bob手机在线登陆学报自然版

2017, 37(11): .

Abstract(427) PDF(218)

Abstract:

2017, 37(11): .

Abstract(467) PDF(462)

Abstract:

Method of the Riemann Solver and Application in Fluids

JIA Yue-ling, CHENG Jun-bo, JIA Xiao-wei

2017, 37(11): 1101-1107. doi:10.15918/j.tbit1001-0645.2017.11.01

Abstract(667) PDF(1750)

Abstract:
A method of the exact Riemann solver was studied to be widely used in multi-fluids, such as pure fluid,non-conservative two phase fluids,as well as the elastic-plastic flows. Firstly, the continuous hyperbolic character of hydro-mechanical partial differential eguation was analyzed based on the characteristic theory. Then, the full wave structure of the Riemann solver was obtained from its right characteristic values. Finally, a disconnected relation formula of the full wave system was developed to establish the Riemann solver automatically. Results show that, the Riemann solver possesses full wave structure of the Riemann problem, includes all mathematics properties of the continuous system, and can obtain the exact physical values across the waves. When it is used in the Lagrangian method or the ALE ones to solve the multi-material problems, the Riemann solver obtains the exact values from the coming wind, shows a high accuracy and less dissipation. Numerical experiments in two-phase flows or the elastic-plastic flows validate the merits and characteristics of the Riemann solver.

Humidity Correction of Air Refractive Index Based on a Phase Shift Interferometry with Three Stabilized Laser Wavelengths

CHEN Qiang-hua, XU Dong, ZHANG Meng-ce, LUO Hui-fu, LUO Jun

2017, 37(11): 1108-1113. doi:10.15918/j.tbit1001-0645.2017.11.02

Abstract(606) PDF(553)

Abstract:
Revised Edlen's equations by G. Boensch and E. Potulski are mostly used to calculate air refractive index at present. Since the correction of the humidity in the equations is performed in a narrow temperature range around 20℃ and the light frequency of the four wavelengths¹¹⁴Cd lamp are not stabile, their applications have been limited in present optical precision measurement. To solve these problems, a refractive index measurement system was presented based on phase step interferometry. First, the configuration and principle of the optical system were introduced, which consisted of a phase step interferometer with three stabilized laser sources and an assistant angle sensitive interference optical path. Then the experimental and computing processes were induced. Finally, the experiments were carried out at different temperature. The corrected coefficients of the humidity on air refractive index were measured and corresponding revised equation was acquired. The comparison results indicate that the correction accuracy with the presented equation is better than that by G. Boensch. Moreover, the applicable temperature range extends to 14.6~24.0℃.

The Design Method of Vertical Screw Conveyer Based on TCP-SHV

SUN Xiao-xia, MENG Wen-jun, LIANG Zhi-jian, YUAN yuan

2017, 37(11): 1114-1121. doi:10.15918/j.tbit1001-0645.2017.11.03

Abstract(686) PDF(660)

Abstract:
In this paper, the gas-solid two-phase flow was studied for the vertical screw conveyor including the analyse of distribution function of the particles circumferential velocity in the radial direction, the decision of the best fill rate, the best screw speed and the critical Reynolds number when TCP-SHV formed in the vertical screw conveyor. Starting with the helix angle and vorticity of the particle flow, the method was carried out based on theoretical analysis and EDEM+FLUENT simulation analysis. Finally, the formula was deduced for the critical Reynolds number and the best throughput under different friction coefficient. Results show that, the method for TCP-SHV solving is efficient and the conveying capacity can be increased by about 20%.

Anomaly Detection Algorithm of On-Station Wagon Operation Time Based on BIRCH-LKD

ZHANG Xiao-dong, DONG Bao-tian, CHEN Guang-wei

2017, 37(11): 1122-1128. doi:10.15918/j.tbit1001-0645.2017.11.04

Abstract(675) PDF(671)

Abstract:
In consideration of the on-station wagon operation anomaly situation, an anomaly detection algorithm of on-station wagon operation time (WOT) was proposed based on BIRCH-LKD. This algorithm was focusing on the WOT sequence and converting the sequence into the spherical cluster with WOT feature vector, without considering the peculiar form of the anomaly. A feature clustering tree of WOT feature vector was developed based on the classification rule to be utilized in the dominant anomaly detection and shortening survey range. After computing the K-distance of the other data object, according to the different variation, the appropriate sequence values were selected as the recessive anomaly. At last, the lower bound of WOT was excluded by using the median anomaly condition. The results show that the algorithm has a high detection rate. The anomaly of the WOT sequence can be identified quickly, and the accuracy can be more than 85%. The WOT sequence becomes more smooth and unbroken after the removal of the anomalies, and conforms to the actual development trend.

