• Land and Housing Review
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• v.2 no.1
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• pp.69-78
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• 2011

The purpose of this research is particle shape evaluation of aggregate using Digital Image Process(DIP). DIP is very useful to measure the roughness and particle shape of aggregates. Couple of aggregates, like standard sand, two different crushed stones, and two different marine aggregates, have been employed. Shape factors of two different marine aggregates are ranged 0.35 to 0.54. Crushed stone I is 0.74 which is highly flat, but standard sand is elongated shape. Especially, two marine aggregate showed a big difference of width and length which meaned a long shape. There is any significant difference of elongation ratio and flatness for each aggregate with different measuring system, like direct measurement of vernier calipers and DIP method. Shape conversion coefficient and equivalent diameter for changing 2D image to 3D image by the Digital Image Process(DIP) have been suggested and modified particle size distribution curve has been showed. The measured flatness ratios of each aggregate were 0.30, 0.36, 0.47 and 0.83, respectively. Also, the conversion shape coefficients of each aggregate were determinded as 0.77, 0.78, 0.84 and 0.92. The size of aggregate has been modified by multiplying the shape conversion coefficient and the aggregate size from DIP. The modified gradation curve with modified volume and weight of aggregate has been suggested. Within the limited test results, DIP is one of useful to get the particle shape of aggregate with limitation of measuring errors and to apply the particle distribution curve.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.57-74
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• 2013

In this study, the virtual fixed point analysis and 3D full-modeling analysis for pile bent structures are conducted by considering various influencing factors and the applicability of the virtual fixed point theory is discussed. Also, a discrete analysis calculating separately both the superstructure and substructure of pile bent structures is performed on the basis of an equivalent base spring model by taking into account the major influencing parameters such as soil conditions, combined loading and pile diameter. The results show that the settlement and lateral deflection of the virtual fixed point theory are smaller than those of 3D full-modeling analysis. On the other hand, the virtual fixed point analysis overestimates the axial force and bending moment compared with 3D full-modeling analysis. It is shown that the virtual fixed point analysis cannot adequately predict the real behavior of pile bent structures. It is also found that discrete analysis gives similar results of lateral deflection and bending moment to those of unified analysis. Based on this study, it is found that discrete analysis considering column-pile interaction conditions is capable of predicting reasonably well the behavior of pile bent structures. It can be effectively used to perform a more economical design of pile bent structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.367-374
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• 2019

We investigate the effect of soil-structure interaction (SSI) on the response of LNG storage tanks to vertical seismic excitation depending on the type of foundation. An LNG storage tank with a diameter of 71 m on a clay layer with a thickness of 30 m upon bedrock, was selected as an example. The nonlinear behavior of the soil was considered in an equivalent linear method. Four types of foundation were considered, including shallow, piled raft, and pile foundations (surface and floating types). In addition, the effect of soil compaction within the group pile on the seismic response of the tank was investigated. KIESSI-3D, an analysis package in the frequency domain, was used to study the SSI and the stress in the outer tank was calculated. Based on an analysis of the numerical results, we arrived at three main conclusions: (1) for a shallow foundation, the vertical stress in the outer tank is less than the fixed base response due to the SSI effect; (2) for foundations supported by piles, the vertical stress can be greater than the fixed base stress due to the increase in the vertical impedance due to the piles and the decrease in radiation damping; and (3) soil compaction had a miniscule impact on the seismic response of the outer tank.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.267-278
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• 2019

Variety of tunnel ahead prediction methods have been performed for safe tunnel construction during tunnel excavation. Pole-pole array among the electrical resistivity survey, which is one of the tunnel ahead prediction method, has been utilized to predict water-bearing sediments or weak zone located within 5 times of tunnel diameter. One of the most important processes is the estimation of virgin ground resistivity and it can be obtained from the following process: 1) calculation of contact area between the electrodes and the medium, and 2) assumption of the electrodes as equivalent spherical electrodes which have a same surface area with the electrodes. This assumption is valid in a small contact area and sufficient distance between the electrodes. Since the measured resistance, in general, varies with the electrode size, shape, and distance between the electrodes, it is necessary to evaluate the influence of these factors. In this study, theoretical equations were derived and experimental tests were conducted considering the electrode size, shape, and distance of cylindrical electrodes which is the most commonly utilized electrode shape. Through this theoretical and experimental study, it is known that one should be careful to use the assumption of the equivalent half-spherical electrode with large ratio between the penetrated depth and radius of the cylindrical electrode, as the error may get larger.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.155-164
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• 2019

