Metareasoning about Security Protocols using Distributed Temporal Logic

We introduce a version of distributed temporal logic for rigorously formalizing and proving metalevel properties of different protocol models, and establishing relationships between models. The resulting logic is quite expressive and provides a natural, intuitive language for formalizing both local (agent specific) and global properties of distributed communicating processes. Through a sequence of examples, we show how this logic may be applied to formalize and establish the correctness of different modeling and simplification techniques, which play a role in building effective protocol tools.     

Nonlinear Computer Model for the Simulation of Lock-in Vibration on Long-Span Bridges

Abstract:   The susceptibility of modern bridges to vortex-shedding-induced vibration is a major concern for researchers and designers. The relevance of this phenomenon is associated with the onset of large-amplitude aeroelastic vibration at moderate wind-velocity regimes due to synchronization, that is, lock-in, of the vortex-shedding frequencies with those corresponding to the natural modes of the structure. Recent observations, either recorded during the monitoring of full-scale bridges or during experimental tests of deck models in wind tunnels, confirm the importance of these aspects during the operational life of the structure. In this article, a computer model for the simulation of the aeroelastic loading associated with vortex shedding in lock-in regime is presented, for a direct application to dynamic analysis of long-span bridges. This approach is based on earlier work focused on the response of slender vertical cylindrical chimneys to vortex-shedding excitation, which is here extended to noncircular cross sections. The numerical model was employed in conjunction with a finite-element code for time-domain nonlinear simulation of the structural dynamic response. The validation of the procedure is performed through numerical simulation, conducted on two specific bridge examples.     

Using X‐Ray Microtomography for Characterisation of Catalyst Particle Pore Structure

The use of a high‐energy synchrotron radiation source has permitted the introduction of high‐resolution X‐ray microtomography imaging as a method of non‐intrusive and non‐destructive three‐dimensional (3D)visualized characterization of porous media. The use of a combination of X‐ray microtomography, along with mercury porosimetry and Low Melting Point Alloy (LMPA) intrusion potentially provides a more complete approach to more accurate catalyst pore structure characterisation and modelling. This combined approach has been applied to the study of an industrial alumina catalysts support. The data collected from the study has been used to develop and generate an improved pore network model basis, in which both heterogeneity and hierarchy are considered in obtaining an improved pore architecture and pore size distribution.     

The Comparative and Concurrent Simulation of discrete-event experiments

Discrete-Event Simulation is a powerful, but underexploited alternative for many kinds of physical experimentation. It permits what is physically impossible or unaffordable, to conduct and run related experiments in parallel, against each other. Comparative and Concurrent Simulation (CCS) is a parallel experimentation method that adds a comparative dimension to discrete-event simulation. As a methodology or style, CCS resembles a many-pronged rake; its effectiveness is proportional to the number of prongs—the number of parallel experiments. It yields information in parallel and in time order, rather than in the arbitrary order of one-pronged serial simulations. CCS takes advantage of the similarities between parallel experiments via the one-for-many simulation of their identical parts; if many experiments are simulated, then it is normally hundreds to thousands times faster than serial simulation. While CCS is a one-dimensional method, a more general, multi-dimensional or multidomain version is MDCCS. MDCCS permits parent experiments to interact and produce offspring experiments, i.e., to produce more, but smaller experiments, and many zero-size/zero-cost experiments. MDCCS is more general, informative, and faster (usually over 100:1) than CCS for most applications. It handles more complex applications and experiments, such as multiple faults, variant executions of a software program, animation, and others.From a forthcoming book by E. Ulrich, V. Agrawal, and J. Arabian, and a Ph.D. thesis on MDCCS by K.P. Lentz, Northeastern University.     

