Probabilistic risk analysis of corrosion associated failures in cast iron water mains

This paper proposes a method using probabilistic risk analysis for application to corrosion associated failures in grey cast iron water mains. External corrosion reduces the capacity of the pipeline to resist stresses. When external stresses exceed the residual ultimate strength, pipe breakage becomes imminent, and the overall reliability of a water distribution network is reduced. Modelling stresses and external corrosion acting on a pipe involves uncertainties inherent in the mechanistic/statistical models and their input parameters. Monte Carlo (MC) simulations were used to perform the probabilistic analysis. The reduction in the factor of safety (FOS) of water mains over time was computed, with a failure defined as a situation in which FOS becomes smaller than 1. The MC simulations yielded an empirical probability density function of time to failure, to which a lognormal distribution was fitted leading to the derivation of a failure hazard function. A sensitivity analysis revealed that the contribution of corrosion parameters to the variability of time to failure was more significant than the combined contributions of all other parameters. Areas where more research is needed are identified.     

A theory of roll coating of viscous and viscoelastic fluids

A theory for roll coating of a fluid onto a moving sheet is developed utilizing the usual “lubrication approximations.” The effects of fluid and operating parameters on coating thickness and pressure distribution are determined for a Newtonian fluid, and for a purely viscous non-Newtonian fluid obeying the Power Law. The results for these cases are obtained analytically, and are rather straightforward. A viscoelastic fluid is considered, of a type which shows typical non-Newtonian shear behavior observed in polymer melts and solutions and which also exhibits normal stress behavior. Analytical solutions are not possible, but a perturbation method, using a viscoelastic perturbation parameter related to a Deborah number, yields an approximate solution. Only terms to first order in the perturbation parameter are given. Subject to that degree of approximation, the following conclusions are drawn:

• 1 Non-Newtonian shear behavior reduces the pressure distribution, and increases the coating thickness.
• 1 Elasticity of the type usually observed in polymer solutions makes only a minor contribution to the roll-separating (load-carrying) force. The contribution is positive, but smaller than the corresponding negative contribution due to the non-Newtonian shear effects.
• 1 An increase in load-carrying capacity would require a different viscoelastic fluid than the type considered here—one that is essentially Newtonian in shear but, independently, capable of developing significant normal stresses.

     

Adiabatic flow distribution of gas and liquid in parallel pipes—Effect of additional restrictions

The distribution of gas and liquid among four parallel pipes was studied with and without orifice restrictions. The results show that the two phases may not be equally distributed among the pipes. It is shown that the two-phase flow mixture can “choose” to flow in one, two, three or in all four pipes depending on gas and liquid flow rates, on pipe inclination and on the orifice plate size. Addition of orifice plates expands the region of stability and the range of flow in all four pipes. The experimental results are in reasonable agreement with the analysis.     

A Statistical Theory for Quantitative Association Rules

Association rules are a key data-mining tool and as such have been well researched. So far, this research has focused predominantly on databases containing categorical data only. However, many real-world databases contain quantitative attributes and current solutions for this case are so far inadequate. In this paper we introduce a new definition of quantitative association rules based on statistical inference theory. Our definition reflects the intuition that the goal of association rules is to find extraordinary and therefore interesting phenomena in databases. We also introduce the concept of sub-rules which can be applied to any type of association rule. Rigorous experimental evaluation on real-world datasets is presented, demonstrating the usefulness and characteristics of rules mined according to our definition.     

Design of Capacitor Bank in Parallel to Photovoltaic Power Plant

The purpose of the paper is to develop a solution for application of PV （photovoltaic） generators in MV （medium voltage） distribution system without unacceptable voltage changes due to drops of PV power output. The proposed solution includes operation of PV with predetermined leading power factor and addition of a capacitor bank in parallel to PV plant in order to compensate the reactive power absorbed by the PV inverters. The analytical expression of required power factor angle is derived. Adding a capacitor bank in parallel to PV power plant may pose a problem because of space limitations. The dimensions and cost of small MV capacitor banks depend significantly on the capacitor bank protection against internal faults. Application of the developed negative-sequence current difference method for the unbalance protection of the capacitor banks enables to achieve a compact and cost-reduced design of the banks connected in parallel to PV power plants. A real-world example of operation of the PV plant in parallel to the capacitor bank with the novel protection scheme is described.     

Automatic MR-PET registration algorithm

We present an algorithm to automatically register magnetic resonance (MR) and positron emission tomographic (PET) images of the human brain. Our algorithm takes an integrated approach: we simultaneously segment the brain in both modalities and register the slices. The algorithm does not attempt to remove the skull from the MR image, but rather uses “templates” constructed from PET images to locate the boundary between the brain and the surrounding tissue in the MR images. The PET templates are a sequence of estimates of the boundary of the brain in the PET images. For each of the templates, the registration algorithm aligns the MR and PET images by minimizing an energy function. The energy function is designed to implicitly model the relevant anatomical structure in the MR image. The template with the lowest energy after registration is the PET brain boundary. The alignment of this template in the MR image marks the MR brain boundary and gives the transformation between the two images. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 46–50, 1998     

On the Feasibility of Extending Oblivious Transfer

Oblivious transfer is one of the most basic and important building blocks in cryptography. As such, understanding its cost is of prime importance. Beaver (in: The 28th STOC, pp 479–488, 1996) showed that it is possible to obtain \(\mathsf{poly}(n)\) oblivious transfers given only n actual oblivious transfer calls and using one-way functions, where n is the security parameter. In addition, he showed that it is impossible to extend oblivious transfer information theoretically. The notion of extending oblivious transfer is important theoretically (to understand the complexity of computing this primitive) and practically (since oblivious transfers can be expensive and thus extending them using only one-way functions is very attractive). Despite its importance, very little is known about the feasibility of extending oblivious transfer, beyond the fact that it is impossible information theoretically. Specifically, it is not known whether or not one-way functions are actually necessary for extending oblivious transfer, whether or not it is possible to extend oblivious transfers with adaptive security, and whether or not it is possible to extend oblivious transfers when starting with \(O(\log n)\) oblivious transfers. In this paper, we address these questions and provide almost complete answers to all of them. We show that the existence of any oblivious transfer extension protocol with security for static semi-honest adversaries implies one-way functions, that an oblivious transfer extension protocol with adaptive security implies oblivious transfer with static security, and that the existence of an oblivious transfer extension protocol from only \(O(\log n)\) oblivious transfers implies oblivious transfer itself.