1D/3D coupling analysis of engine cooling system

In this paper, the FLUENT and KULI soft wares were used to analyze the cooling performance on the radiating module of the cooling system for a heavy vehicle by 1D/3D coupling simulation. According to the analysis, the cooling performance of the existing engine cooling system for heavy vehicles is declined by the gap between the intercooler and radiator in the cooling system. Moreover, the structure of an integrated cooling system was proposed. The wind tunnel experiment model was built in the FLUENT software to analyze the original cooling system and the integrated cooling system by three-dimensional simulation. Then the obtained velocity matrix from 3D simulation was imported into the KULI software to compare the cooling performances of the original system and the integrated system. It was found that the cooling performance of the integrated cooling system is superior to that of the original cooling system

A Class of Wavelet-Based Rayleigh-Euler Beam Element for Analyzing Rotating Shafts

A class of wavelet-based Rayleigh-Euler rotating beam element using B-spline wavelets on the interval (BSWI) is developed to analyze rotor-bearing system. The effects of translational and rotary inertia, torsion moment, axial displacement, cross-coupled stiffness and damping coefficients of bearings, hysteric and viscous internal damping, gyroscopic moments and bending deformation of the system are included in the computational model. In order to get a generalized formulation of wavelet-based element, each boundary node is collocated six degrees of freedom (DOFs): three translations and three rotations; whereas, each inner node has only three translations. Typical numerical examples are presented to show the accuracy and efficiency of the presented method

Analysis on the Noise for the Different Gearboxes of the Heavy Truck

In order to locate the excessive noise caused by gearbox noise when a heavy vehicle is accelerating, the noise and vibration on the key parts of the gearbox were tested and analyzed, and the peak noise frequency of radiating from the subbox of gearbox was found, which is the same as the peak frequency of pass-by noise. Aiming at the larger gear noise of the gearbox subbox, the experiments of pass-by noise by the two ways of the different speed-ratio gearbox, and the transformation of vice-box with helical gear, the pass-by noise was reduced by 5.6 and 3.9 dB(A), and it was made to reach the less GB limit-value. Meanwhile, the effect of the different-ratio gearbox on the vehicle noise was analyzed. So, the methods provide a practical basis for the vehicle noise and the fault diagnosis of gearbox

EDMSpell: Incorporating the error discriminator mechanism into chinese spelling correction for the overcorrection problem

Chinese spelling correction (CSC), which is designed to detect and correct typos in the text, is an important and challenging task that has attracted increasing attention. Current CSC models based on pre-trained language models (PLM) show powerful error correction capabilities, but cause the problem that many correct characters are incorrectly corrected. The problem of overcorrection is particularly serious in real-world application scenarios. To alleviate this situation, we propose a novel post-processing model: EDMSpell, which utilizes two discriminators to post-process the corrected results. Specifically, the final decision to adopt this correction is made by discriminating whether the original sentence and the corrected sentence are correct or not. To verify its effectiveness, we conduct comprehensive experiments and ablation tests. Experiments on the SIGHAN15 benchmarks show that EDMSpell can considerably lower the false-positive rate of the model, with an average reduction of 5.4 points, while also improving the error correction F1 metric by an average of 1.4 points on nine models

Refining the time–frequency characteristic of non-stationary signal for improving time–frequency representation under variable speeds

Abstract Time–frequency ridge not only exhibits the variable process of non-stationary signal with time changing but also provides the information of signal synchronous or non-synchronous components for subsequent detection research. Consequently, the key is to decrease the error between real and estimated ridge in the time–frequency domain for accurate detection. In this article, an adaptive weighted smooth model is presented as a post-processing tool to refine the time–frequency ridge which is based on the coarse estimated time–frequency ridge using newly emerging time–frequency methods. Firstly, the coarse ridge is estimated by using multi-synchrosqueezing transform for vibration signal under variable speed conditions. Secondly, an adaptive weighted method is applied to enhance the large time–frequency energy value location of the estimated ridge. Then, the reasonable smooth regularization parameter associated with the vibration signal is constructed. Thirdly, the majorization–minimization method is developed for solving the adaptive weighted smooth model. Finally, the refined time–frequency characteristic is obtained by utilizing the stop criterion of the optimization model. Simulation and experimental signals are given to validate the performance of the proposed method by average absolute errors. Compared with other methods, the proposed method has the highest performance in refinement accuracy

GEAR FAULT DIAGNOSIS BASED ON THE VMD AND MODULATION SPECTRUM INTENSITY DISTRIBUTION

VMD has better band-pass filtering characteristic, which can non-recursively decomposition a real-valued multi-composition signal into a discrete number of quasi-orthogonal band-limited sub-signals with specific sparsity properties in the spectral. Modulation intensity distribution（MID） combined with VMD is applied to detect second-order cyclostationary components in gear fault diagnosis. Impulsive signatures generally represent the transients in the signals and are often caused by local defect in the gear of rotating machinery. Detecting these signatures is vital for mechanical signal processing and fault diagnosis. The impulsive signatures can be successfully extracted using VMD, meanwhile, Signal-noise can be separated to some extent. It is very useful tool to MID detects modulation components. However, when the analyzed signal contains multiple modulations usually mixed with other harmonic components, visual examination of the spectrum may not be accurate for identification of all carriers together with their modulation signals. Considering the shortcomings of MID in the analysis of multi-harmonic modulation signals, VMD is used as the signal preprocessing before MID analysis. Results of simulation and the experimental analysis have demonstrated the effectiveness of the method

Finite-element-analysis of connection strength of assembled camshafts with different cam-bore profiles using tube hydroforming technology

Abstract The assembled camshaft is a novel manufacturing product which connects the cam and the mandrel by tube hydroforming (THF) technology after they are processed separately. However, in the process of THF, the structure of the cam-bores has a crucial influence on the connection strength of the assembled camshafts. Therefore, three kinds of cam-bores with circular structure, isometric-trilateral profile and logarithmic spiral profile are selected for hydroforming with a hollow mandrel (tube) in this study. The finite-element-analysis is carried out by ABAQUS software, the variations of (residual) contact pressure and contact area under different structures are obtained, and the torsional angle variations after assembly are measured. Further, the connection strength of the assembled camshaft under three structures is discussed. The results show that the evaluation of connection strength of the assembled camshaft is affected by many factors, including contact pressure, maximum residual contact pressure, axial and circular residual contact pressure, contact area and its rate, residual contact area percentage and torsional angle. Through the comprehensive analysis of various factors, the torsional angle of the camshaft with circular structure is the largest, i.e. poor connection strength. By contrast, the torsional strength of the camshaft with isometric-trilateral profile is the largest, namely, the best connection strength