• Journal of Advanced Navigation Technology
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• v.12 no.4
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• pp.311-316
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• 2008

A configuration scheme of optical link effectively compensating chromatic dispersion and nonlinear effects accumulated in optical link with single mode fibers (SMFs) is proposed. The proposed optical link configuration consist of optical phase conjugator (OPC) placed at middle of total transmission length and inline dispersion management (DM) as a role of compensating cumulated in each optical repeater of SMF by dispersion compensating fiber (DCF). Net residual dispersion (NRD) of this optical link is designed to be controlled through precompensation and postcompensating. The precompensation and postcompensation are designed to be determined by DCF after transmitter and before receiver, respectively. It is confirmed that optical link configuration with symmetric dispersion map with respect to OPC, which is implemented by controlling NRD through both precompensation and postcompensation, is better to be effective and adaptive than other configuration with NRD controlled by only precompensation or postcompensation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.958-964
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• 2007

In this paper, we derive the relationship between the bit error probability (BEP) of maximum a posteriori (MAP) bit detection and the bit minimum mean square error (MMSE), that is, the BEP is greater than a quarter of the bit USE and less than a half of the bit MMSE. By using this result, the lower and upper bounds of the derivative of the mutual information are derived from the BEP and the lower and upper bounds are easily obtained in the multiple-input multiple-output (MIMO) communication systems with the bit-linear linear-dispersion (BLLD) codes in the Gaussian channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1A
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• pp.1-9
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• 2005

We have studied the dispersion properties of a 40 channel x 10 Gbit/s wavelength division multiplexer(WDM) transmission link using standard single mode fiber with all EDFA amplification over 30 x 100 km spans. The dispersion map of the link was investigated by adding fiber sections with positive or negative dispersion at the transmitter, within each amplifier span, and at the receiver. Optimum combinations of these dispersive fiber lengths were attained to significantly enhance the overall transmission performance.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.69.2-69.2
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• 2012

NGC 6861 is the brightest S0 galaxy in the Telescopium group. It has unusually high central stellar velocity dispersion (~400 km/s) and clear rotation (~250 km/s). Considering the well-known M-sigma relation, this large central dispersion implies that the central supermassive black hole (SMBH) has mass comparable to the most massive black holes in the Universe. However, the mass implied by the bulge luminosity-SMBH mass relation is an order of magnitude lower than that predicted by the M-sigma relation. In order to determine the origin of this inconsistency, we obtain integral field spectroscopy using the Wide Field Spectrograph (WiFeS) on the ANU 2.3m telescope. The data are used to map the velocity and velocity dispersion fields which show that our measurements are consistent with those from the other literature. The large field of view the WiFeS observations have allows us to map the kinematics of a much greater portion of NGC 6861 and reveals that the eastern part of the galaxy has higher velocity and dispersion than the rest of halo. We discuss the origin of the unusual fast rotation and the discrepancy of two SMBH mass estimations from three plausible perspectives: 1) the interaction between subgroups of NGC 6861 and its counterpart, NGC 6868; 2) the inhibited growth of the stellar bulge by the AGN activity which leads to an underestimate the SMBH mass when using the bulge luminosity-SMBH mass relation; and 3) gas rich minor mergers that could be crucial for increasing both rotation velocity and velocity dispersion during the evolution of NGC 6861.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.27-33
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• 2009

New optical transmission link techniques improving performance of WDM channels, each channel have bit rate of 40 Gbps, are proposed. The proposed optical link configuration consist of optical phase conjugator (OPC) placed at middle of total transmission length, and dispersion management (DM) as a role of compensating dispersion cumulated in transmission line. It is confirmed that Q-factor of total channels are improved by combining OPC and DM in optical transmission link as a result of following fact; DM not only mitigate the cumulated dispersion in total transmission line but also help OPC to compensate optical nonlinearities. And, it is confirmed that the improvement of Q-factor of overall WDM channels depends on net residual dispersion (NRD) of optical link.

