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This paper aims to prepare third-order nonlinear optical (NLO) organic materials with large nonlinear optimization value, high damage threshold and ultrafast response time.

A series of novel symmetric and asymmetric compounds possessing third-order NLO properties were synthesized using 1,3,5-tribromobenzene as the basis. The photophysical and electrochemical properties, as well as the click reactions, were characterized by means of UV–VIS–NIR absorption spectroscopy and cyclic voltammetry.

The donor–acceptor chromophores were inserted into compound, making the molecule to have a broader absorption in the near-infrared regions and a narrower optical and electrochemical band gap. It also formed an electron-delocalized organic system, which has larger effects on achieving a third-order NLO response. The third-order NLO phenomenon of benzene ring complexes was experimentally studied at 532 nm using Z-scan technology, and some compounds showed the expected NLO properties.

The click products exhibit more NLO phenomena by performing different click combinations to the side groups, opening new perspectives on using the system in a variety of photoelectric applications.

The purpose of this paper is to reduce the acoustic noise of helicopter ducted tail rotor.

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.

Compared with the experimental results, the proposed method of acoustic noise is rather desirable.

Then several geometry parameters are modified to investigate the noise reduction of ducted tail rotor by using the numerical prediction method.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Compared with the high stiffness of traditional CNC machine tools, the structural stiffness of industrial robots is usually less than 1 N/µm. Chatter not only affects the quality of robotic milling but also reduces the accuracy of the milling process. The purpose of this paper is to reduce chatter in the robotic machining process.

First, the mode coupling chatter mechanism is analyzed. Then the milling force model and the principal stiffness model are established. Finally, the robot milling stability optimization method is proposed. The method considered functional redundancies, and a new robot milling stability index is proposed to improve the quality of milling operations.

The experimental results prove a significant reduction in force fluctuations and surface roughness after using the proposed robotic milling stability optimization method.

In this paper, a new robot milling stability index and a new robot milling stability optimization method are proposed. This method can significantly increase the milling stability and improve the milling quality, which can be widely used in the industry.

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.

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.

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.

Scale-3 Haar wavelets are used first time for these types of problems. Second, error analysis in new work in this direction.