最新刊期
卷 52 ， 期 2 ， 2018
- 摘要：In 3-D measurement of structured light system, the fringe grayscale degradation caused by the uneven reflectivity and the large curvature change of measured object surface is frequently encountered. A grayscale adjustment method is thus proposed to improve the accuracy of stripe center extraction. The modulation of each image pixel related to the object surface is obtained by projecting pure gray images to the measured object. And the modulation is applied to the fringe pattern point by point to eliminate the grayscale degeneration term by grayscale operation to adjust the fringe grayscale. The tests with a plate in black and white check and a human face model are conducted. It is shown that each stripe basically follows Gauss distribution on its cross section after the grayscale adjustment, and the fringe grayscale is well distributed, so the deviation caused by the mutation of reflectivity is corrected effectively. The local disconnection of the center line caused by the unevenness of fringe brightness in complex object image is solved meanwhile to ensure the integrity of measured data.关键词：structured light measurement;center extraction;grayscale degradation;adjustment545|5|0更新时间：2025-07-09
- 摘要：An objective measurement method for the credibility of evaluation from three aspects: evaluation data, evaluation model and single sample confidence is proposed to solve the problem that effectiveness evaluation credibility cannot be objectively measured for equipment systems. The credibility of evaluation data is determined by analyzing the uncertainty of the evaluation data; and the model classification accuracy is transformed into a credibility index of the evaluation model. A method to calculate the classification confidence is proposed based on the distribution of the different types of samples in a space with high dimension and the method is applicable to most classification algorithms. These aspects are then integrated through a credibility propagation model to get a comprehensive credibility. Finally, the concrete application of the method is discussed in detail by taking the credibility calculation of effectiveness evaluation of a radar anti-jamming efficiency as an example. It is found from the analysis of the application that the method can objectively measure the credibility of effectiveness evaluation without the needs of the knowledge of experts, the results are not affected by evaluation subjects, and the problem that different evaluation experts give different credibility for the same equipment effectiveness evaluation is solved. The calculation accuracy of the proposed method is 10% higher than that of an existing subjective method.关键词：effectiveness evaluation;credibility analysis;classification;objective measurement845|6|2更新时间：2025-07-09
- 摘要：The theory of community structure in fully signed networks is proposed to overcome the difficulty of traditional community structure in analyzing the individual and relation features in the process of collective actions. A community structure in fully signed networks is a kind of network structure that consists of sub-groups and internal nodes within a sub-group having the same attribute and are connected by dense positive edges while the nodes within different sub-groups having different attributes and are connected by sparse negative edges. First, a definition of the community structure in fully signed networks(consisting of both node and edge signs)is proposed by comprehensively considering the attributes of nodes, edges and network structures. Then, a new modularity is proposed, based on the theory of modularity given by Newman and the new modularity considers three factors of nodes, edges and structures. A genetic algorithm is then designed to detect the community structure by optimizing the new proposed modularity. Experiments based on different network attributes and a comparison with the traditional modularity show that the proposed modularity effectively identifies the differences of these attributes and solves the problem that the traditional community-structure-detecting method cannot recognize features of nodes and edges.关键词：community structure;signed networks;modularity;index379|5|0更新时间：2025-07-09
- 摘要：A nonlinear transmission line model of microstrip based on electrothermal coupling effect is proposed to overcome the defects such as single variable and lack of physical mechanism analysis in traditional point source model of microstrip. First, a 3rd order nonlinear resistance parameter is introduced into the traditional transmission line model, and a method to calculate third order passive intermodulation(PIM)power is established. Then, electrothermal coupling effect is considered to explain nonlinear origin in microstrip and a mathematical expression of the nonlinear resistance parameter is given. The relationship of PIM power with line width and frequency is revealed through combining the change of current density Finally, experiments are implemented and experimental results agree well with the theoretical calculation The rationality of the theory is verified. Calculation and experimental results show that compared with the traditional nonlinear point source model the nonlinear transmission line model combined with electrothermal coupling effect is more perfect to the calculation and analysis of intermodulation. The new model reveals the relationship between PIM power and more parameters such as microstrip line width, frequency, input power, etc of the microstrip line in addition to the length of the microstrip line. The new model is more comprehensive in applications of PIM analysis and prediction.关键词：passive intermodulation;transmission line model;electrothermal coupling;print circuit530|5|0更新时间：2025-07-09
