Transactions of Nanjing University of Aeronautics and Astronautics最新文献

{"title":"Test Research of Seepage Monitoring Based on Distributed Optical Fiber","authors":"Zhao Xinming, Gao Yifei, Wang Qianwen, Gao Junqi, Zhou Yong, Wu Gang, Yao Jian","doi":"10.16356/j.1005-1120.2018.02.300","DOIUrl":"https://doi.org/10.16356/j.1005-1120.2018.02.300","url":null,"abstract":"In this paper, a theoretical model of temperature and velocity of a fiber is derived. A test model simulating seepage indoor is designed. The optical fiber heating temperatures under different compaction degree and seepage velocities are measured through applying AC voltage on the optical fiber. The analyzing results show that the optical fiber heating temperature and seepage velocity are related in quadratic function. The quantitative relations of optical fiber temperature and seepage velocity under different soil types and compaction degree are fitted. Analysis on how the compaction degree influences the relation of optical fiber temperature and seepage velocity shows that with the increase of compaction degree, optical fiber heating temperature will gradually decline. The influence of soil type on fiber heating temperature is very complex. In practice, according to the characteristics of the soil, determining quantitative relationship and implementing quantitative monitoring of the seepage velocity are needed.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48019595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantitative Rectangular Notch Detection of Laser-induced Lamb Waves in Aluminium Plates with Wavenumber Analysis","authors":"Liu Zenghua, Feng Xuejian, He Cunfu, Wu Bin","doi":"10.16356/J.1005-1120.2018.02.244","DOIUrl":"https://doi.org/10.16356/J.1005-1120.2018.02.244","url":null,"abstract":"It is difficult to quantitatively detect defects by using the time domain or frequency domain features of Lamb wave signals due to their dispersion and multimodal characteristics. Therefore, it is important to discover an intrinsical parameter of Lamb waves that could be used as a damage sensitive feature. In this paper, quantitative defect detection in aluminium plates is carried out by means of wavenumber analysis approach. The wavenumber of excited Lamb wave mode is a fixed value, given a frequency, a thickness and material properties of the target plate. When Lamb waves propagate to the structural discontinuity, new wavenumber components are created by abrupt wavefield change. The new wavenumber components can be identified in the frequency-wavenumber domain. To estimate spatially dependent wavenumber values, a short-space two-dimensional Fourier transform(FT) method is presented for processing wavefield data of Lamb waves. The results can be used to determine the location, size and depth of rectangular notch. The analysis techniques are demonstrated using simulation examples of an aluminium plate with a rectangular notch. Then, the wavenumber analysis method is applied to simulation data that are obtained through a range of notch depths and widths. The results are analyzed and rules of the technique with regards to estimating notch depth are determined. Based on simulation results, guidelines for using the technique are developed. Finally, experimental wavefield data are obtained in aluminium plates with rectangular notches by a full non-contact transceiving method, i.e., laser-laser method. Band-pass filtering combined with continuous wavelet transform is used to extract a certain frequency component from the full laser-induced wavefield with wide band. Short-space two-dimensional FT method is used for further processing full wavefield data at a certain frequency to estimate spatially dependent wavenumber values. The consistency of simulation and experimental results shows the effectiveness of proposed wavenumber method for quantitative rectangular notch detection.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43295313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Algorithm for Determination of Projectile Attitude Angles in Projectile Trajectory Prediction","authors":"Zha Qicheng, Rui Xiaoting, Yu Hailong, Zhou Qin-bo","doi":"10.16356/J.1005-1120.2018.02.361","DOIUrl":"https://doi.org/10.16356/J.1005-1120.2018.02.361","url":null,"abstract":"A fast and accurate algorithm is established in this paper to increase the precision of ballistic trajectory prediction. The algorithm is based on the six-degree-of-freedom (6DOF) trajectory equations, to estimate the projectile attitude angles in every measuring time. Hereby, the algorithm utilizes the Davidon-Fletcher-Powell (DFP) method to solve nonlinear equations and Doppler radar trajectory test information containing only position coordinates of the projectile to reconstruct the angular information. The ″position coordinates by the test″ and ″angular displacements by reconstruction″ at the end phase of the radar measurement are used as an initial value for the trajectory computation to extrapolate the trajectory impact point. The numerical simulations validate the proposed method and demonstrate that the estimated impact point agrees very well with the real one. Morover, other artillery trajectory can be predicted by the algorithm, and other trajectory models, such as 4DOF and 5DOF models, can also be incorporated into the proposed algorithm.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42826653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Loading Localization by Small-Diameter Optical Fiber Sensors","authors":"Liu Rongmei, Zhu Lujia, Lu Jiyun, L. Dakai","doi":"10.16356/J.1005-1120.2018.02.275","DOIUrl":"https://doi.org/10.16356/J.1005-1120.2018.02.275","url":null,"abstract":"Structural health monitoring (SHM) in service has attracted increasing attention for years. Load localization on a structure is studied hereby. Two algorithms, i.e., support vector machine (SVM) method and back propagation neural network (BPNN) algorithm, are proposed to identify the loading positions individually. The feasibility of the suggested methods is evaluated through an experimental program on a carbon fiber reinforced plastic laminate. The experimental tests involve in application of four optical fiber-based sensors for strain measurement at discrete points. The sensors are specially designed fiber Bragg grating (FBG) in small diameter. The small-diameter FBG sensors are arrayed in 2-D on the laminate surface. The testing results indicate that the loading position could be detected by the proposed method. Using SVM method, the 2-D FBG sensors can approximate the loading location with maximum error less than 14 mm. However, the maximum localization error could be limited to about 1 mm by applying the BPNN algorithm. It is mainly because the convergence conditions (mean square error) can be set in advance, while SVM cannot.