Journal of Mechanical Engineering, Automation and Control Systems
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A study of numerical simulation on extreme flexural stress of ice plate
Get PDFIce plate is general construction component in the cold region and the flexural stress governs its failure pattern. As per the stress equations which were proposed by Westgaard and Masterson, they explained the generic empirical methods to evaluate the extreme and effective flexural stress of ice plate. Based on these equations, most of consequent experiments and simulations referred them directly. Despite of this, there are not any demonstrations about the limitations of these equations by numerical modeling, therefore, it is possible to find the differences between the simulation values and theoretical calculation values by the deployment of numerical simulations from ‘Finite Element Analysis’ perspective, and based on these comparisons, author proposed some assumptions about the limitations of these equations. In the meantime, the simulation process can enhance the understanding of the applications of these equations
Threshold analysis method for aircraft avoiding convective weather
Get PDFConvective weather is an important weather phenomenon that affects aircraft operation, and the determination and analysis of convective weather characteristic thresholds is the basis and premise for airspace availability analysis and aircraft diversion. This paper innovatively proposes a threshold analysis method for aircraft to avoid convective weather. Firstly, the historical meteorological data and the track data are adopted in spatiotemporal and synchronous fusion. Secondly, the K-means clustering algorithm is used to determine the characteristic threshold range of the aircraft to avoid convective weather. Then, combined with the random forest classification algorithm, each threshold is again classified 0-1 through machine learning to determine the best avoidance threshold for weather features. Finally, the new construction index evaluation is used to evaluate the reliability of the algorithm. According to the threshold analysis method, the radar reflectivity factor is taken as the research object to carry out an example analysis. The example shows that when the radar reflectivity value is 34 dBZ, the accuracy rate is 96.58 %, the false alarm rate is 2.45 %, and the missing alarm rate is 0.97 %, all of which are better than the decision tree method, thus verifying the reliability and practicability of the algorithm
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
Is jaw functional orthopedics an efficient tool to treat anterior open bite? A retrospective study
Get PDFAnterior Open Bite (AOB) is a malocclusion for which the choice of a treatment protocol it is challenging. There are some protocols that have been shown to be effective for open bite treatment. The aim of this investigation was to study the behavior of overbite during AOB treatment with Jaw Functional Orthopedics (JFO). The behavior of overbite was studied retrospectively in 17 patients treated in the Specialization Course in (JFO – ABO Muriaé (Muriaé, MG Brazil). Monthly overbite measurements in millimeters were taken with a pachymeter and the data were stored in an individual paper worksheet. Data obtained before functional appliance installation (T0) and after 12-months of treatment (T1) were compared. Wilcoxon non-parametric test for 2 paired samples was use for statical treatment of the data. P= 0.003 for overbite comparison T1-T0. It could be concluded that Functional orthopedic appliance has shown to be an effective tool for treating anterior open bite in the sample studied. Further studies, mainly Randomized Clinical Trials, with larger samples are necessary to confirm this result and to study stability and skeletal behavior in anterior open bite treated with Jaw Functional orthopedics
Seismic response analysis of tunnel with cavity behind lining
Get PDFFor the seismic safety of tunnels with cavity behind lining, based on the finite element method, the viscoelastic artificial boundaries are introduced to study the influence of the location of cavity behind lining on the seismic response of tunnel structure under vertically incident SV wave. The analysis results show that the cavity behind the lining has a significant effect on the seismic response of tunnel structure, and the appearance of cavity behind lining will significantly change the dynamic characteristics of tunnel structure; when the incidence frequency of wave is close to the natural vibration frequency of tunnel structure, the lining stress has the largest amplification when the cavity appears behind the vault; Regardless of the cavity location, the maximum of lining stresses always appears at the arched foot, and the vault stress has the largest amplification; Under the Taft wave, the maximum stress 1.642 MPa of lining without cavity appears at the arched foot, and the minimum 0.118MPa at the arched waist, the stress amplification at the vault can reach about 760 %, which is unfavorable to tunnels. In addition, the soil property also has a great influence on the tunnel; the layered site will lead to the obvious change of the seismic wave, hence the geological data should be collected in detail in the seismic design of tunnel. Meanwhile it is proposed that the PE material can be filled back into the cavities behind the tunnel lining to reduce the earthquake damage of tunnels
