A computational fluid dynamics evaluation of a pneumatic safety relief valve

Safety relief valves are well established components preventing catastrophic failure of pressurised systems when non-normal operating conditions occur. However, it is only recently with developments in CFD techniques that the capability to predict the complex flow conditions occurring in the valves has been possible resulting in only limited studies being found in the literature. This paper presents experimental and theoretical investigations applied to a safety relief valve designed for the refrigeration industry but extended here to consider pneumatic systems since air is the compressible fluid. The discharge flow rate and valve forces are determined both theoretically and experimentally for different valve lift conditions and related to the detailed flow conditions (pressure, temperature and Mach number) in the valve predicted by CFD techniques. The CFD code FLUENT has been used with a two dimensional axisymmetric RANS approach using the k-İ turbulent model to predict the highly compressible flow through the valve. The model has been validated by comparison with experimental measurements and the predicted results show good agreement, providing confidence in the use of CFD techniques for valve design and improvement

Bubble formation at two adjacent submerged orifices in inviscid fluids

A theoretical model has been developed as an extension of single orifice bubble formation to investigate the growth and detachment of vapor/gas bubbles formed at two adjacent submerged orifices in inviscid fluids. The mathematical model treats the two bubbles as an expanding control volume moving to the line of centers above a wall. The movement of the bubbles is obtained by application of force balance acting on the bubble and accounts for surface tension, buoyancy, steam momentum and liquid inertia effects. The liquid inertia effects are determined by applying inviscid and irrotational flow assumptions to allow potential flow theory to calculate the liquid velocity field which then allows the pressure distribution to be calculated. The model is extended to include the mass and energy equations to model the steam bubble formation in sub-cooled water. The theoretical results are compared with the available experimental data of bubble formation during constant mass flow steam bubble formation at two submerged upward facing orifices in sub-cooled water. The model was validated by available experimental data for the growth and detachment processes of two adjacent 1 mm orifices at system pressures of 2 and 3 bars, flow rates of 1.2-4 g/min at sub-cooling of 3.5-35 ºC. The comparisons of theory and experiments indicate that the model successfully predicts the bubbles growth and detachment for the range of conditions studied

The use of interactive multi-player games to enhance second language acquisition of both Mandarin and English

MMORPG have become a popular area of language acquisition research, raising the question of whether games and education can be effectively combined to create a game based on research that has education within its core yet still presents as an engaging gaming experience and provides a mutual learning platform for two languages. The current study is longitudinal and focuses on the question: Can interactive RPGs enhance second language acquisition? <br/

RPGs to enhance the second language acquisition of both Mandarin and English

Research Question: “To what degree can it be evidenced that interactive role playing games enhance the mutual second language acquisition of both Mandarin and English?”♦ Small scale side project to ascertain avatar interaction preferences based on perception.♦ Pilot study will apply psycholinguistic and sociolinguistic research knowledge to specifically designed game

Comparison of the computed flow field around a bubble growing at an orifice using PIV techniques

For bubbles growing rapidly at orifices, the inertia of the liquid displacement and the resultant liquid flow field contribute to the production of an inertia force which tends to retard bubble movement. It is therefore the purpose of this paper to report on a study to examine the validity of liquid velocity fields predicted by potential flow methods and measurements made using Particle Image Velocimetry (PIV) techniques. Air bubbles are generated in water at atmospheric conditions from a 1 mm diameter orifice. The process is transient and occurs over a period of approximately 80 msecs. Therefore a combination of high speed video techniques and PIV image processing has been used to determine the liquid velocity vector fields during the bubble growth, detachment and translation periods. This paper will present a summary of the experimental techniques and the theoretical model and discuss the results of the study

A generalized Fellner-Schall method for smoothing parameter estimation with application to Tweedie location, scale and shape models

We consider the estimation of smoothing parameters and variance components in models with a regular log likelihood subject to quadratic penalization of the model coefficients, via a generalization of the method of Fellner (1986) and Schall (1991). In particular: (i) we generalize the original method to the case of penalties that are linear in several smoothing parameters, thereby covering the important cases of tensor product and adaptive smoothers; (ii) we show why the method's steps increase the restricted marginal likelihood of the model, that it tends to converge faster than the EM algorithm, or obvious accelerations of this, and investigate its relation to Newton optimization; (iii) we generalize the method to any Fisher regular likelihood. The method represents a considerable simplification over existing methods of estimating smoothing parameters in the context of regular likelihoods, without sacrificing generality: for example, it is only necessary to compute with the same first and second derivatives of the log-likelihood required for coefficient estimation, and not with the third or fourth order derivatives required by alternative approaches. Examples are provided which would have been impossible or impractical with pre-existing Fellner-Schall methods, along with an example of a Tweedie location, scale and shape model which would be a challenge for alternative methods

Associations Between Expressed Emotion, Mental Health, and Functioning in Families: Child Asthma Status as a Moderator

