• 한국유체기계학회 논문집
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• 제18권1호
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• pp.20-28
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• 2015

The pump-turbine impeller is the key component of pumped storage power plant. Current design methods of pump-turbine impeller are private and protected from public viewing. Generally, the design proceeds in two steps: the initial hydraulic design and optimization design to achieve a balanced performance between pump mode and turbine mode. In this study, the 3D inverse design method is used for the initial hydraulic impeller design. However, due to the special demand of high performance in both pump and reverse mode, the design method is insufficient. This study is carried out by modifying the geometrical parameters of the blade which have great influence and need special consideration in obtaining the high performance on the both modes, such as blade shape type at low pressure side (inlet of pump mode, outlet of turbine mode) and the blade lean at blade high pressure side (outlet of pump mode, inlet of turbine mode). The influence of the geometrical parameters on the performance characteristic is evaluated by CFD analysis which presents the efficiency and internal flow results. After these investigations of the geometrical parameters, the criteria of designing pump-turbine impeller blade low and high sides shape is achieved.

• 물과 미래
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• 제13권2호
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• pp.49-54
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• 1980

Meandering has been attributed to the earth's rotation, to the excessive slope and energy of a river, to changes in stage, etc. The purpose of this study is a geometrical approach of meander shape and to derive the relationship among meander characteristics. In the analysis of sime field examples, in spite of variety of meander shapes, the sine-generated curve was fit actual quite well and better than alternatives against the channel distance. An attempt is made to find considerable relation among meander characteristics. But width and meanderbelt did not show any defined trend considerable scatter of points was observed.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.89-92
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• 2003

A geometrically uniform code in AWGN channel has strong symmetry properties such as a) the distance profiles form codewords On C to all other codewords are all the same, and b) all Voronoi regions of codewords in C have the same shape. Such properties make the word error probability of geometrically uniform codes be transparent to the transmitted codeword. In this paper, we extend the geometrically uniform codes in AWGN channel to the geometrical uniform codes in fading channel with multiple transmit antennas.

• 한국컴퓨터정보학회논문지
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• 제16권11호
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• pp.103-111
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• 2011

본 논문에서는 윤곽선의 순열을 기반으로 하여 형상 시그너쳐를 추출하고, 주도적 특징을 기반으로 형상 정열 및 정규화한 뒤, 기존 절대각도기반 관계성질 대신 기하 관계성질을 이용하는 새로운 형상 기술자, 기하학적 중심거리값(Geometrical Centroid Contour Distance : GCCD)을 제안하였다. 비교 실험을 통하여 제안 방식은 기존 기술자들에 비해 시간 복잡도와 공간 복잡도가 작아 실시간 처리에 유리하면서, 2차원 객체의 크기와 회전 변화에 강건함을 보였다. 또한 MPEG-7 표준 영상을 대상으로 한 정확도 실험을 통하여 다양한 영상군에 대한 비교를 수행하여 제안 방식이 기존 방식들보다 높은 정확도를 보임을 확인하였다. 하지만 제안 방식은 볼록형 객체에 대한 높은 정확도를 보이는 반면 오목형이면서 복잡한 형상을 가지는 객체에 대하여는 형상 변별력이 제한된다는 것도 알게 되었다.

• Fibers and Polymers
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• 제7권4호
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• pp.414-419
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• 2006

The paper presents information concerning metrological and technical characteristics of KTU-Griff-Tester device, the optimization of its parameters and the cases of its application. It was defined that the behaviour of textile material during its extraction through a rounded hole depends upon its structure. Variations of geometrical shape of woven and knitted specimens can be described by mathematical expressions of shortened epicycloids and Cassini ovals. It is shown that waving process of disc shaped specimen can be predicted on the basis of the law of sine curve. The examples of textiles treatment with different types of commercial softeners are presented, herewith showing the suitability (sensitiveness) of the new device to detect the changes of textile hand. Meantime it is shown that the level of materials anisotropy can be decided on the basis of transformations of specimen's geometrical shape.

• 대한조선학회논문집
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• 제40권1호
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• pp.63-68
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• 2003

Systematic geometrical variation method of hull forms, such as "1 -Cp", "Swinging" and "Lackenby" are widely used in the early stage of a new design from those of a similar parent ship, which shows a better performance through the model test and/or sea trials. This method is simple and easy to modify original hull forms without changing the main characteristics. The shape of the prismatic curie can be easily varied by these methods, however, the frame line shape in the body plan can′t be generated easily, when the section shapes are complicated or have discontinuities or the mismatch of the body plan and the stem and stern profiles. To overcome this drawback of the hull form variations, a simple and useful method has been proposed in the present study.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.102-106
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• 1996

In the ball end-milling process of a 3-dimensional mold, it is important to select cutting conditions and tool path considering the geometrical shape of a workpiece to reduce machining time. In this study, experiments were performed to decide allowable feed rate not breaking stability of system for different geometrical shapes. It was found that downcut is more stable than upcutting in machining side wall and downward is preferable to upward in inclined part depending on the angle of the inclination and depth of cut.

• Coupled systems mechanics
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• 제8권6호
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• pp.473-488
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• 2019

The present work is the study of mechanical behavior due to variation of the geometrical parameters in the core of the sandwich honeycomb panel. This study has allowed us to increase or decrease the strains and stresses of the panel, in changing the angle of alveolus, as explained and described below. In taking into consideration the results obtained previously to improve the mechanical properties and increase the adhesion of different parts of the panel, without changing the adhesive, we have conceived two new models, in increasing the contact surfaces in boundary of each part of the panel and giving a conical hexagonal shape in his corp.

• 오토저널
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• 제9권4호
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• pp.35-40
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• 1987

The experimental study, using constant pressure injection system, is carried out to investigate the effect of the geometrical shape changes of the needle valve of the effective flow area, the spray angle and the Sauter's Mean Diameter according to needle valve lift for a pintle-type injection nozzle. The results are as follows: 1) With the increase of the needle valve lift, the effective flow area is increased, the spray angle is at first increased and later decreased, and the Sauter's Mean Diameter is decreased. 2) It is also shown that the spray angle is maximum at the rapidly increased region of the effective flow area.

• 한국수소및신에너지학회논문집
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• 제14권3호
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• pp.207-216
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• 2003

By using the electrochemical method, the relation between the deformation and the geometrical shape, and the effect of cold work on hydrogen absorption-desorption cycling in palladium were investigated, In order to study this problem, four kinds of the Pd specimens used were plates and bars as cold worked and annealed states. As results, it is found that the deformation of thickness direction in the palladium plates increased whereas other lateral directions decreased. But the palladium bars showed the same deformation ratio in all directions because of uniform distribution of the $\beta$ phase. Grains in the plate specimens were greatly deformed after hydrogenation cycling whereas grains in the bar specimens were pulverized. Also, deterioration of the hydrogen absorption rate of the bar specimen was larger than the plate specimen. And the effect of cold work on hydrogen absorption capacity was relatively small.