• Nuclear Engineering and Technology
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• 제30권1호
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• pp.40-46
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• 1998

A set of experiments using a 1/10 scale model pump which was manufactured to simulate performance of reactor coolant pump(RCP) of Y.G.N # 3 and 4, was executed in single phase(at atmospheric pressure and room temperature) and near-saturation(300 ~ 600kPa). The pump characteristics in single phase flow was similar to the characteristics of the RCP. The pump characteristic curves at nearly saturated state were correlated in terms of flow coefficient and head coefficient for subcooled temperature using the cavitation number defined as (equation omitted), which can be predicted the cavitation possibility. The pump behavior around the saturated temperature almost consists with single phase behavior until the cavitation occurs(When cavitation occurs. When the flow coefficient is about 0.12), the pump head rapidly degrades. In this situation, subcooled temperature is about 1.8~8$^{\circ}C$ and cavitation number of model pump is 1.0 ~ 1.7.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1599-1601
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• 2000

To study invar alloy as a core material for large ampacity over-head transmission line which have high strength and low thermal expansion coefficient simultaneously, thermal expansion coefficient, physical properties and hardness of Fe-Ni-Co-xC alloy have been studied. It is necessary that invar alloy possess low thermal expansion coefficient and high strength for increased capacity over-head transmission line. In this paper we tried to find out the effect of carbon addition related with mechanical and physical properties. It was found that the thermal expansion coefficient and hardness were increased with carbon addition for whole composition range but the saturation magnetization was decreased except for the range of 0.1$\sim$0.4%C.

• Investigative Magnetic Resonance Imaging
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• 제21권2호
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• pp.65-70
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• 2017

Purpose: To optimize the saturation time and maximizing the pH-weighted difference between the normal and ischemic brain regions, on 3-tesla amide proton transfer (APT) imaging using an in vivo rat model. Materials and Methods: Three male Wistar rats underwent middle cerebral artery occlusion, and were examined in a 3-tesla magnetic resonance imaging (MRI) scanner. APT imaging acquisition was performed with 3-dimensional turbo spin-echo imaging, using a 32-channel head coil and 2-channel parallel radiofrequency transmission. An off-resonance radiofrequency pulse was applied with a Sinc-Gauss pulse at a $B_{1,rms}$ amplitude of $1.2{\mu}T$ using a 2-channel parallel transmission. Saturation times of 3, 4, or 5 s were tested. The APT effect was quantified using the magnetization-transfer-ratio asymmetry at 3.5 ppm with respect to the water resonance (APT-weighted signal), and compared with the normal and ischemic regions. The result was then applied to an acute stroke patient to evaluate feasibility. Results: Visual detection of ischemic regions was achieved with the 3-, 4-, and 5-s protocols. Among the different saturation times at $1.2{\mu}T$ power, 4 s showed the maximum difference between the ischemic and normal regions (-0.95%, P = 0.029). The APTw signal difference for 3 and 5 s was -0.9% and -0.7%, respectively. The 4-s saturation time protocol also successfully depicted the pH-weighted differences in an acute stroke patient. Conclusion: For 3-tesla turbo spin-echo APT imaging, the maximal pH-weighted difference achieved when using the $1.2{\mu}T$ power, was with the 4 s saturation time. This protocol will be helpful to depict pH-weighted difference in stroke patients in clinical settings.

• 대한기관식도과학회지
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• 제13권2호
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• pp.40-44
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• 2007

Background and Objectives: Most of tracheal stenosis is resulted from longstanding endotracheal tube insertion. Treatments of tracheal stenosis are divided conservative and reconstructive treatment. The propose of this study was to evaluate the effect of prosthetic tracheal T-tube insertion on tracheal stenostic patients who can not be operated invasive surgery. Subjects and Method : Nine prosthetic tracheal T-tube insertion were studied from 9 patients from January 2002 to April 2007. The effect of silastic T-tube was analyzed according to the factors that were respiratory difficulty, oxygen saturation, phonation, aspiration and significant complications. Results: Four patients were good for respiration and no complication. But five patients occur various complications. A successful group did not have cartilagenous lesions but failed group had catilagenous lesions, infection and necrosis. Conclusion: A silastic T-tube insertion was good for palliative treatment in patients without catilagenous lesions.

