bluuebunny/crossref_metadata_2025 huggingface dataset:
Bionics and fractal configurations in structural engineering
Authors: Tesar Alexander
Published: April 2006

Bionics and fractal configurations mapping the schemes from the nature and adopted in present structural engineering are dealt with in present paper. Theoretical and numerical assessments of such configurations are based on the wave approaches running in neural network models corresponding with the genetic algorithms also appearing in nature. Generalized ultimate behaviour of such configurations and structures is analysed. Some structural applications based on such principles are presented. Copyright © 2006 John Wiley & Sons, Ltd.
Adolescent personality, problem behaviour and the quality of the parent–adolescent relationship
Authors: Manders Willeke A. , Scholte Ron H. J. , Janssens Jan M. A. M. , De Bruyn Eric E. J.
Published: April 2006

The relationship between adolescent personality and problem behaviour has been well established. However, relatively little attention has been given to the role of the social environment in the association between adolescent personality and problem behaviour. We tested the mediating and moderating role of the quality of the parent–adolescent relationship in the associations between adolescents' personality traits and problem behaviour. The sample consisted of 140 adolescents (11 to 18 years of age) and both their parents. Results supported a mediating role of the father/mother–adolescent relationship in the associations between Agreeableness, Emotional Stability, and Conscientiousness and externalizing problem behaviour. The father/mother–adolescent relationships did not mediate the associations between personality traits and internalizing problem behaviour. We also found support for a moderating role of the father/mother–adolescent relationships in the association between Emotional Stability and both externalizing and internalizing problem behaviours. Other moderated effects were specific for parent, personality trait and type of problem behaviour. Copyright © 2006 John Wiley & Sons, Ltd.
Phenylene vinylene‐based electroluminescent polymers with electron transport block in the main chain
Authors: Sun Honghao , Mei Chongyu , Zhou Quanguo , Liu Ze , Ma Dongge , Wang Lixiang , Jing Xiabin , Wang Fosong
Published: April 2006

We report a new route for the design of soluble phenylene vinylene (PV) based electroluminescent polymers bearing electron‐deficient oxadizole (OXD) and triazole (TZ) moieties in the main chains with the aryloxy linkage. Both series of the PV‐based polymers were prepared by Wittig reaction. By properly adjusting the OXD and/or TZ content through copolymerization, we can achieve an enhanced balance of hole‐ and electron injections, such that the device efficiency is significantly improved. Light‐emitting diodes fabricated from P1, P2, P3, P4, P5, P6, and P7 with the configuration of Indium–Tin Oxide (ITO)/Poly (styrene sulfonic acid) doped poly (ethylenedioxythiophene) (PEDOT)/polymer/Ca/Al, emit bright green light with the maximum peak around 500 nm. For the device using the optimal polymer (P4) as emitting layer, a maximum brightness of 1300 cd/m2 at 20 V and a maximum luminance efficiency of 0.325 cd/A can be obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3469–3478, 2006
Synthesis, characterization, and properties of novel epoxy resins and cyanate esters
Authors: Lin Ching Hsuan , Yang Kai Zhi , Leu Tsu Shang , Lin Chun Hung , Sie Jhao Wei
Published: April 2006

We synthesized a novel epoxy (dopotep) and cyanate ester (dopotcy) based on a phosphorus‐containing triphenol (dopotriol). The proposed structures were confirmed by IR, mass spectra, NMR spectra, and epoxy‐equivalent‐weight titration. The synthesized dopotep or dopotcy was copolymerized with diglycidyl ether of bisphenol A (DGEBA), 6′,6‐bis(3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazineyl)methane (F‐a), or dicyanate ester of bisphenol A (BADCY). Thus, copolymers based on DGEBA/dopotep/diphenylmethane (ddm), F‐a/dopotep, BADCY/dopotcy, and DGEBA/dopotcy were developed. The thermal properties, dielectric properties, and flame retardancy of these copolymers were investigated. The curing kinetics of dopotep/ddm and dopotep/diamino diphenylsulfone were studied with differential scanning calorimetry. The microstructure of DGEBA/dopotcy was studied with IR. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3487–3502, 2006
Sonochemical synthesis of novel blue‐emissive, water‐soluble, cationic polysilanes as fluorescent sensors
Authors: Wang Wei‐Zhi , Fan Qu‐Li , Cheng Fan , Zhao Ping , Huang Wei
Published: April 2006

The design, synthesis, and characterization of novel blue‐emissive, cationic, water‐soluble, conjugated polymers based on polysilanes with amino‐terminal groups are described. Water solubility was realized through the quaternization of the amino group to control the cationic degree, which in turn determined the solubility of the polymers in organic solvents and water. The sonochemical synthesis and 2,2′‐azobisisobutyronitrile assistant hydrosilylation reaction well maintained the polysilane molecular weights and polydispersities. A redshift of the absorption and photoluminescence spectra in solutions was distinctly observed with increasing solvent polarity. The water‐soluble polysilanes had better thermal and UV light stability. Before and after quaternization, the polymers showed acceptable photoluminescence quantum yields in solutions. The flexible main chains of the polysilanes, increasing the conformational freedom, adhered tightly to the secondary structure of the analyte, resulting in improved Förster‐resonance‐energy‐transfer efficiencies. These polymers could be highly sensitive and selective materials for chemo‐ and biosensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3513–3525, 2006
Development of novel flame‐retardant thermosets based on boron‐modified phenol–formaldehyde resins
Authors: Martín C. , Ronda J. C. , Cádiz V.
Published: April 2006

