• Bulletin of the Korean Chemical Society
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• v.2 no.3
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• pp.96-104
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• 1981

(1) The flow data of f (stress) and ${\dot{s}$ (strain rate) for Fe and Ti alloys were plotted in the form of f vs. -ln ${\dot{s}$ by using the literature values. (2) The plot showed two distinct patterns A and B; Pattern A is a straight line with a negative slope, and Pattern B is a curve of concave upward. (3) According to Kim and Ree's generalized theory of plastic deformation, pattern A & B belong to Case 1 and 2, respectively; in Case 1, only one kind of flow units acts in the deformation, and in Case 2, two kinds flow units act, and stress is expressed by $f={X_1f_1}+{X_2f_2}$where $f_1\;and\;f_2$ are the stresses acting on the flow units of kind 1 and 2, respectively, and $X_1,\;X_2$ are the fractions of the surface area occupied by the two kinds of flow units; $f_j=(1/{\alpha}_j) sinh^{-1}\;{\beta}_j{{\dot{s}}\;(j=1\;or\;2)$, where $1/{\alpha}_j\;and\;{\beta}_j$ are proportional to the shear modulus and relaxation time, respectively. (4) We found that grain-boundary flow units only act in the deformation of Fe and Ti alloys whereas dislocation flow units do not show any appreciable contribution. (5) The deformations of Fe and Ti alloys belong generally to pattern A (Case 1) and B (Case 2), respectively. (6) By applying the equations, f=$(1/{\alpha}_{g1}) sinh^-1({\beta}_{g1}{\dot{s}}$) and $f=(X_{g1}/{\alpha}_{g1})sinh^{-1}({\beta}_{g1}{\dot{s}})+ (X_{g2}/{\alpha}_{g2})\;shih^{-1}({\beta}_{g2}{\dot{s}})$ to the flow data of Fe and Ti alloys, the parametric values of $x_{gj}/{\alpha}_{gj}\;and\;{\beta}_{gs}(j=1\;or\;2)$ were determined, here the subscript g signifies a grain-boundary flow unit. (7) From the values of ($({\beta}_gj)^{-1}$) at different temperatures, the activation enthalpy ${\Delta}H_{gj}^{\neq}$ of deformation due to flow unit gj was determined, ($({\beta}_gj)^{-1}$) being proportional to , the jumping frequency (the rate constant) of flow unit gj. The ${\Delta}H_{gj}\;^{\neq}$ agreed very well with ${\Delta}H_{gj}\;^{\neq}$ (self-diff) of the element j whose diffusion in the sample is a critical step for the deformation as proposed by Kim-Ree's theory (Refer to Tables 3 and 4). (8) The fact, ${\Delta}H_{gj}\;^{\neq}={\Delta}H_{j}\;^{\neq}$ (self-diff), justifies the Kim-Ree theory and their method for determining activation enthalpies for deformation. (9) A linear relation between ${\beta}^{-1}$ and carbon content [C] in hot-rolled steel was observed, i.e., In ${\beta}^{-1}$ = -50.2 [C] - 40.3. This equation explains very well the experimental facts observed with regard to the deformation of hot-rolled steel..

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.100-106
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• 2019

Ground and high altitude simulated combustion experiments were conducted using a liquid rocket engine with hydrogen peroxide and kerosene as the propellant. A ground and high altitude simulated combustion test facility was constructed by installing a high altitude model diffuser and TMS (Thrust Measuring System) on a vertical combustion test bench. The thrust characteristics according to altitude were investigated using the combustion test equipment. The diffuser was designed on a 1:4.8 scale to verify the characteristics of the high diffusing diffuser and starting pressure. The cold flow tests were conducted using nitrogen gas, and the performance characteristics and starting characteristics of the scale down diffuser were verified. A diffuser and TMS were installed on the vertical combustion test bench, and the thrust correction equations for the system resistance were derived. The thrust correction equations were derived from the step test and vacuum step test before the actual hot firing test. Nozzles with an operating altitude of 10km were designed. Hot firing tests were conducted to analyze the thrust characteristics according to the operating altitude changes. The actual thrust was calculated using each correction equation with the thrust value measured by the TMS.