Expressed emotion (EE), the affective attitudes and behaviors of one toward another, can affect caregivers’ behaviors toward their child. Research examining associations between EE and child/family outcomes is mixed; these associations may be affected by other influences such as the presence of a chronic disease or parent mental health. In this study of families living in an urban area, we examined associations between EE and child outcomes (anxiety/depressive symptoms) and family functioning, with parent anxiety as a covariate. We evaluated child asthma status as a moderator as the presence of a chronic illness may strengthen the association between EE and child/family outcomes. Ninety-four children (mean±SD age=8.83±2.03 years, 48.9% female, 92.6% African American; 47 with asthma) and their parents (81.3% annual household income less than $25,000) completed an observational study including interviews and questionnaires. Measures included the Multidimensional Anxiety Scale for Children (MASC), Children’s Depressive Symptoms Inventory (CDI), Self-Report Family Inventory (SFI), Generalized Anxiety Disorder scale (GAD-7), and Five-Minute Speech Sample (FMSS) coded for EE. To examine study aims, regression analyses were conducted using PROCESS macro version 3.4. Asthma status (yes/no) was examined as a moderator. EE was associated with child anxiety symptoms, controlling for parent anxiety symptoms (F(1,70) =7.67, p=0.007). Criticism was also positively associated with asthma control (F(1,39)=4.33, p=.04, R2=.08). Asthma status did not moderate any of the associations. Results suggested that high levels of caregiver EE were associated with child anxiety symptoms, but asthma status did not moderate associations. It is possible that regardless of additional family demands related to asthma, EE is associated with child anxiety. Further examination into other systemic stressors (e.g., poverty, access to care) that may moderate these associations is warranted, as well as the impact that minimizing parent anxiety might have on overall EE

THE CANADA—BRITAIN–USA TRIAD: CANADIAN PENTECOSTAL PACIFISM IN WWI AND WWII

The story of Canadian Pentecostal pacifism was shaped by its own set of early leaders and the Christian backgrounds they brought into the fledgling movement at the turn of the twentieth century, as well as by two influential relationships: a geographical connection to the United States as a constituent part of North America and a political identity as The Dominion of Canada attached to the British Crown. As a dominion, Canada governed its own internal affairs as a country; however, in foreign affairs, Canada was subject to the decisions of Great Britain. Canada’s own brand of Pentecostal pacifism was shaped by this confluence of a porous border between Canada and the United States that encouraged ideological exchange through magazines, personal visits, joint conventions and other venues, on the one hand, and a long reach across the pond which granted Britain the right to govern the foreign relationships of Canada, on the other hand

Electrostatic Field Classifier for Deficient Data

This paper investigates the suitability of recently developed models based on the physical field phenomena for classification problems with incomplete datasets. An original approach to exploiting incomplete training data with missing features and labels, involving extensive use of electrostatic charge analogy, has been proposed. Classification of incomplete patterns has been investigated using a local dimensionality reduction technique, which aims at exploiting all available information rather than trying to estimate the missing values. The performance of all proposed methods has been tested on a number of benchmark datasets for a wide range of missing data scenarios and compared to the performance of some standard techniques. Several modifications of the original electrostatic field classifier aiming at improving speed and robustness in higher dimensional spaces are also discussed

X-ray Lighthouses of the High-Redshift Universe. II. Further Snapshot Observations of the Most Luminous z>4 Quasars with Chandra

We report on Chandra observations of a sample of 11 optically luminous (Mb<-28.5) quasars at z=3.96-4.55 selected from the Palomar Digital Sky Survey and the Automatic Plate Measuring Facility Survey. These are among the most luminous z>4 quasars known and hence represent ideal witnesses of the end of the "dark age ''. Nine quasars are detected by Chandra, with ~2-57 counts in the observed 0.5-8 keV band. These detections increase the number of X-ray detected AGN at z>4 to ~90; overall, Chandra has detected ~85% of the high-redshift quasars observed with snapshot (few kilosecond) observations. PSS 1506+5220, one of the two X-ray undetected quasars, displays a number of notable features in its rest-frame ultraviolet spectrum, the most prominent being broad, deep SiIV and CIV absorption lines. The average optical-to-X-ray spectral index for the present sample (=-1.88+/-0.05) is steeper than that typically found for z>4 quasars but consistent with the expected value from the known dependence of this spectral index on quasar luminosity. We present joint X-ray spectral fitting for a sample of 48 radio-quiet quasars in the redshift range 3.99-6.28 for which Chandra observations are available. The X-ray spectrum (~870 counts) is well parameterized by a power law with Gamma=1.93+0.10/-0.09 in the rest-frame ~2-40 keV band, and a tight upper limit of N_H~5x10^21 cm^-2 is obtained on any average intrinsic X-ray absorption. There is no indication of any significant evolution in the X-ray properties of quasars between redshifts zero and six, suggesting that the physical processes of accretion onto massive black holes have not changed over the bulk of cosmic time.Comment: 15 pages, 7 figures, accepted for publication in A