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Mechanical Engineering—Special Topic on Ocean Engineering and Technology
The influence of shape parameters of wave energy device floating body on energy capture characteristics
Yanjun LIU,Wei WANG,Zhi CHEN,Donghai WANG,Dengshuai WANG,Gang XUE
2020, 50(6):  1-8,16.  doi:10.6040/j.issn.1672-3961.0.2020.160
Abstract ( 119 )   HTML( 118 )   ( 17 )   PDF (6369KB) ( 118 )   Save
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To clarify the effect of the floating body′s shape parameters on the energy capture performance and working stability, an oscillating float type wave energy converter (WEC) model with linear power take-off system was established. Frequency domain calculation theory was used to deduce the formulas of energy capture power and energy capture width ratio. After introducing the numerical simulation steps of floating body in frequency domain, ANSYS-AQWA software was used to investigate the floater's energy capture power and energy capture width ratio with different bottom shapes and half vertex angles. Influence of shape parameters on the energy capture performance was drawn to provide a theoretical basis for the shape optimization of the floating body applied to the wave power supply device and floating platform. The results showed that the practical fabrication feasibility of circular truncated cone bottom was higher than that of cone and sphere. The energy capture characteristics and stability of circular truncated cone bottom were better than that of general cylindrical floating body in the intermediate wave frequency band. The energy capture performance and working stability of circular truncated cone floating body with big top and small bottom were better. The energy capture performance under intermediate frequency waves could be improved with the increase of the half vertex angle. The optimal power capture performance and working stability could be achieved with a proper apex angle.

Dynamic modeling and position prediction of deep-towed seismic array
ZHU Xiangqian, WEI Zhengrong, PEI Yanliang, YU Kaiben, ZONG Le
2020, 50(6):  9-16.  doi:10.6040/j.issn.1672-3961.0.2020.084
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Given the inversion calculation cannot compute the position of array exactly, the dynamic modeling of towed vehicle-seismic array-drogue was purposed, and the position of array was calculated by dynamic simulation. The position of seismic array was calculated by inversion calculation and dynamic simulation, respectively. Then, the travel times of the reflected wave by seabed were calculated with respect to the position of the array. The comparison between the calculated travel times and real seismic records indicated that the malpositions were shown in the inversion calculation, while the result by dynamic simulation was stable and matched well with real records. Dynamic analysis was an efficient method in position prediction of seismic array.
Power capture influence of the submerged depth for the three-freedom oscillating body wave energy converter
HUANG Shuting, ZHAI Xiaoyu, LIU Yanjun, SHI Hongda
2020, 50(6):  17-22.  doi:10.6040/j.issn.1672-3961.0.2020.035
Abstract ( 59 )   PDF (6421KB) ( 35 )   Save
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To clarify the power capture influence of the submerged depth for the three-degree-of-freedom(3-DOFs)oscillating buoy wave energy converters, two floating and submerged buoy models were established. Power capture characteristics of the submerged buoys were calculated and compared with different depths and wave conditions. The cylindrical buoy was selected. The submerged depth were 0.5, 1.0, 1.5 and 2.0 times of the buoy’s height. The mass of the buoys were the same. The floating buoy was selected as a comparison. Based on linear potential theory and boundary element method, the hydrodynamic model was established, and the hydrodynamic parameters and kinematic responses of the buoy were calculated. And the optimal average output powers were calculated with linear power take-off(PTO)damping. The effect of submerged depth on the power capture of the buoy was analyzed. The results showed that increasing the submerged depth could reduce buoys wave excitation forces and power absorption. For 3-DOFs buoy, the floating one had a better power capture performance under low frequency waves, while the submerged one with a small submerged depth was better under high frequency waves.