Boron‐containing novolac resins were prepared through the modification of a commercial novolac resin with different contents of bis(benzo‐1,3,2‐dioxaborolanyl) oxide. Their thermal and flame‐retardant properties were measured. Then, they were crosslinked with hexamethylenetetramine, and their thermal, thermodynamomechanical, and flame‐retardant properties were evaluated. Their modification degree was related to the segmental motion of the materials. The crosslinking of the boron‐modified novolac resins with hexamethylenetetramine was slower and not as extensive as that of commercial novolac resins because the nitrogen from intermediate species coordinated with boron. The thermal degradation of the boron‐containing novolac resins generated boric acid at high temperatures and gave an intumescent char that slowed the degradation and prevented it from being complete. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3503–3512, 2006
Sensitivity of Uncinula necator to quinoxyfen: evaluation of isolates selected using a discriminatory dose screen
Authors: Green Elizabeth A , Gustafson Gary D
Published: April 2006

Quinoxyfen is a protectant fungicide that provides excellent control of many powdery mildew diseases. Prior to the launch of quinoxyfen in vines in 1998, a leaf disc sporulation assay was developed to assess the sensitivity of Uncinula necator (Schw) Burr to quinoxyfen. The distribution of EC50 values from 56 monoconidial U. necator isolates collected from six countries between 1993 and 1996 was found to range from less than 0.03 to 2.6 mg litre−1. Although this range of EC50 values was quite broad, the inability to establish a minimum inhibitory concentration (MIC) for the majority of these isolates, including some of the most sensitive isolates, was unexpected and suggested that the leaf disc sporulation assay may not reflect the true activity of quinoxyfen in the field. In 2002, following the detection of isolates resistant to quinoxyfen in Blumeria graminis Speer f. sp. tritici Marchal, a discriminatory dose screen was developed to test large populations of U. necator for rare individuals with significantly decreased sensitivity to quinoxyfen. The individual isolates selected by this method were tested with the leaf disc sporulation assay. Although a significant proportion were found to have EC50 values within the original distribution, a number of isolates with apparent reduced sensitivity to quinoxyfen were also detected. However, further examination of a subset of these isolates in a more quantitative germination/germ tube elongation inhibition assay suggested that the magnitude of the reduction in sensitivity for some of these isolates was much less than predicted by the sporulation assay. Thus, for an exclusively protectant fungicide such as quinoxyfen, a leaf disc sporulation assay may overestimate the frequency of isolates with significantly reduced sensitivity and the threat of decreased performance due to resistance. Copyright © 2006 Society of Chemical Industry
Mineralisation of atrazine, metolachlor and their respective metabolites in vegetated filter strip and cultivated soil
Authors: Krutz Larry J , Gentry Terry J , Senseman Scott A , Pepper Ian L , Tierney Dennis P
Published: April 2006

In vegetated filter strips (VFS) the presence of perennial vegetation, rhizodeposition of labile organic substrates and the accumulation of an organic residue thatch layer may enhance microbial numbers and activity, thereby increasing the potential for mineralisation of herbicides and herbicide metabolites retained during run‐off events. The objective of this laboratory experiment was to compare the mineralisation of atrazine and metolachlor with that of their respective metabolites in VFS and cultivated soil. With the exception of total bacteria, propagule density of the microbial groups, endogenous soil enzymes and microbial diversity were higher in the VFS soil. This correlated with increased mineralisation of metolachlor and its metabolites in the VFS soil and indicates potential for VFS to curtail the subsequent transport of these compounds. In contrast, the mineralisation of atrazine and the majority of its metabolites was substantially reduced in VFS soil relative to cultivated soil. Consequently, the potential for subsequent transport of atrazine and many of its metabolites may be greater in VFS soil than in cultivated soil if reduced mineralisation is not offset by increased sorption in the VFS. Copyright © 2006 Society of Chemical Industry
The investigation of levels of the peptide adrenomedullin (ADM) and the enzyme tyrosine hydroxylase (TH) in rat tissue after exposure to physiological stress
Authors: Yürekli Muhittin , Yarpuzlu Ayegül Akbay
Published: April 2006

An organism's ability to respond to the external and internal environments is explained in terms of the concept of biological stress. The causes of these responses are called stressors. They may be physical, chemical, emotional, or traumatic. With continued exposure to the stressor the organism enters the stage of resistance and defense. After prolonged exposure to the same stressor the organism may enter the stage of exhaustion. Catecholamines have an important role in maintaining biological homeostasis to stress. Catecholamine biosynthesis starts from tyrosine and in the first step DOPA is synthesized from tyrosine and catalyzed by the enzyme tyrosine hydroxylase (TH). In rats this enzyme activity varies depending on cold stress, exercise and age. The production of adrenomedullin in adrenal medulla, heart and brain also suggest a role for this peptide in the physiological control of homeostasis.

