Dynamic effects on capillary pressure–Saturation relationships for two‐phase porous flow: Implications of temperature

Work carried out in the last decade or so suggests that the simulators for multiphase flow in porous media should include an additional term, namely a dynamic coefficient, as a measure of the dynamic effect associated with capillary pressure. In this work, we examine the dependence of the dynamic coefficient on temperature by carrying out quasi‐static and dynamic flow simulations for an immiscible perchloroethylene–water system. Simulations have been carried out using a two‐phase porous media flow simulator for a range of temperatures between 20 and 80^°C. Simulation domains represent 3‐D cylindrical setups used by the authors for laboratory‐scale investigations of dynamic effects in two‐phase flow. Results are presented for two different porous domains, namely the coarse and fine sands, which are then interpreted by examining the correlations between dynamic coefficient(s) and temperature, time period(s) required for attaining irreducible water saturation, and the dynamic aqueous/nonaqueous phase saturation and capillary pressure plots. The simulations presented here maintain continuity from our previous work and address the uncertainties associated with the dependency of dynamic coefficient(s) on temperature, thereby complementing the existing database for the characterization of dynamic coefficients and subsequently enabling the users to carry out computationally economical and reliable modeling studies. © 2012 The Authors. AIChE Journal, published by Wiley on behalf of the AIChE. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. AIChE J, 58: 1951–1965, 2012     

Long term storage reliability of antifuse field programmable gate arrays

Field Programmable Gate Arrays (FPGA) with antifuse elements are preferred in aerospace applications due to their non-volatility and demonstrated radiation hardness. Because aerospace applications typically involve long operating life, there is a requirement to store un-programmed antifuse FPGA parts for long periods and program them when necessary to support the system. No study on the long term reliability of un-programmed antifuse FPGAs in the storage environment is reported in literature. In this paper, antifuse structures, programming process, and failure mechanisms of antifuse FPGAs are discussed. A failure modes, mechanisms and effects (FMMEA) analysis was performed for storage conditions and critical failure mechanisms were identified. High temperature storage tests of a select number of antifuse FPGAs were performed to accelerate the identified failure mechanisms. These parts were subsequently programmed and yield data was analyzed to determine the effects of high temperature storage.     

Experimental measurement of dynamic effect in capillary pressure relationship for two‐phase flow in weakly layered porous media

Well‐defined laboratory experiments have been conducted to determine the significance of dynamic effect in capillary pressure relationships for two‐phase flow in weakly heterogeneous (layered) porous media. The heterogeneous layers are composed of a fine sand layer sandwiched between two coarse sand layers. Dynamic and quasi‐static capillary pressure–saturation (P^c–S) and ?S/?t–t relationships are determined, which are then used to determine the dynamic effect, indicated by a dynamic coefficient (τ). As well known, τ establishes the speed at which flow equilibrium (?S/?t = 0) is reached. In consistent with previous studies, τ is found to be a nonlinear function of saturation that depends on the medium permeability and the intensity of heterogeneity. τ values increase in the regions of less permeability (fine sand) in the domain. However, the τ–S functional dependence follows similar trends at different locations within the domain including regions of different permeability. We argue that saturation weighted average of local τ–S curves can be used as an effective τ–S curve for the whole domain which, when done, follows an exponential trend too. The effective τ–S curves suggest that the effective τ values for the porous layers lie between the τ values of coarse and fine sands at the same water saturation, and it is dominated by the τ values of coarse sand as it occupied the maximum volume of the domain. © 2012 The Authors. AIChE Journal, published by Wiley on behalf of the AIChE. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. AIChE J, 59: 1723–1734, 2013     

Life cycle cost impact of using prognostic health management (PHM) for helicopter avionics

Case studies were conducted using a stochastic model to predict the life cycle cost impact associated with the application of prognostic health management (PHM) to helicopter avionics. The life cycle costs of systems that assumed unscheduled maintenance and fixed-interval scheduled maintenance were compared to the costs of precursor-to-failure and life consumption monitoring PHM approaches, and the optimal safety margins and prognostic distances were determined.     

Adaptation fran?aise de "l'Inventaire de risque et d'activation" (IRA).

The aim of this article is to validate in French Taylor and Hamilton's questionnaire "Risk and Excitement Inventory" (REI) which measures "escape" and "compensation." "Escapists" would take risks (e.g., drug use) to escape their self-awareness, whereas "compensatory types" would seek sensations in other risky activities (e.g., high risk sports) to enhance and build up their personality. Analyses show that the French validation has good construct validity: the factorial structure and internal consistency are good. Temporal stability and correlational analyses with other measures confirm the validity of the French questionnaire. Correlations were found between the escape scale and emotional problems (anxiety, neuroticism and impulsivity). These correlations will be discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social cognitive determinants of the intention to wear safety gear among adult in-line skaters

Introduction

In-line skating is increasing in popularity with a concomitant raise in the number of injuries associated with this activity. Studies have emphasized the value of protective gears in reducing the incidence of injuries and the subsequent need to identify the factors and processes involved in decision making about safety gear-wearing. The present study examined the contribution of the theory of planned behaviour (TPB) variables, and perceived susceptibility to and perceived severity of skating injury on the safety gear-wearing intention of adult skaters.

Methods

Skaters (n = 181) completed a questionnaire assessing the constructs of the TPB, perceived susceptibility to and perceived severity of skating injuries, and intention to wear safety gear.

Results

Hierarchical regression analyses revealed significant contributions of instrumental attitude and subjective norm to the prediction of safety gear-wearing intention. In addition, perceived susceptibility to and perceived severity of injuries enhanced the prediction of intentions to wear safety gear over and above the contribution of TPB components.

Conclusion

As the TPB focuses only on behavioural evaluation, it seems promising to include threat perceptions in this theory as another aspect of health-related cognitions motivating intention formation about safety gear use. Practical implications for future campaigns and countermeasures are discussed.