• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.368-368
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• 2016

점착성 유사는 응집현상을 통해 크기와 밀도를 바꾸고 이에 따라 부유 및 이동에 큰 영향을 미치는 침강속도가 지속적으로 변화한다. 따라서 점착성 유사의 거동을 이해하기 위해서는 응집현상에 대한 고려가 필수적으로 이루어져야 한다. 현재까지 이루어진 응집현상 모형은 크게 Population balance equation type 모형(PBE)과 Floc growth type 모형(FGM)으로 나뉜다. PBE 모형은 점착성 유사의 입도분포를 모의할 수 있는 장점이 있는 반면에 닫힌 계에서 질량보존을 만족시키지 못하는 단점을 가진다. FGM 모형은 간단한 식을 통해 질량보존을 만족시키고 수치적으로 효율적인 모의를 할 수 있는 반면 입도분포를 모의할 수 없는 단점을 가진다. 이러한 장단점으로 인해 PBE 모형은 유사이동모형과 결합되어 이용된 사례가 없으며 FGM 모형은 유사이동모형과 결합되어 평균적인 점착성 유사의 거동만을 모의하는 연구에 이용되었다. 본 연구에서는 Stochastic floc growth type 모형(SFGM)의 개발에 따라 이해할 수 있는 점착성 유사이동의 특성과 이를 유사이동 모형과 결합시키는 방향에 대해 검토한다. 현재까지 진행된 연구 결과를 분석하면 SFGM은 질량보존을 만족시키면서도 점착성 유사의 입도분포를 모의할 수 있는 장점을 가지는 것으로 판단된다. 특히 난수발생의 단계에서 적절한 확률분포형을 선정하고 확률매개변수의 보정이 이루어지는 경우에는 높은 정확도를 가지는 입도분포 모의가 가능하다. 가는 모래를 대상으로 하는 비점착성 유사의 경우에는 추계학적인 유사이동 모형의 개발이 활발히 이루어져 왔다. 개발된 모형은 실제 측정값에 적용되어 다양한 학술적 가능성을 보여왔다. 따라서 SFGM의 개발이 점착성 유사의 이동모형과 결합되는 경우에는 점착성 유사가 지배적인 다양한 환경에서의 거동 특성을 이해할 때 매우 유용할 것으로 판단된다. 응집모형은 난류의 강도에 지배적인 영향을 받으며 유사의 입경 및 밀도 변화를 계산한다는 점을 고려할 때 유사이동 모형 역시 난류 강도에 대한 정보를 계산할 수 있는 지배방정식을 필요로 한다. 향후 개발될 추계학적 점착성 유사의 이동모형은 난류에 대한 정보, SFGM의 결합 등을 필요조건으로 가진다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.819-822
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• 2009

환경 소음,진동 개선의 측면에서 철도 레일 하부로 전달되는 진동 및 구조소음을 효과적으로 차단하기 위하여 국내에서도 탄성 이산지지 구조의 플로팅 슬라브를 적용하는 경우가 증가하고 있다. 플로팅 슬라브 구조설계에 있어 주안점은 방진효율 증대와 슬라브 자체 중량의 2~3배 되는 열차 주행간의 동하중에 대한 열차 주행 안정성을 고려해야 하는 점이며 열차의 고속화 경향에 따라 동하중의 증가는 더욱 커지고 있다. 본 연구에서는 이산지지 방진장치를 적용한 철도 슬라브 궤도의 동특성과 이동질량에 의한 응답을 방진장치의 지지 간격, 스프링 상수 등을 설계변수로 하여 수치해석적 방법으로 시뮬레이션하였다.

• Journal of Astronomy and Space Sciences
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• v.10 no.2
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• pp.152-162
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• 1993

We developed the S/W which calculate the Planetary and the Moon ephemerides. The ephemeris of the Solar system objects was obtained from a simultaneous numerical integration of the equations of motion for the nine planets and the Moon. The mathematical model includes contributions from (1) point-mass interactions (2) figure effect (3) earth tides (4) the orientations of the Earth and the Moon. The calculated ephemerides are compared with DE200 data produced by JPL (Jet Propulsion Laboratory).

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.823-826
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• 2002

Experiments were conducted to show the characteristics of the flow on unventilated parallel plane jets. Measurements of mean velocity components and turbulent intensities were carried out with a particle image velocimetry. The measurements range of these experiments was Reynolds number of 5300 based on the nozzle width and the cases of nozzle-to-nozzle distance were 4, 6, 8, and 10 times the width of the nozzle. Results show that a recirculation zone with a sub-atmospheric static pressure was bounded by the inner shear layers of the individual jets and the nozzles plate. The positions, where maximum value of mean turbulent intensities and mean turbulent kinetic energy show, were at the same position with the merging point. The spread of jets in the merging region increases more rapidly than that of jets in the converging and the combined region. As nozzle-to-nozzle distances were increased, it was shown that merging and combined lengths were shorter.

