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    Review on structural resistance to downburst wind loads
    TIAN Li,Wenzhe BI,Sarim Saleem SIDDIQUI,Kaiyue LIU
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 32-41.   DOI: 10.6040/j.issn.1672-3961.0.2020.102
    Abstract832)   HTML27)    PDF(pc) (2558KB)(75)       Save

    Researches of downburst in the field of structural wind resistance were introduced. Concerning all kinds of building structures related to people's production and life, this paper reviewed the research and the existing problems to date on the structural resistance to downburst from five aspects: the field measurements, the analytical models, the numerical simulation of the downburst, the wind-tunnel test for downburst, and the wind-induced response analysis of structures. Some problems in view of the structural resistance to downburst for further study were proposed.

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    Review on development of simultaneous localization and mapping technology
    Jianqing WU,Xiuguang SONG
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 16-31.   DOI: 10.6040/j.issn.1672-3961.0.2021.168
    Abstract821)   HTML239)    PDF(pc) (2986KB)(315)       Save

    As a hot spot in the field of intelligent transportation, simultaneous localization and mapping (SLAM) technology is the key to autonomous path planning for self-driving vehicles. This review focused on four parts with introduction of sensors related to SLAM technology, localization, mapping, and multi-sensor integration. Each step of realization for SLAM technology was introduced from advantages and disadvantages, range of application, probability algorithm, types of map, and integration methods. Based on the investigation of relevant researches about multi-sensor integration, common problems of SLAM technology were analyzed, future development trend and practical engineering application of SLAM technology were prospected.

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    Review and prospect of renewable energy ramp events
    Xueshan HAN,Xinyi WANG,Ming YANG,Yixiao YU
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 53-62.   DOI: 10.6040/j.issn.1672-3961.0.2020.287
    Abstract689)   HTML32)    PDF(pc) (2283KB)(143)       Save

    This article elaborated the wind and solar power ramp events from the three levels: the definition, prediction method and control strategy. The common definitions of wind and solar ramp were listed, and their advantages and disadvantages were analyzed in turn. It summarized the current mainstream prediction methods of ramp events, which were divided into direct method and indirect method according to whether the power prediction results were used, and the commonly used evaluation indicators were evaluated. It elaborated the current commonly used methods of control strategy, taking energy storage participation as a division, it was divided into finite control strategy without energy storage participation and infinite control strategy with energy storage participation. The current research problems and key research directions in the future were summarized and prospected.

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    Research progress of ocean wave energy converters
    Yanjun LIU,Shuang WU,Dengshuai WANG,Ruohong WANG
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 63-75.   DOI: 10.6040/j.issn.1672-3961.0.2021.234
    Abstract658)   HTML42)    PDF(pc) (13090KB)(329)       Save

    In order to accurately keeping the developments of ocean wave energy utilization technology, the important research progress of wave energy converters was reviewed. The forms of wave energy converters had not yet converged. According to the classification principle of different energy capture methods, the working principle and the energy conversion system of three main types of devices, namely, oscillating water column, overtopping and oscillating bodies were introduced. The advantages and disadvantages of each type of converter were analyzed. Typical engineering devices were selected for detailed introduction. The engineering devices which had been completed sea trial in China were summarized. It has been found that the oscillation type was the most popular type of converter in China. The research progress related to the performance evaluation of wave energy converters were summarized, but there was no unified evaluation standard yet. The difficulties and the main breakthrough directions of the developments of wave energy converters were discussed from three aspects of high efficiency and stability, reliability and cost, and the construction of diversified integrated platforms.

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    Review and prospect of the development of heat exchanger structure
    Wenjing DU,Junzhe ZHAO,Lixin ZHANG,Zhan WANG,Wanxiang JI
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 76-83.   DOI: 10.6040/j.issn.1672-3961.0.2020.423
    Abstract582)   HTML39)    PDF(pc) (4892KB)(166)       Save

    The development of heat exchanger for more than 200 years was introduced. The generation and typical applications of heat exchangers with different structures were reviewed. Four heat exchangers with different structures including shell-and-tube heat exchanger, plate heat exchanger, microstructure heat exchanger, and printed circuit heat exchanger were described emphatically, and the development work of related geometric parameter optimization and structure improvement was carried out to realize heat transfer enhancement. The existing problems and limitations in the structure design of the heat exchanger were analyzed, and the specific suggestions and development trends for the structure improvement of the heat exchanger in the future were proposed.