• The Journal of the Korea institute of electronic communication sciences
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• v.1 no.1
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• pp.56-62
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• 2006

Currently, Most of the Backhual and Submarine's networks are being installed using DWDM and EDFA to deal with dramatically increasing internet traffic. In a conventional type optical system, the so-called 3R repeater, fiber non- linearity was not significant factor but it is one of the most important consideration when designing new DWDM network based on the EDFAs. To minimize the signal pulse distortion in long-haul optical network, Zero-dispersion fiber is indispensable but causes the fiber non-linearity. Therefore this conflicting problems should be managed to transmit a high-speed capacity traffic. In this paper, key technologies in DWDM submarine optic network were found out for a high capacity traffic and introduced the dispersion management way for solving the conflicting problems between Zero-dispersion and non-linearity. Lastly designed a dispersion map in section between Korea and Hong-kong.

• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.331-337
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• 2022

The length of optical fiber in dispersion-managed link combined with optical phase conjugation to compensate for signal distortion caused by chromatic dispersion and nonlinear Kerr effect is a major factor determining the compensation effectiveness. The dispersion-managed link consists of several fiber spans in which standard single mode fiber and dispersion compensating fiber are arranged. In this paper, the compensation effect in the link that changes residual dispersion per span only by adjusting the length of one type of optical fiber, which is different in the first half link and the second half link with respect to optical phase conjugator (OPC), has been investigated. It was confirmed that the best compensation for 960 Gb/s wavelength division multiplexed signal could be obtained in the dispersion-managed link, in which the cumulative dispersion profile is symmetric around the OPC, and the cumulative dispersion amount is all positive in the first half, and all the cumulative dispersion amount is distributed negatively in the second half.

• Journal of the Korean Geophysical Society
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• v.6 no.4
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• pp.245-259
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• 2003

Two multichannel analysis of surface wave (MASW) surveys were conducted over a soil site in Tacoma Water's Green River Facility, Washington, where construction of a chemical treatment facility had been planned. The purpose of the surveys was to compare soil stiffness characterized by shear-velocity (Vs) distribution before and after Deep Dynamic Compaction (DDC) operation that was designed to improve the soil stiffness. Site soil consisted of very heterogeneous gravel and cobbles in a sand-and-silt matrix. Results from each survey are represented by two 2-D Vs maps delineating Vs variation of soil below the surveyed lines. One map was constructed from those dispersion curves that were analyzed with a significant amount of subjective judgment involved, whereas the other map was constructed from those dispersion curves analyzed with as much objective information as possible. Comparison of 2-D Vs maps indicates that Vs actually decreased after the DDC operations, possibly due to the loss (or reduction) of cohesive bonding between soil particles caused by the compaction operations.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.96-99
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• 2003

Land cover map is a typical GIS database which shows the Earth's physical surface differentiated by standardized homogeneous land cover types. Satellite images acquired by Landsat TM were primarily used to produce a land cover map of 7 land cover classes; however, it now becomes to produce a more accurate land cover classification dataset of 23 classes thanks to higher resolution satellite images, such as SPOT-5 and IKONOS. The use of the newly produced high resolution land cover map of 23 classes for such activities to estimate non-point sources of pollution like water pollution modeling and atmospheric dispersion modeling is expected to result a higher level of accuracy and validity in various environmental monitoring results. The estimation of pollution from non-point sources using GIS-based modeling with land cover dataset shows fairly accurate and consistent results.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.1
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• pp.1-9
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• 2017

The scale of disaster and damage witnessed in the 2004 Indian Ocean Tsunami and the 2011 Great East Japan Tsunami has motivated researchers in developing foolproof disaster mitigation techniques for safety of coastal communities. This study focuses on developing tsunami hazard map by numerical modeling at Imwon Port to minimize losses of human beings and property damage when a real tsunami event occurs. A hazard map is developed based on inundation maps obtained by numerical modeling of 3 past and 11 virtual tsunami cases. The linear shallow-water equations with manipulation of frequency dispersion and the non-linear shallow-water equations are employed to obtain inundation maps. The inundation map gives the maximum extent of expected flooded area and corresponding inundation depths which helps in identifying vulnerable areas for unexpected tsunami attacks. The information can be used for planning and developing safety zones and evacuation structures to minimize damage in case of real tsunami events.