Aryl hydrocarbon receptor knockout mice (AHR-/-) exhibit liver retinoid accumulation and reduced retinoic acid metabolism

Livers from aryl hydrocarbon receptor-null mice showed a 3-fold increase in retinoids and a 65% decrease in retinoic acid metabolism. Levels of expression of the retinoic acid 4-hydroxylase, P450RAI, did not change, whereas cytochrome P4501A2 levels were lower in the null mouse, as shown earlier; however, this enzyme was found not to be active toward retinoic acid. These data suggest that aryl hydrocarbon receptor controls retinoic acid catabolism, through modulation of an unidentified target gene. Aldehyde dehydrogenases 1 and 2 were down-regulated markedly in the aryl hydrocarbon receptor-deficient mouse liver. 2,3,7,8-Tetrachlorodibenzo-p-dioxin induced cytochrome P4501A2 but not the aldehyde dehydrogenases in wild-type mice, suggesting that aryl hydrocarbon receptor is not involved directly in the down-regulation of this gene. Transglutaminase II, a retinoic acid-responsive gene product, was increased 2-fold, consistent with the liver fibrosis phenotype observed in the null mice. These findings suggest a molecular connection between xenobiotic-activated receptor signaling and retinoid homeostasis.     

Class-Entropy minimisation networks for domain analysis and rule extraction

When applied to supervised classification problems, neural rule extraction aims at making classification mechanisms explicit by reversing the knowledge embedded in a network's connections. To this end, the present research has borrowed notions from information theory; using Conditional Class Entropy as a network cost function improves representation efficiency by forcing the network to emphasize only task-essential information. We present a library of methods to analyse, simplify and rearrange the knowledge embedded in CCE-trained networks; the final result is a hierarchy of if-then rules modelling the classification process in symbolic form. Experimental results on a clinical testbed (diagnosis of Lyme disease) confirmed the effectiveness and the generalisation power of the methodologies described. In addition, satisfactory results obtained on this still unsolved clinical problem endowed this research with interdisciplinary value.     

Pitting corrosion behavior of superferritic stainless steel in waters containing chloride

On a cost-performance basis, superferritic stainless steel (SFSS) grades can now be considered competitive choices for brackish and sea water cooling systems. The pitting corrosion of a SFSS (X2CrNiMoTi 25 3.6 3.5) was tested in a chloride/sulfate solution similar to sea water, as a function of temperature, pH, and salinity. Potentiodynamic polarization techniques and experimental stability diagrams were used to evaluate the pitting conditions. The critical pitting temperature (CPT) was found to be above 50°C, and the re-passivation tendency under critical temperatures was satisfactory even when the pH was less than the depassivation pH, a condition which simulates a propagating occluded cell. The SFSS behavior in the presence of chlorine was evaluated by means of potentiodynamic tests and by studying the cathodic reduction kinetics of Cl₂ and O₂ (air).     

Fast three-dimensional nanoscale metrology in dual-beam FIB–SEM instrumentation

A quantitative surface reconstruction technique has been developed for the geometric characterization of three-dimensional structures by using a combined focused ion beam—scanning electron microscopy (FIB–SEM) instrument. A regular pattern of lines is milled at normal incidence on the sample to be characterized and an image is acquired at a large tilt angle. By analyzing the pattern under the tilted view, a quantitative estimation of surface heights is obtained. The technique has been applied to a test sample and nanoscale resolution has been achieved. The reported results are validated by a comparison with atomic force microscopy measurements.     

Relational self-regulation: Gender differences in risk for dysphoria.

Examined gender differences in the level and psychological significance of discrepancy with own ideal standards (ISs) vs ideal standards held by parents and close others. 190 undergraduates completed the Selves Questionnaire, an interpersonal contingency beliefs measure, and the Beck Depression Inventory. Women showed higher levels of discrepancy with their own ISs than with the inferred ISs of parents and close others, suggesting that women may seek congruency with others' hopes and wishes at the price of failing to attain their own aspirations. Men showed equal levels of discrepancy with their own and significant-other ISs. Discrepancy with own ISs was associated with increased dysphoria in both men and women, but discrepancy with others' ISs was associated with significantly elevated levels of dysphoria only in women. Beliefs that failing to meet others' standards would result in abandonment and rejection contributed independently from discrepancy in predicting dysphoria. The findings suggest that the tendency to modulate affect, self-esteem and behavior from a relational perspective may increase risk for psychological distress. Women may be more likely to adopt this regulatory style as a function of their socialization experiences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)