Table of Content

30 December 2019, Volume 25 Issue 6

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Research Articles

Reliability analysis of rail transit LTE-M communication system

Junjie XIE, Guoxin ZHENG

2019, 25(6):  859-869.  doi:10.12066/j.issn.1007-2861.1984

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Urban rail transit construction is undergoing rapid development in China now. This paper addresses the issue regarding the application of long term evolution-metro (LTE-M) wireless communication system in the communication based train control (CBTC) system. Starting from the theory of reliability, frameworks of different CBTC communication systems using 1.8 GHz LTE-M network have been established and the reliability model proposed with relevant formulas derived. Drawing on the experience of the maglev 38 GHz CBTC system which has high reliability, a system framework based on dual redundancy and double cross connect has been designed. With this new system framework, the reliability of rail transit communication system becomes increased, which in turn provides hope for better use of LTE-M in city rail transit.

Neural network for fatigue life of wind turbine blade numerical calculation of approximate model

Lei WANG, Jingui LU, Lewei LI

2019, 25(6):  870-878.  doi:10.12066/j.issn.1007-2861.2016

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By means of structural approximate analysis based on neural network, approximate calculation model of neural network for fatigue life of wind turbine blade is established. And, the numerical experiments of different parameters for constructing the model of neural network for fatigue life approximation computation of wind turbine are made. The results show the influence of the number of learning samples, the number of hidden layers elements of the neural network, and the learning accuracy on the approximate calculation results of the fatigue life of wind turbine blades. It is helpful for improving the accuracy in calculating the fatigue life value of wind turbine blade based on the approximate model of the wind turbine blade fatigue life neural network. The approximate calculation method of wind turbine blade fatigue life based on neural network provides a new calculation method for calculating the fatigue life performance of wind turbine blades.

An improved artificial potential field method constrained by a dynamic model

Zhijiu HAN, Wenjiang WU, Xiaowei LI, Dan ZHANG, Chunxin LI

2019, 25(6):  879-887.  doi:10.12066/j.issn.1007-2861.2179

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It has been claimed that local minima are an inherent problem of the traditional artificial potential field (APF) algorithm, which is employed for unmanned aerial vehicle (UAV) path planning. An improved APF algorithm is proposed. By introducing a swerving force, a quick escape from the local minimum can be achieved. After analyzing the dynamic characteristics of a UAV, an angular constraint was introduced to improve the APF method. Through simulations, it is verified that the improved algorithm considers the short distance, smoothness, and safety of the path. Therefore, it is more suitable for the path planning of fixed-wing UAVs.

Axis rules of VR film editing of scenes

Tingting ZHANG, Yan ZHANG, Feng TIAN

2019, 25(6):  888-897.  doi:10.12066/j.issn.1007-2861.2160

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A virtual reality (VR) image viewpoint over-axis evaluation experiment was designed to explore the application feasibility of ordinary film montage design elements in VR movies. By analysing the objective data of eye tracking and spatial markers as well as the subjective data of visual continuity perception, spatial perception, immersion, and comfort, the influence of a VR image over-axis lens assembly on the audience is studied; the feasible axis rules are also summarized. The experimental results show that the VR image is not limited by the axis rule of traditional film. VR images have a unique set of rules. As such, when viewing VR images of different angles and different speeds, the objective spatial marker deviation, visual tracking degree, and subjective score can be maintained within the acceptable limits. This demonstrates that it is possible to cross the traditional axis to shoot in VR formats. No discomfort is caused to any users that took part in this research.

Dynamics model of HIV/AIDS intervention in MSM population

Xiaojiao LIANG, Yuhua RUAN, Jie LOU

2019, 25(6):  898-907.  doi:10.12066/j.issn.1007-2861.2013

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This paper addresses the issue of HIV prevention in the men who have sex with men (MSM) population through the dynamics model. It suggests that in the context of "the three 9%" prevention targets set by UNAIDS the most effective measures to be taken at the present stage can be the increase of intervention among susceptible people, and concrete methods include education, increase of condom use and HIV testing. When these measures are in place, HIV infection can be better controlled in the local community.

Local properties of ${p}$-subgroups and ${p}$-nilpotency of finite groups

Lingling HAN, Xiuyun GUO

2019, 25(6):  908-917.  doi:10.12066/j.issn.1007-2861.2031

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Let $G$ be a finite group and $P$ be a Sylow $p$-subgroup of $G$. Several sufficient conditions for a finite group G to be $p$-nilpotent group are given by means of some kind of commutativity of a special $p$-subgroup $\it\Omega(P\cap O^{p}(G))$ in $G$.

