Table of Content

24 February 2018, Volume 36 Issue 1

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Civil Aviation

Integer ambiguity resolution and cycle slip detection of Beidou satellite navigation system

JIAO Weidong, Biligebate

2018, 36(1):  1-5. 

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Confirmation of integer ambiguity and the detection and correction of cycle slip are important quality indices of BDS observed data. Firstly, based on the code pseudorange observation equation and carrier phase observation equation, BDS integer ambiguity resolution method is studied. Secondly, the ionospheric residual method is used to detect cycle slips, and its feasibility for BDS is analyzed by simulation. Results show that it is more suitable to detect cycle slips with ionospheric residuals when the cycle slip is less than 8 weeks; if the cycle is longer than 8 weeks, other methods should be used to detect cycel slip.

Encryption of ACARS data-link communication based on SM4 algorithm

WANG Jian, SONG Yang, HAN Shaocheng

2018, 36(1):  6-10. 

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Threat of ACARS data-link is analyzed and ACARS data-link information is encrypted with SM4 packet symmetric encryption algorithm. According to actual messages from ACARS data-link, this method processes ACARS information with an effective load code and transforms the ACARS information into encrypted bit streams. The bit streams are encrypted with SM4 encryption algorithm and the required cryptograph is obtained.The encryption performance and security of SM4 algorithm are analyzed. Results show that the cryptograph encrypted with the algorithm is not readable and this method satisfies the security standard of ACARS data-link messages.

Timestamp estimation of differential matching filter based on quadratic decision

GONG Fengxun, ZHANG Wanhong, MA Yanqiu

2018, 36(1):  11-14,19. 

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Timestamped mark of single-pulse zero-crossing of differential response filter is analyzed aiming at the problem of TOA detection accuracy under high SNR(signal-to-noise ratio). Improved differential matching filter based on quadratic decision is proposed. Through zero-crossing distribution, TOA measurement of root mean square error and MLAT system positioning accuracy are employed to verify the improved algorithm in zero-crossing detection accuracy and robustness. Simulation results show that the improved algorithm has higher accuracy of timestamp mark, TOA measurement and initial positioning accuracy. With the increase of SNR of the input signal, the improved square root error of improved algorithm approaches to zero. When the SNR is greater than 20 dB, the accuracy of MLAT system is less than 0.87 m.

BICM-ID interference mitigation based on joint compressed sensing and ICI compensation

LIU Haitao, ZENG Weizhong

2018, 36(1):  15-19. 

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To mitigate the deleterious influence of DME (distance measure equipment) interference on OFDM (orthogonal frequency division multiplexing) receiver of L-DACS1 (L-band digital aeronautical communications system 1), a method of BICM-ID interference mitigation based on joint compressed sensing and ICI compensation is proposed. Firstly, soft-symbols are calculated based on interleaved codeword bit soft-information of codeword bit from soft-decoder. Then, the received signal is reconstructed with soft-symbols and frequency response of channel. Blanked samples are compensated with the reconstructed received signal and the position information of blanked samples. After iteration convergence, the soft-information from ICI compensation branch is sent to compressed sensing. At the same time, soft-information from the branch of compressed sensing is sent to the branch of ICI compensation to complete iterative decoding. Simulation results show that the proposed method can significantly suppress the pulse interference of DME and improve the reliability of L -DACS1 system link transmission.

Turbulence spectral width estimation method based on space-time covariance matrix fitting

LI Hai, ZHAN Lei, WU Renbiao

2018, 36(1):  20-24. 

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Atmospheric turbulence is a kind of weather target that aircrafts will encounter at high altitude flight. Aiming at the detection of atmospheric turbulence under low SNR （signal-to-noise ratio）, a method for estimating the turbulence echo spectral width of airborne meteorological radar is proposed based on space-time covariance matrix fitting. Parametric model of the turbulence target space-time covariance matrix is established by using the Gaussian spectrum characteristics of turbulence echo spectrum. Then, the estimated covariance matrix of turbulence echo signal is fitted with the parametric model to construct cost function. Finally, the exact estimation of turbulence wave width is realized by searching the cost function. Simulation results show that the proposed method can accurately estimate the turbulence spectrum in low SNR condition.

Simulation study on multi-factor characteristic judgment of aircraft hard landing

JIA Baohui, YING Chenwei, WANG Yuxin

2018, 36(1):  25-29. 

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Aiming at the low accuracy of aircraft hard landing recognition rate of domestic airlines, and the high false rate and miss rate of hard landing recognition, an improved AdaBoostSVM algorithm hard landing recognition model is proposed. On the basis of fully considering the relevant factors of hard landing, in order to improve the recognition rate of aircraft hard landing, the compressive stroke characteristic of main landing gear buffer pillar is used as the hard landing diagnostic index, adjusting the evaluation coefficients of AdaBoostSVM algorithm weak classifier and increasing the weight of weak classifier with high ability for recognizing hard landing. At the same time, the actual sample data of airlines fleet is simulated and verified, and the accuracy and reliability of hard landing recognition of three algorithms are compared. Simulation results show that in the case of sufficient sample, the improved AdaBoostSVM algorithm could significantly improve the accuracy of hard landing events recognition, reducing the false rate and miss rate of aircraft hard landing as well as security risks of aircraft flight and cutting down airlines爷maintenance cost, having strong practical engineering value.

