• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.2
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• pp.114-117
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• 2004

Rates of $H_2$ uptake into $Pt/MoO_3$ were measured for the noncalcined and $200^{\circ}C$ calcined $Pt/MoO_3$. Amount of $H_2$ uptake for $200^\circ{C}$calcined $Pt/MoO_3$ was greater than the amount of noncalcined $Pt/MoO_3$. From these two experiments, it was found that the rates of $H_2$ desorption were proportional to the increase of desorption temperature. XPS demonstrated that Cl reduced more faster in ITR after calcination at $200^{\circ}C$. This inducd smaller amount of residual chlorine at adlineation sites between Pt and $MoO_3$ substrates. This resulted in opening the more channel of hydrogen pathway into more $MoO_3$particles and controled the kinetics of hydrogen uptake.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.249-254
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• 2004

광의 효율적 사용을 위해 표면에 마이크로 그루브가 새겨진 고성능 광학 부품의 개발이 활발하고, 이들 부품의 다량 생산을 위한 초정밀 금형제조기술이 각광을 받고 있다. 최근의 초정밀 미세 기계가공의 경우 간단한 공정으로 이러한 마이크로 그루브 금형을 제작할 수 있다. 특히 조명각 변조용 렌티큘러 렌즈와 같이 실린더형 그루브 금형의 경우에는 기존의 Lithography, MEMS, LIGA 등 광 에너지를 이용한 다른 제조방법들에서는 가공하기 어려운 점이 있으나, 기계가공에서는 쉽게 제작가능한 장점이 있다. 본 연구에서는 이러한 미세기계가공기술의 장점을 활용하여 U 형 마이크로 그루브를 가진 Lenticular 렌즈용 금형을 가공하고자 하였다. 가공에는 3 축 구동의 초정밀 미세 복합가공기와 단결정 천연 다이아몬드공구가 사용되었고, 가공방식은 마이크로 세이핑 공정을 적용하였으며, 가공 금형 재료에는 Brass와 무전해 Nickel이 사용되었다. 실험을 통하여 금형가공시의 절삭력, 칩 형상, 가공표면 등의 분석이 수행되었으며 이를 기반으로 여러 가지 가공문제점을 해결하고, 최종적으로 양호한 렌티큘러렌즈용 금형을 가공하였다.

• Transactions of Materials Processing
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• v.22 no.4
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• pp.189-195
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• 2013

In this study, the weld strength of extru-rivet spot welding was investigated by simulation and experiment. In order to obtain hot plasticity flow bonding of the two plates by a single rivet, electrodes are used for heating of the two plates and the rivet by electric resistance. Because weld strength is influenced by the temperature in the weld zone, the diameter of the electrodes and the amount of current supplied to the electrodes are important variables. For the simulation, heat distribution and weld strength were calculated using DEFORM-3D. The weld strength in the weld zone was calculated for various values of the experimental parameters. The simulation results showed that the weld strength was the highest when the weld current was 37kA, the electrode diameter was 12mm, and the welding frequency was 90cycle. Aluminum 5052 was used for the experimental study. A total of three aluminum plates, two welding plates with 1mm thickness and one plate with 2mm thickness for the inserting rivet, were used for the experimental extru-rivet spot welding.

• Transactions of Materials Processing
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• v.13 no.6 s.70
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• pp.484-489
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• 2004

This paper employed a systematic analysis using a 2-D hybrid special finite element containing an edge crack in order to describe the fracture behavior of spot-welds in automotive structures. The 2-D hybrid special finite element is derived form a mixed formulation with a complex potential function with the description of the singularity of a stress field. The hybrid special finite element containing an edge crack can give a better description of its singularity with only one hybrid element surrounding one crack. The advantage of this special element is that it can greatly simplify the numerical modeling of the spot welds. Some numerical examples demonstrate the validity and versatility of the present analysis method. The lap-shear, lap-tension and angle-clip specimens are analyzed and some useful fracture parameters such as the stress intensity factor and the initial direction of crack growth are obtained simultaneously.

• Transactions of Materials Processing
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• v.23 no.5
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• pp.282-288
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• 2014

It is difficult to control welding variables during spot welding of non-ferrous metals like aluminum because of the low electrical resistance of the material. It has been suggested that a solid state welding process such as friction stir spot welding or extru-spot welding can be used to spot weld aluminum plates. In the extru-spot welding, there is a need to increase the weld strength by improving the shape of the welding die. The current study shows that the weld strength for an extru-spot welding can be increased by using a pin placed on the inside of the upper electrode in the welding die. In the current study, the deformed shape of the insert rivet and the stress distribution in the welding zone were analyzed by simulation. Extru-rivet spot welding experiments were performed by changing the height of pin on the inside of the upper electrode. From the experimental result, it is shown that the weld strength for an extru-rivet spot welding can be increased by adjusting the height of the pin. The optimal shape of the deformed rivet after the extru-rivet spot welding can be observed from the simulation results. The deformed shape of the insert rivet can also be controlled by the height of pin.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.273-276
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• 2008

