• Title/Summary/Keyword: Trapezoid

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10kW DC/DC Converter using Modified Series Loaded Resonant Topology (향상된 직렬 부하 공진형 컨버터 토폴로지를 이용한 10kW DC/DC 컨버터)

  • Ahn, Suk-Ho;Gong, Ji Woong;Jang, Sung-Roc;Ryoo, Hong-Je
    • Proceedings of the KIPE Conference
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    • 2012.07a
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    • pp.215-216
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    • 2012
  • This paper proposes a modified converter topology from the existing loaded resonant converter and describe the development of 10kW(50~500V, 0~ 50A) DC/DC Converter using the proposed topology. The suggested converter, which revised the topology of the converter operating on the CCM(Continuous Conduction Mode) (above resonance), has the advantage of enhancing the efficiency of rated load operation by rapidly increasing the primary side resonant current and by improving the resonance current in a trapezoid shape. The proposed topology is described with analysis of operating mode and designed using PSpice simulation and the points on design to consider when implementing the topology are described. It is verified that the advantages of the proposed topology centered on rated load are effectively highlighted. Experimental results carried out at different condition and its results shows 98.5% efficiency at full load condition.

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Process Design of Multi-Pass Shape Drawing of Wire with Asymmetric Trapezoid Profiles (비대칭 사다리꼴 단면 선재의 다단 인발 공정설계)

  • Ji, S.I.;Lee, K.H.;Hong, L.S.;Jung, J.Y.;Kim, J.S.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.24 no.3
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    • pp.187-193
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    • 2015
  • The objective of the current study is to determine cross-sectional profile of intermediate dies in order to improve the plastic strain homogeneity which directly affects not only the dimensional accuracy but also the mechanical properties of final product by redesigning the intermediate dies using the conventional electric field analysis (EFA) method. Initially, the multi-pass shape wire drawing was designed by using the equivalent potential lines from EFA. The area reduction ratio was calculated from the number of passes in multi-pass shape wire drawing but constrained by the capacity of the drawing machine and the drawing force. In order to compensate for a concentration of strain in a region of the cross section of the wire, the process for multi pass wire drawing from initial round material to an intermediate die was redesigned again using the electric field analysis. Both drawing process designs were simulated by the finite element method in which the strain distribution and standard deviation plastic strain of the cross section of drawn wires were examined.

Types and Factors of Trail Degradtion in Daisetsuzan National Park, Hokkaido, Northern Japan (일본 홋카이도 다이세츠산 국립공원 등산로의 훼손 유형 및 요인)

  • KIM, Taeho
    • Journal of The Geomorphological Association of Korea
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    • v.19 no.2
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    • pp.187-195
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    • 2012
  • Daisetsuzan National Park in Hokkaido, Japan, has an extensive alpine region due to the topographic feature of lava plateau, and exhibits the surface geology largely composed of pyroclastic materials. In addition, the peak season of mountain climbing in the park coincides with a snow-melting period, resulting in severe soil erosion along hiking trails generated by human trampling, snow-melting water and pipkrake. Trail section has been particularly enlarged because the snow-melting water scours a trail surface and the pipkrake erodes sidewalls of a trapezoid-shaped trail. The scoured tread also forces hikers to walk out of a trail, and then frequently brings about path divergence as well as path widening. The soil particles, which are produced by erosional processes in a slope reach, flow downward, and cause the secondary trail degradation by covering a tread in a flat reach and nearby grassland.

Flow resistance characteristics of tree trunk rips (나무줄기 돌출줄눈의 흐름저항 특성)