• Nuclear Engineering and Technology
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• v.22 no.1
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• pp.20-28
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• 1990

In this study the migration experiment using packed column with crushed tuff was conducted as a basic research to develop migration model of radionuclides through geologic media. The main emphasis was put on evaluating the validity of migration models. For this, two models were introduced: one is the model which is based on the assumption of instantaneous equilibrium reaction and the other the model based on kinetic process such as intraparticle diffusion. The coefficient of hydrodynamic dispersion in packed column was determined using iodine as nonsorbing tracer. The hydrodynamic dispersion coefficient, D$_{L}$ was shown to be 0.11$\times$10$^{-2}$ $\textrm{cm}^2$/min under the condition of the column porosity of 0.483 and the average water velocity of 0.915$\times$10$^{-2}$ cm/min. The distribution coefficient, Kd of Cs-137 on crushed tuff was 11.3 cc/g at the concentration of 2$\times$10$^{-6}$ M and the temperature of 2$0^{\circ}C$. The breakthrough curve of Cs-137 through packed column was shown to have an asymmetric curve in which long trailing tail appears at the end part of the curve. The results obtained from the comparison of introduced models with experimental data indicated that the mass transfer model with intraparticle diffusion as rate-controlling step simulated the behaviors of Cs-137 migration more adequately, when compared with the bulk reaction model in which the assumption of instantaneous equilibrium reaction was maded. Consequently, the intraparticle diffusion was found to be an important factor in the migration of Cs-137 through packed column.n.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.68-75
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• 2021

This study performed simulating water absorption in various pre-cracked concretes. 2D-Finite Element Analysis (2D-FEA) model was developed based on experimental results on the amount of absorbed water in concrete with the exposure time. Results from the 2D-FEA showed that both crack width and crack depth strongly affect the amount of absorbed water in cracked concrete. In addition, water absorption rate is introduced and a predictive equation is suggested to estimate the rate in order to quantify the amount of absorbed water in cracked concrete. It was confirmed that water absorption in concrete having less than 150 mm crack depth was dominated as a main transport factor regardless of crack width. Therefore, considering that steel corrosion caused by chlorides dissolved in water mainly occurs in reinforced concrete structures, it is necessary that crack depth as well as crack width should be investigated in reinforced concrete structures at the time of field-inspection.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.475-483
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• 2019

Special chemical warfare agents are lethal gases that attack the human respiratory system. One of such gases are blood agents that react with the irons present in the electron transfer system of the human body. This reaction stops internal respiration and eventually causes death. The molecular sizes of these agents are smaller than the pores of an activated carbon, making chemical adsorption the only alternative method for removing them. In this study, we carried out a Computational Fluid Dynamics simulation by passing a blood agent: cyanogen chloride gas through an SG-1 gas mask canister developed by SG Safety Corporation. The adsorption bed consisted of a Silver-Zinc-Molybdenum-Triethylenediamine activated carbon impregnated with copper, silver, zinc and molybdenum ions. The kinetic analysis of the chemical adsorption was performed in accordance with the test procedure for the gas mask canister and was validated by the kinetic data obtained from experimental results. We predicted the dynamic behaviors of the main variables such as the pressure drop inside the canister and the amount of gas adsorbed by chemisorption. By using a granular packed bed instead of the Ergun equation that is used to model porous materials in Computational Fluid Dynamics, applicable results of the activated carbon were obtained. Dynamic simulations and flow analyses of the chemical adsorption with varying gas flow rates were also executed.

• Journal of Bio-Environment Control
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• v.28 no.3
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• pp.204-211
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• 2019

The purpose of this study is to provide basic data for setting environmental design standards for domestic greenhouses. We conducted experiments on thermal environment measurement at two commercial greenhouses where hot water heating system is adopted. We analyzed heat transfer characteristics of hot water heating pipes and heat emission per unit length of heating pipes was presented. The average air temperature in two greenhouses was controlled to $16.3^{\circ}C$ and $14.6^{\circ}C$ during the experiment, respectively. The average water temperature in heating pipes was $52.3^{\circ}C$ and $45.0^{\circ}C$, respectively. Experimental results showed that natural convection heat transfer coefficient of heating pipe surface was in the range of $5.71{\sim}7.49W/m^2^{\circ}C$. When the flow rate in heating pipe was 0.5m/s or more, temperature difference between hot water and pipe surface was not large. Based on this, overall heat transfer coefficient of heating pipe was derived as form of laminar natural convection heat transfer coefficient in the horizontal cylinder. By modifying the equation of overall heat transfer coefficient, a formula for calculating the heat emission per unit length of hot water heating pipe was developed, which uses pipe size and temperature difference between hot water and indoor air as input variables. The results of this study were compared with domestic and foreign data, and it was found to be closest to JGHA data. The data of NAAS, BALLS and ASHRAE were judged to be too large. Therefore, in order to set up environmental design standards for domestic greenhouses, it is necessary to fully examine those data through further experiments.

