• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.56-64
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• 2021

Leakage due to deterioration and damage is one of the major causes of volume change by freezing and thawing, and it leads micro-cracking and surface scaling in concrete structures. The deterioration of damaged concrete accelerates with the chloride attack. Thus, in the detailed guidelines for facility performance evaluation (2020), the quality of cover concrete and the freeze-thaw (FT) repetition cycle were newly suggested for concrete durability assessment. The quality of cover concrete should be evaluated by the rebound hammer test and the FT repetition cycle should be also considered in the deterioration environmental assessment. This study suggested the application of fast dynamic based nonlinear ultrasound method to monitor initial micro-scale damage under freezing and thawing environment. Concrete specimens were fabricated with different water-cement ratios (40%, 60%) and air contents (1.5% and 3.0%). The compressive strength, rebound number, relative dynamic modulus, and nonlinear ultrasound were measured with different FT cycles. The scanning electron microscopy was also performed to investigate the micro-scale FT damage. As a result, both the rebound number and the relative dynamic modulus had difficulty to detect early damage but the proposed method showed a potential to detect initial micro-scale damage and predict the FT resistance performance of concrete.

• Progress in Medical Physics
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• v.25 no.2
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• pp.110-115
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• 2014

To compare 2 beam arrangements, circumferential equally angles (EA) beams or partially angles (PA) beams for stereotactic body radiation therapy (SBRT) of primary lung cancer for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) delivery techniques with respect to target, ipsilateral lung, contralateral lung, and organs-at-risk (OAR) dose-volume metrics, as well as treatment delivery efficiency. Data from 12 patients, four treatment plans were generated per data sets ($IMRT_{EA}$, $IMRT_{PA}$, $VMAT_{EA}$, $VMAT_{PA}$). The prescribed dose (PD) was 60 Gy in 4 fractions to 95% of the planning target volume (PTV) for a 6-MV photon beam. When compared with the IMRT and VMAT treatment plan for 2 beams, conformity index, homogeneity index, high dose spillage, D2 cm (Dmax at a distance ${\geq}2cm$ beyond the PTV), R50 (ratio of volume circumscribed by the 50% isodose line and the PTV), resulted in similar. But Dmax of the Organ at risk (OAR), spinal cord, trachea, resulted in differ between four treatment plans. Especially $HDS_{location}$ showed big difference in 21.63% vs. 26.46%.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.3
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• pp.301-307
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• 2015

A bond-based peridynamic model has been shown to be capable of analyzing many of dynamic brittle fracture phenomena. However, there have been issued limitations on handling constitutive models of various materials. Especially, it assumes bonds act independently of each other, so that Poisson's ratio for 3D model is fixed as 1/4 as well as taking only account the bond stretching results in a volume change not a shear change. In this paper a state-based peridynamic model of dynamic brittle fracture is presented. The state-based peridynamic model is a generalized peridynamic model that is able to directly use a constitutive model from the standard theory. It permits the response of a material at a point to depend collectively on the deformation of all bonds connected to the point. Thus, the volume and shear changes of the material can be reproduced by the state-based peridynamic theory. For a linearly elastic solid, a plane stress model is introduced and the damage model suitable for the state-based peridynamic model is discussed. Through a convergence study under decreasing the peridynamic nonlocal region($\delta$-convergence), the dynamic fracture model is verified. It is also shown that the state-based peridynamic model is reliable for modeling dynamic crack propagatoin.

• Radiation Oncology Journal
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• v.16 no.4
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• pp.399-408
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• 1998

Purpose : This study was designed to demonstrate the potential therapeutic advantage of 3-dimensional (3-D) treatment planning over the conventional 2-dimensional (2-D) approach in patients with carcinoma of the nasopharynx. Materials and Methods : The two techniques were compared both qualitatively and quantitatively for the boost portion of the treatment (19.8 Gy of a total 70.2 Gy treatment schedule) in patient with T4. The comparisons between 2-D and 3-D plans were made using dose statistics, dose-volume histogram, tumor control probabilities, and normal tissue complication probabilities. Results : The 3-D treatment planning improved the dose homogeneity in the planning target volume. In addition, it caused the mean dose of the planning target volume to increase by 15.2$\%$ over 2-D planning. The mean dose to normal structures such as the temporal lobe, brain stem, parotid gland, and temporomandibular joint was reduced with the 3-D plan. The probability of tumor control was increased by 6$\%$ with 3-D treatment planning compared to the 2-D planning, while the probability of normal tissue complication was reduced. Conclusion : This study demonstrated the potential advantage of increasing the tumor control by using 3-D planning. but prospective studies are required to define the true clinical benefit.

