• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.124-130
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• 2014

In a mass manufacturing system of optical fibers, the sufficient cooling of glass fibers freshly drawn from a draw furnace is essential, asinadequately cooled glass fibers can lead to poor resin coating on the fiber surface and possibly fiber breakage during the process. In order to improve fiber cooling at a high drawing speed, it is common to use a helium injection into a glass fiber cooling unit in spite of the high cost of the helium supply. The present numerical analysis carried out three-dimensional thermo-fluid computations of the cooling gas flow and heat transfer on moving glass fiber to determine the cooling performance of glass fiber cooling depending on the method of helium injection. The results showed that afront injection of helium is most effective compared to a uniform or rear injection for reducing air entrainment into the unit and thus cooling the glass fibers at a high fiber drawing speed. However, above a certain amount of injected helium, there was no more increase of the cooling effect regardless of the helium injection method.

• Resources Recycling
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• v.27 no.3
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• pp.39-47
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• 2018

According to Vietnam government establishes additional coal-fired power plants to secure generation capacity, emission of ashes is accelerating and processing them is urgent issue. This study targeted utilize fly ashes that occurred in circulating fluidized bed combusion (CFBC) power plant to use ground solidification materials. CFBC fly ashes are used to make solidification with ground granulated blast furnace slag (GGBFS), gypsum and cement. Then produced specimens by mixing with soft ground soil to confirm mixing effect of fly ash in solidification. As a result it was possible to find mixture design that is satisfied 3 MPa compressive strength in age 28 days and reduce weight loss rate over 50% in acid immersion test than plain specimens that using only ordinary portland cement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.159-160
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• 2006

A novel approach to the manufacture of biocompatible ceramic scaffold for tissue engineering using micro-stereolithography system is introduced. Micro-stereolithography is a newly proposed technology that enables to make a 3D micro structure. The 3D micro structures made by this technology can have accurate and complex shape within a few micron error. Therefore, the application based on this technology can vary greatly in nano-bio fields. Recently, tissue-engineering techniques have been regarded as alternative candidate to treat patients with serious bone defects. So many techniques to design and fabricate 3D scaffolds have been developed. But the imperfection of scaffold such as random pore size and porosity causes a limitation in developing optimum scaffold. So scaffold development with controllable pore size and fully interconnected shape have been needed for a more progress in tissue engineering. In this paper, bone scaffold was developed by applying the micro-stereolithography to the mold technology. The scaffold material used was HA(Hydroxyapatite) nano powder. HA is a type of calcium phosphate ceramic with similar characteristic to human inorganic bone component. The bone scaffold made by HA is expected, in the near future, to be an efficient therapy for bone defect.

• Fire Science and Engineering
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• v.28 no.1
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• pp.20-25
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• 2014

Steel column is very important an structural element in steel framed building and plays a key role in sustataining the applied external load. Generally, the fire resistance performance of steel column has been executed by application of fire standard and vertical furnace having a limitation in height. Therefore, the fire resistance test was conducted with a H-section column having 3500 mm in length and hinge to hinge boundary condition. And the fire protective material derived from the fire test can be applied to any kind of boundary conditions and lengths. However, it is hard to determine the fire resistance. In this paper, to make sure the structural stability of them at high temperature according to various boundary conditions and lengths of H-section column, an analysis was done by using the mechanical properties and an heat transfer theory.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.2
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• pp.151-158
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• 2002

The hydorgen storage alloys were produced by melting in arc melting furnace and then solution heat treated at $1,100^{\circ}C$ followed by pulverization. The chemical analysis on the samples showed that the major elements of misch metal(Mm) were La, Ce, Pr and Nd with impurity less than 1wt.%. X-ray diffraction indicated that the structure for these samples were a single phase of hexagonal with $CaCu_5$ type. Compared to the initial particle size $100{\sim}110{\mu}m$, the many fine cracks were found and particle size decreased to $14{\mu}m$ for $MmNi_{4.5}Mn_{0.5}$ after hydriding/dehydring test run. To activate the sample the vessel filled with hydrogen storage alloys was first evacuated for for at $70^{\circ}C$ and then treated for 10.5hr under hydrogen pressure of 20atm for $MmNi_{4.5}Mn_{0.5}$ alloy. The experimental data showed that the hydrogen storage alloy of $MmNi_{4.5}Mn_{0.5}$ had superior adsorption and description properties within a temperature rang of $40^{\circ}C{\sim}80^{\circ}C$ and also they had a good P-C-T curve.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2007.04a
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• pp.25-28
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• 2007

