• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.384.2-384.2
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• 2016

Recent publications reported the self-propelled jumping of coalescing dew droplets on superhydrophobic surfaces [1-2]. We further investigated the initial growth, coalescence, and removal by self-propelled ejection of nano and microscopic water droplets on the superhydrophobic surface of lotus leaves under condensing conditions. By using a high-speed digital camera mounted on an optical microscope, we have found: (1) sub-micrometer droplets form and grow on nanoscale waxy hairs; (2) growing droplets coalesce rapidly upon contact, but never jump off the surface unless the diameter of merged droplets exceeds ${\sim}15{\mu}m$; (3) the diameter and direction of jumping droplets are very narrowly distributed, centered at $20-30{\mu}m$ and ${\sim}20$ degrees from the surface normal, respectively. We present a rationale for these observations on the basis of: (a) the hierarchically rough surface structure on nano- and micro-scales; (b) its chemical composition; and (c) the balance among competing forces of cohesion (surface tension), adhesion and gravity.

• 대한치과의사협회지
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• 제56권10호
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• pp.572-580
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• 2018

Adequate access cavity is the key to achieving endodontic success. The aims of the access cavity can be considered as follows: 1) Creation of a smooth unimpeded pathway for instruments to canal orifices 2) Removal of the entire roof of the pulp chamber in order to inspect the pulp floor, 3) Preservation of natural tooth substance consistent with the above. Recently, contracted endodontic cavities based on minimally invasive endodontics has introduced. This has the benefit of preserving the pericervical dentin more than traditional access cavity with achieving long-term success. However, some studies reported controversial results regarding root canal detection, instrumentation efficacy (noninstrumented canal area, hard tissue debris accumulation, canal transportation, and centering ratio) as well as fracture resistance. Therefore, further studies are required for accepting contracted access cavity, and modified form of traditional and contracted access cavity could be considered.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.339-342
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• 2000

황화수소와 암모니아 함유악취의 동시처리를 위해 Thiobacillus sp.IW가 함유된 3상 생물막유동층반응기를 사용하였다. 본 연구에서 황화수소는 미생물에 의해 산으로 전환되었으며 이어서 유입된 암모니아와 반응하여 황산암모늄이 생성됨으로서 양성분은 제거되었다. 황화수소의 경우 45 mg/l h의 유입량에서도 거의 완전한 처리 효율을 보여주었으나, 암모니아의 경우 유입량이 10 mg/l h에서 증가함에 따라 처리효율은 점차 감소하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.147-150
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• 1999

Glossing Exposure Concrete is a high quality architectural concrete, i.e., appearance of natural stone and a marbling effect concrete to achieve high quality glassy reflective surface for outer wall of the building. In this study to obtain the conservation and durability of gloss of the "glossing exposure concrete" we developed a from practice and the best mix proportion and derived the optimistic removal time of form to bring out the durable glassy reflective surface and durable concrete. Hereby with the "glossing exposure concrete" obtained, we investigate the accelerate carbonation and accelerate durability test to evaluate the durability factor of this type of concrete.is type of concrete.

• 한국세라믹학회지
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• 제24권4호
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• pp.343-348
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• 1987

The effects of salts such as aluminum sulfate as inorganic salt(2-4%), and sodium salts of citrate, tartrate, succinate, potassium tartrate and gelatin as organic salts(0.1%) on the formation of ${\alpha}$-calcium sulfate hemihydrate from by-product gypsum of phosphoric acid process under hydrothermal condition at 123$^{\circ}C$ and 133$^{\circ}C$ were investigated. Aluminum sulfate solution exhibited the catalystic effected on the crystallization of ${\alpha}$-calcium sulfate hemihydrate of which was assumed in the prismatic form, and organic salts solution exhibited little effect on the catalystic action to the crystallization, than inorganic salts. In the acidic solution with sulfuric acid(pH=2), needle like crystal of calcium sulfate hemihydrate was obtained. Hydrothermal process with aluminum sulfate solution also showed certain amounts of impurity removal such as phosphorus penataoxide from calcium sulfate hemihydrate.

