• Journal of Advanced Marine Engineering and Technology
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• 제37권2호
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• pp.156-162
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• 2013

본 연구는 정방형주의 후류측 중심에 분리된 분할판(Detached splitter plate)을 설치한 경우 정방형주의 주위의 유동장을 최신와법으로 파악한 것이다. 레이놀즈 수 $Re=1.0{\times}10^4$ 및 분할판의 폭을 정방형주 한변의 길이(B)로 고정시키고, 특히 항력감소율이 최대인 간격비에 촛점을 맞추어 분할판 유, 무에 따른 정방형주에 주위의 순간 및 평균 속도장 및 압력장을 시뮬레이션하였고, 양, 항력계수의 시간변화도 계산하였다. 계산결과는 측정된 항력계수 및 압력분포와 잘 일치하였다. 분할판 설치에 의해 분할판의 상하부에 서로 반대방향의 볼텍스가 발생했고, 이 볼텍스가 정방형주 뒷면의 압력을 상승시켜 항력을 감소시켰음을 명확하게 나타냈다.

• Corrosion Science and Technology
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• 제2권6호
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• pp.283-288
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• 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 $550^{\circ}C$.

• 수산경영론집
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• 제49권4호
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• pp.69-81
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• 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.

• 한국콘텐츠학회논문지
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• 제19권6호
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• pp.655-662
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• 2019

본 연구는 현상학적 해석학을 바탕으로 저소득 조손가정의 조모와의 심층면담을 통해 조모의 양육의 어려움과 양육스트레스에 대해 이해하고자 질적 연구를 수행하였다. 연구결과 저소득 조손가정 조모의 양육스트레스 경험은 경제적 어려움, 노후의 걸림돌이 된 손자녀, 양육의 막막함으로 나타났다. 이러한 연구결과를 토대로 새롭게 부각되고 있는 조손가정 조모의 양육스트레스를 경감시키고 삶의 질을 향상시키기 위한 사회복지개입 방향과 역할을 구체화할 수 있는 근거를 제공하는데 그 의의가 있다. 연구결과를 바탕으로 몇 가지 제언을 한다면 첫째, 현재 시행 중인 지원사업을 재검토하여 지원내용을 확대할 필요가 있다. 둘째, 저소득 조손가정 조모의 양육스트레스와 우울감을 감소시키기 위해 지지프로그램의 개발과 사회적 지원이 필요하다. 조모의 양육에 도움이 될 수 있는 교육 문화와 더불어 멘토링 프로그램을 만들어 부족한 원조관계망을 보완하는 지원도 함께 고려되어야 할 것이다.

• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1119-1125
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• 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
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• 제36권4호
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• pp.221-236
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• 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
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• 제36권3호
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• pp.175-200
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• 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
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• 제32권4호
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• pp.375-385
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• 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.

• 한국과학교육학회지
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• 제28권6호
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• pp.641-648
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• 2008

본 연구의 목적은 예비과학교사의 교수내용지식을 분석하는 것이다. 이 연구를 위하여 두 명의 사범대학 4학년생들을 선정하였다. 연구의 자료는 인터뷰, CoRe 질문지, 교육실습기간의 수업관찰기록 등의 질적 연구방법을 통해 수집되었다. 자료 분석은 반복적 비교 분석법에 의하여 이루어졌다. 연구결과, 두 예비과학교사의 교수내용지식 수준은 매우 낮았다. 두 예비과학교사의 교육과정에 대한 지식은 서로 달랐으며, 과학 교수지향은 교육실습 기간 동안의 교수경험 후에 바람직하지 않은 방향으로 변화하였다. 두 예비과학교사의 내용지식은 매우 부족하였으며, 학생 이해에 대한 지식수준도 매우 낮았다.

• 대한간호학회지
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• 제25권1호
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• pp.30-44
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• 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.