最新刊期
卷 55 ， 期 9 ， 2021
- 摘要：To verify the feasibility and engineering practice value of the transfer analogy theory between heat transfer and electrology, this paper presents two typical applications addressing practical problems in the field of electrical engineering. Firstly, in view of lack of calculating method for the current carrying capacity of cable lying through unfavorable heat dissipation regions, we establish the radial thermal circuit of cable with the aid of thermal-electrical analogy analysis. The thermal resistance of insulating material and the loss in each layer of cable structure are equivalently evaluated, and further, the thermal circuit model with distributed parameters is constructed. The thought of solving the cable temperature distribution and carrying capacity is given, which compensates the insufficiency of the current calculation method recommended by IEC standard. Secondly, for the limitations of the prediction methods of hot-spot temperature in transformer, we develop the thermal circuit model with centralized parameters by incorporating the heat transfer process of transformer and the thermal-electrical analogy. Applying Kirchhoff current law to the thermal circuit model, a faster prediction method for calculating the hot-spot temperature is proposed. It is verified that the model has higher prediction accuracy than the method recommended by IEC standard. The results indicate that the thermal-electric analogy can solve engineering problems more practically and the transfer analogy can promote innovation and development of many interdisciplinary researches.关键词：thermal-electrical analogy;thermal circuit model;engineering practices;power cable;transformer165|5|0更新时间：2025-07-09
- 摘要：In view of the problems existing in the research on rock fragmentation by TBM(tunnel boring machine)disc cutters that the rock failure mechanism under pre-cut groove condition has not been investigated in depth, and the influence of the pre-cut groove structure on rock fragmentation performance has not been clearly revealed, a discrete element model of equivalent crystalline rock material based on Thiessen polygon algorithm was built, and the processes of dense core evolution, crack propagation and rock fragmentation during cutter penetration assisted by different pre-cut grooves were analyzed and the numerical model was verified by small scaled rock penetration tests. Numerical simulations were carried out to study the influence of pre-cut groove structural parameters such as notch angle, location and spacing, on the crack distribution, rock breaking load and penetration specific energy. The simulation results show that the rock breaking efficiency can be greatly improved using the staggered groove assisted approach whose critical techniques are rock weakening by pre-cut grooves and load transfer by dense cores. The optimal layout mode of the pre-cut grooves is summarized as “narrow straight, staggered distributed, and middle placed”. It means that the notch angle of the grooves is suggested to be 0°, the cutter penetration points and the pre-cut grooves are arranged in a staggered layout and the cutter penetration point is located at the center of two adjacent pre-cut grooves, and the optimal groove spacing is suggested to be 80 mm. This study suggests an effective approach for the study of rock breaking mechanism of TBM disc cutters, and provides a theoretical basis for exploring the reasonable structure of pre-cut grooves.关键词：tunnel boring machine;disc cutter;pre-cut groove;particle-based discrete element method129|6|0更新时间：2025-07-09
- 摘要：Aiming at the problem that it is difficult to identify the dynamic parameters of the SCARA robot end under the load condition, based on the analysis of load effect on the torque of each joint, the structure of SCARA robot was simplified. The Lagrange method was used to establish the dynamic mathematical model of the robot with load, and the dynamic parameters of the robot end that need to be identified were determined. On the basis of the traditional particle swarm optimization(PSO), a random weight PSO was proposed to identify the dynamic parameters of the robot, and its corresponding program was given. The simulation results show that the random weight PSO algorithm can significantly improve the convergence rate and extend the search range of parameter particles; the identified robot torque is basically consistent with the actual output torque, which indicates that the algorithm has higher accuracy. Compared with the genetic algorithm and the basic PSO algorithm, the fitness function optimal value identified by the proposed random weight PSO algorithm is the smallest, and the proposed algorithm is convenient for global search and not easy to fall into the local optimization, and the parameter identification is more accurate.关键词：SCARA robot;dynamics;parameter identification;random weight;particle swarm optimization136|4|0更新时间：2025-07-09
