2020 volumne 41卷 Issue  03
Shang Zhigang 1,2Shen Xiaoyang 1,2Li Mengmeng 1,2Wanhong 1,2
Abstract: Effective connectivity analysis is an important approach to study the interaction between different regions of the brain. At present, the effective connectivity analysis methods based on Granger causality have been widely used by scholars around the world in neural signals analysis of multi-brain regions. First of all, the calculation principle and functional characteristics of representative algorithms commonly used in this kind of method were systematically introduced. Simulation case was carried out to compare the characteristics of different algorithms, and then the key points that should be paid attention to in practical application of this kind of method were summarized. Finally, Generalized Partial Directed Coherence and its improved algorithm were taken as examples to show the application effect on the actual electroencephalogram data set.
Zuo Min,Xu Zelong,Zhang Qingchuan,Bi inscription
Abstract: Simple Question Answering over Knowledge Bases (KB-QA) is a hot topic in Natural Language Processing (NLP) research, and it is also the most widely used case in real life. However, in the process of researching Chinese KB-QA, there are still many technical challenges such as extracting relations from questions which relation names are ambiguous, also have problems such as error propagation between different processes. Based on the self-built food domain knowledge base (FD-KB) and the food field corpus, this paper starts from the two semantic perspectives of Chinese characters and Chinese words to extract relations and mitigate the error propagation. Contrast experimental results show, the model of two-dimensional Chinese semantic analysis that proposed here can get the accuracy of 85.66%.
Li ShuijiaGong Wenxi
Abstract: It is vital to fast and accurately extract the parameters of the photovoltaic (PV) models for the simulation, evaluation, and control of PV systems. Recently, the use of the intelligent optimization methods for parameter extraction of PV models draws growing attention. However, these methods tend to consum e large computational resources. In order to fast and accurately extract the parameters of the PV models, this paper develops a novel adaptive differential evolution algorithm, in which a new m utation strategy is proposed. To verify the performance of proposed algorithm, the single diode model, the double diode model, and the PV module are selected as the test models. The experimental results show that proposed algorithm can extract the parameters of different PV models fast and accurately. Thus, proposed algorithm can be an efficient alternative for parameter extract ion of PV models
Zhang Chengcai,Li Fei,Wang Yanmei,Luo Weiran
Abstract: Fuzzy C-means clustering (FCM) algorithm does not consider the correlation between pixels when classifying remote sensing images. In order to increase the correlation information between pixels, a multi-core fuzzy C-means clustering (MKFCM) algorithm is proposed, in which multiple kernel functions are introduced into FCM algorithm. And automatically filters out the optimal weight combination among kernel functions according to the distribution characteristics of pixels in feature space. The medium-high resolution Landsat8 images and high resolution Pleiades images as research data, and by analyzing the accuracy of classification results of MKFCM and FCM algorithm ,the results show that MKCM algorithm can better distinguish pixels with similar spectral information for different resolution remote sensing images, and whether the accuracy of the single category or the overall classification accuracy is higher than the FCM algorithm, which provides an effective way to accurately extract the regional land cover information
Zhang Duanjin,Guo Lu
Abstract: In this paper, the problem offiltering for networked control systems using delta operator is investigated, which includes two-channel packet dropouts and mixed random delays. Random communication packet dropouts exist in both channels from sensors to controllers and from controllers to actuators. They are represented by two independent Bernoulli distributed white sequences. The mixed random time-delays consist of network induced time delay and discrete infinite distributed delays. A networked-based model is considered with a Markov stochastic process and thefiltering error system is constructed by using Lyapunov-Krasovskii functional in delta domain. A sufficient condition for stochastic stability of the filtering error system with anperformance is obtained in terms of linear matrix inequalities (LMI). The explicit expression of the desiredfilter is given. A numerical example shows the effectiveness of the proposed method.
Chen Liping,Wang Mingyu,Yang Wenzhu,Wang Sile,Chen Xiangyang
Abstract: In order to solve the problem of template drift caused by fast moving and object occlusion in long term target tracking, a Long-term Kernelized Correlation Filter (LKCF) based on improved Kern el Correlation Filter (KCF) was proposed. In this paper, we used the kernel correlation filter algorithm(KCF) as the tracking framework and adopted a highly reliability template update strategy to prevent template destruction. Furthermore, we constructed a conditional target re-detection mechanism to restore the false model caused during tracking. Experimental results indicate that the proposed algorithm not only avoid the problem of template drift effectively but also can track targets steadily for a long time.
