• Progress in Medical Physics
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• v.25 no.1
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• pp.15-22
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• 2014

The IMRT is proper implement to get high dose deliver to tumor as its shape and selective approach in radiation therapy. Since the IMRT is performed as modulated the radiation fluence by the MLC created the open shapes and its irradiation time, the dose of segment of radiation field effects on the cumulated portal dose. The accurate output factor of small and step shape of segment is important to improve the determination of deliver tumor dose as it is directly proportional to dose. This experiment performed with the 6 MV photon beam of Clinac Ex(Varian) from $3{\times}3cm^2$ to $0.5{\times}0.5cm^2$ small field size for collimator jaw in MLC free and/or for MLC open field in fixed collimator jaw $10{\times}10cm^2$ using the CC01 ion chamber, SFD diode, diamond detector and X-Omat film dosimetry. As results of normalized to the reference field of $10{\times}10cm^2$ of MLC, the output factor of $3{\times}3cm^2$ showed $0.899{\pm}0.0106$, $0.855{\pm}0.0106$ for $2{\times}2cm^2$, $0.764{\pm}0.0082$ for $1{\times}1cm^2$ and $0.602{\pm}0.0399$ for $0.5{\times}0.5cm^2$. The output factor of MLC open field has shown a maximum 3.8% higher than that of the collimator jaw open field.

• Progress in Medical Physics
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• v.3 no.2
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• pp.1-12
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• 1992

For intraoperative radiation therapy using electron beams, a cone system to deliver a large dose to the tumor during surgical operation and to save the surrounding normal tissue should be developed and dosimetry for the cone system is necessary to find proper X-ray collimator setting as well as to get useful data for clinical use. We developed a docking type of a cone system consisting of two parts made of aluminum: holder and cone. The cones which range from 4cm to 9cm with 1cm step at 100cm SSD of photon beam are 28cm long circular tubular cylinders. The system has two 26cm long holders: one for the cones larger than or equal to 7cm diamter and another for the smaller ones than 7cm. On the side of the holder is an aperture for insertion of a lamp and mirror to observe treatment field. Depth dose curve. dose profile and output factor at dept of dose maximum. and dose distribution in water for each cone size were measured with a p-type silicone detector controlled by a linear scanner for several extra opening of X-ray collimators. For a combination of electron energy and cone size, the opening of the X-ray collimator was caused to the surface dose, depths of dose maximum and 80%, dose profile and output factor. The variation of the output factor was the most remarkable. The output factors of 9MeV electron, as an example, range from 0.637 to 1.549. The opening of X-ray collimators would cause the quantity of scattered electrons coming to the IORT cone system. which in turn would change the dose distribution as well as the output factor. Dosimetry for an IORT cone system is inevitable to minimize uncertainty in the clinical use.

• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.122-125
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• 2001

I. 목적 : Primus의 Multi Leaf Collimator는 X측이 29쌍으로 이루어 져 있으며 그중27쌍의 leaf은 1cm이고 2쌍은 6.5cm의 leaf으로 구성되어있다. 이러한 이유로 Paraaortic node를 포함하는 자궁경부암 치료시 현재는 Y가 27cm 이상인 경우는 차폐블럭을 제작하여 치료를 시행하나 차폐 블럭의 제작에 따른 업무의 지연과 차폐 블럭이 무거워져 치료시 환자에게 떨어질 위험을 제거 하기 위해 Asymmetric Field로 Multi Leaf Collimator를 사용한 결과를 보고하고자 한다. II. 재료 및 방법 : 모의 치료(Ximatron, Varian, USA)시 $Y_1$측을 15cm을 기준으로 하여 $Y_2$측을 변경하면서 Field size를 결정한다. ($Y_2$측은 20cm가 최대, 즉 Y측은 35cm까지 적용) 이러한 방법으로 Multi Leaf Collimator를 사용한 환자와 기존의 차폐블럭을 제작하여 치료한 환자와의 업무 개선사항을 확인하기 위하여 실제 공작실 업무 담당자의 블럭 제작 시간과 Beam Shaper를 이 용해 Multi Leaf Collimator를 입력하는 시간을 상호 비교하여 단축된 시간을 조사하였다. III. 결과 : 차폐블럭을 대신해 Multi Leaf Collimator를 이용함으로써 치료실에서 환자에 대한 위험요소(차폐블럭이 무겁다)를 사전에 제거 할 수 있었고 공작실에서 블럭 제작 시간과 LANTIS를 이용해 MLC를 입력하는 시간을 실측 한 결과업무의 시간이 120분에서 5분으로 단축되는 효과가 있었다. 전산화 계획 실에서 선량 계산시 OAR Factor값을 고려하여야 한다. IV. 결론 : Paraaortic node를 포함한 자궁경부암 환자의 차폐부위는 모양이 거의 일직선이기 때문에 Mu]ti Leaf Collimator를 사용하기에 용이 한 치료 부위이다. 하지만 큰 Field size로 인한 불편함이 있었다. 이러한 제 약성을 Asymmetric Field를 이용해서 Multi Leaf Collimator의 사용을 가능하게 하고 차폐 블록의 제작과정과 치료 시에 발생되는 근무자의 업무의 손실을 줄이고 환자에 대한 위험성 을 해결하였다.

