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2019, 39(1): .

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2019, 39(1): .

Abstract(693) PDF(298)

Abstract:

A Simplified Simulation Method for Micro-Perforated Panel with Double Layer Micro-Perforated Structure

LU Chi-hua, CHEN Wan, LIU Zhi-en, DU Song-ze

2019, 39(1): 1-6. doi:10.15918/j.tbit1001-0645.2019.01.001

Abstract(1192) PDF(585)

Abstract:
In order to overcome the difficulty caused by micro-punches in finite element meshing for simulating a micro-perforated panel silencer, two different simplified methods were adopted to simulate micro-perforation panel. In the first method, combining the classical micro-perforated panel absorber theory with transfer admittance method and defining a set of transfer admittance coefficients on its inner and outer surfaces, the simulation was simplified for micro-perforated panel. In other method, considering the effect of panel properties on sound absorption capability,the micro-perforated panel was transformed into an equivalent porous material model. Based on above two simplified simulation methods, the transmission loss of a double layer micro-perforated panel muffler with high frequency was calculated, and the results were compared with the impedance tube measurements. Results show that, the two simulation methods can predict acoustic performance of double layer micro-perforated structure efficiently, and are helpful in engineering application.

Thrust Load with Different Balance Holes Pattern of Turbine Hub in a Hydrodynamic Torque Converter

YAN Qing-dong, TAN Lu, WEI Wei, SONG Ze-min

2019, 39(1): 7-13. doi:10.15918/j.tbit1001-0645.2019.01.002

Abstract(894) PDF(485)

Abstract:
The balance holes pattern perforated in the turbine hub can effectively reduce the thrust load of the torque converter and increase its service life. In order to study the influence of balance holes with different design parameters on the thrust force, different parameter models for calculating the thrust force of the torque converter under different balance hole distribution radius, hole number and hole diameter were established. Based on DOE orthogonal test algorithm and single factor test analysis, the influence of various balance hole on the thrust force of the torque converter was studied. The results show that the thrust load of pump and turbine drops with larger distribution radius. The change of the hole number and the hole diameter has no significant effect on the thrust force. Among these three factors, the hole distribution radius has the greatest influence on the thrust force, followed by the hole number and finally the hole diameter. The optimal pattern in the case studied is 5% to 8% better than the original one. Therefore, on the premise of no affecting performance requirements and structural strength, the radius of the balance hole distribution should be enlarged as much as possible. According to the operating condition requirements of the torque converter, the number and the diameter of balance hole should be set reasonably to protect the bearing.

Transient Characteristics Optimal Design of Proportional Solenoid Valve for Hydrodynamic Retarder Discharge Branch

WEI Wei, YANG Yin-yang, KONG Ling-xing, WANG Rui, YAN Qing-dong

2019, 39(1): 14-21. doi:10.15918/j.tbit1001-0645.2019.01.003

Abstract(1136) PDF(416)

Abstract:
In order to improve the transient response performance in liquid filling rate control of hydrodynamic retarders,a dynamic model of proportional solenoid valve was established and verified with experiment data.Optimal Euler hypercube DOE method was used to analyze the sensitivity of typical parameters to determine the influence of the valve's parameters on output pressure characteristics.The results show that the diameter of the spool is most influential to the pressure overshoot of the proportional solenoid valve,and the cross term of equivalent mass and preload come next.The analysis results provide a certain guiding for the proportional solenoid valve's output characteristic experiment verification and the precision control of the parts in the machining process.Multi-objective genetic algorithm is used to optimize the parameters and obtain corresponding Pareto optimal solution.Compared with initial design point,optimized design point can make the pressure overshoot decreased sharply with a maximum drop of 72% when the response time of proportional solenoid valve remains constant.It can effectively improve the transient pressure control characteristics of the proportional solenoid valve for hydrodynamic retarder.

