Papers by Keyword: CA

Abstract: Nanoparticle has been used in agricultural practices such as soil ameliorant. Nanoparticle of volcanic ash and biofertilizer were applied to improve some soil characteristics of Inceptisols. The objective of this research was to optimize the benefit of nanoparticle of volcanic ash and biofertilizer in reducing soil acidity, increasing organic carbon content, and increasing basic cations of Inceptisols. Volcanic ash was obtained from the eruption of Mt. Merapi in Central Java. Nanoparticle was grinded in Nanotechnology and Graphene Research Center, Universitas Padjadjaran. Phosphate solubilizing fungi was used as biofertilizer, isolated in Soil Microbiology Laboratory, Universitas Padjadjaran. A two factors randomized experimental design was used in this research. Nanoparticle of volcanic ash was used as first factor (four levels: 0%, 2%, 4% and 6% of soil weight percentages). Biofertilizer was used as second factor (two levels: 0 and 10 g.kg^-1). These two treatments were combined and mixed evenly and incubated for three months in field condition. Every month during those three months a few soil samples were taken to analyze the change of soil characteristics. The results showed that the treatments increased organic carbon content and potassium basic cation but had no effect to soil acidity.

Abstract: A new type of AZ31-1.3Ca-1.0Sm-0.3La alloy was obtained in this study by adding Ca, Sm and La to AZ31 alloy. Detailed analysis results on second phases showed that Al₂Ca phases, Al₂Sm phases with two kinds of morphologies formed in as-cast AZ31-1.3Ca-1.0Sm-0.3La alloy besides Mg₁₇Al₁₂ phases, and La atoms mainly dissolved in Al₂Ca/Sm phases. The average grain size of as-cast AZ31-1.3Ca-1.0Sm-0.3La alloys was 212 μm and the grain sizes distributions were uniform. After the hot extrusion, the average grain size decreased to 5.4 μm and the grain sizes distributions were uneven. The base texture of as-extruded AZ31-1.3Ca-1.0Sm-0.3La alloy was strong, and the maximum density value was 3.25. The yield strength, ultimate tensile strength and elongation of as-extruded AZ31-1.3Ca-1.0Sm-0.3La alloy was 216 MPa, 280 MPa and 16% at RT, and 145 MPa, 188 MPa and 42% at 150°C, respectively, which are much higher than those of the common MB2 alloy both at the room temperature and 150 °C.

Abstract: Super hydrophobic surface has a good application prospect in industry, agriculture and daily life. By controlling the concentration and etching time of hydrochloric acid, different rough structures were prepared on the aluminum-matrix surface, and the relationship of roughness & CA were established to explore the influence of process parameters on the surface roughness and surface wettability. It is found that the concentration and time of hydrochloric acid significantly affect the surface roughness and contact angle (CA). When the concentration of hydrochloric acid is 1.5mol/L and the etching time is 90s, the surface roughness is the best and the maximum CA is obtained. After sodium hydroxide treatment, the hierarchical structure with micro and macro scale was formed, which significantly reduced the contact area between the water droplet and the surface, and the maximum roughness and CA was achieved. The relationship between surface roughness and CA shows that the roughness can amplify the hydrophile/hydrophobicity. Therefore, a better surface of superhydrophobic surface can be obtained by increasing the surface roughness.

Abstract: The effect of Ca and RE metal additions on the precipitation and microstructure of as-cast AZ91 alloy was systematically investigated. It was found that Ca and RE additions could result in phase and microstructure changes. The XRD pattern showed the crystallite phase of as-cast AZ91 alloys consists of α-Mg matrix and β-Mg₁₇Al₁₂, however, after adding 1.5wt. % Ca and 0.8wt. % RE (0.5wt. % Sm and 0.3wt. % La), peaks coincident with Al₂Ca, Al₂Sm and Al₁₁La₃ intermetallic compounds were found, suggesting the generation of relative precipitates. The SEM images indicated that in as-cast alloys, the Al₂Ca intermetallic compound was located at grain boundaries with a lamellar structure, and the Al₂Sm intermetallic compound was homogeneously distributed in the α-Mg matrix or near the grain boundaries with a polygonal structure, and the Al₁₁La₃ intermetallic compound was located at grain boundaries with a needlelike structure. These intermetallic compounds could reduce the amount of β-Mg₁₇Al₁₂ and refine the microstructure of as-cast AZ91 alloy.

