• 전기의세계
• /
• 제29권8호
• /
• pp.524-531
• /
• 1980

In order to investigate the effect of inorganic dielectric fine particle mixed in Low Density Polyethylene on the deterioration by treeing, a comparative study for initiation and development of the tree has been carried out between the pure thin film specimen and the same geometrical specimen mixed with a constant weight percent by a defiend particle size of $Al_{2}$O$_{3}$ and SiO$_{2}$, having larger dielectric constants than that of the base material. According to the results, it has been observed that as increasing dielectric constant, the initiation of tree is expedited, however, the development of the tree reached at the surface of filler particles shows the suppressive trends. From these facts, a reasonable interpretation may be possible by considering the effect of intensified electrical field around the tip in the presence of filler particles, that the initiation and the development of tree are a mechanical break down process caused by Maxwell stress due to the concentration of electrical field at the tip. This suppressive effect is specifically suggestive for the reason that a discharge route must be constructed around the particle surface because of the intensified field strength near filler, which, in turn, reduces the geometrical curvature of the tip so that the local intensity of electrical field can be relaxed. Further more an experimental evidence for this assumption was able to observe in this investigation.

• 한국세라믹학회지
• /
• 제19권2호
• /
• pp.127-132
• /
• 1982

This experiment has been carried out for the purpose of investigating the effect of additives on densification and grain growth in magnesium oxide by a two-step process; hot pressing and heat treating. MgO powder has been obtained by calcining extra reagent grade MgCO3 at 90$0^{\circ}C$ for 30 minutes, and additives have been added to $MgCO_3$ in the form of soluble salts-Al$(NO_3)_3$$. $9H_2O$ and $Cr(NO_3)_3$.9H_2O$. The hot pressing has been carried out with changes of soaking time at 125$0^{\circ}C$ under the pressure of 250kg/$\textrm{cm}^2$, and the heat treating also at same temperature. The initial particle size of MgO measured by particle size analyzer was 0.86 microns. Densification rate obeyed the equation D=K lnt + C, and grain growth rate obeyed the equation G-G0=kt1/2. It was vaporization of some $Cr_2O_3$ and formation of solid solution that had an influence on desification of MgO containing $Cr_2O_3$. Activation energy for grain growth of pure MgO was 62.4 kcal/mole, therefore grain growth was supposed to be diffusioncontrolled process. But after heat treatmeat, excess additives were expected to slow down the grain growth by the formation of second phase or the solute atoms at grainboundary.

• 박물관보존과학
• /
• 제10권
• /
• pp.21-27
• /
• 2009

죽제조문필통은 직경 80mm정도의 통대 2개를 맞붙이고, 바닥에는"∞"모양의 가중나무 판재를 붙였다. 그리고 외부면에는 용과 구름, 사슴과 소나무 문양이 음·양각 기법으로 각각 정교하고 힘차게 조각되었다. 이 죽제조문필통은 일부가 파손, 결실 그리고 분해된 상태였지만 이번 보존수리를 통해 그 원형을 되찾게 되었다. 결실부에는 토분·호분·아교를 혼합하여 복원재료로 이용하였고, 원형을 되찾은 후 접합부분 안쪽에 얇은 비단 천을 부착하여 터짐을 방지하였다. 또한 복원된 표면은 옻칠을 이용해 고색처리를한것등 전통적인 재료와 수리기법을 응용한 가역적인 처리에 중점을 두었다.

• 한국주거학회논문집
• /
• 제12권2호
• /
• pp.1-12
• /
• 2001

The purpose of this study is to analyze characteristics of apartment housing unit plans based on analyzing overall patterns of housing unit plans and identifying the types of unit plans according to the size and to provide the fundamental data for developing diverse dwelling unit plans of apartment. This study deals with apartment housing unit plans built between 1999 and 2000 in Seoul, the capital region and new town. The major findings of this study are as follows; 1) Most apartment housing unit plans have fixed and uniform layouts. Most apartment housing units have L-DK type meaning they have isolated living room space. Certain layouts(especially $60-85\textrm{m}^2$ sized unit plans) show a "trickle-down" phenomenon with respect to the areas of units according to time series. 2) New plan types are rarely proposed since 2000, especially in large-sized(area more than $120\textrm{m}^2$) and $60-85\textrm{m}^2$ sized plans. 3) Another feature of apartment housing unit plans is increase of the service are (balcony, entrance area, additional kitchen, and storage area), and introduction of masters space (composition of master bedroom, dressing room, powder room, path, and etc.) and etc.)

