• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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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.

• The Korean Journal of Nuclear Medicine
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• v.31 no.1
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• pp.43-49
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• 1997

We studied to investigate the predictive values of gated SPECT for the improvement of wall motion after bypass surgery. As we compared postoperative SPECT with preoperative ones, we defined viability as wall motion improvement. We peformed rest T1-201/s1ress Tc-99m-MIBI gated SPECT in 25 patients before and 3 months after bypass surgery. Myocardial wall motion was graded as normal, hypokinesia, akinesia, and dyskinesia by pair-wise visual analysis of gated pre and postoperative SPECT's on the same monitor screen. Myocardial wall thickening was determined good or poor Among 92 segments with wall motion abnormalities before operation, 69 (75%) improved and 23 did not. Before operation, we could find segments with good systolic thickening in 64 segments among total 92. Thickening of the remaining 28 was poor. Wall motion improved postoperatively in 45 segments (70%) among 64 with good thickening. Twenty four(86%) among 28 segments with poor thickening had also improved. We grouped segments into mild(hypokinetic) and severe(akinetic/dyskinetic) ones. Among 33 segments with severe motion abnormalities, 14 had good thickening and 19 did not. Nine(60%) improved out of 14 segments having severe abnormality with good thickening However, 16(84%) segments out of 19 haying severe abnormality with poor thickening also improved. Neither degree of perfusion decrease nor severity of wall motion abnormalities could explain the high rate of false negatives. In conclusion, as we defined viability as wall motion improvement by comparing pre and postoperative SPECT, systolic thickening observed by gated Tc-99m-MIBI SPECT in myocardial segments with wall motion abnormalities predicted wall motion improvement after bypass surgery. However, poor thickening could not be referred as evidence of nonviable myocardium both in mild and severe contractile dysfunction, so that we might need stimulation study such as dobutamine echocardiography or dobutamine gated SPECT.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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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.

• The Korean Journal of Nuclear Medicine
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• v.17 no.2
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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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• v.38 no.10 s.255
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• pp.685-692
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• 2005

Background: Wall motion abnormalities may be a significant predictor for long-term survival after coronary bypass surgery (CABG). The aim of this study is to see whether post-infarction wall motion abnormality of left ventricle affect on the long-term survival after CABG. Material and Method: One-hundred and thirty-three patients (male/female, 92/41) undergoing CABG more than 9 years ago were included in this study. Fifty-six patients (M/F, 42/14; mean age, $59.2\pm9.2$ years) with LV wall motion abnormalities were compared to 77 patients (M/F, 50/27; mean age, $58.0\pm7.6$ years) without the wall motion abnormalities. Most patients (112/133, $84.2\%$) had undergone on-pump CABG with the in-situ left internal thoracic artery and free grafts of saphenous vein, in which the proximal and distal anastomoses were done for the single aortic cross-clamping period. Result: Ejection fraction of left ventricle was lower in the group with LV wall motion abnormalities (mean ejection fraction, $48.7\pm13.2\%$) compared to the group without wall motion abnormalities (mean ejection fraction, $57.1\pm10.1\%$)(p=0.0001). Risk­unadjusted survivals after CABG in the group without wall motion abnormalities were $85.7\pm4.0\%,\;76.2\pm4.9\%,\;and\;57.2\pm10.3\%$ at 5, 10, and 13 years, respectively, and in the group with wall motion abnormalities were $80.4\pm5.3\%,\;58.7\pm7.3\%,\;and\;51.9\pm7.9\%$ at 5, 10, and 13 years, respectively (p=0.1). In univariate analysis, predictable factors of long-term survival in the patients with LV wall motion abnormalities were LV ejection fraction and post operative outpatient treatment. In multivariate analysis, predictable factor of long-term survival in the patients with the wall motion abnormalities was postoperative outpatient treatment, and that in those without the wall motion abnormalities was female. Conclusion: Although there was no significant survival difference after CABG between the group with LV wall motion abnormalities and that without wall motion abnormalities, the survival in the group with wall motion abnormalities seems to be more decreased. For the patients with LV wall motion abnormalities after myocardial infarction, the post-CABG outpatient treatment is suggested to be an important factor for the long-term survival.

• The Korean Journal of Nuclear Medicine
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• v.31 no.1
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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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• v.12 no.1
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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.

• Structural Engineering and Mechanics
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• v.29 no.4
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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.

• Progress in Medical Physics
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• v.10 no.3
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• pp.115-123
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• 1999

The two dimensional echocardiography is widely used to evaluate regional wall motion abnormality, because of its abilities to depict left ventricular wall motion. A number of researches have been processed for evaluation and quantitative analysis of left ventricular wall motion functions. In this paper, we proposed an algorithm which detects automatically and analyze quantitatively endocardial wall motion during systole. The echocardiograms were obtained in the short-axis views in normal subjects. Automated edge detection and endocardial contour tracking algorithm was applied to each frames, quantitative analysis based on segmentation was performed, pre-defined color overlays superimposed on the gray scale images, and the images was animated. The proposed algorithm provided automated, quantitative diagnosis of regional wall motion abnormality.