Finding countermodels is an effective way of disproving false conjectures. In first-order predicate logic, model finding is an undecidable problem. But if a finite model exists, it can be found by exhaustive search. The finite model generation problem in the first-order logic can also be translated to the satisfiability problem in the propositional logic. But a direct translation may not be ver...

Permeability of porous media in subsurface environments is subject to potentially large uncertainties due to the heterogeneity of natural systems. In this study, a first-order reliability method (FORM) is combined with a lattice Boltzmann method (LBM) to estimate the permeability of randomly generated porous media. The proposed procedure provides an increased ease of addressing complex pore str...

This paper investigates the lifetime of high power IGBTs (insulated gate bipolar transistors) used in large wind turbine applications. Since the IGBTs are critical components in a wind turbine power converter, it is of great importance to assess their reliability in the design phase of the turbine. Minimum, maximum and average junction temperatures profiles for the grid side IGBTs are estimated...

Aeroelastic flutter is a dangerous failure mode, and aircraft structural components are designed under a deterministic flutter margin. Meeting this safety factor may result in overly-conservative structures, however, an alternative approach incorporates uncertainties into the computational models, and imposes a maximum allowable flutter probability during the optimization process. This techniqu...

A simplified fragility analysis of steel building frame is presented which can be used for preliminary estimate of its probability of failure. The risk analysis procedure uses the format of probabilistic Risk Analysis (PRA) and considers band limited white noise at the bed rock as the seismic input. The steel building frame is modeled as a 2D frame and Pushover analysis is then carried out to o...

Chloride induced corrosion in concrete is a well-known issue. Although numerous researchers have attempted to quantify the chloride threshold limits (CT) in different concrete systems (with little consensus), the issue of allowable admixed chlorides (CA) in concrete is still very much unresolved. For example, The CA limits specified by the American Concrete Institute (ACI) committees range from...

The present study presents an algorithm that models uncertainties at the structural component level to estimate the performance reliability of RC structures. The method calculates the performance reliability using a systemic approach and incorporates the improved response surface method based on sampling blocks using the first-order reliability method and conditional reliability indices. The re...

The methodology of fibring is a successful framework for combining logical systems based on combining their semantics. In this paper, we extend the fibring approach to calculi for logical systems: we describe how to uniformly construct a sound and complete tableau calculus for the combined logic from calculi for the component logics. We consider semantic tableau calculi that satisfy certain con...