on its rotor structure will be more complicated, which will lead to the rotor blades being subjected to larger stresses and causing fatigue damage. This paper proposes a combination of fluid-solid coupling and nCode fatigue simulation of helicopter rotor blade structure to study the stress distribution, danger point and fatigue life of rotor blades in hovering and forward flight state, so as to provide a reference basis for the judgement of helicopter rotor blade fatigue damage and the enhancement of safety performance. The results show that the maximum stress of the helicopter in the forward flight state is larger than that in the hovering state, and the maximum stress of the rotor blade in the forward flight state of the helicopter is located at the root of the blade as 166.89 MPa; and the fatigue life in the two states is obtained by the joint simulation method of Workbench-nCode, and the fatigue life in the forward flight state is reduced by 0.726 % compared with that in the hovering state. Therefore, the combined method of fluid-solid coupling and nCode fatigue simulation proposed in this paper can provide an effective research method for the design and optimisation process of helicopter rotor blades
On the decisional problem based on matrix power function defined over non-commutative group
Get PDFIn this paper, we perform statistical analysis for the decisional problem which is fundamental for the security of the key exchange protocol based on matrix power function. We have proven previously that the considered decisional problem is NP-complete and hence our proposal could potentially be quantum-safe. However, we did not explore the dependence of the complexity of the considered problem on the security parameters. Here we show that for small matrices certain information could be gained from the distribution of the entries of the public key matrices. On the other hand, we show that as the size of the matrices grows, the public key matrices are indistinguishable from truly random matrices
Effect of aging process on precipitated phase and properties of mechanical extruded aluminum alloy
Get PDFAs the industrial sector develops, the performance requirements for aluminum alloys are also constantly improving. The study explores how aging and rolling treatment affect aluminum alloys' precipitates and mechanical properties by controlling the parameters of aging process and rolling deformation variables. 7N01 aluminum alloy was selected as the experimental object, and the samples were treated with non-aging, natural aging, artificial aging, and rolling deformation. How aging processes and rolling deforming affected alloys’ mechanical properties was evaluated through performance testing (mechanical and tensile testing) and material fiber characterization methods (advanced electronic instruments). These results confirmed that the combination of three aging pre-treatments + R20 % + 120 °C re-aging could significantly improve the hardness of aluminum alloys and maintain high ductility. As the deformation decreased, the time for the sample to reach the hardness peak was shorter and the hardness was higher. The 20 % deformation sample’s strength was better than the 80 % deformation sample’s. This confirmed that appropriate aging process and deformation combinations could improve the strength and hardness of aluminum alloys. These results have certain guiding significance for optimizing the aging process of mechanical extruded aluminum alloys and provide reference for the study of related alloy properties
Exploring the impacts of daytime sleepiness on gait, physical balance, and the occurrence of orofacial trauma: a narrative review
Get PDFDaytime sleepiness (DS) often accompanies obstructive sleep apnea (OSA), exacerbating its effects. DS can impair cognitive function, attention, reaction time, and motor coordination, increasing the risk of accidents. This study aimed to explore the relationship between DS, changes in gait and balance, and the occurrence of orofacial fractures. A narrative review was conducted using PubMed, Scopus, and Web of Science publications. The analysis revealed the impact of DS and OSA on gait and balance control in older individuals, emphasizing the need for interventions to address these issues and identify associated pathologies. Continuous Positive Airway Pressure (CPAP) therapy was recognized as a potential treatment, although further research is needed to understand DS triggers and treatment options in older populations. The study underscores the importance of analyzing interactions between the central nervous system, medications, balance, and mobility to prevent falls and related injuries. While the literature highlights the vulnerability of elderly individuals and those with OSA to falls, no established link between DS, gait, balance, and orofacial trauma necessitating medical and dental intervention was found. Thus, further research is warranted to address this gap and promote better understanding and management of these conditions
Use of hyperboloid as an adjunct in functional jaw orthopedics – case report
Get PDFAnterior open bite can be defined as a malocclusion with a negative vertical discrepancy between the incisal edges of the upper and lower anterior teeth, which do not have occlusal contacts with the antagonists and sometimes extends to the canines and, less frequently, to the premolars is one of the malocclusions with the greatest aesthetic and/or functional impairment. Anterior open bite can have several etiologies: finger sucking and/or pacifier, oral breathing, onychophagia, lip interposition, atypical swallowing, tongue interposition when uttering phonemes and anterior posture of the tongue at rest. Orofacial myofunctional disorders are present in cases of anterior open bite, generally associated with etiologies and adapt to this altered morphological condition. Regarding the anterior opening amplitude, the anterior open bite is classified as: minimum up to 1 mm, moderate between 1 and 5 mm and severe +5 mm [1]. Open bite can be classified into: maxillary, mandibular and hybrid open bite [2]. Myofunctional therapy is considered a treatment method that can increase muscle strength, cause changes in functional patterns and thus prevent deviations in craniofacial development, as it promotes new posture of structures at rest and during the performance of the functions of the stomatognathic system [3]. The hyperboloid is an instrument for increasing muscle tone and when used in chewing, it is efficient in inducing growth and remodeling. The hyperboloid fills a gap in the modern diet, with the consistency of hard, raw and dry foods [4]. Exercises with a size M hyperboloid with wire were prescribed as an initial approach. After 2 months of treatment, there was an improvement in the interincisor distance. The exercise was maintained for another 5 months. He stopped attending appointments for 2 years and 2 months. Upon his return, the results of the functional examination of swallowing, chewing, protrusion and laterality were observed, and we opted for the installation of the SN3. the hyperboloid, in this case, showed its efficiency in balancing the stomatognathic system
