Journal of Engineering and Thermal Sciences
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Evaluation of segment convergence and settlement of subway shield tunnel in water-rich complex stratum
Get PDFBased on the shield tunnel construction of the left line of Guowei road station-Qingshan lake west station of Nanchang metro line 3, the study focuses on the adverse effects of tunnel segment convergence and settlement deformation of vault and arch bottom on shield construction in the process of shield tunnel construction in water-rich complex stratum. The time-space curves of segment convergence and settlement value on typical monitoring sections are drawn, their variation laws are analyzed, and the deformation values of monitoring data are analyzed and tested. Based on the analysis results, the qualitative and quantitative evaluation of the overall or local deformation state of each monitoring object of tunnel segment is carried out. The results show that the cumulative deformation of each typical monitoring section is lower than the warning value, and the tunnel segment has a systematic offset in the horizontal and vertical directions of the clearance
The interface between dental topography and functional appliances accessories
Get PDFDental topography can be defined as the division of receptive fields that we have in the crown of the tooth. It is necessary that we understand this concept very well because it makes all the difference in clinical practice. We need to understand the receptive fields of the tooth, and we must use this knowledge when prescribing accessories for a functional appliance, understanding its function and where these accessories should touch to generate the expected effect. In this paper we will discuss the fundamentals of dental topography and show some accessories used on the therapeutic arsenal of Jaw Functional Orthopedics
Relationship between mandibular position and support planting in 7-year-old children: pilot study
Get PDFIntroduction: Postural stability can be maintained in balance by muscle tone [1]. Change in the mandibular position or posture, may have influence in the postural reflex, defined as an involuntary defense movement [2] to correct deviations and keep the body in balance. If the postural change is constant, the muscles will move the mandible to a more comfortable position, with consequent postural change2 and plantar support. The aim of the study was to compare the plantar support in centralized and in lateralization mandibular position in seven years’ children. Main text: This study was approved by research ethics committee (No. 4.346.542). A pilot study was carried out with seven-year-old children of both sexes. Photogrammetry was performed with spherical markers in the region of the right tragus and chin symphysis (Fig. 1) concomitantly with baropodometry following (Fig. 2, 3) the protocol established by Bittar et al. [4]. Analysis of mandibular displacement and plantar support were performed with centralized mandibular position (maximum intercuspation) and with lateral displacement to the right and left. Statistical analysis compared the differences in mandibular displacement to the right and left sides using Student’s t test. Differences in plantar support variables with centralized mandibular position and in right and left lateralization position were established by the Anova one way test and the Bonferroni pos test. Significant statistical difference was reached by 5 %. Results: Twelve seven-year-old children were included, 20.8 (3.25) Kg and 1.18 (0.06) meters. The sample present greater lateral displacement of the mandible to the lefts compared to right side. Mandibular lateralization was confirmed with statistical difference compared to mandibular position centralized. No difference in all plantar support variables was observed between the three positions: centralized and left and right lateralization. Conclusions: No differences were observed for plantar support compared position in mandibular lateralization and centralized position. Mandibular lateralization displacements did not change plantar support
Equivalent stiffness calculation of composite hat stiffened laminate
Get PDFThe stiffness is the main reason that restricts the large-scale of composite ships, the basis to solve this problem is to solve the stiffness of composite ships’ skeleton structure. Based on classical laminates theory, this paper calculated the equivalent in-plane stiffness and bending stiffness of composite hat stiffened laminate using equivalent stiffness principle. The hat stiffened laminate can be simplified and equivalent to orthotropic laminates using this solution idea, which solves the problem that it is difficult to obtain the analytical solutions of deformation, stress and strain of stiffened laminate. The research results can be used to calculate the stiffness of composite stiffened laminate and the local or global stiffness of the hull girder with such a skeleton structure
Fault feature extraction method for rolling bearing based on MVMD and complex Fourier transform
