• 한국임상수의학회지
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• 제26권2호
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• pp.160-165
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• 2009

4개월령 수컷 박서 개(체중: 9 Kg)가 심잡음과 운동불내성을 주요 증상으로 내원하였다. 진단검사를 통해 환자는 대동맥 판막하 협착에 이환된 것을 확인할 수 있었다. 협착된 부위의 압력구배는 120 mmHg(와류의 속도: 5.4 m/s)이상이었으며, 환자는 풍선 확장술을 통해 임상증상을 개선하였다. 환자는 시술 후 주기적으로 모니터링 하였으며 다른 임상증상은 관찰되지 않았다. 이는 우리나라에서 대동맥 판막하 협착증에 이환된 환자에게 풍선 확장술을 통해 임상증상을 경감시킨 최초의 증례이다.

• 해양환경안전학회지
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• 제17권2호
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• pp.167-172
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• 2011

표면조도에 의해 발생하는 난류유동은 공학적, 물리적 분야에서 매우 중요하게 다루어지고 있다. 표면조도는 선박에서도 설계, 용접, 도장 등 각각의 단계에서 다양한 측면으로 고려되어야 할 중요한 요소이다. 본 연구는 표면조도 형상을 일반화하여 PIV기법을 적용하여 수조실험을 수행하였다. 표면조도 조건은 거칠기 형상의 간격에 대해 변화를 주었으며, 실험유속은 Re = $1.1{\times}10^4$, Re = $2.0{\times}10^4$, Re = $2.9{\times}10^4$ 에서 시간평균에 대한 난류강도를 알아보았다. 거칠기 계수 증가에 따라 표면 거칠기 형상 근처에서 발생한 난류성분에 의해 난류강도는 강하게 나타났으며, 자유흐름 영역으로 갈수록 유동 방향의 변동이 전혀 없는 흐름이 나타났다. 실험유속 조건 변화에 대한 난류강도의 편차는 크게 영향을 받지 않았다.

• 천문학회지
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• 제28권2호
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• pp.245-253
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• 1995

We have analyzed the time series of Ca II H,K and ${\lambda}8498$ line profiles taken for a sunspot (SPO 5007) with the Echelle spectrograph attached to Vacuum Tower Telescope at Sacramento Peak Solar Observatory. Each set of spectra was taken simultaneously for 20 minutes at a time interval of 30 seconds. A total of 40 photographic films for each line was scanned by a PDS at Korea Astronomy Observatory. The central peak intensity of Ca II H ($I_{max}$), the intensity measured at ${\Delta}{\lambda}=-0.1{\AA}$ from the line center of ${\lambda}8498(I_{{\lambda}8489})$, the radial velocity ($V_r$) and the Doppler width (${\Delta}{\lambda}_D$) estimated from Ca II H have been measured to study the dynamical behaviors of the sunspot chromosphere. Fourier analysis has been carried out for these measured quantities. Our main results are as follows: (1) We have confirmed the 3-minute oscillation being dominant throughout the umbra. The period of oscillations jumps from 180 sec in the umbra to 500 to 1000 sec in the penumbra. (2) The nonlinear character of the umbral oscillation is noted from the observed sawtooth shaped radial velocity fluctuations with amplitudes reaching up to $5{\sim}6\;km/sec$. (3) The spatial distribution of the maximum powers shows that the power of oscillations is stronger in the umbra than in the penumbra. (4) The spatial distributions of the time averaged < $I_{max}$ > and < $V_r$ > across the spot are found to be nearly axially symmetric, implying that the physical quantities derived from the line profiles of Ca II H and ${\lambda}8498$ are inherently associated with the geometry of the magnetic field distribution of the spot. (5) The central peaks of the CaII H emission core lead the upward motions of the umbral atmosphere by $90^{\circ}$, while no phase delay is found in intensities between $I_{max}$ and $I_{{\lambda}8498}$, suggesting that the umbral oscillation is of standing waves.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.345-348
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• 2010

Two-stage light-gas gun은 고압실, 압축실 그리고 발사관으로 비교적 간단한 구조로 구성되며, 짧은 시간동안 초고압을 발생시키기 용이함으로 현재까지 고속충격역학, 발사체 공기역학, 재료역학 등 다양한 공학 분야에서 적용되어왔다. 본 연구는 초고압 액체 제트 분사에 적용하기 위한 기초적 연구로서, 고압실 하류에 설치된 제1격막의 파막 압력의 변화에 따른 발사체의 속도 변화 및 관내 압력 거동을 조사하기위하여, 다양한 격막을 적용하여 실험을 수행하였다. 제1격막의 파막 압력은 발사체의 속도에 지배적인 영향을 미치게 되며, 약 14 Bar이상일 경우 발사관의 압력이 압축튜브의 압력보다 크게 증가하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 추계학술대회 논문집
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• pp.241-246
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• 2005

