• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.83-90
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• 2006

This paper investigates experimentally the fire resistance performance and spatting resistance of high performance reinforced concrete column member subjected to fire containing polypropylene fiber(PP fiber) and cellulose fiber(CL fiber). An increase in PP fiber and CL fiber contents, respectively resulted in a reduction of fluidity due to fiber ball effect. Air content is constant with m increase in fiber content. Compressive strength reached beyond 50 MPa. Based on fire resistance test, severe failure occurred with control concrete specimen, which caused exposure of reinforcing bar. No spall occurred with specimen containing PP fiber. This is due to the discharge of internal vapour pressure. Use of CL fiber superior to control concrete in the side of spatting resistance, localized failure at comer of specimen was observed. Corner of specimen had deeper neutralization than surface of specimen. Specimen containing PP fiber had the least damaged area due to spatting. Neutralization depth ranged between 6 and 8 mm Residual compressive strength of specimen containing PP fiber maintained 40%, which is larger than control concrete with 20% of residual strength. Specimen containing CL fiber had 25% or residual strength.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.6
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• pp.650-657
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• 2001

This paper explains the process of designing a shielded encircling remote field eddy current (RFEC) probe to inspect nuclear fuel cladding tubes and investigates resulting signal characteristics. To force electromagnetic energy from exciter coil to penetrate into the tube, exciter coil is shielded outside by laminations of iron insulated electrically from each other. Effects of shielding and the proper operating frequency are studied by the finite element analysis and the location for sensor coil is decided. However, numerically simulated signals using the designed probe do not clearly show the defect indication when the sensor passes a defect and the other indication appeared as the exciter passes the defect is affected by the shape of shielding structure, which demonstrates that the sensor is directly affected by exciter fields. For this reason, the sensor is also shielded outside and this shielding dramatically improves signal characteristics. Numerical modeling with the finally designed probe shows very similar signal characteristics to those of inner diameter RFEC probe. That is, phase signals show almost equal sensitivity to inner diameter and outer diameter defects and the linear relationship between phase signal strength and defect depth is observed.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.2
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• pp.1-15
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• 2015

Urban flooding threatens human beings and facilities with chemical and physical hazards since the beginning of human civilization. Recent studies have emphasized the integration of data and models for effective urban flood inundation modeling. However, the model set-up process is tend to be time consuming and to require a high level of data processing skill. Furthermore, in spite of the use of high resolution grid data, inundation depth and velocity are varied with building treatment methods in 2-D inundation model, because undesirable grids are generated and resulted in the reliability decline of the simulation results. Thus, it requires building generalization process or enhancing building orthogonality to minimize the distortion of building before converting building footprint into grid data. This study aims to develop building generalization method for 2-dimensional inundation analysis to enhance the model reliability, and to investigate the effect of building generalization method on urban inundation in terms of geographical engineering and hydraulic engineering. As a result to improve the reliability of 2-dimensional inundation analysis, the building generalization method developed in this study should be adapted using Digital Building Model(DBM) before model implementation in urban area. The proposed building generalization sequence was aggregation-simplification, and the threshold of the each method should be determined by considering spatial characteristics, which should not exceed the summation of building gap average and standard deviation.

• Journal of Acupuncture Research
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• v.21 no.2
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• pp.205-222
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• 2004

Objective: To investigate the effects of acupointed Choksamni(ST36), Kokchi(LI11) and Arbitrary acupoint on NADPH-diaphorase, neuronal nitric oxide synthase(nNOS), neuropeptide Y(NPY) and vasoactive intestinal peptide(VIP) in the cerebral cortex of spontaneously hypertensive rats. Methods: The experimental groups were divided into four groups: Normal, Choksamni(ST36), Kokchi(LI11), arbitrary group. Needles were inserted into acupoints at the depth of 0.5 cm with basic insertion method. Such stimulation was applied continuously for 10 minutes, every other day, for 10 sessions of treatments. Thereafter we evaluated changes in NADPH-d-positive neurons histochemically and changes in nNOS, NPY and VIP-positive neurons immunohistochemically. Results : The optical densities of NADPH-d-positive neurons of all the Choksamni & Kokchi groups were significantly different in all areas of cerebral cortex as compared to arbitrary group. In motor1, sensory2, cingulate2, insular, peripheral, visual cortex there was a significant difference between Choksamni & Kokchi group. The optical densities of nNOS-positive neurons of Choksamni group were significantly different in all areas except for auditory, visual and pisiform cortex and Kokchi group in all areas except for auditory and pisiform cortex as compared to arbitrary group. And there was a significant difference in cingulate1, cingulate2, ectohinal, visual cortex between Choksamni & Kokchi group. The optical densities of NPY neurons of Choksamni group were significantly different in cingulate2, insular, pisiform cortex and Kokchi group in motor1, motor2, sensory1, cingulate2, ectorhinal cortex as compared to arbitrary group. And there was no significant difference between Choksamni & Kokchi group. The optical densities of VIP neurons of Choksamni group were significantly different in all areas except for motor1, auditory cortex and Kokchi group in sensory1, insular, ectorhinal, perirhinal, visual, pisiform cortex as compared to arbitrary group. And there was a significant difference in cingulate1, cingulate2, retrosplenial, auditory corterx between Choksamni & Kokchi group. Conclusion : Our results demonstrated that acupuncture on Choksamni(ST36) & Kokchi(LI11) changes the control activities of the NO system in the cerebral cortex of SHR and according to areas there were significant difference between two groups. In all cerebral cortex areas there were distributed NPY & VIP and there were no significant difference among Choksamni(ST36), Kokchi(LI11) and arbitrary group.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.21-31
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• 2018

