• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.317-317
• /
• 2015

강이나 하천에 이수 및 치수의 목적으로 소규모 댐이나 보 등의 수리구조물을 설치한다. 수리구조물의 상하류부에는 하천 하상의 극심한 침식인 국부세굴현상을 방지하여 수리구조물의 안정성을 확보하기 위해 하상보호구조물을 설치하는데, 특히 하류부에 설치하는 하상보호구조물에는 크게, 다양한 형식과 크기의 물받이공, 에너지 감세공, 그리고 끝턱구조물 등이 이에 속한다. 지금까지 국내 외 수리구조물 설계지침에서는 하상보호공의 적절한 길이규모를 산정하기 위한 다양한 공식이 개발 및 적용되었지만, 최근 들어 다양한 목적을 위해 복잡해진 수리구조물의 형식과 다양한 운영방식에 따른 수리학적 분석내용이 적절하게 반영되지 않은 경험공식이 대부분 적용되었다. 따라서 예상보다 매우 큰 하상유실이 발생 하여, 하상보호구조물의 설치역할을 제대로 수행하지 못하고 오히려 수리구조물의 안정성에 위협을 주는 주요한 요인이 되었다. 그리고 최근 국내에는 4 대강 유역에 16개 중 대규모의 다목적 보가 설치되었으나 앞서 언급한 바와 같이 미흡한 설계지침을 기반으로 설치된 보 및 하상보호구조물의 기능이 저하되어 극심한 세굴현상이 발생하였다. 또한 이를 보강하기 위한 추가적인 공사 등으로 경제적인 손실을 야기하였다. 반면 외국의 최근 설계지침에는 하상보호구조물 하류부에서 발생하는 평형최대세굴심의 규모를 고려하거나 흐름 및 난류분포를 고려한 수리학적 분석이 반영되어 있지만 국내 설계지침에는 전무한 실정이다. 따라서 본 연구에서는 기존 국내 설계지침의 한계를 조사하고 현재 외국에서 적절하게 제안되어 적용 중인 하상보호구조물 설계지침을 검토하였다. 특히 수리학적 거동특성과 유사분포 특성이 고려된 최대세굴심 산정공식과 설계지침을 검토하였고, 평형상태에 도달한 세굴공 내에서의 수리학적 특성을 고려하여 하상보호구조물의 길이를 적절히 산정할 수 있는 기존 연구결과를 토대로, 하상보호구조물 길이 산정공식을 제안하였다. 본 연구에서 검토된 외국 설계지침과 함께 수리학적 거동특성이 고려된 하상보호구조물의 길이 산정공식은, 향후 수리구조물의 안정성 확보를 위한 하상보호구조물의 설계에 반영될 필요가 있으며, 이를 통해 수리구조물의 효율적이고 경제적인 유지관리를 위해 적절히 활용될 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.1
• /
• pp.15-21
• /
• 2016

In this paper, we considered a design method of a compact quasi-Yagi antenna for portable UHF RFID readers. The antenna consists of a dipole driver and a reflector printed on a dielectric substrate, and it is fed by a microstrip line. In order to reduce the antenna size, the dipole and reflector are bent and the balun between the feeding microstrip line and coplanar strip (CPS) line is integrated within the CPS line. The effects of the geometrical parameters of the proposed antenna on the antenna performance are examined, and the parameters are adjusted to be suitable for the operation in UHF RFID band (902-928 MHz). The size of the fabricated antenna is $70mm{\times}75mm$, and the experiment results reveal a frequency band of 892-942 MHz for a voltage standing wave ratio < 2, a gain > 3.5 dBi, and a front-to-back ratio > 6.6 dB over the frequency band for UHF RFID.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.12
• /
• pp.2199-2205
• /
• 2016

In this paper, a design method for a coplanar waveguide (CPW)-fed 2-element quasi-Yagi antenna (QYA) is studied. A balun between CPW and coplanar strip (CPS) which feeds a planar dipole is implemented by connecting the one end of ground strips in a CPW to a signal strip. The antenna size is reduced by bent strip dipole and reflector, and an integrated balun. The proposed antenna was designed for the operation in a UHF radio frequency identification (RFID) band of 902-928 MHz, and the effects of various parameters such as dipole length, reflector length, distance between dipole and reflector, feed position were examined. The antenna with a size of $90mm{\times}80mm$ was fabricated on an FR4 substrate, and the experiment results reveal a frequency band of 885-942 MHz for a voltage standing wave ratio < 2, a gain > 4.3 dBi, and a front-to-back ratio > 7 dB over the frequency band for the UHF RFID.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.5
• /
• pp.906-912
• /
• 2017

In this paper, we studied a design method for a broadband 3-element quasi-Yagi antenna (QYA) for indoor digital television (DTV) reception. The proposed QYA employs a novel balun between a microstrip (MS) line and a coplanar strip (CPS) line feeding the driver dipole. The proposed balun is constructed by connecting the end of MS line to CPS line through a shorting pin, and the CPS and ground reflector are connected through a circular ring-type conductor. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV. The antenna fabricated on an FR4 substrate with a size of $270mm{\times}150mm$ showed a good performance such as a frequency band of 470-820 MHz for a voltage standing wave ratio < 2, a gain > 4.0 dBi, and a front-to-back ratio > 8.4 dB over the DTV frequency band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.10a
• /
• pp.59-60
• /
• 2017

