• Research in Plant Disease
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• v.11 no.2
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• pp.193-197
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• 2005

The effect of pH on the survival of R. solanacearum and its transmission via roots of tomato in hydroponic culture were studied in laboratory and greenhouse. In laboratory experiment, R. solanacearum could not survive for 24h in nutrient solution with pH of $4{\cdot}0;or\;4{\cdot}5$, while 1, 14, 51 and $62\%$ of inoculum survived at pH $5{\cdot}0,\;5{\cdot}6\;and\;6{\cdot}5$, respectively. When tomato plants were inoculated with R. solanacearum through wounds on the stems, the bacteria moved downward from the inoculation site to the roots and infectious bacteria were released from the roots into the nutrient solution. Of two pH regimes tested in greenhouse nutrient-film technique(NFT) culture, the R. solanacearum population was significantly lower in pH 5.0 than in pH 6.5 in most sampling data. In treatments in which R. solanacearum was introduced by transplanting two root-inoculated plants, significantly move plants developed wilt at pH $6{\cdot}5$(34 out of 48 plants) than at pH 5.0(11 out of 48 plants). In addition, when the bacterium was introduced by transplanting two stem-inoculated plants at pH $6{\cdot}5$, seven out of 24 plants developed wilt.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.11-20
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• 2016

Objective: This study aimed to compare biomechanical data between elite and beginner cyclists during cycle pedaling by performing a comparative analysis and to provide quantitative data for both pedaling performance enhancement and injury prevention. Methods: The subjects of this study included 5 elite cyclists (age: $18{\pm}0years$, body mass: $64.8{\pm}9.52kg$, height: $173.0{\pm}4.80cm$) and 5 amateur cyclists (age: $20{\pm}0years$, mass: $66.6{\pm}2.36kg$, height: $175.6{\pm}1.95cm$). The subjects pedaled on a stationary bicycle mounted on rollers of the same gear (front: 50 T and rear: 17 T = 2.94) and cadence of 90. The saddle height was adjusted to fit the body of each subject, and all the subjects wore shoes with cleats. In order to obtain kinematic data, 4 cameras (GR-HD1KR, JVC, Japan) were installed and set at 60 frames/sec. An electromyography (EMG) system (Telemyo 2400T, Noraxon, USA) was used to measure muscle activation. Eight sets of data from both the left and right lower extremities were obtained from 4 muscles (vastus medialis oblique [VMO], vastus lateralis oblique [VLO], and semitendinosus [Semitend], and lateral gastrocnemius [Gastro]) bilaterally by using a sampling frequency of 1,500 Hz. Five sets of events ($0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, and $360^{\circ}$) and 4 phases (P1, P2, P3, and P4) were set up for the data analysis. Imaging data were analyzed for kinematic factors by using the Kwon3D XP computer software (Visol, Korea). MyoResearch XP Master Edition (Noraxon) was used for filtering and processing EMG signals. Results: The angular velocity at $360^{\circ}$ from the feet was higher in the amateur cyclists, but accelerations at $90^{\circ}$ and $180^{\circ}$ were higher in the elite cyclists. The amateur cyclists had greater joint angles at $270^{\circ}$ from the ankle and wider knee joint distance at $0^{\circ}$, $180^{\circ}$, and $360^{\circ}$ than the elite cyclists. The EMG measurements showed significant differences between P2 and P4 from both the right VLO and Semitend. Conclusion: This study showed that lower body movements appeared to be different according to the level of cycle pedaling experience. This finding may be used to improve pedaling performance and prevent injuries among cyclists.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.1
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• pp.8-13
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• 1997

The Holocene mud deposits in the southeastern innershelf of the Korean Peninsula were studied using the shallow seismic reflection profiles coupled with sediment sampling. The Holocene mud deposits are developed as a belt in the innershelf area from the mouth of the Nakdong River to off Pohang along the coastline. The surficial sediments in the study area gradually become finer and well sorted from south to north. The seismic facies in the Holocene sequence change northward from parallel reflectors in the mouth of the Nakdong River and northeastward prograding reflectors in the southern part off Ulsan to transparent layer in the nearshore off Ulsan to Pohang. The regional difference of seismic facies indicates that the Holocene sediment characters are varied with localities. By combining the surficial sediments properties with seismic facies patterns, the suspended sediments mostly supplied from the Nakdong River may be transported northward along the shore by the north-flowing Tsushima warm current. The Holocene mud sequence overlying the ravinement surface which is produced by erosion of underlying sediments during a rapid transgression can be interpreted as the highstand system tracts probably formed during the highstand of sea level similar to the present-day sea level.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.153-165
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• 2010