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    Optimal calculation method of pavement shakedown limit based on genetic algorithm
    Xiuguang SONG,Yingchao ZHANG,Peizhi ZHUANG,He YANG,Haifeng ZHANG,Juan WANG
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 1-7.   DOI: 10.6040/j.issn.1672-3961.0.2021.153
    Abstract537)   HTML319)    PDF(pc) (4005KB)(244)       Save

    To solve the problem that road structures are prone to elasto-plastic deformation under the action of long-term reciprocating vehicle loads, based on the static shakedown theorem, the shakedown behavior of the semi-infinite space Mohr-Coulomb structure under the Hertz load was studied, and the genetic algorithm was introduced to construct an efficient calculation method for the lower limit of the shakedown limit of the road structure under the reciprocating vehicle load. The accuracy and efficiency of the new method was verified by comparison with the existing solution method and parameter analysis.

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    Modified calculation method of shaft friction for driven pile considering particle size effect
    Peizhi ZHUANG,Yingchao ZHANG,Xiuguang SONG,He YANG,Zhicheng GUO,Yan HU
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 8-15.   DOI: 10.6040/j.issn.1672-3961.0.2021.161
    Abstract454)   HTML226)    PDF(pc) (7930KB)(159)       Save

    This study aimed to investigate the influence of particle size on the micropile by conducting theoretical analysis and model tests. The empirical relationship between the critical friction angle and the relative roughness at the pile-soil interface was established, and thus the critical friction angle could be determined quantitively in consideration of the particle size of sands. To emphasis the influence of particle size on the additional normal stress at the soil-pile interface, the shear band at the soil-pile interface was modelled as a hollow cylinder and then a new modified method was proposed based on the elastic cavity expansion theory. Only two new parameters, Poisson's ratio and the thickness of the shear band, were involved in the modified method, which was validated by comparison with model tests. It was found that the pile shaft friction was mainly determined by the pile roughness and the ratio of pile diameter to sand median size and the critical state angle at the pile-soil interface, while the additional normal stress mainly results from the pile roughness and the ratio of pile diameter to sand median size, respectively. The research could provide the valueable reference for the bearing capacity design of micropiles.

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    Photovoltaic power prediction method based on NWP irradiance inclination conversion
    Wenling JIANG,Yanqing ZHAO,Bo WANG,Shuanglei FENG,Yan PEI,Fei ZHANG
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 114-121.   DOI: 10.6040/j.issn.1672-3961.0.2020.104
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    Short-term photovoltaic (PV) power predictions statistical methods generally used the horizontal irradiance in numerical weather prediction (NWP) directly, but not the inclined irradiance received by tilt PV panels, which led to the calculation results not accurate enough. This paper proposed a new method to convert horizontal irradiance to inclined one. The method distinguished scattering into molecular scattering and Mie scattering with different properties, and then converted them separately. Using the new method, the paper converted NWP horizontal irradiance to inclined one. Based on inclined one, PV power model and prediction were made. The result of an example showed that the new method, whose root mean square error was 10.25% and correlation coefficient was 0.914 0, was more accurate than the traditional method, which used NWP horizontal irradiance directly.

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    Review of frequency dynamic behavior evolution and analysis method requirements of power system
    Hengxu ZHANG,Yongji CAO,Yi ZHANG,Changgang LI,Jiacheng RUAN,VLADIMIR Terzija
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 42-52.   DOI: 10.6040/j.issn.1672-3961.0.2021.174
    Abstract403)   HTML25)    PDF(pc) (1810KB)(91)       Save

    The development of renewable energies changed the operation states of power systems, which complicated the frequency dynamics and brought about new challenges to frequency security and stability. The process of frequency dynamic response was introduced, whose quantitative characteristics and analysis methods were reviewed. And the strengths and promising prospects of frequency dynamics analysis method based on artificial intelligence were emphasized. From the viewpoints of the strong variability of renewables energies, the low inertia of nonsynchronous power sources, and the high risk of large power deficits and cascading faults, the changes of the operation states of power systems were analyzed, and the new requirements on frequency analysis and control were discussed. The inertia definition of power systems with the rapid development of renewable energies was revealed, and the virtual inertia control methods were reviewed. The strengths and promising prospects of the coordination control of multi-type virtual inertia were emphasized. The important issues to be focused in the research area of frequency analysis and control were summarized, and the suggestions for further studies were provided.

