Applied bearing pressure beneath a reinforced soil foundation used in a geosynthetic reinforced soil integrated bridge system

Geosynthetic reinforced soil integrated bridge system (GRS-IBS) design guidelines recommend the use of a reinforced soil foundation (RSF) to support the dead loads that are applied by the reinforced soil abutment and bridge superstructure, as well as any live loads that are applied by traffic on the bridge or abutment. The RSF is composed of high-quality granular fill material that is compacted and encapsulated within a geotextile fabric. Current GRS-IBS interim implementation design guidelines recommend the use of design methodologies for bearing capacity that are based around rigid foundation behavior, which yield a trapezoidal applied pressure distribution that is converted to a uniform applied pressure that acts over a reduced footing width for purposes of analysis. Recommended methods for determining the applied pressure distribution beneath the RSF for settlement analyses follow conventional methodologies for assessing the settlement of spread footings, which typically assume uniformly applied pressures beneath the base of the foundation that are distributed to the underlying soil layers in a fashion that can reasonably be modeled with an elastic-theory approach. Field data collected from an instrumented GRS-IBS that was constructed over a fine-grained soil foundation indicates that the RSF actually behaves in a fairly flexible way under load, yielding an applied pressure distribution that is not uniform or trapezoidal, and which is significantly different than what conventional GRS-IBS design methodologies assume. This paper consequently presents an empirical approach to determining the applied pressure distribution beneath the RSF in GRS-IBS construction. This empirical approach is a useful first step for researchers, as it draws important attention to this issue, and provides a framework for collecting meaningful field data on future projects which accurately capture real GRS-IBS foundation behavior.     

Limit state design framework for geosynthetic-reinforced soil structures

Conventional design of geosynthetic-reinforced soil structures is divided into two categories, walls and slopes, based on the batter of its facing system. Internal stability, characterized as sufficient reinforcement anchoring and strength, is performed using earth pressure-based design criteria for reinforced walls while reinforced slopes are founded on limit equilibrium (LE) slope stability analyses. LE analyses are also used to assess the global or compound stability of both types of structures, accounting for the geometry of the reinforced, retained and foundation soils. The application of LE-based methods typically results in determination of a slip surface corresponding to the lowest attained Safety Factor (SF), known as the Factor of Safety (Fs); however, it yields little information about reinforcement loading or connection load. In this study, use of the analyzed spatial distribution of SF known as a Safety Map, is modified to attain a prescribed constant Fs at any location in the reinforced soil mass. This modified framework, implemented through an iterative, top-down procedure of LE slope stability analyses originating from the crest of a reinforced structure and exiting at progressively lower elevations on the facing, enables the determination of a Tension Map that illustrates the required distribution of reinforcement tension to attain a prescribed limit state of equilibrium. This tension map is directly constrained by a pullout capacity envelope at both the rear and front of each reinforcement layer, providing a unified, LE-based approach towards assessing an optimal selection of mutually dependent strength and layout of the reinforcement. To illustrate the utility of the Limit State framework, a series of instructive examples are presented. The results demonstrate the effects of facing elements, closely-spaced reinforcements, secondary reinforcement layers, and is compared to conventional design approaches.     

Comparison between the apparent chemical diffusion coefficient evaluated from relaxation experiments by means of electrical conductivity changes and the corresponding theoretical value for a pure and doped p-type oxide

The chemical diffusion coefficient for a p-type oxide either pure or doped with an aliovalent impurity as evaluated from electrical conductivity changes in simulated relaxation experiments is compared with the corresponding theoretical values obtained on the basis of Fick's first law using a convenient model to represent the defect structure of the oxide. It is found that if the relaxation process is purely diffusion controlled, the experimental value of obtained ( ) is in rather good agreement with the theoretical value calculated by considering the diffusion of lattice defects rather than with that obtained by considering the diffusion of the prevailing electronic defects , even when the latter two values differ. This is shown to be the result of relatively small departures from a proportionality (for the pure oxide) or from a linear dependence (for a doped oxide) in the relationship between the deviation from stoichiometry and the concentration of the electron holes in restricted range of oxygen activity as used in relaxation experiments.     

Monte Carlo modelling of wet-chemical lithography with masks

We propose Monte Carlo simulation of the etching process in two dimensions for the manufacture of microchannels and microcavities on a solid substrate. The method combines the effect of two different regimes based on diffusion-limited disaggregation and reaction-limited erosion, respectively. Besides, the role of the selectivity in site extraction is taken into account to foresee the effects of the temperature of the eroding bath. This technique proves to be a valid alternative to more complex analytical methods to describe surface decay processes in the presence of overhangs. The relevant geometries of the etched surfaces are analyzed, and other statistical properties of the cavities are discussed and compared to the ones predicted by continuum models.     

Learning equilibrium as a generalization of learning to optimize

We argue that learning equilibrium is an appropriate generalization to multi-agent systems of the concept of learning to optimize in single-agent setting. We further define and discuss the concept of weak learning equilibrium.     

Self-fulfilling prophecy and gender: Can women be Pygmalion and Galatea?

To date, all published confirmations of the Pygmalion hypothesis among adults have involved men. The few studies among women have had methodological ambiguities. The authors conducted 2 experiments in the Israel Defense Forces to test the Pygmalion hypothesis among women. In both studies, the leaders were led to believe that the trainees randomly assigned to the Pygmalion condition had higher than usual potential. Experiment 1 tested the Pygmalion hypothesis among female officer cadets led by women. Although the treatment did raise expectations, none of the performance measures and none of the mediators or the moderators evidenced any expectancy effects. Experiment 2 tested the Pygmalion hypothesis among women and men taking the same course in gender-segregated platoons. The Pygmalion hypothesis was confirmed among men led by a man and among women led by a man but not among women led by a woman. The authors concluded that the Pygmalion effect can be produced among women but perhaps not by women. Pygmalion research among women leading men is now needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Energy Availability on Immediate and Delayed Emotional Reactions to Work Events.

This study focuses on daily work events as proximal stimuli for discrete emotional reactions and suggests that availability of energy resources required for coping with goal-disruptive events, or for capitalizing on new opportunities offered by goal-enhancing events, influences intensity of emotional reactions. Using experience-sampling methodology with a sample of hospital residents, it is shown that negative emotion and fatigue following disruptive events are intensified when only limited energy resources are available due to current workload. However, positive emotions, promoted by goal-enhancing events, are mitigated due to inability to capitalize on new opportunities or challenges. Aftereffects of work events reveal that the energizing effect of goal-enhancing events mitigates end-of-day fatigue and negative emotion on high-workload days, although the effect of disruptive events is diminished by the end of such days, apparently because of lesser conspicuity against a background of high workload. Theoretical and practical implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pygmalion without interpersonal contrast effects: Whole groups gain from raising manager expectations.

Past Pygmalion research has been susceptible to interpersonal contrast effects, rendering it uncertain whether raising managers' expectations toward subordinates can improve performance without reference to control Ss in the same group. Twenty-nine platoons in the Israel Defense Forces were randomly assigned to Pygmalion or control conditions to test the hypothesis that raising manager expectations boosts performance without contrast effects. Leaders of the Pygmalion platoons were informed that their subordinates on average had unusually high command potential. Platoon-level analysis of performance showed that Pygmalion platoons significantly outscored control platoons, confirming the Pygmalion hypothesis. Manager expectation effects are not dependent on interpersonal contrast effects; in addition, the Pygmalion approach appears well suited to applications involving whole groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)