• Composites Research
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• v.37 no.3
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• pp.179-185
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• 2024

This study quantitatively evaluated and investigated the changes in transverse tensile strength of unidirectional fiber-reinforced composites with initial void defects using a Representative Volume Element (RVE) model. After calculating the appropriate sample size based on margin of error and confidence level for initial void defects, a sample group of 5000 RVE models with initial void defects was generated. Dimensional reduction and density-based clustering analysis were conducted on the sample group to assess similarity, confirming and verifying that the sample group was unbiased. The validated sample analysis results were represented using a Weibull distribution, allowing them to be applied to the reliability analysis of composite structures.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1962-1966
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• 2012

Boehmite sols have been prepared by crystallization of amorphous aluminum hydroxide gel obtained by hydrolysis and peptization of aluminum using acetic acid. The size of the boehmite crystallites could be controlled by Al molar concentration in amorphous gel by means of controlling grain growth at nucleation stage. The size of boehmite increases as a function of Al molar concentration. With increasing boehmite crystallite size, the $d_{(020)}$ spacing and the specific surface area decreases, whereas the pore volume increases along with pore size. Especially, the pore size of the boehmite sol particles is comparable to the crystallite size along the b axis, suggesting that the fibril thickness along the b axis among the crystallite dimensions of the boehmite contributes to the pore size. Therefore, the physical properties of boehmite sols can be determined by the crystallite size controlled as a function of initial Al concentration.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.10a
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• pp.171-174
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• 2000

This paper presents an approach to determine the vehicle fleet size for container shuttle service in a stochastic working environment. The shuttle service can be defined as the repetitive travel between the designated places during working period. The initial number of vehicles is temporarily calculated using the transportation model. Simulation is carried out in order to investigate dynamic behavior of container shuttle. Finally, the equation for estimating the vehicle fleet size is obtained through the multiple regression model based on simulation results.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.12 no.20
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• pp.77-80
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• 1989

A rectifying sampling plan which assumes a prior distribution on the lot percent defective is considered. This sampling is developed for finite lot size N with matching OC curves and generated from an initial plan selected from single sampling by attributes.

• Journal of IKEEE
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• v.6 no.2 s.11
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• pp.111-118
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• 2002

In this paper, we present a variable block method to reduce additive computational requirements in determining step-size of variable step-size LMS (VS-LMS) algorithms. The block length is inversely proportional to the changing of step-size in VS-LMS algorithm. The technique reduces computational requirements of the conventional VS-LMS algorithms without a degradation of performance in convergence rate and steady state error. And a method for deriving initial step-size, when the input is zero mean, white Gaussian sequence, is proposed. For demonstrating the good performances of the proposed method, simulation results are compared with the conventional variable step-size algorithms in convergence speed and computational requirements.

• Korean Chemical Engineering Research
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• v.52 no.6
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• pp.775-780
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• 2014

Micellar enhanced ultrafiltration (MEUF) was used to remove cadmium from an aqueous solution using sodium dodecyl sulfate (SDS) as a surfactant. Operational parameters such as initial permeate flux, retentate pressure, initial cadmium concentration, pH solution, molecular weight cut-off (MWCO), and molar ratio of cadmium to SDS were investigated. Removal efficiency of cadmium from an aqueous solution increased with an increase of retentate pressure, pH solution and molar ratio of cadmium to SDS, and decreased with an increase of initial permeate flux. Higher removal efficiency of cadmium from the aqueous solution was achieved using lower MWCO (smaller membrane pore size). Under optimized experimental condition, cadmium removal efficiency reached 74.6 % within an hour. Using MEUF-ACF hybrid process the removal efficiency of both cadmium and SDS was found to be over 90%.

• Speech Sciences
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• v.11 no.3
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• pp.83-93
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• 2004

The objectives of this study are to analyze Korean speakers' pronunciations of various Japanese /p/ patterns and to provide desirable pronunciation models. This is a part of an ongoing research that aims to propose a useful method of teaching Japanese pronunciation of /p/ to Koreans. The experimental data consist of /p/ phonemes in word initial, word medial, and 'yoon' positions. Yoon must be written in small size after a letter and it only makes a syllable with the preceding letter in Japanese. There were 22 different phoneme positions. They were pronounced by 48 Japanese majoring students (24 females and 24 males), who were in their twenties and were raised in Daejeon and vicinity. The individual pronunciations were collected and digitized into 528 files. The results show that Koreans pronounced the Japanese phoneme /p/ in a variety of ways, according to the auditory environments in which the phoneme was tested: as [ph] in word initial, [pp] or [ph] in word medial, and [ph] in 'yoon', unlike native speakers who pronounced Japanese /p/ as [ph] in word initial, [pp] in word medial and, and [pp] or [ph] in 'yoon'.

• Journal of the Korean Society of Safety
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• v.18 no.1
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• pp.33-37
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• 2003

The objective of the present work is to examine the variation of cooling characteristics due to the Weber number of droplet on a heated surface. The surface temperatures varied from 72.5 - $106.1^{\circ}C$ on steel and Teflon, when Weber number was 60, 180, 300. The results are as follows; In the case of the same droplet size, the initial temperature of solid increases the indepth temperature of solid more drop. In the case of the same surface temperature, Weber number increases with increasing the cooling effect of droplet. The time-average heat flux increases with increasing the initial temperature of solid and Weber number. The evaporation time decreases with increasing the initial temperature of solid and Weber number.

• Journal of Microbiology and Biotechnology
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• v.8 no.2
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• pp.185-187
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• 1998

Pseudomonas putida KCTC 2401 degrades 1,1, 2-trichloroethylene (TCE) using phenol as a cosubstrate. The initial TCE degradation rate decreased with the initial TCE concentration up to 20mg/l of TCE at $30^{\circ}C$ and pH 6.5. The initial degradation rate and total removal efficiency increased with inoculum size. The strain also degraded dichloroacetic acid, which was supposed to be a degradation by-product. Phenol monooxygenase apparently participates in the TCE degradation mechanism.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.59-65
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• 1993

In a spark ignition engine, in order to make research on flame propagation, attentive concentration should be paid on initial combustion stage about the formation and development of flame. In addition, the initial stage of combustion governs overall combustion period in a spark ignition engine. With the increase of the size of flame kernel, it could reach initial flame stage easily, and the mixture could proceed to the combustion of stabilized state. Therefore, we must study the theoretical calculation of minimum flame kernel radius which effects on the formation and development of kernel. To calculate the minimum flame kernel radius, we must know the thermal conductivity, flame temperature, laminar burning velocity and etc. The thermal conductivity is derived from the molecular kinetic theory, the flame temperature from the chemical reaction equations and the laminar burning velocity from the D.K.Kuehl's formula. In order to estimate the correctness of the theoretically calculated minimum flame kernel radius, the researcheres compared it with the RMaly's experimental values.