Evaluation Method of Spindle Performance Degradation Based on Current

WANG Hong-jun, ZOU An-nan, ZUO Yun-bo

2019, 39(1): 22-27. doi:10.15918/j.tbit1001-0645.2019.01.004

Abstract(834) PDF(397)

Abstract:
In order to improve the accuracy of spindle detection for precision machine tools, a method was proposed based on current for evaluating the performance degradation of spindle. A performance degradation model of the spindle was established to facilitate the monitoring and evaluation of the spindle condition. Firstly, the wavelet packet threshold was used to denoise the current signal, and then the multi domain feature space was constructed by extracting the time-frequency features of the denoised current signal. Then the principal component analysis (PCA) was used for data dimensionality reduction, and the dimensionality reduction of samples was used for support vector machine regression modeling. the particle swarm optimization (PSO) algorithm was used to optimize the parameters of the support vector machines (SVM) model to obtain the optimal performance degradation model. Finally, the model was applied to the evaluation of spindle performance degradation in a experiment platform. The experimental results show that the method is correct and can accurately evaluate spindle performance.

Dynamics Analysis on Synchronization Drive Mechanism of Opposed-Piston Hydraulic-Output Engine

LU Yi, ZHAO Chang-lu, ZHANG Fu-jun, ZUO Zhe, WANG Han-zheng

2019, 39(1): 28-33,52. doi:10.15918/j.tbit1001-0645.2019.01.005

Abstract(1000) PDF(425)

Abstract:
Based on the design principle of a new type of opposed-piston hydraulic-output engine (OPHO),a mathematical model was established according to the working principle of the synchronization drive mechanism,and the multi-body dynamics software Adams was used to build the simulation models separately for this mechanism and the conventional crank-link engine to analyze the force of the critical moving parts of the synchronization drive mechanism.The dynamic simulation results show that,compared to the crank engine,the lateral force on the power piston of OPHO engine in the vertical direction is small,which is conducive to reducing the mechanical loss between the piston and the cylinder wall,thus alleviating the phenomenon of cylinder wall wear and extending the life of engine and its parts to a certain extent.On the other hand,the synchronization drive mechanism is of symmetrical arrangement,the vibration and the force of the engine in the horizontal direction can be counteracted,and the overall balance of the engine is better.

Engine Condition Online Prediction Based on Incremental Sparse Kernel Extreme Learning Machine

LIU Min, ZHANG Ying-tang, FAN Hong-bo, LI Zhi-ning

2019, 39(1): 34-40. doi:10.15918/j.tbit1001-0645.2019.01.006

Abstract(909) PDF(433)

Abstract:
Aiming at the problems of sample accumulation, model inflation and slow online updating speed in engine condition online prediction process, an online prediction method based on incremental sparse kernel extreme learning machine(ISKELM)was proposed. Firstly,a sparse measurement matrix was defined for the kernel function matrix of KELM, and the operations of forward sparseness and backward deletion for large-scale samples were performed according to the principle of sample information measurement consisting of coherence minimization and self-information maximization. It improves the efficiency of sample sparseness. Then the sparse measurement matrix was expanded and pruned online by using the effective samples under the best dictionary order, which limited the model inflation. Lastly, the kernel weight matrix of the model was updated in a recursive way through the improved incremental modeling method. So an online learning model of ISKELM with a limited order and sparse structure was established to distinctly improve the online modeling speed. The online prediction experimental results with simulation data and engine condition parameters show that, compared with two existing online prediction methods, ISKELM has higher efficiency of sample sparseness and online modeling. When the engine exhaust temperature is predicted by 120 steps, the prediction speed is increased by 80.50% and 31.72% respectively, and the prediction accuracy is improved by 48.56% and 15.81% respectively.

Driver Model Characterizes Driving Style and Driver's Ability

WANG Chao, GUO Kong-hui, XU Nan, ZHANG Lin, LIU Yang, ZHENG Lei, LIU Tao

2019, 39(1): 41-45. doi:10.15918/j.tbit1001-0645.2019.01.007

Abstract(1005) PDF(366)

Abstract:
Due to the various behavior of the real driver group and different driver's ability, the acceleration decision-making and the real control decision value of the driver is not the optimal decision value. To get the difference in driver's ability and varying degrees of deviation from the optimal decision value, a multi-point and multi-objective decision-making driver model was developed based on the classic optimal preview lateral driver model, and the driving style was described with the driver's vision and decision-making intention. And the driver's ability was modeled based on the normal distribution theory. The simulink/Carsim co-simulation results show that the model including four free parameters can reflect the driving behavior of different drivers and is expected to be used to research on improving the experience of driverless car.

