• Issue 6,2020 Table of Contents
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    • >Special Column: National Young Scholar/Local Science Foundation
    • Design and implementation of BeiDou signal fast acquisition algorithm based on FPGA+DSP

      2020, 41(6):477-485. DOI: 10.7535/hbkd.2020yx06001

      Abstract (1969) HTML (0) PDF 3.14 M (2253) Comment (0) Favorites

      Abstract:In BeiDou satellite receiver, a fast BeiDou signal acquisition algorithm based on coherent down-sampling was proposed to solve the problem that the large amount of data to be processed by the Fourier transform affects the acquisition speed of satellite signals in the traditional parallel frequency acquisition algorithm. On the basis of FPGA+DSP (field-programmable gate arrays+digital signal processors), the coherent down-sampling module was added to the traditional parallel frequency acquisition algorithm, and after the carrier and pseudo random code were stripped, the sampling frequency was reduced to decrease the number of points to be processed in the Fourier transform, and then a three-dimensional search for the satellite signal was performed. Theoretical analysis shows that the algorithm can reduce the amount of calculation by more than 80%; the experiments on the actual BeiDou signal indicate that the average acquisition time of each star is 9.95 ms, and the memory resource consumption is reduced by 42% compared with the traditional parallel frequency acquisition algorithm. This algorithm can effectively improve the acquisition speed while saving resources, which can provide reference for further improving the acquistition performance of the software receiver.

    • >Mechanical, Electronics and Information Science
    • B1C navigation signal acquisition algorithm based on PCO+FFT

      2020, 41(6):486-492. DOI: 10.7535/hbkd.2020yx06002

      Abstract (1948) HTML (0) PDF 1.74 M (1978) Comment (0) Favorites

      Abstract:In order to capture the B1C navigation signal with BOC modulation, a specific acquisition scheme of PCO+FFT was proposed. Firstly, based on in-depth analysis of the characteristics of B1C signal, the segment length and FFT points were selected. Secondly, the algorithm was derived from coherent integral gain, uncorrelated integral gain, Doppler frequency measurement range and resolution, and detection probability. Thirdly, the FPGA implementation scheme based on the algorithm was given. Finally, the simulation performance of the algorithm was given to illustrate the effectiveness of the algorithm. The correctness of the implementation scheme is verified by the actual measurement on the FPGA hardware platform. The method of sub carrier separation and the realization of control core based on state machine have certain reference value for the improvement of navigation signal acquisition algorithm.

    • Pseudolite dynamic tracking and positioning algorithm based on square root UKF

      2020, 41(6):493-499. DOI: 10.7535/hbkd.2020yx06003

      Abstract (1913) HTML (0) PDF 1.67 M (1869) Comment (0) Favorites

      Abstract:In order to solve the limitation of traditional Kalman filter in dealing with nonlinear system and the problem of divergence and poor accuracy of extended Kalman filter (EKF) in dealing with strong nonlinear system, a dynamic tracking and positioning algorithm based on square root UKF was proposed based on the unscented Kalman filter (UKF) algorithm in combination with the problem of target tracking and positioning in dynamic navigation system. In the process of recursive operation, the square root of covariance matrix was used to replace the covariance matrix in the calculation process of covariance algorithm. The MATLAB simulation results show that the accuracy of the square root UKF algorithm is 54.7% higher than that of the EKF algorithm, and 14.8% higher than that of the UKF algorithm. The proposed algorithm solves the limitation of Kalman processing nonlinear system and the problem of the low accuracy of traditional EKF and UKF algorithms, and provides a strong support for the high-precision positioning of pseudolite system.

    • Point-of-interest recommendation algorithm integrating multiple impact factors

      2020, 41(6):500-507. DOI: 10.7535/hbkd.2020yx06004

      Abstract (1929) HTML (0) PDF 1.36 M (1939) Comment (0) Favorites

      Abstract:In order to solve the problem of data sparseness in the task of point-of-interest recommendation and make full use of the diverse information in the location-based social network to further improve the quality of personalized recommendation, a point-of-interest recommendation algorithm integrating multiple impact factors was proposed. Geographic influence modeling and social influence modeling were performed on geographic information and social information, and temporal information and geographic information were combined to model temporal and spatial influence, and the three influence scores were integrated in a weighted summation manner to obtain user preference score. According to the user preference score, each user was provided with a recommendation list containing Top-N points of interest. The experimental results show that on the two public datasets, the point-of-interest recommendation model that integrates multiple impact factors performs better than the baselines. In addition to the user check-in frequency, the geographic-social-spatial-temporal influence is also a key part of the point-of-interest recommendation task, and the modeling of these three influences is of great significance, which provides certain reference value for the research of point-of-interest recommendation integrating key information.

