• Journal of Navigation and Port Research
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• v.40 no.3
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• pp.159-164
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• 2016

The goal of this study is to implement a communication system that can monitor the status of the nacelle using the power cable itself, without the dedicated communication lines such as an UTP cable and optical fiber for the offshore wind turbine. An inductive coupling powerline communication system for a MW class offshore wind turbine was proposed and its communication performance was demonstrated. The inductive couplers was designed for operation at up to 500 A using a ferrite composite materials. Field test was carried out on the wind farms of Jeju island. Using the iperf communication test program, we have obtained more than 15 Mbps data transmission rate through the 100 m power cable that was installed between the nacelle and the bottom of the power converter. In the data transmission stability test for a week, there was no failure ever. The minimum transmission rate was 15 Mbps and the average data rate was about 20 Mbps. Next, we have installed an infrared camera inside the nacelle in order to measure the temperature distribution and variation of the nacelle. The real-time thermal image taken by the camera was successfully sent to the monitoring system without error.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2641-2646
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• 2009

The more growing on home automation system at automatic control, the more efficiency required for energy consumption and for recycling energy in near future. Heating is essential in general apartment. Heating method is two types in apartment. One uses electricity, and other one uses warm water. If use electricity, is not efficient by rise of electric charges. But, It can reduce much in expense aspect, if use warm water. When use warm water, temperature of warm water is not equal from all pipe parts. Therefore, indoor tempera can be unequal with set point. Solution of these problems is as following. Temperature sensor in warm water attach pipe. The measured temperature transmits by real time. Temperature of warm water controls in receiver side. In this paper, we propose an automatic temperature transmission system for the heating pipe at home, that is a low-power based, and supply the energy source from a small AC motor resided in bottom cement mortal. The proposed system is used in power mechanism from a collision process of water-jet using propeller water-difference and also designed a CPU module by Atmega8 at ATMEL co., Inc. and a communication module by CC1020 at Chipcon co., Inc.

• Journal of Navigation and Port Research
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• v.38 no.5
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• pp.485-491
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• 2014

In this paper, it is proposed that the effects of simulator sickness due to scene movement in ship handling simulator can be measured by using center of pressure (COP) and a simulator sickness questionnaire (SSQ). For experiments of simulator sickness, twelve participants are exposed to scenes movement from ship handling simulator according to three steps of sea states. During experiments, COPs for subjects are measured by force plate. After exposure to scenes movement, subjects describe their sickness symptoms by answering the SSQ. Throughput analysing the results of scene movement, SSQ, and COP, the relation between the simulator sickness and COP is investigated. It is suggested that formulations for SSQ score and COP with respect to sea state are obtained by the curve fitting technique, and the longitudinal COP can be used for measuring the simulator sickness.

• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2294-2304
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• 1999

Our research purpose in this paper is to improve the performance of query processing in GIS(Geographic Information System) by enhancing the I/O performance exploiting parallel I/O and efficient disk access. By packing adjacent spatial data, which are very likely to be referenced concurrently, into one block or continuous disk blocks, the number of disk accesses and the disk access overhead for query processing can be decreased, and this eventually leads to the I/O time decrease. So, in this paper, we proposes EPR(Enhanced Parallel R-tree) indexing method which integrates the parallel I/O method of the previous Parallel R-tree method and a packing-based clustering method. The major characteristics of EPR method are as follows. First, EPR method arranges spatial data in the increasing order of proximity by using Hilbert space filling curve, and builds a packed R-tree by bottom-up manner. Second, with packing-based clustering in which arranged spatial data are clustered into continuous disk blocks, EPR method generates spatial data clusters. Third, EPR method distributes EPR index nodes and spatial data clusters on multiple disks through round-robin striping. Experimental results show that EPR method achieves up to 30% or more gains over PR method in query processing speed. In particular, the larger the size of disk blocks is and the smaller the size of spatial data objects is, the better the performance of query processing by EPR method is.

• Journal of Science Education
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• v.44 no.2
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• pp.225-239
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• 2020

This study aims to analyze the characteristics of reflective thoughts of students during experiments in general physics experiments. The participants were 32 college students, they submitted 10 experiment reports including answers to questions for reflective thinking. The results were as follows: First, students show reflective thinking broadly in the experiment, levels were followed by practical reflection, technical reflection, and critical reflection. Also, they actively accepted the knowledge related to experiments, but were passive in connecting new knowledge and experiences obtained through the experiments or forming new questions. Second, the reflective thinking of students show high correlation with experiments related to prior knowledge or the easy-to-understand process. Third, through the qualitative analysis of open-ended questions, it was confirmed that technical reflection occurs in individual evaluation, practical reflection in group evaluation, and practical reflection and critical reflection in improvement proposal. While the students' reflective thinking were superficial or mainly functional, however, they recursively examined the learning contents and the experimental process concurrently.

