最新刊期
卷 54 ， 期 9 ， 2020
- 摘要：To meet the requirements of the high efficiency and stability for compressors and pumps at full load operations, numerous theoretical and experimental studies have been conducted for annular dynamic seals working in pure liquid and multiphase environments, focusing on the special seal leakage and rotordynamic performance. Firstly, the application background in pure liquid and multiphase environments, as well as the fluid-induced excitation mechanism and the mathematical model of rotordynamic coefficients, is introduced for annular dynamic seals. Secondly, the recent advances in the performance analysis method and geometry design are summari-ed for the annular dynamic seals in pure liquid. The research status of the leakage flow, drag loss and rotordynamics is also introduced for the annular dynamic seals in gas-liquid two-phase(gas in liquid)conditions. What is more, the main conclusions from the experimental measurements and numerical simulations on the leakage flow and rotordynamic c关键词：annular dynamic seal;liquid and multiple phases conditions;leakage flow;rotordynamics;experimental measurement;numerical simulation260|4|8更新时间：2025-07-09
- 摘要：Aiming at the bad effect of fault diagnosis of rolling bearing due to complex and changeable working environments, ambient noise influence and insufficient valid sample data, an improved residual neural network method for fault diagnosis is proposed under variable working conditions. The acquired time domain signals of rolling bearing are taken as the inputs, and according to the strong time-varying characteristic of time domain signals of rolling bearing, an improved data pooling layer based on the Inception module is constructed. To extract the feature information effectively, following the Inception module idea, the data pooling layer is constructed by three small 3-3 stacked convolutional layers in series and by adding residual connection. A kind of residual block with a skipping connecting line is designed by adding a skipping connecting line, which can enhance the learning efficiency of characteristic information. Because the dilated convolution can expand the receptive field, t关键词：fault diagnosis;rolling bearing;variable working condition;residual neural network328|5|23更新时间：2025-07-09
- 摘要：A new K-means clustering algorithm with improved moth-flame optimi-ation is proposed to solve the problem that the current K-means clustering(KMC)algorithm has great randomness in selecting the initial clustering center, poor global search ability and low clustering accuracy. The maximum and minimum distance function is adopted to initiali-e the clustering center to avoid the problem that KMC algorithm is sensitive to the random initial clustering center. Then the moth-flame optimi-ation is improved by spline interpolation to heighten the convergence rate and optimi-ation accuracy. The average distance category is taken as the fitness function to guide interpolation moth-flame optimi-ation to optimi-e the clustering center in the process of KMC iteration so as to improve the clustering accuracy. Compared with KMC algorithm, K-means++ algorithm and fu--y c-means clustering algorithm on the international standard data sets Iris, Wine and Seeds, the experimental results show that the IMFO关键词：moth-flame optimi-ation;cluster center;K-means clustering;average distance category;maximum and minimum distance product200|5|12更新时间：2025-07-09
- 摘要：To study the lubrication characteristics of water-lubricated rubber bearings(WLRBs)in mixed-flow state, based on the classical laminar flow and turbulent lubrication theory, the mixed flow lubrication equations were established for WLRBs. Adopting the finite difference method, the variations of Reynolds number, water film thickness, liner deformation and water film pressure with eccentricity, rotational speed, and length to diameter ratio under mixed-flow lubrication were investigated, and the lubrication characteristics in three different lubrication states of laminar, turbulent and mixed flows were studied. The results show that the mixed-flow lubrication equations are more suitable for the actual operating conditions of WLRBs than the laminar and turbulent theories. For the mixed-flow lubrication, the value ranges of water film thickness, liner deformation and water film pressure are all between that of laminar and turbulent lubrications. For the mixed-flow lubrication, the Reynolds关键词：water-lubricated rubber bearing;mixed-flow lubrication;Reynolds number;liner deformation;water film pressure147|4|3更新时间：2025-07-09
- 摘要：To accurately predict the leakage flow and resistance characteristics of brush seals, the multi-block structured mesh and the mesh motion technique are applied to the three-dimensional staggered tube bundle model of brush seals. The application of the multi-block structured mesh ensures that there is no need to set interfaces between the fluid domains of the bristle pack and cavity, hence the interpolation errors due to the existence of the interfaces are eliminated. The mesh motion technique could reali-e the overall axial compactness of the bristle pack. The numerical leakage flow rate of the brush seal is in good agreement with the experimental data and the validation of the developed numerical method is verified. The effects of the pressure ratio(1.5, 2.5, 3.5), sealing clearance(0, 0.1, 0.2 mm)and longitudinal pitch reduction(0 - 0.005 mm)on the leakage flow rate and flow resistance performance of the brush seal are investigated. The results show that the reduction of longitudinal关键词：brush seal;three-dimensional staggered tube bundle model;leakage flow;resistance characteristics;numerical simulation183|4|3更新时间：2025-07-09
