• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1153-1163
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• 2002

A transient analysis on temperatures of fuel and oil in hydraulic and lubrication systems in an aircraft was studied using the finite difference method. Numerical calculation was performed by an explicit method with modified Dufort-Frankel scheme. Among various missions, air superiority mission was considered as a mission model with 20% hot day ambient condition in subsonic region. The ambience of the aircraft was assumed as turbulent flow. Convective heat transfer coefficient were used in calculating heat transfer between the aircraft surface and the ambience. For an aircraft on the ground, an empirical equation represented as a function of free-stream air velocity was used. And the heat transfer coefficient for flat plate turbulent flow suggested by Eckert was employed for in-flight phases. The governing equations used in this analysis are the mass and energy conservation equations on fuel and oils. Here, analysis of fuel and oil temperature in the engine was not carried out. As a result of this analysis, the ground operation phase has shown the highest temperature and the largest rate of temperature increase among overall mission phases. Also, it is shown that fuel flow rate through fuel/oil heat exchanger plays an important role in temperature change of fuel and oil. This analysis could be an important part of studies to ensure thermal stability of the aircraft and can be applicable to thermal design of the aircraft fuel system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.79-88
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• 2015

This study numerically examined the mixing characteristics of rectangular cavity flows by using the hybrid lattice Boltzmann method (HLBM) applied to the finite difference method (FDM). Multi-relaxation time was used along with a passive scalar method which assumes that two substances have the same mass and that there is no interaction. First, we studied numerical results such as the stream function, position of vortices, and velocity profile for a square cavity and rectangular cavity with an aspect ratio of 2. The data were compared with previous numerical results that have been proven to be reliable. We also studied the mixing characteristics of a rectangular cavity flow such as the concentration profile and average Sherwood number at various Pe numbers and aspect ratios.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.269-276
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• 2012

An air core is generated during draining through an axisymmetrically placed circular orifice after rotating a cylindrical tank filled with a liquid. If an air core is generated, the draining flow rate decreases and the draining time increases. In this study, the process of the formation of the air core and internal flow characteristics in a cylindrical tank are studied by numerical methods. Several methods are used in the analysis, and the results are compared with experimental results to obtain the appropriate scheme. Axial, radial, and swirl velocity profiles on a variety of heights are shown graphically, and the internal flow structure is analyzed from the velocity profiles, the vector plot, and the stream function distribution.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.3
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• pp.229-236
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• 2001

One of the basic tasks in hydrological analysis is to delineate drainage basins and channel networks. Characteristics of channel networks and drainage basin parameters have been used widely in hydrologic calculation and modeling. DEMs(Digital Elevation Models) are generally used to automatically map the channel networks and to delineate drainage basins. This paper presents an effort to analyze basin characteristics using various DEMs. The quantitative analysis of channel networks begins with Horton's method of classifying stream according to Horton orders in hydro-geomorphy. HGSIS(Hydro-Geo-Spatial Information System) is possible to extract parameters. Usually, hydrologists. surveyors and GSIS researchers have some difficulties in accessing satellite images and in extracting DEMs from them. Therefore, the extracted DEMs from contours of digital map is widely used to have the basic works of hydrological analysis. This study presents proper DEMs to calculate Horton's orders, width function, drainage area, main channel length, total channel length, basin elevation and basin slope at digital map of 1:25,000 scale.

• International Journal of Vascular Biomedical Engineering
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• v.3 no.2
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• pp.1-9
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• 2005

Flow-induced dilation of blood vessel is the result of a series of bioreaction in vascular endothelial cells(VEC). Shear stress change by blood flow in human artery or vein is sensed by the mechanoreceptor and responsible for such a chain reaction. The inositol(1,4,5)-triphophate($IP_3$) is produced in the first stage to elevate permeability of the intercellular membrane to calcium ions by which the cytosolic calcium concentration is consequently increased. This intracellular calcium transient triggers synthesis of EDRF and prostacyclin. The mathematical model of this VEC calcium dynamics is reproduced from the literature. We then use the Computational Fluid Dynamics(CFD) technique to investigate the blood stream dictating the VEC calcium dynamics. The pulsatile blood flow in a stenosed blood vessel is considered here as a part of study on thrombogenesis. We calculate the pulsating shear stress (thus its temporal change) distributed over the stenosed artery that is implemented to the VEC calcium dynamics model. It has been found that the pulsatile shear stress induces larger intracellular $Ca^{2+}$ transient plus much higher amount of EDRF and prostacyclin release in comparison with the steady shear stress case. It is concluded that pulsatility of the physiological shear stress is important to keep the vasodilation function in the stenosed part of the blood vessel.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.3
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• pp.157-167
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• 2015

In order to provide simple and accurate wave theory in design of offshore structure, an analytical approximation is introduced in this paper. The solution is limited to flat bottom having a constant water depth. Water is considered as inviscid, incompressible and irrotational. The solution satisfies the continuity equation, bottom boundary condition and non-linear kinematic free surface boundary condition exactly. Error for dynamic condition is quite small. The solution is suitable in description of breaking waves. The solution is presented with closed form and dispersion relation is also presented with closed form. In the last century, there have been two main approaches to the nonlinear problems. One of these is perturbation method. Stokes wave and Cnoidal wave are based on the method. The other is numerical method. Dean's stream function theory is based on the method. In this paper, power series method was considered. The power series method can be applied to certain nonlinear differential equations (initial value problems). The series coefficients are specified by a nonlinear recurrence inherited from the differential equation. Because the non-linear wave problem is a boundary value problem, the power series method cannot be applied to the problem in general. But finite number of coefficients is necessary to describe the wave profile, truncated power series is enough. Therefore the power series method can be applied to the problem. In this case, the series coefficients are specified by a set of equations instead of recurrence. By using the set of equations, the nonlinear wave problem has been solved in this paper.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.895-900
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• 2013

