• 한국의학물리학회지:의학물리
• /
• 제7권2호
• /
• pp.3-17
• /
• 1996

방사선 치료분야에서 선량 보상체가 널리 이용되고 있으나, 그 보상효과에 대한 확실한 검증 방법은 알려진 바가 거의 없다. 본 연구에서는 Missing Tissue 뿐 아니라, Internal Tissue Inhomogeneity 까지 고려한 3차원 보상체를 제작하고, Exit Beam Dose Profile의 측정값과 본 연구에서 고안한 방법으로 기대값을 구해 비교함으로써 보상체의 성능을 평가하고자 하였다. 환자정보는 CT Simulator를 사용하여 얻었고, 보상체 정보는 Render Plan 3-D Planning System을 통해 얻었다. Computer Controlled Milling Machine으로 알루미늄 보상체를 제작해서 보상체가 있는 경우와 없는 경우의 선량 프로파일을 측정하여 비교하였다. 측정은 폴리스티렌 팬톰 사이에 필름을 삽입하여 팬톰 내에서의 실제 선량 분포를 구하고, 필름 카셋트를 이용해서 Exit Beam Dose Profile 을 동시에 얻었다. Oblique Beam, Parallel Opposing Beam, Inhomogeneus Human Phantom에 대해 제작된 보상체가 각각 선량보상 효과가 잘 나타남을 볼 수 있었고, 이 연구에서의 성능확인 방법을 통해 보상체의 성능을 확인할 수 있었다.

• 대한기계학회논문집A
• /
• 제22권4호
• /
• pp.834-842
• /
• 1998

This paper examines the crack growth behavior of 7075-T651 and 5052-H32 aluminum alloy under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure ae investigated by compliance method. The applied stress ratios are R=0.15, 0.0, -0.15 and R=-0.15, 0.0, 0.15. The crack growth rate was found to increase as the load amplitude increases. However,${\bigtriangleup}K_eff$ was almost independent on the stress ratio. The experimental constants of 7075-T651 and 5052-H32 in Paris law were c`=1-1.3${\times}{10^-7},m`=3~3.2 and c`=4~6{\times}{10^-9}, m`=4.3-4.8$, respectively. $K_op$ of 7075-T651 and 5052-H32 becomes smaller as the stress ratio decreases. It seems that the crack closure affects $K_op$.

• 한국생산제조학회지
• /
• 제26권4호
• /
• pp.410-417
• /
• 2017

Hydro-forming is being employed increasingly to realize lightweight vehicular parts. The bumper beam produced by this process weighs 30% less than the conventional products with equal stiffness. However, hydro-forming involves complex parameters to obtain the target geometry and low residual stress. Parametric studies are conducted using finite element analysis to obtain optimized process conditions. Through these numerical approaches, the internal and holding pressures and feeder forward stroke along the extruded direction are optimized to achieve low residual stress and to minimize springback. The numerical results are verified by experimental observations made by employing a three-dimensional laser scanner. The numerical and experimental results are compared in terms of the springback. Both results show similar tendencies.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.114-114
• /
• 2012

Metal-oxide-semiconductor field-effect transistors (MOSFETs)의 critical dimension (CD)가 sub 45 nm로 줄어듬에 따라 기존에 gate dielectric으로 사용하고 있는 SiO2에서 발생되는 high gate leakage current 때문에 새로운 high dielectric constant (k) 물질들이 연구되기 시작하였다. 여러 가지 high-k 물질 중에서, aluminum-oxide (Al2O3)는 높은 dielectric constant (~10)와 전자 터널링 barrier height (~2eV) 등을 가지기 때문에 많은 연구가 되고 있다. 그러나 Al2O3를 anisotropic한 patterning을 하기 위해 주로 사용되고 있는 halogen-based 플라즈마 식각 과정에서 나타나는 Al2O3와 하부 layer간의 낮은 식각 selectivity 뿐만 아니라 표면에 발생되는 defect, stoichiometry modification, roughness 변화 등의 많은 문제점들로 인하여 device performance가 감소하기 때문에 이를 해결하기 위한 많은 연구들이 진행중이다. 따라서 본 연구에서는 실리콘 기판위의 atomic layer deposition (ALD)로 증착된 Al2O3를 BCl3/Ar 중성빔을 이용하여 원자층 식각한 후 식각 특성을 분석해 보았다. Al2O3 표면을 BCl3로 absorption시킨 후 Ar 중성빔으로 desorption 시키는 과정에서 volatile한 aluminum-chlorides와 boron oxychloride가 형성되어 layer by layer로 제거됨을 관찰 할 수 있었다.

