最新刊期
卷 52 ， 期 10 ， 2018
- 摘要：A transfer method of emotional instances for unbalanced interactive texts is proposed based on hyperplane distance to focus the problem of poor generalization ability of sentiment classification models when they are trained on an unbalanced interactive text dataset that lacks of minority-class instances. The method uses instances of source dataset between support vectors of the minority class and the majority class as the transferrable instances, and constructs an offset hyperplane based on the classification hyperplane on the target dataset. The method uses the principle of optimal information utility to select the transfer instances based on the shortest distance between the instances and the offset hyperplane, and adopts the migration ratio to control the size of the transfer instances and to generate a synthetic dataset. Experiment results show that when transfer instances increase, the deviation of the synthetic dataset from the original distribution increases, and the generalized classification performance of the trained SMO model rises at the beginning and then decreases after it reaches its maximum, which is similar to the Wundt curve of the information utility. Comparisons with three data layer processing methods(SMOTE, Subsampling and Oversampling)show that five classification models(SMO, LibSVM, random forest, cost sensitive and CNN)trained by the proposed method obtain an average increase of 11% in the F-value of recognizing the minority class, and the optimal range of the migration ratio is [20%, 30%]. It is concluded that the proposed method effectively alleviates the unbalanced characteristics and raises the generalized classification performance of the minority class.关键词：instance transfer;information utility;unbalance classification;hyperplane799|5|0更新时间：2025-07-09
- 摘要：A new dynamic multiobjective optimization algorithm is proposed to solve the problem that the existing dynamic multiobjective optimization algorithms have poor ability to track the rapid changing optimal solutions for practical applications, and the algorithm uses a new prediction model that combines the prediction value of central point and the vertical disturbance component. First, the central point of the optimal solution set before change is calculated as a prediction object, which changes the way that all solutions are usually used for prediction and improves the efficiency of the algorithm. Second, the history information of the algorithmic iterations is combined to select the location, velocity and acceleration as a state vector of prediction. The tracking ability for change in the solution set is ensured in most circumstances. At last, a hyperplane random disturbance that is perpendicular to the predicted direction of change is added to the predicted new solution to enhance the diversity of the knowledge set, and the convergence speed of the algorithm is improved. Experimental results show that the proposed algorithm is superior to the other 3 state-of-the-art dynamic multiobjective evolutionary algorithms in 75% test cases, and the run time of the algorithm is 39% lower than those of dynamic multiobjective optimization algorithms based on Kalman filter.关键词：dynamic multiobjective optimization;evolutionary algorithm;Kalman filter;prediction model914|5|2更新时间：2025-07-09
- 摘要：An effective feature selection method based on an improved Hilbert-Huang transform is proposed to focus on the problem that it is difficult to extract the characteristic features of the defect information in acoustic defect detection systems. Firstly, audio signals are decomposed and reconstructed by the wavelet package to obtain a series of narrow-band signals. Secondly, all of the narrow-band signals are respectively decomposed via the empirical mode decomposition method to obtain several intrinsic mode function components. Then the real intrinsic mode function components are screened out based on mutual information.Instantaneous attributes are obtained from these intrinsic mode function components through Hilbert transformation. Finally, relevant time-frequency features are extracted based on these instantaneous attributes. The extracted features are classified by a back propagation neural network in acoustic defect detection. Results show that the features of audio signals extracted by the proposed method is very effective and the comprehensive classification performance index F improves by 7.7% compared with the original Hilbert-Huang transform.关键词：Hilbert-Huang transform;acoustic defect detection;feature extraction;wavelet packet decomposition;real intrinsic mode function536|5|8更新时间：2025-07-09