- 摘要：To pursue a vehicle suspension with better overall performance, a three-link bionic kangaroo leg suspension with circular arc-buffer structures is investigated based on the kangaroo leg structure jumping in complex terrain for long time(hereinafter the bionic suspension). A double circular arc-buffer structure is designed to simulate the buffering and damping effects of tendons, muscles and the other tissues in the kangaroo leg jumping motion, and it is arranged at the three bionic joints. For exploring the behavioral characteristics of the proposed suspension, a 1/4 vehicle dynamics model is constructed by Lagrange equations. A three-dimensional circular arc-buffer structure is established via Pro/E and imported into ADAMS for suspension dynamics simulation analysis. It is found that there is a serious nonlinear coupling relationship among the kinematic parameters of the bionic suspension, which leads a difficulty in solving the dynamics equations; the solid modeling and motion simulation can be carried out by connecting the sub-element structure with the flexible body and imposing the constraint to the sub-element structure to create a double circular arc constraint; with the increasing road grade and vehicle speed, the values of dynamic characteristic parameters rise up, but they are all within reasonable ranges; the relative growth rate of the body acceleration decreases and the overall transmissibility(10.7%-2%)shows a downward trend; the tire dynamic displacement transmissibility(8.6%-10.6%)increases and the transmissibility change is relatively gentle. The results indicate that the designed suspension structure is reasonable and the bionic suspension is endowed with good road adaptability, high speed comfort, stability and impact resistance. The characteristic parameters of the bionic suspension are better than those of the traditional suspension in the comparative literatures. The bionic suspension has resonance peaks around 2 Hz and 14 Hz, which avoids the sensitive frequency range of human body to demonstrate the good frequency response characteristics.关键词：suspension;three-link imitation kangaroo legs;circular arc-buffer structure;behavioral characteristic;dynamics93|4|0更新时间：2025-07-09
- 摘要：Aiming at variable working conditions and the problem of excessive parasitic power of fuel-cell system caused by over high pressure ratio of fuel-cell centrifugal compressor, a multi-objective and multi-condition aerodynamic optimal design method with constraints for fuel-cell air compressor impeller is proposed based on parametric design, Latin hypercube sampling, radial basis function neural network and multi-objective grey wolf optimization algorithm. The numerical programs are developed independently to realize the design process of aerodynamic optimization. Taking the impellers of a two-stage fuel-cell centrifugal air compressor as the optimization objects, Latin hypercube sampling is used to obtain the sample space of the key design variables of the impeller. Based on the internal code of flow-field analysis, the corresponding aerodynamic performance target parameters of the impeller samples are calculated. On this basis, the neural network program is used to establish the flow-field analysis surrogate model. Taking the efficiency of design point and the efficiency and pressure ratio of non-design point as objectives, and the design pressure ratio as constraint, the multi-objective grey wolf algorithm program is used to carry out the multi-condition and multi-objective aerodynamic optimization of impellers. The results show that the Latin hypercube sampling achieves the uniform distribution of sample points in the design variable space, and the surrogate model established by neural network can accurately describe the mapping relationship between the design variables and the performance targets, and the maximum error between the performance targets obtained by the surrogate model and flow-field calculation is less than 1%. The optimal efficiency and the corresponding impeller profile under the constraint of design pressure ratio are obtained by optimization calculation. After optimization, the low velocity region and entropy increment in the impeller flow field at the design and non-design operating points both reduced, and the isentropic efficiencies of the two impellers at the design operating point were increased by 2.2% and 2%, respectively, and the efficiencies of the two impellers at the non-design operating point were increased by 2.9% and 2.2%, respectively.关键词：fuel cell;air compressor;impeller;aerodynamic optimization design113|4|0更新时间：2025-07-09
