• Journal of Welding and Joining
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• 제32권3호
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• pp.74-80
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• 2014

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from their devices and system. Especially, reliability issue of lead-free solder joint is increasing in car electronics due to ELV (End-of-Life Vehicle) banning from 2016. We have prepared engine control unit (ECU) modules soldered with Sn-40Pb and Sn-3.0Ag-0.5Cu (SAC305) solders, respectively. Degradation characteristics of solder joint strength were compared with various conditions of automobile environment such as cabin and engine room. Thermal cycle test (TC, $-40^{\circ}C$ ~ ($85^{\circ}C$ and $125^{\circ}C$), 1500 cycles) were conducted with automotive company standard. To compare shear strength degradation rate with eutectic and Pb-free solder alloy, we measured shear strength of chip components and its size from cabin and engine ECU modules. Based on the TC test results, finally, we have known the difference of degradation level with solder alloys and use environmental conditions. Solder joints degradation rate of engine room ECU is superior to cabin ECU due to large CTE (coefficient of thermal expansion) mismatch in field condition. Degradation rate of engine room ECU is 50~60% larger than cabin room electronics.

• 한국지반환경공학회 논문집
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• 제23권12호
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• pp.33-39
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• 2022

본 논문은 터널을 구성하고 있는 구성요소(지보재, 주변지반)들의 열화로 인한 터널의 장기거동을 수치해석을 이용하여 예측/분석하였다. 터널의 구성요소들은 시간이 지남에 따라 열화를 겪게 된다. 이러한 열화로 인해 터널의 장기적인 안정성을 예측하는 것은 매우 중요한 이슈이다. 따라서 본 연구에서는 열화를 예측하는 모델을 제시하였으며, 이 모델은 두 개의 파라미터로 구성되어 있다. 그 중 하나는 부재 및 주변지반의 열화로 인해 남아있는 잔류강도를 나타내며, 나머지 하나는 열화되는 모양을 표시한다. 제안한 열화 모델을 이용하여 수치해석을 수행하여 터널의 장기거동을 예측하였다. 그 결과 열화로 인해 터널 주변 지반의 이완응력이 증가하여 터널의 장기적인 안정성에 영향을 미치고 있음을 알 수 있었다.

• 대한환경공학회지
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• 제32권7호
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• pp.649-655
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• 2010

본 연구에서는 난분해성 물질인 페놀을 초음파와 자외선 광선(UV-C)을 이용하여 분해를 알아본 연구이다. 초음파, 자외선, 그리고 초음파와 자외선의 결합반응에서 주파수, 온도, 용액의 pH, 아르곤 가스 purging, 그리고 자외선 세기의 효과를 조사하였다. 초음파 단독 반응의 경우 pH 4, $5^{\circ}C$, 35kHz에서 360분 동안 30%의 페놀의 최적 분해효율을 보였다. 자외선(UV-C) 단독 반응의 경우 $19.3\;mW/cm^2$의 자외선 세기와 pH 4, $5^{\circ}C$에서 60분에 100%의 페놀 분해 효율을 보였다. 이에 반하여 초음파와 자외선의 결합반응에서는 동일 조건에서 45분 동안 페놀이 모두 제거되었다. 초음파와 자외선의 결합 반응에서 페놀은 자외선 강도가 $7.6\;mW/cm^2$일 때 360분 안에 $19.3\;mW/cm^2$일 때는 45분 안에 완전히 분해되었고, 각각의 분해 속도 상수는 $17.3{\times}10^{-3}\;min^{-1}$와 $138.1{\times}10^{-3}\;min^{-1}$이었다. 페놀의 분해반응에서 OH 라디칼의 scavenger로 작용하는 메탄올을 첨가하는 실험을 한 결과 초음파와 자외선 광선의 조합반응에서 페놀 분해의 주요인자는 OH 라디칼이라는 것을 확인할 수 있었다. 페놀 분해의 반응효율 비교는 초음파 + 광반응 조합반응 > 자외선 광선 단독 반응 > 초음파 단독 반응과 같이 확인되었다.

