• Journal of the korean society of oceanography
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• 제32권4호
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• pp.191-201
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• 1997

To test the roles of NO$_3^-$ concentration and light as controlling factors of NO$_3^-$ uptake in the NO$_3^-$-low and -high environments and to assess the significance of night-time nitrogen (N) uptake in estimating the daily N uptake rate, 2 diel studies of N uptake were conducted in NO$_3^-$-low (the eastern part of the Yellow Sea) and NO$_3^-$-high (the marginal ice zone of the northwestern Weddell Sea) environments on June 14 to 15, 1996 and January 15 to 16, 1995, respectively. Ourobservations confirmed that NO$_3\;^-$ uptake by phytoplankton is mainly determined by ambient NO$_3^-$ concentration in NO$_3^-$-low environment and by light in NO$_3^-$-high environment, respectively, Our results suggest the need for diel studies to accurately estimate the daily N uptake rates and thus new and regenerated production because the daily rates calculated without considering the night-time N uptake would be significantly underestimated (up to 41%), particularly in the NO$_3^-$-low environment.

• 한국통신학회논문지
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• 제37권3C호
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• pp.224-232
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• 2012

Priority MAC is an important issue in every communication system when we consider differentiated service applications. In this paper, we propose a mechanism to support priority MAC based on multi-parameters for IEEE 802.15.7 visible light communication (VLC). By using three parameters such as number of backoff times (NB), backoff exponent (BE) and contention window (CW), we provide priority for multi-level differentiated service applications. We consider beacon-enabled VLC personal area network (VPAN) mode with slotted version for random access algorithm in this paper. Based on a discrete-time Markov chain, we analyze the performance of proposed mechanism under non-saturation environments. By building a Markov chain model for multi-parameters, this paper presents the throughput and transmission delay time for VLC system. Numerical results show that we can apply three parameters to control the priority for VLC MAC protocol.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.123.1-123
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• 2001

For Autonomous navigation of the mobile robots, the robots' capability to recognize 3D environment is necessary. In this paper, an on-line 3D map building method for autonomous mobile robots is proposed. To get range data on the environment, we use an sensor system which is composed of a structured light and a CCD camera based on optimal triangulation. The structured laser is projected as a horizontal strip on the scene. The sensor system can rotate $\pm$ $30{\Circ}$ with a goniometer. Scanning the system, we get the laser strip image for the environments and update planes composing the environment by some image processing steps. From the laser strip on the captured image, we find a center point of each column, and make line segments through blobbing these center poings. Then, the planes of the environments are updated. These steps are done on-line in scanning phase. With the proposed method, we can efficiently get a 3D map about the structured environment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.123.5-123
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• 2001

For autonomous navigation of the mobile robots, the robots' capability to recognize 3D environment is necessary. In this paper, an on-line 3D map building method for autonomous mobile robots is proposed. To get range data on the environment, we use a sensor system which is composed of a structured light and a CCD camera based on optimal triangulation. The structured laser is projected as a horizontal strip on the scene. The sensor system can rotate$\pm$30$^{\circ}$ with a goniometer. Scanning the system, we get the laser strip image for the environments and update planes composing the environment by some image processing steps. From the laser strip on the captured image, we find a center point of each column, and make line segments through blobbing these center points. Then, the planes of the environments are updated. These steps are done on-line in scanning phase. With the proposed method, we can efficiently get a 3D map about the structured environment.

• 천문학회보
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• 제43권1호
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• pp.62.3-63
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• 2018

Trends of Type Ia supernova (SN Ia) luminosities with the properties of host galaxies are important to study the underlying physics for an SN progenitor system and explosion mechanism. In the YONSEI SN catalog, we have a sample of ~600 SN and host data in the wider redshift range, and two independent light-curve models, SALT2 and MLCS2k2. From this catalog, here we present that SNe Ia in low-mass, globally and locally star-forming environments are fainter than those in high-mass, globally and locally passive environments, after light-curve shape and color or extinction corrections. Our results are then compared to previous studies, and show consistent results.