- 摘要：Aiming at the problem of low resource utilization of rotor blades in the selection process of aero-engine fan rotor blades, the first-order bending frequency dispersion, first-order torque frequency dispersion, and gravitational moment difference of rotor blades are regarded as the selection criteria, and the minimum number of not selected blades as the optimization goal, an intelligent selection algorithm of the blades is proposed to achieve the goal of efficient selection and full utilization of the rotor blades before assembly. In view of the problems of multiple installations and multiple adjustments as well as low assembly success rate in the assembly of fan rotor blades, the gravitational moment difference between the two blades at a diagonal position of 180 degrees is taken as the constraint condition, and the minimized residual imbalance as the optimization objective, and the improved simulated annealing algorithm is used to optimize the assembly sequence of the rotor blades, which greatly reduces the residual imbalance of the rotor blades as well as the times of rotor assembly and adjustment. Example verifies that the proposed optimization algorithm for selecting blades greatly improves the utilization of blade resources and the selection efficiency: the blade resource utilization rate is increased from 65%-74% currently achieved in enterprise to 83%-93%, and when running the algorithm for 20 times, the minimum single running period is 7.7 seconds and the maximum is 28.7 seconds, indicating the solution efficiency is very high. The optimization algorithm for the assembly sequence planning of the rotor blades provides an optimized assembly sequence for actual assembly of the rotor blades, and the methods for optimal selection and matching of the rotor blades can realize full utilization of blade resource, and facilitate efficient assembly.关键词：intelligent and optimized selection of rotor blades;assembly sequence planning;improved simulated annealing algorithm;optimal selection and matching72|4|0更新时间：2025-07-09
- 摘要：In order to solve the problem of low frequency broadband sound absorption and ventilation, two kinds of nested stepped micro-slit metasurfaces are proposed. Firstly, a stepped micro-slit sound absorption unit is designed, which can obtain lower frequency sound absorption than traditional micro-slit absorber. Secondly, a ventilation hole is introduced into the stepped micro-slit unit to construct a ventilated unit, and it can achieve ventilation effect while ensuring the sound absorption performance in a certain frequency range. Thirdly, a nested parallel method is proposed, which can not only effectively broaden the sound absorption bandwidth, but also overcome the problem that the surface area of the traditional parallel structure increases linearly with the number of units, thus can make the nested structure has a smaller surface area. Finally, two metasurfaces, sound-absorbing type and ventilated type, are designed using the micro-slit units with the nested parallel method. The results show that the sound-absorbing type metasurface can achieve sound absorption from 600 Hz to 1 600 Hz with a thickness of only 70 mm formed by nesting 16 elements, while the ventilated type metasurface formed by nesting 8 units with a thickness of 39.1 mm can achieve sound absorption from 470 to 657 Hz and possess ventilation performance. These two kinds of micro-slit sound absorption metasurfaces can achieve low frequency broadband sound absorption with small size, and have promising applications in engineering practice.关键词：acoustic metasurface;sound absorption;micro-slit absorber;nested structure118|4|0更新时间：2025-07-09
- 摘要：A scale effect model of thermal conductivity for silicon film in fully depleted silicon-on-insulator(FD SOI)metal-oxide-semiconductor field effect transistor(MOSFET)based on an equivalent phonon boundary scattering free path is proposed to address the problem that thermal conductivity of micro-nano scale silicon film suffers a severe scale effect. Phonon relaxation time influenced by bound state and free state electrons was quantified by studying phonon scattering mechanism in silicon materials. The analytical thermal conductivity model of silicon material was derived. In-depth studies of phonon boundary scattering mechanism were carried out. Equivalent phonon boundary scattering mean free path was obtained by solving the attenuation factor function. Phonon boundary scattering and phonon scattering in silicon material were coupled by the Matthiessen rule. An approximate analytical thermal conductivity model for nanoscale FD SOI MOSFET silicon film was established and verified by the original model of Asheghi and experimental tests. Results show that the equivalent mean free path of phonon boundary scattering in silicon film is about 2.5 times the film thickness. Phonon boundary scattering dominates microscale and nanoscale phonon heat transfer process, determining the ultra-fast heat transfer characteristics of phonons in thin silicon films. The thermal conductivity model based on the equivalent boundary scattering free path approximation is in good agreement with original model and experimental data, highlighting the physical significance of the attenuation factor and effectively revealing the thermal conductivity of the nanodevice in a limited space.关键词：silicon-on-insulator;thermal conductivity;phonon boundary scattering;scale effect80|4|0更新时间：2025-07-09
