• 대한기계학회논문집B
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• 제25권1호
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• pp.18-28
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• 2001

The present study investigates flow dynamics between two dimensional compliant plates under sinusoidal flow conditions in order to understand influence of wall motion, impedance phase angle (time delay between pressure and flow waveforms), and non-Newtonian fluid on wall shear stress using computational fluid dynamics. The results showed that wall motion induced additional terms in the streamwise velocity profile and the pressure gradient. These additional terms due to wall motion reduced the amplitude of wall shear stress and also changed the mean wall shear stress. The trend of the changes was very different depending on the impedance phase angle. As the impedance phase angle was changed to more negative values, the mean wall shear stress decreased while the amplitude of wall shear stress increased. As the phase angle was reduced from 0°to -90°under $\pm$4% wall motion, the mean wall shear stress decreased by 12% and the amplitude of wall shear stress increased by 9%. Therefore, for hypertensive patients who have large negative phase angles, the ratio of amplitude and mean of the wall shear stress is raised resulting in a more vulnerable state to atherosclerosis according to the low and oscillatory shear stress theory. We also found that non-Newtonian characteristics of the blood protect atherosclerosis by decreasing the oscillatory shear index.

• 대한기계학회논문집B
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• 제29권4호
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• pp.425-434
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• 2005

In order to analyze pulsating flows in elastic blood vessels, a method based on the ALE concept and finite volume method was reformed and modulated to include wall motion of elastic vessels and impedance phase angle(phase difference between wall motion and blood flow). Our study indicated wall shear rates(WSR) were significantly influenced by the wall motion and the impedance phase angle. For larger wall motion more than $5{\%},$ the computed WSR started to deviate from the results of the perturbation theory that assumed smaller wall motion. The study showed that oscillatory shear index increased as the impedance phase angle became more negative like $-70{\circ}\;or\;-80{\circ}$ due to reduced mean WSR and increased amplitude of WSR. This result indicated that hypertensive patients are more vulnerable to atherosclerosis than normal persons because of the role of more negative impedance phase angles usually observed in these patients.

• 대한핵의학회지
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• 제31권1호
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• pp.43-49
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• 1997

이 연구에서 우리는 관동맥우회로술을 시행한 환자에서 수술 전에 게이트 심근 SPECT에서 심근벽의 수축기 두꺼워짐을 보아 수술 후 심근벽 운동이상의 호전을 예측할 수 있는지 조사하였다. 연구 결과 심근벽의 수축기 두꺼워짐이 좋은 분절은 생존심근이라 할 수 있었으나 심근벽의 수축기 두꺼워짐이 좋지 못하여도 생존심근이 아니라고 단정할 수 없었다. 심근벽 두꺼워짐 여부의 예측능은 심근 관류 감소의 중증도, 심근벽 운동 장애의 정도와 관련이 없었다. 게이트 심근 SPECT로 심근벽 두꺼워짐을 자극할 방법을 도입하고 자극 후 변화를 보는 방법으로 게이트 심근 SPECT를 시행하여 생존심근을 찾는 예민도와 음성예측율을 높일 필요가 있다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.579-582
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• 1997

The two dimnesional echocardiography is widely used to evaluate regional wall motion abnormaility, because of its abilities to depict left ventricluar wall motion. A new method, color kinesis is a technology or echocardiographic assessment of left ventricular wall motion. In this paper, we proposed a algorithm or color kinesis which is based on acoustic quantification and automatically detects endocardial motion during systole on a frame-by-frame basis. The echocardiograms were obtained in the short-axis views in normal subjects. Automated edge detection and endocardial contour tracing algorithm was applied to each frames, quantitative analysis based on segmentation was performed, and pre-defined color overlays superimposed on the gray scale images. Segmental analysis of color kinesis provided automated, quantitative diagnosis of regional wall motion abnormality.

