• Textile Coloration and Finishing
• /
• v.3 no.2
• /
• pp.34-42
• /
• 1991

The effects of electrolyte on dyeing properties of cotton fiber with Congo Red have been studied at 90, 70 and $40^{\circ}C$. Each dyeing carried into an infinite bath with $1\times10^{-4}$ mol/l of Congo Red and with various concentration of electrolytes. The results obtained from this study were as follow; 1. The equilibrium adsorption of dye $(C_\infty)$ values decreased with increasing dyeing temperature, $C_\infty$ values increased in the order KCl>NaCl>LiCl. 2. The values of apparent diffusion coefficients $(D_a)$ increased with increasing dyeing temperature, but $D_a$ values decreased in the order KCl$D_a$ values decreased with increasing electrolyte concentration. 4. Effect of electrolytes decreased with increasing dyeing temperature. 5. The values of standard affinities of dyeing $(-\triangle\mu^{\circ})$, the standard heats of dyeing $(-\triangleH^{\circ})$, and the standard entropies $(-\triangleS^{\circ})$, increased in the order KCl>NaCl>LiCl. 6. Equilibrium adsorption isotherm curve were Freundlich type, and in the Equation y=a.x$^{n}$ , the values of a and n increased in the order KCl>NaCl>LiCl. 7. The value of $-\triangle\mu^{\circ}$, $-\triangleH^{\circ}$, and $-\triangleS^{\circ}$, decreased with increasing electrolyte concentration.

• Journal of Environmental Health Sciences
• /
• v.42 no.3
• /
• pp.160-168
• /
• 2016

Objectives: Materials coming into contact with food may result in the migration of chemical substances into the food. To protect consumers from exposure, Regulation (EU) No. 10/2011 specifies the use of standard migration tests. Polyethylene terephthalate (PET), widely used for food packaging materials, has drawn the attention of researchers because unwanted migration of PET into food might occur when consumers reuse packaging material. The aim of this study was to predict and develop a migration model for two components, acetaldehyde and butyraldehyde in PET, into food simulants under conditions of changing pH and solvents, such as those observed in fermented foods like kimchi or sauerkraut. Methods: Using a migration model based on Fick's second law of diffusion in one dimension, the migration of acetaldehyde and butyraldehyde from PET into a simulant of fermented food at $20^{\circ}C$ over 10 days was evaluated. The simulant for fermented food was modelled as 10% ethanol for three days, followed by 3% acetic acid for seven days. Results: The migration of acetaldehyde into the 10% ethanol was 0.36 times that of a simulated fermented food system, while that of butyraldehyde was 1.34 times greater. These results may have been influenced by the chemical interactions among the migrants, polymers and simulants, as well as by the solubilities of the migrants in polymers and simulants. Conclusion: Because food simulants have a limited capacity to mimic real food systems under the current migration model, an appropriate simulant and migration test should be considered in the case of increasing acidity. Furthermore, since the accuracy of the worst-case estimation of migration predicted by the current model is severely limited under changing food conditions, food simulants and their interactions should be further investigated with respect to conservative migration modelling.

• Applied Biological Chemistry
• /
• v.31 no.1
• /
• pp.13-20
• /
• 1988

The hydration characteristics of four naked baley varieties by different kernel sizes were investigated. The predominant kernel size was 7 mesh, followed by 10 mesh kernel, of which comprised $86{\sim}94%$ of the total kernel. Diffusion coefficients of naked barleys at $40^{\circ}C$ increased as the kernel sizes decreased. The volume increases of naked barleys were linearly related to the moisture gain, regardless variety and kernel size.

