• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.477-482
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• 2009

로켓노즐 유동은 성능에 대단히 중요한 영향을 미치나, 고온 고압의 가스 유동 특성으로 직접적인 측정이 매우 어렵다. 이러한 문제 해결을 위해 수력학적 상사(hydraulic analogy)기법이 개발되었으며, 본 연구에서는 고온 고압의 로켓 노즐 유동에 대한 수력학적 상사의 적용 가능성이 시험되었다. 로켓 모타의 축대칭 De Laval 노즐 내부 유동현상에 관한 연구가 수력학적 상사를 이용하여 설계된 2차원 수문형 시험장치(2-D Sluice-Type Water-Table)에서 수행되었다. 정량적인 시험을 위해서는 $k{\neq}2$인 기체 유동에 대한 비상사성 문제 해결이 필요하며, 본 연구에서는 시험대를 경사시켜 유동방향 중력가속도 영향을 감소시킴으로서 점성에 의한 비상사성 문제 해결을 시도하였다. 유동 가시화를 통해 수력학 상사에 대한 이해를 깊이할 수 있었으며, 수력학적 상사 실험(2차원 등엔트로피 유동)의 관련 분야에 대한 다양한 적용 가능성이 확인되었다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.39-42
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• 2003

Leading edge extension(LEX) in a highly swept shape applied to a delta wing features the modern air-fighters. The LEX vortices generated upon the upper surface of the wing at high angle of attack enhance the lift force of the delta wing by way of increased negative suction pressure over the surfaces. The present 3-D stereo PIV includes the Identification of 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system, removal of error vectors by a statistical method followed by a continuity equation criterion and so on. A delta wing model with or without LEX was immersed in a circulating water channel. Two high-resolution, high-speed digital cameras$(1280pixel\times1024pixel)$ were used to allow the time-resolved animation work. The present dynamic stereo PIV represents the complicated vortex behavior, especially, in terms of time-dependent characteristics of the vortices at given measuring sections. Quantities such as three velocity vector components, vorticity and other flow information can be easily visualized via the 3D time-resolved post-processing to make the easy understanding of the LEX effect or vortex emerging and collapse which are important phenomena occurring in the field of delta wing aerodynamics.

• 대한핵의학회지
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• 제3권2호
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• pp.55-63
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• 1969

In the past few years, scintigraphy has become increasingly important in clinical practice, and the use of a color-printing technique has permited a more accurate interpretation of the scan image. Our liver color scintigrams consist of 51 hepatomas, 35 liver cirrhosis, 22 liver abscessis, 10 hepatitis and other 13 cases of the liver diseases which were clinically arid pathologically diagnosed at Sevarance Hospital, Yonsei Univ., since Feb. 1969 through Sept. 1969. These scintigrams have been analized in terms of various pathologic morphology, such as size, shape, margin of the liver, distribution of radioactivity, and shape of the space occupying lesions. The results are as follows: 1. Enlargement of the liver was the most common finding in the diseased livers. The Rt. lobe enlargement was particularly prominent in the liver abscess. 2. Irregular distribution of radioactivity in the liver (so called mottling) was present in 78% of hepatoma, while it was seen only in 31% of liver abscesses. 3. Liver cirrhosis tends to show perihilar accumulation of the isotope (57%). 4. The deformity of the lower most angle of the Rt. lobe, and the Lt. lateral margin of the Lt. lobe was also impressive throughout the cases ($74{\sim}95%$ of all diseased livers). 5. The frequency of visualization of the spleen was influenced by the size of space occupying lesions and the amount of functioning liver. 6. Differentiation between the liver abscess and hepatoma seems to be possible on scintigram, when shape and margin of defect and patterns of distribution of radioactivity in the remaining liver are clearly demonstrated.

• 한국정밀공학회지
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• 제27권8호
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• pp.62-69
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• 2010

Internal lathe machining with a boring bar is weak with respect to vibration because the bar is long and slender. Therefore, it is important to study the dynamic characteristics of a boring bar. The purpose of this study was to identify the effects of overhang and cutting conditions on the dynamic response characteristics of a boring bar. For an efficient experiment, an $L_g(3^3)$ orthogonal array was applied and the results were quantitatively analyzed by ANOVA. Overhang, feed per revolution, and depth of cut were selected as independent variables. Meanwhile, dynamic stiffness, damping ratio, damping coefficient, and acceleration were chosen as dependent variables. The vibration signal was obtained from an accelerometer attached to the boring bar, followed by visualization by a signal analyzer. The effect of overhang was found to have a significant effect on the dynamic stiffness, damping ratio, and damping coefficient, but the other variables did not. As the length of the overhang increased, the dynamic stiffness decreased and the damping ratio increased. In addition, the damping coefficient increased until the length of the overhang was 4D (where D is the shank diameter), after which it remained constant. The acceleration decreased until the overhang length was 4D, and then increased sharply when the overhang was increased further. From these results, the behavioral trend of the damping characteristics changed when its overhang length was 4D. Consequently, there is a critical point that the dynamic characteristics of boring bar change.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.666-669
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• 2008

