• ALGAE
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• v.24 no.1
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• pp.31-38
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• 2009

The brown algae padina concrescens is widely distributed in the northwestern Pacific Mexico. We described the population of P. concrescens based on population parameters such as cover, density and size structure and reproduc-tion at two levels tide at the intertidal area in the southwestern Baja. California Peninsula. Monthly visits from January to December 2003 were done. Both cover and density were measured in situ by quadrants method. Samples were collected to obtain size structure and percentage of reproductive fronds. Our results show there is sparial vari-ation in the population structure more than temporal. Thus, cover and density peak were at different months ineach tide level studied, the lower tide level shows the high values in cover as well as density. The frond develop-ment was observed in height/width ratio this relation was consistent only in the low tidal zone. Size class distribu-tion has consistently small size plants in both tide levels.Reproduction was seasonal in the tide channel but in both tide levels all the reproductive plants were tetrasporophyte. Our results suggest that this population is pseudopere-nial and it strongly as a consequence of the intense competition in the intertidal zone.

• The Korean Journal of Applied Statistics
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• v.24 no.6
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• pp.1115-1128
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• 2011

Cut-off sampling that discards a part of the population from the sampling frame, is a widely used method for a highly skewed population like a business survey. Usually to the estimate of population total, we need to estimate the total of the take-nothing stratum. Many estimators have been developed to estimate the total of the take-nothing stratum. In this paper, we suggest a new composite estimator which combines the estimator suggested by Sarndal et al. (1992) and a ratio estimator obtained by small samples from the take-nothing stratum. Small simulation studies are performed for the comparison of the estimators and we confirm that the new suggested estimator is superior to the others.

• ALGAE
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• v.26 no.1
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• pp.51-60
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• 2011

Similar to other species of Gigartinaceae Chondrus crispus has an alternation of perennial, isomorphic gametophytic and sporophytic generations. As these two generations co-exist independently within populations and obtain their resources in a similar manner, intraspecific competition is expected. In populations within the southern Gulf of St. Lawrence, fronds of both generations of C. crispus occur in similar numbers. This equivalency can be related to substratum instability, where the population is dynamic with a high turn-over rate of genets. These observations support a stochastic hypothesis to account for distribution of gametophytes and sporophytes in this area. Along the Atlantic coast of Nova Scotia, where the substratum is stable, gametophytes are overwhelmingly predominant. Gametophytic predominance is greatest in the lower littoral zone where C. crispus is abundant and space is limited. Under the fucoid canopy where "free-space" exists, the gametophyte to sporophyte ratio is lower. Gametophytic and sporophytic fronds are distributed equally among different size-classes and size-distribution is not considered a competitive factor. Previous studies have shown that sporophytic fronds of C. crispus are more susceptible to infections by endophytic algae and other pathogens, and are more heavily grazed by herbivores than are gametophytic fronds. Thus, mechanistic factors are strongly implied in the selection of gametophytes in the Atlantic population.

• Korean Journal Plant Pathology
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• v.13 no.1
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• pp.46-56
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• 1997

Based on the principal component analysis (PCA) of Richards' parameter estimates, ginseng field soils were grouped as the principal component 1 (PC1) and the principal component 2 (PC2). The microflora and physico-chemical characteristics of each soil group were compared to elucidate soil environmental factors affecting the disease development of root rot of ginseng seedling. Among 3 soil groups by PC1, there were differences in the populations of total fungi (TF) and Cylindrocarpon plus Fusarium (C+F), and the population ratio of Cylindrocarpon plus Fusarium to total fungi or total bacteria (C+F/TF, C+F/TB) in rhizoplane of ginseng seedlings, the population of total actinomycetes (TA) and the population ratio of total Fusarium to total actinomycetes (Fus/TA) in soil, and soil chemical properties (EC, NO3-N, K, Mn, ect.). Among 4 soil groups by PC2, there were differences in TF, C+F, TB, C+F/TF and C+F/TB in the rhizoplane, Trichoderma plus Gliocladium (T+G) in soil, and P2O5 content in soil. Especially, EC, NO3-N, K, K/Mg and Mn were positively correlated to PC1, and TA was negatively to PC1; however, TF, C+F, TB, C+F/TF and C+F/TB in the rhizoplane were significantly correlated to PC2 positively. On the other hand, microbes in the rhizoplane were not significantly correlated to the stand-missing rate (SMR), although TA and Fe/Mn were negatively correlated, and pH and Ca were positively correlated to SMR.

• Journal of Life Science
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• v.7 no.4
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• pp.347-354
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• 1997

Some attempts were made to investigate the gentic characteristics of the brown planthopper(BPH), Nilaparvata lugens Sta${\aa}$l, biotypes. In terms of egg and nymphal periods, egg hatcgability, emergence ratio, and population change of BPH and plant damage of rice cultivars by the infestation of BPH biotypes and their hybrid progenies in field conditions. The egg and nymphal periods of the three of BPH biotypes and their hybrid progenies on Dongjinbyeo with no resistance gene were shorter than on rice cultivars with resistance gene. But the periods of biotype-2(♀) X 2(♂) (E) on Samgangbyeo with Bph-1 gene and biotype-3(♀) X 3(♂)(I) on Mirying 63 with bph-2 gene were as short as on Dongjinbyeo. The egg hatchability and emergence ratio of the three Bph biotypes and their hybrid progenies on Dongjinbyeo were higher than on the other rice cultivars, and those of E on Samgangbyeo and I on Miryang 63 were as high as on Dongjinbyeo. In rice paddy field, biotype-1(♀) X 1(♂)(A)$\sim$I infested on Dongjinbyeo, E onSamgangbyeo, and I on Miryang 63 were increased their population densities remarkably in next generation. Dongjinbyeo infested by A$\sim$I, and Myryang 63 infested by I were hopperburned at 60 days after infestation and had a damage rating of 0.9. But Samgangbyeo infested by E was no hopperburn(damage rating: 7.3) though it showed high BPH population at 60 days after infestation.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.144-148
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• 1998

