• Journal of Periodontal and Implant Science
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• 제47권6호
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• pp.372-380
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• 2017

Purpose: The aim of this prospective pilot study was to compare alveolar ridge preservation (ARP) procedures with open-healing approach using a single-layer and a double-layer coverage with collagen membranes using radiographic and clinical analyses. Methods: Eleven molars from 9 healthy patients requiring extraction of the maxillary or mandibular posterior teeth were included and allocated into 2 groups. After tooth extraction, deproteinized bovine bone mineral mixed with 10% collagen was grafted into the socket and covered either with a double-layer of resorbable non-cross-linked collagen membranes (DL group, n=6) or with a single-layer (SL group, n=5). Primary closure was not obtained. Cone-beam computed tomography images were taken immediately after the ARP procedure and after a healing period of 4 months before implant placement. Radiographic measurements were made of the width and height changes of the alveolar ridge. Results: All sites healed without any complications, and dental implants were placed at all operated sites with acceptable initial stability. The measurements showed that the reductions in width at the level 1 mm apical from the alveolar crest (including the bone graft) were $-1.7{\pm}0.5mm$ in the SL group and $-1.8{\pm}0.4mm$ in the DL group, and the horizontal changes in the other areas were also similar in the DL and SL groups. The reductions in height were also comparable between groups. Conclusions: Within the limitations of this study, single-layer and double-layer coverage with collagen membranes after ARP failed to show substantial differences in the preservation of horizontal or vertical dimensions or in clinical healing. Thus, both approaches seem to be suitable for open-healing ridge preservation procedures.

• Journal of radiological science and technology
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• 제39권4호
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• pp.571-575
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• 2016

Monte Carlo simulations are widely used as the most accurate technique for dose calculation in radiation therapy. In this paper, the GATE6(Geant4 Application for Tomographic Emission ver.6) code was employed to calculate the dosimetric performance of the photon beams from a linear accelerator(LINAC). The treatment head of a Varian 21EX Clinac was modeled including the major geometric structures within the beam path such as a target, a primary collimator, a flattening filter, a ion chamber, and jaws. The 6 MV photon spectra were characterized in a standard $10{\times}10cm^2$ field at 100 cm source-to-surface distance(SSD) and subsequent dose estimations were made in a water phantom. The measurements of percentage depth dose and dose profiles were performed with 3D water phantom and the simulated data was compared to measured reference data. The simulated results agreed very well with the measured data. It has been found that the GATE6 code is an effective tool for dose optimization in radiotherapy applications.

• Radiation Oncology Journal
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• 제14권4호
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• pp.323-332
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• 1996

Purpose : The wedge filter is the most commonly used beam modifying device during radiation therapy Recently dynamic wedge technique is available through the computer controlled asymmetric collimator, independent jaw. But dosimetric characteristics of dynamic wedge technique is not well known. Therefore we evaluate dosimetric characteristics of dynamic wedge compared to conventional fixed wedge. Materials and Methods : We evaluated dosimetric characteristics of dynamic wedge and fixed wedge by ion chamber, film dosimetry and TLD in phantoms such as water, polystyrene and average breast phantom. Six MV x-ray was used in $15{\times}15cm$ field with 15,30 and 45 degree wedge of dynamic/liked wedge system, Dosimeric characteristics are interpreted by Wellhofer Dosimetrie system WP700/WP700i and contralateral breast dose (CBD) with tangential technique was confirmed by TLD. Results : 1) Percent depth dose through the dynamic wedge technique in tissue equivalent phantom was similar to open field irradiation and there was no beam hardening effect compared to fixed wedge technique. 2) Isodose line composing wedge angle of dynamic wedge is more straight than hard wedge. And dynamic wedge technique was able to make any wedge angle on any depth and field size. 3) The contralateral breast dose in primary breast irradiation was reduced by dynamic wedge technique compared to fixed wedge. When the dynamic wedge technique was applied, the scatter dose was similar to that of open field irradiation. Conclusion : The dynamic wedge technique was superior to fixed wedge technique in dosimetric characteristics and may be more useful in the future.

