• 한국방사선학회논문지
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• 제14권6호
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• pp.733-740
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• 2020

의료종사자의 피폭선량을 줄이기 위한 최근 연구에서, 방사선이 산란될 때 발생하는 광전효과를 이용하여 방사선치료실 입구에서의 선량을 줄이는 방법이 제안되었다. 이 방법은 특히 저에너지 광자에 효과적이기 때문에 본 연구에서는 몬테카를로 시뮬레이션을 이용하여 슬릿형태 구조물의 일반촬영실 산란 엑스선에 대한 차폐성능을 평가하였다. 두께 2 mm, 폭 50 mm, 길이 900 mm인 판을 2 mm 간격으로 수평 적재하는 형태의 슬릿형태 구조물은 알루미늄에 비해 철 또는 납으로 만드는 경우 차폐효과가 뛰어났다. 재질을 철로 한정한 경우 선원과 관심구역 사이에서 결정된 구조물의 설치위치는 차폐효과와 무관했으며, 판의 폭은 차폐효과에 비례했다. 폭 50 mm 철판을 사용한 경우 산란선이 직접 발생하는 바닥 및 환자의 높이를 제외하면 약 99.9% 또는 그 이상의 차폐효과가 있었다.

• Steel and Composite Structures
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• 제16권6호
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• pp.611-637
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• 2014

A single plate shear connection, or shear tab, is a very popular shear connection due to its merit in ease of construction and material economy. However, problems in understanding the connection behavior, both in terms of strength and ductility, have been well-documented. Suggestions or design model for single plate connections in AISC Design Manual have been altered several times, with the latest edition settling down to giving designers pre-calculated design strength tables if the connection details agree with given configurations. Results from many full-scale tests and finite element models in the past suggest that shear strength of a bolt group in single plate shear connections might be affected by yield strength of plate material; therefore, this research was aimed to investigate and clarify effects of plate yield strength and thickness on shear strength of the bolt group in the connections, including the validity of using a plate thickness/bolt diameter ratio ($t_p/d_b$) in design, by using finite element models. More than 20 models have been created by using ABAQUS program with 19.0- and 22.2-mm A325N bolts and A36 and Gr.50 plates with various thicknesses. Results demonstrated that increase of plate thickness or plate yield strength, with the $t_p/d_b$ ratio remained intact, could significantly reduce shear strength of the bolt group in the connection as much as 15 percent. Results also confirmed that the $t_p/d_b$ ratio is a valid indicator to be used for guaranteeing strength sufficiency. Because the actual ratio recommended by AISC Design Manual is $t_p/d_b$ + 1.6 (mm) for connections with a number of bolts less than six and plate yield strength in construction is normally higher than the nominal value used in design, it is proposed that shear strength of a bolt group in single plate connections with a number of bolts equal or greater than seven be reduced by 15 percent and the $t_p/d_b$ ratio be limited to 0.500.

• 대한토목학회논문집
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• 제35권2호
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• pp.377-386
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• 2015

헬리컬 파일은 한 개 이상의 나선형 원판을 중공형 강재 축에 부착한 후 지반에 회전 관입시켜 지지력을 발현하게 하는 말뚝기초의 한 종류로서 별도로 천공작업 및 그라우팅을 필요로 하지 않고, 시공의 편의성과 말뚝 항타 등에 의한 소음이 없다는 장점이 있어 그 이용이 점차 증가되고 있는 추세이다. 본 연구에서는 Cylindrical shear method로 산정된 헬리컬 파일의 요구 지지력을 최소의 자재비용과 최적의 헬리컬 파일의 형상으로 발현할 수 있도록 하모니서치 알고리즘(Harmony search algorithm)을 적용하여 최적화된 설계법을 제안 하였다. 또한 헬리컬 파일의 최적 설계 결과를 2009 International building code (이하, 2009 IBC)를 참고하여 규격화시킨 설계 결과와 비교 검토하여 두 설계법의 경제성을 분석하였다. 본 논문의 재료비 최소화를 위한 헬리컬 파일 형상의 최적 설계 기법은 헬리컬 파일의 경제성을 향상하여 헬리컬 파일 시장 활성화에 기여할 수 있다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.349-351
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• 2013

