• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.122-125
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• 2004

In radiotherapy of tumors in liver, enough planning target volume (PTV) margins are necessary to compensate breathing-related movement of tumor volumes. To overcome the problems, this study aims to obtain patients' body movements by using a moving phantom and an ultrasonic sensor, and to develop respiration gating techniques that can adjust patients' beds by using reversed values of the data obtained. The phantom made to measure patients' body movements is composed of a microprocessor (BS II, 20 MHz, 8K Byte), a sensor (Ultra-Sonic, range 3 cm ${\sim}$3 m), host computer (RS232C) and stepping motor (torque 2.3Kg) etc., and the program to control and operate it was developed. The program allows the phantom to move within the maximum range of 2 cm, its movements and corrections to take place in order, and x, y and z to move successively. After the moving phantom was adjusted by entering random movement data(three dimensional data form with distance of 2cm), and the phantom movements were acquired using the ultra sonic sensor, the two data were compared and analyzed. And then, after the movements by respiration were acquired by using guinea pigs, the real-time respiration gating techniques were drawn by operating the phantom with the reversed values of the data. The result of analyzing the acquisition-correction delay time for the three types of data values and about each value separately shows that the data values coincided with one another within 1% and that the acquisition-correction delay time was obtained real-time (2.34 ${\times}$ 10$^{-4}$sec). This study successfully confirms the clinic application possibility of respiration gating techniques by using a moving phantom and an ultra sonic sensor. With ongoing development of additional analysis system, which can be used in real-time set-up reproducibility analysis, it may be beneficially used in radiotherapy of moving tumors.

• Radiation Oncology Journal
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• v.22 no.4
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• pp.316-324
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• 2004

Purpose : In radiotherapy of tumors in liver, enough planning target volume (PTV) margins are necessary to compensate breathing-related movement of tumor volumes. To overcome the problems, this study aims to obtain patients' body movements by using a moving phantom and an ultrasonic sensor, and to develop respiration sating techniques that can adjust patients' beds by using reversed values of the data obtained. Materials and Methods : The phantom made to measure patients' body movements is composed of a microprocessor (BS II, 20 MHz, 8K Byte), a sensor (Ultra-Sonic, range $3\~3$ m), host computer (RS232C) and stepping motor (torque 2.3 Kg) etc., and the program to control and operate it was developed. The program allows the phantom to move within the maximum range of 2 cm, its movements and corrections to take place In order, and x, y and z to move successively. After the moving phantom was adjusted by entering random movement data (three dimensional data form with distance of 2 cm), and the phantom movements were acquired using the ultra sonic sensor, the two data were compared and analyzed. And then, after the movements by respiration were acquired by using guinea pigs, the real-time respiration gating techniques were drawn by operating the phantom with the reversed values of the data. Results : The result of analyzing the acquisition-correction delay time the three types of data values and about each value separately shows that the data values coincided with one another within $1\%$ and that the acquisition-correction delay time was obtained real-time $(2.34{\times}10^{-4}sec)$. Conclusion : This study successfully confirms the clinic application possibility of respiration gating techniques by using a moving phantom and an ultrasonic sensor. With ongoing development of additional analysis system, which can be used in real-time set-up reproducibility analysis, it may be beneficially used in radiotherapy of moving tumors.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2009.05a
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• pp.239-242
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• 2009