A two-dimensional Stokes flow past a circular cylinder in a channel is analyzed. The circular cylinder is located at the center of the channel, and a plane Poiseuille flow exists upstream and downstream far from the circular cylinder. The Stokes approximation is used, and the flow is investigated analytically by using the eigenfunction expansion and the least square methods. From the analysis, the stream function and pressure distribution are obtained, and the pressure and shear stress distributions on the circular cylinder and channel wall are calculated. The additional pressure drop induced by the circular cylinder and the force exerted on it are calculated as functions of the length of the radius of the circular cylinder. For a typical length of the radius of the circular cylinder, the streamline pattern and pressure distribution are shown.

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.2
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• pp.153-166
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• 2013

Yang deficiency pattern is a representative syndrome differentiation. This article is a study on to which categories of modern diseases yang deficiency is assigned by reference to modern clinical papers and the meaning of yang deficiency interpreted with a perspective of Korean Medicine and a modern perspective. Yang deficiency, yang qi deficiency, lack of yang qi and yang qi debilitation are the words found in "Nei Ching" and yang qi can be interpreted as something to warm, drive and arouse. Zhangzhongjing considered recovery or loss of Yang as the key to life in "Shanghanlun". Danxi proposed "Yang being liable to hyperactivity, Yin being insufficient" and emphasized pathological ministerial fire of Yang exuberance rather than physiological ministerial fire of Yang deficiency. Zhangjingyue proposed "Yang not being in excess, Yin being often deficient" and understood growth and decline of yin qi are all led by yang qi and put emphasis on true yin in addition to yang qi. Diseases of yang deficiency pattern are related with decline of metabolic level, hypofunction of internal secretion, disorder of immune function, disorder of automatic nerve system, sympathetic nerve inhibition, metabolic disorder of microelements, increase of cGMP, change of microcirculation, low speed of blood stream, kidney malfunction. Diseases related with kidney are sterility, polycystic ovary syndrome, spinal stenosis, edema, renal failure, IgA nephropathy, erectile dysfunction, nephritis, prostatitis, benign prostatic hyperplasia, decrease of adrenal cortical hormone by nephrotic syndrome, myelodysplastic syndrome. Disease related with heart are heart failure, arrhythmia, cardiomyopathy, atherosclerosis heart disease, hypertension, hyperlipidemia, pulmonary heart disease. Diseases related with spleen are irritable bowel syndrome, ulcerative colitis. Diseases related with liver are hypothyroidism, liver cirrhosis ascites, hepatitis B, chronic hepatitis, hepatic diabetes. Diseases related with lung are allergic rhinitis, cough variant asthma, bronchial asthma, pulmonary emphysema. And diabetes mellitus, metabolic syndrome, aplastic anemia, headache, encephalatrophy, Alzheimer's disease are also related with yang deficiency.

• Korean Institute of Interior Design Journal
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• v.22 no.2
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• pp.112-119
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• 2013

This study focuses on an innate 'spiritual' quality of arts including building art, or a meaning of the religious philosophy of 'creativity-art'. In particular, this focuses, among two aspects in roots of modernism, especially on the irrational facet veiled by the name of 'a new' religious faith, rather than the rational such as the function. In fact, although modern Avant-gardes' religious philosophical faiths called by different names respectively have generally considered as one of the sources for their designs, nevertheless it had veiled because of the religious 'orthodoxy power' at that time. Arguably, as known well, the creativity of art is intimate relation with a religious ideas. Thus, for this purpose, this study treats this theme in central these three issues; Orientalism, Universalism, and Froebelianism which are intimate in the realm of religious philosophy. Ultimately, through a research on the universal religious philosophy in all three objects as keeping a quality not of pantheism but of 'Panentheism' emphasizing the individual's 'divine' artistic volition, this study deepens the understanding on the Creativity-art as the main characteristic of modernity. Namely, it is very important to draw a distinction between pantheism and Panentheism; because, through the pantheism, it is difficult to comprehend a stream and a characteristic of the twentieth new religious thoughts including those of modern avant-garde artists, as well as their existential free-will as a whole.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.437-441
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• 2009

The modern times is as special as from the river, the river is very important of our life. The importance to preserve the river environment has been issued and the river developing method is being changed to use potential function of nature as well as flood control. Essential element of the river restoration is a vegetation. The flow resistance by vegetation along the river banks is greatly increase the flood stage. Therefore, the flow resistance due to vegetation in the river and roughness coefficient changes to understand the hydraulic characteristics is an important elements in the river restoration. The purpose of this study is to analyze the flood stage and the aspects of riverbed changes due to the corridor restoration with river vegetation. In order to simulate the flood stage and riverbed changes, HEC-RAS, RMA-2, and SED-2D model were applied for the upstream and downstream in study reaches, respectively.