• Bulletin of the Korean Chemical Society
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• v.16 no.5
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• pp.454-458
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• 1995

Inhibiting action of semicarbazide, thiosemicarbazide, sym. diphenylcarbazide towards corrosion of zinc in hydrochloric acid has been investigated. The rate of corrosion depends on the nature of the inhibitor and its concentration. The values of inhibition efficiency from, weight loss, thermometric measurements are in good agreement with those obtained from polarization studies. From the polarization studies, the inhibitors used act as mixed absorption type inhibitors, increased adsorption resulting from an increase in the electron density at the reactive C=S and C=O groups and N-atoms. The thermodynamic parameters of adsorption obtained using Bockris-Swinkels adsorption isotherm reveal a strong interaction of these carbazides on zinc surface.

• Microbiology and Biotechnology Letters
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• v.20 no.6
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• pp.687-692
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• 1992

A simple method to determine viable cell numbers of each species in mixed culture was developed. The oxygen uptake rate (OUR) equals to the product of the specific OUR and the size of the microbial population. In a mixed culture, the OUR is a result of the respiration activities of each sub-population. The OUR was determined from the slope of the linear relationship between time and the decrease of dissolved oxygen concentration when aeration was stopped. The specific OUR was calculated from the slope of the viable cell number versus OUR curve. These values for C. lusitaniae at 20 and $30^{\circ}C$ were $1.36{\times}10^{-9}$ and $3.90{\times}10^{-9}$ and those for P tannoPhilus at 20 and $30^{\circ}C$ were $0.59{\times}10^{-9}$ and $1.86{\times}10^{-9}$ [(%/s)/(cells/ml)J. respectively. Using these values, viable cell numbers were calculated after the OURs of mixed culture at two temperatures were measured. A good agreement between the viable cell numbers determined by this method and by plate count was obtained.

• Korean Journal of Agricultural Science
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• v.42 no.4
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• pp.389-396
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• 2015

This study was performed to investigate the opinions of various related-industries on ban of antibiotics growth promoters (AGPs) in commercial mixed feed. The answers on a total of 21 questions were summarized by response number and percentage. 93% of those surveyed were in agreement of a ban of dietary AGPs. The agreement reasons were the livestock safety (61.5%), the reduction of antibiotic use (23.1%), and decrease of antibiotic-resistant bacteria (11.5%). The negative effects expected by the ban of AGPs were poor growth performance (44.2%), elevated disease emergence (31.4%), increasing the feed cost (18.6%), and quality degradation of livestock (5.8%). As the efficient plans for decline of AGPs use, the feeding environment improvement was the highest with 43%, and farmer training and the consolidation inspection of residual substance on antibiotics in livestock product was 27.9% and 22.1%, respectively. 46.5% of respondent are considering the modification of feed spec and 39.5% of those surveyed have staged a modified feed spec. In conclusion, livestock related-industries approve a ban of AGPs, and they assert that the policy support, improvement of management and environment in the farm, providing technology from related-industries are multiply essential for a stable settlement of a ban policy of AGPs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.105-113
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• 2014

The mode II fracture behavior of a single-layer graphene sheet (SLGS) containing a center crack was characterized with the results of an atomistic simulation and an analytical model. The fracture of zigzag graphene models was analyzed with molecular dynamics and the mode II fracture toughness was found to be $2.04MPa{\sqrt{m}}$. The in-plane shear fracture of a cellular material was analyzed theoretically for deriving the $K_{IIc}$ of SLGS, and FEM results were obtained. Mixed-mode fracture of SLGS was studied for various mode I and mode II ratios. The mixed-mode fracture criterion was determined, and the obtained fracture envelope was in good agreement with that of another study.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.4
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• pp.397-414
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• 2003

The performance of one-particle stochastic Lagrangian models for passive tracer dispersion are evaluated against measurements in horizontally-homogeneous neutrally-stratified atmospheric surface layer. State-of-the-technology models as well as classical Langevin models, all in class of well mixed models are numerically implemented for inter-model comparison study. Model results (far-downstream asymptotic behavior and vertical profiles of the time averaged concentrations, concentration fluxes, and concentration fluctuations) are compared with the reported measurements. The results are: 1) the far-downstream asymptotic trends of all models except Reynolds model agree well with Garger and Zhukov's measurements. 2) profiles of the average concentrations and vertical concentration fluxes by all models except Reynolds model show good agreement with Raupach and Legg's experimental data. Reynolds model produces horizontal concentration flux profiles most close to measurements, yet all other models fail severely. 3) With temporally correlated emissions, one-particle models seems to simulate fairly the concentration fluctuations induced by plume meandering, when the statistical random noises are removed from the calculated concentration fluctuations. Analytical expression for the statistical random noise of one-particle model is presented. This study finds no indication that recent models of most delicate theoretical background are superior to the simple Langevin model in accuracy and numerical performance at well.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.6
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• pp.628-637
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• 2004

