• 대한방사선기술학회지:방사선기술과학
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• 제11권2호
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• pp.3-15
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• 1988

When X-rays were projected into a patient, there occured the phenomena such as penetration, absorption and scattering etc. The penetrating rays were recorded on films as X-ray image used for diagnosis but scattered rays caused the radiation hazard both to the patient, specialist and technicians. The soft tissue includes many organs which are sensitive to the radiation and in may occupy $40{\sim}50%$ of body weight. Therefore X-rays should be carefully projected to the patient and it is strongly recommended to analyse the distribution of X-rays, when ever the patient is exposed to X-rays. In this study, the distribution of X-ray according to the thickness, the radiation field and the tube voltages (kVp) in soft tissue, the following results were obtained: 1. Total transmitted rays which kept the step with X-ray tube voltage (kVp) increased in proportion to the increasing of X-ray tube voltage. 2. The scattered ray rate in the total transmitted ray was not significantly found with X-ray tube voltage. 3. The affecting factors of the scattered ray rate in total transmitted ray were shown through the radiation field and the thickness. 4. The dose of scattered ray by the angle was observed more in direction of primary ray ($0^{\circ}$) and back scattering ($160^{\circ}$) than in direction of $90^{\circ}$. 5. The more the distance from phantom to the patient should be less distribution of scattered ray.

• Steel and Composite Structures
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• 제39권3호
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• pp.275-290
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• 2021

The main purpose of this research work is to investigate the critical buckling load of functionally graded (FG) porous plates with graphene platelets (GPLs) reinforcement using generalized differential quadrature (GDQ) method at thermal condition. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the plate thickness direction. Generally, the thermal distribution is considered to be nonlinear and the temperature changing continuously through the thickness of the nanocomposite plates according to the power-law distribution. To model closed cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme are used, through which mechanical properties of the structures can be extracted. Based on the third order shear deformation theory (TSDT) and the Hamilton's principle, the equations of motion are established and solved for various boundary conditions (B.Cs). The fast rate of convergence and accuracy of the method are investigated through the different solved examples and validity of the present study is evaluated by comparing its numerical results with those available in the literature. A special attention is drawn to the role of GPLs weight fraction, GPLs patterns through the thickness, porosity coefficient and distribution of porosity on critical buckling load. Results reveal that the importance of thermal condition on of the critical load of FGP-GPL reinforced nanocomposite plates.

• Steel and Composite Structures
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• 제38권4호
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• pp.399-414
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• 2021

This paper aims to verify the feasibility of rubber rings to mitigate the shear concentration in perfobond connector (PBL) groups. Firstly, modified push-out tests for five specimens with four holes were conducted to investigate the effects of rubber rings on the shear mechanism of PBL groups. The test results showed that by employing rubber rings on partial holes, more shear forces were distributed to the holes without rubber rings. The rubber rings significantly improved the slip ability of the specimens, and the ductility of PBL groups is dependent on the number and thickness of rubber rings. Subsequently, three-dimensional numerical models were established and validated by the experimental results. According to the plastic strain distribution in concrete dowels, the action principle of rubber rings in PBL groups was explained. Furthermore, the parametric study was conducted to investigate the influential factors on shear distributions, including the width of steel plates, the hole spacing, the number of holes, the rubber ring thickness, and the positions of rubber rings. The parametric analysis results showed that the redistribution of shear forces is significantly affected by the rubber rings with the smallest thickness. By properly employing rubber rings in PBL groups, the shear forces of holes are more even. Finally, an analytical model for PBL groups with rubber rings was proposed to predict the shear distribution at the serviceability stage.

• Advances in nano research
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• 제11권6호
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• pp.621-640
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• 2021

Effect of thickness stretching on mechanical behavior of functionally graded (FG) carbon nanotubes reinforced composite (CNTRC) laminated nanoplates resting on elastic foundation is analyzed in this paper using a novel quasi 3D higher-order shear deformation theory. The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Single-walled carbon nanotubes (SWCNTs) are the reinforced elements and are distributed with four power-law functions which are, uniform distribution, V-distribution, O-distribution and X-distribution. To cover various boundary conditions, an analytical solution is developed based on Galerkin method to solve the governing equilibrium equations by considering the nonlocal strain gradient theory. A modified two-dimensional variable Winkler elastic foundation is proposed in this study for the first time. A parametric study is executed to determine the influence of the reinforcement patterns, power-law index, nonlocal parameter, length scale parameter, thickness and aspect ratios, elastic foundation, thermal environments, and various boundary conditions on stresses, displacements, buckling loads and frequencies of the CNTRC laminated nanoplate.

• Radiation Oncology Journal
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• 제9권2호
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• pp.171-176
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• 1991

8 MHz 고주파 유전형 가열장치로 모형을 가열할 때에 전극의 크기와 모형의 두께에 따른 온도 분포를 알아보기 위하여 다양한 크기의 전극과 다양한 두께의 모형을 조합하여 실험하였다. 전극은 10, 15, 20, 25, 그리고 30 cm 크기를 사용하였고 모형은 10, 15, 20, 25, 그리고 30 cm 두께를 사용하였다. 모형의 두께가 25 cm 이상일 경우에는 전극의 크기가 모형의 두께보다 크거나 혹은 같을때에 중심부에 균일한 온도 분포를 얻을 수 있었으나, 모형의 두께가 20 cm 이하일 경우에는 전극의 크기가 모형의 두께와 같을 때는 균일한 온도 분포를 얻을 수 없었고 전극의 크기가 모형의 두께보다 클 때만 균일한 온도 분포를 얻을 수 있었다. 크기가 다른 한쌍의 전극을 사용하여 가열시에는 작은 전극 쪽으로 가열 부분이 집중되었고 그 현상은 전극크기의 차가 클 수록 심하였다.