• Journal of Biosystems Engineering
• /
• v.27 no.3
• /
• pp.219-226
• /
• 2002

Desorption equilibrium moisture contents of oak mushroom were measured by the static method using salt solutions at flour temperature levels of 35$\^{C}$, 45$\^{C}$, 55$\^{C}$ and 6$\^{C}$ and five relative humidity levels in the range from 11.0% to 90.8%. EMC data were fitted to the modified Henderson, Chung-Pfost, modified Halsey and modified Oswin models using nonlinear regression analysis. Drying tests far oak mushroom were conducted in an experimental dryer equipped with air conditioning unit. The drying test were performed in triplicate at flour air temperatures of 35$\^{C}$, 45$\^{C}$, 55$\^{C}$ and 65$\^{C}$ and three relative humidities of 30%, 50% and 70% respectively. Measured moisture ratio data were fitted to the selected four drying models(Lewis, Page, simplified diffusion and Thompson models) using stepwise multiple regression analysis. The results of comparing root mean square errors for EMC models showed that modified Halsey was the best model, and modified Oswin models could be available far oak mushroom. The results of comparing coefficients of determination and root mean square errors of moisture ratio for four drying models showed that Page model were found to fit adequately to all drying test data with a coefficient of determination of 0.9990 and root mean square error of moisture ratio of 0.00739.

• Journal of Korea Foundry Society
• /
• v.27 no.6
• /
• pp.243-249
• /
• 2007

The effect of Re addition and solidification rate on the directional solidification behavior of Ni-Al model alloy has been investigated. Directional solidification (DS) were carried out using the modified Bridgman furnace with various solidification rates. The solid/liquid interface during directional solidification was preserved by quenching the specimen after the desired volume fraction of original liquid was solidified. The equilibrium partition coefficients of Al and Re Were estimated by measuring the compositions at the quenched solid/liquid interface. Then, the effect of Re addition on the elemental segregation behavior was carefully analyzed. The differential scanning calorimetry results showed that the Re addition results in increased ${\gamma}'$ solvus and freezing range of the alloy. It was also shown that the primary dendrite arm spacing gradually decreases with increasing the Re content, while the secondary dendrite arm spacing appears to be independent on the Re content. The compositional analyses clearly revealed that the segregation of Al increased with increasing the Re content and solidification rate, while that of Re was found to be independent on the solidification rate in the range of $10{\sim}100{\mu}m/s$ due to its sluggish diffusion rate in the Ni solid solution.

• Journal of Korean Society on Water Environment
• /
• v.28 no.2
• /
• pp.292-299
• /
• 2012

The objective of this study is to develop a novel method for evaluating forward osmosis (FO) membrane performances using a non-pressurized FO system. Basic membrane performance parameters including water (A) and solute (B) permeability coefficients and unique parameter for FO membrane such as the support layer structural parameter (S) were determined in two FO modes (i.e., active layer faces feed solution (AL-FS) and active layer faces draw solution (AL-DS)). Futhermore, these parameters were compared with those determined in a pressurized reverse osmosis (RO) system. Theoretical water flux was calculated by employing these parameters to a model that accounts for the effects of both internal and external concentration polarization. Water flux from FO experiment was compared to theoretical water fluxes for assessing the reliability of those parameters determined in three different operation modes (i.e., AL-FS FO, AL-DS FO, and RO modes). It is demonstrated that FO membrane performance parameters can be accurately measured in non-pressurized FO mode. Specifically, membrane performance parameters determined in AL-DS FO mode most accurately predict FO water flux. This implies that the evaluation of FO membrane performances should be performed in non-pressurized FO mode, which can prevent membrane compaction and/or defect and more precisely reflect FO operation conditions.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.1
• /
• pp.24-30
• /
• 2004

