• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.99-102
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• 2006

Optimal flow-field design of bipolar-plates for a commercial class PEM(polymer electrolyte membrane) fuel cell stack was carried out on the basis of three-dimensional computational fluid dynamics(CFD) simulation. A three-dimensional CFD model originally developed by Shimpalee et al., has been utilized for performing large-scale simulation of a single fuel cell consisting of bipolar-plates gas diffusion layers, and a membrane-electrode-assembly(MEA). The CFD model is able to predict the current density, pressure drops, gas velocities, vapor and liquid water contents, temperature distributions, etc. inside a single fuel cell. Depending on simulation results from the CFD modeling of a PEM fuel cell, several flow-fields of bipolar-plates were designed and verified. The final design of the bipolar-plate has been chosen from the simulations and experimental tests and showed the best performance as expected from the simulation results under a normal operating condition. Thus, the CFD simulation approach to design the optimal flow-field of the bipolar-plates was successful. The final design was adopted as the best flow-field to build a commercial scale PEM fuel cell stack, the performance of which shows about 42% higher than that of the older bipolar-plate design.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.38-44
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• 2022

Plasma density in semiconductor fabrication equipment becomes higher to achieve the improved the throughput of the process, but the increase of surface corrosion of the ceramic coated chamber wall has been observed by the increased plasma density. Plasma chamber wall coating with aerosol deposition prefer to be firm and uniform to prevent the potential creation of particle inside the chamber from the deformation of the coating materials, and the aerosol discharge nozzle is a good control factor for the deposited coating condition. In this paper, we investigated the design of the nozzle of the aerosol deposition to form a high-quality coating film. Computational fluid dynamics (CFD) study was employed to minimize boundary layer effect and shock wave. The degree of expansion, and design of simulation approach was applied to found out the relationship between the divergence angle and nozzle length as the key parameter for the nozzle design. We found that the trade-off tendency between divergence angle and nozzle length through simulation and quantitative analysis, and present the direction of nozzle design that can improve the uniformity of chamber wall coating.

• Advances in nano research
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• v.11 no.6
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• pp.657-665
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• 2021

The present work aimed to explore green approach via aqueous leaves extract of Murraya koenigii (ALEMk) for the synthesis of silver nanoparticles (AgNPsMk) in single step. The synthesis process was visualized with a color change and monitored by employing UV/Visible spectroscopy and a clear peak attained at 420 nm confirming the synthesis of AgNPsMk. The possible functional groups present in the extract which participated in the synthesis of AgNPsMk were identified with the help of FTIR spectroscopy. Further characterization using TEM images revealed the spherical shape of AgNPsMk with average particle size of 20 nm displaying well dispersion throughout the solution. Pronounced antioxidant activities of AgNPsMk at increased concentrations observed which evidencing strong radical scavenging ability. Moreover, AgNPsMk exhibited strong antibacterial behavior when tested against bacterial strains of Escherichia coli and Bacillus subtilis. Moving ahead, in vitro cytotoxicity work revealed potent cell viability loss appearing in AU565 and HeLa cancer cell lines on exposure to AgNPsMk at increased concentration. Finally, in vivo assessment carried out inside male Wistar rats indicated non toxic effect on examined liver tissues besides biochemical analysis including bilirubin, alkaline phosphtase (ALP) and serum glutamate pyruvate transaminase (SGPT) which found within the normal range when compared with control. The prior research work profoundly apprises the potential of green synthesized AgNPsMk to play a significant role in biomedical applications and formulations.

• Korean Institute of Interior Design Journal
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• v.18 no.5
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• pp.49-58
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• 2009

Robert Venturi's theories like 'Complexity and Contradiction in Architecture' and 'Symbolism of Architecture' had a major impact on architects in postmodern culture and we could have his contextual understandings in those theories. In his early books, "Complexity and Contradiction in Architecture" and "Learning from Las Vegas", Robert Venturi showed theories related to context several times. But with looking at existing books or papers, we could barely see well-organized studies about his contextual understandings. So this study shows contextual approaches and thoughts with those theories, 'Complex and contradictory architecture', 'Architectural order and conventional architecture', 'Discontinuity in internal and external architecture', and 'Symbolism of architecture' in his two books. In those four theories, Venturi's contextual understandings are as fellows. To begin with, he developed contextual theories in architecture, understanding a whole building embracing each architectural factor, with architectural thoughts of complexity and contradiction. Second, he stressed architectural order to link each contradictory factor and used conventional architecture, as for existing common and ordinary things, to make available communication. Conventional factors were applied to urban viewpoints. Given the fact that contemporaries shared those factors, we could see contextual understandings in his approach. On top of that, unlike modern architects, he understood that functions of the inside and the outside were two different things. Based on contextual thoughts, he tried applying 'facade' that is one side providing an interface between in and out of a building to surroundings. Last, he wanted to express any meaningful connection between present and past, using symbolism in architecture. Presented by symbolism of architecture, architectural functions, architectural uses, historical meaning, ordinary factors, or something were also based on sharing in contemporary people. As the methodology to show these contextual factors, Venturi used an approach of symbolism.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.21-29
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• 2005

The HANARO, a multi-purpose research reactor of 30 MWth open-tank-in-pool type, has been under normal operation since its initial criticality in February, 1995. Recently, ten years after the initial operation of the HANARO, one of the two primary cooling pumps was decontaminated for overhaul maintenance in 2004. Before decontamination exposure doserate and surface contamination level of primary cooling pump measured at 4 points. After final decontamination exposure doserate and surface contamination level of primary cooling pump remeasured by same method done before. It is easy to decontaminate the out side exposed surfaces of the pump, but it is difficult to approach the inside surface due to double volute installed in the casing. Therefore, a new decontamination facility has been developed to solve this problem. A concentrated de-contaminant (DX-300) is rotated in the closed pump casing by the impeller actuated by a temporary motor. Nuclide particles are removed by the emulsification effect of the de-contaminant and the surface contaminants are chemically removed from the pump by the corrosion and dissolution effect. The inside surfaces of the primary cooling pump have been decontaminated by using the facility. As results, the contamination level of the inside surfaces was maintained below the surface contamination limit.

