Abstract:

Abstract:

Abstract:  Pre-grouting reinforcement was a common pattern in subway construction. The grouting model test equipment with an assembly of stable pressurization system, model box system and grouting system was developed  to study diffusion and distribution of slurry in pre-grouting projects. Sodium EDTA titration method was improved to detect the cement content in cement soil. And this was combined with cutting samples in the range of the grouting influence to develop a block titration method and implement a complete grouting test. Results showed that the grouting model test equipment worked well, improved sodium EDTA titration method can detect the cement content in cement soil accurately, a visually clearer and more presentable distribution and diffusion range of slurry can be obtained by block titration method, a reasonable and feasible test method has been established to study the distribution of slurry for similar tests..

Abstract: An accurate understanding of the stress distribution of each layer of ACSR in the temperature field can provide theoretical basis for the safety design and fatigue analysis of overhead conductors . Based on the properties of ACSR materials and its collaborative deformation characteristics, the relationship between stress and temperature of wire strands is studied by theoretical analysis and finite element simulation. And the effects of average temperature and radial temperature difference on the stress of outermost aluminum strands of aluminum strand decreased with the increase of temperature. While the stress of steel core increase with the increase of temperature; when the radial temperature difference was considered, the outer aluminum strand stress increased with the increase of temperature fifference, and steel core aluminum strand internal stress decreased with the increase of temperature difference. When the temperature reached 20ºc, the outer layer of aluminum stress increased about 49%.      

Abstract: In order to analyze the dynamic response of carbon black modified asphalt mixture (CBMAM), the Simple Performance Test (SPT) was conducted on CBMAM and base asphalt mixture under the different test conditions of test temperature and loading frequency. The change law of gynamic modulus and phase angle for the two mixtures was analyzed.Using the Sigmoidal model, the shift factor of dynamic modulus and model parameters were gained according to the data. The master curves of dynamic modulus and phase angle of asphalt mixture are obtained and analyzed comparatively. The results indicate that the activation energy (ΔEa) and the absolute value of shift factor (log[α(T)]) of CBMAM are smaller than those of base asphalt mixture respectively at the temperatures lower than the reference temperature, while they are contrary at the temperatures higher than the reference temperature. The master curve of dynamic modulus goes up like "S" curve continuously with an increase in loading frequency. Phase angles of asphalt mixtures go up firstly and then drop with the increase in frequency. But the master curves of phase angle are not as smooth as those of dynamic modulus especially at high temperatures.The dynamic modulus master curve and shift factor can reflect the effect of loading frequency and temperature on the visco-elastic response of CBMAM. The dynamic modulus of CBMAM is bigger at temperatures lower than 37.8℃, which has better resistance to deformation. When the temperature increases higher than 37.8℃, there is no significant difference in the dynamic response of the two mixtures, the modification effect of carbon black for asphalt mixture is no very significant under the conditions of low frequency and high temperature.

Abstract: The safety margin of FSAE (Formula Student Automobile Equation) racing car should be lager. To meet the requirements of strength and stiffness, fully tap the potential for lightweight frame.This paper optimized topology design and section size of car frame in the SIMP method with the finite element analysis software. Considering the mesh of model remains unchanged and simulating three track actual conditions by the size of optimization method, we change the model parameter values,and the corresponding maximum deformation of car’s frame decreases by 7%, 7.5%, 14.7% respectively under the certain strengh and stiffness of car’s frame. When the maximum stress was less than 200MPa, the quality of the frame was reduced by 32%. Finally, through the modal analysis and test, optimization design of frame could effectively avoid the coupling effect and external excitation, the eight around the ring tesr time could be reduced by 3%. The racing car frame achieveed the purpose of light weight.

Abstract: The graphene oxide (GO) which has high thermal conductivity was mixed with water and glycol to form and the influence of the nanofluid on the heat dissipation of hydrogen internal combustion engine was studied. By comparative analysis of the change regularity for nanofluids’ thermal properties with the volume fraction of GO, while mesh generation and 3D numerical simulation for the cooling water jacket of hydrogen engine based on AVL Fire software, the information of velocity distribution, heat flux change and pressure loss can be obtained when coolant was GO-water and glycol nanofluids(the volume fraction of ethylene glycol is 10%, the volume fraction of graphene oxide were 0%, 1%, 2%, 5%). The results showed that the heat flux gradually increases and heat transfer capability evidently enhances while the concentration of nanoparticles increased, however it was caused total pressure increase between inlet and outlet in the cooling jacket and power loss of water pump also increased.

