• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.2
• /
• pp.156-162
• /
• 2013

The characteristics of the unsteady flowfield of a square prism having a detached splitter plate at the wake side were investigated by advanced vortex method. The instantaneous and average velocity field and pressure field around a square prism without and having splitter plate were calculated by forcing the gap ratio having the maximum drag reduction rate, at Reynolds number $Re=1.0{\times}10^4$ and the width ratio H/B=1.0 of splitter to the prism width. The drag and lift coefficients on the square prism were also obtained. The calculated results agree with the measured drag coefficients and pressure distributions on the square prism. The vortices of the opposite direction at upside and down side of the splitter plate were generated by installing of the plate. And the drag on the square prism was decreased by increasing of the pressure of back face of the prism with the vortices.

• Corrosion Science and Technology
• /
• v.2 no.6
• /
• pp.283-288
• /
• 2003

The cathodic protection method is being widely used in marine structural steel, however a high tensile steel like RE 36 steel for marine structural steel is easy to get hydrogen embrittlement due to over protection during cathodic protection as well as preferential corrosion of HAZ(Heating Affected Zone) part. In this paper, corrosion resistance and mechanical properties such as elongation and hydrogen embrittlement were investigated with not only in terms of electrochemical view but also SSRT(Slow Strain Rate Test) method with applied constant cathodic potential, analysis of SEM fractography in case of both As-welded and PWHT(Post-Weld Heat Treatment) of $550^{\circ}C$. The best effect for corrosion resistance was apparently indicated at PWHT of $550^{\circ}C$ and elongation was increased with PWHT of $550^{\circ}C$ than that of As-welded condition. On the other hand. Elongation was decreased with applied potential shifting to low potential direction which may be caused by hydrogen embrittlement, however the susceptibility of hydrogen embrittlement was decreased with PWHT of $550^{\circ}C$ than that of As-welded condition and Q.C(quasi cleavage) fracture mode was also observed significantly according to increasing of susceptibility of hydrogen embrittlement. Eventually it is suggested that an optimum cathodic protection potential range not causing hydrogen embrittlernent is from -770 mV(SCE) to -850 mV(SCE) in As-welded condition while is from -770 mV(SCE) to -875 mV(SCE) in PWHT of $550^{\circ}C$.

• The Journal of Fisheries Business Administration
• /
• v.49 no.4
• /
• pp.69-81
• /
• 2018

The fishing vessel buyback program, that is, the project of fishing vessel reduction is a complex challenge that needs to take into consideration for both fishing resource protection and industrial restructuring. By the way, the fishing vessel buyback program in Korea is still poorly fruitful and there are few applications for the project in the country. For example, the buyback program of this nation has some problems like uncertainly set goals, conflicts among targets, no flexibility in the program implementation, low participation in the project and lack in follow-up actions. To solve these problems, this study offers the following alternatives. First, it is setting up detailed targets for fishing vessel buyback. Those targets should be what can be actually driven under policy support, such as reduction in illegal fishing, decrease in an exact number of fishing vessels and decline in fishing capacity rather than what seem to be comprehensive such as protection of coastal or offshore fishery and industrial restructuring. Second, it is taking measures for the livelihood of those who would face disadvantages due to fishing vessel reduction. Those measures providing or supporting the re-education and re-employment of fishery workers and building up systems that help the workers transfer fishing to another job. Third, it is adopting the governance system that overcomes lacks in communications between the fishing vessel buyback program and improves the performance effectiveness of that program. Here, governance means that businesses and authorities concerned in the program interact and cooperate with one another in making and implementing policies related to the project of fishing vessel reduction and assessing the results of that project. Fourth, it is taking actions for fishery reorganization after the fishing vessel buyback program. Factors that can be considered as those actions include supporting fishery workers' cost of fishing vessel reduction, decreasing and modernizing fishing fleets and improving the quality of fishing equipment. In conclusion, the fishing vessel buyback program should be prepared with comprehensive actions or measures that can cope well with a variety of problems that may be arisen from it while keeping itself on the track of its original goals.

• The Journal of the Korea Contents Association
• /
• v.19 no.6
• /
• pp.655-662
• /
• 2019

Based on phenomenological view a research utilizing qualitative methodology to understand about parenting difficulty and stress through an in-depth interview with grandmother in low-income grandparent-headed family was administrated. The results indicated that experience with parenting stress of grandmother in low-income grandparent-headed family lead to economic hardship, grandchildren who are a barrier of old-age, and desolate parenting. This article implicates that a basis to guide a direction and role of social welfare intervention to alleviate parenting stress of grandmother in grandparent-headed family and to improve a life quality emergent on the results could be provided. Several considerations on this finding shows as follows. First, with currently active support project re-monitored and re-checked, support program could be needed to enlarge. Second, support program development and social support to decrease parenting stress and depression of grandmother in grandparent-headed family could be necessary. With educational and cultural as well as mentoring program helpful for grandmother parenting designed, a support system to complement non-sufficient support network will be established together.

• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.6_2
• /
• pp.1119-1125
• /
• 2022

The depletion of resources and waste disposal caused by the continuous development of industry have emphasized the need to reduce consumption and production, recycle and reuse, and the importance of remanufacturing has increased in recent years. The spindle part of the aging planner miller, which is currently being remanufactured, is one of the factors that has the greatest impact on the performance of the machine tool. When designing the spindle part of the spindle shaft, there are considerations such as the configuration size bearing performance of the main shaft, but the diameter of the main shaft, the dangerous speed bearing, and the arrangement that affect the machining accuracy should be basically considered. As such, various studies have been conducted on the design of machine tool spindle spindles, but research on the reverse engineering of existing aging machine tool spindle spindles is poor. Reverse engineering is designing in the direction of improving performance by extracting specifications from already finished products, and first scanning the reverse engineered object through a 3D scanner, 3D modeling is performed based on the collected data, and then the process of deriving improvement plans by reverberating to improve performance by identifying wear and damage conditions is followed. Therefore, in this study, the purpose of this study is to provide data on reverse engineering by deriving improvement plans through optimal design for the bearing position of the aging planar Miller spindle spindle using central composite programming.

• Wind and Structures
• /
• v.36 no.4
• /
• pp.221-236
• /
• 2023

The lateral component of turbulence and the vortices shed in the wake of a structure result in introducing dynamic wind load in the acrosswind direction and the resulting level of motion is typically larger than the corresponding alongwind motion for a dynamically sensitive structure. The underlying source mechanisms of the acrosswind load may be classified into motion-induced, buffeting, and Strouhal components. This study proposes a frequency domain framework to decompose the overall load into these components based on output-only measurements from wind tunnel experiments or full-scale measurements. First, the total acrosswind load is identified based on measured acceleration response by solving the inverse problem using the Kalman filter technique. The decomposition of the combined load is then performed by modeling each load component in terms of a Bayesian filtering scheme. More specifically, the decomposition and the estimation of the model parameters are accomplished using the unscented Kalman filter in the frequency domain. An aeroelastic wind tunnel experiment involving a tall circular cylinder was carried out for the validation of the proposed framework. The contribution of each load component to the acrosswind response is assessed by re-analyzing the system with the decomposed components. Through comparison of the measured and the re-analyzed response, it is demonstrated that the proposed framework effectively decomposes the total acrosswind load into components and sheds light on the overall underlying mechanism of the acrosswind load and attendant structural response. The delineation of these load components and their subsequent modeling and control may become increasingly important as tall slender buildings of the prismatic cross-section that are highly sensitive to the acrosswind load effects are increasingly being built in major metropolises.

• Wind and Structures
• /
• v.36 no.3
• /
• pp.175-200
• /
• 2023

The large eddy simulation (LES) of the flow around a circular cylinder is not only affected by the sub-grid scale (SGS) model but also by the grid resolution of the computational domain. To study the influence of different grids on the LES results, the LES simulations of the flow around a circular cylinder with different grids at Reynolds number (Re) = 3900 was performed. A circular computational domain with different radial growth rates and circumferential and spanwise grid numbers was adopted for the simulations. Meanwhile, the aerodynamic forces, wind pressure coefficients, mean and instantaneous flow fields, and the effect of grid resolution on them were comprehensively analyzed. The results indicate that the lift coefficient, wind pressure coefficient, and recirculation length are significantly affected by the radial growth rate of the grid and the circumferential grid number. The spanwise grid number has a significant influence on the three-dimensionality of the flow and plays an important role in velocity fluctuations in the wake region. Nevertheless, the aerodynamic coefficients and recirculation length are not sufficiently sensitive to the grid number in the spanwise direction. By comparing the results, it can be concluded that suitable and reliable LES results can be obtained when the radial growth rate is 1.03 or 1.05, the circumferential grid number is 160, 200, or 240, and the spanwise grid number is 64. A radial growth rate 1.05, circumferential grid number 160, and spanwise grid number 64 are recommended to reduce the grid amount and further improve the efficiency.

