• 한국통신학회논문지
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• 제33권6A호
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• pp.676-684
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• 2008

유럽형 지상파 디지털 방송 표준인 DVB-T 시스템에서는 OFDM방식을 사용하여 신호를 전송하며, 주파수 선택적 페이딩 환경과 충격 잡음 채널에서도 향상된 성능을 제공 할 수 있다. 그러나 이동성이 가정된 시변 채널에서는 도플러 확산의 영향 때문에 한 OFDM 심볼 안에 존재하는 부반송파 사이의 직교성의 파괴, 즉 inter-carrier interference(ICI)가 발생하여 심각한 성능 열화가 발생한다. 본 논문에서는 시간 및 주파수 축에서 채널의 특성과 ICI를 분석하고, OFDM시스템에서 구현이 간단한 LS 알고리즘과 이를 이용한 잡음 및 ICI 감쇄 기법을 사용한 LS 방식을 단말기의 속도에 따라 선택하여 사용하는 적응형 채널 추정 방식을 제안한다. 단말기의 속도를 추정하는 방법을 제안하여 COST207의 TU6 채널 모델을 적용한 시뮬레이션을 통하여 그 동작을 확인하였다. 또한 속도 추정을 위한 연산을 최소화한 알고리즘을 제안하여 하드웨어의 증가를 무시할 정도로 줄였다. 제안된 적응형 채널 추정 알고리즘은 속도가 약 70 km/h 이하인 경우에 잡음 및 ICI 감쇄기법을 위한 하드웨어를 동작시키지 않음으로서 전력의 소모가 현저하게 줄어든다.

• Archives of Plastic Surgery
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• 제47권3호
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• pp.209-216
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• 2020

Background Perforator flaps have led to a revolution in reconstructive surgery by reducing donor site morbidity. However, many surgeons have witnessed partial flap necrosis. Experimental methods to increase inflow have relied on adding a separate pedicle to the flap. The aim of our study was to experimentally determine whether increasing blood flow in the perforator pedicle itself could benefit flap survival. Methods In 30 male Lewis rats, an extended posterior thigh perforator flap was elevated and the pedicle was dissected to its origin from the femoral vessels. The rats were assigned to three groups: control (group I), acute inflow (group II) and arterial preconditioning (group III) depending on the timing of ligation of the femoral artery distal to the site of pedicle emergence. Digital planimetry was performed on postoperative day (POD) 7 and all flaps were monitored using laser Doppler flowmetry perioperatively and postoperatively in three regions (P1-proximal flap, P2-middle of the flap, P3-distal flap). Results Digital planimetry showed the highest area of survival in group II (78.12%±8.38%), followed by groups III and I. The laser Doppler results showed statistically significant higher values in group II on POD 7 for P2 and P3. At P3, only group II recorded an increase in the flow on POD 7 in comparison to POD 1. Conclusions Optimization of arterial inflow, regardless if performed acutely or as preconditioning, led to increased flap survival in a rat perforator flap model.

• 대한한방내과학회지
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• 제20권1호
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• pp.222-231
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• 1999

Uwhangchungsimwon(UC) has been used in the treatment of a wide variety of conditions including stroke, hypertension, arteriosclerosis, autonomic imbalance, mental instablity, etc in Korean traditional hospitals, In particular it is often initialy chosen for emergency care of acute stroke. The aim of this study was to evaluate the effect of UC on cerebral hemodynamics. Using transcranial Doppler ultrasound, we studied changes of mean flow velocity and pulsatility index(PI) of middle cerebral arteries (MCAs) from 11 health young volunteers who were administrated with 1 pill UC and 11 health controls who were not. We obtained hypercapnia with breath-holding and evaluated cerebrovascular reactivity with breath-holding index(BHI). Systolic blood pressure, diastolic blood pressure, and heart rate were measured using ambulatory blood pressure monitoring(ABPM). In UC administration group, the evaluation was performed during basal condition. and repeated at 20, 40, and 60 min after administration. In controls, the evaluation was performed at corresponding time intervals. Mean flow velocity in middle cerebral artery, systolic blood pressure, diastolic blood pressure, and heart rate did not change during the observation period and were not different between these two groups. However, administration of UC was associated with decreases in PI by $3.6{\sim}12.4%$ in BHI by $17.9{\sim}24.8%$ compared with pre-administration period. Decreases in PI and BHI with UC were significantly different compared with control group (p<0.05). These results indicate that UC decreases PI and BHI in cerebral artery, which is due to a dilation of cerebral resistance vessels.

