• Title/Summary/Keyword: $\180^{\circ}$

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Comparative evaluation for leaf position accuracy according to gantry angle variation in MLC quality assurance using electronic portal imaging device(EPID) and GafChromic EBT3 film (전자포탈영상장치(EPID)와 GafChromic EBT3 film을 이용한 다엽콜리메이터 정도관리 시 갠트리 각도 변화에 따른 엽의 위치 정확성 비교 평가)

  • Yang, Myung Sic;Park, Ju Kyeong;Lee, Seung Hun;Lee, Sun Young;Kim, Jung Soo;Kwon, Hyoung Cheol;Kim, Yang Su
    • The Journal of Korean Society for Radiation Therapy
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    • v.29 no.2
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    • pp.83-91
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    • 2017
  • Objectives: The purpose of this study was to evaluate the error of the leaf position accuracy of the MLC due to the gravity effect according to the gantry angle by using picket fence test using EPID and GafChromic EBT3 film. Materials and Methods: A 5 cm solid phantom was placed on the table and the SAD was set to 100 cm. The EBT3 film was placed exactly over the solid phantom and covered a 1.5 cm solid phantom and the picket fence test was performed. The EPID was measured under the same conditions as the EBT3 film at SID 100 cm. The gantry angles were measured at $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$ in order to evaluate the position of the MLC according to the gantry angle. For the geometric evaluation of the MLC, the leaf position accuracy of the MLC was analyzed using the analysis program. Results: In case of EPID, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.18 mm, 0.31 mm, 0.20 mm, 0.26 mm on the average and the maximum values of the errors were respectively 0.44 mm, 0.54 mm, 0.34 mm, 0.44 mm. In case of EBT3 film, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.19 mm, 0.21 mm, 0.19 mm, 0.31 mm on the average and the maximum values of the errors were respectively 0.35 mm, 0.45 mm, 0.36 mm, 0.48 mm. Conclusion: In this study, we analyzed the position error of the leaf of the MLC according to the gantry angle, and confirmed the position error of the leaf by gravity effect. As a result of comparing the leaf position accuracy using EPID and EBT3 film according to the variation of gantry angle, a larger error occurred in the error analysis method using EPID than that of EBT3 film. Therefore, in the case of IMRT based on MLC, as well as verification of accurate dosimetry should be conducted, it is considered that the quality control and verification for the precise operation of the MLC will be needed. and it is necessary to compare and verify the method of analysis.

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Development of Quality Assurance Program for the On-board Imager Isocenter Accuracy with Gantry Rotation (갠트리 회전에 의한 온-보드 영상장치 회전중심점의 정도관리 프로그램 개발)

  • Cheong, Kwang-Ho;Cho, Byung-Chul;Kang, Sei-Kwon;Kim, Kyoung-Joo;Bae, Hoon-Sik;Suh, Tae-Suk
    • Progress in Medical Physics
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    • v.17 no.4
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    • pp.212-223
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    • 2006
  • Positional accuracy of the on-board imager (OBI) isocenter with gantry rotation was presented in this paper. Three different type of automatic evaluation methods of discrepancies between therapeutic and OBI isocenter using digital image processing techniques as well as a procedure stated in the customer acceptance procedure (CAP) were applied to check OBI isocenter migration trends. Two kinds of kV x-ray image set obtained at OBI source angle of $0^{\circ},\;90^{\circ},\;180^{\circ},\;270^{\circ}$ and every $10^{\circ}$ and raw projection data for cone-beam CT reconstruction were used for each evaluation method. Efficiencies of the methods were also estimated. If a user needs to obtain an isocenter variation map with full gantry rotation, a method taking OBI image for every $10^{\circ}$ and fitting with 5th order polynomial was appropriate. However for a mere quality assurance (QA) purpose of OBI isocenter accuracy, it was adequate to use only four OBI Images taken at the OBI source angle of $0^{\circ},\;90^{\circ},\;180^{\circ}\;and\;270^{\circ}$. Maximal discrepancy was 0.44 mm which was observed between the OBI source angle of $90^{\circ}\;and\;180^{\circ}$ OBI isocenter accuracy was maintained below 0.5 mm for a year. Proposed QA program may be helpful to Implement a reasonable routine QA of the OBI isocenter accuracy without great efforts.

