Table of Content

    Machine Learning & Data Mining
    An automatic reading method for pointer meter
    Yanghao ZHOU,Yifan LIU,Li LI
    Journal of Shandong University(Engineering Science). 2019, 49(4):  1-7.  doi:10.6040/j.issn.1672-3961.0.2018.275
    Abstract ( 1107 )   HTML ( 149 )   PDF (4120KB) ( 625 )   Save
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    An automatic reading method for automatically monitoring pointer meter in substation was proposed based on the machine learning and image processing algorithms, which was consisted of two stages: meter detection and pointer recognition. The position of the meter in the input image was detected by using the fully convolutional networks, and then the patch of the meter was extracted. The interference of illumination and shadow on the pointer recognition was reduced by using histogram equalization, median filtering and bilateral filtering, and the tilt of shooting was rectified by using the affine transformation. The position of the pointer was detected via the improved Hough transform. The reading was obtained by computing the angle of the pointer. The results showed that the method could detect the pointer meter and recognize the reading accurately for the pointer instrument in the substation. The method showed good robustness to the disturbances such as illumination and shadow, which could significantly reduce the substation inspection personnel workload and improve the work efficiency.

    An ensemble learning algorithm for unbalanced data classification
    Zongtang ZHANG,Sen WANG,Shilin SUN
    Journal of Shandong University(Engineering Science). 2019, 49(4):  8-13.  doi:10.6040/j.issn.1672-3961.0.2019.050
    Abstract ( 870 )   HTML ( 9 )   PDF (1159KB) ( 315 )   Save
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    For unbalanced data classification problem in underwater acoustic target recognition, a random subspace AdaBoost algorithm called RSBoost was proposed. Subtraining sample set was extracted by random subspace method in different underwater acoustic feature space and base classifier was trained in every subtraining sample set. The base classifier with the maximum margin mean of minority class was chosen as the base classifier of this round, the final ensemble classifier was formed iteratively. The experiment was carried out on the measured data, the performance of RSBoost and AdaBoost in different feature space was evaluated by F-measure and G-mean. The results showed that, compared with AdaBoost, the F-measure of RSBoost improved from 0.07 to 0.22 and the G-mean improved from 0.18 to 0.25, which showed that RSBoost was superior to AdaBoost in underwater acoustic unbalanced classification problem.

    Object tracking algorithm based on deep residual features and entropy energy optimization
    Jinchao HUANG
    Journal of Shandong University(Engineering Science). 2019, 49(4):  14-23.  doi:10.6040/j.issn.1672-3961.0.2018.461
    Abstract ( 578 )   HTML ( 8 )   PDF (10095KB) ( 214 )   Save
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    To solve the low rate of accuracy, real-time and robustness of object tracking algorithm based on model updating, a new algorithm based on deep residual features and entropy energy optimization was proposed. Deep residual features were first extracted from original video sequence by deep residual network. The entropy energy from deep residual features were calculated, and the deep frequency from entropy energy by two-dimension kernel transformation could be calculated, after that we got the deep balance by deep frequency with differential equation, and then the object state by MLE was estimated, including object position and speed. To validate the feasibility and efficiency of the proposed algorithm, the comparing experiments on the object tracking basis (OTB) dataset for the state-of-the-art algorithms were done, and the comparison results showed that the proposed algorithm had significant improvement on tracking accuracy and robustness. By using entropy energy optimization for deep residual features, the proposed algorithm had more flexibility and robustness for object tracking.