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    Analysis of the influence of the underside baffle and deflector of the fume hood on the flow field
    Ruiyi YAN,Zhen DONG,Sen LU,Yanhua LAI,Mingxin LÜ
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 122-130.   DOI: 10.6040/j.issn.1672-3961.0.2021.177
    Abstract395)   HTML24)    PDF(pc) (19825KB)(257)       Save

    For the phenomenon of vortex and gas escape in the flow field of the extant fume hood, the computational fluid dynamics method was used for simulation. This research changed the shape parameters of the underside structure of the fume hood window, used circular arc baffles with different radii, elliptical arc baffles with different lengths, and added deflectors with different radii. Then this research studied the influence of structural changes on the flow field in the fume hood by analyzing the size and location of the vortex to obtain the direction of structural optimization. The results showed that when the height of the underside baffle was low and the length was short, there was obvious large vortex in the center position of the fume hood and near the wall. A baffle with a height greater than 50 mm and a length greater than 90 mm could significantly reduce the vortex at the center of the fume hood and at the junction of the baffle and the side wall. Adding a deflector could optimize the flow field and make the center vortex disappear, and the radius of the deflector should not be greater than 70 mm, otherwise obvious vortices would be excited on the outside and end of the baffle, which provides a basis for the rational design of fume hoods.

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    The analysis of key parameters of hydraulic energy storage system of wave energy converter
    Yingxin LIU,Jian QIN,Yanjun LIU
    Journal of Shandong University(Engineering Science)    2021, 51 (6): 1-8.   DOI: 10.6040/j.issn.1672-3961.0.2020.429
    Abstract341)   HTML27)    PDF(pc) (4298KB)(58)       Save

    To improve the efficiency of wave power generation technology, a mathematical model of the system from wave input to motor output was established. The key parameters that affected the system′s power generation capacity were analyzed by using theoretical modeling and simulating, so as to provide theoretical guidance for the research of the constant speed control strategy of the hydraulic energy conversion system. The hydraulic energy storage system of wave energy generation was composed of 3 parts. The mathematical model of the system was established by analyzing each component′s motion equation and energy equation, and finding the connection parameters between the two components. The key parameters and characteristics of the system were determined qualitatively by analyzing the system′s power equation. To confirm the accuracy of theoretical analysis, the AMEsim simulation platform was used to design and imitate the system. The results showed that the motor′s output power was affected by the height of the wave, period, flow area of the proportional flow valve and the motor displacement. The highest order of the influence was 1, 4, 4 and 2, respectively. The results also verified that the precharging pressure of the accumulator had little influence on the motor′s output power.

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    Cross social network user alignment via fusing node state information
    Jun HU,Dongmei YANG,Li LIU,Fujin ZHONG
    Journal of Shandong University(Engineering Science)    2021, 51 (6): 49-58.   DOI: 10.6040/j.issn.1672-3961.0.2021.281
    Abstract334)   HTML43)    PDF(pc) (3630KB)(46)       Save

    A cross social network user alignment method by fusing node state information was proposed. The local characteristics of nodes and node state information were captured through network representation to obtain the embedded vector of each account, and the aligned users were found by calculating the similarity between corresponding representations of different accounts. Experimental results on two real data sets showed that the proposed method could align more users than other methods. When predicting top-k of different scales, the proposed method could achieve an alignment precision of 50% at top-9 on the data set Twitter-Foursquare with dense network structure. Compared with other methods on the sparse and large network data set DM-ML, the improvement on alignment precision was 12.06%-36.62%. The analysis of F1-score also showed that the proposed method could effectively improve the performance of user alignment.

