• Journal of Information Display
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• 제9권4호
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• pp.30-34
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• 2008

Field emitter arrays (FEAs) were developed using carbon nanotubes (CNTs) as electron emission sources. The CNTs were grown using a selective-positioning technique with a resist-protection layer. The light emission properties were studied through the electron emission of the CNTs on patterned islands, which were modulated with island diameter and spacing. The electron emission of CNT arrays with $5{\mu}m$ diameters and $10{\mu}m$ heights increased with increased spacing (from $10{\mu}m$ to $40{\mu}m$). The electron emission current of the $40-{\mu}m$-island-spacing sample showed a current density of 1.33 mA/$cm^2$ at E = 11 V/${\mu}m$, and a turn-on field of 7 V/${\mu}m$ at $1{\mu}A$ emission current. Uniform electron emission current and light emission were achieved with $40{\mu}m$ island spacing and $5{\mu}m$ island diameter.

• 제어로봇시스템학회논문지
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• 제19권4호
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• pp.379-384
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• 2013

We propose a new global positioning method for the indoor mobile robots. The multiple indoor lights fixed in ceiling are used as the landmarks of positioning system. The ceiling images are acquired by the fisheye lens camera mounted on the moving robot. The position and orientation of the lights are extracted by binarization and labeling techniques. Also the boundary lines between ceiling and walls are extracted to identify the order of each light. The robot position is then calculated from the extracted position and known position of the lights. The proposed system can increase the accuracy and reduce the computation time comparing with the other positioning methods using natural landmark. Experimental results are presented to show the performance of the method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.314-317
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• 2005

As demands of VBNS and VDSL increase, the development of kernel parts of optical communication such as PLC(Planar Light Circuit), Coupler, and WDM elements increases. The alignment and the attachment technology are very important in the fabrication of optical elements. The ultra precision stage wasn't yet applied in the optical alignment and the optical element alignment was taken too many times. In this paper, the optical element alignment of ultra precision positioning stage was studied. The alignment algorithm is comprised of field search and peak search algorithms. The procedure of the alignment algorithms applied to the ultra precision positioning stage are developed by LabView programming.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 춘계학술대회
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• pp.550-551
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• 2021

측위 기술은 증강현실, 스마트 팩토리, 자율주행 등에서 중요한 기능을 수행하고 있다. 측위 기술 중에서 비콘을 이용한 측위 방법은 RSSI(Receiver Signal Strength Indicator) 값의 편차로 인하여 도전적인 과제로 여겨져 왔다. 본 연구는 수신기의 RSSI 값을 입력으로 하고 거리를 목표 값으로 하는 신경망을 학습시켜서 이동하는 객체에 대한 위치를 예측하였다. 이를 수행하기 위해 RSSI 대비 거리 실측값을 수집하였다. 수집한 데이터로 합성 데이터를 만들기 위한 신경망을 도입하였다. 이 신경망을 바탕으로 거리 대비 RSSI 값을 예측하였다.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2020년도 제62차 하계학술대회논문집 28권2호
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• pp.139-142
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• 2020

NB-IoT(Narrow Band Internet of Things) is an emerging LPWAN(Low Power Wide Area Network) radio technology. NB-IoT has many advantages like low power, low cost, and high coverage. However low bandwidth and low sampling rates also lead to poor positioning accuracy. This paper proposed a solution to optimize positioning accuracy under the OTDOA(Observed Time Difference of Arrival) approach by utilizing MLR(Multiple Linear Regression) models. Through the MLR model to predict the influence degree of weather(temperature, humidity, light intensity and air pressure) on the arrival time of signal transmission to improve the measurement accuracy. The improvement of measurement accuracy can greatly improve IoT applications based on NB-IoT.