Abstract: Inoculation is a treatment applied to the liquid base iron, to supply one or more elements, such as Al, Ba, Ca, Zr, Sr, Ce, La etc. with active roles in developing graphite nucleation sites. The efficiency of inoculants is directly dependent on the sulphur level: lower sulphur, lower inoculating power or unpredictable results. The objective of this paper is to examine the effects of a S and O containing inoculant enhancer [S,O,Al,Ca-FeSi alloy] to conventional Ca,Ba-FeSi alloy, in the mold treatment of electrically melted grey iron at 0.035%S, 0.002%Al, 0.0005%Zr, (%Mn) x (%S) < 0.02. The wedge test samples [W3 – ASTM A367] were used to evaluate the influence of the cooling rate and inoculation on the carbides formation. It was re-confirmed that for above mentioned critical chemistry conditions, this iron is sensitive to chill formation, despite the carbon equivalent level at 3.8%. Inoculation enhancement increased the effectiveness of the Ca,Ba-FeSi standard inoculant.

Abstract: The large dimensionality and unknown distributions are often met in a plant biotechnology and phytochemistry investigations. In this paper two methods are presented: principal component analysis allowing to reduce dimensionality and non-parametric Kruskal-Wallis ANOVA allowing to separate factors’ influence even if the distribution is unknown. The paper contains: problem definition, presentation of the measured data and the final analysis. The paper should be potentially useful to other industrial or research approaches.

Abstract: In this paper, samples were digested by high pressure digestion pots, reducing the loss of trace elements during the digestion process. The content of trace elements in Natural Huazi Mushroom such as Ca was determined by ICP-AES, and compared with the results of wet method, the two methods showed no obvious differences. High pressure nitrifying pot method relative standard deviation of Ca element is 3.36%; Wet method to determine the relative standard deviation of Ca elementt is 7.08%. Visible high pressure nitrifying pot method and treatment of samples of precision of the measuring precision and wet processing samples are relatively good, the measuring precision of the former better. The method was suitable for the determination of trace elements in edible fungi with the advantages of being simple, rapid, sensitive, stable and accurate etc., and the results were satisfactory.

Abstract: The aim of this work was to evaluate the microemulsification after incomplete digestion as sample preparation procedure for determination of Ca in leisure foods by high resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Microemulsions were prepared with digestive liquor and n-butyl alcohol as an auxiliary emulsifier after incomplete digestion treatment. The appropriate fuel flow, 70 L/h, and the optimum burner height, 5 mm, were obtained by single factor experimental design. The results showed that the correlation coefficient was better than 0.999, the characteristic concentration was 0.086 mg/L, the precision (RSD) for 6 replicate measurements of Ca was 1.7% and the average of recoveries was 102.1%. F-test and t-test (95% confidence level) in between the proposed method and the comparative method, using microwave digestion-HR-CS FAAS, had no significant difference. Therefore, the proposed method was accurate and stable with a high practical value. It provided scientific basis for determination of metal elements in food.

Abstract: Trust model is the foundation of the whole secure architecture because it determines the trust form adopted and the risk to adopt it in network. So the research of trust model in PKI has been the hot spot of PKI technology. Firstly, some backgrounds of PKI and trust model as well as the problems to be solved by the model are discussed. Through analyzing and comparing several extant CA-based trust model, their advantages and disadvantages are described. Finally, PKI trust models are summarized, and the future research directions were discussed.

Abstract: By the scanning electron microscopy, the microstructure and mechanical properties testing, the effect of Ca and Y on the microstructure and mechanical properties of magnesium alloy AZ81 are investigated in this paper. The results show that with Ca and Y addition, the grain size is refined. And with the β-Mg₁₇Al₁₂ phase reducing significantly, there will be the precipitation of Al₂Ca and Al₂Y. Meanwhile, the mechanical properties of AZ81 magnesium alloy are enhanced at room temperature and 150°C.