• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.9
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• pp.521-530
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• 2005

In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry(TFDR), isproposed to detect and estimate a fault in a transmission line. Traditional reflectometry methodologies have been achieved either in the time domain or in the frequency domain only. However, the TFDR can jump over the performance limits of the traditional reflectometry methodologies because the acquired signal is analyzed in time and frequency domain simultaneously. In the TFDR, the new reference signal and the novel TFDR algorithm are proposed for analyzing the acquired signal in the time-frequency domain. Because the reference signal of Gaussian envelop chirp signal is localized in the time and frequency domain simultaneously, it is suitable to the analysis in the time-frequency domain. In the proposed TFDR algorithm, the time-frequency distribution function and the normalized time-frequency cross correlation function are used to detect and estimate a fault in a transmission line. That algorithm is verified for real-world coaxial cables which are typical transmission line with different types of faults by the TFDR system composed of real instruments. The performance of the TFDR methodology is compared with that o( the commercial time domain reflectomeoy(TDR) experiments, so that concludes the TFDR methodology can detect and estimate the fault with smaller error than TDR methodology.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.2
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• pp.62-67
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• 2000

The uniformity of temperature on a wafer is one of the most important parameters to control the RTP (Rapid Thermal Process) with proper input signals. Since it is impossible to achieve the uniformity of temperature without exact estimation of temperature at all points on the wafer, the difficulty of understanding internal dynamics and structural complexities of the RTP is a primary obstacle to accurately measure the distributed temperatures on the wafer. Furthermore, it is also hard to accomplish desirable estimation because only few pyrometers have been commonly available in the general equipments. In the paper, a thermal model based on the chamber geometry of the AST SHS200 RTP system is developed to effectively control the thermal uniformity on the wafer. First of all, the estimation method of one-point measurement is developed, which is properly extended to the case of multi-point measurements. This thermal model is validated through certain simulation and experiments. The work can be usefully contributed to building a run-by-run or a real-time controls of the RTP.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.191-201
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• 2001

In spite of the increasing construction of segmental PSC box girder bridges, the techniques associated with real-time monitoring, construction control and safety assessment during construction have been less developed compared with the construction techniques. Thus, the development of an integrated system including real-time measurement and monitoring, control and safety assessment system during construction is necessary fur more safe and precise construction of the bridges. This study presents a prototype integrated monitoring system for preventing abnormal behavior and accidents under construction stages, that consist of behavior control system for precise construction, reliability-based safety assessment system, and structural analysis. Also, a prototype software system is developed on the basis of the proposed model. It is successfully applied to the Sea-Hae Grand Bridge built by FCM. The integrated system model and software system can be utilized for the safe and precise construction of segmental PSC bridges during construction.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.2 s.21
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• pp.1-7
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• 2006

Recently, the massive concrete structures have been increasingly built in Korea. Many reinforced concrete structures have been reported to suffer from cracking in construction stages due to heat of hydration arising from mass concrete. This cracking may cause some serious durability problems and thus reduces the safety and service life of the structures. In this study, the stresses, strains, and temperatures were measured and the crack widths and crack Patterns were also observed in the footing and abutment structures. And the causes and mechanism in thermal cracking in the footing and abutment structures are thoroughly analysed. The comparisons of test results with analysis have been made. Efficient crack control techniques were developed form the experimental and analytical studies.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1689-1696
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• 2017

In this paper, the voltage measurement-based coordinated Voltage/VAR control (VMCVVC) algorithm for conservation voltage reduction(CVR) is proposed. The proposed algorithm has the purpose of enhancing the CVR effect through coordinated control of the voltage control devices such as the distributed energy resources and the load tap changer(LTC) transformers. It calculates the references of the voltage control devices such that the bus voltages are maintained at as close to the lower operation limit as possible. For this purpose, firstly, the distribution system is divided into LTC transformer control zones through topological search. Secondly, the reactive power references of the reactive power control devices are determined such that the voltage profile of the section is flattened. Finally, the tap references of the LTC transformers are calculated to lower the voltage profile. The effectiveness of the proposed algorithm is demonstrated through case studies using IEEE test network.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.659-664
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• 2012

