Stochastic Stability of Discrete-time Phase-coupled Oscillators over Uncertain and Random Networks

This paper studies stochastic stability of a class of discrete-time phase-coupled oscillators. We introduce the two new notions of stochastic and ultimate stochastic phase-cohesiveness using the concepts of Harris and positive Harris recurrent Markov chains. Stochastic phase-cohesiveness of oscillators in two types of networks are studied. First, oscillators in a network with an underlying connected topology subject to both multiplicative and additive stochastic uncertainties are considered. Second, we study a special case of the former problem by assuming that the multiplicative uncertainties are governed by the Bernoulli process representing the well known Erd{\H o}s R\'enyi network

Evaluation of the Martin et al. (1975) Pore Pressure Build Up Model Using Laboratory Test Data

Liquefaction has occurred during numerous earthquakes and it has caused damages and catastrophic failures. This phenomenon takes place due to the excess pore pressure development in loose saturated granular soils. Researchers have attempted to predict these phenomena (excess pore water pressure and liquefaction) using constitutive modeling and numerical approaches. In this paper, a numerical modeling procedure is presented to predict the seismic excess pore water pressure using a fully coupled effective stress analysis. A few cyclic and monotonic element tests and a level ground centrifuge test conducted during VELACS project were utilized to calibrate the numerical models. The Mohr-Coulomb elastic-perfectly plastic and the Martin et. al. (1975) excess pore water pressure build up models were concurrently incorporated in the analysis. This study focuses on a reasonable step by step procedure in order to adjust and obtain the calibration parameters of these models. Comparing the excess pore pressure buildup time histories of the numerical and experimental models (both element and centrifuge tests) showed that the Martin et al. (1975) models can be used in the numerical assessment of excess pore water pressure with an acceptable degree of preciseness

Probabilistic Evaluation of Field Liquefaction Potential Using Relative State Parameter Index (ξ\u3csub\u3eR\u3c/sub\u3e)

From the earliest studies of soil behavior under cyclic loading, it is found that the cyclic stress required for liquefaction onset is strongly affected by the relative density (Dr ) and initial effective overburden pressure of the soil. In this paper, relative state parameter index (ξR), which accounts for both relative density and effective stress, is used to evaluate the likelihood of liquefaction initiation in field condition. Two comprehensive databases of field case histories based on SPT and CPT are incorporated in the analyses. Logistic regression method is employed to derive a probabilistic expression that yields the probability of liquefaction initiation in terms of ξR. The most advantage of this expression is its consistency with both field SPT and CPT data. In addition, relative state parameter index has been evolved from dilatancy concept which has a reasonable consistency with liquefaction phenomenon. The boundary curve that obtains 20% likelihood of liquefaction initiation is found to be the most conservative boundary and is recommended as a deterministic ξR -based liquefaction criterion. Finally, a relationship is proposed to correlate liquefaction probability to the factor of safety against liquefaction triggering

Gully erosion susceptibility mapping using multivariate adaptive regression splines-replications and sample size scenarios

Soil erosion is a serious problem affecting numerous countries, especially, gully erosion. In the current research, GIS techniques and MARS (Multivariate Adaptive Regression Splines) algorithm were considered to evaluate gully erosion susceptibility mapping among others. The study was conducted in a specific section of the Gorganroud Watershed in Golestan Province (Northern Iran), covering 2142.64 km2 which is intensely influenced by gully erosion. First, Google Earth images, field surveys, and national reports were used to provide a gully-hedcut evaluation map consisting of 307 gully-hedcut points. Eighteen gully erosion conditioning factors including significant geoenvironmental and morphometric variables were selected as predictors. To model sensitivity of gully erosion, Multivariate Adaptive Regression Splines (MARS) was used while the Area Under the Receiver Operating Characteristic (ROC) Curve (AUC), drawing ROC curves, efficiency percent, Yuden index, and kappa were used to evaluate model efficiency. We used two different scenarios of the combination of the number of replications, and sample size, including 90%/10% and 80%/20% with 10 replications, and 70%/30% with 5, 10, and 15 replications for preparing gully erosion susceptibility mapping (GESM). Each one involves a various subset of both positive (presence), and negative (absence) cases. Absences were extracted as randomly distributed individual cells. Therefore, the predictive competency of the gully erosion susceptibility model and the robustness of the procedure were evaluated through these datasets. Results did not show considerable variation in the accuracy of the model, with altering the percentage of calibration to validation samples and number of model replications. Given the accuracy, the MARS algorithm performed excellently in predictive performance. The combination of 80%/20% using all statistical measures including SST (0.88), SPF (0.83), E (0.79), Kappa (0.58), Robustness (0.01), and AUC (0.84) had the highest performance compared to the other combinations. Consequently, it was found that the performance of MARS for modelling gully erosion susceptibility is quite consistent while changes in the testing and validation specimens are executed. The intense acceptable prediction capability of the MARS model verifies the reliability of the method employed for use of this model elsewhere and gully erosion studies since they are qualified to quickly generating precise and exact GESMs (gully erosion sensitivity maps) to make decisions and management edaphic and hydrologic features

