• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.784-787
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• 2020

폐암 환자의 생존율을 예측할 때 미국암연합회(AJCC)의 TNM병기 분류체계에 의해 진단되는 최종병기를 많이 사용한다. 최종병기는 폐암환자의 임상데이터 중 하나로 종양의 위치, 크기, 전이정도를 고려하여 환자의 폐암 상태를 판별하는 정보이다. 최종병기는 개략적인 환자의 상황을 설명하는 데 효과적이지만, 보다 구체적인 생존분석을 위해서는 임상데이터 뿐만 아니라 PET/CT와 같은 영상 데이터를 함께 분석해야 한다. 이 논문에서는 데이터 과학적 접근을 통해 폐암환자의 임상데이터, CT영상과 PET영상 등 다양한 종류의 데이터를 함께 활용하는 생존분석기법을 검토한다. 실험을 통해 다중 모드 데이터를 활용하는 생존분석을 위해 비선형모델 개발과 Feature임베딩 기법 고도화가 필요함을 확인하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.110-110
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• 2016

금속재료 중 철강은 기계적 성질이 우수하고 대량생산에 의한 뛰어난 경제성을 가지기 때문에 다양한 산업 분야에서 널리 사용되고 있다. 그러나 스테인리스강 등과 같은 일부 특수한 용도의 강을 제외하고는 부식 환경에 취약하기 때문에 그 용도에 따라 표면처리를 함으로서 내식특성을 부여하고 있다. 일반적으로 이러한 철강재료에 대한 부식문제를 해결하기 위한 방법으로는 습식프로세스 중 아연(Zn)도금이 사용되는데, 아연은 그 자체가 보유하고 있는 차폐(barrier)효과는 물론 상대적으로 이온화 경향이 크기 때문에 철에 대하여 전자를 공급하는 희생양극적(Sacrificial anode)역할을 하여 철을 방식하는 원리를 가지고 있다. 하지만 최근에 이르러 기존의 도금 프로세스 처리된 제품의 사용 및 적용분야가 확대되고 가혹해 짐에 따라서 내식성 향상을 위한 새로운 재료 및 신기술 개발이 요구되고 있는 실정이다. 본 연구에서는 친환경 프로세스 방법인 PVD법 중 하나인 스퍼터링(Sputtering)을 이용하여 0.8mm 두께의 냉연강판 (cold rolled steel) 상에 Al에 대한 Mg 함량을 10~30wt.%로 하여 약 $5{\mu}m$ 두께의 막을 제작하였다. 이때 20wt.% 막의 경우 공정압력조건을 증가시켜 증착 막의 결정배향성을 변화시켰다. 뿐만 아니라 제작된 막들에 대해서 $400^{\circ}C$온도에서 10분간 열처리함으로서 코팅막의 성분변화에 따른 영향을 살펴보기 위해 시편을 추가 제작하였다. 이와 같이 제작된 막들에 대한 형성메커니즘과 내식성의 상관관계 해명을 위해 막의 조성분포, 표면 및 단면의 모폴로지 관찰 및 결정구조 등 재료특성분석과 더불어 염수분무(Salt spray test), 침지시험 그리고 양극분극 시험 등을 통해 내식성 평가를 진행하였다. 이상의 종합적인 결과를 살펴보면 제작된 Al-Mg 막은 마그네슘 함량비 및 열처리 조건에 따라 조성분포와 막의 모폴로지 및 결정배향성이 변화한다는 것을 알 수 있었는데, 마그네슘 함량이 증가하고 열처리한 막의 내식성이 가장 양호한 것으로 나타났다. 이것은 Al-Mg 성분이 표면을 중심으로 균일 분산-분포하며, Al에 대한 Mg의 고용으로 인해 안정적으로 형성된 부식생성물과 금속화합물의 단계적 반응 효과에 의해 차폐효과와 희생양극적 특성이 동시에 향상되었기 때문으로 생각된다. 한편 공정 압력을 증가시켜 형성한 막은 결정학적 구조에서 보다 높은 표면 에너지와 증가한 격자 정수에 의해 Mg이 부식환경에서 빠르게 반응하여 안정적 피막을 형성하기 때문에 내식성이 향상된 것으로 보여 진다. 이상의 연구를 통해서 고내식성을 Al-Mg막의 유효성 확인하였으며, 설계에 대한 기초적인 응용지침을 제시할 수 있을 것으로 사료된다.

