• 제목/요약/키워드: Hexagonal plate

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Parametric Studies for the Optimum Design of a Hexagonal Plate Monopole Antenna

  • Park Seong-Bae;Park Joung-Min;Ahn Bierng-Chearl;Kim Kyung-Seok
    • Journal of electromagnetic engineering and science
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    • 제6권1호
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    • pp.53-61
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    • 2006
  • In this paper, we present parametric studies for the optimum design of a hexagonal plate monopole antenna. The dependence of the antenna performance on various geometric parameters is investigated using a commercial electromagnetic software, from which an optimum design of a hexagonal plate monopole antenna is derived. Guidelines for determining initial parameter values are given. The diameter of the circular ground plane is minimized tlo 1/5 wavelength at the lowest operating frequency. The antenna impedance matching is controlled by adjusting the gap between the plate and the ground plane, the plate base width, and the base bevel angle. The antenna proposed in. this paper shows a reflection coefficient less than -10 dB and a $2.0{\sim}6.2$ dBi gain over $3{\sim}20$ GHz frequencies.

ZnO Nanoparticles with Hexagonal Cone, Hexagonal Plate, and Rod Shapes: Synthesis and Characterization

  • Kim, Sun-Young;Lee, In-Su;Yeon, Yun-Seon;Park, Seung-Min;Song, Jae-Kyu
    • Bulletin of the Korean Chemical Society
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    • 제29권10호
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    • pp.1960-1964
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    • 2008
  • The roles of coordinating ligands (TOPO, OA, HDA, and TDPA) for the synthesis of ZnO nanoparticles are investigated. Various shapes (hexagonal cone, hexagonal plate, and rod) and sizes (5-100 nm) of ZnO nanoparticles are prepared in relation to the coordinating ligands. The hexagonal shapes ($\leq$ 100 nm) are synthesized with TOPO and OA, while smaller size nanorods (5 ${\times}$ 30 nm) are with TOPO and TDPA. The relative intensities of two distinctive emission bands centered at 385 and 500 nm, which are related to the exciton and defect states, respectively, depend on the crystal qualities of ZnO nanoparticles affected by the coordinating ligands. The intense UV emissions with the reduced visible emissions are found in the monodisperse nanoparticles such as hexagonal cones and nanorods, suggesting that the monodispersity as well as the crystallinity is closely related to the coordinating ligands. The blue-shift of photoluminescence and absorption edge is observed in the nanorods, because the sizes of the nanorods are in the quantum confinement regime.

Evaluation of Corrosion Resistance Properties of Hexagonal Boron Nitride Based Polymer Composite Coatings for Carbon Steel in a Saline Environment

  • Alabdullah, Fadhel T.;Ali, C.;Mishra, Brajendra
    • Corrosion Science and Technology
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    • 제21권1호
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    • pp.41-52
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    • 2022
  • Herein, we report polyvinyl butyral composites coatings containing various loadings of 72-h bath sonicated hexagonal boron nitride particles (5 ㎛) to enhance barrier properties of coatings. Barrier properties of coatings were determined in 3.5 wt% NaCl after different time periods of immersion via electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization test. Coatings containing sonicated hexagonal boron particles exhibited improved corrosion resistance for longer periods of immersion compared to neat coating. We also discussed effects of hexagonal boron nitride on healing properties of polyvinyl butyral. Coatings containing 1.0 wt% loading of sonicated hexagonal boron nitride showed improved long-term barrier properties than coatings with other compositions. The presence of hexagonal boron nitride also affected the healing properties of polyvinyl butyral coatings besides their barrier properties. Such improved barrier properties of composites coatings were attributed to the high aspect ratio, plate-like shape, and electrically insulated nature of the filler.

산화칼슘의 수화에 의한 수산화칼슘 미분말의 합성과 형상제어 (Synthesis and Shape Control Calcium Hydroxide Fine Powders by Hydration of Calcium Oxide)

  • 민경소;최상흘
    • 한국세라믹학회지
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    • 제28권9호
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    • pp.739-749
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    • 1991
  • Calcium hydroxide fine powders were synthesized by hydration of calcium oxide, and the shapes of powders obtained were examined for each synthethic condition. When distilled water was used as a solvent, irregular and agglomerated submicron powders were obtained, and it was impossible to control of the shapes. In methanol-added solutions, hexagonal plate-like particles were obtained, but addition of ethanol had no effect. However on the occasion that substituted ethylene glycol for ethanol of 5 vol%, hexagonal plate-like powders were obtained. The shapes of powders synthesized in acetic acid and salicylic acid solutions were hexagonal platelike, and were spherical and very fine in citric acid and oxalic acid solutions, respectively. But in some solutions, calcium salts were precipitated by the reaction between calcium and acid added. And the size of powders were very fine using ultrasonic vibration instead of mechanical agitation.