• Journal of Chest Surgery
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• v.32 no.5
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• pp.422-427
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• 1999

Background: Tachycardia induced heart failure model would be the model of choice for the dilated cardiomyopathy. This more closely resembles the clinical syndrome and does not require major surgical trauma, myocardial ischemia and pharmacological or toxic depression of cardiac function. When heart failure is progressive, application of new surgical procedures to the faling heart is highly risky. It has been shown that recovery trajectory from heart failure is a new method in decreasing animal mortality. The purpose is to establish the control datas for recovery trajectory in the canine heart failure model. Material and Method: 21 mongrel dogs were studied at 4 stages(baseline, at the heart failure, 4 and 8 weeks after recovery). Heart failure was induced during 4 weeks of continuous rapid pacing using a pacemaker. Eight weeks of trajectory of recovery period was allowed. Indices of left ventricular function and dimension were measured every 2 weeks and the hemodynamics were measured by use of Swan-Ganz catheterization and thermodilution method every 4 weeks. Values were expressed as mean${\pm}$standard deviation. Result: 4(20%) dogs died due to heart failure. Left ventricular end-diastolic volume at the 4 stages were 40.8${\pm}$7.4, 82.1${\pm}$21.1, 59.9${\pm}$7.7 and 46.5${\pm}$6.5ml. Left ventricular end-systolic volume showed the same trend. Ejection fractions were 50.6${\pm}$4.1, 17.5${\pm}$5.8, 36.3${\pm}$7.3, and 41.5${\pm}$2.4%. Blood pressure and heart rate showed no significant changes. Pressures of central vein, right ventricle, pulmonary artery, and pulmonary capillary wedge showed significant increase during the heart failure period, normalizing at the end of recovery period. Stroke volumes were 21.5${\pm}$8.2, 12.3${\pm}$3.5, 17.9${\pm}$4.6, and 15.5${\pm}$3.4ml. Blood norepinephrine level was 133.3${\pm}$60.0pg/dL at the baseline and 479.4${\pm}$327.3pg/dL at the heart failure stage(p=0.008). Conclusion: Development of tachycardia induced heart failure model is of high priority due to ready availability and reasonable amenability to measurements. Recovery trajectory after cessation of tachycardia showed reduction of cardiac dilatation and heart function. Application of new surgical procedures during the recovery period could decrease animal mortality.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.35-46
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• 2021

Purpose : By comparing and analyzing treatment plans using abdominal compression and The Continuous Positive Air Pressure(CPAP) during SABR of lung cancer, we try to contribute to the improvement of radiotherapy effect. Materials & Methods : In two of the lung SABR patients(A, B patient), we developed a SABR plan using abdominal compression device(the Body Pro-Lok, BPL) and CPAP and analyze the treatment plan through homogeneity, conformity and the parameters proposed in RTOG 0813. Furthermore, for each phase, the X, Y, and Z axis movements centered on PTV are analyzed in all 4D CTs and compared by obtaining the volume and average dose of PTV and OAR. Four cone beam computed tomography(CBCT) were used to measure the directions from the center of the PTV to the intrathoracic contacts in three directions out of 0°, 90°, 180° and 270°, and compare the differences from the average distance values in each direction. Result : Both treatment plans obtained using BPL and CPAP followed recommendations from RTOG, and there was no significant difference in homogeneity and conformity. The X-axis, Y-axis, and Z-axis movements centered on PTV in patient A were 0.49 cm, 0.37 cm, 1.66 cm with BPL and 0.16 cm, 0.12 cm, and 0.19 cm with CPAP, in patient B were 0.22 cm, 0.18 cm, 1.03 cm with BPL and 0.14 cm, 0.11 cm, and 0.4 cm with CPAP. In A patient, when using CPAP compared to BPL, ITV decreased by 46.27% and left lung volume increased by 41.94%, and average dose decreased by 52.81% in the heart. In B patient, volume increased by 106.89% in the left lung and 87.32% in the right lung, with an average dose decreased by 44.30% in the stomach. The maximum difference of A patient between the straight distance value and the mean distance value in each direction was 0.05 cm in the a-direction, 0.05 cm in the b-direction, and 0.41 cm in the c-direction. In B patient, there was a difference of 0.19 cm in the d-direction, 0.49 cm in the e-direction, and 0.06 cm in the f-direction. Conclusion : We confirm that increased lung volume with CPAP can reduce doses of OAR near the target more effectively than with BPL, and also contribute more effectively to restriction of tumor movement with respiration. It is considered that radiation therapy effects can be improved through the application of various sites of CPAP and the combination with CPAP and other treatment machines.