• Fire Science and Engineering
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• v.33 no.2
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• pp.114-123
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• 2019

The paper relates to a study on the changes in performance of insulation sheath resulting from accelerated degradation of IV and HIV insulated wire. To assume insulation degradation of IV and HIV insulated wire, accelerated life tests using Arrhenius equation were conducted among accelerated life test models, and experimental samples of 0 year, 10 years, 20 years, 30 years, and 40 years in equivalent life were produced. Whereas the maximum tensile load were increased as accelerated degradation of IV and HIV insulated wire progressed, elongation percentage, rupture time, and flexibility of insulated wires were found to be gradually reduced. According to the additional surface analysis results for the insulated wires per equivalent life using a scanning electron microscope, mechanical properties of the insulator were observed to be reduced as insulation degradation resulting from aging progressed since phenomena such as formation of crystalline structures and perforation, etc. occurred on the sample surface with progression of accelerated degradation. Consequently, institutional replacement of insulated wires and preparation of repair times considering performance degradation of the insulator installed inside buildings are considered necessary in order to prevent in advance the risks of electrical fire resulting from degradation in insulation performance.

• Resources Recycling
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• v.28 no.3
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• pp.15-20
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• 2019

The recovery of struvite using nitrogen and phosphorus in wastewaters is useful for prevention of eutrophication and use as fertilizer, but there are theoretical and technical issues to be resolved. Through the detailed literature review, this study discusses the possible reasonable prediction of struvite formation reaction by setting a feasible reaction equation with some theoretical considerations. In a technical aspect, the purity of struvite in solid precipitates can be promoted by excluding Ca in an effective way. As for the struvite reaction prediction issue, selection of proper equilibrium reaction as well as its reaction equilibrium coefficient is significant in the neutral and basic pH regions. The equilibrium reaction agrees well with the experimental batch test results. Considering the charge balance of the ions, the pH drop along struvite formation in a diluted solution can be predicted. Also, improvement of struvite purity through elimination of Ca can be expected by providing a highly concentrated ${NH_4}^+-N$ relative to ${HPO_4}^{2-}-P$ because ${NH_4}^+$ can enhance the thermodynamic driving force toward favorable struvite formation. Even though the phosphate reacts rapidly with Ca to form a solid precipitate, the thermodynamic driving force due to the high ${NH_4}^+$ activity can dissociate the phosphate-calcium precipitates and produce struvite.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.592-599
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• 2018

The kinetics and thermodynamics of the adsorption of acid blue 40 from an aqueous solution by activated carbon were examined as a function of the activated carbon dose, pH, temperature, contact time, and initial concentration. The adsorption efficiency in a bathtub was increased at pH 3 and pH 11 due to the presence of sufonate ions ($SO_3{^-}$) and amine ions ($NH_2{^+}$). The equilibrium adsorption data were fitted to the Langmuir, Freundlich and Temkin isotherms. The results indicated that the Langmuir model provides the best correlation of the experimental data. The separation factor of the Langmuir and Freundlich model showed that the adsorption treatment of acid blue 40 by activated carbon could be an effective adsorption process. The adsorption energy determined by the Temkin equation showed that the adsorption step is a physical adsorption process. Kinetics analysis of the adsorption process of acid blue 40 on activated carbon showed that a pseudo second order kinetic model is more consistent than a pseudo second order kinetic model. The estimated activation energy was 42.308 kJ/mol. The enthalpy change (80.088 J/mol) indicated an endothermic process. The free energy change (-0.0553 ~ -5.5855 kJ/mol) showed that the spontaneity of the process increased with increasing adsorption temperature.

• Animal Bioscience
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• v.34 no.4
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• pp.680-691
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• 2021

Objective: This study was conducted to investigate the effect of fermented cottonseed meal (FCSM) on growth performance, carcass traits, and fat deposition in white-feather broiler chickens. Methods: A total of 480 male one-day-old white-feather broiler chickens were selected randomly and divided into four groups with six replicates of 20 chickens in each. The experimental chickens were fed diets including 3%, 6%, or 9% FCSM fermented by Candida tropicalis until 42 days old. In the experiment, the chickens of the control group were fed soybean meal. Results: FCSM supplementation linearly decreased the feed conversion ratio from d 15 to 21 and d 36 to 42, respectively (p<0.05). The percentage of carcass and semi-eviscerate increased in response to dietary FCSM supplementation at d 21 (p<0.05). The percentage of eviscerated and semi-eviscerate of 3FCSM was higher than that in other groups at d 35 (p<0.05). At the age of 42 d, the percentage of carcass increased in a quadratic way among increasing FCSM in diets (p<0.05). The subcutaneous fat thickness linearly decreased with the increasing levels of FCSM at d 21 (p<0.05). Gompertz and Logistic functions provided a better fit on abdominal fat and subcutaneous fat, respectively. The best fitted equation predicted that the maximum growth rate of abdominal fat weight and subcutaneous fat thickness occurred at d 28. FCSM had no significant effects on the shape of growth curve of abdominal fat weight and subcutaneous fat thickness, but reduced the height of the curve. Birds receiving the 6FCSM diet for 21 d had smaller adipocyte surface and lower serum glucose as well as triglyceride concentration. Conclusion: FCSM is beneficial for broiler chickens as it positively affects their growth and carcass in addition to altering their fat deposition.