• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.1063-1071
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• 1999

Fine grid calculations are reported for the developing turbulent flow in a curved duct of square cross-section with a radius of curvature to hydraulic diameter ratio ${\delta}=Rc/D_H=3.357 $ and a bend angle of 720 deg. A sequence of modeling refinements is introduced; the replacement of wall function by a fine mesh across the sublayer and a low Reynolds number algebraic second moment closure up to the near wall sublayer in which the non-linear return to isotropy model and the cubic-quasi-isotropy model for the pressure strain are adopted; and the introduction of a multiple source model for the exact dissipation rate equation. Each refinement is shown to lead to an appreciable improvement in the agreement between measurement and computation.

• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.122-132
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• 2000

Computational fluid dynamic simulation is performed for the floating turbulent premixed flames stabilized in stagnation flows of Cho et al. [1] and Cheng and Shepherd [2]. They are both in the wrinkled flamelet regime far from the extinction limit with $u'/S^{0}_{L}$ less than unity. The turbulent flux is given in the first moment closure as a sum of the classical gradient flux due to turbulent motions and the countergradient flux due to thermal expansion. The parameter $N_{B}'s$ are greater than unity with the countergradient flux dominant over the gradient flux. The countergradient flux is assumed to be zero in $\bar{c}<0.05$. The flame surface density is modeled as a symmetric parabolic function with respect to $\bar{c}$. The product of the maximum flame surface density and the mean stretch factor is considered as a tuning constant to match the flame location. Good agreement is achieved with the measured $\tilde{w}$ and $\bar{c}$ profiles along the axis in both flames.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.3
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• pp.35-43
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• 2004

Reduction of fresh water consumption and effluent discharge provide diverse advantages in raw materials and energy savings. Papermaking system closure, however, reduces the efficiency of additives, decreases retention and dewatering, and causes many other Problems in papermaking. Accumulation of inorganic and organic substances in the process white water is the prime cause of these problems. Understanding of the accumulation phenomena of the detrimental substances in the papermaking process is of great importance for papermaking system closure. In this study a process simulation method was employed to analyze the accumulation phenomena of anionic starch in the process white water as the reuse rate of dry broke and pick up of surface sizing agent is increased. Steady state simulation studies were carried out based on the model developed in previous study. The variation of dissolved starch concentration in each process unit was monitored as a function of reuse rate of dry broke and surface sizing agent pick up rate. The result showed that dissolved starch concentration Increased as reuse rate of dry broke and surface sizing agent pick up rate was increased.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.16 no.2
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• pp.152-157
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• 2005

Background and Objectives : 10 normal Korean native speakers participated subjects to investigate the acoustic and aerodynamic study of Korean fricatives, affricates, and plosives and to make good use of the results for the patients with articulation problems. Materials and Method Their productions of [asa], [as'a], [aca], $[ac^ha]$, (ac'a), (ata) , $[at^ha]$, and [at'a] were analyzed with Lx Speech Studio Program (Laryngogrtaph Ltd, UK) for acoustic analysis and Phonatory Function Analyze. (Nagashima Ltd. Model PS 77H, Tokyo, Japan) for aerodynamic analysis. Results : The results are as follows : 1) Plosives showed higher Qx1 in vocal folds closure ratio than fricatives and affricates. 2) Tense fricatives, affricates, and plosives showed higher Qx2 in vocal folds closure ratio than asperated and 1ax. 3) Asperated showed higher Qx1 in vocal folds closure ratio than tense and 1ax. 4) Asperated showed higer peak flow rate than tense and 1ax. Conclusion This results may be helpful for treatment in articulation disorders.

• Transactions of Materials Processing
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• v.20 no.5
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• pp.339-343
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• 2011

This paper presents methods for analyzing the extent of cylindrical-shaped void closure. In addition, a quantitative relationship between change in void fraction and height reduction ratio of a compressed specimen is proposed. The height reduction ratio, number of deformation steps and billet rotation were chosen as key process parameters influencing the void closing behavior, namely, the changes in void shape and size during hot open die forging of a large ingot. The extent of void closure was analyzed from microscopic observations and estimated from tensile test results. The tensile strengths of specimens with closed voids and those without were compared for various reduction ratios in height. The results confirmed that void closure occurs at reduction ratios greater than 30 %. The void closing behavior could be expressed as a hyperbolic tangent function of reduction ratio in height, number of paths, and billet rotation. The knowledge presented in this paper could be helpful for optimizing deformation paths in open die forging processes.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.118-125
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• 2007

