Abstract:In the vibration of the horn, the damping characteristics of the ultrasonic horn and its coupling with the bolt / tool head will lead to obvious temperature rise. In order to analyze the temperature rise characteristic and explore its influence on the vibration stability of the ultrasonic horn, the total power density and temperature distribution of the longitudinal vibration horn were obtained by numerical simulation. The theoretical temperature rise of the ultrasonic horn was verified by infrared thermal imaging test, and the influence of bolts and tool heads of different materials on the temperature rise was analyzed. Combining the numerical modal analysis and experimental analysis, the influence of temperature rise on the resonant frequency and amplitude of the horn was further discussed. The results show that the temperature rise tends to be balanced during continuous operation of the ultrasonic horn, and the equilibrium point depends on the bolt material, horn material and environmental factors. For low damping TC4 horns, energy loss at bolt is the main heat source, of which 45 steel bolts generate 97.7% of the heat, while TC4 bolts and tool heads can significantly reduce the temperature rise. At the same time, it is found that the resonance frequency of the ultrasonic horn is linearly negatively correlated with the temperature rise. The amplitude is reduced due to the temperature rise, and both of them are stable at the equilibrium temperature point.

Abstract:A mold temperature analysis method for the hot stamping dies of complex formed parts considering the influence of different flow field distribution is proposed. First, the convective heat transfer coefficients at each node of the cooling water pipe wall were calculated by Fluent flow field analysis, and the influence of the differences in the flow field distribution caused by the water channel structure on the heat transfer capacity was considered in this process. Then, the processes of sheet forming and holding and quenching were simulated by LS-DYNA to obtain the temperature data of the blank. Finally, the A-pillar side beam was used as the research object to compare the simulation analysis results with the actual cooling effect on the hot stamping production line. The results show that the distribution of high temperature areas in the analysis result of the mold temperature based on the flow field analysis is consistent with the actual measurement. The maximum error at the 12 temperature monitoring points is 3.6 ℃，and the average error is 0.96 ℃. However, the temperature distribution and the maximum temperature difference point change in the simulation using the average heat transfer coefficient. The maximum error of the monitoring point is 9.1 ℃，and the average error is 4.96 ℃.The comparison between the simulation and experiment shows that the change of the flow rate has a significant effect on the heat transfer coefficient, and the mold temperature analysis method based on flow field analysis takes into account the effect of the differential distribution of the flow rate in the cooling channel of the hot stamping mold，which can be used for the analysis of mold temperature of complex parts and multi-cavity molds.

Abstract:Aiming at the requirement of wheel slip tracking control for automatic driving electric vehicle , this paper presents a full-state feedback wheel slip tracking controller based on fast terminal sliding mode state observer. Firstly, a wheel slip rate tracking control model taking the derivative of wheel braking moment as an input is established to avoid the effect of the discontinuity term in the input on the system stability and performance. Secondly, a fast terminal sliding mode state observer with the characteristic of finite time convergence is designed based on finite time stability and fast terminal sliding mode control theory in order to observe the unknown state information of the system in real time. Based on the estimation of the unknown state information of the system, a fast terminal sliding mode tracking control law is designed independently to realize the continuous and fast tracking control of wheel slip. Finally, a model-in-the-loop test system is built using vehicle dynamics simulation software to verify the feasibility and validity of the proposed wheel slip tracking controller.

Abstract:In order to study the aerodynamic drag reduction effect of the plasma on kind of vans, ground transportation system（GTS） model was taken as the research object. Numerical simulation was used to investigate the aerodynamic drag reduction effect of plasma arrangement angle and excitation voltage at three positions on the GTS model when the incoming wind speed was 20 m/s，and the drag reduction mechanism was analyzed. Then, the combined working conditions were analyzed. The results show that plasma can make the separation point of the flow move back and delay the separation of the flow by inducing the directional flow of gas near the wall, so as to reduce the pressure difference between the front and rear of the GTS model and reduce the aerodynamic drag coefficient of the vehicle. Moreover, plasma should be set behind and close to the flow separation point. The aerodynamic drag reduction effect is the best when plasma is applied to both sides of the tail of GTS at a single position, and the maximum drag reduction rate is 5.09%. The maximum drag reduction rate can reach 6.01% under combined condition. When the incoming wind velocity is constant, the plasma has the optimal arrangement angle and excitation voltage.