In this study, the soil-structure interaction(SSI) effect on the seismic response of LNG storage tanks was investigated according to the type of foundation. For this purpose, a typical of LNG storage tank with a diameter of 71m, which is constructed on a 30m thick clay layer over bedrock was selected, and nonlinearity of the soil was taken into account by the equivalent linearization method. Four different types of foundations including shallow foundation, piled raft foundation, and pile foundations(surface and floating types) were considered. In addition, the effect of soil compaction in group piles on seismic response of the tank was investigated. The KIESSI-3D, which is a SSI analysis package in the frequency domain, was used for the SSI analysis. Stresses in the outer tank, and base shear and overturning moment in the inner tank were calculated. From the comparisons, the following conclusions could be made: (1) Conventional fixed base seismic responses of outer tank and inner tank can be much larger than those of considering the SSI effect; (2) The influence of SSI on the dynamic response of the inner tank and the outer tank depends on the foundation types; and (3) Change in the seismic response of the structure by soil compaction in the piled raft foundation is about 10% and its effect is not negligible in the seismic design of the structure.

• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• Journal of the Korean Institute of Landscape Architecture
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• v.16 no.1
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• pp.27-35
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• 1988

Size characteristics of three widely used landscape trees were analized to establish a methodology of size prediction as time Passes. Tree height, tree width, stem diameter(breast or surface), canopy length and tree age were measured directly and indirectly(by using photograph), and the data were analized by using regression analysis through PC-SAS. The results are summarized as follows : 1. Zelkova serrata MAKINO showed relatively slow growth rate and the tree form was changed as aged. Size predictions were available by using the regression equations listed below : Surface diameter = 0.8293 x AGE Tree height = 0.4109(0.8293 x AGE) - 0.0039(0.7273 x AGE)$^2$Tree width = 0.3240(0.8293 x AGE) - 0.0024(0.1293 x AGE)$^2$Canopy length = 0.1337(0.8293 x AGE) - 0.0020(0.7293 x AGE)$^2$2. Pinus strobus L. showed relatively fast growth rate and the tree form did not change much as aged. Size predictions were available by using the regression equations listed below. Breast diameter = 0.756 x AGE Tree height = 0.7695(0.756 x AGE) - 0.0164(0.75\ulcorner x AGE)$^2$Tree width = 0.4331(0.756 x AGE) - 0.0079(0.75\ulcorner x AGE)$^2$Canopy length = 0.1365(0.756 x AGE) - 0.0032(0.75f x AGE)$^2$ 3. In case of Magnolia denudata DESROUX, tree form was determined relatively earlier than the other two species. Si2e predictions were available by using the regression equations listed below : Surface diameter = 0.88 x AGE Tree height = 0.5412(0.88 x AGE) - 0.0110(0.88 x AGE)$^2$ Tree width = 0.3752(0.88 x AGE) - 7.0061(0.88 x AGE)$^2$Canopy length = 0.1110(0.88 x AGE) - 0.0022(0.88 x AGE)$^2$ This study aimed to find a way to predict size change of landscaping plants. This methodology will be applied to a wide range of landscape plants to provide practical data to landscape designers.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.337-343
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• 2014