- 摘要：A hybrid deduplication method(Hy-Dedup)is adopted to solve the problem that the deduplication efficiency in the cloud storage system is not high for traditional mode online/offline deduplication, and the method performs effective data deduplication by combining online and offline modes. This method clusters fingerprint indices according the type of loads in online deduplication stage by adopting the fingerprint caching technology. The temporal local consistency of the duplicated data in data stream is estimated and the spatial local consistency is evaluated by setting different deduplication thresholds to reduce the disk fragments. The problem that the cache cannot be hit because lack of local consistency in the offline deduplication phase will be solved. The duplicated data is significantly reduced by this method while maintaining the I/O performance and the system throughput. Experimental results and a comparison with iDedup show that Hy-Dedup improves the online deduplication ratio by up to 35.9% and the disk capacity requirement reduces by 41.36%. It is concluded that the proposed method can achieve high-deciding deduplication in the cloud storage system, improve deduplication efficiency, and save storage space.关键词：online deduplication;offline deduplication;cache;cloud storage413|5|0更新时间：2025-07-09
- 摘要：The transition SST k-ω model is used to calculate the total pressure loss and heat transfer coefficients in a turbine blade with trailing edge cutback(gillslot)under different inflow conditions and ejection rates. The effects of the trailing edge cutback on the characteristics of flow and heat transfer in the gillslot blade are obtained and compared with the base vane without gillslot. The computing results of the pressure and heat transfer coefficients are compared with the experimental data to validate the present numerical methods. A comparison with the base vane shows that when the ejection rate is at 1.3%, 2.6% and 5.2%, the pressure coefficient in the throat region of gillslot vane increases by 0.1, 0.15 and 0.2, and the outlet flow angle in gillslot blades increases 0.3°, 0.4° and 0.5°, respectively. The influence region of the cutback on heat transfer is mainly located at the downstream area near suction throat. When the ejection rate increases from 1.3% to 2.6% and 5.2%, the heat transfer coefficients on the suction surface of trailing edge increase by about 3% and 5%, respectively. As the ejection rate increases, the static pressure and the heat transfer coefficient on trailing edge cutback gradually increase. However, when the coolant mass flow rate is fixed, the heat transfer coefficients on the cutback surface are not sensitive to the mainstream Reynolds number. When the ejection rate is 1.3% and 2.6%, the total pressure loss in gillslot blade is about 1% higher than that in base vane, while the ejection rate increases to 5.2%, the total pressure loss in gillslot blade is lower than that in base vane.关键词：gas turbine;trailing-edge cutback;heat transfer;transition566|6|2更新时间：2025-07-09
- 摘要：A new reliability assessment method is proposed to improve the precision and credibility of reliability evaluation for aero-engine rotor bearings under the circumstances of less failure or zero failure data, and the method bases on a hybrid model of proportional covariate model(PCM)and Logistic regression model(LRM). The salient features reflecting equipment degradation process are extracted and selected from existing monitoring data by signal processing technology. These features are used as input of the LRM, and the equipment state data defined by the failure threshold are taken as output of the LRM. The initial reliability is estimated by LRM, and then the system hazard rate function is updated based on the response variables and the basic association variable function through combining with PCM. The mapping relationship between the monitoring data and the bearing reliability is dynamically revealed. Finally, the operational reliability of the aircraft engine bearings is successfully estimated using the updated hazard rate function. Case studies show that the method passes the process of the proportional factor decision between covariate and hazard rate, and avoids the influence coming from the subjective deviation. Its determined life error lies within 5%. It provides a new method for reliability estimation under sparse or zero failure data conditions.关键词：aero-engine rotor bearing;operational reliability evaluation;proportional covariate model;logistic regression model622|6|8更新时间：2025-07-09
