• Journal of Astronomy and Space Sciences
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• v.8 no.2
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• pp.141-148
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• 1991

In order to obtain a complete picture of the time dependent dynamic of 360 fragments in space, the program IODS (ISSA Orbit Determination System) has been set up. Using The program IODS, all fragments orbits of one break-up event can be generated. Perturbations due to the Earth's asymmetrical potential, the Sun, moon, air drag and solar radiation force are considered. We summarize our results as follows : I) Due to J2 term, precessional motion of all fragment orbits are (수식생략) ii) The other perturbations have very small effects.

• Journal of Korean Society for Quality Management
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• v.24 no.2
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• pp.54-64
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• 1996

The inspection policy and inspection error are very critical factors which influence the outgoing quality. In other words, such factors influence the acceptance rate of the incoming matarials. Hence, the outgoing lot size is varied. This paper presents a method to compute the break-even point(pb1, pb2) under these two factors, which canbe used to determine the economic acceptance inspection type.

• Journal of Korea Multimedia Society
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• v.25 no.5
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• pp.739-747
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• 2022

In this study, the effect of augmented reality subtitle content on users was investigated by using a subjective evaluation method and a statistical approach. The human factor was defined as subtitle position and font size. Then, we analyzed the effects of the defined factors on human eye comfort and visibility. Ten participants conducted related survey evaluation tasks with a 1-minute break after viewing the content for 3 minutes.

• Journal of Educational Research in Mathematics
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• v.22 no.4
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• pp.445-458
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• 2012

Current textbooks may provide students and teachers with three improper notions related to the quotient and the remainder in division for decimal numbers as in the following. First, only the calculated results in (natural numbers)${\div}$(natural numbers) is the quotient. Second, when the quotient and the remainder are obtained in division for decimal numbers, the quotient is natural number and the remainder is unique. Third, only when the quotient cannot be divided exactly, the quotient can be rounded off. These can affect students and teachers on their notions of division for decimal numbers, so improvements are needed for to break it. For these improvements, the following measures are required. First, in the curriculum guidebook, the meaning of the quotient and the remainder in division for decimal numbers should be presented clearly, for preventing the possibility of the construction of such improper notions. Second, examples, problems, and the like should be presented in the textbooks enough to break such improper notions. Third, the didactical intention should be presented clearly with respect to the quotient and the remainder in division for decimal numbers in teacher's manual.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.49-55
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• 2017

In the seventies, a number of researchers carried out experiments on pullout tests with prototype equipment, and the pullout test was certified as a reliable nondestructive testing(NDT) method for determining the strength of concrete. To estimate the strength of high-strength concrete, we propose a simplified pullout test that uses as a break-off bolt a standard 10mm bolt with a groove on the shaft, an insert nut, and a pullout instrument that includes a hydraulic oil pump without a load cell. To verify the advantages of the simplified pullout test(low cost, simplicity, and convenience), four wall specimens were tested with two levels of concrete strength, 30 MPa and 50 MPa, using a simplified pullout tester with a load cell. The pullout load and concrete compressive strength were measured every day until day 7, day 14, day 21 and day 28. It was found that the pullout load was very similar to the compressive strength. Therefore, we have verified that a simplified pullout test can be used to evaluate the in-place strength of high-strength concrete in structures. The prediction equation of the groove diameter of the break-off bolt(y) with the concrete strength(x) was derived as y=0.05x+3.79, with a coefficient of determination of 0.88 found through regression analysis.

• International Journal of Industrial Entomology and Biomaterials
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• v.28 no.2
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• pp.58-65
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• 2014

Bumblebees are important pollinators of crops and wildflowers. Bumblebees generally produce one generation per year. One of the key stages for year-round rearing of bumblebees is breaking diapause. To evaluate the effects of a combination method of $CO_2$-narcosis and cold treatment to break the diapause of B. ignitus and B. terrestris queens, we determined whether this method affected their ability to establish a colony after the diapause break. The diapause treatment regimes that were utilized were $CO_2$ ($CO_2$-narcosis), CT-1M (cold treatment at $5^{\circ}C$ for 1 mo), CT-1M-$CO_2$ ($CO_2$-narcosis after cold treatment for 1 mo), CT-2M-$CO_2$ ($CO_2$-narcosis after cold treatment for 2 mo), CT-2M (cold treatment for 2 mo), CT-2.5M-$CO_2$ ($CO_2$-narcosis after cold treatment for 2.5 mo) and CT-2.5M (cold treatment at $5^{\circ}C$ for 2.5 mo). In view of the effects on the colony developmental characteristics of B. ignitus queens, the most favorable diapause treatment was CT-1M-$CO_2$. A combination method of $CO_2$-narcosis and cold temperature treatment yielded better results than that of single $CO_2$-narcosis or cold temperature treatment on the colony development of diapause-broken B. ignitus queens. In the case of B. terrestris queens, we concluded that a combination method of $CO_2$ and cold temperature treatment yielded better results than that of a single cold-temperature (up to 2 mo) treatment. In conclusion, the findings of the present study indicated that the combined application of $CO_2$ and cold temperature was a favorable method for the colony development of diapause-broken B. ignitus and B. terrestris queens compared with only $CO_2$-narcosis or cold temperature treatments. A combination method of $CO_2$ and cold treatment reduced the side effect of $CO_2$-narcosis and shortened the duration of cold treatment by at least 1 mo.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.433-447
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• 2023

