• 대한수학회지
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• 제39권4호
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• pp.543-558
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• 2002

We investigate the fragmentation process developed by Kolmogorov and Filippov, which has been studied extensively by many physicists (independently for some time). One of the most interesting phenomena is the shattering (or disintegration of mass) transition which is considered a counterpart of the well known gelation phenomenon in the coagulation process. Though no masses are subtracted from the system during the break-up process, the total mass decreases in finite time. The occurrence of shattering transition is explained as due to the decomposition of the mass into an infinite number of particles of zero mass. It is known only that shattering phenomena occur for some special types of break-up rates. In this paper, by considering the n-particle system of stochastic fragmentation processes, we find general conditions of the rates which guarantee the occurrence of the shattering transition.

• 대한수학회보
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• 제42권4호
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• pp.855-867
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• 2005

Shattering or disintegration of mass is a well known phenomenon in fragmentation processes first introduced by Kol­mogorov and Filippop and extensively studied by many physicists. Though the mass is conserved in each break-up, the total mass decreases in finite time. We investigate this phenomenon in the n particle system. In this system, shattering can be interpreted such that, in uniformly bounded time on n, order n of mass is located in order o(n) of clusters. It turns out that the tagged particle processes associated with the systems are useful tools to analyze the phenomenon. For the newly defined stochastic shattering based on the above ideas, we derive far sharper conditions of fragmentation kernels which guarantee the occurrence of such a phenomenon than our previous work [9].

• 한국군사과학기술학회지
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• 제15권5호
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• pp.712-719
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• 2012

Penetrator with enhanced lateral effect(PELE) is a newconcept projectile, without dynamite and fuze. It consists of high-density jacket, closed at its rear end and filled with a low-density filling material. To study the explosion characteristics of PELE, by AUTODYN-3D code, the calculation models of projectile body and bullet target are established and the process of penetrating aluminum-2024 alloy target of PELE is simulated, and the scattering characteristics after penetrating aluminum-2024 alloy target of PELE are studied by different initial velocity. The explicit finite element analysis of PELE fragmentation was implemented with stochastic failure criterion in AUTODYN-3D code. As expansion of filling, the fragments were obtained velocities and dispersed laterally and further more enhancing the damage area largely. The number and shape of the PELE fragments were different depend on impact velocity and incidence angle of filling which fragment generated during penetration and lateral dispersion process.

• 대한기계학회논문집A
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• 제36권12호
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• pp.1577-1583
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• 2012

횡방향 관통 효율 강화 탄체(PELE)는 기폭장치가 없는 새로운 개념의 발사체이다. PELE 는 배면이 닫혀있는 고밀도 피복과 저밀도 충전재로 구성되어있다. PELE 의 폭발 특성을 연구하기 위해 AUTODYN-3D code 를 이용하여 발사체와 표적체의 모델을 구축하였다. PELE 의 의해 알루미늄-2024 합금 표적체를 천공하는 과정을 시뮬레이션으로 구현하였으며 또한 다양한 내부 충전재에 의해 분산되는 표적체의 파편 특성도 연구하였다. PELE 파편의 유한요소해석은 AUTODYN-3D code 의 추계학적 파괴기준을 사용하여 구현되었다. 내부 충전재의 팽창으로 인해 파편은 속도를 얻으며 횡방향으로 분산된다. 따라서 손상영역의 범위가 증강한다. 관통 및 횡방향 분산 과정에서 생성되는 파편은 내부 충전재의 충격 압력에 따라 그 양과 형태가 다른 것으로 나타났다.

• Journal of Ecology and Environment
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• 제45권3호
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• pp.97-104
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• 2021

Background: Asarum sieboldii Miq., a species of forest understory vegetation, is an herbaceous perennial belonging to the family Aristolochiaceae. The metapopulation of A. sieboldii is distributed sparsely and has a short seed dispersal distance by ants as their seed distributor. It is known that many flowers of A. sieboldii depend on self-fertilization. Because these characteristics can affect negatively in genetic structure, investigating habitat structure and assessment of genetic structure is needed. A total of 27 individuals in a valley were sampled for measuring genetic diversity, genetic distance, and genetic differentiation by RAPDPCR. Results: The habitat areas of A. sieboldii metapopulation were relatively small (3.78~33.60 m²) and population density was very low (five to seven individuals in 20×20 m quadrat). The habitat of A. sieboldii was a very shady (relative light intensity = 0.9%) and mature forest with a high evenness value (J = 0.81~0.99) and a low dominance value (D = 0.19~0.28). The total genetic diversity of A. sieboldii was quite high (h = 0.338, I = 0.506). A total of 33 band loci were observed in five selected primers, and 31 band loci (94%) were polymorphic. However, genetic differentiation along the valley was highly progressed (G_st = 0.548, N_m = 0.412). The average genetic distance between subpopulations was 0.387. The results of AMOVA showed 52.77% of variance occurs among populations, which is evidence of population structuring. Conclusions: It is expected that a small-scale founder effect had occurred, an individual spread far from the original subpopulation formed a new subpopulation. However, geographical distance between individuals would have been far and genetic flow occurred only within each subpopulation because of the low density of population. This made significant genetic distance between the original and new population by distance. Although genetic diversity of A. sieboldii metapopulation is not as low as concerned, the subpopulation of A. sieboldii can disappear by stochastic events due to small subpopulation size and low density of population. To prevent genetic isolation and to enhance the stable population size, conservative efforts such as increasing the size of each subpopulation or the connection between subpopulations are needed.