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    Horizontal bearing capacity of suction bucket foundation under wave dynamic load
    Haotian LUO,Ke WU,Yameng LI,Jiaxiang XU,Zhihao XING
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 100-106.   DOI: 10.6040/j.issn.1672-3961.0.2020.443
    Abstract306)   HTML21)    PDF(pc) (4920KB)(37)       Save

    For the horizontal ultimate bearing capacity of the suction bucket foundation under horizontal dynamic loads such as waves and wind, the explicit dynamic method was adopted to establish the mechanical model of the suction bucket foundation under the wave dynamic load. Based on the infinite boundary and Rayleigh damping, the model optimization analysis was carried out, and the comparative study of the ultimate bearing performance of the foundation under static load and dynamic load (action time 0.5, 1, 2, 5 s) under the same horizontal displacement conditions was carried out. The research results showed that the horizontal ultimate bearing capacity curve of the bucket foundation under different dynamic load time decreased with the increase of the loading time compared with the static load, and gradually approached the static load bearing capacity curve. Affected by the damping of the rock and soil media on the seabed, the rotation center of the barrel under the horizontal load moved up to the top of the barrel as the time of the dynamic load decreased.

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    Intelligent commutation system of distribution network based on differential evolution algorithm
    Yunlong ZHAO,Renfei CHE,Jiahui CHEN
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 107-113, 121.   DOI: 10.6040/j.issn.1672-3961.0.2020.110
    Abstract305)   HTML24)    PDF(pc) (1771KB)(72)       Save

    The application of three-phase intelligent commutation switch was an effective measure to solve the problem of three-phase load imbalance in low-voltage distribution network. Based on the commutation process of the three-phase intelligent commutation switch, an intelligent commutation system of the distribution network was proposed, which took the differential evolution algorithm as the core and the mixed solid-state switch as the foundation. Aiming at the unbalance degree of three-phase current and the action times of commutation switch, differential evolution algorithm was used to optimize the commutation strategy. The optimal commutation strategy was obtained through initialization, mutation, crossover and selection operation, which improved the real-time and accuracy of the system. In this paper, through the combination of magnetic holding relay and IGBT based solid-state switch, a fast switching method using hybrid solid-state switch was proposed, which the commutation switch showed the characteristics of low power consumption and strong current passing ability, and improved the reliability of the system. The feasibility of the algorithm and switch in fast switching and im-proving the power quality of the commutation process was verified by practical test.

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    Influence of calcite veins on shale anisotropy at the microscopic scale based on digital images
    Huailei SONG,Zhonghu WU,Liping LI,Yili LOU,Wenjibin SUN,Hao LIU,Yujun ZUO
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 91-99, 106.   DOI: 10.6040/j.issn.1672-3961.0.2020.276
    Abstract302)   HTML15)    PDF(pc) (10650KB)(52)       Save

    The Niutitang Formation shale cores were observed by micro-slice observations and core X-ray whole-rock mineral diffraction analysis, and 7 groups of direct tensile numerical tests under different azimuth angles were performed. The test results showed that the calcite veins had a significant effect on the anisotropy of shale tensile strength. When the azimuth angle increased, the tensile strength gradually decreased. The bedding effect coefficient of tensile strength showed a curve-like growth trend with the increase of azimuth angle, which reached the maximum when α=90°, which was 0.127. The failure modes of shale samples at different angles were very complicated, which could be roughly divided into the following three categories: tree root shape (0°, 15°), step shape (30°, 45°, 60°) and river shape (75°, 90°). Fractures preferentially extended along calcite veins, which might inhibit the formation of complex fracture networks in the shale matrix during hydraulic fracturing. There were also significant differences in the release of dissipated energy under the calcite veins at different angles. The release of dissipated energy under the calcite veins at different angles was also significantly different. When α=0°, 15°, 30°, and 45°, the AE energy was small in the early stage, and increased rapidly to the maximum when it approached the peak stress. When α=60°, 75°, 90°, the AE energy was small in the early stage, and began to increase in the middle stage, and it was the largest when it was close to the peak stress. The cumulative AE energy increased roughly exponentially with increasing strain, and the growth process consisted of three stages: flat period, accelerated period and skyrocketing period. The research results had important reference value for the initiation of hydraulic fractures in shale reservoirs, the prediction of expansion, and the enhancement of oil recovery.

