• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.102-107
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• 2006

Recently, rapid developments in computer hardware have enabled reverse-time migration to be applied to various production imaging problems. As a wave-equation technique using the two-way wave equation, reverse-time migration can handle not only multi-path arrivals but also steep dips and overturned reflections. However, reverse-time migration causes unwanted artefacts, which arise from the two-way characteristics of the hyperbolic wave equation. Zero-lag cross correlation with diving waves, head waves and back-scattered waves result in spurious artefacts. These strong artefacts have the common feature that the correlating forward and backward wavefields propagate in almost the opposite direction to each other at each correlation point. This is because the ray paths of the forward and backward wavefields are almost identical. In this paper, we present several tactics to avoid artefacts in shot-domain reverse-time migration. Simple muting of a shot gather before migration, or wavefront migration which performs correlation only within a time window following first arriving travel times, are useful in suppressing artefacts. Calculating the wave propagation direction from the Poynting vector gives rise to a new imaging condition, which can eliminate strong artefacts and can produce common image gathers in the reflection angle domain.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.11 no.3
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• pp.94-106
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• 2008

As populations inhabiting in natural ecosystem are fragmented by artificial barriers and habitats are destructed by development, extinction possibility of species is getting higher. It is necessary to design and to manage conservation areas and corridors considering animals' movement and migration for sustainable species diversity in present circumstances. 'Least-cost modeling' is one commonly employed approach in which dispersal costs are assigned to distinct habitat types and the last-costly dispersal paths among habitat patches are calculated using a geographical information system (GIS). This study aims to design ecological corridor using least-cost path method and to apply it to a regional ecological network considering movability of medium-large size mammals. This study was carried out over the metropolitan area, which has been deforested by rapid urbanization. Nevertheless there is connected with Gangwon province, Baekdudaegan mountain range and DMZ, considered where many forest species can migrate to this region. This study employs such an approach to develop least-cost path models for medium-large size mammals, have inhabited for this entire region. Considering those species, two forest areas as a source of species supply and forest areas more than 1,000ha are selected as focal forest areas. Movement and migration paths from species supply sources to focal forest areas are calculated by applying landscape permeability theory using land cover map, road density map and land slope map. Results showed least-cost paths from species supply sources to focal forest areas on two species. Wildcat and roe deer are different in some least-cost paths caused by their landscape permeability but paths show generally same specifics. The result of considering regional distribution of expected movement and migration paths to regional ecological network, low altitude mountains of western metropolitan area are evaluated important area for species connectivity. In national or regional levels ecological connectivity is essential to promote species diversity and to preserve integrated ecosystem. This study concludes that developing least-cost models from similar empirical data could significantly improve the utility of these tools.

• Economic and Environmental Geology
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• v.52 no.1
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• pp.37-48
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• 2019

In geological $CO_2$ sequestration, the behavior of $CO_2$ within a reservoir can be characterized as two-phase flow in a porous media. For two phase flow, these processes include drainage, when a wetting fluid is displaced by a non-wetting fluid and imbibition, when a non-wetting fluid is displaced by a wetting fluid. In $CO_2$ sequestration, an understanding of drainage and imbibition processes and the resulting NW phase residual trapping are of critical importance to evaluate the impacts and efficiencies of these displacement process. This study aimed to observe migration and residual trapping of immiscible fluids in porous media via cyclic injection of drainage-imbibition. For this purpose, cyclic injection experiments by applying n-hexane and deionized water used as proxy fluid of $scCO_2$ and pore water were conducted in the two dimensional micromodel. The images from experiment were used to estimate the saturation and observed distribution of n-hexane and deionized water over the course drainage-imbibition cycles. Experimental results showed that n-hexane and deionized water are trapped by wettability, capillarity, dead end zone, entrapment and bypassing during $1^{st}$ drainage-imbibition cycle. Also, as cyclic injection proceeds, the flow path is simplified around the main flow path in the micromodel, and the saturation of injection fluid converges to remain constant. Experimental observation results can be used to predict the migration and distribution of $CO_2$ and pore water by reservoir environmental conditions and drainage-imbibition cycles.

• Proceedings of the CALSEC Conference
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• 2001.08a
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• pp.221-240
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• 2001

◈ UN/CEFACT & OASIS가 선도 후원 ◈ XML에 기반 한 개방적 기술 프레임웍 ◈ 업무와 업무, 업무와 사람, 사람과 업무 환경간의 전자적 업무자료의 교환을 내용과 형식에 있어 일관 되게 처리하여 단일의 범세계적 시장을 창출하기 위함 제공 기술 규격이 W3C XML규격에 합치 ebXML규격을 준수하는 전자거래 응용업무간 상호운용성 기존의 EDI 표준과 개발중인 XML 업무표준으로부터 Migration Path를 제공하여 상호 운용성과 효율성의 극대화 추구 신뢰할 만한 국제표준이 되는 것 ◈ 18개월 프로젝트 (1999. 11 -2001. 5)(중략)

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.227-234
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• 2015