• Resources Recycling
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• v.32 no.1
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• pp.50-59
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• 2023

The amount of dust generated during the dissolution of scrap in an electric arc furnace is approximately 1.5% of the scrap metal input, and it is primarily collected in a bag filter. Electric arc furnace dust primarily consists of zinc and ion. The processing of zinc starts with its conversion into pellet form by the addition of a carbon-based reducing agent(coke, anthracite) and limestone (C/S control). These pellets then undergo reduction, volatilization, and re-oxidation in rotary kiln or RHF reactor to recover crude zinc oxide (60%w/w). Next, iron is discharged from the electric arc furnace dust as a solid called Fe clinker (secondary by-product of the Fe-base). Several methods are then used to treat the Fe clinker, which vary depending on the country, including landfilling and recycling (e.g., subbase course material, aggregate for concrete, Fe-source for cement manufacturing). However, landfilling has several drawbacks, including environmental pollution due to leaching, high landfill costs, and wastage of iron resources. To improve Fe recovery in the clinker, we pulverized it into optimal -sized particles and employed specific gravity and magnetic force selection methods to isolate this metal. A carbon-based reducing agent and a binding material were added to the separated coarse powder (>10㎛) to prepare briquette clinker. A small amount (1-3%w/w) of the briquette clinker was charged with the scrap in an electric arc furnace to evaluate its feasibility as an additives (carbonaceous material, heat-generating material, and Fe source).

• Journal of the Korean Society for Railway
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• v.18 no.6
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• pp.552-557
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• 2015

Ballast gravel in a railroad field is often polluted by grease and heavy metals. In this paper, the performances of a dry cleaning method for polluted ballast gravel in which pollutants on the gravel surface can be physically removed was extensively studied. A polluted ballast cleaning device able to shoot emery blasting media onto the surface using compressed air was prepared. Polluted ballast gravel was put into this device for cleaning, with the treatment time varied from 1 to 10 min. The cleaning efficiency of the total petroleum hydrocarbons and heavy metals were studied. The total petroleum hydrocarbon removal efficiency was 70-80% for gravels sampled from a locomotive waiting line, while it was 40-60% for gravels sampled from a turnout area. The heavy metal removal efficiency exceeded 90% for copper and lead, while it was 65-80% for nickel and zinc. This system was found to be effective for the remediation of polluted ballast gravels.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.159-159
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• 2009

RF 스퍼터링법을 이용하여 유리기판위에 ZnO:Al 박막을 증착하고 다양한 조건 하에서 후 열처리를 실시하여 이에 따른 박막의 구조적, 전기적 및 광학적 특성과 HCl 습식 식각 후의 표면형상 변화를 조사하였다. ZnO:Al 투명전도막은 우수한 전기적, 광학적 특성, 수소 플라즈마 안정성 및 저 비용 등으로 실리콘 박막 태양전지 전면 전극용으로 많은 관심을 받고 있다. 기존의 비정질 실리콘 박막 태양전지용으로 많이 사용되고 있는 상용 Asahi-U형 ($SnO_2:F$) 투명전도막의 경우는 수소 플라즈마에 대한 안정성이 낮고 입사광의 장파장 대역에서의 낮은 산란특성으로 인하여 실리콘 박막 태양전지의 고효율화를 위한 적용에 한계를 나타내고 있다. 이를 개선하기 위하여 스퍼터링법으로 우수한 전기적 특성을 갖는 ZnO:Al 박막을 제조한 후 습식 식각을 통한 표면형상 변화를 통하여 입사광의 산란특성을 향상시키는 방법이 개발되어 많은 연구가 이루어지고 있다. 본 연구에서는 2.5 wt%의 $Al_2O_3$가 함유된 ZnO 타겟을 이용하여 ZnO:Al 박막을 RF 스퍼터링으로 증착한 후 $N_2$ 분위기와 진공 분위기 하에서 다양한 시간과 온도에 따라 후열처리를 하여 열처리 전 박막과의 물질 특성을 상호 비교하고 1%로 희석된 HCl로 습식 식각하여 열처리 전 박막의 구조적 특성이 습식 식각 후의 박막 표면형상 변화에 미치는 영향을 조사하였다. 이로부터 후열처리를 통한 ZnO:Al 투명전도막의 특성을 최적화하고 Asahi-U형 투명전도막과의 특성 비교를 통하여 실리콘 박막 태양전지용 전면전극으로의 적용 가능성을 조사하였다.

• Journal of Applied Biological Chemistry
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• v.54 no.4
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• pp.290-295
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• 2011

This study was carried out to investigate the quality of soil, irrigation water, and status of agrochemicals application in relation to good agriculture practices system in the major cultivation area of Disocorea batatas. The concentrations of heavy metals as Cd, Pb, Cu, and Zn in soils and irrigation waters were lower than those of standard level for Environmental Conservation Act of Soil and Water in Korea. The dominant weed have been appeared Digitaria sanguinalis and Portulaca oleraceamite. The dominant insect pests and plant pathogens have been appeared aphid and anthracnose. Average yearly application of pesticide was 2 to 4 times for herbicide and 4 to 6 times for plant pathogens and insect pests. In order to safety production of medicinal crops could be achieved by proper cultivation management such as minimum application of agro-chemicals, effective use of by-product fertilizer, and technology development of organic farming.