Hydrodynamic characteristics of oscillating hydrofoil with trailing edge
SUN Guang, WANG Yong, XIE Yudong, CHEN Chen, ZHANG Yubing
2020, 50(6):  23-29.  doi:10.6040/j.issn.1672-3961.0.2020.052
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In order to improve the energy extraction efficiency of an oscillating hydrofoil, an oscillating hydrofoil structure with trailing edge flaps was proposed. This structure was to install a trailing edge flap at the rear end of a traditional hydrofoil, and used the swing of the trailing edge flap to achieve the purpose of increasing power. The equations of motion of flap oscillations were established and the equivalent angle of attack equation was derived. The model was numerically simulated using the dynamic and moving grid technologies in the CFD software. The simulation results showed that the trailing edge flap structure increased the arch of the hydrofoil and increased the attack angle of the hydrofoil, which in turn increased the lift coefficient and the time-averaged power coefficient. The derived equivalent angle of attack formula was consistent with the simulation results, and the equivalent angle of attack formula can better predictd the simulation results. The negative work of the trailing edge flap occupied a small proportion of the total power collected by the oscillating hydrofoil.
Mechanical characteristics for deep sea wet-mate electrical connectors
HAN Jiazhen, WANG Yong, XIE Yudong, WANG Qixian, ZHANG Xinbiao, GAO Wenbin, LI Ronglan, ZHANG Chuanjun
2020, 50(6):  30-39.  doi:10.6040/j.issn.1672-3961.0.2020.127
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A deep-sea and wet-mate electrical connector at 7 000 meters underwater was chosen as the research subject, aiming at obtaining the mechanical characteristics and dynamic sealing performance of the wet-mate connector under the condition of deep-sea double high pressure. The plug structure and pressure compensation technology of the connector were introduced and a calculation formula of the working volume of the pressure compensator was derived. Finite element models of plug's inner shell component and jack component's dynamic sealing were established by using the software Ansys Workbench, and the strength of the inner shell, pressure balance membrane and inner tank was calculated. The stress distribution and deformation of the membrane under the action of instantaneous pressure difference caused by the connector's wet-mate operation between the inside and outside of the balance membrane were analyzed. The effects of the seal component's radial compression, sealing contact surface's friction coefficient and wet-mate speed on dynamic sealing performance during the wet-mate operation were discussed. The results showed that when the plug was inserted, the stress on the outer surface of the balance membrane was almost unchanged, and its deformation was decreased; when the plug was pulled out, the stress and deformation on the outer surface of the balance membrane were gradually increased. The contact pressure between seal components was obviously affected by the interference fit of the sealing contact surface. Increasing the interference fit could significantly improve the contact pressure and sealing performance of the dynamic sealing area, but also exacerbate the possibility of seal component's failure. The sealing contact surface's friction coefficient and wet-mate speed had little influence on the contact pressure.
Energy harvesting performance analysis on improved motion model of oscillating hydrofoil
QIAO Kai, WANG Qixian, WANG Yong, XIE Yudong
2020, 50(6):  40-47.  doi:10.6040/j.issn.1672-3961.0.2020.202
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In order to improve the hydrodynamic performance and energy harvesting efficiency of the oscillating hydrofoil, an improved motion model was proposed based on the traditional simple harmonic motion model. By introducing the pitch motion coefficient k, the general form of the improved pitch motion law was deduced. The two-dimensional model of the hydrofoil was established using Fluent software, and we further analyzed the effects of different pitch motion coefficients, motion frequency and pitch amplitude on the hydrofoil energy capture performance under the semi-active oscillation model. The results showed that, when compared with the traditional simple harmonic motion model, the improved motion model could make the lift coefficient of hydrofoil maintain a larger value for a longer period of time, meanwhile the lift coefficient and energy capture efficiency of the hydrofoil also were improved. Under the same value of reduced frequency and pitch amplitude, reducing the pitch motion coefficient could increase the angular velocity of the pitch angle rotation, thereby increasing the energy consumed by the pitch motion. Different pitch amplitude corresponded to different optimal reduced frequencies. The lower the reduced frequency, the more unstable energy-capturing performance of the hydrofoil, the greater the pitch amplitude, and the more energy consumed for turning the pitch angle. Under the given parameters, the energy conversion efficiency of the hydrofoil could exceed 40%.
