• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.98-104
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• 2009

Tone injection scheme has been known as one of PAPR(Peak to Average Power Ratio) reduction methods deployable to multi-carrier system like OFDM(Orthogonal Frequency Division Multiplexing). The basic idea in tone injection scheme is to enforce the constellation size larger so that each of original constellation points is mapped into the preassigned distinct points. Along the accomplishment of tone injection, it needs great amount of computations to search out not only an appropriate frequency but a phase. Although there is no loss of transmission rate is expected because of no need to send the overhead, the tone injection scheme has not been preferable due to its enormous computations. To alleviate the amount of complexity, this paper proposes the GA(Genetic Algorithm) based tone injection scheme such that its complexity is reduced comparing with that of the conventional method. The simulation results show that the proposed GA based tone injection scheme approaches the PAPR performance associated with the conventional exhaustive search method at the expense of low computations.

• Journal of Advanced Navigation Technology
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• v.23 no.3
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• pp.237-244
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• 2019

Since SBAS provides users with GNSS orbit, clock, and ionospheric corrections and integrity, the more precise positioning is possible. As the SBAS service area is expanded due to the development of the SBAS and the installation of the additional ground stations, there is a region where two or more SBAS messages can be received. However, the research on multi-constellation SBAS selection method has not carried out. In this study, we compared the result of positioning accuracy after applying the SBAS correction selected by using WAAS priority, EGNOS priority, or error covariance comparison method to LEO satellites in the regions where WAAS and EGNOS signals are transmitted simultaneously. When using WAAS priority method, 3D orbit error is smallest at 2.57 m. The covariance comparison method is outperform at the center of the overlap region far from each WAAS and EGNOS stations. In the eastern region near the EGNOS stations, the 3D orbit errors using EGNOS priority method is 8% smaller than the errors using the WAAS priority method.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.33-37
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• 2006

After USA removed the Selective Availability(SA), Global Positioning System(GPS) has monopolized tile world market and other countries have been depended on GPS, absolutely So the other countries, Russia, European Community(EC) and Japan, which apprehend to monopolize in technical and strategic parts, are developing the next generation GNSS including GLONASS Galileo and JRANS. And the countries are planning to provide the another GNSS. This research has focused on the next generation GNSS system based on GPS and Galileo system with developing a GNSS simulation software, named as GIMS2005, which generates and analyzes satellite constellation and measurements. Based on the software, a variety of simulation tests have been carried out to recognize limits of GPS-only system and potential benefits of integrated GPS/Galileo positioning In terms of satellite geometry strength and solution accuracy.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.18 no.2
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• pp.108-112
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• 2007

Otolaryngological manifestations of acid reflux include a wide range of pharyngeal and laryngeal symptoms ; and the constellation of symptoms has been called laryngopharyngeal reflux (LPR). In the absence of definite diagnostic criteria, LPR disease remains a subjective entity. A diagnosis of LPR is usually based on response of symptoms to empirical treatment. Investigative modalities such as pH monitoring and, more recently, impedance studies are generally reserved for treatment failures. LPR usually requires more aggressive and prolonged treatment to achieve regression of both symptoms and laryngeal findings. The suppression of gastric acid and secretion with anti-secretary agents has been the mainstay of medical treatment for patients with acid-related disorders. The suppression of gastric acid secretion achieved with Hz-receptor antagonist $(H_2RA)$ has proved suboptimal for relief of reflux symptoms. The rapid development of tolerance and rebound acid hypersecretion after the with-drawal of $H_2RA$ limit their clinical use. Proton pump inhibitors (PPI) have been proved to be very effective for suppressing intragastric acidity, but the optimal dose and duration is unknown. Current evidence indicates that pharmacologic intervention should include, at a minimum, a 3 month trial of twice daily PPI. Symptoms of LPR improve over 2 months of therapy. The physical findings of LPR resolve more slowly than the symptoms and this continues through out at least 6 months of treatment. For most patients with LPR, twice daily dosing with a PPI is usually recommended for an initial treatment for a period of no less than 6 months treatment, and lifetime treatment may be required.

• The Journal of Engineering Geology
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• v.32 no.3
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• pp.363-376
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• 2022

An area under construction for a living facility collapsed around 12:48 KST on 13 January 2021 in Sa-dong, Ansan-si, Gyeonggi-do. There were no casualties due to the rapid evacuation measure, but part of the temporary retaining facility collapsed, and several cracks occurred in the adjacent road on the south side. This study used the potential of synthetic aperture radar (SAR) satellite for surface property changes that lies in backscattering characteristic to map the collapsed structure. The interferometric SAR technique can make a direct measurement of the decorrelation among different acquisition dates by integrating both amplitude and phase information. The damage proxy map (DPM) technique has been employed using four high-resolution Constellation of Small Satellites for Mediterranean basin Observation (COSMO-SkyMed) data spanning from 2020 to 2021 during ascending observation to analyze the collapse of the construction. DPM relies on the difference of pre- and co-event interferometric coherences to depict anomalous changes that indicate collapsed structure in the study area. The DPMs were displayed in a color scale that indicates an increasingly more significant ground surface change in the area covered by the pixels, depicting the collapsed structure. Therefore, the DPM technique with SAR data can be used for damage assessment with accurate and comprehensive detection after an event. In addition, we classify the amplitude information using support vector machine (SVM) and maximum likelihood classification algorithms. An investigation committee was formed to determine the cause of the collapse of the retaining wall and to suggest technical and institutional measures and alternatives to prevent similar incidents from reoccurring. The report from the committee revealed that the incident was caused by a combination of factors that were not carried out properly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.1
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• pp.18-27
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• 2004

