• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.11-32
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• 2006

System thermal-hydraulic codes have been used in the past decades in the areas of design, operation, licensing and safety of Nuclear Power Plants (NPPs). The development and validation of these codes have reached a high degree of maturity, through the consideration of huge experiments and advanced numerical models. Nowadays, the analyses are based upon realistic approaches rather than the conservative evaluation models. However the applications of these computational tools require preliminary qualification issues. Although huge amounts of financial and human resources have been invested for the development and improvement of codes, the calculation results are still affected by errors. In the sophisticated nuclear technology, design and safety of NPP, these errors must be quantified. An overview of the state of the art of the current thermal-hydraulic system code is developed and the need of uncertainty analysis in code calculations is emphasized. Several sources of uncertainty have been classified and commented, and typical applications of such methods are shown.

• Journal of Korean Public Health Nursing
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• v.28 no.3
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• pp.590-604
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• 2014

Purpose: The purpose of this study is to develop a nursing competence scale for soon to be graduate nursing students and to verify its validity and reliability. Methods: This study is a methodological study for development of a scale. Based on literature review and group discussion of 13 professional experts, 40 preliminary items were developed and the content validity was verified. Psychometric testing was performed and data were collected from 141 soon to be graduate nursing students of a university. Construct validity was verified by factor analysis and reliability was calculated. Results: The analyses resulted in a scale named the Nursing Competence Scale for Graduating Nursing Students (NCS-GNS), consisting of 30 items covering eight categories: nursing professionalism, integrated nursing through critical thinking, communication skills, nursing leadership, respect for life, stress management, nursing research, and core nursing skills. For the entire scale, the explained variance was 66.72% and Cronbach's alpha was 0.906. Conclusion: NCS-GNS was developed and its validity and reliability were verified. This scale can be used to evaluate nursing competence for graduating nursing students.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.28.4-29
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• 2008

The aim of the test is to provide an experimental basis to validate the prediction of the FEM for high frequency jitter analysis due to reaction wheel. The principle is to measure structural transfer functions between the input disturbances at RWA base plate and the accelerations near the end tips of payload, in a configuration close to the operational model. The spacecraft shall have to be suspended, in order to be representative of on-orbit boundary conditions. The results of the test shall be compared to the output of the FEM analysis, and if needed, local upgrades of the FEM and/or margin policy shall be defined in order to guarantee a good test/FEM consistency. Test results were compared with the transfer functions of the FEM, which is globally tuned based on the results of vibration test and consequently have lower damping coefficients values than 1% in the frequency range of 60~200Hz. The damping coefficients estimated from the figures of FRF test results are different from the theoretical FEM, but the magnitude trend of FRF of the test results is somewhat similar with the analytical, it is expected that the overall jitter effect of final estimation is nearly same with the preliminary analysis result in which the damping coefficients were assumed to be 1% for all modes in FEM.

• Journal of Astronomy and Space Sciences
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• v.29 no.3
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• pp.287-293
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• 2012

Satellite operating agencies are constantly monitoring conjunctions between satellites and space objects. Two line element (TLE) data, published by the Joint Space Operations Center of the United States Strategic Command, are available as raw data for a preliminary analysis of initial conjunction with a space object without any orbital information. However, there exist several sorts of uncertainties in the TLE data. In this paper, we suggest and analyze a method for estimating the uncertainties in the TLE data through mean, standard deviation of state vector residuals and covariance matrix. Also the estimation results are compared with actual results of orbit determination to validate the estimation method. Characteristics of the state vector residuals depending on the orbital elements are examined by applying the analysis to several satellites in various orbits. Main source of difference between the covariance matrices are also analyzed by comparing the matrices. Particularly, for the Korea Multi-Purpose Satellite-2, we examine the characteristics of the residual variation of state vector and covariance matrix depending on the orbital elements. It is confirmed that a realistic consideration on the space situation of space objects is possible using information from the analysis of mean, standard deviation of the state vector residuals of TLE and covariance matrix.

• Proceedings of the KSRS Conference
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• v.1
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• pp.200-203
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• 2006

Cloud detection algorithm is being developed as major one of the 16 baseline products of CMDPS (COMS Meteorological Data Processing System), which is under development for the real-time application of data will be observed from COMS Meteorological Imager. For cloud detection from satellite data, we studied two different algorithms. One is threshold technique based algorithm, which is traditionally used, and another is artificial neural network model. MPEF scene analysis algorithm is the basic idea of threshold cloud detection algorithm, and some modifications are conducted for COMS. For the neural network, we selected MLP with back-propagation algorithm. Prototype software of each algorithm was completed and evaluated by using the MTSAT-1R and GOES-9 data. Currently the software codes are standardized using Fortran90 language. For the preparation as an operational algorithm, we will setup the validation strategy and tune up the algorithm continuously. This paper shows the outline of the two cloud detection algorithm and preliminary test result of both algorithms.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.493-501
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• 2013