    Weak signal detector based on all-digital phase-shifting lock-in method
    Lu WANG,Hong WANG,Guoping CHEN
    Journal of Shandong University(Engineering Science). 2019, 49(4):  24-28.  doi:10.6040/j.issn.1672-3961.0.2018.526
    Abstract ( 507 )   HTML ( 3 )   PDF (3505KB) ( 366 )   Save
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    In order to solve the problem of the uncontrollable phase difference in existing lock-in detection and the vulnerable to interference or high power consumption in analog phase-shifting circuit. The lock-in detection equipment based on all-digital phase-shifting method was designed, which the analog correlation signal was replaced by an all-digital reference signal with frequency traversal and co-frequency shift, then combined with the lock-in correlation detection to extract weak signals in low SNR. The reference signal and the weak signal to be tested were transmitted by direct memory access(DMA), the analog to digital converter(ADC) and digital to analog converter(DAC) were used to realize the transmission of synchronous frequency data with low power and faster transfer speed. The results showed that the lowest SNR detectable by this method was -46 dB with good stability and efficiency in a strong noise environment of 90 dB. It had great practical value for high-precision quality testing in high noise environment passive speaker equipment of the industrial plant.

    Visualization of interactive ThemeRiver based on time-series data
    Xindi CHEN,Tianrui LI,Huanhuan YANG
    Journal of Shandong University(Engineering Science). 2019, 49(4):  29-35, 43.  doi:10.6040/j.issn.1672-3961.0.2017.400
    Abstract ( 789 )   HTML ( 14 )   PDF (3445KB) ( 318 )   Save
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    ThemeRiver was a widely used technique when visualizing time-series data, which showed the whole trend efficiently. But the user often encountered ambiguity when observing a single river due to the influence of the lower river. However, the current visualization technique couldn't solve the issue. The following improvements of ThemeRiver were proposed upon the above issue: The river fluctuation was evaluated by the coefficient of variance instead of standard deviation, and the rivers with smaller fluctuation were arranged in lower position in order to reduce the impact on the upper rivers; The concept of ambiguity point was proposed, and the user could set fluctuation and max contribution as filtering parameters in the user interface so that the ambiguity points would be dynamically displayed by the system; The ambiguity point was visualized as bellow(The peak and valley of a river were represented by triangle and inverted triangle, respectively; The triangles would be filled with the color of the river with max contribution; A reorderable interactive ThemeRiver was proposed, in which the user was able to reorder the rivers by dragging them according to the information given by the ambiguity points). The proposed method was applied on the data containing 20 themes of 2015 from Zhihu and the results showed that the system could efficiently eliminate the ambiguity of ThemeRiver when presenting the trend of a single river and provided a flexible and personalized visualization.

    Civil Engineering
    Crack initiation theory and experimental verification of pre-existing plane cracks with seepage pressure
    Yajuan XIE,Song YU,Bangxiang LI,Xiang XU,Weishen ZHU
    Journal of Shandong University(Engineering Science). 2019, 49(4):  36-43.  doi:10.6040/j.issn.1672-3961.0.2018.140
    Abstract ( 668 )   HTML ( 4 )   PDF (3494KB) ( 149 )   Save
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    In order to study the crack initiation characteristics of pre-existing plane cracks with seepage pressure, cracks were divided into two types: open type and closed type. Theoretical analysis and experimental verification were carried out. The theoretical derivation of crack stress intensity factor, crack initiation angle and crack initiation stress was expounded in detail, and the crack initiation strength formula for closed crack under compression was given. Precast concrete mortar specimens with open-type crack were produced and subjected to biaxial compression experiments. The variation of stress intensity factor and crack initiation angle with crack inclination angle, hydraulic pressure and crack thickness were investigated through experimental verification and analysis. The relationship of crack initiation strength with hydraulic pressure and lateral pressure were also investigated. The results showed that type Ⅰ stress intensity factor of open-type crack with seepage pressure increased with the increase of crack angle. The type Ⅰ crack was most easily initiate when the crack angle was 75°. K decreased with the increase of water pressure and crack thickness. Type Ⅱ stress intensity factor of shear crack was distributed symmetrically with the crack inclination angle, and the maximum value was obtained at the crack inclination angle of 45°, irrespective of hydraulic pressure and crack thickness. Crack initiation angle of open-type crack decreased with the increase of crack dip, hydraulic pressure and crack thickness; crack initiation strength was inversely proportional to hydraulic pressure and proportional to lateral pressure. The research results could provide reference for crack initiation and crack propagation with seepage pressure in geotechnical engineering.

