• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 춘계학술발표회
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• pp.521-522
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• 2005

• 한국지반환경공학회 논문집
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• 제9권4호
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• pp.53-61
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• 2008

지진파는 진원지로부터 지표면으로 전파되는 과정에서 전파경로와 부지증폭정도의 차이, 그리고 비균질한 지반에서의 지진파 산란 등으로 인하여 공간적으로 변이하게 된다. 공간적으로 변이하는 지진파는 교량과 터널과 같이 종단방향 길이가 긴 구조물에 큰 영향을 미칠 수 있다. 지진파의 공간적 변이성이 교량에 미치는 영향에 대해서는 잘 알려져 있지만 터널에 미치는 영향에 대해서는 체계적인 연구가 수행된 바 없다. 본 연구에서는 공간적으로 변이하는 지진파에 대한 터널의 응답을 예측하기 위한 새로운 기법을 개발하였다. 개발된 기법의 핵심은 이격거리별 계산된 공간적으로 변이하는 지진파의 시간이력으로부터 생성되는 종단방향 변위 주상도이다. 종단방향 변위 주상도는 일련의 3차원 유사정적 유한요소해석을 수행하는데 사용되었다. 해석결과, 공간적으로 변이하는 지진파는 터널에 종단방향 휨을 유발하며 터널 라이닝에 큰 축력이 발생할 수 있는 것으로 나타났다. 이는 특히 지반의 특성이 변이하는 경계면에서 영향이 큰 것으로 나타났다.

• 한국해양공학회지
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• 제35권4호
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• pp.266-272
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• 2021

Mooring systems are among the most important elements employed to control the motion of floating offshore structures on the sea. Considering the use of polymer material, a new method is proposed to address the creep characteristics rather than the method of using a tension load cell for measuring the tension of the mooring line. This study uses a synthetic mooring rope made from a polymer material, which usually consists of three parts: center, eye, and splice, and which makes a joint for two successive ropes. We integrate the optical sensor into the synthetic mooring ropes to measure the rope tension. The different structure of the mooring line in the longitudinal direction can be used to measure the loads with the entire mooring configuration in series, which can be defined as SMART (Smart Mooring and Riser Truncation) mooring. To determine the characteristics of the basic SMART mooring, a SMART mooring with a diameter of 3 mm made of three different polymer materials is observed to change the wavelength that responds as the length changes. By performing the longitudinal tension experiment using three different SMART moorings, it was confirmed that there were linear wavelength changes in the response characteristics of the 3-mm-diameter SMART moorings. A 54-mm-diameter SMART mooring is produced to measure the response of longitudinal tension on the center, eye, and splice of the mooring, and a longitudinal tension of 100 t in step-by-step applied for the Maintained Test and Fatigue Cycle Test is conducted. By performing a longitudinal tension experiment, wavelength changes were detected in the center, eye, and splice position of the SMART moorings. The results obtained from each part of the installed sensors indicated a different strain measurement depending on the position of the SMART moorings. The variation of the strain measurement with the position was more than twice the result of the difference measurement, while the applied external load increased step-by-step. It appears that there is a correlation with an externally generated longitudinal tensional force depending on the cross-sectional area of each part of the SMART mooring.

• 대한방사선치료학회지
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• 제24권2호
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• pp.175-181
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• 2012

목 적: Exactrac 6D couch system을 이용한 2D/2D 정합 결과를 분석하여 두경부암 환자의 방사선 치료 시 사용되는 Aquaplastic mask가 실제 임상에서 환자 위치 고정에 어떠한 영향을 미치는지 분석하고자 한다. 대상 및 방법: 본원에서 2010년 6월에서 2011년 6월까지 방사선치료를 받은 두경부암 환자 14명을 대상으로 Exactrac 6D couch system을 이용하여 2D/2D 정합을 통한 영상유도를 실시하였다. 영상 유도 후 획득한 6D 보정 결과 값들을 이용하여 각 값들의 상호 관계 연관성에 대하여 환자에 관련된 부분과 환자에 관련되지 않은 부분으로 나누어 분석하였다. 결 과: 전체 14명의 각 환자에 대한 보정 값들의 환자와 관련된 연관성 분석에서는 Longitudinal 방향과 Pitch 방향의 결정계수($R^2$)값이 0.76, Longitudinal 방향과 Yaw 방향은 0.48, Pitch 방향과 Yaw 방향은 0.42로 나타났으나 환자의 의존도를 제외한 분석에서는 위의 인자들에 대하여 0.03 이하의 값을 나타내었다. 결 론: Aquaplastic mask를 이용한 환자의 고정은 환자와 관련된 여러 가지 인자들로부터 영향을 받는 부분도 있지만 근본적인 mask 자체의 요인도 있음을 확인 할 수 있었다. 이에 대한 보정이 이루어질 경우 두경부암 환자의 치료에 있어 좀 더 정확한 치료가 이루어질 수 있으리라고 사료된다.