Machine Learning & Data Mining
Design pattern classification mining with feature metrics constraints
Zhuoyu XIAO,Pei HE,Guo CHEN,Yunbiao XU,Jie GUO
2020, 50(6):  48-58.  doi:10.6040/j.issn.1672-3961.0.2020.229
Abstract ( 93 )   HTML( 44 )   ( 13 )   PDF (1397KB) ( 44 )   Save
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To solve low accuracy for design pattern mining, a method for design pattern classification mining with feature metrics constraints was presented. 47 feature metrics information based on structural pattern, behavioral pattern and creative pattern was classified and summarized, and definition of design pattern were given, and features of design patterns were described, three benchmark systems and four well-known system experiments for design pattern mining were designed. Experimental results show that proposed method is effective, and the accuracy of the proposed method was 96.13%, 91.67%, 72.23% for Adapter pattern. Command pattern and Factory method pattern for three benchmark systems, and the accuracy of the proposed method is 84.3%, 81.26%, 73.17% for Adapter, Command and Factory Method of design pattern for four well-known systems, compared to well-known methods by experiment of design pattern mining, indicating the effectiveness of the proposed method.

Lung tumor benign-malignant classification based on multi-modal residual neural network and NRC algorithm
HUO Bingqiang, ZHOU Tao, LU Huiling, DONG Yali, LIU Shan
2020, 50(6):  59-67.  doi:10.6040/j.issn.1672-3961.0.2020.235
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A method for the benign and malignant classification of lung tumors was put forward due to Challenges with the training of deep convolutional neural networks, network degradation and a weak ability to express the features based on non-negative representation classification and a multi-modal residual neural network. The pre-trained residual neural network model was initialized using transfer learning. three data sets(CT, PET and PET/CT)were used to train the network and extract the feature vectors of the fully connected layer, then a non-negative representation classifier was used for the non-negative representation of the feature vector, and used to solve the non-negative coefficient matrix. The residual similarity was used to classify benign and malignant lung tumors. Comparative experiments were conducted with the AlexNet, GoogleNet and ResNet-18/50/101 models. The experimental results showed that the classification accuracy of the ResNet-NRC was better than the other models, and the specificity and sensitivity indices were also higher. The proposed method has improved robustness and generalization ability.
Pre-trained based joint model for intent classification and slot filling in Chinese spoken language understanding
MA Changxia, ZHANG Chen
2020, 50(6):  68-75.  doi:10.6040/j.issn.1672-3961.0.2020.236
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We explored a joint model for intent classification and slot filling based on pre-train and attention mechanism because intent classification and slot filling were correlative. We combined bidirectional long short-term memory(BiLSTM), conditional random fields(CRF)and bidirectional encoder representations from transformers(BERT), which supported bidirectional and self-attentional mechanism without relying heavily on hand-crafted features and domain-specific knowledge or resources, into the proposed model. We compared the performance of our proposed architecture with the state-of-the-art models. Experiments on dataset demonstrated that the proposed architecture outperformed the state-of-the-art approaches on both tasks. Furthermore, we presented a new dialogue corpus from autonomous bus information inquiry system(ABIIS), and our methods yielded effective improvement on intent classification accuracy and slot filling F1 compared with a state-of-the-art baseline.