Abstract:It is far more difficult to reduce the temperature differences among cells in a battery module than to reduce the maximum temperature of module. In order that the cells can have better temperature distributing conformity, this paper designed a liquid cooling thermal management system by packing aluminum column in the gaps among the cells and set up an electrochemical-thermal coupling model for the cells. Comparative study of the impacts on the thermal properties of the cells exerted by liquid cooling system of aluminum columns under the combination modes of different entrance velocity，different section length and height was also conducted. The results indicated that the cooling performance of the aluminum column liquid cooling system with gradient variation of cross-section length and height and the temperature distributing conformity among the cells were better than those with the fixed values of section length and height. Under the condition that the discharge rate was 3C and the entrance velocity was 0.1 m/s，the maximum temperature difference among the cells in the module group based on the proposed coupling model was kept within 3.72 ℃，meeting the requirements of thermal management of the battery system. Finally, different discharge rates were verified through the simulation based on this model, indicating that the cells had better temperature distributing conformity.

Abstract:In view of the narrow range and small maximum transmission ratio of the existing Continuously Variable Transmission（CVT），this paper proposes a CVT driven by cam mechanism. The CVT adjusts the position of the intermediate lever fulcrum by the shifting device and changes the force arm to adjust the rotational speed of the follower and achieve the aim of stepless shifting. According to the change rule of the speed in the output end of the rocker arm，the speed of the swing arm is controlled to change according to a certain rule, and the output speed is compensated reversely，which improves the stability of the motion output .With the principle of inversion method, the cam contour curve and the swing arm contour curve are designed, separately, and the four groups of cams in the cam group are evenly staggered by 22.5° to ensure that at least one set of cams is in an effective push state during the operation of the mechanism to keep continuous motion output. The NX10 software is used to simulate the kinematics of the transmission mechanism. By analyzing the speed-time curve of the rocker arm under different gear ratios, the continuous and outputsmooth transmission output can be realized when the total transmission ratio of the CVT is within a certain speed control angle. The CVT can obtain a wide range of transmission and a large transmission ratio, which makes up for the shortcomings of the existing CVT, such as narrow range of transmission and small maximum transmission ratio.

Abstract:To study the cyclic softening/hardening behavior of high-speed railway gear steel 18CrNiMo7-6, RPL 100 electronic creep fatigue tester was used to carry out the uniaxial symmetrical strain cycling experiments on the gear steel under different strain amplitudes. Then, the ratchetting behaviour of gear steel 18CrNiMo7-6 under different stress conditions was tested to study the ratchetting evolution of gear steel under asymmetric stress cycling. The results show that the gear steel（18CrNiMo7-6） exhibits the cyclic softening characteristics under strain cycling and exhibits two stages of decaying ratcheting strain rate and constant ratcheting strain rate under asymmetric stress cycling. Then，a modified elasto-plastic cyclic constitutive model was established by introducing the evolution equation of ratchetting parameters related to the cumulative plastic strain into the Ohno-Abdel-Karim nonlinear kinematic hardening rule. The simulated results show that the model can reasonably predict the cyclic softening characteristics and the ratchetting evolution of gear steel（18CrNiMo7-6）.

Abstract:The inverter nonlinearity, flux spatial harmonics and detection errors give rise to DC offset and harmonics in the back Electromotive Force（EMF） obtained by the sliding mode observer（SMO），which results in harmonic ripple in the position estimates. This paper proposes a fifth-order generalized integrator（FOGI） based rotor position observer to solve the above problems. On the premise of frequency-locked loop（FLL） to ensure frequency adaptation, the FOGI helps to complete the accurate decoupling and improve the control performance of the Interior Permanent Magnet Synchronous Motor（IPMSM） position sensorless drive system. Under the action of the FOGI, the DC components and harmonics of the EMF estimates are more completely filtered.Thereby, the accuracy of rotor position calculated by the Phase-Locked Loop（PLL） can be improved. In this paper, the FOGI is compared with the fifth-order standard integral equation in the classic control system, and its parameter tuning process is fully and reasonably simplified, simultaneously,when the rapid convergence of rotor position estimation system is guaranteed. Finally, after comparing the performance of dynamic response and interference suppression with the traditional second-order generalized integrator（SOGI），the advantages and effectiveness of control strategy are demonstrated through simulation and 1.5 kW dsPACE semi-physical experiments.