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    Influence of concrete aggregate particle size on acoustic emission detection
    Junwei LI,Fei XU,Bing WANG,Yang GAO
    Journal of Shandong University(Engineering Science)    2021, 51 (5): 84-90.   DOI: 10.6040/j.issn.1672-3961.0.2021.016
    Abstract301)   HTML17)    PDF(pc) (4738KB)(76)       Save

    The lead breaking test of concrete specimens with different aggregate sizes was carried out by using acoustic emission technology. The influences of different aggregate particle sizes on the positioning accuracy, sound velocity calibration and time parameter setting of acoustic emission detection concrete materials and the selection of the optimal sensor layout were investigated. The results showed that aggregate was one of the main factors affecting the accuracy of acoustic emission detection. When the aggregate particle size increased 5 mm, the sound velocity decreases by 7.5%. When the aggregate particle size increased 5 mm, the rise time decreased about 3.5%, and the maximum rise time is not more than 200 μs. Perform "multi-multi-point" tests could reasonably determine the optimal sensor arrangement and effectively reduce the positioning error, but it couldn't eliminate the error.

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    Lightweight face super-resolution network based on asymmetric U-pyramid reconstruction
    Tongyu JIANG,Fan CHEN,Hongjie HE
    Journal of Shandong University(Engineering Science)    2022, 52 (1): 1-8, 18.   DOI: 10.6040/j.issn.1672-3961.0.2021.312
    Abstract299)   HTML8)    PDF(pc) (9804KB)(187)       Save

    A lightweight face super-resolution network was proposed in order to solve the problem that the model of deep convolutional neural network was complicated and difficult to be applied in the face super-resolution task. The coder composed of rescoding blocks was used for feature extraction, and pyramid reconstruction was introduced into the decoder to achieve fast and accurate super-resolution. To reduce the parameter number of the up-sampling operation in the decoding block, a non-uniform channel widening strategy based on resolution selection was adopted. To avoid adding extra branches, the prior knowledge of the face was introduced through heatmap loss. Experimental results showed that the model proposed in this paper could achieve light and accurate super-resolution reconstruction of ultra-low resolution face images that achieved better visual quality than the state-of-the-art method with lower model complexity.

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    Fault diagnosis of vehicle-to-vehicle communication in networked traffic environment
    Haigen MIN,Yukun FANG,Xia WU,Wuqi WANG
    Journal of Shandong University(Engineering Science)    2021, 51 (6): 84-92.   DOI: 10.6040/j.issn.1672-3961.0.2021.353
    Abstract249)   HTML24)    PDF(pc) (7549KB)(58)       Save

    With vehicle platoon in intelligent transportation system as the background, this research established a vehicle platoon control model based on the intelligent driver model and analyzed the influence of delay in vehicle-to-vehicle communication on the stability of platoon control. A fault diagnosis method based on the update delay of vehicle-to-vehicle communication was proposed. The statistical characteristics of median and average were used to calculate the decision variables which were used to judge whether a fault had occurred. A two-layer sliding window was designed to smooth the decision variables and adaptively calculate the decision variable in real time. The Jarque-Bera algorithm was used to test the normality of the statistical distribution of the receiver's update delay within a period of time. If the distribution significantly deviated from the normal distribution, it was considered that the communication quality had deteriorated. Collecting vehicle speed data and vehicle-to-vehicle communication delay data at the testbed, simulations were conducted to analyze the statistical distribution characteristics of the vehicle-vehicle communication update delay in different scenarios and verify the influence on vehicle platoon control of vehicle-to-vehicle communication delay. The research results showed that the vehicle-to-vehicle communication delay caused drastic changes in the control rate during the collaborative control process. The communication fault diagnosis method based on the update delay could effectively diagnose whether the vehicle-to-vehicle communication quality had deteriorated.