- 摘要：To improve the distance-based level of detail(LoD)construction in point cloud compression, a prediction residual-based LoD optimization model and a fast LoD generation method are proposed. The relationship between LoD prediction residuals and coding bitrate is firstly deduced. A model of LoD prediction residual and distance is further constructed, and the model parameters can be obtained by pre-coding or online calculation of the point cloud. Relying on this model, the optimal number of LoD layers can be obtained by minimizing the prediction residuals. To lower the complexity of the proposed method, the influences of the model parameters on the coding performance are analyzed. It is found that the number of points in detail layer decreases exponentially with the increasing LoD layers, which makes the impact on coding performance weaken sharply. Following this analysis, the model parameter determination is simplified according to uniform sampling and smooth distribution features of point clouds. The optimal number of LoD layers can be obtained by the proportion of the points in the detail layer to the total points in the point cloud, so as to achieve the optimal coding performance. Furthermore, a fast LoD generation method based on threshold control is proposed to heighten the model practicability. Experimental results show that the proposed method enables to shorten encoding time by 4% and decoding time by 6% without any performance loss.关键词：point cloud compression;level of detail;prediction residuals;lossless compression;coding performance68|4|0更新时间：2025-07-09
- 摘要：Aiming at the disadvantages of traditional flexible eddy current array sensors such as large number of sensing channels and low crack monitoring depth, a tunnel magnetoresistance(TMR)flexible eddy current array sensor(TMR-FECA)with less induction channels is proposed to quantitatively monitor structural surface and subsurface cracks. Simulation experiments on the propagation of cracks in different depths verify that the method of using TMR sensor to measure the y-axis magnetic field component has a better quantitative crack monitoring effect. Through 2-D finite element model established by Comsol software, the effects of different excitation frequencies on the eddy current distribution and the sensitivity of crack identification are analyzed. The experimental results show that the TMR-FECA has good quantitative monitoring effect for surface crack monitoring, and the sensitivity of crack monitoring increases with the excitation frequency. As the excitation frequency increases from 1 kHz to 5 kHz, the crack identification sensitivity increases from 108.41% to 741.64%. For the subsurface cracks 2 mm beneath the surface, when the excitation frequency is 1 kHz, the quantitative crack monitoring effect is not obvious, but the quantitative crack monitoring effect and the sensitivity of crack monitoring can be improved by increasing the excitation frequency. The crack monitoring accuracy of the sensor is 5 mm, which is consistent with the spacing between the excitation lines. This technique can effectively reduce the number of induction units and solve the quantitative monitoring problem of deep cracks.关键词：flexible eddy current sensor;tunnel magnetoresistance sensor;deep crack;quantitative monitoring;sensitivity68|4|0更新时间：2025-07-09
- 摘要：To provide microscopic validation data for n-heptane models over a wide temperature range, microsecond-resolved OH concentration time-histories were measured behind reflected shock waves in the oxidation of stoichiometric n-heptane(volume fraction of 0.1%)/O2/Ar mixtures over the temperature(T5)range of 1 197-1 690 K at the pressures(p5)around 150 kPa. The OH time-histories were monitored by narrow-linewidth ring dye laser absorption near 306.7 nm at the well-characterized R1(5)transition of the OH A-X(0, 0)band. Results reveal that vacuum degree and leaking rates are the two dominant factors affecting peak value of the measured OH concentrations. Three morphologies of OH time-histories in n-heptane oxidation were observed, and the non-ideal physical boundary layer effect caused by incident shock wave shows a significant effect on OH concentration. Five commonly used mechanisms of n-heptane generally show acceptable predictions in the trend of OH time-histories at various temperatures, but are still not satisfactory in predicting both ignition delay time and OH time-histories simultaneously, and it shows that the lower the temperature, the greater the deviation between the model simulations and experimental measurements during induced ignition time. Reaction of(·overC)H3+H(·overO)2=CH3(·overO)+(·overO)H has a great impact on the predictions in ignition delay times of n-heptane models, and further study on the kinetic parameters of this reaction is beneficial to refining the n-heptane models.关键词：n-heptane;absorption spectrum;OH concentration time-histories;kinetic models54|4|0更新时间：2025-07-09
