• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.603-606
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• 2012

M2M 서비스를 통한 통신 모델은 MTC 디바이스와 MTC 서버 통신 모델 기반으로 이루어졌다. 하지만 최근 이동통신 시스템 기반으로 M2M 서비스가 개발되면서 다양한 M2M 서비스 개발을 위해 디바이스간 직접 통신 및 게이트웨이 기반 M2M 서비스 통신 모델에 관한 기술표준이 3GPP SA1에서 추진 중이다. 이와 관련된 기술은 3GPP SA1 TR 22.888(MTCe: Study on Enhancements for MTC) 문서를 통해 개발 중이며 주요 내용은 MTC capillary network 구축 및 MTC 게이트웨이 디바이스 역할 등을 기술하고 있다. MTC capillary network 구성의 목적은 non-3GPP M2M 디바이스를 이동통신 시스템을 통해서 M2M 서비스를 제공하기 위함이다. 본 논문에서는 이와 관련된 표준기술 및 use case를 분석한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.01a
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• pp.93-95
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• 2016

본 논문에서는 사물인터넷 서비스 모델인 OMA LWM2M 구조에서 IoT 게이트웨이가 포함된 확장 모델을 제안한다. 추가적으로 제안된 모델은 스마트폰 기반으로 구현된 IoT 게이트웨이를 가정하여 확장된 모델이다. 본 논문에서 제안하는 확장형 LWM2M 모델은 스마트폰을 이용하여 LWM2M 기반에서 스마트폰의 다양한 자원 및 None-LWM2M 클라이언트 자원을 LWM2M 자원 객체로 활용하여 다양한 IoT 서비스를 효율적이고 경제적으로 제공하는데 활용될 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.116-118
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• 2018

This paper introduces oneM2M global IoT standard middleware platform based smart city service data model support and FIWARENGSI interworking for Orion Broker. Also, service data models implementation using flexContainer resource types and FIWARENGSI interworking using the Interworking Framework (TS-0033) from oneM2M Release 3 are also illustrated. In this system, data model element level access (e.g. for subscription/notification feature) is enabled, which is enhancement compared to contentInstance resource type before, and service agnostic FIWARE NGSI interworking is provided over the Interworking Framework for smart city platform data interworking.

• Journal of Software Assessment and Valuation
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• v.16 no.2
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• pp.53-62
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• 2020

In the end-user domain of an IoT environment, there are more and more intelligent M2M devices that provide resources to create and share application services. Therefore, it can be very useful to manage trust by transferring the role of the existing centralized service provider to end users in a P2P environment. However, in a decentralized M2M computing environment where end users independently provide or consume services, mutual trust building is the most important factor. This is because malicious users trying to build malfunctioning services can cause security problems in M2M computing environments such as IoT. In this paper, we provide an integrated analysis and approach for trust evaluation of M2M application services, and an optimized trust evaluation model that can guarantee reliability among users of the M2M community.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.2
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• pp.107-116
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• 2012

We investigated the accuracy in three dimensional geo-positioning derived by four high resolution satellite images acquired by two different sensors using the vendor-provided rational polynomial coefficients(RPC) based block adjustment in this research. We used two in-track stereo pairs of GeoEye-1 and WorldView-2 satellite and DGPS surveying data. In this experiment, we analyzed accuracies of RPC block adjustment models of two kinds of homogeneous stereo pairs, four kinds of heterogeneous stereo pairs, three 3 triplet image pairs, and one quadruplet image pair separately. The result shows that the accuracies of the models are nearly same. The accuracy without any GCPs reaches about CEP(90) 2.3m and LEP(90) 2.5m and the accuracy with single GCP is about CEP(90) 0.3m and LEP(90) 0.5m.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.1
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• pp.106-118
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• 2009

Satellite imagery with high resolution of about one meter is used widely in commerce and government applications ranging from earth observation and monitoring to national digital mapping. Due to the expensiveness of IKONOS Pro and Precision products, it is attractive to use the low-cost IKONOS Geo product with vendor-provided rational polynomial coefficients (RPCs), to produce highly accurate mapping products. The imaging geometry of IKONOS high-resolution imagery is described by RFs instead of rigorous sensor models. This paper presents four different polynomial models, that are the offset model, the scale and offset model, the Affine model, and the 2nd-order polynomial model, defined respectively in object space and image space to improve the accuracies of the RF-derived ground coordinates. Not only the algorithm for RF-based ground coordinates but also the algorithm for accuracy improvement of RF-based ground coordinates are developed which is based on the four models, The experiment also evaluates the effect of different cartographic parameters such as the number, configuration, and accuracy of ground control points on the accuracy of geopositioning. As the result of a experimental application, the root mean square errors of three dimensional ground coordinates which are first derived by vendor-provided Rational Function models were averagely 8.035m in X, 10.020m in Y and 13.318m in Z direction. After applying polynomial correction algorithm, those errors were dramatically decreased to averagely 2.791m in X, 2.520m in Y and 1.441m in Z. That is, accuracy was greatly improved by 65% in planmetry and 89% in vertical direction.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.457-466
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• 2007