Force Transmission Analysis for the Marbles Screw Loading Device of Dry Disc Brakes

WANG Yan-zhong, JIA Shu-wang, GUO Chao

2019, 39(1): 46-52. doi:10.15918/j.tbit1001-0645.2019.01.008

Abstract(809) PDF(481)

Abstract:
To study the output load loss mechanism of the marbles screw loading device, a force transmission model was established emphatically on frictions and unbalanced loads. Based on the structure and motion characteristics of the device, the impact of frictions and unbalanced loads on the device output was analyzed with Coulomb friction law and Hertz contact theory. The force transmission efficiency formula was deduced from the quasi-static equation of the device. Meanwhile, the relevant parameters in formula were discussed. The results show that the friction at the ball groove seriously affects the force transmission performance, the optimum helix angle of the device is 19.88°, and the matching size of the ball groove and the marble can be adjusted to improve the force transmission characteristics of the bullet.

The Influence of Local Contact of Cu-Based Friction Pairs on Friction Coefficient

LI Ming-yang, MA Biao, LI He-yan, ZHAO Er-hui, DU Qiu, LI Hui-zhu

2019, 39(1): 53-57. doi:10.15918/j.tbit1001-0645.2019.01.009

Abstract(928) PDF(384)

Abstract:
A friction coefficient calculation model was established for heavy pressure local contact of wet Cu-based friction pairs to study the influence of heat fade, temperature, sliding speed and contact pressure on the mixture lubrication oil film and the change rule of friction coefficient. The model was validated by the friction coefficient measuring experiments of pin-plate. The results show that, under the condition of local high pressure the variation of friction coefficient with temperature can be divided into four stages, oil film leading stage of mixed lubrication, asperity domination stage of mixed lubrication, dry friction stage and heat fade stage. Furthermore, the oil film leading stage will be vanished when the sliding speed is low. Under the dry friction condition, sliding speed has little influence on friction coefficient. However, under the mixed lubrication condition, the friction coefficient decreases with the increase of sliding velocity. When the local pressure is not very heavy, the influence on friction coefficient is very little. While the local contact pressure exceeds 100 MPa, pressure begins to affect the friction coefficient.

Antenna Compensation in Near Field RCS Measurement

GAO Chao, CHEN Wen-qiang, WANG Hong-ye, BAI Yang

2019, 39(1): 58-63. doi:10.15918/j.tbit1001-0645.2019.01.010

Abstract(1155) PDF(502)

Abstract:
A method was presented to mitigate the errors from uncompensated antenna pattern effects in circular near-field monostatic radar measurements. Firstly, a near field signal model was formulated in the presence of an antenna pattern based on the same scattering approximation used in the isotropic situation. Then a modified version of the near field to far field was derived with this model, jumping the traces of multi direction antenna demanded in near field extrapolation. Numerical simulation and experiment results show that the technique can remove antenna pattern errors and improve the accuracy of the far field RCS patterns.

An Effective Malicious Domain Detection Framework

CUI Jia, SHI Lei, LI Juan, LIU Zhao-hui, YAO Yuan-gang

2019, 39(1): 64-67. doi:10.15918/j.tbit1001-0645.2019.01.011

Abstract(1078) PDF(551)

Abstract:
Since the lack of sufficient security mechanism, domain system has become the main operational infrastructure for hackers to launch cyber attacks. Therefore, how to discover and block the potential malicious domain and the corresponding IP address quickly and precisely have become an important measure and a hot research direction in preventing unknown cyber attacks area. Based on deep investigation of the achievements in malicious domain detection fields, combining three different malicious domain detecting methods, a novel malicious domain detection framework (MDDF) was proposed. According to the experimental results, MDDF can improve the detection efficiency and provide a preferable completeness.