Design and analysis of tracking differentiator based on SO(3)
Get PDFMotivated by the issue of insufficient dynamic performance and tracking accuracy in SO(3)-based attitude tracking differentiators during large-angle maneuvers and complex trajectory tracking, a novel design approach for a three-degree-of-freedom attitude tracking differentiator within the SO(3) framework is proposed by incorporating second-order system theory and Lie group theory and improving the classical tracking differentiator. The kinematics model and error dynamics model of a rigid body on SO(3) are derived, and a reasonable virtual control input on SO(3) is constructed subsequently in order to achieve better dynamic response and tracking performance. Simulation and experimental results validate that the designed tracking differentiator could realize rapid and smooth convergence during large-angle maneuvers, and the initial large tracking error rapidly drops to near zero in a short period of time; additionally, it can also track expected time-varying curves well in complex trajectory tracking, with initial errors rapidly decreasing and maintaining at normal levels, demonstrating excellent tracking and control capabilities. There are strong application prospects for this new approach in addition to its theoretical significance
Reading Gokturkish text with the Yolo object detection algorithm
Get PDFThis study has important scientific, cultural and economic contributions. From a scientific point of view, the decipherment of Gokturkish texts is of critical importance for research on Turkish culture, history and language. This study will enable historians and researchers to analyze these documents more quickly and effectively. Culturally, the reading of Gokturkish texts will help us gain a deeper understanding of Turkish culture and history. For linguists and cultural researchers, understanding these texts can offer new perspectives on the richness and cultural heritage of the past. From an economic point of view, this thesis argues that computer-assisted reading technology can contribute to a faster and more efficient reading and understanding of Gokturkish texts, making it easier to analyze the documents. This in turn frees up more time and resources for researchers and cultural experts, allowing them to focus on future work
Galerkin-Kantorovich variational method for solving saint venant torsion problems of rectangular bars
Get PDFThe unrestrained torsional analysis of bars is an important theme in elasticity theory, first solved by Saint-Venant using semi-inverse methods. It has been considered and solved by several others using analytical methods and numerical procedures due to the importance in the design of machine parts under torsional moments. In this paper, the Saint Venant torsion problem is solved for rectangular prismatic bars using Galerkin-Kantorovich variational method (GKVM). The work presents a detailed theoretical framework of the problem, deriving using first principles considerations the stress compatibility equation in terms of the Prandtl stress function ϕ(x,y). The derived domain equation which is required to be satisfied over the rectangular cross-sectional domain is a partial differential equation of the Poisson type. GKVM is adopted as the solution method for finding the solution to the domain equation. The unknown Prandtl stress function ϕ(x,y) is assumed, following Kantorovich method to be a product of an unknown function for fx sought to minimize the Galerkin-Kantorovich variational functional (integral) (GKVF) and a known function (y2-b2) which satisfies the boundary conditions at all boundary points in the y-direction, that is, at y=±b. The resulting GKVF is a simplified functional whose integral is a second order inhomogeneous ordinary differential equation (ODE) in fx. The integrand is solved to find fx leading in a full determination of the Prandtl stress function. The expression for stresses, torsional moments and torsional parameters are then found and they satisfy the boundary conditions and the domain equation. The results for the torsional moments and torsional parameters are identical to previous results obtained using double finite sine transform method (DFSTM), and analytical methods. The merit of GKVM is that it has led to the exact solution of the unrestrained torsion problems
Failure analysis of gas turbine in first stage turbine blades in an urban power plant
Get PDFThe Combined Cycle Power Plants (CCPP) are widely known as the most efficient power plants. The concept of CCPP represented in Brayton and Rankin cycles combined to achieve the highest efficiency in power generation. During the fact finding, while performing the major outage, at 77,521 running hours some of the turbine blades at 1st stage found suffering from severe damages and sulfuric acid thick layer accumulated in the cooling airfoils. The blades were new, also known as the most essential and costly component installed after Hot Gas Path Inspection (HGPI) at 42,000 running hours. The main objective of this work is to study the surrounding parameters that directly affect the lifetime of the turbine blades. Furthermore, XRD analysis for new and used turbine blades are studied as well as the EDS analysis for the coating layers which are used to enhance the surface life of gas turbine blades. Corrective maintenance, on the other hand, has been undertaken to overcome the performance deterioration caused by wear, which is the result of any machine or plant’s operation. A gas turbine cannot be run reliably unless wear reserves are checked and, if necessary, restored during inspections and maintenance operations. These are performed to determine the machine's condition and the necessary condition-based repairs. The principal types of gas turbine inspection have been investigated and presented, including minor inspection, hot gas inspection, extended-scope hot gas path examination, and major inspection. Lifetime extension (LTE) measures are derived from these inspection types and go beyond the scope of a major inspection. Nondestructive testing is performed on the gas turbine’s key components. Furthermore, due to the high degree of contamination in the fuel, the turbine section must be cleaned at regular intervals. As a result of the examinations, replacement, and refurbishment intervals for important components, as well as outage time, could be recommended