본 논문에서는 강판 결함 검출 시스템의 아날로그 신호처리를 하기 위해 저전력 이득 조절 증폭기(PGA)를 설계하였다. 설계된 PGA는 홀 센서에서 나오는 신호를 검출 하려는 결함의 종류에 따라 그 이득을 6dB에서 60dB까지 7가지 단계로 조절 가능하다. PGA이득은 선형성 및 칩 크기를 고려하여 스위치의 온-저항과 수동소자 크기에 의해서 조절 되도록 설계하였다. 이득오차는 0.2dB 보다 작으며 소비전력은 0.47mW이다. 전원전압 1.8V에 $0.18{\mu}m$ CMOS 공정을 이용하여 PGA를 설계하였다.

• 한국표면공학회지
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• 제46권4호
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• pp.168-174
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• 2013

In this study, low-cost, high-speed deposition, excellent processability, high mechanical strength and electrical conductivity, chemical stability and corrosion resistance of stainless steel to meet the obsessive-compulsive (0.1 mm or less) were selected CrN thin film. new price reduction to sputter deposition causes - the possibility of sublimation source for inductively coupled plasma Cr rods were attempts by DC bias. 0.6 Pa Ar inductively coupled plasmas of 2.4 MHz, 500 W, keeping Cr Rod DC bias power 30 W (900 V, 0.02 A) is applied, $N_2$ flow rate of 0.5, 1.0, 1.5 sccm by varying the characteristics of were analyzed. $N_2$ flow rate increases, decreases and $Cr_2N$, CrN was found to increase. In addition to corrosion resistance and contact resistance, corrosion resistance, electrical conductivity was evaluated. corrosion current density than $N_2$ 0 sccm was sure to rise in all, $N_2$ 1 sccm at $4.390{\times}10^{-7}$ (at 0.6 V) $A{\cdot}cm^{-2}$, respectively. electrical conductivity process results when $N_2$ 1 sccm 28.8 $m{\Omega}/cm^2$ with the lowest value of the contact resistance was confirmed that came out. The OES (SQ-2000) and QMS (CPM-300) using a reactive deposition process to add $N_2$ to maintain a uniform deposition rate was confirmed that.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.55-55
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• 2009

FGB(Flexible Glasswool Backing) Submerged Arc Welding has been one of the main welding processes for one side butt welding in shipbuilding industries, which can efficiently improve the welding productivity by the addition of a supplementary filler metal into the molten weld pool. As recent ships have become larger in size, the application of high tensile and higher grade of steels has been continuously increased. Single pass FGB SA welding process accompanies such a high heat input when welding thick plates that the mechanical properties of weld metal can be dramatically degraded. This study has been performed in order to obtain high toughness and tensile properties of high heat input FGB SA welds, and to evaluate the effect of alloy elements on their mechanical properties. To complete welding 25mm-thick EH36 grade steel plate by single pass, 1.2mm diameter and 1.0mm long cut wires has been distributed in the groove before welding, and three different test coupons have been made using C-1.5%Mn, C-1.8%Mn-0.5%Mo, and C-1.4%Mn-1.7%Ni cut wires to investigate the influence of nickel(Ni) and molybdenum(Mo) on the mechanical properties of welds. Test results showed that the addition of Ni and Mo effectively promotes the formation of Acicular Ferrite(AF), while significantly reducing the amount of Grain Boundary Ferrite(GBF) in weld metal microstructures, which resulted in a beneficial effect on low temperature impact toughness and strength.

• Journal of Welding and Joining
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• 제16권4호
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• pp.55-62
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• 1998

