Advanced Materials Research Vol. 1016

Abstract: Multiphase flow characterization is an important task for monitoring, measuring or controlling industrial processes. This can be done by means of process tomography. The use of tomographic techniques has been used within the oil industry. One of the potential applications is flow visualization and measurement in producing wells. Research on industrial process tomography consists in obtaining estimated images of a cross section of a pipe or vessel containing or carrying the substances of the process. One category of process tomography is ultrasonic tomography technique. A simple tomography can be built by mounting a number of sensors around the circumference of a horizontal pipe. This includes acquiring and processing ultrasonic signals from the transducers to obtain the information of the spatial distributions of liquid and gas in an experimental column. Analysis on the transducers’ signals will be carrying out to distinguish between the observation time and the Lamb waves. The information obtained from the observation time is useful for further development of the image reconstruction. To obtain the time easily, the time will be calculated from the starting pulse of transmitter signal until the starting peak of receiver signal. Finally Support Vector Machine (SVM) was employed to distinguish of each phase between water and gas.

Abstract: The present work consists of an experimental performances analysis of a suspension system with two degrees of freedom governed by a semi-active modified continuously variable command (MCVC) law. The internal dynamics of Magneto-Rheological (MR) damper used in this study is highlighted by the modified Bouc-Wen model in the mathematical modelling of the secondary suspension system. After the dynamic characterization of the MR damper, a comparison of performance obtained by this control scheme is carried out from the responses calculated using a numerical model and measured experimentally from a test bench of a semi-active suspension incorporating an MR damper and controlled by a dSPACE control chain. For a better representativeness of the modified Bouc-Wen numerical model, a rapprochement between the calculated and measured responses for the same dynamic characteristics of the test bench is possible by adjusting the most influential parameters of the numerical model. Through better management of the suspension during the low speeds, the modified Bouc-Wen model is more representative of the real behaviour of the MR damper, given its sensitivity at these low speeds during transitions between compression and expansion phases of the damper.

Abstract: This paper presents the modeling and analysis method of acoustic noise levels of whole audible frequency range for Chinese Space Station (CSS) module. Using Boundary Element Modeling (BEM), the acoustic analysis model of low frequency range for CSS module was established. The analysis model of high frequency range was created by using Statistical Energy Analysis (SEA) method. Based on the established models, the acoustic noise levels in all areas of CSS module were analyzed and the results for some typical areas are provided. Finally, the acoustic contribution of noise sources according to their spectral characteristics is analyzed and the implementation of noise control methods to reduce acoustic levels in CSS module is discussed.

Abstract: The human model in this paper is simplified as a rigid body of 15 segments and the Roberson-Wittenberg method is used to establish the equation of conservation of angular momentum to obtain the control methods of human self-rotation without external force in a weightless environment. And simulation of human dynamic is completed in ADMAS (Automatic Dynamic Analysis of mechanical Systems). The simulation results show that human can generate corresponding body rotation through own limbs rotation in the weightless, and body rotation velocity and angle increase with the moment of inertia and rotational velocity of active body that adds greater torque to joint. Through the analysis of the impact of the angular velocity and torque on the body rotation, a set of self-rotation control strategy for astronaut is proposed in weightless environment.

Abstract: A widespread application of composite materials requires proper knowledge of both static and dynamic loading properties, particularly for automotive and transportation applications. In this study the behavior of unidirectional glass fiber reinforced polymeric composites under uniaxial loading is determined at quasi-static and intermediate strain rates in the range 0.6–500/s. The tensile tests were performed using different servo-hydraulic testing apparatus. Dynamic tests results are compared with the results of static tensile tests carried out on specimens with identical geometry. Experimental results show a significant increase of the tensile strength with increasing strain rate. The strain to failure is also observed to increase slightly for higher strain rates.

Abstract: Microcrystalline silicon films were deposited using Ar diluted SiH₄ gaseous mixture by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). The effects of power on microstrcture and optical properties of microcrystalline silicon films were investigated. The results show that, with the increasing of the power, the crystallinity increased, but the concentration of hydrogen decreased monotonously. Furthermore, the absorption coefficient of the films increased monotonously, and the optical bandgap changed from 1.89eV to 1.75eV with the microwave power ranging from 400 W to 650W.

Abstract: This paper presents a comparative evaluation of three lignocellulosic residues (coffee husks, spent coffee grounds and pequi husks) as precursor materials in the production of activated carbons (ACs). Results indicate that the precursor material has a significant effect in both physical and chemical aspects of the adsorbent, with the AC based on spent coffee grounds being the most effective for phenol removal, with maximum adsorption capacity comparable to commercial ACs.

Abstract: Self-compacting concrete is characterized as a system that has a mix design that increased strength and reduced amount of empty space within material. Reinforced concrete structures exposed to carbonation and chloride ion, are exposed to environmental conditions that cause degradation. Concrete were exposed to an accelerated carbonation test (3% CO2, 65% relative humidity, and 25 o C temperatures) and next it was tested under complete immersion, in 3.5 wt. % NaCl solution. . Monitoring of open-circuit potential, polarization resistance measurement and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of steel bar.

Abstract: Multilayer coatings [ TiCN / TiNbCN ] n were fabricated with periods of bilayers 1, 50 and 200 deposited on substrates of austenitic steels type fermanal, using R.F. reactive magnetron sputtering with a radio frequency source (13.56 MHz) and two TiC and Nb targets. The multilayers were characterized using X-ray diffraction and scanning electron microscopy. The tribo – electrochemical behavior simulating hostile body environment was evaluated by testing tribocorrosion ( combination of wear and corrosion in aqueous environment ) which were carried out with a Gamry PCI 4 equipment to which adapted a pin on disk tribometer, the tests were made immersed in Hanks solution (Hanks balanced salt solution). A cell comprising a platinum counter-electrode, an Ag/AgCl reference electrode and the and a working electrode ( austenitic steels) at a temperature of 37 ± 0.2 ° C. the evaluation tests were performed using electrochemical techniques of Tafel polarization curves. Regarding the results, the hard coating [ TiCN / TiNbCN ] n improved polarization resistance and lower coefficient of friction than that reported for the substrate is provided , which indicates a good resistance to corrosion and wear.

Abstract: This study aims to assess the stage of drying ceramic composite through kinetic curves of drying , to evaluate the drying time and shrinkage of the material during the process carried out in an oven at 50 oC and microwave at 10 % of maximum power 700 W. For this study, compositions with addition of “São Tomé” stone and clay in a 1:4 mass ratio were prepared and this composite was compared with the samples fabricated only with clay. To evaluate the structure resulting from the drying computed microtomography analysis was performed. The results indicated that the addition of stone “São Tomé” contributed to reducing the processing time by decreasing the conformation water. The use of microwave drying process as favored gain strength of the product due to the lower fraction of pores, and also ensure a shorter processing time due to the increased rate of drying.