This paper analyzes the displacements of CFRD which was completed by field measurement. It is to understand the deformation behavior of the dam body according to the water level change from the impounding time. And it was compared with numerical analysis results. As a result of measuring the behavior of the dam crest and downstream slope according to impounding, horizontal displacements in axis direction of the dam, upstream and downstream displacements and settlements occurred mostly when the water level reaches about half of the dam height. The displacements continued until the water level reached its maximum. After that, it showed a constant convergence regardless of the water level. Horizontal displacements of the face slab which is the most important in CFRD were similar at all locations. The Horizontal displacements of the face slab showed the trends of increasing in winter and decreasing in summer due to the effect of the outside temperature before impounding. Also, the displacements increased until the water level reached about half of the dam height. After that, they decreased with rising in water level. As a result, the face slab behaviors according to seasonal change after impounding as well as water level condition. It is judged because of the material characteristics of the concrete slab. Numerical analysis showed slightly different maximum settlement and depth of occurrence from the measuring data after construction of the dam. It is considered that this is due to various design and construction differences such as the estimation of input parameters in analysis, construction period, and the layer thickness of construction. For the overall period of the dam, the settlements were mostly completed during the construction period and some settlements occurred in the early days of impounding and then converged.

• Journal of Ecology and Environment
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• v.41 no.11
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• pp.302-309
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• 2017

Background: Large-scale land-use change is being caused by various socioeconomic problems. Land-use change is necessarily accompanied by changes in the regional carbon balance in terrestrial ecosystems and affects climate change. Therefore, it is crucial to understand the correlation between environmental factors altered by land-use change and the carbon balance. To address this issue, we studied the characteristics of soil carbon flux and soil moisture content related to rainfall events in mountain pastures converted from deciduous forest in Korea. Results: The average soil moisture contents (SMC) during the study period were 23.1% in the soil respiration (SR) plot and 25.2% in the heterotrophic respiration (HR) plot. The average SMC was increased to 2.1 and 1.1% in the SR and HR plots after rainfall events, respectively. In addition, saturated water content was 29.36% in this grassland. The soil water content was saturated under the consistent rainfall of more than $5mm\;h^{-1}$ rather than short-term heavy rainfall event. The average SR was increased to 28.4% after a rainfall event, but the average HR was decreased to 70. 1%. The correlation between soil carbon flux rates and rainfall was lower than other environmental factors. The correlation between SMC and soil carbon flux rates was low. However, HR exhibited a tendency to be decreased when SMC was 24.5%. In addition, the correlation between soil temperature and respiration rate was significant. Conclusions: In a mountain pasture ecosystem, rainfall induced the important change of soil moisture content related to respiration in soil. SR and HR were very sensitive to change of SMC in soil surface layer about 0-10-cm depth. SR was increased by elevation of SMC due to a rainfall event, and the result was assumed from maintaining moderate soil moisture content for respiration in microorganism and plant root. However, HR was decreased in long-time saturated condition of soil moisture content. Root has obviously contributed to high respiration in heavy rainfall, but it was affected to quick depression in respiration under low rainfall. The difference of SMC due to rainfall event was causative of a highly fluctuated soil respiration rate in the same soil temperature condition. Therefore, rainfall factor or SMC are to be considered in predicting the soil carbon flux of grassland ecosystems for future climate change.

• Imaging Science in Dentistry
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• v.32 no.1
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• pp.35-39
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• 2002

Purpose: The altered gantry angle during scanning for some multiplanar reconstruction CT program (CT/MPR) may cause distortion of the image. The aim of this study was to ascertain whether there is a image distortion in a reformatted image when the gantry and the object are equally inclined using ToothPix and DentaScan program. Materials and Methods: A resin block model with four cylindrical holes and a human dry mandible were used. Two MPR software packages, ToothPix and DentaScan program, were used for reformatted panoramic images. The block and the gantry were equally inclined at 0°, 15°, and 30°. Results: With ToothPix program, a resin block model with empty holes and a dry mandible showed inclined images in the reformatted panoramic image. Increasing the gantry angle, the depth and inclination of the holes were increased in the reformatted central panoramic images. However, a resin block model with gutta perch a in its holes and a dry mandible with a wire in its mandibular canal didn't show image distortion. With DentaScan program, image distortion was not seen in any situation. Conclusion: ToothPix program may distort the reformatted image when the gantry angle is not at zero degrees. However, with DentaScan program, the patient may be positioned comfortably and the gantry can be adjusted to the patient positioning.

