• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.367-373
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• 2015

In this study, fundamental properties of cement were reviewed to apply high fineness cement at low temperature environment. The classified high fineness cement has large proportion of particles below $10{\mu}m$ which affects early hydration: an overall reaction of cement hydration faster. As a result of using high fineness cement, setting time of concrete was reduced and compressive strength was higher than OPC at all ages. Especially, compressive strength was more than double its value compared with OPC after three days curing in low temperature. Faster reaction and higher heat of hydration was verified by calorimetry early and maximum heat of hydration was analyzed by adiabatic temperature raising test. The analysis of this study confirmed that high fineness cement can be suitable to be used in low temperature environment.

• Journal of the Korea Institute of Building Construction
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• v.13 no.4
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• pp.391-399
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• 2013

For high strength concrete of 40~60 MPa, the effects on the early strength and concrete dry shrinkage properties replacing 60~80% of Ordinary Portland Cement with Blast Furnace Slag Powder and using the Alkali Activator (Modified Alkali Sulfate type) are considered in this study. 1% Alkali Activator to the binder, cumulative heat of hydration for 72 hours was increased approximately 45%, indicating that heat of hydration contributes to the early strength of concrete, and the slump flow of concrete decreased slightly by 3.7~6.6%, and the 3- and 7- strength was increased by 8~12%, which that the Alkali Activator (Modified Alkali Sulfate type) is effective for ensuring the early strength when manufacturing High Strength Concrete (60%) of Blast Furnace Slag Powder. Furthermore, the dry shrinkage test, both 40 MPa and 60 MPa specimens had level of length changes in order of BS40 > BS60 > BS60A > BS80A, and the use of the Alkali Activator somewhat improved resistance to dry shrinkage.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.234-238
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• 2016

Solid ash-free coal (AFC) samples recovered from solvent-extracted solution by vacuum drying, dilution precipitation and spray drying methods were compared in terms of physical properties and chemical structure. AFC was prepared by using Kideco coal (Indonesian sub-bituminous coal) and polar N-methyl-2-pyrrolidone (NMP) solvent as raw materials. The physical properties of the AFCs were characterized with proximate, ultimate, and calorific value analysis. In analyzing the chemical structure, FTIR and NMR were used. the proximate analysis showed much reduced ash in the AFCs compared to parent raw coal. The FTIR result showed that the extraction solvent was not fully removed from the AFC prepared by vacuum drying. However, the solvent was not detected in the AFC recovered by using dilution precipitation. Dilution precipitation has advantages over the other two methods, since it can be done at relatively low temperature and separate ash-free coal from extraction solvent more effectively.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.213-217
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• 1999

The electrochemical characteristics of two distinct adsorption sites of H at the polycrystalline Pt/0.2 M LiOH aqueous electrolyte interface have been studied using the phase-shift method. At the forward and backward scans, the under-potentially deposited H (WD H) peak occurs on the cyclic voltammogram. The transition region on the phase-shift profile or the Langmuir adsorption isotherm occurs at ca. -0.66 to -0.96 V vs. SCE. At the transition region (ca. -0.66 to -0.96 V vs. SCE), the equilibrium constant (K) for H adsorption transits from 18.5 to $4.0\times10^{-5}$ and vice versa. Similarly, the standard free energy $({\Delta}G_{ads})$ of H adsorption transits from -7.2 to 25.1kJ/mol and vice versa. The under and over-potentially deposited H (UPD H and OPD H) on the poly-Pt surface act as two distinguishable electroadsorbed H species. An exothermic reaction occurs at the UPD H range. Both the UPD H peak and the transition region are attributed to the two distinct adsorption sites of the UPD H and OPD H on the poly-Pt surface.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.04a
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• pp.35-35
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• 2003

