• Journal of Positioning, Navigation, and Timing
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• v.1 no.1
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• pp.29-34
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• 2012

A software GNSS signal generator for the GPS L1/L2/L5 and Galileo E1/E5 signals is proposed in this paper. And this signal generator is designed and implemented with several components by considering the reuse and expansion of components for similar GNSS signals. The characteristics of the reusability of the components are confirmed with the carrier generation and the band-pass filter components. And the functionality of the GNSS multi-band IF signal generator is validated by using the commercial software GPS L1 receiver, and the performance of signal acquisition, tracking and accuracy of horizontal position error are analyzed for this validation. As a result, the GPS L1 signal generator operates successfully and it could be expected that other signal generators also operate well because most of components are the same as those of the GPS L1 signal generator.

• Journal of Positioning, Navigation, and Timing
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• v.8 no.4
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• pp.165-173
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• 2019

In this paper, we apply a discrete wavelet packet transform (DWPT) to reduce the influence of interference in global positioning system (GPS) signals and compare the interference mitigation performance of various wavelets. By applying DWPT to the received signal, we can gradually divide the received signal band into low-pass and high-pass bands. After calculating the average power for the separate bands, we can determine whether there is interference by comparing the value with the given threshold. For a band that includes interference, we can reconstruct the whole band signal using inverse DWPT (IDWPT) after applying a nulling method that sets all of the wavelet coefficients to 0. The reconstructed signals are correlated with the pseudorandom noise (PRN) codes to acquire GPS signals. The performance evaluation is based on the number of satellite signals whose peak ratio (defined as the ratio of the first and second correlation peak values in the acquisition stage) exceeds the threshold. In this paper, we compare and evaluate the performance of 6 wavelets including Haar, Daubechies, Symlets, Coiflets, Biorthogonal Splines, and Discrete Meyer.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.1
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• pp.1-8
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• 2017

In this study, to design a multi-GNSS receiver using single RF front-end, the receiving performances for various frequency plans were evaluated. For the fair evaluation and comparison of different frequency plans, the same signal needs to be received at the same time. For this purpose, two synchronized RF front-ends were configured using USRP X310, and PC-based software was implemented so that the quality of the digital IF signal received at each front-end could be evaluated. The software consisted of USRP control, signal reception, signal acquisition, signal tracking, and C/N0 estimation function. Using the implemented software and USRP-based hardware, the signal receiving performances for various frequency plans, such as the signal attenuation status, overlapping of different systems, and the use of imaginary or real signal, were evaluated based on the C/N0 value. The results of the receiving performance measurement for the various frequency plans suggested in this study would be useful reference data for the design of a multi-GNSS receiver in the future.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.337-341
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• 2016

Purpose: Evaluation of atmospheric conditions for proper timing of spray application is important to prevent off-target movement of crop protection materials. Susceptible crops can be damaged downwind if proper application procedure is not followed. In our previous study, hourly data indicated unfavorable conditions, primarily between evening 18:00 hrs in the evening and 6:00 hrs next morning, during clear conditions in the hot summer months in the Mississippi delta. With the requirement of timely farm operations, sub-hourly data are required to provide better guidelines for pilots, as conditions of atmospheric stability can change rapidly. Although hourly data can be interpolated to some degree, finer resolution for data acquisition of the order of 15 min would provide pilots with more accurate recommendations to match the data recording frequency of local weather stations. Methods: In the present study, temperature and wind speed data obtained at a meteorological tower were re-sampled to calculate the atmospheric stability ratio for sub-hour and hourly recommendations. High-precision evaluation of temperature inversion periods influencing atmospheric stability was made considering strength, time of occurrence, and duration of temperature inversion. Results and Discussion: The results indicated that atmospheric stability could be determined at different time intervals providing consistent recommendations to aerial applicators, thereby avoiding temperature inversion with minimal off-target drift of the sprayed liquid.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.349-358
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• 2023

The Satellite-Based Augmentation System (SBAS) plays a significant role in the fields of aviation and navigation: it corrects signal errors of the Global Navigation Satellite System (GNSS) and provides integrity information to facilitate precise positioning. These SBAS systems have been adopted as international standards by the International Civil Aviation Organization (ICAO). In recent SBAS system design, the Minimum Operational Performance Standards (MOPS) defined by the Radio Technical Commission for Aeronautics (RTCA) must be followed. In October 2014, South Korea embarked on the development of a Korean GPS precision position correction system, referred to as Korea Augmentation Satellite System (KASS). The goal is to achieve APV-1 Standard of Service Level (SoL) service level and acquisition of CAT-1 test operating technology. The first satellite of KASS, KASS Prototype 1, was successfully launched from the Guiana Space Centre in South America on June 23, 2020. In December 2022 and June 2023, the first and second service signals of KASS were broadcasted, and full-scale KASS correction signal broadcasting is scheduled to start at the end of 2023. The aim of this study is to analyze the precision of both the GNSS system and KASS system by comparing them. KASS is also compared with Japan's Multi-functional Satellite Augmentation System (MSAS), which is available in Korea. The final objective of this work is to validate the usefulness of KASS correction navigation in the South Korean operational environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1133-1143
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• 2005