2010년 내부공간구상이 변화됨에 따라 토지이용과 새만금호 수면적이 변하여 수리현상에 대한 규명이 필요하여 수리모형을 구축하고 상류유량공급, 모형조도, 배수갑문 통과유량, 조석재현에 대한 검보정 실험을 실시하였다. 상류유량공급에 검정 실험결과를 보면 유입유량 제어계측시스템을 통해서 유입되는 유량은 평균적으로 목표유량의 ${\pm}5%$ 범위 내에서 오차를 두고 목표유량의 추세를 따라가고 있다(그림 1). 그리고 유입유량이 $3{\ell}/s$ 미만일 경우와 변곡구간에서 비교적 오차가 크게 난다. 하지만 실험기간동안 누적유량값의 오차는 5% 미만이기 때문에 실험 결과에 미치는 영향은 크지 않다고 판단된다. 조석재현 검정실험을 한 결과는 목표값과 측정값의 큰 차이가 없다. 실험초기에는 목표값과 측정값의 차이가 크게 나타나지만 실험 5분 이후부터는 최대 EL. 0.2m가 차이가 났는데, 조위가 변곡되는 구간에서 나타났다. 실제 실험에서 조위값은 배수갑문의 운영과 관련되어 변곡구간의 조위값보다 상승 하강구간의 조위값(EL. -1.5m~EL. 0.5m)이 실험에 영향을 미치기 때문에 조석발생위어의 조석 재현성은 정밀하다고 판단된다. 모형조도보정 실험은 수치해석 결과와 수리모형실험을 비교하여 실험을 실시하여 해석식과 실험결과값을 근거로 한 조도재료량을 계산하고 이를 배치하여 검보정 실험을 실시하여 조도를 보정하였다. 배수갑문의 통과유량은 현장 관측자료가 부족하여 검 보정이 어려움이 존재한다. 따라서 이에 대한 추후 연구가 필요하다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.444-444
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• 2012

본 연구는 세계적인 기후변화와 물부족 현상에 따라 우리나라에도 향후 물부족에 대비한 농업용수의 친환경적인 적정 관리의 필요성이 절실해지고 있으며 친환경 녹색기술 개발과 농촌수자원의 체계적인 관리가 중요한 국가적인 문제로 대두되고 있다. 농촌은 고령화와 인구감소로 인하여 농업기반 수리시설과 농업용수의 전통적인 인력관리가 어려워지고 있으므로 이를 혁신할 수 있는 친환경, 녹색기술, 정보통신기술(ICT) 융합으로 농촌수자원 관리기술의 개발하고 이에 농업용수를 효율적인 관리를 위하여 농촌지역 수리시설과 농업용수 관리를 위해 정보통신기술과 센서네트워크 계측제어기술 및 모바일기술을 적용하여 농촌수자원 스마트 물관리를 위한 시범지구를 운영 하였다. 시범지구는 섬진강댐 수계의 동진도수로, 김제간선, 정읍간선으로 용수를 공급하는데 이중 수혜면적 17,600 ha, 수로연장 59 km의 김제간선에 시범지구로 선정하였다. 김제간선의 용수공급량은 년평균 163,748천톤의 공급하고 있다. 시범지구 운영은 5개년 중 1차년도(2011년)에는 현장시설 설치 총 87지점에서 15개소를 설치하였으며 시범지구의 영농 및 물관리 특성, 용수공급량 조사 분석하였으며 시범지구의 운영시스템 구축과 Smart 물관리 프로그램(Web, App)개발 하였다. 시범지구 운영은 한국농어촌공사 물관리분야 관련 신기술의 실용화를 위한 인큐베이트 역할을 하며 통합수자원관리시스템과 연계하여 체계적인 현장 물관리 기술의 보급과 공사의 대표적인 물관리 시범지구로 활용 및 사업 홍보 효과에 기여할 것으로 기대되고 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.430-432
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• 2011

An experimental study of the flame response in a turbulent premixed combustor has been conducted in order to investigate mechanisms for combustion instabilities in lean premixed gas turbine combustor. A lab-scale combustor and mixing section system were fabricated to measure the flame transfer function. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function as a function of the modulation frequency and operating conditions.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.4
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• pp.637-644
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• 2019

This paper describes an implementation of a graph-based simultaneous localization and mapping(SLAM) method called the General Graph Optimization. The General Graph Optimization formulates the SLAM problem using nodes and edges. The nodes represent the location and attitude of a robot in time sequence, and the edge between the nodes depict the constraint between the nodes. The constraints are imposed by sensor measurements. The General Graph Optimization solves the problem by optimizing the performance index determined by the constraints. The implementation is verified using the measurement data sets which are open for test of various SLAM methods.

• Journal of the Korean Society of Safety
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• v.34 no.2
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• pp.22-27
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• 2019

Bikers can be subjected to accidents during their bicycling. Helmets are only good, if any, for their head protection. A wearable airbag can protect the human neck area if it is properly designed. This airbag system is composed of an inflater and an airbag. The inflater contains a pressurized gas cylinder and a piercing device. The airbag is an inflatable fabric surrounding the human neck. When a bicycle accident happens, a sensor captures the motion of the biker and a microcomputer sends a signal to open a valve in the inflator to supply the pressurized gas to the airbag. An important issue of this system is that the airbag should be quickly inflated to protect the human neck. This paper deals with the airbag inflation time simulation and some issues to design a wearable airbag system. Also, a prototype was tested to show its feasibility using a human dummy mounted on a running cart.