• The Korean Journal of Ecology
• /
• 제18권4호
• /
• pp.512-523
• /
• 1995

The central theme of Habital heterogeneity is to provide animals with habital complexity or structural diversity and to allow resource partitioning among individuals. In turn, the leads to population stability because prey can escape more easily with more hiding places causing less population fluctuation. Species diversity is characterized due to more potential niches both horizontally and verticall. Empirically, in homogeneous habitats population was less abundant, reproduction and survival were lower, spacing behavior, competition and dispersal were higher than in heterogeneous habitats. The results imply that diversity and conservation of species can be maintained through providing heterogeneous habitats.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제50권12호
• /
• pp.597-603
• /
• 2001

In the mathematical model for the transmission dynamics of HIV infection described in previous papers, the population under consideration is assumed to be homogeneous community of homosexual males for which the parameter x represents the constant rate at which individual members of the population acquire new sexual partners. This is a gross oversimplification since it is well known that individuals vary widely in their levels of sexual activity and in this papers the heterogeneous model is modified to allow for this variation. The pattern on the epidemic character of HIV, the causative agent of AIDS, was analysed by heterogeneous-mixing model. The computer simulation was performed using real date.

• 환경생물
• /
• 제21권4호
• /
• pp.337-341
• /
• 2003

Habitat heterogeneity can enhance biological diversity by providing variation in structural diversity. This paper reviewed heterogeneous habitat serves as a population stability and superior demographic performance (e.g., high density, survivorship, reproductive rate) can be observed compared with organisms with inferior demographic performance. The idea of habitat variation has been further developed in modelling. Furthermore the size and configuration (distribution) of a patch (of a particular habitat type) become effective for the stability of population through hiding places and food resources. Species diversity is related to habitat complexity that provides structural diversity to ground -dwelling organisms. Finally coarse woody debris can enhance habitat complexity thus stabilizing population fluctuation and increasing survivorship.

• The Korean Journal of Ecology
• /
• 제18권4호
• /
• pp.513-513
• /
• 1995

분리된 자원을 공급한다. 소척추동물과 포식자의 관계에서 동질로화된 서식지는 소척추동물의 생태적 지위를 단일화시켰으며, 숨을 곳의 급격한 감소로 인해 소척추동물의 군집 밀도를 큰 규모로 변동시킨다. 동질화된 서식지는 또한 서식지 구조의 복잡성을 사라지게 함으로써 종의 다양성이 감소된다는 연구결과를 검토하였다. 실험적연구에서 동질화된 서식지는 소척추동물의 서식밀도와 안정성의 감소, 세력권의 증가로 인한 종간경쟁, 분산의 증가로 특징지워졌다. 따라서 서식지의 이질성 유지는 종의 다양성과 보존의 기능을 높여주는데 기여함을 알게 되었다.

• Nuclear Engineering and Technology
• /
• 제43권6호
• /
• pp.523-530
• /
• 2011

In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Ito stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.

• Communications for Statistical Applications and Methods
• /
• 제9권3호
• /
• pp.853-864
• /
• 2002

In the analysis of categorical data subject to misclassification errors, the observed cell proportions are adjusted by a misclassification probabilities and estimates of variances are adjusted accordingly. In this case, it is important to determine the extent to which misclassification probabilities are homogeneous within a population. This paper considers methods to evaluate the power of chi-squared tests for homogeneity with complex survey data subject to misclassification errors. Two cases are considered: adjustment with homogeneous misclassification probabilities; adjustment with heterogeneous misclassification probabilities. To estimate misclassification probabilities, logistic regression method is considered.

• Ocean Science Journal
• /
• 제41권3호
• /
• pp.139-148
• /
• 2006

The distribution of the taxonomical composition and the density of meiobenthos depending on the sediment type has been studied in bottom sediments of Nha Trang Bay. The maximal population density and the taxonomical diversity were observed in the silted coarse and heterogeneous sand ($1031.4{\pm}419.7\;ind.\;10\;cm^{-2}$), whereas the minimal level of density and diversity ($588.1{\pm}152.5\;ind.\;10cm^{-2}$) was in the coarse and heterogeneous sand with shell debris and corals. The correlation between the median diameter of sediment particles and population density of meiobenthos has been revealed (r=0.82, p<0.05). In bottom sediments of Nha Trang Bay, twenty six taxonomic groups of meiobenthos were observed. Nematodes dominated in all sediment types. Representatives of four orders, twenty eight families and ninety seven genera of marine nematodes were identified. The vertical distribution of meiobenthos in different sediment types was considered. A sediment column (10 cm height) was sectioned by five 2 cm portions. In the last layer (8-10 cm) the most number of meiobenthic groups was found in sandy sediments. In the lower layers of silt sediments, only nematodes were found.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제9권1호
• /
• pp.137-144
• /
• 2004

The diamondback moth, Plutella xylostella, is notorious because of its extensive potential and actual dispersal ability. Previously, the Korean populations of P. xylostella was extensively collected and analyzed for their genetic population structure using a portion of mitochondrial DNA (mtDNA). One of the postulated characteristics on population genetic structure of the species includes the presence of heterogeneous haplotypes, possibly possessed by some dispersed ones from neighboring countries. In this study, we sequenced ten P. xylostella collected from China (∼2,000 km away from the middle part of Korea) to know the genetic relationships of these to the Korean P. xylostella. Sequence analysis of the identical portion of COI gene resulted in five haplotypes with the sequence divergence ranging from 0.5% (two nucleotides) to 1.1 % (five nucleotides) among them and from 0.7% (three) to 2.5% (11) to the pre-existing 52 Korean haplotypes. Phylogenetic analysis showed that the Chinese P. xylostella were neither clearly separated from the Korean haplotypes nor clustered with one heterogeneous Korean haplotype. This result reinforces the significance of gene flow in this species and suggests to exclude the possibility that the heterogeneous Korean haplotypes may have emigrated from China, where our samples were obtained, although further extensive investigation is required.

• The Korean Journal of Ecology
• /
• 제20권4호
• /
• pp.251-258
• /
• 1997

Few attempts have been made to discover the ecological function of coarse woody debris (CWD) despite its importance to small mammal population. Twenty-five pitfall traps and a hundred live traps were placed in three sites with high amounts of CWD and three sites with low amounts of CWD. Eleven species were caught, and Peromyscus maniculatus was the most abundant (45.6%, n=605). Among 11 speices, abundance of Tamias townsendii and Clethronomys gapperi were higher in sites with high amounts of CWD than in sites with low amounts of CWD. Home range size was larger in breeding season than in non-breeding season indicating mating search. Resident time of Peromyscus maniculatus was longer in sites with high amounts of CWD implying better stability in population. The increasing amount of coarse woody debris (CWD) enhanced the habitat use by small mammals, and animals in high amounts of CWD were more abundant and stable in population fluctuation. This study, therefore, concludes that CWD is a critical habitat element for small mammals in forest ecosystem.

• 한국정보처리학회논문지
• /
• 제6권10호
• /
• pp.2728-2739
• /
• 1999

This paper proposes an effective fusion algorithm for retrieval results from heterogeneous information sources in federated digital libraries. The algorithm determines the population of documents retrieved from involved information sources for a given query and evaluates the degree of relevance between the query and the population. The evaluated results are used as relevance distribution information for collection fusion. The main informations used for the fusion are relevance distribution among collections, the population size N, and ranking information of relevant documents in their origin. We also present th performance evaluation of the algorithm by developing the prototype of a meta-searcher.