• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.390-395
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• 2002

The experimental and numerical study has been conducted on the sleeve repair welding of API 5L X65 pipeline. SMA W and GTAW were applied to weld the sleeve. The macrostructure and hardness of repair welds have been examined. The [mite element analysis of the multi-pass sleeve-fillet welding has been conducted to validate the experiment and investigate the effects of in-service welding conditions. The effect of gas flow rate on the hydrogen cracking was investigated. The effect of internal pressure on residual stresses and plastic strain was investigated. The allowable heat input was predicted considering the maximum temperature of inner surface of pipe and cooling rate at CGHAZ.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.36-41
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• 2002

The experimental and numerical study has been conducted on the sleeve repair welding of API 5L X65 pipeline. SMAW and GTAW were applied to weld the sleeve. The macrostructure and hardness of repair welds have been examined. The finite element analysis of the multi-pass sleeve-fillet welding has been conducted to validate the experiment and investigate the effects of in-service welding conditions. The effect of gas flow rate on the hydrogen cracking was investigated. The effect of internal pressure on residual stresses and plastic strain was investigated. The allowable heat input was predicted considering the maximum temperature of inner surface of pipe and cooling rate at CGHAZ.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2008년도 Spring Scientific Meeting(the 129th) of Korean Academy if Conservative Dentistry
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• pp.169-176
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• 2008

본 연구는 이중 중합형 복합레진에서 재료의 두께, 충전방법 및 중합방법에 따른 중합도를 미세경도 시험을 이용하여 측정하고자 하였다. 이중 중합형 복합레진으로는 MultiCore Flow (Ivovlar Vivadent AG, Schaan, Liechtenstein)와 Bis-Core (Bisco Inc. Schaumburg IL, USA)를 사용하였다. 시편의 제작은 각각 두께가 2 (단일충전). 4 (단일충전), 6 (단일충전과 적층충전), 8 (단일충전과 적층충전) mm의 Teflon mold에 재료를 주입한 다음 할로겐 광중합기 (Optilux 501 Kerr, Danbury, USA)를 사용하여 광중합하거나 암실에서 30분 동안 기다린 후(자가 중합) Teflon mold에서 제거하였다. 제거한 시편은 $37^{\circ}C$ 증류수에 24시간 동안 보관한 후 각 시편의 윗면과 아랫면을 2000번 연마제와 PoGo system (Dentsply, Konstanz, Germany)을 이용하여 마무리하였다. Digital microhardness tester (FM-7, Future-Tech Corp., Tokyo, Japan)를 이용하여 경도값(Knoop hardness number)을 측정하였으며 윗면의 경도값/아랫면의 경도값을 이용하여 경도비를 계산하였다. 계측치는 one-way ANOVA로 통계 분석 후 사후검정은 Scheffe 다중비교법을 이용하였다. 이중 중합형 복합레진의 중합도에 대한 두께의 영향을 보면 재료에 따라 다른 결과를 보였다. 2, 4, 6 mm군에서는 MultiCore Flow와 Bis-Core 모두 두께에 의한 영향을 받지 않았지만 8 mm 군에서는 MultiCore Flow의 아랫면에서 다른 두께의 군보다 낮은 경도값을 보였다. 충전방법에 따른 중합도의 차이를 보면 재료의 두께나 재료에 따라 다른 결과를 보였다. 6 mm 군에서는 단일충전군과 적층충전군 사이에 차이를 보이지 않았으나, 8 mm 군에서는 Bis-Core에서는 차이가 없는 반면 MultiCore Flow에서는 단일충전한 군이 적층충전한 군보다 낮은 경도비를 보였다. 중합방법에 따른 중합도의 차이를 보면, 재료에 따라 다른 결과를 보였다. Bis-Core의 경우에는 윗면과 아랫면 모두에서 이중 중합 시킨군이 자가 중합시킨 군보다 높은 경도값을 보였다. 그러나 MultiCore Flow의 경우, 윗면에서는 이중중합 시킨 군이 더 높은 경도값을 보였지만 아랫면에서는 더 낮은 값을 보였다. 따라서 본 연구의 결과에 따르면 코어용 이중 중합형 복합레진을 깊은 와동에 충전할 경우 적층충전이 추천되며, 또한 광중합을 해줌으로써 더 좋은 물리적 성질을 기대할 수 있을 것으로 사료된다.