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Effects of Tempering Condition on the Microstructure and Mechanical Properties of 30MnB5 Hot-Stamping steel (핫스탬핑용 30MnB5강의 템퍼링 조건에 따른 미세조직 및 기계적 물성 연구)

  • Jeong, Junyeong;Park, Sang-Cheon;Shin, Ga-Young;Lee, Chang Wook;Kim, Tae-Jeong;Choi, Min-Su
    • Korean Journal of Metals and Materials
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    • v.56 no.11
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    • pp.787-795
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    • 2018
  • The effects of tempering condition on the microstructure and mechanical properties of 30MnB5 hot stamping steel were investigated in this study. Before the tempering, hot-stamped 30MnB5 steel was composed of only ${\alpha}^{\prime}$-martensite microstructure without precipitates. After the tempering at $180^{\circ}C$ for 120 min, nano-sized ${\varepsilon}$-carbides were precipitated in the ${\alpha}^{\prime}$-martensite laths. After tempering at $250^{\circ}C$ for 60 min, cementite was precipitated along the ${\alpha}^{\prime}$-martensite lath boundaries. The cementite was also observed in the specimens tempered at $350^{\circ}C$ for 30 min and $450^{\circ}C$ for 6 min, respectively. The globular ${\alpha}$-ferrite appeared at $350^{\circ}C-30min$ tempering, and the volume fraction of ${\alpha}$-ferrite increased when the tempering temperature was increased. The yield strength increased after tempering, and it reached a peak with the tempering condition of $180^{\circ}C-120min$, due to the nano-sized precipitates in the ${\alpha}^{\prime}$-martensite lath. After the tempering, the steel's ultimate tensile strength (UTS) was decreased due to the reduction in dislocation density and C segregation to lath boundaries. The highest elongation was observed at the $180^{\circ}C-120min$ tempering condition, due to the reduction of residual stress, and the lack of precipitates along the lath boundaries. The $180^{\circ}C-120min$ tempering condition was considered to have outstanding crash performance, according to toughness and anti-intrusion calculation results. In drop tower crash tests, the 30MnB5 door impact beam tempered at $180^{\circ}C$ for 120 min showed better crash performance compared to a 22MnB5 door impact beam.

Studies on Thermal Oxidation of Soybean Oil -I. Changes in Some Chemical and Physical Properties of a Soybean Oil during Thermal Oxidation- (대두유의 가열산화중의 특성변화 -제 1 보 : 가열산화중의 대두유의 일부 화학적, 물리적 성질의 변화-)

  • Shin, Ae-Ja;Kim, Dong-Hoon
    • Korean Journal of Food Science and Technology
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    • v.14 no.3
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    • pp.257-264
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    • 1982
  • In the present stud changes of some chemical and physical properties of a soybean oil, aerated at 120 ml/min through a porous gas distributor and oxidized at $45^{\circ}C{\sim}180^{\circ}C$, was investigated. The results of the study were as follows: The peroxide, thiobarbituric acid, and iodine value of the soybean oil which was aerated at 120 ml/min increased rapidly as oxidation temperature exceeded over $80^{\circ}C$. The acid value of the oil increased very rapidly as the oxidation temperature passed over $160^{\circ}C$. The content of the unsaturated fatty acid of the oil decreased considerably as the oxidation temperature exceeded over $80^{\circ}C$, whereas that of the saturated fatty acid did not change appreciably. This related well to the changes of the iodine value of the oil subjected to the same experimental conditions. The viscosity and refractive index of the oil increased rapidly as the oxidation temperature passed over $180^{\circ}C$. The following linear relationship hold for the viscosity and refractive index of the oil in the present study. $$V=Aexp({\frac{E}{RT}})$$ where V=viscosity(poise), A=constant, E=activation energy for viscous flow, R=gas constant, T=oxidation temperature$(^{\circ}K)$. The following relationship also hold for the viscosity and refractive index$({n^{20}}_D)$ of the oil at the present experimental conditions. $${n^{20}}_D=1.4614+7.333{\times}10^{-5}t+2.9612{\times}10^{-3}\;InV$$ where t=temperature$(^{\circ}C)$ at which the viscosity was measured.