- 摘要：To solve the problem of gradient dispersion in stacking auto-encoder(SAE)with large number of parameters, we analyze the distribution of encoding values in each hidden-layer of network. It is found that most of them are distributed in the saturation area of the activation function, which directly leads to a weight gradient loss, thus a normalizing strategy is introduced. The node is normalized according to the sample, then two parameters are introduced to scale and move the encoding values. Then the modified values are passed to the activation function to next layer. The fault diagnosis of rolling bearing is carried out by the normalized SAE, and the spectrum of vibration signal is input into the network. Compared with ordinary SAE, the encoding values of normalized SAE are more well-distributed. For example, the entropy of encoding values in the first level is increased from 0.88 bit to 16.29 bit. The normalized SAE has higher anti-noise ability and faster training rate. When the signal to noise ratio(SNR)is 0 dB, the recognition accuracy is increased from 16.18% to 100% on the rolling bearing data sets of Case Western Reserve University. On laboratory data sets, the training time is decreased by 37.22%, and the recognition accuracy is increased from 97.93% to 99.95%. The introduced normalizing strategy provides a reference for subsequent research on the construction of SAE, and also provides a strategy for fault diagnosis of rolling bearings.关键词：fault diagnosis;stacking auto-encoder;normalization;rolling bearing482|6|15更新时间：2025-07-09
- 摘要：Following the new mechanism of eliminating haze particles by optical gradient force, a test chamber for simulating dynamic haze is constructed. The feasibility of eliminating haze is verified by a laser beam irradiating suspended haze. The forces including air drag force, van der Waals repulsion force and rotary lift force keep the haze particles staying in a stable force balance status in the atmosphere. The interaction between laser and haze particles explains the process of optical gradient force trapping the dielectric particles. When the optical trapping force breaks the balance status of the haze particles, the haze particles are separated from the original force balance system then fall. The experimental results show that the optical gradient force generated by a 2.6 mW He-Ne laser is sufficient to break the original force balance system of haze particles with diameter of 0.3, 0.5 or 1.0 μm. When laser is once applied, the concentration of haze particles declines rapidly, and the decay rate is much faster than the natural decay rate. Thus, the purpose of eliminating haze particles is successfully achieved. In addition, the close relationship between the particle size and elimination of haze is also discussed. It is undoubted that the proposed way of eliminating haze particles can effectively purify air and reduce factory dust to exhibit the great significance for both healthy life and sustainable economic development.关键词：haze particle;optical gradient force;simulation method;experimental investigation568|5|0更新时间：2025-07-09
- 摘要：For the appearance of recast layer and micro-crack in laser drilled micro-holes, electrochemical machining(ECM)is considered to reprocess the holes to eliminate these defects. The experimental system of hybrid processing of laser beam machining with ECM is developed. Nickel based superalloy GH4169 is used in the ECM experiment to explore the influences of electrolytic current, concentration of sodium nitrate solution and parameters of pulse electrochemical machining(PECM)on the electrolytic rate and the removal effect of recast layer. When the current density is larger than 13.8 A/cm2, the electrolytic rate is proportional to the current. The concentration of sodium nitrate solution has no effect on the electrolytic rate in constant current ECM. So the concentration can be determined by the current and the voltage. PECM with low frequency and wide pulse or with high frequency and narrow pulse is beneficial to the improvement of electrolytic rate. In particular, the electrolytic rate can get the maximum value at the frequency of 1 kHz and the duty ratio of 40%-60%. PECM is accompanied by hydrogen pressure wave, which plays a good role in stirring the electrolyte in the machining gap. As a result, it can improve the current efficiency and increase the electrolytic rate. The recast layer of laser drilled micro-holes can be removed completely by choosing appropriate ECM parameters.关键词：laser drilling;recast layer;electrochemical machining;processing parameters569|5|1更新时间：2025-07-09
- 摘要：The life of thermal barrier coatings prepared by large-area laser remelting is affected by change of structure in overlap region. The yttria stabilized zirconia coating was subjected to multi-pass laser remelting, and the change law of the surface and the cross-section microstructure morphology of the remelted coating under different overlap rates were investigated. Thermal shock experiment was conducted at 1 050 ℃ in the resistance heating furnace to analyze the influence of the coating structure with change of the overlap rate on the thermal cycle life. The result observed by scanning electron microscope shows that cracks around the dividing line between adjacent laser remelted coatings cross each other. In overlap region, with the increasing overlap rate, the density of cracks decreases, while the pits and small crumblings increase. After thermal shock experiment, the average width of surface crack decreases to 5 μm, and a large number of pits mostly caused by exfoliation of small fragments appear on the surface of laser remelted coating. As the overlap ratio increases, the deflection angle of the longitudinal cracks in the overlap region increases first and then decreases, while the thermal cycle life of the coating first decreases and then increases. The deflection of section longitudinal cracks in overlap region accelerates the generation of horizontal cracks, and the deflection angle is smallest when the overlap rate is 0.30. When the exfoliation percentage is or more than 20%, the laser remelted coating with 0.30 of overlap rate performs best.关键词：laser remelted;overlap rate;microstructure;thermal shock407|5|1更新时间：2025-07-09
