Abstract:The optimized-section precast slab with structural aesthetics (OPS) is a half precast concrete slab with multi-ribs that optimizes the cross-section by eliminating the unnecessary bottom flanges at mid-span and has good structural performance by utilizing prestressing strands and truss-type shear reinforcements. In addition, it is a member that is designed to highlight the structural aesthetics through the curved shape of a variable cross-section at the bottom of the flange which is created from a natural shape that is formed in the section optimization process. In this study, experimental research was carried out to examine the structural performance of the OPS, which includes flexure and shear tests on the precast concrete unit members for resisting construction loads, the composite members with cast-in-place concrete, and the continuous end section. The experiment results confirm that, in accordance with the current design code, the flexural performance of OPS is on the safe side regardless of the member type, whereas the shear performance of the precast concrete unit member differs slightly from that of the composite member due to the differences in the contributions of the shear reinforcement as the effective depth varies.

Ethanol, the major fermentation product of yeast, is a stress factor in yeast. We previously constructed an ethanol-tolerant mutant yeast iETS3 by using the global transcriptional machinery engineering. However, the ethanol-tolerance mechanism has not been systematically investigated. In this study, global metabolite profiling was carried out, mainly by gas chromatography/time-of-flight mass spectrometry (GC/TOF MS), to investigate the mechanisms of ethanol tolerance in iETS3. A total of 108 intracellular metabolites were identified by GC/TOF MS and high performance liquid chromatography, and these metabolites were mostly intermediates of the central carbon metabolism. The metabolite profiles of iETS3 and BY4741, cultured with or without ethanol, were significantly different based on principal component and hierarchical clustering analyses. Our metabolomic analyses identified the compositional changes in cell membranes and the activation of glutamate metabolism and the trehalose synthetic pathway as the possible mechanisms for the ethanol tolerance. These metabolic traits can be considered possible targets for further improvement of ethanol tolerance in the mutant. For example, the KGD1 deletion mutant, with up-regulated glutamate metabolism, showed increased tolerance to ethanol. This study has demonstrated that metabolomics can be a useful tool for strain improvement and phenotypic analysis of microorganisms under stress.

Although structural concrete is well known for its good economic efficiency, it has limits of structural performance due to the low tensile strength, for which new structural members utilizing various concrete composite materials have been developed. Steel Fiber-Reinforced Concrete(SFRC) has great tensile strength, which is the one of the excellent composite material to complement the weakness of concrete, and it is also considered as a good alternative to prevent the explosive failure of high strength concrete under fire. Also, prestressed concrete members are of great advantages to long span structures and have greater shear strength compared to conventional reinforced concrete members. In this research, thus, a total of 22 direct shear test specimens were fabricated and tested to understand the shear behavior of Steel Fiber-Reinforced Prestressed Concrete(SFR-PSC) members, in which SFRC members combined with prestressing method. Based on the test results, the constitutive equations of shear behavior at crack interfaces were proposed, which provided good estimation on the shear behavior of the SFR-PSC direct shear test specimens.