• Progress in Medical Physics
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• v.30 no.3
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• pp.65-73
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• 2019

Purpose: We evaluated the motion-induced dosimetric effects on the field-in-field (FIF) technique for whole-breast irradiation (WBI) using actual patient organ motion data obtained from cine electronic portal imaging device (cine EPID) images during treatment. Materials and Methods: Ten breast cancer patients who received WBI after breast-conserving surgery were selected. The static FIF (SFIF) plan involved the application of two parallel opposing tangential and boost FIFs. To obtain the amplitude of the internal organ motion during treatment, cine EPID images were acquired five times for each patient. The outside contour of the breast (OCB) and chest wall (CW) contour were tracked using in-house motion analysis software. Intrafractional organ motion was analyzed. The dynamic FIF (DFIF) reflecting intrafractional organ motion incorporated into the SFIF plan was calculated and compared with the SFIF in terms of the dose homogeneity index (DHI_90/10) for the target and V₂₀ for the ipsilateral lung. Results: The average motion amplitudes along the X and Y directions were 1.84±1.09 mm and 0.69±0.50 mm for OCB and 1.88±1.07 mm and 1.66±1.49 mm for CW, respectively. The maximum motion amplitudes along the X and Y directions were 5.53 and 2.08 mm for OCB and 5.22 and 6.79 mm for CW, respectively. Significant differences in DHI_90/10 values were observed between SFIF and DFIF (0.94 vs 0.95, P<0.05) in statistical analysis. The average V₂₀ for the lung in the DFIF was slightly higher than that of the SFIF in statistical analysis (19.21 vs 19.00, P<0.05). Conclusion: Our findings indicate that the FIF technique can form a safe and effective treatment method for WBI. Regular monitoring using cine EPID images can be effective in reducing motion-induced dosimetric errors.

• KSTLE International Journal
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• v.7 no.2
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• pp.27-34
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• 2006

Knudsen number is the ratio of molecular mean free path versus mm thickness and the criterion to determine the flow form. When its value is lower than 0.01, the flow can be assumed to has no slip boundary condition. And in the case that the value is between 0.01 and 10, then the flow has slip boundary condition at both the adjacent walls. The condition of the air flow between the rotating journal and top foil in the air foil bearing is determined by the rotating speed and load, and the Knudsen number is also varied by those values. Because the molecular mean free path is variable to the pressure and temperature, more exact formulation is necessary to understand and analyze the flow regime. In this study, the analysis considering Knudsen number formulated with those variables (pressure, temperature and mm thickness) was executed. The approximate value was examined using the equation to confirm whether the flow has the slip or no-slip boundary condition. From the analytic investigation, it was decided to range approximately 0.01 to 1.0 and the flow can be supposed to have the slip boundary condition. Under the condition of the slip flow, the static characteristics of the air foil bearing were examined using modified Reynolds equations. The results were compared with those considering no slip condition. It shows that the slip condition makes the flow decelerates and the load carrying capacity decreases compared with no slip condition. And as the bearing number and eccentricity ratio increase, the load carrying capacity also increased at both the cases. From this result, it can be supposed that the bearing torque also increases. In the analysis of the dynamic characteristics, the perturbed Knudsen number was taken into consideration. Because the Knudsen number is expressed as the terms of each variable, the perturbed equation can be simply derived. The results of both cases considering and not considering Knudsen number were compared each other. In the case of the direct terms of the stiffness and damping coefficients, the difference between both cases was little and increased as the bearing number and eccentricity ratio increased. And the cross terms have less or more differences.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.51-60
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• 2011

In this study, structural safety capacity analysis of the overpass railway bridge between Konkuk Univ. and Guui station railroad has been performed. The overpass is expected to have suffered durability reduction by deterioration. The weight reduction of the overpass has been implemented to prevent further durability reduction and to improve performance capacity. To reduce the weight, 3 procedures of replacing concrete soundproofing wall to light-weight soundproofing wall, replacing gravel ballast to concrete ballast, and reducing the weight of trough have been performed. The analysis of static/dynamic behaviors and improved capacity of the light-weighted overpass bridge has been performed. The structural safety verification of the improved structure has been implemented by using rating factors of load carrying capacity of PSC I girder. The results have shown that the deflection has been reduced by 2.6mm and tensile strength has been improved by 1.07MPa, which indicate that the structural capacity has effectively been improved. Also, the natural frequency has improved by approximately 30% where vibration reduction and dynamic behavior improvement have been achieved. Moreover, in the rating factor evaluation based on analysis and test results, an improvement from 1.82 to 1.93 has been observed. Therefore, weight reduction method for the overpass is effective considering overall results.

