• Journal of Labour Economics
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• v.39 no.3
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• pp.99-124
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• 2016

This study analyzed the effects of labor unions on the wages of Korean female workers using 'Korean Labor and Income Panel Study.' In the estimation we considered the self-selection bias due to the women's labor force participation decision and a plausible non-response bias from not answering the question about the company size in terms of number of employees. By fixed effect estimation we found that labor unions in Korea do not increase the wages of both the female union workers and non-union workers who work at a company in which a union is organized comparing to female workers who work at company without a union. This results indicates that female workers who work in the company with labor union tend to have unobserved characteristics that are positively correlated with both wages and the probability to enter the company with labor union. We also came to the conclusion that there is no free-rider effects of non-union workers.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.50-56
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• 2015

An efficient fast response hysteretic buck converter suitable for mobile application is propoesed. The problems of large output ripple and difficulty in using of small power inductor that conventional hysteretic converter has are improved by adding ramp generator. and the changeable switching frequency with load current is fixed by adding a delay time control circuit composed of PLL structure resulting in decrease of EMI noise. The circuits are implemented by using BCDMOS 0.35um 2-polt 4-metal process. Measurement results show that the converter operates with a switching frequency of 1.85MHz when drives 80mA load current. As the converter drives over 170mA load current, the switching frequency is fixed on 2MHz. The converter has output ripple voltage of less 20mV and more than efficiency 85% with 50~500mA laod current condition.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.201-208
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• 2014

The performance of a landmine detection system depends on consistent extractions of the features of landmines. Since landmines have diverse sizes, it is critical to select an appropriate window size to represent the landmine region consistently. Conventional detection systems are incapable of extracting consistent landmine features because they employ fixed window sizes. This paper proposes a window size selection method according to the size of a landmine. The proposed method selects an appropriate window size based on the type of a landmine estimated from the response signal of the system. Data on various types of soils and landmines were generated from a simulation program to evaluate the performance of the proposed method. The results verified that the proposed method, which employs an adaptive window size, yields a better landmine detection rate than the conventional methods, which employ fixed window sizes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2749-2757
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• 2014

The purposes of the study are to understand how multicultural efficacy is different and to affecting the multicultural efficacy. To achieve the goals, the study conducted surveys to examine an interrelation of multicultural efficacy on 272 elementary school students in Namyangju-si with questionnaires. First, the results showed that multicultural efficacy of elementary school students scored 2.84 on five point scale. Second, the elements that affected multicultural efficacy of elementary school students include 'openness', 'acceptance', 'respect' of elementary school student toward multiculture awareness, at the same time, elementary students' indirect experience of multiculture and direct experience also make significant influence. The study suggests to develop multiculture-related educational programs, in order to enhance multicultural efficacy and multicultural awareness of elementary students.

• Journal of the Korean Chemical Society
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• v.40 no.8
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• pp.542-548
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• 1996

Electrodes modified with threonine, methionine and serine as ligands, which are incorporated by ion exchange into a polycationic film of electropolymerized $[Ru(v-bpy)_3]^{2+}$, have been employed in the determination of mercury in solution. The redox response of the surface-immobilized mercury/ligand complex was used as the analytical signal. When the polymeric film was electropolymerized, the supporting electrolytes were TBAP and $KPF_6$ to compare the morphology and anodic stripping of resulted polymer electrodes. At the case of the latter, the film had high porosity to give an easy incorporation of dopant anions into polymeric film matrix and a high sensitivity in determination of mercury ion. Especially, this polymer modified electrode exhibited possibility of multiple use in mercury determination over ten times. In all cases, calibration curves which were plotted by log of the surface coverage-normalized redox response vs. log[Hg] exhibited an excellent correlation (r=0.99) for mercury concentrations ranging from 1.0{\times}10^{-8}{\sim}1.0{\times}10^{-2}M$. At these curves relative standard deviation was 5∼8% and saturation response was not observed at high concentration region. Serine of the employed ligands had the best sensitivity in analytical application, which had greater stability constant in forming a complex with mercury than others as $pK_{Hg}=8.54$. The formation constants of threonine and methionine were respectively 7.04 and 7.80.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.2
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• pp.86-97
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• 2005

Accurate estimation of the wave-induced pore water pressure in the seabed is key factor in studying the stability of the seabed in the vicinity of coastal structure. Most of the existing numerical models for wave structure seabed interaction have been linked through applying hybrid numerical technique which is analysis method separating the wave field and seabed regime. Therefore, it is necessary to develope a numerical model f3r simulating accurately wave$\cdot$structure$\cdot$ seabed interaction under wave loadings by the single domain approach for wave field and seabed regime together. In this study, direct numerical simulation is newly proposed. In this model, modeled fluid drag has been used to detect the hydraulic properties according to the varied geometrical shape inside the porous media by considering the turbulence resistance as well as laminar resistance. Contrary to hybrid numerical technique, direct numerical simulation avoids the explicit formulation of the boundary conditions at the fluid/porous media interface. A good agreement has been obtained by the comparison between existed experimental results by hydraulic model test and direct numerical simulation results far wave $\cdot$structure$\cdot$seabed interaction. Therefore, the newly proposed numerical model is a powerful tool for estimating the nonlinear dynamic responses among a structure, its seabed foundation and water waves.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.5
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• pp.648-654
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• 2004

