• Journal of Power System Engineering
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• v.4 no.1
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• pp.39-44
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• 2000

The purpose of this study is to investigate the flame structure and combustion characteristics in the model gas turbine combustor changing equivalence ratio. For this purpose, temperature and ion current were measured and these data were analyzed by the PDF and power spectra technique. We found that the flame length is longer while increasing the equivalence ratio in experimental condition, and especially ${\psi}=0.19$, combustion reaction was active by the stable swirl flow. and these flames were governed by the random three dimensional eddy.

• Journal of Drive and Control
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• v.20 no.2
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• pp.1-6
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• 2023

This study aims to develop a Korean dental chair hydraulic circuit by improving the existing equipment in order to localize foreign leading companies' products. The suggested Hydraulic circuit can be applicable to varied sectors where height and backrest angle control of chair-type equipment are required. The study followed the steps below. First, three kinds of foreign hydraulic circuits were analyzed and three kinds of Korean dental chair hydraulic circuits were suggested. Second, it was determined whether the three kinds of Korean hydraulic circuits operate normally through SimulationX, a software specialized in multi domain analysis, and the effectiveness of each circuit was examined.

• Journal of Pharmaceutical Investigation
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• v.25 no.1
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• pp.55-62
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• 1995

W/O and O/W emulsions of tegafur (50 mg/5 ml/kg) were orally administered to rats to compare with their mesenteric lymphatic delivery effects. And also in order to demonstrate the lymph targeting associated to the oral route, it was deemed necessary to investigate the fate of solution after oral administration as a control. Lymph and plasma samples were periodically taken from each subject of mesenteric lymphatic duct cannulated rats. Then, lymph and plasma levels of tegafur and its active metabolite, 5-FU, were simultaneously observed. Also pharmacokinetic parameters were compared with each others. On the other hand, most previous studies of lymphatic transport have not addressed the question of whether an increase in mesenteric or thoracic lymph transport by the manipulation of a suspected variable was due to a selective delivery to the intestinal lymphatics or an overall increase availability. Therefore, based on a physiologically based pharmacokinetic model which represents the characteristics of lymphatic systems, we are also going to determine the contributions of mesenteric lymph transport versus thoracic lymph transport of tegafur reported in reference(13). In comparison with tegafur solution, AUC and mean residence time of plasma tegafur were significantly increased in W/O emulsion but significantly decreased in O/W emulsion. Lymph flow rates were similar in both solution and W/O emulsion but half in O/W emulsion. AUC of tegafur in mesenteric lymph and in plasma for W/O emulsion were 3.7 times and 2.9 times more than those for O/W emulsion, respectively. And AUC of 5-FU in thoracic lymph for W/O emulsion was 3.7 times more than that for O/W emulsion. These results suggested that lymphatic delivery or tegafur by W/O emulsion was more effective than that by on emulsion due to its differences or formation ability of chylomicrons.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.63-63
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• 2018

최근 이상기후로 인한 국지성 호우의 발생빈도 및 강우강도의 증가는 하천횡단구조물의 안정성에 문제가 되고 있다. 하천 횡단구조물(보, 물받이공 등)의 파괴는 국부 세굴(bed scour), 파이핑(piping), 구조물 본체의 불안정성 등의 원인으로 발생되고 있으며, 이 중에서 구조물 본체의 불안정성은 도수(hydraulic jump)로 인한 압력변이도 주요 원인이 될 수 있다 (Bower and Toso, 1988; Kazemi, F. et al., 2016). 그러나, 현재 직접적인 파괴 원인인 세굴 등에 대한 연구에 비해 압력변이로 인한 구조물의 파괴원인을 분석하는 연구는 미비한 실정이다. 본 연구에서는 다양한 흐름조건을 발생시켜, 하천횡단구조물 주변의 도수특성 및 도수로 인한 압력변이에 대하여 수리실험 및 수치모의를 통하여 검토하고자 한다. 수리실험에 사용하는 수로는 길이 10 m, 폭 0.3 m, 높이 0.4 m이며 상류로부터 2.5 m 떨어진 곳에 보(weir)를 설치하였다. 실험조건은 다양한 흐름조건에 따른 도수 발생을 검토하고자 상하류 수위를 조절을 통해 Froude 수의 범위를 1 < Fr < 10로 설정하였다. 압력변이는 전압형 압력계(Model : UNIK 5000, 압력 측정 변위 : -2 ~ 5 kPa)를 사용하였으며, 보(weir) 하류단에서 2.5 cm 간격으로 천공하여 측정하였다. 또한 3차원 모형인 FLOW-3D 모형을 이용하여 실험수로를 재현하였으며, 도수 발생 위치, 도수 길이, 도수 발생 시 압력변이에 대하여 실험결과와 수치모의 결과를 비교하여 수치모형을 검증하였다. 최종적으로 Froude 수에 따른 도수특성(도수 발생위치, 도수 길이 등) 및 최대 압력변이를 무차원화 하여 나타내었다. 본 연구는 도수 발생 시 압력변이로 인한 구조물 파괴분석에 대한 기초가 되는 기본적인 연구이나, 향후에는 물받이공 길이, 두께 등 하천횡단 구조물 설계인자 도출에 선행연구로 발전할 수 있다고 판단된다.