• Journal of the Korean association of regional geographers
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• v.4 no.1
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• pp.57-76
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• 1998

Yanji(延吉) city is the district seat of the Yanbian(延邊) Korean Autonomous District where is located in the Jilin(吉林) Province in China, and also the largest city with a population of three hundred sixty thousand, Since the mid-1980s, the inter-exchange and cooperation between Yanbian District and South Korea has been increased rapidly. That draw many scholars' attention to studying Yanbian District and Korean Chinese as a research theme for area studies. Unfortunately they neglect the study of the commerce and service industry in Yanbian city, which has indicated its rapid growth by the market economic policy of China, and an inter-exchange between Korean Chinese and Korean. The purpose of this study is to provide an information to many Korean potential investors for an investment strategy of the commerce and service industry in Yanji city. In order to do so, this study consists of three major steps. First of all. we analyzed the regional structure and locational characteristics of the commerce and service industry in Yanji City. Secondly, we investigated the characteristics of consumers behavior toward purchasing goods and service facilities. Finally, we supplied the proper businesses and location information for investment to Korean firms according to the results that identified above. In conclusion, we suggest that the proper businesses to invest are department store, retail clothing store, shoes store, cosmetics store, electronics and home appliances store, oversea branch offices of trading companies, Korean-style restaurant, hotel, nightclubs, Korean-style music room(Noraebang), travel agencies, beauty parlors, video rooms, electronic games, and so on. We also suggest that the proper locational areas to invest those businesses are the core area of the commerce and service industry in Yanji, where are Xinxing(新興) 3-zone and Jinxue(進學) 2-zone expressed in the Yanji city figure.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.405-414
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• 2008

When we evaluate slope stability, we regard the slope homogeneous and evaluate slope stability at the most dangerous portion of slope. However, since conditions and properties of rock mass/soil are different from one location to another within a single slope, slope stability evaluated by current concept can not represent slope correctly. This also result in over-reinforcement at the portion where reinforcement is not necessary. In order to solve these problems, we suggest a cell unit evaluation method in which we apply small rectangular cells in a slope and regard each cell as a single slope. In this method, slopes are classified into soil slope and rock slope depending on materials. Strength of rock, volumetric joint count, spacing of joints, condition of joints, ground water condition and so on are examined and SMR and condition index values are calculated. Finally, all data and results are presented as contour maps. We apply the cell unit evaluation method into 3 cut slopes. SMR values estimated by the new method are larger than those by current concept at most portions of slope, indicating that the new method suggested by this research represent slope stability more correctly than methods which were used. This method will prevent over-reinforcement at the portion of slope where reinforcement is not necessary.

• Journal of Elementary Mathematics Education in Korea
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• v.24 no.2
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• pp.187-205
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• 2020

The purpose of this study is to develop the elementary mathematics education program for the cultivation of humanistic imagination and characters through the link between mathematics and literature to find out its effectiveness. This study has verified the effectiveness of mathematics academic achievement, humanistic imagination and characters with the program development and preliminary program and application of this program for two years. After conducting classes on proportional expression and proportional distribution for 79 sixth-grade elementary school students (39 in the experimental class and 40 in the comparative class) in Seoul and Gyeonggi-do under this program, the researcher analyzed how the application of the program affects students' perception using pre- and post-examinations on mathematics academic achievement, humanistic imagination, and characters, including interviews with students, and analysis of outputs of the students. Studies have shown that the application of the elementary mathematics education program to foster humanities imagination and characters did not make any significant difference in mathematics academic achievement, and there were statistically significant differences in the subcategories of "reflection on life", "positive self-consciousness" and "humanistic imagination" categories, and there were no statistically significant differences in the "purpose of life" and "human relations" categories. However, the responses from the students' interviews showed that their perspectives of humans and the world has become wider and deeper. It also did not produce significant results for characters. As suggestions, the ministry should present the need to develop and distribute concerning materials for teachers, secure time for creative experience activities for convergence subjects, and operate practical and long-term training programs for teachers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.2
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• pp.123-136
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• 1996

A three-dimensional Galerkin-FEM model which can handle the temporal and spatial variation of density is presented. The hydrostatic approximation is used and density effects are included by means of conservation equation of heat and the equation of state. The finite difference grids are used in the horizontal plane and a set of linear-shape functions is used for the vertical expansion. The similarity transform is introduced to solve resultant matrix equations. The proposed model was first applied to the density-driven circulation in an idealized basin in the presence of the heat exchange between the air and the sea. The advection terms in the momentum equation were ignored, while the convection terms were retained in the heat equation. Coefficients of the vertical eddy viscosity and diffusivity were fixed to be constant. Calculation in a non-rotating idealized basin shows that the difference in heat capacity with depth gives rise to the horizontal gradient of temperature. Consequently, there is a steady new in the upper layer in the direction of increasing depth with compensatory counter flow .in the lower layer. With Coriolis force, geostrophic flow was predominant due to the balance between the pressure gradient and the Coriolis force. As a test in region of irregular topography, the model is applied to the Yellow Sea. Although the resultant flow was very complex, the character of the flow Showed to be geostrophic on the whole.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.353-360
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• 2010

The Kyunggi Bay in mid-west of Korea is a relatively large estuarine system that connects the Han River system with Yellow Sea. Due to macro-tidal range of more than 8 m, the urban estuary shows deep tidal channels and wide tidal flats. Since last 30 years, the coastal development is undergoing, yielding noticeable change in environment. Particularly the tidal flat dynamics are generally accepted as being related with tidal residual flows in this area (Kim et al., 2009). We have estimated the annual variation and vertical structure of residual currents with one-year long observed flows in two major tidal channels of Kyunggi Bay. The moving average method and tidal current harmonic analysis yield nearly the same results on residual flow. The residual flow in Jangbong channel ranges from 20 cm/s in summer to 30 cm/s in winter. It is noticeable that the residual flow in Jangbong channel is flood dominant throughout the year, while the flow in Seokmo channel is ebb-dominant residual flow with current speed range of 20-40 cm/s. Due to the baroclinic response of relatively shallow estuary, significant reduction of energy in bottom layers have been observed, indicating the importance of residual circulation to the tidal flat behavior.