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열교환기 관판의 전지작용부식과 방지에 관한 연구 (A Study on the Galvanic corrosion and its Protection on Heat Exchanger Tube Plate)

  • 임우조;홍성희;윤병두
    • Journal of Advanced Marine Engineering and Technology
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    • 제25권2호
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    • pp.344-350
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    • 2001
  • This paper was studied on the characteristics of galvanic corrosion and its protection on heat exchanger tube plate in the sea water. In this paper, behavior of pitting corrosion of Ni-al bronze connected with Ti tube was measured af flow velocity of 0 m/s and 2.4 m/s. To protect galvanic corrosion, the protection characteristics of Ni-Al bronze connected with Ti tube by Zn-base alloys galvanic anode and hexagonal nylon insert was investigated. Main results obtained asre al follows: 1) The galvanic corrosion of Ni-Al bronze connected with Ti-tube is more active than single Ni-al bronze. 2) As the circuit resistance increase under the cathodic protection employing Zn-base alloys galvanic anode, Ni-al bronze connected with Ti tube is cathodically unpolarized. 3) The corrosion of Ni-Al bronze connected with Ti tube by nylon insert controls approximately 73% than not nylon insert.

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열교환기 관판의 전지작용부식과 방지에 관한 연구 (A Study on the Galvanic corrosion and its Protection on Heat Exchanger Tube Plate)

  • 임우조;홍성희;윤병두
    • Journal of Advanced Marine Engineering and Technology
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    • 제25권2호
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    • pp.345-345
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    • 2001
  • This paper was studied on the characteristics of galvanic corrosion and its protection on heat exchanger tube plate in the sea water. In this paper, behavior of pitting corrosion of Ni-al bronze connected with Ti tube was measured af flow velocity of 0 m/s and 2.4 m/s. To protect galvanic corrosion, the protection characteristics of Ni-Al bronze connected with Ti tube by Zn-base alloys galvanic anode and hexagonal nylon insert was investigated. Main results obtained asre al follows: 1) The galvanic corrosion of Ni-Al bronze connected with Ti-tube is more active than single Ni-al bronze. 2) As the circuit resistance increase under the cathodic protection employing Zn-base alloys galvanic anode, Ni-al bronze connected with Ti tube is cathodically unpolarized. 3) The corrosion of Ni-Al bronze connected with Ti tube by nylon insert controls approximately 73% than not nylon insert.

다목적 화물선의 Crane Post설계에 관한연구 (A study on Design of Crane Post for Multi-Purpose Cargo vessel)

  • 전태병;임채환
    • 한국기계연구소 소보
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    • 통권16호
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    • pp.127-136
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    • 1986
  • Recently deck crane of multi purpose cargo vessel (MPCV) is designed to posi¬tion in side instead of in the center line of the upper deck with a view to reduce the transportation cost and shipbuilding cost by shortening the length of ship. In this paper, the crane post was at first designed according to the crane maker’s specification and parent ship and the structure is analysed with Finite Ele¬ment Method. Through the careful reviews on the result of analysis, the final design of crane post was modified. The crane post is designed as a cylindrical in upper part and hexagonal in lower part instead of cylindrical on the whole as before. The connecting part of crane post is designed with the form of mixture of the cylinderical and hexagonal. Since the center of cylindrical and hexagonal section are not on the same line, it is expected to have the stress concentration. So, in order to attenuate the concentrated stress on the connecting part, the upper and lower parts was stiffened by inserting plate to enlarge the area of welding. The structure of deck part includes the tank side floor which is depend on the lower structure of the crane post that would support the force of the crane post by placing with 1.5 frame interval of the vertical plate.

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Morphological characterization of Symbiodinium minutum and S. psygmophilum belonging to clade B

  • Lee, Sung Yeon;Jeong, Hae Jin;Kang, Nam Seon;Jang, Tae Young;Jang, Se Hyeon;Lim, An Suk
    • ALGAE
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    • 제29권4호
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    • pp.299-310
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    • 2014
  • Dinoflagellates in the genus Symbiodinium are known as zooxanthellae and exist as either symbiotic or free-living forms. Among this genus, two species, Symbiodinium minutum and Symbiodinium psygmophilum, were recently established based on genetic characters. However, some critical morphological characters of these species, such as plate formulae and related diagnoses have not been provided yet. In this study, we analyzed the morphology of S. minutum and S. psygmophilum by scanning and transmission electron microscopy. The S. minutum had the Kofoidian plate formula consisting of a small plate (x), elongated amphiesmal vesicle (EAV), 4', 5a, 8", 7s, two cingulum rows, 18-20c, 6''', and 2'''', while S. psygmophilum had x, EAV, 4', 5a, 8", 7-10s, two cingulum rows, 20-22c, 5-6''', and 1''''. These plate formulae are different from any other reported Symbiodinium species. In addition, both species had a pentagonal 1a plate and a hexagonal 2a plate, while other known Symbiodinium species had a hexagonal 1a plate and a pentagonal 2a plate. Thus, we confirm the species status of S. minutum and S. psygmophilum based on morphological and genetic characters and report the detailed morphological characteristics of these two species.

충돌제트/유출냉각기법에서 분사판의 홀배열이 열전달에 미치는 영향 (The Effects of Impingement Hole Size on Heat Transfer of An Impingement/Effusion Cooling System)

  • 최종현;이동호;조형희
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집D
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    • pp.489-496
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    • 2001
  • Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. The two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied for staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained in the hexagonal array.

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충돌제트/유출냉각기법에서 분사판의 홀배열이 열전달에 미치는 영향 (The Effects of Impingement Hole Arrangements on Heat Transfer of an Impingement/Effusion Cooling System)

  • 최종현;이동호;조형희
    • 대한기계학회논문집B
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    • 제26권1호
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    • pp.101-109
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    • 2002
  • Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. Two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied fur staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained for the hexagonal array.