• 한국주조공학회지
• /
• 제31권3호
• /
• pp.145-151
• /
• 2011

Metallic foam has been known as a functional material which can be used for absorption properties of energy and sound. The unique characteristics of Al foam of mechanical, acoustic, thermal properties depend on density, cell size distribution and cell size, and these characteristics expected to apply industry field. Al-Zn-Mg-Cu alloy foams was fabricated by following process; firstly melting the Al alloy, thickening process of addition of Ca granule to increased of viscosity, foaming process of addition of titanium hydride powder to make the pores, holding in the furnace to form of cooling down to the room temperature. Metal foams with various porosity level were manufactured by change the foaming temperature. Compressive strength of the Al alloy foams was 2 times higher at 88% porosity and 1.2 times higher at 92% porosity than pure Al foams. It's sound and vibration absorption coefficient were higher than pure Al foams and with increasing porosity.

• Natural Product Sciences
• /
• 제22권3호
• /
• pp.168-174
• /
• 2016

Anti-melanogenic effects of amaranth (AT), one of the key source of squalene, were investigated in melanocytes. Amaranth seed powder was extracted with water and melan-a cells were treated with various concentrations of AT. By using HPLC, content of myo-inositol, one of potential active components, was measured in the crude extract of AT.AT reduced the melanin content in melan-a melanocytes and down-regulated melanogenic enzyme activity such as tyrosinase, TRP-1 and TRP-2. By regulating melanogenic enzyme activity, AT may be a potential natural source for whitening agent. Myo-inositol was detected in AT by HPLC and may be one of the active compounds from AT involved in the regulation of anti-melanogenesis. In this study, we demonstrated that AT has anti-melanogenesis properties. This new function of amaranth may be useful in the development of new skin-whitening products and its value as food.

• 한국구조물진단유지관리공학회 논문집
• /
• 제6권2호
• /
• pp.255-261
• /
• 2002

Concrete structures stand in poor surrounding than it has ever been met before, because they are installed in severe conditions such as chloride penetration. $CO_2$ gas, water and so on. Therefore, the countermeasure to efficiently protect from the deterioration of concrete structures should be urgently considered. From this point of view, this study was aimed to develop surface treatment systems for concrete structures, which cover physical properties, long term durability and economic consideration. Developing the optimal surface treatment materials, powder type polymer or liquid type polymer was added to inorganic base materials. Three surface treatment materials which had shown best results in primary tests were selected and durability tests were fulfilled. Consequently optimum surface treatment material was developed. The surface treatment materials, which were developed through this study, can efficiently extend the service life of concrete structures. As a result, the life cycle cost should be reduced and the waste of material resources would be cut down.

• 한국결정성장학회지
• /
• 제3권2호
• /
• pp.117-124
• /
• 1993

연속성장법은 crystal growth chamber의 상부에 있는 reservoir에서 원료 분말을 연속적으로 공급하면서 도가니 하부에 용융대를 형성시킨 후, 종자결정을 용융대에 dipping하여 회전시키면서 아래로 끌어내려 단결정을 성장시키는 방법이다. 본 연구에서는 연속 성장법을 이용하여 silicon 단결정을 육성시켰으며 연속성장에 영향을 미치는 인자는 critical melt level, 원료공급속도, 성장속도, graphite crucible과 gruphite susceptor의 형태, work coil의 위치에 따른 graphite susceptor의 수직온도구배, 중력과 종자결정의 회전에 의한 원심력이 용융대의 안정화에 미치는 영향과 용융액 표면에서 일어나는 소결현상에 관해 고찰하였다.