To obtain geographical range and growth-kinetics parameters of mottled sake (Beringraja pulchra) populations in the Yellow Sea, three mark-recapture experiments were carried out. Overall, 991 tagged individuals were released, and 4.1% of them were recaptured with the mean release period of 339 d (range, 8-1,420 d) and the mean growth rate of $1.4cm\;mon^{-1}$ (female, $1.5cm\;mon^{-1}$; male $1.3cm\;mon^{-1}$). In the first experiment, 667 individuals were released at Heuksan Island from April to June, 2007-2009, and 30 individuals were recaptured mainly at the north and the north-east coasts of the island, indicating absence of migration to the south of the island. In the second experiment, 323 individuals were released at several fishing grounds scattered in the Yellow Sea in 2010-2013, and 11 individuals were recaptured at points deviated to all directions from the releasing points. As the last, one individual was released with pop-up satellite archival tag at a costal point ($34^{\circ}37.2$'N, $124^{\circ}59.3$'E) off Hong Island on May 21, 2010. The tagged individual migrated to a north-east location ($35^{\circ}50.4$'N, $126^{\circ}03.6$'E) of Eocheong Island by Aug. 25, 2010. The data archived for the three months in the tag indicated that the migration path had depths of 48-80 m and temperature of $12.6-14.4^{\circ}C$. The results indicated that mottled sake populations had a localized habitat ranges at the north of Heuksan Island and the west of Hong Island while growing at the rate of $1.4cm\;mon^{-1}$.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2005.11a
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• pp.519-522
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• 2005

This paper presents a self-organizing scheme for multi-agent swarm systems based on coupled nonlinear oscillators (CNOs). In this scheme, unicycle robots self-organize to flock and arrange group formation through attractive and repulsive forces among themselves. It is also shown how localized distributed controls are utilized throughout group behaviors such as formation and migration. In the paper, the proposed formation ensures safe separation and good cohesion performance among the robots. Several examples show that the proposed method for group formation performs the group behaviors such as reference path following, obstacle avoidance and flocking, and the formation characteristics such as flexibility and scalability, effectively.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.3
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• pp.222-229
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• 2005

This paper presents a self-organizing scheme for multi-agent swarm systems based on coupled nonlinear oscillators (CNOs). In this scheme, unicycle robots self-organize to flock and arrange group formation through attractive and repulsive forces among themselves. The main result is the maintenance of flexible and scalable formation. It is also shown how localized distributed controls are utilized throughout group behaviors such as formation and migration. In the paper, the proposed formation ensures safe separation and good cohesion performance among the robots. Several examples show that the proposed method for group formation performs the group behaviors such as reference path following, obstacle avoidance and flocking, and the formation characteristics such as flexibility and scalability, effectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.4787-4807
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• 2016

Although the dense interconnection datacenter networks (DCNs) (e.g. FatTree) provide multiple paths and high bisection bandwidth for each server pair, the single-path TCP (SPT) and ECMP which are widely used currently neither achieve high bandwidth utilization nor have good load balancing. Due to only one available transmission path, SPT cannot make full use of all available bandwidth, while ECMP's random hashing results in many collisions. In this paper, we present OFPT, an OpenFlow based Parallel Transport framework, which integrates precise routing and scheduling for better load balancing and higher network throughput. By adopting OpenFlow based centralized control mechanism, OFPT computes the optimal path and bandwidth provision for each flow according to the global network view. To guarantee high throughput, OFPT dynamically schedules flows with Seamless Flow Migration Mechanism (SFMM), which can avoid packet loss in flow rerouting. Finally, we test OFPT on Mininet and implement it in a real testbed. The experimental results show that the average network throughput in OFPT is up to 97.5% of bisection bandwidth, which is higher than ECMP by 36%. Besides, OFPT decreases the average flow completion time (AFCT) and achieves better scalability.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.45-55
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• 2010

While Long Term Evolution-Frequency Division Duplexing (LTE-FDD) is regarded as one of the strong candidates for "4G" wireless broadband access in FDD field, LTE-Time Division Duplexing (TDD) is emerging as one possible migration path for WiMAX-TDD in some cases as well as the migration path for Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). In this paper, we analyze the feasibility of dual mode with LTE-TDD in two combinations: dual mode LTE-FDD/TDD and dual mode Worldwide Interoperability for Microwave Access (WiMAX)-TDD/LTE-TDD. Thanks to the commonality in numerology, terminology, and frame structure between LTE-FDD and LTE-TDD, dual mode LTE-FDD/TDD looks feasible in a cost-effective manner. Thanks to the commonality in scheduling algorithm, control mechanism, and supported spectrum bands, it is shown that dual mode WiMAX-TDD/LTE-TDD looks feasible as well. It should be also noted that the commonality in numerology and frame structure is critical for building a chip while the commonality in algorithms and control mechanisms is critical to make it work.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.253-262
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• 2008

Providing Quality-of-Service (QoS) guarantee requires the reservation of resource needed to accommodate the traffic flow of service for which resource reservation protocol (RSVP) was introduced. However, if any RSVP-capable router on the path fails to accommodate the traffic flow due to lack of resource, the flow is not allowed no matter how much surplus resources other routers on the path have. In order to solve this problem, this paper proposes a resource reservation method with available resource migration between RSVP-capable routers in which the routers use the recently developed latency optimized fair queuing scheduler. The results of the simulation applying the proposed method to an evaluation network show that it may yield the gain of up to 165% compared to that in the original one in terms of the number of admitted flows.