Journal of Mechatronics and Artificial Intelligence in Engineering
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Dynamic performance of compound vibration damping device for sport fitness equipment
Get PDFComposite vibration damping is a crucial aspect in enhancing the performance of shock absorber, with potential for significant application in multi-degree-of-freedom sports facilities. Based on the finite element method, the modal analysis, harmonic response analysis and stiffness analysis of metal rubber shock absorber were realized, and the parameters of natural frequency, acceleration transmissibility and average stiffness were verified. Through ABAQUS, the finite element model of shock absorber was established and reasonably simplified, and the influence of wire diameter and relative density on the comprehensive performance was studied under the condition of prestress modal analysis. The results indicate that the shock absorber with a relative density of 0.35 exhibits higher average stiffness, but lower energy dissipation coefficient. Additionally, it shows larger peak values for natural frequency and acceleration transmissibility, but reduced damping. The simulation findings are in line with the experimental results, demonstrating the accurate acquisition of nonlinear mechanics and dynamic response properties of metal rubber shock absorber
Numerical analysis of the influence of air flow channel on ear pressure during door closure
Get PDFIn this paper, Numerical simulation analysis was conducted on the ear pressure of a certain vehicle model during door closing process. Firstly, relevant airflow channel parameters are formulated based on the benchmark vehicle data, and transient closing ear pressure simulation calculation is carried out using overset grid technology. Then, the impact of key structural parameters on the interior ear pressure of the car was analyzed. Finally, based on the requirements of actual engineering design, the design scheme for the peak pressure of the car was determined, and the results will be a reference for the development and design of later vehicle
Stability analysis of civil air defense tunnel under blasting vibration
Get PDFBased on a large section drilling and blasting excavation project, the dynamic response characteristics of civil air defense tunnels are analyzed by combining field monitoring and numerical simulation. The dynamic response features include particle vibration velocity, main frequency, displacement, and stress, and the stability criterion of the tunnel is analyzed. A safety criterion model based on the ultimate tensile strength of materials is established. The results show that the frequency of the X, Y, and Z directions is mainly distributed in 90-140 Hz. The effective stress increases first and then decreases along the axis of the roadway. The stress near the explosion source is large and the relative reduction is also large. By fitting the relationship between blasting vibration velocity and maximum principal stress, the safe vibration velocity criterion based on tensile strength is obtained, and the safe threshold of vibration velocity is 19.62 cm/s. It can be assumed that blasting does not affect the structure
A precise localization algorithm for unmanned aerial vehicles integrating visual-internal odometry and cartographer
Get PDFAccurate positioning in space is an important foundation for ensuring the stability of autonomous flight and successful mapping and navigation of unmanned aerial vehicles (UAVs). At present, the SLAM algorithm based on the Cartographer algorithm for real-time positioning and mapping is widely used in fields such as robot navigation and autonomous driving. However, in the context of UAV applications, this algorithm has a high dependence on the amount of point cloud information in the surrounding environment, and cannot achieve precise positioning in open spaces with insufficient lighting and fewer feature points, resulting in significant mapping errors. In order to solve the problem of low positioning estimation accuracy in the Cartographer algorithm in above environment, this paper proposes a precise positioning algorithm for UAVs that integrates VIO and Cartographer. This algorithm can continuously output more accurate position estimation information during UAV flight, compensating for the problem of inaccurate position estimation caused by partial feature loss or coordinate system drift in point clouds. In addition, this algorithm ensures navigation obstacle avoidance in narrow spaces by improving positioning accuracy and mapping accuracy, making it more applicable in the field of UAVs. Finally, the effectiveness of the proposed positioning algorithm was verified through experimental analysis of the Cartographer dataset and practical testing of UAVs in real scenarios
Low-level laser therapy parameters in the treatment of Orofacial pain in temporomandibular disorder
