• Journal of Educational Research in Mathematics
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• v.12 no.2
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• pp.291-311
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• 2002

The PISA(Program for International Student Assessment), an international comparative study supervised by OECD, is aimed at producing reliable and internationally comparab1e indicators of students' literacy in reading, mathematics, and science. In mathematical literacy, Korean students ranked the 2nd out of the 32 participating countries in PISA. This result is very encouraging in the sense that the scores in the mathematical literacy is the forecasting indicator for the mathematical level of future citizens who are supposed to lead their countries in every fields. In contrast to the high performance in mathematics, Korean students possess extremely low level of interest in mathematics. On the other hand, Korea's highest top 5% students are not on a par with the best students in New Zealand, Japan, Swiss, Australia, and England. This finding urges Korean education to put serious efforts to pursue academic excellence. Overall, PISA results suggest that Korean mathematics education has been effective and efficient. Korean education system should set goals to meet the world standard and the challenges of the lifelong teaming society.

• Journal of Periodontal and Implant Science
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• v.24 no.1
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• pp.196-204
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• 1994

The purpose of this clinical trial was to study the effectiveness of 5% potassium nitrate dentifrice as a daily home treatment of dentinal hypersensitivity. Thirty subjects with dentinal hypersensitivity were included in a 4-week, double-blind, parallel, comparative study. Stimuli used included mechanical, cold water and compressed air blasts. A subjective assessment of the degree of hypersensitivity for each stimulus was recorded. The results indicated that 5% potassium nitrate dentifrice, in comparision with a conventional fluoride dentifrice, reduced dentinal hypersensitivity to a significant degree. The therapeutic response to potassium nitrate was apparent within 2 weeks and increased continuously for the length of the study period. We conclude that 5% potassium nitrate dentifrice is an effective agent for the daily home treatment of dentinal hypersensitivity.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.381-381
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• 1999

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.635-640
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• 1998

Thermal fluid mixing behavior during a postulated medium-size hot leg break loss of coolant accident is analyzed for the international comparative assessment study on pressurized thermal shock (PTS-ICAS) proposed by OECD-NEA. The applicability of RELAP5 code to analyze thermal fluid mixing behavior is evaluated through a simple modeling relevant to the problem constraints. Based on the calculation result, the onset of Thermal stratification is investigated using Theofanous's empirical correlation. Sensitivity calculations using a fine node model and crossflow model are also performed to evaluate the modeling capability on multi-dimensional characteristics related to thermal fluid mixing.

• Journal of the Korean Solar Energy Society
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• v.23 no.4
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• pp.21-27
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• 2003

The comparative performance of the WAsP in calculating the wind climate in complex terrain has been examined in order to test the predictability of the wind resource assessment computer code in our country. An analysis was carried out of predicted and experimental 10-min averaged wind data collected over 8 months at four monitoring sites in SongDang province, Jeju island, composed of sea, inland flat terrain, a high and a low slope craters. The comparisons show that the WAsP preditions give better agreement with experimental data by adjusting the roughness descriptions, the obstacle list.

• Journal of the Korea Safety Management & Science
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• v.8 no.4
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• pp.249-265
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• 2006

A life cycle assessment(LCA) is increasing its applicability as a powerful tool for an environmental burdens analysis. In this study, some cases are compared in terms of analysis procedures and results obtained with LCAs for evaluating power generation technologies in Korea. For the comparison, 3 power generation technologies are selected because they produces almost 90% of 2003 total electricity generation in Korea. It is shown that the range of evaluation values amounts to maximally the order of about 105, which is rather large discrepancy than the level of 101 in comparison with foreign studies. The difference seems to be due to the simplicity of modeling used in each case study. It is proposed that this large discrepancy should be obviously clarified to improve their reliability in that electricity is a essentialness for all industries and the capacity of LCA of national-level electricity affects the results of LCA for the other sectors.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.380-386
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• 1996

This paper presents the history of heat hydration and the core strength of underwater non-segregation concrete. Three types of cements including Type I, Type V and low-heat cement have been used to make the mass specimens for measurement of heat of hydration and also for coring. Two environments of ambient and underwater conditions have been accounted for the comparison of producing the heat of hydration and for the assessment of core strength in respect to the test specimens made under normal practice.

• Journal of the Korean housing association
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• v.18 no.2
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• pp.75-82
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• 2007

Under the premise that the housing market is not fixed, but changes organically according to social and systematic environment, it has important meaning as the object of this study to identify the recent housing market's movement by deducing the changed characteristics of the factors to compose the recent new houses. By using the following methodology, this study analyzed the characteristics and mutual relations of the economical and house-composing factors, categorized the investigation object into sub-markets, and executed comparative analysis. First, based on the leading studies analyzing the factors of house price determination and the assessment indicators of 'Green Building Certification Program', the composing factors are deduced. Second, the factors are categorized as economic, housing complex planning and geographical condition. Third, to identify the influence of housing environmental factors on economic factors, the correlation between the former and the latter, and the difference between economic factors are analyzed. Fourth, by segmenting and categorizing the housing market into time and location subgroups, the chronicle trend and the geographical characteristics are analyzed.

• Structural Engineering and Mechanics
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• v.14 no.2
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• pp.191-208
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• 2002

A comparative assessment study for a generation of the pressure-temperature (P-T) limit curve of a reactor vessel is performed in accordance with ASME code. Using cooling or heating rate and vessel material properties, stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during reactor cool-down and heat-up. P-T limit curves are analyzed with respect to defect orientation, clad thickness, toughness curve, cooling or heating rate and neutron fluence. The resulting P-T curves are compared each other.

• Structural Engineering and Mechanics
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• v.8 no.1
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• pp.103-118
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• 1999

The structural integrity of the reactor pressure vessel under pressurized thermal shock (PTS) is evaluated in this study. For given material properties and transient histories such as temperature and pressure, the stress distribution is found and stress intensity factors are obtained for a wide range of crack sizes. The stress intensity factors are compared with the fracture toughness to check if cracking is expected to occur during the transient. A round robin problem of the PTS during a small break loss of coolant transient has been analyzed as a part of the international comparative assessment study, and the evaluation results are discussed. The maximum allowable nil-ductility transition temperatures are determined for various crack sizes.