• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.29-29
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• 2015

Clubroot disease is caused by the soil-born obligate plant pathogen Plasmodiophora brassicae. This pathogen can infect all cruciferous vegetables and oil crops, including Brassica rapa, B. oleracea, B. napus, and other Brassica species. Clubroot disease is now considered to be a major problem in Chinese cabbage production in China, Korea, and Japan. We collected several hundreds of P. brassicae infected galls from Korea, and isolated the single spore from the collection. For establishment of novel isolation, and mass-propagation methods for singe spore isolates of P. brassicae pathogen, we developed new filtration method using both cellulose nitrate filter and syringe filter. Accurate detection of P. brassicae pathogen in the field was done by using real-time PCR in the potential infested soil. When we tested the different pathogenicity on commercial Chinese cabbage varieties, P. brassicae from collected galls showed various morphological patterns about clubroot symptom on roots. To date, 8 CR loci have been identified in the B. rapa genome using the quantitative trait loci (QTL) mapping approach, with different resistant sources and isolates. We are trying to develop the molecular marker systems for detect all 8 CR resistant genes. Especially for the study on the interaction between pathogens and CR loci which are not well understood until now, genome wide association studies are doing using the sequenced inbred lines of Chinese cabbage to detect the novel CR genes.

• Journal of the Korean GEO-environmental Society
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• v.16 no.2
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• pp.33-43
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• 2015

This paper investigated the magnitude and distribution of earth pressure on the support system in jointed rock mass by considering different earth pressure coefficients, rock types and joint inclination angles. The study mainly focused on the effect of the earth pressure coefficients on the earth pressure. Based on a physical model test (Son & Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the earth pressure coefficients as well as the rock type and joint inclination angles. The effects of the earth pressure coefficients increased when the rock suffered more weathering and has no joint slide. The test results were also compared with Peck's earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground. This study indicated the earth pressure coefficients considering the rock types and joint inclination angles are important parameters influencing the magnitude and distribution of earth pressure, which should be considered when designing the support systems in jointed rock mass.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.408-412
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• 2004

A total of 23 springs distributed in the southern and northern sides of Mt. Hala in Jeju Island were seasonally sampled and analyzed for their major ion chemistry and oxygen and hydrogen isotope compositions to investigate their hydrogeochemical and isotopic characteristics. Dissolved ion concentrations of the south-side springs slightly increase with decreasing altitude. This indicates that dissolved ion concentrations of groundwater recharged at higher altitudes increase by water-rock interaction during the downgradient migration of groundwater through highly permeable volcanic aquifer. Dissolved ion concentrations of the north-side springs also slightly increase with decreasing altitude, but dramatically increase at ～300 m.a.s.l. This may indicate a sudden input of contaminants to the north-side groundwater system around ～300 m.a.s.l. Springs located in areas above ～300 m.a.s.l. have very low concentrations of dissolved ions, showing little seasonal variations. Whereas springs located in areas below ～300 m.a.s.l. show a big seasonal variation in the concentration of dissolved ions. Seasonal variation of oxygen isotope compositions of springs is ～3$\textperthousand$ for high-altitude springs (～1700 m.a.s.l.) and is ～2$\textperthousand$ near shore, indicating an attenuation of the variation through mixing with other groundwater bodies during migration.

• The Korean Journal of Soil Zoology
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• v.11 no.1_2
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• pp.1-6
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• 2006

The chigger is of importance to humans and animals as an irritating pest and a crucial vector of disease. We observed stylostome formation by larvae of Leptotrombidium pallidum in parasitized striped-field mouse (Apodemus agarius) pinna skin. The stylostome formations were also examined in detail by electron microscopy. The proximal and middle parts of the stylostome were formed as a rod-like structure containing a canal. The stylostome was coated with thick degenerated epidermal cells, and seemed to be formed a hyperplastic epidermis. The stylostome formation may result from an interaction between larval secretions and the host tissue. According to histological and morphological characteristics, the stylostome exhibited considerable inflammation in the epidermis and similar reactivity.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1043-1052
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• 1993

Field experiments were conducted to determine the optimum combination of performance parameters of a single-shank, tractor-mounted oscillating subsoiler. Tests were conducted at frequencies of oscillation of 3.7 , 5.67, 7.58, 9.48 and 11.456Hz ; amplitudes of 18, 21, 23.5, 34 and 36.5 mm ; and forward speeds of 1.84, 2.19 and 3.42 kmph at moisture content close to the plastic limit of the soil. It was observed that there was a reduction in average draft but an a increase in average total power requirement for oscillating than non-oscillating subsoiling. The draft and power ratios were significantly affected by the forward speed, frequency and amplitude. Their combined interaction expressed in terms of the velocity ratio parameter( the ratio of peak tool velocity and forward speed) however has the strongest influence. At the same velocity ratio, the draft reduction and power increase were less at higher amplitude of oscillation . As the oscillating frequency is increased toward the soil resonance the draft requirement becomes less. For the field conditions tested. the optimum operation was obtained at an amplitude of 36.5mm, frequency of 9.48Hz and speed of 2.19 kmph with a draft ratio of 0.33 and a power ratio of only 1.24.