• 항공우주기술
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• 제8권1호
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• pp.207-214
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• 2009

본 연구는 미세중력 모델인 머리하향기울기(Head Down Tilt; HDT) 자세에서 운동 중저산소호흡이 심혈관계 반응에 미치는 영향을 알아보는데 있었다. 8명의 건강한 남성($23{\pm}2$ 세, 신장 $176{\pm}4$ cm, 체중 $75{\pm}8$ kg)은 4가지 조건(앉은 자세에서 정상공기 호흡: SN, 앉은 자세에서 13% 산소호흡; SH, HDT 자세에서 정상공기 호흡; SH, HDT 자세에서 13% 산소호흡; HH)에서 최대산소섭취량의 약 40% 운동강도로 15분간 싸이클링을 실시하였다. 심박수는 SH그룹이 SN그룹보다 높았고(p<0.05), HH그룹이 SH그룹보다 높게 나타났다(p<0.05). 혈중산소포화도는 SH그룹이 SN그룹보다 유의한 감소를 나타내었다(p<0.05). 이완기혈압(p<0.05) 및 평균동맥압(p<0.05)은 안정시 앉은 자세에서보다 HDT 자세에서 유의하게 낮아졌다. 체액변인인 Hb, Hct과 전해질 변인인 나트륨, 칼륨, 염소는 모든 그룹에서 차이가 나타나지 않았다(p>0.05). 대사적 변인 중 Lactate는 SH그룹이 SN그룹보다 유의한 증가를 나타내었다(p<0.05). 결론적으로, 저산소호흡과 자세의 이중자극은 심혈관계반응에 영향을 주지 않았다.

• 한국항공우주학회지
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• 제47권5호
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• pp.388-396
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• 2019

본 논문은 시험발사체에 탑재된 송신기에서 송신되는 S 대역 신호에 의해 위성항법수신기에서 나타난 RF 신호간섭을 설명하고, 그 원인을 분석한다. 능동형 위성항법안테나의 LNA는 항법위성 신호와 비교하여 상대적으로 신호세기가 매우 높은 S 대역 신호에 의해 포화되었으며, 2개의 S 대역 신호가 위성항법안테나에 수신될 때마다 GNSS 대역에 해당하는 상호변조신호가 LNA에서 발생하였다. 이러한 현상으로 인해 위성항법수신기에서 계산된 항법위성신호의 C/N0가 크게 감쇄하였다. S 대역 신호에 의한 RF 신호간섭을 차단하기 위하여 위성항법안테나 LNA의 설계변경을 수행하였고, 설계변경 전 후의 LNA에 대해 수행한 비교시험을 통하여 설계변경된 LNA에서 S 대역 신호에 의한 RF 신호감쇄 현상이 억제될 수 있음을 확인하였다.

• Physical Therapy Rehabilitation Science
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• 제13권2호
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• pp.187-195
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• 2024

Objective: Physical activity can promote physical and mental well-being. University students are more sedentary recently due to the increased use of computers and other technology. The aim of this study was to investigate differences between immersive 360-degree virtual cycling (IVC) and virtual cycling with head-mounted display (VCHMD) on aerobic capacity and usability in young adults. Design: A crossover study. Methods: Twenty-five university students (13 male, 12 female) participated in this study and completed 2 separate 30 min cycling sessions, such as IVC and VCHMD. In the IVC, participants rode on a stationary cycle while watching curved TV where recorded video was played. To enhance the sense of realism, auditory stimulation was given to the headset, and the gyroscope sensor was used to track the screen as the head moved. In the VCHMD, participants rode on the stationary cycle with head-mounted display, and other conditions were the same as IVC. Participants were assessed the aerobic capacity which included gas analyzer and portable near-infrared spectroscopy, and usability which included simulator sickness questionnaire and system usability scale. Results: Aerobic capacity was significantly difference in the IVC compared with the VCHMD except for the total hemoglobin of right and left rectus femoris and muslce oxygen saturation of left rectus femoris (p<0.05). Cybersickness was less in the IVC than VCHMD and usability was high in the IVC than VCHMD (p<0.05). Conclusions: The findings suggested that IVC might be beneficial exericse to improve aerobic capacity and has lower cybersickness and higher usability than VCHMD.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1901-1903
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• 1999

