• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.86-94
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• 2009

Currently, positioning methods for LBS(Location Based Service) are GPS and network-based positioning techniques that use mobile communication networks. In these methods, however, the accuracy of positioning decreases due to the propagation delay caused by the non-line-of-sight(NLOS) effect and the repeater. To address this disadvantage, the CDMA system uses Pattern Matching algorithm. The Pattern Matching algorithm constructs a database of the propagation characteristics of the RF signals measured during the GPS positioning along with the positioned locations, so that the location can be provided by comparing the propagation characteristics of the received signals and the database, upon a user's request. In the area where GPS signals are not received, however, a database cannot be constructed. There are problem that the accuracy of positioning decreases due to the area without a database Because Pattern Matching algorithm depend on database existence. Therefore, this paper proposed a pilot signal strength prediction algorithm to enable construction of databases for areas without databases, so as to improve the performance of the Pattern Matching algorithm. The database was constructed by predicting the pilot signals in the area without a database using the proposed algorithm, and the Pattern Matching algorithm analysed positioning performance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.5
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• pp.488-495
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• 2012

The real-time indoor location technology using radio waves has been studied in a variety of environments. One of them, a ship which consists of steel structure has high reception rate but causes significant ranging error due to the reflection of radio waves. In order to reduce location measurement errors that occurs in such a environment, this paper, based on CSS of IEEE 802.15.4a, presents compensation algorithm for localization using modified bilateration and pyroelectric sensor in a ship. The proposed system reduces the number of fixed nodes by estimating the appropriate reception distance between mobile node and fixed node through the analysis of CSS characteristic in a narrow passage such as ship corridors. Also, in the corner section which the ranging errors are significantly fluctuated due to the reflection and diffraction of radio waves, we recognize the location by tracking the a moving section using modified bilateration technique and pyroelectric sensor. The experimental results show that the location accuracy and efficiency of the proposed algorithm are improved 86.2 % compared to general method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.282-287
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• 2009

본 논문에서는 사각판이 고정단을 경계조건으로 가진 상태에서 충격력을 받았을 때의 굽힘파 전파와 이에 의한 음향 방사가 특정 공간에서 이루는 음장을 유한 차분 시간 영역법을 이용하여 예측하였다. 이와 같은 시도는 향후 구조물에서의 진동과 음장 사이의 관계를 해석하는데 도움이 될 수 있을 것이다. 대상 시뮬레이션 모델은 한 쪽 끝이 철판으로 이루어진 직육면체의 공간이며 예측 결과를 실험값과 비교하였다. 예측 결과는 대체로 파형과 그 특성이 실험값과 잘 일치하였으나, 감쇠 알고리즘을 주파수 대역에 따라 달리 적용하지 못하였고, 사각 평판에서 충격력의 적용 범위가 모호하여, 파형의 크기에 차이가 있었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.1-4
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• 2017

본 논문에서는 2014년도 몽골에 구축된 지진조기경보시스템(EDWS : Earthquake Disaster Warning System)을 효율적으로 운영하기 위한 방안에 대하여 연구하였으며 우리나라 기업에서 구축 운영 중인 몽골 지진조기경보시스템은 VHF망과 위성망을 이용하여 재난 상황 발생 시 즉각적으로 옥외 경보방송과 TV, 라디오를 이용하여 상황을 전파 할 수 있도록 구성되어 있다. 그러나 울란바토르 시내 중심부에는 많은 관공서와 사무실, 극장, 쇼핑몰, 아파트 등이 밀집되어 있어 실내에서 재난경보 방송을 청취하기가 쉽지 않아 재난경보 사각 지대 및 음영지역이 존재하는 상태이다. 본 연구를 통해 정부 유관기관 및 인구밀집지역 건물 내부에 효과적인 옥내경보방송 방법을 제시하여 각종 재난 재해시 경보방송의 활용성을 높이고 몽골 정부기관과 대형 공공 건물에 의무적으로 옥내경보방송 장치 설치를 유도하여 보다 효율적인 경보방송 시스템을 제시하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.715-721
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• 2008