Large-Scale Particle Image Velocimetry (LSPIV) is an extension of particle image velocimetry (PIV) for measurement of flows spanning large areas in laboratory or field conditions. LSPIV is composed of six elements - seeding, illumination, recording, image transformation, image processing, postprocessing - based on PIV. Possible error elements at each step of Mobile LSPIV (MLSPIV), which is a mobile version of LSPIV, in field applications are identified and summarized the effect of the errors which were quantified in the previous studies. The total number of elemental errors is 27, and five error sources were evaluated previously, seven elemental errors are not effective to the current MLSPIV system. Among 15 elemental errors, four errors - sampling time, image resolution, tracer, and wind - are investigated through an experiment at a laboratory to figure out how those errors affect to velocity calculation. The analysis to figure out the effect of the number of images used for image processing on the velocity calculation error shows that if over 50 images or more are used, the error due to it goes below 1 %. The effect of the image resolution on velocity calculation was investigated through various image resolution using digital camera. Low resolution image set made 3 % of velocity calculation error comparing with high resolution image set as a reference. For the effect of tracers and wind, the wind effect on tracer is decreasing remarkably with increasing the flume bulk velocity. To minimize the velocity evaluation error due to wind, tracers with high specific gravity is favorable.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.4
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• pp.398-422
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• 2017

Objectives: The major aim of this study is to construct the database of retrospective exposure assessment for crystalline silica through reviews of literatures in South Korea. Methods: Airborne concentrations of crystalline silica were collected using an academic information search engine, Research Information Service System(RISS), operated by the Korea Education & Research Information Service(KERIS). The key words used for the literature search were 'silica', 'crystalline silica', 'cristobalite', 'quartz' and 'tridymite'. A total number of 18 published documents with the information of crystalline silica level in air or bulk samples were selected and used to estimate retrospective exposures to crystalline silica. Weighted arithmetic mean(WAM) calculated across studies was summarized by industry type. Industries were classified according to Korea Standard Industrial Classification(KSIC) using information provided in the literature. Results: A total of 2,131 individual air sampling data measured from 1987 to 2012 were compiled. Compiled individual measurement data consisted of 827 respirable crystalline silica (RCS), 31 total crystalline silica(TCS), 24 crystalline silica(CS), 778 respirable dust(RD) and 471 total dust(TD). Most of RCS measurements(68.9%) were collected from 'cast of metals(KSIC 243)'. Comparing industry types, 'mining coal and lignite(KISC 051)' showed the highest WAM concentration of RCS, $0.14mg/m^3$, followed by $0.11mg/m^3$ of 'manufacture of other non-metallic mineral products(KSIC 239)', $0.108mg/m^3$ of 'manufacture of ceramic ware(KSIC 232)', $0.098mg/m^3$ of 'heavy construction(KSIC 412)' and $0.062mg/m^3$ of 'cast of metals(KSIC 243)'. In terms of crystalline silica contents in airborne dust, 'manufacture of other non-metallic mineral products(KSIC 239)' showed the highest value of 7.3%(wt/wt), followed by 6.8% of 'manufacture of ceramic ware(KSIC 232)', 5.8% of 'mining of iron ores(KSIC 061)', 4.9% of 'cast of metals(KSIC 243)' and 4.5% of 'heavy construction(KSIC 412)'. WAM concentrations of RCS had no consistent trends over time from 1994 ($0.26mg/m^3$) to 2012 ($0.12mg/m^3$). Conclusion: The data set related RCS exposure level by industries can be used to determine not only the possibility of retrospective exposure to RCS, but also to evaluate the level of quantitative retrospective exposure to RCS.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.464-476
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• 2019

Objectives: This study aimed to assess the exposure levels of tollbooth workers to diesel particulate matter using black carbon (BC) and to find the correlations among variables associated with BC using the motor vehicle management act regulated by the Ministry of Land, Infrastructure and Transport. Methods: This study was performed over 14 days at a university in Seoul. BC levels were monitored using an aethalometer and were conducted around the breathing zones of the workers. There were three sampling locations: inside the tollbooth (front gate and rear gate) and an office as a control group. T-test, correlation, and multiple linear regression analysis were performed using SPSS. Results: The geometric mean (GM) of BC_30min concentrations in the exposure group was 2.44 ㎍/㎥, approximately 1.4 times higher than the control group (1.75 ㎍/㎥). The GM of BC_30min concentrations was 2.75 ㎍/㎥ during the heavy traffic time (9-10 am) and 2.30 ㎍/㎥ during non-heavy traffic times (p<0.001). The multiple linear regression analysis shows that the number of all types of vehicles and PM_2.5 concentrations in the atmosphere were factors increasing the GM of BC(ln(BC_30min)) concentrations (adjusted R²=0.42, p<0.001). The workers were constantly exposed to low concentrations (GM of BC_30min=2.44 ㎍/㎥), but they were exposed to peak concentrations instantly (BC_10sec=3545.04 ㎍/㎥). When the GM of BC_30min concentrations was momentarily represented as high, it was identified that a vehicle mainly using diesel fuel or an aging vehicle had passed. Conclusions: A ventilation system should be installed in the closed tollbooth or aging vehicles should be controlled so as not to pass tollbooths.

