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Analysis of the Ionospheric Effect for Time Offsets per GPS Code Measurements
Donghui Yu,Sangwook Hwang,Youngkyu Lee,Sunghoon Yang,Changbok Lee 보안공학연구지원센터 2015 International Journal of Software Engineering and Vol.9 No.8
This paper shows the analysis results of time offsets using P1, P2 and P3 code in GPS time transfer. The r2cggtts program has been used in GNSS Time Transfer and use the P3 ionosphere free combination of P1 and P2 code measurements. We modified the r2cggtts program in order to calculate and write all kinds of time offsets P3 as well as P1 and P2. The result of the modified r2cggtts program shows that time offsets using P1 and P2 are of wide distribution comparing to time offsets using P3. In order to Figure out the error factors for wide distributions of P1 and P2, we analyze and present the relation between the elevation angle and time offsets in this paper.
Methodology for deploying ASF monitor sites in South Korea
Donghui Yu,Chansik Park,Sangjeong Lee,Sunghoon Yang,Changbok Lee 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
There has been interest in recent years in backup systems in case of the loss of GPS in South Korea. The Ministry of Maritime Affairs and Fisheries had conducted the feasibility study using DGPS beacon signal and recently Ministry of Land, Transport and Maritime Affairs started to examine eLoran (enhanced Loran) system, especially in the Harbor Entrance and Approach (HEA). In order to meet this HEA accuracy requirement, user receivers must employ Additional Secondary Factors (ASFs) in calculating the user’s position. ASFs are time adjustments that modify the receiver’s Times of Arrival (TOA) to account for propagation over non-seawater paths. As these ASFs vary both spatially and temporally, both variations need to be compensated for to meet the HEA accuracy targets. In the proposedeLoran system, the spatial variations are accounted for through the use of grids of ASF values that are known by the receiver a priori. The temporal variations are accounted for by operating in differential mode; specifically, a nearbyreference monitor station estimates and broadcasts the temporal changes in the ASFs relative to the published spatial grids. The U.S. Coast Guard Academy is conducting research and proof-of concept demonstrations of the ability of enhanced Loran to support the HEA navigational requirements. In this paper, we outline the methodology to import and deploy the eLoran system in South Korea; especially, ASF grid development techniques and location of monitor sites and operations in Busan Harbor referring to the efforts of The United States.
A Light-Weight AES Design using LFSR-based S-Box for IoT Applications
Donghui Lee,Myeongjin Kwak,Jungwon Lee,Yongtae Kim,Beomjun Kim 대한전자공학회 2022 IEIE Transactions on Smart Processing & Computing Vol.11 No.2
This paper presents a novel light-weight AES architecture based on linear feedback shift register (LFSR). Since the traditional substitution-box (S-box) of the AES architecture consumes a large amount of hardware resources, we propose LFSR-based S-box and inverse S-box designs to reduce the hardware overheads significantly. In addition, we replace the conventional AES key scheduler with the LFSR-based round key generator to improve the hardware efficiency further. When implemented in a 32-nm CMOS technology, the proposed designs improve the area, delay, power, and energy by 57.4%, 64.3%, 30.1%, and 75% in the AES-128, 52.2%, 12.5%, 21.9%, and 31.7% in the AES-192, and 54.8%, 5.2%, 23.4%, and 27.4% in the AES-256, respectively, when compared to the traditional S-box based AES architecture. In addition, a joint analysis of our designs in terms of area, delay, and energy shows that the proposed AES designs enhance the area-delay product (ADP) and energy-delay product (EDP) by up to 84.7% and 82.5%, respectively, compared to the traditional design.
