Abstract:A high speed and heavy load gas foil journal bearing test rig with cylinder loading device was designed and manufactured，and the three-pad gas foil journal bearing was tested. It is measured that both the lift-off speed and the lift-off torque of the bearing increase as the load increases. The bearing load capacity at the speed of 30 000， 40 000，50 000，60 000 r/min was measured by using temperature method. The test gas foil journal bearing can achieve 380，535，700，810 N respectively at these different speeds. During the test，the test rig can run up to 70 000 r/min，and 1 020 N was loaded at 51 000 r/min. The results showed that test rig was set up successfully.

Abstract:Taking a helical gear pair as the research object，the analytic algorithm of time-varying mesh stiffness of helical gears with temperature was proposed based on slicing method and integral thought. In this algorithm，the tooth profile deformation caused by change of tooth contact temperature，elastic deformation of tooth contact，bending，shear，axial compression and the wheel were taken into account. The accuracy of the algorithm was verified by using finite element method. Then the influence of working parameters，such as friction coefficient，input torque and input speed，on the mesh stiffness of gears was analyzed. The results show that the mesh stiffness of teeth increases in the whole meshing process after considering the influence of temperature. Besides，the body temperature and instantaneous flash temperature of helical gears increase with the increase of friction coefficient，input torque and input speed，so the single mesh stiffness and the mean of total mesh stiffness increase. The research results can provide a theoretical basis for accurate and efficient dynamic analysis of the high-speed and heavy-duty gear system.

Abstract:In the aerodynamic drag reduction optimization of automobile tail structure，there is a phenomenon between geometrical characteristic parameters，which makes optimization become blind and complex. In order to ascertain the interaction law of the key geometrical parameters，this paper carried the CFD simulation research of the three main characteristic parameters on the back of the Ahmed model on the basis of the HD-2 wind tunnel experiment. In order to overcome the blindness of optimization，the integrated optimization platform was applied to optimize the tail characteristic parameters. The results show that the angle of the back inclination has the greatest contribution to drag reduction，the two sides rounded corners on the back has the smaller contribution，the contribution of the top corner of the back is the smallest. The influence of the change of three variables on the aerodynamic resistance is non-monotonic. When the values of the angle of the back inclination，the top corner of the back and the two sides rounded corners on the back are 13°，283 mm and 58 mm respectively，the drag reduction rate reaches 11.76%. This paper provides a reference for the study of the optimization of drag reduction in specific models.

Abstract:In order to explore the influence of suspension performance and saddle structure parameters on the handling stability of articulated vehicles，an anti-roll hydraulically interconnected system was proposed for single-axle semi-trailer suspension. Firstly，the frequency domain model of single-axle hydraulically interconnected suspension was established and verified by the roll displacement transfer function. At the same time，effective stiffness and damping were obtained according to the theory of complex mode vibration. On this basis，an articulated vehicle coupling Hydraulically Interconnected Suspension（HIS） model with saddle characteristics was presented to conduct the simulation. The results show that the hydraulically interconnected suspension system can only enhance the roll stability of the semi-trailer when the saddle stiffness parameters are not taken into account. When the roll stiffness parameters of the saddle are considered，the roll stability，yaw stability and coordination stability of the tractor and semi-trailer under the HIS system are improved，and the improvement effect is more significant when the yaw stiffness of the saddle is increased or the distance between the saddle and mass center of the semi-trailer is reduced. The results provide a theoretical basis for the design optimization of the articulated vehicle fitted with hydraulically interconnected suspension.

Abstract:Based on the Kirchhoff plate theory and the modified couple stress theory (MCST)，this work focuses on the pull-in phenomena of elastic micro-plates with damage. The dynamic governing equation of the micro-plate was derived and then solved via Galerkin method. The effect of damage variable，length scale parameter，initial gap and fringing filed on pull-in voltage of the micro-plate was discussed in detail. Moreover，the reliability of present model was validated by comparing results obtained in this study and the literatures. Numerical results show that damage effect decreases pull-in voltage while size effect increases it; large initial gap results in large pull-in voltage and fringing field has slight influence on it. This research is helpful and useful in electrostatically actuated microstructures applications and provides a theoretical foundation for designers and engineers.