Droplet in miniaturized microfluidic systems have received much focused attention recently. In this work, electrical charging phenomenon of a conducting water droplet on the electrode under the dc electric field is studied and using this phenomenon droplet actuation method for microreactor applications is experimentally demonstrated. To find effects of key factors, the effects of electric field, medium viscosity, and droplet size are investigated. A scaling law of charging for the conducting droplet is derived from the experimental results. Unlike the case of a perfect conductor, the estimated amount of electrical charge ($Q_{est}$) of a water droplet is proportional to the 1.59 power of the droplet radius (R) and the 1.33 power of the electric field strength (E). (For a spherical perfect conductor, Q is proportional to R2 and E.) It is thought that the differences are mainly due to incomplete charging of a water droplet resulted from the combined effect of electrochemical reaction at electrode and the relatively low conductivity of water. Using this phenomenon, we demonstrate the transport of the charged droplet and fusion of two oppositely-charged droplets. When electric field is subjected sequentially on the electrode, the charged droplet is transported on the electrode. For the visualization of fusion of charged droplets, the precipitation reaction is used. When subjected to a DC voltage, two droplets charged are moving and merging toward each other due to the Coulombic force and chemical reaction is simultaneously occurred by coalescence of droplets. It may be due to the interchange effect of charge. It is shown that the droplet can be used for microreactor where transporting, merging etc. of reagents constitute unit operation.

• 대한기계학회논문집B
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• 제25권5호
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• pp.722-730
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• 2001

The local heat transfer of an axisymmetric submerged air jet impinging on a heated flat plate is investigated experimentally with the variation of mesh-screen solidity. The screen installed in front of the nozzle exit modifies the flow structure and local heat transfer characteristics. The mean velocity and turbulence intensity profiles of streamwise velocity component are measured using a hot-wire anemometry. The temperature distribution on the heated flat surface is measured with thermocouples. The smoke-wire flow visualization technique was employed to understand the near-field flow structure qualitatively for different mesh screens. Large-scale toroidal vortices and high turbulence intensity enhance the heat transfer rate in the stagnation region. For a higher solidity, turbulence intensity become higher which increases the local heat transfer at small nozzle-to-plate spacings such as L/D<6. The local and average Nusselt numbers of impinging jet from the $\sigma$(sub)s=0.83 screen at L/D=2 are about 5.6∼7.5% and 7.1% larger than those for the case of no screen, respectively. For the nozzle-to-plate spacings larger than 6, however, the turbulence intensities for all tested screens approach to an asymptotic curve and the mean velocity along the jet centerline decreases monotonically. As the nozzle-to-plat spacing increases for high solidity screens, the heat transfer rate decreases due to the reduction in turbulence intensity and jet momentum.

• Molecules and Cells
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• 제39권2호
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• pp.119-128
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• 2016

Angelica polymorpha Maxim root extract (APRE) is a popular herbal medicine used for treating stomachache, abdominal pain, stomach ulcers, and rheumatism; however the effect of APRE on cancer cells has not yet been explored. Here, we examined APRE cytotoxicity seen on target neuroblastoma cells (NB) using cell viability assays, DAPI visualization of fragmented DNA, and Western blotting analysis of candidate signaling pathways involved in proliferation and apoptosis. We demonstrated that APRE reduced cell viability in NB to a greater extent than in fibroblast cells. In addition, we found that APRE could inhibit the three classes of MAPK proteins and could also down-regulate the PI3K/AKT/GSK-$3{\beta}$ activity all being relevant for proliferation and survival. APRE could also up-regulate Bax expression and down-regulate Bcl-2 and Mcl-1. With APRE treatment, depolarization of mitochondria membrane potential and activation of caspase-3 was demonstrated in the SH-SY5Y cells. We could not found increased activity of death receptor and caspase-8 as markers of the extrinsic apoptosis pathway for the APRE treated cells. In presence of a caspase-3 siRNA and a pan-caspase inhibitor, APRE could not reduce the viability of NB cells to a significant degree. So we predicted that with APRE, the intrinsic pathway was solely responsible for inducing apoptosis as we also showed that the non-caspase autophagy pathway or ER stress-ROS mediated pathways were not involved. These findings demonstrate that an intrinsic mitochondria-mediated apoptosis pathway mediates the apoptotic effects of APRE on SH-SY5Y cells, and that APRE shows promise as a novel agent for neuroblastoma therapy.