Purpose : The aim of this study is to evaluate unwanted scattered dose to ovary by scattering and leakage generated from treatment fields of Tomotherapy for childbearing woman with breast cancer. Materials and Methods : The radiation treatments plans for left breast cancer were established using Tomotherapy planning system (Tomotherapy, Inc, USA). They were generated by using helical and direct Tomotherapy methods for comparison. The CT images for the planning were scanned with 2.5 mm slice thickness using anthropomorphic phantom (Alderson-Rando phantom, The Phantom Laboratory, USA). The measurement points for the ovary dose were determined at the points laterally 30 cm apart from mid-point of treatment field of the pelvis. The measurements were repeated five times and averaged using glass dosimeters (1.5 mm diameter and 12 mm of length) equipped with low-energy correction filter. The measures dose values were also converted to Organ Equivalent Dose (OED) by the linear exponential dose-response model. Results : Scattered doses of ovary which were measured based on two methods of Tomo helical and Tomo direct showed average of $64.94{\pm}0.84mGy$ and $37.64{\pm}1.20mGy$ in left ovary part and average of $64.38{\pm}1.85mGy$ and $32.96{\pm}1.11mGy$ in right ovary part. This showed when executing Tomotherapy, measured scattered dose of Tomo Helical method which has relatively greater monitor units (MUs) and longer irradiation time are approximately 1.8 times higher than Tomo direct method. Conclusion : Scattered dose of left and right ovary of childbearing women is lower than ICRP recommended does which is not seriously worried level against the infertility and secondary cancer occurrence. However, as breast cancer occurrence ages become younger in the future and radiation therapy using high-precision image guidance equipment like Tomotherapy is developed, clinical follow-up studies about the ovary dose of childbearing women patients would be more required.

• Journal of radiological science and technology
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• v.31 no.2
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• pp.183-188
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• 2008

Aim of this study is to investigate the feasibility of 2D ion chamber array as a substitute of the water phantom system in a periodic Linac QA. For the feasibility study, a commercial ion chamber matrix was used as a substitute of the water phantom in the measurement for a routine QA beam properties. The device used in this study was the I'm RT MatriXX (Wellhofer Dosimetrie, Germany). The MatriXX consists of a 1,020 vented ion chamber array, arranged in $24{\times}24\;cm^2$ matrix. Each ion chamber has a volume of $0.08\;cm^3$, spacing of 0.762 cm. We investigated dosimetric parameters such as dose symmetry, energy ($TPR_{20,10}$), and absolute dose for comparing with the water phantom data with a Farmer-type ionization chamber (FC65G, Wellhofer Dosimetrie, Germany). For the MatriXX measurements, we used the white polystyrene phantom (${\rho}:\;1.18\;g/cm^3$) and also considered the intrinsic layer (${\rho}:\;1.06\;g/cm^3$, t: 0.36 cm) of MatriXX to be equivalent to water depth. In the preliminary study of geometrical QA using MatriXX, the rotation axis of collimator and half beam junction test were included and compared with film measurements. Regarding the dosimetrical QA, the MatriXX has shown good agreements within ${\pm}1%$ compared to the water phantom measurements. In the geometrical test, the data from MatriXX were comparable with those from the films. In conclusion, the MatriXX is a good substitute for water phantom system and film measurements. In addition, the results indicate that the MatriXX as a cost-effective novel QA tool to reduce time and personnel power.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.157-168
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• 2008

Statement of problem: Over the past two decades, implant supported fixed prosthesis have been widely used. However, there are few studies conducted systematically and intensively on the splinting effect of implant systems in mandible. Purpose: The purpose of this study was to investigate the changes in stress distributions in the mandibular implants with splinting or non-splinting crowns by performing finite element analysis. Materials and methods: Cortical and cancellous bone were modeled as homogeneous, transversely isotropic, linearly elastic. Perfect bonding was assumed at all interfaces. Implant models were classified as follows. Group 1: $Br{{\aa}}nemark$ length 8.5mm 13mm splinting type Group 2: $Br{{\aa}}nemark$ length 8.5mm 13mm Non-splinting type Group 3: ITI length 8.5mm 13mm splinting type Group 4: ITI length 8.5mm 13mm Non-splinting type An load of 100N was applied vertically and horizontally. Stress levels were calculated using von Mises stresses values. Results: 1. The stress distribution and maximum von Mises stress of two-length implants (8.5mm, 13mm) was similar. 2. The stress of vertical load concentrated on mesial side of implant while the stress of horizontal load was distributed on both side of implant. 3. Stress of internal connection type was spreading through abutment screw but the stress of external connection type was concentrated on cortical bone level. 4. Degree of stress reduction was higher in the external connection type than in the internal connection type.