• 대한핵의학회지
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• 제17권2호
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• pp.25-33
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• 1983

Left ventricular wall motion was observed with EKG gated cardiac blood pool scan in 71 various cardiac diseases and 10 normal controls to evaluate its diagnostic and clinical significance in them. 1) In the presence of left ventricular dysfunction, visual evaluation of the left ventricular wall motion was useful to determine whether it was due to localized or diffuse abnormalities. In cardiomyopathy, marked left ventricular dilatation and severe hypokinesia were noted. 2) In myocardial infarction, regional wall motion abnormalities well represented the location of infarcted areas in majority of cases. Patients with inferior wall infarction had smaller decrease of the left ventricular ejection fraction and wall motion grade than anterior or combined groups. In whom persistent left ventricular failure was present, wall motion analysis with gated cardiac scan provided valuable information for the detection of ventricular aneurysms. 3) Evaluation of the left ventricular wall motion and its grading provided a reliable estimate of the left ventricular function. In conclusion, visual evaluation of left ventricular wall motion and its grading provided valuable information for analyzing the characteristics of regional and global left ventricular dysfunction.

• Journal of Chest Surgery
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• 제38권10호
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• pp.685-692
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• 2005

배경: 좌심실 벽 운동장애는 관상동맥 우회술 후 장기생존율에 영향을 줄 수 있다. 이 연구는 심근경색증 후 발생한 좌심실 벽 운동장애가 관상동맥 우회술 후 장기생존율에 어떠한 영향을 주는가를 알아보았다. 대상 및 방법: 관상동맥 우회술 후 9년이 넘은 환자들 133예(남/여, 92/41)를 대상으로, 심근경색 후 좌심실 벽 운동장애가 있는 환자 56예(남/여 42/14, 평균연령 $59.2\pm9.2$세)와 좌심실 벽 운동장애가 없는 환자 77예(남/여 50/27,평균연령 $58.0\pm7.6$세)로 나누어 비교 분석하였다. 대부분의 환자들(l12/133, $84.2\%$)에서 체외순환 하에 좌측 속 가슴동맥과 하지 큰 두렁정맥을 이용하여 수술하였고 대동맥 차단 상태에서 근위연결 및 원위연결을 시행하는 방법으로 수술하였다. 걸과: 좌심실 벽 운동장애가 있는 환자들의 좌심실 구혈률은 평균 $48.7\pm13.2\%$로 좌심실 벽 운동장애가 없는 환자들(평균$57.1\pm10.1\%$)보다 감소되어 있었다(p=0.0001). 운동장애가 없는 환자군에서 평균 $135.1\pm18.0$개월의 추적으로 5년, 10년, 13년의 생존율은 각각 $85.7\pm4.0\%,\;76.2\;4.9\%,\;57.2\pm10.3\%$였고, 좌심실 운동장애가 있는 환자군에서 평균 $122.8\pm22.7$개월의 추적으로 5년, 10년, 13년의 생존율은 각각 $80.4\pm5.3\%,\;58.7\pm7.3\%,\;11.9\pm7.9\%$이었다(p=0.1). 심근경색에 의한 좌점실 벽 국소 운동장애가 있는 환자의 장기생존율에 영향을 미치는 인자는 좌심실 구혈률과 외래 치료였다. 다변량 분석에서 좌심실 벽 운동장애가 있는 환자군의 장기생존율은 외래 치료를 한 환자에서 우수하였고 좌심실 벽 운동장애가 없는 군의 장기생존율은 여성에서 우수하였다. 결론: 심근경색 후 좌심실 벽의 운동장애가 있는 경우 장기 생존율은 운동장애가 없는 경우보다 떨어지는 경향을 보이며, 그런 환자들에서 수술 후 외래 치료가 장기 생존에 매우 중요하다고 생각한다.

• 대한핵의학회지
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• 제31권1호
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• pp.57-66
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• 1997