• Ocean Systems Engineering
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• v.1 no.4
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• pp.337-353
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• 2011

In the present study, an offshore platform having large partial porous cylindrical members, which are composed of permeable and impermeable cylinders, is suggested. In order to calculate the wave force on large partial porous cylindrical members, the fluid domain is divided into three regions: a single exterior region, N inner regions and N beneath regions, and the scattering wave in each fluid region is expressed by an Eigen-function expansion method. Applying Darcy's law to the porous boundary condition, the effect of porosity is simplified. Wave excitation forces and wave run up on the structures are presented for various wave conditions. For the idealized three-dimensional platform having large partial porous cylindrical members, the dynamic response evaluations of the platform due to wave forces are carried out through the modal analysis. In order to examine the effects of soil-structure interaction, the substructure method is also applied. The displacement and bending stress at the selective nodal points of the structure are computed using various input parameters, such as the shear-wave velocity of soil, the wave height and the wave period. Applying the Monte Carlo Simulation (MCS) method, the reliability evaluations at critical structure members, which contained uncertainties caused by dynamic forces and structural properties, are examined by the reliability index with the results obtained from MCS.

• Geomechanics and Engineering
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• v.15 no.2
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• pp.755-767
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• 2018

This paper uses a finite element based approach to provide a comprehensive understanding to the behaviour and the design performance of buried uPVC pipes with different diameters. It also investigates pipes with good and poor haunch support and proposes minimum safe wall thicknesses for these pipes. The results for pipes with good haunch support showed that the maximum pipe wall stress and deformation increase as the diameter increased. The results for pipes with poor haunch support showed an increase in the dependency of the developed vertical displacement on the haunch support as the diameter or the backfill height increased. Additionally, poor haunch support was found to increase the soil pressure, with the effect increasing as the diameter increased. The design of uPVC pipes for both poor and good haunch support was found to be governed by critical buckling. A key outcome is a new design chart for the minimum wall thickness, which enables the robust and economic design of buried uPVC pipes. Importantly, the methodology adopted in this study can also be applied to the design of flexible pipes manufactured from other materials, buried under different conditions and subjected to different loading arrangements.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.598-613
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• 2013

This paper deals with the dynamic effect of pipeline installation and embedment for the on-bottom stability design of offshore pipelines on soft clay. On-bottom stability analysis of offshore pipelines on soft clay by DNV-RP-F109 (DNV, 2010) results in very unreasonable pipe embedment and concrete coating thickness. Thus, a new procedure of the on-bottom stability analysis was established considering dynamic effects of pipeline installation and pipe-soil interaction at touchdown point (TDP). This analysis procedure is composed of three steps: global pipeline installation analysis, local analysis at TDP, modified on-bottom stability analysis using DNV-RP-F109. Data obtained from the dynamic pipeline installation analysis were utilized for the finite element analysis (FEA) of the pipeline embedment using the non-linear soil property. From the analysis results of the proposed procedure, an optimum design of on-bottom stability of offshore pipeline on soft clay can be achieved. This procedure and result will be useful to assess the on-bottom stability analysis of offshore pipelines on soft clay. The analysis results were justified by an offshore field inspection.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1244-1248
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• 2008

지표수-지하수 통합모형인 SWAT-MODLFOW는 토양수가 침루과정을 거쳐 지하수로 유입되는 일방향 구조를 갖고 있어 지하수위 상승 및 하강에 따른 토양수량, 침루량, 중간유출량 등 수문성분량의 변화를 고려할 수 없다. 따라서 본 연구에서는 지하수위 변화에 따른 토양수의 분포양상 변화를 고려할 수 있도록 토양수-지하수간의 연결 구조를 양방향으로 개선하여 두 영역간의 연결성을 강화하였다. 지하수위가 상승할 경우 토양대와 지하수대간의 중첩 영역이 생기게 되는데, 이 중첩 영역을 지하수대로 간주하여 영역 내 흐름거동이 지하수 유동 메커니즘을 따르는 토양수-지하수 결합루틴을 새롭게 제시하였다. 이 결합루틴은 지하수 상승, 하강에 따라 토양수대의 두께가 변하는 가변 토양층 방식(variable soil layer method)으로 계산을 수행할 수 있도록 코드를 구성하였다. 개선된 SWAT-MODLFOW 모형을 무심천 유역에 적용하여 토양수와 지하수간의 상호작용을 해석하고 하천저지대와 같이 지하수위 상승지역에서의 수문성분량의 분포를 보다 현실적으로 구현할 수 있음을 입증하였다.

• Geotechnical Engineering
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• v.7 no.1
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• pp.33-40
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• 1991

This paper reports the application study of the ground reinforcement under a pipe joint. The soil-reinforcement interaction helps to minimize the stress concentration at joint. The settlement pattern and the earth pressure variation have been evaluated under the pipeline subjected to differential settlement. The pipeline is fixed at one side with the other side set free being loaded with a uniform surface loading. The problem has been studied by means of laboratory model test and flite element technique, and the analysis results are compared for both non-reinforced and reinforced cases to evaluate the effectiveness of the soil reinforcement for restraining the settlement of the pipeline.