Journal of Mechanical Engineering, Automation and Control Systems
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Optimal PMU placements using sea lion optimization for adaptable distribution system
Get PDFThe technological advancements and policy reformations make the electric power distribution system an active network. The modern power system operational regulations encourage coordinated network operations among various entities and customer participation. Unlike traditional operational environments, real-time monitoring has become a mandate for secure and reliable operations. Phasor Measurement Units (PMU) is the most reliable data acquisition tool, and their application for State Estimation (SE) has already been proven. This work extends the application of PMUs for the distribution system. A multi-objective optimization framework is proposed considering the optimal placement of PMU, network reconfiguration, and topology expansion. A novel optimization tool, the sea lion optimizer has been chosen to address the developed optimization problem. The proposed operational model is employed in IEEE RBTS-2 bus system, IEEE 33 node system and 69 node radial distribution network. Numerical results provide new insights into PMUs role in enhancing distribution network operations. The statistical indices confirm that the intended optimizer performs well in the chosen highly constrained optimization environment
Rehabilitation coatings-current challenges and opportunities for the future
Get PDFUnderground pipelines used for oil, gas and water distribution in Saudi Arabia and gulf region are estimated more than 33000 km in length with a range of diameters from 8 and 80 inch. Most of these pipelines are buried in different types of corrosive soil conditions and in most cases an external coating is employed along with cathodic protection (CP). Most of the existing pipelines are over 30 years old now and this is the stage to carry out rehabilitation projects for life extension of this aging infrastructure. The selection of the suitable coating systems for the rehabilitation projects is a very complicated process as it requires in depth understanding the coating/environments interactions in that particular environment along with application challenges. This paper discusses in detail the different types of external underground pipeline coating types and their selection criteria for rehabilitation projects along with recent trends and future recommendations
Structural mechanics analysis of bolt joint of rigid flexible coupling manipulator
Get PDFAs the key connecting part of the rigid flexible coupling manipulator, the structural dynamic characteristics of the bolted joint are analyzed by using the joint simulation technology of pro/e and ANSYS. Based on the spring equivalent principle, the finite element equivalent model of bolt joint is established, the relationship equation between contact surface pressure and bolt preload is derived, and its stress state is analyzed; Based on the micro convex deformation model and Hertz contact theory, the tangential stiffness equation and normal stiffness equation of the bolted joint are derived respectively. The three-dimensional model of the bolted joint is established by using pro/e and imported into ANSYS for joint simulation. The simulation experiments reveal the influence of bolt joint vibration characteristics under different conditions from the aspects of bolt diameter, pre tightening force, bolt group number and bolt distribution. The conclusions have important engineering value for the structural optimization of rigid flexible coupling manipulator
Adaptive feature selection method with FF-FC-MIC for the detection of mutual faults in rotating machinery
Get PDFIn the coupling state of rotor unbalance fault and bearing defect fault for rotor system, the signals contain multiple fault components, and the fault diagnosis of the rotor system needs to contain comprehensive multidimensional feature quantities. However, irrelevant feature information in the multi-dimensional feature quantities increases the complexity of classification calculation and affects the efficiency and accuracy of diagnosis. In order to eliminate redundant and irrelevant features in the feature information, and achieve the goal of fewer diagnostic features and good diagnostic results, this paper proposes an adaptive feature selection based on the maximum information coefficient FF-FC-MIC (Feature-to-Feature and Feature-to-Category Maximum Information Coefficient) method. Firstly, the sparse representation algorithm is used to reconstruct the original signal to improve the signal-to-noise ratio, and the multi-dimensional feature quantity of the reconstructed signal is calculated; Secondly, calculate the correlation between features and features through MIC to obtain a feature set of weak correlation between features; thirdly, use MIC to calculate the correlation between features and signal categories to obtain a feature set with strong correlation between features and signals; Finally, the FF-FC-MIC feature selection method is used for feature adaptive selection and input into SVM to complete fault diagnosis. The method is analyzed by simulation signals and the real experiment signals. The results show that the method can effectively remove redundant and disclosed features in the coupling fault, reducing the characteristic dimension to reduce the fault classification time, and improve classification accuracy. Different experimental cases and various feature selection comparison methods further verify the accuracy and applicability of the proposed method
Study on bearing mechanical and thermal characteristic evolvement rules affected by higher ambient temperature
