Journal of Mechanical Engineering, Automation and Control Systems
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Treatment of vertical problems with jaw functional orthopedics based on scientific evidence. Part 2: deep bite
Get PDFThe vertical problems of the stomatognathic system that alter the overbite, either by increasing in the deep bite (DB) or decreasing in the anterior open bite (AOB), are among the great challenges of the dentofacial corrections in the treatment and the retention and stability protocols. In this paper the state of art of DB treatment with Jaw Functional Orthopedics (JFO) will be discussed. JFO has a unique diagnostic tool for changes in vertical growth of the face, the Articular Compass, developed by Simões. Individuals with hypodivergence and DB are, usually, difficult to treat and more difficult to stabilize the obtained results. Since 1950-decade Planas advocate that the Equiplan – a metal accessory used in functional orthopedic appliances (FOA) is efficient in deep bite treatment by levelling the occlusal plane. Promising results are found with a P = 0,00, but in aweak evidence study design based on the scientific evidence pyramid. Much of the discussion of incisor intrusion or molar extrusion to treat DB seems to be solved with the use of Equiplan, but it still has no scientific evidence, only clinical evidence. In conclusion Randomized Clinical Trials are needed to investigate the efficiency and Modus Operandi of JFO to treat DB
Salival biomarkers in inflamatory oro-cranio-cervical inflamatory alterations
Get PDFDuring the COVID 19 pandemic, the general population suffered from high degrees of stress, the consequence of which was an increase in myofascial pain syndrome. This inflammatory ailment which affects soft tissues causes pain, muscular rigidity, and modifies posture due to hyperactivity. A state of muscular ischemia leads to structural and chemical changes, and to variations in saliva’s electrical conductivity. The objective of this research was to measure the changes in pH and electrical conductivity of saliva samples, and to use these as biomarkers during therapeutical Maxillary Functional Orthopedics (Planas’ Simple Indirect Tracks and Simões Network 20). All the subjects that took part in the study evidenced changes in the beforementioned biomarkers, as well as clinical improvement of their symptoms
Frequency splitting approach using wavelet for energy management strategies in fuel cell ultra-capacitor hybrid system
Get PDFUsing frequency splitting, two energy management strategies (EMS) based on Haar wavelet decomposition and Fourier analysis for fuel cell hybrid vehicle (FCHV) are proposed to manage efficiently the power flow between components. The paper aims to discuss the performances of the proposed EMS in terms of dynamic behavior, robustness operation, real time application and fuel economy. For apply this methodology, two EMS approaches are elaborated and successfully tested for parallel Fuel Cell/UC: conventional approach using Fourier Transform analysis (FT) and Wavelet analysis approach allowing natural frequency splitting. Finally, and to evaluate the performance and relevance of the developed approach, a comparison analysis were conducted. The simulation results exhibit the effectiveness of both strategies. Indeed, Wavelet analysis leads to better results in terms of energy flow and dynamic behavior, excellent robustness and stability of system, as well as energy economy improvement. A very relevant strategy is proposed based on Wavelet analysis using digital filtering techniques, which enables a natural frequency splitting to ensure the best global performances. In addition, the approach remains simple and suitable for real time operation
Simulative analysis on large local deformation features of single-shell and double-shell cylinders subjected to underwater explosion
Get PDFSimulative studies on a series of the cylinders subjected to underwater explosion were presented using coupled acoustic-structural analysis in ABAQUS in order to analyze the large local deformation feature and the influence of the outer water tank. The results revealed that large inward local deformation occurs on the front side of the cylinder, and the plastic hinge locates near the boundary of the spherical projection of the explosion to the cylinder with an approximate elliptic type. The inner water and the outer shell’s thickness of double-shell cylinders have great influence on the large local deformation feature of the inner shell, and with the increase of the outer shell’s thickness, large local inward deformation occurs on the back side of the cylinder, which is caused by the local jet effect of the inner water. The research can provide reference to the design and assessment of underwater anti-explosion structures
Nonlinear dynamic analysis of constant-speed and variable-speed of autonomous vehicle passing uneven road
Get PDFThis paper focuses on the research about the comfort and safety of autonomous vehicles passing consecutive speed control humps (SCHs) at a highway, compares and analyzes the nonlinear dynamic characteristics of vehicles driving on uneven roads at a constant speed or with accelerations or decelerations. Firstly, a speed coupling excitation model of the consecutive SCHs and a four-degree-of-freedom (4-DOF) nonlinear vehicle suspension model are established, and then the numerical simulation is carried out by using the four-order fixed-step Runge-Kutta algorithm. The nonlinear dynamic characteristics are analyzed by means of a bifurcation diagram, phase portrait, Poincaré map, time history and power spectrum. Through the analysis, the relevant nonlinear motion characteristics and the speed critical conditions of chaotic vibration of autonomous vehicle suspension under these three conditions are obtained. The results show that chaotic motion may occur when the vehicle passes the uneven road in all three cases, and motion is not periodic during acceleration. Therefore, the vehicle should not accelerate passing continuous SCHs. The experimental results provide support for the follow-up researches of autonomous vehicle, because they give information on how to avoid chaotic motion, speed adaptive control, driving comfort and driving safety
“The tonic’s not always in a bottle”: a qualitative study investigating a heart rate variability biofeedback coherence intervention for individuals with gastrointestinal disorders
