• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1148-1155
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• 2010

To suggest a modified shallow foundation design method which can be considered the scale effect of foundation on IGM(intermediate geomaterial) soil layer, the weathered soil layer that is uniformly formed up to 8m(2B) with over 50 N-value is selected and 3 times field loading tests are performed on several sized square-shaped shallow foundations with 30, 75, 150, 240 and 400cm in width respectively. Because the soil modulus of elasticity(Es) calculated by soil investigation and 1st field test(PBT) results showed an underestimated tendency, a modified correlation is required for the reasonable estimation of Es on the weathered soil. Also, the N-value was increased with an increasing in depth. However, the N-values around the test foundations showed the different values even though the foundations on the same level because the test site was arranged by excavation. Therefore, the more detail soil investigations are required for the each test foundations respectively. Since Es based on elasticity theory is determined by the stress distribution shape of the foundation and elasticity modulus of the soil, the scale effect considered pressure-settlement curve can be clearly derived from the correlation on stress distribution shape and the variation of soil elasticity modulus with depth. Therefore, the modified correlation will be suggested to estimate a reasonable Es on the weathered soil, and the scale effect considered shallow foundation design method is also developed based on the elastic theory and field tests in this research.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.4
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• pp.101-112
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• 1985

It is important to extract the mechanical informations from the image sequences of the moving object. We have studied the computer algorithms for analysis of the moving heart using X-ray image sequence. A new mathematical method was developed to estimate the local epicardial deformation, wall thickness, and the regional circumferential and longitudinal wall stress using biplane coronary cineangiograms. In this method, the motion images of the coronary artery bifurca-tion points were used as natural landmarks for the kinematic analysis of the ventricular deformation. In four dogs and a normal patient's coronary cineangiograms, the estimation results show the validity of the present analysis, compared with the experimental results based upon the implanted markers. Thus, the present method provides a new method of evaluating the regional wall deformation and wall stress together with the blood vessel conditions using the coronary cineangiography procedure.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.263-270
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• 2016

Corrosion resistance steel has been widely used for port and offshore structures exposed to harsh coastal and oceanic environments, due to lower corrosion rate. New higher strength corrosion resistance steel tubes named STKM500 in KS D 3300 were recently developed by domestic technology and expected to replace foreign ASTM A690 steel. In this study, tensile test results are included to show higher yield and tensile strength of STKM500. Then, buckling test results obtained from 2m, 6m, and 12m steel tubes are demonstrated, based on which an allowable axial compressive stress curve for STKM500 steel tubes is suggested.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.299-310
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• 2008

In this study, the regression analysis method was tested for the estimation of peak stress at stress concentration area in the cervical bone. Submerge type EZ plus implant (Megagen. Daegu, Korea), 4.1 mm in cervical diameter and 9.6 mm in endosseous length, were axisymmetrically modelled together with surrounding alveolar bone of which the width was 10 mm. Vertical force of 100 N was applied to a head of crown above 8.5 mm from the outer surface of the cortical bone. Four different mesh models were composed of differently sized elements in vicinity of sharp corners, and they include 6 stress monitoring points that are located in the same geometrical points regardless of the differences in the meshes. Primary consideration was given to the stresses in the cortical bone surrounding the implant neck. The results showed that virtually all the stresses were concentrated in the cortical bone regardless of mesh designs. The peak stresses were successfully calculated by a regression analysis in a stable manner, as far as the mesh is designed to represent the acute gradient of stresses near the sharp corner.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.10
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• pp.1691-1698
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• 2020

Objective: The study sought to estimate the relationship between body surface temperature (BST) and temperature humidity index (THI) and to present the validity of THI as a heat stress index in the field. Methods: Eight Hanwoo heifers (20 to 32 month) were examined in a field trial, with a space allowance of 10 ㎡ per head. The BST was measured using an infrared thermographic camera. The BST of five body regions (eyes, hindquarters, nose, part of horns, and ears), ambient temperature (AT), and relative humidity (RH) were measured 7 times daily (07, 09, 11, 13, 15, 17, and 19 h) during each season with three replicates. Results: The THI ranged 34.0 to 56.9 during spring (AT, -1.0℃ to 13.4℃), 75.1 to 84.7 during summer (AT, 24.9℃ to 33.6℃), 55.8 to 70.9 during autumn (AT, 13.0℃ to 26.0℃) and 17.5 to 39.2 during winter (AT, -10.4℃ to 1.0℃). In the regression analysis, the coefficient of determination (R²) between THI and BST was 0.88, 0.72, 0.83, 0.86, and 0.85 for the eyes, hindquarters, nose, part of horn, and ears area, respectively. This indicates that BST has a strong correlation with AT and RH. Expression equations were estimated as Y (THI) = 31.54+0.1085X (BST of eyes) and Y (THI) = 30.48+0.1147X (BST of hindquarters) by simple linear regression analysis in this experiment. Conclusion: Consequently, the upper bound for heat stress estimation can be specified ranging from THI of 65 (eyes) to 70 (hindquarters). From this we can expect a precise feeding system for Korean native cattle in the field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.273-281
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• 2010