• Communications of Mathematical Education
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• v.24 no.1
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• pp.145-158
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• 2010

In this paper we study tetrahedron's properties related with center of inscribed sphere using the center of mass. We show that the center of mass of four mass points (A,a), (B,b), (C,c), (D,d) coincide with center of tetrahedron's inscribed sphere, suggest equalities and inequalities related with center of inscribed sphere, and prove theses using the center of mass. Our results can be used in research and education programs, various types of gifted student education.

• Journal of Astronomy and Space Sciences
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• v.12 no.1
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• pp.30-43
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• 1995

New UBVRI observations of triple star $\lambda$ Tau were made at Chungbuk Ntional University Observatory for 31 nights from Dec. 1990 to Jan. 1994. A total of 2930 photometric observations were obtained with 586 points for each filters, and BVRI light curves were constructed. From the primary light curves, the one times of primary minimum light was determined with a new light element. The photometric solutions of light curves for $\lambda$ Tau were calculated by using Wilson-Devinney method with our BVRI light curves and the BV light curves obtained by Grant(1959). We determined spectroscopic solutions that were satisfied with these two light curves and the radial velocity curves had been collected by Fekel and Tomkin (1982). From these values, absolute dimensions for this system were estimated. The radius and mass for the primary star are turned out to be $8.3R_\odot$ and $8.1m_\odot$, and $6.5R_\odot$ and $2.1m_\odot$ for the secondary star, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.12
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• pp.2318-2324
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• 2017

Quantum cryptography, which is emerging as a next generation password, is being studied by quantum cryptographic transfer protocols and quantum secret communication. Quantum key transfer protocol can be used in combination with the modern password because of the inefficiency of the use of the password, or the use of OTP(one time password). In this paper an algorithm for direct communication by means of direct cryptographic communications rather than quantum keys. The method of implementing quantum secure direct community was adopted using 2-channel methods using Einstein gravity field. Two channels were designed to adopt a quantum secret communication protocol that applies time delay between 2-channels of channel to apply time difference between 2-channels. The proposed time delay effect reflects the time delay by reflecting the gravitational lensing phenomenon. Gravity generator with centrifugal acceleration is incorporated in the viscometer, and the time delay using this implies the correlation between the variance of the metametry.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.61-68
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• 1991

The system such as railway bridge can be modelled as the restrained beam with intermediate supports. This kind of structures are subject to the moving load, which has a great effect on dynamic stresses and can cause sever motions, especially at high velocities. Therefore, to analyze the dynamic characteristics of the system due to the moving load is very important. In this paper, the governing equation of motion of a restrained beam subjected to the moving load is derived by using the Hamilton's principle. The orthogonal polynomial functions, which are trial functions and satisfying the geometric and dynamic boundary conditions, are obtained through simple procedure. The dynamic response of the system subjected to the moving loads is obtained by using the Galerkin's method and the numerical time integration technique. The numerical tests for various constraint, velocity and boundary conditions were preformed. Furthermore, the effects of mass of the moving load are studied in detail.

• The Journal of the Petrological Society of Korea
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• v.13 no.3
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• pp.119-125
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• 2004

Using a SHRIMP ion microprobe, we have dated zircon grains of a felsic meta-tuff from the so-cal1ed Munjuri Formation, Ogcheon metamorphic belt. The weighted mean $^{206}$ Pb/$^{238}$ U zircon ages obtained from 13 spot analyses of 10 grains provide an essentially concordant age of 747${\pm}$7Ma. This result corroborates the conventional U-Pb zircon age (756${\pm}$1Ma; Lee et al., 1998) for the Neoproterozoic bimodal volcanism in the Ogcheon belt. Thus, proto-basins associated with intracontinental, high-volcanicity rift in the Ogcheon belt are most likely to have formed at ca. 750 Ma.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.132-137
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• 2017

This paper proposes a transformation method of the zero moment point (ZMP) and the center of mass (CoM) from one walking pattern to other patterns by considering the structure of a robot or walking situations in real time. In general, a humanoid robot has own structure characteristics like height and mass. The structure characteristics make the given CoM/ZMP walking pattern of one human or one humanoid robot to be difficult to apply to other robot directly. For this purpose, we analyze the characteristics of walking patterns according to the step length, duration of walking support phase and the CoM height by using the cart-table model as the simple humanoid robot model. A transformation equation is derived from the analyzation and it is verified with simulation.