• Composites Research
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• v.29 no.5
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• pp.282-287
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• 2016

p-DCPD (poly dicyclopentadiene) is the resin that the versatile mechanical properties can be changeable via the control of inner monomer and catalysts. In this work, to improve the strength of composites, surface treated MGF (milled glass fiber) was used as an reinforcement in p-DCPD by molybdenum (Mo) catalyst matrix. The optimum concentration of surface treatment was obtained and the cohesion of MGF themselves increased with concentration. In case of 0.2 wt% silane concentration, the maximized mechanical properties of MGF/p-DCPD composite exhibited because of minimized MGF cohesion. When butyl silane showing minimizing cohesion was used as the optimized alkyl length, high tensile and flexure strength exhibited due to the steric hindrance effect among MGFs. Mechanical and their fractured surfaces of MGF/p-DCPD composites was compared for 4 different chemical functional groups. Norbornene functional groups containing similar chemical structure to DCPD matrix exhibited higher interfacial adhesion between MGFs and DCPD matrix.

• Economic and Environmental Geology
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• v.41 no.3
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• pp.287-297
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• 2008

In order to estimate the preliminary development feasibility according to the commodity, the content of 8 strategic metallic commoditites(Pb, Zn, Cu, Fe, Mo, W, Au, U) in 68 ore specimens obtained from 34 metallic mines within the Taebaegsan-Hwanggangri mineralized zone were analyzed. Analytical results are as follows. The ore specimen of Sangdong mine contained 23% copper(cut-off grade=0.7%) and those of Cheongil and Samhwanghak mines contained average 5% zinc(cut-off grade=2.0%). Especially, the detailed investigation on the above-mentioned mines is required. And, in case of molybdenum(cut-off grade=0.02%) content in Yeonhwa No. 2(0.04%) and Hong-cheon mine(0.02%), and lead(cut-off grade=0.58%) content in Wongasa mine(0.70%), and gold(cut-off grade=10ppm) content in Dongmyoung(279ppm) and Samhwanghak mine(251ppm), it is required to elastically carry out the revaluation on reopening of mines in terms of the international metal price. On the other hand, in case of uranium, iron and tungsten, it is thought that there are no mines with the development potential value in this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.163-163
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• 2011

셀레늄(Selenium: Se) cracker cell을 이용하여 셀렌화한 $CuInSe_2$ (CIS)박막에 대해 연구한 결과를 발표하고자 한다. 화석연료의 과도한 사용으로 지구온난화라는 환경문제가 대두되면서 영구적이고 무상의 태양에너지 이용에 대한 필요성이 점차 높아지고 있다. 빛에너지를 전기에너지로 변화시키기 위한 태양전지는 재료에 따라 다양하게 개발되고 있으며 그 중 가장 주목을 받고 있는 것 중의 하나가 $CuInSe_2$을 광흡수층으로 하는 CIS 박막 태양전지이다. CIS 박막은 태양전지의 광흡수층으로 사용되는데 직접천이형 밴드구조를 가지고 있고, 약 $10^5$ $cm^{-1}$의 높은 광흡수계수를 가지고 있어 태양전지 광흡수층으로 적합한 물질로 각광받고 있다. CIS는 에너지 밴드갭이 ~1 eV로 실리콘과 유사한 밴드갭을 가지고 있으나 이는 Ga, Al을 In 대신 치환함으로 조절할 할 수 있다. 무엇보다도 sodalime 유리와 같은 저가의 기판위에 스퍼터와 같은 장치로 대면적 CIS 박막태양전지를 만들 수 있다는 것이 산업적인 면에서 장점으로 알려져 있다. 본 연구에서는 sodalime 유리기판 위에 스퍼터 방법으로 CIS 박막을 증착하고 Se cracker cell로 셀렌화하여 CIS 박막을 제조하는 것을 조사연구 하였다. 스퍼터를 이용하여 유리기판위에 Mo (Molybdenum)을 증착하고 그 위에 Cu-In-Se박막을 증착하였다. Cu-In-Se/Mo/유리기판 시료는 동일 챔버에서 Se cracker cell을 이용하여 셀렌화 처리 하였다. 물성비교를 위하여 Knudson-cell을 이용한 셀렌화도 시행하였다. Se cracker cell은 고체 Se를 가열하는 부분(R-zone)과 Se flux를 cracking 하는 부분(C-zone)으로 나누어져 있으며 C-zone은 700$^{\circ}C$로 고정하였다. 셀렌화 기판 온도는 425$^{\circ}C$로 고정하였고 Se cracker 온도는 330~375$^{\circ}C$까지 변화시켜 가며 CIS 박막을 제조하였다. 제조된 CIS 박막의 물성 조사는 사진, 현미경, SEM, EDX, XRD, Hall effects를 이용하였다. Se cracker cell로 셀렌화한 CIS 박막은 island 구조를 하고 있음을 알 수 있었다. CIS 박막의 island의 크기와 모양은 셀렌화시 R-zone 온도(Cu-In-Se 박막에 조사되는 셀레늄의 량)에 큰 영향을 받았다. 셀렌화시 셀레늄량이 적을 때는 island가 커지며 불균일해지고 셀레늄량이 많을 때 island가 작고 균일해지는 경향을 SEM을 통해 관찰할 수 있었다. X-ray 회절을 통해 셀레늄량이 적을 경우 CIS 결정이외의 결정이 박막내에 형성됨을 알 수 있었다. 학술회의에서 Se cracker cell을 이용한 셀렌화에 관한 보다 깊은 연구결과를 발표하고자 한다.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.126-130
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• 2023