    Transverse anti-cracking of bottom slab and layout of transverse pre-stressed tendon of rail transit U-shaped girder
    Xu DONG,Jian GUO,Haican ZHOU,Zhenquan DENG,Shuchen LI
    Journal of Shandong University(Engineering Science). 2019, 49(4):  44-50.  doi:10.6040/j.issn.1672-3961.0.2017.550
    Abstract ( 517 )   HTML ( 4 )   PDF (3093KB) ( 207 )   Save
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    Rail transit U-shaped girder had the structural characteristic of only arranging ordinary regular reinforcements in transverse direction of bottom slab. Based on a rail transit U-shaped girder project in Qingdao, in order to improve its safety and transverse anti-cracking performance, finite element analysis method was used to study the transverse anti-cracking and stress distribution of bottom slab of U-shaped girder. An arrangement method of U-shaped girder transverse pre-stressed tendons was put forward. The results showed that, the transverse tensile stress of bottom slab of midspan was mainly caused by self-weight and design load, while transverse tensile stress of girder ends was influenced by many factors. Under design load, maximum transverse stress of structure was 1.71 MPa, while applying 1.3 times overloading, maximum transverse stress reached 2.04 MPa, which was beyond code requirements. Safety margin of U-shaped girder was low and transverse crack resistance was weak. The proposed layout of transverse pre-stressed tendons effectively decreased transverse tensile stress in bottom slab of girder midspan to -0.117 MPa. The distribution of tensile stress became more uniform and structural safety was significantly improved. The research could provide a reference for transverse reinforcement design of U-shaped girder bottom slab.

    TBM comprehensive advanced geological prediction in a tunnel andits application in Yangling Tunnel
    Jun LIU,Lijun HAN,Qingbin MENG
    Journal of Shandong University(Engineering Science). 2019, 49(4):  51-60.  doi:10.6040/j.issn.1672-3961.0.2018.093
    Abstract ( 689 )   HTML ( 5 )   PDF (5462KB) ( 354 )   Save
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    Advanced geological prediction was used to play an irreplaceable role in the aspect of informative tunnel construction, effective disaster prevention, economical construction support in tunnel engineering. The effectiveness of the advanced geological prediction method in the drilling and blasting method under the tunnel boring machine (TBM) specific construction environment was compared and analyzed. The comprehensive advanced geological prediction system under TBM tunnel construction with "long and short distance, geophysical and drilling exploration, sound wave reflection and electromagnetic method, key and normal" was established. Based on the horizontal sonic profiling (HSP) sound wave reflection, drilling process monitoring (DPM) advanced drilling, transient electromagnetic instrument, the multiple solutions and error superposition of single advanced geological prediction method were suppressed effectively. And then the 3D forward theory calculation was considered as an appropriate way for enhancing the accuracy and reliability. Based on the law of electromagnetic response and the study of removing electromagnetic interference, the results summarized from the paper were used to guide the application of transient electromagnetic method in Yixing Yangling Tunnel and to provide a reference for future projects.

    Experimental research on mechanical features model of prestressed mutual-anchored retaining wall
    Jianhong JIANG,Zhenyu YANG,Qi CHEN,Qingyu MENG,Hongbo ZHANG
    Journal of Shandong University(Engineering Science). 2019, 49(4):  61-69.  doi:10.6040/j.issn.1672-3961.0.2018.165
    Abstract ( 550 )   HTML ( 3 )   PDF (3546KB) ( 198 )   Save
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    To study the mechanical behaviors of the prestressed mutual anchoring retaining walls under different structural parameters, an indoor model test device was designed considering the mechanical mechanism and different prestress levels and different anchor placement positions. The results showed that due to the lateral restraint effect of the anchor (cable) on the wall and under the lateral prestress, the wall moved towards the direction of the filler, and gradually increased with the prestressing of the anchor. It evolved from T-model into the T+RB model. The earth pressure behind the wall gradually increased and it had a parabolic distribution with the peak at the anchor. According to the test results, the optimal anchoring position was recommended, and the range of anchored prestressing and optimal prestressing. The research results could be used to guide the design calculation of the prestressed mutual anchoring retaining walls.