• Elastomers and Composites
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• 제51권4호
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• pp.263-268
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• 2016

In the polymer shaping process that uses molds, the quality of the molded products is determined not only by the flow of the (molten) polymer but also by the air venting in the cavity. Inadequate air venting in the cavity can cause defects in the product, such as voids, short shot, or black streaks. As it is critical to consider the location and size of the vents for proper venting of the air in the cavity, a method that predicts the flow of air and material is required. The venting of air by the flow of rubber inside the cavity was simulated by using a multi-phase computational fluid dynamics method. Through computer simulation, the interface of rubber and air over time was predicted. Then, the velocity and pressure distribution of the venting air were observed. Our research proposes a fundamental method for analyzing the multi-phase flow of polymer materials and air inside the cavity of a mold.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.198-201
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• 2003

The multi-action forging process is one of developing directions of forging technologies. In this study, the multi-action die is designed and developed by the screws mechanism and the forging simulation is conducted by using plasticine to investigate the optimum conditions for the design of the screws. The results show the design variables are optimum when the diameter is 30 mm and the screw angle is $60^{\circ}$ for the upper screw rod and the outer diameter is 60 mm and the screw angle is $23.4^{\circ}$ for the lower screw tube. It makes the relative velocity between the upper punch and the die to be two to one, which is the expected condition. The material flow of the plasticine forgings is uniform. Therefore, it is feasible to use the screw set as the multi-action mechanism for controlling the movement of the multi-action forging die set.

• 분석과학
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• 제30권1호
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• pp.1-9
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• 2017

Starch is a mixture of amylose (AMY) and amylopectin (AMP) which are different in physical properties such as molar mass (M), rms radius ($R_g$) and hydrodynamic diameter ($d_H$). The rheological and functional properties of starch are influenced by various factors including the molecular size, molar mass distribution (MD) and the concentration ratio of AMY and AMP. It is also important to analyze proteinaceous material in starch as they affect the flavor and texture of food to which starch is added. In this study, asymmetrical flow field-flow fractionation (AF4) was employed for separation and quantitation of AMY and AMP in starches (Amaranth, potato, taros and quinoa). AF4 was coupled with a multi-angle light scattering (MALS) and a refractive index (RI) detector for determination of the absolute M, MD and molecular structure. It was found that AMP has the M and $R_g$ ranging $3.7{\times}10^7{\sim}6.5{\times}10^8g/mol$ and 84 ~ 250 nm, respectively. Also the existence of branch was confirmed in higher M. In addition, proteinaceous material in starch was analyzed by AF4 coupled with a fluorescence detector (FS) after fluorescence-labeling. AF4-FS with fluorescence-labelling showed a potential for investigation on existence of proteinaceous material and the interaction between proteinaceous material and polysaccharide in starch.

• Restorative Dentistry and Endodontics
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• 제33권3호
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• pp.169-176
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• 2008

본 연구는 이중 중합형 복합레진에서 재료의 두께, 충전방법 및 중합방법에 따른 중합도를 미세경도 시험을 이용하여 측정하고자 하였다. 이중 중합형 복합레진으로는 MultiCore Flow (Ivovlar Vivadent AG, Schaan, Liechtenstein)와 Bis-Core (Bisco Inc., Schaumburg IL, USA)를 사용하였다. 시편의 제작은 각각 두께가 2(단일충전), 4 (단일충전), 6 (단일충전과 적층충전), 8 (단일충전과 적층충전) ㎜의 Teflon mold에 재료를 주입한 다음 할로겐 광중합기 (Optilux 501, Kerr, Danbury, USA)를 사용하여 광중합하거나 암실에서 30분 동안 기다린 후(자가 중합) Teflon mold에서 제거하였다. 제거한 시편은 $37{\circ}C$ 증류수에 24시간 동안 보관한 후 각 시편의 윗면과 아랫면을 2000번 연마제와 PoGo system (Dentsply, Konstanz, Germany)을 이용하여 마무리하였다. Digital microhardness tester (FM-7, Future-Tech Corp., Tokyo, Japan)를 이용하여 경도값(Knoop hardness number)을 측정하였으며 윗면의 경도값/아랫면의 경도값을 이용하여 경도비를 계산하였다. 계측치는 one-way ANOVA로 통계 분석 후 사후검정은 Scheffe 다중비교법을 이용하였다. 이중 중합형 복합레진의 중합도에 대한 두께의 영향을 보면 재료에 따라 다른 결과를 보였다. 2, 4, 6 mm 군에서는 MulriCore Flow와 Bis-Core 모두 두께에 의한 영향을 받지 않았지만 8 mm 군에서는 MultiCore Flow의 아랫면에서 다른 두께의 군보다 낮은 경도값을 보였다. 충전방법에 따른 중합도의 차이를 보면, 재료의 두께나 재료에 따라 다른 결과를 보였다. 6 mm 군에서는 단일충전군과 적층충전군 사이에 차이를 보이지 않았으나, 8 mm 군에서는 Bis-Core에서는 차이가 없는 반면 MultiCore Flow에서는 단일충전한 군이 적층중전한 군보다 낮은 경도비를 보였다. 중합방법에 따른 중합도의 차이를 보면, 재료에 따라 다른 결과를 보였다. Bis-Core의 경우에는 윗면과 아랫면 모두에서 이중 중합 시킨 군이 자가 중합 시킨 군보다 높은 경도값을 보였다. 그러나 MultiCore Flow의 경우, 윗면에서는 이중중합 시킨 군이 더 높은 경도값을 보였지만 아랫면에서는 더 낮은 값을 보였다. 따라서 본 연구의 결과에 따르면 코어용 이중 중합형 복합레진을 깊은 와동에 충전할 경우 적층충전이 추천되며, 또한 광중합을 해 줌으로써 더 좋은 물리적 성질을 기대할 수 있을 것으로 사료된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.379-384
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• 2000

