• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.187-197
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• 2007

Experimental study for a submerged structure was conducted to protect coastal structures and shorelines. The rectangular submerged structure known as the most efficient shape among various submerged structures in the literature was fabricated at the nose of a rubble mound breakwater. The reflection coefficients and the run-up heights along the slope of a breakwater were measured for different significant wave heights and periods. It is found in this study that the reflection coefficient is affected more relatively by the significant wave period than the significant wave height and the run-up heights are reduced approximately 28% in terms of ${^{RU}}_{2%}$ and 26% in terms of ${^{RU}}_{33%}$, respectively, by the installation of a submerged structure inducing the interception and breaking of waves.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.849-854
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• 2013

Many researches on green ship with increasing on economics, efficiency and convenience have been carried out consistently. One of them is development of diesel engines with electronic control. While small duty one for automobiles had been adopted mainly already, disseminating heavy duty one for ships has trouble due to safety and reliability. In order to solve these problem in this study, performance of electronic control and cam type engine installed in parallel on training ship HANBADA of korea maritime university was analyzed and compared. It is certain that specific fuel oil consumption of the electronic control type is lower than cam type and excellent at lower engine load, especially. And the electronic control type shows more effective characteristic at sea trial on specific fuel oil consumption.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.607-618
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• 1994

Effects of wave grouping on the harbor oscillation are studied in order to clarify the energy source of harbor resonance. The resonant periods of Donghae harbor and Imwon harbor are calculated using the boundary integral equation method. Also, the periods of the group-bounded long waves due to the irregular wave group are calculated using the theory developed in this study. Analyzing from the view point of period, it is concluded that the group-bounded long waves due to the irregular wave group can cause resonance in small harbors such as fishery harbors, and heavy ship motion in large harbors such as industrial ones.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.65-68
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• 2007

DOCSIS 3.0 MAC protocol regulate CM and CMTS Channel transfer times through MAP message. Standards does not include the details of MAP Inter-arrival Time affecting the performance of MAC protocols for DOCSIS 3.0. In this paper, we evaluationed the performance of protocol follow in MAP Inter-arrival Time on DOCSIS 3.0. Based on the evaluation results, we propose the optimal MAP Inter-arrival Time. We found that the protocol shows best performance when the MAP Inter-arrival Time is 0.05sec. The research results can apply to performance element which important for the construction of DOCSIS 3.0 base cable networks.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.1
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• pp.24-34
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• 1997

To find the causes of the downtime problems in Pohang New Harbor, extensive field measurements of short- and long-period waves for 1.5 months and their analyses were made taking into account of wind and downtime records. Measured wave height ratios inside the harbor are appeared to be slightly larger than predicted ones using numerical methods in the previous studies. It is shown that the major causes of the downtime are the wind wave (or swell) higher than loading criteria and also swell with even smaller wave height but longer period(more than 10 sec). Waves of long-period components[0(min)] were recorded as 20 cm high in case of dominant seiche phenomena but they might not be related with the downtime problems.

• Journal of Astronomy and Space Sciences
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• v.15 no.2
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• pp.449-458
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• 1998

The Korea Muliti-Purpose Satellite(KOMPSAT) uses a sun-synchronous orbit with an altitude 685km as mission orbit and undergoes earth eclipses and infrequently lunar eclipses. Lunar eclipses occur when the moon is located between the sun and the satellite and blocks partially or fully the sunlight. The eclipse causes the satellite to increase battery discharge times and affects satellite lifetime and mission operation. The KOMPSAT lunar eclipses can cause additional effects to energy balance and battery disc of the KOMPSAT lunar eclipse for 3 year mission lifetime. Also mission planning scenario is presented for lunar eclipses at the KOMPSAT Grouns Station(KGS).

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.315-323
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• 2010

It is suggested that the service life of the continuous welded rail(CWR) is estimated by the relationship between the rail surface irregularity according to the accumulated passing tonnage and bending fatigue of welded part in CWR. In this study, it measured bending stress of rail according to the rail surface irregularity in the concrete track on the Seoul Metro. In addition, the relationship between rail surface irregularity and bending stress in concrete track is analyzed by results of the field test. Finally, this study clarified the relationship among bending stress(Y) of rail, train speed(U), rail surface irregularity(v, w) in concrete track. The result of this study is able to use the basis data to establishing the periodic replacements criterion of CWR.

• The Korean Journal of Zoology
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• v.36 no.1
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• pp.36-50
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• 1993

한국산 관박쥐(Rhinolophusfewmequinum Jroma의 웅성생식 pattern을 알아보기 위하여 정소의 형태변화와 세정관 정상피의 1년주기를 조사하여 다음과 같은 결론을 얻었다. 정자형성은 5월에 시작되어 10월말에 완료되었다. 7월초부터 10월중순까지는 정자변태과정이며, 정자형성과정의 활성도가 가장 높은 달은 8월 중순경이었다. 또한 교미가 끝난 11월경부터 세정관내에는 미성숙한 정자세포가 Sertoli cell의 식작용과정의 일환으로 포식되어졌고, 91년 12월부터 92년 1월, 2월, 3월, 그리고 동면각성기인 4월의 실험군에서도 역시 점진적으로 식작용 과정을 관찰할 수 있었다. 교미가 끝난 후의 세정관 내에는 새로운 정자를 만들기 위한 준비단계로서 미성숙된 정자들이 Sertoli cell의 식작용에 의해 정화(cleaning)되므로 이 기간을 정화기간(cleaning time)이라 볼 수 있다. 따라서 정소내 세정관의 1년 주기를 볼 때 정화기간은 동면 개시기인 11월부터 익년 4월까지 약 6개월에 걸쳐 이루어 진다. 이상의 결과로 볼때, 정자형성은 동면각성 직후부터 시작하여 10월경에 완료되며 교미개시기에는 정지되고, 동면기 동안 정자형성이 일어나지 않는 점으로 보아 한국산 관박쥐는 'Pipistnfluspottem'에 속한다고 할 수 있다.

• Journal of Korea Water Resources Association
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• v.38 no.11
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• pp.947-954
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• 2005

In this study, laboratory measurements are presented for run-up heights and overtopping of water waves on slopes of rubble-mound breakwaters armored with tetrapods. The effects of wave steepness, surf similarity and wave period on the run-up height and overtopping are investigated in detail. A measurements. A very reasonable agreement is observed. A slopes of breakwaters become milder, run-up heights become smaller. The overtopping rate also is considerably rate also is considerably affected by wave steepness and period.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.164-171
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• 1995

Drying shrinkage and hydration heat are important factors on the initiation of the crack in con crete at early age. Therefore, the stress caused by hydration heat and drying shrinkage should be .analyzed to predict whether the crack occurrs or not. And, mechanical properties of early age concrete is also required for the predicting crack formation In this study, non-destructive test method of resonance frequency was used to find the relation between dynamic modulus and mechanical properties of concrete in early age. Test results were compared with existing equations, and a new equation based on test. results in this study and other data was also proposed