• Restorative Dentistry and Endodontics
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• v.31 no.1
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• pp.20-29
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• 2006

The purpose of this study was to analyze the stress distribution aspect of unrestored and restored combined shape (wedge shape occulusally and saucer shape gingivally) class V cavity, which found frequently in clinical cases. A maxillary second permolar restored with a combined shape class V composite restorations were modeled using the three dimensional finite element method. Static occlusal load of 170 N was applied on lingual incline of buccal cusp at the angle of $45^{\circ}$ with the longitudinal axis of the tooth. And three dimensional finite element analysis was taken by ANSYS (Version 6.0, Swanson Analysis System Co., Houston, U.S.A) program which represent the stress distribution on unrestored and restored cavity wall and margin. The conclusions were as follows. 1. Compared to the unrestored cavity, Von Mises stress at the cementoenamel junction and line angle of the cavity base were reduced and in restored cavity. 2. Von Mises stress at the occlusal and cervical cavity margin and wall were increased in restored cavity in comparison with the unrestored cavity. 3. In the hybrid and hybrid/flowable composite resin restoration, Von Mises stress at the cementoenamel junction and line angle of the cavity base were reduced more than in the flowable restoration. 4. In the hybrid and hybrid/flowable composite resin restoration, Von Mises stress at the occlusal and cervical cavity margin and wall were increased more than in the flowable restoration.

• International Journal of Highway Engineering
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• v.4 no.4 s.14
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• pp.41-52
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• 2002

This study dealt with analysis of size effect of testing apparatus for Kim test which measures rut resistance characteristics of asphalt mixture under static loading. Two columns in different diameter with each column having different radios of round cut (Curvature) at the bottom were used for testing asphalt mixture. Deformation load ($P_{max}$) and deformation strength ($K_D$) were found to have relatively high correlation with rut depth and dynamic stability of asphalt concrete. Diameter of specimen was not a significant factor in this test. From the statistical correlation analysis with rutting properties, the radius of curvature and diameter of loading column were found to be important factor affecting the results of the test. Among the radios (r) of curvatures, r=0.5cm and 1.0cm showed much higher correlation than the column without curvature, and r=1.0cm being better between the two. The column with diameter of 4cm showed better correlation than diameter of 3cm. Therefore, the column of 4cm diameter with r=1.0cm was found to be the best among various apparatus sizes. Prediction models for rut depth and dynamic stability were developed for each aggregate mixture based on Kim test variables using SAS STEPWISE procedure. Therefore, if this test method is validated through further study, Kim test can be used for selecting asphalt mixture with the highest resistance against permanent deformation.

• Progress in Medical Physics
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• v.22 no.3
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• pp.140-147
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• 2011

The purpose of this study was to estimate internal motion using molecular sieve for quantitative improvement of lung tumor and to localize lung tumor in the small animal PET image by evaluated data. Internal motion has been demonstrated in small animal lung region by molecular sieve contained radioactive substance. Molecular sieve for internal lung motion target was contained approximately 37 kBq Cu-64. The small animal PET images were obtained from Siemens Inveon scanner using external trigger system (BioVet). SD-Rat PET images were obtained at 60 min post injection of FDG 37 MBq/0.2 mL via tail vein for 20 min. Each line of response in the list-mode data was converted to sinogram gated frames (2~16 bin) by trigger signal obtained from BioVet. The sinogram data was reconstructed using OSEM 2D with 4 iterations. PET images were evaluated with count, SNR, FWHM from ROI drawn in the target region for quantitative tumor analysis. The size of molecular sieve motion target was $1.59{\times}2.50mm$. The reference motion target FWHM of vertical and horizontal was 2.91 mm and 1.43 mm, respectively. The vertical FWHM of static, 4 bin and 8 bin was 3.90 mm, 3.74 mm, and 3.16 mm, respectively. The horizontal FWHM of static, 4 bin and 8 bin was 2.21 mm, 2.06 mm, and 1.60 mm, respectively. Count of static, 4 bin, 8 bin, 12 bin and 16 bin was 4.10, 4.83, 5.59, 5.38, and 5.31, respectively. The SNR of static, 4 bin, 8 bin, 12 bin and 16 bin was 4.18, 4.05, 4.22, 3.89, and 3.58, respectively. The FWHM were improved in accordance with gate number increase. The count and SNR were not proportionately improve with gate number, but shown the highest value in specific bin number. We measured the optimal gate number what minimize the SNR loss and gain improved count when imaging lung tumor in small animal. The internal motion estimation provide localized tumor image and will be a useful method for organ motion prediction modeling without external motion monitoring system.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.97-110
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• 2019

