• Journal of computational fluids engineering
• /
• v.18 no.3
• /
• pp.67-71
• /
• 2013

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.

• Composites Research
• /
• v.27 no.3
• /
• pp.103-108
• /
• 2014

Fiber reinforced polymer plastic (FRP) structural members are recently available in construction industries due to various material properties such as high specific strength and stiffness, light-weight, and corrosionresistance. The floating PV generation structure can also be an illustration for applying FRP in construction applications. The floating PV generation structure has been recently issued as a representative item for the low carbon and green growth campaign and many related studies have been conducted for the structural safety and commercial viability. Moreover, the floating PV generation structures for the commercial purpose have been constructed. In this paper, the investigation and development processes of elements for the floating PV generation structure are presented during commercialization.

• 보존과학연구
• /
• s.30
• /
• pp.79-91
• /
• 2009

Stone cultural heritages are mostly situated in field, so they are damaged from mechanical, chemical and biological weathering, and their degree of strength is also weaken. Therefore, the scientific conservation of the stone cultural heritages are necessary in order to the long-term maintenance and safety conservation. In this study, we attempt to estimate on the field application of consolidants which are Wacker OH 100, Remmers KSE 300 and 1T1G according to the quality of the rocks. Based on the ultrasonic velocity, conditions of weathering damage before treatment are mainly ranked completely weathering condition (CW) or partly highly weathering condition (HW). After the first treatment, weathering damage conditions are changed by the high weathering condition (HW). These results shows that the internal pores of stone are filled with consolidant materials, so average ultrasonic velocities increases after treatment. And Remmers KSE 300 which is consolidant material is highest rate of increase of average ultrasonic velocities.

• Composites Research
• /
• v.30 no.6
• /
• pp.422-428
• /
• 2017

The moisture absorption behavior, tensile properties, and thermal analysis properties of MWCNT embedded nanocomposites exposed to temperature and moisture were evaluated. The contents of MWCNT were 0 wt%, 1 wt%, and 2 wt%, respectively. The specimens were exposed to immersed conditions at $25^{\circ}C$ and $75^{\circ}C$ for up to 600 hours. According to the results, the apparent moisture content increased as the exposure time increased, but the difference between the maximum moisture content and the moisture content at 600 hours was almost constant. The tensile modulus decreased with increasing exposure time and the degree of decrease was increased significantly as the MWCNT content and exposure temperature increased. The tensile strength decreased with longer exposure time without MWCNT, but increased with MWCNT due to the reinforcing effect of MWCNT. The storage modulus, glass transition temperature, tan d peak magnitude were low as the exposure time increased, but tan d curves with two peaks appeared when exposed to high exposure temperature for more than 300 hours.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.41 no.3
• /
• pp.537-547
• /
• 2017

This study evaluates the wearing performance of a self-contained breathing apparatus (SCBA) belt for firefighters in Korea. A SCBA belt design was suggested based on the wearing evaluation of a SCBA belt; subsequently, prototypes I and II were created. A wearing evaluation of prototypes with improved design and design preference was performed. Six designs elements of the SCBA belt for firefighters were suggested based on the survey results of wearing the SCBA belt and for the SCBA belt design preference for use by firefighters. First, belt material should be made of black high-strength aramid textiles. In addition, Velcro should be used to attach and detach retroreflective and fluorescent materials along with various colors for visibility. Second, the chest belt should be made of the same material used for other parts; in addition, the chest belt should be moved to the center for center of gravity and a cobra buckle should be applied. Third, an O-ring should be applied to the back and the belt connected to the O-ring should distribute the weight in six axes. Fourth, a detachable air respirator should be able to separate by using upper and lower cobra buckles. Fifth, a separable leg belt and a detachable pocket are also suggested. Sixth, a ring for walkie-talkies, alarms and equipment as a fabric ring are also suggested. Prototype III with an improved design was created based on the results of the design suggestion.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.6
• /
• pp.52-57
• /
• 1999

Funtional metal prototypes are often required in numerous industrial applications. These components are typically needed in the early stage of a project to determine form, fit and function. Recent R/P(Rapid Prototyping) part are made of soft materials such as plastics, wax, paper, these master models cannot be employed durable test in real harsh working environment. Parts by direct metal rapid tooling method, such as laser sintering, by now are hard to get net shape, pores of the green parts of powder casting method must be infiltrated to get proper strength as tool, and new type of 3D direct tooling system combining fabrication welding arc and cutting process is reported by song etc. But a system which can build directly 3D parts of high performance functional material as metal part would need long period of system development, massive investment and other serious obstacles, such as patent. In this paper, through the rapid tooling process as silicon rubber molding using R/P master model, and fabricate wax pattern in that silicon rubber mold using vacuum casting method, then we tranlsated the wax patterns to numerous metal prototypes by new investment casting process combined conventional investment casting with rapid pototyping & rapid tooling process. with this wax-injection-mold-free investment casting, we developed new investment casting process of fabricating numerous functional metal prototypes from one master model, combined 3-D CAD, R/P and conventional investment casting and tried to expect net shape measuring total dimension shrinkage from R/P part to metal part.

