• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.3
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• pp.179-187
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• 2005

This study was conducted in order to the experiment of bottom trawl fisheries in the sea mount of central northern pacific($30^{\circ}-40^{\circ}N$, $170^{\circ}-175^{\circ}E$), during the period of July 1 to August 25, 2004 by commercial trawl ship. Fishing experiment was carried out by bottom trawl, with the codend of 110mm mesh size. The number of 101 test fishing was done in the sea mount of central northern pacific during 56 days and the total catches were 198,593kg as 18 fish species, and CPUE/day and catches/day were 8.3 hours towing time and 3,546kg. Catch ratio according to each fishing ground was higher with the order of B, C, and E, and catches for B was 7,171.0kg during the towing time of 13.2 hours. Main target species were Pseudopentaceros richardsoni and Beryx splendens, there was 14.9% of damage ratio for fishing gears on catching the target fishes inhabiting on the rough sea bottom. Catches by water depth was the order of 300m below, 301-350m, 451-500m and 351-400m. It is thought that there was no problem on the mesh size because most of fishes caught from the experimental fishing was 30cm over.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.1
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• pp.20-30
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• 1982

Recent diesel engine has achieved high speed running comparable to that of gasoline engine as a speed improvement effort. Consequently, torsional vibration of high-speed diesel engine induced vibration nosise, reduced horsepower and the like. Viscous damper which is thought to be effective in curtailing the torsional vibration was studied over a wide range of speed. In this investigation, a water cooling, 4-cycle high-speed diesel engine(Msx. 3500 rpm)was used for the study. Theoretical analysis was made by assuming the engine to be an ideal equivalent system(length, moment of inertia) i. e. the multi-degree of freedom equivalent torsional vibration system with damper was analyzed. In the analysis, the inertia moment of suitable damper for this experiment was calculated by varying the relative damping coefficient of damper of engine for each damper. Furthermore, in the torsional vibration experiment, the torsional vibration amplitude of the crankshaft system was measured when the engine was equipped with dampers of different moments of inertia and also when the engine was equipped without dampers. The experimental results were compared with the analytical values and were found to be satisfied. The results of this investigation are summarized below; (1) It was found that for the engine equipped with dampers, the torsional vibration amplitude was reduced to about one third of those without dampers. (2) The optimum value of inertia moment of viscous damper for the engine was found to be about Id=1.05(kg.cm.s$^{2}$) (3) The optimum damping coefficient and the ratio of moment of inertia for the engine were found to be about Ca= 850(kg.cm.s), Rd=0.509, respectively (b1 dapmper).

• Journal of the Korean Society of Earth Science Education
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• v.5 no.1
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• pp.75-87
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• 2012

The purpose of this study is to find out the effects of internet resource-based problem-based learning on the academic achievement in science and the attitude toward science of elementary school students. One experiment class and one control class of grade 6 students were selected to perform a prior investigation on the academic achievement in science and the attitude toward science, then the experiment class attended 4 weeks of lessons that was applied the internet resource-based problem-based learning, and the control class attended the traditional lessons based on the guidelines of teachers. After conducting lessons, a post investigation was performed for each class and the results were analyzed to produce the following conclusions. First, the internet resource-based problem-based learning could be seen to be effective in improving the students' academic achievements in science. The internet resource-based problem-based learning seemed to make students recognize the lesson details better and grasp well the questions given during lessons from the process of finding solutions among many informations and data on the internet. Second, the internet resource-based problem-based learning had a positive effect on all attitudes' areas toward science of students. It looked like that the internet resource-based problem-based learning taught the students to use the internet resources and gave them a friendly feeling, so the children could actively participate in class and had positive recognition on science. Third, from teacher observation and the result of the student recognition investigation, we could know that the students showed lots of interests in the internet resource-based problem-based learning, and they were able to understand the scientific theories in the process of solving problems that were relevant to real life, and thought science in a positive way.