In this study TH enzyme activity and adrenomedullin levels were investigated in rat tissues that were excised from animals exposed to 8°C cold for 3 weeks. After cold exposure TH enzyme activities and adrenomedullin levels were changed but also age was found to be a factor. Copyright © 2006 John Wiley & Sons, Ltd.
User friendly and ‘useworthy’ Stress Barometer
Authors: Brattberg Gunilla
Published: April 2006

The Stress Barometer, which includes stress symptoms, stress types, relationship stress and time stress, was developed as an easy‐to‐use instrument which provides a visual representation of the stress an individual is experiencing. The purpose of this study was to assess the reliability, validity and usefulness of the Stress Barometer. Reliability was tested using a test–retest procedure on 23 pain patients on long‐term sick leave. To assess validity, the results of the instrument were compared to the results of the SF‐36 Health Survey, the Hospital Anxiety and Depression Scale and the Shirom–Melamed Burnout Questionnaire administered to 112 pain and/or emotional exhaustion syndrome patients on long‐term sick leave. Fifty directors who participated in a management leadership course focusing on stress also completed and evaluated the instrument. Reliability was high for most of the subscales included. The results of the validity test showed that the Stress Barometer correlates with the respondents' perceived experience of a variety of health aspects such as anxiety, depression as well as different aspects of burnout/emotional exhaustion. The Stress Barometer is quick to complete and it offers immediate feedback. The study demonstrates that the Stress Barometer is also usable and useworthy. Copyright © 2006 John Wiley & Sons, Ltd.
Forgiveness and rumination: a cross‐cultural perspective comparing India and the US
Authors: Suchday Sonia , Friedberg Jennifer P. , Almeida Maureen
Published: April 2006

Forgiveness is a key component of the tenets of religions across the globe. However, it is only recently that scientific research on health has focused on forgiveness as an important component of well‐being. Research in the West has indicated that forgiveness is associated with increases in physical health and well‐being, and that rumination may mediate the relationship between forgiveness and health. However, little is known about the relationship between forgiveness, rumination, and health in non‐Western populations such as India. The purpose of the current study was to measure forgiveness, rumination, stress, and physical health in Indian college students, and compare their responses to that of a US sample. Participants were 188 college students (92 males and 96 females) from Mumbai, India. Results indicated that lower levels of forgiveness predicted increased rumination and stress, but not physical symptoms. Similar to data in the US, rumination mediated the relationship between forgiveness and stress. There were no significant differences in forgiveness, rumination, or stress between the Indian and US samples. Results suggest the universality of these variables across cultures. Copyright © 2006 John Wiley & Sons, Ltd.
No association between the brain‐derived neurotrophic factor gene Val66Met polymorphism and post‐traumatic stress disorder
Authors: Lee Heon‐Jeong , Kang Rhee‐Hun , Lim Se‐Won , Paik Jong‐Woo , Choi Myoung‐Jin , Lee Min‐Soo
Published: April 2006

Post‐traumatic stress disorder (PTSD) is a chronic anxiety disorder that follows exposure to traumatic events. The etiology of PTSD is unknown, although exposure to a traumatic event constitutes a necessary but not sufficient factor. Recent studies have demonstrated that the brain‐derived neurotrophic factor (BDNF) is related to stress‐related psychiatric conditions. In this study, therefore, the genotype and allele frequencies of the BDNF gene Val66Met polymorphism were analyzed in 106 PTSD patients and 161 unrelated healthy controls using a case‐control design. The genotype and allele frequencies for the BDNF gene polymorphism did not differ between the two groups. These findings suggest that the BDNF polymorphism investigated herein does not play a major role in the susceptibility to PTSD at least in the Korean population. Further studies designed to explore the relationship between genetic variations of BDNF and the incidence of PTSD in a larger population may be warranted. Copyright © 2006 John Wiley & Sons, Ltd.
Counterfactual (‘if only’) thinking in women with chronic widespread pain
Authors: Andersson Sven Ingmar , Hovelius Birgitta
Published: April 2006

