Material invariant properties and reconstruction of microstructure of sandstones by nanoindentation and microporoelastic analysis

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (p. 183-189).The diversity of sandstones and sandstone properties that exist in nature pose a significant problem for engineers who deal with these materials, whether in oil well exploration and exploitation or art and architectural conservation. The solution proposed in this thesis takes a highly reductionist approach to the problem. Properties of the sandstone material are first reduced to material invariant properties of the material phases present in sandstone. These are universal constants which do not vary from one sample to the other. From these material invariants, it is then possible to 'nanoengineer' the properties of a specific sandstone sample based only on a few easily measured properties - the volume fractions of the material phases. To help identify material invariant phases and reconstruct microstructure, a multi-scale think model for sandstone is developed from ESEM images as well as from the results of mineralogy, grain size, and porosimetry experiments. A nanoindentation campaign is performed to characterize sandstones at multiple scales and an innovative technique is used to separate the various indentation responses that can occur on a heterogeneous composite. Material invariant phase properties are obtained for both the sand grains and the clay minerals. A new technique for estimating volume fractions of composite materials using nanoindentation is developed and verified. Clay stiffnesses are found to be highly dependent on microstructure rather than on mineralogy, and material invariant properties are proposed. A comparison of models to estimate elastic and poro-elastic properties reveal shortcomings that motivate the development of a new predictive model.(cont.) A multi-scale model employing a self consistent scheme and a double-porosity model is suggested and applied with excellent results predicting poroelastic properties. This model permits the 'nanoengineering' of a specific sandstone sample based only on the volume fractions of the material phases.by Christopher Philip Bobko.S.M

Assessing the mechanical microstructure of shale by nanoindentation : the link between mineral composition and mechanical properties

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.Includes bibliographical references (leaves 335-351).Shale is a multi-phase, multi-scale sedimentary rock that makes up 75% of the earth's sedimentary basins and is especially critical in petroleum engineering applications. At macroscopic scales, shales possess a diverse set of possible compositions, resulting in a diverse set of mechanical properties. This thesis assesses microstructure and material invariant properties of shale as the link between engineering performance and composition. A comprehensive experimental microporomechanics approach, employing advanced experimental and analytical nanoindentation techniques, provides the basis for assessment of microstructure and material invariant properties. Nanoindentation experiments and analysis tools are designed to probe and infer the elastic and strength properties of the porous clay composite in shale. The results of this investigation show that properties of the porous clay composite scale with the clay packing density in the material, but otherwise do not depend on mineral composition. These scaling relationships are representative of a granular composite of spherical particles, and lead to identification of intrinsically anisotropic material invariant elastic properties and intrinsically isotropic material invariant hardness properties. The material invariant hardness represents a combination of cohesive and frictional behavior that is seen to scale with the average clay packing density in the sample. Nanoindentation results also provide evidence of packing density distributions that are analogous to pore size distributions.(cont.) These observations are combined to define a model of the elementary building block of shale. Exploring the physical origin of this building block suggests that it represents an agglomerated polycrystal group of individual clay minerals. Particles in the porous clay composite exhibit fractal packings, which suggest a quantitative link between contemporary theories about the origin of friction and the experimental scaling of friction in shale. The new understanding provided by this thesis represents a leap forward for predictive models of shale behavior. The model of the elementary building block can be used as a basis for micromechanical homogenization models which predict poroelastic properties and strength behavior of shale at the lab-bench scale based on only two volume fraction parameters. The success of these models validates the elementary building block model and illustrates its engineering significance.by Christoper P. Bobko.Ph.D

Using Noninvasive Brain Measurement to Explore the Psychological Effects of Computer Malfunctions on Users during Human-Computer Interactions

In today’s technologically driven world, there is a need to better understand the ways that common computer malfunctions affect computer users. These malfunctions may have measurable influences on computer user’s cognitive, emotional, and behavioral responses. An experiment was conducted where participants conducted a series of web search tasks while wearing functional nearinfrared spectroscopy (fNIRS) and galvanic skin response sensors. Two computer malfunctions were introduced during the sessions which had the potential to influence correlates of user trust and suspicion. Surveys were given after each session to measure user’s perceived emotional state, cognitive load, and perceived trust. Results suggest that fNIRS can be used to measure the different cognitive and emotional responses associated with computer malfunctions. These cognitive and emotional changes were correlated with users’ self-report levels of suspicion and trust, and they in turn suggest future work that further explores the capability of fNIRS for the measurement of user experience during human-computer interactions

Correlation and regression : principles and applications for industrial organizational psychology and management

xv, 283 p. : il.; 24 cm

Reviewing, Categorizing, and Analyzing the Literature on Black-White Mean Differences for Predictors of Job Performance: Verifying Some Perceptions and Updating/Correcting Others

This article reviews and summarizes the literature on Black-White mean differences for some job performance predictors

A Meta-Analysis of Gender Group Differences for Measures of Job Performance in Field Studies

There are multiple views in human resource management and organizational behavior concerning gender differences in measures of job performance. Some researchers suggest that males generally are evaluated higher than females across a variety of situations that include job performance measurement. At the same time, the presence of specific status cues in expectation states theory (EST; similar to the concept of individuating information) suggests that measures of job performance will be more similar than different for males and females. Previous analyses are unclear in their results for the measurement of the construct of job performance because they have included, and/or focused on, additional constructs (e.g., hiring suitability, leadership performance aggregated with leadership satisfaction) or have used student samples in lab experiments. The authors of this article conducted a meta-analysis of job performance measures from field studies. They found that females generally scored slightly higher than males (mean d = −.11, 80% credibility interval of −.33 to .12). Other analyses suggested that, although job performance ratings favored females, ratings of promotion potential were higher for males. Thus, ratings of promotability may deserve further attention as a potential source of differential promotion rates. These findings and processes are discussed within the context of EST

A note on moran's measure of multiple rank correlation

non-parametric multiple correlation, Kendall's tau,

Investigation of the multidimensional model of job insecurity in China and the USA

Over a decade ago, Ashford, Lee, and Bobko (1989) developed a standard measure for those interested in assessing levels of individual job insecurity. In ensuing years, some researchers have questioned whether the entire measure is necessary. We examined the usefulness of the components of Ashford et al.'s (1989) multidimensional measure of job insecurity in both the United States and China, as well as replicating and extending prior findings regarding antecedents and consequences. Our results suggest that the call to eliminate job features or powerlessness from the fully composite measure of job insecurity is premature in both cultures. We call for more research on the utility of the fully operationalised measure. Implications of our findings are discussed