• Bulletin of the Korean Chemical Society
• /
• 제11권6호
• /
• pp.564-567
• /
• 1990

A lithiated compound $Li_{0.1}Pr^{3+}Ba_2Cu_3O_y$ has been successfully prepared by electrochemical method, which is achieved with a two electrode cell of the type: Metal(Li)/($Li^+\;,\;ClO_4^-$) + propylene carbonate/$PrBa_2Cu_3O_y$. All Pr ions in the lithiated compound are stabilized with a trivalent state as the other rare earths (Ⅲ) substituted in the 90K superconductor lattice ($Y_{1-x}Ln_x^-Ba_2Cu_3O_{7-{\delta}}$). Powder X-ray diffraction analysis shows that both compounds, $PrBa_2Cu_3O_y$ and $Li_{0.1}PrBa_2Cu_3O_y$ are isostructural with the 90 K superconductor, ($YBa_2Cu_3O_{7-{\delta}}$), nevertheless both of them are non-metallic and also non-superconducting down to 10 K. Magnetic susceptibility ${\chi}$ vs. temperature data indicate that Curie contribution from the magnetic ions (Pr and Cu) is weakened on the one hand, but on the other hand temperature-independent part of susceptibility ${\chi}_o$ increases depending upon the rate of lithium intercalation in $PrBa_2Cu_3O_y$ lattice.

• 한국식품과학회지
• /
• 제40권1호
• /
• pp.88-95
• /
• 2008

본 연구는 콩 아이스크림의 품질향상을 위하여 콩을 데치고 동결 건조 한 후 분말화하여 과즙을 첨가하고 혼합 유산균 종균을 배양시켜 대두분말 발효 베이스를 제조한 후 올리고당을 첨가하여 식감개선, 저칼로리 및 혈당 수준의 개선 특성을 가진 콩 아이스크림을 제조하여 그 품질 특성과 혈당개선능을 비교하였다. 대두분말을 $121^{\circ}C$에서 15분간 가압멸균한 후 $30^{\circ}C$로 냉각한 다음, L. acidophillus KTCT 3164와 L. bulgaricus KCTC 3635 현탁액을 $4.6}{\times}106$ CFU/mL의 농도를 1:1 비율로 혼합한 균주(1%)를 접종하고 $33^{\circ}C$에서 24시간 발효시킨 후 비교한 결과, 삶은 대두분말 발효베이스가 볶은 대두분말 발효 베이스에 비해 pH는높았고 점도는 낮았다. 생균수는 접종 후 24시간 배양 후 삶은 대두분말 발효 베이스의 유산균 생육이 우세하였다. 관능검사법으로 평가한 대두분말 발효베이스의 종합적인 기호도는 삶은 대두분말 발효베이스가 콩 특유의 비린 맛과 냄새가 약하면서 상큼한 풍미가 많고 입안의 질감이 부드러워서 관능적인 품질이 양호한 것으로 나타났다.볶은 대두분말 베이스 아이스크림이 overrun과 녹아내리는 정도가 가장 낮았고, 이에 비해 삶은 대두분말 발효베이스 아이스크림은 overrun과 녹아내리는 정도가 증가하여 품질 특성이 현저하게 향상되었다. 냉동에 의한 생균수의 변화는 삶은 대두분말 발효베이스 아이스크림군이 볶은 대두분말 발효베이스 아이스크림군보다 높게 나타났으나, 같은 아이스크림 군 간에는 냉동에의한 생균수의 유의적인 차이는 없었다. 관능검사에 의한 아이스크림의 텍스쳐는 우유아이스크림이 가장 높게 평가되었으나 삶은 대두분말 발효베이스 아이스크림과 유의한 차이는 없었다. 종합적인 기호도는, 우유 아이스크림과 유의한 차이는 보이지 않았음에도 불구하고, 삶은 대두분말 발효베이스 아이스크림이 가장 양호하게 평가되었다. 건강한 20대 여성들을 대상으로 아이스크림의 경구 혈당반응 검사 결과, 설탕 첨가 우유 아이스크림과 올리고당 첨가 삶은 대두분말 발효베이스 아이스크림 사이에 혈당 면적은 유의한 차이가 없었으나, 아이스크림 섭취 후 120분 혈당은 올리고당 첨가 삶은 대두분말 발효베이스 아이스크림을 먹은 경우가 설탕 첨가 우유 아이스크림을 먹은 경우에 비해 유의하게 낮았다. 또한 혈당 증가가 완만하여 식사 후 혈당관리가 중요한 당뇨환자에게는 일반 아이스크림보다 유익할 것으로 사료된다.