Journal of Shandong University(Engineering Science)

Adaptive sliding mode synchronization of a class of nonlinear chaotic systems

Chunrui CHENG,Beixing MAO

Journal of Shandong University(Engineering Science). 2020, 50(5): 1-6. doi:10.6040/j.issn.1672-3961.0.2019.573

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The synchronization of a class of nonlinear chaotic systems with model uncertainties and external disturbances was studied based on adaptive sliding mode control. A novel nonsingular terminal sliding surface was proposed and its stability was proved. On the basis of Lyapunov stability theory, a sliding mode control law was derived to force the trajectory of the synchronization error systems onto the sliding surface and to guarantee the occurrence of the sliding motion. The proposed control scheme was applied to synchronize chaos of integer order and fractional-order nonlinear chaotic systems in the presence of both model uncertainties and external disturbances. A numerical simulation taking the fractional Victor-Carmen system as the example demonstrated the applicability and efficiency of the proposed sliding mode control technique and verified the theoretical results of the research.

Sliding mode synchronization of fractional-order T chaotic systems with logarithmic

MENG Xiaoling, MAO Beixing

Journal of Shandong University(Engineering Science). 2020, 50(5): 7-12. doi:10.6040/j.issn.1672-3961.0.2019.395

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By using the Barbalat lemma and fractional-order stability theory, and constructing proper fractional-order sliding mode surface and fractional-order proportion integral sliding mode surface, the controllers were designed to realize the synchronization control of integer model and fractional-order T chaotic systems. The research conclusion illustrated that the derive-responsive systems of fractional-order T chaotic systems could get sliding mode synchronization under certain conditions. MATLAB numerical simulation proved the correctness of the conclusions.

Fuzzy control of structure vibration mode based on BP neural network algorithm

Zhiwei WANG,Nan GE,Chunwei LI

Journal of Shandong University(Engineering Science). 2020, 50(5): 13-19. doi:10.6040/j.issn.1672-3961.0.2019.509

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In order to control the seismic response of civil engineering structures more reasonably and conveniently, a fuzzy control algorithm based on BP neural network was proposed. The neural network was trained with the structural seismic dynamic response data to establish the structural analysis model, and the time-domain modal coordinates were taken as the controlled variables to reduce the order of the system, so that the number of fuzzy reasoning required to establish the modal fuzzy control rules was within the acceptable range, and the system energy minimum was taken as the control target to formulate the control rules. The fuzzy control numerical model of structural dynamic response was established to evaluate the damping effect of the proposed algorithm based on the calculated value of seismic dynamic response. The results showed that the trained BP neural network could accurately predict the seismic dynamic response of the structure and establish fuzzy control rules accordingly. Using mode fuzzy control only for the first mode of the structure could achieve satisfactory damping effect. When active mass driver(AMD) optimal control amplitude was used as the control domain of each floor, the damping effect of modal fuzzy control was different from it. A better damping effect could be obtained by increasing the control field.

Variation of granular slurry diffusion distance in sand medium

FENG Xiao, XIA Chong, WANG Fenggang, ZHANG Bing

Journal of Shandong University(Engineering Science). 2020, 50(5): 20-25. doi:10.6040/j.issn.1672-3961.0.2019.746

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Based on the mass conservation equation, linear filtration law, Darcy's law and specific boundary conditions, a theoretical diffusion distance model of granular slurry under laminar flow conditions was established. By developing and applying an assembly-type device for permeating grouting, the diffusion rules of grout under different water-cement ratio and flow rate were studied. The value of model test was compared with the theoretical values when the filtration effect was considered or not. The results showed that when the flow velocity v₀ was constant, the theoretical diffusion distance without filtration effect considered was not consistent with reality. Both the water-cement ratio and velocity of grout were positively correlated with diffusion distance. When the water-cement ratio was 1∶1, the deviation between the value of model test and the theoretical calculation with filtration considered was 18.4 to 20.8 cm, with a deviation rate of 68.9% to 71.9%. When the water-cement ratio came to 2 ∶1, corresponding values were within 20.7 to 23.4 cm, and 27.0% to 28.2% respectively. The research results could guide the drilling spacing design of grouting and had some application value for project.