- 摘要：By analyzing the current standard of lightning testing and performance for the optical ground wire(OPGW), the lightning direct effect testing system with an adjustable discharge gap for the OPGW is constructed. The lightning strike characteristics and damage performance of OPGW under different experimental conditions of variable DC currents and discharge gaps are evaluated in the experiments. The mechanism of lightning direct effect and conducting performance of OPGW are explored preliminarily. It is found that as the Al-Steel outer layer of the OPGW, the erosion degree of the aluminum-clad steel wire increases with the increasing transfer charge of DC current C component. When the transfer charge gets about 200 C, the temperature of the OPGW surface after the lightning strikes is estimated for more than 3 700 ℃, and more than 30% of the strands are damaged severely. Moreover, when the length of discharge gap increases from 5 cm to 6 cm, the temperature rise of OPGW due to the lightning strike decreases and the lightning damage degree is reduced over 40%.关键词：optical ground wire;lightning direct effect;transfer charge;discharge gap;temperature distribution;strand breakage423|5|1更新时间：2025-07-09
- 摘要：To improve the incomplete transformer winding model in the circuit simulation software or the low efficiency of frequency response calculation due to many unknowns in the existing algorithm, a research on a matrix algorithm to calculate the frequency response of the equivalent ladder network for double-winding transformer is conducted. Following the equivalent circuit topology, the model is completely described by the impedance branch matrix and the admittance branch matrix. By means of matrix operation, the relationships of the column vectors of impedance branch current and admittance branch current with nodal voltage are obtained. The frequency response of the equivalent circuit model is calculated by solving the nodal voltage column vector. A comparison between the simulated results of matrix algorithm and those obtained by circuit simulation indicates that the correlation coefficient(CC)becomes greater showing good agreement between them. The curves without high amplitude resonance peaks(above -500 dB)coincide perfectly with a CC of 10. The matrix algorithm takes less calculation time than simulation software. Ensuring the integrality and precision of the simulation model, the proposed algorithm is endowed with good computational accuracy and efficiency due to only twice matrix inversions and less unknowns to be solved.关键词：equivalent circuit model;frequency response;circuit simulation;matrix operation473|5|4更新时间：2025-07-09
- 摘要：The accuracy of the model is very important for the control and performance optimization of the energy storage system of supercapacitor(SC). A parameter identification method of SC equivalent circuit model based on weight distribution optimization is proposed to improve the accuracy of models. The SC are tested with various operating conditions on a Neware test platform. On this basis, the recursive least square method and the bilinear transformation method are used to identify the related parameters of each branch of the three-branch equivalent circuit model of the SC. Furthermore, the weight distribution optimization method is introduced to modify the parameters of the SC equivalent circuit model by combining the advantages and disadvantages of the two parameter identification methods under different working steps. An equivalent circuit model of the SC is established to verify the effectiveness of the weight distribution optimization by comparing and analyzing the results calculated from the model and the experimental results. Comparisons with the recursive least squares method and the bilinear transformation method show that the weight distribution optimization method more accurately reflects the characteristics of SC, the accuracy of the proposed model is improved by 1.45% and 1.78%, respectively.关键词：supercapacitor;recursive least square method;bilinear transformation;weight distribution optimization527|5|2更新时间：2025-07-09