The study explored the counterfactual thinking that women with chronic and widespread pain showed in response to what they themselves considered to be particularly stressful situations. Counterfactual thinking in 125 women sick‐listed due to chronic and widespread pain was investigated in terms of structure, function and control focus. The women were asked, for each of three types of problems that they indicated in a questionnaire to affect them most strongly, to describe a typical occurrence of it and to complete a counterfactual sentence in connection with it of the type ‘If only . . .’. The majority of counterfactuals pertained to predominantly somatic problems (e.g. musculo‐skeletal problems, pain and fatigue) classified as being affective rather than preparative and self‐focused rather than external, whereas in counterfactuals relating to predominantly psychological/psychosocial problems a preparative function and an external focus were more prominent. The numbers of problems listed and the numbers of situations responded to counterfactually were positively correlated. The counterfactuals, although often related to somatic problems, generally concerned psychological or psychosocial matters such as finances and paid or unpaid work. A contextual approach to elucidating counterfactual thinking based on subjects' own experiences is seen as providing valuable insight into what bothers them most. Copyright © 2006 John Wiley & Sons, Ltd.
Path analysis of work conditions and work–family spillover as modifiable workplace factors associated with depressive symptomatology
Authors: Franche Renée‐Louise , Williams Alysha , Ibrahim Selahadin , Grace Sherry L. , Mustard Cam , Minore Bruce , Stewart Donna E.
Published: April 2006

Background: Literature pertaining to the relationship between workplace factors and depression has been compartmentalized: work conditions, family conditions, and work–family balance have been studied separately as predictors of depressive symptoms but not concurrently.

Objective: Work conditions and work–family spillover were considered concurrently as modifiable workplace factors associated with depressive symptomatology, while controlling for confounding socio‐economic factors.

Methods: This cross‐sectional study involved 218 female health care workers who completed a survey assessing work conditions [Effort–Reward Imbalance (ERI) scale and Job Content Questionnaire (JCQ)], work–family balance (work–family spillover scale), sociodemographic information, and depressive symptoms [Center for Epidemiological Studies Depression (CES‐D) scale].

Results: Path analysis supported the presence of a direct relationship between depressive symptoms and high effort–reward imbalance, high negative work–family spillover, low positive family‐to‐work spillover, and low education. The indirect effect of low support from work was mediated by negative work‐to‐family spillover and high effort–reward imbalance. The indirect effect of high effort–reward imbalance was mediated by increased negative work‐to‐family spillover. The indirect effect of having children 18 years or younger was mediated by decreased positive family‐to‐work spillover. An indirect effect of low education was mediated by high effort–reward imbalance and high negative work‐to‐family spillover.

Conclusions: The association between work conditions and depressive symptomatology is mediated by increased negative work‐to‐family spillover. The impact of having young children is mediated by decreased positive family‐to‐work spillover. Copyright © 2006 John Wiley & Sons, Ltd.
A proposed physician–patient cycle model
Authors: Williams Eric S. , Savage Grant T. , Linzer Mark
Published: April 2006

Understanding the effect that physician stress and burnout have on patient outcomes is important to improving the quality of care. The physician–patient cycle model documents the virtuous or vicious cycles which can ensue when clinicians deal effectively or ineffectively with stress and burnout. The model starts with excessive stress beginning the physician burnout process. Ineffectual physician responses to burnout, including depersonalizing behaviors, negatively affect the quality of the medical encounter. Poor quality encounters engender low patient satisfaction, poor compliance with medical treatments, and more patient assertiveness. For physicians, these patient attitudes and behaviors may be perceived as patient demands and experienced as additional stressors, perpetuating a vicious cycle. The model contributes to the knowledge base on stress and health by synthesizing various studies that have examined physician stress and burnout as they impact patient outcomes. A major implication is that the well‐being of physicians is a key ingredient to the provision of quality medical care. Copyright © 2006 John Wiley & Sons, Ltd.
Best practices for physical activity programs and behavior counseling in older adult populations
Authors: Cress M. E. , Buchner D. M. , Prohaska T. , Rimmer J. , Brown M. , Macera C. , DePietro L. , Chodzko-Zajko W.
Published: April 2006

Physical activity offers one of the greatest opportunities for people to extend years of active independent life and reduce functional limitations. The purpose of this paper is to identify key practices for promoting physical activity in older adults, with a focus on older adults with chronic disease or low fitness and those with low levels of physical activity. Key practices identified in promotion activity in older adults include: (1) a multidimensional activity program that includes endurance, strength, balance, and flexibility training is optimal for health and functional benefits; (2) principles of behavior change, including social support, self-efficacy, active choices, health contracts, assurances of safety, and positive reinforcement, enhance adherence; (3) management of risk by beginning at low intensity but gradually increasing to moderate physical activity which has a better risk/benefit ratio should be the goal for older adults; (4) an emergency procedure plan is prudent for community-based programs; and (5) monitoring aerobic intensity is important for progression and for motivation. Selected content reviews of physical activity programming from major organizations and institutions are provided. Regular participation in physical activity is one of the most effective ways for older adults, including those with disabilities, to help prevent chronic disease, promote independence, and increase quality of life in old age.
The relationship between monogamous/polygamous family structure and the mental health of bedouin Arab adolescents
Authors: Elbedour S. , Bart William , Hektner Joel
Published: April 2006

