• 대한소아치과학회지
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• 제50권4호
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• pp.396-408
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• 2023

이 연구의 목적은 유구치를 재현한 인공치를 대상으로 인접면 복합레진 수복 시 매트릭스 시스템에 따른 인접면의 외형, 접촉면의 크기 및 수복 전과 후의 부피 차이를 비교해 보는 것이다. 네 가지 종류의 인공치에 Circumferential 매트릭스 시스템에 해당하는 Tofflemire Matrix System과 Sectional 매트릭스 시스템에 해당하는 Palodent V3 Sectional Matrix System, myJunior Kit를 이용하여 복합레진을 수복하고 3D 모델링 과정을 거쳐 분석되었다. Sectional 매트릭스 시스템을 사용한 경우에서 오목한 인접면 외형이 형성될 확률이 높았으며 더 큰 접촉 면적과 부피가 형성되었다. 이는 Sectional 매트릭스 시스템에 사용되는 매트릭스 밴드의 완전 연질(Dead soft) 특성에 의한 변형으로 인해 접촉점 주변으로 과량의 레진이 적용될 수 있기 때문이다. 게다가 Sectional 매트릭스 시스템에 포함된 고무 웨지가 매트릭스 밴드를 와동에 잘 적합 시키지 못할 가능성이 있다. 따라서 이번 연구의 결과를 바탕으로 유구치 인접면을 Sectional 매트릭스 시스템을 이용해 복합레진 수복하는 경우, 형태학적 관점을 고려한 신중한 사용이 요구된다.

• 한국안전학회지
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• 제21권1호
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• pp.96-104
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• 2006

This study is to find out how the sawdust-mixed RC beam with holes acts compared to two case of normal one with sawdust without hole, without sawdust. variables are ED3H1, ED3H2, ED3H1UB, ED3H2L, ED5H1, ED5H1UB, ED5H2, ED5H2L, Normal with sawdust PLA without sawdust. All sand, aggregate, cement are in accordance with KS. mixing design is also in accordance with KS and done at D remicon company in order to decrease any error in mixing manually. ED3H1 showed 7tone of maximum load capacity having only minor tensile deformation around hole, compared to the center of the beam. ED5H2L showed almost same shape of tensile strain between hole area and center of two beam length, while having 9.5 tone load capacity, incase of two holes being in the longitudinal axis. But ED5H2 in case of two holes being in same forcing direction showed 8.4tone of load capacity while having minor tensile chape around hole and normal tensile shape in the center of beam length. Two diameter 3cm hole in longitudinal axis give more effective behavior than the other case, practically. Capacity decrease between 5cm and 3cm in eccentric position form the longitudinal axis is less than percents. There is minor capacity difference between hole diameter 3cm hole, but 13tone difference of load capacity between hole diameter 5cm.

• 한국농공학회논문집
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• 제62권3호
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• pp.29-38
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• 2020

Since some warm-mix asphalt (WMA) concretes were known to show poorer rut resistance than the hot-mix asphalt (HMA) concretes, many studies were performed in efforts of improving its performance at high temperature. The reason is assumed to be due to the moisture remaining in aggregates dried at lower temperature. Therefore, not only the rut resistance, the crack resistance of WMA concrete was also in question. In this study, fatigue life of WMA concrete was evaluated in comparison with HMA using 3-point bending (3PB) beam test. The asphalt mixtures were prepared based on Korean mix-design guide using a 13 mm dense-graded aggregate and 6 binders; two HMA binders and four WMA binders. By 3PB fatigue test, normal (unmodified) and polymer-modified WMA concretes were evaluated in comparison with normal and polymer-modified HMA concretes at a low temperature (-5℃). The results showed that most of WMA concretes showed longer fatigue lives than HMA concretes, even though the same PG binders were used for HMA and WMA. This result indicates that the WMA concretes have stronger resistance against fatigue cracking than HMA at the low temperature, and this result is in contrast to the high-temperature performance test.

• 한국유체기계학회 논문집
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• 제14권3호
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• pp.23-27
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• 2011

Due to a roots type medium vacuum pump is operated in condition of $1{\sim}10^{-3}$ torr vacuum, it could be applied for production and process of industrial parts, such as precise processing, vaporization, enrichment, separation, casting, metaling, welding, transportation. Therefore, the demand of this pump is increasing nowadays in our industrial markets of semiconductor, electric, electronic, automobile, material, environmental and transporting industries. However, the pumps are almost imported, because the domestic pumps are inferior in fields of vacuum range as under $10^{-1}$torr, relevant techniques(design, fabrication, casting, test, etc.) to the imported ones. In this study, essential parts of the development pump are designed with using of CFD and 3D decodes, FEM for analysing strength and deformation, generated heat, vibration and noise control, and are casted with using of mechanochemistry techniques for decreasing of weights, increasing of heat resistances and abrasion durability of materials for pump caing and impellers especially. Besides, in order to achieve ultimate vacuum around $10^{-3}$torr, this pump is composed of 6 stages, among which 1st stage is operated separately from remained stages. Additionally, a test rig for prototype pumps(300$m^3/h$ and 2,500$m^3/h$) is designed and procured as to apply for multi-staged rootz type vacuum pump, with modification of the test method recommended by KS B 6314 "Positive-displacement oil-sealed rotary vacuum pumps".

