• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.58.2-58.2
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• 2010

This paper deals with the simulation of solid particle coating technology via supersonic nozzle in vacuum environment to devote as an aerosol-deposition device. In order to improve efficiencies of nozzle and coating process, effects of shockwave, nozzle geometry, and substrate location were studied computationally under a fixed chamber pressure of 0.01316 bar which is nearly vacuous. Shockwave is the important factor affect to entire flow because shockwave in the jet flow dissipates the kinetic energy of the flow in the supersonic condition. Results show that various nozzle geometries have significant effect on the supersonic flow and we know that the supersonic nozzle should be optimized to minimize the loss of the flow. Another parameter, the distance between substrate and nozzle tip, shows little effect in this study.

• 한국CDE학회논문집
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• 제1권1호
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• pp.65-75
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• 1996

This paper describes an automatic finite element(FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid and shell structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional solid and shell structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.299-304
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• 2008

Catenary and Pantograph are a power supply devices for electric trains and shall be steadily contacted. Rail catenary must be installed precisely and managed for stable train operations. But external factors such as weathers, nature, etc., or aging affect catenary geometry. Changed catenary height causes high voltage spark or instant electric disconnection. Big spark and disconnection damage pantograph shoe and catenary coating and might interrupt rail operations. To prevent a big scale spark or electric disconnection catenary maintenance shall be required with catenary geometry measurement systems. In this paper, we describe the development of catenary height and stagger measurement system. The catenary height and stagger measurement system uses Acuity company's AR4000 Range Finder for distance measurement and AccuRange Line Scanner for degree measurement. This system reports suspicious overhead line sections with excessive height and stagger variance.

• 한국가정과교육학회지
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• 제6권2호
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• pp.133-145
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• 1994

The purposes of this study are to investigate the relationship between the Piaget’s cognitive developmental theory and the practical course subject in elementary school which have the characteristics of skillful subject and living subject, and to discriminate the suitability of contents of the practical course subject for the childrens’level of cognitive development. This work could serve the theoretical background that the practical course subject presents practical experiences which lead the development of logicomathematical thinking abilities. The results of the content analysis shows that create activities develop the logicomathematical thinking abilities such as projective geometry, topology geometry, area conservation, length & distance conservation, and volume & mass conservation. And the most contents of the practical course subject are suitable for the childrens’level of cognitive development.

• ETRI Journal
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• 제37권3호
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• pp.617-625
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• 2015

In this paper, a steering control system for the path tracking of autonomous vehicles is described. The steering control system consists of a path tracker and primitive driver. The path tracker generates the desired steering angle by using the look-ahead distance, vehicle heading, and a lateral offset. A method for applying an autonomous vehicle to path tracking is an advanced pure pursuit method that can reduce cutting corners, which is a weakness of the pure pursuit method. The steering controller controls the steering actuator to follow the desired steering angle. A servo motor is installed to control the steering handle, and it can transmit the steering force using a belt and pulley. We designed a steering controller that is applied to a proportional integral differential controller. However, because of a dead band, the path tracking performance and stability of autonomous vehicles are reduced. To overcome the dead band, a dead band compensator was developed. As a result of the compensator, the path tracking performance and stability are improved.

• 대한수학회지
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• 제60권1호
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• pp.91-113
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• 2023

The polytope of tristochastic tensors of degree three, the Latin polytope, has two kinds of extreme points. Those that are at a maximum distance from the barycenter of the polytope correspond to Latin squares. The remaining extreme points are said to be short. The aim of the paper is to determine the geometry of these short extreme points, as they relate to the Latin squares. The paper adapts the Latin square notion of an intercalate to yield the new concept of a cross-intercalate between two Latin squares. Cross-intercalates of pairs of orthogonal Latin squares of degree three are used to produce the short extreme points of the degree three Latin polytope. The pairs of orthogonal Latin squares fall into two classes, described as parallel and reversed, each forming an orbit under the isotopy group. In the inverse direction, we show that each short extreme point of the Latin polytope determines four pairs of orthogonal Latin squares, two parallel and two reversed.