    Flow characteristics of rough rock fractures under wide range of Reynolds numbers
    Jie LIU,Zhechao WANG,Yupeng ZHANG,Huayang SUN
    Journal of Shandong University(Engineering Science). 2019, 49(4):  70-77, 85.  doi:10.6040/j.issn.1672-3961.0.2018.533
    Abstract ( 674 )   HTML ( 11 )   PDF (6754KB) ( 339 )   Save
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    Through experiments and theoretical analysis, the flow characteristics of rock rough fractures with different geometric parameters were studied, including non-Darcy coefficient β, critical Reynolds number Rec and non-Darcy effect factor E. Testing equipment for fluid flow in fractures was developed and 9 rough single fracture models with different apertures and Joint Roughness Coefficients (JRC) were prepared. Laboratory tests on flow in rough fractures with Reynolds numbers, i.e., from 2 to 5000 were performed. The characteristics of flow in single fractures with different roughness (JRC=2-20) under wide range of Reynolds numbers were obtained. It was shown that fracture roughness had a significant impact on the nonlinear flow characteristics of the fracture. Based on the Forchheimer equation, the effects of fracture roughness on equation parameters were quantitatively studied. The larger fracture roughness was, the more likely it was to cause the nonlinearity of the fracture flow, the smaller critical Reynolds number was, and the stronger non-linear effect would be.

    Mechanical, Energy and Power Engineering
    Impact analysis on construction of large section and small spacing road tunnel
    Mingcai LIU
    Journal of Shandong University(Engineering Science). 2019, 49(4):  78-85.  doi:10.6040/j.issn.1672-3961.0.2018.055
    Abstract ( 644 )   HTML ( 4 )   PDF (3052KB) ( 255 )   Save
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    The construction project of Fo Yangling Tunnel was taken as the research background, the construction was carried out by using benching tunneling construction method. The fast Lagrangian analysis of continua 3D (FLAC3D) finite element software was used as the calculation platform to establish the finite element model of tunnel with large section and small clear distance. The tunnel model was numerically simulated and subsidence, stress of surrounding rock and lining structural were analyzed. And the corresponding monitoring and reinforcement measures were put forward. The results of numerical analysis showed that the settlement of the upper part of the advance tunnel was larger than the subsequent tunnel. The construction of the subsequent tunnel increased the vertical displacement of the advance tunnel, which caused the increase of maximum principal stress and the minimum principal stress. The stress of tunnel lining structure was concentrated in the area from arch waist to arch foot. The support structure of advance tunnel played the role of stabilizing rock mass in the excavation of subsequent tunnel, and the excavation of the subsequent tunnel would make the stress concentration of the middle rock. In the construction, attention should be payed to the surrounding rock and reinforcement measures should be taken. The analysis results could provide a scientific basis for the design and construction of large section and small spacing road tunnel.

    Influence of magnetic suspension rotor driving magnetic field on supporting magnetic field
    Xiaoguang WANG,Zhuang HE,Xianfu LI,Ao PAN
    Journal of Shandong University(Engineering Science). 2019, 49(4):  86-92.  doi:10.6040/j.issn.1672-3961.0.2018.498
    Abstract ( 537 )   HTML ( 10 )   PDF (5966KB) ( 137 )   Save
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    Based on theoretical analysis and finite element simulation analysis, the mutual influence between the driving magnetic field of rotor disk motor and the supporting magnetic field of the magnetic levitation system were studied, the main factor L0 was obtained. The critical dimension L0 value was 11.87 mm to keep the system steady with the influence of the driving magnetic field on the supporting magnetic field. And the critical dimension was tested by equivalent tests. According to the critical dimension L0, the design criteria of the magnetic suspension rotor and a feasible scheme of the magnetic suspension rotor were proposed.