• 한국의류학회지
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• 제40권4호
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• pp.660-668
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• 2016

In the $21^{st}$ century of digital information society, design is changing from an analog era that focuses on logical and rational knowledge to a new paradigm of an era focused on sensible communications that can react fast. Design becomes to fulfill sensible needs; moreover, full efforts are being made in the academic research of sensibility evaluation for the conceptualization, quantization, and visualization of design sensibilities based on the measurement and evaluation of sensibility. This study provides insight into a sensibility evaluation method to understand the global user's sensibility in the fashion design field. As for research methods, first, measurement methods of physical, psychological, and physiological reactions to design sensibility were examined through written research on sensibility evaluation in both domestic and overseas research. Next, studies on sensibility during the past 15 years from 2000 to 2014 in the field of domestic fashion design were analyzed to grasp research trends in sensibility evaluation methods; subsequently, suitable sensibility evaluation methods for current fashion design were discussed. As a result of the study, it was shown that most sensibility evaluation studies in the field of domestic fashion design are based on surveys using sensibility terms. However, it requires the process of translating among different terms in different lingual cultures and within the limits of a uniformed evaluation. In this regard, recent cases of overseas design studies have been applying new methods to measure physiological reactions such as eye tracking methods combined with IT. The analysis of multilateral sensibility evaluation methods in this study have significant meaning for use as basic data to establish a planning for an evaluation scale to measure the sensibility of global consumers towards modern fashion design more quantitatively.

• Spatial Information Research
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• 제14권2호
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• pp.223-234
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• 2006

연안수질의 시공간적 분포특성을 살펴보기 위하여 1997년부터 2004년 사이에 우리나라 연안해역에서 측정된 수질자료(chlorophyll-a, pH, DO, COD, SS, dissolved inorganic nitrogen, dissolved inorganic phosphorous, salinity, temperature)에 대해 GIS 공간분석 기법을 적용하였다. 본 연구에서 사용된 수질자료는 공간상 모든 위치에 그 값이 존재하나, 실제 간의 수집은 고정관측 위치에서만 수행된다. 따라서 공간적으로 연속적으로 존재하는 연안수질의 분포 특성을 파악하기 위해서는 미관측 지점의 값을 예측할 필요가 있다. 본 논문에서는 공간분석 기법인 IDW를 연안수질 측정자료에 적용하였으며, IDW 기법의 적용 가능성을 평가하였다. 또한 IDW 공간보간을 적용한 후, 전국 연안을 46개 구간으로 구분하여 각 구간의 수질특성을 GIS 시각화 기법을 이용하여 분석하였다. 적용결과 공간보간 및 GIS 기법이 다년간 광범위한 범위에서 수집된 수질 자료로부터 시공간적 분포 특성을 파악하는데 유용함을 확인할 수 있었다.

• Journal of Gastric Cancer
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• 제17권2호
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• pp.145-153
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• 2017

Purpose: Identification of the infrapyloric artery (IPA) type is a key component of pylorus-preserving gastrectomy. As the indocyanine green (ICG) fluorescence technique is known to help visualize blood vessels and flow during reconstruction, we speculated that this emerging technique would be helpful in identifying the IPA type. Materials and Methods: From August 2015 to February 2016, 20 patients who underwent robotic or laparoscopic gastrectomy were prospectively enrolled. After intravenous injection of approximately 3 mL of ICG (2.5 mg/mL), a near-infrared fluorescence apparatus was applied. The identified shape of the IPA was confirmed by examining the actual anatomy following infrapyloric dissection. Results: The mean interval time between ICG injection and visualization of the artery was 22.2 seconds (range, 14-30 seconds), and the mean duration of the arterial phase was 16.1 seconds (range, 9-30 seconds). The overall positive predictive value (PPV) of ICG fluorescence in identifying the IPA type was 80% (16/20). The IPA type was incorrectly predicted in four patients, all of whom were obese with a body mass index (BMI) of more than $25kg/m^2$. Conclusions: Our preliminary results indicate that intraoperative vascular imaging using the ICG fluorescence technique may be helpful for robotic or laparoscopic pylorus-preserving gastrectomy.