• The Journal of the Acoustical Society of Korea
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• 제25권3E호
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• pp.131-136
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• 2006

The PML developed for the radio wave propagation is a powerful numerical domain truncation technique. We perform an analytic study on the reflection from the PML inserted in the ocean bottom. In the ocean bottom, we show the PML to have the improved performance but simultaneously the degeneration below the critical angle of the fast ocean bottom. The degeneration of the PML can be simply relaxed by stretching the thickness of the PML or putting the attenuation coefficient to the ocean bottom. As a better solution, we propose the improved truncation technique based on the PML and the non-local boundary condition. Finally, we apply the PML to the acoustic wave propagation using split-step Pade PE solver. For the problems of the ocean waveguide, the numerical efficiency of the PML is examined and the usefulness of the PML is confirmed.

• 한국분무공학회지
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• 제11권2호
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• pp.105-112
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• 2006

A unique feature of fluidic atomizers is that the nozzle geometry produces a thin capillary Jet which is forced to oscillate on a 2-dimensional plane through the use of a passive feedback mechanism. The objective of the current work is to characterize the influence of the stagnation pressure at the nozzle exit, jet oscillation and stretching on the breakup properties of the capillary ligament. To achieve this, shadow graph technique is used to measure size, shape, velocity and the number density of the droplets as a function of the position within the spray fan. The breakup length, defined as the radial distance from the breakup point, is analyzed as a function of the non-dimensional parameters. Finally, a kinematic model is developed to simulate the breakup of the oscillating jets at low stagnation pressures. Using the existing jet breakup theories, the model is used to predict the size and diameter distribution of the droplets after primary atomization.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.158-163
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• 1997

In this paper the tool geometry of the PSS test were optimized in order to assure the reliability of the test. Considering many factors for optimization of the tool geometry, computer-simulation technique using three-dimensional finite element method(FEM) was used. Three design variables -the punch length, punch crown and punch corner radius- are chosen to be optimized according to the Taguchi's experiment technique with the L9 orthogonal array. The optimum condition to ensure the plane strain mode over the overall area of the specimen was clarified. Moreover the simulation results are confirmed by experiment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.171-182
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• 1998

An automated surface-strain measuring system using the image processing technique is developed in the present study, which consists of the hardware to capture and to display digital images, and the software to calculate the 3D informations of grid points from two views. New or improved algorithms the mapping and establishing correspondence of grid points and elements, the camera calibration, and the subpixel measurement of grid points, are implemented. As an application of the present system the surface-strains of deformed blanks in the limitting dome height test, the square cup deep-drawing and punch stretching to obtain the forming limit diagram are measured. The results are compared with those obtained by conventional manual methods.

• 소성∙가공
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• 제7권6호
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• pp.575-585
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• 1998

An automated surface-strain measuring system using the image processing technique is developed in the present study which consists of the hardware to capture and to display digital images. and the software to calculate the 3-D informations of grid points from two views. New or improved algorithms for the mapping and establishing correspondence of grid points and elements the camera calibration and the subpixel measurement of grid points are implemented. As an application of the present system the surface-strains of deformed blanks in the limitting dome height test the square cup deep-drawing and punch stretching to obtain the forming limit diagram are measured. The results are com-pared with those obtained by conventional manual methods.

• Journal of Welding and Joining
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• 제7권3호
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• pp.28-35
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• 1989

It was reported that the toughness for welded region was influenced by various factors such as the gradient for prior austenite grain size, the variation of microhardness and the characteristic microstructure depending on distance from the fusion boundary. Therefore, in order to evaluate the fracture strength of the weldment in which the microstructures change continuously, it is important to assess the peculiar strength of each microstructure in welded region. It was known that the small punch(SP) test technique which was originally developed to study the irradiation damage effect for the structures of nuclear power plant was also useful to investigate the strength evaluating of nonhomogeneous materials. In this paper, by means of a small punch test technique the possibility of evaluating strength of parent and welded region in SS41 and SM53B steels was investigated. The obtained results are summerized as follows: 1) The small punch test which showed markedly the ductile-brittle transition behavior in this experiment may be applied to evaluation for the fracture strength of welded region. 2) It was shown that the ductile-brittle regime lied in Region III(plastic membrane stretching region) of the flow characteristics observed in SP test. 3) The SP test technique which shows a more precipitous energy change transition behavior than the other test technique is able to estimate the more precise transition temperature. 4) It could be seen that in comparision with the structure of parent the structure of weld HAZ in SS41 steel was improved while it in SM53B steel was deteriorated.

