Maintenance, Reliability and Condition Monitoring
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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
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
Welcoming pregnant women as a strategy for adherence to dental prenatal care and health promotion in early childhood
Get PDFThis research deals with implementing Dental Prenatal Care as a public policy in the Brazilian Unified Health System (SUS) to care for pregnant women and their future babies. The legal framework that assures pregnant women's rights of priority in accessing services is usually not enough to guarantee the health promotion coverage goals for this population group, who frequently have low adherence to dental care. Brazilian Unified Healthcare System (SUS) recommends monitoring pregnant women through eight mensal consultations during healthy pregnancy. Oral health is usually not monitored to the same extent, and many pregnant women still go through pregnancy without any dental consultation. This study was proposed to improve dental prenatal care and program adherence by mothers and children in the Basic Healthcare Unit Amaro José de Souza, in the municipality of Barueri, through the increased participation of the dental surgeon in the pregnant women welcoming team. A cross-sectional cohort study was designed to identify and meet the demands of low-risk pregnant women. For six months, all the women attending prenatal care at BHU Amaro José de Souza in Barueri were invited to participate and receive personal guidance from the multi-professional team. Information on dental health was investigated through questions targeting previous knowledge about the recommended moments for the first dental appointment of a child, the importance of exclusive nasal respiration, the identification of craniofacial asymmetries at birth, and general baby care. Attitudes and self-care were also investigated, including prenatal program adherence. Answers were collected in a Google Form platform and analyzed to characterize the group's literacy about prenatal care and breastfeeding and identify information needs about dental health care during pregnancy. At the same time, a welcoming expanded listening, educational, and preventive health action was developed: conversation and sharing experience groups were promoted monthly for pregnant women, breastfeeding mothers, and their families. 90 pregnant women out of the 104 attending the BHU in the six months of the research were invited, and 83 agreed to participate. All the participants declared at least one previous appointment with the healthcare team, 92.8 % of them, with a gynecologist. The nursing team was involved in 53.0 % of the appointments, but only 6.0 % were reported to have been conducted exclusively by a nurse. A dental surgeon appointment was mentioned by 30.1 % of the research participants. The dental health literacy investigation revealed that 57.8 % believed they should only take their babies to a dental appointment after teething, and 27.7 % were aware of the child's craniofacial asymmetries at birth. Only 28.9 % had previous knowledge about the importance of exclusive nasal respiration. Despite only 34.9 % having their first pregnancy, 78.3 % declared they would appreciate receiving information about pregnancy. After the guidance, 72.0 % of the pregnant women had undergone dental prenatal care. Workshops for pregnant women and breastfeeding mothers provided a convenient welcoming space, to listen and provide guidance to pregnant women and their families, in addition to demystifying the fear of dental care during pregnancy and breastfeeding. The intervention to guide pregnant women to perceive the BHU as an educational and health promotion space, not just a curative intervention, effectively increased adherence to dental prenatal care. The contact with the Specialist in Functional Jaw Orthopedics in this first phase of life facilitated dental health education and access to more complex cases. The prenatal program adherence, the pregnant woman’s self-care, and the care of the baby were favored by the welcoming, expanded listening, and personalized service
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
Optimization of reduction gear in anchor winch based on modal analysis
Get PDFIn 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
Introduction of the distribution of Cs in Cu(In,Ga)Se2 photovoltaic absorbers following post-deposition treatment with CsF
Get PDFIn recent years, the device performance of Cu(In,Ga)Se2 (CIGS) solar cells has been improved by heavy alkali element post-deposition treatment (Alkali-PDT). Therefore, it is of great significance to study the mechanism of enhancing CIGS device performance through Alkali-PDT. One aspect to be studied is the distribution of heavy alkali elements in the absorber. In this work, the distribution of the heavy alkali element Cs in the absorber after post deposition treatment of CsF (CsF-PDT) and its effect on the device performance are investigated. The experimental results indicate that Cs can enter both the grain interior (GI) and grain boundaries (GB) via the Cu vacancy (VCu). By comparing the distribution of Na and Cs in the film, it can be noticed that Na is mainly distributed at the GB, while Cs is not differently distributed between the GB and GI. This is mainly due to the fact that the presence of Na at GB inhibits the accumulation of Cs there. The distribution of Cs is beneficial in improving the device’s performance by passivating defects, such as InCu
