2017 volumne 38卷 Issue 01
Xu He,Yang Yi,Lei Zhipeng
Abstract: Based on vector tools and modeling software,this paper analyzed and summarized the structure characteristics of cicada’s wings.And then the element Beam189 and element Shell93 were used to construct finite element model which could reflect the main characteristics of cicada’s wings.The mechanical properties of cicada’s wings in gliding state were simulated and analyzed.In that state,the whole structure of cicada’s wings was found warping shape,and the maximum deformation and stress were close to the far nervure.With the change of sectional size of all kinds of nervure in same ratio,comparative calculation was done to obtain the maximum deformation of the corresponding cicada’s wings.The results showed that the increasing of cicada’s wings’ deformation corresponding to three kind nervure were 121.3% 、34.8% 、17.4% respectively,so their contribution to the stiffness decreased.Among them,front nervure provided main stiffness for cicada’s wings.With the change of the quality coefficient of reinforcement nervure,modal analysis was done to analyze the fundamental frequency changes which could prove suppression effect of reinforcement nervure on flutter.When the quality coefficient of reinforcement nervure was 22,the fundamental frequency decreases about 30%.
Zeng Falin,Zeng Shaobo,Li Jiankang
Abstract: The connecting rod was widely used in the automotive and mechanical structure of which main failure mode is vibration-damage.Vibration-damage was the main failure mode of connecting rod.The dynamic characteristics of the connecting rod were the main factors which affect the vibration of it.Therefore,by establishing vibration equation and using finite element software MIDAS,the modal analysis was done and the results showed that there was a certain regularity between the diameter ratio and,the natural frequencies,the angle and natural frequencies of the various model shapes at a fixed location and cross-section.This conclusion had been verified on the tractor-trailer.It provided a theoretical basis for the structural design or further structural optimization.
Zhang Hao1,Yang Ling2,Guo Yuancheng1
Abstract: In order to reveal the dynamic response rules of soft soil foundation beneath low embankment under traffic load,the in-situ tests for the dynamic pore water pressure in soft soil stratum were conducted.The distribution laws of pore water pressure under different embankment thickness and different running speed were analyzed.In addition,the additional settlement of soft soil stratum under long-term traffic load was analyzed by numerical simulation.The results showed that embankment fills could reduce the dynamic effect of traffic load.The dynamic response of underling soft soil foundation increased with the decrease of the embankment thickness,and the dynamic pore water pressure declined with the depth increases.Moreover,the long-term addition settlement of soft soil foundation could be expressed as exponential function of time under traffic load.
Qu Tongming, Wang Shuying, Liu Pengfei
Abstract: In order to clarify the disturbance mechanism of the soil around the earth pressure balance (EPB) shield affected by the squeezed and exhausted soil situation of tunneling,discrete element method (DEM) was adopted to establish two groups of two-dimensional numerical models of EPB shield tunneling.The comparisons were carried out to analyze the mesomechanical characteristics of soil at the tunnel face and its surrounding strata during the shield tunneling.This research shows that the shield squeezed the surrounding strata obviously when the soil in the chamber was not exhausted.The vertical displacement developed ovally,while the horizontal displacement developed circularly,all of which decreased with an increase in distance along the horizontal direction.When the soil in the chamber was exhausted,the soil ahead of the cutterhead was not densified obviously,the horizontal displacement was low,and the vertical displacement developed to be irregularly funnel-shaped and higher.When the soil in chamber was not exhausted,the influence of shield tunneling on soil stress ahead of the tunnel face was significant,and the distribution of the average horizontal stress at the tunnel face was uniform.However,with the soil being exhausted,the stress of soil ahead of tunnel face was similar to the initial soil condition,and the distribution of the average horizontal stress at the tunnel face varied greatly due to the soil exhausting.
Zhang Jun, Li Zhihong, Jia Hong
Abstract: The adhesively bonding technology has been widely used.The delamination and cracking failure is main failure form of adhesive structure.This paper used the VUMAT subroutine and bonding structure models based on the bond behavior of the contact interface to establish the adhesive structure of five layers.The different crack processes of butt joint and lap joint were simulated.The results showed that the adhesive structure failures was consistent with the predicted under the bonding strength of interface less than or greater than the adhesive layer.The fracture occurre on the weak bonding layer.The adhesive layer and the bonding interface occurre failure simultaneously under the bonding strength of interface equal to the adhesive layer.The fracture mechanisms of lap joint are the same with the butt joints.These findings can be useful in practical engineering analysis of the bonding strength.
Zhong Committee1,Duanmu Weike2,Li Hualin2,Liang Tianshui2
Abstract: When a fire occurd in tunnel,the longitudinal ventilation was used for personnel evacuation and smoke extraction.The stratification of smoke layer would be destroyed under high ventilation velocity,and would lead to smoke bifurcation flow,which was harmful to evacuation.The numerical simulations were conducted to investigate the influence of transverse fire locations on smoke bifurcation flow.The phenomena of smoke bifurcation flow with different transverse fire locations were studied.The results showed that the bifurcation flow was symmetric when fire located in the central line of tunnel;and a S-shaped flow occursed in a near wall fire situation.The critical velocity of smoke bifurcation flow increased exponentially when fire source moved to the sidewall.