Thermo dynamic properties of spin-orbit-coupled two-dimensional Fermi gases

Chenggong LIANG, Yunbo ZHANG

2019, 25(6):  914-923.  doi:10.12066/j.issn.1007-2861.2150

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Using the mean-field theory, we investigate the thermodynamic properties of two-dimensional Fermi gases with spin-orbit coupling and Zeeman field. By solving the gap and particle-number equations, we discuss the influences of spin-orbit coupling and Zeeman field on the isothermal compressibility, pressure, superfluid order parameter and entropy, and find some anomalous behaviors different from the three-dimensional systems. It is indicated that due to the influences of spin-orbit coupling and Zeeman field, the isothermal compressibility and the pressure do not change with the interatomic interactions in the Bose-Einstein condensate (BEC) limits, which is distinctly different from the case of three-dimensional systems, where these two thermodynamic quantities change linearly with the interactions. In the Bardeen, Cooper and Schrieffer (BCS) limits, the isothermal compressibility and the pressure sensitively depends on the strengths of spin-orbit coupling and Zeeman field. In appropriate parameters, by adjusting the spin-orbit coupling and the Zeeman field we also observe non-monotonic changes of the isothermal compressibility, pressure, superfluid order parameter and entropy. In addition, it is found that the spin-orbit coupling and the Zeeman field leads to opposite changes of the entropy between the normal phase and the superfluid phase.

Degradation of Simazine in aqueous solution by electron beam

Wen MAO, Minghong WU, Cheng PENG, Hang CHENG, Gang XU

2019, 25(6):  924-932.  doi:10.12066/j.issn.1007-2861.1945

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Simazine as a widely used triazine herbicide is toxic to human body and is detected in surface water. It is necessary to remove Simazine. Traditional methods cannot break the triazine ring of Simazine and therefore cannot mineralize Simazine. Electron beam was used to degrade Simazine. The results show that degradation rate of 1 mg/L Simazine reaches 99.0% under 4 kGy irradiation. This indicates that electron beam can effectively remove Simazine according to the first order kinetics. Acidic condition (pH=5) and 2 mmol/L H$_2$O$_2$ can greatly promote degradation. The effects of different radical scavengerson degradation and concentration variation of ions produced in the degradation process indicate that both hydroxyl and hydrated electrons are important in the process. A possible degradation path is proposed in combination with the products detected with LC-MS/MS.

Degradation behavior of antidepressant amitriptyline under electron beam irradiation

Fei DENG, Xu LI, Debao YUAN, Tao ZHAO, Wen MAO, Minghong WU, Gang XU

2019, 25(6):  933-942.  doi:10.12066/j.issn.1007-2861.1955

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Antidepressants are an important part of pharmaceutical contaminants that are new pollutants becoming potential threat to the environment. The existing sewage treatment techniques can hardly treat them effectively. This study focuses on the application of electron beam irradiation to degradation of antidepressant amitriptyline (AMI). The influencing factors include initial concentration, irradiation dose, pH, amount of H$_{2}$O$_{2}$, various atmosphere conditions and different ions. The degradation behavior of AMI in real water environment was simulated, and possible degradation paths were proposed according to the product analysis. The above mentioned factors have shown important influences on the irradiation degradation of AMI. Degradation of target AMI obeyed the pseudo first-order kinetic equation. When the dose of irradiation was 5 kGy, the target pollutant was completely degraded, meaning that electron beam irradiation is an effective means to treat wastewater containing AMI.

Non-enzymatic glucose biosensor based on Ag/AgCl/Polydopamine-Graphene composite

Rui WANG, Yiyang HU, Xiaomeng JIANG, Pandeng ZHAO, Lingli CHENG, Zheng JIAO

2019, 25(6):  943-949.  doi:10.12066/j.issn.1007-2861.1947

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According to self-polymerization property of dopamine and reductibility, polydopamine/silver composite/graphene was synthesized in one step. In addition, the graphene compound fixing on the surface of glassy carbon electron as a working electrode was used to construct a non-enzymatic glucose sensor. With a series of characterization methods such as X-ray power diffraction (XRD) and Raman spectrum, polydopamine/silver composite/graphene is synthesized successfully. Further, concentration of polydopamine/silver composite can be controlled by the reactive time. Electrochemical performance was tested with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The biosensor has shown a good linear relationship under the condition that concentration of glucose is between 5 mmol/L and 9 mmol/L

Preparation and properties of hollow ZnCo$_\textbf{2}$O$_\textbf{4}$/ZnO nanoboxes derived from MOFs as anode materials for lithium ion batteries

