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Lee, Sak,Chang, Byung-Chul,Youn, Young-Nam,Kwak, Young-Lan,Yoo, Kyung-Jong Japanese Circulation Society. 2007 CIRCULATION JOURNAL Vol.71 No.10
<P><B>Background</B> An association of mitral regurgitation (MR) with ischemic cardiomyopathy (I-CMP) increases the risk of heart failure and its surgical management remains controversial. <B>Methods and Results</B> Between July 2001 and June 2006, a total of 49 patients with I-CMP underwent surgical ventricular restoration (SVR) and coronary revascularization with or without concomitant mitral annuloplasty (MAP). The mean age was 59.8 years, and all patients had New York Heart Association (NYHA) class III or IV heart failure (mean left ventricular ejection fraction (LVEF) = 24.8%). Nineteen patients had MR >grade 3 (MR group). SVR and coronary artery bypass grafting were performed in all patients, and concomitant MAP was performed in the MR group. Echocardiography was performed preoperatively, postoperatively, and at mean of 19 months after operation. Preoperative left ventricular (LV) end-diastolic and end-systolic dimensions, left atrial volume index, and MR grade were statistically significantly increased in the MR group. On the early postoperative echocardiogram, mean LVEF was significantly improved, with reduction of LV dimensions, in both groups; however, at follow up, these parameters were more significantly improved in the MR group, but unchanged in non-MR group, reaching almost the same levels as the non-MR group. <B>Conclusion</B> In patients with I-CMP, MR increases early and late mortality; however, after SVR and concomitant MAP, LV function seems to continuously improve with more significant reduction in the LV dimensions than in the non-MR group. (<I>Circ J</I> 2007; <B>71:</B> 1516 - 1520)</P>
이삭(Sak LEE),이동원(Dong-Won LEE),김병지(Byung-Ji KIM),권순범(Soon-Bum KWON) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Jets issuing from a conventional nozzle and convergent nozzles of a constant expansion rates and a certain normal using an annular slit are compared to investigate the characteristics of the 3 jets. In experiments, to compare the characteristics between jets, the nozzle exit mean velocity is fixed as 90㎧. The pressures along the jet axis and radial directions is measured by scanning valve system moving with 3-axis auto-traverse unit, and the velocity distribution can be obtained by calculation from the measured static and total pressures. To obtain the highly stable and convergency jets, a nozzle has to be designed with an annular slit connected to an conical cylinder, furthermore, the flow through aconstant expansion rate nozzle using annular slit is the most probable. And the pressure drop along the nozzle for the constant expansion rate nozzle is small.
CW 신호 간 주파수 간격 조정을 통한 MF R-Mode 성능 향상 연구
이삭(Lee Sak),신장환(Shin Jang Hwan),안재민(Ahn Jae Min) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
본 논문은 글로벌 해양 분야에서 위성항법시스템(GNSS, Global Navigation Satellite System)의 백업항법시스템으로 주목받고 있는 중파(MF, Medium Frequency) 위성항법보정시스템(DGNSS, Differential Global Navigation Satellite System) 을 개량한 지상파통항항법시스템(R-Mode, Ranging-Mode) CW 신호의 주파수 간격 조정을 제안하고, 시뮬레이션을 통해 수신부에서의 위상 및 거리 추정 성능이 향상될 수 있는 가능성을 확인하였다.
초등 영어 학습에서 실제 자료와 제작 자료의 효과 고찰
이삭(Lee Sak) 한국초등영어교육학회 2016 초등영어교육 Vol.22 No.2
This research investigates the effects of authentic materials and artificial materials on English learning in the primary school classrooms in terms of language learning, task involvement, and learner interest. The two types of materials were alternately used to teach English to 38 students in the two intact classes of grade 6 in a counterbalanced manner. The effects of material types were tested through language skills (i.e., speaking, listening, reading, and writing), observation scales, surveys and interviews in order to see if there are any differential effects on leaners. A confounding variable was the learner’s level of English proficiency. The statistical analyses of data revealed that there were significant interactional effects between the type of material and the learner level. For the upper-level learners, authentic materials were effective only in listening with no significant differences in the other skills. For the mid-level learners, artificial materials were effective only in writing with no differences in the other skills. For the low-level learners, artificial materials worked much more effectively on all four skills. As for task involvement, the upper-level learners obtained higher scores with authentic materials whereas the low-level learners did so with artificial materials. The mid-level learners showed no statistical differences in the type of material. As for learner interest, the upper-level learners showed more interests with authentic materials, whereas the low-level learners did so with artificial materials. The mid-level learners did not show any preferences for the type of material. This study suggests that teachers need to take careful consideration of learner level when exploiting teaching materials in English classes.