Guo Xiali1,Zhang Fanying1,Chen Hongkun2,Luo Yating1
Abstract: The effects of various concentrations of glucose and Mn (Ⅱ) on degradation of sulfametoxydiazine sodium (SMD-Na) by Phanerochaete chrysosporium were investigated through batch experiments.The results showed that the degradation efficiency of SMD-Na and the fungal biomass were very low without glucose and increased with the rise glucose concentration from 3 g/L to 10 g/L.At the same time,the SMD-Na biodegradation had the positive relevance of manganese peroxidase (MnP) and lignin peroxidase (LiP).The removal efficiency of SMD-Na and MnP activity increased with the rise Mn(Ⅱ) concentration from 0.01 mmol/L to 0.1 mmol/L.However,the Mn(Ⅱ) concentration had no significant effect on LiP.
Wang Dingbiao, Zhang Xiying, Han Yong, Deng Jing, Dong Zhen
Abstract: ANSYS Workbench is widely used for multiobjective optimization,by which we made an optimization study on phase-change heat transfer of the plate heat exchanger with the fusiform dimples.And the influence of R,L,D on the thermal-hydraulic performance was explored with Nu,f and PEC serving as the objective function.The results showed that the volume fraction of water vapor around the fusiform dimples was significantly higher than the smooth plate which was far away from fusiform dimples.It proved that the plate with the fusiform dimples has a very good strengthening effect on phase-change heat transfer.And that with the corresponding parameter setting the thermal-hydraulic performance of the fusiform dimples was higher than the circular dimples.Within the scope of the study,the optimal structure parameters was R =3 mm、L =5 mm、P =24 mm,and the objective function was PEC =2.16,Nu =137.15,f=0.187 4.
Wang Yongqing1,Zhu Bing2,Zhao Di1,Jin Zunlong1
Abstract: The characteristics of a flow duct with orthogonal waves were numerical studied by using CFD code Fluent with a lower Reynolds number.The numerical simulations were verified by experimental results.The result indicated that heat transfer was enhanced in the duct with a lower fluid velocity.With the impact of duct geometry and fluid vicious force,the relative positions between streamlines and distribution of fluid velocity varied greatly with the fluid locations.Second flow came into being on cross sections along the duct.Fluid continually received strong function of stretching and folding,bearing varied bigger transverse velocity component.The magnitude and direction of fluid changed with the locations,and the intensity of stretching and folding changed as well.A complex 3D flow field was formed in the duct,which enhanced fluid mixing and heat transfer.The results and method could provide references for mechanism analysis and structure development.
Wang Weishu,Cui Qiang,Zheng Mengxing,Chen Gang
Abstract: In view of the temperature characteristics of semi circumference heated membrane water-walls in a 350 MW supercritical pressure boiler,a calculation program was built to obtain spiral membrane water-wall temperature distribution under different furnace loads.The results showed that:the uneven distribution of furnace heat load led to uneven heat of water-walls;temperature on the facing flame side of water-walls fluctuated within a narrow range,which was the same as the fin.The distribution of temperature on the facing flame side was low in the middle and higher on other sides.With the increase of height of furnace,temperature of waterwall rose and there was a certain fluctuation.The highest temperature appeared on the facing flame side of the fin,and the lowest temperature appeared on the inner wall of water-wall bus bar when BMCR load was 75%.
Liu Weiguo, Huo Da, Tan Bo, Gong Chao
Abstract: In view of commutation torque ripple in two sets of parallel winding with difference of 30 electrical degrees in dual-redundancy brushless DC motor,a technique with variable structure and current feed-forward was put forward.Current could be adjusted independently by this strategy,combined with the characteristic of the difference of 30 electrical degrees in the corresponding phase to ensure the stability of commutation torque.In order to increase the response from current,feed-forward control was proposed to improve the current charge rate.The results showed that,compared with traditional method,it could minimize the commutation torque ripple in double-winding permanent brushless DC motor and enhance the stability of the operating system.
Sun Xiaoyan, Shi Liangzhen, Xu Ruidong, Zhang Yong
Abstract: The wind power forecasting was essential to the stability control of the grid connected operation,the economical dispatch,and so on.However,due to the variety of nature of wind,wind power had great uncertainties.Effectively expressing the uncertainties in wind power forecasting is crucial for improving the reliability of the forecast.Most existing methods focued on point forecasting,which can hardly quantify the uncertainties.To overcome the weekness,this paper proposed a novel interval-based forecasting model to quantify the uncertainties.A new interval sample selection method was firstly presented to reflect the uncertainties of wind power based on similar days and interval similar metric.Secondly,the echo state network were designed to predict the interval-based wind power in a short time due to its merits in time series predictions.The outstanding stability of the forecasting model was guaranteed by employing the recursive least squares algorithm to adjust the output weights of the echo state network.The prediction interval coverage probability (PICP) and mean prediction interval width (MPIW) were applied to evaluate the performance of our interval forecast on wind power.The experiments empirically demonstrated the feasibility and effectiveness of the proposed algorithm.
