• Structural Engineering and Mechanics
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• 제55권2호
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• pp.349-364
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• 2015

Analytical solutions for modeling geotextile tubes during the filling process and approximation method to determine the densified tube shape are reviewed. The geotextile tube filling analysis is based on Plaut & Suherman's two-dimensional solution for geotextile tubes having a weightless and frictionless inextensible membrane resting on a rigid horizontal foundation subjected to internal and external hydrostatic pressures. The approximation for the densified tube shape developed by Leshchinsky et al. was adopted. A modified method for approximating the densified tube shape based on an areal-strain deformation analysis is introduced. Design diagrams useful for approximating geotextile tube measurements in the design process are provided.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1994년도 특별강연 및 추계학술발표 개요집
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• pp.85-88
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• 1994

• Journal of Advanced Marine Engineering and Technology
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• 제31권3호
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• pp.263-271
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• 2007

The heat transfer coefficient and pressure drop during 9as cooling process of $CO_2$ (R744) in a helically coiled copper tube with the inner diameter of 4.55 mm and outer diameter of 6.35 mm were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump. a mass flow meter a pre-heater and a helically coiled type gas cooler (test section). The refrigerant mass fluxes are varied from 200 to $800kg/m^2s$ and the inlet pressures of gas cooler are 7.5 to 10.0 MPa. The heat transfer coefficients of $CO_2$ in a helically coiled tube are higher than those in a horizontal tube. The Pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those predicted by Ito's correlation developed for single-phase in a helically coiled tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However. at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al correlation. Therefore, various experiments in helically coiled tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in a helically coiled tube.

• 한국의학물리학회지:의학물리
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• 제23권4호
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• pp.279-284
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• 2012

X선은 방사선 진단과 치료 분야에 있어서 다양하고 광범위하게 이용되고 있으며, 최근에는 방사선 치료용 초소형 X선관이 개발되었다. 초소형 X선관은 조사 목적 부위에 직접 삽입하여 사용되므로 제작 시준기에 따라 다양한 각도로 X선 조사가 가능하고, 검사 목적 외의 환자 피폭선량을 최소화한다. 이러한 초소형 X선관의 장점을 이용해서 X선 영상을 획득하는데 적용한다면 X선 진단 분야의 새로운 장을 열 것으로 기대된다. 하지만 초소형 X선관은 본래 치료용으로 설계되었기 때문에 진단용 장비에 적합한 시준기, 필터(added filter) 등이 필요하다. 따라서 자체 제작한 시준기와 필터를 적용하여 초소형 X선관의 빔 특성이 진단용에 적합한지 평가 하였고, 이를 위해서 다이오드 검출기를 이용하여 반가층을 측정하고 측정의 가능성을 평가하였다. 본 연구에서는 Si PIN Photodiode type인 Piranha 검출기(Piranha, RTI, Sweden)를 사용하여 필터 적용 유무에 따른 초소형 X선관의 반가층을 측정하고, 알루미늄 필터를 사용한 측정을 통하여 Piranha 검출기의 반가층 측정의 정확성을 평가하였다. 측정 결과에 따르면 초소형 X선관의 반가층은 필터의 장착에 따라 약 1.9배 증가하여 진단용 방사선 발생 장치의 적합성을 확인하였다. Piranha 검출기의 반가층 자동 측정값은 필터를 미장착한 경우에 실제 반가층 측정값에 비해 50% 높게 측정되어 적용이 불가능하나, 필터를 장착한 경우에는 실제 반가층 측정값과 약 15%의 차이로 감소되었다. 따라서 진단용 필터를 적용했을 경우는 Piranha 검출기의 반가층 자동측정이 가능하여 kV-X선 특성평가를 수월하게 수행할 것으로 기대된다.

• Structural Engineering and Mechanics
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• 제9권4호
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• pp.339-347
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• 2000

The creep deformation of pure bending (hold constant moment for a period of time) tests were conducted in this paper. Thin-walled tubes of 304 stainless steel were used in this investigation. The curvature-ovalization measurement apparatus, designed by Pan et al. (1998), was used for conducting the present experiments. It has been found that as soon as the creep deformation is started, the magnitudes of the tube curvature and ovalization of tube cross-section quickly increase. The magnitudes of the creep curvature and ovalization of tube cross-section increase fast with a higher hold moment than that with a lower one. Owing to the continuously increasing curvature during the creep deformation, the tube specimen buckles eventually.

• Tribology and Lubricants
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• 제23권4호
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• pp.143-148
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• 2007

The surface defects of an aluminum tube for an OPC drum have been analyzed using a scanning microscopy(SEM) and an energy dispersive X-ray analyze.(EDX). The SEM/EDX system, which may provide good information on the surface defects and their distributions, provides an optical diameter of an impurity and a chemical composition. These are strongly related on the coated film thickness and quality of an OPC drum, which is a key element of a toner cartridge for a laser printer. The experimental results show that the local deformations, scratch wear, and flaws are produce the non-uniform coating layers, which may be removed by a manufacturing process of an aluminum tube. The major parameters on the coating quality of an OPC drum are the impurities of an aluminum tube such as silicon, oxygen, calcium, carbon, sulphur, chlorine, and others. These impurities may be removed by an ingot molding, extrusion and drawing, quality control, and packing processes with a strict manufacturing technology.

• Geomechanics and Engineering
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• 제6권1호
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• pp.65-77
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• 2014

Geosynthetic tubes inflated with water, clay slurry or sand have been widely used for large dike construction in land reclamation projects. In this paper, analytical solutions for geosynthetic tube resting on rigid foundation is presented by adopting an approach similar to that presented by Leshchinsky et al. (1996). The proposed method allows a quick preliminary design to be made for using a closed-form solution. To simplify the analysis, relationships between geometrical parameters and pumping pressure are established using numerical method. The analytical solutions were compared with several existing solutions and good agreements were achieved.

• International Journal of Precision Engineering and Manufacturing
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• 제6권2호
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• pp.26-33
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• 2005

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effect of process variables such as gap height, relative gap width and die comer radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• 한국정밀공학회지
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• 제20권12호
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• pp.168-175
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• 2003

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effects of process variables such as gap height, relative gap width and die corner radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• Advances in nano research
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• 제10권5호
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• pp.493-507
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• 2021

This article focused on studying the buckling behavior of two-dimensional functionally graded (2D-FG) nanosize tubes, including porosity based on first shear deformation and higher-order theory of tube. The nano-scale tube is simulated based on the nonlocal gradient strain theory, and the general equations and boundary conditions are derived using Hamilton's principle for the Zhang-Fu's tube model (as higher-order theory) and Timoshenko beam theory. Finally, the derived equations are solved using a numerical method for both simply-supported and clamped boundary conditions. The parametric study is performed to study the effects of different parameters such as axial and radial FG power indexes, porosity parameter, nonlocal gradient strain parameters on the buckling behavior of di-dimensional functionally graded porous tube.