Applied Mechanics and Materials Vol. 421

Abstract: RANS / NLAS numerical simulation method is adopted in this paper to carry out study on the aerodynamic noise analysis of basic landing gear configuration. Reynolds average N-S equation is solved with nonlinear turbulence model to establish the landing gear initial flow field, based on which, the NLAS (nonlinear acoustic solver) processed the turbulence fluctuation reconstruction to obtain the near-field acoustic characteristics of landing gear. Combined with the flow characteristics and the associated noise spectrum analysis, aerodynamic noise characteristics of landing gear are achieved. The work in this paper can provide useful research foundation on the following noise reduction design of landing gear.

Abstract: The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM applications. As a result, comparing to the past result, the maximum prediction error of resonant frequency was within 3 percent and peak dither rate was within 5 percent. It was found that the theoretical equations can be feasible for the mechanical performance of dither.

Abstract: In this letter, an in-fiber integrated Michelson interformeteris proposed and experimentally demonstrated. The device consists in the combination of multi-mode fiber (MMF) and a single-mode fiber (SMF) tip which is covered by thick silver film. The MMF excites cladding modes into downstream SMF via the mismatch-core splicing interface. The core-cladding modes are reflected back by the silver and recoupled to fiber core through the MMF. By the reason of fiber-core mismatch and core-cladding modes interference, a well-defined interference pattern is obtained. A stable dual-wavelength fiber laser based on a hybrid gain medium combined with the interferometer filter is realized.

Abstract: CFRP (Carbon Fiber Reinforced Plastic) occupied an important ratio in composite material for its high strength and high modulus. So CFRP/Al laminated construction was applied in airplane industry more and more popular, which was mainly joined by interference-fit connection. In joining process, interference amount is difficult to control. In this article, process parameters such as working voltage and rivet hole clearance was selected to study the relationship between the parameter and interference amount by experimental test method. Besides interference amount is different at CFRP end and metal end, and lays the foundation for theoretical analysis and numerical calculation of interference amount.

Abstract: When the satellites CMG (Control Moment Gyroscope) generate the control moment, they will also generate the periodic and broadband disturbance vibration force, and will have a greater impact on the performance of instruments with high pointing precision and stability. This paper analyze a large CMG of 70Nms belonging to a remote sensing satellite, its feature is the mass of moving parts. So when it is installed to the test table that we designed independently, the fundamental frequency of the system as a whole will significantly reduce. Based on past study the purpose of this paper is mainly focused on the testing techniques of the heavy moving parts, and the technical method to isolate the test tables stiffness from test results.

Abstract: Image halftoning is the core technique of digital image output, which determines the quality of the color and tonal gradation reproduction. In this paper, the existing halftoning techniques were analyzed and evaluated, such as FM halftoning and AM halftoning, etc. And a new halftoning mode, frequency conversion amplitude modulation (FCAM), was proposed. This method is still based on AM halftoning, but it uses the different screen frequency for halftoning image of the different color version, so as to avoid moiré fringes on the smaller superposition angle. The use of new halftoning model can achieve halftoning image output which is more than 4 colors (such as 6 colors or 7 colors) without visual moirè pattern when overprinting. By the new technique, high-fidelity printing is achieved, and the color gamut of the output image is expanded, and we can get more vivid realistic effect of image transmission. We tested color gamut expansion of 6 colors and 7 colors high-fidelity printing, and obtained the expected conclusion by quantitative analysis.

Abstract: In order to predict the micro-vibration disturbance of reaction wheel, an improved experience model has been provided, which expresses the effect of the reaction wheels natural frequencies being the dominating factor in amplifying the disturbance. WLS-SVR algorithm is applied to identify the parameters of this model. The robust characteristic of this algorithm promises the global optimal estimation can be achieved. Experiment has been set up to measure the disturbance of the reaction wheel. Data achieved from the experiment are used to get the parameters of model and verify the identification results of WLS-SVR algorithm. The results show the improved model describes the properties of disturbance more precisely and the WLS-SVR algorithm can achieve accurately identification results.

Abstract: Operation principal of Electronic Oxygen Regulator (EOR) was explained in this paper. A mathematic model was established on Matlab/Simulink platform to study the maximum flow of pulmonic valve and design method of compression spring rigidity. Selecting criteria for main parameters of EOR is determined quickly and efficiently through simulation. Conclusion of simulation is of great reference value for EOR engineering.

Abstract: This paper proposes a novel method to on-machine determine the three error components of a precision linear slide: the straightness motion, the yaw and the roll under the effect of thermal distortion caused by friction and drive. The Integrated Sensing System (ISS) is then introduced for implementing this novel method on an illustrative model of a linear slide. The error separation algorithm used in the system is based on the Fourier Eight Sensor (F8S) method. The theory and procedures are presented, and computer results are analyzed. The effectiveness of the novel method is validated through computer simulations.

Abstract: The boundary layer aerodynamic flow acceleration with one atmosphere uniform induced by multiple dielectric-barrier-discharge plasma actuation were studied based on PIV. Through double actuators alternating discharge, the multiple dielectric barrier discharge mode have been proposed and tested. The efficiencies of the plasma actuators in Pulsed-pulsed, Steady-steady, Pulsed-steady and Steady-pulsed discharge modes were explored. Based on the above results, the boundary layer flow acceleration performance of multiple plasma actuators has been discussed and the more efficient discharge pattern has been proposed. The results of this study indicate that the airflow acceleration effect of multiple plasma actuators mainly occurs in paraelectric direction and the pulsed-pulsed is the more efficient multiple plasma actuation mode.