    • Khmer multi-document extractive summarization method based on hierarchical maximal marginal relevance

      2020, 41(6):508-517. DOI: 10.7535/hbkd.2020yx06005

      Abstract (1947) HTML (0) PDF 1.22 M (1840) Comment (0) Favorites

      Abstract:In order to solve the problem of ineffective utilization of the semantic information between documents in the traditional multi-document extractive summarization method and the excessive redundant content in the summary result, a Khmer multi-document extractive summarization method based on hierarchical maximal marginal relevance(MMR)was proposed. Firstly, the Khmer multi-document text was input into the trained deep learning model to extract all the single-document summaries. Then, all single document summaries were iteratively merged according to a similar hierarchical waterfall method, and the improved MMR algorithm was used to reasonably select summary sentences to obtain the final multi-document summary. The experimental results show that the R1, R2, R3, RL values of the Khmer multi-document summary obtained by using the deep learning method combined with the hierarchical MMR algorithm increases by 4.31%, 5.33%, 645% and 4.26% respectively compared with other methods. The Khmer multi-document extractive summarization method based on hierarchical MMR can effectively improve the quality of Khmer multi-document summary while ensuring the diversity and difference of the summary sentences.

    • A survey of text aspect-based sentiment classification

      2020, 41(6):518-527. DOI: 10.7535/hbkd.2020yx06006

      Abstract (1989) HTML (0) PDF 1.24 M (2929) Comment (0) Favorites

      Abstract:With the development of deep learning, aspect-based sentiment classification has achieved a lot of results in a single field and a single language, but there is room for improvement in multi-fields. By summarizing up the methods of text aspect-based sentiment classification in recent years, the specific application scenarios of sentiment classification were introduced, and the commonly used data sets of aspect-based sentiment classification were categorized. The development of aspect-based sentiment classification were summarized and prospected, and further research can be carried out in the following areas: exploring methods based on graph neural networks to make up for the limitations of deep learning methods; learning to fuse multi-modal data to enrich the emotional information of a single text; developing more targeted research work on multilingual texts and low-resource languages.

    • >Chemistry and Chemical Industry
    • Research progress on synthesis and application of caffeic acid phenethyl ester in propolis

      2020, 41(6):528-536. DOI: 10.7535/hbkd.2020yx06007

      Abstract (1909) HTML (0) PDF 1.98 M (1889) Comment (0) Favorites

      Abstract:Propolis has been widely used in foods and health care products to prevent diseases due to its various and prominent biological activities. Caffeic acid phenethyl ester(CAPE) is the main active component of propolis, which has been widely studied for its various pharmacological effects such as antioxidation, anti-inflammation, antitumor, antibacterial activities, immunovegularion, and so on. The content of CAPE is very low in nature, and the traditional extraction method of CAPE is time-consuming and costly, so efficient and mass preparation for CAPE has become a research hotspot. The CAPE with high purity can be obtained by ultrasonic extraction. Knoevenagel condensation reaction can be applied to its industrial production with high yield. Based on the analysis of the latest progress in extraction and separation, synthetic methods, pharmacological activity, and other aspects of CAPE, the research status of CAPE was reviewed, and the development prospect and the research trend of CAPE were provided, which are to explore the preparation method with high practicability and generality and relatively simple operation, and to conduct in-depth and detailed research on the mechanism of CAPE.

    • >Material Science
    • Effect of quenching and tempering processes on microstructure and wear resistance of high-carbon hot grinding disc

      2020, 41(6):537-543. DOI: 10.7535/hbkd.2020yx06008

      Abstract (2002) HTML (0) PDF 3.25 M (1859) Comment (0) Favorites

      Abstract:In order to solve the problem of wear failure during the service of the hot grinding discs, the microstructure changes and wear resistance of high-carbon hot grinding discs during quenching and tempering were investigated. Taking high chromium high carbon cast iron as the research object, the microstructure and performance of the heat-treated specimen were studied by means of metallographic microscope, X-ray diffraction, hardness tester and wear tester. The results show that the original microstructure consists of primary (Cr,Fe)7C3, eutectic (Cr,Fe)7C3, martensite and austenite. When tempering at a lower temperature, the carbides are not obviously changed and the matrix is tempered martensite and austenite; with the increase of temperature, the carbides gradually increases and the tempered martensite gradually decreases; the tempered martensite disappears and the matrix microstructure changes to ferrite and austenite over 450 ℃. The hardness first decreases slightly, then increases and finally decreases, and the maximum value is 63.4HRC at 450 ℃. The wear resistance of uniformly distributed carbides is increased by 2.53 times. The results of the effect of quenching and tempering process on the microstructure and wear resistance of high-carbon hot grinding disc provide a theoretical basis for improving the wear resistance and service life of high-carbon hot grinding disc.