- 摘要：Considering the lack of understanding of the flow and heat transfer mechanism of the double swirl cooling structure at the leading edge of turbine blades, a reasonable tangential double swirl cooling structure model was established. The SST k- turbulence model was solved by using the Reynolds averaged Navier-Stokes(RANS)equation. The flow and heat transfer characteristics of the double swirl chamber were analy-ed when the circumferential angle is 60- - 120- and the diameter ratio is 0.435 - 1.2. The results show that, compared with the single swirl cooling, the opposite vortex pair is formed in the double swirl chamber, and the phenomenon of impingement and reattachment appears in the fusion -one, which makes the comprehensive heat transfer performance better. With the increase of the circumferential angle, the Nusselt number of the swirl chamber wall increases first and then decreases, while the friction coefficient shows an opposite trend. It is estimated that the comprehensive hea关键词：double swirl cooling;circumferential angle;diameter ratio;Nusselt number;friction coefficient162|4|3更新时间：2025-07-09
- 摘要：To solve the problem of uneven load distribution in the engineering application of the concentric torque split face gear transmission, the mechanism of uneven load distribution and the dynamic load sharing characteristics of this type of gear transmission are studied. From the point of view of power flow, the uneven load distribution of the concentric torque split face gear transmission is analy-ed. The mechanism of uneven load distribution is deduced based on the basic principle of deformation coordination, and the main factors affecting load distribution are pointed out. A lumped parameter dynamic model coupling with flexional, torsional and axial motion is established by using the fast modeling method of the multi-meshing gear system. Based on the solution of dynamic meshing force, a method for measuring the dynamic load sharing performance of the system is defined. The meshing error of each gear pair of the concentric torque split face gear transmission system is analy-ed, and the关键词：face gear;torque split gear transmission;uneven load distribution mechanism;load sharing characteristics140|4|1更新时间：2025-07-09
- 摘要：The transient DDES(delayed detached eddy simulation)methods were adopted to investigate the unsteady fluid flow and film cooling performance in a gas turbine blade with trailing edge cutback and land extensions. The film cooling effectiveness on trailing edge cutback was studied under three different blowing ratios(M=0.2, 0.8, 1.25). The flow and cooling effects in a trailing edge cutback model with land extensions were compared to that without lands. The reliability and accuracy of the transient numerical methods were validated with the existing experimental data with respect to the discharge coefficients in slot and the cooling effectiveness on cutback surface. The results show that the DDES methods are able to provide reliable predictions for the vortex shedding in trailing edge cutback region and capture the developments of vortices effectively. The computational results of discharge coefficients and cooling effectiveness are in good agreement with the experimental data. The discha关键词：gas turbine;trailing edge cutback;cooling;land extension;blowing ratio135|4|3更新时间：2025-07-09
- 摘要：To solve the problem of lacking sensitive elements in the neutron energy spectrum measuring device caused by the shortage of 3He gas and the increasingly expensive price, a set of BF3 proportional counter multisphere spectrometer system is developed. Based on the Monte Carlo method, the detailed structure of the multisphere spectrometer system is modeled, and the energy sensitivity of the detector is obtained through simulation calculation. The energy response sensitivity of the spectrometer system is calibrated using 2.86 MeV and 14.84 MeV energy neutrons on the Cockcroft-Walton accelerator in China Institute of Atomic Energy, and the energy response sensitivity of the spectrometer system under experimental conditions is determined with the simulation results. Using this spectrometer system, the energy spectrum of the 241Am-Be neutron source is measured, and the measurement results are deconvoluted using the self-edited Gravel algorithm. Comparison of关键词：Bonner multisphere spectrometer;Monte Carlo method;241Am-Be neutron source;unfolding spectrum144|4|2更新时间：2025-07-09