Previous studies of polygamy and child mental health have primarily focused on younger children. The present studies are among the first to focus on adolescents. The first study involved 210 randomly selected Bedouin Arab adolescents (mean age 15.9), who were administered instruments assessing their family environment and mental health. The second study involved 182 Bedouin Arab adolescents in which the student participants completed a single instrument about themselves and in which the teachers of the students completed the Teachers’ Report Form of the Child Behaviour Checklist by Achenbach. The Bedouin Arab adolescents fell into two groups: (a) adolescents in monogamous family structures and (b) adolescents in polygamous family structures. The findings of the first study suggest that the two groups did not differ significantly in the majority of the assessed variables, even though there were significant differences obtained between groups for 4 of the 13 assessed variables. The two groups did not differ significantly in the second study. Results were discussed in terms of their cultural and developmental significance.
Kelvin-Helmholtz waves in the ocean?
Authors: Mahony J. J.
Published: April 2006

Large amplitude short waves confined near the crests of a swell have been observed when a stiff breeze was blowing against the swell. This would seem to imply the existence of both a wavelength-selective generating mechanism and a trapping mechanism, neither of which is to be expected of surface gravity waves of the observed length. It is suggested that there are significant changes in the dynamics of such waves if allowance is made for the dynamic coupling between wind and waves. For a Kelvin-Helmholtz model it is shown that energy transfer rates from the turbulent pressure fluctuations are greatly enhanced for subcritical conditions by the inclusion of the dynamic coupling. The group velocity of subcritical waves is profoundly affected, becoming infinite at the stability boundary. Thus subcritical waves could be trapped on a swell. An examination of the effects of wind shear suggest that Kelvin-Helmholtz type instability could still be present, although for stronger winds, particularly for rather longer waves.

The energy and momentum fed from the mean wind, being trapped at crests of the swell, may contribute significantly to the attenuation of the swell. The profound wave dynamic effects of the coupling between the wind and the swell for short gravity waves may be of significance in other oceanic phenomena, even when the Kelvin-Helmholtz type of instability is not present.
Nonlinear wave propagation in a two-dimensional steady transonic flow
Authors: Prasad Phoolan , Krishnan E. V.
Published: April 2006

When we look at photographs of real transonic flows which are predicted to be shockless, we find a very large number of weak shocks almost perpendicular to the streamlines. These are no more than almost-trapped upstream-propagating nonlinear waves. In this paper we try to obtain a simple approximate equation which gives their complete history and takes into account both their turning effect, owing to a non-zero gradient of the fluid velocity in a direction normal to the streamlines, and also the finite radius of curvature of the wave front. We first give a brief discussion of a few results which can be easily obtained from the solution of the approximate equation and then compute the history of two nonlinear pulses by numerically integrating the equation.
Influence of the amplitude of a solid wavy wall on a turbulent flow. Part 1. Non-separated flows
Authors: Zilker Daniel P. , Cook Gerald W. , Hanratty Thomas J.
Published: April 2006

Measurements of the shear-stress variation along and the velocity profiles above a solid wavy wall bounding a turbulent flow are presented for waves with height-to-length ratios of 2a/λ = 0·0312 and 0·05. These are compared with previous measurements of the wall shear stress reported by Thorsness (1975) and by Morrisroe (1970) for 2a/λ = 0·012. The investigation covered a range of conditions from those for which a linear behaviour is observed to those for which a separated flow is just being initiated.

Pressure measurements indicate a linear response in that the spatial variation is described quite well by a single harmonic with a wavelength equal to that of the surface. However, the variation of τw for waves with 2a/λ = 0·0312 and 0·05 can be more rapid on the leeward side of the wave. The degree of departure from a sinusoidal variation increases with increasing wave height and fluid velocity and, from the results reported in this paper, it is suggested that nonlinear behaviour will become evident when au*/v [ges ] 27.

Many aspects of the flow for all three waves are described by a solution of the linear momentum equations previously presented by Thorsness (1975) and by Thorsness & Hanratty (1977). These include the phase and amplitude of the pressure profile and the first harmonic of the shear-stress profile and the velocity field outside the viscous wall region.

These results suggest that up to separation the flow is approximated quite well by linear theory. Nonlinearities affect the flow only in a region very close to the wave surface and are manifested by the appearance of higher harmonics in the variation of τw.
Turbulent mixing of passive and chemically reacting species in a low-speed shear layer
Authors: Batt R. G.
Published: April 2006