A Motion Awareness Based Routing Algorithm for Delay Tolerant Network

HU Hao, YANG De-wei, WANG Hua, KUANG Jing-ming

2019, 39(1): 68-74. doi:10.15918/j.tbit1001-0645.2019.01.012

Abstract(1122) PDF(569)

Abstract:
Taking the characteristics of VANET(vehicular ad-hoc network) into account, a DTN (delay-tolerant networks) routing algorithm called motion-aware spray and search router (motion-aware spray and seek, MASS) was proposed based upon spray and wait router optimization design, and the method of optimization and specific procedures of the algorithm were described. Subsequently, several classic DTN routers and MASS router were simulated on ONE platform. Comparing the routing algorithms by picturing the statistics mentioned above, the different performance of each router on the VANET was analyzed. Finally, the effectiveness and reliability of the MASS router was proved.

Dimensionality Reduction of Phased Array and 4-Channel Monopulse Angle Measurement of Sum and Difference Beams

TAO Hai-hong, GUO Xiao-shuang, SUN Chen-wei, LIU Yang, DAI Pin-pin

2019, 39(1): 75-80. doi:10.15918/j.tbit1001-0645.2019.01.013

Abstract(1118) PDF(345)

Abstract:
To overcome the larger deflection of angle measurement, existing in subarray division of large arrays, weight optimization and the monopulse angle estimation, the large number of arrays, the weight approach algorithm and the large bias of the target departing more than 3 dB from the antenna, a 4-channel monopulse angle measurement method was proposed based on dimensionality reduction of phased array with an additional delt-delt channel. Combining the particle swarm optimization algorithms and weight optimization algorithm, the 4-channel monopulse angle measurement method was designed to greatly decrease the number of the channel, reduce project implementation difficulty and keep fine beam shape, to improve the monopulse angle estimation and the angle measurement accuracy of the beam departing more than 3 dB from the antenna, and to improve the efficiency of angle estimation and reduce the loss of angle measuring range. The simulation results and performance analysis show the effectiveness and feasibility of the presented algorithm.

Research on the Security of the Root Detection Mechanism in Google SafetyNet

ZHU Shu-yang, LIANG Bin, BAI Shi-lei, YANG Chao-qun, SHI Wen-chang

2019, 39(1): 81-87. doi:10.15918/j.tbit1001-0645.2019.01.014

Abstract(1342) PDF(431)

Abstract:
Android Rooting refers to making the target application perform privileged operations (as root user) by exploiting system vulnerabilities or flashing devices. Some user might root their devices to customize devices or run the Apps that require root privileges. Unfortunately, rooting a device will introduce some serious security risks. Attackers' application can perform malicious actions by requesting root privileges, such as installing malicious application stealthy, stealing user sensitive data and tempering the application. Considering the security risks, Android platform vendor (Google) and some sensitive applications developers don't want the device to be rooted. Consequently, Google developed Root detection mechanisms in platform level. However, the security of these Root detection mechanisms is still unclear. To analyze the evadable ability of their detection by sophisticated Root methods, the reverse engineering techniques were employed to investigate the security of the Root detection mechanism. Analyzing the implementation of some popular Root detection mechanisms, the weakness was found based on the Root technical principle. Some attack experiments were carried out to demonstrate a number of Root detection mechanisms. Results show that, the Root detection mechanism developed by Google possesses a high security risk, and the proposed Root methods can evade the attacks successfully. And this work implies that the security of the current Root detection mechanisms should be further improved.