The firtst-order conditional moment closure (CMC) model is applied to CH4/air swirl diffusion flame in a gas turbine model combustor. The flow and mixing fields are calculated by fast chemistry assumption with SLFM library and a beta function pdf for mixture fraction. RNG k-e model is used to consider the swirl flame in a confined wall. Reacting scalar fields are calculated by elliptic CMC formulation with chemical kinetic mechanism, GRI Mech 3.0. Validation is done against measurement data for mean flow and scalar fields in the model combustor [1]. Results show reasonable agreement with the mean mixture fraction and its variance, while temperature is overpredicted as the level of local extinction increases. The second-order CMC model is needed to consider local extinction with considerable conditional fluctuations near the nozzle.

• Speech Sciences
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• v.5 no.1
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• pp.23-33
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• 1999

Mallat has shown that, with a proper choice of wavelet function, the local maxima of wavelet transformed signal indicate a sharp variation in the signal. Since the glottal closure causes sharp discontinuities in the speech signal, dyadic wavelet transform can be useful for detecting abrupt change in the voiced sounds, i.e., epochs. In this paper, we investigate the glottal closure instants obtained from the wavelet analysis of speech signal and compare them with those obtained from the EGG signal. Then, we detect pitch period of speech signal on the basis of these results. Experimental results demonstrated that local maxima of wavelet transformed signal give accurate estimation of epoch and pitch periods of voiced sound obtained by the proposed algorithm also correspond to those from EGG well.

• Journal of the Korean Mathematical Society
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• v.49 no.4
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• pp.867-879
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• 2012

For ${\beta}$ > 1, let $T_{\beta}$ : [0, 1] ${\rightarrow}$ [0, 1) be the ${\beta}$-transformation. We consider an invariant $T_{\beta}$-orbit closure contained in a closed interval with diameter 1/${\beta}$, then define a function ${\Xi}({\alpha},{\beta})$ by the supremum such $T_{\beta}$-orbit with frequency ${\alpha}$ in base ${\beta}$, i.e., the maximum value in $T_{\beta}$-orbit closure. This paper effectively determines the maximal domain of ${\Xi}$, and explicitly specifies all possible minimal intervals containing $T_{\beta}$-orbits.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.80-85
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• 2014

Side jet thruster using nozzle closure separation device provides a solid rocket with a trajectory shift function. Side jet thruster consists of low combustion temperature propellant, neutral type propellant grain and nozzle closure separation device. If a trajectory shift is required, side jet thrust is generated on the rocket by separating some nozzle closures located in the opposite direction to thrust. After completing trajectory shift, the other nozzle closures located in the thrust direction are separated to cease side jet thrust. The operation process is verified through ground static test. The result in this study can be applied to changing rocket trajectory by controlling side jet thrust through nozzle closure separation.

• Archives of Plastic Surgery
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• v.38 no.2
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• pp.143-147
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• 2011

Purpose: A Tessier classification number 7 cleft is an uncommon malformation that results from a failure of mesenchymal fusion within the maxillary and mandibular prominences of the 1st pharyngeal arch. Many operative techniques of the number 7 cleft repair have been proposed to restore function and improve aesthetics. Fifteen patients underwent repair of a number 7 cleft over 13 years by a modification of the surgical Technique, and an appraisal of the operative outcome is reported herein. Methods: A retrospective review was conducted involving 15 patients with number 7 clefts who underwent surgery from 1996 to 2009. The changes in surgical technique included skin closure, attachment of the orbicularis oris muscle, and position of the repaired commissure; the changes were analysed with a review of the medical records and the outcomes of surgery were analysed via photographs. Specifically, the technique of skin closure was changed from the a Z-plasty to a linear closure, the orbicularis oris muscle overlapped attachment was replaced by a side-to-side approximation with horizontal mattress sutures, and the position of the repaired commissure was changed from 1 mm laterally to 1 mm medially in reference to the non-cleft side. Results: A Z-plasty caused additional cutaneous scarring, an overlapped attachment of the orbicularis oris muscle caused a thick oral commissure, and the repaired commissure migrated to the lateral side, so a 1 mm, laterally-positioned commissure caused asymmetry. The altered procedure included a linear skin closure, a side-to-side orbicularis oris muscle approximation, and a 1 mm, medially-positioned commissure, which together resulted in a good outcome. Conclusion: The altered procedure for repair of a number 7 cleft as described herein, yields a short scar, no functional problems with the orbicularis oris muscle, a thin oral commissure, and symmetry of the repaired commissure.