• Journal of Chest Surgery
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• 제27권8호
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• pp.656-663
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• 1994

Evaluation of heart function is of importance in assessing the results of valvular heart surgery. Information on volume and functional change of heart chamber can be obtained by cardiac catheterization and echocardiography. We studied 41 patients with mitral stenosis[MS] and 23 patients with mitral regurgitation[MR] using M-mode echocardiography before and after mitral valve replacement[MVR] at Pusan Paik Hospital. Preoperative cardiac catheterization was available in 56 cases, and the results were obtained as follows. 1. In patients with MS, preoperative average LV end-diastolic dimension[EDD] and end-systolic dimension[ESD] were remained within normal range, but postoperative EDD and ESD were significantly decreased[P<0.01]. The preoperative and postoperative LV ejection fraction[EF] were remained within the normal range and no significant change[P>0.05]. The preoperative left atrial dimension[LAD] was enlarged considerably above normal[P<0.01], but was significantly decreased after surgery[P<0.001]. The preoperative LV posterior wall thickness[PWTh] was within normal range, and no significant change after surgery[P>0.05]. 2. In patients with MR, preoperative average end-diastolic dimension[EDD] and end-systolic dimension[ESD] were significantly greater than normal[P<005], but postoperative EDD and ESD were significantly decreased[P<0.01]. The preoperative LV ejection fraction[EF] and fractional shortening[FS] were within normal range, and no significant change after surgery[P>0.05].The preoperative left atrial dimension[LAD] was enlarged considerably above normal [P<0.01], but was significantly decreased after surgery[P<0.001].The preoperative LV posterior wall thickness[PWTh] was within normal range, and no significant change after surgery[P>0.05].

• 천문학회지
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• 제55권3호
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• pp.67-74
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• 2022

In this study, we perform a statistical investigation of the kinematic classification of 4,264 coronal mass ejections (CMEs) from 1996 to 2015 observed by SOHO/LASCO C3. Using the constant acceleration model, we classify these CMEs into three groups: deceleration, constant velocity, and acceleration motion. For this, we devise three different classification methods using fractional speed variation, height contribution, and visual inspection. The main results of this study can be summarized as follows. First, the fractions of three groups depend on the method used. Second, about half of the events belong to the groups of acceleration and deceleration. Third, the fractions of three motion groups as a function of CME speed are consistent with one another. Fourth, the fraction of acceleration motion decreases as CME speed increases, while the fractions of other motions increase with speed. In addition, the acceleration motions are dominant in low speed CMEs whereas the constant velocity motions are dominant in high speed CMEs.

• The Korean Journal of Physiology and Pharmacology
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• 제26권6호
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• pp.511-518
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• 2022

Sepsis-associated myocardial injury, an invertible myocardial depression, is a common complication of sepsis. Neogambogic acid is an active compound in garcinia and exerts anthelmintic, anti-inflammatory, and detoxification properties. The role of neogambogic acid in sepsis-associated myocardial injury was assessed. Firstly, mice were pretreated with neogambogic acid and then subjected to lipopolysaccharide treatment to induce sepsis. Results showed that lipopolysaccharide treatment induced up-regulation of biomarkers involved in cardiac injury, including lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), and troponin I (cTnI). However, pretreatment with neogambogic acid reduced levels of LDH, CK-MB, and cTnI, and ameliorated histopathological changes in the heart tissues of septic mice. Secondly, neogambogic acid also improved cardiac function in septic mice through reduction in left ventricular end-diastolic pressure, and enhancement of ejection fraction, fractional shortening, and left ventricular systolic mean pressure. Moreover, neogambogic acid suppressed cardiac apoptosis and inflammation in septic mice and reduced cardiac fibrosis. Lastly, protein expression of p-p38, p-JNK, and p-NF-κB in septic mice was decreased by neogambogic acid. In conclusion, neogambogic acid exerted anti-apoptotic, anti-fibrotic, and anti-inflammatory effects in septic mice through the inactivation of MAPK/NF-κB pathway.

• Geomechanics and Engineering
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• 제29권1호
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• pp.53-63
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• 2022

Simplified analytical solutions are developed for the dynamic analyses of an axially loaded pile foundation embedded in a transverse-isotropic, fluid-filled, poro-visco-elastic soil with rigid substratum. The pile is modeled as a viscoelastic Rayleigh-Love rod, while the surrounding soil is regarded as a transversely isotropic, liquid-saturated, viscoelastic, porous medium of which the mechanical behavior is represented by the Boer's poroelastic media model and the fractional derivative model. Upon the separation of variables, the frequency-domain responses for the impedance function of the pile top, and the vertical displacement and the axial force along the pile shaft are gained. Then by virtue of the convolution theorem and the inverse Fourier transform, the time-domain velocity response of the pile head is derived. The presented solutions are validated, compared to the existing solution, the finite element model (FEM) results, and the field test data. Parametric analyses are made to show the effect of the soil anisotropy and the excitation frequency on the pile-soil dynamic responses.

