Yacong Wu, Jun Huang, Mingxu Yi and Chaopu Zhang
The purpose of this paper is to introduce the theoretical basis of N-order spectral spreading-compressing (SSC) frequency shift interference algorithm and expand it to active…
Abstract
Purpose
The purpose of this paper is to introduce the theoretical basis of N-order spectral spreading-compressing (SSC) frequency shift interference algorithm and expand it to active cancellation. An active cancellation simulation and verification system based on N-order SSC algorithm is established and carried out; simultaneously, the absorbing material coating stealth simulation of two kinds of thickness is carried out to compare the stealth effect with active cancellation system.
Design/methodology/approach
The active cancellation method based on N-order SSC algorithm is proposed based on theoretical formula derivation; the active cancellation simulation and verification system is established in MATLAB/Simulink. The full-size model is built by CATIA and meshed by hypermesh. The omnidirectional radar cross section (RCS) is calculated in cadFEKO, and the results are analyzed in postFEKO.
Findings
The simulations are implemented on a stealth fighter, and results show that after active cancellation, the peak of spectrum analyzer has reduced in all azimuths, the omnidirectional RCS has also decreased and the detection probability of almost all azimuths has dropped under 50 per cent. The absorbing material coating stealth simulations of two kinds of thickness are carried out, and results show that the stealth effect of active cancellation is much better than absorbing material coating.
Practical implications
An active cancellation system based on SSC algorithm is proposed in this paper, and the effect of active cancellation is verified and compared with that of absorbing materials. A new method for the current active stealth is provided in this paper.
Originality/value
Active cancellation simulation and verification system is established. RCS calculation module, signal-to-noise-ratio (SNR) calculation module and detection probability module are built to verify the effect of active cancellation system. Simultaneously, the absorbing material coating stealth simulation is carried out, and the stealth effect of absorbing material coating and active cancellation are compared and analyzed.
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Xiaonan Chen, Jun Huang, Mingxu Yi and Yalin Pan
The purpose of this paper is to develop a flexible design-oriented development cost method for commercial aviation aircraft based on small sample and poor information.
Abstract
Purpose
The purpose of this paper is to develop a flexible design-oriented development cost method for commercial aviation aircraft based on small sample and poor information.
Design/methodology/approach
To predict the development cost of commercial aviation aircraft accurately, the methodology is based on the collected cost data and actual technical, and then the cost prediction relationships derived from an exhaustive statistical and filtered from regression analysis are incorporated. A series of regression equations with high regression coefficient are yielded after the cost driving factors of the development cost are fixed. Next, several sets of equations with high regression coefficient are selected for final integration. It is a flexible method that can be used efficiently to predict the cost of commercial aviation aircraft.
Findings
The development of commercial aviation aircraft has relatively a late start and no cost prediction model has been suitable for small sample, the proposed method is expected and is rather desirable.
Practical implications
By comparing the approach with the ordinary regression model and back propagation (BP) neural network, the scheme in this work is more efficient and convenient.
Originality/value
The results obtained in this paper show that the proposed method not only has a certain degree of versatility, but also can provide a preliminary prediction of the development cost of commercial aviation aircraft.
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Xiaonan Chen, Shiyong Chu, Guanglin Zhang, Xuanyou Chen, Jun Huang and Mingxu Yi
General aviation aircraft has a wide range of applications, and effective cost management is one of the hot spots in the research of general aviation manufacturers. The purpose of…
Abstract
Purpose
General aviation aircraft has a wide range of applications, and effective cost management is one of the hot spots in the research of general aviation manufacturers. The purpose of this paper is to build a flexible engineering method to predict maintenance cost of general aviation aircraft.
Design/methodology/approach
To establish a reasonable general aviation aircraft maintenance cost prediction model, it is necessary to analyze the influencing factors and extract the main components of maintenance cost. The maintenance cost is divided by engineering method, and the estimation model of each component cost is established. Then, the general aviation aircraft maintenance cost model is obtained. The results show that the relative error of this method is between 13% and 20%, which has a good estimation accuracy and can be effectively used to estimate the maintenance cost of general aviation aircraft.
Findings
The maintenance cost plays an important role in the life cycle cost of general aviation aircraft. Accurate cost prediction method is of great significance to the optimal design of general aviation aircraft. However, there are few prediction models suitable for maintenance cost, the proposed approach is meaningful and quite desirable.
Originality/value
To some extent, this method overcomes the shortage of the work on maintenance cost prediction for general aviation aircraft. The model established in this paper has certain generality, which can provide some reference for general aviation aircraft design and operation enterprises.
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Abstract
Purpose
By reducing the coating thickness of the weak scattering source, the coating weight of the absorbing material can be reduced by 35% with little effect on the RCS.
Design/methodology/approach
To alleviate the weight-increasing problem caused by a large number of coating of absorbing materials, a method for zonal coating of absorbing materials for a stealth helicopter was proposed. By appropriately reducing the thickness of the coating at the secondary scattering locations, the amount of coating used is significantly reduced.
Findings
Compared with the full-coated, the zonal coating scheme achieves the corresponding RCS reduction effect.
Practical implications
Zonal coating design can achieve the effect of reducing coating weight and cost.
Originality/value
The effects of different coating methods on RCS were verified by electromagnetic scattering simulation, and the applicability of the zonal coating design of the absorbing material to the stealth helicopter was verified.
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Abstract
Purpose
The purpose of this paper is to reduce the acoustic noise of helicopter ducted tail rotor.
Design/methodology/approach
To predict the noise accurately, a thin-body boundary element method (BEM)/Ffowcs Williams–Hawkings method is developed in this paper. It is a hybrid method combining the BEM with computational aeroacoustics and can be used efficiently to predict the propagation of sound wave in the duct.
Findings
Compared with the experimental results, the proposed method of acoustic noise is rather desirable.
Practical implications
Then several geometry parameters are modified to investigate the noise reduction of ducted tail rotor by using the numerical prediction method.
Originality/value
The aerodynamic and acoustic performance of different modification tasks is discussed. These results demonstrate the validity of design parameters modification of ducted tail rotor in acoustic noise reduction.
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This paper aims to propose a novel approach based on uniform scale-3 Haar wavelets for unsteady state space fractional advection-dispersion partial differential equation which…
Abstract
Purpose
This paper aims to propose a novel approach based on uniform scale-3 Haar wavelets for unsteady state space fractional advection-dispersion partial differential equation which arises in complex network, fluid dynamics in porous media, biology, chemistry and biochemistry, electrode – electrolyte polarization, finance, system control, etc.
Design/methodology/approach
Scale-3 Haar wavelets are used to approximate the space and time variables. Scale-3 Haar wavelets converts the problems into linear system. After that Gauss elimination is used to find the wavelet coefficients.
Findings
A novel algorithm based on Haar wavelet for two-dimensional fractional partial differential equations is established. Error estimation has been derived by use of property of compactly supported orthonormality. The correctness and effectiveness of the theoretical arguments by numerical tests are confirmed.
Originality/value
Scale-3 Haar wavelets are used first time for these types of problems. Second, error analysis in new work in this direction.