• Structural Engineering and Mechanics
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• v.84 no.5
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• pp.633-649
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• 2022

In this study, the effect of circle tunnel on the force distribution around underground rectangular gallery was investigated using theoretical approach, experimental test and Particle flow code simulation (PFC). Gypsum model with dimension of 1500×1500 mm was built. Tensile strength of material was 1 MPa. Dimension of central gallery was 100 mm×200 mm and diameter of adjacent tunnel in its right side was 20 mm, 40 mm and 60 mm. Horizontal distance between tunnel wall and gallery edge were 25, 50, 75, 100 and 125 mm. using beam theory, the effect of tunnel diameter and distance between tunnel and gallery on the induced force around gallery was analyzed. In the laboratory test, the rate of loading displacement was set to 0.05 millimeter per minute. Also sensitivity analysis has been done. Using PFC2D, interaction between tunnel and gallery was simulated and its results were compared with experimental and theoretical analysis. The results show that the tensile force concentration has maximum value in center of the rectangular space. The tensile force concentration at the right side of the axisymmetric line of gallery has more than its value in the left side of the galleries axisymmetric line. The tensile force concentration was decreased by increasing the distance between tunnel and rectangular space. In whole of the configurations, the angles of micro cracks fluctuated between 75 and 105 degrees, which mean that the variations of tunnel situation have not any influence on the fracture angle.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.4
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• pp.265-273
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• 2002

In this paper, wave absorbing characteristics of a horizontal submerged punching plate are investigated throughout the calculation and the experiment. The punching plate with the array of circular holes can force the flow to separate and to form eddies of high vorticity and cause significant energy loss. As an analytic tool, the linear water wave theory and the eigenfunction expansion method is applied. Darcy's law that the normal velocity of the fluid passing through the punching plate is linearly proportional to the pressure difference between two sides of the punching plate is assumed. The proportional constant called the porous coefficient is deeply dependent to the porosity. To obtain the relationship between the porosity and the porous coefficient the systematic model test for the punching plates with 6 different porosities is conducted at 2-dimensional wave tank. It is found that the porous coefficient is linearly proportional to the porosity(b=57.63P-0.9717). It is also noted that the optimal porosity value is near P=0.1 and the optimal range of submergence depth is $d/h\\leq0.2$ within entire frequency range.

• Journal of the Korean Society of Systems Engineering
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• v.13 no.1
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• pp.33-39
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• 2017

This paper describes the system engineering approach for the heat transfer analysis of plus7 fuel rod for APR1400 using, a commercial software, ANSYS. The fuel rod is composed of fuel pellets, fill gas, end caps, plenum spring and cladding. The heat is transferred from the pellet outward by conduction through the pellet, fill gas and cladding and further by convection from the cladding surface to the coolant in the flow channel. The goal of this paper is to demonstrate the temperature and heat flux change from the fuel centerline to the cladding surface when having maximum fuel centerline temperature at 100% power. This phenomenon is modelled using the ANSYS FEM code and analyzed for steady state temperature distribution across the fuel pellet and clad and the results were compared to the standard values given in APR1400 SSAR. Specifically the applicability of commercial software in the evaluation of nuclear fuel temperature distribution has been accounted. It is note that special codes have been used for fuel rod mechanical analysis which calculates interrelated effects of temperature, pressure, cladding elastic and plastic behavior, fission gas release, and fuel densification and swelling under the time-varying irradiation conditions. To satisfactorily meet this objective we apply system engineering methodologies to formulate the process and allow for verification and validation of the results acquired. The close proximity of the results obtained validated the accuracy of the FEM analysis of the 2D axisymmetric model and 3D model. This result demonstrated the validity of commercial software instead of proprietary in-house code that is more costly to develop and maintain.