Get PDFTemporomandibular disorder (TMD) comprises a group of dysfunctions of the masticatory system involving joint, myofascial, and even sensory alterations. The main symptom of TMD is orofacial pain, which has a negative impact on the quality of life of TMD sufferers, affecting their productivity at work and school, the quality of their sleep, their appetite, and their satisfaction with life. An alternative for the treatment of TMD is the low-level laser therapy (LLLT), which stimulates cellular functions and promotes therapeutic effects. However, there is no consensus in the literature. Objective: This review aimed to elucidate the parameters of low-level laser therapy in the treatment of orofacial pain in patients with temporomandibular disorder. Methods: A search was carried out for scientific articles published between 2013 and 2023 in the MEDLINE, PEDro, LILACS and SciELO databases. Results: A total of 21 studies were previously selected and after the eligibility criteria, 10 studies were included. Can be suggest a protocol for treating patients with temporomandibular disorder by low-level laser therapy with the following parameters: infrared wavelength, energy density less than 10 J/cm2, output power from 100 to 250 mW and at least 8 sessions of treatment. Conclusion: The low-level laser therapy improves orofacial pain in patients with temporomandibular disorder
Evaluation and design of a bite force measuring load cell
Get PDFThe measurement of bite force can be essential for assessing oral health and the functioning of the stomatognathic system. However, its use in dental offices is limited due to operational complexities and costs. This study focused on evaluating the mechanical strength of the user-friendly and low manufacturing cost load cell under development within LABBIO – Bioengineering Laboratory at UFMG, the gnathodynamometer, tailored for children. 3D modeling in SolidWorks and Finite Element Method (FEM) structural analysis were employed to ensure its ability to withstand the desired 1000 N load. Initially, the device did not meet the desired load, resulting in iterations to modify its geometry. After iterations including the replacement of the initial material with a more suitable alternative, removal of edges, and other adjustments, a final prototype meeting mechanical strength and functionality requirements was developed
Transforming data with the arcsine distribution for random walks
Get PDFThis article delves into a pioneering methodology for optimizing the analysis of random walk data by implementing the arcsine distribution. The application of the arcsine distribution serves as an imperceptible yet potent solution, mitigating asymmetry and introducing bounds while effectively modeling the nuanced characteristics intrinsic to random walk patterns. Through a meticulous exploration of the mathematical foundations and practical applications of this distribution, this study discreetly advances statistical methodologies for handling random walk data. The article illuminates the theoretical underpinnings, subtle advantages, and pragmatic implications of arcsine distribution utilization, showcasing its imperceptible yet impactful role in capturing and reshaping random walk dynamics. Through a meticulous exploration of the mathematical foundations and practical applications of this distribution, this study discreetly advances statistical methodologies for handling random walk data, particularly in the context of financial modeling
A bulk queue’s analysis with two-stage heterogeneous services, multiple vacations, closedown with server breakdown, and two types of renovation
Get PDFA queueing system with two stages of heterogeneous services, multiple vacations, and closedown upon server failure is considered in this study for MX/Ga,b data. Two different services must be provided to a group of customers one at a time. At time C, the server finishes its shut-down procedures following the conclusion of each SPS. A server that has a queue length shorter than a takes numerous, different-duration vacations. Upon returning from vacation, if the server detects that there are less than a customers in the queue, they will continue to serve the following batch if the server determines that there are at least a customers waiting for service. During the server’s first phase of operation, the service channels will momentarily fail with a probability of (π1) at any time, and during the server’s second phase of operation, the service channels will fail with a probability of (π2) at any time
Sector orifice with a correlation-based analysis
Get PDFIn single and multiphase flows, an orifice is a vital flow-measuring and flow-controlling device that operates on Bernoulli’s theorem on the determination of the pressure drop (∆p). Laboratory, petroleum, energy, nuclear, mining, chemical, processing, and food industries all depend on flow monitoring and flow regulations. A sector or segmental orifice meter is a much simpler device used for drainage and sediment-laden type non-homogeneous flow. Sector orifice meter analysis is the rate of flow, pressure and velocity profile concerning input parameters to find out the ∆p and coefficient of discharge (Cd) of an orifice meter. The present study varies with different sector angles (θ), Reynolds number (Re) and space ratio (s/d) of the sector orifice for the flow analysis with the use of CFD (Ansys. Inc) based study. The numerical simulation range considered for θ (30°-180°), Re (10000-100000), and s/d (0.1-0.9). To compute the flow rate, ∆p and Cd by using air as a working fluid to present a flow problem through high viscous flow. The simulation also presents the pressure and velocity profiles along the flow on the variant of Re, θ and s/d. Based on the numerical data a correlation developed which will help the measurement through sector orifice for wide range of future application. With the comparison of the existing literature, this will give a good contribution to sector orifice for accurate flow measurement for high viscous flow
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
Get PDFKnowing 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