최근 3 차원 측정 기술을 활용한 운동 기능성의 향상을 위한 연구가 활발히 진행되고 있다. 그 예로 3 차원 인체 정보를 이용한 의복패턴 제작 시에 필요한 절개선으로 피부상에서 동작 시 늘어나지 않는 선(Lines of Non-Extension, LoNE)을 찾아내어 활용한 연구가 발표된 바 있다. 이러한 LoNE 은 기존 의복구성을 위한 봉제선이나 기능선으로 활용될 때 동작기능성을 저해하지 않는 특징이 있다. 이에 본 연구에서는 스포츠웨어에서 활동성이 큰 상체의 어깨부위에서 Lines of Non-Extension 을 탐색하고자 하였다. 연구 방법으로는 20 대 후반 남성 2 명을 대상으로 체표의 등 부분에서 3cm 간격으로 계측점을 표시한 후 3D 인체 데이터 (Cyberware, WB)를 획득하였다. 측정시의 자세는 팔을 $30^{\circ}$, $90^{\circ}$, $135^{\circ}$, $180^{\circ}$ 외전시켰다. 피부 표면에서의 길이 변화는 구획의 크기를 달리하면서 가로, 세로, 사선방향으로 동작에 따라서 측정하였다. 변화량은 정자세($30^{\circ}$)를 기준으로 A 라 하였을 때, 기준자세와의 차이가 가장 큰 변화량을 보인 자세를 B 라 하고 A 와 B 간의 차이로 계산하였다. 연구결과, NASA 의 Biosuit 에서 소개된 Iberall(1970)의 LoNE 중 진동둘레를 포함한 팔 부위와 등, 어깨 부위에서 유사한 라인을 찾았다. 본 연구에서와 같이 구획별 사선방향 피부 변화량을 측정하는 것은 피부면에 숨겨진 인간공학적 의복 기능선을 탐색하는 데 효과적임을 확인하였다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.59-59
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• 2011

파랑의 전파와 변형에 대한 연구에는 수심방향으로 적분한 2차원방정식인 완경사방정식과 Boussinesq 방정식을 기반으로 한 수치모형을 이용한 연구가 최근까지 가장 활발하게 진행되어 오고 있다. 그러나 실제 구조물의 설계에는 2차원 수치모형에서 고려할 수 없는 수심방향 유속에 기인한 정확도의 문제로 인해 구조물의 형상과 재원을 설계하기 위한 정교한 수치모형실험이 어려워 주로 수리모형실험에 의존해 왔다. 수리모형실험은 실제 현상을 가장 잘 재현해낼 수 있어 신뢰성이 매우 높지만 다양한 실험을 수행하기가 어렵고 많은 시간과 비용이 소요되는 단점이 있다. 이에 따라 최근 수심방향으로 완전한 운동방정식인 Navier-Stokes 방정식을 푸는 3차원 수치모형에 대한 연구가 활발히 진행되고 있다. 이론적으로 매우 우수한 모형이긴 하나 정확도 높은 결과를 얻기 위해서는 매우 조밀한 격자를 필요로 하기 때문에 아직까지 막대한 계산시간이 필요하다는 단점이 있으나 컴퓨터 기술이 급격한 속도로 발전하고 있어 Navier-Stokes 방정식 모형의 적용 가능성은 계속 높아지고 있다. 파랑변형을 다루는 수치모형실험을 수행할 때 외부조파를 사용할 경우 구조물이나 지형에 의해 반사되어 나온 파랑이 조파지점에 도달할 때 실험영역으로 재 반사되는 문제가 발생한다. 이를 해결하기 위해 내부조파기법의 개발에 대한 연구가 필수적이었으며, 자유수면변위를 변수로 사용하는 모형의 경우 그 연구가 매우 활발하게 진행되어 왔다. 한편, Navier-Stokes 방정식 모형의 경우 자유수면변위를 변수로 사용하는 2차원 모형에 비해 상대적으로 연구가 미흡하였다. 본 연구에서는 기존의 연직 2차원 Navier-Stokes 방정식 모형에 사용된 연속방정식에 질량 원천항을 추가하는 내부조파기법을 도입하여 3차원 수치모형에서 고립파를 내부조파하고, 급경사에서의 고립파의 처오름 및 처내림 현상을 수리모형 실험결과와 비교 및 분석하였다. 수치모형은 Navier-Stokes 방정식을 엇갈림 격자체계에서 계산하는 동수압 모형으로서, Two-step projection 기법을 사용하는 유한차분모형을 사용하였다. 본 수치모형은 난류의 해석을 위해서 상대적으로 큰 에디(eddy)만을 고려하는 SANS(spatially averaged Navier-Stokes) 방정식을 계산하는 LES(large-eddy-simulation) 기반의 수치모형으로, 난류 모델링을 위해 Smagorinsky LES 모형을 사용한다. 또한, 압력장의 계산을 위해 Bi-CGSTAB 기법을 이용하여 Poisson 방정식의 해를 구하였으며, 자유수면 추적을 위하여 2차 정확도의 VOF(volume-of-fluid) 기법을 사용하였다. 수치모형실험이 전체적으로 수리모형실험에서 관측한 파랑의 처오름 및 처내림 현상을 잘 재현하고 있는 것으로 나타났으며, 정량적인 비교를 통해 수치모형의 성능을 검증하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.140-140
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• 2018

