Journal of Mechanical Engineering, Automation and Control Systems
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Analysis and optimization of pre-stressed modal features of ship anchor support parts
No full textIn order to solve the problems of excessive weight and unreasonable structure of anchor machine parts caused by traditional design methods, a lightweight optimization method was proposed based on pre-stressed modal analysis. The design variables were determined, and the parameterized model was established by using ANSYS Workbench. Under ultimate load conditions, the strength of wall frame board and lower box bodies was simulated and calculated. Through modal analysis, the discretized natural frequencies under different design variables could be obtained. The multi-objective genetic algorithm and sequence quadratic programming were respectively used to calculate the lightweight analysis model. The results showed that the weight of the supporting components in ship anchor can be reduced by more than 5 % without reducing strength and equivalent stiffness
Lightweight small target detection based on aerial remote sensing images
No full textWith the upgrading of aviation space technology, the amount of information contained in remote sensing images in the aviation is gradually increasing, and the detection technology based on small targets has developed. For lightweight small targets, pixels per unit area contain more information than large targets, and their area is too small, which is easily overlooked by conventional detection models. To enhance the attention of such algorithms, this study first introduces a Control Bus Attention Mechanism (CBAM) in the fifth generation You Only Look Once (YOLOv5) algorithm to increase the algorithm’s attention to small targets and generate optimization algorithms. Then convolutional neural network is used to mark feature pixels of the optimization algorithm, eliminate redundant information, and generate fusion algorithm, which is used to generate redundant information with high similarity when the optimization algorithm surveys pixel blocks. The novelty of this study lies in using CBAM to improve YOLOv5 algorithm. CBAM module can extract important features from images by adaptively learning the channel and spatial attention of feature maps. By weighting the channel and spatial attention of the feature map, the network can pay more attention to important features and suppress irrelevant background information. This attention mechanism can help the network better capture the characteristics of small targets and improve the accuracy and robustness of detection. Embedding CBAM module into YOLOv5 detection network can enhance the network's perception of small targets. CBAM module can improve the expressive ability and feature extraction ability of the network without increasing the complexity of the network. By introducing CBAM module, YOLOv5 can better capture the characteristics of small targets in aerial remote sensing images, and improve the detection accuracy and recall rate. Finally, the proposed fusion algorithm is used for experiments on the Tiny-Person dataset and compared with the fifth, sixth, and seventh generations of You Only Look Once. When the fusion algorithm tests the target, the classification accuracy of Sea-person is 39 %, the classification accuracy of Earth-person is 31 %, and the probability of being predicted as the background is 56 % and 67 %, respectively. And the overall accuracy of this algorithm is 0.987, which is the best among the four algorithms. The experimental results show that the fusion algorithm proposed in the study has precise positioning for lightweight small targets and can achieve good application results in aerial remote sensing images
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
Ferroresonance phenomena in power systems
Get PDFIt is a known fact that the world's dependence on electrical energy is increasing day by day. The fact that electrical energy has some advantages over other types of energy, the increasing world population and changing living conditions can be considered among the reasons for this increase. This increase in dependence on electrical energy can be met by expanding existing facilities and establishing new facilities. In these studies, the transmission of electrical energy from the place where it is produced to the place where it is consumed poses important problems as the system expands. Some work is required to eliminate these technical and economic problems and to ensure stable operation of the system. These are problems that were not considered beforehand as the system grew. One of these problems is the ferroresonance phenomenon that occurs at the fundamental frequency due to the nonlinear magnetization characteristics of transformers. Ferroresonance is a resonance phenomenon that occurs in an electrical circuit containing an iron-core self-coil as a nonlinear element. This resonance manifests itself with sudden oscillations in the output size of the system caused by a small change in the amplitude or frequency of a magnitude applied to the input of the system. High voltage transmission lines are double-circuit lines that share the same pole. In special cases such as maintenance or malfunction of such a transmission system, one of the lines can be disconnected from the system and continue energy transmission with the other line. In the high voltage transmission line, the system may oscillate due to the stored energy in the magnetic field of the transformer inductance on the disabled line and the electric field of the line capacity. This oscillation disappears after a certain period of time due to iron losses and other circuit losses. When these losses are covered by the other transmission line, permanent oscillations and over voltages may occur at the transformer terminals. All these events are the negative effects of ferroresonance on transmission systems. In the energy transmission system, ferroresonance phenomenon occurs. Over voltages may occur in case of idle power transformers in star point/isolated networks. In medium voltage networks, ferroresonance occurs due to the melting of a fuse, the opening and closing of voltage transformers with one pole, and the dissymmetry that occurs as a result of a connection process. These negative effects caused by ferroresonance in the energy transmission power system are discussed in detail within the subject of this study