There is a growing demand for the stability of existing dams due to abnormal climate and the aging of dams. Emergency Action Plans (EAPs) for reservoir or dam failure only consider a single rainfall event. Therefore, this study simulates dam failure caused by continuous rainfall events, and proposes the establishment of EAP by selecting the optimal shelters. We define a mega rainfall event scenario caused by continuous rainfall events with 500-year frequency in the Chungju Dam watershed and estimate the mega flood. The mega flood event scenario is divided into two cases: scenario A represents the flooding case caused by discharge release from a dam, while scenario B is the case of a dam break. As a result of flood inundation analysis, the flooded damage area by the scenario A is 50.06 km² and the area by the scenario B is 6.1 times of scenario A (307.45 km²). We select optimal shelters for each administrative region in the city of Chungju, which has the highest inundation rate in the urban area. Seven shelter evaluation indicators from domestic and foreign shelter selection criteria are chosen, and Analytical Hierarchy Process (AHP) method is used to evaluate the alternatives. As a result of the optimal shelter selection, the six shelters are selected and five are schools. This study considers continuous rainfall events for inundation analysis and selection of optimal shelters. Also, the results of this study could be used as a reference for establishment of the EAP.

• Nuclear Engineering and Technology
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• v.35 no.5
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• pp.426-441
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• 2003

A reactor inlet header break experiment, B9401, performed in the RD-14M multi channel test facility was analyzed using RELAP5/MOD3.2 and RELAP5/CANDU[1]. The RELAP5 has been developed for the use in the analysis of the transient behavior of the pressurized water reactor. A recent study showed that the RELAP5 could be feasible even for the simulation of the thermal hydraulic behavior of CANDU reactors. However, some deficiencies in the prediction of fuel sheath temperature and transient behavior in athe headers were identified in the RELAP5 assessments. The RELAP5/CANDU has been developing to resolve the deficiencies in the RELAP5 and to improve the predictability of the thermal-hydraulic behaviors of the CANDU reactors. In the RELAP5/CANDU, critical heat flux model, horizontal flow regime map, heat transfer model in horizontal channel, etc. were modified or added to the RELAP5/MOD3.2. This study aims to identify the applicability of both codes, in particular, in the multi-channel simulation of the CANDU reactors. The RELAP5/MOD3.2 and the RELAP5/CANDU analyses demonstrate the code's capability to predict reasonably the major phenomena occurred during the transient. The thermal-hydraulic behaviors of both codes are almost identical, however, the RELAP5/CANDU predicts better the heater sheath temperature than the RELAP5/MOD3.2. Pressure differences between headers govern the flow characteristics through the heated sections, particularly after the ECI. In determining header pressure, there are many uncertainties arisen from the complicated effects including steady state pressure distribution. Therefore, it would be concluded that further works are required to reduce these uncertainties, and consequently predict appropriately thermal-hydraulic behaviors in the reactor coolant system during LOCA analyses.

• Journal of Biosystems Engineering
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• v.28 no.3
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• pp.199-208
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• 2003

In order to solve the shortage of roughage supply for dairy farm in Korea, winter cereal forage production after harvesting of rice in the fallow paddy field is studied. This study consist of two parts. One is the model development of the mechanized production which was already reported at the preview paper. This is the 2nd parts of the study. Also, the mechanized production model for cereal forage production in winter was reported in the previous study. In this paper, coverage area and mechanized wrap silge production cost are analyzed and compared to the other available feeds in Korea. Results of the research are summarized as follows; The coverage area for the winter cereal wrap silage production system in Korea is estimated to be 33.7 ha in case of working with a tractor and a set of implements. If two or three tractors are available, the coverage area is estimated to be 68.0 and 101.3 ha, respectively. The break even point (BEP) of the farming size is analyzed as 10 ha and its production(operating) cost is estimated to be 317 to 443 won/TDN-kg at the BEP point. The cost is lowered to 182 won/TDN-kg at 100ha-working, and is much lower compared with prices of imported feeds of 360∼600 won/TDN-kg. Therefore, winter cereal wrap silage model is judged to be feasible and desirable for a large scale production of forage in winter fallow paddy field.

• Korean Journal of Animal Reproduction
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• v.17 no.2
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• pp.75-83
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• 1993

Purine has been identified in the preparation of follicular fluid and shown an activity in maintaining oocyte meiotic arrest. Therefore this study was performed to examine the inhibitory effect of purine on germinal vesicle break down(GVBD) in the presence and absence of human fetal cord serum(HFCS) or human mature follicular fluid(HMFF), as a protein source, in vitro culture. Immature oocytes(GV stage) were collected from ovaries of 21∼28 days old ICR mice by puncturing the antral follicles with a fine needle, at 48 hrs after PMSG injection. Some of the oocytes were denuded by drawing the cumulus-enclosed(complex) oocytes in and out of a pasteur pipet. Complex oocytes and denuded oocytes were cultured 3 hrs. in T6 media containing 0.75mM adenosine or/and 4mM hypoxanthine, with HFCS or HMFF. Their GVBD rates were observed at every 1 hr. during the culture time. Both adenosine and hypoxanthine have shown a time-dependent inhibitory effect on GVBD in complex and denuded oocytes and the inhibitory effect was maximized in culture medium containing hypoxanthine and adenosine. HFCS and HMFF increased the GVBD rates in the presence of the purines, thus HFCS and HMFF may contain a factor that could reverse the inhibitory effect of purines. Also complex oocytes were more sensitive to not only the inhibitory effect of purines but the promoting action of HMFF on GVBD than denuded oocytes. Therefore it was reconfirmed that granulosa cells play an important part in meiotic arrest and resumption.