Abstract:In view of the fact that the traditional materials used in the present chiral structures do not possess the ability of self-recovery after large deformation， a metallic material with in-plane unfolding and folding capability was proposed for the chiral structures of six ligaments. The influences of four factors，including the node spacing，the node diameter，the node height and the ligament thickness，on the maximum stress of the hexagonal ligament chiral structure after folding and unfolding were analyzed by finite element method. Taking the maximum stress after unfolding as the index，the effect of each factor was analyzed by orthogonal experiment. The order of influence is the node spacing，the ligament thickness，the node height and the node diameter. As a result，a set of optimal parameters can be obtained by range analysis and variance analysis，namely，the node height 8 mm，the node spacing 70 mm，the ligament thickness 0.06 mm，and the node diameter 22 mm. Meanwhile，the reliability of the simulation model was verified and the chiral structure has the ability of self-recovery after large deformation by experiments.

Abstract:The chatter in the follow-up grinding process will affect the quality of camshaft grinding. In order to suppressing chatter，the regenerative chatter model of follow-up grinding based on regenerative chatter theory and the characteristics of follow-up grinding was built，considering the regenerative chatter of both camshaft and grinding wheel. Based on the regenerative chatter model，the stability limit diagram was portrayed to study the regenerative chatter stability of the follow-up grinding. The grinding tests on the camshaft grinding machine were carried out to verify this model. The vibration features of the grinding machine were inspected in both frequency domain and time-frequency domain，and the results agreed well with the stability limit diagram. It testified the regenerative chatter model and feasibility of the chatter predicting and the machining parameters' optimizing by stability limit diagram.

Abstract:Aiming at the uncertainty of Symplectic Geometry Mode Decomposition (SGMD) method，an Improved Symplectic Geometry Mode Decomposition (ISGMD) method was proposed. Firstly，the phase space transformation of the original time series was carried out to obtain the trajectory matrix. Then the eigenvalues and the corresponding eigenvectors were obtained by symplectic geometric similarity transformation，and a series of initial symplectic geometric components were obtained by diagonal average. Finally，the hierarchical cluster method was employed to adaptively restructure the initial symplectic geometry components to obtain the final Cluster Symplectic Geometry Component (CSGC). The experimental results indicate that the ISGMD method can effectively extract features from composite fault signals of rotating machinery and improve the accuracy of fault diagnosis.

Abstract:Aiming at the characteristic of the transmission and development of fault in complex electro-mechanical products，a method of fault root causes tracing analysis for electro-mechanical products based on action unit was proposed. Firstly，the transfer process between action units was analyzed after the basic action unit was obtained by structuring decomposition of the whole machine function which was “function-motion-action”. Then a Bayesian network model was established based on action unit and fault phenomenon，and combined with reasoning algorithm of Bayesian networks to calculate the occurrence rate of each node and trace the maximum probability path to diagnose the fault action unit and its propagation process at the motion level. To find out the root cause of the failure of the action unit，the fault graph was used to describe the failure model of fault action unit and its transfer and development process. The trace diagnosis from the fault phenomenon to the fault cause can be realized through the diagnosis and analysis at action layer and in the interior of action unit of complex electro-mechanical products. Finally，the method of fault root causes tracing analysis based on action unit was used to deal with the root cause of the NC rotary table of some machining center，the results show that the proposed traceability diagnosis method can effectively diagnose the fault action unit and its propagation process，and reflect the transmission and development process of the internal components of the action unit from the angle of motion，which is convenient to find out the root cause of the fault and improve the efficiency of fault diagnosis for electro-mechanical products.