Abstract:The electromagnetic losses generated at the armor rod segment of lighting wire are the main heat source for the high temperature of armor rod segment. The local high temperature may cause damage to the lightning wire. Based on the actual distribution characteristics of the contact points between the lightning wire and armor rod, a three-dimensional electromagnetic field simulation model of armor rod segment was established by Comsol. The electromagnetic losses density distribution of armor rod segment obtained by simulation was analyzed and discussed. Subsequently, the steady-state temperature rise experiment and the contact resistance measurement experiment were combined to verify the accuracy of the simulation model. Based on the simulation model, the relationship between the electromagnetic losses of armor rod segment and the relative permeability of steel and twisting parameters of stranded wires was explored. The research results show that the simulation models are accurate enough and the error is less than 6%. The electromagnetic losses of armor rod segment are mainly concentrated on the contact points between lightning wire and armor rod. The electromagnetic losses of each row of contact points gradually decrease with the increase of the axial distance. In addition, the electromagnetic losses of the armor rod segment are positively related to the relative permeability of steel and the axial distance of adjacent contact points.

Abstract:In order to extract the disturbance features accurately in strong noisy environment, a power quality disturbance detection and location algorithm based on improved wavelet threshold function denoising and Variational Mode Decomposition（VMD） is proposed. The improved wavelet threshold function is used to denoise the noisy power quality disturbance signal. The default scale can be determined by the Fourier transform. This paper uses the variational mode decomposition to decompose signals into some intrinsic modes. Hilbert transform is used to extract the characteristic information such as the amplitude and frequency of each mode. Meanwhile, the effective location of the start and stop time of the disturbance signal is realized by the principle of singular value decomposition. A power quality disturbance detection platform based on PXI and LabVIEW is also built based on the above algorithm. The accuracy and effectiveness of the proposed algorithm are verified by single disturbance, complex disturbance and actual disturbance data. Compared with the existing empirical mode decomposition and ensemble empirical mode decomposition, the proposed algorithm not only has the ability of resisting modal aliasing and false components, but also has high accuracy and robustness under the environment of strong noise.

Abstract:For the tedious parameter settings of sliding mode controller of bridge crane and insufficient global searching ability of Cuckoo Search（CS），an improved Cuckoo Search algorithm based on adaptive crossover operation point selection（ASCP-CS） was proposed and applied to the adjustment of parameters for the sliding mode controllor of bridge crane. The ASCP-CS algorithm improves the adaptive searching steps based on the CS algorithm, and introduces the adaptive selecting chromosome crossover points in the crossover operation. The test results of four typical optimization functions show that ASCP-CS algorithm has better optimization accuracy and search ability. The sliding mode controller of bridge crane is tuned by different optimization algorithms. It is showed in the simulation results that the controller based on ASCP-CS algorithm can locate the payload more quickly, suppress the swing of the payload more effectively and has strong robustness.

Abstract:SOI CMOS technologies feature high cut-off frequencies and superior temperature stability, which can meet different kinds of application requirements for microwave and millimeter wave radar transceivers. A class-A Stacked-FET power amplifier using 90 nm SOI CMOS technology was designed with output matching network omitted. The saturated output power and reliability of power amplifier were improved. A 24 GHz signal generator was designed based on this power amplifier. Influences of Dummy filled in semiconductor process on the performance of spiral inductor were studied and analyzed using electromagnetic simulations. The circuit was fabricated and tested. Measured results indicated that this chip can transmit a signal operating at 22.2~24.7 GHz with an average output power of 8.83 dBm and a peak output power of 10.5 dBm. The phase noise of the Voltage Controlled Oscillator（VCO） at 1 MHz offset and 10 MHz offset was -91 dBc/Hz and -123 dBc/Hz, respectively. The area of the entire chip was 1.4 mm × 1.4 mm.

Abstract:To achieve the demanding of high data transmission and meet large dynamic range under wideband conditions, a wide-band and high dynamic range variable gain amplifier with dB-linear characteristic based on the Global Foundries 55 nm CMOS process is presented. In this variable gain amplifier, a modified Cherry-Hooper amplifier gain cell is adopted to expand the dynamic range and the bandwidth of circuit, and the tunable characteristics of the transistor are used to make the dynamic range more linear and solve the problem that the amplifier's gain variation is nonlinear with the control voltage in the CMOS circuit without any additional exponential circuit. Meanwhile, a high-pass filter with a low cut-off frequency is added to eliminate the DC offset of the variable gain amplifier and reduce its bit error rate. The layout simulation results show that the variable gain amplifier achieves a ultra gain range of -33.4~46.9 dB with dB-linear characteristic, the 3-dB bandwidth is 1.89 GHz which is from 0.000 12 to 1.9 GHz, and the area of the variable gain amplifier chip（core area, excluding PAD） is only 0.006 mm2. All indicators in variable gain amplifier are suitable for the 5G wide-band wireless communication system totally.