• Journal of Korean Society of Disaster and Security
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• v.12 no.4
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• pp.1-13
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• 2019

Recently, as the occurrence frequency of sudden floods due to climate change increased, it is necessary to install the facilities that can cope with the initial stormwater. Most researches have been conducted on the design of facilities applying the Low Impact Development (LID) and the reduction effect on rainfall runoff to examine with 1D or 2D numerical models. However, the studies on the examination about flow characteristics and stability of pipe network systems were relatively insufficient in the literature. In this study, the stability of the pipe network system in rainwater storage tank was examined by using 3D numerical model, FLOW-3D. The changes of velocity and dynamic pressure were examined according to the number of rainwater storage tank and compared with the design criteria to derive the optimal design plan for a rainwater storage tank. As a results of numerical simulation with the design values in the previous study, it was confirmed that the velocity became increased as the number of rainwater storage tank increased. And magnitude of the velocity in pipes was formed within the design criteria. However, the velocity in the additional rainwater storage pipe was about 3.44 m/s exceeding the allowable range of the design criteria, when three or more additional rainwater storage tanks were installed. In the case of turbulence intensity and bottom shear stress, the bottom shear stress was larger than the critical shear stress as the additional rainwater storage was increased. So, the deposition of sediment was unlikely to occur, but it should be considered that the floc was formed by the reduction of the turbulence intensity. In addition, the dynamic pressure was also satisfied with the design criteria when the results were compared with the allowable internal pressure of the pipes generally used in the design of rainwater storage tank. Based on these results, it was suitable to install up to two additional rainwater storage tanks because the drainage becomes well when increasing of the number of storage tank and the velocity in the pipe becomes faster to be vulnerable to damage the pipe. However, this study has a assumption about the specifications of the rainwater storage tanks and the inflow of stormwater and has a limitation such that deriving the suitable rainwater storage tank design by simply adding the storage tank. Therefore, the various storage tank types and stormwater inflow scenarios will be asked to derive more efficient design plans in the future.

• Computers and Concrete
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• v.20 no.4
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• pp.429-437
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• 2017

In this study, the effect of the tensile strength and ratio of disc spacing to penetration depth on the efficiency of tunnel boring machine (TBM) is investigated using Particle flow code (PFC) in two dimensions. Models with dimensions of $150{\times}70mm$ made of rocks with four different tensile strength values of 5 MPa, 10 MPa, 15 MPa and 20 MPa were separately analyzed and two "U" shape cutters with width of 10 mm were penetrated into the rock model by velocity rate of 0.1 mm/s. The spacing between cutters was also varied in this study. Failure patterns for 5 different penetration depths of 3 mm, 4 mm, 5 mm, 6 mm, and 7 mm were registered. Totally 100 indentation test were performed to study the optimal tool-rock interaction. An equation relating mechanical rock properties with geometric characteristics for the optimal TBM performance is proposed. The results of numerical simulations show that the effective rock-cutting condition corresponding to the minimum specific energy can be estimated by an optimized disc spacing to penetration depth, which, in fact, is found to be proportional to the rock's tensile strength.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.691-706
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• 2021

This paper aims to numerically investigate violent sloshing in a partially filled three-dimensional (3D) prismatic tank with or without a baffle, further to clarify the suppressing performance of the baffle and the damping mechanism of sloshing. The numerical model is based on a Cartesian grid multiphase flow method, and it is well validated by nonlinear sloshing in a 3D rectangular tank with a vertical baffle. Then, sloshing in an unbaffled and baffled prismatic tank is parametrically studied. The effects of chamfered walls on the resonance frequency and the impact pressure are analyzed. The resonance frequencies for the baffled prismatic tank under different water depths and baffle heights are identified. Moreover, we investigated the effects of the baffle on the impact pressure and the free surface elevation. Further, the free surface elevation, pressure and vortex contours are analyzed to clarify the damping mechanism between the baffle and the fluid.