• The KIPS Transactions:PartC
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• v.16C no.1
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• pp.51-56
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• 2009

Time synchronization algorithm in wireless sensor networks is essential to various applications such as object tracking, data encryption, duplicate detection, and precise TDMA scheduling. This paper describes CDRS that is a time synchronization algorithm using the Clock Drift rate and Reference Signals between two sensor nodes. CDRS is composed of two steps. At first step, the time correction is calculated using offset and the clock drift rate between the two nodes based on the LTS method. Two nodes become a synchronized state and the time variance can be compensated by the clock drift rate. At second step, the synchronization node transmits reference signals periodically. This reference signals are used to calculate the time difference between nodes. When this value exceeds the maximum error tolerance, the first step is performed again for resynchronization. The simulation results on the performance analysis show that the time accuracy of the proposed algorithm is improved, and the energy consumption is reduced 2.5 times compared to the time synchronization algorithm with only LTS, because CDRS reduces the number of message about 50% compared to LTS and reference signals do not use the data space for timestamp.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.40-53
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• 1996

In this paper, the wave drift damping is studied. An approximate method is adopted to calculate the wave drift damping for the sake of practical applications. By assuming the ship's forward speed to be low, the Green function and the velocity potential are expanded asymptotically with respect to the Brard number(${\tau}$) and terms up to the first order of ${\tau}$ are retained. Mean wave drift forces are computed straightforwardly. The wave drift damping is estimated as the change rate of the mean wave drift force with respect to the ship's speed. In order to validate the present method, Series 60(Cb=0.7) ship is exemplified for forward speed of Fn=0, 0.02 and 0.04. To predict the wave drift damping experimentally, three geosym models of the Esso-Osaka tanker are used. Also the effect of drift angle on the wave drift damping is also considered. Comparisons between numerical and experimental results show reasonable agreements.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.179-180
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• 2008

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.11a
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• pp.36-37
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• 2017

실내공간에서 사람 검출 및 인식은 지능영상정보 시스템에서 중요한 기능중의 하나이다. 실내공간에서 사람검출을 위한 트랙킹 과정에서 발생하는 표류(drifting)는 성능 저하의 큰 원인을 제공한다. 표류로 인한 비사람의 트랙킹을 방지하기 위해서 사람여부를 결정하는 것이 필요하다. 이를 위해서 합성곱 신경망을 적용한 결과 80%의 사람 인식율을 얻었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.11a
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• pp.9-10
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• 2018

실내공간에서 사람 검출 및 인식은 지능영상정보 시스템에서 중요한 기능중의 하나이다. 실내공간에서 사람검출을 위한 트랙킹 과정에서 발생하는 표류(drifting)는 성능 저하의 큰 원인을 제공한다. 표류로 인한 비사람의 트랙킹을 방지하기 위해서 사람여부를 결정하는 것이 필요하다. 이를 위해서 합성곱 신경망을 적용한 결과 80%의 사람 인식율을 얻었다.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.8-16
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• 2022

This paper presents the orbital control for positioning micro synthetic aperture radar (SAR) satellites for all-weather monitoring around the Korean Peninsula. In Small SAR technology experimental project (S-STEP) developed in Korea, multiple satellites are placed at equal intervals in multiple orbital planes to secure an average revisit period for the region around the Korean Peninsula. Satellites entering the same orbital plane use ion thrusters to control their orbits and the separation velocity from the launch vehicle to distribute them evenly across the orbit. For an orbital that places the satellites equally spaced in the same orbital plane, the shape of the satellite constellation is formed by adjusting the difference in drift rates between the satellites. This paper presents, different types of satellite constellations, and the results of satellite constellation placement according to launch strategies are presented. In addition, a method and limitations in shortening the duration of orbital deployment are presented.

