• 한국컴퓨터정보학회논문지
• /
• 제25권4호
• /
• pp.97-103
• /
• 2020

무선 센서 네트워크는 인간의 개입 없이 다양한 환경에서 센싱 데이터를 수집하고 분석한다. 센서 네트워크는 초기에 설치된 라우팅 프로토콜들에 따라 네트워크 수명이 변경된다. 게다가, 네트워크가 운영 중에 라우팅 경로를 변경하기 위해 센서들은 많은 에너지를 소모해야 한다. 센서 네트워크를 실제 필드에 구축하기 전에 시뮬레이션을 통해 성능 측정하는 것은 중요하다. 본 논문은 DEVS 커널 모델들을 사용하여 저전력 적응형 클러스터링 계층 프로토콜을 위한 WSN 모델을 제안한다. 제안 모델은 커널 모델인 브로드캐스트 모델과 컨트롤드 모델로 구현된다. 실험 결과, 컨트롤드 기반의 WSN 모델은 데이터 전송 부분에서는 효율적이지만, 컨트롤드 모델에서 특정 모델을 선택하기 위해 CPU 사용량이 높은 것을 확인했다.

• 한국항해항만학회지
• /
• 제38권6호
• /
• pp.577-583
• /
• 2014

A ship-to-ship (STS) lightering operation takes place in order to transfer cargo (e.g. crude oil or petroleum products) between an ocean-going ship and a service ship alongside it. Instrumental measurements to accurately determine the relative speeds and distances during the approach between the vessels would benefit the operational safety and efficiency. A velocity information GPS (VI-GPS) system, which uses the instantaneous velocity measures from carrier-phase Doppler measurement, has been applied in a field observation onboard a service ship (Aframax tanker) approaching a ship-to-be-lightered (VLCC) in open waters. This article proposes to apply VI-GPS as the input sensor to a guidance and decision-support system aiming to provide accurate velocity information to the officer in charge of an STS operation. A method for precise velocity measurement using VI-GPS was described and the measurement results were compared each other with the results of Voyage Data Recorder (VDR) and VI-GPS that showed the concept of a guidance and decision-support system applying VI-GPS with the field test results during STS operations. Also, it turned out that VI-GPS has sufficient accuracy to serve as an input sensor from the field test results.

• Asian Journal of Atmospheric Environment
• /
• 제8권3호
• /
• pp.162-174
• /
• 2014

An abnormal decrease in ozonesonde sensor signal occurred during air-pollution study campaigns in November 2011 and March 2012 in Mexico City Metropolitan Area (MCMA). Sharp drops in sensor signal around 5 km above sea level and above were observed in November 2011, and a reduction of signal over a broad range of altitude was observed in the convective boundary layer in March 2012. Circumstantial evidence indicated that $SO_2$ gas interfered with the electrochemical concentration cell (ECC) ozone sensors in the ozonesonde and that this interference was the cause of the reduced sensor signal output. The sharp drops in November 2011 were attributed to the $SO_2$ plume from Popocat$\acute{e}$petl volcano southeast of MCMA. Experiments on the response of the ECC sensor to representative atmospheric trace gases showed that only $SO_2$ could cause the observed abrupt drops in sensor signal. The vertical profile of the plume reproduced by a Lagrangian particle diffusion simulation supported this finding. A near-ground reduction in the sensor signal in March 2012 was attributed to an $SO_2$ plume from the Tula industrial complex north-west of MCMA. Before and at the time of ozonesonde launch, intermittent high $SO_2$ concentrations were recorded at ground-level monitoring stations north of MCMA. The difference between the $O_3$ concentration measured by the ozonesonde and that recorded by a UV-based $O_3$ monitor was consistent with the $SO_2$ concentration recorded by a UV-based monitor on the ground. The vertical profiles of the plumes estimated by Lagrangian particle diffusion simulation agreed fairly well with the observed profile. Statistical analysis of the wind field in MCMA revealed that the effect Popocat$\acute{e}$petl was most likely to have occurred from June to October, whereas the effect of the industries north of MCMA, including the Tula complex, was predicted to occur throughout the year.