In this paper, we presents an analytical simulation procedure for evaluation in baseband digital modulated signals distortions in the present of RF power amplifier(SSPA) nonlinear behavior and backoff operations of OFDM wireless transmission system. we obtained the optimum nonlinear transfer function of designed SSPA with the SiGe HBT bias currents of OFDM multi-channel wireless transmission system and compared this transfer function to SSPA nonlinear modeling functions mathematically, we finds optimum bias conditions of designed SSPA. With the derived nonlinear modeling function of SSPA, We analysed the PSD characteristics of in-band and out-band output powers of SSPA EVM measurement results of distorted constellation signals with the input power levels of SSPA. The results of paper can be applied to find the SSPA linearly with optimum bias currents and determine the SSPA input backoff bias for AGC control circuits of SSPA.

• Archives of design research
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• v.19 no.5 s.67
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• pp.223-232
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• 2006

This is a study related to CI and BI, focusing on the change of an organization: a corporation. The organization of a corporation, in order to achieve the goal of an organization, get the injection(labor, technology, resources) and send it out to society by transforming them into a form of products(goods and services). While this production means the organization plays a social part for the accomplishment of a goal of the society, it indicates the society exerts influence on the process of setting the goal of an organization. On the other hand, a society influences the existence of a corporation through need and change directly or indirectly and in order to adjust to this, a corporation adapt the form of the organization to the need and change of a society. This study presents the causes of change from CI to BI according to the organizational changes of a corporation and theoretical basis through Elbin Toefler's "The Adaptive Corporation".

• Journal of Astronomy and Space Sciences
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• v.26 no.3
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• pp.375-402
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• 2009

Korean historical constellations and their names are similar to Chinese ones. Although Korean historical astronomy is influenced by China, they have distinct differences in each shape and names of the constellations. We, therefore, compare Bocheonga (步天歌) of the early Joseon dynasty (朝鮮, $1392{\sim}1910$) preserved in Gyujanggark (奎章閣) with that of the Sui dynasty ((隋代, $581{\sim}618$ of China written by Wang Ximing(王希明) in terms of star charts and descriptions of the contents. We find out that the two books are partly different all over the books. First, there are definite differences in preface, three area of constellations (三垣) in the heaven, and the description of the Milky Way. Second, some of constellations show different in shape, the number of stars. Especially connecting pattern in some constellations shows different in each other. Third, Joseon Bocheonga describes their colors for some stars. These mean that Joseon has a unique tradition of star maps unlike Chinese one. We also summarize the differences and distinctive characteristics of Joseon star charts compared with Chinese ones.

• Journal of Navigation and Port Research
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• v.29 no.8 s.104
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• pp.763-770
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• 2005

Global Navigation Satellite System (GNSS) has become an indispensable tool for providing precise position, velocity and time information for many applications like traditional surveying and navigation etc. However, Global Positioning System (GPS), which was developed and is maintained and operated by the U.S. Department of Defence (DoD), has monopolized the world industry and market, and hence there exists the situation that most of GNSS users absolutely depend upon the GPS. In order to overcome the monopoly, some countries, such as Russia, Japan and European Union (EU), have developed their own GNSSs, so-called GLONASS, JRANS and Galileo systems. Among them, the most prospective system in near future is EU's Galileo system scheduled to launch in 2008. This research has focused on the next generation GNSS system based on GPS and Gralileo system with developing a GNSS simulation software, named as GIMS2005, which generates and analyzes satellite constellation and measurements. Based on the software, a variety of simulation tests have been carried out to recognize limits of GPS-only system and potential benefits of integrated GPS/Galileo positioning. Geometry simulation results have showed that comparing with GPS-only case, the number qf visual satellites, Dilution of Precision (DOP) values, internal reliabilities and external reliabilities.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.24-31
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• 2007

DVB-T (Digital Video Broadcasting-Terrestrial) is an important multimedia broadcasting technology capable of high data-rate transmission and adopted by Europe. OFDM (Orthogonal Frequency Division Multiplexing) is the backbone technique employed in DVB-T to support multimedia services that have various bandwidths. Unfortunately, an OFDM signal has a large PAPR (Peak-to-Average Power Ratio). In this paper, we investigate the performance of a simple PAPR reduction scheme for the DVB-T system, which requires no change of a receiver structure or no additional information transmission. The approach we employed is clipping in the time and frequency domains. The time-domain clipping is carried out with a predetermined clipping level while the frequency-domain clipping is done within EVM (Error Vector Magnitude). This approach is suboptimal with lower computational complexity compared to the optimal method. The simulation results demonstrate that the proposed one is getting more effective at lower modulation levels and with more allowed constellation error.