bob手机在线登陆学报自然版

2021, 41(8): .

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2021, 41(8): .

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Influence of Guided Wave Mode Types on the Non-Destructive Testing of Grouting Rock Bolts

NIU Panyu, ZHANG Changsuo, ZHAO Jinchang, LI Peng

2021, 41(8): 791-799. doi:10.15918/j.tbit1001-0645.2020.236

Abstract(596) PDF(257)

Abstract:
Longitudinal mode, torsional mode and flexural mode ultrasonic guided waves have different attenuation properties in anchored rock bolt. Therefore, the study of the transmission law of the three modes of ultrasonic guided waves has important guiding significance for the selection of test waves in non-destructive testing (NDT). The global matrix method and numerical simulation were used to obtain the dispersion curves and time-domain waveforms corresponding to these three modes, respectively. The characteristics of these three modes obtained by theory calculation and numerical simulation are in good agreement with each other. The results indicate that the attenuation of longitudinal mode ultrasonic guided waves ranges from 20~44 dB/m with high frequency. Attenuations for all torsional mode ultrasonic guided waves are greater than 180 dB/m. Moreover, attenuations for flexural mode ultrasonic guided waves are greater than 50 dB/m. Thus, longitudinal ultrasonic guided waves with high frequency are the most applicable modes because of low attenuation and easy excitation.

Influence of Nanocrystalline Magnetic Ring on the Sensitivity of Wear Particle Sensor

ZHENG Changsong, WANG Xu, YU Liang, WEI Chengsi, HOU Rui, DU Jinbo

2021, 41(8): 800-807. doi:10.15918/j.tbit1001-0645.2020.188

Abstract(498) PDF(211)

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In order to improve the sensitivity of the on-line wear particle monitoring sensor,an electromagnetic wear particle sensor with a built-in nanocrystalline magnetic ring was proposed.By establishing a numerical model of the sensor's internal magnetic field distribution and output induced electromotive force,the influence of size properties of the induction coil ring and the excitation coil rings on the sensitivity of wear particle monitoring sensor was systematically analyzed.The simulation and experimental results show that the nanocrystalline magnetic ring has a significant influence on the sensor sensitivity.Moreover,adding magnetic rings to both the excitation coil and the induction coil can dramatically increase the amplitude of electromotive force induced by wear particles to 4~7 times.Therefore,the monitoring ability of the designed sensor can improve effectively,especially for the small wear particles of 50μm to 100μm.The study is of great significance for the early fault diagnosis and fault warning of large mechanical equipment.

Simulation Analysis on Humid Air-Water Evaporative Cooling Characteristics Among Staggered Tube Bundles

MA Hongqiang, LIU Yemin, LIANG Nuo, JIA Jiwei, LUO Xinmei, HOU Caiqin, QU Dehu, WANG Gang, ZHANG Na

2021, 41(8): 808-819. doi:10.15918/j.tbit1001-0645.2020.189

Abstract(530) PDF(184)

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Based on the Euler-Lagrange method coupled with DPM (discrete phase models)-WFM (wall film models),a new model was established to investigate the heat and mass transfer characteristics of spray water-humid air and spray water-tube wall among staggered tube bundlesand to design the movement of spray water among staggered tube bundles and the heat/mass transfer process.Firstly,the reliability of the model was verified according to the literature experimental data,showing only 1.1% maximum error.Secondly,the influence of operating parameters was analyzed for heat and mass transfer performance of humid air-wateramong staggered tube bundles.The results show that the influence of air flow rate on heat and mass transfer performance among staggered tube bundles is more significant than that of spray water flow.Therefore,the spray water flow rate can be appropriately reduced to improve the energy efficiency of circulating water pump.The increase of dry bulb temperature and wet bulb temperature will have a negative effect on the heat and mass transfer performance among staggered tube bundles.However,the effect of wet bulb temperature on heat and mass transfer performance among staggered tube bundles is greater than that of dry bulb temperature.Increasing the spray water temperature can improve the Nusselt number between spray water and tube wall,but the average temperature of tube bundle wall also increases,which means that the performance of the cooling-water machine is reduced.The above research results can provide a basis for the thermal design and calculation of staggered tube bundles.