• Journal of Microbiology and Biotechnology
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• 제28권2호
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• pp.330-337
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• 2018

Polycyclic aromatic hydrocarbons (PAHs), including naphthalene, are widely distributed in nature. Naphthalene has been regarded as a model PAH compound for investigating the mechanisms of bacterial PAH biodegradation. Pseudomonas sp. AS1 isolated from an arseniccontaminated site is capable of growing on various aromatic compounds such as naphthalene, salicylate, and catechol, but not on gentisate. The genome of strain AS1 consists of a 6,126,864 bp circular chromosome and the 81,841 bp circular plasmid pAS1. Pseudomonas sp. AS1 has multiple dioxygenases and related enzymes involved in the degradation of aromatic compounds, which might contribute to the metabolic versatility of this isolate. The pAS1 plasmid exhibits extremely high similarity in size and sequences to the well-known naphthalene-degrading plasmid pDTG1 in Pseudomonas putida strain NCIB 9816-4. Two gene clusters involved in the naphthalene degradation pathway were identified on pAS1. The expression of several nah genes on the plasmid was upregulated by more than 2-fold when naphthalene was used as a sole carbon source. Strains have been isolated at different times and places with different characteristics, but similar genes involved in the degradation of aromatic compounds have been identified on their plasmids, which suggests that the transmissibility of the plasmids might play an important role in the adaptation of the microorganisms to mineralize the compounds.

• Environmental Engineering Research
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• 제12권2호
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• pp.81-91
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• 2007

A membrane bioreactor (MBR) was used to investigate the aerobic degradation of foam active substance - non-ionic surfactant, APG 2000 UP. The surface aeration using the propeller loop reactor (PLR) guaranteed sufficient $O_2$ for substrate removal and bacteria growth and avoided foam development. Moreover, the cross-flow membrane filtration enabled the separation of the bacteria still loaded with surfactant in the collecting container. The biological degradation of the surfactant with varying hydraulic retention time (HRT) and influent concentration $c_{S0}$ showed high substrate removal of nearly 95% at high volumetric loading rates up to $7.4\;kgCOD\;m^{-3}d^{-1}$ and at sludge loading rates up to 1.8 kgCOD $(kgVSS\;d)^{-1}$ for biomass concentration $c_B\;{\approx}\;constant $. The increasing $c_B$ from 3.4 to $14.5\;gL^{-1}$ TSS respectively sludge retention time (SRT) from 5.1 to 442 d under complete biomass retention by the membrane filtration resulted in high removal of substrate ${\alpha}\;>\;90%$ with reducing excess sludge production.

• The Journal of Asian Finance, Economics and Business
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• 제4권4호
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• pp.61-66
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• 2017

Environmental awareness and its relation to the development of economy has garnered increased attention in recent years. Researchers, over the years, have argued that sustainable development warrants for minimizing environmental degradation since one depends on the other. This study analyzes the relationship between environmental degradation (carbon emission taken as proxy for degradation), economic growth, total energy consumption and industrial production index growth in Bangladesh from year 1998 to 2013. This study uses Vector Autoregression (VAR) Model and variance decomposition of VAR to analyze the effect of these variables on carbon emission and vice-versa. The findings of VAR model suggest that industrial production and GDP per capita has significant relationship with carbon emission. Further analysis through variance decomposition shows carbon emission has consistent impact on industrial production over time, whereas, industrial production has high impact on emission in the short run which fades in the long run which is consistent with Environmental Kuznets Curve (EKC) hypothesis. Carbon emission rising along with GDP per capita and at the same time having low impact in the long run on industrial index indicates there may be other sources of pollution introduced with the rise in income of the economy over time.

• 한국환경농학회지
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• 제9권1호
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• pp.1-8
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• 1990

담수토양중(湛水土壤中) fenitrothion의 분해(分解)에 미치는 각종환경조건(各種條件條件)에 영향(影響)에 대하여 연구(硏究) 검토(檢討)하였다. Fenitrothion은 습윤조건(濕潤條件)에서보다 담수조건(湛水條件0에서 월등(越等)히 빨리 분해(分解)되었으며, 토양중(土壤中) 분해반감기(分解半減期)는 4일이하(日以內)였다. 분해속도(分解速度)는 토양종류(土壤種類)에 따라 차이(差異)를 보였으며, 저온(低溫)($15^{\circ}C$)에서보다 고온(高溫)($35^{\circ}C$)에서 현저히 빨리 분해(分解)되었다. Fenitrothion은 저농도처리(低濃度處理)(10ppm)에서보다 고농도처리(高濃度處理)(30ppm)에서 분해(分解)가 느렸다. Fenitrothion의 반부처리(反復處理)는 분해속도(分解速度)를 크게 촉진(促進)시켰다. 토양중(土壤中) fenitrothion의 분해(分解)는 볏짚 첨가(添加)에 의하여 현저히 촉진(促進)되었으나, 복합비료첨가(複合肥料添加)나 살균제(殺菌劑) IBP와 제초제(除草劑) butachlor의 혼합처리(混合處理)에 의하여는 거의 영향(影響)을 받지 않았다. 토양(土壤)중에 있어서 fenitrothion분해균(分解菌)의 증식(增殖)과 fenitrothion분해정도(分解程度)는 비례(比例)하였다.