다수의 자연 하천은 사행의 형태를 가지고 있으며 자연 상태에서의 직선 하천 형태는 비율이 20% 이하이다. 이러한 하천의 사행 형상으로 인하여 편수위 발달, 횡방향 압력의 불균형, 그리고 수심차에 의한 원심력이 발생하여 이차류 흐름이 발생된다. 정확한 이차류 구현을 위해서는 3차원 모형을 사용하는 것이 바람직하나, 3차원 모형의 격자 구성과 사용에서는 상당한 시간 및 노력이 요구되기 때문에 수심적분 2차원 모형을 사용하면서도 이차류의 영향을 구현하기 위한 연구들이 이루어졌다. 본 연구에서는 이러한 이차류의 영향을 2차원 모형으로 구현하고자 하였으며 이를 위해 이차류 연직 분포에 대한 기존 연구를 검토하여 새로운 이차류 공식을 개발하였다. 그리고 한국건설기술연구원 하천실험센터의 실규모 실험을 통해서 이차류 공식에 사용되는 계수를 보정하였다. 이처럼 개발된 식은 이차원 수리해석 모형인 HDM-2D에 적용되었다. HDM-2D는 수심 적분된 2차원 운동량 방정식을 지배방정식으로 사용하는 수리해석모형으로서, 이차류의 영향을 반영하기 위하여 개발한 황방향 유속의 연직분포식을 분산 응력항에 대입하여 이차류에 의한 전단 효과를 구현하였다. HDM-2D 흐름 모의 수행 결과와 하천실험센터 실험결과와 비교하여 이차류 효과가 주 흐름 유속의 분포에 미치는 영향을 확인하였다. 분석 결과, 모의 결과는 실험에서 발생하는 유속의 주 흐름 분포가 바깥쪽으로 편중되는 현상을 적절하게 재현함을 알 수 있었다. 모의 결과를 통해 HDM-2D 모형이 이러한 이차류 영향을 구현할 수 있음을 확인하였으며, 사행수로에서 주 흐름분포의 재분배는 하천 환경에서 유사 이동 및 오염물 이동에 큰 영향을 미칠 것으로 판단된다.

• Water for future
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• v.27 no.3
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• pp.115-121
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• 1994

Cohesie sediment movement in estuarine systems is strongly affected by the phenomena of aggregation and flocculation. Aggregation is the process where primary particles are clustered together in tightly-packed formations; flocculation is the process where aggregates and single particles are bonded together to form large particle groups of very low specific density. The size, shape and strength of the flocculants control the rate of deposition and the processes of pollutant exchange between suspended sediments and ambient water. In estuarine waters, suspended sediments above the lutocline form the mobile suspension zone while below the lutocline they form the stationary suspension zone. Suspended particles in the mobile zone are generally in a dispersed state and the controlling forces are the Brownian motion and the turbulent flow fluctuations. In the stationary suspension zone, the driving force is the gravity. This paper discusses the settling and particle flocculation characteristics under quiescient flow conditions. Particles are entering the study domain randomly. Particles in the mobile suspension zone are simulated by using the Smoluchowski's model. Flocs created in the mobil suspension zone are moving into the stationary suspension zone where viscosity and drag effects are important. Utilizing the concepts of the maximum Feret's diameter and the Minkowski's sausage logic, the fractal dimension of the flocs within the stationary suspension is estimated and then compared with results obtained by other studies.

