• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.5
• /
• pp.586-592
• /
• 2014

This study looks at the design of a 100 kW blade geometry for a horizontal marine current turbine using the Blade Element Momentum Theory (BEMT) and by using (CFD), the power output, performance and characteristics of the the fluid flow over the blade is estimated. Three basic airfoils; FFA-W3-301, DU-93-W210 and NACA-63418, are used along the blade span and The distribution of the chord length and twist angles along the blade are obtained from the hydrodynamic optimization procedure. The power coefficient curve shows maximum peak at the rated tip speed ratio of 5.17, and the maximum power reaches about 101.82 kW at the power coefficient of 0.495.

• Journal of Advanced Navigation Technology
• /
• v.24 no.4
• /
• pp.299-304
• /
• 2020

This paper proposes the design of circular sector shaped power divider-combiner with a planar structure. This structure can be constructed in series, and due to the circular sector shape, it is possible to simplify circuit configuration and improve the amplitude and phase balanced characteristics of the output. It has a simple input matching circuit and an RC parallel circuit was inserted between the output ports to improve the reflection coefficient and isolation of the output. Since the designed divider-combiner are structurally designed in a symmetrical shape of a sector, even if the output ports are composed of two or four output ports, they have excellent characteristics with an amplitude balance of ± 0.1 dB and a phase balance of ± 1o between outputs. To prove these characteristics, it was confirmed that the characteristics of the planar power divider-combiner fabricated at an operating frequency of 2 GHz are in good agreement with the simulation.

• Aerospace Engineering and Technology
• /
• v.4 no.2
• /
• pp.117-125
• /
• 2005

Generally, the inertial navigation and guidance unit uses AF(Analog-to-Frequency) converters which convert analog signals into frequency signals to enhance a measurement accuracy of gyroscope and accelerometer outputs. The confidence level of AF converter is guaranteed by a prudential decision of calibration procedure and a performance of periodic calibration test. In this paper, we focus on the synchronous charge balance type AF converter which has a separate positive or negative current input and its calibration method is described. The calibration tests are classified into the scale factor error calibration and the bias calibration. These tests are automatically performed by the calibration program.

• Korean Journal of Optics and Photonics
• /
• v.10 no.1
• /
• pp.53-57
• /
• 1999

We established the laser oscillator using Nd:YAG crystal grown at Ssang Yong company in Korea and investigated the characteristics of oscillation, Q-switching and wave front of output beam. We measured the single pass gain by controlling the threshold input energy with two output couplers of different output reflectances. Moreover, we compared the gain measured by different output couplers with the gain directly measured by the laser amplifier. The peak power of Q-switching, the pulse width, and the single pass gain coefficient at the threshold energy were 1.5 MW, 30ns, and 0.0958 cm-$^1$ respectively and they were compared with those of the commercial Nd:YAG crystal. Our crystal was proved to be as good as the commercial crystal.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.37 no.4
• /
• pp.56-64
• /
• 2000

The design of filters for pattern recognition that have optimal trade-off for the criteria of noise robustness, peak sharpness and Homer efficiency, when input scene noise is spatially disjoint (nonoverlapping) with the target, are presented Three different criteria, ie, signal-to-noise ratio, peak-to-output energy ratio and light efficiency are used to design the filter. Computer simulation is made for the various types of noise and parameters to illustrate filter performance for optical pattern recognition. When we compare the new trade-off filter with the original optimal trade-off filter, the performance of trade-off filter for nonoverlapping background is better than that of trade-off filter for overlapping background.

• The KSFM Journal of Fluid Machinery
• /
• v.15 no.1
• /
• pp.21-26
• /
• 2012

In this investigation, the aerodynamic performance evaluation of a 1MW class blade has been performed with the purpose of the verification of target output and its clear understanding of flow field using CFD commercial code, ANSYS FLUENT. Before making progress of CFD analysis the HERACLES V2.0 software based on blade element momentum theory was applied for confirmation of quick and approximate performance in the preliminary stage. The blade was designed to produce the target output of a 1MW class at a rated wind speed of 12m/s, which consists of five different airfoils such as FFA W-301, DU91-W250, DU93-W-210, NACA 63418 and NACA 63415 from hub to tip. The mechanical power by CFD is approximately 1.195MW, which is converted into the electrical power of 1.075MW if the system loss is considered to be 0.877.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.6
• /
• pp.593-596
• /
• 2015