Thermoplastic resin takes place stress relaxation and creep according to temperature and time. In room temperature, time dependent deformation (TDD) of polymer was carried out at previous study. In this study, it evaluates time dependent deformation to relate temperature. Nanoscale indents can be used as cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. Therefore, it is important to control pattern depth for change of indent depth by creep when using Nanoindenter. For evaluating TDD at high temperature, it is occurred thermal-nanoindentation test by changing hold time at maximum load. Temperature is putted at $90^{\circ}C$, hold time at maximum loads are putted at 1, 10, 50, 100, 200, 300 and 500s.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.5-12
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• 2011

Numerous studies on the improvement of low strength for soft ground have been performed. EPS, light weight filling material, is used at the study site for stability on consolidation settlement. However, several problems such as settlement of pavement layer and damage of curb occurs. The elevation is lower 1 m than that of designed value by consolidation. It is caused by excessive load during construction. In this study, problems due to overloading on the soft ground where the EPS is used were analyzed and some cases for reasonable improvement method were described. From the results, instructions for design and construction are suggested.

• Korean Journal of Food Science and Technology
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• v.21 no.3
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• pp.453-459
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• 1989

A strictly aerobic bacterium forming yeller pigment and a highly viscous polysaccharide was isolated. The bacterium was identified as Pseudomonas mendocia. The polysaccharide was presumed to be ${\beta}-glucan$ with o-acetyl group in its structure and the constituent sugar components were glucose and rhamnose in the molar ratio of 2.1: 1.0. The intrinsic viscosity was 64.73dl/g. The apparent viscosity of 1% aqueous solution was 428 mPa.s. at $42\;sec^{-1}$ and the yield stress of the solution was 8.89Pa. The polysaccharide did not have thermal stability but show pH and salt stability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1227-1240
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• 2014

Abandoned mines often cause environmental problems, such as alteration of landscape, metal contamination, and landslides due to a heavy rainfall. Geotechnical and rheological tests were performed on waste materials corrected from Imgi waste rock dump, located in Busan Metropolitan City. Debris flow mobility was examined with the help of 1-D BING model which was often simulated in both subaerial and subaqueous environments. To determine flow curve, we used a vane-penetrated rheometer. The shear stress (${\tau}$)-shear rate (${\dot{\gamma}}$) and viscosity(${\eta}$)-shear rate (${\dot{\gamma}}$) relationships were plotted using a shear stress control mode. Well-known rheological models, such as Bingham, bilinear, Herschel-Bulkley, Power-law, and Papanastasiou concepts, were compared to the rheological data. From the test results, we found that the tested waste materials exhibited a typical shear shinning behavior in ${\tau}$-${\dot{\gamma}}$ and and ${\eta}$-${\dot{\gamma}}$ plots, but the Bingham behavior is often observed when the water contents increased. The test results show that experimental data are in good agreement with rheological models in the post-failure stage during shearing. Based on the rheological properties (i.e., Bingham yield stress and viscosity as a function of the volumetric concentration of sediment) of waste materials, initial flowing shape (5 m, 10 m, and 15 m) and yield stress (100 Pa, 200 Pa, 300 Pa, and 500 Pa) were input to simulate the debris flow motion. As a result, the runout distance and front velocity of debris flow are in inverse propositional to yield stress. In particular, when the yield stress is less than 500 Pa, most of failed masses can flow into the stream, resulting in a water contamination.

• Journal of the Mineralogical Society of Korea
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• v.32 no.4
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• pp.273-285
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• 2019

This study is aimed to interpret the raw material characteristics and manufacturing technology through physical, mineral and geochemical analysis of the brown-glazed stonewares and roof tiles excavated from the Hong Nang Sida temple in Laos, which was built in the 12th century. The glaze of brown-glazed stoneware is a typical lime serial with CaO content of more than 15 % and they were vitrified. The body is the combination of quartz, mullite and cristobalite, but had not vitrified texture, and therefore, which is assumed to have been fired more than 950 ℃. Meanwhile, The roof tiles are unglazed and its outer color is reddish brown, whitish grey and bluish grey. The bluish gray tiles has sandwich structure, which seem to experience imperfect reducing environment. The tile samples with a number of amorphous iron oxide nodule had a very similar chemical composition. In conclusion, it is assumed that the clay source was made from raw material produced from the same bedrock. The firing temperature of roof tiles were divided into less than 900 ℃, 900~950 ℃ and greater than 950 ℃ according to detection of micas, hercynite and mullite.