Abstract:The spectrum and characteristic values of acoustic emission signals of single diamond grit scratching alumina and zirconia ceramics at different cutting depths were studied experimentally. A time series Auto Regressive Moving Average (ARMA) model was established for the acoustic emission of diamond grit scratching alumina and zirconia ceramics by appropriate time series model and model order. The main frequency of single diamond grit scratching on alumina and zirconia ceramics is dominant on the frequency band of 0~110 kHz．The results show that the main frequency band energy of scratch alumina Acoustic Emission (AE) signal increases with the increase of cutting depth，and the maximum amplitude of AE signal is at a higher frequency in the main frequency band. The main frequency band energy of scratch zirconia Acoustic Emission (AE) signal decreases with the increase of cutting depth，and the maximum amplitude of AE signal is at a lower frequency in the main frequency band. The eigenvalues of the acoustic emission signal will increase with the increase of the depth of cut. The appropriate ARMA model has a high similarity with the acoustic emission signal of diamond grit scratching alumina and zirconia ceramics，and the linear relationship between the characteristic value and the cutting depth is also good. It shows that the appropriate ARMA model can better characterize the acoustic emission signal characteristics of single diamond grit scratching alumina and zirconia ceramics. The real time analysis of scratching depth of single diamond grit can be done by use of the appropriate ARMA model.

Abstract:Aiming at the frequency distortion problem in the design of frequency weighting digital filter based on bilinear transformation，an evolutionary method based on Modified Imperialist Competitive Algorithm（MICA）has been proposed to design digital IIR filter. In order to help the algorithm to escape from local minima，this paper introduced a chaotic function to make the search range wider in the assimilation operation of Imperialist Competitive Algorithm (ICA). Meanwhile，a clone evolution operator was introduced in the competition operation，guiding the search for global optimization efficiently. Then，the optimization model of modified ICA of the filter in sound-level meter was designed based on the research of the source of error in IIR filter. The coefficients of frequency weighted were searched based on the MICA. The results of both simulation and application show the performance of the design method to find better solution，indicating that the proposed method can significantly improve the precision and the error can be controlled within the order of 10-3 dB. Finally，the test of frequency weighting under different acoustic signal level with noise verifies that the error of the MICA test can be maintained in the order of 10-2 dB，which fully meets the design requirements of sound level meter (Class 1) in the national standard of GB/T 3241-2010.

Abstract:In the detection of Synthetic Aperture Radar（SAR） image ship targets，the traditional artificial feature-based target detection method is less effective due to the complex background. Based on the single-stage target detection algorithm RetinaNet in deep learning，this paper combined the characteristics of SAR image with less feature information，adopted the idea of multi-feature layer fusion and proposed a more appropriate loss function calculation method. Then we used the SAR ship detection dataset（SSDD） data set to train the network，and improve the robustness and convergence speed of the algorithm through data augmentation and transfer learning. Finally，we compared the method with other target detection algorithms based on deep learning through experiments. The results show that our method has higher detection accuracy.

Abstract:Conform mesh technique is usually adopted to eliminate the step approximation error caused by the traditional Finite Difference Time Domain(FDTD) method. In this paper，the conformal mesh technique was introduced into the derivation of passive Maxwell's equations. To update the electric field iterative equation of the traditional Finite Difference Time Domain method，a linear weighted average method was used to obtain the equivalent conductivity of the edge electric field. Using the projection theory，the position coordinates of the conformal mesh were calculated，and then the conformal parameters of the target body were obtained. The electromagnetic responses of this method are consistent with that of the finite element method. Compared with the step approximation method，the conformal mesh technique shows a higher computational accuracy when calculating a three-dimensional anomaly with a curved surface. The more the electric field is required to be processed conformally，the more obvious the effect of the conformal mesh technique is，the accuracy is also improved greatly as a result. This method sets the fundamental to calculate complex underground anomalies of airborne electromagnetic.