A series of experiments has been conducted in a low-speed wind tunnel in which measurements were performed in a two-dimensional turbulent shear layer experiencing the mixing of both a passive and a chemically reacting species. The low-temperature air in the jet's primary flow was seeded with dilute concentrations of N2O4so that the dissociation reaction N2+ N2O4[harr ] 2NO2+ N2occurred in a near-equilibrium manner within the mixing layer owing to the turbulent mixing properties and the imposed temperature gradient. Mean and fluctuating values of velocity, temperature and NO2concentration were measured up to axial distances of 25 in. for jet velocities of 23 and 50ft/s (Rex[les ] 7 × 105) and for three primary temperatures (252, 273 and 305°K). Velocity and temperature measurements were performed with hot-wire probes, whereas a fibre optics light sensor probe was used to measure NO2concentrations. Local correlations between species and other fluid properties were obtained by positioning a hot-wire sensor within the light gap of the fibre optics probe and simultaneously recording output signals from both probes. A relatively complete set of turbulent statistics was measured for the non-reacting shear layer, including such results as temperature/species correlations, probability densities, filtered and unfiltered moving-frame velocities, skewness and flatness factors, spectra, velocity and temperature integral scales, intermittency factors for velocity, temperature and passive species, and conventional intensities. Some typical results from the investigation are as follows: the turbulent Schmidt and Lewis numbers were 0·5 and 1·0 respectively; the correlation between passive NO2concentration and temperature was approximately 0·95; dramatic changes consistent with equilibrium chemistry occurred in NO2concentration profiles with chemical reaction; velocity, temperature and concentration spectra were comparable over a 2½-decade range in wavenumber (k−2); spectra, probability densities, time-trace data and smoke-seeded shear-layer photographs indicate that, for axial locationsx=x0[ges ] 18·5 in. and for speedsu1[ges ] 23ft/s, undisturbed edge fluid rarely penetrates completely across the mixing region. Although not specifically addressed during the current study, measured results herein suggest that the turbulent motion for the present shear layer is characterized more by random and/or three-dimensionality effects than by large-scale two-dimensional coherent structures, as has been observed recently in other shear-layer investigations.
Inertial convection at low Prandtl number
Authors: Proctor Michael R. E.
Published: April 2006

The problem of Rayleigh-Bénard convection at low Prandtl number σ is investigated in a circular geometry. Jones, Moore & Weiss (1976) have formulated, but not solved analytically, an asymptotic nonlinear problem in the limit σ → 0 at small velocities. It is shown that the problem they posed can be solved exactly in this geometry. The solutions are extended by means of expansions in the amplitude ε and the reciprocal of the Reynolds number σε−1, both assumed small. The problem is related to one that occurs in nonlinear mean-field dynamo theory (Malkus & Proctor 1975) and it is surmised that similar problems may be expected to appear in a variety of physical situations.
The starting mechanism of wave-induced flow through a sharp-edged orifice
Authors: Evans R. A. , Bloor M. I. G.
Published: April 2006

Following weak plane shock diffraction at a knife-edge situated in a duct, a two-dimensional vortex sheet springs from the salient edge. The method of ‘vortex discretization’ is used, in conjunction with a Schwarz-Christoffel transformation, to develop a two-dimensional potential model for this constrained form of vortex generation. The analysis is independent of empirical parameters and describes, qualitatively, the pattern of streamlines through the orifice.

Flow-visualization photographs are presented which illustrate the spiral shape of the starting vortex. Although of a limited nature, quantitative experimental vortex growth rates have been obtained and are compared with initial growth rates predicted theoretically. The results are discussed together with other aspects of the problem, including the limitations of the theory.

An extension of vortex discretization is developed whereby the pressure distribution remote from the vortex sheet can be calculated. The combination of flow separation and the associated static wall pressure distribution gives theoretical insight into the mechanism of flow through an orifice.
Long-term dispersion of contaminants in small estuaries
Authors: Smith Ronald
Published: April 2006

It is shown that the use of axes moving with the tide (Shinoharaet al.1969) simplifies the analysis of contaminant dispersion in estuaries. Attention is restricted to estuaries which are small in the sense that cross-sectional mixing is rapid and that the tidal elevation can be taken to be constant along the estuary. In agreement with the work of Fischer (1972a, b) it is found that the dominant mechanism for dispersion is the transverse shear and not the vertical shear. Results are presented to illustrate the dependence of the upstream penetration of salt upon the estuary geometry as well as upon the fresh-water discharge rate.
Upstream influence and Long's model in stratified flows
Authors: Baines P. G.
Published: April 2006

This paper describes an experimental study of a stratified fluid which is flowing over a smooth two-dimensional obstacle which induces no flow separation and in which effects of viscosity and diffusion are not important. The results are restricted to fluid of finite depth. Various properties of the flow field, in particular the criterion for the onset of gravitational instability in the lee-wave field, are measured and compared with the theoretical predictions of Long's model. The agreement is found to be generally poor, and the consequent inapplicability of Long's model is explained by the failure of Long's hypothesis of no upstream influence, which is demonstrably invalid when stationary lee waves are possible. The obstacle generates upstream motions with fluid velocities which appear to be of first order in the obstacle height. These motions have some of the character of shear fronts or columnar disturbance modes and have the same vertical structure as the corresponding lee-wave modes generated downstream. They result in a reduced fluid velocity upstream below the level of the top of the obstacle, together with a jet of increased fluid velocity above this level which pours down the lee side of the obstacle. This phenomenon becomes more pronounced as the number of modes is increased.
The return to isotropy of homogeneous turbulence
Authors: Lumley John L. , Newman Gary R.
Published: April 2006