- 摘要：Aiming at the potential corrosion problem of thermal power equipment structural materials in high temperature CO2 environment, the interval sampling and comparison method was used to study the corrosion behaviors of the heat-resistant steels T92, TP347H and TP347HFG with scratches on the surface at 600 ℃ CO2environment. The composition, distribution and content of corrosion products were characterized by XRD, SEM and EDS. Experimental results show that the corrosion kinetic curves of the three experimental materials all follow a parabolic law. The surface scratches may aggravate the internal oxidation of the heat-resistant steel T92, and result in spalling inside the scratches on the surface of TP347H and TP347HFG. According to corrosion thermodynamic calculations, the Cr-C-O phase diagram of TP347H in a CO2 environment at 600 ℃ was given, and the distribution of carbides was clarified. Comparing TP347H and TP347HFG, it is found that the grain refinement intensifies the carburizing behavior, worsens the Cr-poor area and destroys the Cr-rich oxide film, thereby reducing the corrosion resistance of TP347HFG.关键词：high temperature CO2;heat-resistant steel;scratch;spalling;grain refinement;corrosion behavior83|5|0更新时间：2025-07-09
- 摘要：In order to expand the application area of meshless moving particle semi-implicit method and extend it to the application field of acoustic calculation, a sound field control equation using moving particle semi-implicit method based wave propagation model(MPS-WP)is established based on Lagrange description under the assumption of flow-sound separation. The discrete particle model of acoustic hard boundary and absorbing boundary is realized. The influences of the key parameters such as CFL number and particle spacing on the calculation accuracy are studied. It is found that the model can maintain a small error level within certain CFL number and particle spacing ranges. The Gaussian pulse propagation example is used to verify the two-dimensional sound field calculation of MPS-WP at hard boundary and absorbing boundary. The calculation of sound pressure is in good agreement with the analytical solution, showing the effectiveness and accuracy of this method. On this basis, the propagation characteristics of acoustic waves at multiple pulse superposition in the static field and in the uniform flow field are simulated and analyzed, and the calculation results are in good agreement with the analytical solution. This work provides a new research method for acoustic calculation under complex flow conditions.关键词：acoustic wave propagation;moving particle semi-implicit method;Gauss pulse;boundary condition49|4|0更新时间：2025-07-09
- 摘要：To investigate the regulation mechanism of reformed exhaust gas recirculation(REGR)technology on the combustion and emission of natural gas engines, a numerical simulation study on the combustion process of the spark-ignition natural gas engine was conducted. The results show that the effects of hydrogen-rich reformed gas addition on the combustion process of natural gas engines are inverse to that of increasing excess air coefficient. Specifically, the ignition time of fuel advances by 1.42° and the combustion duration is shortened with the increase of the reformed gas addition rate(REGR rate). However, with the increase of excess air coefficient, the in-cylinder pressure and the heat release rate both decrease, and also, the ignition time is delayed by 2.24°. When REGR rate increases by 16%, the total hydrocarbon(THC)and NOx emission are reduced by 26.98% and 62.52%, respectively; but the engine power will be reduced by 9.52%. Thereout, the influences of REGR rate on the fuel combustion process and pollutant formation process of liquefied natural gas engines were further analyzed from the perspective of chemical kinetics. It shows that the proportion of OH radical participating in CH4 consumption reaction increases with the REGR rate. Consequently, the combustion phase is advanced by accelerating the elementary reaction rate, and the unburned HC emission is reduced as well.关键词：natural gas engine;reformed exhaust gas recirculation;combustion reaction process;chemical kinetics analysis71|4|0更新时间：2025-07-09
- 摘要：Aiming at the problems that the displacement is small and the self-driving is difficult to realize for traditional disc-seal single screw pump(DSSP), this paper proposes a new type of 8-shaped disc seal screw pump, and the profile equation of the screw rotor-disc seal is established based on the spatial meshing theory. The profile equation is used to study the meshing characteristics of the 8-shaped disc seal, and the influence of structural parameters of the meshing pairs on meshing characteristics is analyzed. The results indicate that the fluctuation degree of the meshing angle is different at different central angle sections. The fluctuation degree of the meshing angle is the most severe when the central angle β is close to 0. The meshing parts are mainly concentrated below the neutral surface when β∈(0, π/2), and above the neutral surface when β∈(-π/2, 0). The radius of the big circle of the 8-shaped disc seal has the greatest influence on the variation degree of the meshing angle, while the center distance and the chamfering radius of the 8-shaped disc seal have little influence. This research may have certain guiding significance for the design and further development of 8-shaped disc seal screw pump.关键词：8-shaped disc seal screw pump;meshing pair;meshing characteristics53|4|0更新时间：2025-07-09