• 대한전자공학회논문지SP
• /
• 제48권3호
• /
• pp.62-70
• /
• 2011

CFA(Color Filter Array)를 사용하는 이미지 센서에서는 컬러정보를 획득하기 위해 디모자이킹 과정을 거치게 된다. 이상적인 컬러특성을 갖는 이미지센서에 적용되는 디모자이킹 방식은 실제로 이미지센서에 바로 적용할 경우 올바른 동작을 장담할 수 없는데, 이는 센서마다 그 특성이 다르기 때문이다. 따라서 디모자이킹 알고리즘을 적용할 때에는 각 센서의 특성에 따라서 다르게 적용이 되어야만 한다. 본 논문에서는 Honeycomb CFA방식을 사용하는 CCD 이미지 센서에서 사용되는 디모자이킹 알고리즘을 제안하고, 실제 이미지 센서(CBN385B)의 컬러특성을 고려하여 필터의 계수를 보정함으로써 개선된 성능을 갖는 디모자이킹 알고리즘을 제안한다. 또한 디모자이킹 알고리즘을 하드웨어로 구현하여 그 성능을 비교한다. 제안한 알고리즘을 검증하기 위한 방법으로 전체 ISP시스템을 구현 했으며, 성능을 확인할 지표로 알고리즘 자체성능은 PSNR로 이미지센서의 필터특성의 적용의 결과는 RGB분포도를 이용하였다. 결과적으로 기존의 방법에 비해 PSNR 값이 4~8dB 증가하였으며, 실제 이미지센서(CBN385B)에서 Red 성분으로 편중된 현상도 제거하였다. 또한 하드웨어 설계를 통해 소프트웨어적인 연산의 복잡성을 해결하였으며 검증을 위해 Spartan-3E FPGA가 사용되었다. 총 게이트 수는 45K개이며 25 frame/sec의 속도를 보였다.

• 센서학회지
• /
• 제16권1호
• /
• pp.1-6
• /
• 2007

A silver indium sulfide ($AgInS_{2}$) epilayer was grown by the hot wall epitaxy method, which has not been reported in the literature. The grown $AgInS_{2}$ epilayer has found to be a chalcopyrite structure and evaluated to be high quality crystal. From the photocurrent measurement in the temperature range from 30 K to 300 K, the two peaks of A and B were only observed, whereas the three peaks of A, B, and C were seen in the PC spectrum of 10 K. These peaks are ascribed to the band-to-band transition. The valence band splitting of $AgInS_{2}$ was investigated by means of the photocurrent measurement. The crystal field splitting, ${\Delta}cr$, and the spin orbit splitting, ${\Delta}so$, have been obtained to be 0.150 eV and 0.009 eV at 10 K, respectively. And, the energy band gap at room temperature has been determined to be 1.868 eV. Also, the temperature dependence of the energy band gap, $E_{g}$(T), was determined.

• 한국IT서비스학회지
• /
• 제18권5호
• /
• pp.85-97
• /
• 2019

In this study, we developed the Field-Experiential Learning Framework Using the Location Based Mobil-learning System (LBMS) and it is mobile Augmented Reality (AR) for smart learning system which is advanced e-learning. AR is technology that seamlessly overlays computer graphics on the real world. LBMS-AR has become widely available because of mobile AR. Mobile AR is possible to get information from real world anytime, anywhere. Nowadays, there are various areas using AR such as entertainment, marketing, location-based AR. We analysed the result of survey and implemented the functions. Also, for survey about application's effectiveness, we have focus group interview (FGI). Then we demonstrated and explained the application to them. The result of survey about application's effectiveness shows that application have higher utilization in education area. One of the most promising areas is education. AR in education shows lifelike images to users for realism. It's a good way for improving concentration and attention. We utilize only a beacone for image-based AR without other sensor.