On the microstructure and mechanical properties of an Fe-10Ni-7Mn martensitic steel processed by high-pressure torsion.

High-pressure torsion (HPT) processing was applied to an Fe-10Ni-7Mn (wt.%) martensitic steel at room temperature and the grain size was reduced from an initial value of ~5.5 μm to an ultrafine value of ~185 nm for the ferritic phase and around 30 nm for the austenitic phase after 20 HPT turns. The microstructure and mechanical properties of the as-processed material were evaluated using X-ray diffraction (XRD), electron backscatter diffraction (EBSD), field emission scanning electron microscopy (FESEM), microhardness measurements and tensile testing. In addition, annealing of an as-processed specimen was analyzed by differential scanning calorimetry (DSC). The results show that HPT processing increases the hardness and ultimate tensile strength to ~690 Hv and ~2230 MPa, respectively, but the ductility is decreased from ~16.5% initially to ~6.4% and ~3.1% after 10 and 20 turns, respectively. The hardness distributions and EBSD images show that a reasonably homogeneous microstructure is formed when applying a sufficient level of pressure and torsional strain. The DSC results demonstrate that processing by HPT reduces the start and finish temperatures of the reverse transformation of martensite to austenite and there is continuous re-crystallization after the recovery process

Comparison of Various Compressible Vorticity Confinement Methods and Development Two New Confinement Parameters

In this paper, vorticity confinement parameters are successfully developed for compressible flows. The first new confinement parameter is proportional to spectral radii of the flux Jacobian matrix. Therefore, the confinement parameter implicitly contains the local conditions of the flow field. This new method is named as lambda vorticity confinement method. In order to gain confidence in the applicability of vorticity confinement, it would be ideal to completely eliminate constant coefficients from confinement parameters. Because these constant coefficients should be determined for every problem by trial and error and it takes a long time. In the next part of this paper, a suitable relation is introduced for the vorticity confinement parameter that doesn’t need any constant coefficient. This new method is named as adaptive vorticity confinement method. Then the capability of these new methods is compared with the other vorticity confinement methods for solving shock-vortex interaction and three dimensional moving vortex problems

Efficacy of a modified bier�s block in patients undergoing upper limb bone surgery

Background: Intravenous regional block, called the Bier's block, refers to an analgesic technique applied for soft tissue surgeries and closed bone manipulations of the limbs. There are a number of complications in traditional method of block, including pain in tourniquet site, immediate return of pain after tourniquet deflation, wound hemostasis and some others. Objectives: The aim of this study was to assess the outcomes and complications of our new method of blockage. Patients and Methods: In this experimental study, twenty-five patients undergoing hand surgery were prospectively studied. Induced anesthesia was a modifcation of the Bier's block with two concurrent changes including insertion of the intravenous cannula at the antecubital region rather than distal and the proximal anesthetic direction by an elastic band wrapped tightly around the proximal forearm distal to the cannulation site. The pain relief was measured by the verbal descriptive scale at intervals after block, during the operation, after deflation of the tourniquet and one hour after the operation. Results: This study showed the presence of analgesia at surgical and tourniquet sites during the operation in 96 of patients, as well as considerable pain relief at surgical site during one hour after deflation of the tourniquet. Conclusions: The study indicated advantages of this modified Bier's block compared to the traditional one including ability to perform surgery on upper limb bones and considerable pain relief at surgical and tourniquet sites during the operation until one hour thereafter. © 2015, Iranian Society of Regional Anesthesia and Pain Medicine (ISRAPM)