• 한국재료학회지
• /
• 제20권1호
• /
• pp.37-41
• /
• 2010

Creep tests were conducted under a condition of constant stress on two aluminum-based alloys containing particles: Al-5% Mg-0.25% Fe and Al-5% Zn-0.22% Fe. The role of grain boundary sliding was examined in the plane of the surface using a square grid printed on the surface by carbon deposition and perpendicular to the surface using two-beam interferometry. Estimates of the contribution of grain boundary sliding to the total strain, $\varepsilon_{gbs}/\varepsilon_t$ reveal two trends; (i) the sliding contribution is consistently higher in the Al-Mg-Fe alloy, and (ii) the sliding contribution is essentially independent of strain in the Al-Mg-Fe alloy, but it shows a significant decrease with increasing strain in the Al-Zn-Fe alloy. Sliding is inhibited by the presence of particles and its contributions to the total strain are low. This inhibition is attributed to the interaction between the grain boundary dislocations responsible for sliding and particles in the boundaries.

• 한국표면공학회지
• /
• 제41권3호
• /
• pp.109-113
• /
• 2008

High strength 7xxx series Al-Zn-Mg alloy have been investigated for using light weight automotive parts especially for bump back beam. The composition of commercial 7xxx aluminum has the Zn/Mg ratio about 3 and Cu over 2 wt%, but this composition isn't adequate for appling to automotive bump back beam due to its high resistance to extrusion and bad weldability. In this study the Zn/Mg ratio was increased for better extrusion and Cu content was reduced for better welding. With this new composition we investigated the effect of composition on the resistivity against stress corrosion cracking. As the Zn/Mg ratio is increased fracture energy obtained by slow strain rate test was decreased, which means degradation of SCC resistance. While the fracture energy was increased with Cu contents although it is below 1%, which means improvement of SCC resistance. These effects of composition change on the SCC resistivity were identified by observing the fracture surface and crack propagation.

• 한국구조물진단유지관리공학회 논문집
• /
• 제3권3호
• /
• pp.237-243
• /
• 1999

Recently, there has been considerable interest in the development of fiber-optic sensors based on fiber Bragg gratings (FBGs), which can be made into Ge-doped fiber's core by UV phase mask or holographic methods. A good sensitivity and small size of this sensor make it an ideal candidate for distributed sensing in smart structures or other structural monitoring applications. In this study, fiber optic Bragg grating sensor, which could be applied to measure the absolute strains, was constructed and the strain sensitivity of this sensor was investigated in order to apply to the structural health monitoring. Fiber Fabry-Perot (FFP) filter has been used to detect the optical signals instead of optical spectrum analyzer. It has been convenient to determine the structural strains from the output signal of FBGs. The fiber optic Bragg grating sensor was attached on the aluminum beam near the electrical strain gage to measure the same strain. The relationship between strain and fiber signal was linearly fitted. The strain sensitivity of the fiber optic Bragg grating sensor was determined as $l.57{\mu}{\varepsilon}/{\mu}sec$ from the aluminum beam test.

