Papers by Keyword: Comparison

Abstract: The use of rice husk ash (RHA) as filler in polymeric materials has been studied in different polymers. Research reported that RHA may successfully replace silica. The silica production process using ore demands high energy input and produces considerable amounts of waste. Therefore, the replacement of silica by RHA may be economically and environmentally advantageous, reducing environmental impact and adding value to a waste material. In this context, this study characterizes and compares RHA of different sources (moving grate and fluidized bed reactor) with commercially available silicas to assess performance as filler in polymeric materials. Samples were characterized by X-ray fluorescence, loss on ignition, X-ray diffraction, grain size, specific surface area, specific weight, and scanning electron microscopy. The results show that RHA may be used as a filler in several polymeric materials.

Abstract: Aluminum and its alloys are widely used materials; they are next to steel in use mainly in the automobile industry due to their high strength – to – weight ratio and corrosion resistance beside its other attractive properties. Against their attractive properties; they have the disadvantage of solidifying in columnar structure which tends to reduce their mechanical characteristics and surface quality. Therefore it became customary to grain refine them either by Ti or Ti+B to overcome this discrepancy. In this paper, comparison between Molybdenum addition to commercially pure aluminum grain refined by Ti and Ti+B on its grain size and mechanical characteristics both in the cast and after pressing by the ECAP process is investigated and the obtained results are presented and discussed.

Abstract: Magnesium and its alloys are the lightest constructional available materials on earth with a maximum density of 1.78 g /cc and melting point of 650 ͦC, with good damping characteristics. Therefore; they are alloyed or micro alloyed with other elements. In this paper comparison between the addition of Ti and Ti+ B to this alloy on its grain size and its mechanical characteristics is investigated both in the cast and after direct extrusion and the obtained results are presented and discussed.

Abstract: This paper investigates such concrete properties which determine the stress magnitude of concrete caused by its volume changes. The magnitude of induced stress is given by shrinkage or swelling value and corresponding modulus of elasticity value. It is essential to know these properties of concrete from the beginning of its skeletal frame formation since the volume changes occur almost immediately after mixing of water with cement. In addition, the humidity effect of ambient environment when the early age concrete matured was considered. Thereby was achieved relevant comparison between ordinary concrete mixture and optimized one. For experiments was used micro-concrete (with maximum aggregate size 1.6 mm) with respect to cost reduction. After the suitable composition of micro-concrete was found the analogue investigation was carried out with the optimized concrete.

Abstract: Al-6wt.%Si-3.5wt.%Cu alloy (A319) were prepared by casting and powder metallurgy (PM) methods to investigate the influence of processing procedure on properties. The casting samples were cast into a horizontal mold after degassing by argon. The PM samples were extruded after hot-press sintering before which Al-11wt.%Si master alloy powder, pure Al powder and 48 h ball-milled Al-40wt.%Cu powder were blended for 12 h at rotation speed of 250rpm. The samples underwent a T6 temper, i.e. solution, water quenching and artificial aging. Microstructures were observed by optical microscope (OM) and scanning electron microscope (SEM), and phases were determined by X-ray diffraction (XRD). The tensile testing was carried out on universal testing machine. The results showed that heat treatment could greatly improve the tensile strength of the samples, especially for the casting counterpart. Discussion was made to analyze the reason that the properties differed.

Abstract: The contribution deals with a comparison of measured and calculated values of sound reduction index R (dB) and weighted sound reduction index R_w (dB) of simple walls from various materials. In this way it verifies the exactness of a modified calculation-graphic method according to Watters and an appropriateness of its application for simple walls from various materials with the focus on the aerated concrete walls.

Abstract: The paper deals with the estimation of modal parameters and its main purpose is to compare differences in the values of natural frequencies and damping ratios, which were estimated using three different extraction methods: Rational Fraction Polynomial method, Complex Mode Indicator Function and Polyreference Time Domain Technique. These methods are well suited to the more general application to multi-FRF data, both of the SIMO and the MIMO types. The object of measurement was a freely suspended steel rod of circular cross section. The responses of the analyzed structure were measured by accelerometer and laser vibrometer. The results of these measurements are also discussed in the paper.

Abstract: Self-compacting concrete has been accepted as a quality product. A Suitable method for estimating the instantaneous deflection for SFRSCC is not available. In this study an effective moment of inertia function has been formulated with a power coefficient obtained from authors and others data. The proposed method is found to predict the instantaneous deflections satisfactorily.

Abstract: The soil pedotransfer functions (PTFs) provide an easily way to estimate the unsaturated hydraulic conductivity, and it predicts missing characteristics from already available basic soil data. In this paper, a review was made on the most common PTFs for the estimation of unsaturated hydraulic conductivity in recent years, including the methods of Rosetta, Rawls, Campbell and Vauclin. Based on the methods, a summary of necessary input parameters and basic properties of the PTFs was made to in this paper. Finally it was pointed out that the future study will focus on how to improve the accuracy and reliability of PTFs and the multi scale study.

Abstract: The pavement performance study of bituminous mixture at surface course is very important. This paper focused on comparing the pavement performance of AC-l6C, AC-l6F, Super-12.5 and SMA-16 bituminous mixtures. First the gradations and material we used were illustrated. Then the dynamic stability, water stability and texture depth of these bituminous mixtures was tested. After comparing the test data, we found that the SMA-16 bituminous mixture has the best comprehensive pavement performance and it is most suitable for the surface layer bituminous mixture of freeways in Chinese Hubei Province. Super-12.5 and AC-l6C is applicable too, but AC-l6F is improper in this region.