• Journal of The Korean Association For Science Education
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• v.24 no.5
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• pp.886-901
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• 2004

The purpose of this study was to document the changes in astronomical concepts for preservice and inservice elementary school teachers after being presented with the newly devised Earth Motions Centric Solar System Model. The subjects of the study were 31 preservice and 30 inservice elementary schools teachers in the Jeonbuk Province. First, the author investigated the naive theories of the subjects, and then, compared that data to the data obtained after their exposure to the model. The total number of items on the instrument for this study was 10. These items included questions about the motion of interior planets, the phases and sizes of interior planets, and the motion of exterior planets and comets. After analyzing the answers to the items before the experiment, the author was able to confirm the existence of the naive theories regarding astronomical phenomena. Also, after the experiment, the author was able to observe the conceptual change in thought of the preservice and inservice elementary school teachers. Results showed that learning through the new model had positive effects on the preservice and inservice elementary school teachers' conceptualization of the interior planets' motion, phases and sizes, and the exterior planets' motion.

• Journal of the Korea Safety Management & Science
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• v.16 no.4
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• pp.371-378
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• 2014

Manual materials handling tasks are the main risk factors for the work-related musculoskeletal disorders. Many assistant tools for manual materials handling are being used in various kind of industries. One of them is a 4-wheeled cart which is widely used in manufacturing factories, hospitals, etc. The major force required to control the 4-wheeled cart is pushing and pulling. There are two types of handles being used for the 4-wheeled cart : vertical type (two vertical handles), and horizontal type (one horizontal handle). This study tried to investigate the pushing forces and subjective discomforts (hand/writst, shoulder, low back, and overall) of the two handle types with different handle height and distance conditions. Twelve healthy male students (mean age = 23.4 years) participated in the experiment. The independent variables were handle angle (horizontal, vertical), handle height (low, medium, high), and handle distance (narrow, medium, wide). The full factorial design was used for the experiment and the maximum pushing forces were measured in 18 different conditions ($2{\times}3{\times}3$). Analysis of variance (ANOVA) procedure was conducted to test the effects of the independent variables on the pushing force and discomfort levels. Handle height and angle were found to be the critical design factors that affect the maximal pushing forces and subjective discomfort. In the middle height, subjects exerted higher pushing forces, and experience lower discomfort levels compared to the high, and low height. There was no statistical influence of the handle distance to the pushing forces and subjective discomfort levels. It was found out that the effects of the handle angle (horizontal and vertical) on both pushing force and subjective discomfort were statistically significant (p < 0.05). The vertical handle revealed higher pushing force and lower discomfort level than the horizontal handle. The reason for that was thought to be the different postures of the hand when grasping the handles. The horizontal handle induced pronaton of the hand and made hand posture more deviated from the neutral position.

• Journal of Veterinary Clinics
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• v.22 no.3
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• pp.206-213
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• 2005

This experiment was conducted to find out the therapeutic effect of Artemisia capillaris extracts on hepatic damage in rats induced by carbon tetrachloride ($CCl_{4}$). In this experiment, 96 Sprague-Dawley rats were used as experimental groups, which were divided into 4 groups; control group(A), $CCl_{4}$-treated group(B), $CCl_{4}$+Artemisia extract-treated group(C) and $CCl_{4}$+silymarin-treated group(D). The B, C, D group were administrated single dose of $CCl_{4}$(2.5 ml/kg) to induce acute hepatic injury. C group was administrated with Artemisia capillaris extract(200 mg/kg/day) and D group treated with silymarin(50 mg/kg/day) for 7 days. Hematological, ultrasonographical, histological examinations and examination of antioxidant activity were also performed in all groups. AST and ALT activities of C group were significantly decreased compared with B group. The activities of AST and ALT in C and D groups returned to the normal range more rapidly than those of B group. In ultrasonographic examination, the echogenicity of liver in C group was significantly decreased compared with B group. Also C and D group had tended to recover faster than B group on liver histogram. Histologically, the percentage of degenerative regions and degenerative cell numbers in peri-central vein hepatic parenchyma of C and D group were significantly decreased compared with B group. In examination of lipid peroxidation, malondialdehyde of hepatic tissue in C group was decreased as compared with B group. In examination of antioxidant enzyme activity in liver, glutathione peroxidase and catalase activities were significantly increased compared with B group. As results of this study, it is thought that A. capillaris extract has therapeutic effects on hepatic injury induced by carbon tetrachloride, and has the similar therapeutic effects as silymarin in rats.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.4
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• pp.39-50
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• 2002

