• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.311-316
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• 2008

This study aimed to obtain equilibrium concentration on adsorption removal of ammonia nitrogen by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical characteristics of activated carbon and dynamics of ammonia nitrogen removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. It was noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon was $4.6{\times}10^{-8}$ which is bigger than that of granular activated carbon. The adsorption rate constant on ammonia nitrogen of powered activated carbon with high porosity and low effective diameter was highest as 0.416 hr-1 and the effective pore diffusivity ($D_e$) was lowest as $1.17{\times}10^{-6}cm^2/hr$, and the value of ammonia nitrogen adsorption rate constant of granular activated carbon was $0.149{\sim}0.195hr^{-1}$. It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter and bigger porosity was better and its rate constant was also high. With a little adsorbent dosage of 2 g, there was no difference removal ability of ammonia nitrogen as change of adsorption properties.

• Journal of Korean Society on Water Environment
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• v.26 no.3
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• pp.491-496
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• 2010

This study aimed to obtain equilibrium concentration on adsorption removal of phosphorus by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical properties of activated carbon and dynamics of phosphorus removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. Phosphorus adsorption equilibrium reaching time of powdered activated carbon was reduced as the dosage of activated carbon increases, while granular activated carbon despite increased dosage did not have influence on adsorption equilibrium reaching times of phosphorus as well, taking more than 10 hours. It was also noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon on phosphorus was 4.26 which is bigger than those of granular activated carbon. The adsorption rate constant on phosphorus of powered activated carbon with low effective diameter and iodine number was highest as $8.888hr^{-1}$ and the effective pore diffusivity ($D_e$) was lowest as $2.45{\times}10^{-5}cm^2/hr$, and the value of phosphorus adsorption rate constant of granular activated carbon was $0.174{\sim}0.372hr^{-1}$, It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter was better and its rate constant was also high.

• Korean Journal of Weed Science
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• v.12 no.3
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• pp.230-260
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• 1992

The paper was reviewed the research results on weed dynamics and effective control methods in direct-seeded rice crop. Direct seeding method resulted in drastic increment of weed growth compared to transplanting method and also changed in troublesome weed flora. Two to three fold more weeds were harvested at the direct seeded rice and weed flora of dominant species shifted toward $C_4$type grass weeds. Some of the important troublesome weeds in direct seeded rice were Echinochloa crus-galle, Oryza saliva ssp spontanea, Leptochloa chinensis. Setaria viridus. Digitaria adsendens, Sesbania exaltata, Aeschynomene indica, Algae, etc. Yield loss due to weed competiton was about 40-60% for water-seeded and about 70-100% for dry-seeded rice while these for transplanted rice were about 25-35% for mechanical transplanting and about 10-20% for manual transplanting, respectively. Integrated weed management concept was neede to approach weed control effectively. Several cultural technologies were very effective to suppress the weed growth. These were tillage operation, water management, seeding date and seeding rate. Crop residues of barley, rice, wheat, oat and italian ryegrass were also effectivly suppressed the paddy weeds particularly to Potamogeton distiuctus, a perennial broadleaf weed. A pathogen of Epicoccosorus nematosporus identified from Eleocharis kuroguwai was an excellent potential bioagent to control the most troublesome perennial sedge weed of E. Kuroguwai without arising any detrimental effect. The herbicidal efficacy of this pathogen was as high as bentazon herbicide. Plant growth regulator of paclobutrazol (pp-333) was another possible alternative to reduce the herbicide use. In current, herbicide exhibited the most conspicuous results to control weeds in direct-seeded rice even though the application technologies were not fully established. Recommendations for herbicide application were suggested for in both water-and dry-seeded rice in USA, Japan and Korea, respectively. To make better and comprehensive recommendations further studies on weed ecology and herbicide development were emphasized.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.3
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• pp.30-39
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• 2011

In this note, a systematic design of a new robust nonlinear continuous variable structure control system(VSCS) based on the modified state dependent nonlinear form is presented for the control of uncertain affine nonlinear systems with mismatched uncertainties and matched disturbance. After an affine uncertain nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a new robust nonlinear VSCS is presented. The uncertainty of the nonlinear system function is separated into the tow parts, i.e., state dependent term and state independent term for extension of target plants. To be linear in the closed loop resultant dynamics and in order to easily satisfy the existence condition of the sliding mode, the transformed linear sliding surface is applied. A corresponding control input is proposed to satisfy the closed loop exponential stability and the existence condition of the sliding mode on the linear transformed sliding surface, which will be investigated in Theorem 1. For practical application, the discontinuity of the control input as the inherent property of the VSS is improved dramatically. Through a design example and simulation studies, the usefulness of the proposed controller is verified.