In this study we measured the changes according to time respectively on the basis of 0, 30, 60 and 90 minutes, taking into consideration the decline in fluidity of concrete according to elapsed time to analyze manufacturing capability of batcher plant according to elapsed time of ready-mixed concrete manufactured in batcher plant, and offer basic data for mixture design of ultra-high strength concrete. The proportion of water-binder was 23.55, water content was 160kg/m3, proportion of replacement of crushed sand was 0, 20 and 40% at 3 level, and we applied to the same condition of triaxial component using blast furnace slag powder and silica fume as admixture. And to meet the demand of certain fluidity, we measured respectively on property before and after hardening of ultra-high strength concrete using superplasticizer. As a result of experiment, before hardening of ultra-high strength concrete showed the best fluidity in conditions of crushed sand replacement rates of 20% and superplasticizer composition of 1.95%, but it appeared that fluidity drops as time goes by in the same composition condition. And it appeared that when it comes to hardened, the changes of compression strength according to elapsed time by crushed sand replacement rates were within 1MPa. Therefore, it turned out that the difference of strength according to elapsed time was low and compression strength of 280dys in composition mentioned above appeared highly as 88MPa.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.537-540
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• 2008

Up to now, the RC structures have been recognized as being socially semi-permanent. But in recent years there were reports about the cases of early deterioration of RC structures. Most of all pore structure effects on the durability of concrete as well as mechanical properties of concrete. Therefore, in this study, mixing design was proportioned with the water-binder ratio 0.55 binder compositions corresponding to cement without any supplementary materials(OPC), cement with 50% blast-furnace slag replacement (BFS50), cement with 15% fly ash replacement (FA15), and ternary cement with cement, 15% fly ash, and 35% slag replacement (BFS35+FA15). And this study is to compare pore structure property of concrete by carbonation to investigate the effect of the permeation of deterioration factors such as $CO_2$ and chloride ion under the combined deterioration environments. The results showed that pore volume effects on the diffusibility of chloride ion.

• Journal of the Korean Institute of Gas
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• v.9 no.2 s.27
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• pp.1-7
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• 2005

The thermochemical parameters for safe handling, storage, transport, operation and process design of flammable substances are explosive limit, flash point, autoignition temperature, minimum oxygen concentration, heat of combustion etc.. Explosive limit and autoignition temperature are the major physical properties used to determine the fire and explosion hazards of the flammable substances. Explosive limit and autoignition temperature of methane fur LNG process safety were investigated. By using the literatures data, the lower and upper explosive limits of methane recommended 4.8 vol$\%$ and 16 vol$\%$, respectively. Also autoignition temperatures of methane with ignition sources recommended $540^{\circ}C$ at the electrically heated cruicible furnace (the whole surface heating) and recommended about $1000^{\circ}C$ in the local hot surface. The new equations for predicting the temperature dependence and the pressure dependence of the lower explosive limits for methane are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.399-406
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• 2009

In this study, Polynomial Radial Basis Function Neural Network(pRBFNN) based on Fuzzy Inference System is designed and its parameters such as learning rate, momentum coefficient, and distributed weight (width of RBF) are optimized by means of Particle Swarm Optimization. The proposed model can be expressed as three functional module that consists of condition part, conclusion part, and inference part in the viewpoint of fuzzy rule formed in 'If-then'. In the condition part of pRBFNN as a fuzzy rule, input space is partitioned by defining kernel functions (RBFs). Here, the structure of kernel functions, namely, RBF is generated from HCM clustering algorithm. We use Gaussian type and Inverse multiquadratic type as a RBF. Besides these types of RBF, Conic RBF is also proposed and used as a kernel function. Also, in order to reflect the characteristic of dataset when partitioning input space, we consider the width of RBF defined by standard deviation of dataset. In the conclusion part, the connection weights of pRBFNN are represented as a polynomial which is the extended structure of the general RBF neural network with constant as a connection weights. Finally, the output of model is decided by the fuzzy inference of the inference part of pRBFNN. In order to evaluate the proposed model, nonlinear function with 2 inputs, waster water dataset and gas furnace time series dataset are used and the results of pRBFNN are compared with some previous models. Approximation as well as generalization abilities are discussed with these results.

• Advances in concrete construction
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• v.8 no.3
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• pp.225-237
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• 2019

Although applying self-consolidating concrete (SCC) in many modern structures is an inevitable fact, the high consumption of cement in its mixing designs has led to increased production costs and adverse environmental effects. In order to find economically viable sources with environmentally friendly features, natural pozzolan pumice and blast furnace slag in 10-50% of replacement binary designs have been investigated for experiments on the properties of fresh concrete, mechanical properties, and durability. As a natural pozzolan, pumice does not require advanced equipment to prepare for consumption and only needs to be powdered. Pumice has been the main focus of this research because of simple preparation. Also to validate the results, in addition to the control specimens of each design, fly ash as a known powder has been evaluated. Moreover, ternary mixes of pumice and silica fume were investigated to enhance the obtained results of binary mixes. It was concluded that pumice and slag powders indicated favorable performance in the high percentage of replacement.