• International Journal of Advanced Culture Technology
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• v.6 no.2
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• pp.80-85
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• 2018

In the 1990s, South Korea recently launched Space Development and is pushing for a step toward Space. In the Space Launch Vehicle field, the development of Practical satellite type Launch Vehicle (Korea Space Launch Vehicle II) has progressed to the stage of proprietary development, and in the field of Satellite development, they also have a great deal of competitiveness. This study will be a shortcut to rediscovering our potential and looking for breakthroughs by reviewing and re-examining the effects of past Space development.

• Journal of the Korean Data and Information Science Society
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• v.17 no.1
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• pp.141-147
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• 2006

BOK-X12-ARIMA has been developed by the Bank of Korea in order to accomodate special features such as lunar effect, labor day and election effect which are intrinsic in Korean seasonal time series. Irregular component resulting from BOK-X12-ARIMA is usually treated as white noise time series. If this shows dependency structure, it may be advisable to incorporate dependency in irregular component into prediction. This article illustrates how to refine point forecast using dependency structure in irregular component.

• Development and Reproduction
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• v.14 no.1
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• pp.21-25
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• 2010

Nile tilapia (Oreochromis niloticus) are mouth-brooders so that the females holding eggs in their mouth sacrifice their somatic growth for reproduction. For this reason, artificial control of reproduction for the culture of this species has been of interest. Manipulation of photoperiod is an emerging technique for such purpose, but little information is available to establish appropriate photoperiod regime. To obtain necessary basic information, sexually mature females were individually accommodated to glass aquarium, and the spawning activity of these females were monitored for two years under natural photoperiod regime. Female tilapia spawned most frequently on March, April and May when the day length gradually increased from 11 hours to 14 hours and least frequently on September, October, November and December when the day length gradually decreased from 13 hours to less than 10 hours in the first year. The decrease of spawning frequency as day length decreased was also observed in the second year, although the increase of spawning frequency as day length increased was less clear. Spawning of female tilapia was less active when the night was dark due to the disappearance of moonlight (Dark Phase), compared to the Phase of Getting Lighter, Light Phase and Phase of Getting Darker. Results from this study suggest that long day length, particularly increasing phase, is favoured for active spawning of Nile tilapia, and that this species, as a tropical fish species, may utilize changing lunar phases as a secondary environmental cue for reproduction.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.4
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• pp.693-703
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• 2017

Rover wheel's mobility depends on soil's condition and wheel's design. The purpose of this study is to evaluate the effect of soil conditions, which are Jumunjin sand and Korean lunar soil simulant (KLS-1), on wheel's motion performance. The experiments were performed by using a single wheel testbed with a wheel which grouser height is 15mm on Jumunjin sand and KLS-1, respectively. Also the influence of grouser length to wheel's mobility performance was studied. The experimental results of torque, drawbar pull and sinkage relating to slip ratio were discussed and analyzed to evaluate wheel's motion performance. Results showed wheel moving on KLS-1 has high performance than Jumunjin sand. Wheel's mobility performance was influenced by soil's properties of cohesion and frictional angle. In addition, wheel's performance of drawbar pull and Torque increased with the increasing of grouser length.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.78-89
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• 1995

We solved n-body problem about 9 planets, moon, and 4 minor planets with relativistic effect related to the basic equation of motion of the solar system. Perturbations including flgure potential of the earth and the moon and solid earth tidal effect were considered on this relativistic equation of motion. The orientations employed precession and nutation for the earth, and lunar libration model with Eckert's lunar libration model based on J2000.0 were used for the moon. Finally, we developed heliocentric ecliptic position and velocity of each planet using this software package named the SSEG (Solar System Ephemerides Generator) by long-term (more than 100 years) simulation on CRAY-2S super computer, through testing each subroutine on personal computer and short-time(within 800 dyas) running on SUN3/280 workstation. Epoch of input data JD2440400.5 were adopted in order to compare our results to the data archived from JPL's DE 200 by Standish and Newhall. Above equation of motion was integrated numerically having 1-day step-size interval through 40,000 days (about 110 years long) as total computing interval. We obtained high-precision ephemerides of the planets with maximum error, less $than\pm2\times10^{-8}AU(\approx\pm3km)$ compared with DE200 data (except for mars and moon).

• Journal of the East Asian Society of Dietary Life
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• v.5 no.1
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• pp.41-51
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• 1995

