• 한국정보과학회논문지:데이타베이스
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• 제37권3호
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• pp.137-145
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• 2010

유비쿼터스 컴퓨팅 환경이 일반화되면서 센서의 역할이 중요해지고 있다. 응용에 따라 단순히 주변의 환경 정보를 수집하는 기능보다는 그 자체가 계산 기능을 가지고 다양한 역할을 수행할 수 있게 되었다. 이러한 센서를 활용한 과제에서 중요한 고려사항 중 하나는 에너지의 효율성이다. 본 연구에서는 무선 센서네트워크에서 속성 질의 처리를 수행할 수 있는 알고리즘을 개발하고자 한다. 이를 위해 각 센서들은 모든 자식 노드들의 속성값에 대한 부분 정보를 유지하도록 한다. 하지만 정보의 양이 너무 커지면, 정보 유지 비용이 커지게 된다. 또한 정보의 갱신 비용 역시 무시할 수 없다. 따라서 각 노드가 수집한 속성값 자체를 전달하는 대신 그 값의 범위를 표현한 비트값 즉, AVB(Attribute-Value Bits),을 보내도록 한다. 이는 적은 공간으로 모든 자손노드들의 속성값에 대한 영역 범위를 유지할 수 있어서 질의 처리 과정동안 필요한 메시지의 수를 크게 줄일 수 있다. 이에 대한 실험을 통하여, 제안한 기법의 다양한 속성을 살펴보았다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.727-731
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• 2003

ASTER image has some advantages for classification such as 15 spectral bands and 15m ${\sim}$ 90m spatial resolution. However, in the classification using general remote sensing image, shadow areas are often classified into water area. It is very difficult to divide shadow and water. Because reflectance characteristics of water is similar to characteristics of shadow. Many land cover items are consisted in one pixel which is 15m spatial resolution. Nowadays, very high resolution satellite image (IKONOS, Quick Bird) and Digital Surface Model (DSM) by air borne laser scanner can also be used. In this study, mixed pixel analysis of ASTER image has carried out using IKONOS image and DSM. For mixed pixel analysis, high accurated geometric correction was required. Image matching method was applied for generating GCP datasets. IKONOS image was rectified by affine transform. After that, one pixel in ASTER image should be compared with corresponded 15×15 pixel in IKONOS image. Then, training dataset were generated for mixed pixel analysis using visual interpretation of IKONOS image. Finally, classification will be carried out based on Linear Mixture Model. Shadow extraction might be succeeded by the classification. The extracted shadow area was validated using shadow image which generated from 1m${\sim}$2m spatial resolution DSM. The result showed 17.2% error was occurred in mixed pixel. It might be limitation of ASTER image for shadow extraction because of 8bit quantization data.

• 한국광학회지
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• 제16권4호
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• pp.392-396
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• 2005

본 논문에서는 파장 분할 다중화 방식 광통신에의 적용을 목적으로 하는 다채널 가변형 파장 변환기(Wavelnength Convertor)를 구성하여 이의 성능을 분석하였다. 파장 변환기는 반도체 광증폭기(SOA : Semiconductor Optical Amplifier)의 상호 이득 변조(XGM : Cross Gain Modulation) 특성을 이용한 파장 변환 방식이 이용되었다. 2.5 Gbps 광통신 기반 100 CHz의 채널 간격을 갖는 다채널 신호들에 대한 파장 변환 성능을 측정, 분석하였다. 본 파장 변환기의 상호 이득 변조 성능을 측정한 결과, 소광비(Extinction Ratio)와 비트 오류율(BER : Bit Error Rate) 등의 검증에서 2.5 Gbps 기반의 파장 분할 다중화 방식 광통신에 사용하기에 충분한 성능을 보였으며, 이를 통해 최근 개발된 상호 위상 변조 방식(XPM Cross Phase Modulation)의 다채널 파장 변환기와 비교해 상대적으로 간단한 구조를 가지고 제작 및 변조 효율에 우위를 보이는 파장 변환기로서 대체될 수 있음을 밝힌다.

