Table of Content

29 February 2020, Volume 38 Issue 1

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Civil Aviation

Realization of dual-frequency localizer horizontal radiation characteristics#br#

NI Yude, WANG Ning, FAN Yi

2020, 38(1):  1-6. 

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ILS provides precision approach service for civil aviation. The horizontal radiation characteristics of LOC that provides horizontal guidance information directly affects the navigation performance of ILS. Using 3D electromagnetic simulation software FEKO, an LPDA composed of seven symmetric oscillators which is widely used in LOC, is designed. Combined with dual-frequency LOC feeding mode, the radiation pattern of dual-frequency 12-cell LOC is realized through simulation. Results show that the designed LPDA basically meets the HPBW requirements of LOC array element, and the horizontal radiation characteristics of LOC array antenna meet the coverage requirements of the relevant standards of ICAO.


Design and implementation of self-adaptive ADS-B anti-interference receiver monitoring software#br#

WU Renbiao, ZHANG Lulu, HU Tieqiao

2020, 38(1):  7-12. 

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The increasingly complex space electromagnetic environment makes ADS-B system facing various interference problems. Most current ADS-B receivers in and abroad do not have the capability of autonomous anti-interference. A real-time receiver monitoring software is designed according to the special requirements of ADS-B self-adaptive anti-interference receiver for monitoring system, including software system composition, key unit design and performance test. Results show that the proposed software can quickly and accurately transmit receiving data,working status, control commands and other information, and generate a visual interface, providing reference for
the development of ADS-B anti-interference receiver monitoring system.


Numerical simulation on aero-engine turbine rim sealing#br#

TAO Liquan, MA Zhen, QIU Xuewang

2020, 38(1):  13-18. 

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Aero-engine turbine rim sealing is vital for rotor-stator system protection. In order to avoid main flow high temperature gas ingesting into rotor-stator system, it is necessary to induce low temperature gas inflow to rotorstator system. 2D RANS model and SST turbulence model are used to study the effect of different sealing flow on sealing efficiency, the minimum sealing flow is determined by pressure parameter method, the influence of different seal heights on sealing efficiency is studied. Results show that with the increase of sealing flow, the turbine flange is gradually sealed and the sealing efficiency of turbine rim increases. At the same time, the outflow of sealing gas from turbine cavity into mainstream results in the increase of mainstream pressure, which makes the sealing gas has a certain influence on the main stream. Because the sealing gas is filled with disk cavity, it is difficult for the high-temperature mainstream gas to enter the disk cavity, and the heat exchange between mainstream gas and sealing gas occurs in the entrance area of layer seal, which makes great change of temperature, mainstream gas and improves the sealing efficiency; meanwhile, experimental results show that
different sealing layer heights has no effect on sealing efficiency.


Aero-engine baseline mining based on chaotic PSO_Elman network#br#

QU Hongchun, LIN Wenbin, XU Wangshan, GUO Longfei

2020, 38(1):  19-23. 

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In order to improve the fitting precision of engine baseline, an Elman neural network model optimized by chaotic particle swarm is proposed. The position formula of PSO is improved by chaos algorithm to solve the local optimization problem. A nonlinear decreasing function is proposed to improve the PSO particle velocity formula to solve the problem of low convergence accuracy. The model is applied in baseline fitting and the fitting errors are compared with those of traditional BP network, Elman network and SVM. Results show that the fitting accuracy of chaotic PSO_Elman model is higher than that of other traditional models with the same training and testing data and the same training times. When the training samples get fewer, the fitting accuracy is still higher than the traditional models, proving the stronger learning ability of the model.


Task packeting optimization model of civil aircraft planned maintenance#br#

ZHANG Peng, FU Jie, ZHAO Shiwei

2020, 38(1):  24-28. 

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The continuous expansion of domestic airline fleets has led to the rapid growth of maintenance workload. The manual packeting of maintenance task is commonly unreasonable and inefficient. Through analyses on maintenance task attributes and interval parameter conversion rules, the man hours and the parking time of aircraft to finish the maintenance task package are taken as constraints, and the maximizing accumulative total time of executing all maintenance task packages during post-flight parking is taken as objective function. A model for civil aircraft maintenance task packeting optimization is established. According to the interval deviation regulations from AC-121-53, an algorithm is constructed to solve the model. Simulating verification is conducted taking B737NG as instance. Results show that maintenance task package which meets both the required maintenance capability and the post-flight parking time can be obtained via this model, balancing the manpower demand, improving the aircraft utilization and reducing the maintenance cost.


Influential factor analyses of aircraft cabin thermal comfort#br#

JI Yuchu, LI Ze

2020, 38(1):  29-33. 

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Cabin thermal comfort may decrease because of unreasonable operation of ground air conditioner during ground working, therefore the cabin environmental factors which may influence passenger爷s comfort should be comprehensively evaluated. According to the characteristics of cabin environment, PMV is selected as thermal comfort evaluation index. Employing simplified PMV model, the influence of cabin environmental factors (temperature,humidity, air flow speed) on PMV index is analyzed. Results show that cabin temperature has the greatest impact on cabin thermal comfort, air flow speed is the second factor, and humidity has least impact. Cabin thermal environment control based on PMV is more efficient and energy-saving than traditional way (constant and fixed cold/hot air supply).


