• Journal of Radiation Protection and Research
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• 제40권3호
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• pp.147-154
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• 2015

The scatter photons and photoneutrons from high energy photon beams (more than 10 MV) will increase the undesired dose to the patient and the staff working in linear accelerator room. This undesired dose which is found at out-of-field area can increase the probability of secondary malignancy. The purpose of this study is to determine the equivalent dose of scatter photons and neutrons generated by 3 different treatment techniques: 3D-conformal, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The measurement was performed using two types of the optically stimulation luminescence detectors (OSL and OSLN) in the Alderson Rando phantom that was irradiated by 3 different treatment techniques following the actual prostate cancer treatment plans. The scatter photon and neutron equivalent dose were compared among the 3 treatments techniques at the surface in the out-of-field area and the critical organs. Maximum equivalent dose of scatter photons and neutrons was found when using the IMRT technique. The scatter neutrons showed average equivalent doses of 0.26, 0.63 and $0.31mSv{\cdot}Gy^{-1}$ at abdominal surface region which was 20 cm from isocenter for 3D, IMRT and VMAT, respectively. The scattered photons equivalent doses were 6.94, 10.17 and $6.56mSv{\cdot}Gy^{-1}$ for 3D, IMRT and VMAT, respectively. For the 5 organ dose measurements, the scattered neutron and photon equivalent doses in out of field from the IMRT plan were highest. The result revealed that the scatter equivalent doses for neutron and photon were higher for IMRT. So the suitable treatment techniques should be selected to benefit the patient and the treatment room staff.

• 한국강구조학회 논문집
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• 제15권5호통권66호
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• pp.531-539
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• 2003

노스리지 지진 발생시 구조체 손상이 발생했던 현장용접 모멘트골조와 달리 기둥-보 브라켓형식의 모멘트골조에는 지진의 영향을 조정하고 감소시키는 도구(tool)가 바로 보에 이음부(splice)이다. 지진발생 중에 보의 이음부는 연성의 퓨즈(fuse)로서 작용할 수 있고, 골조에 발생할 수 있는 흼모멘트를 포함한 힘의 크기를 제한할 수 있다. 국내에서는 모멘트 골조의 대부분이 기둥-보 브라켓 형식으로 이루어진다. 본 논문에서는 이음하지 않은 H형강보를 제작하여 단순가력 실험을 수행하였고, 고력볼트를 이용하여 전강도설계된 실물실험체와 플랜지볼트 열수를 각각 75%, 50% 및 0%로 줄여서 이음부를 제작한 H형강 보를 단순가력 실험을 수행하였다. 이들 실험을 통해 기둥-보 브라켓형식의 모멘트 골조에서 보의 이음부(Beam Splice)가 악보(Week Beam)의 임계위치(Critical Point)로서 작용할 수 있는 가능성을 타진하고자 하는 연구에 기초자료를 제공하는 것이 본 연구의 목적이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.619-619
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• 2009

Recently, silica nanostructures are widely used in various applicationary areas such as chemical sensors, biosensors, nano-fillers, markers, catalysts, and as a substrate for quantum dots etc, because of their excellent physical, chemical and optical properties. Additionally, these days, semiconductor silica and silicon with high purity is a key challenge because of their metallurgical grade silicon (MG-Si) exhibit purity of about 99% produced by an arc discharge method with high cast. Tremendous efforts are being paid towards this direction to reduce the cast of high purity silicon for generation of photovoltaic power as a solar cell. In this direction, which contains a small amount of impurities, which can be further purified by acid leaching process. In this regard, initially the low cast rice-husk was cultivated from local rice field and washed well with high purity distilled water and were treated with acid leaching process (1:10 HCl and $H_2O$) to remove the atmospheric dirt and impurity. The acid treated rice-husk was again washed with distilled water and dried in an oven at $60^{\circ}C$. The dried rice-husk was further annealed at different temperatures (620 and $900^{\circ}C$) for the formation of silica nanospheres. The confirmation of silica was observed by the X-ray diffraction pattern and X-ray photoelectron spectroscopy. The morphology of obtained nanostructures were analyzed via Field-emission scanning electron microscope(FE-SEM) and Transmission electron microscopy(TEM) and it reveals that the size of each nanosphares is about 50-60nm. Using the Inductively coupled plasma mass spectrometry(ICP-MS), Silica was analyzed for the amount of impurities.