• ETRI Journal
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• 제45권2호
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• pp.338-345
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• 2023

A filtering power divider based on air-filled substrate-integrated waveguide (AFSIW) technology is proposed in this study. The AFSIW structure is used in the proposed filtering power divider for substantially reducing the transmission losses. This structure occupies a large area because of the use of air as a dielectric instead of typical dielectric materials. A filtering power divider provides power division and frequency selectivity simultaneously in a single device. The proposed filtering power divider comprises three AFSIW cavities. The filtering function is achieved using symmetrical inductive posts. The input and output ports of the proposed circuit are realized by directly connecting coaxial lines to the AFSIW cavities. This transition from the coaxial line to the AFSIW cavity eliminates the additional transitions, such as AFSIW-SIW and SIW-conductor-backed coplanar waveguide, applied in existing AFSIW circuits. The proposed power divider with a second-order bandpass filtering response is fabricated and measured at 5.5 GHz. The measurement results show that this circuit has a minimum insertion loss of 1 dB, 3-dB fractional bandwidth of 11.2%, and return loss exceeding 11 dB.

• 한국음향학회지
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• 제27권6호
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• pp.263-270
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• 2008

초음파 어레이 센서의 성능은 구성 불성과 많은 구소 변수들에 의해 결정된다. 본 연구에서는 유한 요소해석을 통하여 구조적인 변화에 따른 초음파 어레이 센서의 성능변화를 해석하였다. 해석 결과를 기초로 하여 초음파 어레이 센서가 주파수 대역폭, 중심 주파수 그리고 -20 dB pulse length와 같은 요구 사항을 모두 만족시키며 최대의 감도를 가지도록 구조를 최적화하였다. 최적화 방법으로는 초음파 어레이 센서의 성능을 목적 함수로 하는 SQP-PD 방법을 사용하였다. 최적화된 초음파 어레이 센서는 의료 영상 진단에 적용되기 위한 모든 요구 조건을 만족하였으며, 본 설계 기술은 유사한 형태의 다른 배열형 초음파 센서에 응용 가능하다

• 한국전자파학회논문지
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• 제18권1호
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• pp.7-14
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• 2007

본 논문에서는 직사각형 개방형 도파관들이 삼각 격자 형태로 배열된 구조의 조향 특성을 연구하였다. 무한배열 해석 이론에서의 도파관 모드와 플로케 모드 함수를 이용하여 도파관 내부와 외부의 전계 성분을 적분방정식으로 유도하고 이를 프로그램화하여 조향 소자 패턴과 조향 임피던스를 수치해석하였다. CST사의 MWS(Microwave Studio)와 Ansoft사의 HFSS(High Frequency Structure Simulator)를 이용하여 얻어진 시뮬레이션 결과와 계산된 결과를 비교하였고, 아울러 $8{\times}8$ 부배열을 제작하고 측정하여 시뮬레이션과 계산 결과와 비교함으로써 접근 방법의 타당성을 검증하였다. 제작된 부배열 안테나는 X-대역에 있는 중심주파수의 10.5 % 대역 내에서 E-면(방위각)과 H-면(고각) 조향 범위 ${\pm}45^{\circ}C,\;{\pm}20^{\circ}C$ 내에서 평탄한 이득을 갖고 또한 -10 dB 이하의 반사 손실을 갖는 것을 확인하였다.

• Korean Journal of Radiology
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• 제22권5호
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• pp.759-769
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• 2021

Objective: To evaluate the application of laplacian-regularized mean apparent propagator (MAPL)-MRI to brain glioma-induced corticospinal tract (CST) injury. Materials and Methods: This study included 20 patients with glioma adjacent to the CST pathway who had undergone structural and diffusion MRI. The entire CSTs of the affected and healthy sides were reconstructed, and the peritumoral CSTs were manually segmented. The morphological characteristics of the CST (track number, average length, volume, displacement of the affected CST) were examined and the diffusion parameter values, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), mean squared displacement (MSD), q-space inverse variance (QIV), return-to-origin probability (RTOP), return-to-axis probabilities (RTAP), and return-to-plane probabilities (RTPP) along the entire and peritumoral CSTs, were calculated. The entire and peritumoral CST characteristics of the affected and healthy sides as well as those relative CST characteristics of the patients with motor weakness and normal motor function were compared. Results: The track number, volume, MD, RD, MSD, QIV, RTAP, RTOP, and RTPP of the entire and peritumoral CSTs changed significantly for the affected side, whereas the AD and FA changed significantly only in the peritumoral CST (p < 0.05). In patients with motor weakness, the relative MSD of the entire CST, QIV of the entire and peritumoral CSTs, and the AD, MD, RD of the peritumoral CST were significantly higher, whereas the RTPP of the entire and peritumoral CSTs and the RTOP of the peritumoral CST were significantly lower than those in patients with normal motor function (p < 0.05 for all). In contrast, no significant changes were found in the CST morphological characteristics, FA, or RTAP (p > 0.05 for all). Conclusion: MAPL-MRI is an effective approach for evaluating microstructural changes after CST injury. Its sensitivity may improve when using the peritumoral CST features.