• 대한한의학방제학회지
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• 제7권1호
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• pp.121-130
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• 1999

Oriental medicine prescription has been used for the treatment of various clinical symptoms associated with cerebral apoplexy. However, single herb drug does not used cerebral apoplexy and there mechanisms of action have not been defined, and it is not yet known what effects they have on the hemodynamics of cerebral circulation. The study was aimed to investigate the effect batryticatus bombycis(BB) on the vascular systems including changes in blood pressure (BP), and regional cerebral blood flow (rCBF) and of male Sprague-Dawely rats. The changes in rCBF were determinated by laser-Doppler flowmetry. 1. Blood pressure was not affected by BB in rats. 2. rCBF was increased by BB in a dose-dependent manner. 3. Pretreatment with methylene blue(1mg/kg), and propranolol(1mg/kg) did not inhibited BB induced increased in rCBF. 4. Pretreatment with propranolol(1mg/kg) was increased by BB in a dose-dependent manner in blood perssure. 5. Pretreatment with ODQ($10{\mu}g/kg$) and L-NNA(1mg/kg) were inhibited BB induced increased in rCBF. 6. Pretreatment with L-NNA(1mg/kg) was increased rCBF in a dose-dependent manner. These results suggest that BB causes a diverse response of blood pressure and regional cerebral blood flow(rCBF). The increased in rCBF is also mediated by nitric oxide synthease and guanylate cyclase.

• Annals of Clinical Neurophysiology
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• 제17권2호
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• pp.68-72
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• 2015

Background: The effects of omega-3 polyunsaturated fatty acids (PUFAs) on cerebral vessels have not been clarified until now. Thus we investigated the efficacy of omega-3 PUFAs supplementation on cerebral blood flow velocity and vascular resistance via transcranial doppler (TCD). Methods: Consecutive twenty patients (13 male and 7 female) with at least 1 cerebrovascular risk factor or a known cerebrovascular disease were enrolled. Patients were treated with omega-3 PUFAs (1 g, two times per day) for 12 weeks. Cerebral blood flow velocity, resistance index, and pulsatile index were checked before and after 12 weeks of treatment using TCD. Results: The change of resistance index in right MCA (from $0.58{\pm}0.07$ to $0.55{\pm}0.07$, p = 0.042) and left PCA (from $0.56{\pm}0.07$ to $0.53{\pm}0.06$, p = 0.037) showed significant improvement after 12 weeks of omega-3 PUFAs treatment. The changes in other vessels, however, failed to show any significant changes compared to the baseline. Conclusions: Omega-3 PUFAs treatment showed feasible efficacies for cerebral vascular resistances in this open label trial. To confirm these results, larger samples of patients and longer period of follow-up is warranted.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.141-148
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• 2003

This paper presents a rotating ann test for assessment of an underwater hybrid navigation system for a semi-autonomous underwater vehicle. The navigation system consists of an inertial measurement unit (IMU), an ultra-short baseline (USBL) acoustic navigation sensor and a doppler velocity log (DVL) accompanying a magnetic compass. The errors of inertial measurement units increase with time due to the bias errors of gyros and accelerometers. A navigational system model is derived to include the error model of the USBL acoustic navigation sensor and the scale effect and bias errors of the DVL, of which the state equation composed of the navigation states and sensor parameters is 25 in the order. The conventional extended Kalman filter was used to propagate the error covariance, update the measurement errors and correct the state equation when the measurements are available. The rotating ann tests are conducted in the Ocean Engineering Basin of KRISO, KORDI to generate circular motion in laboratory, where the USBL system was absent in the basin. The hybrid underwater navigation system shows good tracking performance against the circular planar motion. Additionally this paper checked the effects of the sampling ratio of the navigation system and the possibility of the dead reckoning with the DVL and the magnetic compass to estimate the position of the vehicle.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.944-951
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• 2011

