• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.355-372
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• 2006

Mission opportunities and trajectory characteristics for the future Korean Mars mission have designed and analyzed using KSIV-III(Korea Space Launch Vehicle-III). Korea's first space center, 'NARO space center' is selected as a launch site. For launch opportunities, year 2033 is investigated under considering the date of space center's completion with KSLV series development status. Optimal magnitude of various maneuvers, Trans Mars Injection (TMI) maneuver, Trajectory Correction Maneuver (TCM), Mars Orbit Insertion (MOI) maneuver and Orbit Trim Maneuver(OTM), which are required during the every Mars mission phases are computed with the formulation of nonlinear optimization problems using NPSOL software. Finally, mass budgets for upper stage (launcher for KSIV-III and spacecraft are derived using various optimized maneuver magnitudes. For results, daily launch window from NARO space center for successful Korean Mars mission is avaliable for next 27 minutes starting from Apr. 16. 2033. 12:17:26 (UTC). Maximum spacecraft gross mass which can delivered to Mars is about 206kg, with propellant mass of 109kg and structure mass of 97kg, when on board spacecraft thruster's Isp is assumed to have 290 sec. For upper stage, having structure ratio of 0.15 and Isp value of 280 sec, gross mass is about 1293kg with propellant mass of 1099kg and structure mass of 194kg. However, including 10% margins to computed optimal maneuver values, spacecraft gross mass is reduced to about 148kg with upper stage's mass of 1352kg. This work will give various insights, requiring performances to developing of KSIV-III and spacecraft design for future Korean Mars missions.

• 대한공업교육학회지
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• v.40 no.1
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• pp.121-141
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• 2015

The study applied a narrative inquiry to the undergraduate interdisciplinary course taught for three years(2012~2014). Narratively I have described interactions among teachers' and students' performing the interdisciplinary consilience course with various situations such as place, curriculum and class interaction. I have specifically illuminated a three-dimensional narrative inquiry space embracing the dilemma of the consilience curriculum, PBL(Problem Based Learning) and TBL(Team Based Learning), and an effective presentation. The result of the study is as follows: First, the ratio of giving lecture is high. The burden of doing project will be reduce if the teacher decreases the lecture up to one fourth, gives students enough time to finish their tasks, and gives them advice for a better project. Second, for opening the interdisciplinary consilience class maintaining previous college curriculum, each department has to put a 'consilience course' on the existing curriculum that allows teachers open the consilience course whenever they need to teach with other department teachers. Third, an effective teaching method using the PBL(Problem Based Learning) in Team Based Learning environment is making students to consider projects as problem situations to solve and to apply the problem situations to PBL method. Lastly, teachers should give students lots of opportunities for presenting what they have learned in the class. Three times of presentation as a team member is ideal in a semester but the way of presenting has to be changed. The students in next year will relieve the tension of 30 minute instead of 15 minute, two days instead of one day for the team presentation.

• Archives of design research
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• v.16 no.3
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• pp.319-328
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• 2003

The purpose of this study was to investigate the actual size of tables and chairs in small restaurants. The examined objets were 48 restaurants serving flour-based, korean style and japanese style meals. Those restaurants are currently being operated at six universities in Seoul, and their sizes are limited under $66m^2$. The results of this study were as follows ; 1 . In small restaurants, the size of the seat for one person is $0.346m^2$on the average. The range of the size starts from $0.285m^2$to $0.403m^2$, showing a great difference. 2. The most common size of tables in small restaurants is the oblong style of $600{\times}900$ for four people. The smallest size is $440{\times}710$, while the biggest one is $700{\times}1000$, showing a great number of variation. If the most common size of tables is set to be the general size of tables in small restaurants, it will be $600{\times}900$. 3. The sizes of the seats for chairs used in small restaurants start from $270{\times}270$ to $430{\times}430$. The most common size of the seats for chairs is $400{\times}400$, only showing a small number. For the cases of tables with the most common size of $600{\times}900$, the width of the seats for chairs should be under 400. 4. For the height between the table and the seats of the chair, the distance from 270 to 300 is relevant. However, according to the results of the investigation, it seems that there are more cases of the distance from 250 to 260 than that from 270 to 300.

