• 한국전기전자재료학회논문지
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• 제17권6호
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• pp.622-632
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• 2004

We have studied how liquid crystal's rubbing direction and voltage driving method affect generation of disclination line. At first, generation of disclination line in vertical alignment(VA) cell and VA-twisted nematic(TN) cell has been examined. When liquid crystal's rubbing direction of bottom substrate was 0$^{\circ}$, the degree of generated disclination line was the smallest value. Further, the generation of disclination line above the electrode is less in the frame inversion than in the line inversion. Secondly, we have examined a generation of disclination line in reflective fringe-field switching cell. When the distance between common electrodes is over 3 ${\mu}{\textrm}{m}$ with on-state of one pixel and off-state of neighboring pixels, the reflectance appears only on-state pixel without generating reflectance in adjacent pixels.

• 한국가시화정보학회지
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• 제21권1호
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• pp.94-102
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• 2023

Three design parameters were considered in this study: outlet nozzle angle (30°, 60°, 80°), neck length (1 mm, 3 mm), and flow rate (0.5, 0.6, 0.7, 0.8 lpm). A neck diameter of 0.5 mm induced cavitation flow at a venture nozzle. A secondary transparent chamber was connected after ejection to increase bubble duration and shape visibility. The bubble size was estimated using a Gaussian kernel function to identify bubbles in the acquired images. Data on bubble size were used to obtain Sauter's mean diameter and probability density function to obtain specific bubble state conditions. The degree of bubble generation according to the bubble size was compared for each design variable. The bubble diameter increased as the flow rate increased. The frequency of bubble generation was highest around 20 ㎛. With the same neck length, the smaller the CV number, the larger the average bubble diameter. It is possible to increase the generation frequency of smaller bubbles by the cavitation method by changing the magnification angle and length of the neck. However, if the flow rate is too large, the average bubble diameter tends to increase, so an appropriate flow rate should be selected.

• 한국어교육
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• 제28권1호
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• pp.49-78
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• 2017

This study aims to analyze the effect of attitudes of Korean residents in Japan towards learning the Korean language and their motivational intensity on their Korean proficiency. Data for this study came from a survey on language use of Korean residents in Japan which was conducted in 2016, and questionnaire items referred to language attitude, language use and the degree of understanding language; language use; language learning and Korean ethnic identity. The main results are as follows. First, there were significant differences in Korean language proficiency depending on age, education levels and generation. Second, the control for socio-demographic characteristics, the influence of attitudes towards Korean language on Korean proficiency was statistically significant. However, Korean proficiency was not significantly influenced by motivational intensity. Lastly, moderated effects of immigrant generation in the relation between Korean language attitudes and Korean proficiency were significant. Therefore, the effect of Korean language attitudes on Korean proficiency was more influential on second and third generation Korean-Japanese learners than first generation Korean-Japanese learners. Based on these results, this study suggests that in order to promote Korean language education for Korean residents in Japan, it is required to build positive attitudes toward Korean language, and to consider immigrant generation as a major factor.

• 한국안전학회지
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• 제28권3호
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• pp.95-99
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• 2013

The goal of this study was to investigate some significant factors to influence level of safety at plant construction field and analyze degree of risk by work classification. Currently, there are lots of construction fields for the nuclear power plant for electricity generation, and our government also planned constructing more nuclear power plant in near future. However, much of the safety literature neglected the degree of risk factors on the plant construction field. Safety managers participated in the brainstorming session for drawing decision criteria of the degree of risk (i.e., significant factors). Then, they were asked to answer a structured questionnaire which was developed for drawing most important factors. Finally, the analytic hierarchy process (AHP) was used to analyze level of risk by work classification. The following results were obtained. First, total twelve factors judging degree of risk were found in the brainstorming session. Second, the questionnaire showed four significant factors, including number of workers, working environments, skill of craft and accident experience. Third, the results of AHP showed Architecture work is the most dangerous work among 6 work types. The results could be used to reduce degree of risk in construction field of the nuclear power plant.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권3호
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• pp.57-62
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• 2001

Falling film heat transfer analyses with aqueous lithium bromide solution were performed to investigate the transfer characteristics of the copper tubes. Finned (knurled) tube and a smooth tube were selected as test specimens. Averaged generation fluxes of water and the heat flux were obtained. As the film flow rate of the solution increased, the generation fluxes of water decreased for both tubes due to the fact that the heat transfer resistance increased with the film thickness. The effect of the enlarged surface area at the knurled tube was supposed to be dominant at a small flow rate. The generation fluxes of water increased with the increasing degree of tube wall superheat. Nucleate boiling is supposed to occur at a wall superheat of 20K for a smooth tube, and at 10K for a knurled tube. The increased performance of the knurled tube was supposed to mainly come from the effect of the increased heating surface area.