)를 금속와이어에 인가하면 저항발열에 의해 와이어가 미세한 입자나 금속증기상태로 폭발하는 현상을 이용한 것으로 기상합성법에 속한다고 할 수 있다. 선폭법은 다른 제조법에 비해 공정이 간단하여 생산비용이 저렴하며, 원재료의 조성을 갖는 분말의 합성과 금속간화합물, 융점차이가 나는 재료의 합금화 등이 가능하다. 인가에너지의 크기와 폭발 시 분위기를 제어함으로써 분말의 평균크기와 분포 제어 또한 가능하다. 본 연구는 러시아의 우수한 기초기술을 바탕으로 Pb-Sn계 합금은 전기폭발법으로 극미세분말을 제조하였으며, 분말의 형상, 상 화학조성의 변화를 조사하였다. 본 실험에 사용된 Sn-Pb계(All-Union State Standard 1499-70, 0.53mm)합금와이어는 자동시스템(1-0.6Hz)에 의해 챔버안으로 공급되었다. 이 때 임계폭발 와이어 길이는 50-80nm으로 실험을 행하였다. 챔버 압력은 1.4~2.0atm으로 유지하였다. 제조된 분말의 특성은 XRD, XRPES, SEM등을 이용하여 분말의 형상과 상, 화학조성, 표면분석을 행하였으며 DSC, TGA, BET분석을 통하여 온도변화에 따른 금속분말의 열량변화, 질량변화, 비표면적을 측정하였다. 제조된 Sn-Pb계 분말은 모두 평균 입도 117nm~220nm의 구형형상이었다. 이때 합금분말의 조성은 51.17~63.21 at%Sn, 35.47~46.37 at%Pb로 나타났다. 와이어에 인가되는 비에너지(W/Wc)가 감소된에 EK라 표면층의 Pb함량이 증가함을 보였다. 이는 와이어 내부 저항의 감소로 인한 공정시간의 지연과 Sn, Pb의 확산계수 차이에 의한 것으로 사료된다. 열분석 결과, Sn~Pb계 화합물의 융점은 167~$169^{\circ}C$로 관찰되었으며, $10^{\circ}C$/min로 $920^{\circ}C$까지 승은 하였을 때 17.1~18 wt%의 질량증가를 보였다.TEX>계 나노복합분말이 얻어짐을 알 수 있었다. 이 때 X션 회절피크의 line broadening으로부터 복합분말의 Fe 명균 결정립 크기는 24nm로 초미세 결정럽의 분말합금이었다. 포화자화값은 볼밀처리에 따라 점점 증가하여 MA 30시간에는 20.3emu/g로 포화됨을 알 수 있었다. 또한 보자력 Hc는 MA초기단계에 350e로 매우 낮으나 30시간 후에는 Hc값이 2600e로 매우 큰 값을 나타내었다. 이것은 환원반응결과 초기에 생성된 Fe의 결정립이 비교적 크고 결정결함이 적으나 볼밀처리를 30시간까지 행하면 Fe 결정렵의 미세화 빛 strain 증가로 magnetic hardening이 일어나기 때문인 것으로 사료된다.길이가 50, 30cm인 압출재를 제조하였다. 열간압출한 후의 미세조직을 광학현미경으로 압출방향에 평행한 방향과 수직방향으로 관찰하였고, 열간 압출재 이방성을 검토하기 위하여 X선 회절분석을 실실하여 결정방위를 확인하였다. 전기 비저항 및 Seebeck 계수 측정을 위하여 각각 2$\times$2$\times$10$mm^3$ 그리고 5$\times$5$\times$10TEX>$mm^3$ 크기의 시편을 준비하였다.준비하였다.전류를 구성하는 주요 입자의 에너지 영역(75~l13keV)에서 가장 높은(0.80) 상관계수를 기록했다. 넷째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰 자기폭풍일수록 현저했다. 주상에서 관측된 이러한 특성은 서브스톰 확장기 활동이 자기폭풍의 발달과 밀접한 관계가 있음을 시사한다.se that were all low in two aspects, named "the Nonsignificant group". And the issues were high risk perception in general setting and lo

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1040-1046
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• 2010

The main disadvantage of rapid setting concrete is the occurrence of cracking because of fast hydration reaction due to high thermal expansion and shrinkage. However, if the fly ash is used in concrete, it is possible to prevent cracking since the hydration heat can be decreased. Although Very-Early Strength-Latex Modified Concrete(VES-LMC) is an excellent material, occurrence of cracking has been reported because of high hydration heat. In the present study, new method which can apply the fly ash to the VES-LMC was developed. Research for the new method to improve the safety for the cracking was conducted. Safety was confirmed by reducing the shrinkage and hydration heat in the condition of overcoming the low early-age strength. Detailed conclusions are follows. Early-age compressive strength was decreased a little with increase of UFFA content. However, 28-d compressive strength was statistically insignificant regardless of UFFA contents. If the UFFA is replaced 15% to 20% of unit cement weight in concrete, maximum shrinkage can be reduced up to 43% to 47%. Usage of UFFA in VES-LMC guarantees the safety for cracking since it is very effective to control of early-age shrinkage.