In this paper, we studied a design method for obtaining broadband property by loading a chip capacitor on a coplanar waveguide(CPW)-fed compact quasi-Yagi antenna(QYA). The proposed antenna is a three-element QYA with dipole, reflector, and director. To reduce the size, the ends of both dipole and reflector are bent, and balun is incorporated in the antenna. To improve impedance matching, the loading position and capacitance value of chip capacitor were determined. From some simulations, the proposed antenna using an FR4 substrate with a size of 90 mm by 90 mm was designed for the operation in a broadband covering the UHF RFID and GPS systems. The antenna showed a good performance with a broadband of 850-1,626 MHz(62.7%) for a VSWR ${\leq}2$, a gain ${\geq}3dBi$, and a frong-to-back ratio ${\geq}4.6dB$.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.6 s.52
• /
• pp.125-132
• /
• 2006

This paper presents the feasibility of a lateral mode piezoelectric oscillator to detect damages in civil infrastructures. The lateral mode oscillator sensor is composed of an electronic feedback oscillator circuit and a piezoelectric lateral mode vibrator to be attached to a structure of interest. Damage to the structure causes a change in the impedance spectrum of the structure, which results in a corresponding change of a resonant frequency of the structure. The oscillator sensors can instantly detect the frequency change in a very simple manner. Feasibility of the piezoelectric oscillator sensor was verified in this work with a sample aluminum plate where artificial cracks of different lengths and number were imposed in sequence. Validity of the measurement was confirmed through comparison of the experimental data with the results of finite element analyses of a plate with cracks.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.2
• /
• pp.44-55
• /
• 1996

Since the use of computer for the ship structural design around mid 1960``s, specially many researches on the midship section optimum design were carried out from 1980. For a rule-based optimum design case, there has been a problem of handling a discrete design variable such as plate thickness for a practical use. To deal with the discrete design variable problems and to develop an effective new method using artificial neural network for the ship structural design applications, Neuro-Optimizer combing Hopfield Neural Network and other Simulated Annealing is proposed as a new optimization method and then applied to the fundamental skeletal structures and Midship section of Tanker. From the numerical results, it is confirmed that Neuro-Optimizer could be used effectively as a new optimization method for the structural design.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.6
• /
• pp.488-494
• /
• 2014

Rocket Plumes can cause serious damage to launch vehicles and adjacent structures. This paper describes the impact of an adjacent structure by a rocket plume. Each parameter related with dynamic behavior of a missile is modeled with probabilistic distributions of variables. Flyout analyses of initial behavior of a vertically launched missile are performed using Monte-Carlo simulation and flow-motion analyses were conducted by using CFD. In this way, when a missile is fired by a ship, the impact of an adjacent structure by a rocket plume was analyzed.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.420-420
• /
• 2011

결정질 태양전지에서 고효율 달성을 위한 LBC(Local Back Contact) 구조의 중요성이 강조되고 있다. LBC 구조에서 후면 passivation 형성을 위한 SiNX layer를 PECVD로 형성 시, 실리콘 bulk 내로 H+ 원자가 침투하여 Boron과 결합하게 되면 Boron이 bulk 내에서 dopant로 작용을 하지 못하게 되어, 후면에서 p-층을 형성하고, 이는 VOC의 저하를 야기 시킨다. 본 연구에서는 LBC 구조에서 후면 passivation 시 bluk 내 B-H결합으로 인한 태양전지 특성 저하 문제를 해결하기 위해, SiNX를 증착하기 전에 얇은 산화막 barrier를 성장시켜 Bulk 내에 H+ 침투를 최소화 하였다. PECVD를 이용한 N2O 플라즈마 처리, HNO3 Wet Chemical Oxidation의 방법을 통해 substrate와 SiNX 사이에 얇은 oxide 층을 형성하였으며, 각각의 조건에 대해 lifetime 측정을 실시하였다. 그 결과 SiON/SiNx를 이용한 막의 lifetime이 $94.5{\mu}s$로 가장 우수하였고, Reference에 비해 25.4% 증가함을 확인할 수 있었다. 그러나 HNO3/SiNx에서는 30.6%, SiON에서는 84.3% 감소함을 확인하였다. Voc 측정 결과 또한 SiON/SiNx를 이용한 막이 670mV로 가장 우수함을 확인할 수 있었다. 본 연구를 통해 LBC구조에서 후면에 얇게 SiON/SiNx막을 형성함으로서 H+이온의 침투를 저지하여 후면 B-H결합을 막아 태양전지 특성 저하를 감소시키는 것을 확인할 수 있었다.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• 2008.11a
• /
• pp.163-169
• /
• 2008

The application of robot technology on construction sites is recognized an effective solution to the problems caused by labor shortage on the construction industry, and relevant studies are being carried out increasingly. Automatic construction system for frames of high-rise building was developed in Japan in 1990's. Practical use o F the system, however, was failed due to inefficiency Now, we are developing economic and practical automatic construction system that is lighter and suitable for building construction In Korea. This study has discussed developing the system of construction factory and climbing control system, which is the core technology of the automatic construction system in Korea.