• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2007년도 추계학술대회 논문집
• /
• pp.79-79
• /
• 2007

• Smart Structures and Systems
• /
• 제22권6호
• /
• pp.675-687
• /
• 2018

In the previous studies on the porous rock strength the effect of pore number and its diameter is not explicitly defined. In this paper crack initiation, propagation and coalescence in Brazilian model disc containing a single cylindrical hole and or multiple holes have been studied numerically using PFC3D. In model with internal hole, the ratio of hole diameter to model diameter was varied between 0.03, 0.17, 0.25, 0.33, and 0.42. In model with multiple hole number of holes was different in various model, i.e., one hole, two holes, three holes, four holes, five holes, six holes, seven holes, eight holes and nine holes. Diameter of these holes was 5 mm, 10 mm and 12 mm. The pre-holed Brazilian discs are numerically tested under Brazilian test. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured. The mechanism of cracks propagation in the wall of the ring type specimens is also studied. In the case of multi-hole Brazilian disc, the cracks propagation and b cracks coalescence are also investigated. The results shows that breaking of the pre-holed disc specimens is due to the propagation of radially induced tensile cracks initiated from the surface of the central hole and propagating toward the direction of diametrical loading. In the case of disc specimens with multiple holes, the cracks propagation and cracks coalescence may occur simultaneously in the breaking process of model under diametrical compressive loading. Finally the results shows that the failure stress and crack initiation stress decreases by increasing the hole diameter. Also, the failure stress decreases by increasing the number of hole which mobilized in failure. The results of these simulations were comprised with other experimental and numerical test results. It has been shown that the numerical and experimental results are in good agreement with each other.

• Journal of Pharmaceutical Investigation
• /
• 제41권3호
• /
• pp.147-151
• /
• 2011

This paper demonstrates the development of a method for preparing micropatterned microdiscs in order to increase contact area with cells and to change the release pattern of drugs. The microdiscs were manufactured with hot embossing, where a polyurethane master structure was pressed onto both solid and porous microparticles made of polylactic-co-glycolic acid at various temperatures to form a micropattern on the microdiscs. Flat microdiscs were formed by hot embossing of porous microparticles; the porosity allowed space for flattening of the microdiscs. Three types of micro-grooves were patterned onto the flat microdiscs using prepared micropatterned molds: (1) 10 ${\mu}M$ deep, 5 ${\mu}M$ wide, and spaced 2 ${\mu}M$ apart; (2) 10 ${\mu}M$ deep, 9 ${\mu}M$ wide, and spaced 5 ${\mu}M$ apart; and (3) 10 ${\mu}M$ deep, 50 ${\mu}M$ wide, and spaced 50 ${\mu}M$ apart. This novel microdisc preparation method using hot embossing to create micropatterns on flattened porous microparticles provides the opportunity for low-cost, rapid manufacture of microdiscs that can be used to control cell adhesion and drug delivery rates.

• 열처리공학회지
• /
• 제12권2호
• /
• pp.136-144
• /
• 1999

The study on the wear characteristics of compound layers formed during gaseous nitrocarburising in the medium carbon boron steels and the plain carbon steel has been carried out by using a pin-on-disc type wear test machine under the oil lubricating condition at room temperature and by varying applied loads, sliding speeds and wear distances. Values of friction coefficient measured at the sliding speed of 0.4m/sec under the oil lubricating condition have been shown to decrease considerably with increasing applied load and become gradually a constant value as load is increased to a higher value, showing that the transition load for friction coefficient appears at an applied load of 247.2N. The length and volume wear rates of compound layer have been revealed to relatively constantly increase, also showing that the wear life per unit thickness of compound layer turns out to be superior as porous layer has a denser and thinner appearance. As the sliding speed increases during wear test performed by varying sliding speed at a load of 63.2N under the oil lubricating condition for medium carbon boron steel nitrocarburised in gas atmosphere, the wear rate has been found to increase, the friction coefficient to decrease and the wear life per unit thickness of compound layer to decrease considerably.

• 공업화학
• /
• 제29권4호
• /
• pp.382-387
• /
• 2018

본 연구에서는 Pd-Ni-YSZ 촉매의 형태 및 공급되는 가스 조성에 따른 수증기-이산화탄소 복합개질 반응 특성을 평가하였다. 촉매는 분말 형태와 다공성 디스크 형태로 제조되었으며 주입 가스는 $CH_4/CO_2/H_2O$ ratio를 각각 다르게 하여 공급하였다. 그 결과 분말 형태의 촉매와 비교하여 다공성 디스크 형태 촉매를 사용하였을 때 $CH_4$와 $CO_2$ 전환율이 전반적으로 향상되었으며, 공급가스의 $CH_4/CO_2/H_2O$ ratio를 1 : 0.5 : 0.5로 하였을 때 $H_2/CO$ ratio가 2에 가깝게 조절되었다. 하지만 탄소침적에 의해 반응 시작 6 h 이후 $CH_4$ 전환율이 일부 감소하였으며 압력 강하가 0.1에서 0.8로 증가하였다. 이를 해결하기 위하여 공급되는 가스의 $CH_4/CO_2/H_2O$ ratio를 조절하여 수분 비율을 최적화한 결과, 1 : 0.5 : 1의 비율로 가스를 공급할 경우 탄소 침적 방지를 통한 내구성 확보가 가능하였으며 전환율 역시 비교적 높은 수준으로 유지됨을 확인하였다.

