• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.3
• /
• pp.135-142
• /
• 2017

In this study, we prepared the board of vermiculite materials utilizing coal bottom ash from the Western thermal power stations in Korea and obtained experimental data in applications for building interior materials with the characteristics of sound absorption. To produce the mixture materials of vermiculite and coal bottom ash, we used a microwave drying process. In addition, a ball milling process was used to produce particles of coal bottom ash with a uniform size of $65{\mu}m$. When the board made from mixture materials of vermiculite and coal bottom ash were produced with bottom ash sulfur concentrations of 5, 10 wt%, maximum bending loads were analyzed. These experimental results would contribute much to fundamental data essential to the recycling technology of coal bottom ash.

• Journal of the Semiconductor & Display Technology
• /
• v.21 no.2
• /
• pp.144-149
• /
• 2022

A cryogenic Mixed Refrigerant Joule-Thomson refrigeration cycle was designed to be applied to the semiconductor etching process with non-flammable constituents. 3-stage cascade refrigerator, single mixed refrigerant Joule-Thomson refrigerator, and 2-stage cascade type mixed refrigerant Joule-Thomson refrigerator are analyzed to figure out the coefficient of performance. Non-flammable mixture of argon(Ar), tetrafluoromethane(R14), trifluoromethane (R23) and octafluoropropane(R218) were utilized to analyze the refrigeration cycle efficiency. The designed refrigeration cycle was adapted to cool down the coolant of HFE7200(Ethoxy-nonafluorobutane, C₄F₉OC₂H₅) with certain constraints. Maximum coefficient of performance of the refrigeration system is obtained as 0.289 for the cooling temperature lower than -100℃. The detailed result of the coefficient of performance according to the mixture composition is discussed in this study.

• Membrane and Water Treatment
• /
• v.15 no.4
• /
• pp.153-162
• /
• 2024

The current research project focuses on the feasibility of recycling and reusing utilized osmosis membranes from the Beni Saf water seawater desalination station in the province of Ain Temouchent. The composite Reverse Osmosis (RO) membrane, which is referenced BW30-400-FR and manufactured by Dow Filmtec TM, is used for all the tests. Three solvents are tested: potassium permanganate (KMnO₄), sodium hydroxide (NaOH), hydrogen peroxide (H₂O₂), and the mixture of NaOH with KMnO₄ for the degradation of the active layer of the RO membrane. A frontal filtration of wastewater using these modified membranes was carried out. An analysis of the physicochemical properties of the filtrate was performed using a spectrophotometer. The results of the frontal filtration performed under perpendicular pressure using a filtration ramp show that the membranes immersed in the NaOH and KMnO₄ mixture for 24 hours produced a higher hydraulic flux compared to those immersed in NaOH and H₂O₂. At the end of the proposed treatment, the samples are analyzed by scanning electron microscopy (SEM) in addition to analyzing the clogging powder by EDX. The obtained results show the effectiveness of the proposed treatment for the degradation of the active layer in order to transform it into microfiltration and/or ultrafiltration.

• Journal of the Korean Chemical Society
• /
• v.59 no.5
• /
• pp.454-465
• /
• 2015

The goal of this study is to investigate pre-service chemistry teachers’ understanding of the boiling process of a liquid mixture. We surveyed 65 students in the chemistry program of the College of Education about the boiling point of a 50%(by mole) ethanol aqueous solution and the temperature changes during heating. We then interviewed 9 of these students. According to the survey results, the percent of the pre-service teachers who thought that the boiling point of the ethanol solution would be ‘between the boiling points of ethanol and water (78-100 ℃)’ and ‘the same as that of ethanol’ were 52.3% and 35.4%, respectively. The majority of those who stated the former explained that the boiling point of the ethanol solution increased due to the effects of attraction or blocking by water molecules. Most of those who believed the latter explained that physical properties such as the boiling point would not be changed by the addition of water. With regard to the temperature change during heating, 69.2% of the teachers thought that the temperature would increase gradually while boiling, which some thought resulted from the increasing amount of water in the solution as the ethanol boiled off. Others thought that two temperature plateaus would be observed as each component of the liquid mixture underwent phase transition at its specific boiling point. When asked about the particle model of the gas phase during the boiling and evaporation process, some students drew both ethanol and water during evaporation but only ethanol when boiling. We discussed several alternative concepts of pre-service chemistry teachers about the boiling process of liquid mixtures and ways to improve their understanding.

