• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.30 no.2
• /
• pp.71-77
• /
• 1994

A serious of study is carried out to practical use of the three-slot cambered otter board improved by the authors. As the first step, we designed main plates, slots and accessories, such as holding plate, fan-shaped towing plate, normans, center ring, etc. Standing on this design, we made the simple cambered and three-slot cambered model otter board with accessories in a linear scale 6:1. and carried out model test to examine the efficiency of these boards. The obtained results can be summarized as follows: 1. On the simple cambered board with accessories, the values of the maximum shear coefficient($C _{LX}$ ). drag coefficient(($C _{D}$) and hydrodynamic efficiency($C _{L}$/$C _{D}$ ) are 1.39, 0.56, 2.48 at $22^{\circ}$ of the angle of stall respectively. 2. On the three-slot cambered board with accessories, $C _{LX}$/$C _{D}$ and $C _{I}$/$C _{D}$ are 1.67, 0.92, 1.82 at $32^{\circ}$ of the angle of stall respectively. 3.$C _{LX}$ of board with accessories is smaller 10~12% than that of only the main plate, and the angle of stall is almost same. 4. $C _{LX}$ and the angle of stall of the three-slot cambered board with accessories are greater 20% and $10^{\circ}$ than that of the simple cambered board respectively.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.3
• /
• pp.138-145
• /
• 2006

It is well known that the accurate calculation of the field distribution is essential for the design of electrical machines. The analytical techniques for electromagnetic field can quickly and exactly determine airgap magnetic field distribution in electrical machines. Many analytical techniques have been investigated to predict the magnetic field distribution in PM machines equipped with permanent magnets. Using the analytical technique by transfer relations, D. L. Trumper and K. R. Davey already presented the design and analysis of linear permanent-magnet machines and induction machines, respectively. Using the transfer relations (Melcher's general methodology) to describe electromagnetic phenomena, this paper deals with the analysis on the magnetic field distribution due to PM and winding current, the induced voltage and the static torque characteristics in surface-mounted slotless type permanent magnet machine. The validity of the analysis results is confirmed by finite element (FE) analysis.

• Journal of the Korea Society of Computer and Information
• /
• v.13 no.7
• /
• pp.157-164
• /
• 2008

In this paper we suggest a scheduling algorithm that transmits periodic traffics efficiently in tree-structured wireless sensor networks (WSNs). The related research[l] showed the problems such as increasing the energy consumption and decreasing the data throughput as the depth of tree increases. To solve these problems. we use idle time slots and avoid the redundancy at data transmission. Also we suggest the algorithm that transmits the control packet when it is similar to a previously measured data. And if emergency data is occurred, our proposed algorithm transits that data in EDP(Emergency Data Period) for reducing the wait time. The proposed algorithm shows more data throughput and less energy consumption than that of the related research.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.12 s.91
• /
• pp.1178-1183
• /
• 2004

In this paper, a novel microstrip patch antenna with switchable polarization is proposed. The proposed antenna has a simple structure, consisting of a square radiating patch, a pair of L-type spur-lines, and a microstrip line feed. It can produce either linear polarization or circular polarization by setting the diode on or off From the measured results, low cross polarization levels when operated in the linear polarization, and good axial ratios in the circular state have been observed.

• Journal of Bio-Environment Control
• /
• v.1 no.1
• /
• pp.72-83
• /
• 1992

우리 나라 축사는 생산효율 제고를 위하여 대형화, 밀폐화, 고밀도화, 자동화 경향이 뚜렷하다. 대형의 밀폐된 고밀도 축사는 쾌적한 실내환경을 전제로 하기 때문에 기계적으로 실내환경을 적절히 제어하지 않으면 안된다. 제한된 공간에 먼지, 병원성 미생물, 유해기체, 수분이나 열의 과도한 집적은 생산과 재생산효율에 심각한 영향을 미친다. 그러므로 축사내 생산주체인 가축과 작업인이 쾌적한 실내환경에서 생산활동을 할 수 있도록 열적, 화학적/생물학적 환경을 물리적으로 제어하지 않으면 안된다. 본 연구는 실험축사내 가축이 일정한 열을 발생할 때 실내공기의 유동형태를 예측하기 위해서 수행하였다. 이 연구의 결과를 실내환경제어를 위한 환기시스템 책략 개발의 기초자료로 활용할 수 있다. 실험축사내의 공기유동을 예측하기 위해 Body-Fitted Coordinate(BFC)의 격자배열과 k-$\varepsilon$ 난류모형 및 SIMPLE계열 solution scheme을 사용하였으며, 예측의 유효성 검정은 Boon(1978)의 실험결과를 이용하였다. 예측한 공기유동의 형태와 실험한 공기유동의 형태를 비교한 결과 대체로 만족할만한 결과를 얻었다. 그러나 유입공기의 온도가 1$0^{\circ}C$인 경우의 공기유동은 실험유동형태와 약간의 차이가 있었다. 즉, 실험에서는 수평슬롯으로 유입 된 공기가 바로 아래로 굴절되어 유동하였으나, 예측의 결과는 일정 거리로 수평방향으로 유동하다가 아래로 굴절하였다. 이런 유동의 차이는 k-$\varepsilon$ 난류모형 자체가 경험적으로 부력에 민감하게 반응않는 결함이 원인이 될 수도 있으며, 실험의 부적절한 수행이 원인이 될 수도 있다. 이 유동의 경우 Reynolds 수가 3,000정도의 난류이며, 완전발달유동 (fully-developed flow)이므로 관성력 (inertia force)이 부력 (buoyancy force)보다 커, 일정거리 수평으로 유동하다가 아래로 굴절할 수도 있기 때문이다. 앞으로 이를 규명하기 위한 보다 깊이 있는 연구가 이루어져야 할 것이다.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.6
• /
• pp.1015-1022
• /
• 2023