• Smart Structures and Systems
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• v.19 no.2
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• pp.115-126
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• 2017

In this paper, size dependent bending and free flexural vibration behaviors of functionally graded (FG) nanobeams are investigated using a nonlocal quasi-3D theory in which both shear deformation and thickness stretching effects are introduced. The nonlocal elastic behavior is described by the differential constitutive model of Eringen, which enables the present model to become effective in the analysis and design of nanostructures. The present theory incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect, and furthermore accounts for both shear deformation and thickness stretching effects by virtue of a hyperbolic variation of all displacements through the thickness without using shear correction factor. The material properties of FG nanobeams are assumed to vary through the thickness according to a power law. The neutral surface position for such FG nanobeams is determined and the present theory based on exact neutral surface position is employed here. The governing equations are derived using the principal of minimum total potential energy. The effects of nonlocal parameter, aspect ratio and various material compositions on the static and dynamic responses of the FG nanobeam are discussed in detail. A detailed numerical study is carried out to examine the effect of material gradient index, the nonlocal parameter, the beam aspect ratio on the global response of the FG nanobeam. These findings are important in mechanical design considerations of devices that use carbon nanotubes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.4
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• pp.21-26
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• 1981

SnO2/n-Si and ITO/n-Si SIS solar cells have been fabricated ty mears of electron-beam deposition. The optimum oxidation and heat-treatment condition for SnO2/n-Si cells and ITO/n-Si cells are 50$0^{\circ}C$-5min., 30$0^{\circ}C$-10min., and 50$0^{\circ}C$-5min., 30$0^{\circ}C$-20min. respectively. The open-circuit Voltage(Voc), short-circuit current density(Jsc), fill factor(FF), and efficiency (η) under AMI(100mW/$\textrm{cm}^2$) illumination were 0.4V, 34mA/$\textrm{cm}^2$, 0.44, and 6.0%(active area efficiency, 6.9%) for SnO2/n-Si solar cells, and 0.44V, 36mA/$\textrm{cm}^2$, 0.53, and 8.45%(active area efficiency, 9.71%) for ITO/n-Si solar calls.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.177-186
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• 1999

The purpose of this study is to analyze the interface debonding of RC beams strengthened by carbon fiber sheet(CFS). The behavior of damaged RC beams strengthened with CFS is analytically investigated next using linear elastic fracture mechanics(LEFM) approach and the finite element method. The study includes an investigation of the separation mode by interface fracture of the strengthening materials due to the interfacial shear and normal stresses. The numerical method is presented to obtain the value of interfacial fracture parameter such as the strain energy release rate. Based on the results of this study, it is found that the critical case occurs when the interfacial cracks occur within a short region of the flexural crack. The CFS strengthening has not an adequate factor of safety against interfacial debonding of CFS. Furthermore, for the thicknesses of the adhesive studied[1mm~3mm], it is no noticeable effect on the strain energy release rate.