• The Korean Journal of Ecology
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• v.18 no.3
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• pp.307-321
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• 1995

Division of ecoregions having respective functions was attempted through quantitative and qualitative analysis on vegetation diversity, and heterogeneity and on soil environment of the study sites. Field research was carried out in a square of 81 ㎢ around Andongpo (126°38'E, 37°30'N), Kimpo-gun, Kyonggi provice. Conventional methods applied are as follows: classical syntaxonomy by the Zurich-Montpellier School, interpolation method to determine the degree of diversity, heterogeneity and distribution pattern of vegetation, and correlation analysis between soil properties and plant communities. 41 plant communities were identified and composed of 6 forests, 4 mantle and 31 herb communities including 6 saltmarsh plant communities. In a mesh, number of plant communities was highly correlated to the number of species. The highest number of plant community and species was 25 communities·km-2·mesh-1 and 381 species· km-2·mesh-1 ,and the highest value of vegetation heterogeneity was 28.1 species· community-1·mesh-1. Their lowest numbers were 4 communities·km-2·mesh-1. and 28 species·km-2·mesh-1. and 7 species·community-1·mesh-1, respectively. Contour map on vegetation diversity and heterogeneity enabled us to establish two regions; coastal and inland vegetation. Isoline 〔150〕,〔10〕and〔10〕and〔15〕on the species diversity, the community diversity and the vegetation heterogeneity, respectively, were regarded as ecolines in the study area. Cl- content was recognized as the most important factor from correlation analysis between soil properties. Ordination of sites indicated that the study area be divided into two edaphic types: inland and coastal habitats. It was considered that the extent of desalinization in soil played a major role in determining the species composition in the reclamed area. By matching edaphic division of habitats with division of vegetation structures, designation of ecoregion was endorsed. The approach of current study was suggested as an effective tool to implement an assessment of the vegetation dynamics by the disparity of natural environment and anthropogenic interferences.

• Journal of Ecology and Environment
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• v.33 no.4
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• pp.289-298
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• 2010

A number of characteristics of the Lake H$\ddot{o}$vsg$\ddot{o}$l watershed, such as the lake's location at the edge of the Central Asian continuous permafrost zone, provide a unique opportunity to evaluate possible anthropogenic impacts in this remote area in northern Mongolia. In this study, we compared stream solute concentrations in six sub-watersheds in the Lake H$\ddot{o}$vsg$\ddot{o}$l watershed. Water samples were collected during the summer months between 2003 and 2005. Concentrations of $Cl^-$ ranged from 9.8 to $51.3\;{\mu}mol/L$; average nitrate concentrations were very low and ranged from undetectable to $1.1\;{\mu}mol/L$ and average ${SO_4}^{2-}$ concentration at sampling stations with minimal animal grazing ranged from 66 to $294\;{\mu}mol/L$. Average dissolved organic carbon (DOC) concentrations ranged from 642 to $1,180\;{\mu}mol$ C/L. We did not find statistically significant differences in DOC concentrations among the six streams, although DOC concentrations tended to be higher in the two northernmost streams, possibly related to differences in the active layer above the permafrost. Dissolved organic nitrogen (DON) concentrations were correlated with DOC concentration, and followed the same spatial pattern as those for DOC. In streams in this remote watershed, total dissolved nitrogen was made up of mostly organic N, as has been found for other regions distant from anthropogenic N sources. Overall, these results suggest that future research on the dynamics of DOC and DON in this watershed will be especially insightful in helping to understand how changes in climate and land use patterns will affect transformations, retention, and export of dissolved organic matter within these sub-watersheds in the Lake H$\ddot{o}$vsg$\ddot{o}$l region.

• Journal of Forest and Environmental Science
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• v.34 no.5
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• pp.359-375
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• 2018

The long term ecological effects have been reported in natural forest ecosystem due to various anthropogenic disturbances, especially in tropics of the world. The present study was carried out in the sanctuary area of central India to assess the changes on litter biomass, litterfall pattern and soil attributes under different disturbance regimes. The study area includes three forest circles i.e., Bhoramdeo, Jamunpani and Salehwara each comprising three disturbances regimes viz., high, medium and low severity of biotic pressure. A noticeable variation and impact were recorded in different sites. The impact varies significantly from least disturbed sites to highly disturbed sites across the circle and among different disturbances level. The seasonal mean total forest floor biomass across the forest circles varied from 2.18 to $3.30t\;ha^{-1}$. It was found highest under lightly disturbed site and lowest under heavily disturbed site. Total litterfall varied from 5.11 to $7.06t\;ha^{-1}\;yr^{-1}$ across the forest circle. Lowest litterfall was recorded at heavily disturbed site while highest in lightly disturbed site. Annual turnover of litter varied from 69-73% and the turnover time ranged between 1.37-1.45 years. The turn over time was higher for heavily disturbed site and lower for lightly disturbed site. The heavily disturbed site of all the circle showed the sandy loam soil texture, whereas moderately and lightly disturbed site comprised of sandy loam, sandy clay loam and clay soil texture, respectively. The bulk density decreases from heavily disturbed site to lightly disturbed site and the pH of soils ranged from 5.57-6.89 across the circle. Across the circle the total soil nitrogen ranged from 0.12-0.21%, phosphorus from 10.03-24.00 kg and Potassium from $139.88-448.35kg\;ha^{-1}$, respectively. Our results demonstrate that anthropogenic disturbances regime significantly influences forest floors in terms of mass, composition and dynamics along with litterfall rate and soil properties.

