Maintenance, Reliability and Condition Monitoring
Not a member yet
1200 research outputs found
Sort by
Propagation characteristics of vibrations due to rock blasting in silt-rock strata
Get PDFThe geological effects of rock blasting in silt-rock strata are complex, and the vibrations caused by the blasting threaten the safety of inhabitable areas. Based on measured data for the vibrations at the site and dynamic finite element simulations, the propagation characteristics of vibrations in silt-rock strata were studied. The propagation of the vibrations of the surface, the propagation characteristics of the vertical vibration velocities from the surface to the tunnel, and the attenuation of the blasting vibrations along the tunnel’s axis were analyzed. The results of this study are as followings: in the direction of the tunnel’s axis and in the direction vertical to the tunnel’s axis, the peak particle velocities (PPVs) of the surface decreases with increasing horizontal distance from the explosion source. The magnitudes of the PPVs of the surface under five working conditions are the same when the surface particle is right above the center of the explosion source and 10 m away from the center. In the vertical direction from the surface to the explosion source, the vertical direction of the silt-rock strata and the vertical direction of the silt stratum, the PPVs increases gradually with the increasing distance from the surface in the vertical direction. The change in the thickness of the artificial fill and silt in the shield interval strata has little effect on the PPVs along the tunnel’s axis. The results of this study provide a reference for identifying the safety distance around the inhabitable areas of rock blasting under similar geological conditions
Deep learning method for visual question answering in the digital radiology domain
Get PDFComputer vision applications in the medical field are widespread, and language processing models have gained more and more interest as well. However, these two different tasks often go separately: disease or pathology detection is often based purely on image models, while for example patient notes are treated only from the natural language processing perspective. However, there is an important task between: given a medical image, describe what is inside it – organs, modality, pathology, location, and stage of the pathology, etc. This type of area falls into the so-called VQA area – Visual Question Answering. In this work, we concentrate on blending deep features extracted from image and language models into a single representation. A new method of feature fusion is proposed and shown to be superior in terms of accuracy compared to summation and concatenation methods. For the radiology image dataset VQA-2019 Med [1], the new method achieves 84.8 % compared to 82.2 % for other considered feature fusion methods. In addition to increased accuracy, the proposed model does not become more difficult to train as the number of unknown parameters does not increase, as compared with the simple addition operation for fusing features
Service performance evaluation of long-span cable-stayed bridge based on health monitoring data
Get PDFService performance evaluation is of great significance to the safety, durability, and reliability of bridge engineering. Over the last decade, structural health monitoring (SHM) systems have been widely used for condition monitoring of cable-stayed bridges, massive monitoring data are measured and stored by the sensing subsystems, which provides the basis for service performance evaluation of bridge engineering. Meanwhile, the load test is a common method to assess the construction and service performance of bridges. Combined the SHM systems and a load test of a thousand-meter level cable-stayed bridge after ten years of service, this paper investigates the operating conditions of main structures, including bridge towers, main girders, and steel cables. 52 trucks were used to conduct a quasi-static load on three key sections of bridges. Meanwhile, the GPS displacement of towers and main girders, stress of the main girders and acceleration responses of cables were measured synchronously by the SHM systems. Based on the health monitoring data, the dynamic responses, structural deformation, and cable tension of the bridge were investigated and evaluated by comparing with the finite element (FE) model load test at construction stage. The results show that the service performance of the bridge is basically within the designed conditions
Occlusal plane parallel to camper plane: reality or fallacy? A tomographic study on human Sambaqui skeletal remains
Get PDFIntroduction: Since long time ago, dentists had used parallelism with Camper plane as a reference to establish a correct occlusal plane. However, in the literature, there are several different landmarks used to trace the occlusal plane and there are also many researchers questioning this parallelism. To evaluate it, we used ancient skulls from Human Sambaqui skeletal remains. The authors choose an ancient population because they were submitted to same environmental conditions, avoiding bias in craniofacial growth epigenetic stimuli. Methodology: For this work we analyzed tomographies of 27 well preserved adult skulls. The program used was Vista Dent Pro 2.1. Camper plane was determined according to the original points described by Peter Camper. We used the four occlusal planes more cited in the literature. Results: None of the occlusal planes evaluated on this study, showed parallelism with Camper plane. The occlusal plane determined by posterior teeth was the one that showed less divergence but still with a high SD and mediana. Conclusion: In Sambaqui ancient population, Camper plane was not a reliable reference to trace occlusal plane. It is necessary further investigations to find a better reference for prosthetic, orthodontic, functional orthopedics or orthognathic surgery purpose
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
Experimental and numerical analysis for improving the suction capacity of the manufactured water jet ejectors
