• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.267-274
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• 2011

The effect of internal ring stiffeners is numerically evaluated for reinforcement of tubular K-joints. Finite element analyses are performed to compute stress of un-stiffened and ring-stiffened K-joints subjected to axial loading. The influence of loading condition and geometrical parameters of ring stiffener on joint behavior is assessed to determine the installation effect of single and double ring stiffeners. The arrangement effect of ring stiffener are evaluated using quantitative analysis compared single ring with double ring stiffeners. Based on the numerical results, practical size of ring stiffener is proposed for design of tubular K-joints.

• Steel and Composite Structures
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• v.3 no.2
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• pp.123-140
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• 2003

The importance of the research on moment-resistant properties of unstiffened tubular joints and the research background are introduced. The performed experimental research on the bending rigidity and capacity of the joints is reported. The emphasis is put on the discussion of the flexural behavior of the joints including sets of geometrical parameters of the joints and several loading combinations. Procedures and results of loading tests on four full size joints in planar KK and X configuration are described in details at first. Mechanical models are proposed to analyze the joint specimens. Three-dimensional nonlinear FE models are established and verified with the experimental results. By comparing the experimental data with the results of the analysis, it is reported reasonable to carry out the structural analysis under the assumption that the joint is fully rigidly connected, and their bending capacities can assure the strength of the members connected under certain limitation. Furthermore, a parametric formula for inplane bengding rigidity of T and Y type tubular joints is proposed on the basis of FE calculation and regression analysis. Compared with test results, it is shown that the parametric formula developed in this paper has good applicability.

• Steel and Composite Structures
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• v.25 no.3
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• pp.375-388
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• 2017

This paper presents a combined experimental, numerical, and analytical study on elliptical concrete-filled steel tubular (E-CFT) and rebar-stiffened elliptical concrete-filled steel tubular (RE-CFT) subjected to axial loading. ABAQUS was used to establish 3D finite element (FE) models for the composite columns and the FE results agreed well with the experimental results. It was found that the ultimate load-bearing capacity of RE-CFT stub columns was 20% higher than that of the E-CFT stub columns. Such improvement was attributed to the reinforcement effects from the internal rebar-stiffeners, which effectively enhanced the confinement effect on the core concrete, thereby significantly improved both the ultimate bearing capacity and the ductility of the E-CFT columns. Based on the results, equations were also established in this paper to predict the bearing capacities of E-CFT and RE-CFT stub columns under axial loading. The predicted results agreed well with both experimental and numerical results, and had much higher accuracy than other available methods.

• The Korean Journal of Zoology
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• v.36 no.2
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• pp.264-275
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• 1993

서식수 염분농도의 변화에 따른 guppy(Poecilia reticulotus) 아가미 상피내 염소세포(chloride cell)의 미세구조적 변화를 전자현미경으로 관찰하고, 특히 증가하는 염분농도에 따라 주요변화를 보여주는 염소세포내 미토콘드리아와 tubular system의 면적을 영상 분석기로 측정하여 다음의 결과를 얻었다. 염소세포는 주로 guppy 아가미궁의 일차 총판상피에 위치하는데 담수에서는 하나씩 독립적으로 존재하며 자유면이 apical pit를 형성하여 외부환경에 노출되는 반면. 서식수의 염분농도가 증가하면 여러개의 염소세포들이 다세포복합체를 형성하고 이 세포들의 자유면이 함께 하나의 apical pit를 구성하게 된다. 서식수의 염분농도가 증가함에 따라 염소세포내의 미토콘드리아와 tubular system은 점점 더 조밀하게 분포하는 것으로 관찰되었다 염소세포의 단위면적당 미토콘드리아가 차지하는 면적은 서식수가 담수(0%의 염분농도)인 경우는 24$\pm$5%였고, 1%에서는 26$\pm$5%, 2%에서는 33$\pm$7% 그리고 해수(3.2% 염분농도)에 적응된 경우는 42$\pm$7%로 담수환경의 것과 비교하여 약 18%까지 증가하였다 또한 염소세포의 측면과 기저측 세포막 함입의 결과로 형성되는 tubular system은 세포의 단위면적당 차지하는 면적이 담수에 적응된 개체들에서 38$\pm$9%였고 서식환경의 염분농도에 따라 점차 증가하다가 해수에서는 61$\pm$9%로 약 16%까지 높아졌다.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.7
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• pp.1044-1050
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• 2008

Most of developed countries, the consumption of fossil fuels has been serious problems that cause serious environment pollution like acid rain, global warming. Also, we have faced that limitation fossil fuels will be exhausted. Currently, small hydropower attracts attention because of its small, clean, renewable, and abundant energy resources to develop. By using a small hydropower generator of which main concept is based on using the different water pressure levels in pipe lines, energy which was initially wasted by use of a reducing valve at the end of the pipeline, is collected by turbine in the hydropower generator. A propeller shaped hydroturbine has been used in order to use this renewable pressure energy. In this study, in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the flow coefficient are examined in detail. Tubular-turbine among small hydraulic power generation can be used at low-head. The purpose of this study is to research turbine's efficiency due to runner vane angle using CFD analysis.