공동주택에서의 음환경 성능은 실내환경의 질과 연관시켜 설계단계부터 충분한 검토가 필요한 성능항목이다. '국토해양부'는 '공통주택 성능등급 표시제도'에서 Air Duct를 통해 상하층간 전파되는 소음을 제어하기 위한 대책을 요구하고 있다. 이에 화장실에 적합한 구조 및 재질로 소음 저감기를 개발하고, 소음기 성능평가 장치를 구성하여 이론과 비교평가하고, 실제 현장에 설치 시 적용효과를 분석하였다.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.466-469
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• 2009

본 논문에서는 T-DMB 시스템에서 위치인식을 위한 워터마킹 기법에 대해 소개하고 성능을 분석하여 보았다. T-DMB 방송용 전송신호에 확산 코드를 이용한 워터마킹 기법을 행하는 기술은 방송용 송신기를 식별하는 기능을 목적으로 사용되고 있다. 송신기 식별을 위해 GPS 기술이 가장 널리 사용되고 있지만, 전파 신호가 미약하고 음영지역이나 실내에서는 수신이 안 되는 단점이 있다. 이러한 관점에서 볼 때 이용요금이 거의 무료이며, 수신 전계강도는 강하면서 다수의 음영지역문제를 해결해 줄 수 있는 새로운 위치인식기술이 필요한 상황이라고 할 수 있고, 지상파 방송신호를 기반으로 위치인식기능과 부가적 정보를 제공해 줄 수 있는 송신기 식별기술은 새로운 솔루션을 제공한다고 할 수 있다.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.121-130
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• 1999

It is necessary to measure pressure, temperature, chemical equilibrium and the shape of flame in order to understand the combustion process in a combustion chamber. In particular, the flame formulation and combustion process of divided combustion chamber are different from those of a single chamber, And the variable diameter of a jet hole can effect not only physical properties like ejection velocity, temperature and time of combustion but also a chemical property like the reaction mechanism. Accordingly temperature is one of the most important factors which influence the combustion mechanism. This paper observed shape of flame by using the schlieren photographs and measured the pressure in a combustion chamber and the reaching time of the flame by ion probe By doing these, we investigation the formulation of the flame and the process of propagation. These measurement methods can be advanced in understanding the combustion process and process and propagation of flame.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.1-8
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• 1997

A prediction model is proposed to describe the path loss in propagation environment of indoor microcell. This model includes the lineal corridor for line--of-sight(LOS) and T-shaped corridor for non-line-of-sight(NLOS). In computation of receiving power the ray tracing technique based on image method is utilized and also reflected waves bounced on the walls and ceilings are considered. To check validity of the computed resuls cross checks between the predicted and measured are being made, which shows a close agreement for LOS case whereas somewhat disagreement for NLOS case. UTD technique is incorporated with propagation path determination algorithm in the treatment of NLOS case.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.10
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• pp.60-67
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• 1997

This paper presents a 3-D finite difference time domain (FDTD) method used for indoor propagation simulations where the electromagnetic wav eis uniformly excited on th eone of the wall in a building and affected by an indoor obstacles. In cases of simulation and measurement, the frequency of 851 MHz is used. The conductivities of walls, floor, ceiling and indoor obstacles are measured and used for simulations. These simulations are carried out using different boundary condition such as mur's absorbing boundary condition (ABC) and perfectly matched layer (PML) technique. The PML technique is found to be well-suited to this analysis because of it's smaller computational domain than mur's ABC. The measured signal strengths are compared to simulated values with good agreement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2169-2180
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• 1992

Solid propellant combustion is investigated for its response to several imposed pressure histories. For this purpose, it is assumed that combustion takes place in a premixed gas evaporated from a uniform melt of solid propellant. One-dimensional unsteady problem is than numerically solved for a pressure coupling, with a steady state as an initial state. The results in response to pressure of finite sinusoidal waves show that unsteady mass fluxes are sometimes quite different from those predicted by the classical quasisteady burning law of Vieile. In addition, abnormal mass flux excursions are captured for a large pressure exponent and a lower melting point.