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Volume Resistivity Properties due to the Curing Condition of Silicone Gel for Semiconductor (반도체용 실리콘 젤의 경화조건에 따른 체적고유저항 특성)

  • 조경순
    • Journal of the Korea Computer Industry Society
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    • v.3 no.12
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    • pp.1747-1758
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    • 2002
  • In order to study the electrical properties of silicone gel due to the curing condition, AC breakdown test is researched. For experiment, we have made up several samples cured during each 30[Min], 1[H], 2[H] at 100[$^{\circ}C$], 125[$^{\circ}C$], 150[$^{\circ}C$], 160[$^{\circ}C$], 170[$^{\circ}C$], 180[$^{\circ}C$]. The equipment for this test can measure the dipole output voltage to 50[kV], with increasing rate of about 3[kV] per second. A material of electrode using to the breakdown test is a copper(purity : 99%), the gap between electrodes is to 1[mm]~3[mm], and it thickness is 0.2[mm]. As a result of the experiment, the electrical properties of specimen cured at 170[$^{\circ}C$] for 2[H] is superior.

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The Effects of Knee Extensor, Flexor Muscle Strength and Joint Position Sense in Squat Exercise on Variety Surface (다양한 지지면에서의 스쿼트 운동이 무릎관절 근력 및 위치감각 향상에 미치는 영향)

  • Kang, Donghun;Yu, Ilyeong;Lee, Geoncheol
    • Journal of The Korean Society of Integrative Medicine
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    • v.1 no.2
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    • pp.47-57
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    • 2013
  • Purpose : The purpose of this study was to compare the Effects of Knee Extensor, Flexor Muscle Strength and Joint Position Sense in Squat Exercise on Variety Surface. Method : Subjuects were consisit of 30 male and female who had non disorder knee joint. we had devided 3 group(control group, balance pad group, and togu group) and we measured that knee joint $15^{\circ}/45^{\circ}$proprioception(position sense) and Peak Torque of knee extensor, flexor muslce at $60^{\circ}/sec$, $180^{\circ}/sec$ angular velocity. Result : First, knee joint $15^{\circ}$proprioception(position sense) of balance pad and togu group was significantly different after exercise(p<.05), but only balance pad group was significantly different at knee joint $45^{\circ}$. Second, knee extensor Peak Torque of balance pad and togu group was significantly different at $60^{\circ}/sec$, $180^{\circ}/sec$ angular velocity(p<.05). Third, knee flexor Peak Torque of balance pad and togu group was significantly different at $60^{\circ}/sec$, $180^{\circ}/sec$ angular velocity(p<.05). Conclusion : Squat exercises on the balance pad and togu were affects knee joint proprioception and muscle strength improvement. These results suggest that squat exercise on the unstable surface is effective for prevention of knee joint injury and functional activity.

Characteristics of Aerodynamic Damping on Helical-Shaped Super Tall Building (나선형 형상의 초고층건물의 공력감쇠의 특성)

  • Kim, Wonsul;Yi, Jin-Hak;Tamura, Yukio
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.1
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    • pp.9-17
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    • 2017
  • Characteristics of aerodynamic damping ratios of a helical $180^{\circ}$ model which shows better aerodynamic behavior in both along-wind and across-wind responses on a super tall building was investigated by an aeroelastic model test. The aerodynamic damping ratio was evaluated from the wind-induced responses of the model by using Random Decrement (RD) technique. Further, various triggering levels in evaluation of aerodynamic damping ratios using RD technique were also examined. As a result, it was found that when at least 2000 segments were used for evaluating aerodynamic damping ratio for ensemble averaging, the aerodynamic damping ratio can be obtained more consistently with lower irregular fluctuations. This is good agreement with those of previous studies. Another notable observation was that for square and helical $180^{\circ}$ models, the aerodynamic damping ratios in along-wind direction showed similar linear trends with reduced wind speeds regarding of building shapes. On the other hand, for the helical $180^{\circ}$ model, the aerodynamic damping ratio in across-wind direction showed quite different trends with those of the square model. In addition, the aerodynamic damping ratios of the helical $180^{\circ}$ model showed very similar trends with respect to the change of wind direction, and showed gradually increasing trends having small fluctuations with reduced wind speeds. Another observation was that in definition of triggering levels in RD technique on aerodynamic damping ratios, it may be possible to adopt the triggering levels of "standard deviation" or "${\sqrt{2}}$ times of the standard deviation" of the response time history if RD functions have a large number of triggering points. Further, these triggering levels may result in similar values and distributions with reduced wind speeds and either may be acceptable.

