• 한국재료학회지
• /
• 제15권4호
• /
• pp.217-223
• /
• 2005

Thermal, electrical and mechanical properties of high purity niobium and tantalum refractory rare metals were investigated tn evaluate the physical purity. Higher purity niobium and tantalum metals showed lower hardness due to smaller solution hardening effect. Temperature dependence of electrical resistivity showed a typical metallic behavior. Remarkable decrease in electrical resistivity was observed for a high purity specimen at low temperature. However, thermal conductivity increased for a high purity specimen, and abrupt increase in thermal conductivity was observed at very low temperature, indicating typical temperature dependence of thermal conductivity for high purity metals. It can be known that reduction of electron-phonon scattering leads to increase in thermal conductivity of high purity niobium and tantalum metals at low temperature.

• 한국토양비료학회지
• /
• 제48권4호
• /
• pp.305-311
• /
• 2015

Both low and high temperatures affect plant growth and development at whole plant level, tissue and even cell level through a variety of metabolic changes. Temperature stress is one of frequently occurring problems in greenhouse crops in summer and winter seasons due to the wide-spread year-round cultivation. In the present study, we investigated the extent of the inhibition of growth, macro-element uptake and soluble carbohydrate production, and the effect of extra-supply of minerals as a means of the recovery from temperature damage. Tomato plants were grown five different growth temperatures (15/8, 20/13, 28/21, 33/23 and $36/26^{\circ}C$), and extra-supply of minerals was composed of 1.5- and 2.0-fold stronger than the standard nutrition (1/2 strength of Hoagland's solution). Temperature stress significantly adversely affected tomato growth and mineral uptake, whereas soluble carbohydrate accumulation represented temperature-dependent response, more accumulation at low temperature and more consumption at high temperature. The soluble sugars in leaves and stems were mostly declined with the supply of extra-minerals at low and optimal temperatures, whereas remained unchanged at high temperature. The starch levels also remained unchanged or slightly decreased.

• 한국세라믹학회지
• /
• 제32권2호
• /
• pp.171-182
• /
• 1995

Five eucryptite and ten spodumene compositional powders were syntehsized from three sillimanite group, two kaolin group, and five pyrophyllite group silicate minerals. Those powders were isotatically pressed and fired at 1200~135$0^{\circ}C$ for 2 hrs, and then the sintered bodies were characterized. Silicate minerals with molar ratio of Al2O3 to SiO2 correspond to those of eucryptite and spodumene are kaolin and pyrophyllite group silicate minerals, respectively. Sintering characteristics of eucryptite from kaolin group and spodumene from pyrophyllite group mineral were superior to those from other silicate minerals. Eucryptite sintered bodies with 95~97% relative densities and densified microstructures can be obtained using Hadong pink kaolin as starting materials by sintering over broad temperature zone(1250~135$0^{\circ}C$). The eucryptite sintered bodies which were fired at 130$0^{\circ}C$ for 2hrs, from Hadong pink kaolin had within 3.0wt% microstructural compositional variations compaired with stoichiometric compound, and had good negative thermal expansiion property with -3.55$\times$10-6/$^{\circ}C$ thermal expansion coefficient. Spodumene sintered bodies which were prepared from pyrophyllite group silicate minerals, had dense microstructures and high densities by densification through liquid phase sintering with enlarged temperature range. The specimens which were fired at 130$0^{\circ}C$ for 2 hrs from Gusipyrophillite, had dense microstructure with crystallines mainly, and low thermal expansion property with 0.62$\times$10-6/$^{\circ}C$ thermal expansion coefficient. The porous texture and residual glass phase in LAS system ceramics which were prepared from silicate minerals, tend to increase the thermal expansion properties of sintered bodies to positive direction.

