Synthesis of Al 2 O 3 /AlN composite powders by plasma processed Al 2 O 3 with various additives

A novel method was developed to produce Al 2 O 3 /AlN composite powders. The composite powders were synthesized by the direct nitridation of Al 2 O 3 using various additives by plasma processed with two different types of gas (Ar/N 2 and N 2 plasma). The effects of these two different plasma gases and additives on the formation of the Al 2 O 3 /AlN composites were studied. The x-ray diffraction results in the composite powders showed that the cubic AlN was converted to the major phase while transient ␥-Al 2 O 3 was the minor phase when the composite powder was fully melted using nitrogen as the sole working gas. In contrast, the main phase was still ␣-Al 2 O 3 when the composite powder was not well melted using the mixture of argon and nitrogen as the working gas. Carbon was found as an effective conversion additive to increase the cubic AlN of this composite powder up to 49 vol%. The reaction mechanism of forming this composite powder was also analyzed

Tooling design and microwave curing technologies for the manufacturing of fiber-reinforced polymer composites in aerospace applications

The increasing demand for high-performance and quality polymer composite materials has led to international research effort on pursuing advanced tooling design and new processing technologies to satisfy the highly specialized requirements of composite components used in the aerospace industry. This paper reports the problems in the fabrication of advanced composite materials identified through literature survey, and an investigation carried out by the authors about the composite manufacturing status in China’s aerospace industry. Current tooling design technologies use tooling materials which cannot match the thermal expansion coefficient of composite parts, and hardly consider the calibration of tooling surface. Current autoclave curing technologies cannot ensure high accuracy of large composite materials because of the wide range of temperature gradients and long curing cycles. It has been identified that microwave curing has the potential to solve those problems. The proposed technologies for the manufacturing of fiber-reinforced polymer composite materials include the design of tooling using anisotropy composite materials with characteristics for compensating part deformation during forming process, and vacuum-pressure microwave curing technology. Those technologies are mainly for ensuring the high accuracy of anisotropic composite parts in aerospace applications with large size (both in length and thickness) and complex shapes. Experiments have been carried out in this on-going research project and the results have been verified with engineering applications in one of the project collaborating companies

Association between Interpersonal Trust, Reciprocity, and Depression in South Korea: A Prospective Analysis

Background: A growing body of empirical evidence indicates that low-level social capital is related to poor mental health outcomes. However, the prospective association between social capital and depression remains unclear, and no published studies have investigated the association with longitudinal data in East-Asian countries. Methods: We analyzed data from the ongoing Korean Welfare Panel Study to prospectively investigate association between social capital and depression. Social capital was measured at the individual level by two items specific to interpersonal trust and reciprocity. Depression was annually assessed as a dichotomous variable using the Center for Epidemiologic Studies Depression Scale. After excluding participants who had depression in 2006, logistic regression models were applied to estimate the association between each social capital indicator and new-onset depression developed in 2007 or long-term depression in both 2007 and 2008. We also examined the association in a subpopulation restricted to healthy participants after excluding individuals with any pre-existing disability, chronic disease, or poor self-rated health condition. Results: Compared to the high interpersonal trust group, the odds ratios of developing new-onset and long-term depression among the low interpersonal trust group were 1.22 (95% CI: 1.08∼1.38) and 1.23 (95% CI: 1.03∼1.50), respectively, and increased to 1.32 (95% CI: 1.10∼1.57) and 1.47 (95% CI: 1.05∼2.08) in the subpopulation analyses restricted to healthy individuals. Although the low and intermediate reciprocity group also had significantly higher odds of developing new-onset depression compared to the high reciprocity group, the effects were attenuated and statistically non-significant in the subpopulation analyses. Conclusion: Low interpersonal trust appears to be an independent risk factor for new-onset and long-term depression in South Korea

2013 WSES guidelines for management of intra-abdominal infections

Peer reviewe

Carbonate Co-precipitation of Gd 2 O 3 -doped CeO 2 solid solution nano-particles

Abstract This paper reports on the synthesis of 20 mol% Gd 2 O 3 -doped CeO 2 solid solution (20 GDC) nano-particles via carbonate co-precipitation. Precursors and calcined particles were characterized using TGA, XRD, BET, FESEM, and TEM. From the diffraction pattern using XRD with TEM, it was shown that the Gd 3+ replaced the Ce 4+ lattice in the fluorite structure (FCC) of CeO 2 , as opposed to it being a second phase in the CeO 2 structure. The 20 GDC particles were calcined at 700 • C for 2 h, and sintered to >99% density at a very low sintering temperature of 1150 • C for 4 h