To investigate invar alloy as a core material for increased capacity over-head transmission line which have high strength and low thermal expansion coefficient, hardness and thermal expansion coefficient of Fe-Ni-Co alloy have been studied. It is necessary that invar alloy have low thermal expansion coefficient and high strength for increased capacity over-head transmission line. In this paper. we tried to find out the effect of Ni and Co which has ferromagnetic properties and high saturation magnetization. It was found that Ni decrease thermal expansion coefficient and hardness, Co decrease thermal expansion coefficient but increase hardness in Fe-xNi-Co system. In Fe-(29-x)Ni-Co system, the material has no low thermal expansion properties substituting Co instead of Ni in concentration range of $1\sim7$%Co.

• 한국자기학회지
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• 제2권1호
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• pp.50-55
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• 1992

히스테리시스 특성을 갖는 자기기록장치의 재생과정을 수치모사할 수 있는 방법을 구현 하였다. 수치해거시 기록과정뿐만 아니라 재생과정에서도 히스테리시스 특성을 고려해 주어야 한다. 수치해석기법으로 유한요소법(finite element metho)을 사용하고 히스테리시스 특성을 묘사하기 위 하여 spin curling 모드를 이용한 Stoner-Wohlfarth 모델보다 정밀한 해석이 가능한 Preisach 모델 을 사용하여 알고리즘을 구성한 후 재생전압을 구하기 위한 수식을 유도하고 이 것을 2층매체와 폴 형헤드를 갖는 수직자기 기록장치에 적용하였다. 정보가 기록된 매체위를 헤드가 지나갈 때 코일을 통과하는 자속밀도와 코일에 유기되는 재생전압의 크기가 포화되는 특성을 구함으로써 이것으로부 터 기록과정에서 헤드에 흘려줄 최적의 전류를 구하였다.

• Journal of Trauma and Injury
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• 제33권2호
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• pp.88-95
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• 2020

Purpose: The present study will identify risk factors for aspiration in severe trauma patients by comparing patients who showed a sign of aspiration lung disease on chest computed tomography (CT) and those who did not. Methods: We conducted a retrospective review of the Korean Trauma Data Bank between January 2014 and December 2019 in a single regional trauma center. The inclusion criteria were patients aged ≥18 years with chest CT, and who had an Injury Severity Score ≥16. Patients with Abbreviated Injury Scale (AIS)-chest score ≥1 and lack of medical records were excluded. General characteristics and patient status were analyzed. Results: 425 patients were included in the final analysis. There were 48 patients showing aspiration on CT (11.2%) and 377 patients showing no aspiration (88.7%). Aspiration group showed more endotracheal intubation in the ER (p=0.000) and a significantly higher proportion of severe Glasgow Coma Scale (GCS) (p=0.000) patients than the non-aspiration group. In AIS as well, the median AIS head score was higher in the aspiration group (p=0.046). Median oxygen saturation was significantly lower in the aspiration group (p=0.002). In a logistic regression analysis, relative to the GCS mild group, the moderate group showed an odds ratio (OR) for aspiration of 2.976 (CI, 1.024-8.647), and the severe group showed an OR of 5.073 (CI, 2.442-10.539). Conclusions: Poor mental state and head injury increase the risk of aspiration. To confirm for aspiration, it would be useful to perform chest CT for severe trauma patients with a head injury.