Optimization of damping pad distribution on body-in-white car structure
Get PDFStructure-born noise is one of the most important contributors to the interior noise in a vehicle cabin. This can be effectively reduced by placing damping pads with special material properties along the chassis and on the large, radiating panels. This paper proposes a new methodology for the optimization of placing these pads as a part of a full vehicle acoustic simulation in Actran Virtual SEA. With this new strategy, it was possible to reduce the among of damping pads on a real car structure by 33 % while keeping the same acoustic performance. This was validated by investigating the mean velocity of the floor panel in two load cases and compared to the original damping pad layout to the optimized one
Research on the heat transfer and internal residual stress of multi-phase systems
Get PDFThe incompatibility of inherent physical properties of the individual constituents often leads to the failures of the whole multi-phase system during the service. We need to investigate the residual stress caused by different inherent properties of the constituents that could finally cause the failure of the whole system and predict the severe time. This paper synthesized a special network-structure composite as the investigated system. The hybrid composites have a honey-comb structure with the high thermal conductivity HfB2 encapsuling the low thermal conductivity B4C. Although the overall thermal conductivity is greatly improved, the different thermal expansivity of the composites can result in a severe residual stress within the composite, which will finally evolve into macroscopy cracks and becomes a threat to the normal operation of the whole system. It is therefore necessary to investigate the magnitude of residual stress and its corresponding distribution. We employed the real-situation modeling and finite element analysis to probe the residual stress caused by the incompatibility of thermal expansivity. This method is effective and has its practical value when applying in relevant industries applications for the prediction and preventing the possible accidents
Making humanoid robots teaching assistants by using natural language processing (NLP) cloud-based services
Get PDFHumanoid robots have a substantial potential to serve as teaching and social assistants. However, the expectations of the children from robots to interact like humans are huge. This study presents a general model for understanding the natural language in human-robot interaction by applying Generative Pre-trained Transformer (GPT) language models as a service in the Internet of Things. Thus, the physical presence of the robot can help in fine-tuning the GPT model by prompts derived from the environmental context and subsequent robot actions for embodiment understanding of the GPT outputs. The model uses web or cloud services for Natural Language Processing (NLP) to produce and play human-like text, question answering or text generation. Verbal questions are processed either via a local speech recognition software or via a Speech-to-Text (STT) cloud service. The converted question into machine-readable code is sent to one of the GPT language models with zero- or few-shot learning prompts. GPT-J model has been tested and deployed either in the web or cloud with options for varying the parameters for controlling the haphazardness of the generated text. The robot produces human-like text by using Text-to-Speech (TTS) cloud services that convert the response into audio format rendered on the robot to be played. Useful requirements how the model to be used in order to be feasible were determined based on the evaluation of the outputs given from the different NLP and GPT-J web or cloud-services. We designed and implemented the model in order to be used by a humanoid NAO-type robot in the speech language therapy practice, however it can be used for other open-source and programmable robots and in different contexts
Research on 3D MFL testing of wire rope based on empirical wavelet transform and SRCNN
Get PDFMagnetic flux leakage (MFL) testing is one of the most effective methods in nondestructive testing of wire rope. However, traditional MFL testing devices have problems such as low recognition rate, single detection dimension and fuzzy magnetic leakage image. Based on the non-saturated magnetic excitation 3D MFL testing device, this paper proposes a wavelet denoising method based on empirical wavelet transform (EWT) to denoise the collected 3D MFL signal. After noise reduction, the Signal-to-Noise Ratio (SNR) and Root Mean Squared Error (RMSE) of the three dimensions have improved. Color imaging technology is used to fuse defect grayscale images into color images, and Super-Resolution Convolutional Neural Network (SRCNN) is applied to MFL images of broken wires. After SRCNN reconstruction, the resolution of defect color images is improved. The color moment feature of the defect color image is extracted as the input of the Elman neural network to quantitatively identify broken wires. Experimental results show that the noise reduction algorithm can effectively suppress the noise in three dimensions, and the broken wires recognition rate after reconstruction has been significantly improved, which verifies the effectiveness of SRCNN in wire rope MFL images