Design and mechanical properties of prestressed hollow bar

LIN Chao, ZHANG Chenglin, WANG Yong

Journal of Shandong University(Engineering Science). 2020, 50(5): 26-32. doi:10.6040/j.issn.1672-3961.0.2019.425

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To meet the needs of the seismic performance of concrete at the node joints of assembled buildings, a self-balancing prestressing hollow bar was used to realize the effect of pre-stressing the short rod at the joint position. According to the force balancing mechanism, pressure was applied to the steel rod inside the structure, which led to the coordinated tension in the steel tube outside the structure to achieve the design. After pre-stressing and locking by the nut, bury the rod into the concrete of the joints of the assembled nodes, pour the early-strength grout, and wait for the consolidation to reach the predetermined level. Strength-releasing reaction rods, relying on the self-anchoring of the bond between the external threaded structure and the concrete to achieve the pre-stress applied to the joint concrete. The stress changes and losses in the tensile and static relaxation phases of the rod were investigated, and the tensile and static relaxation phases of the rod were verified. The validity of stress storage from completion until release was verified by analyzing parameters such as stress distribution and prestressing losses after the rod was released. The mechanism and effectiveness of stress transmission after application for odal concrete and the analysis of stresses in prestressed concrete members using finite element method distribution pattern. The pre-stressing hollow bar technology acting on the assembly nodal joints concreted has high seismic and energy-consuming capacity for assembly building the realization of high seismic performance of nodal concrete provides a new technical approach.

Influence of concealed karst cave on surrounding rock stability and its treatment technology

CHEN Yucheng, WANG Zhaoyang, GUO Ming, LIN Peng

Journal of Shandong University(Engineering Science). 2020, 50(5): 33-43. doi:10.6040/j.issn.1672-3961.0.2020.042

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On the basis of the investigation and statistical analysis of karst caves of tunnel project in E-Xi mountains area, they were classified according to the karst cave volume, shape, cavity filling material and water gushing channel type. The result presented that the karst cavities in the mountains area of E-Xi were of different sizes, various shapes, various cavity filling materials and complicated water gushing channel. The changes of stress field and displacement field of tunnel surrounding rock under the influence of different location of hidden karst cave were studied through numerical simulation analysis, which showed that the high stress area and low stress area of surrounding rock were different with different location of hidden karst cave. With the changes of location of karst cave, the maximum settlement value from large to small were spandrel extension line, sidewall, spandrel extension line, top of arch, bottom of slab. With the descend of the location of the karst cave, the distribution rule of the maximum horizontal convergence from large to small were spandrel extension line, above the arch crown, sidewall, below the bottom plate, spandrel extension line. With the descend of the location of the karst cave, the deformation law of surrounding rock the settlement of tunnel from large to small were vault, haunch, arch foot, base plate. Based on the characteristics of karst type, the results of numerical simulation of stress field and displacement change of surrounding rock, the prevention and control principles of karst cave were sorted out. Huaguoshan tunnel was taken as an example to explain in detail and the treatment scheme was put forward.

Application of pure steel fiber concrete segment in hard rock tunnel

XU Zhen, LI Deming, WANG Bin, ZHAN Guyi, ZHANG Shijie

Journal of Shandong University(Engineering Science). 2020, 50(5): 44-49. doi:10.6040/j.issn.1672-3961.0.2020.085

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Based on the previous steel fiber reinforced concrete material property test and segment mechanical performance test, FLAC 3D was used to numerically simulate steel fiber reinforced concrete segments in hard rock tunnels, and field tests were conducted on Qingdao Metro Line 1 to test the segments. The results showed that the pure steel fiber reinforced concrete segment had better crack resistance than the ordinary segment, which could effectively reduce the cracks and about 60% edge loss and angle drop. Using pure steel fiber concrete segment could control the surface settlement, the convergence and the vault settlement more efficiently. Under normal conditions of hard rock tunnels, the segments were under full-section compression, and without configuring tensile steel, it was feasible to completely replace the steel bars by steel fiber.