Hippocampal segmentation combining residual attention mechanism and generative adversarial networks
ZHANG Yuefang, DENG Hongxia, HU Chunxiang, QIAN Guanyu, LI Haifang
2020, 50(6):  76-81.  doi:10.6040/j.issn.1672-3961.0.2020.230
Abstract ( 91 )   PDF (3203KB) ( 48 )   Save
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This research discussed a deep learning method based on an improved generative adversarial network to segment the hippocampus. Different convolutional configurations were proposed to capture the information obtained by the segmentation network. The generative adversarial network based on Pixel2Pixel was proposed. The generator was a codec structure combining residual network and attention mechanism to capture more detailed information. The discriminator used a convolutional neural network to discriminate the segmentation results of the generated model and the expert segmentation results. Through generator and discriminator continuously transmitted losses, the generator reached the optimal state of segmenting the hippocampus. Using the T1-weighted MRI scans and related hippocampus labels of 130 healthy subjects from the ADNI data set as training and test data, and the similarity coefficient as the evaluation index, the accuracy rate reached 89.46%. Results showed that the network model could achieve efficient automatic segmentation of hippocampus, which had important practical significance for the correct diagnosis of diseases such as Alzheimer's disease.
Civil Engineering
Optimal structure of pressure cast-situ-pile with spray-expanded frustum
Lianxiang LI,Hongxia XING,Jinliang LI,Hengli HUANG,Lei WANG
2020, 50(6):  82-91.  doi:10.6040/j.issn.1672-3961.0.2020.090
Abstract ( 50 )   HTML( 27 )   ( 12 )   PDF (6556KB) ( 27 )   Save
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According to the field test results of pressure cast-situ-pile with spray-expanded frustum, with the help of Abaqus to establish the numerical model of the experiment, the influence rule of expanded body with frustum (hereinafter referred to as frustum) on surrounding soil under vertical load was obtained. It was clarified that the soil mass had squeezing effect within the 2D~3D range (D is frustum's diameter) and it reached the limit at 0.5 m under the frustum. Stress relaxation occured in the upper soil of frustum, which reached the limit value at the top of the frustum, and of which the vertical influence range was extended by 1.25D and the horizontal influence range was 1.5D~2.5D. Revealed that the optimal spray angle for frustum expanding was 50°~55°, the optimum expanding ratio was 2~2.75, the optimal position was in the D~2D range of upper part of pile, and it was optimal when the fixed spray wing was 7~8 m below the pile top. The optimal construction model could increase the bearing capacity by 19%, therefore it was suggested to adopt the optimal structural pile type to further improve efficiency and promote application of the pile.

Analysis of pipe roof grouting reinforcement effect at tunnel entrance in loose stratum
YU Jun, WENG Xianjie, FAN Wensheng, ZHANG Lianzhen
2020, 50(6):  92-100.  doi:10.6040/j.issn.1672-3961.0.2020.277
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Based on Lianhua Tunnel in Pinglian Express Way, three-dimensional calculation model was established to study excavation stability considering pipe roof grouting reinforcement effect. Effect of different pipe roof grouting parameters on excavation stability was analyzed quantitatively, such as mechanical parameters of grouted body, pipe roof interval, grouting radius. In the end, numerical simulation results were used and verified in engineering project. Research results showed that there existed plastic failure zone at vault and region below tunnel face. Pipe roof grouting method had effect on limiting deformation of surrounding rock, reducing volume strain of surrounding rock and cutting off connection between plastic failure zone on vault and tunnel. In whole affected area of pipe roof grouting, maximum settlement of pipe roof settlement appeared around tunnel face. Maximum settlement of pipe roof settlement was negatively related with elastic modulus of grouted body and grouting radius, positively related with pipe roof interval. However, influence level of pipe roof interval was lower than elastic modulus of grouted body or grouting radius.