• 한국환경과학회지
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• 제22권7호
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• pp.863-871
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• 2013

Dielectric discharges are an emerging technique in environmental pollutant degradation, which that are characterized by the production of hydroxyl radicals as the primary degradation species. For practical application of the plasma reactor, reactor that can handle large amounts of water are needed. Plasma research to date has focused on small-scale water treatment. This study was carried out basic study for scale-up of a single DBD (dielectric barrier discharge) plasma reactor. The degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicator of the generation of OH radical) was used as a performance indicator of multi-plasma reactor. The experiments is divided into two parts: design parameters [effect of distance of single plasma module (1~14 cm), arrangement of ground electrode (single and multi), rector number (1~5) and power number (1~5)]; operation parameter [effect of applied voltage (60~220 V), air flow rate (1~5 L/min), electric conductivity of solution ($1.4{\mu}S/cm$, deionized water)~18.8 mS/cm (addition of NaCl 10 g/L) and pH (5~9)]. Considering the electric stability of the plasma reactor, optimum spacing between the single plasma module was 2 cm. Multi discharge electrodes - single ground electrode array was selected. Combination of power 3-plasma module 5 was the optimal combination for maximum RNO degradation. The optimum 1st voltage and air flow rate for RNO degradation were 180 V and 4 L/min, respectively. The pH and conductivity of the solution was not influencing the RNO degradation.

• 유기물자원화
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• 제13권1호
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• pp.124-130
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• 2005

매립은 폐기물의 최종처분방법으로 광범위하게 이용되며, 매립된 폐기물은 미생물의 활동에 의해 분해된다. 미생물에 의한 생분해는 수분함량, 산화환원전위, pH, Alkalinity, 황산염, 영양물질과 미량원소, 방해인자, 미량이온, 온도와 같은 여러 인자에 의해 영향을 받는다. 특히, 수분은 미생물의 활성에 주요한 인자이다. 본 연구에서는 수분이 고형폐기물(MSW)의 분해에 미치는 영향을 조사하여 분석하였다. 이를 위해 총 8기의 모의매립조에 고형폐기물을 충전하였고, 수분함량을 20, 30, 40, 50% 4개로 하여 운전하였다. 그 결과 수분함량이 높을수록 $CO_2$의 농도가 높았고, 매립가스 또한 많이 발생 하였다. 이는 수분함량이 높을수록 미생물 분해가 효과적임을 의미한다.

• Journal of Microbiology and Biotechnology
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• 제14권5호
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• pp.901-905
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• 2004

The degradation and mineralization of crude oil were investigated over 50-days in three soils, loamy sand, sand, and combusted loamy, which were artificially contaminated with crude oil (50 g $kg^{-1}$) and inoculated with Nocardia sp. H17-1. The degradation efficiency of total petroleum hydrocarbon (TPH) in sand was the highest at 76% among the three soils. The TPH degradation rate constants $(k_{TPH})$ in loamy sand, sand, and combusted loamy sand were 0.027 $d^{-1}$, 0.063 $d^{-1}$, and 0.016 $d^{-1}$, respectively. In contrast, the total amount of $CO_2$ evolved was the highest at 146.1 mmol in loamy sand. The $CO_2$ evolution rate constants (k_{CO2})$ in loamy sand, sand, and combusted loamy sand were 0.057 $d^{-1}$, 0.066 $d^{-1}$, and 0.037 $d^{-1}$, respectively. Therefore, it seems that the degradation of crude oil in soils can be proportional to the soil pore space and that mineralization can be accelerated with the increase of organic substance.