• 대한의용생체공학회:의공학회지
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• 제10권2호
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• pp.165-172
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• 1989

본 논문에서는 초음파 반사신호에 내포되어 있는 정량적인 정보로부터 감쇠계수, 전파속도 파라메타를 매개로 조직의 온도특성에 대해 검토하고 이를 기초로 무침습적인 심부 온도추정의 가능성에 대해서 고찰하였다. 실험에 사용한 기초시료는 아크릴과 돼지의 근육, 간, 지방이며 온도분해능이 $0.25^{\circ}C$이하로 조절되는 항은수조를 제작하여 시료의 온도를 변화시켰다. 일련의 실험을 통하여 조직의 온도변화에 따른 초음파 파라메타의 변화가 근시적 선형성을 가짐이 확인되었으며 이는 표준적인 실험조건과 기준치의 설정을 전제로 무침습적 심부 온도추정이 가능함을 시사하는 것이다.

• Journal of Chest Surgery
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• 제20권2호
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• pp.223-229
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• 1987

Doppler echocardiography provides valuable information regarding prosthetic heart valve function rather than structure. There are three methods of expressing the severity of mitral valve obstruction: the transvalvular pressure gradient, effective valve area, and pressure half-time. Of these, the transvalvular pressure gradient [~p] can be determined by the measurement of maximum transvalvular blood flow velocity [V] according to the modified Bernoulli`s equation [gp=4V*]. Eleven patients, who underwent mitral valve replacement with Duromedics mechanical prostheses, and 17 normal persons were investigated. There were significantly higher calculated pressure gradients in prosthetic than normal mitral valves [9.*10*2.22mmHg-vs-3.26*0.99mmHg:p<0,01], and there was a inverse relationship between pressure gradient and prosthetic valve size [11.17*0.%mmHg in size 27mm and 29mm -v- 7.38*1.12mmHg in size 31mm and 33mm; r=0.85, p<0.01] The noninvasive Doppler technique should be useful in the diagnosis of prosthetic valve obstruction.

• Journal of Chest Surgery
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• 제24권3호
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• pp.265-270
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• 1991

Since advent of the prosthetic cardiac valve replacement, much efforts for accurate assessing value function in-vivo have been attempted. To evaluate the postoperative functional and morphological status of the replaced cardiac valve prosthesis, 33 patients with valve replacement were studied by transthoracic and transesophageal 2-dimensional echocardiac imaging as well as by color Doppler flow velocity imaging. Twenty four patients had mitral valve replacement. 6 patients had aortic valve replacement and 3 patients had both mitral and aortic valve replacement. There were 34 mechanical and 2 biological prosthesis. Comparing to transthoracic echocardiography, transesophageal approach showed transvalvular regurgitant jet flow amid the prosthetic mitral valve ring during. systole and much clear visualization of cardiac chamber behind prosthesis which could give shadowing effect to ultrasound beam. According to the quantitative grading by the length and area of mitral regurgitant flow, 24 out of 27 mitral valves revealed mild degree regurgitation considered as physiological after prosthetic bileaflet valve replacement and the other 3 valves including 2 biological prosthesis had moderate degree regurgitation which was regarded as pathologic one. 2 cases of left atrial thromboses and 1 case of paravalvular leakage which were not visible by transthoracic approach were identified by transesophageal echocardiography in patients with mitral valve replacement and patients with aortic valve replacement respectively. We conclude that in patients with prosthetic mitral valve replacement, transesophageal 2-dimensional imaging with color Doppler can suggest reliable information beyond that available from the transthoracic access even though it gives patient some discomfort to proceed.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.246-251
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• 2020

Dimethyl Ether(DME) engine use a highly efficient alternative fuel having a great quantity of oxygen and has a advantage no polluting PM gas. The existing DME fuel cam material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding piston shoe and contact area which demands high characteristics is needed. The development of WC-Ni base carbide alloy optimal bonding composition technique was accomplished in this study. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. The hardness of specimen and bonding rate were measured using ultrasound equipment. The bonding state of each condition was excellent, and the thickness of mid-layer, temperature and maintaining time were measured. The mid-layer thickness according to bonding temperature and maintaining time were observed with optical microscope. We analyzed the micro-structural analysis, formation of bonding specimen, wafer fabrication and fuel cam abrasion test. Throughout this study, we confirmed that the fuel cam for DME engine which demands high durability against velocity and pressure is excellent.