The Mass Flow Controller(MFC) has become crucial in semiconductor manufacturing equipments. It is an important element because the quality and the yield of a semiconductor process are decided by the accurate flow control of gas. Therefore, the demand for implementing the high speed and the highly accurate control of MFCs has been increasing. It is hard to find an article of the control algorithm applied to MFCs. But, it is known that commercially available MFCs adopt PID control algorithms. Particularly, when the system detects the flow by way of heat transfer, the MFC control problem includes the slow response and the nonlinearity. In this paper, MFC control algorithm with a superior performance to the conventional PID algorithm is discussed and the superiority is demonstrated through the experiment. A fuzzy controller was utilized in order to compensate the nonlinearity and the slow response, and the performance is compared with that of an MFC currently available in the market. The control system, in this paper, consists of a personal computer, the data acquisition board and the control algorithm carried out by LabWindows/CVI program on the PC. In addition, a method of estimating the actual flow from the sensor output with the slow response is presented. In conclusion, according to the result of the experiment, the proposed algorithm shows better accuracy and is faster than the conventional controller.

• Journal of The Korean Association For Science Education
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• v.22 no.3
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• pp.617-631
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• 2002

This study has examined 5-year students in the kindergarten and students in the 2nd, 4th, and 6th grade in the primary school to analyze their perceptions about scientists. science, and how they apply science in their daily lives. First, students have 4 stereotypic images on scientists, specifically in 'indoor', 'male', 'lab coat'. and 'scientific instrument'. There were significant differences in stereotypic images on scientists depending on genders and ages. Girls and primary students showed higher scores than boys and kindergarten students did. respectively, in stereotypic images on scientists. No differences were observed for the stereotypic images on scientists among primary students, regardless of their grades. Second, most of students were interested in science. Depending on grades, there were significant differences in their preference for science. Students in higher grades showed lower scores than those in lower grades did. In addition, only a few of them hoped to be a scientist in the future. Boys showed higher scores in their hope to be a scientist in the future than girls did. The students in lower grades showed higher scores than those in higher grades. Third, most of children thought themselves doing activity-oriented science in school. Outside school, however, they did not use the knowledge and skills they had learned for science in school. Students in the primary school showed more concept-oriented perception for science than those in kindergarten did. This perception was gradually increased as the grades of the students go up.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.60-71
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• 2014

Cable-stayed bridge, which is one of the representative long-spanned bridge, needs prompt maintenances when a stay cable is damaged because it may cause structural failure of the entire bridge. Many researches are being conducted to develop abnormal behavior detection algorithms for the purpose of shortening the reaction time after the occurrence of structural damage. To improve the accuracy of the damage detection algorithm, ample observation data from various kinds of damage responses is needed. However, it is difficult to measure an abnormal response by damaging an existing bridge, numerical simulation can be an effective alternative. In most previous studies, which simulate the damage responses of a cable-stayed bridge, the damages has been considered as a load variation without regard to its stiffness variation. The analyses of using these simplification could not calculate exact responses of damaged structure, though it may reserve a sufficient accuracy for the purpose of bridge design. This study suggests Gradual Bilinear Method (GBM) which simulate the damage responses of cable-stayed bridge considering the stiffness and mass variation, and develops an analysis program. The developed program is verified from the responses of a simple model. The responses of a existing cable-stayed bridge model are analyzed with respect to the fracture delay time and damage ratio. The results of this study can be used to develop and verify the highly accurate abnormal behavior detection algorithm for safety management of architecture/large structures.

• Journal of dental hygiene science
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• v.14 no.3
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• pp.417-423
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• 2014

The aim of this study was to evaluate the relationship between prosthetic status and health related quality of elderly by using EuroQol-5 dimension (EQ-5D) which is a standardized instrument used as a measure of health outcome. Data from 1,179 elderly subjects (over 65 years old) from the fifth Korea National Health and Nutrition Examination Survey were used in our analysis. Oral examination were conducted to obtain wearing prosthetic and needed prosthetic. EQ-5D is a widely used health condition measuring instrument. It consists of the five dimensions: Mobility, Self-care, Usual activities, Pain/discomfort and Anxiety/depression. EQ-5D index is a score calculated out of a weighting system. In this study, the mean score of the EQ-5D index among the elderly was 0.86. For EQ-5D index gender, female showed statistically significantly lower quality of life than male. The related factors EQ-5D index, when the lower demand for fixed prosthodontics and full denture. Wearers in partial and complete denture than non-wearers showed higher EQ-5D index. In order to improve EQ-5D index among the elderly who demand prosthetic status, which has lost its function through providing proper dental prostheses.