• 자원환경지질
• /
• 제25권4호
• /
• pp.463-477
• /
• 1992

The study area consists of sedimentary and volcanic rocks of Gyeongsang Supergroup, granitoid intrusives, and hornfelses around the granitoids. Granitoid intrusives occur in small stocks in Nijeon-ri, Uggogri, and Yul-ri area. The masses in Nijeon-ri and Uggog-ri are hornblende-biotite granodiorite, biotite granodiorite respectively, and Yul-ri mass is biotite granite. Surrounding sediments of these masses were thermally metamorphosed and contact aureoles were formed. The studied granitoids are considered to be formed by sequential crystallization-differentiation from calc-alkalic granitoid magma. Metamorphic minerals occurring in contact aureole are chlorite, actinolite, epidote, and biotite. Diopside and hornblende are observed in small amount in some lithology around contact aureole. The lithology of contact aureole is predominantly silty and sandy, and characteristic metamorphic minerals were poorly developed because of low temperature metamorphism. Low temperature in contact aureole could be deduced from the facts that the intrusions were small size, shallow depth, low temperature, and rare movement of volatiles from magma.

• 기술사
• /
• 제16권1호
• /
• pp.71-77
• /
• 1983

Meat itself contains all the essential nutrients for the organisms, because it is high in moisture, rich in nitrogenous, Plentifully supplied with minerals and accessory growth factors, usually has come fermantable carbohydrates and is at a faverable PH for most microorganisms. So, microorganisn can grow and multiply rapidly well in it and caused spoilage of meat and their Product. Therefore, storage and handling of meat must be Strictly controlled on contamination and growth of organism by a low temperature, among the low temperature control, chilling control of meat is one of the best method as good retention for meat quality.

• 대한건축학회논문집:구조계
• /
• 제35권12호
• /
• pp.149-156
• /
• 2019

Recently, skyscraper building and apartment fires, which were rapidly spread out from a low floor to a rooftop, have become a frequent occurrence in mass media. This fire problems have a fatal disadvantage that the exterior wall finish of the building emits toxic gas in case of fire by using dry bit method or organic insulating material. Therefore, in order to remedy these problems, many exterior wall finishing construction methods have been proposed, but the current trend is to use existing construction methods due to problems such as economy, weight, and durability. On the other hand, in countries such as Germany and Japan, ceramic sidings are used as exterior finishing material for buildings, which is environmentally friendly, excellent natural beauty, long life, easy maintenance and high-quality exterior materials. However, those ceramic sidings have still the problems such as manufacturing cost and weight problem because of boosting the sintering temperature up to 1,350℃ or more. Also, conventional CRC, MgO, FRP sidings which are composed of pulp, glass fiber and organic materials, have been reports of deformation due to ultraviolet rays, discoloration, corrosion and scattering, surface rupture, lifting and peeling. Therefore, in this study as an alternative to solve this problem, halosite nano kaolin produced in Sancheong in Korea and frit flux were used to satisfy the required properties as ceramic siding using low temperature sintering (below 1,000℃) and lightweight materials such as pearlite. This study aims to design the optimal formulation and process of materials and to study the characteristics of nano-coated ceramic siding material development and to present relevant basic data. The findings show that ceramic siding for nanocoated building materials is excellent as a natural ceramic siding building material. The fire resistance of natural minerals and nano particle refining technology satisfy the bending strength of 80kgf / cm2, the volume ratio of 2.0 and the absorption rate of less than 10.0%.

• 한국자원리싸이클링학회:학술대회논문집
• /
• 한국자원리싸이클링학회 2005년도 춘계임시총회 및 제25회 학술발표대회
• /
• pp.178-182
• /
• 2005

본 연구에서는 추출제가 함유된 추출레진$(75{\sim}150{\mu}m)$으로 채워진 저압액체크로마토그래피를 이용하여 용리온도$(20{\sim}60^{\circ}C)$와 유속$(1.41{\sim}7.04cm/min)$에 따른 Dy와 Ho의 분리특성을 조사하였다. 용리액인 HCl의 농도는 $0.25{\sim}0.5mol/L$가 적절한 것으로 판단되며, HCl $0.5mol/L$ 이상에서는 분리효과가 거의 없었다. 일정한 용리액 농도에서 유속이 느릴수록, column의 온도가 높을수록 분리도와 해상도는 개선되었으며, 유속이 느릴수록 용리액의 소모량은 감소, 분리시간은 증가하였다. 적정조건인 용리온도 $60^{\circ}C$, 유속 7.04cm/min, HCl 0.25mol/L에서 분리도는 ${\alpha}_{Dy}^{Ho}=1.36$로 가장 높았다.

