• 조명전기설비학회논문지
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• 제30권1호
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• pp.72-78
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• 2016

In terms of power components which use environmentally-friendly dry air that can substitute SF6, there have been studies on the electrical properties of the solid insulation "spacer" for the purpose of securing dielectric strength as they become smaller. This study laminated solid insulation to keep the creeping distance the same in the dry air and investigated vertical surface discharge characteristics by shape. The three sheets of disk-type solid insulation(Bakelite) were laminated in a manner to keep the creeping distance the same. The lamination was categorized as follows: "Type A" in which the insulations with the same disk diameter were laminated; "Type B" in which the insulations whose middle disk diameter was large were laminated; and "Type C" in which the ones whose middle disk diameter was small were laminated. For a vertical surface discharge experiment, dry air was injected into the test chamber depending on the shape of the laminated solid insulation, and chamber pressure was adjusted in a range of 0.1-0.6MPa. As volume decreased, surface discharging voltage by unit volume increased. This was because of dielectric polarization according to the structural characteristics of the shape of lamination. The highest surface discharging voltage was found in "Type C."

• 대한기계학회논문집B
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• 제41권6호
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• pp.429-434
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• 2017

분자-연속체 하이브리드 기법은 연속체 유체역학으로 예측하기 어려운 마이크로/나노 스케일 유동에 대해 개발되고 발전해 왔다. 분자동역학은 고체표면 주변 영역에서 사용되고, 나머지 영역에서는 나비아스톡스 방정식이 사용된다. 본 연구에서는 나노채널에서 고체-액체 상호작용과 표면 거칠기의 영향을 연구하기 위해 분자-연속체 하이브리드 기법을 이용하여 쿠에트 유동을 해석하였다. 우리는 고체-액체 상호작용 힘인 표면 에너지와 표면 거칠기가 유동의 표면 경계조건에 영향을 주는 것을 발견하였다. 표면 에너지가 낮을 때에는 유동이 고체 표면에서 미끄러짐이 발생하였고, 표면 에너지가 증가함에 따라 미끄러짐의 크기가 감소하였다. 표면 에너지가 높을 때에는 로킹(locking) 경계조건이 형성되었다. 또한 표면 거칠기는 유동이 고체 표면에서 미끄러지는 것을 방해하여 로킹 경계조건이 잘 형성되도록 영향을 주었다.

• 조명전기설비학회논문지
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• 제26권3호
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• pp.9-15
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• 2012

In this paper, we deal with a surface discharge that caused an aggravation of the dielectric strength in the $N_2/O_2$ mixture gas, When composit dielectrics were formed from the use of a solid dielectric. It was found from this study that the surface discharge voltage was deeply involved in the mixture ratio of $O_2$, the electrical property of the solid dielectric, kind of the solid dielectric, an electric field at the triple junction and a medium effect. These results expect basic data that will be used to transmission and distribution power system equipment using the $N_2/O_2$ mixture gas.

• 한국분말재료학회지
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• 제31권3호
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• pp.263-271
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• 2024

This study focused on improving the solubility of silodosin, a drug poorly soluble in water, by utilizing solid dispersions. Three types of dispersions were examined and compared against the drug powder: surface-attached (SA), solvent-wetted (SW), and solvent-evaporated (SE). Polyvinyl alcohol (PVA) was identified as the most effective polymer in enhancing solubility. These dispersions were prepared using spray-drying techniques with silodosin and PVA as the polymer, employing solvents such as water, ethanol, and a water-acetone mix. The physicochemical properties and solubility of the dispersions were evaluated. The surface-attached dispersions featured the polymer on a crystalline drug surface, the solvent-wetted dispersions had the amorphous drug on the polymer, and the solvent-evaporated dispersions produced nearly round particles with both components amorphous. Testing revealed that the order of improved solubility was: solvent-evaporated, solvent-wetted, and surface-attached. The results demonstrated that the preparation method of the solid dispersions significantly impacted their physicochemical properties and solubility enhancement.