• Journal of the Society of Naval Architects of Korea
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• 제29권4호
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• pp.152-172
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• 1992

The ship sailing among waves are suffered the various wave loads that comes from its motion throughout its life. Because there are dynamic, the analysis of ship structure must be considered as the dynamic problem precisely. In the rationally-based design, the dynamic structural analysis is carried out using dynamic wave loads provided from the results of the ship mouton calculation as the rigid body. This method is based on the linear theory assumed low wave height and small amplitude of motion. But at the rough sea condition, high wave height, relatively ship's depth, is induced the large ship motion, so the ship section configulation below water line is rapidly changed at each time. This results in non-linear problem. Considering above situation in this paper, the strength analysis method is introduced for the hull glider among waves considering non-linear hydrodynamic forces. This paper considers that the overall or primary level of the ship structural dynamic loading and dynamic response provided from the non-linear wave forces, and bottom and bow flare impact forces estimated by momentum slamming theory, in which the ship is idealized as a hollow thin-walled box beam using thin-walled beam theory and the finite element method. This method is applied to 40,000 Ton Double-Skin Tanker and attention is paid to the influence of the response of ship speed, wave length and wave height compared with linear strip theory.

• Journal of the Korea Concrete Institute
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• 제23권1호
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• pp.3-12
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• 2011

The structural behavior of continuous reinforced concrete deep beams is mainly controlled by the mechanical relationships associated with the shear span-to-effective depth ratio, flexural reinforcement ratio, load and support conditions, and material properties. In this study, a simple indeterminate strut-tie model which reflects characteristics of the complicated structural behavior of the continuous deep beams is presented. In addition, the reaction and load distribution ratios defined as the fraction of load carried by an exterior support of continuous deep beam and the fraction of load transferred by a vertical truss mechanism, respectively, are proposed to help structural designers for the analysis and design of continuous reinforced concrete deep beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratio, a concept of balanced shear reinforcement ratio requiring a simultaneous failure of inclined concrete strut and vertical steel tie is introduced to ensure a ductile shear failure of reinforced concrete deep beams, and the primary design variables including the shear span-to-effective depth ratio, flexural reinforcement ratio, and concrete compressive strength are implemented after thorough parametric numerical analyses. In the companion paper, the validity of the presented model and load distribution ratio was examined by applying them in the evaluation of the ultimate strength of multiple continuous reinforced concrete deep beams, which were tested to failure.

• Journal of the Korea Concrete Institute
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• 제13권2호
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• pp.107-113
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• 2001

This study was conducted preliminarily to develop the crack source location technique for plain concrete beam using acoustic emission(AE). Before the main experiment, the test of virtual An source location was achieved in plain concrete block. The sensor layout was mutually compared between triangular layout and rectangular layout. As the results of test, AE source location by triangular layout was evaluated more effective than that by rectangular layout. The specimen to apply he source location technique was man in total nine specimens (each three in 40 %, 50%, 60% of W/C ratio) which the experiment variable was the compressive strength level(W/C ratio). The bending loading method is selected by cyclic loadings to evaluate the degree of concrete damage. It is seen that Kaiser effect and Felicity effect exists through analysis of AE parameters in coming failure experiment. As a result of analyzing the felicity ratio(FR) values, it is shown that this values can be used for evaluating the degree of concerto damage. AE activity is started highly at the 70% of failure load without the compressive strength level. Thus considered by a index in constructing the system of the failure warning at application of the field structure. And the results compared the real cracking location with the source location has perceived by AE monitoring before it is appeared the primary crack by visual observation.

• Journal of the Korean Society of Hazard Mitigation
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• 제8권1호
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• pp.1-7
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• 2008

When historical or cultural buildings need to be repaired or reinforced, the changes of original features should be minimized, and the strengths of structures should be improved. Among the existing methods to reinforce historical wood structures, the carbon fiber reinforcement polymer (CFRP) installation method is one of the best ones to achieve the afore-mentioned requirements. Therefore, this study aims at investigating the reinforcing effects and failure modes of timber beams reinforced with the inserted CFRP, a part of roof trusses in modern wood structures, and at providing the fundamental test data to estimate the CFRP rein-forced timber beam in the application of this reinforcing method. The primary parameters in this study were the layout and amount of CFRP. It was observed that, when $0.3{\sim}0.7%$ of CFRP were installed, the strengths of reinforced timber beams increased up to 173% compared to its original strength, but their strengthening effects were heavily influenced by the characteristics of timber such as burls. In order to improve the applicability of this strengthening method, fundamental understandings on the characteristics of wood would be necessary, and there would be in need of researches on the non-destructive test for wood structures as well.