• Korean Institute of Interior Design Journal
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• v.17 no.1
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• pp.19-29
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• 2008

The purpose of this study is to reveal that the concept of relation in the postwar CIAM's debate was the hot issue which leaded to the collapse of CIAM, and that Aldo van Eyck developed it into the concept of "in-between". The postwar CIAM's young members voiced a critique of the universalizing attitude toward dwelling that CIAM had pursued since 1928 and looked for a new approach that would take into account the relation around dwelling. So, this study reviews the concepts of relation which were proposed by the postwar CIAM's young members. As a result, it is revealed that Aldo van Eyck extended the concept of "in-between" not to have the polarities, such as inside/outside, close/open, part/whole, neutralize or cancel one another out, but to attune them in such a way that they reinforce each other by mutual contrast, while the other young CIAM's members limited it to transition or connection. And, this paper analyzes the Municipal Orphanage in Amsterdam which was presented in CIAM 10. Through the analysis, it is revealed that the building presents many polarities simultaneously such as those; indoor and out door realms, dynamics and immutability, part and whole, and so on. In conclusion, it is possible to recognize that the concept of "in-between" is the fundamental binary-compound relation that lies at the root of Aldo van Eyck's architectural thought and bears on an interaction on a reciprocal relation between the inhabitant and the built environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.13-22
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• 2015

In this study, a new RCSF (Reinforced Concrete Steel Frame) external connection method is proposed for seismic strengthening of medium-and low-rise reinforced concrete buildings. The RCSF method, proposed in this study, is capable of carrying out the seismic retrofitting construction while residents can live inside structures. The method is one of the strength design approach by retrofit which can easily increase the ultimate lateral load capacity of concrete buildings controlled by shear. The pseudo-dynamic test, designed using a existing school building in Korea, was carried out in order to verify the seismic strengthening effects of the proposed method in terms of the maximum load carrying capacity and ductility. Test results revealed that the proposed RCSF strengthening method installed in RC frame enhanced conspicuously the strength and displacement capacities, and the method can resist markedly under the large scaled earthquake intensity level.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.387-393
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• 2012

It is very difficult to determine suitable cutting conditions in order to obtain accurate cutting profiles because machining errors caused by tool deflection depend upon cutting conditions. In this study the relationship between real cutting profiles (inclined shapes and machining errors) and cutting conditions was modeled in order to fabricate draft angle on micro molds. CCD (Central Composite Design) of DOE (Design Of Experiment) and RSM (Response Surface Method) were applied in order to model the relationship between cutting conditions and machining errors. In order to use CCD the range of radial depth of cut was chosen by $10-90{\mu}m$ and the range of feedrate was chosen by 200-300mm/min, and 9 points of cutting conditions were chosen inside determined ranges. Then, actual cutting processes were carried out as respect to 9 points of cutting conditions, draft angles and real cutting profiles were measured on cutting profiles, each response surface function was determined by conducting response surface analysis and the functions were represented by 3-dimensional graphs, contour lines and $101{\times}101$ matrices. Consequently it is possible to determine suitable cutting conditions in order to obtain arbitrary given draft angles and cutting profiles by using modeling. To validate proposed approach in this study suitable cutting conditions were determined by modeling in order to obtain arbitrary given draft angle and cutting profile, and actual cutting processes were carried out. About 95% of good agreement between predicted and measured values was obtained.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.147-155
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• 2015

A new SRCF (Steel Reinforced Concrete Frame) external connection method for seismic strengthening of medium-and low-rise reinforced concrete buildings is reported in this paper. The SRCF method, proposed in this study, is capable of carrying out the seismic retrofitting construction while residents can live inside building. The method is one of the strength design approach by retrofit which can easily increase the ultimate lateral load capacity of concrete buildings controlled by shear. The pseudo-dynamic test, designed using a existing school building in Korea, was carried out in order to verify the seismic strengthening effects of the proposed method in terms of the maximum load carrying capacity and deformation. Test results revealed that the proposed SRCF strengthening method installed in RC frame enhanced conspicuously the strength and deformation capacities, and the method can resist markedly under the large scaled earthquake intensity level.

• Journal of the Korea Computer Graphics Society
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• v.14 no.3
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• pp.31-46
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• 2008

The depth of field is the range that the objects inside of this range treated to be focused. Objects that are placed out of this range are out of focus and become blurred. In computer graphics, generating depth of field effects gives a great reality to rendered images. The previous researches on the depth of field in computer graphics can be divided into two major categories. One of them is the distributed ray tracing that samples the lens area against each pixel. It is possible to obtain precise results without noise if enough number of samples are taken. However, to make a good result, a great number of samples are needed, resulting in an enormous timing requirement. The other approach is the method that approximates depth of field effect by post-processing an image and its depth values computed using a pin-hole camera. Though the second technique is not that physically correct like distributed ray tracing, many approaches which using this idea have been introduced because it is much faster than the first approach. But the post-processing have some limitations because of the lack of ray information. In this paper, we first present an improvement technique that corrects the previous post-processing methods and then propose another one that accelerates the distributed ray tracing by using a radiance caching method.