Ziming GAO, Jingyu DONG, Dayong CHEN, Shoushuang HUANG, Zhangjun HU, Zhiwen CHEN

2019, 25(6):  950-956.  doi:10.12066/j.issn.1007-2861.1946

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Graphite is commonly used as an anode material in lithium ion batteries. However, it cannot meet the increasing needs of higher capacity because of low specific capacity (372.0 mA$\cdot$h/g). Thus, rationally synthesis and design of high performance anode materials is a key factor in improving energy density and electrochemistry properties of lithium ion batteries. ZIF-8 was synthesized and encapsulated with ZIF-67 to form core-shell ZIF-8@ZIF-67. This was followed by a subsequent annealing treatment to obtain hollow ZnCo$_2$O$_4$/ZnO nanoboxes. Morphologies and structures of hollow ZnCo$_2$O$_4$/ZnO nanoboxes were characterized with XRD, SEM and TEM. When tested as anode materials for lithium ionbatteries, the hollow ZnCo$_2$O$_4$/ZnO nanoboxes exhibited enhanced performance. Specifically, discharge capacity of 1 536.8 mA$\cdot$h/g was achieved in the first cycle, and retains 780 mA$\cdot $h/g after 100 cycles at a current density of 100 mA/g.

Determination of basic parameters of SWCC for clayer soils

Dean SUN, Zhou ZHANG, You GAO, Bo CHEN

2019, 25(6):  957-964.  doi:10.12066/j.issn.1007-2861.1977

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A pressure plate method and vapor equilibrium technique with saturated salt solutions are used to investigate the water retention behavior of Shanghai soft clay in a wide suction range. From the relation between suction and degree of saturation, the air entry value is about 580 kPa and residual suction value is about 13.8 MPa for Shanghai soft clay layer. A method for determining air entry value using the relation between suction and water content is proposed, which is practical for the specimens with large volumetric shrinkage or deformation due to drying. Based on the deformation characteristics of the soil, the air entry value is about 600 kPa and residual suction value is about 13 MPa determined by using the above method, which is consistent with actual values. The air enter value and residual point of the specimens are determined with large volumetric shrinkage or deformation difficult to measure due to drying, as proposed by the water content versus suction relationship. This method can be used to avoid the effect of the volume measurement on the determinationof the air entry value and residual point.

Vibration analysis of cracked beam based on crack's equivalent rotational spring model

Yuan DAI, Tianyu WANG, Xiao YANG

2019, 25(6):  965-977.  doi:10.12066/j.issn.1007-2861.1978

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Based on an equivalent rotational spring model of crack, computation methods of dynamic characteristics and dynamic responses of cracked beams were investigated. On the basis of the equivalent flexural rigidity of the cracked beam, a method for obtainingageneral solution to the dynamic governing equation of cracked beam is established. A unified explicit expression of the vibration mode of the Euler-Bernoulli beam with an arbitrary number of cracks is presented. Natural frequencies of simply-supported, cantilever and clamped-clamped cracked beams are analyzed numerically. The dynamic response of the simply-supported cracked beam subject to a concentrated harmonic load is studied. Influences of depth and number of cracks on the dynamic characteristics and dynamic response are examined, revealing that the natural frequencies decrease with increased depth and number of cracks, and influence of the crack depth on the natural frequencies is more remarkable when the crack depth is large. There is a cusp on the mode curve of the cracked beam at the crack location, and slope change of the mode curve at the crack location increases with the increase of the crack depth.The crack has no influence on the natural frequencies and the modes of the cracked beam when the bending moment of the beam at the crack location is zero. Furthermore, the mode superposition method can be usedto analyze dynamic responses of acracked beam due to orthogonality of the modes of the cracked beam.

Analytical solution for free vibration of Timoshenko beam with different modulus

Yang YANG, Wenjuan YAO

2019, 25(6):  978-989.  doi:10.12066/j.issn.1007-2861.1976

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Free vibration of a beam with different modulus in tension and compression was studied. Unit body under a pure shear condition with different modulus in tension and compression was used to derivean expression of shear elasticity modulus with variational elasticity modulus. Based on elastic mechanics, structural mechanics, and the theory of different modulus, a vibration differential equation of Timoshenko Beam and Euler-Bernoulli beam is established, and the free vibration frequency of a simply supported Timoshenko Beam calculated. Considering different modulus, the position of neutral axis have a step change in the period of vibration, making the principle mode function piecewise. The results indicate that different modulus of a material has a great influence on the natural frequency of beam, which induces decrease in then at ural frequencies and therefore is worth consideration in structural vibration.