Lee, Donghui,Jung, Yunji,Ha, Myeongjin,Ahn, Hyungju,Lee, Keun Hyung,Seo, Myungeun The Royal Society of Chemistry 2019 Journal of Materials Chemistry C Vol.7 No.23
<P>We report self-assembly of a statistical copolymer poly(styrene-<I>co</I>-methyl methacrylate) (P(S-<I>co</I>-MMA)) containing ionic liquid (IL)-philic methyl methacrylate (MMA) and IL-phobic styrene (S) repeating units in IL for fabrication of electrolyte-gated organic transistors. P(S-<I>co</I>-MMA)s with high MMA contents were synthesized by copolymerization of styrene and MMA <I>via</I> a reversible addition-fragmentation chain transfer (RAFT) process, and their behavior in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]) was investigated. While dynamic light scattering analysis showed formation of a micellar solution at low concentration, the elastic modulus of the viscoelastic solution increased significantly more than the loss modulus at high concentration. Small angle X-ray scattering analysis suggested ill-defined phase separation between PS-rich segments and PS-lean segments swollen in [EMI][TFSI]. The resulting P(S-<I>co</I>-MMA)/[EMI][TFSI] mixture exhibited increased ionic conductivity compared to the PS-<I>b</I>-PMMA-<I>b</I>-PS block polymer gel, as well as superior device performance in transistor gating experiments.</P>
FORECASTING GOLD FUTURES PRICES CONSIDERING THE BENCHMARK INTEREST RATES
Donghui Lee,Donghyun Kim,Ji-Hun Yoon 충청수학회 2021 충청수학회지 Vol.34 No.2
This study uses the benchmark interest rate of the Federal Open Market Committee (FOMC) to predict gold futures prices. For the predictions, we used the support vector machine (SVM) (a machine-learning model) and the long short-term memory (LSTM) deep-learning model. We found that the LSTM method is more accurate than the SVM method. Moreover, we applied the Boruta algorithm to demonstrate that the FOMC benchmark interest rates correlate with gold futures.
PREDICTION OF U.S. GOLD FUTURES PRICES USING WAVELET ANALYSIS; A STUDY ON DEEP LEARNING MODELS
LEE, Donghui,KIM, Donghyun,YOON, Ji-Hun The Korean Society for Computational and Applied M 2021 Journal of applied mathematics & informatics Vol.39 No.1
This study attempts to predict the price of gold futures, a real financial product, using ARIMA and LSTM. The wavelet analysis was applied to the data to predict the price of gold futures through LSTM and ARIMA. As results, it is confirmed that the prediction performance of the existing model of predict was improved. the case of predict of price of gold futures, we confirmed that the use of a deep learning model that is not affected by the non-stationary series data is suitable and the possibility of improving the accuracy of prediction through wavelet analysis.
이동희(Donghui Lee),장한익(Han-Ik Jang),윤지훈(Ji-Hun Yoon) 한국경영과학회 2020 經營 科學 Vol.37 No.2
The 2007 U.S. subprime mortgage crisis shows the housing market crisis could expand into the financial market. Thus, if there is an early indicator of the housing market crisis, the financial crisis can be predicted in advance. This study calculates a volatility index for housing prices and examines whether the volatility index can account for information in the housing market, such as housing prices and the rate of change. The calculated volatility index confirmed that an increase over a fall in domestic housing prices was the predominant factor, especially the continued upward pressure on housing prices since 2016. On the other hand, the housing market has shifted from an upward trend to a downward trend since the second half of 2018 with each volatile index rising. As such, the ability to explain the housing price volatility indicators calculated for changes in the housing market was identified and the volatility indicators produced by them could be used as evidence to predict the housing market.
이상복(Sangbok Lee),하동휘(Donghui Ha),이형진(Hyoung Jin Lee),노태성(Tae-Seong Roh) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.12
액체 수소를 연료로 사용하는 팽창기 사이클 액체 로켓 엔진에 대한 성능해석을 수행하였다. 액체수소의 물성치는 온도에 따른 para 수소와 ortho 수소의 비율을 적용하였으며 펌프 및 터빈 전후에서의 물성치와 질유량 등을 계산하도록 구성하였다. Vinci 엔진의 성능과 비교하여 연소실과 노즐에서는 1% 이내의 오차를 나타내었고 펌프와 터빈에서도 압력 및 유량에 대해서 최대 오차 5% 이내의 결과를 나타내었다. Analysis of liquid hydrogen rocket engine using expander cycle has been performed. The thermodynamic Properties of hydrogen were determined by the ratio of para-hydrogen to ortho-hydrogen. The properties and the mass flow rate before and after the pump and the turbine were set to be calculated. Compared to the Vinci engine performance, the errors are less than 1% in the combustion chamber and the nozzle, and less than 5% in the pumps and turbines about mass flow rate and pressure.