Classification of instabilities in parallel two-phase flow

There is extensive literature on the stability of parallel two-phase flow, both in the context of liquid-liquid as well as gas-liquid flow. Aimed at making this literature more transparent, this paper presents a classification,scheme for the various instabilities arising in parallel two-phase flow. To achieve such a classification, the equation governing the rate of change of the linetic energy of the disturbances is evaluated for relevant values of the physical parameters. This shows the existence of five different ways of energy transfer from the primary to the disturbed flow, which have their origin in density stratification, velocity profile curvature, viscosity stratification or shear effects. Each class is discussed on the basis of references covering the developments over the last 35 years

A Chebyshev collocation method for solving two-phase flow stability problems

This paper describes a Chebyshev collocation method for solving the eigenvalue problem that governs the stability of parallel two-phase flow. The method is based on the expansion of the eigenfunctions in terms of Chebyshev polynomials, point collocation, and the subsequent solution of the resulting generalized eigenvalue problem with the QZ-algorithm. We concentrate on the question how to handle difficulties that arise when these ¿standard¿ techniques are applied to the stability problem of a thin film of liquid that is sheared by a gas. After discussing this specific problem in detail, it is argued that the method of solution can readily be applied to other two-phase flow configurations as well

Paule Marshall\u27s Critique of Contemporary Neo-Imperialisms Through the Trope of Travel

This study examines Marshall\u27s use of the trope of travel within and between the United States and the Caribbean to critique ideologies of Development, tourism, and globalization as neo-imperial. This examination of travel in Marshall\u27s To Da-Duh, In Memoriam; The Chosen Place, The Timeless People; Praisesong for the Widow; and Daughters exposes the asymmetrical structures of power that exist between the two regions. In so doing, my study locates Marshall\u27s concern about the imposition of power in the post-colonial period rather than exclusively in the Caribbean\u27s colonial past. My close reading of these texts draws upon the vexed tradition of travel to the Caribbean including colonization, Development initiatives, tourism, and globalization. The trajectory of this study follows Marshall\u27s concerns about the growing influence of the United States on the Caribbean as the 20th century unfolds. Chapter One looks at To Da-Duh, In Memoriam to show how a young girl\u27s travel to see her maternal grandmother in Barbados reveals the formidable presence of the United States as an emblem of modernity--and a potential antagonist to Barbadian sovereignty--on the eve of Barbados\u27 independence. Chapter Two examines the travel of Development practitioners in The Chosen Place, The Timeless People to challenge the efficacy of Development practice in the Caribbean. Chapter Three considers how Marshall uses the travel of tourism in Praisesong for the Widow to question unambiguous representations of nationalism. Chapter Four looks at the travel by a bi-national, transnational elite protagonist in Daughters to show, on one level, how Marshall ultimately recognizes the inevitability of the United States\u27 influence in the Caribbean, and, in turn, how she exposes the perpetuation of inequality that frames the seeming borderlessness of globalization. By analyzing what may appear to be a rather simplistic trope of travel in Marshall\u27s fiction within the vexed history of human interaction through travel between the United States and the Caribbean, this study shows how Marshall locates the later 20th century encounter between the United States and the Caribbean on a continuum of hegemony against the Caribbean from colonialism to the present

The effect of anchoring vignettes on factor structures: Student effort as an example

Anchoring vignettes are used as a methodological technique for removing differential interpretation of response categories (DIRC) from scores on subjective self-report measures (King, Murray, Slomon, & Tandon, 2004). This technique requires participants to read one or more short scenarios, or vignettes, designed to represent various levels of a construct. Vignette ratings are used as an indication of DIRC, which is a source of differential item functioning (DIF). Prior research primarily used indirect methods for evaluating vignette quality. In response, the present set of studies proposes using invariance testing as a more direct evaluation of how the use of anchoring vignettes impacts the presence of DIRC. The effort subscale from the Student Opinion Scale (SOS) is used to demonstrate this set of procedures. It is also argued that DIRC will manifest as non-uniform DIF given that corrections using anchoring vignettes should impact the rank order of cases. In these studies, 819 participants were randomly assigned to either a control group (n = 478) or a group that received vignettes (n = 341) prior to responding to the SOS. Invariance testing was completed in two studies. The first study examined the factor structure between the control group and the vignette group before adjusting scores using the vignettes to determine what effect reading the vignettes may have had on the factor structure. The second study examined the invariance between the control group and the vignette group after score adjustment to determine what effect adjusting scores using the vignettes may have had on the factor structure. Results for the first study supported strict factorial invariance (configural, metric, and scalar invariance, and residuals) and equivalent latent means, which suggests that just viewing the vignettes had insubstantial impact on the factor structure of the SOS effort subscale. Results for the second study also supported strict factorial invariance, but there was a substantial difference in the group’s latent means. This result suggests that DIRC was not removed from the sample, however using anchoring vignettes to adjust scores resulted in systematically lower observed scores after adjustment. Implications for measuring effort along with general conclusions about using invariance testing to evaluate anchoring vignettes is also provided

The Role of Self-Esteem in Social Feedback: An fMRI Study

In this study we investigated the role of trait self-esteem in social feedback in 53 women, using questionnaires and functional magnetic resonance imaging (fMRI). Results showed that women with higher trait self-esteem did not feel worse after social feedback and showed brain activity during negative feedback in areas involved in emotion regulation. Women with lower trait self-esteem did feel worse after social feedback and showed more brain activity during positive feedback compared to negative and neutral feedback. We concluded that women with lower trait self-esteem display a preference for positive feedback and do not cope effectively with negative feedback