Field experiment was performed to investigate water and nutrient mass balances in paddy field with groundwater irrigation from May to October, 2001. The total water inflow was about 1,183mm in which rainfall, overflow from upstream paddy, and groundwater irrigation accounted for 43, 30, and 27%, respectively. Notice that the precipitation of the study period was less than the average annual precipitation. The total drainage was almost balanced with the inflow and more than half of it was occurred by surface drainage. From the nutrient mass balance analysis, the T-P output (17.56kg/ha) was estimated slightly lower than the input (20.90kg/ha) and the T-N output (130.41kg/ha) was slightly greater than the input(129.24kg/ha). However, the difference was within the expectation and the nutrient mass was thought to be balanced considering uncertainties in field experiment and other activities not included in the study such as algae and soil microorganisms. The surface discharge of nutrient, which was about 10% of total nutrient output, was mainly affected by fertilization and rainfall runoff. Therefore, prudent surface drainage plan might be necessary particularly for the fertilization period to prevent degradation of receiving water quality. The study was performed under abnormally low rainfall compared to the average annual rainfall record, and further monitoring in diverse rainfalls and irrigation methods is recommended to estimate nutrient behavior in the paddy field more reasonably.

• Journal of the Ergonomics Society of Korea
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• v.30 no.5
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• pp.621-628
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• 2011

Objective: The aim of this study is to give interest about usability of cellular phone keypad for left-handed person. Background: Although there are being a lot of attempts to design suitable product on user's request in process that design cellular phone keypad, ergonomic access about left-handed person who compose decimal class is unprepared. Especially, in early user's occasion, left-handed persons need more efforts than right-handed person to master Hangul character input process skill level. But, since realization about this left-handed person's discomfort has not spread, the importance has not been well thought in the society. Method: (1) After extracting emblem to use in comparison in questionnaire, applied emblem uniformly to different 3 kind of cellular phone. (2) Measured Hangul input time and mistyping number by dominant hand's position and skill level to reagent. (3) Taking the result through ANOVA. Conclusion: In the result of the experiment about Hangul input time and mistyping number according to dominant hand's position and skill level, left-handed person's group on the low skill level has shown the dullest use capability among 4 experiment groups. Application: In the future, analysis result may be used to the data of realization conversion in process design of various products including cellular phone keypad to consider left-handed person.

• Journal of the Korea Convergence Society
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• v.12 no.12
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• pp.49-57
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• 2021

With the advent of the era of the fourth industry, more and more scientific techniques are being used to solve decision-making problems. In particular, big data analysis technology is developing as it becomes easier to collect numerical data. Therefore, in this study, in order to overcome the limitations of qualitatively analyzing investment trends, the association of various products was analyzed using associated analysis techniques. For the experiment, two experimental periods were divided based on the COVID-19 economic crisis, and sales information from individuals, institutions, and foreign investors was collected, and related analysis algorithms were implemented through r software. As a result of the experiment, institutions and foreigners recently invested in the KOSPI and KOSDAQ markets and bought futures and products such as ETF. Individuals purchased ETN and ETF products together, which is presumed to be the result of the recent great interest in sector investment. In addition, after COVID-19, all investors tended to be passive in investing in high-risk products of futures and options. This paper is thought to be a useful reference for product sales and product design in the financial field.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.216-222
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• 2021

This is an experiment to complement new ways of using concentrated water discharged from the seawater desalination plant. In this study, metakaolin, which has excellent chloride ion immobilization effect, was used as the main binder, and 10% and 20% of calcium oxide were substituted with the activator. In addition, tap-water(TW) and reverse osmosis brine water(RW) were used as mixed water. As a result of the experiment, the mixture using RW showed higher compressive strength than TW. It also showed low water absorption and high density. In the mixture using RW as mixed water, a hydration reaction substance called Friedel's salt could be observed. Considering the corrosion problem of steel, RW is considered to be applicable to products such as non-reinforced concrete, brick, and curb stone. Through this study, it is thought that it is meaningful to propose a new application method other than the ocean release of RW.