• Toxicological Research
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• v.19 no.2
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• pp.83-90
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• 2003

Since histopathological examination was known to be the most sensitive evaluation for testicular toxicity, regulatory authorities have been published the guidelines on practical testicular assay approach. Those guidelines specified details of evaluation including fixation, embedding, stain-ing, histological examination and also seminiferous tubular staging methods. However, there have been confusing understanding among toxicologists and even pathologists on staging theory and its application on industrial testicular toxicity. Guidelines did not intend to conduct quantitative assay with staging but recommended the use of knowledge of staging. To count each tubular stage with statistical analysis is known to be time consuming and labor burdening work but the significance of toxicity has little value. It also has been pointed out that the application of staging theory for longer-term toxicity considered to be lacking of rationale. It could be recommended that qualitative assay with aware-ness of germ cell loss is more efficient method rather than quantitative counting of each tubular stage. Therefore it would be required that comprehensive understanding of testicular toxicity evaluation and the use of testicular staging method.

• Steel and Composite Structures
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• v.17 no.4
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• pp.431-452
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• 2014

The present study focuses on the mechanical behaviour of concrete filled double skin steel tubular (CFDST) stub columns confined by fiber reinforced polymer (FRP). A series of axial compression tests have been conducted on two CFDST stub columns, eight CFDST stub columns confined by FRP and a concrete-filled steel tubular (CFST) stub column confined by FRP, respectively. The influences of hollow section ratio, FRP wall thickness and fibre longitudinal-circumferential proportion on the load-strain curve and the concrete stress-strain curve for stub columns with annular section were discussed. The test results displayed that the FRP jacket can obviously enhance the carrying capacity of stub columns. Based on the test results, a new model which includes the effects of confinement factor, hollow section ratio and lateral confining pressure of the outer steel tube was proposed to calculate the compressive strength of confined concrete. Using the present concrete strength model, the formula to predict the carrying capacity of CFDST stub columns confined by FRP was derived. The theoretically predicted results agree well with those obtained from the experiments and FE analysis. The present method is also adapted to calculate the carrying capacity of CFST stub columns confined by FRP.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.77-82
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• 2015

In this paper, we perform a study on LED Fluorescent Lamp applying Circuit Driven Method to Tubular LED Lamp Converter. The energy efficiency of LED fluorescent lamp converter requires exceptional protection circuit design, circuit design and structure, because it can not take advantage of Heat-sink structure of the heightened degree Reflector for Fluorescent Lamp. In this paper, we performed a study on LED fluorescent lamp applying circuit driven method to tubular LED lamp converter, Also, we designs LED lamp and converter which can supply DC power common commercial power source.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.104-110
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• 2008

This paper presents demonstration study results derived through field testing of a part load solar energized cooling system for the library of a cultural center building located in Gwangju, Korea. First operating demonstration system was set up in Gwangju in 2005. These system comprises the $200m^2$ evacuated tubular solar collector, a $6m^3$ heat storage tank. In a 2006, daily average of insolation showed about $506W/m^2$, the solar collector efficiency was 44%. In a 2007, daily average of insolation showed about$507W/m^2$, the solar collector efficiency was 42%. As a result, evacuated tubular solar collector kept the high efficiency for two years.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.694-699
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• 2002

In autobody assembly, thin-wall, tubular connections have been used for the frame structure. Recent interest in light materials, such as aluminum or magnesium alloys, has been rapidly growing for weight reduction and fuel efficiency. Due to higher thermal expansion coefficient, low stiffness/strength, and low softening temperature of aluminum and magnesium alloys, control of welding-induced distortion in these connections becomes a critical issue. In this study, the material sensitivity to welding distortion was investigated using a T-tubular connection of three types materials; low carbon steel (A500 Gr. A), aluminum alloy (5456-H116) and magnesium alloy (AZ91C-T6). An uncoupled thermal and mechanical finite element analysis scheme using the ABAQUS software program was developed to model and simulate the welding process, welding procedure and material behaviors. The predicted angular distortions were correlated to the cumulative plastic strains. A unique relationship between distortion and plastic strains exists for all three materials studied. The amount of distortion is proportional to the magnitude and distribution of the cumulative plastic strains in the weldment. The magnesium alloy has the highest distortion sensitivity, followed by the other two materials with the steel connection having the least distortion. Results from studies of thin-aluminum plates show that welding distortion can be minimized by reducing the cumulative plastic strains by preventing heat diffusion into the base metal using a strong heat sink placed directly beneath the weld. A rapid cooling method is recommended to reduce welding distortion of magnesium tubular connections.