• 제목/요약/키워드: Mechanical obstruction

검색결과 88건 처리시간 0.03초

단일 카메라를 이용한 이상유동 기포율 측정방법의 개발과 응용 (A Void Fraction Measurement Technique by Single Camera and Its Application)

  • 최동환;유정열;송진호;성재용
    • 대한기계학회논문집B
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    • 제31권11호
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    • pp.904-911
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    • 2007
  • A measurement technique fur void fraction has been proposed using a time-resolved two-phase PIV system and the bubble dynamics has been investigated in gas-liquid two-phase flows. For the three-dimensional evaluation of the bubble information, both the images from the front and side views are simultaneously recorded into a high speed CCD camera by reflecting the side view image on a $45^{\circ}$ oriented mirror to be juxtaposed with the front view image. Then, a stereo-matching technique is applied to calculate the void fraction, bubble size and shape. To obtain the rising bubble velocities, the 2-frame PTV method was adopted. The present technique is applied to freely rising bubby flows in stagnant liquid. The results show that the increase of bubble flow rate gives rise to the increase of bubble size and rising velocity at first. If it goes over a certain level, the rising velocity becomes constant and the horizontal velocity grows bigger instead due to the obstruction of other bubbles.

DME 예혼합 압축착화 엔진에서 질소와 이산화탄소의 영향 (Effect of Nitrogen and Carbon Dioxide on DME Homogeneous Charge Compression Ignition Engine)

  • 장진영;배충식
    • 한국자동차공학회논문집
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    • 제16권5호
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    • pp.171-178
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    • 2008
  • The combustion and exhaust emission characteristics were investigated in an DME fueled HCCI engine. Carbon dioxide, nitrogen and mixed gas, which was composed of carbon dioxide and nitrogen, were used as control parameters of combustion and exhaust emission. As the oxygen concentration in induction air, which was occurred by carbon dioxide, nitrogen and mixed gas, was reduced, the start of auto-ignition was retarded and the burn duration was extended due to obstruction of combustion and reduction of combustion temperature. Due to these fact, indicated mean effective pressure was increased and indicated combustion efficiency was decreased by carbon dioxide, nitrogen and mixed gas. In case of exhaust emission, hydrocarbon and carbon monoxide was increased by reduction of oxygen concentration in induction air. Especially, partial burning was appeared at lower than about 18% of oxygen concentration by supplying carbon dioxide. However it was overcome by intake air heating.

대퇴골 동맥 모델내에 카테터 삽입시 유량 및 압력 변화 측정 (Measurements of Flow Rate and Pressure Changes in Femoral Artery Model during Catheterization)

  • 김중경;박찬영;정찬일;장준근;한동철;유정열;민병구
    • 대한의용생체공학회:학술대회논문집
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    • 대한의용생체공학회 1996년도 추계학술대회
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    • pp.7-10
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    • 1996
  • The purpose of this experimental investigation is to examine the influence of the catheter on local pressure changes and flow rate in an arterial branch model similar to the femoral artery of man. Effects of branch to main lumen flow rate ratios and the locations of catheter tip were found to be significant on the local pressure changes. Relatively large pressure drops due to obstruction effects may induce endothelial cell damage, which have been reported to be the primary cause of the initiation of the atherosclerosis.

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액상가압공정으로 제조된 탄탈륨 연속섬유 강화 비정질 복합재료의 미세조직과 기계적 성질 (Microstructure and Mechanical Properties of Tantalum-Continuous-Fiber-Reinforced Amorphous Matrix Composites Fabricated by Liquid Pressing Process)

  • 이규홍;이상복;이상관;이성확
    • 대한금속재료학회지
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    • 제46권7호
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    • pp.403-411
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    • 2008
  • Zr-based amorphous alloy matrix composites reinforced with tantalum continuous fibers were fabricated by liquid pressing process, and their microstructures and mechanical properties were investigated. About 60 vol.% of tantalum fibers were homogeneously distributed inside the amorphous matrix, which contained a small amount of polygonal crystalline particles. The ductility of the tantalum-continuous-fiber-reinforced composite under tensile or compressive loading was dramatically improved over that of the monolithic amorphous alloy, while maintaining high strength. The consequential observation of the tensile deformation and fracture behavior of the composite showed the formation of multiple shear bands and multiple necking, crack deflection in the amorphous matrix, and obstruction of crack propagation by ductile fibers, thereby resulting in very high tensile elongation of 7.2%. These findings suggested that the liquid pressing process was useful for the development of amorphous matrix composites with improved ductility.

Ultrasonic Targeting of NK Cell in Vessel Bifurcation for Immunotherapy: Simulation and Experimental Validation

  • Saqib Sharif;Hyeong-Woo Song;Daewon Jung;Hiep Xuan Cao;Jong-Oh Park;Byungjeon Kang;Eunpyo Choi
    • 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.

