• 대기
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• 제33권4호
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• pp.387-398
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• 2023

The double Fourier series (DFS) spectral dynamical core is evaluated for the two idealized test cases in comparison with the spherical harmonics (SPH) spectral dynamical core. A new approach in calculating the meridional expansion coefficients of DFS, which was recently developed to alleviate a computational error but only applied to the 2D spherical shallow water equation, is also tested. In the 3D deformational tracer transport test, the difference is not conspicuous between SPH and DFS simulations, with a slight outperformance of the new DFS approach in terms of undershooting problem. In the baroclinic wave development test, the DFS-simulated wave pattern is quantitatively similar to the SPH-simulated one at high resolutions, but with a substantially lower computational cost. The new DFS approach does not offer a salient advantage compared to the original DFS while computation cost slightly increases. This result suggests that the current DFS spectral method can be a practical and alternative dynamical core for high-resolution global modeling.

• 천문학회지
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• 제38권2호
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• pp.207-210
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• 2005

We study the influence of rotation on the dynamical evolution of collisional single-mass stellar clusters up to core-collapse by using N-body simulations. Rotating King models which are characterized by dimensionless central potential parameter $W_o$ and the rotation parameter $W_o$ are used as initial models. Our results show that inner shells slowly contract until core-collapse phase is reached, followed by a slow expansion. Angular momentum is transported outward, while the core is rotating even faster than before, as predicted by gravogyro catastrophe theory. We confirm that rotation plays an important role in accelerating the dynamical evolution of stellar cluster, in particular in accelerating the core collapse.

• 천문학회보
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• 제36권1호
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• pp.47.1-47.1
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• 2011

We studied the evolution of the two mass components system with NFW initial density distribution by direct integration of the Fokker-Planck equations. The low mass component is regarded the dark matter particles while the high mass component is assumed to be conglomerates of baryonic matter in order to depict the 'stars'. While the true mass ratio between these two types of particles should be extremely large, our adopted mass ratio is about 1000 beyond which the dynamical evolution and density distribution tend to converge. Since the dynamical evolution is dominated by the dynamical friction, the high mass component slowly moves toward the central part, and eventually undergoes the core collapse. The system reaches the core-collapse at about $7.1{\times}10^{-3}$ $t_{fh}$ in NFW models, where $t_{fh}$is the dynamical friction time at half-mass radius. The distribution of the high mass component is well fitted by the Sersic profiles or modified Hubble profile when the mass segregation is established. From these results, the surface brightness of elliptical galaxies may be explained by the high mass component experiencing dynamical friction by the dark matter particles. In order for the mass segregation to be effective within Hubble time, the mass of the luminous component should be greater than $10^5M_{\bigodot}$.

• Journal of Astronomy and Space Sciences
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• 제8권1호
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• pp.11-23
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• 1991

The dynamical evolution of globular clusters is studied using the orbit-averaged multicomponent Fokker-Planck equation. The original code developed by Cohn(1980) is modi-fied to include the effect of stellar evolutions. Plommer's model is chosen as the initial density distribution with the initial mass function index $\alpha$=0.25, 0.65, 1.35, 2.35, and 3.35. The mass loss rate adopted in this work follows that of Fusi-Pecci and Renzini(1976). The stellar mass loss acts as the energy source, and thus affects the dynamical evolution of globular clusters by slowing down the evolution rate and extending the core collapse time Tcc. And the dynamical length scale $$R_c, $$R_h is also extended. This represents the expansion of cluster due to the stellar mass loss.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.633-636
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• 2000

The decoupling of the systems is to let the inputs and outputs correspond one to one, by performing the state feedback or the output feedback on the given systems. In this paper, we propose a method for decoupling the separable-denominator two-dimensional systems. And, we study about the realization dimension of the dynamical feedback and the dynamical feedforward performed for decoupling.

• Journal of Astronomy and Space Sciences
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• 제20권1호
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• pp.63-82
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• 2003

Schwarzschild의 선형 계획법을 사용하여 평형상태에서의 구형은하를 기술하는 비 충돌 볼쯔만 방정식의 일반적인 해를 얻었다. 이 계산으로부터 de Vaucouleurs의 광도 법칙을 만족하고 무거운 헤일로를 포함하는 등방성 구형은하의 존재를 확인할 수 있었다. 타원은하에서 속도 분산 곡선이 편평하거나 서서히 증가하는 현상은 암흑물질에 의한 질량대 광도비의 증가로 해석할 수 있다. 이런 경우 암흑물질의 밀도 분포는 core반경이 은하의 유효반경보다 훨씬 작은 값을 갖는다는 사실을 확인할 수 있었다.

• 대기
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• 제33권2호
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• pp.73-104
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• 2023

Over the past 60 years, Korean numerical weather prediction (NWP) has advanced rapidly with the collaborative effort between the science community and the operational modelling center. With an improved scientific understanding and the growth of information technology infrastructure, Korea is able to provide reliable and seamless weather forecast service, which can predict beyond a 10 days period. The application of NWP has expanded to support decision making in weather-sensitive sectors of society, exploiting both storm-scale high-impact weather forecasts in a very short range, and sub-seasonal climate predictions in an extended range. This article gives an approximate chronological account of the NWP over three periods separated by breakpoints in 1990 and 2005, in terms of dynamical core, physics, data assimilation, operational system, and forecast application. Challenges for future development of NWP are briefly discussed.

• Structural Engineering and Mechanics
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• 제83권5호
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• pp.609-615
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• 2022

A numerical approach for dynamic stability analysis of sandwich plates has been provided using Chebyshev-Ritz-Bolotin approach. The sandwich plate with porous core has been formulated according to a higher-order plate. All of material properties are assumed to be dependent of porosity factor which determines the amount or volume of pores. The sandwich plate has also been assumed to be under periodic in-plane loading of compressive type. It will be shown that stability boundaries of the sandwich plate are dependent on static and dynamical load factors, porosity factor, porosity variation and core thickness.

• 천문학회보
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• 제42권1호
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• pp.51.1-51.1
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• 2017

The galaxy cluster Abell 115 shows ongoing merger features, which suggest that it might be in an intermediate phase of dynamical evolution. As merging clusters often show, the characteristic hints of A115's merging activities include radio relics, double X-ray peaks, and large offsets between the cluster member galaxies and the X-ray distributions. To constrain the exact stage of the merger, it is necessary to obtain its dark matter distribution. In this study, we carry out a precision weak lensing study of this interesting system based on Subaru images. We present our mass reconstruction together with descriptions on our core procedure of the analysis: Subaru data reduction, galaxy shape measurement, and source selection. We find that Abell 115 consists of two massive dark matter clumps, which closely follow the cluster galaxies. Our weak lensing mass estimate is a few factors lower than the published dynamical mass obtained from velocity dispersion. This large mass discrepancy may be attributed to a significant departure from dynamical equilibrium.

• Design & Manufacturing
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• 제10권3호
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• pp.46-50
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• 2016

Laminate products for motor core are developed with a structure in which the importance of quality level and clamping force is influenced by the recent performance and safety of the product. It has been confirmed that the accuracy of the mold is emphasized, and that the accuracy of the tightening force produced by the stacked product for the motor core is greatly influenced by the change in the bottom dead center displacement of the aged high speed press. The reason why setting the mold, and test the effect of bottom dead center of high speed press is to improve product pull force in embossing process at mold. We have applied the system to minimize the effect on the damping displacement under the dynamical degree of the equipment by applying the emboss complement device which can test the influence and complement in the process.