bob手机在线登陆学报自然版

2018, 38(11): .

Abstract(495) PDF(194)

Abstract:

2018, 38(11): .

Abstract(414) PDF(320)

Abstract:

Quantitative Identification of Magnetic Flux Leakage of Fatigue Crack Based on PSO-LSSVM

QIU Zhong-chao, ZHANG Wei-min, GAO Xuan-yi, ZHANG Rui-lei

2018, 38(11): 1101-1104,1140. doi:10.15918/j.tbit1001-0645.2018.11.001

Abstract(1024) PDF(499)

Abstract:
To solve the problem of fatigue cracks quantitative identification, a modeling method combining principal component analysis(PCA) and particle swarm optimization least squares support vector machine(PSO-LSSVM) was proposed to establish a nonlinear mapping relationship between magnetic flux leakage signals and fatigue cracks for quantitative identification of the fatigue crack width and depth. Firstly, a magnetic flux leakage detection system was built, and a series of fatigue crack samples were prepared by fatigue tensile test. Then, the quantitative identification experiments of fatigue crack magnetic flux were carried out to establish a magnetic flux leakage defect sample library. Finally, the feasibility of the quantitative identification method of fatigue crack magnetic flux leakage based on PSO-LSSVM was verified. The results show that the method can effectively identify the width and depth of fatigue cracks with a size less than 1 mm, and the error is about 0.1 mm.

Experimental Study on Ultrasonic Assistant Micro-Milling of 45# Steel Under Different Grain Size Conditions

XU Lin-hong, LIU Zhong, HAN Guang-chao, WANG Rui-dong

2018, 38(11): 1105-1110. doi:10.15918/j.tbit1001-0645.2018.11.002

Abstract(654) PDF(468)

Abstract:
Ultrasonic vibration assisted micro milling is a kind of ultrasonic vibration, exerting a certain frequency and amplitude on the tool or the workpiece during the micro milling process, which can change the material removal mechanism and improve the micro milling characteristics. Taking Steel 45# as an example, the effect of grain size on ultrasonic vibration aided micro milling results was investigated, the orthogonal experiment was used to study the micro-milling of 45# steel with different grain sizes. The effects of grain size and ultrasonic vibration on milling force, dimensional accuracy and surface roughness were analyzed in the orthogonal experiment. It is proved that the material with large grain size corresponds to the smaller milling force under the same process parameters, and the material with larger grain size can obtain better processing surface quality.

Teeth Profile Design and Meshing Force Analysis of the Swing Output Cam Mechanism with Movable Teeth

LI Jian-feng, YU Yang, ZHANG Lei-yu, ZHAO Hong-wei

2018, 38(11): 1111-1119. doi:10.15918/j.tbit1001-0645.2018.11.003

Abstract(646) PDF(413)

Abstract:
In order to transform constant rotation motion into variable oscillation traverse output motion, a theoretical tooth profile, which could realize to output oscillation traverse motion in continuous or batch process, was designed, and then the working profile equations were derived for enclosed slot of actuating plate and the swing plate. On this basis, contact force models and algorithms of meshing pair were established in the light of force/torque balance equation and theory of Hertz, and taking the same load and equal swing angle as the example, the characteristics of meshing force of cam mechanism with movable teeth in the condition of different steel ball numbers and various motion laws were analyzed. The acquired result of meshing force analysis can be adopted as the theoretical basis for bearing capacity analysis, stiffness estimation, as well as structure design of the swing output cam mechanism with movable teeth.

Study on the Machining Process of Circular Arc Gear with Interference Fit

ZHOU Yang, DING Li, NIU Peng-hui, LI Da-lei

2018, 38(11): 1120-1125. doi:10.15918/j.tbit1001-0645.2018.11.004

Abstract(659) PDF(336)

Abstract:
In order to study the effect of interference fit on circular arc gear machining, a mathematical model of circular arc tooth profile was established based on the end face coordinates of circular arc gear. Also, the helical surface equation was obtained according to the end face coordinates. Based on the circular arc gear model, the stress and deformation of interference surface between gear and shaft were analyzed, and the allowable maximum deformation and contact stress of the interface were solved. The effect of interference fit on the machining process was studied based on the deformation of tooth profile. The machining process of circular arc profile by bulb milling cutter was simulated, and the influence of deformation on the machining of tooth profile was analyzed. The results show that, the calculation and analysis methods can provide a theoretical support for the machining and selection of the interference fit between gear and shaft.