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    Method for generation planning with the temporal and spatial correlation of wind and solar power
    Wensheng LI,Xian WANG,Yuanze MI,Yongji CAO,Xiaoming LIU,Hengxu ZHANG,Zihan LIU
    Journal of Shandong University(Engineering Science)    2022, 52 (1): 111-119, 127.   DOI: 10.6040/j.issn.1672-3961.0.2020.424
    Abstract223)   HTML5)    PDF(pc) (4265KB)(30)       Save

    A generation planning method considering multi-dimensional spatial-temporal correlation of wind and solar energy was proposed. Based on Copula theory and probability distribution of wind power and photovoltaic, a wind power and photovoltaic output model considering multi-dimensional spatial-temporal correlation of wind power and photovoltaic was established. The output scenario was applied to the bi-level generation planning model, and a generation planning method considering the multi-dimensional spatial-temporal correlation of wind power and photovoltaic was proposed. Among them, the upper level was the investment decision-making model with the minimum total planning cost as the objective function, and the lower level was the short-term operation optimization model with the optimal operation economy and peak shaving characteristics as the objective. The effectiveness of the proposed method was verified by a case study in a certain area, and the influence of the spatial-temporal correlation of wind power and photovoltaic on the generation planning scheme was compared and analyzed.

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    Survey on student academic performance prediction from the perspective of task granularity
    Xiushan NIE,Yuling MA,Huiyan QIAO,Jie GUO,Chaoran CUI,Zhiyun YU,Xingbo LIU,Yilong YIN
    Journal of Shandong University(Engineering Science)    2022, 52 (2): 1-14.   DOI: 10.6040/j.issn.1672-3961.0.2021.489
    Abstract214)   HTML16)    PDF(pc) (1393KB)(86)       Save

    As one of the important research branches in educational data mining domain, student performance prediction was intensively studied. However, a comprehensive review of student performance prediction was still underexplored from the perspective of real applications. This paper detailed the technologies and methods exploited in student performance prediction research from the perspective of task granularity, and then introduced several application-oriented cases of student performance prediction, so as to provide targeted reference information for scientific researchers and educators.

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    Research progress of building structure under typhoon
    Li TIAN,Laiyi ZHANG,Yanming WANG,Juncai LIU
    Journal of Shandong University(Engineering Science)    2022, 52 (1): 28-38.   DOI: 10.6040/j.issn.1672-3961.0.2020.406
    Abstract209)   HTML3)    PDF(pc) (1920KB)(43)       Save

    Through the wind field simulation, field measurement, wind tunnel test, and the wind-induced vibration of structure under the effect of the domestic and foreign typhoon, the research progresses of four aspects were discussed. This article focused on the great influence people's production and life of all kinds of building structure, based on the structure under the action of typhoon research present situation and the existing problems. The problems that needed to be further studied under the influence of typhoon were prospected.

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    Recognition learning based on multivariate functional principal component representation
    Yinfeng MENG,Qingfang LI
    Journal of Shandong University(Engineering Science)    2022, 52 (3): 1-8.   DOI: 10.6040/j.issn.1672-3961.0.2021.314
    Abstract114)   HTML4)    PDF(pc) (6668KB)(77)       Save

    Aiming at the problem of multi-dimensional information fusion in recognition learning, a recognition method based on multivariate functional principal component representation was proposed. The numerical calculation method of multivariate functional principal components was given. The joint covariance operator was used to calculate eigenvalues and eigenvectors, and the key distinguishing features were extracted. Based on these comprehensive features, the random forest method was used to recognize and learn multivariate functional data. The recognition performance of multivariate functional principal component representation method was compared with other representation methods on simulated data and real data. The experimental results showed that the accuracy was equal to 1 in the simulation dataset, English handwritten dataset and Chinese handwritten dataset, and 0.954 4 in the motion dataset. Compared with other methods, multivariate functional principal component analysis (MFPCA) had better recognition effect and improved the recognition accuracy effectively.