Get PDFWater jet ejectors are the silent pumping fluid devices which doesn’t have any rotating parts in functional industrial applications. The dimensionless geometrical parameters effects ejector suction capacity. In this study, it is found that optimum design intervals have been determined by using the Response Surface Method (RSM). Design ranges determined in the dimensionless study have been used in the improvement of the suction capacity of an existing ejector. The suction capacity of the existing ejector is investigated via numerical and experimental analysis. Two new water jet ejector designs (D1 and D2) are built to improve the suction capacity of the initial water jet ejector (D0). The generated design parameters have been analyzed by using SolidWorks flow analysis and optimization software. The suction capacity of the ejector has been determined through the iterative numerical analysis for the selected geometrical parameters under the applied design conditions. The effect of design parameters on the suction capacity of the water jet ejectors is unveiled through numerical and experimental analysis. The established designs were produced as two novel bronze water jet ejectors. The suction capacities of the produced bronze water jet ejectors have been investigated experimentally. The numerical results have been validated using the experimental results. It is achieved that the suction capacity of the manufactured water jet ejector with the improved design (D2) is suddenly increased from 52.05 m3/h to 103.4 m3/h
Detection of weak joints and damages for beams using machine learning
Get PDFFor maintaining the safe operation of structures, it is necessary to develop SHM methods that can detect not only the presence of cracks in the structure but also any alterations of its fastening conditions. The current paper presents a method for developing an Artificial Intelligent model that can detect if a beam is affected by transverse cracks and at the same time, by improper boundary conditions. To this aim, a cantilever steel beam is considered as the in the current study. The training data for the artificial neural network (ANN) is created using an original analytic method which allows calculating the natural frequency loss caused by the occurrence of transverse cracks even if the beam is improperly fastened. The intelligent model is trained by employing the MATLAB software and tested using data acquired from numerical simulations. The results show very high accuracy in determining the presence of transverse cracks, and the capability of detecting the presence and severity of improper clamping conditions
Modelling and experimental investigation of the vibratory conveyor operating conditions
Get PDFThe paper’s objective is to study the dynamic parameters and operating conditions of the vibratory conveyor, which is based on the double-mass oscillatory system and equipped with the pull-type (single-cycle) electromagnetic exciter. The scientific novelty consists in substantiating the conveying capacity of various standard sizes of bolts at different operating conditions defined by the input parameters, particularly supplied voltage. In order to describe the conveying tray vibrations, the simplified mathematical model of the conveyor’s double-mass oscillatory system is developed using the Euler-Lagrange equations and is numerically solved in the Mathematica software with the help of the Runge-Kutta methods. The experimental investigations are carried out at the Vibroengineering Laboratory of Lviv Polytechnic National University and are focused on testing the conveying speed of various bolts at different motion conditions: detachable (bouncing, hopping, jumping over the conveying surface) and non-detachable (sliding along the conveying surface). The obtained results show the basic kinematic parameters of the conveying tray motion at different voltages supplied to the actuating electromagnet and the dependencies of the conveying speeds of various bolts at different motion conditions mentioned above. The paper may be useful for designers and researchers while improving and implementing similar vibratory equipment in various industries
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
Dynamic stiffness and vibration analysis model of angular contact ball bearing considering vibration and friction state variation
Get PDFForce and thermal effect are dominant in giving rise to variation of bearing dynamic stiffness and vibration. On the basis of test and theoretical analysis, the dynamic stiffness and vibration model of angle contact ball bearing considering vibration and friction state variation is established. Firstly, based on the quasi-statics of bearing and hydrodynamic lubrication theory, the motion and force relation between each parts are determined by considering the force and thermal effect. Secondly, the friction power consumption of bearing is calculated adopting integrated method, besides, the conduction heat resistance and convection heat resistance in the bearing system are achieved. A steady-state temperature calculation model of angle contact ball bearing-shaft-house system is built based on thermal network method. Finally, the dynamic stiffness and vibration model of angular contact ball bearing including the thermal-solid coupling effect is obtained, which is employed to realize the theoretical analysis of bearing dynamic stiffness and vibration, its accuracy is verified through typical test results. The calculation results shows that there is a good agreement between house test temperature and calculation temperature. The evolution rule of contact deformation and contact stiffness between ball and outer/inner ring over the whole life under excessive preload is the same. So does the oil film thickness and oil film stiffness. However, the curve shape and amplitude of contact angular between ball and outer/inner ring over the whole life is different. Bearing radial stiffness value has a more significant change than axial stiffness value, both of them represent an overall upward tendency. The radial clearance holds a negative correlation with house temperature, however, the radial displacement has a positive correlation with house temperature. The evolvement curve of contact angular affected by various preload and speed is opposite. The contact load between ball and outer/inner ring has the same trend influenced by preload and speed with EHL. The variation of preload has bigger effect on temperature rise than speed change. The oil film has little influence on contact angular, contact load and temperature under dry-lubricated or lightly lubricated condition