Airport flight delay prediction based on SVM regression

HE Yang, ZHU Jinfu, ZHOU Qinyan

2018, 36(1):  30-36,41. 

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Flight delay prediction is significant for busy airports. Aiming at the difficulty of predicting the number and duration of delays in busy airport flights, SVM(support vector machine) regression method is used to establish the flight arrival/departure delay prediction model. First of all, according to the flight operating data, data mining and backward stepwise selection algorithm are used to determine the most relevant factors of number and duration of delay per hour respectively. Secondly, grid-search and cross-check methods are used to select the optimal model parameters. Finally, historical data of LAX(Los Angeles International Airport)and PVG(Pudong International Airport)are used to train the model, and multivariate linear regression model and SVM regression model are applied to test the current model. Comparison results show that the SVM regression model can achieve better prediction effect.

Semantic consistency verification of radiotelephony communication based on deep CNN

YANG Jinfeng, LU Weibing, JIA Guimin, SHI Yihua

2018, 36(1):  37-41. 

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The accuracy of readback plays an important role in flight safety. However, readback semantic inconsistency may occurs during radiotelephony communication. Thus, a method based on deep CNN (convolutional neural network) is proposed to verify semantic consistency of readback content. Words in radiotelephony communication corpus are transformed into word vectors. On top of the word vectors, CNN model is used to obtain the semantic vectors of readback sentence pairs, then cosine measurement is applied to measure the semantic similarity of readback sentence pairs. Finally, consistency verification is implemented by classifier. Experiment results show that semantic consistency of radiotelephony communication can be verified by CNN model effectively. The average accuracy of the experiments is up to 82.5%.

Check-in queue length prediction model of departure passengers in fully open check-in island

XING Zhiwei, Yang Yang, LUO Qian

2018, 36(1):  42-46,64. 

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Aiming at the domestic departure passengers checking-in scenario with the serpentine queuing form in the fully open check-in island, passenger agglomeration rule is analyzed, proving the multiple peaks of arriving passengers on multiple flights. Then, for this scene, before the number of open counters changed, the queuing length prediction model of departure passengers in fully open check-in island is established by cumulative algorithm and discretized analysis. Queuing length of adjacent timing is analyzed in discrete way. Accuracy of the current model is proved by comparative test.

Analysis of bearing capacity of airport pavement with polymer reinforcement subsidence

CHENG Guoyong, CHEN Pengpeng

2018, 36(1):  47-52. 

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It is a new developing direction to carry out non-stop reinforcement of airport pavement with excessive polymer material. Considering safety factors such as bearing performance, there is no engineering practice at domestic airports. Firstly, the polymer constraining force at channel bottom is studied by numerical simulation. Density of polymer solidified body is obtained according to the density-constraining force relationship when the polymer material is solidified. Results show that the degree of common pavement structure parameters based on slab corner filling polymer materials can be obtained with density of 0.303~0.372 8 g/cm³, density of polyer material at the edge of the plate is 0.263~0.315 g/cm³, density of polyer material at middle plate is 0.207~0.25 g/cm³. Based on the above results, the improvement of bearing capacity of pavement with different degrees of subsidence is analyzed. Results show that the bending stress at the bottom of pavement is reduced by 9.5%~25.7% at the plate angle, and this stress at the bottom of pavement is reduced by 7.1%~23.1% at the plate edge, pavement bottom bending stress is decreased by 3.5%~20.3% at the plate position .

Engineering and Technology

Influence of temperature on n-heptane liquid injection characteristics through PIV experiment

TIAN Jing, DU Lichao, ZHOU Weixing, WU Chuanwei, LAN Zhenzhong

2018, 36(1):  53-57. 

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N-heptane injection characteristics under different temperatures and pressures is studied basing on PIV (particle image velocimetry)experimental system and is used for the design of engine fuel supply system. Under the condition of temperature rising, macro images have been taken at different temperatures and injection pressures forthestudyofn-heptanejetcharacteristics.Resultsshowthatamongtheliquid n-heptaneinjection characteristics,maximum spray-cone angle increases with increasing pressure; while, with the increasing temperature, spraycone angle and injection maximum width first increase and then decrease. In the experiment, when the pressure is less than 0.5 MPa, temperature of injection cone increases significantly with increasing pressure. When the pressure is greater than 0.5 MPa, the temperature of this moment decreases with increasing pressure.

Malware classification method based on text mining

WANG Chong, LI Bingchen, WANG Jinbao

2018, 36(1):  58-64. 

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To classify malwares effectively, a malware classification method based on text mining is proposed. Code string extracting stage can decorticate and disassemble malwares and extract structured code strings of malwares.Hierarchical clustering algorithm is used to cluster malwares into malware families. Then quantitative analysis on malware families is conducted, and the malware families. feature vector is obtained. Distance between malwares captured by mobile honeypot and malware families are calculated. Then the nearest malwares are devided into corresponding malware families. Classification experiment result proves the accuracy and efficiency of the new classification method.