The effect of depth correction in the coastal sea has been investigated through a series of tide simulations in the area of $115{\sim}150^{\circ}E,\;20{\sim}52^{\circ}N$ of northwestern Pacific with $1/12^{\circ}$ resolution. Comparison of the solutions varying the minimum depth from 10m to 35 m with the 5m interval shows that the amplitude accuracies of $M_2,\;S_2,\;K_1$ tide using the minimum depth of 25 m have been improved up to 42%, 32%, 26%, respectively, comparing to those using the minimum depth of 10m. The discrepancy between model results using different minimum depth is found to be up to 20 cm for $M_2$ tidal amplitude around Cheju Islands and the positions of amphidromes are dramatically changed in the Bohai Sea. The calculated ARE(Averaged Relative Error) values have been minimized when the bottom frictional coefficient and the minimum depth is 0.0015 and 25 m, respectively.

• Korean Journal of Remote Sensing
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• v.33 no.2
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• pp.135-147
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• 2017

We, for the first time, estimated daily and monthly surface nitrogen dioxide ($NO_2$) volume mixing ratio (VMR) using three regression models with $NO_2$ tropospheric vertical column density (OMIT-rop $NO_2$ VCD) data obtained from Ozone Monitoring Instrument (OMI) in Seoul in South Korea at OMI overpass time (13:45 local time). First linear regression model (M1) is a linear regression equation between OMI-Trop $NO_2$ VCD and in situ $NO_2$ VMR, whereas second linear regression model (M2) incorporates boundary layer height (BLH), temperature, and pressure obtained from Atmospheric Infrared Sounder (AIRS) and OMI-Trop $NO_2$ VCD. Last models (M3M & M3D) are a multiple linear regression equations which include OMI-Trop $NO_2$ VCD, BLH and various meteorological data. In this study, we determined three types of regression models for the training period between 2009 and 2011, and the performance of those regression models was evaluated via comparison with the surface $NO_2$ VMR data obtained from in situ measurements (in situ $NO_2$ VMR) in 2012. The monthly mean surface $NO_2$ VMRs estimated by M3M showed good agreements with those of in situ measurements(avg. R = 0.77). In terms of the daily (13:45LT) $NO_2$ estimation, the highest correlations were found between the daily surface $NO_2$ VMRs estimated by M3D and in-situ $NO_2$ VMRs (avg. R = 0.55). The estimated surface $NO_2$ VMRs by three modelstend to be underestimated. We also discussed the performance of these empirical modelsfor surface $NO_2$ VMR estimation with respect to otherstatistical data such asroot mean square error (RMSE), mean bias, mean absolute error (MAE), and percent difference. This present study shows a possibility of estimating surface $NO_2$ VMR using the satellite measurement.

• The Journal of Engineering Geology
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• v.33 no.3
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• pp.403-411
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• 2023

The possibility of utilizing radiant solar energy as a renewable energy resource in Tajikistan was investigated by assessing solar irradiance using XGBoost algorithm. Through training, validation, and testing, the seasonality of solar irradiance was clear in both actual and predicted values. Calculation of hourly values of solar irradiance on 1 July 2016, 2017, 2018, and 2019 indicated maximum actual and predicted values of 1,005 and 1,009 W/m², 939 and 997 W/m², 1,022 and 1,012 W/m², 1,055 and 1,019 W/m², respectively, with actual and predicted values being within 0.4~5.8%. XGBoost is thus a useful tool in predicting solar irradiance in Tajikistan and evaluating the possibility of utilizing radiant solar energy.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.77-84
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• 1999

The XX company that is handling the class IV hazardous materials, located in Bu-Chon City and the LPG station in front of the XX company which is about 20 meters apart, was chosen as the standard model for this study In carrying out the consequence analysis, PHAST and Super-Chems were used for the study and utilizing the output of the simulation, we have evaluated the consequences throughout the probit analysis and explosion overpressure analysis. In case of Acetone, the effect distance of the damage on facilities-that is the result of radiation heat flux of $37.5kW/m^2$ by TNO model-is 68.51m by PHAST model and 40.93m by Super-Chem model. The risk assessment of the LPG station which is based on the explosion resulted as the analysis of the fire ball showed the diameter 125.2m, the height 206.2m and the duration 11.28sec and the effect distance for the radiant heat flux $37.5kW/m^2$ was 137.0m.