Processing piano audio: research on an automatic transcription model for sound signals
Get PDFAutomatic transcription of sound signals can convert audio to musical notes, which has significant research value. This paper extracted dual-channel constant Q transform (CQT) spectra from piano audio as features. In the design of the automatic transcription model, a CNN was employed to extract local features and then combined with a Transformer model to obtain global features. A CNN-Transformer automatic transcription model was established using a two-layer CNN and three-layer Transformers. Experiments were conducted on the MAPS and MAESTRO datasets. The results showed that dual-channel CQT outperformed short-time Fourier transform (STFT) and mono CQT in auto-transcription. Dual-channel CQT achieved the best results on frame-level transcription for the MAPS dataset, with a P value of 0.9115, an R value of 0.8055, and an F1 value of 0.8551. A sliding window with seven frames yielded the best transcription results. Compared with the deep neural network and CNN models, the CNN-Transformer model demonstrated superior performance, achieving an F1 value of 0.8551 and 0.9042 at the frame level for MAPS and MAESTRO datasets, respectively. These findings confirm the designed model's reliability for automatic piano audio transcription and highlight its practical applicability
Analysis of the force and power characteristics of a twin crank-type mechanism of an enhanced vibration exciter
Get PDFThe crank-type vibration exciters represent innovative and promising actuators for a variety of vibratory technological equipment. Extensive research has demonstrated their potential for generating specific trajectories of the working components of various technological machines. This study builds upon previous investigations of the authors, focusing on the kinematics and dynamics of crank-type vibration exciters, with a specific emphasis on analyzing the forces, moments, and torques acting on the elements of the twin crank-type actuating mechanism. The research methodology involves the development of a simplified dynamic diagram of the mechanism and derivation of the analytical expressions to describe its force parameters. Mathematical modeling and computer simulation are then conducted to analyze the forces, moments, and torques experienced by the mechanism during its motion under different operational conditions and design parameters. The results obtained provide time-dependent profiles of these parameters across various conditions and design configurations of the twin crank-type mechanism. A key scientific contribution of this paper consists in the development of the theoretical basis for creating novel techniques of dynamic and strength analysis and optimization of design and operational parameters of enhanced vibration exciters equipped with twin crank-type mechanisms. The research findings offer valuable insights for engineers involved in the development and enhancement of vibratory technological machines equipped with crank-type vibration exciters
Numerical study on sloshing in coaxial shells
Get PDFSloshing in coaxial shells partially filled with liquid is investigated using reduced boundary element method. Conical shells are considered as storage tanks. An ideal and incompressible fluid is assumed in the shells. The spectral boundary problem for the liquid vibrations in rigid shells is solved. The results demonstrate the high accuracy of the presented approach
Effect of pier bearing construction on nearby high-speed rail line bridges
Get PDFIn order to analyze the impact of the new pier bearing platform construction on the bridge section adjacent to the high-speed railway line, a new pier bearing platform project adjacent to the high-speed railway line in the soft soil area of the Yangtze River Delta is taken as the background of the project, and the finite element software Plaxis 3D is used to study the impact of the pier bearing platform construction on the bridge section adjacent to the high-speed railway line, and to analyze the effect of distance on the horizontal displacement and settlement of the bridge foundation soil body. The neighboring high-speed rail line bridge is displaced horizontally toward the foundation, with the maximum horizontal displacement of 1.5 mm and the maximum settlement of 5.5 mm; the existing pier bearing platforms are also displaced in the same direction, with the maximum horizontal displacement of 2.7 mm and the maximum settlement of 5.4 mm, and the pier bearing platforms in the middle are affected the most