• Korean Journal of Community Nutrition
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• v.25 no.1
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• pp.48-60
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• 2020

Objectives: Most cohort studies used food frequency questionnaires (FFQ) to evaluate coffee consumption as it assesses habitual dietary patterns, whereas some studies have used the 24-hour recalls (24HR) as it elicits in-depth description of foods and the amount eaten. The aim of this study was to compare FFQs and 24HR to assess the consumption of various types of coffee. Methods: We included 25,904 participants aged 40 years or older from the Health Examinees (HEXA) Study of the Korean Genome and Epidemiologic Study (KoGES). Each participant completed one FFQ and one-day (n=11,280) or two-day 24HR (n=14,624). We classified coffee types into: black coffee, coffee with sugar and cream, and coffee with sugar alone or cream alone. We compared the proportions of nondrinkers, black coffee, and coffee with sugar and cream through FFQ and 24HR. Results: Among those who completed one FFQ and one-day 24HR, 39.4% of "nondrinkers" on one-day 24HR reported that they did not drink coffee on their FFQs. Whereas among those who complete two-day 24HR, 71.2% of "nondrinkers" on two-day 24HR said that they did not drink coffee on their FFQs. Among those who completed one FFQ and oneday 24HR, 58.3% marked "black coffee" on one-day 24HR said that they drank black coffee on their FFQs. Among those who complete two-day 24HR, 58.8% marked "black coffee" on two-day 24HR said that they drank black coffee on their FFQs. The kappa coefficients and percent agreements were 0.4 and 59.6%, respectively, for the comparison of coffee intake between FFQ and one-day 24HR, and 0.6 and 72.8%, respectively, for the comparison of coffee intake between FFQ and two-day 24HR. Conclusions: We found discrepancies between FFQs and 24HR in the types of coffee consumed. Such limitations should be considered when using the 24HR data to examine the effect of coffee consumption on disease development.

• The Journal of Engineering Geology
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• v.11 no.1
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• pp.81-99
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• 2001

In order to clarify an effect of the cutoff grouting, a series of field experiments were performed during construction of the waterway tunnel from the River Gilancheon(Andong) to the Youngcheon dam. The experiments were conducted in three different ways based on the grouting time in the construction sequence, i.e., the pre-grouting, after-grouting and consolidation grouting tests. And those were also planned to compare the efficiency of grouting in relation to the material types of grout, base rock types and other geologic factors such as discontinuities, depth and direction of grouting holes, and number of grouting stages. Among the materials of grout employed in the experiments, such as a common Portland cement, a micro-cement, a micro-cement with sodium silicate, and a urethane, the urethane was the most effective as the cutoff grouting. And for the same grout material, the pre-grouting was more effective to cutoff the water inflow comparing to the after-grouting and the consolidation grouting. For the rock types, the grouting efficiency in the sedimentary rocks as a base rock was less than the other rocks such as granite and volcanic rocks, which is believed due to the smaller separation of joints and the abundance of infilling materials in the joints developed in the sedimentary rocks. There was no direct relationship between the total RMR value of the rock mass and the grouting efficiency, however, the joint separation which is one of the RMR criteria is believed to have positive relation to the grouting efficiency. And the direction of the grouting holes might not so much affect on the grouting efficiency while increasing the number of grouting stage showed the better results.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.483-494
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• 2019

This study aimed to determine the extent of artificial aquifer recharge and to evaluate appropriate recharge techniques based on field investigations and comparative analysis of each recharge method. Characteristics of the aquifer determine the target aquifer and the recharge method for artificial groundwater recharge. Electrical conductivity surveys, drilling, permeability tests, and grain-size analysis indicate that the hydraulic conductivity of weathered soil and weathered rock is higher than that of upper unconsolidated soil. Pumping tests indicate that the groundwater level was stable at a depth of 12 m until 9 hours of pumping, but after that it dropped again, indicating anisotropic aquifer characteristics. Three types of artificial recharge method were reviewed, including recharge wells, ditches, and ponds, and a combination of two methods is proposed: a recharge well system directly injecting into weathered soil and rock sections with good permeability, and an injection ditch that can increase the recharge effect by line-type injection in the upstream area. The extent of groundwater recharge by the selected methods will be evaluated through on-site tests and if their applicability is verified, they will contribute to securing water in areas of water shortage.