Jaw Functional Orthopedics and Cranoficial Growth
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Optimization of reduction gear in anchor winch based on modal analysis
No full textIn order to achieve more scientific design of the reduction gear and reduce material waste, pre-stressed modal analysis method was combined with multi-objective optimization algorithm to optimize the structure of the reduction gear basic body. The model was simplified and parameterized and the maximum stress and equivalent stiffness under different parameter size combinations were obtained through finite element analysis. Separately, genetic clustering method, neural network method, and Kriging method were used to construct the response surface function. Through error verification and comparison, it was found that the Kriging method was more suitable for the gear model. In the design of variable extremum search, multi-objective genetic algorithm and sequential quadratic programming were compared and analyzed. The results show that the mass of the gear can be reduced by 39.9 %, while the maximum stress remains unchanged, the equivalent stiffness is not reduced, and a good optimization design effect is achieved
Triangular state stress and deformation analysis of deformable tracked wheel
No full textThe Variable Morphology Wheel-Track Mechanism (VMWTM) is an innovative mobile platform design designed to overcome the limitations of traditional track and wheel designs in different terrains and mission requirements. Based on the importance of the crawler wheel in the tracked vehicle, the vehicle transmission shaft transmits the power and torque of the power source to the crawler chassis, so the overall working performance of the vehicle depends to a certain extent on the performance of the crawler wheel. In-depth and detailed research on the structure of the track wheel module is an important issue in the current vehicle design and manufacturing work. Based on the relevant theories and technologies of the finite element method, this paper conducts in-depth analysis and design. Taking the whole crawler wheel mechanism and the key components as the analysis object, the basic research method is the finite element method. The working principle of the crawler wheel is analyzed, and the load calculation, stress characteristics and structural strength of the key components of the triangular crawler wheel module are deeply explored according to the technical requirements and actual working conditions
Exploring the impacts of daytime sleepiness on gait, physical balance, and the occurrence of orofacial trauma: a narrative review
No full textDaytime 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
Failure analysis of gas turbine in first stage turbine blades in an urban power plant
No full textThe 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
Prevalence of child malocclusion and its association with time of breastfeeding and/or deleterial habits in children from 2 to 6 years old at public schools in Bento Gonçalves, Rio Grande do Sul, Brazil – pilot project
No full textKnowing that the worldwide prevalence of malocclusion in early childhood is 54 %, we carried out a pilot project in the first half of 2022 at Public Schools in Bento Gonçalves RS, evaluating 1938 children between 2 and 6 years old. The prevalence of malocclusion found was 23 %. Anterior open bite, whether or not accompanied by posterior crossbite, was the most prevalent malocclusion. About 70 % of the children were not breastfed or breastfed for less than 6 months, presenting a non-nutritive sucking habit. Assessing 5 years old children alone, this prevalence rose to 54 %. The results reinforce the need of public health policies that promote and support prolonged breastfeeding, which expand the knowledge of parents or guardians and school staff about the adverse effects caused by the use of pacifiers and baby bottles, with the adoption of transdisciplinary measures for the prevention, interception and treatment of malocclusions in a timely manner
Adoption of metal additive manufacturing in nnpc limited: current state and challenges
No full textMetal 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
An improved wavelet threshold function denoising method based on IGA optimization
No full textIn single crystal diamond tool grinding, cutting-edge quality is affected by various parameters, with tool vibration playing a crucial role. Due to environmental factors and the complexity of the process, vibration signals are often noisy and non-stationary. This study proposes a denoising method that optimizes the wavelet threshold function using an Improved Genetic Algorithm (IGA). The method introduces a configurable value α in the wavelet threshold function, which is optimized with IGA to improve denoising. MATLAB R2018b simulations show that this approach achieves better denoising, a higher signal-to-noise ratio, and lower mean square error
Tensor analysis of tornadoes: a new analytical and numerical model
No full textThis research proposes a new mathematical formulation of tornadoes based on the theory of tensor analysis and simulation in a non-inertial dynamics framework, both in two and three dimensions. This model may show the spherical upward movement of air in a tornado without taking into account vertical convection. A tornado requires several elements, including geocentric latitude, the Coriolis effect, increased airspeed in the upper atmosphere, and increased air pressure. Computing the three-dimensional location of the tornado or hurricane, as well as the mathematical models of airflow motion and the Earth's rotation in three-dimensional (3D) space, can determine a tornado's airflow characteristics. To show tornado patterns, we employed computer software that computed motion dynamics and did numerical computations. The results of 2-D modeling and simulation indicated that the greater the initial tornado angular speed, the larger the tornado area. Three-dimensional modeling and simulation also show that tornadoes are more powerful at higher geocentric latitude angles. The novelty of this study is that this model can be used to explain tornado patterns. In our research, we combine tensor analysis, computational modeling, as well as 2D and 3D simulations for simulating tornadoes for the first time. The scientific application of this finding is that researchers at the Meteorology, Climatology, and Geophysics Agency will be able to analyze a tornado and geophysical phenomena more readily with simulations and models
Common fixed-point theorem for commuting maps on a metric space
No full textSeveral novel uses of theorems for fixed points in commuting mapping in a fully metric domain are presented. Several conclusions from full metric fixed point theory are improved and extended by our work. Our proofs are inspired by the study of commuting mappings [B. Fisher and S. Sessa, on a fixed point theorem of Gregus, 1986] and [P. Sumati Kumari, Fixed and periodic point theory in certain spaces, 2013]
Analysis of aerodynamic characteristics of drone wing based on CFD
No full textIn order to improve the aerodynamic characteristics of the drone wings, CFD method was used to simulate and calculate the lift coefficient, drag coefficient, and lift-drag ratio under different relative inflow velocities, as well as the velocity and pressure fields under different attack angles. Modal calculations were conducted on the wing to obtain the first four modal shapes, providing a basis for analyzing flutter characteristics. An iterative calculation method of incompressible potential flow-boundary layer based on surface element method was combined with the software XFOIL to optimize the airfoil at low wind speeds. The results indicate that the airfoil is susceptible to stall at high angles of attack, with the pressure of the separation flow being nearly equivalent to that at the separation point. Subsequent to separation, there is an increase in differential pressure resistance, resulting in a marked rise in the drag coefficient. At the optimized angle of attack, the lift-drag ratio of the optimized wing increases by 12.58 %, while there is a decrease of 0.084 % in lift coefficient and an increase of 11.21 % in drag coefficient