The present study investigates the performance of dynamic mixed model (DMM; Zang et ai.) in a channel with strong wall injection through a Large eddy simulation (LES) technique. The DMM results are compared with those of DNS and the results obtained with popular dynamic Smagorinsky model (DSM). Better agreement is achieved when using the DMM with box filter than DSM and coarse DNS in predicting the first and second order statistics as well as large-scale structures of velocity and temperature fields. Such favorable features of DMM are attributed to the fact that it explicitly calculates the modified Leonard stress term and only models the remaining cross and the SGS Reynolds stress terms and, thus, it reduces the excessive burden put on the model coefficient of DSM. Also it is demonstrated that the DMM can be successfully extended to the prediction of temperature (passive scalar) field where strong streamwise inhomogeneity exists.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.193-203
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• 1983

The mixed convective heat transfer problems are characterized by the relatively significant contribution of buoyancy force to the transport processes of momentum and heat. Past analytical studies on this kind of problems have been carried out by employing either the conventional R-.epsilon. turbulence model which includes constant turbulent Prandtl number .sigma.$_{+}$ 1 or an extended R-.epsilon. turbulence model which takes account of the buoyancy effect in appropriate length scale equations. But in the latter case, the temperature variance .the+a.$^{2}$ over bar is approximated by a model under local equilibrium condition and the time scale ratio between velocity and temperature is assumed to be constant. These approximation is known to break down when the buoyancy effect is dominant. The present study is aimed at development of new computational turbulence closure level which can be applied to this rather complex turbulent process. The temperature variance is obtained directly by solving its dynamic transport equation and the time scale ratio which is variable in space is computed by a solution of a dynamic equation for the rate of scalar dissipation .epsilon.$_{\thetod}$ It was found that the computational results are in good agreement with available experimental data of wide range of unstable conditions.

• Journal of the Korean Applied Science and Technology
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• v.19 no.4
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• pp.339-348
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• 2002

Self-diffusion coefficients of colloidal ass9Ciation structures in the aqueous solutions of anionic ammonium dodecyl sulfate (ADS) and cationic octadecyltrimethylammonium chloride (OTAC) surfactants were measured by pulsed-gradient spin echo NMR. The results were interpreted on the basis of the ADS/OTAC/water phase diagram. Crossing the phase boundaries, significant changes in self diffusion coefficients were observed and well correlated to the phase diagram. For the micelles their apparent radii were obtained from Stokes-Einstein equation. Their values were 15 for the ADS micelles and 54 ${{\AA}}$ for the OTAC micelles, respectively. For vesicles which were formed spontaneously at different relative amounts of the surfactants and total surfactant concentrations, the radius was measured as 50 to 200 nm. This result is in fair agreement with those by TEM and light scattering.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.322-329
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• 2001

A study of the shock wave turbulent boundary layer interaction is presented. The focus of the study is the interactions of the shock waves with the turbulent boundary layer on the falt plate. Three examples are investigated. The computations are performed, using mixed explicit-implicit generalized Galerkin finite element method. The linear equations at each time step are solved by a preconditioned GMRES algorithm. Numerical results indicate that the implicit scheme converges to the asymptotic steady state much faster than the explicit counterpart. The computed surface pressures and skin friction coefficients display good agreement with experimental data. The flowfield manifests a complex shock wave system and a pair of counter-rotating vortices.

• Korean Journal of Radiology
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• v.23 no.1
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• pp.30-41
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• 2022

Objective: Computed tomography enterography (CTE) and magnetic resonance enterography (MRE) are considered substitutes for each other for evaluating Crohn's disease (CD). However, the adequacy of mixing them for routine periodic follow-up for CD has not been established. This study aimed to compare MRE alone with the mixed use of CTE and MRE for the periodic follow-up of small bowel inflammation in patients with CD. Materials and Methods: We retrospectively compared two non-randomized groups, each comprising 96 patients with CD. One group underwent CTE and MRE (MRE followed by CTE or vice versa) for the follow-up of CD (interval, 13-27 months [median, 22 months]), and the other group underwent MRE alone (interval, 15-26 months [median, 21 months]). However, these two groups were similar in clinical characteristics. Three independent readers from three different institutions determined whether inflammation had decreased, remained unchanged, or increased within the entire small bowel and the terminal ileum based on sequential enterography of the patients after appropriate blinding. We compared the two groups for inter-reader agreement and accuracy (terminal ileum only) using endoscopy as the reference standard for enterographic interpretation. Results: The inter-reader agreement was greater in the MRE alone group for the entire small bowel (intraclass correlation coefficient [ICC]: 0.683 vs. 0.473; p = 0.005) and the terminal ileum (ICC: 0.656 vs. 0.490; p = 0.030). The interpretation accuracy was higher in the MRE alone group without statistical significance (70.9%-74.5% vs. 57.9%-64.9% in individual readers; adjusted odds ratio = 3.21; p = 0.077). Conclusion: The mixed use of CTE and MRE was inferior to MRE alone in terms of inter-reader reliability and could probably be less accurate than MRE alone for routine monitoring of small bowel inflammation in patients with CD. Therefore, the consistent use of MRE is favored for this purpose.