• 한국CDE학회논문집
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• 제10권1호
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• pp.70-75
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• 2005

A 3D solid element mesh generation algorithm was newly developed. 3D surface points of global rectangular coordinates were supplied by a 3D laser scanner. The algorithm is strait forward and simple but it generates mixed solid elements such as hexagonal, pyramid and prism types. Then, the surface triangular or rectangular elements were generated from the solid elements. The key of the algorithm is elimination of elements and 3D adaptive surface smoothing using given 3D surface point data.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.260-266
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• 2001

The surface temperature at the interface of bodies in a sliding contact is one of the most important factors influencing the behavior of machine components. So the calculation of the surface temperature at a sliding contact interface has long been an interesting and important subject for tribologist. Several methods for calculating surface temperature have been devised. Several numerical methods have been used to predict the temperature rise of sliding surface. but those need much time to calculate. In this study to reduce the calculation time the hybrid method using both semi-infinite solid analysis and FVM was used. It is founded that the computing time of hybrid method was shorter than that of FVM.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.201-201
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• 2011

Recently, mussel-inspired surface modification, called polydopamine coating has been extensively implemented to many areas, due to its material versatility and ease to use. In particular, incubation of substrates in an alkaline dopamine solution resulted in self-polymerization of dopamine and modified variety of material surfaces, including noble metals, metal oxides, ceramics, and synthetic polymers. However, the polydopamine coating has a drawback to practical use; it takes more than 12 hrs to introduce sufficient polydopamine layers to solid substrates. Here, we investigated the rate-enhanced polydopamine coating by varying reaction conditions: pH, concentration, and the addition of the oxidizing agent. As a result, the optimum condition for fast polydopamine coating was found, and solid substrates were efficiently coated with polydopamine layers in just few minutes using the condition. The polydopamine-modified surface was characterized by XPS and contact angle goniometry, and the biocompatibility of the modified surface was also proved by cell attachment test.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.236.1-236.1
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• 2003

Evaluation of solid surface properties is very important for formulation of solid dosage form, specially insoluble drugs. The contact angle of insoluble drugs was measured by the penetration rate into powder bed using Washburn equation and wicking method. From the measured contact angle data, the surface free energy value of pharmaceutical powders ${\gamma}$s was divided and analysized into the polar component, ${\gamma}$s$\^$p/ and the dispersion component, ${\gamma}$s$\^$d/. Furthermore, the data was interpreted for acid part, ${\gamma}$s$\^$+/ and base part, ${\gamma}$s$\^$$\square$/ of surface free energy. (omitted)

• 한국가시화정보학회지
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• 제21권3호
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• pp.7-14
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• 2023

In this study, we investigated the freezing delay time on surfaces with different patterns under -30° conditions through visualization experiments. Among various pattern structures, we fabricated the shape and surface of liquid from the spacing using circular filaments and hole structures. Additionally, using a high-speed camera, we visualized the freezing scenes, enabling us to obtain freezing images and measure the freezing time of the liquid. For each structure, the contact angle and solid fraction of the surface varied. We observed that the freezing delay time was longest when the contact angle was largest and the solid fraction was smallest within the experimental results. We analyzed the variation in anti-icing time using the heat exchange equation between the patterned surface and the liquid.

• 펄프종이기술
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• 제34권3호
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• pp.1-8
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• 2002

The object of this study was to determine the surface energy of hydrophobically modified micro-crystalline cellulose (MCC) with AKD and evaluate the effect of surface energy of the solid particles dispersed in aqueous medium on flotation efficiency. Especially to eliminate the complication derives from the diverse parameters of solid particles including particle size, type, etc. MCC's modified with AKD have been used. The surface energy Parameters were calculated from advancing contact angles of apolar and polar liquids on MCC pellets using the Lifshitz-van der Waals acid-base (LW:AB) approach. Total surface energy of hydrophobic MCC ranged from 46.19 mN/m to 48.60 mN/m. The contribution of the acid-base components to the total surface energy ranged form 13% to 17% for hydrophobic MCC's. The effect of surface characteristics on the flotation efficiency was evaluated. It was shown that there exist critical values of surface energies to increase flotation efficiency. Total surface energy and polar component of solid particles should be lower than 47 mN/m and 7 mN/m, respectively, for effective removal in the flotation process.