• Title/Summary/Keyword: SAR model

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Preliminary Results of Thermal Effects due to Mobile Phones

  • Sik, Yoo-Done
    • Proceedings of the Korean Society of Medical Physics Conference
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    • 2002.09a
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    • pp.471-473
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    • 2002
  • Public concerns associated with the electromagnetic field (EMF) exposures from mobile phones on human body are increased. Although studies on the effects of the EMF exposures on human have been carried out for a long time, it is not proved yet whether the EMF effect is harmful or not. Based on the scientific results by experts, EMF exposure limits have been regulated as a precautionary approach on the assumption that the EMF effect may be harmful. It is well known that absorbed EMF can be transformed into heat within biological tissues and that thermal effects are related with the specific absorption rate (SAR) distribution. However, the relative magnitude and distribution of the energies are not well defined. Although there is comprehensive information of the thermal effects, most of them come from animal and in vitro studies. Considerable efforts have been made to analyze the EMF absorption model while the actual temperature in the human body has been rarely measured. Temperature changes on the face of a healthy male volunteer were studied. A digital mobile phone of 1.8GHz was used. A digital infrared imaging system (IRIS-5000, Medicore, Seoul, Korea) was applied to take infrared pictures of the face every minute while the volunteer talked over the mobile phone for 20 minutes. The specification of the imaging system was as follows: Temperature resolution = 0.1$^{\circ}C$; Range of temperature measurement = 17~40$^{\circ}C$; Pixel size = 0.9mm ${\times}$ 0.9mm; Frame time = 2.6s; Active temperature of detector = 77$^{\circ}$K. The result showed that temperature of the ear region was increased during the phone call and the region of the temperature increase on the face was expanded as the phone call time increased. Further study is necessary to investigate the temperature rise analytically and quantitatively.

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Sampling-based Control of SAR System Mounted on A Simple Manipulator (간단한 기구부와 결합한 공간증강현실 시스템의 샘플 기반 제어 방법)

  • Lee, Ahyun;Lee, Joo-Ho;Lee, Joo-Haeng
    • Korean Journal of Computational Design and Engineering
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    • v.19 no.4
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    • pp.356-367
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    • 2014
  • A robotic sapatial augmented reality (RSAR) system, which combines robotic components with projector-based AR technique, is unique in its ability to expand the user interaction area by dynamically changing the position and orientation of a projector-camera unit (PCU). For a moving PCU mounted on a conventional robotic device, we can compute its extrinsic parameters using a robot kinematics method assuming a link and joint geometry is available. In a RSAR system based on user-created robot (UCR), however, it is difficult to calibrate or measure the geometric configuration, which limits to apply a conventional kinematics method. In this paper, we propose a data-driven kinematics control method for a UCR-based RSAR system. The proposed method utilized a pre-sampled data set of camera calibration acquired at sufficient instances of kinematics configurations in fixed joint domains. Then, the sampled set is compactly represented as a set of B-spline surfaces. The proposed method have merits in two folds. First, it does not require any kinematics model such as a link length or joint orientation. Secondly, the computation is simple since it just evaluates a several polynomials rather than relying on Jacobian computation. We describe the proposed method and demonstrates the results for an experimental RSAR system with a PCU on a simple pan-tilt arm.

Regulated Peak Power Tracking (RPPT) System Using Parallel Converter Topologies

  • Ali, Muhammad Saqib;Bae, Hyun-Su;Lee, Seong-Jun;Cho, Bo-Hyung
    • Journal of Power Electronics
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    • v.11 no.6
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    • pp.870-879
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    • 2011
  • Regulated peak power tracking (RPPT) systems such as the series structure and the series-parallel structures are commonly used in satellite space power systems. However, these structures process the solar array power or the battery power to the load through two cascaded regulators during one orbit cycle, which reduces the energy transfer efficiency. Also the battery charging time is increased due to placement of converter between the battery and the solar array. In this paper a parallel structure has been proposed which can improve the energy transfer efficiency and the battery charging time for satellite space power RPPT systems. An analogue controller is used to control all of the required functions, such as load voltage regulation and solar array stabilization with maximum power point tracking (MPPT). In order to compare the system efficiency and the battery charging efficiency of the proposed structure with those of a series (conventional) structure and a simplified series-parallel structure, simulations are performed and the results are analyzed using a loss analysis model. The proposed structure charges the battery more quickly when compared to the other two structures. Also the efficiency of the proposed structure has been improved under different modes of solar array operation when compared with the other two structures. To verify the system, experiments are carried out under different modes of solar array operation, including PPT charge, battery discharge, and eclipse and trickle charge.