Trajectory Optimization of Glide Vehicles Based on Tabular Aerodynamic Data

SUN Yibo, MENG Xiuyun, QIU Wenjie

2021, 41(8): 820-829,839. doi:10.15918/j.tbit1001-0645.2020.099

Abstract(543) PDF(211)

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High-precision aerodynamic data is usually expressed in table form. To fitting tabular aerodynamic data in trajectory optimization of glide vehicles, a two-dimensional smoothing and shape-preserving fitting method was proposed. Firstly, one-dimensional smoothing and shape-preserving fitting was performed on the tabular aerodynamic data. And then the fitting dimension was expanded by the tensor product method. Finally, the proposed fitting method was validated by fitting typical tabular aerodynamic data. The results show that, under the given fitting accuracy constraints, the method can fit second-order continuous surfaces with the monotonicity maintained in the tabular data. Establishing a trajectory optimization model of glide vehicles based on the tabular aerodynamic data fitted by this method, and optimizing the trajectory using adaptive Legendre-Gauss-Radau collocation method, a trajectory simulation was carried out taking the pitch angle of the optimized trajectory as open-loop control commands. The trajectory optimization results correspond exactly with the simulation results.

Spectrum Efficiency Optimization of Multi-UAV Communication Network Based on Cooperative Spectrum Sensing

ZHANG Hongwei, DA Xinyu, HU Hang, NI Lei, PAN Yu

2021, 41(8): 830-839. doi:10.15918/j.tbit1001-0645.2020.122

Abstract(563) PDF(175)

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Aiming at the low spectrum efficiency (SE) in application scenarios of unmanned air vehicles (UAV), an average SE optimization scheme of multi-UAV communication network combined with cognitive radio (CR) was proposed. Firstly,based on cooperative spectrum sensing (CSS), a cognitive UAV network model was established for multi-UAV cooperation in air to ground (A2G) channel, setting the optimization parameters such as number of UAVs, sensing time and cooperative decision threshold. Then,the average SE optimization problem of UAV was investigated, and a joint optimization algorithm was proposed to solve the non-convex optimization problem. Finally, the change of SE in the flight course of UAV was analyzed. The simulation results show that there is an optimal sensing time to maximize the SE, and the number of UAVs and decision threshold will affect the optimal value of SE. In addition, the proposed algorithm has better convergence and can effectively improve the average SE of UAVs in the secondary network.

Autonomous Cross-Domain Obstacle Negotiation Research of a Variable Structure Land-Air Robot

WANG Jianzhong, YOU Yu, WANG He

2021, 41(8): 840-846. doi:10.15918/j.tbit1001-0645.2020.237

Abstract(476) PDF(241)

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Land and air robots have attracted much attention due to their flexible maneuverability. In order to better utilize the characteristic of cross-domain obstacle negotiation, based on the variable structure land-air robot, the depth image was binarized to extract the edge contour of the obstacle ahead, and the minimum rectangle matching method was used to model the obstacles to obtain the distance and height of the obstacles. Furthermore, the autonomous cross-domain obstacle negotiation strategy was proposed according to the obstacle detection results and obstacle negotiation performance of terrestrial locomotion. The experimental results demonstrate that the robot can detect the distance and height of the obstacles ahead accurately, and cross the obstacle to reach the target point autonomously. The obstacle detection method and autonomous cross-domain obstacle negotiation strategy proposed in this paper are effective.

Turbulence Details Simulation Toward Smoothed Particle Hydrodynamics(SPH)Fluid

BAN Xiaojuan, ZHOU Jing, WANG Xiaokun, LIU Sinuo, XU Yanrui

2021, 41(8): 847-854. doi:10.15918/j.tbit1001-0645.2020.015

Abstract(527) PDF(182)

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To reduce the numerical dissipation of smoothed particle hydrodynamics (SPH) method with artificial viscosity, a method to restore vortex and turbulence details was studied. First, according to the kinetic energy change rate in the cause of viscous force, the vorticity at discrete points was corrected. Then, the vorticity was restored to velocity field based on stream function to avoid the time-consuming process for Biot-Savart integral solution. Based on the calculation of the vorticity, the proposed method can not only enhance the existing vortex, but also generate new turbulence at potential locations, and easy integrate into existing SPH methods. Experiment results show that this method can realistically simulate turbulent details and achieve enhancement effects at different intensity levels.

