• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.315-318
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• 2003

Recently, condenser tube which is used for a cooling system of automobiles is mainly manufactured by the conform extrusion but this method is inferior as compared with direct extrusion in productivity per the unit time and in the equipment investment. Therefore, it is essential for the conversion of direct extrusion with porthole die. The direct extrusion with porthole die can produce condenser tube which has the competitive power in costs and qualities compared with the existing conform extrusion. This study is designed to evaluate metal flow, welding pressure, extrusion load tendency of mandrel deflection that is affected by variation of porthole shape in porthole die. Estimation is carried out using finite element method under the non-steady state. Also this study was examined into the cause of mandrel fracture through investigating elastic deformation of mandrel during the extrusion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.271-278
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• 2008

A study has been conducted on the bulging process of liquid rocket engine nozzle which is essential to the manufacturing regenerative cooling combustion chamber. Mechanical properties of the material used for the bulging were experimentally obtained by tension tests. Deformation of the bulged nozzle was confirmed by a structural analysis. The developed bulging process and the deformation analysis result were confirmed by manufacturing of the bulged nozzle specimens and the bulging test. There has been a bulging failure among 7 bulged specimens due to the necking of the material. The cause of necking was investigated by comparing microstructure of the material. The investigation has revealed grain size of the material has considerable effect on the occurrence of the necking.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.527-534
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• 2012

Thermal batteries are primary batteries that use molten salts as an electrolyte and employ an internal pyrotechnic source to heat the battery stack to operating temperatures, typically between 450 and $550^{\circ}C$. The unit cell of thermal batteries consists of an anode, an electrolyte, a cathode, a heat pellet and a current collector. The heat source for such batteries is typically heat pellets based on $Fe/KClO_4$. The elevated temperature by combustion of heat pellet is supposed to cause a flatness non-uniformity, buckling, with a lateral extension diameter of current collector. This paper mainly focused on the combustion and buckling model of current collector to simulate the effect of heat source. Mechanical stresses in the current collector caused by thermal stress is a critical design consideration of thermal batteries because the internal short circuit could be occurred.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.6
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• pp.1081-1088
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• 2022

The harmonics of synchronous generators increase iron and copper loss, which is the cause of fever. For harmonic reduction, the armature winding method is used as a distribution winding, a short pitch winding. In this paper, we want to improve the waveform of the instrument voltage by reducing the harmonics in a new way to the shape of the permanent magnet. The method cuts both ends of the permanent magnet and adjusts the air gap by increasing and decreasing the area according to the set value. By varying the distribution of magnetic flux density, the resulting electromotive voltage and strain were compared. This compares the shape-changing models of permanent magnets and shows an effective deformation method.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.3
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• pp.148-156
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• 2015

Deck plates of ships or offshore structures would make out-of-plane distortion for their thin thickness. These distortions are usually straightened by thermal straightening such as flame heating method. After thermal straightening, the blocks are lifted and moved by cranes to assemble it at dry-dock stage. After this lifting process, out-of-plane deformation again happens frequently. And then, they continuously cause quality and accuracy problems in the final dry-dock process. So, it takes more time for repair and correction working. According to preceding research, the lifting process by cranes would offset the effect on thermal straightening. The target of this study is to develop a methodology analyzing the remaining efficiency of thermal straightening after block lifting. The development was based on the assumption of yield state at straightening region. Therefore the remaining efficiency was obtained by different stiffness slope while lifting & relieving. The efficiency formula was designed using inherent strain, and we made a table of zero-efficiency by cooling speed and class rule's steels. As a result, if the stress orthogonal to straightened line is calculated during lifting analysis by FEA, the efficiency can be obtained linearly to the values in the table. Finally, even optimized carling position can be designed by considering the regional data from series project and welding region on deck.

• Journal of Genetic Medicine
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• v.5 no.2
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• pp.94-99
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• 2008

Congenital malformation is observed in about 2-5% of newborns and is a leading cause of infant mortality. The prognosis of malformation is dictated mainly by proper treatment followed by correct diagnosis at an early age. In practice, etiological consideration and classification of a malformation is critical for diagnosis. Malformations can be classified as belonged to minor or major anomaly. It is clinically important to clarify the pathogenesis of the anomalies among malformation, deformation, disruption, and dysruption. Genetic counseling aids this process by helping patients or family members understand and the nature of the malformation and risk assessment.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.4
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• pp.5-13
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• 2004

This study explains the effects of lubricant and surface treatment on the life of hot forging dies. The thermal load and thermal softening, that occur when there is contact between the hotter billet and the cooler dies in hot forging, cause wear, thermal cracking and fatigue, and plastic deformation. Because the cooling effect and low friction are essential to the long life of dies, the proper selection of lubricant and surface treatment is very important in hot forging process. The two main factors that decide friction and heat transfer conditions are lubricant and surface treatment, which are directly related to friction factor and surface heat transfer coefficient. Experiments were performed for obtaining the friction factors and the surface heat transfer coefficients in different lubricants and surface treatments. For lubrication, oil-base and water-base graphite lubricants were used, and ion-nitride and carbon-nitride were used as surface treatment conditions. The methods for estimating die service life that are suggested in this study were applied to a finisher die during the hot forging of an automobile part. The new techniques developed in this study for estimating die service life can be used to develop more feasible ways to improve die service life in the hot forging process.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.4
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• pp.203-208
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• 2011

Recently, from general machine parts and automobile parts using carbon steel to a mold, there has been efforts for improving durability and attrition resistance of these parts. Especially, heat treatment with laser which works fast and automatically can be used for the mass production with high quality. Moreover, local heat treatment can be used to handle with complex and precise parts. Accordingly, we analyzed hardening characteristics of carbon steel using the finite element method and compare the experimental results to have more reliability. We also proved the cause of thermal deformation with temperature and stress distribution by heat treatment. After these analysis and experimental, we found that each maximum hardness of the two tests was 728 Hv and 700 Hv, on condition of $1050^{\circ}C$ heating temperature, and 2 mm/sec laser speed. We also found that difference of surface stress-distribution was occurred, and this makes deformation mode up after heat treatment.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.93-100
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• 2007

During tunnel excavation, drawdown of groundwater table or discharge from tunnel faces may not only reduce stability of tunnel and work efficiency but cause environmental problems. We have investigated the applicability of electrical resistivity survey for the establishment of the monitoring system for groundwater behavior and detecting flow channel of groundwater during tunnel excavation. The groundwater level was continuously measured at several points for 1 year. Survey was conduted at every 3 months using preinstalled electrical resistivity cables on site. The results show that observed changes in resistivity ratios in the area can be explained with observed changes in groundwater level. Thus, we believed that electrical resistivity analysed together with groundwater data can be applied for the monitoring of groundwater in tunnel area.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.66-71
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• 2013

Soft bending pipe is widely used for freezing equipment and shipbuilding. These pipe have some problems that they cause occasionally outside wrinkle, crack, wall thinning phenomena. However, vending machines which have been made to solve the problems completely, are not yet. In this study, to settle these problems, we proved the effectiveness of the self-made mandrel by results of simulation as the basic for the development of precision high-quality vending machine ; presents the solution method of the wall thinning phenomena by analyzing circular deformation and damage of bending pipe.