The direct numerical simulation database from Shin et al. (J. Fluid Mech., vol. 823, 2017, pp. 1–25) is used to study three-dimensional vortical and very-large-scale coherent structures in a turbulent round jet at a Reynolds number of $7300$. In particular, horseshoe vortices and their role in the formation of very-large-scale coherent structures in the jet near and intermediate fields are assessed. The swirling strength criterion together with conditional averaging are used to visualize volumetric vortical structures. It is shown that, similar to wall-bounded turbulent flows, the turbulent jet is populated with symmetric and asymmetric horseshoe-like vortices, which induce high-momentum and low-momentum regions in the flow. However, unlike what is found for wall-bounded flows, inverse horseshoe-like vortices are common in the turbulent jet. They prevail in the shear region around the potential core in the jet near field and contribute to the mixing of the potential core in the jet. In the jet near field, groups of axially aligned horseshoe structures induce long streaky structures, which are periodic in the azimuthal and streamwise directions. In the jet intermediate field, very-large-scale motions (VLSMs) consisting of high-momentum regions, flanked on either side by low-momentum regions, are found to be associated with groups of horseshoe vortices. Instantaneous three-dimensional flow fields suggest that horseshoe vortices tend to concatenate and form organized spiral as well as axially aligned coherent VLSMs. A detection scheme is introduced to identify and average over these VLSMs. This conditional averaging reveals that spiral VLSMs and axially aligned VLSMs constitute $72\,\%$ and $28\,\%$ of the total VLSMs, respectively.

The flow in a decelerating turbulent round jet is investigated using direct numerical simulation. The simulations are initialised with a flow field from a statistically stationary turbulent jet. Upon stopping the inflow, a deceleration wave passes through the jet, behind which the velocity field evolves towards a new statistically unsteady self-similar state. Assumption of unsteady self-similar behaviour leads to analytical relations concerning the evolution of the centreline mean axial velocity and the shapes of the radial profiles of the velocity statistics. Consistency between these predictions and the simulation data supports the use of the assumption of self-similarity. The mean radial velocity is predicted to reverse in direction near to the jet centreline as the deceleration wave passes, contributing to an approximately threefold increase in the normalised mass entrainment rate. The shape of the mean axial velocity profile undergoes a relatively small change across the deceleration transient, and this observation provides direct evidence in support of previous models that have assumed that the mean axial velocity profile, and in some cases also the jet spreading angle, remain approximately constant within unsteady jets.

Fluid residence time is a key concept in the understanding and design of chemically reacting flows. In order to investigate how turbulent mixing affects the residence time distribution within a flow, this study examines statistics of fluid residence time from a direct numerical simulation (DNS) of a statistically stationary turbulent round jet with a jet Reynolds number of 7290. The residence time distribution in the flow is characterised by solving transport equations for the residence time of the jet fluid and for the jet fluid mass fraction. The product of the jet fluid residence time and the jet fluid mass fraction, referred to as the mass-weighted stream age, gives a quantity that has stationary statistics in the turbulent jet. Based on the observation that the statistics of the mass fraction and velocity are self-similar downstream of an initial development region, the transport equation for the jet fluid residence time is used to derive a model describing a self-similar profile for the mean of the mass-weighted stream age. The self-similar profile predicted is dependent on, but different from, the self-similar profiles for the mass fraction and the axial velocity. The DNS data confirm that the first four moments and the shape of the one-point probability density function of mass-weighted stream age are indeed self-similar, and that the model derived for the mean mass-weighted stream-age profile provides a useful approximation. Using the self-similar form of the moments and probability density functions presented it is therefore possible to estimate the local residence time distribution in a wide range of practical situations in which fluid is introduced by a high-Reynolds-number jet of fluid.

This paper describes analyses of the nonlinear dynamics of harmonically forced, turbulent premixed flames. A key objective of this work is to analyse the ensemble-averaged dynamics of the flame front position, $\langle \xi \rangle $, excited by harmonic forcing of amplitude $\varepsilon $, in the presence of stochastic flow fluctuations of amplitude $\mu $. Low-amplitude and/or near-field effects are quantified by a third-order perturbation analysis, while the more general case is analysed computationally by solving the three-dimensional level-set equation, extracting the instantaneous flame position, and ensemble averaging the results. We show that different mechanisms contribute to smoothing of flame wrinkles, manifested as progressive decay in the magnitude of $\langle \xi \rangle $. Near the flame holder, random phase jitter, associated with stochastic velocity fluctuations tangential to the flame, is dominant. Farther downstream, propagation of the ensemble-averaged front normal to itself at the time-averaged turbulent burning velocity, $ \overline{{S}_{T, eff} } $, leads to destruction of wrinkles, analogous to the laminar case, an effect that scales with $\mu $. A second, new result is the demonstration that the ensemble-averaged turbulent burning velocity, ${S}_{T, eff} (s, t)$, is modulated by the harmonic forcing, i.e. ${S}_{T, eff} (s, t)= \overline{{S}_{T, eff} (s)} + { S}_{T, eff}^{\prime } (s, t)$, where ${ S}_{T, eff}^{\prime } $ has an inverse dependence upon the instantaneous, ensemble averaged-flame curvature, an effect that scales with $\varepsilon $ and $\mu $. We show that this curvature dependence follows from basic application of Huygens propagation to flames with stochastic wrinkling superimposed upon base curvature. This effect also leads to smoothing of flame wrinkles and is analogous to stretch processes in positive-Markstein-length, laminar flames.