Get PDFIn this paper, the bearing mechanical characteristics and thermal characteristics as it is running under constant speed (2400 r/min) and constant temperature (100 ℃) adopting bearing mechanical-thermal coupling model built on the basis of quasi-statics and elastohydrodynamic lubrication theory are discussed. Among which, the contact deformation between ball and inner/outer ring has same evolution law, besides, the same as the amplitude. Whose curve shape changes in the form of “circular-oblique D”, its amplitude rearches minimum value at 10thd3h between the location of 120° and 270°. The curve shapes belonging to contact angular between ball and inner/outer ring are similar to “circular”. There is opposite trend of them within the range of 90-300°. The amplitude of contact angular between ball and outer ring is the minimum at 10thd3h and 11thd1h. At the same time, the amplitude of that between ball and inner ring is the maximum. The evolution rules of contact stiffness between ball and inner/outer ring are generally consistent, which are similar to “crab”. But the amplitude of that between ball and outer ring is dominant. The maximum value of them occurs at 10thd3 and 11thd1h. The evolvement tendency of node temperatures maintains stable. Thereinto, the temperature of inner ring equals to that of contact location between ball and inner ring, which is the maximum value. It is obvious that ME, MD, MS, MCB, MCR and MOil devote themselves to heat production, the contribution rates of ME, MS, MCB and MCR are 100 %, the contribution rate of MD ranges from 52.6 % to 65.2 %. However, the amplitudes of friction moments have the opposite trend compared to “heat contribution factor”. The expansion amount owing to heat production is dominant in displacement variation and the effect of clearance on displacement can be ignored, whose evolution rules are contrary. The evolution rules of oil film thickness and oil film stiffness between ball and inner/outer ring are alike. Among which, the oil film thickness between ball and outer ring is dominant, its maximum value emerges at 10thd3h. The curve shapes of oil film stiffness between ball and outer/inner ring are oblique “D”, their amplitudes reach the maximum at 11thd1h-11thd3h
Vibration characteristics of mistuned multistage bladed disks of the aero-engine compressor
Get PDFIn order to analyze the vibration characteristics of mistuned multistage bladed disks of an aero-engine compressor, a finite element reduction model of mistuned multistage bladed disks is established based on substructure modal synthesis method. The accuracy of the substructure model was verified by comparing calculation accuracy of the substructure model and the integral model. The influence of different modal truncation numbers on the calculation results are discussed. The vibration modes of each stage of the bladed disks are obtained, the forced response is analyzed from the perspective of strain energy. The result shows that modal truncation number, rotation softening effect, and speed have significant effects on the dynamic frequency calculation results of the multistage bladed disks. The typical mode shapes of the first 200 orders of multistage bladed disks are obtained. With the increase of mistuning standard deviation, the strain energy of multistage bladed disk system decreases gradually
Carbon deposition fault diagnosis of small piston engine based on optimized VMD
Get PDFAiming at the small piston engine carbon deposition fault in the process of running, based on the cylinder pressure and cylinder head vibration signal of the engine, a fault diagnosis method combining variational mode decomposition and support vector machine is used to diagnose the engine carbon deposition fault. Firstly, particle swarm optimization algorithm is used to optimize the parameters of the variational mode decomposition. Then, the intrinsic mode function is obtained by processing the pressure signal and cylinder head vibration signal of the engine. Then, the singular spectrum entropy is calculated by singular value decomposition of the intrinsic mode function. Finally, the singular spectrum entropy is input into the support vector machine classifier as the feature data set for training and testing. The results show that this method can identify the carbon deposition fault of the starting motor well, and the accuracy of fault identification and classification of cylinder pressure and cylinder head vibration signal is 98.33 % and 99.17 % respectively, which verifies the effectiveness of this method
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
Bruxism and masticatory pattern: an understudied relationship
Get PDFBruxism as a pathophysiological entity, both day and night bruxism, has been the subject of innumerable investigations. Among the probable causes that have been raised are biochemical alterations in the central and/or peripheral nervous system, which can be seen reflected in an alteration of the rhythmic movements of the masticatory musculature of the stomatognathic system. On the other hand, chewing is recognized as one of the main functions of the stomatognathic system, responsible for maxillofacial growth and determining a rhythm in the movements of the masticatory musculature, depending in turn on a functional demand of the individual, in other words, the type of food consumed and the way to process it in the mouth. Objective: To determine the existence of a relationship between bruxism and the type of masticatory pattern installed in the patient. Methodology: Functional examinations and application of Fonseca questionnaires and bruxism self-report were performed in 27 adult patients, without distinction of sex, who have been diagnosed with possible and probable bruxism. Results: 100 % of the sample of subjects diagnosed with bruxism presented an altered masticatory pattern. Conclusions: The high correlation found in the sample between bruxism and masticatory pattern suggests that it is vital for the success of a bruxism treatment or a DTM to consider the way of processing food, by educating the patient with Masticatory Orientation. Based on the above, it proposes to conduct a study to evaluate the efficiency of a functional treatment for future Bruxism therapies
Cephalometric components and their implications in mandibular positioning
Get PDFThe mandibular position is determined by several physiological factors, which should be considered for diagnosis, therapy and stability. Sixty-eight lateral skull radiographs were taken and plotted to determine the relationship of the occlusal plane with the mandibular position among others. A Spearman statistical analysis was performed to determine the relationship between these variables. The occlusal plane showed a statistically significant correlation with mandibular position