Remaining Useful Life Prediction of Power-Shift Steering Transmission Based on Degradation Data

YAN Shu-fa, MA Biao, ZHENG Chang-song, WANG Li-yong, ZHU Li-an, MA Yuan

2018, 38(11): 1126-1133. doi:10.15918/j.tbit1001-0645.2018.11.005

Abstract(814) PDF(534)

Abstract:
Remaining useful life (RUL) prediction of power-shift steering transmission(PSST) was presented based on multidimensional degradation monitoring data under uncertain measurement. The state space model and principle component analysis (PCA) was used to establish the degradation degree index. The RUL of PSST was defined based on the concept of first hit time (FHT) of stochastic process, and a PSST's degradation model was established based on Wiener process, considering the stochastic degradation and uncertain measurement. And then the maximum likelihood method was utilized to estimate the model parameter. The Kalman filtering technique was used to estimate and update the degradation state, and the RUL distribution was derived. Test results show that the proposed method can objectively describe the degradation law of the PSST, which is superior to the method without considering uncertain measurement, and can improve the accuracy of RUL prediction, which is helpful to the condition based maintenance.

Surface Reconstruction of Complex Shapes Based on Free Form Deformation and External Axes Projection

LIU Xu, BAN Xiao-juan, LIU Xi, HE Liang-liang

2018, 38(11): 1134-1140. doi:10.15918/j.tbit1001-0645.2018.11.006

Abstract(653) PDF(415)

Abstract:
A method was proposed for surface reconstruction of complex shapes. Taking slice image as input source, the corresponding relationship of upper and lower contours was established based on free-form deformation (FFD). The branching problem was converted into one-to-one case by the external axes projection (EAP). The framework could naturally deal with sparse input source and contours of arbitrary topology with high match, parallel and efficiency. Experimental results show that the approach performs can well handle complicated situations.

Radio Tomographic Imaging Method Based on Exponential Moving Average

GAO Fei, WANG Ji-yong, SUN Cheng

2018, 38(11): 1141-1148. doi:10.15918/j.tbit1001-0645.2018.11.007

Abstract(872) PDF(393)

Abstract:
To improve the tracking accuracy of moving objects in radio tomographic imaging (RTI) and reduce the multipath effect, exponential moving average (EMA) was used as the parameter to evaluate the signal changes in RTI. Long-term EMA was used as an alternative benchmark to avoid the measurement of the background information in advance for the area. Two single-moving person localization experiments were performed in outdoor through walls and indoor multipath environments. Compared with SRTI and KRTI, results show that the RTI method based on EMA can obtain better localization accuracy without obvious increasing of time consuming.

Software Refactoring for Java Threads

ZHANG Yang, LIU Chen-guang, ZHANG Dong-wen, ZHENG Kun, ZHENG Ya-jie

2018, 38(11): 1149-1155. doi:10.15918/j.tbit1001-0645.2018.11.008

Abstract(807) PDF(427)

Abstract:
Java thread mechanisms, such as Thread and Executor, are different in the thread management pattern, code and the performance. To implement the automated refactoring between different thread mechanism and help programmers to choose the right thread mechanism, an automated refactoring method was proposed for Java thread mechanism able refactoring between Thread and Executor. To test the validity of the method, an automated refactoring tool named Rethreader was developed in Eclipse JDT. In the experimentation, several programs in the Java Grande Form (JGF) were tested, including Series, Crypt, Lufact, Sparsematmult and montecarlo. The experimental results show that the Rethreader can successfully implement the automatic refactoring from Thread to Executor within 1 s.

A Method of Text Sentiment Classification by Extending Semantic Similar Sentiment Words

LUO Sen-lin, MAO Yan-ying, PAN Li-min, CHEN Qian-rou, WEI Cao

2018, 38(11): 1156-1162,1176. doi:10.15918/j.tbit1001-0645.2018.11.009

Abstract(794) PDF(337)

Abstract:
To solve the effect problem of sentiment classification due to the insufficient use of emotional semantic features and unpromising dimension reduction effects, a novel high-precision sentiment classification method was proposed in this paper for online comments by extending semantic similar emotional words and employing the statistical features between words. Firstly, a neural network skip-gram model was employed to generate word embedding and extend the semantic similar words to emotional feature by the measure of embedding word similarity. Then the feature dimension was reduced by employing the statistical features between words. At last, sentiment classification of online comments was carried out by the Adaboost classification model which was constructed by weighting multiple weak classifiers. Experiment results on hotel reviews and mobile comments show that, the accuracy of sentiment classification with new method can reach 90.96% and 93.67% respectively. Expanding semantic similarity emotion words is helpful to enrich the semantic features of emotion. Employing statistical features between words has better feature reduction effect. Both two procedures effectively improve the performance of text sentiment classification.