• Smart Structures and Systems
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• 제17권1호
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• pp.31-43
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• 2016

Applications of ultrasonic tomography to concrete structures have been reported for many years. However, practical and effective application of this tool for nondestructive assessment of internal concrete condition is hampered by time consuming transducer coupling that limits the amount of ultrasonic data that can be collected. This research aims to deploy recent developments in air-coupled ultrasonic measurements of solids, described in Part 1 of this paper set, to concrete in order to image internal inclusions. Ultrasonic signals are collected from concrete samples using a fully air-coupled (contactless) test configuration. These air coupled data are compared to those collected using partial semi-contact and full-contact test configurations. Two samples are considered: a 150 mm diameter cylinder with an internal circular void and a prism with $300mm{\times}300mm$ square cross-section that contains internal damaged regions and embedded reinforcement. The heterogeneous nature of concrete material structure complicates the application and interpretation of ultrasonic measurements and imaging. Volumetric inclusions within the concrete specimens are identified in the constructed velocity tomograms, but wave scattering at internal interfaces of the concrete disrupts the images. This disruption reduces defect detection accuracy as compared with tomograms built up of data collected from homogeneous solid samples (PVC) that are described in Part 1 of this paper set. Semi-contact measurements provide some improvement in accuracy through higher signal-to-noise ratio while still allowing for reasonably rapid data collection.

• 한국산학기술학회논문지
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• 제8권5호
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• pp.1047-1056
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• 2007

기본적으로 초음파 영상 시스템은 반사 계수를 보는 B-모드와 혈류의 속도를 구하는 도플러 영상 모드를 구비하고 있다. 본 논문에서는 도플러 영상 모드에서 혈류의 속도를 나타내는 도플러 주파수가 펄스반복주파수의 1/2을 초과하는 경우 발생하는 에일리어싱 현상을 검출해 보상하는 새로운 방법을 제시하고 컴퓨터 시뮬레이션을 통하여 타당성을 보여준다. 본 논문에서 제안하는 방법은 추정 가능한 도플러 주파수를 확장시켜 줄 뿐만 아니라 잡음에 대해서도 강인한 특성을 가진다. 시뮬레이션 결과 신호 대 잡음비가 약 20dB로 낮은 경우에도 에일리어싱을 제대로 보상할 수 있음을 알 수 있었다.

• 센서학회지
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• 제32권6호
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• pp.418-424
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• 2023

Natural killer (NK) cells play a crucial role in combating infections and tumors. However, their therapeutic application in solid tumors is hindered by challenges, such as limited lifespan, tumor penetration, and delivery precision. Our research introduces a novel ultrasonic actuation technique to navigate NK cells more effectively in the vascular system, particularly at vessel bifurcations where targeted delivery is most problematic. We use a hemispherical ultrasonic transducer array that generates phase-modulated traveling waves, focusing on an ultrasound beam to steer NK cells using blood-flow dynamics and a focused acoustic field. This method enables the precise obstruction of non-target vessels and efficiently directs NK cells toward the tumor site. The simulation results offer insights into the behavior of NK cells under various conditions of cell size, radiation pressure, and fluid velocity, which inform the optimization of their trajectories and increase targeting efficiency. The experimental results demonstrate the feasibility of this ultrasonic approach for enhancing NK cell targeting, suggesting a potential leap forward in solid tumor immunotherapy. This study represents a significant step in NK cell therapeutic strategies, offering a viable solution to the existing limitations and promising enhancement of the efficacy of cancer treatments.