• Environmental and Resource Economics Review
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• v.13 no.4
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• pp.735-761
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• 2004

As a possible alternative to Traditional Discounted Cash Flow Method, "Option Pricing Model" has drawn academic attentions for the last a few decades. However, it has failed to replace traditional DCF method practically due to its mathematical complexity. This paper introduces an option pricing valuation model specifically adjusted for the natural resource development projects. We add market information and industry-specific features into the model so that the model remains objective as well as realistic after the adjustment. The following two features of natural resource development projects take central parts in model construction; product price is a unique source of cash flow's uncertainty, and the projects have cost structure from capital-intense industry, in which initial capital cost takes most part of total cost during the projects. To improve the adaptability of Option Pricing Model specifically to the natural resource development projects, we use Two-Factor Model and Long-term Asset Model for the analysis. Although the model introduced in this paper is still simple and reflects limited reality, we expect an improvement in applicability of option pricing method for the evaluation of natural resource development projects can be made through the process taken in this paper.

• Journal of Applied Biological Chemistry
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• v.58 no.1
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• pp.39-50
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• 2015

Stabilization of heavy metals such as Pb, Cd, Zn, and Cu was evaluated in contaminated soil treated with poultry manure (PM) as well as its biochars pyrolyzed at $300^{\circ}C$ (PBC300) and $700^{\circ}C$ (PBC700) at the application rates of 2.5, 5.0, and 10.0 wt% along with the control, prior to 21-days incubation. After incubation, soil pH was increased from 6.94 (control) to 7.51, 7.24, and 7.88 in soils treated with PM 10 wt%, PBC300 10 wt%, and PBC700 10 wt% treatments, respectively, mainly due to alkalinity of treatments. In the soil treated with PM, the concentrations of the toxicity characteristic leaching procedure (TCLP)-extractable Pb, Cd, Zn, and Cu were increased by up to 408, 77, 24, and 955%, respectively, compared to the control. These increases may possibly be associated with an increased dissolved organic carbon concentration by the PM addition. However, in the soil treated with PBC700, TCLP-extractable Pb, Cd, Zn, and Cu concentrations were reduced by up to 23, 38, 52, and 36%, respectively, compared to the control. Thermodynamic modelling using the visual MINTEQ was done to predict the precipitations of $Pb(OH)_2$, $Cu(OH)_2$ and P-containing minerals, such as chloropyromorphite [$Pb_5(PO_4)_3Cl$] and hydroxypyromorphite [$Pb_5(PO_4)_3OH$], in the PBC700 10 wt% treated soil. The SEM-elemental dot mapping analysis further confirmed the presence of Pb-phosphate species via dot mapping of PBC700 treated soil. These results indicate that the reduction of Pb concentration in the PBC700 treated soil is related to the formations of chloropyromorphite and hydroxypyromorphite which have very low solubility.

• Membrane Journal
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• v.30 no.3
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• pp.158-172
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• 2020

In the aspect of saving energy and water, facilitating the separation membrane for the water treatment has been rising recently as one of the possible solutions. However, microbial biofouling effect is the biggest obstacle that hinders reaching higher permeability over a prolonged period of nanofiltration operation. To solve this problem and fully utilize the filtration membranes with enhanced performance, largely two kinds of solutions are studied and the first and the most commonly mentioned type is the one using the silver nanoparticles. Since silver nanoparticles are important to be well tailored on membrane surface, various methods have been applied and suggested. Using silver nanoparticles however also has the drawbacks or possible toxicity risks, raising the need for other types of utilizing non silver particles to functionalize the membrane, such as copper, graphene or zinc oxides, and amine moieties. Each attempt included in either kind has produced some notable results in killing, preventing, or repelling the bacteria while at the same time, left some unsolved points to be evaluated. In this review, the effects of metal nanoparticles and other materials on the antifouling properties of water treatment membranes are summarized.

• Resources Recycling
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• v.33 no.1
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• pp.15-21
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• 2024

The demand for electric vehicles powered by lithium-ion batteries is continuously increasing. Recovery of valuable metals from waste lithium-ion batteries will be necessary in the future. This research investigated the effect of reaction temperature on the lithium recovery ratio from hydrogen reduction followed by water leaching from lithium-ion battery NCM-based cathode materials. As the reaction temperature increased, the weight loss ratio observed after initiation increased rapidly owing to hydrogen reduction of NiO and CoO; at the same time, the H₂O amount generated increased. Above 602 ℃, the anode materials Ni and Co were reduced and existed in the metallic phases. As the hydrogen reduction temperature was increased, the Li recovery ratio also increased; at 704 ℃ and above, the Li recovery ratio reached a maximum of approximately 92%. Therefore, it is expected that Li can be selectively recovered by hydrogen reduction as a waste lithium-ion battery pretreatment, and the residue can be reprocessed to efficiently separate and recover valuable metals.