• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.358-363
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• 2009

The HSPF (Hydrological Simulation Program-Fortran) model was applied to the Kyoungan stream watershed to analyze effects of watershed management plans on receiving water qualities. Utilizing BASINS 3.1 GIS program, the Kyoungan stream watershed was divided into 57 sub-basins and model input parameters were obtained, from DEM (Digital Elevation Model), land use type, stream map, and wastewater treatment facilities, etc.. The hydrologic module of the model was validated based on the measured meteorological data and stream flow data. Then the model was calibrated and verified against the field measurements of water qualities, including temperature, DO, BOD, $NO_3-N$, $NH_3-N$, Org-N, TN and TP. In most cases, there were reasonable agreements between measurements and predictions. The validated model was used to analyze the water quality improvements in the main stream of Kyoungan stream according to the watershed management plans in sub-basins, which are three different scenarios: water quality improvement in tributaries through watershed management activities, expansion and up-grade of wastewater treatment plants, and application of first and second scenarios together. It was concluded that expansion and upgrade of wastewater treatment plants would be more effective than watershed management activities. In order to improve water qualities to the satisfactory level, both watershed management and point source control must be required in the Kyoungan stream.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.761-768
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• 2010

This paper presents an effective method to achieve the wideband waveform for high resolution SAR(Synthetic Aperture Radar) using the frequency multiplication technique. And also this paper analyzes the root causes for the spectral regrowth due to 3rd-order intermodulation in chirp bandwidth expansion scheme using quadrature modulator and frequency multipliers. The amplitude and phase imbalance requirement are defined based on the simulation results in terms of quadrature channel imbalance. This minimizes the degradation of range resolution, peak sidelobe ratio and integrated sidelobe ratio. The wideband chirp generator using the frequency multiplier and memory map scheme was manufactured and the compensation technique was presented to reduce the spectral regrowth of SAR waveform by minimizing the amplitude and phase imbalance. After I and Q channel imbalance adjustment, the carrier level reduces －28.7 dBm to －53.4 dBm. Chirp signal with 150 MHz bandwidth at S-band expands to 600 MHz bandwidth at X-band. The sidelobe levels are reduced by about 8 to 9 dB by compensating the amplitude balance between I and Q channels.

• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.194-198
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• 2012

Crystalline silicon solar cell remains the major player in the photovoltaic marketplace with 80% of the market, despite the development of various thin film technologies. Silicon's excellent efficiency, stability, material abundance and low toxicity have helped to maintain its position of dominance. However, the cost of silicon materials remains a major barrier to reducing the cost of silicon photovoltaics. Using the crystalline silicon wafer with thinner thickness is the promising way for cost and material reduction in the solar cell production. However, the thinner the silicon wafer is, the worse bow phenomenon is induced. The bow phenomenon is observed when two or more layers of materials with different temperature expansion coefficiencies are in contact, in this case silicon and aluminum. In this paper, the solar cells were fabricated with different thicknesses of Al layer in order to reduce the bow phenomenon. With less amount of paste applications, we observed that the bow could be reduced by up to 40% of the largest value with 120 micron thickness of the wafer even though the conversion efficiency decrease by 0.5% occurred. Since the bowed wafers lead to unacceptable yield losses during the module construction, the reduction of bow is indispensable on thin crystalline silicon solar cell. In this work, we have studied on the counterbalance between the bow and conversion efficiency and also suggest the formation of enough back surface field (BSF) with thinner Al layer application.

• Geomechanics and Engineering
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• v.23 no.2
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• pp.127-137
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• 2020

To study the reverse fault formation process and the stress evolution feature, a simulation test system of reverse fault formation is developed based on the analysis of reverse fault formation mechanism. The system mainly consists of simulation laboratory module, operation console and horizontal loading control system, and data monitoring system. It can represent the fault formation process, induce fault crack initiation and simulate faults of different throws. Simulation tests on reverse fault formation process are conducted by using the simulation test system: horizontal loading is added to one side of the model. the bottom rock layer cracks under the effect of the induction device. The crack dip angle is about 29°. A reverse fault is formed with the expansion of the crack dip angle towards the upper right along the fracture surface and the slippage of the hanging wall over the foot wall. Its formation process unfolds five stages: compressive deformation of rock, local crack initiation, reverse fault penetration, slippage of the hanging wall over the foot wall and compaction of fault plane. There is residual structural stress inside rock after fault formation. The study methods and results have guiding and referential significance for further study on reverse fault formation mechanism and rock stress evolution.