• Fire Science and Engineering
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• v.26 no.6
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• pp.15-23
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• 2012

Indirect Test Method is often used instead of direct test method in test method for extinguishing performance of $CO_2$ extinguishing facility because of high cost, environment problems and difficulties of procedure. But in the danger facilities for a unit of nation, such as a petrochemical plant, a nuclear power plant, or etc. is better to verify the performance of the extinguishment through direct discharge test. In $CO_2$ extinguishing system for total flooding system installed in dangerous facilities in Korea, each protected area in surface fire and deep-seated fire had selected and verified of extinguishing performance of $CO_2$ extinguishing facilities. To get recognized as extinguishing performance, discharged $CO_2$ concentration to protected area should be equivalence with design concentration standards (NFSC and NFPA). The Design Concentration means that $CO_2$ extinguishing agent is considerate of concentration for percentage of allowance (20 %) from extinguishing concentration which available to control of flame. As test result, surface fire and deep seated fire in protected area is obtained $CO_2$ design concentration and maintained design concentration more than 20 minutes as deep-seated fire. Through this study, we introduced direct discharging test method and decision method. And furthermore, especially in the dangerous facilities as a unit of Nation, we suggested necessity about reliability of extinguishing facilities to use direct test method.

• Journal of Korean Society of Forest Science
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• v.87 no.1
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• pp.82-89
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• 1998

This study was carried out to investigate working time, performance, and to predict performance that related to the factor of forest road in earth work using excavator. It was found that the real working time was 503 minutes in a day. The ratio of real working time and allowance per total working time was approximately 85.7% and 14.3% individually. The rate of soil movement(Sm) to net working time was 38.6%, and earth cutting(Ec) was 32.5%. According to performance analysis, performance of earth work using excavator($0.8m^3$) in straight part was 1.4 times larger than curve part and rock work using excavator($0.8m^3$) which had breaker in straight was 9.1 times larger than earth work using excavator($0.8m^3$) which had bucket. Performance of earth work using excavator($1.0m^3$) was 1.3 times larger than using excavator($0.8m^3$) in straight and curve part. Working performance in earth work using excavator($0.8m^3$) was influenced by the conditions of radius of curve, width of roadway, slope gradient. It is not influenced by diameter and number of root stock.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.239-249
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• 2019

Recently, the Korean government has implemented a policy to expand renewable energy sources. Large-scale PV systems are being actively interconnected with the distribution system. On the other hand, when a large-scale PV system is installed and operated, the customer voltages could violate the allowable voltage limit due to reverse power flow of the PV system. To overcome these problems, an enhancement method for hosting the capacity of the PV system in a distribution system is being actively conducted. Therefore, to improve the hosting capacity of the PV system, this paper proposes a model of a reconfiguration of the distribution system, which is composed of three sections and three connections based on PSCAD/EMTDC S/W, and proposes an evaluation algorithm for the feeder reconfiguration to maximize an adaption of the PV system. In addition, this paper presents the optimal method of the feeder reconfiguration section to evaluate the maximum capacity of the PV system to keep customer voltages within the allowable voltage limits based on various operation scenarios, such as the capacity of a PV system and section of feeder reconfiguration. From the simulation results based on the PSCAD/EMTDC modeling and evaluation algorithm, it was confirmed that they are a useful and practical tool to enhance hosting the capacity of a PV system in a distribution system.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.24-32
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• 2017

In this paper, a low power 4th order delta-sigma modulator was designed with a high resolution of 12 bits or more for the biological signal processing. Using time-interleaving technique, 4th order delta-sigma modulator was designed with one operational amplifier. So power consumption can be reduced to 1/4 than a conventional structure. To operate stably in the big difference between the two capacitor for kT/C noise and chip size, the variable-stage amplifier was designed. In the first phase and second phase, the operational amplifier is operating in a 2-stage. In the third and fourth phase, the operational amplifier is operating in a 1-stage. This was significantly improved the stability of the modulator because the phase margin exists within 60~90deg. The proposed delta-sigma modulator is designed in a standard $0.18{\mu}m$ CMOS n-well 1 poly 6 Metal technology and dissipates the power of $354{\mu}W$ with supply voltage of 1.8V. The ENOB of 11.8bit and SNDR of 72.8dB at 250Hz input frequency and 256kHz sampling frequency. From measurement results FOM1 is calculated to 49.6pJ/step and FOM2 is calculated to 154.5dB.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.193-201
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• 2014