• 마이크로전자및패키징학회지
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• 제30권1호
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• pp.71-78
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• 2023

외부로부터 전원이 인가되지 않은 바이폴라 전극의 정량적 고찰을 통해 도금 두께 산포 개선의 가능성을 살펴보고자 하였다. 헐셀은 양극에 대해 기울어진 음극을 가짐으로써, 음극의 각 영역에서 양극에 대한 경로차에 의한 iR drop의 차이로 음극 근처의 전해액에서는 전위 분포가 다르게 되어 한눈에 다양한 반응 과전압에서의 전기화학적 반응성을 평가할 수 있다. 본 연구는 이러한 헐셀의 불균일한 전위분포에 대해 보조 양극이 있는 경우에 바이폴라 특성을 관찰하고자 하였다. 특히 이러한 바이폴라 특성을 활용하여 음극의 불균일 두께 산포를 개선할 수 있는 가능성을 평가하기 위해, 실험 및 시뮬레이션을 통해 검증하였으며, 이를 통해 바이폴라가 형성된 주변의 전위 및 전류밀도 분포를 분석해 보았다. 10 mA/cm² 전류밀도로 75분동안 도금을 진행하여, 평균 두께가 약 16 ㎛로 도금을 진행하였다. 보조 양극을 사용하지 않은 일반 헐셀에서는 두께의 표준 편차가 10 ㎛인 반면에 보조 양극을 사용한 경우에는 3.5 ㎛로 나타났다. 시뮬레이션 계산에서도 8.9 ㎛와 3.3 ㎛로 나타났으며, 비교적 실험결과와 시뮬레이션 결과의 정합성이 높은 것으로 나타났다. 이러한 보조 양극을 통해 외부에서 전원 인가를 하지 않더라도 바이폴라 현상에 의해 두께 산포가 개선될 수 있음을알 수 있었다.

• 한국분무공학회지
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• 제26권1호
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• pp.26-32
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• 2021

In this study, the thickness of the liquid sheet formed by two low speed impinging jets was measured by the direct contact method. The effects of jet velocity and liquid viscosity on the thickness were analyzed and the results were compared with theoretical modeling and optical thickness measurement results. The liquid film thickness decreased as the radius and circumferential angle increased. The jet velocity did not affect the liquid film thickness as predicted in theoretical modeling. In the theoretical modeling, there was no influence of the fluid properties on thickness, but in the case of low viscosity liquids, the thickness was predicted high, and it was well matched in high viscosity liquids. The direct measurement results showed no significant difference from the optical measurement results, thus confirming the reliability of the optical measurement method.

• 한국구조물진단유지관리공학회 논문집
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• 제28권2호
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• pp.17-26
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• 2024

최근 콘크리트 타설 중 구조체, 거푸집 및 동바리 사고가 계속해서 발생하고 있으며, 특히 슬래브 두께가 증가하는 다층지지 RC 구조에서 붕괴 사고가 빈번하게 발생하였다. 이전 연구에서는 모든 슬래브 두께가 일정한 경우에 대한 연구가 주로 수행되었으나 일부 슬래브의 두께가 다른 경우, 슬래브 단면 강성의 변화로 전체 슬래브 강성 비율이 달라져 시공 하중의 분포가 달라질 수 있어 이에 대한 연구가 요구된다. 이 연구에서는 슬래브 두께를 변수로 설정하여 슬래브 두께 변화가 콘크리트 강성과 구조물에 미치는 영향을 고려하여 시공 하중의 분포를 분석하였으며, 슬래브 두께가 변화하는 경우 콘크리트 재료 강성 뿐만이 아닌 슬래브 단면 강성도 시공 하중 산정에 고려되어야 함을 확인하였다. 슬래브 두께가 증가 할 경우 두께가 증가하는 층에 작용하는 최대 시공 하중과 최대 손상 변수는 크게 증가하였으며 두께 증가가 클수록 더욱 높은 비율의 시공 하중이 작용함을 확인하였다.

• 소성∙가공
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• 제7권5호
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• pp.439-444
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• 1998

Recently many automotive parts have been made with stainless steels by deep drawing processes, But there are various problems occurred in deep drawing works of stainless steels compared with low carbon steels. For the severe deep drawing of complex cylindrical housing optimum process planning is required to eliminate intermediate annealing improve shape accuracy and maintain surface integrity without drawing defects such as tears wrinkles and scratches or galling. Therefore in this study a sample process planning of the severe of the severe deep drawing process is applied to a complex cylindrical housing needed for a 6 multi-stepped deep drawing of type STS 305 . A series of experiments are performed to investigate optimum process variables such as drawing rate radius and clearance. Through experiments the variations of the thickness strain distribution and hardness distribution in each drawing step are observed. Also the effects of other factors on formability such as drawing oil, blank holding force and die geometry are examined and discussed.

• 한국생산제조학회지
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• 제18권4호
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• pp.395-400
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• 2009

As the variables affecting the fatigue behavior have uncertainty, the fatigue crack propagation is stochastic in nature. Therefore, the fatigue life prediction is critical for the design and the maintenance of many structural components. In this study, fatigue experiments are conducted on the specimens of magnesium alloy under the different thicknesses of specimen. The effects of specimen thickness on the probability distribution of the fatigue crack propagation life and the crack size are estimated experimentally. The probability distribution of the crack size and the fatigue life for different specimen thicknesses are investigated by Anderson-Darling test and the best fit for those probability distributions are also presented.