In this paper, a method to predict the fatigue life of an axle drive shaft by the calibrated accelerated life test (CALT) method is proposed. The CALT method is very effective for predicting lifetimes, significantly reducing test time, and quantifying reliability. The fatigue test is performed by considering two high stress and one low stress levels, and the lifetime at the normal stress level is predicted by extrapolation. In addition, in this study, the major reliability parameters such as the lifetime, accelerated power index, shape parameter, and scale parameter are determined by conducting various experiments. The lifetime prediction of the axle drive shaft is verified by comparing the experimental results with load spectrum data. The results confirm that the CALT method is effective for lifetime prediction and requires a short test time.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.3
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• pp.217-224
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• 2014

Ground-based remote sensing can be used as one of the non-destructive, fast, and real-time diagnostic tools for predicting yield, biomass, and nitrogen stress during growing season. The objectives of this study were: 1) to assess biomass and nitrogen (N) status of tobacco (Nicotiana tabacum L.) plants under N stress using ground-based remote sensors; and 2) to evaluate the feasibility of spectral reflectance indices for estimating an application rate of N and predicting yield of tobacco. Dry weight (DW), N content, and N uptake at the 40th and 50th day after transplanting (DAT) were positively correlated with chlorophyll content and normalized difference vegetation indexes (NDVIs) from all sensors (P<0.01). Especially, Green NDVI (GNDVI) by spectroradiometer and Crop Circle-passive sensors were highly correlated with DW, N content and N uptake. The yield of tobacco was positively correlated with canopy reflectance indices measured at each growth stage (P<0.01). The regression of GNDVI by spectroradiometer on yield showed positively quadratic curve and explained about 90% for the variability of measured yield. The sufficiency index (SI) calculated from data/maximum value of GNDVI at the $40^{th}$ DAT ranged from 0.72 to 1.0 and showed the same positively quadratic regression with N application rate explaining 84% for the variability of N rate. These results suggest that use of reflectance indices measured with ground-based remote sensors may assist in determining application rate of fertilizer N at the critical season and estimating yield in mid-season.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.155-163
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• 2013

This study explores the structural behavior of module joints in floating concrete structures subjected to shear. Crack patterns, shear behavior and shear capacity of shear keys in joints of concrete module were investigated. Test parameters included shear key shape, or inclination of shear keys, confining stress levels and compressive strength of concrete. Test results showed that shear strength of joints increased as shear key inclination increased. Test results also showed that shear strength of concrete module joints increased with the increase of confining stress levels. The equation for predicting shear strength of joints was suggested, which was based on the test results. Shear strength prediction by using the equation suggested in this study showed good agreement with test results.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.1
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• pp.63-70
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• 2019

We aimed to propose a novel computational approach to predict the electromechanical performance of pre- and post-mitral valve cerclage annuloplasty (MVCA). Furthermore, we tested a virtual estimation method to optimize the left ventricular basement tightening scheme using a pre-MVCA computer model. The present model combines the three-dimensional (3D) electromechanics of the ventricles with the vascular hemodynamics implemented in a lumped parameter model. 3D models of pre- and post-MVCA were reconstructed from the computed tomography (CT) images of two patients and simulated by solving the electromechanical-governing equations with the finite element method. Computed results indicate that reduction of the dilated heart chambers volume (reverse remodeling) appears to be dependent on ventricular stress distribution. Reduced ventricular stresses in the basement after MVCA treatment were observed in the patients who showed reverse remodeling of heart during follow up over 6 months. In the case who failed to show reverse remodeling after MVCA, more virtual tightening of the ventricular basement diameter than the actual model can induce stress unloading, aiding in heart recovery. The simulation result that virtual tightening of the ventricular basement resulted in a marked increase of myocardial stress unloading provides in silico evidence for a functional impact of MVCA treatment on cardiac mechanics and post-operative heart recovery. This technique contributes to establishing a pre-operative virtual rehearsal procedure before MVCA treatment by using patient-specific cardiac electromechanical modeling of pre-MVCA.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.3
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• pp.334-340
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• 2019

Objective: The objective of this study was to investigate the genetic components of daily milk yield and to re-rank bulls in South Korea by estimated breeding value (EBV) under heat stress using the temperature-humidity index (THI). Methods: This study was conducted using 125,312 monthly test-day records, collected from January 2000 to February 2017 for 19,889 Holstein cows from 647 farms in South Korea. Milk production data were collected from two agencies, the Dairy Cattle Genetic Improvement Center and the Korea Animal Improvement Association, and meteorological data were obtained from 41 regional weather stations using the Automated Surface Observing System (ASOS) installed throughout South Korea. A random regression model using the THI was applied to estimate genetic parameters of heat tolerance based on the test-day records. The model included herd-year-season, calving age, and days-in-milk as fixed effects, as well as heat tolerance as an additive genetic effect, permanent environmental effect, and direct additive and permanent environmental effect. Results: Below the THI threshold (${\leq}72$; no heat stress), the variance in heat tolerance was zero. However, the heat tolerance variance began to increase as THI exceeded the threshold. The covariance between the genetic additive effect and the heat tolerance effect was -0.33. Heritability estimates of milk yield ranged from 0.111 to 0.176 (average: 0.128). Heritability decreased slightly as THI increased, and began to increase at a THI of 79. The predicted bull EBV ranking varied with THI. Conclusion: We conclude that genetic evaluation using the THI function could be useful for selecting bulls for heat tolerance in South Korea.