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    Preparation method and system of engineering nanoparticle aerosol
    Yi HAN,Zhen XU,Tian GUAN,Yang CUI,Hui HU,Liming MA
    Journal of Shandong University(Engineering Science)    2022, 52 (3): 109-116.   DOI: 10.6040/j.issn.1672-3961.0.2022.004
    Abstract100)   HTML1)    PDF(pc) (7468KB)(17)       Save

    A carbon nanoparticle aerosol preparation system with adjustable flow rate and mass concentration was designed based on the atomization method of nanomaterial suspension. The clean air and carbon nanotube material dispersion were sprayed and mixed in a stainless steel atomizing chamber to obtain an unstable aerosol. With the embedded temperature control system, flow control system and mass concentration control system, the unstable aerosol could be heated at a constant temperature in expansion chamber. Then the unstable aerosol expanded rapidly and reached uniformity. A relatively stable and uniform nanoparticle aerosol flow was obtained by controlling the valve body with an adjustable opening. It was demonstrated by experiments that under the condition of ideal temperature control system, the maximum error between the flow rate and the set value was 9.312 mL/min, and the maximum error between the mass concentration and the set value was 0.206 mg/m3. Nanoparticle aerosol with stable flow and mass concentration was generated basically.

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    Shear capacity of beams with cracks and without web reinforcement
    Wenjie LIU,Xueying YANG,Bo ZHANG,Zhixin FAN,Chengxin LI,Huiming YANG,Jinglong LI
    Journal of Shandong University(Engineering Science)    2022, 52 (3): 42-50.   DOI: 10.6040/j.issn.1672-3961.0.2021.004
    Abstract93)   HTML2)    PDF(pc) (10009KB)(30)       Save

    In order to investigate the effect of the position and angle of the pre-existing cracks on the shear capacity of beams without web reinforcement, a number of experiment beams with pre-existing cracks were fabricated, the three-point bending experiment of the beam was carried out. The influence of pre-existing cracks located in the basic arch of the beam span and the beam side on the shear capacity of beams without web reinforcement and the law of crack propagation were studied. The results showed that the pre-existing cracks on the beam had a weakening effect on the shear capacity of the beam, which made the beam more prone to diagonal tensile failure. Under the same conditions, when the crack tip of the pre-existing crack in the beam span was closer to the middle point of the bottom of the beam, the greater the weakening effect on the shear bearing capacity of the beam without web reinforcement. When the coincidence degree of the angle of the pre-existing cracks on the beam side and the basic arch was higher, the greater the weakening effect on the shear bearing capacity of the beam without web reinforcement, and the cracks at the bottom of the beam propagate through the two crack tips of the pre-existing cracks was easier. Conversely, the cracks at the bottom of the beam could extend to the middle of the pre-existing cracks.

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    A machine vision system for measuring screw pitch with image processing techniques
    Tianyu HAN,Changhou LU,Jianmei LI,Ang YIN,Qiulin HOU
    Journal of Shandong University(Engineering Science)    2022, 52 (3): 80-85.   DOI: 10.6040/j.issn.1672-3961.0.2020.509
    Abstract90)   HTML1)    PDF(pc) (6708KB)(6)       Save

    In order to solve problems of damage to workpiece and high-cost of measuring equipment by contact measuring method, a low-cost and high-precision screw pitch measuring system based on machine vision was designed. The system was built on MATLAB and consisted of four sub-systems: image acquisition system, mechanical system, stepping control system, image and data processing system. Sub-pixel mosaic algorithm was used to splice the sub-images of the lead screw and a complete lead screw image could be obtained. Image quality was improved by image enhancement and filtering. Morphological edge extraction and sub-pixel edge location algorithm were used to extract the screw edge accurately, and pitch errors were measured automatically by data processing program. The experimental results showed that the relative error of the machine vision system and standard instrument (JCS-040A) for the measurement results of the three types of ball screw pitches didn't exceed 0.04%、0.06%、0.09%, respectively. The feasibility of the system in industrial measurement of lead screw was validated.

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    Research progress on preparation methods of engineering nano material particle aerosol
    Hui HU,Ningye TANG,Siyu WANG,Haisen WANG
    Journal of Shandong University(Engineering Science)    2022, 52 (4): 1-11.   DOI: 10.6040/j.issn.1672-3961.0.2022.009
    Abstract77)   HTML2)    PDF(pc) (3186KB)(40)       Save

    With the development of nanotechnology and biochemistry, higher requirements were put forward for the particle size and manufacturing process of micro particles. Aerosol, as a common engineering nano material particle, was widely used in all walks of life. The research progress of common aerosol preparation methods, which starts from the aerosol preparation methods and systematically based on a large number of relevant literatures, the applicable scenarios of different aerosol preparation methods, the application requirements were summarized of different aerosol preparation methods were defined, the advantages and disadvantages of were compared and analyzed different aerosol preparation methods. On this basis, the optimization and improvement of various methods by domestic and foreign scholars in different periods were further ummarized, and the experimental and research results of domestic and foreign scholars were deeply analyzed, and the application of supercritical fluid technology in aerosol preparation was analyzed and prospected.