본 논문은 ADCP 계측기기 부근에서 음향학적인 그리고 ADCP 계기로 인해 발생하는 흐름의 교란에 기인한 속도 오차에 대한 원인들을 실험 및 수치모의를 통해 고찰한다. 실험실에서의 연구는 선박에 탑재되지 않은 독립된 ADCP에 대해 수행하였고, 수평 및 수직면에서 ADCP에 의해 유발되는 흐름 교란은 ADV를 이용하여 관측하였다. 그리고 ADCP와 ADV의 동시적 측정이 ADCP계측에 있어 추가적인 계측기기 부근의 영향들을 고려하기 위해 수행되었다. 수치모의는 ADCP가 선박에 탑재되었을 때 ADCP 계기 부근에 발생하는 잠재적인 오차에 대해 연구하기 위해 설계되었다. 수치해석 기법 사용된 LES (Large Eddy Simulation)는 선박에 탑재된 ADCP에 작용하는 항력과 계기와 선박의 막음효과에 의해 발생하는 흐름의 교란의 크기와 범위를 모의하였다. 결과로 ADCP에 의해 관측된 속도는 계측기기 하단의 제한된 범위 내에서 일정 정도 오차를 보였고 교란되지 않은 하천의 흐름 조건에 따라 오차가 실질적으로 다르게 나타났다.

• 대한토목학회논문집
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• 제39권5호
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• pp.587-594
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• 2019

하천 내 흐름에 대한 식생 밀도의 영향을 조사하기 위해 버드나무가 활착된 하천 규모의 자연형 수로에서 유동 측정 실험을 수행하였다. 식생 내 흐름에 대한 하천 규모 실험은 식생의 반 잠김 조건에 대해 수행되었다. 수로 내 식생대(vegetation patch)는 교차로 형성된 사주의 형상으로 배열되었고 식생 구간과 비식생 구간에서의 흐름을 비교하였다. 3차원 유동 구조는 초음파 유속계(Acoustic Doppler Velocimeter)에 의해 측정되었고 종방향 속도의 연직 분포는 다양한 지점에서의 측정값으로부터 분석되었다. 유속은 식생대의 밀도에 따라 다른 양상을 보여 주는데, 식생 구간와 비식생 구간에서의 흐름 속도의 차이는 밀집된 식생대 주변에서 크게 나타나며 흐름 분포의 형태는 식생대의 하류방향 하단에서 복잡한 모습을 나타낸다. 하류에 위치한 식생대 주변의 흐름은 상류에 설치된 식생대에 의해 교란된 흐름에도 불구하고 유사한 분포를 보여준다.

• Journal of Veterinary Science
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• 제22권5호
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• pp.64.1-64.12
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• 2021

Background: Pituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses. Objectives: To determine whether pergolide induces valvular disease in horses or affects the cardiac function. Methods: Standard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in horses with diagnosed PPID based on adrenocorticotropic hormone dosage. Measurements taken in horses treated with pergolide were compared with those from untreated horses with nonparametric t-tests. Furthermore, measurements from follow-up examinations performed at least three months after the initial exam were compared with a Wilcoxon signed rank test for repeated measurements in each group. Results: Twenty-three horses were included. None of the 12 horses under treatment developed valvular regurgitation. Furthermore, no differences in the measurements of the left ventricular systolic or diastolic function could be seen between the group of horses with treatment and those without treatment. Measurements taken in the follow-up exam did not differ compared to those taken in the initial exam in both groups. Conclusions: No changes of the left ventricular function assessed by TDE and STE could be shown in a small population of horses with confirmed PPID. Treatment with pergolide did not affect the ventricular function nor induce valvular disease.

• 한국정보전자통신기술학회논문지
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• 제13권6호
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• pp.545-555
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• 2020

본 논문에서는 부 대역 처리를 이용하는 수중 통신에서 은밀성과 성능 향상 관점에서 효율적인 송수신 구조를 제시하였다. 은밀성적인 측면에서는 암호화된 부호화 비트를 블록으로 나누어 각 비트의 정보를 이용하여 중심 주파수와 부 대역을 결정하므로 은밀성을 유지하는 측면에서 효과적이다. 수중 통신에서 성능적인 측면에서는 다중 경로 특성, 도플러 확산, 프레임 동기 등이 성능에 영향을 미치는 결정적인 요소이다. 따라서 본 논문에서는 이러한 요소들을 극복하기 위해, 비동기 에너지 검출 방식과 터보 등화 기법, 그리고 최적의 프레임 동기 방식을 제안하여 수신부에 적용하였다. 호수 실험에서 최적의 프레임 동기 방식을 수신부에 적용한 결과 다섯 개의 프레임 중에서 네 개의 프레임에서 오류를 모두 정정함을 확인하였다.