• 한국정보통신학회논문지
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• 제15권11호
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• pp.2321-2326
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• 2011

경추는 머리와 몸통을 이어주는 중요한 요충지이기 때문에 매우 중요한 기관이며 매우 복잡한 구조로 되어있다. 본 논문에서는 경추 초음파 영상에서 경추 부분에 존재하는 흉쇄유돌근을 자동으로 검출하는 방법을 제안한다. 경추 초음파 영상에서 촬영 정보나 눈금자 등의 필요 없는 부분을 제외한 ROI(Region of Interest)영상을 추출하고 Ends-In Search Stretching 알고리즘을 적용하여 명암 대비를 강조한다. Stretching된 영상에 20 이상의 명암도를 가지는 픽셀을 대상으로 평균 이진화를 적용한 후, 잡음을 제거한다. 잡음이 제거된 영상에 흉쇄유돌근을 둘러싸고 있는 근막의 위치 정보를 이용하여 근막을 추출한 후, 근막의 객체 수에 따라서 각기 다른 방법을 적용하여 근육을 추출한다. 근막 객체가 하나인 경우에는 위에서 아래로 탐색하여 1차 근육 영역을 추출하고, 오른쪽에서 왼쪽으로 탐색하여 2차 근육 영역을 추출한 후, 1차와 2차 근육 영상을 하나로 합쳐 최종 근육 영역을 추출한다. 근막 객체가 두 개인 경우에는 근막 객체의 상단과 하단까지의 영역을 모두 추출한 후, 근막 객체 영역을 제거하는 방법으로 근육 영역을 추출한다. 추출된 근육 영역 중에서 두께가 가장 두꺼운 부분을 근육의 두께로 측정한다. 본 논문에서 제안된 방법을 경추 초음파 영상 30장을 대상으로 실험하여 물리치료사가 분석한 결과, 제안된 방법이 흉쇄유돌근을 정확히 추출되는 것을 확인하였다.

• 대한물리치료과학회지
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• 제31권1호
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• pp.1-15
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• 2024

Background: This study was conducted to apply active release techniques to male youth basketball players to help improve physical development and damage prevention and improve performance through improved balance and functional movement. Design: Randomized control trial. Methods: The subjects included 33 youth basketball players who were randomly assigned to the experimental group (n=17) and the control group (n=16). For the experimental group, the active release technique was applied to the hip muscles, calf muscles, posterior thigh muscles based on the distribution of injuries surveyed in youth basketball players in the Korean Basksetball League. The Y-balance test and the functional reach test (FRT) were used to assess balance and the Functional Movement Screen (FMS) was used to assess functional movement. Interventions were conducted twice a week for 4 weeks at 40 minutes per session. The experimental group was the active release technique group, and static stretching, a common exercise therapy technique, and self-myofascial release using a foam roller were applied for 20 minutes. The control group received general exercise therapy and placebo active release technique. The placebo active release technique applies pressure only. results:The experimental group showed a greater improvement in balance, as evidenced by the FRT, compared to the control group, which received general exercise treatment. However, there was no statistically significant difference in improvement between the 2 groups. In the case of the experimental group, the difference in the Y balance test before and after the intervention was larger than that of the control group, but there was no statistically significant difference. Significant improvement was found in functional movement, as evidence by the FMS, for the trunk stability test (p < 0.05), in-line lunge test (p < 0.05), rotational stability test (p < 0.05), total score (p < 0.05). Conclusion: In this study, the active release technique improved the balance and functional movement of young basketball players more than general exercise therapy. The application of the active release technique is therefore expected to assist in physical development, prevent damage, and improve the performance of youth basketball players.

• 한국항공우주학회지
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• 제34권1호
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• pp.42-48
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• 2006

연구에서는 다분야 통합 최적설계를 위한 시스템 근사화 기법으로 RRSET (Repetitive Response Surface Enhancement Technique)를 제안하였다. 2차 다항식만으로는 어려운 반응면의 표현을 위해 RRSET는 설계공간을 변형할 수 있는 스트레칭 함수를 도입하고 전역 최적화 알고리즘인 담금질 모사기법을 이용하여 반응면을 최적화 하였다. 도출된 최적점은 반복적으로 다음 순기의 반응면의 구성에 이용하여 반응면의 신뢰도를 더욱 높일 수 있었다. 제안된 기법을 수치예제 등에 적용한 결과, 비교적 적은 수의 실험 회수로 비선형적인 반응면을 잘 표현하고 최적 설계점을 도출해낼 수 있음이 확인되었다. 정밀한 근사화 기법의 중요성이 강화되고 있는 현재, 본 연구에서 제시된 근사화 기법은 차후의 연구에서 다분야 통합 최적화 기법에의 적용이 가능하리라 사료된다.

• 대한화학회지
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• 제19권5호
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• pp.317-324
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• 1975

$Na^+,\;Ca^{2+},\;Ni^{2+},\;Al^{3+}$ 이온이 포화된 montmorillonite상에 여러 溫度에서 일어난 $H_2O와\;D_2O$의 氣相吸着에 관하여 연구하였다. 吸着으로 인하여 생긴 OH의 IR 신축진동 band를 computer에 의하지 않고 4개의 Gauss 成分으로 나누었다. 물과 silanol OH기와의 共鳴理論은 $3625cm^{-1}와\;2680cm^{-1}$로 증명되었다. $3400cm^{-1}$와 2475cm 에서의 broad한 吸收는 吸着된 물과 水素結合을 일으키고 있는 silanol OH의 신축진동에 의한 것이었고 $3650cm^{-1}와\;2345cm^{-1}$ band는 吸着된 $H_2O와\;D_2O$에 의한 것이었다. 吸着水와 表面 OH사이의 水素結合은 精電氣的 相互作用에 의한 것임이 밝혀졌다.