The Quantification Test Method of Electromagnetic Radiation Susceptibility for Equipment Under Test in Reverberation Chamber

WEI Guanghui, PAN Xiaodong

2021, 41(8): 855-863. doi:10.15918/j.tbit1001-0645.2020.127

Abstract(438) PDF(169)

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Aiming at the technical requirements for the quantitative test of the electromagnetic radiation susceptibility in reverberation chambers, the limitation of the existing testing methods was analyzed and the key problems were pointed out. Based on the statistical distribution rules of the electromagnetic field in reverberation chamber and the electromagnetic radiation effect mechanism, the relationship between the critical interference field intensity of the equipment under test (EUT) and the effective mean value of the electric field intensity in reverberation chamber, the interference probability of the EUT and the maximum value of the equivalent antenna directivity factor was established. Considering the effect types and the coupling efficiency of the equivalent antenna, the selection principle and the fitting formula of the directivity factor of the EUT equivalent antenna were presented in three aspects, the interference and damage effect for the spectrum-dependent equipment, the high intensity electromagnetic radiation effect for EUT and the disturbance effect for the measurement and control equipment. A test was arranged with the condition, 10%~60% interference probability of the EUT and the stirring position number 30~50 in the reverberation chamber. The test results show that the result error of the EUT critical interference field intensity between the reverberation chamber environment and the uniform field environment is about 3 dB. A military ultra-short wave communication radio was selected as EUT to test the out-band high intensity radiation shutdown-restart effects and the measurement control disturbance effects of the power module. The test results indicate that the rule of the electromagnetic radiation critical interference field intensity varies with the radiation frequency for EUT, it is the same between the reverberation chamber and the uniform field environment. The maximum test error value is 5 dB, which can satisfy the requirements of the engineering test.

Text Semantic Matching Method for Information and Communication (ICT) Supply Chain Network Portrait Construction

LUO Senlin, YANG Junnan, PAN Limin, WU Zhouting

2021, 41(8): 864-872. doi:10.15918/j.tbit1001-0645.2020.132

Abstract(438) PDF(173)

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To extract information and communications technology (ICT) supply relationships from public text, it is necessary to achieve the matching of ICT bidding projects and supplier products accurately. However, the information on the supplier's official website related to the bidding project is distributed in the product name (entity) and product introduction (document), being difficult to establish its mapping association directly. Therefore, it is necessary to analyze the semantic of the text and to establish an accurate matching. Due to multi types and complex forms of ICT projects and product data, it is difficult to extract their matching semantic information. In addition, the existing text matching models can not differentiate the indiscrimination encoding in different levels of text, causing noise introduction and poor matching performance. To solve the problems, an entity-document level joint matching model was proposed. The model was arranged to use the TextCNN encoder to extract the local semantic information from the product name and the bidding project to eliminate the interference of irrelevant information in the product introduction. Then the CNN-SA encoder was used to extract the local and global information of the product introduction. Finally, the entity-level and document-level matching information was combined to make decisions. Experiment results show that the accuracy of matching mapping between bidding projects and supplier products can reach up to 92%. The method can be provided directly to practice application.

A Novel SNR Estimation Method Based on Spread Spectrum Signal in Troposcatter Communication

SHEN Binsong, QIN Jiancun

2021, 41(8): 873-877. doi:10.15918/j.tbit1001-0645.2020.142

Abstract(484) PDF(212)

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To solve the problem that the signal to noise ratio(SNR) estimation error is large in the scattering multipath fading channel,a novel SNR estimation method based on spread spectrum signal was presented.Firstly,a troposcatter communication SNR estimation model was established to provide the scheme of SNR estimation and the data frame structure.Then,according to the characteristics that linearity frequency modulation(LFM) signal could separate multipath,a SNR estimation method based on spread spectrum signal was put forward,and the calculating formula of combined SNR was presented.Meanwhile an equivalent SNR calculation method based on specific received signal processing algorithm was proposed to represent the actual SNR in communication.The simulation results show that the method can provide accurate SNR estimation,the calculation method of equivalent SNR can educe more correct results and suit for a wider estimation range compared with other SNR estimation methods,can effectively carry out accurate SNR estimation of multipath channel.