Compression of 3D Mesh Based on Normal Data Prediction

GAO Yuan, SHI Yun-hui, HAN Yan-yan, ZENG Ping, YIN Bao-cai

2019, 39(1): 88-94. doi:10.15918/j.tbit1001-0645.2019.01.015

Abstract(1065) PDF(465)

Abstract:
As an important data type of digital geometric media, 3D mesh can accurately record the geometric information on the surface of models. The complexity and precision of 3D meshes have been increased, which has brought huge pressure for storage and transmission. In order to improve the compression performance of 3D mesh, a geometry and normal intra-inter prediction encoding method was proposed. Utilizing the correlation of internal components of the normal data (intra-frame) and the correlation between the geometric and normal data (inter-frame), the method was designed to realize the compression of 3D mesh and to effectively maintain geometric characteristics of decoded 3D mesh. Experimental results show that, in comparison with compressing the normal and geometric data respectively, the proposed prediction encoding methods can significantly increase compression efficiency for 3D mesh with normal data.

A Matching Method Based on Fracture Surface for Rigid Blocks with Different Scale

ZHAO Fu-qun, ZHOU Ming-quan, GENG Guo-hua

2019, 39(1): 95-100. doi:10.15918/j.tbit1001-0645.2019.01.016

Abstract(770) PDF(441)

Abstract:
Aiming at rigid blocks with a certain thickness, a scaling rigid block matching method was proposed to solve the problems of rigid transformation and scale transformation in block matching process. At first, the surface of each block was segmented by an improved region growing algorithm, and the fracture surfaces of the block were extracted according to its roughness. Then, an improved iterative closest point (ICP) algorithm was proposed by integrating scale matrix, rotation angle constraint and active iterative coefficient to ICP algorithm. Finally, the improved ICP algorithm was used to complete fracture surfaces matching of rigid blocks. The experimental results show that, compared with ICP algorithm, the improved ICP algorithm can overcome the problem of scaling transformation; And compared with scaling ICP (SICP) algorithm, the improved ICP algorithm can get much higher accuracy and convergence rate in fracture surface matching process.

Attack Graph Generation Method Based on Privilege Escalation Matrix

QIN Hu, WANG Jian-li, PENG Xiao-yao

2019, 39(1): 101-105. doi:10.15918/j.tbit1001-0645.2019.01.017

Abstract(1057) PDF(408)

Abstract:
Attack graph is a visual display of the attack paths. It can reveal the relation of the vulnerabilities and damage may be caused. Attack graph provides a more intuitive and in-depth analysis method for risk assessment and penetration test. The complexity of current attack graph generation algorithms is too high to apply to large-scale network environments. In this paper, studying the process of constructing attack graph, an attack graph generation method was proposed based on privilege escalation matrix, attack pattern bank and describing target model. With the use of matrixes to describe the process of privilege escalation, the complexity of attack graph generation algorithms was lowered greatly. Finally, an experimental network was built as a case to illustrate the attack graph generation process.

Interactions Between Aptamer, Bovine Thrombin and Active Molecules in Dragon's Blood by CZE

LI Yu-juan, SUN Xin-xin, LI Pan-pan, OU Wan-lu, QU Feng

2019, 39(1): 106-110. doi:10.15918/j.tbit1001-0645.2019.01.018

Abstract(1021) PDF(474)

Abstract:
Interactions between Apt29, bovine thrombin (B-Thr) and five active molecules in Dragon's blood were investigated based on capillary zone electrophoresis (CZE). The CZE conditions were set as following:effective capillary length of 40 cm, injection volume of 3.45 kPa, injection time of 5 s, voltage of +15 kV, temperature of 15℃, detection wavelength of 214 nm and 330 nm. The results show thatK_bbetween Loureirin A and B-Thr is 4.73×10⁴L/mol, and Loureirin B, Loureirin C, Resveratrol 7,4-dihydroxyflavanone are no bound with B-Thr obviously. TheK_bbetween Loureirin B, DHF and Apt29 are 1.98×10⁴, 1.83×10⁴L/mol, respectively. Loureirin A, Loureirin C and Resveratrol are no bound with Apt29 obviously. The study indicates the interactions between B-Thr, Apt29 and active molecules in Dragon's blood. It can provide a basis for speculating the potential binding site of dragon's blood with thrombin, and delivering Dragon's blood to thrombin with aptamer as target delivery tool.

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