• Journal of Korea Water Resources Association
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• v.45 no.4
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• pp.349-360
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• 2012

A horizontally curvilinear non-hydrostatic free surface model that was applicable to three-dimensional viscous flows was developed. The proposed model employed a top-layer equation to close kinematic free-surface boundary condition, and an isotropic k-${\varepsilon}$ model to close turbulence viscosity in the Reynolds averaged Navier-Stokes equation. The model solved the governing equations with a fractional step method, which solved intermediate velocities in the advection-diffusion step, and corrects these provisional velocities by accounting for source terms including pressure gradient and gravity acceleration. Numerical applications were implemented to the wind-driven currents in a two-dimensional closed basin, the flow in a steep-sided trench, and the flow in a strongly-curved channel accounting for secondary current by the centrifugal force. Through the numerical simulations, the model showed its capability that were in good agreement with experimental data with respect to free surface elevation, velocity, and turbulence characteristics.

• Journal of the Korean earth science society
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• v.32 no.2
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• pp.200-211
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• 2011

The purpose of this study is to investigate the effects of astronomical animation module on students' conceptual change regarding the concepts of diurnal motion of stars. Four students participated in this study, who never learned about the diurnal motion of stars. An animation module was developed by using Flash MX to readily understand the concept of space. In addition, we inserted a teacher's voice with supplementary materials into the animation module to help students learn individually. The animation module was comprised of the movement of the Earth, the Moon and the planet. The earth science gifted students' preconception on diurnal motion of stars was analyzed with pre-test using questionnaires and interviews. After the instruction with animation module, the effect of conceptual change was examined by comparing pre and post-test. The results indicated that three students correctly presented about the motion of the star by all directions in middle latitude. Four students showed their understanding that stars travelled straight in all directions. Finally, all of four students whose preconceptions were that the star rotated perpendicularly showed the conceptual change of diurnal motion that the star traveled diagonally.

• Journal of the Korean association of regional geographers
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• v.11 no.6
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• pp.530-542
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• 2005

In this study, GIS method has been used to get fractal characteristics. Using the projected area and surface area, 2 dimensional fractal characteristic of terrain was found out. Correlation of fractal dimension and mean slope were also checked over. Results are as below. 1) To get a fractal dimension, the method which is using the surface area is also directly proportional to complexity of the terrain as other fractal dimension. 2) Fractal dimensions using the surface area, that is proposed in this thesis are carried out as below : Uiseong : $2.02{\sim}2.15$ Yeongcheon : $2.10{\sim}2.24$. These values are in a range of fractal $2.10{\sim}2.20$ dimensions which has known. 3) Correlation of mean slope and fractal dimension is diminished about 30% in a region which is more than $25^{\circ}$ of mean slope. So, in this region using the fractal dimension method is better than using the mean slope. From this study, on formula using the projected area and surface area is still good to get a fractal dimension that has been found. But to confirm this method the region of research should be wider and be set up the correlation of mean slope, surface area and fractal dimension. It can be applicable to restoration of terrain and traffic flow analysis in the future research.

• Investigative Magnetic Resonance Imaging
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• v.14 no.2
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• pp.115-120
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• 2010

Purpose : To separate and evaluate the low frequency spontaneous fluctuation BOLD signals from the functional magnetic resonance imaging data using sensorimotor active task. Materials and Methods : Twenty female archery players and twenty three control subjects were included in this study. Finger-tapping task consisted of three cycles of right finger tapping, with a subsequent 30 second rest. Blood oxygenation level-dependent (BOLD) data were collected using $T2^*$-weighted echo planar imaging at a 3.0 T scanner. A 3-D FSPGR T1-weighted images were used for structural reference. Image processing and statistical analyses were performed using SPM5 for active finger-tapping task and GIFT program was used for statistical analyses of low frequency spontaneous fluctuation BOLD signal. Results : Both groups showed the activation in the left primary motor cortex and supplemental motor area and in the right cerebellum for right finger-tapping task. ICA analysis using GIFT revealed independent components corresponding to contralateral and ipsilateral sensorimotor network and cognitive-related neural network. Conclusion : The current study demonstrated that the low frequency spontaneous fluctuation BOLD signals can be separated from the fMRI data using finger tapping paradigm. Also, it was found that these independent components correspond to spontaneous and coherent neural activity in the primary sensorimotor network and in the motor-cognitive network.