• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1033-1041
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• 2011

In this paper, a collision avoidance maneuver frequency for the KOMPSAT-2 and the KOMPSAT-5 is analyzed. For the statistical prediction of the avoidance maneuver frequency, mission orbits, responsive time, accepted collision probabilities, and positional uncertainties of primary and secondary objects are considered. In addition, the collision avoidance maneuver frequency of the KOMPSAT-2 is compared to the case that NORAD catalog during one year is used to calculate that of the KOMPSAT-2. As a result, the collision avoidance maneuver frequency is one per year on average and effective factors on the statistical prediction of the avoidance maneuver frequency are investigated. Efforts to improve its prediction accuracy are also discussed.

• Journal of Astronomy and Space Sciences
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• v.5 no.1
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• pp.19-30
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• 1988

The existence of the j-type collision periodic orbit is examined on the condition of mass ratio 0.9878449 and Jacobian constant 2.9∼3.4. Using the Birckhoff's regularization method and the 5th order Runge-Kutta variable step-sized numerical roution introduced by Fehlberg (1968). we test their periodicities. As the results, 4 j-type collision orbits and 5 peculiar orbits are represented. There are good agreements in this collision orbits with the relationship between the period and the shape of orbit proposed by Pinotsis Zikides(1984).

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.364-371
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• 2017

TPMS is a vehicle electric system that measures the air pressure of a tire, and informs the driver of current tire states. The TPMS sensor typically uses unidirectional communication for small size, light weight, and low power. The transmission period of the sensor indicates the service quality of monitoring the tire. In order to determine the optimal transmission period, frame collision probability and the life time of the sensor should be analyzed. In this paper, collision probability model using Venn diagram is designed in low power TPMS with the normal and warning mode. And the life time and a collision probability were analyzed with the ratio(n) of the normal mode to warning mode transmission period. As a result, $T_{nP}=31sec$ and $T_{wP}=2.4sec$ at 5 years, and $T_{nP}=71sec$ and $T_{wP}=2.5sec$ at 7 years.

• Fire Science and Engineering
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• v.16 no.2
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• pp.38-42
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• 2002

This experiment is to understand a characteristics of smoke layer formation affected periodicity of fire plumes. The ON-OFF jet was used to constitute the oscillating flow, which was formed by a mixture of nitrogen gas with kerosene particles. The instantaneous images was obtained by digital video camera using laser sheet technique. The results were confirmed that the smoke layer in the near fire source comprise vortices which are formed by impingement from the periodicity of fire plume. The periodic impinging of plumes were thickened the smoke layer and produced the back-flow.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.269-282
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• 2003

We examined the hypothesis that the crater formation rate exhibits periodicity, employing data sets of Grieve (1991), Moon et al. (2001), and the Earth Impact Database(2002; DB02). DB02 is known to supercede previous compilations in terms of its accuracy and precision of the ages; it is the first time that this database has been used for periodicity analysis. For data sets comprising impact structures with $D{\geq}5km$(and also those with $D{\geq}20km$), there is no convincing evidence for periodicities in the crater ages, according to our Fourier analysis. However, we detected two peaks at 16.1Myr and 34.7Myr for craters with $D{\geq}30km$; we confirm that the age distribution of impact craters with $D{\geq}45km$ has dominant power at 16.1Myr. Thus, we may conjecture a probable periodic shower of Earth impactors with sizes $d{\geq}1.5km$. In addition, we found that the selection of data sets, the lower limits on the ages and diameters of impact craters, as well as the accuracy and precision of the ages, all constitute crucial factors in reconstructing the impact cratering history of the Earth.