- 摘要：An optimization design strategy for process parameters considering the manufacturing cell performance is proposed to solve the problem that the process parameter design of extruded-blown-molded product is affected by the product quality requirement and the equipment ability. According to the requirement of product quality, the constraint relation between product quality evaluation index and process parameters is established. The regression equation of the influencing relation is obtained via analysis of the experimental data, and the set of process parameters satisfying the quality objective is sought out. The optimal process parameters satisfying both the quality requirement and manufacturing cell performance can be identified by synthetically considering the objective of satisfying the performance of the manufacturing cell, defining the manufacturing cell performance index, and establishing the constraint and optimization function between the process parameters and the manufacturing cell performance index. A case study on the optimization of the parameters in extruding-blowing-molding process is provided to verify the feasibility of the proposed strategy. The results show that analyzing the experimental data by the quality evaluation index and manufacturing cell performance index can optimize the process parameters of the extruding-blowing-molding manufacturing process with satisfactory quality target and manufacturing cell performance. This strategy effectively solves the problem that the process parameters do not match performance stability of manufacturing cell, and ensures product productivity and quality stability.关键词：extruding-blowing-molding process;quality target;manufacturing cell performance;process parameters387|5|0更新时间：2025-07-09
- 摘要：Traditional contacted GIS breakdown point location methods require a large number of sensors and have poor anti-interference ability. In the withstand voltage test for a GIS, especially in the impulse voltage test, these methods cannot locate the breakdown point in most cases. In order to improve the efficiency and effectiveness of the positioning, this paper puts forward a simple and accurate two-dimensional location method of breakdown points in GIS based on the theory of spatial audible sound waves. By analyzing the characteristics of acoustic waves from the breakdown of GIS, a peak-threshold method to determine the time delay of a GIS breakdown sound wave arriving at different sensors is presented. The digital positioning system is set up by using the horizontal arrangement of three acoustic sensors, and the sensors have no physical contact with the detected GIS. Results show that the acoustic waveform caused by GIS breakdown has an obvious high amplitude impulse in time domain, and mainly distributes from 2 kHz to 8 kHz in frequency domain, which can be clearly distinguished from the background noise and provide useful information for localization. Experimental results of 330 kV GIS show that the location error of the proposed system is under 5%, and compared with the ultrasonic and UHF location methods, the audible sound method reduces the difficulty and cost in positioning of breakdown points in GIS. The attenuation of waveform, the position of the sensor system and the barrier between GIS and the positioning system may influence the positioning result, so the positioning system should be reasonably arranged in practical application.关键词：audible sound waves;GIS;breakdown;location method;peak-threshold method376|5|4更新时间：2025-07-09
- 摘要：Graphene oxide films are prepared in situ by the ultraviolet light and the ozone(UVO)method and then combined with a two-terminal electronic device to construct gas sensing sensors with high performance. The sensitivity, time response, selectivity and retention rate of the graphene oxide gas sensing sensor to NH3 are tested. Results show that the graphene oxide gas sensing sensor obtained by the UVO method has fast response speed, good recovery performance and nigh stability. The processing parameters such as UVO treatment time have significant influences on the performance of the graphene oxide gas sensing sensor. When the time of UVO process is 7 min, the sensitivity of the graphene oxide gas sensing sensor to NH3 reaches the maximum, and power consumption is low(test power is less than 1 mW)and the long-term retention rate is nigh. The sensor shows obvious selectivity for NH3 compared with acetone and absolute ethanol. Graphene oxide prepared by the UVO method has less pollution to devices than that by the chemical method. The patterning process of graphene oxide film is compatible with the integrated circuit manufacturing process.关键词：graphene;ultraviolet light and ozone method;gas sensor;sensitivity;selectivity542|5|3更新时间：2025-07-09