Get PDFGastrointestinal disorders (GID) affect psychological and physical health and can be impacted by stress and ability to self-regulate emotions. The aim of this study was to gain an in-depth understanding of individuals with GID experiences of a Heart Rate Variability biofeedback (HRV-BF) coherence intervention. Six patients, who had already been diagnosed with GID, were interviewed using a semi-structured interview schedule to investigate how engaging in an HRV-BF coherence intervention affected their levels of stress and their GID condition. All transcripts were explored using Interpretative Phenomenological Analysis (IPA). Analysis of the accounts indicated four superordinate themes: (1) Autonomy, (2) Self-regulation, (3) Acceptance, (4) Mind-Body-Spirit. The field of HRV-BF interventions in the area of gastroenterology is promising. However, it is recommended that further studies involving psycho-physiological interventions, with mixed-method designs and larger samples, are undertaken
Research on IGOA-LSSVM based fault diagnosis of power transformers
Get PDFPower transformer is an important part of power equipment, and its functionality affects the proper operation of the whole power network. In order to diagnose power transformer faults effectively, the authors propose a fault diagnosis strategy based on an improved locust optimization algorithm for least squares vector machines (IGOA-LSSVM). Firstly, it was required to address the problem that the diagnostic prediction accuracy of the least squares vector machine is reduced due to its parameters. So this paper introduces the locust optimization algorithm with simple algorithm structure and good performance for optimizing the parameters. And at the same time, the authors generate an improved locust optimization algorithm with self-learning factors, proportional weight coefficients and Levy flight strategy. Secondly, the improved locust optimization algorithm is used for optimizing the least squares vector machine parameters. Finally, in the simulation experiments, the results of the benchmark test function illustrate that the IGOA algorithm has better performance, and the test results of a fault samples diagnosis of the power transformer equipment illustrate that the IGOA-LSSVM has good prediction effect and improves the fault identification accuracy compared with ACO-LSSVM and PSO-LSSVM in five types of fault diagnosis
Measurement of natural frequency and mechanical damping of thin brass diaphragm by pulsed laser generated vibrations
Get PDFDamped harmonic oscillator model based fitting of nanosecond pulsed laser induced amplitude variations of clamped vibrating circular plate is used to estimate the mechanical damping and natural frequency of the sample in current work. Laser Pulses of 50 mJ energy, 20 ns duration, and focused at a spot of 4 mm diameter at the center of the circular thin brass sheet of 100 µm thickness is used to generate vibrations in the target. Quadrature Michelson interferometer (QMI) with CW laser focused on the opposite side of the target surface is used to measure the amplitude of vibrations. Variations of fringe frequencies are identified in the frequency domain. Finite element based numerical modal analyses are also performed in ANSYS Workbench for the verification of experimental results for the same geometry and materials. Experimental frequencies of vibrations are found to match nearly 2 percent of FEM modes. Moreover, Elastic parameters are also found using the first two mode frequencies and a reasonable agreement is observed while comparing with the elastic parameter data of brass. Current work in itself is a unique attempt of getting mechanical parameters for the determination of elastic parameters in a single laser pulse impulse excited measurement for thin clamped targets
Vibration characteristics of axial compressor blade under complex loads
No full textIn this study, 3D models of a compressor blade for an aero engine with three different levels of surface accuracy (with 4, 6 and 10 section profiles) were obtained via reverse engineering by fitting point-cloud data. Then, finite element and flow-field models of the blade were established and validated. The vibration characteristics of the blade under typical operating conditions were analyzed by considering the interaction between the aerodynamic load by airflow and the centrifugal load by blade rotating. The results showed that, under complex centrifugal and aerodynamic loads, the three blade models differed significantly in their high-order dynamic frequencies, and the modal frequencies that were dominated by a torsional mode of vibration were sensitive to the aerodynamic load. Hence, considering both the aerodynamic excitation and the centrifugal load increased the accuracy of the numerical computation of the blade vibration characteristics. Moreover, a comparison of the computational results from the three blade models showed that models B6 and B10 differed only insignificantly, and B6 decreased the complexity of the modeling process while satisfying the required computational accuracy. Thus, model B6 is the best option for engineering analysis and computation
Motion characteristics and energy efficiency of potential energy recycling system of telescopic handler
Get PDFTelescopic handler is combined of truck crane and forklift. Equipped with different accessories, the telescopic handler can achieve fork loading, lifting and other operations. Large amount of energy is needed to maintain lifting and lowering in large range with high frequency of the working device of telescopic handler. There is no energy recycling device for the working device that leads to the large dissipating of gravitational potential energy. In order to recycle the wasted energy, a three-chamber hydraulic cylinder boom system (TCCBS) is proposed. In this paper, the recycling principle is described. Then the energy consumption characteristics are analyzed. Further, the mode of TCCBS of telescopic handler is established and analyzed. Compared with the double chamber cylinder boom system (DCCBS), the single-action time of the boom is reduced 4.15 s. The velocity shock decrease from 0.12 m/s to 0.02 m/s at the beginning of the boom lowering process. The peak pressure decreased from 24 MPa to 21 MPa and the average pressure decreased from 17 MPa to 13 MPa during boom lifting process. The potential energy recycling of the working device is 139 kJ, which accounts for about 47.1 % of total potential energy. The cumulative output energy of TCCBS is 311 kJ, which is 92 kJ less than the DCCBS. The comprehensive energy saving efficiency is 22.3 %. The results show that the TCCBS can realize the potential energy recycling