• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.8
• /
• pp.989-996
• /
• 2010

Statistical regression and/or interpolation models have been used for data analysis and response prediction using the results of the physical experiments and/or computer simulations in structural engineering fields. These models have been employed during the last decade to develop a variety of design methodologies. However, these models only handled responses with respect to space variables such as size and shape of structures and cannot handle time-variant dynamic responses, i.e. response varying with time. In this research, statistical space-time metamodels based on multiple response approach that can handle responses with respect to both space variables and a time variable are proposed. Regression and interpolation models such as the response surface model (RSM) and kriging model were developed for handling time-variant dynamic responses of structural engineering. We evaluate the accuracies of the responses predicted by the two statistical space-time metamodels by comparing them with the responses obtained by the physical experiments and/or computer simulations.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.6
• /
• pp.821-826
• /
• 2013

When the values of design variables change, mode switching can often occur. If the mode of interest is not tracked, the frequencies and modes for design optimization may be miscalculated owing to modes that differ from the intended ones. Thus, mode tracking must be employed to identify the frequencies and modes of interest whenever the values of design variables change during optimization. Furthermore, reliability-based design optimization (RBDO) must be performed for design problems with design variables containing uncertainty. In this research, we perform RBDO considering the mode tracking of a compressive coil spring, i.e., a component of the joint spring that supports a compressor, with design variables containing uncertainty by using only kriging metamodels based on multiple responses approach (MRA) without existing mode tracking methods. The reliability analyses for RBDO are employed using kriging metamodel-based Monte Carlo simulation.

• Computational Structural Engineering
• /
• v.11 no.3
• /
• pp.187-198
• /
• 1998

지하구조물의 건전성을 평가하기 위한 비파괴시험으로써 탄성응력파를 이용한 충격반향탐사법을 수치해석적인 방법을 통하여 수행하였다. 즉, 일면만으로 접근 가능한 터널 면에서의 충격가진과 동적응답의 측정으로 이질면을 포함한 내부의 상태를 예측할 수 있다. 연구의 수행은 탄성거동을 하는 매질 내부에서 전파되는 탄성응력파의 특성을 이해하고, 이를 동적 유한요소해석으로 모형화하여 충격반향탐사법을 수치해석적으로 수행한다. 이질재료가 2개의 층을 이루고 있는 경우 표면층의 두께를 쉽게 측정할 수 있었으며, 구조물의 병진운동, 휨운동과 구조물 내에서 다중반사되는 탄성응력파에 의한 복합적인 영향을 받는 터널과 같은 원통형 구조물에서 동적응답의 주파수 특성으로부터 터널라이닝 내부에 형성된 공동의 위치와 크기의 예측이 가능하였다. 수치해석적인 방법과 병행하여 다양한 형태의 경계조건을 가지는 구조물에 대한 충격반향탐사법의 실험을 수행할 경우 실제적인 문제에 적용, 건전성 평가의 지표를 마련할 수 있을 것으로 사료된다.

• Explosives and Blasting
• /
• v.37 no.3
• /
• pp.13-24
• /
• 2019

This paper was prepared to investigate the behavior of fragments in underwater torpedo explosion beneath a frigate or surface ship by using an explicit finite element analysis. In this study, a fluid-structure interaction (FSI) methodology, called the multi-material arbitrary Lagrangian-Eulerian (MM-ALE) approach in LS-DYNA, was employed to obtain the responses of the torpedo fragments and frigate hull to the explosion. The Euler models for the analysis were comprised of air, water, and explosive, while the Lagrange models consisted of the fragment and the hull. The focus of this modeling was to examine whether a worst-case fragment could penetrate the frigate hull located close (4.5 m) to the exploding torpedo. The simulation was performed in two separate steps. At first, with the assumption that the expanding skin of the torpedo had been torn apart by consuming 30% of the explosive energy, the initial velocity of the worst-case fragment was sought based on a well-known experimental result concerning the fragment velocity in underwater bomb explosion. Then, the terminal velocity of the worst-case fragment that is expected to occur before the fragment hit the frigate hull was sought in the second step. Under the given conditions, the possible initial velocities of the worst-case fragment were found to be very fast (400 and 1000 m/s). But, the velocity difference between the fragment and the hull was merely 4 m/s at the instant of collision. This result was likely to be due to both the tremendous drag force exerted by the water and the non-failure condition given to the frigate hull. Anyway, at least under the given conditions, it is thought that the worst-case fragment seldom penetrate the frigate hull because there is no significant velocity difference between them.

• Journal of Korean Society of Archives and Records Management
• /
• v.20 no.2
• /
• pp.85-106
• /
• 2020

This study aims to identify the relationship between commitment to the profession and commitment to the organization, and the effect of professional development on the dual commitments to the organization and the profession. After establishing concepts through a literature review, the study designed a questionnaire survey in which 104 out of 135 (77.0%) record management field officials responded. This study provides a firm basis for urging the army to change its perception toward record management professionals' specialty and their commitment to the profession. Furthermore, this change will ultimately lead to a higher commitment to the organization.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.2
• /
• pp.329-338
• /
• 2018

This study was conducted to examine musculoskeletal disorder and analyze the effects of musculoskeletal pain control and self-efficacy on musculoskeletal disorders in dental hygienists. Material and Methods; 483 dental hygienists residing in Gwangju were collected by the convenience sampling method and the self-administered questionnaire survey was conducted. Frequency analysis, crosstab analysis, t-test, and multiple logistic regression analysis were used for analysis. Results: the prevalence of musculoskeletal pain among subjects was 83.9% for the prior year, with 29.8% of patients being afflicted by musculoskeletal disorders. The factors influencing musculoskeletal disorders were musculoskeletal pain resolution. For pain resolution, the odds ratio of musculoskeletal disorders of the group who answered treatment in a hospital, an Oriental medicine clinic, or a pharmacy was 0.22 (95% confidence interval, 0.14-0.34) compared with the group who answered sick leave or task change, suggesting a negative relationship. These findings indicate that people with musculoskeletal disorders were not treated in the hospital, Oriental medicine clinic, or pharmacy. Therefore, it is necessary to improve medical management (oriental medicine, intravenous injection or medication, heat therapy or cryotherapy, steroid treatment, counseling, endovascular treatment using spinal cord stimulation, physical therapy, stretching, rehabilitation, and manual therapy) and job environment and to make a good approach to the prevention of musculoskeletal disorders to control dental hygienists' musculoskeletal pain.