• 한국동물위생학회지
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• 제23권2호
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• pp.105-112
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• 2000

This survey was conducted to evaluate the microbiological quality of raw beef and pork products from January to December in 1999. A total of 107 beef and 157 hog carcasses were collected from two abattoirs located in Seoul. The result showed that beef carcasses had an average bacterial loading around 139,000 bacteria/$\textrm{cm}^2$ of carcass surface, indicating a little bit higher count than the results reported in USA and Australian meat. However, overall hygienic status was found to be acceptable for all examined carcasses because 84.4% of product rated excellent, good or acceptable comparable to USA of 91.6% and Australia of 88%. The analysis of data on overnight-chilled to weekend-chilled carcasses indicated that the microbiological growth occurred in the chiller during the weekend chill with increases in total viable count from 130,000cfu/$\textrm{cm}^2$ to 400,000cfu/$\textrm{cm}^2$. Qualitative testing for escherichia coli, EC + MUG was used as a most probable number (MPN) method along with the petrifilm method. The average of MPN/$\textrm{cm}^2$ of E coli biotype 1 was 29MPN/$\textrm{cm}^2$ for beef carcasses and 1,100 MPN/$\textrm{cm}^2$ for hog carcasses, respectively. However, 41% of beef and 16.3% of hog carcasses were shown to be less than < 3 MPN/$\textrm{cm}^2$ in E coli biotype 1 examination. Although salmonella enteritis, S typhimurium and E coli O157:H7 were all negative, listeria monocytogenes was recovered from only one hog surface samples of the 89 carcasses tested.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.617-626
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• 2020

The drilling mud is essentially used in oil and gas development. There are several roles of using the drilling mud, such as cleaning the bottomhole, cooling and lubricating the drill bit and string, transporting the cuttings to the surface, keeping and adjusting the wellbore pressure, and preventing the collapse of the wellbore. The fragments from rocks and micro-sized bubbles generated by the high pressure are mixed in the drilling mud. The systems to separate those mixtures and to keep the uniformly maintained quality of drilling mud are required. In this study, the simulation is conducted to verify the performance of the mud tank's agitation capacity. The primary role of the mud tank is the mixing of mud at the surface with controlling the mud condition. The container type is chosen as a mud tank pursuing efficient transport and better management of equipment. The single- and two-phase simulations about the agitation in the mud tank are performed to analyze and identify the inner flow behavior. The convergence of results is obtained for the vertical- and axis-direction velocity vector fields based on the grid-dependency tests. The mixing time analysis depending on the multiphase flow conditions indicates that the utilization of a two-stepped impeller with a smaller size provides less time for mixing. This study's results are expected to be utilized as the preliminary data to develop the mixing and integrating equipment of the onshore drilling mud system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권8호
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• pp.4092-4104
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• 2017

In this paper, an efficient 4K and 8K UHD(Ultra High Definition) transmission scheme is proposed on the convergence networks with broadcasting and LTE(Long Term Evolution) by using CoMP(Coordinated Multi-Point). A video data is compressed and divided into BL(Base Layer), E(Enhanced layer)1, E2 and E3 by scalable HEVC(High Efficiency Video Coding). The divided layers can be combined by the scalable HEVC such as mobile HD, full HD, 4K and 8K UHD(Ultra High Definition). The divided layers are transmitted through the convergence networks with DVB-T2(Digital Video Broadcasting-$2^{nd}$ Generation Terrestrial) broadcasting system and LTE CoMP. This scheme transmits mobile HD and full HD layers through DVB-T2 broadcasting system by using M-PLP(Multiple-physical Layer Pipes), and adaptively transmits 4K or 8K UHD layer through LTE CoMP with MMT(MPEG Media Transport) server. An adaptive transmitting and receiving scheme in the LTE CoMP system provides 4K or 8K UHD layer to a user according to the user status. The proposed scheme is verified by showing the system-level simulation results which is better BER(bit-error-rate) performance than the conventional scheme. The results show that the proposed scheme provides the stable video contents to the user especially at the cell edge.

• 대한의용생체공학회:의공학회지
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• 제17권4호
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• pp.449-458
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• 1996

Most of the conventional electrocardiowaphs foil to detect signals other than P-QRS-T due to the limited SNR and bandwidth. High-resolution electrocardiography(HRECG) provides better SNR and wider bandwidth for the detection of micro-potentials with higher frequency components such as vontricular late potentials(LP). We have developed a HRECG using uncorrected XYZ lead for the detection of LPs. The overall gain of the amplifier is 4000 and the bandwidth is 0.5-300Hz without using 60Hz notch filter. Three 16-bit A/D converters sample X, Y, and Z signals simultaneously with a sampling frequency of 2000Hz. Sampled data are transmitted to a PC via a DMA-controlled, optically-coupled serial communication channel. In order to further reduce the noise, we implemented a signal averaging algorithm that averaged many instances of aligned beats. The beat alignment was carried out through the use of a template matching technique that finds a location maximizing cross-correlation with a given beat tem- plate. Beat alignment error was reduced to $\pm$0.25ms. FIR high-pass filter with cut-off frequency of 40Hz was applied to remove the low frequency components of the averaged X, Y, and Z signals. QRS onset and end point were determined from the vector magnitude of the sigrlaIL and some parameters needed to detect the existence of LP were estimated. The entire system was designed for the easy application of the future research topics including the optimal lead system, filter design, new parameter extraction, etc. In the developed HRECG, without signal averaging, the noise level was less than 5$\mu$V$_rms RTI$. With signal averaging of at least 100 beats, the noise level was reduced to 0.5$\mu$V$_rms RTI$, which is low enough to detect LPs. The developed HRECG will provide a new advanced functionality to interpretive ECG analyzers.