In this paper, we propose DLP(Dual Linear Polarization) antenna with aperture coupled feeding structure for private network. The proposed antenna has general aperture coupled structure and design two port between top and bottom layer to obtain the enhanced isolation. Also, The size of each substrate(top and bottom layer) is 34.0 mm(W)×34.0 mm(L), which is designed on the FR-4 substrate which thickness (h) is 1.0 mm, and the dielectric constant is 4.4. Also, the size of patch antenna is 12.70 mm(W2)×14.60 mm(L3), and it is located on the top layer. The size of feeding line is 24.0 mm(W2)×1.6 mm(L3), and is located at the bottom layer Also, rectangular slot is located on the ground plane between top layer and bottom layer. From the fabrication and measurement results, bandwidths of 300 MHz (4.52 to 4.82 GHz) for feeding port 1, and 170 MHz (4.65 to 4.82 GHz) for feeding port 2 are obtained on the basis of -10 dB return loss and transmission coefficient S21 is got under the -30 dB. Also, cross polarization isolation between each feeding port obtained

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.9 s.100
• /
• pp.917-925
• /
• 2005

In this paper, the quad-band antenna for mobile handsets is proposed and developed. The operating frequency bands include GSM(880 MHz${\~}$960 MHz), GPS(1,575 MHz$\pm$10 MHz), DCS(1,710 MHz${\~}$l,880MHz), and PCS(1,850 MHz${\~}$l,990 MHz). The proposed antenna consists of a feed line, a shorting post, and a radiating element of the feed loop. The multi-band operation is achieved by using the fundamental and higher resonant modes of the radiating element. Based on analysis of the current distribution on the radiator, the resonant frequency of each mode can be adjusted by adding the different sizes of slots on the radiator. The radiator of the feed loop is designed to be symmetrical so that the energy is symmetrically distributed on the radiator, which results in omni-directional radiation pattern. The ground plane under the radiator is removed in order to improve the bandwidth. The measured impedance bandwidths are $10.1\%$ in GSM band(VSWR<2.5), $26.8\%$ in GPS band, and DCS/US-PCS bands(VSWR<2.5), respectively. The maximum gains on the H-plane of the fabricated antenna are measured about -0.37 dBi${\~}$2.55 dBi for all operating frequency bands.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.40 no.10
• /
• pp.110-118
• /
• 2003

The paper describes a design process of the connection control function that performs overall procedures of optical network control system in the Next Generation - Synchronous Digital Hierarchy (NG-SDH) based transport system. Here, the NG-SDH means a new SDH technology that could perform automatic connection control with a granularity of VC-3 (about 50M) or VC-4 (about 150M) according to the increase and decrease of traffic, which is different from the existing technology that could perform connection control only with a granularity of a physical SDH link (STM-l, STM-4, STM-16, STM-64, STM-256 etc). The NG-SDH based connection control allows an ingress NG-SDH node to control the appropriate connection establishment process according to connection types such as Permanent Connection (PC), Soft Permanent Connection (SPC), Switched Connection (SC) over various SDH and Ethernet line cards.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.7
• /
• pp.617-624
• /
• 2009

In this paper, an electromagnetic analysis methodology using reaction theorem based on reciprocity theorem is presented for the aspheric ogival radome applied to a missile and/or airborne radar. The presented analysis methodology is verified using actual measured data. The type of antenna assumed to develope the methodology is a waveguide slot array antenna, and has the structure of 2 axes monopulse of "X" type. The shape of radome is assumed as Von Karman and the ratio of length to base diameter(L/D) is assumed to be 2:1. The electrical characteristics of the radome are measured using radome measurement system and the results are compared to the values estimated using the presented analysis methodology. It is found that the comparison shows good agreement. It is expected that the presented methodology can be applied for the development of missile and airborne radome.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.37 no.1
• /
• pp.1-8
• /
• 2001

This study deals with the experimental and numerical investigations to design the high performance otter board. Experiment was carried out to determine the most effective slot size of single-slot cambered otter board in the circulation water channel of BAEK KYUNG IND. Co. LTD. Numerical analysis was done by the commercial CFD code, FLUENT, to provide some valuable physical interpretations and finally to design the otter board section by numerical method. The major results are as follows ; 1. In experiment, the maximum lift and drag coefficients of simple cambered type otterboard were 1.41, 0.55, respectively, at the angle of attack $28^\circ$, while those of slot one with slot size 0.02C (C denotes the chord length) were 1.72, 0.42 at the angle of attack $24^\circ$. 2. The hydrodynamic characteristics depending upon slot size shows the greatest at 0.02C of the slot size. 3. Numerical results well visualized the streamlines, pressure fields, and speed vectors of a simple cambered and slot cambered otter board with slot size 0.02C. The slot cambered one with slot size 0.02C was shown that pressure field was distributed moderately on front and back side of otter board. And, the delay and decrease of separation were favorably achieved by flow through slot. 4. Computed result on the pattern of hydrodynamic field and the values of $C_L$ and $C_D$ by the commercial CFD code, FLUENT, show almost the same as those of the experimental result.