Ash Reduction and the Change of Fuel Properties for Spent Mushroom Substrates by Acid Solution Extraction (산(acid) 첨가 용매 추출에 의한 폐버섯배지 회분 감소 및 연료특성 변화)

  • Lee, Eun-Jee;Oh, Doh-gun;Kim, Sun-Mee;Park, Eun-Suk;We, Sung-Gook
    • Korean Chemical Engineering Research
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    • v.48 no.3
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    • pp.365-374
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    • 2010
  • The ash reduction effects and fuel property changes of spent mushroom substrates by acid solution extraction, and the production possibilities of wood pellet fuel using them were studied. The ash weight of spent Pleurotus eryngii substrates was reduced from 8.81%(w/w) to 3.33%(w/w), and calorific value was increased from 3,958.3 kcal/kg to 4219.2 kcal/kg when extracted with a mixture of Acetic acid 2%(w/w) and Anhydrous citric acid 1%(w/w) in condition of liquid ratio 1:8, extraction temperature $55^{\circ}C$ and extraction time 180 min. The ash weight of spent Flammulina velutipes substrates was reduced from 14.91%(w/w) to 4.07%(w/w), and calorific value was increased from 4,190.3 kcal/kg to 4,219.2 kcal/kg when extracted with a mixture of Acetic acid 3%(w/w) and Anhydrous citric acid 1%(w/w) in condition of liquid ratio 1:8, extraction temperature $65^{\circ}C$ and extraction time 180 min. The ash weight of spent Pleurotus osteratus substrates was reduced from 3.31%(w/w) to 0.59%(w/w), and the smallest reduction was in calorific value from 4,558.6 kcal/kg to 4,216.2 kcal/kg when extracted with a mixture of Acetic acid 1%(w/w) and Anhydrous citric acid 1%(w/w) in condition of liquid ratio 1:8, extraction temperature $65^{\circ}C$ and extraction time 180 min.

Optimization of Roasting Process as Pre-treatment for Extraction of Omija(Schizandra chinensis Baillon) (오미자 추출을 위한 전처리로서의 볶음공정 최적화)

  • Mok, Chul-Kyoon;Song, Ki-Tae;Lee, Sang-Ki;Na, Young-Jin;Park, Jong-Hyun;Kwon, Young-An;Lee, Seung-Ju
    • Korean Journal of Food Science and Technology
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    • v.33 no.3
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    • pp.333-337
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    • 2001
  • The effect of roasting of Omija (Schizandra chinensis Baillon) on the physicochemical properties and the sensory quality of the extract was investigated in order to improve the quality of Omija beverage. The response surface methodology was introduced to optimize the roasting condition of Omija based on the sensory quality of the extract. The titratable acidity, the soluble solid content and the reducing sugar content of the extract increased with a mild roasting, but decreased with an excessive roasting. Prolonged roasting at high temperature decomposed red pigment making the color of the extract lighter, less red and less yellow. A mild roasting of Omija improved the sensory quality of the extract, and the highest sensory quality of the extract was provided with the roasting at $180^{\circ}C$ for 10 min, indicating the optimum roasting condition of Omija. The extract of the roasted Omija was superior in sensory properties to that of the unroasted one.

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A Study on Velocity Distribution Characteristics for Each Location and Effectiveness of Straight Duct Length in a Square-sectional 180° Bended Duct (정사각형 단면을 갖는 180° 곡관에서 위치별 속도분포특성 및 직관거리의 유효성에 관한 연구)

  • Chen, Jing-Jing;Yoon, Jun-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.10
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    • pp.618-627
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    • 2016
  • This study numerically analyzes the characteristics of the velocity distribution for each location of a square-sectional $180^{\circ}$ bent duct using a Reynolds Stress Turbulent model. The flow parameters were varied, including the working fluids, inlet velocity, surface roughness, radius of curvature, and hydraulic diameter. The boundary conditions for computational fluid dynamics analysis were inlet temperatures of air and water of 288 K and 293 K, inlet air velocity of 3-15 m/s, inner surface roughness of 0-0.001 mm, radius of curvature of 2.5-4.5 D, and hydraulic diameter of 70-100 mm. The working fluid characteristics were highly affected by changes in the viscous force. The maximum velocity profiles in the bent duct were indicated when the $90^{\circ}$ section was in the region of X/D=0.8 and the $180^{\circ}$ section was in the region of Y/D=0.8. Lower surface roughness and higher radius of curvature resulted in a higher rate of velocity change. Also, an efficient measuring location downstream of the bent duct is suggested since the flow deviations were the most stable when the straight duct length was in the region of L/D=30. The minimum deviations at the same velocity conditions according to the hydraulic diameter were mostly indicated in the range of L/D=15-30 based on the standard deviation characteristics.