• Journal of the Korean Society of Radiology
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• 제15권1호
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• pp.85-91
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• 2021

The purpose of this study is to derive an equation to verify the accuracy of the dose rate for each component calculated at the measurement point outside the maze door when designing the maze door of 6 MV X-ray beam. Based on the component-specific dose rate calculation formula for the measurement point outside the maze door described in NCRP Report 151 and IAEA Safety Report Series 47, the dose rate calculation formula for each component when applying the values of the drawing-based parameters and the dose rate calculation formula for each component when applying the values of conservative parameters are derived. From the two dose rate calculation formulas for each component, the dose rate verification formula for each component at the measurement point outside the maze door was derived. The resulting dose rate verification formula for each component at the measurement point outside the maze door can be compared and analyzed whether the dose rate for each component at the measurement point outside the maze door calculated by the designer falls within the range of the dose rate obtained from the derived dose rate verification formula for each component. This verification formula is considered to be practically useful in verifying the accuracy of the dose rate for each component calculated by the designer.

• Progress in Medical Physics
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• 제11권2호
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• pp.91-99
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• 2000

This is a preliminary study for developing the method of the dose reconstruction in the patients, irradiated by mega-voltage photon beams from the linear accelerator, using the transit dose distributions. In this study we present the method of three-dimensional dose reconstruction and evaluate the method by computer simulation. To acquire the dose distributions in the patients (or phantoms) we first calculate the differences between the doses at the arbitrary points in the patients and the doses at the corresponding points where the transit doses are measured. Then, we can get the dose in the patients from the measured transit dose and the calculated value of the difference. The dose differences are calculated by applying the inverse square law and using the linear attenuation coefficient. The scatter to primary dose ratios, which are calculated by the Monte Carlo program using the CT data of the patient (or phantoms), are also used in the calculations. For the evaluation of this method we used various kinds of homogeneous and inhomogeneous phantoms and calculated the transit dose distributions with the Monte Carlo program. From the distributions we reconstructed the dose distributions in the phantom. We used mono-energy Photon beam of 1.5MeV and Monte Carlo program EGS4. The comparison between the dose distributions reconstructed using the method and the distributions calculated by the Monte Carlo program was done. They agreed within errors of -4%∼+2%. This method can be used to predict the dose distributions in the patient

• Korean Journal of Head & Neck Oncology
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• 제21권2호
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• pp.132-138
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• 2005

Purpose: The purpose of this study was to establish general guidelines for the treatment of patients with early glottic cancer(T1-2N0M0), by assessing the role of primary radiation therapy and by analyzing the tumor-related and treatment-related factors that influence treatment results. We also studied the results of hypofractionated radiation therapy for early glottic cancer. Material and Methods: This retrospective study comprised 48 patients who suffered from early glottic cancer and were treated by primary radiotherapy at Inha University Hospital, between May 1997 and October 2004. T-stage distribution showed 38 patients as T1 and 10 patients as stage T2. Thirty-eight patients underwent hypofractionated radiotherapy using a 6 MY photon beam, a total tumor dose of 63Gy, in 5 weekly fractions of 2.25Gy, with an overall radiation treatment time of 38 days. Ten patients in the T2 stage tolerated a total dose of 63-72 Gy(median 68.4Gy) in 5 weekly fractions of 1.8-2.0Gy, with an overall radiation treatment time of 40-87 days(median 51 days). All patients were followed up for at least 3 years. Univariate and multivariate analyses were performed to identify the prognostic factors affecting the treatment results. Result: The 5-year survival rate was 92% for all patients, 94% for T1 patients and 91% for T2 patients. The local control rate was 93.5% for all patients, 95% for T1 and 92.2% for T2 patients. Three patients suffered a relapse following radiotherapy, and underwent subsequent salvage surgery. We included T-stage, tumor location, total radiation dose, field size and overall radiation treatment time as potential prognostic factors. Only T-stage was found to be statistically significant in the univariate analysis, but in the multivariate analysis, it was not found to be significant. Conclusion: High curative and voice preservation rates were obtained with hypofractionated radiotherapy. Further study with a larger number of patients is needed to determine the prognostic factors affecting treatment results.