• 한국임상수의학회지
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• 제41권1호
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• pp.43-48
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• 2024

A two-year-old, intact female Golden Retriever had previously been diagnosed with a portosystemic shunt (PSS) during an ultrasonographic examination at a local animal hospital. The serum biochemistry revealed elevated liver enzymes and bile acid levels. The abdominal radiographic examination revealed mild serosal detail loss and microhepatica, while abdominal ultrasonography revealed mild ascites and high-velocity flow to the caudal vena cava (CVC) suspected as a PSS. The gallbladder was not observed within the hepatic parenchyma during ultrasonography. Computed tomography (CT) revealed an absent gallbladder and dilation of the common bile duct (CBD). Dilations of the gastroduodenal, splenic, colic and renal veins were also observed. A dilated left phrenico-abdominal vein that entered the CVC was previously misinterpreted as a PSS on the ultrasound examination. Based on the imaging examinations, the dog was diagnosed with congenital gallbladder agenesis associated CBD dilation.

• 대한한방내과학회지
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• 제25권3호
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• pp.440-450
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• 2004

Objectives: Uwhangchungsim-won(UC) has been used in the treatment of a wide variety of conditions including stroke, hypertension, arterosclerosis, autonomic imbalance, and mental instability, in Korean traditional hospitals. The aim of this study was to evaluate the effect of DC on cerebral hemodynamics and to determine the appropriate dosage. Methods: We studied changes in hyperventilation-induced cerebrovascular reactivity and mean blood flow velocity of the middle cerebral arteries(MCAs) were studied by means of transcranial Doppler ultrasound. Changes in mean blood pressure, pulse rate and expiratory CO2(PECO2) were observed using Cardiocap TM/5. Six healthy young volunteers who were administrated with full doses of DC for group A, and half doses for group B. Six other healthy subjects comprised the control group. The evaluation was performed during basal condition, and repeated at 20, 40, 60, 120, and 180 minutes after administration. Results: Increases of cerebrovascular reactivity and mean blood flow velocity in the middle cerebral artery in group A were significantly different compared with group B and the control group (p<0.1). Mean blood pressure, pulse rate and expiratory CO2 did not change during the observation and were not different among these three groups. We observed that in cerebrovascular reactivity induced hyperventilation, group A was most effective at 40 minutes after administration, and its effectiveness lasted for 120 minutes. Conclusions: This study provides evidence for UC, in full doses, as an agent for dilation of the cerebral arteriols to increase hyperventilation-induced cerebrovascular reactivity as a consequence of faster recovery of blood flow velocity.

• 감성과학
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• 제27권2호
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• pp.81-90
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• 2024

본 연구에서는 경피신경전기자극(TENS)을 이용하여 다양한 자극 강도에 따른 뇌혈관에 미치는 영향을 확인하고자 한다. 특히 비지각적 감각의 전기자극을 통해 총경동맥(CCA)에서의 혈류 변화 및 혈관의 구조적인 변화를 확인해 보고자 한다. 본 연구에는 20대의 건강한 성인 24명이 참여하였다. 자극 강도는 감각 역치 미만, 감각 역치, 그리고 감각 역치 초과 세 가지를 각각 랜덤 순서로 적용하였다. 측정위치는 CCA 분기점의 1cm 하단에서 측정하였고, 혈류속도는 C-mode 도플러, 혈관의 구조는 B-mode 영상을 통해 측정하였다. 측정은 각각의 자극별로 중재 전, 중재 중, 그리고 중재 후에 수행하였고 각 세션마다 혈압의 변화를 측정하였다. 그 결과 최고 수축기 속도(PSV)는 역치미만의 비지각적 감각자극에서 중재 후 유의하게 감소함이 확인되었다(p = .008). 역치 미만의 자극 후 PSV는 자극 전보다 평균 3.04% 유의하게 감소한 것으로 나타났다(p = .011). 반면 CCA의 혈관 직경의 변화는 모든 강도에서 자극 전후 유의한 변화가 나타나지 않았다. 본 연구에서 적용한 단시간의 비지각적 전기자극이 혈관의 직경이나 혈압의 유의한 변화를 주지 않으면서 즉각적인 혈류속도 감소에 효과가 있음을 발견했다. 따라서 본 연구는 경동맥 부위에 환자의 불편함과 부작용이 없는 전기자극을 통해 뇌혈류의 조절이 가능하다는 것을 보여주는 중요한 시도로 평가될 수 있다.