• Korean Journal of Microbiology
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• v.37 no.4
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• pp.277-283
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• 2001

The emergence of extended spectrum beta-lactamase(ESBL) producing bacteria is causing very serious problems in Korea. Although there have been many reports about these bacteria isolated from patients and clinical specimens, there is no report of ESBL-producing organisms isolated from natural evironment in Korea. This is the first study on the ESBL producing bacteria out of the medical system in Korea. Twenty-six ESBL producing bacteria were isolated only from sewerage plant drain water at Kwang-an beach among the sampling collected sites including snakehead fish plants in Myungi, Aquaculture Engineering Lab. in Pukyong National University and two public-bathrooms in Pusan, Korea. ESBL producing bacteria were identified by double-disk synergy test, conjugation, isoelectric focusing values and PCR. The species of ESBL producing bacteria were Enterobacter cloacae(4 strains), E. sakazakii(8 strains), Klebsiella pneumoniae subsp. pneumoniae(8 strains) and K. pneumoniae subsp. ozaenae(6 strains). TEM and SHV specific PCR products were detected from all the ESBL strains produced TEM+SHV products on the PCR plates. The pI values of ESBL produced by Klebsiella pneumoniae subsp. pneumoniae, K. pneumoniae subsp. ozaenae, Enterobacter cloacae, and E. sakazakii were 5.9, 5.9+5.4; 5.9, $5.9+5.4;{\ge}8.5$, 8.0+5.4, and 8.0+5.4, respectively on the IEF. Seven strains of the isolates were transfered their genes to E. coli RG488 $Rif^r$ by conjugation.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.267-274
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• 2004

Using geo-statistical method, yield data of different fields were analyzed to examine their field variability according to examining year, analysis method. Semivariogram and Kriged maps of geo-statistical analysis were used to examine their spatial dependence within a filed. The results obtained were as follows. 1) Descriptive statistical results of the yield showed that the yield and the difference of yield ranged from 100 to 946kg/10a and from 272 to 653kg/10a, respectively within a field. The coefficient of variation also ranged from 5.9 to 22.4 %. 2) More than 90% of yield data were placed between 350 to 850kg/10a. e results indicated that the gram mass flow sensor should have the measuring range from 0.34 to 0.82kg/s considering the yields when 4 rows head-feeding combine with 0.8 m/s of working speed was utilized. 3) A high spatial dependence was found within paddy field. The Q values ranged from 0.20 to 0.97, and the range of spatial dependence was from 6.9 to 53.3m. From this result, the rational sampling interval for yield investigation was estimated 6.9m. 4) Yields within a field between observation years showed considerable variability even if the field was evenly cultivated and managed. To apply precision agriculture in a paddy field, the field test should be continued to build a solid data-base including meteorological data, blight damage and insect damage.

• The Journal of Engineering Geology
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• v.15 no.1
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• pp.29-39
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• 2005

For detecting a ground contamination survey, soil sampling method have been used a drilling or coring technique in general. However these methods are very difficult to systematically real-time monitoring of variation of contamination degree in field. ]'n this research frequency Domain Reflectometry (FDR) system was suggested and carried out to experimental approaches for determination of oil contamination on surface and underground. Experimental method using FDR method was discussed with feasibility of measurement in the laboratory column test. It is determined to degree of oil contamination due to response of dielectric constant re-lated with volumetric water content(θ/sub w/) and volumetric oil content( θ/sub al/ ) of saturated and unsaturated soil media. And physical properties such as effective porosity and oil residual ratio of saturated soil media were also measured through real-time monitoring works using installed FDR measurement sensors, which are defected characteristics of oil movement in the saturated soil media under the soil column tests. In the results of these experiments, a range of effective porosity was estimated to about 0.35 compared with initial porosity 0.40 of manufactured saturated soil media, which is also calculated to about 87.5% to the ratio of initial porosity to effective porosity. Finally oil residual ratio which is compared with volumetric water content and volumetric oil content was calculated about 62.5%.

• Journal of The Korean Society of Grassland and Forage Science
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• v.27 no.2
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• pp.137-144
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• 2007

To investigate the effect of large patch infection on oxidative stress induction, super-oxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were compared between pathogen-infected and healthy (control) zoysiagrass. The sampling for leaves and roots were carried out every 2 days for a period of 6 days. The SOD activity was not significantly affected by pathogen-infection until day 2, but significant increase of both leaves (+48%) and roots (+49%) were observed at day 6 compared with control. The CAT activity was remarkedly increased by +25% in leaves and +101% in roots within the first 2 days and then rapidly decreased. The POD activity in pathogen-infected leaves was significantly increased by 74% at day 6. The increase of POD activity in pathogen-infected roots was 2-fold higher than that of the control at day 6. These results indicated that large patch-infection induce oxidative stress, and that SOD-CAT-POD antioxidant system of zoysiagrass was effectively operated.