In this paper, we design a high efficiency class E power amplifier operating at low drain bias voltage for wireless power transfers. A 13.56 MHz power amplifier is designed at drain bias voltage of 12.5 V using Si MOSFET with the breakdown voltage of 40 V. High quality-factor solenoidal inductor is designed and fabricated for use in output matching circuit to improve output power and efficiency. Input matching circuit simply consists of resistor and inductor to reduce the circuit area and improve the stability. The fabricated power amplifier shows the measured output power of 38.6 dBm with the gain of 16.6 dB and power added efficiency of 89.3 % at 13.56 MHz.

• Journal of the Society of Naval Architects of Korea
• /
• v.56 no.6
• /
• pp.497-506
• /
• 2019

Literature survey was conducted on the 2013 Interim Guidelines for determining the minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions. The International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC) documents related with the Guidelines were reviewed. Compatibility of the present Guidelines can be checked by two different levels: (Level 1) minimum power lines assessment and (Level 2) simplified assessment. The IHS (Information Handling Services) sea-web data on the bulk carriers and the tankers, which were built after 2000, were used to examine the Level 1 assessment. KVLCC2 was used to examine the Level 2 assessment. Regarding the Level 2 assessment, effects of the adverse weather conditions, the added resistance due to waves, the wake fractions and the thrust deduction factors were discussed.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.08a
• /
• pp.222-223
• /
• 2000

지금까지 gold-coated 반사체, cusp-shaped 반사체, 복합 포물 반사체(CPC), 난반사 공동체 등 다양한 형태의 반사체가 횡펌핑을 이용한 Nd:YAG 레이저의 개발을 위하여 고안되어졌다. 횡여기되는 Nd:YAG 레이저의 광학적 효율은 반사체의 형태, 다이오드 레이저의 파장, Nd:YAG 결정의 지름, Nd$^3$의 도핑농도에 따라 영향을 받는다.$^{(1)}$ 본 연구에서는 고출력의 횡여기 Nd:YAG 레이저를 개발할 목적으로 광여기 공동으로 사용된 난반사 공동체의 내부지름과 레이저 매질인 Nd:YAG 결정의 흡수계수 등 매개변수를 변화시켜 흡수분포와 출력을 계산하였으며, 이러한 매개변수들이 기울기 효율에 미치는 영향을 수치 해석적으로 연구해 보았다. 광선추적법에서 사용한 매개변수 중에서 다이오드 레이저의 파장은 808 nm이고, 반사율은 90%이며, 여기 다이오드 출력은 1080 W이다. 난반사 공동체$^{(2)}$ 의 반사율은 95.7%이고, 결정의 투과율은 90%이며, 결정의 반지름은 2.5 mm이다. 사용된 여기 구조도는 그림 1과 같다. 여기헤드는 Nd:YAG 결정, 난반사 공동체, 그리고 3개의 360 W급 다이오드 어레이들로 구성되어 있다. (중략)

• Proceedings of the KIEE Conference
• /
• 2008.04a
• /
• pp.97-98
• /
• 2008

본 논문에서는 다중 출력을 가지는 퍼지 관계 기반 퍼지뉴럴네트워크를 설계한다. 퍼지 관계 기반 퍼지뉴럴네트워크는 선체 인력 변수에 따른 입력 공간을 분할함으로서 네트워크를 구성한다. 규칙의 전반부는 앞서 언급한 전체 입력 공간을 분할하여 표현하고, 규칙의 후반부는 다항식으로서 표현되며 오류역전파 알고리즘을 이용하여 연결가중치인 후반부 다항식을 학습한다. 또한, 각 입력에 대만 전반부 멤버쉽함수의 정점과 학습률 및 모멤텀 계수를 유전자 알고리즘을 이용하여 최적 동조한다. 따라서 유전자 알고리즘을 이용하여 퍼지뉴럴네트워크를 최적 설계한다. 마지막으로 제안된 모델은 표준 모델로서 널리 사용되는 수치적인 예를 통하여 평가한다.