Analysis of Radio Frequency (RF) Characteristics and Effectiveness according to the Number of Gores of Mesh Antenna (그물형 안테나의 고어 개수에 따른 Radio Frequency (RF) 특성 분석)

  • Kim, Jin-Hyuk;Lee, Si-A;Park, Tae-Yong;Choi, Han-Sol;Kim, Hongrae;Chae, Bong-Geon;Oh, Hyun-Ung
    • Journal of Space Technology and Applications
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    • v.1 no.3
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    • pp.364-374
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    • 2021
  • This research discusses the change in radio frequency (RF) characteristics according to the number of Gores on the deployable mesh antennas for potential micro-satellite applications. The deployable type of lightweight mesh antenna can be used for various space missions such as communication/SAR/ SIGINT. In order to implement an ideal curvature of antenna surface, sufficient number of antenna rib structures are required. However, the increase in antenna ribs affects various design factors of the antenna system, especially total system mass, complexity of deployable mechanism and reliability. In this paper, the proper number of ribs for the mesh antenna were derived by comparison of electro-magnetic (EM) simulation results of example of antenna model in accordance with the various number of ribs.

Soil moisture estimation of YongdamDam watershed using vegetation index from Sentinel-1 and -2 satellite images (Sentinel-1 및 Sentinel-2 위성영상기반 식생지수를 활용한 용담댐 유역의 토양수분 산정)

  • Son, Moobeen;Chung, Jeehun;Lee, Yonggwan;Woo, Soyoung;Kim, Seongjoon
    • Proceedings of the Korea Water Resources Association Conference
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    • 2021.06a
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    • pp.161-161
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    • 2021
  • 본 연구에서는 금강 상류의 용담댐 유역(930.0 km2)을 대상으로 Sentinel-1 SAR(Synthetic Aperture Radar) 및 Sentinel-2 MultiSpectral Instrument(MSI) 위성영상을 활용한 토양수분 산출연구를 수행하였다. 연구에 사용된 자료는 10 m 해상도의 Sentinel-1 IW(Interferometric Wide swath) mode GRD(Ground Range Detected) product의 VV(Vertical transmit-Vertical receive) 및 VH(Vertical transmit-Horizontal receive) 편파자료와 Sentinel-2 Level-2A Bottom of Atmosphere(BOA) reflectance 자료를 2019년에 대해 각 6일 및 5일 간격으로 구축하였다. 위성영상의 Image processing은 SNAP(SentiNel Application Platform)을 활용하여 Sentinel-1 영상의 편파 별(VV, VH) 후방산란계수와 Sentinel-2의 적색(Band-4) 및 근적외(Band-8) 영상을 생성하였다. 토양수분 산출 모형은 다중선형회귀모형(Multiple Linear Regression Model)을 활용하였으며, 각 지점에 해당하는 토양 속성별로 모형을 생성하였다. 모형의 입력자료는 Sentinel-1 위성의 편파별 후방산란계수, Sentinel-1 위성에서 산출된 식생지수 RVI(Radar Vegetation Index)와 Sentinel-2 위성에서 산출된 NDVI(Normalized Difference Vegetation Index)를 활용하여 식생의 영향을 반영하고자 하였다. 모의 된 토양수분을 검증하기 위해 6개 지점의 TDR(Time Domain Reflectometry) 기반 실측 토양수분 자료를 수집하고, 상관계수(Correlation Coefficient, R), 평균제곱근오차(Root Mean Square Error, RMSE) 및 IOA(Index of Agreement)를 활용하여 전체 기간 및 계절별로 나누어 검증할 예정이다.