• Journal of Korea Water Resources Association
• /
• v.35 no.1
• /
• pp.109-124
• /
• 2002

This study is an effort to develop a stochastic model of precipitation series that preserves the pattern of occurrence of precipitation events throughout the year as well as several characteristics of the duration, amount, and intensity of precipitation events. In this study an event cluster model is used to describe the occurrence of precipitation events. A logarithmic negative mixture distribution is used to describe event duration and separation. The number of events within each cluster is also described by the Poisson cluster process. The duration of each event within a cluster and the separation of events within a single cluster are described by a logarithmic negative mixture distribution. The stochastic model for hourly precipitation occurrence process is fitted to historical precipitation data by estimating the model parameters. To allow for seasonal variations in the precipitation process, the model parameters are estimated separately for each month. an analysis of thirty-four years of historical and simulated hourly precipitation data for Seoul indicates that the stochastic model preserves many features of historical precipitation. The seasonal variations in number of precipitation events in each month for the historical and simulated data are also approximately identical. The marginal distributions for event characteristics for the historical and simulated data were similar. The conditional distributions for event characteristics for the historical and simulated data showed in general good agreement with each other.

• Journal of the Korean Society of Industry Convergence
• /
• v.2 no.1
• /
• pp.121-130
• /
• 1999

It is necessary to measure pressure, temperature, chemical equilibrium and the shape of flame in order to understand the combustion process in a combustion chamber. In particular, the flame formulation and combustion process of divided combustion chamber are different from those of a single chamber, And the variable diameter of a jet hole can effect not only physical properties like ejection velocity, temperature and time of combustion but also a chemical property like the reaction mechanism. Accordingly temperature is one of the most important factors which influence the combustion mechanism. This paper observed shape of flame by using the schlieren photographs and measured the pressure in a combustion chamber and the reaching time of the flame by ion probe By doing these, we investigation the formulation of the flame and the process of propagation. These measurement methods can be advanced in understanding the combustion process and process and propagation of flame.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2000.11a
• /
• pp.902-905
• /
• 2000

As the manufacturing processes of automotive engine piston, gravity die-casting, squeeze casting, hot forging and powder forging process are generally used for the various specifications. As the semi-solid forming(SSF) is compared with conventional casting such as gravity die-casting and squeeze casting for the characteristics of its process, the product without inner defects such as gas porosity and segregation can be obtained and its microstructure is globular grain. In SSF process, the materials are heated up to the temperature between the solvus and liquidus line at which the materials exists in the form of liquid-solid mixture. In this time, Discussion is given about reheating process of row material and results are presented regarding accurate temperature and process variables controlling for right solid fractions.

• Journal of the Korean Applied Science and Technology
• /
• v.28 no.2
• /
• pp.135-139
• /
• 2011

In order to make high-purity ferro-manganese from $Mn_3O_4$ waste dust, the application of aluminothermite process to the reduction of the waste dust was investigated. The mixture from $Mn_3O_4$ dust as metallic source and Al metal powder as the reductant ignited, and reduced with an extremely intense exothermic reaction. The rapid propagation of the aluminothermite reaction occurred spontaneously and stably by ignition of the mixture. The Manganese having some alloy elements emerged as liquids due to the high temperatures reached up to about $2,500^{\circ}C$ and separated from the liquid by their differences of specific gravity. The result of thermite reaction showed the fact that can be obtained high purity ferro-manganese which have over about 90% of manganese content and lower impurities such as C, P, S than those of KS D3712 specification. The recovery of manganese from $Mn_3O_4$ dust was lower level of about 65% than about 75% from manganese ore by electric furnace process, that is due to spatter loss because of its extremely intense thermite reaction. But it will be improved by the process designed to provide CaO as the cooler or to use the Al metal powder having larger particle size distribution.

• Korean Chemical Engineering Research
• /
• v.43 no.3
• /
• pp.371-379
• /
• 2005

Adsorption equilibria of the gases $H_2$, $CH_4$, and $C_2H_4$ and their binary mixtures on activated carbon (Calgon co.) have been measured by static volumetric method in the pressure range of 0 to 18 atm at temperatures of 293.15, 303.15, and 313.15 K. From the parameters obtained from single component adsorption isotherm, multi-component adsorption equilibria could be predicted and compared with experimental data. The binary experimental data were applied to four models : extended Langmuir, extended Langmuir-Freundlich, Ideal Adsorbed Solution theory (IAST), and Vacancy Solution Model (VSM). The models were found to describe the experimental data with a reasonable accuracy. Extended L-F model predicts equilibria of mixture better than any other model.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.4
• /
• pp.754-760
• /
• 2013

We investigated an electrochemical properties for Langmuir-Blodgett (LB) monolayer films of sphingomyelin(SP) and polyamic acid(PAA) mixture(1:1, 2:1 and 3:1 molar ratio). LB monolayer films of mixture was deposited by the LB method on the indium tin oxide(ITO) glass. The electrochemical properties measured by cyclic voltammetry with three-electrode system in 0.1N $KClO_4$ solution. As a result, LB monolayer films of SP and PAA mixture was appeared on irreversible process caused by the reduction current from the cyclic voltammogram. Diffusion coefficient(D) in the SP and PAA mixture was calculated $2.670{\times}10^{-5}$, $3.562{\times}10^{-5}$ and $1.005{\times}10^{-5}cm^2s^{-1}$ at 1:1, 2:1 and 3:1 molar ratio, respectively.