  • Park, Ho kook;Park, Sang Deog;Shin, Seung Sook
    • Proceedings of the Korea Water Resources Association Conference
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    • 2019.05a
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    • pp.137-137
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    • 2019
  • 돌출줄눈은 산지하천의 만곡부의 빠른 유속을 감소시키기 위하여 활용된다. 본 연구에서는 친환경 디자인의 나무줄기 돌출줄눈(Tree Trunk Rip, TTR)과 사다리꼴 돌출줄눈(Trapezoid Rip, TR)의 흐름저항을 비교 분석하기 위하여 개수로 수리실험을 수행하였다. 실험은 길이 9m, 폭이 0.6m이며 경사가 0.0035로 고정된 개수로의 한쪽 측벽에 돌출줄눈을 설치하여 진행하였다. 사다리 꼴 돌출줄눈의 형상은 밑변 각이 $63^{\circ}$이며 무차원 설치간격 ${\lambda}_{nv}$가 6, 9, 12인 경우이다. 나무줄기 돌출줄눈의 기본 형상은 사다리꼴이고 표면은 나무껍질 무늬이며 ${\lambda}_{nv}$가 약 10이다. 나무줄기 돌출줄눈의 간격은 사다리꼴 돌출줄눈의 최적 설치 간격 9~12배 범위에 해당되고 평균 마찰계수는 사다리꼴 돌출줄눈의 9~12배의 평균 마찰계수 범위에 포함되었다. 사다리꼴 돌출줄눈의 ${\lambda}_{nv}$가 9, 12일 때의 전체 저항에 대한 형상저항의 비는 평균 $69.4{\pm}5.8%$였으며 나무줄기 돌출줄눈은 $70.2{\pm}2.1%$로 사다리꼴 돌출줄눈과 유사하다. 산지하천 흐름저항을 위한 돌출줄눈 설치에 있어 친환경적 디자인을 고려한 나무줄기가 사다리꼴 돌출줄눈보다 활용도가 클 것으로 기대된다.

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Performance Assessment of MDO Optimized 1-Stage Axial Compressor (MDO 최적화 설계기법을 이용해 설계된 1단 축류형 압축기의 성능평가)

  • Kang, Young-Seok;Park, Tae-Choon;Yang, Soo-Seok;Lee, Sae-Il;Lee, Dong-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.397-400
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    • 2011
  • MDO Optimization for a low pressure axial compressor rotor has been carried out to improve aerodynamic performance and structural stability. Global optimized solution was obtained from an artificial neural network model with genetic algorithm. Optimized rotor model has a high blade loading near hub and near zero incidence flow angle near tip region to reduce the incidence loss and flow separation at trailing edge region. Also the rotor shape is converged to a trapezoid shape to reduce the maximum stress occurred at the root of the blade. Numerical simulation results show that rotor has 87.6% rotor efficiency and safety factor over than 3.

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Seismic evaluation of cemented material dams -A case study of Tobetsu Dam in Japan

  • Arefian, Amir;Noorzad, Ali;Ghaemian, Mohsen;Hosseini, Abbas
    • Earthquakes and Structures
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    • v.10 no.3
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    • pp.717-733
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    • 2016
  • Trapezoidal Cemented Sand and Gravel Dam, namely Trapezoid CSG, is a new type of dam. Due to lack of dynamic studies in the field of CSG dam, this research was performed to analyze Trapezoidal CSG dam using dynamic Finite element method with ABAQUS Software. To investigate possible earthquake-induced damages, fragility curves are plotted based on damage index, the length of the cracks created at the dam base and the area of cracked elements in the dam. The seismic analysis indicated that minimum and maximum tensions are generated in the heel and toe of the dam, respectively. According to the fragility curves, with increase in PGA, the possibility of the exceeding the defined limit state is increased. However, the rate of increment is significantly reduced after PGA=0.4 g. Also, the same result is achieved for the second limit state. The "area of cracked elements" is more conservative criterion than the "crack length at the dam base", especially at PGA<0.4 g. As conclusion, CSG dams, despite of being made of poor materials in comparison with concrete dams, show good resistance, and even in some situations, better performance than the weighted concrete dams.

Defect Extraction of Ceramic Image using Fuzzy Clustering Based Enhanced Fuzzy Binarization (퍼지 클러스터링 기반 개선된 Fuzzy Binarization 기법을 이용한 세라믹 영상에서의 결함 추출)