Bone mass accretion during puberty appears to be critical in the development of peak bone mass. Although bone density of females in Korea has been studied, only a few studies have related bone mass with anthropometric patterns or puberty in the pubescent girls. This study was conducted as part of a study of major determinants of bone development during puberty. Subjects were aged 14∼16 yr(mean 14.97), and had no history of disorders or dedication use likely to influence bone or calcium metabolism. Bone mineral density and content were measured by dual energy X-ray absorptiometry using a Lunar DPX+Scanner (Lunar Madison, WI). Also, total body fat, and total lean body mass were assessed using a Lunar DPX dual-energy X-ray absorptiometer, Pubertal status was assessed according to the Marshall and Tanner guidelines. Serum levels of osteocalcin was measured by RIA using a commercial kit assay. Skinfold measurements were taken with a skinfold caliper(Lange Caliper, USA). Data were analyzed using the regression and GLM procedure of the statistical package SAS. The results indicated that the observed means for lumbar spine BMD and femoral BMD correspond to approximately 91% and 96% of the means for young adult females, respec tively. All subjects were menarchal, with the majority being in the middle to end stages of pubertal development. Total body BMD was positively related to fat mass(P<0.001), lean body mass and time since menarche, and negatively related to urine pyridinoline, serum alkaline phosphatase and osteocalcin. The data indicate that girls who reported lower age for menarche had significantly higher bone densities than girls who reported higher age for menarche. Attaining peak skeletal bone mass during puberty may reduce the incidence of osteoporosis in later life. this finding suggests that early menarche may augment peak bone mass, influencing the extent of bone loss later in adulthood. The results suggest that good nutrition in childhood appears to be needed not for growth and development, but possibly also to assure an optimal peak of bone mass and thus greater latitude for the maintenance or skeletal integrity in the face of bone losses. Troeps skinfold thickness was a better predictor of total BMD and total BMC than was any other skinfold thickness. The study did not find a relationship between total BMD and body fat %, but total fat was significantly positively related to total BMD(r=0.49) and total BMC(r=0.60). It supports earlier report that there was a significant correlation between TBMD and body weight. Conclusively, total fat, lean body mass and pubertal development could influence BMD in pubescent girls. Clearly, longitudinal studies are required to assess the effect of puberty on peak bone mass, and to define further the potential determinants of peak bone mass.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.389-396
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• 2002

In XXI century it is necessary to expect the recommencement and development of activities on mastering the Moon. In the long term it is construction of manned lunar bases with industrial, astrophysical, procuring, repair equipment and services. Interplanetary flights from the Moon demand smaller power expenditures, than from the Earth, therefore it is favourable to use its surface for the construction of space-vehicle launching sites. Flights of devices in libration points in the system 'Earth - Moon' are considered. Experience of engineering system creation for the Moon displays the great complexity in provision of serviceability and reliability of friction units. Open friction units should operate under following conditions on the Moon: pressure of environment (vacuum) $p\;>10\;^{-10}$ Pa; wide range of temperature change $+150^{\circ}C\;...170^{\circ}C$; high evaporability of lubricants; influence of temperature gradients and warping of constructions; sublimation of elements of constructional materials; irradiation of different physical nature; effect of micrometeorites; reduced gravitation; influence of abrasive particles of lunar ground; requirements on minimization of size and weight characteristics of a construction (high tension); undesirability (impossibility) of application of liquid and plastic lubricants; vibration, shock, acoustic loadings during start and landings to the Earth; difficulties in repair-regenerative operations in conditions of the Moon etc. Adhesive interaction of conjugated surfaces is the principal reason of possible failures of rubbed units on the Moon. In the research of the Moon automatic interplanetary stations of 'Luna' (USSR), 'Surveyer', 'Apollo' (USA) series were used. Stations executed functions of flying, landing, artificial satellites of the Moon, moon-rovers and manned spacecrafts such as 'Apollo'. The experimental- theoretical researches carried out in the sixtieth years on tribology for conditions of the Moon appeared to be rather useful to engineering of an outer space exploration and the decision of complex problems for the friction units operating in extreme conditions on the Earth. For the creation of highly loaded friction units for the long service life on the Moon it is required not only to use accumulated experience and designed technologies, but also to carry out wide scientific research.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.12-22
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• 2016

Lidar-based hazard avoidance landing system for lunar lander calculates hazard cost with respect to the desired local landing area in order to identify hazard and designate safe landing point where the cost is minimum basically using slope and roughness of the landing area. In this case, if the parameters are only considered, chosen landing target can be designated near hazard threatening the lander. In order to solve this problem and select optimal safe landing point, hazard cost based on relative distance to hazard should not be considered as well as cost based on terrain parameters. In this paper, the effect of hazard cost based on relative distance to hazard on safe landing performance was analyzed and it was confirmed that landing site designation with two relative distances to hazard results in the best safe landing performance by an experiment using three-dimensional depth camera.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.5
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• pp.94-102
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• 2005

This paper performs analysis the load patterns for the all the special days and studies the change of the load patterns for the last 15 years using Expert system based on the load record and the weather condition record. The Expert system is one of the four major load forecasting methods of the power system And it is used for forecasting. loads of the special days based on the Know-how of the load forecasting Experts. After the author simulates the load forecasting using hourly relative factors of the load patterns based on the past load records, there is considerable improved effect. The average errors of past 5 days load forecasting of lunar New Year's Day (year 2002 and 2003) is $3.23{[\%]}$. Using the new method the author forecast loads of the lunar new year's days (the year 2005) and it shows only $1.78{[\%]}$ error. A field manual for the load forecast can be made using proposed method. The authors expect this article could give a guidance to those who wish to be load forecast expert.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.692-697
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• 1992

This study concerns about the orbit prediction and orbit determination of Korean future communication satellite, called "Moogunghwa", which will be motioned in the geo-stationary orbit. Perturbation effect on the satellite orbit due to nonspherical geopotential term, lunar and solar gravity, drag force of the atmosphere and solar radiation pressure was investigated. Cowell's method is used for orbit prediction. Orbit determination was performed by using EKF which is suitable for real-time orbit determination. The result shows that the characteristics of the satellite orbit has drift. So the periodic control time and control value in the view of the periodic of error can be provided. The orbit determination demonstrated the effectiveness since the convergence performance on the position and velocity error , and state error standard deviation is reasonable.easonable.