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46109706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zemax-Based Optimum Structural Design of Probe of an Optical-Fiber Sensor","authors":"Hang Tianyuan, W. Xiaolei, Liu Feng, Ye Song, Cheng Zhentao","doi":"10.16356/j.1005-1120.2018.02.309","DOIUrl":"https://doi.org/10.16356/j.1005-1120.2018.02.309","url":null,"abstract":"Bubble plumes are important during the process of air-sea exchange, and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves. This paper designs a new optical-fiber probe (OFP) made of sapphire to overcome the limitations of existing materials (e.g., high brittleness, poor corrosion resistance, and narrow bandwidth) and thereby enhance the detection performance of the OFP by improving its structure. Based on total internal reflection and light refraction, a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips. The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°. Tests are then conducted on a bespoke OFP sensor, the results of which are consistent with those predicted theoretically. The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics. The findings could also be applied to OFPs with multiple tips.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49058291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Curing Age on Chloride Diffusion Coefficient of Recycled Aggregate Concrete Subjected to Compressive Stresses","authors":"Tang Jinzhi, Wu Jin, Wan Wenjian, W. Zhe, Wu Guanzheng","doi":"10.16356/j.1005-1120.2018.02.326","DOIUrl":"https://doi.org/10.16356/j.1005-1120.2018.02.326","url":null,"abstract":"The effect of curing age on chloride diffusion coefficient of recycled aggregate concrete subjected to different compressive stresses was investigated. A compression loading setup was both designed and fabricated. The chloride diffusion coefficients of recycled aggregate concrete under compressive stresses were measured by the rapid chloride ion migration (RCM) method. The experimental results show that the chloride diffusion coefficients of recycled aggregate concrete (RAC) under different compressive stress ratios generally decrease with the increase of curing age. For RAC subjected to the same compressive stress ratios, the chloride diffusion coefficients approximately have power functions with curing ages and the relationship models are proposed. Moreover, the influence of curing age on chloride diffusion coefficient firstly decreases and then increases as the compressive stress ratio increases.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44093779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Perturbation Theory of Fractional Lagrangian System and Fractional Birkhoffian System","authors":"Song Chuanjing, Z. Yi","doi":"10.16356/J.1005-1120.2018.02.353","DOIUrl":"https://doi.org/10.16356/J.1005-1120.2018.02.353","url":null,"abstract":"Perturbation to symmetry and adiabatic invariants are studied for the fractional Lagrangian system and the fractional Birkhoffian system in the sense of Riemann-Liouville derivatives. Firstly, the fractional Euler-Lagrange equation, the fractional Birkhoff equations as well as the fractional conservation laws for the two systems are listed. Secondly, the definition of adiabatic invariant for fractional mechanical system is given, then perturbation to symmetry and adiabatic invariants are established for the fractional Lagrangian system and the fractional Birkhoffian system under the special and general infinitesimal transformations, respectively. Finally, two examples are devoted to illustrate the results.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43619606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aircraft Engine Gas Path Fault Diagnosis Based on Hybrid PSO-TWSVM","authors":"Du Yanbin, X. Lingfei, Cheng Yusheng, Ding Runze","doi":"10.16356/j.1005-1120.2018.02.334","DOIUrl":"https://doi.org/10.16356/j.1005-1120.2018.02.334","url":null,"abstract":"Twin support vector machine (TWSVM) is a new development of support vector machine (SVM) algorithm. It has the smaller computation scale and the stronger ability to cope with unbalanced problems. In this paper, TWSVM is introduced into aircraft engine gas path fault diagnosis. The generalization capacity of Gauss kernel function usually used in TWSVM is relatively weak. So a mixed kernel function is used to improve performance to ensure that the TWSVM algorithm can better balance a strong generalization ability and a good learning ability. Experimental results prove that the cross validation training accuracy of TWSVM using the mixed kernel function averagely increases 2%. Grid search is usually applied in parameter optimization of TWSVM, but it heavily depends on experience. Therefore, the hybrid particle swarm algorithm is introduced. It can intelligently and rapidly find the global optimum. Experiments prove that its training accuracy is better than that of the classical particle swarm algorithm by 5%.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45271582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aero-engine Thrust Estimation Based on Ensemble of Improved Wavelet Extreme Learning Machine","authors":"Zhou Jun, Zhang Tianhong","doi":"10.16356/J.1005-1120.2018.02.290","DOIUrl":"https://doi.org/10.16356/J.1005-1120.2018.02.290","url":null,"abstract":"Aero-engine direct thrust control can not only improve the thrust control precision but also save the operating cost by reducing the reserved margin in design and making full use of aircraft engine potential performance. However, it is a big challenge to estimate engine thrust accurately. To tackle this problem, this paper proposes an ensemble of improved wavelet extreme learning machine (EW-ELM) for aircraft engine thrust estimation. Extreme learning machine (ELM) has been proved as an emerging learning technique with high efficiency. Since the combination of ELM and wavelet theory has the both excellent properties, wavelet activation functions are used in the hidden nodes to enhance non-linearity dealing ability. Besides, as original ELM may result in ill-condition and robustness problems due to the random determination of the parameters for hidden nodes, particle swarm optimization (PSO) algorithm is adopted to select the input weights and hidden biases. Furthermore, the ensemble of the improved wavelet ELM is utilized to construct the relationship between the sensor measurements and thrust. The simulation results verify the effectiveness and efficiency of the developed method and show that aero-engine thrust estimation using EW-ELM can satisfy the requirements of direct thrust control in terms of estimation accuracy and computation time.","PeriodicalId":39730,"journal":{"name":"Transactions of Nanjing University of Aeronautics and Astronautics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41395619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}