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A Study on the Dielectric Properties of SBS/Conductive Filler/Dielectrics Composites for Phantom Model (팬텀 모델 제작을 위한 SBS/도전체/유전체 3상 복합재료의 유전특성 연구)

  • Kim, Yoon-Jin;Choi, Hyung-Do;Cho, Kwang-Yun;Yoo, Don-Sik;Yoon, Ho-Gyu;Suh, Kwang-Seok
    • Polymer(Korea)
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    • v.25 no.1
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    • pp.98-107
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    • 2001
  • Dielectric properties and shape memory characteristics of SBS composites filled with carbon black as conductive filler and (Ba,Ca)$(Sn,Ti)O_3$ or $SrTiO_3$ as dielectrics were investigated for the development of phantom model. SBS/carbon black composite showed an increment of complex dielectric constant with increasing the content of carbon black and the frequency dependence that the dielectric constant decreases with the frequency. The complex dielectric constant and the conductivity of SBS/carbon black/dielectrics composites increased with the increase of dielectrics and the characteristics of the frequency dependence also occurred by the effect of carbon black. Phantom materials with the dielectric properties and the conductivity corresponding to human tissues for the measurement of specific absorption rate(SAR) within the frequency range of current mobile phones(775MHz~2GHz) could be developed by adjusting the composition ratios of carbon black, dielectrics and SBS and by controlling the characteristic of frequency dependence of composite. From thermomechanical cycling test good shape recoverability could be obtained in SBS composite even though the residual strain was increased by the effect of filler.

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A Study on Estimating Tourism Elasticities using Autoregressive Distributed Lag(ARDL) model (ARDL 모형을 이용한 관광탄력성 추정에 대한 연구)

  • Lee, Kyung-Hee;Kim, Kyung-Soo
    • Management & Information Systems Review
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    • v.36 no.2
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    • pp.81-92
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    • 2017
  • This study was to investigate the elasticity in tourism demand of Chinese tourists visiting Malaysia through ARDL models by using Chinese tourists arrivals, GDP, CPI, transportation costs and others. When China was implementing an open-door policy with foreign countries in the early 15th century, the movement of Chinese was very limited, and then communication between China and other countries was very weak. However, the Chinese government persistently and entirely implemented an open-door policy by participating in the World Trade Organization(WTO) in 2001. The Chinese government has opened the economy through foreign direct investment by providing various incentives for foreign investment. As a result, inbound and outbound Chinese movements increased in the early 21st century. China was one of the top five most visited tourist destinations in the world by 2016, and also Chinese tourists traveling abroad increased, so they made Malaysia a popular tourists destination because of increase sharply to around 1.41 million. This study examined the significance of major economic factors affecting the increase in Chinese tourists arriving in Malaysia. Other factors that induced their arrival included income, tourism prices, transportation costs and promotional activities. Short-run shocks from the Asian economic crisis and the outbreak of SARS were included to understand how tourism demand in Malaysia was affected. Finally this study found that the combination of the ARDL and the Error Correction Model were useful to statistically estimate the elasticities of tourism demand.

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Estimation of the Amount of Mining and Waste Rocks at Musan Mine in North Korea Using a Historical Map and SRTM and Copernicus Global Digital Elevation Models (조선지형도와 SRTM 및 Copernicus 글로벌 수치지형모델을 이용한 북한 무산광산의 채광량 및 폐석 적치량 추정)