• 한국항해항만학회지
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• 제35권10호
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• pp.811-816
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• 2011

이 논문에서는 저전력 통신 기법 가운데 하나인 PSPM(Phase Shift Pulse position Modulation) 전송 기법이 근거리 수중음향 채널에서 어떠한 성능을 나타낼지 고찰하기 위해 해상실험을 통해 분석하였다. PSPM은 QPSK(Quadrature Phase Shift Keying)와 PPM(Pulse Position Modulation) 기법을 서로 혼합한 형태로 WBAN(Wireless Body Area Network) 시스템에서 저전력 통신을 위해 제안된 기법이다. 이는 기존의 일반적인 전송 방식에 비해 대역효율은 떨어지지만 전력효율은 증가하는 것으로 알려져 있다. 이 논문에서는 실해역에서 취득한 PSPM 데이터를 통해 BER 성능을 분석한다. 실험 결과 QPSK의 경우 총 56,000개의 전송 데이터 비트 중 오차 비트 수가 3,384개로 BER이 약 $6.04{\times}10^{-2}$이고, PSPM의 경우는 19,652개로 BER이 약 $3.5{\times}10^{-1}$를 얻었다. 또한 영상 데이터 전송에 따른 PSNR(Peak signal-to-noise ratio)을 비교한 결과 QPSK의 경우 9.37 dB 였으며, PSPM의 경우 9.11 dB 였다.

• 드라이브 ㆍ 컨트롤
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• 제14권4호
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• pp.1-8
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• 2017

The Down-the-Hole hammer is one of the pneumatic drill equipment used for grinding, drilling, and mining. One the advantages of which is that a reduction work efficiency at deep site are relatively small compared to other drilling methods. Due to the large vibration in the underground area, it is difficult to measure the performance of the hammer, and hammer testing requires substantial production cost and operating expenses so research on the development of the hammer is insufficient. Therefore, this study has developed a dynamic simulation model that apprehends the operating principles of an 8-inch DTH hammer and calculates performance data such as performance impact force, piston speed, and BPM. By using the simulation model, design factors related to strike force and BPM were selected, and the influence of each design factors on performance was analyzed through ANOVA analysis. As a result, be the most important for BPM and the strike force are position of upper port that push the piston in the direction of the bit and in BPM, the size of the empty space between the bits and the piston is the second most important design factor.

• 한국정보통신학회논문지
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• 제11권11호
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• pp.2121-2126
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• 2007

본 논문에서는 다중 수신안테나가 제공하는 공간적인 다이버시티를 이용하여 고속의 데이터 전송률을 달성하기 위한 초광대역 통신시스템의 성능 향상에 대해 연구한다. 다중사용자 간섭 신호들이 존재하는 환경에서 2PPM(Binary Pulse Position Modulation) THMA(Time Hopping Multiple Access) UWB 시스템의 성능을 이론적으로 분석하기 위해서 다중 수신안테나를 통해서 수신되는 공간적인 신호들을 결합한 후의 수신 SINR 표현식을 유도하고 BER 성능을 수치적인 시뮬레이션에 의해 평가된다. 또한 2PPM에 의한 시스템의 성능 결과들을 2PAM(Binary Pulse Amplitude Modulation) THMA UWB 시스템의 이론적인 성능 결과와도 비교한다. 공간적인 다이버시티가 2PPM과 2PAM THMA UWB 시스템의 성능에 미치는 영향을 분석한다. 다중 수신안테나의 수가 증가함에 따라 BER 성능이 향상됨을 보인다. 또한 다중사용자 간섭 신호들이 존재할 때 2PAM THMA UWB 시스템의 성능이 2PPM THMA UWB 시스템의 성능보다 상당히 우수하다는 것을 확인한다.