- 摘要：A switching sliding mode control(SSMC)strategy for auxiliary energy source Buck converter is proposed to solve the problems that the implementation of the sliding mode control(SMC)strategy for auxiliary energy source system in electric vehicle is too complicated, and the output voltage of the system might be unstable. The output voltage and target voltage of the auxiliary energy source are compared to output a voltage error. Then, the voltage error is regulated under some restrictive conditions, so that negative output of the change rate of the voltage error is effectively avoided, and the efficient control of MOSFET switch is realized. A simulation model and an experimental platform are established to verify the effectiveness of the proposed SSMC strategy. Results show that the proposed SSMC strategy for auxiliary energy source Buck converter effectively eliminates the singularity problem and reduces the implementation complexity. Moreover, the dynamic response speed and stability of the auxiliary energy source system with Buck converter are guaranteed. A comparison with the SMC strategy shows that the proposed SSMC strategy has 25% improvement in the settling-time of start-up response for the auxiliary energy source system with Buck converter. The anti-interference ability and robustness of the system are improved.关键词：auxiliary energy source;Buck converter;switching sliding mode control;restrictive conditions362|5|0更新时间：2025-07-09
- 摘要：A joint resource optimization algorithm of distributed MIMO radar system for multiple targets tracking is proposed to solve the problems that existing researches on joint resource allocations for distributed MIMO radar systems focus on only transmitters and system power without optimization of receivers, and lack estimation of tracking capability and resource demands for random radar layouts. Firstly, the maximum of Cramer-Rao lower bound in multiple targets location is calculated and the objective is to minimize the maximum value. Next, an optimization model that considers transmitting power, transmitters and receivers is established under constraints of transmitting power and total number of selected transmitters and receivers. Then, a joint resource optimization algorithm based on cyclic minimization is proposed to solve the problem via combining the heuristic algorithm for antenna selection and the sequential parametric convex approximation algorithm for power allocation. Experimental results of static and random target trajectories in a given size of environment show that the number of selected transmitters is smaller than that of receivers when the total transmitting power is limited. Comparisons with existing resource allocation researches show that the proposed algorithm can evaluate the least target tracking accuracy, the number of targets, and the minimum corresponding resource demands of the system in any radar array situation. The algorithm may have some reference value for the structure design and resource reserve of distributed MIMO radar systems.关键词：MIMO radar;distributed;multiple targets tracking;joint resource optimization367|5|1更新时间：2025-07-09
- 摘要：A hybrid algorithm for group split detection and extension estimation is proposed to improve the performance of tracking the separation of group targets. The traditional random matrix algorithm is employed to calculate the size of a group and to analyze the situation of the group. When a group splitting is detected, big subgroups are divided into some small subgroups by k-means clustering. The least square method is then employed to fit effective measurements of each subgroup into several ellipses, and trajectory association is finally conducted. The proposed algorithm deals with measurements of groups based on the clustering, and describes extensions of splitted subgroups with multiple ellipses according to clustering result. The algorithm has a convergence rate faster than that of the traditional algorithm. Simulation results and a comparison with the single random matrix algorithm show that the proposed algorithm accurately estimates the extensions of splitted subgroups. A comparison with the semi-positive programming algorithm shows that single Monte Carlo simulation time reduces by 2 orders of magnitude. These results prove the validity and practicability of the proposed algorithm.关键词：group target;tracking;group split;random matrix;least-square;k-means clustering374|5|3更新时间：2025-07-09