• 대한토목학회논문집
• /
• 제37권1호
• /
• pp.217-229
• /
• 2017

보의 표면에 부착된 압전웨이퍼를 통해 가진되고 측정되는 고주파수 대역의 전기역학적 신호는 보에 발생한 미세 손상에 매우 민감하다. 이러한 부착형 압전웨이퍼의 장점을 이용한 보의 손상 진단을 효과적으로 수행하기 위해서는 압전웨이퍼의 탐지범위 예측이 필요하다. 고주파수 대역에서 압전웨이퍼의 탐지범위에 영향을 주는 여러 가지 요인 중 가장 지배적인 인자는 보의 감쇠이다. 이 연구에서는 보에 부착된 압전웨이퍼의 전기역학적 신호를 이용하여 보의 감쇠를 추정할 수 있는 기법을 제시한다. 공진이 발생하는 과정에서 보의 감쇠효과를 고려하여 압전웨이퍼의 전기역학적 신호를 파전달 관점에서 정식화한다. 실제 계측된 전기역학적 신호로부터 구한 측정 감쇠비 함수값과 정식화된 전기역학적 신호로부터 계산된 감쇠비 함수값의 차이를 최소화하는 최소자승법을 통해 보의 감쇠비를 추정한다. 제시된 방법을 압전웨이퍼가 병치되어 있는 알루미늄 보 수치 및 실험 예제에 적용하여 타당성을 검증한다.

• Medical Lasers
• /
• 제8권1호
• /
• pp.24-27
• /
• 2019

Seborrheic keratoses (SKs) have been treated with non-ablative longpulsed (LP) lasers, including LP 532-nm neodymium (Nd): yttrium aluminum garnet (YAG), LP 695-nm ruby, LP 755-nm alexandrite (Alex), and LP 1,064-nm Nd:YAG lasers, with a pulse durations of 1-300 msec. Dual-wavelength LP 755-nm Alex/1,064-nm Nd:YAG laser systems have been used to remove hair follicles and treat various vascular and pigmented disorders by sequentially delivering two pulses of different wavelengths with interpulse intervals in the millisecond range. This paper reports the case of a female patient with multiple, discrete, light brown SKs on the dorsum of both hands that were treated effectively with one session of dual-wavelength LP 1,064-nm Nd:YAG/755-nm Alex laser treatment. The treatment settings for the LP Nd:YAG laser were comprised of a wavelength of 1,064 nm, fluence of 50 J/cm², pulse duration of 5 msec, and beam size of 3 mm. The settings for the LP Alex laser were comprised of a wavelength of 755 nm, fluence of 50 J/cm², pulse duration of 5 msec, and beam size of 3 mm. A hybrid mode was used to automatically deliver LP Nd:YAG and LP Alex laser pulses in succession at interpulse intervals of 20 msec. Six weeks after treatment, the patient exhibited remarkable improvement of the light brown seborrheic keratoses and was satisfied with the results.

• Steel and Composite Structures
• /
• 제51권2호
• /
• pp.153-172
• /
• 2024

Due to the fast development of constructions in recent years, there has been a rapid consumption of fresh water and river sand. In the production of concrete, alternatives such as sea water and sea sand are available. The near surface mounted (NSM) technique is one of the most important methods of strengthening. Aluminum alloy (AA) bars are non-rusting and suitable for usage with sea water and sand concrete (SSC). The goal of this study was to enhance the shear behaviour of SSC-beams strengthened with NSM AA bars. Twenty-four RC beams were cast from fresh water river sand concrete (FRC) and SSC before being tested in four-point flexure. All beams are the same size and have the same internal reinforcement. The major factors are the concrete type (FRC or SSC), the concrete degree (C25 or C50 with compressive strength = 25 and 50 MPa, respectively), the presence of AA bars for strengthening, the direction of AA bar reinforcement (vertical or diagonal), and the AA bar ratio (0, 0.5, 1, 1.25 and 2 %). The beams' failure mechanism, load-displacement response, ultimate capacity, and ductility were investigated. Maximum load and ductility of C25-FRC-specimens with vertical and diagonal AA bar ratios (1%) were 100,174 % and 140, 205.5 % greater, respectively, than a matching control specimen. The ultimate load and ductility of all SSC-beams were 16-28 % and 11.3-87 % greater, respectively, for different AA bar methods than that of FRC-beams. The ultimate load and ductility of C25-SSC-beams vertically strengthened with AA bar ratios were 66.7-172.7 % and 89.6-267.9 % higher than the unstrengthened beam, respectively. When compared to unstrengthened beams, the ultimate load and ductility of C50-SSC-beams vertically reinforced with AA bar ratios rose by 50-120 % and 45.4-336.1 %, respectively. National code proposed formulae were utilized to determine the theoretical load of tested beams and compared to matching experimental results. The predicted theoretical loads were found to be close to the experimental values.