• Title, Summary, Keyword: Nearly rectangular

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Study on the Friction Characteristics of Circular bead and rectangular bead in Drawbead Forming of Cold Rolled Steels for Automotive Parts (자동차용 냉간압연재의 드로우비드 성형시 비드 형상별 마찰특성에 관한 연구)

  • Kim D. W.;Kim W. T.;Lee D. H.;Moon Y. H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.137-144
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    • 2004
  • The drawbead is one of the most important factors in sheet metal forming for automotive parts. So clarifying the friction characteristics between sheets and drawbead is essential to improve the formability of sheet metal. Therefore in this study, drawbead friction test was performed at circular shape bead and rectangular shape bead. The results show that the tendency of drawing force for rectangular bead is nearly similar with circular bead and the drawing force is nearly proportional to friction coefficient.

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Rectangular Waveguide-NRD Waveguide Transition having the NRD Waveguide Built-in Structure (NRD 도파관에 내장된 구조를 갖는 구형 도파관-NRD 도파관 트랜지션)

  • Yoo, Young-Geun;Choi, Jae-Ha
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.4
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    • pp.391-396
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    • 2008
  • In this paper, we proposed the new rectangular waveguide-NRD waveguide transition in which the transition function about the standard waveguide is built in within the NRD waveguide ifself. The newly proposed rectangular waveguide-NRD waveguide transition was realized use of NRD waveguide input/output side wall thickness and hole width. In the case of the wall thickness, it was nearly identical with the half of the NRD waveguide guide wavelength and the width of an hole was nearly coincide with the length of the long side of the standard waveguide connected with the NRD waveguide. This kind of the principles is applicable to be unrelated with the frequency band. In this paper, it made in 38 GHz band with the rectangular waveguide-NRD waveguide transition and the feasibility was confirmed. In the back-to-back structure, the rectangular waveguide-NRD waveguide transition manufactured in 38 GHz band has the insertion loss less than 0.4 dB and also has the return loss less than 20 dB.

Optimum Air-Gap Flux Distribution with Third Harmonic Rotor Flux Orientation Adjustment for Five-Phase Induction Motor

  • Kang, Min;Yu, Wenjuan;Wang, Zhengyu;Kong, Wubin;Xiao, Ye
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.315-325
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    • 2018
  • This paper investigates optimum air-gap flux distribution with third harmonic rotor flux orientation adjustment for five-phase induction motor. The technique of objective is to generate a nearly rectangular air-gap flux, and it improves iron utilization under variation loading conditions. The proportional relations between third harmonic and fundamental plane currents is usually adopted in the conventional method. However, misalignment between fundamental and third harmonic component occurs with variation loading. The iron of stator teeth is saturated due to this misalignment. This problem is solved by third harmonic rotor flux orientation adjustment simultaneously, and direction and amplitude are changed with mechanical load variation. The proposed method ensures that the air-gap flux density is near rectangular for a maximum value from no load to rated load. It is confirmed that the proposed method guarantees complete both planes decoupling with third harmonic flux orientation adjustment. The effectiveness of the proposed technique is validated experimentally.

Base Station Antenna with Rectangular Radiation Pattern using Strip Feeding Planar Monopole Array (스트립 급전 평면 모노폴 배열을 이용한 직사각형 방사패턴 기지국용 안테나)

  • 신헌철;문상만;우종명
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.6
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    • pp.1018-1024
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    • 2001
  • In this paper, an array antenna is designed far base station of a street micro-cell in urban areas. It has a rectangular radiation pattern. The current distribution of the array is decided by using a modified Woodward-Lawson sampling pattern synthesis method. To confirm the realization of the array antenna with rectangular pattern, 12 array antenna with a planar type monopole fed by stripline is fabricated and measured. In the results of the measured values, H-plane pattern of the antenna nearly yields a rectangular radiation pattern.

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Calculation of Input Impedance of Nonuniformly Ridged Rectangular Waveguide (비균일 Ridge 구형 도파관의 입력 임피던스 계산)

  • 김세윤;박종국;김상욱
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.7 no.2
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    • pp.167-177
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    • 1996
  • The cutoff frequencies of a double ridged rectangular waveguide are calculated by applying the modal analysis to its cross-section. And the characteristic impedance of its $TE_{10}$ mode is evaluated in a frequency range of 6 to 18 GHz. When both ends of a linearly tapered rectangular wa- veguide consists of single and double ridged rectangular cross-sections, the equivalent nonuniform transmission line of its $TE_{10}$ mode is solved numerically. It is shown that the input impedance at its single ridged terminal becomes nearly constant in the wide bandwidth.

