• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.88-94
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• 2000

The adsorption characteristics of Tharonil on granular activated carbon were experimentally investigated in an adsorber and in a packed column. It was estabilished that the adsorption equilibrium of Tharonil on granular activated carbon was more successfully fitted by Freundlich isotherm equation than Langmuir isotherm equation in the concentration range from 1 to 1000 mg/1. Intraparticle diffusivities (pore and surface diffusivity) of Tharonil were estimated by the concentration-time curve and adsorption isotherm. The estimated values of pore diffusivity and surface diffusivity are $6.70{\times}10^{-6}$ and $2.0{\times}10^{-9}cm^2/s$, respectively. From comparison of intraparticle diffusivities, it was found that surface diffusion was the limiting step for adsorption rate. The break time and breakthrough curve predicted by constant pattern-linear driving force model were shown to agree with the experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.96-103
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• 2005

One of the major problems limiting the accuracy of piezoelectric transducers fur cylinder pressure measurements in an internal combustion (IC) engine is the thermal shock. Thermal shock is generated from the temperature variation during the cycle. This temperature variation results in contraction and expansion of the diaphragm and consequently changes the force acting on the quartz in the pressure transducer An empirical equation for compensation of the thermal shock error was derived from consideration of the diaphragm thermal deformation and actual pressure data. The result indicate that the thermal shock equation provides reliable correction based on known surface temperature swing.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1940-1954
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• 1992

Fine grid computations were attempted to analyze the turbulent flows in the near wall low Reynolds number region and the numerical analyses were incorporated by a finite-volume discretization with full find grid system and low Reynolds number k-.epsilon. model was employed in this region. For the improvement of low Reynolds number k-.epsilon. model, modification coefficient of eddy viscosity $f_{\mu}$ was derived as a function of turbulent Reynolds number $R_{+}$ and nondimensional length $y^{+}$ from the concept of two length scales of dissipation rate of turbulent kinetic energy. The modification coefficient $f_{\epsilon}$ in .epsilon. transport equation was also derived theoretically. In the turbulent kinetic energy equation, pressure diffusion term was added in order to consider low Reynolds number region effect. The main characteristics of this low Reynolds number k-.epsilon. model were founded as : (1) In high Reynolds number region, the present model has limiting behavior which approaches to the high Reynolds number model. (2) Present low Reynolds number k-.epsilon. model dose not need additional empirical constants for the transport equations of turbulent kinetic energy and dissipation of turbulent kinetic energy in order to consider wall effect. Present low Reynolds number turbulence model was tested in the pipe flow and obtained improved results in velocity profiles and Reynolds stress distributions compared with those from other k-.epsilon. models.s.s.

• Journal of the Korean institute of surface engineering
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• v.44 no.4
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• pp.131-136
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• 2011

A kinetic study has been made for the growth of nanocrystalline diamond (NCD) particles to a continuous thin film on silicon substrate in a microwave plasma chemical vapor deposition reactor. Parameters of deposition have been microwave power of 1.2 kW, the chamber pressure of 110 Torr, and the Ar/$CH_4$ ratio of 200/2 sccm. The deposition has been carried out at temperatures in the range of $400\sim700^{\circ}C$ for the times of 0.5~16 h. It has been revealed that a continuous diamond film evolves from the growth and coalescence of diamond crystallites (or particles), which have been heterogeneously nucleated at the previously scratched sites. The diamond particles grow following an $h^2$ = k't relationship, where h is the height of particles, k' is the particle growth rate constant, and t is the deposition time. The k' values at the different deposition temperatures satisfy an Arrhenius equation with the apparent activation energy of 4.37 kcal/mol or 0.19 eV/ atom. The rate limiting step should be the diffusion of carbon species over the Si substrate surface. The growth of diamond film thickness (H) shows an H = kt relationship with deposition time, t. The film growth rate constant, k, values at the different deposition temperatures show another Arrhenius-type expression with the apparent activation energy of 3.89 kcal/mol or 0.17 eV/atom. In this case, the rate limiting step might be the incorporation reaction of carbon species from the plasma on the film surface.

• Journal of the Korean Chemical Society
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• v.19 no.1
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• pp.3-10
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• 1975

The partial molal volumes and relative viscosities of tetraethylammonium chloride in a series of dimethyl sulfoxide (DMSO)-water mixtures were measured at $30^{\circ}C$. A maximum structuredness of solvent, that leads to a minimum viscosity A-coefficient and a maximum viscosity B-coefficient of the Jones-Dole equation(${\eta}_r=1+AC^{1/2}$ + BC), was found at 0.2${\sim}$0.3 mole fraction of DMSO. The solvent structure, that leads to a minimum partial molal volume due to the maximum electrostrictive effect of chloride ion and to a minimum viscosity B-coefficient, was found at 0.4${\sim}$0.5 mole fraction of DMSO. An approximate relationship between the limiting effective flowing volume, $V_e^{\circ}$, and the B-coefficient was found to be B = 2.5 $V_e^{\circ}$ in the Einstein equation.