In response to environmental demands, pyrolysis is one of the practical methods for obtaining reusable oils from waste plastics. However, the waste plastic pyrolysis oils (WPPO) are consumed as low-grade fuel oil due to their impurities. Thus, this study focused on the upgrading method to obtain naphtha catalytic cracking feedstocks from WPPO by the hydroprocessing, including hydrotreating and hydrocracking reaction. Especially, various transition metal sulfides supported catalysts were investigated as hydrotreating and hydrocracking catalysts. The catalytic performance was evaluated with a 250 ml-batch reactor at 370~400 ℃ and 6.0 MPa H₂. Sulfur-, nitrogen-, and chlorine-compounds in WPPO were well eliminated with nickel-molybdenum/alumina catalysts. The NiMo/ZSM-5 catalyst has the highest naphtha yield.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.103-109
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• 2006

A target for a high-brightness microfocus x-ray tube, which is based on carbon nanotubes (CNT) as electron source, is designed. The x-ray tube has the following specifications: brightness of $1\times10^{11}phs/s.mm^2. mrad^2$, spot size $\~5{\mu}m$, and average x-ray energy of $20\~40 keV$. In order to meet the specifications, the design parameters of the target, such as configuration, material, thickness of the target as well as the required beam current, were optimized using computer code MCNPX. The design parameters were determined from the calculation of both x-ray spectrum and intensity distribution for a transmission type configuration. For the thin transmission type target to withstand vacuum pressure and localized thermal loading, the structural stability and temperature distribution were also considered. The material of the target was selected as molybdenum(Mo) and the optimized thickness was $7.2{\mu}m$ to be backed by $150{\mu}m$ beryllium (Be). In addition, the calculations revealed that the maximum temperature of the transmission target can be maintained within the limits of stable operation.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.595-600
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• 2016

The diagnostic multileaf collimator(MLC) was designed for patient dose reduction in diagnostic radiography We used monte carlo simulation code (MCNPX, LANL, USA) to evaluate efficiency of shielding material for making diagnostic MLC as preliminary study. The diagnostic radiography unit was designed using SRS-78 program according to tube voltage (80,100,120 kVp) and acquired energy spectrums. The shielding material was SKD11 alloy tool steel that is composed of 1.6% carbon(C), 0.4% silicon(Si), 0.6% manganese (Mn), 5% chromium (Cr), 1% molybdenum(Mo) and vanadium(V). The density of it was $7.89g/cm^3$.Using tally card 6, we calculated the shielding efficiency of MLC according to tube voltage. The results was that 98.3% (80 kVp), 95.7 %(100 kVp), 93.6% (120 kVp). We certified efficiency of diagnostic MLC fabricated from SKD11 alloy steel by monte calro simulation. Based on the results, we designed the diagnostic MLC and will develop the diagnostic MLC for reduction of patient dose in diagnostic radiography.

• Economic and Environmental Geology
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• v.42 no.4
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• pp.301-314
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• 2009

The Taebaeksan mineralized province, which is the most important one in South Korea, is rich in zinc-lead-tungsten-iron-copper-molybdenum-silver-gold mineral resources and has a diversity of deposit styles. These deposits principally coexist in time and space with porphyry-related epigenetic deposit such as skarn, hydrothermal replacement, mesothermal vein, and Carlin-like deposits. The magmatic-hydrothermal systems in the Taebaek fold belt is genetically characterized by the Bulguksa subvolcanic rocks(ca. $110{\sim}50\;Ma$) related to northwestward subduction of the paleo-Pacific Plate. The most important zinc-lead deposits in the area are the Uljin, Yeonhwa II and Shinyemi skarn, the Janggun hydrothermal replacement, and the Yeonhwa I intermediate-mixed (skarn/hydrothermal replacement) ones. In the present study, we present a compilation of metal production and mineral assemblage of the zinc-lead deposits. The metal difference of deposit styles in the area indicates a cooling path from intermediate-sulfidation to low-sulfidation state in the polymetallic hydrothermal system, reflecting spatial proximity to a magmatic source.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.11-22
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• 2014

