Current Issue : October - December Volume : 2020 Issue Number : 4 Articles : 5 Articles
Within this study, monolithic three-dimensional silica aerogel (SA) composite parts with\nsuper insulating properties are presented. A generic part based on fiber-reinforced (FR) silica\naerogel for thermal insulation of the exhaust tubing system-to keep the exhaust gases as hot as\npossible to improve the efficiency of the catalyst system-was produced via a sol-gel-based molding\nprocess in combination with a supercritical drying using scCO2. A thermal conductivity of 16 mW\nm-1 K-1 was measured via a heat flow meter technique. In this manuscript, we present a full cycle of\nthe material compound design, starting with fundamental material evaluation including aerogel\noptimization, opacifier influence, and casting process. The obtained generic part in shape of a halfshell\nfor pipe insulation is characterized under real conditions....
The aircraft wake vortex has important influence on the operation of the airspace utilization ratio. Particularly, the identification of\naircraft wake vortex using the pulsed Doppler lidar characteristics provides a new knowledge of wake turbulence separation\nstandards. This paper develops an efficient pattern recognition-based method for identifying the aircraft wake vortex measured\nwith the pulsed Doppler lidar. The proposed method is outlined in two stages. (i) First, a classification model based on support\nvector machine (SVM) is introduced to extract the radial velocity features in the wind fields by combining the environmental\nparameters. (ii) Then, grid search and cross-validation based on soft margin SVM with kernel tricks are employed to identify the\naircraft wake vortex, using the test dataset. The dataset includes wake vortices of various aircrafts collected at the Chengdu\nShuangliu International Airport from Aug 16, 2018, to Oct 10, 2018. The experimental results on dataset show that the proposed\nmethod can identify the aircraft wake vortex with only a small loss, which ensures the satisfactory robustness in\ndetection performance....
This paper defines a methodology for the evaluation of the technical and economic performance of aeronautical engines through the upgrades introduced during its life. The CFM56 is a high-bypass turbofan engine. The variants share a common design, but the details are different. The fan and booster evolved over the different iterations of the engine, as did the compressor, combustor, and turbine sections. Maintenance consists of the activities carried out during the life cycle of an engine to ensure safe, reliable, and economic operation. Maintenance costs represent 20-25% of an airlineâ??s operating costs, of which 35-40% refer to the engine. The changes in the performance parameters indicate the state of the engine in the medium to long term: for example, it is possible to detect blade fouling or data on vibrations, and highlight changes in the characteristic behavior of an engine. This work investigates the behavior of the performance parameters in the period prior to an engine development event: a comparison is made with the monitoring of engine vibrations. In the conclusions, a final expressive graph makes us aware of the significant progress, over the years, achieved with the methodology here presented....
Operational modal parameter identification is a tough problem in aerospace engineering due to the complex mechanics\nenvironment, various noises, and limited computational resources. In this paper, a novel, recursive, robust, and highefficiency\nmodal parameter identification approach is proposed for this issue. The kernelized time-dependent autoregressive\nmoving average (TARMA) model is adopted to model the nonstationary responses, a recursive estimator is\nestablished based on the maximum correntropy criterion, and sliding-window technique is applied to fix the computational\ncomplexity, which ensures the approach its estimation accuracy, robustness, and high efficiency. Finally, steps of\nthe identification procedure and model selection are presented. An experimental scheme is proposed for validation, and\nthe proposed approach is comparatively assessed against the classical recursive pseudo-linear regression TARMA method\nvia Monte Carole tests of a time-varying experimental system. The results of the comparative study demonstrate that the\nproposed method achieves similar estimation accuracy and higher computation efficiency under the Gaussian environment.\nMoreover, a superior estimation accuracy and enhanced robustness are rendered under additive non-Gaussian\nimpulsive noise....
The main objective of this research is to review and investigate the influence of carbon nanotube structure on the properties of\ncarbon nanotube and carbon nanotube-reinforced epoxy. Carbon nanotube and carbon nanotube-reinforced epoxy are currently\nbeing frequently used in many applications such as aerospace, automotive, and electronics industries due to their excellent\nproperties such as high tensile strength, high Youngâ??s modulus, and electrical and thermal conductivity. In this study, the\nobstacles to apply carbon nanotubes as fibers within the matrix have been introduced and discussed. Additionally, the epoxy\nproperties and application have been cited, and failure mechanisms of carbon nanotube-reinforced epoxy and geometries of\ncarbon nanotubes have been reviewed. Furthermore, with using experimental data and applying an analytical method, the effect\nof carbon nanotube diameter on interlaminar shear stress within the carbon nanotube-reinforced epoxy interface has been\nevaluated. Additionally, the effect of temperature variation on the value of interlaminar shear stress within the single-walled\ncarbon nanotube-reinforced epoxy interface has been discussed. Finally, the influence of the number of hexagons in the unit cell\non the Youngâ??s modulus of zigzag and armchair single-walled carbon nanotubes has been evaluated....
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