• 한국전산유체공학회지
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• 제16권2호
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• pp.24-29
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• 2011

Immersed boundary lattice Boltzmann method has been applied to analyze the characteristics of the self-propelled fish motion swimming robot. The airfoil NACA0012 with caudal fin stroke model was considered to examine the characteristics. The foil in steady forward motion and a combination of steady-state harmonic deformation produces thrust through the formation of a flow downstream from the trailing edge. The harmonic motion of the foil causes unsteady shedding of vorticity from the trailing edge, while forming the vortices at the leading edge as well. The resultant thrust is developed by the pressure difference formed on the upper and lower surface of the airfoil. and the time averaged thrust coefficient increases as Re increase in the region of $Re{\leqq}700$. The suggested numerical method is suitable to develop the fish-motion model to control the swimming robot, however It would need to extend in 3D analysis to examine the higher Re and to determine the more detail mechanism of thrust production.

• 한국인쇄학회지
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• 제30권3호
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• pp.23-33
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• 2012

We studied simultaneously the electronically written data affected in the use of thermal transfer discs and the recoding strategy between recoding drives for the stable long term preservation of optical discs which are commonly used in an electronic data storage device. The most important thing in the archiving preservation might be a choice of a device, however the use of thermal transfer recording discs is not good for long term data preservation because the thermal effect on the recoding data is critical which means that the data are recorded not under best condition but under bad condition. We inspect the strategies of recoding data from 12 brands of optical discs and drives of 7 brands and it turns out the recoding strategy is needed first for the long term preservation of electronic recording data. Thus, without affecting data quality and deformation of optical discs, the choice of optimal disc and drive in recoding data will be a solution for the long term preservation of recoding data.

• 한국인쇄학회지
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• 제30권3호
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• pp.77-88
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• 2012

In this report, we performed the measurements of physical properties of optical discs as a long term preservation electronic recording device and showed how to improve the preservation method of them. We collect the 1,993 optical discs from the archives of the National Archives of Korea and tested various measurements. We used DVDT-SD4 equipment to measure the quality of data, deformation of disc, the various writing strategy and manufacturer derives, which can be happened in optical discs by physical factors. We found that th quality of data are closely related with write strategy between discs and drives. This relation gives us information about data quality in optical discs for long term preservation that can be obtained from the state between empty discs and optical drives before recording. Thus, the initial selection of optimal discs and drives is critical for long term recording data preservation and the data quality after long time preservation will not be much different from that of the initial ones.

• Geomechanics and Engineering
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• 제10권4호
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• pp.455-470
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• 2016

In ballasted railway tracks, ballast fouling due to finer material intrusion has been identified as a challenging issue in track maintenance works. In this research, deformation characteristics of crushed stone-sand mixtures, simulating fresh and fouled ballasts were studied from laboratory and a 3-D discrete element method (DEM) triaxial compression tests. The DEM simulation was performed using a recently developed DEM approach, named, Yet Another Dynamic Engine (YADE). First, void ratio characteristics of crushed stone-sand mixtures were studied. Then, triaxial compression tests were conducted on specimens with 80 and 50% of relative densities simulating dense and loose states respectively. Initial DEM simulations were conducted using sphere particles. As stress-strain behaviour of crushed stone-sand mixtures evaluated by sphere particles were different from laboratory specimens, in next DEM simulations, the particles were modeled by a clump particle. The clump shape was selected using shape indexes of the actual particles evaluated by an image analysis. It was observed that the packing behaviour of laboratory crushed stone-sand mixtures were matched well with the DEM simulation with clump particles. The results also showed that the strength properties of crushed stone deteriorate when they are mixed by 30% or more of sand, specially under dense state. The results also showed that clump particles give closer stress-strain behaviour to laboratory specimens than sphere particles.

• Steel and Composite Structures
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• 제18권1호
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• pp.273-288
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• 2015

As one of the most common failure types of arch bridges, stability is one of the critical aspects for the design of arch bridges. Using 3D finite element model in ABAQUS, this paper has studied the stability performance of an arch bridge with inclined arch ribs and hangers, and the analysis also took the effects of geometrical and material nonlinearity into account. The impact of local buckling and residual stress of steel plates on global stability and the applicability of fiber model in stability analysis for steel arch bridges were also investigated. The results demonstrate an excellent stability of the arch bridge because of the transverse constraint provided by transversely-inclined hangers. The distortion of cross section, local buckling and residual stress of ribs has an insignificant effect on the stability of the structure, and the accurate ultimate strength may be obtained from a fiber model analysis. This study also shows that the yielding of the arch ribs has a significant impact on the ultimate capacity of the structure, and the bearing capacity may also be approximately estimated by the initial yield strength of the arch rib.

• 동력기계공학회지
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• 제21권1호
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• pp.57-62
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• 2017

The flexible joint with bellows and flange is made by welding bellows and flange in general. The welded parts cause a crack or demage in the flexible joint due to continuous vibration and fatigue limit. This paper is concerned with development of flexible joint with non-welded, free rotation of flange and non-packing to improve fatigue failure condition between bellows and flange. The support box and support plate that are components of press part are designed to compress fore-end of bellows only without demage of bellows. The production system of flexible joint is designed with piston attached on the compression side. The simulation is performed using Deform 3D software. As the result of simulation, the shape of compressed bellows was most proper in the compression power of $157kg{\cdot}f$ and any deformation has not occurred at a part besides fore-end. The result show that the production possibility of the designed flexible joint.