Experimental studies on the tripping behavior of narrow T-stiffened flat plates subjected to hydrostatic pressure and underwater shock

An experimental investigation was conducted to determine the static and dynamic responses of a specific stiffened flat plate design. The air-backed rectangular flat plates of 6061-T6 aluminum with an externally machined longitudinal narrow-flanged T-stiffener and clamped boundary conditions were subjected to static loading by water hydropump pressure and shock loading from an eight pound TNT charge detonated underwater. The dynamic test plate was instrumented to measure transient strains and free field pressure. The static test plate was instrumented to measure transient strains, plate deflection, and pressure. Emphasis was placed upon forcing static and dynamic stiffener tripping, obtaining relevant strain and pressure data, and studying the associated plate-stiffener behavior

The shadow banking system: implications for fi nancial regulation

The current financial crisis has highlighted the changing role of financial institutions and the growing importance of the “shadow banking system” that grew on the back of the securitisation of assets and the integration of banking with capital market developments. This trend has been most pronounced in the United States, but has had a profound influence for the global financial system as a whole. In a market-based financial system, banking and capital market developments are inseparable, and funding conditions are closely tied to the fluctuations of leverage of market-based fi nancial intermediaries. Balance sheet growth of market-based financial intermediaries provides a window on liquidity in the sense of availability of credit, while contractions of balance sheets have tended to precede the onset of financial crises. Securitisation was intended as a way to disperse credit risk to those who were better able to absorb losses, but instead securitisation served to increase the fragility of the financial system as a whole by allowing banks and other intermediaries to leverage up by buying each others’ securities. In the new, post-crisis financial system, the role of securitisation is likely to be held in check by more stringent financial regulation and the recognition of the importance of preventing excessive leverage and maturity mismatch in undermining financial stability.

Liquidity and financial contagion.

There is an apparent puzzle at the heart of the 2007 credit crisis. The subprime mortgage sector is small relative to the financial system as a whole and the exposure was widely dispersed through securitization. Yet the crisis in the credit market has been potent. Traditionally, financial contagion has been viewed through the lens of defaults, where if A has borrowed from B and B has borrowed from C, then the default of A impacts B, which then impacts C, etc. However, in a modern market-based financial system, the channel of contagion is through price changes and the measured risks and marked-to-market capital of financial institutions. When balance sheets are marked to market, asset price changes show up immediately on balance sheets and elicit response from financial market participants. Even if exposures are dispersed widely throughout the financial system, the potential impact of a shock can be amplified many-fold through market price changes.

Fair value accounting and financial stability.

Market prices give timely signals that can aid decision making. However, in the presence of distorted incentives and illiquid markets, there are other less benign effects that inject artifi cial volatility to prices that distorts real decisions. In a world of marking-to-market, asset price changes show up immediately on the balance sheets of financial intermediaries and elicit responses from them. Banks and other intermediaries have always responded to changes in economic environment, but marking-to-market sharpens and synchronises their responses, adding impetus to the feedback effects in financial markets. For junior assets trading in liquid markets (such as traded stocks), marking-to-market is superior to historical cost in terms of the trade-offs. But for senior, long-lived and illiquid assets and liabilities (such as bank loans and insurance liabilities), the harm caused by distortions can outweigh the benefi ts. We review the competing effects and weigh the arguments.

A class of Heisenberg models with the orthogonal dimer ground states

Extensions of the Shastry-Sutherland model are possible in various ways. In particular, it is possible to construct a natural model in three dimensions which has the exact dimer ground state. Recently found spin gap system SrCu_2(BO_3)_2 has this structure. The exchange constants between the layers is expected to be smaller than the intra-layer couplings. However, the exactness of the dimer state for the three dimensional structure is important to understand why magnetic properties of SrCu_2(BO_3)_2 are described well by the two dimensional model.Comment: 3 pages, 5 figures, to appear in Journal of Physics: Condensed Matte