• 한국분말재료학회지
• /
• 제22권4호
• /
• pp.229-233
• /
• 2015

Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ metallic glass powder under of 0.2 kJ generated by a $450{\mu}F$ capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at $150^{\circ}C$ for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped $Fe_2O_3$ and needle-shaped $Fe_3O_4$ are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.

• 한국태양에너지학회 논문집
• /
• 제29권1호
• /
• pp.44-49
• /
• 2009

Steam reforming of methane in the high temperature solar chemical reactor bas advantage in its heating method. Using concentrated solar energy as a heating source of the reforming reaction can reduce the $CO_2$ emission by 20% compared to hydrocarbon fuel. In this paper, the simulation result of methane-steam reforming on a high temperature solar chemical reactor(SCR) using Fluent 6.3.26 is presented. The high temperature SCR is designed for the Inha Dish-1, a Dish type solar concentrator installed in Songdo city. Basic SCR performance factors are referred to the former researches of the same laboratory. Inside the SCR porous metal is used for a receiver/reactor. The porous metal is carved like a dome shape on the incident side to increase the heat transfer. Also, ring-disc set of baffle is inserted in the porous metal region to increase the path length. Numerical and physical models are also used from the former researches. Methane and steam is mixed with the same mole fraction and injected into the SCR. The simulation is performed for a various inlet mass flow rate of the methane-steam mixture gas. The result shows that the average reactor temperature and the conversion rate change appreciably by the inlet mass flow rate of 0.0005 kg/s.

• 폴리머
• /
• 제37권6호
• /
• pp.669-676
• /
• 2013

탈미네랄화된 골분(demineralized bone particle, DBP)은 연골 형성의 유도인자로 사용되기 때문에 조직공학에서 널리 사용되는 생체재료이다. 본 연구에서는 in vivo 환경에서 디스크 재생 효과를 연구하기 위해 DBP를 poly(lactic-co-glycolic acid) (PLGA)에 첨가하여 다공성 지지체를 제조하였다. 디스크의 섬유륜 조직을 반으로 절개한 후, 수핵 조직을 제거하여 디스크 결손을 유발시켰다. 빈 공간에 PLGA, DBP/PLGA 지지체를 이식하여 in vivo 환경에서 조직공학적 디스크 재생을 관찰하였다. 1, 2 및 3개월 후 디스크를 적출하여 글리코스아미노글라이칸(glycosaminoglycan, sGAG) 및 콜라겐 합성 정도를 측정하였으며 조직학적 평가로 H&E, Safranin-O, Alcian blue 염색과 면역조직학적 평가로 제 I형 콜라겐, 제 II형 콜라겐 염색을 수행하였다. 그 결과 DBP/PLGA 지지체에서 sGAG 및 콜라겐 함량이 높은 것을 확인하였으며 추간판 디스크 재생의 가능성을 확인하였다.

• 한국진공학회지
• /
• 제12권S1호
• /
• pp.21-27
• /
• 2003

Micro-arc discharge oxidation (MDO) is a cost-effective plasma electrolytic process which can be used to improve the wear and corrosion resistance of Al-alloy parts by forming a alumina coating on the component surface. However, the MDO coated Al-alloy components often exhibit relatively high friction coefficients and low wear resistance fitted with many counterface materials, additionally, the pitting corrosion for the MDO coated AI-alloy components, especially for a thinner alumina coating, often occurs in atmosphere circumstance due to the porous alumina coats. Therefore, a duplex treatment, combining a MDO coated ahumina thin layer with a TiN coating, prepared by magnetron sputtering (MS), has been investigated. The Vicker's microhardness, pin-on-disc, electrochemical measurement, salt spray, XRD and SEM tests were used to characterize and analyze the treated samples. The work demonstrates that the MDO/MS coated samples have a combination of a very low friction coefficient and good wear resistance as well as corrosion since the micro-holes on alumina coating are partly or fully covered by TiN material.

• Archives of Plastic Surgery
• /
• 제47권4호
• /
• pp.310-316
• /
• 2020

Background To produce patient-specific nasal implants, it is necessary to harvest and grow autologous cartilage. It is crucial to the proliferation and growth of these cells for scaffolds similar to the extracellular matrix to be prepared. The pore size of the scaffold is critical to cell growth and interaction. Thus, the goal of this study was to determine the optimal pore size for the growth of chondrocytes and fibroblasts. Methods Porous disc-shaped scaffolds with 100-, 200-, 300-, and 400-㎛ pores were produced using polycaprolactone (PCL). Chondrocytes and fibroblasts were cultured after seeding the scaffolds with these cells, and morphologic evaluation was performed on days 2, 14, 28, and 56 after cell seeding. On each of those days, the number of viable cells was evaluated quantitatively using an MTT assay. Results The number of cells had moderately increased by day 28. This increase was noteworthy for the 300- and 400-㎛ pore sizes for fibroblasts; otherwise, no remarkable difference was observed at any size except the 100-㎛ pore size for chondrocytes. By day 56, the number of cells was observed to increase with pore size, and the number of chondrocytes had markedly increased at the 400-㎛ pore size. The findings of the morphologic evaluation were consistent with those of the quantitative evaluation. Conclusions Experiments using disc-type PCL scaffolds showed (via both morphologic and quantitative analysis) that chondrocytes and fibroblasts proliferated most extensively at the 400-㎛ pore size in 56 days of culture.