• Journal of Ecology and Environment
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• v.35 no.3
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• pp.177-188
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• 2012

We analyzed crown development in Aucuba japonica Thunb. var. japonica resulting from the responses of phytoelements to habitat light conditions over a long period of time. Over the years, the degree of extension unit (EU) dimorphism and the degree of anisophylly were higher under shaded conditions than in brighter conditions. An overall temporally increasing pattern in the degree of EU dimorphism was found while no clear-cut trend was found in the case of anisophylly. EU length and number of leaves per EU co-varied in a spatio-temporal context. The number of terminal buds and their sizes acted as the key initiators of morphological differences of phytoelements which were further amplified following bud break. Leaf area density was displayed mostly in the apex peripheral layer of the crown and the apex layer received most of the incident light. There was a tradeoff between annual leaf production and mean leaf size. Depending on the heterogeneity of irradiance level within a crown, correlative growth inhibition caused higher EU mortality at brighter sites. Due to high mortality, shorter EUs had a mere role in the construction of structural framework of the crown except for the formation of some gaps. There was a strong convergence of EU dimorphism, anisophylly, EU extension growth and variations in leaf size towards formation of functional crown to reduce potential self-shading. Depending on the irradiance level, Aucuba japonica Thunb. var. japonica showed two different modes of crown expansion. At the brighter sites, individual crown expansion was progressive while at the darker sites, individual crown expanded in a diminishing manner and maintained a stable size. A plant's "growth diminishing phase" appeared earlier at shaded sites than brighter sites.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.3
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• pp.376-389
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• 2012

Ethnic entrepreneurship, an important means by which immigrants improve economic status, is widely believed to be facilitated by their residential concentration, i.e. ethnic enclaves. However, the recent immigrants' residential dispersion and re-clustering in some selected well-to-do suburbs portend changes in the role of ethnic enclave as a nest of immigrant entrepreneurship. This paper investigates the impacts of the residential dispersal on ethnic entrepreneurship with a case study of Korean small businessmen in Chicago, Illinois PMSA. The research utilizes the Public Use Microdata Sample (PUMS) to know the overall changes in Korean entrepreneurship through 1990s and conducts a survey to understand reactions and surviving strategies of Korean enclave businessmen to the residential shifts. Relevant to those analyses is the enclave-economy hypothesis which argues benefit from spatial clustering of co-ethnic entrepreneurs by yielding more business opportunities and higher returns.

• Journal of The Korean Astronomical Society
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• v.53 no.5
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• pp.103-115
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• 2020

We analyze the spatially resolved kinematics of gas and stars for a sample of ten hidden type 1 AGNs in order to investigate the nature of their central sources and the scaling relation with host galaxy stellar velocity dispersion. We select our sample from a large number of hidden type 1 AGNs, which are identified based on the presence of a broad (full width at half maximum ≳1000 km s^-1) component in the Hα line profile and which are frequently mis-classified as type 2 AGNs because AGN continuum and broad emission lines are weak or obscured in the optical spectral range. We used the Blue Channel Spectrograph at the 6.5-m Multiple Mirror Telescope to obtain long-slit data with a spatial scale of 0.3 arcsec pixel^-1. We detected broad Hβ lines for only two targets; however, the presence of strong broad Hα lines indicates that the AGNs we selected are all low-luminosity type 1 AGNs. We measured the velocity, velocity dispersion, and flux of stellar continuum and gas emission lines (i.e., Hβ and [O III]) as a function of distance from the center. The spatially resolved gas kinematics traced by Hβ or [O III] are generally similar to the stellar kinematics except for the inner center, where signatures of gas outflows are detected. We compare the luminosity-weighted effective stellar velocity dispersions with the black hole masses and find that our hidden type 1 AGNs, which have relatively low back hole masses, follow the same scaling relation as reverberation-mapped type 1 AGN and more massive inactive galaxies.