This study provided safe sailing speed and appropriate passing time to areas of known strong current water to prevent marine accident of the ships. To the interpretation of these data which target Myeongnyang waterway, AIS data of the ship was collected from $12^{th}$ July to $15^{th}$ July 2010 and site environment was investigated on $4^{th}$ September 2010. On the basis of the collected data, the 'Minimum Navigation Speed' and 'Optimum Navigation Speed' were calculated. It has also considered the 'Spare control force' or allowance and the 'Respond Rudder Angle' for each tidal current speed. Additionally, it suggested the safe passing time to strong current area by analyzing tidal level and tidal current speed. The conclusion of the research are as follows : (1) If the flow rate is greater than 4.4 kn, it is difficult for the model ship to control herself by her own steering power and to cope with tidal current pressure force and yaw moment caused by the tidal current.. (2) The minimum navigation speed should be over 2.3 times the tidal current and the optimum navigation speed should be over 4.0 times the tidal current. (3) When spring tide, the optimum passing time at Myeongnyang waterway is between 30 minutes to 1 hour before the time of high/low water, and at 5 hours after high/low water, passing of ships should be avoided because it is time when the flow rate is over 4 kn.

• 한국노년학
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• v.30 no.3
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• pp.683-694
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• 2010

This study was to investigate the effects of aquarobics exercise on body composition, fitness and health related quality of life (sf-36) in elderly women and to provide basic data to exercise prescription. The subjects were the 60~70 years old seniors who participated in exercise program at health promotion center and had been divided into exercise(N=25) and control(N=30) group, respectively. Aquarobics exercise was performed twice per week for 8 weeks at 40~70% heart rate reserve(exercise intensity) and body composition, fitness and SF-36 were measured before and after exercise. In body composition, there were significance in weight(p=0.044), body mass index(p=0.038), and %fat(p=0.005) between groups before and after. In fitness, there were no significance in fitness such as chair stand, and chair sit and reach, but there were significance in 2-minute step(p<0.001), arm curl(p=0.005), back scratch(p=0.023), and 8-ft up and go(p<0.001) between groups. In SF-36, there were no significance in physical functioning, role limitation-physical, role limitation-emotional, social functioning, mental health, and vitality, but there were significance in bodily pain(p=0.039), and general health(p=0.024) between groups. It was found that aquarobics exercise was one of the good exercise types for the elderly to improve body composition and fitness. Also, there was positive effect on health-related quality of life partially.

• Journal of agricultural medicine and community health
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• v.20 no.2
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• pp.133-148
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• 1995

This study was to identify the factors affecting the performance in health promoting lifestyle and measuring health promoting lifestyle. The subjects for this study were all adult in rural area, Kakbuk Nyun, Chung-do Gun, Kyungpook, Korea. The data were collected during the period from April 1 to April 30, 1995. The instruments used for this study were the health promoting lifestyle by Park(1995). The results of this study are as follows. Health condition felt by the subjects was worse in female group and was getting worse according as the age increase. According to health promoting life style implementation questionnaire, more than half of the subjects responded "never" in deep breathing 3 times a day item and non-smoking item; more than half of the subjects responded "yes" in 3 meal a day item, home-cooked meals item, never to omit breakfast item and frequent wearing of cotton underwear item. Health promoting life style implementation by health condition is higher in healthy group and frequency of consulting a specialist is higher in unhealthy group. Health promoting life style implementation by sex is higher in male group. Frequency, of consulting a specialist and non-excessive drinking are higher in female group. Health promoting life style implementation by age showed that the implementation of never omitting breakfast, keeping early hours and proper sleeping is higher in old age group ; that of enjoying hobby, pastime, cleaning as well as reading health books is higher in young age group. Health promoting life style implementation by religion showed that the implementation of deep breathing 3 times more a day, regular checking of blood pressure, never having non-healthful food and keeping right posture in sitting and standing is higher in religion group. Health promoting life style implementation by education is higher in highly-educated group ; the implementation of keeping early hours is higher in low-educated group. Health promoting life style implementation by marriage state showed that the implementation of deep breathing 3 times more a day, twenty minutes of brisk physical movement three or four times a week, enjoying his or her own time, relaxation to relieve from tension and pressure and equalized movement of each part of body is higher in unmarred group ; that of having elaborately cooked food, never omitting three meals a day and keeping early hours is higher in married group. Health promoting life style implementation by the number of family members showed that more-member-group has more plans and objectives for their future. Health promoting life style implementation by family type showed that the implementation of reading health books and articles, living with positive way of thinking and enjoying favorite hobby in pastime is higher in nuclear families ; that of having three meals a day never omitting breakfast is higher in large families.