• Journal of Advanced Marine Engineering and Technology
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• 제39권9호
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• pp.959-966
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• 2015

본 논문에서는 Walsh code를 이용하여 중첩된 Light emitting diode(LED) 송신신호들을 수신부에서 각각의 LED 송신신호로 식별하고 조명의 깜박임 현상을 제거할 수 있는 Manchester code 기반 가시광 통신 실내 위치인식 시스템을 제안한다. 제안한 시스템은 고정된 LED 광원의 위치정보들과 수신부에서 그들로부터 수신된 신호들을 람버시안 방사 특성과 삼변 측량법을 이용하여 수신부의 상대적인 위치를 추정할 수 있다. 제안한 논문의 타당성을 검증하기 위하여 16개의 LED 조명을 설치한 $6{\times}6{\times}1.5m^3$의 실내 공간에서 모의실험을 수행하였다. 그 결과, 중첩된 송신신호들은 수신부에서 분리가 가능하고 측위 오차는 최대 0.2977 m, 평균 오차 0.0536 m로 정밀한 위치 인식이 가능하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권4호
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• pp.1200-1215
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• 2023

With the development of IoT and artificial intelligence, location-based services are getting more and more attention. For solving the current problem that indoor positioning error is large and generalization is poor, this paper proposes a Model Stacking Algorithm for Indoor Positioning System using WiFi fingerprinting. Firstly, we adopt a model stacking method based on Bayesian optimization to predict the location of indoor targets to improve indoor localization accuracy and model generalization. Secondly, Taking the predicted position based on model stacking as the observation value of particle filter, collaborative particle filter localization based on model stacking algorithm is realized. The experimental results show that the algorithm can control the position error within 2m, which is superior to KNN, GBDT, Xgboost, LightGBM, RF. The location accuracy of the fusion particle filter algorithm is improved by 31%, and the predicted trajectory is close to the real trajectory. The algorithm can also adapt to the application scenarios with fewer wireless access points.

• 한국통신학회논문지
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• 제41권1호
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• pp.37-41
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• 2016

Localization is one of the key issues of demandable applications, especially smart services. Beside the traditional GPS based localization technique, the localization issue by visible light communications is promising market because of possibility of combining visible light communications with positioning technique for a high accurate, especially indoor localization service. This paper provides the overview and new image sensor scheme for localization issue based on visible light communication. The survey is introduced from core techniques to enhancement issues of localization. We hope these will be the essential references for the impact selection method in implementation and standardization issues.

• Current Optics and Photonics
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• 제5권3호
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• pp.220-228
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• 2021

To improve the measurement accuracy of a solar-radiation observer instrument, aiming at the problem of multiorder-stray-light interference caused by the diffraction of the flat-field concave grating in the spectroscopic system, straylight suppression methods for different forms of optical traps are studied. According to the grating surface-scattering distribution-function model, the bidirectional scattering distribution function (BSDF) of a dust-polluted surface and the flat-field concave grating's transition area of the spectroscopic system is calculated, and a Lyot stop with blade baffle is designed to suppress this kind of stray light. For diffraction multiorder stray light, based on the theory of light-energy transmission, a design for precise positioning of the trench optical trap is proposed. The superiority of the method is verified through simulation and actual measurement. The simulation results show that in a spectroscopic system approximately 160 mm × 140 mm × 80 mm in size, the energy of the stray light is reduced by one order of magnitude by means of the trench optical trap and Lyot stop, and the number of beams is reduced from 5664 to 1040. The actual measurements show that the stray-light-suppression efficiency is about 69.4%, which is effective reduction of the amount of stray light.

• 한국통신학회논문지
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• 제30권10C호
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• pp.992-998
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• 2005

본 논문에서는 고정밀 차량위치 추적 기반의 교통신호등 제어를 위한 저전송율 초광대역 무선통신 시스템에서의 Ultra Fast Acquisition 알고리즘을 연구하였다. 현재 CDMA에서 사용되는 acquisition방식으로는 저전송율 UWB시스템에서 회로가 복잡해지고 빠른 acquisition을 기대할 수 없기 때문에 새로운 Ultra Fast Acquisition방식이 필요하다. 기본적으로 Sequential Estimation방식을 사용하며 trinomial m-시퀀스를 사용하여 유비쿼터스 센서 네트워크용 U시스템에서 long PN code를 사용하는 경우에도 회로의 복잡도를 줄이고 FCC Emission limit을 만족시키면서, $1\~3{\mu}sec$이내의 acquisition을 가능하도록 설계하였다.