High-Tc superconducting current leads with multi-step and continually varied cross-sectional area are studied to reduce heat leak into cryostat and material use. Assuming conduction-cooled lead the cross-sectional area is reduced along the heat flow direction according to the increase of critical current density which increases with decreasing temperature. In this study, we also analyze the multi-step cross-sectional area High-Tc current leads. The multi-st데 current leads changes the cross-sectional area to have constant safety-factor at changed section. The heat leak into cryostat, total voume, safety-factor and the temperature profiles are compared to those of the constant safety-factor current leads. The developed methods are applied to the Bi-2223 superconductor sheathed with Ag-Au alloy.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.873-879
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• 2024

A sodium-cooled fast reactor (SFR) core has a potential of prompt criticality due to a change of core material distribution during a severe accident, and the resultant energy release has been one of the safety issues of SFRs. In this study, the safety assessment of an unprotected loss-of-flow (ULOF) in a small SFR (SSFR) has been performed using the SIMMER-IV computer code, which couples the models of space- and time-dependent neutronics and multi-component, multi-field thermal hydraulics in three dimensions. The code, therefore, is applicable to the simulations of transient behaviors of extended disrupted core material motion and its reactivity effects during the transition phase (TP) of ULOF, including a potential of prompt-criticality power excursions driven by fuel compaction. Several conservative assumptions are used in the TP analysis by SIMMER-IV. It was found out that one of the important mechanisms that drives the reactivity-inserting fuel motion was sodium vapor pressure resulted from a fuel-coolant interaction (FCI), which itself was non-energetic local phenomenon. The uncertainties relating to FCI is also evaluated in much conservative way in the sensitivity analysis. From this study, the ULOF characteristics in an SSFR have been understood. Occurrence of recriticality events under conservative assumptions are plausible, but their energy releases are limited.

• 품질경영학회지
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• 제50권1호
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• pp.153-167
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• 2022

Purpose: The purpose of this study is to guide the operation managers who plan daily production of large mass-processing facility that services multi-customers with multi-product, small-batch item characteristics by providing the practical best production quantity and the inventory allowed to build. Methods: Close observation of a subcontract paint-shop operator captured the daily decision process which was reflected in the subcontractor-unique mathematical model and the system dynamics simulation model. Multiple simulations were run to find the practical best production quantity and the maximum allowable stock level of inventory that did not undermine the profit from practical best daily production. Actual data and a few constant values were obtained from the firm under study. Results: While the inventory holding cost for the customer-owned material harms the total profit of the subcontractor, the running cost of the processing facility hinders production in small batches. This balances the maximum possible productions and results in practical best daily production which can be found through simulation runs with actual data. The maximum level of stocked inventory is deduced from the practical best daily production. Conclusion: To build a large volume that enables economy-of-scale production, operators should deal with multi-product small-batch items from multiple customers. When the planned schedule of the time and amount of material in-flow tend not to be reliable, operators can find it practical to execute level production across the planning horizon instead of adjusting to day-to-day in-flow fluctuations.