• Resources Recycling
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• v.8 no.5
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• pp.34-43
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• 1999

An elecmc arc cracking reaclor is developed for the productiol~o f ieusuble fuel gas by the thennal destruction of waste oil. The churaclensucs of product gas and ~esiduesf rom arc crachng of wnste lubr~cat~nogil are sludird. Thc product gas is mainly coruposcd of hydrogen 135-4076), acetylene (13-4076), ethylene 13-476) and olher hgdrocnrbons. The contenr of carbon monomde, one or the main product in a conventional low-temperature Lhennal cracking umt, 1s very slnvll in lhis atc cracking expcnmcnt. Total calocctic wlue of product gas shows 11,000-13.000 kcizlkg, which is hiph cnough to use as a ~ L I I I Cga~ s . and the concentralions oC loxic gases arc well below the rcguliltury emission critena The GCIMS analysis of llquld-phase residues shows that the high rnalccular welgllt hydrocilrbons in the waste oil arc cracked into the low malecular weight hydrocarbons snd hydroem,. The dehydrogcnntion is found lo be Lhe main cracking rcacuon due lo the high temperalure ~ ~ ~ d ubcyc edle ctric arc. The average parucle size of soot as the solid-phase residue is 10 3 wm, and the conlents of cabon a ~ hdea vy metals are abovc 60% and under 0.01 ppm, respecttrely. Thc utllizvtion or sool, as industl-id1 rcsource seems lo he reasible aIter refimng.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.4
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• pp.436-443
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• 2019

Lyme disease is a national notifiable infectious disease as of September 2018. The number of cases of Lyme disease has recently been increasing. This study analyzed the epidemiological features and clinical symptoms of domestic and imported. From 2011 to December 31, 2018, of the 119 cases, 48 confirmed cases, 63 probable cases, and 8 suspected cases. 70 cases (58.8%) were reported in Korea and 49 cases (41.2%) of imported. In addition, 91 cases (76.5%) were reported during the summer~autumn season (June~November). In 2017, the highest number of 31 cases. The time needed to make a diagnosis was 2.8±14.7 days for domestic occurrences versus 1.4±4.5 days for those cases that infection occurred imported. Among the clinical symptoms, fever and rash were statistically significant (P<0.001). Clinical trials included early localized 31 cases (52.1%), early disseminated 43 cases (35.3%), and late disseminated 15 cases (12.6%). The estimated regions of infection in Korea were Chungnam 12 cases (17.1%), Gyeonggi 12 cases (17.1%), and Gangwon 8 cases (11.4%), Patient care is also considered to be very important as this disease occurs of all ages. Therefore, the promotion of preventive education and identification of epidemiological features are of paramount importance and should be implemented. The study's findings can be used as basic data for the prevention and management of patients with lyme disease.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.1046-1057
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• 2017

Country-specific emission factors should be developed and used instead of IPCC defaults to improve national GHG inventories to Tier 2 and above. Since the country-specific emission factors depend on the type of energy source, energy process, and time trend, identifying the value of each energy source is an important part of building an accurate inventory. In this study, calorific value and carbon emission factor for petroleum energy sources on the basis of calorific value conversion standard for energy source, which are notified in Korea, are collected by 2013 and 2016, and calorific value, carbon content and carbon emission factor And a comparative analysis was conducted. In addition, net calorific values and carbon emission factors calculated for each petroleum based energy source are compared with those shown in 2006 IPCC Guideline.

• Resources Recycling
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• v.13 no.4
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• pp.23-31
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• 2004

Basic studies have been conducted regarding the attempt of the utilization of waste Undaria pinnatifida as an adsorbent for the adsorption treatment of lead-containing wastewater. Undaria pinnatifida was found to be chiefly composed of hyo-carbonaceous compounds and have a fairly high specific surface area, which suggesting the possibility of its application as a Potential adsorbent. The electrokinetic Potential of Undaria pinnatifida particles was observed to be negatively highest at around pH 8 and the fact that its electrokinetic potentials are negative at the whole pH range supported it might be an efficient adsorbent especially for cationic adsorbates. Under the experimental conditions, $Pb^{2+}$ was found to mostly adsorb onto Undaria pinnatifida within a few minutes and reach the equilibrium in adsorption within ca. 30 minutes. The adsorption of $Pb^{2+}$ was exothermic and explained well by e Freundlich model. Acidic pretreatment of Undaria pinnatifida enhanced its adsorption capacity for $Pb^{2+}$ , however, the reverse was observed for alkaline pretreatment. The formation of organometallic complex between $Pb^{2+}$ and some functional groups on the surface of Undaria pinnatifida was considered to be one of the main drives for adsorption. Finally the adsorbability of$ Pb^{2+}$ was examined to be rather affected by several solution features such as the coexistence of other adsorbate, the variation of ionic strength, and the concentration of complexing agent.