In this paper, we propose an enhanced two-step search scheme for rapid and reliable signal acquisition in UWB systems under multipath channels. The proposed TSS-LS (Two-Step Search scheme with the Linear search based Second step) achieves rapid acquisition performance comparable to the conventional TSS-BS (Two-Step Search scheme with the Bit reversal search based Second step) already proposed by the authors, based on the single-dwell search with two-step thresholds and search windows. However, unlike the TSS-BS which employs the bit reversal search in the second step, the proposed TSS-LS utilizes the linear search in the second step to improve the reliability of signal acquisition. Simulation results with multipath channel models by IEEE 802.15.3a show that the two-step search schemes for the UWB signal acquisition can achieve sig nificant reduction of the required mean acquisition time as compared to general search schemes. In addition, we observe that the proposed TSS-LS achieves quite good bit error rate performance for large signal-to-noise ratios, which is favorably comparable to the case of ideal perfect timing.

• Journal of Contemporary Eastern Asia
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• v.16 no.1
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• pp.93-113
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• 2017

This study aimed to determine the changes in the local fiscal structure brought about by the change in the transaction tax, including the acquisition tax, by the central government. The review of the analysis results proved the following. First, the government's transaction tax exemption policy effectively influenced the expansion of the local fiscal budget. Transaction tax exemptions such as acquisition tax exemptions would not contribute to the expansion of the local fiscal budget in the short run, but may do so in the long run. Second, the review of the effect of the transaction tax exemption policy by the central government on the local fiscal structure confirmed that its impact on the local fiscal structure may vary depending on the timing of such tax exemption. Third, the overall local fiscal structure as a result of the transaction tax exemption by the central government was confirmed to have been influenced more by the fiscal capability of the local government than by the income level of the local residents. In conclusion, the stimulation of real estate transactions using tax tools may positively influence the overall fiscal structure of local governments, but it would also put pressure on the fiscal management of local governments because it is largely influenced by the fiscal capability of the local governments.

• Journal of Distribution Science
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• v.18 no.5
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• pp.71-81
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• 2020

Purpose: This case study illustrates the successful entry of Saudi Aramco in the Korean market and how it grows to become one of the world's largest integrated energy enterprises. Research design, data and methodology: This case investigates diverse secondary sources to examine the entry strategy of Aramco in Korea, such as several interviews including public and anonymous dialogues, periodicals, dispatches (i.e. news articles and magazines), annual reports, industrial reports, and others. Results: The main concern for the international strategic approaching of Saudi Aramco is to enter into Korean market by joint venture with SsangYong Oil (today's S-Oil Corporation) in 1991 and finally, ending by Acquisition of S-Oil in 2015. This acquisition of local No.3 company, S-Oil, in Korea is the successful case in Asian Markets overcoming liability of foreignness. Moreover, Saudi Aramco's global distribution strategy through localization in the Korean market is appropriate given the market conditions, timing, effectiveness, and efficiency by sharing their resources and collaborating. Conclusions: It would be valuable, unique, and real story to analyze global leading company's entry and globalization strategy in overseas market. In addition, this study provides decision-makers with a significant and more strategic implication for the overseas expansion of businesses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.874-881
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• 2008

This paper presents an automatic frequency control algorithm for RTLS DS-SS modem based on the standard of ISO/IEC 24730-2. The presented automatic frequency control algorithm consists of frequency acquisition mode and frequency tracking mode, and the frequency acquisition mode is divided into the angle estimation step for frequency offset estimation and the verification step for removing the angle ambiguity. In the angle estimation step, three different sub-bit angles are estimated according to the timing intervals, then the estimates are used to re move the angle ambiguity in the verification step. The theoretical analysis and the simulation results of the proposed frequency control algorithm are presented.

• Journal of Distribution Science
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• v.17 no.1
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• pp.47-56
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• 2019

Purpose - This case study illustrates the story of eBay Korea, which owns two most leading Korean open market companies, AUCTION and Gmarket. The main concerns are to take over the Korean top domestic companies one by one, then, emerge these two giants through its well-developed post-merger Integration by eBay, an American multinational corporation. Research design, data, and methodology - This case explores various secondary resources such as periodicals, annual reviews, magazine, news articles, commentaries, even some interview materials related to 'eBay Korea' and industry source on condition of anonymity based on the critical reviewing of existing studies on these topics as well. Results - The findings of this study show the merger and acquisition of two market leaders in Korea is the only successful case in Asian Markets. The eBay's choice of entry mode is appropriate considering the timing, synergy and efficiency by sharing their resources. Conclusions - This study examines the successful entry and settlement process of foreign, multinational company through mergers and acquisitions in the Korean market. This would be a valuable in the studies of International Business and Global entry or distribution strategy in the e-commerce and open market dealing with M&A and its post-merger integration.