The buffer capacity of food waste lowers during the collecting and transportation period. Food waste usually shows deficiency of micro nutrients especially molybdenum(Mo) and cobalt(Co). Therefore, food waste can be considered as a good mixture of livestock waste to enhance methane production. The objective of this study was to investigate the correlation between properties of substrates (local food waste and livestock manure) and methane yields for successive anaerobic fermentation process and its stable management. Food wastes were taken at an intermediate storage or treatment system provided by eight local authorities (Gangnam, Gangdong, Gwanak, Guro, Dongjak, Songpa, Yeongdeungpo, and Younsan) in Seoul. The solid content and potential methane yield of food wastes were average of 16% and $446.6STP-m{\ell}/g-VS$ (range from 334.8 to $567.5STP-m{\ell}/g-VS$) respectively. As for the beef cattle manure, the solid content and potential methane yield had an average of 26% and $280.6STP-m{\ell}/g-VS$ respectively. Potential methane yield had a positive correlation with fat content, and hydrogen content and a negative correlation with carbohydrate content ($r^2>0.8$). Therefore, the potential methane yield can be predicted based on the substrate characterization results with reasonable accuracy. Further research may be needed to investigate the relation of the properties of the mixture substrate and methane production rate. The mixtures may include food waste, livestock waste, and bulking agents (saw dust, rice hull, or agricultural byproducts etc.) to determine best combination of these substrates for maximum methane production rate.

• Journal of Environmental Health Sciences
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• v.44 no.1
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• pp.55-62
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• 2018

Objectives: This study set out to measure the heavy metal concentrations in waste water produced in the casting pickling process at dental technical laboratories and examine the actual state of its treatment. Methods:The investigator measured the concentrations of each heavy metal at 55 dental technical laboratories using an inductively coupled plasma optical emission system. Results: The annual usage of electrolytes was under 10 L in 50 (90.9%), and was 10L or more in five (9.1%) laboratories. Among the laboratories, 15 (27.3%) commissioned the treatment of waste,12 (21.8%) treated the waste with general sewage,and 28 (50.9%) treated the waste in aseptic tank. The arithmetic $mean{\pm}standard$ deviation and the geometric mean of chrome(Cr) were $75.3{\pm}50.9$ and 58.3 mg/L; those of cobalt (Co) were $112.3{\pm}106.7$ and 66.1 mg/L; those of nickel (Ni) were $62.9{\pm}83.5$ and 8.9 mg/L; those of molybdenum (Mo) were $17.1{\pm}13.4$ and 12.0 mg/L; those of iron (Fe) were $31.5{\pm}44.1$ and 6.2 mg/L; those of lead (Pb) were $0.3{\pm}0.3$ and 0.3 mg/L; those of beryllium (Be) were $3.6{\pm}3.6$ and 2.0 mg/L. The hydrogen ion concentration was under pH 2 across all the samples. Conclusions: The findings show that the dental technical laboratories were not doing well with the separation, storage, collection, and treatment of the electrolytes they discarded, and that most of the electrolytes were introduced through the general sewage or aseptic tank. The causes of this include alack of perception among the practitioners at dental technical laboratories and contracted companies avoiding collection for economic reasons. There is a need for education to improve the perceptions of waste water treatment among the practitioners at dental technical laboratories. Environment-related departments should be stricter with legal applications in the central and local governments. It is also required to provide proper management of commissioned treatment.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.244-252
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• 2019

This study investigated the effect of addition of aromatics such as Toluene/LCO/resin on the coke depression and asphaltene conversion. The experiment was carried out with vacuum residue as a feedstock with Molybdenum dispersed catalysts under the slurry-phase hydrocracking condition (Temp. of $425^{\circ}C$, $H_2$ pressure of 80 bar at $80^{\circ}C$, reaction time of 4 hr, Mo-concentration of 500 ppm). As results, the coke reduction was shown to be similar irrespective of types of aromatics, while asphaltene was more converted to gas and maltene when LCO and resin with higher dipole moment were added. The addition of aromatics with change of reaction time showed no difference in terms of depression of coke formation. But the addition of LCO rather increased the coke yield after 2 hr. And it was found that asphaltene in liquid phase had the higher aromaticity index so that asphaltene is difficult to disperse in oil phase.