Analysis model for the two-phase catalytic reactor is presented. With the progress in development of micro thermofluidic devices, needs fur understanding of the phenomena in two phase reaction in cm scale has been arisen. To investigate thermal and reactive performance of down scaled two phase reactor simple analysis model that is a kind of lumped flow model is proposed. Analysis model presented is based on the experiment on mm scale model reactor. Target experiment is catalytic decomposition of 70wt％ hydrogen peroxide with existence of perovskite L $a_{0.8}$S $r_{0.2}$Co $O_3$ catalyst. It is composed of balance equations of mass and energy. Each phase is considered to be a species fur the simplicity. Axial diffusion and transversal distribution of properties are neglected. Two phase catalytic reaction is modeled as successive gasification of liquid lump around catalyst and reaction in gas phase. Heat transfer is modeled by model function ofNu number. Modeled Nu is expressed as Nu=N $u_{0}$ (1＋ $a_1$( $a_2$ $T^{-}$ $a_3$)exp( $a_4$ $T^{-1}$)exp( $a_{5}$ z). Transfer coefficients are determined by the comparison of experimental results. With the model, heat transfer characteristics are investigated. Also by the mass transfer coefficient, characteristics in mass transfer is investigated. With the result basic understanding on design and analysis of mm scale two-phase reactive device is obtained. Also it can be further applied to micro scale reactive device fabricated by micromachining.ing..

• Korean Chemical Engineering Research
• /
• v.58 no.2
• /
• pp.171-175
• /
• 2020

In the proton exchange membrane fuel cells (PEMFC), the development of a reinforced membrane with improved durability by a support is actively in progress in Korea. In this study, the initial performance and characteristics of four types of reinforced membranes were compared. Reinforced membranes with higher amounts of C-F chains in the polymer membrane showed lower water diffusion coefficients due to the hydrophobicity of the C-F chains. The thicker the polymer membrane, the more the hydrogen permeability decreased and the higher the OCV. Membrane with short resistance below 1.5 Ωcm² showed OCV below 0.9 V and the lowest performance, so short resistance should be above 3.0 Ωcm². Compared with the current standard membrane, there was a similar domestic membrane, which could confirm the possibility of localization of PEMFC polymer membrane.

• Journal of the Korean Chemical Society
• /
• v.45 no.5
• /
• pp.429-435
• /
• 2001

The monomer N,N'-bis(2-pyrrol-1-yl-propyl)-4,4'-bipyridine(bpb) was electrochemically polymerized on the glassy carbon electrode surface, which was modified with 1:1 ratio of erichrome black T(EBT) and glutathione(GSSG) to give a type of GC/poly-bpb, EBT, GSSG electrode for depositing Zn(II). The diffusion coefficients of the incorporated ions were 2.43${\times}10^{-15}$ and 9.14${\times}10^{-15} cm^2s^{-1}$ before taking Zn(II) ions and after them respectively. The modified electrodes are stable at the electrode process. The polymerized poly-bpb of 2.83${\times}10^4gmol^{-1}$ can deposit 2.15${\times}10^4gmol^{-1}$ of Zn(II). The number of pumping ions involving in the redox procedure at 0.77 V was 81.7% of the captured 180 ions into the polymer matrix, which was 3 times larger than that of the electrode modified with EBT alone.

• 한국해양학회지
• /
• v.30 no.4
• /
• pp.288-301
• /
• 1995

Rates of the sedimentation and particle mixing have been estimated by applying uranium-series disequilibrium techniques to three sediment cores collected from the korea Deep Ocean Study (KODOS) site between the clarion and Clipperton Fracture Zones (CCFZ) of the Equatorial Pacific. Sedimentation rates based on the profiles of excess /SUP 230/Th activity and /SUP 230/ Th/SUB xs//SUP 232/ Th activity ratios at the southeastern part of the study area were estimated to be in the order of a few millimeters per thousand year, while at the northwestern part a factor of ten lower. Excess activities of /SUP 230/Th and /SUP 230/Th ratios showed intervals of constant values in the upper part of the sediment cores, probably generated by biological particle mixing. A "two-box" advection-diffusion steady state mixing model was employed in order to estimate particle mixing rates in the upper and the lower layers, based on the distribution profiles of excess /SUP 210/Pb activities. Particle mixing coefficients were estimated to be in the order of 10$^1$ cm$^2$/y in the upper layer and 10/SUP -1/-10/SUP 0/ cm$^2$/y in the lower layer.