• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.10
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• pp.889-900
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• 2012

In wireless sensor networks, the positioning scheme using received signal strength (RSS) has been widely considered. Appropriate estimation of path-loss exponent (PLE) between a sensor node and an anchor node plays a key role in reducing position error in this RSS-based positioning scheme. In the conventional researches, a sensor node directly uses the PLEs measured by its nearest anchor node to calculate its position. However, the actual PLE between a sensor node and the anchor node can be different from the PLE measured by its nearest anchor node. Thus, if a sensor node directly uses the PLEs measured by its nearest anchor node, the estimated position is different from the actual position of the sensor node with a high probability. In this paper, we describe the method how a sensor node estimates PLEs from the anchor nodes of interest by itself and calculates its position based on these self-estimated PLEs. Especially, our proposal suggests the mechanism to iteratively calculate the PLEs depending on the estimated distances between a sensor node and anchor nodes. Based on the recalculated PLEs, the sensor node reproduces its position. Through simulations, we show that our proposed positioning scheme outperforms the traditional scheme in terms of position error.

• Journal of the Korean Society of Radiology
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• v.8 no.1
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• pp.43-49
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• 2014

PACS is needed medical imaging with large-capacity storage device. Slower transmission degrades the performance of the PACS. Thus, the image read by the reading of the long-term stored image without compromising the quality of the video, which does not affect future readings in the range will be compressed and stored. Compression and video storage, and video transport Noise generated during storage and transmission of medical images and the resulting loss of information that occurs when the monitor output from many problems. The study estimates server display monitor and client display monitor of philips DSA system, and suggests that the evaluation and improvement about PSNR, process from server display signal obtaining to client display monitor. P company DSA is used in the test. Two monitors that are $1280{\times}1024$ pixel monitor of P company and 1536x2048 pixel monitor of Wide are used displaying angiography picture. MARO-view is taken in PACS program, and Visual $C^{++}$ is taken as accomplishing PSNR measurement program. As a result of experiment, no change in No 1, 3 of PSNR appear that there is no error in telephotograph and display. In terms of compressibility, low compressibility has small change of definition, and there was not remarkable drawback of compressibility which has little change in definition.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.2
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• pp.214-227
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• 2018

An object oriented crop model was developed to perform crop growth simulation taking into account complex interaction between biotic and abiotic factors in an agricultural ecosystem. A set of classes including Atmosphere class, Plant class, Soil class, and Grower class were designed to represent weather, crop, soil, and crop management, respectively. Objects, which are instance of class, were linked to construct an integrated system for crop growth simulation. In a case study, yield of corn and soybean, which was obtained at an experiment farm in Rural Development Administration from 1984 to 1986, were compared with yield simulated using the integrated system. The integrated system had relatively low error rate of corn yield, e.g., <4%, under sole and intercropping conditions. In contrast, the system had a relatively large underestimation error for above ground biomass except for grain compared with those observed for corn and soybean. For example, estimates of biomass of corn leaf and stem was 31% lower than those of observed values. Although the integrated system consisted of simple models, the system was capable of simulating crop yield under an intercropping condition. This result suggested that an existing process-based model would be used to have more realistic simulation of crop growth once it is reengineered to be compatible to the integration system, which merits further studies for crop model improvement and implementation in object oriented paradigm.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.221-228
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• 2019