Clutter Reduction Method for Radar Cross Section (RCS) Measurement Based on InSAR Principle

NING Chao, LÜ Ming, GAO Chao, WAN Hao

2021, 41(8): 878-885. doi:10.15918/j.tbit1001-0645.2021.024

Abstract(487) PDF(162)

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In order to reduce the clutter in near-field electromagnetic scattering measurement, a clutter filtering method in height dimension based on InSAR principle was proposed in this paper. Firstly, two radar two-dimensional images of the target are obtained by twice linear scanning of the antenna at different heights. Then, the amplitude and phase of scattering centers were extracted from the radar images data, and the height of the scattering center can be calculated by using some information, including the phase difference of the scattering center and antenna height between the two measurements. Afterwards, according to the target height range, the filter in height dimension was set to reduce clutter outside the target height range. Finally, the RCS of the target was constructed after filtering so as to reduce the clutter and improve the accuracy of RCS data. The result of simulation demonstrates that the mean RCS error is reduced to within 1 dB with applying the proposed method. And the scattering centers of an aircraft model are accurately extracted from a strong clutter experiment environment, which has the equivalent scattering intensity with the target.

Regulating miR-642a-5p for Phycocyanin to Inhibit Proliferation and Migration of LTEP-a2 Cells

HAO Shuai, LI Shuang, LIU Yuanpu, WANG Jing, ZHAO Lei, WANG Chengtao

2021, 41(8): 886-893. doi:10.15918/j.tbit1001-0645.2020.054

Abstract(426) PDF(214)

Abstract:
To explore the mechanism of phycocyanin in inhibiting the proliferation and migration of LTEP-a2 non-small cell lung cancer cells, a high-throughput miRNA transcription set (miRNA-Seq) was performed to screen differential miRNAs in the cells treated by phycocyanin. An in-vitro over-expression mimic method was taken to verify the proliferation and migration ability of differential miRNA in LTEP-a2 cells. Analysis results show that phycocyanin can improve the expression of miR-642a-5p in LTEP-a2 cells. Over-expression of miR-642a-5p can obviously decrease the proliferation and migration ability of LTEP-a2 cells. Phycocyanin can activate NF-κB signaling pathway by up-regulating miR-642a-5p expression, reduce protein phosphorylation level, and then inhibit the proliferation and migration of LTEP-a2 cells. The results provide a theoretical basis for the application of phycocyanin and the treatment of non-small cell lung cancer.

Machinability Research on the Ultrasonic Assisted Micro-Milling for Graphene Based Aluminum Matrix Composite

XU Linhong, CHEN Yong, HAN Guangchao, NA Haobo

2021, 41(8): 894-900. doi:10.15918/j.tbit1001-0645.2020.125

Abstract(454) PDF(220)

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As a new composite processing technology, ultrasonic assisted micro-milling represents unique advantage in processing hard and brittle materials and composites. In order to solve the problems of difficult machining, high machining accuracy requirement and low processing efficiency in industrial applications of graphene-based aluminum matrix composites, a pure aluminum and graphene-based aluminum matrix composite were taken as research objects to carry out ultrasonic assisted micro-milling experiments for graphene-based aluminum matrix composites with different ratios. The effects of graphene content, feed rate per tooth and ultrasonic amplitude on milling force and surface roughness were analyzed based on orthogonal experiment, and the optimal process parameters of graphene aluminum matrix composite under ultrasonic assisted micro milling were determined. The results show that the graphene-Al matrix composites can put up a best processing performance under 1μm/z feed per tooth and 3.05μm ultrasonic amplitude.

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