Abstract:In the present study, the phase behaviors of the bulk columnar phase AB diblock copolymers under spherical and prolate confinements are studied by the self-consistent field theory. By changing the size of the confined spaces, the developing law of phase morphology, free energy, conformational entropy and interaction energy of AB diblock copolymers are systematically summarized and compared. The results show that，in the confined spaces, diblock copolymers possess various phases. In the spherical confinement, the phase structures of diblock copolymers exhibit better symmetrical characteristics due to the identical frustration suffered from different dimensions. However, because the different frustrations and orientations of polymer chain in different dimension directions are introduced by prolate confinements, the phase structural symmetry of diblock copolymers was significantly broken.

Abstract:Three kinds of 2219 aluminum alloy with different iron Fe mass fractions were produced by ultrasonic semi-continuous casting method. The influence of Fe mass fraction on microstructure and properties of 2219 aluminum alloy was investigated by OM, SEM, tensile tests and electrochemical corrosion experiment. The results showed that the mechanical properties and corrosion resistance decreased obviously with the increase of Fe mass fraction, which was attributed to the generation of massive primary Al7Cu2（FeMn） phase and the increase of volume fraction of residual crystalline phases. The tensile fracture behavior of 2219 aluminum alloy at room temperature was mainly influenced by the brittle fracture of Al7Cu2（FeMn） phase, the crack direction of Al2Cu phase formed in the forging process and the low bonding strength at coarse residual crystalline phase/ Al matrix interfaces.

Abstract:In mine backfilling, it is of great significance to calculate the slurry pressure loss in the pipeline transportation. In order to seek a simple and efficient method to predict the pressure loss through applying the friction factor correlations, this paper summarized seven friction factor correction models for non-Newtonian flow according to the flow state classication. After that, details on how to utilize the models to predict the pressure loss through a case study were presented. The results show that choosing a proper model is very important, where the practical flow type and conditions should be considered. For Bingham plastic laminar flow, the Darby-Melson and Swamee-Aggarwal model, which are approximations of the Buckingham-Reiner equation, are the first choices since their prediction results are in good agreement with the actual monitoring results of the pressure loss. However, the Danish-Kumar model underestimates the pressure drop and is suitable for flow with a large Hedstrom Number. Besides, monitoring fluctuations for the velocity and pressure loss in practice can be observed due to the slightly changeable slurry mixing proportion, the variability of the aggregate, the particle settling and mild segregation of the slurry during transportation, and the change of the stowing gradient. Finally, the pressure loss prediction for the transition flow region is still an engineering challenge.

Abstract:In view of the poor sintering resistance of La2Ce2O7 and the low thermal expansion coefficient of La2Zr2O7，the La2Ce2O7 core was first synthesized by hydrothermal method, and then the La2Ce2O7@La2Zr2O7 core-shell nano-powder was successfully synthesized by coprecipitation method. The powder was pre-pressed into pellets and then sintered at 1 100 ℃、1 300 ℃ and 1 500 ℃ for different hours and sintered at 1 100 ~1 500 ℃ for 6 hours, so as to investigate the effect of temperature on its sintering resistance. The morphology and composition of the materials were analyzed by scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometer. The density and micro-hardness of the samples were also tested. Experimental results showed that the La2Ce2O7 core had a cubic or octahedral shape with the average size of about 200 nm. The La2Zr2O7 shell was amorphous structure, and exhibited good enveloping effect on forming a La2Ce2O7@La2Zr2O7 core-shell structure. Constant temperature sintering tests found that the density change rate of the core-shell structure was kept within 2.1%, which was much lower than that of La2Ce2O7 and La2Zr2O7. The distribution of pore and grain size was uniform without cracks and sintering. When sintering temperature was below 1 300 ℃, the La2Ce2O7@La2Zr2O7 was uniformly porous, its density change rate was stable within 10.6%, the grain size was maintained at about 450 nm, and the grain growth rate was close to that of La2Zr2O7，proving its good sintering resistance. When the temperature was higher than 1 300 ℃, however, obvious sintering phenomenon occurred. The densification of La2Ce2O7@La2Zr2O7 accelerated, and its pore size increased and grains grew rapidly, nearly reaching to that of La2Ce2O7. Moreover, the micro-hardness of La2Ce2O7@La2Zr2O7 was slightly higher than that of La2Ce2O7，but much lower than that of La2Zr2O7.