The effects of wind speed on the temperature change during day time could be insignificant in a region with a complex terrain. The objective of this study was to derive empirical relationship between solar radiation and hourly temperature under a windy condition for the period from sunrise to sunset in order to improve hourly air temperature at a site-specific scale. The deviation of the temperature measurements was analyzed along with the changes of the hourly sunlight at weather observation sites located on the east and west slopes under given wind speed. An empirical model where wind speed use used as an independent variable was obtained to quantify the solar effects on the temperature change (MJ/㎡). This model was verified estimating the hourly temperature during the daytime (0600-1900 h) at 25 weather observation sites located in the study area that has complex topography for the period from January to December 2018. The mean error (ME) and root mean square error (RMSE)of the estimated and measured values ranged from -0.98 to 0.67 ℃, and from 0.95 to 2.04 ℃, respectively. The daytime temperature at 1500 h were estimated using new and previous models. It was found that to the model proposed in the present study reduced the measurement errors of the hourly temperature in the afternoon in comparison with the previous model. For example, the ME and RMSE of the previous model were (ME -0.91 ℃ and 1.47 ℃, respectively. In contrast, the values of ME and RMSE were -0.45 ℃ and 1.22 ℃ for the new model, respectively. Our results suggested that the reliability of hourly temperature estimates at a specific site could be improved taking into account the effect of wind as well as solar radiation.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.4
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• pp.131-141
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• 2014

Over the last decade, the Global Navigation Satellite System (GNSS) has been increasingly utilized as a meteorological research tool. The Korea Astronomy and Space Science Institute (KASI) has also been developing a near real-time GNSS precipitable water vapor (PWV) information management system that can produce a precise PWV for the Korean Peninsula region using GNSS data processing and meteorological measurements. The goal of this paper is to evaluate whether the precise point positioning (PPP) strategy will be used as the new data processing strategy of the GNSS-PWV information management system. For this purpose, quality assessment has been performed by means of a comparative analysis of the troposphere zenith total delay (ZTD) estimates from KASI PPP solutions (KPS), KASI network solutions (KNS), and International GNSS Service (IGS) final troposphere products (IFTP) for ten permanent GNSS stations in the Korean Peninsula. The assessment consists largely of two steps: First, the troposphere ZTD of the KNS are compared to those of the IFTP for only DAEJ and SUWN, in which the IFTP are used as the reference. Second, the KPS are compared to the KNS for all ten GNSS stations. In this step, the KNS are used as a new reference rather than the IFTP, because it was proved in the previous step that the KNS can be a suitable reference. As a result, it was found that the ZTD values from both the KPS and the KNS followed the same overall pattern, with an RMS of 5.36 mm. When the average RMS was converted into an error of GNSS-PWV by considering the typical ratio of zenith wet delay and PWV, the GNSS-PWV error met the requirement for PWV accuracy in this application. Therefore, the PPP strategy can be used as a new data processing strategy in the near real-time GNSS-PWV information management system.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1193-1201
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• 2020

This study aims to develop a regression model that estimates a low-flow index that can be applied to ungauged basins. A total of 30 midsized basins in South Korea use long-term runoff data provided by the National Integrated Water Management System (NIWMS) to calculate average low-flow, average minimum streamflow, and low-flow index duration and frequency. This information is used in the correlation analysis with 18 basin factors and 3 climate change factors to identify the basin area, average basin altitude, average basin slope, water system density, runoff curve number, annual evapotranspiration, and annual precipitation in the low-flow index regression model. This study evaluates the model's accuracy by using the root-mean-square error (RMSE) and the mean absolute error (MAE) for 10 ungauged, verified basins and compares them with the previous model's low-flow calculations to determine the effectiveness of the newly developed model. Comparative analysis indicates that the new regression model produces average low-flow, attributed to the consideration of varied basin and hydrologic factors during the new model's development.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1315-1328
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• 2022

Sinduri beach is a typical sedimentary landform that forms sand dunes due to the influence of the northwest wind in winter. Due to the its large scale and well-developed nature, it has been recognized for conservation value and is currently designated as Natural Monument No. 431, and continuous monitoring is required in terms of the preservation of topographical values. In this study, aerial images, drone images, and drone-based LiDAR data during 36 years were used for long-term topographical change observation of the Sinduri coastal sand dunes located in Taean-gun, Chungcheongnam-do. To implement this, the amount of change in elevation and volume for each period was calculated by applying the difference of Digital Elevation Model (DEM) based on raster calculation using the numerical elevation model generated from the raw data. Also, the amount of change in volume based on probability was calculated using the error propagation law for the intrinsic error of each data source. As a result, it can be seen that from 1986 to 2022, deposition of 35,119 m³ occurred in region of interest A (area: 17,960 m²) and 54,954 m³ of deposition occurred in region of interest B (area: 17,686 m²).