Vibration characteristics of flexible-blade Rushton impeller

Xin LIU,Fengling YANG

Journal of Shandong University(Engineering Science). 2020, 50(5): 50-55. doi:10.6040/j.issn.1672-3961.0.2020.009

Abstract ( 986 )

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A natural frequency of a new type of flexible-blade Rushton impeller was studied to avoid a resonance phenomenon. The vibration characteristics of this impeller under stationary and rotating working conditions were experimentally investigated. Frequency domain characteristics were obtained by making Fast Fourier Transformation (FFT) of time domain characteristics. The results showed that a vibration energy of the impeller was mainly concentrated in a frequency band of 1-7Hz under the stationary state. A vibration energy of a rotating impeller with different speeds was mainly concentrated in a frequency bands corresponding to their respective peaks. Specifically, a peak acceleration distribution of acceleration data was shown in a frequency band of 47-52Hz. The acceleration amplitude increased significantly at 2.5r/s, and a main vibration frequency was equal to the natural frequency, which was 2.5Hz. So it was judged that resonance occured at this time. Therefore, the method of obtaining the resonance rotational speed through the test provided a basis for a reasonable selection of the rotational speed of the flexible-blade impeller.

Experimental and theoretical studies on 1-D model of heat and mass transfer performance for wet flue gas desulfurization scrubber

CHEN Baokui, SUN Fengzhong, GAO Ming, SHI Yuetao

Journal of Shandong University(Engineering Science). 2020, 50(5): 56-63. doi:10.6040/j.issn.1672-3961.0.2019.539

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To predict the slurry temperature in wet flue gas desulfurization(WFGD)system, a concept of insulation saturation temperature of wet flue gas was put forward, and the functional relationship between slurry temperature and inlet flue gas temperature and moisture content was deduced. Based on the predicted slurry temperature, a 1-D coupled mathematical model of droplets motion, heat and mass transfer and pressure loss of liquid-gas two phases was established, the influence of three-dimensional inhomogeneity of desulfurization system on model accuracy was analyzed. In terms of the main operating variables in desulfurization system(diameter of slurry particle, inlet temperature of flue gas and ratio of liquid to gas), the 1-D distribution law of the related parameters was obtained by the Runge-Kutta iteration method. In order to verify the model, the field test and physical model test were carried out respectively. The results showed that the predicted slurry temperature was in good agreement with the measured parameters, the maximum error was 4.56%; the diameter of slurry particle was the main factor affecting heat and mass transfer; the velocity of particles decayed rapidly in the process of decline, and tended to the final invariant value; the temperature of the flue gas was distributed exponentially with the height of the tower. Compared with the predicted values, the maximum errors of temperature and pressure distribution from the experimental results were 4.72% and 6.46% respectively. The model had high accuracy, which was of guiding significance to the design, operation and study on mass transfer of SO₂ in WFGD system.

Optimization of the inner deflector of the shrimp-waist elbow

Jinsheng QI,Hongzhen CAO,Yan SHI,Wenjing DU,Zhan WANG

Journal of Shandong University(Engineering Science). 2020, 50(5): 64-69, 76. doi:10.6040/j.issn.1672-3961.0.2020.093

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In order to study the distribution of the flow field and improve the uniformity of the flow field in a shrimp-waist bend, a series of three-dimensional numerical simulation studies on the turbulent secondary flow in a bend before and after the installation of the deflector was carried out by using the Realizable k-ε model. The results showed that when the deflector was not arranged in the shrimp-waist bend pipe, a large range of low-speed zones appeared in the horizontal straight pipe section after the fluid turns, and a backflow phenomenon occured at the same time. The airflow distribution was extremely uneven and the pressure resistance was large. After the deflector was arranged, the flow characteristics of the fluid in the elbow were effectively improved and the energy loss of the system was reduced. Based on the analysis of the influence of different number, structure and arrangement of deflectors on the uniformity of flow field and pressure drop loss of the bend, the optimal arrangement of deflectors in the shrimp-waist bend was proposed as follows: the number of deflectors was 3, the deflectors′ center angle was 60°, and the deflectors were all arranged backward.

