• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.257-270
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• 2000

The objective of this study is to develop a damage model based on damage mechanics that can be used to analyze the mechanical behavior of structures with defects and the global behavior of damaged structures. A modified second order damage tensor that can be applied to finite element analysis is used to reflect the effect of damage. The damage stress computed from the effective stress is considered as an additional loading term acting on nodes and can represent the effect of crack surface. The accuracy of the proposed algorithm is verified by comparing the analysis results with the experimental data from other studies and the analysis results based on transverse isotropic theory. The developed damage model is applied to the analyses of structures with cracks under linear elastic condition. The comparisons confirmed that the quantitative analysis of the structural behavior due to crack orientation and multiple sets of cracks is possible. Also, the damage caused by rock excavation and fault zone is analyzed. The results also showed that the developed model can effectively analyze the global behavior of damaged structures.

• Computational Structural Engineering
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• v.10 no.2
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• pp.255-263
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• 1997

The optimum design of most structural systems used in practice requires considering design variables as discrete quantities. The present paper shows that the linear approximation method is very effective as a tool for the discrete optimum designs of unsymmetric composite laminates. The formulated design problem is subjected to a multiple in-plane loading condition due to shear and axial forces, bending and twisting moments, which is controlled by maximum strain criterion for each of the plys of a composite laminate. As an initial approach, the process of continuous variable optimization by FDM is required only once in operating discrete optimization. The nonlinear discrete optimization problem that has the discrete and continuous variables is transformed into the mixed integer programming problem by SLDP. In numerical examples, the discrete optimum solutions for the unsymmetric composite laminates consisted of six plys according to rotated stacking sequence were found, and then compared the results with the nonlinear branch and bound method to verify the efficiency of present method.

• Journal of Korean Clinical Nursing Research
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• v.27 no.3
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• pp.279-293
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• 2021

Purpose: The purpose of this study was to develop a Korean nursing work environment scale for critical care nurses (KNWES-CCN) and verify its validity and reliability. Methods: A total of 46 preliminary items were selected using content validity analysis of experts on 64 candidate items derived through literature reviews and in-depth interviews with critical care nurses. 535 critical care nurses from 21 hospitals responded to the preliminary questionnaire from February to March 2021. The collected data were analysed using construct, convergent and discriminant validities, and internal consistency and test-retest reliability. Results: The 23 items in 4 factors accounted for 55.6% of the total variance were identified through item analysis and exploratory factor analysis (EFA). EFA was performed with maximum likelihood method including direct oblimin method. In the confirmatory factor analysis, KNWES-CCN consisted of 21 items in 4 factors by deleting the items that were not meet the condition that the factor loading over .50 or the squared multiple correlation over .30. This model was considered to be suitable because it satisfied the fit index and acceptable criteria of the model [𝒳²=440.47 (p<.001), CMIN/DF=2.41, GFI=.86, SRMR=.06, RMSEA=.07, TLI=.90, CFI=.91]. The item total correlation values ranged form .32 to .73 and its internal consistency was Cronbach's α=.92. The reliability of the test-retest correlation coefficient was .72 and the intra-class correlation coefficient was .83. Conclusion: The KNWES-CCN showed good validity and reliability. Therefore, it is expected that the use of this scale would measure and improve nursing work environment for critical care nurses in Korea.

• Ocean Systems Engineering
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• v.12 no.2
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• pp.225-245
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• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• International Area Studies Review
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• v.17 no.4
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• pp.109-130
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• 2013

This study aims to identify the priority for the Gwangyang and Qingdao hinterlands which are in the same category of benchmarking crowed paths. This study has been mainly done with comparison. There is certain limitation to use competitive factors of existing research so, this study has had proper competitive factors deriving from factors analysis and studied hinterland priority of competing factors by AHP. Major results are as follows. First, the factor analysis resulted in 20 factor that were 0.6 or higher loading level of commonality and then these 20 factors were divided into groups: operating factors, service factors, cost factors, port infrastructure factors, and hinterland conditions factors with the rotated component matrix analysis. Second, according to the result of top competitive factors, the best factor was the hinterland condition(0.256). The other factors such as infrastructure, economy, accessibility, incentive, and port traffic in hinterland were highly ranked in terms of general importance using multiple weights. Third, the result of detailed properties importance about the final alternative, Gwangyang hinterland was considered more highly than Qingdao hinterland in the port information system, the support a variety of administrative services, the efficiency of the customs, and the tax benefits.

• Journal of the Korean Applied Science and Technology
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• v.38 no.6
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• pp.1687-1698
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• 2021

This study is to produce multiple layers of liposomes in a supercritical state and encapsulates active ingredients in order to stably encapsulate thermodynamically unstable active ingredients. In order to form a liposome in a supercritical state, a mixed surfactant development including vegetable-derived hydrogenated phosphatidyl choline and their delivative, hydrogenated sucrose distearate was synthesized as high purity. It describes a manufacturing method of injecting liquid carbon dioxide into a reactor to create a supercritical state and stirring to produce a giant liposome, and adding and loading genistein and quercetin. The HLB of the mixed lipid complex (SC-Lipid Complex) was 12.50, and multiple layers of liposome vesicles were formed even at very low concentrations. This surfactant had a specific odor with a pale yellow flake, the specific gravity was 0.972, and the acid value was 0.12, indicating that it was synthesized with high purity. As a result of the emulsifying capacity experiment using 20 wt% capric/capric triglyceride and triethylhexanoin using SC-Lipid Complex, it was found to have 96.2% emulsifying power. SC LIPOSOME GENISTEIN was confirmed that a multi-layer liposome vesicle was formed through a transmission electron microscope (Cryo-TEM) for the supercritical liposome encapsulated with genistein. The primary liposome particle size in which genistein was encapsulated was 253.9 nm, and the secondary capsule size was 18.2 ㎛. Using genistein as the standard substance, the encapsulation efficiency of supercritical liposomes was 99.5%, and general liposomes were found to have an efficiency of 93.6%. In addition, the antioxidant activity experiment in which quercetin was sealed was confirmed by the DPPH method, and it was found that the supercritical liposome significantly maintained excellent antioxidant activity. In this study, thermodynamically unstable raw materials were sealed into liposomes without organic solvents in a supercritical state. Based on these results, it is expected that it can be applied to various forms such as highly functional skincare cosmetics, makeup cosmetics, and scalp protection cosmetics.