  • Choi, Cheol Ho;Lee, Jin Yu;Park, Heon Sung;Kim, Kwang Baek
    • Proceedings of the Korean Society of Computer Information Conference
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    • 2019.01a
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    • pp.23-26
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    • 2019
  • 본 논문에서는 X-Ray 영상에서 용접한 부분의 기공이나 균열 등의 결함 영역을 추출하는 새로운 방법을 제안한다. 제안된 방법은 세라믹 X-Ray 영상에서 비등방성 확산 필터를 적용하여 영상의 잡음을 제거하고, 수직 및 수평 히스토그램을 각각 적용하여 용접 영역을 추출한 후, 최소 자승법을 적용하여 배경 밝기를 제거하고, 사다리꼴 형태의 Fuzzy Stretching기법을 적용하여 명암 값을 강조하여 결함 영역과 그 외의 영역간의 명암 대비를 강조한다. 그리고 Fuzzy C_Means 알고리즘을 적용하여 결함 영역을 세분화한 후, Fuzzy C_Means을 적용하여 생성된 클러스터들의 중심 명암 값을 이용하여 ${\alpha}_-cut$을 설정한 후에 임계구간을 구하고 영상을 이진화하여 최종적으로 결함 영역을 추출한다. 제안된 방법의 결함 추출 성능을 확인하기 위하여 세라믹 X-Ray 영상을 대상으로 실험한 결과, 기존의 방법보다 결함 영역이 정확히 추출되는 것을 확인할 수 있었다.

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A Study on Evaluating the Applicability of Trapezoidal-shaped Grooves to Airport Runways (사다리꼴 형상 그루빙의 공항 활주로 적용성 평가 연구)

  • Cho, Nam-Hyun;Kim, Dong-Chul;Phi, Seung-Woo;Shin, Joong-Ha
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.29 no.4
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    • pp.78-87
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    • 2021
  • This study is to evaluate the applicability and performance of trapezoidal-shaped grooves on domestic airport runways. For this, the constructability, drainage performance, and friction resistance characteristics of trapezoidal-shaped grooves compared to square-shaped grooves were evaluated through test construction on pavement at Incheon Airport. As a result of the test construction, the trapezoidal-shaped grooves satisfies the required geometry standards and tolerance, and secured a macrotexture that was 25% improved compared to the square-shaped grooves. It was confirmed that trapezoid-shaped grooves secured drainage performance of more than 7-9%, and surface friction performance improved compared to existing grooves when the surface of the pavement was wet as the test speed increased in the dry state. In addition, after trapezoidal-shaped grooves was installed on the RWY 16R/34L of Incheon Airport, the friction coefficient was 0.84, which satisfies the design level of the new runway surface of 0.82 at the test speed.

Visualization analysis of the progressive failure mechanism of tunnel face in transparent clay

  • Lei, Huayang;Zhai, Saibei;Liu, Yingnan;Jia, Rui
    • Geomechanics and Engineering
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    • v.29 no.2
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    • pp.193-205
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    • 2022
  • The face stability of shield tunnelling is the most important control index for safety risk management. Based on the reliability of the transparent clay (TC) model test, a series of TC model tests under different buried depth were conducted to investigate the progressive failure mechanism of tunnel face. The support pressure was divided into the rapid descent stage, the slow descent stage and the basically stable stage with company of the local failure and integral failure in the internal of the soil during the failure process. The relationship between the support pressure and the soil movement characteristics of each failure stage was defined. The failure occurred from the soil in front of the tunnel face and propagated as the slip zone and the loose zone. The fitted formulas were proposed for the calculation of the failure process. The failure mode in clay was specified as the basin shape with an inverted trapezoid shape for shallow buried and appeared as the basin shape with a teardrop-like shape in deep case. The implications of these findings could help in the safety risk management of the underground construction.

A Study of the Style Type and Formative Properties of Short Front and Long Back Skirts in the Early Joseon Dynasty (조선 전기 전단후장형 치마의 스타일 유형과 조형적 특성 연구)

  • Yi Ji Hwang;Sohee Kim
    • Journal of the Korean Society of Clothing and Textiles
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    • v.47 no.2
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    • pp.215-231
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    • 2023
  • This study classifies short front long back skirts from the Joseon Dynasty by style type, identifies their formative characteristics based on their external morphological properties and internal composition, and examines their correlation with Korean thought. A literature review and empirical research were conducted for this study. The style of short front long back skirts is classified as inverted "b"-shaped, lower lip, wavy, trapezoid with a raised center hem, or half-circle. As such, this skirt possesses the formative properties of imbalance, variability of shape, intentional three-dimensionality, and confluence. In other words, with an imbalance resulting from the difference in length between the front and back, these skirts are characterized by variability in shape created by intentional three-dimensionality expressed as intentional three-dimensional beauty, the confluence of planes and dimensions, as well as of materials and colors. These properties are correlated with Korean ways of viewing the world. This study contributes to the development of Korean designs.