Interval prediction of short-term regional photovoltaic power based on BP neural network

SUN Donglei, WANG Yan, YU Yixiao, HAN Xueshan, YANG Ming, YAN Fangqing

Journal of Shandong University(Engineering Science). 2020, 50(5): 70-76. doi:10.6040/j.issn.1672-3961.0.2019.706

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High penetration photovoltaic power brought severe challenges to the sage and stable operation of power systems. Considering the limitations of individual photovoltaic power prediction, this paper proposed an interval prediction method of regional photovoltaic power based on BP neural network, which extracted correlation through mutual information, and applied principal component analysis(PCA)to data dimensionality reduction. Taking the advantages of the data mining and nonlinear relation fitting for BP neural network, the uncertainty of regional photovoltaic power prediction could be quantified by the combining the neural networks and nonparametric probabilistic prediction methods. Experimental example used 10 photovoltaic plants in an area in China and compared the method of no data dimension reduction of original data with the proposed method in this paper. The 80% and 90% confidence intervals of the two models were calculated, which showed that the confidence intervals of the proposed mothed were narrower. At the same time, the proposed model predicted the 80% and 90% confidence intervals with 72 hours in advance, the results verified the feasibility and advance of the proposed method.

Numerical simulation of the tangent circular-to-rectangular transition duct

CAO Hongzhen, QI Jinsheng, YUAN Baoqiang, DU Wenjing, WANG Zhan

Journal of Shandong University(Engineering Science). 2020, 50(5): 77-82. doi:10.6040/j.issn.1672-3961.0.2020.169

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ANSYS Fluent was used to simulate the circular-to-rectangular transition duct. The accuracy of the numerical model was verified by experimental data. The difference between the concentric and tangent CRD(circular to rectangular duct)was compared,then the influence of the diffusion tube length on the flow field was explored, and the tangent CRD with high diffusion angle was optimized by adding deflectors. The simulation results showed that the length(diffusion angle)had a nonlinear relationship with the total pressure drop of the flue and the uniformity of the flow field. For tangent CRD with high diffusion angle, adding deflectors was more effectual to reduce local loss of the pipeline and improve the uniformity of the flow field.

Effect of gas components on the discharge characteristics of the wet electrostatic precipitator

WANG Lei, ZHANG Yulei, LI Zhaodong, ZHANG Jinfeng, WANG Xiang

Journal of Shandong University(Engineering Science). 2020, 50(5): 83-89. doi:10.6040/j.issn.1672-3961.0.2019.748

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To study the effects of gas components on the corona discharge characteristics of the wet electrostatic precipitator, a test bench was built. The effect of O₂, H₂O, and dust concentration on the discharge current were discussed in detail, results show than the O₂, H₂O and, dust in the flue gas had an inhibitory effect on the corona discharge and the negative ion concentration and electrostatic-field uniform were greatly improved with the increase of the O₂, H₂O, and dust concentration in the flue gas. The inhibitory effect of these components on the discharge current became weaker on a higher applied voltage. The descending rate of the discharge current was not a constant with the increase of O₂ concentration in the flue gas when the O₂ concentration was higher than 6%, the discharge current descended rapidly. The distribution of the electricfieldon the surface of the discharge electrode was twisted because of the aggregation of the liquid droplets. Wet electrostatic precipitator had a wide range of operating voltages and the onset voltage was lower and the breakdown voltage was higher under high water content in the flue gas. Dust concentration showed a linear correlation of the discharge current and the inhibitory effect increased when the dimensions of dust were smaller.

