• 한국미생물·생명공학회지
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• 제13권2호
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• pp.115-118
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• 1985

리파마이신 B 산화효소의 활성을 갖고 있는 Humicola spp. (ATCC 20620)를 아세톤 처리 한 후 cellulose acetate로 고정화하여 그 특성을 조사하였다. 고정화 효소에 있어서 pH는 7.2온도는 50-55%에서 최대 활성을 보였으며, 비고정화 효소에 비하여 pH와 온도변화에 덜 민감하였다. 외경 3mm bead size에서 20%의 활성회수율을 보였으며, storage stability는 4$0^{\circ}C$ 이하에서는 아주 좋았으며 5$0^{\circ}C$ 이상에서는 급격히 활성이 감소하였다. 고정화 담체로서 cellulose acetate는 물리적으로 견고하여 삼상반응기의 packing material로써 적당하였다.

• Journal of Periodontal and Implant Science
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• 제32권1호
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• pp.161-172
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• 2002

The present study evaluated the effects of guided tissue regeneration using xenograft material(deproteinated bovine bone powder), with and without biodegradable membrane in beagle dogs. Contralateral fenestration defects (6 ${\times}$ 4mm) were created 4 mm apical to the buccal alveolar crest of maxillary premolar teeth in 5 beagle dogs. Deproteinated bovine bone powders were implanted into fenestration defect and one randomly covered biodegradable membrane (experimental group). Biodegradable membrane was used to provide GTR. Tissue blocks including defects with soft tissues which were harvested following four & eight weeks healing interval, prepared for histo-phathologic analysis. The results of this study were as follows. 1. In control group, at 4 weeks after surgery, new bony trabecular contacted with interstitial tissue and osteocytes like cell were arranged in new bony trabecule. Bony lamellation was not observed. 2. In control gruop, at 8 weeks after surgery, scar-like interstitial tissue was filled defect and bony trabecule form lamellation. New bony trabecular was contacted with interstitial tissue but defect was not filled yet. 3. In experimental group, at 4 weeks after surgery, new bony trabecular partially recovered around damaged bone. But new bony trabecular was observed as irregularity and lower density. 4. In experimental group, at 8 weeks after surgery, lamella bone trabecular developed around bone cavity and damaged tissue was replaced with dense interstitial tissue. In conclusion, new bone formation regenerated more in experimental than control groups and there was seen observe more regular bony trabecular in experimental than control groups at 4 weeks after surgery. In control group, at 8 weeks after surgery, the defects was filled with scar-like interstitial tissue but, in experimental group, the defects was connected with new bone. Therefore xenograft material had osteoconduction but could not fill the defects. We thought that the effective regeneration of periodontal tissue, could be achieved using GTR with biodegradable membrane.

• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.319-324
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• 2002

In this study, the reduce of plasma etching damage in PZT thin film with addictive gas and re-annealing after etching have been investigated. The PZT thin films were etched as a function of $Cl_2/CF_4$ with addition of Ar and $O_2$ with inductively coupled plasma. The etch rates of PZT thin films were 1450 ${\AA}/min$ at 30% additive Ar and 1100 ${\AA}/min$ at 10% auditive $O_2$ into $Cl_2/CF_4$ gas mixing ratio of 8/2. In order to reduce plasma damage of PZT thin films after etching, the etched PZT thin films were re-annealed at various temperatures at $O_2$ atmosphere. From the hysteresis curries, the ferroelectric properties are improved by $O_2$ re-annealing process. The improvement of ferroelectric behavior at annealed PZT films is consistent wish the increase of the (100) and (200) PZT peaks revealed by x-ray diffraction (XRD). From x ray photoelectron spectroscopy (XPS) analysis, the intensity of Pb-O, Zr-O and Ti-O peak are increased and the chemical residue peak is reduced by $O_2$ re-annealing. The ferroelectric behavior consistent with the dielectric nature of $Ti_xO_y$ is recovered by $O_2$ recombination during rapid thermal annealing process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.21-25
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• 2001