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
Trajectory-based synthesis of a slider-crank mechanism for applications in inertial vibration exciters
Get PDFSlider-crank mechanisms are widely used in various industrial and technological machines. This paper considers a generalized diagram of a slider-crank mechanism, on the connecting rod of which an imbalanced mass can be fixed. In such a case, the slider-crank mechanism can be employed as an inertial vibration exciter. The aim of this research is to justify the geometric parameters of the mechanism to ensure a predetermined elliptical trajectory of the imbalanced mass motion. The research methodology involves the analytical derivation of the motion equations for a connecting rod point and solving the problem of synthesizing the geometric parameters of the mechanism based on the given trajectory of this point. The obtained results are presented in the form of displacements and trajectories for the connecting rod point of a specific slider-crank mechanism. The major novelty of this research lies in the further development of the theory of slider-crank mechanism synthesis for use in inertial vibration exciters. The derived analytical dependencies can be utilized by designers and engineers in the development of new types of vibration exciters for various industrial and technological vibratory equipment
Performance improvement technology of sludge roadbed based on vibration slow release
Get PDFIn order to improve the anti-vibration properties and bearing capacity of solidified sludge, this article takes silt soil as the research object and selects sludge solidification materials with good solidification performance. The chemical element composition of muddy soil was analyzed using an energy dispersive X-ray spectrometer (EDS). The microstructure and characteristics of muddy soil and solidifying agent were characterized by transmission electron microscopy experiments (TEM). The optimal moisture content and maximum dry density of solidified sludge were analyzed using compaction tests. The unconfined compressive strength test was used to evaluate the bearing capacity and strength variation of solidified sludge. The vibration characteristics of sludge under different testing times and frequencies was studied. The research results indicate that the solidifying agent could reduce the moisture content of muddy soil significantly, improve the anti-vibration properties and bearing capacity of muddy soil effectively, which provide relevant basis for improving the performance and anti-vibration performance of solidified sludge used for roadbed filling. This study could provide innovative reference for the vibration and performance of solidified sludge used in roadbed filling
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
Modal characteristics analysis of agricultural vehicle support frame
Get PDFThe support frame of large agricultural vehicles was simulated using the finite element method to ensure stability and reliability. Modal experiments were conducted to verify the simulation accuracy, and mesh division and optimization were performed based on different size and structure types. Three types of loads were applied according to different working conditions. The natural frequency, vibration mode, stress, and deformation characteristics of the model under prestressed mode condition were calculated to determine the weak structure of the support frame. Modal measurement points for calibration during test modal analysis were used to generate a test modal model with force hammer, acceleration sensor, signal acquisition instrument, and other devices. The results showed that there was good agreement between finite element modal analysis and experimental modal analysis with a maximum error in natural frequency of 2.2 %, verifying the accuracy of the finite element model
Determination of kinematic and dynamic characteristics of a reversible vibratory conveyor with an electromagnetic drive
Get PDFThe paper considers the design parameters that must be provided during the practical implementation of small-sized reversible vibratory conveyors with an electromagnetic drive. The proposed conveyor is developed on the basis of a classical two-mass oscillatory system. Two oscillating masses are connected by symmetrically assembled round-shaped rods. In order to avoid angular (torsional) oscillations of the vibratory conveyor, the geometrical centers of mass and stiffness of the spring system are aligned at the same point. The analysis of kinematic characteristics is performed by means of numerical solving of the system of nonlinear Lagrange-Maxwell differential equations. The influence of the phase shift angle between the electromagnetic excitation of horizontal and vertical oscillations on the trajectories of the mass center of the conveying member is analyzed. The first two frequencies and forms of natural oscillations of the vibratory conveyor are determined for estimating its dynamic characteristics. The novelty of this study lies in the development of a new design of a vibratory conveyor with a controllable independent electromagnetic drive that provides the conveying reversibility and efficiency