- 摘要：A dynamic volt-ampere characteristic test platform of CFRP is established and the dynamic volt-ampere characteristic measurement method of carbon fiber composite is studied to solve the problem of lightning damage mechanism and non-destructive testing of carbon fiber reinforced polymer(CFRP)in aerospace applications. The dynamic voltammetry behavior of CFRP under non-destructive pulsed current is studied by testing the dynamic current flowing through CFRP and the dynamic voltage at both ends. It is found that the amplitude, waveform of impact current and measurement electrode have significant effects on the dynamic voltammetry behavior of CFRP. With the amplitude of impact current increasing, the dynamic voltammetry characteristic curve of CFRP shows a significant upward shift in the current rise phase; the dynamic amplitude of the dynamic voltammetry curve will shift downward until it tends to overlap in the current falling stage. When the wavelength of the impulse current applied to the CFRP becomes longer, it is clearly observed that the surrounded zones by ascent stage and descent stage of the dynamic volt-ampere characteristic of the CFRP becomes smaller. When the measured electrode size increases, the dynamic current amplitude flowed through the CFRP increases by 15%, and the dynamic voltammetry characteristic curve gradually moves down. When the impact current amplitude increases, the dynamic voltammetry characteristic curves with different measured electrodes are getting closer. These results provide a certain experimental basis and theoretical basis for the study of the conductive behavior and the damage mechanism of the carbon fiber composite material in the direct action of the lightning. It also provides a new experimental idea for the non-destructive testing of the carbon fiber composite.关键词：carbon fiber composite;impact current;dynamic voltammetric behavior;non-destructive testing793|5|1更新时间：2025-07-09
- 摘要：Due to the special physical and chemical properties of the low viscosity and high saturated vapor pressure of water, the design theory of oil hydraulic damping orifice for water one will produce greater deviation and the existing water hydraulic components experiment has the problems of damping orifice diameter being too large, the water pressure being too low and so on. Numerical simulation and experimental studies have been carried out to investigate the flow and cavitation characteristics of water hydraulic damping orifices with diameter≤1 mm. The experimental results verify the correctness of the simulation model, the average flow error is 5.22%, and the flow coefficient error is less than 15%. The discipline of cavitation phenomenon has been studied by numerical simulation, and it is found that the cavitation first occurs at the inlet of orifices and then shifts to the outlet gradually with the increase of the pressure difference. The effects of characteristic size and backpressure on the flow characteristics and cavitation characteristics of micro-damping orifices have been studied by numerical simulation and experiments, and it is found that the flow rate of the damping orifice is nonlinear with the diameter and the length to diameter ratio. The flow coefficient and the flow rate through the damping orifice with backpressure are greater than those without the backpressure, and the flow saturation phenomenon is more pronounced than that without backpressure; cavitation is more prone to happen in the damping orifice with a larger diameter, and the damping orifice with length to diameter ratio l/d=7 has the best anti-cavitation ability. Obviously, increasing the backpressure can improve the anti-cavitation ability. In the design of micro-damping orifice, a small diameter and aspect ratio l/d=7 damping orifice can be selected. Increasing the backpressure can reduce the erosion and damage to the damping hole by cavitation.关键词：water hydraulics;micro damping orifice;flow characteristic;cavitation527|5|0更新时间：2025-07-09
- 摘要：In view of 3-D two-phase flow with spontaneous condensation in cryogenic turbo-expanders, a mathematical model of non-equilibrium condensation is employed to predict the condensation nucleation and droplet growth in gas repaid expansion, where the nucleation model corrected for non-isothermal effect and Gyarmathy droplet growth model are considered. Following the analysis for simulation results, the effects of inlet superheat degree and rotation on the spontaneous condensation in impeller flow passage are investigated, and the distributions of droplet number density, droplet diameter and wetness are obtained. A higher inlet superheat degree results in that repaid nucleation occurs in guiding section and consequently the process develops slowly, thus the gas remains in a higher supercooled state and the nucleation region is enlarged. Because of the interaction of condensation and secondary flow in impeller flow passage, the adverse temperature gradient causes an additional thermodynamic loss. Moreover, the strength of adverse pressure temperature gradient promotes the separation of boundary layer and further causes additional flow loss. For radial and mixed-flow turbines, the small droplets very likely gather and form bigger ones in the secondary flow region, wall of suction side and wake flow region, which leads to secondary nucleation, secondary droplets on a large-scale and the further additional mechanical loss.关键词：turbo-expander;spontaneous condensation;cryogenic two-phase flow;nucleation484|5|1更新时间：2025-07-09