• The Transactions of the Korea Information Processing Society
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• v.3 no.7
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• pp.1687-1696
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• 1996

Most of the main memory database systems use two-phase locking(2PL)for concurrency control. The 2PL method is preferred over other methods for concurrency control because of its simplicity and common usage. However, conventional concurrency control solution will function poorly when the data are memory resident. In this paper, we propose a new optimistic concurrency control protocol for a main memory database system. In our proposed protocol, transaction conflict information is used in validation phase to improve data conflict resolution decisions. Our experiments show that the proposed protocol performs better than 2PL in terms of throughput for main memory database system enshrinements.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.01a
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• pp.131-132
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• 2017

본 논문에서는 쿼드콥터 드론의 충돌방지를 위한 효율적인 자동제어 방법을 제안한다. 이 제어방법은 RC 조종기에서 노브를 이용하여 사용자가 제어하는 신호를 쿼드콥터의 리시버단에서 수신한 뒤 출력되는 PWM 신호들 중에서 쓰로틀, 피치, 롤 제어정보를 필요시 변경하는 방법으로 충돌을 방지한다. 충돌을 예측하기 위해서 전후, 좌우, 상하 6방향에 레이저 거리측정센서를 장착하고 주기적으로 거리를 측정한다. 그리고 측정 거리를 이용하여 장애물 유무를 판정하고 충돌이 예상되면 수신된 PWM 신호를 변경하여 쿼드콥터의 비행제어부로 전달함으로써 충돌을 방지하도록 한다. 본 논문에서 제안하는 충돌방지 방법을 쿼드콥터에 적용하여 실험을 통해 검증한 결과, 조종자 부주의 혹은 조종 미숙으로 인해 발생할 수 있는 충돌을 방지할 수 있어 안전성이 향상됨을 보였다.

• Journal of Astronomy and Space Sciences
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• v.12 no.2
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• pp.204-215
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• 1995

We observed SL-9 impact sites on Jupiter with a CCD and a R filter on the KyungHee University 30-inch telescope between July 17 and September 3, 1994. We identified impact sites of A, C, E, G, H, K, L, Q1, W and G-group, We calculated the moving velocity relative to System II and rotation period of the G, L sites to be from -8.0 to 8.8m/s, and $9^h55^m39.4^s\pm34^s$, respectively. The diameters of G and L sites in our first observation were $1.95\times10^4km,\;and\;2.20\times10^4km$, respectively. In particular, we investigated the evolution of the impact sites by calculating the diffusing rates of the impact clouds.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.921-924
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• 2001

실시간 처리 시스템에서 발생하는 트랜잭션은 장시간이 요구되는(CAD/CAM) 긴 트랜잭션이 아닌 일반적인 트랜잭션을 처리하는 환경이 대부분이다. 주 메모리 실시간 DBMS는 디스크에 비하여 상대적으로 빠른 접근시간과 균일한 성능 특성 때문에 실시간 처리 환경에 적합하다. 그러나, 기존의 주기억 데이터베이스에서 동시성제어는 2단계 로킹 기법을 사용하고 있다. 이 기법은 특징은 첫째, 록 획득과 해제가 실제 트랜잭션 처리 보다 많은 오버헤드가 발생되고, 또한, 처리속도가 빠르기 때문에 데이터 충돌 발생률이 적다. 이러한 문제를 해결하기 위한 새로운 동시성제어 모델을 제안한다. 제안된 기법은 동시에 여러 트랜잭션을 처리 할 수 있고, 신속히 충돌여부를 결정할 수 있도록 디렉토리별로 정보를 기록하여 실시간에 적합하도록 모델을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04b
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• pp.154-156
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• 2001

실시간처리 시스템에서 발생하는 트랜잭션은 장시간이 요구되는(CAD/CAM) 긴 트랜잭션이 아닌 일반적인 트랜잭션을 처리하는 환경이 대부분이다. 주메모리 실시간 DBMS는 디스크에 비하여 상대적으로 빠른 접근시간과 균일한 성능 특성 때문에 실시간 처리 환경에 적합하다. 그러나, 기존의 주기억 데이터베이스에서 병행수행 제어는 2단계 로킹 기법을사용하고 있다. 이 기법은 특징은 첫째, 록 획득과 해제가 실제 트랜잭션 처리 보다 많은 오버헤드가 발생되고, 또한, 처리속도가 빠르기 문에 데이터 충돌 발생률이 적다. 이러한 문제를 해결하기 위한 새로운 동시성제어 모델을 제안한다. 제안된 기법은 동시에 여러 트랜잭션을 처리 할 수 있고, 신속히 충돌여부를 결정할 수 있도록 디렉토리별로 정보를 기록하여 실시간에 적합하도록 모델을 제안한다.을 제안한다.