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    Pre-allocation of resources based on trajectory prediction in heterogeneous networks
    Xiaobin XU,Qi WANG,Bin GAO,Zhiyu SUN,Zhongjun LIANG,Shangguang WANG
    Journal of Shandong University(Engineering Science)    2022, 52 (4): 12-19.   DOI: 10.6040/j.issn.1672-3961.0.2021.547
    Abstract45)   HTML1)    PDF(pc) (3698KB)(38)       Save

    Aiming at the problems of insufficient trajectory feature learning, low precision of trajectory prediction results, and coarse particles in the research of network resource management methods for trajectory prediction, a trajectory prediction algorithm of bidirectional recurrent neural network was proposed. Through in-depth mining of the user′s movement rules, the user′s movement prediction was realized. According to the user′s mobile prediction information, the network resource pre-allocation plan was designed and the mobile behavior was divided into network resources, then the collaborative resource optimization management of multiple cells was realized. The simulation results showed that in the trajectory prediction problem, the trajectory prediction algorithm of the bidirectional recurrent neural networked had better comprehensive performance than the ordinary neural network algorithm. In the problem of network resource management, the network resource management pre-allocation scheme of trajectory prediction could accurately predict the base station connected by users, so that the base station had a higher resource utilization rate.

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    Research and optimization of hollow form of precast concrete pavement slab
    Xuhao WANG,Qianqian LIU,Hucheng LI,cheng LI,Peng LI,Yifeng LING
    Journal of Shandong University(Engineering Science)    2022, 52 (4): 139-150.   DOI: 10.6040/j.issn.1672-3961.0.2022.046
    Abstract30)   HTML0)    PDF(pc) (7509KB)(10)       Save

    In order to reduce the self-weight of precast concrete pavement slab, the concrete hollow slab was studied by using ABAQUS, the optimal length, width and thickness and circular hollow type of precast concrete solid slab were recommended. The local sizes of the circular section were optimized, and the influences of the radius, numbers and height of circle on the maximum flexural-stress, the maximum vertical displacement, the maximum compressive stress and shear stress of the slab were analyzed. Entropy weight method and technique for order preference by similarity to an ideal solution method were introduced to optimize multiple parameters, and the optimal hollow combination was obtained as 10 circles with a radius of 60 mm and a center height of 160 mm. By comparing the mechanical performance of hollow slab with solid slab, it was found that the difference was marginal, while optimized hollow slab could lead to a 970 kg self-weight reduction. The precast concrete hollow slab, the circular hollow type and its local size were proposed and recommended.

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    Mechanical characteristics of TBM tunnel segment in composite stratum
    Weiqin ZHENG,Jie XU,Jie SUN,Ke WU
    Journal of Shandong University(Engineering Science)    2022, 52 (4): 210-213.   DOI: 10.6040/j.issn.1672-3961.0.2021.259
    Abstract29)   HTML1)    PDF(pc) (4433KB)(11)       Save

    Based on the redistribution of soil stress around the excavated tunnel due to the large buried depth of the tunnel during the construction of the composite stratum by the full section hard rock tunnel boring machine (TBM), considering that the surrounding rocks would produce the force of squeezing into the tunnel, segment damage might occur in the tunnel construction. The large-scale finite element numerical software ANSYS and finite difference software FLAC3D were used to simulate the underpass formation. The stress and strain of tunnel construction segments were comprehensively analyzed, and reasonable monitoring methods and protection measures were put forward. The main conclusions were as follows, when only considering the influence of stratum stress redistribution on lining segments after double tunnel construction, it was suggested that double tunnels should be constructed at the same time, and the displacement of segments was less affected by the direction of tunnel construction; In the construction process, the two adjacent sides of the double tunnel segment would have large horizontal displacement. If necessary, the inner side of the segment should be monitored and reinforced.

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