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선인장 양심실 보조장치의 설계 및 임상적용을 위한 평가
민병구,박찬영,최재순,이혁수,황창모,김삼성,윤걸중,김종원,선경,이경갑,정종태,김원곤 제주대학교 인공심장이식연구소 2001 인공심장 연구 Vol.2 No.1
현재 개발되고 있는 맥동형 이식형 인공심장은 완전이식형 인공심장과 좌심실보조장치 뿐이다. 좌심실보조장치를 장착한 환자의 10~15%가 우심실의 보조를 필요로하고 완전이식형 인공심장의 장착을 위해서는 자연심장을 제거해야하는 상황에서 이식형 양심실보조장치에 대한 필요성이 대두되고 있다. 본 연구진은 완전이식형 인공심장으로 개발된 한국형 인공심장을 개선하여 양심 실 보조장치를 개발하였다. 양심실보조장치는 이동형 작동기식 미케니즘을 이용하고 있으며 에너지 변환장치와 감속기로 구성된 작동기와 혈액주머니, 그리고 내장형 제어기로 구성되어 있다. 선인장 펌프로 명명된 KAH350은 캐뉼라의 연결을 위한 커넥터를 포함하여 길이 177mm, 폭 164mm, 높이 67 이고 무게 780g이며 최대 심박출량은 5L/min 이다. 양심실보조장치로 개발된 선인장펌프는 좌심실보조장치로도 응용이 가능하다. 이식적합성과 생체적합성을 평가하기 위하여 좌심실보조장치로 5회, 양싱실보조장치로 6회의 동물실험을 수행하였다. 각각 최장 28일간 생존하였으며 11회의 동물실험중 장치의 결함에 의한 것이 3회 있었는데 이들은 모두 전자장치의 결함과 방수처리문제였다. 현재 이식적합성과 일박출량을 향상시킨 KAH400모델이 개발중이다. The types of pulsatile implantable artificial hearts that are on the way of development and have been developed are totally implantable artificial heart and implantable left ventricular assist device (LVAD). Approximately 10% to 15% of all patients Implanted with wearable VADs have required right heart support with another device. And it is reluctant to patient who should remove his or her own heart to be implanted with total artificial heart. These situations drive the development of implantable bi-ventricular assist device (BVAD). The Korean BVAD was develophed by modifying the moving actuator type Korean artificial heart. This electro-mechanical BVAD comprises actuator including energy converter and reduction gear train, blood sacs, and internal motor and energy controllers. The KAH350 which is named as 'Cactus Pump' is 177mm in length, 164mm in width, and 67mm in thickness including connectors and nuts. The weight and maximum cardiac output of Cactus Pump is 780g and 5L/min, respectively. The Cactus Pump that was developed as BVAD could be used as LVAD by attaching compliance caps on the 2 ports of one ventricle. The animal experiments were undergone 5 times for LVAD, and 6 times for BVAD. The best records were 28 days survival in both applications. There were 3 times of device failure and they were all associated with electrical connection and hermetic sealing. The KAH400 that has improved anatomical fitting characterisitcs and stroke volume is on development.
Effects of ALR and Configuration Ratio on Turbulent Structures in Swirling Flows
Sam-Goo, Lee 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.6
To assess the significant physics associated with the increase of ALR and configuration ratio of the nozzle tip in pneumatic swirling flows, comprehensive observations using a 3-D PDPA system were experimentally carried out. Profiles of mean velocities, turbulence intensities, SMD variations, and correlations between droplet size and turbulence components were quantitatively acquired. As discussed in a previous literature, axisymmetric swirl angle of 30o is selected for this investigation because of its strong turbulence levels in the flowfield and finer droplet disintegrations. Various ALRs (Air-to-Liquid Mass Ratio) as well as the length-to-diameter ratios of nozzle tip as parameters were chosen. Due to the complex interactions in swirling flows under these variables, this experimental observation will be of fundamental importance to the understanding of turbulence structures. From the observations, it indicated that increasing the ALR causes the spray development to be positively fluctuated on the atomization in both axial and tangential RMS velocities. Also, it can be concluded that the SMD decreases continuously with increase of ALR, substantiating the fact that the fluctuations are inversely proportional to the SMD variation. Meanwhile, the spray behavior is characteristic with a reduction of length-to-diameter ratio; smaller the configuration ratio, the higher the turbulence intensities and smaller SMD variations in the flowfield.