• Radiation Oncology Journal
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• v.28 no.3
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• pp.177-183
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• 2010

Purpose: Simulation using computed tomography (CT) is now widely available for radiation treatment planning for breast cancer. It is an important tool to help define the tumor target and normal tissue based on anatomical features of an individual patient. In Korea, most patients have small sized breasts and the purpose of this study was to review the margin of treatment field between conventional two-dimensional (2D) planning and CT based three-dimensional (3D) planning in patients with small breasts. Materials and Methods: Twenty-five consecutive patients with early breast cancer undergoing breast conservation therapy were selected. All patients underwent 3D CT based planning with a conventional breast tangential field design. In 2D planning, the treatment field margins were determined by palpation of the breast parenchyma (In general, the superior: base of the clavicle, medial: midline, lateral: mid - axillary line, and inferior margin: 2 m below the inframammary fold). In 3D planning, the clinical target volume (CTV) ought to comprise all glandular breast tissue, and the PTV was obtained by adding a 3D margin of 1 cm around the CTV except in the skin direction. The difference in the treatment field margin and equivalent field size between 2D and 3D planning were evaluated. The association between radiation field margins and factors such as body mass index, menopause status, and bra size was determined. Lung volume and heart volume were examined on the basis of the prescribed breast radiation dose and 3D dose distribution. Results: The margins of the treatment field were smaller in the 3D planning except for two patients. The superior margin was especially variable (average, 2.5 cm; range, -2.5 to 4.5 cm; SD, 1.85). The margin of these targets did not vary equally across BMI class, menopause status, or bra size. The average irradiated lung volume was significantly lower for 3D planning. The average irradiated heart volume did not decrease significantly. Conclusion: The use of 3D CT based planning reduced the radiation field in early breast cancer patients with small breasts in relation to conventional planning. Though a coherent definition of the breast is needed, CT-based planning generated the better plan in terms of reducing the irradiation volume of normal tissue. Moreover it was possible that 3D CT based planning showed better CTV coverage including postoperative change.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.3
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• pp.219-225
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• 2011

The physicochemical properties of rice endosperm from five rice varieties and effects of milling on baking bread properties of rice flour were investigated. Five rice varieties exhibited different level of amylose content. The ratio of longer amylopectin chain length to the distribution of endosperm starches was the highest in Goami3. According to the RVA measurement of rice flours, the pasting temperatures of Seolgaengbyeo and Goamibyeo were lower than those of the other rice varieties. There were differences in the changes of swelling power of rice flour under increasing temperature. Each rice flour sample for bread-making was processed into two different particle size by using an air-classification mill, and significant differences were observed among cultivars in the average particle size and damaged starch content of rice flours. Rice flour of Seolgaengbyeo with fine particle size showed the highest value in specific volume after baking.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.21-32
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• 2023

Interrill erosion dominates in forest areas, and the erosion rate in surface-disturbed areas is significantly increased by the development and expansion of rill. In this study, soil erosion experiments using simulated rainfall and inflow were performed to understand the development and the micromorphological changes of rill on steep slopes. The characteristic factors of the micromorphology, such as the rill cross section, rill volume, rill density, rill order, and rill sharpness, were analyzed according to steepness and location (upper or lower) of slope. The head-cut of the simultaneous incised rills by rainfall simulation moved rapidly upslope, and the randomly developed rills expanded deeply and widely with their connection. The rill cross section evolved to downslope gradually increased. The rill volume occupied about 78 % of the sediment volume, confirming that the contribution of the sediment from the rill erosion is greater than that of the interrill erosion. Although the rate of increase in rill order slowed as the slope increased, the total length and density of the rill generally increased. As the slope increased from 15° to 20°, the bed incision of rills became larger than the sidewall expansion, and the rill sharpness increased by 1.6 times. The runoff coefficient on the lower slope decreased by 12.3 % than that on the upper slope. It was evaluated that the subsoil exposures and formation changes by the rill expansion increased the infiltration rate. Although the sediment accompanying the rills generally increased with slope increase, it was directly influenced by the hydraulic velocity of enhanced rill with the local convergence and expansion in the process of the rill evolution.

• Tunnel and Underground Space
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• v.29 no.4
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• pp.262-279
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• 2019

In the engineering barriers of high-level radioactive waste disposal, gases could be generated through a number of processes. If the gas production rate exceeds the gas diffusion rate, the pressure of the gas increases and gases could migrate through the bentonite buffer. Because people and the environment can be exposed to radioactivity, it is very important to clarify gas migration in terms of long-term integrity of the engineered barrier system. In particular, it is necessary to identify the hydro-mechanical mechanism for the dilation flow, which is a very important gas flow phenomenon only in medium containing large amounts of clay materials such as bentonite buffer, and to develop and validate new numerical approach for the quantitative evaluation of the gas migration phenomenon. Therefore, in this study, we developed a two-phase flow model considering the mechanical damage model in order to simulate the gas migration in the engineered barrier system, and validated with 1D gas flow modelling through saturated bentonite under constant volume boundary conditions. As a result of numerical analysis, the rapid increase in pore water pressure, stress, and gas outflow could be simulated when the dilation flow was occurred.