Cryptographic Function Location Based on Binary Entropy

JIAO Long-long, LUO Sen-lin, DING Yong, PAN Li-min, ZHANG Ji

2018, 38(11): 1163-1167. doi:10.15918/j.tbit1001-0645.2018.11.010

Abstract(740) PDF(325)

Abstract:
To solve the accurate problem of cryptographic function location for fuzz testing of binary program, a location method based on binary entropy was proposed. Firstly, instruction features of binary program were modeled to locate key code. Then binary entropy of data handled before and after key code was calculated. Finally, the cryptographic function was located according to binary entropy relationship before and after key code. Experimental results show that this method can locate cryptographic functions in binary program effectively and the accurate rate is more than 99%. This method can enhance the ability of fuzz testing.

Influence Factor Analysis for the Radiated Interference E-field Threshold Testing in Reverberation Chambers

HU De-zhou, WEI Guang-hui, PAN Xiao-dong, JI Kai-fu

2018, 38(11): 1168-1176. doi:10.15918/j.tbit1001-0645.2018.11.011

Abstract(780) PDF(324)

Abstract:
In order to standardize and complete the radiated interference E-field threshold testing in reverberation chambers proposed previously, the influence factors on the measurement accuracy were analyzed in this paper, obtaining the error variation with different test conditions. It is revealed that the electrical size of the equipment under test (EUT) is the main restricted factor to the application range of the proposed method. Decreasing the electrical size of the EUT, an experiment was implemented to study the influence of the electrical size on measurement accuracy. The result shows that the measurement error can be decreased to less than 3 dB when the testing factors are reasonably chosen and the electrical size of the EUT is large enough. However, when the electrical size of the EUT is too small, the measurement uncertainty level may be larger than 3 dB. Accordingly, the proposed method is more proper for the EUTs with large electrical sizes.

Impact of Dimensions on Thermal-Mechanical Reliability of Low Resistivity Silicon-TSVs and Copper TSVs

CHEN Zhi-ming, XIE Yi, WANG Shi-wei, YU Si-qi

2018, 38(11): 1177-1181. doi:10.15918/j.tbit1001-0645.2018.11.012

Abstract(1084) PDF(362)

Abstract:
Through-silicon-vias (TSVs) has been identified as one of the most significant devices in 3D-integration. This paper addresses the comparative studies of two types of TSVs, i.e. copper-based TSVs (Cu-TSV) and low resistivity silicon pillar based TSVs (LRS-TSV), focusing on impact of geometric dimensions on their thermal-mechanical reliabilities. During the studies, finite element analysis (FEA) were utilized. First, based on the experimental dimension of the two kinds of TSV, the maximal protrusion height and thermal stress were simulated and compared under 350℃. Second, by changing the factors of experimental model such as TSV diameter, height and pitch, the difference of their thermal mechanical characteristics was investigated and compared. The results show that the LRS-TSV performs better in terms of thermal mechanical properties.

Intra-Session Linear Network Coding Against Pollution Attacks

HAN Xiao-dong, GAO Fei

2018, 38(11): 1182-1187,1204. doi:10.15918/j.tbit1001-0645.2018.11.013

Abstract(709) PDF(273)

Abstract:
Traditional network routing cannot reach Shannon capacity limit of the "maximum flow-minimum cut" theory in multicast network, but network coding is a very good solution to these problems, it can increase the throughput also balance network load, and improve bandwidth utilization ratio. But malicious attacks in network can introduce error packets, it will bring packets of "error propagation" problem under the linear network coding and waste a large number of resources. Therefore, how to improve the security of communication network while optimizing network transmission performance is an urgent problem to be solved. In this paper, the homomorphism of the classic linear block code in linear network coding was proposed for the case of binary field and its extensions for network error-control, in order to resolve the problem of pollution attacks in multicast network. And the safety performance and transmission performance were analyzed. Experimental results demonstrate that homomorphic error-control codes for linear network coding can detect and correct error packets timely based on not destroy packet encoding rules. It can get good performance in error control, improve network performance and save the cost of network consumption.