- 摘要：A CMOS temperature sensor with high precision using a charge-balance analog-to-digital converter(ADC)is presented to solve the problems of low accuracy, high power consumption and narrow measuring range of conventional CMOS temperature sensor chips. The temperature sensing circuit based on parasitic bipolar junction transistors generates a voltage proportional to absolute temperature and a voltage inversely proportional to absolute temperature to avoid high-precision bandgap voltage reference, and then a charge-balanced ADC is used to alternatively quantify these two voltages and to obtain the 15 bit digital result corresponding to the real-time temperature. Sensing errors due to process variation are calibrated with an external reference voltage. A temperature sensing circuit is designed in a 0.18 μm CMOS process and is used for simulation. Results show that the measuring accuracy is ±0.2 ℃ in a temperature range from -40 ℃ to 125 ℃, while the duration for one measuring cycle is 42 ms, the operating current is only 130 μA, and the layout area of the core circuit is only 0.55 mm2. The proposed temperature sensor can be applied in the systems that require temperature sensor chips with high accuracy, low power consumption and wide measuring range, such as implantable medical devices, radio frequency identification tags and the Internet of Things.关键词：temperature sensor;high-precision;low power consumption;wide measuring range516|7|2更新时间：2025-07-09
- 摘要：A new type of multi-target detection and tracking algorithm based on net classifiers and historical trajectories is proposed to focus the problem that most existing popular environmental perception algorithms for intelligent vehicles are designed for specific type of targets and they have been proved to be low recognition accuracy in complicated urban conditions where occlusion of different targets and abrupt light change are frequent. Images are scanned from a multi-scale sliding window and then fused by a fusion model according to occlusion relations among pedestrians, vehicles and traffic signs. Historical detection results are obtained based on correlation of target features through short trajectory generation, long trajectory generation and reliability verification of trajectories, and are used to generate a library of historical trajectories, which is used to predict and to fuse detection results in the next step. Then, the standard deviation classifier, the nearest neighbor classifier and historical trajectories are updated by new detection and tracking results. Multi-target long-time tracking in complicated conditions is realized in this way. Field experiment shows that the proposed algorithm exhibits excellent performance of multi-target long-time tracking in complicated urban conditions such as rainy, shade, luminance changes. The average recognition rates for KITTI database samples is up to 77.17%～81.32% and calculation time of single frame picture is only 0.05 s. These results show a promising algorithm for real-time application.关键词：intelligent vehicle;urban condition;net classifier;multi-target detection;historical trajectories413|5|0更新时间：2025-07-09
- 摘要：To solve the problem that redundancy or irrelevant features in high-dimensional datasets reduce the classification accuracy of machine learning model, a feature selection algorithm based on approximate Markov blanket is proposed and named as normal max-relevance and min-redundancy(nmRMR)algorithm. Firstly, the algorithm uses the criteria of maximum relevance and minimum redundancy to perform feature relevance ranking. Then, it adopts the approximate Markov blanket to remove redundant features or irrelevant features, and maximize the correlation between features to obtain the optimal feature subset. Experimental results on UCI's eight open datasets show that: the proposed nmRMR algorithm achieves on average 6.875, 20.56 and 3.187 5 reduction in the selected number of feature subsets, as well as 0.78%, 1.88% and 0.825% improvement in the average classification accuracy, compared with the mRMR algorithm, the FullSet algorithm, and the FCBF algorithm, respectively. It is concluded that the proposed nmRMR algorithm is superior to other algorithms.关键词：feature selection;feature relevance;redundancy feature;approximate Markov blanket286|5|8更新时间：2025-07-09