Abstract:Aiming at the problem that the current SOH estimation method requires a large sample size and is not suitable for tracking the results of the whole life cycle，this paper proposed a lithium battery health state estimation method based on Interacting Multiple Model（IMM） and Unscented Particle Filter（UPF） algorithm. Through the establishment of IMM model based on polynomial model，double exponential model and integrated model and the use of UPF filter to solve the problem of particle dilution in resampling process，the SOH of lithium battery was predicted according to the results of filter，and the accurate estimation of SOH in the whole life cycle of lithium battery was realized. In this paper，the selection basis and modeling method of IMM were discussed，the detailed SOH estimation algorithm was given，and the different models were compared by simulation and experiment. The simulation and experiment results show that the standard deviation of probability density function of the proposed IMM-UPF based SOH estimation result of lithium battery is only 19，which achieves high estimation accuracy.

Abstract:A CMOS current comparator circuit based on Wilson current source is proposed to solve the problems of high-power consumption and low precision of traditional current comparator. It consists of Wilson current source， differential amplifier and output gain stage. Because Wilson current source has better constant current characteristics and higher output impedance， the current comparator has higher comparative accuracy and low delay propagation characteristics. The HSPICE model parameters of TSMC 0.18 CMOS process are used to simulate the performance of the current comparator. The circuit has a high precision of 5 nA. When the input differential current is 1 μA， the delay is 2.2 ns， and the power consumption of the circuit is 95 μW at TT (typical) process angle. The results show that the CMOS current comparator has a high speed/power ratio， and its performance is less affected by the process deviation which is suitable for high-speed and low-power current-mode integrated circuits.

Abstract:There exist problems of high energy consumption and high Service Level Agreement (SLA) violation rates in cloud data centers，which urgently need to be resolved. In order to solve the above problems，a Multi-objective Virtual Machine Consolidation Algorithm (MOVMC) was proposed to reduce energy consumption and SLA violation. Taking into account multiple factors including energy consumption，service quality and migration overhead，the virtual machine consolidation problem was constructed as a resource-constrained multi-objective optimization problem. Ant colony system algorithm was employed to perform virtual machine consolidation and obtain the near-optimal mapping relation between virtual machines and hosts as the solution to the multi-objective optimization problem. In order to reduce the algorithm complexity，the double thresholds of CPU utilization were leveraged to judge the host load status and a multi-stage consolidation was performed according to the host load status，in which different consolidation strategies were used. Simulation experiments were conducted on CloudSim platform for MOVMC algorithm and six other virtual machine consolidation algorithms. The experimental results show that，compared with the existing virtual machine consolidation algorithm，the proposed algorithm has significant optimization in terms of energy consumption and SLA violation，and an excellent comprehensive performance.

Abstract:Due to privacy concerns in the genome-wide association studies of rheumatoid arthritis，there has been applying differential privacy to protect phenotype information (disease status) from being leaked while returning highly associated SNP（Single-Nucleotide Polymorphism). The trade-off between privacy protection intensity and data availability is a great problem. In order to solve the problem，a novel differential privacy protection method based on EWT (Empirical Wavelet Transform) was proposed. This method achieved the balance between privacy protection intensity and data availability by processing the noise introduced by differential privacy. Firstly，the data with differential privacy noise mechanism was processed by EWT approach; secondly，the kurtosis values of each EWT component were calculated，then some account of noise components was filtered out. At last，the data was reconstructed. After the above steps，the new data was obtained; it would be sorted according to the correlation degree of pathogenic genes. The experimental results show that the novel method can improve the data availability while ensuring the differential privacy protection intensity，and achieve a reasonable trade-off between the privacy protection intensity and the data availability.

Abstract:This paper proposed a Fast Outlier Detection algorithm Over Uncertain Data Streams (FOD_OUDS). Firstly，an index inspired by hierarchical ideas was designed to manage uncertain data stream，and some storage information was added for the leaf nodes in the index structure，so that the newly inflowed data points can directly perform batch filtering by using the intermediate result information when the data is updated，thereby achieving the purpose of reducing the calculation cost. Secondly，by analyzing the recursive rules of outlier probability values in calculation，a novel outlier probability value solution scheme was presented，which can avoid as much as possible the calculating cost of nearest neighbor set，reduce the processing cost of a large number of inliers，thus speeding up processing. At last，a large amount of experiments show that the FOD_OUDS algorithm can effectively improve the detection efficiency.