While excellent joint quality has been obtained using dry chamber underwater welding methods, the size limitations imposed by this process restrict its use for underwater construction work. The wet underwater shielded metal-arc welding eliminates this restriction but suffers from poor weld properties by the 1-pass bead-on-plate welding due to the excessive diffusible hydrogen. On the other hand, in the wet underwater welding, it is well known that the quantity of diffusible hydrogen in multi-pass welded parts reduce to less than that in 1-pass welded parts. Therefore, in this paper, welding experiments are made the 3-pass bead-on-plate welds by using TMCP and normalized steel plates and E4301 and cellulose coated electrode. After that, The amounts of the hydrogen absorbed into the 3-pass welded area were measured according to the JIS Z 3118 specification. The microstructural changes as well as the microhardness distribution after the underwater 3-pass welding were also investigated using Vickers microhardness tester and S.E.M and O.M. The results indicated that the quantity of diffusible hydrogen in 3-pass welded areas was reduced little less than a half of one of that in 1-pass welded areas at the specific welding condition. As a result, the cold cracking of 3-pass welded areas decreased by reduced effect of diffusible hydrogen. In the underwater 3-pass welding, the micrography of cold cracking fracture surface showed mainly the cleavage of hydrogen embrittlement.

• Journal of Welding and Joining
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• 제17권1호
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• pp.88-96
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• 1999

The effects of root gap on welding residual stress and deformation are dealt with the multi-pass weldment with three kinds(0, 6, 30mm) of root gap by F.E.M common code, and then compared with experiment data. In this analysis, an 100% ramp heat input model was used to avoid numerical convergence problem due to an instantaneous increase in temperature near the fusion zone, and the effect of a moving arc in a two dimensional plane was also included. During the analysis, a small time increment was applied in a period with instantaneous temperature fluctuation while a large time increment was used in the rest period. The residual stress is distributed as symmetric types and maximum value is also equivalent when the weldment with 0mm and 6mm root gap is welded. In the case of 30mm root gap welding, the distribution of the residual stress extends over a wide range as asymmetric types due to the built-up weld, and most of the residual stress is biased in the side of a built-up weld part. In case of 0mm gap welding and 6mm gap welding, a little angular distortion occurs, but the level of deformation is small. When the weldment with 30mm root gap is welded, the angular deformation of the asymmetric types, however, occurs larger than the other specimens. The experimental and the analytic results show good coincidence and indicate that the welding residual stress and deformation distribution of 30 mm root gap specimen may be asymmetric and the amplitude is larger than those of root gap specimen under standard.

• 한국방사선학회논문지
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• 제6권6호
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• pp.477-481
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• 2012

엑스선 회절분석기는 비파괴적인 방법으로 시료의 정보를 정성 및 정량적으로 분석할 수 있다. 엑스선 회절분석기에는 다양한 광학소자가 사용된다. 평행빔 광학소자는 광축에 평행한 빔을 통과시키고 발산하는 빔을 제거하는 역할을 한다. 와이어 컷 제작과 스테인리스 스틸 평판을 연마하여 평행빔 광학소자를 제작하였고 엑스선 영상장치를 이용하여 그 평행도를 평가하였다. 설계된 6 mrad과 매우 가까운 6.6 mrad의 평행도를 갖는 평행빔 광학소자를 제작하였다. 엑스선 영상을 이용하면 개개의 평판의 평행도를 예측할 수 있을 뿐만 아니라 다양한 광학소자 평가에도 사용될 수 있을 것이다.

• Structural Engineering and Mechanics
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• 제38권6호
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• pp.697-714
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• 2011

Assessing the ductility of reinforced concrete sections and members has been a complex and intractable problem for many years. Given the complexity in estimating ductility, members are often designed specifically for strength whilst ductility is provided implicitly through the use of ductile steel reinforcing bars and by ensuring that concrete crushing provides the ultimate limit state. As such, the empirical hinge length and neutral axis depth approaches have been sufficient to estimate ductility and moment redistribution within the bounds of the test regimes from which they were derived. However, being empirical, these methods do not have a sound structural mechanics background and consequently have severe limitations when brittle materials are used and when concrete crushing may not occur. Structural mechanics based approaches to estimating rotational capacities and rotation requirements for given amounts of moment redistribution have shown that FRP plated reinforced concrete (RC) sections can have significant moment redistribution capacities. In this paper, the concept of moment redistribution in beams is explained and it is shown specifically how an existing RC member can be retrofitted with FRP plates for both strength and ductility requirements. Furthermore, it is also shown how ductility through moment redistribution can be used to maximise the increase in strength of a member. The concept of primary and secondary hinges is also introduced and it is shown how the response of the non-hinge region influences the redistribution capacity of the primary hinges, and that for maximum moment redistribution to occur the non-hinge region needs to remain elastic.