• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.488-494
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• 2013

For the activeness and autonomy of a sensor network, the efficient migration method of a mobile agent and the consistent naming services are the required components of a sensor network. Accordingly, this paper presented the implementation of backward migration of an active rule mobile agent applying the naming method based on RMI that used the meta_table including the informations about the components of a sensor network. This study implemented based on the extension of the forward migration[12], and the results of the various experiments present the efficacy of mobile agent middleware system and the possibility of constructing efficient sensor network application environment. And, the results of this study are able to enhance the adaptability on dynamic changes of environment in sensor network application development.

• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.934-937
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• 2012

Since a migration method of the mobile agent is a factor that affects the overall performance of the entire distributed system, it is necessary to find efficient migration methods of the mobile agent within the sensor network using the various metadata related on the sensor network. Accordingly, this paper proposes the directional(forward and backward) migration methods of an active rule mobile agent applying the naming method that used the information of the meta_table. The results of the various experiments in this study present the efficacy of mobile agent middleware system and the possibility of constructing efficient sensor network application environment.

• The Transactions of the Korea Information Processing Society
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• v.6 no.7
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• pp.1770-1776
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• 1999

Mobile agent technology has received great attention in the last years as a new paradigm for distributed processing systems. Mobile agents are autonomous objects that can migrate from node to node of a computer network. But, due to hosts or communication nodes failures, mobile agents may be blocked or crashes even if there are other nodes available that could continue processing. To cope with above, this paper proposes an efficient policy by introducing the path reordering and backward recovery to ensure the migration of mobile agents. The proposed migration policy will be provided the migration reliability of mobile agents as autonomously as possible, and it is implemented in the MOS, a mobile object system model developed by the Java language.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.6
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• pp.666-684
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• 2019

The horizontal distributions of eggs and larvae of chub mackerel Scomber japonicus were extensively surveyed in the vicinity of Korean waters between 31°75'N and 36°50'N during May and June in 2016 and 2017 (total of four surveys). We used a coupled bio-physical model (DisMELS) that combines an individual-based model (IBM) incorporating vertical migration of larvae and temperature-dependent survival to understand transport processes in the early life stage. Using the distributions of eggs and larvae from surveys, the potential spawning grounds were estimated at the northwest and southeast of Jeju Island and the central East China Sea in May, and at the southwestern East Sea and southern West Sea in June by running the model backward in time. In forward experiments within 30 days from the backward results, most larvae were transported to both the Korean and Japanese sides of the East Sea through the Korea Strait. However, the larvae released in the central East China Sea were transported to the Japanese side only, while those released in the southern West Sea were retained within that region. The survival rates at 30 days after release based on the simulation incorporating temperature-dependent survival throughout May and June were 29.7% in 2016 and 28.8% in 2017.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.1
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• pp.37-47
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• 2023

The black cutworm, Agrotis ipsilon (Hufnagel), is an important crop pest worldwide that feeds more than 80 plant species including cabbage, potato, maize, wheat and bean, and this moth is a typical pest attacking underground parts of crops. It has been known in farm booklets that the larvae of A. ipsilon overwinter in the soil in Korea, but no definitive data exist yet. This study was conducted to evaluate that the specific appearance time of A. ipsilon observed actually in the field could be explained when we assumed that this pest overwinters in a form of larvae or pupae. Degree day-based phenology models were applied for tracking forward or backward to find the predicted developmental stage which developed at a specific stage found in the field. As a result of the analysis, it was confirmed that an initial population could be established in a group that does not overwinter as larvae or pupae in Korea. In other words, the appearance of adults in early March to April could not be explained by the presence of domestic overwintering populations. Populations that overwinter as larvae or pupae in Korea were able to emerge as adults in June to July at the earliest. Therefore, the group of adults appearing in early spring is highly likely to be a population that migrated from outside Korea. Taken together, it was estimated that the colony of A. ipsilon in Korea would be formed by a mixture of a migrant population through long-distance migration and a overwintering population.

• Geophysics and Geophysical Exploration
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• v.5 no.1
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• pp.33-45
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• 2002

It was necessary to devise new techniques to overcome and enhance the resolution limits of traveltime tomography. Waveform inversion has been one of the methods for giving very high resolution result. High resolution image could be acquired because waveform inversion used not only phase but amplitude. But waveform inversion was much time consuming Job because forward and backward modeling was needed at each iteration step. Velocity-stress method was used for effective modeling. Resolution limits of imaging methods such as travel time inversion, acoustic and elastic waveform inversion were investigated with numerical models. it was investigated that Resolution limit of waveform inversion was similar tn resolution limit of migration derived by Schuster. Horizontal resolution limit could be improved with increased coverage by adding VSP data in cross hole that had insufficient coverage. Also, waveform inversion was applied to realistic models to evaluate applicability and using initial guess of travel time tomograms to reduce non-linearity of waveform inversion showed that the better reconstructed image could be acquired.

• Journal of Environmental Science International
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• v.29 no.1
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• pp.55-68
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• 2020

The purpose of this study is to investigate the relationship of fine dust PM₁₀ and heavy metals in PM₁₀ in Asian dust flowing into Gwangju from 2013 to 2018. The migration pathways of Asian dust was analyzed by backward trajectory analysis using HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model, and the change of heavy metal concentration and heavy metal content per 1 ㎍/㎥ of fine dust PM₁₀ in Gwangju area were analyzed. Also, the characteristics of the heavy metals were analyzed using the correlation between the heavy metals in PM₁₀. As a result of analyzing Asian dust entering the Gwangju region for 6 years, the average concentration of PM₁₀ measured in Asian dust was 148 ㎍/㎥, which was about 4.5 times higher than in non-Asian dust, 33 ㎍/㎥. A total of 13 Asian dust flowed into the Gwangju during 6 years, and high concentration of PM10 and heavy metals in that were analyzed in the C path flowing through the Gobi/Loess Plateau-Korean Peninsula. As a result of the correlation analysis, in case of Asian dust, there was a high correlation between soil components in heavy metals, so Asian dust seems to have a large external inflow. On the other hand, in case of non-Asian dust, the correlation between find dust PM₁₀ and artificial heavy metal components was high, indicating that the influence of industrial activities in Gwangju area was high.