- 摘要：Aiming at the problem that the model trained by public data set cannot be directly applied to the auxiliary diagnosis of different clinical devices and there is not sufficient manpower to label the clinical data, few-shot domain adaptation for the identification of clinical image in dermatology is proposed. The ISIC dermatological public data set is taken as the source domain with known label, and the actual clinical dataset is taken as the target domain to be predicted, small amount of clinical data are marked by the doctor to train few-shot domain adaptive model of feature extractor and classifier implemented by convolutional neural network. The maximum correntropy criterion is adopted to improve the accuracy and generali-ation ability of the recognition model. If there are only a small number of labeled target samples in each class, the distribution gap between different domains is reduced while extracting discriminative features by alternating maximum and minimum conditional entrop关键词：convolutional neural network;domain adaption;few-shot;dermatological recognition;maximum correntropy criterion207|4|0更新时间：2025-07-09
- 摘要：For the aim of improving accuracy and reducing training time in automatic gesture recognition, a new gesture recognition model based on Fisher Score(FS)feature reduction combined with machine learning method is proposed. Firstly, the feature set is extracted from four-channel surface electromyography signals, involving the features of time domain, frequency domain, time-frequency domain and nonlinear dynamics. Then, FS and principal component analysis(PCA)are used for feature reduction respectively, and linear discriminant analysis(LDA)and support vector machine(SVM)are adopted as classifiers. Finally, different gesture recognition models are constructed by the two classifiers with and without two feature reduction methods, and their classification performance is compared. Experimental results demonstrate that the feature reduction method can help classifier improve accuracy and reduce training time significantly. Furthermore, compared with PCA, FS is a simple and effective feature red关键词：surface electromyography;feature extraction;feature reduction;machine learning;Fisher Score232|7|6更新时间：2025-07-09
- 摘要：Current study of the neural mechanism of epilepsy based on electroencephalography(EEG)is limited to the epilepsy-related local brain regions. This study uses microstate to reveal the cerebral neural mechanism of epilepsy from a global perspective. The modified K-means algorithm is used to cluster typical microstates of epileptic patients, and the sequence of the microstates is obtained by fitting the microstates with the continuous EEG signals. The duration, coverage and occurrence are calculated to compare the relative trend difference of parameters between patients and healthy people. Then wavelet transform is employed to test the fractal characteristics of EEG microstates sequence. Results show that the mean duration of epileptic patients- microstate D is(101.42-22.91)ms, the proportion of microstate D in the entire time series is(30.86-9.79)%, and the occurrence of microstate D is(3.10-0.94)times per second. The values of the parameters of microstate D are significantly larger关键词：epilepsy;interictal phase;electroencephalography;microstate;fractal analysis142|4|2更新时间：2025-07-09
- 摘要：To improve the adsorption capacity of cationic dyes methylene blue(MB)and rhodamine B(RhB)in wastewater, the negatively charged metal-organic framework(MOFs)materialUiO-66-(COOH)2 was prepared by introducing carboxyl groups. The MOFs samples were carefully characteri-ed by X-ray diffraction, scanning electron microscopy, N2 absorption-desorption isotherm, thermogravimetric analy-er and Fourier transform infrared spectroscopy. The adsorption properties and mechanisms ofUiO-66-(COOH)2 to MB and RhB in wastewater were deeply investigated. The results show that the effect of static electricity lead the adsorption properties ofUiO-66-(COOH)2 improved by 32.4% and 51.8% respectively compared with UiO-66, and the adsorption properties are much higher than that of activated carbon and other carboxyl modified materials. In the pH range of 3 - 10,UiO-66-(COOH)2 exhibits better adsorption properties and stronger pH adaptability. Analy-ing the关键词：metal-organic framework material;UiO-66-(COOH)2;methylene blue;rhodamine B;adsorption157|5|4更新时间：2025-07-09
- 摘要：Hydrogenated biodiesel-diesel binary blends(PHC10, PHC20, PHC30)and hydrogen-ated biodiesel-ethanol-diesel ternary blends(PHC5E5, PHC10E10, PHC15E15)were prepared to conduct the combustion and emissions research on a common rail diesel engine under the conditions of 25%, 50%, 75% and 100% loads at 1 800 r/min. It was revealed that the ignition timings of the binary blends and ternary blends were advanced and lagged respectively under 100% load, due to different cetane numbers of hydrogenated biodiesel and ethanol. Owing to the less combustible mixture in the ignition delay affected by the advance of ignition timing of binary blends, the smaller lower-heating value, and the higher kinematic viscosity of hydrogenated biodiesel, the maximum cylinder pressure and heat release rate of the binary blends in the main combustion term were lower than those of diesel. The heat released from the initial combustion term could overcome the disadvantage of latent heat of vapori-ation of ethanol. Mean关键词：hydrogenated biodiesel;ethanol;ternary blend;common rail diesel engine;combustion;emission145|4|4更新时间：2025-07-09
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