Taking into account the increasingly stringent legislation on emissions from marine engines, this work aims to analyze several internal engine modifications to reduce $NO_x$ (nitrogen oxides) and other pollutants. To this end, a numerical model was employed to simulate the operation cycle and characterize the exhaust gas composition. After a preliminary validation process was carried out using experimental data from a four-stroke, medium-speed marine engine, the numerical model was employed to study the influence of several internal modifications, such as water addition from 0 to 100% water to fuel ratios, exhaust gas recirculation from 0 to 100% EGR rates, modification of the overlap timing from 60 to $120^{\circ}$, modification of the intake valve closing from 510 to $570^{\circ}$, and modification of the cooling water temperature from 70 to $90^{\circ}C$. $NO_x$ was reduced by nearly 100%. As expected, it was found that, by lowering the combustion temperature, there is a notable reduction in $NO_x$, but an increase in CO (carbon monoxide), HC (hydrocarbons) and consumption.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.153-160
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• 2010

This paper deals with the topology optimized design of the riser support structures for floating production storage and offloading units (FPSOs) under global and local loading conditions. For a preliminary study and validation of the numerical approach, a simplified plate under static loading is first evaluated with the representative topology optimization methods, the Homogenization Design Method (HDM) and Density Method (DM) or Simple Isotropic Material with Penalization (SIMP). In the context of the corresponding riser support structures, the design problem is formulated such that structure shapes based on design domain variables are determined by minimizing the compliance subject to a mass target, considering the stress criterion. An initial design model is generated based on an actual FPSO riser support configuration. The topology optimization results present improved design performances under various loading conditions, while staying within the allowable limit of the offshore area.

• Korean Journal of Child Studies
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• v.34 no.4
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• pp.83-104
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• 2013

The purpose of this study is to develop assessment tools to diagnose the child friendly level in a given community. To develop such assessment tools, the literature related to this issue was reviewed, and in order to reflect Korea specific social and cultural characteristics, 198 children and adolescents and 104 parents were interviewed in depth. The questionnaires were classified as objective tools and subjective tools by means of a content validity test by experts and a verification by preliminary survey. Objective tools are defined as those which are used by professionals to check facts based on laws and institutions. 20 objective questionnaires were created and completed. In contrast, subjective tools were used to check the subjective perceptions of children, adolescents and parents on their community environments. Subjective tools were collected as the basis for the data for construct validity and was calculated to verify the validity. For this purpose, 432 children and adolescents between 11 and 18 and 201 parents living in Seoul, Daejeon and Hwaseong (n=633) were surveyed. Subjective tools, 33 questions in 6 areas were created and completed for parents and for children and adolescents, 30 questions in 5 areas were created and completed.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1095-1103
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• 2003

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. In this study, the holographic particle velocimetry system was used to measure the sizes and velocities of droplets produced by a commercial full cone spray nozzle. As a preliminary validation experiment, the velocities of glass beads on a rotating disk were measured with uncertainty analysis to identify the sources of all relevant errors and to evaluate their magnitude. The error of the particle velocity measured by the holographic method was 0.75 ㎧, which was 4.5% of the known velocity estimated by the rotating speed of disk. The spray droplet velocities ranged from 10.3 to 13.3 ㎧ with average uncertainty of ${\pm}$ 1.6 ㎧, which was ${\pm}$ 14% of the mean droplet velocity. Compared with relatively small uncertainty of velocity components in the normal direction to the optical axis, uncertainty of the optical axis component was very high. This is due to the long depth of field of droplet images in the optical axis, which is inherent feature of holographic system using forward-scattering object wave of particles.

• English Language & Literature Teaching
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• v.10 no.3
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• pp.191-210
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• 2004

The scores of TOEFL, TOEIC and TEPS have been increasingly used for many purposes in Korea In particular, these test scores are being used as a measure of the test-takers' overall communicative competence. Nonetheless, few studies have been conducted that investigate the validity of the test scores used for this purpose. As a preliminary step to explore the validity of the test scores, we conducted a small scale study by comparing 30 university students' scores in TOEFL, TOElC and TEPS with their class performances in English conversation and composition courses. The correlations between the test scores and the grade point averages of the courses show that the test scores are much harder to use as a valid measure of test-takers' overall communicative competence than usually thought to be and that the score in TOEFL is, nonetheless, a more reliable measure than the ones in the other tests. Although tins study has a few limitations such as the small number of participants, the homogeneity of the sample as a group, etc, it provides some insight into the use of the three tests for measurement of overall communicative proficiency and suggests need for conducting further validation studies in these areas.