• The Journal of Korean Association of Computer Education
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• v.5 no.3
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• pp.127-133
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• 2002

In this paper a web-based real-time education system, which is able to support education through multimedia, is suggested for the expansion of learner's creative ability in the school. This system is designed so that it can support three things: 1) a real time interaction between instructors and learners, 2) individual learning through such an interaction, and 3) a coercive distribution of display by instructions for preventing the deviation of learners from learning. Also, this system, which UML is applied to, makes efficient interaction possible through the module for the real-time exchange and management of messages even in the multi-user environment. Through this system, not only the simulation by learners can be made for experiments and practices, but also Questions and respondence can be supported on the procedure of experiments and the analysis of their results. This system is built on constructivism, and aimed at helping the learning progress and knowledge formation of learners.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.276-282
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• 2015

Until recently, power amplifiers using LDMOS were Class-AB and Doherty type, and showed 55 % efficiency for narrowband of 60 MHz bandwidth. However, owing to the RRH application of base stations power amplifier module, a bandwidth expansion of at least 100 MHz and high efficiency power amplifiers of at least 60 % power efficiency are required. In this study, a Class-J power amplifier was designed by optimizing an output matching circuit so that the second harmonic load will contain a pure reactance element only and have broadband characteristics by using GaN HEMT. The measurements showed that a 45 W Class-J power amplifier with a power added efficiency of 60~75 % was achieved when continuous wave signals were input at 1.6~2.3 GHz, including W-CDMA application.

• Health Policy and Management
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• v.27 no.4
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• pp.324-335
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• 2017

Background: The aim of this study is to analyze determinants of welfare attitudes toward healthcare services in South Korea, using three main theories: self-interest (positive welfare attitudes if the policy fulfills people's personal interests), symbolic attitudes (positive welfare attitudes if the person is politically progressive or egalitarian), and sociotropic perception (positive welfare attitudes if the person experienced positive aggregated collective experiences of societal events and trends regarding the policy). Although the definition of the welfare attitude is rather ambiguous in literatures, in this investigation, we operationalize the concept as the 'willingness to pay higher taxes to improve the level of health care services for all people in Korea' which shows individuals' actional propensity. Methods: We used the health module from the International Social Survey Program 2011 for the analysis (N= 1,391). Five logistic regression models were built successively using two variables for each theory to measure key concepts of self-interest, symbolic attitudes, and sociotropic perceptions as independent variables. Results: The result showed self-interest and symbolic attitudes factors to be strong determinants of welfare attitudes towards healthcare services in South Korea, whereas sociotropic perception factors have inconsistent effects. Conclusion: For a more politically elaborated healthcare reform in South Korea and elsewhere, there needs to be further research on various dimensions and determinants of welfare attitudes to understand popular basis of welfare expansion, especially in the era of inequality.

• 한국정보교육학회:학술대회논문집
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• 2010.08a
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• pp.59-66
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• 2010

Opensource LMS Moodle consists of module of various forms and can mount learning materials of various forms. We can mount the number of contents on the Web in Moodle. In doing so, We can configure effective courses for teaching-learning activity. Moodle can reflect course design of a wide variety of teacher using a variety of learning resources and learning activities. The results of operating during 1 semester, all faculty or students were satisfied with course using Moodle. Class in the classroom is interactive systems of teacher and students, but class has one-way system in reality. E-learning can be used to complement this phenomenon. Moodle gives a free and powerful features in designing e-learning courses. In this reserch we made up course applying typical teaching-learning of design and model the process of Glaser. We analyed teaching - learning activity case of Understanding and Application of Information science course of 2010year 1 semester in Seoul national University of Education using LMS Moodle and pursued future expansion plan of Moodle.

• Journal of Korea Multimedia Society
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• v.14 no.11
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• pp.1401-1408
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• 2011

This dissertation present a chip with Multi-Access Memory System(MAMS) and parallel processor for 16 Processing Elements of image processing purpose. MAMS is a kind of parallel access memory system and can simultaneously access to random pixel datas with eight types. It is possible to set a interval about pixel datas to access, too. The parallel processor built-in MAMS actually has been realized in 2003 but its performance fell short of a real time process for high-definition images. I designed a improved parallel processing system by means of addition and expansion of Memory Modules and Processing Elements of previous one. It is feasible to perform a Morphological Closing at the speed of 3 times of the previous one and 6 times of serial system.

• Journal of Digital Convergence
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• v.18 no.11
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• pp.207-214
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• 2020

This study analyzes the method for easily constructing a simple space in various environments. It also analyzes cases of modular prefab construction structures and explores various solutions and development directions that can form temporary residential spaces. This research intends to propose the diverse methods and solutions for constructing residential space for users' stable living environment in various unpredictable situations. This study amis to collect and analyze cases of various foreign patents related to the subject. With the analysis on the patents case, the prefab structures are mainly grouped into 4 types of 1) Assembly method using small parts, 2) Prefab module stacking method, 3) Space expansion method, and 4) Production methods of detailed elements. Based on the results, future research will inquire the lower cost and more efficient way of constructing prefab structure.