    Laminar flow field characteristics in the stirred vessel equipped with an eccentric-shaft impeller
    Meiting LI,Wei LI,Xiaoguang LI,Fengling YANG
    Journal of Shandong University(Engineering Science). 2019, 49(4):  93-98, 107.  doi:10.6040/j.issn.1672-3961.0.2018.530
    Abstract ( 727 )   HTML ( 5 )   PDF (2868KB) ( 558 )   Save
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    For the purpose of improving mixing efficiency of the stirred tank with high viscosity fluid laminar flow condition, an eccentric-shaft agitation method was proposed. With a purity of 99% glycerol as medium, and the traditional 2-flat-blade impeller as the research object, the laminar flow fields were numerically studied. The inner diameter of the stirred vessel was 0.3m and the agitated fluid was glycerol. The modeling reliability and simulation methods of the concentric agitation were validated by experimental results. In comparison with the concentric agitation, flow fields generated by eccentric and eccentric-shaft agitation were asymmetrical, and theoverall volume weitghted average velocity of the groove fluid generated by eccentric-shaft agitation could be raised by 68%. And furthermore, when operated under the same speed, the power consumption of eccentric-shaft agitation increased 15.3% than that of concentric agitation. However, the eccentric shaft agitation increased the speed in the tank and expanded the range of disturbance. Accordingly, the superiority of eccentric-shaft agitation of improving the mixing efficiency in the tank was apparent.

    Phase change characteristics of paraffin in rectangular storage unit
    Huilin ZHOU,Yan QIU
    Journal of Shandong University(Engineering Science). 2019, 49(4):  99-107.  doi:10.6040/j.issn.1672-3961.0.2019.018
    Abstract ( 684 )   HTML ( 8 )   PDF (3235KB) ( 693 )   Save
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    To study the heat transfer characteristics of phase change material (PCM) in a storage unit and improve the heat transfer efficiency of phase change heat exchanger, the enthalpy-porous media model and FLUENT program were used to carry out a numerical investigation on the heat transfer process of paraffin in a rectangular heat storage unit. The element liquid fraction β and dimensionless Fo, Ste and Ra were introduced to analyze the influences of different positions outside the tube and inlet temperatures of heat transfer fluid on the melting and solidification process of paraffin. The results showed that the paraffin outside the tube was melted in order from the upper to the left/right part, then the lower part. The total melting time of paraffin in upper part was shorten by at least 20% compared with other parts. Conversely, in the heat release process, the paraffin was solidified in order from the lower, the left/right part and the upper part. The heat transfer mechanism in the unit changed gradually from heat conduction to natural convection in the thermal storage process. The efficiency of heat storage and release could be improved significantly by increasing the temperature difference between heat transfer fluid and paraffin. The criterion of β was obtained by polynomial fitting.

    Non-equilibrium molecular dynamics simulation of the influence of nanostructures on water infiltration characteristics
    Haowei HU,Shuang LIU,Tingyong FANG
    Journal of Shandong University(Engineering Science). 2019, 49(4):  108-114, 122.  doi:10.6040/j.issn.1672-3961.0.2018.476
    Abstract ( 581 )   HTML ( 6 )   PDF (5705KB) ( 196 )   Save
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    To clarify the law of fluid flow in a complex nanochannel, the molecular dynamics method was employed to investigate the infiltration characteristic of pressure-driven droplet into the nanochannel with different wettability. The nonequilibrium molecular dynamics model of liquid water/nanochannel with different wettability was established to study effects of driving pressure, surface wettability, and nanoscale roughness on infiltration characteristics. The simulation results indicated that droplets more rapidly entered into the hydrophilic nanochannel than the hydrophobic nanochannel under an identical driving pressure. And compared to the smooth nanochannel, effects of the surface tension of the droplet was obvious due to the structures of nanoscale roughness. Simultaneously, it could be found that the nanoscale roughness had a certain impact on both droplet infiltration velocity and density profiles. As the distance between the nanoscale roughness and nanochannel entrance decreased, the flow resistance in the infiltration process of droplets improved. It suggested that the volumetric flux of the infiltration of water into the nanochannels was reduced. The findings could provide a theoretical basis for uncovering the transport mechanism of liquid water in the complex nanochannel.

