• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2430-2434
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• 2011

Dynamic response is an important consideration because of the possibility of resonance according to KTX running over a railway bridges. When KTX runs over the bridge at critical speed, dynamic response is very depending on damping ratio. Current damping ratio for design of high-speed railway bridges adopted EUROCODE without verification of domestic railway bridges. The purpose of this study is to obtain the coherent damping ratio of high-speed railway bridges. Free vibration signal after KTX runs over a high-speed railway bridge was applied. The representative value from distribution of damping ratio was considered.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1135-1140
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• 2001

The purpose of this study is to investigate the shrinkage properties of high strength concrete according to the S/A ratio at early age. The main parameters are as follows : S/A ratio is 30, 35, 38, 41, 45%, W/B ratio 24.9%, SF/B ratio 8%. FA/B 15%. The size of specimen is l0$\times$10$\times$40cm and the shrinkage is measured by the embedded gage at each end of the specimens. From the test, it was found that the slump-flow of concrete was high, and also autogenous shrinkage increased and drying shrinkage decreased as S/A ratio increased.

• Architectural research
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• v.19 no.4
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• pp.109-115
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• 2017

This study is done to evaluate how existence of shear-span ratio and shear reinforcing bar effects on shear performance from through shear experiment using PVA fiber reinforced ferroconcrete building. Ratio of shear-span was set 1, 1.7, and arrangement of shear reinforcing bar was set with KCI2012 regulation. In result, subject with less shear-span ratio, and shear reinforcing bar with arrangement of bar shows high stiffness. Subjects with high shear-span ratio show large difference depending on existence of shear reinforcing bar. Therefore, theoretical shear strength followed by CEB code underestimates experimental shear strength by 43.9%. Shear strength of the deep beam with headed bars is more affected by the bearing strength of head than the bond strength of bar.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.47-53
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• 2005

Microholes with high aspect ratio are required in microstructures. Among various methods for producing the microhole, micro electrical discharge machining (MEDM) is very effective and useful process. But, it is difficult to machine the high aspect ratio holes below $100\;{\mu}m$ in diameter because machining condition becomes unstable due to bad removal of debris at deep hole. In this paper, ultrasonic vibration is applied to MEDM work fluid to make a high aspect ratio micro hole. It is shown that the vibration is effective in circulating the debris and increasing the machining rate. As a result, produced was a micro hole with $92\;{\mu}m$ entrance diameter, $81\;{\mu}m$ exit diameter and aspect ratio 23.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.901-906
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• 2007

Lightweight body due to the decrease of panel thickness and reinforcing member might cause low stiffness. On the other hand, high stiffness body requires an increase of mass. Front pillar section area has been decreased for increasing the driver's visual field. Global vehicle stiffness is affected by stiffness distribution ratio between upper part and lower part at a side body structure. This paper describes a process used to evaluate the stiffness distribution ratio based on strain energy. In addition, optimum design schemes are presented for high stiffness and lightweight body structure considering the investigated stiffness distribution ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.931-937
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• 2008

A high motive pressure thermal vapor compressor(TVC) for a commercial multi-effect desalination(MED) plant is designed to have a high entraining performance and its robustness is also considered in the respect of operating stability at the abrupt change of the operating pressures like the motive and suction steam pressure which can be easily fluctuated by the external disturbance. The TVC having a good entraining performance of more than entrainment ratio 6.0 is designed through the iterative CFD analysis for the various primary nozzle diameter, mixing tube diameter and mixing tube length. And then for a couple of TVC having a similar entrainment ratio, the changes of the entrainment ratio are checked along the motive and suction pressure change. The system stability is diagnosed through the analyzing the changing pattern of the entrainment ratio.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.3
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• pp.520-529
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• 1994

High-ratio cakes made from the formulas with more sugar (140% based on flour weight) than flour have come to be preferred recently. To produced good light cake structure, cake batter must retain the many finely divided gas bubbles formed during mixing . Thermal setting of cake structure is mainly caused by starch gelatinization . The formula controls the temperature at which the cake batter changes from a fluid to a solid. Especially, the relatively large amount of sugar used in the formula delays gelatinization, so that air bubbles can be properly expanded by carbon dioxide gas and water vapor before the cake sets. To get a non collapsing high ratio cake structure after baking , the proper degree of gelatinization of the starch granule, the control of gelatinization temperature, and sufficient gel strength ar all important. The role of ingredients (flour , sugar, proteins, chemical leavening agents, water shortening , and emulsifiers) is reviewed with relation to the formation of satisfactory cake structure.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.79-85
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• 2004

This study was performed to evalute mechanical and drying shrinkage properties of polypropylene fiber reinforced high flow concrete. The compressive strength and drying shrinkage ratio were increased with increasing the binder volume ratio and decreased with increasing the content of polypropylene fiber. The splitting tensile strength was increased with increasing the binder volume ratio and the content of polypropylene fiber. The flexural strength was increased with increasing the binder volume ratio and increased by the polypropylene fiber content 0.4%, but above the polypropylene fiber content 0.6% was decreased. This concrete can be used for high flow concrete.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.77-80
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• 1998

Recently, extending the local broadcasting and increasing lots of informations. The low-loss communication cable is required in proportion as frequency .The reason of transportation loss causes to using the high frequencies like hundreds of MHz or decades of GHz. For the low transportation loss. It is required the developing-technology of foaming and the high foamed insulator with the dielectric ratio of the nearest to 1. Therefor, there is the purpose of developing the insulating materials for the low dielectric ratio. Also it is important to measure the attenuation, which is one of the important parameters.sa the evaluation of transportation characteristic with frequency in the communication cable. In this paper,the result showed that the dielectric ratio(1.4) of the nearest to 1 and low attenuation with high frequency were very related to the transportation and reflection characteristics such as propagation velocity (82.27%). Delay time and voltage standing wave ratio(VSWR).

• Journal of the Korea Institute of Building Construction
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• v.4 no.2
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• pp.81-88
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• 2004

The purpose of this study is to investigate the chemical shrinkage and autogenous shrinkage of high strength cement paste and silica fume and fly ash and sand to cement ratio by the method of volumetric tests, and also investigate the autogenous shrinkage of high measurement method, and compare the results of volumetric test and linear length measurement test. A series of cement paste which have W/C ratio of 25%, 35%, 45% respectively were planed to study the effect of the W/C ratio to the shrinkages, and a series of cement paste which were replaced the cement by the silica fume and fly ash with 5%, 10%, 15% as the mass of cement respectively were planed to investigate the effects of poazolana to the shrinkages. A series of mortar which have a C/S ratio of 1:1, 1:1.5, 1:2 respectively were planed to investigate the shrinkage resistant effect of aggregate.