• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1118-1127
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• 2008

The position and size of holes in the partition of a double cavity are known to strongly affect the eigenfrequency of the longitudinal eigenmodes of the double cavity. To maximize or minimize the eigenfrequency of the hole-partitioned double cavity, two acoustical topology optimization problems are formulated and solved. While two sub-cavities are filled with air, a partition between them is assumed to consist of sub-partitions of variable acoustical properties. One design variable is assigned to each sub-partition, whose material properties are interpolated as those of an intermediate material between air and a rigid body. The penalty parameter of the used interpolation function is adjusted to obtain a distinct air and rigid body distribution at the converged stage in each acoustical topology optimization problem. A special attention is paid to the selection of initial values of design variables to obtain solutions as close to global optimum and symmetric as possible. To show numerical characteristics of these optimization problems, the formulated problems are first solved for the one-dimensional partition design domain and then for the two-dimensional partition design domain.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.177-186
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• 2000

An improved multi-level（IML) optimization algorithm using automatic differentiation (AD) for multi-objective optimum design of framed structures is proposed in this paper. In order to optimize the steel frames under seismic load, two main objective functions need to be considered for minimizing the structural weight and maximizing the strain energy. For the efficiency of the proposed algorithm, multi-level optimization techniques using decomposition method that separately utilizes both system-level and element-level optimizations and an artificial constraint deletion technique are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments, frequencies, and strain energy with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.101-108
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• 2000

An optimum design algorithm using efficient reanalysis is proposed for reliability-based optimization problems formulated as the minimization of initial cost and expected failure cost with reliability constraints. The reliability-based optimization is high cost to evaluate objective function and constraints needed reliability analysis. Therefore the sensitivity analysis of reliability index for approximated reanalysis is necessary. In this paper, three solution approaches are suggested and tested. The approaches include : (1) sensitivity analysis using finite difference; (2) sensitivity analysis using automatic differentiation (AD); and (3) sensitivity analysis with respect to intermediate variables using AD. Numerical example is optimized to show the reliability and effectiveness of the new algorithm.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.143-157
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• 1992

For the design of structural systems having the prescribed or optimum dynamic characteristics, some design changes of the initially designed system are required. In these cases, if the sensitivity analysis which can predict the changes of dynamic characteristics due to the changes of design variables is applied, the design changes can be carried out rationally and very efficiently. For many structural systems, it is well known that the analysis by the transfer matrix method(TMM) and the combined finite element-transfer matrix method(FETMM) is more efficient than the analysis by the finite element method. However, most known studies on the sensitivity analysis of structural systems premise using the finite element method. In this paper, the sensitivity analysis methods by the TMM and the FETMM are presented and some numerical investigations on the beam-column with elastically restrained ends and intermediate contraints and the stiffened plate having subsystems are carried out. The results of the numerical examples show good accuracy and computational efficiency of the presented methods, and show that the application of sensitivity analysis in the dynamic characteristic reanalysis give good results within the practically changeable range of design variables.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.18 no.1
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• pp.71-78
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• 2011

Purpose: The purpose of this study was to investigate the critical thinking disposition, problem solving ability, and clinical competence of nursing students in a 4-year baccalaureate university program. Methods: In this study, a descriptive survey design was used with convenience sample of 228 nursing students at a University in Chungbuk Province. Data were analyzed using descriptive statistics, independent t-test, ANOVA, Pearson correlation coefficient, and multiple stepwise regression. Results: The mean scores for critical thinking disposition, problem solving ability, and clinical competence were at the intermediate level. Significant positive correlations among critical thinking disposition, problem solving ability, and clinical competence were found. The regression model explained 46.8% of clinical competence. Problem solving confidence was the most significant predictor of clinical competence, other variables were intellectual fairness, intellectual eagerness/curiosity, and prudence. Conclusion: The study findings suggest that nursing students with higher levels of critical thinking disposition and problem solving ability will have a higher level of clinical competence. Furthermore, problem solving confidence might be the most important predictor in clinical competence. Therefore, it is necessary to introduce the new teaching strategies in nursing education, strategies that will improve critical thinking disposition, problem solving ability, and clinical competence.