• Journal of Astronomy and Space Sciences
• /
• 제25권1호
• /
• pp.43-52
• /
• 2008

2007년에 Giove-A 실험위성의 항법메시지 송신 시험이 성공적으로 끝마침으로써, 차세대 위성 항법시스템인 갈릴레오 계획이 초기궤도 검증단계를 앞두고 있다. 한국천문연구원의 우주측지연구부와 전파천문연구부는 제주 탐라대학교 내 유치 후보지에 대한 갈릴레오 센서 스테이션 전파 수신환경 공동조사를 2006년 8월 3일부터 5일까지 실시했다. 전계강도 스펙트럼은 전 대역$(800{\sim}2000MHz)$과 내 대역(E5, E6, L1 밴드)에 대해서 24시간 주파수 영역 관측을 했다. 이 단계에서 관측된 강한 내 대역 간섭 신호에 대해서 시간영역 분석을 했다.

• 센서학회지
• /
• 제16권6호
• /
• pp.419-427
• /
• 2007

Single crystal $ZnIn_{2}S_{4}$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $450^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the polycrystal source of $ZnIn_{2}S_{4}$ at $610^{\circ}C$ prepared from horizontal electric furnace. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $ZnIn_{2}S_{4}$ thin films measured with Hall effect by van der Pauw method are $8.51{\times}10^{17}\;electron/cm^{-3}$, $291{\;}cm^{2}/v-s$ at 293 K, respectively. The photocurrent and the absorption spectra of $ZnIn_{2}S_{4}$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10 K. The temperature dependence of the energy band gap of the $ZnIn_{2}S_{4}$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)$=2.9514 eV. ($7.24{\times}10^{-4}\;eV/K$)$T^{2}$/(T+489 K). Using the photocurrent spectra and the Hopfield quasicubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) for the valence band of the $ZnIn_{2}S_{4}$ have been estimated to be 167.8 meV and 14.8 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1}$-, $B_{1}$-, and $C_{41}$-exciton peaks.

• ETRI Journal
• /
• 제37권3호
• /
• pp.606-616
• /
• 2015

In this paper, we propose a novel method for road recognition using 3D point clouds based on a Markov random field (MRF) framework in unstructured and complex road environments. The proposed method is focused on finding a solution for an analysis of traversable regions in challenging environments without considering an assumption that has been applied in many past studies; that is, that the surface of a road is ideally flat. The main contributions of this research are as follows: (a) guidelines for the best selection of the gradient value, the average height, the normal vectors, and the intensity value and (b) how to mathematically transform a road recognition problem into a classification problem that is based on MRF modeling in spatial and visual contexts. In our experiments, we used numerous scans acquired by an HDL-64E sensor mounted on an experimental vehicle. The results show that the proposed method is more robust and reliable than a conventional approach based on a quantity evaluation with ground truth data for a variety of challenging environments.

• Journal of Biosystems Engineering
• /
• 제33권4호
• /
• pp.260-268
• /
• 2008

Optical diffuse reflectance sensing has potential for rapid and reliable on-site estimation of soil properties. For good results, proper calibration to measured soil properties is required. One issue is whether it is necessary to develop calibrations using samples from the specific area or areas (e.g., field, soil series) in which the sensor will be applied, or whether a general "factory" calibration is sufficient. A further question is if specific calibration is required, how many sample points are needed. In this study, these issues were addressed using data from 42 paddy fields representing 14 distinct soil series accounting for 74% of the total Korean paddy field area. Partial least squares (PLS) regression was used to develop calibrations between soil properties and reflectance spectra. Model evaluation was based on coefficient of determination ($R^2$) root mean square error of prediction (RMSEP), and RPD, the ratio of standard deviation to RMSEP. When sample data from a soil series were included in the calibration stage (full information calibration), RPD values of prediction models were increased by 0.03 to 3.32, compared with results from calibration models not including data from the test soil series (calibration without site-specific information). Higher $R^2$ values were also obtained in most cases. Including some samples from the test soil series (hybrid calibration) generally increased RPD rapidly up to a certain number of sample points. A large portion of the potential improvement could be obtained by adding about 8 to 22 points, depending on the soil properties to be estimated, where the numbers were 10 to 18 for pH, 18-22 for EC, and 8 to 22 for total C. These results provide guidance on sampling and calibration requirements for NIR soil property estimation.