Background: The influences of demographics, culture, language, and environmental changes on Mini-Mental State Examination (MMSE) scores are considerable.

Methods: Using a sample of 7452 healthy, community-dwelling elderly Koreans, aged 55 to 94 years, who participated in the four ongoing geriatric cohorts in Korea, we investigated demographic influences on MMSE scores and derived normative data for this population. Geropsychiatrists strictly excluded subjects with cognitive disorders according to the protocol of the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K) Clinical Assessment Battery (CERAD-K-C).

Results: Education (standardized β = 0.463), age (standardized β = −0.303), and gender (standardized β = −0.057) had significant effects on MMSE scores (p < 0.001). The score of MMSE increase 0.379 point per 1-year education, decrease 0.188 per 1-year older, and decrease 0.491 in women compared to men. Education explained 30.4% of the scores’ total variance, which was much larger than the variances explained by age (8.4%) or gender (0.3%). Accordingly, we present normative data for the MMSE stratified by education (0, 1–3, 4–6, 7–9, 10–12, and ≥ 13 years), age (60–69, 70–79, and 80–89 years), and gender.

Conclusions: We provide contemporary education-, age-, and gender-stratified norms for the MMSE, derived from a large, community-dwelling elderly Korean population sample, which could be useful in evaluating individual MMSE scores.

Market demand for touch panel/lens has been exceptionally high for the recent years due to smartphones, tablet PCs, etc. Among the available technologies to envision touch functionality, capacitive touch screen has received the great attention due to the various superiorities over the competing ones. Capacitive touch screen features two transparent conductive electrodes, such as ITO (indium tin oxide). However, the difference in refractive indices of ITO, substrate, and air, ITO pattern is clearly visible if there is no proper countermeasure. Most of touch screen makers and ITO substrate supplier utilize “index-matching technology” to prevent this phenomenon.

Even though of the attempts to minimize visible ITO pattern in final product, there are many technical and process challenges. In this study, the causes around visible ITO pattern were investigated to understand and provide the proper countermeasures.

One of the possible causes for visible ITO pattern was improper annealing process in ITO especially for film substrate. According to XPS (X-ray photoelectron spectroscopy)/ESCA (electron spectroscopy for chemical analysis) and other analysis results, ITO, which is normally deposited through sputtering, is not fully transformed to oxidized state. After aligning and adjusting annealing condition, acknowledged visible ITO pattern was disappeared.

Other causes for visible patterns were also discussed in detail, and the relevant countermeasures were provided.

A study was made to investigate cavity growth behavior during the superplastic deformation of submicrometer-grained titanium alloy and to compare that to cavity growth in a coarse-grained counterpart. A series of tension tests were performed at a temperature of 973 K and a strain rate of 10−4 s−1. Microstructures revealed that both the size and the volume fraction of the cavities obviously decreased as the grain size decreased. Working within the framework provided by creep models for understanding cavity growth behavior, we found the dominant growth mechanism to be superplastic diffusion, which leads to high-tensile ductility in submicrometer-grained titanium alloy.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

The thermodynamic stability of the solder channels at a scalloplike Cu6Sn5 layer formed between Sn-containing solders and Cu substrate was evaluated by studying the penetration behavior of the liquid solders into the grain boundaries of a Cu6Sn5 substrate. The orientational relationship between the grains of the Cu6Sn5 layer formed during reflow soldering was also analyzed using the electron backscattered diffraction technique. The results showed that liquid solders penetrate into the grain boundaries at an order of faster speed than the growth rate of the layer, which provided a direct evidence of thermodynamic stability of the channel.

Soft magnetic properties and microstructure evolutions of FeTaNC films were investigated, and compared with those of FeTaN and FeTaC films. Effects of substrate species (glass vs. CaTiO3) on the magnetic properties were also investigated. Co-addition of N and C enhances the grain refinements and soft magnetism compared with N or C only addition. Good soft magnetic characteristics of coercivity of 0.17 Oe, permeability of 4000 (5 MHz), and magnetic flux density of 17 kG can be obtained in the FeTaNC films with the relatively wide process ranges. While these values appear to be similar to those of FeTaN films on glass substrate, the most distinctive difference between FeTaNC and FeTaN (or C) films is the effects of substrate. Whereas FeTaNC films show good magnetic characteristics on both glass and CaTiO3 substrates, FeTaN (or C) films show substantial degradation on the CaTiO3 substrate.