본 연구는 컨테이너 크레인이 강풍에 대비하여 크레인을 고정하는 계류 시에 75m/s의 풍하중이 50ton급 컨테이너 크레인에 작용될 때, 풍향변화와 기계실의 위치 변화가 50ton급 컨테이너 크레인의 구조적 안정성에 미치는 영향을 분석하였다.. 본 연구에 적용된 설계 풍하중은 "건축물 하중 기준"에 의거하여 산출하였으며. 풍향은 $0^{\circ}\~180^{\circ}$를 $15^{\circ}$ 간격으로 적용하여 각 지지점에서의 반력을 분석하였다. 그리고 전체 자중의 $15\%$를 차지하는 기계실의 위치 변화가 컨테이너 크레인의 구조 안정성에 미치는 영향을 분석하였다. 그리고 이 결과들을 바탕으로 컨테이너 크레인의 전도방지장치인 타이다운(Tie-down)의 설계기준을 제시하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 춘계학술대회 및 창립 30주년 심포지엄(논문집)
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• pp.349-354
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• 2006

본 연구는 풍하중이 컨테이너 크레인에 작용할 때, 풍향에 따라서 컨테이너 크레인의 유동장을 분석하였다. 본 연구를 위해 사용된 모델은 50ton급 컨테이너 크레인으로 현재 항만시설에 가장 많이 사용되는 모델이다. 유동장은 원통으로 모델링하였으며, 직경, 300m 높이 200m로 설정하였다. 본 연구는 멱급수를 적용하여 풍속 50m/s의 설계 기준에서 고도에 따라 풍속을 고려하였다. 또한 풍향은 $0^{\circ}{\sim}180^{\circ}$ 를 $30^{\circ}$ 간격으로 적용하였으며, CFX-10을 사용하여 전산유동해석을 수행하였다. 본 연구에서는 풍향에 따른 풍압력을 분석하였으며, 향후 유동 연성 해석을 통한 컨테이너 크레인의 구조 안정성 평가를 할 것이다.

• Journal of Preventive Medicine and Public Health
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• 제44권6호
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• pp.260-266
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• 2011

Objectives: We evaluated the association between common carotid artery intima-media thickness (CCA-IMT), brachialankle pulse wave velocity (baPWV), carotid plaque, and peripheral arterial disease (PAD) as indicators of macroangiopathy and diabetic retinopathy as an indicator of microangiopathy in type 2 diabetic patients. Methods: We analyzed 605 type 2 diabetic patients registered at a public health center in Korea. Following overnight fasting, venous blood and urine samples were collected and analyzed. The CCA-IMT, levels of carotid plaque, baPWV, and ankle-brachial index (ABI) of the subjects were assessed. We used non-mydriatic fundus photography to diagnose diabetic retinopathy. Multiple logistic regression analyses were used to evaluate the association between macroangiopathy and diabetic retinopathy. CCA-IMT and baPWV were divided into tertiles: CCA-IMT, 0.39 to 0.65 mm, 0.66 to 0.78 mm, and 0.79 to 1.30 mm; baPWV, 9.9 to 15.8 m/s, 15.9 to 18.9 m/s, and 19.0 to 38.0 m/s. Results: The association between baPWV and diabetic retinopathy remained significant after adjustment, with an increasing odds ratio (OR) in the second tertile (OR, 2.41; 95% confidence interval [CI], 1.27 to 4.55) and the third tertile (OR, 4.63; 95% CI, 2.33 to 9.21). No significant differences were observed in carotid plaque, PAD, and each tertile of CCA-IMT. Conclusions: BaPWV was associated with diabetic retinopathy, while CCA-IMT, carotid plaque, and PAD were not. This study suggests that the association between macroangiopathy and microangiopathy may be attributable to functional processes rather than structural processes within the vascular system.

