13,742 research outputs found

    Creating Fragility Functions for Performance-Based Earthquake Engineering

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    The Applied Technology Council is adapting PEER's performance-based earthquake engineering methodology to professional practice. The methodology's damage-analysis stage uses fragility functions to calculate the probability of damage to facility components given the force, deformation, or other engineering demand parameter (EDP) to which each is subjected. This paper introduces a set of procedures for creating fragility functions from various kinds of data: (A) actual EDP at which each specimen failed; (B) bounding EDP, in which some specimens failed and one knows the EDP to which each specimen was subjected; (C) capable EDP, where specimen EDPs are known but no specimens failed; (D) derived, where fragility functions are produced analytically; (E) expert opinion; and (U) updating, in which one improves an existing fragility function using new observations. Methods C, E, and U are all introduced here for the first time. A companion document offers additional procedures and more examples

    New instabilities of de Sitter spacetimes

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    We construct an instanton describing the pair production of non-Kaluza Klein bubbles of nothing in higher odd dimensional de Sitter spaces. In addition to showing that higher dimensional de Sitter spaces have a nonzero probability to become topologically nontrivial, this process provides direct evidence for the association of entropy with cosmological horizons and that non-Kaluza Klein bubbles of nothing are a necessary ingredient in string theory or any other consistent quantum theory of gravity in higher dimensions.Comment: 19 pages, 1 figur

    Reflecting on Whether Checklists Can Tick the Box for Cloud Security

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    Private Crop Insurers and the Reinsurance Fund Allocation Decision

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    This research investigates the strategic behavior of private crop insurance firms reinsured by the USDA through the Standard Reinsurance Agreement. This arrangement allows the private firm to strategically allocate individual policies into different risk sharing arrangements. Thus, firm earnings are conditioned upon accurately forecasting policy loss experience. Our analysis begins with models investigating the characteristics explaining the placement of policies into the assigned risk fund. Then a simulation model of the SRA is used to compare the post-SRA returns of actual firm allocations to two alternative allocation strategies based on aggregate models and a policy-level econometric forecasting model.Risk, insurance, reinsurance, logit, policy

    The cyclical behavior of state employment during the postwar period

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    This study documents a substantial decline in employment volatility at business-cycle frequencies over the postwar period using state-industry level data. The distribution of total employment volatilities at the state level has become less disperse over time, and mean volatility has fallen. Similar results are obtained using employment data on one-digit sectors across states: all sectors have seen a decline in employment volatility over the postwar period, and state-sectors are more alike in terms of volatility levels. A key source of the decline in volatility appears to be widespread (across states and industries) decreases in the size of shocks hitting employment levels. Shifts in the demographic factors, and industrial structures of state economies have had little or no impact. Neither have inter-state employment shifts, such as migrations from the Frostbelt to the Sunbelt. The sources of the smaller employment shocks are unclear, although the evidence points to macroeconomic phenomena.Employment (Economic theory)

    On the stability of employment growth: a postwar view from the U.S. states.

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    In 1952, the average quarterly volatility of U.S. state employment growth stood at 1.5 percent. By 1995, employment growth volatility came in at just under 0.5 percent. While all states shared in the decline, some states declined much more dramatically than others. We analyze aspects of this decline using new data covering industry employment by state during the postwar period. Estimates from a pooled cross-section/time-series model corrected for spatial dependence indicate that fluctuations in state-specific and aggregate variables have both played an important role in explaining volatility trends. However, state-level differences in responses to aggregate shocks account for less of the postwar fluctuations in employment growth volatility than do state-specific forces.Employment (Economic theory)
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