The return to isotropy of homogeneous turbulence without mean velocity gradients is attacked by considering changes to be slow relative to turbulence time scales. This single assumption permits the problem to be cast as one of finding the form of three invariant functions. Examination of limiting behaviour for large Reynolds number and small anisotropy, as well as small Reynolds number and arbitrary anisotropy, places restrictions on the form of the functions. Realizability conditions (requiring that energies be non-negative) reduce the problem to two functions subject to further restrictions. A convenient interpolation form is found for the functions, satisfying all the restrictions, and it is shown that predictions based on this are in excellent agreement with all available data.
On choking flutter
Authors: Tanida Y. , Saito Y.
Published: April 2006

The purpose of the present study is to assess the possibility of the so-called choking flutter in a transonic cascade operating under choking conditions. In the experiment, measurements of the unsteady aerodynamic moment acting on an aerofoil which is oscillating in pitch about the midchord in a transonic channel flow are performed for channel height-to-chord ratios H/c = 0·5−3 and oscillation frequencies up to 120 Hz. For a large channel height such as H/c = 3, the unsteady aerodynamic behaviour is similar to that of an isolated aerofoil, and the system will be aeroelastically stable in the transonic region as well as in the subsonic one. For smaller channel heights such as H/c = 0·5, however, the flow chokes and the aerodynamic behaviour becomes significantly different from that at large channel heights. As soon as a shock appears, i.e. in the incipient transonic region, the aerodynamic derivatives change discontinuously, so that the subsonic and transonic regions can be clearly separated. In this case, the aerodynamic damping becomes negative in the transonic region.

In order to understand the transonic features, a one-dimensional unsteady analysis is undertaken for small channel heights H/c [les ] 0·5. The numerical results show good qualitative agreement with the experimental ones, predicting in the incipient transonic region a discontinuous variation of the aerodynamic moment which results in system instability.

It is concluded that choking flutter may occur in transonic channel flow with a moderately small channel height when the passage is choked.
The blast waves from asymmetrical explosions
Authors: Chiu K. W. , Lee J. H. , Knystautas R.
Published: April 2006

From Whitham's ray-shock theory and the Brinkley-Kirkwood theory of shock propagation, a general theory for the propagation of asymmetrical blast waves of arbitrary shapes and strengths is developed in this paper. The general theory requires the simultaneous numerical solution of a set of partial differential equations and a pair of ordinary differential equations. If the shock shape is assumed to be known and remains invariant with time then the geometrical and the dynamical relationships in the theory can be decoupled. In this case the solution simply requires the integration of the ordinary differential equations governing the dynamics of the blast motion since the geometry is already known. As a specific example the asymmetrical blast waves generated by the rupture of a pressurized ellipsoid are studied. The peak pressure is calculated by assuming that the shock surface remains ellipsoidal for all times and that the peak overpressure decay rate of the blast depends on the local curvature. For weak shocks, it is found that the degree of directionality is more pronounced than for stronger shocks. For weak blasts the present theory agrees with the solution based on acoustic theory. Experimental results on the shock trajectories for asymmetrical blast waves generated by exploding wires are found to agree with the present theory.
Numerical analysis of turbulent end-wall boundary layers of intense vortices
Authors: Chi Joseph
Published: April 2006

After a careful consideration of the laws of generation, advection, diffusion and dissipation of turbulent kinetic energy proposed by Prandtl (1945) and Emmons (1954), equations of motion and turbulent kinetic energy for the vortex flow near a solid end wall are established. These equations are then evaluated by a numerical procedure. Care is taken to specify boundary conditions such that satisfactory matching of the solution with the main vortex is assured. The agreement between the predicted mean velocity distribution and the experimental data is remarkably good. In addition, several interesting characteristics are predicted by the theory: (i) the vertical distribution of horizontal velocity is oscillatory in the inner region, whilst it is of the ordinary boundary-layer type in the outer region; (ii) the maximum velocity in the boundary layer can exceed that in the main vortex by a considerable amount and (iii) the minimum pressure of the vortex does not occur in the vortex-core root as has been generally believed.
A contribution to an inviscid vortex-shedding model for an inclined flat plate in uniform flow
Authors: Kiya Masaru , Arie Mikio
Published: April 2006

Unsteady separated flow behind an inclined flat plate is numerically studied through the use of the discrete-vortex approximation, in which the shear layers emanating from the edges of the plate are represented by an array of discrete vortices introduced into the flow field at appropriate time intervals at some fixed points near the edges of the plate. The strengths of the nascent vortices are chosen so as to satisfy the Kutta condition at the edges of the plate. Numerical calculations are performed for a plate at 60° incidence impulsively started from rest in an otherwise stationary incompressible fluid, by systematically changing the distance between the location of the nascent vortices and the edges of the plate. The temporal changes in the drag force, the rate of vorticity transport at both edges of the plate and the velocity of the separated shear layers are given together with the flow patterns behind the plate on the basis of this model. The results of the computation show that the vortex street behind the plate inclines as a whole towards the direction of the time-averaged lift force exerted on the plate. It is also predicted from the calculations that the vortex shedding at one edge of the plate will not occur at the mid-interval of the successive vortex shedding at the other edge. The predicted flow patterns are not inconsistent with a few experimental observations based on the flow-visualization technique.
An inviscid numerical simulation of vortex shedding from an inclined flat plate in shear flow
Authors: Kiya Masaru , Arie Mikio
Published: April 2006