Comprehensive benefits analysis of power supply side of regional power grid with electrode-type electric boiler

GE Weichun, LI Zhao, ZHAO Dong, LI Zhenyu, YE Qing, FU Yu, YU Na

Journal of Shandong University(Engineering Science). 2020, 50(5): 90-98. doi:10.6040/j.issn.1672-3961.0.2019.571

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To improve the comprehensive benefits of regional power grid after the consumption capacity of wind power accommodation, and use the existing trading rules of electric peak regulation ancillary services, this paper established a comprehensive evaluation index of regional power grid comprehensive benefits based on entropy weight method. Considering the uncertainty of wind power and the peak-shaving auxiliary services, the comprehensive benefits evaluation model of regional power grid was established based on the holistic model method. The correctness of the proposed model was verified by simulation. The results showed that the scheme with electrode type electric boiler on the power supply side could improve the wind power consumption capacity of regional power grid compared with the alternative scheme. At the same time, it provided enough flexibility for system and effectively improved the comprehensive benefits of the power side of regional power grid.

Faulty phase and line selection method based on the feature extraction of the phase current in the selected frequency band

ZHANG Hejun, WANG Peng, XU Kai, SHI Fang

Journal of Shandong University(Engineering Science). 2020, 50(5): 99-106. doi:10.6040/j.issn.1672-3961.0.2020.024

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In order to improve the accuracy of the faulty phase and faulty line selection, a method of faulty phase selection and faulty line selection is proposed based on the wavelet analysis of the three phase transient current signal. The fault phase was identified by the difference of transient current correlation between faulty phase and healthy phase. Then the transient current of each line was decomposed and reconstructed by wavelet packet, the reconstruction coefficient ratio is calculated for each line based on the transient current energy in the selected frequency band, and the ratio difference was used to identify the faulty line. A 10 kV distribution network consisting of overhead-cable hybrid line was built in PSCAD software, several simulation cases were used to verify the correctness of the proposed scheme considering different neutral grounded mode and fault resistance.

Research advance in the source, water pollution status and treatment processes of perchlorate

Baoyu GAO,Wen SONG,Guangping YAO,Qinyan YUE

Journal of Shandong University(Engineering Science). 2020, 50(5): 107-117. doi:10.6040/j.issn.1672-3961.0.2019.572

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Perchlorate was widely used in military manufacturing, aerospace and industrial production, which had high stability, high water solubility, strong oxidizability and low volatility. With the flow of air and water migration, increasingly serious perchlorate water pollution caused widespread concern worldwide. Therefore, many countries carried out a comprehensive research and investigation on the source, water pollution status and treatment technology of perchlorate. However, China still had a few reports on perchlorate study, seriously neglecting the situation and treatment research of perchlorate pollution and lacking relevant environmental quality standards and safety concentration limits. This paper reviewed the source, hazard and water pollution status of perchlorate, analized the existing worldwide perchlorate concentration limit standards, and summarized the research progress of perchlorate treatment process in order to provide some references for further development of perchlorate study and formulation of relevant regulations in China.

Spatial and temporal analysis of network public opinion evolution of typhoon “Mangkhut” based on Weibo data

ZHANG Yan, LI Yingbing, ZHENG Xiang

Journal of Shandong University(Engineering Science). 2020, 50(5): 118-126. doi:10.6040/j.issn.1672-3961.0.2019.371

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Internet public opinion was the sum of the public various emotions, attitudes and opinions on related topics. This paper applied the sentiment analysis model, dynamic evolution model, topic clustering model, network community model and geographic visualization technology to the typhoon disaster assessment. This research fully illustrated how the public opinion on typhoon “Mangkhut” evolved by analyzing the 25 798 Weibo related from the two perspectives of emotional value and discussion heat. By utilizing LDA clustering method the negative impacts of typhoon “Mangkhut”'s landing and “Hunan toll station event” on public sentiment were found. After collecting the geographical location information of those typhoon “Mangkhut” related Weibo, a network-community model of 21 cities in Guangdong province was established and the model tested the ability to explore the affected cities through such indicators as users' sentiments, city word frequency, users' location, and network node activity. Spatial interpolation was performed based on the 24 h maximum rainfall data from 38 meteorological stations in Guangdong province. Precipitation was mainly concentrated in the southern part of Guangdong. Heavy rains occurred in Yangjiang City, which caused severe flooding and the lowest emotional value.

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