Abstract: In order to increase the utilization rate of lipase, the immobilization of lipase by azidation magnetic chitosan was investigated. The magnetic chitosan microspheres with particle size of 40~60 µm were prepared by suspension croddlinking method. The microspheres were modified by grafting and azide. Response surface methodology was used to investigate the effect of reaction conditions on the immobilized enzyme, and the optimum conditions for lipase immobilization were concentration of enzyme 4 mg/ml, reaction time 8.4h, reaction temperature 39.3ºc and the ph 7.0. In the optimum conditions, the immobilized enzyme amount of magnetic chitosan microsheres was 64.4 mg/g, with the actual value showing a good fit to the predicted value. The results suggested that this method could be uaed to immobilized lipase.

Abstract: The possible effects of microbial oxidation and removal of  As^Ⅲ in the presence of zero valent iron （ZVI）were studied. Quartz sand and that loaded with ZVI were filled into two up-flow fixed-bed reactors(R1 and R2) as support materials and microorganisms were inoculated and domesticated. The regularity of microbial oxidation of  As^Ⅲ was studied with varied hydraulic retention time t_HR.The results showed that we could get the highest capacity of icrobial oxidation at the bottom of the reactors. At higher t_HR, almost 100% of As^Ⅲ was oxidized in R1 and R2. When t_HR was changed to 0.67 h, R2 exhibited higher oxidation performance that R1. The presence of ZVI was more favorable for microbial oxidation of As^Ⅲ.

Abstract: Based on the cooling characteristics of the electric vehicle drive motor, a novel cooling structure the circumferential multi spiral structure, was proposed. The three dimensional numerical model of fluid flow and heat transfer in the shell was established. The flow field and temperature field of different water cooling schemes were calculated based on CFD technology. The numerical results showed that the temperature uniformity and cooling performance of Circumferential "Z" structure is better than the circumferential multi spiral structure; and the circumferential "Z" structure was suitable for the cooling of 135KW electric vehicle drive motor under the condition of inlet water temperature was 65ºC, with the optimal water flow rate 9.8L/min. However, the circumferential multi spiral structure could be used for higher power density of the motor cooling for the better performance of pressure resistance. The research provided a theoretical basis for cooling design and optimization of the small size and high power density motor.   

Abstract: In order to investigate the impact factors of single aerobic phosphorus removal process, sequencing batch reactor (SBR) was applied. Through altering reaction time and influent C/P, variations of PO43--P concentration, poly-β-hydroxybutyrate (PHB), on line parameters such as DO and ORP were investigated. The results showed that, when DO was below 0.6 mg•L-1, stable biological phosphorus removal was existed in single aerobic system. And decrease aeration time properly was helpful to enhance the phosphorus removal effect. The relation between C/P and phosphorus removal was complex, when PO43--P concentration was constant, increase C/P could enhance the processes of phosphorus release and uptake significantly; when carbon source concentration was constant, the effect of increase C/P was limited. The sludge PHB content at the end of feeding period was in proportion to the released phosphorus content, and showed little relation with influent C/P. The variation tendency of ORP could distinctly indicate the phosphorus removal progress, when ORP was below -150mv, significantly phosphorus release would happen. Under low DO condition, the micro-anaerobic environment caused by mass transfer resistance was the key reason for the take place of single biological phosphorus removal.

Abstract: In order to predict the accidents of oil drilling process in real time and accurately, an early warning method based on Continuous Hidden Markov Model (CHMM) was constructed. The patameters of average vaule in long-time and short-time were utilized to construct the characteristic which could reflect the changing trend of the original parameters. The CHMM model was established based on the characteristic variables and was trained by the history data. Then the matching probability was calculated by the forwardalgorithm and the threshold of the warning system was determined by the statistical method. For each kind of drilling faults, the strategy for judging the warning results based on multiple parameters was designed. The results of experiment proved that the CHMM waring model could predict the drilling accidents more promptly and effectively. 

Abstract: The stochastic small signal stability of single machine infinite bus power systems was investigated with consideration of the relationship between the system parameters and the stochastic disturbance in this paper. Firstly, according to the three different characteristics of the eigenvalues of the system coeffcient matrix, the mean stability and mean and square stability were discussed. It was showen that if the power system was asymptotically stable under no stochastic disturbance. Its mean stable and mean were aquare stable under small stochastic disturbance. The function of the bound of mean and mean square value with respect to the variance and random perturbation relation between stochastic intensity and system parameters was given. Finally, the powersystm was simulated under different stochastic intensity and the correctness of the proposed results was verified.

