Microstructures and oxidation behaviors of the Nb-Si-B and Nb-Mo-Si-B intermetallics

Two ternary phases in Nb-Si-B system, T2(Cr5B3-type tetragonal structure) and D88(Mn5Si3-type hexagonal structure), were prepared. The oxidation resistances of both T2 and D88 were found better than binary Nb5Si3 at 1000 0C, but still inadequate. The oxide scale is the mixture of Nb2O5 and borosilicate glass. The severe cracks were developed in the matrix and scale due to the large volume expansion associated with the formation of Nb2O5, SiO2 and B203. In Nb-Mo-Si-B system, all observed phases contain both Mo and Nb because Nb/Mo substitution occurs. The suitable Nb/Mo substitution can avoid the formation of Mo3Si and offer the possibility of ductile phase toughening. The lattice parameters for T1, T2 and D88 increase linearly with the increase of the Nb/Mo ratio. Oxidation tests indicated that the substitution of Nb for Mo decreased the oxidation resistance of boron doped Mo5Si3 dramatically. All specimen exhibited catastrophic oxidation behavior at 800 0C and converted to oxides completely after 20-50 hours exposure to flowing air. Although a parabolic behavior was achieved for most compositions at 12000C, the high rate constants indicated that the scales formed are not protective. The existence of four layers in scale implies that the oxidation mechanism is complex and need further study in detail

Information Security Investment with Different Information Types: A Two-Firm Analysis

We analyze information security investment decisions by two firms that possess imperfectly substitutable information assets. Information assets are imperfectly substitutable if information at each firm is valuable and becomes more valuable when combined. When compared to optimal investment decisions made by a central planner, we find diametrically opposite results in the case where these decisions are made independently: substitutable assets lead to an “arms race” in which both firms over-invest whereas complementary assets lead to under-provision of “public goods” in which both firms under-invest. We also find that firms with highly substitutable information assets may not necessarily increase the amount of security investment in a centralized investment environment as the intensity of the deflected cross traffic increases

1,3-Dioxo-2,3-dihydro-1H-isoindol-2-yl 2,3,4-tri-O-acetyl-β-d-xyloside

The title compound, C19H19NO10, was obtained from the reaction of α-d-1-bromo-2,3,4-tri-O-acetylxylose with N-hy­droxy­phthalimide in the presence of potassium carbonate. The asymmetric unit contains two independent mol­ecules, in which the O—CH—O—N torsion angles are 73.0 (4) and 65.0 (4)°. The hexa­pyranosyl rings adopt chair conformations and the substituent groups are in equatorial positions. In the crystal, mol­ecules are linked by nonclassical C—H⋯O hydrogen bonds