• 한국강구조학회 논문집
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• 제21권6호
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• pp.563-574
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• 2009

본 논문은 기하학적 비선형성을 가진 보존적 단일 하중 매개변수의 탄성 상태 공간구조의 탄성 분기 좌굴이론에 관한 수치 해석적 기본 방법 및 경로 추적, pin-pointing, 경로 전환을 기술하고 있다. 비선형 탄성 불안정 상태는 극한점과 분기점으로 분류될 수 있으며, 평형경로상의 평형점의 계산 및 평형경로상의 특이점을 찾기 위한 pin-pointing 반복계산을 수행하는 일반적인 비선형 수치해석법으로 극한점을 계산할 수 있다. 그러나 분기좌굴 해석을 위해서는 좌굴 후 분기경로의 추적을 위한 분기경로 전환 알고리즘이 추가적으로 필요하다. 본문에서는 에너지이론에 기초한 일반 탄성안정이론을 소개하고, 평형경로 추적, 다분기 좌굴점을 찾기 위한 간접법과 다분기의 경로 전환에 관한 이론을 전개한다. 분기좌굴 해석예제로 트러스로 이루어진 스타돔, 핀지지의 평면아치의 분기좌굴 해석을 수행하여 본문에서 제시한 수치해석법의 정확성 및 적용성을 검증한다.

• 한국재료학회지
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• 제25권5호
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• pp.253-257
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• 2015

The implanting of metal products is performed with numerous surface treatments because of toxicity and adhesion. Recently, the surface modification of metal products has been actively studied by coating the surface of the TiC or TiN film. We prepared a Ti(10%)Ag Target which may be used in dental oral material by, using the AIP(arc ion plating) system TiAgN coating layer that was deposited on Ti g.23. The purpose of this study was to establish the optimal bias voltage conditions of the coated TiAgN layer formed by the AIP process. The TiAgN coatings were prepared with different bias voltage parameters (0V to -500V) to investigate the effect of bias voltage on their mechanical and chemical properties. The SEM(scanning electron microscope), EDS(energy dispersive X-ray spectrometer), XRD(X-ray diffraction), micro-hardness, and potentiodynamic polarization were measured and the surface characteristics of the TiAgN coating layers were evaluated. The TiAgN coating layer had different mechanical characteristics based on the bias voltage, which also showed differences in thickness and composition.

• Journal of Biosystems Engineering
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• 제27권6호
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• pp.529-536
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• 2002

The performance of stilting engine, in particular, its energy conversion efficiencies are critically influenced by the regenerator characteristics. The regenerator characteristics are influenced by effectiveness, void fraction. heat transfer loss and fluid friction loss in the regenerator matrix. These factors were influenced by the surface geometry and material properties of the regenerator matrix. The regenerator design goals arc good heat transfer and low pressure drop of working Bas across the regenerator. Various data for designing a wire screen matrix have been given by Kays and London(1984). The mesh number of their experiment. however, was confined below the No. 60. which seems rather small for the Stirling engine applications. In this paper. in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed mettled of matrix in oscillating flow as the same condition of operation in a Stirling engine. Seven kinds of sing1e wire screen meshes were used as the regenerator matrices. The results are summarized as follows; 1. While the working fluid flew slowly in the regenerator. the temperature difference was great at the both hot-blow(the working fluid flows from healer to cooler) and cold-blow(the working fluid flows from cooler to healer). On the other hand. while the working fluid flew fast. the temperature difference was not distinguished. 2. The No.150 wire screen used as the regenerator matrix showed excellent performance than tile others. 3. Phase angle variation and filling rate affected heat transfer or regenerator matrices. 4. Temperature difference between the inlet and outlet of the regenerator is very hish in degree of 120 phase angle.

• 열처리공학회지
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• 제9권1호
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• pp.34-44
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• 1996

Austenite stainless steel was produced by arc welding with current 650A, voltage 50V and welding speed 10cm/min. It was post-welded and then heat treated at $1,050^{\circ}C$ for 120min. And then it was immersed in water or in air. The microstructural changes, ferrite contents, mechanical properties, and stress corrosion cracking(SCC) were investigated. The SCC was studied in 42wt% boiling $MgCl_2$($140^{\circ}C$) under the constant stress using SCC elongation curve. The results showed that; 1. The as-welded spedimen seemed to increase ${\delta}$-ferrite content largely, and revealed continuous network of lathy and vermicular type. The post-welded heat treatment changed the morphologies of ferrite from continuous type to island type. 2. The as-welded, air and water quenched specimens had the ${\delta}$-ferrite content 9.7%, 3.2% and 2.1% respectively. We also showed that ${\delta}$-ferrite was Cr-rich and Ni-poor by EPMA. 3. The time of failure on the SCC was measured and it was used for corrosion elongation curve. The condition of SCC was investigated under $35kgf/mm^2$ load and the results were as follows; 4. The intergranullar cracking by stress corrosion was most distinct in weld metal while the transgranular cracking occurred in the air cooled specimen.