    Electrical Engineering
    Comprehensive decision-making method for large-scale photovoltaic system integrated to receiving-end power grid
    Xiaoming LIU,Yini CONG,Wenbo LI,Yutian LIU
    Journal of Shandong University(Engineering Science). 2019, 49(4):  115-122.  doi:10.6040/j.issn.1672-3961.0.2019.029
    Abstract ( 526 )   HTML ( 9 )   PDF (1413KB) ( 196 )   Save
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    This paper proposed a comprehensive decision-making method based on fuzzy analytic hierarchy process (FAHP) and technique for order preference by similarity to ideal solution (TOPSIS) for large-scale photovoltaic system integrated to receiving-end power grid. A decision-making evaluation index system was established to quantify the indexes of grid-connection schemes, in which main influence factors considered were security and stability, intermittence of PV, economy, and extendibility. Taking into account the fuzziness of the preferences of decision-makers, the FAHP algorithm was applied to determine the weights of indexes. The TOPSIS algorithm was adopted to make the multi-objective decision between schemes to get the TOPSIS solution as the best grid-connection scheme. The case study on Shandong power grid demonstrated the whole process of the comprehensive decision-making method and indicated that the method could reflect the merits and demerits of different schemes visually, with which we could get the reasonable decision results.

    Analytic hierarchy process based quantitative performance evaluation of second-use battery energy storage system
    Xiandong LI,Fei WANG,Yongji CAO,Lilong WANG,Lin WANG,Yi LU,Zihan LIU
    Journal of Shandong University(Engineering Science). 2019, 49(4):  123-129.  doi:10.6040/j.issn.1672-3961.0.2018.554
    Abstract ( 577 )   HTML ( 2 )   PDF (1950KB) ( 187 )   Save
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    In order to assess the operation performance of second-use battery energy storage system, a comprehensive assessment method was proposed based on the analytic hierarchy process, in which the operation benefits and electrical characteristics were considered simultaneously. A quantitative assessment frame was constructed, where the amount and fluctuation of exchanging power between the active distribution network and the main grid were utilized to quantify the operation benefits and the voltage fluctuation, three-phase imbalance factor and harmonic current of grid-connection point were utilized to quantify the electrical characteristics. The weights of indices at the same level were obtained by the analytic hierarchy process and the comprehensive index value was calculated by the weighted summing of quantitative index values. 15 kW/30 (kW·h) prototype of second-use battery energy storage system was developed based on the dynamic reconstructing strategy and applied to the ten-day on-line test, from which the field data were obtained and used to validate the effectiveness of the proposed method. The case study results indicated that the second-use battery energy storage system had satisfactory electrical characteristics and could decrease the exchanging power, smooth the power fluctuation and improve the renewable energy accommodation.

    A doubly-selected channel estimation method based on an unscented Kalman filter
    Na LU,Li GAO,Xuanfan SHEN
    Journal of Shandong University(Engineering Science). 2019, 49(4):  130-136.  doi:10.6040/j.issn.1672-3961.0.2018.175
    Abstract ( 495 )   HTML ( 8 )   PDF (1399KB) ( 199 )   Save
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    Due to selective fading in time domain and frequency domain (doubly-selective fading) causes the inter carrier interference (ICI) in the orthogonal frequency division multiplexing (OFDM) system, the communication quality would be declined in high speed environment. The basis expansion model (BEM) decreased the spatial complexity of the channel estimation algorithm while eliminating the ICI impact effectively. For the non-linear channel state space model under the BEM, the unscented Kalman filter (UKF) was adopted to track the channel response in time and improve channel estimation accuracy. Simulation results showed that the BEM-UKF was able to effectively improve the accuracy of channel estimation and had better bit error rate (BER) performance and robustness than traditional algorithms.