Stability analysis of reinforced slopes based on strength reduction theory

Jie GU, Mengxi ZHANG

2019, 25(6):  990-1002.  doi:10.12066/j.issn.1007-2861.2033

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Based on finite element method ABAQUS and strength reduction theory, the numerical simulation and sensitivity analysis of the soil slope with and without reinforcement were conducted. The influence of geometrical parameters of slope, strength and stiffness of soil, permutations and combinations pavement of geogrids on the slope stability was studied. The results suggested that soil cohesion had the most obvious impact on the safety of slope, and that other factors like soil internal friction angle, slope angle, permutations and combinations of spacing of geogrids were also significant in affecting the safety of slope. It was noted that when geogrids buried across the potential sliding surface (the plastic region of unreinforced slope), the displacement of slope could be confined obviously and the slope stability could get improved efficiently.

Exploring factors influencing deformation of retaining structure in orthogonal tests

Xu LIU, Jinming XU, Shaofeng LIU

2019, 25(6):  1003-1012.  doi:10.12066/j.issn.1007-2861.1950

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Excavation of deep foundation pit may result in deformation of supporting structures and surrounding soils. These deformations have different sensitivities to different influencing factors. Taking Shanghai Yangtze River Tunnel Project as an example, this study establishes a geometrical model of the foundation pit excavation based on actual soil distributions. The finite element analysis software ABAQUS was used to simulate the excavation process of the foundation pit. Horizontal displacements of the diaphragm wall were examined during excavation. Comparison between the field monitoring data and the simulated ones was made. Three factors influencing horizontal displacement of the diaphragm wall were chosen: thickness of diaphragm wall and width/depth of narrow excavation, and for each factor tree levels were set. Thus a total of 9 numerical simulation tests were performed based on the orthogonal table L$_9$(3$^4$) using an orthogonal test technique. Range analysis and variance analysis were then made. The simulation results are close to the field monitoring data. Factors affecting horizontal displacement of diaphragm wall in a descending order are thickness of diaphragm wall, depth of excavation of narrow foundation pit, and width of excavation of narrow foundation pit. Thickness and horizontal displacement of the diaphragm wall show a positive relation, while width and depth of excavation of the narrow foundation pit and horizontal displacement of the diaphragm wall show a negative relation. The results may provide references in analyzing deformation of retaining structures in foundation pit construction.

Non-Gaussian wind pressure prediction based on LSSVM with spatial multipoint input

Zhiting LOU, Chunxiang LI

2019, 25(6):  1013-1022.  doi:10.12066/j.issn.1007-2861.2043

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In order to enhance the generalization performance and prediction accuracy of Least Square Support Vector Machines for the wind pressure on the building surface, the method of increasing the number of input points has been proposed in this paper. Through increasing the number of input points, more information can be providedfor least squares support vector machines, which in turn optimizes the performance of the forecasting model of least squares support vector machines. Then interpolation prediction and extrapolation prediction of measured wind pressure at different lengths are carried out respectively. Experiment results show thatwhen interpolation prediction and extrapolation prediction are used, the performance of wind pressure prediction can be improved through the increase of the number of input points, but with interpolation prediction,the performance is better than that of extrapolation prediction. When the number of training sets increases, increasing the number of input points has little effect on prediction performance.

Dynamic inventory and pricing joint decision model for substitutable apparel products with demand learning

Junjun GAO, Junxia YUAN

2019, 25(6):  1023-1033.  doi:10.12066/j.issn.1007-2861.1958

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This study is based on the current management practice in the supply chain of Chinese apparel companies. The impact of demand learning and demand substitution on the inventory management and pricing is examined. Apparel products with short selling seasons in an apparel supply chain comprised of a retailer and a manufacturer are considered. Assume that the products are supplied in two batches that are mutually substitutable in the same category. The selling season is divided into two periods: The initial order is placed at pre-season and delivered at the start of the selling season, and the final order is updated after learning the actual demand in the first period of selling season. In this framework, a joint decision model of dynamic inventory and pricing is established to help retailers and manufacturers determine the optimal quantity of orders and the wholesale price. Numerical experiments show effectiveness of the model and the application results.

Corporate disclosure Nash equilibrium of public companies

Jiameng MA, Sujia GUO, Yuanqin LI

2019, 25(6):  1034-1040.  doi:10.12066/j.issn.1007-2861.2117

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This study explores the mechanism of corporate disclosure governing corporate decisions andin doing so, explains the mixed evidence observed in previous literature. By establishing game theory models of corporate finance and considering the percentage of professional investorsin a company, this study analyses pure strategy Nash equilibrium and mixed strategy Nash equilibrium.It also reveals how information disclosure is indispensable in ensuring the smooth operation of capital markets. The study finds that a smaller proportion of professional investors is associated with greater total social benefit as a result of mandatory corporate disclosure. When the proportion of professional investors is below a certain threshold, mandatory disclosure is necessary to maintain market stability and avoid market failure. Compulsory disclosure causes a greater increase in total social benefit in the following cases: significant differences in return on investment, a larger investment scale, higher financing costs, and a greater non-disclosure penalty.