    • >Civil and Architectural Engineering
    • Design and numerical analysis of internal support for long strip deep foundation pit in sensitive environment

      2020, 41(6):544-550. DOI: 10.7535/hbkd.2020yx06009

      Abstract (1874) HTML (0) PDF 3.13 M (1887) Comment (0) Favorites

      Abstract:In order to explore what kind of internal support layout can ensure the safety and stability of adjacent existing buildings in the sensitive environment of long strip deep foundation pit, taking an actual project as the background, MIDAS GTS NX was used to analyze the three-dimensional interaction of soil and structure in the foundation pit, and the deformation control indexes of the surrounding buildings and foundation pit under various types of internal support were compared, which were also compared with the monitoring alarm value and field monitoring data. The results show that internal support of the opposite brace and angle brace type is more suitable than other types; the layout of the internal support has a significant effect on the change of the basement uplift, but has little effect on the amount of the uplift; it is suggested to increase the stiffness of the weak point when using the corner brace type support and the double circular ring beam type inner support. The opposite brace and angle brace type internal support can not only ensure the safety of foundation pit, but also better control the deformation of adjacent existing buildings, which has certain reference value for the design, construction and deformation control of similar projects.

    • >Special Column: New Energy Resources, Energy Conservation and Environmental Protection
    • Numerical simulation of nautilus equiangular spiral wind turbine and analysis of building turbulence

      2020, 41(6):551-556. DOI: 10.7535/hbkd.2020yx06010

      Abstract (1890) HTML (0) PDF 1.60 M (1843) Comment (0) Favorites

      Abstract:In order to improve the overall performance of wind turbines and solve the problem that the wind turbine is affected by the building in actual operation, the simulation analysis software Fluent was used to study the aerodynamic performance of the new Nautilus equiangular spiral wind turbine with different numbers of blades. The layout model of buildings and wind turbines were established, the turbulence characteristics of buildings were analyzed, and the torque performance of wind turbines in the turbulent environment were compared. The results show that the overall performance of the three-blade wind turbine is more superior; there is turbulence area at the lower position of the building, and the tangential speed is significantly increased; the performance of the new Nautilus equiangular spiral wind turbine near the building are significantly improved, which verifies the feasibility of installing the Nautilus equiangular spiral wind turbine near the building. The proposed arrangement of wind turbines can effectively improve the performance of wind turbines, and provide references for the optimal design of wind turbine structures and the arrangement of wind turbines near buildings.

    • Optimization of microwave remediation of naphthalene contaminated soil by response surface methodology

      2020, 41(6):557-564. DOI: 10.7535/hbkd.2020yx06011

      Abstract (1872) HTML (0) PDF 1.49 M (1871) Comment (0) Favorites

      Abstract:In order to study the best technology of remediation of petroleum contaminated soil, naphthalene (NAP), a typical semi volatile organic compounds in petroleum contaminated soil was selected as the target pollutant, the simulated NAP contaminated soil was taken as the test soil, and the microwave(f=2.45 GHz) was used to restore the soil. On the basis of single factor experiment, the Box-Behnken experiment design of response surface method was adopted, and the removal rate of NAP was taken as the response value. A quadratic multiple regression model was established with microwave power, irradiation time, soil thickness and soil moisture content as the influencing factors. The ANOVA model reached a very significant level, in which the microwave power had the most significant effect. The best process parameters were obtained as follows: the wave power was 768 W, the irradiation time was 19 min, the soil thickness was 3.2 cm, the water content was 16%, and the removal rate of NAP was 97.3% under these conditions. The verification results show that the removal rate of NAP is 97.0%, which is only 0.31% different from the predicted results. The process parameters optimized by response surface methodology are reasonable and feasible, which may provide some reference for the industrial application of microwave remediation of soil.

Editor in chief:朱立光

Inauguration:

International standard number:ISSN 1008-1542

Unified domestic issue:CN 13-1225/TS

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