Zhang Sanchuan,Miao Shuaibin
Abstract: In order to solve the problem of compact layout design of the internal battery module of electric vehicle battery enclosure, the thermal simulation method was used to study the dimensional parameters (column distance, line spacing, margin, entrance and exit diameter) of the flow channel formed between the battery modules and the heat dissipation effect in the battery enclosure. The relationship between the highest temperature, the highest temperature difference and the characteristic dimensions of the internal arrangement of the battery box is established. The application example shows that the error between the calculation result of the compact design formula and the thermal simulation result is less than 5%, which meets the engineering needs and can guide related research. The size of the margin of the local battery box is optimized; the number and radius of the rounded corners of the battery box are optimized. When the battery box adopts the final optimized structural parameters (Di=120mm), the maximum temperature of the battery box drops by 8.77%, the maximum temperature difference decreases by 3.88%,the area of high temperature area above 32.5 °C ST32.5 decreased by 65.68%,, and the ST30 decreases by 60.77%. When cooled by 15m/s wind speed, the maximum temperature dropped to 28.63 °C, and the maximum temperature difference was less than 5 °C.
Abstract: Based on the principle of the traditional inversion method, using ADAMS software to design the cam contour curve of the cam design, only the steeple follower. This is because the contact point between the push rod and the cam is not fixed in the cam mechanism with flat bottom follower. The cam contour is actually the envelope of the push rod contour. In order to solve this problem, this paper discretizes the contour of the push rod, generates several curves by using the discrete contact points, intersects these curves, and obtains the ideal cam contour curve, which provides a new method for the design of flat-bottomed follower cam in ADAMS. In this paper, the cam mechanism is simulated and compared with the design objective. The relationship between the number of discrete points and the accuracy of design is discussed. It is concluded that increasing the number of discrete points can improve the accuracy of cam design
Qiu Zhengxin1,Liu Benxue2,Zhang Saipeng3,Li Fuyong1,Ao Ming3,Feng Shitao3,Zhang Ren1
Abstract: High voltage isolation switch is widely used in power grid. Its performance directly determines the safety of electricity consumption. In order to evaluate the performance of gw46-126 high-voltage isolation switch at different ambient temperatures, the experimental research on the contact clamping force, contact relative position, mechanism operating torque, output Angle of mechanism, circuit resistance and other parameters of the isolation switch under the temperature within the temperature range of ±60℃ in climate laboratory are conducted to get the trend and relationship between the qualities and temperature. Through experimental data collection and analysis, the influence law of environmental temperature change on the characteristics of isolation switch is determined, which provides important data support for further optimizing the performance of GW46-126 high-voltage isolation switch and improving the applicability of environmental temperature
Liu Zhuli 1,Chen Yun 1,Wang Zhuxin 2
Abstract: ANSYS finite element software is used as a tool to simulate the compressive residual stress of carburizing and quenching gear by applying prestress to gear. Since the compressive residual stress varies with the depth of material, in order to facilitate the simulation of the compressive residual stress in each layer by layering the surface layer of gear teeth. Under the same load conditions, the compressive residual stress gear produced by carburizing and quenching and the absence of compressive residual stress gear are respectively analyzed for flexural strength and fatigue life, in order to study the compressive residual stress’s influence on flexural strength and fatigue life of gear. The results of the analysis show that the compressive residual stress can make gear flexural fatigue resistance improved
ZHOU Yang, XU Gaijiao, LI Dalei
Abstract: In order to study the influence of shaft-gear interference fit on tooth profile, the calculation model of the tooth deformation was proposed by combining the shaft-gear interference which based on Lame equation and involute equation was established by finite element method in this paper. At the same time, the corresponding calculation program was compiled based on MATLAB, and the influence of the friction coefficient, interference and other parameters on the radial displacement of the gear tooth shape was studied. The results showed that the radial deformation of the gear increased with the increase of the friction coefficient and interference, and decreased with the increase of the number of teeth.
Li ZongkunWang TeGe WeiSong Ziyuan
Abstract: The construction system of artificial island of Hong Kong-Zhui-Macao Bridge is complex and uncertain. This paper constructed the WBS-RBS judgment matrix to identify the risk factors in each construction stage, calculated the weight and risk degree of each index layer by using AHP method and risk degree theory, and evaluated the project comprehensively according to the five-level risk standard. The result shows that the overall risk level of the artificial island construction of the Hong Kong-Zhuhai-Macao Bridge is 3-level medium risk, which is in line with the actual project. It indicates that the method is reasonable and feasible, and can provide reference for the construction of risk evaluation system for similar projects.
