• Title/Summary/Keyword: Geometric Characteristics

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Optimum Geometric and Electrical Parameter for minimization Torque Ripple of Switched Reluctance Motor (스위치드 릴럭턴스 전동기의 토오크 리플 저감을 위한 기하학적인 파라미터와 전기적인 파라미터의 최적화)

  • Jung, S.I.;Choi, J.H.;Kim, Y.H.;Kim, S.;Lee, J.;Ju, M.S.;Choi, D.H.
    • Proceedings of the KIEE Conference
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    • 2001.07b
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    • pp.608-610
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    • 2001
  • In this paper, 6/4 Switched Reluctance Motor(SRM) which has simple structure and little switching element is selected basic analysis model. In order to reduce torque ripple causing noise and vibration, we execute optimization of geometric parameters (stator and rotor pole arc) and electrical parameters (turn-on angle and turn-of angle) by means of combining Fletcher-Reeves's Conjugate Directions and Finite Element Method (FEM) considering driving circuits. When considering the switching condition according to inductance profile, torque characteristics is influenced by geometric and electrical parameters importantly. The pole arc and switching angle of the optimum can also obtain the low torque ripple without high currents.

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Effects of geometric shape of LWSCR (lazy-wave steel catenary riser) on its global performance and structural behavior

  • Kim, Seungjun;Kim, Moo-Hyun
    • Ocean Systems Engineering
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    • v.8 no.3
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    • pp.247-279
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    • 2018
  • This study aims to investigate the behavioral characteristics of the LWSCR (lazy-wave steel catenary riser) for a turret-moored FPSO (Floating Production Storage Offloading) by using fully-coupled hull-mooring-riser dynamic simulation program in time domain. In particular, the effects of initial geometric profile on the global performance and structural behavior are investigated in depth to have an insight for optimal design. In this regard, a systematic parametric study with varying the initial curvature of sag and arch bend and initial position of touch down point (TDP) is conducted for 100-yr wind-wave-current (WWC) hurricane condition. The FPSO motions, riser dynamics, constituent structural stress results, accumulated fatigue damage of the LWSCR are presented and analyzed to draw a general trend of the relationship between the LWSCR geometric parameters and the resulting dynamic/structural performance. According to this study, the initial curvature of the sag and arch bend plays an important role in absorbing transferred platform motions, while the position of TDP mainly affects the change of static-stress level.

Effect of Wavy Flow of Vertical Falling Film on the Absorption Performance (흡수성능에 미치는 수직 액막 파동의 영향에 관한 연구)

  • 김정국;조금남
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.2
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    • pp.194-201
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    • 2004
  • In the present study, the improvement of absorption characteristics on combined heat and mass transfer process in a falling film of a vertical absorber by change of geometric parameters were studied experimentally and analytically. The energy and diffusion equations are solved simultaneously to give the temperature and concentration variations at the liquid solution-refrigerant vapor interface and at the wall. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by refrigerant vapor in the absorber. Effects of film Reynolds number, geometric parameters by insert device (spring) and flow pattern on heat and mass transfer performances have been also investigated. Especially, effects of the flow pattern by geometric parameters have been considered to observe the total heat and mass transfer rates through falling film along the absorber. As a numerical and experimental result, maximum absorption rate was shown at the wave-flow by insert device (spring). The error ranges between experiment and analysis were from 5.8 to 12% at Re$_{f}$ > 100.0.

Study on Characteristics by Aerodynamic Diameter of Airborne Suspended Particulate Matters (대기 부유분진의 입경별 특성에 관한 연구)

  • 김성천;강달선;차영희
    • Journal of Environmental Health Sciences
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    • v.26 no.2
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    • pp.108-115
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    • 2000
  • The mass fraction of PM10 had a bimodal distribution in the middle of between 2.1 ${\mu}{\textrm}{m}$, and the average mass fraction of particles less than 2.1~3.1 ${\mu}{\textrm}{m}$ was 54.1% for Pb and 890.8 ng/㎥ for Fe, respectively. For the concentration of PM10 and metallic elements by seasonal variation, PM10 showed bimodal distribution, while metallic elements showed different distributions by their sources. The ratios of fine particles to total mass were 0.45 for PM10, 0.41 for Cr, and 0.20 for Fe, 0.57 for Zn, 0.68 for Cd and 0.63 for Pb, respectively. That facts indicated that PM10, Zn, Cd, Cr and Pb were from anthropogenic sources, and Fe was from natural source. The geometric means and geometric standard deviations by seasonal variations were 3.6 ${\mu}{\textrm}{m}$ , 2.31 ${\mu}{\textrm}{m}$ in winter, 3.0 ${\mu}{\textrm}{m}$ , 2.49 ${\mu}{\textrm}{m}$ in spring, 2.7 ${\mu}{\textrm}{m}$ , 2.03 ${\mu}{\textrm}{m}$ in summer respectively. And, total efficiency of cascade impactor by seasonal variations were 49.6% in winter, 45.9% in spring and 44.5% in summer.