Abstract: In order to solve the modeling errors and external disturbances in the system,a stable robust hybrid tracking control scheme for wheeled robotic system with nonholonomic constraint is proposed. The hybrid control scheme combined DRNN neural network with nonlinear H_∞ method. DRNN neural network was employed to approximate the system uncertainty terms,and H_∞ control was utilized to achieve a desired robust tracking performance. Based on Lyapunov stability theory, the tracking errors of the closed-loop system were bounded. In addition, a specified H_∞ tracking performance was obtained by the proposed robust hybrid control even though the disturbances were merely integral bounded. Finally, the proposed control scheme was compaed with the computed torque control for nonholonomic mobile robotic system under the uncertainties and external disturbances. Simulation experiments showed that the proposed control strategy was effective.

Abstract: Aiming at locating the atarting time of autonomous motion, the EMG signal before the volunteers autonomous motion was taken as the research object. The EMG activation trigger point was selected as the starting time of autonomous motion, and then the effective time segment was determined. The frequency section of the motion preparation potential was difficult to be determined, the effective frequency band was determined by the method of combining the wavelet packet transform and the power spectrum analysis. The energy, mean and variance of the extracted signal were characterized by the support vector machine (SVM) for single detection of RP. The experimental resultts showed that: in the process of self motion of single detection RP, 15subjects in 9 experiment the highest detection rate was 77.5%-91.3%;each participant of the 9 groups the average detection rate was 68.2%-91.2%. The results of this paper could be useful to the application of motion preparation potential in asynchronous BCI system.

Abstract: The low-does CT（LDCT）scanning is an effective way to reduce the X-ray radiation dose. However, quantum noise caused by the reduction of radiation dose leads to degradation of image quality. We proposed a quality improvement algorithm of low-dose CT images based on the shearlet transformation. Firstly, LDCT image was transformed using the Anscombe transform, and the quantum noise was transformed into noise which approx imately obeyed Gaussian distribution. Secondly, the transformed image is decomposed into low-frequency coefficient sub-bands and multi-directional high-frequency coefficient sub-bands based on shearlet transform. Then, for high-frequency coefficient sub-bands of the low signal noise ratio, a noise variance estimation method basedon the residual autocorrelation power (RAP) was proposed, which was combined with Bayesian maximumposterior probability method to obtain the more accurate non-noise high-frequency cofficients. Finally, the reconstructed image was obtained using the shearlet inverse transform and anscombe inverse transform. A series of experimental results of quantitative evakuation and visual effects showed that the proposed algorithm outperformed the de-noising method based on wavelet domain. The quality of the reconstructed image, compared with the denoising algorithm based on wavelet domain, the Peak Signal Noise Ratio(PSNR) was increased averagely by 52.2%,and the Mean Structure Similarity(MSSIM) was increased by 34.4%.

Abstract: The paper investigates the modified function projective synchronization of complex dynamical networks with uncertain parameters 、external disturbance and time-varying coupling delay. Based on Lyapunov stability theory and some inequality techniques, the adaptive robust controller was designed, by which the drive and response systems can realize synchronize to a desired scaling function matrix and estimate the unknown parameters. The feedback control gains were determined by adaptive updated laws. The controller could overcome the effects of the external disturbances and time-varying coupling delay effectively. Numerical simulations illustrate the effectiveness of the proposed method.

Abstract: The method of extracting degradation features was proposed based on MEMD and MMSE to solve the problem that non-stationarity of fault signals of roller bearing and degradation condition, which was characteristic of non-ststionarity and hard to recognize. The character of MEMD was adopted to catch different scales of signals effectively during the process of multiscalization,  which made complexity of different degradation condition distinguished better than other methods. Firstly, multichannel signals corresponding to various degradation condition of roller bearing were decomposed adaptively using MEMD, then, the reconstructed signals by multiscale IMF was dealt with MSE analysis. The results showed that the proposed method could efficiently evaluate the degradation trend of roller bearing by handing the experimental signals.

Abstract: Drum brake is the core component to ensure safety of commercial vehicles. In order to solve the problem of dynamic performance in braking process, the coupling effect of braking force and friction heat on the brake drum under the braking conditions of emergency, repetitive and continuous braking was studied using ANSYS simulation method. The results show that it is prone to appear high temperature flash point on the inner surface of the brake drum under the emergency braking condition. Under the repetitive braking condition, the temperature and the stress of the brake drum are relatively large, which will cause decrease of the brake performance and crack generation. And under the continuous braking condition, the high temperature will cause the equivalent stress to increase, and it is possible to appear the heat fade.