Buoyantly-driven two-phase countercurrent flow in liquid discharge from a vessel with an unvented gas space

This paper details experiments and analyses regarding the phenomenon of liquid discharge into a gaseous atmosphere from the bottom of a vessel with an unvented, upper gas space. The primary goal is the development of a simple model that predicts the rate of liquid discharge under the prevailing unvented condition. A literature survey of previous work on this phenomenon yielded only simple experiments and analyses that were limited in scope. Experiments were subsequently undertaken with an air-water system, using a larger volume and a wide range of drain line diameters. In addition to flowrate data, visual information was acquired regarding the physical mechanism possibly governing the prevalent flow regimes. The governing physical mechanism is identified as the stability of a gas-liquid interface, perturbed by buoyancy, at the drain line entrance. G.I. Taylor's fundamental analysis of interfacial stability lead to the determination of criteria for flow regime transition among the three prevalent flow regimes, corresponding to so-called small, medium, and large diameters. Also, analysis of the growth of interfacial instabilities lead to the application of flooding models for drainage rates within each regime. The models for moderate and large diameters were then compared against data, which confirmed their success in predicting discharge rates under the unvented condition.The motivation for this effort, besides the basic scientific significance of studying such a fundamental phenomenon, was its numerous applications, one of which is commercial nuclear reactor systems. Specifically, the phenomenon prevails in liquid coolant discharge from a PWR pressurizer, with an unvented steam volume, into a steam atmosphere existing in the adjoining hot coolant leg. Such a phenomenon could occur as part of a transient, or severe accident, scenario, entailing saturated conditions and steam production in the normally subcooled primary heat transport loop. The developed model was implemented in the Modular Accident Analysis Program (MAAP), a computer code designed to predict reactor system behavior in response to postulated off-normal conditions, including severe accident scenarios.     

CHEMICAL BASIS OF MIDDLE DISTILLATE FUEL INSTABILITY: Interactive Effects of Selected Nitrogen Heterocycles with Organic Bases in a Shale-Derived Diesel Fuel.

Fuel instability reactions are defined in terms of the formation of deleterious products such as filterable sediments and peroxides. Gravimetric stability tests have been carried out at 80^°C using two model nitrogen heterocycles: 2,5-dimethy1pyrrole, DMP, and 3-methylindole, 3-MI, in an otherwise stable shale derived middle distillate fuel. Potential interactive effects for these model nitrogen heterocycles have been described by the presence of organic base co-dopants. Organic bases employed included: tri-n-butylamine, N, N-dimethyl-aniline, and 4-dimethylaminopyridine. Simple organic amines exerted only minor interactive effects, usually an increase in filterable sediment in the range of 5-15%. However, the diamine species, 4-dimethylaminopyridine, interacted in a strong positive fashion to generate increased amounts, 22-44%, of sediment.     

Validity and construct contamination of the Racial Identity Attitude Scale—Long Form.

The Racial Identity Attitude Scale—Long Form (RIAS–L; J. E. Helms & T. A. Parham, 1996) is likely to be the instrument of choice in future research on African American racial identity development, but little is known about its psychometric properties. RIAS-L data from 275 African American community members and students were collected, and a series of analyses (i.e., correlations, multiple regressions, and confirmatory modeling) was conducted to explore convergent and discriminant validity. Overall, results were mixed, generally revealing limited support for the RIAS-L's convergent and discriminant validity and highlighting concerns regarding the Preencounter and Encounter subscales. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

微导通孔的电镀填孔技术

本文主介绍了电镀填孔技术,并探讨了DC和PPR电镀填孔技术的优缺点和影响填孔效果的相关因素。     

Effective Computation of Rational Approximants and Interpolants

This paper considers the problem of effective algorithms for some problems having structured coefficient matrices. Examples of such problems include rational approximation and rational interpolation. The corresponding coefficient matrices include Hankel, Toeplitz and Vandermonde-like matrices. Effective implies that the algorithms studied are suitable for implementation in either a numeric environment or else a symbolic environment.The paper includes two algorithms for the computation of rational interpolants which are both effective in symbolic environments. The algorithms use arithmetic that is free of fractions but at the same time control the growth of coefficients during intermediate computations. One algorithm is a look-around procedure which computes along a path of closest normal points to an offdiagonal path while the second computes along an arbitrary path using a look-ahead strategy. Along an antidiagonal path the look-ahead recurrence is closely related to the Subresultant PRS algorithm for polynomial GCD computation. Both algorithms are an order of magnitude faster than alternative methods which are effective in symbolic environments.     

Supported gold clusters and cluster-based nanomaterials: characterization, stability and growth studies by in situ GISAXS under vacuum conditions and in the presence of hydrogen

This contribution is devoted to study of the thermal stability and growth of gold nanoparticles supported on SiO₂/Si(111) and Al₂O₃/SiO₂/Si(111) as a function of initial cluster size, support material and level of surface coverage. Experimental evidence for “flipping” of two dimensional cluster structures from vertical orientation to horizontal on the support is presented.     

Links between physical fitness and cardiovascular reactivity and recovery to psychological stressors: A meta-analysis.

A meta-analysis of published studies with adult human participants was conducted to evaluate whether physical fitness attenuates cardiovascular reactivity and improves recovery from acute psychological stressors. Thirty-three studies met selection criteria; 18 were included in recovery analyses. Effect sizes and moderator influences were calculated by using meta-analysis software. A fixed effects model was fit initially; however, between-studies heterogeneity could not be explained even after inclusion of moderators. Therefore, to account for residual heterogeneity, a random effects model was estimated. Under this model, fit individuals showed significantly attenuated heart rate and systolic blood pressure reactivity and a trend toward attenuated diastolic blood pressure reactivity. Fit individuals also showed faster heart rate recovery, but there were no significant differences in systolic blood pressure or diastolic blood pressure recovery. No significant moderators emerged. Results have important implications for elucidating mechanisms underlying effects of fitness on cardiovascular disease and suggest that fitness may be an important confound in studies of stress reactivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The importance of a common in-group identity in ethnically diverse groups.

The purpose of this study was to examine the effects of a common in-group identity in attenuating the negative effects of ethnic dissimilarity. Specifically, it was hypothesized that a common in-group identity would moderate the relationship between ethnic dissimilarity and satisfaction with coworkers. Data were gathered from 87 persons working in groups. Moderated regression analysis provided support for the hypothesis, in that when a common in-group identity was not present, demographic dissimilarity was related to less satisfaction, but when a common in-group identity was present, there was a positive relationship between ethnic dissimilarity and coworker satisfaction. Further, for ethnically dissimilar persons, coworker satisfaction was higher when a common in-group identity was present than when it was not. Results are discussed in relation to the study's contribution to social psychology and diversity management literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)