• Journal of Bio-Environment Control
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• v.1 no.1
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• pp.52-60
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• 1992

The optimum management of nutrient solution needs the effective combination of fertilizers as well as the accurate control of nutrient solution. This study was attempt to make a supporting system for effective fertilizer combination by using computer and also to develop a EC predicting equation for keeping the EC of solution within the allowable range after application of combined fertilizers. The supporting system consists of three parts : (1) data bases, (2) rules for deciding the kinds and amounts of fertilizers and (3) main control. With input data, the main control automatically constructs the network connecting the related data bases and subsequently executes the operation of searching proper fertilizers through it. For more effective searching, fertilizers are classified into two levels(level 1 and level 2) in consideration of solubility, price, and frequency in use, and searched in that order. The EC prediction equation, a extended form of the Robinson and Stroke's theoretical equation only available for a binary electrolyte, is suggested for predicting the EC of the nutrient solution containing many kinds of inorganic compounds. The comparison of predicted and measured ECs showed good agreements with the high correlation between the predicted EC decrement by ion interaction and the actual one(limiting EC minus measured EC).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.5 s.98
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• pp.527-535
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• 2005

This paper explains a general coupling system in terms of the system parameters. impedance of a cavity or mobility of a structure. To easily access the mechanism of the structural-acoustic coupled system, a simple expression is derived. A general coupled equation is also derived of a general coupled problem constituted a flexible structure and an opening boundary in terms of vector and matrix notation, and is analyzed the coupling phenomena using the understanding acquired simple coupled system. The paper shows that the general coupled equation is expanded version of the simple coupled equation by some limiting checks. The paper also shows that the degree of coupling is proportioned to a stiffness of the acoustic system and a modal coupling coefficient, but is in inverse proportion to a mass of the structural system and the difference of the excitation frequency and resonant frequency of the acoustic or structural system.

• Steel and Composite Structures
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• v.30 no.5
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• pp.471-481
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• 2019

Beam-columns are structural members subjected to a combination of axial and bending forces. Lateral-torsional buckling is one of the main failure modes. Beam-columns that are bent about its strong axis may buckle out of the plane by deflecting laterally and twisting as the values of the applied loads reach a limiting state. Lateral-torsional buckling failure occurs suddenly in beam-column elements with a much greater in-plane bending stiffness than torsional or lateral bending stiffness. This study intends to establish a unique convenient closed-form equation that it can be used for calculating critical elastic lateral-torsional buckling load of beam-column in the presence of a known axial load. The presented equation includes first order bending distribution, the position of the loads acting transversely on the beam-column and mono-symmetry property of the section. Effects of axial loads, slenderness and load positions on lateral torsional buckling behavior of beam-columns are investigated. The proposed solutions are compared to finite element simulations where thin-walled shell elements including warping are used. Good agreement between the analytical and the numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of beam-columns with mono-symmetric sections can be determined by the presented equation and can be safely used in design procedures.

• Membrane and Water Treatment
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• v.1 no.1
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• pp.13-37
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• 2010

The performance of an electrodialyzer for concentrating seawater is predicted by means of a computer simulation, which includes the following five steps; Step 1 mass transport; Step 2 current density distribution; Step 3 cell voltage; Step 4 NaCl concentration in a concentrated solution and energy consumption; Step 5 limiting current density. The program is developed on the basis of the following assumption; (1) Solution leakage and electric current leakage in an electrodialyzer are negligible. (2) Direct current electric resistance of a membrane includes the electric resistance of a boundary layer formed on the desalting surface of the membrane due to concentration polarization. (3) Frequency distribution of solution velocity ratio in desalting cells is equated by the normal distribution. (4) Current density i at x distant from the inlets of desalting cells is approximated by the quadratic equation. (5) Voltage difference between the electrodes at the entrance of desalting cells is equal to the value at the exits. (6) Limiting current density of an electrodialyzer is defined as average current density applied to an electrodialyzer when current density reaches the limit of an ion exchange membrane at the outlet of a desalting cell in which linear velocity and electrolyte concentration are the least. (7) Concentrated solutions are extracted from concentrating cells to the outside of the process. The validity of the computer simulation model is demonstrated by comparing the computed results with the performance of electrodialyzers operating in salt-manufacturing plants. The model makes it possible to discuss optimum specifications and operating conditions of a practical-scale electrodialyzer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.20-23
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• 2003

The operational characteristics of flux-lock type high-Tc superconducting fault currentlimiters(HTSC-FCLs) was described and currents equation at each coil was derived from equivalent circuit. $YBa_{2}Cu_{3}O_{7-x}$(YBCO) thin film was used as the current limiting elements of the flux-lock type HTSC-FCL, which were fabricated by etching the YBCO thin film into 2 mm wide and 420 mm long meander line consisting of foureen stripes with different length. The 2nd peak on the current of coil 2 after a fault disappeared by current of the 3rd winding, which was installed in the flux-lock type HTSC-FCL.