Get PDFThe vibration signals caused by rolling bearing defects in different directions may be different, and the fault diagnosis based on single channel vibration signals may be made incorrectly, and the observation results may be understood wrong. To avoid it, a new rolling bearing fault feature extraction method based on multivariate variational mode decomposition (MVMD) and complex Fourier transform (CFT) were proposed. First, the orthogonally sampled vibration signals were combined into a multivariate signal, and the multivariate signal was decomposed into several intrinsic mode functions (IMFs) using the MVMD. As per this method, a unified mathematical model was used to model vibration signals in two directions, ensuring that fault features were decomposed to the same level. Finally, the CFT was applied to fuse the envelope signals in two directions in order to obtain a clearer and comprehensive amplitude-frequency feature. Simulation and test results verify the feasibility and superiority of the proposed method
Analysis of electromechanical coupling characteristics of electrics vehicle electric drive system considering current harmonic excitation
Get PDFIn order to study the electromechanical coupling dynamics characteristics of the drive motor and gear transmission system in the electric vehicle electric drive system, firstly, an electromechanical coupling dynamics model of the electric vehicle electric drive system is established; the electromechanical coupling vibration characteristics of the electric drive system under current harmonic excitation is compared and analyzed. The influence law of permanent magnet synchronous motor current harmonics on the meshing vibration of gear transmission system is revealed. The simulation results show that there is an obvious electromechanical coupling effect in the electric drive system; the harmonics of the drive motor can aggravate seriously the vibration state of the mechanical drive system; the research results provide a theoretical reference for further research on the vibration source positioning and active vibration reduction control strategy for the electric drive system of electric vehicles
Research on dynamic and vibration behaviors of a flip-flow screen with crankshaft-link structure
Get PDFA flip-flow screen with crankshaft-link structure (FFSCLS) is an effective solution for screening of high-water and fine materials due to its good performance. The dynamical characteristics largely affects the screen performance and the processing capacity of the FFSCLS. In this paper, a dynamic model governing the dynamical characteristics of the FFSCLS was proposed. In addition, the motion trajectory and vibration data of the FFSCLS were investigated by vibration experimental technology. The results show that the experiment results can be fully described by the dynamic model whit the maximum deviation was within 6.26 %. Moreover, the mass ratio between outer box and inner box determined the dynamical characteristics of the flip-flow screen, and these parameters should be optimized. This work can provide useful references for efficient operation and optimal design for the flip-flow screen
Optimization on the jet characteristics of the main nozzle of hot-blowing snow removal device
Get PDFThe exhaust devices used by snow removal vehicles are mainly based on hot-blowing snow removal. Due to the inherent characteristics of the turbojet engine such as low flow rate and high exhaust temperature, the modified hot-blowing snow removal device has problems of low snow removal efficiency and the possibility of ablation and damage to the road surface. In order to solve the problem, transforming the turbofan engine with a high flow rate and a low exhaust temperature into a hot-blowing snow removal device is an important improvement to achieve efficient and safe snow removal operations. In order to convert a medium bypass ratio turbofan engine into a hot-blowing snow removal device, the computational fluid dynamics (CFD) software CFX was used to analyze the internal and external flow field characteristics of the main nozzle of an exhaust device under the 60 % rated condition of the engine. The effective area sizes of the jet velocity and temperature predicted by the external flow field were used to optimize the layout of the main nozzle
Railway foreign body vibration signal detection based on wavelet analysis
Get PDFBased on the wavelet packet analysis method with time-frequency analysis characteristics, the measurement signal of the vibration system is processed for noise reduction, the soft-hard threshold compromise wavelet denoising method used has the advantages of soft threshold and hard threshold denoising, and through the introduction of compromise factors, signal processing can be performed more flexibly in signal analysis. For the denoised signal, the fundamental wavelet time-energy spectrum analysis, the main components of the signal can be clearly displayed, and according to the distribution of its energy in each frequency band, the signal characteristics can be displayed intuitively. Experimental results show: It can be determined that there is a foreign body intrusion incident at a position 520 m away from the monitoring point, rather than a normal train travel incident. In fact, we are walking back and forth at a distance of about 520 m from the monitoring point, simulating the intrusion of illegal foreign objects such as pedestrians and livestock beside the railroad tracks prove that analysis and judgment can be known, the wavelet analysis proposed by the author can realize the monitoring and judgment of some illegal foreign body intrusion incidents such as pedestrians and livestock
On a three-dimensional neural network model
Get PDFThe dynamics of a model of neural networks is studied. It is shown that the dynamical model of a three-dimensional neural network can have several attractors. These attractors can be in the form of stable equilibria and stable limit cycles. In particular, the model in question can have two three-dimensional limit cycles