• Current Optics and Photonics
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• 제1권4호
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• pp.289-294
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• 2017

A high-performance time-division multiplexing (TDM) -based multiuser (MU) multiple-input multipleoutput (MIMO) system for efficient indoor visible-light communication (VLC) is presented. In this work, a MIMO technique based on RGB light-emitting diodes (LEDs) with selection combining (SC) is utilized for data transmission. That is, the proposed scheme employs RGB LEDs for parallel transmission of user data and transmits MU data in predefined slots of a time frame with a simple and efficient design, to schedule the transmission times for multiple users. Simulation results demonstrate that the proposed scheme offers an approximately 6 dB gain in signal-to-noise ratio (SNR) at a bit error rate (BER) of $3{\times}10^{-5}$, as compared to conventional MU single-input single-output (SISO) systems. Moreover, a data rate of 66.7 Mbps/user at a BER of $10^{-3}$ is achieved for 10 users in indoor VLC environments.

• 한국콘텐츠학회논문지
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• 제9권9호
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• pp.41-50
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• 2009

기존의 미들웨어 시스템은 유선 환경을 중심으로 개발되었기 때문에 미들웨어 및 관련 응용 프로그램들의 규모 또는 운용성이 크다. 따라서 이동 단말의 CPU 및 메모리 등 하드웨어 자원의 취약성과 네트워크의 낮은 대역폭을 가진 무선 이동성 환경에 적용하기 어렵다는 문제가 발생한다. 본 논문은 이러한 문제점을 극복하기 위해서 미들웨어 응용 및 실행 단위가 모바일 환경에 적합하게 최소 및 최적화되고 이동시에도 끊어짐 없는 서비스를 제공하기 위한 경량 모바일 미들웨어 시스템인 "LightMware"시스템을 설계 및 제안한다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2023년도 추계학술발표대회
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• pp.634-636
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• 2023

Surveillance systems play a pivotal role in ensuring the safety and security of various environments, including public spaces, critical infrastructure, and private properties. However, detecting abnormal human behavior in lowlight conditions is a critical yet challenging task due to the inherent limitations of visual data acquisition in such scenarios. This paper introduces a spatiotemporal framework designed to address the unique challenges posed by low-light environments, enhancing the accuracy and efficiency of human abnormality detection in surveillance camera systems. We proposed the pre-processing using lightweight exposure correction, patched frames pose estimation, and optical flow to extract the human behavior flow through t-seconds of frames. After that, we train the estimated-action-flow into autoencoder for abnormal behavior classification to get normal loss as metrics decision for normal/abnormal behavior.

• Journal of the Optical Society of Korea
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• 제19권5호
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• pp.514-520
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• 2015

This paper presents a novel shore-to-sea maritime data transmission system based on time-code diversity, using visible light in maritime environments to overcome the limitations of conventional maritime wireless communications. The proposed system is primarily comprised of existing LED-based lighthouses and maritime transceivers (marine beacons, buoys, etc.), and thus is considered cost-effective in terms of implementation. We first analyze maritime visible-light communications on the basis of the unique properties of a maritime environment, i.e. sea states (wave height, wind speed, etc.), plus atmospheric turbulence, using the Pierson-Moskowitz (PM) and JONSWAP (JS) spectrum models. It is found that the JS model outperforms the PM model, and that the coverage distance depends on the LED power and sea states. To combat maritime fading conditions that significantly degrade performance and coverage distance, we propose a time-code diversity (TCD) scheme in which the delayed versions of the original data are retransmitted using orthogonal Walsh codes. This TCD scheme is found to be superior, in that it offers three orders of magnitude in terms of BER performance, compared to a conventional (non-TCD) transmission scheme. The proposed scheme is robust and efficient in overcoming the effect of impairments present in maritime environments with a BER of approximately $10^{-5}$and a data rate of 100 Kbps at a distance of 1 km.

• 한국전자거래학회지
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• 제2권2호
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• pp.155-169
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• 1997

The CALS integrated database is a key information technology in which CALS implements an information sharing system to enable digital data transfers for technical and non-technical information in distributed and heterogeneous environments. Such heterogeneously distributed CALS information needs to be systematically incorporated so that it can provide a global data view for CALS users. In this paper, we investigated the technologies of CALS integrated database, and proposed a system prototype to implement an integrated data environment (IDE) utilizing distributed object environments CORBA (Common Object Request Broker Architecture).