• Korean Circulation Journal
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• 제54권4호
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• pp.203-217
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• 2024

Background and Objective: The effects of radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF) on right ventricular (RV) function are not well known. Methods: Patients who underwent RFCA for AF and underwent pre- and post-procedural echocardiography were enrolled consecutively. Fractional area change (FAC), RV free-wall longitudinal strain (RVFWSL), and RV 4-chamber strain including the ventricular septum (RV4CSL) were measured. Changes in FAC, RVFWSL, and RV4CSL before and after RFCA were compared among paroxysmal AF (PAF), persistent AF (PeAF), and long-standing persistent AF (LSPeAF) groups. Results: A total of 164 participants (74 PAF, 47 PeAF, and 43 LSPeAF; age, 60.8 ± 9.8 years; men, 74.4%) was enrolled. The patients with PeAF and LSPeAF had worse RV4CSL (p<0.001) and RVFWSL (p<0.001) than those with PAF and reference values. Improvements in RVFWSL and RV4CSL after RFCA were significant in the PeAF group compared with the PAF and LSPeAF groups (ΔRV4CSL, 8.4% [5.1, 11.6] in PeAF vs. 1.0% [-1.0, 4.1] in PAF, 1.9% [-0.2, 4.4] in LSPeAF, p<0.001; ΔRVFWSL, 9.0% [6.9, 11.5] in PeAF vs. 0.9% [-1.4, 4.9] in PAF, 1.0% [-1.0, 3.6] in LSPeAF, p<0.001). In patients without recurrence, improvements in RVFWSL and RV4CSL after RFCA were significant in the PeAF group compared to the LSPeAF group. Conclusions: RV systolic function is more impaired in patients with PeAF and LSPeAF than in those with PAF. RV systolic function is more improved after RFCA in patients with PeAF than in those with PAF or LSPeAF.

• Journal of Chest Surgery
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• 제32권4호
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• pp.353-357
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• 1999

배경: 건삭보존 승모판 치환술이 승모판막질환에 있어서 좌심실 기능의 보존 및 술후 합병증을 줄일 수 있다고 알려져 있다. 대상 및 방법: 1995년 1월부터 1996년 7월까지 전북대학교 병원 흉부외과학 교실에서 승모판 치환술시 건삭을 절제한 20예(기존치환군)와 건삭을 보존한 10예(보존치환군)의 술후 단기성적을 비교하였다. 결과: 술 전 두 그룹간의 성별, 나이, NYHA 기능적 분류, 심흉비 및 심전도 소견, 심초음파 소견 및 관류량, 대동맥 차단시간등의 차이는 없었다. 술 전 심흉비에 대한 술 후 1개월 심흉비 비교에 있어서 두 그룹 모두 통계적으로 유의한 감소를 보였으나 두 그룹 사이의 통계적 차이는 없었다. 술 전 심흉비에 대한 술 후 3개월 심흉비 감소는 두 그룹 모두 통계적인 의미는 없었다. 술 전 심전도 소견상 대부분 심방세동이 동반되고 있었으며 심방세동이 술 후에 동성 리듬으로 변화된 경우가 기존치환군에서 2예 있었다. 심초음파에 의한 좌심실의 기능 비교에 있어서 보존치환군은 술전에비해 구혈분획(Ejection Fraction) 및, 단축분획률(Fractional Shortening)의 감소가 심하지 않았으나(p =0.47, p= 0.12), 기존치환군에서는 구혈분획 및, 단축분획률의 감소가 통계적으로 유의한 감소를 보였으며(p=0.03, p=0.04), 두 그룹간에 통계적으로 유의한 차이를 보였다(p=0.03, p=0.02). 또한 보존치환군에 비해 기존치환군에서 월등히 높은 합병증 발생률을 보였다. 결론: 승모판막 질환에 있어서 건삭 보존 승모판막 치환술이 기존 승모판 치환술에 비해 수술 후 좌심실 기능을 보존하는데 효과가 있으며, 낮은 합병증 발생률을 보였다.