Zhang Zhen, Liu Bo, Li Long
Abstract: In this paper,an iris recognition method of multiple features extraction and fusion was proposed,which was different from the classical iris recognition methods that focused on a single texture feature.Firstly,the collected iris images were preprocessed.Secondly,features of the iris were extracted by using Log-Gabor filter and Haar wavelet respectively,and two similarity values were calculated by adopting Hamming Distance and Weighted Euclidean Distance.Finally,the Support Vector Machine was used to fuse the values of similarity and classify.The experimental results verified that the proposed method is effective and a higher recognition rate was achieved.
Dong Hailong, Tang Minan, Cheng Haipeng
Abstract: In order to alleviate traffic congestion and reduce the time of vehicles waiting,of unbalaned intersection,this paper adopted a traffic signal control method based on artificial fish swarm algorithm,which could achieve multi-phase and variable phase sequence intelligent control at five-road intersection.Firstly,the passable urgency of a red light phase was decided according to its vehicle queuing length and the red light duration;and the highest passable urgency phase should be the next green light phase.Secondly,the current vehicle queuing length of green light phase and the difference between vehicle queuing length of the next and current green light phase were taken as the inputs.The fuzzy neural network controller was used to control delays of the green light.In order to avoid fuzzy neural network falling into local minimum,artificial fish swarm algorithm had optimized the parameters of it.After simulation studies in the case of different rates of vehicle arrival,the results showed that this method was better than the traditional control in automatically adjusting the signal cycle,which reduced the average delay of vehicles for about 7.2%.
Han Jie, Zhang Qianlong
Abstract: In order to accurately diagnose the wind turbine gear box fault,the application of full vector spectrum was fully introduced in an experimental data processing of wind turbine drivetrain diagnostics simulator (WTDS).The result showed that full vector spectrum technology which based on homologous information fusion could find the correct preset fault location and accurately determine the nature of the fault on WTDS.
Tao Zheng, Hu Bin, Liu Xu
Abstract: The computation accuracy was often insufficient in the rod-type ultrasonic motor design because of the adopted continuous composite structure finite element model.In this paper,a method for modeling the rodtype ultrasonic motor vibrator based on bolt pretension was presented and the influence of bolt pretension and contact surface friction coefficients on modal frequency was analyzed.Experiments showed that,the deviation of motor working mode frequency is 0.05%,0.47%,0.64% respectively through this finite element analysis method with consideration of bolted-joint nonlinear factors.Consequently,the calculation accuracy was good.It was shown that the finite element model based on bolted-joint nonlinear system was more conducive to motor performance design and estimation.
Zheng Jin1,Zhang Zhenya2,Wang Long2,Liu Wentao2,Zhu Chengshen2
Abstract: PA66/SiO2 nanocomposites were prepared by the in-situ polymerization method.The structure of SiO2 in polymer matrix was studied by TEM and SEM,and the melting and crystallization behaviors of composite materials were analyzed by DSC.Mechanical and heat properties were tested,too.The results indicated that SiO2 dispersed well in PA66 with nano-scale when the SiO2 was 0.8%,the mechanical properties and thermal stability of PA66/SiO2 nanocomposites were superior to neat PA66,meanwhile,the crystallinitywas improved.
Qin Cong,Wang Yan,Chen Zehua,Sun Guang
Abstract: CuO and α-Fe2O3 nanomaterials were prepared by the chemical precipitation method.And,the pn type semiconductor metal oxide composite was successfully prepared by the deposition-precipitation method.The structure and morphology of the as-prepared samples were characterized by the techniques of powder X-ray diffraction (XRD),scanning electron microscope (SEM),transmission electron microscopy (TEM) and Xray photoelectron spectroscopy (XPS).The analysis results indicated that when the content of CuO was small,the CuO nanoparticles were high dispersed on the surface of α-Fe2O3.When the content of CuO over 30mol%,the new phase of CuFe2O4 was formed.The SEM and TEM images showed that the obtained sample consisted of the nanoparticles with the size of about 10 nm.
Patiman Nizamuddin,Abuliz Imiti
Abstract: In this paper,in order to optimize the preparation conditions and to improve the sensitivity of LiFePO4 thin film gas sensor,the LiFePO4 was synthesized by hydrothermal method and dispersed in polyvinyl alcohol (PVA).The PVA dispersed LiFePO4 thin film/tin-diffused glass optical waveguide sensing element was fabricated via spin-coating a LiFePO4-PVA dispersion solution onto the surface of tin diffused glass optical waveguide;In the end,the gas sensing properties was monitored using the planar optical waveguide detection system.The testing results indicated that,the best condition for fabrication of sensing film was:the dispersant concentration was of 2wt.%,the ultrasonic vibration time was 2 h,dispersion temperature was 25 ℃,and the corresponding sensing element exhibited good responsible to BTXs (benzene,toluene,xylene).The detection limits for the PVA dispersed LiFePO4 thin film/tin-diffused glass optical waveguide sensor was 1 × 10-8-1 × 10-3.After the dispersion,the sensitivity was increased.
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