Control Strategy Study on Four-Wheel Steering Vehicle Based on Improved Sliding Model Control

ZHANG Ting-fang, ZHANG Chao-min, LIU Ming-chun, HE Xin-yi, QU Zhi-lin

2017, 37(11): 1129-1136. doi:10.15918/j.tbit1001-0645.2017.11.05

Abstract(1278) PDF(1365)

Abstract:
In order to solve the problem that active 4-wheel steering(4WS) vehicle might lose its handling stability when it suffers lateral interference or changes its driving route, a 4WS vehicle driven system was built based on the single-point preview driver modeland a dynamic vehicle model with 3 degree of freedom & an improved sliding model controller on 4WS. A double lane driving path model was designed to test the new system. Meanwhile, a simulation model of this vehicle driven system was built and simulated with Matlab/Simulink software. The simulation results were compared with those of 4WS with classical type sliding model control and the uncontrol front wheel steering (FWS) under similar parameter condition. The simulation results indicate that the model can more effectively track the given double lane driving path, realize the expected yaw rate and ensure side-slip angle, keep the body roll angle and roll angular speed in a small size. And it behaves favorable performs in robustness under lateral interference.

Optimization Model of Target Tracking Based on Multi-Source Collaborative Awareness

ZHAO Zhong-nan, WANG Jian, QIAO Pei-li

2017, 37(11): 1137-1143. doi:10.15918/j.tbit1001-0645.2017.11.06

Abstract(1014) PDF(794)

Abstract:
Facing the mid-high speed wireless sensor network applied in occasions like internet of things and multimedia transmission, a key issue that how to transmit information with high speed under conditions of limited resources is needed to be solved urgently for the applications. For that reason, an optimization model of target tracking based on multi-source collaborative awareness was proposed in this paper. In the model, the multiple source information was obtained by means of collaborative perception from nodes in the process of tracking targets, and considering multi-index of that the energy threshold and throughput comprehensively, an algorithm for multi-objective optimization was used to achieve high performance of transmission with effective energy consumption. Comparing with the related algorithms, experiment results show that, the proposed model can represent a better performance and validity under a variety of network indicators.

Image Annotation by Sentences Based on Word Sequence Blocks Building Model

ZHANG Hong-bin, YIN Yi, JI Dong-hong, REN Ya-feng

2017, 37(11): 1144-1149. doi:10.15918/j.tbit1001-0645.2017.11.07

Abstract(629) PDF(492)

Abstract:
Based on image annotation by sentences, the cross-media correlations between the images and the texts were constructed to improve the information retrieval accuracy and users' retrieval experiences ultimately. The KDES model was applied to extract image features effectively and the MK-KDES features were obtained in turn by fusing the extracted features in the multiple kernel learning model to interpret the key visual characteristics of the images. A new natural language generation model named word sequence blocks building (WSBB) was designed to evaluate the semantic correlations between the words and the images. And several key words were summarized for generating sentences. According to the semantic correlations and syntactic mode constraints between words, manyNgram word sequences were made up of those summarized words to better interpret the images. Finally, sentences were generated by inputting theNgram word sequences into the templates. Experimental results show that, the MK-KDES-1 feature can focus on describing the key texture and shape characteristics of the images, which helps to improve the BLEU-1 scores. Moreover, semantic correlation between the words is an important premise of improving the BLEU-2 scores as well as the syntactic mode constraints.

Chinese Place Name Recognition Based on Deep Learning

SHEN Si, ZHU Dan-hao

2017, 37(11): 1150-1155. doi:10.15918/j.tbit1001-0645.2017.11.08

Abstract(906) PDF(2194)

Abstract:
Based on recurrent neural network and the nature of Chinese word and character, the input and output of place name recognition task were redefined and a label model of recurrent network was proposed for Chinese character level based on deep learning method. Compared with recurrent network based on word level, the model proposed based on Chinese character level in this paper, achieves significant improvement on precision, recalling andFvalue, theFvalue gets an improvement of 2.88%. When place names contain rare words, the model can improve theFvalue more to 26.41%.

Detection and Evolution of Dynamic Communities in Online Social Network

QI Jin-shan, LIANG Xun, ZHANG Shu-sen, CHEN Yan-fang

2017, 37(11): 1156-1162. doi:10.15918/j.tbit1001-0645.2017.11.09

Abstract(826) PDF(1234)

Abstract:
It is a critical issue to detect dynamic communities and track their evolution process in online social networks, which can help the controller understand the latent topology, discover anomaly events, predict its evolution trend and control the networks. Firstly, the current flaws of dynamic community detection and its evolution were analyzed. And then a novel approach of dynamic evolution of communities was proposed, including community extract in each time snapshot based on a static community mining algorithm, the calculation of evolution influence between the neighboring snapshots in the community, and generating the evolution process of community structure among continuous snapshots. Finally, tests were carried out based on the large-scale data-sets (e.g. Micro-blog, Gnutella) to validate the approach. The results show the high effectiveness of the approach in community evolution analyzing. In addition, the experiments also analyze the frequency, at which the social network nodes appear and disappear, will affect the community stability and the evolution of the structure.