Piles that support offshore wind turbine structures are dominantly subjected to cyclic lateral loads of wind, waves, and tidal forces. For a successful design, it is imperative to investigate the behavior of the cyclic laterally loaded piles; the p-y curve method, in which the pile and soil are characterized as an elastic beam and nonlinear springs, respectively, has been typically utilized. In this study, model pile tests were performed in a 1 g gravitational field so as to investigate the p-y behaviors of cyclic laterally loaded piles installed in saturated dense silty sand. Test results showed that cyclic lateral loads gradually reduced the overall stiffness of the p-y curves (initial stiffness and ultimate soil reaction). This is because the cyclic lateral loads disturbed the surrounding soil, which led to the decrement of the soil resistance. The decrement effects of the overall stiffness of the p-y curves became more apparent as the magnitude of cyclic lateral load increased and approached the soil surface. From the test results, the cyclic p-y curve was developed using a p-y backbone curve method. Pseudo-static analysis was also performed with the developed cyclic p-y curve, confirming that it was able to properly predict the behaviors of cyclic laterally loaded pile installed in saturated dense silty sand.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.3
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• pp.139-148
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• 2000

In this paper, the interaction of oblique incident waves with a bottom-mounted and fluid-filled flexible membrane structure is investigated in the frame of linear hydro-elastic theory. The static shape of a membrane structure containing the fluid of a specific density is initially unknown and must be calculated before the hydrodynamic analysis. To solve hydrodynamic problem, the fluid domain is divided into the inner and outer region. The inner solution based on discrete membrane dynamic model and simple-source distribution over the entire fluid boundaries is matched to the outer solution ba~ed on an eigenfunction expansion method. The numerical results were compared to a series of Ohyama's experimental results. The measured reflection and tran¬smission coefficients reasonably follow the trend of predicted values. Using the computer program developed, the performance of a bottom-mounted and fluid-filled flexible membrane strocture is tested with various system parameters (membrane shape, internal pressure, density ratio) and wave characteristics (wave frequencies, incident wave angle). It is found that a bottom-mounted and fluid-filled flexible membrane structure can be an effel;tive wave barrier if properly designed.

• Journal of the Korean Geographical Society
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• v.42 no.4
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• pp.632-647
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• 2007

Lots of geographic phenomena have dynamic spatial patterns with time changes, and there have been lots of researches on exploring these dynamic spatial patterns. However, most of these researches focused on the static pattern analysis in a given period, rather than dealing with dynamic changes in the spatial pattern over time with the continual or cumulative perspective. For this reason, investigation of the inertia of spatial process in terms of temporal changes is needed. From this background, the purpose of this paper is to propose the methodology to explore the changes in spatial pattern cumulatively by considering the inertia of the spatial statistics over time, and to apply it to the case study That is, we introduce the new spatial statistic, and produce the z-values of the statistic using Monte Carlo Simulation, and then to explore the changes in spatial patterns over time cumulatively. To do this, the method to combine the J statistic with CUSUM statistic for exploring spatial patterns, and to apply it to the changes in the commercial landuse in Erie County, New York State. Through the proposed method for spatio-temporal Patterns, we could explore continual changes effectively in the spatial patterns reflecting the statistics by temporal spot cumulatively.

• Geotechnical Engineering
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• v.7 no.1
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• pp.41-52
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• 1991

A study of the effects of dynamic pile-soil-structure interactions on the response of super- structures, supported by group piles, are presented in this paper. The dynamic impedance functions of single pile generated by soil-pile interactions are obtained and compared among others using the methods proposed by Novak, Gazetas, and Kuhlemeyer, and using the equivalent cantilever method. Group pile effects are also considered by the following approaches : neglecting interaction effects : group efficiency ratio concept : static interaction approach . and dynamic interaction approach. The responses of a nuclear containment structure are obtained by using the elastic half-space analysis, based on the impedance functions mentioned above. Main conclusions drawn from this study are as follows : 1. The numerical results of the impedance functions calculated by each method were quite different : the Novak's was the smallest, and the Kuhlemeyer's the highest. Considering group effects, similar values in each approach were obtained for the stiffness : the difference was very big for the damping. 2. The top displacement of the structure was reduced by 20% or more by pile installations. However, the base shear force, the base moment, and the resonance frequency were increased by more than two times due to stiffening effect of the ground by pile installations. 3. Whether frequency dependant impedence functions or frequency independant functions were used, the responses of the structure were not so much affected by the choice of the impedance functions. 4. The reduction effect of the top displacement increased with the increase of the maximum ground acceleration.