Soil microorganisms including bacteria, fungi, and actinomycetes were seasonally isolated at depths (0.5~2, $10{\pm}1$, $50{\pm}1cm$) of field. The frequency of microbial isolates was employed for the determination of microbial population (CFU/g dry soil) and distribution ratio (%) in soil. Both bacteria (24-fold) and actinomycetes (7-fold) exhibited the biggest change at the depth of $50{\pm}1cm$, whereas fungi showed the maximum (13-fold) at $10{\pm}1cm$. On the whole, the bacterial population was high in spring soil, fungi in winter, and actinomycetes in autumn. Soil microorganisms also exhibited the seasonal variation on their distribution ratio (%). The maximum distribution ratio (85.7%) of bacteria was observed at the depth of $50{\pm}1cm$ in spring, whereas bacteria showed the minimum (35.2%) at the depth of $10{\pm}1cm$ in spring. The maximum distribution ratio (23.0%) of fungi was found at the depth of $50{\pm}1cm$ in spring, whereas its minimum (0.5%) at the depth of $10{\pm}1cm$ in spring. Actinomycetes exhibited the maximum distribution ratio (45.2%) at the depth of $10{\pm}1cm$ in spring, whereas its minimum (12.2%) was showed at the depth of $50{\pm}1cm$ in spring.

• Journal of Korean Neurosurgical Society
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• v.67 no.3
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• pp.345-353
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• 2024

Objective : Blood-blister aneurysms (BBAs) of the internal carotid artery (ICA) are challenging lesions with high morbidity and mortality rates. Although research on BBAs is well documented in different populations, the study of BBAs in the Tibetan population is extremely rare. This study aimed to evaluate the characteristics of BBAs and analyze the treatment modalities and long-term outcomes in the Tibetan population in comparison with the Han population. Methods : The characteristics of patients with BBAs of the ICA from January 2009 to January 2021 at our institution were reviewed. The features of aneurysms, treatment modalities, complications, and follow-up outcomes were retrospectively analyzed. Results : A total of 130 patients (41 Tibetan and 89 Han patients) with BBAs of the ICA who underwent treatment were enrolled. Compared with the Han group, the Tibetan group significantly demonstrated a high ratio of BBAs among ICAs (8.6%, 41/477 vs. 1.6%, 89/5563; p<0.05), a high ratio of vasospasm (34.1%, 14/41 vs. 6.7%, 6/89; p=0.001), a high risk of ischemic events (43.9%, 18/41 vs. 22.5%, 20/89; p<0.05), and a low ratio of good outcomes (modified Rankin scale, 0-2) at the 1-year follow-up (51.2%, 21/41 vs. 74.2%, 66/89; p<0.05). The multivariate regression model showed that ischemic events significantly contributed to the prediction of outcomes at 1 year. Further analysis revealed that microsurgery and vasospasm were associated with ischemic events. Conclusion : In comparison with Han patients, the Tibetan population had a high ratio of BBA occurrence, a high incidence of ischemic events, and a high ratio of poor outcomes. The endovascular approach showed more benefits in BBA patients.

• Journal of the Korean Statistical Society
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• v.32 no.2
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• pp.93-101
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• 2003

This paper deals with testing the equality of the coefficients of variation in two inverse Gaussian populations. The likelihood ratio, Lagrange-multiplier and Wald tests are presented. Monte-Carlo simulations are performed to compare the powers of these tests. In a simulation study, the likelihood ratio test appears to be consistently more powerful than the Lagrange-multiplier and Wald tests when sample size is small. The powers of all the tests tend to be similar when sample size increases.

• Communications for Statistical Applications and Methods
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• v.17 no.5
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• pp.625-637
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• 2010

In this paper we propose generalized multi-phase multivariate ratio estimators in the presence of multiauxiliary variables for estimating population mean vector of variables of interest. Some special cases have been deduced from the suggested estimator in the form of remarks. The expressions for mean square errors of proposed estimators have also been derived. The suggested estimators are theoretically compared and an empirical study has also been conducted.

• Journal of the Korean Regional Science Association
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• v.33 no.3
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• pp.101-113
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• 2017

This study examines the mobility of the disadvantaged population groups in terms of public transportation using the 2014 smart card data in Seoul, Korea. Particularly, we focus on the disadvantaged population such as senior group, junior group, and low-income population group. Based on the spatial distributions of public transportation mobility levels and the disadvantaged population groups, we identify specific areas where public transportation service should be improved for the disadvantaged population. As a result, we identify 15 administrative-dongs where the ratio of the disadvantaged population is high while the mobility index of public transit is low. The main contributions of this study are as follows. First, we use the smart card data which contains the information of actual trip made by individuals and develop the evaluation process of urban mobility for the disadvantaged population groups. Second, we identify the specific areas where public transportation service should be improved for the different group of the disadvantaged population. Lastly, we discuss policy implications to improve the urban mobility of the disadvantaged population.