• Wind and Structures
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• 제19권4호
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• pp.421-441
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• 2014

With the assistance of typhoon field data at aerial elevation level observed by meteorological satellites and wind velocity and direction records nearby the ground gathered in Guangzhou Weather Station between 1985 and 2001, some key wind field parameters under typhoon climate in Guangzhou region were calibrated based on Monte-Carlo stochastic algorithm and Meng's typhoon numerical model. By using Peak Over Threshold method (POT) and Generalized Pareto Distribution (GPD), Wind field characteristics during typhoons for various return periods in several typical engineering fields were predicted, showing that some distribution rules in relation to gradient height of atmosphere boundary layer, power-law component of wind profile, gust factor and extreme wind velocity at 1-3s time interval are obviously different from corresponding items in Chinese wind load Codes. In order to evaluate the influence of typhoon field parameters on long-span flexible bridges, 1:100 reduced-scale wind field of type B terrain was reillustrated under typhoon and normal conditions utilizing passive turbulence generators in TJ-3 wind tunnel, and wind-induced performance tests of aero-elastic model of long-span Guangzhou Xinguang arch bridge were carried out as well. Furthermore, aerodynamic admittance function about lattice cross section in mid-span arch lib under the condition of higher turbulence intensity of typhoon field was identified via using high-frequency force-measured balance. Based on identified aerodynamic admittance expressions, Wind-induced stochastic vibration of Xinguang arch bridge under typhoon and normal climates was calculated and compared, considering structural geometrical non-linearity, stochastic wind attack angle effects, etc. Thus, the aerodynamic response characteristics under typhoon and normal conditions can be illustrated and checked, which are of satisfactory response results for different oncoming wind velocities with resemblance to those wind tunnel testing data under the two types of climate modes.

• Yonsei Medical Journal
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• 제59권9호
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• pp.1115-1122
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• 2018

Purpose: To investigate biomechanical properties of the cornea using a dynamic Scheimpflug analyzer according to age. Materials and Methods: In this prospective, cross-sectional, observational study, participants underwent ophthalmic investigations including corneal biomechanical properties, keratometric values, intraocular pressure (IOP), and manifest refraction spherical equivalent (MRSE). We determined the relationship of biomechanical parameters and ocular/systemic variables (participant's age, MRSE, IOP, and mean keratometric values) by piecewise regression analysis, association of biomechanical parameters with variables by Spearman's correlation and stepwise multiple regression analyses, and reference intervals (RI) by the bootstrap method. Results: This study included 217 eyes of 118 participants (20-81 years of age). Piecewise regression analysis between Corvis-central corneal thickness (CCT) and participant's age revealed that the optimal cut-off value of age was 45 years. No clear breakpoints were detected between the corneal biomechanical parameters and MRSE, IOP, and mean keratometric values. Corneal velocity, deformation amplitude, radius, maximal concave power, Corvis-CCT, and Corvis-IOP exhibited correlations with IOP, regardless of age (all ages, 20-44 years, and over 44 years). With smaller deformation amplitude and corneal velocity as well as increased CorvisIOP and Corvis-CCT, IOP became significantly increased. We provided the results of determination of confidence interval from RI data using bootstrap method in three separate age groups (all ages, 20-44 years, and over 44 years). Conclusion: We demonstrated multiple corneal biomechanical parameters according to age, and reported that the corneal biomechanical parameters are influenced by IOP.

• The Korean journal of internal medicine
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• 제39권4호
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• pp.612-624
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• 2024

Background/Aims: The predictive value of the estimated pulse wave velocity (ePWV) for the development of metabolic syndrome has not yet been extensively explored. This study aimed to fill this gap by evaluating ePWV as a potential predictor of metabolic syndrome development in middle-aged Korean adults. Methods: Using prospective data obtained from the Ansan-Ansung cohort database, participants without metabolic syndrome at baseline were studied. ePWV was calculated using specific equations based on age and blood pressure. The primary outcome was the incidence of metabolic syndrome during a median follow-up period of 187 months. Results: Among the 6,186 participants, 2,726 (44.1%) developed metabolic syndrome during the follow-up period. ePWV values were categorized into tertiles to assess their predictive value for the development of metabolic syndrome. An ePWV cut-off of 7.407 m/s was identified as a predictor of metabolic syndrome development, with a sensitivity of 0.743 and a specificity of 0.464. Participants exceeding this cut-off, especially those in the third tertile (8.77-14.63 m/s), had a notably higher risk of developing metabolic syndrome. Specifically, the third tertile exhibited a 52.8% cumulative incidence compared with 30.8% in the first tertile. After adjustments, those in the third tertile faced a 1.530-fold increased risk of metabolic syndrome (95% confidence interval, 1.330-1.761). Conclusions: ePWV is a significant predictor of the development of metabolic syndrome. This finding underscores the potential of ePWV as a cardiometabolic risk assessment tool and can thus provide useful information for primary prevention strategies.