Full Polarimetric Brightness Temperature Reconstruction in Full Polarization Interferometric Radiometer

YANG Xiao-cheng, WU Lin, YAN Jing-ye, WU Long, LÜ Wen-tao

2017, 37(11): 1163-1170. doi:10.15918/j.tbit1001-0645.2017.11.10

Abstract(907) PDF(587)

Abstract:
Full polarization interferometric radiometer (FPIR), which combines the interferometric synthetic aperture imaging technology with full polarimetric information obtaining technology, is one of the most efficient ways in passive microwave remote sensing. It is difficult to obtain full polarization information for synthetic aperture interferometric radiometer. In order to obtain full polarization information and reduce the reconstruction bias, an improved reconstruction algorithm applied in FPIR system was presented, and the impact of cross-polarization on each component of full polarimetric brightness temperature was analyzed. The simulation results show that the improved reconstruction algorithm can greatly reduce the reconstruction bias, compared with conventional reconstruction algorithm. The improved reconstruction algorithm can obtain high accurate data of full polarimetric brightness temperature to meet the requirements of measuring soil moisture, sea surface salinity, sea surface wind vectors and so on.

Modeling of Aircraft Nonlinear Unsteady Aerodynamics at High Angle Attack Based on Random Forest

ZHAO Qing-jie, LIU Ruo-yu

2017, 37(11): 1171-1177. doi:10.15918/j.tbit1001-0645.2017.11.11

Abstract(812) PDF(988)

Abstract:
A new modeling technique for aircraft nonlinear unsteady aerodynamics and aerodynamic moments at high angle attack was proposed. Traditional modeling methods based on the physical mechanism analysis and experimental observation possess some limitations leading to lower model accuracy. Aiming at the problem, a random forest method was proposed for modeling. Combining with the principle of random forest, the input features of the random forest model were determined according to the characteristics of large amplitude pitch oscillations in the wind tunnel. Through error analysis experiment, some key parameter values of the random forest model were determined, including the number of the decision trees, the number of variables randomly sampled as candidates at each split, and so on. Finally, experiments were carried out with the data obtained in the low speed tunnel with F-18 shrinkage ratio model. The results show that, the prediction of random forest model is closer to the wind tunnel data compared to polynomial model, which verifies random forest can be more effective for modeling the nonlinear unsteady aerodynamics and aerodynamic moments at high angle of attack.

Relative Attitude Solution for Multi-Spacecraft Formation Based on Relative Line-of-Sight Vector Measurement

ZHANG Xu, CUI Nai-gang, WANG Xiao-gang, CUI Hu-tao, QIN Wu-tao

2017, 37(11): 1178-1182. doi:10.15918/j.tbit1001-0645.2017.11.12

Abstract(919) PDF(542)

Abstract:
The spacecraft relative attitude solution is a precondition of the formation control and maintain. To address the problem of relative attitude solution for long-distance formation, the relative attitude determination method based on relative line-of-sight measurement was presented for multi-spacecraft formation. Considering the formation was composed of three spacecrafts, and each spacecraft was assumed to be equipped with vision sensors to measure the relative line-of-sight to the other two spacecrafts. Deterministic attitude solution algorithm was deduced and a mathematical simulation was carried out based on the visual sensor measurement model. Simulation results show that relative attitude solution method for multi-spacecraft formation can be used to estimate relative attitude between the spacecraft effectively and obtains a high accuracy. In addition, the method can meet the demand for spacecraft formation control and solves the limitation of visual sensor application for long-distance formation.

A Novel Signal Reconstruction Method Based on Linear Canonical Transform for the Nonuniform Sampling

XIE Yan-an, LI Bing-zhao

2017, 37(11): 1183-1189. doi:10.15918/j.tbit1001-0645.2017.11.13

Abstract(925) PDF(702)

Abstract:
A new kind of signal reconstruction method was proposed based on linear canonical transform (LCT) for the nonuniform sampling signal. Firstly, a new discrete LCT was defined according as the properties of periodic nonuniform sampling model. And then, the relationship between the discrete and the continuous LCT spectrum of the signal was derived, and a LCT field with this relationship was proposed based on the signal reconstruction arithmetic for the periodic nonuniform sampling. Finally, a simulation experiment was carried out with one-dimensional periodic nonuniform sampling signal to verify the correctness of the derived results. The simulation results show that the reconstructed signal is basically the same as the original signal.