- 摘要：A novel model to predict video frames of road conditions is proposed to solve the problem that in the prediction area of road condition video frames, most of predicting models are of such as low resolution, image blurring and lack of local details, and the model uses residual blocks to generate adversarial networks. Multi-cascade residual units are used to extract feature maps preliminarily and two discriminators are adopted to raise the quality of images generated by the GANs. The model power to extract feature maps is improved by using perceptual loss network, and the Adam optimizer is used to update network weights. The proposed model produces future frames in the next moment which have great temporal coherency with the input frames through using semi-supervised deep learning framework. The model is trained and tested using datasets KITTI, and the results show that the generated frames by the proposed model have the resolution of 256×512, which are 2 to 4 times higher than the results from pixel mean based functions and past foreign works, the sharpness accuracy increases by 1 to 2 magnitudes, and the generated frames are more responsive to human visual perception. The frame images predicted by the model are of higher quality and more practical value, and provide more effective features for other downstream models such as detection algorithms.关键词：generative adversarial networks;deep learning;auto driving;road condition frames prediction483|5|0更新时间：2025-07-09
- 摘要：For the traditional signal processing algorithms, it is difficult to process the complicated vibration signals of rotor in startup or shut down process due to the huge calculation task and poor ability to extract wide-band signals. Following zero-phase filter and phase demodulation principle, a novel method for extracting the fundamental vibration component of rotor is proposed. The wide-band fundamental vibration component can be demodulated into a narrow-band interval via once nonlinear phase demodulation, which is segregated with the band of other higher-order harmonics in frequency domain, then the fundamental component is extracted by a zero-phase filter. The simulation calculation and experimental validation demonstrate that the proposed method outperforms the traditional signal processing algorithms by its simple mechanism, quick calculation and little limit to the band between adjacent components. The visual selection of filtering parameters can be directly realized in frequency domain and the extracted amplitude and phase of the fundamental components are accurate for the further calculation and analysis.关键词：rotor startup/shut down;harmonic component;filter;phase demodulation372|5|0更新时间：2025-07-09
- 摘要：The effects of Ti(C,N)content on microstructure and mechanical properties of Ti(C,N)-304 stainless steel cermet are analyzed. Scanning electron microscopy and transmission electron microscopy are adopted to observe the microstructures, fracture morphology, crack propagation and microcrack in the cermet with different hard phase content. The contiguity of the hard phase and the binder mean free path are discussed following the stereological principle. The relative density, hardness and transverse rupture strength of the cermet are measured with Archimedes principle, Rockwell hardness tester and three-point-bending method, respectively. With the increasing hard phase content, the average particle diameter of the hard phase firstly decreases and then increases. When the hard phase content is 75%, the cermet obtains the maximum relative density(98.4%), maximum hardness(HRA 89.2)and maximum transverse rupture strength(1 291 MPa). In the process of crack propagation, intergranular fracture and transgranular fracture simultaneously appear, but the former is in majority. Large Ti(C,N)grains are more prone to appear transgranular fracture. The stress concentration due to sharp corners of large particles leads to microcrack, which is not conducive to improve the mechanical properties of the material.关键词：Ti(C,N)stainless steel cermet;hard phase content;mechanical properties374|5|1更新时间：2025-07-09
- 摘要：Modeling vibroacoustic problems with coupled fast boundary element method and finite element method(BEM-FEM)can maximize the advantages of the various numerical methods, hence can get a vibroacoustic simulation system with excellent performance. The direct coupling scheme is used to establish the vibroacoustic equation, and the selected scheme is discussed in detail to achieve a fast solution for a large-scale coupling system. Then the common mismatch between the sound field meshes and the structural meshes on the coupling interface is considered, and the data-exchange matrices between higher-order non-matching meshes are constructed with weight residual method to realize the highly accurate data exchange. The implementation theory for fast directional algorithm(FDA)suitable for broadband issues is introduced, and the traditional BEM matrices in BEM-FEM matrix are compressed efficiently in entire band by FDA. The correctness and effectiveness of this method are validated by introducing analytical examples and a large-scale complex example over 400,000 degrees of BEM-FEM freedom. In particular, this method is of higher accuracy and suitable for a broader band, which is 3 to 4 times that of the existing similar methods.关键词：vibroacoustics;boundary element method;finite element method;fast directional algorithm;non-matching mesh;data exchange375|5|0更新时间：2025-07-09
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