• International Journal of Highway Engineering
• /
• v.7 no.3 s.25
• /
• pp.71-78
• /
• 2005

This study focuses on finding out engineering characteristics of asphalt concrete mixtures using mineral fillers with recycled waste lime, which is a by-product in the Soda Ash(Na2CO3) production course. The materials tested in this study were made with 25%, 50%, 75% and 100% of mixing ratio based on the conventional mineral filler ratio to analyze the recycle possibility of the waste lime. The asphalt concrete mixtures with recycled waste lime and hydrated lime, and conventional asphalt concrete mixtures were evaluated through their fundamental engineering properties such as Marshall stability, indirect tensile strength, resilient modulus, permanent deformation characteristics, moisture susceptibility and fatigue resistance. The results indicate that the application of recycled waste lime as mineral filler improves the permanent deformation characteristics, stiffness and fatigue endurance of asphalt concrete mixtures at the wide range of temperatures. It is also found that the mixtures with recycled waste lime show higher resistance against stripping than conventional asphalt concrete mixtures. It is concluded from various test results that the waste lime can be used as mineral fillers and especially can greatly improve resistance to permanent deformation of asphalt concrete mixtures at high temperatures.

• Journal of Conservation Science
• /
• v.36 no.5
• /
• pp.339-350
• /
• 2020

This study attempted to apply a hybrid technology that integrated mineral-based fillers and water-repellent agents to control the efflorescence that results from the use of inorganic binders, for the conservation treatment (surface finishing) of cultural heritage materials made up of stone. Herein, different types of mixing ratios of a filler (silica fume 3.4%) and a water repellent (silane-siloxane 1%) were selected for fabricating the inorganic binder, and it was determined that the ratio selected by weight is effective in controlling efflorescence substances. In addition, it was identified that the inorganic binder with the mixing ratio resulted in a higher compressive strength than the standard (20MPa), and the water permeability resistance was high with low water absorption. The result of ion elution from the bilder showed that a smaller number of ions was observed to affect the efflorescence (directly and indirectly) as compared to that of the control group, which was considered to be relatively stable.

• Applied Chemistry for Engineering
• /
• v.7 no.3
• /
• pp.424-432
• /
• 1996

The fiber reinforced thermoplastic composites(FRTP) were prepared with polypropylene fiber(PPF) as matrix and vinylon(VF), Aramid(KF) or nylon fiber(PAF) as reinforcing materials using the integrated fiber mixing apparatus. The composite sheets were prepared by compression molding and their impact and morphological properties were characterized. VF/PP system showed the maximum value in Izod impact strength, while KF/PP system showed the maximum value in high rate impact properties. Ductility Index(DI) order was VF/PP>KF/PP>PAF/PP. A maximum DI for VF/PP, 2.43, was obtained when the weight fraction of VF was 20%. The optimum amount of the reinforcing organic fiber was found to be 20~30%. As a result, it is concluded that VF/PP system has better interfacial adhesion properties than either KF/PP or PAF/PP.

• Korean Journal of Food Science and Technology
• /
• v.20 no.4
• /
• pp.470-475
• /
• 1988

The extrusion-cooking method was used to make gelatinized rice extrudate from rice grits of the Chuchung and the Samgang varieties. The water contents of raw rice grits varied from 15% to 25%, and the physicochemical properties of extrudates were evaluated. Low moisture content showed high expansion ratio in rice extrudate and resulted in some decrease in gelatinization, bulk density and break strength. Increasing the water content to 25% resulted in increase in water absoption index but decrease in water solubility index. With regards to Brabender Amylograph values and rheological patterns, higher moisture content in raw materials revealed stronger pseudoplastic flow behavior with lower viscogram property. Hunter's color values of rice flours extruded at low water content were low in b values. Scanning electron microscopy demonstrated the break-down of starch granules during extrusion.