Catechol-O-Methyltransferase Activity in Cholestatic Rat's Liver Induced by Bile Duct Ligation

  • Mun, Kyo-Cheol
    • BMB Reports
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    • 제29권2호
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    • pp.142-145
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    • 1996
  • To investigate the cause of increased plasma catecholamine levels in liver disease, catechol-O-methyltransferase (COMT), which provides a major route of catabolism for circulating catecholamines, was studied under the cholestasis induced by mechanical biliary obstruction in rats. Monoamine oxidase (MAO) activity and the $K_m$ and $V_{max}$ values for both enzymes were also measured. Cytosolic, microsomal, and mitochondrial COMT activities in the cholestatic liver were significantly decreased throughout the experiment. Microsomal, and mitochondrial MAO activity in the cholestatic liver were also significantly decreased. Vmax values of COMT and MAO were lower. Serum COMT and MAO activities were detected after CBD ligation. These results indicate that plasma catecholamine levels are increased in liver disease due to decreased hepatic degradation of catecholamines by decreased activities of COMT and MAO. The decreased activity of these enzymes is caused by decreased biosynthesis and by flowage into the blood from the damaged hepatocyte.

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뇌실-복강 단락 원위도관의 심장내전위 - 증례보고 - (A Case of Intracardiac Migration of Distal Ventriculo-Peritonal(V-P) Shunt Catheter - Case Report -)

  • 김병주;차승헌;박동준;송근성;최창화;이영우
    • Journal of Korean Neurosurgical Society
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    • 제29권2호
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    • pp.270-273
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    • 2000
  • Ventriculoperitoneal(V-P) shunt has been used as a popular method for surgical treatment of hydrocephalus. But complications such as infection, mechanical obstruction and failure of flow rate sometimes make painful stress to neurosurgeons and patients. Of particular, migration of distal V-P shunt catheter to extraperitoneal space has rarely been reported. Even rarer is intracardiac migration of distal V-P shunt catheter. Authors report a such case and discuss the possible mechanism and preventive method.

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A Study on the Safe Position from the Local Fire in the Ship's Engine Rooms

  • Kim, Mann-Eun;Lee, Kyoung-Woo;Lee, Young-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • 제32권3호
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    • pp.446-454
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    • 2008
  • Control devices for fire safety systems located in a engine room are to be arranged at a safe position which is easily accessible during a fire. To develop an interpretation for the safe position in engine rooms, calculation and experiments are carried out to determine a correlation between radiant heat and distance from fire in this paper. On the basis of results of this research, the control devices for a main engine are to be installed in the behind side of an obstruction to reduce radiant heat from the fire of the main engine. In case of other control devices, they are also to be provided in the same manner of control devices for the main engine or are to be placed with 5 meters far from fire hazards.

식도 운동 질환에 있어서 동위원소 식도 통과 검사의 의의 (Radionuclide Esophageal Transit Study in the Esophageal Motility Disorders)

  • 최재걸;이민재;송치욱
    • 대한핵의학회지
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    • 제27권2호
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    • pp.233-238
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    • 1993
  • Esophageal motility was evaluated from the analysis of 10 consecutive swallows using liquid bolus containing 0.5 mCi of $^{99m}Tc$ tin colloid. We have reviewed our experience of esophageal transit study in the 20 normal volunteers and 55 patients with dysphagia that was not related to mechanical obstruction. The purpose of this study is to measure the esophageal transit in normal subjects and in patients with various esophageal motility disorders. The overall sensitivity and specificity of radionuclide esophageal transit study in detecting esophageal motor abnormality were compared with manometric results as a gold standard, which were 80% and 100% respectively. Radionuclide transit study is a safe, rapid, noninvasive test and suitable as a screening test for esophageal motor disorders.

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밀폐된 동시회전 디스크 유동장에 대한 열선 지지대의 영향 (The Effect of a Hot-wire Supporter on the Flow Between Corotating Disks in Shroud)

  • 공대위;주원구
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2002년도 학술대회지
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    • pp.663-666
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    • 2002
  • Hard disk drived (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. The distribution of pressure disturbance on disks has relation to flow structure. To investigate the flow structure, time-resolved hot-wire measurements of the circumferential velocity component were obtained for the flow between the center pair of four disks of common radius $R_2$ coretating at angular velocity ${\Omega}$ in a fixed cylindrical enclosure. Hot-wire supporter acts as an obstruction in this case. The effects of rotating speed and size of hot-wire supporter diameter between disks on the flow driven by disks were investigated. Velocity spectra at the fixed space were measured to obtain the structure of inner and outer region in flow field.

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