Lee, Sam-Goo,Song, Kyu-Keun,Park, Byung-Joon The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.4
The experimental measurements were carried out to examine turbulent disintegration characteristics ejecting from a counter-flowing internal mixing pneumatic nozzle under variable conditions of swirl angles and air pressures. The air injection pressure was varied from 60 kPa to 180 kPa and four counter-flowing internal mixing nozzles with axi-symmetric tangential-drilled holes at swirl angle of 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, and 60$^{\circ}$to the central axis have been specially designed. The experimental results were quantitatively analyzed, focusing mainly on the comparison of turbulent atomization characteristics issuing from an internal mixing swirl nozzle. To illustrate the swirl phenomena, the distributions of mean velocities, turbulence intensities, volume flux, and SMD (Sauter Mean Diameter, or D$\sub$32/) were comparatively analyzed.
Space Time Rake Receivers for Time Division Synchronous CDMA Base Stations
Sam-Goo Cho,Yang Xiao,Kwang-Jae Lee,Moon-Ho Lee 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.2
In this paper, we develop space-time(ST) Rake receivers for Time Division Synchronous Code Division Multiple Access(TD-SCDMA) base stations(BS). The beamforming of BS transforms the uplink MIMO channel space into many sub-sectors' channels to be nearly orthogonal, thus, well established 1-D Rake technology can be used to TD-SCDMA base station to construct ST Rake, which simplified the system's implementation as well as enlarged users' capacity by the beamforming. The construction and capacity of MIMO sub-sectors by multi-beamforming have been presented. The proposed ST Rake algorithm include the multi-beamforming algorithm for MIMO sub-sectors and classical 1-D Rake algorithm. The calculating formulas for interference plus noise ratio(SINR) and bit error rate(BER) have been derived. Simulations verify that the proposed ST Rake receiver for BS is effective, and the BS systems can get higher system capacity and can be of better performance than presented TD-SCDMA systems.
Atomization Characteristics in Pneumatic Counterflowing Internal Mixing Nozzle
Lee, Sam-Goo,Rho, Byung-Joon The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.10
In an effort to illustrate the global variation of SMD (Sauter mean diameter, or $D_{32}$) and AMD (Arithmetic mean diameter, or $D_{10}$) at five axial downstream locations (i. e., at Z=30, 50, 80, 120, and 170 mm) under the different experimental conditions, the radial coordinate is normalized by the spray half-width. Experimental data to analyze the atomization characteristics concerning with an internal mixing type have been obtained using a PDPA(Phase Doppler Particle Analyzer). The air injection pressure was varied from 40 kPa to 120 kPa. In this study, counterflowing internal mixing nozzles manufactured at an angle of $15^{\circ}$with axi-symmetric tangential-drilled four holes have been considered. By comparing the results, it is clearly possible to discern the effects of increasing air pressure, suggesting that the disintegration process is enhanced and finer spray droplets can be obtained under higher air assist. The variations in $D_{32}$ are attributed to the characteristic feature of internal mixing nozzle in which the droplets are preferentially ejected downward with strong axial momentum, and dispersed with the larger droplets which are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup by higher shear stresses at farther axial locations. The poor atomization around the centre close to the nozzle exit is attributed to the fact that the relatively lower rates of spherical particles are detected and these drops are not subject to instantaneous breakup in spite of the strong axial momentum. However, substantial increases in SMD from the central part toward the edge of the spray as they go farther downstream are mainly due to the fact that the relative velocity of droplet is too low to cause any subsequent disintegration.