A Polarimetric Robust Adaptive Subspace Detector

LIU Zhi-wen, YANG Lei-lei, XU You-gen

2018, 38(11): 1188-1192. doi:10.15918/j.tbit1001-0645.2018.11.014

Abstract(790) PDF(323)

Abstract:
A method of polarimetric robust adaptive target detection in Gaussian clutter and noise was presented. There potentially exist many reasons, such as imperfectly calibrated arrays, pointing errors, etc., which may lead to the detection loss due to the mismatch between the presumed target steering vector and the actual one. A subspace based robust detector against model imperfection was proposed by adding some steering vectors close to the presumed one in the subspace constraint. Simulation results show that the proposed method performs well in the case of large target steering vector error.

Cold Plate of Metal Flow Channels Based on Carbon Nanospheres Masking Process for Cooling of High-Power T/R Module

GUI Jin-le, YU Huai-qiang, YAN Yang-yang, WANG Teng, HUANG Bo, TIAN Ye, JIANG Chuang-xin, TANG Jin-song

2018, 38(11): 1193-1197. doi:10.15918/j.tbit1001-0645.2018.11.015

Abstract(1075) PDF(468)

Abstract:
Due to the complex processing technology and poor heat transfer performance of the cold plate of metal flow channels, a processing method was proposed for cold plate of metal flow channels based on carbon nanospheres masking process. And a cold plate of metal flow channels was manufactured for a certain type of high-power T/R module. Some numerical simulation and experiments were carried out to study the flow characteristics and heat transfer performance of cold plate of metal flow channels. Results show that, when the heat dissipation of the T/R module is at 500 W and the flow rate is at 3.5 L/min, the simulated and measured results of the highest case temperature of the power amplifier device are 38.7℃ and 43.7℃ respectively. The new processing technology is simple and easy to implement, can provide better flow characteristics and heat transfer performance, that can meet the heat dissipation requirements of various high-power electronic components/modules.

Quantitative Reconstruction ofγRadioactive Sources in Metal Barrel

ZHANG Xiao-jian, ZHANG Feng-yue, CHEN Bing, WEI Meng-fu, WEN Jun-hai

2018, 38(11): 1198-1204. doi:10.15918/j.tbit1001-0645.2018.11.016

Abstract(630) PDF(329)

Abstract:
With the increasing application of nuclear power and nuclear technology in energy, military, industrial and medical fields, a large number of different types of radioactive solid waste have been producing in nuclear fuel plant, reactor, military facilities, hospitals and research institutions. The rapid and accurate determination of the distribution, location and dosage of radioactive wastes is of great significance for safe operation of nuclear facilities, assessment and treatment. In view of the fact that fewer gamma camera projection data could be obtained in actual radiation source measurements, a sparse reconstruction technique based on compressed sensing was used to reconstruct the 3D distribution of the unknown sources inside the metal barrel. According to the reconstruction of two sets of projection data from the real sources and simulated sources experiments, the results show that the algorithm can accurately reconstruct the radiation sources' 3D position, shape, relative intensity in the sparse projection conditions, and achieves quantitative 3D reconstruction of the radiation source in the metal barrel.

Study on Curing Kinetics and Properties of AFG-90 Based Solid Buoyancy Materials

YU Si-zhu, LI Xiao-dong, ZOU Mei-shuai, GUO Xiao-yan, JIN Xin

2018, 38(11): 1205-1210. doi:10.15918/j.tbit1001-0645.2018.11.017

Abstract(854) PDF(383)

Abstract:
In order to determine the curing process of N,N-diglycidyl p-aminophenol glycidyl ether epoxy resin (AFG-90)/tetrahydrophthalic anhydride (THPA), curing reaction kinetics was studied by non-isothermal differential scanning calorimetry (DSC) method, and the solid buoyancy material with hollow glass microbeads (HGM) was prepared. Results show that the best ratio of AFG-90/THPA is 1:1. The apparent activation energy (E) and pre-exponential factor (lgA) obtained by Kissinger method are 67.72 kJ· mol^-1and 8.20 s^-1, respectively. The most probable mechanism function of curing process can be described as Avrami-Erofeev equation. The curing process is 100℃, 1.0 h and 125℃, 2.5 h. The density and compressive strength of solid buoyancy material are 0.90 g· cm^-3and 113 MPa, respectively.

Submission System

Author Related

Writing Norms

Links

2018 Vol. 38, No. 11

Archive