• Geomechanics and Engineering
• /
• v.32 no.4
• /
• pp.375-385
• /
• 2023

There are many joint fissures distributed in the engineering rock mass. In the process of geological history, the underground rock mass undergoes strong geological processes, and undergoes complex geological processes such as fracture breeding, expansion, recementation, and re-expansion. In this paper, the damage-stick-slip process (DSSP), an analysis model used for rock mass failure slip, was established to examine the master control and time-dependent mechanical properties of the new and primary fractures of a multi-fractured rock mass under the action of stress loading. The experimental system for the recemented multi-fractured rock mass was developed to validate the above theory. First, a rock mass failure test was conducted. Then, the failure stress state was kept constant, and the fractured rock mass was grouted and cemented. A secondary loading was applied until the grouted mass reached the intended strength to investigate the bearing capacity of the recemented multi-fractured rock mass, and an acoustic emission (AE) system was used to monitor AE events and the update of damage energy. The results show that the initial fracture angle and direction had a significant effect on the re-failure process of the cement rock mass; Compared with the monitoring results of the acoustic emission (AE) measurements, the master control surface, key blocks and other control factors in the multi-fractured rock mass were obtained; The triangular shaped block in rock mass plays an important role in the stress and displacement change of multi-fracture rock mass and the long fissure and the fractures with close fracture tip are easier to activate, and the position where the longer fractures intersect with the smaller fractures is easier to generate new fractures. The results are of great significance to a multi-block structure, which affects the safety of underground coal mining.

• Journal of The Korean Association For Science Education
• /
• v.28 no.6
• /
• pp.641-648
• /
• 2008

The purpose of this study is to analyze pre-service science teachers' pedagogical content knowledge. For this study, two senior education students were selected. The data of this study were collected through interviews, CoRe questionnaire, and classroom observation recordings during the period of student-teacher practice. Data were analyzed using the constant comparative method. The results indicated that the two pre-service science teachers had low level pedagogical content knowledge. Two pre-service science teachers' knowledges of science curriculum were different from each other. Orientations toward teaching science shifted to undesirable direction after the experience of a student-teacher's practice-teaching. Their subject matter knowledges were imperfect. They also had low levels of knowledge of students' understanding.

• Journal of Korean Academy of Nursing
• /
• v.25 no.1
• /
• pp.30-44
• /
• 1995

This study aimed at analyzing the trend of re-search on pain in Korea, suggesting direction future pain research, and contributing to the use of pain interventions in nursing practice. Research studies on pain were selected from journals of medical and nursing schools, the Korean Nurse, the Korean Nurses' Academic Society Journal, the Central Journal of Medicine, the New Medical Journal, and from theses and dissertations, which were conducted between 1970 and 1994. The total number of the studies was 93. These studies were analyzed for 1) time of publication or presentation, 2) thesis for a degree or nondegree, 3) research design, 4) characteristics of subjects used in each study, 5) measurement tool, 6) types of correlated variables, 7) Korean terms for pain 8) types of nursing interventions, and 9) results of studies. The findings of the analysis can be summerized as follows : 1) The number of studies related to pain has increased rapidly since the early 1980's. The number of experimental research studies related to pain has increased chronologically, but the number of survey research studies related to pain was highest from 1981 to 1985, after that it decreased slowly. 2) The subjects in 19 studies were healthy people and, in 73 studies, patients with various illnesses. Thirty two studies were conducted with surgical patients. 3) Sixty one pain research studies were done for a thesis for a degree and 32 were nondegree research studies. 4) As measurement tools for pain, self- report pain scales were used in 54 studies and more than two tools were used in 28 studies. In the experimental studies, the trend was to use more than two tools. And in the nonexperirnental studies, the trend was to use self-report pain scales only. 5) There were 11 correlational studies. In these studies, the trend was to study anxiety, depression and variables such as intravenous infusion as related to pain.6) In the thirty six experimental studies, the effects of 16 types of nursing interventions weretested. Teaching and information, and relaxation technique were the most popular interventions for pain. 7) In eighteen methodological studies, the majority were studies testing the validity and re-liability of Dr. Lee's Korean Pain Rating Questionnaire. The following suggestions are made based on the above findings : 1) The patterns of these studies related to pain in Korea need to be compared with trends in other countries. 2) Meta - analysis should be done to analyze and integrate the results of various studies. 3) This analysis of pain research is needed to identify the present trend of pain research and to suggest the direction of future pain research, so these patterns of studies should be done in 5 to 10 year intervals. 4) More replicated pain research is needed to prove the effect of nursing interventions and more qualitative research on pain is needed to identify indepth the meaning of pain. 5) Pain researchers should make an effort to apply research result in various clinical settings and try to carry out team research with clinical nurses or with other multidiscipinary researchers.