• Journal of Korea Trade
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• v.23 no.5
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• pp.66-86
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• 2019

Purpose - This paper describes the use of trade preferences under the EU-Korea free trade agreement (FTA) and empirically examines potential reasons for the less than full use, using data on daily EU imports from Korea at the product level. Design/methodology - We employ a probit model to analyse the relationship between the use of trade preferences on the one hand and variables such as potential duty savings, rules of origin and the characteristics of the good traded (intermediate input or final product) on the other. Findings - The paper finds that EU imports from Korea make good use of trade preferences with an overall preference utilisation rate of close to 90% in 2016, which is up from about 80% in 2012. It further shows that potential duty savings influence preference utilisation positively and that more than one quarter of the observations in our sample made use of preferences under EU-Korea FTA in 2012, despite duty savings standing at €10 or less. Originality/value - The finding that a non-negligible share of observations use preferences even when the duty savings are low has not yet figured in the literature. We further show how preference utilisation rates differ by importing EU Member State and by section of the Harmonised System and estimate the marginal impact of an increase in potential duty savings on the preference utilisation rate by broad product group, which is novel.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.341-354
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• 2024

Today, the principles of green chemistry are being fundamentally applied in the chemical industry, such as the nitrobenzene industry, which is an essential intermediate for various commercial products. Research on the application of response surface methodology (RSM) to optimize nitrobenzene synthesis was conducted using a sulfated silica (SO₄/SiO₂) catalyst and batch microwave reactor. The nitrobenzene synthesis process was carried out according to RSM using a central composite design (CCD) design for three independent variables, consisting of sulfuric acid concentration on the silica (%), stirring time (min), and reaction temperature (℃), and the response variable of nitrobenzene yield (%). The results showed that a three-factorial design using the response surface method could determine the optimum conditions for obtaining nitrobenzene products in a batch microwave reactor. The optimum condition for a nitrobenzene yield of 63.38 % can be obtained at a sulfuric acid concentration on the silica of 91.20 %, stirring time of 140.45 min, and reaction temperature of 58.14 ℃. From the 20 experiments conducted, the SO₄/SiO₂ catalyst showed a selectivity of 100 %, which means that this solid acid catalyst can potentially work well in converting benzene to nitrobenzene.

• The Journal of Korean society of community based occupational therapy
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• v.8 no.2
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• pp.15-28
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• 2018

Objective : This study sought to characterize and determine the qualitative level of a single target study for stroke patients. Methods : The National Science and Technology Information Center (NDSL), DBpia (DBpia), RISS (Radical Research Information Service), Korea Research Information (KISS), and the National Assembly Library's original case study from 2002 to 2017. A total of 24 single target research papers were selected through the screening process to analyze the quality level of research methods and research design. Results : ABA design was th most common study design method. One person was the most with 12(50%). and three were the second with 8(33.3%). Imagination was the most used as an independent lawyer. Dependent variables had the highest level of situability and one-sidedness. The study was also conducted with a variety of target behaviors, including 'memory', 'visual attention', 'dysphagia', 'visual-motor coordination', 'balance', 'activity of daily life' and 'edema' behaviors. It also showed a positive effect on all dependent variables. The Qualitative level was found to be above the intermediate level except for one study. Conclusion : It is academic significance that this study analyzes the items to be prepared for in the performance of a single target study and further studies may require the establishment of a weak but good-quality single target study for researchers conducting research in local communities and clinical sites.

• Journal of Science Education
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• v.45 no.3
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• pp.304-316
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• 2021

The purpose of this study is to analyze high school students' critical opinions on others' inquiries in small group open inquiry. Forty-one high school students participated in these activities at the inquiry planning stage and the intermediate stage of inquiry. In the two activities, 595 and 233 opinions were presented respectively, and analyzed into categories based on the inquiry process. The main research results are as follows: first, many opinions were presented in the areas of 'problem recognition and hypothesis setting' and 'design of inquiry' in the feedback on the inquiry plan, especially related to 'revision and addition of research problems,' 'research targets and conditions,' and 'control of variables.' Second, in the feedback on the results of the inquiry, there were many opinions related to 'report preparation' and 'design of inquiry' area. Based on the research results, implications related to the application of critical opinion activity were discussed.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.2
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• pp.332-342
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• 2012

The current research aims at classifying the bus stops as transfer center in order to establish the rational bus transfer systems. Existing research typically identifies characteristics of demands for bus stops and land use surrounding the bus stops and classifies and profiles the bus stops. A common problem with this type of research is that the results with cross-sectional characteristics of land use and bus stop usage do not capture the details of trip chain, the fundamental characteristics of the trips with transfer. This paper therefore examines bus stop classifications with such variables as transport mode chains, intermediate stop chains and timing chains. The analysis on the data collected on Monday 20 April 2009 for passengers of Gyeong-gi bus results in a clear classification among bus stops in terms of such trip chain variables. The research would provide useful information for the decision support of transfer stops location choice and infrastructure design.