VELOCITY FLUCTUATIONS IN NON-HOMOGENEOUS DRAG REDUCTION

Non-homogeneous drag reduction is obtained by injecting a polymer solution thread into the center of a turbulent pipe flow. Under the proper conditions the magnitude of this non-homogeneous drag reduction is much larger than that for the same polymer molecules uniformly distributed in the flowing solvent. In this work the axial velocities and velocity fluctuations near the wall were examined in such a non-homogeneous drag reduction and also in the flow of a homogeneous (pre-mixed) solution of poly(ethylene oxide). The drag reduction and the Reynolds number were the same for both fluids. Significant differences were found in the velocity profile and in the statistical analysis of the velocity fluctuations. The skewness profile for the non-homogeneous case remained positive to a much greater distance from the wall than the skewness profile for the premix solution. In the injection case the velocity fluctuation spectra had the same sharp peak at 5-10 Hz for y₊ between 11 and 50. This peak corresponded to the bursting frequency measured from the short time autocorrelation. In the pre-mix case a broad increase in velocity fluctuation spectra was seen at y₊ = 11 which was attributed to polymer molecule rotations in the laminar shear flow near the wall. This band was absent in the non-homogeneous drag reduction, suggesting that no polymers were present at y₊ = 11. The observations imply that non-homogeneous drag reduction involves a modification of the large eddy structure.     

Indexing Kossel patterns

Procedures for the indexing of Kossel patterns are fully explained with reference to the use of pattern symmetry, diffraction curve intensity, line curvature and Kossel curve intersections. The indexing methods are illustrated by analysis of a face centred cubic pattern. General application of the concepts described here to the more difficult indexing problems experienced with hexagonal and orthorhombic crystal structures is included.     

The Kinetics of Fading of Dyes and the Filter Effect

A study of the kinetics of fading for a series of model disperse dyes on nylon 6.6 and direct dyes on cellulose is described. The results confirm the importance of the filtereffect in determining the rates of fading, and a rate equation which allows for the filter effect is given. It is shown that this equation holds for the change in the rate of fading with concentration of several direct dyes on cellulose.     

Foundations for a model of knowing: II. Fallible but functional knowledge.

Argues that an evolving theory known as "constructivism" challenges the traditional view of how individuals generate and revise knowledge. Constructivism helps address a major issue raised by modern scholars of the history and philosophy of science and decision theory. The question relates to how to reduce the search and solution space of complex and changing environments to "mind size" (i.e., to fit person's limited memory and computational capacity). One emerging answer is that individuals rely heavily on robust presuppositions and simplified representations of environmental structure. Two issues are addressed: Under what conditions knowledge can be highly fallible and at the same time be highly functional and whether one can make a plausible case, within this constructivist frame of reference, for realism, for knowledge that approximates "reality." (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptions of heterosexual bias in professional psychology programs: A survey of graduate students.

64 professional psychology student members of the American Psychological Association's Division 44 (Society for the Psychological Study of Lesbian and Gay Issues) were surveyed regarding experiences of perceived heterosexual bias and discrimination in their graduate programs. Instances of bias, discrimination, or both were reported in the following areas: (a) textbooks and other course materials, (b) instructor comments, (c) research supervision, (d) clinical practica and internships, (e) interactions with program administrators and other faculty, (f) teaching assistantships, and (g) course content. Specific examples are detailed, and educational reforms are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Support for affirmative action, justice perceptions, and work attitudes: A study of gender and racial–ethnic group differences.

Do gender and race-ethnicity moderate people's reactions to perceptions that their organization supports affirmative action/equal opportunity (AA/EO)? This study compared relationships between perceptions of support for AA/EO, distributive and procedural justice, career development opportunities, and work attitudes in 4 groups of federal employees: White men (n?=?4,919), White women (n?=?1,622), Blacks/Hispanics (n?=?492), and Asians (n?=?195). Surprisingly, White men did not associate support for AA/EO with a loss in career development opportunities, organizational injustice, or negative work attitudes. For women and racial-ethnic minorities, support for AA/EO was positively linked to perceptions of organizational justice and increased career development opportunities. As predicted, Blacks/Hispanics had more positive reactions than other employee groups. We conclude that support for AA/EO is generally viewed as fair and has positive attitudinal consequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

GRAPHICAL METHODS FOR DETERMINING THE PRESENCE OF PERIODIC CORRELATION

Abstract. Methods for determining whether an observed time series is, or contains, a periodically correlated sequence are presented. They are based on the fact that the support of the spectral measure for a harmonizable periodically correlated stochastic sequence is contained in a set of equally spaced lines parallel to the main diagonal in the bifrequency plane. We show how a coherence statistic devised by N. R. Goodman can be used to test for the presence of spectral support (correlation) along diagonal lines, thus providing a test for the presence of periodic correlation. Plots of this coherence statistic as a function of two frequency variables visually reveal the presence of diagonal support lines. Two additional tests for the presence of diagonal support lines are constructed by collapsing the two-dimensional coherence plots into one-dimensional plots of difference frequency.     

Static semantics, types, and binding time analysis

Part 1 of this paper is an analysis of problems concerning type systems and static semantics relevant to designing and implementing new programming languages. Part 2 proposes and exemplifies a way to derive a static semantics from a language's dynamic semantics, using a technique known as binding time analysis known from partial evaluation (Ershov's “mixed computation”) [20, 21]. The goal is to analyze the language's type structure during the design process without the need for hand construction of a type system. Ideally, one might automate the construction of a type checker, given only the dynamic semantics as input. In particular, binding time analysis of the interpreter program can be used to distinguish statically detectable errors from dynamic ones, and a static semantics is seen as a mechanism for deciding whether the program to be interpreted can give rise to any of the static errors. Our basic viewpoint is operational: to see how and where in the interpreter immediately observable type errors manifest themselves; to classify them as static or dynamic; and to design the static semantics to detect all static errors in a given program.