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Characteristics of Eddy Current Signals of Axial Notches in Steam Generator U-bend Tubes using Rotating Pancake Coils (회전코일 와전류신호를 이용한 증기발생기 곡관형 튜브의 축방향노치 신호의 특성)

  • Kim, Chang-Soo;Moon, Yong-Sig
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.8 no.3
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    • pp.7-12
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    • 2012
  • Steam generator tubes are critical boundary of the primary and secondary side in nuclear power plants. Eddy current testing is commonly used as the method of non-destructive testing for the safety and integrity of steam generator tubes in the nuclear power plants. Changes in the geometric shape act as a stress concentration factor likely to cause a defect during the steam generator operation. The mixed-signals with the geometric shape are distorted and attributes that are difficult to detect signals. An example is bending stress due to compression process at a U-bend occurring in the intrados region which has a small radius of curvature. The resulting change in the geometric shape may lead to a dent like occurrences. The dent can cause stress concentration and generates stress corrosion cracks. In this study, the steam generator tubes of nuclear power plant were selected to study for analysis of mixed-signal containing dent and stress corrosion cracks.

A Study on the characteristics of baroque in Architecture of Paolo Portogheshi (파올로 포르토게시 건축에 나타난 바로크적 특성 연구)

  • Han, Myoung-Sik
    • Korean Institute of Interior Design Journal
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    • v.18 no.6
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    • pp.52-59
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    • 2009
  • In the study will look into how Baroque concepts are expressed in architectural space by analyzing the concepts of Baroque formative vocabularies applied in his architecture through a Spanish architect Paolo Portoghesi. Baroque is regarded as the philosophical thought that means enlargement toward diversity of a firm and fixed trend beyond the concept of a certain epochal form of 16th and 17th century architecture. In addition, it is from the free attitude and the intelligent and formal stereotype, and signifies common conditions more than one style in architecture history. Paolo Portoghesi proposes to express gestalt approach by Baroque precedent in his architecture through plasticity and geometric collision technique. Here, the expression of plasticity means the effect that gives formative rhythm to Baroque curved structures. That is the method to expand the formative possibility by changing various materials such as bricks, concrete, and timbers. Second, the geometric collision technique is the technique to constitute the flat form of overall space through the juxtaposition technique, Baroque symmetrical and homogeneous geometric manipulation technique. Accordingly, this study will overcome Inlimitation of formative monotony and expression of abstraction that modernism architecture has, and examine formative waste and conflicts which may be derived from impractical architectural languages of the concept of excessive disorder or the minimum form. This discussion is considered as the first step to tune balance between productivity and formativeness in modern architecture.

Seismic performance assessment of reinforced concrete bridge piers supported by laminated rubber bearings

  • Kim, T.H.;Kim, Y.J.;Shin, H.M.
    • Structural Engineering and Mechanics
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    • v.29 no.3
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    • pp.259-278
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    • 2008
  • This paper presents a nonlinear finite element procedure accounting for the effects of geometric as well as material nonlinearities for reinforced concrete bridge piers supported by laminated rubber bearings. Reinforced concrete bridge piers supported by laminated rubber bearings and carrying a cyclic load were analyzed by using a special purpose, nonlinear finite element program, RCAHEST. For reinforced concrete, the proposed robust nonlinear material model captures the salient response characteristics of the bridge piers under cyclic loading conditions and addresses with the influence of geometric nonlinearity on post-peak response of the bridge piers by transformations between local and global systems. Seismic isolator element to predict the behaviors of laminated rubber bearings is also developed. The seismic performance of reinforced concrete bridge piers supported by laminated rubber bearings is assessed analytically. The results show good correlation between the experimental findings and numerical predictions, and demonstrate the reliability and robustness of the proposed analytical model. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of reinforced concrete bridge piers supported by laminated rubber bearings.

Surface Quality of Products according to the Material and Coating Condition of the Forming Tool in Incremental Sheet Forming (점진성형공구 코팅처리 및 소재에 따른 성형품 표면품질 분석)

  • H. W. Youn;N. Park
    • Transactions of Materials Processing
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    • v.32 no.6
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    • pp.360-366
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    • 2023
  • This study is concerned with the surface quality of products according to the material and coating condition of the forming tool in incremental sheet forming. Three forming tools, SKD11 with and without diamond-like-coating (DLC) and polymer tool tip, were used to form conical and pyramidal geometries to take into account the influence of friction between the forming tool and the sheet on the surface quality including geometric accuracy of deformed samples. Each test was performed using SUS304 with a thickness of 0.4 mm according to different incremental depths per lap of 0.5 mm, 1.0 mm, and 1.5 mm for the contour tool path, considering the increase in normal force which is associated with the frictional behavior during local deformation. The surface quality was then investigated through surface roughness measured with KEYENCE VR-6000 and relative strain distribution including deformed shape analyzed with ARGUS which is a non-contact optical strain measurement system. Differences between 3D CAD surfaces and captured geometry from experiments were evaluated to compare the effect of friction on geometric accuracy. From comparisons of experimental results, it was revealed that the polymer-based tool tip can improve surface quality and geometric accuracy by reducing the undesired material flow due to local friction in the increment sheet forming process.