- 摘要：Most existing single image blind deblurring methods based on statistical priors suffer a poor texture restoration and ringing artifacts. A multi-scale blind image deblurring method based on patch-wise local maximum gradient prior and low rank prior is proposed in this paper. Specifically, we choose a coarse-to-fine multi-scale framework to construct an image pyramid via gray-scale and down-sampling operations layer by layer. At the single-scale level, the patch-wise local maximum gradient prior and the low-rank prior are put into the MAP framework, and then both the intermediate latent image and blur kernel are estimated with the alternating direction method of multiplier and the half-quadratic splitting method. We finally obtain the sharp image by performing non-blind deconvolution for the blurred image and estimated kernel based on hyper-Laplacian prior and total variation-L2 method. Solving the low-rank regularization directly is computationally expensive, we thus transform the sub-problem of low-rank regularization term constrained by weighted Schatte-1/2 norm into a sub-problem of non-convex weighted L1/2-norm, and then adopt the generalized soft-thresholding method(GST)to achieve the global optimal solution. Experimental results and comparisons with the existing classical image deblurring methods on the benchmark datasets show that the proposed method facilitates a better image deblurring performance. After image deblurring on Köhler synthetic dataset, the average peak signal-to-noise ratio reaches 30.06 dB, the average structural similarity reaches 0.946 5, and the estimated blur kernel gets more accurate.关键词：blind image deblurring;L0-norm;weighted Schatte-1/2 norm;generalized soft-thresholding method68|4|0更新时间：2025-07-09
- 摘要：To improve the accuracy of network security defense decision, according to the characteristics of competitive decision and the limitations of traditional Nash equilibrium(NE), the heterogeneous population evolutionary game model and decision method of network security defense are proposed. Analyzing the difference in decision behavior standards between the attackers and defenders, and introducing the biological population concept to distinguish the two sides as different game populations, a dual heterogeneous population evolutionary game model of network security defense is constructed. Then an improved replicator dynamic equation is proposed based on the reflection mechanism. Considering the deterministic demand of network defense decision-making and the limitations of NE, introducing the potential function and designing the stabilized pure strategy, the optimal defense pure strategy selection algorithm is proposed. It is concluded that a strict NE is just the necessary and sufficient condition for dual heterogeneous population evolutionary game stability, and the stability proof and simulation analysis are carried out for the strict NE combining with the global monotone property of potential function. The theoretical analysis and simulations show that the proposed game model and decision-making method can ensure stable convergence of the defense strategy, and provide a practical and credible defense strategy for the precise decision-making of actual network attack and defense.关键词：network security defense;decision-making method;dual heterogeneous population evolutionary game;replicator dynamic equation;potential function76|4|0更新时间：2025-07-09
- 摘要：Aiming at the problem that the association rule extraction based on formal concept analysis focuses on positive association and ignores negative association between attributes, an association rule extraction method based on three-way concept analysis, named 3ARM, is proposed. The intent of object-induced three-way concept is composed of two parts, including the positive attribute subset that expresses the semantics of “jointly possessed” and the negative attribute subset that expresses the semantics of “jointly not possessed”. The 3ARM algorithm uses these characteristics of object-induced three-way concept and the generalization and instantiation structure of three-way concept lattice to efficiently extract the positive and negative association rules. Based on the characteristics of the closed itemsets of three-way concepts, candidate concepts containing frequent itemsets are selected from three-way concept lattices for mining, so unnecessary searches are reduced. By studying the relationship between three-way concepts, extracting non-redundant positive and negative association rules from parent-child concepts, and then extracting the positive and negative rules from sibling concepts to supplement the rule set, the knowledge in three-way concept lattices can be fully dug up. Experimental results on the MovieLens dataset show that using the 3ARM algorithm, when the minimum support is 10%, 86 027 positive rules and 93 685 negative rules are obtained. The number of positive rules obtained by 3ARM is 0.9-1.5 times more than that of FARM, reducing the redundant negative rules of FISM by up to 28.3%, and reducing the running time of the FISM and FARM algorithms by 44%-63% and 27%-62% respectively.关键词：three-way concept analysis;three-way concept lattice;association rule;positive association;negative association80|4|0更新时间：2025-07-09
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