Electrical Engineering
Electric vehicle virtual energy storage available capacity modeling
Bei LI,Song ZHAO,Zhijia XIE,Meng NIU
2020, 50(6):  101-111.  doi:10.6040/j.issn.1672-3961.0.2020.128
Abstract ( 72 )   HTML( 36 )   ( 11 )   PDF (2357KB) ( 36 )   Save
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In order to efficiently implement the virtual energy storage dispatch of electric vehicles in a wide area, the article focused on the types of electric vehicles that respond to electric vehicle virtual energy storage (EVVES) services by clustering, combined with the use habits of all kinds of electric vehicle owners (such as daily driving mileage, charging and discharging rules, expected standby travel electricity, etc.), the impact of market on EVVES responsiveness, redundant design of available energy storage capacity and other factors, a virtual energy storage (VES) capacity estimation model was established. Combined with the technical requirements of power system for energy storage to participate in system services, such as emergency power support, smooth renewable energy output, UPS/EPS, etc., the matching basis of supply and demand was proposed. Based on Monte Carlo simulation method, the practicability of the model to estimate the available capacity of response VES service in different time periods was verified, which layed the foundation for the operation practice of EVVES in future.

Primary and secondary integration simulation technology of distribution network based on RTDS
LI Zhi, YU Shaofeng, SU Yifang, WANG Wei, JIANG Hongtu, ZHANG Wei
2020, 50(6):  112-117.  doi:10.6040/j.issn.1672-3961.0.2019.683
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A simulation technology of primary and secondary equipment integration in distribution network based on RTDS was proposed. Firstly, the basic requirements and overall framework of the primary and secondary equipment integration simulation system for distribution network were described, and the overall design method of the simulation system was given. Then, from the aspects of data acquisition, interface, conversion and algorithm selection of primary and secondary equipment, the specific implementation method of the simulation system was proposed. An example of relay protection in distribution network was simulated by using the proposed simulation system, the response time of the whole simulation system 2~3 simulation steps, which verified the feasibility and validity of the proposed primary and secondary equipment integration simulation technology.
The effect of barbed electrodes parameters on the discharge characteristics and particles removal efficiency
WANG Lei, LI Mingzhen, WANG Xiang
2020, 50(6):  118-128.  doi:10.6040/j.issn.1672-3961.0.2019.574
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To study the effect of design parameters on discharge characteristic and particles removal efficiency of the barbed electrodes, a test bench was built and the discharge current and PM2.5、PM10 removal efficiency of the discharge electrode with various barb thickness δ and spacing L under different applied voltage and dust concentration were studied. The results showed that the thinner barb was better at discharging and removing fine particles than the thicker one, especially for the particles in 0.2~2 μm. The effect of the thinner barb on the particles removal efficiency was dramatically obvious in the case of a lower applied voltages and higher mass concentration. The discharge current and particles removal efficiency firstly increased to the maximum and then decreased with barb spacing decreasing. The discharge current was the largest when the barb spacing was 50 mm, while the particles removal efficiency was highest when the barb spacing was 80 mm. The results could provide references for the selection and design of barbed discharge electrodes in the electrostatic precipitator.
Condensation heat transfer characteristics of steam containing non-condensable gas on sawtooth surface
YAN Jiqing, WANG Xiaojia, TIAN Maocheng
2020, 50(6):  129-134.  doi:10.6040/j.issn.1672-3961.0.2020.295
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To obtain higher thermal efficiency in the condensation process of steam containing non-condensing gas, a new sawtooth heat transfer strengthening plate was proposed and its two-dimensional model was established. The difference of condensation heat transfer characteristics between serrated plate and corrugated plate with the same specification was analyzed by Fluent software. A condensation heat transfer model to calculate both non-condensable gas layer and liquid film layer at the same time was established and compiled by user defined functions in the numerical simulation. The model reliability was verified by comparing with the experimental values in the same working conditions. The two-phase flow and heat and mass transfer characteristics of different plate surfaces are obtained, and the results showed that compared with the corrugated plate, the sawtooth plate could significantly improve the turbulence of the non-condensable gas layer, which was beneficial to the heat and mass transfer process on the liquid film surface. The liquid film of the sawtooth plate would be periodically fractured at the tooth peak of the wave node and then re-formed on the downstream wall surface and reached the maximum thickness at the trough. Compared with the corrugated plate, the heat transfer capacity of the sawtooth plate was improved by more than 60%.
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