In this study, recovery of plasma etching damage in PZT thin film with additive gas and re-annealing after etching have been investigated. The PZT thin films were etched as a function of Cl$_2$/CF$_4$ with addition of Ar and $O_2$ with inductively induced plasma. The etch rates of PZT thin films were 1450$\AA$/min at 30% additive Ar into (Cl$_2$(80%)+CF$_4$ (20%)) and 1100$\AA$/min at 10% additive $O_2$ into C(Cl$_2$(80%)+CF$_4$ (20%)). In order to recovery properties of PZT thin films after etching, the etched PZT thin films were re-annealed at various temperatures in at $O_2$ atmosphere. From the hysteresis curves, ferroelectrical properties are improved by $O_2$ re-annealing process. The improvement of ferroelectric behavior at annealed sample is consistent with the increase of the (100) and (200) PZT peaks revealed by x-ray diffraction (XRD). From x-ray photoelectron spectroscopy (XPS) analysis, intensity of Pb-O, Zr-O and Ti-O peak are increased and the chemical residue peak is reduced by $O_2$ re-annealing. The ferroelectric behavior consistent with the dielectric nature of Ti$_{x}$O$_{y}$ is recovered by $O_2$ recombination during rapid thermal annealing process.s.s.

• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.245-248
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• 2020

The wettability of silicon carbide (SiC) crystal, which has 6H-SiC and 4H-SiC regions prepared using the physical vapor transport (PVT) method, is quantitatively analyzed using dispensed deionized (DI) water droplets. Regardless of the polytypes in SiC, the average of five contact angle measurements showed a difference of about 6° between the Si-face and C-face. The contact angle on the Si-face (C-face) is measured after the removal of the native oxide using BOE (6:1), and revealed a significant decrease of the contact angle from 74.9° (68.4°) to 47.7° (49.3°) and from 75.8° (70.2°) to 51.6° (49.5°) for the 4H-SiC and 6H-SiC regions, respectively. The contact angle of the Si-face recovered over time during room temperature oxidation in air; in contrast, that of the C-face did not recover to the initial value. This study shows that the contact angle is very sensitive to SiC surface polarity, specific surface conditions, and process time. Contact angle measurements are expected to be a rapid way of determining the surface polarity and wettability of SiC crystals.

• 자원리싸이클링
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• 제11권3호
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• pp.10-16
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• 2002

폐리튬이온전지로부터 추출한 $LiCoO_2$의 침출에서 황산, 질산과 같은 강산은 Co와 Li을 완전 용해시키므로 Co와 Li을 분리하여 회수하기 위해서는 별도의 공정이 필요하다. 낮은 pH에서 Co oxalate의 용해도가 낮다는 점을 착안한 oxalic acid 침출에서 양극활물질로부터 Co를 선택적으로 회수하는 연구를 수행하였다. 변수실험으로 도출된 최적조건, oxalic acid 3M, 침출온도 $80^{\circ}C$, 초기 광액농도 50g/L.의 조건에서 순수한 $LiCoO_2$를 침출한 결과, Li이 95% 이상 용해되는 반면에 Co는 1% 이하의 침출율을 나타내었다. 같은 침출조건에서 폐리튬이온전지로부터 선별한 양극활물질을 침출한 결과, Co와 Li의 침출율은 각각 0.25%, 99%로 높은 선택성을 보였다. 용액 중에 잔류하는 Li은 $Na_2$$CO_3$혹은 LiOH을 첨가하여 Li 탄산염 흑은 Li 수산화물의 형태로 회수할 수 있다.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.308-320
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• 2022