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Gap States and Edge Properties of Rectangular Graphene Quantum Dot in Staggered Potential

  • Jeong, Y.H.;Eric Yang, SR.
    • Journal of the Korean Physical Society
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    • v.71 no.5
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    • pp.283-288
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    • 2017
  • We investigate edge properties of a gapful rectangular graphene quantum dot in a staggered potential. In such a system gap states with discrete and closely spaced energy levels exist that are spatially located on the left or right zigzag edge. We find that, although the bulk states outside the energy gap are nearly unaffected, spin degeneracy of each gap state is lifted by the staggered potential. We have computed the occupation numbers of spin-up and -down gap states at various values of the strength of the staggered potential. The electronic and magnetic properties of the zigzag edges depend sensitively on these numbers. We discuss the possibility of applying this system as a single electron spintronic device.

Effects of Specimen Length on Flexural Compressive Strength of Polymer Concrete (부재의 길이가 폴리머 콘크리트의 휨압축 강도에 미치는 영향)

  • 연규석;김남길;주명기;유근우;권윤환
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.99-104
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    • 2002
  • In this paper the influence or specimen length on flexural compressive strength and parameter or equivalent rectangular stress block of polymer concrete was evaluated. For this purpose, a series of C-shaped specimens subjected to eccentric compression were tested using four different length-to-depth ratios(from 1.0, 2.0, 3.0 and 4.0) of specimens with compressive strength of 1,020kgf/cm$^2$. Results indicate that for the region of h/c$\leq$3.0 the reduction in equivalent rectangular stress block depth and flexural compressive strength with increase of length-to-depth ratios was apparent but for the region of h/c$\geq$3.0 they were nearly constant. It means that for the region of h/c$\geq$3.0 effect of specimen length on equivalent rectangular stress block depth and flexural compressive strength was negligible. It was also founded that the effect of specimen length on v, a coefficient of strength, that was from 0.84 to 0.86 regardless of h/c was petty. Finally, predictive equation is, suggested by using modified law of effect of specimen length and results.

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Effect of a Variation of a Main Duct Area on Flow Distribution of Each Branch (주덕트의 단면적 변화가 분지덕트의 유량분배에 미치는 영향)

  • Lee Jai-Ho;Kim Beom-Jun;Cho Dae-Jin;Yoon Suck-Ju
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.4
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    • pp.386-395
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    • 2005
  • With the development of a living standard, the importance of indoor air conditioning system in all kinds of buildings and vehicles has increased. A lot of researches on energy losses in a duct and various kinds of flow pattern in branches or junctions have been carried out over many years, because the primary object of a duct system used in HVAC is to provide equal flow rate in the interior of each room by minimizing pressure drop. In this study, to get equal flow distribution in each branch, a blockage is applied to the rectangular duct system. The flow analysis for flow distribution of a rectangular duct with two branches was performed by CFD. By using SIMPLE algorithm and finite volume method, flow analysis is performed in the case of 3-D, incompressible, turbulent flow. Also, the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent fluid flow. The distribution diagrams of static pressure, velocity vector, turbulent energy and kinetic energy in accordance with variation of Reynolds number and blockages location in a rectangular duct show that flow distribution at duct outlets is improved by a blockage. In this rectangular duct system, mean velocity and flow rate distribution in two branch outlets are nearly constant regardless of variation of Reynolds number, and a flow pattern of the internal duct has a same tendency as well.

A STUDY ON THE SELF-MATCHED LINE PULSE GENERATOR (자기정합 선로형 펄스 발생기에 관한 연구)

  • Paek, Yong-Hyun;Sohn, Jae-Hoon
    • Proceedings of the KIEE Conference
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    • pp.184-187
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    • 1990
  • This paper presents the self-matched line pulse generator and the concerned principles on its operation and characteristics are mentioned. The circuit consists of a charged transmission line and a high speed switch, and it generates a square wave pulse with the very fast rise time. The generated waveform depends on the load resistance. As the load resistance is infinite, a single rectangular wave pulse is generated and its efficiency is nearly unity.

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Measurement of Heat Transfer and Friction Coefficients for Flow of Air in Noncircular Ducts At High Surface Temperatures. (공기유동에 대한 고온상태의 비원형 도과내에서의 열전달 및 압력강하의 측정)

  • 이동렬
    • Journal of the Korean Society of Marine Engineering
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    • v.25 no.3
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    • pp.552-562
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    • 2001
  • Measurement of average of heat transfer and friction coefficients were obtained with air flowing through electrically heated ducts having square, rectangular(aspect ration, 5), and triangular cross section for range of surface temperature from $540^{\circ}$to $1780^{\circ}$ R and Reynolds number from 1000 to 330,000. The results indicates that the effect of heat flux on correlations of the average heat transfer and friction coefficients is similar to that obtained for circular tubes in previous investigation and was nearly eliminated by evaluating the physical properties and density of the air a film temperature halfway between the average surface and fluid bulk temperatures, With the Nusselt and Reynolds numbers on the hydraulic diameter of the ducts, the data for the noncircular ducts could be represented by the same equations obtained in the previous investigation for circular tubes. Correlation of the average difference between the surface corner and midwall temperatures for the square duct was in agreement with predicted values from a previous analysis. However, for the rectangular and triangular ducts, the measured corner temperature was greater by approximately 20 and 35 percent, respectively, than the values predicted by analysis.

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