• 전기화학회지
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• 제16권3호
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• pp.138-144
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• 2013

Electrochemical reductions of $UO_2$ at various anode-to-cathode distances (1.3, 2.3, 3.2, 3.7 and 5.8 cm) were carried out to investigate the effect of the anode-to-cathode distance on the electrochemical reduction rate. The geometry of the electrolysis cell in this study, apart from the anode-to-cathode distance, was identical for all of the electrolysis runs. Porous $UO_2$ pellets were electrolyzed by controlling a constant cell voltage in molten $Li_2O-LiCl$ at $650^{\circ}C$. A steel basket containing the porous $UO_2$ pellets and a platinum plate were used as the cathode and anode, respectively. The metallic products were characterized by means of a thermogravimetric analyzer, an X-ray diffractometer and a scanning electron microscope. The electrolysis runs conducted during this study revealed that a short anode-to-cathode distance is advantageous to achieve a high current density and accelerate the electrochemical reduction process.

• Computers and Concrete
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• 제33권1호
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• pp.13-25
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• 2024

In this study, contact analysis in a functionally graded (FG) layer loaded with two circular punches is solved using the finite element method (FEM). The problem is consisted of a functionally graded layer that resting on an elastic semi-infinite plane and is loaded with two rigid punches of circular geometry. External loads P and Q are transferred to the layer via two rigid punches. The finite element model of the functionally graded layer is created using the ANSYS package program and a 2-dimensional analysis of the problem is analyzed. The contact lengths, obtained as a result of the analysis are compared with the analytical solution in the literature. In the study, the effects of parameters such as distances between punches, loads, inhomogenity parameter on contact zones, initial separation loads and distances, normal stresses, stresses across depth and contact stresses are investigated. As a result, in this study, it can be said that the magnitude of the stresses occurring in the FG layer is less than the homogeneous layer, therefore the life of FG materials will be longer than the homogeneous layer. When the distance between the punches is 2.25, the initial separation distance is 6.98, and when the distance between the punches is 4, the initial separation distance decreases to 6.10. In addition, when the load increased in the second punch, the initial separation load decreased from 55 to 18. The obtained results are presented in the form of graphs and tables.

• 대한기계학회논문집B
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• 제36권3호
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• pp.285-291
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• 2012

비예혼합 화염의 안정성에 관한 종래의 연구는 연료노즐이나 퀄의 형상에 초점을 많은 맞추어 왔으나 화염안정화에 중요한 연료의 후퇴거리 및 공기노즐의 홀 형상에 대한 연구는 상대적으로 부족하여 이에 관한 연구가 절실한 실정이다. 따라서, 본 연구에서는 메탄 분류 후퇴거리 및 2 차 공기의 홀 형상에 따른 연소특성을 관찰하기 위해 동축 삼중관 형태의 버너를 설계하였다. 1 차 공기는 스월러를 통하여 분류하였고, 2 차 공기는 홀 형상 및 슬릿 형상의 각 노즐로부터 분류되었다. 본 연구에 사용된 실험실 스케일 버너로부터 2 차 공기의 유속은 화염의 형태에 영향을 끼치는 것을 알 수 있었다. 후퇴거리의 경우 공급관외경의 절반에 해당하는 거리로 설정했을 때 화염이 안정적으로 존재하고, 휘도는 더욱 높아짐을 알 수 있었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.530-533
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• 2010

This paper presents numerical analysis and design optimization of various turbine blade cooling techniques with three-dimensional Reynolds-averaged Navier-Stokes(RANS) analysis. The fluid flow and heat transfer have been performed using ANSYS-CFX 11.0. A fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness with the radial basis neural network method. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. The impingement jet cooling has been performed to investigate heat transfer characteristic with geometry variables. Distance between jet nozzle exit and impingement plate, inclination of nozzle and aspect ratio of nozzle hole are considered as geometry variables. The area averaged Nusselt number is evaluated each geometry variables. A rotating rectangular channel with staggered array pin-fins has been investigated to increase heat transfer performance ad to decrease friction loss using KRG modeling. Two non-dimensional variables, the ratio of the eight diameter of the pin-fins and ratio of the spacing between the pin-fins to diameter of the pin-fins selected as design variables. A rotating rectangular channel with staggered dimples on opposite walls are formulated numerically to enhance heat transfer performance. The ratio of the dimple depth and dimple diameter are selected as geometry variables.