Hanwha Strong1Chen Shengshui1Wang Zhanjun2,3Zheng Chengfeng1Fu Hua1
Abstract: Strength and deformation characteristics are two basic indexes that reflect the mechanical properties of mother rock. But the influence of mother rock deformation on the mechanical properties of rockfill is seldom or even neglected in present studies. Based on the large-scale static three axis instrument and the large permeability apparatus, the triaxial tests and permeability tests were carried on two kinds of rockfill materials. Finally, the variations of strength, deformation and permeability characteristics with different lithological rockfill materials were obtained, and the influence mechanisms of deformation characteristics of mother rock on mechanical properties of rockfill materials were preliminary analyzed. The result shows that the deformation characteristics of mother rock also play an important role in the mechanical properties of rockfill materials, namely, the influence of mother rock on the mechanical properties of rockfill materials mainly lies in the strength and deformation characteristics, while the influence on permeability characteristics of rockfill is relatively small. The strength of different rockfill materials is not the same even though the mother rocks under the same uniaxial compressive strength. The influence mechanism of deformation characteristics of mother rock on the mechanical properties of rockfill materials is mainly reflected in two aspects: particle crushing and shear shrinkage. The initial deformation index of rockfill materials has a positive correlation with the deformation index of the mother rock, and in the initial stage of shearing, the more the deformation index of mother rock, the faster and the greater the strength of rockfill materials under the same strain condition, while the cumulative volume deformation and particle breakage are relatively small. With the development of rockfill strain, when a certain stress level is reached, rockfill materials with relatively small deformation index of the mother rock accumulated a relatively large volume deformation due to the shear shrinkage, which lead a slow tendency of rockfill materials strength growth is relatively small. While the crushing amount of rockfill materials with large deformation index increases significantly, and lead a relatively slow growth of rockfill strength. It is possible to obtain a larger peak strength even the deformation index of mother rock is low. Research conclusions indicate that the influence of mother rock on the mechanical properties of rockfill should be studied from two aspects of strength and deformation characteristics
Zhang Shuangsheng1,2,strong static 3,Liu Han Lake 1,Liu Xikun 2,Sun Shaohua 4
Abstract: Aiming at the problem of the result affected by samples’ initial values with classical MCMC method, when the inverse problems of underground water pollution were solved by Bayesian statistical methods, an improved MCMC method based on latin hypercube sampling was presented. An underground water pollution source identification model was built by coupling Bayesian statistical methods to two-dimensional water quality convection-diffusion equation. An example of a pollutant in the underground aquifer discharged instantly was put forward, and the pollution source information including source’’s position, intensity and discharging time was solved by classical MCMC method and improved MCMC method separately. The example showed that the inversion results affected by initial values with classical MCMC method were locally optimal or difficult to convergence; on the contrary, the improved MCMC method could achieve a global optimization. The computed values solved by the improved MCMC method were basically the same as the truth values. The accuracy and stability were improved significantly.
Zhang Yaqin 1,Yang Ping 1,Jiang Wangyang 1,Zhang Ting 1,Chen Liang 2
Abstract: Artificial frozen soil uniaxial compressive strength and elastic modulus is the key parameters of artificial freezing method design, accurate understanding of the change rule is extremely important.So the experimental study on uniaxial compression strength of artificial frozen soil with silty clay was carried out under the conditions of different water content and strain rate. The results show that most samples showed drum type failure, with the increase of water content, the stress-strain curve gradually change from stress softening to stress hardening. There is an optimum moisture content to peak strength, for Nanjing typical silty clay the moisture content is 22%, close to saturation moisture content; elastic modulus of remolded silty clay increased with water content increasing, but the growth rate declined; the uniaxial compressive strength and elastic modulus decrease with increasing strain rate; The resilient modulus increases gradually with the increase of loading and unloading times, when loading and unloading times up to 7 times, the resilient modulus is basically stable. The stress - strain curve of the remolded soil specimen is more smooth than the original soil sample, and the compressive strength and modulus of elasticity are improved.
Dynasty 1,Zhao Guifeng 2,Liu Ran 2,Chen Yiwen 2
Abstract: finite element model of a typical substation framework with lightning rods was established by using ANSYS software. The static bearing capacity and wind-induced dynamic response analysis were carried out under the design load combination conditions. The results show that the stress concentration phenomenon is easy to occur due to the structural defects in the T type tubular joint of the typical substation structure with lightning rods, and it can be effectively relieved by installing stiffening ribs in the T type tubular joint area. Furthermore, the lightning rod designed by the current standard static method is unsafe. In actual design, it is suggested that the results of the pseudo static method be multiplied by a dynamic amplification factor of less than 1.6 to take into account the adverse effects of the pulsating wind on the structure
Zhang Xueyan,He Feng
Abstract: To consider the uncertainty of transportation system and travelers’ perceived errors and risk-decision behavior, the stochastic user equilibrium condition with combined modes are analyzed based on cumulative prospect theory. The corresponding variational inequality model is proposed, the equivalence of model and the existence of solutions are also analyzed. A path-based method of successive average algorithm is used to solve this problem. A super network is introduced as the example network to verify the proposed model and make sensitive analysis of the input parameters. The results show that, based on cumulative prospect theory, the traffic assignment model with combined modes can more effectively describe the travelers’ choosing behaviors of traffic modes and transfer stations in uncertain transportation environment. This study could provide theoretical support to the urban traffic mode split and site selection of transfer stations.
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