• 한국세라믹학회지
• /
• 제31권11호
• /
• pp.1401-1413
• /
• 1994

The synthesis of kaolinite mineral from domestic diatomite for silica resource, commercial vailable gibbsite or alumina for alumina resource were made under various hydrothermal treatment, and the sythetic effect of acidic mineralizers, temperature treatment with time duration, particle size of alumina on formation of kaolinite mineral and the plastic properties of synthesized kaolinite were investigated. The various acidic mineralizers which are HCl, HNO3, H2SO4 and Oxalic acid were employed for hydrothermal reaction in the range of 0.01 mol/ι to 2 mol/ι concentration of each mineralizers. It was found that HCl in the level of 1 mol/ι solution produced highly yields of well-crystallized and platy form kaolinite mineral and gave the most effective extraction of iron oxide, compared to that of others, that HNO3 produced highly yield of kaolinite but lower extraction of iron oxide, that H2SO4 produced low yield of kaolinite and formed alunite mineral, and that oxialic acid formed spherical crystalline kaolinite and gave low extraction of iron oxide. Moreover, it showed that kaolinite minerals were well synthesized in a wide range of less than 2 mol/ι acids, but were poorly synthesized at more than 2 mol/ι acids. However, boehmite and kaolinite were coexistently formed in the temperature range of 18$0^{\circ}C$ and 20$0^{\circ}C$ when the calcined diatomite and gibbsite were involved. The well-ordered kaolinite mineral as a platy form was highly synthesized in the temperature range of 220 and 24$0^{\circ}C$, when the same marterials as above were used with treatment of 1 mol/ι HCl solution. The results also revealed that the size of crystalline platy form kaolinite, synthesized from alumina and calcined diatomite with treatment in 1 mol/ιHCl solution at 24$0^{\circ}C$, was much larger than that of gibbsite and calcined diatomite shown previously, and that kaolinite and corundum minerals were coexistently formed under any hydrothermal treatment conditions. The plasticity of synthesized kaolinite from under 2 ${\mu}{\textrm}{m}$ alumina and calcined diatomite was very poor, and that of the synthesized kaolinite from raw diatomite and gibbsite gave higher than that of calcined diatomite and gibbsite.

• 한국지구과학회지
• /
• 제29권7호
• /
• pp.531-538
• /
• 2008

경북 포항의 장기층군에서 산출된 규화목의 산출상태로부터 판단하면 규화목은 모두 이지성 화석임을 지시한다. 장기층군에는 규화목과 함께 탄화목, 목탄도 발견되며, 일부의 규화목에는 껍질부분에 갈탄화된 유기물이 일부 남아있는 것도 있다. 규화목의 X선 회절 분석으로부터 Opal-CT, Opal-C, 석영+크리스토발라이트의 3가지 유형이 확인되었다. 이러한 광물의 존재는 규화작용이 비교적 낮은 온도에서 일어났음을 지시한다. 실리카($SiO_2$)의 주공급원은 응회암으로 추정된다. 규화목의 구성광물의 종류와 조직 보존 상태로부터 판단하면 규화작용은 주로 치환에 의해 일어난 것으로 추정된다.

• 보존과학연구
• /
• 통권23호
• /
• pp.5-39
• /
• 2002

The scientific analysis and provenance study of potteries excavated from kiln sites at Jeonla Nam. Buk-do were carried out using XRD,ICP-AES and NAA. We can summarize the following consequence. First, as a result of XRD analysis, it showed that soft potteries consist of quartz, feldspar and clay minerals while hard potteries consist of high temperature crystals such as mullite, tridymite, cristobalite. In case of firing temperature which are determined by crystals using XRD, potteries are composed of quartz, feldspar and clay minerals had very low firing temperature. While potteries having only cristobalite ranged above$1200^{\circ}C$. Second, as a result of correlation analysis using trace element, the selected characteristic elements which was able to distinguish from each kiln site was Ce, Lu, Cs, Sc, Eu. Third, discriminant analytical results showed that kiln site of the Jeonla Namdo were classified into five groups and that of the Jeolna Buk-do into three groups. This suggests that there are no correlations between the raw materials used in each kiln sites.