• 한국표면공학회지
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• 제44권1호
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• pp.13-20
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• 2011

This study investigated the high temperature oxidation behavior of Fe-22%Cr-5.8%Al alloy and the oxidation kinetics of the alloy were discussed. Bulk samples were prepared by VAM (vacuum arc melting) and hot forging. High temperature oxidation testes were isothermally conducted up to 100 hours in 79%$N_2$+21%$O_2$ environment at three different temperatures ($900^{\circ}C$, $1000^{\circ}C$, $1100^{\circ}C$). The weight gain was measured after oxidation according to oxidation time (2, 4, 6, 8, 10, 15, 20, 25, 30, 60, 80, 100 hours). The weight gain significantly increased with increasing oxidation temperature. As the temperature increased, the oxidized samples showed sequential formation of $Al_2O_3$, Cr-rich oxide, Fe-rich oxide. The activation energy of high temperature oxidation was obtained as 306.63 KJ/mol. $Al_2O_3$ were developed on the surface in the early stage of oxidation, representing protective role of oxidation. However, Fe-based and Cr-based oxides leaded to breakaway of oxide layer, thus resulted in the significant increase of additional oxidation.

• 대한치과보철학회지
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• 제39권1호
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• pp.1-13
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• 2001

An absolutely passive fit at the interface with the superstructure and the abutment cylinders is need for implant longevity. In this study, a method of cast framework correction using spark erosion technology was evaluated. Electric discharge machining(EDM) is a process that uses electrical discharges, or sparks, to machine metal, The surface being machined is bombared with high-intensity electrical energy pulses that gradually melt away the stock until the desired configuration is obtained. Master model was fabricated by using metal block impression analogue, which fired 5 Branemark squared impression coping in an arc shaped metal block. Then framework using 4mm standard gold cylinder and type IV gold alloy was fabricated. In order to measure the fit of the framework we used both contact and noncontact coordinate measurement machine and data was processed by computer program. After superimposition of gold framework and master model numeric image data the distances between gold cylinder bearing surfaces and abutment replica bearing surfaces, and the angle deviations between gold cylinder and abutment replica centroid points were calculated. The results were as follows 1 The total mean distance (p<0.01) and standard deviation (p<0.001) between the gold cylinders and abutment bearing surfaces were significantly decreased after EDM 2. The total mean of maximum distances was significantly decreased after EDM (p<0.05). 3. After EDM, the mean angle deviation between centroid points was decreased.

• 대한치과보철학회지
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• 제45권6호
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• pp.769-779
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• 2007

Statement of problem. When TiN coating is applied to the abutment screw, occurrence of greater preload and prevention of the screw loosening could be expected due to decrease of frictional resistance. However, the proper thickness of TiN coating on abutment screw has not been yet reported. Purpose. The purpose of this study is to find out the appropriate TiN coating thickness by evaluating the detorque force and the surface change of titanium abutment screw with various TiN coating thickness. Material and methods. 1. Material Thirty five non-coated abutment screws were prepared for TiN coating. TiN coatings were prepared by Arc ion plating method. Depending on the coating deposition time(CDT), experimental groups were divided into 6 groups(CDT 30min, 60min, 90min, 120min, 150min, 180min) and those of 1 group was not coated as a control group. Each group was made up of 5 abutment screws. 2. Methods FE-SEM(Field Emission Scanning Electron Microscoper) and EDX(Energy Dispersive X-ray Spectroscopy) were used to observe the surface of the abutment screw. Electric scales was used to measure the weight of the abutment screw after the repeated closing and opening of 10 trials. Detorque force was measured with digital torque gauge, at each trial. Results. 1. As the coating deposition time increased, the surface became more consistent and smooth. 2. As for the abutment screws that were TiN coated for more than 60 minutes, no surface change was found after the repeated closing and opening. 3. The TiN coated abutment screws showed less weight change than the non-coated abutment screws. 4. The TiN coated abutment screws showed higher mean detorque force than the noncoated abutment screws. 5. The abutment screw coated for 60 minutes showed the highest mean detorque force. Conclusion. The coating layer of proper thickness is demanded to obtain consistent and smooth coating surface, resistance to wear, and increased detorque force of the abutment screw. In conclusion, the coating deposition time of 60 minutes indicated improved mechanical property, when TiN coating was conducted on titanium abutment screw.