Two-dimensional vortex shedding behind an inclined flat plate in uniform shear flow is numerically investigated by means of an inviscid discrete-vortex approximation. The points of appearance of the vortices are fixed in the plane of the plate at a short distance downstream of the edges of the plate. The strengths of the vortices are determined from the Kutta condition. On the assumption that the steadily periodic flow patterns are independent of initial conditions, the numerical calculations are performed for an inclined flat plate immersed in an incompressible fluid which is set in motion impulsively from rest with the velocity profile of uniform shear flow. The results of analysis show that the Strouhal number of vortex shedding and the time-averaged values of other hydrodynamic characteristics of the flow such as the outer-edge velocity of the separated shear layers, the convective velocity of the shear layers and the drag force exerted on the plate vary closely linearly with the shear parameter of the approaching shear flow. A linear relation between the Strouhal number and the shear parameter is confirmed by an air-tunnel experiment. The effects of the shear parameter on the calculated vortex patterns in the wake are also presented.
Shear layer instability of an inviscid compressible fluid. Part 3
Authors: Drazin P. G. , Davey A.
Published: April 2006

This note corrects and augments the results of Blumen, Drazin & Billings (1975) on the linear instability of a shear layer between two streams of an inviscid compressible fluid at the same temperature. The main conclusion of these authors, that the shear layer is unstable to two-dimensional disturbances however large the Mach number, is confirmed in the present paper. Also a third mode of instability is discovered and the character of all three modes revealed by a series of accurate calculations.
Characterization of the formation of base sheet paper using spectral moments determined from time-series models
Authors: Devries Warren R. , Wu S. M.
Published: April 2006

The fibre distribution in a sheet of paper, referred to as the formation, is largely the result of turbulence, a stochastic process. Continuous time-series models developed from discrete light-transmission profiles are used to characterize formation. The models are used to obtain explicit expressions for the spectral moments of the profiles. From the moments, estimates of two characteristic lengths of the fibre distribution can be obtained and are interpreted as the average and largest flock size. These lengths are used to develop an index for evaluating the formation of four samples of base sheet paper. The results of this characterization agree with other methods, but this technique has the advantage of providing a physical interpretation of the index.
The initial region of subsonic coaxial jets. Part 2
Authors: Kwan A. S. H. , Ko N. W. M.
Published: April 2006

Earlier investigations by the authors have suggested that coherent structures, in the form of two different arrays of vortices, exist in the initial region of coaxial jets. The present investigation was aimed at obtaining further information on the characteristics of the vortices in coaxial jets. Single- and two-point correlation covariance measurements of the fluctuating pressure and the axial and radial velocity fluctuations have been made in the initial region of coaxial jets. Detailed analysis of the correlograms indicates the combined effect of the two vortex trains on the correlograms. Further, the analysis enables the phase relationship between the pressure and axial and radial velocity fluctuations to be obtained. From the correlation results the phase properties obtained within the whole initial region of coaxial jets are found to agree with the results for single jets. This good agreement supports the formally suggested simple approach to the understanding of the complicated flow in coaxial jets.
Stress in a suspension near rigid boundaries
Authors: TÖZeren Aydin , Skalak Richard
Published: April 2006

The stress system near a rigid boundary in a suspension of neutrally buoyant spheres is considered under the assumption of small Reynolds number. The suspending fluid is assumed to be Newtonian and incompressible. An ergodic principle is formulated for parallel mean flows, and the bulk stress is expressed as a surface average. Only dilute suspensions are considered and particle interactions are neglected. A uniform shear flow past a plane wall with a single spherical particle is studied first. A series solution is developed and the mean velocity and stress fields are computed for a force-free and couple-free sphere and also for spheres with couples applied by external means. The translational and angular velocities of the particle and the stress distribution on the surface of the particle are calculated. Properties of dilute suspensions of spheres are found by appropriate surface averages over the solutions for a single particle. The mean stress on a plane parallel to the wall is shown to reduce to the Einstein value when the distance from the boundary is sufficiently large. Mean velocity profiles of the suspension for Couette flow and Poiseuille flow are developed. It is shown that in an average sense particles rotate more slowly than the ambient fluid in a region approximately three sphere radii thick adjacent to the plane wall. But for the suspension as a whole, an apparent slip velocity always develops in this region. This results in an apparent viscosity which is less than the infinite-suspension value of Einstein.
Solution of three-dimensional incompressible flow problems
Authors: Richardson S. M. , Cornish A. R. H.
Published: April 2006

A method for solving quite general three-dimensional incompressible flow problems, in particular those described by the Navier–Stokes equations, is presented. The essence of the method is the expression of the velocity in terms of scalar and vector potentials, which are the three-dimensional generalizations of the two-dimensional stream function, and which ensure that the equation of continuity is satisfied automatically. Although the method is not new, a correct but simple and unambiguous procedure for using it has not been presented before.