The high internal resistance (R_int) that develops across the sediment microbial fuel cells (SMFC) limits their power production (~4/10 mW m^-2) that can be recovered from an initial oil-contaminated sediment (OCS). In the anolyte, R_int is related to poor biodegradation activity, quality and quantity of contaminant content in the sediment and anode material. While on the catholyte, R_int depends on the properties of the catholyte, the oxygen reduction reaction (ORR), and the cathode material. In this work, the main factors limiting the power output of the SMFC have been minimized. The power output of the SMFC was increased (47 times from its initial value, ~4 mW m^-2) minimizing the SMFC R_int (28 times from its initial value, 5000 ohms), following the main modifications. Anolyte: the initial OCS was amended with several amounts of gasoline and kerosene. The best anaerobic microbial activity of indigenous populations was better adapted (without more culture media) to 3 g of kerosene. Catholyte: ORR was catalyzed in birnessite/carbon fabric (CF)-cathode at pH 2, 0.8M Na₂SO₄. At the class level, the main microbial groups (Gammaproteobacteria, Coriobacteriia, Actinobacteria, Alphaproteobacteria) with electroactive members were found at C-anode and were associated with the high-power densities obtained. Gasoline is more difficult to biodegrade than kerosene. However, in both cases, SMFC biodegradation activity and power output are increased when ORR is performed on birnessite/CF in 0.8 M Na₂SO₄ at pH 2. The work discussed here can focus on bioremediation (in heavy OCS) or energy production in future work.

• 한국결정성장학회지
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• 제32권2호
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• pp.61-67
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• 2022

폐리튬이차전지 스크랩으로부터 회수한 유가금속인 니켈, 코발트, 망간을 정제하여 제조한 리튬이차전지 전구체 금속염 용액으로 테일러반응을 통해 NCM 811 전구체를 제조하였다. 반응 시간에 따른 전구체 형태 변화를 SEM, PSA, ICP 분석 결과를 기반으로 합성 조건을 확립하였다. 이에 상업용 전구체와 재활용하여 합성한 전구체의 전기 화학적 특성인 충·방전 특성, 율특성, 수명특성 등을 평가하여 비교 연구하였으며, 상업용 전구체와 비교 시 큰 차이가 없거나 일부 특성에서는 우수한 특성을 확인할 수 있었다.

• 열처리공학회지
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• 제36권1호
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• pp.22-32
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• 2023

In general, when scrap is dissolved in an electric arc furnace, the amount of electric furnace steel dust (EAFD) generated is about 1.5% of the scrap charge amount, and the electric furnace steel dust collected by the bag filter is charged into the Rotary Kiln or Rotary Hearth Furnace (RHF), and the zinc component is recovered as crude zinc oxide, at which time a clinker of Fe-Base is generated. In this research, first, for the efficient resource conversion of electric furnace steel dust, a reduction and roasting experiment was conducted and the reaction kinetics was examined. As a result of the experiment, it was observed that the reduction and roasting reaction was actively conducted in the range of 1100~1150℃, and melting occurred in the range of 1250℃. In the past, this clinker was widely used as a roadbed material for road construction and an Fe-Source for cement production, but in recent years, it has been mainly reclaimed due to strengthening environmental standards. However, landfill treatment is by no means a desirable treatment method due to environmental pollution caused by leachate, expensive landfill costs, and waste of Fe resources. Therefore, in order to more actively recycle the Fe component in the clinker, first of all the clinker was pulverized into an optimal particle size, and anthracite and binder (starch) were added to the magnetic material obtained by specific gravity and magnetic separation for briquet. As a experimental results, it was possible to efficiently separate clinker as Fe component and other slag component by specific gravity and magnetic force. As a results of loading and dissolving the manufactured briquet clinker in an electric arc furnace, it was observed that the unit of power and production yield were clearly improved and the carbon addition effect in molten metal was also somewhat.

• KIEAE Journal
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• 제15권1호
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• pp.103-109
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• 2015

Recently, the usage of renewable energy system has been recommended because of the energy saving and depletion of fossil fuel. Especially, ground source heat pump system(GSHP) has a high efficiency by using annual stable ground temperature. Also, wood pellet is low cost and a high calorific value compared to fossil fuel. However, only small number of farms have applied renewable energy system to horticultural facility because of a high initial costs and uncertainty of its cost efficiency. In this study, in order to analyze the feasibility for the horticulture, TRNSYS simulation based on the standard horticultural facility was conducted in different weather and covering material conditions. Then, comparative feasibility analysis of each energy supplying system was conducted. As a result, we have found out that a high initial cost of renewable energy system was recovered by the economics of the energy cost. Due to the energy cost reduction, the payback periods were 10-11 years in the case of GSHP and 4-6 years in the case of wood pellet boiler.