  • Yongjae Chu;Hoonyol Lee
    • Korean Journal of Remote Sensing
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    • v.39 no.5_1
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    • pp.495-505
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    • 2023
  • The Musan mine, situated in Musan County, Hamgyong Province, North Korea, stands as a prominent open-pit iron mine on the Korean Peninsula. This study focuses on estimating the mining and dumping activities within the Musan mine area by analyzing digital elevation model (DEM) changes. To calculate the long-term volume changes in the Musan mine, we digitized and converted the 1:200,000-scale third topographic map of the Joseon published in 1918 and compared with interferometric synthetic aperture radar (InSAR) DEMs, including Shuttle Radar Topography Mission DEM (2000) and Copernicus DEM (2011-2015). The findings reveal that over a century, Musan mine yielded around 1.37 billion tons of iron ore, while approximately 1.06 billion tons of waste rock were dumped. This study is particularly significant as it utilizes a historical topographic map predating the full-scale development of Musan mine to estimate a century's mining production and waste rock deposition. It is expected that this research provides valuable insights for future investigation of surface change of North Korea where the acquisition of in situ data remains challenging.

Spatial Data Analysis for the U.S. Regional Income Convergence,1969-1999: A Critical Appraisal of $\beta$-convergence (미국 소득분포의 지역적 수렴에 대한 공간자료 분석(1969∼1999년) - 베타-수렴에 대한 비판적 검토 -)

  • Sang-Il Lee
    • Journal of the Korean Geographical Society
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    • v.39 no.2
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    • pp.212-228
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    • 2004
  • This paper is concerned with an important aspect of regional income convergence, ${\beta}$-convergence, which refers to the negative relationship between initial income levels and income growth rates of regions over a period of time. The common research framework on ${\beta}$-convergence which is based on OLS regression models has two drawbacks. First, it ignores spatially autocorrelated residuals. Second, it does not provide any way of exploring spatial heterogeneity across regions in terms of ${\beta}$-convergence. Given that empirical studies on ${\beta}$-convergence need to be edified by spatial data analysis, this paper aims to: (1) provide a critical review of empirical studies on ${\beta}$-convergence from a spatial perspective; (2) investigate spatio-temporal income dynamics across the U.S. labor market areas for the last 30 years (1969-1999) by fitting spatial regression models and applying bivariate ESDA techniques. The major findings are as follows. First, the hypothesis of ${\beta}$-convergence was only partially evidenced, and the trend substantively varied across sub-periods. Second, a SAR model indicated that ${\beta}$-coefficient for the entire period was not significant at the 99% confidence level, which may lead to a conclusion that there is no statistical evidence of regional income convergence in the US over the last three decades. Third, the results from bivariate ESDA techniques and a GWR model report that there was a substantive level of spatial heterogeneity in the catch-up process, and suggested possible spatial regimes. It was also observed that the sub-periods showed a substantial level of spatio-temporal heterogeneity in ${\beta}$-convergence: the catch-up scenario in a spatial sense was least pronounced during the 1980s.

Early Estimation of Rice Cultivation in Gimje-si Using Sentinel-1 and UAV Imagery (Sentinel-1 및 UAV 영상을 활용한 김제시 벼 재배 조기 추정)

  • Lee, Kyung-do;Kim, Sook-gyeong;Ahn, Ho-yong;So, Kyu-ho;Na, Sang-il
    • Korean Journal of Remote Sensing
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    • v.37 no.3
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    • pp.503-514
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    • 2021
  • Rice production with adequate level of area is important for decision making of rice supply and demand policy. It is essential to grasp rice cultivation areas in advance for estimating rice production of the year. This study was carried out to classify paddy rice cultivation in Gimje-si using sentinel-1 SAR (synthetic aperture radar) and UAV imagery in early July. Time-series Sentinel-1A and 1B images acquired from early May to early July were processed to convert into sigma naught (dB) images using SNAP (SeNtinel application platform, Version 8.0) toolbox provided by European Space Agency. Farm map and parcel map, which are spatial data of vector polygon, were used to stratify paddy field population for classifying rice paddy cultivation. To distinguish paddy rice from other crops grown in the paddy fields, we used the decision tree method using threshold levels and random forest model. Random forest model, trained by mainly rice cultivation area and rice and soybean cultivation area in UAV image area, showed the best performance as overall accuracy 89.9%, Kappa coefficient 0.774. Through this, we were able to confirm the possibility of early estimation of rice cultivation area in Gimje-si using UAV image.