• Journal of Broadcast Engineering
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• v.28 no.1
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• pp.145-148
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• 2023

Open-loop Octonion space-time block code for 4 transmit antenna system is considered and random phases are applied to 4 transmit antennas for physical layer security. When an illegal hacker estimates the random phases of 1 through 4 transmit antennas with maximum likelihood (ML), this letter analyzes the bit error rate (BER) performances versus signal-to-noise ratio (SNR). And the Octonion code in the literature[1] does not have full orthogonality so, this letter employs the perfect orthogonal Octonion code. When the hacker knows that the random phases are 2-PSK constellations and he should estimate all the 4 random phases, the hacking is impossible until 100dB. When the hacker possibly know that some of the random phases, bit error rate goes down to 10^-3 so, the transmit message could be hacked.

• Korean Journal of Ecology and Environment
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• v.56 no.2
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• pp.161-171
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• 2023

The medium-large cladoceran species Simocephalus spp. predominantly occur in habitats with developed aquatic vegetation. Accordingly, due to Simocephalus' high contribution to zooplankton community biomass in the lake's littoral zone and wetland habitats, estimating their biomass is important to understand the matter cycling based on biological interactions within the aquatic food web. In this study, we reviewed the length-weight regression equations used previously to estimate Simocephalus biomass, directly measured S. serrulatus' body specification (length, width and area) and their biomass(dry weight) using instruments such as a microscopic digital camera and a microscale, and performed regression analysis between each other. When S. serrulatus biomass was estimated using the equation (Kawabata and Urabe, 1998) presented in 『Biomonitoring Survey and Assessment Manual』, Korea, errors between estimates and measures were relatively large compared to the S. serrulatus species-specific biomass estimate equation developed by Lemke and Benke (2003). In addition, both equations showed not only increasing trends in error (estimate-measure) with increasing S. serrulatus' body length, but also in error variance among similar-sized individuals. The results of regression analysis with dry weight by body specifications indicated that the most appropriate equation for estimating the biomass of S. serrulatus was derived from the width-dry weight exponential regression equation (R²=0.9555). The review and development study of such species-specific biomass estimation equations for zooplankton can be used as a tool to understand their role and function in aquatic ecosystem food webs.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.3
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• pp.129-141
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• 2023

Crop models have been used to predict yield under diverse environmental and cultivation conditions, which can be used to support decisions on the management of forage crop. Cultivar parameters are one of required inputs to crop models in order to represent genetic properties for a given forage cultivar. The objectives of this study were to compare calibration and ensemble approaches in order to minimize the uncertainty of crop yield estimates using the SIMPLE crop model. Cultivar parameters were calibrated using Log-likelihood (LL) and Generic Composite Similarity Measure (GCSM) as an objective function for Metropolis-Hastings (MH) algorithm. In total, 20 sets of cultivar parameters were generated for each method. Two types of ensemble approach. First type of ensemble approach was the average of model outputs (E_em), using individual parameters. The second ensemble approach was model output (E_pm) of cultivar parameter obtained by averaging given 20 sets of parameters. Comparison was done for each cultivar and for each error calculation methods. 'Jowoo' and 'Yeongwoo', which are forage rice cultivars used in Korea, were subject to the parameter calibration. Yield data were obtained from experiment fields at Suwon, Jeonju, Naju and I ksan. Data for 2013, 2014 and 2016 were used for parameter calibration. For validation, yield data reported from 2016 to 2018 at Suwon was used. Initial calibration indicated that genetic coefficients obtained by LL were distributed in a narrower range than coefficients obtained by GCSM. A two-sample t-test was performed to compare between different methods of ensemble approaches and no significant difference was found between them. Uncertainty of GCSM can be neutralized by adjusting the acceptance probability. The other ensemble method (E_pm) indicates that the uncertainty can be reduced with less computation using ensemble approach.