Triangular mesh method of RTK height fitting based on external coincidence accuracy#br#

JIAO Weidong, ZENG Lanfeng

2020, 38(1):  34-37. 

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RTK height fitting method based on DT mesh can not obviously improve the external coincidence accuracy in the case of fewer fitting points. Two methods to improve the external coincidence accuracy of triangular mesh are proposed. In the first method, the minimum external coincidence accuracy is regarded as the limit criterion for triangular mesh connection without consideration about the characteristics of DT mesh. In the second method,both detection points and fitting points are used to generate a DT mesh which makes the external coincidence accuracy achieving the optimal value. Results show that these two methods can effectively improve the fitting
accuracy of triangular meshes, and can meet the fourth-class leveling standard of engineering survey application.


Constrained random coding method for high-intensity distribution of image texture#br#

GAO Qingji, PENG Chuanbo, FANG Rong

2020, 38(1):  38-42. 

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Aiming at the difficulties during stereo matching of weak-texture-object in binocular stereo vision system, a constrained random coding image generation algorithm is proposed for enhancement of texture quality. Firstly,according to the search strategy of stereo matching algorithm and calculation method of cost aggregation, the pixel coding rules of the projected image are designed, and the calculation method under local uniqueness constraint of projection and target hybrid image position pixels is established to form a high-intensity texture distribution image. The constrained random coded image generated by the algorithm is projected onto the surface of air baggage, the 3D reconstruction of air baggage surface is performed by stereo matching algorithm, and the reconstruction result is evaluated. The reconstruction experimental results of standard parts and actual baggage show that the proposed algorithm can accurately and reliably model the air baggage with solid color or weak texture features.


Seismic signal separation method based on EWT#br#

FEI Chunguo, DOU Jiachen, WANG Yang, JI Yuchu

2020, 38(1):  43-48. 

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Seismic signals generated by ground target movement can be used for target location and recognition. When there exist multiple types of ground targets, the signal aliasing phenomenon may interfere signal analysis. EWT algorithm divides the spectrum into several segments according to its maxima value, and transform the signals by constructing orthogonal wavelet functions in each segment to obtain multiple empirical mode signals. However, if the segments are merely devided according to the maxima value, dense peaks may result in too many modes. To solve this problem, spectrum envelope is extracted repeatedly to reduce the number of peaks, and then spectral threshold segmentation algorithm is proposed to enhance discrimination among different signals. Experiments show that improved EWT algorithm has better separation effect for seismic signals from different targets.


Temperature field boundary layer parameters ofpermafrost subgrade in Mohe district#br#

QI Chunxiang, LI Yao, MA Lin, DONG Bin

2020, 38(1):  49-53. 

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Integrating the second and third upper boundary conditions, permafrost subgrade temperature field distribution of airfield runway in Mohe district is simulated by using ABAQUS, the application of boundary layer theory in Mohe district is discussed, the boundary layer parameters and temperature function of permafrost subgrade temperature field in Mohe district are studied. Result shows that the boundary layer thickness of asphalt concrete runway pavement in Mohe district is 0.12 m, initial value of subgrade temperature at the bottom of boundary layer is 1.90 ℃and the amplitude is 25.09 ℃; Thickness of boundary layer of natural ground is 0.06 m, initial value of subgrade temperature at the bottom of boundary layer is 1.03 ℃and the amplitude is 25.20 ℃. Finally, the applying districts of boundary layer theory is expanded, providing research basis for of airfield runway subgrade stability in Mohe district.


Engineering and Technology

Synchronous acquiring system design of multimodal finger image#br#

YANG Jingfeng, LI Changfu

2020, 38(1):  54-59. 

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In the fusion of multimodal finger identification, pose synchronization of three-modal finger images including finger vein, finger-knuckle-print and finger print is crucial for recognition performance improvement. Firstly, a new hardware imaging mode is adopted to make consistent imaging pose of multimodal finger traits. Secondly, random plane-rotation of finger pose is corrected through finger posture angle calculation to reduce finger imaging posture change using algorithm. Finally, ROI coordination of finger vein and finger-knuckle-print is conducted by image space mapping. Experimental results prove the stable performance of the proposed image acquisition
scheme, which basically resolves the finger pose variation.


Multi-particle erosion mechanism of elastic coating based on cohesive element#br#

XU Jianxin, ZHU Xiahong, GUO Qiaorong, LI Dinghe

2020, 38(1):  60-64. 

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A multi-particle erosion model of elastic coating is established based on cohesive elements, the stress distribution on coating and bonding layer with erosion caused pit damage is analyzed. The influence of erosion density, particle distance and erosion times on stress distribution on coating and bonding layer are discussed. Results show that: with the same pit depth, the maximum values of radial contact stress and shear stress of bonding layer locate at the contact edge. The bigger erosion density of particles is, the smaller the maximum tensile stress of the coating becomes, the less likely it is to crack. The maximum radial stress on coating locates at the contact edge of the outermost particles. There is no interaction between particles when the distance between circle centers is bigger than the sum of their diameters. The locations of crack and delamination get closer to the contact edge when the stress produced by repeated erosion is smaller than single erosion.