Centrifugal modelling of the landslides triggering mechanism in layered fill slopes

Concerns over loosely compacted fill slopes stability in Hong Kong arouse in the past few decades, since the Sau Mau Ping disasters in 1972 and 1976. Research conducted on loose fill slopes in the past few years aimed to understand the failure mechanisms of a loosely compacted fill slope. Recently, layering effect has been hypothesised to be a possible condition in the fill slopes leading to a fast flowslide triggered by a rise of water table. Centrifuge experiments were conducted to investigate the layering effect on a model granular slope and hence to determine the triggering mechanisms of seepage induced slope failure. Test results showed that slope failure can be easily triggered in layered fill model slopes when seepage is restricted and localised pore water pressure is allowed to build up within the slope. © 2006 Taylor & Francis Group, London.

A 5-step reduced mechanism for combustion of CO/H2/H2O/CH4/CO2 mixtures with low hydrogen/methane and high H2O content

In this study a 5-step reduced chemical kinetic mechanism involving nine species is developed for combustion of Blast Furnace Gas (BFG), a multi-component fuel containing CO/H2/CH4/CO2, typically with low hydrogen, methane and high water fractions, for conditions relevant for stationary gas-turbine combustion. This reduced mechanism is obtained from a 49-reaction skeletal mechanism which is a modified subset of GRI Mech 3.0. The skeletal and reduced mechanisms are validated for laminar flame speeds, ignition delay times and flame structure with available experimental data, and using computational results with a comprehensive set of elementary reactions. Overall, both the skeletal and reduced mechanisms show a very good agreement over a wide range of pressure, reactant temperature and fuel mixture composition. © 2012 The Combustion Institute..

The destruction mechanism in GCTs

This paper focuses on the causes that lead to the final destruction in standard gate-commutated thyristor (GCT) devices. A new 3-D model approach has been used for simulating the GCT which provides a deep insight into the operation of the GCT in extreme conditions. This allows drawing some conclusions on the complex mechanisms that drive these devices to destruction, previously impossible to explain using 2-D models. © 1963-2012 IEEE.

Uncertainty increases pain: evidence for a novel mechanism of pain modulation involving the periaqueductal gray.

Predictions about sensory input exert a dominant effect on what we perceive, and this is particularly true for the experience of pain. However, it remains unclear what component of prediction, from an information-theoretic perspective, controls this effect. We used a vicarious pain observation paradigm to study how the underlying statistics of predictive information modulate experience. Subjects observed judgments that a group of people made to a painful thermal stimulus, before receiving the same stimulus themselves. We show that the mean observed rating exerted a strong assimilative effect on subjective pain. In addition, we show that observed uncertainty had a specific and potent hyperalgesic effect. Using computational functional magnetic resonance imaging, we found that this effect correlated with activity in the periaqueductal gray. Our results provide evidence for a novel form of cognitive hyperalgesia relating to perceptual uncertainty, induced here by vicarious observation, with control mediated by the brainstem pain modulatory system.

The mechanism of high temperature aqueous corrosion of steel

A new model is presented which describes the growth of the duplex layers of Fe3O4 on mild steel in high temperature, deoxygenated, neutral or alkaline aqueous solutions. It is shown that the layers grow by the ingress of water along oxide micropores to the metal-oxide interface and by the rate-limiting outward diffusion of Fe ions along oxide grain boundaries. The new model accounts for the observed temperature-dependence and pH-dependence of the corrosion, the morphology of inner and outer layer crystallites, the segregation of alloying elements, and the location of hydrogen evolution. The model can also be generalized to other steels and alloys. © 1989.

Shock transmission in a coupled beam system

This paper investigates the circumstances under which high peak acceleration can occur in the internal parts of a system when subjected to impulsive driving on the outside. Motivating examples include the design of packaging for transportation of fragile items. The system is modelled in an idealised form using two beams coupled with point connections. A Rayleigh-Ritz model of such coupled beams was validated against measurements on a particular beam system, then the model was used to explore the acceleration response to impulsive driving in the time, frequency and spatial domains. This study is restricted to linear vibration response and additional mechanisms for high internal acceleration due to nonlinear effects such as internal impacts are not considered. Using Monte Carlo simulation in which the indirectly driven beam was perturbed by randomly placed point masses a wide range of system behaviour was explored. This facilitates identification of vulnerable configurations that can lead to high internal acceleration. The results from the study indicate the possibility of curve veering influencing the peak acceleration amplification. The possibility of veering within an ensemble was found to be dependent on the relative coupling strength of the modes. Understanding of the mechanism may help to avoid vulnerable cases, either by design or by preparatory vibration testing. © 2013 Elsevier Ltd.