• 한국환경과학회지
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• 제6권2호
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• pp.113-124
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• 1997

The basic mechanism of the granular sludge formation which is the most important factor in the start-up and stable operators is not confirmed yet. In this study, the effect of granular sludge formation was investigated with the different substrate concentrations and the various ratios of substrate supply/deficiency. The granular sludge formation in the UASB reactor was closely related to the substrate concentrations and the ratio of substrate supply/deficlency The granular sludge formation was not accelerated at low substrate concentration. It was convinced that granular sludge formation was accelerated when the substrate supply with high concentration was stopped at UASB reactor. From this experiment, it was estimated that granular sludge was formed by the combination of hydrogen utilizing bacteria that form hydrogen condition and acid forming bacteria at substrate deficit condition by mutual symbiosis. Though the removal efficiency of organic matter was decreased as the influent substrate concentration was Increased, the higher the influent substrate the better the granular sludge formation.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.676-679
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• 2003

혐기성 반응조는 침강성이 좋고 활성이 높은 생물을 어떻게 고농도로 반응기내에 축적시키기까지 자연적인 조건에서 6개월이라는 장시간이 요구된다. 하지만 유 ${\cdot}$ 무기 복합 고분자를 이용하여 단기간에 입상슬러지를 형성한 후, Fed-Batch 실험을 통하여 폐수에 대한 입상슬러지의 적응 기간을 알아보았다. 반복 실험의 결과, $30{\sim}40$일 정도의 적응기간 동안 유 ${\cdot}$ 무기 복합 고분자를 이용하여 형성된 입상슬러지는 실플랜트의 입상슬러지와 비슷한 $80{\sim}90%$의 COD제거율을 보였다.

• 한국생산제조학회지
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• 제23권1호
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• pp.32-37
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• 2014

Open-cell silicon foam is difficult to cut using conventional machining processes because of its low stiffness. That is, open-cell silicon foam is easily pressed down when the tool is engaged, which makes it difficult to remove the material in the form of chip. This study proposes an advanced method of machining open-cell silicon foam by freezing the material using liquid nitrogen. Furthermore, the machining conditions are optimized to maximize the efficiency of material removal and minimize the usage of liquid nitrogen by conducting experiments under various machining conditions. The results show that open-cell silicone foam products with free surface can be successfully machined by employing the proposed method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.551-554
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• 2002

The paper discusses new approach for machining operation simulation using enhanced Z map algorithm. To extract the required geometric information from NC code, suggested algorithm uses supersampling method to enhance the efficiency of a simulation process. By executing redundant Boolean operations in a grid cell and averaging down calculated data, presented algorithm can accurately represent material removal volume though tool swept volume is negligibly small. Supersampling method is the most common form of antialiasing and usually used with polygon mesh rendering in computer graphics. The key advantage of enhanced Z map model is that the data structure is same with conventional Z map model, though it can acquire higher accuracy and reliability with same or lower computation time. By simulating machining operation efficiently, this system can be used to improve the reliability and efficiency of NC machining process as well as the quality of the final product.

• International Journal of Precision Engineering and Manufacturing
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• 제8권1호
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• pp.46-51
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• 2007

Environmental contamination creates shortages of potable water. In such situations, the leakage of water due to breakage or aging of rubber valve seats is a serious problem. Rubber is apt to break when it is placed between two materials that contact each other. One way to avoid water leakage due to rubber damage and breakdown is to replace the rubber with metal, which is currently taking place in water distribution systems. In tribology, a severe form of wear is characterized by local macroscopic material transfer or removal, or by problems with sliding protrusions when two solid surfaces experience relative sliding under load. One of the major problems when metal slides is the occurrence of galling. Experimentally, various conditions influence incipient galling, such as hardness, surface roughness, temperature, load, velocity, and the external environment. This study sought to verify the galling tendencies of metal according to its hardness, surface roughness, load, and sliding velocity, and determine the quantitative effect of each factor on the galling tendencies.