- 摘要：The comprehensive performances of flow resistance, heat transfer and loading capacity of serrated fin in plate-fin heat exchangers are numerically simulated with CFD method and the structure is optimized. Analyzing full 2nd-order polynomial response surface generated by calculating many combinations of input parameters, the effects of the fin height, fin space, fin thickness and fin interrupted length on flow resistance, heat transfer and stress distribution are investigated. Combining response surface with multi-objective genetic algorithm(MOGA), the fin structure is optimized comprehensively by setting the j factor, f factor and maximum stress as the objective functions. Three groups of optimal fin structure are put forward. To demonstrate the effectiveness of optimized structures, the comparison between the original design and optimized structure 3 is performed. The results show that the maximum stress is located on the joint region connecting the right angle of fin structure of first row and clipboard; the effect of fin interrupted length on heat exchange, the effect of fin thickness on flow resistance and the effect of fin interrupted length and fin thickness on stress get the greatest. The FTEF factor of the optimized structure 3 increases by 10.62%, and the maximum stress decreases by 7.9%.关键词：plate-fin heat exchanger;serrated fin;stress analysis;response surface;multi-objective genetic algorithm500|5|7更新时间：2025-07-09
- 摘要：A fast dynamic mesh method based on spatially distributed elasticity modulus is developed to settle the mesh distortion of the fast dynamic mesh method based on one single elasticity modulus. The space distribution of elasticity modulus is set according to the size distribution of meshes in space of meshes. The stiffness matrix of the whole pseudo elastic solid is derived by combining element stiffness matrixes of all meshes. Then the dynamic equation for the structure-pseudo elastic solid system is derived using the static equilibrium equation of the pseudo elastic solid, the vibration equation of the structure and the displacement interpolation equation of the fluid structure interface. Deformation is calculated for the structure and the pseudo elastic solid using the modal superposition of the structure-pseudo elastic solid system. A flow mesh with the minimum face angle equal to 0 deg is called an illegal mesh. The present method is tested on an illegal mesh with the standard beam and Agard Wing 445.6. The minimum face angle after deformation given by the present method is above 67deg for the flow mesh of the beam and the minimum face angle after deformation is above 36deg for the flow mesh of the wing.关键词：fast dynamic mesh method;mesh distortion;one single elasticity modulus;spatially distributed elasticity modulus437|5|0更新时间：2025-07-09
- 摘要：An improved seven states Markov stochastic process model based on current channel structure information is proposed to elucidate and forecast Cav1.2complex gating kinetic in the interactive cell environment regulated by multiple factors which plays a key role in the Ca2+ metabolic cycle in functioning cells. Seven states are abstracted to present the limited conformational changes of Cav1.2channel including VDI and CDI. Based on the Bayesian framework, the experiment data are then used to estimate the parameters of rate function between seven states via JAGS, which implements MCMC algorithm Gibbs sampler to sample the posterior distribution. The stochastic model is applied separately to stochastic PDEs profiling the Ca2+ transient in the subspace and the changed electrophysiological behavior induced by the channel mutations G406R/G432N. The computational results show that the improved Cav1.2 Markov framework coincides well with the broad electrophysiological observations at the macroscopic level, and it also has a better predictability in the field of cardiomyocytes microstructure and channel genes pathology.关键词：Markov model;voltage-dependent inactivation;Ca2+-dependent inactivation;G406R/G432N mutation643|5|0更新时间：2025-07-09
- 摘要：Aiming at the phenomenon that the most existing methods of automatic seizures detection are used to low frequency EEG and ignored the high-frequency components, we attempt to adopt the high frequency component of long term scalp EEG to detect seizures in focal epilepsy patients in this research. Gamma band is extracted in 19 channel EEG using discrete wavelet transform in a sliding window, and the information flow characteristics of each band is evaluated with directional transfer function algorithm. The intensity characteristics of the outgoing information are used to reduce the dimensions. The features are classified by support vector machine(SVM). Five-fold cross validation indicates that the proposed strategy achieves an excellent performance with the average accuracy of 98.4%, the average selectivity of 60.7%, the average sensitivity of 93.4%, the average specificity of 98.4% and the average detection rate of 95.9%, and the gamma band is endowed with higher classification effect. For patients with focal epilepsy, the intensity of the gamma band outflow during seizure attack is significantly concentrated and enhanced in some brain regions. Simultaneously it validates the point that seizure attack is related to high frequency components in the literatures.关键词：seizure detection;Directed Transfer Function;difference of information flow;gamma band;support vector machine431|6|1更新时间：2025-07-09
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