K-Band CMOS Reflection-Type Passive Phase Shifter

QI Quan-wen, WANG Yi-fan, WANG Xing-hua

2017, 37(11): 1190-1194. doi:10.15918/j.tbit1001-0645.2017.11.14

Abstract(810) PDF(585)

Abstract:
A design method of differential reflection-type passive phase shifter was studied for K-band phased array transceiver system. A 5-bit phase shifter was fabricated in TSMC 90 nm CMOS technology. The reflective load was made up of an inductor and a varactor in parallel connection. Measurement results show that, the phase error is less than 6° from 23 to 25 GHz and less than 15° from 22 to 26 GHz. Based on the same process, an improved 6-bit phase shifter was proposed. A MOM (metal oxide metal) capacitor array with a relatively high quality factor was used to replace the traditional varactor of the reflective load. The capacitance value change was carried out by switch control. Simulation results show that the phase error of the new phase shifter is less than 4° from 23 to 25 GHz and less than 8° from 22 to 26 GHz.

Research and Implementation on Continuous Wave Information Demodulation Technology in Measurement While Drilling

YUAN Quan, LI De-zhi, WANG Zhen-yong, GUO Qing, LÜ Hai-bo

2017, 37(11): 1195-1199,1210. doi:10.15918/j.tbit1001-0645.2017.11.15

Abstract(669) PDF(656)

Abstract:
To solve the continuous wave information demodulation problem of measurement while drilling (MWD), a kind of 2DPSK demodulation scheme for continuous wave was proposed. Analyzing the transmission characteristics of measurement system with drilling, a math model was established. According to the characteristics of measurement system, a series of continuous signal modulation techniques were analyzed and compared, showing the suitability of 2DPSK signal for continuous wave information modulation under well. Then, the types of the underground noise were analyzed and a digital filter algorithm was designed for the continuous wave information demodulation system. According to the above analysis, an implementation scheme of the 2DPSK demodulation system was determined and the continuous wave information demodulation was achieved with FPGA. The results show that the demodulation system can recover the initial data accurately in the white noise channel.

An Improved Locating Algorithm Based on Double Baselines Rotating Interferometer

ZHANG Jin-xiu, TAO Hai-hong, WANG Yuan

2017, 37(11): 1200-1204. doi:10.15918/j.tbit1001-0645.2017.11.16

Abstract(677) PDF(654)

Abstract:
The traditional double long baselines interferometer (DLBI) requires the baselines to be strictly co-prime for locating algorithm. Besides, it is sensitive to the phase error and the performance becomes seriously bad with higher fuzzy number. To solve the problems, an improved direction-finding algorithm with double baselines rotating interferometer (DBRI) was proposed. In the DBRI, two baselines were designed with arbitrary length and palstance to rotate in the opposite direction. The locating was carried out according to the phase difference gotten from the improved direction-finding algorithm, obtaining better location precision with high fuzzy number and better robust to the phase discrimination error. Finally, the effectiveness and validity of the proposed algorithm were verified by computer simulations.

An Algorithm for Decreasing the Noise of Dynamic Baseline Vector Based on Previous Baseline Length

LIU Shuo, ZHANG Lei, LI Jian, LONG Teng

2017, 37(11): 1205-1210. doi:10.15918/j.tbit1001-0645.2017.11.17

Abstract(695) PDF(844)

Abstract:
For global navigation satellite system (GNSS) carrier phase relative positioning, the baseline vector can be filtered in each dimension to decrease the noise in static situation. However, the baseline vector may change in dynamic situation, so the filtering method cannot be used. The baseline length is taken as constant in some situations such as orientation and attitude determination. The noise of averaged baseline length is far less than the noise of the single epoch baseline vector if different baseline lengths are averaged by the previous results. Therefore based on previous baseline length, an algorithm was proposed in this paper to decrease the noise of dynamic baseline vector. A mathematical model was developed to combine the averaged baseline length and current baseline vector,and a weight matrix of the mathematical model was deduced. A theoretical expression was found for the noise decreasing on the basis of variation transmission. Simulation and field tests were carried out to evaluate the performance of the proposed algorithm. The results show that, test result matches with the result of theoretical analysis, the proposed algorithm is easy to be implemented, and can effectively decrease the noise of the baseline vector to 80% approximately without additional hardware resources.

Submission System

Author Related

Writing Norms

Links

2017 Vol. 37, No. 11

Archive