• 한국지능시스템학회논문지
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• 제2권3호
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• pp.29-39
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• 1992

We investigate a systematic design procedure of automatic rule generation of fuzzy logic based controllers for highly nonlinear dynamic systems such as an engine dynamic modle. By "automatic rule generation" we mean autonomous clustering or collection of such meaningful transitional relations from one conditional subspace to another. During the design procedure, we also consider optimaly control strategies such as minimum squared error, near minimum time, minimum energy or combined performance critiera. Fuzzy feedback control systems designed by our method have the properties of closed-loop stability, robustness under parameter variabitions, and a certain degree of optimality. Most of all, the main advantage of the proposed approach is that reliability can be potentially increased even if a large grain of uncertainty is involved within the control system under consideration. A numerical example is shown in which we apply our strategic fuzzy controller dwsign to a highly nonlinear model of engine idling speed control.d control.

• 한국전기전자재료학회논문지
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• 제11권6호
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• pp.481-485
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• 1998

We investigated the generation of high pretilt angle for nematic liquid crystal (NLC) in a cell with obilique non-polarized ultraviolet (UV) light irradiation on mixtured polyimide surface. It was found that the monodomain alignment of NLC is obtained with an angle of incidence of 75∼85 degrees on PI surface. We consider that the monodomain alignment of NLC is attributed to anisotropic dispersion force effect to photo-depolymerization of polymer. We successfully observed that the pretilt angle of NLC is generated above 5 degree with an angle of incidence of 75∼85 degrees. It is considered that the pretilt angle generation NLC is attributed to interaction between the LC molecules and the polymer surfaces.

• 한국정밀공학회지
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• 제24권7호
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• pp.39-48
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• 2007

This paper presents a method of a line balanced assembly sequence generation based on the verification of a disassemblability and a work time. To derive the disassemblability for a part to be disassembled, first we inference collision free assembly directions by extracting separable directions fur the part. And we determine the disassemblability defined by the separability and stability cost. The separability cost represents a facility of the part disassembly operation, and the stability cost which represents a degree of the stability for the base assembly motion. Based upon the results, we propose a new approach of evaluating work time using neural networks. The proposed assembly sequence generation provides an effective means of solving the line balancing problem and gives a design guidance of planning assembly lay-out in flexible manufacturing application. Example study is given to illustrate the concepts and procedure of the proposed schemes.

• 대한전기학회논문지
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• 제43권4호
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• pp.569-579
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• 1994

A 5.9kW phosphoric acid fuel cell(PAFC) power generation system that consists of a reformer, a stack, heat exchangers, an automatic data acquisition and control system was designed, fabricated and analyzed. This system which was firstly fabricated in Korea has been operated for 140 hours with an electricity generation of 684kWh. The PAFC generate electricity in the range of 38-52V and 50-160A and has a typical I-V characteristics of a fuel cell. Using the reformed fuel, the system performance is decreased in some degree due to CO content, compared to using the simulated fuel. At steady state operation condition, the total efficency of this system was 45.2%.

• 한국전기전자재료학회논문지
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• 제11권6호
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• pp.477-480
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• 1998

In this paper, we investigated the liquid crystal(LC) alignment and generation of pretilt angle by using photo-alignment techniques on two kinds of polyimide(PI) surface, It was found that the uniform alignment for nematic(N) LC is obtained in a cell with slanted UV light irradiation on PI surface without side chain. We successfully observed that the pretilt angle of NLC is generated about $3^{\circ}$ with an incident angle of 70 degree on the PI surface without side chain. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecules and the polymer surfaces.