• International Journal of Concrete Structures and Materials
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• v.9 no.2
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• pp.159-172
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• 2015

Estimation of the residual strength of corroded reinforced concrete beams has been studied from experimental and theoretical perspectives. The former is arduous as it involves casting beams of various sizes, which are then subjected to various degrees of corrosion damage. The latter are static; hence cannot be generalized as new coefficients need to be re-generated for new cases. This calls for dynamic models that are adaptive to new cases and offer efficient generalization capability. Computational intelligence techniques have been applied in Construction Engineering modeling problems. However, these techniques have not been adequately applied to the problem addressed in this paper. This study extends the empirical model proposed by Azad et al. (Mag Concr Res 62(6):405-414, 2010), which considered all the adverse effects of corrosion on steel. We proposed four artificial neural networks (ANN) models to predict the residual flexural strength of corroded RC beams using the same data from Azad et al. (2010). We employed two modes of prediction: through the correction factor ($C_f$) and through the residual strength ($M_{res}$). For each mode, we studied the effect of fixed and random data stratification on the performance of the models. The results of the ANN models were found to be in good agreement with experimental values. When compared with the results of Azad et al. (2010), the ANN model with randomized data stratification gave a $C_f$-based prediction with up to 49 % improvement in correlation coefficient and 92 % error reduction. This confirms the reliability of ANN over the empirical models.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.6
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• pp.736-744
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• 2005

Statement of problem. Initial stability of implant is an important factor for predicting osseointegration. It requires a rapid, non-invasive, user-friendly technique to frequently assess the implant stability and the degree of osseointegration. Purpose. The aim of this study was to evaluate the correlation between the resonance frequency analysis (RFA) and the radiographic method for peri-implant bone change under in vitro conditions. Material and Method. Twenty implants of 3.75 mm in diameter(Neoplant, Neobiotech, Korea) were used. To simulate peri-implant bone change, 2 mm-deep $45^{\circ}$ range horizontal defect and 2 mm-deep $90^{\circ}$ range horizontal defect area were serially prepared perpendicular to the X-ray beam after conventional implant insertion. Customized film holding device was fabricated to standardize the projection geometry for serial radiographs of implants and direct digital image was obtained. ISQ values and gray values inside threads were measured before and after peri-implant bone defect preparation. Results. Within a limitation of this study, ISQ value of resonance frequency analysis was changed according to peri-implant bone change (p<0.05) and gray value of radiographic method was changed according to peri-implant bone change (p<0.05). There was no correlation between the ISQ value and the gray value for peri-implant bone change (p>0.05). But, in horizontal defect condition, relatively positive correlation were between ISQ and gray values(r=0.663). Conclusion. This results provided a possibility that peri-implant bone change may be evaluated by both RFA and radiographic method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.2
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• pp.108-116
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• 2014

With the increasing the importance of emotional quality of vehicle, the sound quality of systems with electric motor components has become increasingly important. Electric motors are used for windows, seats, sun roof, mirrors, steering columns, windshield wiper and climate control blowers, etc. In this paper, a study was conducted to identify sound quality factors that contribute to customer's satisfaction and preference of the window lift system. Jury test for subjective evaluation was carried out and sound quality index was developed. Averaged sound pressure level and sharpness were significant factors when glass moves down. Also, maximum loudness at stop section and averaged loudness were significant factor when glass moves up. Next, noise source identification was carried out using beam forming method during glass transferred section and impulsive noise at stop section. Several improvement methods were applied using the source identification result. And finally, the degree of sound quality improvement was judged using sound quality index.

• Journal of the Korean Wood Science and Technology
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• v.19 no.3
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• pp.62-71
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• 1991

An evaluation of bending test of composite I and Box beams for determining the ultimate strength limit design criteria was presented. Maxium loads of composite I beams were found in beams composed of thicker upper flanges and/or vertical LVL flanges. These loads of plywood web beams were greater than those of PB web beams. Maximum loads of unsymmetrical box beams were less than those of symmetrical box beams. Thus, it took on different phase in box type beams. Ultimate loads of composite beams were greater than those of solid. The failure of composite beams were abrupt and failure mode was classified into following categories; Edgewise shear failure in web, delamination in flange-web joint, tension failure and tearing in LVL flanges, and web delamination. These failures of composite beams were appeared at the mixed mode. The influence factor affecting the performance of tested composite beams was shear strength of PB-web composite beams and compressive strength in plywood-web composite beams. It was also assumed that the influence factors on structural performance on composite beams were flange quality, web material and geometry of cross section. As one of the design methods resisting to compressive stress that was required in the case of small span to depth ratio and deep beams. composite I-beams composed of thicker upper flanges comparing to lower flanges were very effective in structural performance.