Characteristics of Geometric Conditions Affecting Freeway Traffic Safety at Nighttime, Sunrise, and Sunset (야간 및 일출몰 시간대 교통안전에 영향을 미치는 고속도로 기하구조 특성분석)

  • Hong, Sung-Min;Kim, Joon-Ki;Oh, Cheol
    • Journal of Korean Society of Transportation
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    • v.30 no.4
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    • pp.95-106
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    • 2012
  • Driver's capability of identifying the change in freeway alignments and environments is one of important factors associated with traffic safety on freeways. In particular, driver's visibility and recognition capability are highly dependent on the altitude of the sun by sunset, sunrise, and nighttime. The purpose of this study is to identify the characteristics of geometric conditions affecting crash occurrences at sunset, sunrise, and nighttime. Poisson and negative binomial regressions were adopted to predict freeway crash frequency in this study. Freeway crash data during 2007~2010 were used for developing the crash frequency models. A set of variables representing the characteristics of geometric conditions were identified as significant ones affecting crash occurrences. The results of this study would be useful in deriving effective countermeasures for preventing traffic crashes that mainly occur at sunset, sunrise, and nighttime on freeways.

A Study on the Nordic Sweaters (노르딕 스웨터에 관한 연구)

  • 이선명
    • Journal of the Korea Fashion and Costume Design Association
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    • v.4 no.2
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    • pp.139-161
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    • 2002
  • This study investigates the characteristics of Nordic sweaters works from a historical perspective. Specifically, this study deals with the following research topics: 1) development of Nordic sweaters, 2) the characteristics of Nordic sweaters industry according to the change of times, 3) the comparison of local knitting patterns, 4) the symbolic meaning of the designs in the Nordic sweaters and patterns. The results of the study are summarized as follows. 1. Knitted work developed mostly in Northern Europe, a cold area, and the barren, mountainous coastal areas where people frequently used woolen materials for clothes. It was also developed in Scandinavian regions which lead the fashion in modern days. Scandinavian knitting techniques have been diffused into the east coast of England and Northern Europe by Vikings. 2. Scandinavian countries are distinguished from other countries by their conservative but creative cultural tradition. Their knitting patterns are characterized by small geometric figures such as dots, triangles, squares, rhombuses, and crosses used often with stars and roses. Scandinavian knitting is also salient for its vertical stripes and simple motifs repeating at short intervals. 1) Norway ; Simple and geometric Norwegian patterns are classified into three groups of motifs: (a) the motifs of cross, diamond, X, and swastika (equation omitted). (b) the motifs of human figures, animals and birds, (c) floral motifs (especially eight-petal roses). Their use of color is also simple, and is limited to more than two colors. (2) Sweden ; Swedish patterns are colorful and geometric. They are characterized by features such as brocade, complex embroidery, and contrast of red and black colors. They also show Guernsey patterns. Initials and production years were knitted in sweaters which have different patterns in their trunks and sleeves. 3) Denmark ; The Danish pattern is the purl stitch knitted against the stockinette stitch. The technique is used to copy woven damask motifs. The patterns are seen most clearly when they are knit with smooth yarn. The Faeroe sweaters are the representative work of Danish knitting. Faeroe knitting, incorporates stranded pattern and is knit in the round, either with circular needles. 4) Finland ; Finnish patterns are similar to Norwegian patterns. Finnish knitted work show very colorful, variety and free-flowing geometric patterns. 5) Iceland ; Icelandic knitting shows original ribbon pattern. Lope sweater is the representative work. 3. The traditional knitting patterns not only carried symbolic meanings but also served as means of communication. First of all, patterns had incantatory meanings. Patterns were symbolic of one's social standing, too. The colors, motifs and their arrangements were very important features symbolizing one's social position or family line. People often communicated by certain pieces of knitted work or patterns. In short, the knitted work in the Nordic sweaters served the function of admiring the beauty of nature and symbolizing various meanings. The unique designs and colors of the knitted work reflected the characteristics of the culture those works belonged to. This study also turns our attention to the issue of how the traditional colors and designs of the knitted work can contribute to the development of modern designs, and by doing so, if makes us realize the importance of knitted works in modern society.

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