We performed 1st day Tc-99m-sestamibi gated SPECT with dipyridamole/rest T1-201 SPECT and 2nd day 24 hour delay T1-201 SPECT/rest Tc-99m-sestamibi gated SPECT in 27 patients with coronary artery disease(24) or having chest pain(3). Stress and rest Tc-99m-sestamibi gated SPECT was acquired at 60min post-injection. A 4-point scoring system(0 to 3 for normal to absent tracer uptake) for 17 segments was used. Wall motion was scored on another 4 point scale(0 to 3 for normal to dyskinesia) in the 1st day post-stress gated and the 2nd day rest gated SPECT. Post-stress gated SPECT showed wall motion abnormality in 94 segments(20%). Fifty-five segments among these 94 showed the same wall motion between post-stress and rest gated SPECT: i.e. 1-1 23 segments, 2-2: 29 segments, 3-3: 3 segments. Remaining 39 segments(41.5%) showed different wall motion between post- stress and rest Tc-99m-sestamibi gated SPECT. Twenty one segments with wall motion abnormality had normal perfusion(rest : 15 segments, 24 hour delay: 6 segments) at either rest or 24 hour delay. Fifteen among these 21 segments showed persistent post-stress and the 2nd day rest wall motion abnormality(persistent stunning). However, in 6 segments with pro-longed (1 hour after stress) stunning, abnormal wall motion did improve in the 2nd day rest Tc-99m-sestamibi gated SPECT(transient prolonged stunning). These 6 segments had normal perfusion at rest(n=4) or at 24 hour delay(n=2). Post stress wall motions showed significantly higher scores in persistent stunning than in prolonged transient stunning(P value<0.05). It was concluded that we could find stunned myocardium with gated Tc-99m-sestamibi SPECT at either post-stress or rest and that some myocardial walls of post-stress 1 hour gated SPECT did not show truly rest wall motion. So, we should be cautious if we use post-stress Tc-99m-sestamibi wall motion to assess rest wall motion.

• Journal of Magnetics
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• 제12권1호
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• pp.1-6
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• 2007

The spin transfer torque generated by a spin-polarized current can induce the shift of the magnetic domain-wall position. In this work, we study theoretically the current-induced domain-wall motion by using the collective coordinate approach [Gen Tatara and Hiroshi Kohno, Phys. Rev. Lett. 92, 86601 (2004)]. The approach is extended to include not only the domain-wall position and the polarization angle changes but also the domain-wall width variation. It is demonstrated that the width variation affects the critical current.

• 한국의학물리학회지:의학물리
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• 제10권3호
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• pp.115-123
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• 1999

2 차원 심초음파는 좌심실벽 운동을 실시간으로 보여줄 수 있어 국소 좌심실벽 운동장애를 진단하는 데 널리 사용되고 있다. 심초음파를 통하여 국소 좌심실벽 운동기능을 평가하고 정량화하기 위한 많은 연구들이 진행되어왔다. 본 논문에서는 국소 좌심실벽 운동장애의 진단을 위한 좌심실벽 운동 추 적 및 정량적 분석 알고리듬을 제안하였다. 정상 피검자들과 국소 좌심실벽 운동이상 환자로부터 얻은 심초음파 흉골연단축단면 영상들이 알고리듬의 시험을 위해 사용되었다. 자동화된 경계선 검출과 좌심실내벽 윤곽선 연결 알고리듬을 각 프레임들에 적용하였고 영역분할에 기초한 정량적 분석을 수행하였으며 운동량을 의미하는 칼라가 프레임 및 영역별로 심초음파 영상들 위에 덧씌워졌고 칼라화된 영상들이 동영상으로 구현되었다. 제안된 알고리듬은 좌심실벽 운동장애의 자동화된 정량적 진단을 제공하였다.

• Structural Engineering and Mechanics
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• 제29권4호
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• pp.433-453
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• 2008

The equation of motion of a one way (vertical) spanning strip wall, as an assembly of two rigid bodies, is presented. Only one degree of freedom is needed to completely describe the wall response as the bodies are assumed to be perfectly rectangular and are allowed to rock but not to slide horizontally. Furthermore, no arching action occurs since vertical motion of the upper body is not restrained. Consequently, the equation of motion is nonlinear, with non constant coefficients and a Coriolis acceleration term. Phenomena associated with overburden to self weight ratio, motion triggering, impulsive energy dissipation, amplitude dependency of damping and period of vibration, and scale effect are discussed, contributing to a more complete understanding of experimental observations and to an estimation of system parameters based on the wall characteristics, such as intermediate hinge height and energy damping, necessary to perform nonlinear time history analyses. A comparison to a simple standing, or parapet, wall is developed in order to better highlight the characteristics of this assembly.