• Korean Journal of Weed Science
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• v.7 no.3
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• pp.337-347
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• 1987

Spary and vapor drift injuries of apple, pear, and peach seedling caused by soil-applied oxyfluorfen were studied in a greenhouse. Bud bursting rate of all fruit trees was reduced by both spray and vapor drifts of oxyfluorfen, but reduction in bud bursting rate of pear and peach was greater than that of apple trees. Reduction in the number of leaves per shoot of apple and peach was greater than that of pear trees. Leaf injury of pear was most severe and occurred earliest, but leaves of peach were least injured, Leaf injuries of pear and apple were caused by both spray and vapor drifts, but leaves of peach was injured largely by vapor drift. Reduction in shoot growth of and pear was greater than that of peach trees. Shoot growth of pear was more rapidly retared compared with apple trees. In the field, oxyfluorfen delayed the time of bud bursting in young apple trees. Oxyfluorfen applied between initiation and completion of bud bursting delayed bud bursting more than earlier application although ultimate number of bursted buds was similar to control. The number of leaves per shoot and total length of shoots were lower than control until 40 days after application of oxyfluorfen, and then were similar to control because of vigorous growth after May.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.2
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• pp.137-147
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• 1970

From November 1968 to March 1970, a series of drift bottle experiments were carried out in waters adjacent to and in Chinju Bay with the following results. Of the bottles released, $50\~69$ per cent were recovered. 1. The circulation of Chinju Bay is usually caused by the tidal current except during the winter season when the northwest monsoon prevails to cause a wind-drift current. 2. Sea water in the southern part of Chinju Bay flows northward at ebb tide. The ebb current east of the central submarine bank in Chinju Bay flows northeastward toward Samchonpo Channel through the eastern depression of the bank contributing to form a cyclonic eddy. The ebb current west of the bank, however, flows northward toward Noryang Channel through the western depression of the bank. 3. The ebb current nea. the southernmost part of Chinju Bay flows eastward toward Chijok Channel. 4. At flood tide, the main stream of the tidal current in Noryang Channel flows eastward. Turning smoothly to the right, the southern branch of the flood current flows southward through the depression and along the isobaths at the western margin of the central submarine bank, while the northern branch, turning to the left, flows into the Chin-gyo Bay of Hadong. 5. flood current in the eastern area of Kwang-yang Inlet runs northeastward toward Noryang Channel. A small eddy develops near Kwanumpo of Namhae Island. 6. The results suggest that such a drift bottle experiment can be recommended for the attestation of currents, although it is not suitable for a quantitative study of coastal currents.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.7
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• pp.518-524
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• 2013

A pilot-scale test-bed was operated employing three soils with different grain sizes dredged from the Nakdong River to obtain the design and operation parameters of the multi-purpose filtration pond, such as the filtrate productivity of the filter sand, the appropriate removal period of the surface clogging and the contaminant removal efficiency. The cross-flow velocities were applied stepwise ranging from 0 to 40 cm/sec in order to simulate the various velocities in the artificial stream of the pond. Results showed that a filtrate production rate of 5~3 $m^3/m^2-day$ was maintained by removing the surface clogging every 7 to 13 days and that the filtrate quality was not affected by the factors of the filtrate production rate, the grain size of the filter sand and the cross-flow velocity. Results also showed that most of the removal occurred within 50 cm of the top soil and that the removal efficiencies with the filtration distance of 2.4 m were 80~95% for turbidity, 20~30% for COD, 75~90% for BOD, 5~20% for total nitrogen and 20~60% for total phosphorus, which suggested that particulate matters had a high removal efficiency.

• 월간 한농연
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• s.81
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• pp.14-17
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• 2009

6월 임시국회가 여야간 입장차이로 표류하고 있다. 한나라당에서는 민생현안 처리를 등원카드로 민주당의 압박하면서 단독 국회개원 불사방침을 밝히고 있고 노무현 전 대통령 서거 이후 지지율이 급상승한 민주당은 대통령 사과와 국정쇄신을 강력하게 요구하면서 한나라당의 법안 강행 처리시도에 대비해 국회를 점거하면서 대립하고 있다. 이로 인해 농업계가 가장 크게 우려하고 있는 한미FTA비준안 처리시도는 지연이 불가피할 것으로 보인다. 한농연과 한여농은 국회비준을 앞두고 각 시군구 차량집회를 개최하여 정치권에 비준반대 입장과 요구사항을 전달하는 등 적극적인 활동을 전개했다.