• Design & Manufacturing
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• 제17권4호
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• pp.33-41
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• 2023

Excessive use of plastic bottles contributes to a significant environmental issue due to the high volume of plastic waste generated. To address this, efforts are needed to reduce the weight of plastic bottles. However, indiscriminate weight reduction may compromise the essential rigidity required for plastic bottles. Extensive research on rib shape for pressure vessels are exists, but there is a few research of rib shapes to enhance the stiffness of plastic bottles. The following results were obtained from the analyses conducted in this study. 1) Among the rib cross-sections of square, trapezoid, and triangle, the buckling critical load of PET bottles with square-shaped ribs is improved by about 14% compared to the buckling critical load of PET bottles without ribs. 2) The buckling critical load is improved by about 18% when a square-shaped rib with an aspect ratio of 0.2 is applied, compared to the buckling critical load of the bottle without the rib. 3) When longitudinal and transverse square ribs were applied to the axial direction of the PET bottle, the buckling critical load was improved by about 32% and 58% compared to the buckling critical load of the PET bottle without ribs, respectively, indicating that applying longitudinal ribs is effective in reinforcing the stiffness of PET bottles. 4) When 14 transverse ribs were applied, the maximum improvement was about 48% compared to the buckling critical load of the plastic bottle without ribs. 5) When 3 longitudinal ribs were applied on each side, the maximum improvement was about 76% compared to the buckling critical load of the bottle without ribs. Therefore, it was concluded that for effective stiffness reinforcement of a 500ml square bottle with a thickness of 0.5mm, 3 square-shaped ribs with an aspect ratio of 0.2 should be applied in the longitudinal direction relative to the axial direction of the bottle.

• 대한기계학회논문집A
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• 제30권1호
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• pp.8-17
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• 2006

When subjected to severe shear deformation by ECAP, microstructure of Al2024 becomes extremely refined. To measure the strength of that, small punch(SP) testing method was adopted as a substitute for the conventional uniaxial tensile testing because the size of material processed by ECAP were limited to ${\psi}12\;mm$ in transverse direction. SP tests were performed with specimens in longitudinal and transverse directions of Al2024 ECAP metal. For comparing the strength values with those assessed by SP tests, uniaxial tensile tests were also conducted with specimens in longitudinal direction. Failure surfaces of the tested SP specimens showed that failure mode was shear deformation and Al 2024 ECAP metal has an anisotropy in strength. Thus, conventional equations proposed for assessing the strength characteristics were improper to assess those of Al2024 ECAP metal. In this paper a way of assessing the strength of Al 2024 ECAP metal was proposed and was proven to be effective.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.69-79
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• 1996

Dynamic stress intensity factors are derives when the crack is propagating with constant velocity under longitudinal shear stress in orthotropic disk plate. General stress fields of crack tip propagating with constant velocity and least square method are used to obtain the dynamic stress intensity factor. The dynamic stress intensity factors of GLV/GTV=1(=isotropic material or transversely isotropic material) which is obtained in out study nearly coincides with Chiang's results when mode Ⅲ stress is applied to boundary of isotropic disk. The D.S.I.F. of mode Ⅲ stress is greater when α(=angle of crack propagation direction with fiber direction) is 90° than that when α is 0°. In case of a/D(a:crack length, D:disk diameter)<0. 58, the faster crack propagation velocity, the less D.S.I.F. but when crack propagation velocity arrive on ghear stress wave velocity, the D.S.I.F. but when crack propagation velocity arrive on shear stress wave velocity, the D.S.I.F. unexpectedly increases and decreases to zero.

• 임산에너지
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• 제18권1호
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• pp.1-5
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• 1999

잦나무 조림목의 유용한 이용과 적합한 용도개발을 위한 수간내 재질변동을 조사하였다. 수고방향(수고 약 20m중 0.3, 1.3, 2.3, 5.3m부위)의 가도관장, 가도관폭, 마이크로피크릴경사각, 압축강도를 측정하고, 그들의 변동에 관하여 Duncan의 다중검정법에 의하여 조사하였다. 그 결과 가도관장, 가도관폭 및 압축강도는 대체로 유의차를 보이지 않았으나 마이크로피브릴경각은 유의차를 나타냈다. 그러나 마이크로피브릴경각은 수고에 따라 높아지거나 또는 낮아지는 등 일정한 경향을 보이지는 않았다.

• 소성∙가공
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• 제25권3호
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• pp.182-188
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• 2016

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to producing multi-curvature surfaces by controlling the strain distribution along longitudinal direction. In FRRF, a sheet metal is shaped into the desired curvature by using reconfigurable rollers and gaps between the rollers. As FRRF technology and equipment are under development, a simulation model corresponding to the physical FRRF would aid in investigating how the shape of a sheet varies with input parameters. To facilitate the investigation, the current study exploits regression analysis to construct a predictive model for the longitudinal curvature of the sheet. Variables considered as input parameters are sheet compression ratio, radius of curvature in the transverse direction, and initial blank width. Samples were generated by a three-level, three-factor full factorial design, and both convex and saddle curvatures are represented by a quadratic regression model with two-factor interactions. The fitted quadratic equations were verified numerically with R-squared values and root mean square errors.

• 소성∙가공
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• 제21권8호
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• pp.479-484
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• 2012

The objective of this study is to compensate the elastic recovery in the flexible forming process using the predictive models. The target shape was limited to two-dimensional shape having only one curvature radius in the longitudinal-direction. In order to predict the shape error the regression and neural network models were established based on the finite element (FE) simulations. A series of simulations were conducted considering input variables such as the elastic pad thickness, the thickness of plate, and the objective curvature radius. Then, at sampling points in the longitudinal-direction, the shape errors between formed and objective shapes could be calculated from the FE simulations as an output variable. These shape errors were expressed to a representative error value by the root mean square error (RMSE). To obtain the correct objective shape the die shape was adjusted by the closed-loop using the neural network model since the neural network model shows a higher capability of estimating the shape error than the regression model. Finally the experimental result shows that the formed shape almost agreed with the objective shape.